Suzaku Observations Of Near-relativistic Outflows In The Bal Quasar APM 08279+5255.

NASA Astrophysics Data System (ADS)

Saez, Cristian; Chartas, G.; Brandt, N.

2009-12-01

We present results from three Suzaku observations of the z =3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. We detect strong and broad absorption at rest-frame energies of <2 keV (low-energy) and 7-12 keV (high-energy). The detection of these features confirms the results of previous long-exposure (80-90 ks) Chandra and XMM-Newton observations. The low and high-energy absorption is detected in both the back-illuminated (BI) and front-illuminated (FI) Suzaku XIS spectra (with an F-test significance of <99%). We interpret the low-energy absorption as arising from a low ionization absorber with logNH 23 and the high-energy absorption as due to lines arising from highly ionized iron in a near-relativistic outflowing wind. Assuming this interpretation we find that the velocities in the outflow range between 0.1c and 0.6c. We constrain the angle between the outflow direction of the X-ray absorber and our line of sight to be <36 degrees. We also detect possible variability of the absorption lines (at the <99.9% and <98% significance levels in the FI and BI spectra, respectively) with a rest-frame time scale of 1 month. Assuming that the detected high-energy absorption features arise from FeXXV, we estimate that the fraction of the total bolometric energy injected over the quasar's lifetime into the intergalactic medium in the form of kinetic energy to be >10%.

Decorating MOF-Derived Nanoporous Co/C in Chain-Like Polypyrrole (PPy) Aerogel: A Lightweight Material with Excellent Electromagnetic Absorption

PubMed Central

Sun, Xiaodong; Lv, Xuliang; Sui, Mingxu; Weng, Xiaodi; Li, Xiaopeng; Wang, Jijun

2018-01-01

To clear away the harmful effects of the increment of electromagnetic pollution, high performance absorbers with appropriate impedance matching and strong attenuation capacity are strongly desired. In this study, a chain-like PPy aerogel decorated with MOF-derived nanoporous Co/C (Co/C@PPy) has been successfully prepared by a self-assembled polymerization method. With a filler loading ratio of 10 wt %, the composite of Co/C@PPy could achieve a promising electromagnetic absorption performance both in intensity and bandwidth. An optimal reflection loss value of −44.76 dB is achieved, and the effective bandwidth (reflection loss lower than −10 dB) is as large as 6.56 GHz. Furthermore, a composite only loaded with 5 wt % Co/C@PPy also achieves an effective bandwidth of 5.20 GHz, which is even better than numerous reported electromagnetic absorption (EA) materials. The result reveals that the as-fabricated Co/C@PPy—with high absorption intensity, broad bandwidth, and light weight properties—can be utilized as a competitive absorber. PMID:29751650

Decorating MOF-Derived Nanoporous Co/C in Chain-Like Polypyrrole (PPy) Aerogel: A Lightweight Material with Excellent Electromagnetic Absorption.

PubMed

Sun, Xiaodong; Lv, Xuliang; Sui, Mingxu; Weng, Xiaodi; Li, Xiaopeng; Wang, Jijun

2018-05-11

To clear away the harmful effects of the increment of electromagnetic pollution, high performance absorbers with appropriate impedance matching and strong attenuation capacity are strongly desired. In this study, a chain-like PPy aerogel decorated with MOF-derived nanoporous Co/C (Co/C@PPy) has been successfully prepared by a self-assembled polymerization method. With a filler loading ratio of 10 wt %, the composite of Co/C@PPy could achieve a promising electromagnetic absorption performance both in intensity and bandwidth. An optimal reflection loss value of −44.76 dB is achieved, and the effective bandwidth (reflection loss lower than −10 dB) is as large as 6.56 GHz. Furthermore, a composite only loaded with 5 wt % Co/C@PPy also achieves an effective bandwidth of 5.20 GHz, which is even better than numerous reported electromagnetic absorption (EA) materials. The result reveals that the as-fabricated Co/C@PPy—with high absorption intensity, broad bandwidth, and light weight properties—can be utilized as a competitive absorber.

Target-specific nanoparticles containing a broad band emissive NIR dye for the sensitive detection and characterization of tumor development.

PubMed

Behnke, Thomas; Mathejczyk, Julia E; Brehm, Robert; Würth, Christian; Gomes, Fernanda Ramos; Dullin, Christian; Napp, Joanna; Alves, Frauke; Resch-Genger, Ute

2013-01-01

Current optical probes including engineered nanoparticles (NPs) are constructed from near infrared (NIR)-emissive organic dyes with narrow absorption and emission bands and small Stokes shifts prone to aggregation-induced self-quenching. Here, we present the new asymmetric cyanine Itrybe with broad, almost environment-insensitive absorption and emission bands in the diagnostic window, offering a unique flexibility of the choice of excitation and detection wavelengths compared to common NIR dyes. This strongly emissive dye was spectroscopically studied in different solvents and encapsulated into differently sized (15, 25, 100 nm) amino-modified polystyrene NPs (PSNPs) via a one-step staining procedure. As proof-of-concept for its potential for pre-/clinical imaging applications, Itrybe-loaded NPs were surface-functionalized with polyethylene glycol (PEG) and the tumor-targeting antibody Herceptin and their binding specificity to the tumor-specific biomarker HER2 was systematically assessed. Itrybe-loaded NPs display strong fluorescence signals in vitro and in vivo and Herceptin-conjugated NPs bind specifically to HER2 as demonstrated in immunoassays as well as on tumor cells and sections from mouse tumor xenografts in vitro. This demonstrates that our design strategy exploiting broad band-absorbing and -emitting dyes yields versatile and bright NIR probes with a high potential for e.g. the sensitive detection and characterization of tumor development and progression. Copyright © 2012 Elsevier Ltd. All rights reserved.

Unveiling the X-ray/UV properties of AGN winds using Broad and mini-Broad Absorption Line Quasars

NASA Astrophysics Data System (ADS)

Giustini, M.

2015-07-01

BAL/mini-BALs are observed in the UV spectra of ˜ 20-30% of optically selected AGN as broad absorption troughs blueshifted by several thousands km/s, indicative of powerful nuclear winds. They could be representative of the average AGN if their winds cover only 20-30% of the continuum source, and/or represent an evolutionary state analogous to the high-soft state of BHB, when the jet emission is quenched and strong X-ray absorbing equatorial disk winds are virtually ubiquitous. High-quality, possibly time-resolved X-ray/UV studies are crucial to assess the global amount and 'character' of absorption in BAL/mini-BAL QSOs and to constrain the physical mechanism responsible for the launch and acceleration of their winds, therefore placing them in the broader context of AGN geometry and evolution. I will review here the known X-ray properties of BAL/mini-BAL QSOs, and present new results from a comprehensive X-ray spectral analysis of all the Palomar-Green BAL/mini-BAL QSOs with available XMM-Newton observations, for a total of 51 pointings of 14 different sources. These will include the most recent results from a high-quality simultaneous XMM/HST observational campaign on the mini-BAL QSO PG 1126-041, that unveiled with stunning details the X-ray/UV connection in action in an AGN disk wind through correlated X-ray/UV absorption variability.

Compton scattering of self-absorbed synchrotron emission

NASA Astrophysics Data System (ADS)

Gao, He; Lei, Wei-Hua; Wu, Xue-Feng; Zhang, Bing

2013-11-01

Synchrotron self-Compton (SSC) scattering is an important emission mechanism in many astronomical sources, such as gamma-ray bursts (GRBs) and active galactic nuclei. We give a complete presentation of the analytical approximations for the Compton scattering of synchrotron emission with both weak and strong synchrotron self-absorption. All possible orders of the characteristic synchrotron spectral breaks (νa, νm and νc) are studied. In the weak self-absorption regime, i.e. νa < νc, the electron energy distribution is not modified by the self-absorption process. The shape of the SSC component broadly resembles that of synchrotron, but with the following features: The SSC flux increases linearly with frequency up to the SSC break frequency corresponding to the self-absorption frequency νa; and the presence of a logarithmic term in the high-frequency range of the SSC spectra makes it harder than the power-law approximation. In the strong absorption regime, i.e. νa > νc, heating of low-energy electrons due to synchrotron absorption leads to pile-up of electrons, and form a thermal component besides the broken power-law component. This leads to two-component (thermal + non-thermal) spectra for both the synchrotron and SSC spectral components. For νc < νa < νm, the spectrum is thermal (non-thermal) dominated if ν _a > √{ν _m ν _c} (ν _a < √{ν _m ν _c}). Similar to the weak-absorption regime, the SSC spectral component is broader than the simple broken power-law approximation. We derive the critical condition for strong absorption (electron pile-up), and discuss a case of GRB reverse shock emission in a wind medium, which invokes νa > max(νm, νc).

Reversible pressure pre-amorphization of a piezochromic metal-organic framework.

PubMed

Andrzejewski, M; Casati, N; Katrusiak, A

2017-11-07

The piezochromic metal-organic framework Co 2 (Bdc) 2 Dabco·4DMF·H 2 O (Bdc denotes 1,4-benzenedicarboxylate, Dabco - 1,4-diazabicyclo[2.2.2]octane, and DMF - dimethylformamide) under ambient conditions is tetragonal (phase α) and at about 1.9 GPa undergoes a strong pressure-induced shortening of translational correlations in the sample. A broad gradual pre-amorphization process starting at about 0.7 GPa reduces the tetragonal symmetry and is described as phase β. The pre-amorphization mechanism involves several competing distortions of the Bdc linkers and Co(ii)-coordination schemes. These in turn, affect the crystal field around the cations and their optical absorption. The compression strongly affects the VIS absorption of this piezochromic compound visibly changing its colour from blue to red.

The role of tachysterol in vitamin D photosynthesis - a non-adiabatic molecular dynamics study

NASA Astrophysics Data System (ADS)

Cisneros, Cecilia; Thompson, Travis; Baluyot, Noel; Smith, Adam C.; Tapavicza, Enrico

To investigate the role of tachysterol in the photophysical/chemical regulation of vitamin D photosynthesis, we studied its electronic absorption properties and excited state dynamics using time-dependent density functional theory (TDDFT), coupled cluster theory (CC2), and non-adiabatic molecular dynamics. In excellent agreement with experiments, the simulated electronic spectrum shows a broad absorption band covering the spectra of the other vitamin D photoisomers. The broad band stems from the spectral overlap of four different ground state rotamers. After photoexcitation, the first excited singlet state (S1) decays within 882 fs. The S1 dynamics is characterized by a strong twisting of the central double bond. 96% of all trajectories relax without chemical transformation to the ground state. In 2.3 % of the trajectories we observed [1,5]-sigmatropic hydrogen shift forming the partly deconjugated toxisterol D1. 1.4 % previtamin D formation is observed via hula-twist double bond isomerization. We find a strong dependence between photoreactivity and dihedral angle conformation: hydrogen shift only occurs in cEc and cEt rotamers and double bond isomerization occurs mainly in cEc rotamers. Our study confirms the hypothesis that cEc rotamers are more prone to previtamin D formation than other isomers. We also observe the formation of a cyclobutene-toxisterol in the hot ground state (0.7 %). Due to its strong absorption and unreactive behavior, tachysterol acts mainly as a sun shield suppressing previtamin D formation. Tachysterol shows stronger toxisterol formation than previtamin D. Absorption of low energy UV light by the cEc rotamer can lead to previtamin D formation. Our study reinforces a recent hypothesis that tachysterol can act as a previtamin D source when only low energy ultraviolet light is available, as it is the case in winter or in the morning and evening hours of the day.

The Hubble Space Telescope Quasar Absorption Line Key Project: The Unusual Absorption-Line System in the Spectrum of PG 2302+029--Ejected or Intervening?

NASA Technical Reports Server (NTRS)

Jannuzi, B. T.; Hartig, G. F.; Kirhakos, S.; Sargent, W. L. W.; Turnshek, D. A.; Weymann, R. J.; Bahcall, J. N.; Bergeron, J.; Boksenberg, A.; Savage, B. D.;

DISCOVERY OF THE TRANSITION OF A MINI-BROAD ABSORPTION LINE INTO A BROAD ABSORPTION LINE IN THE SDSS QUASAR J115122.14+020426.3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hidalgo, Paola Rodriguez; Eracleous, Michael; Charlton, Jane

We present the detection of a rare case of dramatic strengthening in the UV absorption profiles in the spectrum of the quasar J115122.14+020426.3 between observations {approx}2.86 yr apart in the quasar rest frame. A spectrum obtained in 2001 by the Sloan Digital Sky Survey shows a C IV ''mini-broad'' absorption line (FWHM = 1220 km s{sup -1}) with a maximum blueshift velocity of {approx}9520 km s{sup -1}, while a later spectrum from the Very Large Telescope shows a significantly broader and stronger absorption line, with a maximum blueshift velocity of {approx}12, 240 km s{sup -1} that qualifies as a broadmore » absorption line. A similar variability pattern is observed in two additional systems at lower blueshifted velocities and in the Ly{alpha} and N V transitions as well. One of the absorption systems appears to be resolved and shows evidence for partial covering of the quasar continuum source (C{sub f} {approx} 0.65), indicating a transverse absorber size of, at least, {approx}6 Multiplication-Sign 10{sup 16} cm. In contrast, a cluster of narrower C IV lines appears to originate in gas that fully covers the continuum and broad emission line sources. There is no evidence for changes in the centroid velocity of the absorption troughs. This case suggests that at least some of the absorbers that produce ''mini-broad'' and broad absorption lines in quasar spectra do not belong to intrinsically separate classes. Here, the ''mini-broad'' absorption line is most likely interpreted as an intermediate phase before the appearance of a broad absorption line due to their similar velocities. While the current observations do not provide enough constraints to discern among the possible causes for this variability, future monitoring of multiple transitions at high resolution will help achieve this goal.« less

Structural and optical properties of CuO in zinc phosphate glasses and effects of gamma irradiation

NASA Astrophysics Data System (ADS)

Ouis, M. A.; ElBatal, H. A.; Abdelghany, A. M.; Hammad, Ahmed H.

2016-01-01

Collective optical and infrared measurements have been employed to investigate the state of increasing copper ions in host 0.5ZnO-0.5P2O5 glass composition. The same spectral measurements were repeated after gamma irradiation with a dose of 20 and 80 KGy. Optical absorption spectra reveal strong UV absorption due to trace ferric ions present as unavoidable impurities within the chemicals used in the preparation of the glasses. Copper containing glasses show an additional broad visible-near infrared band due to distorted octahedrally coordinated Cu2+ ions which at high CuO contents exhibit splitting to several component absorption peaks. Gamma irradiation causes several variations between the response of the base host zinc phosphate glass and effect of increasing CuO. These changes are correlated with both the formation of induced defects through suggested photochemical reactions in the UV region and some shielding effects with increasing CuO in the visible-near infrared spectrum. Infrared absorption spectra reveal repetitive vibrational bands due to phosphate groups mainly from metaphosphate units and the spectra show some variations with the increase of CuO content visualize by the increase of the intensity of the mid broad band extending in the range 800-1500 cm-1.

Influence of CuO content on the structure of lithium fluoroborate glasses: Spectral and gamma irradiation studies.

PubMed

Abdelghany, A M; ElBatal, H A; EzzElDin, F M

2015-10-05

Glasses of lithium fluoroborate of the composition LiF 15%-B2O3 85% with increasing CuO as added dopant were prepared and characterized by combined optical and FTIR spectroscopy before and after gamma irradiation. The optical spectrum of the undoped glass reveals strong UV absorption with two distinct peaks at about 235 and 310 nm and with no visible bands. This strong UV absorption is related to the presence of unavoidable trace iron impurity (Fe(3+)) within the materials used for the preparation of this glass. After irradiation, the spectrum of the undoped glass shows a decrease of the intensity of the UV bands together with the resolution of an induced visible broad band centered at about 520 nm. The CuO doped glasses reveal the same UV absorption beside a very broad visible band centered at 780 nm and this band shows extension and splitting to several component peaks with higher CuO contents. Upon gamma irradiation, the spectra of all CuO-doped glasses reveal pronounced decrease of their intensities. The response of irradiation on the studied glasses is correlated with suggested photochemical reactions together with some shielding effect of the copper ions. The observed visible band is related to the presence of copper as distorted octahedral Cu(2+) ions. Infrared absorption spectra of the prepared glasses show repetitive characteristic triangular and tetrahedral borate units similar to that published from alkali or alkaline earth oxides B2O3 glasses. A suggested formation of (BO3/2F) tetrahedral units is advanced through action of LiF on B2O3 and these suggested units showing the same position and number as BO4 tetrahedra. Copyright © 2015 Elsevier B.V. All rights reserved.

X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta

2009-11-10

We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jetmore » can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.« less

Synergistic thermoradiotherapy based on PEGylated Cu3BiS3 ternary semiconductor nanorods with strong absorption in the second near-infrared window.

PubMed

Li, Ang; Li, Xiang; Yu, Xujiang; Li, Wei; Zhao, Ruyi; An, Xiao; Cui, Daxiang; Chen, Xiaoyuan; Li, Wanwan

2017-01-01

In this work, we report a successful synthesis of copper bismuth sulfide nanorods (NRs) with broad and strong photoabsorption ranging from ultraviolet (UV) to near-infrared (NIR) wavelengths, which can be used as a 1064 nm-laser-driven photothermal agent with the photothermal conversion efficiency of 40.7%, noticeably higher than most of the reported PTT agents working in NIR-II window. The as-prepared PEGylated Cu 3 BiS 3 NRs were used as photoacoustic imaging (PAI) and CT imaging agents due to their strong NIR absorption and large X-ray attenuation coefficient of bismuth. We are the first to demonstrate that a small quantity of PEGylated Cu 3 BiS 3 NRs in tumors can concentrate radiation energy and trigger mild PTT under NIR-II irradiation and thus, these particles could be used as a novel, synergistic thermoradiotheraputic agent that enhances the efficacy of radiotherapy. Copyright © 2016 Elsevier Ltd. All rights reserved.

First Spectroscopic Identification of Massive Young Stellar Objects in the Galactic Center

NASA Technical Reports Server (NTRS)

An, Deokkeun; Ramirez, V.; Sellgren, Kris; Arendt, Richard G.; Boogert, A. C.; Schultheis, Mathias; Stolovy, Susan R.; Cotera, Angela S.; Robitaille, Thomas P.; Smith, Howard A.

2009-01-01

We report the detection of several molecular gas-phase and ice absorption features in three photometrically-selected young stellar object (YSO) candidates in the central 280 pc of the Milky Way. Our spectra, obtained with the Infrared Spectrograph (IRS) onboard the Spitzer Space Telescope, reveal gas-phase absorption from CO2 (15.0 microns), C2H2 (13.7 microns) and HCN (14.0 microns). We attribute this absorption to warm, dense gas in massive YSOs. We also detect strong and broad 15 microns CO2 ice absorption features, with a remarkable double-peaked structure. The prominent long-wavelength peak is due to CH3OH-rich ice grains, and is similar to those found in other known massive YSOs. Our IRS observa.tions demonstra.te the youth of these objects, and provide the first spectroscopic identification of massive YSOs in the Galactic Center.

Observations of the peculiar object MWC 560 in outburst

NASA Technical Reports Server (NTRS)

Michalitsianos, A. G.; Maran, S. P.; Oliversen, R. J.; Bopp, B.; Kontizas, E.

1991-01-01

The results of ultraviolet spectroscopy, photoelectric photometry, and supplemental high-resolution H(alpha) spectroscopy of a photometric outburst of MWC 560 are discussed. Ultraviolet spectra are shown to be consistent with the ejection of an optically thick shell that produced strong absorption blends of Fe II and Cr II. The velocities reported exceed by far those previously found in symbiotic stars or recurrent novas. In addition to the variable high-velocity system of broad absorption features, a relatively stable system of Mg II, Mg I, Fe II, Cr II, and other ionic absorptions is observed. It is pointed out that the spectroscopic phenomena in MWC 560 resemble those found in XX Ophiuchi, but the velocities in the MWC 560 are an order of magnitude higher than those found in XX Oph.

Photothermal ablation cancer therapy using homogeneous CsxWO3 nanorods with broad near-infra-red absorption

NASA Astrophysics Data System (ADS)

Guo, Chongshen; Yin, Shu; Yu, Haijun; Liu, Shaoqin; Dong, Qiang; Goto, Takehiro; Zhang, Zhiwen; Li, Yaping; Sato, Tsugio

2013-06-01

Recently, photothermal ablation therapy (PTA) employing near-infrared radiation (NIR) has been extensively investigated as an emerging modality for cancer management. However, the clinical translation of this promising approach is limited by the lack of PTA agents with broad NIR absorption, low cost and high photothermal conversion efficiency. Herein, we have developed PEGylated homogeneous CsxWO3 nanorods (a mean size ~69.3 nm × 12.8 nm) with broad photo-absorption (780-2500 nm) as a novel NIR absorbent for PTA treatment of human cancer. The prepared CsxWO3 nanocrystals displayed strong near-infrared optical absorption with a high molar extinction coefficient (e.g. 4.8 × 1010 M-1 cm-1 at 980 nm), thus generated significant amounts of heat upon excitation with near-infrared light. The PTA study in two human carcinoma cell lines (i.e. A549 lung cancer cells and HeLa ovarian cancer cells) demonstrated that CsxWO3 nanorods can efficiently cause cell death via hyperthermia induced lysosome destruction, cytoskeleton protein degradation, DNA damage and thereafter cellular necrosis or apoptosis. Our study also confirmed the migration of healthy cells migrated from unirradiated areas to dead cell cycle, which is essential for tissue reconstruction and wound healing after photodestruction of tumor tissue. The prompted results reported in the current study imply the promising potential of CsxWO3 nanorods for application in PTA cancer therapy.Recently, photothermal ablation therapy (PTA) employing near-infrared radiation (NIR) has been extensively investigated as an emerging modality for cancer management. However, the clinical translation of this promising approach is limited by the lack of PTA agents with broad NIR absorption, low cost and high photothermal conversion efficiency. Herein, we have developed PEGylated homogeneous CsxWO3 nanorods (a mean size ~69.3 nm × 12.8 nm) with broad photo-absorption (780-2500 nm) as a novel NIR absorbent for PTA treatment of human cancer. The prepared CsxWO3 nanocrystals displayed strong near-infrared optical absorption with a high molar extinction coefficient (e.g. 4.8 × 1010 M-1 cm-1 at 980 nm), thus generated significant amounts of heat upon excitation with near-infrared light. The PTA study in two human carcinoma cell lines (i.e. A549 lung cancer cells and HeLa ovarian cancer cells) demonstrated that CsxWO3 nanorods can efficiently cause cell death via hyperthermia induced lysosome destruction, cytoskeleton protein degradation, DNA damage and thereafter cellular necrosis or apoptosis. Our study also confirmed the migration of healthy cells migrated from unirradiated areas to dead cell cycle, which is essential for tissue reconstruction and wound healing after photodestruction of tumor tissue. The prompted results reported in the current study imply the promising potential of CsxWO3 nanorods for application in PTA cancer therapy. Electronic supplementary information (ESI) available: EDS spectra, XRD patterns, TG plot of CsxWO3 nanorod are provided in the ESI. Additionally, linear correlations between NIR absorbance and CsxWO3-PEGS nanorod concentrations, cytotoxicity results, TEM image of intracellular distribution of CsxWO3-PEGS nanorods and fluorescence images can be found in the ESI. See DOI: 10.1039/c3nr01025b

On the origin of a very close similarity between the spectra of the supernova type 1 in NGC 3198 and the absorption of DQ HeR

NASA Technical Reports Server (NTRS)

Mustel, E. R.

1979-01-01

The type 1 supernova discovered late in 1966 in NGC 3198 has broad minima in its spectrum break down into a number of significantly narrower absorption bands. The broad minima of tau, sigma and mu, which usually show no details in the spectra of type supernovas, contain a number of narrow absorption bands. The reality of most of these absorption bands is demonstrated by comparison of recordings of spectra of the supernova presented for two moments in time. These minima (particularly of tau and mu,) are a result of blending of several broad absorption bands. The minimum of tau should be a blend of intensive and very broad Fe absorption lines, in which the lower level is metastable. The wavelengths of these line are: 5169, 5198, 5235, 5276, 5317, 5363A.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krelowski, J.; Galazutdinov, G.; Kolos, R., E-mail: jacek@astri.uni.torun.pl, E-mail: runizag@gmail.com, E-mail: robert.kolos@ichf.edu.pl

The recent assignment of two broad diffuse interstellar bands (DIBs) near 4882 and 5450 A to the propadienylidene (l-C{sub 3}H{sub 2}) molecule is examined using a statistically meaningful sample of targets. Our spectra clearly show that the strength ratio of two broad DIBs is strongly variable, contrary to what should be observed if both features are due to l-C{sub 3}H{sub 2}, since the proposed transitions are lifetime broadened and start from the same level. Moreover, even in directions where the 4882 DIB and 5450 DIB are strong, the third expected l-C{sub 3}H{sub 2} band, in the 5165-5185 A region, ismore » absent. Another puzzling characteristic of l-C{sub 3}H{sub 2} as the proposed carrier of both broad diffuse bands is its column density of several 10{sup 14} cm{sup -2}, inferred from the equivalent width of the 5450 DIB. This value is one order of magnitude higher than N(CH) toward the same objects and two to three orders of magnitude higher than N(H{sub 2}CCC), measured at radio frequencies in absorption, for comparable samples of the diffuse medium. We conclude that the proposed identification of broad DIBs is unjustified.« less

Gamma ray interaction with vanadyl ions in barium metaphosphate glasses; spectroscopic and ESR studies

NASA Astrophysics Data System (ADS)

Abdelghany, A. M.; ElBatal, H. A.; EzzElDin, F. M.

2017-11-01

Optical, FTIR, ESR investigations of prepared undoped barium metaphosphate glass and other samples with the same basic composition containing varying V2O5 contents (0.5, 1, 2, 3%) were carried out before and after gamma irradiation. The undoped glass shows a strong UV optical absorption which is correlated with unavoidable contaminated trace iron impurities. The V2O5-doped samples reveal two additional strong broad visible bands centered at 450 and 680 nm. Such extra peculiar and strong two broad visible bands are related to both tetravalent and trivalent vanadium ions in measurable percent due to the reducing behavior of barium phosphate host glass. Gamma irradiation on the undoped glass results in the generation of collective induced UV and visible bands which are originating from positive hole and electron centers. Glasses containing V2O5 reveal upon gamma irradiation induced defects in the UV as the undoped sample together with distinct splitting within the first broad visible band while the second broad band remains unchanged. This behavior is related to limited photoionization upon the addition of V2O5 indicating specific shielding effect of the vanadium ions towards gamma irradiation. It was noticed that irradiation causes no distinct variations in the FTIR spectra due to the presence of 50% of heavy metal oxide (BaO) and some shielding effect of vanadium ions.

1E 0104.2 + 3153 - A broad absorption-line QSO viewed through a giant elliptical galaxy

NASA Technical Reports Server (NTRS)

Stocke, J. T.; Liebert, J.; Schild, R.; Gioia, I. M.; Maccacaro, T.

1984-01-01

The optical identification of the X-ray source 1E 0104.2 + 3153 is complicated by the close projection of a broad absorption-line (BAL) QSO (z = 2.027) 10 arcsec from a giant elliptical galaxy (z = 0.111) at the center of a compact group of galaxies. At only 1.2 de Vaucouleur radii (16 kpc for H sub 0 = 100 km/s Mpc) this QSO-galaxy projection is the closest yet discovered. Based upon current observations, the source of the X-ray emission cannot be conclusively determined. Present in the BAL QSO spectrum are extremely strong Ca II H and K absorption lines due to the intervening galaxy, the first optical detection of the cold interstellar medium in an elliptical galaxy. The strength of these lines (EW = 2 and 1 A) requires observation through several interstellar clouds in the line of sight to the QSO. By its proximity to the central regions of the elliptical galaxy and the relative distances of the galaxy and QSO, this QSO is a particularly good candidate for observing dramatic transient gravitational lensing phenomena due to halo stars in the foreground galaxy.

Fresh Exposures of Fe-Allophane/Opal in Association with Channels and Debris Aprons in Coprates Chasma, Mars

NASA Astrophysics Data System (ADS)

Weitz, C. M.; Bishop, J. L.; Baker, L.; Berman, D. C.

2014-04-01

We have discovered relatively fresh deposits of a hydrated, amorphous material resembling Fe-rich allophane or opal along the wallrock slopes in Coprates Chasma, Mars (Fig. 1). The deposits appear similar to numerous mass wasting flows and debris aprons visible along the wallrock slopes. It is only with the aid of CRISM visible and near-infrared reflectance spectral data that these deposits appear distinct. Spectra extracted from the deposits exhibit broad absorptions at 1.42, 1.94, and ~2.25 μm. These broad absorptions and peaks shifted to longer wavelengths relative to spectra of allophane and opal are most consistent with Fe-allophane/opal produced synthetically in the laboratory. The three absorptions, especially the 1.4 μm, are very strong relative to most martian hydrated spectra, suggesting high water content that is relatively fresh and has not altered or lost water since formation/exposure. The confinement and concentration of Fe-allophane/opal into channels suggests that there was movement downslope, but the channels may have formed previously and could have been used as a conduit by the younger Fe-allophane/opal debris.

The X-ray Absorber in the X-ray Transient NLS1 WPVS 007

NASA Astrophysics Data System (ADS)

Grupe, Dirk

This proposal is for a funding request for an approved XMM-Newton observations of the X-ray transient Narrow-Line Seyfert 1 galaxy WPVS 007. The request is for 4 month of salary for the PI for one year in order to do the data analysis, publish the results, and attend an international AGN meeting. XMM will observe WPVS 007 in June 2010 simultaneously with HST, Chandra, and Swift. The goal is to establish a tight connection between the UV broad absorption line troughs found in FUSE observations and the strong partial covering absorber feature found by Swift. WPVS 007 showed a dramatic transformation into a Broad Absorption line QSO like AGN between a 1996 HST observation and a 2003 FUSE observation. Several Swift monitoring observations have suggested that the absorber may have started to disappear. Therefore it is crucial for our HST COS UV spectroscopy to know what the status of the X-ray absorber is. The XMM observation will provide a well-exposed X-ray spectrum even if WPVS 007 will be in a low flux state. This spectrum will enable us to put constraints on the absorption column density and covering fraction of the partial covering absorber.

A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Third Data Release

NASA Astrophysics Data System (ADS)

Trump, Jonathan R.; Hall, Patrick B.; Reichard, Timothy A.; Richards, Gordon T.; Schneider, Donald P.; Vanden Berk, Daniel E.; Knapp, Gillian R.; Anderson, Scott F.; Fan, Xiaohui; Brinkman, J.; Kleinman, S. J.; Nitta, Atsuko

2006-07-01

We present a total of 4784 unique broad absorption line quasars from the Sloan Digital Sky Survey Third Data Release. An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum over a velocity range of at least 1000 km s-1 in the C IV and Mg II absorption regions. The model continuum was selected as the best-fit match from a set of template quasar spectra binned in luminosity, emission line width, and redshift, with the power-law spectral index and amount of dust reddening as additional free parameters. We characterize our sample through the traditional ``balnicity'' index and a revised absorption index, as well as through parameters such as the width, outflow velocity, fractional depth, and number of troughs. From a sample of 16,883 quasars at 1.7<=z<=4.38, we identify 4386 (26.0%) quasars with broad C IV absorption, of which 1756 (10.4%) satisfy traditional selection criteria. From a sample of 34,973 quasars at 0.5<=z<=2.15, we identify 457 (1.31%) quasars with broad Mg II absorption, 191 (0.55%) of which satisfy traditional selection criteria. We also provide a supplementary list of 39 visually identified z>4.38 quasars with broad C IV absorption. We find that broad absorption line quasars may have broader emission lines on average than other quasars.

The fraction and mid-infrared properties of broad absorption line quasars from the Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Pu, Xingting

2014-02-01

We present the results of a study which uses a sample of 1822 Sloan Digital Sky Survey (SDSS) quasars with reliable Wide-field Infrared Survey Explorer (WISE) detections in the redshift range 1.7≤ z≤4.38 to investigate the mid-infrared fraction of broad absorption line (BAL) quasars. The BAL quasars in the sample include both high-ionization BAL (HiBAL) quasars that show broad absorption from C iv and low-ionization BAL (LoBAL) quasars that show additional broad absorption from Mg ii. The fraction of C iv BAL quasars with nonzero absorption index (AI) is found to be 38.7±1.2 %, in good agreement with that derived for the Two Micron All Sky Survey (2MASS) sample. The C iv BAL quasar fractions remain constant with magnitude in the WISE 3.4 μm (W1) and 4.6 μm (W2) bands, and increase rapidly with decreasing magnitude in the WISE 12 μm (W3) and 22 μm (W4) bands. The nonzero AI fraction of 44.5±2.1 % determined in the WISE W4 band is more likely to represent the intrinsic BAL quasar fraction. No evidence that the fraction is a strong function of redshift is found. At 1.7≤ z≤2.15, the overall mid-infrared LoBAL fraction is and the fractions increase significantly with decreasing magnitude in all four of WISE bands. Moreover, it is found that the mean optical-to-WISE colors of BAL quasars are ≃0.2 mag redder than that of non-BAL quasars, while the traditional (nonzero balnicity) BAL quasars are redder than the nontraditional BAL quasars by ≃0.15 mag, which suggest a continuum of more reddening from non-BAL to nontraditional BAL to traditional BAL. No evidence that nontraditional BALs are a distinct class from traditional BALs is found. Finally, it is shown that the mean optical-to-WISE colors of LoBALs are ≃0.4 mag redder than that of HiBALs at 1.7≤ z≤2.15.

Systematic determination of absolute absorption cross-section of individual carbon nanotubes

PubMed Central

Liu, Kaihui; Hong, Xiaoping; Choi, Sangkook; Jin, Chenhao; Capaz, Rodrigo B.; Kim, Jihoon; Wang, Wenlong; Bai, Xuedong; Louie, Steven G.; Wang, Enge; Wang, Feng

2014-01-01

Optical absorption is the most fundamental optical property characterizing light–matter interactions in materials and can be most readily compared with theoretical predictions. However, determination of optical absorption cross-section of individual nanostructures is experimentally challenging due to the small extinction signal using conventional transmission measurements. Recently, dramatic increase of optical contrast from individual carbon nanotubes has been successfully achieved with a polarization-based homodyne microscope, where the scattered light wave from the nanostructure interferes with the optimized reference signal (the reflected/transmitted light). Here we demonstrate high-sensitivity absorption spectroscopy for individual single-walled carbon nanotubes by combining the polarization-based homodyne technique with broadband supercontinuum excitation in transmission configuration. To our knowledge, this is the first time that high-throughput and quantitative determination of nanotube absorption cross-section over broad spectral range at the single-tube level was performed for more than 50 individual chirality-defined single-walled nanotubes. Our data reveal chirality-dependent behaviors of exciton resonances in carbon nanotubes, where the exciton oscillator strength exhibits a universal scaling law with the nanotube diameter and the transition order. The exciton linewidth (characterizing the exciton lifetime) varies strongly in different nanotubes, and on average it increases linearly with the transition energy. In addition, we establish an empirical formula by extrapolating our data to predict the absorption cross-section spectrum for any given nanotube. The quantitative information of absorption cross-section in a broad spectral range and all nanotube species not only provides new insight into the unique photophysics in one-dimensional carbon nanotubes, but also enables absolute determination of optical quantum efficiencies in important photoluminescence and photovoltaic processes. PMID:24821815

Systematic determination of absolute absorption cross-section of individual carbon nanotubes.

PubMed

Liu, Kaihui; Hong, Xiaoping; Choi, Sangkook; Jin, Chenhao; Capaz, Rodrigo B; Kim, Jihoon; Wang, Wenlong; Bai, Xuedong; Louie, Steven G; Wang, Enge; Wang, Feng

2014-05-27

Optical absorption is the most fundamental optical property characterizing light-matter interactions in materials and can be most readily compared with theoretical predictions. However, determination of optical absorption cross-section of individual nanostructures is experimentally challenging due to the small extinction signal using conventional transmission measurements. Recently, dramatic increase of optical contrast from individual carbon nanotubes has been successfully achieved with a polarization-based homodyne microscope, where the scattered light wave from the nanostructure interferes with the optimized reference signal (the reflected/transmitted light). Here we demonstrate high-sensitivity absorption spectroscopy for individual single-walled carbon nanotubes by combining the polarization-based homodyne technique with broadband supercontinuum excitation in transmission configuration. To our knowledge, this is the first time that high-throughput and quantitative determination of nanotube absorption cross-section over broad spectral range at the single-tube level was performed for more than 50 individual chirality-defined single-walled nanotubes. Our data reveal chirality-dependent behaviors of exciton resonances in carbon nanotubes, where the exciton oscillator strength exhibits a universal scaling law with the nanotube diameter and the transition order. The exciton linewidth (characterizing the exciton lifetime) varies strongly in different nanotubes, and on average it increases linearly with the transition energy. In addition, we establish an empirical formula by extrapolating our data to predict the absorption cross-section spectrum for any given nanotube. The quantitative information of absorption cross-section in a broad spectral range and all nanotube species not only provides new insight into the unique photophysics in one-dimensional carbon nanotubes, but also enables absolute determination of optical quantum efficiencies in important photoluminescence and photovoltaic processes.

Suzaku Observations of Near-Relativistic Outflows in the BAL Quasar APM 08279+5255

NASA Astrophysics Data System (ADS)

Saez, C.; Chartas, G.; Brandt, W. N.

2009-05-01

We present results from three Suzaku observations of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. We detect strong and broad absorption at rest-frame energies of lsim2 keV (low energy) and 7-12 keV (high energy). The detection of these features confirms the results of previous long-exposure (80-90 ks) Chandra and XMM-Newton observations. The low- and high-energy absorption is detected in both the back-illuminated (BI) and front-illuminated (FI) Suzaku X-ray Imaging Spectrometer spectra (with an F-test significance of gsim99%). We interpret the low-energy absorption as arising from a low-ionization absorber with log N H ~ 23 and the high-energy absorption as due to lines arising from highly ionized (2.75 lsim logξ lsim 4.0, where ξ is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation we find that the velocities in the outflow range between 0.1c and 0.6c. We constrain the angle between the outflow direction of the X-ray absorber and our line of sight to be lsim36°. We also detect likely variability of the absorption lines (at the gsim99.9% and gsim98% significance levels in the FI and BI spectra, respectively) with a rest-frame timescale of ~1 month. Assuming that the detected high-energy absorption features arise from Fe XXV, we estimate that the fraction of the total bolometric energy injected over the quasar's lifetime into the intergalactic medium in the form of kinetic energy to be gsim10%.

First XMM-Newton Observations of an Isolated Neutron Star: RXJ0720.4-3125

NASA Technical Reports Server (NTRS)

Paerels, Frits; Mori, Kaya; Motch, Christian; Haberl, Frank; Zavlin, Vyacheslav E.; Zane, Silvia; Ramsay, Gavin; Cropper, Mark

2000-01-01

We present the high resolution spectrum of the isolated neutron star RXJ0720.4-3125, obtained with the Reflection Grating Spectrometer on XMM-Newton, complemented with the broad band spectrum observed with the EPIC PN camera. The spectrum appears smooth, with no evidence for strong photospheric absorption or emission features. We briefly discuss the implications of our failure to detect structure in the spectrum.

Unveiling the X-ray/UV properties of disk winds in active galactic nuclei using broad and mini-broad absorption line quasars

NASA Astrophysics Data System (ADS)

Giustini, M.

2016-05-01

We present the results of the uniform analysis of 46 XMM-Newton observations of six BAL and seven mini-BAL QSOs belonging to the Palomar-Green Quasar catalogue. Moderate-quality X-ray spectroscopy was performed with the EPIC-pn, and allowed to characterise the general source spectral shape to be complex, significantly deviating from a power law emission. A simple power law analysis in different energy bands strongly suggests absorption to be more significant than reflection in shaping the spectra. If allowing for the absorbing gas to be either partially covering the continuum emission source or to be ionised, large column densities of the order of 1022-1024 cm-2 are inferred. When the statistics was high enough, virtually every source was found to vary in spectral shape on various time scales, from years to hours. All in all these observational results are compatible with radiation driven accretion disk winds shaping the spectra of these intriguing cosmic sources.

Broad absorption-line time variability in the QSO CSO 203

NASA Technical Reports Server (NTRS)

Barlow, Thomas A.; Junkkarinen, Vesa T.; Burbidge, E. M.; Weymann, Ray J.; Morris, Simon L.; Korista, Kirk T.

1992-01-01

We present spectroscopy of the BALQSO CSO 203 during four epochs over a 17-month time span. These data show three distinct levels in the broad absorption lines (BALs) of Si IV 1397A and C IV 1549A. We also note possible variations in the N V 1240A and Al III 1857A absorption troughs. A broad-band monitoring effort during this period shows that the continuum level remained constant to within 10 percent. We argue that the triggering mechanism for the absorption-line changes is most likely synchronous with the continuum source photons; however, no correlation with the central source has yet been found. The observed variations are consistent with changes in the ionization level in the broad absorption-line region (BALR). We discuss possible mechanisms for these changes and the implications for the structure of the BALR.

Constructing Repairable Meta-Structures of Ultra-Broad-Band Electromagnetic Absorption from Three-Dimensional Printed Patterned Shells.

PubMed

Song, Wei-Li; Zhou, Zhili; Wang, Li-Chen; Cheng, Xiao-Dong; Chen, Mingji; He, Rujie; Chen, Haosen; Yang, Yazheng; Fang, Daining

2017-12-13

Ultra-broad-band electromagnetic absorption materials and structures are increasingly attractive for their critical role in competing with the advanced broad-band electromagnetic detection systems. Mechanically soft and weak wax-based materials composites are known to be insufficient to serve in practical electromagnetic absorption applications. To break through such barriers, here we developed an innovative strategy to enable the wax-based composites to be robust and repairable meta-structures by employing a three-dimensional (3D) printed polymeric patterned shell. Because of the integrated merits from both the dielectric loss wax-based composites and mechanically robust 3D printed shells, the as-fabricated meta-structures enable bear mechanical collision and compression, coupled with ultra-broad-band absorption (7-40 and 75-110 GHz, reflection loss  smaller than -10 dB) approaching state-of-the-art electromagnetic absorption materials. With the assistance of experiment and simulation methods, the design advantages and mechanism of employing such 3D printed shells for substantially promoting the electromagnetic absorption performance have been demonstrated. Therefore, such universal strategy that could be widely extended to other categories of wax-based composites highlights a smart stage on which high-performance practical multifunction meta-structures with ultra-broad-band electromagnetic absorption could be envisaged.

Solar absorption by elemental and brown carbon determined from spectral observations.

PubMed

Bahadur, Ranjit; Praveen, Puppala S; Xu, Yangyang; Ramanathan, V

2012-10-23

Black carbon (BC) is functionally defined as the absorbing component of atmospheric total carbonaceous aerosols (TC) and is typically dominated by soot-like elemental carbon (EC). However, organic carbon (OC) has also been shown to absorb strongly at visible to UV wavelengths and the absorbing organics are referred to as brown carbon (BrC), which is typically not represented in climate models. We propose an observationally based analytical method for rigorously partitioning measured absorption aerosol optical depths (AAOD) and single scattering albedo (SSA) among EC and BrC, using multiwavelength measurements of total (EC, OC, and dust) absorption. EC is found to be strongly absorbing (SSA of 0.38) whereas the BrC SSA varies globally between 0.77 and 0.85. The method is applied to the California region. We find TC (EC + BrC) contributes 81% of the total absorption at 675 nm and 84% at 440 nm. The BrC absorption at 440 nm is about 40% of the EC, whereas at 675 nm it is less than 10% of EC. We find an enhanced absorption due to OC in the summer months and in southern California (related to forest fires and secondary OC). The fractions and trends are broadly consistent with aerosol chemical-transport models as well as with regional emission inventories, implying that we have obtained a representative estimate for BrC absorption. The results demonstrate that current climate models that treat OC as nonabsorbing are underestimating the total warming effect of carbonaceous aerosols by neglecting part of the atmospheric heating, particularly over biomass-burning regions that emit BrC.

Million Degree Plasmas in Extreme Ultraviolet (EUV) Astrophysics. White Paper in Response to Astro2010 Science Call

DTIC Science & Technology

2010-01-01

photometry , timing measurements of suitable cadence, and advanced theory are the keys to understanding the physics of million degree plasmas in...Disentangling these components requires time - and phase- resolved spectroscopic observations of a sample that spans a range of mass accretion rates...many narrow lines, or a continuum with strong, broad absorption features. Key Objective: Obtaining time - and phase- resolved high-resolution EUV

Wide-band 'black silicon' with atomic layer deposited NbN.

PubMed

Isakov, Kirill; Perros, Alexander Pyymaki; Shah, Ali; Lipsanen, Harri

2018-08-17

Antireflection surfaces are often utilized in optical components to reduce undesired reflection and increase absorption. We report on black silicon (b-Si) with dramatically enhanced absorption over a broad wavelength range (250-2500 nm) achieved by applying a 10-15 nm conformal coating of NbN with atomic layer deposition (ALD). The improvement is especially pronounced in the near infrared (NIR) range of 1100-2500 nm where absorption is increased by >90%. A significant increase of absorption is also observed over the ultraviolet range of 200-400 nm. Preceding NbN deposition with a nanostructured ALD Al 2 O 3 (n-Al 2 O 3 ) coating to enhance the NbN texture was also examined. Such texturing further improves absorption in the NIR, especially at longer wavelengths, strong absorption up to 4-5 μm wavelengths has been attested. For comparison, double side polished silicon and sapphire coated with 10 nm thick NbN exhibited absorption of only ∼55% in the NIR range of 1100-2500 nm. The results suggest a positive correlation between the surface area of NbN coating and optical absorption. Based on the wide-band absorption, the presented NbN-coated b-Si may be an attractive candidate for use in e.g. spectroscopic systems, infrared microbolometers.

Can H2CCC be the Carrier of Broad Diffuse Bands?

NASA Astrophysics Data System (ADS)

Krełowski, J.; Galazutdinov, G.; Kołos, R.

2011-07-01

The recent assignment of two broad diffuse interstellar bands (DIBs) near 4882 and 5450 Å to the propadienylidene (l-C3H2) molecule is examined using a statistically meaningful sample of targets. Our spectra clearly show that the strength ratio of two broad DIBs is strongly variable, contrary to what should be observed if both features are due to l-C3H2, since the proposed transitions are lifetime broadened and start from the same level. Moreover, even in directions where the 4882 DIB and 5450 DIB are strong, the third expected l-C3H2 band, in the 5165-5185 Å region, is absent. Another puzzling characteristic of l-C3H2 as the proposed carrier of both broad diffuse bands is its column density of several 1014 cm-2, inferred from the equivalent width of the 5450 DIB. This value is one order of magnitude higher than N(CH) toward the same objects and two to three orders of magnitude higher than N(H2CCC), measured at radio frequencies in absorption, for comparable samples of the diffuse medium. We conclude that the proposed identification of broad DIBs is unjustified. Based on observations collected at the European Organization for Astronomical Research in the Southern Hemisphere, Chile; programs 073.C-0337(A) and 082.C-0566(A).

Broadly tunable terahertz difference-frequency generation in quantum cascade lasers on silicon

NASA Astrophysics Data System (ADS)

Jung, Seungyong; Kim, Jae Hyun; Jiang, Yifan; Vijayraghavan, Karun; Belkin, Mikhail A.

2018-01-01

We report broadly tunable terahertz (THz) sources based on intracavity Cherenkov difference-frequency generation in quantum cascade lasers transfer-printed on high-resistivity silicon substrates. Spectral tuning from 1.3 to 4.3 THz was obtained from a 2-mm long laser chip using a modified Littrow external cavity setup. The THz power output and the midinfrared-to-THz conversion efficiency of the devices transferred on silicon are dramatically enhanced, compared with the devices on a native semi-insulating InP substrate. Enhancement is particularly significant at higher THz frequencies, where the tail of the Reststrahlen band results in a strong absorption of THz light in the InP substrate.

Anomalous photoluminescence in InP1−xBix

PubMed Central

Wu, Xiaoyan; Chen, Xiren; Pan, Wenwu; Wang, Peng; Zhang, Liyao; Li, Yaoyao; Wang, Hailong; Wang, Kai; Shao, Jun; Wang, Shumin

2016-01-01

Low temperature photoluminescence (PL) from InP1−xBix thin films with Bi concentrations in the 0–2.49% range reveals anomalous spectral features with strong and very broad (linewidth of 700 nm) PL signals compared to other bismide alloys. Multiple transitions are observed and their energy levels are found much smaller than the band-gap measured from absorption measurements. These transitions are related to deep levels confirmed by deep level transient spectroscopy, which effectively trap free holes and enhance radiative recombination. The broad luminescence feature is beneficial for making super-luminescence diodes, which can theoretically enhance spatial resolution beyond 1 μm in optical coherent tomography (OCT). PMID:27291823

Evidence for active galactic nucleus feedback in the broad absorption lines and reddening of MRK 231 {sup ,}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leighly, Karen M.; Baron, Eddie; Lucy, Adrian B.

2014-06-20

We present the first J-band spectrum of Mrk 231, which reveals a large He I* λ10830 broad absorption line with a profile similar to that of the well-known Na I broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by Veilleux et al. is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in Type Ia supernovae. The nuclear starburst may be the origin and location of the dust. Spatially resolved emission in the broad absorption line trough suggests nearly fullmore » coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the He I* lines (produced in the quasar-photoionized H II region) compared with the Na I and Ca II lines (produced in the corresponding partially ionized zone). Cloudy simulations show that a density increase is required between the H II and partially ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies ∼100 pc from the central engine. These results suggest that the He I* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the Ca II and Na I lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of Na I absorption lines; without the compression along our line of sight, Mrk 231 would appear as an ordinary iron low-ionization, broad absorption line quasar.« less

Eclipsing damped Ly α systems in the Sloan Digital Sky Survey Data Release 12

NASA Astrophysics Data System (ADS)

Fathivavsari, H.; Petitjean, P.; Jamialahmadi, N.; Khosroshahi, H. G.; Rahmani, H.; Finley, H.; Noterdaeme, P.; Pâris, I.; Srianand, R.

2018-07-01

We present the results of our automatic search for proximate damped Ly α absorption (PDLA) systems in the quasar spectra from the Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500 km s-1 from the quasar to make sure that the broad DLA absorption trough masks most of the strong Ly α emission from the broad-line region (BLR) of the quasar. When the Ly α emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Ly α emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with log N(H I) ≥ 21.10. We divide our statistical sample into three subsamples based on the strength of the NEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorptions from high ionization species are stronger in DLAs with stronger NEL in their absorption core. Moreover, absorption from the excited states of species like SIII are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Ly α NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar. We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High-resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs.

Enhancement of Fe diffusion in ZnSe/S laser crystals under hot isostatic pressing

NASA Astrophysics Data System (ADS)

Gafarov, Ozarfar; Martinez, Alan; Fedorov, Vladimir; Mirov, Sergey

2017-02-01

Many organic molecules have strong and narrow absorption features in the middle Infrared (mid-IR) spectral range. The ability to directly probe absorption features of molecules enables numerous mid-IR applications in non-invasive medical diagnosis, industrial processing and process control, environmental monitoring, etc. Thus, there is a strong demand for lasers operating in mid-IR spectral range. Transition metal (TM) doped II-VI semiconductors such as Fe/Cr:ZnSe/S are the material of choice for fabrication of mid-IR gain media due to favorable combination of properties: a four level energy structure, absence of excited state absorption , broad mid-IR vibronic absorption and emission bands. Despite the significant progress in post-growth thermal diffusion technology of TM:II-VI fabrication there are still some difficulties associated with diffusion of certain TM's in these materials. In this work we address the issue of poor diffusion of Fe in ZnSe/S polycrystals. It is well known that with the temperature increase the diffusion rate of impurity also increases. However, simple application of high temperatures during the diffusion process is problematic for ZnSe/S crystals due to their strong sublimation. The sublimation processes can be suppressed by application of high pressures. Hot isostatic pressing was utilized as the means for simultaneous application of high temperatures (1300°C) and high pressures (1000atm, 3000atm). It was determined that diffusion coefficient of Fe was improved 13 and 14 fold in ZnSe and ZnS, respectively, as compared to the standard diffusion at 950°C. The difference in diffusion coefficients can be due to strong increase in the grain size of polycrystals.

Investigating the reasons of variability in Si IV and C IV broad absorption line troughs of quasars

NASA Astrophysics Data System (ADS)

Stathopoulos, Dimitrios; Lyratzi, Evangelia; Danezis, Emmanuel; Antoniou, Antonios; Tzimeas, Dimitrios

2017-09-01

In this paper we analyze the C IV and Si IV broad absorption troughs of two BALQSOs (J101056.69+355833.3, J114548.38+393746.6) to the individual components they consist of. By analyzing a BAL trough to its components we have the advantage to study the variations of the individual absorbing systems in the line of sight and not just the variations of the whole absorption trough or the variations of selected portions of BAL troughs exhibiting changes. We find that the velocity shifts and FWHMs (Full Width at Half Maximum) of the individual components do not vary between an interval of six years. All variable components show changes in the optical depths at line centers which are manifested as variations in the EW (Equivalent Width) of the components. In both BALQSOs, over corresponding velocities, Si IV has higher incidence of variability than C IV. From our analysis, evidence is in favour of different covering fractions between C IV and Si IV. Finally, although most of our results favour the crossing cloud scenario as the cause of variability, there is also strong piece of evidence indicating changing ionization as the source of variability. Thus, a mixed situation where both physical mechanisms contribute to BAL variability is the most possible scenario.

"CHON" particles: The interstellar component of cometary dust

NASA Technical Reports Server (NTRS)

Lien, David J.

1998-01-01

Interstellar dust is characterized by strong absorption in the ultraviolet and the mid-IR. Current models of interstellar dust are based on three chemically distinct components: a form of carbon (usually graphite), a silicate, and a blend of polycyclic aromatic hydrocarbons or other carbonaceous material. Previous work using effective medium theories to understand the optical properties of cometary dust suggested that an amalgam of materials could reproduce the observed interstellar and cometary dust features. Recently, Lawler and Brownlee (1992) re-analyzed the PIA and PUMA-1 data sets from the Giotto flyby of P/Halley and discovered that the so-called "CHON" particles were actually composed of a blend of carbon-bearing and silicon-bearing materials. Based on effective medium theories, the absorption spectrum of such a material would display the spectral features of each of the components - strong UV absorption from the carbonaceous component and strong absorption in the IR from the silicate component. To test this idea, vapor-deposited samples were created using two different deposition techniques: sputtering with an argon RF magnetron and deposition from an argon plasma torch. Two different compositions were tested: a blend of graphite and silica in a 7:1 ratio and an amalgam of materials whose approximate composition matches the "CHON"-silicate abundances for the uncompressed PIA data set of Lawler and Brownlee: graphite, iron oxide, magnesium oxide, ammonium sulfate, calcium carbonate, and silica in mass ratios of 6:4.3:4:2.2:1:9. The samples were finely ground and pressed into 2" diameter disks using a 40 ton press. In all, four different experiments were performed: one with each of the compositions (C:SiO and "CHON") in both the RF magnetron and the plasma torch chambers. The RF magnetron created a uniform dark thin film on the substrate surface, and the plasma torch created a coating of small (<100 micron) diameter grey particles. The spectra of all four samples show a strong, broad absorption feature at around 220 nm as well as a strong but narrower absorption peak near 10 microns. The RF magnetron sputtered samples showed some sub-structure in the UV, and the peak of the absorption was shifted toward longer wavelengths. The UV absorption in the plasma torch deposited samples have no sub-structure, and the peak absorption is very near 220 nm. Strong absorption near 9 microns is seen in the spectra from both sample preparation techniques, and is consistent with the IR spectra of some terrestrial silicates. Other features, particularly at 6.2 and 8.6 microns, are seen in the interstellar medium. A strong feature near 2 microns is due to absorbed water in the sample. Based on the results of these experiments, there is evidence that a material with a composition similar to that detected in "CHON" particles in the coma of P/Halley have a spectral signature which reproduces the main absorption features of interstellar dust. This suggests that the "CHON" particles could be the interstellar component of cometary dust.

Nonheme-iron absorption in first-degree relatives is highly correlated: a stable-isotope study in mother-child pairs.

PubMed

Zimmermann, Michael B; Harrington, Mary; Villalpando, Salvador; Hurrell, Richard F

2010-03-01

Iron absorption in humans is highly variable even after iron status and dietary components that influence iron absorption are controlled for. Inherited factors may help explain this variance. Our objective was to compare nonheme-iron absorption from a noninhibitory, stable-isotope-labeled test meal in preschool-aged children and their mothers. We provided 72 test meals based on degermed maize flour and milk powder and fortified with [(57)Fe]ferrous fumarate or [(58)Fe]ferrous sulfate to healthy Mexican preschool children [n = 18; mean (+/-SD) age: 3.6 +/- 1.0 y] and their mothers [n = 18; mean (+/-SD) age: 28.0 +/- 5.2 y]. Iron absorption was calculated on the basis of incorporation of isotopes into erythrocytes after 14 d and was adjusted for differences in iron status. There was a wide variation in iron absorption from the test meals: in the mothers and children, the median fractional absorption of ferrous sulfate was 22.55% (range: 1.65-54.83%) and 5.51% (range: 2.23-17.20%), respectively (P < 0.0001). After adjustment for serum ferritin, the significant difference in absorption between mothers and their children disappeared. Despite this broad range of iron absorption, corrected fractional iron absorption from the ferrous fumarate-fortified (r(2) = 0.582) and the ferrous sulfate-fortified test meals (r(2) = 0.557) was strongly correlated in mothers and their children (P < 0.0001). There was a striking positive correlation between the mean corrected fractional iron absorption from both test meals in mothers and their children (r(2) = 0.782, P < 0.0001). In regression analyses that included age, sex, and hemoglobin, the only significant predictor of corrected fractional iron absorption in children was corrected fractional iron absorption in their mothers (standardized beta = 0.884, P < 0.001). Nonheme-iron absorption exhibits a strong familial tendency. After differences in meal matrix and serum ferritin are accounted for, these data suggest that inheritance and/or shared environmental factors explain most of the variance in dietary iron absorption.

Stellar wind variations in HD 45166: The continuing story. [Wolf-Rayet star

NASA Technical Reports Server (NTRS)

Willis, Allan J.; Stickland, David J.; Heap, Sara R.

1988-01-01

High resolution SWP IUE spectra of HD 45166 (qWR+B8V) obtained over a 36 hr continuous run, together with earlier observations, reveal 2 distinct modes of UV variability in this object. Gross, epoch-linked changes are seen in the strengths of the qWR emission lines, accompanied by large changes in its highly ionized photospheric absorption spectrum. Rapid (hours) variability in strong, multiple, high velocity, wind discrete absorption components (DAC), in the CIV lambda 1550 resonance lines, which superpose to give the appearance of a broad P Cygni absorption profile at many epochs is also observed. These multiple DAC's (often at least 3 are seen) propagate in velocity, from 0.6 to 1.0 v inf, on a timescale of 1 day, implying an acceleration of 180 cm/s comparable to that seen in O-type stars.

Application of semiclassical and geometrical optics theories to resonant modes of a coated sphere.

PubMed

Bambino, Túlio M; Breitschaft, Ana Maria S; Barbosa, Valmar C; Guimarães, Luiz G

2003-03-01

This work deals with some aspects of the resonant scattering of electromagnetic waves by a metallic sphere covered by a dielectric layer, in the weak-absorption approximation. We carry out a geometrical optics treatment of the scattering and develop semiclassical formulas to determine the positions and widths of the system resonances. In addition, we show that the mean lifetime of broad resonances is strongly dependent on the polarization of the incident light.

Ultraviolet studies of nova-like variables with the IUE

NASA Technical Reports Server (NTRS)

Guinan, E. F.

1983-01-01

KQ Mon is a new UX UMa-type nova-like variable. Optical spectra taken in 1978 reveal very shallow Balmer absorption lines and He I (wavelength 4471) absorption. There was no evidence of orbital variations but the appearance of the optical spectrum and the presence of low amplitude flickering suggested a strong similarity to CD-42 degrees 14462 (=V3885 Sgr) and other members of the UX UMa class. KQ Mon was observed at low dispersion with the IUE satellite. Six spectra taken with the short wavelength prime (SWP) camera are dominated by strong broad absorption lines due to N V, O I, Si III, Si IV, C IV, He II, N IV, and A1 III. There is little evidence of orbital phase modulation over the time baseline of the observations. Unlike UV observations of other UX UMa-type objects, KQ Mon exhibits no emission lines or P Cygni-type profiles and the velocity displacements appear to be smaller, suggesting the absence of a hot, high velocity wind characterizing other UX UMa stars. The relationship of KQ Mon to other UX UMa disk stars is discussed and a model is suggested to explain their observed properties and the lack of major outbursts.

Photo-physical properties and triplet-triplet absorption of platinum(II) acetylides in solid PMMA matrices

NASA Astrophysics Data System (ADS)

Glimsdal, Eirik; Westlund, Robert; Lindgren, Mikael

2009-05-01

Because of their strong nonlinear optical properties, Platinum(II) acetylides are investigated as potential chromophores for optical power limiting (OPL) applications. The strong excited state absorption and efficient intersystem crossing to the triplet states in these materials are desired properties for good OPL performance. We recently reported on OPL and photo-physical properties of Pt(II)-acetylide chromophores in solution, modified with thiophenyl or triazole groups. [R. Westlund et al. J. Mater. Chem. 18, 166 (2008); E. Glimsdal et al. Proc. SPIE 6740, 67400M (2007)] The chromophores were later incorporated into poly(methyl-methacrylate) (PMMA) glasses. A variety of doped organic solids were prepared, reaching concentrations of up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices proved that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photo-physical properties (absorption, emission and inter-system crossing) observed for the solute molecules in THF are maintained also in the solid state. In particular, the phosphorescence lifetime stays in the order of μs to ms, just as in the oxygen evacuated liquid samples. Also, the wavelength dependence and time-dynamics of the triplet absorption spectra of the dyes, dissolved in THF solution and dispersed in solid PMMA matrices, were investigated and compared. Ground state UV absorption spectra between 300 and 420 nm have corresponding broad band visible triplet-triplet absorption between 400 and 800 nm. The triplet state extinction coefficients were determined to be in the order of 104 M-1cm-1.

Relativistic Iron K Emission and Absorption in the Seyfert 1.9 Galaxy MCG-05-23-16

NASA Technical Reports Server (NTRS)

Braito, V.; Reeves, J. N.; Dewangan, G. C.; George, I.; Griffiths, R.; Markowitz, A.; Nandra, K.; Porquet, D.; Ptak, A.; Turner, T. J.;

Broad-spectrum enhanced absorption of graphene-molybdenum disulfide photovoltaic cells in metal-mirror microcavity.

PubMed

Jiang-Tao, Liu; Yun-Kai, Cao; Hong, Tong; Dai-Qiang, Wang; Zhen-Hua, Wu

2018-04-06

The optical absorption of graphene-molybdenum disulfide photovoltaic cells (GM-PVc) in wedge-shaped metal-mirror microcavities (w-MMCs) combined with a spectrum-splitting structure was studied. Results showed that the combination of spectrum-splitting structure and w-MMC can enable the light absorption of GM-PVcs to reach about 65% in the broad spectrum. The influence of processing errors on the absorption of GM-PVcs in w-MMCs was 3-14 times lower than that of GM-PVcs in wedge photonic crystal microcavities. The light absorption of GM-PVcs reached 60% in the broad spectrum, even with the processing errors. The proposed structure is easy to implement and may have potentially important applications in the development of ultra-thin and high-efficiency solar cells and optoelectronic devices.

Broad-spectrum enhanced absorption of graphene-molybdenum disulfide photovoltaic cells in metal-mirror microcavity

NASA Astrophysics Data System (ADS)

Jiang-Tao, Liu; Yun-Kai, Cao; Hong, Tong; Dai-Qiang, Wang; Zhen-Hua, Wu

2018-04-01

The optical absorption of graphene-molybdenum disulfide photovoltaic cells (GM-PVc) in wedge-shaped metal-mirror microcavities (w-MMCs) combined with a spectrum-splitting structure was studied. Results showed that the combination of spectrum-splitting structure and w-MMC can enable the light absorption of GM-PVcs to reach about 65% in the broad spectrum. The influence of processing errors on the absorption of GM-PVcs in w-MMCs was 3-14 times lower than that of GM-PVcs in wedge photonic crystal microcavities. The light absorption of GM-PVcs reached 60% in the broad spectrum, even with the processing errors. The proposed structure is easy to implement and may have potentially important applications in the development of ultra-thin and high-efficiency solar cells and optoelectronic devices.

[Dust absorption capacities of eight evergreen broad-leaved plants in Beijing, China.

PubMed

Fan, Shu Xin; Cai, Yu; Dong, Li

2017-02-01

Aiming at selecting the evergreen broad-leaved plants with excellent dust capturing capacity that can be applied in Beijing area for improving the urban vegetation dust removal, this study selected 8 evergreen (including semi-evergreen) broad-leaved plants used in urban green-space in Beijing area to measure the dust absorption per unit leaf area by the elution-mass method during winter and early spring in 2014. The dust deposition per leaf and per plant of each species was further calculated for tested species. Based on the dust capturing capacity measured in different units, cluster analysis on the comprehensive dust absorption capacities of different plants was carried out from the corresponding aspect. Results showed that the dust absorption ability differed significantly among the 8 evergreen broad-leaved (including semi-evergreen) species including Buxus sinica, Euonymus japonicus, Ligustrum quihoui, L. vicaryi, E. kiautschovicus, Indocalamus tessellatus, Phyllostachys violascens and Ph. aureosulcata. E. japonicus was best in dust absorption per unit leaf area and per plant, with 1.36 g·m -2 and 59.63 g·plant -1 . I. tessellates (with 1.62 mg·leaf -1 ) had the strongest dust absorption ability per leaf. With different measurement units selected, the ranking changed. The cluster analysis based on the multi index comprehensive dust absorption capacities could roughly divided the 8 evergreen broad-leaved species into 4 categories representing different dust absorption capacity levels. E. japonicus and Ph. sviolascens had the outstanding comprehensive dust capturing capacity, while B. sinica, L. vicaryi and Ph. aureosulcata showed the weak performance.

Synthesis and optical properties of Pr and Ti doped BiFeO{sub 3} ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Vikash, E-mail: vikash.singh@abes.ac.in; Applied Science and Humanities, ABES EC, Ghaziabad; Sharma, Subhash

2016-05-23

Bi{sub 1-x}Pr{sub x}Fe{sub 1-x}Ti{sub x}O{sub 3} ceramics with x = 0.00, 0.10 and 0.20 were synthesized by solid state reaction method. Rietveld fitting of diffraction data reveals structural transition from rhombohedral phase (R{sub 3C}) for x ≤ 0.10 to orthorhombic phase (P{sub nma}) for x = 0.20. FTIR spectra exhibit broad absorption bands, which may be due to the overlapping of Fe-O and Bi-O vibrations in these ceramics. UV-visible spectroscopy results show strong absorption of light in the spectral range of 400-600 nm, indicating optical band gap in the visible region for these samples.

Discovery of an Ultraviolet Counterpart to an Ultrafast X-Ray Outflow in the Quasar PG 1211+143

NASA Astrophysics Data System (ADS)

Kriss, Gerard A.; Lee, Julia C.; Danehkar, Ashkbiz; Nowak, Michael A.; Fang, Taotao; Hardcastle, Martin J.; Neilsen, Joseph; Young, Andrew

2018-02-01

We observed the quasar PG 1211+143 using the Cosmic Origins Spectrograph on the Hubble Space Telescope in 2015 April as part of a joint campaign with the Chandra X-ray Observatory and the Jansky Very Large Array. Our ultraviolet spectra cover the wavelength range 912–2100 Å. We find a broad absorption feature (∼ 1080 {km} {{{s}}}-1) at an observed wavelength of 1240 Å. Interpreting this as H I Lyα, in the rest frame of PG 1211+143 (z = 0.0809), this corresponds to an outflow velocity of ‑16,980 {km} {{{s}}}-1 (outflow redshift {z}{out}∼ -0.0551), matching the moderate ionization X-ray absorption system detected in our Chandra observation and reported previously by Pounds et al. With a minimum H I column density of {log} {N}{{H}{{I}}}> 14.5, and no absorption in other UV resonance lines, this Lyα absorber is consistent with arising in the same ultrafast outflow as the X-ray absorbing gas. The Lyα feature is weak or absent in archival ultraviolet spectra of PG 1211+143, strongly suggesting that this absorption is transient, and intrinsic to PG 1211+143. Such a simultaneous detection in two independent wavebands for the first time gives strong confirmation of the reality of an ultrafast outflow in an active galactic nucleus.

Optical Properties of ZnCdS:I Orange and ZnSTe:I White Thin Film Phosphor for High Ra White LED

NASA Astrophysics Data System (ADS)

Fujii, Satoshi; Tasaki, Norio; Shinomura, Naohiko; Kurai, Satoshi; Yamada, Yoichi; Taguchi, Tsunemasa

In order to develop visible thin film phosphors, we have for the first time prepared ZnCdS and ZnSTe doped with Iodine (I) using low-pressure MOCVD method. ZnCdS:I, of which Cd composition was calibrated to match the lattice constant to that of substrate and the band gap to absorption peak, showed a orange broad emission consist of yellow near band edge emission and red SA emission. Isoelectronic Te in ZnS indicates strong blue-green emissions, whilst I donor impurity in ZnS shows strong red SA emissions. A typical ZnSTe:I thin film shows two broad emission bands locating at around 500 and 680 nm, respectively, indicating Ra˜90. It was shown that high Ra thin film phosphor can be realized by single material (ZnSTe:I), and that MOCVD method is capable for controlling the thickness and doping profile to obtain uniform white emission pattern.

Eclipsing damped Lyα systems in the Sloan Digital Sky Survey Data Release 12★

NASA Astrophysics Data System (ADS)

Fathivavsari, H.; Petitjean, P.; Jamialahmadi, N.; Khosroshahi, H. G.; Rahmani, H.; Finley, H.; Noterdaeme, P.; Pâris, I.; Srianand, R.

2018-04-01

We present the results of our automatic search for proximate damped Lyα absorption (PDLA) systems in the quasar spectra from the Sloan Digital Sky Survey Data Release 12. We constrain our search to those PDLAs lying within 1500 km s-1 from the quasar to make sure that the broad DLA absorption trough masks most of the strong Lyα emission from the broad line region (BLR) of the quasar. When the Lyα emission from the BLR is blocked by these so-called eclipsing DLAs, narrow Lyα emission from the host galaxy could be revealed as a narrow emission line (NEL) in the DLA trough. We define a statistical sample of 399 eclipsing DLAs with log N(H I) ≥ 21.10. We divide our statistical sample into three subsamples based on the strength of the NEL detected in the DLA trough. By studying the stacked spectra of these subsamples, we found that absorption from high ionization species are stronger in DLAs with stronger NEL in their absorption core. Moreover, absorption from the excited states of species like Si II are also stronger in DLAs with stronger NEL. We also found no correlation between the luminosity of the Lyα NEL and the quasar luminosity. These observations are consistent with a scenario in which the DLAs with stronger NEL are denser and physically closer to the quasar. We propose that these eclipsing DLAs could be the product of the interaction between infalling and outflowing gas. High resolution spectroscopic observation would be needed to shed some light on the nature of these eclipsing DLAs.

What Drives the Outflows in Broad Absorption Line QSOs?

NASA Technical Reports Server (NTRS)

Begelman, Mitchell C.

1997-01-01

We have made progress in the areas related to the propulsion and confinement of gas responsible for broad absorption troughts in QSOs: Radiative Acceleration in BALQSOs; The "Ghost" of Lyman (alpha); and Magnetic Confinement of Absorbing Gas.

Surprises from a Deep ASCA Spectrum of the Broad Absorption Line Quasar PHL 5200

NASA Technical Reports Server (NTRS)

Mathur, Smita; Matt, G.; Green, P. J.; Elvis, M.; Singh, K. P.

2002-01-01

We present a deep (approx. 85 ks) ASCA observation of the prototype broad absorption line quasar (BALQSO) PHL 5200. This is the best X-ray spectrum of a BALQSO yet. We find the following: (1) The source is not intrinsically X-ray weak. (2) The line-of-sight absorption is very strong, with N(sub H) = 5 x 10(exp 23)/sq cm. (3) The absorber does not cover the source completely; the covering fraction is approx. 90%. This is consistent with the large optical polarization observed in this source, implying multiple lines of sight. The most surprising result of this observation is that (4) the spectrum of this BALQSO is not exactly similar to other radio-quiet quasars. The hard X-ray spectrum of PHL 5200 is steep, with the power-law spectral index alpha approx. 1.5. This is similar to the steepest hard X-ray slopes observed so far. At low redshifts, such steep slopes are observed in narrow-line Seyfert 1 (NLS1) galaxies, believed to be accreting at a high Eddington rate. This observation strengthens the analogy between BALQSOs and NLS1 galaxies and supports the hypothesis that BALQSOs represent an early evolutionary state of quasars. It is well accepted that the orientation to the line of sight determines the appearance of a quasar: age seems to play a significant role as well.

Theory and Simulation of Exoplanetary Atmospheric Haze: Giant Spectral Line Broadening

NASA Astrophysics Data System (ADS)

Sadeghpour, Hossein; Felfeli, Zineb; Kharchenko, Vasili; Babb, James; Vrinceanu, Daniel

2018-01-01

Prominent spectral features in observed transmission spectra of exoplanets are obscured. Atmospheric haze is the leading candidate for the flattening of spectral transmission of expolanetray occultation, but also for solar system planets, Earth and cometary atmospheres. Such spectra which carry information about how the planetary atmospheres become opaque to stellar light in transit, show broad absorption where strong absorption lines from sodium or potassium and water are predicted to exist. In this work, we develop a detailed atomistic theoretical model, taking into account interaction between an atomic or molecular radiator with dust and haze particulates. Our model considers a realistic structure of haze particulates from small seed particles up to sub-micron irregularly shaped aggregates. This theory of interaction between haze and radiator particles allows to consider nearly all realistic structure, size and chemical composition of haze particulates. The computed shift and broadening of emission spectra will include both quasi-static (mean field) and collisional (pressure) shift and broadening. Our spectral calculations will be verified with available laboratory experimental data on spectra of alkali atoms in liquid droplet, solid ice, dust and dense gaseous environments. The simplicity, elegance and generality of the proposed model makes it amenable to a broad community of users in astrophysics and chemistry. The verified models can be used for analysis of emission and absorption spectra of alkali atoms from exoplanets, solar system planets, satellites and comets.

High Velocity Absorption during Eta Car B's Periastron Passage

NASA Technical Reports Server (NTRS)

Nielsen, Krister E.; Groh, J. H.; Hillier, J.; Gull, Theodore R.; Owocki, S. P.; Okazaki, A. T.; Damineli, A.; Teodoro, M.; Weigelt, G.; Hartman, H.

2010-01-01

Eta Car is one of the most luminous massive stars in the Galaxy, with repeated eruptions with a 5.5 year periodicity. These events are caused by the periastron passage of a massive companion in an eccentric orbit. We report the VLT/CRIRES detection of a strong high-velocity, (<1900 km/s) , broad absorption wing in He I at 10833 A during the 2009.0 periastron passage. Previous observations during the 2003.5 event have shown evidence of such high-velocity absorption in the He I 10833 transition, allowing us to conclude that the high-velocity gas is crossing the line-of-sight toward Eta Car over a time period of approximately 2 months. Our analysis of HST/STlS archival data with observations of high velocity absorption in the ultraviolet Si IV and C IV resonance lines, confirm the presence of a high-velocity material during the spectroscopic low state. The observations provide direct detection of high-velocity material flowing from the wind-wind collision zone around the binary system, and we discuss the implications of the presence of high-velocity gas in Eta Car during periastron

Photophysical and quantum chemical study on a J-aggregate forming perylene bisimide monomer.

PubMed

Ambrosek, David; Marciniak, Henning; Lochbrunner, Stefan; Tatchen, Jörg; Li, Xue-Qing; Würthner, Frank; Kühn, Oliver

2011-10-21

Perylene bisimides (PBIs) are excellent dyes and versatile building blocks for supramolecular structures. Only recently have PBIs been shown to depict absorption characteristics of J-aggregates. We apply electronic structure calculations and femtosecond pump-probe spectroscopy to the monomeric, bay-substituted building-block of a PBI aggregate in dichloromethane to investigate its electronically excited states in order to provide the ingredients for the description of excitons in the aggregates and their annihilation processes. The PBI S(1)←S(0) absorption spectrum and the S(1)→S(0) emission spectrum have been assigned based on time-dependent Density Functional Theory calculations for the geometry-optimized electronic ground state and excited state structures in the gas phase. The monomeric absorption spectrum contains a strong transition at 580 nm and a broad shoulder between 575-500 nm, both features are attributed to a vibrational progression with an effective vibrational mode of 1415 cm(-1) whose major contributing vibrational normal modes are breathing modes of the perylene body. The effective vibrational mode of the emission spectrum is characterized by a frequency of 1369 cm(-1), whose major contributing vibrational normal modes are characterized by perylene and phenol (bay-substituent) CH bendings. The S(n)←S(1) excited state absorption spectrum is assigned based on Multi-Reference Configuration Interaction methodology. Here, we identify three transitions which give rise to two broad experimental features, one being located between 500 and 600 nm and the other one ranging from 650 to 750 nm. This journal is © the Owner Societies 2011

Spectroscopic properties of a perfluorinated ketone for PLIF applications

NASA Astrophysics Data System (ADS)

Roy, Arnab; Gustavsson, Jonas P. R.; Segal, Corin

2011-11-01

This work identifies the fluorescence characteristics of a perfluorinated ketone, 2-trifluoromethyl-1,1,1,2,4,4,5,5,5-nonafluoro-3-pentanone, further referred to as fluoroketone. This compound is suitable for use with the third harmonic of an Nd:YAG laser for quantitative concentration measurements, as it exhibits strong emission even for relatively low excitation and has a near-linear response of fluorescence intensity with concentration. This makes it suitable for a broad range of fluorescence applications. The absorption cross-section of 3.81 × 10-19 cm2 was found to be constant for a temperature range of 293-441 K and a pressure range of 1-18 atm. A calibration line has been generated that relates the concentration of gaseous and liquid fluoroketone with its absorption coefficient.

Iron Low-ionization Broad Absorption Line quasars - the missing link in galaxy evolution?

NASA Astrophysics Data System (ADS)

Lawther, Daniel Peter; Vestergaard, Marianne; Fan, Xiaohui

2015-08-01

A peculiar and rare type of quasar with strong low-ionization iron absorption lines - known as FeLoBAL quasars - may be the missing link between star forming (or starbursting) galaxies and quasars. They are hypothesized to be quasars breaking out of their dense birth blanket of gas and dust. In that case they are expected to have high rates of star formation in their galaxies. With the aim of addressing and settling this issue we have studied deep Hubble Space Telescope restframe UV and optical imaging of a subset of such quasars in order to characterize the host galaxy properties of these quasars. We present the results of this study along with simulations to characterize the uncertainties and robustness of our results.

Inherited Fe and Ti electron transition spectroscopic features in altered ultramafic-carbonatite intrusives

NASA Astrophysics Data System (ADS)

Shavers, E. J.; Ghulam, A.; Encarnacion, J. P.

2016-12-01

Spectroscopic reflectance in the visible to short-wave infrared region is an important tool for remote geologic mapping and is applied at scales from satellite to field measurements. Remote geologic mapping is challenging in regions subject to significant surficial weathering. Here we identify absorption features found in altered volcanic pipes and dikes in the Avon Volcanic District, Missouri, that are inherited from the original ultramafic and carbonatite lithology. Alteration ranges from small degree hydrothermal alteration to extensive laterization. The absorption features are three broad minima centered near 690, 890, and 1100 nm. Features in this region are recognized to be caused by ferric and ferrous Fe minerals including olivine, carbonates, chlorite, and goethite all of which are found among the Avon pipes and dikes that are in various stages of alteration. Iron-related intervalence charge transfer and crystal field perturbations of ions are the principal causes of the spectroscopic features in the visible to near-infrared region yet spectra are also distorted by factors like texture and the presence of opaque minerals known to reduce overall reflectance. In the Avon samples, Fe oxide content can reach >15 wt% leading to prominent absorption features even in the less altered ultramafics with reflectance curve maxima as low as 5%. The exaggerated minima allow the altered intrusive rocks to stand out among other weathered lithologies that will often have clay features in the region yet have lower iron concentration. The absorption feature centered near 690 nm is particularly noteworthy. Broad mineral-related absorption features centered at this wavelength are rare but have been linked to Ti3+ in octahedral coordination. The reduced form of Ti is not common in surface lithologies. Titanium-rich andradite has Ti3+ in the octahedral position, is resistant to weathering, is found among the Avon lithologies including ultramafic, carbonatite, and carbonated breccia, and is identified here as the cause of the 690 nm absorption feature. The Ti3+ absorption feature centered near 690 nm and strong Fe absorption features at 890 and 1100 nm may be useful indicators of rare intrusive lithologies in remote geologic mapping.

