Gigahertz-peaked Spectra Pulsars and Thermal Absorption Model

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

Kijak, J.; Basu, R.; Lewandowski, W.

2017-05-10

We present the results of our radio interferometric observations of pulsars at 325 and 610 MHz using the Giant Metrewave Radio Telescope. We used the imaging method to estimate the flux densities of several pulsars at these radio frequencies. The analysis of the shapes of the pulsar spectra allowed us to identify five new gigahertz-peaked spectra (GPS) pulsars. Using the hypothesis that the spectral turnovers are caused by thermal free–free absorption in the interstellar medium, we modeled the spectra of all known objects of this kind. Using the model, we were able to put some observational constraints on the physicalmore » parameters of the absorbing matter, which allows us to distinguish between the possible sources of absorption. We also discuss the possible effects of the existence of GPS pulsars on future search surveys, showing that the optimal frequency range for finding such objects would be from a few GHz (for regular GPS sources) to possibly 10 GHz for pulsars and radio magnetars exhibiting very strong absorption.« less

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

Sharp Absorption Peaks in THz Spectra Valuable for Crystal Quality Evaluation of Middle Molecular Weight Pharmaceuticals

NASA Astrophysics Data System (ADS)

Sasaki, Tetsuo; Sakamoto, Tomoaki; Otsuka, Makoto

2018-05-01

Middle molecular weight (MMW) pharmaceuticals (MW 400 4000) are attracting attention for their possible use in new medications. Sharp absorption peaks were observed in MMW pharmaceuticals at low temperatures by measuring with a high-resolution terahertz (THz) spectrometer. As examples, high-resolution THz spectra for amoxicillin trihydrate, atorvastatin calcium trihydrate, probucol, and α,β,γ,δ-tetrakis(1-methylpyridinium-4-yl)porphyrin p-toluenesulfonate (TMPyP) were obtained at 10 K. Typically observed as peaks with full width at half-height (FWHM) values as low as 5.639 GHz at 0.96492 THz in amoxicillin trihydrate and 8.857 GHz at 1.07974 THz for probucol, many sharp peaks of MMW pharmaceuticals could be observed. Such narrow absorption peaks enable evaluation of the crystal quality of MMW pharmaceuticals and afford sensitive detection of impurities.

First-principles C band absorption spectra of SO2 and its isotopologues

NASA Astrophysics Data System (ADS)

Jiang, Bin; Kumar, Praveen; Kłos, Jacek; Alexander, Millard H.; Poirier, Bill; Guo, Hua

2017-04-01

The low-energy wing of the C ˜ B12 ←X˜ 1A1 absorption spectra for SO2 in the ultraviolet region is computed for the 32S,33S,34S and 36S isotopes, using the recently developed ab initio potential energy surfaces (PESs) of the two electronic states and the corresponding transition dipole surface. The state-resolved absorption spectra from various ro-vibrational states of SO2(X˜ 1A1 ) are computed. When contributions of these excited ro-vibrational states are included, the thermally averaged spectra are broadened but maintain their key characters. Excellent agreement with experimental absorption spectra is found, validating the accuracy of the PESs. The isotope shifts of the absorption peaks are found to increase linearly with energy, in good agreement with experiment.

Two-photon absorption spectra of carotenoids compounds

NASA Astrophysics Data System (ADS)

Vivas, Marcelo Gonçalves; Silva, Daniel Luiz; Boni, Leonardo de; Zalesny, Robert; Bartkowiak, Wojciech; Mendonca, Cleber Renato

2011-05-01

Carotenoids are biosynthetic organic pigments that constitute an important class of one-dimensional π-conjugated organic molecules with enormous potential for application in biophotonic devices. In this context, we studied the degenerate two-photon absorption (2PA) cross-section spectra of two carotenoid compounds (β-carotene and β-apo-8'-carotenal) employing the conventional and white-light-continuum Z-scan techniques and quantum chemistry calculations. Because carotenoids coexist at room temperature as a mixture of isomers, the 2PA spectra reported here are due to samples containing a distribution of isomers, presenting distinct conjugation length and conformation. We show that these compounds present a defined structure on the 2PA spectra, that peaks at 650 nm with an absorption cross-section of approximately 5000 GM, for both compounds. In addition, we observed a 2PA band at 990 nm for β-apo-8'-carotenal, which was attributed to a overlapping of 11Bu+-like and 21Ag--like states, which are strongly one- and two-photon allowed, respectively. Spectroscopic parameters of the electronic transitions to singlet-excited states, which are directly related to photophysical properties of these compounds, were obtained by fitting the 2PA spectra using the sum-over-states approach. The analysis and interpretations of the 2PA spectra of the investigated carotenoids were supported by theoretical predictions of one- and two-photon transitions carried out using the response functions formalism within the density functional theory framework, using the long-range corrected CAM-B3LYP functional.

Substituent and solvent effects on electronic absorption spectra of some N-(substitutedphenyl)benzene sulphonamides

NASA Astrophysics Data System (ADS)

Suganya, Krishnasamy; Kabilan, Senthamaraikannan

2004-04-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 23 ortho- and para-N-(substitutedphenyl)benzene sulphonamides in the range of 200-400 nm. The effects of substituents on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

Absorption Spectra of Gold Nanoparticle Suspensions

NASA Astrophysics Data System (ADS)

Anan'eva, M. V.; Nurmukhametov, D. R.; Zverev, A. S.; Nelyubina, N. V.; Zvekov, A. A.; Russakov, D. M.; Kalenskii, A. V.; Eremenko, A. N.

2018-02-01

Three gold nanoparticle suspensions are obtained, and mean radii in distributions - (6.1 ± 0.2), (11.9 ± 0.3), and (17.3 ± 0.7) nm - are determined by the transmission electron microscopy method. The optical absorption spectra of suspensions are obtained and studied. Calculation of spectral dependences of the absorption index of suspensions at values of the gold complex refractive index taken from the literature showed a significant deviation of experimental and calculated data in the region of 450-800 nm. Spectral dependences of the absorption of suspensions are simulated within the framework of the Mie-Drude theory taking into account the interband absorption in the form of an additional term in the imaginary part of the dielectric permittivity of the Gaussian type. It is shown that to quantify the spectral dependences in the region of the plasmon absorption band of nanoparticles, correction of the parameters of the interband absorption is necessary in addition to the increase of the relaxation parameter of the Drude theory. Spectral dependences of the dielectric permittivity of gold in nanodimensional state are refined from the solution of the inverse problem. The results of the present work are important for predicting the special features of operation of photonic devices and optical detonators based on gold nanoparticles.

Substituent and solvent effects on electronic absorption spectra of some N-(substitutedphenyl)benzene sulphonamides.

PubMed

Suganya, Krishnasamy; Kabilan, Senthamaraikannan

2004-04-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 23 ortho- and para-N-(substitutedphenyl)benzene sulphonamides in the range of 200-400 nm. The effects of substituents on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed. Copyright 2003 Elsevier B.V.

Automated generation and ensemble-learned matching of X-ray absorption spectra

NASA Astrophysics Data System (ADS)

Zheng, Chen; Mathew, Kiran; Chen, Chi; Chen, Yiming; Tang, Hanmei; Dozier, Alan; Kas, Joshua J.; Vila, Fernando D.; Rehr, John J.; Piper, Louis F. J.; Persson, Kristin A.; Ong, Shyue Ping

2018-12-01

X-ray absorption spectroscopy (XAS) is a widely used materials characterization technique to determine oxidation states, coordination environment, and other local atomic structure information. Analysis of XAS relies on comparison of measured spectra to reliable reference spectra. However, existing databases of XAS spectra are highly limited both in terms of the number of reference spectra available as well as the breadth of chemistry coverage. In this work, we report the development of XASdb, a large database of computed reference XAS, and an Ensemble-Learned Spectra IdEntification (ELSIE) algorithm for the matching of spectra. XASdb currently hosts more than 800,000 K-edge X-ray absorption near-edge spectra (XANES) for over 40,000 materials from the open-science Materials Project database. We discuss a high-throughput automation framework for FEFF calculations, built on robust, rigorously benchmarked parameters. FEFF is a computer program uses a real-space Green's function approach to calculate X-ray absorption spectra. We will demonstrate that the ELSIE algorithm, which combines 33 weak "learners" comprising a set of preprocessing steps and a similarity metric, can achieve up to 84.2% accuracy in identifying the correct oxidation state and coordination environment of a test set of 19 K-edge XANES spectra encompassing a diverse range of chemistries and crystal structures. The XASdb with the ELSIE algorithm has been integrated into a web application in the Materials Project, providing an important new public resource for the analysis of XAS to all materials researchers. Finally, the ELSIE algorithm itself has been made available as part of veidt, an open source machine-learning library for materials science.

A Novel Acoustic Sensor Approach to Classify Seeds Based on Sound Absorption Spectra

PubMed Central

Gasso-Tortajada, Vicent; Ward, Alastair J.; Mansur, Hasib; Brøchner, Torben; Sørensen, Claus G.; Green, Ole

2010-01-01

A non-destructive and novel in situ acoustic sensor approach based on the sound absorption spectra was developed for identifying and classifying different seed types. The absorption coefficient spectra were determined by using the impedance tube measurement method. Subsequently, a multivariate statistical analysis, i.e., principal component analysis (PCA), was performed as a way to generate a classification of the seeds based on the soft independent modelling of class analogy (SIMCA) method. The results show that the sound absorption coefficient spectra of different seed types present characteristic patterns which are highly dependent on seed size and shape. In general, seed particle size and sphericity were inversely related with the absorption coefficient. PCA presented reliable grouping capabilities within the diverse seed types, since the 95% of the total spectral variance was described by the first two principal components. Furthermore, the SIMCA classification model based on the absorption spectra achieved optimal results as 100% of the evaluation samples were correctly classified. This study contains the initial structuring of an innovative method that will present new possibilities in agriculture and industry for classifying and determining physical properties of seeds and other materials. PMID:22163455

Observation of soft X-ray spectra from a Seyfert 1 and a narrow emission-line galaxy

NASA Technical Reports Server (NTRS)

Singh, K. P.; Garmire, G. P.; Nousek, J.

1985-01-01

The 0.2-40 keV X-ray spectra of the Seyfert 1 galaxy Mrk 509 and the narrow emission-line galaxy NGC 2992 are analyzed. The results suggest the presence of a steep soft X-ray component in Mrk 509 in addition to the well-known Gamma = 1.7 component found in other active galactic nuclei in the 2-40 keV energy range. The soft X-ray component is interpreted as due to thermal emission from a hot gas, probably associated with the highly ionized gas observed to be outflowing from the galaxy. The X-ray spectrum of NGC 2992 does not show any steepening in the soft X-ray band and is consistent with a single power law (Gamma = 1.78) with very low absorbing column density of 4 x 10 to the 21st/sq cm. A model with partial covering of the nuclear X-ray source is preferred, however, to a simple model with a single power law and absorption.

The Intervening Galaxies Hypothesis of the Absorption Spectra of Quasi-Stellar Objects: Some Statistical Studies

NASA Astrophysics Data System (ADS)

Duari, Debiprosad; Narlikar, Jayant V.

This paper examines, in the light of the available data, the hypothesis that the heavy element absorption line systems in the spectra of QSOs originate through en-route absorption by intervening galaxies, halos etc. Several statistical tests are applied in two different ways to compare the predictions of the intervening galaxies hypothesis (IGH) with actual observations. The database is taken from a recent 1991 compilation of absorption line systems by Junkkarinen, Hewitt and Burbidge. Although, prima facie, a considerable gap is found between the predictions of the intervening galaxies hypothesis and the actual observations despite inclusion of any effects of clustering and some likely selection effects, the gap narrows after invoking evolution in the number density of absorbers and allowing for the incompleteness and inhomogeneity of samples examined. On the latter count the gap might be bridgeable by stretching the parameters of the theory. It is concluded that although the intervening galaxies hypothesis is a possible natural explanation to account for the absorption line systems and may in fact do so in several cases, it seems too simplistic to be able to account for all the available data. It is further stressed that the statistical techniques described here will be useful for future studies of complete and homogenous samples with a view to deciding the extent of applicability of the IGH.

Unified analysis of optical absorption spectra of carotenoids based on a stochastic model.

PubMed

Uragami, Chiasa; Saito, Keisuke; Yoshizawa, Masayuki; Molnár, Péter; Hashimoto, Hideki

2018-05-03

The chemical structures of the carotenoid molecules are very simple and one might think that the electronic feature of it is easily predicted. However, it still has so much unknown information except the correlation between the electronic energy state and the length of effective conjugation chain of carotenoids. To investigate the electronic feature of the carotenoids, the most essential method is measuring the optical absorption spectra, but simulating it from the resonance Raman spectra is also the effective way. From this reason, we studied the optical absorption spectra as well as resonance Raman spectra of 15 different kinds of cyclic carotenoid molecules, recorded in tetrahydrofuran (THF) solutions at room temperature. The whole band shapes of the absorption spectra of all these carotenoid molecules were successfully simulated based on a stochastic model using Brownian oscillators. The parameters obtained from the simulation made it possible to discuss the intermolecular interaction between carotenoids and solvent THF molecules quantitatively. Copyright © 2018. Published by Elsevier Inc.

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

Phyllosilicate absorption features in main-belt and outer-belt asteroid reflectance spectra.

PubMed

Vilas, F; Gaffey, M J

1989-11-10

Absorption features having depths up to 5% are identified in high-quality, high-resolution reflectance spectra of 16 dark asteroids in the main belt and in the Cybele and Hilda groups. Analogs among the CM2 carbonaceous chondrite meteorites exist for some of these asteroids, suggesting that these absorptions are due to iron oxides in phyllosilicates formed on the asteroidal surfaces by aqueous alteration processes. Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances.

Phyllosilicate absorption features in main-belt and outer-belt asteroid reflectance spectra

NASA Technical Reports Server (NTRS)

Vilas, Faith; Gaffey, Michael J.

1989-01-01

Absorption features having depths up to 5 percent are identified in high-quality, high-resolution reflectance spectra of 16 dark asteroids in the main belt and in the Cybele and Hilda groups. Analogs among the CM2 carbonaceous chondrite meteorites exist for some of these asteroids, suggesting that these absorptions are due to iron oxides in phyllosilicates formed on the asteroidal surfaces by aqueous alteration processes. Spectra of ten additional asteroids, located beyond the outer edge of the main belt, show no discernible absorption features, suggesting that aqueous alteration did not always operate at these heliocentric distances.

Ultra-narrow EIA spectra of 85Rb atom in a degenerate Zeeman multiplet system

NASA Astrophysics Data System (ADS)

Rehman, Hafeez Ur; Qureshi, Muhammad Mohsin; Noh, Heung-Ryoul; Kim, Jin-Tae

2015-05-01

Ultra-narrow EIA spectral features of thermal 85Rb atom with respect to coupling Rabi frequencies in a degenerate Zeeman multiplet system have been unraveled in the cases of same (σ+ -σ+ , π ∥ π) and orthogonal (σ+ -σ- , π ⊥ π)polarization configurations. The EIA signals with subnatural linewidth of ~ 100 kHz even in the cases of same circular and linear polarizations of coupling and probe laser have been obtained for the first time theoretically and experimentally. In weak coupling power limit of orthogonal polarization configurations, time-dependent transfer of coherence plays major role in the splitting of the EIA spectra while in strong coupling power, Mollow triplet-like mechanism due to strong power bring into broad split feature. The experimental ultra-narrow EIA features using one laser combined with an AOM match well with simulated spectra obtained by using generalized time-dependent optical Bloch equations.

Determination of the major groups of phytoplankton pigments from the absorption spectra of total particulate matter

NASA Technical Reports Server (NTRS)

Hoepffner, Nicolas; Sathyendranath, Shubha

1993-01-01

The contributions of detrital particles and phytoplankton to total light absorption are retrieved by nonlinear regression on the absorption spectra of total particles from various oceanic regions. The model used explains more than 96% of the variance in the observed particle absorption spectra. The resulting absorption spectra of phytoplankton are then decomposed into several Gaussian bands reflecting absorption by phytoplankton pigments. Such a decomposition, combined with high-performance liquid chromatography data on phytoplankton pigment concentrations, allows the computation of specific absorption coefficients for chlorophylls a, b, and c and carotenoids. The spectral values of these in vivo absorption coefficients are then discussed, considering the effects of secondary pigments which were not measured quantitatively. We show that these coefficients can be used to reconstruct the absorption spectra of phytoplankton at various locations and depths. Discrepancies that do occur at some stations are explained in terms of particle size effect. These coefficients can be used to determine the concentrations of phytoplankton pigments in the water, given the absorption spectrum of total particles.

Reassignment of the Iron (3) Absorption Bands in the Spectra of Mars

NASA Technical Reports Server (NTRS)

Sherman, D. M.

1985-01-01

Absorption features in the near-infrared and visible region reflectance spectra of Mars have been assigned to specific Fe (3+) crystal-field and o(2-) yields Fe(3+) charge transfer transitions. Recently, near-ultraviolet absorption spectra of iron oxides were obtained and the energies of o(2-) yields Fe(3+) charge-transfer (LMCT) transitions were determined from accurate SCF-X # alpha-SW molecular orbital calculations on (FeO6)(9-) and (FeO4)(5-) clusters. Both the theoretical and experimental results, together with existing data in the literature, show that some of the previous Fe(3+) band assignments in the spectra of Mars need to be revised. The theory of Fe(3+) spectra in minerals is discussed and applied to the spectrum of Mars.

Infrared absorption spectra of metal carbides, nitrides and sulfides

NASA Technical Reports Server (NTRS)

Kammori, O.; Sato, K.; Kurosawa, F.

1981-01-01

The infrared absorption spectra of 12 kinds of metal carbides, 11 kinds of nitrides, and 7 kinds of sulfides, a total of 30 materials, were measured and the application of the infrared spectra of these materials to analytical chemistry was discussed. The measurements were done in the frequency (wave length) range of (1400 to 400/cm (7 to 25 mu). The carbides Al4C3, B4C, the nitrides AlN, BN, Si3N4, WB, and the sulfides Al2S3, FeS2, MnS, NiS and PbS were noted to have specific absorptions in the measured region. The sensitivity of Boron nitride was especially good and could be detected at 2 to 3 micrograms in 300 mg of potassium bromide.

An investigation of a mathematical model for atmospheric absorption spectra

NASA Technical Reports Server (NTRS)

Niple, E. R.

1979-01-01

A computer program that calculates absorption spectra for slant paths through the atmosphere is described. The program uses an efficient convolution technique (Romberg integration) to simulate instrument resolution effects. A brief information analysis is performed on a set of calculated spectra to illustrate how such techniques may be used to explore the quality of the information in a spectrum.

Effect of ladder diagrams on optical absorption spectra in a quasiparticle self-consistent GW framework

NASA Astrophysics Data System (ADS)

Cunningham, Brian; Grüning, Myrta; Azarhoosh, Pooya; Pashov, Dimitar; van Schilfgaarde, Mark

2018-03-01

We present an approach to calculate the optical absorption spectra that combines the quasiparticle self-consistent GW method [Phys. Rev. B 76, 165106 (2007), 10.1103/PhysRevB.76.165106] for the electronic structure with the solution of the ladder approximation to the Bethe-Salpeter equation for the macroscopic dielectric function. The solution of the Bethe-Salpeter equation has been implemented within an all-electron framework, using a linear muffin-tin orbital basis set, with the contribution from the nonlocal self-energy to the transition dipole moments (in the optical limit) evaluated explicitly. This approach addresses those systems whose electronic structure is poorly described within the standard perturbative GW approaches with density-functional theory calculations as a starting point. The merits of this approach have been exemplified by calculating optical absorption spectra of a strongly correlated transition metal oxide, NiO, and a narrow gap semiconductor, Ge. In both cases, the calculated spectrum is in good agreement with the experiment. It is also shown that for systems whose electronic structure is well-described within the standard perturbative GW , such as Si, LiF, and h -BN , the performance of the present approach is in general comparable to the standard GW plus Bethe-Salpeter equation. It is argued that both vertex corrections to the electronic screening and the electron-phonon interaction are responsible for the observed systematic overestimation of the fundamental band gap and spectrum onset.

In situ phytoplankton absorption, fluorescence emission, and particulate backscattering spectra determined from reflectance

NASA Technical Reports Server (NTRS)

Roesler, Collin S.; Pery, Mary Jane

1995-01-01

An inverse model was developed to extract the absortion and scattering (elastic and inelastic) properties of oceanic constituents from surface spectral reflectance measurements. In particular, phytoplankton spectral absorption coefficients, solar-stimulated chlorophyll a fluorescence spectra, and particle backscattering spectra were modeled. The model was tested on 35 reflectance spectra obtained from irradiance measurements in optically diverse ocean waters (0.07 to 25.35 mg/cu m range in surface chlorophyll a concentrations). The universality of the model was demonstrated by the accurate estimation of the spectral phytoplankton absorption coefficents over a range of 3 orders of magnitude (rho = 0.94 at 500 nm). Under most oceanic conditions (chlorophyll a less than 3 mg/cu m) the percent difference between measured and modeled phytoplankton absorption coefficents was less than 35%. Spectral variations in measured phytoplankton absorption spectra were well predicted by the inverse model. Modeled volume fluorescence was weakly correlated with measured chl a; fluorescence quantum yield varied from 0.008 to 0.09 as a function of environment and incident irradiance. Modeled particle backscattering coefficients were linearly related to total particle cross section over a twentyfold range in backscattering coefficents (rho = 0.996, n = 12).

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

Absorption spectra of PTCDI: A combined UV-Vis and TD-DFT study

NASA Astrophysics Data System (ADS)

Oltean, Mircea; Calborean, Adrian; Mile, George; Vidrighin, Mihai; Iosin, Monica; Leopold, Loredana; Maniu, Dana; Leopold, Nicolae; Chiş, Vasile

2012-11-01

Absorption spectra of PTCDI (3,4,9,10-perylene-tetracarboxylic-diimide) have been investigated in chloroform, N,N'-dimethylformamide (DMF) and dimethylsulfoxide (DMSO). While no signature of assembled PTCDI molecules is observed in chloroform solution, distinct bands assigned to their aggregation have been identified in DMF and DMSO solutions. PTCDI monomers show very similar absorption patterns in chloroform and DMSO solutions. Experimental data, including the vibronic structure of the absorption spectra were explained based on the Franck-Condon approximation and quantum chemical results obtained at PBE0-DCP/6-31+G(d,p) level of theory. Geometry optimization of the first excited state leads to a nice agreement between the calculated adiabatic transition energies and experimental data.

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*.

Leaf Level Chlorophyll Fluorescence Emission Spectra: Narrow Band versus Full 650-800 nm Retrievals

NASA Astrophysics Data System (ADS)

Middleton, E.; Zhang, Q.; Campbell, P. K.; Huemmrich, K. F.; Corp, L.; Cheng, Y.

2012-12-01

Recently, chlorophyll fluorescence (ChlF) retrievals in narrow spectral regions (< 1 nm, between 750-770 nm) of the near infrared (NIR) region of Earth's reflected radiation have been achieved from satellites, including the Japanese GOSAT and the European Space Agency's Sciamachy/Envisat. However, these retrievals sample the total full-spectrum ChlF and are made at non-optimal wavelengths since they are not located at the peak fluorescence emission features. We wish to estimate the total full-spectrum ChlF based on emissions obtained at selected wavelengths. For this, we drew upon leaf emission spectra measured on corn leaves obtained from a USDA experimental cornfield in MD (USA). These emission spectra were determined for the adaxial and abaxial (i.e., top and underside) surfaces of leaves measured throughout the 2008 and 2011 growing seasons (n>400) using a laboratory instrument (Fluorolog-3, Horiba Scientific, USA), recorded in either 1 nm or 5 nm increments with monochromatic excitation wavelengths of either 532 or 420 nm. The total ChlF signal was computed as the area under the continuous spectral emission curves, summing the emission intensities (counts per second) per waveband. The individual narrow (1 or 5 nm) waveband emission intensities were linearly related to full emission values, with variable success across the spectrum. Equations were developed to estimate total ChlF from these individual wavebands. Here, we report the results for the average adaxial/abaxial emissions. Very strong relationships were achieved for the relatively high fluorescence intensities at the red chlorophyll peak, centered at 685 nm (r2= 0.98, RMSE = 5.53 x 107 photons/s) and in the nearby O2-B atmospheric absorption feature centered at 688 nm (r2 = 0.94, RMSE = 4.04 x 107), as well as in the far-red peak centered at 740 nm (r2=0.94, RMSE = 5.98 x107). Very good retrieval success occurred for the O2-A atmospheric absorption feature on the declining NIR shoulder centered at 760

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.;

Temperature-dependent mid-IR absorption spectra of gaseous hydrocarbons

NASA Astrophysics Data System (ADS)

Klingbeil, Adam E.; Jeffries, Jay B.; Hanson, Ronald K.

2007-10-01

Quantitative mid-IR absorption spectra (2500 3400 cm-1) for 12 pure hydrocarbon compounds are measured at temperatures ranging from 25 to 500 °C using an FTIR spectrometer. The hydrocarbons studied are n-pentane, n-heptane, n-dodecane, 2,2,4-trimethyl-pentane (iso-octane), 2-methyl-butane, 2-methyl-pentane, 2,4,4-trimethyl-1-pentene, 2-methyl-2-butene, propene, toluene, m-xylene, and ethylbenzene. Room-temperature measurements of neat hydrocarbon vapor were made with an instrument resolution of both 0.1 and 1 cm-1 (FWHM) to confirm that the high-resolution setting was required only to resolve the propene absorption spectrum while the spectra of the other hydrocarbons could be resolved with 1 cm-1 resolution. High-resolution (0.1 cm-1), room-temperature measurements of neat hydrocarbons were made at low pressure (˜1 Torr, 133 Pa) and compared to measurements of hydrocarbon/N2 mixtures at atmospheric pressure to verify that no pressure broadening could be observed over this pressure range. The temperature was varied between 25 and 500 °C for atmospheric-pressure measurements of hydrocarbon/N2 mixtures (Xhydrocarbon˜0.06 1.5%) and it was found that the absorption cross section shows simple temperature-dependent behavior for a fixed wavelength over this temperature range. Comparisons with previous FTIR data over a limited temperature range and with high-resolution laser absorption data over a wide temperature range show good agreement.

Theoretical studies on absorption, emission, and resonance Raman spectra of Coumarin 343 isomers

NASA Astrophysics Data System (ADS)

Wu, Wenpeng; Cao, Zexing; Zhao, Yi

2012-03-01

The vibrationally resolved spectral method and quantum chemical calculations are employed to reveal the structural and spectral properties of Coumarin 343 (C343), an ideal candidate for organic dye photosensitizers, in vacuum and solution. The results manifest that the ground-state energies are dominantly determined by different placements of hydrogen atom in carboxylic group of C343 conformations. Compared to those in vacuum, the electronic absorption spectra in methanol solvent show a hyperchromic property together with the redshift and blueshift for the neutral C343 isomers and their deprotonated anions, respectively. From the absorption, emission, and resonance Raman spectra, it is found that the maximal absorption and emission come from low-frequency modes whereas the high-frequency modes have high Raman activities. The detailed spectra are further analyzed for the identification of the conformers and understanding the potential charge transfer mechanism in their photovoltaic applications.

Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

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

Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria

2015-07-01

A systematic study of the absorption spectra of Fricke Xylenol Orange gel dosimeters has been performed, in the wavelength range from 300 nm to 700 nm. The spectrum of Xylenol Orange (without ferrous sulphate solution) has been achieved, in order to subtract its contribution from the absorption spectra of the irradiated Fricke Xylenol Orange gel dosimeters. The absorbance due to ferric ions chelated by Xylenol Orange has been studied for various irradiation doses. Two absorbance peaks are visible, mainly at low doses: the first peak increases with the dose more slowly than the second one. This effect can explain themore » apparent threshold dose that was frequently evidenced. (authors)« less

First Principles Optical Absorption Spectra of Organic Molecules Adsorbed on Titania Nanoparticles

NASA Astrophysics Data System (ADS)

Baishya, Kopinjol; Ogut, Serdar; Mete, Ersen; Gulseren, Oguz; Ellialtioglu, Sinasi

2012-02-01

We present results from first principles computations on passivated rutile TiO2 nanoparticles in both free-standing and dye-sensitized configurations to investigate the size dependence of their optical absorption spectra. The computations are performed using time-dependent density functional theory (TDDFT) as well as GW-Bethe-Salpeter-Equation (GWBSE) methods and compared with each other. We interpret the first principles spectra for free-standing TiO2 nanoparticles within the framework of the classical Mie-Gans theory using the bulk dielectric function of TiO2. We investigate the effects of the titania support on the absorption spectra of a particular set of perylene-diimide (PDI) derived dye molecules, namely brominated PDI (Br2C24H8N2O4) and its glycine and aspartine derivatives.

Excitation of photosystem I by 760 nm femtosecond laser pulses: transient absorption spectra and intermediates

NASA Astrophysics Data System (ADS)

Cherepanov, Dmitry A.; Shelaev, Ivan V.; Gostev, Fedor E.; Mamedov, Mahir D.; Petrova, Anastasia A.; Aybush, Arseniy V.; Shuvalov, Vladimir A.; Semenov, Alexey Yu; Nadtochenko, Victor A.

2017-09-01

Excitation of photosystem I (PS I) by a femtosecond 760 nm pump leads to one- and two-photon absorption. The one-photon excitation produces intermediates with transient absorption spectra similar to the spectra of the primary [{{{P}}700}+{{{A}}0}-{{A}}1] and secondary [{{{P}}700}+{{A}}0{{{A}}1}-] ion-radical pairs in the PS I reaction center. The two-photon absorption generates the upper level excited states of chlorophyll (Chl) and carotenoid molecules in the antenna. These excited states are converted into the long-lived intermediates and can be tentatively attributed to the excited and charge-transfer ion-radical states of Chl molecules and to the excited states of carotenoids in the antenna. The transient spectra of intermediates generated by two-photon excitation differ from the transient one-photon spectra of the primary and secondary ion-radical pairs.

Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using Density Functional Theory

DTIC Science & Technology

2013-08-20

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--13-9479 Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using ...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption Spectra of Fe, Mn, and Mg Water Complexes Calculated Using Density...structure associated with Fe, Mn, and Mg water complexes using time-dependent density functional theory (TD-DFT). Calculation of excited state resonance

Exciton Absorption Spectra by Linear Response Methods:Application to Conjugated Polymers

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

Mosquera, Martin A.; Jackson, Nicholas E.; Fauvell, Thomas J.

The theoretical description of the timeevolution of excitons requires, as an initial step, the calculation of their spectra, which has been inaccessible to most users due to the high computational scaling of conventional algorithms and accuracy issues caused by common density functionals. Previously (J. Chem. Phys. 2016, 144, 204105), we developed a simple method that resolves these issues. Our scheme is based on a two-step calculation in which a linear-response TDDFT calculation is used to generate orbitals perturbed by the excitonic state, and then a second linear-response TDDFT calculation is used to determine the spectrum of excitations relative to themore » excitonic state. Herein, we apply this theory to study near-infrared absorption spectra of excitons in oligomers of the ubiquitous conjugated polymers poly(3-hexylthiophene) (P3HT), poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV), and poly(benzodithiophene-thieno[3,4-b]thiophene) (PTB7). For P3HT and MEH-PPV oligomers, the calculated intense absorption bands converge at the longest wavelengths for 10 monomer units, and show strong consistency with experimental measurements. The calculations confirm that the exciton spectral features in MEH-PPV overlap with those of the bipolaron formation. In addition, our calculations identify the exciton absorption bands in transient absorption spectra measured by our group for oligomers (1, 2, and 3 units) of PTB7. For all of the cases studied, we report the dominant orbital excitations contributing to the optically active excited state-excited state transitions, and suggest a simple rule to identify absorption peaks at the longest wavelengths. We suggest our methodology could be considered for further evelopments in theoretical transient spectroscopy to include nonadiabatic effects, coherences, and to describe the formation of species such as charge-transfer states and polaron pairs.« less

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.

Trident: A Universal Tool for Generating Synthetic Absorption Spectra from Astrophysical Simulations

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

Hummels, Cameron B.; Smith, Britton D.; Silvia, Devin W.

Hydrodynamical simulations are increasingly able to accurately model physical systems on stellar, galactic, and cosmological scales; however, the utility of these simulations is often limited by our ability to directly compare them with the data sets produced by observers: spectra, photometry, etc. To address this problem, we have created trident, a Python-based open-source tool for post-processing hydrodynamical simulations to produce synthetic absorption spectra and related data. trident can (i) create absorption-line spectra for any trajectory through a simulated data set mimicking both background quasar and down-the-barrel configurations; (ii) reproduce the spectral characteristics of common instruments like the Cosmic Origins Spectrograph;more » (iii) operate across the ultraviolet, optical, and infrared using customizable absorption-line lists; (iv) trace simulated physical structures directly to spectral features; (v) approximate the presence of ion species absent from the simulation outputs; (vi) generate column density maps for any ion; and (vii) provide support for all major astrophysical hydrodynamical codes. trident was originally developed to aid in the interpretation of observations of the circumgalactic medium and intergalactic medium, but it remains a general tool applicable in other contexts.« less

Trident: A Universal Tool for Generating Synthetic Absorption Spectra from Astrophysical Simulations

NASA Astrophysics Data System (ADS)

Hummels, Cameron B.; Smith, Britton D.; Silvia, Devin W.

2017-09-01

Hydrodynamical simulations are increasingly able to accurately model physical systems on stellar, galactic, and cosmological scales; however, the utility of these simulations is often limited by our ability to directly compare them with the data sets produced by observers: spectra, photometry, etc. To address this problem, we have created trident, a Python-based open-source tool for post-processing hydrodynamical simulations to produce synthetic absorption spectra and related data. trident can (I) create absorption-line spectra for any trajectory through a simulated data set mimicking both background quasar and down-the-barrel configurations; (II) reproduce the spectral characteristics of common instruments like the Cosmic Origins Spectrograph; (III) operate across the ultraviolet, optical, and infrared using customizable absorption-line lists; (IV) trace simulated physical structures directly to spectral features; (v) approximate the presence of ion species absent from the simulation outputs; (VI) generate column density maps for any ion; and (vii) provide support for all major astrophysical hydrodynamical codes. trident was originally developed to aid in the interpretation of observations of the circumgalactic medium and intergalactic medium, but it remains a general tool applicable in other contexts.

Hierarchy of stochastic Schrödinger equation towards the calculation of absorption and circular dichroism spectra.

PubMed

Ke, Yaling; Zhao, Yi

2017-05-07

A theoretically solid and numerically exact method is presented for the calculation of absorption and circular dichroism (CD) spectra of molecular aggregates immersed in a harmonic bath constituted as the combination of some prominent quantized vibrational modes and continuous overdamped Brownian oscillators. The feasibility and the validity of newly proposed method are affirmed in the analytical monomer spectra. To go beyond the independent local bath approximation, all the correlations of site energy fluctuations and excitonic coupling fluctuations are included in our strategy, and their influence on the absorption and CD spectra is investigated based on the Frenkel exciton model of homodimer. In the end, a good fit of the absorption and part of CD spectra for the entire B800-B850 ring in the light-harvesting complexes 2 of purple bacteria to the experimental data is given, and the simulation results suggest that the asymmetry in the 800 nm region of CD spectra is actually an indication of B800-B850 inter-ring coupling.

Hierarchy of stochastic Schrödinger equation towards the calculation of absorption and circular dichroism spectra

NASA Astrophysics Data System (ADS)

Ke, Yaling; Zhao, Yi

2017-05-01

A theoretically solid and numerically exact method is presented for the calculation of absorption and circular dichroism (CD) spectra of molecular aggregates immersed in a harmonic bath constituted as the combination of some prominent quantized vibrational modes and continuous overdamped Brownian oscillators. The feasibility and the validity of newly proposed method are affirmed in the analytical monomer spectra. To go beyond the independent local bath approximation, all the correlations of site energy fluctuations and excitonic coupling fluctuations are included in our strategy, and their influence on the absorption and CD spectra is investigated based on the Frenkel exciton model of homodimer. In the end, a good fit of the absorption and part of CD spectra for the entire B800-B850 ring in the light-harvesting complexes 2 of purple bacteria to the experimental data is given, and the simulation results suggest that the asymmetry in the 800 nm region of CD spectra is actually an indication of B800-B850 inter-ring coupling.

Absorption spectra and light penetration depth of normal and pathologically altered human skin

NASA Astrophysics Data System (ADS)

Barun, V. V.; Ivanov, A. P.; Volotovskaya, A. V.; Ulashchik, V. S.

2007-05-01

A three-layered skin model (stratum corneum, epidermis, and dermis) and engineering formulas for radiative transfer theory are used to study absorption spectra and light penetration depths of normal and pathologically altered skin. The formulas include small-angle and asymptotic approximations and a layer-addition method. These characteristics are calculated for wavelengths used for low-intensity laser therapy. We examined several pathologies such as vitiligo, edema, erythematosus lupus, and subcutaneous wound, for which the bulk concentrations of melanin and blood vessels or tissue structure (for subcutaneous wound) change compared with normal skin. The penetration depth spectrum is very similar to the inverted blood absorption spectrum. In other words, the depth is minimal at blood absorption maxima. The calculated absorption spectra enable the power and irradiation wavelength providing the required light effect to be selected. Relationships between the penetration depth and the diffuse reflectance coefficient of skin (unambiguously expressed through the absorption coefficient) are analyzed at different wavelengths. This makes it possible to find relationships between the light fields inside and outside the tissue.

Near infrared cavity enhanced absorption spectra of atmospherically relevant ether-1, 4-Dioxane.

PubMed

Chandran, Satheesh; Varma, Ravi

2016-01-15

1, 4-Dioxane (DX) is a commonly found ether in industrially polluted atmosphere. The near infrared absorption spectra of this compound has been recorded in the region 5900-8230 cm(-1) with a resolution of 0.08 cm(-1) using a novel Fourier transform incoherent broadband cavity-enhanced absorption spectrometer (FT-IBBCEAS). All recorded spectra were found to contain regions that are only weakly perturbed. The possible combinations of fundamental modes and their overtone bands corresponding to selected regions in the measured spectra are tabulated. Two interesting spectral regions were identified as 5900-6400 cm(-1) and 8100-8230 cm(-1). No significant spectral interference due to presence of water vapor was observed suggesting the suitability of these spectral signatures for spectroscopic in situ detection of DX. The technique employed here is much more sensitive than standard Fourier transform spectrometer measurements on account of long effective path length achieved. Hence significant enhancement of weaker absorption lines above the noise level was observed as demonstrated by comparison with an available measurement from database. Copyright © 2015 Elsevier B.V. All rights reserved.

Studies of Time-Resolved Fluorescence Spectroscopy and Resolved Absorption Spectra of Nucleic Acid Components.

NASA Astrophysics Data System (ADS)

Fu, Yingxian

1993-01-01

There is considerable uncertainty about dynamic aspects of the photophysics of the adenylyl chromophore, stemming from the discordant values reported for the room temperature fluorescence lifetimes (tau_1 = 5 ps, tau_2 = 330 ps for 9MeAde; tau_1 = 290 ps, tau_2 = 4.17 ns for ATP). Spectra reported in conjunction with these lifetimes create difficulties in assignment of emission. To clarify this situation I have investigated the fluorescence decay times and time -resolved emission spectra of adenylyl compounds under a variety of conditions (concentration, pH, solvent) using sub-ns laser excitation at 265 nm together with gated fast sampling (100 ps) detection and signal averaging. Multi -component decays and spectra are observed in aqueous solution. Major slow components (tau = 4.4 +/- 0.2 ns) with emission maxima at 380 nm are found for all components at pH 1.1 and for ATP at pH 4.4. At pH 7 a fast component (<100 ps) predominates. There is no marked evidence for a concentration dependence, the oscillator strengths are 10^ {-3}-10^{-5} and transitions must be classified as weakly forbidden. Single component emission is observed in acetonitrile and ethanol. The UV absorption spectra of biomolecules d(CG) and polyd(GC)cdotpolyd(GC) exhibit the different hypochromic effects due to different interactions between guanosine(G) and cytidine(C) in stacked form. The present work has been carried out to explain this quantitatively. To approach this problem the absorption spectra of G and C have been resolved into gaussian components using the PeakFit program. The absorption spectra (220-310 nm) of d(CG) and polyd(GC)cdotpolyd(GC) have been fitted with gaussian components of G and C (in the order of increasing energy, G1 and G2, and C1, C2 and C3, respectively), and the contribution to both spectra from individual gaussians is estimated in terms of oscillator strengths. The fitting results suggest that the small hypochromism in absorption spectrum of d(CG) may be attributed

Photoluminescence and gain/absorption spectra of a driven-dissipative electron-hole-photon condensate

NASA Astrophysics Data System (ADS)

Hanai, Ryo; Littlewood, Peter B.; Ohashi, Yoji

2018-06-01

We investigate theoretically nonequilibrium effects on photoluminescence and gain/absorption spectra of a driven-dissipative exciton-polariton condensate, by employing the combined Hartree-Fock-Bogoliubov theory with the generalized random phase approximation extended to the Keldysh formalism. Our calculated photoluminescence spectra is in semiquantitative agreement with experiments, where features such as a blue shift of the emission from the condensate, the appearance of the dispersionless feature of a diffusive Goldstone mode, and the suppression of the dispersive profile of the mode are obtained. We show that the nonequilibrium nature of the exciton-polariton condensate strongly suppresses the visibility of the Bogoliubov dispersion in the negative energy branch (ghost branch) in photoluminescence spectra. We also show that the trace of this branch can be captured as a hole burning effect in gain/absorption spectra. Our results indicate that the nonequilibrium nature of the exciton-polariton condensate strongly reduces quantum depletion, while a scattering channel to the ghost branch is still present.

Protonation effects on the UV/Vis absorption spectra of imatinib: a theoretical and experimental study.

PubMed

Grante, Ilze; Actins, Andris; Orola, Liana

2014-08-14

An experimental and theoretical investigation of protonation effects on the UV/Vis absorption spectra of imatinib showed systematic changes of absorption depending on the pH, and a new absorption band appeared below pH 2. These changes in the UV/Vis absorption spectra were interpreted using quantum chemical calculations. The geometry of various imatinib cations in the gas phase and in ethanol solution was optimized with the DFT/B3LYP method. The resultant geometries were compared to the experimentally determined crystal structures of imatinib salts. The semi-empirical ZINDO-CI method was employed to calculate the absorption lines and electronic transitions. Our study suggests that the formation of the extra near-UV absorption band resulted from an increase of imatinib trication concentration in the solution, while the rapid increase of the first absorption maximum could be attributed to both the formation of imatinib trication and tetracation. Copyright © 2014 Elsevier B.V. All rights reserved.

Narrow chaotic compound autoionizing states in atomic spectra

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

Flambaum, V.V.; Gribakina, A.A.; Gribakin, G.F.

1996-09-01

Simultaneous excitation of several valence electrons in atoms gives rise to a dense spectrum of compound autoionizing states (AIS). These states are almost chaotic superpositions of large numbers of many-electron basis states built of single-electron orbitals. The mean level spacing {ital D} between such states is very small (e.g., {ital D}{lt}0.01 eV for the numerical example of {ital J}{sup {pi}}=4{sup {minus}} states of Ce just above the ionization threshold). The autoionization widths of these states estimated by perturbations, {gamma}=2{pi}{vert_bar}{ital W}{vert_bar}{sup 2}, where {ital W} is the Coulomb matrix element coupling the AIS to the continuum, are also small, but comparablemore » with {ital D} in magnitude: {gamma}{approximately}{ital D}. Hence the nonperturbative interaction of AIS with each other via the continuum is very essential. It suppresses greatly the widths of the autoionizing resonances ({Gamma}{approx_equal}{ital D}{sup 2}/3{gamma}{lt}{ital D}), and leads to the emergence of a {open_quote}{open_quote}collective{close_quote}{close_quote} doorway state which accumulates a large share of the total width. This state is in essence a modified single-particle continuum decoupled from the resonances due to its large width. Narrow compound AIS should be a common feature of atomic spectra at energies sufficient for excitation of several electrons above the ground-state configuration. The narrow resonances can be observed as peaks in the photoabsorption, or, in electron-ion scattering, as Fano-type profiles on the background provided by the wide doorway-state resonance. It is also shown that the statistics of electromagnetic and autoionization amplitudes involving compound states are close to Gaussian. {copyright} {ital 1996 The American Physical Society.}« less

A Simple Demonstration of Absorption Spectra Using Tungsten Holiday Lights

ERIC Educational Resources Information Center

Birriel, Jennifer J.

2009-01-01

In a previous paper submitted to the Demonstrations section (Birriel 2008, "Astronomy Education Review," 7, 147), I discussed using commercially available incandescent light bulbs for the purpose of demonstrating absorption spectra in the classroom or laboratory. This demonstration solved a long-standing problem that many of astronomy instructors…

Plasma Reflection in Multigrain Layers of Narrow-Bandgap Semiconductors

NASA Astrophysics Data System (ADS)

Zhukov, N. D.; Shishkin, M. I.; Rokakh, A. G.

2018-04-01

Qualitatively similar spectral characteristics of plasma-resonance reflection in the region of 15-25 μm were obtained for layers of electrodeposited submicron particles of InSb, InAs, and GaAs and plates of these semiconductors ground with M1-grade diamond powder. The most narrow-bandgap semiconductor InSb (intrinsic absorption edge ˜7 μm) is characterized by an absorption band at 2.1-2.3 μm, which is interpreted in terms of the model of optical excitation of electrons coupled by the Coulomb interaction. The spectra of a multigrain layer of chemically deposited PbS nanoparticles (50-70 nm) exhibited absorption maxima at 7, 10, and 17 μm, which can be explained by electron transitions obeying the energy-quantization rules for quantum dots.

Absorption in X-ray spectra of high-redshift quasars

NASA Technical Reports Server (NTRS)

Elvis, Martin; Fiore, Fabrizio; Wilkes, Belinda; Mcdowell, Jonathan; Bechtold, Jill

1994-01-01

We present evidence that X-ray absorption is common in high-redshift quasars. We have studied six high-redshift (z approximately 3) quasars with the ROSAT Position Sensitive Proportional Counter (PSPC) of which four are in directions of low Galactic N(sub H). Three out of these four show excess absorption, while only three in approximately 50 z approximately less than 0.4 quasars do, indicating that such absorption must be common, but not ubiquitous, at high redshifts, and that the absorbers must lie at z greater than 0.4. The six quasars were: S5 0014+81, Q0420-388, PKS 0438-436, S4 0636+680. PKS 2000-330, PKS 2126-158, which have redshifts between 2.85 and 3.78. PKS 0438-436 and PKS 2126-158 show evidence for absorption above the local Galactic value at better than 99.999% confidence level. If the absorber is at the redshift of the quasar, then values of N(sub H) = (0.86(+0.49, -0.28)) x 10(exp 22) atoms/sq cm for PKS 0438-436, and N(sub H) = (1.45(+1.20, -0.64)) x 10(exp 22) atoms/ sq cm for PKS 2126-158, are implied, assuming solar abundances. The spectrum of S4 0636+680 also suggests the presence of a similarly large absorption column density at the 98% confidence level. This absorption reverses the trend for the most luminous active galactic nuclei (AGN) to have the least X-ray absorption, so a new mechanism is likely to be responsible. Intervening absorption due to damped Lyman(alpha) systems is a plausible cause. We also suggest, as an intrinsic model, that intracluster material, e.g., a cooling flow, around the quasar could account for both the X-ray spectrum and other properties of these quasars. All the quasars are radio-loud and three are gigahertz peaked (two of the three showing absorption). No excess absorption above the Galactic value is seen toward Q0420-388. This quasar has two damped Lyman(alpha) systems at z = 3.08. The limit on the X-ray column density implies a low ionization fraction, N(H I)/N(H) approximately greater than 4 x 10(exp -3) (3

THERMAL ABSORPTION AS THE CAUSE OF GIGAHERTZ-PEAKED SPECTRA IN PULSARS AND MAGNETARS

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

Lewandowski, Wojciech; Rożko, Karolina; Kijak, Jarosław

2015-07-20

We present a model that explains the observed deviation of the spectra of some pulsars and magnetars from the power-law spectra that are seen in the bulk of the pulsar population. Our model is based on the assumption that the observed variety of pulsar spectra can be naturally explained by the thermal free–free absorption that takes place in the surroundings of the pulsars. In this context, the variety of the pulsar spectra can be explained according to the shape, density, and temperature of the absorbing media and the optical path of the line of sight across it. We have putmore » specific emphasis on the case of the radio magnetar SGR J1745–2900 (also known as the Sgr A* magnetar), modeling the rapid variations of the pulsar spectrum after the outburst of 2013 April as due to the free–free absorption of the radio emission in the electron material ejected during the magnetar outburst. The ejecta expands with time and consequently the absorption rate decreases and the shape of the spectrum changes in such a way that the peak frequency shifts toward the lower radio frequencies. In the hypothesis of an absorbing medium, we also discuss the similarity between the spectral behavior of the binary pulsar B1259–63 and the spectral peculiarities of isolated pulsars.« less

Ionic species produced on gamma radiolysis: Studies by matrix isolation technique—I. Electronic absorption spectra of perfluorosubstituted aromatic radical anions

NASA Astrophysics Data System (ADS)

Shou-te, Lian C. T.; Mittal, Jai P.

The absorption spectra of several perfluorosubstituted aromatic radical anions are compared with the corresponding perhydro compounds in which the various transitions involved have been assigned to those predicted theoretically. The electronic absorption spectra were obtained for pentafluorostyrene, pentafluorobenzaldehyde, pentafluorobenzoic acid, pentafluorobenzonitride, tetrafluorophthalic acid and pentafluoroaniline, by gamma radiolysis in 2-methyltetrahydrofuran at 77 K. A general similarity in the absorption spectra between the perfluorinated and the corresponding perhydro radical anion is observed except for a shift in the absorption band.

Absorption and emission spectra of Li atoms trapped in rare gas matrices

NASA Astrophysics Data System (ADS)

Wright, J. J.; Balling, L. C.

1980-10-01

Pulsed-dye-laser excitation has been used to investigate the optical absorption and emission spectra of Li atoms trapped in Ar, Kr, and Xe matrices at 10 °K. Attempts to stabilize Li atoms in a Ne matrix at 2 °K were unsuccessful. Results for all three rare gases were qualitatively the same. White light absorption scans showed a single absorption with three peaks centered near the free-atom 2s→2p transition wavelength. The intensity of fluorescence produced by dye-laser excitation within this absorption band was measured as a function of emission wavelength. Excitation of the longest- and shortest-wavelength absorption peaks produced identical emission profiles, but no distinct fluorescence signal was detected when the laser was tuned to the central absorption peaks, indicating that the apparent absorption triplet is actually the superposition of a singlet and a doublet absorption originating from two different trapping sites. No additional absorption bands were detected.

Effect of pyridine on infrared absorption spectra of copper phthalocyanine.

PubMed

Singh, Sukhwinder; Tripathi, S K; Saini, G S S

2008-02-01

Infrared absorption spectra of copper phthalocyanine in KBr pellet and pyridine solution in 400-1625 and 2900-3200 cm(-1)regions are reported. In the IR spectra of solid sample, presence of weak bands, which are forbidden according to the selection rules of D4h point group, is explained on the basis of distortion in the copper phthalocyanine molecule caused by the crystal packing effects. Observation of a new band at 1511 cm(-1) and change in intensity of some other bands in pyridine are interpreted on the basis of coordination of the solvent molecule with the central copper ion.

Applications of principal component analysis to breath air absorption spectra profiles classification

NASA Astrophysics Data System (ADS)

Kistenev, Yu. V.; Shapovalov, A. V.; Borisov, A. V.; Vrazhnov, D. A.; Nikolaev, V. V.; Nikiforova, O. Y.

2015-12-01

The results of numerical simulation of application principal component analysis to absorption spectra of breath air of patients with pulmonary diseases are presented. Various methods of experimental data preprocessing are analyzed.

Calculation of optical and K pre-edge absorption spectra for ferrous iron of distorted sites in oxide crystals

NASA Astrophysics Data System (ADS)

Vercamer, Vincent; Hunault, Myrtille O. J. Y.; Lelong, Gérald; Haverkort, Maurits W.; Calas, Georges; Arai, Yusuke; Hijiya, Hiroyuki; Paulatto, Lorenzo; Brouder, Christian; Arrio, Marie-Anne; Juhin, Amélie

2016-12-01

Advanced semiempirical calculations have been performed to compute simultaneously optical absorption and K pre-edge x-ray absorption spectra of Fe2 + in four distinct site symmetries found in minerals. The four symmetries, i.e., a distorted octahedron, a distorted tetrahedron, a square planar site, and a trigonal bipyramidal site, are representative of the Fe2 + sites found in crystals and glasses. A particular attention has been paid to the definition of the p -d hybridization Hamiltonian which occurs for noncentrosymmetric symmetries in order to account for electric dipole transitions. For the different sites under study, an excellent agreement between calculations and experiments was found for both optical and x-ray absorption spectra, in particular in terms of relative intensities and energy positions of electronic transitions. To our knowledge, these are the first calculations of optical absorption spectra on Fe2 + placed in such diverse site symmetries, including centrosymmetric sites. The proposed theoretical model should help to interpret the features of both the optical absorption and the K pre-edge absorption spectra of 3 d transition metal ions and to go beyond the usual fingerprint interpretation.

The absorption spectra of the complexes of uranium (VI) with some β-diketones

USGS Publications Warehouse

Feinstein, H.I.

1956-01-01

The absorption spectra of the complexes of uranium (VI) with four β-dike tones were determined under various conditions of pH, concentration of uranium, and alcohol concentration. Under optimum conditions, the maximum molar absorptivity (31,200) is obtained using 2-furoyltrifluoroacetone. This compares with about 4,000 and 19,000 for the thiocyanate and dibenzoylmethane complexes, respectively.

Dependence of the electronic absorption spectra of aqueous solutions of iodine monochloride on the conditions of dilution and storage time

NASA Astrophysics Data System (ADS)

Klyubin, V. V.; Klyubina, K. A.; Makovetskaya, K. N.

2017-04-01

The electronic absorption spectra of aqueous solutions of iodine monochloride ICl are studied. The spectra of as-prepared solutions display the absorption band associated with hydrated ICl molecules. An additional band indicating that molecular iodine was formed in the solution emerges in the spectrum as dissolution takes place. Only the band belonging to iodine monochloride remains in the absorption spectra, and no additional bands appear after chloride anions Cl- are added to the solution. The absorption spectrum becomes more complex when ICl is dissolved in an alkaline medium. The band belonging to molecular iodine emerges in the spectra at low alkali concentrations, while being transformed to other shorter-wavelength bands at high alkali concentrations (pH ≥ 12).

The Associated Absorption Features in Quasar Spectra of the Sloan Digital Sky Survey. I. Mg II Absorption Doublets

NASA Astrophysics Data System (ADS)

Chen, Zhi-Fu; Huang, Wei-Rong; Pang, Ting-Ting; Huang, Hong-Yan; Pan, Da-Sheng; Yao, Min; Nong, Wei-Jing; Lu, Mei-Mei

2018-03-01

Using the SDSS spectra of quasars included in the DR7Q or DR12Q catalogs, we search for Mg II λλ2796, 2803 narrow absorption doublets in the spectra data around Mg II λ2798 emission lines. We obtain 17,316 Mg II doublets, within the redshift range of 0.3299 ≤ z abs ≤ 2.5663. We find that a velocity offset of υ r < 6000 km s‑1 is a safe boundary to constrain the vast majority of associated Mg II systems, although we find some doublets at υ r > 6000 km s‑1. If associated Mg II absorbers are defined by υ r < 6000 km s‑1, ∼33.3% of the absorbers are supposed to be contaminants of intervening systems. Removing the 33.3% contaminants, ∼4.5% of the quasars present at least one associated Mg II system with {W}{{r}}λ 2796≥slant 0.2 \\mathringA . The fraction of associated Mg II systems with high-velocity outflows correlates with the average luminosities of their central quasars, indicating a relationship between outflows and the quasar feedback power. The υ r distribution of the outflow Mg II absorbers is peaked at 1023 km s‑1, which is smaller than the corresponding value of the outflow C IV absorbers. The redshift number density evolution of absorbers (dn/dz) limited by υ r > ‑3000 km s‑1 differs from that of absorbers constrained by υ r > 2000 km s‑1. Absorbers limited by υ r > 2000 km s‑1 and higher values exhibit profiles similar to dn/dz. In addition, the dn/dz is smaller when absorbers are constrained with larger υ r . The distributions of equivalent widths, and the ratio of {W}rλ 2796/{W}rλ 2803, are the same for associated and intervening systems, and independent of quasar luminosity.

Exploration of faint absorption bands in the reflectance spectra of the asteroids by method of optimal smoothing: Vestoids

NASA Astrophysics Data System (ADS)

Shestopalov, D. I.; McFadden, L. A.; Golubeva, L. F.

2007-04-01

An optimization method of smoothing noisy spectra was developed to investigate faint absorption bands in the visual spectral region of reflectance spectra of asteroids and the compositional information derived from their analysis. The smoothing algorithm is called "optimal" because the algorithm determines the best running box size to separate weak absorption bands from the noise. The method is tested for its sensitivity to identifying false features in the smoothed spectrum, and its correctness of forecasting real absorption bands was tested with artificial spectra simulating asteroid reflectance spectra. After validating the method we optimally smoothed 22 vestoid spectra from SMASS1 [Xu, Sh., Binzel, R.P., Burbine, T.H., Bus, S.J., 1995. Icarus 115, 1-35]. We show that the resulting bands are not telluric features. Interpretation of the absorption bands in the asteroid spectra was based on the spectral properties of both terrestrial and meteorite pyroxenes. The bands located near 480, 505, 530, and 550 nm we assigned to spin-forbidden crystal field bands of ferrous iron, whereas the bands near 570, 600, and 650 nm are attributed to the crystal field bands of trivalent chromium and/or ferric iron in low-calcium pyroxenes on the asteroids' surface. While not measured by microprobe analysis, Fe 3+ site occupancy can be measured with Mössbauer spectroscopy, and is seen in trace amounts in pyroxenes. We believe that trace amounts of Fe 3+ on vestoid surfaces may be due to oxidation from impacts by icy bodies. If that is the case, they should be ubiquitous in the asteroid belt wherever pyroxene absorptions are found. Pyroxene composition of four asteroids of our set is determined from the band position of absorptions at 505 and 1000 nm, implying that there can be orthopyroxenes in all range of ferruginosity on the vestoid surfaces. For the present we cannot unambiguously interpret of the faint absorption bands that are seen in the spectra of 4005 Dyagilev, 4038

Infrared absorption spectra of molecular crystals: Possible evidence for small-polaron formation?

