These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Models of the iron K_alpha fluorescence line and the Compton shoulder in irradiated accretion disk spectra  

E-print Network

We present a full set of model atmosphere equations for the accretion disk around a supermassive black hole irradiated by hard X-ray lamp of power-law spectral distribution. Model equations allow for multiple Compton scattering of radiation on free electrons, and for large relative photon-electron energy exchange at the time of scattering. We present spectra in specific intensities integrated over the disk surface. Theoretical outgoing intensity spectra show soft X-ray excess below 1 keV, and distinct K_alpha and K_beta fluorescent lines of iron. We demonstrate the existence of the Compton Shoulder and claim that it can contribute to the asymmetry and equivalent widths of some observed Fe K_alpha lines in AGN. Our models exhibit the effect of limb-brightening in reflected X-rays.

Rozanska, A

2008-01-01

2

Models of the iron K_alpha fluorescence line and the Compton shoulder in irradiated accretion disk spectra  

E-print Network

We present a full set of model atmosphere equations for the accretion disk around a supermassive black hole irradiated by hard X-ray lamp of power-law spectral distribution. Model equations allow for multiple Compton scattering of radiation on free electrons, and for large relative photon-electron energy exchange at the time of scattering. We present spectra in specific intensities integrated over the disk surface. Theoretical outgoing intensity spectra show soft X-ray excess below 1 keV, and distinct K_alpha and K_beta fluorescent lines of iron. We demonstrate the existence of the Compton Shoulder and claim that it can contribute to the asymmetry and equivalent widths of some observed Fe K_alpha lines in AGN. Our models exhibit the effect of limb-brightening in reflected X-rays.

Agata Ró?a?ska; Jerzy Madej

2008-04-08

3

XMM-Newton Observation of Fe K(alpha) Emission from a BAL QSO: Mrk 231  

NASA Technical Reports Server (NTRS)

We present results from a 20 ksec XMM-Newton observation of Mrk 231. EPIC spectral data reveal strong line emission due to Fe K alpha, which has rarely been detected in this class, as BAL QSOs are very faint in the X-ray band. The line energy is consistent with an origin in neutral Fe. The width of the line is equivalent to a velocity dispersion approximately 18,000 kilometers per second and thus the line may be attributed to transmission and/or reflection from a distribution of emitting clouds. If, instead, the line originates in the accretion disk then the line strength and flat X-ray continuum support some contribution from a reflected component, although the data disfavor a model where the hard X-ray band is purely reflected X-rays. The line parameters are similar to those obtained for the Fe Ka line detected in another BAL QSO, H1413 + 117.

Turner, T. J.; Kraemer, S. B.

2003-01-01

4

Evolution of Iron K Alpha Line Emission in the Black Hole Candidate GX 339-4  

NASA Technical Reports Server (NTRS)

GX 339-4 was regularly monitored with the Rossi X-Ray Timing Explorer during a period (in 1999) when its X-ray flux decreased significantly (from 4.26 x 10(exp -10) to 7.6 x 10(exp -12) ergs in the 3-20 keV band), as the source settled into the 'off state.' Our spectral analysis revealed the presence of a prominent iron K alpha line in the observed spectrum of the source for all observations. The line shows an interesting evolution: it is centered at approx. 6.4 keV when the measured flux is above 5 x 10(exp -1) ergs per sq cm/s but is shifted to approx. 6.7 keV at lower fluxes. The equivalent width of the line appears to increase significantly toward lower fluxes, although it is likely to be sensitive to calibration uncertainties. While the fluorescent emission of neutral or mildly ionized iron atoms in the accretion disk can perhaps account for the 6.4 keV line, as is often invoked for black hole candidates, it seems difficult to understand the 6.7 keV line with this mechanism because the disk should be less ionized at lower fluxes (unless its density changes drastically). On the other hand, the 6.7 keV line might be due to a recombination cascade of hydrogen- or helium-like iron ions in an optically thin, highly ionized plasma. We discuss the results in the context of proposed accretion models.

Feng, Y. X.; Zhang, S. N.; Sun, X.; Durouchoux, Ph.; Chen, Wan; Cui, Wei

2001-01-01

5

Interpretation of the Si K{alpha} x-ray spectra accompanying the stopping of swift Ca ions in low-density SiO{sub 2} aerogel  

SciTech Connect

This article presents a detailed analysis of the K{alpha} x-ray spectra of Si induced by 11.4 MeV/u Ca projectiles penetrating a low-density SiO{sub 2} aerogel target measured with high spectral and spatial resolution at the UNILAC accelerator at GSI-Darmstadt. The low-density material used in the experiment was crucial for the space-resolved studies of the Si x-ray radiation (for different energies of stopping Ca ions). The stopping length of the 11 MeV/u Ca ions reaches up to 10 mm in the low-density SiO{sub 2} aerogel, whereas in regular quartz solid targets it is about 100 times shorter. The analysis of the x-ray spectra emitted by the stopping medium has shown a high level of the L-shell ionization, especially in the later considered phase (E{sub p{approx}}5 MeV/u) of the stopping process. It has been further demonstrated that the population of the highly ionized states produced in the ion-atom collisions can be substantially reduced in the time between the collision and the x-ray emission due to the very intense rearrangement processes occurring in Si situated in the chemical environment of oxygen atoms. Moreover, comparison of the experimental values of the K{alpha} L-shell satellite energy shifts with the results of the multiconfiguration Dirac-Fock calculations allows us to find that Si valence electron configuration is enriched due to electron transfer from valence-electron-rich oxygen atoms into highly ionized silicon atoms. Our results indicate that the Coulomb explosion in a highly ionized track core is prevented by rapid neutralization in the femtosecond time scale.

Rzadkiewicz, J. [Andrzej Soltan Institute for Nuclear Studies, PL-05-400 Swierk (Poland); Institute of Plasma Physics and Laser Microfusion, Hery 23, PL-01-497 Warsaw (Poland); Gojska, A. [Andrzej Soltan Institute for Nuclear Studies, PL-05-400 Swierk (Poland); Rosmej, O. [Gesellschaft fuer Schwerionenforschung mbH, Plasma Physik, Darmstadt (Germany); Polasik, M.; Slabkowska, K. [Faculty of Chemistry, Nicholas Copernicus University, PL-87-100 Torun (Poland)

2010-07-15

6

A POSSIBLE ULTRA STRONG AND BROAD Fe K{alpha} EMISSION LINE IN SEYFERT 2 GALAXY IRAS 00521-7054  

SciTech Connect

We present XMM-Newton spectra of the Seyfert 2 Galaxy IRAS 00521-7054. A strong feature at {approx}6 keV (observer's frame) can be formally fitted with a strong (EW = 1.3 {+-} 0.3 keV in the rest frame) and broad Fe K{alpha} line, extending down to 3 keV. The underlying X-ray continuum could be fitted with an absorbed power law (with {Gamma} = 1.8 {+-} 0.2 and N{sub H} 5.9{sup +0.6}{sub -0.7} Multiplication-Sign 10{sup 22} cm{sup -2}) plus a soft component. If due to relativistically smeared reflection by an X-ray illuminated accretion disk, the spin of the supermassive black hole (SMBH) is constrained to be 0.97{sup +0.03}{sub -0.13} (errors at 90% confidence level for one interesting parameter), and the accretion system is viewed at an inclination angle of 37 Degree-Sign {+-} 4 Degree-Sign . This would be the first type 2 active galactic nucleus reported with strong red Fe K{alpha} wing detected which demands a fast rotating SMBH. The unusually large EW would suggest that the light bending effect is strong in this source. Alternatively, the spectra could be fitted by a dual-absorber model (though with a global {chi}{sup 2} higher by {approx}6 for 283 dof) with N{sub H1} 7.0 {+-} 0.8 Multiplication-Sign 10{sup 22} cm{sup -2} covering 100% of the X-ray source, and N{sub H2} = 21.7{sup +5.6}{sub -5.4} Multiplication-Sign 10{sup 22} cm{sup -2} covering 71%, which does not require an extra broad Fe K{alpha} line.

Tan, Y.; Wang, J. X.; Shu, X. W.; Zhou Youyuan, E-mail: tanyin29@mail.ustc.edu.cn, E-mail: jxw@ustc.edu.cn, E-mail: xwshu@mail.ustc.edu.cn, E-mail: yyzhou@ustc.edu.cn [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2012-03-15

7

The Seyfert 2 galaxy NGC 2110: hard X-ray emission observed by NuSTAR and variability of the iron K$\\alpha$ line  

E-print Network

We present NuSTAR observations of the bright Seyfert 2 galaxy NGC 2110 obtained in 2012, when the source was at the highest flux level ever observed, and in 2013, when the source was at a more typical flux level. We include archival observations from other X-ray satellites, namely XMM-Newton, Suzaku, BeppoSAX, Chandra and Swift. Simultaneous NuSTAR and Swift broad band spectra (in the 3-80 keV range) indicate a cutoff energy $E_{\\rm c}>210$ keV, with no detectable contribution from Compton reflection. NGC 2110 is one of the very few sources where no evidence for distant Compton thick scattering is found and, by using temporal information collected over more than a decade, we investigate variations of the iron K$\\alpha$ line on time scales of years. The Fe K$\\alpha$ line is likely the sum of two components: one constant (originating from distant Compton-thick material) and the other one variable and linearly correlated with the source flux (possibly arising from Compton-thin material much closer to the black h...

Marinucci, A; Bianchi, S; Lu, T N; Arevalo, P; Balokovi?, M; Ballantyne, D; Bauer, F E; Boggs, S E; Christensen, F E; Craig, W W; Gandhi, P; Hailey, C J; Harrison, F; Puccetti, S; Rivers, E; Walton, D J; Stern, D; Zhang, W

2014-01-01

8

The role of hot electron refluxing in laser-generated K-alpha sources  

NASA Astrophysics Data System (ADS)

A study of the contribution of refluxing electrons in the production of K-alpha radiation from high-intensity laser irradiated thin targets has been performed. Thin copper foils both freestanding, and backed by a thick substrate were irradiated with laser pulses of energies around 100 J at intensities ranging from below 1017 to above 1019 W/cm2. At high laser intensities we find a strong reduction in the K-alpha yield from targets backed by the substrate. The observed yield reduction is in good agreement with a simple model using hot electron spectra from particle-in-cell simulations or directly inferred from the measured bremsstrahlung emission and can therefore be interpreted as due to the suppression of hot electron refluxing. The study shows that refluxing electrons play a dominant role in high-intensity laser driven K- alpha generation and have to be taken into account in designing targets for laser driven high-flux K-alpha sources.

Neumayer, P.; Aurand, B.; Basko, M.; Ecker, B.; Gibbon, P.; Hochhaus, D. C.; Karmakar, A.; Kazakov, E.; Kühl, T.; Labaune, C.; Rosmej, O.; Tauschwitz, An.; Zielbauer, B.; Zimmer, D.

2010-10-01

9

DYNAMIC SPECTRA OF JUPITER'S DECAMETRIC EMISSION, 1961  

Microsoft Academic Search

Sources for the decametric emission from Jupiter are suggested and ; evidence for their existence presented. Dynamic spectra for negative and ; positive drift emission and composite spectra are displayed and discussed. An ; explanation of the emission based on Jupiter's possession of energetic radiation ; belts similar to earth's is presented. (D.C.W.);

James W. Warwick

1963-01-01

10

Diffuse emission and pathological Seyfert spectra  

NASA Technical Reports Server (NTRS)

In this annual ROSAT status report, the diffuse emission and spectra from Seyfert galaxies are examined. Three papers are presented and their contents include the soft x-ray properties and spectra of a binary millisecond pulsar, the PSPC and HRI observations of a Starburst/Seyfert 2 Galaxy, and an analysis of the possibility of x-ray luminous starbursts in the Einstein Medium Sensitivity Survey.

Halpern, Jules P.

1995-01-01

11

Detection of climate forcing using emission spectra  

NASA Technical Reports Server (NTRS)

We discuss the use of thermal emission spectra recorded by satellites to construct climate indices that can detect the evolution of a specific climate forcing in a time series. The two important issues are selectivity against climate forcings other than one that is sought, and sensitivity to the required forcing. We show that indices with selectivity can be found, and that their sensitivity can be high.

Goody, Richard; Haskins, Robert; Abdou, Wedad; Chen, Luke

1995-01-01

12

Relativistic Fe K$\\alpha$ Line Revealed in the Composite X-ray Spectrum of Narrow Line Seyfert 1 Galaxies --- do their black holes have averagely low or intermediate spins?  

E-print Network

While a broad profile of the Fe K$\\alpha$ emission line is frequently found in the X-ray spectra of typical Seyfert galaxies, the situation is unclear in the case of Narrow Line Seyfert 1 galaxies (NLS1s)---an extreme subset which are generally thought to harbor less massive black holes with higher accretion rates. In this paper, the ensemble property of the Fe K$\\alpha$ line in NLS1s is investigated by stacking the X-ray spectra of a large sample of 51 NLS1s observed with {\\it XMM-Newton}. The composite X-ray spectrum reveals a prominent, broad emission feature over 4--7 keV, characteristic of the broad Fe K$\\alpha$ line. In addition, there is an indication for a possible superimposing narrow (unresolved) line, either emission or absorption, corresponding to Fe XXVI or Fe XXV, respectively. The profile of the broad emission feature can well be fitted with relativistic broad-line models, with the line energy consistent either with 6.4 keV (i.e., neutral Fe) or with 6.67 keV (i.e., highly ionized Fe), in the c...

Liu, Zhu; Lu, Youjun; Zhou, Xin-Lin

2014-01-01

13

Extraction Of Emissivities From Thermal Infrared Spectra  

NASA Technical Reports Server (NTRS)

Report presents evaluation of two techniques for processing multispectral data. One technique for extraction of emissivity data called "model emittance calculation." Other technique called "thermal log residuals."

Hook, Simon J.; Kahle, Anne B.

1994-01-01

14

Mineral abundance determination: Quantitative deconvolution of thermal emission spectra  

Microsoft Academic Search

A linear retrieval (spectral deconvolution) algorithm is developed and applied to high-resolution laboratory infrared spectra of particulate mixtures and their end- members. The purpose is to place constraints on, and test the viability of, linear spectral deconvolution of high-resolution emission spectra. The effects of addition of noise, data reproducibility, particle size variation, an increasing number of minerals in the mixtures,

Michael S. Ramsey; Philip R. Christensen

1998-01-01

15

Observations of neutral iron emission in twilight spectra  

NASA Technical Reports Server (NTRS)

A method is presented for the analysis of twilight airglow spectra that may be contaminated by atmospheric continuum emission of unknown brightness. The necessity of correcting for this continuum emission when measuring weak airglow features in twilight is illustrated by application of the method to the neutral iron line at 3860 A.

Tepley, C. A.; Meriwether, J. W., Jr.; Walker, J. C. G.; Mathews, J. D.

1981-01-01

16

Modeling microwave emission spectra of layered snowpacks  

Microsoft Academic Search

A thermal microwave emission model of layered snowpacks (MEMLS) (Wiesmann and Matzler, 1997) was developed for the frequency range, 5 to 100 GHz. It is based on radiative transfer, using six-flux theory to describe multiple volume scattering and absorption, including radiation trapping due to internal reflection and a combination of coherent and incoherent superpositions of reflections between layer interfaces. The

A. Wiesmann; C. Hatzler; D. Hiltbrunner

1998-01-01

17

Martian Analogues Emissivity Spectra From the Berlin Emissivity Database (BED)  

Microsoft Academic Search

Remote sensing infrared spectroscopy is the principal field of investigation for planetary surfaces composition. Past, present and future missions to bodies in the solar system include in their payload instruments measuring the emerging radiation in the infrared range. For the interpretation of the measured data an emissivity spectral library of planetary analog materials is needed. The Berlin Emissivity Database (BED)

A. Maturilli; J. Helbert; L. Moroz

2006-01-01

18

Mineral abundance determination: Quantitative deconvolution of thermal emission spectra  

Microsoft Academic Search

A linear retrieval (spectral deconvolution) algorithm is developed and applied to high-resolution laboratory infrared spectra of particulate mixtures and their end-members. The purpose is to place constraints on, and test the viability of, linear spectral deconvolution of high-resolution emission spectra. The effects of addition of noise, data reproducibility, particle size variation, an increasing number of minerals in the mixtures, and

Michael S. Ramsey; Philip R. Christensen

1998-01-01

19

FIGARO : measuring neutron emission spectra with a white neutron source /.  

SciTech Connect

Neutron emission spectra from reactions induced by fast neutrons are of importance in basic physics and applications. Very few data are available in the literature over a wide range of incident neutron energies such as produced with a white neutron source. The FIGARO facility at the WNR/LANSCE neutron source has been established to measure such neutron emission over a range of incident neutron energies from 1 to over 100 MeV. Using the time-of-flight technique twice (once to determine the incident neutron energy and again to determine the outgoing neutron energy), we are measuring neutron emission spectra for several reactions such as (n,n') and (n,f). Neutron emission from inelastic scattering gives information on the level density of excited states of the target nucleus. Our first measurements are on structural materials such as iron.

Haight, Robert C.; O'Donnell, J. M.; Zanini, L.; Devlin, M.; Rochman, D. (Dimitri)

2002-01-01

20

Optical emission spectra of chromium doped nanocrystalline zinc gallate  

Microsoft Academic Search

Optical emission spectra of nanocrystalline zinc gallate (ZnGa2O4) and trivalent chromium ion doped zinc gallate (ZnGa2O4:Cr3+) are reported for different concentrations of the dopant ion. The measurements have been carried out over the temperature range between 77 and 296 K. The emission spectrum of nanocrystalline ZnGa2O4 shows two broad peaks. The intensity variation in these peaks, with temperature, is indicative

P. Dhak; U. K. Gayen; S. Mishra; P. Pramanik; A. Roy

2009-01-01

21

Hot Electron Generation and Transport Using K(alpha) Emission  

SciTech Connect

We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40{micro}m diameter wire emulating a 40{micro}m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of prepulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.

Akli, K U; Stephens, R B; Key, M H; Bartal, T; Beg, F N; Chawla, S; Chen, C D; Fedosejevs, R; Freeman, R R; Friesen, H; Giraldez, E; Green, J S; Hey, D S; Higginson, D P; Hund, J; Jarrott, L C; Kemp, G E; King, J A; Kryger, A; Lancaster, K; LePape, S; Link, A; Ma, T; Mackinnon, A J; MacPhee, A G; McLean, H S; Murphy, C; Norreys, P A; Ovchinnikov, V; Patel, P K; Ping, Y; Sawada, H; Schumacher, D; Theobald, W; Tsui, Y Y; Van Woerkom, L D; Wei, M S; Westover, B; Yabuuchi, T

2009-10-15

22

Spectra  

NSDL National Science Digital Library

Spectra is a very informative website about how astronomers use spectra to understand what stars are made of, their structures, and their evolution. The page begins with an introduction to the electromagnetic spectrum and then goes into great detail about the properties of light. Then it talks about how matter both creates and destroys radiation. Then it discusses how to interpret absorption and emission lines. The website ends with how astronomers use spectra to understand stars, galaxies, other objects in the universe.

Kaler, James

2004-07-16

23

Spreadsheet-Based Program for Simulating Atomic Emission Spectra  

ERIC Educational Resources Information Center

A simple Excel spreadsheet-based program for simulating atomic emission spectra from the properties of neutral atoms (e.g., energies and statistical weights of the electronic states, electronic partition functions, transition probabilities, etc.) is described. The contents of the spreadsheet (i.e., input parameters, formulas for calculating…

Flannigan, David J.

2014-01-01

24

Fluorescence emission spectra of plant leaves and plant constituents  

Microsoft Academic Search

Summary The UV-B radiation (e.g. 337 nm) induced blue fluorescence (BF) and red chlorophyll fluorescence spectra (RF) of green leaves from plants with different leaf structure were determined and the possible nature and candidates of the blue fluorescence emission investigated. The blue fluorescence BF is characterized by a main maximum in the 450 nm region and in most cases by

M. Lang; F. Stober; H. K. Lichtenthaler

1991-01-01

25

A CORRELATION BETWEEN STELLAR ACTIVITY AND HOT JUPITER EMISSION SPECTRA  

SciTech Connect

We present evidence for a correlation between the observed properties of hot Jupiter emission spectra and the activity levels of the host stars measured using Ca II H and K emission lines. We find that planets with dayside emission spectra that are well-described by standard one-dimensional atmosphere models with water in absorption (HD 189733, TrES-1, TrES-3, WASP-4) orbit chromospherically active stars, while planets with emission spectra that are consistent with the presence of a strong high-altitude temperature inversion and water in emission orbit quieter stars. We estimate that active G and K stars have Lyman {alpha} fluxes that are typically a factor of 4-7 times higher than quiet stars with analogous spectral types and propose that the increased UV flux received by planets orbiting active stars destroys the compounds responsible for the formation of the observed temperature inversions. In this paper, we also derive a model-independent method for differentiating between these two atmosphere types using the secondary eclipse depths measured in the 3.6 and 4.5 {mu}m bands on the Spitzer Space Telescope and argue that the observed correlation is independent of the inverted/non-inverted paradigm for classifying hot Jupiter atmospheres.

Knutson, Heather A.; Howard, Andrew W.; Isaacson, Howard, E-mail: hknutson@berkeley.ed [Department of Astronomy, University of California, Berkeley, CA 94720-3411 (United States)

2010-09-10

26

Analysis of far-infrared emission Fourier transform spectra  

NASA Technical Reports Server (NTRS)

An analysis method that uses the nonlinear least-squares fit technique has been developed for emission spectra obtained with a Fourier transform spectrometer. This method is used for the analysis of submillimeter-region atmospheric emission spectra obtained with a balloon-borne FT spectrometer that was carried out as a correlative measurement for the Limb IR Monitor of the Stratosphere (LIMS) satellite experiment. The retrieved mixing ratios of H2O and O3 in the stratosphere from four spectral intervals have standard deviations of about 10 percent, and the average values agree to within 10 percent of corresponding results from the LIMS satellite experiment which used a broadband emission radiometer in the IR region.

Park, J. H.; Carli, B.

1986-01-01

27

Structural Effects of Oncogenic PI3K alpha Mutations  

SciTech Connect

Physiological activation of PI3K{alpha} is brought about by the release of the inhibition by p85 when the nSH2 binds the phosphorylated tyrosine of activated receptors or their substrates. Oncogenic mutations of PI3K{alpha} result in a constitutively activated enzyme that triggers downstream pathways that increase tumor aggressiveness and survival. Structural information suggests that some mutations also activate the enzyme by releasing p85 inhibition. Other mutations work by different mechanisms. For example, the most common mutation, His1047Arg, causes a conformational change that increases membrane association resulting in greater accessibility to the substrate, an integral membrane component. These effects are examples of the subtle structural changes that result in increased activity. The structures of these and other mutants are providing the basis for the design of isozyme-specific, mutation-specific inhibitors for individualized cancer therapies.