DISENTANGLING THE CIRCUMNUCLEAR ENVIRONS OF CENTAURUS A. II. ON THE NATURE OF THE BROAD ABSORPTION LINE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Espada, D.; Matsushita, S.; Sakamoto, K.

2010-09-01

We report on atomic gas (H I) and molecular gas (as traced by CO(2-1)) redshifted absorption features toward the nuclear regions of the closest powerful radio galaxy, Centaurus A (NGC 5128). Our H I observations using the Very Long Baseline Array allow us to discern with unprecedented sub-parsec resolution H I absorption profiles toward different positions along the 21 cm continuum jet in the inner 0.''3 (or 5.4 pc). In addition, our CO(2-1) data obtained with the Submillimeter Array probe the bulk of the absorbing molecular gas with little contamination by emission, which was not possible with previous CO single-dishmore » observations. We shed light on the physical properties of the gas in the line of sight with these data, emphasizing the still open debate about the nature of the gas that produces the broad absorption line ({approx}55 km s{sup -1}). First, the broad H I line is more prominent toward the central and brightest 21 cm continuum component than toward a region along the jet at a distance {approx}20 mas (or 0.4 pc) further from the nucleus. This indicates that the broad absorption line arises from gas located close to the nucleus, rather than from diffuse and more distant gas. Second, the different velocity components detected in the CO(2-1) absorption spectrum match well with other molecular lines, such as those of HCO{sup +}(1-0), except the broad absorption line that is detected in HCO{sup +}(1-0) (and most likely related to that of the H I). Dissociation of molecular hydrogen due to the active galactic nucleus seems to be efficient at distances r {approx}< 10 pc, which might contribute to the depth of the broad H I and molecular lines.« less

TESTING RELATIVISTIC REFLECTION AND RESOLVING OUTFLOWS IN PG 1211+143 WITH XMM-NEWTON AND NuSTAR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lobban, A. P.; Pounds, K.; Vaughan, S.

We analyze the broad-band X-ray spectrum (0.3–50 keV) of the luminous Seyfert 1/quasar PG 1211+143—the archetypal source for high-velocity X-ray outflows—using near-simultaneous XMM-Newton and NuSTAR observations. We compare pure relativistic reflection models with a model including the strong imprint of photoionized emission and absorption from a high-velocity wind, finding a spectral fit that extrapolates well over the higher photon energies covered by NuSTAR . Inclusion of the high signal-to-noise ratio XMM-Newton spectrum provides much tighter constraints on the model parameters, with a much harder photon index/lower reflection fraction compared to that from the NuSTAR data alone. We show that puremore » relativistic reflection models are not able to account for the spectral complexity of PG 1211+143 and that wind absorption models are strongly required to match the data in both the soft X-ray and Fe K spectral regions. In confirming the significance of previously reported ionized absorption features, the new analysis provides a further demonstration of the power of combining the high throughput and resolution of long-look XMM-Newton observations with the unprecedented spectral coverage of NuSTAR .« less

Ultraviolet Broad Absorption Features and the Spectral Energy Distribution of the QSO PG 1351+64. 3.1

NASA Technical Reports Server (NTRS)

Zheng, W.; Kriss, G. A.; Wang, J. X.; Brotherton, M.; Oegerle, W. R.; Blair, W. P.; Davidsen, A. F.; Green, R. F.; Hutchings, J. B.; Kaiser, M. E.;

Ultraviolet Broad Absorption Features and the Spectral Energy Distribution of the QSO PG 1351+641. 2.5

NASA Technical Reports Server (NTRS)

Zheng, W.; Kriss, G. A.; Wang, J. X.; Brotherton, M.; Oegerle, W. R.; Blair, W. P.; Davidsen, A. F.; Green, R. F.; Hutchings, J. B.; Kaiser, M. E.;

Deep and tapered silicon photonic crystals for achieving anti-reflection and enhanced absorption.

PubMed

Hung, Yung-Jr; Lee, San-Liang; Coldren, Larry A

2010-03-29

Tapered silicon photonic crystals (PhCs) with smooth sidewalls are realized using a novel single-step deep reactive ion etching. The PhCs can significantly reduce the surface reflection over the wavelength range between the ultra-violet and near-infrared regions. From the measurements using a spectrophotometer and an angle-variable spectroscopic ellipsometer, the sub-wavelength periodic structure can provide a broad and angular-independent antireflective window in the visible region for the TE-polarized light. The PhCs with tapered rods can further reduce the reflection due to a gradually changed effective index. On the other hand, strong optical resonances for TM-mode can be found in this structure, which is mainly due to the existence of full photonic bandgaps inside the material. Such resonance can enhance the optical absorption inside the silicon PhCs due to its increased optical paths. With the help of both antireflective and absorption-enhanced characteristics in this structure, the PhCs can be used for various applications.

Preparation of gold nanoparticle aggregates and their photothermal heating property.

PubMed

Kim, Jun-Hyun; Lavin, Brian W

2011-01-01

This report describes simple synthetic strategies to prepare partially aggregated gold nanoparticles (GNPs) and their ability to produce photothermally-induced heating of an aqueous medium upon exposure to broadband light. The formation of various GNPs and their aggregates were accomplished in the absence of surfactants at room temperature. The morphologies, structures, and absorption properties of these GNPs were carefully characterized. Given that the resulting GNPs possessing strong and wide absorption bands fall in the most intense solar radiation spectrum, the photothermally-induced heating of water was examined in the presence of the GNPs via irradiation with a solar simulator (i.e., 100 mW/cm2; 1-sun condition). Our GNPs exhibited a slightly greater increase in the water temperature (3-4 degrees C) than that of conventional citrate-stabilized GNPs. This superior photothermal heating property of our GNPs directly indicated that the intense and broad absorption band effectively improved the conversion of highly absorbed photon energy into heat.

Near-infrared spectra of the Martian surface: Reading between the lines

NASA Technical Reports Server (NTRS)

Crisp, D.; Bell, J. F., III

1993-01-01

Moderate-resolution near-infrared (NIR) spectra of Mars have been widely used in studies of the Martian surface because many candidate surface materials have distinctive absorption features at these wavelengths. Recent advances in NIR detector technology and instrumentation have also encouraged studies in this spectral region. The use of moderate spectral resolution has often been justified for NIR surface observations because the spectral features produced by most surface materials are relatively broad, and easily discriminated at this resolution. In spite of this, NIR spectra of Mars are usually very difficult to interpret quantitatively. One problem is that NIR surface absorption features are often only a few percent deep, requiring observations with great signal-to-noise ratios. A more significant problem is that gases in the Martian atmosphere contribute numerous absorption features at these wavelengths. Ground-based observers must also contend with variable absorption by several gases in the Earth's atmosphere (H2O, CO2, O3, N2O, CH4, O2). The strong CO2 bands near 1.4, 1.6, 2.0, 2.7, 4.3, and 4.8 micrometers largely preclude the analysis of surface spectral features at these wavelengths. Martian atmospheric water vapor also contributes significant absorption near 1.33, 1.88, and 2.7 micrometers, but water vapor in the Earth's atmosphere poses a much larger problem to ground-based studies of these spectral regions. The third most important NIR absorber in the Martian atmosphere is CO. This gas absorbs most strongly in the relatively-transparent spectral windows near 4.6 and 2.3 micrometers. It also produces 1-10 percent absorption in the solar spectrum at these NIR wavelengths. This solar CO absorption cannot be adequately removed by dividing the Martian spectrum by that of a star, as is commonly done to calibrate ground-based spectroscopic observations, because most stars do not have identical amounts of CO absorption in their spectra. Here, we describe tow effective methods for eliminating contamination of Martian surface spectra by absorption in the solar, terrestrial, and Martian atmospheres. Both methods involve the use of very-high-resolution spectra that completely resolve the narrow atmospheric absorption lines.

SN2012ab: a peculiar Type IIn supernova with aspherical circumstellar material

NASA Astrophysics Data System (ADS)

Bilinski, Christopher; Smith, Nathan; Williams, G. Grant; Smith, Paul; Zheng, WeiKang; Graham, Melissa L.; Mauerhan, Jon C.; Andrews, Jennifer E.; Filippenko, Alexei V.; Akerlof, Carl; Chatzopoulos, E.; Hoffman, Jennifer L.; Huk, Leah; Leonard, Douglas C.; Marion, G. H.; Milne, Peter; Quimby, Robert M.; Silverman, Jeffrey M.; Vinkó, Jozsef; Wheeler, J. Craig; Yuan, Fang

2018-03-01

We present photometry, spectra, and spectropolarimetry of supernova (SN) 2012ab, mostly obtained over the course of ˜300 d after discovery. SN 2012ab was a Type IIn (SN IIn) event discovered near the nucleus of spiral galaxy 2MASXJ12224762+0536247. While its light curve resembles that of SN 1998S, its spectral evolution does not. We see indications of CSM interaction in the strong intermediate-width emission features, the high luminosity (peak at absolute magnitude M = -19.5), and the lack of broad absorption features in the spectrum. The Hα emission undergoes a peculiar transition. At early times it shows a broad blue emission wing out to -14 000 km s-1 and a truncated red wing. Then at late times (>100 d) it shows a truncated blue wing and a very broad red emission wing out to roughly +20 000 km s-1. This late-time broad red wing probably arises in the reverse shock. Spectra also show an asymmetric intermediate-width Hα component with stronger emission on the red side at late times. The evolution of the asymmetric profiles requires a density structure in the distant CSM that is highly aspherical. Our spectropolarimetric data also suggest asphericity with a strong continuum polarization of ˜1-3 per cent and depolarization in the Hα line, indicating asphericity in the CSM at a level comparable to that in other SNe IIn. We estimate a mass-loss rate of \\dot{M} = 0.050 M_{⊙} yr^{-1} for vpre = 100 km s-1 extending back at least 75 yr prior to the SN. The strong departure from axisymmetry in the CSM of SN 2012ab may suggest that the progenitor was an eccentric binary system undergoing eruptive mass loss.

Interaction Between the Broad-Lined Type Ic Supernova 2012ap and Carriers of Diffuse Interstellar Bands

NASA Technical Reports Server (NTRS)

Milisavljevic, Dan; Margutti, Raffaella; Crabtree, Kyle N.; Foster, Jonathan B.; Soderberg, Alicia M.; Fesen, Robert A.; Parrent, Jerod T.; Sanders, Nathan E.; Drout, Maria R.; Kamble, Atish;

Experimental Near Infrared Spectroscopy of Polycyclic Aromatic Hydrocarbons Between 0.7 to 2.5 microns

NASA Technical Reports Server (NTRS)

Mattioda, A. L.; Hudgins, D. M.; Allamandola, L. J.

2005-01-01

The near infrared (NIR) spectra and absolute band strengths of 27 polycyclic aromatic hydrocarbon (PAH) cations and anions ranging in size from C14H10 to C50H22, are reported. The spectra from 0.7 to 2.5 microns (14,000 to 4000/cm) are presented for the fifteen PAHs ranging in size from C40H18 to C50H22 whereas the spectra of the remaining twelve span the narrower range from 0.7 to 1.1 microns (14,000 to 9000/cm). The spectra of all the ionized PAHs we have studied to date have strong, broad absorption bands in the NIR arising from electronic transitions. This work shows that ionized PAHs have significant absorption bands at longer wavelengths than predicted by the current astronomical models which consider PAHs in their treatment of the radiation balance of the interstellar medium. Two implications are 1)-ionized interstellar PAHs should add weak, broad band structure to the NIR portion of the interstellar extinction curve and 2)- UV poor radiation fields can pump the PAH emission bands provided ionized PAHs are present.

Broad Absorption Line Quasar catalogues with Supervised Neural Networks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Scaringi, Simone; Knigge, Christian; Cottis, Christopher E.

2008-12-05

We have applied a Learning Vector Quantization (LVQ) algorithm to SDSS DR5 quasar spectra in order to create a large catalogue of broad absorption line quasars (BALQSOs). We first discuss the problems with BALQSO catalogues constructed using the conventional balnicity and/or absorption indices (BI and AI), and then describe the supervised LVQ network we have trained to recognise BALQSOs. The resulting BALQSO catalogue should be substantially more robust and complete than BI-or AI-based ones.

Extreme Variability in a Broad Absorption Line Quasar

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stern, Daniel; Jun, Hyunsung D.; Graham, Matthew J.

CRTS J084133.15+200525.8 is an optically bright quasar at z = 2.345 that has shown extreme spectral variability over the past decade. Photometrically, the source had a visual magnitude of V ∼ 17.3 between 2002 and 2008. Then, over the following five years, the source slowly brightened by approximately one magnitude, to V ∼ 16.2. Only ∼1 in 10,000 quasars show such extreme variability, as quantified by the extreme parameters derived for this quasar assuming a damped random walk model. A combination of archival and newly acquired spectra reveal the source to be an iron low-ionization broad absorption line quasar withmore » extreme changes in its absorption spectrum. Some absorption features completely disappear over the 9 years of optical spectra, while other features remain essentially unchanged. We report the first definitive redshift for this source, based on the detection of broad H α in a Keck/MOSFIRE spectrum. Absorption systems separated by several 1000 km s{sup −1} in velocity show coordinated weakening in the depths of their troughs as the continuum flux increases. We interpret the broad absorption line variability to be due to changes in photoionization, rather than due to motion of material along our line of sight. This source highlights one sort of rare transition object that astronomy will now be finding through dedicated time-domain surveys.« less

Optical and UV Spectra of the Remnant of SN 1885 (S And) in M31

NASA Astrophysics Data System (ADS)

Fesen, Robert A.; Weil, Kathryn E.; Hamilton, Andrew J. S.; Höflich, Peter A.

2017-10-01

We present multi-slit, 1D and 2D optical and UV spectra of the remnant of supernova 1885 (SN 1885; S And) taken using the Hubble Space Telescope’s Imaging Spectrograph (HST/STIS). These spectra of this probable subluminous Type Ia remnant, seen in silhouette against the central bulge of the Andromeda galaxy (M31), show strong and broad absorptions from neutral and singly ionized species of calcium, magnesium, and iron but with strikingly different distributions. Calcium H and K absorption indicates spherically distributed Ca-rich ejecta, densest in a lumpy shell expanding at 2000-6000 km s-1. Equally broad but weaker Ca I 4227 Å absorption is seen to extend out to velocities of ˜13,000 km s-1. Magnesium-rich ejecta in the remnant are detected for the first time through Mg I 2852 Å and Mg II 2796, 2803 Å absorptions concentrated in a shell with expansion velocities from ≃ 7000 {km} {{{s}}}-1 to at least 10,000 km s-1. Fe I 3720 Å absorption is detected as two discrete blueshifted and redshifted absorptions suggestive of an Fe I shell with expansion velocities of ±2000-8000 km s-1. Weak Fe II resonance absorptions in the wavelength region 2300-2700 Å are consistent with prior HST UV images showing Fe II-rich ejecta confined to a small number of optically thick plumes. The presence of such iron plumes extending out from the remnant’s core plus layered shells of calcium and magnesium point to a delayed-detonation explosion. The spectra also suggest a roughly spherical explosion, contrary to that expected by a merger or collision of two white dwarfs. We conclude that SN 1885 likely was an off-center, delayed-detonation explosion leading to a subluminous SN Ia similar to SN 1986G. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract No. NAS5-26555.

Tailoring double Fano profiles with plasmon-assisted quantum interference in hybrid exciton-plasmon system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Dongxing; Wu, Jiarui; Gu, Ying, E-mail: ygu@pku.edu.cn

2014-09-15

We propose tailoring of the double Fano profiles via plasmon-assisted quantum interference in a hybrid exciton-plasmon system. Tailoring is performed by the interference between two exciton channels interacting with a common localized surface plasmon. Using an applied field of low intensity, the absorption spectrum of the hybrid system reveals a double Fano lineshape with four peaks. For relatively large field intensity, a broad flat window in the absorption spectrum appears which results from the destructive interference between excitons. Because of strong constructive interference, this window vanishes as intensity is further increased. We have designed a nanometer bandpass optical filter formore » visible light based on tailoring of the optical spectrum. This study provides a platform for quantum interference that may have potential applications in ultracompact tunable quantum devices.« less

Study of the Variability of the Reflection Component in Seyfert 1 Galaxies: Connecting the Fe K Variability with the Compton Hump

NASA Astrophysics Data System (ADS)

Ponti, G.; Miniutti, G.; Malaguti, G.; Gallo, L.; Goldwurm, A.

2009-05-01

We present preliminary results of an ongoing project devoted to the study of the continuum and Fe K band variability in a sample of bright AGNs. These kind of studies may break the spectral degeneracy between the different absorption/emission models, allowing ``safe'' measurements of the disc and black hole properties from the broad line shapes. In fact, the Fe K band, alone, allows a first separation between the different components. Here we show the case of NGC 3783 which shows both a constant and a variable reflection component as well as strong ionized absorption. We show that a fundamental contribution will be given by Simbol-X that will allow to simultaneously measure not only the Fe K variability, but also the connected reflection hump variations.

UV laser photoactivation of hexachloroplatinate bound to individual nucleobases in vacuo as molecular level probes of a model photopharmaceutical.

PubMed

Matthews, Edward; Sen, Ananya; Yoshikawa, Naruo; Bergström, Ed; Dessent, Caroline E H

2016-06-01

Isolated molecular clusters of adenine, cytosine, thymine and uracil bound to hexachloroplatinate, PtCl6(2-), have been studied using laser electronic photodissociation spectroscopy to investigate photoactivation of a platinum complex in the vicinity of a nucleobase. These metal complex-nucleobase clusters represent model systems for identifying the fundamental photochemical processes occurring in photodynamic platinum drug therapies that target DNA. This is the first study to explore the specific role of a strongly photoactive platinum compound in the aggregate complex. Each of the clusters studied displays a broadly similar absorption spectra, with a strong λmax ∼ 4.6 eV absorption band and a subsequent increase in the absorption intensity towards higher spectral-energy. The absorption bands are traced to ligand-to-metal-charge-transfer excitations on the PtCl6(2-) moiety within the cluster, and result in Cl(-)·nucleobase and PtCl5(-) as primary photofragments. These results demonstrate how selective photoexcitation can drive distinctive photodecay channels for a model photo-pharmaceutical. In addition, cluster absorption due to excitation of nucleobase-centred chromophores is observed in the region around 5 eV. For the uracil cluster, photofragments consistent with ultrafast decay of the excited state and vibrational predissociation on the ground-state surface are observed. However, this decay channel becomes successively weaker on going from thymine to cytosine to adenine, due to differential coupling of the excited states to the electron detachment continuum. These effects demonstrate the distinctive photophysical characteristics of the different nucleobases, and are discussed in the context of the recently recorded photoelectron spectra of theses clusters.

Strong photocurrent enhancements in plasmonic organic photovoltaics by biomimetic nanoarchitectures with efficient light harvesting.

PubMed

Leem, Jung Woo; Kim, Sehwan; Park, Chihyun; Kim, Eunkyoung; Yu, Jae Su

2015-04-01

We propose the biomimetic moth-eye nanoarchitectures as a novel plasmonic light-harvesting structure for further enhancing the solar-generated photocurrents in organic photovoltaics (OPVs). The full moth-eye nanoarchitectures are composed of two-dimensional hexagonal periodic grating arrays on surfaces of both the front zinc oxide (ZnO) and rear active layers, which are prepared by a simple and cost-effective soft imprint nanopatterning technique. For the 380 nm period ZnO and 650 nm period active gratings (i.e., ZnO(P380)/Active(P650)), the poly(3-hexylthiophene-2,5-diyl):indene-C60 bis-adduct (P3HT:ICBA)-based plasmonic OPVs exhibit an improvement of the absorption spectrum compared to the pristine OPVs over a broad wavelength range of 350-750 nm, showing absorption enhancement peaks at wavelengths of ∼370, 450, and 670 nm, respectively. This leads to a considerable increase of short-circuit current density (Jsc) from 10.9 to 13.32 mA/cm(2), showing a large Jsc enhancement percentage of ∼22.2%. As a result, the strongly improved power conversion efficiency (PCE) of 6.28% is obtained compared to that (i.e., PCE = 5.12%) of the pristine OPVs. For the angle-dependent light-absorption characteristics, the plasmonic OPVs with ZnO(P380)/Active(P650) have a better absorption performance than that of the pristine OPVs at incident angles of 20-70°. For optical absorption characteristics and near-field intensity distributions of plasmonic OPVs, theoretical analyses are also performed by a rigorous coupled-wave analysis method, which gives a similar tendency with the experimentally measured data.

Visible Spectroscopic Observation Of Asteroid 162173 (1999ju3) With The Gemini-s Telescope

NASA Astrophysics Data System (ADS)

Sugita, Seiji; Kuroda, D.; Kameda, S.; Hasegawa, S.; Kamata, S.; Abe, M.; Ishiguro, M.; Takato, N.; Yoshikawa, M.

2012-10-01

Asteroid 162173 (1999JU3; hereafter JU3) is the target of the Hayabusa-2 mission. Its visible reflectance spectra have been observed a few times [1,2], and obtained spectra exhibit a wide variety of spectral patterns ranging from a spectra with absorption in the UV region (May 1999) to a flat spectrum with a faint broad absorption centered around 0.6 microns (September 2007) and that with UV absorption and strong broad absorption centered around 0.7 micron (July 2007). The apparent large spectral variation may be due to variegation on the asteroid surface. Such variegation would make a large influence on remote sensing strategy for Hayabusa-2 before its sampling operations. In order to better constraint the spectral properties of JU3, we conducted visible spectroscopic observations at the GEMINI-South observatory 8.1-m telescope with the GMOS instrument. We could obtain three different sets of data in June and July 2012. Although the JU3 rotation phases of two of the observation are close to each other, the other is about 120 degrees away from the two. Our preliminary analyses indicate that these three spectra are slightly reddish but generally flat across the observed wavelength range (0.47 - 0.89 microns). The observed flat spectra are most similar to the spectrum obtained in September 2007, which probably has the highest signal-to-noise ratio among the previous three spectra. This result suggests that material with a flat spectrum probably covers a dominant proportion of the JU3 surface and that the other two types of previously obtained spectra may not cover a very large fraction of the JU3 surface. [1] Binzel, R. P. et al. (2001) Icarus, 151, 139-149; [2] Vilas, F. (2008) AJ, 135, 1101-1105.

Measuring the Outflow Properties of FeLoBAL Quasars

NASA Astrophysics Data System (ADS)

Dabbieri, Collin; Choi, Hyunseop; MacInnis, Francis; Leighly, Karen; Terndrup, Donald

2018-01-01

Roughly 20 percent of the quasar population shows broad absorption lines, which are indicators of an energetic wind. Within the broad absorption line class of quasars exist FeLoBAL quasars, which show strong absorption lines from the Fe II and Fe III transitions as well as other low-ionization lines. FeLoBALs are of particular interest because they are thought to possibly be a short-lived stage in a quasar's life where it expels its shroud of gas and dust. This means the winds we see from FeLoBALs are one manifestation of galactic feedback. This idea is supported by Farrah et al. (2012) who found an anti correlation between outflow strength and contribution from star formation to the total IR luminosity of the host galaxy when examining a sample of FeLoBAL quasars. We analyze the sample of 26 FeLoBALs from Farrah et al. (2012) in order to measure the properties of their outflows, including ionization, density, column density and covering fraction. The absorption and continuum profiles of these objects are modeled using SimBAL, a program which creates synthetic spectra using a grid of Cloudy models. A Monte-Carlo method is employed to determine posterior probabilities for the physical parameters of the outflow. From these probabilities we extract the distance of the outflow, the mass outflow rate and the kinetic luminosity. We demonstrate SimBAL is capable of modeling a wide range of spectral morphologies. From the 26 objects studied we observe interesting correlations between ionization parameter, distance and density. Analysis of our sample also suggests a dearth of objects with velocity widths greater than or equal to 300 km/s at distances greater than or equal to 100 parsecs.

Variability of the broad absorption lines in the QSO UM 232

NASA Technical Reports Server (NTRS)

Barlow, Thomas A.; Junkkarinen, Vesa T.; Burbidge, E. Margaret

1989-01-01

Low-resolution spectra of UM 232 taken in 1978, 1979, and 1988 at Lick Observatory are presented. Large changes in the Si IV lambda 1397, CIV lambda 1549, and Al III lambda 1857 broad absorption lines are apparent. The decrease in column density in all three ions and an observed brightening of the QSO suggests that these changes are due to an increase in the ionization level driven by an increase in the central source luminosity. This mechanism has been proposed by Smith and Penston to explain small changes in the absorption spectrum of the QSO 1246-057. The spectra of UM 232 show that the fractional decrease in optical depth is smaller at higher outflow velocies. The structure of the broad absorption-line region (BALR) is investigted by estimating an ionization parameter for each ion species as a function of velocity.

Multi-gas sensing with quantum cascade laser array in the mid-infrared region

NASA Astrophysics Data System (ADS)

Bizet, Laurent; Vallon, Raphael; Parvitte, Bertrand; Brun, Mickael; Maisons, Gregory; Carras, Mathieu; Zeninari, Virginie

2017-05-01

Wide tunable lasers sources are useful for spectroscopy of complex molecules that have broad absorption spectra and for multiple sensing of smaller molecules. A region of interest is the mid-infrared region, where many species have strong ro-vibrational modes. In this paper a novel broad tunable source composed of a QCL DFB array and an arrayed waveguide grating (also called multiplexer) was used to perform multi-species spectroscopy (CO, C2H2, CO2). The array and the multiplexer are associated in a way to obtain a prototype that is non-sensitive to mechanical vibrations. A 2190-2220 cm^{-1} spectral range is covered by the chip. The arrayed waveguide grating combines beams to have a single output. A multi-pass White cell was used to demonstrate the efficiency of the multiplexer.

Vanishing absorption and blueshifted emission in FeLoBAL quasars

NASA Astrophysics Data System (ADS)

Rafiee, Alireza; Pirkola, Patrik; Hall, Patrick B.; Galati, Natalee; Rogerson, Jesse; Ameri, Abtin

2016-07-01

We study the dramatic decrease in iron absorption strength in the iron low-ionization broad absorption line quasar SDSS J084133.15+200525.8. We report on the continued weakening of absorption in the prototype of this class of variable broad absorption line quasar, FBQS J140806.2+305448. We also report a third example of this class, SDSS J123103.70+392903.6; unlike the other two examples, it has undergone an increase in observed continuum brightness (at 3000 Å rest frame) as well as a decrease in iron absorption strength. These changes could be caused by absorber transverse motion or by ionization variability. We note that the Mg II and UV Fe II lines in several FeLoBAL quasars are blueshifted by thousands of km s-1 relative to the H β emission line peak. We suggest that such emission arises in the outflowing winds normally seen only in absorption.

Gas-phase Absorption of {{\\rm{C}}}_{70}^{2+} below 10 K: Astronomical Implications

NASA Astrophysics Data System (ADS)

Campbell, E. K.; Holz, M.; Maier, J. P.

2017-02-01

The electronic spectrum of the fullerene dication {{{C}}}702+ has been measured in the gas phase at low temperature in a cryogenic radiofrequency ion trap. The spectrum consists of a strong origin band at 7030 Å and two weaker features to higher energy. The bands have FWHMs of 35 Å indicating an excited state lifetime on the order of one-tenth of a picosecond. Absorption cross-section measurements yield (2 ± 1) × 10-15 cm2 at 7030 Å. These results are used to predict the depth of diffuse interstellar bands (DIBs) due to the absorption by {{{C}}}702+. At an assumed column density of 2 × 1012 cm-2 the attenuation of starlight at 7030 Å is around 0.4% and thus the detection of such a shallow and broad interstellar band would be difficult. The electronic spectrum of {{{C}}}602+ shows no absorptions in the visible. Below 4000 Å the spectra of C60, {{{C}}}60+ and {{{C}}}602+ are similar. The large intrinsic FWHM of the features in this region, ˜200 Å for the band near 3250 Å, make them unsuitable for DIB detection.

Characterization of Structural and Pigmentary Colors in Common Emigrant (Catopsilia Pomona) Butterfly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghate, Ekata; Kulkarni, G. R.; Bhoraskar, S. V.

2011-10-20

Study of structural colors in case of insects and butterflies is important for their biomimic and biophotonics applications. Structural color is the color which is produced by physical structures and their interaction with light while pigmentary color is produced by absorption of light by pigments. Common Emigrant butterfly is widely distributed in India. It is of moderate size with wing span of about 60-80 mm. The wings are broadly white with yellow or sulphur yellow coloration at places as well as few dark black patches. It belongs to family Pieridae. A study of structural color in case of Common Emigrantmore » butterfly has been carried out in the present work. The characterization of wing color was performed using absorption spectroscopy. Scanning electron microscopic study of the wings of Common Emigrant butterfly showed that three different types of scales are present on the wing surface dorsally. Diffracting structures are present in certain parts of the surfaces of the various scales. Bead like structures are embedded in the intricate structures of the scales. Absorption spectra revealed that a strong absorption peak is seen in the UV-range. Crystalline structure of beads was confirmed by the X-ray diffraction analysis.« less

Using high spectral resolution spectrophotometry to study broad mineral absorption features on Mars

NASA Technical Reports Server (NTRS)

Blaney, D. L.; Crisp, D.

1993-01-01

Traditionally telescopic measurements of mineralogic absorption features have been made using relatively low to moderate (R=30-300) spectral resolution. Mineralogic absorption features tend to be broad so high resolution spectroscopy (R greater than 10,000) does not provide significant additional compositional information. Low to moderate resolution spectroscopy allows an observer to obtain data over a wide wavelength range (hundreds to thousands of wavenumbers) compared to the several wavenumber intervals that are collected using high resolution spectrometers. However, spectrophotometry at high resolution has major advantages over lower resolution spectroscopy in situations that are applicable to studies of the Martian surface, i.e., at wavelengths where relatively weak surface absorption features and atmospheric gas absorption features both occur.

Optical properties of Y and Ti co-substituted BiFeO{sub 3} multiferroics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Vikash, E-mail: rk.dwivedi@jiit.ac.in; Sharma, Subhash, E-mail: rk.dwivedi@jiit.ac.in; Kumar, Manoj, E-mail: rk.dwivedi@jiit.ac.in

2014-04-24

Pure and co substituted Bi{sub 1−x}Y{sub x}Fe{sub 1−x}Ti{sub x}O{sub 3} (x ≤ 0.24) ceramics were synthesized by solid state reaction method. X-ray diffraction patterns of Y and Ti codoped samples have shown single phase formation. Increasing Y and Ti concentration reveals structural transition from rhombohedral phase (R3c) for x ≤ 0.16 to orthorhombic phase (Pnma) for x = 0.24. FT-IR spectra exhibit broad absorption bands, which may be due to the overlapping of Fe-O and Bi-O vibrations. UV-visible spectroscopy results show strong absorption of light in the spectral range of 400-720 nm, indicating optical band gap in the visible regionmore » for these samples. These interesting optical properties of co-substituted BFO samples in visible region may find potential applications in optoelectronic devices.« less

Candle soot nanoparticles-polydimethylsiloxane composites for laser ultrasound transducers

NASA Astrophysics Data System (ADS)

Chang, Wei-Yi; Huang, Wenbin; Kim, Jinwook; Li, Sibo; Jiang, Xiaoning

2015-10-01

Generation of high power laser ultrasound strongly demands the advanced materials with efficient laser energy absorption, fast thermal diffusion, and large thermoelastic expansion capabilities. In this study, candle soot nanoparticles-polydimethylsiloxane (CSNPs-PDMS) composite was investigated as the functional layer for an optoacoustic transducer with high-energy conversion efficiency. The mean diameter of the collected candle soot carbon nanoparticles is about 45 nm, and the light absorption ratio at 532 nm wavelength is up to 96.24%. The prototyped CSNPs-PDMS nano-composite laser ultrasound transducer was characterized and compared with transducers using Cr-PDMS, carbon black (CB)-PDMS, and carbon nano-fiber (CNFs)-PDMS composites, respectively. Energy conversion coefficient and -6 dB frequency bandwidth of the CSNPs-PDMS composite laser ultrasound transducer were measured to be 4.41 × 10-3 and 21 MHz, respectively. The unprecedented laser ultrasound transduction performance using CSNPs-PDMS nano-composites is promising for a broad range of ultrasound therapy applications.

Small hydrocarbons on metal surfaces: adsorption-induced changes in electronic and geometric structure as seen by X-ray absorption spectroscopy.

PubMed

Wöll, C

2001-03-01

Monolayers of several unsaturated and saturated hydrocarbons (ethylene, acetylene, benzene, n-hexane, cyclohexane, n-octane, n-hexatriacontane) adsorbed on a number of different metal surfaces [Cu(111), Au(111), Ru(0001) and Pt(111)] have been investigated by carbon K-edge X-ray absorption spectroscopy (XAS). Whereas the corresponding multilayer data qualitatively resemble the core-excitation spectra observed for the free molecules, generally significant modifications are observed in the monolayer data. For the saturated hydrocarbons, a strong quenching of the Rydberg R resonance at 287.7 eV and the appearance of a new broad feature at around 285.1 eV (M resonance) is observed for molecules in direct contact with the metal surfaces. In the case of the unsaturated hydrocarbons, for a number of metals, distinct new features are seen in the XAS data, revealing significant intramolecular distortions.

The Surprising Absence of Absorption in the Far-ultraviolet Spectrum of Mrk 231

NASA Technical Reports Server (NTRS)

Veilleux, S.; Trippe, M.; Hamann, F.; Rupke, D. S. N.; Tripp, T. M.; Netzer, H.; Lutz, D.; Sembach, K. R.; Krug, H.; Teng, Stacy H.;

Fusion of Ultraviolet-Visible and Infrared Transient Absorption Spectroscopy Data to Model Ultrafast Photoisomerization.

PubMed

Debus, Bruno; Orio, Maylis; Rehault, Julien; Burdzinski, Gotard; Ruckebusch, Cyril; Sliwa, Michel

2017-08-03

Ultrafast photoisomerization reactions generally start at a higher excited state with excess of internal vibrational energy and occur via conical intersections. This leads to ultrafast dynamics which are difficult to investigate with a single transient absorption spectroscopy technique, be it in the ultraviolet-visible (UV-vis) or infrared (IR) domain. On one hand, the information available in the UV-vis domain is limited as only slight spectral changes are observed for different isomers. On the other hand, the interpretation of vibrational spectra is strongly hindered by intramolecular relaxation and vibrational cooling. These limitations can be circumvented by fusing UV-vis and IR transient absorption spectroscopy data in a multiset multivariate curve resolution analysis. We apply this approach to describe the spectrodynamics of the ultrafast cis-trans photoisomerization around the C-N double bond observed for aromatic Schiff bases. Twisted intermediate states could be elucidated, and isomerization was shown to occur through a continuous complete rotation. More broadly, data fusion can be used to rationalize a vast range of ultrafast photoisomerization processes of interest in photochemistry.

Design of a polarization-independent, wide-angle, broadband visible absorber

NASA Astrophysics Data System (ADS)

Jia, Xiuli; Wang, Xiaoou

2018-01-01

Many optical systems benefit from elements that can absorb a broad range of wavelengths over a wide range of angles, independent of polarization. In this paper, we present a polarization-independent, wide-angle, broadband absorber in the visible regime that exploits strong symmetric and asymmetric resonance modes of electromagnetic dipoles. It makes use of a bilayer cross-pattern structure which is simple, having five layers that include two stacks of metal ribbon in cross-patterns, two dielectric spacers and a metal reflecting layer. Simulations show that the design exhibits a significantly enhanced absorption property when compared to a device with a bilayer metal film structure or any other complex structure of cross-patterns that have no intersection angle. The maximum absorption efficiency of the device is 100% at resonances, and its absorption characteristics can be maintained over a wide range of angles of incidence - up to ± 60° - regardless of the incident polarization. This strategy can, in principle, be applied to other material systems and could be useful in diverse applications, including thermal emitters, photovoltaics and photodetectors.

O VI ABSORBERS TRACING HOT GAS ASSOCIATED WITH A PAIR OF GALAXIES AT z = 0.167

DOE Office of Scientific and Technical Information (OSTI.GOV)

Savage, B. D.; Narayanan, A.; Wakker, B. P.

2010-08-20

High signal-to-noise observations of the QSO PKS 0405-123 (z {sub em} = 0.572) with the Cosmic Origins Spectrograph from 1134 to 1796 A with a resolution of {approx}17 km s{sup -1} are used to study the multi-phase partial Lyman limit system (LLS) at z = 0.16716, which has previously been studied using relatively low signal-to-noise spectra from STIS and FUSE. The LLS and an associated H I-free broad O VI absorber likely originate in the circumgalactic gas associated with a pair of galaxies at z = 0.1688 and 0.1670 with impact parameters of 116 h {sup -1} {sub 70} andmore » 99 h {sup -1} {sub 70}. The broad and symmetric O VI absorption is detected in the z = 0.16716 rest frame with v = -278 {+-} 3 km s{sup -1}, log N(O VI) = 13.90 {+-} 0.03, and b = 52 {+-} 2 km s{sup -1}. This absorber is not detected in H I or other species with the possible exception of N V. The broad, symmetric O VI profile and the absence of corresponding H I absorption indicate that the circumgalactic gas in which the collisionally ionized O VI arises is hot (log T {approx} 5.8-6.2). The absorber may represent a rare but important new class of low-z intergalactic medium absorbers. The LLS has strong asymmetrical O VI absorption with log N(O VI) = 14.72 {+-} 0.02 spanning a velocity range from -200 to +100 km s{sup -1}. The high and low ions in the LLS have properties resembling those found for Galactic highly ionized high-velocity clouds where the O VI is likely produced in the conductive and turbulent interfaces between cool and hot gas.« less

Spectroscopic and structural investigation of 2,5-dicarboxy-1-methylpyridinium inner salt

NASA Astrophysics Data System (ADS)

Barczyński, P.; Komasa, A.; Katrusiak, A.; Dega-Szafran, Z.; Nowaczyk, Ł.; Ratajczak-Sitarz, M.; Szafran, M.

2014-03-01

The structure of 2,5-dicarboxy-1-methylpyridinium inner salt (1), has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FTIR, Raman and NMR spectroscopy. The molecules are linked by short intermolecular and asymmetric Osbnd H⋯O hydrogen bonds of 2.486(2) Å between carboxyl and carboxylate groups of neighboring molecules into infinite chains. The hydrogen bonds in the molecules optimized by the B3LYP/6-311G(d,p) approach in trimer (2) and dimer (3) are slightly longer than in the crystal. The FTIR spectrum of the investigated inner salt is dominated by a broad and intense absorption in the 1500-800 cm-1 region attributed to the νas(OHO) and γ(OHO) vibrations of the strong hydrogen bond. In the Raman spectrum the broad absorption is absent. Linear correlations, δexp = a + b σcalc between the experimental 1H and 13C NMR chemical shifts (δexp) of the investigated inner salt in D2O and the calculated magnetic isotropic shielding constants (σcalc) for the optimized monomer (4a) solvated in water are reported. The pKa value for 1 of 2.31 ± 0.02 was determined by the potentiometric titration.

THE UNUSUAL TEMPORAL AND SPECTRAL EVOLUTION OF THE TYPE IIn SUPERNOVA 2011ht

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roming, P. W. A.; Bayless, A. J.; Pritchard, T. A.

2012-06-01

We present very early UV to optical photometric and spectroscopic observations of the peculiar Type IIn supernova (SN) 2011ht in UGC 5460. The UV observations of the rise to peak are only the second ever recorded for a Type IIn SN and are by far the most complete. The SN, first classified as an SN impostor, slowly rose to a peak of M{sub V} {approx} -17 in {approx}55 days. In contrast to the {approx}2 mag increase in the v-band light curve from the first observation until peak, the UV flux increased by >7 mag. The optical spectra are dominated bymore » strong, Balmer emission with narrow peaks (FWHM {approx} 600 km s{sup -1}), very broad asymmetric wings (FWHM {approx} 4200 km s{sup -1}), and blueshifted absorption ({approx}300 km s{sup -1}) superposed on a strong blue continuum. The UV spectra are dominated by Fe II, Mg II, Si II, and Si III absorption lines broadened by {approx}1500 km s{sup -1}. Merged X-ray observations reveal a L{sub 0.2-10} = (1.0 {+-} 0.2) Multiplication-Sign 10{sup 39} erg s{sup -1}. Some properties of SN 2011ht are similar to SN impostors, while others are comparable to Type IIn SNe. Early spectra showed features typical of luminous blue variables at maximum and during giant eruptions. However, the broad emission profiles coupled with the strong UV flux have not been observed in previous SN impostors. The absolute magnitude and energetics ({approx}2.5 Multiplication-Sign 10{sup 49} erg in the first 112 days) are reminiscent of normal Type IIn SN, but the spectra are of a dense wind. We suggest that the mechanism for creating this unusual profile could be a shock interacting with a shell of material that was ejected a year before the discovery of the SN.« less

Reddening and He i{sup ∗} λ 10830 Absorption Lines in Three Narrow-line Seyfert 1 Galaxies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Shaohua; Zhou, Hongyan; Shi, Xiheng

We report the detection of heavy reddening and the He i* λ 10830 absorption lines at the active galactic nucleus (AGN) redshift in three narrow-line Seyfert 1 galaxies: SDSS J091848.61+211717.0, SDSS J111354.66+124439.0, and SDSS J122749.13+321458.9. They exhibit very red optical to near-infrared colors, narrow Balmer/Paschen broad emission lines and He i* λ 10830 absorption lines. The ultraviolet-optical-infrared nucleus continua are reddened by the SMC extinction law of E ( B − V ) ∼ 0.74, 1.17, and 1.24 mag for three objects, which are highly consistent with the values obtained from the broad-line Balmer decrements, but larger than those ofmore » narrow emission lines. The reddening analysis suggests that the extinction dust simultaneously obscures the accretion disk, the broad emission-line region, and the hot dust from the inner edge of the torus. It is possible that the dust obscuring the AGN structures is the dusty torus itself. Furthermore, the Cloudy analysis of the He i* λ 10830 absorption lines proposes the distance of the absorption materials to be the extend scale of the torus, which greatly increases probabilities of the obscure and absorption materials being the dusty torus.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hagglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo

In this study, when optical resonances interact strongly, hybridized modes are formed with mixed properties inherited from the basic modes. Strong coupling therefore tends to equalize properties such as damping and oscillator strength of the spectrally separate resonance modes. This effect is here shown to be very useful for the realization of near-perfect dual-band absorption with ultrathin (~10 nm) layers in a simple geometry. Absorber layers are constructed by atomic layer deposition of the heavy-damping semiconductor tin monosulfide (SnS) onto a two-dimensional gold nanodot array. In combination with a thin (55 nm) SiO 2 spacer layer and a highly reflectivemore » Al film on the back, a semiopen nanocavity is formed. The SnS-coated array supports a localized surface plasmon resonance in the vicinity of the lowest order antisymmetric Fabry–Perot resonance of the nanocavity. Very strong coupling of the two resonances is evident through anticrossing behavior with a minimum peak splitting of 400 meV, amounting to 24% of the plasmon resonance energy. The mode equalization resulting from this strong interaction enables simultaneous optical impedance matching of the system at both resonances and thereby two near-perfect absorption peaks, which together cover a broad spectral range. When paired with the heavy damping from SnS band-to-band transitions, this further enables approximately 60% of normal incident solar photons with energies exceeding the band gap to be absorbed in the 10 nm SnS coating. Thereby, these results establish a distinct relevance of strong coupling phenomena to efficient, nanoscale photovoltaic absorbers and more generally for fulfilling a specific optical condition at multiple spectral positions.« less

Nonlinearities of polymethine and squarylium molecules for optical limiting

NASA Astrophysics Data System (ADS)

Lim, Jin Hong

Optical limiting, a process that reduces transmittance at high laser input energies (irradiance, fluence), is of interest in applications where sensitive optical components, e.g. detectors, are vulnerable to damage by the laser beam. Polymethine and squarylium dyes show strong reverse saturable absorption (RSA) at 532 nm. RSA is a process by which weak linear absorption populates excited states which subsequently absorb strongly. Thus, low inputs are transmitted while high inputs are absorbed. This nonlinear absorption is determined by the ground and excited-state absorption cross sections as well as excited state lifetimes of the molecular system. We characterized a series of polymethine and squarine molecules in ethanol and polyurethane acrylate polymeric host (PUA) using Z-scan and pump-probe techniques at the second harmonic of the Nd:YAG laser system. A comparison of the properties in these two hosts is made. Some of these dyes show a large ratio of excited to ground state absorption cross section, ~200, which is larger than any previously reported values. In order to determine the wavelength dependence of the nonlinearities of these molecules, we also performed Z-scan and pump-probe experiments at wavelengths from 440 to 650 nm using a picosecond optical parametric oscillator (OPO) which is synchronously pumped by the third-harmonic of a modelocked train of Nd:YAG laser pulses. The OPO is continuously tunable from 400 to 700 nm using two critically phase-matched BBO crystals mounted for walkoff compensation. A polymethine dye in PUA (PD #3), which is one of the best polymethine dyes at 532 nm, shows strong RSA over a broad spectral range from 480 to 620 nm. while a squarylium dye shows RSA over a relatively narrow spectral range from 500 to 560 nm. However, the excited state lifetimes (~2.5 ns in PUA) are shorter than desirable for good nanosecond optical limiting (10 ns) and at high inputs (>=0.36 J/cm2) the limiting properties are reduced. Extensive measurements of these molecules along with computer modeling indicate that the reduced limiting at high inputs is due to molecular degradation induced after a trans-cis conformational change. Evidence for this and possible methods to eliminate this problem are presented.

Tuning the optical properties of ZnO nanorods by variation of precursor concentration through hydrothermal method

NASA Astrophysics Data System (ADS)

Kumari, Lakshmi; Kar, Asit Kumar

2018-05-01

ZnO nanorods with varying precursor concentration have been successfully synthesized by the hydrothermal method. The effect of the precursor concentration on the structural, morphological and optical properties of the resulting nanorods was investigated by means of X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), UV-Vis spectroscopy and photoluminescence (PL) spectroscopy. The crystalline structural characterization demonstrated that the synthesized materials crystallize in pure ZnO wurtzite structure without any other secondary phase. SEM micrographs demonstrate nanorod type features in all the samples. In addition, they show that increase of precursor concentration changes the length and diameter of nanorods. The UV-Vis studies show a strong absorption band in UV region at 373 nm attributed to the band-edge absorption of wurtzite hexagonal ZnO, blue shifted relative to its bulk form (380 nm). The PL spectra of obtained nanorods excited at 360 nm present broad visible emission. Moreover, as the visible region (from 510 to 550 nm) is concerned, it is speculated that the increase of the precursor concentration affects strongly the kind of interstitial defects (Oi, Zni and Vo) formed in ZnO nanorods. The luminescence intensity decreases with the increase of precursor concentration.

The XMM-Newton Wide Angle Survey (XWAS): the X-ray spectrum of type-1 AGN

NASA Astrophysics Data System (ADS)

Mateos, S.; Carrera, F. J.; Page, M. J.; Watson, M. G.; Corral, A.; Tedds, J. A.; Ebrero, J.; Krumpe, M.; Schwope, A.; Ceballos, M. T.

2010-02-01

Aims: We discuss the broad band X-ray properties of one of the largest samples of X-ray selected type-1 AGN to date (487 objects in total), drawn from the XMM-Newton Wide Angle Survey (XWAS). The objects presented in this work cover 2-10 keV (rest-frame) luminosities from 1042-1045 erg s-1 and are detected up to redshift 4. We constrain the overall properties of the broad band continuum, soft excess and X-ray absorption, along with their dependence on the X-ray luminosity and redshift. We discuss the implications for models of AGN emission. Methods: We fitted the observed 0.2-12 keV broad band spectra with various models to search for X-ray absorption and soft excess. The F-test was used with a significance threshold of 99% to statistically accept the detection of additional spectral components. Results: We constrained the mean spectral index of the broad band X-ray continuum to <Γ> = 1.96 ± 0.02 with intrinsic dispersion {σ< Γ >} = 0.27-0.02+0.01. The continuum becomes harder at faint fluxes and at higher redshifts and hard (2-10 keV) luminosities. The dependence of Γ with flux is likely due to undetected absorption rather than to spectral variation. We found a strong dependence of the detection efficiency of objects on the spectral shape. We expect this effect to have an impact on the measured mean continuum shapes of sources at different redshifts and luminosities. We detected excess absorption in ⪆3% of our objects, with rest-frame column densities a few ×1022 cm-2. The apparent mismatch between the optical classification and X-ray properties of these objects is a challenge for the standard orientation-based AGN unification model. We found that the fraction of objects with detected soft excess is 36%. Using a thermal model, we constrained the soft excess mean rest-frame temperature and intrinsic dispersion to kT 100 eV and σkT 34 eV. The origin of the soft excess as thermal emission from the accretion disk or Compton scattered disk emission is ruled out on the basis of the temperatures detected and the lack of correlation of the soft excess temperature with the hard X-ray luminosity over more than 2 orders of magnitude in luminosity. Furthermore, the high luminosities of the soft excess rule out an origin in the host galaxy.

Strong coupling of plasmon and nanocavity modes for dual-band, near-perfect absorbers and ultrathin photovoltaics

DOE PAGES

Hagglund, Carl; Zeltzer, Gabriel; Ruiz, Ricardo; ...

2016-01-29

In this study, when optical resonances interact strongly, hybridized modes are formed with mixed properties inherited from the basic modes. Strong coupling therefore tends to equalize properties such as damping and oscillator strength of the spectrally separate resonance modes. This effect is here shown to be very useful for the realization of near-perfect dual-band absorption with ultrathin (~10 nm) layers in a simple geometry. Absorber layers are constructed by atomic layer deposition of the heavy-damping semiconductor tin monosulfide (SnS) onto a two-dimensional gold nanodot array. In combination with a thin (55 nm) SiO 2 spacer layer and a highly reflectivemore » Al film on the back, a semiopen nanocavity is formed. The SnS-coated array supports a localized surface plasmon resonance in the vicinity of the lowest order antisymmetric Fabry–Perot resonance of the nanocavity. Very strong coupling of the two resonances is evident through anticrossing behavior with a minimum peak splitting of 400 meV, amounting to 24% of the plasmon resonance energy. The mode equalization resulting from this strong interaction enables simultaneous optical impedance matching of the system at both resonances and thereby two near-perfect absorption peaks, which together cover a broad spectral range. When paired with the heavy damping from SnS band-to-band transitions, this further enables approximately 60% of normal incident solar photons with energies exceeding the band gap to be absorbed in the 10 nm SnS coating. Thereby, these results establish a distinct relevance of strong coupling phenomena to efficient, nanoscale photovoltaic absorbers and more generally for fulfilling a specific optical condition at multiple spectral positions.« less

SN REFSDAL: CLASSIFICATION AS A LUMINOUS AND BLUE SN 1987A-LIKE TYPE II SUPERNOVA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelly, P. L.; Filippenko, A. V.; Graham, M. L.

We have acquired Hubble Space Telescope (HST) and Very Large Telescope near-infrared spectra and images of supernova (SN) Refsdal after its discovery as an Einstein cross in fall 2014. The HST light curve of SN Refsdal has a shape consistent with the distinctive, slowly rising light curves of SN 1987A-like SNe, and we find strong evidence for a broad H α P-Cygni profile and Na I D absorption in the HST grism spectrum at the redshift ( z = 1.49) of the spiral host galaxy. SNe IIn, largely powered by circumstellar interaction, could provide a good match to the lightmore » curve of SN Refsdal, but the spectrum of a SN IIn would not show broad and strong H α and Na I D absorption. From the grism spectrum, we measure an H α expansion velocity consistent with those of SN 1987A-like SNe at a similar phase. The luminosity, evolution, and Gaussian profile of the H α emission of the WFC3 and X-shooter spectra, separated by ∼2.5 months in the rest frame, provide additional evidence that supports the SN 1987A-like classification. In comparison with other examples of SN 1987A-like SNe, photometry of SN Refsdal favors bluer B - V and V - R colors and one of the largest luminosities for the assumed range of potential magnifications. The evolution of the light curve at late times will provide additional evidence about the potential existence of any substantial circumstellar material. Using MOSFIRE and X-shooter spectra, we estimate a subsolar host-galaxy metallicity (8.3 ± 0.1 dex and <8.4 dex, respectively) near the explosion site.« less

Many-body and spin-orbit aspects of the alternating current phenomena

NASA Astrophysics Data System (ADS)

Glenn, Rachel M.

The thesis reports on research in the general field of light interaction with matter. According to the topics addressed, it can be naturally divided into two parts: Part I, many-body aspects of the Rabi oscillations which a two-level systems undergoes under a strong resonant drive; and Part II, absorption of the ac field between the spectrum branches of two-dimensional fermions that are split by the combined action of Zeeman and spin-orbit (SO) fields. The focus of Part I is the following many-body effects that modify the conventional Rabi oscillations: Chapter 1, coupling of a two-level system to a single vibrational mode of the environment. Chapter 2, correlated Rabi oscillations in two electron-hole systems coupled by tunneling with strong electron-hole attraction. In Chapter 1, a new effect of Rabi-vibronic resonance is uncovered. If the frequency of the Rabi oscillations, OR, is close to the frequency o0 of the vibrational mode, the oscillations acquire a collective character. It is demonstrated that the actual frequency of the collective oscillations exhibits a bistable behavior as a function of OR - o0. The main finding in Chapter 2 is, that the Fourier spectrum of the Rabi oscillations in two coupled electron-hole systems undergoes a strong transformation with increasing O R. For OR smaller than the tunneling frequency, the spectrum is dominated by a low-frequency (<< OR ) component and contains two additional weaker lines; conventional Rabi oscillations are restored only as OR exceeds the electron-hole attraction strength. The highlight of Part II is a finding that, while the spectrum of absorption between either Zeeman-split branches or SO-split branches is close to a delta-peak, in the presence of both, it transforms into a broad line with singular behavior at the edges. In particular, when the magnitudes of Zeeman and SO are equal, absorption of very low (much smaller than the splitting) frequencies become possible. The shape of the absorption spectrum is highly anisotropic with respect to the exciting field. This peculiar behavior of the absorption is also studied in wire geometry, where the interplay between two couplings (Zeeman and spin-orbit splitting) affects the shape of numerous absorption peaks.

Enhanced Broadband Electromagnetic Absorption in Silicon Film with Photonic Crystal Surface and Random Gold Grooves Reflector

PubMed Central

Chen, Zhi-Hui; Qiao, Na; Yang, Yibiao; Ye, Han; Liu, Shaoding; Wang, Wenjie; Wang, Yuncai

2015-01-01

We show a hybrid structure consisting of Si film with photonic crystal surface and random triangular gold grooves reflector at the bottom, which is capable of realizing efficient, broad-band, wide-angle optical absorption. It is numerically demonstrated that the enhanced absorption in a broad wavelength range (0.3–9.9 μm) due to the scattering effect of both sides of the structure and the created resonance modes. Larger thickness and period are favored to enhance the absorption in broader wavelength range. Substantial electric field concentrates in the grooves of surface photonic crystal and in the Si film. Our structure is versatile for solar cells, broadband photodetection and stealth coating. PMID:26238270

Changes in the Far UV Spectrum of Eta Carinae Near the 2003 Minimum

NASA Technical Reports Server (NTRS)

Iping, R. C.; Gull, T. R.; Sonneborn, G.; Massa, D.; Vieira, G. L.; Nielsen, K. E.

2004-01-01

High resolution 905-1180 spectra of \\eta Carinae have been obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite at nine epochs between February 2000 and June 2003 . This period of time extends from the broad maximum up to the very beginning of the minimum of the 5.52-year period initially discovered by A. Damineli. The flux levels were unchanged between February 2000 through February 2003 with minor spectral differences. The X-Ray minimum started on June 29, 2003 . Three observations were accomplished on June 10, June 17 and June 27 leading up to the minimum. Substantial changes were present in the June 10 and June 17 spectra, but a very significant change occurred by June 27, 2003. Longward of 1100A, the overall flux dropped 10 to 30 %. Shortward of 1100A, there are spectral intervals with NO decrease in flux even down to the shortest wavelengths (920--950 ). This indicates that dust absorption has a negligible role in the observed spectral changes and that line absorptions play a major role. Throughout the spectrum there are intervals ranging in width of 3-10A with strong increased absorption. Significant absorptions may be associated with the red portion of the following stellar wind lines: C III 977, O VI 1031,1037, P V 1117, while other absorption features are much broader, more extended and not clearly associated with well-known spectral transitions. Given the complexity of the STIS echelle spectra taken in this period of time, many of these absorption features are likely due to multiple absorption lines

The Suzaku Observation of NGC 3516: Complex Absorption and the Broad and Narrow Fe K Lines

NASA Technical Reports Server (NTRS)

Markowitz, Alex; Reeves, James N.; Miniutti, Giovanni; Serlemitsos, Peter; Kunieda, Hideyo; Taqoob, Tahir; Fabian, Andrew C.; Fukazawa, Yasushi; Mushotzky, Richard; Okajima, Takashi;

Physical conditions in broad and associated narrow absorption-line systems toward APM 08279+5255

NASA Astrophysics Data System (ADS)

Srianand, R.; Petitjean, P.

2000-05-01

Results of a careful analysis of the absorption systems with z_abs =~ z_em seen toward the bright, z_em ~ 3.91, gravitationally lensed quasar APM 08279+5255 are presented. Two of the narrow-line systems, at z_abs = 3.8931 and z_abs = 3.9135, show absorptions from singly ionized species with weak or no N v and O vi absorptions at the same redshift. Absorption due to fine structure transitions of C ii and S ii i (excitation energies corresponding to, respectively, 156mu m and 34mu m) are detected at z_abs = 3.8931. Excitation by IR radiation is favored as the column density ratios are consistent with the shape of APM 08279+5255 IR spectrum. The low-ionization state of the system favors a picture where the cloud is closer to the IR source than to the UV source, supporting the idea that the extension of the IR source is larger than ~ 200 pc. The absence of fine structure lines at z_abs = 3.9135 suggests that the gas responsible for this system is farther away from the IR source. Abundances are ~ 0.01 and 1 Zsun at z_abs = 3.913 and 3.8931 and aluminum could be over-abundant with respect to silicon and carbon by at least a factor of two and five. All this suggests that whereas the z_abs = 3.8931 system is probably located within 200 pc from the QSO and ejected at a velocity larger than 1000 km s-1, the z_abs = 3.9135 system is farther away and part of the host-galaxy. Several narrow-line systems have strong absorption lines due to C iv, O vi and N v and very low neutral hydrogen optical depths. This probably implies metallicities Z>= Z_sun although firm conclusion cannot be drawn as the exact value depends strongly on the shape of the ionizing spectrum. The C iv broad absorption has a complex structure with mini-BALs (width <= 1000 km s-1) and narrow components superposed on a continuous absorption of smaller optical depth. The continuous absorption is much stronger in O vi indicating that the corresponding gas-component is of higher ionization than the other components in the flow and that absorption structures in the BAL-flow are mainly due to density inhomogeneities. There is a tendency for mini-BALs to have different covering factors for different species. It is shown that a few of the absorbing clouds do not cover all the three QSO images, especially we conclude that the z_abs = 3.712 system covers only image C. Finally we identify narrow components within the BAL-flow with velocity separations within 5 km s-1 of the O vi, N v and S ii v doublet splittings suggesting that line driven radiative acceleration is an important process to explain the out-flow. Based on observations collected at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Searching for Variability of NV Intrinsic Narrow Absorption Line Systems

NASA Astrophysics Data System (ADS)

Rodruck, Michael; Charlton, Jane; Ganguly, Rajib

2018-01-01

The majority of quasar absorption line systems with NV detected are found within the associated region (within 5000 km/s of the quasar redshift) and many/most are believed to be related to the quasar accretion disk wind or outflows. The most definite evidence that these NV absorbers are "intrinsic" is partial covering of the quasar continuum source and/or broad line region. Over 75 quasars containing NV narrow absorption lines have observations obtained at different times with the Keck/HIRES and the VLT/UVES spectrographs at high resolution. The interval between these observations range from months to a decade in the quasar rest frame. While variability is common for intrinsic broad and mini-broad absorption lines, intrinsic narrow absorption lines have been found to be less likely to vary, though systematic studies with large, high quality datasets have been limited. The variability timescales are useful for deriving gas densities and thus the distances from the central engines. This is important in mapping the quasar surroundings, understanding the accretion disk wind mechanism, and assessing the effect the wind has on the galaxy surroundings. We report on the results of a systematic study of variability of NV NALs, exploiting the overlap of targets for observations in the archives of Keck and VLT, and discuss the consequences for interpretation of the origin of intrinsic narrow absorption lines.

Complex Resonance Absorption Structure in the X-Ray Spectrum of IRAS 13349+2438

NASA Technical Reports Server (NTRS)

Sako, M.; Kahn, S. M.; Behar, E.; Kaastra, J. S.; Brinkman, A. C.; Boller, Th.; Puchnarewicz, E. M.; Starling, R.; Liedahl, D. A.; Clavel, J.

2000-01-01

The luminous infrared-loud quasar IRAS 13349+2438 was observed with the XMM - Newton Observatory as part of the Performance Verification program. The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (FWHM - 1400 km/s) absorption lines from highly ionized elements including hydrogen- and helium-like carbon, nitrogen, oxygen, and neon, and several iron L - shell ions (Fe XVII - XX). Also shown in the spectrum is the first astrophysical detection of a broad absorption feature around lambda = 16 - 17 A identified as an unresolved transition array (UTA) of 2p - 3d inner-shell absorption by iron M-shell ions in a much cooler medium; a feature that might be misidentified as an O VII edge when observed with moderate resolution spectrometers. No absorption edges are clearly detected in the spectrum. We demonstrate that the RGS spectrum of IRAS 13349+2438 exhibits absorption lines from two distinct regions, one of which is tentatively associated with the medium that produces the optical/UV reddening.

The hot DOA1 degenerate HZ 21 - A search for circumstellar/photospheric metals and peculiar absorption at He II

NASA Technical Reports Server (NTRS)

Fritz, M. L.; Leckenby, H.; Sion, E. M.; Vauclair, G.; Liebert, J.

1990-01-01

A high-resolution IUE spectrum of the hot DO1 degenerate HZ 21 was obtained by combining US1 + European 2 low-background observing shifts. The SWP image reveals a rich spectrum of interstellar absorption lines with an average velocity in the line of sight to HZ 21 of -30 km/s. However, there is no clear evidence of any highly or lowly ionized metal features which could be attributed to circumstellar, wind, or photospheric absorption. There is, however, a broad absorption trough at He II (1640) which was not unexpected, given the clear presence of He II (4686) absorption in this star's optical spectrum. The velocity width of He II (1640) appears consistent with photospheric absorption wings which appear to flank the geocoronal Ly-alpha emission feature. The He II (1640) feature reveals what appears to be a broad (310 km/s) emission reversal. Evidence is provided that the emission reversal is probably real.

Broad [C II] Line Wings as Tracer of Molecular and Multi-phase Outflows in Infrared Bright Galaxies

NASA Astrophysics Data System (ADS)

Janssen, A. W.; Christopher, N.; Sturm, E.; Veilleux, S.; Contursi, A.; González-Alfonso, E.; Fischer, J.; Davies, R.; Verma, A.; Graciá-Carpio, J.; Genzel, R.; Lutz, D.; Sternberg, A.; Tacconi, L.; Burtscher, L.; Poglitsch, A.

2016-05-01

We report a tentative correlation between the outflow characteristics derived from OH absorption at 119 μm and [C II] emission at 158 μm in a sample of 22 local and bright ultraluminous infrared galaxies (ULIRGs). For this sample, we investigate whether [C II] broad wings are a good tracer of molecular outflows, and how the two tracers are connected. Fourteen objects in our sample have a broad wing component as traced by [C II], and all of these also show OH119 absorption indicative of an outflow (in one case an inflow). The other eight cases, where no broad [C II] component was found, are predominantly objects with no OH outflow or a low-velocity (≤100 km s-1) OH outflow. The FWHM of the broad [C II] component shows a trend with the OH119 blueshifted velocity, although with significant scatter. Moreover, and despite large uncertainties, the outflow masses derived from OH and broad [C II] show a 1:1 relation. The main conclusion is therefore that broad [C II] wings can be used to trace molecular outflows. This may be particularly relevant at high redshift, where the usual tracers of molecular gas (like low-J CO lines) become hard to observe. Additionally, observations of blueshifted Na I D λλ 5890, 5896 absorption are available for 10 of our sources. Outflow velocities of Na I D show a trend with OH velocity and broad [C II] FWHM. These observations suggest that the atomic and molecular gas phases of the outflow are connected.

Method for calculation of light field characteristics in optical diagnosis problems and personalized laser treatment of biological tissues

NASA Astrophysics Data System (ADS)

Lisenko, S. A.; Kugeiko, M. M.

2013-05-01

We have developed a simple method for solving the radiation transport equation, permitting us to rapidly calculate (with accuracy acceptable in practice) the diffuse reflection coeffi cient for a broad class of biological tissues in the spectral region of strong and weak absorption of light, and also the light flux distribution over the depth of the tissue. We show that it is feasible to use the proposed method for quantitative estimates of tissue parameters from its diffuse reflectance spectrum and also for selecting the irradiation dose which is optimal for a specifi c patient in laser therapy for various diseases.

Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301.

PubMed

Mathur; Green; Arav; Brotherton; Crenshaw; deKool; Elvis; Goodrich; Hamann; Hines; Kashyap; Korista; Peterson; Shields; Shlosman; van Breugel W; Voit

2000-04-20

We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (NH greater, similar1024 cm-2) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.

NuSTAR Reveals Extreme Absorption in z < 0.5 Type 2 Quasars

NASA Astrophysics Data System (ADS)

Lansbury, G. B.; Gandhi, P.; Alexander, D. M.; Assef, R. J.; Aird, J.; Annuar, A.; Ballantyne, D. R.; Baloković, M.; Bauer, F. E.; Boggs, S. E.; Brandt, W. N.; Brightman, M.; Christensen, F. E.; Civano, F.; Comastri, A.; Craig, W. W.; Del Moro, A.; Grefenstette, B. W.; Hailey, C. J.; Harrison, F. A.; Hickox, R. C.; Koss, M.; LaMassa, S. M.; Luo, B.; Puccetti, S.; Stern, D.; Treister, E.; Vignali, C.; Zappacosta, L.; Zhang, W. W.

2015-08-01

The intrinsic column density (NH) distribution of quasars is poorly known. At the high obscuration end of the quasar population and for redshifts z < 1, the X-ray spectra can only be reliably characterized using broad-band measurements that extend to energies above 10 keV. Using the hard X-ray observatory NuSTAR, along with archival Chandra and XMM-Newton data, we study the broad-band X-ray spectra of nine optically selected (from the SDSS), candidate Compton-thick (NH > 1.5 × 1024 cm-2) type 2 quasars (CTQSO2s); five new NuSTAR observations are reported herein, and four have been previously published. The candidate CTQSO2s lie at z < 0.5, have observed [O iii] luminosities in the range 8.4\\lt {log}({L}[{{O} {{III}}]}/{L}⊙ )\\lt 9.6, and show evidence for extreme, Compton-thick absorption when indirect absorption diagnostics are considered. Among the nine candidate CTQSO2s, five are detected by NuSTAR in the high-energy (8-24 keV) band: two are weakly detected at the ≈3σ confidence level and three are strongly detected with sufficient counts for spectral modeling (≳90 net source counts at 8-24 keV). For these NuSTAR-detected sources direct (i.e., X-ray spectral) constraints on the intrinsic active galactic nucleus properties are feasible, and we measure column densities ≈2.5-1600 times higher and intrinsic (unabsorbed) X-ray luminosities ≈10-70 times higher than pre-NuSTAR constraints from Chandra and XMM-Newton. Assuming the NuSTAR-detected type 2 quasars are representative of other Compton-thick candidates, we make a correction to the NH distribution for optically selected type 2 quasars as measured by Chandra and XMM-Newton for 39 objects. With this approach, we predict a Compton-thick fraction of {f}{CT}={36}-12+14 %, although higher fractions (up to 76%) are possible if indirect absorption diagnostics are assumed to be reliable.

Broad absorption line symbiotic stars: highly ionized species in the fast outflow from MWC 560

NASA Astrophysics Data System (ADS)

Lucy, Adrian B.; Knigge, Christian; Sokoloski, J. L.

2018-07-01

In symbiotic binaries, jets and disc winds may be integral to the physics of accretion on to white dwarfs from cool giants. The persistent outflow from symbiotic star MWC 560 (≡V694 Mon) is known to manifest as broad absorption lines (BALs), most prominently at the Balmer transitions. We report the detection of high-ionization BALs from C IV, Si IV, N V, and He II in International Ultraviolet Explorer spectra obtained on 1990 April 29-30, when an optical outburst temporarily erased the obscuring `iron curtain' of absorption troughs from Fe II and similar ions. The C IV and Si IV BALs reached maximum radial velocities at least 1000 km s-1 higher than contemporaneous Mg II and He II BALs; the same behaviours occur in the winds of quasars and cataclysmic variables. An iron curtain lifts to unveil high-ionization BALs during the P Cygni phase observed in some novae, suggesting by analogy a temporary switch in MWC 560 from persistent outflow to discrete mass ejection. At least three more symbiotic stars exhibit broad absorption with blue edges faster than 1500 km s-1; high-ionization BALs have been reported in AS 304 (≡V4018 Sgr), while transient Balmer BALs have been reported in Z And and CH Cyg. These BAL-producing fast outflows can have wider opening angles than has been previously supposed. BAL symbiotics are short-time-scale laboratories for their giga-scale analogues, broad absorption line quasars (BALQSOs), which display a similarly wide range of ionization states in their winds.

Broad absorption line symbiotic stars: highly ionized species in the fast outflow from MWC 560

NASA Astrophysics Data System (ADS)

Lucy, Adrian B.; Knigge, Christian; Sokoloski, J. L.

2018-04-01

In symbiotic binaries, jets and disk winds may be integral to the physics of accretion onto white dwarfs from cool giants. The persistent outflow from symbiotic star MWC 560 (≡V694 Mon) is known to manifest as broad absorption lines (BALs), most prominently at the Balmer transitions. We report the detection of high-ionization BALs from C IV, Si IV, N V, and He II in International Ultraviolet Explorer spectra obtained on 1990 April 29 - 30, when an optical outburst temporarily erased the obscuring `iron curtain' of absorption troughs from Fe II and similar ions. The C IV and Si IV BALs reached maximum radial velocities at least 1000 km s-1 higher than contemporaneous Mg II and He II BALs; the same behaviors occur in the winds of quasars and cataclysmic variables. An iron curtain lifts to unveil high-ionization BALs during the P Cygni phase observed in some novae, suggesting by analogy a temporary switch in MWC 560 from persistent outflow to discrete mass ejection. At least three more symbiotic stars exhibit broad absorption with blue edges faster than 1500 km s-1; high-ionization BALs have been reported in AS 304 (≡V4018 Sgr), while transient Balmer BALs have been reported in Z And and CH Cyg. These BAL-producing fast outflows can have wider opening angles than has been previously supposed. BAL symbiotics are short-timescale laboratories for their giga-scale analogs, broad absorption line quasars (BALQSOs), which display a similarly wide range of ionization states in their winds.

FTIR microspectroscopy and SIMS study of water-poor cordierite from El Hoyazo, Spain: Application to mineral and melt devolatilization

NASA Astrophysics Data System (ADS)

Della Ventura, Giancarlo; Bellatreccia, Fabio; Cesare, Bernardo; Harley, Simon; Piccinini, Massimo

2009-12-01

This paper reports the microchemical and microspectroscopic FTIR study of cordierite from a partially melted graphite-bearing granulitic enclave within the dacitic lava dome of El Hoyazo (SE Spain). Optically transparent single-crystals, hand picked from the rock, were oriented using X-ray diffraction and studied by Fourier-transform infrared (FTIR). Single-crystal FTIR spectroscopy shows that the examined cordierite is CO 2-rich and almost H 2O-free. Two weak and sharp peaks are observed at 3708 and 3595 cm - 1 , respectively, which are strongly polarised for E // a. These peaks are assigned to combination modes of CO 2. Very weak bands due to H 2O molecules oriented with the H…H vector // c (type I water) are occasionally observed in certain zones of the grains, associated with absorptions due to hydrated inclusions of alteration products. The very intense bands observed in the 2600-2000 cm - 1 region are assigned to CO 2 molecules oriented // a; the spectra also show the presence of 13C and 18O, and weak amounts of CO in the sample. Microspectrometric mapping shows that the distribution of C is relatively homogeneous, whereas that of H 2O is complicated by a very broad absorption extending from 3700 to 3100 cm - 1 . High-resolution FTIR imaging, done using a focal-plane array of detectors, shows that this broad absorption is associated with microfractures. SIMS analyses give an average concentration of H 2O = 0.033 ± 0.007 wt.% and CO 2 = 0.21 ± 0.07 wt.%. On the basis of these data, molar absorption coefficients can be calibrated for CO 2: ɛiCO2 (integrated) = 11,000 ± 4000 l/(mol cm - 2 ) and ɛlCO2 (linear) = 800 ± 250 l/(mol cm - 1 ). Due to the extremely low amount of H 2O and its inhomogeneous distribution, calibration of absorption ɛH2O coefficients is unreliable. The very low H 2O contents in the El Hoyazo cordierite indicate continued mineral-melt volatile exchange during decompression from ˜ 5 kbar to significantly shallower levels.

THE SLOAN DIGITAL SKY SURVEY REVERBERATION MAPPING PROJECT: RAPID C iv BROAD ABSORPTION LINE VARIABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grier, C. J.; Brandt, W. N.; Trump, J. R.

2015-06-10

We report the discovery of rapid variations of a high-velocity C iv broad absorption line trough in the quasar SDSS J141007.74+541203.3. This object was intensively observed in 2014 as a part of the Sloan Digital Sky Survey Reverberation Mapping Project, during which 32 epochs of spectroscopy were obtained with the Baryon Oscillation Spectroscopic Survey spectrograph. We observe significant (>4σ) variability in the equivalent width (EW) of the broad (∼4000 km s{sup −1} wide) C iv trough on rest-frame timescales as short as 1.20 days (∼29 hr), the shortest broad absorption line variability timescale yet reported. The EW varied by ∼10%more » on these short timescales, and by about a factor of two over the duration of the campaign. We evaluate several potential causes of the variability, concluding that the most likely cause is a rapid response to changes in the incident ionizing continuum. If the outflow is at a radius where the recombination rate is higher than the ionization rate, the timescale of variability places a lower limit on the density of the absorbing gas of n{sub e} ≳ 3.9 × 10{sup 5} cm{sup −3}. The broad absorption line variability characteristics of this quasar are consistent with those observed in previous studies of quasars, indicating that such short-term variability may in fact be common and thus can be used to learn about outflow characteristics and contributions to quasar/host-galaxy feedback scenarios.« less

Quasars with P v broad absorption in BOSS data release 9

NASA Astrophysics Data System (ADS)

Capellupo, D. M.; Hamann, F.; Herbst, H.; Brandt, W. N.; Ge, J.; Pâris, I.; Petitjean, P.; Schneider, D. P.; Streblyanska, A.; York, D.

2017-07-01

Broad absorption lines (BALs) found in a significant fraction of quasar spectra identify high-velocity outflows that might be present in all quasars and could be a major factor in feedback to galaxy evolution. Understanding the nature of these flows requires further constraints on their physical properties, including their column densities, for which well-studied BALs, such as C IV λλ1548,1551, typically provide only a lower limit because of saturation effects. Low-abundance lines, such as P v λλ1118,1128, indicate large column densities, implying that outflows more powerful than measurements of C IV alone would indicate. We search through a sample of 2694 BAL quasars from the Sloan Digital Sky Survey III/Baryon Oscillation Spectroscopic Survey data release 9 quasar catalogue for such absorption, and we identify 81 'definite' and 86 'probable' detections of P v broad absorption, yielding a firm lower limit of 3.0-6.2 per cent for the incidence of such absorption among BAL quasars. The P v-detected quasars tend to have stronger C IV and Si IV absorption, as well as a higher incidence of LoBAL absorption, than the overall BAL quasar population. Many of the P v-detected quasars have C IV troughs that do not reach zero intensity (at velocities where P v is detected), confirming that the outflow gas only partially covers the UV continuum source. P v appears significantly in a composite spectrum of non-P v-detected BAL quasars, indicating that P v absorption (and large column densities) is much more common than indicated by our search results. Our sample of P v detections significantly increases the number of known P v detections, providing opportunities for follow-up studies to better understand BAL outflow energetics.

C IV BROAD ABSORPTION LINE ACCELERATION IN SLOAN DIGITAL SKY SURVEY QUASARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grier, C. J.; Brandt, W. N.; Trump, J. R.

2016-06-20

We present results from the largest systematic investigation of broad absorption line (BAL) acceleration to date. We use spectra of 140 quasars from three Sloan Digital Sky Survey programs to search for global velocity offsets in BALs over timescales of ≈2.5–5.5 years in the quasar rest frame. We carefully select acceleration candidates by requiring monolithic velocity shifts over the entire BAL trough, avoiding BALs with velocity shifts that might be caused by profile variability. The C iv BALs of two quasars show velocity shifts consistent with the expected signatures of BAL acceleration, and the BAL of one quasar shows amore » velocity-shift signature of deceleration. In our two acceleration candidates, we see evidence that the magnitude of the acceleration is not constant over time; the magnitudes of the change in acceleration for both acceleration candidates are difficult to produce with a standard disk-wind model or via geometric projection effects. We measure upper limits to acceleration and deceleration for 76 additional BAL troughs and find that the majority of BALs are stable to within about 3% of their mean velocities. The lack of widespread acceleration/deceleration could indicate that the gas producing most BALs is located at large radii from the central black hole and/or is not currently strongly interacting with ambient material within the host galaxy along our line of sight.« less

Ultra-bright red-emitting photostable perylene bisimide dyes: new indicators for ratiometric sensing of high pH or carbon dioxide.

PubMed

Pfeifer, David; Klimant, Ingo; Borisov, Sergey M

2018-05-08

New pH sensitive perylene bisimide indicator dyes were synthesised and used for fabrication of optical sensors. The highly photostable dyes show absorption/emission bands in the red/near-infrared (NIR) region of the electromagnetic spectrum, high molar absorption coefficients (up to 100 000 M-1 cm-1) and fluorescence quantum yields close to unity. The absorption and emission spectra show strong bathochromic shift upon deprotonation of imidazole nitrogen which makes the dyes promising as ratiometric fluorescent indicators. Physical entrapment of the indicators into polyurethane hydrogel enables pH determination in alkaline pH. It is also shown that plastic carbon dioxide solid state sensor can be manufactured via immobilization of the pH indicator in a hydrophilic polymer, along with a quaternary ammonium base. The influence of plasticizer, different lipophilic bases and humidity on the sensitivity of the sensor material were systematically investigated. The disubstituted perylene, particularly, features two deprotonation equilibria enabling sensing over a very broad range from 0.5 to 1000 hPa pCO2. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano-photonic light trapping near the Lambertian limit in organic solar cell architectures.

PubMed

Biswas, Rana; Timmons, Erik

2013-09-09

A critical step to achieving higher efficiency solar cells is the broad band harvesting of solar photons. Although considerable progress has recently been achieved in improving the power conversion efficiency of organic solar cells, these cells still do not absorb upto ~50% of the solar spectrum. We have designed and developed an organic solar cell architecture that can boost the absorption of photons by 40% and the photo-current by 50% for organic P3HT-PCBM absorber layers of typical device thicknesses. Our solar cell architecture is based on all layers of the solar cell being patterned in a conformal two-dimensionally periodic photonic crystal architecture. This results in very strong diffraction of photons- that increases the photon path length in the absorber layer, and plasmonic light concentration near the patterned organic-metal cathode interface. The absorption approaches the Lambertian limit. The simulations utilize a rigorous scattering matrix approach and provide bounds of the fundamental limits of nano-photonic light absorption in periodically textured organic solar cells. This solar cell architecture has the potential to increase the power conversion efficiency to 10% for single band gap organic solar cells utilizing long-wavelength absorbers.