NASA Astrophysics Data System (ADS)

Pržulj, Željko; Čevizović, Dalibor; Zeković, Slobodan; Ivić, Zoran

2008-09-01

The temperature dependence of the position of the so-called anomalous band peaked at 1650cm in the IR-absorption spectrum of crystalline acetanilide (ACN) is theoretically investigated within the small-polaron theory. Its pronounced shift towards the position of the normal band is predicted with the rise of temperature. Interpretation of the IR-absorption spectra in terms of small-polaron model has been critically assessed on the basis of these results.

Aprotic solvents effect on the UV-visible absorption spectra of bixin

NASA Astrophysics Data System (ADS)

Rahmalia, Winda; Fabre, Jean-François; Usman, Thamrin; Mouloungui, Zéphirin

2014-10-01

We describe here the effects of aprotic solvents on the spectroscopic characteristics of bixin. Bixin was dissolved in dimethyl sulfoxide, acetone, dichloromethane, ethyl acetate, chloroform, dimethyl carbonate, cyclohexane and hexane, separately, and its spectra in the resulting solutions were determined by UV-visible spectrophotometry at normal pressure and room temperature. We analyzed the effect of aprotic solvents on λmax according to Onsager cavity model and Hansen theory, and determined the approximate absorption coefficient with the Beer-Lambert law. We found that the UV-visible absorption spectra of bixin were found to be solvent dependent. The S0 → S2 transition energy of bixin in solution was dependent principally on the refractive index of the solvents and the bixin-solvent dispersion interaction. There was a small influence of the solvents dielectric constant, permanent dipole interaction and hydrogen bonding occurred between bixin and solvents. The absorbance of bixin in various solvents, with the exception of hexane, increased linearly with concentration.

Calculation of Vibrational and Electronic Excited-State Absorption Spectra of Arsenic-Water Complexes Using Density Functional Theory

DTIC Science & Technology

2016-06-03

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--16-9681 Calculation of Vibrational and Electronic Excited-State Absorption Spectra...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Calculation of Vibrational and Electronic Excited-State Absorption Spectra of Arsenic-Water Complexes Using...Unclassified Unlimited Unclassified Unlimited 59 Samuel G. Lambrakos (202) 767-2601 Calculations are presented of vibrational and electronic excited-state

Single crystal absorption spectra of synthetic Ti, Fe-substituted pyropes

NASA Astrophysics Data System (ADS)

Khomenko, V. M.; Langer, K.; Andrut, M.; Koch-Müller, M.; Vishnevsky, A. A.

1994-11-01

Synthetic pyrope crystals up to 0.5 mm in diameter, substituted by titanium or by titanium plus iron, were grown under defined conditions of P, T, f_{O_2 } in the presence of water using a piston-cylinder device. The crystals were characterized by X-ray and microprobe techniques. Their single-crystal optical absorption spectra were measured by means of a microscope-spectrometer. Two absorption bands at 16100 and 22300 cm{cm-1} in the spectra of pale-blue Fe-free Ti-bearing pyropes, grown under reduced conditions, were identified as originating from spin-allowed transitions, derived from 2 T 2g → 2 E g of octahedral Ti3+ ions. The splitting value of the excited 2E g state, 6200 cm-1, and the crystal field parameter of Ti3+ in pyrope Δ 0 = 19 200 cm-1 are both in agreement with literature data. In spectra of brown Fe, Ti-bearing garnets, a broad band at 23000 cm-1 was interpreted as a Fe2+[8] → Ti4+[6] charge-transfer band. The spectral position and width of this band agree with those observed for a FeTi charge transfer band in natural garnets. Fe, Ti-containing garnets synthesized at relatively high oxygen fugacity (10-11,0 atm), which permits a fraction of Fe3+ to enter the garnet, show an additional Fe2+[8] → Fe3+[6] charge transfer band at 19800 cm-1.

Electronic spectra of astrophysically interesting cations

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

Maier, John P., E-mail: j.p.maier@unibas.ch; Rice, Corey A., E-mail: j.p.maier@unibas.ch; Mazzotti, Fabio J., E-mail: j.p.maier@unibas.ch

2015-01-22

The electronic spectra of polyacetylene cations were recorded at 20K in the laboratory in an ion trap instrument. These can then be compared with diffuse interstellar band (DIB) absorptions. Examination of recently published data shows that the attribution of a weak DIB at ∼506.9 nm to diacetylene cation is not justified. Study of the higher excited electronic states of polyacetylene cations shows that their widths can still be sufficiently narrow for consideration as DIB carriers.

Understanding the features in the ultrafast transient absorption spectra of CdSe quantum dots

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Do, Thanh Nhut; Ong, Xuanwei; Chan, Yinthai; Tan, Howe-Siang

2016-12-01

We describe a model to explain the features of the ultrafast transient absorption (TA) spectra of CdSe core type quantum dots (QDs). The measured TA spectrum consists of contributions by the ground state bleach (GSB), stimulated emission (SE) and excited state absorption (ESA) processes associated with the three lowest energy transition of the QDs. We model the shapes of the GSB, SE and ESA spectral components after fits to the linear absorption. The spectral positions of the ESA components take into account the biexcitonic binding energy. In order to obtain the correct weightage of the GSB, SE and ESA components to the TA spectrum, we enumerate the set of coherence transfer pathways associated with these processes. From our fits of the experimental TA spectra of 65 Å diameter QDs, biexcitonic binding energies for the three lowest energy transitions are obtained.

[Study on the effect of solar spectra on the retrieval of atmospheric CO2 concentration using high resolution absorption spectra].

PubMed

Hu, Zhen-Hua; Huang, Teng; Wang, Ying-Ping; Ding, Lei; Zheng, Hai-Yang; Fang, Li

2011-06-01

Taking solar source as radiation in the near-infrared high-resolution absorption spectrum is widely used in remote sensing of atmospheric parameters. The present paper will take retrieval of the concentration of CO2 for example, and study the effect of solar spectra resolution. Retrieving concentrations of CO2 by using high resolution absorption spectra, a method which uses the program provided by AER to calculate the solar spectra at the top of atmosphere as radiation and combine with the HRATS (high resolution atmospheric transmission simulation) to simulate retrieving concentration of CO2. Numerical simulation shows that the accuracy of solar spectrum is important to retrieval, especially in the hyper-resolution spectral retrieavl, and the error of retrieval concentration has poor linear relation with the resolution of observation, but there is a tendency that the decrease in the resolution requires low resolution of solar spectrum. In order to retrieve the concentration of CO2 of atmosphere, the authors' should take full advantage of high-resolution solar spectrum at the top of atmosphere.

Substituent and Solvent Effects on the Absorption Spectra of Cation-π Complexes of Benzene and Borazine: A Theoretical Study.

PubMed

Sarmah, Nabajit; Bhattacharyya, Pradip Kr; Bania, Kusum K

2014-05-29

Time-dependent density functional theory (TDDFT) has been used to predict the absorption spectra of cation-π complexes of benzene and borazine. Both polarized continuum model (PCM) and discrete solvation model (DSM) and a combined effect of PCM and DSM on the absorption spectra have been elucidated. With decrease in size of the cation, the π → π* transitions of benzene and borazine are found to undergo blue and red shift, respectively. A number of different substituents (both electron-withdrawing and electron-donating) and a range of solvents (nonpolar to polar) have been considered to understand the effect of substituent and solvents on the absorption spectra of the cation-π complexes of benzene and borazine. Red shift in the absorption spectra of benzene cation-π complexes are observed with both electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). The same trend has not been observed in the case of substituted borazine cation-π complexes. The wavelength of the electronic transitions corresponding to cation-π complexes correlates well with the Hammet constants (σ p and σ m ). This correlation indicates that the shifting of spectral lines of the cation-π complexes on substitution is due to both resonance and inductive effect. On incorporation of solvent phases, significant red or blue shifting in the absorption spectra of the complexes has been observed. Kamlet-Taft multiparametric equation has been used to explain the effect of solvent on the absorption spectra of complexes. Polarity and polarizability are observed to play an important role in the solvatochromism of the cation-π complexes.

Laboratory absorption spectra of molecules at interstellar cloud temperatures - First measurements on CO at about 97 nm

NASA Technical Reports Server (NTRS)

Smith, P. L.; Yoshino, K.; Stark, G.; Ito, K.; Stevens, M. H.

1991-01-01

In the 91-100 nm spectral region, where absorption of photons by interstellar CO usually leads to dissociation, laboratory spectra obtained at 295 K show that most CO bands are both overlapped and perturbed. Reliable band oscillator strengths cannot be extracted from such spectra. As a consequence, synthetic extreme-ultraviolet absorption spectra for CO at the low temperatures that prevail in interstellar clouds are uncertain. A supersonic expansion technique has been used to cool CO to 30 K and three bands in the 97-nm region have been studied with high spectral resolution. The measured spectrum at 30 K is in reasonable agreement with some published modeled spectra, but the ratios of integrated cross sections are somewhat different from those determined from low resolution spectra obtained at 295 K, in which the bands are blended.

X-ray absorption spectra: Graphene, h-BN, and their alloy

NASA Astrophysics Data System (ADS)

Bhowmick, Somnath; Rusz, Jan; Eriksson, Olle

2013-04-01

Using first-principles density functional theory calculations, in conjunction with the Mahan-Nozières-de Dominicis theory, we calculate the x-ray absorption spectra of the alloys of graphene and monolayer hexagonal boron nitride on a Ni (111) substrate. The chemical neighborhood of the constituent atoms (B, C, and N) inside the alloy differs from that of the parent phases. In a systematic way, we capture the change in the K-edge spectral shape, depending on the chemical neighborhood of B, C, and N. Our work also reiterates the importance of the dynamical core-hole screening for a proper description of the x-ray absorption process in sp2-bonded layered materials.

Universal formulation of excitonic linear absorption spectra in all semiconductor microstructures

NASA Astrophysics Data System (ADS)

Lefebvre, Pierre; Christol, Philippe; Mathieu, Henry

1995-01-01

We present a generalization of the well-known exciton absorption calculations of Elliott [Phys. Rev. 108, 1384 (1957)], in the 3-dimensional case, and of Shinada and Sugano [J. Phys. Soc. Japan 21, 1936 (1966)], for 2-dimensional media: We calculate the optical absorption spectra of bound and unbound exciton states, by using a metric space with a noninteger dimension α (1 < α), obtaining almost exactly the same theoretical lineshapes as those resulting from accurate but costly numerical approaches [Chuang et al. Phys. Rev. B, 43, 1500 (1991); Benner and Haug, Phys. Rev. B 47, 15750 (1993)].

Aprotic solvents effect on the UV-visible absorption spectra of bixin.

PubMed

Rahmalia, Winda; Fabre, Jean-François; Usman, Thamrin; Mouloungui, Zéphirin

2014-10-15

We describe here the effects of aprotic solvents on the spectroscopic characteristics of bixin. Bixin was dissolved in dimethyl sulfoxide, acetone, dichloromethane, ethyl acetate, chloroform, dimethyl carbonate, cyclohexane and hexane, separately, and its spectra in the resulting solutions were determined by UV-visible spectrophotometry at normal pressure and room temperature. We analyzed the effect of aprotic solvents on λmax according to Onsager cavity model and Hansen theory, and determined the approximate absorption coefficient with the Beer-Lambert law. We found that the UV-visible absorption spectra of bixin were found to be solvent dependent. The S0→S2 transition energy of bixin in solution was dependent principally on the refractive index of the solvents and the bixin-solvent dispersion interaction. There was a small influence of the solvents dielectric constant, permanent dipole interaction and hydrogen bonding occurred between bixin and solvents. The absorbance of bixin in various solvents, with the exception of hexane, increased linearly with concentration. Copyright © 2014 Elsevier B.V. All rights reserved.

A wavelet analysis for the X-ray absorption spectra of molecules

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

Penfold, T. J.; Ecole polytechnique Federale de Lausanne, Laboratoire de chimie et biochimie computationnelles, ISIC, FSB-BCH, CH-1015 Lausanne; SwissFEL, Paul Scherrer Inst, CH-5232 Villigen

2013-01-07

We present a Wavelet transform analysis for the X-ray absorption spectra of molecules. In contrast to the traditionally used Fourier transform approach, this analysis yields a 2D correlation plot in both R- and k-space. As a consequence, it is possible to distinguish between different scattering pathways at the same distance from the absorbing atom and between the contributions of single and multiple scattering events, making an unambiguous assignment of the fine structure oscillations for complex systems possible. We apply this to two previously studied transition metal complexes, namely iron hexacyanide in both its ferric and ferrous form, and a rheniummore » diimine complex, [ReX(CO){sub 3}(bpy)], where X = Br, Cl, or ethyl pyridine (Etpy). Our results demonstrate the potential advantages of using this approach and they highlight the importance of multiple scattering, and specifically the focusing phenomenon to the extended X-ray absorption fine structure (EXAFS) spectra of these complexes. We also shed light on the low sensitivity of the EXAFS spectrum to the Re-X scattering pathway.« less

First-Principles Predictions of Near-Edge X-ray Absorption Fine Structure Spectra of Semiconducting Polymers

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

Su, Gregory M.; Patel, Shrayesh N.; Pemmaraju, C. D.

The electronic structure and molecular orientation of semiconducting polymers in thin films determine their ability to transport charge. Methods based on near-edge X-ray absorption fine structure (NEXAFS) spectroscopy can be used to probe both the electronic structure and microstructure of semiconducting polymers in both crystalline and amorphous films. However, it can be challenging to interpret NEXAFS spectra on the basis of experimental data alone, and accurate, predictive calculations are needed to complement experiments. Here, we show that first-principles density functional theory (DFT) can be used to model NEXAFS spectra of semiconducting polymers and to identify the nature of transitions inmore » complicated NEXAFS spectra. Core-level X-ray absorption spectra of a set of semiconducting polymers were calculated using the excited electron and core-hole (XCH) approach based on constrained-occupancy DFT. A comparison of calculations on model oligomers and periodic structures with experimental data revealed the requirements for accurate prediction of NEXAFS spectra of both conjugated homopolymers and donor–acceptor polymers. The NEXAFS spectra predicted by the XCH approach were applied to study molecular orientation in donor–acceptor polymers using experimental spectra and revealed the complexity of using carbon edge spectra in systems with large monomeric units. The XCH approach has sufficient accuracy in predicting experimental NEXAFS spectra of polymers that it should be considered for design and analysis of measurements using soft X-ray techniques, such as resonant soft X-ray scattering and scanning transmission X-ray microscopy.« less

Recording of absorption spectra by a three-beam integral technique with a tunable laser and external cavity

NASA Astrophysics Data System (ADS)

Korolenko, P. V.; Nikolaev, I. V.; Ochkin, V. N.; Tskhai, S. N.

2014-04-01

An integral method is considered for recording absorption using three laser beams transmitted through and reflected from an external cavity with the absorbing medium (R-ICOS). The method is the elaboration of a known single-beam ICOS method and allows suppression of the influence of radiation phase fluctuations in the resonator on recording weak absorption spectra. First of all, this reduces high-frequency instabilities and gives a possibility to record spectra during short time intervals. In this method, mirrors of the resonator may have moderate reflection coefficients. Capabilities of the method have been demonstrated by the examples of weak absorption spectra of atmospheric methane and natural gas in a spectral range around 1650 nm. With the mirrors having the reflection coefficients of 0.8-0.99, a spectrum can be recorded for 320 μs with the accuracy sufficient for detecting a background concentration of methane in atmosphere. For the acquisition time of 20 s, the absorption coefficients of ~2×10-8 cm-1 can be measured, which corresponds to a 40 times less molecule concentration than the background value.

The Mid-Infrared Absorption Spectra of Neutral PAHs in Dense Interstellar Clouds

NASA Technical Reports Server (NTRS)

Bernstein, M. P.; Sandford, S. A.; Allamandola, L. J.

2005-01-01

Polycyclic aromatic hydrocarbons (PAHs) are common throughout the universe and are expected to be present in dense interstellar clouds. In these environments, some P.4Hs may be present in the gas phase, but most should be frozen into ice mantles or adsorbed onto dust grains and their spectral features are expected to be seen in absorption. Here we extend our previous work on the infrared spectral properties of the small PAH naphthalene (C10H8) in several media to include the full mid-infrared laboratory spectra of 11 other PAHs and related aromatic species frozen in H2O ices. These include the molecules 1,2-dihydronaphthalene, anthracene, 9,1O-dihydroanthracene, phenanthrene, pyrene, benzo[e]pyrene, perylene, benzo(k)fluoranthene, pentacene, benzo[ghi]perylene, and coronene. These results demonstrate that PAHs and related molecules, as a class, show the same spectral behaviors as naphthalene when incorporated into H2O-rich matrices. When compared to the spectra of these same molecules isolated in inert matrices (e.g., Ar or N2), the absorption bands produced when they are frozen in H2O matrices are broader (factors of 3-10), show small position shifts in either direction (usually < 4/cm, always < 10/cm), and show variable changes in relative band strengths (typically factors of 1-3). There is no evidence of systematic increases or decreases in the absolute strengths of the bands of these molecules when they are incorporated in H2O matrices. In H2O-rich ices, their absorption bands are relatively insensitive to concentration over the range of 10 < H2O/PAH < 200): The absorption bands of these molecules are also insensitive to temperature over the 10 K < T < 125 K range, although the spectra can show dramatic changes as the ices are warmed through the temperature range in which amorphous H2O ice converts to its cubic and hexagonal crystalline forms (T > 125 Kj. Given the small observed band shifts cause by H2O, the current database of spectra from Ar matrix

Power and polarization dependences of ultra-narrow electromagnetically induced absorption (EIA) spectra of 85 Rb atoms in degenerate two-level system

NASA Astrophysics Data System (ADS)

Qureshi, Muhammad Mohsin; Rehman, Hafeez Ur; Noh, Heung-Ryoul; Kim, Jin-Tae

2016-05-01

We have investigated ultra-narrow EIA spectral features with respect to variations of polarizations and powers of pump laser beam in a degenerate two-level system of the transition of 85 Rb D2 transition line. Polarizations of the probe laser beam in two separate experiments were fixed at right circular and horizontal linear polarizations, respectively while the polarizations of the pump lasers were varied from initial polarizations same as the probe laser beams to orthogonal to probe polarizations. One homemade laser combined with AOMs was used to the pump and probe laser beams instead of two different lasers to overcome broad linewidths of the homemade lasers. Theoretically, probe absorption coefficients have been calculated from optical Bloch equations of the degenerate two level system prepared by a pump laser beam. In the case of the circular polarization, EIA signal was obtained as expected theoretically although both pump and probe beams have same polarization. The EIA signal become smaller as power increases and polarizations of the pump and probe beams were same. When the polarization of the pump beam was linear polarization, maximum EIA signal was obtained theoretically and experimentally. Experimental EIA spectral shapes with respect to variations of the pump beam polarization shows similar trends as the theoretical results.

Multi-Photon Absorption Spectra: A Comparison Between Transmittance Change and Fluorescence Methods

DTIC Science & Technology

2015-05-21

AFRL-OSR-VA-TR-2015-0134 multi-photon absorption spectra Cleber Mendonca INSTITUTO DE FISICA DE SAO CARLOS Final Report 05/21/2015 DISTRIBUTION A...5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Instituto de Fisica de Sao Carlos - Universidade de Sao Paulo Av

Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks

PubMed Central

Shu, Shiwei; Zhan, Yawen; Lee, Chris; Lu, Jian; Li, Yang Yang

2016-01-01

Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-selective asymmetric absorption behavior persists for wide angles, does not depend on polarization, and can be ascribed to the lossy characteristics of the Bragg stacks. Moreover, interesting Fano resonance with easily tailorable peak profiles can be realized using the lossy Bragg stacks. PMID:27251768

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;

Optical Absorption Spectra of Nuclear Filters Modified by Deposition of Silver Nano- and Microparticles

NASA Astrophysics Data System (ADS)

Smolyanskii, A. S.; Kozlova, N. V.; Zheltova, A. V.; Aksyutina, A. S.; Shvedov, A. S.; Lakeev, S. G.

2015-07-01

Light scattering and interference patterns are studied in the optical absorption spectra of nuclear filters based on polyethylene terephthalate fi lms modifi ed by dry aerosol deposition of silver nano- and microparticles. Surface plasmon polaritons and localized plasmons formed by the passage of light through porous silver films are found to have an effect on the diffraction and interference modes. The thickness of silver nano- and microparticle coatings on the surface of the nuclear fi lters was determined from the shift in the interference patterns in the optical absorption spectra of the modified nuclear filters relative to the original nuclear filters. A correlation was found between the estimated coating thickness and the average surface roughness of the nuclear filters modified by layers of silver nano- and microparticles.

Simulations of absorption spectra of conjugated oligomers: role of planar conformation and aggregation in condensed phase

NASA Astrophysics Data System (ADS)

Yuan, Xiang-Ai; Wen, Jin; Zheng, Dong; Ma, Jing

2018-04-01

This Review highlights the structure/property relationship underlying the morphology modulation through various factors towards the exploration of light-absorbing materials for efficient utilisation of solar power. Theoretical study using a combination of molecular dynamics imulations and the time-dependent density functional theory demonstrated that the planarity plays an important role in tuning spectral properties of oligomer aggregates. The aggregation-induced blue-shift in absorption spectra of oligothiophenes and the red-shift for oligofluorenols were rationalised in a unified way from the reduced (and increased) content of planar conformations in molecular aggregates. The planarity versus non-planarity of oligomers can be modulated by introduction of alkyl side chain or steric bulky substituents. The substitution with various groups in the ortho-position of azobenzene leads to the distorted backbone, breaking symmetry, and hence the red-shift in spectra, expanding the application in biological systems with visible light absorption. The donor-acceptor substituent groups in conjugated oligomers can increase the degree of planarity, electron delocalisation and polarisation, and charge separation, giving rise to the red-shift in spectra and enhancement in polarisability and charge mobility for device applications. The solvent dependent and pH-sensitive properties and intramolecular hydrogen bonds also caused the shift of absorption spectra with the appearance of planar conformers.

Near-edge X-ray absorption spectra for metallic Cu and Mn

NASA Astrophysics Data System (ADS)

Greaves, G. N.; Durham, P. J.; Diakun, G.; Quinn, P.

1981-11-01

The measurement of X-ray absorption fine structure of metals- both in the extended region (EXAFS) as well as in the near edge region (XANES)-has been widely discussed (see refs 1-6 for Cu and refs 7-9 for Mn). The recent availability of intense X-ray fluxes from storage rings has usually been exploited for EXAFS leaving the XANES often with poorer resolution than earlier work performed on conventional sources (for example, compare the near edge structure for copper in ref. 1 with refs 3 or 6). In addition, whilst the theory and analysis of EXAFS is relatively well-established2,10, a theory for the strong scattering regime near to the absorption edge has only recently been developed11. We report here the first high resolution XANES spectra for Cu and Mn which were performed at the SRS storage ring at Daresbury. Although both metals have close-packed structures consisting of atoms of similar size their local atomic structure is different in detail. Significant differences are found in their respective XANES reflecting the senstivity of this region of the X-ray absorption fine structure to the local atomic structure. Spectra for the two metals have been analysed using the new multiple scattering formalism. This is a real space calculation and unlike a conventional band structure approach it does not require structural periodicity but works from the local arrangement of atoms.

Excitation Dynamics in Phycoerythrin 545: Modeling of Steady-State Spectra and Transient Absorption with Modified Redfield Theory

PubMed Central

Novoderezhkin, Vladimir I.; Doust, Alexander B.; Curutchet, Carles; Scholes, Gregory D.; van Grondelle, Rienk

2010-01-01

Abstract We model the spectra and excitation dynamics in the phycobiliprotein antenna complex PE545 isolated from the unicellular photosynthetic cryptophyte algae Rhodomonas CS24. The excitonic couplings between the eight bilins are calculated using the CIS/6-31G method. The site energies are extracted from a simultaneous fit of the absorption, circular dichroism, fluorescence, and excitation anisotropy spectra together with the transient absorption kinetics using the modified Redfield approach. Quantitative fit of the data enables us to assign the eight exciton components of the spectra and build up the energy transfer picture including pathways and timescales of energy relaxation, thus allowing a visualization of excitation dynamics within the complex. PMID:20643051

Equilibrium Structures and Absorption Spectra for SixOy-nH2O Molecular Clusters using Density Functional Theory

DTIC Science & Technology

2017-05-04

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--17-9723 Equilibrium Structures and Absorption Spectra for SixOy-nH2O Molecular...Absorption Spectra for SixOy-nH2O Molecular Clusters using Density Functional Theory L. Huang, S.G. Lambrakos, and L. Massa1 Naval Research Laboratory, Code...and time-dependent density functional theory (TD-DFT). The size of the clusters considered is relatively large compared to those considered in

Polarized electronic absorption spectra of Cr2SiO4 single crystals

NASA Astrophysics Data System (ADS)

Furche, A.; Langer, K.

Polarized electronic absorption spectra, E∥a(∥X), E∥b(∥Y) and E∥c(∥Z), in the energy range 3000-5000 cm-1 were obtained for the orthorhombic thenardite-type phase Cr2SiO4, unique in its Cr2+-allocation suggesting some metal-metal bonding in Cr2+Cr2+ pairs with Cr-Cr distance 2.75 Å along [001]. The spectra were scanned at 273 and 120 K on single crystal platelets ∥(100), containing optical Y and Z, and ∥(010), containing optical X and Z, with thicknesses 12.3 and 15.6 μm, respectively. Microscope-spectrometric techniques with a spatial resolution of 20 μm and 1 nm spectral resolution were used. The orientations were obtained by means of X-ray precession photographs. The xenomorphic, strongly pleochroic crystal fragments (X deeply greenish-blue, Y faint blue almost colourless, Z deeply purple almost opaque) were extracted from polycrystalline Cr2SiO4, synthesized at 35 kbar, above 1440 °C from high purity Cr2O3, Cr (10% excess) and SiO2 in chromium capsules. The Cr2SiO4-phase was identified by X-ray diffraction (XRD). Four strongly polarized bands, at about 13500 (I), 15700 (II), 18700 (III) and 19700 (IV) cm-1, in the absorption spectra of Cr2SiO4 single crystals show properties (temperature behaviour of linear and integral absorption coefficients, polarization behaviour, molar absorptivities) which are compatible with an assignment to localized spin-allowed transitions of Cr2+ in a distorted square planar coordination of point symmetry C2. The crystal field parameter of Cr2+ is estimated to be 10 Dq =10700 cm-1. A relatively intense, sharp band at 18400 cm-1 and three other minor features can, from their small half widths, be assigned to spin-forbidden dd-transitions of Cr2+. The intensity of such bands strongly decreases on decreasing temperature. The large half widths, near 5000 cm-1 of band III are indicative of some Cr-Cr interactions, i.e. δ-δ* transitions of Cr24+, whereas the latter alone would be in conflict with the strong

Simultaneous measurement of displacement current and absorption spectra of Langmuir film

NASA Astrophysics Data System (ADS)

Xu, Xiaobin; Kubota, Tohru; Iwamoto, Mitsumasa

1995-07-01

A Maxwell-displacement-current measuring system coupled with the system used for the measurement of absorption spectra of monolayers on a water surface has been developed. Using this system, the displacement current and the absorbance across monolayers of squarylium dye at the air/water surface were detected. It was found that the change in J aggregate in the monolayers with monolayer compression was detectable using the system.

VizieR Online Data Catalog: BOSS narrow CIV absorption lines. I. zem<=2.4 (Chen+, 2014)

NASA Astrophysics Data System (ADS)

Chen, Z.-F.; Qin, Y.-P.; Pan, C.-J.; Huang, W.-R.; Qin, M.; Wu, H.-N.

2014-01-01

We identify absorption doublets, such as CIVλλ1548,1551 in the quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), which is a part of the SDSS-III (Eisenstein et al. 2011AJ....142...72E). BOSS aims to obtain over 150000 quasar spectra with zem>2.15 using the same 2.5m telescope as the SDSS did. The spectra of BOSS span a wavelength range of 3600-10400Å at a resolution of 1300

Infrared band absorptance correlations and applications to nongray radiation. [mathematical models of absorption spectra for nongray atmospheres in order to study air pollution

NASA Technical Reports Server (NTRS)

Tiwari, S. N.; Manian, S. V. S.

1976-01-01

Various mathematical models for infrared radiation absorption spectra for atmospheric gases are reviewed, and continuous correlations for the total absorptance of a wide band are presented. Different band absorptance correlations were employed in two physically realistic problems (radiative transfer in gases with internal heat source, and heat transfer in laminar flow of absorbing-emitting gases between parallel plates) to study their influence on final radiative transfer results. This information will be applied to the study of atmospheric pollutants by infrared radiation measurement.

Iodine absorption cells quality evaluation methods

NASA Astrophysics Data System (ADS)

Hrabina, Jan; Zucco, Massimo; Holá, Miroslava; Šarbort, Martin; Acef, Ouali; Du-Burck, Frédéric; Lazar, Josef; Číp, Ondřej

2016-12-01

The absorption cells represent an unique tool for the laser frequency stabilization. They serve as irreplaceable optical frequency references in realization of high-stable laser standards and laser sources for different brands of optical measurements, including the most precise frequency and dimensional measurement systems. One of the most often used absorption media covering visible and near IR spectral range is molecular iodine. It offers rich atlas of very strong and narrow spectral transitions which allow realization of laser systems with ultimate frequency stabilities in or below 10-14 order level. One of the most often disccussed disadvantage of the iodine cells is iodine's corrosivity and sensitivity to presence of foreign substances. The impurities react with absorption media and cause spectral shifts of absorption spectra, spectral broadening of the transitions and decrease achievable signal-to-noise ratio of the detected spectra. All of these unwanted effects directly influence frequency stability of the realized laser standard and due to this fact, the quality of iodine cells must be precisely controlled. We present a comparison of traditionally used method of laser induced fluorescence (LIF) with novel technique based on hyperfine transitions linewidths measurement. The results summarize advantages and drawbacks of these techniques and give a recommendation for their practical usage.

Effect of solvent on absorption spectra of all-trans-{beta}-carotene under high pressure

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

Liu, W. L.; Zheng, Z. R.; Liu, Z. G.

The absorption spectra of all-trans-{beta}-carotene in n-hexane and carbon disulfide (CS{sub 2}) solutions are measured under high pressure at ambient temperature. The common redshift and broadening in the spectra are observed. Simulation of the absorption spectra was performed by using the time-domain formula of the stochastic model. The pressure dependence of the 0-0 band wavenumber is in agreement with the Bayliss theory at pressure higher than 0.2 GPa. The deviation of the linearity at lower pressure is ascribed to the reorientation of the solvent molecules. Both the redshift and broadening are stronger in CS{sub 2} than that in n-hexane becausemore » of the more sensitive pressure dependence of dispersive interactions in CS{sub 2} solution. The effect of pressure on the transition moment is explained with the aid of a simple model involving the relative dimension, location, and orientation of the solute and solvent molecules. The implication of these results for light-harvesting functions of carotenoids in photosynthesis is also discussed.« less

Intrinsic, Narrow N V Absorption Reveals a Clumpy Outflow in z < 0.4 Radio-Loud Quasars

NASA Astrophysics Data System (ADS)

DeMarcy, Bryan; Serra, Viktoriah; Culliton, Chris; Ganguly, Rajib; Runnoe, Jessie; Charlton, Jane; Eracleous, Michael; Misawa, Toru; Narayanan, Anand

2018-01-01

Quasar outflows are often invoked in models for galaxy evolution to inject energy and momentum into the gas in the host galaxy and influence its star formation history. Thus, the study of quasar outflows is essential for understanding galaxy evolution. N V absorption systems within the associated region (|Δv| ≤ 5000 km s-1) of the quasar are thought to be intrinsic since many show evidence for partial covering of the quasar. A recent archival study of quasar spectra taken with COS/G130M or G160M found 39/181 radio-quiet quasars show intrinsic N V absorption, while none of the 31 radio-loud quasars have N V absorption detected (Culliton et al. 2017). Further investigation of these radio-loud quasars showed a clear bias towards compact morphologies as revealed by FIRST 1.4 GHz imaging and comparatively flat radio spectra. This suggests we are viewing more face-on orientations which prevent us from seeing absorption outflows. The cause for such bias within the HST archive is still unknown; however, it could explain the lack of radio-loud intrinsic N V absorption seen by Culliton et al. (2017). Alternatively, the quasar wind structure may be fundamentally different between radio-loud and radio-quiet objects. We used COS/G130M or G160M to obtain rest-frame UV spectra (1195 Å - 1250 Å) of 14 low-redshift SDSS radio-loud quasars which show lobe-dominated FIRST morphologies to distinguish between these possibilities. Intrinsic N V absorption was detected in 6 of our 14 quasars. This suggests the lack of detections in the archival study was a result of an orientation effect/sampling bias rather than to differences in wind structure between radio-loud and radio-quiet quasars. Interestingly, we find significant overlap in radio core fractions between quasars with and without N V detection. Quasars in our sample with N V detection span a range of core fractions from < 0.01 up to 0.89 while those without detected N V range from 0.04 up to 0.93. A laminar outflow with a

Optical absorption and scattering spectra of pathological stomach tissues

NASA Astrophysics Data System (ADS)

Giraev, K. M.; Ashurbekov, N. A.; Lakhina, M. A.

2011-03-01

Diffuse reflection spectra of biotissues in vivo and transmission and reflection coefficients for biotissues in vitro are measured over 300-800 nm. These data are used to determine the spectral absorption and scattering indices and the scattering anisotropy factor for stomach mucous membranes under normal and various pathological conditions (chronic atrophic and ulcerous defects, malignant neoplasms). The most importan tphysiological (hemodynamic and oxygenation levels) and structural-morphological (scatterer size and density) parameters are also determined. The results of a morphofunctional study correlate well with the optical properties and are consistent with data from a histomorphological analysis of the corresponding tissues.

Detection of absorption lines in the spectra of X-ray bursts from X1608-52

NASA Astrophysics Data System (ADS)

Nakamura, Norio; Inoue, Hajime; Tanaka, Yasuo

X-ray bursts from X 1608-52 were observed with the gas scintillation proportional counters on the Tenma satellite. Absorption features were detected in the spectra of three bursts among 17 bursts observed. These absorption features are consistent with a common absorption line at 4.1 keV. The energy and the properties of the absorption lines of the X 1608-52 bursts are very similar to those observed from the X 1636-53 bursts by Waki et al. (1984). Near equality of the absorption-line energies for X 1636-53 and X 1608-52 would imply that mass and radius of the neutron stars in these two systems are very similar to each other.

High Resolution Spectroscopy of X-ray Quasars: Searching for the X-ray Absorption from the Warm-Hot Intergalactic Medium

NASA Technical Reports Server (NTRS)

Fang, Taotao; Canizares, Claude R.; Marshall, Herman L.

2004-01-01

We present a survey of six low to moderate redshift quasars with Chandra and XMM-Newton. The primary goal is to search for the narrow X-ray absorption lines produced by highly ionized metals in the Warm-Hot Intergalactic Medium. All the X-ray spectra can be well fitted by a power law with neutral hydrogen absorption. Only one feature is detected at above 3-sigma level in all the spectra, which is consistent with statistic fluctuation. We discuss the implications in our understanding of the baryon content of the universe. We also discuss the implication of the non-detection of the local (z approx. 0) X-ray absorption.

Comparison of sub-Doppler-width resonances in transmission and reflection spectra of micrometer-thick Cs vapor layers

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

Krasteva, A., E-mail: anna0kr0stz@gmail.com; Cartaleva, S., E-mail: stefka-c@ie.bas.bg; Vartanyan, T., E-mail: tigran@vartanyan.com

2016-03-25

We report experimental study of resonance sign reversal at the hyperfine F{sub g} = 4 → F{sub e} = 5 transition on D{sub 2} line of {sup 133}Cs. Alkali vapors are confined in an optical cell with micrometric thickness. For circular polarization of the irradiating light, transmission and reflection spectra, recorded at different laser intensities and different temperature of alkali vapor, are studied and compared. At low laser intensity, in the transmission spectra we observe a narrow resonance of increased absorption (bright resonance) at the F{sub g} = 4 → F{sub e} = 5 transition, however in reflection spectra, recordedmore » at the same experimental conditions, this bright resonance transforms into a dark resonance of reduced absorption. A simple explanation is proposed in order to explain the observed difference between the transmission and reflection spectra.« less

Numerical indicators of absorption spectra of green leaf extract obtained from plants of different life forms.

PubMed

Koldaev, Vladimir M; Manyakhin, Artem Yu

2018-06-05

The study was carried out using 58 species of terrestrial plants of different life forms at the start of their fruiting stage. Photoreceptive systems of the leaves were assessed by means of unconventional numerical indicators of absorption spectra, relative photoabsorption coefficient, photosynthetic pigments' integral absorption intensity and relative absorption intensity coefficient. As the study showed, the leaves of all trees and light-demanding grasses favoring open spaces, which were subjected to the study were featured by the lowest values of numerical indicators of absorption spectra (NIAS). Shade-demanding grasses, which grow beneath the canopy, by contrast, were featured by the highest NIAS values. These values of the shrub leaves were in between those of light-demanding plants and shade-demanding ones. The results obtained are consistent with modern visions concerning the biochemistry and the physiology of plants' photoreceptive system. It is appropriate to apply the NIAS, which were used in this study and reflect a leaf's photoreceptive properties, as spectrophotometric criteria for monitoring and environmental management of natural plant resources and agricultural plants. Copyright © 2018 Elsevier B.V. All rights reserved.

Absorption spectra analysis of hydrated uranium(III) complex chlorides

NASA Astrophysics Data System (ADS)

Karbowiak, M.; Gajek, Z.; Drożdżyński, J.

2000-11-01

Absorption spectra of powdered samples of hydrated uranium(III) complex chlorides of the formulas NH 4UCl 4 · 4H 2O and CsUCl 4 · 3H 2O have been recorded at 4.2 K in the 4000-26 000 cm -1 range. The analysis of the spectra enabled the determination of crystal-field parameters and assignment of 83 and 77 crystal-field levels for the tetrahydrate and trihydrate, respectively. The energies of the levels were computed by applying a simplified angular overlap model as well as a semiempirical Hamiltonian representing the combined atomic and crystal-field interactions. Ab initio calculations have enabled the application of a simplified parameterization and the determination of the starting values of the AOM parameters. The received results have proved that the AOM approach can quite well predict both the structure of the ground multiplet and the positions of the crystal-field levels in the 17 000-25 000 cm -1 range, usually obscured by strong f-d bands.

Influence of temperature on water and aqueous glucose absorption spectra in the near- and mid-infrared regions at physiologically relevant temperatures.

PubMed

Jensen, Peter Snoer; Bak, Jimmy; Andersson-Engels, Stefan

2003-01-01

Near- and mid-infrared absorption spectra of pure water and aqueous 1.0 g/dL glucose solutions in the wavenumber range 8000-950 cm-1 were measured in the temperature range 30-42 degrees C in steps of 2 degrees C. Measurements were carried out with an FT-IR spectrometer and a variable pathlength transmission cell controlled within 0.02 degree C. Pathlengths of 50 microns and 0.4 mm were used in the mid- and near-infrared spectral region, respectively. Difference spectra were used to determine the effect of temperature on the water spectra quantitatively. These spectra were obtained by subtracting the 37 degrees C water spectrum from the spectra measured at other temperatures. The difference spectra reveal that the effect of temperature is highest in the vicinity of the strong absorption bands, with a number of isosbestic points with no temperature dependence and relatively flat plateaus in between. On the basis of these spectra, prospects for and limitations on data analysis for infrared diagnostic methods are discussed. As an example, the absorptive properties of glucose were studied in the same temperature range in order to determine the effect of temperature on the spectral shape of glucose. The change in water absorption associated with the addition of glucose has also been studied. An estimate of these effects is given and is related to the expected level of infrared signals from glucose in humans.

Impact of pentacene film thickness on the photoresponse spectra: Determination of the photocarrier generation mechanism

NASA Astrophysics Data System (ADS)

Gorgolis, S.; Giannopoulou, A.; Anastassopoulos, D.; Kounavis, P.

2012-07-01

Photocurrent response, optical absorption, and x-ray diffraction (XRD) measurements in pentacene films grown on glass substrates are performed in order to obtain an insight into the mobile photocarriers generation mechanism. For film thickness of the order of 50 nm and lower, the photocurrent response spectra are found to follow the optical absorption spectra demonstrating the so-called symbatic response. Upon increasing the film thickness, the photoresponse demonstrates a transition to the so-called antibatic response, which is characterized by a maximum and minimum photocurrent for photon energies of minimum and maximum optical absorption, respectively. The experimental results are not in accordance with the model of important surface recombination rate. By taking into account the XRD patterns, the experimental photoresponse spectra can be reproduced by model simulations assuming efficient exciton dissociation at a narrow layer of the order of 20 nm near the pentacene-substrate interface. The simulated spectra are found sensitive to the film thickness, the absolute optical absorption coefficient, and the diffusion exciton length. By comparing the experimental with the simulated spectra, it is deduced that the excitons, which are created by optical excitation in the spectral region of 1.7-2.2 eV, diffuse with a diffusion length of the order of 10-80 nm to the pentacene-substrate interface where efficiently dissociate into mobile charge carriers.

Quantitative comparison of the absorption spectra of the gas mixtures in analogy to the criterion of Pearson

NASA Astrophysics Data System (ADS)

Kistenev, Yu. V.; Kuzmin, D. A.; Sandykova, E. A.; Shapovalov, A. V.

2015-11-01

An approach to the reduction of the space of the absorption spectra, based on the original criterion for profile analysis of the spectra, was proposed. This criterion dates back to the known statistics chi-square test of Pearson. Introduced criterion allows to quantify the differences of spectral curves.

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

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.

Measurements of trace constituents from atmospheric infrared emission and absorption spectra, a feasibility study

NASA Technical Reports Server (NTRS)

Goldman, A.; Williams, W. J.; Murcray, D. G.

1974-01-01

The feasibility of detecting eight trace constituents (CH4, HCl, HF, HNO3, NH3, NO, NO2 and SO2) against the rest of the atmospheric background at various altitudes from infrared emission and absorption atmospheric spectra was studied. Line-by-line calculations and observational data were used to establish features that can be observed in the atmospheric spectrum due to each trace constituent. Model calculations were made for experimental conditions which approximately represent state of the art emission and absorption spectrometers.

Emission from water vapor and absorption from other gases at 5-7.5 μm in Spitzer-IRS Spectra Of Protoplanetary Disks

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

Sargent, B. A.; Forrest, W.; Watson, Dan M.

We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph 5-7.5 μm spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 μm due to the ν{sub 2} = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures >500 K, though some of these spectra also show indications of an absorption band, likely from another molecule. This water vapor emission contrasts with the absorption from warm water vapor seenmore » in the spectrum of the FU Orionis star V1057 Cyg. The other 6 of the 13 stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 μm, which for some is consistent with gaseous formaldehyde (H{sub 2}CO) and for others is consistent with gaseous formic acid (HCOOH). There are indications that some of these six stars may also have weak water vapor emission. Modeling of these stars' spectra suggests these gases are present in the inner few AU of their host disks, consistent with recent studies of infrared spectra showing gas in protoplanetary disks.« less

Far-ultraviolet absorption spectra of quasars: How to find missing hot gas and metals

NASA Technical Reports Server (NTRS)

Verner, D. A.; Tytler, David; Barthel, P. D.

1994-01-01

We show that some high-redshift QSO absorption systems that reveal only the H I Lyman series lines at wavelengths visible from the ground maybe a new class of ultra-high-ionization metal line systems, with metal lines in the far-UV region which is now being explored with satellites. At high temperatures or in intense radiation fields metal systems will not show the usual C IV absorption, and O VI will become the most prominent metal absorber. At still higher ionization, O IV also becomes weak and the strongest metal lines are from Ne VIII, Mg X and Si XII, which have doublets in the rangs 500-800 A. Hence very high ionization metal systems will not show metal lines in existing spectra. Recent X-ray observations show that galaxy halos contain hot gas, so we predict that far-UV spectra of QSOs will also show this gas.

Intensity dependence narrowing of electromagnetically induced absorption in a Doppler-broadened medium

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

Dimitrijevic, J.; Arsenovic, D.; Jelenkovic, B. M.

In this paper, we present a theoretical model for studying the interaction between linearly polarized laser light and near-degenerated Zeeman sublevels for a multiple V-type atomic system of {sup 2}S{sub 1/2}F{sub g}=2{yields}{sup 2}P{sub 3/2}F{sub e}=3 transition in {sup 87}Rb. We have calculated the laser absorption in a Hanle configuration, as well as the amplitudes and the widths of electromagnetically induced absorption (EIA) in the range of laser intensities from 0.01 to 40 mW/cm{sup 2}. Our results, showing nonvanishing EIA amplitude, a nonmonotonic increase of the EIA width for the increase of laser intensity, and pronounced shape differences of the Hanlemore » EIA curves at different laser intensities, are in good agreement with recent experimental results. We have found that the EIA behaves differently than the electromagnetically induced transparency (EIT) as a function of the laser intensity. Both the amplitude and width of the EIA have narrow maximums at 1 to 2 mW/cm{sup 2}. We have shown the strong influence of Doppler broadening of atomic transition on Hanle resonances and have suggested the explanation of it.« less

Kα X-Ray Emission Spectra and K X-Ray Absorption-Edge Structures of Fluorine in 3d Transition-Metal Difluorides

NASA Astrophysics Data System (ADS)

Sugiura, Chikara

1991-08-01

The fluorine Kα emission spectra in fluorescence from a series of 3d transition-metal difluorides MF2 (M=Mn, Fe, Co, Ni, Cu and Zn) have been measured with a high-resolution two-crystal vacuum spectrometer. It is shown that the observed FWHM of the Kα1,2 emission band is closely related to the difference in the electronegativity between the metal and fluorine atoms. The measured emission spectra are presented along with the UPS or XPS spectra of the valence bands and the fluorine K absorption spectra of the metal difluorides, reported previously. The structures at the fluorine K absorption edges are interpreted in terms of a molecular orbital (MO) model.

Optical absorption and emission bands of Tm 3+ ions in calcium niobium gallium garnet crystal

NASA Astrophysics Data System (ADS)

Tsuboi, Taiju; Tanigawa, Masayuki; Shimamura, Kiyoshi

2000-12-01

Absorption spectra of Tm 3+ ions in Ca 3Nb 1.6875Ga 3.1875O 12 (CNGG) crystal have been investigated at various temperatures between 15 and 296 K. Luminescence spectra in a spectral region of 400-1750 nm are investigated under excitation into various excited states of Tm 3+ and the conduction band of CNGG at room temperature. The absorption and emission bands of Tm 3+ in CNGG are observed to be broader than those observed in other Tm 3+-doped crystals such as LiNbO 3. This is due to the disordered structure of CNGG. From the temperature dependence of absorption spectra, five Stark levels are derived for the 3H 6 ground state. The highest Stark level is found to be 351 cm -1 above the ground level. It is suggested that the low efficiency of the 2.02 μm lasing at room temperature is due to the narrow splitting of the Stark levels.

Ultraviolet absorption spectra of shock-heated carbon dioxide and water between 900 and 3050 K

NASA Astrophysics Data System (ADS)

Schulz, C.; Koch, J. D.; Davidson, D. F.; Jeffries, J. B.; Hanson, R. K.

2002-03-01

Spectrally resolved UV absorption cross-sections between 190 and 320 nm were measured in shock-heated CO 2 between 880 and 3050 K and H 2O between 1230 and 2860 K. Absorption spectra were acquired with 10 μs time resolution using a unique kinetic spectrograph, thereby enabling comparisons with time-dependent chemical kinetic modeling of post-shock thermal decomposition and chemical reactions. Although room temperature CO 2 is transparent (σ<10 -22 cm2) at wavelengths longer than 200 nm, hot CO 2 has significant absorption (σ>10 -20 cm2) extending to wavelengths longer than 300 nm. The temperature dependence of CO 2 absorption strongly suggests sharply increased transition probabilities from excited vibrational levels.

TD-M06-2X insights into the absorption and emission spectra of dichlorvos and its molecularly imprinted recognition by methacrylic acid.

PubMed

Cheng, Xueli

2016-11-01

The absorption and emission spectra of dichlorvos and the dichlorvos-MAA complex in methanol, water, and chloroform in the molecularly imprinted recognition were investigated systematically. The M06-2X results revealed that: 1) the hydroxyl groups in polar solvents such as methanol and water may markedly influence the weak interactions, and then alter the adsorption and emission spectra; 2) the electronic excitation in absorption spectra of dichlorvos is dominated by the configuration HOMO → LUMO, but in the most stable dichlorvos-MAA it becomes the ππ* excitation of HOMO → LUMO + 1; 3) Mulliken charges reveal that dichlorvos almost dissociates to Cl - and a cation in its S 1 excitation state; 4) the phosphorescence spectra of dichlorvos-MAA are relatively weak. Graphical Abstract The absorption and emission spectra of dichlorvos and the dichlorvos-MAA complex in the molecularly imprinted recognition of dichlorvos were investigated systematically in methanol, water, and chloroform as solvents.

Theoretical infrared and electronic absorption spectra of C16H10 isomers, their ions and doubly ions

NASA Astrophysics Data System (ADS)

Naganathappa, Mahadevappa; Chaudhari, Ajay

2012-09-01

Polycyclic aromatic hydrocarbons (PAHs) or PAH-related molecules are considered to be responsible for the unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, 8.6 and 11.2 μm. However, the exact identification of PAH or PAH-related molecules is difficult. There have been several investigations on the spectroscopic characterization of PAH molecules. But none of them compared the spectra of isomers of PAHs, which might have help in the identification of the UIR emission features. This work presents the infrared and electronic absorption spectra of isomers of C16H10. The aim of the present work is to compare infrared and electronic absorption spectra of four isomers of C16H10 PAH viz. pyrene, aceanthrylene, acephenanthrylene and fluoranthene, their ions and doubly ions. We also compare the spectra of pyrene in the gas-phase and in H2O ice. We have used the density functional theory with B3LYP exchange and correlation functional and 6-311++g** basis set to study the infrared spectra. The time-dependent density functional theory (TDDFT) has been used to obtain the electronic absorption spectra. Significant difference in the CC stretching, CH in-plane bending and CH out-of-plane bending vibration modes is observed for the isomers of C16H10 whereas there is no large difference in the CH stretching vibration band. A significant change in the vibrational band is observed for pyrene in H2O ice compared to gas-phase pyrene. Though isomers of C16H10 PAH have the same number of carbon and hydrogen atoms, their spectroscopic characteristics are different. This study should help in identifying the isomers of C16H10, their ions and doubly cation in the interstellar medium.

Crossovers from excitons to plasmons in narrow-gap carbon nanotubes

NASA Astrophysics Data System (ADS)

Uryu, Seiji

2018-06-01

Plasmons and excitons, bound states of electrons and holes, are collective charge excitations in solids. In this study, we numerically show that in most metallic carbon nanotubes, which are called narrow-gap carbon nanotubes, excitons cross over to plasmons as the wave vector increases. This indicates that resonance with the excitons changes to that with the plasmons by changing the nanotube length, which can explain the origin of observed peaks in the terahertz or far-infrared region in the optical absorption spectra of metallic carbon nanotubes. In the crossovers from excitons to plasmons, a depolarization effect on the many-body wave functions of the plasmons and excitons is clarified.

Theoretical calculations on the electron absorption spectra of selected Polycyclic Aromatic Hydrocarbons (PAH) and derivatives

NASA Technical Reports Server (NTRS)

Du, Ping

1993-01-01

As a theoretical component of the joint effort with the laboratory of Dr. Lou Allamandola to search for potential candidates for interstellar organic carbon compound that are responsible for the visible diffuse interstellar absorption bands (DIB's), quantum mechanical calculations were performed on the electron absorption spectra of selected polycyclic aromatic hydrocarbons (PAH) and derivatives. In the completed project, 15 different species of naphthalene, its hydrogen abstraction and addition derivatives, and corresponding cations and anions were studied. Using semiempirical quantum mechanical method INDO/S, the ground electronic state of each species was evaluated with restricted Hartree-Fock scheme and limited configuration interaction. The lowest energy spin state for each species was used for electron absorption calculations. Results indicate that these calculations are accurate enough to reproduce the spectra of naphthalene cation and anion observed in neon matrix. The spectral pattern of the hydrogen abstraction and addition derivatives predicted based on these results indicate that the electron configuration of the pi orbitals of these species is the dominant determinant. A combined list of 19 absorptions calculated from 4500 A to 10,400 A were compiled and suggested as potential candidates that are relevant for the DIB's absorptions. Continued studies on pyrene and derivatives revealed the ground state symmetries and multiplicities of its neutral, anionic, and cationic species. Spectral calculations show that the cation (B(sub 3g)-2) and the anion (A(sub u)-2) are more likely to have low energy absorptions in the regions between 10 kK and 20 kK, similar to naphthalene. These absorptions, together with those to be determined from the hydrogen abstraction and addition derivatives of pyrene, can be used to provide additional candidates and suggest experimental work in the search for interstellar compounds that are responsible for DIB's.

Cold Atomic Hydrogen, Narrow Self-Absorption, and the Age of Molecular Clouds

NASA Technical Reports Server (NTRS)

Goldsmith, Paul F.

2006-01-01

This viewgraph presentation reviews the history, and current work on HI and its importance in star formation. Through many observations of HI Narrow Self Absorption (HINSA) the conclusions are drawn and presented. Local molecular clouds have HI well-mixed with molecular constituents This HI is cold, quiescent, and must be well-shielded from the UV radiation field The density and fractional abundance (wrt H2) of the cold HI are close to steady state values The time required to convert these starless clouds from purely HI initial state to observed present composition is a few to ten million years This timescale is a lower limit - if dense clouds being swept up from lower density regions by shocks, the time to accumulate material to get A(sub v) is approximately 1 and provide required shielding may be comparable or longer

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. III. Exact stochastic path integral evaluation.

PubMed

Moix, Jeremy M; Ma, Jian; Cao, Jianshu

2015-03-07

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters.

Substitution effects on the absorption spectra of nitrophenolate isomers.

PubMed

Wanko, Marius; Houmøller, Jørgen; Støchkel, Kristian; Suhr Kirketerp, Maj-Britt; Petersen, Michael Åxman; Nielsen, Mogens Brøndsted; Nielsen, Steen Brøndsted; Rubio, Angel

2012-10-05

Charge-transfer excitations highly depend on the electronic coupling between the donor and acceptor groups. Nitrophenolates are simple examples of charge-transfer systems where the degree of coupling differs between ortho, meta and para isomers. Here we report the absorption spectra of the isolated anions in vacuo to avoid the complications of solvent effects. Gas-phase action spectroscopy was done with two different setups, an electrostatic ion storage ring and an accelerator mass spectrometer. The results are interpreted on the basis of CC2 quantum chemical calculations. We identified absorption maxima at 393, 532, and 399 nm for the para, meta, and ortho isomer, respectively, with the charge-transfer transition into the lowest excited singlet state. In the meta isomer, this π-π* transition is strongly redshifted and its oscillator strength reduced, which is related to the pronounced charge-transfer character, as a consequence of the topology of the conjugated π-system. Each isomer's different charge distribution in the ground state leads to a very different solvent shift, which in acetonitrile is bathochromic for the para and ortho, but hypsochromic for the meta isomer.

First principles absorption spectra of Cu{sub n} (n = 2 - 20) clusters.

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

Baishya, K.; Idrobo, J. C.; Ogut, S.

2011-06-17

Optical absorption spectra for the computed ground state structures of copper clusters (Cu{sub n}, n = 2-20) are investigated from first principles using time-dependent density functional theory in the adiabatic local density approximation (TDLDA). The results are compared with available experimental data, existing calculations, and with results from our previous computations on silver and gold clusters. The main effects of d electrons on the absorption spectra, quenching the oscillator strengths, and getting directly involved in low-energy excitations increase in going from Ag{sub n} to Au{sub n} to Cu{sub n} due to the increase in the hybridization of the occupied, yetmore » shallow, d orbitals and the partially occupied s orbitals. We predict that while Cu nanoparticles of spherical or moderately ellipsoidal shape do not exhibit Mie (surface plasmon) resonances, unlike the case for Ag and Au, extremely prolate or oblate Cu nanoparticles with eccentricities near unity should give rise to Mie resonances in the lower end of the visible range and in the infrared. This tunable resonance predicted by the classical Mie-Gans theory is reproduced with remarkable accuracy by our TDLDA computations on hypothetical Cu clusters in the form of zigzag chains with as few as 6 to 20 atoms.« less

Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra

DOE PAGES

Fallot, M.; Porta, A.; Meur, L. Le; ...

2017-09-13

Here, the accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several studies have shown that the underlying nuclear physicsmore » required for the conversion of these spectra into antineutrino spectra is not totally understood. An alternative to such converted spectra is a complementary approach that consists of determining the antineutrino spectrum by means of the measurement and processing of nuclear data. The beta properties of some key fission products suffer from the pandemonium effect which can be circumvented by the use of the Total Absorption Gamma-ray Spectroscopy technique (TAGS). The two main contributors to the Pressurized Water Reactor antineutrino spectrum in the region where the spectral distortion has been observed are 92Rb and 142Cs, which have been measured at the radioactive beam facility of the University of Jyvaskyla in two TAGS experiments. We present the results of the analysis of the TAGS measurements of the β-decay properties of 92Rb along with preliminary results on 142Cs and report on the measurements already performed.« less

Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra

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

Fallot, M.; Porta, A.; Meur, L. Le

Here, the accurate determination of reactor antineutrino spectra remains a very active research topic for which new methods of study have emerged in recent years. Indeed, following the long-recognized reactor anomaly (measured antineutrino deficit in short baseline reactor experiments when compared with spectral predictions), the three international reactor neutrino experiments Double Chooz, Daya Bay and Reno have recently demonstrated the existence of spectral distortions in their measurements with respect to the same predictions. These spectral predictions were obtained through the conversion of integral beta-energy spectra obtained at the ILL research reactor. Several studies have shown that the underlying nuclear physicsmore » required for the conversion of these spectra into antineutrino spectra is not totally understood. An alternative to such converted spectra is a complementary approach that consists of determining the antineutrino spectrum by means of the measurement and processing of nuclear data. The beta properties of some key fission products suffer from the pandemonium effect which can be circumvented by the use of the Total Absorption Gamma-ray Spectroscopy technique (TAGS). The two main contributors to the Pressurized Water Reactor antineutrino spectrum in the region where the spectral distortion has been observed are 92Rb and 142Cs, which have been measured at the radioactive beam facility of the University of Jyvaskyla in two TAGS experiments. We present the results of the analysis of the TAGS measurements of the β-decay properties of 92Rb along with preliminary results on 142Cs and report on the measurements already performed.« less

Computing the Absorption and Emission Spectra of 5-Methylcytidine in Different Solvents: A Test-Case for Different Solvation Models.