S Gabelli; C Huang; D Mandelker; O Schmidt-Kittler; B Vogelstein; L Amzel

2011-12-31

28

Study of silver K{alpha} and bremsstrahlung radiation from short-pulse laser-matter interactions with applications for x-ray radiography  

SciTech Connect

Measurements of K{alpha} radiation yield and x-ray bremsstrahlung emission from thin-foil silver targets are presented. The targets were irradiated by a short pulse laser with intensities from 5x10{sup 16} to 10{sup 18} W/cm{sup 2} at 40 ps. Single hit charge-coupled device detectors, differential filter-stack detectors, and a crystal spectrometer were used to investigate the angular distribution of the K{alpha} and bremsstrahlung x-rays. This study is the first to use a broadband detector to estimate the absolute numbers of K{alpha} photons and to determine K{alpha} to bremsstrahlung ratios. The relevance of this work in the context of x-ray diffraction and x-ray radiography is discussed.

Westover, B.; Beg, F. N. [Center for Energy Research, University of California, San Diego, California 92093-0411 (United States); MacPhee, A.; Chen, C.; Hey, D.; Maddox, B.; Park, H.-S.; Remington, B. [Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); Ma, T. [Center for Energy Research, University of California, San Diego, California 92093-0411 (United States); Lawrence Livermore National Laboratory, Livermore, California 94551 (United States)

2010-08-15

29

A K-alpha x-ray source using high energy and high repetition rate laser system for phase contrast imaging  

PubMed Central

K-alpha x-ray sources from laser produced plasmas provide completely new possibilities for x-ray phase-contrast imaging applications. By tightly focusing intense femtosecond laser pulses onto a solid target K-alpha x-ray pulses are generated through the interaction of energetic electrons created in the plasma with the bulk target. In this paper, we present a continuous and efficient Mo K-alpha x-ray source produced by a femtosecond laser system operating at 100 Hz repetition rate with maximum pulse energy of 110 mJ before compression. The source has an x-ray conversion efficiency of greater than 10?5 into K-alpha line emission. In preparation for phase contrast imaging applications, the size of the resultant K-alpha x-ray emission spot has been also characterized. The source exhibits sufficient spatial coherence to observe phase contrast. We observe a relatively small broadening of the K-alpha source size compared to the size of the laser beam itself. Detailed characterization of the source including the x-ray spectrum and the x-ray average yield along with phase contrast images of test objects will be presented. PMID:20046807

Fourmaux, Sylvain; Kieffer, Jean-Claude; Kincaid, Russell; Krol, Andrzej

2009-01-01

30

Infrared emission spectra of candidate interstellar aromatic molecules  

NASA Technical Reports Server (NTRS)

Interstellar dust is responsible, through surface reactions, for the creation of molecular hydrogen, the main component of the interstellar clouds in which new stars form. Intermediate between small, gas-phase molecules and dust are the polycyclic aromatic hydrocarbons (PAHs). Such molecules could account for 2-30% of the carbon in the Galaxy, and may provide nucleation sites for the formation of carbonaceous dust. Although PAHs have been proposed as the sources of the unidentified infrared emission bands that are observed in the spectra of a variety of interstellar sources, the emission characteristics of such molecules are still poorly understood. Here we report laboratory emission spectra of several representative PAHs, obtained in conditions approximating those of the interstellar medium, and measured over the entire spectral region spanned by the unidentified infrared bands. We find that neutral PAHs of small and moderate size can at best make only a minor contribution to these emission bands. Cations of these molecules, as well as much larger PAHs and their cations, remain viable candidates for the sources of these bands.

Schlemmer, S.; Balucani, N.; Wagner, D. R.; Steiner, B.; Saykally, R. J.

1996-01-01

31

Emission Spectra of Fallback Disks Around Young Neutron Stars  

E-print Network

The nature of the energy source powering anomalous X-ray pulsars is uncertain. Proposed scenarios involve either an ultramagnetized neutron star, or accretion onto a neutron star. We consider the accretion model proposed recently by Chatterjee, Hernquist & Narayan, in which a disk is fed by fallback material following a supernova. We compute the optical, infrared, and submillimeter emission expected from such a disk, including both viscous dissipation and reradiation of X-ray flux impinging on the disk from the pulsar. We find that it is possible with current instruments to put serious constraints on this and on other accretion models of AXPs. Fallback disks could also be found around isolated radio pulsars and we compute the corresponding spectra. We show that the excess emission in the R and I bands observed for the pulsar PSR 0656+14 is broadly consistent with emission from a disk.

Rosalba Perna; Lars Hernquist; Ramesh Narayan

1999-12-15

32

Investigating the origin of emissivity features in airless body spectra  

NASA Astrophysics Data System (ADS)

It has long been noted that mid-infrared emissivity features remote observations of airless bodies do not generally match reflectance and ambient thermal emission laboratory measurements. Recently Vernazza et al., (2012) conducted reflectance experiments and successfully reproduced spectral differences by doping a fine (<30 micron) particulate samples of meteorite and/or minerals with KBr (potassium bromide) powder, which is transparent in the infrared. Their results suggest that porosity and/or cavity effects are significant in modifying the observed spectra of asteroids and derived values of surface thermal inertia. At similar wavelengths, the lunar community has long supported the theory that radiative transfer was a driving phenomenon through the creation of strong thermal gradients in the upper 100 microns of a particulate surface (e.g. Logan et al., 1973; Henderson et al., 1995). These thermal gradients are steep within the depth of thermal emission causing a strong wavelength dependence to the observed thermal emission spectrum. For example, strong absorptions like Reststrahlen Bands emit from the colder, shallower surface while strongly transparent features such as the Christiansen Feature emit from the warmer, deeper surface. To study these effects, we have built simulated airless body thermal emission chambers at University of Oxford and JPL (Thomas et al., 2012). In this study we investigate both radiative transfer and porosity phenomenon by measuring KBr-doped samples in reflectance and both ambient and simulated airless body emission.

Greenhagen, B. T.; Bowles, N. E.; Thomas, I.; Donaldson Hanna, K. L.

2013-12-01

33

Infrared emission spectra from operating elastohydrodynamic sliding contacts  

NASA Technical Reports Server (NTRS)

Infrared emission spectra from an operating EHD sliding contact were obtained through a diamond window for an aromatic polymer solute present in equal concentration in four different fluids. Three different temperature ranges, three different loads, and three different speeds for every load were examined. Very sensitive Fourier spectrophotometric (Interferometric) techniques were employed. Band Intensities and band intensity ratios found to depend both on the operating parameters and on the fluid. Fluid film and metal surface temperatures were calculated from the spectra and their dependence on the mechanical parameters plotted. The difference between these temperatures could be plotted against shear rate on one curve for all fluids. However, at the same shear rate the difference between bulk fluid temperature and diamond window temperature was much higher for one of the fluids, a traction fluid, than for the others.

Lauer, J. L.

1976-01-01

34

Interpreting the ionization sequence in AGN emission-line spectra  

NASA Astrophysics Data System (ADS)

We investigate the physical cause of the great range in the ionization level seen in the spectra of narrow-lined active galactic nuclei (AGN). We used a recently developed technique called mean field independent component analysis to identify examples of individual Sloan Digital Sky Survey galaxies whose spectra are not dominated by emission due to star formation (SF), which we therefore designate as AGN. We assembled high signal-to-noise ratio (S/N) composite spectra of a sequence of these AGN defined by the ionization level of their narrow-line regions (NLR), and extending down to very low ionization cases. We then used a local optimally emitting cloud (LOC) model to fit emission-line ratios in this AGN sequence, including the weak lines that can be measured only in the co-added spectra. These weak line ratios provide consistency checks on the density, temperature, abundances and ionizing continuum of Seyfert galaxies determined from strong-line ratios. After integrating over a wide range of clouds at different radii and densities, our models indicate that the radial extent of the NLR is the major parameter in determining the position of higher to moderate ionization AGN along our sequence. This provides a physical interpretation for their systematic variation. Higher ionization AGN contain optimally emitting clouds that are more concentrated towards the central continuum source than in lower ionization AGN. Our LOC models indicate that for the special set of objects that lie on our AGN sequence, the ionizing luminosity is anti-correlated with the NLR ionization level, and hence anticorrelated with the radial concentration and actual physical extent of the NLR. A possible interpretation that deserves further exploration is that the ionization sequence might be an age sequence where low ionization objects are older and have systematically cleared out their central regions by radiation pressure. We consider the alternative that our AGN sequence instead represents a mixing curve combining SF and AGN spectra in different proportions, but argue that while many galaxies in fact do have this type of composite spectra, our AGN sequence appears to be a special set of objects with negligible SF excitation.

Richardson, Chris T.; Allen, James T.; Baldwin, Jack A.; Hewett, Paul C.; Ferland, Gary J.

2014-01-01

35

A Thermal Infrared Emission Spectra Library for Unpowdered Meteorites  

NASA Astrophysics Data System (ADS)

Mid-infrared thermal emission spectra have been obtained for whole-rock (unpowdered) samples of the following 25 meteorites: Abee, Admire, Allende, Bondoc, Brahin, Bruderheim, Canyon Diablo, Carichic, Clover Springs, Dhofar 007, Estherville, Holbrook, Juancheng, Kapoeta, Long Island, Marion, Modoc, ALH77225, ALH77233, ALH84082, LEW85322, ALH85025, ALH79029, ALH77004, and LEW86015. Meteorites were provided through the Center for Meteorite Studies at ASU, Johnson Space Center and the NASA Antarctic Meteorite Working Group, and from private collections. The database was prepared to aid in the on-going detection and interpretation of meteorites on Mars using the Miniature Thermal Emission Spectrometer (Mini-TES) instruments on both Mars Exploration Rovers. It therefore includes several specimens of low, moderate, and high weathering intensities, reflecting different levels of water exposure in desert and non-desert environments. Unweathered falls are also considered. Samples represent all three chondrite classes, stony irons (mesosiderites and pallasites), and select achondrites. Special consideration is given to dust-covered iron-nickel meteorites as part of a separate study designed to evaluate the Mini-TES spectra of iron-nickel meteorites on Mars. All samples were analyzed at or near a temperature of 80° C using a modified Nicolet Nexus 670 FT-IR spectrometer at the Mars Space Flight Facility at Arizona State University. Data were collected within the 2000 to 200 wavenumber (5 to 50 microns) mid-infrared range. The results show that many meteorite types display moderate to wide variability in the depth and position of prominent absorption features, making them easily distinguishable from each other. Most previous meteorite spectroscopy studies have either focused on near-infrared reflectance spectra [e.g. 1], and/or involved powdered samples to represent asteroid regoliths in the mid-infrared [e.g. 2 & 3]. Particle size- related issues are often at the heart of interpretation of asteroid spectroscopic studies in the mid-infrared [4]. However, the high-resolution Itokawa imaging results of the Hayabusa mission have shown that not all asteroid surfaces are dominated by powdered materials [e.g. 5]. It is therefore anticipated that whole-rock, mid-infrared emission spectra may serve a further purpose in studies conducted with Spitzer Space Telescope and other space-born observatories equipped with mid-infrared detectors. The library will therefore continue to be augmented with additional spectra, to include unweathered carbonaceous chondrites and achondrites at a minimum. All spectra are available through the Arizona State University Thermal Emission Spectral Library. References: [1] Sato K. and Miyamoto M. (1998) Antarctic Meteorite Research 11, 155-162. [2] Salisbury J.W. et al. (1991) NASA Technical Memorandum #4300, 262-204. [3] Dameron S.N. and Burbine T.H. (2006) LPSC XXXVII, abstract #1828. [4] Emery J.P. et al. (2006) Icarus 182, 496-512. [5] Miyamoto et al. (2007) Science 316, 1011- 1014.

Ashley, J. W.; Christensen, P. R.

2007-12-01

36

Cross-sectional characteristics of visible emission spectra in partially premixed flames  

Microsoft Academic Search

Visible spectral characteristics of cross-sectional emissions from a partially premixed methane\\/air flame and a propane\\/air flame have been investigated. An optical train with a two-axis scanning mirror system was used to record line-of-sight emission spectra from 354nm to 618nm, and inversion technique was applied to obtain cross-sectional emission spectra. By analyzing the reconstructed emission spectra, cross-sectional intensities of CH and

K. S. Ha; S. Choi

1999-01-01

37

Neutron emission profiles and energy spectra measurements at JET  

NASA Astrophysics Data System (ADS)

The Joint European Toras (JET, Culham, UK) is the largest tokamak in the world. It is devoted to nuclear fusion experiments of magnetic confined Deuterium (D) or Deuterium-Tritium (DT) plasmas. JET has been upgraded over the years and recently it has also become a test facility of the components designed for ITER, the next step fusion machine under construction in Cadarache (France). JET makes use of many different diagnostics to measure the physical quantities of interest in plasma experiments. Concerning D or DT plasmas neutron production, various types of detectors are implemented to provide information upon the neutron total yield, emission profile and energy spectrum. The neutron emission profile emitted from the JET plasma poloidal section is reconstructed using the neutron camera (KN3). In 2010 KN3 was equipped with a new digital data acquisition system capable of high rate neutron measurements (<0.5 MCps). A similar instrument will be implemented on ITER and it is currently in its design phase. Various types of neutron spectrometers with different view lines are also operational on JET. One of them is a new compact spectrometer (KM12) based on organic liquid scintillating material which was installed in 2010 and implements a similar digital data acquisition system as for KN3. This article illustrates the measurement results of KN3 neutron emission profiles and KM 12 neutron energy spectra from the latest JET D experimental campaign C31.

Giacomelli, L.; Conroy, S.; Belli, F.; Gorini, G.; Horton, L.; Joffrin, E.; Lerche, E.; Murari, A.; Popovichev, S.; Riva, M.; Syme, B.; JET EFDA Contributors

2014-08-01

38

Fast-electron transport and heating of solid targets in high-intensity laser interactions measured by K{alpha} fluorescence  

SciTech Connect

We present experimental results on fast-electron energy deposition into solid targets in ultrahigh intensity laser-matter interaction. X-ray K{alpha} emission spectroscopy with absolute photon counting served to diagnose fast-electron propagation in multilayered targets. Target heating was measured from ionization-shifted K{alpha} emission. Data show a 200 {mu}m fast-electron range in solid Al. The relative intensities of spectrally shifted Al K{alpha} lines imply a mean temperature of a few tens of eV up to a 100 {mu}m depth. Experimental results suggest refluxing of the electron beam at target rear side. They were compared with the predictions of both a collisional Monte Carlo and a collisional-electromagnetic, particle-fluid transport code. The validity of the code modeling of heating in such highly transient conditions is discussed.

Martinolli, E.; Koenig, M.; Baton, S.D.; Santos, J.J.; Amiranoff, F. [Laboratoire pour l'Utilisation des Lasers Intenses, UMR7605, CNRS-CEA-Universite Paris VI-Ecole Polytechnique, 91128 Palaiseau (France); Batani, D.; Perelli-Cippo, E.; Scianitti, F. [Dipartimento di Fisica 'G. Occhialini', Universita di Milano-Bicocca, Piazza della Scienza 3, 20126 Milan (Italy); Gremillet, L.; Melizzi, R.; Decoster, A.; Rousseaux, C. [Commissariat a l'Energie Atomique-DAM, Bruyeres-le-Chatel (France); Hall, T. A. [University of Essex, Colchester CO4 3SQ (United Kingdom); Key, M.H.; Snavely, R.; MacKinnon, A.J.; King, J.A. [Lawerence Livermore National Laboratory, Livermore, California (United States); Freeman, R.R. [University of California Davis, Davis, California (United States); Stephens, R. [Inertial Fusion Technology Division, Energy Group, General Atomics, San Diego, California 92121 (United States); Neely, D. [Central Laser Facility, Rutherford Appleton Laboratory, Chilton (United Kingdom)] (and others)

2006-04-15

39

Electron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar Flares  

E-print Network

to the hard X-ray emission from solar flares, the latter is normally ignored. Such an omission in the study of hard X-ray spectra from solar flares. With the high-resolution hard X- ray spectra madeElectron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar

Piana, Michele

40

Theoretical Studiesof Transannular Interactions. 111. The Absorption and Emission Spectra of a  

E-print Network

to be constructed using all 24 carbon 2p7r atomic orbitals. Experimental Details The low-temperature emission5063 Theoretical Studiesof Transannular Interactions. 111. The Absorption and Emission Spectra June 13, 1966 Abstract: An interpretationof the absorption and emission spectra of a multilayered

Glass, Leon

41

Optical emission spectra of chromium doped nanocrystalline zinc gallate  

NASA Astrophysics Data System (ADS)

Optical emission spectra of nanocrystalline zinc gallate (ZnGa2O4) and trivalent chromium ion doped zinc gallate (ZnGa2O4:Cr3+) are reported for different concentrations of the dopant ion. The measurements have been carried out over the temperature range between 77 and 296 K. The emission spectrum of nanocrystalline ZnGa2O4 shows two broad peaks. The intensity variation in these peaks, with temperature, is indicative of the effect of symmetry breaking in the electronic band structure of ZnGa2O4 in nanocrystalline samples. In addition, we find that the relative intensities of the sharp spectral lines of Cr3+ in nanocrystalline ZnGa2O4:Cr3+ are quite different from those reported for corresponding bulk samples. The spectral profiles of the so-called R1, R2, N1, and N2 lines have also been studied. The data are analyzed using crystal field theory, which includes an exchange interaction between the nearest neighbor Cr3+ pairs in ZnGa2O4. We estimate the exchange parameters for Cr3+ in nanocrystalline ZnGa2O4:Cr3+. Though, in the literature, there exist reports on optical properties of the corresponding bulk spinel, our approach and consequent results on nanocrystalline ZnGa2O4:Cr3+ are not only interesting from the physics point of view but also can be of use in nanotechnology.

Dhak, P.; Gayen, U. K.; Mishra, S.; Pramanik, P.; Roy, A.

2009-09-01

42

Fluorescence emission spectra of calcofluor stained yeast cell suspensions: heuristic assessment of basis spectra for their linear unmixing.  

PubMed

Fluorescence emission spectra of yeast cell suspensions stained with calcofluor have recently been identified as promising markers of variations in the quality of yeast cell wall. It is shown in this paper how the raw fluorescence spectra of calcofluor can be transformed to reliable spectral signatures of cell wall quality, which are independent of actual dye-to-cell concentrations of examined cell suspensions. Moreover, the presented approach makes it possible to assess basis fluorescence spectra that allows for the spectral unmixing of raw fluorescence spectra in terms of respective fluorescence contributions of calcofluor solvated in the suspension medium and bound to yeast cell walls. PMID:22538834

Plášek, Jaromír; Dostál, Marek; Gášková, Dana

2012-07-01

43

Phase-contrast x-ray imaging with intense Ar K{alpha} radiation from femtosecond-laser-driven gas target  

SciTech Connect

Intense Ar K{alpha} x ray with very little continuum background has been generated using a dense Ar gas irradiated with an intense femtosecond laser, with the measured flux of 1.2x10{sup 3} photons/mrad{sup 2}/pulse. This compact quasimonochromatic x-ray source, with a source size of only 12 {mu}m, has been applied to x-ray radiographic imaging of a biological specimen, resulting in high-resolution, high quality phase-contrast images. Correlation between this intense K{alpha} emission with the laser channeling in the Ar gas is discussed.

Chen, L. M.; Kando, M.; Ma, J.; Kotaki, H.; Fukuda, Y.; Hayashi, Y.; Daito, I.; Homma, T.; Ogura, K.; Mori, M.; Pirozhkov, A. S.; Koga, J.; Daido, H.; Bulanov, S. V.; Kimura, T.; Tajima, T.; Kato, Y. [Advanced Photon Research Center, Japan Atomic Energy Agency, 8-1 Umemidai Kizugawa, Kyoto 619-0215 (Japan)

2007-05-21

44

Orbits and emission spectra from the 2014 Camelopardalids  

NASA Astrophysics Data System (ADS)

We have analysed the meteor activity associated with meteoroids of fresh dust trails of Comet 209P/LINEAR, which produced an outburst of the Camelopardalid meteor shower (IAU code #451, CAM) in 2014 May. With this aim, we have employed an array of high-sensitivity CCD video devices and spectrographs deployed at 10 meteor observing stations in Spain in the framework of the Spanish Meteor Network. Additional meteoroid flux data were obtained by means of two forward-scatter radio systems. The observed peak zenithal hourly rate was much lower than expected, of around 20 meteors h-1. Despite of the small meteor flux in the optical range, we have obtained precise atmospheric trajectory, radiant and orbital information for 11 meteor and fireball events associated with this stream. The ablation behaviour and low tensile strength calculated for these particles reveal that Camelopardalid meteoroids are very fragile, mostly pristine aggregates with strength similar to that of the Orionids and the Leonids. The mineral grains seem to be glued together by a volatile phase. We also present and discuss two unique emission spectra produced by two Camelopardalid bright meteors. These suggest a non-chondritic nature for these particles, which exhibit Fe depletion in their composition.

Madiedo, José M.; Trigo-Rodríguez, Josep M.; Zamorano, Jaime; Izquierdo, Jaime; de Miguel, Alejandro Sánchez; Ocaña, Francisco; Ortiz, José L.; Espartero, Francisco; Morillas, Lorenzo G.; Cardeñosa, David; Moreno-Ibáñez, Manuel; Urzáiz, Marta

2014-12-01

45

Low energy particle composition. [energy spectra, particle emission - solar flares  

NASA Technical Reports Server (NTRS)

The energy spectra and composition of the steady or 'quiet-time' particle flux, whose origin is unknown was studied. Particles and photons which are associated with solar flares or active regions on the sun were also studied. Various detection techniques used to measure the composition and energy spectra of low energy particles are discussed. Graphs of elemental abundance and energy spectra are given.

Gloeckler, G.