Estimating the Mg# and AlVI content of biotite and chlorite from shortwave infrared reflectance spectroscopy: Predictive equations and recommendations for their use

NASA Astrophysics Data System (ADS)

Lypaczewski, Philip; Rivard, Benoit

2018-06-01

Shortwave infrared (SWIR, 1000-2500 nm) reflectance spectra of biotite and chlorite were investigated to establish quantitative relationships between spectral metrics and mineral chemistry, determined by electron microprobe analysis (EMPA). Samples spanning a broad range of mineral compositions were used to establish regression equations to Mg#, which can be estimated to ±3 and ±5 Mg#, and to AlVI content, which can be estimated to ±0.044 AlVI (11 O) and ±0.09 AlVI (14 O), respectively for biotite and chlorite. Both minerals have absorptions at common positions (1400, 2250, 2330 nm), and spectral interference may occur in mineral mixtures. For an equivalent Mg#, absorptions of chlorite are offset to 1-15 nm higher wavelengths relative to those of biotite. If the incorrect mineral is identified, errors in the estimation of composition may occur. Additionally, the 2250 nm absorption, which is related to Al(Mg,Fe)-OH in both minerals, is strongly affected by both the AlVI content and Mg#. This can lead to erroneous Mg# estimations in low AlVI samples. Recommendations to mitigate these issues are presented.

Discovery of Hα Absorption in the Unusual Broad Absorption Line Quasar SDSS J083942.11+380526.3

NASA Astrophysics Data System (ADS)

Aoki, Kentaro; Iwata, Ikuru; Ohta, Kouji; Ando, Masataka; Akiyama, Masayuki; Tamura, Naoyuki

2006-11-01

We discovered Hα absorption in the broad Hα emission line of an unusual broad absorption line quasar, SDSS J083942.11+380526.3, at z=2.318, through near-infrared spectroscopy with the Cooled Infrared Spectrograph and Camera for OHS (CISCO) on the Subaru telescope. The presence of nonstellar Hα absorption is known only in the Seyfert galaxy NGC 4151 to date; thus, our discovery is the first case for quasars. The Hα absorption line is blueshifted by 520 km s-1 relative to the Hα emission line, and its redshift almost coincides with those of UV low-ionization metal absorption lines. The width of the Hα absorption (~340 km s-1) is similar to those of the UV low-ionization absorption lines. These facts suggest that the Hα and low-ionization metal absorption lines are produced by the same low-ionization gas, which has a substantial amount of neutral gas. The column density of the neutral hydrogen is estimated to be ~1018 cm-2 by assuming a gas temperature of 10,000 K from the analysis of the curve of growth. The continuum spectrum is reproduced by a reddened [E(B-V)~0.15 mag for the SMC-like reddening law] composite quasar spectrum. Furthermore, the UV spectrum of SDSS J083942.11+380526.3 shows a remarkable similarity to that of NGC 4151 in its low state, suggesting that the physical condition of the absorber in SDSS J083942.11+380526.3 is similar to that of NGC 4151 in the low state. As proposed for NGC 4151, SDSS J083942.11+380526.3 may also be seen through the edge of the obscuring torus. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

Metal-core/semiconductor-shell nanocones for broadband solar absorption enhancement.

PubMed

Zhou, Lin; Yu, Xiaoqiang; Zhu, Jia

2014-02-12

Nanostructure-based photovoltaic devices have exhibited several advantages, such as reduced reflection, extraordinary light trapping, and so forth. In particular, semiconductor nanostructures provide optical modes that have strong dependence on the size and geometry. Metallic nanostructures also attract a lot of attention because of the appealing plasmonic effect on the near-field enhancement. In this study, we propose a novel design, the metal-core/semiconductor-shell nanocones with the core radius varying in a linearly gradient style. With a thin layer of semiconductor absorber coated on a metallic cone, such a design can lead to significant and broadband absorption enhancement across the entire visible and near-infrared solar spectrum. As an example of demonstration, a layer of 16 nm thick crystalline silicon (c-Si) coated on a silver nanocone can absorb 27% of standard solar radiation across a broad spectral range of 300-1100 nm, which is equivalent to a 700 nm thick flat c-Si film. Therefore, the absorption enhancement factor approaching the Yablonovitch limit is achieved with this design. The significant absorption enhancement can be ascribed to three types of optical modes, that is, Fabry-Perot modes, plasmonic modes, and hybrid modes that combine the features of the previous two. In addition, the unique nanocone geometry enables the linearly gradient radius of the semiconductor shell, which can support multiple optical resonances, critical for the broadband absorption. Our design may find general usage as elements for the low cost, high efficiency solar conversion and water-splitting devices.

Evidence for Fluorescent Fe II Emission from Extended Low Ionization Outflows in Obscured Quasars

NASA Astrophysics Data System (ADS)

Wang, Tinggui; Ferland, Gary J.; Yang, Chenwei; Wang, Huiyuan; Zhang, Shaohua

2016-06-01

Recent studies have shown that outflows in at least some broad absorption line (BAL) quasars are extended well beyond the putative dusty torus. Such outflows should be detectable in obscured quasars. We present four WISE selected infrared red quasars with very strong and peculiar ultraviolet Fe II emission lines: strong UV Fe II UV arising from transitions to ground/low excitation levels, and very weak Fe II at wavelengths longer than 2800 Å. The spectra of these quasars display strong resonant emission lines, such as C IV, Al III and Mg II but sometimes, a lack of non-resonant lines such as C III], S III and He II. We interpret the Fe II lines as resonantly scattered light from the extended outflows that are viewed nearly edge-on, so that the accretion disk and broad line region are obscured by the dusty torus, while the extended outflows are not. We show that dust free gas exposed to strong radiation longward of 912 Å produces Fe II emission very similar to that observed. The gas is too cool to collisionally excite Fe II lines, accounting for the lack of optical emission. The spectral energy distribution from the UV to the mid-infrared can be modeled as emission from a clumpy dusty torus, with UV emission being reflected/scattered light either by the dusty torus or the outflow. Within this scenario, we estimate a minimum covering factor of the outflows from a few to 20% for the Fe II scattering region, suggesting that Fe II BAL quasars are at a special stage of quasar evolution.

The spectroscopic orbits and the geometrical configuration of the symbiotic binary AR Pavonis

NASA Astrophysics Data System (ADS)

Quiroga, C.; Mikołajewska, J.; Brandi, E.; Ferrer, O.; García, L.

2002-05-01

We analyze optical and near infrared spectra of intermediate and high resolution of the eclipsing symbiotic system AR Pavonis. We have obtained the radial velocity curves for the red and the hot component from the M-giant absorption lines and from the wings of Hα , Hβ and He II lambda 4686 emission profiles, respectively. From the orbital elements we have derived the masses, Mg=2.5 Msun and Mh=1.0 Msun, for the red giant and the hot component, respectively. We also present and discuss radial velocity patterns in the blue cF absorption spectrum as well as various emission lines. In particular, we confirm that the blue absorption lines are associated with the hot component. The radial velocity curve of the blue absorption system, however, does not track the hot companion's orbital motion in a straightforward way, and its departures from an expected circular orbit are particularly strong when the hot component is active. We suggest that the cF-type absorption system is formed in material streaming from the giant presumably in a region where the stream encounters an accretion disk or an extended envelope around the hot component. The broad emission wings originate from the inner accretion disk or the envelope around the hot star. We also suggest that the central absorption in H profiles is formed in a neutral portion of the cool giant's wind which is strongly concentrated towards the orbital plane. The nebula in AR Pav seems to be bounded by significant amount of neutral material in the orbital plane. The forbidden emission lines are probably formed in low density ionized regions extended in polar directions and/or the wind-wind interaction zone. Based on observations taken at Complejo Astronómico El Leoncito (CASLEO), operated under an agreement between the Consejo Nacional de Investigaciones Científicas y Técnicas de la República Argentina, the Secretaría de Ciencia y Tecnología de la Nación and the National Universities of La Plata, Córdoba and San Juan.

The Ionization and Metallicity of the Intervening O VI Absorber at z=0.1212 in the Spectrum of H1821+643

NASA Technical Reports Server (NTRS)

Tripp, Todd M.; Giroux, Mark L.; Stocke, John T.; Tumlinson, Jason; Oegerle, William R.; Fisher, Richard R. (Technical Monitor)

2001-01-01

We use high-resolution UV (ultraviolet) spectra of the radio-quiet QSO (quasi-stellar object) H1821+643 (z(sub em) = 0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE), to study the ionization and metallicity of an intervening O VI absorption line system at z(sub abs) = 0.1212. This absorber has the following notable properties: (1) Several galaxies are close to the sight line at the absorber redshift, including an actively star-forming galaxy at a projected distance of 144 h(sub 75)(exp -1) kpc. (2) There is a complex cluster of H I Ly(alpha) absorption lines near the O VI redshift, including at least five components spread over a velocity range of approximately 700 km s(exp -1). (3) The strongest Ly(alpha) line in the cluster appears to be composed of a mildly saturated component with a typical b-value blended with a remarkably broad component with b approximately equals 85 km s(exp -1). (4) The O VI absorption is not aligned with the strongest (saturated) H I absorption, but instead is well-aligned with the very broad component. (5) The only detected species (at the 4(sigma) level) are O VI and H I despite coverage of strong transitions of abundant elements (e.g., C II, C III, and C IV). Based on these constraints, we find that the absorption line properties can be produced in collisionally ionized gas with 10(exp 5.3) is equal to or less than T is equal to or less than 10(exp 5.6) K and -1.8 is equal to or less than [O/H] is equal to or less than -0.6. However, we find that photoionization is also viable if the pathlength l through the absorbing gas is long enough; simple photoionization models require 85 is equal to or less than l is equal to or less than 1900 kpc and -1.1 is equal to or less than [O/H] is equal to or less than -0.3. We briefly discuss how observations of X-ray absorption lines due to O VII and O VIII could be used, in principle, to break the ionization mechanism degeneracy, and we conclude with some comments regarding the nature of O VI absorbers.

Hg-Xe exciplex formation in mixed Xe/Ar matrices: molecular dynamics and luminescence study.

PubMed

Lozada-García, Rolando; Rojas-Lorenzo, Germán; Crépin, Claudine; Ryan, Maryanne; McCaffrey, John G

2015-03-19

Luminescence of Hg((3)P1) atoms trapped in mixed Ar/Xe matrices containing a small amount of Xe is reported. Broad emission bands, strongly red-shifted from absorption are recorded which are assigned to strong complexes formed between the excited mercury Hg* and xenon atoms. Molecular dynamics calculations are performed on simulated Xe/Ar samples doped with Hg to follow the behavior of Hg* in the mixed rare gas matrices leading to exciplex formation. The role of Xe atoms in the first solvation shell (SS1) around Hg was investigated in detail, revealing the formation of two kinds of triatomic exciplexes; namely, Xe-Hg*-Xe and Ar-Hg*-Xe. The first species exists only when two xenon atoms are present in SS1 with specific geometries allowing the formation of a linear or quasi-linear exciplex. In the other geometries, or in the presence of only one Xe in SS1, a linear Ar-Hg*-Xe exciplex is formed. The two kinds of exciplexes have different emission bands, the most red-shifted being that involving two Xe atoms, whose emission is very close to that observed in pure Xe matrices. Simulations give a direct access to the analysis of the experimental absorption, emission, and excitation spectra, together with the dynamics of exciplexes formation.

The Spectral Energy Distribution of the Seyfert Galaxy Ton S180

NASA Technical Reports Server (NTRS)

Turner, T. J.; Romano, P.; Kraemer, S. B.; George, I. M.; Yaqoob, T.; Crenshaw, D. M.; Storm, J.; Alloin, D.; Lazzaro, D.; DaSilva, L.;

RW Sextantis, a disk with a hot, high-velocity wind

NASA Astrophysics Data System (ADS)

Greenstein, J. L.; Oke, J. B.

1982-07-01

The continuum spectrum of the flickering blue variable RW Sex was observed from 10,000 to 1150 A. The star is a cataclysmic variable currently stabilized at maximum, and the spectrum is dominated by an accretion disk, with flat spectrum in the ultraviolet, except at more than 5000 A, where a blackbody near 7000 K is seen. A distance of 400 pc is derived, if the latter arises from an F type main sequence star. The accretion rate required is near 10 to the -8th solar masses per year. Only weak emission is seen, except for Lyman alpha; strong, broad UV absorption lines are seen with centers displaced up to -3000 km/s, with terminal velocities up to -4500 km/s, the velocity of escape from a white dwarf. The low X-ray flux may arise from absorption within an unusually dense, hot wind from the innermost portions of the disk. The estimated mass loss rate is nearly 10 to the -12th solar masses per year.

RW Sextantis, a disk with a hot, high-velocity wind

NASA Technical Reports Server (NTRS)

Greenstein, J. L.; Oke, J. B.

1982-01-01

The continuum spectrum of the flickering blue variable RW Sex was observed from 10,000 to 1150 A. The star is a cataclysmic variable currently stabilized at maximum, and the spectrum is dominated by an accretion disk, with flat spectrum in the ultraviolet, except at more than 5000 A, where a blackbody near 7000 K is seen. A distance of 400 pc is derived, if the latter arises from an F type main sequence star. The accretion rate required is near 10 to the -8th solar masses per year. Only weak emission is seen, except for Lyman alpha; strong, broad UV absorption lines are seen with centers displaced up to -3000 km/s, with terminal velocities up to -4500 km/s, the velocity of escape from a white dwarf. The low X-ray flux may arise from absorption within an unusually dense, hot wind from the innermost portions of the disk. The estimated mass loss rate is nearly 10 to the -12th solar masses per year.

Line intensities and temperature-dependent line broadening coefficients of Q-branch transitions in the v2 band of ammonia near 10.4 μm

NASA Astrophysics Data System (ADS)

Sur, Ritobrata; Spearrin, R. Mitchell; Peng, Wen Y.; Strand, Christopher L.; Jeffries, Jay B.; Enns, Gregory M.; Hanson, Ronald K.

2016-05-01

We report measured line intensities and temperature-dependent broadening coefficients of NH3 with Ar, N2, O2, CO2, H2O, and NH3 for nine sQ(J,K) transitions in the ν2 fundamental band in the frequency range 961.5-967.5 cm-1. This spectral region was chosen due to the strong NH3 absorption strength and lack of spectral interference from H2O and CO2 for laser-based sensing applications. Spectroscopic parameters were determined by multi-line fitting using Voigt lineshapes of absorption spectra measured with two quantum cascade lasers in thermodynamically-controlled optical cells. The temperature dependence of broadening was measured over a range of temperatures between 300 and 600 K. These measurements aid the development of mid-infrared NH3 sensors for a broad range of gas mixtures and at elevated temperatures.

A long-term space astrophysics research program: The evolution of the quasar continuum

NASA Technical Reports Server (NTRS)

Elvis, M.

1993-01-01

The research program supported by this grant now has great momentum. Numerous papers are in progress, and a strong multi-wavelength observing program is rapidly accumulating data on samples of high redshift quasars across the spectrum. ROSAT spectra of quasars continue to yield surprises. Of four z = 3 quasars with X-ray spectra, three show strong absorption. This contrasts strongly with the situation for luminous AGN at low redshifts where fewer than 1 in 20 show X-ray absorption. A new site for this absorption is probably needed, either around the quasar (e.g. in a cluster cooling flow) or along the line of sight (e.g. in a Damped Lyman-alpha system). The unabsorbed quasar allows limits on the physical conditions in a damped Lyman-alpha cloud to be calculated, and will allow a X-ray Gunn-Peterson test to be applied that will limit the fraction of the closure mass in an intergalactic medium. The X-ray spectral indices of these z = 3 quasars show no change from those of similar objects at low z, suggesting that 'short-lifetime' models apply. Eight other z = 3-4 quasars have been detected and their energy distributions from X-rays to Infrared (using new infrared spectrographs) have been compiled. These are now being compared with the low z continua from the 'Atlas of Quasar Energy Distributions' to search for evolutionary changes. The discovery of a likely warm absorber in 3C351 made recognition of another example simple. Also, modeling of the conditions in the absorber in 3C351 using the OVI absorption line from HST and the high ionization emission lines, suggests that the broad line region is indeed the origin of the warm absorber in this quasar, and by extension, others. Warm absorbers can now be used as a new diagnostic of this region. The X-ray spectrum of a 'Red Quasar', 3C212, has a cut-off spectrum, which could be fitted by an absorbed power-law, or more remarkably, by an unabsorbed black body. Using our quasi-simultaneous optical data and photoionization modeling we are able to rule out this latter possibility. The long-sought key to understanding red quasars has now been found. (Reddening was earlier ruled out because no 2175A absorption feature was seen. This is now seen to have been misleading.)

Effect of 3d-transition metal doping on the shielding behavior of barium borate glasses: a spectroscopic study.

PubMed

ElBatal, H A; Abdelghany, A M; Ghoneim, N A; ElBatal, F H

2014-12-10

UV-visible and FT infrared spectra were measured for prepared samples before and after gamma irradiation. Base undoped barium borate glass of the basic composition (BaO 40%-B2O3 60mol.%) reveals strong charge transfer UV absorption bands which are related to unavoidable trace iron impurities (Fe(3+)) within the chemical raw materials. 3d transition metal (TM)-doped glasses exhibit extra characteristic absorption bands due to each TM in its specific valence or coordinate state. The optical spectra show that TM ions favor generally the presence in the high valence or tetrahedral coordination state in barium borate host glass. Infrared absorption bands of all prepared glasses reveal the appearance of both triangular BO3 units and tetrahedral BO4 units within their characteristic vibrational modes and the TM-ions cause minor effects because of the low doping level introduced (0.2%). Gamma irradiation of the undoped barium borate glass increases the intensity of the UV absorption together with the generation of an induced broad visible band at about 580nm. These changes are correlated with suggested photochemical reactions of trace iron impurities together with the generation of positive hole center (BHC or OHC) within the visible region through generated electrons and positive holes during the irradiation process. Copyright © 2014 Elsevier B.V. All rights reserved.

Core-based intrinsic fiber-optic absorption sensor for the detection of volatile organic compounds

NASA Astrophysics Data System (ADS)

Klunder, Gregory L.; Russo, Richard E.

1995-03-01

A core-based intrinsic fiber-optic absorption sensor has been developed and tested for the detection of volatile organic compounds. The distal ends of transmitting and receiving fibers are connected by a small cylindrical section of an optically clear silicone rubber. The silicone rubber acts both as a light pipe and as a selective membrane into which the analyte molecules can diffuse. The sensor has been used to detect volatile organics (trichloroethylene, 1,1-dichloroethylene, and benzene) in both aqueous solutions and in the vapor phase or headspace. Absorption spectra obtained in the near-infrared (near-IR) provide qualitative and quantitative information about the analyte. Water, which has strong broad-band absorption in the near-IR, is excluded from the spectra because of the hydrophobic properties of the silicone rubber. The rate-limiting step is shown to be the diffusion through the Nernstian boundary layer surrounding the sensor and not the diffusion through the silicone polymer. The rate of analyte diffusion into the sensor, as measured by the t(sub 90) values (the time required for the sensor to reach 90% of the equilibrium value), is 30 min for measurements in aqueous solutions and approximately 3 min for measurements made in the headspace. The limit of detection obtained with this sensor is approximately 1.1 ppm for trichloroethylene in an aqueous solution.

A faint galaxy redshift survey behind massive clusters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Frye, Brenda Louise

1999-05-01

This thesis is concerned with the gravitational lensing effect by massive galaxy clusters. We have explored a new technique for measuring galaxy masses and for detecting high-z galaxies by their optical colors. A redshift survey has been obtained at the Keck for a magnitude limited sample of objects (I<23) behind three clusters, A1689, A2390, and A2218 within a radius of 0.5M pc. For each cluster we see both a clear trend of increasing flux and redshift towards the center. This behavior is the result of image magnifications, such that at fixed redshift one sees further down the luminosity function. Themore » gradient of this magnification is, unlike measurements of image distortion, sensitive to the mass profile, and found to depart strongly from a pure isothermal halo. We have found that V RI color selection can be used effectively as a discriminant for finding high-z galaxies behind clusters and present five 4.1 < z < 5.1 spectra which are of very high quality due to their high mean magnification of ~20, showing strong, visibly-saturated interstellar metal lines in some cases. We have also investigated the radio ring lens PKS 1830-211, locating the source and multiple images and detected molecular absorption at mm wavelengths. Broad molecular absorption of width 1/40kms is found toward the southwest component only, where surprisingly it does not reach the base of the continuum, which implies incomplete coverage of the SW component by molecular gas, despite the small projected size of the source, less than 1/8h pc at the absorption redshift.« less

Synthesis of Optode Thin Layer using Sol Gel Hybrid of Trietoxysiloxane monomer and 3-(Trimethoxysilyl) Propilamine with Ionophore 4-(2-Pyridilazo)-1,3-Benzenadiol (PAR)

NASA Astrophysics Data System (ADS)

Wahyuningsih, S.; Rahmawati, F.; Kamal, S.; Slamet, S.; Yunianto, M.; Rahmawati, P.; Aini, F. N.

2018-03-01

Optode (Optical sensors) is one of the modern chemical sensors in the field of analytical chemistry that has utilized of inorganic polymers. The optode based on MLCT (Metal to Ligand Charge Transfer) (or MMLL’CT, Mixing Metal-Ligand to Ligand Charge Transfer) or LMCT (Ligand to Metal Charge Transfer) phenomenons have beed generated from oktyltrietxysilane, aminopropyltrimethoxysilane and 4-(2-pyrydilazo) resorcinol (abbreviated as OTES-APTS-PAR) for Cu(II), Cr(III), Ni(II), Fe(III), Cd(II), and Zn(II) ions target. The syntheses of thin layer optode were performed by sol gel method followed by evaporation in glass substrat. The formation of 4-(2-pyrydilazo) resorcinol complexes with ions target have gained strong absorption spectras in visible region because of charge transfer phenomenons. The optical sensor of OTES-APTS-PAR was analysed thermal properties using Differential Thermal Analysis (DTA). DTA thermogram showed a glass transition peaks at a temperature of 315.5 °C. Fourier transform Infrared (FTIR) spectras have showed that the optode materials consisted NH aryl groups indicated IR absorption at 1577.7 cm-1 and also –CH aromatic at 1469.0 cm-1. Synthesized optode materials have strong broad visible absorption with the maximum wavelengths (λmax) = 405 nm and 508.5 nm, respectively. This material have excellent optical responds to several metal ions such as Cu(II), Cr(III), Ni(II), Fe(III), Cd(II), and Zn(II) that was showed from huge Δλmax and the increase of Ktotal

Lens-Aided Multi-Angle Spectroscopy (LAMAS) Reveals Small-Scale Outflow Structure in Quasars

NASA Astrophysics Data System (ADS)

Green, Paul J.

2006-06-01

Spectral differences between lensed quasar image components are common. Since lensing is intrinsically achromatic, these differences are typically explained as the effect of either microlensing, or as light path time delays sampling intrinsic quasar spectral variability. Here we advance a novel third hypothesis: some spectral differences are due to small line-of-sight differences through quasar disk wind outflows. In particular, we propose that variable spectral differences seen only in component A of the widest separation lens SDSS J1004+4112 are due to differential absorption along the sight lines. The absorber properties required by this hypothesis are akin to known broad absorption line (BAL) outflows but must have a broader, smoother velocity profile. We interpret the observed C IV emission-line variability as further evidence for spatial fine structure transverse to the line of sight. Since outflows are likely to be rotating, such absorber fine structure can consistently explain some of the UV and X-ray variability seen in AGNs. The implications are many: (1) Spectroscopic differences in other lensed objects may be due to this ``lens-aided multi-angle spectroscopy'' (LAMAS). (2) Outflows have fine structure on size scales of arcseconds, as seen from the nucleus. (3) Assuming either broad absorption line region sizes proposed in recent wind models, or typically assumed continuum emission region sizes, LAMAS and/or variability provide broadly consistent absorber size scale estimates of ~1015 cm. (4) Very broad smooth absorption may be ubiquitous in quasar spectra, even when no obvious troughs are seen.

Strong plasmon-exciton coupling in a hybrid system of gold nanostars and J-aggregates

PubMed Central

2013-01-01

Hybrid materials formed by plasmonic nanostructures and J-aggregates provide a unique combination of highly localized and enhanced electromagnetic field in metal constituent with large oscillator strength and extremely narrow exciton band of the organic component. The coherent coupling of localized plasmons of the multispiked gold nanoparticles (nanostars) and excitons of JC1 dye J-aggregates results in a Rabi splitting reaching 260 meV. Importantly, broad absorption features of nanostars extending over a visible and near-infrared spectral range allowed us to demonstrate double Rabi splitting resulting from the simultaneous coherent coupling between plasmons of the nanostars and excitons of J-aggregates of two different cyanine dyes. PMID:23522305

Ultrafast Extreme Ultraviolet Spectroscopy of Methylammonium Lead Iodide Perovskite for Carrier Specific Photophysics

NASA Astrophysics Data System (ADS)

Verkamp, Max A.; Lin, Ming-Fu; Ryland, Elizabeth S.; Benke, Kristin; Vura-Weis, Josh

2017-06-01

Methyl ammonium lead iodide (perovskite) is a leading candidate for next-generation solar cell devices. However, the fundamental photophysics responsible for its strong photovoltaic qualities are not fully understood. Ultrafast extreme ultraviolet (XUV) spectroscopy was used to investigate relaxation dynamics in perovskite with carrier specific signals arising from transitions from the common inner-shell level (I 4d) to the valence and conduction bands. Ultrashort (30 fs) pulses of XUV radiation in a broad spectrum (40-70 eV) were obtained using high-harmonic generation in a tabletop instrument. Transient absorption measurements with visible pump and XUV probe directly observed the dynamics of charge carriers after above-band and band-edge excitation.

Broad Absorption Lines in Qsos: Observations and Implications for Models.

NASA Astrophysics Data System (ADS)

Turnshek, David Alvin

Spectroscopic observations of fourteen broad absorption line (BAL) QSOs are presented and analyzed. Other observations are summarized. The following major conclusions are reached. Broad absorption lines (BALs) are probably present in 3 to 10 percent of the spectra of moderate to high redshift QSOs. The BALs exhibit a variety of velocity structures, from seemingly smooth, continuous absorption to complexes of individual absorption lines. Outflow velocities up to 40,000 km s(' -1) are observed. The level of ionization is high. The minimum total absorption column densities are 10('20) to 10('22) cm('-2). The emission line properties of BAL QSOs appear to be different from those of non-BAL QSOs. For example, N V emission is generally stronger in BAL QSOs and the emission near C III} (lamda)1909 is generally broader in BAL QSOs. The distribution of multiplicities for isolated absorption troughs suggests that the large -scale spatial distribution of BAL clouds is non-random, possibly described by a disk geometry. The BAL clouds are incapable of accounting for all of the observed broad emission lines, particularly C III} (lamda)1909 and Mg II (lamda)2798. Therefore, if the BAL clouds give rise to observable emission, the generally adopted (optically thick, single component) model for the emission line region must be incorrect. Also, photoionization models, which utilize solar abundances and take the ionizing continuum to be a simple power law, are incapable of explaining the level of ionization in the BAL clouds. By considering the observed percentage of QSOs with BALs and resonance line scattering models, it is found that the absorption covering factor in BAL QSOs is between 3 and 20 percent. This suggests that possibly all, but not less than 15 percent, of the QSOs have BAL clouds associated with them. The amount of observable emission and polarization expected to be produced by the BAL clouds from resonance line scattering and collisional excitation is considered in detail. It seems likely that the BAL clouds contribute to the observed high ionization emission. A model worth exploring is one in which an inner, optically thick component gives rise to the low ionization emission, whereas an outer BAL cloud region gives rise to much of the high ionization emission.

EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

NASA Astrophysics Data System (ADS)

De Vicente, F. S.; Santos, F. A.; Simões, B. S.; Dias, S. T.; Siu Li, M.

2014-12-01

Antimony phosphate glasses (SbPO) doped with 3 and 6 mol% of Cr3+ were studied by Electron Paramagnetic Resonance (EPR), UV-VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr3+-doped glasses showed two principal resonance signals with effective g values at g = 5.11 and g = 1.97. UV-VIS optical absorption spectra of SbPO:Cr3+ presented four characteristics bands at 457, 641, 675, and 705 nm related to the transitions from 4A2(F) to 4T1(F), 4T2(F), 2T1(G), and 2E(G), respectively, of Cr3+ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr3+ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B = 2.48 indicates that Cr3+ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr3+ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr3+-doped glasses excited with 350 nm revealed weak emission bands from 400 to 600 nm due to the 3P1 → 1S0 electronic transition from Sb3+ ions. Cr3+-doped glasses excited with 415 nm presented Cr3+ characteristic luminescence spectra composed by two broad bands, one band centered at 645 nm (2E → 4A2) and another intense band from 700 to 850 nm (4T2 → 4A2).

EVIDENCE FOR PHOTOIONIZATION-DRIVEN BROAD ABSORPTION LINE VARIABILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Tinggui; Yang, Chenwei; Wang, Huiyuan

2015-12-01

We present a qualitative analysis of the variability of quasar broad absorption lines using the large multi-epoch spectroscopic data set of the Sloan Digital Sky Survey Data Release 10. We confirm that variations of absorption lines are highly coordinated among different components of the same ion or the same absorption component of different ions for C iv, Si iv, and N v. Furthermore, we show that the equivalent widths (EWs) of the lines decrease or increase statistically when the continuum brightens or dims. This is further supported by the synchronized variations of emission and absorption-line EWs when the well-established intrinsicmore » Baldwin effect for emission lines is taken into account. We find that the emergence of an absorption component is usually accompanied by the dimming of the continuum while the disappearance of an absorption-line component is accompanied by the brightening of the continuum. This suggests that the emergence or disappearance of a C iv absorption component is only the extreme case, when the ionic column density is very sensitive to continuum variations or the continuum variability the amplitude is larger. These results support the idea that absorption-line variability is driven mainly by changes in the gas ionization in response to continuum variations, that the line-absorbing gas is highly ionized, and in some extreme cases, too highly ionized to be detected in UV absorption lines. Due to uncertainties in the spectroscopic flux calibration, we cannot quantify the fraction of quasars with asynchronized continuum and absorption-line variations.« less

Effective D-A-D type chromophore of fumaronitrile-core and terminal alkylated bithiophene for solution-processed small molecule organic solar cells.

PubMed

Nazim, M; Ameen, Sadia; Seo, Hyung-Kee; Shin, Hyung Shik

2015-06-12

A new and novel organic π-conjugated chromophore (named as RCNR) based on fumaronitrile-core acceptor and terminal alkylated bithiophene was designed, synthesized and utilized as an electron-donor material for the solution-processed fabrication of bulk-heterojunction (BHJ) small molecule organic solar cells (SMOSCs). The synthesized organic chromophore exhibited a broad absorption peak near green region and strong emission peak due to the presence of strong electron-withdrawing nature of two nitrile (-CN) groups of fumaronitrile acceptor. The highest occupied molecular orbital (HOMO) energy level of -5.82 eV and the lowest unoccupied molecular orbital (LUMO) energy level of -3.54 eV were estimated for RCNR due to the strong electron-accepting tendency of -CN groups. The fabricated SMOSC devices with RCNR:PC60BM (1:3, w/w) active layer exhibited the reasonable power conversion efficiency (PCE) of ~2.69% with high short-circuit current density (JSC) of ~9.68 mA/cm(2) and open circuit voltage (VOC) of ~0.79 V.

Effective D-A-D type chromophore of fumaronitrile-core and terminal alkylated bithiophene for solution-processed small molecule organic solar cells

PubMed Central

Nazim, M.; Ameen, Sadia; Seo, Hyung-Kee; Shin, Hyung Shik

2015-01-01

A new and novel organic π-conjugated chromophore (named as RCNR) based on fumaronitrile-core acceptor and terminal alkylated bithiophene was designed, synthesized and utilized as an electron-donor material for the solution-processed fabrication of bulk-heterojunction (BHJ) small molecule organic solar cells (SMOSCs). The synthesized organic chromophore exhibited a broad absorption peak near green region and strong emission peak due to the presence of strong electron-withdrawing nature of two nitrile (–CN) groups of fumaronitrile acceptor. The highest occupied molecular orbital (HOMO) energy level of –5.82 eV and the lowest unoccupied molecular orbital (LUMO) energy level of –3.54 eV were estimated for RCNR due to the strong electron-accepting tendency of –CN groups. The fabricated SMOSC devices with RCNR:PC60BM (1:3, w/w) active layer exhibited the reasonable power conversion efficiency (PCE) of ~2.69% with high short-circuit current density (JSC) of ~9.68 mA/cm2 and open circuit voltage (VOC) of ~0.79 V. PMID:26066557

The Mysterious 6565 Å Absorption Feature of the Galactic Halo

NASA Astrophysics Data System (ADS)

Sethi, Shiv K.; Shchekinov, Yuri; Nath, Biman B.

2017-12-01

We consider various possible scenarios to explain the recent observation of what has been called a broad Hα absorption in our Galactic halo, with peak optical depth τ ≃ 0.01 and equivalent width W≃ 0.17 \\mathringA . We show that the absorbed feature cannot arise from the circumgalactic and ISM Hα absorption. As the observed absorption feature is quite broad ({{Δ }}λ ≃ 30 \\mathringA ), we also consider CNO lines that lie close to Hα as possible alternatives to explain the feature. We show that such lines could also not account for the observed feature. Instead, we suggest that it could arise from diffuse interstellar bands (DIBs) carriers or polyaromatic hydrocarbons (PAHs) absorption. While we identify several such lines close to the Hα transition, we are unable to determine the molecule responsible for the observed feature, partly because of selection effects that prevent us from identifying DIBs/PAHs features close to Hα using local observations. Deep integration of a few extragalactic sources with high spectral resolution might allow us to distinguish between different possible explanations.

Self-assembly of highly efficient, broadband plasmonic absorbers for solar steam generation.

PubMed

Zhou, Lin; Tan, Yingling; Ji, Dengxin; Zhu, Bin; Zhang, Pei; Xu, Jun; Gan, Qiaoqiang; Yu, Zongfu; Zhu, Jia

2016-04-01

The study of ideal absorbers, which can efficiently absorb light over a broad range of wavelengths, is of fundamental importance, as well as critical for many applications from solar steam generation and thermophotovoltaics to light/thermal detectors. As a result of recent advances in plasmonics, plasmonic absorbers have attracted a lot of attention. However, the performance and scalability of these absorbers, predominantly fabricated by the top-down approach, need to be further improved to enable widespread applications. We report a plasmonic absorber which can enable an average measured absorbance of ~99% across the wavelengths from 400 nm to 10 μm, the most efficient and broadband plasmonic absorber reported to date. The absorber is fabricated through self-assembly of metallic nanoparticles onto a nanoporous template by a one-step deposition process. Because of its efficient light absorption, strong field enhancement, and porous structures, which together enable not only efficient solar absorption but also significant local heating and continuous stream flow, plasmonic absorber-based solar steam generation has over 90% efficiency under solar irradiation of only 4-sun intensity (4 kW m(-2)). The pronounced light absorption effect coupled with the high-throughput self-assembly process could lead toward large-scale manufacturing of other nanophotonic structures and devices.

Photophysical properties of C60 colloids suspended in water with Triton X-100 surfactant: excited-state properties with femtosecond resolution.

PubMed

Clements, Andrew F; Haley, Joy E; Urbas, Augustine M; Kost, Alan; Rauh, R David; Bertone, Jane F; Wang, Fei; Wiers, Brian M; Gao, De; Stefanik, Todd S; Mott, Andrew G; Mackie, David M

2009-06-11

We examine the photophysics of a colloidal suspension of C(60) particles in a micellar solution of Triton X-100 and water, prepared via a new synthesis which allows high-concentration suspensions. The particle sizes are characterized by transmission electron microscopy and dynamic light scattering and found to be somewhat polydisperse in the range of 10-100 nm. The suspension is characterized optically by UV-vis spectroscopy, femtosecond transient absorption spectroscopy, laser flash photolysis, and z-scan. The ground-state absorbance spectrum shows a broad absorbance feature centered near 450 nm which is indicative of colloidal C(60). The transient absorption dynamics, presented for the first time with femtosecond resolution, are very similar to that of thin films of C(60) and indicate a strong quenching of the singlet excited state on short time scales and evidence of little intersystem crossing to a triplet excited state. Laser flash photolysis reveals that a triplet excited-state absorption spectrum, which is essentially identical in shape to that of molecular C(60) solutions, does indeed arise, but with much lower magnitude and somewhat shorter lifetime. Z-scan analysis confirms that the optical response of this material is dominated by nonlinear scattering.

Space Telescope and Optical Reverberation Mapping Project VI. Variations of the Intrinsic Absorption Lines in NGC 5548

NASA Astrophysics Data System (ADS)

Kriss, Gerard A.; Agn Storm Team

2015-01-01

The AGN STORM collaboration monitored the Seyfert 1 galaxy NGC 5548 over a six-month period, with observations spanning the hard X-ray to mid-infrared wavebands. The core of this campaign was an intensive HST COS program, which obtained 170 far-ultraviolet spectra at approximately daily intervals, with twice-per-day monitoring of the X-ray, near-UV, and optical bands during much of the same period using Swift. The broad UV absorption lines discovered by Kaastra et al. (2014) and associated with the new soft X-ray obscurer are continuously present in the STORM campaign COS spectra. Their strength varies with the degree of soft X-ray obscuration as revealed by the Swift X-ray spectra. The narrow associated absorption lines in the UV spectrum of NGC 5548 remain strong. The lower-ionization transitions that appeared concurrently with the soft X-ray obscuration vary in response to the changing UV flux on a daily basis. Their depths over the longer term, however, also respond to the strength of the soft X-ray obscuration, indicating that the soft X-ray obscurer has a significant influence on the ionizing UV continuum that is not directly tracked by the observable UV continuum itself.

Self-assembly of highly efficient, broadband plasmonic absorbers for solar steam generation

PubMed Central

Zhou, Lin; Tan, Yingling; Ji, Dengxin; Zhu, Bin; Zhang, Pei; Xu, Jun; Gan, Qiaoqiang; Yu, Zongfu; Zhu, Jia

2016-01-01

The study of ideal absorbers, which can efficiently absorb light over a broad range of wavelengths, is of fundamental importance, as well as critical for many applications from solar steam generation and thermophotovoltaics to light/thermal detectors. As a result of recent advances in plasmonics, plasmonic absorbers have attracted a lot of attention. However, the performance and scalability of these absorbers, predominantly fabricated by the top-down approach, need to be further improved to enable widespread applications. We report a plasmonic absorber which can enable an average measured absorbance of ~99% across the wavelengths from 400 nm to 10 μm, the most efficient and broadband plasmonic absorber reported to date. The absorber is fabricated through self-assembly of metallic nanoparticles onto a nanoporous template by a one-step deposition process. Because of its efficient light absorption, strong field enhancement, and porous structures, which together enable not only efficient solar absorption but also significant local heating and continuous stream flow, plasmonic absorber–based solar steam generation has over 90% efficiency under solar irradiation of only 4-sun intensity (4 kW m−2). The pronounced light absorption effect coupled with the high-throughput self-assembly process could lead toward large-scale manufacturing of other nanophotonic structures and devices. PMID:27152335

Chemical Properties of Brown Carbon Aerosol Generated at the Missoula Fire Sciences Laboratory

NASA Astrophysics Data System (ADS)

Washenfelder, R. A.; Womack, C.; Franchin, A.; Middlebrook, A. M.; Wagner, N.; Manfred, K.

2017-12-01

Aerosol scattering and absorption are still among the largest uncertainties in quantifying radiative forcing. Biomass burning is a major source of light-absorbing carbonaceous aerosol in the United States. These aerosol are generally classified into two categories: black carbon (graphitic-like aerosol that absorbs broadly across the ultraviolet and visible spectral regions) and brown carbon (organic aerosol that absorbs strongly in the ultraviolet and near-visible spectral regions). The composition, volatility, and chemical aging of brown carbon are poorly known, but are important to understanding its radiative effects. We deployed three novel instruments to the Missoula Fire Sciences Laboratory in 2016 to measure brown carbon absorption: a photoacoustic spectrometer, broadband cavity enhanced spectrometer, and particle-into-liquid sampler coupled to a liquid waveguide capillary cell. The instruments sampled from a shared inlet with well-characterized dilution and thermal denuding. We sampled smoke from 32 controlled burns of fuels relevant to western U.S. wildfires. We use these measurements to determine the volatility of water-soluble brown carbon, and compare this to the volatility of water-soluble organic aerosol and total organic aerosol. We further examine the wavelength-dependence of the water-soluble brown carbon absorption as a function of denuder temperature. Together this gives new information about the solubility, volatility, and chemical composition of brown carbon.

Spectrophotometry of six broad absorption line QSOs

NASA Technical Reports Server (NTRS)

Junkkarinen, Vesa T.; Burbidge, E. Margaret; Smith, Harding E.

1987-01-01

Spectrophotometric observations of six broad absorption-line QSOs (BALQSOs) are presented. The continua and emission lines are compared with those in the spectra of QSOs without BALs. A statistically significant difference is found in the emission-line intensity ratio for (N V 1240-A)/(C IV 1549-A). The median value of (N V)/(C IV) for the BALQSOs is two to three times the median for QSOs without BALs. The absorption features of the BALQSOs are described, and the column densities and limits on the ionization structure of the BAL region are discussed. If the dominant ionization mechanism is photoionization, then it is likely that either the ionizing spectrum is steep or the abundances are considerably different from solar. Collisional ionization may be a significant factor, but it cannot totally dominate the ionization rate.

Sonic spectrometer and treatment system

DOEpatents

Slomka, B.J.

1997-06-03

A novel system and method is developed for treating an object with sonic waveforms. A traveling broad-band sonic waveform containing a broad-band of sonic frequencies is radiated at the object. A traveling reflected sonic waveform containing sonic frequencies reflected by the object is received in response to the traveling broad-band sonic waveform. A traveling transmitted sonic waveform containing sonic frequencies transmitted through the object is also received in response to the traveling broad-band sonic waveform. In a resonance mode, the frequency spectra of the broad-band and reflected sonic waveforms is analyzed so as to select one or more sonic frequencies that cause the object to resonate. An electrical resonance treatment sonic waveform containing the sonic frequencies that cause the object to resonate is then radiated at the object so as to treat the object. In an absorption mode, the frequency spectra of the electrical broad-band, reflected, and transmitted sonic waveforms is compared so as to select one or more sonic frequencies that are absorbed by the object. An electrical absorption treatment sonic waveform containing the sonic frequencies that are absorbed by the object is then radiated at the object so as to treat the object. 1 fig.

Sonic spectrometer and treatment system

DOEpatents

Slomka, Bogdan J.

1997-06-03

A novel system and method for treating an object with sonic waveforms. A traveling broad-band sonic waveform containing a broad-band of sonic frequencies is radiated at the object. A traveling reflected sonic waveform containing sonic frequencies reflected by the object is received in response to the traveling broad-band sonic waveform. A traveling transmitted sonic waveform containing sonic frequencies transmitted through the object is also received in response to the traveling broad-band sonic waveform. In a resonance mode, the frequency spectra of the broad-band and reflected sonic waveforms is analyzed so as to select one or more sonic frequencies that cause the object to resonate. An electrical resonance treatment sonic waveform containing the sonic frequencies that cause the object to resonate is then radiated at the object so as to treat the object. In an absorption mode, the frequency spectra of the electrical broad-band, reflected, and transmitted sonic waveforms is compared so as to select one or more sonic frequencies that are absorbed by the object. An electrical absorption treatment sonic waveform containing the sonic frequencies that are absorbed by the object is then radiated at the object so as to treat the object.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reddy, N.R.S.; Kolaczkowski, S.V.; Small, G.J.

Reddy et al. (Science, accepted) have reported persistent, nonphotochemical hole-burned (NPHB) spectra for the Q[sub y] states of the reaction center of Rhodopseudomonas viridis. The photoinduced structural transformation was shown to be highly localized on the special pair. This transformation leads to a red shift of the special pair's lowest-energy absorption band, P960, of 150 cm[sup [minus]1] and a comparable blue shift for a state at 850 nm, which, as a consequence, could be assigned as being most closely associated with the upper dimer component. Additional experimental results are presented here together with a theoretical analysis of the extent tomore » which the NPHB spectra provide information on the contribution from the bacteriochlorophyll monomers of the special pair to the Q[sub y] states that absorb higher in energy than P960. Structured photochemical hole-burned (PHB) spectra of P960 are also presented that underscore the importance of strong electron-phonon coupling from a broad distribution of modes with a mean frequency of 30 cm[sup [minus]1] for an understanding of the P960 absorption profile. These spectra also identify the zero-phonon hole of the strongly damped special pair marker mode (145 cm[sup [minus]1]) and its associated phonon sideband structure. Calculated spectra are presented which are in good agreement with the experimental PHB spectra. 30 refs., 6 figs., 4 tabs.« less

Optical, structural and thermal properties of sodium metaphosphate glasses containing Bi2O3 with interactions of gamma rays

NASA Astrophysics Data System (ADS)

Marzouk, M. A.; ElBatal, F. H.; ElBadry, K. M.; ElBatal, H. A.

2017-01-01

Sodium metaphosphate glasses with successive increasing added Bi2O3 contents (5-40%) were prepared to improve their chemical stability and increase their optical and thermal properties through the additional building BiO6 and BiO3 units. The optical spectrum of the base metaphosphate glass reveals strong UV absorption due to the presence of trace iron (Fe3 +) ions present as impurities. Glasses containing additional 5, 7.5 and 10% Bi2O3 show further band around 406 nm which can be related to absorption of Bi3 + ions. With increasing the Bi2O3 content, this near visible band is observed to disappear indicating peculiar behavior needing further work. Gamma irradiation causes only minor changes in the position of the strong UV peaks but an obvious induced visible broad band centered at 452-460 nm in the base and Bi2O3 containing glasses. This induced band is related to the generation of phosphorus oxygen hole center or non bridging oxygen hole center as revealed by various authors. FTIR results reveal characteristic vibrational bands due to phosphate groups and with the addition of Bi2O3, some interference of Bisbnd O vibrational units are expected. Gamma irradiation causes limited changes in the IR spectra due to suggested shielding effect of the heavy metal oxide Bi2O3.

The Physical Constraints on a New LoBAL QSO at z = 4.82

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yi, Weimin; Bai, Jin-Ming; Green, Richard

Very few low-ionization broad absorption line (LoBAL) QSOs have been found at high redshifts, to date. One high-redshift LoBAL QSO, J0122+1216, was recently discovered by the Lijiang 2.4 m Telescope, with an initial redshift determination of 4.76. Aiming to investigate its physical properties, we carried out follow-up observations in the optical and near-IR spectroscopy. Near-IR spectra from UKIRT and P200 confirm that it is a LoBAL, with a new redshift determination of 4.82 ± 0.01 based on the Mg ii emission-line. The new Mg ii redshift determination reveals strong blueshifts and asymmetry of the high-ionization emission lines. We estimate amore » black hole mass of ∼2.3 × 10{sup 9} M {sub ⊙} and Eddington ratio of ∼1.0 according to the empirical Mg ii-based single-epoch relation and bolometric correction factor. It is possible that strong outflows are the result of an extreme quasar environment driven by the high Eddington ratio. A lower limit on the outflowing kinetic power (>0.9% L {sub Edd}) is derived from both emission and absorption lines, indicating that these outflows play a significant role in the feedback process that regulates the growth of its black hole, as well as host galaxy evolution.« less

ASASSN-15LH: A SUPERLUMINOUS ULTRAVIOLET REBRIGHTENING OBSERVED BY SWIFT AND HUBBLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Peter J.; Yang, Yi; Wang, Lifan

2016-09-01

We present and discuss ultraviolet and optical photometry from the Ultraviolet/Optical Telescope, X-ray limits from the X-Ray Telescope on Swift, and imaging polarimetry and ultraviolet/optical spectroscopy with the Hubble Space Telescope , all from observations of ASASSN-15lh. It has been classified as a hydrogen-poor superluminous supernova (SLSN I), making it more luminous than any other supernova observed. ASASSN-15lh is not detected in the X-rays in individual or co-added observations. From the polarimetry we determine that the explosion was only mildly asymmetric. We find the flux of ASASSN-15lh to increase strongly into the ultraviolet, with an ultraviolet luminosity 100 times greatermore » than the hydrogen-rich, ultraviolet-bright SLSN II SN 2008es. We find that objects as bright as ASASSN-15lh are easily detectable beyond redshifts of ∼4 with the single-visit depths planned for the Large Synoptic Survey Telescope. Deep near-infrared surveys could detect such objects past a redshift of ∼20, enabling a probe of the earliest star formation. A late rebrightening—most prominent at shorter wavelengths—is seen about two months after the peak brightness, which is itself as bright as an SLSN. The ultraviolet spectra during the rebrightening are dominated by the continuum without the broad absorption or emission lines seen in SLSNe or tidal disruption events (TDEs) and the early optical spectra of ASASSN-15lh. Our spectra show no strong hydrogen emission, showing only Ly α absorption near the redshift previously found by optical absorption lines of the presumed host. The properties of ASASSN-15lh are extreme when compared to either SLSNe or TDEs.« less

Weak Hard X-Ray Emission from Two Broad Absorption Line Quasars Observed with NuStar: Compton-Thick Absorption or Intrinsic X-Ray Weakness?

NASA Technical Reports Server (NTRS)

Luo, B.; Brandt, W. N.; Alexander, D. M.; Harrison, F. A.; Stern, D.; Bauer, F. E.; Boggs, S. E.; Christensen, F. E.; Comastri, A.; Craig, W. W..;

Dependence of the Broad Absorption Line Quasar Fraction on Radio Luminosity

NASA Astrophysics Data System (ADS)

Shankar, Francesco; Dai, Xinyu; Sivakoff, Gregory R.

2008-11-01

We find that the fraction of classical broad absorption line quasars (BALQSOs) among the FIRST radio sources in the Sloan Data Release 3, is 20.5+ 7.3-5.9% at the faintest radio powers detected (L1.4 GHz ~ 1032 erg s-1), and rapidly drops to lesssim8% at L1.4 GHz ~ 3 × 1033 erg s-1. Similarly, adopting the broader absorption index (AI) definition of Trump et al., we find the fraction of radio BALQSOs to be 44+ 8.1-7.8%, reducing to 23.1+ 7.3-6.1% at high luminosities. While the high fraction at low radio power is consistent with the recent near-IR estimates by Dai et al., the lower fraction at high radio powers is intriguing and confirms previous claims based on smaller samples. The trend is independent of the redshift range, the optical and radio flux selection limits, or the exact definition of a radio match. We also find that at fixed optical magnitude, the highest bins of radio luminosity are preferentially populated by non-BALQSOs, consistent with the overall trend. We do find, however, that those quasars identified as AI-BALQSOs but not under the classical definition do not show a significant drop in their fraction as a function of radio power, further supporting independent claims that these sources, characterized by lower equivalent width, may represent an independent class from the classical BALQSOs. We find the balnicity index, a measure of the absorption trough in BALQSOs, and the mean maximum wind velocity to be roughly constant at all radio powers. We discuss several plausible physical models which may explain the observed fast drop in the fraction of the classical BALQSOs with increasing radio power, although none is entirely satisfactory. A strictly evolutionary model for the BALQSO and radio emission phases requires a strong fine-tuning to work, while a simple geometric model, although still not capable of explaining polar BALQSOs and the paucity of FRII BALQSOs, is statistically successful in matching the data if part of the apparent radio luminosity function is due to beamed, non-BALQSOs.

Ultraviolet Spectroscopy of Tidal Disruption Flares

NASA Astrophysics Data System (ADS)

Cenko, Stephen B.

2017-08-01

When a star passes within the sphere of disruption of a massive black hole, tidal forces will overcome self-gravity and unbind the star. While approximately half of the stellar debris is ejected at high velocities, the remaining material stays bound to the black hole and accretes, resulting in a luminous, long-lived transient known as a tidal disruption flare (TDF). In addition to serving as unique laboratories for accretion physics,TDFs offer the hope of measuring black hole masses in galaxies much too distant for resolved kinematic studies.In order to realize this potential, we must better understand the detailed processes by which the bound debris circularizes and forms an accretion disk. Spectroscopy is critical to this effort, as emission and absorption line diagnostics provide insight into the location and physical state (velocity, density, composition) of the emitting gas (in analogy with quasars). UV spectra are particularly critical, as most strong atomic features fall in this bandpass, and high-redshift TDF discoveries from LSST will sample rest-frame UV wavelengths.Here I present recent attempts to obtain UV spectra of tidal disruption flares. I describe the UV spectrum of ASASSN-14li, in which we detect three classes of features: narrow absorption from the Milky Way (probably a high-velocity cloud), and narrow absorption and broad (2000-8000 km s-1) emission lines at or near the systemic host velocity. The absorption lines are blueshifted with respect to the emission lines by 250-400 km s-1. Due both to this velocity offset and the lack of common low-ionization features (Mg II, Fe II), we argue these arise from the same absorbing material responsible for the low-velocity outflow discovered at X-ray wavelengths. The broad nuclear emission lines display a remarkable abundance pattern: N III], N IV], and He II are quite prominent, while the common quasar emission lines of C III] and Mg II are weak or entirely absent. Detailed modeling of this spectrum will help elucidate fundamental questions regarding the nature of the emission processes at work in TDFs, while future UV spectroscopy of ASASSN-14li would help to confirm (or refute) the previously proposed connection between TDFs and “N-rich” quasars.

WEAK HARD X-RAY EMISSION FROM TWO BROAD ABSORPTION LINE QUASARS OBSERVED WITH NuSTAR: COMPTON-THICK ABSORPTION OR INTRINSIC X-RAY WEAKNESS?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, B.; Brandt, W. N.; Alexander, D. M.

We present Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray observations of two X-ray weak broad absorption line (BAL) quasars, PG 1004+130 (radio loud) and PG 1700+518 (radio quiet). Many BAL quasars appear X-ray weak, probably due to absorption by the shielding gas between the nucleus and the accretion-disk wind. The two targets are among the optically brightest BAL quasars, yet they are known to be significantly X-ray weak at rest-frame 2-10 keV (16-120 times fainter than typical quasars). We would expect to obtain Almost-Equal-To 400-600 hard X-ray ({approx}> 10 keV) photons with NuSTAR, provided that these photons are not significantlymore » absorbed (N{sub H} {approx}< 10{sup 24} cm{sup -2}). However, both BAL quasars are only detected in the softer NuSTAR bands (e.g., 4-20 keV) but not in its harder bands (e.g., 20-30 keV), suggesting that either the shielding gas is highly Compton-thick or the two targets are intrinsically X-ray weak. We constrain the column densities for both to be N{sub H} Almost-Equal-To 7 Multiplication-Sign 10{sup 24} cm{sup -2} if the weak hard X-ray emission is caused by obscuration from the shielding gas. We discuss a few possibilities for how PG 1004+130 could have Compton-thick shielding gas without strong Fe K{alpha} line emission; dilution from jet-linked X-ray emission is one likely explanation. We also discuss the intrinsic X-ray weakness scenario based on a coronal-quenching model relevant to the shielding gas and disk wind of BAL quasars. Motivated by our NuSTAR results, we perform a Chandra stacking analysis with the Large Bright Quasar Survey BAL quasar sample and place statistical constraints upon the fraction of intrinsically X-ray weak BAL quasars; this fraction is likely 17%-40%.« less

Proton tunneling in low dimensional cesium silicate LDS-1

NASA Astrophysics Data System (ADS)

Matsui, Hiroshi; Iwamoto, Kei; Mochizuki, Dai; Osada, Shimon; Asakura, Yusuke; Kuroda, Kazuyuki

2015-07-01

In low dimensional cesium silicate LDS-1 (monoclinic phase of CsHSi2O5), anomalous infrared absorption bands observed at 93, 155, 1210, and 1220 cm-1 are assigned to the vibrational mode of protons, which contribute to the strong hydrogen bonding between terminal oxygen atoms of silicate chain (O-O distance = 2.45 Å). The integrated absorbance (oscillator strength) for those modes is drastically enhanced at low temperatures. The analysis of integrated absorbance employing two different anharmonic double-minimum potentials makes clear that proton tunneling through the potential barrier yields an energy splitting of the ground state. The absorption bands at 93 and 155 cm-1, which correspond to the different vibrational modes of protons, are attributed to the optical transition between the splitting levels (excitation from the ground state (n = 0) to the first excited state (n = 1)). Moreover, the absorption bands at 1210 and 1220 cm-1 are identified as the optical transition from the ground state (n = 0) to the third excited state (n = 3). Weak Coulomb interactions in between the adjacent protons generate two types of vibrational modes: symmetric mode (93 and 1210 cm-1) and asymmetric mode (155 and 1220 cm-1). The broad absorption at 100-600 cm-1 reveals an emergence of collective mode due to the vibration of silicate chain coupled not only with the local oscillation of Cs+ but also with the proton oscillation relevant to the second excited state (n = 2).

Enhancing absorption in coated semiconductor nanowire/nanorod core-shell arrays using active host matrices

NASA Astrophysics Data System (ADS)

Jule, Leta; Dejene, Francis; Roro, Kittessa

2016-12-01

In the present work, we investigated theoretically and experimentally the interaction of radiation field phenomena interacting with arrays of nanowire/nanorod core-shell embedded in active host matrices. The optical properties of composites are explored including the case when the absorption of propagating wave by dissipative component is completely compensated by amplification in active (lasing) medium. On the basis of more elaborated modeling approach and extended effective medium theory, the effective polarizability and the refractive index of electromagnetic mode dispersion of the core-shell nanowire arrays are derived. ZnS(shell)-coated by sulphidation process on ZnO(shell) nanorod arrays grown on (100) silicon substrate by chemical bath deposition (CBD) has been used for theoretical comparison. Compared with the bare ZnO nanorods, ZnS-coated core/shell nanorods exhibit a strongly reduced ultraviolet (UV) emission and a dramatically enhanced deep level (DL) emission. Obviously, the UV and DL emission peaks are attributed to the emissions of ZnO nanorods within ZnO/ZnS core/shell nanorods. The reduction of UV emission after ZnS coating seems to agree with the charge separation mechanism of type-II band alignment that holes transfer from the core to shell, which would quench the UV emission to a certain extent. Our theoretical calculations and numerical simulation demonstrate that the use of active host (amplifying) medium to compensate absorption at metallic inclusions. Moreover the core-shell nanorod/nanowire arrays create the opportunity for broad band absorption and light harvesting applications.

Resonant absorption induced fast melting studied with mid-IR QCLs.

PubMed

Lu, Jie; Lv, Yankun; Ji, Youxin; Tang, Xiaoliang; Qi, Zeming; Li, Liangbin

2017-02-01

We demonstrate the use of a pump-probe setup based on two mid-infrared quantum cascade lasers (QCLs) to investigate the melting and crystallization of materials through resonant absorption. A combination of pump and probe beams fulfills the two-color synchronous detection. Furthermore, narrow linewidth advances the accuracy of measurements and the character of broad tuning range of QCLs enables wide applications in various sample and multiple structures. 1-Eicosene was selected as a simple model system to verify the feasibility of this method. A pulsed QCL was tuned to the absorption peak of CH 2 bending vibration at 1467 cm -1 to resonantly heat the sample. The other QCL in continuous mode was tuned to 1643 cm -1 corresponding the C=C stretching vibration to follow the fast melting dynamics. By monitoring the transmission intensity variation of pump and probe beams during pump-probe experiments, the resonant absorption induced fast melting and re-crystallization of 1-Eicosene can be studied. Results show that the thermal effect and melting behaviors strongly depend on the pump wavelength (resonant or non-resonant) and energy, as well as the pump time. The realization and detection of melting and recrystallization can be performed in tens of milliseconds, which improves the time resolution of melting process study based on general mid-infrared spectrum by orders of magnitude. The availability of resonant heating and detections based on mid-infrared QCLs is expected to enable new applications in melting study.

Photoluminescence of transparent glass-ceramics based on ZnO nanocrystals and co-doped with Eu3+, Yb3+ ions

NASA Astrophysics Data System (ADS)

Arzumanyan, Grigory M.; Kuznetsov, Evgeny A.; Zhilin, Aleksandr A.; Dymshits, Olga S.; Shemchuk, Daria V.; Alekseeva, Irina P.; Mudryi, Alexandr V.; Zhivulko, Vadim D.; Borodavchenko, Olga M.

2016-12-01

Glasses of the K2Osbnd ZnOsbnd Al2O3sbnd SiO2 system co-doped with Eu2O3 and Yb2O3 were prepared by the melt-quenching technique. Transparent zincite (ZnO) glass-ceramics were obtained by secondary heat-treatments at 680-860 °C. At 860 °C, traces of Eu oxyapatite appeared in addition to ZnO nanocrystals. The average crystal size obtained from the X-ray diffraction data was found to range between 14 and 35 nm. Absorption spectra of the initial glasses are composed of an absorption edge and absorption bands due to electronic transitions of Eu3+ ions. With heat-treatment, the absorption edge pronouncedly shifts to the visible spectral range. The luminescence properties of the glass and glass-ceramics were studied by measuring their excitation and emission spectra at 300, 78, and 4.2 K. Strong red emission of Eu3+ ions dominated by the 5D0-7F2 (612 nm) electric dipole transition was detected. Changes in the luminescence properties of the Eu3+-related excitation and emission bands were observed after heat-treatments at 680 °C and 860 °C. The ZnO nanocrystals showed both broad luminescence (400-850 nm) and free-exciton emission near 3.3 eV at room temperature. The upconversion luminescence spectrum of the initial glass was obtained under excitation of the 976 nm laser source.

3D metamaterial absorber for attomole molecular detection (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tanaka, Takuo; Ishikawa, Atsushi

2016-09-01

3D Metamaterial absorber was used for a background-suppressed surface-enhanced molecular detection technique. By utilizing the resonant coupling of plasmonic modes of a metamaterial absorber and infrared (IR) vibrational modes of a self-assembled monolayer (SAM), attomole level molecular sensitivity was experimentally demonstrated. IR absorption spectroscopy of molecular vibrations is of importance in chemical, material, medical science and so on, since it provides essential information of the molecular structure, composition, and orientation. In the vibrational spectroscopic techniques, in addition to the weak signals from the molecules, strong background degrades the signal-to-noise ratio, and suppression of the background is crucial for the further improvement of the sensitivity. Here, we demonstrate low-background resonant Surface enhanced IR absorption (SEIRA) by using the metamaterial IR absorber that offers significant background suppression as well as plasmonic enhancement. The fabricated metamaterial consisted of 1D array of Au micro-ribbons on a thick Au film separated by a transparent gap layer made of MgF2. The surface structures were designed to exhibit an anomalous IR absorption at 3000 cm-1, which spectrally overlapped with C-H stretching vibrational modes. 16-Mercaptohexadecanoic acid (16-MHDA) was used as a test molecule, which formed a 2-nm thick SAM with their thiol head-group chemisorbed on the Au surface. In the FTIR measurements, the symmetric and asymmetric C-H stretching modes were clearly observed as reflection peaks within a broad plasmonic absorption of the metamaterial.

On the origin of gamma-rays in Fermi blazars: beyondthe broad-line region

NASA Astrophysics Data System (ADS)

Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

2018-07-01

The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the broad-line region (BLR), the so-called BLR external Compton (EC) scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. This result holds also dividing the spectra in high- and low-flux states, and for powerful blazars with large BLR. Only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that (i) EC on BLR photons is disfavoured as the main gamma-ray mechanism, versus IC on IR photons from the torus or synchrotron self-Compton; (ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photon spectrum; and (iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

On the origin of gamma rays in Fermi blazars: beyond the broad line region.

NASA Astrophysics Data System (ADS)

Costamante, L.; Cutini, S.; Tosti, G.; Antolini, E.; Tramacere, A.

2018-05-01

The gamma-ray emission in broad-line blazars is generally explained as inverse Compton (IC) radiation of relativistic electrons in the jet scattering optical-UV photons from the Broad Line Region (BLR), the so-called BLR External Compton scenario. We test this scenario on the Fermi gamma-ray spectra of 106 broad-line blazars detected with the highest significance or largest BLR, by looking for cut-off signatures at high energies compatible with γ-γ interactions with BLR photons. We do not find evidence for the expected BLR absorption. For 2/3 of the sources, we can exclude any significant absorption (τmax < 1), while for the remaining 1/3 the possible absorption is constrained to be 1.5-2 orders of magnitude lower than expected. This result holds also dividing the spectra in high and low-flux states, and for powerful blazars with large BLR. Only 1 object out of 10 seems compatible with substantial attenuation (τmax > 5). We conclude that for 9 out of 10 objects, the jet does not interact with BLR photons. Gamma-rays seem either produced outside the BLR most of the time, or the BLR is ˜100 × larger than given by reverberation mapping. This means that i) External Compton on BLR photons is disfavoured as the main gamma-ray mechanism, vs IC on IR photons from the torus or synchrotron self-Compton; ii) the Fermi gamma-ray spectrum is mostly intrinsic, determined by the interaction of the particle distribution with the seed-photons spectrum; iii) without suppression by the BLR, broad-line blazars can become copious emitters above 100 GeV, as demonstrated by 3C 454.3. We expect the CTA sky to be much richer of broad-line blazars than previously thought.

Semiconducting polymer dot as a highly effective contrast agent for photoacoustic imaging

NASA Astrophysics Data System (ADS)

Yuan, Zhen; Zhang, Jian

2018-02-01

In this study, we developed a novel PIID-DTBT based semiconducting polymer dots (Pdots) that have broad and strong optical absorption in the visible-light region (500 nm - 700 nm). Gold nanoparticles (GNPs) and gold nanorods (GNRs) that have been verified as an excellent photoacoustic contrast agent were compared with Pdots based on photoacoustic imaging method. Both ex vivo and in vivo experiment demonstrated Pdots have a better photoacoustic conversion efficiency at 532 nm than GNPs and similar photoacoustic performance with GNRs at 700 nm at the same mass concentration. Our work demonstrates the great potential of Pdots as a highly effective contrast agent for precise localization of lesions relative to the blood vessels based on photoacoustic tomography imaging.

Carbon dioxide UV laser-induced fluorescence in high-pressure flames

NASA Astrophysics Data System (ADS)

Bessler, W. G.; Schulz, C.; Lee, T.; Jeffries, J. B.; Hanson, R. K.

2003-07-01

Laser-induced fluorescence (LIF) of carbon dioxide is investigated with excitation between 215 and 255 nm with spectrally resolved detection in 5-40 bar premixed CH 4/O 2/Ar and CH 4/air flat-flames at fuel/air ratios between 0.8 and 1.9. The LIF signal consists of a broad (200-450 nm) continuum with a faint superimposed structure, and this signal is absent in similar H 2/O 2/Ar flames. There is strong evidence this signal arises from CO 2, as the signal variations with excitation wavelength, equivalence ratio and flame temperature all correlate with CO 2 absorption cross-sections. The signal is linear with pressure and laser fluence within the investigated ranges.

Broad-band frequency references in the near-infrared: Accurate dual comb spectroscopy of methane and acetylene

NASA Astrophysics Data System (ADS)

Zolot, A. M.; Giorgetta, F. R.; Baumann, E.; Swann, W. C.; Coddington, I.; Newbury, N. R.

2013-03-01

The Doppler-limited spectra of methane between 176 THz and 184 THz (5870-6130 cm-1) and acetylene between 193 THz and 199 THz (6430-6630 cm-1) are acquired via comb-tooth resolved dual comb spectroscopy with frequency accuracy traceable to atomic standards. A least squares analysis of the measured absorbance and phase line shapes provides line center frequencies with absolute accuracy of 0.2 MHz, or less than one thousandth of the room temperature Doppler width. This accuracy is verified through comparison with previous saturated absorption spectroscopy of 37 strong isolated lines of acetylene. For the methane spectrum, the center frequencies of 46 well-isolated strong lines are determined with similar high accuracy, along with the center frequencies for 1107 non-isolated lines at lower accuracy. The measured methane line-center frequencies have an uncertainty comparable to the few available laser heterodyne measurements in this region but span a much larger optical bandwidth, marking the first broad-band measurements of the methane 2ν3 region directly referenced to atomic frequency standards. This study demonstrates the promise of dual comb spectroscopy to obtain high resolution broadband spectra that are comparable to state-of-the-art Fourier-transform spectrometer measurements but with much improved frequency accuracy.Work of the US government, not subject to US copyright.

High-efficiency, broad-band and wide-angle optical absorption in ultra-thin organic photovoltaic devices.

PubMed

Wang, Wenyan; Hao, Yuying; Cui, Yanxia; Tian, Ximin; Zhang, Ye; Wang, Hua; Shi, Fang; Wei, Bin; Huang, Wei

2014-03-10

Metal nanogratings as one of the promising architectures for effective light trapping in organic photovoltaics (OPVs) have been actively studied over the past decade. Here we designed a novel metal nanowall grating with ultra-small period and ultra-high aspect-ratio as the back electrode of the OPV device. Such grating results in the strong hot spot effect in-between the neighboring nanowalls and the localized surface plasmon effect at the corners of nanowalls. These combined effects make the integrated absorption efficiency of light over the wavelength range from 400 to 650 nm in the active layer for the proposed structure, with respect to the equivalent planar structure, increases by 102% at TM polarization and by 36.5% at the TM/TE hybrid polarization, respectively. Moreover, it is noted that the hot spot effect in the proposed structure is more effective for ultra-thin active layers, which is very favorable for the exciton dissociation and charge collection. Therefore such a nanowall grating is expected to improve the overall performance of OPV devices.

InAs/InGaSb Type-II strained layer superlattice IR detectors

NASA Astrophysics Data System (ADS)

Nathan, Vaidya; Anselm, K. Alex; Lin, C. H. T.; Johnson, Jeffrey L.

2002-05-01

InAs/InGaSb type2 strained layer superlattice (SLS) combines the advantages of III-V materials technology with the strong, broad-band absorption, and wavelength tunability of HgCdTe. In fact, the significantly reduced tunneling and Auger recombination rates in SLS compared to those in HgCdTe should enable SLS detectors to outperform HgCdTe. We report the results of our investigation of InAs/InGaSb type2 strained layer superlattices (SLS)for LWIR photovoltaic detector development. We modeled the band structure, and absorption spectrum of SLS's, and achieved good agreement with experimental data. We systematically investigated the SLS growth conditions, resulting in good uniformity, and the elimination of several defects. We designed, developed and evaluated 16x16 array of 13 micron cutoff photovoltaic detectors. Photodiodes with cutoff wavelengths of 13 and 18microns were demonstrated, which are the longest wavelengths demonstrated for this material system. Quantum efficiencies commensurate with the superlattice thickness were demonstrated and verified at AFRL. The electrical properties show excessive leakage current, most likely due to trap-assisted tunneling.

Depth-resolved mid-infrared photothermal imaging of living cells and organisms with submicrometer spatial resolution.

PubMed

Zhang, Delong; Li, Chen; Zhang, Chi; Slipchenko, Mikhail N; Eakins, Gregory; Cheng, Ji-Xin

2016-09-01

Chemical contrast has long been sought for label-free visualization of biomolecules and materials in complex living systems. Although infrared spectroscopic imaging has come a long way in this direction, it is thus far only applicable to dried tissues because of the strong infrared absorption by water. It also suffers from low spatial resolution due to long wavelengths and lacks optical sectioning capabilities. We overcome these limitations through sensing vibrational absorption-induced photothermal effect by a visible laser beam. Our mid-infrared photothermal (MIP) approach reached 10 μM detection sensitivity and submicrometer lateral spatial resolution. This performance has exceeded the diffraction limit of infrared microscopy and allowed label-free three-dimensional chemical imaging of live cells and organisms. Distributions of endogenous lipid and exogenous drug inside single cells were visualized. We further demonstrated in vivo MIP imaging of lipids and proteins in Caenorhabditis elegans . The reported MIP imaging technology promises broad applications from monitoring metabolic activities to high-resolution mapping of drug molecules in living systems, which are beyond the reach of current infrared microscopy.

Constraining physical parameters of ultra-fast outflows in PDS 456 with Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Hagino, K.; Odaka, H.; Done, C.; Gandhi, P.; Takahashi, T.

2014-07-01

Deep absorption lines with extremely high velocity of ˜0.3c observed in PDS 456 spectra strongly indicate the existence of ultra-fast outflows (UFOs). However, the launching and acceleration mechanisms of UFOs are still uncertain. One possible way to solve this is to constrain physical parameters as a function of distance from the source. In order to study the spatial dependence of parameters, it is essential to adopt 3-dimensional Monte Carlo simulations that treat radiation transfer in arbitrary geometry. We have developed a new simulation code of X-ray radiation reprocessed in AGN outflow. Our code implements radiative transfer in 3-dimensional biconical disk wind geometry, based on Monte Carlo simulation framework called MONACO (Watanabe et al. 2006, Odaka et al. 2011). Our simulations reproduce FeXXV and FeXXVI absorption features seen in the spectra. Also, broad Fe emission lines, which reflects the geometry and viewing angle, is successfully reproduced. By comparing the simulated spectra with Suzaku data, we obtained constraints on physical parameters. We discuss launching and acceleration mechanisms of UFOs in PDS 456 based on our analysis.

Broad NE 8 lambda 774 emission from quasars in the HST-FOS snapshot survey (ABSNAP)

NASA Technical Reports Server (NTRS)

Hamann, Fred; Zuo, Lin; Tytler, David

1995-01-01

We discuss the strength and frequency of broad Ne VIII lambda 774 emission from quasars measured in the Hubble Space Telescope Faint Object Spectrograph (HST-FOS) snapshot survey (Absnap). Five sources in the survey have suitable redshifts (0.86 less than or equal to Z(sub em) less than or equal to 1.31), signal-to-noise ratios and no Lyman limit absorptions. Three of the five sources have a strong broad emission line near 774 A (rest), and the remaining two sources have a less securely measured line near this wavelength. We identify these lines with Ne VIII lambda 774 based on the measured wavelengths and theoretical estimates of various line fluxes (Hamann et al. 1995a). Secure Ne VIII detections occur in both radio-loud and radio-quiet sources. We tentatively conclude that broad Ne VIII lambda 774 emission is common in quasars, with typical strengths between approximately 25% and approximately 200% of O VI lambda 1034. These Ne VIII lambda 774 measurements imply that the broad emission line regions have a much hotter and more highly ionized component than previously recognized. They also suggest that quasar continua have substantial ionizing flux out to energies greater than 207 eV (greater than 15.2 ryd, lambda less than 60 A). Photoionization calculations using standard incident spectra indicate that the Ne VIII emission requires ionization parameters U greater than or = 5, total column densities N(sub H) greater than or = 10(sub 22)/sq cm and covering factors greater than or = 25%. The temperatures could be as high as approximately 10(exp 5) K. If the gas is instead collisionally ionized, strong Ne VIII would imply equilibrium temperatures in the range approximately 400,000 less than or approximately = T(sub e) less than or approximately = 10(exp 6) K. In either case, the highly ionized Ne VIII emission regions would appear as X-ray 'warm absorbers' if they lie along our line of sight to the X-ray continuum source.

Q2122-444: A NAKED ACTIVE GALACTIC NUCLEUS FULLY DRESSED

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gliozzi, M.; Satyapal, S.; Panessa, F.

Based on previous spectral and temporal optical studies, Q2122-444 has been classified as a naked active galactic nucleus (AGN) or true type 2 AGN, that is, an AGN that genuinely lacks a broad-line region (BLR). Its optical spectrum seemed to possess only narrow forbidden emission lines that are typical of type 2 (obscured) AGNs, but the long-term optical light curve, obtained from a monitoring campaign over more than two decades, showed strong variability, apparently ruling out the presence of heavy obscuration. Here we present the results from a {approx}40 ks XMM-Newton observation of Q2122-444 carried out to shed light onmore » the energetics of this enigmatic AGN. The X-ray analysis was complemented with Australia Telescope Compact Array radio data to assess the possible presence of a jet, and with new NTT/EFOSC2 optical spectroscopic data to verify the actual absence of a BLR. The higher-quality optical data revealed the presence of strong and broad Balmer lines that are at odds with the previous spectral classification of this AGN. The lack of detection of radio emission rules out the presence of a jet. The X-ray data combined with simultaneous UV observations carried out by the Optical Monitor (OM) aboard XMM-Newton confirm that Q2122-444 is a typical type 1 AGN without any significant intrinsic absorption. New estimates of the black hole mass independently obtained from the broad Balmer lines and from a new scaling technique based on X-ray spectral data suggest that Q2122-444 is accreting at a relatively high rate in Eddington units.« less

VNIR spectral features observed by the Mars Exploration Rover Opportunity in hematite-bearing materials at Meridiani Planum

NASA Astrophysics Data System (ADS)

Farrand, W. H.; Bell, J. F.; Morris, R. V.; Joliff, B. L.; Squyres, S. W.; Souza, P. A.

2004-12-01

The Mars Exploration Rover Opportunity was sent to Meridiani Planum based largely on MGS TES spectroscopic evidence of a large surface exposure of coarse grained gray hematite. The presence of hematite at Meridiani Planum has been confirmed through thermal infrared spectroscopy by the rover's Mini-TES instrument and by in-situ measurements by its Moessbauer (MB) spectrometer. Several types of hematite, as expressed by differences in MB spectral parameters, have been associated with various rocks and soils examined in Eagle crater and on the surrounding plains. The host materials include the small spherules (informally known as "blueberries") littering the floor of Eagle crater and the plains of Meridiani, the outcrop rock itself, specific types of soils, and two measurements on unique rocks in the Shoemaker's Patio area of Eagle crater. At the visible to near infrared (VNIR) wavelengths covered by the rover's multispectral Panoramic camera (Pancam), gray hematite is spectrally neutral. However, multispectral observations by Pancam of some of these hematite-bearing materials show discernable spectral features. Specifically, portions of the outcrop visible in the walls of Eagle crater display a strong 535 nm absorption feature. This feature resembles a similar feature in laboratory spectra of red hematite, but the characteristic 860 nm absorption of red hematite is either absent or is instead replaced by a longer wavelength absorption centered on Pancam's 900 nm channel. The blueberries display a deep and broad absorption centered on 900 nm and as well as an increase in reflectance in the 1009 nm band. The shape of the absorption feature in the blueberries is consistent with that seen in red hematite, but again the band minimum is displaced to a longer wavelength than would be expected for red hematite. The blueberries also lack the prominent absorption at the shortest wavelengths that would be expected of red hematite. The unique hematite-bearing (or coated) rocks at Shoemaker's Patio lack the very strong 535 nm band depth of other portions of the outcrop but still have a stronger 535 nm feature than most of the outcrop. Interestingly, VNIR spectra more consistent with that expected for red hematite have been found in cuttings released by grinding into outcrop by the rover's Rock Abrasion Tool. The cause of the observed spectral features in the portions of outcrop with strong 535 nm band depths and of the reddish rocks in the Shoemaker's Patio area is believed to be attributable either to red hematite mixed with other Fe3+ - bearing phases (such as jarosite and/or schwertmannite) or, at the longer wavelengths, with Fe2+ - bearing phases (such as pyroxenes). Determination of the nature of these iron-bearing materials will further elucidate the geologic, aqueous and diagenetic history of the rocks at Meridiani Planum.

Discovery of an X-ray Violently Variable Broad Absorption Line Quasar

NASA Technical Reports Server (NTRS)

Ghosh, Kajal K.; Gutierrez, Carlos M.; Punsly, Brian; Chevallier, Loic; Goncalves, Anabela C.

2006-01-01

In this letter, we report on a quasar that is violently variable in the X-rays, XVV. It is also a broad absorption line quasar (BALQSO) that exhibits both high ionization and low ionization UV absorption lines (LoBALQSO). It is very luminous in the X-rays (approximately 10(exp 46) ergs s(sup -l) over the entire X-ray band). Surprisingly, this does not over ionize the LoBAL outflow. The X-rays vary by a factor of two within minutes in the quasar rest frame, which is shorter than 1/30 of the light travel time across a scale length equal to the black hole radius. We concluded that the X-rays are produced in a relativistic jet beamed toward earth in which variations in the Doppler enhancement produce the XVV behavior.