PubMed

Martínez-Fernández, L; Pepino, A J; Segarra-Martí, J; Banyasz, A; Garavelli, M; Improta, R

2016-09-13

The optical spectra of 5-methylcytidine in three different solvents (tetrahydrofuran, acetonitrile, and water) is measured, showing that both the absorption and the emission maximum in water are significantly blue-shifted (0.08 eV). The absorption spectra are simulated based on CAM-B3LYP/TD-DFT calculations but including solvent effects with three different approaches: (i) a hybrid implicit/explicit full quantum mechanical approach, (ii) a mixed QM/MM static approach, and (iii) a QM/MM method exploiting the structures issuing from molecular dynamics classical simulations. Ab-initio Molecular dynamics simulations based on CAM-B3LYP functionals have also been performed. The adopted approaches all reproduce the main features of the experimental spectra, giving insights on the chemical-physical effects responsible for the solvent shifts in the spectra of 5-methylcytidine and providing the basis for discussing advantages and limitations of the adopted solvation models.

Broadening of effective photonic band gaps in biological chiral structures: From intrinsic narrow band gaps to broad band reflection spectra

NASA Astrophysics Data System (ADS)

Vargas, W. E.; Hernández-Jiménez, M.; Libby, E.; Azofeifa, D. E.; Solis, Á.; Barboza-Aguilar, C.

2015-09-01

Under normal illumination with non-polarized light, reflection spectra of the cuticle of golden-like and red Chrysina aurigans scarabs show a structured broad band of left-handed circularly polarized light. The polarization of the reflected light is attributed to a Bouligand-type left-handed chiral structure found through the scarab's cuticle. By considering these twisted structures as one-dimensional photonic crystals, a novel approach is developed from the dispersion relation of circularly polarized electromagnetic waves traveling through chiral media, to show how the broad band characterizing these spectra arises from an intrinsic narrow photonic band gap whose spectral position moves through visible and near-infrared wavelengths.

Fluorescence, Absorption, and Excitation Spectra of Polycyclic Aromatic Hydrocarbons as a Tool for Quantitative Analysis

ERIC Educational Resources Information Center

Rivera-Figueroa, A. M.; Ramazan, K. A.; Finlayson-Pitts, B. J.

2004-01-01

A quantitative and qualitative study of the interplay between absorption, fluorescence, and excitation spectra of pollutants called polycyclic aromatic hydrocarbons (PAHs) is conducted. The study of five PAH displays the correlation of the above-mentioned properties along with the associated molecular changes.

NARROW Na AND K ABSORPTION LINES TOWARD T TAURI STARS: TRACING THE ATOMIC ENVELOPE OF MOLECULAR CLOUDS

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

Pascucci, I.; Simon, M. N.; Edwards, S.

2015-11-20

We present a detailed analysis of narrow Na i and K i absorption resonance lines toward nearly 40 T Tauri stars in Taurus with the goal of clarifying their origin. The Na i λ5889.95 line is detected toward all but one source, while the weaker K i λ7698.96 line is detected in about two-thirds of the sample. The similarity in their peak centroids and the significant positive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. The absorption lines are present toward both disk and diskless young stellar objects, which excludes cold gas within themore » circumstellar disk as the absorbing material. A comparison of Na i and CO detections and peak centroids demonstrates that the atomic gas and molecular gas are not co-located, the atomic gas being more extended than the molecular gas. The width of the atomic lines corroborates this finding and points to atomic gas about an order of magnitude warmer than the molecular gas. The distribution of Na i radial velocities shows a clear spatial gradient along the length of the Taurus molecular cloud filaments. This suggests that absorption is associated with the Taurus molecular cloud. Assuming that the gradient is due to cloud rotation, the rotation of the atomic gas is consistent with differential galactic rotation, whereas the rotation of the molecular gas, although with the same rotation axis, is retrograde. Our analysis shows that narrow Na i and K i absorption resonance lines are useful tracers of the atomic envelope of molecular clouds. In line with recent findings from giant molecular clouds, our results demonstrate that the velocity fields of the atomic and molecular gas are misaligned. The angular momentum of a molecular cloud is not simply inherited from the rotating Galactic disk from which it formed but may be redistributed by cloud–cloud interactions.« less

Analysis of atmospheric trace constituents from high resolution infrared balloon-borne and ground-based solar absorption spectra

NASA Technical Reports Server (NTRS)

Goldman, A.; Murcray, F. J.; Rinsland, C. P.; Blatherwick, R. D.; Murcray, F. H.; Murcray, D. G.

1991-01-01

Results of ongoing studies of high-resolution solar absorption spectra aimed at the identification and quantification of trace constituents of importance in the chemistry of the stratosphere and upper troposphere are presented. An analysis of balloon-borne and ground-based spectra obtained at 0.0025/cm covering the 700-2200/cm interval is presented. The 0.0025/cm spectra, along with corresponding laboratory spectra, improves the spectral line parameters, and thus the accuracy of quantifying trace constituents. Results for COF2, F22, SF6, and other species are presented. The retrieval methods used for total column density and altitude distribution for both ground-based and balloon-borne spectra are also discussed.

Implications of New Methane Absorption Coefficients on Uranus Vertical Structure Derived from Near-IR Spectra

NASA Astrophysics Data System (ADS)

Fry, Patrick M.; Sromovsky, L. A.

2009-09-01

Using new methane absorption coefficients from Karkoschka and Tomasko (2009, submitted to Icarus, "Methane Absorption Coefficients for the Jovian Planets from Laboratory, Huygens, and HST Data"), we fit Uranus near-IR spectra previously analyzed in Sromovsky et al. (2006, Icarus 182, 577-593, Fink and Larson, 1979 J- and H-band), Sromovsky and Fry (2008, Icarus 193, 252-266, 2006 NIRC2 J- and H-band, 2006 SpeX) using Irwin et al. (2006, Icarus 181, 309-319) methane absorption coefficients. Because the new absorption coefficients usually result in higher opacities at the low temperatures seen in Uranus' upper troposphere, our previously derived cloud altitudes are expected to generally rise to higher altitudes. For example, using Lindal et al. (1987, JGR 92, 14987-15001) model D temperature and methane abundance profiles, we are better able to fit the J-band 43-deg. south bright band with the new coefficients (chi-square=205, vs. 315 for Irwin), with the pressure of the upper tropospheric cloud decreasing to 1.6 bars (from 2.4 bars using Irwin coefficients). Improvements in fitting H-band spectra from the same latitude are not as readily obtained. Derived upper tropospheric cloud pressures are very similar using the two absorption datasets (1.6-1.7 bars), but the character of the fits differs. New Karkoschka and Tomasko coefficients better fit some details in the 1.5-1.58 micron region, but Irwin fits the broad absorption band wing at 1.61-1.62 microns better, and the fit chi-square values are similar (K&T: 243, Irwin: 220). Results for a higher methane concentration (Lindal et al. model F) were similar. Whether the new coefficients will simply raise derived altitudes across the planet or will result in fundamental changes in structure is as yet unclear. This work was suported by NASA planetary astronomy and planetary atmospheres programs.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic-Inorganic Lead Halide Perovskites.

PubMed

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; Sadoughi, Golnaz; Habisreutinger, Severin N; Félix, Roberto; Wilks, Regan G; Snaith, Henry J; Bär, Marcus; Draxl, Claudia

2018-04-19

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3 ) hybrid inorganic-organic perovskite and its binary phase PbI 2 . The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. The theoretical analysis complementing experimental observations provides the conceptual insights required for a full characterization of this complex material.

Electronic absorption spectra of chromium-bearing sapphirine

NASA Astrophysics Data System (ADS)

Langer, K.; Platonov, A. N.; Matsuk, S. S.; Andrut, M.

1994-05-01

Violet, non-pleochroic and greenish-blue, pleochroic chromium-substituted sapphirines were found in corundum-bearing spinel-websterite xenolites from the Yakutian kimberlite pipes Noyabrskaya (N) and Sludyanka (Sl), respectively. The crystallochemical formulae of sapphirine crystals from such xenolites were determined by EMP to be (Mg3.40Fe0.23Al3.25Cr0.16)[6] Al{1.00/[6]}[O2/Al4.53Si1.47O18] (N) and (Mg2.53Fe0.55 Mn0.04Ti{0.03/4+}Al3.55Cr{0.08/3+})[6]Al{1.00/[16]}[O2/Al4.28Si1.73O18] (Sl). Single crystal spectra in the range 35000 6000 cm1- showed a slightly polarization dependent absorption edge near 3200 cm1- (N) or 30000 cm1- (Sl) and unpolarized bands at 25300 and 17300 cm1-, typical of spin-allowed transitions, derived from 4A2g→4T1g and 4A2g→4T2g, of Cr3+ in octahedral sites, with point symmetry C1, of the structure. Another weak band at 23000 cm-1 in the sapphirine-N spectra is attributed to low symmetry splitting of the excited 4T1 (F)-State of Cr3+. These assignments lead to crystal field parameters Dq=1730cm-1 and B= 685cm-1 of Cr3+ in sapphirine. Crystallochemical and spectroscopic arguments suggest that Cr3+ subsitutes for Al in the M(1) or M(8) sites of the sapphirine structure. In addition to Cr3+-transitions, spectra of Sl exhibit weak dd-bands of Fe2+ at 10000 and 7700 cm1-, which are unpolarized in consistency with the C1 site symmetry of the octahedra in the structure. Spectra of Sl show also prominent, broad bands (Δv1/2˜-5000 cm1-) at 15000 and 11000 cm1-, which occur in E//Y(//b) and E//Z(//c=12°) only and exhibit an intensity ratio αY∶αz close to 1∶3. This result, the large half width, as well as band energy — MM distance considerations suggest that these bands originate from Fe2+[6]-Fe3+[6] charge-transfer transitions in wall octahedra M(1)M(2), M(6)M(7) etc., forming MM vectors of 30° with the c-axis. The lack of Fe2+-Fe3+ charge-transfer bands in sapphirine N might indicate a lower oxygen fugacity during the formation of

[Study of high temperature water vapor concentration measurement method based on absorption spectroscopy].

PubMed

Chen, Jiu-ying; Liu, Jian-guo; He, Jun-feng; He, Ya-bai; Zhang, Guang-le; Xu, Zhen-yu; Gang, Qiang; Wang, Liao; Yao, Lu; Yuan, Song; Ruan, Jun; Dai, Yun-hai; Kan, Rui-feng

2014-12-01

Tunable diode laser absorption spectroscopy (TDLAS) has been developed to realize the real-time and dynamic measurement of the combustion temperature, gas component concentration, velocity and other flow parameters, owing to its high sensitivity, fast time response, non-invasive character and robust nature. In order to obtain accurate water vapor concentration at high temperature, several absorption spectra of water vapor near 1.39 μm from 773 to 1273 K under ordinary pressure were recorded in a high temperature experiment setup using a narrow band diode laser. The absorbance of high temperature absorption spectra was calculated by combined multi-line nonlinear least squares fitting method. Two water vapor absorption lines near 7154.35 and 7157.73 cm(-1) were selected for measurement of water vapor at high temperature. A model method for high temperature water vapor concentration was first proposed. Water vapor concentration from the model method at high temperature is in accordance with theoretical reasoning, concentration measurement standard error is less than 0.2%, and the relative error is less than 6%. The feasibility of this measuring method is verified by experiment.

The manifestation of optical centers in UV-Vis absorption and luminescence spectra of white blood human cells

NASA Astrophysics Data System (ADS)

Terent'yeva, Yu G.; Yashchuk, V. M.; Zaika, L. A.; Snitserova, O. M.; Losytsky, M. Yu

2016-12-01

A white blood human cells spectral investigation is presented. The aim of this series of experiments was to obtain and analyze the absorption and luminescence (fluorescence and phosphorescence) spectra at room temperature and at 78 K of newly isolated white blood human cells and their organelles. As a result the optical centers and possible biochemical components that form the studied spectra where identified. Also the differences between the spectra of abnormal cells (B-cell chronic lymphocytic leukemia BCLL) and normal ones were studied for the whole cells and individual organelles.

The absorption, fluorescence and phosphorescence spectra of α and β-F, Cl, Br-naphthalenes in crystalline matrixes at 77 K

NASA Astrophysics Data System (ADS)

Iliescu, T.; Milea, I.; Abdolrahman, P. M.

1984-03-01

The paper studies the absorption, fluorescence and phosphorescence spectra of α and β-F, Cl, Br-naphtalenes (α, β-F, Cl,BrN) in different matrixes at 77 K and different concentrations. From these spectra one obtaines the vibrational frequences.

X-Ray Absorption Spectra of Amorphous Ices from GW Quasiparticle Calculation

NASA Astrophysics Data System (ADS)

Kong, Lingzhu; Car, Roberto

2013-03-01

We use a GW approach[2] to compute the x-ray absorption spectra of model low- and high-density amorphous ice structures(LDA and HDA)[3]. We include the structural effects of quantum zero point motion using colored-noise Langevin molecular dynamics[4]. The calculated spectra differences in the main and post edge region between LDA and HDA agree well with experimental observations. We attribute these differences to the presence of interstitial molecules within the first coordination shell range in HDA. This assignment is further supported by a calculation of the spectrum of ice VIII, a high-pressure structure that maximizes the number of interstitial molecules and, accordingly, shows a much weaker post-edge feature. We further rationalize the spectral similarity between HDA and liquid water, and between LDA and ice Ih in terms of the respective similarities in the H-bond network topology and bond angle distributions. Supported by grants DOE-DE-SC0005180, DOE DE-SC0008626 and NSF-CHE-0956500.

Determination of absorption coefficient of nanofluids with unknown refractive index from reflection and transmission spectra

NASA Astrophysics Data System (ADS)

Kim, Joong Bae; Lee, Seungyoon; Lee, Kyungeun; Lee, Ikjin; Lee, Bong Jae

2018-07-01

It has been shown that the absorption coefficient of a nanofluid can be actively tuned by changing material, size, shape, and concentration of the nanoparticle suspension. In applications of engineered nanofluids for the direct absorption of solar radiation, it is important to experimentally characterize the absorption coefficient of nanofluids in the solar spectrum. If the refractive index of the base fluid (i.e., the solution without nanoparticles) is known a priori, the absorption coefficient of nanofluids can be easily determined from the transmission spectrum. However, if the refractive index of the base fluid is not known, it is not straightforward to extract the absorption coefficient solely from the transmission spectrum. The present work aims to develop an analytical method of determining the absorption coefficient of nanofluids with unknown refractive index by measuring both reflection and transmission spectra. The proposed method will be validated with deionized water, and the effect of measurement uncertainty will be carefully examined. Finally, the general applicability of the proposed method will also be demonstrated for Therminol VP-1 as well as the Therminol VP-1 - graphite nanofluid.

Retrieval of phytoplankton cell size from chlorophyll a specific absorption and scattering spectra of phytoplankton.

PubMed

Zhou, Wen; Wang, Guifen; Li, Cai; Xu, Zhantang; Cao, Wenxi; Shen, Fang

2017-10-20

Phytoplankton cell size is an important property that affects diverse ecological and biogeochemical processes, and analysis of the absorption and scattering spectra of phytoplankton can provide important information about phytoplankton size. In this study, an inversion method for extracting quantitative phytoplankton cell size data from these spectra was developed. This inversion method requires two inputs: chlorophyll a specific absorption and scattering spectra of phytoplankton. The average equivalent-volume spherical diameter (ESD v ) was calculated as the single size approximation for the log-normal particle size distribution (PSD) of the algal suspension. The performance of this method for retrieving cell size was assessed using the datasets from cultures of 12 phytoplankton species. The estimations of a(λ) and b(λ) for the phytoplankton population using ESD v had mean error values of 5.8%-6.9% and 7.0%-10.6%, respectively, compared to the a(λ) and b(λ) for the phytoplankton populations using the log-normal PSD. The estimated values of C i ESD v were in good agreement with the measurements, with r 2 =0.88 and relative root mean square error (NRMSE)=25.3%, and relatively good performances were also found for the retrieval of ESD v with r 2 =0.78 and NRMSE=23.9%.

Phase-dependent absorption features in X-ray spectra of X-ray Dim Isolated Neutron Stars

NASA Astrophysics Data System (ADS)

Borghese, A.; Rea, N.; Coti Zelati, F.; Turolla, R.; Tiengo, A.; Zane, S.

2017-12-01

A detailed phase-resolved spectroscopy of archival XMM-Newton observations of X-ray Dim Isolated Neutron Stars (XDINSs) led to the discovery of narrow and strongly phase-dependent absorption features in two of these sources. The first was discovered in the X-ray spectrum of RX J0720.4-3125, followed by a new possible candidate in RX J1308.6+2127. Both spectral lines have similar properties: they are detected for only ˜ 20% of the rotational cycle and appear to be stable over the timespan covered by the observations. We performed Monte Carlo simulations to test the significance of these phase-variable features and in both cases the outcome has confirmed the detection with a confidence level > 4.6σ. Because of the narrow width and the strong dependence on the pulsar rotational phase, the most likely interpretation for these spectral features is in terms of resonant proton cyclotron absorption scattering in a confined high-B structure close to the stellar surface. Within the framework of this interpretation, our results provide evidence for deviations from a pure dipole magnetic field on small scales for highly magnetized neutron stars and support the proposed scenario of XDINSs being aged magnetars, with a strong non-dipolar crustal B-field component.

Perfect narrow band absorber for sensing applications.

PubMed

Luo, Shiwen; Zhao, Jun; Zuo, Duluo; Wang, Xinbing

2016-05-02

We design and numerically investigate a perfect narrow band absorber based on a metal-metal-dielectric-metal structure which consists of periodic metallic nanoribbon arrays. The absorber presents an ultra narrow absorption band of 1.11 nm with a nearly perfect absorption of over 99.9% in the infrared region. For oblique incidence, the absorber shows an absorption more than 95% for a wide range of incident angles from 0 to 50°. Structure parameters to the influence of the performance are investigated. The structure shows high sensing performance with a high sensitivity of 1170 nm/RIU and a large figure of merit of 1054. The proposed structure has great potential as a biosensor.

Determining CDOM Absorption Spectra in Diverse Aquatic Environments Using a Multiple Pathlength, Liquid Core Waveguide System

NASA Technical Reports Server (NTRS)

Miller, Richard L.; Belz, Mathias; DelCastillo, Carlos; Trzaska, Rick

2001-01-01

We evaluated the accuracy, sensitivity and precision of a multiple pathlength, liquid core waveguide (MPLCW) system for measuring colored dissolved organic matter (CDOM) absorption in the UV-visible spectral range (370-700 nm). The MPLCW has four optical paths (2.0, 9.8, 49.3, and 204 cm) coupled to a single Teflon AF sample cell. Water samples were obtained from inland, coastal and ocean waters ranging in salinity from 0 to 36 PSU. Reference solutions for the MPLCW were made having a refractive index of the sample. CDOM absorption coefficients, aCDOM, and the slope of the log-linearized absorption spectra, S, were compared with values obtained using a dual-beam spectrophotometer. Absorption of phenol red secondary standards measured by the MPLCW at 558 nm were highly correlated with spectrophotometer values and showed a linear response across all four pathlengths. Values of aCDOM measured using the MPLCW were virtually identical to spectrophotometer values over a wide range of concentrations. The dynamic range of aCDOM for MPLCW measurements was 0.002 - 231.5 m-1. At low CDOM concentrations spectrophotometric aCDOM were slightly greater than MPLCW values and showed larger fluctuations at longer wavelengths due to limitations in instrument precision. In contrast, MPLCW spectra followed an exponential to 600 nm for all samples.

Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera

NASA Astrophysics Data System (ADS)

Wan, Yuhang; Carlson, John A.; Kesler, Benjamin A.; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A.; Lim, Sung Jun; Smith, Andrew M.; Dallesasse, John M.; Cunningham, Brian T.

2016-07-01

A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid’s absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics.

Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera.

PubMed

Wan, Yuhang; Carlson, John A; Kesler, Benjamin A; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A; Lim, Sung Jun; Smith, Andrew M; Dallesasse, John M; Cunningham, Brian T

2016-07-08

A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid's absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics.

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

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

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

Exciton-Dominated Core-Level Absorption Spectra of Hybrid Organic–Inorganic Lead Halide Perovskites

DOE PAGES

Vorwerk, Christian; Hartmann, Claudia; Cocchi, Caterina; ...

2018-03-23

In a combined theoretical and experimental work, we investigate X-ray absorption near-edge structure spectroscopy of the I L 3 and the Pb M 5 edges of the methylammonium lead iodide (MAPbI 3) hybrid inorganic-organic perovskite and its binary phase PbI 2. The absorption onsets are dominated by bound excitons with sizable binding energies of a few hundred millielectronvolts and pronounced anisotropy. The spectra of both materials exhibit remarkable similarities, suggesting that the fingerprints of core excitations in MAPbI 3 are essentially given by its inorganic component, with negligible influence from the organic groups. Furthermore, the theoretical analysis complementing experimental observationsmore » provides the conceptual insights required for a full characterization of this complex material.« less

VizieR Online Data Catalog: BOSS narrow CIV absorption lines. II. zem>2.4 (Chen+, 2014)

NASA Astrophysics Data System (ADS)

Chen, Z.-F.; Qin, Y.-P.; Qin, M.; Pan, C.-J.; Pan, D.-S.

2015-01-01

We identify absorption doublets, such as CIVλλ1548,1551 in the quasar spectra of the Baryon Oscillation Spectroscopic Survey (BOSS), which is a part of the SDSS-III (Eisenstein et al. 2011AJ....142...72E). This work continues the analysis of Paper I (Chen+, 2014, J/ApJS/210/7; 2014ApJS..212...17C) by expanding the quasar sample to those quasars with zem>2.4. (1 data file).

IR absorption and surface-enhanced Raman spectra of the isoquinoline alkaloid berberine

NASA Astrophysics Data System (ADS)

Strekal', N. D.; Motevich, I. G.; Nowicky, J. W.; Maskevich, S. A.

2007-01-01

We present the IR absorption and surface-enhanced Raman scattering (SERS) spectra of the isoquinoline alkaloid berberine adsorbed on a silver hydrosol and on the surface of a silver electrode for different potentials. Based on quantum chemical calculations, for the first time we have assigned the vibrations in the berberine molecule according to vibrational mode. The effect of the potential of the silver electrode on the geometry of sorption of the molecule on the surface is considered, assuming a short-range mechanism for enhancement of Raman scattering.

Application of support vector machine method for the analysis of absorption spectra of exhaled air of patients with broncho-pulmonary diseases

NASA Astrophysics Data System (ADS)

Bukreeva, Ekaterina B.; Bulanova, Anna A.; Kistenev, Yury V.; Kuzmin, Dmitry A.; Tuzikov, Sergei A.; Yumov, Evgeny L.

2014-11-01

The results of the joint use of laser photoacoustic spectroscopy and chemometrics methods in gas analysis of exhaled air of patients with respiratory diseases (chronic obstructive pulmonary disease, pneumonia and lung cancer) are presented. The absorption spectra of exhaled breath of all volunteers were measured, the classification methods of the scans of the absorption spectra were applied, the sensitivity/specificity of the classification results were determined. It were obtained a result of nosological in pairs classification for all investigated volunteers, indices of sensitivity and specificity.

Electronic and nuclear contributions to time-resolved optical and X-ray absorption spectra of hematite and insights into photoelectrochemical performance

DOE PAGES

Hayes, Dugan; Hadt, Ryan G.; Emery, Jonathan D.; ...

2016-11-02

Ultrafast time-resolved studies of photocatalytic thin films can provide a wealth of information crucial for understanding and thereby improving the performance of these materials by directly probing electronic structure, reaction intermediates, and charge carrier dynamics. The interpretation of transient spectra, however, can be complicated by thermally induced structural distortions, which appear within the first few picoseconds following excitation due to carrier–phonon scattering. Here we present a comparison of ex situ steady-state thermal difference spectra and transient absorption spectra spanning from NIR to hard X-ray energies of hematite thin films grown by atomic layer deposition. We find that beyond the firstmore » 100 picoseconds, the transient spectra measured for all excitation wavelengths and probe energies are almost entirely due to thermal effects as the lattice expands in response to the ultrafast temperature jump and then cools to room temperature on the microsecond timescale. At earlier times, a broad excited state absorption band that is assigned to free carriers appears at 675 nm, and the lifetime and shape of this feature also appear to be mostly independent of excitation wavelength. The combined spectroscopic data, which are modeled with density functional theory and full multiple scattering calculations, support an assignment of the optical absorption spectrum of hematite that involves two LMCT bands that nearly span the visible spectrum. Lastly, our results also suggest a framework for shifting the ligand-to-metal charge transfer absorption bands of ferric oxide films from the near-UV further into the visible part of the solar spectrum to improve solar conversion efficiency.« less

Self-interaction-corrected time-dependent density-functional-theory calculations of x-ray-absorption spectra

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

Tu, Guangde; Rinkevicius, Zilvinas; Vahtras, Olav

We outline an approach within time-dependent density functional theory that predicts x-ray spectra on an absolute scale. The approach rests on a recent formulation of the resonant-convergent first-order polarization propagator [P. Norman et al., J. Chem. Phys. 123, 194103 (2005)] and corrects for the self-interaction energy of the core orbital. This polarization propagator approach makes it possible to directly calculate the x-ray absorption cross section at a particular frequency without explicitly addressing the excited-state spectrum. The self-interaction correction for the employed density functional accounts for an energy shift of the spectrum, and fully correlated absolute-scale x-ray spectra are thereby obtainedmore » based solely on optimization of the electronic ground state. The procedure is benchmarked against experimental spectra of a set of small organic molecules at the carbon, nitrogen, and oxygen K edges.« less

A Statistical Study of the Southern Fermi Bubble in UV Absorption Spectra

NASA Astrophysics Data System (ADS)

Karim, Md. Tanveer; Fox, Andrew; Jenkins, Edward; Bordoloi, Rongmon; Wakker, Bart; Savage, Blair D.; Lockman, Felix; Crawford, Steve; Bland-Hawthorn, Joss; Jorgenson, Regina A.

2018-01-01

The Fermi Bubbles are two giant lobes of plasma situated at the center of the Milky Way, extending 55° above and below the Galactic Midplane. Although the Bubbles have been widely studied in multiple wavelengths, few studies have been done in UV absorption. Here we present a statistical study of the Southern Fermi Bubble using 17 QSO sightlines — 6 inside the Bubble, 11 outside — using UV absorption spectra from the Hubble Space Telescope Cosmic Origins Spectrograph (HST/COS). We searched for high-velocity clouds (HVCs) in 11 metal lines from ions of Aluminium, Carbon and Silicon. We detected HVCs in 83% of the sightlines inside the Bubble and 64% outside the Bubble, showing an enhancement in the covering fraction of HVCs in the Southern Bubble region. We also observed a decrease in vLSR of the HVCs as a function of the galactic latitude, consistent with a scenario where the identified HVCs trace the Galactic nuclear outflow, as sightlines closer to the central engine are expected to show a higher velocity. Combined with previous studies, our analysis indicates that the Southern Fermi Bubble is a dynamic environment giving rise to complex absorption features.

Identifying Student and Teacher Difficulties in Interpreting Atomic Spectra Using a Quantum Model of Emission and Absorption of Radiation

ERIC Educational Resources Information Center

Savall-Alemany, Francisco; Domènech-Blanco, Josep Lluís; Guisasola, Jenaro; Martínez-Torregrosa, Joaquín

2016-01-01

Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two…

Measurements of spectral parameters of water-vapour transitions near 1388 and 1345 nm for accurate simulation of high-pressure absorption spectra

NASA Astrophysics Data System (ADS)

Liu, Xiang; Jeffries, Jay B.; Hanson, Ronald K.

2007-05-01

Quantitative near-infrared absorption spectroscopy of water-vapour overtone and combination bands at high pressures is complicated by pressure broadening and shifting of individual lines and the blending of neighbouring transitions. An experimental and computational methodology is developed to determine accurate high-pressure absorption spectra. This case study investigates two water-vapour transitions, one near 1388 nm (7203.9 cm-1) and the other near 1345 nm (7435.6 cm-1), for potential two-line absorption measurements of temperature in the range of 400-1050 K with a pressure varying from 5-25 atm. The required quantitative spectroscopy data (line strength, collisional broadening, and pressure-induced frequency shift) of the target transitions and their neighbours (a total of four H2O vapour transitions near 1388 nm and six transitions near 1345 nm) are measured in neat H2O vapour, H2O-air and H2O-CO2 mixtures as a function of temperature (296-1000 K) at low pressures (<800 Torr). Precise values of the line strength S(T), pressure-broadening coefficients γair(T) and \\gamma _{CO_2 } (T), and pressure-shift coefficients δair(T) and \\delta _{CO_2 } (T) for the ten transitions were inferred from the measured spectra and compared with data from HITRAN 2004. A hybrid spectroscopic database was constructed by modifying HITRAN 2004 to incorporate these values for simulation of water-vapour-absorption spectra at high pressures. Simulations using this hybrid database are in good agreement with high pressure experiments and demonstrate that data collected at modest pressures can be used to simulate high-pressure absorption spectra.

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime

NASA Astrophysics Data System (ADS)

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V.

2012-06-01

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime

PubMed Central

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro

2012-01-01

Abstract. Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed. PMID:22734767

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime.

PubMed

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V

2012-06-01

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

VizieR Online Data Catalog: Sgr B2 los molecular absorption line spectra (Corby+, 2018)

NASA Astrophysics Data System (ADS)

Corby, J. F.; McGuire, B. A.; Herbst, E.; Remijan, A. J.

2017-11-01

Spectra covering transitions of c-C3H2, c-H1 SO, CCS, H2CS, HCS+, OH, SiO, 29SiO, H2CO, H2(13C)O, l-C3H, and l-C3H+ with line-of-sight absorption observed in the 1-50 GHz data from the PRebiotic Interstellar MOlecular Survey (PRIMOS) taken with the Robert C. Byrd Green Bank Telescope (GBT). Data were observed between 2001 and 2014, with the majority of the data obtained in 2007 in GBT Key Science project ID GBT07A-051. Spectra have been baseline-subtracted using best fit polynomials as described in the paper, and normalized by the continuum, so that the y-axis represents (T/TC-1). Data are provided in the FITS format; each FITS file contains all lines of a single molecule that are observed to have foreground absorption. Please refer to Table 1 of the paper to obtain molecular transition rest frequencies, energies, GBT beam sizes, and transition quantum numbers. (2 data files).

Evolution of synchrotron-radiation-based Mössbauer absorption spectroscopy for various isotopes

NASA Astrophysics Data System (ADS)

Seto, Makoto; Masuda, Ryo; Kobayashi, Yasuhiro; Kitao, Shinji; Kurokuzu, Masayuki; Saito, Makina; Hosokawa, Shuuich; Ishibashi, Hiroki; Mitsui, Takaya; Yoda, Yoshitaka; Mibu, Ko

2017-11-01

Synchrotron-radiation-based Mössbauer spectroscopy that yields absorption type Mössbauer spectra has been applied to various isotopes. This method enables the advanced measurement by using the excellent features of synchrotron radiation, such as Mössbauer spectroscopic measurement under high-pressures. Furthermore, energy selectivity of synchrotron radiation allows us to measure 40K Mössbauer spectra, of which observation is impossible by using ordinary radioactive sources because the first excited state of 40K is not populated by any radioactive parent nuclides. Moreover, this method has flexibility of the experimental setup that the measured sample can be used as a transmitter or a scatterer, depending on the sample conditions. To enhance the measurement efficiency of the spectroscopy, we developed a detection system in which a windowless avalanche photodiode (APD) detector is combined with a vacuum cryostat to detect internal conversion electrons adding to X-rays accompanied by nuclear de-excitation. In particular, by selecting the emission from the scatterer sample, depth selective synchrotron-radiation-based Mössbauer spectroscopy is possible. Furthermore, limitation of the time window in the delayed components enables us to obtain narrow linewidth in Mössbauer spectra. Measurement system that records velocity dependent time spectra and energy information simultaneously realizes the depth selective and narrow linewidth measurement.

Compact characterization of liquid absorption and emission spectra using linear variable filters integrated with a CMOS imaging camera

PubMed Central

Wan, Yuhang; Carlson, John A.; Kesler, Benjamin A.; Peng, Wang; Su, Patrick; Al-Mulla, Saoud A.; Lim, Sung Jun; Smith, Andrew M.; Dallesasse, John M.; Cunningham, Brian T.

2016-01-01

A compact analysis platform for detecting liquid absorption and emission spectra using a set of optical linear variable filters atop a CMOS image sensor is presented. The working spectral range of the analysis platform can be extended without a reduction in spectral resolution by utilizing multiple linear variable filters with different wavelength ranges on the same CMOS sensor. With optical setup reconfiguration, its capability to measure both absorption and fluorescence emission is demonstrated. Quantitative detection of fluorescence emission down to 0.28 nM for quantum dot dispersions and 32 ng/mL for near-infrared dyes has been demonstrated on a single platform over a wide spectral range, as well as an absorption-based water quality test, showing the versatility of the system across liquid solutions for different emission and absorption bands. Comparison with a commercially available portable spectrometer and an optical spectrum analyzer shows our system has an improved signal-to-noise ratio and acceptable spectral resolution for discrimination of emission spectra, and characterization of colored liquid’s absorption characteristics generated by common biomolecular assays. This simple, compact, and versatile analysis platform demonstrates a path towards an integrated optical device that can be utilized for a wide variety of applications in point-of-use testing and point-of-care diagnostics. PMID:27389070

Long-Range Chemical Sensitivity in the Sulfur K-Edge X-ray Absorption Spectra of Substituted Thiophenes

PubMed Central

2015-01-01

Thiophenes are the simplest aromatic sulfur-containing compounds and are stable and widespread in fossil fuels. Regulation of sulfur levels in fuels and emissions has become and continues to be ever more stringent as part of governments’ efforts to address negative environmental impacts of sulfur dioxide. In turn, more effective removal methods are continually being sought. In a chemical sense, thiophenes are somewhat obdurate and hence their removal from fossil fuels poses problems for the industrial chemist. Sulfur K-edge X-ray absorption spectroscopy provides key information on thiophenic components in fuels. Here we present a systematic study of the spectroscopic sensitivity to chemical modifications of the thiophene system. We conclude that while the utility of sulfur K-edge X-ray absorption spectra in understanding the chemical composition of sulfur-containing fossil fuels has already been demonstrated, care must be exercised in interpreting these spectra because the assumption of an invariant spectrum for thiophenic forms may not always be valid. PMID:25116792

The origin of absorptive features in the two-dimensional electronic spectra of rhodopsin.

PubMed

Farag, Marwa H; Jansen, Thomas L C; Knoester, Jasper

2018-05-09

In rhodopsin, the absorption of a photon causes the isomerization of the 11-cis isomer of the retinal chromophore to its all-trans isomer. This isomerization is known to occur through a conical intersection (CI) and the internal conversion through the CI is known to be vibrationally coherent. Recently measured two-dimensional electronic spectra (2DES) showed dramatic absorptive spectral features at early waiting times associated with the transition through the CI. The common two-state two-mode model Hamiltonian was unable to elucidate the origin of these features. To rationalize the source of these features, we employ a three-state three-mode model Hamiltonian where the hydrogen out-of plane (HOOP) mode and a higher-lying electronic state are included. The 2DES of the retinal chromophore in rhodopsin are calculated and compared with the experiment. Our analysis shows that the source of the observed features in the measured 2DES is the excited state absorption to a higher-lying electronic state and not the HOOP mode.

All-optical laser spectral narrowing and line fixing at atomic absorption transition by injection competition and gain knock-down techniques

NASA Astrophysics Data System (ADS)

Gacheva, Lazarina I.; Deneva, Margarita A.; Kalbanov, Mihail H.; Nenchev, Marin N.

2008-12-01

We present two original, all optical techniques, to produce a narrowline laser light, fixed at the frequency of a chosen reference atomic absorption transition. The first type of systems is an essential improvement of our method 3,4 for laser spectral locking using a control by two frequency scanned, competitive injections with disturbed power ratio by the absorption at the reference line. The new development eliminates the narrowing limiting problem, related with the fixed laser longitudinal mode structure. We have proposed an original new technique for continuously tunable single mode laser operation in combination with synchronously and equal continuous tuning of the modes of the amplifier. By adapting the laser differential rate equations, the system is analyzed theoretically in details and is shown its feasibility. The results are in agreement with previous our experiments. The essential advantage, except simplicity of realization, is that the laser line can be of order of magnitude and more narrowed than the absorption linewidth. The second system is based of the laser amplifier arrangement with a gain knock-down from the competitive frequency scanned pulse, except at the wavelength of the desired absorption reference line. The essential advantages of the last system are that the problem of fixing laser mode presence is naturally avoided. The theoretical modeling and the numerical investigations show the peculiarity and advantages of the system proposed. The developed approaches are of interest for applications in spectroscopy, in DIAL monitoring of the atmospheric pollutants, in isotope separation system and potentially - for creation of simple, all optical, frequency standards for optical communications. Also, the continuously tunable single mode laser (and the combination with the simultaneously tunable amplifier) presents itself the interest for many practical applications in spectroscopy, metrology, and holography. We compare the action and the

Substituent and solvent effects on the UV/vis absorption spectra of 5-(3- and 4-substituted arylazo)-4,6-dimethyl-3-cyano-2-pyridones

NASA Astrophysics Data System (ADS)

Mijin, Dušan Ž.; Ušćumlić, Gordana S.; Perišić-Janjić, Nada U.; Valentić, Nataša V.

2006-01-01

Absorption spectra of seventeen 5-(3- and 4-substituted arylazo)-4,6-dimethyl-3-cyano-2-pyridones have been recorded in 12 protic and aprotic solvents in the range 200-600 nm. The effects of substituents on the absorption spectra of these new azo dyes are interpreted by correlation of absorption frequencies with Hammett equation. The solute-solvent interactions were clarified on the basis of linear solvation energy relationships concept proposed by Kamlet and Taft. The 2-pyridone/2-hydroxypiridine tautomeric equilibration is found to depend upon substituents as well as on solvents.

The IR Absorption Spectra of Aqueous Solutions of Dimethylsulfoxide over the Frequency Range 50-300 cm-1 and the Mobility of Water Molecules

NASA Astrophysics Data System (ADS)

Klemenkova, Z. S.; Novskova, T. A.; Lyashchenko, A. K.

2008-04-01

The IR absorption spectra of aqueous solutions of dimethylsulfoxide (DMSO) with concentrations from 100% H2O to 100% DMSO were recorded over the frequency range 50-500 cm-1. The absorption spectra were described using the theoretical scheme of hindered rotators. A model was developed according to which orientation relaxation in solution was related to separate rotations of H2O and DMSO molecules through fixed small and (or) large angles in a unified network of H-bonds consisting of several subsystems ordered to various degrees. The calculated absorption spectra were in agreement with the experimental data in the far IR region. Elementary motions of molecules were found to slow down in the passage from pure dimethylsulfoxide to its aqueous solutions. The special features of the hydrophilic and hydrophobic hydration of DMSO polar and nonpolar groups were considered.

Carbon X-ray absorption in the local ISM: fingerprints in X-ray Novae spectra

NASA Astrophysics Data System (ADS)

Gatuzz, Efraín; Ness, J.-U.; Gorczyca, T. W.; Hasoglu, M. F.; Kallman, Timothy R.; García, Javier A.

2018-06-01

We present a study of the C K-edge using high-resolution LETGS Chandra spectra of four novae during their super-soft-source (SSS) phase. We identified absorption lines due to C II Kα, C III Kα and C III Kβ resonances. We used these astronomical observations to perform a benchmarking of the atomic data, which involves wavelength shifts of the resonances and photoionization cross-sections. We used improved atomic data to estimate the C II and C III column densities. The absence of physical shifts for the absorption lines, the consistence of the column densities between multiple observations and the high temperature required for the SSS nova atmosphere modeling support our conclusion about an ISM origin of the respective absorption lines. Assuming a collisional ionization equilibrium plasma the maximum temperature derived from the ratio of C II/C III column densities of the absorbers correspond to Tmax < 3.05 × 104 K.

Investigation of the multiplet features of SrTiO 3 in X-ray absorption spectra based on configuration interaction calculations

DOE PAGES

Wu, M.; Xin, Houlin L.; Wang, J. O.; ...

2018-04-24

Synchrotron-based L 2,3-edge absorption spectra show strong sensitivities to the local electronic structure and chemical environment. However, detailed physical information cannot be extracted easily without computational aids. Here in this study using the experimental Ti L 2,3-edges absorption spectrum of SrTiO 3as a fingerprint and considering full multiplet effects, calculations yield different energy parameters characterizing local ground state properties. The peak splitting and intensity ratios of the L 3 and L 2 set of peaks are carefully analyzed quantitatively, giving rise to a small hybridization energy around 1.2 eV, and the different hybridization energy values reported in the literature aremore » further addressed. Finally, absorption spectra with different linearly polarized photons under various tetragonal crystal fields are investigated, revealing a non-linear orbital–lattice interaction, and a theoretical guidance for material engineering of SrTiO 3-based thin films and heterostructures is offered. Finally, detailed analysis of spectrum shifts with different tetragonal crystal fields suggests that the e g crystal field splitting is a necessary parameter for a thorough analysis of the spectra, even though it is not relevant for the ground state properties.« less

Investigation of the multiplet features of SrTiO 3 in X-ray absorption spectra based on configuration interaction calculations

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

Wu, M.; Xin, Houlin L.; Wang, J. O.

Synchrotron-based L 2,3-edge absorption spectra show strong sensitivities to the local electronic structure and chemical environment. However, detailed physical information cannot be extracted easily without computational aids. Here in this study using the experimental Ti L 2,3-edges absorption spectrum of SrTiO 3as a fingerprint and considering full multiplet effects, calculations yield different energy parameters characterizing local ground state properties. The peak splitting and intensity ratios of the L 3 and L 2 set of peaks are carefully analyzed quantitatively, giving rise to a small hybridization energy around 1.2 eV, and the different hybridization energy values reported in the literature aremore » further addressed. Finally, absorption spectra with different linearly polarized photons under various tetragonal crystal fields are investigated, revealing a non-linear orbital–lattice interaction, and a theoretical guidance for material engineering of SrTiO 3-based thin films and heterostructures is offered. Finally, detailed analysis of spectrum shifts with different tetragonal crystal fields suggests that the e g crystal field splitting is a necessary parameter for a thorough analysis of the spectra, even though it is not relevant for the ground state properties.« less

Influence of polarity of solvents on IR absorption and Raman spectra of ascorbic acid

NASA Astrophysics Data System (ADS)

Kutsenko, S. A.; Danyaeva, Y. S.; Maximova, S. V.

2018-04-01

The results of numerical calculations of IR absorption and Raman spectra of ascorbic acid in polar and nonpolar solutions are presented. The dependence of the change in the total energy and the dipole moment of the molecule on the characteristics of the solvents was investigated using the two solvation models. Spectral bands and the corresponding structural groups of the molecule are found, the characteristics of which are most vulnerable to solvents.

One- and two-photon absorption spectra of the yellow fluorescent protein citrine: effects of intramolecular electron-vibrational coupling and intermolecular interactions

NASA Astrophysics Data System (ADS)

Chen, Fasheng; Zhao, Xinyi; Liang, WanZhen

2018-04-01

Both the vibrationally resolved and statistically averaged one-photon absorption (OPA) and two-photon absorption (TPA) spectra of the anionic form of chromophore (AC) in its micro-environment of yellow fluorescent protein (YFP) Citrine have been calculated. The result comparison has been made with those of the AC model compounds in vacuo and methanol solution, which allows us to allocate the individual contribution of the intramolecular electron-vibrational coupling, the electrostatic π-stacking interaction between Tyr203 and AC, and the interaction between AC and its micro-environment to the spectra. The results reveal that the non-Condon vibronic coupling effect is responsible for the blue shift of TPA absorption maximum compared with its OPA counterpart corresponding to S0 → S1, and that the π-stacking interaction between Tyr203 and AC alters the relative intensities of TPA maxima, which further enhances the higher-energy vibronic peaks and weakens the lowest-energy peak. The statically averaged OPA and TPA spectra calculated by quantum mechanics/molecular mechanics (QM/MM) methods based on Born-Oppenheimer molecular dynamics simulation largely deviate the experimental spectral lineshapes, which further verifies the significant contribution of non-Condon vibronic coupling effect on the spectra. The interaction of individual amino acid residue or water close to AC+Tyr203 has different effects on the spectra, which may increase/decrease the excitation energy depending on its position and electronic property.

Absorption and electroabsorption spectra of carotenoid cation radical and dication

NASA Astrophysics Data System (ADS)

Krawczyk, Stanisław

1998-05-01

Radical cations and dications of two carotenoids astaxanthin and canthaxanthin were prepared by oxidation with FeCl 3 in fluorinated alcohols at room temperature. Absorption and electroabsorption (Stark effect) spectra were recorded for astaxanthin cations in mixed frozen matrices at temperatures about 160 K. The D 0→D 2 transition in cation radical is at 835 nm. The electroabsorption spectrum for the D 0→D 2 transition exhibits a negative change of molecular polarizability, Δ α=-1.2·10 -38 C·m 2/V (-105 A 3), which seems to originate from the change in bond order alternation in the ground state rather than from the electric field-induced interaction of D 1 and D 2 excited states. Absorption spectrum of astaxanthin dication is located at 715-717 nm, between those of D 0→D 2 in cation radical and S 0→S 2 in neutral carotenoid. Its shape reflects a short vibronic progression and strong inhomogeneous broadening. The polarizability change on electronic excitation, Δ α=2.89·10 -38 C·m 2/V (260 A 3), is five times smaller than in neutral astaxanthin. This value reflects the larger energetic distance from the lowest excited state to the higher excited states than in the neutral molecule.

Optical absorption spectra of substitutional Co2+ ions in Mgx Cd1-x Se alloys

NASA Astrophysics Data System (ADS)

Jin, Moon-Seog; Kim, Chang-Dae; Jang, Kiwan; Park, Sang-An; Kim, Duck-Tae; Kim, Hyung-Gon; Kim, Wha-Tek

2006-09-01

Optical absorption spectra of substitutional Co2+ ions in Mgx Cd1-x Se alloys were investigated in the composition region of 0.0 x 0.4 and in the wavelength region of 300 to 2500 nm at 4.8 K and 290 K. We observed several absorption bands in the wavelength regions corresponding to the 4A2(4F) 4T1(4P) transition and the 4A2(4F) 4T1(4F) transition of Co2+ at a tetrahedral Td point symmetry point in the host crystals, as well as unknown absorption bands. The several absorption bands were analyzed in the framework of the crystal-field theory along with the second-order spin-orbit coupling. The unknown absorption bands were assigned as due to phonon-assisted absorption bands. We also investigated the variations of the crystal-field parameter Dq and the Racah parameter B with composition x in the Mgx Cd1-x Se system. The results showed that the crystal-field parameter (Dq ) increases, on the other hand, the Racah parameter (B ) decreases with increasing composition x, which may be connected with an increase in the covalency of the metal-ligand bond with increasing composition x in the Mgx Cd1-x Se system.

VizieR Online Data Catalog: Quasars narrow absorption lines from SDSS (Chen+, 2015)

NASA Astrophysics Data System (ADS)

Chen, Z.-F.; Gu, Q.-S.; Chen, Y.-M.; Cao, Y.

2017-11-01

The Baryon Oscillation Spectroscopic Survey (BOSS: Eisenstein et al. 2011AJ....142...72E; Paris et al. 2012, Cat. VII/269) is the main dark-time legacy survey of the third stage of the SDSS, which used the same 2.5-m telescope (Gunn et al. 2006AJ....131.2332G; Ross et al. 2012, J/ApJS/199/3) as the first and second stages of the SDSS (hereafter SDSS-I/II). SDSS-I/II spectra have a wavelength coverage from 3800-9200Å with a spectral resolution of 1800-2200 (e.g. York et al. 2000AJ....120.1579Y). BOSS spectra span a range from 3600-10500Å at a resolution of 1300-2500 (Paris et al. 2012, Cat. VII/269). During the first two years, BOSS detected 87822 quasars over an area of 3275 deg2, including 7932 quasars that were observed by SDSS-I/II as well. Quasars observed by both SDSS-I/II and BOSS provide a remarkable chance to study the variabilities of absorption lines in a large population. Throughout this work, we take the quasar emission redshifts provided by Hewett & Wild (2010, J/MNRAS/405/2302, http://das.sdss.org/va/HewettWilddr7qso_newz/) directly. (2 data files).

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents

PubMed Central

Zheng, Dong; Yuan, Xiang-Ai; Ma, Haibo; Li, Xiaoxiong; Wang, Xizhang; Liu, Ziteng

2018-01-01

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o-cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o-cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o-cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260–280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o-cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o-cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively. PMID:29657794

Unexpected solvent effects on the UV/Vis absorption spectra of o-cresol in toluene and benzene: in contrast with non-aromatic solvents.

PubMed

Zheng, Dong; Yuan, Xiang-Ai; Ma, Haibo; Li, Xiaoxiong; Wang, Xizhang; Liu, Ziteng; Ma, Jing

2018-03-01

Cresol is a prototype molecule in understanding intermolecular interactions in material and biological systems, because it offers different binding sites with various solvents and protonation states under different pH values. It is found that the UV/Vis absorption spectra of o -cresol in aromatic solvents (benzene, toluene) are characterized by a sharp peak, unlike the broad double-peaks in 11 non-aromatic solvents. Both molecular dynamics simulations and electronic structure calculations revealed the formation of intermolecular π-complexation between o -cresol and aromatic solvents. The thermal movements of solvent and solute molecules render the conformations of o -cresol changing between trans and cis isomers. The π-interaction makes the cis configuration a dominant isomer, hence leading to the single keen-edged UV/Vis absorption peak at approximately 283 nm. The free conformation changes between trans and cis in aqueous solution rationalize the broader absorption peaks in the range of 260-280 nm. The pH dependence of the UV/Vis absorption spectra in aqueous solutions is also rationalized by different protonation states of o -cresol. The explicit solvent model with long-ranged interactions is vital to describe the effects of π-complexation and electrostatic interaction on the UV/Vis absorption spectra of o -cresol in toluene and alkaline aqueous (pH > 10.3) solutions, respectively.

Collision-Induced Absorption Spectra of Binary Mixtures of Molecular Hydrogen with Molecular Deuterium and Argon and of Pure Hydrogen, D

NASA Astrophysics Data System (ADS)

Hsieh, Chang-Tsang William

In the present research project a systematic study of the collision-induced infrared absorption (CIA) spectra of the binary mixtures of H_2 - D_2 in the region of the double fundamental vibrations of H_2 and D_2, and H_2 - Ar in the fundamental band of H_2, and of pure HD in its fundamental and first overtone regions was undertaken. The experiments were carried out with a 2.0 m high-pressure low-temperature transmission-type absorption cell at 77, 201 and 296 K at total gas densities up to 550 amagat. Infrared prism and grating spectrometers equipped with a microprocessor -controlled stepping motor were used to record the spectra. All the experimental results obtained represent first-time observations in collision-induced absorption. Collision-induced infrared absorption spectra of the double transitions of H_2(v=1>=ts 0) and D_2(v=1>=ts 0) have been observed at 77 and 201 K in the spectral region 7000-8000 cm^{-1} for total gas densities up to 550 amagat with a partial gas density ratio of 1:1 of H_2 and D_2. The observed spectra are interpreted in terms of the transitions, Q_1(J) of H_2+Q_1(J) of D _2, Q_1(J) of H_2+S _1(J) of D_2, S_1(J) of H_2 + Q_1(J) of D_2, and S_1(J) of H_2 + S_1(J) of D_2 for J = 0 and 1 for H _2 and J = 0, 1, and 2 for D_2. Analysis of the experimental absorption profiles was carried out using appropriate lineshape functions. The absorption coefficients, lineshape parameters, etc., are obtained from the analysis. Collision-induced enhancement absorption spectra of the fundamental band of H_2 in H_2 - Ar mixtures were recorded at room temperature for a base density of 72 amagat of H_2 for several partial densities of Ar up to 440 amagat. Hexadecapole-induced U transitions, U_1(1), U_1(2), Q_1(0)+U _0(1), and Q_1(1) + U_0(1) have been identified in the spectral region 5400 -6200 cm^{-1}. A "cage" model has been proposed to account for the double transitions of H_2 - H_2 in the H _2 - Ar enhancement spectra. From the analysis of the

Predicting the Shifts of Absorption Maxima of Azulene Derivatives Using Molecular Modeling and ZINDO CI Calculations of UV-Vis Spectra

ERIC Educational Resources Information Center

Patalinghug, Wyona C.; Chang, Maharlika; Solis, Joanne

2007-01-01

The deep blue color of azulene is drastically changed by the addition of substituents such as CH[subscript 3], F, or CHO. Computational semiempirical methods using ZINDO CI are used to model azulene and azulene derivatives and to calculate their UV-vis spectra. The calculated spectra are used to show the trends in absorption band shifts upon…

Quantification of optical absorption coefficient from acoustic spectra in the optical diffusive regime using photoacoustic microscopy

NASA Astrophysics Data System (ADS)

Guo, Zijian; Favazza, Christopher; Wang, Lihong V.

2012-02-01

Photoacoustic (PA) tomography (PAT) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Multi-wavelength PAT can noninvasively monitor hemoglobin oxygen saturation (sO2) with high sensitivity and fine spatial resolution. However, accurate quantification in PAT requires knowledge of the optical fluence distribution, acoustic wave attenuation, and detection system bandwidth. We propose a method to circumvent this requirement using acoustic spectra of PA signals acquired at two optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560 and 575 nm were quantified with errors of ><5%.

Wavelet based de-noising of breath air absorption spectra profiles for improved classification by principal component analysis

NASA Astrophysics Data System (ADS)

Kistenev, Yu. V.; Shapovalov, A. V.; Borisov, A. V.; Vrazhnov, D. A.; Nikolaev, V. V.; Nikiforova, O. Yu.

2015-11-01

The comparison results of different mother wavelets used for de-noising of model and experimental data which were presented by profiles of absorption spectra of exhaled air are presented. The impact of wavelets de-noising on classification quality made by principal component analysis are also discussed.

The P K-near edge absorption spectra of phosphates

NASA Astrophysics Data System (ADS)

Franke, R.; Hormes, J.

1995-12-01

The X-ray absorption near edge structure (XANES) at the P K-edge in several orthophosphates with various cations, in condensed, and in substituted sodium phosphates have been measured using synchrotron radiation from the ELSA storage ring at the University of Bonn. The measured spectra demonstrate that chemical changes beyond the PO 4- tetrahedra are reflected by energy shifts of the pre-edge and continuum resonances, by the presence of characteristic shoulders and new peaks and by differences in the intensity of the white line. We discuss the energy differences between the white line positions and the corresponding P ls binding energies as a measure of half of the energy gap. The corresponding values correlate with the valence of the cations and the intensity of the white lines. The energy positions of the continuum resonances are discussed on the basis of an empirical bond-length correlation supporting a 1/ r2 - dependence.

Substituent and solvent effects on the UV/Vis absorption spectra of 5-(4-substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridones

NASA Astrophysics Data System (ADS)

Ušćumlić, Gordana S.; Mijin, Dusanˇ Z. ˇ; Valentić, Nataša V.; Vajs, Vlatka V.; Sušić, Biljana M.

2004-10-01

Absorption spectra of ten 5-(4-substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridones have been recorded in fifteen solvents in the range 200-600 nm. The substituents at the phenyl nucleus are as follows: OH, OCH 3, CH 3, C 2H 5, H, Cl, Br, I, COOH and NO 2. The effects of substituents on the absorption spectra of investigated compounds are interpreted by correlation of absorption frequencies with simple Hammett equation. The effects of solvent polarity and solvent/solute hydrogen bonding interactions are analyzed by means of linear solvation energy relationships concept proposed by Kamlet and Taft. The azo-hydrazone tuatomeric equilibration is found to depend upon substituents as well as on solvents.

Artifact suppression in electron paramagnetic resonance imaging of 14N- and 15N-labeled nitroxyl radicals with asymmetric absorption spectra

NASA Astrophysics Data System (ADS)

Takahashi, Wataru; Miyake, Yusuke; Hirata, Hiroshi

2014-10-01

This article describes an improved method for suppressing image artifacts in the visualization of 14N- and 15N-labeled nitroxyl radicals in a single image scan using electron paramagnetic resonance (EPR). The purpose of this work was to solve the problem of asymmetric EPR absorption spectra in spectral processing. A hybrid function of Gaussian and Lorentzian lineshapes was used to perform spectral line-fitting to successfully separate the two kinds of nitroxyl radicals. This approach can process the asymmetric EPR absorption spectra of the nitroxyl radicals being measured, and can suppress image artifacts due to spectral asymmetry. With this improved visualization method and a 750-MHz continuous-wave EPR imager, a temporal change in the distributions of a two-phase paraffin oil and water/glycerin solution system was visualized using lipophilic and hydrophilic nitroxyl radicals, i.e., 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy (16-DOXYL stearic acid) and 4-hydroxyl-2,2,6,6-tetramethylpiperidine-d17-1-15N-1-oxyl (TEMPOL-d17-15N). The results of the two-phase separation experiment verified that reasonable artifact suppression could be achieved by the present method that deals with asymmetric absorption spectra in the EPR imaging of 14N- and 15N-labeled nitroxyl radicals.

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

Determining CDOM Absorption Spectra in Diverse Coastal Environments Using a Multiple Pathlength, Liquid Core Waveguide System. Measuring the Absorption of CDOM in the Field Using a Multiple Pathlength Liquid Waveguide System

NASA Technical Reports Server (NTRS)

Miller, Richard L.; Belz, Mathias; DelCastillo, Carlos; Trzaska, Rick

2000-01-01

We evaluated the accuracy, sensitivity and precision of a multiple pathlength, liquid core waveguide (MPLCW) system for measuring colored dissolved organic matter (CDOM) absorption in the UV-visible spectral range (370-700 nm). The MPLCW has four optical paths (2.0, 9.8, 49.3, and 204 cm) coupled to a single Teflon AF sample cell. Water samples were obtained from inland, coastal and ocean waters ranging in salinity from 0 to 36 PSU. Reference solutions for the MPLCW were made having a refractive index of the sample. CDOM absorption coefficients, a(sub CDOM), and the slope of the log-linearized absorption spectra, S, were compared with values obtained using a dual-beam spectrophotometer. Absorption of phenol red secondary standards measured by the MPLCW at 558 nm were highly correlated with spectrophotometer values (r > 0.99) and showed a linear response across all four pathlengths. Values of a(sub CDOM) measured using the MPLCW were virtually identical to spectrophotometer values over a wide range of concentrations. The dynamic range of a(sub CDOM) for MPLCW measurements was 0.002 - 231.5/m. At low CDOM concentrations (a(sub 370) < 0.1/m) spectrophotometric a(sub CDOM) were slightly greater than MPLCW values and showed larger fluctuations at longer wavelengths due to limitations in instrument precision. In contrast, MPLCW spectra followed an exponential to 600 nm for all samples. The maximum deviation in replicate MPLCW spectra was less than 0.001 absorbance units. The portability, sampling, and optical characteristics of a MPLCW system provide significant enhancements for routine CDOM absorption measurements in a broad range of natural waters.

Absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissues

NASA Astrophysics Data System (ADS)

Ivashko, Pavlo; Peresunko, Olexander; Zelinska, Natalia; Alonova, Marina

2014-08-01

We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

UV-Vis absorption spectra and electronic structure of merocyanines in the gas phase

NASA Astrophysics Data System (ADS)

Ishchenko, Alexander A.; Kulinich, Andrii V.; Bondarev, Stanislav L.; Raichenok, Tamara F.

2018-02-01

Gas-phase absorption spectra of a merocyanine vinylogous series have been studied for the first time. In vapour, their long-wavelength absorption bands were found to be considerably shifted hypsochromically, broader, more symmetrical, less intense, and their vinylene shift much smaller than even in low-polarity n-hexane. This indicates that in the gas phase their electronic structure closely approaches the nonpolar polyene limiting structure. The TDDFT calculations of the long-wavelength electronic transitions in the studied merocyanines in vacuo demonstrated good-to-excellent correlation - depending on the functional used - with the obtained experimental data. For comparison, the solvent effects was accounted for using the polarizable continuum model (PCM) with n-hexane and ethanol as low-polarity and high-polarity media, and compared with the UV-Vis spectral data in these solvents. In this case, the discrepancy between theory and experiment was much greater, increasing at that with the polymethine chain length.

A narrow band pattern-matching model of vowel perception

NASA Astrophysics Data System (ADS)

Hillenbrand, James M.; Houde, Robert A.

2003-02-01

The purpose of this paper is to propose and evaluate a new model of vowel perception which assumes that vowel identity is recognized by a template-matching process involving the comparison of narrow band input spectra with a set of smoothed spectral-shape templates that are learned through ordinary exposure to speech. In the present simulation of this process, the input spectra are computed over a sufficiently long window to resolve individual harmonics of voiced speech. Prior to template creation and pattern matching, the narrow band spectra are amplitude equalized by a spectrum-level normalization process, and the information-bearing spectral peaks are enhanced by a ``flooring'' procedure that zeroes out spectral values below a threshold function consisting of a center-weighted running average of spectral amplitudes. Templates for each vowel category are created simply by averaging the narrow band spectra of like vowels spoken by a panel of talkers. In the present implementation, separate templates are used for men, women, and children. The pattern matching is implemented with a simple city-block distance measure given by the sum of the channel-by-channel differences between the narrow band input spectrum (level-equalized and floored) and each vowel template. Spectral movement is taken into account by computing the distance measure at several points throughout the course of the vowel. The input spectrum is assigned to the vowel template that results in the smallest difference accumulated over the sequence of spectral slices. The model was evaluated using a large database consisting of 12 vowels in /hVd/ context spoken by 45 men, 48 women, and 46 children. The narrow band model classified vowels in this database with a degree of accuracy (91.4%) approaching that of human listeners.

Temperature dependence of the optical absorption spectra of InP/ZnS quantum dots

NASA Astrophysics Data System (ADS)

Savchenko, S. S.; Vokhmintsev, A. S.; Weinstein, I. A.

2017-03-01

The optical-absorption spectra of InP/ZnS (core/shell) quantum dots have been studied in a broad temperature range of T = 6.5-296 K. Using the second-order derivative spectrophotometry technique, the energies of optical transitions at room temperature were found to be E 1 = 2.60 ± 0.02 eV (for the first peak of excitonic absorption in the InP core) and E 2 = 4.70 ± 0.02 eV (for processes in the ZnS shell). The experimental curve of E 1( T) has been approximated for the first time in the framework of a linear model and in terms of the Fan's formula. It is established that the temperature dependence of E 1 is determined by the interaction of excitons and longitudinal acoustic phonons with hω = 15 meV.

CMOS image sensor with organic photoconductive layer having narrow absorption band and proposal of stack type solid-state image sensors

NASA Astrophysics Data System (ADS)

Takada, Shunji; Ihama, Mikio; Inuiya, Masafumi

2006-02-01

Digital still cameras overtook film cameras in Japanese market in 2000 in terms of sales volume owing to their versatile functions. However, the image-capturing capabilities such as sensitivity and latitude of color films are still superior to those of digital image sensors. In this paper, we attribute the cause for the high performance of color films to their multi-layered structure, and propose the solid-state image sensors with stacked organic photoconductive layers having narrow absorption bands on CMOS read-out circuits.

Path integral Monte Carlo study on the structure and absorption spectra of alkali atoms (Li, Na, K) attached to superfluid helium clusters

NASA Astrophysics Data System (ADS)

Nakayama, Akira; Yamashita, Koichi

2001-01-01

Path integral Monte Carlo calculations have been performed to investigate the microscopic structure and thermodynamic properties of the AkṡHeN (Ak=Li, Na, K,N⩽300) clusters at T=0.5 K. Absorption spectra which correspond to the 2P←2S transitions of alkali atoms are also calculated within a pairwise additive model, which employs diatomic Ak-He potential energy curves. The size dependences of the cluster structure and absorption spectra that show the influence of the helium cluster environment are examined in detail. It is found that alkali atoms are trapped in a dimple on the helium cluster's surface and that, from the asymptotic behavior, the AkṡHe300 cluster, at least semiquantitatively, mimics the local structure of experimentally produced large helium clusters in the vicinity of alkali atoms. We have successfully reproduced the overall shapes of the spectra and explained their features from a static and structural point of view. The positions, relative intensities, and line widths of the absorption maxima are calculated to be in moderate agreement with experiments [F. Stienkemeier, J. Higgins, C. Callegari, S. I. Kanorsky, W. E. Ernst, and G. Scoles, Z. Phys. D 38, 253 (1996)].

Transition metal atomic multiplets in the ligand K-edge x-ray absorption spectra and multiple oxidation states in the L2,3 emission of strongly correlated compounds

NASA Astrophysics Data System (ADS)

Jiménez-Mier, J.; Olalde-Velasco, P.; Yang, W.-L.; Denlinger, J.

2014-07-01

We present results that show that atomic multiplet ligand field calculations are in very good agreement with experimental x-ray absorption spectra at the L2,3 edge of transition metal (TM) di-fluorides (MF2, MCrCu). For chromium more than one TM oxidation state is needed to achieve such an agreement. We also show that signature of the TM atomic multiplet can be found at the pre-edge of the fluorine K-edge x-ray absorption spectra. TM atomic multiplet ligand field calculations with a structureless core hole show good agreement with the observed pre-edges in the experimental fluorine absorption spectra. Preliminary results for the comparison between calculated and experimental resonant x-ray emission spectra for nominal CrF2 with more than one oxidation state indicate the presence of three chromium oxidation states in the bulk.

Ground-based Photon Path Measurements from Solar Absorption Spectra of the O2 A-band

NASA Technical Reports Server (NTRS)

Yang, Z.; Wennberg, P. O.; Cageao, R. P.; Pongetti, T. J.; Toon, G. C.; Sander, S. P.

2005-01-01

High-resolution solar absorption spectra obtained from Table Mountain Facility (TMF, 34.38degN, 117.68degW, 2286 m elevation) have been analyzed in the region of the O2 A-band. The photon paths of direct sunlight in clear sky cases are retrieved from the O2 absorption lines and compared with ray-tracing calculations based on the solar zenith angle and surface pressure. At a given zenith angle, the ratios of retrieved to geometrically derived photon paths are highly precise (approx.0.2%), but they vary as the zenith angle changes. This is because current models of the spectral lineshape in this band do not properly account for the significant absorption that exists far from the centers of saturated lines. For example, use of a Voigt function with Lorentzian far wings results in an error in the retrieved photon path of as much as 5%, highly correlated with solar zenith angle. Adopting a super-Lorentz function reduces, but does not completely eliminate this problem. New lab measurements of the lineshape are required to make further progress.

Analysis of Atmospheric Trace Constituents from High Resolution Infrared Balloon-Borne and Ground-Based Solar Absorption Spectra

NASA Technical Reports Server (NTRS)

Goldman, A.; Murcray, F. J.; Rinsland, C. P.; Blatherwick, R. D.; Murcray, F. H.; Murcray, D. G.

1991-01-01

Recent results and ongoing studies of high resolution solar absorption spectra will be presented. The analysis of these spectra is aimed at the identification and quantification of trace constituents important in atmospheric chemistry of the stratosphere and upper troposphere. Analysis of balloon-borne and ground-based spectra obtained at 0.0025/ cm covering the 700-2200/ cm interval will be presented. Results from ground-based 0.02/ cm solar spectra, from several locations such as Denver, South Pole, M. Loa, and New Zealand will also be shown. The 0.0025/ cm spectra show many new spectroscopic features. The analysis of these spectra, along with corresponding laboratory spectra, improves the spectral line parameters, and thus the accuracy of trace constituents quantification. The combination of the recent balloon flights, with earlier flights data since 1978 at 0.02/ cm resolution, provides trends analysis of several stratospheric trace species. Results for COF2, F22, SF6, and other species will be presented. Analysis of several ground-based solar spectra provides trends for HCl, HF and other species. The retrieval methods used for total column density and altitude distribution for both ground-based and balloon-borne spectra will be presented. These are extended for the analysis of the ground-based spectra to be obtained by the high resolution interferometers of the Network for Detection of Stratospheric Change (NDSC). Progress or the University of Denver studies for the NDSC will be presented. This will include intercomparison of solar spectra and trace gases retrievals obtained from simultaneous scans by the high resolution (0.0025/ cm) interferometers of BRUKER and BOMEM.

Absorption and fluorescence spectra of heterocyclic isomers from long-range-corrected density functional theory in polarizable continuum approach.

PubMed

Kityk, Andriy V

2012-03-22

Long-range-corrected (LC) DFT/TDDFT methods may provide adequate description of ground and excited state properties; however, accuracy of such an approach depends much on a range separation (exchange screening) representing adjustable model parameter. Its relation to a size or specific of molecular systems has been explored in numerous studies, whereas the effect of solvent environment is usually ignored during the evaluation of state properties. To benchmark and assess the quality of the LC-DFT/TDDFT formalism, we report the optical absorption and fluorescence emission energies of organic heterocyclic isomers, DPIPQ and PTNA, calculated by LC-BLYP DFT/TDDFT method in the polarizable continuum (PCM) approach. The calculations are compared with the optical absorption and fluorescence spectra measured in organic solvents of different polarity. Despite a considerable structural difference, both dyes exhibit quite similar range separations being somewhat different for the optical absorption and fluorescence emission processes. Properly parametrized LC-BLYP xc-potential well reproduces basic features of the optical absorption spectra including the electronic transitions to higher excited states. The DFT/TDDFT/PCM analysis correctly predicts the solvation trends although solvatochromic shifts of the electronic transition energies appear to be evidently underestimated in most cases, especially for the fluorescence emission. Considering the discrepancy between the experiment and theory, evaluated state dipole moments and solvation corrections to the exchange screening are analyzed. The results of the present study emphasize the importance of a solvent-dependent range separation in DFT/TDDFT/PCM calculations for investigating excited state properties. © 2012 American Chemical Society

Using of laser spectroscopy and chemometrics methods for identification of patients with lung cancer, patients with COPD and healthy people from absorption spectra of exhaled air

NASA Astrophysics Data System (ADS)

Bukreeva, Ekaterina B.; Bulanova, Anna A.; Kistenev, Yury V.; Kuzmin, Dmitry A.; Nikiforova, Olga Yu.; Ponomarev, Yurii N.; Tuzikov, Sergei A.; Yumov, Evgeny L.

2014-11-01

The results of application of the joint use of laser photoacoustic spectroscopy and chemometrics methods in gas analysis of exhaled air of patients with chronic respiratory diseases (chronic obstructive pulmonary disease and lung cancer) are presented. The absorption spectra of exhaled breath of representatives of the target groups and healthy volunteers were measured; the selection by chemometrics methods of the most informative absorption coefficients in scan spectra in terms of the separation investigated nosology was implemented.

Reionization through Trickery: How to Find the True FUV Spectra of z>6 Quasars

NASA Astrophysics Data System (ADS)

O'Dowd, Matthew; Schiminovich, D.; Webster, R. L.; Haiman, Z.

2011-01-01

Studies of absorption in the vicinity of z > 6 quasars will enable characterization of the final stages of the epoch of reionization, and measurement of the last remnants of the neutral fraction from the cosmic dark ages. Before this can happen, we will need to know the intrinsic shape of the rest-frame FUV spectrum of luminous quasars, and in particular of the Lyman-Alpha emission line. To date, such measurements have only been possible for local, low luminosity quasars and Seyferts whose FUV spectra are not strongly absorbed in the IGM. These AGN are poor models of their high-luminosity cousins, and the BELR physics driving the Ly-alpha line may be very different. I will outline two approaches to measuring the true, unabsorbed FUV spectra of luminous quasars. First, by observing differential microlensing of strongly lensed quasars at z > 3, I will show how we can algebraically reconstruct the true FUV spectrum, and recover the absorption spectrum and measure the proximity effect to boot. Second, by targeting a narrow redshift range at z 1, we can identify a subsample of luminous quasars that have avoided significant absorption, but are nonetheless genuine analogs of our z > 6 quasars. I will show some preliminary GALEX data of these quasars.

Studies in mid-infrared spectropolarimetry - II. An atlas of spectra

NASA Astrophysics Data System (ADS)

Smith, Craig H.; Wright, Christopher M.; Aitken, David K.; Roche, Patrick F.; Hough, James H.

2000-02-01

We present 8-13μm spectropolarimetry of 55 sources and 16-22μm spectropolarimetry of six of these. This represents a substantial fraction of star formation regions that can be observed in this way with current technology on 4-m class telescopes (i.e. brighter than about 20Jy at 10μm in a 4-arcsec beam). Most of the sources are embedded young stellar objects (YSOs), Hii regions containing sites of star formation or bipolar protoplanetary nebulae (PPN), although a few other sources (e.g. NGC 1068, MWC 349) are also included. The majority have oxygen-rich chemistry but there are three carbon-rich sources. Many of the oxygen-rich sources show deep silicate absorption overlying featureless or optically thin silicate emission. Absorptive polarization with polarization per optical depth (paτ)~=1-3 per cent is common, and many also show evidence for an emissive polarization component as well, although pure polarization in emission is rare. The observed ranges of paτ and pe are very similar, rather surprising in view of their origin from very different environments. Typically the absorptive polarization profiles are similar to the archetypal silicate polarization found in OMC1 BN, but an exception is AFGL 2591, which displays an additional narrow polarization feature at 11.2μm, which has been attributed to annealed silicates. Many of the intensity absorption spectra also show an inflection near 11.2μm, which might also be attributable to annealed silicates. The carbon-rich sources have nearly featureless polarizations in the 0.5-1per cent range, which we ascribe to dichroism in carbon-based grains; this is the first evidence that such grains can be aligned. In two of these sources the polarization appears to be caused by absorption by SiC. A few of the polarization spectra have no straightforward interpretation.

Vibrationally high-resolved electronic spectra of MCl2 (M=C, Si, Ge, Sn, Pb) and photoelectron spectra of MCl2(.).

PubMed

Ran, Yibin; Pang, Min; Shen, Wei; Li, Ming; He, Rongxing

2016-10-05

We systematically studied the vibrational-resolved electronic spectra of group IV dichlorides using the Franck-Condon approximation combined with the Duschinsky and Herzberg-Teller effects in harmonic and anharmonic frameworks (only the simulation of absorption spectra includes the anharmonicity). Calculated results showed that the band shapes of simulated spectra are in accordance with those of the corresponding experimental or theoretical ones. We found that the symmetric bend mode in progression of absorption is the most active one, whereas the main contributor in photoelectron spectra is the symmetric stretching mode. Moreover, the Duschinsky and anharmonic effects exert weak influence on the absorption spectra, except for PbCl2 molecule. The theoretical insights presented in this work are significant in understanding the photophysical properties of MCl2 (M=C, Si, Ge, Sn, Pb) and studying the Herzberg-Teller and the anharmonic effects on the absorption spectra of new dichlorides of this main group. Copyright © 2016 Elsevier B.V. All rights reserved.

Disentangling atomic-layer-specific x-ray absorption spectra by Auger electron diffraction spectroscopy

NASA Astrophysics Data System (ADS)

Matsui, Fumihiko; Matsushita, Tomohiro; Kato, Yukako; Hashimoto, Mie; Daimon, Hiroshi

2009-11-01

In order to investigate the electronic and magnetic structures of each atomic layer at subsurface, we have proposed a new method, Auger electron diffraction spectroscopy, which is the combination of x-ray absorption spectroscopy (XAS) and Auger electron diffraction (AED) techniques. We have measured a series of Ni LMM AED patterns of the Ni film grown on Cu(001) surface for various thicknesses. Then we deduced a set of atomic-layer-specific AED patterns in a numerical way. Furthermore, we developed an algorithm to disentangle XANES spectra from different atomic layers using these atomic-layer-specific AED patterns. Surface and subsurface core level shift were determined for each atomic layer.

Dynamics of intramolecular electron transfer reaction of FAD studied by magnetic field effects on transient absorption spectra.

PubMed

Murakami, Masaaki; Maeda, Kiminori; Arai, Tatsuo

2005-07-07

The kinetics of intermediates generated from intramolecular electron-transfer reaction by photo irradiation of the flavin adenine dinucleotide (FAD) molecule was studied by a magnetic field effect (MFE) on transient absorption (TA) spectra. Existence time of MFE and MFE action spectra have a strong dependence on the pH of solutions. The MFE action spectra have indicated the existence of interconversion between the radical pair and the cation form of the triplet excited state of flavin part. All rate constants of the triplet and the radical pair were determined by analysis of the MFE action spectra and decay kinetics of TA. The obtained values for the interconversion indicate that the formation of cation radical promotes the back electron-transfer reaction to the triplet excited state. Further, rate constants of spin relaxation and recombination have been studied by the time profiles of MFE at various pH. The drastic change of those two factors has been obtained and can be explained by SOC (spin-orbit coupling) induced back electron-transfer promoted by the formation of a stacking conformation at pH > 2.5.

DFT study of electron absorption and emission spectra of pyramidal LnPc(OAc) complexes of some lanthanide ions in the solid state

NASA Astrophysics Data System (ADS)

Hanuza, J.; Godlewska, P.; Lisiecki, R.; Ryba-Romanowski, W.; Kadłubański, P.; Lorenc, J.; Łukowiak, A.; Macalik, L.; Gerasymchuk, Yu.; Legendziewicz, J.

2018-05-01

The electron absorption and emission spectra were measured for the pyramidal LnPc(OAc) complexes in the solid state and co-doped in silica glass, where Ln = Er, Eu and Ho. The theoretical electron spectra were determined from the quantum chemical DFT calculation using four approximations CAM-B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ, B3LYP/LANL2DZ and B3LYP/CC-PVDZ. It was shown that the best agreement between the calculated and experimental structural parameters and spectroscopic data was reached for the CAM-B3LYP/LANL2DZ model. The emission spectra were measured using the excitations both in the ligand and lanthanide absorption ranges. The possibility of energy transfer between the phthalocyanine ligand and excited states of lanthanide ions was discussed. It was shown that the back energy transfer from metal states to phthalocyanine state is responsible for the observed emission of the studied complexes both in the polycrystalline state and silica glass.

Electronic structure of some adenosine receptor antagonists. III. Quantitative investigation of the electronic absorption spectra of alkyl xanthines

NASA Astrophysics Data System (ADS)

Moustafa, H.; Shalaby, Samia H.; El-sawy, K. M.; Hilal, Rifaat

2002-07-01

Quantitative and comparative investigation of the electronic absorption spectra of theophylline, caffeine and their derivatives is reported. The spectra of theophylline, caffeine and theobromine were compared to establish the predominant tautomeric species in solution. This comparison, analysis of solvent effects and assignments of the observed transitions via MO computations indicate the exits of only one tautomeric species in solution that is the N7 form. A low-lying triplet state was identified which corresponds to a HOMO-LUMO transition. This relatively long-lived T 1 state is always less polar than the ground state and may very well underlie the photochemical reactivity of alkyl xanthines. Substituents of different electron donating or withdrawing strengths and solvent effects are investigated and analyzed. The present analysis is facilitated via computer deconvolution of the observed spectra and MO computation.

The absorption- and luminescence spectra of Mn3+ in beryl and vesuvianite

NASA Astrophysics Data System (ADS)

Czaja, Maria; Lisiecki, Radosław; Chrobak, Artur; Sitko, Rafał; Mazurak, Zbigniew

2018-05-01

The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite.

The absorption- and luminescence spectra of Mn3+ in beryl and vesuvianite

NASA Astrophysics Data System (ADS)

Czaja, Maria; Lisiecki, Radosław; Chrobak, Artur; Sitko, Rafał; Mazurak, Zbigniew

2017-12-01

The electron absorption-, photoluminescence- and electron paramagnetic-resonance spectra of Mn3+ in red beryl from Wah Wah Mountains (Utah USA) and of pink- and purple vesuvianite from Jeffrey Mine (Asbestos, Canada) were measured at room- and low temperatures. The crystal field stabilization energies are equal to 130.9 kJ/mol for the red beryl, and 151.5-158.0 and 168.0 kJ/mol for for the pink- and the purple vesuvianite, respectively. The red photoluminescence of Mn3+ was not intensive either at room- or at low temperatures. The high Mn content in the crystals caused the emergence of an additional emission band and short photoluminescence-decay lifetimes. The latter are only 183 μs for beryl and 17 μs for vesuvianite.

Molecfit: A general tool for telluric absorption correction. II. Quantitative evaluation on ESO-VLT/X-Shooterspectra

NASA Astrophysics Data System (ADS)

Kausch, W.; Noll, S.; Smette, A.; Kimeswenger, S.; Barden, M.; Szyszka, C.; Jones, A. M.; Sana, H.; Horst, H.; Kerber, F.

2015-04-01

Context. Absorption by molecules in the Earth's atmosphere strongly affects ground-based astronomical observations. The resulting absorption line strength and shape depend on the highly variable physical state of the atmosphere, i.e. pressure, temperature, and mixing ratio of the different molecules involved. Usually, supplementary observations of so-called telluric standard stars (TSS) are needed to correct for this effect, which is expensive in terms of telescope time. We have developed the software package molecfit to provide synthetic transmission spectra based on parameters obtained by fitting narrow ranges of the observed spectra of scientific objects. These spectra are calculated by means of the radiative transfer code LBLRTM and an atmospheric model. In this way, the telluric absorption correction for suitable objects can be performed without any additional calibration observations of TSS. Aims: We evaluate the quality of the telluric absorption correction using molecfit with a set of archival ESO-VLT/X-Shooter visible and near-infrared spectra. Methods: Thanks to the wavelength coverage from the U to the K band, X-Shooter is well suited to investigate the quality of the telluric absorption correction with respect to the observing conditions, the instrumental set-up, input parameters of the code, the signal-to-noise of the input spectrum, and the atmospheric profiles. These investigations are based on two figures of merit, Ioff and Ires, that describe the systematic offsets and the remaining small-scale residuals of the corrections. We also compare the quality of the telluric absorption correction achieved with molecfit to the classical method based on a telluric standard star. Results: The evaluation of the telluric correction with molecfit shows a convincing removal of atmospheric absorption features. The comparison with the classical method reveals that molecfit performs better because it is not prone to the bad continuum reconstruction, noise, and

Electronic Absorption and MCD Spectra for Pd(AuPPh(3))(8)(2+), Pt(AuPPh(3))(8)(2+), and Related Platinum-Centered Gold Cluster Complexes.

PubMed

Adrowski, Michael J.; Mason, W. Roy

1997-03-26

Electronic absorption and 7.0 T magnetic circular dichroism (MCD) spectra in the UV-vis region, 1.6 to approximately 4.0 &mgr;m(-)(1) (1 &mgr;m(-)(1) = 10(4) cm(-)(1)) are reported for [Pd(AuPPh(3))(8)](NO(3))(2) and [Pt(AuPPh(3))(8)](NO(3))(2) in acetonitrile solutions at room temperature. The MCD spectra are better resolved than the absorption spectra and consist of both A and B terms. The spectra are interpreted in terms of D(4)(d)() skeletal geometry and MO's that are approximated by 5s and 6s orbitals for Pd and Pt/Au atoms, respectively. The lowest energy excited configurations and states are attributed to intraframework (IF) Au(8)(2+) transitions. Evidence is also presented for Pt 5d --> Au 6s transitions in the MCD spectra for Pt(AuPPh(3))(8)(2+). Acetonitrile solution absorption and MCD spectra for the related Pt-centered cluster complexes [Pt(CO)(AuPPh(3))(8)](NO(3))(2), [Pt(AuP(p-tolyl)(3))(8)](NO(3))(2), [Pt(CuCl)(AuPPh(3))(8)](NO(3))(2), [Pt(AgNO(3))(AuPPh(3))(8)](NO(3))(2), [Pt(Hg)(2)(AuPPh(3))(8)](NO(3))(2), [Pt(HgCl)(2)(AuPPh(3))(8)](BF(4))(2), and [Pt(HgNO(3))(2)(AuPPh(3))(8)](BF(4))(2) are also reported and interpreted within the context of the model developed for the M(AuPPh(3))(8)(2+) complexes.

X-ray K-edge absorption spectra of Fe minerals and model compounds: II. EXAFS

NASA Astrophysics Data System (ADS)

Waychunas, Glenn A.; Brown, Gordon E.; Apted, Michael J.

1986-01-01

K-edge extended X-ray absorption fine structure (EXAFS) spectra of Fe in varying environments in a suite of well-characterized silicate and oxide minerals were collected using synchrotron radiation and analyzed using single scattering approximation theory to yield nearest neighbor Fe-O distances and coordination numbers. The partial inverse character of synthetic hercynite spinal was verified in this way. Comparison of the results from all samples with structural data from X-ray diffraction crystal structure refinements indicates that EXAFS-derived first neighbor distances are generally accurate to ±0.02 Å using only theoretically generated phase information, and may be improved over this if similar model compounds are used to determine EXAFS phase functions. Coordination numbers are accurate to ±20 percent and can be similarly improved using model compound EXAFS amplitude information. However, in particular cases the EXAFS-derived distances may be shortened, and the coordination number reduced, by the effects of static and thermal disorder or by partial overlap of the longer Fe-O first neighbor distances with second neighbor distances in the EXAFS structure function. In the former case the total information available in the EXAFS is limited by the disorder, while in the latter case more accurate results can in principle be obtained by multiple neighbor EXAFS analysis. The EXAFS and XANES spectra of Fe in Nain, Labrador osumulite and Lakeview, Oregon plagioclase are also analyzed as an example of the application of X-ray absorption spectroscopy to metal ion site occupation determination in minerals.

Temperature-dependence laws of absorption line shape parameters of the CO2 ν3 band

NASA Astrophysics Data System (ADS)

Wilzewski, J. S.; Birk, M.; Loos, J.; Wagner, G.

2018-02-01

To improve the understanding of temperature-dependence laws of spectral line shape parameters, spectra of the ν3 rovibrational band of CO2 perturbed by 10, 30, 100, 300 and 1000 mbar of N2 were recorded at nine temperatures between 190 K and 330 K using a 22 cm long single-pass absorption cell in a Bruker IFS125 HR Fourier Transform spectrometer. The spectra were fitted employing a quadratic speed-dependent hard collision model in the Hartmann-Tran implementation extended to account for line mixing in the Rosenkranz approximation by means of a multispectrum fitting approach developed at DLR. This enables high accuracy parameter retrievals to reproduce the spectra down to noise level and we present the behavior of line widths, shifts, speed-dependence-, collisional narrowing- and line mixing-parameters over this 140 K temperature range.

A search for formic acid in the upper troposphere - A tentative identification of the 1105-per cm nu-6 band Q branch in high-resolution balloon-borne solar absorption spectra

NASA Technical Reports Server (NTRS)

Goldman, A.; Murcray, F. H.; Murcray, D. G.; Rinsland, C. P.

1984-01-01

Infrared solar absorption spectra recorded at 0.02-per cm resolution during a balloon flight from Alamogordo, NM (33 deg N), on March 23, 1981, have been analyzed for the possible presence of absorption by formic acid (HCOOH). An absorption feature at 1105 per cm has been tentatively identified in upper tropospheric spectra as due to the nu-6 band Q branch. A preliminary analysis indicates a concentration of about 0.6 ppbv and 0.4 ppbv near 8 and 10 km, respectively.

Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442

NASA Astrophysics Data System (ADS)

Shi, Xi-Heng; Pan, Xiang; Zhang, Shao-Hua; Sun, Lu-Ming; Wang, Jian-Guo; Ji, Tuo; Yang, Chen-Wei; Liu, Bo; Jiang, Ning; Zhou, Hong-Yan

2017-07-01

We present new optical spectra of the well-known broad absorption line (BAL) quasar PG 1411+442, using the DBSP spectrograph at the Palomar 200 inch telescope in 2014 and 2017 and the YFOSC spectrograph at the Lijiang 2.4 m telescope in 2015. A blueshifted narrow absorption line system is clearly revealed in 2014 and 2015 consisting of hydrogen Balmer series and metastable He I lines. The velocity of these lines is similar to the centroid velocity of the UV BALs, suggesting that both originate from the outflow. The Balmer lines vary significantly between the two observations and vanished in 2017. They were also absent in the archived spectra obtained before 2001. The variation is thought to be driven by photoionization change. Besides, the absorption lines show inversed Balmer decrement, I.e., the apparent optical depths of higher-order Balmer absorption lines are larger than those of lower-order lines, which is inconsistent with the oscillator strengths of the transitions. We suggest that such anomalous line ratios can be naturally explained by the thermal structure of a background accretion disk, which allows the obscured part of the disk to contribute differently to the continuum flux at different wavelengths. High-resolution spectroscopic and photometric monitoring would be very useful to probe the structure of the accretion disk as well as the geometry and physical conditions of the outflow.

Synthesis and evaluation of changes induced by solvent and substituent in electronic absorption spectra of some azo disperse dyes

NASA Astrophysics Data System (ADS)

Mohammadi, Asadollah; Yazdanbakhsh, Mohammad Reza; Farahnak, Lahya

2012-04-01

Five azo disperse dyes were prepared by diazotizing 4'-aminoacetophenone and p-anisidine and coupling with varies N-alkylated aromatic amines. Characterization of the dyes was carried out by using UV-vis, FTIR and 1H NMR spectroscopic techniques. The electronic absorption spectra of dyes are determined at room temperature in fifteen solvents with different polarities. The solvent dependent maximum absorption band shifts, were investigated using dielectric constant (ɛ), refractive index (n) and Kamlet-Taft polarity parameters (hydrogen bond donating ability (α), hydrogen bond accepting ability (β) and dipolarity/polarizability polarity scale (π*)). Acceptable agreement was found between the maximum absorption band of dyes and solvent polarity parameters especially with π*. The effect of substituents of coupler and/or diazo component on the color of dyes was investigated. The effects of acid and base on the visible absorption maxima of the dyes are also reported.

Interstellar absorption in the Mg II resonance line k2 and h2 emissions

NASA Technical Reports Server (NTRS)

Boehm-Vitense, E.

1981-01-01

High-resolution (0.2 A) IUE spectra for the long wavelength range (1800-3000 A) have been studied. It is shown that narrow interstellar Mg II lines are seen in the center of the k2 and h2 emissions from nearby stars with large rotational velocities. For all observed stars, the radial velocity of the central k3 absorption component in the rest system of the star is strongly correlated with the mirror image of the radial velocity of the stars; this shows that a major fraction if not all of the k3 absorption is due to interstellar absorption in the solar neighborhood. The violet to red asymmetry of the k2 emission also correlates with the radial velocities of the star; this shows that the shift of k3 is due to the velocity shift of the local interstellar cloud with respect to the star.

Narrow-Line Seyfert 1 Galaxies

NASA Technical Reports Server (NTRS)

Leighly, Karen M.

2000-01-01

The primary work during this year has been the analysis and interpretation of our HST spectra from two extreme Narrow-line Seyfert 1 galaxies (NLS1s) Infrared Astronomy Satellite (IRAS) 13224-3809 and 1H 0707-495. This work has been presented as an invited talk at the workshop entitled "Observational and theoretical progress in the Study of Narrow-line Seyfert 1 Galaxies" held in Bad Honnef, Germany December 8-11, as a contributed talk at the January 2000 AAS meeting in Atlanta, Georgia, and as a contributed talk at the workshop "Probing the Physics of Active Galactic Nuclei by Multiwavelength Monitoring" held at Goddard Space Flight Center June 20-22, 2000.

Laboratory Measurements of Mass Specific Absorption Spectra for Suites of Black Carbon-like, Biomass Burning and Mineral Dust Aerosols

NASA Astrophysics Data System (ADS)

Radney, J.; Zangmeister, C.

2017-12-01

Light-absorbing atmospheric aerosols can be grouped into three categories: black carbon (BC), brown carbon (BrC) or mineral dust (MD). In many cases, the absorption of these species is best quantified using a mass-specific absorption cross section (MAC) since the particles are in the Rayleigh regime (BC) or optically thin (BrC and MD); notably, MAC values are both traceable to the SI and transferrable between photoacoustic spectroscopy and filter-based absorption measurements. Here, we present laboratory measurements of MAC for all three light-absorbing aerosol classes. Particles were size- and mass-selected using a differential mobility analyzer and aerosol particle mass analyzer, respectively, with absorption coefficients (αabs) and number concentrations (N) being measured by a broadband photoacoustic spectrometer and condensation particle counter, respectively. This suite of instrumentation allows for direct quantification of MAC from the measured parameters (MAC = αabs/Nmp). Further, the measurements contained > 8 data points spanning λ = 405 nm to 840 nm allowing for spectral curvatures (i.e. the Absorption Angstrom Exponent or AAE) to be fit from many data points versus the more common 2-point interpolations. For the carbonaceous, BC-like aerosols - five samples generated from flames, spark discharge soot (i.e. fullerene soot), graphene, reduced graphene oxide (rGO), and fullerene (C60) - we found: 1) measured MAC ranged between 2.4 m2 g-1 and 8.6 m2 g-1 at λ = 550 nm, 2) most AAEs ranged between 0.5 and 1.3; C60 AAE was 7.5 ± 0.9 and 3) MAC spectra were dependent on fuel type and formation conditions. For BrC particles generated from smoldering combustion of 3 hardwood (Oak, Hickory and Mesquite) and 3 softwood species (Western redcedar, Blue spruce and Baldcypress), we found: 1) median MAC values ranged from 1.4 x 10-2 m2 g-1 to 7.9 x 10-2 m2 g-1 at λ = 550 nm, 2) AAE values ranged between 3.5 and 6.2, and 3) Oak, Western redcedar and Blue spruce

DFT study of electron absorption and emission spectra of pyramidal LnPc(OAc) complexes of some lanthanide ions in the solid state.

PubMed

Hanuza, J; Godlewska, P; Lisiecki, R; Ryba-Romanowski, W; Kadłubański, P; Lorenc, J; Łukowiak, A; Macalik, L; Gerasymchuk, Yu; Legendziewicz, J

2018-05-05

The electron absorption and emission spectra were measured for the pyramidal LnPc(OAc) complexes in the solid state and co-doped in silica glass, where Ln=Er, Eu and Ho. The theoretical electron spectra were determined from the quantum chemical DFT calculation using four approximations CAM-B3LYP/LANL2DZ, CAM-B3LYP/CC-PVDZ, B3LYP/LANL2DZ and B3LYP/CC-PVDZ. It was shown that the best agreement between the calculated and experimental structural parameters and spectroscopic data was reached for the CAM-B3LYP/LANL2DZ model. The emission spectra were measured using the excitations both in the ligand and lanthanide absorption ranges. The possibility of energy transfer between the phthalocyanine ligand and excited states of lanthanide ions was discussed. It was shown that the back energy transfer from metal states to phthalocyanine state is responsible for the observed emission of the studied complexes both in the polycrystalline state and silica glass. Copyright © 2018. Published by Elsevier B.V.

Twelve years of IUE spectra of the interacting binary VV Cephei

NASA Technical Reports Server (NTRS)

Bauer, W. H.; Stencel, R. E.; Neff, D. H.

1991-01-01

All well-exposed high-resolution IUE spectra obtained of the eclipsing binary system VV Cephei (M2Iabep + B) are examined. High-temperature absorption features attributable to the hot companion were detected, indicating that the companion (or the inner regions of its accretion disk) are not as hot as a B1-B2 star. Doubling of Fe II (UV 1) lines, with an additional narrow component redshifted by about 60 km/sec, occurs only when the B star is behind the plane of the sky containing the M supergiant, suggesting the existence of mass transfer from the red to the blue star. Absorption features from neutral elements weaken dramatically during egress, while those from ionized elements remain at nearly constant strength. During egress from primary eclipse, the Mg II resonance doublet shows asymmetric double-peaked emission indicative of formation in an expanding chromosphere. It is concluded that the outer atmosphere of the M supergiant is highly clumped.

DFT study of the effect of substituents on the absorption and emission spectra of Indigo

PubMed Central

2012-01-01

Background Theoretical analyses of the indigo dye molecule and its derivatives with Chlorine (Cl), Sulfur (S), Selenium (Se) and Bromine (Br) substituents, as well as an analysis of the Hemi-Indigo molecule, were performed using the Gaussian 03 software package. Results Calculations were performed based on the framework of density functional theory (DFT) with the Becke 3- parameter-Lee-Yang-Parr (B3LYP) functional, where the 6-31 G(d,p) basis set was employed. The configuration interaction singles (CIS) method with the same basis set was employed for the analysis of excited states and for the acquisition of the emission spectra. Conclusions The presented absorption and emission spectra were affected by the substitution position. When a hydrogen atom of the molecule was substituted by Cl or Br, practically no change in the absorbed and emitted energies relative to those of the indigo molecule were observed; however, when N was substituted by S or Se, the absorbed and emitted energies increased. PMID:22809100

First Time Rapid and Accurate Detection of Massive Number of Metal Absorption Lines in the Early Universe Using Deep Neural Network

NASA Astrophysics Data System (ADS)

Zhao, Yinan; Ge, Jian; Yuan, Xiaoyong; Li, Xiaolin; Zhao, Tiffany; Wang, Cindy

2018-01-01

Metal absorption line systems in the distant quasar spectra have been used as one of the most powerful tools to probe gas content in the early Universe. The MgII λλ 2796, 2803 doublet is one of the most popular metal absorption lines and has been used to trace gas and global star formation at redshifts between ~0.5 to 2.5. In the past, machine learning algorithms have been used to detect absorption lines systems in the large sky survey, such as Principle Component Analysis, Gaussian Process and decision tree, but the overall detection process is not only complicated, but also time consuming. It usually takes a few months to go through the entire quasar spectral dataset from each of the Sloan Digital Sky Survey (SDSS) data release. In this work, we applied the deep neural network, or “ deep learning” algorithms, in the most recently SDSS DR14 quasar spectra and were able to randomly search 20000 quasar spectra and detect 2887 strong Mg II absorption features in just 9 seconds. Our detection algorithms were verified with previously released DR12 and DR7 data and published Mg II catalog and the detection accuracy is 90%. This is the first time that deep neural network has demonstrated its promising power in both speed and accuracy in replacing tedious, repetitive human work in searching for narrow absorption patterns in a big dataset. We will present our detection algorithms and also statistical results of the newly detected Mg II absorption lines.

FSFE: Fake Spectra Flux Extractor

NASA Astrophysics Data System (ADS)

Bird, Simeon

2017-10-01

The fake spectra flux extractor generates simulated quasar absorption spectra from a particle or adaptive mesh-based hydrodynamic simulation. It is implemented as a python module. It can produce both hydrogen and metal line spectra, if the simulation includes metals. The cloudy table for metal ionization fractions is included. Unlike earlier spectral generation codes, it produces absorption from each particle close to the sight-line individually, rather than first producing an average density in each spectral pixel, thus substantially preserving more of the small-scale velocity structure of the gas. The code supports both Gadget (ascl:0003.001) and AREPO.

The calculated in vitro and in vivo chlorophyll a absorption bandshape.

PubMed Central

Zucchelli, Giuseppe; Jennings, Robert C; Garlaschi, Flavio M; Cinque, Gianfelice; Bassi, Roberto; Cremonesi, Oliviero

2002-01-01

The room temperature absorption bandshape for the Q transition region of chlorophyll a is calculated using the vibrational frequency modes and Franck-Condon (FC) factors obtained by line-narrowing spectroscopies of chlorophyll a in a glassy (Rebane and Avarmaa, Chem. Phys. 1982; 68:191-200) and in a native environment (Gillie et al., J. Phys. Chem. 1989; 93:1620-1627) at low temperatures. The calculated bandshapes are compared with the absorption spectra of chlorophyll a measured in two different solvents and with that obtained in vivo by a mutational analysis of a chlorophyll-protein complex. It is demonstrated that the measured distributions of FC factors can account for the absorption bandshape of chlorophyll a in a hexacoordinated state, whereas, when pentacoordinated, reduced FC coupling for vibrational frequencies in the range 540-850 cm(-1) occurs. The FC factor distribution for pentacoordinated chlorophyll also describes the native chlorophyll a spectrum but, in this case, either a low-frequency mode (nu < 200 cm(-1)) must be added or else the 262-cm(-1) mode must increase in coupling by about one order of magnitude to describe the skewness of the main absorption bandshape. PMID:11751324

Impurity-induced photoconductivity of narrow-gap Cadmium–Mercury–Telluride structures

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

Kozlov, D. V., E-mail: dvkoz@impras.ru; Rumyantsev, V. V.; Morozov, S. V.

2015-12-15

The photoconductivity (PC) spectra of CdHgTe (MCT) solid solutions with a Cd fraction of 17 and 19% are measured. A simple model for calculating the states of doubly charged acceptors in MCT solid solutions, which makes it possible to describe satisfactorily the observed photoconductivity spectra, is proposed. The found lines in the photoconductivity spectra of narrow-gap MCT structures are associated with transitions between the states of both charged and neutral acceptor centers.

DFT Calculation of IR Absorption Spectra for PCE-nH2O, TCE-nH2O, DCE-nH2O, VC-nH2O for Small and Water-Dominated Molecular Clusters

DTIC Science & Technology

2017-10-31

of isolated molecules and that of bulk systems. DFT calculated absorption spectra represent quantitative estimates that can be correlated with...spectra, can be correlated with the presence of these hydrocarbons (see reference [1]). Accordingly, the molecular structure and IR absorption spectra of...associated with different types of ambient molecules, e.g., H2O, in order to apply background subtraction or spectral-signature- correlation algorithms

Electromagnetically-induced-absorption resonance with high contrast and narrow width in the Hanle configuration

NASA Astrophysics Data System (ADS)

Brazhnikov, D. V.; Taichenachev, A. V.; Tumaikin, A. M.; Yudin, V. I.

2014-12-01

The method for observing the high-contrast and narrow-width resonances of electromagnetically induced absorption (EIA) in the Hanle configuration under counter-propagating pump and probe light waves is proposed. Here, as an example, we study a ‘dark’ type of atomic dipole transition {{F}\\text{g}}={1}\\to {{F}\\text{e}}={1} in D1 line of 87Rb, where usually the electromagnetically induced transparency can be observed. To obtain the EIA signal one should properly choose the polarizations of light waves and intensities. In contrast to regular schemes for observing EIA signals (under a single traveling light wave in the Hanle configuration or under a bichromatic light field consisting of two traveling waves), the proposed scheme allows one to use buffer gas for significantly improving the properties of the resonance. Also the dramatic influence of atomic transition openness on the contrast of the resonance is revealed, which is advantageous in comparison with cyclic atomic transitions. The nonlinear resonances in a probe-wave transmitted signal with contrast close to 100% and sub-kHz widths can be obtained. The results are interesting in high-resolution spectroscopy, nonlinear and magneto-optics.

Comparison of absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissue

NASA Astrophysics Data System (ADS)

Peresunko, O. P.; Zelinska, N. V.; Prydij, O. G.; Zymnyakov, D. A.; Ushakova, O. V.

2013-12-01

We studied a methods of assessment of a connective tissue of cervix in terms of specific volume of fibrous component and an optical density of staining of connective tissue fibers in the stroma of squamous cancer and cervix adenocarcinoma. An absorption spectra of blood plasma of the patients suffering from squamous cancer and cervix adenocarcinoma both before the surgery and in postsurgical periods were obtained. Linear dichroism measurements transmittance in polarized light at different orientations of the polarization plane relative to the direction of the dominant orientation in the structure of the sample of biotissues of stroma of squamous cancer and cervix adenocarcinoma were carried. Results of the investigation of the tumor tissues showed that the magnitude of the linear dichroism Δ is insignificant in the researched spectral range λ=280-840 nm and specific regularities in its change observed short-wave ranges.

Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

USGS Publications Warehouse

Majzlan, Juraj; Alpers, Charles N.; Bender Koch, Christian; McCleskey, R. Blaine; Myneni, Satish B.C.; Neil, John M.

2011-01-01

The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and M??ssbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe2O3/FeO): szomolnokite, rozenite, siderotil, halotrichite, r??merite, voltaite, copiapite, monoclinic Fe2(SO4)3, Fe2(SO4)3??5H2O, kornelite, coquimbite, Fe(SO4)(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750-4000cm-1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe3+ octahedra and sulfate tetrahedra. M??ssbauer spectra of selected samples were obtained at room temperature and 80K for ferric minerals jarosite and rhomboclase and mixed ferric-ferrous minerals r??merite, voltaite, and copiapite. Values of Fe2+/[Fe2++Fe3+] determined by M??ssbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases. ?? 2011 Elsevier B.V.

Vibrational, X-ray absorption, and Mössbauer spectra of sulfate minerals from the weathered massive sulfide deposit at Iron Mountain, California

USGS Publications Warehouse

Majzlan, Juraj; Alpers, Charles N.; Bender Koch, Christian; McCleskey, R. Blaine; Myneni, Satish B.C.; Neil, John M.

2014-01-01

The Iron Mountain Mine Superfund site in California is a prime example of an acid mine drainage (AMD) system with well developed assemblages of sulfate minerals typical for such settings. Here we present and discuss the vibrational (infrared), X-ray absorption, and Mössbauer spectra of a number of these phases, augmented by spectra of a few synthetic sulfates related to the AMD phases. The minerals and related phases studied in this work are (in order of increasing Fe2O3/FeO): szomolnokite, rozenite, siderotil, halotrichite, römerite, voltaite, copiapite, monoclinic Fe2(SO4)3, Fe2(SO4)3·5H2O, kornelite, coquimbite, Fe(SO4)(OH), jarosite and rhomboclase. Fourier transform infrared spectra in the region 750–4000 cm−1 are presented for all studied phases. Position of the FTIR bands is discussed in terms of the vibrations of sulfate ions, hydroxyl groups, and water molecules. Sulfur K-edge X-ray absorption near-edge structure (XANES) spectra were collected for selected samples. The feature of greatest interest is a series of weak pre-edge peaks whose position is determined by the number of bridging oxygen atoms between Fe3+ octahedra and sulfate tetrahedra. Mössbauer spectra of selected samples were obtained at room temperature and 80 K for ferric minerals jarosite and rhomboclase and mixed ferric–ferrous minerals römerite, voltaite, and copiapite. Values of Fe2+/[Fe2+ + Fe3+] determined by Mössbauer spectroscopy agree well with those determined by wet chemical analysis. The data presented here can be used as standards in spectroscopic work where spectra of well-characterized compounds are required to identify complex mixtures of minerals and related phases.

The effect of pathological processes on absorption and scattering spectra of samples of bile and pancreatic juice

NASA Astrophysics Data System (ADS)

Giraev, K. M.; Ashurbekov, N. A.; Magomedov, M. A.; Murtazaeva, A. A.; Medzhidov, R. T.

2015-07-01

Spectra of optical transmission coefficients and optical reflectance for bile and pancreatic juice samples were measured experimentally for different forms of pathologies of the pancreas within the range of 250-2500 nm. The absorption and scattering spectra, as well as the spectrum of the anisotropy factor of scattering, were determined based on the results obtained using the reverse Monte Carlo method. The surface morphology for the corresponding samples of the biological media was studied employing electron microscopy. The dynamics of the optical properties of the biological media was determined depending on the stage of the pathology. It has been demonstrated that the results of the study presented are in a good agreement with pathophysiological data and could supplement and broaden the results of conventional methods for diagnostics of the pancreas.

Deriving the intermediate spectra and photocycle kinetics from time-resolved difference spectra of bacteriorhodopsin. The simpler case of the recombinant D96N protein

NASA Technical Reports Server (NTRS)

Zimanyi, L.; Lanyi, J. K.

1993-01-01

The bacteriorhodopsin photocycle contains more than five spectrally distinct intermediates, and the complexity of their interconversions has precluded a rigorous solution of the kinetics. A representation of the photocycle of mutated D96N bacteriorhodopsin near neutral pH was given earlier (Varo, G., and J. K. Lanyi. 1991. Biochemistry. 30:5008-5015) as BRhv-->K<==>L<==>M1-->M2--> BR. Here we have reduced a set of time-resolved difference spectra for this simpler system to three base spectra, each assumed to consist of an unknown mixture of the pure K, L, and M difference spectra represented by a 3 x 3 matrix of concentration values between 0 and 1. After generating all allowed sets of spectra for K, L, and M (i.e., M1 + M2) at a 1:50 resolution of the matrix elements, invalid solutions were eliminated progressively in a search based on what is expected, empirically and from the theory of polyene excited states, for rhodopsin spectra. Significantly, the average matrix values changed little after the first and simplest of the search criteria that disallowed negative absorptions and more than one maximum for the M intermediate. We conclude from the statistics that during the search the solutions strongly converged into a narrow region of the multidimensional space of the concentration matrix. The data at three temperatures between 5 and 25 degrees C yielded a single set of spectra for K, L, and M; their fits are consistent with the earlier derived photocycle model for the D96N protein.

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.

Correlation of vapor phase infrared spectra and regioisomeric structure in synthetic cannabinoids

NASA Astrophysics Data System (ADS)

Smith, Lewis W.; Thaxton-Weissenfluh, Amber; Abiedalla, Younis; DeRuiter, Jack; Smith, Forrest; Clark, C. Randall

2018-05-01

The twelve 1-n-pentyl-2-, 3-, 4-, 5-, 6- and 7-(1- and 2-naphthoyl)-indoles each have the same substituents attached to the indole ring, identical elemental composition (C24H23NO) yielding identical nominal and accurate masses. These twelve isomers cover all possible positions of carbonyl bridge substitution for both indole (positons 2-7) and naphthalene rings (positions 1 and 2). Regioisomeric compounds can represent significant challenges for mass based analytical methods however, infrared spectroscopy is a powerful tool for the identification of positional isomers in organic compounds. The vapor phase infrared spectra of these twelve uniquely similar compounds were evaluated in GC-IR experiments. These spectra show the bridge position on the indole ring is a dominating influence over the carbonyl absorption frequency observed for these compounds. Substitution on the pyrrole moiety of the indole ring yields the lowest Cdbnd O frequency values for position 2 and 3 giving a narrow range from 1656 to 1654 cm-1. Carbonyl absorption frequencies are higher when the naphthoyl group is attached to the benzene portion of the indole ring yielding absorption values from 1674 to 1671 cm-1. The aliphatic stretching bands in the 2900 cm-1 region yield a consistent triplet pattern because the N-alkyl substituent tail group remains unchanged for all twelve regioisomers. The asymmetric CH2 stretch is the most intense of these three bands. Changes in positional bonding for both the indole and naphthalene ring systems results in unique patterns within the 700 wavenumber out-of-plane region and these absorption bands are different for all 12 regioisomers.

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.

VARIABLE REDDENING AND BROAD ABSORPTION LINES IN THE NARROW-LINE SEYFERT 1 GALAXY WPVS 007: AN ORIGIN IN THE TORUS

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

Leighly, Karen M.; Cooper, Erin; Grupe, Dirk

2015-08-10

We report the discovery of an occultation event in the low-luminosity narrow-line Seyfert 1 galaxy WPVS 007 in 2015 February and March. In concert with longer timescale variability, these observations place strong constraints on the nature and location of the absorbing material. Swift monitoring has revealed a secular decrease since ∼2010 accompanied by flattening of the optical and UV photometry that suggests variable reddening. Analysis of four Hubble Space Telescope COS observations since 2010, including a Director’s Discretionary time observation during the occultation, shows that the broad-absorption-line velocity offset and the C iv emission-line width both decrease as the reddeningmore » increases. The occultation dynamical timescale, the BAL variability dynamical timescale, and the density of the BAL gas show that both the reddening material and the broad-absorption-line gas are consistent with an origin in the torus. These observations can be explained by a scenario in which the torus is clumpy with variable scale height, and the BAL gas is blown from the torus material like spray from the crest of a wave. As the obscuring material passes into our line of sight, we alternately see high-velocity broad absorption lines and a clear view to the central engine, or low-velocity broad absorption lines and strong reddening. WPVS 007 has a small black hole mass, and correspondingly short timescales, and so we may be observing behavior that is common in BALQSOs, but is not typically observable.« less

Discovery of Variable Hydrogen Balmer Absorption Lines with Inverse Decrement in PG 1411+442

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

Shi, Xi-Heng; Pan, Xiang; Zhang, Shao-Hua

We present new optical spectra of the well-known broad absorption line (BAL) quasar PG 1411+442, using the DBSP spectrograph at the Palomar 200 inch telescope in 2014 and 2017 and the YFOSC spectrograph at the Lijiang 2.4 m telescope in 2015. A blueshifted narrow absorption line system is clearly revealed in 2014 and 2015 consisting of hydrogen Balmer series and metastable He i lines. The velocity of these lines is similar to the centroid velocity of the UV BALs, suggesting that both originate from the outflow. The Balmer lines vary significantly between the two observations and vanished in 2017. Theymore » were also absent in the archived spectra obtained before 2001. The variation is thought to be driven by photoionization change. Besides, the absorption lines show inversed Balmer decrement, i.e., the apparent optical depths of higher-order Balmer absorption lines are larger than those of lower-order lines, which is inconsistent with the oscillator strengths of the transitions. We suggest that such anomalous line ratios can be naturally explained by the thermal structure of a background accretion disk, which allows the obscured part of the disk to contribute differently to the continuum flux at different wavelengths. High-resolution spectroscopic and photometric monitoring would be very useful to probe the structure of the accretion disk as well as the geometry and physical conditions of the outflow.« less

Application of artificial neural networks and genetic algorithms to modeling molecular electronic spectra in solution

NASA Astrophysics Data System (ADS)

Lilichenko, Mark; Kelley, Anne Myers

2001-04-01

A novel approach is presented for finding the vibrational frequencies, Franck-Condon factors, and vibronic linewidths that best reproduce typical, poorly resolved electronic absorption (or fluorescence) spectra of molecules in condensed phases. While calculation of the theoretical spectrum from the molecular parameters is straightforward within the harmonic oscillator approximation for the vibrations, "inversion" of an experimental spectrum to deduce these parameters is not. Standard nonlinear least-squares fitting methods such as Levenberg-Marquardt are highly susceptible to becoming trapped in local minima in the error function unless very good initial guesses for the molecular parameters are made. Here we employ a genetic algorithm to force a broad search through parameter space and couple it with the Levenberg-Marquardt method to speed convergence to each local minimum. In addition, a neural network trained on a large set of synthetic spectra is used to provide an initial guess for the fitting parameters and to narrow the range searched by the genetic algorithm. The combined algorithm provides excellent fits to a variety of single-mode absorption spectra with experimentally negligible errors in the parameters. It converges more rapidly than the genetic algorithm alone and more reliably than the Levenberg-Marquardt method alone, and is robust in the presence of spectral noise. Extensions to multimode systems, and/or to include other spectroscopic data such as resonance Raman intensities, are straightforward.

Absorption spectra and optical transitions in InAs/GaAs self-assembled quantum dots

NASA Astrophysics Data System (ADS)

Cusack, M. A.; Briddon, P. R.; Jaros, M.

1997-08-01

We have applied the multiband effective mass/valence force field method to the calculation of optical transitions and absorption spectra in InAs/GaAs self-organized dots of different sizes. We have found that the apparently conflicting assignments of luminescence features to optical transitions in different experiments are in fact entirely compatible with each other. Whether the optical signature of a dot is constructed from transitions between states of the same quantum numbers, or via additional processes between the ground conduction state and a low-lying valence state depends on the aspect ratio of the quantum dot radius and height. The states involved can be predicted from a simple particle in a rigid rectangular box model.

Time-varying sodium absorption in the Type Ia supernova 2013gh

DOE PAGES

Ferretti, Raphael; Amanullah, R.; Goobar, A.; ...