1975-01-01

46

New laboratory measurements of mid-IR emission spectra of simulated planetary surfaces  

Microsoft Academic Search

We present emission spectra of particulate quartz measured in an environment cham- ber designed to simulate the conditions on actual planetary surfaces. The goal was to investigate near-surface thermal gradients and their effects on emission spectra for other planetary environ- ments. Our experiment parallels that of Logan et al. ( 1973) but is different, in that our samples were heated

Bradley G. Henderson; Paul G. Lucey; Bruce M. Jakosky

1996-01-01

47

New laboratory measurements of mid-IR emission spectra of simulated planetary surfaces  

Microsoft Academic Search

We present emission spectra of particulate quartz measured in an environment chamber designed to simulate the conditions on actual planetary surfaces. The goal was to investigate near-surface thermal gradients and their effects on emission spectra for other planetary environments. Our experiment parallels that of Logan et al. [1973] but is different, in that our samples were heated at the base

Bradley G. Henderson; Paul G. Lucey; Bruce M. Jakosky

1996-01-01

48

Derivation of global hyperspectral resolution surface emissivity spectra from advanced infrared sounder radiance measurements  

Microsoft Academic Search

The global IR surface emissivity spectra are very important for retrieving products such as dust properties, land surface temperature, trace gases, and cloud-top properties, as well as assimilating hyperspectral resolution IR radiances in NWP models over land. In this study, global IR surface emissivity spectra have been generated by using AIRS radiance measurements from NASA's EOS Aqua platform. A one-dimensional

Jun Li; Jinlong Li

2008-01-01

49

Anisotropic Bremsstrahlung Emission and the form of Regularized Electron Flux Spectra in Solar Flares  

E-print Network

,3 , & John C. Brown4 ABSTRACT The cross-section for bremsstrahlung photon emission in solar flares is in gen a regularized inversion technique to high- resolution hard X-ray spectra from solar flares in order to recoverAnisotropic Bremsstrahlung Emission and the form of Regularized Electron Flux Spectra in Solar

Piana, Michele

50

The iron K-alpha response in an X-ray illuminated relativistic disc and a black hole mass estimate  

NASA Astrophysics Data System (ADS)

A method is proposed for the estimate of the black hole mass in an active galactic nucleus which is based on the response of the intensity, centroid energy and width of the iron K-alpha fluorescence line to variations of the ionizing continuum. The method is illustrated for the case of a geometrically thin and optically thick, X-ray illuminated disk, in Keplerian rotation around a Schwarzschild black hole, using a detailed model of the line emissivity. This method is complementary to the one that makes use of variations in detailed line profiles, and could be applied also to measurements obtained at moderate energy resolution.

Matt, Giorgio; Perola, G. C.

1992-12-01

51

Emissivity spectra derived from TIMS data acquired over a partially vegetated area  

Microsoft Academic Search

TIMS (Thermal Infrared Multispectral Scanner) data of a partially vegetated area were processed using a new temperature-emissivity separation algorithm. This algorithm is based on an empirical relationship between the mean and the variation of spectral emissivity in thermal infrared region. Analysis using simulated mixture data showed that the algorithm can reduce errors caused by varying mixing ratio. Emissivity spectra of

Tsuneo Matsunaga

1993-01-01

52

Muonic K beta \\/ K alpha ratios from pure elements  

Microsoft Academic Search

K beta \\/ beta alpha ratios of muonic X-ray spectra from 28 pure elements have been measured with Ge detectors. The correlation of these ratios with properties of the target material and positron life-times is analyzed with statistical correlation theory.

R. Bergmann; H. Daniel; T. von Egidy; F. J. Hartmann; J. J. Reidy; W. Wilhelm

1979-01-01

53

Conversion efficiency and spectral broadening of the K-{alpha} line emitted from planar titanium targets irradiated with ultra-short laser pulses of high intensity  

SciTech Connect

A study of the conversion efficiency and line shape of the K-{alpha} x-ray line radiation from a planar titanium target irradiated by an ultra-short laser pulse is performed. The conversion efficiency and spectral broadening are studied as a function of laser intensity (5 x 10{sup 16}-10{sup 18} W cm{sup -2}), laser pulse duration (45 fs-800 fs), and laser fluence (2 x 10{sup 3}-4.2 x 10{sup 4} J cm{sup -2}). The K-{alpha}{sub 1} line (4510 eV) is observed to be broadened (up to {approx}9 eV), predominantly towards the higher energy side and strongly depends on the laser fluence rather than on laser intensity. The reason for the spectral broadening is attributed to K-{alpha} emission in warm dense plasma. The role of hot electrons and direct laser heating on spectral broadening is outlined. In addition to this, our observations indicates that the presence of pre-plasma strongly contribute to the observed broadening through the inner-shell transitions in multiply charged titanium ions in the pre-plasma. The appropriate laser irradiation parameters to achieve high conversion efficiency and minimum spectral width of the K-{alpha} radiation are identified. The study is important, since the control of the spectral profile is of general interest for diffraction or scattering experiments in view of its potential in increasing temporal resolution.

Arora, V.; Singhal, H.; Naik, P. A.; Gupta, P. D. [Laser Plasma Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India)

2011-10-15

54

Search for an OI Emission at 1304A in Jovian Auroral Spectra  

Microsoft Academic Search

Recent discovery of an Io-related features in Jupiter's auroral regions prompted us to search fot an OI multiplet at 1304 A in IUE aurora spectra. In three independent IUE spectra taken on January 18, 1981, we found an emission structure at 1304 A, with a signal-to-noise of about three. If the structure is due to the OI emission, then it

Sang J. Kim; Yong H. Kim

1995-01-01

55

Imaging Emission Spectra with Handheld and Cellphone Cameras  

ERIC Educational Resources Information Center

As point-and-shoot digital camera technology advances it is becoming easier to image spectra in a laboratory setting on a shoestring budget and get immediate results. With this in mind, I wanted to test three cameras to see how their results would differ. Two undergraduate physics students and I used one handheld 7.1 megapixel (MP) digital Cannon…

Sitar, David

2012-01-01

56

Research of the growth and nucleation mechanisms of diamond film by optical emission spectra and Raman spectra  

Microsoft Academic Search

The optical emission spectra of dc arc-plasma CVD diamond thin film deposition are presently studied for various ratios of CH4\\/H2 and C2H2\\/H2, in order to ascertain the nucleation and growth mechanisms in question. The key factor in high quality\\/high growth rate diamond thin film deposition is the prominence of atomic H in the arc-discharge plasma. Carbon sources and H2-dilution ratios,

Fangqing Zhang; Yafei Zhang; Yinghu Yang; Wenjun Zhang; Guanghua Chen; Xiangliu Jiang

1991-01-01

57

Spontaneous emission spectra of optically pumped vertical-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

We study the spontaneous emission spectra of optically pumped vertical-cavity surface-emitting lasers (VCSELs) operating below threshold. By spatial and angular filtering of the spontaneous emission spectra we can relate the observed asymmetrical shape of these spectra to the subthreshold guiding properties of the VCSELs. We find a substantial difference between VCSELs with a thin gain medium, consisting of quantum wells, and VCSELs with a thick gain medium, consisting of bulk GaAs; this difference is explained by analyzing the relative weights of thermal index guiding and carrier-induced index anti-guiding.

Hendriks, R. F. M.; Willemsen, M. B.; van Exter, M. P.; Woerdman, J. P.; Weegels, L.; Gulden, K. H.; Moser, M.

1998-04-01

58

Relativistic Iron Line Emission from the Neutron Star Low-mass X-ray Binary 4U 1636-536  

E-print Network

We present an analysis of XMM-Newton and RXTE data from three observations of the neutron star LMXB 4U 1636-536. The X-ray spectra show clear evidence of a broad, asymmetric iron emission line extending over the energy range 4-9 keV. The line profile is consistent with relativistically broadened Fe K-alpha emission from the inner accretion disk. The Fe K-alpha line in 4U 1636-536 is considerably broader than the asymmetric iron lines recently found in other neutron star LMXBs, which indicates a high disk inclination. We find evidence that the broad iron line feature is a combination of several K-alpha lines from iron in different ionization states.

Dirk Pandel; Philip Kaaret; Stephane Corbel

2008-08-15

59

Kennard-Stepanov relation connecting absorption and emission spectra in an atomic gas.  

PubMed

The Kennard-Stepanov relation describes a thermodynamic, Boltzmann-type scaling between the absorption and emission spectral profiles of an absorber, which applies in many liquid state dye solutions as well as in semiconductor systems. Here we examine absorption and emission spectra of rubidium atoms in a dense argon buffer gas environment. We demonstrate that the Kennard-Stepanov relation between absorption and emission spectra is well fulfilled in the collisionally broadened atomic gas system. Our experimental findings are supported by a simple theoretical model. PMID:25148322

Moroshkin, Peter; Weller, Lars; Sass, Anne; Klaers, Jan; Weitz, Martin

2014-08-01

60

Kennard-Stepanov Relation Connecting Absorption and Emission Spectra in an Atomic Gas  

NASA Astrophysics Data System (ADS)

The Kennard-Stepanov relation describes a thermodynamic, Boltzmann-type scaling between the absorption and emission spectral profiles of an absorber, which applies in many liquid state dye solutions as well as in semiconductor systems. Here we examine absorption and emission spectra of rubidium atoms in a dense argon buffer gas environment. We demonstrate that the Kennard-Stepanov relation between absorption and emission spectra is well fulfilled in the collisionally broadened atomic gas system. Our experimental findings are supported by a simple theoretical model.

Moroshkin, Peter; Weller, Lars; Saß, Anne; Klaers, Jan; Weitz, Martin

2014-08-01

61

Characteristics of Remote Sensing Emission Spectra of Composite Igneous Rocks  

Microsoft Academic Search

Analysis of rock spectrum is a fundamental work for rocks and minerals detection by using remote sensing. Our work is focused on characteristics of composite igneous rocks within 8~14 um, and studying the relationship between emissivity of rocks and their mineral ingredient, structure, alteration, as well as intergrowth conditions. Continuum removal method is used to normalize the spectrum. Shape parameters

Le Yu; Xiang Li; Dengrong Zhang; Chuanwan Dong

2008-01-01

62

Classification of Spectra of Emission-line Stars Using Feature Extraction Based on Wavelet Transform  

NASA Astrophysics Data System (ADS)

Our goal is to automatically identify spectra of emission (Be) stars in large archives and classify their types based on a typical shape of the H? emission line. Due to the length of spectra, of the original data is very time-consuming. In order to lower computational requirements and enhance the separability of the classes, we have to find a reduced representation of spectral features, however conserving most of the original information content. As the Be stars show a number of different shapes of emission lines, it is not easy to construct simple criteria (like e.g. Gaussian fits) to distinguish the emission lines in an automatic manner. We proposed to perform the wavelet transform of the spectra, calculate statistical metrics from the wavelet coefficients, and use them as feature vectors for classification. In this paper, we compare different wavelet transforms, different wavelets, and different statistical metrics in an attempt to identify the best method.

Bromová P.; Ba?ina, D.; Škoda, P.; Vážný, J.; Zendulka, J.

2014-05-01

63

Separation of Atmospheric and Surface Spectral Features in Mars Global Surveyor Thermal Emission Spectrometer (TES) Spectra  

NASA Technical Reports Server (NTRS)

We present two algorithms for the separation of spectral features caused by atmospheric and surface components in Thermal Emission Spectrometer (TES) data. One algorithm uses radiative transfer and successive least squares fitting to find spectral shapes first for atmospheric dust, then for water-ice aerosols, and then, finally, for surface emissivity. A second independent algorithm uses a combination of factor analysis, target transformation, and deconvolution to simultaneously find dust, water ice, and surface emissivity spectral shapes. Both algorithms have been applied to TES spectra, and both find very similar atmospheric and surface spectral shapes. For TES spectra taken during aerobraking and science phasing periods in nadir-geometry these two algorithms give meaningful and usable surface emissivity spectra that can be used for mineralogical identification.

Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.

2000-01-01

64

Imaging Emission Spectra with Handheld and Cellphone Cameras  

NASA Astrophysics Data System (ADS)

As point-and-shoot digital camera technology advances it is becoming easier to image spectra in a laboralory setting on a shoestring budget and get immediale results. With this in mind, I wanted to test three cameras to see how their results would differ. Two undergraduate physics students and I used one handheld 7.1 megapixel (MP) digital Cannon point-and-shoot auto focusing camera and two different cellphone cameras: one at 6.1 MP and the other at 5.1 MP.

Sitar, David

2012-12-01

65

Spectra  

NSDL National Science Digital Library

Learners construct a spectroscope out of a shoe box or mailing tube, diffraction grating, and other simple materials. They then use their spectroscope to observe spectra, the colors that make up light. Learners compare the spectra of various light sources. Use this activity to introduce learners to basic principles of light and color. Also, look at a related page about auroras to understand how distinguishing spectra of different atoms helps scientists understand the universe.

Exploratorium, The

2012-06-26

66

Quantitative study of fluorescence excitation and emission spectra of bean leaves.  

PubMed

A quantitative and comprehensive knowledge of leaf fluorescence is required for the interpretation of fluorescence signals at the canopy level and also for the modelling of leaf and canopy fluorescence. In this work we present full range fluorescence excitation and emission spectra of intact leaves, expressed in units of apparent spectral fluorescence yield, from both the adaxial and the abaxial sides of the leaves, and for both front-side and back-side geometries. Emission spectra were measured for incident radiations in the blue and the green spectral range. The red/far-red fluorescence ratio depended on the measurement geometry and on the excitation wavelength. Excitation spectra were measured for emissions at 687 and 760 nm. When the abaxial side was illuminated, the measured spectra always had a larger intensity compared to adaxial side that is explained by the higher scattering of the spongy tissues. At 760 nm, the spectra had the same shape for front-side and back-side geometry, indicating that scattering predominated. At 687 nm, the shape of the spectra was very different for front-side and back-side geometry due to re-absorption of red fluorescence within the leaf. The comparison of excitation spectra measured from the adaxial or the abaxial side revealed differences in carotenoid absorption. PMID:16798007

Louis, Juliette; Cerovic, Zoran G; Moya, Ismaël

2006-10-01

67

A novel zirconium K{alpha} imager for high energy density physics research  

SciTech Connect

We report on the development and characterization of a zirconium K{alpha} imager for high energy density physics research. The imager consists of a spherically bent quartz crystal operating at 15.7 keV photon energy. We compare the performance of the imager in terms of integrated reflectivity (R{sub int}) and temperature dependent collection efficiency ({eta}{sub Te}) to that of the widely used Cu K{alpha} imager. Our collisional-radiative simulations show that the new imager can be reliably used up to 250 eV plasma temperature. Monte Carlo simulations show that for a 25 {mu}m thick tracer layer of zirconium, the contribution to K{alpha} production from photo-pumping is only 2%. We present, for the first time, 2D spatially resolved images of zirconium plasmas generated by a high intensity short pulse laser interacting with Zr solid targets.

Akli, K. U.; Jiang, S.; Storm, M. S.; Krygier, A.; Freeman, R. R. [The Ohio State University, Columbus, Ohio 43210 (United States); Sanchez del Rio, M. [European Synchrotron Radiation Facility (France); Stephens, R. B. [General Atomics, San Diego, California 92121 (United States); Pereira, N. R. [Ecopulse Inc., Springfield, Virginia 22152 (United States); Baronova, E. O. [RRC Kurchatov Institute, Moscow (Russian Federation); Theobald, W. [Laboratory for Laser Energetics, Rochester, New York 14623 (United States); Ping, Y.; McLean, H. S.; Patel, P. K.; Key, M. H. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2011-12-15

68

Research of the growth and nucleation mechanisms of diamond film by optical emission spectra and Raman spectra  

NASA Astrophysics Data System (ADS)

The optical emission spectra of dc arc-plasma CVD diamond thin film deposition are presently studied for various ratios of CH4/H2 and C2H2/H2, in order to ascertain the nucleation and growth mechanisms in question. The key factor in high quality/high growth rate diamond thin film deposition is the prominence of atomic H in the arc-discharge plasma. Carbon sources and H2-dilution ratios, however, also exert an influence. As a carbon source, CH4 is noted to be superior to C2H2.

Zhang, Fangqing; Zhang, Yafei; Yang, Yinghu; Zhang, Wenjun; Chen, Guanghua; Jiang, Xiangliu

69

Far-infrared emission spectra of selected gas-phase PAHs: Spectroscopic fingerprints  

SciTech Connect

The emission spectra of the gaseous polycyclic aromatic hydrocarbons (PAHs) naphthalene, chrysene, and pyrene were recorded in the far-infrared (far-IR) region. The vibrational bands that lie in the far IR are unique for each PAH molecule and allow discrimination among the three PAH molecules. The far-IR PAH spectra, therefore, may prove useful in the assignment of unidentified spectral features from astronomical objects. 23 refs., 1 fig., 1 tab.

Zhang, K.; Guo, B.; Colarusso, P.; Bernath, P.F. [Univ. of Waterloo, Ontario (Canada)] [Univ. of Waterloo, Ontario (Canada)

1996-10-25

70

Cross-sectional characteristics of visible emission spectra in partially premixed flames  

SciTech Connect

Visible spectral characteristics of cross-sectional emissions from a partially premixed methane/air flame and a propane/air flame have been investigated. An optical train with a two-axis scanning mirror system was used to record line-of-sight emission spectra from 354 nm to 618 nm, and inversion technique was applied to obtain cross-sectional emission spectra. By analyzing the reconstructed emission spectra, cross-sectional intensities of CH and C{sub 2} radicals were separated from the background emission. The blue flame edge and yellow flame edge were also obtained by image processing technique for edge detection with color photographs of the flames. These edges were compared with radial distributions of CH, C{sub 2} radicals and background emission. The CH radicals were observed at the blue flame edge. The background emission was generated by soot precursors at upstream of the flame and by soot at downstream of the flame. The C{sub 2} radicals in the propane/air flame were more noticeable than those in the methane/air flame.

Ha, K.S.; Choi, S.

1999-11-01

71

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems: I. Cumulant expansions  

E-print Network

We study the F\\"orster resonant energy transfer (FRET) rate in multichromophoric systems. The multichromophoric FRET rate is determined by the overlap integral of the donor's emission and acceptor's absorption spectra, which are obtained via 2nd-order cumulant expansion techniques developed in this work. We calculate the spectra and multichromophoric FRET rate for both localized and delocalized systems. (i) The role of the initial entanglement between the donor and its bath is found to be crucial in both the emission spectrum and the multichromophoric FRET rate. (ii) The absorption spectra obtained by the cumulant expansion method are quite close to the exact one for both localized and delocalized systems, even when the system-bath coupling is far from the perturbative regime. (iii) For the emission spectra, the cumulant expansion can give very good results for the localized system, but fail to obtain reliable spectra of the high excitations of a delocalized system, when the system-bath coupling is large and the thermal energy is small. (iv) Even though, the multichromophoric FRET rate is good enough since it is determined by the overlap integral of the spectra.

Jian Ma; Jianshu Cao

2014-02-24

72

a Fast NIR Emission Spectrometer for Examining Explosive Events: Emission Spectra of Petn Explosions Containing Silver and Aluminum  

NASA Astrophysics Data System (ADS)

A fast Near-Infrared (NIR) spectrometer was constructed to make temporally and spectrally resolved emission measurements during post-detonation combustion of pure pentaerythritol tetranitrate (PETN) charges and PETN charges doped with 10% (by mass) Ag and Al microparticles. The post-detonation spectra are observed between 750 nm and 1500 nm at rates up to 46,992-spectra/sec, and key features are identified. Immediately following break-out of the detonation, all measured spectra are highly structured due to atomic and molecular emission. This emission decays within the first 40 ?s following break-out and is found to have lifetimes similar to that of emission from various species collected in the visible (390-600 nm) by a time-resolved streak spectrometer. For the particle-doped charges, broadband NIR emission signals can be used to determine time-resolved gray-body temperatures of the particles. At early time (0-40 ?s after breakout) gray-body temperatures in the range of 3000 to 4500 K are measured, between 60 ?s and 350 ?s after breakout the particle temperature is found to cool significantly to the range of 1200 K to 1800 K. Complementary two-color pyrometry (800 and 1150 nm) temperature measurements are found to be in fair agreement with early time data (0-25 ?s).

Piecuch, S. R.; Koch, J. D.; Lightstone, J. M.; Carney, J. R.

2009-12-01

73

High-resolution measurements, line identification, and spectral modeling of K{alpha} transitions in Fe XVIII-XXV  

SciTech Connect

The iron K{alpha} emission spectrum covering the wavelength region from 1.840 to 1.940 {Angstrom} is analyzed. Measurements are made with a high-resolution Bragg crystal spectrometer on the Princeton Large Torus (PLT) tokamak for plasma conditions which closely resemble those of solar flares. A total of 40 features are identified consisting of either single or multiple lines from eight charge states in iron, Fe XVIII through Fe XXV, and their wavelengths are determined with an accuracy of 0.1--0.4 m{Angstrom}. Many of these features are identified for the first time. In the interpretation of our observations we rely on model calculations that determine the ionic species abundances from electron density and temperature profiles measured independently with non-spectroscopic techniques and that incorporate theoretical collisional excitation and dielectronic recombination rates resulting in the excitation of the 1s2s{sup r}2p{sup s} configurations. The model calculations also include the effect of diffusive ion transport. Good overall agreement between the model calculations and the observations is obtained, which gives us confidence in our line identifications and spectral modeling capabilities. The results are compared with earlier analyses of the K{alpha} emission from the Sun. While many similarities are found, a few differences arise from the somewhat higher electron density in tokamak plasmas (10{sup 13} cm{sup {minus}3}), which affects the fine-structure level populations of the ground states of the initial ion undergoing electron-impact excitation or dielectronic recombination. We also find that several spectral features are comprised of different transitions from those reported in earlier analyses of solar data.

Beiersdorfer, P.; Phillips, T. [Lawrence Livermore National Lab., CA (United States); Jacobs, V.L. [Naval Research Lab., Washington, DC (United States). Condensed Matter and Radiation Sciences Div.; Hill, K.W.; Bitter, M.; von Goeler, S. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Kahn, S.M. [California Univ., Berkeley, CA (United States)

1992-11-01

74

High-resolution measurements, line identification, and spectral modeling of K[alpha] transitions in Fe XVIII-XXV  

SciTech Connect

The iron K[alpha] emission spectrum covering the wavelength region from 1.840 to 1.940 [Angstrom] is analyzed. Measurements are made with a high-resolution Bragg crystal spectrometer on the Princeton Large Torus (PLT) tokamak for plasma conditions which closely resemble those of solar flares. A total of 40 features are identified consisting of either single or multiple lines from eight charge states in iron, Fe XVIII through Fe XXV, and their wavelengths are determined with an accuracy of 0.1--0.4 m[Angstrom]. Many of these features are identified for the first time. In the interpretation of our observations we rely on model calculations that determine the ionic species abundances from electron density and temperature profiles measured independently with non-spectroscopic techniques and that incorporate theoretical collisional excitation and dielectronic recombination rates resulting in the excitation of the 1s2s[sup r]2p[sup s] configurations. The model calculations also include the effect of diffusive ion transport. Good overall agreement between the model calculations and the observations is obtained, which gives us confidence in our line identifications and spectral modeling capabilities. The results are compared with earlier analyses of the K[alpha] emission from the Sun. While many similarities are found, a few differences arise from the somewhat higher electron density in tokamak plasmas (10[sup 13] cm[sup [minus]3]), which affects the fine-structure level populations of the ground states of the initial ion undergoing electron-impact excitation or dielectronic recombination. We also find that several spectral features are comprised of different transitions from those reported in earlier analyses of solar data.