K-shell Photoabsorption of Oxygen Ions

NASA Technical Reports Server (NTRS)

Garcia, J.; Mendoza, C.; Bautista, M. A.; Gorczyca, T. W.; Kallman, T. R.; Palmeri, P.

2005-01-01

The high spectral resolutions of the Chandra and XMM-Newton X-ray observatories have unveiled the useful diagnostic possibilities of oxygen K absorption. To mention a few, strong O VII and O VIII edges are almost ubiquitous in the spectra of Seyfert 1 galaxies which have been used by Lee et al. (2001) to predict of a warm dust absorber along the line of sight; although this conclusion has been criticized in the light of a data reanalysis (SA0 et al. 2003), Steenbrugge et al. (2003) have detected inner-shell transitions of O III-O VI in the spectrum of NGC 5548 that point to a warm absorber that spans three orders of magnitude in ionization parameter. Moreover, Behar et al. (2003) have stressed that, in the case of both Seyfert 1 and Seyfert 2 galaxies, a broad range of oxygen charge states are usually observed along the line of sight that must be fitted simultaneously, and may imply strong density gradients of 2-4 orders of magnitude over short distances.

Direct observation of narrow mid-infrared plasmon linewidths of single metal oxide nanocrystals

DOE PAGES

Johns, Robert W.; Bechtel, Hans A.; Runnerstrom, Evan L.; ...

2016-05-13

Infrared-responsive doped metal oxide nanocrystals are an emerging class of plasmonic materials whose localized surface plasmon resonances (LSPR) can be resonant with molecular vibrations. This presents a distinctive opportunity to manipulate light-matter interactions to redirect chemical or spectroscopic outcomes through the strong local electric fields they generate. Here we report a technique for measuring single nanocrystal absorption spectra of doped metal oxide nanocrystals, revealing significant spectral inhomogeneity in their mid-infrared LSPRs. Our analysis suggests dopant incorporation is heterogeneous beyond expectation based on a statistical distribution of dopants. The broad ensemble linewidths typically observed in these materials result primarily from sammore » ple heterogeneity and not from strong electronic damping associated with lossy plasmonic materials. In fact, single nanocrystal spectra reveal linewidths as narrow as 600 cm -1 in aluminium-doped zinc oxide, a value less than half the ensemble linewidth and markedly less than homogeneous linewidths of gold nanospheres.« less

Synthesis and optical properties of Mg-Al layered double hydroxides precursor powders

NASA Astrophysics Data System (ADS)

Lin, Chia-Hsuan; Chu, Hsueh-Liang; Hwang, Weng-Sing; Wang, Moo-Chin; Ko, Horng-Huey

2017-12-01

The synthesis and optical properties of Mg-Al layered double hydroxide (LDH) precursor powders were investigated using X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution TEM (HRTEM), UV-transmission spectrometer, and fluorescence spectrophotometer. The FT-IR results show that the intense absorption at around 1363-1377 cm-1 can be assigned to the antisymmetric ν3 mode of interlayer carbonate anions because the LDH phase contains some CO32-. The XRD results show that all of the Mg-Al LDH precursor powders contain only a single phase of [Mg0.833Al0.167(OH)2](CO3)0.083.(H2O)0.75 but have broad and weak intensities of peaks. All of Mg-Al LDHs precursor powders before calcination have the same photoluminescence (PL) spectra. Moreover, these spectra were excited at λex = 235 nm, and the broad emission band was in the range 325-650 nm. In the range, there were relatively strong intensity at around 360, 407 and 510 nm, respectively.

Spectral Analysis of the Accretion Flow in NGC 1052 with Suzaku

NASA Technical Reports Server (NTRS)

Brenneman, L. W.; Weaver, K. A.; Kadler, M.; Tueller, J.; Marscher, A.; Ros, E.; Zensus,A.; Kovalev, Y. Y.; Aller, M.; Aller, H.;

A 21 Centimeter Absorber Identified with a Spiral Galaxy: Hubble Space Telescope Faint Object Spectrograph and Wide-Field Camera Observations of 3CR 196

NASA Technical Reports Server (NTRS)

Cohen, Ross D.; Beaver, E. A.; Diplas, Athanassios; Junkkarinen, Vesa T.; Barlow, Thomas A.; Lyons, Ronald W.

1996-01-01

We present imaging and spectroscopy of the quasar 3CR 196 (z(sub e) = 0.871), which has 21 cm and optical absorption at z(sub a) = 0.437. We observed the region of Ly alpha absorption in 3CR 196 at z(sub a) = 0.437 with the Faint Object Spectrograph on the Hubble Space Telescope. This region of the spectrum is complicated because of the presence of a Lyman limit and strong lines from a z(sub a) approx. z(sub e) system. We conclude that there is Ly alpha absorption with an H I column density greater than 2.7 x 10(exp 19) cm(exp -2) and most probably 1.5 x 10(exp 20) cm(exp -2). Based on the existence of the high H I column density along both the optical and radio lines of sight, separated by more than 15 kpc, we conclude that the Ly alpha absorption must arise in a system comparable in size to the gaseous disks of spiral galaxies. A barred spiral galaxy, previously reported as a diffuse object in the recent work of Boisse and Boulade, can be seen near the quasar in an image taken at 0.1 resolution with the Wide Field Planetary Camera 2 on the HST. If this galaxy is at the absorption redshift, the luminosity is approximately L(sub *) and any H I disk should extend in front of the optical quasar and radio lobes of 3CR 196, giving rise to both the Ly alpha and 21 cm absorption. In the z(sub a) approx. z(sub e) system we detect Lyman lines and the Lyman limit, as well as high ion absorption lines of C III, N V, S VI, and O VI. This absorption probably only partially covers the emission-line region. The ionization parameter is approximately 0.1. Conditions in this region may be similar to those in broad absorption line QSOs.

Generation of colour centres in yttria-stabilized zirconia by heavy ion irradiations in the GeV range.

PubMed

Costantini, Jean-Marc; Beuneu, François; Schwartz, Kurt; Trautmann, Christina

2010-08-11

We have studied the colour centre production in yttria-stabilized zirconia (ZrO(2):Y(3 +)) by heavy ion irradiation in the GeV range using on-line UV-visible optical absorption spectroscopy. Experiments were performed with 11.4 MeV amu(-1) (127)Xe, (197)Au, (208)Pb and (238)U ion irradiations at 8 K or room temperature (RT). A broad and asymmetrical absorption band peaked at a wavelength about 500 nm is recorded regardless of the irradiation parameters, in agreement with previous RT irradiations with heavy ions in the 100 MeV range. This band is de-convoluted into two broad Gaussian-shaped bands centred at photon energies about 2.4 and 3.1 eV that are respectively associated with the F(+)-type centres (involving a singly ionized oxygen vacancy, VO· and T centres (i.e. Zr(3+) in a trigonal symmetry) observed by electron paramagnetic resonance (EPR) spectroscopy. In the case of 8 K Au ion irradiation at low fluences, six bands are used at about 1.9, 2.3, 2.7, 3.1 and 4.0 eV. The three bands near 2.0-2.5 eV can be assigned to oxygen divacancies (i.e. F(2)(+) centres). No significant effect of the irradiation temperature is found on the widths of all absorption bands for the same ion and fluence. This is attributed to the inhomogeneous broadening arising from the static disorder due to the native charge-compensating oxygen vacancies. However, the colour centre production yield is strongly enhanced at 8 K with respect to RT. When heating irradiated samples from 8 K to RT, the extra colour centres produced at low temperature do not recover completely to the level of RT irradiation. The latter results are accounted for by an electronically driven defect recovery process.

The quantitative analysis of OH in vesuvianite: a polarized FTIR and SIMS study

NASA Astrophysics Data System (ADS)

Bellatreccia, Fabio; della Ventura, Giancarlo; Ottolini, Luisa; Libowitzky, Eugen; Beran, Anton

2005-05-01

A well-characterized suite of vesuvianite samples from the volcanic ejecta (skarn or syenites) from Latium (Italy) was studied by single-crystal, polarized radiation, Fourier-transform infrared (FTIR) spectroscopy and secondary-ion mass-spectrometry (SIMS). OH-stretching FTIR spectra consist of a rather well-defined triplet of broad bands at higher-frequency (3,700 3,300 cm-1) and a very broad composite absorption below 3,300 cm-1. Measurements with E//c or E⊥c show that all bands are strongly polarized with maximum absorption for E//c. They are in agreement with previous band assignments (Groat et al. Can Mineral 33:609, 1995) to the two O(11) H(1) and O(10) H(2) groups in the structure. Pleochroic measurements with changing direction of the E vector of the incident radiation show that the orientation of the O(11) H(1) dipole is OH∧c~35°, in excellent agreement with the neutron data of Lager et al. (Can Mineral 37:763, 1999). A SIMS-based calibration curve at ~10% rel. accuracy has been worked out and used as reference for the quantitative analysis of H2O in vesuvianite by FTIR. Based on previous SIMS results for silicate minerals (Ottolini and Hawthorne in J Anal At Spectrom 16:1266, 2001; Ottolini et al. in Am Mineral 87:1477, 2002) the SiO2 and FeO content of the matrix were assumed as the major factors to be considered at a first approximation in the selection of the standards for H. The lack of vesuvianite standards for quantitative SIMS analysis of H2O has been here overcome by selecting low-silica elbaite crystals (Ottolini et al. in Am Mineral 87:1477, 2002). The resulting integrated molar absorption FTIR coefficient for vesuvianite is ɛi=100.000±2.000 l mol-1 cm-2. SIMS data for Li, B, F, Sr, Y, Be, Ba REE, U and Th are also provided in the paper.

Are There Intrinsically X-Ray Quiet Quasars

NASA Technical Reports Server (NTRS)

Gallagher, S. C.; Brandt, W. N.; Laor, A.; Elvis, Martin; Mathur, S.; Wills, Beverly J.; Iyomoto, N.; White, Nicholas (Technical Monitor)

2000-01-01

Recent ROSAT studies have identified a significant population of Active Galactic Nuclei (AGN) that are notably faint in soft X-rays relative to their optical fluxes. Are these AGN intrinsically X-ray weak or are they just highly absorbed? Brandt, Laor & Wills have systematically examined the optical and UV spectral properties of a well-defined sample of these soft X-ray weak (SXW) AGN drawn from the Boroson & Green sample of all the Palomar Green AGN 00 with z < 0.5. We present ASCA observations of three of these SXW AGN: PG 1011-040, PG 1535+547 (Mrk 486), and PG 2112+059. In general, our ASCA observations support the intrinsic absorption scenario for explaining soft X-ray weakness; both PG 1535+547 and PG 2112+059 show significant column densities (NH is approximately 10(exp 22) - 10(exp 23)/sq cm) of absorbing gas. Interestingly, PG 1011-040 shows no spectral evidence for X-ray absorption. The weak X-ray emission may result from very strong absorption of a partially covered source, or this AGN may be intrinsically X-ray weak. PG 2112+059 is a Broad Absorption Line (BAL) QSO, and we find it to have the highest X-ray flux known of this class. It shows a typical power-law X-ray continuum above 3 keV; this is the first direct evidence that BAL QSOs indeed have normal X-ray continua underlying their intrinsic absorption. Finally, marked variability between the ROSAT and ASCA observations of PG 1535+547 and PG 2112+059 suggests that the soft X-ray weak designation may be transient, and multi-epoch 0.1-10.0 KeV X-ray observations are required to constrain variability of the absorber and continuum.

Three-wave mixing in conjugated polymer solutions: Two-photon absorption in polydiacetylenes

NASA Astrophysics Data System (ADS)

Chance, R. R.; Shand, M. L.; Hogg, C.; Silbey, R.

1980-10-01

Three-wave-mixing spectroscopy is used to determine the dispersive and absorptive parts of a strongly allowed two-photon transition in a series of polydiacetylene solutions. The data analysis yields the energy, width, symmetry assignment, and oscillator strength for the two-photon transition. The data conclusively demonstrate that strong two-photon absorption is a fundamental property of the polydiacetylene backbone. The remarkably large two-photon absorption coefficients are explained by large oscillator strengths for both transitions involved in the two-photon absorption combined with strong one-photon resonance effects. The experimental results are shown to be consistent with a simple theoretical model for the energies and oscillator strengths of the one- and two-photon-allowed transitions.

Grain size-sensitive viscoelastic relaxation and seismic properties of polycrystalline MgO

NASA Astrophysics Data System (ADS)

Barnhoorn, A.; Jackson, I.; Fitz Gerald, J. D.; Kishimoto, A.; Itatani, K.

2016-07-01

Torsional forced-oscillation experiments on a suite of synthetic MgO polycrystals, of high-purity and average grain sizes of 1-100 µm, reveal strongly viscoelastic behavior at temperatures of 800-1300°C and periods between 1 and 1000 s. The measured shear modulus and associated strain energy dissipation both display monotonic variations with oscillation period, temperature, and grain size. The data for the specimens of intermediate grain size have been fitted to a generalized Burgers creep function model that is also broadly consistent with the results for the most coarse-grained specimen. The mild grain size sensitivity for the relaxation time τL, defining the lower end of the anelastic absorption band, is consistent with the onset of elastically accommodated grain boundary sliding. The upper end of the anelastic absorption band, evident in the highest-temperature data for one specimen only, is associated with the Maxwell relaxation time τM marking the transition toward viscous behavior, conventionally ascribed a stronger grain size sensitivity. Similarly pronounced viscoelastic behavior was observed in complementary torsional microcreep tests, which confirm that the nonelastic strains are mainly recoverable, i.e., anelastic. With an estimated activation volume for the viscoelastic relaxation, the experimentally constrained Burgers model has been extrapolated to the conditions of pressure and temperature prevailing in the Earth's uppermost lower mantle. For a plausible grain size of 10 mm, the predicted dissipation Q-1 ranges from 10-3 to 10-2 for periods of 3-3000 s. Broad consistency with seismological observations suggests that the lower mantle ferropericlase phase might account for much of its observed attenuation.

Communication: Broad manifold of excitonic states in light-harvesting complex 1 promotes efficient unidirectional energy transfer in vivo

NASA Astrophysics Data System (ADS)

Sohail, Sara H.; Dahlberg, Peter D.; Allodi, Marco A.; Massey, Sara C.; Ting, Po-Chieh; Martin, Elizabeth C.; Hunter, C. Neil; Engel, Gregory S.

2017-10-01

In photosynthetic organisms, the pigment-protein complexes that comprise the light-harvesting antenna exhibit complex electronic structures and ultrafast dynamics due to the coupling among the chromophores. Here, we present absorptive two-dimensional (2D) electronic spectra from living cultures of the purple bacterium, Rhodobacter sphaeroides, acquired using gradient assisted photon echo spectroscopy. Diagonal slices through the 2D lineshape of the LH1 stimulated emission/ground state bleach feature reveal a resolvable higher energy population within the B875 manifold. The waiting time evolution of diagonal, horizontal, and vertical slices through the 2D lineshape shows a sub-100 fs intra-complex relaxation as this higher energy population red shifts. The absorption (855 nm) of this higher lying sub-population of B875 before it has red shifted optimizes spectral overlap between the LH1 B875 band and the B850 band of LH2. Access to an energetically broad distribution of excitonic states within B875 offers a mechanism for efficient energy transfer from LH2 to LH1 during photosynthesis while limiting back transfer. Two-dimensional lineshapes reveal a rapid decay in the ground-state bleach/stimulated emission of B875. This signal, identified as a decrease in the dipole strength of a strong transition in LH1 on the red side of the B875 band, is assigned to the rapid localization of an initially delocalized exciton state, a dephasing process that frustrates back transfer from LH1 to LH2.

Design of a graphene-based dual-slot hybrid plasmonic electro-absorption modulator with high-modulation efficiency and broad optical bandwidth for on-chip communication.

PubMed

Wu, Zhongwei; Xu, Yin

2018-04-20

The hybrid plasmonic effect with lower loss and comparable light confinement than surface plasmon polariton opens new avenues for strengthening light-matter interactions with low loss. Here, we propose and numerically analyze a graphene-based electro-absorption modulator (EAM) with high-modulation efficiency and broad optical bandwidth using a dual-slot hybrid plasmonic waveguide (HPW), which consists of a central dual-slot HPW connected with two taper transitions and two additional dual-slot HPWs for coupling it with the input and output silicon nanowires, where graphene layers are located at the bottom and top side of the whole dual-slot HPW region. By combining the huge light enhancement effect of the dual-slot HPW and graphene's tunable conductivity, we obtain a high-modulation efficiency (ME) of 1.76 dB/μm for the graphene-based dual-slot HPW (higher ME of 2.19 dB/μm can also be obtained). Based upon this promising result, we further design a graphene-based hybrid plasmonic EAM, achieving a modulation depth (MD) of 15.95 dB and insertion loss of 1.89 dB @1.55 μm, respectively, in a total length of only 10 μm, where its bandwidth can reach over 500 nm for keeping MD>15  dB; MD can also be improved by slightly increasing the device length or shrinking the waveguide thickness, showing strong advantages for applying it into on-chip high-performance silicon modulators.

Mid-infrared Flare of TDE Candidate PS16dtm: Dust Echo and Implications for the Spectral Evolution

NASA Astrophysics Data System (ADS)

Jiang, Ning; Wang, Tinggui; Yan, Lin; Xiao, Ting; Yang, Chenwei; Dou, Liming; Wang, Huiyuan; Cutri, Roc; Mainzer, Amy

2017-11-01

PS16dtm was classified as a candidate tidal disruption event in a dwarf Seyfert 1 galaxy with a low-mass black hole (˜ {10}6 {M}⊙ ) and has presented various intriguing photometric and spectra characteristics. Using the archival Wide-field Infrared Survey Explorer and the newly released NEOWISE data, we found that PS16dtm is experiencing a mid-infrared (MIR) flare that started ˜11 days before the first optical detection. Interpreting the MIR flare as a dust echo requires close pre-existing dust with a high covering factor and suggests that the optical flare may have brightened slowly for some time before it became bright detectable from the ground. More evidence is given at the later epochs. At the peak of the optical light curve, the new inner radius of the dust torus has grown to a much larger size (I.e., a factor of seven of the initial radius) due to the strong radiation field. At ˜150 days after the first optical detection, the dust temperature has dropped well below the sublimation temperature. Other peculiar spectral features shown by PS16dtm are the transient, prominent Fe II emission lines and outflows indicated by broad absorption lines detected during the optical flare. Our model explains the enhanced Fe II emission from iron that is newly released from the evaporated dust. The observed broad absorption line outflow could be explained by accelerated gas in the dust torus due to the radiation pressure.

A Very Large Array Survey of Polar BAL Quasar Candidates

NASA Astrophysics Data System (ADS)

Olson, Kianna Alexandra; Brotherton, Michael S.; DiPompeo, Michael; Maithil, Jaya

2018-06-01

Polar broad absorption line quasars posses flat radio spectra and jets seen at small angles to the line of sight. Using the VLA we observed twelve polar broad absorption line quasar candidates at L (1.5GHz), C (4.5-5.5GHz), and X (8.5-9.5GHz) bands, and found that their cores display flat spectra. Compared to previous observations in the NVSS and First surveys, the peak flux densities all show significant variation σvar > 3, and brightness temperatures TB ≥ 1012K. Based on these findings, our quasars have the properties expected for objects that posses jets seen nearly pole on.

Synthesis, characterization and evaluation of the photocatalytic performance of Ag-CdMoO{sub 4} solar light driven plasmonic photocatalyst

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adhikari, Rajesh; Malla, Shova; Gyawali, Gobinda

2013-09-01

Graphical abstract: - Highlights: • Ag-CdMoO{sub 4} solar light driven photocatalyst was successfully synthesized. • Photocatalyst exhibited strong absorption in the visible region. • Photocatalytic activity was significantly enhanced. • Enhanced activity was caused by the SPR effect induced by Ag nanoparticles. - Abstract: Ag-CdMoO{sub 4} plasmonic photocatalyst was synthesized in ethanol/water mixture by photo assisted co-precipitation method at room temperature. As synthesized powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analyzer. Photocatalytic activity was evaluated by performing the degradation experiment over methylenemore » blue (MB) and indigo carmine (IC) as model dyes under simulated solar light irradiation. The results revealed that the Ag-CdMoO{sub 4} showed the higher photocatalytic performance as compared to CdMoO{sub 4} nanoparticles. Dispersion of Ag nanoparticles over the surface of CdMoO{sub 4} nanoparticles causes the surface plasmon resonance (SPR) and enhances the broad absorption in the entire visible region of the solar spectrum. Hence, dispersion of Ag nanoparticles over CdMoO{sub 4} nanoparticles could be the better alternative to enhance the absorption of visible light by scheelite crystal family for effective photocatalysis.« less

STIS Observations of the Intrinsic UV Absorption in the Dwarf Seyfert Nucleus of NGC 4395

NASA Astrophysics Data System (ADS)

Kraemer, Steven

2002-07-01

The Sd IV dwarf galaxy NGC 4395 is one of the nearest {d 4.2 Mpc} and least luminous {L_bol 10^41 ergs s^-1} examples of Seyfert 1 galaxies. Furthermore, it is the only known example of an active nucleus within a bulgeless, extreme late-type galaxy. This unique object possesses all of the classic Seyfert 1 properties in miniature, including broad and narrow emission lines and highly variable X-ray emission, presumably powered by a small {few x 10^4 M_odot} black hole. Furthermore, we have discovered evidence for blueshifted, intrinsic absorption lines in the UV {C IV LambdaLambda1548.2, 1550.8}, while X-ray spectra show the presence of bound-free edges from O VII and O VIII. We propose HST/STIS echelle observations to determine the properties {ionization states, column densities, velocity coverages, covering factors} of the intrinsic UV absorbers in NGC 4395. Due to the high covering factor of its narrow-line emission, NGC 4395 offers the best case for testing the connection between the absorbers and the narrow-line region {NLR}. Furthermore, an empirical comparison of its absorption properties with those in higher luminosity active galactic nuclei {AGN} will provide valuable constraints on dynamical models of the absorbers, which make predictions that are strongly dependent on luminosity and/or central black hole mass.

Detailed Spectral Analysis of the 260 ks XMM-Newton Data of 1E 1207.4-5209 and Significance of a 2.1 keV Absorption Feature

NASA Astrophysics Data System (ADS)

Mori, Kaya; Chonko, James C.; Hailey, Charles J.

2005-10-01

We have reanalyzed the 260 ks XMM-Newton observation of 1E 1207.4-5209. There are several significant improvements over previous work. First, a much broader range of physically plausible spectral models was used. Second, we have used a more rigorous statistical analysis. The standard F-distribution was not employed, but rather the exact finite statistics F-distribution was determined by Monte Carlo simulations. This approach was motivated by the recent work of Protassov and coworkers and Freeman and coworkers. They demonstrated that the standard F-distribution is not even asymptotically correct when applied to assess the significance of additional absorption features in a spectrum. With our improved analysis we do not find a third and fourth spectral feature in 1E 1207.4-5209 but only the two broad absorption features previously reported. Two additional statistical tests, one line model dependent and the other line model independent, confirmed our modified F-test analysis. For all physically plausible continuum models in which the weak residuals are strong enough to fit, the residuals occur at the instrument Au M edge. As a sanity check we confirmed that the residuals are consistent in strength and position with the instrument Au M residuals observed in 3C 273.

SimBAL: A Spectral Synthesis Approach to Analyzing Broad Absorption Line Quasar Spectra

NASA Astrophysics Data System (ADS)

Terndrup, Donald M.; Leighly, Karen; Gallagher, Sarah; Richards, Gordon T.

2017-01-01

Broad Absorption Line quasars (BALQSOs) show blueshifted absorption lines in their rest-UV spectra, indicating powerful winds emerging from the central engine. These winds are essential part of quasars: they can carry away angular momentum and thus facilitate accretion through a disk, they can distribute chemically-enriched gas through the intergalactic medium, and they may inject kinetic energy to the host galaxy, influencing its evolution. The traditional method of analyzing BALQSO spectra involves measuring myriad absorption lines, computing the inferred ionic column densities in each feature, and comparing with the output of photonionization models. This method is inefficient and does not handle line blending well. We introduce SimBAL, a spectral synthesis fitting method for BALQSOs, which compares synthetic spectra created from photoionization model results with continuum-normalized observed spectra using Bayesian model calibration. We find that we can obtain an excellent fit to the UV to near-IR spectrum of the low-redshift BALQSO SDSS J0850+4451, including lines from diverse ionization states such as PV, CIII*, SIII, Lyalpha, NV, SiIV, CIV, MgII, and HeI*.

Metamaterial absorber for molecular detection and identification (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tanaka, Takuo

2017-03-01

Metamaterial absorber was used for a background-suppressed surface-enhanced molecular detection technique. By utilizing the resonant coupling between plasmonic modes of a metamaterial absorber and infrared (IR) vibrational modes of a self-assembled monolayer (SAM), attomole level molecular sensitivity was experimentally demonstrated. IR absorption spectroscopy of molecular vibrations is of importance in chemical, material, medical science and so on, since it provides essential information of the molecular structure, composition, and orientation. In the vibrational spectroscopic techniques, in addition to the weak signals from the molecules, strong background degrades the signal-to-noise ratio, and suppression of the background is crucial for the further improvement of the sensitivity. Here, we demonstrate low-background resonant Surface enhanced IR absorption (SEIRA) by using the metamaterial IR absorber that offers significant background suppression as well as plasmonic enhancement. By using mask-less laser lithography technique, metamaterial absorber which consisted of 1D array of Au micro-ribbons on a thick Au film separated by a transparent gap layer made of MgF2 was fabricated. This metamaterial structure was designed to exhibit an anomalous IR absorption at 3000 cm-1, which spectrally overlapped with C-H stretching vibrational modes. 16-Mercaptohexadecanoic acid (16-MHDA) was used as a test molecule, which formed a 2-nm thick SAM with their thiol head-group chemisorbed on the Au surface. In the FTIR measurements, the symmetric and asymmetric C-H stretching modes were clearly observed as reflection peaks within a broad plasmonic absorption of the metamaterial, and 1.8 attomole molecular sensitivity was experimentally demonstrated.

On Local Ionization Equilibrium and Disk Winds in QSOs

NASA Astrophysics Data System (ADS)

Pereyra, Nicolas A.

2014-11-01

We present theoretical C IV λλ1548,1550 absorption line profiles for QSOs calculated assuming the accretion disk wind (ADW) scenario. The results suggest that the multiple absorption troughs seen in many QSOs may be due to the discontinuities in the ion balance of the wind (caused by X-rays), rather than discontinuities in the density/velocity structure. The profiles are calculated from a 2.5-dimensional time-dependent hydrodynamic simulation of a line-driven disk wind for a typical QSO black hole mass, a typical QSO luminosity, and for a standard Shakura-Sunyaev disk. We include the effects of ionizing X-rays originating from within the inner disk radius by assuming that the wind is shielded from the X-rays from a certain viewing angle up to 90° ("edge on"). In the shielded region, we assume constant ionization equilibrium, and thus constant line-force parameters. In the non-shielded region, we assume that both the line-force and the C IV populations are nonexistent. The model can account for P-Cygni absorption troughs (produced at edge on viewing angles), multiple absorption troughs (produced at viewing angles close to the angle that separates the shielded region and the non-shielded region), and for detached absorption troughs (produced at an angle in between the first two absorption line types); that is, the model can account for the general types of broad absorption lines seen in QSOs as a viewing angle effect. The steady nature of ADWs, in turn, may account for the steady nature of the absorption structure observed in multiple-trough broad absorption line QSOs. The model parameters are M bh = 109 M ⊙ and L disk = 1047 erg s-1.

Terahertz circular dichroism spectroscopy of biomolecules

NASA Astrophysics Data System (ADS)

Xu, Jing; Galan, Jhenny; Ramian, Gerald; Savvidis, Pavlos; Scopatz, Anthony; Birge, Robert R.; Allen, S. James; Plaxco, Kevin

2004-02-01

Biopolymers such as proteins, DNA and RNA fold into large, macromolecular chiral structures. As charged macromolecules, they absorb strongly in the terahertz due to large-scale collective vibrational modes; as chiral objects, this absorption should be coupled with significant circular dichroism. Terahertz circular dichroism (TCD) is potentially important as a biospecific sensor, unobscured by spectral features related to abiological material. We have constructed atomistic simulations and elastic continuum models of TCD. These models estimate the magnitude of the TCD and the relation between TCD spectroscopic signatures (zero crossings) and the structure, charge distribution and mechanical properties of biomaterials. A broad band TCD spectrometer based on a polarizing interferometer is developed to explore TCD in biomolecules in aqueous solution. Preliminary results on TCD in lysozyme in water at several terahertz frequencies is presented.

Rotational velocities of newly discovered, low-mass members of the Alpha Persei cluster

NASA Technical Reports Server (NTRS)

Stauffer, John R.; Hartmann, Lee W.; Jones, Burton F.

1989-01-01

About 30 new, low-mass members of the young open cluster Alpha Persei are identified via a proper-motion study and subsequent photometric and spectroscopic observations. Membership in the cluster is confirmed for a number of the fainter proper-motion candidates from Heckman, Dieckvoss, and Kox (1956). Coordinates, finding charts, BVRI photometry, and rotational velocities are provided for most of the stars. At least two of the stars show peculiar H-alpha emission profiles, with weak but very broad emission wings, and relatively narrow absorption reversals. The rotational velocity distribution for low-mass stars in the Alpha Per cluster are compared with recently derived rotational velocity distributions for T Tauri stars, placing strong constraints on the mechanisms for angular momentum loss during pre-main-sequence evolution.

On the dielectric dispersion and absorption in nanosized manganese zinc mixed ferrites.

PubMed

Veena Gopalan, E; Malini, K A; Sakthi Kumar, D; Yoshida, Yasuhiko; Al-Omari, I A; Saravanan, S; Anantharaman, M R

2009-04-08

The temperature and frequency dependence of dielectric permittivity and dielectric loss of nanosized Mn(1-x)Zn(x)Fe(2)O(4) (for x = 0, 0.2, 0.4, 0.6, 0.8, 1) were investigated. The impact of zinc substitution on the dielectric properties of the mixed ferrite is elucidated. Strong dielectric dispersion and broad relaxation were exhibited by Mn(1-x)Zn(x)Fe(2)O(4). The variation of dielectric relaxation time with temperature suggests the involvement of multiple relaxation processes. Cole-Cole plots were employed as an effective tool for studying the observed phenomenon. The activation energies were calculated from relaxation peaks and Cole-Cole plots and found to be consistent with each other and indicative of a polaron conduction.

Emergence of Very Broad Infrared Absorption Band By Hyperdoping of Silicon with Chalcogens

DTIC Science & Technology

2013-06-03

measured by Hall effect in Ref. 9 (crosses) as functions of implanted sulfur dose. (c) Calculated reflectivity by Kramers- Kronig transformation of the...MIR band is small enough, this assumption is reasonable according to the Kramers- Kronig relationship between optical absorption and reflectivity...calculated by a Kramers- Kronig transformation of the absorption spectrum shown in Fig. 1(a) and the results are shown in Fig. 1(c). However, the a value

Optical, structural and thermal properties of sodium metaphosphate glasses containing Bi2O3 with interactions of gamma rays.

PubMed

Marzouk, M A; ElBatal, F H; ElBadry, K M; ElBatal, H A

2017-01-15

Sodium metaphosphate glasses with successive increasing added Bi 2 O 3 contents (5-40%) were prepared to improve their chemical stability and increase their optical and thermal properties through the additional building BiO 6 and BiO 3 units. The optical spectrum of the base metaphosphate glass reveals strong UV absorption due to the presence of trace iron (Fe 3+ ) ions present as impurities. Glasses containing additional 5, 7.5 and 10% Bi 2 O 3 show further band around 406nm which can be related to absorption of Bi 3+ ions. With increasing the Bi 2 O 3 content, this near visible band is observed to disappear indicating peculiar behavior needing further work. Gamma irradiation causes only minor changes in the position of the strong UV peaks but an obvious induced visible broad band centered at 452-460nm in the base and Bi 2 O 3 containing glasses. This induced band is related to the generation of phosphorus oxygen hole center or non bridging oxygen hole center as revealed by various authors. FTIR results reveal characteristic vibrational bands due to phosphate groups and with the addition of Bi 2 O 3 , some interference of BiO vibrational units are expected. Gamma irradiation causes limited changes in the IR spectra due to suggested shielding effect of the heavy metal oxide Bi 2 O 3 . Copyright © 2016 Elsevier B.V. All rights reserved.

Theoretical Prediction of Si 2–Si 33 Absorption Spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Li -Zhen; Lu, Wen -Cai; Qin, Wei

Here, the optical absorption spectra of Si 2–Si 33 clusters were systematically studied by a time-dependent density functional theory approach. The calculations revealed that the absorption spectrum becomes significantly broad with increasing cluster size, stretching from ultraviolet to the infrared region. The absorption spectra are closely related to the structural motifs. With increasing cluster size, the absorption intensity of cage structures gradually increases, but the absorption curves of the prolate and the Y-shaped structures are very sensitive to cluster size. If the transition energy reaches ~12 eV, it is noted that all the clusters have remarkable absorption in deep ultravioletmore » region of 100–200 nm, and the maximum absorption intensity is ~100 times that in the visible region. Further, the optical responses to doping in the Si clusters were studied.« less

Theoretical Prediction of Si 2–Si 33 Absorption Spectra

DOE PAGES

Zhao, Li -Zhen; Lu, Wen -Cai; Qin, Wei; ...

2017-07-07

Here, the optical absorption spectra of Si 2–Si 33 clusters were systematically studied by a time-dependent density functional theory approach. The calculations revealed that the absorption spectrum becomes significantly broad with increasing cluster size, stretching from ultraviolet to the infrared region. The absorption spectra are closely related to the structural motifs. With increasing cluster size, the absorption intensity of cage structures gradually increases, but the absorption curves of the prolate and the Y-shaped structures are very sensitive to cluster size. If the transition energy reaches ~12 eV, it is noted that all the clusters have remarkable absorption in deep ultravioletmore » region of 100–200 nm, and the maximum absorption intensity is ~100 times that in the visible region. Further, the optical responses to doping in the Si clusters were studied.« less

Silver nanocube aggregation gradient materials in search for total internal reflection with high phase sensitivity

NASA Astrophysics Data System (ADS)

König, Tobias A. F.; Ledin, Petr A.; Russell, Michael; Geldmeier, Jeffrey A.; Mahmoud, Mahmoud. A.; El-Sayed, Mostafa A.; Tsukruk, Vladimir V.

2015-03-01

We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging.We fabricated monolayer coatings of a silver nanocube aggregation to create a step-wise optical strip by applying different surface pressures during slow Langmuir-Blodgett deposition. The varying amount of randomly distributed nanocube aggregates with different surface coverages in gradient manner due to changes in surface pressure allows for continuous control of the polarization sensitive absorption of the incoming light over a broad optical spectrum. Optical characterization under total internal reflection conditions combined with electromagnetic simulations reveal that the broadband light absorption depends on the relative orientation of the nanoparticles to the polarization of the incoming light. By using computer simulations, we found that the electric field vector of the s-polarized light interacts with the different types of silver nanocube aggregations to excite different plasmonic resonances. The s-polarization shows dramatic changes of the plasmonic resonances at different angles of incidence (shift of 64 nm per 10° angle of incidence). With a low surface nanocube coverage (from 5% to 20%), we observed a polarization-selective high absorption of 80% (with an average 75%) of the incoming light over a broad optical range in the visible region from 400 nm to 700 nm. This large-area gradient material with location-dependent optical properties can be of particular interest for broadband light absorption, phase-sensitive sensors, and imaging. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06430e

Search for correlated UV and x ray absorption of NGC 3516

NASA Technical Reports Server (NTRS)

Martin, Christopher; Halpern, Jules P.; Kolman, Michiel

1991-01-01

NGC 3516, a low-luminosity Seyfert galaxy, is one of a small fraction of Seyfert galaxies that exhibit broad absorption in a resonance line. In order to determine whether the UV and x ray absorption in NGC 3516 are related, 5 IUE observations were obtained, quasi-simultaneously with 4 Ginga observations. The results are presented and discussed. The following subject areas are covered: short-term UV variability; emission lines; galactic absorption lines; the C IV, N V, and Si IV absorption features; lower limit on the carbon column density; estimate of the distance from the absorber to the continuum source; variability in the continuum and absorption; a comparison with BAL QSO's; and the x ray-UV connection.

Individual and collective modes of surface magnetoplasmon in thiolate-protected silver nanoparticles studied by MCD spectroscopy

NASA Astrophysics Data System (ADS)

Yao, Hiroshi; Shiratsu, Taisuke

2016-05-01

Large magneto-optical (MO) responses at the energy of localized surface plasmon resonance (LSPR), namely, surface magnetoplasmons, are demonstrated for the first time in thiolate-protected silver nanoparticles with magnetic circular dichroism (MCD) spectroscopy. The samples examined are decanethiol (DT)-, azobenzenethiol (ABT)-, and ABT/DT mixed-monolayer-protected Ag nanoparticles. ABT-protected Ag nanoparticles are somewhat aggregated and thus exhibit a broad, collective mode of plasmonic absorption, whereas other samples with highly-dispersed nanoparticles show an individual mode of LSPR absorption. In all Ag nanoparticles, a derivative-like MCD signal is observed under an applied magnetic field of 1.6 T, which can be explained in terms of two circular modes of magnetoplasmon caused by the increase (or decrease) in the Lorentz force imparted on the free electrons that oscillate in the left (or right) circular orbits in the nanosphere. For the Ag nanoparticles exhibiting an individual LSPR mode, in particular, simultaneous deconvolution analysis of UV-vis absorption and MCD spectra reveal that (i) the amplitude of the magnetoplasmonic component with lower frequency (ω-), resulting from the reduction in the confinement strength of collective electrons by the Lorentz force, is stronger than that with a higher frequency (ω+) (ii) the accurate shift or cyclotron frequency between two magnetoplasmonic modes (ωc = ω+ - ω-) is size-dependent, and presents a very large value with implications for the apparent enhancement of the local magnetic-field in the Ag nanoparticles. These results strongly suggest that the Ag-thiolate layer or Ag-S bonding on the nanoparticle surface plays a significant role in the MO enhancement.Large magneto-optical (MO) responses at the energy of localized surface plasmon resonance (LSPR), namely, surface magnetoplasmons, are demonstrated for the first time in thiolate-protected silver nanoparticles with magnetic circular dichroism (MCD) spectroscopy. The samples examined are decanethiol (DT)-, azobenzenethiol (ABT)-, and ABT/DT mixed-monolayer-protected Ag nanoparticles. ABT-protected Ag nanoparticles are somewhat aggregated and thus exhibit a broad, collective mode of plasmonic absorption, whereas other samples with highly-dispersed nanoparticles show an individual mode of LSPR absorption. In all Ag nanoparticles, a derivative-like MCD signal is observed under an applied magnetic field of 1.6 T, which can be explained in terms of two circular modes of magnetoplasmon caused by the increase (or decrease) in the Lorentz force imparted on the free electrons that oscillate in the left (or right) circular orbits in the nanosphere. For the Ag nanoparticles exhibiting an individual LSPR mode, in particular, simultaneous deconvolution analysis of UV-vis absorption and MCD spectra reveal that (i) the amplitude of the magnetoplasmonic component with lower frequency (ω-), resulting from the reduction in the confinement strength of collective electrons by the Lorentz force, is stronger than that with a higher frequency (ω+) (ii) the accurate shift or cyclotron frequency between two magnetoplasmonic modes (ωc = ω+ - ω-) is size-dependent, and presents a very large value with implications for the apparent enhancement of the local magnetic-field in the Ag nanoparticles. These results strongly suggest that the Ag-thiolate layer or Ag-S bonding on the nanoparticle surface plays a significant role in the MO enhancement. Electronic supplementary information (ESI) available: EDX spectroscopic analysis of various Ag nanoparticle samples; MCD signals normalized to absorbance for the Ag(DT)L and Ag(DT)S samples; deconvolution of UV-vis absorption and MCD spectra using three Lorentzian components; IR spectral changes upon photoisomerization; thermal cis-to-trans relaxation of azobenzene in the Ag(ABT) sample; UV-vis absorption spectra of Ag nanoparticle samples in the presence/absence of a magnetic field of 1.6 T. See DOI: 10.1039/c6nr00631k

Optical reading of field-effect transistors by phase-space absorption quenching in a single InGaAs quantum well conducting channel

NASA Astrophysics Data System (ADS)

Chemla, D. S.; Bar-Joseph, I.; Klingshirn, C.; Miller, D. A. B.; Kuo, J. M.

1987-03-01

Absorption switching in a semiconductor quantum well by electrically varying the charge density in the quantum well conducting channel of a selectively doped heterostructure transistor is reported for the first time. The phase-space absorption quenching (PAQ) is observed at room temperature in an InGaAs/InAlAs grown on InP FET, and it shows large absorption coefficient changes with relatively broad spectral bandwidth. This PAQ is large enough to be used for direct optical determination of the logic state of the FET.

Detection and monitoring of H2O and CO2 ice clouds on Mars

USGS Publications Warehouse

Bell, J.F.; Calvin, W.M.; Ockert-Bell, M. E.; Crisp, D.; Pollack, James B.; Spencer, J.

1996-01-01

We have developed an observational scheme for the detection and discrimination of Mars atmospheric H2O and CO2 clouds using ground-based instruments in the near infrared. We report the results of our cloud detection and characterization study using Mars near IR images obtained during the 1990 and 1993 oppositions. We focused on specific wavelengths that have the potential, based on previous laboratory studies of H2O and CO2 ices, of yielding the greatest degree of cloud detectability and compositional discriminability. We have detected and mapped absorption features at some of these wavelengths in both the northern and southern polar regions of Mars. Compositional information on the nature of these absorption features was derived from comparisons with laboratory ice spectra and with a simplified radiative transfer model of a CO2 ice cloud overlying a bright surface. Our results indicate that both H2O and CO2 ices can be detected and distinguished in the polar hood clouds. The region near 3.00 ??m is most useful for the detection of water ice clouds because there is a strong H2O ice absorption at this wavelength but only a weak CO2 ice band. The region near 3.33 ??m is most useful for the detection of CO2 ice clouds because there is a strong, relatively narrow CO2 ice band at this wavelength but only broad "continuum" H2O ice absorption. Weaker features near 2.30 ??m could arise from CO2 ice at coarse grain sizes, or surface/dust minerals. Narrow features near 2.00 ??m, which could potentially be very diagnostic of CO2 ice clouds, suffer from contamination by Mars atmospheric CO2 absorptions and are difficult to interpret because of the rather poor knowledge of surface elevation at high latitudes. These results indicate that future ground-based, Earth-orbital, and spacecraft studies over a more extended span of the seasonal cycle should yield substantial information on the style and timing of volatile transport on Mars, as well as a more detailed understanding of the role of CO2 condensation in the polar heat budget. Copyright 1996 by the American Geophysical Union.

GHRS observations of cool, low-gravity stars. 1: The far-ultraviolet spectrum of alpha Orionis (M2 Iab)

NASA Technical Reports Server (NTRS)

Carpenter, Kenneth G.; Robinson, Richard D.; Wahlgren, Glenn M.; Linsky, Jeffrey L.; Brown, Alexander

1994-01-01

We present far-UV (1200-1930 A) observations of the prototypical red supergiant star alpha Ori, obtained with the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). The observations, obtained in both low- (G140L) and medium- (G160/200M) resolution modes, unamibiguously confirm that the UV 'continuum' tentatively seen with (IUE) is in fact a true continuum and is not due to a blend of numerous faint emission features or scattering inside the IUE spectrograph. This continuum appears to originate in the chromospheric of the star at temperatures ranging from 3000-5000 K, and we argue that it is not related to previously reported putative companions or to bright spots on the stellar disk. Its stellar origin is further confirmed by overlying atomic and molecular absorptions from the chromosphere and circumstellar shell. The dominant structure in this spectral region is due to nine strong, broad absorption bands of the fourth-positive A-X system of CO, superposed on this continuum in the 1300-1600 A region. Modeling of this CO absorption indicates that it originates in the circumstellar shell in material characterized by T = 500 K, N(CO) = 1.0 x 10(exp 18) per sq cm, and V(sub turb) = 5.0 km per sec. The numerous chromospheric emission features are attributed mostly to fluorescent lines of Fe II and Cr II (both pumped by Lyman Alpha) and S I lines, plus a few lines of O I, C I, and Si II. The O I and C I UV 2 multiplets are very deficient in flux, compared to both the flux observed in lines originating from common upper levels but with markedly weaker intrinsic strength (i.e., O I UV 146 and C I UV 32) and to the UV 2 line fluxes seen in other cool, less luminous stars. This deficiency appears to be caused by strong self-absorption of these resonance lines in the circumstellar shell and/or upper chromosphere of alpha Ori. Atomic absorption features, primarily due to C I and Fe II are clearly seen in the G160M spectrum centered near 1655 A. These Fe II features are formed at temperatures that can occur only in the chromosphere of the star and are clearly not photospheric or circumstellar in origin.

The Gaseous Environments of Quasars: Outflows, Feedback & Cold Mode Accretion

NASA Astrophysics Data System (ADS)

Chen, Chen; Hamann, Fred

2018-06-01

The early stages of massive galaxy evolution can involve galaxy-scale outflows driven by a starburst or a central quasar and cold-mode accretion (infall) that adds to the mass buildup in the galaxies. I will describe three related studies that use quasar absorption lines to measure outflows, infall, and the general gaseous environments of quasars across a range of spatial scales. The three studies are: 1) High-resolution spectroscopy with Keck-HIRES and VLT-UVES to study associated absorption lines (AALs) that have redshifts greater than the emission redshifts indicating infall and/or rich multi-component AAL complexes that might be interstellar clouds in the host galaxies that have been shredded and dispersed by a fast unseen quasar-driven wind. The data provide strong constraints on the gas kinematics, spatial structure, column densities, metallicities, and energetics. 2) A complete inventory of high-velocity CIV 1548,1550 mini-BAL outflows in quasars using high-resolution high signal-to-noise spectra in the public VLT-UVES and Keck-HIRES archives. This sensitive mini-BAL survey fills an important niche between previous work on narrow absorption lines (NALs) and the much-studied broad absorption lines (BALs) to build a more complete picture of quasar outflows. I will report of the mini-BAL statistics, the diversity of lines detected, and some tests for correlations with the quasar properties. We find, for example, that mini-BALs at v > 4000 km/s in at least 10% of 511 quasars studied, including 1% at v > 0.1 c. Finally, 3) Use the much larger database of NALs measured in 262,449 BOSS quasars by York et al. (in prep.) to study their potential relationships to the quasars and, specifically, their origins in quasar outflows. This involves primarily comparisons of the incidence and properties of NALs at different velocity shifts to other measured properties of the quasars such as BAL outflows, emission line characteristics, radio-loudness, and red colors. We find, for example, that the extreme high-velocity NALs (0.1 ‑ 0.2c) correlate strongly with AALs, indicating that a significant fraction of these NALs is ejected from the quasars.

IUE detector saturation and the new 2800 A absorption feature 'discovered' by Karim, Hoyle, and Wickramasinghe

NASA Astrophysics Data System (ADS)

Savage, B. D.; Sitko, M. L.

1984-03-01

The 2800 A feature of Karim et al. (1983) is shown to be the result of IUE detector saturation effects in overexposed spectra. A properly exposed spectrum and an overexposed one are shown. The latter shows a broad absorption peak at 2800 A while the former does not.

CuTaS 3 : Intermetal d–d Transitions Enable High Solar Absorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Heo, Jaeseok; Yu, Liping; Altschul, Emmeline

To realize the fundamental limits of photovoltaic device efficiency, solar absorbers must exhibit strong absorption and abrupt absorption onsets. Ideally, onsets to maximum absorption (a > 105 cm-1) occur over a few tenths of an electronvolt. First-principles calculations predict CuTaS3 represents a potentially new class of materials with such absorption characteristics. Narrow metallic d bands in both the initial and final states present high joint densities of states and, therefore, strong absorption. Specifically, a mixture of metal d (Cu1+, d10) and S p characterizes states near the valence band maximum, and metal d (Ta5+, d0) dominates near the conduction bandmore » minimum. Optical absorption measurements on thin films confirm the abrupt onset to strong absorption a > 105 cm-1 at Eg + 0.4 eV (Eg = 1.0 eV). Theoretical CuTaS3 solar cell efficiency is predicted to be 28% for a 300 nm film based on the metric of spectroscopic limited maximum efficiency, which exceeds that of CuInSe2. This sulfide may offer new opportunities to discover and develop a new class of mixed d-element solar absorbers.« less

The Time-domain Spectroscopic Survey: Target Selection for Repeat Spectroscopy

NASA Astrophysics Data System (ADS)

MacLeod, Chelsea L.; Green, Paul J.; Anderson, Scott F.; Eracleous, Michael; Ruan, John J.; Runnoe, Jessie; Nielsen Brandt, William; Badenes, Carles; Greene, Jenny; Morganson, Eric; Schmidt, Sarah J.; Schwope, Axel; Shen, Yue; Amaro, Rachael; Lebleu, Amy; Filiz Ak, Nurten; Grier, Catherine J.; Hoover, Daniel; McGraw, Sean M.; Dawson, Kyle; Hall, Patrick B.; Hawley, Suzanne L.; Mariappan, Vivek; Myers, Adam D.; Pâris, Isabelle; Schneider, Donald P.; Stassun, Keivan G.; Bershady, Matthew A.; Blanton, Michael R.; Seo, Hee-Jong; Tinker, Jeremy; Fernández-Trincado, J. G.; Chambers, Kenneth; Kaiser, Nick; Kudritzki, R.-P.; Magnier, Eugene; Metcalfe, Nigel; Waters, Chris Z.

2018-01-01

As astronomers increasingly exploit the information available in the time domain, spectroscopic variability in particular opens broad new channels of investigation. Here we describe the selection algorithms for all targets intended for repeat spectroscopy in the Time Domain Spectroscopic Survey (TDSS), part of the extended Baryon Oscillation Spectroscopic Survey within the Sloan Digital Sky Survey (SDSS)-IV. Also discussed are the scientific rationale and technical constraints leading to these target selections. The TDSS includes a large “repeat quasar spectroscopy” (RQS) program delivering ∼13,000 repeat spectra of confirmed SDSS quasars, and several smaller “few-epoch spectroscopy” (FES) programs targeting specific classes of quasars as well as stars. The RQS program aims to provide a large and diverse quasar data set for studying variations in quasar spectra on timescales of years, a comparison sample for the FES quasar programs, and an opportunity for discovering rare, serendipitous events. The FES programs cover a wide variety of phenomena in both quasars and stars. Quasar FES programs target broad absorption line quasars, high signal-to-noise ratio normal broad line quasars, quasars with double-peaked or very asymmetric broad emission line profiles, binary supermassive black hole candidates, and the most photometrically variable quasars. Strongly variable stars are also targeted for repeat spectroscopy, encompassing many types of eclipsing binary systems, and classical pulsators like RR Lyrae. Other stellar FES programs allow spectroscopic variability studies of active ultracool dwarf stars, dwarf carbon stars, and white dwarf/M dwarf spectroscopic binaries. We present example TDSS spectra and describe anticipated sample sizes and results.

Interpreting the spectral behavior of MWC 314

NASA Astrophysics Data System (ADS)

Frasca, A.; Miroshnichenko, A. S.; Rossi, C.; Friedjung, M.; Marilli, E.; Muratorio, G.; Busà, I.

2016-01-01

Context. MWC 314 is one of the most luminous stars in the Milky Way. Its fundamental parameters are similar to those of luminous blue variables (LBVs), although no large photometric variations have been recorded. Moreover, it shows no evidence of either a dust shell or a relevant spectral variability. Aims: The main purpose of this work is to clarify the origin of the radial velocity and line profile variations exhibited by absorption and emission lines. Methods: We analyzed the radial velocity (RV) variations displayed by the absorption lines from the star's atmosphere using high-resolution optical spectra and fitting the RV curve with an eccentric orbit model. We also studied the RV and profile variations of some permitted and forbidden emission lines of metallic ions with a simple geometric model. The behavior of the Balmer and He I lines has also been investigated. Results: Fourier analysis applied to the RV of the absorption lines clearly shows a 60-day periodicity. A dense coverage of the RV curve allowed us to derive accurate orbital parameters. The RV of the Fe II emission lines varies in the same way, but with a smaller amplitude. Additionally, the intensity ratio of the blue/red peaks of these emission lines correlates with the RV variations. The first three members of the Balmer series as well as [N II] lines display a nearly constant RV and no profile variations in phase with the orbital motion instead. The He I λ5876 Å line shows a strongly variable profile with broad and blue-shifted absorption components that reach velocities of ≤-1000 km s-1 in some specific orbital phases. Conclusions: Our data and analysis provide strong evidence that the object is a binary system composed of a supergiant B[e] star and an undetected companion. The emission lines with a non-variable RV could originate in a circumbinary region. For the Fe II emission lines, we propose a simple geometrical two-component model where a compact source of Fe II emission, moving around the center of mass, is affected by a static extra absorption that originates from a larger area. Finally, the blue-shifted absorption in the He I λ5876 Å line could be the result of density enhancements in the primary star wind that is flowing towards the companion, and which is best observed when projected over the disk of the primary star. Based on observations made at the 0.91 m of Catania Observatory, the OHP telescopes and the 1.83 m telescope of the Asiago Observatory.

Temperature Dependences of Mechanisms Responsible for the Water-Vapor Continuum Absorption

NASA Technical Reports Server (NTRS)

Ma, Qiancheng

2014-01-01

The water-vapor continuum absorption plays an important role in the radiative balance in the Earth's atmosphere. It has been experimentally shown that for ambient atmospheric conditions, the continuum absorption scales quadratically with the H2O number density and has a strong, negative temperature dependence (T dependence). Over the years, there have been three different theoretical mechanisms postulated: far-wings of allowed transition lines, water dimers, and collision-induced absorption. The first mechanism proposed was the accumulation of absorptions from the far-wings of the strong allowed transition lines. Later, absorption by water dimers was proposed, and this mechanism provides a qualitative explanation for the continuum characters mentioned above. Despite the improvements in experimental data, at present there is no consensus on which mechanism is primarily responsible for the continuum absorption.

Probing the Inflow/Out-flow and Accretion Disk of Cyg X-1 in the High State with HETG/Chandra

NASA Technical Reports Server (NTRS)

Feng, Y. X.; Tennant, A. F.; Zhang, S. N.

2003-01-01

Cyg X- 1 was observed in the high state at the conjunction orbital phase (0) with HETG/Chandra. Strong and asymmetric absorption lines of highly ionized species were detected, such as Fe XXV, Fe XXIV, Fe XXIII, Si XIV, S XVI, Ne X, and etc. In the high state the profile of the absorption lines are composed of an extended red wing and a less extended blue wing. The red wings of higher ionized species are more extended than that of lower ionized species. The detection of these lines provides a way to probe the properties of the flow around the companion and the black hole in Cyg X-1 during the high state. A broad emission feature around 6.5 keV was significantly detected from the both spectra of HETG/Chandra and PCA/RXTE. This feature appears to be symmetric and can be fitted with a Gaussian function rather than the Laor disk line model of fluorescent Fe K$ \\alpha$ line from an accretion disk. The implications of these results on the structure of the accretion flow of Cyg X-1 in the high state are discussed.

Ultra-broadband nonlinear saturable absorption of high-yield MoS2 nanosheets

NASA Astrophysics Data System (ADS)

Wei, Rongfei; Zhang, Hang; Hu, Zhongliang; Qiao, Tian; He, Xin; Guo, Qiangbing; Tian, Xiangling; Chen, Zhi; Qiu, Jianrong

2016-07-01

High-yield MoS2 nanosheets with strong nonlinear optical (NLO) responses in a broad near-infrared range were synthesized by a facile hydrothermal method. The observation of saturable absorption, which was excited by the light with photon energy smaller than the gap energy of MoS2, can be attributed to the enhancement of the hybridization between the Mo d-orbital and S p-orbital by the oxygen incorporation into MoS2. High-yield MoS2 nanosheets with high modulation depth and large saturable intensity generated a stable, passively Q-switched fiber laser pulse at 1.56 μm. The high output power of 1.08 mW can be attained under a very low pump power of 30.87 mW. Compared to recently reported passively Q-switched fiber lasers utilizing exfoliated MoS2 nanosheets, the efficiency of the laser for our passive Q-switching operation is larger and reaches 3.50%. This research may extend the understanding on the NLO properties of MoS2 and indicate the feasibility of the high-yield MoS2 nanosheets to passively Q-switched fiber laser effectively at low pump strengths.

Mineral Spectra from Nili Fossae, Mars

NASA Technical Reports Server (NTRS)

2008-01-01

Spectra collected by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) indicate the presence of three distinct minerals. The graphed information comes from an observation of terrain in the Nili Fossae area of northern Mars. CRISM is one of six science instruments on NASA's Mars Reconnaissance Orbiter.

Iron-magnesium smectite clay is formed through alteration of rocks by liquid water and is characterized by distinctive absorptions at 1.4, 1.9, and 2.3 micrometers due to water (H2O) and OH in the atomic structure of the mineral. Olivine is an iron magnesium silicate and primary igneous mineral, and water is not in its structure. Its spectrum is characterized by a strong and broad absorption at 1.0 micrometer due to ferrous iron (Fe2+). Carbonate is an alteration mineral identified by the distinctive paired absorptions at 2.3 and 2.5 micrometers. The precise band positions at 2.31 and 2.51 micrometers identify the carbonate at this location as magnesium carbonate. The broad 1.0 micrometer band indicates some small amount of ferrous iron is also present and the feature at 1.9 micrometers indicates the presence of water. CRISM researchers believe the magnesium carbonate found in the Nili Fossae region formed from alteration of olivine by water.

The data come from a CRISM image catalogued as FRT00003E12. The spectra shown here are five-pixel-by-five-pixel averages of CRISM L-detector spectra taken from three different areas within the image that have then been ratioed to a five-pixel-by-five-pixel common denominator spectrum taken from a spectrally unremarkable area with no distinctive mineralogic signatures. This technique highlights the spectral contrasts between regions due to their unique mineralogy. The spectral wavelengths near 2.0 micrometers are affected by atmospheric absorptions and have been removed for clarity.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, manages the Mars Reconnaissance Orbiter for the NASA Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The Johns Hopkins University Applied Physics Laboratory led the effort to build the CRISM instrument and operates CRISM in coordination with an international team of researchers from universities, government and the private sector.

Physicochemical and functional properties of gelatin extracted from Yak skin.

PubMed

Xu, Mengqi; Wei, Lixin; Xiao, Yuancan; Bi, Hongtao; Yang, Hongxia; Du, Yuzhi

2017-02-01

Different molecular weight distribution (MWD) gelatin was extracted from Yak skin after enzymatic pretreatments and their physicochemical and functional properties (SDS-PAGE, UV-vis absorption spectra, DSC, FT-IR, Amino acid analysis, AFM, emulsibility and foamability) were analyzed. The gelatin was extracted by pepsin and got different MWD of Yak skin gelatin by controlling the enzymolysis time. The SDS-PAGE showed the MWD of the Yak skin gelatin. The UV-vis absorption turned out that the broad MWD of Yak skin gelatin had a higher maximum absorption peaks. The FT-IR and AFM indicated that the gelatin structures and microstructures changed with the change of the MWD. The broad MWD of the Yak skin gelatin had a higher denaturation temperature (T D ), and it was higher than most of the other mammals and marine biological gelatin. The broad MWD gelatin also had higher imino acids (proline and hydroxyproline) contents and lower foamability and emulsibility compared to the narrow MWD gelatin. These findings, obtained for the first time for Yak skin gelatin, showed that it has great potential for application as an alternative to commercial gelatin due to its good thermotolerance, particularly in the applications of the biological materials, stabilizer of thermo-tolerant and so on. Copyright © 2016 Elsevier B.V. All rights reserved.

Stellar Contrails in Quasi-stellar Objects: The Origin of Broad Absorption Lines

NASA Astrophysics Data System (ADS)

Scoville, Nick; Norman, Colin

1995-10-01

Active galactic nuclei (AGNs) and quasars often exhibit infrared excesses at λ = 2-10 microns attributable to thermal dust emission. In this paper we propose that this hot dust is supplied by circumstellar mass loss from evolved stars in the nuclear star cluster. The physics of the mass-loss dust, specifically the evaporation temperature, is a critical parameter in determining the accretion rate of mass-loss material onto the central AGN. For standard interstellar dust grains with an evaporation temperature of 1800 K the dust is destroyed inside a radius of 1 pc from a central luminosity source of 5 × 10 Lsun. The mass-loss material inside 1 pc will therefore have a lower radiation pressure efficiency and accrete inward. Outside this critical radius, dust may survive, and the mass loss is accelerated outward owing to the high radiation pressure efficiency of the dust mixed with the gas. The outflowing material will consist of discrete trails of debris shed by the individual mass-loss stars, and we suggest that these trails produce the broad absorption lines (BALs) seen in 5%-10% of QSOs. The model accounts naturally for the maximum outflow velocities seen in the BALs (˜30,000 km s-1 and varying as L¼) since this maximum terminal velocity occurs for matter originating at the inner edge of the radiative equilibrium dust survival zone. Although the radiation pressure acts on the dust, individual grains will be highly charged (Z ˜ 103+), and the grains are therefore strongly coupled to the gas through the ambient magnetic fields. Numerical hydrodynamic calculations were done to follow the evolution of mass-loss material. As the orbiting debris is driven outward by radiation pressure, the trail forms a spiral with initially high pitch angle (˜85°). The trails are compressed into thin ribbons in the radial direction initially by the radiation pressure gradients due to absorption within the trail. After reaching > 104 km s-1 radial velocity, the compression can be maintained by ram pressure due to an ambient gas of modest density (˜102 cm-3). Each of the stellar contrails will have mean column density ˜1019-1021 cm-2, volume density ˜108-109 cm-3, and thickness 1011-1012 cm along the line of sight to the AGN corresponding to parameters deduced from observations of the BAL clouds. Assuming minimal expansion perpendicular to the line of sight at the speed of sound, the width of the trails is 1015-1016 cm, or 102-103 times the line-of-sight depth. Since the UV-emitting accretion disk probably has a radius of about 2 × 1016 cm, a single trail will only partially cover the continuum, but for the column densities quoted above the observed absorption lines (e.g., C IV) will be optically thick with τ > 10. Since the contrails are nearly radial just after leaving the star when the maximum outward acceleration occurs, a large range of velocities (˜4000 km s-1) will be seen in absorption of the QSO light from each trail, and only a few disk-crossing trails are needed to account for the full width of broad absorption line troughs.

The X-ray evolution of inflows and outflows in active galactic nuclei

NASA Astrophysics Data System (ADS)

Saez, Cristian

The evolution of the space density of AGNs might have spectral counterparts which could be observable in X-rays. The main objective of this thesis is to study the spectral properties of AGNs in X-rays in order to increase our current knowledge of AGN evolution. In chapter 2, we present results from a statistical analysis of 173 bright radio-quiet AGNs selected from the Chandra Deep Field-North and Chandra Deep Field-South surveys (hereafter, CDFs) in the redshift range of 0.1 ≲z≲ 4. We find that the X-ray power-law photon index (Gamma) of radio-quiet AGNs is correlated with their 2--10 keV rest-frame X-ray luminosity ( LX) at the > 99.5% confidence level in two redshift bins, 0.3 ≲z≲ 0.96, and 1.5 ≲z≲ 3.3 and is slightly less significant in the redshift bin 0.96 ≲z≲ 1.5. The X-ray spectral slope steepens as the X-ray luminosity increases for AGNs in the luminosity range 1042 to 1045 erg s-1. Combining our results from the CDFs with those from previous studies in the redshift range 1.5 ≲z≲ 3.3, we find that the Gamma -- L X correlation has a null-hypothesis probability of 1.6 x 10 -9. We investigate the redshift evolution of the correlation between the power-law photon index and the hard X-ray luminosity and find that the slope and offset of a linear fit to the correlation change significantly (at the > 99.9% confidence level) between redshift bins of 0.3 ≲z≲ 0.96 and 1.5 ≲z≲ 3.3. We explore physical scenarios explaining the origin of this correlation and its possible evolution with redshift in the context of steady corona models focusing on its dependency on variations of the properties of the hot corona with redshift. In chapter 3, we present results from three Suzaku observations of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. We detect strong and broad absorption at rest-frame energies of ≲ 2 keV (low-energy) and 7--12 keV (high-energy). The detection of these features confirms the results of previous long-exposure (80--90 ks) Chandra and XMM-Newton observations. The low and high-energy absorption is detected in both the back-illuminated (BI) and front-illuminated (FI) Suzaku XIS spectra (with an F-test significance of ≳ 99%). We interpret the low-energy absorption as arising from a low-ionization absorber with log (NH/cm-2) ˜ 23 and the high-energy absorption as due to lines arising from highly ionized (2.75 ≲ log xi ≲ 4.0; where xi is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation we find that the velocities in the outflow range between 0.1c and 0.6c. We constrain the angle between the outflow direction of the X-ray absorber and our line of sight to be ≲ 36°. We also detect likely variability of the absorption lines (at the ≳ 99.9% and ≳ 98% significance levels in the FI and BI spectra, respectively) with a rest-frame time scale of ˜1 month. Assuming that the detected high-energy absorption features arise from Fe XXV, we estimate that the fraction of the total bolometric energy injected over the quasar's lifetime into the intergalactic medium in the form of kinetic energy to be ≳ 10%. In chapter 4, we present an expansion of our previous work on the study of X-ray outflows on APM 08279+5255. The main conclusions from our multi-epoch spectral analysis of Chandra, XMM-Newton and Suzaku observations of the z = 3.91 gravitationally lensed broad absorption line (BAL) quasar APM 08279+5255 are: (1) In every observation we confirm the presence of two strong features, one at rest-frame energies between 1--4 keV, and the other between 7--18 keV. (2) The low-energy absorption is interpreted as arising (1--4 keV rest-frame) from a low-ionization absorber with log (N H/cm-2) ˜ 23 and the high-energy absorption (7--18 keV rest-frame) as due to lines arising from highly ionized (3 ≲ log xi ≲ 4; where xi is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation, we find that the velocities on the outflow could get up to ˜ 0.7c. We also present results obtained from fits to all the long exposure observations of APM 08279+5255 with a new outflow model. (Abstract shortened by UMI.)

Absorption features in the quasar HS 1603 + 3820 II. Distance to the absorber obtained from photoionisation modelling

NASA Astrophysics Data System (ADS)

Różańska, A.; Nikołajuk, M.; Czerny, B.; Dobrzycki, A.; Hryniewicz, K.; Bechtold, J.; Ebeling, H.

2014-04-01

We present the photoionisation modelling of the intrinsic absorber in the bright quasar HS 1603 + 3820. We constructed the broad-band spectral energy distribution using the optical/UV/X-ray observations from different instruments as inputs for the photoionisation calculations. The spectra from the Keck telescope show extremely high CIV to HI ratios, for the first absorber in system A, named A1. This value, together with high column density of CIV ion, place strong constraints on the photoionisation model. We used two photoionisation codes to derive the hydrogen number density at the cloud illuminated surface. By estimating bolometric luminosity of HS 1603 + 3820 using the typical formula for quasars, we calculated the distance to A1. We could find one photoionization solution, by assuming either a constant density cloud (which was modelled using CLOUDY), or a stratified cloud (which was modelled using TITAN), as well as the solar abundances. This model explained both the ionic column density of CIV and the high CIV to HI ratio. The location of A1 is 0.1 pc, and it is situated even closer to the nucleus than the possible location of the Broad Line Region in this object. The upper limit of the distance is sensitive to the adopted covering factor and the carbon abundance. Photoionisation modelling always prefers dense clouds with the number density n0 = 1010 - 1012 cm-3, which explains intrinsic absorption in HS 1603 + 3820. This number density is of the same order as that in the disk atmosphere at the implied distance of A1. Therefore, our results show that the disk wind that escapes from the outermost accretion disk atmosphere can build up dense absorber in quasars.

Resonance behaviour of whole-body averaged specific energy absorption rate (SAR) in the female voxel model, NAOMI

NASA Astrophysics Data System (ADS)

Dimbylow, Peter

2005-09-01

Finite-difference time-domain (FDTD) calculations have been performed of the whole-body averaged specific energy absorption rate (SAR) in a female voxel model, NAOMI, under isolated and grounded conditions from 10 MHz to 3 GHz. The 2 mm resolution voxel model, NAOMI, was scaled to a height of 1.63 m and a mass of 60 kg, the dimensions of the ICRP reference adult female. Comparison was made with SAR values from a reference male voxel model, NORMAN. A broad SAR resonance in the NAOMI values was found around 900 MHz and a resulting enhancement, up to 25%, over the values for the male voxel model, NORMAN. This latter result confirmed previously reported higher values in a female model. The effect of differences in anatomy was investigated by comparing values for 10-, 5- and 1-year-old phantoms rescaled to the ICRP reference values of height and mass which are the same for both sexes. The broad resonance in the NAOMI child values around 1 GHz is still a strong feature. A comparison has been made with ICNIRP guidelines. The ICNIRP occupational reference level provides a conservative estimate of the whole-body averaged SAR restriction. The linear scaling of the adult phantom using different factors in longitudinal and transverse directions, in order to match the ICRP stature and weight, does not exactly reproduce the anatomy of children. However, for public exposure the calculations with scaled child models indicate that the ICNIRP reference level may not provide a conservative estimate of the whole-body averaged SAR restriction, above 1.2 GHz for scaled 5- and 1-year-old female models, although any underestimate is by less than 20%.

Resonance behaviour of whole-body averaged specific energy absorption rate (SAR) in the female voxel model, NAOMI.

PubMed

Dimbylow, Peter

2005-09-07

Finite-difference time-domain (FDTD) calculations have been performed of the whole-body averaged specific energy absorption rate (SAR) in a female voxel model, NAOMI, under isolated and grounded conditions from 10 MHz to 3 GHz. The 2 mm resolution voxel model, NAOMI, was scaled to a height of 1.63 m and a mass of 60 kg, the dimensions of the ICRP reference adult female. Comparison was made with SAR values from a reference male voxel model, NORMAN. A broad SAR resonance in the NAOMI values was found around 900 MHz and a resulting enhancement, up to 25%, over the values for the male voxel model, NORMAN. This latter result confirmed previously reported higher values in a female model. The effect of differences in anatomy was investigated by comparing values for 10-, 5- and 1-year-old phantoms rescaled to the ICRP reference values of height and mass which are the same for both sexes. The broad resonance in the NAOMI child values around 1 GHz is still a strong feature. A comparison has been made with ICNIRP guidelines. The ICNIRP occupational reference level provides a conservative estimate of the whole-body averaged SAR restriction. The linear scaling of the adult phantom using different factors in longitudinal and transverse directions, in order to match the ICRP stature and weight, does not exactly reproduce the anatomy of children. However, for public exposure the calculations with scaled child models indicate that the ICNIRP reference level may not provide a conservative estimate of the whole-body averaged SAR restriction, above 1.2 GHz for scaled 5- and 1-year-old female models, although any underestimate is by less than 20%.

Highly vibrationally excited O2 molecules in low-pressure inductively-coupled plasmas detected by high sensitivity ultra-broad-band optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Foucher, Mickaël; Marinov, Daniil; Carbone, Emile; Chabert, Pascal; Booth, Jean-Paul

2015-08-01

Inductively-coupled plasmas in pure O2 (at pressures of 5-80 mTorr and radiofrequency power up to 500 W) were studied by optical absorption spectroscopy over the spectral range 200-450 nm, showing the presence of highly vibrationally excited O2 molecules (up to vʺ = 18) by Schumann-Runge band absorption. Analysis of the relative band intensities indicates a vibrational temperature up to 10,000 K, but these hot molecules only represent a fraction of the total O2 density. By analysing the (11-0) band at higher spectral resolution the O2 rotational temperature was also determined, and was found to increase with both pressure and power, reaching 900 K at 80 mTorr 500 W. These measurements were achieved using a new high-sensitivity ultra-broad-band absorption spectroscopy setup, based on a laser-plasma light source, achromatic optics and an aberration-corrected spectrograph. This setup allows the measurement of weak broadband absorbances due to a baseline variability lower than 2   ×   10-5 across a spectral range of 250 nm.

THz spectra of cortisone and the related medicine

NASA Astrophysics Data System (ADS)

Ma, Shihua; Ge, Min; Liu, Guifeng; Song, Xiyu; Zhang, Peng; Wang, Wenfeng

2009-07-01

THz-TDS are used to study four kinds of drug: cortisone, hydrocortisone, prednisone and prednisolone. The THz spectra of them are obtained and analyzed from 0.2 - 1.6 THz. The experimental results shows the four samples have the different THz spectra. Cortisone has a peak at 1.5 THz and a broad absorption peak at 0.96 THz, while hydrocortisone has a weak absorption peak that lies at 1.27 THz. At the same time the prednisone has the stronger absorption peaks than the others, and its two peaks shows at 1.24 THz and 1.5 THz. Prednisolone has a weak broad peak at 1.43 THz. The results of the theoretical calculation were performed using Gaussian 03 software with Density Functional Theory at the basis set of 6-31+G (d, p). The theoretical vibrational frequencies are compared with the experimental results, and the deviations are discussed. The THz spectra of the medicine show THz technique may be help to distinguish some different chemical bond and functional group.

Optical spectroscopy of interplanetary dust collected in the earth's stratosphere

NASA Technical Reports Server (NTRS)

Fraundorf, P.; Patel, R. I.; Shirck, J.; Walker, R. M.; Freeman, J. J.

1980-01-01

Optical absorption spectra of interplanetary dust particles 2-30 microns in size collected in the atmosphere at an altitude of 20 km by inertial impactors mounted on NASA U-2 aircraft are reported. Fourier transform absorption spectroscopy of crushed samples of the particles reveals a broad feature in the region 1300-800 kaysers which has also been found in meteorite and cometary dust spectra, and a weak iron crystal field absorption band at approximately 9800 kaysers, as is observed in meteorites. Work is currently in progress to separate the various components of the interplanetary dust particles in order to evaluate separately their contributions to the absorption.

Fully suspended slot waveguide platform

NASA Astrophysics Data System (ADS)

Zhou, Wen; Cheng, Zhenzhou; Wu, Xinru; Sun, Xiankai; Tsang, Hon Ki

2018-02-01

A fully suspended slot waveguide (FSSWG) platform, including straight slot waveguides, 90° bends, high-Q racetrack resonators, and strip-to-slot mode converters, is demonstrated for broadband and low-loss operation in the mid-infrared spectral region. The proposed FSSWG platform has inherent merits of a broad spectral range of transparency which is limited only by the absorption of silicon, strong light-analyte interaction, good mechanical stability, and single lithography step fabrication process. By using asymmetric FSSWGs, the propagation loss, bending loss, and intrinsic optical Q factor are demonstrated to be 2.8 dB/cm, 0.15 dB/90°, and 12 600, respectively. The average conversion efficiency of a mode converter is 95.4% over a bandwidth of 170 nm and 97.0% at 2231 nm. The FSSWG platform would be promising for a long-range and cavity-enhanced light-analyte interaction.

Io's Thermal Regions and Non-SO2 Spectral Features

NASA Technical Reports Server (NTRS)

Smythe, W. D.; Soderblom, L. A.; Lopes, R. M. C.

2003-01-01

Several absorptions have been identified in the Galileo NIMS spectra of Io that are not related to SO2. [1,2]. These absorptions have band centers at 2.97, 3.15, 3.85, and 3.91 microns. There are also broad absorptions in the regions 1-1.3 and 3- 3.4 microns. Patterning noise in wavelength registration, arising from the pushbroom imaging and grating motion of the NIMS instrument have previously inhibited reliable mapping of weak absorptions. Recent improvements in techniques to remove the coherent pattern noise from the NIMS dataset have been made by Soderblom. This greatly improves the signal to noise ratio and enables mapping of weak spectral signatures such as the 3.15 micron absorption on Io.

Absorption of Dy3+ and Nd3+ ions in Ba R 2F8 single crystals

NASA Astrophysics Data System (ADS)

Apollonov, V. V.; Pushkar', A. A.; Uvarova, T. V.; Chernov, S. P.

2008-09-01

The Dy3+ absorption and excitation spectra of BaY2F8 and BaYb2F8 single crystals are investigated in the ultraviolet, vacuum ultraviolet, and visible ranges at a temperature of 300 K. These crystals exhibit intense broad absorption bands due to the spin-allowed 4 f-5 d transitions in the range (56-78) × 10-3 cm-1 and less intense absorption bands that correspond to the spin-forbidden transitions in the range (50-56) × 10-3 cm-1. The Nd3+ absorption spectra of BaY2F8 single crystals are studied in the range (34-82) × 10-3 cm-1 at 300 K for different crystal orientations.

Exchange coupling and microwave absorption in core/shell-structured hard/soft ferrite-based CoFe2O4/NiFe2O4 nanocapsules

NASA Astrophysics Data System (ADS)

Feng, Chao; Liu, Xianguo; Or, Siu Wing; Ho, S. L.

2017-05-01

Core/shell-structured, hard/soft spinel-ferrite-based CoFe2O4/NiFe2O4 (CFO/NFO) nanocapsules with an average diameter of 17 nm are synthesized by a facile two-step hydrothermal process using CFO cores of ˜15 nm diameter as the hard magnetic phase and NFO shells of ˜1 nm thickness as the soft magnetic phase. The single-phase-like hysteresis loop with a high remnant-to-saturation magnetization ratio of 0.7, together with a small grain size of ˜16 nm, confirms the existence of exchange-coupling interaction between the CFO cores and the NFO shells. The effect of hard/soft exchange coupling on the microwave absorption properties is studied. Comparing to CFO and NFO nanoparticles, the finite-size NFO shells and the core/shell structure enable a significant reduction in electric resistivity and an enhancement in dipole and interfacial polarizations in the CFO/NFO nanocapsules, resulting in an obvious increase in dielectric permittivity and loss in the whole S-Ku bands of microwaves of 2-18 GHz, respectively. The exchange-coupling interaction empowers a more favorable response of magnetic moment to microwaves, leading to enhanced exchange resonances in magnetic permeability and loss above 10 GHz. As a result, strong absorption, as characterized by a large reflection loss (RL) of -20.1 dB at 9.7 GHz for an absorber thickness of 4.5 mm as well as a broad effective absorption bandwidth (for RL<-10 dB) of 8.4 GHz (7.8-16.2 GHz) at an absorber thickness range of 3.0-4.5 mm, is obtained.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fares, Hssen; Férid, Mokhtar; Elhouichet, Habib, E-mail: habib.elhouichet@fst.rnu.tn

Tellurite glasses doped Er³⁺ ions and containing Silver nanoparticles (Ag NPs) are prepared using melt quenching technique. The nucleation and growth of Ag NPs were controlled by a thermal annealing process. The X-ray diffraction pattern shows no sharp peak indicating an amorphous nature of the glasses. The presence of Ag NPs is confirmed from transmission electron microscopy micrograph. Absorption spectra show typical surface plasmon resonance (SPR) band of Ag NPs within the 510–550 nm range in addition to the distinctive absorption peaks of Er³⁺ ions. The Judd-Ofelt (J-O) intensity parameters, oscillator strengths, spontaneous transition probabilities, branching ratios, and radiative lifetimesmore » were successfully calculated based on the experimental absorption spectrum and the J-O theory. It was found that the presence of silver NPs nucleated and grown during the heat annealing process improves both of the photoluminescence (PL) intensity and the PL lifetime relative to the ⁴I 13/2 → ⁴I 15/2 transition. Optimum PL enhancement was obtained after 10 h of heat-treatment. Such enhancements are mainly attributed to the strong local electric field induced by SPR of silver NPs and also to energy transfer from the surface of silver NPs to Er³⁺ ions, whereas the quenching is ascribed to the energy transfer from Er³⁺ ions to silver NPs. Using the Mc Cumber method, absorption cross-section, calculated emission cross-section, and gain cross-section for the ⁴I 13/2 → ⁴I 15/2 transition were determined and compared for the doped and co-doped glasses. The present results indicate that the glass heat-treated for 10 h has good prospect as a gain medium applied for 1.53 μm band broad and high-gain erbium-doped fiber amplifiers.« less

The polarization and ultraviolet spectrum of Markarian 231

NASA Technical Reports Server (NTRS)

Smith, Paul S.; Schmidt, Gary D.; Allen, Richard G.; Angel, J. R. P.