2016-07-18

Context. Temporal variability of narrow absorption lines in high-resolution spectra of Type Ia supernovae (SNe Ia) is studied to search for circumstellar matter. Time series which resolve the profiles of absorption lines such as Na I D or Ca II H&K are expected to reveal variations due to photoionisation and subsequent recombination of the gases. The presence, composition, and geometry of circumstellar matter may hint at the elusive progenitor system of SNe Ia and could also affect the observed reddening law. Aims. To date, there are few known cases of time-varying Na I D absorption in SNe Ia, all ofmore » which occurred during relatively late phases of the supernova (SN) evolution. Photoionisation, however, is predicted to occur during the early phases of SNe Ia, when the supernovae peak in the ultraviolet. We attempt, therefore, to observe early-time absorption-line variations by obtaining high-resolution spectra of SNe before maximum light. Methods. In this paper, we have obtained photometry and high-resolution spectroscopy of SNe Ia 2013gh and iPTF 13dge, to search for absorption-line variations. Furthermore, we study interstellar absorption features in relation to the observed photometric colours of the SNe. Results. Both SNe display deep Na I D and Ca II H&K absorption features. Furthermore, small but significant variations are detected in a feature of the Na I D profile of SN 2013gh. The variations are consistent with either geometric effects of rapidly moving or patchy gas clouds or photoionisation of Na I gas at R ≈ 10 19 cm from the explosion. Conclusions. Our analysis indicates that it is necessary to focus on early phases to detect photoionisation effects of gases in the circumstellar medium of SNe Ia. Different absorbers such as Na I and Ca II can be used to probe for matter at different distances from the SNe. Finally, the nondetection of variations during early phases makes it possible to put limits on the abundance of the species at those

Signatures of a conical intersection in photofragment distributions and absorption spectra: Photodissociation in the Hartley band of ozone

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

Picconi, David; Grebenshchikov, Sergy Yu., E-mail: Sergy.Grebenshchikov@ch.tum.de

Photodissociation of ozone in the near UV is studied quantum mechanically in two excited electronic states coupled at a conical intersection located outside the Franck-Condon zone. The calculations, performed using recent ab initio PESs, provide an accurate description of the photodissociation dynamics across the Hartley/Huggins absorption bands. The observed photofragment distributions are reproduced in the two electronic dissociation channels. The room temperature absorption spectrum, constructed as a Boltzmann average of many absorption spectra of rotationally excited parent ozone, agrees with experiment in terms of widths and intensities of diffuse structures. The exit channel conical intersection contributes to the coherent broadeningmore » of the absorption spectrum and directly affects the product vibrational and translational distributions. The photon energy dependences of these distributions are strikingly different for fragments created along the adiabatic and the diabatic paths through the intersection. They can be used to reverse engineer the most probable geometry of the non-adiabatic transition. The angular distributions, quantified in terms of the anisotropy parameter β, are substantially different in the two channels due to a strong anticorrelation between β and the rotational angular momentum of the fragment O{sub 2}.« less

FIRST ULTRAVIOLET REFLECTANCE SPECTRA OF PLUTO AND CHARON BY THE HUBBLE SPACE TELESCOPE COSMIC ORIGINS SPECTROGRAPH: DETECTION OF ABSORPTION FEATURES AND EVIDENCE FOR TEMPORAL CHANGE

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

Stern, S. A.; Spencer, J. R.; Shinn, A.

We have observed the mid-UV spectra of both Pluto and its large satellite, Charon, at two rotational epochs using the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) in 2010. These are the first HST/COS measurements of Pluto and Charon. Here we describe the observations and our reduction of them, and present the albedo spectra, average mid-UV albedos, and albedo slopes we derive from these data. These data reveal evidence for a strong absorption feature in the mid-UV spectrum of Pluto; evidence for temporal change in Pluto's spectrum since the 1990s is reported, and indirect evidence for a near-UV spectralmore » absorption on Charon is also reported.« less

Space Telescope and Optical Reverberation Mapping Project: Unraveling the Broad Line Region and the Intrinsic Absorption in NGC 5548

NASA Astrophysics Data System (ADS)

Kriss, G.; Storm Team

2015-07-01

The Space Telescope and Optical Reverberation Mapping (STORM) project monitored the Seyfert 1 galaxy NGC 5548 over a six-month period, obtaining 171 far-ultraviolet HST/COS spectra at approximately daily intervals. We find significant correlated variability in the continuum and broad emission lines, with amplitudes ranging from a factor of two in the emission lines to a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He II lagging by ˜ 2.5 days and Ly&alpha,; C IV, and Si IV lagging by 5 to 6 days. 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 absorption lines associated with the historical warm absorber varied in response to the changing UV flux on a daily basis with lags of 3 to 8 days. The ionization response allows precise determinations of the locations, mass flux, and kinetic luminosities of the absorbers.

Galaxy properties from J-PAS narrow-band photometry

NASA Astrophysics Data System (ADS)

Mejía-Narváez, A.; Bruzual, G.; Magris, C. G.; Alcaniz, J. S.; Benítez, N.; Carneiro, S.; Cenarro, A. J.; Cristóbal-Hornillos, D.; Dupke, R.; Ederoclite, A.; Marín-Franch, A.; de Oliveira, C. Mendes; Moles, M.; Sodre, L.; Taylor, K.; Varela, J.; Ramió, H. Vázquez

2017-11-01

We study the consistency of the physical properties of galaxies retrieved from spectral energy distribution (SED) fitting as a function of spectral resolution and signal-to-noise ratio (SNR). Using a selection of physically motivated star formation histories, we set up a control sample of mock galaxy spectra representing observations of the local Universe in high-resolution spectroscopy, and in 56 narrow-band and 5 broad-band photometry. We fit the SEDs at these spectral resolutions and compute their corresponding stellar mass, the mass- and luminosity-weighted age and metallicity, and the dust extinction. We study the biases, correlations and degeneracies affecting the retrieved parameters and explore the role of the spectral resolution and the SNR in regulating these degeneracies. We find that narrow-band photometry and spectroscopy yield similar trends in the physical properties derived, the former being considerably more precise. Using a galaxy sample from the Sloan Digital Sky Survey (SDSS), we compare more realistically the results obtained from high-resolution and narrow-band SEDs (synthesized from the same SDSS spectra) following the same spectral fitting procedures. We use results from the literature as a benchmark to our spectroscopic estimates and show that the prior probability distribution functions, commonly adopted in parametric methods, may introduce biases not accounted for in a Bayesian framework. We conclude that narrow-band photometry yields the same trend in the age-metallicity relation in the literature, provided it is affected by the same biases as spectroscopy, albeit the precision achieved with the latter is generally twice as large as with the narrow-band, at SNR values typical of the different kinds of data.

C IV broad absorption line variability in QSO spectra from SDSS surveys

NASA Astrophysics Data System (ADS)

De Cicco, Demetra; Brandt, William N.; Grier, Catherine J.; Paolillo, Maurizio

2017-12-01

Broad absorption lines (BALs) in the spectra of quasi-stellar objects (QSOs) are thought to arise from outflowing winds along our line of sight; winds, in turn, are thought to originate from the accretion disk, in the very surroundings of the central supermassive black hole (SMBH), and they likely affect the accretion process onto the SMBH, as well as galaxy evolution. BALs can exhibit variability on timescales typically ranging from months to years. We analyze such variability and, in particular, BAL disappearance, with the aim of investigating QSO physics and structure. We search for disappearing C IV BALs in the spectra of 1319 QSOs from different programs from the Sloan Digital Sky Survey (SDSS); the analyzed time span covers 0.28-4.9 yr (rest frame), and the source redshifts are in the range 1.68-4.27. This is to date the largest sample ever used for such a study. We find 67 sources (5.1_{-0.6}^{+0.7}% of the sample) with 73 disappearing BALs in total (3.9_{-0.5}^{+0.5}% of the total number of C IV BALs detected; some sources have more than one BAL that disappears). We compare the sample of disappearing BALs to the whole sample of BALs, and investigate the correlation in the variability of multiple troughs in the same spectrum. We also derive estimates of the average lifetime of a BAL trough and of the BAL phase along our line of sight.

Cost and sensitivity of restricted active-space calculations of metal L-edge X-ray absorption spectra.

PubMed

Pinjari, Rahul V; Delcey, Mickaël G; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

2016-02-15

The restricted active-space (RAS) approach can accurately simulate metal L-edge X-ray absorption spectra of first-row transition metal complexes without the use of any fitting parameters. These characteristics provide a unique capability to identify unknown chemical species and to analyze their electronic structure. To find the best balance between cost and accuracy, the sensitivity of the simulated spectra with respect to the method variables has been tested for two models, [FeCl6 ](3-) and [Fe(CN)6 ](3-) . For these systems, the reference calculations give deviations, when compared with experiment, of ≤1 eV in peak positions, ≤30% for the relative intensity of major peaks, and ≤50% for minor peaks. When compared with these deviations, the simulated spectra are sensitive to the number of final states, the inclusion of dynamical correlation, and the ionization potential electron affinity shift, in addition to the selection of the active space. The spectra are less sensitive to the quality of the basis set and even a double-ζ basis gives reasonable results. The inclusion of dynamical correlation through second-order perturbation theory can be done efficiently using the state-specific formalism without correlating the core orbitals. Although these observations are not directly transferable to other systems, they can, together with a cost analysis, aid in the design of RAS models and help to extend the use of this powerful approach to a wider range of transition metal systems. © 2015 Wiley Periodicals, Inc.

Absorption spectra of 4f electron transitions of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid and diethylamine systems and its analytical application

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

Wang Naixing; Qi Ping

1992-06-01

In this paper the absorption spectra of 4f electron transitions of the systems of neodymium and erbium with 8-hydroxyquinoline-5-sulphonic acid and diethylamine have been studied by normal and third-derivative spectrophotometry. Their molar absorptivities are 80 1.mol{sup {minus}1}.cm{sup {minus}1} for neodymium and 65 1.mol{sup {minus}1}.cm{sup {minus}1} for erbium. Use of the third-derivative spectra, eliminates the interference by other rare earths and increases the sensitivity for Nd and Er. The derivative molar absorptivities are 390 1.mol{sup {minus}1}.cm{sup {minus}1} for Nd and 367 1.mol{sup {minus}1}.cm{sup {minus}1} for Er. The calibration graphs were linear up to 11.8 {mu}g/ml of Nd and 12.3 {mu}g/ml ofmore » Er, respectively. The relative standard deviations evaluated from eleven independent determinations of 7.2 {mu}g/ml (for Nd) and 8.3 {mu}g/ml (for Er) are 1.3% and 1.4%, respectively. The detection limits are 0.2 {mu}g/ml for Nd and 0.3 {mu}g/ml for Er. The method has been developed for determining those two elements in mixture of lanthanides by means of the third-derivative spectra and the analytical results obtained are satisfactory.« less

Composition and structure of fresh ammonia clouds on Jupiter based on quantitative analysis of Galileo/NIMS and New Horizons/LEISA spectra

NASA Astrophysics Data System (ADS)

Sromovsky, L. A.; Fry, P. M.

2018-06-01

Ammonia gas has long been assumed to be the main source of condensables for the upper cloud layer on Jupiter, but distinctive spectral features associated with ammonia have been seen only rarely. Since both ammonia and NH4SH absorb in the 3 μm region, and widespread absorption in the 3 μm region was present (Sromovsky and Fry, 2010), identification of the 2 μm absorption feature of NH3 provided an opportunity to clearly establish its presence in Jovian clouds. Baines et al. (2002) succeeded in finding in Near Infrared Mapping Spectrometer (NIMS) observations one feature that had both 2 μm and 3 μm absorption, and many which were known to have absorption at 2.73 μm. They named these Spectrally Identifiable Ammonia Clouds (SIACs). They also argued that these were fresh ammonia clouds that would eventually succumb to some process that would obscure their absorption features. Detection of many more of the 2 μm features was later achieved by New Horizon's Linear Etalon Imaging Spectral Array (LEISA) instrument, which provided both the spatial and spectral resolution needed to identify these features. Here we report on the first quantitative modeling that uses NIMS spectra over a broad (1-5.2 μm) spectral range and LEISA spectra over a much narrower (1.25-2.5 μm) spectral range to constrain the cloud structure and composition of these rare cloud features and compare them to background clouds. We find that the absorption signature at 2 μm, which is well characterized in LEISA spectra, is relatively subtle and easily matched by model clouds containing spherical particles of ammonia ice with radii of 2-4 μm. The NIMS spectra, which cover both reflected sunlight as well as thermal emission regions are more difficult to model with cloud materials plausibly present in Jupiter's atmosphere. The best signal/noise spectra obtained from NIMS provide a relatively sparse sampling of the spectrum, which does not establish the detailed shape of the 3 μm absorption region

Infrared Measurements of Atmospheric Ethane (C2H6) From Aircraft and Ground-Based Solar Absorption Spectra in the 3000/ cm Region

NASA Technical Reports Server (NTRS)

Coffey, M. T.; Mankin, W. G.; Goldman, A.; Rinsland, C. P.; Harvey, G. A.; Devi, V. Malathy; Stokes, G. M.

1985-01-01

A number or prominent Q-branches or the upsilon(sub 7) band or C2H6 have been identified near 3000/ cm in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The, ground-based spectra yield a column of 9.0 x 10(exp 15) molecules/sq cm above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv.

Infrared measurements of atmospheric ethane (C2H6) from aircraft and ground-based solar absorption spectra in the 3000/cm region

NASA Technical Reports Server (NTRS)

Coffey, M. T.; Mankin, W. G.; Goldman, A.; Rinsland, C. P.; Harvey, G. A.; Devi, V. M.; Stokes, G. M.

1985-01-01

A number of prominent Q-branches of the nu-7 band of C2H6 have been identified near 3000/cm in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The ground-based spectra yield a column of 9.0 x 10 to the 15th molecules/sq cm above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv.

Investigating the Near-Infrared Properties of Planetary Nebulae II. Medium Resolution Spectra. 2; Medium Resolution Spectra

NASA Technical Reports Server (NTRS)

Hora, Joseph L.; Latter, William B.; Deutsch, Lynne K.

1998-01-01

We present medium-resolution (R approximately 700) near-infrared (lambda = 1 - 2.5 micrometers) spectra of a sample of planetary nebulae (PNe). A narrow slit was used which sampled discrete locations within the nebulae; observations were obtained at one or more positions in the 41 objects included in the survey. The PN spectra fall into one of four general categories: H1 emission line-dominated PNe, H1 and H2 emission line PNe, H2 emission line-dominated PNe, and continuum-dominated PNe. These categories correlate with morphological type, with the elliptical PNe falling into the first group, and the bipolar PNe primarily in the H2 and continuum emission groups. The categories also correlate with C/O ratio, with the O-rich objects falling into the first group and the C-rich objects in the groups. Other spectral features were observed in all catagories, such as continuum emission from the central star, and warm dust continuum emission towards the long wavelength end of the spectra. H2 was detected in four PNe in this survey for the first time. An analysis was performed using the H2 line ratios in all of the PN spectra in the survey where a sufficient number of lines were observed to determine the ortho-to-para ratio and the rotational and vibrational excitation temperatures of the H-2 in those objects. One unexpected result from this analysis is that the H-2 is excited by absorption of ultraviolet photons in most of the PNe, although there are several PNe in which collisional excitation plays an important role. The correlation between bipolar morphology and H2 emission has been strengthened with the new detections of H2 in this survey.

Investigating powerful jets in radio-loud narrow-line Seyfert 1s

DOE PAGES

Orienti, M.; D'Ammando, F.; Larsson, J.; ...

2015-09-14

Here, we report results on multiband observations from radio to γ-rays of the two radio-loud narrow-line Seyfert 1 (NLSy1) galaxies PKS 2004-447 and J1548+3511. Furthermore, both sources show a core–jet structure on parsec scale, while they are unresolved at the arcsecond scale. The high core dominance and the high variability brightness temperature make these NLSy1 galaxies good γ-ray source candidates. Fermi-Large Area Telescope detected γ-ray emission only from PKS 2004-447, with a γ-ray luminosity comparable to that observed in blazars. There was no γ-ray emission observed for J1548+3511. Both sources are variable in X-rays. J1548+3511 shows a hardening of themore » spectrum during high activity states, while PKS 2004-447 has no spectral variability. A spectral steepening likely related to the soft excess is hinted below 2 keV for J1548+3511, while the X-ray spectra of PKS 2004-447 collected by XMM–Newton in 2012 are described by a single power law without significant soft excess. No additional absorption above the Galactic column density or the presence of an Fe line is detected in the X-ray spectra of both sources.« less

Complex polarization propagator approach in the restricted open-shell, self-consistent field approximation: the near K-edge X-ray absorption fine structure spectra of allyl and copper phthalocyanine.

PubMed

Linares, Mathieu; Stafström, Sven; Rinkevicius, Zilvinas; Ågren, Hans; Norman, Patrick

2011-05-12

A presentation of the complex polarization propagator in the restricted open-shell self-consistent field approximation is given. It rests on a formulation of a resonant-convergent, first-order polarization propagator approach that makes it possible to directly calculate the X-ray absorption cross section at a particular frequency without explicitly addressing the excited states. The quality of the predicted X-ray spectra relates only to the type of density functional applied without any separate treatment of dynamical relaxation effects. The method is applied to the calculation of the near K-edge X-ray absorption fine structure spectra of allyl and copper phthalocyanine. Comparison is made between the spectra of the radicals and those of the corresponding cations and anions to assess the effect of the increase of electron charge in the frontier orbital. The method offers the possibility for unique assignment of symmetry-independent atoms. The overall excellent spectral agreement motivates the application of the method as a routine precise tool for analyzing X-ray absorption of large systems of technological interest.

Restricted active space calculations of L-edge X-ray absorption spectra: from molecular orbitals to multiplet states.

PubMed

Pinjari, Rahul V; Delcey, Mickaël G; Guo, Meiyuan; Odelius, Michael; Lundberg, Marcus

2014-09-28

The metal L-edge (2p → 3d) X-ray absorption spectra are affected by a number of different interactions: electron-electron repulsion, spin-orbit coupling, and charge transfer between metal and ligands, which makes the simulation of spectra challenging. The core restricted active space (RAS) method is an accurate and flexible approach that can be used to calculate X-ray spectra of a wide range of medium-sized systems without any symmetry constraints. Here, the applicability of the method is tested in detail by simulating three ferric (3d(5)) model systems with well-known electronic structure, viz., atomic Fe(3+), high-spin [FeCl6](3-) with ligand donor bonding, and low-spin [Fe(CN)6](3-) that also has metal backbonding. For these systems, the performance of the core RAS method, which does not require any system-dependent parameters, is comparable to that of the commonly used semi-empirical charge-transfer multiplet model. It handles orbitally degenerate ground states, accurately describes metal-ligand interactions, and includes both single and multiple excitations. The results are sensitive to the choice of orbitals in the active space and this sensitivity can be used to assign spectral features. A method has also been developed to analyze the calculated X-ray spectra using a chemically intuitive molecular orbital picture.

Infrared absorption spectra of N(CxF2x+1)3, x = 2-5 perfluoroamines

NASA Astrophysics Data System (ADS)

Bernard, François; Papanastasiou, Dimitrios K.; Papadimitriou, Vassileios C.; Burkholder, James B.

2018-05-01

Infrared absorption spectra of the perfluoroamines (N(C2F5)3, N(C3F7)3, N(C4F9)3, and N(C5F11)3) were measured over the 500-4000 cm-1 spectral region at 294 K using Fourier transform infrared (FTIR) spectroscopy at 1 cm-1 resolution. Spectral measurements were performed using static measurements of dilute perfluoroamines mixtures and by infusion of the pure compound into a calibrated gas flow. The perfluoroamines absorb strongly in the "atmospheric window" with integrated band strengths (10-17 cm2 molecule-1 cm-1) between 570 and 1500 cm-1 of 59.9, 74.9, 88.9, and 98.7 for N(C2F5)3, N(C3F7)3, N(C4F9)3, and N(C5F11)3, respectively. Radiative efficiencies (RE) for the perfluoroamines were estimated to be 0.61, 0.75, 0.87, and 0.95 W m-2 ppb-1 for atmospherically well-mixed conditions and including a +10% stratospheric temperature correction for N(C2F5)3, N(C3F7)3, N(C4F9)3, and N(C5F11)3, respectively. Theoretical calculations of the perfluoroamines were performed at the B97-1/6-311++G(2df,2p) level of theory and optimized perfluoroamine geometries, vibrational band positions, and band strengths are reported. The theoretically calculated infrared spectra are in good agreement with the experimental spectra, while comparison of individual bands was not attempted due to the significant overlap of vibrational bands in the experimental spectra.

On the Widths of Bands in the Infrared Spectra of Oxyanions.

PubMed

Griffiths, Peter R; Eastman Fries, Brandy; Weakley, Andrew T

2018-01-01

It is well known that the antisymmetric stretching (ν 3 ) band in the mid-infrared spectra of oxyanion salts is usually very broad, whereas all the other fundamental bands are narrow. In this paper, we propose that the underlying cause of the increased width is the effect of the very high absorption index of this band for samples prepared with a range of particle sizes. When oxyanion salts are ground, the diameter of the resulting particles usually varies from less than 100 nm to about 2 µm. While the peak absorbance of the ν 3 band of the smaller particles (diameter < 200 nm) is less than 1, that of the larger particles can be as high as 6. We show that the average transmittance of these particles leads to a significant band broadening, especially when there are small voids in the resulting sample. Although the effect is always seen in the spectra of alkali halide disks and mineral oil mulls, it is also seen in diffuse reflection and attenuated total reflection (ATR) spectra. Because the depth of penetration of infrared radiation below 1500 cm -1 is less than 1 µm for ATR spectra measured with a germanium internal reflection element (IRE), the width of the ν 3 band is lower than that of ATR spectra measured with an IRE of lower refractive index such as diamond on zinc selenide.

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.

Substituent and solvent effects on electronic spectra of some substituted phenoxyacetic acids.

PubMed

Shanthi, M; Kabilan, S

2007-06-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 19 para- and ortho-substituted phenoxyacetic acids in the range of 200-400 nm. The effects of substituent on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

Substituent and solvent effects on electronic spectra of some substituted phenoxyacetic acids

NASA Astrophysics Data System (ADS)

Shanthi, M.; Kabilan, S.

2007-06-01

The effects of substituents and solvents have been studied through the absorption spectra of nearly 19 para- and ortho-substituted phenoxyacetic acids in the range of 200-400 nm. The effects of substituent on the absorption spectra of compounds under present investigation are interpreted by correlation of absorption frequencies with simple and extended Hammett equations. Effect of solvent polarity and hydrogen bonding on the absorption spectra are interpreted by means of Kamlet equation and the results are discussed.

Experimental Study of Temperature-Dependence Laws of Non-Voigt Absorption Line Shape Parameters

NASA Astrophysics Data System (ADS)

Wilzewski, Jonas; Birk, Manfred; Loos, Joep; Wagner, Georg

2017-06-01

To improve the understanding of temperature-dependence laws of spectral line shape parameters, spectra of the ν_3 rovibrational band of CO_2 perturbed by 10, 30, 100, 300 and 1000 mbar of N_2 were measured at nine temperatures between 190 K and 330 K using a 22 cm long single-pass absorption cell in a Bruker IFS125 HR Fourier Transform spectrometer. The spectra were fitted employing a quadratic speed-dependent hard collision model in the Hartmann-Tran implementation extended to account for line mixing in the Rosenkranz approximation by means of a multispectrum fitting approach developed at DLR This enables high accuracy parameter retrievals to reproduce the spectra down to noise level and we will present the behavior of line widths, shifts, speed-dependence-, collisional narrowing- and line mixing-parameters over this 140 K temperature range. Tran et al. JQSRT 129, 199-203 (2013); JQSRT 134, 104 (2014). Loos et al., 2014; http://doi.org/10.5281/zenodo.11156. Ngo et al. JQSRT 29, 89-100 (2013); JQSRT 134, 105 (2014).

Simulation of X-ray absorption spectra with orthogonality constrained density functional theory.

PubMed

Derricotte, Wallace D; Evangelista, Francesco A

2015-06-14

Orthogonality constrained density functional theory (OCDFT) [F. A. Evangelista, P. Shushkov and J. C. Tully, J. Phys. Chem. A, 2013, 117, 7378] is a variational time-independent approach for the computation of electronic excited states. In this work we extend OCDFT to compute core-excited states and generalize the original formalism to determine multiple excited states. Benchmark computations on a set of 13 small molecules and 40 excited states show that unshifted OCDFT/B3LYP excitation energies have a mean absolute error of 1.0 eV. Contrary to time-dependent DFT, OCDFT excitation energies for first- and second-row elements are computed with near-uniform accuracy. OCDFT core excitation energies are insensitive to the choice of the functional and the amount of Hartree-Fock exchange. We show that OCDFT is a powerful tool for the assignment of X-ray absorption spectra of large molecules by simulating the gas-phase near-edge spectrum of adenine and thymine.

Circular dichroism and optical absorption spectra of mononuclear and trinuclear chiral Cu(II) amino-alcohol coordinated compounds: A combined theoretical and experimental study

NASA Astrophysics Data System (ADS)

Valencia, Israel; Ávila-Torres, Yenny; Barba-Behrens, Norah; Garzón, Ignacio L.

2015-04-01

Studies on the physicochemical properties of biomimetic compounds of multicopper oxidases are fundamental to understand their reaction mechanisms and catalytic behavior. In this work, electronic, optical, and chiroptical properties of copper(II) complexes with amino-alcohol chiral ligands are theoretically studied by means of time-dependent density functional theory. The calculated absorption and circular dichroism spectra are compared with experimental measurements of these spectra for an uncoordinated pseudoephedrine derivative, as well as for the corresponding mononuclear and trinuclear copper(II)-coordinated complexes. This comparison is useful to gain insights into their electronic structure, optical absorption and optical activity. The optical absorption and circular dichroism bands of the pseudoephedrine derivative are located in the UV-region. They are mainly due to transitions originated from n to π anti-bonding orbitals of the alcohol and amino groups, as well as from π bonding to π anti-bonding orbitals of carboxyl and phenyl groups. In the case of the mononuclear and trinuclear compounds, additional signals in the visible spectral region are present. In both systems, the origin of these bands is due to charge transfer from ligand to metal and d-d transitions.

Optical Absorption Spectra of Hydrogenated Microcrystalline Silicon Films by Resonant Photothermal Bending Spectroscopy

NASA Astrophysics Data System (ADS)

Kunii, Toshie; Yoshida, Norimitsu; Hori, Yasuro; Nonomura, Shuichi

2006-05-01

A resonant photothermal bending spectroscopy (PBS) is demonstrated for the measurement of absorption coefficient spectra in hydrogenated microcrystalline silicon (μc-Si:H) and hydrogenated microcrystalline cubic silicon carbide (μc-3C-SiC:H) films. The resonant vibration technique utilized in PBS establishes the sensitivity as α d˜ 5× 10-5 in a vacuum measurement. Appling resonant PBS to μc-Si:H films, a new extra absorption coefficient αex spectrum is observed from 0.6 to 1.2 eV. The αex spectrum has a peak at ˜1.0 eV, and the localized states inducing the αex are located ˜0.35 eV below the conduction band edge of μc-Si:H. A possible explanation for the observed localized state is that an oxidation produces weak bonds at the grain boundaries and/or amorphous silicon tissues. In μc-3C-SiC:H film, an optical band-gap energy of ˜2.2 eV was demonstrated assuming an indirect optical transition. The temperature coefficient of the optical band-gap energy was ˜2.3× 10-4 eV K-1. The αex spectrum of μc-3C-SiC:H film is plateau-shaped and its magnitude is in accord with an increase in grain size.

Absorption and resonance Raman spectra of Pb2, Pb3 and Pb4 in xenon matrices

NASA Technical Reports Server (NTRS)

Stranz, D. D.; Khanna, R. K.

1980-01-01

Lead metal was vaporized and trapped in solid xenon at 12K. Electronic absorption and resonance Raman spectra were recorded of the resulting matrix, which was shown to contain Pb2, Pb3, and possibly Pb4 molecular species. The vibrational frequency for Pb2 is determined to be 108/cm for the ground state, with a dissociation energy of 82000/cm. Ad3h symmetry is indicated for the Pb3 species, with nu sub 1=117/cm and nu sub 2 = 96 /cm. The existence of Pb4 is suggested by a fundamental and overtone of 111/cm spacing.

Impact effects of gamma irradiation on the optical and FT infrared absorption spectra of some Nd3+-doped soda lime phosphate glasses

NASA Astrophysics Data System (ADS)

Marzouk, M. A.; Elkashef, I. M.; Elbatal, H. A.

2018-04-01

The main aim of the present work is to study by two collective optical and FTIR spectral measurements some prepared Nd2O3-doped soda lime phosphate glasses before and after gamma irradiation with dose (9 Mrad). The spectral data reveal two strong UV absorption peaks which are correlated with unavoidable trace iron impurities beside extended additional characteristic bands due to Nd3+ ions. Gamma irradiation on the undoped glass produces slight decrease of the intensity of the UV absorption and the generation of an induced visible band and these effects are controlled with two photochemical reduction of some Fe3+ ions to Fe2+ ions together with the formation of nonbridging oxygen hole center (NBOHC) or phosphorous oxygen hole center (POHC). The impact effect of gamma irradiation on the spectra of Nd2O3-doped glasses is limited due to suggested shielding behavior of neodymium ions. FT-infrared spectra show vibrational modes due to main Q2-Q3 phosphate groups and the response of gamma irradiation of the IR spectra is low and the limited variations are related to suggested changes in some bond angles and bond lengths which cause the observed decrease to the intensities of some IR bands.

Effects of solvent polarity on the absorption and fluorescence spectra of chlorogenic acid and caffeic acid compounds: determination of the dipole moments.

PubMed

Belay, Abebe; Libnedengel, Ermias; Kim, Hyung Kook; Hwang, Yoon-Hwae

2016-02-01

The effects of solvent polarity on absorption and fluorescence spectra of biologically active compounds (chlorogenic acid (CGA) and caffeic acids (CA)) have been investigated. In both spectra pronounced solvatochromic effects were observed with shift of emission peaks larger than the corresponding UV-vis electronic absorption spectra. From solvatochromic theory the ground and excited-state dipole moments were determined experimentally and theoretically. The differences between the excited and ground state dipole moment determined by Bakhshiev, Kawski-Chamma-Viallet and Reichardt equations are quite similar. The ground and excited-state dipole moments were determined by theoretical quantum chemical calculation using density function theory (DFT) method (Gaussian 09) and were also similar to the experimental results. The HOMO-LUMO energy band gaps for CGA and CFA were calculated and found to be 4.1119 and 1.8732 eV respectively. The results also indicated the CGA molecule is more stable than that of CFA. It was also observed that in both compounds the excited state possesses a higher dipole moment than that of the ground state. This confirms that the excited state of the hydroxycinnamic compounds is more polarized than that of the ground state and therefore is more sensitive to the solvent. Copyright © 2015 John Wiley & Sons, Ltd.

Narrow polarized components in the OH 1612-MHz maser emission from supergiant OH-IR sources

NASA Technical Reports Server (NTRS)

Cohen, R. J.; Downs, G.; Emerson, R.; Grimm, M.; Gulkis, S.; Stevens, G.

1987-01-01

High-resolution (300 Hz) OH 1612-MHz spectra of the supergiant OH-IR sources VY CMa, VX Sgr, IRC 10420, and NML Cyg are presented. Linewidths as small as 550 Hz (0.1 km/s) are found for narrow components in the spectra. The present results are consistent with current models for maser line-narrowing and for the physical properties in the OH maser regions. A significant degree of circular polarization is noted in many of the narrow components. The circular polarization suggests the presence of magnetic fields of about 1 mG in the circumstellar envelopes which would be strong enough to influence the outflow from the stars, and which may explain asymmetries found in the circumstellar envelopes.

Multiconfigurational and DFT analyses of the electromeric formulation and UV-vis absorption spectra of the superoxide adduct of ferrous superoxide reductase.

PubMed

Attia, Amr A A; Cioloboc, Daniela; Lupan, Alexandru; Silaghi-Dumitrescu, Radu

2016-12-01

The putative initial adduct of ferrous superoxide reductase (SOR) with superoxide has been alternatively formulated as ferric-peroxo or ferrous-superoxo. The ~600-nm UV-vis absorption band proposed to be assigned to this adduct (either as sole intermediate in the SOR catalytic cycle, or as one of the two intermediates) has recently been interpreted as due to a ligand-to-metal charge transfer, involving thiolate and superoxide in a ferrous complex, contrary to an alternative assignment as a predominantly cysteine thiolate-to-ferric charge transfer in a ferric-peroxo electromer. In an attempt to clarify the electromeric formulation of this adduct, we report a computational study using a multiconfigurational complete active space self-consistent field (MC-CASSCF) wave function approach as well as modelling the UV-vis absorption spectra with time-dependent density functional theory (TD-DFT). The MC-CASSCF calculations disclose a weak interaction between iron and the dioxygenic ligand and a dominant configuration with an essentially ferrous-superoxo character. The computed UV-vis absorption spectra reveal a marked dependence on the choice of density functional - both in terms of location of bands and in terms of orbital contributors. For the main band in the visible region, besides the recently reported thiolate-to-superoxide charge transfer, a more salient, and less functional-dependent, feature is a thiolate-to-ferric iron charge transfer, consistent with a ferric-peroxo electromer. By contrast, the computed UV-vis spectra of a ferric-hydroperoxo SOR model match distinctly better (and with no qualitative dependence on the DFT methodology) the 600-nm band as due to a mainly thiolate-to-ferric character - supporting the assignment of the SOR "600-nm intermediate" as a S=5/2 ferric-hydroperoxo species. Copyright © 2016 Elsevier Inc. All rights reserved.

Application of Time-Dependent Density Functional and Natural Bond Orbital Theories to the UV-vis Absorption Spectra of Some Phenolic Compounds.

PubMed

Marković, Svetlana; Tošović, Jelena

2015-09-03

The UV-vis properties of 22 natural phenolic compounds, comprising anthraquinones, neoflavonoids, and flavonoids were systematically examined. The time-dependent density functional theory (TDDFT) approach in combination with the B3LYP, B3LYP-D2, B3P86, and M06-2X functionals was used to simulate the UV-vis spectra of the investigated compounds. It was shown that all methods exhibit very good (B3LYP slightly better) performance in reproducing the examined UV-vis spectra. However, the shapes of the Kohn-Sham molecular orbitals (MOs) involved in electronic transitions were misleading in constructing the MO correlation diagrams. To provide better understanding of redistribution of electron density upon excitation, the natural bond orbital (NBO) analysis was applied. Bearing in mind the spatial and energetic separations, as well as the character of the π bonding, lone pair, and π* antibonding natural localized molecular orbitals (NLMOs), the "NLMO clusters" were constructed. NLMO cluster should be understood as a part of a molecule characterized with distinguished electron density. It was shown that all absorption bands including all electronic transitions need to be inspected to fully understand the UV-vis spectrum of a certain compound, and, thus, to learn more about its UV-vis light absorption. Our investigation showed that the TDDFT and NBO theories are complementary, as the results from the two approaches can be combined to interpret the UV-vis spectra. Agreement between the predictions of the TDDFT approach and those based on the NLMO clusters is excellent in the case of major electronic transitions and long wavelengths. It should be emphasized that the approach for investigation of UV-vis light absorption based on the NLMO clusters is applied for the first time.

How Continuous Observations of Shortwave Reflectance Spectra Can Narrow the Range of Shortwave Climate Feedbacks

NASA Astrophysics Data System (ADS)

Feldman, D.; Collins, W. D.; Wielicki, B. A.; Shea, Y.; Mlynczak, M. G.; Kuo, C.; Nguyen, N.

2017-12-01

Shortwave feedbacks are a persistent source of uncertainty for climate models and a large contributor to the diagnosed range of equilibrium climate sensitivity (ECS) for the international multi-model ensemble. The processes that contribute to these feedbacks affect top-of-atmosphere energetics and produce spectral signatures that may be time-evolving. We explore the value of such spectral signatures for providing an observational constraint on model ECS by simulating top-of-atmosphere shortwave reflectance spectra across much of the energetically-relevant shortwave bandpass (300 to 2500 nm). We present centennial-length shortwave hyperspectral simulations from low, medium and high ECS models that reported to the CMIP5 archive as part of an Observing System Simulation Experiment (OSSE) in support of the CLimate Absolute Radiance and Refractivity Observatory (CLARREO). Our framework interfaces with CMIP5 archive results and is agnostic to the choice of model. We simulated spectra from the INM-CM4 model (ECS of 2.08 °K/2xCO2), the MIROC5 model (ECS of 2.70 °K/2xCO2), and the CSIRO Mk3-6-0 (ECS of 4.08 °K/2xCO2) based on those models' integrations of the RCP8.5 scenario for the 21st Century. This approach allows us to explore how perfect data records can exclude models of lower or higher climate sensitivity. We find that spectral channels covering visible and near-infrared water-vapor overtone bands can potentially exclude a low or high sensitivity model with under 15 years' of absolutely-calibrated data. These different spectral channels are sensitive to model cloud radiative effect and cloud height changes, respectively. These unprecedented calculations lay the groundwork for spectral simulations of perturbed-physics ensembles in order to identify those shortwave observations that can help narrow the range in shortwave model feedbacks and ultimately help reduce the stubbornly-large range in model ECS.

Experimental and theoretical comparison of the O K-edge nonresonant inelastic X-ray scattering and X-ray absorption spectra of NaReO4.

PubMed

Bradley, Joseph A; Yang, Ping; Batista, Enrique R; Boland, Kevin S; Burns, Carol J; Clark, David L; Conradson, Steven D; Kozimor, Stosh A; Martin, Richard L; Seidler, Gerald T; Scott, Brian L; Shuh, David K; Tyliszczak, Tolek; Wilkerson, Marianne P; Wolfsberg, Laura E

2010-10-06

Accurate X-ray absorption spectra (XAS) of first row atoms, e.g., O, are notoriously difficult to obtain due to the extreme sensitivity of the measurement to surface contamination, self-absorption, and saturation affects. Herein, we describe a comprehensive approach for determining reliable O K-edge XAS data for ReO(4)(1-) and provide methodology for obtaining trustworthy and quantitative data on nonconducting molecular systems, even in the presence of surface contamination. This involves comparing spectra measured by nonresonant inelastic X-ray scattering (NRIXS), a bulk-sensitive technique that is not prone to X-ray self-absorption and provides exact peak intensities, with XAS spectra obtained by three different detection modes, namely total electron yield (TEY), fluorescence yield (FY), and scanning transmission X-ray microscopy (STXM). For ReO(4)(1-), TEY measurements were heavily influenced by surface contamination, while the FY and STXM data agree well with the bulk NRIXS analysis. These spectra all showed two intense pre-edge features indicative of the covalent interaction between the Re 5d and O 2p orbitals. Density functional theory calculations were used to assign these two peaks as O 1s excitations to the e and t(2) molecular orbitals that result from Re 5d and O 2p covalent mixing in T(d) symmetry. Electronic structure calculations were used to determine the amount of O 2p character (%) in these molecular orbitals. Time dependent-density functional theory (TD-DFT) was also used to calculate the energies and intensities of the pre-edge transitions. Overall, under these experimental conditions, this analysis suggests that NRIXS, STXM, and FY operate cooperatively, providing a sound basis for validation of bulk-like excitation spectra and, in combination with electronic structure calculations, suggest that NaReO(4) may serve as a well-defined O K-edge energy and intensity standard for future O K-edge XAS studies.

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.

Effect of narrow band nonuniformity on unsteady heat up of water vapor under radiation-conduction combined heat transfer

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

Okamoto, Tatsuyuki; Tanaka, Tomohiro; Morimune, Atsushi

Effect of narrow band nonuniformity on unsteady heat up process of water vapor under radiation-conduction combined heat transfer is examined by comparing the result of numerical simulations with and without incorporation of narrow band nonuniformity. The authors propose a rational and comprehensive computational approach for incorporating the narrow band nonuniformity into numerical simulations of radiative heat transfer when the considered field is nonisothermal. Results of examination exhibited that the contribution of radiative heat transfer to the heat up rate of water vapor may be almost twice overestimated, if the narrow band nonuniformity effect is neglected. Separate analyses of radiative energymore » attributed to wall emission and gas emission clarified that the absorption of wall emission is overestimated and, on the contrary, the absorption of radiation energy emitted by water vapor itself is underestimated if the narrow band nonuniformity is neglected. The reason why such over- or under-estimation is induced is understood by examining the influence of line overlap parameter on the transmittance averaged within a narrow band. Smaller value of line overlap parameter {gamma}/d means more violent narrow band nonuniformity. The broken lines show the narrow band transmittance for flat incident power spectrum, and the solid lines show that for the radiative emission from the absorbing gas itself. It is also clarified that the disregard of the narrow band nonuniformity give rise to serious error in the estimation of absorption rate of wall and gas emission even in the case where the disregard of narrow band nonuniformity bring little change to the temperature distribution. The results illustrated in this paper suggest that the narrow band nonuniformity should not be neglected.« less

Effect of Pressure on Absorption Spectra of Lycopene in n-Hexane and CS2 Solvents

NASA Astrophysics Data System (ADS)

Zhang, Wei; Liu, Wei-Long; Zheng, Zhi-Ren; Huo, Ming-Ming; Li, Ai-Hua; Yang, Bin

2010-01-01

The absorption spectra of lycopene in n-hexane and CS2 are measured under high pressure and the results are compared with β-carotene. In the lower pressure range, the deviation from the linear dependence on the Bayliss parameter (BP) for β-carotene is more visible than that for lycopene. With the further increase of the solvent BP, the 0-0 bands of lycopene and β-carotene red shift at almost the same rate in n-hexane; however, the 0-0 band of lycopene red shifts slower than that of β-carotene in CS2. The origins of these diversities are discussed taking into account the dispersion interactions and structures of solute and solvent molecules.

Mid and Near-IR Absorption Spectra of PAH Neutrals and Ions in H20 Ice to Facilitate their Astronomical Detection

NASA Technical Reports Server (NTRS)

Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.

2004-01-01

Polycyclic aromatic hydrocarbons (PAHs) are believed to be the most abundant and widespread class of organic compounds in the universe, having been observed in emission towards energetic regions and absorption towards colder ones.We will present IR spectra of PAHs and their cations in H20 ice measured in the laboratory in the hopes that this will facilitate the detection of these features in the interstellar medium.

Analysis of Absorption Spectra of Polycyclic Aromatic Hydrocarbons in Gaseous- and Particle- Phase Emissions from Peat Fuel Combustion Under Controlled Conditions

NASA Astrophysics Data System (ADS)

Connolly, J. I.; Samburova, V.; Moosmüller, H.; Khlystov, A.

2015-12-01

Biomass and fossil fuel burning processes emit important organic pollutants called polycyclic aromatic hydrocarbons (PAHs) into the atmosphere. Smoldering combustion of peat is one of the largest contributors (up to 70%) of carbonaceous species and, therefore, it may be one of the main sources of these PAHs. PAHs can be detrimental to health, they are known to be potent mutagens and suspected carcinogens. They may also contribute to solar light absorption as the particles absorb in the blue and near ultraviolet (UV) region of the solar spectrum ("brown carbon" species). There is very little knowledge and large ambiguity regarding the contribution of PAHs to optical properties of organic carbon (OC) emitted from smoldering biomass combustion. This study focuses on quantifying and analyzing PAHs emitted from peat smoldering combustion to gain more knowledge on their optical properties. Five peat fuels collected in different regions of the world (Russia, USA) were burned under controlled conditions (e.g., relative humidity, combustion efficiency, fuel-moisture content) at the Desert Research Institute Biomass Burning facility (Reno, NV, USA). Combustion aerosols collected on TIGF filters followed by XAD resin cartridges were extracted and analyzed for gas-phase (semi-volatile) and particle-phase PAHs. Filter and XAD samples were extracted separately with dichloromethane followed by acetone using Accelerated Solvent Extractor (ACE 300, Dionex). To determine absorption properties, absorption spectra of extracts and standard PAHs were recorded between 190 and 900 nm with a UV/VIS spectrophotometer (PerkinElmer, Lambda 650). This poster will discuss the potential contribution of PAHs to brown carbon emitted from peat combustion and give a brief comparison with absorption spectra from biomass burning aerosols.

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

The Fundamental Quadrupole Band of (14)N2: Line Positions from High-Resolution Stratospheric Solar Absorption Spectra

NASA Technical Reports Server (NTRS)

Rinsland, C. P.; Zander, R.; Goldman, A.; Murcray, F. J.; Murcray, D. G.; Grunson, M. R.; Farmer, C. B.

1991-01-01

The purpose of this note is to report accurate measurements of the positions of O- and S-branch lines of the (1-0) vibration-rotation quadrupole band of molecular nitrogen ((14)N2) and improved Dunham coefficients derived from a simultaneous least-squares analysis of these measurements and selected infrared and far infrared data taken from the literature. The new measurements have been derived from stratospheric solar occultation spectra recorded with Fourier transform spectrometer (FTS) instruments operated at unapodized spectral resolutions of 0.002 and 0.01 /cm. The motivation for the present investigation is the need for improved N2 line parameters for use in IR atmospheric remote sensing investigations. The S branch of the N2 (1-0) quadrupole band is ideal for calibrating the line-of-sight airmasses of atmospheric spectra since the strongest lines are well placed in an atmospheric window, their absorption is relatively insensitive to temperature and is moderately strong (typical line center depths of 10 to 50% in high-resolution ground-based solar spectra and in lower stratospheric solar occultation spectra), and the volume mixing ratio of nitrogen is constant in the atmosphere and well known. However, a recent investigation has'shown the need to improve the accuracies of the N2 fine positions, intensities, air-broadened half-widths, and their temperature dependences to fully exploit this calibration capability (1). The present investigation addresses the problem of improving the accuracy of the N2 line positions.

Two-Photon Absorption Spectroscopy of Rubidium with a Dual-Comb Tequnique

NASA Astrophysics Data System (ADS)

Nishiyama, Akiko; Yoshida, Satoru; Hariki, Takuya; Nakajima, Yoshiaki; Minoshima, Kaoru

2017-06-01

Dual-comb spectroscopies have great potential for high-resolution molecular and atomic spectroscopies, thanks to the broadband comb spectrum consisting of dense narrow modes. In this study, we apply the dual-comb system to Doppler-free two-photon absorption spectroscopy. The outputs of two frequency combs excite several two-photon transitions of rubidium, and we obtained broadband Doppler-free spectra from dual-comb fluorescence signals. The fluorescence detection scheme circumvents the sensitivity limit which is effectively determined by the dynamic range of photodetectors in absorption-based dual-comb spectroscopies. Our system realized high-sensitive, Doppler-free high-resolution and broadband atomic spectroscopy. A part of observed spectra of 5S_{1/2} - 5D_{5/2} transition is shown in the figure. The hyperfine structures of the F" = 1 - F' = 3,2,1 transitions are fully-resolved and the spectral widths are approximately 5 MHz. The absolute frequency axis is precisely calibrated from comb mode frequencies which were stabilized to a GPS-disciplined clock. This work was supported by JST through the ERATO MINOSHIMA Intelligent Optical Synthesizer Project and Grant-in-Aid for JSPS Fellows (16J02345). A. Nishiyama, S. Yoshida, Y. Nakajima, H. Sasada, K. Nakagawa, A. Onae, K. and Minoshima, Opt. Express 24, 25894 (2016). A. Hipke, S. A. Meek, T. Ideguchi, T.W. Hänsch, and N. Picqué, Phys. Rev. A 90, 011805(R) (2014).

Absorption and emission spectroscopic characterisation of 8-amino-riboflavin

NASA Astrophysics Data System (ADS)

Tyagi, A.; Zirak, P.; Penzkofer, A.; Mathes, T.; Hegemann, P.; Mack, M.; Ghisla, S.

2009-10-01

The flavin dye 8-amino-8-demethyl- D-riboflavin (AF) in the solvents water, DMSO, methanol, and chloroform/DMSO was studied by absorption and fluorescence spectroscopy. The first absorption band is red-shifted compared to riboflavin, and blue-shifted compared to roseoflavin (8-dimethylamino-8-demethyl-D-riboflavin). The fluorescence quantum yield of AF in the studied solvents varies between 20% and 50%. The fluorescence lifetimes were found to be in the 2-5 ns range. AF is well soluble in DMSO, weakly soluble in water and methanol, and practically insoluble in chloroform. The limited solubility causes AF aggregation, which was seen in differences between measured absorption spectra and fluorescence excitation spectra. Light scattering in the dye absorption region is discussed and approximate absorption cross-section spectra are determined from the combined measurement of transmission and fluorescence excitation spectra. The photo-stability of AF was studied by prolonged light exposure. The photo-degradation routes of AF are discussed.

The influence of coordination geometry and valency on the K-edge absorption near edge spectra of selected chromium compounds

NASA Astrophysics Data System (ADS)

Pantelouris, A.; Modrow, H.; Pantelouris, M.; Hormes, J.; Reinen, D.

2004-05-01

X-ray absorption spectra at the chromium K-edge are reported for a number of selected chromium compounds of known chemical structure. The spectra were obtained with use of synchrotron radiation available at the ELectron Stretcher Accelerator ELSA in Bonn. The compounds studied include the tetrahedrally coordinated compounds Ca 2Ge 0.8Cr 0.2O 4, Ba 2Ge 0.1Cr 0.9O 4, Sr 2CrO 4, Ca 2(PO 4) x(CrO 4) 1- xCl ( x=0.25,0.5), Ca 5(CrO 4) 3Cl, CrO 3, the octahedrally coordinated compounds Cr(II)-acetate, CrCl 3, CrF 3, Cr 2O 3, KCr(SO 4) 2 · 12H 2O, CrO 2 and cubic coordinated metallic chromium. In these compounds chromium exhibits a wide range of formal oxidation states (0 to VI). The absorption features in the near edge region are shown to be characteristic of the spatial environment of the absorbing atom. The occurrence of a single pre-edge line easily allows one to distinguish between tetrahedral and octahedral coordination geometry, whereas the energy position of the absorption edge is found to be very sensitive to the valency of the excited chromium atom. Calculations of the ionisation potential of Cr in different oxidation states using the non-relativistic Hartree-Fock method (Froese-Fischer) confirm that the ionisation limit shifts to higher energy with increasing Cr valency. More detailed information on the electronic structure of the different compounds is gained by real-space full multiple scattering calculations using the FEFF8 code.

Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium: The Chandra Grating Spectra of XTE J1817-330

NASA Technical Reports Server (NTRS)

Gatuzz, E.; Garcia, J.; Menodza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

2013-01-01

We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(sub H) = 1.38 +/- 0.01 x 10(exp 21) cm(exp -2); ionization parameter of log xi = .2.70 +/- 0.023; oxygen abundance of A(sub O) = 0.689(exp +0.015./-0.010); and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval (1998), a rescaling with the revision by Asplund et al. (2009) yields A(sub O) = 0.952(exp +0.020/-0.013, a value close to solar that reinforces the new standard. We identify several atomic absorption lines.K-alpha , K-beta, and K-gamma in O I and O II; and K-alpha in O III, O VI, and O VII--last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated to ISM cold absorption.

Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium:. [The Chandra Grating Spectra of XTE J1817-330

NASA Technical Reports Server (NTRS)

Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

2013-01-01

We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Angstrom broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Angstroms) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N(sub H) = 1.38 +/- 0.01 × 10(exp 21) cm(exp -2); an ionization parameter of log xi = -2.70 +/- 0.023; an oxygen abundance of A(sub O) = 0.689 (+0.015/-0.010); and ionization fractions of O(sub I)/O = 0.911, O(sub II)/O = 0.077, and O(sub III)/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse & Sauval, a rescaling with the revision by Asplund et al. yields A(sub O) = 0.952(+0.020/-0.013), a value close to solar that reinforces the new standard.We identify several atomic absorption lines-K(alpha), K(beta), and K(gamma) in O(sub I) and O(sub II) and K(alpha) in O(sub III), O(sub VI), and O(sub VII)-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated with ISM cold absorption.

MODELING THE HARD TeV SPECTRA OF BLAZARS 1ES 0229+200 AND 3C 66A WITH AN INTERNAL ABSORPTION SCENARIO

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

Zacharopoulou, O.; Aharonian, F. A.; Khangulyan, D.

2011-09-10

We study the applicability of the idea of internal absorption of {gamma}-rays produced through synchrotron radiation of ultrarelativistic protons in highly magnetized blobs to 1ES 0229+200 and 3C 66A, the two TeV blazars which show unusually hard intrinsic {gamma}-ray spectra after being corrected for the intergalactic absorption. We show that for certain combinations of reasonable model parameters, even with quite modest energy requirements, the scenario allows a self-consistent explanation of the non-thermal emission of these objects in the keV, GeV, and TeV energy bands.

Optically trapped atomic resonant devices for narrow linewidth spectral imaging

NASA Astrophysics Data System (ADS)

Qian, Lipeng

This thesis focuses on the development of atomic resonant devices for spectroscopic applications. The primary emphasis is on the imaging properties of optically thick atomic resonant fluorescent filters and their applications. In addition, this thesis presents a new concept for producing very narrow linewidth light as from an atomic vapor lamp pumped by a nanosecond pulse system. This research was motivated by application for missile warning system, and presents an innovative approach to a wide angle, ultra narrow linewidth imaging filter using a potassium vapor cell. The approach is to image onto and collect the fluorescent photons emitted from the surface of an optically thick potassium vapor cell, generating a 2 GHz pass-band imaging filter. This linewidth is narrow enough to fall within a Fraunhefer dark zone in the solar spectrum, thus make the detection solar blind. Experiments are conducted to measure the absorption line shape of the potassium resonant filter, the quantum efficiency of the fluorescent behavior, and the resolution of the fluorescent image. Fluorescent images with different spatial frequency components are analyzed by using a discrete Fourier transform, and the imaging capability of the fluorescent filter is described by its Modulation Transfer Function. For the detection of radiation that is spectrally broader than the linewidth of the potassium imaging filter, the fluorescent image is seen to be blurred by diffuse fluorescence from the slightly off resonant photons. To correct this, an ultra-thin potassium imaging filter is developed and characterized. The imaging property of the ultra-thin potassium imaging cell is tested with a potassium seeded flame, yielding a resolution image of ˜ 20 lines per mm. The physics behind the atomic resonant fluorescent filter is radiation trapping. The diffusion process of the resonant photons trapped in the atomic vapor is theoretically described in this thesis. A Monte Carlo method is used to simulate the

Low Temperature Reflectance Spectra of Titan Tholins

NASA Technical Reports Server (NTRS)

Roush, T. L.; Dalton, J. B.; Fonda, Mark (Technical Monitor)

2001-01-01

Compositional interpretation of remotely obtained reflectance spectra of outer solar system surfaces is achieved by a variety of methods. These include matching spectral curves, matching spectral features, quantitative spectral interpretation, and theoretical modeling of spectra. All of these approaches rely upon laboratory measurements of one kind or another. The bulk of these laboratory measurements are obtained with the sample of interest at ambient temperatures and pressures. However, surface temperatures of planets, satellites, and asteroids in the outer solar system are significantly cooler than ambient laboratory conditions on Earth. The infrared spectra of many materials change as a function of temperature. As has been recently demonstrated it is important to assess what effects colder temperatures have on spectral properties and hence, compositional interpretations. Titan tholin is a solid residue created by energetic processing of H-, C-, and N-bearing gases. Such residues can also be created by energetic processing if the gases are condensed into ices. Titan tholin has been suggested as a coloring agent for several surfaces in the outer solar system. Here we report laboratory measurements of Titan tholin at a temperature of 100 K and compare these to measurements of the same sample near room temperature. At low temperature the absorption features beyond 1 micrometer narrow slightly. At wavelengths greater than approx. 0.8 micrometer the overall reflectance of the sample decreases slightly making the sample less red at low temperatures. We will discuss the implications of the laboratory measurements for interpretation of cold outer solar system surfaces.

Subgap Absorption in Conjugated Polymers

DOE R&D Accomplishments Database

Sinclair, M.; Seager, C. H.; McBranch, D.; Heeger, A. J; Baker, G. L.

1991-01-01

Along with X{sup (3)}, the magnitude of the optical absorption in the transparent window below the principal absorption edge is an important parameter which will ultimately determine the utility of conjugated polymers in active integrated optical devices. With an absorptance sensitivity of < 10{sup {minus}5}, Photothermal Deflection Spectroscopy (PDS) is ideal for determining the absorption coefficients of thin films of transparent'' materials. We have used PDS to measure the optical absorption spectra of the conjugated polymers poly(1,4-phenylene-vinylene) (and derivitives) and polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our spectra show that the shape of the absorption edge varies considerably from polymer to polymer, with polydiacetylene-4BCMU having the steepest absorption edge. The minimum absorption coefficients measured varied somewhat with sample age and quality, but were typically in the range 1 cm{sup {minus}1} to 10 cm{sup {minus}1}. In the region below 1 eV, overtones of C-H stretching modes were observed, indicating that further improvements in transparency in this spectral region might be achieved via deuteration of fluorination.

Expansion joint noise reduction on the new Tacoma Narrows Bridge.

DOT National Transportation Integrated Search

2011-12-01

"Washington State Department of Transportation (WSDOT) responded to citizen complaints about expansion joint noise on the new Tacoma Narrows Bridge (TNB) by installing new wall coated in noise absorptive materials. The goal of the project was to redu...

Optimization of advanced Wiener estimation methods for Raman reconstruction from narrow-band measurements in the presence of fluorescence background

PubMed Central

Chen, Shuo; Ong, Yi Hong; Lin, Xiaoqian; Liu, Quan

2015-01-01

Raman spectroscopy has shown great potential in biomedical applications. However, intrinsically weak Raman signals cause slow data acquisition especially in Raman imaging. This problem can be overcome by narrow-band Raman imaging followed by spectral reconstruction. Our previous study has shown that Raman spectra free of fluorescence background can be reconstructed from narrow-band Raman measurements using traditional Wiener estimation. However, fluorescence-free Raman spectra are only available from those sophisticated Raman setups capable of fluorescence suppression. The reconstruction of Raman spectra with fluorescence background from narrow-band measurements is much more challenging due to the significant variation in fluorescence background. In this study, two advanced Wiener estimation methods, i.e. modified Wiener estimation and sequential weighted Wiener estimation, were optimized to achieve this goal. Both spontaneous Raman spectra and surface enhanced Raman spectra were evaluated. Compared with traditional Wiener estimation, two advanced methods showed significant improvement in the reconstruction of spontaneous Raman spectra. However, traditional Wiener estimation can work as effectively as the advanced methods for SERS spectra but much faster. The wise selection of these methods would enable accurate Raman reconstruction in a simple Raman setup without the function of fluorescence suppression for fast Raman imaging. PMID:26203387

Time-varying sodium absorption in the Type Ia supernova 2013gh

NASA Astrophysics Data System (ADS)

Ferretti, R.; Amanullah, R.; Goobar, A.; Johansson, J.; Vreeswijk, P. M.; Butler, R. P.; Cao, Y.; Cenko, S. B.; Doran, G.; Filippenko, A. V.; Freeland, E.; Hosseinzadeh, G.; Howell, D. A.; Lundqvist, P.; Mattila, S.; Nordin, J.; Nugent, P. E.; Petrushevska, T.; Valenti, S.; Vogt, S.; Wozniak, P.