Beiersdorfer, P.; Phillips, T. (Lawrence Livermore National Lab., CA (United States)); Jacobs, V.L. (Naval Research Lab., Washington, DC (United States). Condensed Matter and Radiation Sciences Div.); Hill, K.W.; Bitter, M.; von Goeler, S. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Kahn, S.M. (California Univ., Berkeley, CA (United States))

1992-11-01

75

Emission spectra of selected SSME elements and materials  

NASA Technical Reports Server (NTRS)

Stennis Space Center (SSC) is pursuing the advancement of experimental techniques and theoretical developments in the field of plume spectroscopy for application to rocket development testing programs and engine health monitoring. Exhaust plume spectral data for the Space Shuttle Main Engine (SSME) are routinely acquired. The usefulness of this data depends upon qualitative and quantitative interpretation of spectral features and their correlation with the engine performance. A knowledge of the emission spectral characteristics of effluent materials in the exhaust plume is essential. A study of SSME critical components and their materials identified 30 elements and 53 materials whose engine exhaust plume spectral might be required. The most important were evaluated using SSC's Diagnostic Testbed Facility Thruster (DTFT), a 1200-lbf, liquid oxygen/gaseous hydrogen rocket engine which very nearly replicates the temperature and pressure conditions of the SSME exhaust plume in the first Mach diamond. This report presents the spectral data for the 10 most important elements and 27 most important materials which are strongly to moderately emitting in the DTFT exhaust plume. The covered spectral range is 300 to 426 nm and the spectral resolution is 0.25 nm. Spectral line identification information is provided and line interference effects are considered.

Tejwani, Gopal D.; Vandyke, David B.; Bircher, Felix E.; Gardner, Donald G.; Chenevert, Donald J.

1992-01-01

76

Solvent Effect on the Absorption and Fluorescence Emission Spectra of Some Purine Derivatives: Spectrofluorometric Quantitative Studies  

Microsoft Academic Search

The absorption and emission spectra of six purine derivatives: adenine (I), N(9)-hydroxyethyladenine (II), N(6)-acetyladenine (III), N(6)-isobutyryladenine (IV), guanine (V), and N(2),N(9)-diacetylguanine (VI) have been investigated. The effects of solvent and pH on the positions of ?\\u000a max? (absorption) and ?\\u000a max? (emission) of these compounds were determined. Correlations between the absorption wavelength (?\\u000a max?) of these organic compounds and the

Hassan H. Hammud; Kamal H. Bouhadir; Mamdouh S. Masoud; Amer M. Ghannoum; Sulaf A. Assi

2008-01-01

77

Quantitative analysis of directional spontaneous emission spectra from light sources in photonic crystals  

E-print Network

Quantitative analysis of directional spontaneous emission spectra from light sources in photonic disorder. Using a model comprising diffuse light transport and photonic band structure, we quantitatively of spontaneously emitted light in real photonic crystals, which is essential in the interpretation of quantum

Vos, Willem L.

78

Near infrared emission spectra of CoH and CoD Iouli E. Gordon a  

E-print Network

Near infrared emission spectra of CoH and CoD Iouli E. Gordon a , Robert J. Le Roy b , Peter F spectroscopy; Near infrared; Spin­orbit splitting 1. Introduction Molecules containing 3d-transition metal observed in our spectrum of CoH. In addition, a new [13.3]4 electronic state was found by observing [13

Le Roy, Robert J.

79

A Safe and Interactive Method of Illuminating Discharge Tubes for Studying Emission Spectra  

ERIC Educational Resources Information Center

Discharge tubes are useful tools for teaching emission spectra and the discrete energy levels of the Bohr model. A new setup uses a plasma globe to illuminate the discharge tube and allows a higher degree of interactivity owing to the omission of a traditional, high-voltage power source. The decreased power consumption also reduces the heating of…

Lu, Zhe

2012-01-01

80

Dielectric tensor of tetracene single crystals: The effect of anisotropy on polarized absorption and emission spectra  

Microsoft Academic Search

The full UV-visible dielectric tensor and the corresponding directions of the principal axes of triclinic tetracene crystals are reported as deduced either by polarized absorption and ellipsometry measurements or by calculations based on the molecular and crystallographic data. The results allow the attribution of the polarized bands observed in both absorption and photoluminescence emission spectra. In particular, the spectral line

S. Tavazzi; L. Raimondo; L. Silvestri; P. Spearman; A. Camposeo; M. Polo; D. Pisignano

2008-01-01

81

Modulation of Harmonic Emission Spectra from Intense Laser-Plasma Interactions  

E-print Network

Modulation of Harmonic Emission Spectra from Intense Laser-Plasma Interactions T.J.M. Boyd1 and R carried out to investigate the interaction of intense laser light with overdense plasma and in particular may be misguided. I. INTRODUCTION The interaction of high power laser pulses with ultradense plasma

Paris-Sud XI, Université de

82

The Thermal Emission and Albedo of Super-Earths with Flat Transmission Spectra  

NASA Astrophysics Data System (ADS)

Vast resources have been dedicated to characterizing the handful of planets with radii between Earth’s and Neptune’s that are accessible to current telescopes. Observations of their transmission spectra have been inconclusive and do not constrain the atmospheric composition. Here, we present a path forward for understanding this class of small planets: by understanding the thermal emission and reflectivity of small planets, we can break these degeneracies and constrain the atmospheric composition. Of the ~four small planets studied to date, all have radii in the near-IR consistent with being constant in wavelength. This suggests either that these planets all have higher mean molecular weight atmospheres than expected for hydrogen-dominated bulk compositions, or that the atmospheres of small planets are consistently enshrouded in thick hazes and clouds. For the particularly well-studied planet GJ 1214b, the measurements made using HST/WFC3 can rule out atmospheres with high mean molecular weights, leaving clouds as the sole explanation for the flat transmission spectrum. We showed in Morley et al. 2013 that these clouds and hazes can be made of salts and sulfides, which condense in the upper atmosphere of a cool H-rich atmosphere like GJ 1214b, or made of photochemical hazes such as soots, which result from methane photodissociation and subsequent carbon chemistry. Here, we explore how clouds thick enough to obscure the transmission spectrum change both thermal emission spectra and albedo spectra. These observations are complementary to transmission spectra measurements. Thermal emission probes deeper layers of the atmosphere, potentially below the high haze layer obscuring the transmission spectra; albedo spectra probe reflected starlight largely from the cloud particles themselves. Crucially, these complementary observations of planets with flat transmission spectra may allow us to break the degeneracies between cloud materials, cloud height and longitude, and bulk composition of the atmosphere. We make predictions for the observability of known planets for current and future telescopes.

Morley, Caroline; Fortney, Jonathan; Marley, Mark

2014-11-01

83

Rat epileptic seizures evoked by BmK {alpha}IV and its possible mechanisms involved in sodium channels  

SciTech Connect

This study showed that rat unilateral intracerebroventricular injection of BmK {alpha}IV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK {alpha}IV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK {alpha}IV on intrasynaptosomal free calcium concentration [Ca{sup 2+}]{sub i} and sodium concentration [Na{sup +}]{sub i} revealed that BmK {alpha}IV-evoked glutamate release from synaptosomes was associated with an increase in Ca{sup 2+} and Na{sup +} influx. Moreover, BmK {alpha}IV-mediated glutamate release and ion influx was completely blocked by tetrodotoxin, a blocker of sodium channel. Together, these results suggest that the induction of BmK {alpha}IV-evoked epileptic seizures may be involved in the modulation of BmK {alpha}IV on tetrodotoxin-sensitive sodium channels located on the nerve terminal, which subsequently enhances the Ca{sup 2+} influx to cause an increase of glutamate release. These findings may provide some insight regarding the mechanism of neuronal action of BmK {alpha}IV in the central nervous system for understanding epileptogenesis involved in sodium channels.

Chai Zhifang [Graduate School of the Chinese Academy of Sciences, Shanghai Institute of Physiology, Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031 (China); Bai Zhantao [Graduate School of the Chinese Academy of Sciences, Shanghai Institute of Physiology, Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031 (China); Zhang Xuying [Graduate School of the Chinese Academy of Sciences, Shanghai Institute of Physiology, Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031 (China); Membrane Signaling Group, Laboratory of Neurobiology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709 (United States); Liu Tong [Graduate School of the Chinese Academy of Sciences, Shanghai Institute of Physiology, Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031 (China); Pang Xueyan [School of Life Sciences of Shanghai University, Shang-Da Road 99, Shanghai 200444 (China); Ji Yonghua [School of Life Sciences of Shanghai University, Shang-Da Road 99, Shanghai 200444 (China)]. E-mail: yhji@server.shcnc.ac.cn

2007-05-01

84

Peculiarities of spectra of induced emission of polymethine dye solutions at low temperatures  

NASA Technical Reports Server (NTRS)

Results from studying the induced emission spectra with monochromatic excitation (superluminescent regime) within a temperature range of 300 K - 5.2 K are presented. The significant feature of such operations is the appearance of quasi-lines whose minimum width is realized at 4.2 K. The frequency distribution of the quasi-lines unambiguously characterizes the dye investigated. When interpreting these results, the idea of an inhomogeneous broadening of the polymethine dye spectra in the solution being studied experimentally was used for the first time. The quasi-lines observed are interpreted as a manifestation of the electron vibration structure of singlet states of a complex molecule.

Melishchuk, M. V.; Tikhonov, Y. A.; Shpak, M. T.

1981-01-01

85

Relativistic configuration-interaction calculation of $K\\alpha$ transition energies in beryllium-like iron  

E-print Network

We perform relativistic configuration-interaction calculations of the energy levels of the low-lying and core-excited states of beryllium-like iron, Fe$^{22+}$. The results include the QED contributions calculated by two different methods, the model QED operator approach and the screening-potential approach. The uncertainties of theoretical energies are estimated systematically. The predicted wavelengths of the K\\alpha transitions in beryllium-like iron improve previous theoretical results and compare favorably with the experimental data.

Yerokhin, V A; Fritzsche, S

2014-01-01

86

Emission Lines between 1 and 2 keV in Cometary X-Ray Spectra  

NASA Astrophysics Data System (ADS)

We present the detection of new cometary X-ray emission lines in the 1.0-2.0 keV range using a sample of comets observed with the Chandra X-Ray Observatory and ACIS spectrometer. We have selected five comets from the Chandra sample with good signal-to-noise spectra. The surveyed comets are C/1999 S4 (LINEAR), C/1999 T1 (McNaught-Hartley), 153P/2002 (Ikeya-Zhang), 2P/2003 (Encke), and C/2008 8P (Tuttle). We modeled the spectra with an extended version of our solar wind charge exchange (SWCX) emission model. Above 1 keV, we find Ikeya-Zhang to have strong emission lines at 1340 and 1850 eV which we identify as being created by SWCX lines of Mg XI and Si XIII, respectively, and weaker emission lines at 1470, 1600, and 1950 eV formed by SWCX of Mg XII, Mg XI, and Si XIV, respectively. The Mg XI and XII and Si XIII and XIV lines are detected at a significant level for the other comets in our sample (LS4, MH, Encke, 8P), and these lines promise additional diagnostics to be included in SWCX models. The silicon lines in the 1700-2000 eV range are detected for all comets, but with the rising background and decreasing cometary emission, we caution that these detections need further confirmation with higher resolution instruments.

Ewing, Ian; Christian, Damian J.; Bodewits, Dennis; Dennerl, Konrad; Lisse, Carey M.; Wolk, Scott J.

2013-01-01

87

Plasma processes and emission spectra in laser induced plasmas: A point of view  

NASA Astrophysics Data System (ADS)

In this paper emission spectra of the plasma produced by laser-matter interaction are discussed in terms of the correlation between the elementary plasma processes and the evolution of plasma parameters during the expansion. Three main stages have been identified and discussed in details: high density plasma, near equilibrium plasma and non-equilibrium plasma including molecular formation. In order to develop a comprehensive point of view on the correlation between plasma mechanisms and spectral emission features several concepts already discussed and elucidated in the plasma science have been adapted to the description of the laser induced plasma and to its ionizing and recombining character.

De Giacomo, A.; Dell'Aglio, M.; De Pascale, O.; Gaudiuso, R.; Palleschi, V.; Parigger, C.; Woods, A.

2014-10-01

88

Detection of silicate emission features in the 8- to 13-micron spectra of main belt asteroids  

NASA Technical Reports Server (NTRS)

A presentation is given of 8.0-13.0 micron spectra (Delta lambda/lambda = 0.02-0.03) for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina.

Feierberg, M. A.; Witteborn, F. C.; Lebofsky, L. A.

1983-01-01

89

First results from a laboratory facility for measurement of emission spectra under simulated planetary conditions  

NASA Technical Reports Server (NTRS)

We have developed a laboratory spectroscopic facility for the measurement of emission spectra under simulated planetary conditions. Spectral measurements are made from 6 to 13 microns with a scanning grating monochromator equipped with a HgCdTl detector. An environment chamber in service in Hawaii for several years in which we can control the temperature from 77 K to 500 K, the pressure from 10(exp -5) torr to two atmospheres, has been equipped with a 77 K or 273 K cold shield. The shield serves to minimize light reflected off the sample and to aid in development of thermal gradients for obtaining spectra under conditions simulating the thermal environment of airless bodies. Samples are placed in small cups on a temperature controlled substrate allowing measurements of emission due to heating from below by the substrate, or from illumination from a solar simulation source.

Lucey, Paul G.; Domergue-Schmidt, Natalie; Henderson, Bradley G.; Jakosky, Bruce

1993-01-01

90

TL emission spectra measurements using a spectrometer coupled to the Risoe TL/OSL reader  

NASA Astrophysics Data System (ADS)

A high sensitivity spectrometer (Ocean Optics QE65 Pro) was coupled to the Risoe TL/OSL reader to measure TL emission spectra of four different dosimeters. This spectrometer is based on a Hamamatsu FFT-CCD detector with a 2-D arrangement of pixels (1044×64), which detects luminescence in a range of 200-950 nm. An optical fiber was used to guide the signal from the sample to the spectrometer. TL spectra from LiF, CaSO4:Dy, BeO and Al2O3:C detectors were obtained and they are presented in this work. The proposed detection system showed good response; spectra shape, in accordance with the literature, were obtained, validating the system.

Yoshizumi, Maíra T.; Caldas, Linda V. E.

2014-11-01

91

Study of dynamic emission spectra from lubricant films in an elastohydrodynamic contact using Fourier transform spectroscopy  

NASA Technical Reports Server (NTRS)

Infrared emission spectra were obtained through a diamond window from lubricating fluids in an operating sliding elastohydrodynamic contact and analyzed by comparison with static absorption spectra under similar pressures. Different loads, shear rates and temperatures were used. Most of the spectra exhibited polarization characteristics, indicating directional alignment of the lubricant in the EHD contact. Among the fluids studied were a "traction" fluid, an advanced ester, and their mixtures, a synthetic paraffin, a naphthenic reference fluid (N-1), both neat and containing 1 percent of p-tricresyl phosphate as an anti-wear additive, and a C-ether. Traction properties were found to be nearly proportional to mixture composition for traction fluid and ester mixtures. The anti-wear additive reduced traction and fluid temperature under low loads but increased them under higher loads, giving rise to formation of a friction polymer.

Lauer, J. L.

1978-01-01

92

Combined infrared emission spectra and radar reflectivity studies of cirrus clouds  

Microsoft Academic Search

Thermal-infrared emission spectra from cirrus clouds taken with a unique prism spectrograph are combined with Ka-band radar reflectivity measurements to obtain mass concentration and size information on the cirrus ice crystals. A two-stream radiation transfer model utilizing Mie scattering theory was used to infer the averaged effective ice sphere diameter which, for the cirrus studied, was near 50 ?m

A. Jay Palmer; S. Y. Matrosov; B. E. Martner; T. Uttal; D. K. Lynch; M. A. Chatelain; J. A. Hackwell; R. W. Russell

1993-01-01

93

Thermal emission spectra of terrestrial alkaline volcanic rocks: Applications to Martian remote sensing  

Microsoft Academic Search

The long-standing assessment that Martian igneous compositions are strictly subalkaline has recently been brought into question by the detection of alkaline rocks at Gusev crater. In this study, we assess the utility of thermal emission spectra (5?25 ?m at 10 cm?1 spectral sampling) in identifying and classifying terrestrial alkalic volcanic rocks, and then apply our results to MGS\\/TES data. Using

Tasha L. Dunn; Harry Y. McSween Jr; Philip R. Christensen

2007-01-01

94

Thermal emission spectra of terrestrial alkaline volcanic rocks: Applications to Martian remote sensing  

Microsoft Academic Search

The long-standing assessment that Martian igneous compositions are strictly subalkaline has recently been brought into question by the detection of alkaline rocks at Gusev crater. In this study, we assess the utility of thermal emission spectra (5-25 mum at 10 cm-1 spectral sampling) in identifying and classifying terrestrial alkalic volcanic rocks, and then apply our results to MGS\\/TES data. Using

Tasha L. Dunn; Harry Y. McSween; Philip R. Christensen

2007-01-01

95

Formation of x-ray line emission spectra of excimer-laser-produced plasmas  

Microsoft Academic Search

Time and space-integrated emission spectra in the 748 eV to 1245 eV photon energy region have been measured in plasma produced by 308 nm wavelength XeCl laser radiation (IL = (4-10) × 1012 W\\/cm2, tau = 10 ns) and by 248 nm wavelength KrF laser pulse train radiation (IL = 5 × 1015 W\\/cm2, tau = 7 ps, 16 pulses

A. I. Magunov; A. Ya Faenov; I. Yu Skobelev; T. A. Pikuz; D. Batani; M. Milani; A. Conti; A. Masini; M. Costato; A. Pozzi; E. Turcu; R. Allot; N. Lisi; M. Koenig; A. Benuzzi; F. Flora; T. Letardi; L. Palladino; A. Reale

1997-01-01

96

Identification of the 4486,4504A emission lines in O-type spectra  

E-print Network

Inspired by an appeal to the community from Walborn (these proceedings) we decided to solve the long-standing problem concerning the nature of the 4486,4504A emission lines, which are frequently observed in O-type spectra and which are particularly prominent in supergiants. We claim that these lines emerge from sulfur, namely by de-excitation of a highly excited S IV doublet state. We prove this by an exploratory NLTE calculation with a detailed model atom.

K. Werner; T. Rauch

2001-02-01

97

Luminescence, emission spectra and hydrogen content of crystalline Lu2SiO5:Ce  

Microsoft Academic Search

Thermally stimulated luminescence and emission spectra of cerium-doped Lu2SiO5 have been measured in the temperature interval 10K ? T ? 310K. Eight glow peaks occur with the most intense peak exhibiting a maximum at 306 K. Data analyses show that the peaks generally obey first-order kinetics with thermal activation energies ranging from 0.085 to 0.907 eV. The relatively short lifetime

D. W. Cooke; B. L. Bennett; K. J. McClellan; R. E. Muenchausen; J. R. Tesmer; C. J. Wetteland

2002-01-01

98

Theoretical studies of electronic absorption and emission spectra of Pt(saloph)  

Microsoft Academic Search

The performance of ab initio calculations for the ground and excited states of the Pt(saloph) complex is examined in detail. The S0–Si and T1–Ti absorption spectra are calculated, and the transition between the ground S0 state and the excited S1 state involves the HOMO-2, HOMO-1, HOMO and LUMO. Moreover, calculations show that the emissive singlet is of mixed MLCT\\/LLCT characteristic.

Zhi-Xiao Liao; Yi Wang; Xiu-Pei Yang; Zai-De Zhou; Dan Xiao

2007-01-01

99

Ab initio study of absorption and emission spectra of PM567  

Microsoft Academic Search

The visible-light absorption and emission excitation energies of PM567 dye have been studied with different ab initio methods (TDHF, CIS, MP2, MP3 and CISD). The results show that its visible-light spectra are mainly due to a transition between the HOMO to the LUMO, with the CISD size consistency corrections values being the most accurate respect to the experimental data. In

P. Acebal; S. Blaya; L. Carretero

2003-01-01

100

Atomic Emission Spectra Diagnosis and Electron Density Measurement of Semiconductor Bridge (SCB) Plasma  

Microsoft Academic Search

Emission spectra of a semiconductor bridge (SCB) plasma in a visible range was studied in air. The electron density was measured in a conventional way from the broadening of the A1 I 394.4 nm Stark width. Based on the Saha equation, a system for recording the intensity of Si I 390.5 nm and Si II 413.1 nm was designed. With

Hongyan Feng; Shunguan Zhu; Lin Zhang; Xiaoxia Wan; Yan Li; Ruiqi Shen

2010-01-01

101

EVIDENCE FOR SECONDARY EMISSION AS THE ORIGIN OF HARD SPECTRA IN TeV BLAZARS  

SciTech Connect

We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy {gamma}-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE {gamma}-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy {gamma}-rays, especially the shape of the VHE {gamma}-ray tail of the observed spectra, can be explained by secondary {gamma}-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

Zheng, Y. G.; Kang, T., E-mail: ynzyg@sohu.com [Department of Physics, Yunnan Normal University, Kunming 650092 (China)

2013-02-20

102

Soft x-ray emission spectra and ferromagnetism in wide-gap doped semiconductors  

NASA Astrophysics Data System (ADS)

A study is made of the resonant and nonresonant L x-ray emission spectra of impurities in the semiconducting compounds ZnS:Mn, ZnO:Mn, ZnO:Co, and Co2O:Mn. An analysis of the Mn L2,3 x-ray emission spectra of Zn1-xMnxS (x=0.1-0.3) reveals that the Mn impurities do not form clusters in the ZnS lattice. Studies of the Mn L2,3 spectra and electronic structure of epitaxial films of Zn0.8Mn0.2O annealed at different temperatures show that the cause of the observed suppression of ferromagnetism at T >600°C is segregation of Mn atoms. In this case the Mn atoms occupy both Zn sites and interstitial positions. For Zn1-xCoxO (x =0.02, 0.06, and 0.10) the absence of free carriers that could mediate an exchange interaction between Co ions is established. Mn L2,3 x-ray emission measurements show that in Mn-doped oxides Cu2O synthesized at 650 and 800°C the Mn atoms are found both in interstitial positions and occupy Cu sites, but the configurations of these defects depend on the synthesis temperature. A decrease of the Curie temperature with increasing synthesis temperature may be explained as a manifestation of antiferromagnetic superexchange between substituent Mn atoms via oxygen.

Surkova, T. P.; Galakhov, V. R.; Kurmaev, É. Z.