1995-01-01

Ultraviolet spectropolarimetry acquired with the Hubble Space Telescope (HST) of the peculiar Seyfert galaxy Mrk 231 is combined with new high-quality ground-based measurements to provide the first, nearly complete, record of its linear polarization from 1575 to 7900 A. The accompanying ultraviolet spectrum portrays the heavily extinguished emission-line spectrum of the active nucleus plus the emergence of a blue continuum shortward of approximately 2400 A. In addition, absorption features due to He I lambda 3188, Mg I lambda 2853, Mg II lambda 2798, and especially several resonance multiplets of Fe II are identified with a well-known optical absorption system blueshifted approximately 4600 km/s with respect to emission lines. The continuum is attributed to approximately 10(exp 5) hot, young stars surrounding the nucleus. This component dilutes the polarized nuclear light, implying that the intrinsic polarization of the active galactic nucleus (AGN) spectrum approaches 20% at 2800 A. The rapid decline in degree of polarization toward longer wavelengths is best explained by the strongly frequency-dependent scattering cross section of dust grains coupled with modest starlight dilution. Peculiar S-shaped inflections in both the degree and position angle of polarization through H alpha and other major emission lines are interpreted as effects of scattering from two regions offset in velocity by several hundred km/s. A third source of (weakly) polarized flux is required to explain a nearly 40 deg rotation in position angle between 3200 and 1800 A. The displaced absorption features, polarimetry, and optical/infrared properties of Mrk 231 all point to its classification as a low-ionization, or Mg II broad absorption line quasar, in which most, if not all, lines of sight to the active nucleus are heavily obscured by dust and low-ionization gas clouds.

Resonant two-photon ionization and laser induced fluorescence spectroscopy of jet-cooled adenine

NASA Astrophysics Data System (ADS)

Kim, Nam Joon; Jeong, Gawoon; Kim, Yung Sam; Sung, Jiha; Keun Kim, Seong; Park, Young Dong

2000-12-01

Electronic spectra of the jet-cooled DNA base adenine were obtained by the resonant two-photon ionization (R2PI) and the laser induced fluorescence (LIF) techniques. The 0-0 band to the lowest electronically excited state was found to be located at 35 503 cm-1. Well-resolved vibronic structures were observed up to 1100 cm-1 above the 0-0 level, followed by a slow rise of broad structureless absorption. The lowest electronic state was proposed to be of nπ* character, which lies ˜600 cm-1 below the onset of the ππ* state. The broad absorption was attributed to the extensive vibronic mixing between the nπ* state and the high-lying ππ* state.

Role of surface electromagnetic waves in metamaterial absorbers

DOE PAGES

Chen, Wen -Chen; Cardin, Andrew; Koirala, Machhindra; ...

2016-03-18

Metamaterial absorbers have been demonstrated across much of the electromagnetic spectrum and exhibit both broad and narrow-band absorption for normally incident radiation. Absorption diminishes for increasing angles of incidence and transverse electric polarization falls off much more rapidly than transverse magnetic. We unambiguously demonstrate that broad-angle TM behavior cannot be associated with periodicity, but rather is due to coupling with a surface electromagnetic mode that is both supported by, and well described via the effective optical constants of the metamaterial where we achieve a resonant wavelength that is 19.1 times larger than the unit cell. Furthermore, experimental results are supportedmore » by simulations and we highlight the potential to modify the angular response of absorbers by tailoring the surface wave.« less

The active nucleus of the ULIRG IRAS F00183-7111 viewed by NuSTAR

NASA Astrophysics Data System (ADS)

Iwasawa, K.; Spoon, H. W. W.; Comastri, A.; Gilli, R.; Lanzuisi, G.; Piconcelli, E.; Vignali, C.; Brusa, M.; Puccetti, S.

2017-10-01

We present an X-ray study of the ultra-luminous infrared galaxy IRAS F00183-7111 (z = 0.327), using data obtained from NuSTAR, Chandra X-ray Observatory, Suzaku and XMM-Newton. The Chandra imaging shows that a point-like X-ray source is located at the nucleus of the galaxy at energies above 2 keV. However, the point source resolves into diffuse emission at lower energies, extending to the east, where the extranuclear [Oiii]λ5007 emission, presumably induced by a galactic-scale outflow, is present. The nuclear source is detected by NuSTAR up to the rest-frame 30 keV. The strong, high-ionization Fe K line, first seen by XMM-Newton, and subsequently by Suzaku and Chandra, is not detected in the NuSTAR data. The line flux appears to have been declining continuously between 2003 and 2016, while the continuum emission remained stable to within 30%. Further observations are needed to confirm this. The X-ray continuum below 10 keV is characterised by a hard spectrum caused by cold absorption of NH 1 × 1023 cm-2, compatible to that of the silicate absorption at 9.7 μm, and a broad absorption feature around 8 keV which we attribute to a high-ionization Fe K absorption edge. The latter is best described by a blueshifted, high-ionization (log ξ 3) absorber with a column density of NH 1 × 1024 cm-2, similar to the X-ray high-velocity outflows observed in a number of active nuclei. No extra hard component, which would arise from a strongly absorbed (I.e. Compton-thick) source, is seen in the NuSTAR data. While a pure reflection scenario (with a totally hidden central source) is viable, direct emission from the central source of L2-10 keV ≃ 2 × 1044 erg s-1, behind layers of cold and hot absorbing gas may be an alternative explanation. In this case, the relative X-ray quietness (Lx/Lbol,AGN ≤ 6 × 10-3), the high-ionization Fe line, strong outflows inferred from various observations, and other similarities to the well-studied ULIRG/QSO Mrk 231 point that the central source in this ULIRG might be accreting close to the Eddington limit. This research has also made use of data obtained from ESO telescopes at the La Silla Paranal Observatory. The ESO VLT data are under programme IDs 386.B-0346, 088.B-0405, and 090.B-0098.

Heat exchanger bypass system for an absorption refrigeration system

DOEpatents

Reimann, Robert C.

1984-01-01

A heat exchanger bypass system for an absorption refrigeration system is disclosed. The bypass system operates to pass strong solution from the generator around the heat exchanger to the absorber of the absorption refrigeration system when strong solution builds up in the generator above a selected level indicative of solidification of strong solution in the heat exchanger or other such blockage. The bypass system includes a bypass line with a gooseneck located in the generator for controlling flow of strong solution into the bypass line and for preventing refrigerant vapor in the generator from entering the bypass line during normal operation of the refrigeration system. Also, the bypass line includes a trap section filled with liquid for providing a barrier to maintain the normal pressure difference between the generator and the absorber even when the gooseneck of the bypass line is exposed to refrigerant vapor in the generator. Strong solution, which may accumulate in the trap section of the bypass line, is diluted, to prevent solidification, by supplying weak solution to the trap section from a purge system for the absorption refrigeration system.

Re-examining the XMM-Newton spectrum of the black hole candidate XTE J1652-453

NASA Astrophysics Data System (ADS)

Chiang, Chia-Ying; Reis, R. C.; Walton, D. J.; Fabian, A. C.

2012-10-01

The XMM-Newton spectrum of the black hole candidate XTE J1652-453 shows a broad and strong Fe Kα emission line, generally believed to originate from reflection of the inner accretion disc. These data have been analysed by Hiemstra et al. using a variety of phenomenological models. We re-examine the spectrum with a self-consistent relativistic reflection model. A narrow absorption line near 7.2 keV may be present, which if real is likely the Fe XXVI absorption line arising from highly ionized, rapidly outflowing disc wind. The blueshift of this feature corresponds to a velocity of about 11 100 km s-1, which is much larger than the typical values seen in stellar mass black holes. Given that we also find the source to have a low inclination (i ≲ 32°; close to face-on), we would therefore be seeing through the very base of outflow. This could be a possible explanation for the unusually high velocity. We use a reflection model combined with a relativistic convolution kernel which allows for both prograde and retrograde black hole spin, and treat the potential absorption feature with a physical model for a photoionized plasma. In this manner, assuming the disc is not truncated, we could only constrain the spin of the black hole in XTE J1652-453 to be less than ˜0.5 Jc/GM2 at the 90 per cent confidence limit.

Near-infrared spectroscopy of the proto-planetary nebula CRL 618 and the origin of the hydrocarbon dust component in the interstellar medium.

PubMed

Chiar, J E; Pendleton, Y J; Geballe, T R; Tielens, A G

1998-11-01

A new 2.8-3.8 micrometers spectrum of the carbon-rich protoplanetary nebula CRL 618 confirms the previous detection of a circumstellar 3.4 micrometers absorption feature in this object (Lequeux & Jourdain de Muizon). The high resolution and high signal-to-noise ratio of our spectrum allow us to derive the detailed profile of this absorption feature, which is very similar to that observed in the spectrum of the Galactic center and also resembles the strong 3.4 micrometers emission feature in some post-asymptotic giant branch stars. A weak 3.3 micrometers unidentified infrared band, marginally detected in the CRL 618 spectrum of Lequeux & Jourdain de Muizon, is present in our spectrum. The existence of the 3.4 micrometers feature implies the presence of relatively short-chained, aliphatic hydrocarbon materials (-CH2-/-CH3 approximately = 2-2.5) in the circumstellar environment around CRL 618. It also implies that the carriers of the interstellar 3.4 micrometers feature are produced at least in part in circumstellar material, and it calls into question whether any are produced by the processing of interstellar ices in dense interstellar clouds, as has been previously proposed. Other features in the spectrum are recombination lines of hydrogen, rotational and vibration-rotation lines of molecular hydrogen, and a broad absorption probably due to a blend of HCN and C2H2 bands.

CuO, MnO2 and Fe2O3 doped biomass ash as silica source for glass production in Thailand

NASA Astrophysics Data System (ADS)

Srisittipokakun, N.; Ruangtaweep, Y.; Rachniyom, W.; Boonin, K.; Kaewkhao, J.

In this research, glass productions from rice husk ash (RHA) and the effect of BaO, CuO, MnO2 and Fe2O3 on physical and optical properties were investigated. All properties were compared with glass made from SiO2 using same preparations. The results show that a higher density and refractive index of BaO, CuO, MnO2 and Fe2O3 doped in RHA glasses were obtained, compared with SiO2 glasses. The optical spectra show no significant difference between both glasses. The color of CuO glasses show blue from the absorption band near 800 nm (2B1g → 2B2g) due to Cu2+ ion in octahedral coordination with a strong tetragonal distortion. The color of MnO2 glasses shows brown from broad band absorption at around 500 nm. This absorption band is assigned to a single allowed 5Eg → 5T2g transition which arises from the Mn3+ ions (3d4 configuration) in octahedral symmetry. The yellow color derives from F2O3 glass due to the homogeneous distribution of Fe3+ (460 nm) and Fe2+ (1050 nm) ions in the glass matrices. Glass production from RHA is possible and is a new option for recycling waste from biomass power plant systems and air pollution reduction.

Near-infrared spectroscopy of the proto-planetary nebula CRL 618 and the origin of the hydrocarbon dust component in the interstellar medium

NASA Technical Reports Server (NTRS)

Chiar, J. E.; Pendleton, Y. J.; Geballe, T. R.; Tielens, A. G.

1998-01-01

A new 2.8-3.8 micrometers spectrum of the carbon-rich protoplanetary nebula CRL 618 confirms the previous detection of a circumstellar 3.4 micrometers absorption feature in this object (Lequeux & Jourdain de Muizon). The high resolution and high signal-to-noise ratio of our spectrum allow us to derive the detailed profile of this absorption feature, which is very similar to that observed in the spectrum of the Galactic center and also resembles the strong 3.4 micrometers emission feature in some post-asymptotic giant branch stars. A weak 3.3 micrometers unidentified infrared band, marginally detected in the CRL 618 spectrum of Lequeux & Jourdain de Muizon, is present in our spectrum. The existence of the 3.4 micrometers feature implies the presence of relatively short-chained, aliphatic hydrocarbon materials (-CH2-/-CH3 approximately = 2-2.5) in the circumstellar environment around CRL 618. It also implies that the carriers of the interstellar 3.4 micrometers feature are produced at least in part in circumstellar material, and it calls into question whether any are produced by the processing of interstellar ices in dense interstellar clouds, as has been previously proposed. Other features in the spectrum are recombination lines of hydrogen, rotational and vibration-rotation lines of molecular hydrogen, and a broad absorption probably due to a blend of HCN and C2H2 bands.

A Compton-thick Wind in the High Luminosity Quasar, PDS 456

NASA Technical Reports Server (NTRS)

Reeves, J. N.; O'Brien, P. T.; Behar, E.; Miller, L.; Turner, T. J.; Braito, V.; Fabian, A. C.; Kaspi, S.; Mushotzky, R.; Ward, M.

2009-01-01

PDS 456 is a nearby (z=0.184), luminous (L(sub bol) approximately equal to 10(exp 47) ergs(exp -1) type I quasar. A deep 190 ks Suzaku observation in February 2007 revealed the complex, broad band X-ray spectrum of PDS 456. The Suzaku spectrum exhibits highly statistically significant absorption features near 9 keV in the quasar rest-frame. We show that the most plausible origin of the absorption is from blue-shifted resonance (1s-2p) transitions of hydrogen-like iron (at 6.97 keV in the rest frame). This indicates that a highly ionized outflow may be present moving at near relativistic velocities (0.26-0.31c). A possible hard X-ray excess is detected above 15 keV with HXD (at 99.8% confidence), which may arise from high column density gas (N(sub H) greater than 10(exp 24)cm(exp -2) partially covering the X-ray emission, or through strong Compton reflection. Here we propose that the iron K-shell absorption in PDS 456 is associated with a thick, possibly clumpy outflow, covering about 20% of 4(pi) steradian solid angle. The outflow is likely launched from the inner accretion disk, within 15-100 gravitational radii of the black hole. The kinetic power of the outflow may be similar to the bolometric luminosity of PDS 456. Such a powerful wind could have a significant effect on the co-evolution of the host galaxy and its supermassive black hole, through feedback.

Non-noble metal vanadium phosphites with broad absorption for photocatalytic hydrogen evolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Jun-Ling, E-mail: s070054@e.ntu.edu.sg; State Key Laboratory of Structural Chemistry, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002; Zhang, Jian-Han

2016-05-15

We reported the synthesis and crystal structures of alkali metal and alkali-earth metal phosphite, namely, CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} (1), and Ba{sub 3}V{sub 2}(HPO{sub 3}){sub 6} (2). Both compounds were prepared by hydrothermal reactions and feature unique new structures. They both exhibit 3D complicated frameworks based on VO{sub 6} octahedra which are connected by HPO{sub 3} tetrahedra via corner-sharing. Alkali or alkali earth metal cations are filled in the different channels of the frameworks. Topological analysis shows that the framework of CsV{sub 2}(H{sub 3}O) (HPO{sub 3}){sub 4} (1) is a new 3,3,3,4,5-connected network with the Schläfli symbol of {4.6"2}{submore » 2}{4"2.6"6.8"2}{6"3}{6"5.8}. The investigations of X-ray photoelectron spectroscopy (XPS) and magnetic measurement on CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} suggest a +3 oxidation state of the vanadium ions in compound 1. Photocatalytic performance was evaluated by photocatalytic H{sub 2} evolution and degradation of methylene blue, which shows that both compounds exhibit activity under visible-light irradiation. IR spectrum, UV–vis-NIR spectrum and thermogravimetric analysis (TGA) of compounds were also investigated. - Graphical abstract: Metal vanadium phosphites with broad absorption for photocatalytic hydrogen evolution and the degradation of methylene blue aqueous solution. - Highlights: • Two new vanadium phosphites, CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} and Ba{sub 3}V{sub 2}(HPO{sub 3}){sub 6}, are reported. • CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} and Ba{sub 3}V{sub 2}(HPO{sub 3}){sub 6} feature complicated 3D framework structures with different channels. • CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} and Ba{sub 3}V{sub 2}(HPO{sub 3}){sub 6} exhibit strong and broad absorptions in the visible and Near IR region. • Photocatalytic properties of CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} and Ba{sub 3}V{sub 2}(HPO{sub 3}){sub 6} are investigated. • The magnetic measurement of CsV{sub 2}(H{sub 3}O)(HPO{sub 3}){sub 4} was performed in the temperature range of 2–300 K.« less

Synchrotron FTIR imaging of OH in quartz mylonites

NASA Astrophysics Data System (ADS)

Kronenberg, Andreas K.; Hasnan, Hasnor F. B.; Holyoke, Caleb W., III; Law, Richard D.; Liu, Zhenxian; Thomas, Jay B.

2017-10-01

Previous measurements of water in deformed quartzites using conventional Fourier transform infrared spectroscopy (FTIR) instruments have shown that water contents of larger grains vary from one grain to another. However, the non-equilibrium variations in water content between neighboring grains and within quartz grains cannot be interrogated further without greater measurement resolution, nor can water contents be measured in finely recrystallized grains without including absorption bands due to fluid inclusions, films, and secondary minerals at grain boundaries.Synchrotron infrared (IR) radiation coupled to a FTIR spectrometer has allowed us to distinguish and measure OH bands due to fluid inclusions, hydrogen point defects, and secondary hydrous mineral inclusions through an aperture of 10 µm for specimens > 40 µm thick. Doubly polished infrared (IR) plates can be prepared with thicknesses down to 4-8 µm, but measurement of small OH bands is currently limited by strong interference fringes for samples < 25 µm thick, precluding measurements of water within individual, finely recrystallized grains. By translating specimens under the 10 µm IR beam by steps of 10 to 50 µm, using a software-controlled x - y stage, spectra have been collected over specimen areas of nearly 4.5 mm2. This technique allowed us to separate and quantify broad OH bands due to fluid inclusions in quartz and OH bands due to micas and map their distributions in quartzites from the Moine Thrust (Scotland) and Main Central Thrust (Himalayas).Mylonitic quartzites deformed under greenschist facies conditions in the footwall to the Moine Thrust (MT) exhibit a large and variable 3400 cm-1 OH absorption band due to molecular water, and maps of water content corresponding to fluid inclusions show that inclusion densities correlate with deformation and recrystallization microstructures. Quartz grains of mylonitic orthogneisses and paragneisses deformed under amphibolite conditions in the hanging wall to the Main Central Thrust (MCT) exhibit smaller broad OH bands, and spectra are dominated by sharp bands at 3595 to 3379 cm-1 due to hydrogen point defects that appear to have uniform, equilibrium concentrations in the driest samples. The broad OH band at 3400 cm-1 in these rocks is much less common. The variable water concentrations of MT quartzites and lack of detectable water in highly sheared MCT mylonites challenge our understanding of quartz rheology. However, where water absorption bands can be detected and compared with deformation microstructures, OH concentration maps provide information on the histories of deformation and recovery, evidence for the introduction and loss of fluid inclusions, and water weakening processes.

Synchrotron FTIR imaging of OH in quartz mylonites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kronenberg, Andreas K.; Hasnan, Hasnor F. B.; Holyoke III, Caleb W.

Previous measurements of water in deformed quartzites using conventional Fourier transform infrared spectroscopy (FTIR) instruments have shown that water contents of larger grains vary from one grain to another. However, the non-equilibrium variations in water content between neighboring grains and within quartz grains cannot be interrogated further without greater measurement resolution, nor can water contents be measured in finely recrystallized grains without including absorption bands due to fluid inclusions, films, and secondary minerals at grain boundaries.Synchrotron infrared (IR) radiation coupled to a FTIR spectrometer has allowed us to distinguish and measure OH bands due to fluid inclusions, hydrogen point defects,more » and secondary hydrous mineral inclusions through an aperture of 10 µm for specimens > 40 µm thick. Doubly polished infrared (IR) plates can be prepared with thicknesses down to 4–8 µm, but measurement of small OH bands is currently limited by strong interference fringes for samples < 25 µm thick, precluding measurements of water within individual, finely recrystallized grains. By translating specimens under the 10 µm IR beam by steps of 10 to 50 µm, using a software-controlled x- y stage, spectra have been collected over specimen areas of nearly 4.5 mm 2. This technique allowed us to separate and quantify broad OH bands due to fluid inclusions in quartz and OH bands due to micas and map their distributions in quartzites from the Moine Thrust (Scotland) and Main Central Thrust (Himalayas).Mylonitic quartzites deformed under greenschist facies conditions in the footwall to the Moine Thrust (MT) exhibit a large and variable 3400 cm -1 OH absorption band due to molecular water, and maps of water content corresponding to fluid inclusions show that inclusion densities correlate with deformation and recrystallization microstructures. Quartz grains of mylonitic orthogneisses and paragneisses deformed under amphibolite conditions in the hanging wall to the Main Central Thrust (MCT) exhibit smaller broad OH bands, and spectra are dominated by sharp bands at 3595 to 3379 cm -1 due to hydrogen point defects that appear to have uniform, equilibrium concentrations in the driest samples. The broad OH band at 3400 cm -1 in these rocks is much less common. The variable water concentrations of MT quartzites and lack of detectable water in highly sheared MCT mylonites challenge our understanding of quartz rheology. However, where water absorption bands can be detected and compared with deformation microstructures, OH concentration maps provide information on the histories of deformation and recovery, evidence for the introduction and loss of fluid inclusions, and water weakening processes.« less

A Massive X-ray Outflow From The Quasar PDS 456

NASA Technical Reports Server (NTRS)

Reeves, J. N.; O'Brien, P. T.; Ward, M. J.

2003-01-01

We report on XMM-Newton spectroscopic observations of the luminous, radio-quiet quasar PDS 456. The hard X-ray spectrum of PDS 456 shows a deep absorption trough (constituting 50% of the continuum) at energies above 7 keV in the quasar rest frame, which can be attributed to a series of blue-shifted K-shell absorption edges due to highly ionized iron. The higher resolution soft X-ray grating RGS spectrum exhibits a broad absorption line feature near 1 keV, which can be modeled by a blend of L-shell transitions from highly ionized iron (Fe XVII - XXIV). An extreme outflow velocity of approx. 50000 km/s is required to model the K and L shell iron absorption present in the XMM-Newton data. Overall, a large column density (N(sub H) = 5 x 10(exp 23)/sq cm) of highly ionized gas (log xi = 2.5) is required in PDS 456. A large mass outflow rate of approx. 10 solar mass/year (assuming a conservative outflow covering factor of 0.1 steradian) is derived, which is of the same order as the overall mass accretion rate in PDS 456. This represents a substantial fraction (approx. 10%) of the quasar energy budget, whilst the large column and outflow velocity place PDS 456 towards the extreme end of the broad absorption line quasar population.

Absorption and Reflection Experiments on High-Mobility 2DEGs in the Regime of Microwave-Induced Resistance Oscillations

NASA Astrophysics Data System (ADS)

Studenikin, S. A.; Potemski, M.; Sachrajda, A. S.; Hilke, M.; Pfeiffer, L. N.; West, K. W.

2005-04-01

We have performed microwave absorption and near-field reflection experiments on a high mobility GaAs/AlGaAs heterostructure for the same conditions for which Microwave-Induced Resistance Oscillations (MIROs) are observed. It is shown that the electrodynamic aspect of the problem is important in these experiments. In the absorption experiments a broad CR line was observed due to a large reflection from the highly conductive electron gas. There were no additional features observed related to absorption at harmonics of the cyclotron resonance. In near-field reflection experiments a very different oscillation pattern was revealed when compared to MIROs. The oscillation pattern observed in the reflection experiments is probably due to plasma effects occurring in a finite-size sample. The whole microscopic picture of MIROs is more complicated than simply a resonant absorption at harmonics of the cyclotron resonance. Nevertheless, the experimental observations are in good agreement with the model by Durst et al. involving the photo-assisted scattering in the presence of a crossed magnetic field and dc bias. The observed damping factor of MIROs may be attributed to a change in the electron mobility as a function of temperature. MIROs may be considered as a light-induced drift effect, a broad class of phenomena associated with a light-induced asymmetry in the velocity distribution function.

Absorption and Reflection Experiments on High-Mobility 2DEGs in the Regime of Microwave-Induced Resistance Oscillations

NASA Astrophysics Data System (ADS)

Studenikin, S. A.; Potemski, M.; Sachrajda, A. S.; Hilke, M.; Pfeiffer, L. N.; West, K. W.

We have performed microwave absorption and near-field reflection experiments on a high mobility GaAs/AlGaAs heterostructure for the same conditions for which Microwave-Induced Resistance Oscillations (MIROs) are observed. It is shown that the electrodynamic aspect of the problem is important in these experiments. In the absorption experiments a broad CR line was observed due to a large reflection from the highly conductive electron gas. There were no additional features observed related to absorption at harmonics of the cyclotron resonance. In near-field reflection experiments a very different oscillation pattern was revealed when compared to MIROs. The oscillation pattern observed in the reflection experiments is probably due to plasma effects occurring in a finite-size sample. The whole microscopic picture of MIROs is more complicated than simply a resonant absorption at harmonics of the cyclotron resonance. Nevertheless, the experimental observations are in good agreement with the model by Durst et al. involving the photo-assisted scattering in the presence of a crossed magnetic field and dc bias. The observed damping factor of MIROs may be attributed to a change in the electron mobility as a function of temperature. MIROs may be considered as a light-induced drift effect, a broad class of phenomena associated with a light-induced asymmetry in the velocity distribution function.

Real-time trace gas sensor using a multimode diode laser and multiple-line integrated cavity enhanced absorption spectroscopy.

PubMed

Karpf, Andreas; Rao, Gottipaty N

2015-07-01

We describe and demonstrate a highly sensitive trace gas sensor based on a simplified design that is capable of measuring sub-ppb concentrations of NO2 in tens of milliseconds. The sensor makes use of a relatively inexpensive Fabry-Perot diode laser to conduct off-axis cavity enhanced spectroscopy. The broad frequency range of a multimode Fabry-Perot diode laser spans a large number of absorption lines, thereby removing the need for a single-frequency tunable laser source. The use of cavity enhanced absorption spectroscopy enhances the sensitivity of the sensor by providing a pathlength on the order of 1 km in a small volume. Off-axis alignment excites a large number of cavity modes simultaneously, thereby reducing the sensor's susceptibility to vibration. Multiple-line integrated absorption spectroscopy (where one integrates the absorption spectra over a large number of rovibronic transitions of the molecular species) further improves the sensitivity of detection. Relatively high laser power (∼400  mW) is used to compensate for the low coupling efficiency of a broad linewidth laser to the optical cavity. The approach was demonstrated using a 407 nm diode laser to detect trace quantities of NO2 in zero air. Sensitivities of 750 ppt, 110 ppt, and 65 ppt were achieved using integration times of 50 ms, 5 s, and 20 s respectively.

Iron K Features in the Quasar E 1821+643: Evidence for Gravitationally Redshifted Absorption?

NASA Technical Reports Server (NTRS)

Yaqoob, Tahir; Serlemitsos, Peter

2005-01-01

We report a Chandra high-energy grating detection of a narrow, redshifted absorption line superimposed on the red wing of a broad Fe K line in the z = 0.297 quasar E 1821+643. The absorption line is detected at a confidence level, estimated by two different methods, in the range approx. 2 - 3 sigma. Although the detection significance is not high enough to exclude a non-astrophysical origin, accounting for the absorption feature when modeling the X-ray spectrum implies that the Fe-K emission line is broad, and consistent with an origin in a relativistic accretion disk. Ignoring the apparent absorption feature leads to the conclusion that the Fe-K emission line is narrower, and also affects the inferred peak energy of the line (and hence the inferred ionization state of Fe). If the absorption line (at approx. 6.2 keV in the quasar frame) is real, we argue that it could be due to gravitationally redshifted Fe XXV or Fe XXVI resonance absorption within approx. 10 - 20 gravitational radii of the putative central black hole. The absorption line is not detected in earlier ASCA and Chandra low-energy grating observations, but the absorption line is not unequivocally ruled out by these data. The Chandra high-energy grating Fe-K emission line is consistent with an origin predominantly in Fe I-XVII or so. In an ASCA observation eight years earlier, the Fe-K line peaked at approx. 6.6 keV, closer to the energies of He-like Fe triplet lines. Further, in a Chandra low-energy grating observation the Fe-K line profile was double-peaked, one peak corresponding to Fe I-XVII or so, the other peak to Fe XXVI Ly alpha. Such a wide range in ionization state of Fe is not ruled out by the HEG and ASCA data either, and is suggestive of a complex structure for the line-emitter.

Temperature dependence of the ClONO2 UV absorption spectrum

NASA Technical Reports Server (NTRS)

Burkholder, James B.; Talukdar, Ranajit K.; Ravishankara, A. R.

1994-01-01

The temperature dependence of the ClONO2 absorption spectrum has been measured between 220 and 298 K and between 195 and 430 nm using a diode array spectrometer. The absorption cross sections were determined using both: (1) absolute pressure measurements at 296 K and (2) measurements at various temperatures relative to 296 K using a dual absorption cell arrangement. The temperature dependence of the ClONO2 absorption spectrum shows very broad structure. The amplitude of the temperature dependence relative to that at 296 K is weak at short wavelengths, less than 2% at 215 nm and 220 K, but significant at the wavelengths important in the stratosphere, about 30% at 325 nm and 220 K. Our ClONO2 absorption cross section data are in good general agreement with the previous measurements of Molina and Molina (1979).

500 days of SN 2013dy: spectra and photometry from the ultraviolet to the infrared

NASA Astrophysics Data System (ADS)

Pan, Y.-C.; Foley, R. J.; Kromer, M.; Fox, O. D.; Zheng, W.; Challis, P.; Clubb, K. I.; Filippenko, A. V.; Folatelli, G.; Graham, M. L.; Hillebrandt, W.; Kirshner, R. P.; Lee, W. H.; Pakmor, R.; Patat, F.; Phillips, M. M.; Pignata, G.; Röpke, F.; Seitenzahl, I.; Silverman, J. M.; Simon, J. D.; Sternberg, A.; Stritzinger, M. D.; Taubenberger, S.; Vinko, J.; Wheeler, J. C.

2015-10-01

SN 2013dy is a Type Ia supernova (SN Ia) for which we have compiled an extraordinary data set spanning from 0.1 to ˜ 500 d after explosion. We present 10 epochs of ultraviolet (UV) through near-infrared (NIR) spectra with Hubble Space Telescope/Space Telescope Imaging Spectrograph, 47 epochs of optical spectra (15 of them having high resolution), and more than 500 photometric observations in the BVrRiIZYJH bands. SN 2013dy has a broad and slowly declining light curve (Δm15(B) = 0.92 mag), shallow Si II λ 6355 absorption, and a low velocity gradient. We detect strong C II in our earliest spectra, probing unburned progenitor material in the outermost layers of the SN ejecta, but this feature fades within a few days. The UV continuum of SN 2013dy, which is strongly affected by the metal abundance of the progenitor star, suggests that SN 2013dy had a relatively high-metallicity progenitor. Examining one of the largest single set of high-resolution spectra for an SN Ia, we find no evidence of variable absorption from circumstellar material. Combining our UV spectra, NIR photometry, and high-cadence optical photometry, we construct a bolometric light curve, showing that SN 2013dy had a maximum luminosity of 10.0^{+4.8}_{-3.8} × 10^{42} erg s-1. We compare the synthetic light curves and spectra of several models to SN 2013dy, finding that SN 2013dy is in good agreement with a solar-metallicity W7 model.

The Spectral Variability of the T Tauri Star DF Tauri

NASA Astrophysics Data System (ADS)

Johns-Krull, Christopher M.; Basri, Gibor

1997-01-01

We analyze 117 echelle spectra of the T Tauri star DF Tau, concentrating on variations in the optical continuum veiling and the strong emission lines. Although this star was the inspiration for the original suggestion of magnetospheric accretion in T Tauri stars (TTSs), this hypothesis is only partially supported in our data. We find that variations in the Ca II infrared triplet lines correlate with the veiling variations; there is some evidence that the broad component of the He I line does, too. The narrow component of He I is shown to arise at the stellar surface, but it correlates with the broad component. There is a surprising lack of periodicity in the lines, and it does not occur where expected when seen. The correlation between continuum veiling and the line components expected to be most related to the veiling is poor. There is a great deal of variability in all the lines and line components; a snapshot spectrum is a poor way to characterize the star as a whole. The total Balmer line fluxes are poorly correlated with the veiling, unlike previous results on a large sample of TTSs. Redshifted absorption components are found in the weaker lines but are not common. The strength of the blueshifted absorption feature in Hα is correlated with the veiling, but changes in it perhaps occur before veiling changes by about one day. This time delay supports the idea that the wind originates at some distance from the stellar surface and is related to accretion. Spherically symmetric wind models are unable to reproduce well the relative absorption levels on the blue side of the Hα and Hβ lines simultaneously. Hα does not display the asymmetries expected of magnetospheric accretion, but it is sometimes suggestive of azimuthally asymmetric corotating structures. The line wings indicate that the formation region of the Hα line is dominated by high turbulence. Hβ does show more of the asymmetry expected of magnetospheric accretion. Based on observations obtained at the Lick Observatory operated by the University of California.

A RUNAWAY BLACK HOLE IN COSMOS: GRAVITATIONAL WAVE OR SLINGSHOT RECOIL?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Civano, F.; Elvis, M.; Lanzuisi, G.

2010-07-01

We present a detailed study of a peculiar source detected in the COSMOS survey at z = 0.359. Source CXOC J100043.1+020637, also known as CID-42, has two compact optical sources embedded in the same galaxy. The distance between the two, measured in the HST/ACS image, is 0.''495 {+-} 0.''005 that, at the redshift of the source, corresponds to a projected separation of 2.46 {+-} 0.02 kpc. A large ({approx}1200 km s{sup -1}) velocity offset between the narrow and broad components of H{beta} has been measured in three different optical spectra from the VLT/VIMOS and Magellan/IMACS instruments. CID-42 is also themore » only X-ray source in COSMOS, having in its X-ray spectra a strong redshifted broad absorption iron line and an iron emission line, drawing an inverted P-Cygni profile. The Chandra and XMM-Newton data show that the absorption line is variable in energy by {Delta}E = 500 eV over four years and that the absorber has to be highly ionized in order not to leave a signature in the soft X-ray spectrum. That these features-the morphology, the velocity offset, and the inverted P-Cygni profile-occur in the same source is unlikely to be a coincidence. We envisage two possible explanations, both exceptional, for this system: (1) a gravitational wave (GW) recoiling black hole (BH), caught 1-10 Myr after merging; or (2) a Type 1/Type 2 system in the same galaxy where the Type 1 is recoiling due to the slingshot effect produced by a triple BH system. The first possibility gives us a candidate GW recoiling BH with both spectroscopic and imaging signatures. In the second case, the X-ray absorption line can be explained as a BAL-like outflow from the foreground nucleus (a Type 2 AGN) at the rearer one (a Type 1 AGN), which illuminates the otherwise undetectable wind, giving us the first opportunity to show that fast winds are present in obscured active galactic nuclei (AGNs), and possibly universal in AGNs.« less

Far-infrared response of spherical quantum dots: Dielectric effects and the generalized Kohn's theorem

NASA Astrophysics Data System (ADS)

Movilla, J. L.; Planelles, J.

2007-05-01

The influence of the dielectric environment on the far-infrared (FIR) absorption spectra of two-electron spherical quantum dots is theoretically studied. Effective mass and envelope function approaches with realistic steplike confining potentials are used. Special attention is paid to absorptions that are induced by the electron-electron interaction. High confining barriers make the FIR absorption coefficients almost independent of the quantum dot dielectric environment. Low barrier heights and strong dielectric mismatches preserve the strong fundamental (Kohn) mode but yield the cancellation of excited absorptions, thus monitoring dielectrically induced phase transitions from volume to surface states.

Step-scan differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS): a spectral deconvolution method for weak absorber detection in the presence of strongly overlapping background absorptions.

PubMed

Liu, Lixian; Mandelis, Andreas; Huan, Huiting; Michaelian, Kirk H

2017-04-01

The determination of small absorption coefficients of trace gases in the atmosphere constitutes a challenge for analytical air contaminant measurements, especially in the presence of strongly absorbing backgrounds. A step-scan differential Fourier transform infrared photoacoustic spectroscopy (DFTIR-PAS) method was developed to suppress the coherent external noise and spurious photoacoustic (PA) signals caused by strongly absorbing backgrounds. The infrared absorption spectra of acetylene (C₂H₂) and local air were used to verify the performance of the step-scan DFTIR-PAS method. A linear amplitude response to C₂H₂ concentrations from 100 to 5000 ppmv was observed, leading to a theoretical detection limit of 5 ppmv. The differential mode was capable of eliminating the coherent noise and dominant background gas signals, thereby revealing the presence of the otherwise hidden C₂H₂ weak absorption. Thus, the step-scan DFTIR-PAS modality was demonstrated to be an effective approach for monitoring weakly absorbing gases with absorption bands overlapped by strongly absorbing background species.

Detecting Isotopic Signatures and Measuring Isotopic Ratios on Solid Icy Surfaces:Implications for Origin and Evolution

NASA Astrophysics Data System (ADS)

Clark, R. N.; Brown, R. H.; Swayze, G. A.; Cruikshank, D. P.

2017-12-01

Infrared spectroscopy has long been used to detect isotopes in planetaryatmospheres and in the galaxy. Given sufficient spectral resolution,or large enough changes in mass, isotopes are also detectable in solids.Gas absorption lines can be quite narrow, but in some solids, e.g. H2Oice, absorptions are very broad with little to no fine structure. H2O icehas broad absorptions due to its orientationally disordered structure butmany ices, minerals, and other compounds display sufficiently narrowabsorptions to enable detection of isotopes with small mass changes atmoderate spectral resolution.D2O ice and HDO ice also show orientationally-disordered spectra withvery broad absorption bands. But as deuterium decreases to low levelsdeuterium apparently goes into ordered sites in the H2O ice structure,producing narrow absorptions and shifting to longer wavelengths.Trace D2O condensed on basalt at 80 Kelvin shows an O-D stretch at 4.0microns, but at D/H 0.1 or less in H2O ice, the D-O stretch occursnear 4.13 microns with a width in reflectance decreasing to 0.027 micronas D/H decreases. The narrow D-O stretch absorption shows an absorptioncoefficient of 80,000 cm^-1 enabling detection below Vienna Standard MeanOcean Water (VSMOW) with achievable S/N in the lab and from spacecraft.Isotopes of carbon have been detected in CO2 on Saturn's satelliteswith 16 nm FWHM using the VIMS instrument on the Cassini spacecraft.Deuterium has been detected at close to terrestrial levels in Saturn'srings and on Rhea, and an apparent enhancement on Phoebe using VIMSdata. The ocean world Enceladus is currently being analyzed. We alsodetect an enhancement in 13C on Phoebe, but not on Iapetus or Rhea,consistent with the suggestion from previous studies that suggest Phoebe'sorigin might be external to the Saturn system. The MISE instrumenton the Europa Clipper mission has the capability to detect deuteriumand carbon isotopes in the Jupiter system. The higher temperaturesin the Jupiter system may result in more fractionation, depending upona given isotope and the physical processes involved, potentially withimplications for origin and evolution.

Observation of two distinct negative trions in tungsten disulfide monolayers

NASA Astrophysics Data System (ADS)

Boulesbaa, Abdelaziz; Huang, Bing; Wang, Kai; Lin, Ming-Wei; Mahjouri-Samani, Masoud; Rouleau, Christopher; Xiao, Kai; Yoon, Mina; Sumpter, Bobby; Puretzky, Alexander; Geohegan, David

2015-09-01

Ultrafast pump-probe spectroscopy of two-dimensional tungsten disulfide monolayers (2 D W S2) grown on sapphire substrates revealed two transient absorption spectral peaks that are attributed to distinct negative trions at ˜2.02 eV (T1) and ˜1.98 eV (T2) . The dynamics measurements indicate that trion formation by the probe is enabled by photodoped 2D WS2 crystals with electrons remaining after trapping of holes from excitons or free electron-hole pairs at defect sites in the crystal or on the substrate. Dynamics of the characteristic absorption bands of excitons XA and XB at ˜2.03 and ˜2.40 eV , respectively, were separately monitored and compared to the photoinduced absorption features. Selective excitation of the lowest exciton level XA using λpump<2.4 eV forms only trion T1, implying that the electron remaining from dissociation of exciton XA is involved in the creation of this trion with a binding energy ˜10 meV with respect to XA. The absorption peak corresponding to trion T2 appears when λpump<2.4 eV , which is just sufficient to excite exciton XB. The dynamics of trion T2 formation are found to correlate with the disappearance of the bleach of the XB exciton, indicating the involvement of holes participating in the bleach dynamics of exciton XB. Static electrical-doping photoabsorption measurements confirm the presence of an induced absorption peak similar to that of T2. Since the proposed trion formation process here involves exciton dissociation through hole trapping by defects in the 2D crystal or substrate, this discovery highlights the strong role of defects in defining optical and electrical properties of 2D metal chalcogenides, which is relevant to a broad spectrum of basic science and technological applications.

Allophane on Mars: Evidence from IR Spectroscopy and TES Spectral Models

NASA Technical Reports Server (NTRS)

Ming, Douglas W.; Rampe, E. B.; Kraft, M. D.; Sharp. T. G.; Golden, D. C.; Christensen, P. C.

2010-01-01

Allophane is an alteration product of volcanic glass and a clay mineral precursor that is commonly found in basaltic soils on Earth. It is a poorly-crystalline or amorphous, hydrous aluminosilicate with Si/Al ratios ranging from approx.0.5-1 [Wada, 1989]. Analyses of thermal infrared (TIR) spectra of the Martian surface from TES show high-silica phases at mid-to-high latitudes that have been proposed to be primary volcanic glass [Bandfield et al., 2000; Bandfield, 2002; Rogers and Christensen, 2007] or poorly-crystalline secondary silicates such as allophane or aluminous amorphous silica [Kraft et al., 2003; Michalski et al., 2006; Rogers and Christensen, 2007; Kraft, 2009]. Phase modeling of chemical data from the APXS on the Mars Exploration Rover Spirit suggest the presence of allophane in chemically weathered rocks [Ming et al., 2006]. The presence of allophane on Mars has not been previously tested with IR spectroscopy because allophane spectra have not been available. We synthesized allophanes and allophanic gels with a range of Si/Al ratios to measure TIR emission and VNIR reflectance spectra and to test for the presence of allophane in Martian soils. VNIR reflectance spectra of the synthetic allophane samples have broad absorptions near 1.4 m from OH stretching overtones and 1.9 m from a combination of stretching and bending vibrations in H2O. Samples have a broad absorption centered near 2.25 microns, from AlAlOH combination bending and stretching vibrations, that shifts position with Si/Al ratio. Amorphous silica (opaline silica or primary volcanic glass) has been identified in CRISM spectra of southern highland terrains based on the presence of 1.4, 1.9, and broad 2.25 m absorptions [Mustard et al., 2008]; however, these absorptions are also consistent with the presence of allophane. TIR emission spectra of the synthetic allophanes show two spectrally distinct types: Si-rich and Al-rich. Si-rich allophanes have two broad absorptions centered near 1080 and 430 cm-1 from Si(Al)-O stretching and Si(Al)-O bending vibrations, respectively, and Al-rich allophanes have three broad absorptions centered near 950, 540, and 430 cm-1. We used a spectral library commonly used to deconvolve TES spectra and four allophane spectra to model nine spectrally distinct regions on Mars [from Rogers et al., 2007]. Regions previously modeled with high-silica phases contain significant amounts of allophane (>10 vol.%) in our models. Our models of northern Acidalia, the type locality for surface type 2 materials, contain 40 vol.% Si-rich allophane. The presence of allophane in multiple surface regions of Mars indicates a more widespread occurrence of low-temperature aqueous alteration at moderate pH than has been previously recognized. The regional variations in modeled abundances and the types of allophane (Si- vs. Al-rich) suggest regional differences in Mars weathering processes.

Quantification and parametrization of non-linearity effects by higher-order sensitivity terms in scattered light differential optical absorption spectroscopy

NASA Astrophysics Data System (ADS)

Puķīte, Jānis; Wagner, Thomas

2016-05-01

We address the application of differential optical absorption spectroscopy (DOAS) of scattered light observations in the presence of strong absorbers (in particular ozone), for which the absorption optical depth is a non-linear function of the trace gas concentration. This is the case because Beer-Lambert law generally does not hold for scattered light measurements due to many light paths contributing to the measurement. While in many cases linear approximation can be made, for scenarios with strong absorptions non-linear effects cannot always be neglected. This is especially the case for observation geometries, for which the light contributing to the measurement is crossing the atmosphere under spatially well-separated paths differing strongly in length and location, like in limb geometry. In these cases, often full retrieval algorithms are applied to address the non-linearities, requiring iterative forward modelling of absorption spectra involving time-consuming wavelength-by-wavelength radiative transfer modelling. In this study, we propose to describe the non-linear effects by additional sensitivity parameters that can be used e.g. to build up a lookup table. Together with widely used box air mass factors (effective light paths) describing the linear response to the increase in the trace gas amount, the higher-order sensitivity parameters eliminate the need for repeating the radiative transfer modelling when modifying the absorption scenario even in the presence of a strong absorption background. While the higher-order absorption structures can be described as separate fit parameters in the spectral analysis (so-called DOAS fit), in practice their quantitative evaluation requires good measurement quality (typically better than that available from current measurements). Therefore, we introduce an iterative retrieval algorithm correcting for the higher-order absorption structures not yet considered in the DOAS fit as well as the absorption dependence on temperature and scattering processes.

From nanoscale to macroscale: Engineering biomass derivatives with nitrogen doping for tailoring dielectric properties and electromagnetic absorption

NASA Astrophysics Data System (ADS)

Wang, Yana; Zhou, Zhili; Chen, Mingji; Huang, Yixing; Wang, Changxian; Song, Wei-Li

2018-05-01

Since achievement in electromagnetic (EM) technology dramatically promotes the critical requirement in developing advanced EM response materials, which are required to hold various advantageous features in light weight, small thickness, strong reflection loss and broadband absorption, the most important requirements, i.e. strong reflection loss and broadband absorption, are still highly pursued because of the intrinsic shortage in conventional EM absorbers. For addressing such critical problems, a unique three-dimensional nitrogen doped carbon monolith was demonstrated to understand the effects of the nitrogen doping on the dielectric and microwave absorption performance. The chemical components of the nitrogen doped carbon monoliths have been quantitatively determined for fully understanding the effects of nanoscale structures on the macroscopic composites. A modified Cole-Cole plot is plotted for guiding the chemical doping and material process, aiming to realizing the best matching conditions. The results have promised a universal route for achieving advanced materials with strong and broadband EM absorption.

Characterization of Ambient Black Carbon Aerosols

NASA Astrophysics Data System (ADS)

Zhang, R.; Levy, M. E.; Zheng, J.; Molina, L. T.

2013-12-01

Because of the strong absorption over a broad range of the electromagnetic spectra, black carbon (BC) is a key short-lived climate forcer, which contributes significantly to climate change by direct radiative forcing and is the second most important component causing global warming after carbon dioxide. The impact of BC on the radiative forcing of the Earth-Atmosphere system is highly dependent of the particle properties. In this presentation, emphasis will be placed on characterizing BC containing aerosols in at the California-Mexico border to obtain a greater understanding of the atmospheric aging and properties of ambient BC aerosols. A comprehensive set of directly measured aerosol properties, including the particle size distribution, effective density, hygroscopicity, volatility, and several optical properties, will be discussed to quantify the mixing state and composition of ambient particles. In Tijuana, Mexico, submicron aerosols are strongly influenced by vehicle emissions; subsequently, the BC concentration in Tijuana is considerably higher than most US cities with an average BC concentration of 2.71 × 2.65 g cm-3. BC accounts for 24.75 % × 9.44 of the total submicron concentration on average, but periodically accounts for over 50%. This high concentration of BC strongly influences many observed aerosol properties such as single scattering albedo, hygroscopicity, effective density, and volatility.

Broad band solar EUV absorption in the earth's upper atmosphere.

NASA Technical Reports Server (NTRS)

Allen, K. H.; Rense, W. A.

1973-01-01

Observation data on solar radiation intensity, based on measurements performed as a function of time for three broad wavelength bands between 280 and 1030 A by a wheel spectrometer on Oso 5 during sunrise and sunset, are compared with predicted intensity variations based on Cira models. The differences between sunrise and sunset data, as well as those between observed and predicted data are discussed.

Preparation and characterization of Ba0.2Sr0.2La0.6MnO3 nanoparticles and investigation of size & shape effect on microwave absorption

NASA Astrophysics Data System (ADS)

Peymanfar, Reza; Javanshir, Shahrzad

2017-06-01

In this paper, the design and characterization of a radar absorbing material (RAM) was investigated at microwave frequency. Ba0.2Sr0.2La0.6MnO3 magnetic nanoparticles was synthesized thru a facile hydrothermal method in the presence of polymethyl methacrylate (PMMA) and the possibility of shape and size-controlled synthesis of nanoparticles (NPs) over the range 15-50 Nm was also explored. Afterward, the effect of shape and size of the synthesized Ba0.2Sr0.2La0.6MnO3 NPs on microwave absorption properties was investigated in KU-band. The crystal structures and morphology of as-synthesized nanoparticles were characterized and confirmed by FESEM, XRD, VSM, FTIR analysis. The RAM samples were prepared by dispersion of magnetic NPs in silicone rubber in an ultrasonic bath. The maximum reflection loss (RL) values NPs were 12.04 dB at 14.82 GHz and a broad absorption band (over 1.22 GHz) with RL values <-10 dB are obtained and the maximum reflection loss (RL) values of decrease and shaped NPs were 22.36 dB at 14.78 GHz and a broad absorption band (over 2.67 GHz) with RL values <-10 dB are obtained. The results indicated that the particle size and shape play a major role on the absorption properties of the composites in the 12.4-18 GHz frequency range. It is observed that microwave absorption properties increased with the decrease in average particle size of NPs.

Tables of nuclear cross sections for galactic cosmic rays: Absorption cross sections

NASA Technical Reports Server (NTRS)

Townsend, L. W.; Wilson, J. W.

1985-01-01

A simple but comprehensive theory of nuclear reactions is presented. Extensive tables of nucleon, deuteron, and heavy-ion absorption cross sections over a broad range of energies are generated for use in cosmic ray shielding studies. Numerous comparisons of the calculated values with available experimental data show agreement to within 3 percent for energies above 80 MeV/nucleon and within approximately 10 percent for energies as low as 30 MeV/nucleon. These tables represent the culmination of the development of the absorption cross section formalism and supersede the preliminary absorption cross sections published previously in NASA TN D-8107, NASA TP-2138, and NASA TM-84636.

Homeotropic alignment and Förster resonance energy transfer: The way to a brighter luminescent solar concentrator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tummeltshammer, Clemens; Taylor, Alaric; Kenyon, Anthony J.

2014-11-07

We investigate homeotropically aligned fluorophores and Förster resonance energy transfer (FRET) for luminescent solar concentrators using Monte-Carlo ray tracing. The homeotropic alignment strongly improves the trapping efficiency, while FRET circumvents the low absorption at homeotropic alignment by separating the absorption and emission processes. We predict that this design doped with two organic dye molecules can yield a 82.9% optical efficiency improvement compared to a single, arbitrarily oriented dye molecule. We also show that quantum dots are prime candidates for absorption/donor fluorophores due to their wide absorption band. The potentially strong re-absorption and low quantum yield of quantum dots is notmore » a hindrance for this design.« less

Ultrasensitive, real-time trace gas detection using a high-power, multimode diode laser and cavity ringdown spectroscopy.

PubMed

Karpf, Andreas; Qiao, Yuhao; Rao, Gottipaty N

2016-06-01

We present a simplified cavity ringdown (CRD) trace gas detection technique that is insensitive to vibration, and capable of extremely sensitive, real-time absorption measurements. A high-power, multimode Fabry-Perot (FP) diode laser with a broad wavelength range (Δλ_laser∼0.6  nm) is used to excite a large number of cavity modes, thereby reducing the detector's susceptibility to vibration and making it well suited for field deployment. When detecting molecular species with broad absorption features (Δλ_absorption≫Δλ_laser), the laser's broad linewidth removes the need for precision wavelength stabilization. The laser's power and broad linewidth allow the use of on-axis cavity alignment, improving the signal-to-noise ratio while maintaining its vibration insensitivity. The use of an FP diode laser has the added advantages of being inexpensive, compact, and insensitive to vibration. The technique was demonstrated using a 1.1 W (λ=400  nm) diode laser to measure low concentrations of nitrogen dioxide (NO₂) in zero air. A sensitivity of 38 parts in 10¹² (ppt) was achieved using an integration time of 128 ms; for single-shot detection, 530 ppt sensitivity was demonstrated with a measurement time of 60 μs, which opens the door to sensitive measurements with extremely high temporal resolution; to the best of our knowledge, these are the highest speed measurements of NO₂ concentration using CRD spectroscopy. The reduced susceptibility to vibration was demonstrated by introducing small vibrations into the apparatus and observing that there was no measurable effect on the sensitivity of detection.

Broad Band Intra-Cavity Total Reflection Chemical Sensor

DOEpatents

Pipino, Andrew C. R.

1998-11-10

A broadband, ultrahigh-sensitivity chemical sensor is provided that allows etection through utilization of a small, extremely low-loss, monolithic optical cavity. The cavity is fabricated from highly transparent optical material in the shape of a regular polygon with one or more convex facets to form a stable resonator for ray trajectories sustained by total internal reflection. Optical radiation enters and exits the monolithic cavity by photon tunneling in which two totally reflecting surfaces are brought into close proximity. In the presence of absorbing material, the loss per pass is increased since the evanescent waves that exist exterior to the cavity at points where the circulating pulse is totally reflected, are absorbed. The decay rate of an injected pulse is determined by coupling out an infinitesimal fraction of the pulse to produce an intensity-versus-time decay curve. Since the change in the decay rate resulting from absorption is inversely proportional to the magnitude of absorption, a quantitative sensor of concentration or absorption cross-section with 1 part-per-million/pass or better sensitivity is obtained. The broadband nature of total internal reflection permits a single device to be used over a broad wavelength range. The absorption spectrum of the surrounding medium can thereby be obtained as a measurement of inverse decay time as a function of wavelength.

Temperature dependence of the ClONO{sub 2} UV absorption spectrum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burkholder, J.B.; Talukdar, R.K.; Ravishankara, A.R.

1994-04-01

The temperature dependence of the ClONO{sub 2} absorption spectrum has been measured between 220 and 298 K and between 195 and 430 nm using a diode array spectrometer. The absorption cross sections were determined using both: (1) absolute pressure measurements at 296 K and (2) measurements at various temperatures relative to 296 K using a dual absorption cell arrangement. The temperature dependence of the ClONO{sub 2} absorption spectrum shows very broad structure. The amplitude of the temperature dependence relative to that at 296 K is weak at short wavelengths, < 2% at 215 nm and 220 K, but significant atmore » the wavelengths important in the stratosphere, {approximately} 30% at 325 nm and 220 K. The authors ClONO{sub 2} absorption cross section data are in good general agreement with the previous measurements of Molina and Molina.« less

Optical detection of tracer species in strongly scattering media.

PubMed

Brauser, Eric M; Rose, Peter E; McLennan, John D; Bartl, Michael H

2015-03-01

A combination of optical absorption and scattering is used to detect tracer species in a strongly scattering medium. An optical setup was developed, consisting of a dual-beam scattering detection scheme in which sample scattering beam overlaps with the characteristic absorption feature of quantum dot tracer species, while the reference scattering beam is outside any absorption features of the tracer. This scheme was successfully tested in engineered breakthrough tests typical of wastewater and subsurface fluid analysis, as well as in batch analysis of oil and gas reservoir fluids and biological samples. Tracers were detected even under highly scattering conditions, conditions in which conventional absorption or fluorescence methods failed.

Achieving an ultra-narrow multiband light absorption meta-surface via coupling with an optical cavity.

PubMed

Liu, Zhengqi; Liu, Guiqiang; Liu, Xiaoshan; Huang, Shan; Wang, Yan; Pan, Pingping; Liu, Mulin

2015-06-12

Resonant plasmonic and metamaterial absorbers are of particular interest for applications in a wide variety of nanotechnologies including thermophotovoltaics, photothermal therapy, hot-electron collection and biosensing. However, it is rather challenging to realize ultra-narrow absorbers using plasmonic materials due to large optical losses in metals that inevitably decrease the quality of optical resonators. Here, we theoretically report methods to achieve an ultra-narrow light absorption meta-surface by using photonic modes of the optical cavities, which strongly couple with the plasmon resonances of the metallic nanostructures. Multispectral light absorption with absorption amplitude exceeding 99% and a bandwidth approaching 10 nm is achieved at the optical frequencies. Moreover, by introducing a thick dielectric coupling cavity, the number of absorption bands can be strongly increased and the bandwidth can even be narrowed to less than 5 nm due to the resonant spectrum splitting enabled by strong coupling between the plasmon resonances and the optical cavity modes. Designing such optical cavity-coupled meta-surface structures is a promising route for achieving ultra-narrow multiband absorbers, which can be used in absorption filters, narrow-band multispectral thermal emitters and thermophotovoltaics.

A new type of artificial structure to achieve broadband omnidirectional acoustic absorption

NASA Astrophysics Data System (ADS)

Zheng, Li-Yang; Wu, Ying; Zhang, Xiao-Liu; Ni, Xu; Chen, Ze-Guo; Lu, Ming-Hui; Chen, Yan-Feng

2013-10-01

We present a design for a two-dimensional omnidirectional acoustic absorber that can achieve 98.6% absorption of acoustic waves in water, forming an effective acoustic black hole. This artificial black hole consists of an absorptive core coated with layers of periodically distributed polymer cylinders embedded in water. Effective medium theory describes the response of the coating layers to the acoustic waves. The polymer parameters can be adjusted, allowing practical fabrication of the absorber. Since the proposed structure does not rely on resonances, it is applicable to broad bandwidths. The design might be extended to a variety of applications.

Interstellar proteins and the discovery of a new absorption feature at lambda = 2800 A

NASA Astrophysics Data System (ADS)

Karim, L. M.; Hoyle, F.; Wickramasinghe, N. C.

1983-07-01

In order to check the presence of biogenic materials in interstellar grains, the spectra of three early-type, heavily reddened stars recorded by the IUE were examined. These stars showed comparatively weak absorption at 2200 A, minimizing the effect of graphite grains. A broad absorption feature centered on 2800 A is discovered in HD 14250 and interpreted to be due to the amino acid tryptophan. Comparison of the spectrum with that of the calculated extinction behavior of graphite spheres of radii 0.02 microns suggests that the latter are not responsible for the observed spectrum.

Composite Spectra of Broad Absorption Line Quasars in SDSS-III BOSS

NASA Astrophysics Data System (ADS)

Herbst, Hanna; Hamann, Fred; Paris, Isabelle; Capellupo, Daniel M.

2017-01-01

We present preliminary results from a study of broad absorption line (BAL) quasars in the SDSS-III BOSS survey. We’re particularly interested in BALs because they arise from quasar outflows, which may be a source of feedback to the host galaxy. We analyze median composite spectra for BOSS QSOs in the redshift range 2.1 to 3.4 sorted by the strength of the BAL absorption troughs, parameterized by the Balnicity Index (BI), to study trends in the emission and absorption properties of BAL quasars. The wavelength coverage and high number of quasars observed in the BOSS survey allow us to examine BALs in the Lyman forest. Our main preliminary results when sorting the quasars by BI are 1) doublet absorption lines such as P V 1128A show a 1:1 ratio across all BI, indicating large column densities at all BI. This suggests that weaker BAL troughs result from smaller covering fractions rather than lower column densities. 2) The He II emission line, which is a measure of the far-UV/near-UV hardness of the ionizing continuum, is weaker in the larger BI composite spectra, indicating a far-UV spectral softening correlated with BI. This is consistent with the radiatively-driven BAL outflows being helped by intrinsically weaker ionizing continuum shapes (e.g., Baskin, Laor, and Hamann 2013). We also find a trend for slightly redder continuum slopes in the larger BI composite spectra, suggesting that the slope differences in the near-UV are also intrinsic.

UV-Photochemistry of the Disulfide Bond: Evolution of Early Photoproducts from Picosecond X-ray Absorption Spectroscopy at the Sulfur K-Edge.

PubMed

Ochmann, Miguel; Hussain, Abid; von Ahnen, Inga; Cordones, Amy A; Hong, Kiryong; Lee, Jae Hyuk; Ma, Rory; Adamczyk, Katrin; Kim, Tae Kyu; Schoenlein, Robert W; Vendrell, Oriol; Huse, Nils

2018-05-30

We have investigated dimethyl disulfide as the basic moiety for understanding the photochemistry of disulfide bonds, which are central to a broad range of biochemical processes. Picosecond time-resolved X-ray absorption spectroscopy at the sulfur K-edge provides unique element-specific insight into the photochemistry of the disulfide bond initiated by 267 nm femtosecond pulses. We observe a broad but distinct transient induced absorption spectrum which recovers on at least two time scales in the nanosecond range. We employed RASSCF electronic structure calculations to simulate the sulfur-1s transitions of multiple possible chemical species, and identified the methylthiyl and methylperthiyl radicals as the primary reaction products. In addition, we identify disulfur and the CH 2 S thione as the secondary reaction products of the perthiyl radical that are most likely to explain the observed spectral and kinetic signatures of our experiment. Our study underscores the importance of elemental specificity and the potential of time-resolved X-ray spectroscopy to identify short-lived reaction products in complex reaction schemes that underlie the rich photochemistry of disulfide systems.

Impact of vanadium ions in barium borate glass

NASA Astrophysics Data System (ADS)

Abdelghany, A. M.; Hammad, Ahmed H.

2015-02-01

Combined optical and infrared spectral measurements of prepared barium borate glasses containing different concentrations of V2O5 were carried out. Vanadium containing glasses exhibit extended UV-visible (UV/Vis.) bands when compared with base binary borate glass. UV/Vis. spectrum shows the presence of an unsymmetrical strong UV broad band centered at 214 nm attributed to the presence of unavoidable trace iron impurities within the raw materials used for the preparation of such glass. The calculated direct and indirect optical band gaps are found to decrease with increasing the vanadium content (2.9:137 for indirect and 3.99:2.01 for direct transition). This change was discussed in terms of structural changes in the glass network. Infrared absorption spectra of the glasses reveal the appearance of both triangular and tetrahedral borate units. Electron spin resonance analyses indicate the presence of unpaired species in sufficient quantity to be identified and to confirm the spectral data.

The ultraviolet and visible spectrum of the polycyclic aromatic hydrocarbon C10H8(+) - Possible contributions to the diffuse interstellar bands and to the ultraviolet-visible extinction

NASA Technical Reports Server (NTRS)

Salama, F.; Allamandola, L. J.

1992-01-01

The properties of the cation of the PAH naphthalene (C10H8(+)) isolated in inert gas matrices under conditions relevant to astrophysical environments are described. The band at 6741 A is the strongest and falls close to the weak 6742 A diffuse interstellar bands (DIBs). Five other weaker bands also fall remarkably close to the positions of known DIBs. A very intense and broad continuum extended from the UV to the visible, which seems to be associated with the ion, is reported. The molar absorption coefficient at the peak of the continuum is 2.0 x 10 exp 6 cu dm/mol cm. If a continuum is a general property of PAH cations, this characteristic will have a strong impact on the understanding of how PAHs convert interstellar UV and visible radiation into IR radiation.

A short review of relativistic iron lines from stellar-mass black holes

NASA Astrophysics Data System (ADS)

Miller, J. M.

2006-12-01

% In this contribution, I briefly review recent progress in detecting and measuring the properties of relativistic iron lines observed in stellar-mass black hole systems, and the aspects of these lines that are most relevant to studies of similar lines in Seyfert-1 AGN. In particular, the lines observed in stellar-mass black holes are not complicated by complex low-energy absorption or partial-covering of the central engine, and strong lines are largely independent of the model used to fit the underlying broad-band continuum flux. Indeed, relativistic iron lines are the most robust diagnostic of black hole spin that is presently available to observers, with specific advantages over the systematics-plagued disk continuum. If accretion onto stellar-mass black holes simply scales with mass, then the widespread nature of lines in stellar-mass black holes may indicate that lines should be common in Seyfert-1 AGN, though perhaps harder to detect.

Terahertz sensing of highly absorptive water-methanol mixtures with multiple resonances in metamaterials.

PubMed

Chen, Min; Singh, Leena; Xu, Ningning; Singh, Ranjan; Zhang, Weili; Xie, Lijuan

2017-06-26

Terahertz sensing of highly absorptive aqueous solutions remains challenging due to strong absorption of water in the terahertz regime. Here, we experimentally demonstrate a cost-effective metamaterial-based sensor integrated with terahertz time-domain spectroscopy for highly absorptive water-methanol mixture sensing. This metamaterial has simple asymmetric wire structures that support multiple resonances including a fundamental Fano resonance and higher order dipolar resonance in the terahertz regime. Both the resonance modes have strong intensity in the transmission spectra which we exploit for detection of the highly absorptive water-methanol mixtures. The experimentally characterized sensitivities of the Fano and dipole resonances for the water-methanol mixtures are found to be 160 and 305 GHz/RIU, respectively. This method provides a robust route for metamaterial-assisted terahertz sensing of highly absorptive chemical and biochemical materials with multiple resonances and high accuracy.

Absorption Reconstruction Improves Biodistribution Assessment of Fluorescent Nanoprobes Using Hybrid Fluorescence-mediated Tomography

PubMed Central

Gremse, Felix; Theek, Benjamin; Kunjachan, Sijumon; Lederle, Wiltrud; Pardo, Alessa; Barth, Stefan; Lammers, Twan; Naumann, Uwe; Kiessling, Fabian

2014-01-01

Aim: Fluorescence-mediated tomography (FMT) holds potential for accelerating diagnostic and theranostic drug development. However, for proper quantitative fluorescence reconstruction, knowledge on optical scattering and absorption, which are highly heterogeneous in different (mouse) tissues, is required. We here describe methods to assess these parameters using co-registered micro Computed Tomography (µCT) data and nonlinear whole-animal absorption reconstruction, and evaluate their importance for assessment of the biodistribution and target site accumulation of fluorophore-labeled drug delivery systems. Methods: Besides phantoms with varying degrees of absorption, mice bearing A431 tumors were imaged 15 min and 48 h after i.v. injection of a fluorophore-labeled polymeric drug carrier (pHPMA-Dy750) using µCT-FMT. The outer shape of mice and a scattering map were derived using automated segmentation of the µCT data. Furthermore, a 3D absorption map was reconstructed from the trans-illumination data. We determined the absorption of five interactively segmented regions (heart, liver, kidney, muscle, tumor). Since blood is the main near-infrared absorber in vivo, the absorption was also estimated from the relative blood volume (rBV), determined by contrast-enhanced µCT. We compared the reconstructed absorption with the rBV-based values and analyzed the effect of using the absorption map on the fluorescence reconstruction. Results: Phantom experiments demonstrated that absorption reconstruction is possible and necessary for quantitative fluorescence reconstruction. In vivo, the reconstructed absorption showed high values in strongly blood-perfused organs such as the heart, liver and kidney. The absorption values correlated strongly with the rBV-based absorption values, confirming the accuracy of the absorption reconstruction. Usage of homogenous absorption instead of the reconstructed absorption map resulted in reduced values in the heart, liver and kidney, by factors of 3.5, 2.1 and 1.4, respectively. For muscle and subcutaneous tumors, which have a much lower rBV and absorption, absorption reconstruction was less important. Conclusion: Quantitative whole-animal absorption reconstruction is possible and can be validated in vivo using the rBV. Usage of an absorption map is important when quantitatively assessing the biodistribution of fluorescently labeled drugs and drug delivery systems, to avoid a systematic underestimation of fluorescence in strongly absorbing organs, such as the heart, liver and kidney. PMID:25157277

Probing the Inflow/Outflow and Accretion Disk of Cygnus X-1 in the High State with the Chandra High Energy Transmission Grating

NASA Technical Reports Server (NTRS)

Feng, Y. X.; Tennant, A. F.; Zhang, S. N.

2003-01-01

Cygnus X-1 was observed in the high state at the conjunction orbital phase (0) with Chandra High Energy Transmission Grating (HETG). Strong and asymmetric absorption lines of highly ionized species were detected, such as Fe xxv, Fe xxiv, Fe xxiii, Si xiv, S xvi, Ne x, etc. In the high state the profile of the absorption lines is composed of an extended red wing and a less extended blue wing. The red wings of higher ionized species are more extended than those of lower ionized species. The detection of these lines provides a way to probe the properties of the flow around the companion and the black hole in Cyg X-1 during the high state. A broad emission feature around 6.5 keV was significantly detected from the spectra of both the Chandra/HETG and the RXTE/Proportional Counter Array. This feature appears to be symmetric and can be fitted with a Gaussian function rather than the Laor disk line model of the fluorescent Fe K(alpha) line from an accretion disk. The implications of these results on the structure of the accretion flow of Cyg X-1 in the high state are discussed.

Near-Infrared Plasmonic-Enhanced Solar Energy Harvest for Highly Efficient Photocatalytic Reactions.

PubMed

Cui, Jiabin; Li, Yongjia; Liu, Lei; Chen, Lin; Xu, Jun; Ma, Jingwen; Fang, Gang; Zhu, Enbo; Wu, Hao; Zhao, Lixia; Wang, Leyu; Huang, Yu

2015-10-14

We report a highly efficient photocatalyst comprised of Cu7S4@Pd heteronanostructures with plasmonic absorption in the near-infrared (NIR)-range. Our results indicated that the strong NIR plasmonic absorption of Cu7S4@Pd facilitated hot carrier transfer from Cu7S4 to Pd, which subsequently promoted the catalytic reactions on Pd metallic surface. We confirmed such enhancement mechanism could effectively boost the sunlight utilization in a wide range of photocatalytic reactions, including the Suzuki coupling reaction, hydrogenation of nitrobenzene, and oxidation of benzyl alcohol. Even under irradiation at 1500 nm with low power density (0.45 W/cm(2)), these heteronanostructures demonstrated excellent catalytic activities. Under solar illumination with power density as low as 40 mW/cm(2), nearly 80-100% of conversion was achieved within 2 h for all three types of organic reactions. Furthermore, recycling experiments showed the Cu7S4@Pd were stable and could retain their structures and high activity after five cycles. The reported synthetic protocol can be easily extended to other Cu7S4@M (M = Pt, Ag, Au) catalysts, offering a new solution to design and fabricate highly effective photocatalysts with broad material choices for efficient conversion of solar energy to chemical energy in an environmentally friendly manner.

The Discovery of a High-Redshift Quasar without Emission Lines from Sloan Digital Sky Survey Commissioning Data.

PubMed

Fan; Strauss; Gunn; Lupton; Carilli; Rupen; Schmidt; Moustakas; Davis; Annis; Bahcall; Brinkmann; Brunner; Csabai; Doi; Fukugita; Heckman; Hennessy; Hindsley; Ivezic; Knapp; Lamb; Munn; Pauls; Pier; Rockosi; Schneider; Szalay; Tucker; York

1999-12-01

We report observations of a luminous unresolved object at redshift z=4.62, with a featureless optical spectrum redward of the Lyalpha forest region, discovered from Sloan Digital Sky Survey commissioning data. The redshift is determined by the onset of the Lyalpha forest at lambda approximately 6800 Å and a Lyman limit system at lambda=5120 Å. A strong Lyalpha absorption system with weak metal absorption lines at z=4.58 is also identified in the spectrum. The object has a continuum absolute magnitude of -26.6 at 1450 Å in the rest frame (h0=0.5, q0=0.5) and therefore cannot be an ordinary galaxy. It shows no radio emission (the 3 sigma upper limit of its flux at 6 cm is 60 µJy), indicating a radio-to-optical flux ratio at least as small as that of the radio-weakest BL Lacertae objects known. It is also not linearly polarized to a 3 sigma upper limit of 4% in the observed I band. Therefore, it is either the most distant BL Lac object known to date, with very weak radio emission, or a new type of unbeamed quasar, whose broad emission line region is very weak or absent.

Real Time Quantification of Ultrafast Photoinduced Bimolecular Electron Transfer Rate: Direct Probing of the Transient Intermediate.

PubMed

Mukherjee, Puspal; Biswas, Somnath; Sen, Pratik

2015-08-27

Fluorescence quenching studies through steady-state and time-resolved measurements are inadequate to quantify the bimolecular electron transfer rate in bulk homogeneous solution due to constraints from diffusion. To nullify the effect of diffusion, direct evaluation of the rate of formation of a transient intermediate produced upon the electron transfer is essential. Methyl viologen, a well-known electron acceptor, produces a radical cation after accepting an electron, which has a characteristic strong and broad absorption band centered at 600 nm. Hence it is a good choice to evaluate the rate of photoinduced electron transfer reaction employing femtosecond broadband transient absorption spectroscopy. The time constant of the aforementioned process between pyrene and methyl viologen in methanol has been estimated to be 2.5 ± 0.4 ps using the same technique. The time constant for the backward reaction was found to be 14 ± 1 ps. These values did not change with variation of concentration of quencher, i.e., methyl viologen. Hence, we can infer that diffusion has no contribution in the estimation of rate constants. However, on changing the solvent from methanol to ethanol, the time constant of the electron transfer reaction has been found to increase and has accounted for the change in solvent reorganization energy.

Manipulation of enhanced absorption with tilted hexagonal boron nitride slabs

NASA Astrophysics Data System (ADS)

Wu, Xiaohu; Fu, Ceji

2018-04-01

The wavevector of electromagnetic wave propagation in a hexagonal boron nitride (hBN) slab can be controlled by tilting its optical axis. This property can be used to manipulate the absorption in a hBN slab. By carefully analyzing the dependence of the absorptivity of a thin hBN slab on the tilted angle of its optical axis, we propose a structure that can realize great absorptivity enhancement in a band by stacking hBN slabs of different tilted angles. Our numerical results show that the absorptivity of a structure made of 91 stacked hBN slabs can be achieved higher than 0.94 in the wavenumber range from 1367 to 1580 cm-1 when the tilted angles of the slabs are properly arranged. The strong absorption is attributed to the combination of impedance matching at the slab interfaces and enlarged wavevectors in the slabs. This work reveals a novel way to realize strong absorption with anisotropic materials for applications in areas such as thermal radiative energy harvesting and conversion.

Formation of graded vanadium oxide (V-O compound) under strong gravitational field

NASA Astrophysics Data System (ADS)

Khandaker, Jahirul Islam; Tokuda, Makoto; Ogata, Yudai; Januszko, Kamila; Nishiyama, Tadao; Yoshiasa, Akira; Mashimo, Tsutomu

2015-05-01

Sedimentation of atoms induced under strong gravitational field gives a tool for controlling elemental compositions in condensed matter. We performed a strong-gravity experiment (0.397 × 106 G at 400 °C for 24 h) on a V2O5 polycrystal using the high-temperature ultracentrifuge to examine the composition change and further the structure change. The graded composition structure of V and O was formed along gravity direction, where V increases and O decreases with gravity. It was found by the x-ray diffraction and Raman scattering method that VO2 and V2O3 phases appeared and the amounts increased, while one of the V2O5 phase decreased gradually along gravity direction. The X-ray absorption near edge structure spectra analysis identified the chemical valency decrease (+5 to +3). The UV-Vis absorption spectroscopy addressed the shifting in center of major absorption peak to longer wavelength (red shift) with the increase in gravitational field. The tail absorption peak (band gap 2.09 eV) at strong gravity region in the graded structure showed transparent conductive oxide.

An Unusual Strong Visible-Light Absorption Band in Red Anatase TiO2 Photocatalyst Induced by Atomic Hydrogen-Occupied Oxygen Vacancies.

PubMed

Yang, Yongqiang; Yin, Li-Chang; Gong, Yue; Niu, Ping; Wang, Jian-Qiang; Gu, Lin; Chen, Xingqiu; Liu, Gang; Wang, Lianzhou; Cheng, Hui-Ming

2018-02-01

Increasing visible light absorption of classic wide-bandgap photocatalysts like TiO 2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible-light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO 2 , an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO 2 by intentionally introducing atomic hydrogen-mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo-electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide-bandgap semiconductors to fully capture solar light. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasmonic Control of Radiation and Absorption Processes in Semiconductor Quantum Dots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paiella, Roberto; Moustakas, Theodore D.

This document reviews a research program funded by the DOE Office of Science, which has been focused on the control of radiation and absorption processes in semiconductor photonic materials (including III-nitride quantum wells and quantum dots), through the use of specially designed metallic nanoparticles (NPs). By virtue of their strongly confined plasmonic resonances (i.e., collective oscillations of the electron gas), these nanostructures can concentrate incident radiation into sub-wavelength “hot spots” of highly enhanced field intensity, thereby increasing optical absorption by suitably positioned absorbers. By reciprocity, the same NPs can also dramatically increase the spontaneous emission rate of radiating dipoles locatedmore » within their hot spots. The NPs can therefore be used as optical antennas to enhance the radiation output of the underlying active material and at the same time control the far-field pattern of the emitted light. The key accomplishments of the project include the demonstration of highly enhanced light emission efficiency as well as plasmonic collimation and beaming along geometrically tunable directions, using a variety of plasmonic excitations. Initial results showing the reverse functionality (i.e., plasmonic unidirectional absorption and photodetection) have also been generated with similar systems. Furthermore, a new paradigm for the near-field control of light emission has been introduced through rigorous theoretical studies, based on the use of gradient metasurfaces (i.e., optical nanoantenna arrays with spatially varying shape, size, and/or orientation). These activities have been complemented by materials development efforts aimed at the synthesis of suitable light-emitting samples by molecular beam epitaxy. In the course of these efforts, a novel technique for the growth of III-nitride quantum dots has also been developed (droplet heteroepitaxy), with several potential advantages in terms of compositional and geometrical control. The results of these studies provide fundamental new understanding of optical processes at the nanoscale, including near-field energy transfer between quantum emitters and photonic nanostructures, dissipation phenomena of plasmonic excitations, and radiation from nanoantennas. Furthermore, they may open the way to entirely new device concepts and applications, in a broad range of disciplines including optoelectronics, sensing, spectroscopy, photovoltaics, and quantum information science. A specific application of particularly strong relevance to the DOE mission is the development of energy efficient LED active materials for solid-state lighting, based on plasmonic enhancement effects.« less

Optical absorption properties of Ge 2–44 and P-doped Ge nanoparticles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qin, Wei; Lu, Wen-Cai; Zhao, Li-Zhen

The optical absorption properties of non-crystalline and crystalline Ge nanoparticles with the sizes from ~ 2.5 to 15 Å have been studied at the B3LYP/6-31G level using time-dependent density functional theory. Hydrogen passivation and phosphorus doping on some selected Ge nanoparticles were also calculated. With the increase of cluster size, the optical absorption spectra of the non-crystalline Ge nanoparticles change from many peaks to a continuous broad band and at the same time exhibit a systematic red-shift. Doping phosphorus also causes the absorption spectra to shift toward the lower energy region for both non-crystalline and crystalline Ge nanoparticles. The non-crystallinemore » Ge nanoparticles are found to have stronger absorption in the visible region in comparison with the crystalline ones, regardless phosphorus doping.« less

Optical absorption properties of Ge 2–44 and P-doped Ge nanoparticles

DOE PAGES

Qin, Wei; Lu, Wen-Cai; Zhao, Li-Zhen; ...