2016-07-01

Context. Temporal variability of narrow absorption lines in high-resolution spectra of Type Ia supernovae (SNe Ia) is studied to search for circumstellar matter. Time series which resolve the profiles of absorption lines such as Na I D or Ca II H&K are expected to reveal variations due to photoionisation and subsequent recombination of the gases. The presence, composition, and geometry of circumstellar matter may hint at the elusive progenitor system of SNe Ia and could also affect the observed reddening law. Aims: To date, there are few known cases of time-varying Na I D absorption in SNe Ia, all of which occurred during relatively late phases of the supernova (SN) evolution. Photoionisation, however, is predicted to occur during the early phases of SNe Ia, when the supernovae peak in the ultraviolet. We attempt, therefore, to observe early-time absorption-line variations by obtaining high-resolution spectra of SNe before maximum light. Methods: We have obtained photometry and high-resolution spectroscopy of SNe Ia 2013gh and iPTF 13dge, to search for absorption-line variations. Furthermore, we study interstellar absorption features in relation to the observed photometric colours of the SNe. Results: Both SNe display deep Na I D and Ca II H&K absorption features. Furthermore, small but significant variations are detected in a feature of the Na I D profile of SN 2013gh. The variations are consistent with either geometric effects of rapidly moving or patchy gas clouds or photoionisation of Na I gas at R ≈ 1019 cm from the explosion. Conclusions: Our analysis indicates that it is necessary to focus on early phases to detect photoionisation effects of gases in the circumstellar medium of SNe Ia. Different absorbers such as Na I and Ca II can be used to probe for matter at different distances from the SNe. The nondetection of variations during early phases makes it possible to put limits on the abundance of the species at those distances. Full Tables 2 and 3 are only

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.

Amplification of anharmonicities in multiphoton vibrational action spectra.

PubMed

Calvo, F; Parneix, P

2012-01-16

The influence of one or several infrared laser pulses on the stability of bare and argon-tagged sodium chloride clusters is investigated theoretically by a combination of computational methods involving explicit molecular dynamics and properly calibrated unimolecular rate theories. The fragmentation spectra obtained by varying the laser frequency in the far-IR range is compared to the linear absorption spectrum resulting from the dipole moment autocorrelation function. Under appropriate laser field parameters, the action spectra are found to resemble the absorption spectra quite accurately in terms of positions, line widths, and even relative intensities. However, the action spectra exhibit residual and systematic redshifts of a few percent, which are partly due to the finite spectral bandwidth but are amplified by the progressive heating by the laser. A quantitative analysis suggests that these anharmonicity effects should generally arise upon multiple photon absorption. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Photonic bandgap narrowing in conical hollow core Bragg fibers

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

Ozturk, Fahri Emre; Yildirim, Adem; Kanik, Mehmet

2014-08-18

We report the photonic bandgap engineering of Bragg fibers by controlling the thickness profile of the fiber during the thermal drawing. Conical hollow core Bragg fibers were produced by thermal drawing under a rapidly alternating load, which was applied by introducing steep changes to the fiber drawing speed. In conventional cylindrical Bragg fibers, light is guided by omnidirectional reflections from interior dielectric mirrors with a single quarter wave stack period. In conical fibers, the diameter reduction introduced a gradient of the quarter wave stack period along the length of the fiber. Therefore, the light guided within the fiber encountered slightlymore » smaller dielectric layer thicknesses at each reflection, resulting in a progressive blueshift of the reflectance spectrum. As the reflectance spectrum shifts, longer wavelengths of the initial bandgap cease to be omnidirectionally reflected and exit through the cladding, which narrows the photonic bandgap. A narrow transmission bandwidth is particularly desirable in hollow waveguide mid-infrared sensing schemes, where broadband light is coupled to the fiber and the analyte vapor is introduced into the hollow core to measure infrared absorption. We carried out sensing simulations using the absorption spectrum of isopropyl alcohol vapor to demonstrate the importance of narrow bandgap fibers in chemical sensing applications.« less

Tunneling induced absorption with competing Nonlinearities

PubMed Central

Peng, Yandong; Yang, Aihong; Xu, Yan; Wang, Peng; Yu, Yang; Guo, Hongju; Ren, Tingqi

2016-01-01

We investigate tunneling induced nonlinear absorption phenomena in a coupled quantum-dot system. Resonant tunneling causes constructive interference in the nonlinear absorption that leads to an increase of more than an order of magnitude over the maximum absorption in a coupled quantum dot system without tunneling. Resonant tunneling also leads to a narrowing of the linewidth of the absorption peak to a sublinewidth level. Analytical expressions show that the enhanced nonlinear absorption is largely due to the fifth-order nonlinear term. Competition between third- and fifth-order nonlinearities leads to an anomalous dispersion of the total susceptibility. PMID:27958303

Tunneling induced absorption with competing Nonlinearities.

PubMed

Peng, Yandong; Yang, Aihong; Xu, Yan; Wang, Peng; Yu, Yang; Guo, Hongju; Ren, Tingqi

2016-12-13

We investigate tunneling induced nonlinear absorption phenomena in a coupled quantum-dot system. Resonant tunneling causes constructive interference in the nonlinear absorption that leads to an increase of more than an order of magnitude over the maximum absorption in a coupled quantum dot system without tunneling. Resonant tunneling also leads to a narrowing of the linewidth of the absorption peak to a sublinewidth level. Analytical expressions show that the enhanced nonlinear absorption is largely due to the fifth-order nonlinear term. Competition between third- and fifth-order nonlinearities leads to an anomalous dispersion of the total susceptibility.

On the nature of absorption features toward nearby stars

NASA Astrophysics Data System (ADS)

Kohl, S.; Czesla, S.; Schmitt, J. H. M. M.

2016-06-01

Context. Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in τ Boo. Aims: We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars τ Boo, HD 33608, and α CrB. Methods: We focus our analysis on a strong DIB located at 5780.61 Å and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, τ Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of τ Boo, HD 33608, and α CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles. Results: The intercomparison between τ Boo and HD 33608 reveals that the difference in the line depth is 6.85 ± 1.48 mÅ at the DIB location which is, however, unlikely to be caused by DIB absorption. The comparison between PHOENIX models and observed spectra yields an upper limit of 34.0 ± 0.3 mÅ for any additional interstellar absorption in τ Boo; similar results are obtained for HD 33608 and α CrB. For all objects we derive unrealistically large values for the radial velocity of any presumed interstellar clouds. In τ Boo we find Na D absorption with an equivalent width of 0.65 ± 0.07 mÅ and 2.3 ± 0.1 mÅ in the D2 and D1 lines. For the other Na, absorption of the same magnitude could only be detected in the D2 line. Our comparisons between model and data show that the interstellar absorption toward τ Boo is not abnormally high. Conclusions: We find no significant DIB absorption in any of our target stars. Any differences between modeled and

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

Search for narrow resonances and quantum black holes in inclusive and b-tagged dijet mass spectra from pp collisions at $$ \\sqrt{s}=7 $$ TeV

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

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

A search for narrow resonances and quantum black holes is performed in inclusive and b-tagged dijet mass spectra measured with the CMS detector at the LHC. The data set corresponds to 5 inverse femtobarns of integrated luminosity collected in pp collisions at sqrt(s) = 7 TeV. No narrow resonances or quantum black holes are observed. Model-independent upper limits at the 95% confidence level are obtained on the product of the cross section, branching fraction into dijets, and acceptance for three scenarios: decay into quark-quark, quark-gluon, and gluon-gluon pairs. Specific lower limits are set on the mass of string resonances (4.31more » TeV), excited quarks (3.32 TeV), axigluons and colorons (3.36 TeV), scalar color-octet resonances (2.07 TeV), E(6) diquarks (3.75 TeV), and on the masses of W' (1.92 TeV) and Z' (1.47 TeV) bosons. The limits on the minimum mass of quantum black holes range from 4 to 5.3 TeV. In addition, b-quark tagging is applied to the two leading jets and upper limits are set on the production of narrow dijet resonances in a model-independent fashion as a function of the branching fraction to b-jet pairs.« less

Search for narrow resonances and quantum black holes in inclusive and b-tagged dijet mass spectra from pp collisions at sqrt{s}=7 TeV

NASA Astrophysics Data System (ADS)

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; Adam, W.; Aguilo, E.; Bergauer, T.; Dragicevic, M.; Erö, J.; Fabjan, C.; Friedl, M.; Frühwirth, R.; Ghete, V. M.; Hörmann, N.; Hrubec, J.; Jeitler, M.; Kiesenhofer, W.; Knünz, V.; Krammer, M.; Krätschmer, I.; Liko, D.; Mikulec, I.; Pernicka, M.; Rabady, D.; Rahbaran, B.; Rohringer, C.; Rohringer, H.; Schöfbeck, R.; Strauss, J.; Taurok, A.; Waltenberger, W.; Wulz, C.-E.; Mossolov, V.; Shumeiko, N.; Gonzalez, J. Suarez; Alderweireldt, S.; Bansal, M.; Bansal, S.; Cornelis, T.; De Wolf, E. A.; Janssen, X.; Luyckx, S.; Mucibello, L.; Ochesanu, S.; Roland, B.; Rougny, R.; Van Haevermaet, H.; Van Mechelen, P.; Van Remortel, N.; Van Spilbeeck, A.; Blekman, F.; Blyweert, S.; D'Hondt, J.; Suarez, R. Gonzalez; Kalogeropoulos, A.; Maes, M.; Olbrechts, A.; Tavernier, S.; Van Doninck, W.; Van Mulders, P.; Van Onsem, G. P.; Villella, I.; Clerbaux, B.; De Lentdecker, G.; Dero, V.; Gay, A. P. R.; Hreus, T.; Léonard, A.; Marage, P. E.; Mohammadi, A.; Reis, T.; Thomas, L.; Vander Velde, C.; Vanlaer, P.; Wang, J.; Adler, V.; Beernaert, K.; Cimmino, A.; Costantini, S.; Garcia, G.; Grunewald, M.; Klein, B.; Lellouch, J.; Marinov, A.; Mccartin, J.; Rios, A. A. Ocampo; Ryckbosch, D.; Sigamani, M.; Strobbe, N.; Thyssen, F.; Tytgat, M.; Walsh, S.; Yazgan, E.; Zaganidis, N.; Basegmez, S.; Bruno, G.; Castello, R.; Ceard, L.; Delaere, C.; du Pree, T.; Favart, D.; Forthomme, L.; Giammanco, A.; Hollar, J.; Lemaitre, V.; Liao, J.; Militaru, O.; Nuttens, C.; Pagano, D.; Pin, A.; Piotrzkowski, K.; Selvaggi, M.; Garcia, J. M. Vizan; Beliy, N.; Caebergs, T.; Daubie, E.; Hammad, G. H.; Alves, G. A.; Correa Martins, M.; Martins, T.; Pol, M. E.; Souza, M. H. G.; Júnior, W. L. Aldá; Carvalho, W.; Chinellato, J.; Custódio, A.; Da Costa, E. M.; De Jesus Damiao, D.; De Oliveira Martins, C.; De Souza, S. Fonseca; Malbouisson, H.; Malek, M.; Figueiredo, D. Matos; Mundim, L.; Nogima, H.; Da Silva, W. L. Prado; Santoro, A.; Jorge, L. Soares; Sznajder, A.; Manganote, E. J. Tonelli; Pereira, A. Vilela; Anjos, T. S.; Bernardes, C. A.; Dias, F. A.; Tomei, T. R. Fernandez Perez; Gregores, E. M.; Lagana, C.; Marinho, F.; Mercadante, P. G.; Novaes, S. F.; Padula, Sandra S.; Genchev, V.; Iaydjiev, P.; Piperov, S.; Rodozov, M.; Stoykova, S.; Sultanov, G.; Tcholakov, V.; Trayanov, R.; Vutova, M.; Dimitrov, A.; Hadjiiska, R.; Kozhuharov, V.; Litov, L.; Pavlov, B.; Petkov, P.; Bian, J. G.; Chen, G. M.; Chen, H. S.; Jiang, C. H.; Liang, D.; Liang, S.; Meng, X.; Tao, J.; Wang, J.; Wang, X.; Wang, Z.; Xiao, H.; Xu, M.; Zang, J.; Zhang, Z.; Asawatangtrakuldee, C.; Ban, Y.; Guo, Y.; Li, W.; Liu, S.; Mao, Y.; Qian, S. J.; Teng, H.; Wang, D.; Zhang, L.; Zou, W.; Avila, C.; Montoya, C. A. Carrillo; Gomez, J. P.; Moreno, B. Gomez; Oliveros, A. F. Osorio; Sanabria, J. C.; Godinovic, N.; Lelas, D.; Plestina, R.; Polic, D.; Puljak, I.; Antunovic, Z.; Kovac, M.; Brigljevic, V.; Duric, S.; Kadija, K.; Luetic, J.; Mekterovic, D.; Morovic, S.; Tikvica, L.; Attikis, A.; Galanti, M.; Mavromanolakis, G.; Mousa, J.; Nicolaou, C.; Ptochos, F.; Razis, P. A.; Finger, M.; Finger, M.; Assran, Y.; Elgammal, S.; Kamel, A. Ellithi; Awad, A. M. Kuotb; Mahmoud, M. A.; Radi, A.; Kadastik, M.; Müntel, M.; Murumaa, M.; Raidal, M.; Rebane, L.; Tiko, A.; Eerola, P.; Fedi, G.; Voutilainen, M.; Härkönen, J.; Heikkinen, A.; Karimäki, V.; Kinnunen, R.; Kortelainen, M. J.; Lampén, T.; Lassila-Perini, K.; Lehti, S.; Lindén, T.; Luukka, P.; Mäenpää, T.; Peltola, T.; Tuominen, E.; Tuominiemi, J.; Tuovinen, E.; Ungaro, D.; Wendland, L.; Korpela, A.; Tuuva, T.; Besancon, M.; Choudhury, S.; Couderc, F.; Dejardin, M.; Denegri, D.; Fabbro, B.; Faure, J. L.; Ferri, F.; Ganjour, S.; Givernaud, A.; Gras, P.; de Monchenault, G. 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Lobelle; Martschei, D.; Mueller, S.; Müller, Th.; Niegel, M.; Nürnberg, A.; Oberst, O.; Oehler, A.; Ott, J.; Quast, G.; Rabbertz, K.; Ratnikov, F.; Ratnikova, N.; Röcker, S.; Schilling, F.-P.; Schott, G.; Simonis, H. J.; Stober, F. M.; Troendle, D.; Ulrich, R.; Wagner-Kuhr, J.; Wayand, S.; Weiler, T.; Zeise, M.; Anagnostou, G.; Daskalakis, G.; Geralis, T.; Kesisoglou, S.; Kyriakis, A.; Loukas, D.; Manolakos, I.; Markou, A.; Markou, C.; Ntomari, E.; Gouskos, L.; Mertzimekis, T. J.; Panagiotou, A.; Saoulidou, N.; Evangelou, I.; Foudas, C.; Kokkas, P.; Manthos, N.; Papadopoulos, I.; Bencze, G.; Hajdu, C.; Hidas, P.; Horvath, D.; Sikler, F.; Veszpremi, V.; Vesztergombi, G.; Zsigmond, A. J.; Beni, N.; Czellar, S.; Molnar, J.; Palinkas, J.; Szillasi, Z.; Karancsi, J.; Raics, P.; Trocsanyi, Z. L.; Ujvari, B.; Beri, S. B.; Bhatnagar, V.; Dhingra, N.; Gupta, R.; Kaur, M.; Mehta, M. Z.; Mittal, M.; Nishu, N.; Saini, L. K.; Sharma, A.; Singh, J. 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M.; Lista, L.; Meola, S.; Merola, M.; Paolucci, P.; Azzi, P.; Bacchetta, N.; Bellan, P.; Bisello, D.; Branca, A.; Carlin, R.; Checchia, P.; Dorigo, T.; Dosselli, U.; Gasparini, F.; Gasparini, U.; Gozzelino, A.; Kanishchev, K.; Lacaprara, S.; Lazzizzera, I.; Margoni, M.; Meneguzzo, A. T.; Nespolo, M.; Pazzini, J.; Ronchese, P.; Simonetto, F.; Torassa, E.; Vanini, S.; Zotto, P.; s, G.; Gabusi, M.; Ratti, S. P.; Riccardi, C.; Torre, P.; Vitulo, P.; Biasini, M.; Bilei, G. M.; Fanò, L.; Lariccia, P.; Mantovani, G.; Menichelli, M.; Nappi, A.; Romeo, F.; Saha, A.; Santocchia, A.; Spiezia, A.; Taroni, S.; Azzurri, P.; Bagliesi, G.; Bernardini, J.; Boccali, T.; Broccolo, G.; Castaldi, R.; D'Agnolo, R. T.; Dell'Orso, R.; Fiori, F.; Foà, L.; Giassi, A.; Kraan, A.; Ligabue, F.; Lomtadze, T.; Martini, L.; Messineo, A.; Palla, F.; Rizzi, A.; Serban, A. T.; Spagnolo, P.; Squillacioti, P.; Tenchini, R.; Tonelli, G.; Venturi, A.; Verdini, P. 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S.; Kwon, E.; Lee, B.; Lee, J.; Lee, S.; Seo, H.; Yu, I.; Bilinskas, M. J.; Grigelionis, I.; Janulis, M.; Juodagalvis, A.; Castilla-Valdez, H.; De La Cruz-Burelo, E.; La Cruz, I. Heredia-de; Lopez-Fernandez, R.; Martínez-Ortega, J.; Sanchez-Hernandez, A.; Villasenor-Cendejas, L. M.; Moreno, S. Carrillo; Valencia, F. Vazquez; Ibarguen, H. A. Salazar; Linares, E. Casimiro; Pineda, A. Morelos; Reyes-Santos, M. A.; Krofcheck, D.; Bell, A. J.; Butler, P. H.; Doesburg, R.; Reucroft, S.; Silverwood, H.; Ahmad, M.; Asghar, M. I.; Butt, J.; Hoorani, H. R.; Khalid, S.; Khan, W. A.; Khurshid, T.; Qazi, S.; Shah, M. A.; Shoaib, M.; Bialkowska, H.; Boimska, B.; Frueboes, T.; Górski, M.; Kazana, M.; Nawrocki, K.; Romanowska-Rybinska, K.; Szleper, M.; Wrochna, G.; Zalewski, P.; Brona, G.; Bunkowski, K.; Cwiok, M.; Dominik, W.; Doroba, K.; Kalinowski, A.; Konecki, M.; Krolikowski, J.; Misiura, M.; Wolszczak, W.; Almeida, N.; Bargassa, P.; David, A.; Faccioli, P.; Parracho, P. G. 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V.; Vinogradov, A.; Azhgirey, I.; Bayshev, I.; Bitioukov, S.; Grishin, V.; Kachanov, V.; Konstantinov, D.; Krychkine, V.; Petrov, V.; Ryutin, R.; Sobol, A.; Tourtchanovitch, L.; Troshin, S.; Tyurin, N.; Uzunian, A.; Volkov, A.; Adzic, P.; Djordjevic, M.; Ekmedzic, M.; Krpic, D.; Milosevic, J.; Aguilar-Benitez, M.; Maestre, J. Alcaraz; Arce, P.; Battilana, C.; Calvo, E.; Cerrada, M.; Chamizo Llatas, M.; Colino, N.; De La Cruz, B.; Delgado Peris, A.; Domínguez Vázquez, D.; Fernandez Bedoya, C.; Fernández Ramos, J. P.; Ferrando, A.; Flix, J.; Fouz, M. C.; Garcia-Abia, P.; Lopez, O. Gonzalez; Lopez, S. Goy; Hernandez, J. M.; Josa, M. I.; Merino, G.; Puerto Pelayo, J.; Quintario Olmeda, A.; Redondo, I.; Romero, L.; Santaolalla, J.; Soares, M. S.; Willmott, C.; Albajar, C.; Codispoti, G.; de Trocóniz, J. F.; Brun, H.; Cuevas, J.; Fernandez Menendez, J.; Folgueras, S.; Gonzalez Caballero, I.; Lloret Iglesias, L.; Piedra Gomez, J.; Cifuentes, J. A. Brochero; Cabrillo, I. J.; Calderon, A.; Chuang, S. H.; Campderros, J. Duarte; Felcini, M.; Fernandez, M.; Gomez, G.; Gonzalez Sanchez, J.; Graziano, A.; Jorda, C.; Lopez Virto, A.; Marco, J.; Marco, R.; Martinez Rivero, C.; Matorras, F.; Munoz Sanchez, F. J.; Rodrigo, T.; Rodríguez-Marrero, A. Y.; Ruiz-Jimeno, A.; Scodellaro, L.; Vila, I.; Cortabitarte, R. Vilar; Abbaneo, D.; Auffray, E.; Auzinger, G.; Bachtis, M.; Baillon, P.; Ball, A. H.; Barney, D.; Benitez, J. F.; Bernet, C.; Bianchi, G.; Bloch, P.; Bocci, A.; Bonato, A.; Botta, C.; Breuker, H.; Camporesi, T.; Cerminara, G.; Christiansen, T.; Coarasa Perez, J. A.; D'Enterria, D.; Dabrowski, A.; De Roeck, A.; De Visscher, S.; Di Guida, S.; Dobson, M.; Dupont-Sagorin, N.; Elliott-Peisert, A.; Frisch, B.; Funk, W.; Georgiou, G.; Giffels, M.; Gigi, D.; Gill, K.; Giordano, D.; Girone, M.; Giunta, M.; Glege, F.; Garrido, R. Gomez-Reino; Govoni, P.; Gowdy, S.; Guida, R.; Hammer, J.; Hansen, M.; Harris, P.; Hartl, C.; Harvey, J.; Hegner, B.; Hinzmann, A.; Innocente, V.; Janot, P.; Kaadze, K.; Karavakis, E.; Kousouris, K.; Lecoq, P.; Lee, Y.-J.; Lenzi, P.; Lourenço, C.; Magini, N.; Mäki, T.; Malberti, M.; Malgeri, L.; Mannelli, M.; Masetti, L.; Meijers, F.; Mersi, S.; Meschi, E.; Moser, R.; Mulders, M.; Musella, P.; Nesvold, E.; Orsini, L.; Palencia Cortezon, E.; Perez, E.; Perrozzi, L.; Petrilli, A.; Pfeiffer, A.; Pierini, M.; Pimiä, M.; Piparo, D.; Polese, G.; Quertenmont, L.; Racz, A.; Reece, W.; Antunes, J. Rodrigues; Rolandi, G.; Rovelli, C.; Rovere, M.; Sakulin, H.; Santanastasio, F.; Schäfer, C.; Schwick, C.; Segoni, I.; Sekmen, S.; Sharma, A.; Siegrist, P.; Silva, P.; Simon, M.; Sphicas, P.; Spiga, D.; Tsirou, A.; Veres, G. I.; Vlimant, J. R.; Wöhri, H. K.; Worm, S. D.; Zeuner, W. D.; Bertl, W.; Deiters, K.; Erdmann, W.; Gabathuler, K.; Horisberger, R.; Ingram, Q.; Kaestli, H. C.; König, S.; Kotlinski, D.; Langenegger, U.; Meier, F.; Renker, D.; Rohe, T.; Bachmair, F.; Bäni, L.; Bortignon, P.; Buchmann, M. A.; Casal, B.; Chanon, N.; Deisher, A.; Dissertori, G.; Dittmar, M.; Donegà, M.; Dünser, M.; Eller, P.; Eugster, J.; Freudenreich, K.; Grab, C.; Hits, D.; Lecomte, P.; Lustermann, W.; Marini, A. C.; Martinez Ruiz del Arbol, P.; Mohr, N.; Moortgat, F.; Nägeli, C.; Nef, P.; Nessi-Tedaldi, F.; Pandolfi, F.; Pape, L.; Pauss, F.; Peruzzi, M.; Ronga, F. J.; Rossini, M.; Sala, L.; Sanchez, A. K.; Starodumov, A.; Stieger, B.; Takahashi, M.; Tauscher, L.; Thea, A.; Theofilatos, K.; Treille, D.; Urscheler, C.; Wallny, R.; Weber, H. A.; Wehrli, L.; Amsler, C.; Chiochia, V.; Favaro, C.; Rikova, M. Ivova; Kilminster, B.; Mejias, B. Millan; Otiougova, P.; Robmann, P.; Snoek, H.; Tupputi, S.; Verzetti, M.; Chang, Y. H.; Chen, K. H.; Ferro, C.; Kuo, C. M.; Li, S. W.; Lin, W.; Lu, Y. J.; Singh, A. P.; Volpe, R.; Yu, S. S.; Bartalini, P.; Chang, P.; Chang, Y. H.; Chang, Y. W.; Chao, Y.; Chen, K. F.; Dietz, C.; Grundler, U.; Hou, W.-S.; Hsiung, Y.; Kao, K. Y.; Lei, Y. J.; Lu, R.-S.; Majumder, D.; Petrakou, E.; Shi, X.; Shiu, J. G.; Tzeng, Y. M.; Wan, X.; Wang, M.; Asavapibhop, B.; Simili, E.; Srimanobhas, N.; Suwonjandee, N.; Adiguzel, A.; Bakirci, M. N.; Cerci, S.; Dozen, C.; Dumanoglu, I.; Eskut, E.; Girgis, S.; Gokbulut, G.; Gurpinar, E.; Hos, I.; Kangal, E. E.; Karaman, T.; Karapinar, G.; Topaksu, A. Kayis; Onengut, G.; Ozdemir, K.; Ozturk, S.; Polatoz, A.; Sogut, K.; Cerci, D. Sunar; Tali, B.; Topakli, H.; Vergili, L. N.; Vergili, M.; Akin, I. V.; Aliev, T.; Bilin, B.; Bilmis, S.; Deniz, M.; Gamsizkan, H.; Guler, A. M.; Ocalan, K.; Ozpineci, A.; Serin, M.; Sever, R.; Surat, U. E.; Yalvac, M.; Yildirim, E.; Zeyrek, M.; Gülmez, E.; Isildak, B.; Kaya, M.; Kaya, O.; Ozkorucuklu, S.; Sonmez, N.; Bahtiyar, H.; Barlas, E.; Cankocak, K.; Günaydin, Y. O.; Vardarlí, F. I.; Yücel, M.; Levchuk, L.; Brooke, J. J.; Clement, E.; Cussans, D.; Flacher, H.; Frazier, R.; Goldstein, J.; Grimes, M.; Heath, G. P.; Heath, H. F.; Kreczko, L.; Metson, S.; Newbold, D. M.; Nirunpong, K.; Poll, A.; Senkin, S.; Smith, V. J.; Williams, T.; Basso, L.; Bell, K. W.; Belyaev, A.; Brew, C.; Brown, R. M.; Cockerill, D. J. A.; Coughlan, J. A.; Harder, K.; Harper, S.; Jackson, J.; Kennedy, B. W.; Olaiya, E.; Petyt, D.; RadburnSmith, B. C.; Shepherd-Themistocleous, C. H.; Tomalin, I. R.; Womersley, W. J.; Bainbridge, R.; Ball, G.; Beuselinck, R.; Buchmuller, O.; Colling, D.; Cripps, N.; Cutajar, M.; Dauncey, P.; Davies, G.; Della Negra, M.; Ferguson, W.; Fulcher, J.; Futyan, D.; Gilbert, A.; Bryer, A. Guneratne; Hall, G.; Hatherell, Z.; Hays, J.; Iles, G.; Jarvis, M.; Karapostoli, G.; Kenzie, M.; Lyons, L.; Magnan, A.-M.; Marrouche, J.; Mathias, B.; Nandi, R.; Nash, J.; Nikitenko, A.; Pela, J.; Pesaresi, M.; Petridis, K.; Pioppi, M.; Raymond, D. M.; Rogerson, S.; Rose, A.; Seez, C.; Sharp, P.; Sparrow, A.; Stoye, M.; Tapper, A.; Acosta, M. Vazquez; Virdee, T.; Wakefield, S.; Wardle, N.; Whyntie, T.; Chadwick, M.; Cole, J. E.; Hobson, P. R.; Khan, A.; Kyberd, P.; Leggat, D.; Leslie, D.; Martin, W.; Reid, I. D.; Symonds, P.; Teodorescu, L.; Turner, M.; Hatakeyama, K.; Liu, H.; Scarborough, T.; Charaf, O.; Cooper, S. I.; Henderson, C.; Rumerio, P.; Avetisyan, A.; Bose, T.; Fantasia, C.; Heister, A.; John, J. St.; Lawson, P.; Lazic, D.; Rohlf, J.; Sperka, D.; Sulak, L.; Alimena, J.; Bhattacharya, S.; Christopher, G.; Cutts, D.; Demiragli, Z.; Ferapontov, A.; Garabedian, A.; Heintz, U.; Jabeen, S.; Kukartsev, G.; Laird, E.; Landsberg, G.; Luk, M.; Narain, M.; Segala, M.; Sinthuprasith, T.; Speer, T.; Breedon, R.; Breto, G.; De La Barca Sanchez, M. Calderon; Caulfield, M.; Chauhan, S.; Chertok, M.; Conway, J.; Conway, R.; Cox, P. T.; Dolen, J.; Erbacher, R.; Gardner, M.; Houtz, R.; Ko, W.; Kopecky, A.; Lander, R.; Mall, O.; Miceli, T.; Nelson, R.; Pellett, D.; Ricci-Tam, F.; Rutherford, B.; Searle, M.; Smith, J.; Squires, M.; Tripathi, M.; Sierra, R. Vasquez; Yohay, R.; Andreev, V.; Cline, D.; Cousins, R.; Duris, J.; Erhan, S.; Everaerts, P.; Farrell, C.; Hauser, J.; Ignatenko, M.; Jarvis, C.; Rakness, G.; Schlein, P.; Traczyk, P.; Valuev, V.; Weber, M.; Babb, J.; Clare, R.; Dinardo, M. E.; Ellison, J.; Gary, J. W.; Giordano, F.; Hanson, G.; Liu, H.; Long, O. R.; Luthra, A.; Nguyen, H.; Paramesvaran, S.; Sturdy, J.; Sumowidagdo, S.; Wilken, R.; Wimpenny, S.; Andrews, W.; Branson, J. G.; Cerati, G. B.; Cittolin, S.; Evans, D.; Holzner, A.; Kelley, R.; Lebourgeois, M.; Letts, J.; Macneill, I.; Mangano, B.; Padhi, S.; Palmer, C.; Petrucciani, G.; Pieri, M.; Sani, M.; Sharma, V.; Simon, S.; Sudano, E.; Tadel, M.; Tu, Y.; Vartak, A.; Wasserbaech, S.; Würthwein, F.; Yagil, A.; Yoo, J.; Barge, D.; Bellan, R.; Campagnari, C.; D'Alfonso, M.; Danielson, T.; Flowers, K.; Geffert, P.; George, C.; Golf, F.; Incandela, J.; Justus, C.; Kalavase, P.; Kovalskyi, D.; Krutelyov, V.; Lowette, S.; Villalba, R. Magaña; Mccoll, N.; Pavlunin, V.; Ribnik, J.; Richman, J.; Rossin, R.; Stuart, D.; To, W.; West, C.; Apresyan, A.; Bornheim, A.; Chen, Y.; Di Marco, E.; Duarte, J.; Gataullin, M.; Ma, Y.; Mott, A.; Newman, H. B.; Rogan, C.; Spiropulu, M.; Timciuc, V.; Veverka, J.; Wilkinson, R.; Xie, S.; Yang, Y.; Zhu, R. Y.; Azzolini, V.; Calamba, A.; Carroll, R.; Ferguson, T.; Iiyama, Y.; Jang, D. W.; Liu, Y. F.; Paulini, M.; Vogel, H.; Vorobiev, I.; Cumalat, J. P.; Drell, B. R.; Ford, W. T.; Gaz, A.; Lopez, E. Luiggi; Smith, J. G.; Stenson, K.; Ulmer, K. A.; Wagner, S. R.; Alexander, J.; Chatterjee, A.; Eggert, N.; Gibbons, L. K.; Heltsley, B.; Hopkins, W.; Khukhunaishvili, A.; Kreis, B.; Mirman, N.; Kaufman, G. Nicolas; Patterson, J. R.; Ryd, A.; Salvati, E.; Sun, W.; Teo, W. D.; Thom, J.; Thompson, J.; Tucker, J.; Weng, Y.; Winstrom, L.; Wittich, P.; Winn, D.; Abdullin, S.; Albrow, M.; Anderson, J.; Bauerdick, L. A. T.; Beretvas, A.; Berryhill, J.; Bhat, P. C.; Burkett, K.; Butler, J. N.; Chetluru, V.; Cheung, H. W. K.; Chlebana, F.; Elvira, V. D.; Fisk, I.; Freeman, J.; Gao, Y.; Green, D.; Gutsche, O.; Hanlon, J.; Harris, R. M.; Hirschauer, J.; Hooberman, B.; Jindariani, S.; Johnson, M.; Joshi, U.; Klima, B.; Kunori, S.; Kwan, S.; Leonidopoulos, C.; Linacre, J.; Lincoln, D.; Lipton, R.; Lykken, J.; Maeshima, K.; Marraffino, J. M.; Outschoorn, V. I. Martinez; Maruyama, S.; Mason, D.; McBride, P.; Mishra, K.; Mrenna, S.; Musienko, Y.; Newman-Holmes, C.; O'Dell, V.; Prokofyev, O.; Sexton-Kennedy, E.; Sharma, S.; Spalding, W. J.; Spiegel, L.; Taylor, L.; Tkaczyk, S.; Tran, N. V.; Uplegger, L.; Vaandering, E. W.; Vidal, R.; Whitmore, J.; Wu, W.; Yang, F.; Yun, J. C.; Acosta, D.; Avery, P.; Bourilkov, D.; Chen, M.; Cheng, T.; Das, S.; De Gruttola, M.; Di Giovanni, G. P.; Dobur, D.; Drozdetskiy, A.; Field, R. D.; Fisher, M.; Fu, Y.; Furic, I. K.; Gartner, J.; Hugon, J.; Kim, B.; Konigsberg, J.; Korytov, A.; Kropivnitskaya, A.; Kypreos, T.; Low, J. F.; Matchev, K.; Milenovic, P.; Mitselmakher, G.; Muniz, L.; Park, M.; Remington, R.; Rinkevicius, A.; Sellers, P.; Skhirtladze, N.; Snowball, M.; Yelton, J.; Zakaria, M.; Gaultney, V.; Hewamanage, S.; Lebolo, L. M.; Linn, S.; Markowitz, P.; Martinez, G.; Rodriguez, J. L.; Adams, T.; Askew, A.; Bochenek, J.; Chen, J.; Diamond, B.; Gleyzer, S. V.; Haas, J.; Hagopian, S.; Hagopian, V.; Jenkins, M.; Johnson, K. F.; Prosper, H.; Veeraraghavan, V.; Weinberg, M.; Baarmand, M. M.; Dorney, B.; Hohlmann, M.; Kalakhety, H.; Vodopiyanov, I.; Yumiceva, F.; Adams, M. R.; Apanasevich, L.; Bai, Y.; Bazterra, V. E.; Betts, R. R.; Bucinskaite, I.; Callner, J.; Cavanaugh, R.; Evdokimov, O.; Gauthier, L.; Gerber, C. E.; Hofman, D. J.; Khalatyan, S.; Lacroix, F.; O'Brien, C.; Silkworth, C.; Strom, D.; Turner, P.; Varelas, N.; Akgun, U.; Albayrak, E. A.; Bilki, B.; Clarida, W.; Dilsiz, K.; Duru, F.; Griffiths, S.; Merlo, J.-P.; Mermerkaya, H.; Mestvirishvili, A.; Moeller, A.; Nachtman, J.; Newsom, C. R.; Norbeck, E.; Ogul, H.; Onel, Y.; Ozok, F.; Sen, S.; Tan, P.; Tiras, E.; Wetzel, J.; Yetkin, T.; Yi, K.; Barnett, B. A.; Blumenfeld, B.; Bolognesi, S.; Fehling, D.; Giurgiu, G.; Gritsan, A. V.; Guo, Z. J.; Hu, G.; Maksimovic, P.; Swartz, M.; Whitbeck, A.; Baringer, P.; Bean, A.; Benelli, G.; Kenny, R. P., Iii; Murray, M.; Noonan, D.; Sanders, S.; Stringer, R.; Tinti, G.; Wood, J. S.; Barfuss, A. F.; Bolton, T.; Chakaberia, I.; Ivanov, A.; Khalil, S.; Makouski, M.; Maravin, Y.; Shrestha, S.; Svintradze, I.; Gronberg, J.; Lange, D.; Rebassoo, F.; Wright, D.; Baden, A.; Calvert, B.; Eno, S. C.; Gomez, J. A.; Hadley, N. J.; Kellogg, R. G.; Kirn, M.; Kolberg, T.; Lu, Y.; Marionneau, M.; Mignerey, A. C.; Pedro, K.; Peterman, A.; Skuja, A.; Temple, J.; Tonjes, M. B.; Tonwar, S. C.; Apyan, A.; Bauer, G.; Bendavid, J.; Busza, W.; Butz, E.; Cali, I. A.; Chan, M.; Dutta, V.; Gomez Ceballos, G.; Goncharov, M.; Kim, Y.; Klute, M.; Krajczar, K.; Levin, A.; Luckey, P. D.; Ma, T.; Nahn, S.; Paus, C.; Ralph, D.; Roland, C.; Roland, G.; Rudolph, M.; Stephans, G. S. F.; Stöckli, F.; Sumorok, K.; Sung, K.; Velicanu, D.; Wenger, E. A.; Wolf, R.; Wyslouch, B.; Yang, M.; Yilmaz, Y.; Yoon, A. S.; Zanetti, M.; Zhukova, V.; Dahmes, B.; De Benedetti, A.; Franzoni, G.; Gude, A.; Kao, S. C.; Klapoetke, K.; Kubota, Y.; Mans, J.; Pastika, N.; Rusack, R.; Sasseville, M.; Singovsky, A.; Tambe, N.; Turkewitz, J.; Cremaldi, L. M.; Kroeger, R.; Perera, L.; Rahmat, R.; Sanders, D. A.; Avdeeva, E.; Bloom, K.; Bose, S.; Claes, D. R.; Dominguez, A.; Eads, M.; Keller, J.; Kravchenko, I.; Lazo-Flores, J.; Malik, S.; Snow, G. R.; Godshalk, A.; Iashvili, I.; Jain, S.; Kharchilava, A.; Kumar, A.; Rappoccio, S.; Wan, Z.; Alverson, G.; Barberis, E.; Baumgartel, D.; Chasco, M.; Haley, J.; Nash, D.; Orimoto, T.; Trocino, D.; Wood, D.; Zhang, J.; Anastassov, A.; Hahn, K. A.; Kubik, A.; Lusito, L.; Mucia, N.; Odell, N.; Ofierzynski, R. A.; Pollack, B.; Pozdnyakov, A.; Schmitt, M.; Stoynev, S.; Velasco, M.; Won, S.; Berry, D.; Brinkerhoff, A.; Chan, K. M.; Hildreth, M.; Jessop, C.; Karmgard, D. J.; Kolb, J.; Lannon, K.; Luo, W.; Lynch, S.; Marinelli, N.; Morse, D. M.; Pearson, T.; Planer, M.; Ruchti, R.; Slaunwhite, J.; Valls, N.; Wayne, M.; Wolf, M.; Antonelli, L.; Bylsma, B.; Durkin, L. S.; Hill, C.; Hughes, R.; Kotov, K.; Ling, T. Y.; Puigh, D.; Rodenburg, M.; Smith, G.; Vuosalo, C.; Williams, G.; Winer, B. L.; Berry, E.; Elmer, P.; Halyo, V.; Hebda, P.; Hegeman, J.; Hunt, A.; Jindal, P.; Koay, S. A.; Pegna, D. Lopes; Lujan, P.; Marlow, D.; Medvedeva, T.; Mooney, M.; Olsen, J.; Piroué, P.; Quan, X.; Raval, A.; Saka, H.; Stickland, D.; Tully, C.; Werner, J. S.; Zenz, S. C.; Zuranski, A.; Brownson, E.; Lopez, A.; Mendez, H.; Vargas, J. E. Ramirez; Alagoz, E.; Barnes, V. E.; Benedetti, D.; Bolla, G.; Bortoletto, D.; De Mattia, M.; Everett, A.; Hu, Z.; Jones, M.; Koybasi, O.; Kress, M.; Laasanen, A. T.; Leonardo, N.; Maroussov, V.; Merkel, P.; Miller, D. H.; Neumeister, N.; Shipsey, I.; Silvers, D.; Svyatkovskiy, A.; Marono, M. Vidal; Yoo, H. D.; Zablocki, J.; Zheng, Y.; Guragain, S.; Parashar, N.; Adair, A.; Akgun, B.; Boulahouache, C.; Ecklund, K. M.; Geurts, F. J. M.; Li, W.; Padley, B. P.; Redjimi, R.; Roberts, J.; Zabel, J.; Betchart, B.; Bodek, A.; Chung, Y. S.; Covarelli, R.; de Barbaro, P.; Demina, R.; Eshaq, Y.; Ferbel, T.; Garcia-Bellido, A.; Goldenzweig, P.; Han, J.; Harel, A.; Miner, D. C.; Vishnevskiy, D.; Zielinski, M.; Bhatti, A.; Ciesielski, R.; Demortier, L.; Goulianos, K.; Lungu, G.; Malik, S.; Mesropian, C.; Arora, S.; Barker, A.; Chou, J. P.; Contreras-Campana, C.; Contreras-Campana, E.; Duggan, D.; Ferencek, D.; Gershtein, Y.; Gray, R.; Halkiadakis, E.; Hidas, D.; Lath, A.; Panwalkar, S.; Park, M.; Patel, R.; Rekovic, V.; Robles, J.; Rose, K.; Salur, S.; Schnetzer, S.; Seitz, C.; Somalwar, S.; Stone, R.; Thomas, S.; Walker, M.; Cerizza, G.; Hollingsworth, M.; Spanier, S.; Yang, Z. C.; York, A.; Eusebi, R.; Flanagan, W.; Gilmore, J.; Kamon, T.; Khotilovich, V.; Montalvo, R.; Osipenkov, I.; Pakhotin, Y.; Perloff, A.; Roe, J.; Safonov, A.; Sakuma, T.; Sengupta, S.; Suarez, I.; Tatarinov, A.; Toback, D.; Akchurin, N.; Damgov, J.; Dragoiu, C.; Dudero, P. R.; Jeong, C.; Kovitanggoon, K.; Lee, S. W.; Libeiro, T.; Volobouev, I.; Appelt, E.; Delannoy, A. G.; Florez, C.; Greene, S.; Gurrola, A.; Johns, W.; Kurt, P.; Maguire, C.; Melo, A.; Sharma, M.; Sheldon, P.; Snook, B.; Tuo, S.; Velkovska, J.; Arenton, M. W.; Balazs, M.; Boutle, S.; Cox, B.; Francis, B.; Goodell, J.; Hirosky, R.; Ledovskoy, A.; Lin, C.; Neu, C.; Wood, J.; Gollapinni, S.; Harr, R.; Karchin, P. E.; Don, C. Kottachchi Kankanamge; Lamichhane, P.; Sakharov, A.; Anderson, M.; Belknap, D. A.; Borrello, L.; Carlsmith, D.; Cepeda, M.; Dasu, S.; Friis, E.; Gray, L.; Grogg, K. S.; Grothe, M.; Hall-Wilton, R.; Herndon, M.; Hervé, A.; Klabbers, P.; Klukas, J.; Lanaro, A.; Lazaridis, C.; Loveless, R.; Mohapatra, A.; Mozer, M. U.; Ojalvo, I.; Palmonari, F.; Pierro, G. A.; Ross, I.; Savin, A.; Smith, W. H.; Swanson, J.

2013-01-01

A search for narrow resonances and quantum black holes is performed in inclusive and b-tagged dijet mass spectra measured with the CMS detector at the LHC. The data set corresponds to 5 fb-1 of integrated luminosity collected in pp collisions at sqrt{s}=7 TeV. No narrow resonances or quantum black holes are observed. Model-independent upper limits at the 95% confidence level are obtained on the product of the cross section, branching fraction into dijets, and acceptance for three scenarios: decay into quark-quark, quark-gluon, and gluon-gluon pairs. Specific lower limits are set on the mass of string resonances (4.31 TeV), excited quarks (3.32 TeV), axigluons and colorons (3.36 TeV), scalar color-octet resonances (2.07 TeV), E6 diquarks (3.75 TeV), and on the masses of W' (1.92 TeV) and Z' (1.47 TeV) bosons. The limits on the minimum mass of quantum black holes range from 4 to 5.3 TeV. In addition, b-quark tagging is applied to the two leading jets and upper limits are set on the production of narrow dijet resonances in a model-independent fashion as a function of the branching fraction to b-jet pairs.[Figure not available: see fulltext.

Finite temperature effects on the X-ray absorption spectra of energy related materials

NASA Astrophysics Data System (ADS)

Pascal, Tod; Prendergast, David

2014-03-01

We elucidate the role of room-temperature-induced instantaneous structural distortions in the Li K-edge X-ray absorption spectra (XAS) of crystalline LiF, Li2SO4, Li2O, Li3N and Li2CO3 using high resolution X-ray Raman spectroscopy (XRS) measurements and first-principles density functional theory calculations within the eXcited electron and Core Hole (XCH) approach. Based on thermodynamic sampling via ab-initio molecular dynamics (MD) simulations, we find calculated XAS in much better agreement with experiment than those computed using the rigid crystal structure alone. We show that local instantaneous distortion of the atomic lattice perturbs the symmetry of the Li 1 s core-excited-state electronic structure, broadening spectral line-shapes and, in some cases, producing additional spectral features. This work was conducted within the Batteries for Advanced Transportation Technologies (BATT) Program, supported by the U.S. Department of Energy Vehicle Technologies Program under Contract No. DE-AC02-05CH11231.

Two-photon absorption spectra of luminescent conducting polymers measured over wide spectral range

NASA Astrophysics Data System (ADS)

Meyer, Ron K.; Liess, Martin; Benner, Robert E.; Gellermann, Werner; Vardeny, Z. Valy; Ozaki, Masanori; Yoshino, Katsumi; Ding, Yi W.; Barton, Thomas J.

1997-12-01

We report the two-photon absorption (TPA) spectra of poly(2,5-dibutoxy-p-phenylene acetylene) (PPA-DBO), poly(2,5-dioctyloxy-p-phenylene vinylene) (PPV-DOO), and poly(3-hexylthiophene) in the spectral range extending from 576 nm to 846 nm. Using the Z-scan technique on the polymers in solution, we measured a strong two-photon allowed transition in all three materials which we attribute to the mAg essential state. In the case of PPA-DBO and PPV-DOO, TPA peaks were coincident with dispersion in the nonlinear refractive indices as detected by reduced aperture Z scan. In all three polymers this peak occurs at approximately 1.3 the bandgap energy. The excitonic nature of the excited electronic states in PPA-DBO is indicated by the lack of a TPA band at or near the 1Bu exciton position. Saturation was observed in the nonlinear index of refraction near spectral peaks, as well as an apparent reverse Kramers- Kronig effect.

Extraction of ice absorptions in comet spectra, and application to VIRTIS/Rosetta

NASA Astrophysics Data System (ADS)

Erard, Stéphane; Despan, Daniela; Leyrat, Cédric; Drossart, Pierre; Capaccioni, Fabrizio; Filacchione, Gianrico

2014-05-01

Detection of ice spectral features can be difficult on comet surfaces, due to the mixing with dark opaque materials, as shown by Deep Impact and Epoxi observations. We study here the possible use of high-level spectral detection techniques in this context. A method based on wavelet decomposition and a multiscale vision model, partly derived from image analysis techniques, was presented recently (Erard, 2013). It is here used to extract shallow features from spectra in reflected light, up to ~3 µm. The outcome of the analysis is a description of the bands detected, and a quantitative and reliable confidence parameter. The bands can be described either by the most appropriate wavelet scale only (for rapid analyses) or after reconstruction from all scales involved (for more precise measurements). An interesting side effect is the ability to separate even narrow features from random noise, as well as to identify low-frequency variations i.e., wide and shallow bands. Tests are performed on laboratory analogues spectra and available observational data. The technique is expected to provide detection of ice in the early stages of Rosetta observations of 67P this year, from VIRTIS data (Coradini et al., 2009). Strategies are devised to quickly analyze large datasets, e. g., by applying the extraction technique to components first identified by an ACI (Erard et al., 2011). The exact position of the bands can be diagnostic of surface temperature, in particular at 1.6 µm (e. g., Fink & Larson, 1975) and 3.6 µm (Filacchione et al., 2013), and may complement estimates retrieved from the onset of thermal emission longward of 3.5 µm. Erard, S. (2013) 8th EPSC EPSC2013-520. Coradini et al (2009), Rosetta book, Schulz et al Eds. Erard, S. et al (2011) Planet & Space Sc 59, 1842-1852 Fink, U. & Larson, H. (1975) Icarus 24, 411-420 Filacchione et al (2013) AGU Fall Meeting Abstracts A7

Narrow band perfect absorber for maximum localized magnetic and electric field enhancement and sensing applications

PubMed Central

Yong, Zhengdong; Zhang, Senlin; Gong, Chensheng; He, Sailing

2016-01-01

Plasmonics offer an exciting way to mediate the interaction between light and matter, allowing strong field enhancement and confinement, large absorption and scattering at resonance. However, simultaneous realization of ultra-narrow band perfect absorption and electromagnetic field enhancement is challenging due to the intrinsic high optical losses and radiative damping in metals. Here, we propose an all-metal plasmonic absorber with an absorption bandwidth less than 8 nm and polarization insensitive absorptivity exceeding 99%. Unlike traditional Metal-Dielectric-Metal configurations, we demonstrate that the narrowband perfect absorption and field enhancement are ascribed to the vertical gap plasmonic mode in the deep subwavelength scale, which has a high quality factor of 120 and mode volume of about 10−4 × (λres/n)3. Based on the coupled mode theory, we verify that the diluted field enhancement is proportional to the absorption, and thus perfect absorption is critical to maximum field enhancement. In addition, the proposed perfect absorber can be operated as a refractive index sensor with a sensitivity of 885 nm/RIU and figure of merit as high as 110. It provides a new design strategy for narrow band perfect absorption and local field enhancement, and has potential applications in biosensors, filters and nonlinear optics. PMID:27046540

Photovoltaic measurement of bandgap narrowing in moderately doped silicon

NASA Astrophysics Data System (ADS)

del Alamo, Jesus A.; Swanson, Richard M.; Lietoila, Arto

1983-05-01

Solar cells have been fabricated on n-type and p-type moderately doped Si. The shrinkage of the Si bandgap has been obtained by measuring the internal quantum efficiency in the near infrared spectrum ( hv = 1.00-1.25 eV) around the fundamental absorption edge. The results agree with previous optical measurements of bandgap narrowing in Si. It is postulated that this optically-determined bandgap narrowing is the rigid shrinkage of the forbidden gap due to many-body effects. The "device bandgap narrowing" obtained by measuring the pn product in bipolar devices leads to discrepant values because (i) the density of states in the conduction and valence band is modified due to the potential fluctuations originated in the variations in local impurity density, and (ii) the influence of Fermi-Dirac statistics.

Cavity mode-width spectroscopy with widely tunable ultra narrow laser.

PubMed

Cygan, Agata; Lisak, Daniel; Morzyński, Piotr; Bober, Marcin; Zawada, Michał; Pazderski, Eugeniusz; Ciuryło, Roman

2013-12-02

We explore a cavity-enhanced spectroscopic technique based on determination of the absorbtion coefficient from direct measurement of spectral width of the mode of the optical cavity filled with absorbing medium. This technique called here the cavity mode-width spectroscopy (CMWS) is complementary to the cavity ring-down spectroscopy (CRDS). While both these techniques use information on interaction time of the light with the cavity to determine absorption coefficient, the CMWS does not require to measure very fast signals at high absorption conditions. Instead the CMWS method require a very narrow line width laser with precise frequency control. As an example a spectral line shape of P7 Q6 O₂ line from the B-band was measured with use of an ultra narrow laser system based on two phase-locked external cavity diode lasers (ECDL) having tunability of ± 20 GHz at wavelength range of 687 to 693 nm.

First light with Trident: multi-platform synthetic quasar spectra

NASA Astrophysics Data System (ADS)

Silvia, Devin W.; Hummels, Cameron B.; Smith, Britton

2017-01-01

Observational efforts to better understand the nature of the intergalactic and circumgalactic media have relied heavily on the information encoded in the absorption line systems of quasar spectra. Numerical simulations of large-scale structure and galaxy evolution are well-suited to explore the properties of those same media owing to the relative ease with which one can access physical quantities from complex, three-dimensional data. However, a difficulty arises when one tries to make direct “apple-to-apples” comparisons between observed spectra and simulated data. In an effort to provide a common language capable of linking theory and observation, we announce the release of Trident. Trident is a publicly available software tool that enables the creation of realistic synthetic absorption spectra from virtually all widely-used hydrodynamics simulation codes. Through user-controlled levels of spectral realism, direct comparisons between simulated and observed data become not only possible, but greatly simplified. We present the methods for extracting artificial quasar sightlines and generating spectra as well as early-stage applications of those spectra to intergalactic and circumgalactic absorption line studies.

Investigation of absorption spectra of Gafchromic EBT2 film's components and their impact on UVR dosimetry

NASA Astrophysics Data System (ADS)

Aydarous, Abdulkadir

2016-05-01

The absorption spectra of the EBT2 film's components were investigated in conjunction with its use for UVA dosimetry. The polyester (topside) and adhesive layers of the EBT2 film have been gently removed. Gafchromic™ EBT2 films with and without the protected layers (polyester and adhesive) were exposed to UVR of 365 nm for different durations. Thereafter, the UV-visible spectra were measured using a UV-visible spectrophotometer (Model Spectro Dual Split Beam, UVS-2700). Films were digitized using a Nikon CanoScan 9000F Mark II flatbed scanner. The dosimetric characteristics including film's uniformity, reproducibility and post-irradiation development were investigated. The color development of EBT2 and new modified EBT2 (EBT2-M) films irradiated with UVA was relatively stable (less than 1%) immediately after exposure. Based on this study, the sensitivity of EBT2 to UVR with wavelength between ~350 nm and ~390 nm can significantly be enhanced if the adhesive layer (~25 μm) is removed. The polyester layer plays almost no part on absorbing UVR with wavelength between ~320 nm and ~390 nm. Furthermore, various sensitivities for the EBT2-M film has been established depending on the wavelength of analysis.

Electronic absorption and MCD spectra of M sub 2 (TMB) sub 4 sup 2+ , M = Rh and Ir. A valence-bond description of the upper electronic excited states

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

Smith, D.C.; Miskowski, V.M.; Gray, H.B.

1990-05-09

Electronic absorption and magnetic circular dichroism (MCD) spectra of Rh{sub 2}(TMB){sub 4}{sup 2+} and Ir{sub 2}(TMB){sub 4}{sup 2+} are reported along with polarized single-crystal absorption spectra of (Ir{sub 2}(TMB){sub 4})(B(C{sub 6}H{sub 5}){sub 4}){sub 2} {times} CH{sub 3}C{sub 6}H{sub 5} (TMB = 2,5-diisocyano-2,5-dimethylhexane). Interpretation of the spectra is based on a valence-bond model that accommodates highly perturbed dimer transitions as well as monomer-like dimer excitations. In this model, half of the dimer electronic excited states possess ionic character; these states involve metal-to-metal charge transfer (MMCT). The most prominent of the weak features ({approximately} 430 nm) is assigned to the transition tomore » {sup 1}A{sub 1g} (a single-center d{sub z{sup 2}} {yields} p{sub z} excitation). High-energy features ({lambda} < 300 nm) in the spectra of Rh{sub 2}(TMB){sub 4}{sup 2+} and Ir{sub 2}(TMB){sub 4}{sup 2+} are assigned to MMCT arising from d{sub xzyz} {yields} p{sub z} excitations.« less

Detection of a z=0.0515, 0.0522 absorption system in the QSO S4 0248+430 due to an intervening galaxy

NASA Technical Reports Server (NTRS)

Womble, Donna S.; Junkkarinen, Vesa T.; Cohen, Ross D.; Burbidge, E. Margaret

1990-01-01

In some of the few cases where the line of sight to a Quasi-Stellar Object (QSO) passes near a galaxy, the galaxy redshift is almost identical to an absorption redshift in the spectrum of the QSO. Although these relatively low redshift QSO-galaxy pairs may not be typical of the majority of the narrow heavy-element QSO absorption systems, they provide a direct measure of column densities in the outer parts of galaxies and some limits on the relative abundances of the gas. Observations are presented here of the QSO S4 0248+430 and a nearby anonymous galaxy (Kuhr 1977). The 14 second separation of the line of sight to the QSO (z sub e = 1.316) and the z=0.052 spiral galaxy, (a projected separation of 20 kpc ((h sub o = 50, q sub o = 0)), makes this a particularly suitable pair for probing the extent and content of gas in the galaxy. Low resolution (6A full width half maximum), long slit charge coupled device (CCD) spectra show strong CA II H and K lines in absorption at the redshift of the galaxy (Junkkarinen 1987). Higher resolution spectra showing both Ca II H and K and Na I D1 and D2 in absorption and direct images are reported here.

Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

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

Serebryannikov, Andriy E., E-mail: andser@amu.edu.pl; Nanotechnology Research Center—NANOTAM, Bilkent University, 06800 Ankara; Nojima, S.

2015-10-07

The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables themore » efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and

Temperature dependence of Fe/++/ crystal field spectra - Implications to mineralogical mapping of planetary surfaces

NASA Technical Reports Server (NTRS)

Sung, C.-M.; Singer, R. B.; Parkin, K. M.; Burns, R. G.; Osborne, M.

1977-01-01

Results are reported of Fe(++) crystal field spectral measurements for olivines and pyroxenes up to 400 C. The results are correlated with crystal structure data at elevated temperatures, and the validity of remote-sensed identifications of minerals on hot surfaces of the moon and Mercury is assessed. Two techniques were used to obtain spectra of minerals at elevated temperatures using a spectrophotometer. One employed a diamond cell assembly or a specially designed sample holder to measure polarized absorption spectra of heated single crystals. For the other technique, a sample holder was designed to attach to a diffuse reflectance accessory to produce reflectance spectra of heated powdered samples. Polarized absorption spectra of forsterite at 20-400 C are shown in a graph. Other graphs show the temperature dependence of Fe(++) crystal field bands in olivines, the diffuse reflectance spectra of olivine at 40-400 C, the polarization absorption spectra of orthopyroxene at 30-400 C, the diffuse reflectance spectra of pigeonite at 40-400 C, and unpolarized absorption spectra of lunar pyroxene from Apollo 15 rock 15058.