2009-01-01

103

Non-Detection of X-Ray Emission From Sterile Neutrinos in Stacked Galaxy Spectra  

E-print Network

We conduct a comprehensive search for X-ray emission lines from sterile neutrino dark matter, motivated by recent claims of unidentified emission lines in the stacked X-ray spectra of galaxy clusters and the centers of the Milky Way and M31. Since the claimed emission lines lie around 3.5 keV, we focus on galaxies and galaxy groups (masking the central regions), since these objects emit very little radiation above ~2 keV and offer a clean background against which to detect emission lines. We develop a formalism for maximizing the signal-to-noise of sterile neutrino emission lines by weighing each X-ray event according to the expected dark matter profile. In total, we examine 81 and 89 galaxies with Chandra and XMM-Newton respectively, totaling 15.0 and 14.6 Ms of integration time. We find no significant evidence of any emission lines, placing strong constraints on the mixing angle of sterile neutrinos with masses between 4.8-12.4 keV. In particular, if the 3.57 keV feature from Bulbul et al. (2014) were due to 7.1 keV sterile neutrino emission, we would have detected it at 4.4 sigma and 11.8 sigma in our two samples. Unlike previous constraints, our measurements do not depend on the model of the X-ray background or on the assumed logarithmic slope of the center of the dark matter profile.

Michael E. Anderson; Eugene Churazov; Joel N. Bregman

2014-08-18

104

Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols  

SciTech Connect

Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of SOA generated from two monoterpenes, limonene and a-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ~100 ppb ammonia vapor in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (~0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for excitation = 420+- 50 nm and emission = 475 +- 38 nm. The window of the strongest fluorescence shifted to excitation = 320 +- 25 nm and emission = 425 +- 38 nm for the a-pinene-derived SOA. Both regions overlap with the excitation-emission matrix (EEM) spectra of some of the fluorophores found in primary biological aerosols. Our study suggests that, despite the low quantum yield, the aged SOA particles should have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols.

Lee, Hyun Ji; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A.

2013-05-10

105

Gamma Emission Spectra from Neutron Resonances in 234,236,238U Measured Using the Dance Detector at Lansce  

NASA Astrophysics Data System (ADS)

An accurate knowledge of the radiative strength function and level density is needed to calculate of neutron-capture cross sections. An additional constraint on these quantities is provided by measurements of ?-ray emission spectra following capture. We present ?-emission spectra from several neutron resonances in 234,236,238U, measured using the DANCE detector at LANSCE. The measurements are compared to preliminary calculations of the cascade. It is observed that the generalized Lorentzian form of the E1 strength function cannot reproduce the shape of the emission spectra, but a better description is made by adding low-lying M1 Lorentzian strength.

Ullmann, J. L.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wouters, J. M.; Wilhelmy, J. B.; Wu, C. Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

2013-03-01

106

Emissitivity spectra obtained from field and laboratory measurements using the temperature and emissivity separation algorithm  

SciTech Connect

Surface emissivities play an important role in thermal remote sensing, since knowledge of them is required to estimate land surface temperature with enough accuracy. They are also important in other environmental or geological studies.We show the results obtained for the emissivity spectra of different natural surfaces (water, green, and senescent vegetation) by applying the temperature and emissivity separation (TES) algorithm to ground-based measurements collected at the field with a multiband thermal radiometer. The results have been tested with data included in spectral libraries, and rms errors lower than 0.01 have been found, except for senescent vegetation. Two methods are also proposed to apply the TES algorithm to measurements achieved in the laboratory: (i) by heating the sample and (ii) using a box with reflective walls.

Jimenez-Munoz, Juan C.; Sobrino, Jose A

2006-09-20

107

Calcium pyroxenes at Mercurian surface temperatures: investigation of in-situ emissivity spectra and thermal expansion  

NASA Astrophysics Data System (ADS)

The European Space Agency and Japan Aerospace Agency mission to Mercury, named BepiColombo, will carry on board the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) that will be able to provide surface Thermal Infra-Red (TIR) emissivity spectra from 7 to 14 ?m. This range of wavelengths is very useful to identify the fine-scale structural properties of several silicates. For mineral families as pyroxenes, the emissivity peak positions are good indicators of the composition. A complication in the interpretation of MERTIS data could arise from the extreme daily surface temperature range of Mercury (70 to 725 K) that significantly affects the crystal structure and density of minerals and consequently should affect the TIR spectral signature of each single mineral present on the surface of the planet. In preparation for the MERTIS data analysis, we are extensively investigating at high temperatures conditions several mineral phases potentially detectable on the surface of Mercury. Two C2/c augitic pyroxenes, with constant calcium content and very different magnesium to iron ratio, were studied by in situ high-temperature thermal infrared spectroscopy (up to 750 K) and in situ high-temperature single-crystal X-ray diffraction (up to 770 K). The emissivity spectra of the two samples show similar band center shifts of the main three bands toward lower wavenumbers with increasing temperature. Our results indicate that the center position of bands 1 and 2 is strictly dependent on temperature, whereas the center position of band 3 is a strong function of the composition regardless the temperature. These data suggest that MERTIS spectra will be able to provide indications of C2/c augitic pyroxene with different magnesium contents and will allow a correct interpretation independently on the spectra acquisition temperature.

Ferrari, S.; Nestola, F.; Helbert, J.; Maturilli, A.; D'Amore, M.; Alvaro, M.; Domeneghetti, M.; Massironi, M.; Hiesinger, H.

2013-12-01

108

Reinvestigation of the Emission Spectra Following the 266 NM Photolysis of Iodomethanes  

NASA Astrophysics Data System (ADS)

Nascent emission spectra following the 266 nm photolysis of iodomethanes (CHI_3, CH_2I_2, CH_3I, and CH_2ICl) were recorded in a slow flow system, and are similar to those following the 266 nm photolysis of bromomethanes except a number of unknown bands that appear between 520 nm and 820 nm. Interestingly, there are no isotopic shifts in these unknown bands even when the precursors were replaced by the deuterated or ^{13}C-substituted isotopomers (CD_2I_2, CD_3I, and ^{13}CH_2I_2). This indicates that the carrier of these unknown bands does not contain any hydrogen or carbon atoms. Laser-induced fluorescence (LIF) excitation and dispersed-fluorescence (DF) spectra were recorded, but these spectra show different vibrational structures than those of the unknown bands. While the LIF and DF spectra can be well described by the I_2 b^3 ? _{0,u} ^+ - X^1 ? _g ^+ transition, there exist systematic deviations between the unknown bands and the I_2 b-X transition. We have improved the signal-to-noise (S/N) ratios and the resolution for these unknown bands. Our new analysis shows that the unknown bands consist of several band systems including the I_2 b-X transition. Moreover, the excited state iodine atom was found in the nascent emission spectra, but its formation mechanism still remains unsolved. The details of our current progress will be presented. S.-X. Yang, G.-Y. Hou, J.-H. Dai, C-.H. Chang, and B.-C. Chang, J. Phys. Chem. A 114, 4785 (2010). J.-J. Du, C.-H. Chen, and B.-C. Chang, 67^{th} OSU International Symposium on Molecular Spectroscopy, WG04 (2012).

Tu, Cian-Ping; Cheng, Hsin-I.; Chang, Bor-Chen

2013-06-01

109

Method of Fission Product Beta Spectra Measurements for Predicting Reactor Anti-neutrino Emission  

E-print Network

The nuclear fission process that occurs in the core of nuclear reactors results in unstable, neutron rich fission products that subsequently beta decay and emit electron anti-neutrinos. These reactor neutrinos have served neutrino physics research from the initial discovery of the neutrino to current precision measurements of neutrino mixing angles. The prediction of the absolute flux and energy spectrum of the emitted reactor neutrinos hinges upon a series of seminal papers based on measurements performed in the 1970s and 1980s. The steadily improving reactor neutrino measurement techniques and recent re-considerations of the agreement between the predicted and observed reactor neutrino flux motivates revisiting the underlying beta spectra measurements. A method is proposed to use an accelerator proton beam delivered to an engineered target to yield a neutron field tailored to reproduce the neutron energy spectrum present in the core of an operating nuclear reactor. Foils of the primary reactor fissionable isotopes placed in this tailored neutron flux will ultimately emit beta particles from the resultant fission products. Measurement of these beta particles in a time projection chamber with a perpendicular magnetic field provides a distinctive set of systematic considerations for comparison to the original seminal beta spectra measurements. Ancillary measurements such as gamma-ray emission and post-irradiation radiochemical analysis will further constrain the absolute normalization of beta emissions per fission. The requirements for unfolding the beta spectra measured with this method into a predicted reactor neutrino spectrum are explored.

D. M. Asner; K. Burns; L. W. Campbell; B. Greenfield; M. S. Kos; J. L. Orrell; M. Schram; B. VanDevender; 1 L. S. Wood; D. W. Wootan

2014-03-01

110

Iron K-alpha resonant absorption in warm absorbers around active galactic nuclei  

NASA Astrophysics Data System (ADS)

Recent ROSAT observations have established the presence of ionized matter along the line of sight in active galactic nuclei (the warm absorber). Here we investigate the iron K-alpha resonant absorption from the ionized matter, and find that the total equivalent width could be very relevant, up to several tens of eV. We point out its importance in determining the physical status and the geometry of the warm absorber. On the other hand, we warn that it can confuse, if neglected, the measurement of the broad iron line emitted by the accretion disk.

Matt, Giorgio

1994-04-01

111

TIR Emissivity Spectra of Thermally Processed Sulfates, Carbonates and Phyllosilicates as Analog Materials for Asteroid Surfaces  

NASA Astrophysics Data System (ADS)

At the Planetary Emissivity Laboratory (PEL) of the German Aerospace Center (DLR) in Berlin we are building a database of spectral measurements of several meteorites and other analogs for asteroid surfaces. Bi-directional reflectance of samples in the 1 to 100 ?m spectral range, are measured by using an evacuated (10-4 bar) Bruker Vertex 80V FTIR spectrometer and a Bruker A513 reflection unit, allowing phase angles between 26° and 170°. Emissivity in the 1 to 100 ?m spectral range is measured with the same instrument coupled with an external emissivity chamber, for sample temperatures ranging from low (50° C) to very high (above 800° C). We present here new measurements on sulfates, carbonates, and phyllosilicates in various grain size ranges. The setup was configured to simulate the thermal history of surface minerals on the asteroid 2008 EV5 during its revolution around the Sun. This asteroid is the scientific target of the ESA Marco Polo-R mission. The samples in vacuum (< 0.8 mbar) are measured at surface temperature around 70° C, then the same samples are heated to 220° C, and maintained at this temperature for one hour. Slowly the sample temperature is reduced back again to 70° C and a second measurement is taken. Emissivity spectra before and after thermal processing of the samples are complemented with reflectance measurements on samples fresh and after thermal processing. This comparison show us that for some minerals no spectral/structural changes appear, while others show signs of dehydration and among them some species show structural changes. We conclude that a proper spectral library of emissivity spectra for asteroid analogue materials must include thermally processed samples, reproducing the thermal evolution for the asteroid that is target of the actual investigation.

Maturilli, A.; Helbert, J.; D'Amore, M.; Ferrari, S.

2013-12-01

112

Excitation-emission spectra and fluorescence quantum yields for fresh and aged biogenic secondary organic aerosols.  

PubMed

Certain biogenic secondary organic aerosols (SOA) become absorbent and fluorescent when exposed to reduced nitrogen compounds such as ammonia, amines, and their salts. Fluorescent SOA may potentially be mistaken for biological particles by detection methods relying on fluorescence. This work quantifies the spectral distribution and effective quantum yields of fluorescence of water-soluble SOA generated from two monoterpenes, limonene and ?-pinene, and two different oxidants, ozone (O3) and hydroxyl radical (OH). The SOA was generated in a smog chamber, collected on substrates, and aged by exposure to ?100 ppb ammonia in air saturated with water vapor. Absorption and excitation-emission matrix (EEM) spectra of aqueous extracts of aged and control SOA samples were measured, and the effective absorption coefficients and fluorescence quantum yields (?0.005 for 349 nm excitation) were determined from the data. The strongest fluorescence for the limonene-derived SOA was observed for ?excitation = 420 ± 50 nm and ?emission = 475 ± 38 nm. The window of the strongest fluorescence shifted to ?excitation = 320 ± 25 nm and ?emission = 425 ± 38 nm for the ?-pinene-derived SOA. Both regions overlap with the EEM spectra of some of the fluorophores found in primary biological aerosols. Despite the low quantum yield, the aged SOA particles may have sufficient fluorescence intensities to interfere with the fluorescence detection of common bioaerosols. PMID:23663151

Lee, Hyun Ji Julie; Laskin, Alexander; Laskin, Julia; Nizkorodov, Sergey A

2013-06-01

113

Emission Spectra of Working Mixtures of a HgBr/HgCl Excimer Lamp  

NASA Astrophysics Data System (ADS)

A study of emission spectra of a gas-discharge plasma produced in a HgBr/HgCl excimer lamp, which is filled with multicomponent working mixtures at atmospheric pressure (HgBr2 and HgCl2 with additions of molecular nitrogen and xenon), are reported. A gas-discharge plasma was produced by high-frequency (pulses ˜100 ns long with a repetition rate of up to 2000 Hz) barrier and surface discharges, which took place simultaneously. Emission of HgBr* and HgCl* excimer molecules, the second positive system of molecular oxygen, and helium and xenon lines in the UV, visible, and IR spectral regions was observed. The strongest emission of HgBr* and HgCl* molecules (the emission intensities were in the ratio 10:1) was observed in the HgBr2: HgCl2: N2: He mixture. Regularities in spectral and integrated characteristics of gas-discharge plasma emission are discussed.

Malinin, A. N.; Gu?van, N. N.; Shimon, L. L.

2000-12-01

114

Emission spectra and intrinsic optical bistability in a two-level medium  

NASA Astrophysics Data System (ADS)

Scattering of resonant radiation in a dense two-level medium is studied theoretically accounting for local field effects and renormalisation of the resonance frequency. Intrinsic optical bistability is viewed as switching between different spectral patterns of fluorescent light controlled by the incident field strength. Response spectra are calculated analytically for the entire hysteresis loop of atomic excitation. The equations to describe the non-linear interaction of an atomic ensemble with light are derived from the Bogolubov-Born-Green-Kirkwood-Yvon hierarchy for reduced single particle density matrices of atoms and quantised field modes and their correlation operators. The spectral power of scattered light with separated coherent and incoherent constituents is obtained straightforwardly within the hierarchy. The formula obtained for emission spectra can be used to distinguish between possible mechanisms suggested to produce intrinsic bistability in experiments.

Gladush, M. G.; Kuznetsov, D. V.; Roerich, Vl. K.

2011-10-01

115

Emission spectra of the cations of some fluoro-substituted phenols in the gaseous phase  

USGS Publications Warehouse

Emission spectra of the cations of 2,5- and 3,5-difluorophenol, of 2,3,4- and 2,4,5-trifluorophenol, of 2,3,5,6-tetrafluorophenol and of 2,3,4,5,6-pentafluorophenol have been obtained in the gas phase using low-energy electron beam excitation. The band systems are assigned to the B??(??-1) ??? X??(??-1) electronic transitions of these cations by reference to photoelectron spectroscopic data. The He(I??) photoelectron spectra and the ionisation energies of ten fluoro-substituted phenols are reported. The symmetries of the four lowest electronic states of these cations are inferred from the radiative decay studies. The lifetimes of the lowest vibrational levels of the B??(??-1) state of the six fluoro-substituted phenol cations above have also been measured. ?? 1980.

Maier, J.P.; Marthaler, O.; Mohraz, M.; Shiley, R.H.

1980-01-01

116

Discovery of the Red-Skewed K-alpha Iron Line in Cyg X-2 with Suzaku  

NASA Technical Reports Server (NTRS)

We report on the Suzaku observation of neutron star low-mass X-ray binary Cygnus X-2 which reveals strong iron K-alpha emission line. The line profile shows a prominent red wing extending down to 4 keV. This discovery increases the number of neutron star sources where red-skewed iron lines were observed and strongly suggests that this phenomenon is common not only in black holes but also in other types of compact objects. We examine the line profile by fitting it with the model which attributes its production to the relativistic effects due to disk reflection of X-ray radiation. We also apply an alternative model where the red wing is a result of down-scattering effect of the first order with respect to electron velocity in the wind outflow. Both models describe adequately the observed line profile. However, the X-ray variability in a state similar to that in the Suzaku observation which we establish by analysing RXTE observation favors the wind origin of the line formation.

Shaposhnikov, Nikolai; Titarchuk, Lev; Laurent, Philippe

2008-01-01

117

On the dynamical spectra of S-bursts in the Jovian radio emission. II. Observations and analysis  

Microsoft Academic Search

Available observational data on the dynamical spectra of S-bursts in Jupiter's radio emission are analyzed and classified on the basis of the theoretical model put forward in Part I of this study. The observed dynamical spectra can be explained by the effect of surface perturbations in the Io-Jupiter flux tube on the transformation of plasma waves to the electromagnetic waves.

A. G. Boev; M. Yu. Luk'yanov; N. A. Tsvyk

1993-01-01

118

Calcium Pyroxenes at Mercurian Surface Temperatures: Investigation of In-Situ Emissivity Spectra.  

NASA Astrophysics Data System (ADS)

Several observations point to the possibility that Ca-rich (and low-Fe) clinopyroxenes could be common constituent minerals of the surface of Mercury. The upcoming ESA-JAXA BepiColombo mission to Mercury will carry on board the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) that will provide surface emissivity spectra in the wavelength range from 7-14 ?m. This spectral range is very useful to identify the fine-scale structural properties of several silicates including pyroxenes. The extreme daily surface temperature range of Mercury (70 to 725 K) that significantly affects the spectral signature of minerals will make the interpretation of MERTIS observations challenging. It has been shown that spectra of clinopyroxenes with similar calcium content display a deepening of the main absorption bands, and a shift of the band minima toward higher wavelengths with increasing temperatures. Similar shifts can also be observed at constant temperature with increasing iron content in the M2 site. Therefore, the thermal expansion induced by the increasing temperature simulates the presence of a larger cation (e.g., iron vs. magnesium) within the mineral structure. Interestingly, each band shifts by a different amount, representing a marker for the real chemistry of the sample. A detailed study of the described mineral behavior is fundamental to localize those spectral bands sensitive to the daily temperature range of the Mercury surface. In combination with the temperature measurements obtained independently by the radiometer channel of MERTIS this will help to further constrain the mineralogical interpretation of the MERTIS spectral data. Here we present high-temperature (up to 750 K) laboratory emissivity spectra of several augitic pyroxenes with different calcium contents and very different magnesium to iron ratios. The spectra were derived from individual well-preserved natural crystals of several pyroxenes of less than 125 ?m in size, which approaches the presumable size of Mercurian regolith particles. The emissivity measurements of the heated samples under vacuum have been conducted using the Mercury simulation chamber at the Planetary Emissivity Laboratory (PEL) in Berlin.

Ferrari, Sabrina; Maturilli, Alessandro; Helbert, Jörn; Rossi, Manuela; Nestola, Fabrizio; D'Amore, Mario; Hiesinger, Harald

2014-05-01

119

t-SURFF: fully differential two-electron photo-emission spectra  

NASA Astrophysics Data System (ADS)

The time-dependent surface flux (t-SURFF) method is extended to single and double ionization of two-electron systems. Fully differential double emission spectra by strong pulses at extreme UV and infrared wavelengths are calculated using simulation volumes that only accommodate the effective range of the atomic binding potential and the quiver radius of free electrons in the external field. For a model system, we found a pronounced dependence of shake-up and non-sequential double ionization on the phase and duration of the laser pulse. The extension to fully three-dimensional calculations is discussed.

Scrinzi, Armin

2012-08-01

120

The hard X-ray emission spectra from accretion columns in intermediate polars  

NASA Technical Reports Server (NTRS)

We consider the hard (greater than 2 keV) X-ray emission from accretion columns in an intermediate polar system, GK Per, using a simple settling solution. The rate of photon emission per logarithmic energy interval can be fitted with a power law, E(exp -gamma), with gamma approximately 2.0, in agreement with observations. This index is only weakly dependent on the mass accretion rate, dot-M, for dot-M in the range of a few times 10(exp 16-18) g/s. The peak energy of the photon spectra (after photoelectric absorption) is expected to be E(sub p) approximately (5 keV) gamma(exp -1/3) (N(sub H)/10(exp 23)/sq cm)(exp 1/3) where N(sub H) is the hydrogen column density along the line of sight. The observed spectra of GK Per and possibly of V1223 Sgr suggest N(sub H) approximately 10(exp 23)/sq cm. This large N(sub H) may be due to partially ionized preshock column material. Alternatively, we also consider absorption by the cool outer parts of an accretion disk. In this case the photoelectric absorption depth in the disk is a sensitive function of inclination. For GK Per the required inclination is approximately 83 deg. For mass accretion rates larger than a critical rate of approximately 10(exp 18) g/s, X-ray emission from the column accretion is significantly affected by radiation drag. Although the mass accretion rate increases dramatically during outbursts, the observed hard (greater than 2 keV) X-ray luminosity will not rise proportionately. The slope and peak energy of the outburst spectra are only weakly affected. We conclude that the observed X-ray spectra can be explained by this simple analytic solution and that the production of hard X-rays from the accretion shock at the magnetic poles in the intermediate polars is in general agreement with the observations. However, since the X-ray emission and absorption depend on the mass accretion rate in a complicated manner, observed hard X-ray luminosities (greater than 2 keV) are not a good indicator of the mass accretion rate in the X-ray emitting regions.

Yi, Insu; Vishniac, Ethan T.