2017-09-15

The optical absorption properties of non-crystalline and crystalline Ge nanoparticles with the sizes from ~ 2.5 to 15 Å have been studied at the B3LYP/6-31G level using time-dependent density functional theory. Hydrogen passivation and phosphorus doping on some selected Ge nanoparticles were also calculated. With the increase of cluster size, the optical absorption spectra of the non-crystalline Ge nanoparticles change from many peaks to a continuous broad band and at the same time exhibit a systematic red-shift. Doping phosphorus also causes the absorption spectra to shift toward the lower energy region for both non-crystalline and crystalline Ge nanoparticles. The non-crystallinemore » Ge nanoparticles are found to have stronger absorption in the visible region in comparison with the crystalline ones, regardless phosphorus doping.« less

Assessment of the Polycyclic Aromatic Hydrocarbon-Diffuse Interstellar Band Proposal

NASA Technical Reports Server (NTRS)

Salama, Farid; Bakes, F.; Allamandola, L.; Tielens, A. G. G. M.; Witteborn, Fred C. (Technical Monitor)

1995-01-01

The potential link between neutral and/or ionized polycyclic aromatic hydrocarbons (PAHs) and the diffuse interstellar band (DIB) carriers is examined. Based on the study of the general physical and chemical properties of PAHs, an assessment is made of their possible contribution to the DIB carriers. It is found that, under the conditions reigning in the diffuse interstellar medium, PAHs can be present in the form of neutral molecules as well as positive and/or negative ions. The charge distribution of small PAHs is dominated, however, by two charge states at one time with compact PAHs present only in the neutral and cationic forms. Each PAH has a distinct spectral signature depending on its charge state. Moreover, the spectra of ionized PAHs are always clearly dominated by a single band in the DIB spectral range. In the case of compact PAH ions, the strongest absorption band is of type A (i.e., the band is broad, falls in the high energy range of the spectrum, and possess a large oscillator strength), and seems to correlate with strong and broad DIBs. In the case of non-compact PAH ions, the strongest absorption band is of type I (i.e., the band is narrow, falls in the low energy range of the spectrum, and possess a small oscillator strength), and seems to correlate with weak and narrow DIBs. Potential molecular size and structure constraints for interstellar PAHs are derived by comparing known DIB characteristics to the spectroscopic properties of PAHs. It is found that: (i) Only neutral PAHs larger than about 30 carbon atoms could, if present, contribute to the DIBs. (ii) For compact PAHs, only ions with less than about 250 carbon atoms could, if present, contribute to the DIBs. (iii) The observed distribution of the DIBs between strong/moderate and broad bands on the one hand and weak and narrow bands on the other hand can easily be interpreted in the context of the PAH proposal by a distribution between compact and non-compact PAH ions, respectively. A plausible correlation between PAH charge states and DIB "families" is thus provided by the PAH-DIB proposal. Following this proposal, DIB families would provide tracers of conditions within a cloud which globally determine the relative importance of cations, anions, and neutral species, rather than tracers of a specific species. Observational predictions are given to establish the viability of the PAH hypothesis. It is concluded that small PAH ions are very promising candidates as DIB carriers provided their population is dominated by a finite number (100-200) of species. A key test for the PAH proposal, consisting of laboratory and astronomical investigations of the ultraviolet range, is called for.

Assessment of the polycyclic aromatic hydrocarbon-diffuse interstellar band proposal

NASA Technical Reports Server (NTRS)

Salama, F.; Bakes, E. L.; Allamandola, L. J.; Tielens, A. G.

1996-01-01

The potential link between neutral and/or ionized polycyclic aromatic hydrocarbons (PAHs) and the diffuse interstellar band (DIB) carriers is examined. Based on the study of the general physical and chemical properties of PAHs, an assessment is made of their possible contribution to the DIB carriers. It is found that, under the conditions reigning in the diffuse interstellar medium, PAHs can be present in the form of neutral molecules as well as positive and/or negative ions. The charge distribution of small PAHs is dominated, however, by two charge states at one time with compact PAHs present only in the neutral and cationic forms. Each PAH has a distinct spectral signature depending on its charge state. Moreover, the spectra of ionized PAHs are always clearly dominated by a single band in the DIB spectral range. In the case of compact PAH ions, the strongest absorption band is of type A (i.e., the band is broad, falls in the high-energy range of the spectrum, and possesses a large oscillator strength), and seems to correlate with strong and broad DIBs. For noncompact PAH ions, the strongest absorption band is of type I (i.e., the band is narrow, falls in the low-energy range of the spectrum, and possesses a small oscillator strength), and seems to correlate with weak and narrow DIBs. Potential molecular size and structure constraints for interstellar PAHs are derived by comparing known DIB characteristics to the spectroscopic properties of PAHs. It is found that (i) only neutral PAHs larger than about 30 carbon atoms could, if present, contribute to the DIBs. (ii) For compact PAHs, only ions with less than about 250 carbon atoms could, if present, contribute to the DIBs. (iii) The observed distribution of the DIBs between strong/moderate and broad bands on the one hand and weak and narow bands on the other can easily be interpreted in the context of the PAH proposal by a distribution of compact and noncompact PAH ions, respectively. A plausible correlation between PAH charge states and DIB "families" is thus provided by the PAH-DIB proposal. Following this proposal, DIB families would reflect conditions within a cloud which locally determine the relative importance of cations, anions, and neutral species, rather than tracers of a specific species. Observational predictions are given to establish the viability of the PAH hypothesis. It is concluded that small PAH ions are very promising candidates as DIB carriers provided their population is dominated by a finite number (100-200) of species. A key test for the PAH proposal, consisting of laboratory and astronomical investigations in the ultraviolet range, is called for.

Volcanogenic Sulfur on Earth and Io: Composition and Spectroscopy

USGS Publications Warehouse

Kargel, J.S.; Delmelle, P.; Nash, D.B.

1999-01-01

The causes of Io's variegated surface, especially the roles of sulfur, and the geochemical history of sulfur compounds on Io are not well understood. Suspecting that minor impurities in sulfur might be important, we have investigated the major and trace element chemistry and spectroscopic reflectance of natural sulfur from a variety of terrestrial volcanic-hydrothermal environments. Evidence suggests that Io may be substantially coated with impure sulfur. On Earth, a few tenths of a percent to a few percent of chalcophile trace elements (e.g., As and Se) comonly occur in sulfur and appear to stabilize material of yellow, brown, orange, and red hues, which may persist even at low temperatures. Percentage levels of chalcophile impurities are reasonably expected to occur on Io in vapor sublimate deposits and flows derived from such deposits. Such impurities join a host of other mechanisms that might explain Io's reds and yellows. Two-tenths to two percent opaque crystalline impurities, particularly pyrite (FeS2), commonly produces green, gray, and black volcanic sulfur on Earth and might explain areas of Io having deposits of these colors. Pyrite produces a broad absorption near 1 ??m that gradually diminishes out to 1.6 ??m - similar but not identical to the spectrum of Io seen in Galileo NIMS data. Percentage amounts of carbonaceous impurities and tens of percent SiO2 (as silicates) also strongly affect the spectral properties of Earth's sulfur. Io's broad absorption between 0.52 and 0.64 ??m remains unexplained by these data but could be due to sodium sulfides, as suggested previously by others, or to As, Se, or other impurities. These impurities and others, such as P and Cl (which could exist on Io's surface in amounts over 1% that of sulfur), greatly alter the molecular structure of molten and solid sulfur. Minor impurities could impact Io's geology, such as the morphology of sulfur lava flows and the ability of sulfur to sustain high relief. We have not found any natural sulfur containing significant Na beyond that attributable to silicate inclusions. In sum, the unique physical-chemical properties of S-rich systems and the strong affinity of certain elements for S may have broad implications for the appearance, spectroscopic interpretation, and geologic processes of Io. Identification of impurities in sulfur may be helpful in tracing the geochemical evolution of surface deposits on Io. Perhaps foretelling of new areas of investigation, Cl has recently been reported in the Io torus (M. Kueppers and N. M. Schneider 1999, Eos Trans.80, 5207), suggesting the presence on Io of either salts, such as halite, or sulfur chlorides. Further evidence of minor iogenic impurities should be sought in Io's neutral cloud and plasma torus as well as in further scrutiny of Io's reflectance spectra. ?? 1999 Academic Press.

Super-Eddington QSO RX J0439.6-5311 - II. Multiwavelength constraints on the global structure of the accretion flow

NASA Astrophysics Data System (ADS)

Jin, Chichuan; Done, Chris; Ward, Martin; Gardner, Emma

2017-10-01

We present a detailed multiwavelength study of an unobscured, highly super-Eddington Type-1 QSO RX J0439.6-5311. We combine the latest XMM-Newton observation with all archival data from infrared to hard X-rays. The optical spectrum is very similar to that of 1H 0707-495 in having extremely weak [O III] and strong Fe II emission lines, although the black hole mass is probably slightly higher at 5-10 × 106 M⊙. The broad-band spectral energy distribution is uniquely well defined due to the extremely low Galactic and intrinsic absorption, so the bolometric luminosity is tightly constrained. The optical/UV accretion disc continuum is seen down to 900 Å, showing that there is a standard thin disc structure down to R ≥ 190-380 Rg and determining the mass accretion rate through the outer disc. This predicts a much higher bolometric luminosity than observed, indicating that there must be strong wind and/or advective energy losses from the inner disc, as expected for a highly super-Eddington accretion flow. Significant outflows are detected in both the narrow-line region (NLR) and broad-line region (BLR) emission lines, confirming the presence of a wind. We propose a global picture for the structure of a super-Eddington accretion flow where the inner disc puffs up, shielding much of the potential NLR material, and show how inclination angle with respect to this and the wind can explain very different X-ray properties of RX J0439.6-5311 and 1H 0707-495. Therefore, this source provides strong supporting evidence that 'simple' and 'complex' super-Eddington NLS1s can be unified within the same accretion flow scenario but with different inclination angles. We also propose that these extreme NLS1s could be the low-redshift analogues of weak emission-line quasars.

What Quasars Really Look Like: Unification of the Emission and Absorption Line Regions

NASA Technical Reports Server (NTRS)

Elvis, Martin

2000-01-01

We propose a simple unifying structure for the inner regions of quasars and AGN. This empirically derived model links together the broad absorption line (BALS), the narrow UV/X-ray ionized absorbers, the BELR, and the 5 Compton scattering/fluorescing regions into a single structure. The model also suggests an alternative origin for the large-scale bi-conical outflows. Some other potential implications of this structure are discussed.

A new X-ray spectral observation of NGC 1068

NASA Technical Reports Server (NTRS)

Marshall, F. E.; Netzer, H.; Arnaud, K. A.; Boldt, E. A.; Holt, S. S.; Jahoda, K. M.; Kelley, R.; Mushotzky, R. F.; Petre, R.; Serlemitsos, P. J.

1993-01-01

A new X-ray observation of NGC 1068, in which improved spectral resolution (R is approximately equal to 40) and broad energy range provide important new constraints on models for this galaxy, is reported. The observed X-ray continuum of NGC 1068 from 0.3 to 10 keV is well fitted as the sum of two power-law spectra with no evidence for absorption intrinsic to the source. Strong Fe K emission lines with a total equivalent width of 2700 eV were detected due to iron less ionized than Fe XX and to iron more ionized than Fe XXIII. No evidence was seen for lines due to the recombination of highly ionized oxygen with an upper limit for the O Ly-alpha emission line of 40 eV. The discovery of multiple Fe K and Fe L emission lines indicates a broad range of ionization states for this gas. The X-ray emission from the two components is modeled for various geometries using a photoionization code that calculates the temperature and ionization state of the gas. Typical model parameters are a total Compton depth of a few percent, an inner boundary of the hot component of about 1 pc, and an inner boundary of the warm component of about 20 pc.

Individual and collective modes of surface magnetoplasmon in thiolate-protected silver nanoparticles studied by MCD spectroscopy.

PubMed

Yao, Hiroshi; Shiratsu, Taisuke

2016-06-07

Large magneto-optical (MO) responses at the energy of localized surface plasmon resonance (LSPR), namely, surface magnetoplasmons, are demonstrated for the first time in thiolate-protected silver nanoparticles with magnetic circular dichroism (MCD) spectroscopy. The samples examined are decanethiol (DT)-, azobenzenethiol (ABT)-, and ABT/DT mixed-monolayer-protected Ag nanoparticles. ABT-protected Ag nanoparticles are somewhat aggregated and thus exhibit a broad, collective mode of plasmonic absorption, whereas other samples with highly-dispersed nanoparticles show an individual mode of LSPR absorption. In all Ag nanoparticles, a derivative-like MCD signal is observed under an applied magnetic field of 1.6 T, which can be explained in terms of two circular modes of magnetoplasmon caused by the increase (or decrease) in the Lorentz force imparted on the free electrons that oscillate in the left (or right) circular orbits in the nanosphere. For the Ag nanoparticles exhibiting an individual LSPR mode, in particular, simultaneous deconvolution analysis of UV-vis absorption and MCD spectra reveal that (i) the amplitude of the magnetoplasmonic component with lower frequency (ω-), resulting from the reduction in the confinement strength of collective electrons by the Lorentz force, is stronger than that with a higher frequency (ω+); (ii) the accurate shift or cyclotron frequency between two magnetoplasmonic modes (ωc = ω+-ω-) is size-dependent, and presents a very large value with implications for the apparent enhancement of the local magnetic-field in the Ag nanoparticles. These results strongly suggest that the Ag-thiolate layer or Ag-S bonding on the nanoparticle surface plays a significant role in the MO enhancement.

The opacity of the universe and the strong equivalence principle

NASA Technical Reports Server (NTRS)

Canuto, V. M.; Goldman, I.

1983-01-01

A possible explanation of why the advanced solutions of Maxwell's equations are not observed in nature is by way of absorption by an opaque universe. As Davies has shown, the ever expanding, general relativistic cosmological models fail to provide the needed absorption. The absorption mechanism calling for an interplay between local physics and cosmology, is usually developed adopting the strong equivalence principle, SEP, which precludes such interplay. It is shown that complete absorption of electromagnetic radiation by ionized intergalactic plasma is obtained provided a violation of the SEP, of the order of the Hubble's constant, is allowed to occur. The same degree of violation was previously found to be compatible with a large body of observational data.

Performance of Ultrathin Silicon Solar Microcells with Nanostructures of Relief Formed by Soft Imprint Lithography for Broad Band Absorption Enhancement

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shir, Daniel J.; Yoon, Jongseung; Chanda, Debashis

2010-08-11

Recently developed classes of monocrystalline silicon solar microcells can be assembled into modules with characteristics (i.e., mechanically flexible forms, compact concentrator designs, and high-voltage outputs) that would be impossible to achieve using conventional, wafer-based approaches. This paper presents experimental and computational studies of the optics of light absorption in ultrathin microcells that include nanoscale features of relief on their surfaces, formed by soft imprint lithography. Measurements on working devices with designs optimized for broad band trapping of incident light indicate good efficiencies in energy production even at thicknesses of just a few micrometers. These outcomes are relevant not only tomore » the microcell technology described here but also to other photovoltaic systems that benefit from thin construction and efficient materials utilization.« less

Using the Properties of Broad Absorption Line Quasars to Illuminate Quasar Structure

NASA Astrophysics Data System (ADS)

Yong, Suk Yee; King, Anthea L.; Webster, Rachel L.; Bate, Nicholas F.; O'Dowd, Matthew J.; Labrie, Kathleen

2018-06-01

A key to understanding quasar unification paradigms is the emission properties of broad absorption line quasars (BALQs). The fact that only a small fraction of quasar spectra exhibit deep absorption troughs blueward of the broad permitted emission lines provides a crucial clue to the structure of quasar emitting regions. To learn whether it is possible to discriminate between the BALQ and non-BALQ populations given the observed spectral properties of a quasar, we employ two approaches: one based on statistical methods and the other supervised machine learning classification, applied to quasar samples from the Sloan Digital Sky Survey. The features explored include continuum and emission line properties, in particular the absolute magnitude, redshift, spectral index, line width, asymmetry, strength, and relative velocity offsets of high-ionisation C IV λ1549 and low-ionisation Mg II λ2798 lines. We consider a complete population of quasars, and assume that the statistical distributions of properties represent all angles where the quasar is viewed without obscuration. The distributions of the BALQ and non-BALQ sample properties show few significant differences. None of the observed continuum and emission line features are capable of differentiating between the two samples. Most published narrow disk-wind models are inconsistent with these observations, and an alternative disk-wind model is proposed. The key feature of the proposed model is a disk-wind filling a wide opening angle with multiple radial streams of dense clumps.

Comparing the VIRTIS Spectrum of 67P/Churyumov-Gerasimenko to Wild 2 and in Primitive Interplanetary Dust Particles

NASA Astrophysics Data System (ADS)

Flynn, George

2016-04-01

The Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument, a point spectrometer with high spectral resolution covering the range from 2 to 5 microns, on the ESA Rosetta spacecraft obtained spectra of the surface of Comet 67P/Churyumov-Gerasimenko. The spectral region covered by VIRTIS has been well studied in meteorites, interplanetary dust particles (IDPs) collected by NASA from the Earth's stratosphere, and the samples of Comet 81P/Wild 2 that were delivered to Earth by the NASA Stardust spacecraft. Infrared spectra of the nucleus of Comet 67P/Churyumov-Gerasimenko acquired by VIRTIS show a broad absorption band observed at ~3.3 μm, a region of the spectrum where C-H, O-H, and N-H stretching features occur (Capaccioni et al., 2015). This broad feature is similar to the O-H feature exhibited by hydrous minerals, but shifted to a significantly longer wavelength. Capaccioni et al. (2015) compared the VIRTIS spectra to laboratory spectra of carbonaceous chondrite meteorites of the CI, CM, and CR types and concluded that none of the typical features of these meteorite spectra are compatible with the spectra of the surface of 67P/Churyumov-Gerasimenko. Comparison of VIRTIS spectra of 67P/ Churyumov-Gerasimenko to the laboratory spectra of well-characterized extraterrestrial materials including the Wild 2 dust and the IDPs, a significant fraction of which are believed to be cometary, could aid in the interpretation of the 67P/Churyumov-Gerasimenko spectra. None of the Wild 2 particles examined by infrared spectroscopy exhibit an O-H feature, but this may be due to the high temperature reached during their capture in the aerogel collection medium. The O-H feature is also absent in all anhydrous IDPs. The hydrous IDPs exhibit varying strengths of both aliphatic C-H absorption features and the O-H absorption feature, but, as with the meteorites, the O-H feature occurs at a significantly shorter wavelength than the broad feature detected in 67P/Churyumov-Gerasimenko. Only one of the more than 50 IDPs analyzed by infrared spectroscopy has an infrared spectrum similar to that of 67P/Churyumov-Gerasimenko. This large, hydrous IDP, L2021 C10, has a broad absorption feature centered at the same position as the feature observed in 67P/Churyumov-Gerasimenko. In the case of L2021 C10 this feature is attributed to an O-H absorption feature in the position normally seen in hydrous minerals as well as a broad aromatic C-H feature, rarely detected in IDPs, and the aliphatic C-H feature seen in all IDPs examined thus far (Flynn et al., 2004). In the case of the VIRTIS spectrum of 67P/Churyumov-Gerasimenko the apparent shift of the broad O-H feature may actually result from the superposition of O-H and aromatic C-H features, both at their normal wavelengths. References: Capaccioni, F. et al. (2015) Science, 347 no. 6220, DOI: 10.1126/science.aaa0628. Flynn, G. J. et al. (2004) Advances in Space Research, 33, 57-66.

Strong-field two-photon transition by phase shaping

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Sangkyung; Lim, Jongseok; Ahn, Jaewook

2010-08-15

We demonstrate the ultrafast coherent control of a nonlinear two-photon absorption in a dynamically shifted energy level structure. We use a spectrotemporal laser-pulse shaping that is programed to preserve the resonant absorption condition during the intense laser-field interaction. Experiments carried out in the strong-field regime of two-photon absorption in the ground state of atomic cesium reveal that the analytically obtained offset and curvature of a laser spectrum compensate the effect of both static and dynamic energy shifts of the given light-atom interaction.

Modulation of intersubband light absorption and interband photoluminescence in double GaAs/AlGaAs quantum wells under strong lateral electric fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Balagula, R. M., E-mail: rmbal@spbstu.ru; Vinnichenko, M. Ya., E-mail: mvin@spbstu.ru; Makhov, I. S.

The effect of a lateral electric field on the mid-infrared absorption and interband photoluminescence spectra in double tunnel-coupled GaAs/AlGaAs quantum wells is studied. The results obtained are explained by the redistribution of hot electrons between quantum wells and changes in the space charge in the structure. The hot carrier temperature is determined by analyzing the intersubband light absorption and interband photoluminescence modulation spectra under strong lateral electric fields.

Triple loop heat exchanger for an absorption refrigeration system

DOEpatents

Reimann, Robert C.

1984-01-01

A triple loop heat exchanger for an absorption refrigeration system is disclosed. The triple loop heat exchanger comprises portions of a strong solution line for conducting relatively hot, strong solution from a generator to a solution heat exchanger of the absorption refrigeration system, conduit means for conducting relatively cool, weak solution from the solution heat exchanger to the generator, and a bypass system for conducting strong solution from the generator around the strong solution line and around the solution heat exchanger to an absorber of the refrigeration system when strong solution builds up in the generator to an undesirable level. The strong solution line and the conduit means are in heat exchange relationship with each other in the triple loop heat exchanger so that, during normal operation of the refrigeration system, heat is exchanged between the relatively hot, strong solution flowing through the strong solution line and the relatively cool, weak solution flowing through the conduit means. Also, the strong solution line and the bypass system are in heat exchange relationship in the triple loop heat exchanger so that if the normal flow path of relatively hot, strong solution flowing from the generator to an absorber is blocked, then this relatively, hot strong solution which will then be flowing through the bypass system in the triple loop heat exchanger, is brought into heat exchange relationship with any strong solution which may have solidified in the strong solution line in the triple loop heat exchanger to thereby aid in desolidifying any such solidified strong solution.

Twenty-two emission-line AGNs from the HEAO-1 X-ray survey

NASA Technical Reports Server (NTRS)

Remillard, R. A.; Bradt, H. V. D.; Brissenden, R. J. V.; Buckley, D. A. H.; Roberts, W.; Schwartz, D. A.; Stroozas, B. A.; Tuohy, I. R.

1993-01-01

We report 22 emission-line AGN as bright, hard X-ray sources. All of them appear to be new classifications with the exception of one peculiar IRAS source which is a known quasar and has no published spectrum. This sample exhibits a rich diversity in optical spectral properties and luminosities, ranging from a powerful broad-absorption-line quasar to a weak nucleus embedded in a nearby NGC galaxy. Two cases confer X-ray luminosities in excess of 10 exp 47 erg/s. However, there is a degree of uncertainty in the X-ray identification for the AGN fainter than V about 16.5. Optically, several AGN exhibit very strong Fe II emission. One Seyfert galaxy with substantial radio flux is an exception to the common association of strong Fe II emission and radio-quiet AGN. The previously recognized IRAS quasar shows extreme velocities in the profiles of the forbidden lines; the 0 III pair is broadened to the point that the lines are blended. Several of these AGN show evidence of intrinsic obscuration, illustrating the effectiveness of hard X-ray surveys in locating AGN through high column density.

Investigation and characterization of ZnO single crystal microtubes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Al-Naser, Qusay A.H.; Zhou, Jian, E-mail: jianzhou@whut.edu.cn; Liu, Guizhen

2016-04-15

Morphological, structural, and optical characterization of microwave synthesized ZnO single crystal microtubes were investigated in this work. The structure and morphology of the ZnO microtubes are characterized using X-ray diffraction (XRD), single crystal diffraction (SCD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The results reveal that the as-synthesized ZnO microtube has a highly regular hexagonal cross section and smooth surfaces with an average length of 650–700 μm, an average outer diameter of 50 μm and wall thickness of 1–3 μm, possessing a single crystal wurtzite hexagonal structure. Optical properties of ZnOmore » single crystal microtubes were investigated by photoluminescence (PL) and ultraviolet-visible (UV-vis) absorption techniques. Room-temperature PL spectrum of the microtube reveal a strong UV emission peak at around 375.89 nm and broad and a weak visible emission with a main peak identified at 577 nm, which was assigned to the nearest band-edge emission and the deep-level emission, respectively. The band gap energy of ZnO microtube was found to be 3.27 eV. - Highlights: • ZnO microtube length of 650–700 μm, diameter of 50 μm, wall thickness of 1–3 μm • ZnO microtube possesses a single crystal wurtzite hexagonal structure. • The crystal system is hexahedral oriented along a-axis with indices of (100). • A strong and sharp UV emission at 375.89 nm (3.29 eV) • One prominent absorption band around 378.88 nm (3.27 eV)« less

Spectral, thermal, XRD and SEM studies of charge-transfer complexation of hexamethylenediamine and three types of acceptors: π-, σ- and vacant orbital acceptors that include quinol, picric acid, bromine, iodine, SnCl4 and ZnCl2 acceptors

NASA Astrophysics Data System (ADS)

Adam, Abdel Majid A.; Refat, Moamen S.; Saad, Hosam A.

2013-11-01

In this work, structural, thermal, morphological and pharmacological characterization was performed on the interactions between a hexamethylenediamine (HMDA) donor and three types of acceptors to understand the complexation behavior of diamines. The three types of acceptors include π-acceptors (i.e., quinol (QL) and picric acid (PA)), σ-acceptors (i.e., bromine and iodine) and vacant orbital acceptors (i.e., tin(IV) tetrachloride (SnCl4) and zinc chloride (ZnCl2)). The characterization of the obtained CT complexes was performed using elemental analysis, infrared (IR), Raman, 1H NMR and electronic absorption spectroscopy, powder X-ray diffraction (XRD) and thermogravimetric (TG) analysis. Their morphologies were studied using scanning electron microscopy with energy-dispersive X-ray analysis (SEM-EDX). The biological activities of the obtained CT complexes were tested for their antibacterial activities. The complex containing the QL acceptor exhibited a remarkable electronic spectrum with a strong, broad absorption band, which had an observed λmax that was at a much longer wavelength than those of the free reactants. In addition, this complex exhibited strong antimicrobial activities against various bacterial and fungal strains compared to standard drugs. The complexes containing the PA, iodine, Sn(IV) and Zn(II) acceptors exhibited good thermal stability up to 240, 330, 275 and 295 °C, respectively. The complexes containing bromine, Sn(IV) and Zn(II) acceptors exhibited good crystallinity. In addition to its good crystallinity properties, the complex containing the bromine acceptor exhibits a remarkable morphology feature.

C IV absorption-line variability in X-ray-bright broad absorption-line quasi-stellar objects

NASA Astrophysics Data System (ADS)

Joshi, Ravi; Chand, Hum; Srianand, Raghunathan; Majumdar, Jhilik

2014-07-01

We report the kinematic shift and strength variability of the C IV broad absorption-line (BAL) trough in two high-ionization X-ray-bright quasi-stellar objects (QSOs): SDSS J085551+375752 (at zem ˜ 1.936) and SDSS J091127+055054 (at zem ˜ 2.793). Both these QSOs have shown a combination of profile shifts and the appearance and disappearance of absorption components belonging to a single BAL trough. The observed average kinematic shift of the whole BAL profile resulted in an average deceleration of ˜-0.7 ± 0.1, -2.0 ± 0.1 cm s-2 over rest-frame time-spans of 3.11 and 2.34 yr for SDSS J085551+375752 and SDSS J091127+055054, respectively. To our knowledge, these are the largest kinematic shifts known, exceeding by factors of about 2.8 and 7.8 the highest deceleration reported in the literature; this makes both objects potential candidates to investigate outflows using multiwavelength monitoring of their line and continuum variability. We explore various possible mechanisms to understand the observed profile variations. Outflow models involving many small self-shielded clouds, probably moving in a curved path, provide the simplest explanation for the C IV BAL strength and velocity variations, along with the X-ray-bright nature of these sources.

Polypyrrole coated phase-change contrast agents for sono-photoacoustic imaging (Conference Presentation)

NASA Astrophysics Data System (ADS)

Li, David S.; Yoon, Soon Joon; Matula, Thomas J.; O'Donnell, Matthew; Pozzo, Lilo D.

2017-03-01

A new light and sound sensitive nanoemulsion contrast agent is presented. The agents feature a low boiling point liquid perfluorocarbon core and a broad light spectrum absorbing polypyrrole (PPy) polymer shell. The PPy coated nanoemulsions can reversibly convert from liquid to gas phase upon cavitation of the liquid perfluorocarbon core. Cavitation can be initiated using a sufficiently high intensity acoustic pulse or from heat generation due to light absorption from a laser pulse. The emulsions can be made between 150 and 350 nm in diameter and PPy has a broad optical absorption covering both the visible spectrum and extending into the near-infrared spectrum (peak absorption 1053 nm). The size, structure, and optical absorption properties of the PPy coated nanoemulsions were characterized and compared to PPy nanoparticles (no liquid core) using dynamic light scattering, ultraviolet-visible spectrophotometry, transmission electron microscopy, and small angle X-ray scattering. The cavitation threshold and signal intensity were measured as a function of both acoustic pressure and laser fluence. Overlapping simultaneous transmission of an acoustic and laser pulse can significantly reduce the activation energy of the contrast agents to levels lower than optical or acoustic activation alone. We also demonstrate that simultaneous light and sound cavitation of the agents can be used in a new sono-photoacoustic imaging method, which enables greater sensitivity than traditional photoacoustic imaging.

Ultra-wideband microwave absorber by connecting multiple absorption bands of two different-sized hyperbolic metamaterial waveguide arrays.

PubMed

Yin, Xiang; Long, Chang; Li, Junhao; Zhu, Hua; Chen, Lin; Guan, Jianguo; Li, Xun

2015-10-19

Microwave absorbers have important applications in various areas including stealth, camouflage, and antenna. Here, we have designed an ultra-broadband light absorber by integrating two different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has wide but different absorption bands due to broadband slow-light response, into a unit cell. Both the numerical and experimental results demonstrate that in such a design strategy, the low absorption bands between high absorption bands with a single-sized tapered HMM waveguide array can be effectively eliminated, resulting in a largely expanded absorption bandwidth ranging from 2.3 to 40 GHz. The presented ultra-broadband light absorber is also insensitive to polarization and robust against incident angle. Our results offer a further step in developing practical artificial electromagnetic absorbers, which will impact a broad range of applications at microwave frequencies.

Anisotropic localized surface plasmon resonances in CuS nanoplates prepared by size-selective precipitation

NASA Astrophysics Data System (ADS)

Hamanaka, Yasushi; Yamada, Kaoru; Hirose, Tatsunori; Kuzuya, Toshihiro

2018-05-01

CuS nanoplates were synthesized by a colloidal method and separated into four fractions of nanoplates with different aspect ratios by a size-selective precipitation. In addition to a strong near infrared absorption band ascribed to the in-plane mode of the localized surface plasmon resonance (LSPR), we found a weak absorption band on the high frequency tail of the in-plane LSPR band. The frequency of the weak absorption band was almost constant and independent of the aspect ratio, while the in-plane LSPR band exhibited a strong aspect ratio dependence. These characteristics suggested that the weak absorption band is ascribed to the out-of-plane LSPR. Although the out-of-plane LSPR was expected to be difficult to observe for CuS nanoplates due to its low intensity and overlap with the strong in-plane resonance, we could successfully identify the out-of-plane mode by reducing the width of the size distribution and spectral broadening caused thereby.

Strong anisotropic optical conductivity in two-dimensional puckered structures: The role of the Rashba effect

NASA Astrophysics Data System (ADS)

Saberi-Pouya, S.; Vazifehshenas, T.; Salavati-fard, T.; Farmanbar, M.; Peeters, F. M.

2017-08-01

We calculate the optical conductivity of an anisotropic two-dimensional system with Rashba spin-flip excitation within the Kubo formalism. We show that the anisotropic Rashba effect caused by an external field significantly changes the magnitude of the spin splitting. Furthermore, we obtain an analytical expression for the longitudinal optical conductivity associated with interband transitions as a function of the frequency for arbitrary polarization angle. We find that the diagonal components of the optical conductivity tensor are direction dependent and the optical absorption spectrum exhibits a strongly anisotropic absorption window. The height and width of this absorption window are very sensitive to the anisotropy of the system. While the height of absorption peak increases with increasing effective mass anisotropy ratio, the peak intensity is larger when the light polarization is along the armchair direction. Moreover, the absorption peak width becomes broader as the density-of-states mass or Rashba interaction is enhanced. These features in the optical absorption spectrum can be used to determine parameters relevant for spintronics.

Multiband coherent perfect absorption in a water-based metasurface.

PubMed

Zhu, Weiren; Rukhlenko, Ivan D; Xiao, Fajun; He, Chong; Geng, Junping; Liang, Xianling; Premaratne, Malin; Jin, Ronghong

2017-07-10

We design an ultrathin water-based metasurface capable of coherent perfect absorption (CPA) at radio frequencies. It is demonstrated that such a metasurface can almost completely absorb two symmetrically incident waves within four frequency bands, each having its own modulation depth of metasurface absorptivity. Specifically, the absorptivity at 557.2 MHz can be changed between 0.59% and 99.99% via the adjustment of the phase difference between the waves. The high angular tolerance of our metasurface is shown to enable strong CPA at oblique incidence, with the CPA frequency almost independent of the incident angle for TE waves and varying from 557.2 up to 584.2 MHz for TM waves. One can also reduce this frequency from 712.0 to 493.3 MHz while retaining strong coherent absorption by varying the water layer thickness. It is also show that the coherent absorption performance can be flexibly controlled by adjusting the temperature of water. The proposed metasurface is low-cost, biocompatible, and useful for electromagnetic modulation and switching.

Type-II GaSb/GaAs quantum-dot intermediate band with extended optical absorption range for efficient solar cells

NASA Astrophysics Data System (ADS)

Boustanji, Hela; Jaziri, Sihem

2018-02-01

GaSb/GaAs type-II quantum-dot solar cells (QD SCs) have attracted attention as highly efficient intermediate band SCs due to their infrared absorption. Type-II QDs exhibited a staggered confinement potential, where only holes are strongly confined within the dots. Long wavelength light absorption of the QDSCs is enhanced through the improved carriers number in the IB. The absorption of dots depends on their shape, material quality, and composition. Therefore, the optical properties of the GaSbGaAs QDs before and after thermal treatment are studied. Our intraband studies have shown an extended absorption into the long wavelength region 1.77 μ {m}. The annealed QDs have shown significantly more infrared response of 7.2 μ {m} compared to as-grown sample. The photon absorption and hole extraction depend strongly on the thermal annealing process. In this context, emission of holes from localized states in GaSb QDs has been studied using conductance-voltage ( G- V ) characteristics.

Effects of γ-ray irradiation on optical absorption and laser damage performance of KDP crystals containing arsenic impurities.

PubMed

Guo, D C; Jiang, X D; Huang, J; Wang, F R; Liu, H J; Xiang, X; Yang, G X; Zheng, W G; Zu, X T

2014-11-17

The effects of γ-irradiation on potassium dihydrogen phosphate crystals containing arsenic impurities are investigated with different optical diagnostics, including UV-VIS absorption spectroscopy, photo-thermal common-path interferometer and photoluminescence spectroscopy. The optical absorption spectra indicate that a new broad absorption band near 260 nm appears after γ-irradiation. It is found that the intensity of absorption band increases with the increasing irradiation dose and arsenic impurity concentration. The simulation of radiation defects show that this absorption is assigned to the formation of AsO₄⁴⁻ centers due to arsenic ions substituting for phosphorus ions. Laser-induced damage threshold test is conducted by using 355 nm nanosecond laser pulses. The correlations between arsenic impurity concentration and laser induced damage threshold are presented. The results indicate that the damage performance of the material decreases with the increasing arsenic impurity concentration. Possible mechanisms of the irradiation-induced defects formation under γ-irradiation of KDP crystals are discussed.

Terahertz spectral change associated with glass transition of poly-ε-caprolactone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komatsu, Marina, E-mail: mkomatsu@toki.waseda.jp; Mizuno, Maya; Fukunaga, Kaori

2015-04-07

We measured absorption spectra of unidirectionally stretched poly-ε-caprolactone (PCL) film in a range from 0.3 to 3.6 THz at temperatures from 10 to 300 K. Several absorption peaks were observed, when the electric field of THz waves was set in directions parallel and perpendicular to the stretching direction. The absorption bandwidths became significantly broad at around 200 K and above at least in two specific peaks. This temperature is close to the glass transition temperature of PCL. Further, it is shown by quantum chemical calculations that all the peaks obtained experimentally originate in skeletal vibrations of PCL. Therefore, it has become clear thatmore » a specific feature appears in the THz absorption spectrum of PCL associated with its glass transition.« less

X-Ray Absorbed, Broad-Lined, Red AGN and the Cosmic X-Ray Background

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Wilkes, Belinda

2005-01-01

We have obtained XMM spectra for five red, 2MASS AGN, selected from a sample observed by Chandra to be X-ray bright and to cover a range of hardness ratios. Our results confirm the presence of substantial absorbing material in three sources which have optical classifications ranging from Type 1 to Type 2, with an intrinsically flat (hard) power law continuum indicated in the other two. The presence of both X-ray absorption and broad optical emission lines with the usual strength suggests either a small (nuclear) absorber or a favored viewing angle so as to cover the X-ray source but not the broad emission line region (BELR). A soft excess is detected in all three Type 1 sources. We speculate that this soft X-ray emission may arise in an extended region of ionized gas, perhaps linked with the polarized (scattered) light which is a feature of these sources. The spectral complexity revealed by XMM emphasizes the limitations of the low S/N Chandra data. Overall, the new XMM results strengthen our conclusions (Wilkes et al. 2002) that the observed X-ray continua of red AGN are unusually hard at energies greater than 2 keV. Whether due to substantial line-of-sight absorption or to an intrinsically hard or reflection-dominated spectrum, these 'red' AGN have an observed spectral form consistent with contributing significantly to the missing had absorbed population of the Cosmic X-ray Background (CXRB). When absorption and or reflection is taken into account, all these AGN have power law slopes typical of broad-line (Type 1) AGN (Gamma approximately 1.9). This appears to resolve the spectral paradox which for so long has existed between the CXRB and the AGN thought to be the dominant contributors. It also suggests two scenarios whereby Type 1 AGN/QSOs may be responsible for a significant fraction of the CXRB at energies above 2 keV: 1) X-ray absorbed AGN/QSOs with visible broad emission lines; 2) AGN/QSOs with complex spectra whose hardness greater than 2 keV is not detectable in the typically low S/N data of X-ray surveys. Even if absorption is present in only half of the population, the large number of 'red' AGN suggests a development of unification models, where the continuum source is surrounded, over a substantial solid angle, by the wind or atmosphere of an accretion disk/torus. X-ray observations of such AGN not only provide a check on the presence of absorption, but also a unique probe of the absorbing material. Improved information on their space density, in particular as a function of redshift, will soon be provided by Spitzer-Chandra wide area surveys, allowing better estimates of both the importance of red AGN to the full AGN population and their contribution to the CXRB.

Gas-phase broadband spectroscopy using active sources: progress, status, and applications

PubMed Central

Cossel, Kevin C.; Waxman, Eleanor M.; Finneran, Ian A.; Blake, Geoffrey A.; Ye, Jun; Newbury, Nathan R.

2017-01-01

Broadband spectroscopy is an invaluable tool for measuring multiple gas-phase species simultaneously. In this work we review basic techniques, implementations, and current applications for broadband spectroscopy. We discuss components of broad-band spectroscopy including light sources, absorption cells, and detection methods and then discuss specific combinations of these components in commonly-used techniques. We finish this review by discussing potential future advances in techniques and applications of broad-band spectroscopy. PMID:28630530

Origin of the 900 cm{sup −1} broad double-hump OH vibrational feature of strongly hydrogen-bonded carboxylic acids

DOE Office of Scientific and Technical Information (OSTI.GOV)

Van Hoozen, Brian L.; Petersen, Poul B.

2015-03-14

Medium and strong hydrogen bonds are common in biological systems. Here, they provide structural support and can act as proton transfer relays to drive electron and/or energy transfer. Infrared spectroscopy is a sensitive probe of molecular structure and hydrogen bond strength but strongly hydrogen-bonded structures often exhibit very broad and complex vibrational bands. As an example, strong hydrogen bonds between carboxylic acids and nitrogen-containing aromatic bases commonly display a 900 cm{sup −1} broad feature with a remarkable double-hump structure. Although previous studies have assigned this feature to the OH, the exact origin of the shape and width of this unusualmore » feature is not well understood. In this study, we present ab initio calculations of the contributions of the OH stretch and bend vibrational modes to the vibrational spectrum of strongly hydrogen-bonded heterodimers of carboxylic acids and nitrogen-containing aromatic bases, taking the 7-azaindole—acetic acid and pyridine—acetic acid dimers as examples. Our calculations take into account coupling between the OH stretch and bend modes as well as how both of these modes are affected by lower frequency dimer stretch modes, which modulate the distance between the monomers. Our calculations reproduce the broadness and the double-hump structure of the OH vibrational feature. Where the spectral broadness is primarily caused by the dimer stretch modes strongly modulating the frequency of the OH stretch mode, the double-hump structure results from a Fermi resonance between the out of the plane OH bend and the OH stretch modes.« less

Dramatically Variable C IV Mini-Broad Absorption Line System in the Quasar HS 1603+3820

NASA Astrophysics Data System (ADS)

Misawa, T.; Eracleous, M.; Charlton, J. C.; Chartas, G.; Kashikawa, N.

2008-10-01

We observed the quasar HS 1603+3820 (z_{em} = 2.542, first discovered by Dobrzycki et al. 1996) six times over an interval of 4.2 yrs (1.2 yrs in the quasar rest frame) using the High Dispersion Spectrograph on Subaru telescope. The purpose was to study the mini-broad absorption line (mini-BAL; FWHM ˜ 1,000 km s^{-1}) that is blue-shifted from the quasar by ˜ 9,500 km s^{-1}. We found significant time variability, which supported the physical association of the mini-BAL gas with an outflow from the quasar. We have narrowed down the cause of the variability to two possible scenarios. We also used archival Chandra x-ray data to study the x-ray properties of this quasar. The results constrain the location of the absorbing gas relative to the overall outflow.

Infrared radiation models for atmospheric methane

NASA Technical Reports Server (NTRS)

Cess, R. D.; Kratz, D. P.; Caldwell, J.; Kim, S. J.

1986-01-01

Mutually consistent line-by-line, narrow-band and broad-band infrared radiation models are presented for methane, a potentially important anthropogenic trace gas within the atmosphere. Comparisons of the modeled band absorptances with existing laboratory data produce the best agreement when, within the band models, spurious band intensities are used which are consistent with the respective laboratory data sets, but which are not consistent with current knowledge concerning the intensity of the infrared fundamental band of methane. This emphasizes the need for improved laboratory band absorptance measurements. Since, when applied to atmospheric radiation calculations, the line-by-line model does not require the use of scaling approximations, the mutual consistency of the band models provides a means of appraising the accuracy of scaling procedures. It is shown that Curtis-Godson narrow-band and Chan-Tien broad-band scaling provide accurate means of accounting for atmospheric temperature and pressure variations.

Aerosol Absorption Retrievals from the PACE Broad Spectrum Ocean Color Instrument (OCI)

NASA Technical Reports Server (NTRS)

Mattoo, Shana; Remer, Lorraine A.; Levy, Robert C.; Gupta, Pawan; Ahmad, Ziauddin; Martins, J. Vanderlei; Lima, Adriana Rocha; Torres, Omar

2016-01-01

The PACE (Pre-­Aerosol, Clouds and ocean Ecosystem) mission, anticipated for launch in the early 2020s, is designed to characterize oceanic and atmospheric properties. The primary instrument on-­-board will be a moderate resolution (approximately 1 km nadir) radiometer, called the Ocean Color Instrument (OCI). OCI will provide high spectral resolution (5 nm) from the UV to NIR (350 - 800 nm), with additional spectral bands in the NIR and SWIR. The OCI itself is an excellent instrument for atmospheric objectives, providing measurements across a broad spectral range that in essence combines the capabilities of MODIS and OMI, but with the UV channels from OMI to be available at moderate resolution. (Image credit: PACE Science Definition Team Report). Objective: Can we make use of the UV-­SWIR measurements to derive information about aerosol absorption when aerosol loading is high?

The dependence of C IV broad absorption line properties on accompanying Si IV and Al III absorption: relating quasar-wind ionization levels, kinematics, and column densities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filiz Ak, N.; Brandt, W. N.; Schneider, D. P.

2014-08-20

We consider how the profile and multi-year variability properties of a large sample of C IV Broad Absorption Line (BAL) troughs change when BALs from Si IV and/or Al III are present at corresponding velocities, indicating that the line of sight intercepts at least some lower ionization gas. We derive a number of observational results for C IV BALs separated according to the presence or absence of accompanying lower ionization transitions, including measurements of composite profile shapes, equivalent width (EW), characteristic velocities, composite variation profiles, and EW variability. We also measure the correlations between EW and fractional-EW variability for Cmore » IV, Si IV, and Al III. Our measurements reveal the basic correlated changes between ionization level, kinematics, and column density expected in accretion-disk wind models; e.g., lines of sight including lower ionization material generally show deeper and broader C IV troughs that have smaller minimum velocities and that are less variable. Many C IV BALs with no accompanying Si IV or Al III BALs may have only mild or no saturation.« less

When galaxies collide: understanding the broad absorption-line radio galaxy 4C +72.26

NASA Astrophysics Data System (ADS)

Smith, D. J. B.; Simpson, C.; Swinbank, A. M.; Rawlings, S.; Jarvis, M. J.

2010-05-01

We present a range of new observations of the `broad absorption-line radio galaxy' 4C +72.26 (z ~ 3.5), including sensitive rest-frame ultraviolet integral field spectroscopy using the Gemini/GMOS-N instrument and Subaru/CISCO K-band imaging and spectroscopy. We show that 4C +72.26 is a system of two vigorously star-forming galaxies superimposed along the line of sight separated by ~1300 +/- 200 km s-1 in velocity, with each demonstrating spectroscopically resolved absorption lines. The most active star-forming galaxy also hosts the accreting supermassive black hole which powers the extended radio source. We conclude that the star formation is unlikely to have been induced by a shock caused by the passage of the radio jet, and instead propose that a collision is a more probable trigger for the star formation. Despite the massive starburst, the ultraviolet-mid-infrared spectral energy distribution suggests that the pre-existing stellar population comprises ~1012Msolar of stellar mass, with the current burst only contributing a further ~2 per cent, suggesting that 4C +72.26 has already assembled most of its final stellar mass.

Ultraviolet and infrared absorption spectra of Cr2O3 doped-sodium metaphosphate, lead metaphosphate and zinc metaphosphate glasses and effects of gamma irradiation: a comparative study.

PubMed

Marzouk, M A; ElBatal, F H; Abdelghany, A M

2013-10-01

The effects of gamma irradiation on spectral properties of Cr2O3-doped phosphate glasses of three varieties, namely sodium metaphosphate, lead metaphosphate and zinc metaphosphate have been investigated. Optical spectra of the undoped samples reveal strong UV absorption bands which are attributed to the presence of trace iron impurities in both the sodium and zinc phosphate glasses while the lead phosphate glass exhibits broad UV near visible bands due to combined absorption of both trace iron impurities and divalent lead ions. The effect of chromium oxide content has been investigated. The three different Cr2O3-doped phosphate glasses reveal spectral visible bands varying in their position and intensity and splitting due to the different field strengths of the Na(+), Pb(2+), Zn(2+) cations, together with the way they are housed in the network and their effects on the polarisability of neighboring oxygens ligands. The effects of gamma irradiation on the optical spectral properties of the various glasses have been compared. The different effects for lead and zinc phosphate are related to the ability of Pb(2+), and Zn(2+) to form additional structural units causing stability of the network towards gamma irradiation. Also, the introduction of the transition metal chromium ions reveals some shielding behavior towards irradiation. Infrared absorption spectra of the three different base phosphate glasses show characteristic vibrations due to various phosphate groups depending on the type of glass and Cr2O3 is observed to slightly affect the IR spectra. Gamma irradiation causes minor variations in some of the intensities of the IR spectra but the main characteristic bands due to phosphate groups remain in their number and position. Copyright © 2013 Elsevier B.V. All rights reserved.

[Development of photothermal microactuator based on spectral analysis of photothermal expansion material].

PubMed

Liu, Chao; Zhang, Dong-Xian; Zhang, Hai-Jun

2009-11-01

The spectral characteristic of materials is the key factor of the photothermal microactuator's performance. The present article introduces the operating principle, and analyzes the relationship between the material spectral characteristic and its expansion. As the photothermal microactuator is an innovative microactuator based on photothermal expansion that absorbs the laser energy and converts it into internal energy to realize the microdrive, the optimal photothermal expansion material with proper absorption spectrum characteristic matching the spectrum of light driving source needs to be found. The reflection and absorption spectra of four types of polymeric material, including PVC, HDPE, LDPE and PET, were obtained by using the single integrating sphere method. The results indicate that the reflection spectrum of the dyed high-density polyethylene (HDPE) is of double-peak structure in visible band, and there is strong absorption within the range of 600-690 nm, which means it would match the light driving source quite well in the broad spectral range. Therefore, HDPE was chosen as the photothermal expansion material. In order to check out the feasibility and performance of the photothermal microactuactor based on HDPE, a prototyping microactuator 1 500 mm in length and 30 mm in thickness was manufactured by using an excimer laser micromachining system. With a laser diode (10 mW/650 nm) as the external power source to activate the microactuator, performance measurement experiments were carried out by using a self-produced video movement measurement system with a CCD-coupled microscope. The experiment results demonstrate that the deflection of the microactuator reaches 18.7 mm at 10 mW of laser power, showing that the characteristics of spectral absorption and light-heat transition are quite well at 650 nm. This novel photothermal microactuator has simple structure, adjustable displacement output, and more mobility, and can be controlled remotely, so it will be quite useful for applications in the fields of micro-optical-electro-mechanical systems (MOEMS).

Inelastic losses in X-ray absorption theory

NASA Astrophysics Data System (ADS)

Campbell, Luke Whalin

There is a surprising lack of many body effects observed in XAS (X-ray Absorption Spectroscopy) experiments. While collective excitations and other satellite effects account for between 20% and 40% of the spectral weight of the core hole and photoelectron excitation spectrum, the only commonly observed many body effect is a relatively structureless amplitude reduction to the fine structure, typically no more than a 10% effect. As a result, many particle effects are typically neglected in the XAS codes used to predict and interpret modern experiments. To compensate, the amplitude reduction factor is simply fitted to experimental data. In this work, a quasi-boson model is developed to treat the case of XAS, when the system has both a photoelectron and a core hole. We find that there is a strong interference between the extrinsic and intrinsic losses. The interference reduces the excitation amplitudes at low energies where the core hole and photo electron induced excitations tend to cancel. At high energies, the interference vanishes, and the theory reduces to the sudden approximation. The x-ray absorption spectrum including many-body excitations is represented by a convolution of the one-electron absorption spectrum with an energy dependent spectral function. The latter has an asymmetric quasiparticle peak and broad satellite structure. The net result is a phasor sum, which yields the many body amplitude reduction and phase shift of the fine structure oscillations (EXAFS), and possibly additional satellite structure. Calculations for several cases of interest are found to be in reasonable agreement with experiment. Edge singularity effects and deviations from the final state rule arising from this theory are also discussed. The ab initio XAS code FEFF has been extended for calculations of the many body amplitude reduction and phase shift in x-ray spectroscopies. A new broadened plasmon pole self energy is added. The dipole matrix elements are modified to include a projection operator to calculate deviations from the final state rule and edge singularities.

Lyα vs. fundamental properties of galaxies

NASA Astrophysics Data System (ADS)

Wofford, Aida; Leitherer, Claus; Salzer, John; COS Science Team

2013-03-01

We obtained HST COS Lyα spectroscopy for 20 galaxies that were Hα-selected from the Kitt Peak International Spectroscopic Survey data release. We cover redshifts of z=0.02-0.06 and a broad range in metallicity, reddening, and luminosity. We investigate correlations between the properties of the Lyα-lines and fundamental properties of the galaxies. Our seven emitters have: equivalent widths in the range EW(Lyα)=1-12 Å, i.e., below the completeness limits of higher redshift studies; extinction corrected Lyα/Hα ratios of at most 12-15% of the case B recombination theory value; and O I λ1302 ISM absorptions blueshifted to = - 117±40 km/s, which are consistent with H I gas outflows. Six emitters have P-Cygni-like Lyα profiles with peaks redshifted to =172±25 km/s, and one of our face-on spiral galaxies has two Lyα peaks separated by 370 km/s. The latter peaks are such that the blueshifted peak is twice as strong as the redshifted peak. The rest of the galaxies show Lyα absorption troughs centered at =19 km/s and O I λ1302 absorptions centered at = - 34±25 km/s, which is consistent with static or low velocity H I gas. Our two most metal poor and least reddened galaxies, which have large Hα equivalent widths are absorbers. The spiral galaxies in our sample have Lyα in single emission, double emission, or absorption. There appears to be a correlation between the Hα derived SFR and the strength of the Lyα emission but our sample is small. Our observations cover regions of at most 3 kpc in diameter and may miss a significant fraction of the resonantly scattered Lyα emission. This work is supported by NASA grant N1317.

Laser absorption waves in metallic capillaries

NASA Astrophysics Data System (ADS)

Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Kanevskii, M. F.; Kondrashov, V. V.

1987-07-01

The propagation of laser absorption waves in metallic capillaries was studied experimentally and numerically during pulsed exposure to CO2 laser radiation. The dependence of the plasma front propagation rate on the initial air pressure in the capillary is determined. In a broad range of parameters, the formation time of the optically opaque plasma layer is governed by the total laser pulse energy from the beginning of the exposure to the instant screening appears, and is weakly dependent on the pulse shape and gas pressure.

Optical absorption studies on biodegradable PVA/PVP blend polymer electrolyte system

NASA Astrophysics Data System (ADS)

Basha, S. K. Shahenoor; Reddy, K. Veera Bhadra; Rao, M. C.

2018-05-01

Biodegradable blend polymer electrolytes of PVA/PVP with different wt% ratios of MgCl2.6H2O have been prepared using solution cast technique. Optical absorption studies were carried-out on to the prepared films at room temperature using JASCO V-670 Spectrophotometer in the wavelength region 200-600 nm. Due to the clusters between the vibrations of molecules a broad peak is obtained due to п-п* transition in the wavelength region 310-340 nm.

Apparatus And Methods For Launching And Receiving A Broad Wavelength Range Source

DOEpatents

Von Drasek, William A.; Sonnenfroh, David; Allen, Mark G.; Stafford-Evans, Joy

2006-02-28

An apparatus and method for simultaneous detection of N gas species through laser radiation attenuation techniques is disclosed. Each of the N species has a spectral absorption band. N laser sources operate at a wavelength ?N in a spectral absorption band separated by the cutoff wavelength for single-mode transmission. Each laser source corresponds to a gas species and transmits radiation through an optical fiber constructed and arranged to provide single-mode transmission with minimal power loss.

Spectroscopy of Reaction Intermediates in Nitramine Decomposition and Combustion

DTIC Science & Technology

1991-06-20

Dakhis and co-workers, s the very strong absorption of MMN near 1332 cm - 1 did not appear. Unassigned absorptions appeared near 930, 1240, 1460, 2990, and...sharp NO2 absorption. In Table I, the positions of these absorptions are compared with the infrared absorptions of MMN reported by Dakhis and co-workers...Chemistry and Physics of Energetic Materials, S. N. Bulusu, Ed., pp. 51-78 (Kluwer Academic Publishers, Dordrecht, 1990). 56. M. I. Dakhis , V. G. Dashevsky

Spectroscopy of Reaction Intermediates in Nitramine Decomposition and Combustion

DTIC Science & Technology

1991-06-20

absorptions of gas-phase MMN reported by Dakhis and co-workers,5 6 the very strong absorption of MMN near 1332 cm - ’ did not appear. Unassigned...sharp NO 2 absorption. In Table I, the positions of these absorptions are compared with the infrared absorptions of MMN reported by Dakhis and co-workers...Chemistry and Physics of Energetic Materials, S. N. Bulusu, Ed., pp. 51-78 (Kluwer Academic Publishers, Dordrecht, 1990). 56. M. I. Dakhis , V. G

WPVS 007: Dramatic Broad Absorption Line Variability in a Narrow-line Seyfert 1

NASA Astrophysics Data System (ADS)

Cooper, Erin M.; Leighly, K.; Hamann, F. W.; Grupe, D.; Dietrich, M.

2014-01-01

Blue-shifted broad absorption lines are the manifestation of gaseous outflows in astrophysical phenomena. In active galaxies, these outflowing winds may play a key role in the central engine physics by removing angular momentum and in influencing host galaxy evolution by imparting energy and chemically enriched gas to the surrounding medium. AGN wind variability affords us a valuable tool to study this still poorly understood phenomenon. The existence of a high velocity broad line outflow in WPVS007 is especially extraordinary, as Seyfert-luminosity active galaxies are unexpected to produce them. With its lower luminosity and compact size, the NLS1 galaxy WPVS007 (M_V=-19.7, z=0.02882) provides us the ability to study even colossal variability on merely human timescales. Since its 1996 FOS observation, displaying miniBALs but no true broad absorption lines, WPVS007 has experienced a short but rich history of UV BAL variability. By the 2003 FUSE observation, WPVS007 had developed a BAL with v_max ~ 6000km/s, indicating an optically thick, high velocity outflow. We present the 2010 and 2013 June and December HST COS spectra. Between 2003 and 2010, both the maximum and minimum outflow velocity had increased substantially. As of 2013 June, the continuum emission has since dimmed by a factor of ~2 and the BALs have appeared to weaken, with both decreased maximum and minimum velocities. Such dramatic shifts in BAL velocity are unprecedented, as BAL variability is typically confined to changes in optical depth. What is the nature of the variability in this BAL wind? The upcoming (as of the writing of this abstract) December observation should give us more insight into tackling that question, whether it be the transient response of a continuous flow to a fluctuating continuum or perhaps the continued decline of a discrete outflow event.

Consequences of hot gas in the broad line region of active galactic nuclei

NASA Technical Reports Server (NTRS)

Kallman, T.; Mushotzky, R.

1985-01-01

Models for hot gas in the broad line region of active galactic nuclei are discussed. The results of the two phase equilibrium models for confinement of broad line clouds by Compton heated gas are used to show that high luminosity quasars are expected to show Fe XXVI L alpha line absorption which will be observed with spectrometers such as those planned for the future X-ray spectroscopy experiments. Two phase equilibrium models also predict that the gas in the broad line clouds and the confining medium may be Compton thick. It is shown that the combined effects of Comptonization and photoabsorption can suppress both the broad emission lines and X-rays in the Einstein and HEAO-1 energy bands. The observed properties of such Compton thick active galaxies are expected to be similar to those of Seyfert 2 nuclei. The implications for polarization and variability are also discussed.

Characterization by combined optical and FT infrared spectra of 3d-transition metal ions doped-bismuth silicate glasses and effects of gamma irradiation.

PubMed

ElBatal, F H; Abdelghany, A M; ElBatal, H A

2014-03-25

Optical and infrared absorption spectral measurements were carried out for binary bismuth silicate glass and other derived prepared samples with the same composition and containing additional 0.2% of one of 3d transition metal oxides. The same combined spectroscopic properties were also measured after subjecting the prepared glasses to a gamma dose of 8 Mrad. The experimental optical spectra reveal strong UV-near visible absorption bands from the base and extended to all TMs-doped samples and these specific extended and strong UV-near visible absorption bands are related to the contributions of absorption from both trace iron (Fe(3+)) ions present as contaminated impurities within the raw materials and from absorption of main constituent trivalent bismuth (Bi(3+)) ions. The strong UV-near visible absorption bands are observed to suppress any further UV bands from TM ions. The studied glasses show obvious resistant to gamma irradiation and only small changes are observed upon gamma irradiation. This observed shielding behavior is related to the presence of high Bi(3+) ions with heavy mass causing the observed stability of the optical absorption. Infrared absorption spectra of the studied glasses reveal characteristic vibrational bands due to both modes from silicate network and the sharing of Bi-O linkages and the presence of TMs in the doping level (0.2%) causes no distinct changes within the number or position of the vibrational modes. The presence of high Bi2O3 content (70 mol%) appears to cause stability of the structural building units towards gamma irradiation as revealed by FTIR measurements. Copyright © 2013 Elsevier B.V. All rights reserved.

A diode laser-based velocimeter providing point measurements in unseeded flows using modulated filtered Rayleigh scattering (MFRS)

NASA Astrophysics Data System (ADS)

Jagodzinski, Jeremy James

2007-12-01

The development to date of a diode-laser based velocimeter providing point-velocity-measurements in unseeded flows using molecular Rayleigh scattering is discussed. The velocimeter is based on modulated filtered Rayleigh scattering (MFRS), a novel variation of filtered Rayleigh scattering (FRS), utilizing modulated absorption spectroscopy techniques to detect a strong absorption of a relatively weak Rayleigh scattered signal. A rubidium (Rb) vapor filter is used to provide the relatively strong absorption; alkali metal vapors have a high optical depth at modest vapor pressures, and their narrow linewidth is ideally suited for high-resolution velocimetry. Semiconductor diode lasers are used to generate the relatively weak Rayleigh scattered signal; due to their compact, rugged construction diode lasers are ideally suited for the environmental extremes encountered in many experiments. The MFRS technique utilizes the frequency-tuning capability of diode lasers to implement a homodyne detection scheme using lock-in amplifiers. The optical frequency of the diode-based laser system used to interrogate the flow is rapidly modulated about a reference frequency in the D2-line of Rb. The frequency modulation is imposed on the Rayleigh scattered light that is collected from the probe volume in the flow under investigation. The collected frequency modulating Rayleigh scattered light is transmitted through a Rb vapor filter before being detected. The detected modulated absorption signal is fed to two lock-in amplifers synchronized with the modulation frequency of the source laser. High levels of background rejection are attained since the lock-ins are both frequency and phase selective. The two lock-in amplifiers extract different Fourier components of the detected modulated absorption signal, which are ratioed to provide an intensity normalized frequency dependent signal from a single detector. A Doppler frequency shift in the collected Rayleigh scattered light due to a change in the velocity of the flow under investigation results in a change in the detected modulated absorption signal. This change in the detected signal provides a quantifiable measure of the Doppler frequency shift, and hence the velocity in the probe volume, provided that the laser source exhibits acceptable levels of frequency stability (determined by the magnitude of the velocities being measured). An extended cavity diode laser (ECDL) in the Littrow configuration provides frequency tunable, relatively narrow-linewidth lasing for the MFRS velocimeter. Frequency stabilization of the ECDL is provided by a proportional-integral-differential (PID) controller based on an error signal in the reference arm of the experiment. The optical power of the Littrow laser source is amplified by an antireflection coated (AR coated) broad stripe diode laser. The single-mode, frequency-modulatable, frequency-stable O(50 mW) of optical power provided by this extended cavity diode laser master oscillator power amplifier (ECDL-MOPA) system provided sufficient scattering signal from a condensing jet of CO2 to implement the MFRS technique in the frequency-locked mode of operation.

A photothermal Mach-Zehnder interferometer for measuring caffeine and proteins in aqueous solutions using external cavity quantum cascade lasers

NASA Astrophysics Data System (ADS)

Kristament, Christian; Schwaighofer, Andreas; Montemurro, Milagros; Lendl, Bernhard

2018-02-01

One of the advantages of mid-IR spectroscopy in biomedical research lies in its capability to provide direct information on the secondary structure of proteins in their natural, often aqueous, environment. One impediment of direct absorption measurements in the correspondent spectral region is the strong absorbance of the native solvent (H2O). In this regard, the advent of broadly-tunable external cavity quantum cascade lasers (EC-QCL) allowed to significantly increasing the optical path length employed in transmission measurements due to their high spectral power densities. Low measured S/N ratios were improved by elaborated data analysis protocols that corrected mechanical flaws in the tuning mechanism of ECQCLs and allow for S/N ratios comparable to research grade FTIR spectrometers. Recent development of new optical set-ups outpacing direct absorption measurements led to further advancements. We present a dedicated Mach-Zehnder interferometer for photothermal measurements in balanced detection mode. In this highly sensitive design, the interferometer is illuminated by a HeNe laser to detect the refractive index change induced by the heat insertion of the EC-QCL. Here, we present photothermal phase shift interferometry measurements of caffeine in ethanol as well as casein in water. Further, the dependency of the signal amplitude on varying modulation frequencies was investigated for different liquids.

Modeling of light distribution in the brain for topographical imaging

NASA Astrophysics Data System (ADS)

Okada, Eiji; Hayashi, Toshiyuki; Kawaguchi, Hiroshi

2004-07-01

Multi-channel optical imaging system can obtain a topographical distribution of the activated region in the brain cortex by a simple mapping algorithm. Near-infrared light is strongly scattered in the head and the volume of tissue that contributes to the change in the optical signal detected with source-detector pair on the head surface is broadly distributed in the brain. This scattering effect results in poor resolution and contrast in the topographic image of the brain activity. We report theoretical investigations on the spatial resolution of the topographic imaging of the brain activity. The head model for the theoretical study consists of five layers that imitate the scalp, skull, subarachnoid space, gray matter and white matter. The light propagation in the head model is predicted by Monte Carlo simulation to obtain the spatial sensitivity profile for a source-detector pair. The source-detector pairs are one dimensionally arranged on the surface of the model and the distance between the adjoining source-detector pairs are varied from 4 mm to 32 mm. The change in detected intensity caused by the absorption change is obtained by Monte Carlo simulation. The position of absorption change is reconstructed by the conventional mapping algorithm and the reconstruction algorithm using the spatial sensitivity profiles. We discuss the effective interval between the source-detector pairs and the choice of reconstruction algorithms to improve the topographic images of brain activity.

Development of CdS Nanostructures by Thermal Decomposition of Aminocaproic Acid-Mixed Cd-Thiourea Complex Precursor: Structural, Optical and Photocatalytic Characterization.

PubMed

Patel, Jayesh D; Mighri, Frej; Ajji, Abdellah; Chaudhuri, Tapas K

2015-04-01

The present work deals with two different CdS nanostructures produced via hydrothermal and solvothermal decompositions of aminocaproic acid (ACA)-mixed Cd-thiourea complex precursor at 175 °C. Both nanostructures were extensively characterized for their structural, morphological and optical properties. The powder X-ray diffraction characterization showed that the two CdS nanostructures present a wurtzite morphology. Scanning electron microscopy and energy-dispersive X-ray characterizations revealed that the hydrothermal decomposition produced well-shaped CdS flowers composed of six dendritic petals, and the solvothermal decomposition produced CdS microspheres with close stoichiometric chemical composition. The UV-vis absorption and photoluminescence spectra of CdS dendritic flowers and microsphere nanostructures showed that both nanostructures present a broad absorption between 200 and 700 nm and exhibit strong green emissions at 576 and 520 nm upon excitations at 290 nm and 260 nm, respectively. The transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) characterizations confirmed that CdS microspheres were mesoporous and were composed of small nanocrystals. A possible growth mechanism in the formation of the CdS nanostructures was proposed based on morphology evolution as a function of the reaction time. Furthermore, the as-synthesized CdS nanostructures were found to exhibit highly efficient photocatalytic activities for the degradation of methyl orange (MeO) and rhodamine B (RhB) dyes.

Lightweight NiFe2O4 with controllable 3D network structure and enhanced microwave absorbing properties

NASA Astrophysics Data System (ADS)

Wang, Fen; Wang, Xing; Zhu, Jianfeng; Yang, Haibo; Kong, Xingang; Liu, Xiao

2016-11-01

3D network structure NiFe2O4 was successfully synthesized by a templated salt precipitation method using PMMA colloid crystal as templates. The morphology, phase composition and microwave absorbing properties of as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vector network analyzer (VNA), and so on. The results revealed that the 3D network structure was configurated with smooth spherical walls composed of NiFe2O4 nanocrystals and their pore diameters being in the range of 80-250 nm. The microwave absorption properties of the 3D network structure NiFe2O4 were crucially determined by the special structure. The synergy of intrinsic magnetic loss of magnetic NiFe2O4 and the interfacial polarization enhanced by 3D network structure and the interaction of multiple mechanisms endowed the sample with the feature of strong absorption, broad bandwidth and lightweight. There is more than one valley in the reflection loss curves and the maximum reflection loss is 27.5 dB with a bandwidth of 4 GHz. Moreover, the 3D network structure NiFe2O4 show a greater reflection loss with the same thickness comparing to the ordinary NiFe2O4 nanoparticles, which could achieve the feature of lightweight of the microwave absorbing materials.

Lightweight NiFe2O4 with controllable 3D network structure and enhanced microwave absorbing properties

PubMed Central

Wang, Fen; Wang, Xing; Zhu, Jianfeng; Yang, Haibo; Kong, Xingang; Liu, Xiao

2016-01-01

3D network structure NiFe2O4 was successfully synthesized by a templated salt precipitation method using PMMA colloid crystal as templates. The morphology, phase composition and microwave absorbing properties of as-prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), vector network analyzer (VNA), and so on. The results revealed that the 3D network structure was configurated with smooth spherical walls composed of NiFe2O4 nanocrystals and their pore diameters being in the range of 80–250 nm. The microwave absorption properties of the 3D network structure NiFe2O4 were crucially determined by the special structure. The synergy of intrinsic magnetic loss of magnetic NiFe2O4 and the interfacial polarization enhanced by 3D network structure and the interaction of multiple mechanisms endowed the sample with the feature of strong absorption, broad bandwidth and lightweight. There is more than one valley in the reflection loss curves and the maximum reflection loss is 27.5 dB with a bandwidth of 4 GHz. Moreover, the 3D network structure NiFe2O4 show a greater reflection loss with the same thickness comparing to the ordinary NiFe2O4 nanoparticles, which could achieve the feature of lightweight of the microwave absorbing materials. PMID:27897209

ORIGIN OF THE COMPLEX RADIO STRUCTURE IN BAL QSO 1045+352

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kunert-Bajraszewska, Magdalena; Gawronski, Marcin P.; Janiuk, Agnieszka

2010-08-01

We present new, more sensitive, high-resolution radio observations of a compact broad absorption line (BAL) quasar, 1045+352, made with the EVN+MERLIN at 5 GHz. These observations allowed us to trace the connection between the arcsecond structure and the radio core of the quasar. The radio morphology of 1045+352 is dominated by a knotty jet showing several bends. We discuss possible scenarios that could explain such a complex morphology: galaxy merger, accretion disk instability, precession of the jet, and jet-cloud interactions. It is possible that we are witnessing an ongoing jet precession in this source due to internal instabilities within themore » jet flow; however, a dense environment detected in the submillimeter band and an outflowing material suggested by the X-ray absorption could strongly interact with the jet. It is difficult to establish the orientation between the jet axis and the observer in 1045+352 because of the complex structure. Nevertheless, taking into account the most recent inner radio structure, we conclude that the radio jet is oriented close to the line of sight, which can mean that the opening angle of the accretion disk wind can be large in this source. We also suggest that there is no direct correlation between the jet-observer orientation and the possibility of observing BALs.« less

A Pharmacological and Toxicological Profile of Silver as an Antimicrobial Agent in Medical Devices

PubMed Central

Lansdown, Alan B. G.

2010-01-01

Silver is used widely in wound dressings and medical devices as a broad-spectrum antibiotic. Metallic silver and most inorganic silver compounds ionise in moisture, body fluids, and secretions to release biologically active Ag+. The ion is absorbed into the systemic circulation from the diet and drinking water, by inhalation and through intraparenteral administration. Percutaneous absorption of Ag+ through intact or damaged skin is low. Ag+ binds strongly to metallothionein, albumins, and macroglobulins and is metabolised to all tissues other than the brain and the central nervous system. Silver sulphide or silver selenide precipitates, bound lysosomally in soft tissues, are inert and not associated with an irreversible toxic change. Argyria and argyrosis are the principle effects associated with heavy deposition of insoluble silver precipitates in the dermis and cornea/conjunctiva. Whilst these changes may be profoundly disfiguring and persistent, they are not associated with pathological damage in any tissue. The present paper discusses the mechanisms of absorption and metabolism of silver in the human body, presumed mechanisms of argyria and argyrosis, and the elimination of silver-protein complexes in the bile and urine. Minimum blood silver levels consistent with early signs of argyria or argyrosis are not known. Silver allergy does occur but the extent of the problem is not known. Reference values for silver exposure are discussed. PMID:21188244

Ultraviolet Changes of the Central Source and the Very Nearby Ejecta

NASA Technical Reports Server (NTRS)

Gull, Theodore R.; Nielsen, Krister; Vierira, Gladys; Hillier, John; Walborn, Nolan; Davidson, Kris

2004-01-01

We utilized the high spatial and high spectral resolution of the HST/STIS MAMA echelle modes in the ultraviolet (0.025 inch spatial resolution and 30,000 to 120,000 spectral resolving power) to view changes in and around Eta Carinae before and after the X-Ray drop which occurred on June 29, 2003 (M. Corcoran, IAUC 8160). Major changes in the spectra of the Central Source and nearby nebulosities occurred between June 22 and July 5. Visibility of the Central Source dropped, especially between 1175 and 1350 Angstroms, but not uniformly throughout the ultraviolet. This fading is likely due to multiple line absorptions both in the source and in the intervening ejecta. Nebular emission of Si III] and Fe III, located 0.09 sec. to the west, disappeared. By July 29, a bright feature extending up to 0.071 sec. east of the Central Source became prominent in broad emission lines near 2500 Angstroms, but was not noticeable longward of 2900 Angstroms. ACS/HRC imagery and STIS CCD spectra taken concurrently are being examined for larger scale changes. Numerous narrow velocity components between -146 and -585 kilometers per second were identified in spectra before the minimum. New components appeared primarily in Fe II absorption lines with velocities between -170 and -380 kilometers per second. While the lines of the -513 kilometers per second component did not change, most lines of the -146 kilometers per second component changed considerably. Lines originating from high energy levels diminished or disappeared, while lines originating from lower energy levels strengthened. Strong absorption lines of Ti II, not present before the X-Ray drop, appeared within seven days, but disappeared by July 29. Further analysis of these unprecedented data will provide significant new information about the structure of Eta Carinae and its periodic variations.

NuSTAR + XMM-Newton monitoring of the neutron star transient AX J1745.6-2901

NASA Astrophysics Data System (ADS)

Ponti, G.; Bianchi, S.; Muñoz-Darias, T.; Mori, K.; De, K.; Rau, A.; De Marco, B.; Hailey, C.; Tomsick, J.; Madsen, K. K.; Clavel, M.; Rahoui, F.; Lal, D. V.; Roy, S.; Stern, D.

2018-01-01

AX J1745.6-2901 is a high-inclination (eclipsing) transient neutron star (NS) low-mass X-ray binary showcasing intense ionized Fe K absorption. We present here the analysis of 11 XMM-Newton and 15 NuSTAR new data sets (obtained between 2013 and 2016), therefore tripling the number of observations of AX J1745.6-2901 in outburst. Thanks to simultaneous XMM-Newton and NuSTAR spectra, we greatly improve on the fitting of the X-ray continuum. During the soft state, the emission can be described by a disc blackbody (kT ∼ 1.1-1.2 keV and inner disc radius rDBB ∼ 14 km), plus hot (kT ∼ 2.2-3.0 keV) blackbody radiation with a small emitting radius (rBB ∼ 0.5 - 0.8 km) likely associated with the boundary layer or NS surface, plus a faint Comptonization component. Imprinted on the spectra are clear absorption features created by both neutral and ionized matter. Additionally, positive residuals suggestive of an emission Fe K α disc line and consistent with relativistic ionized reflection are present during the soft state, while such residuals are not significant during the hard state. The hard-state spectra are characterized by a hard (Γ ∼ 1.9-2.1) power law, showing no evidence for a high energy cut-off (kTe > 60-140 keV) and implying a small optical depth (τ < 1.6). The new observations confirm the previously witnessed trend of exhibiting strong Fe K absorption in the soft state that significantly weakens during the hard state. Optical (GROND) and radio (GMRT) observations suggest for AX J1745.6-2901 a standard broad-band spectral energy distribution as typically observed in accreting NSs.

Ionized Absorbers in Active Galactic Nuclei and Very Steap Soft X-Ray Quasars

NASA Technical Reports Server (NTRS)

Fiore, Fabrizio; White, Nicholas (Technical Monitor)

2000-01-01

Steep soft X-ray (0.1-2 keV) quasars share several unusual properties: narrow Balmer lines, strong Fe II emission, large and fast X-ray variability, and a rather steep 2-10 keV spectrum. These intriguing objects have been suggested to be the analogues of Galactic black hole candidates in the high, soft state. We present here results from ASCA observations for two of these quasars: NAB 0205 + 024 and PG 1244 + 026. Both objects show similar variations (factor of approximately 2 in 10 ks), despite a factor of approximately 10 difference in the 0.5-10 keV luminosity (7.3 x 10(exp 43) erg/s for PG 1244 + 026 and 6.4 x 10(exp 44) erg/s for NAB 0205 + 024, assuming isotropic emission, H(sub 0) = 50.0 and q(sub 0) = 0.0). The X-ray continuum of the two quasars flattens by 0.5-1 going from the 0.1-2 keV band towards higher energies, strengthening recent results on another half-dozen steep soft X-ray active galactic nuclei. PG 1244 + 026 shows a significant feature in the '1-keV' region, which can be described either as a broad emission line centered at 0.95 keV (quasar frame) or as edge or line absorption at 1.17 (1.22) keV. The line emission could be a result of reflection from a highly ionized accretion disc, in line with the view that steep soft X-ray quasars are emitting close to the Eddington luminosity. Photoelectric edge absorption or resonant line absorption could be produced by gas outflowing at a large velocity (0.3-0.6 c).

Water redistribution in experimentally deformed natural milky quartz single crystals—Implications for H2O-weakening processes

NASA Astrophysics Data System (ADS)

Stünitz, H.; Thust, A.; Heilbronner, R.; Behrens, H.; Kilian, R.; Tarantola, A.; Fitz Gerald, J. D.

2017-02-01

Natural quartz single crystals were experimentally deformed in two orientations: (1) ⊥ to one prism plane and (2) in O+ orientation at 900 and 1000°C, 1.0 and 1.5 GPa, and strain rates of 1 × 10-6 s-1. In addition, hydrostatic and annealing experiments were performed. The starting material was milky quartz, which consisted of dry quartz with a large number of fluid inclusions of variable size up to several 100 µm. During pressurization fluid inclusions decrepitated producing much smaller fluid inclusions. Deformation on the sample scale is anisotropic due to dislocation glide on selected slip systems and inhomogeneous due to an inhomogeneous distribution of fluid inclusions. Dislocation glide is accompanied by minor dynamic recovery. Strongly deformed regions show a pointed broad absorption band in the 3400 cm-1 region consisting of a superposition of bands of molecular H2O and three discrete absorption bands (at 3367, 3400, and 3434 cm-1). In addition, there is a discrete absorption band at 3585 cm-1, which only occurs in deformed regions and reduces or disappears after annealing, so that this band appears to be associated with dislocations. H2O weakening in inclusion-bearing natural quartz crystals is assigned to the H2O-assisted dislocation generation and multiplication. Processes in these crystals represent recycling of H2O between fluid inclusions, cracking and crack healing, incorporation of structurally bound H in dislocations, release of H2O from dislocations during recovery, and dislocation generation at very small fluid inclusions. The H2O weakening by this process is of disequilibrium nature because it depends on the amount of H2O available.

Laboratory Determination of the Infrared Band Strengths of Pyrene Frozen in Water Ice: Implications for the Composition of Interstellar Ices

NASA Technical Reports Server (NTRS)

Hardegree-Ullman, E.E.; Gudipati, M.S.; Boogert, A.C.A.; Lignell, H.; Allamandola, L.J.; Stapelfeldt, K. R.; Werner, M.

2014-01-01

Broad infrared emission features (e.g., at 3.3, 6.2, 7.7, 8.6, and 11.3 micrometers) from the gas phase interstellar medium have long been attributed to polycyclic aromatic hydrocarbons (PAHs). A significant portion (10 to 20%) of the Milky Way's carbon reservoir is locked in PAH molecules, which makes their characterization integral to our understanding of astrochemistry. In molecular clouds and the dense envelopes and disks of young stellar objects (YSOs), PAHs are expected to be frozen in the icy mantles of dust grains where they should reveal themselves through infrared absorption. To facilitate the search for frozen interstellar PAHs, laboratory experiments were conducted to determine the positions and strengths of the bands of pyrene mixed with H2O and deuterium oxide ices. The deuterium oxide mixtures are used to measure pyrene bands that are masked by the strong bands of H2O, leading to the first laboratory determination of the band strength for the CH stretching mode of pyrene in water ice near 3.25 micrometers. Our infrared band strengths were normalized to experimentally determined ultraviolet (UV) band strengths, and we find that they are generally approximately 50% larger than those reported by Bouwman et al. (2011) based on theoretical strengths. These improved band strengths were used to reexamine YSO spectra published by Boogert et al. (2008) to estimate the contribution of frozen PAHs to absorption in the 5 to 8 micrometer spectral region, taking into account the strength of the 3.25 micrometer CH stretching mode. It is found that frozen neutral PAHs contain 5 to 9% of the cosmic carbon budget, and account for 2 to 9% of the unidentified absorption in the 5 to 8 micrometer region.