Absorption spectra of localized surface plasmon resonance observed in an inline/picoliter spectrometer cell fabricated by a near ultraviolet femtosecond laser

NASA Astrophysics Data System (ADS)

Shiraishi, Masahiko; Nishiyama, Michiko; Watanabe, Kazuhiro; Kubodera, Shoichi

2018-03-01

Absorption spectra based on localized surface plasmon resonance (LSPR) were obtained with an inline/picoliter spectrometer cell. The spectrometer cell was fabricated into an optical glass fiber by focusing a near UV (NUV) femtosecond laser pulses at a wavelength of 400 nm with an energy of 30 μJ. The laser beam was focused from two directions opposite to each other to fabricate a through-hole spectrometer cell. A diameter of the cell was approximately 3 μm, and the length was approximately 62.5 μm, which was nearly equal to the core diameter of the optical fiber. Liquid solution of gold nanoparticles (GNPs) with a diameter of 5-10 nm was injected into the spectrometer cell with its volume of 0.4 pL. The absorption peak centered at 518 nm was observed. An increase of absorption associated with the increase of the number of nanoparticles was in agreement with the numerical calculation based on the Lambert-Beer law.

Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.

NASA Astrophysics Data System (ADS)

Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.

2007-12-01

Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the

Absorption spectra and nonlinear transmission (at λ = 2940 nm) of a diffusion-doped Fe{sup 2+}:ZnSe single crystal

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

Bufetova, G A; Gulyamova, E S; Il'ichev, N N

2015-06-30

Transmission spectra of a ZnSe sample diffusion-doped with Fe{sup 2+} ions have been measured in the wavelength range 500 – 7000 nm. A broad absorption band in the range 500 – 1500 nm has been observed in both doped and undoped regions of the sample. This band is possibly due to deviations from stoichiometry in the course of diffusion doping. The transmission of the Fe{sup 2+}:ZnSe sample at a wavelength of 2940 nm has been measured at various dopant concentrations and high peak pulse intensities (up to 8 MW cm{sup -2}). The samples have been shown to be incompletely bleached:more » during a laser pulse, the transmission first increases, reaches a maximum, and then falls off. Our results suggest that the incomplete bleaching cannot be accounted for by excited-state absorption. The incomplete bleaching (as well as the transmission maximum) is due to the heating of the sample, which leads to a reduction in upper level lifetime and, accordingly, to an increase in absorption saturation intensity. (nonlinear optical phenomena)« less

Review of the absorption spectra of solid O2 and N2 as they relate to contamination of a cooled infrared telescope

NASA Technical Reports Server (NTRS)

Smith, S. M.

1977-01-01

During contamination studies for the liquid helium cooled shuttle infrared telescope facility, a literature search was conducted to determine the absorption spectra of the solid state of homonuclear molecules of O2 and N2, and ascertain what laboratory measurements of the solid have been made in the infrared. With the inclusion of one unpublished spectrum, the absorption spectrum of the solid oxygen molecule has been thoroughly studied from visible to millimeter wavelengths. Only two lines appear in the solid that do not also appear in the gas or liquid. A similar result is implied for the solid nitrogen molecule because it also is homonuclear. The observed infrared absorption lines result from lattice modes of the alpha phase of the solid, and disappear at the warmer temperatures of the beta, gamma, and liquid phases. They are not observed from polycrystalline forms of O2, while strong scattering is. Scattering, rather than absorption, is considered to be the principal natural contamination problem for cooled infrared telescopes in low earth orbit.

Novel absorptivity centering method utilizing normalized and factorized spectra for analysis of mixtures with overlapping spectra in different matrices using built-in spectrophotometer software

NASA Astrophysics Data System (ADS)

Lotfy, Hayam Mahmoud; Omran, Yasmin Rostom

2018-07-01

A novel, simple, rapid, accurate, and economical spectrophotometric method, namely absorptivity centering (a-Centering) has been developed and validated for the simultaneous determination of mixtures with partially and completely overlapping spectra in different matrices using either normalized or factorized spectrum using built-in spectrophotometer software without a need of special purchased program. Mixture I (Mix I) composed of Simvastatin (SM) and Ezetimibe (EZ) is the one with partial overlapping spectra formulated as tablets, while mixture II (Mix II) formed by Chloramphenicol (CPL) and Prednisolone acetate (PA) is that with complete overlapping spectra formulated as eye drops. These procedures do not require any separation steps. Resolution of spectrally overlapping binary mixtures has been achieved getting recovered zero-order (D0) spectrum of each drug, then absorbance was recorded at their maxima 238, 233.5, 273 and 242.5 nm for SM, EZ, CPL and PA, respectively. Calibration graphs were established with good correlation coefficients. The method shows significant advantages as simplicity, minimal data manipulation besides maximum reproducibility and robustness. Moreover, it was validated according to ICH guidelines. Selectivity was tested using laboratory-prepared mixtures. Accuracy, precision and repeatability were found to be within the acceptable limits. The proposed method is good enough to be applied to an assay of drugs in their combined formulations without any interference from excipients. The obtained results were statistically compared with those of the reported and official methods by applying t-test and F-test at 95% confidence level concluding that there is no significant difference with regard to accuracy and precision. Generally, this method could be used successfully for the routine quality control testing.

Novel absorptivity centering method utilizing normalized and factorized spectra for analysis of mixtures with overlapping spectra in different matrices using built-in spectrophotometer software.

PubMed

Lotfy, Hayam Mahmoud; Omran, Yasmin Rostom

2018-07-05

A novel, simple, rapid, accurate, and economical spectrophotometric method, namely absorptivity centering (a-Centering) has been developed and validated for the simultaneous determination of mixtures with partially and completely overlapping spectra in different matrices using either normalized or factorized spectrum using built-in spectrophotometer software without a need of special purchased program. Mixture I (Mix I) composed of Simvastatin (SM) and Ezetimibe (EZ) is the one with partial overlapping spectra formulated as tablets, while mixture II (Mix II) formed by Chloramphenicol (CPL) and Prednisolone acetate (PA) is that with complete overlapping spectra formulated as eye drops. These procedures do not require any separation steps. Resolution of spectrally overlapping binary mixtures has been achieved getting recovered zero-order (D 0 ) spectrum of each drug, then absorbance was recorded at their maxima 238, 233.5, 273 and 242.5 nm for SM, EZ, CPL and PA, respectively. Calibration graphs were established with good correlation coefficients. The method shows significant advantages as simplicity, minimal data manipulation besides maximum reproducibility and robustness. Moreover, it was validated according to ICH guidelines. Selectivity was tested using laboratory-prepared mixtures. Accuracy, precision and repeatability were found to be within the acceptable limits. The proposed method is good enough to be applied to an assay of drugs in their combined formulations without any interference from excipients. The obtained results were statistically compared with those of the reported and official methods by applying t-test and F-test at 95% confidence level concluding that there is no significant difference with regard to accuracy and precision. Generally, this method could be used successfully for the routine quality control testing. Copyright © 2018 Elsevier B.V. All rights reserved.

Method and apparatus for aerosol particle absorption spectroscopy

DOEpatents

Campillo, Anthony J.; Lin, Horn-Bond

1983-11-15

A method and apparatus for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

Synthetic and natural plagioclases: iron variations and its influence on VNIR reflectance spectra

NASA Astrophysics Data System (ADS)

Carli, Cristian; Orlando, Andrea; Borini, Daniele; Giuli, Gabriele; Serventi, Giovanna; Pratesi, Giovanni; Sgavetti, Maria

2017-04-01

Besides being one of the most important rock-forming phases, plagioclase (pl) is a common surface mineral in several Solar System bodies. In particular, pl is present in meteorites and lunar samples, both in lunar Highland, where it is the dominant phase, and Maria samples. Moreover, pl has been detected in Martian meteorites, as well as in HEDs. In visible and near-infrared (VNIR) reflectance spectroscopy this phase is characterized by a crystal field (C.F.) absorption band in iron-bearing samples. In particular, Burns (1993) summarized the electronic absorptions due to iron, pointing out: 1) a broad absorption around 1.25 μm related to a C.F. transition due to Fe2+ replacing Ca2+ in seven-fold coordinated sites; 2) narrow absorptions around 0.4 μm related to tetrahedrally coordinated Fe3+ ions replacing Al in the tetrahedral sites. A better understanding of the spectral properties of Fe2+-pl can be an important tool to investigate the spectral influence of pl in regolith material in which it can be mixed with variable amount of other components with variable abundance. This goal can be reached working on synthetic pl with variable FeO and An contents, which must be well characterized to be sure about the attribution of absorption bands seen in reflectance spectra, as well as working on well characterized (in term of An, iron amount and Fe2+/Fe3+) terrestrial pl. Future rover mission will have onboard hyperspectral instrument working in the VNIR with relative high spatial resolution and, so, with the possibility of measured pl crystals. For this reason, working more in detail on iron bearing plagioclase can be an important task. Here, we present our results on synthetic An90 mol% pl with different iron contents (0, 0.5 and 1.0 FeO wt%) with the aim to investigate the effects of iron substitution on the VNIR spectra of pl. Reagent-grade oxides and carbonates reactants used as starting materials were thoroughly mixed to ensure homogeneity. Each experimental charge

Dynamical effects in x-ray absorption spectra of graphene and monolayered h -BN on Ni(111)

NASA Astrophysics Data System (ADS)

Rusz, J.; Preobrajenski, A. B.; Ng, May Ling; Vinogradov, N. A.; Mårtensson, N.; Wessely, O.; Sanyal, B.; Eriksson, O.

2010-02-01

We present first-principles calculations of x-ray absorption spectra of graphene and hexagonal BN monolayer on the Ni(111) substrate. Including dynamical core-hole screening effects according to the theory of Mahan-Nozières-de Dominics (MND) results in an overall good agreement with previously published experimental data and our new observations. This approach provides a unified first-principles description of the electronic structure and core excitations in the sp2 -bonded materials on metal surfaces and a better insight into the dynamics of screening effects. We demonstrate in particular that the observed spectral features of graphene and hexagonal BN can be well reproduced with the MND theory, and that they are determined by a delicate balance between initial and final-state effects.

Specific features of the spectra and relaxation kinetics of long-wavelength photoconductivity in narrow-gap HgCdTe epitaxial films and heterostructures with quantum wells

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

Rumyantsev, V. V., E-mail: rumyantsev@ipmras.ru; Ikonnikov, A. V.; Antonov, A. V.

2013-11-15

The spectra and relaxation kinetics of interband photoconductivity are investigated in narrow-gap Hg{sub 1-x}Cd{sub x}Te epitaxial films with x = 0.19-0.23 and in structures with HgCdTe-based quantum wells (QWs), having an interband-transition energy in the range of 30-90 meV, grown by molecular-beam epitaxy on GaAs (013) substrates. A long-wavelength sensitivity band caused by impurities or defects is found in the spectra of the structures with quantum wells in addition to the interband photoconductivity. It is shown that the lifetimes of nonequilibrium carriers in the structures with QWs is less than in bulk samples at the same optical-transition energy. From themore » measured carrier lifetimes, the ampere-watt responsivity and the equivalent noise power for a film with x = 0.19 at a wavelength of 19 {mu}m are estimated. When investigating the relaxation kinetics of the photoconductivity at 4.2 K in high excitation regime, it is revealed that radiative recombination is dominant over other mechanisms of nonequilibrium-carrier recombination.« less

UV laser long-path absorption spectroscopy

NASA Technical Reports Server (NTRS)

Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

1994-01-01

Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive

Vibronic spectra of Cu(2+) in ZnTe

NASA Technical Reports Server (NTRS)

Volz, M. P.; Su, C.-H.; Lehoczky, S. L.; Szofran, F. R.

1992-01-01

Infrared-absorption spectra of substitutional Cu(2+) ions in ZnTe have been measured at 4.6 K. Several distinct absorption peaks are observed between 800 and 2000/cm. Absorption peaks at 1002 and 1069/cm are identified as zero-phonon lines arising from 2T2-2E transitions. Between 1069 and 2000/cm, several sets of sharp absorption lines are seen to recur regularly at an interval of 210/cm, corresponding to the LO phonon energy. Within each set distinct vibronic sidebands that cannot be identified with critical-point energies of TA, LA, TO or LO phonon modes are observed. A dynamic Jahn-Teller effect, involving coupling between a single-phonon mode and the electronic states of the 2E level, is proposed to account for the observed spectra.

Ultrafast X-Ray Absorption Spectroscopy of Isochorically Heated Warm Dense Matter

NASA Astrophysics Data System (ADS)

Engelhorn, Kyle Craig

This dissertation will present a series of new tools, together with new techniques, focused on the understanding of warm and dense matter. We report on the development of a high time resolution and high detection efficiency x-ray camera. The camera is integrated with a short pulse laser and an x-ray beamline at the Advanced Light Source synchrotron. This provides an instrument for single shot, broadband x-ray absorption spectroscopy of warm and dense matter with 2 picosecond time resolution. Warm and dense matter is created by isochorically heating samples of known density with an ultrafast optical laser pulse, and X-ray absorption spectroscopy probes the unoccupied electronic density of states before the onset of hydrodynamic expansion and electron-ion equilibrium is reached. Measured spectra from a variety of materials are compared with first principle molecular dynamics and density functional theory calculations. In heated silicon dioxide spectra, two novel pre-edge features are observed, a peak below the band gap and absorption within the band gap, while a reduction was observed in the features above the edge. From consideration of the calculated spectra, the peak below the gap is attributed to valence electrons that have been promoted to the conduction band, the absorption within the gap is attributed to broken Si-O bonds, and the reduction above the edge is attributed to an elevated ionic temperature. In heated copper spectra, a time-dependent shift and broadening of the absorption edge are observed, consistent with and elevated electron temperature. The temporal evolution of the electronic temperature is accurately determined by fitting the measured spectra with calculated spectra. The electron-ion equilibration is studied with a two-temperature model. In heated nickel spectra, a shift of the absorption edge is observed. This shift is found to be inconsistent with calculated spectra and independent of incident laser fluence. A shift of the chemical potential

Prediction of Iron K-Edge Absorption Spectra Using Time-Dependent Density Functional Theory

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

George, S.DeBeer; Petrenko, T.; Neese, F.

2009-05-14

Iron K-edge X-ray absorption pre-edge features have been calculated using a time-dependent density functional approach. The influence of functional, solvation, and relativistic effects on the calculated energies and intensities has been examined by correlation of the calculated parameters to experimental data on a series of 10 iron model complexes, which span a range of high-spin and low-spin ferrous and ferric complexes in O{sub h} to T{sub d} geometries. Both quadrupole and dipole contributions to the spectra have been calculated. We find that good agreement between theory and experiment is obtained by using the BP86 functional with the CP(PPP) basis setmore » on the Fe and TZVP one of the remaining atoms. Inclusion of solvation yields a small improvement in the calculated energies. However, the inclusion of scalar relativistic effects did not yield any improved correlation with experiment. The use of these methods to uniquely assign individual spectral transitions and to examine experimental contributions to backbonding is discussed.« less

Luminescence and Absorption Spectra of C sub 60 Films

DTIC Science & Technology

1991-02-01

J. McKeirnan, J.L Zink, R. Stanley Williams, W.M. Tong, D.A.A. Ohlberg and R.L. Whetten Submitted t DTIC Physical Review Letters ELECT E SFEB 2? 7,19...range at 20K. A 1400 cm"& progression in the a soccerball inflation mode is observed. The low-temperature absorption spectrum exhibits similar fine...ag soccerball inflation mode is observed. The low temperature absorption spectrum exhibits similar fine structure. The characterization of vibronic

Signatures in vibrational and UV-visible absorption spectra for identifying cyclic hydrocarbons by graphene fragments.

PubMed

Meng, Yan; Wu, Qi; Chen, Lei; Wangmo, Sonam; Gao, Yang; Wang, Zhigang; Zhang, Rui-Qin; Ding, Dajun; Niehaus, Thomas A; Frauenheim, Thomas

2013-12-21

To promote possible applications of graphene in molecular identification based on stacking effects, in particular in recognizing aromatic amino acids and even sequencing nucleobases in life sciences, we comprehensively study the interaction between graphene segments and different cyclic organic hydrocarbons including benzene (C6H6), cyclohexane (C6H12), benzyne (C6H4), cyclohexene (C6H10), 1,3-cyclohexadiene (C6H8(1)) and 1,4-cyclohexadiene (C6H8(2)), using the density-functional tight-binding (DFTB) method. Interestingly, we find obviously different characteristics in Raman vibrational and ultraviolet visible absorption spectra of the small molecules adsorbed on the graphene sheet. Specifically, we find that both spectra involve clearly different characteristic peaks, belonging to the different small molecules upon adsorption, with the ones of ionized molecules being more substantial. Further analysis shows that the adsorptions are almost all due to the presence of dispersion energy in neutral cases and involve charge transfer from the graphene to the small molecules. In contrast, the main binding force in the ionic adsorption systems is the electronic interaction. The results present clear signatures that can be used to recognize different kinds of aromatic hydrocarbon rings on graphene sheets. We expect that our findings will be helpful for designing molecular recognition devices using graphene.

On the nitrogen-induced far-infrared absorption spectra

NASA Technical Reports Server (NTRS)

Dore, P.; Filabozzi, A.

1987-01-01

The rototranslational absorption spectrum of gaseous N2 is analyzed, considering quadrupolar and hexadecapolar induction mechanisms. The available experimental data are accounted for by using a line-shape analysis in which empirical profiles describe the single-line translational profiles. Thus, a simple procedure is derived that allows the prediction of the N2 spectrum at any temperature. On the basis of the results obtained for the pure gas, a procedure to compute the far-infrared spectrum of the N2-Ar gaseous mixture is also proposed. The good agreement between computed and experimental N2-Ar data indicates that it is possible to predict the far-infrared absorption induced by N2 on the isotropic polarizability of any interacting partner.

Type Ia supernovae with and without blueshifted narrow Na I D lines - how different is their structure?

NASA Astrophysics Data System (ADS)

Hachinger, S.; Röpke, F. K.; Mazzali, P. A.; Gal-Yam, A.; Maguire, K.; Sullivan, M.; Taubenberger, S.; Ashall, C.; Campbell, H.; Elias-Rosa, N.; Feindt, U.; Greggio, L.; Inserra, C.; Miluzio, M.; Smartt, S. J.; Young, D.

2017-10-01

In studies on intermediate- and high-resolution spectra of Type Ia supernovae (SNe Ia), some objects exhibit narrow Na I D absorptions often blueshifted with respect to the rest wavelength within the host galaxy. The absence of these in other SNe Ia may reflect that the explosions have different progenitors: blueshifted Na I D features might be explained by the outflows of 'single-degenerate' systems (binaries of a white dwarf with a non-degenerate companion). In this work, we search for systematic differences among SNe Ia for which the Na I D characteristics have been clearly established in previous studies. We perform an analysis of the chemical abundances in the outer ejecta of 13 'spectroscopically normal' SNe Ia (five of which show blueshifted Na lines), modelling time series of photospheric spectra with a radiative-transfer code. We find only moderate differences between 'blueshifted-Na', 'redshifted-Na' and 'no-Na' SNe Ia, so that we can neither conclusively confirm a 'one-scenario' nor a 'two-scenario' theory for normal SNe Ia. Yet, some of the trends we see should be further studied using larger observed samples: models for blueshifted-Na SNe tend to show higher photospheric velocities than no-Na SNe, corresponding to a higher opacity of the envelope. Consistently, blueshifted-Na SNe show hints of a somewhat larger iron-group content in the outer layers with respect to the no-Na subsample (and also to the redshifted-Na subsample). This agrees with earlier work where it was found that the light curves of no-Na SNe - often appearing in elliptical galaxies - are narrower, that is, decline more rapidly.

Ultra-narrow band perfect absorbers based on Fano resonance in MIM metamaterials

NASA Astrophysics Data System (ADS)

Zhang, Ming; Fang, Jiawen; Zhang, Fei; Chen, Junyan; Yu, Honglin

2017-12-01

Metallic nanostructures have attracted numerous attentions in the past decades due to their attractive plasmonic properties. Resonant plasmonic perfect absorbers have promising applications in a wide range of technologies including photothermal therapy, thermophotovoltaics, heat-assisted magnetic recording and biosensing. However, it remains to be a great challenge to achieve ultra-narrow band in near-infrared band with plasmonic materials due to the large optical losses in metals. In this letter, we introduced Fano resonance in MIM metamaterials composed of an asymmetry double elliptic cylinders (ADEC), which can achieve ultra-narrow band perfect absorbers. In theoretical calculations, we observed an ultranarrow band resonant absorption peak with the full width at half maximum (FWHM) of 8 nm and absorption amplitude exceeding 99% at 930 nm. Moreover, we demonstrate that the absorption increases with the increase of asymmetry and the absorption resonant wavelength can be tuned by changing the size and arrangement of the unit cell. The asymmetry metallic nanostructure also exhibit a higher refractive sensitivity as large as 503 nm/RIU with high figure of merit of 63, which is promising for high sensitive sensors. Results of this work are desirable for various potential applications in micro-technological structures such as biological sensors, narrowband emission, photodetectors and solar thermophotovoltaic (STPV) cells.

Cryogenic Infrared Reflectance Spectra of Organic Ices and Their Relevance to the Surface Composition of Titan

NASA Astrophysics Data System (ADS)

Curchin, John; Clark, R. N.; Hoefen, T. M.

2006-09-01

In order to properly interpret reflectance spectra of Titan's surface, laboratory spectra of candidate materials for comparative analysis is needed. Although the common cosmochemical species (H2O, CO2, CO, NH3, and CH4) are well represented in the spectroscopic literature, comparatively little reflectance work has been done on organics at cryotemperatures at visible to near infrared wavelengths. Measurement of reflectance is required for characterizing weak features not seen in transmittance. Such features may be important in remote sensing of planetary surfaces. The USGS Spectroscopy Laboratory uses Nicolet FT-IR and ASD field spectrometers in combination with cryogenic chambers to acquire reflectance spectra of organic ices at approximately 80-90 ºK in a wavelength range of 0.35 to 15.5 microns. This region encompasses the fundamental absorptions and many overtones and combinations of major organic molecules including those with hydrogen-carbon, carbon-carbon (single, double and triple bonds), carbon-oxygen, oxygen-hydrogen, carbon-nitrogen, and nitrogen-hydrogen bonds. Because most organic compounds belong to families with similar structure and composition, individual species identification within a narrow wavelength range may be ambiguous. Only by measuring spectral reflectance of the pure laboratory ices from the visible through the near and mid-infrared can absorption bands unique to each be observed, cataloged and compared to planetary reflectance data. We present here spectra of organic ices belonging to eight families, the alkanes, cycloalkanes, alkenes, alkynes, aromatics, nitriles, amines, and cyanides. Many of these compounds are predicted to coat the surface of Titan and indeed, a number of atmospheric windows, particularly at 5 microns, have allowed their identification with VIMS (Clark et al., DPS 2006, this volume). The spectral properties of these materials have applications to other solar system surfaces and remote sensing of terrestrial

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.

Computational study of the absorption spectrum of defected ZnS nanoparticles

NASA Astrophysics Data System (ADS)

Michos, F. I.; Sigalas, M. M.

2018-04-01

Energy levels and absorption spectra of defected ZnS nanoparticles (NPs) were calculated with Density Functional Theory (DFT) and Time Dependent DFT. Several types of defects were examined such as vacancies and substitutions. NPs with S vacancies were found to have their absorption spectra moved to lower energies well inside the visible spectrum with significantly high oscillator strength. Also, NPs with substitution of S atoms with Cl, Br, or I showed significant absorption. In general, this type of defect moves the absorption spectra in lower energies, thus bringing the absorption edge into the visible spectrum, while the unperturbed NPs have absorption edges in the UV region. In addition, ZnS NPs are made from more abundant and less toxic elements than the more commonly used CdSe NPs. For that reason, they may find significant applications in solar cells and other photonic applications, as well as in biosensing applications as biomarkers.

Line Narrowing Parameter Measurement by Modulation Spectroscopy

NASA Technical Reports Server (NTRS)

Dharamsi, Amin N.

1998-01-01

Accurate Characterization of Oxygen A-Band Line Parameters by Wavelength Modulation Spectroscopy with tunable diode lasers is an ongoing research at Old Dominion University, under sponsorship from NASA Langley research Center. The work proposed here will be undertaken under the guidance of Dr. William Chu and Dr. Lamont Poole of the Aerosol Research Branch at NASA Langley-Research Center in Hampton, Virginia. The research was started about two years ago and utilizes wavelength modulation absorption spectroscopy with higher harmonic detection, a technique that we developed at Old Dominion University, to obtain the absorption line characteristics of the Oxygen A-band rovibronic lines. Accurate characterization of this absorption band is needed for processing of data that will be obtained in experiments such as the NASA Stratospheric Aerosol and Gas Experiment III (SAGE III) as part of the US Mission to Planet Earth. The research work for Summer Fellowship undertook a measurement of the Dicke line-narrowing parameters of the Oxygen A-Band lines by using wavelength modulation spectroscopy. Our previous theoretical results had indicated that such a measurement could be done sensitively and in a convenient fashion by using this type of spectroscopy. In particular, theoretical results had indicated that the signal magnitude would depend on pressure in a manner that was very sensitive to the narrowing parameter. One of the major tasks undertaken during the summer of 1998 was to establish experimentally that these theoretical predictions were correct. This was done successfully and the results of the work are being prepared for publication. Experimental Results were obtained in which the magnitude of the signal was measured as a function of pressure, for various harmonic detection orders (N = 1, 2, 3, 4, 5). A comparison with theoretical results was made, and it was shown that the agreement between theory and experiment was very good. More importantly, however, it was shown

Particle-in-a-box model of exciton absorption and electroabsorption in conjugated polymers

NASA Astrophysics Data System (ADS)

Pedersen, Thomas G.

2000-12-01

The recently proposed particle-in-a-box model of one-dimensional excitons in conjugated polymers is applied in calculations of optical absorption and electroabsorption spectra. It is demonstrated that for polymers of long conjugation length a superposition of single exciton resonances produces a line shape characterized by a square-root singularity in agreement with experimental spectra near the absorption edge. The effects of finite conjugation length on both absorption and electroabsorption spectra are analyzed.

Structure and electronic absorption spectra of nematogenic alkoxycinnamic acids - a comparative study based on semiempirical and DFT methods.

PubMed

Praveen, Pogula Lakshmi; Ojha, Durga Prasad

2012-04-01

Structure of nematogenic p-n-Alkoxy cinnamic acids (nOCAC) with various alkyl chain carbon atoms (n = 2, 4, 6, 8) has been optimized using density functional B3LYP with 6-31+G (d) basis set using crystallographic geometry as input. Using the optimized geometry, electronic structure of the molecules has been evaluated using the semiempirical methods and DFT calculations. Molecular charge distribution and phase stability of these systems have been analyzed based on Mulliken and Löwdin population analysis. The electronic absorption spectra of nOCAC molecules have been simulated by employing DFT method, semiempirical CNDO/S and INDO/S parameterizations. Two types of calculations have been performed for model systems containing single and double molecules of nOCAC. UV-Visible spectra have been calculated for all single molecules. The UV stability of the molecules has been discussed in light of the electronic transition oscillator strength (f). The dimer complexes of higher homologues (n = 6, 8) have also been reported to enable the comparison between single and double molecules.

Molecular dynamics simulation and TDDFT study of the structures and UV-vis absorption spectra of MCT-β-CD and its inclusion complexes.

PubMed

Lu, Huijuan; Wang, Yujiao; Xie, Xiaomei; Chen, Feifei; Li, Wei

2015-01-01

In this research, the inclusion ratios and inclusion constants of MCT-β-CD/PERM and MCT-β-CD/CYPERM inclusion complexes were measured by UV-vis and fluorescence spectroscopy. The inclusion ratios are both 1:1, and the inclusion constants are 60 and 342.5 for MCT-β-CD/PERM and MCT-β-CD/CYPERM, respectively. The stabilities of inclusion complexes were investigated by MD simulation. MD shows that VDW energy plays a vital role in the stability of inclusion complex, and the destruction of inclusion complex is due to the increasing temperature. The UV-vis absorption spectra of MCT-β-CD and its inclusion complexes were studied by time-dependent density functional theory (TDDFT) method employing BLYP-D3, B3LYP-D3 and M06-2X-D3 functionals. BLYP-D3 well reproduces the UV-vis absorption spectrum and reveals that the absorption bands of MCT-β-CD mainly arise from n→π(∗) and n→σ(∗) transition, and those of inclusion complexes mainly arise from intramolecular charge transfer (ICT). ICT results in the shift of main absorption bands of MCT-β-CD. Copyright © 2015 Elsevier B.V. All rights reserved.

Importance of the green color, absorption gradient, and spectral absorption of chloroplasts for the radiative energy balance of leaves.

PubMed

Kume, Atsushi

2017-05-01

Terrestrial green plants absorb photosynthetically active radiation (PAR; 400-700 nm) but do not absorb photons evenly across the PAR waveband. The spectral absorbance of photosystems and chloroplasts is lowest for green light, which occurs within the highest irradiance waveband of direct solar radiation. We demonstrate a close relationship between this phenomenon and the safe and efficient utilization of direct solar radiation in simple biophysiological models. The effects of spectral absorptance on the photon and irradiance absorption processes are evaluated using the spectra of direct and diffuse solar radiation. The radiation absorption of a leaf arises as a consequence of the absorption of chloroplasts. The photon absorption of chloroplasts is strongly dependent on the distribution of pigment concentrations and their absorbance spectra. While chloroplast movements in response to light are important mechanisms controlling PAR absorption, they are not effective for green light because chloroplasts have the lowest spectral absorptance in the waveband. With the development of palisade tissue, the incident photons per total palisade cell surface area and the absorbed photons per chloroplast decrease. The spectral absorbance of carotenoids is effective in eliminating shortwave PAR (<520 nm), which contains much of the surplus energy that is not used for photosynthesis and is dissipated as heat. The PAR absorptance of a whole leaf shows no substantial difference based on the spectra of direct or diffuse solar radiation. However, most of the near infrared radiation is unabsorbed and heat stress is greatly reduced. The incident solar radiation is too strong to be utilized for photosynthesis under the current CO 2 concentration in the terrestrial environment. Therefore, the photon absorption of a whole leaf is efficiently regulated by photosynthetic pigments with low spectral absorptance in the highest irradiance waveband and through a combination of pigment density

Accounting for nanometer-thick adventitious carbon contamination in X-ray absorption spectra of carbon-based materials.

PubMed

Mangolini, Filippo; McClimon, J Brandon; Rose, Franck; Carpick, Robert W

2014-12-16

Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is a powerful technique for characterizing the composition and bonding state of nanoscale materials and the top few nanometers of bulk and thin film specimens. When coupled with imaging methods like photoemission electron microscopy, it enables chemical imaging of materials with nanometer-scale lateral spatial resolution. However, analysis of NEXAFS spectra is often performed under the assumption of structural and compositional homogeneity within the nanometer-scale depth probed by this technique. This assumption can introduce large errors when analyzing the vast majority of solid surfaces due to the presence of complex surface and near-surface structures such as oxides and contamination layers. An analytical methodology is presented for removing the contribution of these nanoscale overlayers from NEXAFS spectra of two-layered systems to provide a corrected photoabsorption spectrum of the substrate. This method relies on the subtraction of the NEXAFS spectrum of the overlayer adsorbed on a reference surface from the spectrum of the two-layer system under investigation, where the thickness of the overlayer is independently determined by X-ray photoelectron spectroscopy (XPS). This approach is applied to NEXAFS data acquired for one of the most challenging cases: air-exposed hard carbon-based materials with adventitious carbon contamination from ambient exposure. The contribution of the adventitious carbon was removed from the as-acquired spectra of ultrananocrystalline diamond (UNCD) and hydrogenated amorphous carbon (a-C:H) to determine the intrinsic photoabsorption NEXAFS spectra of these materials. The method alters the calculated fraction of sp(2)-hybridized carbon from 5 to 20% and reveals that the adventitious contamination can be described as a layer containing carbon and oxygen ([O]/[C] = 0.11 ± 0.02) with a thickness of 0.6 ± 0.2 nm and a fraction of sp(2)-bonded carbon of 0.19 ± 0.03. This

Calculation of the visible-UV absorption spectra of hydrogen sulfide, bisulfide, polysulfides, and As and Sb sulfides, in aqueous solution

PubMed Central

Tossell, JA

2003-01-01

Recently we showed that visible-UV spectra in aqueous solution can be accurately calculated for arsenic (III) bisulfides, such as As(SH)3, As(SH)2S- and their oligomers. The calculated lowest energy transitions for these species were diagnostic of their protonation and oligomerization state. We here extend these studies to As and Sb oxidation state III and v sulfides and to polysulfides Sn2-, n = 2–6, the bisulfide anion, SH-, hydrogen sulfide, H2S and the sulfanes, SnH2, n = 2–5. Many of these calculations are more difficult than those performed for the As(iii) bisulfides, since the As and Sb(v) species are more acidic and therefore exist as highly charged anions in neutral and basic solutions. In general, small and/or highly charged anions are more difficult to describe computationally than larger, monovalent anions or neutral molecules. We have used both Hartree-Fock based (CI Singles and Time-Dependent HF) and density functional based (TD B3LYP) techniques for the calculations of absorption energy and intensity and have used both explicit water molecules and a polarizable continuum to describe the effects of hydration. We correctly reproduce the general trends observed experimentally, with absorption energies increasing from polysulfides to As, Sb sulfides to SH- to H2S. As and Sb(v) species, both monomers and dimers, also absorb at characteristically higher energies than do the analogous As and Sb(III)species. There is also a small reduction in absorption energy from monomeric to dimeric species, for both As and Sb III and v. The polysufides, on the other hand, show no simple systematic changes in UV spectra with chain length, n, or with protonation state. Our results indicate that for the As and Sb sulfides, the oxidation state, degree of protonation and degree of oligomerization can all be determined from the visible-UV absorption spectrum. We have also calculated the aqueous phase energetics for the reaction of S8 with SH- to produce the polysulfides

Franck-Condon Simulations including Anharmonicity of the Ã(1)A''-X̃(1)A' Absorption and Single Vibronic Level Emission Spectra of HSiCl and DSiCl.

PubMed

Mok, Daniel W K; Lee, Edmond P F; Chau, Foo-Tim; Dyke, John M

2009-03-10

RCCSD(T) and/or CASSCF/MRCI calculations have been carried out on the X̃(1)A' and Ã(1)A'' states of HSiCl employing basis sets of up to the aug-cc-pV5Z quality. Contributions from core correlation and extrapolation to the complete basis set limit were included in determining the computed equilibrium geometrical parameters and relative electronic energy of these two states of HSiCl. Franck-Condon factors which include allowance for anharmonicity and Duschinsky rotation between these two states of HSiCl and DSiCl were calculated employing RCCSD(T) and CASSCF/MRCI potential energy functions, and were used to simulate the Ã(1)A'' ← X̃(1)A' absorption and Ã(1)A'' → X̃(1)A' single vibronic level (SVL) emission spectra of HSiCl and DSiCl. Simulated absorption and experimental LIF spectra, and simulated and observed Ã(1)A''(0,0,0) → X̃(1)A' SVL emission spectra, of HSiCl and DSiCl are in very good agreement. However, agreement between simulated and observed Ã(1)A''(0,1,0) → X̃(1)A' and Ã(1)A''(0,2,1) → X̃(1)A' SVL emission spectra of DSiCl is not as good. Preliminary calculations on low-lying excited states of HSiCl suggest that vibronic interaction between low-lying vibrational levels of the Ã(1)A'' state and highly excited vibrational levels of the ã(3)A'' is possible. Such vibronic interaction may change the character of the low-lying vibrational levels of the Ã(1)A'' state, which would lead to perturbation in the SVL emission spectra from these vibrational levels.

Molecular hydrogen absorption systems in Sloan Digital Sky Survey

NASA Astrophysics Data System (ADS)

Balashev, S. A.; Klimenko, V. V.; Ivanchik, A. V.; Varshalovich, D. A.; Petitjean, P.; Noterdaeme, P.

2014-05-01

We present a systematic search for molecular hydrogen absorption systems at high redshift in quasar spectra from the Sloan Digital Sky Survey (SDSS)-II Data Release 7 and SDSS-III Data Release 9. We have selected candidates using a modified profile fitting technique taking into account that the Lyα forest can effectively mimic H2 absorption systems at the resolution of SDSS data. To estimate the confidence level of the detections, we use two methods: a Monte Carlo sampling and an analysis of control samples. The analysis of control samples allows us to define regions of the spectral quality parameter space where H2 absorption systems can be confidently identified. We find that H2 absorption systems with column densities log NH2 > 19 can be detected in only less than 3 per cent of SDSS quasar spectra. We estimate the upper limit on the detection rate of saturated H2 absorption systems (NH2 > 19) in damped Lyα (DLA) systems to be about 7 per cent. We provide a sample of 23 confident H2 absorption system candidates that would be interesting to follow up with high-resolution spectrographs. There is a 1σ r - i colour excess and non-significant AV extinction excess in quasar spectra with an H2 candidate compared to standard DLA-bearing quasar spectra. The equivalent widths of C II, Si II and Al III (but not Fe II) absorptions associated with H2 candidate DLAs are larger compared to standard DLAs. This is probably related to a larger spread in velocity of the absorption lines in the H2-bearing sample.

Molecular and electronic structure, magnetotropicity and absorption spectra of benzene-trinuclear copper(I) and silver(I) trihalide columnar binary stacks.

PubMed

Tsipis, A C; Stalikas, A V

2012-02-20

The molecular and electronic structures, stabilities, bonding features, magnetotropicity and absorption spectra of benzene-trinuclear Cu(I) and Ag(I) trihalide columnar binary stacks with the general formula [c-M(3)(μ(2)-X)(3)](n)(C(6)H(6))(m) (M = Cu, Ag; X = halide; n, m ≤ 2) have been investigated by means of electronic structure calculation methods. The interaction of c-M(3)(μ(2)-X)(3) clusters with one and two benzene molecules yields 1:1 and 1:2 binary stacks, while benzene sandwiched 2:1 stacks are formed upon interaction of two c-M(3)(μ(2)-X)(3) clusters with one benzene molecule. In all binary stacks the plane of the alternating c-M(3)(μ(2)-X)(3) and benzene components adopts an almost parallel orientation. The separation distance between the centroids of the benzene and the proximal c-M(3)(μ(2)-X)(3) metallic cluster found in the range 2.97-3.33 Å at the B97D/Def2-TZVP level is indicative of a π···π stacking interaction mode, for the centroid separation distance is very close to the sum of the van der Waals radii of Cu···C (3.10 Å) and Ag···C (3.44 Å). Energy decomposition analysis (EDA) at the SSB-D/TZP level revealed that the dominant term in the c-M(3)(μ(2)-X)(3)···C(6)H(6) interaction arises from dispersion and electrostatic forces while the covalent interactions are predicted to be negligible. On the other hand, charge decomposition analysis (CDA) illustrated very small charge transfer from C(6)H(6) toward the c-M(3)(μ(2)-X)(3) clusters, thus reflecting weak π-base/π-acid interactions which are further corroborated by the respective electrostatic potentials and the fact that the total dipole moment vector points to the center of the metallic ring of the c-M(3)(μ(2)-X)(3) cluster. The absorption spectra of all aromatic columnar binary stacks simulated by means of TD-DFT calculations showed strong absorptions in the UV region. The main features of the simulated absorption spectra are thoroughly analyzed, and assignments of

On the nature of solvatochromic effect: The riboflavin absorption spectrum as a case study

NASA Astrophysics Data System (ADS)

Daidone, Isabella; Amadei, Andrea; Aschi, Massimiliano; Zanetti-Polzi, Laura

2018-03-01

We present here the calculation of the absorption spectrum of riboflavin in acetonitrile and dimethyl sulfoxide using a hybrid quantum/classical approach, namely the perturbed matrix method, based on quantum mechanical calculations and molecular dynamics simulations. The calculated spectra are compared to the absorption spectrum of riboflavin previously calculated in water and to the experimental spectra obtained in all three solvents. The experimentally observed variations in the absorption spectra upon change of the solvent environment are well reproduced by the calculated spectra. In addition, the nature of the excited states of riboflavin interacting with different solvents is investigated, showing that environment effects determine a recombination of the gas-phase electronic states and that such a recombination is strongly affected by the polarity of the solvent inducing significant changes in the absorption spectra.

Extended Narrow-Line Region in Seyfert Galaxies

NASA Astrophysics Data System (ADS)

Congiu, Enrico; Contini, Marcella.; Ciroi, Stefano; Cracco, Valentina; Di Mille, Francesco; Berton, Marco; Frezzato, Michele; La Mura, Giovanni; Rafanelli, Piero

2017-10-01

We present our recent results about the extended narrow-line region (ENLR) of two nearby Seyfert 2 galaxies (IC 5063 and NGC 7212) obtained by modelling the observed line profiles and spectra with composite models (photoionization+shocks) in the different regions surrounding the AGN. Then, we compare the Seyfert 2 ENLRs with the very extended one recently discovered in the narrow-line Seyfert 1 (NLS1) galaxy Mrk 783. We have found several evidences of interaction between the ISM of the galaxies and their radio jets, such as a) the contribution of shocks in ionizing the high velocity gas, b) the complex kinematics showed by the profile of the emission lines, c) the high fragmentation of matter, etc. The results suggest that the ENLR of IC 5063 have a hollow bi-conical shape, with one edge aligned to the galaxy disk, which may cause some kind of dependence on velocity of the ionization parameter. Regarding the Mrk 783 properties, it is found that the extension of the optical emission is almost twice the size of the radio one and it seems due to the AGN activity, although there is contamination by star formation around 12 arcsec from the nucleus. Diagnostic diagrams excluded the contribution of star formation in IC 5063 and NGC 7212, while the shock contribution was used to explain the spectra emitted by their high velocity gas.

Absorption spectra measurements of the x-ray radiation heated SiO2 aerogel plasma in 'dog-bone' targets irradiated by high power laser pulses

NASA Astrophysics Data System (ADS)

Zhang, Y.; Dong, Q.-L.; Wang, S.-J.; Li, Y.-T.; Zhang, J.; Wei, H.-G.; Shi, J.-R.; Zhao, G.; Zhang, J.-Y.; Wen, T.-S.; Zhang, W.-H.; Hu, X.; Liu, S.-Y.; Ding, Y.-K.; Zhang, L.; Tang, Y.-J.; Zhang, B.-H.; Zheng, Z.-J.; Nishimura, H.; Fujioka, S.; Takabe, H.

2008-05-01

We studied the opacity effect of the SiO2 aerogel plasma heated by x-ray radiation produced by high power laser pulses irradiating the inner surface of golden 'dog-bone' targets. The PET crystal spectrometer was used to measure the absorption spectra of the plasmas in the range from 6.4 Å to 7.4 Å, among which the line emissions involving the K shell of Si ions from He-like to neutral atom were located. The experimental results were analyzed with Detailed-Level-Accounting method. As the plasma temperature increased, the characteristic lines of highly ionized ions gradually dominated the absorption spectrum.

Titan solar occultation observations reveal transit spectra of a hazy world.

PubMed

Robinson, Tyler D; Maltagliati, Luca; Marley, Mark S; Fortney, Jonathan J

2014-06-24

High-altitude clouds and hazes are integral to understanding exoplanet observations, and are proposed to explain observed featureless transit spectra. However, it is difficult to make inferences from these data because of the need to disentangle effects of gas absorption from haze extinction. Here, we turn to the quintessential hazy world, Titan, to clarify how high-altitude hazes influence transit spectra. We use solar occultation observations of Titan's atmosphere from the Visual and Infrared Mapping Spectrometer aboard National Aeronautics and Space Administration's (NASA) Cassini spacecraft to generate transit spectra. Data span 0.88-5 μm at a resolution of 12-18 nm, with uncertainties typically smaller than 1%. Our approach exploits symmetry between occultations and transits, producing transit radius spectra that inherently include the effects of haze multiple scattering, refraction, and gas absorption. We use a simple model of haze extinction to explore how Titan's haze affects its transit spectrum. Our spectra show strong methane-absorption features, and weaker features due to other gases. Most importantly, the data demonstrate that high-altitude hazes can severely limit the atmospheric depths probed by transit spectra, bounding observations to pressures smaller than 0.1-10 mbar, depending on wavelength. Unlike the usual assumption made when modeling and interpreting transit observations of potentially hazy worlds, the slope set by haze in our spectra is not flat, and creates a variation in transit height whose magnitude is comparable to those from the strongest gaseous-absorption features. These findings have important consequences for interpreting future exoplanet observations, including those from NASA's James Webb Space Telescope.

Terahertz Absorption by Cellulose: Application to Ancient Paper Artifacts

NASA Astrophysics Data System (ADS)

Peccianti, M.; Fastampa, R.; Mosca Conte, A.; Pulci, O.; Violante, C.; Łojewska, J.; Clerici, M.; Morandotti, R.; Missori, M.

2017-06-01

Artifacts made of cellulose, such as ancient documents, pose a significant experimental challenge in the terahertz transmission spectra interpretation due to their small optical thickness. In this paper, we describe a method to recover the complex refractive index of cellulose fibers from the terahertz transmission data obtained on single freely standing paper sheets in the (0.2-3.5)-THz range. By using our technique, we eliminate Fabry-Perot effects and recover the absorption coefficient of the cellulose fibers. The obtained terahertz absorption spectra are explained in terms of absorption peaks of the cellulose crystalline phase superimposed to a background contribution due to a disordered hydrogen-bond network. The comparison between the experimental spectra with terahertz vibrational properties simulated by density-functional-theory calculations confirms this interpretation. In addition, evident changes in the terahertz absorption spectra are produced by natural and artificial aging on paper samples, whose final stage is characterized by a spectral profile with only two peaks at about 2.1 and 3.1 THz. These results can be used to provide a quantitative assessment of the state of preservation of cellulose artifacts.

Microscopic Theory and Simulation of Quantum-Well Intersubband Absorption

NASA Technical Reports Server (NTRS)

Li, Jianzhong; Ning, C. Z.

2004-01-01

We study the linear intersubband absorption spectra of a 15 nm InAs quantum well using the intersubband semiconductor Bloch equations with a three-subband model and a constant dephasing rate. We demonstrate the evolution of intersubband absorption spectral line shape as a function of temperature and electron density. Through a detailed examination of various contributions, such as the phase space filling effects, the Coulomb many-body effects and the non-parabolicity effect, we illuminate the underlying physics that shapes the spectra. Keywords: Intersubband transition, linear absorption, semiconductor heterostructure, InAs quantum well

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2013 CFR

2013-07-01

... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The absorbance...

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2012 CFR

2012-07-01

... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The absorbance...

40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

Code of Federal Regulations, 2014 CFR

2014-07-01

... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The absorbance...

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

Enhanced UV Absorption in Carbonaceous Aerosols during MILAGRO and Identification of Potential Organic Contributors.

NASA Astrophysics Data System (ADS)

Mangu, A.; Kelley, K. L.; Marchany-Rivera, A.; Kilaparty, S.; Gunawan, G.; Gaffney, J. S.; Marley, N. A.

2007-12-01

Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) during the month of March, 2006 by using a 7- channel aethalometer (Thermo-Anderson). These measurements, obtained at 370, 470, 520, 590, 660, 880, and 950 nm at a 5 minute time resolution, showed an enhanced absorption in the UV over that expected from carbon soot alone. Samples of fine atmospheric aerosols (less than 0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. The samples were collected on quartz fiber filters with high volume impactor samplers. The samples have been characterized for total carbon content (stable isotope ratio mass spectroscopy) and natural radionuclide tracers (210Pb, 210Po, 210Bi, 7Be, 13C, 14C, 40K, 15N). Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV-visible spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples (1). The continuous spectra also show an enhanced UV absorption over that expected from carbon soot and the general profiles are quite similar to those observed for humic and fulvic acids found as colloidal materials in surface and groundwaters (2), indicating the presence of humic-like substances (HULIS) in the fine aerosols. The spectra also show evidence of narrow band absorbers below 400 nm typical of polycyclic aromatics (PAH) and nitrated aromatic compounds. Spectra were also obtained on NIST standard diesel soot (SRM 2975), NIST standard air particulate matter (SRM 8785

Ultraviolet spectra of quenched carbonaceous composite derivatives: Comparison to the '217 nanometer' interstellar absorption feature

NASA Technical Reports Server (NTRS)

Sakata, Akira; Wada, Setsuko; Tokunaga, Alan T.; Narisawa, Takatoshi; Nakagawa, Hidehiro; Ono, Hiroshi

1994-01-01

QCCs (quenched carbonaceous composite) are amorphus carbonaceous material formed from a hydrocarbon plasma. We present the UV-visible spectra of 'filmy QCC; (obtained outside of the beam ejected from the hydrocarbon plasma) and 'dark QCC' (obtained very near to the beam) for comparison to the stellar extinction curve. When filmy QCC is heated to 500-700 C (thermally altered), the wavelength of the absorption maximum increases form 204 nm to 220-222 nm. The dark QCC has an absorption maximum at 217-222 nm. In addition, the thermally altered filmy QCC has a slope change at about 500 nm which resmbles that in the interstellar extinction curve. The resemblance of the extinction curve of the QCCs to that of the interstellar medium suggests that QCC derivatives may be representative of the type of interstellar material that produces the 217 nm interstellar medium feature. The peak extinction of the dark QCC is higher than the average interstellar extinction curve while that of the thermally altered filmy QCC is lower, so that a mixture of dark and thermally altered filmy QCC can match the peak extinction observed in the interstellar medium. It is shown from electron micrographs that most of the thermally altered flimy QCC is in the form of small grainy structure less than 4 nm in diameter. This shows that the structure unit causing the 217-222 nm feature in QCC is very small.

Photoluminescence from narrow InAs-AlSb quantum wells

NASA Technical Reports Server (NTRS)

Brar, Berinder; Kroemer, Herbert; Ibbetson, James; English, John H.

1993-01-01

We report on photoluminescence spectra from narrow InAs-AlSb quantum wells. Strong, clearly resolved peaks for well widths from 2 to 8 monolayers were observed. Transmission electron micrographs show direct evidence for the structural quality of the quantum well structures. The transition energies of the narrowest wells suggest a strong influence of the AlSb X-barrier on the electronic states in the conduction band.

Electromagnetic-radiation absorption by water.

PubMed

Lunkenheimer, P; Emmert, S; Gulich, R; Köhler, M; Wolf, M; Schwab, M; Loidl, A

2017-12-01

Why does a microwave oven work? How does biological tissue absorb electromagnetic radiation? Astonishingly, we do not have a definite answer to these simple questions because the microscopic processes governing the absorption of electromagnetic waves by water are largely unclarified. This absorption can be quantified by dielectric loss spectra, which reveal a huge peak at a frequency of the exciting electric field of about 20 GHz and a gradual tailing off toward higher frequencies. The microscopic interpretation of such spectra is highly controversial and various superpositions of relaxation and resonance processes ascribed to single-molecule or molecule-cluster motions have been proposed for their analysis. By combining dielectric, microwave, THz, and far-infrared spectroscopy, here we provide nearly continuous temperature-dependent broadband spectra of water. Moreover, we find that corresponding spectra for aqueous solutions reveal the same features as pure water. However, in contrast to the latter, crystallization in these solutions can be avoided by supercooling. As different spectral contributions tend to disentangle at low temperatures, this enables us to deconvolute them when approaching the glass transition under cooling. We find that the overall spectral development, including the 20 GHz feature (employed for microwave heating), closely resembles the behavior known for common supercooled liquids. Thus water's absorption of electromagnetic waves at room temperature is not unusual but very similar to that of glass-forming liquids at elevated temperatures, deep in the low-viscosity liquid regime, and should be interpreted along similar lines.

Electromagnetic-radiation absorption by water

NASA Astrophysics Data System (ADS)

Lunkenheimer, P.; Emmert, S.; Gulich, R.; Köhler, M.; Wolf, M.; Schwab, M.; Loidl, A.

2017-12-01

Why does a microwave oven work? How does biological tissue absorb electromagnetic radiation? Astonishingly, we do not have a definite answer to these simple questions because the microscopic processes governing the absorption of electromagnetic waves by water are largely unclarified. This absorption can be quantified by dielectric loss spectra, which reveal a huge peak at a frequency of the exciting electric field of about 20 GHz and a gradual tailing off toward higher frequencies. The microscopic interpretation of such spectra is highly controversial and various superpositions of relaxation and resonance processes ascribed to single-molecule or molecule-cluster motions have been proposed for their analysis. By combining dielectric, microwave, THz, and far-infrared spectroscopy, here we provide nearly continuous temperature-dependent broadband spectra of water. Moreover, we find that corresponding spectra for aqueous solutions reveal the same features as pure water. However, in contrast to the latter, crystallization in these solutions can be avoided by supercooling. As different spectral contributions tend to disentangle at low temperatures, this enables us to deconvolute them when approaching the glass transition under cooling. We find that the overall spectral development, including the 20 GHz feature (employed for microwave heating), closely resembles the behavior known for common supercooled liquids. Thus water's absorption of electromagnetic waves at room temperature is not unusual but very similar to that of glass-forming liquids at elevated temperatures, deep in the low-viscosity liquid regime, and should be interpreted along similar lines.

Electronic Absorption Spectra of Mass-Selected Hydrocarbon Cations in Solid Neon: C_nH_4+ (n=5-8,10,12)

NASA Astrophysics Data System (ADS)

Nagy, A.; Fulara, J.; Garkusha, I.; Maier, J. P.

2011-05-01

Small, unsaturated hydrocarbons, C_nH_m (n,m≤6), play an important role in astrochemical models as they have been detected in various space objects such as the interstellar medium or envelopes of carbon-rich stars. Although identification of most of these species was based on rotational studies, they are candidate carriers of the infamous diffuse interstellar bands. It has been proposed that corresponding cationic species formed upon UV radiation may also be of astrophysical relevance; therefore, their optical spectra need to be determined. In this contribution, electronic absorption spectra of mass-selected C_nH_4+ (n=5-8,10,12) ions trapped in neon matrices are presented. The cations were produced in a hot-cathode discharge source, guided through a series of electrostatic lenses, mass filtered and co-deposited with excess of neon onto a rhodium-coated sapphire plate held at 6 K. In the same experiments, neutral species were generated from the cations by a photobleaching procedure.

Quasar Absorption Studies

NASA Technical Reports Server (NTRS)

Mushotzky, Richard (Technical Monitor); Elvis, Martin

2004-01-01

The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

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.

Measurement of two-photon-absorption spectra through nonlinear fluorescence produced by a line-shaped excitation beam.

PubMed

Hasani, E; Parravicini, J; Tartara, L; Tomaselli, A; Tomassini, D

2018-05-01

We propose an innovative experimental approach to estimate the two-photon absorption (TPA) spectrum of a fluorescent material. Our method develops the standard indirect fluorescence-based method for the TPA measurement by employing a line-shaped excitation beam, generating a line-shaped fluorescence emission. Such a configuration, which requires a relatively high amount of optical power, permits to have a greatly increased fluorescence signal, thus avoiding the photon counterdetection devices usually used in these measurements, and allowing to employ detectors such as charge-coupled device (CCD) cameras. The method is finally tested on a fluorescent isothiocyanate sample, whose TPA spectrum, which is measured with the proposed technique, is compared with the TPA spectra reported in the literature, confirming the validity of our experimental approach. © 2018 The Authors Journal of Microscopy © 2018 Royal Microscopical Society.

Balmer Absorption Lines in FeLoBALs

NASA Astrophysics Data System (ADS)

Aoki, K.; Iwata, I.; Ohta, K.; Tamura, N.; Ando, M.; Akiyama, M.; Kiuchi, G.; Nakanishi, K.

2007-10-01

We discovered non-stellar Balmer absorption lines in two many-narrow-trough FeLoBALs (mntBALs) by the near-infrared spectroscopy with Subaru/CISCO. Presence of the non-stellar Balmer absorption lines is known to date only in the Seyfert galaxy NGC 4151; thus our discovery is the first cases for quasars. Since all known active galactic nuclei with Balmer absorption lines share similar characteristics, it is suggested that there is a population of BAL quasars which have unique structures at their nuclei or unique evolutionary phase.

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.

OH absorption spectroscopy in a flame using spatial heterodyne spectroscopy

NASA Astrophysics Data System (ADS)

Bartula, Renata J.; Ghandhi, Jaal B.; Sanders, Scott T.; Mierkiewicz, Edwin J.; Roesler, Fred L.; Harlander, John M.

2007-12-01

We demonstrate measurements of OH absorption spectra in the post-flame zone of a McKenna burner using spatial heterodyne spectroscopy (SHS). SHS permits high-resolution, high-throughput measurements. In this case the spectra span ~308-310 nm with a resolution of 0.03 nm, even though an extended source (extent of ~2×10-7 m2 rad2) was used. The high spectral resolution is important for interpreting spectra when multiple absorbers are present for inferring accurate gas temperatures from measured spectra and for monitoring weak absorbers. The present measurement paves the way for absorption spectroscopy by SHS in practical combustion devices, such as reciprocating and gas-turbine engines.

Titan solar occultation observations reveal transit spectra of a hazy world

PubMed Central

Robinson, Tyler D.; Maltagliati, Luca; Marley, Mark S.; Fortney, Jonathan J.

2014-01-01

High-altitude clouds and hazes are integral to understanding exoplanet observations, and are proposed to explain observed featureless transit spectra. However, it is difficult to make inferences from these data because of the need to disentangle effects of gas absorption from haze extinction. Here, we turn to the quintessential hazy world, Titan, to clarify how high-altitude hazes influence transit spectra. We use solar occultation observations of Titan’s atmosphere from the Visual and Infrared Mapping Spectrometer aboard National Aeronautics and Space Administration’s (NASA) Cassini spacecraft to generate transit spectra. Data span 0.88–5 μm at a resolution of 12–18 nm, with uncertainties typically smaller than 1%. Our approach exploits symmetry between occultations and transits, producing transit radius spectra that inherently include the effects of haze multiple scattering, refraction, and gas absorption. We use a simple model of haze extinction to explore how Titan’s haze affects its transit spectrum. Our spectra show strong methane-absorption features, and weaker features due to other gases. Most importantly, the data demonstrate that high-altitude hazes can severely limit the atmospheric depths probed by transit spectra, bounding observations to pressures smaller than 0.1–10 mbar, depending on wavelength. Unlike the usual assumption made when modeling and interpreting transit observations of potentially hazy worlds, the slope set by haze in our spectra is not flat, and creates a variation in transit height whose magnitude is comparable to those from the strongest gaseous-absorption features. These findings have important consequences for interpreting future exoplanet observations, including those from NASA’s James Webb Space Telescope. PMID:24876272

Core-level spectra and molecular deformation in adsorption: V-shaped pentacene on Al(001)

PubMed Central

Lin, He; Brivio, Gian Paolo; Floreano, Luca; Fratesi, Guido

2015-01-01

Summary By first-principle simulations we study the effects of molecular deformation on the electronic and spectroscopic properties as it occurs for pentacene adsorbed on the most stable site of Al(001). The rationale for the particular V-shaped deformed structure is discussed and understood. The molecule–surface bond is made evident by mapping the charge redistribution. Upon X-ray photoelectron spectroscopy (XPS) from the molecule, the bond with the surface is destabilized by the electron density rearrangement to screen the core hole. This destabilization depends on the ionized carbon atom, inducing a narrowing of the XPS spectrum with respect to the molecules adsorbed hypothetically undistorted, in full agreement to experiments. When looking instead at the near-edge X-ray absorption fine structure (NEXAFS) spectra, individual contributions from the non-equivalent C atoms provide evidence of the molecular orbital filling, hybridization, and interchange induced by distortion. The alteration of the C–C bond lengths due to the V-shaped bending decreases by a factor of two the azimuthal dichroism of NEXAFS spectra, i.e., the energy splitting of the sigma resonances measured along the two in-plane molecular axes. PMID:26734516

VizieR Online Data Catalog: QSOs narrow absorption line variability (Hacker+, 2013)

NASA Astrophysics Data System (ADS)

Hacker, T. L.; Brunner, R. J.; Lundgren, B. F.; York, D. G.