1994-01-01

121

Removing the Shock from the Thermal Emission Spectra of Shocked Terrestrial and Martian Basalts  

NASA Astrophysics Data System (ADS)

An abundance of impact craters on the martian surface and shock effects in the martian meteorites indicate that the surface of Mars has been shocked. The thermal infrared (TIR) spectra of plagioclase feldspars experimentally shocked to various pressures have enabled the amount of shock to be correlated with changes in the TIR spectra [Johnson et al., 2002, 2003]. With these, estimates on the amount of shocked plagioclase feldspar on the martian surface has been investigated [Johnson et al., in press]. However, in relation to the use of shocked plagioclase feldspars as end-members for the deconvolution of remote TIR data, similar work need to be performed on the laboratory spectra of shocked rocks and subsequent deconvolutions with these shocked mineral end-members. In this work, laboratory TIR spectra of a shocked terrestrial basalt and it unshocked counterpart are deconvolved and compared to assess the possibility of removing the spectral contribution of shocked plagioclase feldspar from a shocked martian basalt spectrum. It has been suggested that the modal abundances of martian meteorite Los Angeles [Rubin et al., 2000] are similar to mineral abundances derived from the deconvolution of Thermal Emission Spectrometer (TES) Surface Type 1 (ST1) [Bandfield, 2002]. TIR spectra of shocked basalt from Lonar Crater, India were collected and deconvolved with an end-member library containing experimentally shocked calcic plagioclase feldspars [Johnson et al., 2002]. The deconvolution-derived mineral abundances were compared to those from deconvolutions of unshocked basalt, and it was determined that the spectrum of the original, unshocked bulk rock could be replicated by removing from the spectrum of a shocked basalt the shocked plagioclase end-member spectrum (scaled by its abundance). The same methodology was performed on another shocked basalt, martian meteorite Los Angeles. The TIR spectra of Los Angeles was deconvolved with an end-member library containing shocked plagioclase feldspar (An75), revealing an abundance of maskelynite (~46%) that closely matches modal abundances from petrographic studies (~45%) [Rubin et al., 2000]. TIR spectra of shocked intermediate calcic plagioclase feldspars such as those found in Los Angeles (An56-38) do not exist and therefore are not contained within the spectral library used here. A mean percentage of 46% of the shocked plagioclase feldspar end-member was removed from the bulk rock spectra of Los Angeles and replaced with unshocked labradorite. Similar to the Lonar Crater basalts, this should recreate the spectra of the pre-impact, unshocked basalt. This end-member replacement results in a TIR spectrum of a basalt with a Christiansen feature moved to lower wavenumbers, agreeing with previous work that suggested the position of this feature varies with the amount of shock [Johnson et al., 2002]. The new "unshocked" Los Angeles TIR spectrum is not an exact match for ST1, but it is more similar to TES spectra than a shocked Los Angeles spectrum is. Whereas laboratory TIR spectra of shergottites provide poor matches to orbital TES data [Hamilton et al., 2003], using this unshocked basalt spectrum as an end-member might provide additional constraints on the source region of Los Angeles. Further, it is suggested here that TIR spectra be acquired for various experimentally shocked end members of plagioclase feldspar solid solution series for better deconvolutions of shocked rocks.

Wright, S. P.; Bandfield, J. L.; Christensen, P. R.; Johnson, J. R.

2004-12-01

122

Bidimensional characterization of the emission spectra in a direct current atmospheric pressure glow discharge  

NASA Astrophysics Data System (ADS)

An in-house atmospheric pressure glow discharge source, designed to be used as ionization/desorption source for ambient mass spectrometry, has been electrically characterized, and its optical emission spectra evaluated in detail. Electrical characterization showed that the plasma regime can vary from glow discharge to arc discharge depending on operating conditions (i.e. He flow rate and inter electrode distance). Furthermore, bidimensional images of the optical emission of some plasma species using filters as wavelength selectors, were registered from inside and outside the discharge chamber (inner region and afterglow region respectively), showing the spatial distribution of excited species (i.e. He*, N2+ and O*). These distribution patterns are useful to study the chemistry of the discharge plasma, since different production pathways and different excitation energies affect the presence of these species in the plasma regions.

Orejas, Jaime; Pisonero, Jorge; Bordel, Nerea; Nelis, Thomas; Guillot, Philippe; Sanz-Medel, Alfredo

2012-10-01

123

Phosphorescent Molecularly Doped Light-Emitting Diodes with Blended Polymer Host and Wide Emission Spectra  

PubMed Central

Stable green light emission and high efficiency organic devices with three polymer layers were fabricated using bis[2-(4?-tert-butylphenyl)-1-phenyl-1H-benzoimidazole-N,C2?] iridium(III) (acetylacetonate) doped in blended host materials. The 1?wt% doping concentration showed maximum luminance of 7841?cd/cm2 at 25.6?V and maximum current efficiency of 9.95?cd/A at 17.2?V. The electroluminescence spectra of devices indicated two main peaks at 522?nm and 554?nm coming from phosphor dye and a full width at half maximum (FWHM) of 116?nm. The characteristics of using blended host, doping iridium complex, emission spectrum, and power efficiency of organic devices were investigated. PMID:24324387

Wang, Jun; Gou, Jun; Li, Weizhi

2013-01-01

124

Voltage-induced evolution of emission spectra in organic light-emitting diodes  

NASA Astrophysics Data System (ADS)

A simple model for the voltage-induced alteration of emission spectra from single- as well as multilayer organic light-emitting diodes (LEDs) based on low-molecular-weight materials is reported. The relative contribution of the redshifted emission spectrum component of a dopant or a separate film in multilayer structure can be changed by electric-field-induced quenching of its excited states and/or voltage evolution of the recombination zone. The effect is demonstrated on N,N'-diamine (TPD) single-layer LEDs nonuniformly doped with a perylene bisimide pigment (PBP) and double heterostructure TPD/Alq3/PBP with 8-hydroxyquinoline aluminum, Alq3. While in the first class of LEDs the color changes from red to blue dependent on the applied voltage and average concentration of the PBP dye, the second-type structures operate in the red-green range as the blue emission from TPD is eliminated. Analytic considerations are presented relating the relative contribution of different color emission bands to the driving current and applied electric field as well as to the composition and structure parameters of LEDs such as dopant concentration or thickness of the layers.

Kalinowski, J.; Di Marco, P.; Fattori, V.; Giulietti, L.; Cocchi, M.

1998-04-01

125

Fourier transform infrared emission spectra of MgH and MgD A. Shayesteh and D. R. T. Appadoo  

E-print Network

Fourier transform infrared emission spectra of MgH and MgD A. Shayesteh and D. R. T. Appadoo, Ontario, N2L 3G1, Canada Received 9 February 2004; accepted 8 March 2004 High resolution Fourier transform the emission spectrum of the A 2 X 2 transition of MgH using a magnesium hollow cathode discharge and a Fourier

Le Roy, Robert J.

126

A method to remove residual OH emission from near infrared spectra  

E-print Network

I present a technique to remove the residual OH airglow emission from near infrared spectra. Historically, the need to subtract out the strong and variable OH airglow emission lines from 1-2.5um spectra has imposed severe restrictions on observational strategy. For integral field spectroscopy, where the field of view is limited, the standard technique is to observe blank sky frames at regular intervals. However, even this does not usually provide sufficient compensation if individual exposure times are longer than 2-3minutes due to (1) changes in the absolute flux of the OH lines, (2) variations in flux among the individual OH lines, and (3) effects of instrumental flexure which can lead to `P-Cygni' type residuals. The data processing method presented here takes all of these effects into account and serendipitously also improves background subtraction between the OH lines. It allows one, in principle, to use sky frames taken hours or days previously so that observations can be performed in a quasi-stare mode. As a result, the observing efficiency (i.e. fraction of time spent on a source) at the telescope can be dramatically increased.

R. I. Davies

2006-12-11

127

Computer-controlled densitometer for the analysis of photographically recorded optical emission spectra  

SciTech Connect

A computer-controlled densitometer for data acquisition and high speed analysis of photographically recorded optical emission spectra has been developed. The instrument scans and digitizes spectra and stores the data sequentially in computer memory. A high-resolution linear measurement transducer mounted on a Jarrell-Ash densitometer monitors the plate position as the spectrum is scanned. The transducer measurement is accurate to within 0.001% over a range of about 340-mm on a glass photoplate. Computer algorithms for locating and identifying peaks and for calculating the wavelengths of spectral lines from their positions in the spectrum are described. With the use of a calibration curve based on the measured positions of three known spectral lines, the wavelength of any spectral line can be determined to within 0.005 nm, and the transmittance of a peak in the recorded spectrum can be measured to within 1%. The wavelengths and transmittances of all detectable spectral lines in the digitized emission spectrum are determined in less than two minutes.

Hareland, W.A.; Grant, S.E.; Ward, S.P.; Anderson, D.R.

1987-11-01

128

The Effects of Varying Environmental Conditions on the Emission Spectra of Meteorites  

NASA Astrophysics Data System (ADS)

With NASA's OSIRIS-REx mission due to launch to asteroid 101955 Bennu (previously known as 1999 RQ36) in 2016, preparations are well underway [4]. Once there, the OTES (OSIRIS-Rex Thermal Emission Spectrometer) instrument will map the asteroid's surface to derive thermal and compositional properties [4], by comparing spectra to those of known samples measured in the laboratory. Previous studies have shown that samples can exhibit differen ces in emission spectra due to composition, grain size and the environmental conditions in which they are measured [3,5,7], however the magnitude of these variations for asteroidal material require more study. The aim of this work is to determine whether laboratory samples need to be measured in a thermal environment like that on the asteroid's surface for correct interpretation of returning data from OTES: to do this, the Lunar Environment Chamber in the Planetary Spectroscopy Facility at Oxford University [7] was used to simulate the expected conditions on Bennu while a selection of ground meteorite samples were measured.

Thomas, I. R.; Bowles, N. E.; Connolly, H. C.; Kilgore, M.; Lauretta, D. S.

2013-09-01

129

Near-infrared emission spectra of TeS, TeSe and Te2  

NASA Astrophysics Data System (ADS)

Emission spectra of the radicals TeS, TeSe and Te2 in the near-infrared spectral region have been measured with a high-resolution Fourier-transform spectrometer. The molecules were generated in a fast-flow system by reacting microwave-discharged mixtures of Tex, Sx, and/or Sex vapour and Ar carrier gas and excited by energy transfer and energy pooling processes in collisions with metastable oxygen O2(a1?g). The b1?+(b0+) ? X3?-(X10+,X21) electric dipole transitions of TeS and TeSe and the b1?+g(b0+g) ? X3?-g(X21g) magnetic dipole transition of Te2 were measured at medium and high spectral resolution. A very weak emission at 3356 cm-1 observed in the spectrum of TeSe was identified to be the 0-0 band of the hitherto unknown a1?(a2) ? X3?-(X21) transition of the molecule. Analyses of the spectra have yielded a number of new or improved spectroscopic parameters of the molecules.

Setzer, K. D.; Fink, E. H.

2014-10-01

130

Detection of H2 Emission from Mira B in UV Spectra from the Hubble Space Telescope  

E-print Network

We present ultraviolet spectra of Mira's companion star from the Space Telescope Imaging Spectrograph (STIS) instrument on board the Hubble Space Telescope (HST). The companion is generally assumed to be a white dwarf surrounded by an accretion disk fed by Mira's wind, which dominates the UV emission from the system. The STIS UV spectrum is dominated by numerous, narrow H2 lines fluoresced by H I Ly-alpha, which were not detected in any of the numerous observations of Mira B by the International Ultraviolet Explorer (IUE). The high temperature lines detected by IUE (e.g., C IV 1550) still exist in the STIS spectrum but with dramatically lower fluxes. The continuum fluxes in the STIS spectra are also much lower, being more than an order of magnitude lower than ever observed by IUE, and also an order of magnitude lower than fluxes observed in more recent HST Faint Object Camera objective prism spectra from 1995. Thus, the accretion rate onto Mira B was apparently much lower when STIS observed the star, and this change altered the character of Mira B's UV spectrum.

Brian E. Wood; Margarita Karovska; Warren Hack

2001-07-02

131

Retrieval of tropospheric profiles from IR emission spectra: preliminary results with the DBIS  

NASA Astrophysics Data System (ADS)

Recently, Smith and collaborators from University of Wisconsin-Madison have clearly established the possibilities of sounding tropospheric temperature and water vapor profiles with a ground-based uplooking interferometer. With the same perspective but for somewhat different applications, the Defence Research Establishment Valcartier (DREV) has initiated a project with the aim of exploring the many possible avenues of similar approaches. DREV, in collaboration with BOMEM (Quebec, Canada), has developed an instrument referred to as the Double Beam Interferometer Sounder (DBIS). This sounder has been conceived to match the needs encountered in many remote sensing scenarios: slant path capability, small field of view, very wide spectral coverage, and high spectral resolution. Preliminary tests with the DBIS have shown sufficient accuracy for remote sensing applications. In a series of field measurements, jointly organized by the Geophysics Directorate/PL, Hanscom AFB, and DREV, the instrument has been run in a wide variety of sky conditions. Several atmospheric emission spectra recorded with the sounder have been compared to calculations with FASCODE and MODTRAN models. The quality of measurement-model comparisons has prompted the development of an inversion algorithm based on these codes. The purpose of this paper is to report the recent progress achieved in this research. First, the design and operation of the instrument are reviewed. Second, recent field measurements of atmospheric emission spectra are analyzed and compared to models predictions. Finally, the simultaneous retrieval approach selected for the inversion of DBIS spectra to obtain temperature and water vapor profiles is described and preliminary results are presented.

Theriault, Jean-Marc; Anderson, Gail P.; Chetwynd, James H., Jr.; Murphy, Randall E.; Turner, Vernon; Cloutier, M.; Smith, A.; Moncet, Jean-Luc

1993-11-01

132

Theoretically predicted soft X-ray emission and absorption spectra of fullerene-like carbon nitride (C 24N 36)  

Microsoft Academic Search

Theoretical C K and N K X-ray emission\\/absorption spectra of fullerene-like-structured carbon nitride (C24N36) clusters were obtained using discrete-variational (DV)-X? molecular orbital calculations. These calculations predicted that the energy widths of the C K and N K X-ray emission peaks would be about 8 and 6 eV, respectively; three low-energy satellites would appear in each emission spectrum; and there would

Yasuji Muramatsu; Takayoshi Hayashi; Rupert C. C. Perera

1999-01-01

133

Thermal emission spectra of Mars (5.4-10.5 microns) - Evidence for sulfates, carbonates, and hydrates  

Microsoft Academic Search

Spectra of the Martian thermal emission in the 5.4-10.5 micron region are reported. Emission features at 7.8 and 9.7 microns are attributed to surface silicates, and an emission feature at 6.1 micron is attributed to a molecular water component of the surface material. An absorption band at 8.7 micron and a possible one at 9.8 microns is attributed to sulfate

James B. Pollack; Ted Roush; Fred Witteborn; Jesse Bregman; Diane Wooden; Carol Stoker; Owen B. Toon; David Rank; Brad Dalton; Richard Freedman

1990-01-01

134

Analysis of Emission Spectra from Arc-jet Shock Layer Flows  

NASA Technical Reports Server (NTRS)

This paper reports computational comparisons with experimental studies of a nonequilibrium blunt body shock layer in a high enthalpy arc-jet wind tunnel at NASA Ames Research Center. The primary objective of this work is to investigate the existence of a thermochemical equilibrium region in the shock layer. The existence of such an equilibrium region is of interest for following reasons: (1) to understand the equilibration process behind the shock in an arc-jet flow environment; (2) to interpret measured surface heat transfer data for purpose of determining surface catalytic efficiency, and (3) to determine the total enthalpy from the spectroscopic measurements. The paper will present an analysis of the experimental data obtained in the arc-jet wind tunnel. Experimental data includes measurements of emission spectra of radiation emanating from a shock layer formed in front of a 6-inch flat-faced cylinder. The measurements, obtained using a two dimensional CCD camera mounted on a spectrograph, provide spatially resolved spectra along the stagnation streamline of the model. Computational analysis includes simulation of nonequilibrium flow in the arc-jet facility (flow in the conical nozzle and shock layer in front of a flat-faced cylinder) using 2-D/axisymmetric Navier-Stokes codes and prediction of the radiation spectra from the axisymmetric flowfield using NEQAIR radiation code. Various line-of-sight averaged flow properties such as vibrational and rotational temperatures, species number densities within the shock layer are deduced from the experimental spectra. Comparison of the computed and experimental line-of-sight averaged flow properties provides assessment of thermochemical equilibration processes in an arc-jet shock layer.

Gokcen, T.; Park, C. S.; Newfield, M. E.; Fletcher, D. G.; Langhoff, Stephen R. (Technical Monitor)

1997-01-01

135

Consistency of atomic data for the interpretation of beam emission spectra  

NASA Astrophysics Data System (ADS)

Several collisional-radiative (CR) models (Anderson et al 2000 Plasma Phys. Control. Fusion 42 781-806, Hutchinson 2002 Plasma Phys. Control. Fusion 44 71-82, Marchuk et al 2008 Rev. Sci. Instrum. 79 10F532) have been developed to calculate the attenuation and the population of excited states of hydrogen or deuterium beams injected into tokamak plasmas. The datasets generated by these CR models are needed for the modelling of beam ion deposition and (excited) beam densities in current experiments, and the reliability of these data will be crucial to obtain helium ash densities on ITER combining charge exchange and beam emission spectroscopy. Good agreement between the different CR models for the neutral beam (NB) is found, if corrections to the fundamental cross sections are taken into account. First the H? and H? beam emission spectra from JET are compared with the expected intensities. Second, the line ratios within the Stark multiplet are compared with the predictions of a sublevel resolved model. The measured intensity of the full multiplet is ?30% lower than expected on the basis of beam attenuation codes and the updated beam emission rates, but apart from the atomic data this could also be due to the characterization of the NB path and line of sight integration and the absolute calibration of the optics. The modelled n = 3 to n = 4 population agrees very well with the ratio of the measured H? to H? beam emission intensities. Good agreement is found as well between the NB power fractions measured with beam emission in plasma and on the JET Neutral Beam Test Bed. The Stark line ratios and ?/? intensity ratio deviate from a statistical distribution, in agreement with the CR model in parabolic states from Marchuk et al (2010 J. Phys. B: At. Mol. Opt. Phys. 43 011002).

Delabie, E.; Brix, M.; Giroud, C.; Jaspers, R. J. E.; Marchuk, O.; O'Mullane, M. G.; Ralchenko, Yu; Surrey, E.; von Hellermann, M. G.; Zastrow, K. D.; Contributors, JET-EFDA

2010-12-01

136

K-(alpha) X-ray Thomson Scattering From Dense Plasmas  

SciTech Connect

Spectrally resolved Thomson scattering using ultra-fast K-{alpha} x-rays has measured the compression and heating of shocked compressed matter. The evolution and coalescence of two shock waves traveling through a solid density LiH target were characterized by the elastic scattering component. The density and temperature at shock coalescence, 2.2 eV and 1.7 x 10{sup 23}cm{sup -3}, were determined from the plasmon frequency shift and the relative intensity of the elastic and inelastic scattering features in the collective scattering regime. The observation of plasmon scattering at coalescence indicates a transition to the dense metallic state in LiH. The density and temperature regimes accessed in these experiments are relevant for inertial confinement fusion experiments and for the study of planetary formation.

Kritcher, A L; Neumayer, P; Castor, J; Doppner, T; Falcone, R W; Landen, O L; Lee, H J; Lee, R W; Morse, E C; Ng, A; Pollaine, S; Price, D; Glenzer, S H

2009-05-07

137

Spectra of 7 H? emission line stars in MBM 18 (Brand+ 2012)  

NASA Astrophysics Data System (ADS)

Data in tabular form (wavelength and flux) are presented of the spectra of seven candidate H? emission line stars in the direction of translucent cloud MBM 18. The data were obtained on 5 different nights in 2009 and 2010 with the 3.58-m Telescopio Nazionale Galileo (TNG; La Palma, Canary Islands, Spain). The spectra are shown in the appendix of the paper, only visible in the on line version. The spectra were taken with the low-resolution spectrograph DOLORES on the TNG, using long-slit spectroscopy. We used grism VHR-R, which covers a wavelength range of 6240-7720 Angstrom with a dispersion of 0.80Å/pix. The scale of the CCD detector is 0.252 arcsec/pixel. The observations were carried out with a slit width of 1 or 1.5 arcsec, depending on the seeing, resulting in a spectral resolution of 3.2Å and 4.8Å, respectively. To avoid problems with cosmic rays, 2 to 4 separate spectra per star were obtained. Two of the stars (Ha4 and Ha6) were observed simultaneously with another target (Ha1 and Ha5, respectively) by positioning the slit at an appropriate angle. The integration time was based on the brighter star in the slit, thus the signal-to-noise ratio for the other target is smaller than for the primary one. To allow absolute flux calibration the standard star Feige24 or Feige34 (for Ha5-Ha6) was observed immediately before or after the target observations, using the same instrumental setup as for the target observations. Flat-fielding was performed using 10 (5 for Ha5-Ha6) frames, which were uniformly illuminated by a halogen lamp. Wavelength calibration was performed using an arc-spectrum of an Ar, Ne+Hg, and Kr lamp, or a Ne+Hg (for Ha7) comparison lamp. A bias frame, to be subtracted from the other frames before analysis, was constructed from ten individual bias frames. Flat-, arc-, and bias-frames were obtained on the same day as the science observations and with the same instrumental setup. Data were reduced with the IRAF package. From all science frames a bias was subtracted, after which they were divided by the normalised flat field. From each of the science frames the trace(s) of the star(s) were extracted and these were wavelength-calibrated using one of the frames with the arc-spectrum. Each target was wavelength-calibrated with the arc-spectrum extracted at the same location on the detector, to compensate for small deviations that might occur in the alignment of the reference emission lines across the detector. The spectra were then corrected for extinction, and flux-calibrated using the standard star observations. The individual one-dimensional wavelength- and flux-calibrated spectra of each target were then averaged into a final spectrum. To further correct the wavelength calibration, we used the sky lines that were subtracted from the stellar spectra. For each spectrum, Gaussian fits were made to tens of sky lines, and their wavelengths were compared to those listed in Osterbrock et al. (1996PASP..108..277O, Cat. III/211. Three stars were found to need a small correction: Ha2 (-1.5Å) and Ha5 and 6 (both -2.2Å); these corrections have been applied in the tables. For the other four stars the difference was negligible, although for the sky lines in Ha1 and Ha4 (which were observed in the same slit) the deviation between measured and literature wavelengths varied slightly, but systematically, with wavelengths between 6250Å and 7600Å, while at longer wavelengths the deviations became rapidly larger (up to several Angstroms). (8 data files).

Brand, J.; Wouterloot, J. G. A.; Magnani, L.

2012-10-01

138

Simulated emission spectra of samples at non-uniform temperature based on numerical solutions of the general radiative transfer equation  

NASA Astrophysics Data System (ADS)

Infrared spectroscopic methods are increasingly being used for analysis in the food industry. A potentially attractive approach is that of infrared emission spectroscopy: in many food processes, the raw materials are subjected to heating, and once hot, act as sources of infrared radiation. If the emitted radiation is steered directly into a spectrometer with the conventional source removed, an emission spectrum may be obtained of the sample without any further light guiding requirement. However, for bulk samples, the spectra obtained are not very useful, due to the mechanism of self-absorption, whereby chemically different samples give rise to the same, featureless spectral profile. Promising strategies for overcoming this problem are Transient Infrared Emission and Transient Infrared Transmission Spectroscopies (TIRES and TIRTS), in which thermal gradients are induced at the sample surface, enabling composition-specific features to be seen in the emission spectrum. In this paper mathematical models of the effect of thermal gradients on emission spectra are presented, based on numerical solutions of the Radiative Transfer Equation (RTE) for the non-uniform temperature case, using parameters determined experimentally. This provides a method of relating the nature of thermal gradient within a sample to the information content expected in its emission spectrum. Thus, the conditions required to obtain useful emission spectra from bulk samples can be determined, and the potential of emission spectroscopy as an analysis tool in food production processes assessed.

Kemsley, E. K.; Belton, P. S.

1995-03-01

139

Kinetic energy spectra in thermionic emission from small tungsten cluster anions: evidence for nonclassical electron capture.  