Modelling the light absorption coefficients of oceanic waters: Implications for underwater optical applications

NASA Astrophysics Data System (ADS)

Prabhakaran, Sai Shri; Sahu, Sanjay Kumar; Dev, Pravin Jeba; Shanmugam, Palanisamy

2018-05-01

Spectral absorption coefficients of particulate (algal and non-algal components) and dissolved substances are modelled and combined with the pure seawater component to determine the total light absorption coefficients of seawater in the Bay of Bengal. Two parameters namely chlorophyll-a (Chl) concentration and turbidity were measured using commercially available instruments with high sampling rates. For modelling the light absorption coefficients of oceanic waters, the measured data are classified into two broad groups - algal dominant and non-algal particle (NAP) dominant. With these criteria the individual absorption coefficients of phytoplankton and NAP were established based on their concentrations using an iterative method. To account for the spectral dependence of absorption by phytoplankton, the wavelength-dependent coefficients were introduced into the model. The CDOM absorption was determined by subtracting the individual absorption coefficients of phytoplankton and NAP from the measured total absorption data and then related to the Chl concentration. Validity of the model is assessed based on independent in-situ data from certain discrete locations in the Bay of Bengal. The total absorption coefficients estimated using the new model by considering the contributions of algal, non-algal and CDOM have good agreement with the measured total absorption data with the error range of 6.9 to 28.3%. Results obtained by the present model are important for predicting the propagation of the radiant energy within the ocean and interpreting remote sensing observation data.

The librational band of water ice in AFGL 961: revisited

NASA Astrophysics Data System (ADS)

Smith, R. G.; Wright, C. M.

2011-07-01

Of all the water ice absorption bands seen in the laboratory, the librational band near 12-13 μ m has proven the most difficult to conclusively identify in observational spectra. Cox reported the detection of this band in the IRAS spectrum of the massive protostar AFGL 961 near 13.6 μ m; however, the details of the structure of the band were limited by the quality of the IRAS spectrum and the accuracy of the subtracted silicate absorption. AFGL 961 is also a double system comprising two point-like components separated by ˜6 arcsec (AFGL 961E and AFGL 961W) so the IRAS aperture included both components - it is unclear how the combination of the intrinsic spectra of these two sources may have affected the resultant IRAS spectrum. In this paper we report Spitzer and European Southern Observatory (ESO) 3.6-m mid-infrared spectroscopic observations of each component of AFGL 961. We find a broad absorption feature near 13.1 μ m common to both AFGL 961E and W. The profile and peak wavelength of this feature are well matched by the laboratory spectrum of the librational band of amorphous H2O ice in the temperature range 10-30 K, in agreement with the Cox result. Both AFGL 961E and W also have strong CO2 ice absorption near 15.2 μ m, indistinguishable in profile between the two. However, AFGL 961E shows silicates in absorption near 9.7 μ m, while AFGL 961W shows polycyclic aromatic hydrocarbons in emission and, in a small aperture, also silicates in emission. Uncertainty in where the true continuum lies in the 8-13 μ m spectral region for both AFGL 961E and W means we cannot rule out the possibility that a combination of silicate emission and absorption could be responsible for at least some of the features we see in this region. In this case, a much weaker librational band could still be present, but not as a distinct feature. In either case, the ice must be located in a cool, outer envelope surrounding both stars or a cool foreground cloud, far enough away that the ice is not appreciably modified by the local environment of either one.

Quasi-Fermi level splitting and sub-bandgap absorptivity from semiconductor photoluminescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Katahara, John K.; Hillhouse, Hugh W., E-mail: h2@uw.edu

A unified model for the direct gap absorption coefficient (band-edge and sub-bandgap) is developed that encompasses the functional forms of the Urbach, Thomas-Fermi, screened Thomas-Fermi, and Franz-Keldysh models of sub-bandgap absorption as specific cases. We combine this model of absorption with an occupation-corrected non-equilibrium Planck law for the spontaneous emission of photons to yield a model of photoluminescence (PL) with broad applicability to band-band photoluminescence from intrinsic, heavily doped, and strongly compensated semiconductors. The utility of the model is that it is amenable to full-spectrum fitting of absolute intensity PL data and yields: (1) the quasi-Fermi level splitting, (2) themore » local lattice temperature, (3) the direct bandgap, (4) the functional form of the sub-bandgap absorption, and (5) the energy broadening parameter (Urbach energy, magnitude of potential fluctuations, etc.). The accuracy of the model is demonstrated by fitting the room temperature PL spectrum of GaAs. It is then applied to Cu(In,Ga)(S,Se){sub 2} (CIGSSe) and Cu{sub 2}ZnSn(S,Se){sub 4} (CZTSSe) to reveal the nature of their tail states. For GaAs, the model fit is excellent, and fitted parameters match literature values for the bandgap (1.42 eV), functional form of the sub-bandgap states (purely Urbach in nature), and energy broadening parameter (Urbach energy of 9.4 meV). For CIGSSe and CZTSSe, the model fits yield quasi-Fermi leveling splittings that match well with the open circuit voltages measured on devices made from the same materials and bandgaps that match well with those extracted from EQE measurements on the devices. The power of the exponential decay of the absorption coefficient into the bandgap is found to be in the range of 1.2 to 1.6, suggesting that tunneling in the presence of local electrostatic potential fluctuations is a dominant factor contributing to the sub-bandgap absorption by either purely electrostatic (screened Thomas-Fermi) or a photon-assisted tunneling mechanism (Franz-Keldysh). A Gaussian distribution of bandgaps (local E{sub g} fluctuation) is found to be inconsistent with the data. The sub-bandgap absorption of the CZTSSe absorber is found to be larger than that for CIGSSe for materials that yield roughly equivalent photovoltaic devices (8% efficient). Further, it is shown that fitting only portions of the PL spectrum (e.g., low energy for energy broadening parameter and high energy for quasi-Fermi level splitting) may lead to significant errors for materials with substantial sub-bandgap absorption and emission.« less

Charge transfer effects, thermo and photochromism in single crystal CVD synthetic diamond.

PubMed

Khan, R U A; Martineau, P M; Cann, B L; Newton, M E; Twitchen, D J

2009-09-09

We report on the effects of thermal treatment and ultraviolet irradiation on the point defect concentrations and optical absorption profiles of single crystal CVD synthetic diamond. All thermal treatments were below 850 K, which is lower than the growth temperature and unlikely to result in any structural change. UV-visible absorption spectroscopy measurements showed that upon thermal treatment (823 K), various broad absorption features diminished: an absorption band at 270 nm (used to deduce neutral single substitutional nitrogen (N(S)(0)) concentrations) and also two broad features centred at approximately 360 and 520 nm. Point defect centre concentrations as a function of temperature were also deduced using electron paramagnetic resonance (EPR) spectroscopy. Above ∼500 K, we observed a decrease in the concentration of N(S)(0) centres and a concomitant increase in the negatively charged nitrogen-vacancy-hydrogen (NVH) complex (NVH(-)) concentration. Both transitions exhibited an activation energy between 0.6 and 1.2 eV, which is lower than that for the N(S)(0) donor (∼1.7 eV). Finally, it was found that illuminating samples with intense short-wave ultraviolet light recovered the N(S)(0) concentration and also the 270, 360 and 520 nm absorption features. From these results, we postulate a valence band mediated charge transfer process between NVH and single nitrogen centres with an acceptor trap depth for NVH of 0.6-1.2 eV. Because the loss of N(S)(0) concentration is greater than the increase in NVH(-) concentration we also suggest the presence of another unknown acceptor existing at a similar energy to NVH. The extent to which the colour in CVD synthetic diamond is dependent on prior history is discussed.

The Evolution of Quasar C IV and Si IV Broad Absorption Lines over Multi-year Timescales

NASA Astrophysics Data System (ADS)

Gibson, Robert R.; Brandt, W. N.; Gallagher, S. C.; Hewett, Paul C.; Schneider, Donald P.

2010-04-01

We investigate the variability of C IV λ1549 broad absorption line (BAL) troughs over rest-frame timescales of up to ≈7 yr in 14 quasars at redshifts z >~ 2.1. For nine sources at sufficiently high redshift, we also compare the C IV and Si IV λ1400 absorption variation. We compare shorter and longer term variability using spectra from up to four different epochs per source and find complex patterns of variation in the sample overall. The scatter in the change of absorption equivalent width (EW), ΔEW, increases with the time between observations. BALs do not, in general, strengthen or weaken monotonically, and variation observed over shorter (lsimmonths) timescales is not predictive of multi-year variation. We find no evidence for asymmetry in the distribution of ΔEW that would indicate that BALs form and decay on different timescales, and we constrain the typical BAL lifetime to be gsim30 yr. The BAL absorption for one source, LBQS 0022+0150, has weakened and may now be classified as a mini-BAL. Another source, 1235+1453, shows evidence of variable, blue continuum emission that is relatively unabsorbed by the BAL outflow. C IV and Si IV BAL shape changes are related in at least some sources. Given their high velocities, BAL outflows apparently traverse large spatial regions and may interact with parsec-scale structures such as an obscuring torus. Assuming BAL outflows are launched from a rotating accretion disk, notable azimuthal symmetry is required in the outflow to explain the relatively small changes observed in velocity structure over times up to 7 yr.

A Search for H I Lyα Counterparts to Ultrafast X-Ray Outflows

NASA Astrophysics Data System (ADS)

Kriss, Gerard A.; Lee, Julia C.; Danehkar, Ashkbiz

2018-06-01

Prompted by the H I Lyα absorption associated with the X-ray ultrafast outflow at ‑17,300 km s‑1 in the quasar PG 1211+143, we have searched archival UV spectra at the expected locations of H I Lyα absorption for a large sample of ultrafast outflows identified in XMM-Newton and Suzaku observations. Sixteen of the X-ray outflows have predicted H I Lyα wavelengths falling within the bandpass of spectra from either the Far Ultraviolet Spectroscopic Explorer or the Hubble Space Telescope, although none of the archival observations were simultaneous with the X-ray observations in which ultrafast X-ray outflows (UFOs) were detected. In our spectra broad features with FWHM of 1000 km s‑1 have 2σ upper limits on the H I column density of generally ≲2 × 1013 cm‑2. Using grids of photoionization models covering a broad range of spectral energy distributions (SEDs), we find that producing Fe XXVI Lyα X-ray absorption with equivalent widths >30 eV and associated H I Lyα absorption with {N}{{H}{{I}}}< 2× {10}13 {cm}}-2 requires total absorbing column densities {N}{{H}}> 5× {10}22 {cm}}-2 and ionization parameters log ξ ≳ 3.7. Nevertheless, a wide range of SEDs would predict observable H I Lyα absorption if ionization parameters are only slightly below peak ionization fractions for Fe XXV and Fe XXVI. The lack of Lyα features in the archival UV spectra indicates that the UFOs have very high ionization parameters, that they have very hard UV-ionizing spectra, or that they were not present at the time of the UV spectral observations owing to variability.

Simultaneous X-ray and Far-Ultraviolet Spectra of AGN with ASCA and HUT

NASA Technical Reports Server (NTRS)

Kriss, Gerard A.

1997-01-01

We obtained ASCA spectra of the Seyfert 1 galaxy NGC 3516 in March 1995. Simultaneous far-UV observations were obtained with the Hopkins Ultraviolet Telescope on the Astro-2 shuttle mission. The ASCA spectrum shows a lightly absorbed power law of energy index 0.78. The low energy absorbing column is significantly less than previously seen. Prominent 0 VII and 0 VIII absorption edges are visible, but, consistent with the much lower total absorbing column, no Fe K absorption edge is detectable. A weak, narrow Fe K(alpha) emission line from cold material is present as well as a broad Fe K(alpha) line. These features are similar to those reported in other Seyfert 1 galaxies. A single warm absorber model provides only an imperfect description of the low energy absorption. In addition to a highly ionized absorber with ionization parameter U = 1.66 and a total column density of 1.4 x 10(exp 22)/sq cm, adding a lower ionization absorber with U = 0.32 and a total column of 6.9 x 10(exp 21)/sq cm significantly improves the fit. The contribution of resonant line scattering to our warm absorber models limits the Doppler parameter to less than 160 km/s at 90% confidence. Turbulence at the sound speed of the photoionized gas provides the best fit. None of the warm absorber models fit to the X-ray spectrum can match the observed equivalent widths of all the UV absorption lines. Accounting for the X-ray and UV absorption simultaneously requires an absorbing region with a broad range of ionization parameters and column densities.

A P25/(NH4)xWO3 hybrid photocatalyst with broad spectrum photocatalytic properties under UV, visible, and near-infrared irradiation

NASA Astrophysics Data System (ADS)

Yang, Linfen; Liu, Bin; Liu, Tongyao; Ma, Xinlong; Li, Hao; Yin, Shu; Sato, Tsugio; Wang, Yuhua

2017-04-01

In this study, a series of hybrid nanostructured photocatalysts P25/(NH4)xWO3 nanocomposites with the average crystallite size of P25 and (NH4)xWO3 of the sample was calculated to be about 30 nm and 130 nm, were successfully synthesized via a simple one-step hydrothermal method. The as-obtained samples was characterized by transmission electron microscopy (TEM), which implies that the P25/(NH4)xWO3 nanocomposites are fabricated with favourable nanosizd interfacial. The XPS results confirmed that the obtained sample consists of mixed chemical valences of W5+ and W6+, the low-valance W5+ sites could be the origin of NIR absorption. As revealed by optical absorption results, P25/(NH4)xWO3 nanocomposites possess high optical absorption in the whole solar spectrum of 200-2500 nm. Benefiting from this unique photo-absorption property and the synergistic effect of P25 and (NH4)xWO3, broad spectrum response photocatalytic activities covering UV, visible and near infrared regions on degradation of Rhodamine B have been realized by P25/(NH4)xWO3 nanocomposites. Meanwhile, the stability of photocatalysts was examined by the XRD and XPS of the photocatalysts after the reaction. The results show that P25/(NH4)xWO3 photocatalysts has a brilliant application prospect in the energy utilization to solve deteriorating environmental issues.

H I absorption in nearby compact radio galaxies

NASA Astrophysics Data System (ADS)

Glowacki, M.; Allison, J. R.; Sadler, E. M.; Moss, V. A.; Curran, S. J.; Musaeva, A.; Deng, C.; Parry, R.; Sligo, M. C.

2017-05-01

H I absorption studies yield information on both active galactic nucleus (AGN) feeding and feedback processes. This AGN activity interacts with the neutral gas in compact radio sources, which are believed to represent the young or recently re-triggered AGN population. We present the results of a survey for H I absorption in a sample of 66 compact radio sources at 0.040 < z < 0.096 with the Australia Telescope Compact Array. In total, we obtained seven detections, five of which are new, with a large range of peak optical depths (3-87 per cent). Of the detections, 71 per cent exhibit asymmetric, broad (ΔvFWHM > 100 km s-1) features, indicative of disturbed gas kinematics. Such broad, shallow and offset features are also found within low-excitation radio galaxies which is attributed to disturbed circumnuclear gas, consistent with early-type galaxies typically devoid of a gas-rich disc. Comparing mid-infrared colours of our galaxies with H I detections indicates that narrow and deep absorption features are preferentially found in late-type and high-excitation radio galaxies in our sample. These features are attributed to gas in galactic discs. By combining XMM-Newton archival data with 21-cm data, we find support that absorbed X-ray sources may be good tracers of H I content within the host galaxy. This sample extends previous H I surveys in compact radio galaxies to lower radio luminosities and provides a basis for future work exploring the higher redshift universe.

A P25/(NH4)xWO3 hybrid photocatalyst with broad spectrum photocatalytic properties under UV, visible, and near-infrared irradiation

PubMed Central

Yang, Linfen; Liu, Bin; Liu, Tongyao; Ma, Xinlong; Li, Hao; Yin, Shu; Sato, Tsugio; Wang, Yuhua

2017-01-01

In this study, a series of hybrid nanostructured photocatalysts P25/(NH4)xWO3 nanocomposites with the average crystallite size of P25 and (NH4)xWO3 of the sample was calculated to be about 30 nm and 130 nm, were successfully synthesized via a simple one-step hydrothermal method. The as-obtained samples was characterized by transmission electron microscopy (TEM), which implies that the P25/(NH4)xWO3 nanocomposites are fabricated with favourable nanosizd interfacial. The XPS results confirmed that the obtained sample consists of mixed chemical valences of W5+ and W6+, the low-valance W5+ sites could be the origin of NIR absorption. As revealed by optical absorption results, P25/(NH4)xWO3 nanocomposites possess high optical absorption in the whole solar spectrum of 200–2500 nm. Benefiting from this unique photo-absorption property and the synergistic effect of P25 and (NH4)xWO3, broad spectrum response photocatalytic activities covering UV, visible and near infrared regions on degradation of Rhodamine B have been realized by P25/(NH4)xWO3 nanocomposites. Meanwhile, the stability of photocatalysts was examined by the XRD and XPS of the photocatalysts after the reaction. The results show that P25/(NH4)xWO3 photocatalysts has a brilliant application prospect in the energy utilization to solve deteriorating environmental issues. PMID:28368032

A P25/(NH4)xWO3 hybrid photocatalyst with broad spectrum photocatalytic properties under UV, visible, and near-infrared irradiation.

PubMed

Yang, Linfen; Liu, Bin; Liu, Tongyao; Ma, Xinlong; Li, Hao; Yin, Shu; Sato, Tsugio; Wang, Yuhua

2017-04-03

In this study, a series of hybrid nanostructured photocatalysts P25/(NH 4 ) x WO 3 nanocomposites with the average crystallite size of P25 and (NH 4 ) x WO 3 of the sample was calculated to be about 30 nm and 130 nm, were successfully synthesized via a simple one-step hydrothermal method. The as-obtained samples was characterized by transmission electron microscopy (TEM), which implies that the P25/(NH 4 ) x WO 3 nanocomposites are fabricated with favourable nanosizd interfacial. The XPS results confirmed that the obtained sample consists of mixed chemical valences of W 5+ and W 6+ , the low-valance W 5+ sites could be the origin of NIR absorption. As revealed by optical absorption results, P25/(NH 4 ) x WO 3 nanocomposites possess high optical absorption in the whole solar spectrum of 200-2500 nm. Benefiting from this unique photo-absorption property and the synergistic effect of P25 and (NH 4 ) x WO 3 , broad spectrum response photocatalytic activities covering UV, visible and near infrared regions on degradation of Rhodamine B have been realized by P25/(NH 4 ) x WO 3 nanocomposites. Meanwhile, the stability of photocatalysts was examined by the XRD and XPS of the photocatalysts after the reaction. The results show that P25/(NH 4 ) x WO 3 photocatalysts has a brilliant application prospect in the energy utilization to solve deteriorating environmental issues.

The reflection component in the average and heartbeat spectra of the black-hole candidate IGR J17091-3642 during the 2016 outburst

NASA Astrophysics Data System (ADS)

Wang, Yanan; Méndez, Mariano; Altamirano, Diego; Court, James; Beri, Aru; Cheng, Zheng

2018-05-01

We present simultaneous NuSTAR and Swift observations of the black hole transient IGR J17091-3642 during its 2016 outburst. By jointly fitting six NuSTAR and four Swift spectra, we found that during this outburst the source evolves from the hard to the hard/soft intermediate and back to the hard state, similar to the 2011 outburst. Unlike in the previous outburst, in this case we observed both a broad emission and an moderately broad absorption line in our observations. Our fits favour an accretion disc with an inclination angle of ˜45° with respect to the line of sight and a high iron abundance of 3.5 ± 0.3 in units of the solar abundance. We also observed heartbeat variability in one NuSTAR observation. We fitted the phase-resolved spectra of this observation and found that the reflected emission varies independently from the direct emission, whereas in the fits to the average spectra these two quantities are strongly correlated. Assuming that in IGR J17091-3642 the inner radius of the disc both in the average and the phase-resolved spectra is located at the radius of the innermost stable circular orbit, with 90% confidence the spin parameter of the black hole in this system is -0.13 ≤ a* ≤ 0.27.

Lensless, ultra-wideband fiber optic rotary joint for biomedical applications.

PubMed

Kim, Wihan; Chen, Xi; Jo, Javier A; Applegate, Brian E

2016-05-01

The demands of optical fiber-based biomedical applications can, in many cases, outstrip the capabilities of lens-based commercially available fiber optic rotary joints. In some circumstances, it is necessary to use very broad spectral bandwidths (near UV to short-wave IR) and specialized optical fibers, such as double-clad fiber, and have the capacity to accommodate high rotational velocities. The broad spectrum, stretching down into the UV, presents two problems: (1) adequate chromatic correction in the lenses across the entire bandwidth and (2) strong UV absorption by the fluids used to lubricate the rotary joint. To accommodate these types of applications, we have developed an ultra-wideband lensless fiber optic rotary joint based on the principle that when two optical fibers are coaligned and placed in contact (or very close), the optical losses at the junction are very low. The advances demonstrated here enable excellent performance (<0.2  dB insertion loss), even down into the UV and spanning a wavelength range of at least 355-1360 nm with single-mode, multimode, and double-clad fibers. We also demonstrate excellent performance, ∼0.38  dB insertion loss, at rotational velocities up to 8800 rpm (146 Hz). To the best of our knowledge, this is the first demonstration of this type of rotary joint capable of such a wide bandwidth and high rotational velocities.

Tracking coherent population transfer and thermal population relaxation in condensed system by broad-band transient grating spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, Wei; Liu, Xiaosong; Wu, Honglin; Song, Yunfei; Liu, Weilong; Yang, Yanqiang

2018-04-01

Broad-band transient grating (BB-TG) spectroscopy was proposed to track both coherent population transfer (CPT) and thermal population relaxation processes in a condensed system of solvated molecules in solution (Rhodamine101 in methanol). A broad band around 1500 cm‑1 and a relative narrow band near 2900 cm‑1 emerge in TG and transient absorption contour plots when pump and probe pulses overlap in the sample. The experimental results matched well with the vibrational modes of Rhodamine101 that were obtained by theoretical calculation. In addition, it was found that the population of CPT particles can be evaluated quantitatively through the intensity of the TG signal.

Broadband nonlinear optical response of monolayer MoSe2 under ultrafast excitation

NASA Astrophysics Data System (ADS)

Nie, Zhonghui; Trovatello, Chiara; Pogna, Eva A. A.; Dal Conte, Stefano; Miranda, Paulo B.; Kelleher, Edmund; Zhu, Chunhui; Turcu, Ion Crisitan Edmond; Xu, Yongbing; Liu, Kaihui; Cerullo, Giulio; Wang, Fengqiu

2018-01-01

Due to their strong light-matter interaction, monolayer transition metal dichalcogenides (TMDs) have proven to be promising candidates for nonlinear optics and optoelectronics. Here, we characterize the nonlinear absorption of chemical vapour deposition (CVD)-grown monolayer MoSe2 in the 720-810 nm wavelength range. Surprisingly, despite the presence of strong exciton resonances, monolayer MoSe2 exhibits a uniform modulation depth of ˜80 ± 3% and a saturation intensity of ˜2.5 ± 0.4 MW/cm2. In addition, pump-probe spectroscopy is performed to confirm the saturable absorption and reveal the photocarrier relaxation dynamics over hundreds of picoseconds. Our results unravel the unique broadband nonlinear absorptive behavior of monolayer MoSe2 under ultrafast excitation and highlight the potential of using monolayer TMDs as broadband ultrafast optical switches with customizable saturable absorption characteristics.

Absorption spectra of deuterated water at DF laser wavelengths.

PubMed

Bruce, C W; Jelinek, A V

1982-11-15

Absorption coefficients for deuterated water have been measured at twenty-two deuterium fluoride (DF) laser wavelengths and presented for atmospheric conditions classified as midlatitude-summer (14.3 T water vapor, standard temperature, and pressure). The HDO vapor was produced from a liquid mixture of H(2)O and D(2)O. The proportions of the resulting equilibrium mixture involving these constituents and HDO were calculated using previously measured constants and produced strong HDO absorption at the 3.5-4.1-microm DF laser wavelengths relative to those of the H(2)O and D(2)O vapors. Predicted and measured pressure dependencies at constant mixing ratios are compared for several laser wavelengths having strong HDO absorption. Absorption coefficients are in fairly close agreement with those of the current Air Force Geophysical Laboratory line-by-line model for standard temperature and pressure conditions. At lower total pressures, the comparison is less satisfactory and suggests inaccurate line parameters in the predictive data base.

Corrosion inhibitor for aqueous ammonia absorption system

DOEpatents

Phillips, Benjamin A.; Whitlow, Eugene P.

1998-09-22

A method of inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425.degree. F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25.degree. C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425.degree. F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer.

Corrosion inhibitor for aqueous ammonia absorption system

DOEpatents

Phillips, B.A.; Whitlow, E.P.

1998-09-22

A method is described for inhibiting corrosion and the formation of hydrogen and thus improving absorption in an ammonia/water absorption refrigeration, air conditioning or heat pump system by maintaining the hydroxyl ion concentration of the aqueous ammonia working fluid within a selected range under anaerobic conditions at temperatures up to 425 F. This hydroxyl ion concentration is maintained by introducing to the aqueous ammonia working fluid an inhibitor in an amount effective to produce a hydroxyl ion concentration corresponding to a normality of the inhibitor relative to the water content ranging from about 0.015 N to about 0.2 N at 25 C. Also, working fluids for inhibiting the corrosion of carbon steel and resulting hydrogen formation and improving absorption in an ammonia/water absorption system under anaerobic conditions at up to 425 F. The working fluids may be aqueous solutions of ammonia and a strong base or aqueous solutions of ammonia, a strong base, and a specified buffer. 5 figs.

Black carbon absorption at the global scale is affected by particle-scale diversity in composition.

PubMed

Fierce, Laura; Bond, Tami C; Bauer, Susanne E; Mena, Francisco; Riemer, Nicole

2016-09-01

Atmospheric black carbon (BC) exerts a strong, but uncertain, warming effect on the climate. BC that is coated with non-absorbing material absorbs more strongly than the same amount of BC in an uncoated particle, but the magnitude of this absorption enhancement (Eabs) is not well constrained. Modelling studies and laboratory measurements have found stronger absorption enhancement than has been observed in the atmosphere. Here, using a particle-resolved aerosol model to simulate diverse BC populations, we show that absorption is overestimated by as much as a factor of two if diversity is neglected and population-averaged composition is assumed across all BC-containing particles. If, instead, composition diversity is resolved, we find Eabs=1-1.5 at low relative humidity, consistent with ambient observations. This study offers not only an explanation for the discrepancy between modelled and observed absorption enhancement, but also demonstrates how particle-scale simulations can be used to develop relationships for global-scale models.

Black Carbon Absorption at the Global Scale Is Affected by Particle-Scale Diversity in Composition

NASA Technical Reports Server (NTRS)

Fierce, Laura; Bond, Tami C.; Bauer, Susanne E.; Mena, Francisco; Riemer, Nicole

2016-01-01

Atmospheric black carbon (BC) exerts a strong, but uncertain, warming effect on the climate. BC that is coated with non-absorbing material absorbs more strongly than the same amount of BC in an uncoated particle, but the magnitude of this absorption enhancement (E(sub abs)) is not well constrained. Modelling studies and laboratory measurements have found stronger absorption enhancement than has been observed in the atmosphere. Here, using a particle-resolved aerosol model to simulate diverse BC populations, we show that absorption is overestimated by as much as a factor of two if diversity is neglected and population-averaged composition is assumed across all BC-containing particles. If, instead, composition diversity is resolved, we find E(sub abs) = 1 - 1.5 at low relative humidity, consistent with ambient observations. This study offers not only an explanation for the discrepancy between modelled and observed absorption enhancement, but also demonstrates how particle-scale simulations can be used to develop relationships for global-scale models.

Experimental study on the sound absorption characteristics of continuously graded phononic crystals

NASA Astrophysics Data System (ADS)

Zhang, X. H.; Qu, Z. G.; He, X. C.; Lu, D. L.

2016-10-01

Novel three-dimensional (3D) continuously graded phononic crystals (CGPCs) have been designed, and fabricated by 3D printing. Each of the CGPCs is an entity instead of a combination of several other samples, and the porosity distribution of the CGPC along the incident direction is nearly linear. The sound absorption characteristics of CGPCs were experimentally investigated and compared with those of uniform phononic crystals (UPCs) and discretely stepped phononic crystals (DSPCs). Experimental results show that CGPCs demonstrate excellent sound absorption performance because of their continuously graded structures. CGPCs have higher sound absorption coefficients in the large frequency range and more sound absorption coefficient peaks in a specific frequency range than UPCs and DSPCs. In particular, the sound absorption coefficients of the CGPC with a porosity of 0.6 and thickness of 30 mm are higher than 0.56 when the frequency is 1350-6300 Hz and are all higher than 0.2 in the studied frequency range (1000-6300 Hz). CGPCs are expected to have potential application in noise control, especially in the broad frequency and low-frequency ranges.

On the correlation of absorption cross-section with plasmonic color generation.

PubMed

Rezaei, Soroosh Daqiqeh; Ho, Jinfa; Ng, Ray Jia Hong; Ramakrishna, Seeram; Yang, Joel K W

2017-10-30

Through numerical simulations, we investigate the correlation between the absorption cross-section and the color saturation of plasmonic nanostructures of varying density. Understanding this correlation, enables the prediction of an optimal nanostructure separation, or combinations of different nanostructure sizes for plasmonic color printing applications. Here, we use metal-insulator-metal (MIM) aluminum nanostructures that support gap-plasmons. Large absorption cross-sections were observed that exceed twelve times the physical cross-section of the nanostructure disks. We derive a set of equations to determine the optimal separation for a periodic array using the absorption cross-section of an individual structure to realize saturated colors. Using the optimum pitch and enabled by the large absorption cross-sections of our structures, we employ color mixing strategies to realize a wider color gamut. The simulated color gamut exceeds the sRGB gamut for some colors, and includes dark tones. Color mixing using structures with large absorption cross-sections is a practical approach to generate a broad range of colors, in comparison to fabricating structures with continuously varying sizes.

Optical absorption, TL and IRSL of basic plagioclase megacrysts from the pinacate (Sonora, Mexico) quaternary alkalic volcanics.

PubMed

Chernov, V; Paz-Moreno, F; Piters, T M; Barboza-Flores, M

2006-01-01

The paper presents the first results of an investigation on optical absorption (OA), thermally and infrared stimulated luminescence (TL and IRSL) of the Pinacate plagioclase (labradorite). The OA spectra reveal two bands with maxima at 1.0 and 3.2 eV connected with absorption of the Fe3+ and Fe2+ and IR absorption at wavelengths longer than 2700 nm. The ultraviolet absorption varies exponentially with the photon energy following the 'vitreous' empirical Urbach rule indicating exponential distribution of localised states in the forbidden band. The natural TL is peaked at 700 K. Laboratory beta irradiation creates a very broad TL peak with maximum at 430 K. The change of the 430 K TL peak shape under the thermal cleaning procedure and dark storage after irradiation reveals a monotonous increasing of the activation energy that can be explained by the exponential distribution of traps. The IRSL response is weak and exhibits a typical decay behaviour.

The similarity of broad iron lines in X-ray binaries and active galactic nuclei

NASA Astrophysics Data System (ADS)

Walton, D. J.; Reis, R. C.; Cackett, E. M.; Fabian, A. C.; Miller, J. M.

2012-05-01

We have compared the 2001 XMM-Newton spectra of the stellar mass black hole binary XTE J1650-500 and the active galaxy MCG-6-30-15, focusing on the broad, excess emission features at ˜4-7 keV displayed by both sources. Such features are frequently observed in both low-mass X-ray binaries and active galactic nuclei (AGN). For the former case it is generally accepted that the excess arises due to iron emission, but there is some controversy over whether their width is partially enhanced by instrumental processes, and hence also over the intrinsic broadening mechanism. Meanwhile, in the latter case, the origin of this feature is still subject to debate; physically motivated reflection and absorption interpretations are both able to reproduce the observed spectra. In this work we make use of the contemporaneous BeppoSAX data to demonstrate that the breadth of the excess observed in XTE J1650-500 is astrophysical rather than instrumental, and proceed to highlight the similarity of the excesses present in this source and MCG-6-30-15. Both optically thick accretion discs and optically thin coronae, which in combination naturally give rise to relativistically broadened iron lines when the disc extends close to the black hole, are commonly observed in both classes of object. The simplest solution is that the broad emission features present arise from a common process, which we argue must be reflection from the inner regions of an accretion disc around a rapidly rotating black hole; for XTE J1650-500 we find spin constraints of 0.84 ≤a*≤ 0.98 at the 90 per cent confidence level. Other interpretations proposed for AGN add potentially unnecessary complexities to the theoretical framework of accretion in strong gravity.

Diffusion of Small Sticky Nanoparticles in a Polymer Melt: A Dynamic Light Scattering Study

NASA Astrophysics Data System (ADS)

Carroll, Bobby; Bocharova, Vera; Cheng, Shiwang; Yamamoto, Umi; Kisliuk, Alex; Schweizer, Ken; Sokolov, Alexei

The study of dynamics in complex fluids such as polymers has gained a broad interest in advanced materials and biomedical applications. Of particular interest is the motion of nanoparticles in these systems, which influences the mechanical and structural properties of composite materials, properties of colloidal systems, and biochemical processes in biological systems. Theoretical work predicts a violation of Stokes-Einstein (SE) relationship for diffusion of small nanoparticles in strongly-entangled polymer melt systems, with diffusion of nanoparticles much faster than expected DSE. It is attributed to differences between local and macroscopic viscosity. In this study, the diffusion of nanoparticles in polymer melts below and above entanglement molecular weight is measured using dynamic light scattering. The measured results are compared with simulations that provide quantitative predictions for SE violations. Our results are two-fold: (1) diffusion at lower molecular weights is slower than expected DSE due to chain absorption; and (2) diffusion becomes much (20 times) faster than DSE, at higher entanglements due to a reduced local viscosity.

Selectively enhanced photocurrent generation in twisted bilayer graphene with van Hove singularity

PubMed Central

Yin, Jianbo; Wang, Huan; Peng, Han; Tan, Zhenjun; Liao, Lei; Lin, Li; Sun, Xiao; Koh, Ai Leen; Chen, Yulin; Peng, Hailin; Liu, Zhongfan

2016-01-01

Graphene with ultra-high carrier mobility and ultra-short photoresponse time has shown remarkable potential in ultrafast photodetection. However, the broad and weak optical absorption (∼2.3%) of monolayer graphene hinders its practical application in photodetectors with high responsivity and selectivity. Here we demonstrate that twisted bilayer graphene, a stack of two graphene monolayers with an interlayer twist angle, exhibits a strong light–matter interaction and selectively enhanced photocurrent generation. Such enhancement is attributed to the emergence of unique twist-angle-dependent van Hove singularities, which are directly revealed by spatially resolved angle-resolved photoemission spectroscopy. When the energy interval between the van Hove singularities of the conduction and valance bands matches the energy of incident photons, the photocurrent generated can be significantly enhanced (up to ∼80 times with the integration of plasmonic structures in our devices). These results provide valuable insight for designing graphene photodetectors with enhanced sensitivity for variable wavelength. PMID:26948537

Impact of vanadium ions in barium borate glass.

PubMed

Abdelghany, A M; Hammad, Ahmed H

2015-02-25

Combined optical and infrared spectral measurements of prepared barium borate glasses containing different concentrations of V2O5 were carried out. Vanadium containing glasses exhibit extended UV-visible (UV/Vis.) bands when compared with base binary borate glass. UV/Vis. spectrum shows the presence of an unsymmetrical strong UV broad band centered at 214 nm attributed to the presence of unavoidable trace iron impurities within the raw materials used for the preparation of such glass. The calculated direct and indirect optical band gaps are found to decrease with increasing the vanadium content (2.9:137 for indirect and 3.99:2.01 for direct transition). This change was discussed in terms of structural changes in the glass network. Infrared absorption spectra of the glasses reveal the appearance of both triangular and tetrahedral borate units. Electron spin resonance analyses indicate the presence of unpaired species in sufficient quantity to be identified and to confirm the spectral data. Copyright © 2014 Elsevier B.V. All rights reserved.

MoS2 /Carbon Nanotube Core-Shell Nanocomposites for Enhanced Nonlinear Optical Performance.

PubMed

Zhang, Xiaoyan; Selkirk, Andrew; Zhang, Saifeng; Huang, Jiawei; Li, Yuanxin; Xie, Yafeng; Dong, Ningning; Cui, Yun; Zhang, Long; Blau, Werner J; Wang, Jun

2017-03-08

Nanocomposites of layered MoS 2 and multi-walled carbon nanotubes (CNTs) with core-shell structure were prepared by a simple solvothermal method. The formation of MoS 2 nanosheets on the surface of coaxial CNTs has been confirmed by scanning electron microscopy, transmission electron microscopy, absorption spectrum, Raman spectroscopy, and X-ray photoelectron spectroscopy. Enhanced third-order nonlinear optical performances were observed for both femtosecond and nanosecond laser pulses over a broad wavelength range from the visible to the near infrared, compared to those of MoS 2 and CNTs alone. The enhancement can be ascribed to the strong coupling effect and the photoinduced charge transfer between MoS 2 and CNTs. This work affords an efficient way to fabricate novel CNTs based nanocomposites for enhanced nonlinear light-matter interaction. The versatile nonlinear properties imply a huge potential of the nanocomposites in the development of nanophotonic devices, such as mode-lockers, optical limiters, or optical switches. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fluorine-free preparation of titanium carbide MXene quantum dots with high near-infrared photothermal performances for cancer therapy.

PubMed

Yu, Xinghua; Cai, Xingke; Cui, Haodong; Lee, Seung-Wuk; Yu, Xue-Feng; Liu, Bilu

2017-11-23

Titanium carbide MXene quantum dots (QDs) were synthesized using an effective fluorine-free method as a biocompatible and highly efficient nanoagent for photothermal therapy (PTT) applications. In contrast to the traditional, hazardous and time-consuming process of HF pretreatment, our fluorine-free method is safe and simple. More importantly, abundant Al oxoanions were found to be modified on the MXene QD surface by the fluorine-free method, which endowed the QDs with strong and broad absorption in the NIR region. As a result, the as-prepared MXene QDs exhibited an extinction coefficient as large as 52.8 Lg -1 cm -1 at 808 nm and a photothermal conversion efficiency as high as 52.2%. Both the values are among the best reported so far. The as-prepared MXene QDs achieved simultaneous photoacoustic (PA) imaging and the remarkable PTT effect of tumors. Moreover, MXene QDs showed great biocompatibility without causing noticeable toxicity in vitro and in vivo, indicating their high potential for clinical applications.

Gold Nanoparticles in Photonic Crystals Applications: A Review

PubMed Central

Venditti, Iole

2017-01-01

This review concerns the recently emerged class of composite colloidal photonic crystals (PCs), in which gold nanoparticles (AuNPs) are included in the photonic structure. The use of composites allows achieving a strong modification of the optical properties of photonic crystals by involving the light scattering with electronic excitations of the gold component (surface plasmon resonance, SPR) realizing a combination of absorption bands with the diffraction resonances occurring in the body of the photonic crystals. Considering different preparations of composite plasmonic-photonic crystals, based on 3D-PCs in presence of AuNPs, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tunable functionality of these crystals. Several chemical methods for fabrication of opals and inverse opals are presented together with preparations of composites plasmonic-photonic crystals: the influence of SPR on the optical properties of PCs is also discussed. Main applications of this new class of composite materials are illustrated with the aim to offer the reader an overview of the recent advances in this field. PMID:28772458

UV-active plasmons in alkali and alkaline-earth intercalated graphene

NASA Astrophysics Data System (ADS)

Despoja, V.; Marušić, L.

2018-05-01

The interband π and π +σ plasmons in pristine graphene and the Dirac plasmon in doped graphene are not applicable, since they are broad or weak, and weakly couple to an external longitudinal or electromagnetic probe. Therefore, the ab initio density functional theory is used to demonstrate that the chemical doping of the graphene by the alkali or alkaline-earth atoms dramatically changes the poor graphene excitation spectrum in the ultraviolet frequency range (4-10 eV). Four prominent modes are detected. Two of them are the intralayer plasmons with square-root dispersion, characteristic of the two-dimensional modes. The remaining two are the interlayer plasmons, very strong in the long-wavelength limit but damped for larger wave vectors. The optical absorption calculations show that the interlayer plasmons are both optically active, which makes these materials suitable for small-organic-molecule sensing. This is particularly intriguing because the optically active two-dimensional plasmons have not been detected in other materials.

Photoabsorption of the molecular IH cation at the iodine 3 d absorption edge

NASA Astrophysics Data System (ADS)

Klumpp, Stephan; Guda, Alexander A.; Schubert, Kaja; Mertens, Karolin; Hellhund, Jonas; Müller, Alfred; Schippers, Stefan; Bari, Sadia; Martins, Michael

2018-03-01

Yields of atomic iodine Iq + (q ≥2 ) fragments resulting from photoexcitation and photoionization of the target ions IH+ and I+ have been measured in the photon-energy range 610-680 eV, which comprises the thresholds for iodine 3 d ionization. The measured ion-yield spectra show two strong and broad resonance features due to the excitation of the 3 d3 /2 ,5 /2 electrons into ɛ f states rather similar for both parent ions. In the 3 d pre-edge range, excitations into (n p π ) -like orbitals and into an additional σ* orbital are found for IH+, which have been identified by comparison of the atomic I+ and molecular IH+ data and with the help of (time-dependent) density functional theory (DFT) and atomic Hartree-Fock calculations. The (5 p π ) orbital is almost atomlike, whereas all other resonances of the IH+ primary ion show a more pronounced molecular character, which is deduced from the chemical shifts of the resonances and the theoretical analysis.

Anomalous optical emission in hot dense oxygen

NASA Astrophysics Data System (ADS)

Santoro, Mario; Gregoryanz, Eugene; Mao, Ho-kwang; Hemley, Russell J.

2007-11-01

We report the observation of unusually strong, broad-band optical emission peaked between 590 and 650 nm when solid and fluid oxygen are heated by a near infrared laser at pressures from 3 to 46 GPa. In situ Raman spectra of oxygen were collected and corresponding temperatures were measured from the Stokes/anti-Stokes intensity ratios of vibrational transitions. The intense optical emission overwhelmed the Raman spectrum at temperatures exceeding 750 K. The spectrum was found to be much narrower than Planck-type thermal emission, and the intensity increase with input power was much steeper than expected for the thermal emission. The result places an important general caveat on calculating temperatures based on optical emission spectra in high-pressure laser-heating experiments. The intense emission in oxygen is photo-induced rather than being purely thermal, through multiphoton or multi-step single photon absorption processes related to the interaction with infrared radiation. The results suggest that short lived ionic species are induced by this laser-matter interaction.

Gold Nanoparticles in Photonic Crystals Applications: A Review.

PubMed

Venditti, Iole

2017-01-24

This review concerns the recently emerged class of composite colloidal photonic crystals (PCs), in which gold nanoparticles (AuNPs) are included in the photonic structure. The use of composites allows achieving a strong modification of the optical properties of photonic crystals by involving the light scattering with electronic excitations of the gold component (surface plasmon resonance, SPR) realizing a combination of absorption bands with the diffraction resonances occurring in the body of the photonic crystals. Considering different preparations of composite plasmonic-photonic crystals, based on 3D-PCs in presence of AuNPs, different resonance phenomena determine the optical response of hybrid crystals leading to a broadly tunable functionality of these crystals. Several chemical methods for fabrication of opals and inverse opals are presented together with preparations of composites plasmonic-photonic crystals: the influence of SPR on the optical properties of PCs is also discussed. Main applications of this new class of composite materials are illustrated with the aim to offer the reader an overview of the recent advances in this field.

The Radiative Heat Transfer Properties of Molten Salts and Their Relevance to the Design of Advanced Reactors

NASA Astrophysics Data System (ADS)

Chaleff, Ethan Solomon

Molten salts, such as the fluoride salt eutectic LiF-NaF-KF (FLiNaK) or the transition metal fluoride salt KF-ZrF4, have been proposed as coolants for numerous advanced reactor concepts. These reactors are designed to operate at high temperatures where radiative heat transfer may play a significant role. If this is the case, the radiative heat transfer properties of the salt coolants are required to be known for heat transfer calculations to be performed accurately. Chapter 1 describes the existing literature and experimental efforts pertaining to radiative heat transfer in molten salts. The physics governing photon absorption by halide salts is discussed first, followed by a more specific description of experimental results pertaining to salts of interest. The phonon absorption edge in LiF-based salts such as FLiNaK is estimated and the technique described for potential use in other salts. A description is given of various spectral measurement techniques which might plausibly be employed in the present effort, as well as an argument for the use of integral techniques. Chapter 2 discusses the mathematical treatments required to approximate and solve for the radiative flux in participating materials. The differential approximation and the exact solutions to the radiative flux are examined, and methods are given to solve radiative and energy equations simultaneously. A coupled solution is used to examine radiative heat transfer to molten salt coolants. A map is generated of pipe diameters, wall temperatures, and average absorption coefficients where radiative heat transfer will increase expected heat transfer by more than 10% compared to convective methods alone. Chapter 3 presents the design and analysis of the Integral Radiative Absorption Chamber (IRAC). The IRAC employs an integral technique for the measurement of the entire electromagnetic spectrum, negating some of the challenges associated with the methods discussed in Chapter 1 at the loss of spectral information. The IRAC design is validated by modeling the experiment in Fluent which shows that the IRAC should be capable of measuring absorption coefficients within 10%. Chapter 4 contains a parallel effort to experimental techniques, whereby information on absorption in salts is pursued using the Density Functional Theory code VASP. Photon-electron interactions are studied in pure salts such as LiF and are shown to be broadly transparent. Transition metal Fluoride salts such as KF-ZrF4 are shown to be broadly opaque. The addition of small amounts of transition metal impurities is studied by insertion of Chromium into the salt mixtures, which causes otherwise transparent salts to exhibit absorption coefficients significant to heat transfer. The spectral absorption coefficient for FLiNaK with Chromium is presented as is the average absorption coefficient as a function of impurity concentration. Chapter 5 discusses experimental efforts undertaken at The Ohio State University. Challenges with the constructed experimental apparatus are discussed and suggestions for future improvement on the technique are included. Finally, Chapter 6 contains broad conclusions pertaining to radiative transfer in advanced reactors.

Tunable, high-sensitive measurement of inter-dot transition via tunneling induced absorption

NASA Astrophysics Data System (ADS)

Peng, Yandong; Yang, Aihong; Chen, Bing; Li, Lei; Liu, Shande; Guo, Hongju

2016-10-01

A tunable, narrow absorption spectrum induced by resonant tunneling is demonstrated and proposed for measuring interdot tunneling. Tunneling-induced absorption (TIA) arises from constructive interference between different transition paths, and the large nonlinear TIA significantly enhances the total absorption. The narrow nonlinear TIA spectrum is sensitive to inter-dot tunneling, and its sensor characteristics, including sensitivity and bandwidth, are investigated in weak-coupling and strong-coupling regimes, respectively.

Glycerol-bonded 3C-SiC nanocrystal solid films exhibiting broad and stable violet to blue-green emission.

PubMed

Wang, J; Xiong, S J; Wu, X L; Li, T H; Chu, Paul K

2010-04-14

We have produced glycerol-bonded 3C-SiC nanocrystal (NC) films, which when excited by photons of different wavelengths, produce strong and tunable violet to blue-green (360-540 nm) emission as a result of the quantum confinement effects rendered by the 3C-SiC NCs. The emission is so intense that the emission spots are visible to the naked eyes. The light emission is very stable and even after storing in air for more than six months, no intensity degradation can be observed. X-ray photoelectron spectroscopy and absorption fine structure measurements indicate that the Si-terminated NC surfaces are completely bonded to glycerol molecules. Calculations of geometry optimization and electron structures based on the density functional theory for 3C-SiC NCs with attached glycerol molecules show that these molecules are bonded on the NCs causing strong surface structural change, while the isolated levels in the conduction band of the bare 3C-SiC NCs are replaced with quasi-continuous bands that provide continuous tunability of the emitted light by changing the frequencies of exciting laser. As an application, we demonstrate the potential of using 3C-SiC NCs to fabricate full-color emitting solid films by incorporating porous silicon.

Main-Sequence O Stars in NGC 6231: Enhanced Winds

NASA Astrophysics Data System (ADS)

Morrison, Nancy D.

Three late O-type main-sequence stars in the open cluster NGC 6231 will be observed with IUE at high dispersion, and their C IV and N V resonance-line profiles will be studied. From low-dispersion IUE observations, 10 members of the cluster have been found to have anomalously strong C IV resonance lines for their spectral types. Massa, Savage, and Cassinelli (1984) observed two of these "UV peculiar" stars (spectral types B0.5 V and B1 V) at high dispersion. They found that the C IV lines have a strong, broad, shortward-shifted absorption component, which suggests a greatly enhanced wind relative to the average for the spectral type. They proposed that the enhancement is due to an overabundance of C. Recently, however, Grigsby, Gordon, Morrison, and Zimba (1992) showed from optical spectra that these stars have normal C abundances. Thus, there is not yet a convincing explanation for these strikingly anomalous stellar winds. By extending the temperature range over which the phenomenon has been studied at high dispersion, however, we expect to gain new physical information. From wind modeling of the line profiles, we will derive mass-loss rates and terminal velocities, and we will test whether these winds are described by radiation-driven wind theory.

A Model Study of Zonal Forcing in the Equatorial Stratosphere by Convectively Induced Gravity Waves

NASA Technical Reports Server (NTRS)

Alexander, M. J.; Holton, James R.

1997-01-01

A two-dimensional cloud-resolving model is used to examine the possible role of gravity waves generated by a simulated tropical squall line in forcing the quasi-biennial oscillation (QBO) of the zonal winds in the equatorial stratosphere. A simulation with constant background stratospheric winds is compared to simulations with background winds characteristic of the westerly and easterly QBO phases, respectively. In all three cases a broad spectrum of both eastward and westward propagating gravity waves is excited. In the constant background wind case the vertical momentum flux is nearly constant with height in the stratosphere, after correction for waves leaving the model domain. In the easterly and westerly shear cases, however, westward and eastward propagating waves, respectively, are strongly damped as they approach their critical levels, owing to the strongly scale-dependent vertical diffusion in the model. The profiles of zonal forcing induced by this wave damping are similar to profiles given by critical level absorption, but displaced slightly downward. The magnitude of the zonal forcing is of order 5 m/s/day. It is estimated that if 2% of the area of the Tropics were occupied by storms of similar magnitude, mesoscale gravity waves could provide nearly 1/4 of the zonal forcing required for the QBO.

Tuning Ag29 nanocluster light emission from red to blue with one and two-photon excitation.

PubMed

Russier-Antoine, Isabelle; Bertorelle, Franck; Hamouda, Ramzi; Rayane, Driss; Dugourd, Philippe; Sanader, Željka; Bonačić-Koutecký, Vlasta; Brevet, Pierre-François; Antoine, Rodolphe

2016-02-07

We demonstrate that the tuning of the light emission from red to blue in dihydrolipoic acid (DHLA) capped Ag29 nanoclusters can be trigged with one and two photon excitations. The cluster stoichiometry was determined with mass spectrometry and found to be Ag29(DHLA)12. In a detailed optical investigation, we show that these silver nanoclusters exhibit a strong red photoluminescence visible to the naked eye and characterized by a quantum yield of nearly ∼2% upon one-photon excitation. In the nonlinear optical (NLO) study of the properties of the clusters, the two-photon excited fluorescence spectra were recorded and their first hyperpolarizability obtained. The two-photon absorption cross-section at ∼800 nm for Ag29(DHLA)12 is higher than 10(4) GM and the hyperpolarizability is 106 × 10(-30) esu at the same excitation wavelength. The two-photon excited fluorescence spectrum appears strongly blue-shifted as compared to the one-photon excited spectrum, displaying a broad band between 400 and 700 nm. The density functional theory (DFT) provides insight into the structural and electronic properties of Ag29(DHLA)12 as well as into interplay between metallic subunit or core and ligands which is responsible for unique optical properties.

Mid-infrared two photon absorption sensitivity of commercial detectors

NASA Astrophysics Data System (ADS)

Boiko, D. L.; Antonov, A. V.; Kuritsyn, D. I.; Yablonskiy, A. N.; Sergeev, S. M.; Orlova, E. E.; Vaks, V. V.

2017-10-01

We report on broad-band two-photon absorption (TPA) in several commercially available MIR inter-band bulk semiconductor photodetectors with the spectral cutoff in the range of 4.5-6 μm. The highest TPA responsivity of 2 × 10-5 A.mm2/W2 is measured for a nitrogen-cooled InSb photovoltaic detector. Its performance as a two-photon detector is validated by measuring the second-order interferometric autocorrelation function of a multimode quantum cascade laser emitting at the wavelength of 8 μm.

FURTHER CONSTRAINTS ON THE OPTICAL TRANSMISSION SPECTRUM OF HAT-P-1b

DOE Office of Scientific and Technical Information (OSTI.GOV)

Montalto, M.; Santos, N. C.; Martins, J. H. C.

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo. Our measurements imply an average planet to star radius ratio equal to R{sub p}/R{sub *} = (0.1159 ± 0.0005). This result is consistent with the value obtained from recent near-infrared measurements of this object, but differs from previously reported optical measurements, being lower by around 4.4 exoplanet scale heights. Analyzing the data over five different spectral bins of ∼600 Åmore » wide, we observed a single peaked spectrum (3.7 σ level) with a blue cutoff corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in-between 6180 and 7400 Å. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.« less

Enhanced photothermal lens using a photonic crystal surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Yunfei; Liu, Longju; Zhao, Xiangwei

2016-08-15

A photonic crystal (PC)-enhanced photothermal lens (PTL) is demonstrated for the detection of optically thin light absorption materials. The PC-enhanced PTL system is based on a pump-probe scheme consisting of a PC surface, pump laser beam, and probe laser beam. Heated by the pump beam, light absorption materials on the PC surface generate the PTL and cause a substantial change to the guided-mode resonance supported by the PC structure. The change of the PC resonance is detected using the probe laser beam by measuring its reflectivity from the PC surface. When applied to analyze dye molecules deposited on the PCmore » substrate, the developed system is capable of enhancing the PTL signal by 10-fold and reducing the lowest distinguishable concentration by 8-fold, in comparison to measuring without utilizing the PC resonance. The PC-enhanced PTL was also used to detect gold nanoparticles on the PC surface and exhibited a 20-fold improvement of the lowest distinguishable concentration. The PC-enhanced PTL technology offers a potential tool to obtain the absorption signatures of thin films in a broad spectral range with high sensitivity and inexpensive instrumentation. As a result, this technology will enable a broad range of applications of photothermal spectroscopy in chemical analysis and biomolecule sensing.« less

Further Constraints on the Optical Transmission Spectrum of HAT-P-1b

NASA Astrophysics Data System (ADS)

Montalto, M.; Iro, N.; Santos, N. C.; Desidera, S.; Martins, J. H. C.; Figueira, P.; Alonso, R.

2015-09-01

We report on novel observations of HAT-P-1 aimed at constraining the optical transmission spectrum of the atmosphere of its transiting hot-Jupiter exoplanet. Ground-based differential spectrophotometry was performed over two transit windows using the DOLORES spectrograph at the Telescopio Nazionale Galileo. Our measurements imply an average planet to star radius ratio equal to Rp/R* = (0.1159 ± 0.0005). This result is consistent with the value obtained from recent near-infrared measurements of this object, but differs from previously reported optical measurements, being lower by around 4.4 exoplanet scale heights. Analyzing the data over five different spectral bins of ∼600 Å wide, we observed a single peaked spectrum (3.7 σ level) with a blue cutoff corresponding to the blue edge of the broad absorption wing of sodium and an increased absorption in the region in-between 6180 and 7400 Å. We also infer that the width of the broad absorption wings due to alkali metals is likely narrower than the one implied by solar abundance clear atmospheric models. We interpret the result as evidence that HAT-P-1b has a partially clear atmosphere at optical wavelengths with a more modest contribution from an optical absorber than previously reported.

Models of filter-based particle light absorption measurements

NASA Astrophysics Data System (ADS)

Hamasha, Khadeejeh M.

Light absorption by aerosol is very important in the visible, near UN, and near I.R region of the electromagnetic spectrum. Aerosol particles in the atmosphere have a great influence on the flux of solar energy, and also impact health in a negative sense when they are breathed into lungs. Aerosol absorption measurements are usually performed by filter-based methods that are derived from the change in light transmission through a filter where particles have been deposited. These methods suffer from interference between light-absorbing and light-scattering aerosol components. The Aethalometer is the most commonly used filter-based instrument for aerosol light absorption measurement. This dissertation describes new understanding of aerosol light absorption obtained by the filter method. The theory uses a multiple scattering model for the combination of filter and particle optics. The theory is evaluated using Aethalometer data from laboratory and ambient measurements in comparison with photoacoustic measurements of aerosol light absorption. Two models were developed to calculate aerosol light absorption coefficients from the Aethalometer data, and were compared to the in-situ aerosol light absorption coefficients. The first is an approximate model and the second is a "full" model. In the approximate model two extreme cases of aerosol optics were used to develop a model-based calibration scheme for the 7-wavelength Aethalometer. These cases include those of very strong scattering aerosols (Ammonium sulfate sample) and very absorbing aerosols (kerosene soot sample). The exponential behavior of light absorption in the strong multiple scattering limit is shown to be the square root of the total absorption optical depth rather than linear with optical depth as is commonly assumed with Beer's law. 2-stream radiative transfer theory was used to develop the full model to calculate the aerosol light absorption coefficients from the Aethalometer data. This comprehensive model allows for studying very general cases of particles of various sizes embedded on arbitrary filter media. Application of this model to the Reno Aerosol Optics Study (Laboratory data) shows that the aerosol light absorption coefficients are about half of the Aethalometer attenuation coefficients, and there is a reasonable agreement between the model calculated absorption coefficients at 521 nm and the measured photoacoustic absorption coefficients at 532 nm. For ambient data obtained during the Las Vegas study, it shows that the model absorption coefficients at 521 nm are larger than the photoacoustic coefficients at 532 nm. Use of the 2-stream model shows that particle penetration depth into the filter has a strong influence on the interpretation of filter-based aerosol light absorption measurements. This is likely explanation for the difference found between model results for filter-based aerosol light absorption and those from photoacoustic measurements for ambient and laboratory aerosol.

Measuring the Impact of AGN Outflows via Intensive UV and X-ray Monitoring Campaigns

NASA Astrophysics Data System (ADS)

Kriss, Gerard

2015-08-01

Observations of AGN outflows have progressed from the era of single-object surveys to intensive monitoring campaigns spanning weeks to months. The combination of multiple observations, improved temporal coverage, multi-wavelength monitoring in both the X-ray and UV bands, and the baseline of prior historical observations has enabled determinations of the locations, mass flux, and kinetic luminosities of the outflowing absorbing gas in several AGN, notably Mrk 509, NGC 5548, Mrk 335, and NGC 985. Another intensive campaign is planned for 2015-2016 on NGC 7469. In all cases, the mass flux and kinetic energy is dominated by the higher-ionization X-ray absorbing gas. But the higher-resolution UV observations give a kinematically resolved picture of the overall outflow. In most cases, the outflowing gas is located at parsec to kpc scales, with insufficient kinetic luminosity to have an evolutionary impact on the host galaxy. Typically, the kinetic luminosity is less than a percent of the Eddington luminosity. In some cases, transient, broad UV absorption troughs have appeared (e.g., Mrk 335 and NGC 5548), with variability timescales suggesting locations near the broad-line region of the AGN. Yet these higher-velocity outflows also have low-impact kinetic luminosities. In the best-studied case of NGC 5548, the strength of the broad UV absorption lines varies with the degree of soft X-ray obscuration first revealed by XMM-Newton spectra. The lower-ionization, narrow associated absorption lines in the UV spectrum of NGC 5548 that appeared concurrently with the soft X-ray obscuration vary in response to the changing UV flux on a daily basis. The intensive monitoring allows us to fit time-dependent photoionization models to the UV-absorbing gas, allowing precise determinations of the locations, mass flux, and kinetic luminosities of the absorbers.

Broad band nonlinear optical absorption measurements of the laser dye IR26 using white light continuum Z-scan

NASA Astrophysics Data System (ADS)

Dey, Soumyodeep; Bongu, Sudhakara Reddy; Bisht, Prem Ballabh

2017-03-01

We study the nonlinear optical response of a standard dye IR26 using the Z-scan technique, but with the white light continuum. The continuum source of wavelength from 450 nm to 1650 nm has been generated from the photonic crystal fiber on pumping with 772 nm of Ti:Sapphire oscillator. The use of broadband incident pulse enables us to probe saturable absorption (SA) and reverse saturable absorption (RSA) over the large spectral range with a single Z-scan measurement. The system shows SA in the resonant region while it turns to RSA in the non-resonant regions. The low saturation intensity of the dye can be explained based on the simultaneous excitation from ground states to various higher energy levels with the help of composite energy level diagram. The cumulative effects of excited state absorption and thermal induced nonlinear optical effects are responsible for the observed RSA.

Hydrothermal growth of TiO2 nanowire membranes sensitized with CdS quantum dots for the enhancement of photocatalytic performance

PubMed Central

2014-01-01

In this paper, TiO2 nanowires (NWs) on Ti foils were prepared using a simple hydrothermal approach and annealing treatment. CdS quantum dots (QDs) were assembled onto the crystallized TiO2 NWs by sequential chemical bath deposition. Ultraviolet-visible absorption spectra showed that CdS adds bands in the visible to the TiO2 absorption and exhibited a broad absorption band in the visible region, which extended the scope of absorption spectrum and helped improve the photocatalytic degradation efficiency. The results of photocatalytic experiment revealed that CdS-TiO2 NWs possessed higher photocatalytic activities toward methyl orange than pure TiO2 nanowires. The degradation efficiency of 96.32% after ten cycles indicated that the as-prepared CdS-TiO2 composite exhibited excellent long-time recyclable ability and can be reused for the degradation of contaminants. PMID:24936164

UV absorption spectrum of allene radical cations in solid argon

NASA Astrophysics Data System (ADS)

Chin, Chih-Hao; Lin, Meng-Yeh; Huang, Tzu-Ping; Wu, Yu-Jong

2018-05-01

Electron bombardment during deposition of an Ar matrix containing a small proportion of allene generated allene cations. Further irradiation of the matrix sample at 385 nm destroyed the allene cations and formed propyne cations in solid Ar. Both cations were identified according to previously reported IR absorption bands. Using a similar technique, we recorded the ultraviolet absorption spectrum of allene cations in solid Ar. The vibrationally resolved progression recorded in the range of 266-237 nm with intervals of about 800 cm-1 was assigned to the A2E ← X2E transition of allene cations, and the broad continuum absorption recorded in the region of 229-214 nm was assigned to their B2A1 ← X2E transition. These assignments were made based on the observed photolytic behavior of the progressions and the vertical excitation energies and oscillator strengths calculated using time-dependent density functional theory.

Accurate predictions of iron redox state in silicate glasses: A multivariate approach using X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyar, M. Darby; McCanta, Molly; Breves, Elly

2016-03-01

Pre-edge features in the K absorption edge of X-ray absorption spectra are commonly used to predict Fe3+ valence state in silicate glasses. However, this study shows that using the entire spectral region from the pre-edge into the extended X-ray absorption fine-structure region provides more accurate results when combined with multivariate analysis techniques. The least absolute shrinkage and selection operator (lasso) regression technique yields %Fe3+ values that are accurate to ±3.6% absolute when the full spectral region is employed. This method can be used across a broad range of glass compositions, is easily automated, and is demonstrated to yield accurate resultsmore » from different synchrotrons. It will enable future studies involving X-ray mapping of redox gradients on standard thin sections at 1 × 1 μm pixel sizes.« less

Accurate predictions of iron redox state in silicate glasses: A multivariate approach using X-ray absorption spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyar, M. Darby; McCanta, Molly; Breves, Elly

2016-03-01

Pre-edge features in the K absorption edge of X-ray absorption spectra are commonly used to predict Fe 3+ valence state in silicate glasses. However, this study shows that using the entire spectral region from the pre-edge into the extended X-ray absorption fine-structure region provides more accurate results when combined with multivariate analysis techniques. The least absolute shrinkage and selection operator (lasso) regression technique yields %Fe 3+ values that are accurate to ±3.6% absolute when the full spectral region is employed. This method can be used across a broad range of glass compositions, is easily automated, and is demonstrated to yieldmore » accurate results from different synchrotrons. It will enable future studies involving X-ray mapping of redox gradients on standard thin sections at 1 × 1 μm pixel sizes.« less

White-Light Emission from Layered Halide Perovskites.

PubMed

Smith, Matthew D; Karunadasa, Hemamala I

2018-03-20

With nearly 20% of global electricity consumed by lighting, more efficient illumination sources can enable massive energy savings. However, effectively creating the high-quality white light required for indoor illumination remains a challenge. To accurately represent color, the illumination source must provide photons with all the energies visible to our eye. Such a broad emission is difficult to achieve from a single material. In commercial white-light sources, one or more light-emitting diodes, coated by one or more phosphors, yield a combined emission that appears white. However, combining emitters leads to changes in the emission color over time due to the unequal degradation rates of the emitters and efficiency losses due to overlapping absorption and emission energies of the different components. A single material that emits broadband white light (a continuous emission spanning 400-700 nm) would obviate these problems. In 2014, we described broadband white-light emission upon near-UV excitation from three new layered perovskites. To date, nine white-light-emitting perovskites have been reported by us and others, making this a burgeoning field of study. This Account outlines our work on understanding how a bulk material, with no obvious emissive sites, can emit every color of the visible spectrum. Although the initial discoveries were fortuitous, our understanding of the emission mechanism and identification of structural parameters that correlate with the broad emission have now positioned us to design white-light emitters. Layered hybrid halide perovskites feature anionic layers of corner-sharing metal-halide octahedra partitioned by organic cations. The narrow, room-temperature photoluminescence of lead-halide perovskites has been studied for several decades, and attributed to the radiative recombination of free excitons (excited electron-hole pairs). We proposed that the broad white emission we observed primarily stems from exciton self-trapping. Here, the exciton couples strongly to the lattice, creating transient elastic lattice distortions that can be viewed as "excited-state defects". These deformations stabilize the exciton affording a broad emission with a large Stokes shift. Although material defects very likely contribute to the emission width, our mechanistic studies suggest that the emission mostly arises from the bulk material. Ultrafast spectroscopic measurements support self-trapping, with new, transient, electronic states appearing upon photoexcitation. Importantly, the broad emission appears common to layered Pb-Br and Pb-Cl perovskites, albeit with a strong temperature dependence. Although the emission is attributed to light-induced defects, it still reflects changes in the crystal structure. We find that greater out-of-plane octahedral tilting increases the propensity for the broad emission, enabling synthetic control over the broad emission. Many of these perovskites have color rendering abilities that exceed commercial requirements and mixing halides affords both "warm" and "cold" white light. The most efficient white-light-emitting perovskite has a quantum efficiency of 9%. Improving this value will make these phosphors attractive for solid-state lighting, particularly as large-area coatings that can be deposited inexpensively. The emission mechanism can also be extended to other low-dimensional systems. We hope this Account aids in expanding the phase space of white-light emitters and controlling their exciton dynamics by the synthetic, spectroscopic, theoretical, and engineering communities.

Polycyclic aromatic hydrocarbon ions and the diffuse interstellar bands

NASA Technical Reports Server (NTRS)

Salama, F.; Allamandola, L. J.

1995-01-01

Neutral naphthalene (C10H8), phenanthrene (C14H10), and pyrene (C16H10) absorb strongly in the ultraviolet and may contribute to the extinction curve. High abundances are required to produce detectable structures. The cations of these Polycyclic Aromatic Hydrocarbons (PAHs) absorb in the visible. C10H8(+) has 12 discrete absorption bands which fall between 6800 and 5000 A. The strongest band at 6741 A falls close to the weak 6742 A diffuse interstellar band (DIB). Five other weaker bands also match DIBs. The possibility that C10H8(+) is responsible for some of the DIBs can be tested by searching for new DIBS at 6520, 6151, and 5965 A, other moderately strong naphthalene cation band positions. If C10H8(+) is indeed responsible for the 6742 A feature, it accounts for 0.3% of the cosmic carbon. The spectrum of C16H10(+) is dominated by a strong band at 4435 A in an Ar matrix and 4395 A in a Ne matrix, a position which falls very close to the strongest DIB, that at 4430 A. If C16H10(+), or a closely related pyrene-like ion is indeed responsible for the 4430 A feature, it accounts for 0.2% of the cosmic carbon. We also report an intense, very broad UV-to-visible continuum which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR.

Neutral and ionized polycyclic aromatic hydrocarbons, diffuse interstellar bands and the ultraviolet extinction curve

NASA Technical Reports Server (NTRS)

Salama, Farid; Allamandola, Louis John

1993-01-01

Neutral naphthalene C10H8, phenanthrene C14H10 and pyrene C16H10 absorb strongly in the ultraviolet region and may contribute to the extinction curve. High abundances are required to produce detectable structures. The cations of these polycyclic aromatic hydrocarbons (PAHs) absorb in the visible C10H8(+) has 13 discrete absorption bands which fall between 6800 and 4500 A. The strongest band at 6741 A falls close to the weak 6742 A diffuse interstellar band (DIB). Five other weaker bands also match DIBs. The possibility that C10H8(+) is responsible for some of the DIBs can be tested by searching for new DIBs at 6520 and 6151 A, other strong naphthalene cation band positions. If C10H8(+) is indeed responsible for the 6742 A feature, it accounts for 0.3% of the cosmic carbon. The spectrum of C16H10(+) is dominated by a strong band at 4435 A in an Ar matrix and 4395 A in Ne, wavelengths which fall very close to the strongest DIB at 4430 A. If C16H10(+) or a closely related pyrene-like ion, is indeed responsible for the 4430 A feature, it accounts for 0.2% of the cosmic carbon. An intense, very broad UV-to-visible continuum is reported which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR radiation.

Assessment of the actual light dose in photodynamic therapy.

PubMed

Schaberle, Fabio A

2018-06-09

Photodynamic therapy (PDT) initiates with the absorption of light, which depends on the spectral overlap between the light source emission and the photosensitizer absorption, resulting in the number of photons absorbed, the key parameter starting PDT processes. Most papers report light doses regardless if the light is only partially absorbed or shifted relatively to the absorption peak, misleading the actual light dose value and not allowing quantitative comparisons between photosensitizers and light sources. In this manuscript a method is presented to calculate the actual light dose delivered by any light source for a given photosensitizer. This method allows comparing light doses delivered for any combination of light source (broad or narrow band or daylight) and photosensitizer. Copyright © 2018. Published by Elsevier B.V.

Quantum state-resolved probing of strong-field-ionized xenon atoms using femtosecond high-order harmonic transient absorption spectroscopy.

PubMed

Loh, Zhi-Heng; Khalil, Munira; Correa, Raoul E; Santra, Robin; Buth, Christian; Leone, Stephen R

2007-04-06

Femtosecond high-order harmonic transient absorption spectroscopy is used to resolve the complete |j,m quantum state distribution of Xe+ produced by optical strong-field ionization of Xe atoms at 800 nm. Probing at the Xe N4/5 edge yields a population distribution rhoj,|m| of rho3/2,1/2ratiorho1/2,1/2ratiorho3/2,3/2=75+/-6 :12+/-3 :13+/-6%. The result is compared to a tunnel ionization calculation with the inclusion of spin-orbit coupling, revealing nonadiabatic ionization behavior. The sub-50-fs time resolution paves the way for tabletop extreme ultraviolet absorption probing of ultrafast dynamics.

Laser damage comparisons of broad-bandwidth, high-reflection optical coatings containing TiO 2, Nb 2O 5, or Ta 2O 5 high-index layers

DOE PAGES

Field, Ella Suzanne; Bellum, John Curtis; Kletecka, Damon E.

2016-09-21

Broad bandwidth coatings allow angle of incidence flexibility and accommodate spectral shifts due to aging and water absorption. Higher refractive index materials in optical coatings, such as TiO 2, Nb 2O 5, and Ta 2O 5, can be used to achieve broader bandwidths compared to coatings that contain HfO 2 high index layers. We have identified the deposition settings that lead to the highest index, lowest absorption layers of TiO 2, Nb 2O 5, and Ta 2O 5, via e-beam evaporation using ion-assisted deposition. We paired these high index materials with SiO 2 as the low index material to createmore » broad bandwidth high reflection coatings centered at 1054 nm for 45 deg angle of incidence and P polarization. Furthermore, high reflection bandwidths as large as 231 nm were realized. Laser damage tests of these coatings using the ISO 11254 and NIF-MEL protocols are presented, which revealed that the Ta 2O 5/SiO 2 coating exhibits the highest resistance to laser damage, at the expense of lower bandwidth compared to the TiO 2/SiO 2 and Nb 2O 5/SiO 2 coatings.« less

Energy-Cascaded Upconversion in an Organic Dye-Sensitized Core/Shell Fluoride Nanocrystal.

PubMed

Chen, Guanying; Damasco, Jossana; Qiu, Hailong; Shao, Wei; Ohulchanskyy, Tymish Y; Valiev, Rashid R; Wu, Xiang; Han, Gang; Wang, Yan; Yang, Chunhui; Ågren, Hans; Prasad, Paras N

2015-11-11

Lanthanide-doped upconversion nanoparticles hold promises for bioimaging, solar cells, and volumetric displays. However, their emission brightness and excitation wavelength range are limited by the weak and narrowband absorption of lanthanide ions. Here, we introduce a concept of multistep cascade energy transfer, from broadly infrared-harvesting organic dyes to sensitizer ions in the shell of an epitaxially designed core/shell inorganic nanostructure, with a sequential nonradiative energy transfer to upconverting ion pairs in the core. We show that this concept, when implemented in a core-shell architecture with suppressed surface-related luminescence quenching, yields multiphoton (three-, four-, and five-photon) upconversion quantum efficiency as high as 19% (upconversion energy conversion efficiency of 9.3%, upconversion quantum yield of 4.8%), which is about ~100 times higher than typically reported efficiency of upconversion at 800 nm in lanthanide-based nanostructures, along with a broad spectral range (over 150 nm) of infrared excitation and a large absorption cross-section of 1.47 × 10(-14) cm(2) per single nanoparticle. These features enable unprecedented three-photon upconversion (visible by naked eye as blue light) of an incoherent infrared light excitation with a power density comparable to that of solar irradiation at the Earth surface, having implications for broad applications of these organic-inorganic core/shell nanostructures with energy-cascaded upconversion.

Microporous Co@C Nanoparticles Prepared by Dealloying CoAl@C Precursors: Achieving Strong Wideband Microwave Absorption via Controlling Carbon Shell Thickness.

PubMed

Li, Da; Liao, Haoyan; Kikuchi, Hiroaki; Liu, Tong

2017-12-27

Excellent magnetic features make Co-based materials promising candidates as high-performance microwave absorbers. However, it is still a significant challenge for Co-based absorbers to possess high-intensity and broadband absorption simultaneously, owing to the lack of dielectric loss and impedance matching. Herein, microporous Co@C nanoparticles (NPs) with carbon shell thicknesses ranging from 1.8-4.9 nm have been successfully synthesized by dealloying CoAl@C precursors. All of the samples exhibit high microwave absorption performance. The microporous Co@C sample possessing a carbon shell of 1.8 nm exhibits the highest absorption intensity among these samples with a minimum reflection loss (RL) of -141.1 dB, whose absorption bandwidth for RL ≤ -10 dB is 7.3 GHz. As the thickness of the carbon shell increases, the absorption bandwidth of the NPs becomes wider. For the sample with the carbon shell thickness of 4.9 nm, the absorption bandwidth for RL ≤ -10 dB reaches a record high of 13.2 GHz. The outstanding microwave attenuation properties are attributed to the dielectric loss of the carbon shell, the magnetic loss of the Co core, and the cooperation of the core-shell structure and microporous morphology. The strong wideband microwave absorption of the carbon-coated microporous Co NPs highlights their potential applications in microwave absorbing systems.

Are non-linearity effects of absorption important for MAX-DOAS observations?

NASA Astrophysics Data System (ADS)

Pukite, Janis; Wang, Yang; Wagner, Thomas

2017-04-01

For scattered light observations the absorption optical depth depends non-linearly on the trace gas concentrations if their absorption is strong. This is the case because the Beer-Lambert law is generally not applicable for scattered light measurements due to many (i.e. more than one) light paths contributing to the measurement. While in many cases a linear approximation can be made, for scenarios with strong absorption non-linear effects cannot always be neglected. This is especially the case for observation geometries with spatially extended and diffuse light paths, especially in satellite limb geometry but also for nadir measurements as well. Fortunately the effects of non-linear effects can be quantified by means of expanding the radiative transfer equation in a Taylor series with respect to the trace gas absorption coefficients. Herewith if necessary (1) the higher order absorption structures can be described as separate fit parameters in the DOAS fit and (2) the algorithm constraints of retrievals of VCDs and profiles can be improved by considering higher order sensitivity parameters. In this study we investigate the contribution of the higher order absorption structures for MAX-DOAS observation geometry for different atmospheric and ground properties (cloud and aerosol effects, trace gas amount, albedo) and geometry (different Sun and viewing angles).

In Situ Infrared Spectroelectrochemistry.

DTIC Science & Technology

1986-07-30

The serious if the solvent is water , which staLe of the incident light, mechanism of absorption involves in- absorbs strongly throughout most of In...reflection uses a 3b shows spectra taken with the same thin-layer cell. where bulk electrolyses potentials as in 3a (this time using a of solution species...away from tion of both s-polarized and p-polar- ing neutral species and the highly con- the regions of strong water absorpt ion. ized light, and thought

Studies of Quasar Outflows

NASA Technical Reports Server (NTRS)

Arav, Nahum

2002-01-01

The main aim of this research program is to determine the ionization equilibrium and abundances in quasar outflows. Especially in the broad absorption line QSO PG 0946+301. We find that the outflow's metalicity is consistent with being solar, while the abundance ratio of phosphorus to other metals is at least ten times solar. These findings are based on diagnostics that are not sensitive to saturation and partial covering effects in the BALs (Broad Adsorption Lines), which considerably weakened previous claims for enhanced metalicity. Ample evidence for these effects is seen in the spectrum.

Noise abatement in a pine plantation

Treesearch

R. E. Leonard; L. P. Herrington

1971-01-01

Observations on sound propagation were made in two red pine plantations. Measurements were taken of attenuation of prerecorded frequencies at various distances from the sound source. Sound absorption was strongly dependent on frequencies. Peak absorption was at 500 Hz.

Surface waves in an incompressible fluid - Resonant instability due to velocity shear

NASA Technical Reports Server (NTRS)

Hollweg, Joseph V.; Yang, G.; Cadez, V. M.; Gakovic, B.

1990-01-01

The effects of velocity shear on the resonance absorption of incompressible MHD surface waves are studied. It is found that there are generally values of the velocity shear for which the surface wave decay rate becomes zero. In some cases, the resonance absorption goes to zero even for very small velocity shears. It is also found that the resonance absorption can be strongly enhanced at other values of the velocity shear, so the presence of flows may be generally important for determining the effects of resonance absorption, such as might occur in the interaction of p-modes with sunspots. Resonances leading to instability of the global surface mode can exist, and instability can occur for velocity shears significantly below the Kelvin-Helmholtz threshold. These instabilities may play a role in the development or turbulence in regions of strong velocity shear in the solar wind or the earth's magnetosphere.

Slow light enhanced gas sensing in photonic crystals

NASA Astrophysics Data System (ADS)

Kraeh, Christian; Martinez-Hurtado, J. L.; Popescu, Alexandru; Hedler, Harry; Finley, Jonathan J.

2018-02-01

Infrared spectroscopy allows for highly selective and highly sensitive detection of gas species and concentrations. Conventional gas spectrometers are generally large and unsuitable for on-chip applications. Long absorption path lengths are usually required and impose a challenge for miniaturization. In this work, a gas spectrometer is developed consisting of a microtube photonic crystal structure. This structure of millimetric form factors minimizes the required absorption path length due to slow light effects. The microtube photonic crystal allows for strong transmission in the mid-infrared and, due to its large void space fraction, a strong interaction between light and gas molecules. As a result, enhanced absorption of light increases the gas sensitivity of the device. Slow light enhanced gas absorption by a factor of 5.8 in is experimentally demonstrated at 5400 nm. We anticipate small form factor gas sensors on silicon to be a starting point for on-chip gas sensing architectures.