2013-06-01

Catalogues of 2,522 QAL systems and 33 variable NAL systems detected in SDSS DR7 quasars with repeat observations. The object identifiers, position coordinates, and plate-MJD-fibre designations are taken from the SpecObjAll table in the SDSS Catalogue Archive Server (CAS) while the quasar redshifts (zqso) are from Hewett & Wild (2010, Cat. J/MNRAS/405/2302). The absorption system redshift (zabs), system grade, and detected lines are outputs of the York et al. (2013, in. prep.) QAL detection pipeline. Some absorption lines are flagged based on alternate identifications (a), proximity of masked pixels (b), or questionable continuum fits (c). (3 data files).

Spectroscopic identification of individual fluorophores using photoluminescence excitation spectra.

PubMed

Czerski, J; Colomb, W; Cannataro, F; Sarkar, S K

2018-01-25

The identity of a fluorophore can be ambiguous if other fluorophores or nonspecific fluorescent impurities have overlapping emission spectra. The presence of overlapping spectra makes it difficult to differentiate fluorescent species using discrete detection channels and unmixing of spectra. The unique absorption and emission signatures of fluorophores provide an opportunity for spectroscopic identification. However, absorption spectroscopy may be affected by scattering, whereas fluorescence emission spectroscopy suffers from signal loss by gratings or other dispersive optics. Photoluminescence excitation spectra, where excitation is varied and emission is detected at a fixed wavelength, allows hyperspectral imaging with a single emission filter for high signal-to-background ratio without any moving optics on the emission side. We report a high throughput method for measuring the photoluminescence excitation spectra of individual fluorophores using a tunable supercontinuum laser and prism-type total internal reflection fluorescence microscope. We used the system to measure and sort the photoluminescence excitation spectra of individual Alexa dyes, fluorescent nanodiamonds (FNDs), and fluorescent polystyrene beads. We used a Gaussian mixture model with maximum likelihood estimation to objectively separate the spectra. Finally, we spectroscopically identified different species of fluorescent nanodiamonds with overlapping spectra and characterized the heterogeneity of fluorescent nanodiamonds of varying size. © 2018 The Authors Journal of Microscopy © 2018 Royal Microscopical Society.

Soft X-Ray Absorption Spectroscopy of High-Abrasion-Furnace Carbon Black

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

Muramatsu, Yasuji; Harada, Ryusuke; Gullikson, Eric M.

2007-02-02

The soft x-ray absorption spectra of high-abrasion-furnace carbon black were measured to obtain local-structure/chemical-states information of the primary particles and/or crystallites. The soft x-ray absorption spectral features of carbon black represent broader {pi}* and {sigma}* peak structures compared to highly oriented pyrolytic graphite (HOPG). The subtracted spectra between the carbon black and HOPG, (carbon black) - (HOPG), show double-peak structures on both sides of the {pi}* peak. The lower-energy peak, denoted as the 'pre-peak', in the subtracted spectra and the {pi}*/{sigma}* peak intensity ratio in the absorption spectra clearly depend on the specific surface area by nitrogen adsorption (NSA). Therefore,more » it is concluded that the pre-peak intensity and the {pi}*/{sigma}* ratio reflect the local graphitic structure of carbon black.« less

Determination of Seed Soundness in Conifers Cryptomeria japonica and Chamaecyparis obtusa Using Narrow-Multiband Spectral Imaging in the Short-Wavelength Infrared Range

PubMed Central

Matsuda, Osamu; Hara, Masashi; Tobita, Hiroyuki; Yazaki, Kenichi; Nakagawa, Toshinori; Shimizu, Kuniyoshi; Uemura, Akira; Utsugi, Hajime

2015-01-01

Regeneration of planted forests of Cryptomeria japonica (sugi) and Chamaecyparis obtuse (hinoki) is the pressing importance to the forest administration in Japan. Low seed germination rate of these species, however, has hampered low-cost production of their seedlings for reforestation. The primary cause of the low germinability has been attributed to highly frequent formation of anatomically unsound seeds, which are indistinguishable from sound germinable seeds by visible observation and other common criteria such as size and weight. To establish a method for sound seed selection in these species, hyperspectral imaging technique was used to identify a wavelength range where reflectance spectra differ clearly between sound and unsound seeds. In sound seeds of both species, reflectance in a narrow waveband centered at 1,730 nm, corresponding to a lipid absorption band in the short-wavelength infrared (SWIR) range, was greatly depressed relative to that in adjacent wavebands on either side. Such depression was absent or less prominent in unsound seeds. Based on these observations, a reflectance index SQI, abbreviated for seed quality index, was formulated using reflectance at three narrow SWIR wavebands so that it represents the extent of the depression. SQI calculated from seed area-averaged reflectance spectra and spatial distribution patterns of pixelwise SQI within each seed area were both proven as reliable criteria for sound seed selection. Enrichment of sound seeds was accompanied by an increase in germination rate of the seed lot. Thus, the methods described are readily applicable toward low-cost seedling production in combination with single seed sowing technology. PMID:26083366

Solvatochromic Effects on the Absorption Spectrum of 2-Thiocytosine

PubMed Central

2017-01-01

The solvatochromic effects of six different solvents on the UV absorption spectrum of 2-thiocytosine have been studied by a combination of experimental and theoretical techniques. The steady-state absorption spectra show significant shifts of the absorption bands, where in more polar solvents the first absorption maximum shifts to higher transition energies and the second maximum to lower energies. The observed solvatochromic shifts have been rationalized using three popular solvatochromic scales and with high-level multireference quantum chemistry calculations including implicit and explicit solvent effects. It has been found that the dipole moments of the excited states account for some general shifts in the excitation energies, whereas the explicit solvent interactions explain the differences in the spectra recorded in the different solvents. PMID:28452483

Sound absorption by clamped poroelastic plates.

PubMed

Aygun, H; Attenborough, K

2008-09-01

Measurements and predictions have been made of the absorption coefficient and the surface acoustic impedance of poroelastic plates clamped in a large impedance tube and separated from the rigid termination by an air gap. The measured and predicted absorption coefficient and surface impedance spectra exhibit low frequency peaks. The peak frequencies observed in the absorption coefficient are close to those predicted and measured in the deflection spectra of the clamped poroelastic plates. The influences of the rigidity of the clamping conditions and the width of the air gap have been investigated. Both influences are found to be important. Increasing the rigidity of clamping reduces the low frequency absorption peaks compared with those measured for simply supported plates or plates in an intermediate clamping condition. Results for a closed cell foam plate and for two open cell foam plates made from recycled materials are presented. For identical clamping conditions and width of air gap, the results for the different materials differ as a consequence mainly of their different elasticity, thickness, and cell structure.

Comparison of experimental and calculated chiroptical spectra for chiral molecular structure determination.

PubMed

Polavarapu, Prasad L; Covington, Cody L

2014-09-01

For three different chiroptical spectroscopic methods, namely, vibrational circular dichroism (VCD), electronic circular dichroism (ECD), and Raman optical activity (ROA), the measures of similarity of the experimental spectra to the corresponding spectra predicted using quantum chemical theories are summarized. In determining the absolute configuration and/or predominant conformations of chiral molecules, these similarity measures provide numerical estimates of agreement between experimental observations and theoretical predictions. Selected applications illustrating the similarity measures for absorption, circular dichroism, and corresponding dissymmetry factor (DF) spectra, in the case of VCD and ECD, and for Raman, ROA, and circular intensity differential (CID) spectra in the case of ROA, are presented. The analysis of similarity in DF or CID spectra is considered to be much more discerning and accurate than that in absorption (or Raman) and circular dichroism (or ROA) spectra, undertaken individually. © 2014 Wiley Periodicals, Inc.

Computer-Graphics Emulation of Chemical Instrumentation: Absorption Spectrophotometers.

ERIC Educational Resources Information Center

Gilbert, D. D.; And Others

1982-01-01

Describes interactive, computer-graphics program emulating behavior of high resolution, ultraviolet-visible analog recording spectrophotometer. Graphics terminal behaves as recording absorption spectrophotometer. Objective of the emulation is study of optimization of the instrument to yield accurate absorption spectra, including…

Persistent optical hole-burning spectroscopy of nano-confined dye molecules in liquid at room temperature: Spectral narrowing due to a glassy state and extraordinary relaxation in a nano-cage

NASA Astrophysics Data System (ADS)

Murakami, Hiroshi

2018-04-01

Persistent optical hole-burning spectroscopy has been conducted for a dye molecule within a very small (˜1 nm) reverse micelle at room temperature. The spectra show a spectral narrowing due to site-selective excitation. This definitely demonstrates that the surroundings of the dye molecule are in a glassy state regardless of a solution at room temperature. On the other hand, the hole-burning spectra exhibit large shifts from excitation frequencies, and their positions are almost independent of excitation frequencies. The hole-burning spectra have been theoretically calculated by taking account of a vibronic absorption band of the dye molecule under the assumption that the surroundings of the dye molecule are in a glassy state. The calculated results agree with the experimental ones that were obtained for the dye molecule in a polymer glass for comparison, where it has been found that the ratio of hole-burning efficiencies of vibronic- to electronic-band excitations is quite high. On the other hand, the theoretical results do not explain the large spectral shift from the excitation frequency and small spectral narrowing observed in the hole-burning spectra measured for the dye-containing reverse micelle. It is thought that the spectral shift and broadening occur within the measurement time owing to the relaxation process of the surroundings that are hot with the thermal energy deposited by the dye molecule optically excited. Furthermore, the relaxation should be temporary because the cooling of the inside of the reverse micelle takes place with the dissipation of the excess thermal energy to the outer oil solvent, and so the surroundings of the dye molecule return to the glassy state and do not attain the thermal equilibrium. These results suggest that a very small reverse micelle provides a unique reaction field in which the diffusional motion can be controlled by light in a glassy state.

X-ray absorption of a warm dense aluminum plasma created by an ultra-short laser pulse

NASA Astrophysics Data System (ADS)

Lecherbourg, L.; Renaudin, P.; Bastiani-Ceccotti, S.; Geindre, J.-P.; Blancard, C.; Cossé, P.; Faussurier, G.; Shepherd, R.; Audebert, P.

2007-05-01

Point-projection K-shell absorption spectroscopy has been used to measure absorption spectra of transient aluminum plasma created by an ultra-short laser pulse. The 1s-2p and 1s-3p absorption lines of weakly ionized aluminum were measured for an extended range of densities in a low-temperature regime. Independent plasma characterization was obtained using frequency domain interferometry diagnostic (FDI) that allows the interpretation of the absorption spectra in terms of spectral opacities. A detailed opacity code using the density and temperature inferred from the FDI reproduce the measured absorption spectra except in the last stage of the recombination phase.

On the inclusion of the hydrogen dimer in the analysis of Voyager IRIS spectra

NASA Technical Reports Server (NTRS)

Carlson, Barbara E.; Ma, Qiancheng; Lacis, Andrew

1992-01-01

Empirical formulas are fitted to existing theoretical absorption spectra of H2-H2 pairs in the far-infrared allowing the inclusion of dimer absorption, parameterized with the height dependence of the para-hydrogen profile, in the calculations. Comparison between synthetic and Voyager IRIS spectra shows that once the dimer absorption is included it is now possible to reproduce the hydrogen portion of the IRIS spectrum to within the precision of the measurements.

Optical absorption spectra and g factor of MgO: Mn2+explored by ab initio and semi empirical methods

NASA Astrophysics Data System (ADS)

Andreici Eftimie, E.-L.; Avram, C. N.; Brik, M. G.; Avram, N. M.

2018-02-01

In this paper we present a methodology for calculations of the optical absorption spectra, ligand field parameters and g factor for the Mn2+ (3d5) ions doped in MgO host crystal. The proposed technique combines two methods: the ab initio multireference (MR) and the semi empirical ligand field (LF) in the framework of the exchange charge model (ECM) respectively. Both methods of calculations are applied to the [MnO6]10-cluster embedded in an extended point charge field of host matrix ligands based on Gellé-Lepetit procedure. The first step of such investigations was the full optimization of the cubic structure of perfect MgO crystal, followed by the structural optimization of the doped of MgO:Mn2+ system, using periodic density functional theory (DFT). The ab initio MR wave functions approaches, such as complete active space self-consistent field (CASSCF), N-electron valence second order perturbation theory (NEVPT2) and spectroscopy oriented configuration interaction (SORCI), are used for the calculations. The scalar relativistic effects have also been taken into account through the second order Douglas-Kroll-Hess (DKH2) procedure. Ab initio ligand field theory (AILFT) allows to extract all LF parameters and spin-orbit coupling constant from such calculations. In addition, the ECM of ligand field theory (LFT) has been used for modelling theoptical absorption spectra. The perturbation theory (PT) was employed for the g factor calculation in the semi empirical LFT. The results of each of the aforementioned types of calculations are discussed and the comparisons between the results obtained and the experimental results show a reasonable agreement, which justifies this new methodology based on the simultaneous use of both methods. This study establishes fundamental principles for the further modelling of larger embedded cluster models of doped metal oxides.

Computer Processing Of Tunable-Diode-Laser Spectra

NASA Technical Reports Server (NTRS)

May, Randy D.

1991-01-01

Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.

Coherent backscattering effect in spectra of icy satellites and its modeling using multi-sphere T-matrix (MSTM) code for layers of particles

NASA Astrophysics Data System (ADS)

Pitman, Karly M.; Kolokolova, Ludmilla; Verbiscer, Anne J.; Mackowski, Daniel W.; Joseph, Emily C. S.

2017-12-01

The coherent backscattering effect (CBE), the constructive interference of light scattering in particulate surfaces (e.g., regolith), manifests as a non-linear increase in reflectance, or opposition surge, and a narrow negative polarization feature at small solar phase angles. Due to a strong dependence of the amplitude and angular width of this opposition surge on the absorptive characteristics of the surface material, CBE also produces phase-angle-dependent variations in the near-infrared spectra. In this paper we present a survey of such variations in the spectra of icy satellites of Saturn obtained by the Cassini spacecraft's Visual and Infrared Mapping Spectrometer (VIMS) and in the ground-based spectra of Oberon, a satellite of Uranus, obtained with TripleSpec, a cross-dispersed near-infrared spectrometer on the Astrophysical Research Consortium 3.5-m telescope located at the Apache Point Observatory near Sunspot, New Mexico. The paper also presents computer modeling of the saturnian satellite spectra and their phase-angle variations using the most recent version of the Multi-Sphere T-Matrix (MSTM) code developed to simulate light scattering by layers of randomly distributed spherical particles. The modeling allowed us not only to reproduce the observed effects but also to estimate characteristics of the icy particles that cover the surfaces of Rhea, Dione, and Tethys.

Unusual continuous dual absorption peaks in Ca-doped BiFeO3 nanostructures for broadened microwave absorption

NASA Astrophysics Data System (ADS)

Li, Zhong-Jun; Hou, Zhi-Ling; Song, Wei-Li; Liu, Xing-Da; Cao, Wen-Qiang; Shao, Xiao-Hong; Cao, Mao-Sheng

2016-05-01

Electromagnetic absorption materials have received increasing attention owing to their wide applications in aerospace, communication and the electronics industry, and multiferroic materials with both polarization and magnetic properties are considered promising ceramics for microwave absorption application. However, the insufficient absorption intensity coupled with the narrow effective absorption bandwidth has limited the development of high-performance multiferroic materials for practical microwave absorption. To address such issues, in the present work, we utilize interfacial engineering in BiFeO3 nanoparticles via Ca doping, with the purpose of tailoring the phase boundary. Upon Ca-substitution, the co-existence of both R3c and P4mm phases has been confirmed to massively enhance both dielectric and magnetic properties via manipulating the phase boundary and the destruction of the spiral spin structure. Unlike the commonly reported magnetic/dielectric hybrid microwave absorption composites, Bi0.95Ca0.05FeO3 has been found to deliver unusual continuous dual absorption peaks at a small thickness (1.56 mm), which has remarkably broadened the effective absorption bandwidth (8.7-12.1 GHz). The fundamental mechanisms based on the phase boundary engineering have been discussed, suggesting a novel platform for designing advanced multiferroic materials with wide applications.Electromagnetic absorption materials have received increasing attention owing to their wide applications in aerospace, communication and the electronics industry, and multiferroic materials with both polarization and magnetic properties are considered promising ceramics for microwave absorption application. However, the insufficient absorption intensity coupled with the narrow effective absorption bandwidth has limited the development of high-performance multiferroic materials for practical microwave absorption. To address such issues, in the present work, we utilize interfacial engineering in BiFeO3

Carbon X-ray absorption spectra of fluoroethenes and acetone: A study at the coupled cluster, density functional, and static-exchange levels of theory

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

Fransson, Thomas; Norman, Patrick; Coriani, Sonia

2013-03-28

Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as themore » state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger {pi}-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to {pi}*-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate {pi}*-peak separations due to spectral compressions, a characteristic which is inherent to

Carbon X-ray absorption spectra of fluoroethenes and acetone: a study at the coupled cluster, density functional, and static-exchange levels of theory.

PubMed

Fransson, Thomas; Coriani, Sonia; Christiansen, Ove; Norman, Patrick

2013-03-28

Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger π-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to π∗-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate π∗-peak separations due to spectral compressions, a characteristic which is inherent to this

Kinetics and its accompanying thermodynamics studies on simultaneous complexation of heterobimetallic neodymium (III) with zinc (II) and L-tryptophan in aquated DMF using 4f-4f absorption spectra.

PubMed

Huidrom, Bimola; Singh, N Rajmuhon

2014-01-24

The 4f-4f absorption spectra of the simultaneous heterobimetallic complexation of trivalent neodymium ion with l-tryptophan and divalent zinc ion in aquated DMF (50%, v/v) at pH 6.0 was recorded at the time interval of 1h. From the observed absorption spectra, the values of intensity parameters such as oscillator strength (P) and Judd-Ofelt intensity (Tλ) parameters, kinetics and thermodynamics parameters were evaluated. The rate constant increases with an increase in the temperature along with the oscillator strengths and Judd-Ofelt intensity parameters. The positive values of the change in the standard enthalpy (ΔH°) and entropy (ΔS°) indicate that the complexation is endothermic. The negative values of the change in the standard free energy (ΔG°) in the range from 293.15 K to 308.15 K, indicate that the reaction occurs spontaneously and hence the formation of heterobimetallic complex in the solution is favored kinetically and thermodynamically. Copyright © 2013 Elsevier B.V. All rights reserved.

Kinetics and its accompanying thermodynamics studies on simultaneous complexation of heterobimetallic neodymium (III) with zinc (II) and L-tryptophan in aquated DMF using 4f-4f absorption spectra

NASA Astrophysics Data System (ADS)

Huidrom, Bimola; Rajmuhon Singh, N.

2014-01-01

The 4f-4f absorption spectra of the simultaneous heterobimetallic complexation of trivalent neodymium ion with L-tryptophan and divalent zinc ion in aquated DMF (50%, v/v) at pH 6.0 was recorded at the time interval of 1 h. From the observed absorption spectra, the values of intensity parameters such as oscillator strength (P) and Judd-Ofelt intensity (Tλ) parameters, kinetics and thermodynamics parameters were evaluated. The rate constant increases with an increase in the temperature along with the oscillator strengths and Judd-Ofelt intensity parameters. The positive values of the change in the standard enthalpy (ΔH°) and entropy (ΔS°) indicate that the complexation is endothermic. The negative values of the change in the standard free energy (ΔG°) in the range from 293.15 K to 308.15 K, indicate that the reaction occurs spontaneously and hence the formation of heterobimetallic complex in the solution is favored kinetically and thermodynamically.

IDEOS: Fitting Infrared Spectra from Dusty Galaxies

NASA Astrophysics Data System (ADS)

Viola, Vincent; Rupke, D.

2014-01-01

We fit models to heavily obscured infrared spectra taken by the Spitzer Space Telescope and prepare them for cataloguing in the Infrared Database of Extragalactic Observables from Spitzer (IDEOS). When completed, IDEOS will contain homogeneously measured mid-infrared spectroscopic observables of more than 4200 galaxies beyond the Local Group. The software we use, QUESTFit, models the spectra using up to three extincted blackbodies (including silicate, water ice, and hydrocarbon absorption) and PAH templates. We present results from a sample of the approximately 200 heavily obscured spectra that will be present in IDEOS.

Measurement of Absorption Coefficient of Paraformaldehyde and Metaldehyde with Terahertz Spectroscopy

NASA Astrophysics Data System (ADS)

Zhang, J.; Xia, T.; Chen, Q.; Sun, Q.; Deng, Y.; Wang, C.

2018-03-01

The characteristic absorption spectra of paraformaldehyde and metaldehyde in the terahertz frequency region are obtained by terahertz time-domain spectroscopy (THz-TDS). In order to reduce the absorption of terahertz (THz) wave by water vapor in the air and the background noise, the measurement system was filled with dry air and the measurements were conducted at the temperature of 24°C. Meanwhile, the humidity was controlled within 10% RH. The THz frequency domain spectra of samples and their references from 0 to 2.5 THz were analyzed via Fourier transform. The refractive index and absorption coefficients of the two aldehydes were calculated by the model formulas. From 0.1 to 2.5 THz, there appear two weak absorption peaks at 1.20 and 1.66 THz in the absorption spectra of paraformaldehyde. Only one distinct absorption peak emerges at 1.83 THz for metaldehyde. There are significant differences between the terahertz absorption coefficients of paraformaldehyde and metaldehyde, which can be used as "fingerprints" to identify these substances. Furthermore, the relationship between the average absorption coefficients and mass concentrations was investigated and the average absorption coefficient-mass concentration diagrams of paraformaldehyde and metaldehyde were shown. For paraformaldehyde, there is a linear relationship between the average absorption coefficient and the natural logarithm of mass concentration. For metaldehyde, there exists a simpler linear relationship between the average absorption coefficient and the mass concentration. Because of the characteristics of THz absorption of paraformaldehyde and metaldehyde, the THz-TDS can be applied to the qualitative and quantitative detection of the two aldehydes to reduce the unpredictable hazards due to these substances.

Ultra-violet and visible absorption characterization of explosives by differential reflectometry.

PubMed

Dubroca, Thierry; Moyant, Kyle; Hummel, Rolf E

2013-03-15

This study presents some optical properties of TNT (2,4,6-trinitrotoluene), RDX, HMX and tetryl, specifically their absorption spectra as a function of concentration in various solvents in the ultraviolet and visible portion of the electromagnetic spectrum. We utilize a standoff explosives detection method, called differential reflectometry (DR). TNT was diluted in six different solvents (acetone, acetonitrile, ethanol, ethyl acetate, methanol, and toluene), which allowed for a direct comparison of absorption features over a wide range of concentrations. A line-shape analysis was adopted with great accuracy (R(2)>0.99) to model the absorption features of TNT in differential reflectivity spectra. We observed a blue shift in the pertinent absorption band with decreasing TNT concentration for all solvents. Moreover, using this technique, it was found that for all utilized solvents the concentration of TNT as well as of RDX, HMX, and tetryl, measured as a function of the transition wavelength of the ultra-violet absorption edge in differential reflectivity spectra shows three distinct regions. A model is presented to explain this behavior which is based on intermolecular hydrogen bonding of explosives molecules with themselves (or lack thereof) at different concentrations. Other intermolecular forces such as dipole-dipole interactions, London dispersion forces and π-stacking contribute to slight variations in the resulting spectra, which were determined to be rather insignificant in comparison to hydrogen bonding. The results are aimed towards a better understanding of the DR spectra of explosives energetic materials. Copyright © 2012 Elsevier B.V. All rights reserved.

Simulation of Infrared Spectra of Carbonaceous Grains

NASA Astrophysics Data System (ADS)

Dadswell, G.; Duley, W. W.

1997-02-01

Random covalent network (RCN) theory is applied to describe the infrared spectroscopic properties of carbonaceous solids with compositions containing a mixture of aromatic, aliphatic, and diamond-like hydrocarbons. Application of this technique to carbonaceous dust is equivalent to the synthesis of solids whose structure and bonding satisfy stoicheometry while minimizing strain energy. The result involves a range of compositions compatible with carbon bonding and the hydrogen concentration incorporated in the network. In general, only a limited range of compositions is available rather than the infinite number of possible compositions expected without the inclusion of these constraints. When compositions have been defined in this way, infrared spectra may be synthesized for comparison with astronomical spectra of interstellar carbonaceous solids. Such spectra contain components corresponding to absorption by CHn groups in which n = 1-3. We find, however, that additional spectral features, not included in our simple chemical model, must be present also in dust. We give plots of such spectra in the 3100-2800 cm-1 (3.2-3.6 μm) region for comparison with infrared spectra of interstellar dust. We have also developed an RCN formalism that incorporates oxygen into the carbon network as OH groups, and we show that this inclusion introduces a strong additional absorption band in the 3300 cm-1 (3.0 μm) region.

Data Processing Algorithm for Diagnostics of Combustion Using Diode Laser Absorption Spectrometry.

PubMed

Mironenko, Vladimir R; Kuritsyn, Yuril A; Liger, Vladimir V; Bolshov, Mikhail A

2018-02-01

A new algorithm for the evaluation of the integral line intensity for inferring the correct value for the temperature of a hot zone in the diagnostic of combustion by absorption spectroscopy with diode lasers is proposed. The algorithm is based not on the fitting of the baseline (BL) but on the expansion of the experimental and simulated spectra in a series of orthogonal polynomials, subtracting of the first three components of the expansion from both the experimental and simulated spectra, and fitting the spectra thus modified. The algorithm is tested in the numerical experiment by the simulation of the absorption spectra using a spectroscopic database, the addition of white noise, and the parabolic BL. Such constructed absorption spectra are treated as experimental in further calculations. The theoretical absorption spectra were simulated with the parameters (temperature, total pressure, concentration of water vapor) close to the parameters used for simulation of the experimental data. Then, spectra were expanded in the series of orthogonal polynomials and first components were subtracted from both spectra. The value of the correct integral line intensities and hence the correct temperature evaluation were obtained by fitting of the thus modified experimental and simulated spectra. The dependence of the mean and standard deviation of the evaluation of the integral line intensity on the linewidth and the number of subtracted components (first two or three) were examined. The proposed algorithm provides a correct estimation of temperature with standard deviation better than 60 K (for T = 1000 K) for the line half-width up to 0.6 cm -1 . The proposed algorithm allows for obtaining the parameters of a hot zone without the fitting of usually unknown BL.

[The study of CO2 cavity enhanced absorption and highly sensitive absorption spectroscopy].

PubMed

Pei, Shi-Xin; Gao, Xiao-Ming; Cui, Fen-Ping; Huang, Wei; Shao, Jie; Fan, Hong; Zhang, Wei-Jun

2005-12-01

Cavity enhanced absorption spectroscopy (CEAS) is a new spectral technology that is based on the cavity ring down absorption spectroscopy. In the present paper, a DFB encapsulation narrow line width tunable diode laser (TDL) was used as the light source. At the center output, the TDL radiation wavelength was 1.573 microm, and an optical cavity, which consisted of two high reflectivity mirrors (near 1.573 microm, the mirror reflectivity was about 0.994%), was used as a sample cell. A wavemeter was used to record the accurate frequency of the laser radiation. In the experiment, the method of scanning the optical cavity to change the cavity mode was used, when the laser frequency was coincident with one of the cavity mode; the laser radiation was coupled into the optical cavity and the detector could receive the light signals that escaped the optical cavity. As a result, the absorption spectrum of carbon dioxide weak absorption at low pressure was obtained with an absorption intensity of 1.816 x 10(-23) cm(-1) x (molecule x cm(-2)(-1) in a sample cell with a length of only 33.5 cm. An absorption sensitivity of about 3.62 x 10(-7) cm(-1) has been achieved. The experiment result indicated that the cavity enhanced absorption spectroscopy has the advantage of high sensivity, simple experimental setup, and easy operation.

The far-ultraviolet spectra and geometric albedos of Jupiter and Saturn

NASA Technical Reports Server (NTRS)

Clarke, J. T.; Moos, H. W.; Feldman, P. D.

1982-01-01

Spectra and geometric albedoes in the range 1200 to 1940 A are compiled for Jupiter and Saturn on the basis of IUE observations. The spectra of both planets are dominated by H Lyman-alpha emission line at 1216 A, although absorption bands of C2H2 are apparent at longer wavelengths, particularly in the spectrum of Saturn, and the C I line at 1657 A is also observed. Geometric albedoes show emission features corresponding to the weak H2 Lyman and Werner bands around 1230-1280 A, auroral Lyman band emission, C I emission, and C2H2 absorption from 1600 to 1900 A. A model of atmospheric absorption in homogeneously mixed atmospheres of H2 and trace molecular absorbers is then presented and fit to the Jupiter albedo, resulting in a predicted atmosphere containing C2H2 and an unidentified molecular or particulate absorber. Finally, north-south maps of Jupiter continuum emission show limb darkening, and a comparison of equatorial and polar spectra indicates a polar increase in C2H2 absorption and weaker polar H2 emissions than previously reported.

White light photothermal lens spectrophotometer for the determination of absorption in scattering samples.

PubMed

Marcano, Aristides; Alvarado, Salvador; Meng, Junwei; Caballero, Daniel; Moares, Ernesto Marín; Edziah, Raymond

2014-01-01

We developed a pump-probe photothermal lens spectrophotometer that uses a broadband arc-lamp and a set of interference filters to provide tunable, nearly monochromatic radiation between 370 and 730 nm as the pump light source. This light is focused onto an absorbing sample, generating a photothermal lens of millimeter dimensions. A highly collimated monochromatic probe light from a low-power He-Ne laser interrogates the generated lens, yielding a photothermal signal proportional to the absorption of light. We measure the absorption spectra of scattering dye solutions using the device. We show that the spectra are not affected by the presence of scattering, confirming that the method only measures the absorption of light that results in generation of heat. By comparing the photothermal spectra with the usual absorption spectra determined using commercial transmission spectrophotometers, we estimate the quantum yield of scattering of the sample. We discuss applications of the device for spectroscopic characterization of samples such as blood and gold nanoparticles that exhibit a complex behavior upon interaction with light.

[The change in optical spectra from solid and liquid solution of copper phthalocyanines derivatives].

PubMed

Zheng, Xiao-pan; He, Zhi-qun; Zhang, Chun-xiu; Xu, Zheng; Wang, Yong-sheng

2006-06-01

In the present work, the change in electronic absorption spectra from three copper phthalocyanines (CuPc, tb-CuPc, oo-CuPc) in different environments was investigated. The mechanism of red shift Q-band absorption from the three species in an organic solvent before and after protonation was discussed. This was used to compare with those dispersed in solid films. The relation between the molecular interactions and the spectra change was studied. In a combination of POM, DSC and XRD techniques, the structure and morphology of the thin films were characterised. It was found that the molecules in the doped matrices of PC were associated or aggregated. This association and hence the corresponding change in absorption spectra cannot be altered by the modification of dopant concentration.

UV-Visible Spectra of PAHs and Derivatives Seeded in Supersonic Jet. Astrophysical Implications

NASA Astrophysics Data System (ADS)

Salma, Bejaoui; Salama, Farid

2018-06-01

Laboratory absorption spectra of Polycyclic Aromatic Hydrocarbons (PAHs) and PAH derivatives measured under astrophysical relevant conditions are crucial to test the PAHs-DIBs hypothesis as well as the PAH model for the IR emission bands. Our dedicated experimental setup on the COsmic SImulation Chamber (COSmIC) provides an excellent platform to study neutral and ionized PAHs under the low temperature and pressure conditions that are representative of interstellar environments [1]. In this work, we study the effect of the substitution of CH bond(s) by a nitrogen atom(s) on the electronic spectra of phenanthrene. The electronic transitions associated with the lower excited states of neutral phenanthrene (C14H10) and phenanthridine (C13H9N) are measured in gas phase in the 315-345 nm region. Molecules are seeded in a supersonic expansion of argon gas and the absorption spectra are measured using the Cavity Ring Down Spectroscopy (CRDS) technique. Additional measurements of the absorption spectra of phenanthrene, phenantridine and 1,10-phenanthroline (C12H8N2) isolated in 10 K argon matrices are also performed. The comparison between the CRDS spectra with the absorption of the matrix-isolated molecules highlight the matrix-induced perturbations in band position, profiles and broadening and illustrates the need of gas phase measurements for more accurate comparisons with astronomical spectra.[1] Salama, F., Galazutdinov, G., Krelowski, et al. ApJ 728, 154[FS1] (2011).[2] A. Tielens, ApJ 526 Pt 1265–273 (2008),Acknowledgements: This research is supported by the APRA Program of NASA SMD

Nonlinear optical and electroabsorption spectra of polydiacetylene crystals and films

NASA Astrophysics Data System (ADS)

Mukhopadhyay, D.; Soos, Z. G.

1996-01-01

Vibronic structure of nonlinear optical (NLO) coefficients is developed within the Condon approximation, displaced harmonic oscillators, and crude adiabatic states. The displacements of backbone modes of conjugated polymers are taken from vibrational data on the ground and 1B excited state. NLO resonances are modeled by three excitations and transition moments taken from Pariser-Parr-Pople (PPP) theory and optimized to polydiacetylene (PDA) spectra in crystals and films, with blue-shifted 1B exciton. The joint analysis of third-harmonic-generation, two-photon absorption, and nondegenerate four-wave-mixing spectra of PDA crystals and films shows weak two-photon absorption to 2A below 1B, leading to overlapping resonances in the THG spectrum, strong two-photon absorption to an nA state some 35% above 1B, and weak Raman resonances in nondegenerate FWM spectra. The full π-π* spectrum contributes to Stark shifts and field-induced transitions, as shown by PPP results for PDA oligomers. The Stark shift dominates high-resolution electroabsorption (EA) spectra of PDA crystals below 10 K. The close correspondence between EA and the first-derivative I'(ω) of the linear absorption above the 1B exciton in PDA crystals provides an experimental separation of vibrational and electronic contributions that limits any even-parity state in this 0.5 eV interval. An oscillator-strength sum rule is applied to the convergence of PDA oligomers with increasing length, N, and the crystal oscillator strengths are obtained without adjustable parameters. The sum rule for the 1B exciton implies large transition moments to higher-energy Ag states, whose locations in recent models are contrasted to PPP results. Joint analysis of NLO and EA spectra clarifies when a few electronic excitations are sufficient, distinguishes between vibrational and electronic contributions, and supports similar π-electron interactions in conjugated molecules and polymers.

Determination of equilibrium structures of bromothymol blue revealed by using quantum chemistry with an aid of multivariate analysis of electronic absorption spectra

NASA Astrophysics Data System (ADS)

Shimada, Toru; Hasegawa, Takeshi

2017-10-01

The pH dependent chemical structures of bromothymol blue (BTB), which have long been under controversy, are determined by employing a combined technique of multivariate analysis of electronic absorption spectra and quantum chemistry. Principle component analysis (PCA) of the pH dependent spectra apparently reveals that only two chemical species are adequate to fully account for the color changes, with which the spectral decomposition is readily performed by using augmented alternative least-squares (ALS) regression analysis. The quantity variation by the ALS analysis also reveals the practical acid dissociation constant, pKa‧. The determination of pKa‧ is performed for various ionic strengths, which reveals the thermodynamic acid constant (pKa = 7.5) and the number of charge on each chemical species; the yellow form is negatively charged species of - 1 and the blue form that of - 2. On this chemical information, the quantum chemical calculation is carried out to find that BTB molecules take the pure quinoid form in an acid solution and the quinoid-phenolate form in an alkaline solution. The time-dependent density functional theory (TD-DFT) calculations for the theoretically determined chemical structures account for the peak shift of the electronic spectra. In this manner, the structures of all the chemical species appeared in equilibrium have finally been confirmed.

Infrared absorption cross sections of propane broadened by hydrogen

NASA Astrophysics Data System (ADS)

Wong, A.; Hargreaves, R. J.; Billinghurst, B.; Bernath, P. F.

2017-09-01

Fourier transform infrared absorption cross-sections of pure propane (C3H8) and propane broadened with H2 have been calculated from transmittance spectra recorded at temperatures from 292 K to 205 K. Transmittance spectra were recorded at the Canadian Light Source (CLS) Far-Infrared beamline, utilizing both the synchrotron source and the internal glowbar source. The absorption cross-sections have been calibrated to Pacific Northwest National Laboratory (PNNL) reference cross-sections of propane and can be used to interpret astronomical observations of giant planets such as Jupiter and Saturn as well as exoplanets.

FTIR spectrometer with 30 m optical cell and its applications to the sensitive measurements of selective and nonselective absorption spectra

NASA Astrophysics Data System (ADS)

Ponomarev, Yu. N.; Solodov, A. A.; Solodov, A. M.; Petrova, T. M.; Naumenko, O. V.

2016-07-01

A description of the spectroscopic complex at V.E. Zuev Institute of Atmospheric Optics, SB RAS, operating in a wide spectral range with high threshold sensitivity to the absorption coefficient is presented. Measurements of weak lines and nonselective spectra of CO2 and H2O were performed based on the built setup. As new application of this setup, positions and intensities of 152 weak lines of H2O were measured between 2400 and 2560 cm-1 with threshold sensitivity of 8.6×10-10 cm-1, and compared with available calculated and experimental data. Essential deviations between the new intensity measurements and calculated data accepted in HITRAN 2012 and GEISA 2015 forthcoming release are found.

VUV absorption spectroscopy of bacterial spores and DNA components

NASA Astrophysics Data System (ADS)

Fiebrandt, Marcel; Lackmann, Jan-Wilm; Raguse, Marina; Moeller, Ralf; Awakowicz, Peter; Stapelmann, Katharina

2017-01-01

Low-pressure plasmas can be used to inactivate bacterial spores and sterilize goods for medical and pharmaceutical applications. A crucial factor are damages induced by UV and VUV radiation emitted by the plasma. To analyze inactivation processes and protection strategies of spores, absorption spectra of two B. subtilis strains are measured. The results indicate, that the inner and outer coat of the spore significantly contribute to the absorption of UV-C and also of the VUV, protecting the spore against radiation based damages. As the sample preparation can significantly influence the absorption spectra due to salt residues, the cleaning procedure and sample deposition is tested for its reproducibility by measuring DNA oligomers and pUC18 plasmid DNA. The measurements are compared and discussed with results from the literature, showing a strong decrease of the salt content enabling the detection of absorption structures in the samples.

Absorption coefficients of solid NH3 from 50 to 7000 per cm

NASA Technical Reports Server (NTRS)

Sill, G.; Fink, U.; Ferraro, J. R.

1980-01-01

Thin-film spectra of solid NH3 at a resolution of 1 per cm were used to determine its absorption coefficient over the range 50-7000 per cm. The thin films were formed inside a liquid N2 cooled dewar using a variety of substrates and dewar windows. The spectra were recorded with two Fourier spectrometers, one covering the range from 1 to 4 microns and the other from 2.6 to 200 microns. The thickness of the films was measured with a laser interference technique. The absorption coefficients were determined by application of Lambert's law and by a fitting procedure to the observed spectra using thin-film theory. Good agreement was found with the absorption coefficients recently determined by other investigators over a more restricted wavelength range. A metastable phase was observed near a temperature of 90 K and its absorption coefficient is reported. No other major spectral changes with temperature were noted for the range 88-120 K.

Broadband, high-resolution investigation of advanced absorption line shapes at high temperature

NASA Astrophysics Data System (ADS)

Schroeder, Paul J.; Cich, Matthew J.; Yang, Jinyu; Swann, William C.; Coddington, Ian; Newbury, Nathan R.; Drouin, Brian J.; Rieker, Gregory B.

2017-08-01

Spectroscopic studies of planetary atmospheres and high-temperature processes (e.g., combustion) require absorption line-shape models that are accurate over extended temperature ranges. To date, advanced line shapes, like the speed-dependent Voigt and Rautian profiles, have not been tested above room temperature with broadband spectrometers. We investigate pure water vapor spectra from 296 to 1305 K acquired with a dual-frequency comb spectrometer spanning from 6800 to 7200 c m-1 at a point spacing of 0.0033 c m-1 and absolute frequency accuracy of <3.3 ×10-6c m-1 . Using a multispectral fitting analysis, we show that only the speed-dependent Voigt accurately models this temperature range with a single power-law temperature-scaling exponent for the broadening coefficients. Only the data from the analysis using this profile fall within theoretical predictions, suggesting that this mechanism captures the dominant narrowing physics for these high-temperature conditions.

Electronic absorption spectra of hydrogenated protonated naphthalene and proflavine

NASA Astrophysics Data System (ADS)

Bonaca, A.; Bilalbegović, G.

2011-09-01

We study hydrogenated cations of two polycyclic hydrocarbon molecules as models of hydrogenated organic species that form in the interstellar medium. Optical spectra of the hydrogenated naphthalene cation Hn-C10H+8 for n= 1, 2 and 10, as well as the astrobiologically interesting hydrogenated proflavine cation Hn-C13H11N+3 for n= 1 and 14, are calculated. The pseudopotential time-dependent density functional theory is used. It is found that the fully hydrogenated proflavine cation H14-C13H11N+3 shows a broad spectrum in which the positions of individual lines are almost lost. The positions, shapes and intensities of lines change in hydronaphthalene and hydroproflavine cations, showing that hydrogen additions induce substantially different optical spectra in comparison with base polycyclic hydrocarbon cations. One calculated line in the visible spectrum of H10-C10H+8 and one in the visible spectrum of H-C13H11N+3 are close to the measured diffuse interstellar bands. We also present the positions of near-ultraviolet lines.

Reflection spectra, 2.5-7 microns, of some solids of planetary interest

NASA Technical Reports Server (NTRS)

Fink, U.; Burk, S. D.

1973-01-01

Reflection spectra of 42 compounds of possible planetary interest were run from 2.5 to 7 microns. They were supplemented by some transmission spectra extending the wavelength coverage to 15 microns. The spectra were organized according to their constituent radicals and an attempt was made at the identification of the absorption features.

Iron oxide bands in the visible and near-infrared reflectance spectra of primitive asteroids

NASA Technical Reports Server (NTRS)

Jarvis, Kandy S.; Vilas, Faith; Gaffey, Michael J.

1993-01-01

High resolution reflectance spectra of primitive asteroids (C, P, and D class and associated subclasses) have commonly revealed an absorption feature centered at 0.7 microns attributed to an Fe(2+)-Fe(3+) charge transfer transition in iron oxides and/or oxidized iron in phyllosilicates. A smaller feature identified at 0.43 microns has been attributed to an Fe(3+) spin-forbidden transition in iron oxides. In the spectra of the two main-belt primitive asteroids 368 Haidea (D) and 877 Walkure (F), weak absorption features which were centered near the location of 0.60-0.65 microns and 0.80-0.90 microns prompted a search for features at these wavelengths and an attempt to identify their origin(s). The CCD reflectance spectra obtained between 1982-1992 were reviewed for similar absorption features located near these wavelengths. The spectra of asteroids in which these absorption features have been identified are shown. These spectra are plotted in order of increasing heliocentric distance. No division of the asteroids by class has been attempted here (although the absence of these features in the anhydrous S-class asteroids, many of which have presumably undergone full heating and differentiation should be noted). For this study, each spectrum was treated as a continuum with discrete absorption features superimposed on it. For each object, a linear least squares fit to the data points defined a simple linear continuum. The linear continuum was then divided into each spectrum, thus removing the sloped continuum and permitting the intercomparison of residual spectral features.

Improving Optical Absorption Models for Harsh Planetary Atmospheres: Laboratory Spectroscopy at Venus Surface Conditions

NASA Astrophysics Data System (ADS)

Cole, Ryan Kenneth; Schroeder, Paul James; Diego Draper, Anthony; Rieker, Gregory Brian

2018-06-01

Modelling absorption spectra in high pressure, high temperature environments is complicated by the increased relevance of higher order collisional phenomena (e.g. line mixing, collision-induced absorption, finite duration of collisions) that alter the spectral lineshape. Accurate reference spectroscopy in these conditions is of interest for mineralogy and radiative transfer studies of Venus as well as other dense planetary atmospheres. We present a new, high pressure, high temperature absorption spectroscopy facility at the University of Colorado Boulder. This facility employs a dual frequency comb absorption spectrometer to record broadband (500nm), high resolution (~0.002nm) spectra in conditions comparable to the Venus surface (730K, 90bar). Measurements of the near-infrared spectrum of carbon dioxide at high pressure and temperature will be compared to modeled spectra extrapolated from the HITRAN 2016 database as well as other published models that include additional collisional physics. This comparison gives insight into the effectiveness of existing absorption databases for modeling the lower Venus atmosphere as well as the need to expand absorption models to suit these conditions.

Measurements and modeling of absorption by CO2 + H2O mixtures in the spectral region beyond the CO2 ν3-band head

NASA Astrophysics Data System (ADS)

Tran, H.; Turbet, M.; Chelin, P.; Landsheere, X.

2018-05-01

In this work, we measured the absorption by CO2 + H2O mixtures from 2400 to 2600 cm-1 which corresponds to the spectral region beyond the ν3 band head of CO2. Transmission spectra of CO2 mixed with water vapor were recorded with a high-resolution Fourier-transform spectrometer for various pressure, temperature and concentration conditions. The continuum absorption by CO2 due to the presence of water vapor was determined by subtracting from measured spectra the contribution of local lines of both species, that of the continuum of pure CO2 as well as of the self- and CO2-continua of water vapor induced by the H2O-H2O and H2O-CO2 interactions. The obtained results are in very good agreement with the unique previous measurement (in a narrower spectral range). They confirm that the H2O-continuum of CO2 is significantly larger than that observed for pure CO2. This continuum thus must be taken into account in radiative transfer calculations for media involving CO2+ H2O mixture. An empirical model, using sub-Lorentzian line shapes based on some temperature-dependent correction factors χ is proposed which enables an accurate description of the experimental results.

Nonlinear control of absorption in one-dimensional photonic crystal with graphene-based defect.

PubMed

Vincenti, M A; de Ceglia, D; Grande, M; D'Orazio, A; Scalora, M

2013-09-15

Perfect, narrow-band absorption is achieved in an asymmetric 1D photonic crystal with a monolayer graphene defect. Thanks to the large third-order nonlinearity of graphene and field localization in the defect layer we demonstrate the possibility to achieve controllable, saturable absorption for the pump frequency.

Tunable electromagnetically induced absorption based on graphene

NASA Astrophysics Data System (ADS)

Cao, Maoyong; Wang, Tongling; Zhang, Huiyun; Zhang, Yuping

2018-04-01

In this paper, an electronically induced absorption (EIA) structure based on graphene at the infrared frequency is proposed. A pair of nanorods is coupled to a ring resonator, resulting in electronically induced transparency (EIT), and then, Babinet's principle is applied to transform the EIT structure into an EIA structure. Based on the bright and dark modes of the coupling schemes, the adjustment of the coupling strength between the dark and bright modes can be achieved by changing the asymmetry degree. In addition, the transparency window and the absorption peak can be tuned by changing the Fermi energy of graphene. This graphene-based EIA structure can develop the path in narrow-band filtering and, absorptive switching in the future.

Collision-Induced Infrared Absorption by Hydrogen-Helium gas mixtures at Thousands of Kelvin

NASA Astrophysics Data System (ADS)

Abel, Martin; Frommhold, Lothar; Li, Xiaoping; Hunt, Katharine L. C.

2010-10-01

The interaction-induced absorption by collisional pairs of H2 molecules is an important opacity source in the atmospheres of the outer planets and cool stars ^[1]. The emission spectra of cool white dwarf stars differ significantly in the infrared from the expected blackbody spectra of their cores, which is largely due to absorption by collisional H2--H2, H2--He, and H2--H complexes in the stellar atmospheres. Using quantum-chemical methods we compute the atmospheric absorption from hundreds to thousands of kelvin ^[2]. Laboratory measurements of interaction-induced absorption spectra by H2 pairs exist only at room temperature and below. We show that our results reproduce these measurements closely ^[2], so that our computational data permit reliable modeling of stellar atmosphere opacities even for the higher temperatures ^[2]. [1] L. Frommhold, Collision-Induced Absorption in Gases, Cambridge University Press, Cambridge, New York, 1993 and 2006 [2] Xiaoping Li, Katharine L. C. Hunt, Fei Wang, Martin Abel, and Lothar Frommhold, ``Collision-Induced Infrared Absorption by Molecular Hydrogen Pairs at Thousands of Kelvin'', International Journal of Spectroscopy, vol. 2010, Article ID 371201, 11 pages, 2010. doi: 10.1155/2010/371201

High-resolution reflectance spectra of Mars in the 2.3-μm region: evidence for the mineral scapolite

USGS Publications Warehouse

Clark, Roger N.; Swayze, Gregg A.; Singer, Robert B.; Pollack, James B.

1990-01-01

patially resolved reflectance spectra of Mars in the 2.2- to 2.4-μm spectral region were obtained in August 1988 using the NASA 3-m Infrared Telescope Facility. The spectra show weak absorption features due to Martian atmospheric carbon monoxide and a surface mineral. Both CO and the mineral absorptions are composed of overlapping narrow features, but in many locations, such as Hellas, Chryse, Eden, and Moab, the mineral absorptions are quite strong, at least 3 times stronger than at the most absorbing wavelengths of CO near 2.33 μm. Therefore CO complicates the analysis of the surface mineral but does not always overwhelm its signature. Model removal of the Martian atmospheric CO has been performed, and the remaining absorption bands are identified as scapolite. Relatively strong absorptions that match bands in the spectrum of scapolite and have little or no CO absorption interference are seen near 2.41, 2.39, and 2.29 μm. Absorption also occurs at the scapolite bands at 2.36 and 2.33 μm, but the analysis is complicated by uncertainty in the atmospheric CO removal at these wavelengths. Weaker scapolite bands are seen at 2.44 and 2.23 μm where there is virtually no atmospheric interference. The scapolite bands observed on Mars are due to HCO3− and HSO4− ions in the scapolite structure. The bicarbonate and bisulfate contents appear to vary with location: the scapolite in Hellas is more bisulfate-rich relative to that in the Chryse/Moab/Eden area. Other locations contain little (Arabia, Syrtis Major, Hellespontica, and Isidis) or no scapolite (e.g., Margaritifer, Ausonia, and Erythraeum). The calculated abundances are unconstrained because the amounts of HCO3− and HSO4− in the Martian scapolites as well as their grain sizes are not known. If the scapolites contain about 3 wt % of each, near the maximum possible, the scapolite abundances probably range from about 5 wt % scapolite at Eden and Hellas; 3–5% at Chryse, Moab, and Oxia Palus; 2–3% at

Hybrid silicon–carbon nanostructures for broadband optical absorption

DOE PAGES

Yang, Wen -Hua; Lu, Wen -Cai; Ho, K. M.; ...

2017-01-25

Proper design of nanomaterials for broadband light absorption is a key factor for improving the conversion efficiency of solar cells. Here we present a hybrid design of silicon–carbon nanostructures with silicon clusters coated by carbon cages, i.e., Si m@C 2n for potential solar cell application. The optical properties of these hybrid nanostructures were calculated based on time dependent density function theory (TDDFT). The results show that the optical spectra of Si m@C 2n are very different from those of pure Si m and C 2n clusters. While the absorption spectra of pure carbon cages and Si m clusters exhibit peaksmore » in the UV region, those of the Si m@C 2n nanostructures exhibit a significant red shift. Superposition of the optical spectra of various Si m@C 2n nanostructures forms a broad-band absorption, which extends to the visible light and infrared regions. As a result, the broadband adsorption of the assembled Si m@C 2n nanoclusters may provide a new approach for the design of high efficiency solar cell nanomaterials.« less

[Absorption Characteristics and Simulation of LLM-105 in the Terahertz Range].

PubMed

Meng, Zeng-rui; Shang, Li-ping; Du, Yu; Deng, Hu

2015-07-01

2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105), a novel explosive with high energy and low sensibility. In order to study the molecular structure characteristics of the explosive, the absorption spectra of LLM-105 in the frequency range of 0.2-2.4 THz were detected by terahertz time-domain spectroscopy (THz-TDS). The results showed that a number of characteristic absorption peaks with different intensity located at 1.27, 1.59, 2.00, 2.08, 2.20, 2.29 THz. The article also simulated the absorption spectra of LLM-105 molecular crystal within 0.2-2.5 THz region by using Materials Studio 6.0 software based on density functional theory (DFT), and the simulated results agreed well with the experimental data except for the peak at 2.29 THz, which verified theoretically the accuracy of the experimental data. In addition, the vibrational modes of the characteristic peaks in the experimental absorption spectra were analyzed and identified, the results showed that the forming of the characteristic absorption peaks and the molecular vibration were closely related, which further provided important laboratory and technology support for the study of the transformation of molecule structure of LLM-105. There was no simulated frequency agreed with the experimental absorption peak at 2.29 THz, which may be caused by the vibration of the crystal lattice or other reasons.

Realistic absorption coefficient of ultrathin films

NASA Astrophysics Data System (ADS)

Cesaria, M.; Caricato, A. P.; Martino, M.

2012-10-01

Both a theoretical algorithm and an experimental procedure are discussed of a new route to determine the absorption/scattering properties of thin films deposited on transparent substrates. Notably, the non-measurable contribution of the film-substrate interface is inherently accounted for. While the experimental procedure exploits only measurable spectra combined according to a very simple algorithm, the theoretical derivation does not require numerical handling of the acquired spectra or any assumption on the film homogeneity and substrate thickness. The film absorption response is estimated by subtracting the measured absorption spectrum of the bare substrate from that of the film on the substrate structure but in a non-straightforward way. In fact, an assumption about the absorption profile of the overall structure is introduced and a corrective factor accounting for the relative film-to-substrate thickness. The method is tested on films of a well known material (ITO) as a function of the film structural quality and influence of the film-substrate interface, both deliberately changed by thickness tuning and doping. Results are found fully consistent with information obtained by standard optical analysis and band gap values reported in the literature. Additionally, comparison with a conventional method demonstrates that our route is generally more accurate even if particularly suited for very thin films.

Luminescence and photoinduced absorption in ytterbium-doped optical fibres

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

Rybaltovsky, A A; Aleshkina, S S; Likhachev, M E

2011-12-31

Photochemical reactions induced in the glass network of an ytterbium-doped fibre core by IR laser pumping and UV irradiation have been investigated by analysing absorption and luminescence spectra. We have performed comparative studies of the photoinduced absorption and luminescence spectra of fibre preforms differing in core glass composition: Al{sub 2}O{sub 3} : SiO{sub 2}, Al{sub 2}O{sub 3} : Yb{sub 2}O{sub 3} : SiO{sub 2}, and P{sub 2}O{sub 5} : Yb{sub 2}O{sub 3} : SiO{sub 2}. The UV absorption spectra of unirradiated preform core samples show strong bands peaking at 5.1 and 6.5 eV, whose excitation plays a key role inmore » photoinduced colour centre generation in the glass network. 'Direct' UV excitation of the 5.1- and 6.5-eV absorption bands at 244 and 193 nm leads to the reduction of some of the Yb{sup 3+} ions to Yb{sup 2+}. The photodarkening of ytterbium-doped fibres by IR pumping is shown to result from oxygen hole centre generation. A phenomenological model is proposed for the IR-pumping-induced photodarkening of ytterbium-doped fibres. The model predicts that colour centre generation in the core glass network and the associated absorption in the visible range result from a cooperative effect involving simultaneous excitation of a cluster composed of several closely spaced Yb{sup 3+} ions.« less

Resonant Raman spectra of diindenoperylene thin films

NASA Astrophysics Data System (ADS)

Scholz, R.; Gisslén, L.; Schuster, B.-E.; Casu, M. B.; Chassé, T.; Heinemeyer, U.; Schreiber, F.

2011-01-01

Resonant and preresonant Raman spectra obtained on diindenoperylene (DIP) thin films are interpreted with calculations of the deformation of a relaxed excited molecule with density functional theory (DFT). The comparison of excited state geometries based on time-dependent DFT or on a constrained DFT scheme with observed absorption spectra of dissolved DIP reveals that the deformation pattern deduced from constrained DFT is more reliable. Most observed Raman peaks can be assigned to calculated A_g-symmetric breathing modes of DIP or their combinations. As the position of one of the laser lines used falls into a highly structured absorption band, we have carefully analyzed the Raman excitation profile arising from the frequency dependence of the dielectric tensor. This procedure gives Raman cross sections in good agreement with the observed relative intensities, both in the fully resonant and in the preresonant case.

Resonant Raman spectra of diindenoperylene thin films.

PubMed

Scholz, R; Gisslén, L; Schuster, B-E; Casu, M B; Chassé, T; Heinemeyer, U; Schreiber, F

2011-01-07

Resonant and preresonant Raman spectra obtained on diindenoperylene (DIP) thin films are interpreted with calculations of the deformation of a relaxed excited molecule with density functional theory (DFT). The comparison of excited state geometries based on time-dependent DFT or on a constrained DFT scheme with observed absorption spectra of dissolved DIP reveals that the deformation pattern deduced from constrained DFT is more reliable. Most observed Raman peaks can be assigned to calculated A(g)-symmetric breathing modes of DIP or their combinations. As the position of one of the laser lines used falls into a highly structured absorption band, we have carefully analyzed the Raman excitation profile arising from the frequency dependence of the dielectric tensor. This procedure gives Raman cross sections in good agreement with the observed relative intensities, both in the fully resonant and in the preresonant case.

Applications of absorption spectroscopy using quantum cascade lasers.

PubMed

Zhang, Lizhu; Tian, Guang; Li, Jingsong; Yu, Benli

2014-01-01

Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.

New in situ Aerosol Spectral Optical Measurements over 300-700 nm, Extinction and Total Absorption, Paired with Absorption from Water- and Methanol-soluble Aerosol Extracts