PubMed

The delayed electron emission from small mass-selected anionic tungsten clusters W(n)(-) has been studied for sizes in the range 9 < or = n < or = 21. Kinetic energy spectra have been measured for delays of about 100 ns after laser excitation by a velocity-map imaging spectrometer. They are analyzed in the framework of microreversible statistical theories. The low-energy behavior shows some significant deviations with respect to the classical Langevin capture model, which we interpret as possibly due to the influence of quantum dynamical effects such as tunneling through the centrifugal barrier, rather than shape effects. The cluster temperature has been extracted from both the experimental kinetic energy spectrum and the absolute decay rate. Discrepancies between the two approaches suggest that the sticking probability can be as low as a few percent for the smallest clusters. PMID:20232960

Concina, Bruno; Baguenard, Bruno; Calvo, Florent; Bordas, Christian

2010-03-14

140

Simulated infrared emission spectra of highly excited polyatomic molecules: a detailed model of the PAH-UIR hypothesis  

NASA Technical Reports Server (NTRS)

A detailed description of the polycyclic aromatic hydrocarbon (PAH)/unidentified infrared band (UIR) mechanism is presented in which experimental spectral bandshape functions are used to simulate IR emission spectra for individual molecules. These spectra are additively superimposed to produce a conglomerate spectrum representative of a family of PAH molecules. Ab initio vibrational frequencies and intensities for nine PAHs (neutral and cationic) as large as ovalene are used in conjunction with measured bandshape and temperature-dependent redshift data to simulate the UIR bands. The calculated spectra of cations provide a closer match to the UIRs than do those of the neutrals. However, the PAH cations used in the simulations fail to reproduce the details of the UIR emission spectra. The discrepancies are potentially alleviated if both larger PAHs and a greater number of PAHs were included in the simulation.

Cook, D. J.; Saykally, R. J.

1998-01-01

141

Frequency spectra of cosmic ray air shower radio emission measured with LOPES  

E-print Network

AIMS: We wish to study the spectral dependence of the radio emission from cosmic-ray air showers around 100 PeV (1017 eV). METHODS: We observe short radio pulses in a broad frequency band with the dipole-interferometer LOPES (LOFAR Prototype Station), which is triggered by a particle detector array named Karlsruhe Shower Core and Array Detector (KASCADE). LOFAR is the Low Frequency Array. For this analysis, 23 strong air shower events are selected using parameters from KASCADE. RESULTS: The resulting electric field spectra fall off to higher frequencies. An average electric field spectrum is fitted with an exponential, or alternatively, with a power law. The spectral slope obtained is not consistent within uncertainties and it is slightly steeper than the slope obtained from Monte Carlo simulations based on air showers simulated with CORSIKA (Cosmic Ray Simulations for KASCADE). One of the strongest events was measured during thunderstorm activity in the vicinity of LOPES and shows the longest pulse length measured of 110 ns and a spectral slope of -3.6. CONCLUSIONS: We show with two different methods that frequency spectra from air shower radio emission can be reconstructed on event-by-event basis, with only two dozen dipole antennae simultaneously over a broad range of frequencies. According to the obtained spectral slopes, the maximum power is emitted below 40 MHz. Furthermore, the decrease in power to higher frequencies indicates a loss in coherence determined by the shower disc thickness. We conclude that a broader bandwidth, larger collecting area, and longer baselines, as will be provided by LOFAR, are necessary to further investigate the relation of the coherence, pulse length, and spectral slope of cosmic ray air showers.

A. Nigl

2008-09-16

142

Deriving chlorophyll fluorescence emissions of vegetation canopies from high resolution field reflectance spectra  

NASA Astrophysics Data System (ADS)

Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll fluorescence (ChlF) peaks centered at 685 nm and 735 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SIF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops and small tree plots of three deciduous species (red maple, tulip poplar, sweet gum). Leaf level measurements were also made of foliage which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and nitrogen (N) contents). As part of ongoing experiments, measurements were made on N application plots within corn (280, 140, 70, and 0 kg N/ha) and tree (0, 37.5, 75, 112.5, 150 kg N /ha) sites at the USDA/Agriculture Research Service in Beltsville, MD. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrow- band regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red SIF ratio (SIFratio) derived from these field reflectance spectra successfully discriminated foliar pigment ratios altered by N application rates in both corn crops. This ratio was also positively correlated to the C/N ratio at leaf and canopy levels, for the available corn data (e.g., 2004). No consistent N treatment or species differences in SIF were detected in the tree foliage, but additional 2005 data are forthcoming. This study has relevance to future passive satellite remote sensing approaches to monitoring C dynamics from space.

Middleton, Elizabeth M.; Corp, Lawrence A.; Daughtry, Craig S.; Entcheva Campbell, Petya K.; Butcher, L. Maryn

2005-11-01

143

Deconvolving Contributions to the Narrow Emission-Line Spectra of Narrow-Line Seyfert 1s  

NASA Astrophysics Data System (ADS)

We present a continuation of our study of ground-based spectra of a sample of 12 Narrow-Line Seyfert 1s (NLSy1s), obtained using the 1.5m telescope at CTIO. Previously, we had found similar emission line ratios in both NLSy1s and Broad-Line Seyfert 1s (BLSy1s), which suggests similar ionizing continua, although we noted that low-ionization lines, such as [O I] 6300A and such as [S II] 6716,6731A may be somewhat weaker in NLSy1s. Based on photo-ionization modeling, the spectra from both types must include a strong contribution from dense, highly ionized gas in the inner narrow-line region (NLR), as has been noted in the literature. Notably, we find that the average [O III] 5007A/[OII] 3727A ratio is ~ 3.5 in NLSy1s, as compared to ~ 6.5 in a similar-sized sample of BLSy1s, consistent with a strong contribution from star-formation in the former. It is unclear whether star-formation is more prevalent in NLSy1s, suggesting a unique stage in the evolution of the AGN, or whether they tend to lack an extended NLR, which overwhelms any contribution from star-formationand may be due to the orientation of the AGN with the host galaxy.

Kraemer, Steven B.; Crenshaw, D. M.; Schmitt, H. R.; Dietrich, M.

2014-01-01

144

Measurements of L-shell ion line emission spectra for diagnostics of stellar atmospheres  

NASA Astrophysics Data System (ADS)

Chandra and XMM-Newton observations have found many unidentified relatively weak emission lines in astrophysical spectra taken in the 20 -- 70 ° region, which may arise from L-shell ions of astrophysically abundant elements. Current line lists are insufficient for identifying these ions. We have conducted laboratory measurements employing the Livermore electron beam ion traps to record spectra of the relevant ions at densities similar to stellar atmospheres (? 10^12 cm-1. We completed line lists of the nell arrow 2ell transitions for Ar IX -- Ar XVI, S VII -- S XIV, and Si V -- Si XII. Our measurements are compared to calculations using the HULLAC set of atomic computer codes, which are used to confirm line identifications. Comparing our data to Chandra observations of Procyon, we confirm identifications of some smaller lines and correct others, misidentified to element or charge state. This work was supported by NASA SARA grant W-19,878 and performed under auspices of DOE by UC-LLNL under Contract W-7405-Eng-48.

Lepson, Jaan; Beiersdorfer, Peter; Behar, Ehud; Kahn, Steven

2004-05-01

145

Emission spectra and kinetics of copolymer films of styrene and 2,3,4,5,6-pentafluorostyrene  

NASA Technical Reports Server (NTRS)

The temperature-dependent steady-state emission spectra and fluorescence kinetics of copolymer films of styrene and 2,3,4,5,6-pentafluorostyrene are reported. The polystyrene excimer emission is efficiently quenched in the presence of relatively small amounts of the pentafluorophenyl quencher in spite of the fact that direct energy transfer from the excimer to the quencher chromophores is not possible. The quenching of the polystyrene excimer emission at room temperature and of the polystyrene monomer emission at 13 K is attributed to the interception of the migrating monomer excitation by the quencher. The data suggest that this quenching mechanism is independent of temperature.

O'Connor, Donald B.; Scott, Gary W.; Coulter, Daniel R.; Yavrouian, Andre

1991-01-01

146

Lyman-alpha emission from the Lyman-alpha forest. [in high red shift quasar spectra due to molecular clouds  

NASA Technical Reports Server (NTRS)

It is suggested that high-dispersion long-slit spectra or very narrow-band etalon images of 'blank' sky could reveal patches of Ly-alpha line emission from the population of clouds whose absorption produces the 'Ly-alpha forest' in QSO spectra. A nonobservation can put limits on the ionizing background at high redshift which are better than those obtainable by direct measurements of background light.

Hogan, Craig J.; Weymann, Ray J.

1987-01-01

147

X-ray resonant photoexcitation: line widths and energies of K{\\alpha} transitions in highly charged Fe ions  

E-print Network

Photoabsorption by and fluorescence of the K{\\alpha} transitions in highly charged iron ions are essential mechanisms for X-ray radiation transfer in astrophysical environments. We study photoabsorption due to the main K{\\alpha} transitions in highly charged iron ions from heliumlike to fluorinelike (Fe 24+...17+) using monochromatic X-rays around 6.6 keV at the PETRA III synchrotron photon source. Natural linewidths were determined with hitherto unattained accuracy. The observed transitions are of particular interest for the understanding of photoexcited plasmas found in X-ray binaries and active galactic nuclei.

Rudolph, J K; Epp, S W; Steinbrügge, R; Beilmann, C; Brown, G V; Eberle, S; Graf, A; Harman, Z; Hell, N; Leutenegger, M; Müller, A; Schlage, K; Wille, H -C; Yavas, H; Ullrich, J; López-Urrutia, J R Crespo

2013-01-01

148

Generation and Modulation of Harmonic Emission Spectra from Intense Laser-Plasma Interactions  

SciTech Connect

We report results from recent investigations of the interaction of intense laser light with overdense plasma with particular emphasis on the harmonic emission spectrum generated in these interactions. The harmonic spectrum is governed by both the photon and electron densities, though dependence on the latter has been largely overlooked. To illustrate the effects of the plasma density we examine the characteristics of low-order harmonics by means of a simplified one-dimensional model and compare the spectra with particle-in-cell (PIC) simulations. Recent observations record a spectrum of harmonics showing distinct, if variable, modulation of between two and four harmonics. This spectral feature proved highly sensitive to the incident intensity, with more pronounced modulation at higher intensities. In this paper we report on features of the emission spectrum across a wide parameter range and its dependence on the detailed structure of the plasma density profile. We find clear evidence of a modulated spectrum and identify the plasma frequency as the modulation frequency.

Boyd, T. J. M. [Centre for Theoretical Physics, University of Essex, Colchester CO4 3SQ, U.K. (United Kingdom); Ondarza-Rovira, R. [ININ, A.P. 18-1027, Mexico 11801, D.F. (Mexico)

2006-12-04

149

Time resolved spectra in the infrared absorption and emission from shock heated hydrocarbons. [in interstellar medium  

NASA Technical Reports Server (NTRS)

The wavelength range of a previously constructed multichannel fast recording spectrometer was extended to the mid-infrared. With the initial configuration, light intensities were recorded simultaneously with a silicon-diode array simultaneously at 20 adjacent wavelengths, each with a 20-micron time resolution. For studies in the infrared, the silicon diodes were replaced by a 20-element PbSe array of similar dimensions, cooled by a three-stage thermoelectric device. It is proposed that infrared emissions could be due to shock-heated low molecular-weight hydrocarbons. The full Swan band system appeared in time-integrated emission spectra from shock-heated C2H2; no soot was generated. At low resolution, the profiles on the high-frequency side of the black body maximum show no distinctive features. These could be fitted to Planck curves, with temperatures that declined with time from an initial high that was intermediate between T5 (no conversion) and T5(eq).

Bauer, S. H.; Borchardt, D. B.

1990-01-01

150

Nebular and auroral emission lines of [Cl iii] in the optical spectra of planetary nebulae  

PubMed Central

Electron impact excitation rates in Cl III, recently determined with the R-matrix code, are used to calculate electron temperature (Te) and density (Ne) emission line ratios involving both the nebular (5517.7, 5537.9 ?) and auroral (8433.9, 8480.9, 8500.0 ?) transitions. A comparison of these results with observational data for a sample of planetary nebulae, obtained with the Hamilton Echelle Spectrograph on the 3-m Shane Telescope, reveals that the R1 = I(5518 ?)/I(5538 ?) intensity ratio provides estimates of Ne in excellent agreement with the values derived from other line ratios in the echelle spectra. This agreement indicates that R1 is a reliable density diagnostic for planetary nebulae, and it also provides observational support for the accuracy of the atomic data adopted in the line ratio calculations. However the [Cl iii] 8433.9 ? line is found to be frequently blended with a weak telluric emission feature, although in those instances when the [Cl iii] intensity may be reliably measured, it provides accurate determinations of Te when ratioed against the sum of the 5518 and 5538 ? line fluxes. Similarly, the 8500.0 ? line, previously believed to be free of contamination by the Earth's atmosphere, is also shown to be generally blended with a weak telluric emission feature. The [Cl iii] transition at 8480.9 ? is found to be blended with the He i 8480.7 ? line, except in planetary nebulae that show a relatively weak He i spectrum, where it also provides reliable estimates of Te when ratioed against the nebular lines. Finally, the diagnostic potential of the near-UV [Cl iii] lines at 3344 and 3354 ? is briefly discussed. PMID:10759562

Keenan, Francis P.; Aller, Lawrence H.; Ramsbottom, Catherine A.; Bell, Kenneth L.; Crawford, Fergal L.; Hyung, Siek

2000-01-01

151

Variable reduction algorithm for atomic emission spectra: application to multivariate calibration and quantitative analysis of industrial samples  

Microsoft Academic Search

A variable selection procedure has been developed and used to reduce the number of wavelength data points necessary to formulate a predictive multivariate model for Pt, Pd and Rh using full atomic emission spectra (5684 wavelength data points per spectrum) obtained using a Segmented-Array Charge-Coupled Device Detector (SCCD) for inductively coupled plasma atomic emission spectrometry (ICP-AES). The first stage was

Michael L. Griffiths; Daniel Svozil; Paul Worsfold; Sue Denham; E. Hywel Evans

2002-01-01

152

Charge Exchange Spectra of Hydrogenic and He-like Iron  

E-print Network

We present H-like Fe XXVI and He-like Fe XXV charge-exchange spectra resulting from collisions of highly charged iron with N2 gas at an energy of 10 eV/amu in an electron beam ion trap. Although individual high-n emission lines are not resolved in our measurements, we observe that the most likely level for Fe25+ --> Fe24+ electron capture is n~9, in line with expectations, while the most likely value for Fe26+ --> Fe25+ charge exchange is significantly higher. In the Fe XXV spectrum, the K-alpha emission feature dominates, whether produced via charge exchange or collisional excitation. The K-alpha centroid is lower in energy for the former case than the latter (6666 versus 6685 eV, respectively), as expected because of the strong enhancement of emission from the forbidden and intercombination lines, relative to the resonance line, in charge-exchange spectra. In contrast, the Fe XXVI high-n Lyman lines have a summed intensity greater than that of Ly-alpha, and are substantially stronger than predicted from theoretical calculations of charge exchange with atomic H. We conclude that the angular momentum distribution resulting from electron capture using a multi-electron target gas is significantly different from that obtained with H, resulting in the observed high-n enhancement. A discussion is presented of the relevance of our results to studies of diffuse Fe emission in the Galactic Center and Galactic Ridge, particularly with ASTRO-E2/Suzaku.

B. J. Wargelin; P. Beiersdorfer; P. A. Neill; R. E. Olson; J. H. Scofield

2005-08-02

153

Iron K-alpha line from X-ray illuminated relativistic disks  

NASA Astrophysics Data System (ADS)

The intensity and profile of the iron K-alpha fluorescence line from a flat, optically thick accretion disk rotating around a Schwarzschild black hole and illuminated by a central X-ray source are computed using a fully relativistic treatment of the photon intensity and shifts. The X-ray source is modeled as an isotropic point source located on the symmetry axis at a height h in units of the gravitational radius. These calculations represent a refinement and an extension of those presented elsewhere for h = 20, carried out using a weak field approximation and therefore of validity limited to inclination angles less than 70 deg. Here it is shown that at high inclination angles purely relativistic effects lead to the growth of features between the two Doppler horns and that, as a consequence, the line equivalent width maintains a sizeable value, while the centroid energy and the line width go through a broad maximum at about 80 percent. The statistical implications for the expected distribution of the line parameters in a sample of randomly oriented disks in Seyfert galaxies are briefly discussed.

Matt, G.; Perola, G. C.; Piro, L.; Stella, L.

1992-04-01

154

Iron K-alpha lines from X-ray photoionized accretion discs  

NASA Astrophysics Data System (ADS)

The paper calculates the properties of the iron K-alpha line emitted by an accretion disk illuminated by an external X-ray source for different values of the disk accretion rate, m-dot, and for two different source geometries: a point source located on the disk axis and an extended source above the innermost part of the disk. It is found that for large values of m-dot the matter can be significantly ionized, and the iron line equivalent width can reach values as high as 250 eV for the point source, and up to about 400 eV for the extended source; the line centroid energy, in the emitting rest frame, is significantly higher than 6.4 keV, the value for neutral iron. A further increase of m-dot leads to a strong decrease of the line intensity, because the iron becomes fully stripped in the inner region of the disk. The line profiles in the Schwarzschild metric are also calculated, and for the point source they appear much more complex than those obtained assuming neutral matter.

Matt, G.; Fabian, A. C.; Ross, R. R.

1993-05-01

155

Determination of total primary zero loss intensities in measured electron emission spectra of bare and oxidised metals  

Microsoft Academic Search

A method is presented to determine the total metallic primary zero loss (PZL) intensity and the total oxidic PZL intensity for each core-electron level in measured electron emission spectra of bare and oxidised free-electron like metals (and semiconductors like Si and Ge), from the resolved PZL intensity of only the corresponding metallic main peak and the corresponding oxidic main peak,

L. P. H. Jeurgens; W. G. Sloof; C. G. Borsboom; F. D. Tichelaar; E. J. Mittemeijer

2000-01-01

156

Chlorophyll Fluorescence Emissions of Vegetation Canopies From High Resolution Field Reflectance Spectra  

NASA Technical Reports Server (NTRS)

A two-year experiment was performed on corn (Zea mays L.) crops under nitrogen (N) fertilization regimes to examine the use of hyperspectral canopy reflectance information for estimating chlorophyll fluorescence (ChlF) and vegetation production. Fluorescence of foliage in the laboratory has proven more rigorous than reflectance for correlation to plant physiology. Especially useful are emissions produced from two stable red and far-red chlorophyll ChlF peaks centered at 685V10 nm and 735V5 nm. Methods have been developed elsewhere to extract steady state solar induced fluorescence (SF) from apparent reflectance of vegetation canopies/landscapes using the Fraunhofer Line Depth (FLD) principal. Our study utilized these methods in conjunction with field-acquired high spectral resolution canopy reflectance spectra obtained in 2004 and 2005 over corn crops, as part of an ongoing multi-year experiment at the USDA/Agriculture Research Service in Beltsville, MD. A spectroradiometer (ASD-FR Fieldspec Pro, Analytical Spectral Devices, Inc., Boulder, CO) was used to measure canopy radiances 1 m above plant canopies with a 22deg field of view and a 0deg nadir view zenith angle. Canopy and plant measurements were made at the R3 grain fill reproductive stage on 3-4 replicate N application plots provided seasonal inputs of 280, 140, 70, and 28 kg N/ha. Leaf level measurements were also made which included ChlF, photosynthesis, and leaf constituents (photosynthetic pigment, carbon (C), and N contents). Crop yields were determined at harvest. SIF intensities for ChlF were derived directly from canopy reflectance spectra in specific narrowband regions associated with atmospheric oxygen absorption features centered at 688 and 760 nm. The red/far-red S F ratio derived from these field reflectance spectra successfully discriminated foliar pigment levels (e.g., total chlorophyll, Chl) associated with N application rates in both corn crops. This canopy-level spectral ratio was also positively correlated to the foliar C/N ratio (r = 0.89, n = go), as was a leaf-level steady state fluorescence ratio (Fs/Chl, r = 0.92). The latter ratio was inversely correlated with crop grain yield (Kg 1 ha) (r = 0.9). This study has relevance to future passive satellite remote sensing approaches to monitoring C dynamics from space.

Middleton, E. M.; Corp, L. A.; Daughtry, C. S. T.; Campbell, P. K. Entcheva

2006-01-01

157

On-the-fly ab initio semiclassical dynamics: Identifying degrees of freedom essential for emission spectra of oligothiophenes  

E-print Network

Vibrationally resolved spectra provide a stringent test of the accuracy of theoretical calculations. We combine the thawed Gaussian approximation (TGA) with an on-the-fly ab initio (OTF-AI) scheme to calculate the vibrationally resolved emission spectra of oligothiophenes with up to five rings. The efficiency of the OTF-AI-TGA permits treating all vibrational degrees of freedom on an equal footing even in pentathiophene with 105 vibrational degrees of freedom, thus obviating the need for the global harmonic approximation, popular for large systems. Besides reproducing almost perfectly the experimental emission spectra, in order to provide a deeper insight into the associated physical and chemical processes, we also develop a novel systematic approach to assess the importance and coupling between individual vibrational degrees of freedom during the dynamics. This allows us to explain how the vibrational line shapes of the oligothiophenes change with increasing number of rings. Furthermore, we observe the dynam...

Wehrle, Marius; Vanicek, Jiri

2014-01-01

158

The infrared emission spectra of compositionally inhomogeneous aggregates composed of irregularly shaped constituents  

E-print Network

In order to deduce properties of dust in astrophysical environments where dust growth through aggregation is important, knowledge of the way aggregated particles interact with radiation, and what information is encoded in the thermal radiation they emit, is needed. The emission characteristics are determined by the size and structure of the aggregate and the composition and shape of the constituents. We thus aim at performing computations of compositionally inhomogeneous aggregates composed of irregularly shaped constituents. In addition we aim at developing an empirical recipe to compute the optical properties of such aggregates in a fast and accurate manner. We performed CDA computations for aggregates of irregularly shaped particles with various compositions. The constituents of the aggregate are assumed to be in the Rayleigh regime, and in addition we assume that the dominant interaction of the aggregate constituents is through dipole-dipole interactions. We computed the spectral structure of the emission efficiency in the 10 micron region for aggregates with 30% amorphous carbon and 70% silicates by volume with various fractions of crystalline and amorphous components. We find that the spectral appearance of the various components of the aggregate are very different and depend on their abundances. Most notably, materials that have a very low abundance appear spectroscopically as if they were in very small grains, while more abundant materials appear, spectroscopically to reside in larger grains. We construct a fast empirical approximate method, based on the idea of an effective medium approximation, to construct the spectra for these aggregates which almost perfectly reproduces the more exact computations. This new method is fast enough to be easily implemented in fitting procedures.