Optical evidence of strong coupling between valence-band holes and d -localized spins in Zn1-xMnxO

NASA Astrophysics Data System (ADS)

Sokolov, V. I.; Druzhinin, A. V.; Gruzdev, N. B.; Dejneka, A.; Churpita, O.; Hubicka, Z.; Jastrabik, L.; Trepakov, V.

2010-04-01

We report on optical-absorption study of Zn1-xMnxO (x=0-0.06) films on fused silica substrates taking special attention to the spectral range of the fundamental absorption edge (3.1-4 eV). Well-pronounced excitonic lines observed in the region 3.40-3.45 eV were found to shift to higher energies with increasing Mn concentration. The optical band-gap energy increases with x too, reliably evidencing strong coupling between oxygen holes and localized spins of manganese ions. In the 3.1-3.3 eV region the optical-absorption curve in the manganese-contained films was found to shift to lower energies with respect to that for undoped ZnO. The additional absorption observed in this range is interpreted as a result of splitting of a localized Zhang-Rice-type state into the band gap.

Growth and Spectral Assessment of Yb3+-Doped KBaGd(MoO4)3 Crystal: A Candidate for Ultrashort Pulse and Tunable Lasers

PubMed Central

Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Wang, Guofu

2013-01-01

In order to explore new more powerful ultrashort pulse laser and tunable laser for diode-pumping, this paper reports the growth and spectral assessment of Yb3+-doped KBaGd(MoO4)3 crystal. An Yb3+:KBaGd(MoO4)3 crystal with dimensions of 50×40×9 mm3 was grown by the TSSG method from the K2Mo2O7 flux. The investigated spectral properties indicated that Yb3+:KBaGd(MoO4)3 crystal exhibits broad absorption and emission bands, except the large emission and gain cross-sections. This feature of the broad absorption and emission bands is not only suitable for the diode pumping, but also for the production of ultrashort pulses and tunability. Therefore, Yb3+:KBaGd(MoO4)3 crystal can be regarded as a candidate for the ultrashort pulse and tunable lasers. PMID:23349892

Growth and spectral assessment of Yb(3+)-doped KBaGd(MoO4)3 crystal: a candidate for ultrashort pulse and tunable lasers.

PubMed

Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Wang, Guofu

2013-01-01

In order to explore new more powerful ultrashort pulse laser and tunable laser for diode-pumping, this paper reports the growth and spectral assessment of Yb(3+)-doped KBaGd(MoO(4))(3) crystal. An Yb(3+):KBaGd(MoO(4))(3) crystal with dimensions of 50×40×9 mm(3) was grown by the TSSG method from the K(2)Mo(2)O(7) flux. The investigated spectral properties indicated that Yb(3+):KBaGd(MoO(4))(3) crystal exhibits broad absorption and emission bands, except the large emission and gain cross-sections. This feature of the broad absorption and emission bands is not only suitable for the diode pumping, but also for the production of ultrashort pulses and tunability. Therefore, Yb(3+):KBaGd(MoO(4))(3) crystal can be regarded as a candidate for the ultrashort pulse and tunable lasers.

Direct Observations of Clouds on Brown Dwarfs: A Spitzer Study of Extreme Cases

NASA Astrophysics Data System (ADS)

Burgasser, Adam; Cruz, Kelle; Cushing, Michael; Kirkpatrick, J. Davy; Looper, Dagny; Lowrance, Patrick; Marley, Mark; Saumon, Didier

2008-03-01

Clouds play a fundamental role in the emergent spectral energy distributions and observed variability of very low mass stars and brown dwarfs, yet hey have only been studied indirectly thus far. Recent indications of a broad silicate grain absorption feature in the 8-11 micron spectra of mid-type L dwarfs, and evidence that the strength of this absorption varies according to broad-band near-infrared color, may finally allow the first direct studies of clouds and condensate grain properties in brown dwarf atmospheres. We propose to observe a sample of 18 ``extreme'' L dwarfs - objects with unusually blue and red near-infrared colors - with IRAC and IRS to study the 8-11 micron feature in detail (including grain size distributions and bulk compositions), and to constrain advanced condensate cloud atmosphere models currently in development. Our program provides a unique examination of the general processes of cloud formation by focusing on the relatively warm photospheres of late-type brown dwarfs.

X-Ray Continua of Broad Absorption Line Quasars

NASA Technical Reports Server (NTRS)

Mathur, S.

1999-01-01

The targets for this program, PG1416-129 and LBQS 2212-1759 were known to be Broad Absorption Line Quasars (BALQSOs). BALQSOs are highly absorbed in soft X-rays. Good high energy response of Rossi-XTE made them ideal targets for observation. We observed LBQS 2212-1759 with PCA. We have now analyzed the data and found that the source was not detected. Since our target was expected to be faint, reliable estimate of background was very important. With the release of new FTOOLS (version 4.1) we were able to do so. We also analyzed a well known bright object and verified our results with the published data. This gave us confidence in the non-detection of our target LBQS 2212-1759. We are currently investigating the implications of this non-detection. Due to some scheduling problems, our second target PG1416-129 was not observed in A01. It was observed on 06/26/98. This target was detected with RXTE. We are now working on the spectral analysis with XSPEC.

Photoluminescence properties of LiF bismuth silicate glass

NASA Astrophysics Data System (ADS)

Krishnan, M. Laya; Kumar, V. V. Ravi Kanth

2018-04-01

The sample (60-X) Bi2O3-30SiO2-XLiF where X=10, 15, 25 were prepared by conventional melt quenching method. X-ray diffraction pattern conformed the amorphous nature of the prepared sample and a broad peak at 2θ=30°. The Raman spectra confirmed that the Bi can exist both network former (BiO3 pyramidal) and network modifier (BiO6 octahedral)in the glass matrix. The samples showing broad absorption at 470nm is due to the presence of Bi2+ ions, because of increasing optical basicity the absorption edge of the sample is blue shifted. The photoluminescence spectra of the glass under 350nm excitation are showing two main peaks at 430nm and 630 nm due to Bi3+ and Bi2+ respectively and 25 LBS glass showing yellow, 15LBS showing near bluish white and 10LBS showing blue luminescence. The color purity and correlated color temperature are also calculated.

Highly ionized gas absorption in the disk and halo toward HD 167756 at 3.5 kilometers per second resolution

NASA Technical Reports Server (NTRS)

Savage, Blair D.; Sembach, Kenneth R.; Cardelli, Jason A.

1994-01-01

High-resolution spectra of interstellar Si IV, C IV, and N V absorption lines along the 4 kpc path to the inner Galaxy star HD 167756 at z = -0.85 kpc are presented. The spectra were obtained with the echelle mode of Goddard High Resolution Spectrograph (GHRS) aboard the Hubble Space Telescope (HST) and have signal-to-noise ratios ranging from 23 to 38. The high resolution of the measurements full width at half maximum (FWHM = 3.5 km/s) results in fully resolved line profiles for the highly ionized gas absorption. The measurements provide information on the column density per unit velocity, N(v), as a function of velocity for Si IV, C IV, and N V. The C IV and N V profiles extend from -70 to +70 km/s, while the Si IV profiles extend from -40 to +70 km/s. The integrated logarithmic column densities are long N(Si IV) = 13.09 +/- 0.02, log N(C IV) = 13.83 +/- 0.02, and log N(N V) = 13.56 +/- 0.03. The N V profile is broad, asymmetric, and featureless, while the Si IV profile contains narrow absorption components near V(sub LSR) = -19, 0, +20, and +52 km/s with Doppler spread parameters, b about = 10-12 km/s. The C IV profile contains both broad and narrow structure. The high ion feature near +52 km/s is also detected in the low-ionization lines of Ca II, O I, Si II, and Fe II. The other narrow Si IV and C IV components occur within several km/s of components seen in low-ionization species. The sight line contains at least two types of highly ionized gas. One type gives rise to a broad N V profile, and the other results in the more structured Si IV profile. The C IV profile contains contributions from both types of highly ionized gas. The broad but asymmetric N V profile is well represented by a large Galactic scale height gas which is participating in Galactic rotation and has a combination of thermal and turbulent broadening with b(sub tot) about = 42 km/s. The C IV to N V abundance ratio of 1.0 +/- 0.3 for the gas implies T about 1.6 x 10(exp 5) K or about 8 x 10(exp 5) K if the gas is in collisional ionization equilibrium and has a solar carbon to nitrogen abundance ratio. This absorption may be associated with cooling hot gas situated in Galactic shells and supershells along the sight line. The gas producing the narrow Si IV and C IV absorption components has line widths that are compatible with origins in conductive interfaces between the warm and hot interstellar medium. Kinematic flows associated with the photoionized edges of clouds might also produce Si IV and C IV lines with Doppler spread parameters similar to those observed, but the C IV to Si IV ratio in this gas is 3.5, which leads us to favor the conductive interface interpretation.

New method in muon-hadron absorption on Thx DUO2 nano material structure at 561 MHz quantum gyro-magnetic

NASA Astrophysics Data System (ADS)

Hardiyanto, M.; Ermawaty, I. R.

2018-01-01

We present an experimental of muan-hadron tunneling chain investigation with new methods of Thx DUO2 nano structure based on Josephson’s tunneling and Abrikosov-Balseiro-Russel (ABR) formulation with quantum quadrupole interacting with a strongly localized high gyro-magnetic optical field as encountered in high-resolution near-field optical microscopy for 1.2 nano meter lambda-function. The strong gradients of these localized gyro-magnetic fields suggest that higher-order multipolar interactions will affect the standard magnetic quadrupole transition rates in 1.8 x 103 currie/mm fuel energy in nuclear moderator pool and selection rules with quatum dot. For muan-hadron absorption in Josephson’s tunnelling quantum quadrupole in the strong confinement limit we calculated the inter band of gyro-magnetic quadrupole absorption rate and the associated selection rules. Founded that the magnetic quadrupole absorption rate is comparable with the absorption rate calculated in the gyro-magneticdipole approximation of ThxDUO2 nano material structure. This implies that near-field optical techniques can extend the range of spectroscopic measurements for 545 MHz at quantum gyro-magnetic field until 561 MHz deployment quantum field at B around 455-485 tesla beyond the standard dipole approximation. However, we also show that spatial resolution could be improved by the selective excitation of ABR formulation in quantum quadrupole transitions.

Unveiling the nucleus of NGC 7172

NASA Astrophysics Data System (ADS)

Smajić, S.; Fischer, S.; Zuther, J.; Eckart, A.

2012-08-01

Aims: We present the results of near-infrared (NIR) H + K European Southern Observatory SINFONI integral field spectroscopy (IFS) of the Seyfert 2 galaxy NGC 7172. We investigate the central 800 pc, concentrating on excitation conditions, morphology, and stellar content. NGC 7172 was selected from a sample of the ten nearest Seyfert 2 galaxies from the Veron-Cetty & Veron catalogue. All objects were chosen as test cases for adaptive optics (AO) assisted observations that allow a detailed study (at high spatial and spectral resolution) of the nuclear and host environments. NGC 7172 has a prominent dustlane crossing the central galaxy region from east to west, which makes it an ideal candidate to investigate the effect of obscuration by strong galactic extinction on (active) galaxies and their classification. Methods: The NIR is less influenced by dust extinction than optical light and is sensitive to the mass-dominating stellar populations. SINFONI integral field spectroscopy combines NIR imaging and spectroscopy and provides us with the opportunity to analyze several emission and absorption lines to investigate the stellar populations and ionization mechanisms over the 4″ × 4″ field of view (FOV). Results: We present emission and absorption line measurements in the central 800 pc of NGC 7172. The detection of [Si vi] and broad Paα and Brγ components are clear signs of an accreting super-massive black hole hiding behind the prominent dustlane at visible wavelengths. Hot temperatures of about 1300 K are indicative of a dusty torus in the nuclear region. Narrow components of Paα and Brγ enable us to make an extinction measurement. Our measures of the molecular hydrogen lines, hydrogen recombination lines, and [Fe ii] indicate that the excitation of these lines is caused by an active galactic nucleus. The central region of the galactic disk is predominantly inhabited by gas, dust, and an old K-M type giant stellar population. The gaseous, molecular, and stellar velocity maps show a related disturbed disk structure and similar velocities. Conclusions: We find evidence of nuclear activity located behind the prominent dustlane crossing the central region of the galaxy. The nucleus of NGC 7172, which is optically classified as a Seyfert 2 nucleus without any trace of broad emission lines, is a Seyfert 1 nucleus either surrounded by a molecular dust torus or hidden behind the strong galactic extinction. Our observation provides support for the unified model scheme. However, an evolutionary scenario cannot be ruled out by our observation. Based on the ESO-VLT STS-Cologne GTO proposal ID: 083.B-0620(A).

The absorption budget of fresh biomass burning aerosol from realistic laboratory fires

NASA Astrophysics Data System (ADS)

Wagner, N. L.; Adler, G. A.; Franchin, A.; Lamb, K.; Manfred, K.; Middlebrook, A. M.; Selimovic, V.; Schwarz, J. P.; Washenfelder, R. A.; Womack, C.; Yokelson, R. J.

2017-12-01

Wildfires are expected to increase globally due to climate change. The smoke from these wildfires has a highly uncertain radiative effect, largely due to the lack of detailed understanding of its optical properties. As part of the NOAA FIREX project, we have measured the optical properties of smoke primarily from laboratory burning of North American fuels at the Missoula Fire Sciences Laboratory. Here, we present a budget of the aerosol absorption from a portion of the laboratory fires. The total aerosol absorption was measured with photoacoustic spectrometers (PAS) at four wavelengths (405 nm, 532 nm, 660 nm, 870 nm) spanning the visible spectral region. The aerosol absorption is attributed to black carbon which absorbs broadly across the visible and ultraviolet (UV) spectral region and brown carbon (BrC) which absorbs in the blue and UV spectral regions. Then aerosol absorption measurements are compared with measurements of refractory black carbon (rBC) concentration by laser induced incandescence (SP2) and measurements of BrC concentration from a particle-into-liquid sampler coupled to a liquid absorption cell (BrC-PILS). Periodically, a thermodenuder was inserted upstream of all of the instruments to constrain the relationship between aerosol volatility and absorption. We synthesize these measurements to constrain the various contributors to total absorption including effects of lensing on rBC absorption, and of BrC that is not volatilized in the thermodenuder.

Distribution of phyllosilicates on Ceres

NASA Astrophysics Data System (ADS)

Ammannito, Eleonora; De Sanctis, Maria Cristina; Ciarniello, Mauro; Frigeri, Alessandro; Giacomo Carrozzo, Filippo; Combe, Jean Philippe; Ehlmann, Bethany; Marchi, Simone; McSween, Hap Y.; Raponi, Andrea; Castillo-Rogez, Julie C.; Toplis, Michael J.; Tosi, Federico; Longobardo, Andrea; Palomba, Ernesto; Pieters, Carle M.; Raymond, Carol A.; Schenk, Paul; Zambon, Francesca; Russell, Christopher T.

2016-04-01

Studies of the dwarf planet Ceres using ground-based and orbiting telescopes proposed a variety of possible surficial composition including water in clay minerals [1], ammoniated phyllosilicates [2], or a mixture of brucite, Mg2CO3 and iron-rich serpentine [3, 4]. But the lack of spectral data in the 2.5 to 2.9 μm interval has precluded definitive identifications. The Dawn spacecraft has been acquiring spectra of the surface of Ceres since January 2015 [5, 6, 7]. The average thermally corrected reflectance spectrum of Ceres shows that the 2.6-4.2μm region is characterized by a broad asymmetric feature, characteristic of H2O/OH bearing materials, with several distinct narrower absorption bands [8]. This spectrum is compatible with the presence on the surface of a mixture of ammoniated-phyllosilicates, Mg-phyllosilicates, carbonates, and dark materials [8]. A strong 2.7-μm absorption dominates the overall spectral properties, and it has been attributed to OH-stretching vibrations in phyllosilicates [9] while the weaker 3.05 μm absorption has been attributed to the presence of NH4+ in phyllosilicates [10]. The spectral parameters of the absorption features at 2.7 and 3.05 μm have been computed to study their position and intensity. The computed spectral position of both absorption features is remarkably homogeneous. The average values are 2.727±0.005 and 3.061±0.005 μm respectively. Since the position of both features is sensitive to the chemical composition of the phyllosilicates, we conclude that the composition of phyllosilicates does not significantly change across the mapped portion of Ceres' surface. The computed values are indicative of Mg-OH phases, like antigorite (Mg-serpentine) or saponite (Mg-smectite) [9]. The presence of Mg-, rather than Fe-serpentine on Ceres may be interpreted as an indication that alteration had been extensive, while the lack of geochemical variation indicates that this is true throughout the exposed upper layer with no significant compositional gradients. The computed spectral intensity of both absorption features shows some variability. For the 2.7 absorption, the average value is 0.251±0.006, while the range of variability is between 0.20 and 0.29. For the 3.05 absorption, the average value is 0.055±0.012, while the range of variability is between 0.03 and 0.09. Interestingly, the distributions of the intensities of the two bands broadly match. Among several possibilities, the most likely explanation for the variability in intensity is a changing abundance of phyllosilicates within the assemblage forming the surface of Ceres. In conclusion, while the chemical composition of the phyllosilicates is remarkably constant, their abundance is variable. The compositional homogeneity characterized by the pervasive presence of Mg- and NH4-bearing phyllosilicates indicates endogenous formation by a globally widespread and extensive alteration processes while the variations in the amount of phyllosilicate suggest the existence of a vertically stratified upper crust. References: [1] Lebofsky, L. et al. (1981) Icarus, 48, 453-459. [2] King T. et al. (1992) Science, 255, 1551-1553. [3] Rivkin A.S. et al. (2006) Icarus, 185, 563-567. [4] Milliken R.E. and Rivkin A.S. (2009) Nature Geosci., 2, 258-261. [5] Russell C.T. and Raymond C.A. (2011) Space Sci. Rev., 163, 3-23. [6] Russell C.T. et al. (2015) EPSC. [7] De Sanctis M.C. et al. (2011) Space Sci. Rev., 163, 329-369. [8] De Sanctis M.C. et al. (2015) Nature. [9] Bishop J.L. et al. (2008) ClayMiner., 43, 35-54. [10] Bishop J.L. et al. (2002) Planet. Space Sci., 50.

Line Identifications in the Far Ultraviolet Spectrum of the Eclipsing Binary System 31 Cygni

NASA Astrophysics Data System (ADS)

Hagen Bauer, Wendy; Bennett, P. D.

2011-05-01

The eclipsing binary system 31 Cygni (K4 Ib + B3 V) was observed at several phases with the Far Ultraviolet Spectrosocopic Explorer (FUSE) satellite. During total eclipse, a rich emission spectrum was observed, produced by scattering of hot star photons in the extended wind of the K supergiant. The system was observed during deep chromospheric eclipse, and 2.5 months after total eclipse ended. We present an atlas of line identifications in these spectra. During total eclipse, emission features from C II , C III, N I, N II, N III, O I, Si II, P II, P III, S II, S III, Ar I, Cr III, Fe II, Fe III, and Ni II were detected. The strongest emission features arise from N II. These lines appear strongly in absorption during chromospheric eclipse, and even 2.5 months after total eclipse, the absorption bottoms out on the underlying emission seen during total eclipse. The second strongest features in the emission spectrum arise from Fe III. Any chromospheric Fe III absorption is buried within strong chromospheric absorption from other species, mainly Fe II. The emission profiles of most of the doubly-ionized species are red-shifted relative to the systemic velocity, with asymmetric profiles with a steeper long-wavelength edge. Emission profiles from singly-ionized species tend to be more symmetric and centered near the systemic velocity. In deep chromospheric eclipse, absorption features are seen from neutral and singly-ionized species, arising from lower levels up to 3 eV. Many strong chromospheric features are doubled in the observation obtained during egress from eclipse. The 31 Cygni spectrum taken 2.5 months after total eclipse ended ws compared to single-star B spectra from the FUSE archives. There was still some additional chromospheric absorption from strong low-excitation Fe II, O I and Ar I.

Simulating the escaping atmospheres of hot gas planets in the solar neighborhood

NASA Astrophysics Data System (ADS)

Salz, M.; Czesla, S.; Schneider, P. C.; Schmitt, J. H. M. M.

2016-02-01

Absorption of high-energy radiation in planetary thermospheres is generally believed to lead to the formation of planetary winds. The resulting mass-loss rates can affect the evolution, particularly of small gas planets. We present 1D, spherically symmetric hydrodynamic simulations of the escaping atmospheres of 18 hot gas planets in the solar neighborhood. Our sample only includes strongly irradiated planets, whose expanded atmospheres may be detectable via transit spectroscopy using current instrumentation. The simulations were performed with the PLUTO-CLOUDY interface, which couples a detailed photoionization and plasma simulation code with a general MHD code. We study the thermospheric escape and derive improved estimates for the planetary mass-loss rates. Our simulations reproduce the temperature-pressure profile measured via sodium D absorption in HD 189733 b, but show still unexplained differences in the case of HD 209458 b. In contrast to general assumptions, we find that the gravitationally more tightly bound thermospheres of massive and compact planets, such as HAT-P-2 b are hydrodynamically stable. Compact planets dispose of the radiative energy input through hydrogen Lyα and free-free emission. Radiative cooling is also important in HD 189733 b, but it decreases toward smaller planets like GJ 436 b. Computing the planetary Lyα absorption and emission signals from the simulations, we find that the strong and cool winds of smaller planets mainly cause strong Lyα absorption but little emission. Compact and massive planets with hot, stable thermospheres cause small absorption signals but are strong Lyα emitters, possibly detectable with the current instrumentation. The absorption and emission signals provide a possible distinction between these two classes of thermospheres in hot gas planets. According to our results, WASP-80 and GJ 3470 are currently the most promising targets for observational follow-up aimed at detecting atmospheric Lyα absorption signals. Simulated atmospheres are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A75

GAMMA–GAMMA ABSORPTION IN THE BROAD LINE REGION RADIATION FIELDS OF GAMMA-RAY BLAZARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Böttcher, Markus; Els, Paul, E-mail: Markus.Bottcher@nwu.ac.za

2016-04-20

The expected level of γγ absorption in the Broad Line Region (BLR) radiation field of γ -ray loud Flat Spectrum Radio Quasars (FSRQs) is evaluated as a function of the location of the γ -ray emission region. This is done self-consistently with parameters inferred from the shape of the spectral energy distribution (SED) in a single-zone leptonic EC-BLR model scenario. We take into account all geometrical effects both in the calculation of the γγ opacity and the normalization of the BLR radiation energy density. As specific examples, we study the FSRQs 3C279 and PKS 1510-089, keeping the BLR radiation energymore » density at the location of the emission region fixed at the values inferred from the SED. We confirm previous findings that the optical depth due to γγ absorption in the BLR radiation field exceeds unity for both 3C279 and PKS 1510-089 for locations of the γ -ray emission region inside the inner boundary of the BLR. It decreases monotonically, with distance from the central engine and drops below unity for locations within the BLR. For locations outside the BLR, the BLR radiation energy density required for the production of GeV γ -rays rapidly increases beyond observational constraints, thus making the EC-BLR mechanism implausible. Therefore, in order to avoid significant γγ absorption by the BLR radiation field, the γ -ray emission region must therefore be located near the outer boundary of the BLR.« less

Phononic glass: a robust acoustic-absorption material.

PubMed

Jiang, Heng; Wang, Yuren

2012-08-01

In order to achieve strong wide band acoustic absorption under high hydrostatic pressure, an interpenetrating network structure is introduced into the locally resonant phononic crystal to fabricate a type of phononic composite material called "phononic glass." Underwater acoustic absorption coefficient measurements show that the material owns high underwater sound absorption coefficients over 0.9 in 12-30 kHz. Moreover, the quasi-static compressive behavior shows that the phononic glass has a compressive strength over 5 MPa which is crucial for underwater applications.

Ground-based Characterization of Hayabusa2 Mission Target Asteroid 162173 Ryugu

NASA Astrophysics Data System (ADS)

Le Corre, Lucille; Reddy, Vishnu; Sanchez, Juan A.; Takir, Driss; Cloutis, Edward; Thirouin, Audrey; Becker, Kris J.; Li, Jian-Yang; Sugita, Seiji; Tatsumi, Eri

2017-10-01

In preparation for the arrival of the Japanese Space Agency’s (JAXA) Hayabusa2 sample return mission to near-Earth asteroid (NEA) (162173) Ryugu, we took the opportunity to characterize the target with a ground-based telescope. We observed Ryugu using the SpeX instrument in Prism mode on NASA Infrared Telescope Facility on Mauna Kea, Hawaii, on July, 12 2016 when the asteroid was 18.87 visual magnitude, at a phase angle of 13.3°. The NIR spectra were used to constrain Ryugu’s surface composition, meteorite analogs and spectral affinity to other asteroids. We also modeled its photometric properties using archival data. Using the Lommel-Seeliger model we computed the predicted flux for Ryugu at a wide range of viewing geometries as well as albedo quantities such as geometric albedo, phase integral, and spherical Bond albedo. Our computed albedo quantities are consistent with results from Masateru et al. (2014). Our spectrum of Ryugu has a broad absorption band at 1 µm, a slope change at 1.6 µm, and a second broad absorption band near 2.2 µm, but no well-defined absorption features over the 0.8-2.5 µm range. The two broad absorption features, if confirmed, are consistent with CO and CV chondrites. The shape of Ryugu’s spectrum matches very well those of NEA (85275) 1994 LY and Mars-crossing asteroid (316720) 1998 BE7, suggesting that their surface regolith have similar composition. We also compared the spectrum of Ryugu with that of main belt asteroid (302) Clarissa, the largest asteroid in the Clarissa asteroid family, suggested as the source of Ryugu by Campins et al. (2013). We found that the spectrum of Clarissa shows significant differences with our NIR spectrum of Ryugu. Our analysis shows Ryugu’s spectrum best matches two CM2 carbonaceous chondrites, Mighei and ALH83100. We expect the surface regolith of Ryugu to be altered by a range of factors including temperature, contamination by exogenic material, and space weathering, posing challenges to link spacecraft and ground-based data, and sample site selection.

The Swift Burst Alert Telescope Detected Seyfert 1 Galaxies: X-Ray Broadband Properties and Warm Absorbers

NASA Technical Reports Server (NTRS)

Winter, Lisa M.; Veilleux, Sylvain; McKernan, Barry; Kallman, T.

2012-01-01

We present results from an analysis of the broadband, 0.3-195 keV, X-ray spectra of 48 Seyfert 1-1.5 sources detected in the very hard X-rays with the Swift Burst Alert Telescope (BAT). This sample is selected in an all-sky survey conducted in the 14-195 keV band. Therefore, our sources are largely unbiased toward both obscuration and host galaxy properties. Our detailed and uniform model fits to Suzaku/BAT and XMM-Newton/BAT spectra include the neutral absorption, direct power-law, reflected emission, soft excess, warm absorption, and narrow Fe I K[alpha] emission properties for the entire sample. We significantly detect O VII and O VIII edges in 52% of our sample. The strength of these detections is strongly correlated with the neutral column density measured in the spectrum. Among the strongest detections, X-ray grating and UV observations, where available, indicate outflowing material. The ionized column densities of sources with O VII and O VIII detections are clustered in a narrow range with Nwarm [approx] 1021 cm-2, while sources without strong detections have column densities of ionized gas an order of magnitude lower. Therefore, we note that sources without strong detections likely have warm ionized outflows present but at low column densities that are not easily probed with current X-ray observations. Sources with strong complex absorption have a strong soft excess, which may or may not be due to difficulties in modeling the complex spectra of these sources. Still, the detection of a flat [Gamma] [approx] 1 and a strong soft excess may allow us to infer the presence of strong absorption in low signal-to-noise active galactic nucleus spectra. Additionally, we include a useful correction from the Swift BAT luminosity to bolometric luminosity, based on a comparison of our spectral fitting results with published spectral energy distribution fits from 33 of our sources.

Optical properties of La{sub 2}CuO{sub 4} and La{sub 2-x}Ca{sub x}CuO{sub 4} crystallites in UV-vis-NIR region synthesized by sol-gel process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li Yifeng; Huang Jianfeng, E-mail: hjfnpu@163.com; Cao Liyun

2012-02-15

La{sub 2}CuO{sub 4} and La{sub 2-x}Ca{sub x}CuO{sub 4} crystallites were prepared via a simple sol-gel process. The as-prepared La{sub 2}CuO{sub 4} and La{sub 2} {sub -x}Ca{sub x}CuO{sub 4} crystallites were characterized by X-ray diffraction, transmission electron microscope and UV-vis-NIR spectra. Results show that the grain size of La{sub 2}CuO{sub 4} crystallites increases with the increase of heat treatment temperature from 600 Degree-Sign C to 800 Degree-Sign C. Optical properties show that La{sub 2}CuO{sub 4} crystallites have broad absorption both in the UV-vis region and in the NIR region. The band gap of the as-prepared crystallites decreases from 1.367 eV tomore » 1.284 eV with the increase of calcination temperature from 600 Degree-Sign C to 800 Degree-Sign C. In the series of La{sub 2-x}Ca{sub x}CuO{sub 4} compounds (x = 0.05, 0.08, 0.10, 0.12, 0.15 and 0.20), all of the samples exhibit an orthogonal crystal structure and the solubility limit of Ca{sup 2+} in La{sub 2}CuO{sub 4} is within the range of x = 0.12-0.15. In the whole UV-vis-NIR region, La{sub 2-x}Ca{sub x}CuO{sub 4} crystallites exhibit a broad absorption and the corresponding band gap first increases and then decreases with increasing of Ca{sup 2+} content. - Highlights: Black-Right-Pointing-Pointer The optical band gap can be tuned by adjusting the grain size and Ca{sup 2+} content. Black-Right-Pointing-Pointer La{sub 2}CuO{sub 4} crystallites exhibit a broad absorption band both in the UV-vis region and in the NIR region. Black-Right-Pointing-Pointer The band gap increases from 1.284 eV to 1.319 eV with the decrease of heat treatment temperature. Black-Right-Pointing-Pointer In the whole UV-vis-NIR region, the La{sub 2-x}Ca{sub x}CuO{sub 4} crystallites displayed a broad absorption. Black-Right-Pointing-Pointer The band gap of La{sub 2-x}Ca{sub x}CuO{sub 4} increases linearly with doping level when 0 {<=} x {<=} 0.12.« less

X-ray absorption spectroscopy: EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alp, E.E.; Mini, S.M.; Ramanathan, M.

1990-04-01

The x-ray absorption spectroscopy (XAS) had been an essential tool to gather spectroscopic information about atomic energy level structure in the early decades of this century. It has also played an important role in the discovery and systematization of rare-earth elements. The discovery of synchrotron radiation in 1952, and later the availability of broadly tunable synchrotron based x-ray sources have revitalized this technique since the 1970's. The correct interpretation of the oscillatory structure in the x-ray absorption cross-section above the absorption edge by Sayers et. al. has transformed XAS from a spectroscopic tool to a structural technique. EXAFS (Extended X-raymore » Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. An excellent description of the principles and data analysis techniques of EXAFS is given by Teo. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles. Today, there are about 50 experimental stations in various synchrotrons around the world dedicated to collecting x-ray absorption data from the bulk and surfaces of solids and liquids. In this chapter, we will give the basic principles of XAS, explain the information content of essentially two different aspects of the absorption process leading to EXAFS and XANES, and discuss the source and samples limitations.« less

The relative importance of aerosol scattering and absorption in remote sensing

NASA Technical Reports Server (NTRS)

Fraser, R. S.; Kaufman, Y. J.

1985-01-01

Previous attempts to explain the effect of aerosols on satellite measurements of surface properties for the visible and near-infrared spectrum have emphasized the amount of aerosols without consideration of their absorption properties. In order to estimate the importance of absorption, the radiances of the sunlight scattered from models of the earth-atmosphere system are computed as functions of the aerosol optical thickness and absorption. The absorption effect is small where the surface reflectance is weak, but is important for strong reflectance. These effects on classification of surface features, measuring vegetation index, and measuring surface reflectance are presented.

Laser-absorption effect on pulse-compression under Ohmic and weak-relativistic ponderomotive nonlinearity in plasmas

NASA Astrophysics Data System (ADS)

Singh, Mamta; Gupta, D. N.

2018-01-01

The inclusion of laser absorption in plasmas plays an important role in laser-plasma interactions. In this work, the laser pulse compression in weakly relativistic plasmas has been revisited by incorporating the collision-based laser absorption effects. By considering the role of laser absorption in plasmas, a set of coupled nonlinear equations is derived to describe the evolution of pulse compression. The laser pulse compression is reduced due to the collisional absorption in the plasmas. Fast dispersion is also observed with increasing the absorption coefficient, which is obviously due to the strong energy attenuation in plasmas. Using our theoretical model, the involvement and importance of a particular absorption mechanism for pulse compression in plasmas is analyzed.

A facile synthesis of metal nanoparticle - graphene composites for better absorption of solar radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Bindu; Mulla, Rafiq; Rabinal, M. K., E-mail: mkrabinal@yahoo.com

2015-06-24

Herein, a facile chemical approach has been adopted to prepare silver nanoparticles (AgNPs)- graphene (G) composite to study photothermal effect. Sodium borohydride (SBH), a strong reducing agent has been selected for this work. Effect of SBH concentrations on optical behavior of AgNPs-G composite was also investigated. Resultant materials were characterized by various techniques including X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), optical absorption, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM micrographs confirm wrapping of AgNPs into graphene whereas XRD analysis reveals their particle size variation between 47 nm to 69 nm. Optical studies throw a light on theirmore » strong absorption behavior towards solar radiation.« less

Absorptive coating for aluminum solar panels

NASA Technical Reports Server (NTRS)

Desmet, D.; Jason, A.; Parr, A.

1979-01-01

Method for coating forming coating of copper oxide from copper component of sheet aluminum/copper alloy provides strong durable solar heat collector panels. Copper oxide coating has solar absorption characteristics similar to black chrome and is much simpler and less costly to produce.

Impact of one-dimensional photonic crystal back reflector in thin-film c-Si solar cells on efficiency

NASA Astrophysics Data System (ADS)

Jalali, Tahmineh

2018-05-01

In this work, the effect of one-dimensional photonic crystal on optical absorption, which is implemented at the back side of thin-film crystalline silicon (c-Si) solar cells, is extensively discussed. The proposed structure acts as a Bragg reflector which reflects back light to the active layer as well as nanograting which couples the incident light to enhance optical absorption. To understand the optical mechanisms responsible for the enhancement of optical absorption, quantum efficiency and current density for all structures are calculated and the effect of influential parameters, such as grating period is investigated. The results confirm that our proposed structure have a great deal for substantial efficiency enhancement in a broad range from 400 to 1100 nm.

The X-ray and ultraviolet absorbing outflow in 3C 351

NASA Astrophysics Data System (ADS)

Mathur, Smita; Wilkes, Belinda; Elvis, Martin; Fiore, Fabrizio

1994-10-01

3C 351 (z = 0.371), and X-ray-'quiet' quasar, is one of the few quasars showing signs of a 'warm absorber' in its X-ray spectrum; i.e., partially ionized absorbing material in the line of sight whose opacity depends on its ionization structure. The main feature in the X-ray spectrum is a K-edge due to O VII or O VIII. 3C 351 also shows unusually strong, blueshifted, associated, absorption lines in the ultraviolet (Bahcall et al. 1993) including O VI (lambda lambda 1031, 1037). This high ionization state strongly suggests an identification with the X-ray absorber and a site within the active nucleus. In this paper we demonstrate that the X-ray and UV absorption is due to the same material. This is the first confirmed UV/X-ray absorber. Physical conditions of the absorber are determined through the combination of constraints derived from both the X-ray and UV analysis. This highly ionized, outflowing, low-density, high-column density absorber situated outside the broad emission line region (BELR) is a previously unknown component of nuclear material. We rule out the identification of the absorber with a BELR cloud as the physical conditions in the two regions are inconsistent with one another. The effect of the X-ray quietness and IR upturn in the 3C 351 continuum on the BELR is also investigated. The strengths of the high-ionization lines of C IV lambda-1549 and O VI lambda-1034 with respect to Lyman-alpha are systematically lower (up to a factor of 10) in the material ionized by the 3C 351 continuum as compared to those produced by the 'standard' quasar continuum, the strongest effect being on the strength of O VI lambda-1034. We find that for a 3C 351-like continuum, C III) lambda-1909 ceases to be a density indicator.

Sea urchin like shaped cdse nanoparticles grown in aqueous solutions via electron beam irradiation.

PubMed

Singh, Shalini; Guleria, Apurav; Rath, M C; Singh, A K; Adhikari, S; Sarkar, S K

2013-08-01

Cadmium selenide (CdSe) nanoparticles have been grown from an aqueous solutions containing equimolar ammoniated cadmium sulphate and sodium selenosulphate as precursors in presence of citric acid as a capping agent, via electron beam irradiation. The radiolytic processes occurring in the medium result in the formation of CdSe nanoparticles through the reactions mediated by hydrated electrons (e(aq)-). The dynamics of the formation of these nanoparticles was investigated by pulse radiolysis studies. The size of the primary nanoparticles as estimated from the absorption spectra recorded immediately was less than 3 nm. These nanoparticles exhibited strong excitonic absorption pattern and broad photoluminescence at room temperature, which has been attributed to the presence of surface states/defects. This has been confirmed by Raman spectral studies, where CdSe nanoparticles exhibited characteristic surface phonon modes at around 250 cm(-1). The photoluminescence lifetime decay measurements further supported the existence of surface defects on the as-grown CdSe nanoparticles. These nanoparticles were found to exist in the agglomerated form of sea urchin like shapes of uniform size of about 500 nm as revealed from TEM and SEM images. These sea urchin like shaped CdSe nanoparticles grown in this route were found to be very stable under the ambient conditions. We infer that citric acid influences the growth as well as stability of these nanoparticles. It is expected that these nanomaterials could find potential applications in the field of sensors, catalysis and photovoltaics.

Bimodal Exciplex Formation in Bimolecular Photoinduced Electron Transfer Revealed by Ultrafast Time-Resolved Infrared Absorption.

PubMed

Koch, Marius; Licari, Giuseppe; Vauthey, Eric

2015-09-03

The dynamics of a moderately exergonic photoinduced charge separation has been investigated by ultrafast time-resolved infrared absorption with the dimethylanthracene/phthalonitrile donor/acceptor pair in solvents covering a broad range of polarity. A distinct spectral signature of an exciplex could be identified in the -C≡N stretching region. On the basis of quantum chemistry calculations, the 4-5 times larger width of this band compared to those of the ions and of the locally excited donor bands is explained by a dynamic distribution of exciplex geometry with different mutual orientations and distances of the constituents and, thus, with varying charge-transfer character. Although spectrally similar, two types of exciplexes could be distinguished by their dynamics: short-lived, "tight", exciplexes generated upon static quenching and longer-lived, "loose", exciplexes formed upon dynamic quenching in parallel with ion pairs. Tight exciplexes were observed in all solvents, except in the least polar diethyl ether where quenching is slower than diffusion. The product distribution of the dynamic quenching depends strongly on the solvent polarity: whereas no significant loose exciplex population could be detected in acetonitrile, both exciplex and ion pair are generated in less polar solvents, with the relative population of exciplex increasing with decreasing solvent polarity. These results are compared with those reported previously with donor/acceptor pairs in different driving force regimes to obtain a comprehensive picture of the role of the exciplexes in bimolecular photoinduced charge separation.

Microwave absorbance properties of zirconium–manganese substituted cobalt nanoferrite as electromagnetic (EM) wave absorbers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Khan, Kishwar, E-mail: kknano@hotmail.com; Rehman, Sarish

2014-02-01

Highlights: • Good candidates for EM materials with low reflectivity. • Good candidates for broad bandwidth at microwave frequency. • Microwave absorbing bandwidth was modulated simply by manipulating the Zr–Mn. • Higher the Zr–Mn content, the higher absorption rates for the electromagnetic radiation. • The predicted reflection loss shows that this can be used for thin ferrite absorber. - Abstract: Nanocrystalline Zr–Mn (x) substituted Co ferrite having chemical formula CoFe{sub 2−2x}Zr{sub x}Mn{sub x}O{sub 4} (x = 0.1–0.4) was prepared by co-precipitation technique. Combining properties such as structural, electrical, magnetic and reflection loss characteristics. Crystal structure and surface morphology of themore » calcined samples were characterized by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). By using two point probe homemade resistivity apparatus to find resistivity of the sample. Electromagnetic (EM) properties are measured through RF impedance/materials analyzer over 1 MHz–3 GHz. The room-temperature dielectric measurements show dispersion behavior with increasing frequency from 100 Hz to 3 MHz. Magnetic properties confirmed relatively strong dependence of saturation magnetization on Zr–Mn composition. Curie temperature is also found to decrease linearly with addition of Zr–Mn. Furthermore, comprehensive analysis of microwave reflection loss (RL) is carried out as a function of substitution, frequency, and thickness. Composition accompanying maximum microwave absorption is suggested.« less

On improved understanding of plasma-chemical processes in complex low-temperature plasmas

NASA Astrophysics Data System (ADS)

Röpcke, Jürgen; Loffhagen, Detlef; von Wahl, Eric; Nave, Andy S. C.; Hamann, Stephan; van Helden, Jean-Piere H.; Lang, Norbert; Kersten, Holger

2018-05-01

Over the last years, chemical sensing using optical emission spectroscopy (OES) in the visible spectral range has been combined with methods of mid infrared laser absorption spectroscopy (MIR-LAS) in the molecular fingerprint region from 3 to 20 μm, which contains strong rotational-vibrational absorption bands of a large variety of gaseous species. This optical approach established powerful in situ diagnostic tools to study plasma-chemical processes of complex low-temperature plasmas. The methods of MIR-LAS enable to detect stable and transient molecular species in ground and excited states and to measure the concentrations and temperatures of reactive species in plasmas. Since kinetic processes are inherent to discharges ignited in molecular gases, high time resolution on sub-second timescales is frequently desired for fundamental studies as well as for process monitoring in applied research and industry. In addition to high sensitivity and good temporal resolution, the capacity for broad spectral coverage enabling multicomponent detection is further expanding the use of OES and MIR-LAS techniques. Based on selected examples, this paper reports on recent achievements in the understanding of complex low-temperature plasmas. Recently, a link with chemical modeling of the plasma has been provided, which is the ultimate objective for a better understanding of the chemical and reaction kinetic processes occurring in the plasma. Contribution to the Topical Issue "Fundamentals of Complex Plasmas", edited by Jürgen Meichsner, Michael Bonitz, Holger Fehske, Alexander Piel.

Thin film optical coatings for the ultraviolet spectral region

NASA Astrophysics Data System (ADS)

Torchio, P.; Albrand, G.; Alvisi, M.; Amra, C.; Rauf, H.; Cousin, B.; Otrio, G.

2017-11-01

The applications and innovations related to the ultraviolet field are today in strong growth. To satisfy these developments which go from biomedical to the large equipment like the Storage Ring Free Electron Laser, it is crucial to control with an extreme precision the optical performances, in using the substrates and the thin film materials impossible to circumvent in this spectral range. In particular, the reduction of the losses by electromagnetic diffusion, Joule effect absorption, or the behavior under UV luminous flows of power, resistance to surrounding particulate flows... become top priority which concerns a broad European and international community. Our laboratory has the theoretical, experimental and technological tools to design and fabricate numerous multilayer coatings with desirable optical properties in the visible and infrared spectral ranges. We have extended our expertise to the ultraviolet. We present here some results on high reflectivity multidielectric mirrors towards 250 nm in wavelength, produced by Ion Plating Deposition. The latter technique allows us to obtain surface treatments with low absorption and high resistance. We give in this study the UV transparent materials and the manufacturing technology which have been the best suited to meet requirements. Single UV layers were deposited and characterized. HfO2/SiO2 mirrors with a reflectance higher than 99% at 300 nm were obtained. Optical and non-optical characterizations such as UV spectrophotometric measurements, X-Ray Diffraction spectra, Scanning Electron Microscope and Atomic Force Microscope images were performed

The red edge in arid region vegetation: 340-1060 nm spectra

NASA Technical Reports Server (NTRS)

Ray, Terrill W.; Murray, Bruce C.; Chehbouni, A.; Njoku, Eni

1993-01-01

The remote sensing study of vegetated regions of the world has typically been focused on the use of broad-band vegetation indices such as NDVI. Various modifications of these indices have been developed in attempts to minimize the effect of soil background, e.g., SAVI, or to reduce the effect of the atmosphere, e.g., ARVI. Most of these indices depend on the so-called 'red edge,' the sharp transition between the strong absorption of chlorophyll pigment in visible wavelengths and the strong scattering in the near-infrared from the cellular structure of leaves. These broadband indices tend to become highly inaccurate as the green canopy cover becomes sparse. The advent of high spectral resolution remote sensing instrument such as the Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) has allowed the detection of narrow spectral features in vegetation and there are reports of detection of the red edge even for pixels with very low levels of green vegetation cover by Vane et al. and Elvidge et al., and to characterize algal biomass in coastal areas. Spectral mixing approaches similar to those of Smith et al. can be extended into the high spectral resolution domain allowing for the analysis of more endmembers, and potentially, discrimination between material with narrow spectral differences. Vegetation in arid regions tends to be sparse, often with small leaves such as the creosote bush. Many types of arid region vegetation spend much of the year with their leaves in a senescent state, i.e., yellow, with lowered chlorophyll pigmentation. The sparseness of the leaves of many arid region plants has the dual effect of lowering the green leaf area which can be observed and of allowing more of the sub-shrub soil to be visible which further complicates the spectrum of a region covered with arid region vegetation. Elvidge examined the spectral characteristics of dry plant materials showing significant differences in the region of the red edge and the diagnostic ligno-cellulose absorptions at 2090 nm and 2300 nm. Ray et al. detected absorption at 2100 nm in AVIRIS spectra of an abandoned field known to be covered by a great deal of dead plant litter. In order to better study arid region vegetation remote sensing data, it is necessary to better characterize the reflectance spectra of in situ, living, arid region plants.

A high spectral resolution map of the nuclear emitting regions of NGC 7582

NASA Astrophysics Data System (ADS)

Braito, Valentina; Reeves, J. N.; Bianchi, S.; Nardini, E.; Piconcelli, E.

2017-04-01

We present the results of the spatial and spectral analysis of the deep ( 200 ks) Chandra HETG observation of the changing look AGN NGC 7582. During this long Chandra observation, NGC 7582 was in a highly obscured state. Therefore, we also consider a short ( 24 ks) Suzaku observation, which caught NGC 7582 in a Compton thick state. This allows us to determine the underlying continuum model and the amount of absorption [NH = (1.2 ± 0.2) × 1024 cm-2]. A wealth of emission lines (from Mg, Si, S, and Fe) are detected in the Chandra data, which allows us to map the structure of the circumnuclear emitters. The high resolution spectrum reveals that the soft X-ray emission originates in a hybrid gas, which is ionized in part by the strong circumnuclear star-forming activity and in part by the central AGN. The high resolution images confirm that the emitting region is highly inhomogeneous and extends up to a few hundred pc from the nuclear source. The X-ray images are more extended in the lower energy lines (Ne and Mg) than in the higher energy lines (Si, Fe); the former are dominated by the collisionally ionized gas from the starburst and the latter by the photoionized AGN emission. This is supported by the analysis of the He-like triplets in the grating spectra. We deduce that a low density (ne 0.3-1 cm-3) photoionized gas is responsible for the strong forbidden components, which is likely to originate from extended AGN narrow line region gas at distances of 200-300 pc from the black hole. We also detect an absorption feature at 6.7 keV that is consistent with the rest frame energy of the resonance absorption line from Fe xxv (Elab = 6.7 keV), which traces the presence of a sub-parsec scale ionized circumnuclear absorber. The emerging picture is in agreement with our new view of the circumnuclear gas in AGN, where the medium is clumpy and stratified in both density and ionization. These absorbers and emitters are located on different scales, from the sub-pc broad line region gas out to the kpc scale of the galactic absorber.

Nonlinear absorption and optical limiting in gold-precipitated glasses induced by a femtosecond laser

NASA Astrophysics Data System (ADS)

Qu, Shiliang; Gao, Yachen; Jiang, Xiongwei; Zeng, Huidan; Song, Yinglin; Qiu, Jianrong; Zhu, Congshan; Hirao, K.

2003-09-01

Nonlinear absorptions of Au nanoparticles precipitated silicate glasses by irradiation of a focused femtosecond pulsed laser were investigated using Z-scan technique with 8 ns pulses at 532 nm. Optical limiting (OL) effects in such glasses have been also measured. It is observed that the behaviors of transition from saturable absorption to reverse saturable absorption and the OL performances for different samples are significantly different, which depend drastically on the irradiation power density of the femtosecond laser used for the Au nanoparticles precipitation in the glass. Strong nonlinear absorptions in these samples are mainly attributed to the surface plasmon resonance (SPR) and free carrier absorptions of the precipitated Au nanoparticles.

Efficient Vacuum-Deposited Ternary Organic Solar Cells with Broad Absorption, Energy Transfer, and Enhanced Hole Mobility.

PubMed

Shim, Hyun-Sub; Moon, Chang-Ki; Kim, Jihun; Wang, Chun-Kai; Sim, Bomi; Lin, Francis; Wong, Ken-Tsung; Seo, Yongsok; Kim, Jang-Joo

2016-01-20

The use of multiple donors in an active layer is an effective way to boost the efficiency of organic solar cells by broadening their absorption window. Here, we report an efficient vacuum-deposited ternary organic photovoltaic (OPV) using two donors, 2-((2-(5-(4-(diphenylamino)phenyl)thieno[3,2-b]thiophen-2-yl)thiazol-5-yl)methylene)malononitrile (DTTz) for visible absorption and 2-((7-(5-(dip-tolylamino)thiophen-2-yl)benzo[c]-[1,2,5]thiadiazol-4-yl)methylene)malononitrile (DTDCTB) for near-infrared absorption, codeposited with C70 in the ternary layer. The ternary device achieved a power conversion efficiency of 8.02%, which is 23% higher than that of binary OPVs. This enhancement is the result of incorporating two donors with complementary absorption covering wavelengths of 350 to 900 nm with higher hole mobility in the ternary layer than that of binary layers consisting of one donor and C70, combined with energy transfer from the donor with lower hole mobility (DTTz) to that with higher mobility (DTDCTB). This structure fulfills all the requirements for efficient ternary OPVs.

Cavity-enhanced measurements of hydrogen peroxide absorption cross sections from 353 to 410 nm.

PubMed

Kahan, Tara F; Washenfelder, Rebecca A; Vaida, Veronica; Brown, Steven S

2012-06-21

We report near-ultraviolet and visible absorption cross sections of hydrogen peroxide (H(2)O(2)) using incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS), a recently developed, high-sensitivity technique. The measurements reported here span the range of 353-410 nm and extend published electronic absorption cross sections by 60 nm to absorption cross sections below 1 × 10(-23) cm(2) molecule(-1). We have calculated photolysis rate constants for H(2)O(2) in the lower troposphere at a range of solar zenith angles by combining the new measurements with previously reported data at wavelengths shorter than 350 nm. We predict that photolysis at wavelengths longer than those included in the current JPL recommendation may account for up to 28% of the total hydroxyl radical (OH) production from H(2)O(2) photolysis under some conditions. Loss of H(2)O(2) via photolysis may be of the same order of magnitude as reaction with OH and dry deposition in the lower atmosphere; these processes have very different impacts on HO(x) loss and regeneration.

Integrated three-dimensional photonic nanostructures for achieving near-unity solar absorption and superhydrophobicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuang, Ping; Lin, Shawn-Yu, E-mail: sylin@rpi.edu; Hsieh, Mei-Li

2015-06-07

In this paper, we proposed and realized 3D photonic nanostructures consisting of ultra-thin graded index antireflective coatings (ARCs) and woodpile photonic crystals. The use of the integrated ARC and photonic crystal structure can achieve broadband, broad-angle near unity solar absorption. The amorphous silicon based photonic nanostructure experimentally shows an average absorption of ∼95% for λ = 400–620 nm over a wide angular acceptance of θ = 0°–60°. Theoretical studies show that a Gallium Arsenide (GaAs) based structure can achieve an average absorption of >95% for λ = 400–870 nm. Furthermore, the use of the slanted SiO{sub 2} nanorod ARC surface layer by glancing angle deposition exhibits Cassie-Baxter statemore » wetting, and superhydrophobic surface is obtained with highest water contact angle θ{sub CB} ∼ 153°. These properties are fundamentally important for achieving maximum solar absorption and surface self-cleaning in thin film solar cell applications.« less

A survey with Copernicus of interstellar O VI absorption

NASA Technical Reports Server (NTRS)

Jenkins, E. B.; Meloy, D. A.

1974-01-01

The presence of broad, shallow absorptions caused by O VI ions were revealed from UV spectra observations recorded by the Copernicus satellite for thirty-two stars. A table lists survey data on the stars observed for which values of the O VI column densities or their upper limits are extracted. Interstellar rather than circumstellar origin is evident from observation of the lack of correspondence between radical velocities of the stars and those of the O VI profiles. The presence of a low-density high-temperature phase of interstellar gas produced by supernova explosions is suggested.

Tunable emission and excited state absorption induced optical limiting in Tb2(MoO4)3: Sm3+/Eu3+ nanophosphors

NASA Astrophysics Data System (ADS)

Mani, Kamal P.; Sreekanth, Perumbilavil; Vimal, G.; Biju, P. R.; Unnikrishnan, N. V.; Ittyachen, M. A.; Philip, Reji; Joseph, Cyriac

2016-12-01

Photoluminescence properties and optical limiting behavior of pure and Sm3+/Eu3+ doped Tb2(MoO4)3 nanophosphors are investigated. The prepared nanophosphors exhibit excellent emission when excited by UV light. Color-tunable emissions in Tb2-xSmx(MoO4)3 and Tb2-xEux(MoO4)3 are realized by employing different excitation wavelengths or by controlling the doping concentration of Sm3+ and Eu3+. Luminescence quantum yield and CIE chromatic coordinates of the prepared phosphors were also presented. Optical limiting properties of the samples are investigated by open aperture Z-scan technique using 5 ns laser pulses at 532 nm. Numerical fitting of the measured Z-scan data to the relevant nonlinear transmission equations reveals that the nonlinear absorption is arising from strong excited state absorption, along with weak absorption saturation and it is found that the optical nonlinearity of Tb2(MoO4)3 increases with Sm3+/Eu3+doping. Parameters such as saturation fluence, excited state absorption cross section and ground state absorption cross section of the samples have been determined numerically, from which the figure of merit for nonlinear absorption is calculated. The excited state absorption cross-section of the samples is found to be one order of magnitude higher than that of the ground state absorption cross-section, indicating strong reverse saturable absorption. These results indicate that Sm3+/Eu3+ doped Tb2(MoO4)3 nanophosphors are efficient media for UV/n-UV pumped LEDs, and are also potential candidates for designing efficient optical limiting devices for the protection of human eyes and sensitive optical detectors from harmful laser radiation.

How does the plasmonic enhancement of molecular absorption depend on the energy gap between molecular excitation and plasmon modes: a mixed TDDFT/FDTD investigation.

PubMed

Sun, Jin; Li, Guang; Liang, WanZhen

2015-07-14

A real-time time-dependent density functional theory coupled with the classical electrodynamics finite difference time domain technique is employed to systematically investigate the optical properties of hybrid systems composed of silver nanoparticles (NPs) and organic adsorbates. The results demonstrate that the molecular absorption spectra throughout the whole energy range can be enhanced by the surface plasmon resonance of Ag NPs; however, the absorption enhancement ratio (AER) for each absorption band differs significantly from the others, leading to the quite different spectral profiles of the hybrid complexes in contrast to those of isolated molecules or sole NPs. Detailed investigations reveal that the AER is sensitive to the energy gap between the molecular excitation and plasmon modes. As anticipated, two separate absorption bands, corresponding to the isolated molecules and sole NPs, have been observed at a large energy gap. When the energy gap approaches zero, the molecular excitation strongly couples with the plasmon mode to form the hybrid exciton band, which possesses the significantly enhanced absorption intensity, a red-shifted peak position, a surprising strongly asymmetric shape of the absorption band, and the nonlinear Fano effect. Furthermore, the dependence of surface localized fields and the scattering response functions (SRFs) on the geometrical parameters of NPs, the NP-molecule separation distance, and the external-field polarizations has also been depicted.

Tunable Spectrum Selectivity for Multiphoton Absorption with Enhanced Visible Light Trapping in ZnO Nanorods.

PubMed

Tan, Kok Hong; Lim, Fang Sheng; Toh, Alfred Zhen Yang; Zheng, Xia-Xi; Dee, Chang Fu; Majlis, Burhanuddin Yeop; Chai, Siang-Piao; Chang, Wei Sea

2018-04-17

Observation of visible light trapping in zinc oxide (ZnO) nanorods (NRs) correlated to the optical and photoelectrochemical properties is reported. In this study, ZnO NR diameter and c-axis length respond primarily at two different regions, UV and visible light, respectively. ZnO NR diameter exhibits UV absorption where large ZnO NR diameter area increases light absorption ability leading to high efficient electron-hole pair separation. On the other hand, ZnO NR c-axis length has a dominant effect in visible light resulting from a multiphoton absorption mechanism due to light reflection and trapping behavior in the free space between adjacent ZnO NRs. Furthermore, oxygen vacancies and defects in ZnO NRs are associated with the broad visible emission band of different energy levels also highlighting the possibility of the multiphoton absorption mechanism. It is demonstrated that the minimum average of ZnO NR c-axis length must satisfy the linear regression model of Z p,min = 6.31d to initiate the multiphoton absorption mechanism under visible light. This work indicates the broadening of absorption spectrum from UV to visible light region by incorporating a controllable diameter and c-axis length on vertically aligned ZnO NRs, which is important in optimizing the design and functionality of electronic devices based on light absorption mechanism. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Dynamic Optoelectronic Properties in Perovskite Oxide Thin Films Measured with Ultrafast Transient Absorption & Reflectance Spectroscopy

NASA Astrophysics Data System (ADS)

Smolin, Sergey Y.

Ultrafast transient absorption and reflectance spectroscopy are foundational techniques for studying photoexcited carrier recombination mechanisms, lifetimes, and charge transfer rates. Because quantifying photoexcited carrier dynamics is central to the intelligent design and improvement of many solid state devices, these transient optical techniques have been applied to a wide range of semiconductors. However, despite their promise, interpretation of transient absorption and reflectance data is not always straightforward and often relies on assumptions of physical processes, especially with respect to the influence of heating. Studying the material space of perovskite oxides, the careful collection, interpretation, and analysis of ultrafast data is presented here as a guide for future research into novel semiconductors. Perovskite oxides are a class of transition metal oxides with the chemical structure ABO3. Although traditionally studied for their diverse physical, electronic, and magnetic properties, perovskite oxides have gained recent research attention as novel candidates for light harvesting applications. Indeed, strong tunable absorption, unique interfacial properties, and vast chemical flexibility make perovskite oxides a promising photoactive material system. However, there is limited research characterizing dynamic optoelectronic properties, such as recombination lifetimes, which are critical to know in the design of any light-harvesting device. In this thesis, ultrafast transient absorption and reflectance spectroscopy was used to understand these dynamic optoelectronic properties in highquality, thin (<50 nm) perovskite oxide films grown by molecular beam epitaxy. Starting with epitaxial LaFeO3 (LFO) grown on (LaAlO 3)0.3(Sr2AlTaO6)0.7 (LSAT), transient absorption spectroscopy reveals two photoinduced absorption features at the band gap of LFO at 2.4 eV and at the higher energy absorption edge at 3.5 eV. Using a combination of temperature-dependent, variable-angle spectroscopic ellipsometry and time-resolved ultrafast optical spectroscopy on a type I heterostructure, we clarify thermal and electronic contributions to spectral transients in LaFeO3. Upon comparison to thermally-derived static spectra of LaFeO3, we find that thermal contributions dominate the transient absorption and reflectance spectra above the band gap. A transient photoinduced absorption feature below the band gap at 1.9 eV is not reproduced in the thermally derived spectra and has significantly longer decay kinetics from the thermallyinduced features; therefore, this long lived photoinduced absorption is likely derived, at least partially, from photoexcited carriers with lifetimes much longer than 3 nanoseconds. LaFeO3 has a wide band gap of 2.4 eV but its absorption can be decreased with chemical substitution of Sr for Fe to make it more suitable for various applications. This type of A-site substitution is a common route to change static optical absorption in perovskite oxides, but there are no systematic studies looking at how A-site substitution changes dynamic optoelectronic properties. To understand the relationship between composition and static and dynamic optical properties we worked with the model system of La1-xSrxFeO 3-delta epitaxial films grown on LSAT, uncovering the effects of A-site cation substitution and oxygen stoichiometry. Variable-angle spectroscopic ellipsometry was used to measure static optical properties, revealing a linear increase in absorption coefficient at 1.25 eV and a red-shifting of the optical absorption edge with increasing Sr fraction. The absorption spectra can be similarly tuned through the introduction of oxygen vacancies, indicating the critical role that nominal Fe valence plays in optical absorption. Dynamic optoelectronic properties were studied with ultrafast transient reflectance spectroscopy with broadband visible (1.6 eV to 4 eV) and near-infrared (0.9 eV to 1.5 eV) probes. The sign of the reflectance change in the near-infrared region in LSFO is indicative of carrier bandfilling of newly created electronic states by photoexcited carriers. Moreover, we find that similar transient spectral trends can be induced with A-site substitution or through oxygen vacancies, which is a surprising result. Probing the near-infrared region reveals similar nanosecond (1-3 ns) photoexcited carrier lifetimes for oxygen deficient and stoichiometric films. These results demonstrate that while the static optical absorption is strongly dependent on nominal Fe valence tuned through cation or anion stoichiometry, oxygen vacancies do not appear to play a significantly detrimental role in long lived recombination kinetics. Although this thesis represents one of the first comprehensive studies using broad band transient absorption and reflectance spectroscopy to study dynamic optoelectronic phenomena in perovskite oxides, it can also serve as a guide for the implementation and interpretation of ultrafast spectroscopy in other material systems. Moreover, the ultrafast work on perovskite oxides indicates that these materials have long nanosecond lifetimes required for light harvesting devices and should be investigated further.

7 CFR 29.2436 - Wrappers (A Group).

Code of Federal Regulations, 2014 CFR

2014-01-01

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7 CFR 29.2436 - Wrappers (A Group).

Code of Federal Regulations, 2010 CFR

2010-01-01

..., firm, rich in oil, elastic, strong, bright finish, deep color intensity, broad, 95 percent uniform, and..., deep color intensity, broad, 95 percent uniform, and 5 percent injury tolerance. A2D Fine Dark-brown...

7 CFR 29.2436 - Wrappers (A Group).

Code of Federal Regulations, 2012 CFR

2012-01-01

..., firm, rich in oil, elastic, strong, bright finish, deep color intensity, broad, 95 percent uniform, and..., deep color intensity, broad, 95 percent uniform, and 5 percent injury tolerance. A2D Fine Dark-brown...

7 CFR 29.2436 - Wrappers (A Group).

Code of Federal Regulations, 2011 CFR

2011-01-01

..., firm, rich in oil, elastic, strong, bright finish, deep color intensity, broad, 95 percent uniform, and..., deep color intensity, broad, 95 percent uniform, and 5 percent injury tolerance. A2D Fine Dark-brown...

7 CFR 29.2436 - Wrappers (A Group).

Code of Federal Regulations, 2013 CFR

2013-01-01

..., firm, rich in oil, elastic, strong, bright finish, deep color intensity, broad, 95 percent uniform, and..., deep color intensity, broad, 95 percent uniform, and 5 percent injury tolerance. A2D Fine Dark-brown...

A STUDY OF THE X-RAYED OUTFLOW OF APM 08279+5255 THROUGH PHOTOIONIZATION CODES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saez, Cristian; Chartas, George, E-mail: saez@astro.psu.edu, E-mail: chartasg@cofc.edu

2011-08-20

We present new results from our study of the X-rayed outflow of the z = 3.91 gravitationally lensed broad absorption line quasar APM 08279+5255. These results are based on spectral fits to all the long exposure observations of APM 08279+5255 using a new quasar-outflow model. This model is based on CLOUDY{sup 3} CLOUDY is a photoionization code designed to simulate conditions in interstellar matter under a broad range of conditions. We have used version 08.00 of the code last described by Ferland et al. (1998). The atomic database used by CLOUDY is described in Ferguson et al. (2001) and http://www.pa.uky.edu/{approx}verner/atom.html.more » simulations of a near-relativistic quasar outflow. The main conclusions from our multi-epoch spectral re-analysis of Chandra, XMM-Newton, and Suzaku observations of APM 08279+5255 are the following. (1) In every observation, we confirm the presence of two strong features, one at rest-frame energies between 1-4 keV and the other between 7-18 keV. (2) We confirm that the low-energy absorption (1-4 keV rest frame) arises from a low-ionization absorber with log(N{sub H}/cm{sup -2}) {approx} 23 and the high-energy absorption (7-18 keV rest frame) arises from highly ionized (3 {approx}< log {xi} {approx}< 4, where {xi} is the ionization parameter) iron in a near-relativistic outflowing wind. Assuming this interpretation, we find that the velocities on the outflow could get up to {approx}0.7c. (3) We confirm a correlation between the maximum outflow velocity and the photon index and find possible trends between the maximum outflow velocity and the X-ray luminosity, and between the total column density and the photon index. We performed calculations of the force multipliers of material illuminated by absorbed power laws and a Mathews-Ferland spectral energy distribution (SED). We found that variations of the X-ray and UV parts of the SEDs and the presence of a moderate absorbing shield will produce important changes in the strength of the radiative driving force. These results support the observed trend found between the outflow velocity and X-ray photon index in APM 08279+5255. If this result is confirmed it will imply that radiation pressure is an important mechanism in producing quasar outflows.« less

Photophysics of C60 Colloids

DTIC Science & Technology

2012-11-28

strong linear absorption giving rise to thermionic emission, resulting in avalanche ionization and thus, nanoplasmas that absorb and scatter the...point of water is reached before the sublimation point of carbon black. If nanoplasmas are the source of the nonlinear absorption seen in CBS-1, then

High Resolution Spectrometry of Leaf and Canopy Chemistry for Biochemical Cycling

NASA Technical Reports Server (NTRS)

Spanner, M. A.; Peterson, D. L.; Acevedo, W.; Matson, P.

1985-01-01

High-resolution laboratory spectrophotometer and Airborne Imaging Spectrometer (AIS) data were used to analyze forest leaf and canopy chemistry. Fundamental stretching frequencies of organic bonds in the visible, near infrared and short-wave infrared are indicative of concentrations and total content of nitrogen, phosphorous, starch and sugar. Laboratory spectrophotometer measurements showed very strong negative correlations with nitrogen (measured using wet chemistry) in the visible wavelengths. Strong correlations with green wet canopy weight in the atmospheric water absorption windows were observed in the AIS data. A fairly strong negative correlation between the AIS data at 1500 nm and total nitrogen and nitrogen concentration was evident. This relationship corresponds very closely to protein absorption features near 1500 nm.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, H.; Chang, C.; Cheng, H. H., E-mail: hhcheng@ntu.edu.tw

We report an investigation on the absorption mechanism of a GeSn photodetector with 2.4% Sn composition in the active region. Responsivity is measured and absorption coefficient is calculated. Square root of absorption coefficient linearly depends on photon energy indicating an indirect transition. However, the absorption coefficient is found to be at least one order of magnitude higher than that of most other indirect materials, suggesting that the indirect optical absorption transition cannot be assisted only by phonon. Our analysis of absorption measurements by other groups on the same material system showed the values of absorption coefficient on the same ordermore » of magnitude. Our study reveals that the strong enhancement of absorption for the indirect optical transition is the result of alloy disorder from the incorporation of the much larger Sn atoms into the Ge lattice that are randomly distributed.« less

Optical (diffuse reflectance) and Mossbauer spectroscopic study of nontronite and related Fe-bearing smectites

USGS Publications Warehouse

Sherman, David M.; Vergo, N.

1988-01-01

Near-ultraviolet to near-infrared optical (diffuse reflectance) spectra of several nontronites and related Fe-bearing smectites [(Fe2+,Fe3+)-bearing saponite and (Fe2+,Fe3+)-bearing montmorillonite] are presented and interpreted. Mossbauer spectra at 298 K are also presented to help interpret the optical spectra. The optical spectra of nontronites are dominated by the ligand field transitions of Fe3+ in octahedral coordination sites. In addition to the ligand field transitions of single Fe3+ cations, a broad absorption band centered near 22000 cm-1 is observed that may be due to the simultaneous excitation of two Fe3+ cations to the 4T1g (4G) state. Alternatively, this band may represent excitations to the 2A2g and 2T1g ligand field states. For most samples, the amount of tetrahedrally coordinated Fe3+ was below that detectable by Mossbauer spectroscopy (1-3% of total Fe). However, the optical spectra of all of the nontronites show an absorption band near 23000 cm-1. This band is assigned to the 6A1 ??? 4E,4A1 transition of tetrahedrally coordinated Fe3+. The optical spectra of mixed-valence Fe-bearing smectites show a broad absorption band at 14000-15000 cm-1 owing to Fe2+ ??? Fe3+ charge transfer. -from Authors

Cooling quasiparticles in A 3C 60 fullerides by excitonic mid-infrared absorption

NASA Astrophysics Data System (ADS)

Nava, Andrea; Giannetti, Claudio; Georges, Antoine; Tosatti, Erio; Fabrizio, Michele

2018-02-01

Long after its discovery, superconductivity in alkali fullerides A3C60 still challenges conventional wisdom. The freshest inroad in such ever-surprising physics is the behaviour under intense infrared excitation. Signatures attributable to a transient superconducting state extending up to temperatures ten times higher than the equilibrium Tc ~ 20 K have been discovered in K3C60 after ultra-short pulsed infrared irradiation--an effect which still appears as remarkable as mysterious. Motivated by the observation that the phenomenon is observed in a broad pumping frequency range that coincides with the mid-infrared electronic absorption peak still of unclear origin, rather than to transverse optical phonons as has been proposed, we advance here a radically new mechanism. First, we argue that this broad absorption peak represents a `super-exciton' involving the promotion of one electron from the t1u half-filled state to a higher-energy empty t1g state, dramatically lowered in energy by the large dipole-dipole interaction acting in conjunction with the Jahn-Teller effect within the enormously degenerate manifold of (t1u)2(t1g)1 states. Both long-lived and entropy-rich because they are triplets, the infrared-induced excitons act as a sort of cooling mechanism that permits transient superconductive signals to persist up to much higher temperatures.

Optical Properties of Vibronically Coupled Cy3 Dimers on DNA Scaffolds.

PubMed

Cunningham, Paul D; Kim, Young C; Díaz, Sebastián A; Buckhout-White, Susan; Mathur, Divita; Medintz, Igor L; Melinger, Joseph S

2018-05-17

We examine the effect of electronic coupling on the optical properties of Cy3 dimers attached to DNA duplexes as a function of base pair (bp) separation using steady-state and time-resolved spectroscopy. For close Cy3-Cy3 separations, 0 and 1 bp between dyes, intermediate to strong electronic coupling is revealed by modulation of the absorption and fluorescence properties including spectral band shape, peak wavelength, and excited-state lifetime. Using a vibronic exciton model, we estimate coupling strengths of 150 and 266 cm -1 for the 1 and 0 bp separations, respectively, which are comparable to those found in natural light-harvesting complexes. For the strongest electronic coupling (0 bp separation), we observe that the absorption band shape is strongly affected by the base pairs that surround the dyes, where more strongly hydrogen-bonded G-C pairs produce a red-shifted absorption spectrum consistent with a J-type dimer. This effect is studied theoretically using molecular dynamics simulation, which predicts an in-line dye configuration that is consistent with the experimental J-type spectrum. When the Cy3 dimers are in a standard aqueous buffer, the presence of relatively strong electronic coupling is accompanied by decreased fluorescence lifetime, suggesting that it promotes nonradiative relaxation in cyanine dyes. However, we show that the use of a viscous solvent can suppress this nonradiative recombination and thereby restore the dimer fluorescent emission. Ultrafast transient absorption measurements of Cy3 dimers in both standard aqueous buffer and viscous glycerol buffer suggest that sufficiently strong electronic coupling increases the probability of excited-state relaxation through a dark state that is related to Cy3 torsional motion.

Infrared absorption band in deformed qtz crystals analyzed by combining different microstructural methods

NASA Astrophysics Data System (ADS)

Stunitz, Holger; Thust, Anja; Behrens, Harald; Heilbronner, Renee; Kilian, Ruediger

2016-04-01

Natural single crystals of quartz have been experimentally deformed in two orientations: (1) normal to one prism-plane, (2) In O+ orientation at temperatures of 900 and 1000°C, pressures of 1.0 and 1.5 GPa, and strain rates of ~1 x 10-6s-1. The starting material is milky quartz, consisting of dry quartz (H2O contents of <150 H/106Si) with fluid inclusions (FI). During pressurization many FÍs decrepitate. Cracks heal and small neonate FÍs form, increasing the number of FÍs drastically. During subsequent deformation, the size of FÍs is further reduced (down to ~10 nm). Sample deformation occurs by dominant dislocation glide on selected slip systems, accompanied by some dynamic recovery. Strongly deformed regions show FTIR spectra with a pointed broad absorption band in the ~3400 cm-1 region as a superposition of molecular H2O bands and three discrete absorption bands (at 3367, 3400, and 3434 cm-1). In addition, there is a discrete absorption band at 3585 cm-1, which only occurs in deformed regions. The 3585 cm-1 band is reduced or even disappears after annealing. This band is polarized and represents structurally bound H, its H-content is estimated to be 1-3% of the total H2O-content and appears to be associated with dislocations. The H2O weakening effect in our FI-bearing natural quartz crystals is assigned to the processes of dislocation generation and multiplication at small FÍs. The deformation processes in these crystals represent a recycling of H2O between FÍs, dislocation generation at very small fluid inclusions, incorporation of structurally bound H into dislocation cores, and release of H2O from dislocations back into FÍs during recovery. Cracking and crack healing play an important role in the recycling process and imply a close interrelationship between brittle and crystal plastic deformation. The H2O weakening by this process is of a disequilibrium nature and thus depends on the amount of H2O available.

FE K EMISSION AND ABSORPTION FEATURES IN THE XMM-EPIC SPECTRUM OF THE SEYFERT GALAXY IC 4329A

NASA Technical Reports Server (NTRS)

Markowitz, A.; Reeves, J. N.; Braito, V.

2001-01-01

We present a re-analysis of the XMM-Newton long-look of the X-ray bright Seyfert galaxy IC 4329a. The Fe K bandpass is dominated by two peaks, consistent with emission from neutral or near-neutral Fe Ka and KP. A relativistic diskline model whereby both peaks are the result of one doubly-peaked diskline profile is found to be a poor description of the data. Models using two relativistic disklines are found to describe the emission profile well. A low-inclination, moderately-relativistic dual-diskline model is possible if the contribution from narrow components, due to distant material, is small or absent. A high-inclination, moderately relativistic profile for each peak is possible if there are roughly equal contributions from both the broad and narrow components. Upper limits on Fe XXV and Fe XXVI emission and absorption at the systemic velocity of IC 4329a are obtained. We also present the results of RXTE monitoring of this source obtained so far; the combined XMM-Newton and RXTE data sets allow us to explore the time-resolved spectral behavior of this source on time scales ranging from hours to 2 years. We find no strong evidence for variability of the Fe Ka emission line on any time scale probed, likely due to the minimal level of continuum variability. We detect a narrow absorption line, at a energy of 7.68 keV in the rest frame of the source; its significance has been confirmed using Monte Carlo simulations. This feature is most likely due to absorption from Fe XXVI blueshifted to approximately 0.1c relative to the systemic velocity, making IC 4329a the lowest-redshift AGN known with a high-velocity, highly-ionized outflow component. As is often the case with similar outflows seen in high-luminosity quasars, the estimated mass outflow rate is larger than the inflow accretion rate, signaling that the outflow represents a substantial portion of the total energy budget of the AGN. The outflow could arise from a radiatively-driven disk wind, or it may be in the form of a discrete, transient blob of ejected material.

Influence of stereoelectronic effects on the non-opioid analgesics gaboxadol and gaboxadol hydrochloride: Spectral and DFT study

NASA Astrophysics Data System (ADS)

Leenaraj, D. R.; Joe, I. Hubert

2018-05-01

The stereoelectronic properties of the molecular structure of most stable conformers of gaboxadol and gaboxadol hydrochloride have been studied using DFT/B3P86-LANL2DZ methodology. The energies of stable conformers of gaboxadol and gaboxadol hydrochloride are -494.2689 and -510.0117 hartrees, respectively. The stability of the molecules arising from stereoelectronic interactions, leading to its bioactivity, has been confirmed using natural bond orbital analysis. The natural bond orbital analysis of donor-acceptor (σ→σ* and n→σ*) interactions showed that the stereoelectronic hyperconjugative and anomeric interactions are exhibited in gaboxadol hydrochloride and gaboxadol, respectively. Lengthening of the axial and equatorial C-H bond lengths and natural population analysis support these results. Spectral features of gaboxadol hydrochloride have been explored by the Fourier transform infrared, Raman and Nuclear magnetic resonance spectroscopic techniques combined with density functional theory computations. NH+ … Cl- hydrogen bonding has been noticeable as a broad and strong absorption in the 2800-2400 cm-1 region. Broad peaks obtained by proton NMR are a result of the quadrupole effect of the N+ atom. Docking studies using representative GABA receptor crystal structures revealed that molecules containing azinane and isoxazole cores fit within the ligand binding domains, and the gaboxadol hydrochloride molecule shows the best binding energy with the 3D32 GABA receptor. Also, gaboxadol hydrochloride has obtained a high value of HOMO energy and a narrow HOMO- LUMO energy gap, which enhances reactivity.

In vivo spatial frequency domain spectroscopy of two layer media

NASA Astrophysics Data System (ADS)

Yudovsky, Dmitry; Nguyen, John Quan M.; Durkin, Anthony J.

2012-10-01

Monitoring of tissue blood volume and local oxygen saturation can inform the assessment of tissue health, healing, and dysfunction. These quantities can be estimated from the contribution of oxyhemoglobin and deoxyhemoglobin to the absorption spectrum of the dermis. However, estimation of blood related absorption in skin can be confounded by the strong absorption of melanin in the epidermis and epidermal thickness and pigmentation varies with anatomic location, race, gender, and degree of disease progression. Therefore, a method is desired that decouples the effect of melanin absorption in the epidermis from blood absorption in the dermis for a large range of skin types and thicknesses. A previously developed inverse method based on a neural network forward model was applied to simulated spatial frequency domain reflectance of skin for multiple wavelengths in the near infrared. It is demonstrated that the optical thickness of the epidermis and absorption and reduced scattering coefficients of the dermis can be determined independently and with minimal coupling. Then, the same inverse method was applied to reflectance measurements from a tissue simulating phantom and in vivo human skin. Oxygen saturation and total hemoglobin concentrations were estimated from the volar forearms of weakly and strongly pigmented subjects using a standard homogeneous model and the present two layer model.

Contribution of mycosporine-like amino acids and colored dissolved and particulate matter to sea ice optical properties and ultraviolet attenuation

PubMed Central

Uusikivi, Jari; Vähätalo, Anssi V.; Granskog, Mats A.; Sommaruga, Ruben

2010-01-01

In the Baltic Sea ice, the spectral absorption coefficients for particulate matter (PM) were about two times higher at ultraviolet wavelengths than at photosynthetically available radiation (PAR) wavelengths. PM absorption spectra included significant absorption by mycosporine-like amino acids (MAAs) between 320 and 345 nm. In the surface ice layer, the concentration of MAAs (1.37 μg L−1) was similar to that of chlorophyll a, resulting in a MAAs-to-chlorophyll a ratio as high as 0.65. Ultraviolet radiation (UVR) intensity and the ratio of UVR to PAR had a strong relationship with MAAs concentration (R2 = 0.97, n = 3) in the ice. In the surface ice layer, PM and especially MAAs dominated the absorption (absorption coefficient at 325 nm: 0.73 m−1). In the columnar ice layers, colored dissolved organic matter was the most significant absorber in the UVR (< 380 nm) (absorption coefficient at 325 nm: 1.5 m−1). Our measurements and modeling of UVR and PAR in Baltic Sea ice show that organic matter, both particulate and dissolved, influences the optical properties of sea ice and strongly modifies the UVR exposure of biological communities in and under snow-free sea ice. PMID:20585592