M. Min; J. W. Hovenier; L. B. F. M. Waters; A. de Koter

2008-06-25

159

Single particle size and fluorescence spectra from emissions of burning materials in a tube furnace to simulate burn pits  

NASA Astrophysics Data System (ADS)

A single-particle fluorescence spectrometer (SPFS) and an aerodynamic particle sizer were used to measure the fluorescence spectra and particle size distribution from the particulate emissions of 12 different burning materials in a tube furnace to simulate open-air burning of garbage. Although the particulate emissions are likely dominated by particles <1 ?m diameter, only the spectra of supermicron particles were measured here. The overall fluorescence spectral profiles exhibit either one or two broad bands peaked around 300-450 nm within the 280-650 nm spectral range, when the particles are illuminated with a 263-nm laser. Different burning materials have different profiles, some of them (cigarette, hair, uniform, paper, and plastics) show small changes during the burning process, and while others (beef, bread, carrot, Styrofoam, and wood) show big variations, which initially exhibit a single UV peak (around 310-340 nm) and a long shoulder in visible, and then gradually evolve into a bimodal spectrum with another visible peak (around 430-450 nm) having increasing intensity during the burning process. These spectral profiles could mainly derive from polycyclic aromatic hydrocarbons with the combinations of tyrosine-like, tryptophan-like, and other humic-like substances. About 68 % of these single-particle fluorescence spectra can be grouped into 10 clustered spectral templates that are derived from the spectra of millions of atmospheric aerosol particles observed in three locations; while the others, particularly these bimodal spectra, do not fall into any of the 10 templates. Therefore, the spectra from particulate emissions of burning materials can be easily discriminated from that of common atmospheric aerosol particles. The SFFS technology could be a good tool for monitoring burning pit emissions and possibly for distinguishing them from atmospheric aerosol particles.

Pan, Yong-Le; Houck, Joshua D. T.; Clark, Pamela A.; Pinnick, Ronald G.

2013-08-01

160

Influence of Oil-in-Water Emulsions on Fluorescence Properties as Observed by Excitation-Emission Spectra  

NASA Astrophysics Data System (ADS)

Oil poses a major threat to marine ecosystems. This work describes a set of studies focused on introducing an efficient method for the identification of oil in the form of oil emulsions through fluorescence spectra analyses. Hence the concept of classification of oil pollution in seawater based on fluorescence spectroscopy using a high sensitive fluorimeter [1] suitable for laboratory and in situ measurements is introduced. We consider that this approach, in the future, will make it possible to collect specific fluorescence information allowing us to build a base of the oil standards. Here we examined excitation-emission fluorescence spectra (EEMs) of water containing oil-in-water emulsion prepared artificially under laboratory conditions. Water polluted with oil-in-water emulsion was studied with the objective to estimate differences in three-dimensional fluorescence spectra. Studies included various types of oils and oil concentrations. Essential differences in fluorescence spectra for various oils are indicated.

Baszanowska, E.; Zielinski, O.; Otremba, Z.; Toczek, H.

2013-10-01

161

NUMERICAL MODELING OF MULTI-WAVELENGTH SPECTRA OF M87 CORE EMISSION  

SciTech Connect

Spectral fits to M87 core data from radio to hard X-ray are generated via a specially selected software suite, comprised of the High-Accuracy Relativistic Magnetohydrodynamics GRMHD accretion disk model and a two-dimensional Monte Carlo radiation transport code. By determining appropriate parameter changes necessary to fit X-ray-quiescent and flaring behavior of M87's core, we assess the reasonableness of various flaring mechanisms. This shows that an accretion disk model of M87's core out to 28 GM/c{sup 2} can describe the inner emissions. High spin rates show GRMHD-driven polar outflow generation, without citing an external jet model. Our results favor accretion rate changes as the dominant mechanism of X-ray flux and index changes, with variations in density of approximately 20% necessary to scale between the average X-ray spectrum and flaring or quiescent spectra. The best-fit parameters are black hole spin a/M > 0.8 and maximum accretion flow density n {<=} 3 Multiplication-Sign 10{sup 7} cm{sup -3}, equivalent to horizon accretion rates between m-dot = M-dot / M-dot{sub Edd}{approx}2 Multiplication-Sign 10{sup -6} and 1 Multiplication-Sign 10{sup -5} (with M-dot{sub Edd} defined assuming a radiative efficiency {eta} = 0.1). These results demonstrate that the immediate surroundings of M87's core are appropriate to explain observed X-ray variability.

Hilburn, G.; Liang, E. P., E-mail: guy.l.hilburn@rice.edu [Physics and Astronomy Department, Rice University, Houston, TX 77005 (United States)

2012-02-10

162

The nebular spectra of SN 2012aw and constraints on stellar nucleosynthesis from oxygen emission lines  

NASA Astrophysics Data System (ADS)

We present nebular-phase optical and near-infrared spectroscopy of the Type IIP supernova SN 2012aw combined with non-local thermodynamic equilibrium radiative transfer calculations applied to ejecta from stellar evolution/explosion models. Our spectral synthesis models generally show good agreement with the ejecta from a MZAMS = 15 M? progenitor star. The emission lines of oxygen, sodium, and magnesium are all consistent with the nucleosynthesis in a progenitor in the 14-18 M? range. We also demonstrate how the evolution of the oxygen cooling lines of [O I] ?5577, [O I] ?6300, and [O I] ?6364 can be used to constrain the mass of oxygen in the non-molecularly cooled ashes to <1 M?, independent of the mixing in the ejecta. This constraint implies that any progenitor model of initial mass greater than 20 M? would be difficult to reconcile with the observed line strengths. A stellar progenitor of around MZAMS = 15 M? can consistently explain the directly measured luminosity of the progenitor star, the observed nebular spectra, and the inferred pre-supernova mass-loss rate. We conclude that there is still no convincing example of a Type IIP supernova showing the nucleosynthesis products expected from an MZAMS > 20 M? progenitor.

Jerkstrand, A.; Smartt, S. J.; Fraser, M.; Fransson, C.; Sollerman, J.; Taddia, F.; Kotak, R.

2014-04-01

163

Emission Lines of O III in The Optical and Ultraviolet Spectra of Planetary Nebulae  

NASA Technical Reports Server (NTRS)

Recent R-matrix calculations of electron impact excitation rates in 0 III are used to calculate electron temperature and density-dependent emission line ratios R (sub 1) = I(4363 Angstroms)/ I(4960 Angstroms + 5007 Angstroms), R (sub 2) = I(1661 Angstroms + 1667 Angstroms)/ I(4960 Angstroms + 5007 Angstroms) and R (sub 3)= I(2322 Angstroms)/ I(1661 Angstroms + 1667 Angstroms), for a range of electron temperatures (7500 less than or equal to Te less than or equal to 30 000 K) and densities (10 (exp 4) less than or equal to N (sub e) less than or equal to 10 (exp 7) per cubic centimeters) applicable to gaseous nebulae. The ratio-ratio diagrams (R (sub 1), R (sub 2)) and (R (sub 1), R (sub 3)) should, in principle, allow the simultaneous determination of T (sub e) and N (sub e) from measurements of the 0 III features in a spectrum. Plasma parameters derived for a sample of high-excitation planetary nebulae from (R (sub 1), R (sub 2)) and (R (sub 1), R (sub 3)) measurements, produced using a combination of ultraviolet spectra obtained with the International Ultraviolet Explorer (IUE) and optical data from a number of observing runs, are found to show excellent internal consistency. They also show, in general, good agreement with the values of Te and Ne estimated from other line ratios in the nebulae, therefore providing observational support for the accuracy of the theoretical ratios and hence the atomic data adopted in their derivation.

Crawford, F. L.; Keenan, F. P.; Aggarwal, K. M.; Aller, L. H.; Feibelman, W. A.; Fisher, Richard R. (Technical Monitor)

2000-01-01

164

Comparison of Cathodoluminescent and Photoluminescent Emission Spectra of LuPO4 with Different Dopants  

SciTech Connect

The current interest in returning human exploration to the Moon and Mars makes cost-effective and low-mass health monitoring sensors essential for spacecraft development. In space, there are many surface measurements that are required to monitor the condition of the spacecraft including: surface temperature, radiation dose, and impact. Through the use of tailored phosphors, these conditions can be monitored. Practical space-based phosphor sensors will depend heavily upon research investigating the resistance of phosphors to ionizing radiation and their ability to anneal or 'self-heal' from damage caused by ionizing radiation. For the present research, a group of lutetium orthophosphate (LuPO{sub 4}) crystals with dopants including europium, erbium, and neodymium were characterized. Cathodoluminescence (CL) testing was performed using the low energy electron system located at the NASA Marshall Space Flight Center in Huntsville, Alabama. The data were collected using an Ocean Optics HR4000 spectrometer and a fiber optic feed-through. Previous research has shown that increases in both beam energy and current density improved the CL fluorescence yield. While the total electron dose was small, the intention was to maximize the number of irradiated materials. Additionally, these samples were evaluated using a PTI Quantum Master Spectrophotometer to determine the photoluminescence emission spectra.

Goedeke, Shawn [ORNL; Hollerman, William Andrew [ORNL; Allison, Stephen W [ORNL; Gray, P A [Integrated Concepts and Research Corporation - Huntsville, AL; Lewis, Linda A [ORNL; Smithwick III, Robert W [ORNL; Boatner, Lynn A [ORNL; Glasgow, David C [ORNL; Wise, H. [Integrated Concepts and Research Corporation - Huntsville, AL

2008-01-01

165

ANALYSIS OF OPTICAL Fe II EMISSION IN A SAMPLE OF ACTIVE GALACTIC NUCLEUS SPECTRA  

SciTech Connect

We present a study of optical Fe II emission in 302 active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. We group the strongest Fe II multiplets into three groups according to the lower term of the transition (b{sup 4} F, a{sup 6} S, and a{sup 4} G terms). These approximately correspond to the blue, central, and red parts, respectively, of the 'iron shelf' around H{beta}. We calculate an Fe II template that takes into account transitions into these three terms and an additional group of lines, based on a reconstruction of the spectrum of I Zw 1. This Fe II template gives a more precise fit of the Fe II lines in broad-line AGNs than other templates. We extract Fe II, H{alpha}, H{beta}, [O III], and [N II] emission parameters and investigate correlations between them. We find that Fe II lines probably originate in an intermediate line region. We note that the blue, red, and central parts of the iron shelf have different relative intensities in different objects. Their ratios depend on continuum luminosity, FWHM H{beta}, the velocity shift of Fe II, and the H{alpha}/H{beta} flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of Fe II and [O III] on continuum luminosity. We find that there is a Baldwin effect for [O III] but an inverse Baldwin effect for the Fe II emission. The [O III]/Fe II ratio thus decreases with L {sub {lambda}5100}. Since the ratio is a major component of the Boroson and Green Eigenvector 1 (EV1), this implies a connection between the Baldwin effect and EV1 and could be connected with AGN evolution. We find that spectra are different for H{beta} FWHMs greater and less than {approx}3000 km s{sup -1}, and that there are different correlation coefficients between the parameters.

Kovacevic, Jelena; Popovic, Luka C.; Dimitrijevic, Milan S., E-mail: jkovacevic@aob.bg.ac.r [Astronomical Observatory, Volgina 7, 11060 Belgrade (Serbia)

2010-07-15

166

MID-INFRARED ATOMIC FINE-STRUCTURE EMISSION-LINE SPECTRA OF LUMINOUS INFRARED GALAXIES: SPITZER/IRS SPECTRA OF THE GOALS SAMPLE  

SciTech Connect

We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies (LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We readily detect emission lines of [S IV], [Ne II], [Ne V], [Ne III], [S III]{sub 18.7{sub ?m}}, [O IV], [Fe II], [S III]{sub 33.5{sub ?m}}, and [Si II]. More than 75% of these galaxies are classified as starburst-dominated sources in the mid-infrared, based on the [Ne V]/[Ne II] line flux ratios and equivalent width of the 6.2 ?m polycyclic aromatic hydrocarbon feature. We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. Comparing the [S IV]/[Ne II] and [Ne III]/[Ne II] line ratios to the Starburst99-Mappings III models with an instantaneous burst history, the emission-line ratios suggest that the nuclear starbursts in our LIRGs have ages of 1-4.5 Myr, metallicities of 1-2 Z{sub ?}, and ionization parameters of 2-8 × 10{sup 7} cm s{sup –1}. Based on the [S III]{sub 33.5{sub ?m}}/[S III]{sub 18.7{sub ?m}} ratios, the electron density in LIRG nuclei is typically one to a few hundred cm{sup –3}, with a median electron density of ?300 cm{sup –3}, for those sources above the low density limit for these lines. We also find that strong shocks are likely present in 10 starburst-dominated sources of our sample. A significant fraction of the GOALS sources (80) have resolved neon emission-line profiles (FWHM ?600 km s{sup –1}) and five show clear differences in the velocities of the [Ne III] or [Ne V] emission lines, relative to [Ne II], of more than 200 km s{sup –1}. Furthermore, six starburst and five active galactic nucleus dominated LIRGs show a clear trend of increasing line width with ionization potential, suggesting the possibility of a compact energy source and stratified interstellar medium in their nuclei. We confirm a strong correlation between the sum of the [Ne II]{sub 12.8{sub ?m}} and [Ne III]{sub 15.5{sub ?m}} emission, as well as [S III]{sub 33.5{sub ?m}}, with both the infrared luminosity and the 24 ?m warm dust emission measured from the spectra, consistent with all three lines tracing ongoing star formation. Finally, we find no correlation between the hardness of the radiation field or the emission-line width and the ratio of the total infrared to 8 ?m emission (IR8), a measure of the strength of the starburst and the distance of the LIRGs from the star-forming main sequence. This may be a function of the fact that the infrared luminosity and the mid-infrared fine-structure lines are sensitive to different timescales over the starburst, or that IR8 is more sensitive to the geometry of the region emitting the warm dust than the radiation field producing the H II region emission.

Inami, H. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Armus, L.; Stierwalt, S.; Díaz-Santos, T.; Surace, J.; Howell, J.; Marshall, J. [Spitzer Science Center, California Institute of Technology, CA 91125 (United States); Charmandaris, V. [Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, GR-71003 Heraklion (Greece); Groves, B. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Kewley, L. [Research School of Astronomy and Astrophysics, The Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Petric, A. [Department of Astronomy, California Institute of Technology, MS 320-47, Pasadena, CA 91125 (United States); Rich, J. [The Observatories, Carnegie Institute of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Haan, S. [CSIRO Astronomy and Space Science, Marsfield, NSW 2122 (Australia); Evans, A. S. [Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904 (United States); Mazzarella, J.; Lord, S. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Appleton, P. [NASA Herschel Science Center, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Spoon, H. [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States); Frayer, D. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Matsuhara, H., E-mail: inami@noao.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency (Japan); and others

2013-11-10

167

Near-surface thermal gradients and their effects on mid-infrared emission spectra of planetary surfaces  

NASA Astrophysics Data System (ADS)

We model the heat transfer by radiation and conduction in the top few millimeters of a planetary surface to determine the magnitude of near-surface (approximately 100 micrometers) thermal gradients and their effects on mid-infrared emission spectra for a number of planetary environments. The model is one-dimensional and uses a finite difference scheme for approximately 10 micrometers layers. Calculations are peformed for samples heated at the base and from above by sunlight. Our results indicate that near-surface radiative cooling creates significant thermal gradients in the top few hundred microns of surfaces in which radiation is an important heat transfer mechanism. The effect is maximized in evacuated, underdense particulate media with sufficiently high temperatures. Near-surface thermal gradients will be significant in fine-grained particulate surfaces on the Moon (40-60 K/100 micrometers) and Mercury (approximately 80 K/100 micrometers), increasing spectral contrast and creating emission maxima in the transparent regions of the spectra. They will be of lesser importance on the surface of Mars, with a maximum value of around 5 k/100 micrometers in areas of low thermal inertia, and will be negligible on planets with more substantial atmospheres (less than 1 K/100 micrometers). We conclude that the effects that thermal gradients have on mid-IR emission spectra are predictable and do not negate the utility of emission spectroscopy for remote determination of planetary surface composition.

Henderson, B. G.; Jakosky, B. M.

1994-09-01

168

(??1) ? (??1), (??1) emission spectra of chlorofluorobenzene cations in the gaseous phase and their lifetimes in the (0o) states  

USGS Publications Warehouse

The radiative decay of seventeen electronically excited chlorofluorobenzene cations in the gaseous phase has been detected. The reported emission spectra, which have been obtained using low energy electron beam excitation, are assigned to the B(??-1 ??? X(??-1 electronic transitions of these cations on the basis of their Ne(I) photoelectron spectra. In another sixteen chloroflourobenzene cations, the B ??? X radiative decay could not be detected, from which is inferred that the B states are now associated with Cl 3p(??-1 ionisation processes. The lifetimes of the studied cations in the lowest vibrational levels of the B(??-1 state have been measured. ?? 1980.

Maier, J. P.; Marthaler, O.; Mohraz, M.; Shiley, R. H.

1980-01-01

169

Excitation Emission Matrix Spectra (EEMS) of Chromophoric Dissolved Organic Matter Produced during Microbial Incubation  

NASA Astrophysics Data System (ADS)

The chromophoric or light-absorbing fraction of dissolved organic matter (CDOM) is present ubiquitously in natural waters and has a significant impact on ocean biogeochemistry, affecting photosynthesis and primary production as well direct and indirect photochemical reactions (Siegel et al., 2002; Nelson et al., 2007). It has been largely researched in the past few decades, however the exact chemical composition remains unknown. Instrumental methods of analysis including simultaneous excitation-emission fluorescence spectra have allowed for further insight into source and chemical composition. While certain excitation-emission peaks have been associated with ';marine' sources, they have not been exclusively linked to bacterial production of CDOM (Coble, 1996; Zepp et al., 2004). In this study, ';grazer diluted' seawater samples (70% 0.2?m filtered water; 30% whole water) were collected at the Bermuda Atlantic Time Series (BATS) site in the Sargasso Sea (31° 41' N; 64° 10' W) and incubated with an amendment of labile dissolved organic carbon (10?M C6H12O6), ammonium (1?M NH4Cl) and phosphate (0.1?M K2HPO4) to facilitate bacterial production. These substrates and concentrations have been previously shown to facilitate optimum bacterial and CDOM production (Nelson et al., 2004). Sample depths were chosen at 1m and 200m as water at these depths has been exposed to UV light (the Subtropical Mode Water at 200m has been subducted from the surface) and therefore has low initial concentrations of CDOM. After the samples were amended, they were incubated at in-situ temperatures in the dark for 72 hours, with bacteria counts, UV-Vis absorption and EEMS measurements taken at 6-8 hour intervals. Dissolved organic carbon (DOC) measurements were collected daily. For the surface water experiment specific bacteria populations were investigated using Fluorescence In-Situ Hybridization (FISH) analysis. Results showed a clear production of bacteria and production of CDOM, which can be linked to this bacterial production. FISH analysis showed percentage abundance of Pelagibacter ubique (SAR 11) and of Alteromonas. On-going and future work will ascertain if specific microbial communities produce CDOM more readily than others, and if these different populations produce varying fluorescence peaks, thus indicating a range of chromophoric groups being produced by bacteria. An additional suite of probes will be used for further FISH analysis to identify percentages of other populations, and seasonal/temporal variations will be investigated.

McDonald, N.; Nelson, N. B.; Parsons, R.

2013-12-01

170

Calculation of emission and absorption spectra of LTE plasma by the STA (Super Transition Array) method  

SciTech Connect

Recent improvements in the Super Transition Array (STA) method for calculating Bound-Bound (BB) and Bound-Free (BF) emission and absorption spectra for LTE plasma are described and illustrated. The method accounts for all possible BB and BF radiative transitions in the plasma. Full detailed first order quantum relativistic treatment is used for calculating transition energies and probabilities. The enormous number of configurations are divided into sets of superconfigurations comprised of a collection of energetically grouped configurations. The contribution of the transition array between two superconfigurations to a specific one-electron transition is then represented by a Gaussian whose moments are calculated accurately using a technique that bypasses the necessity of direct summation over all the levels involved. The calculation of these moments involves the populations of the configurations given by their statistical weights and the Boltzmann factor. For each configuration within the super configuration we use zeroeth order energies in the Boltzmann factor corrected by a super configuration averaged first order term. The structure of the spectrum is increasingly revealed by splitting each STA into a number of smaller STAs. When the spectrum converges it describes the detailed UTA' structure, where each configuration-to-configuration array is represented by a separate Gaussian with first order energy in the Boltzmann factor. Convergence is reached with only a few thousand STAs, at most, which makes the calculations practical. It should be pointed out that in this treatment the STA moments are obtained by summing over all level-to-level transitions, rather than configuration-to-configuration average transitions. 4 refs., 9 figs.

Bar-Shalon, A.; Oreg, J. (Israel Atomic Energy Commission, Beersheba (Israel). Nuclear Research Center-Negev); Goldstein, W.H. (Lawrence Livermore National Lab., CA (USA))

1991-01-11

171

c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines  

NASA Astrophysics Data System (ADS)

Context. A survey of mid-infrared gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer “Cores to Disks” (c2d) legacy program. Aims: The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. The mid-IR spectral range hosts a suite of diagnostic lines which can distinguish them. A key point is to spatially resolve the emission in the Spitzer-IRS spectra to separate extended PDR and shock emission from compact source emission associated with the circumstellar disk and jets. Methods: An optimal extraction method is used to separate both spatially unresolved (compact, up to a few hundred AU) and spatially resolved (extended, thousand AU or more) emission from the IRS spectra. The results are compared with the c2d disk sample and literature PDR and shock models to address the physical nature of the sources. Results: Both compact and extended emission features are observed. Warm (T_ex few hundred K) H2, observed through the pure rotational H2 S(0), S(1) and S(2) lines, and [S i] 25 ?m emission is observed primarily in the extended component. [S i] is observed uniquely toward truly embedded sources and not toward disks. On the other hand hot (T_ex ? 700 K) H2, observed primarily through the S(4) line, and [Ne ii] emission is seen mostly in the spatially unresolved component. [Fe ii] and [Si ii] lines are observed in both spatial components. Hot H2O emission is found in the spatially unresolved component of some sources. Conclusions: The observed emission on ?1000 AU scales is characteristic of PDR emission and likely originates in the outflow cavities in the remnant envelope created by the stellar wind and jets from the embedded young stars. Weak shocks along the outflow wall can also contribute. The compact emission is likely of mixed origin, comprised of optically thick circumstellar disk and/or jet/outflow emission from the protostellar object.

Lahuis, F.; van Dishoeck, E. F.; Jørgensen, J. K.; Blake, G. A.; Evans, N. J.

2010-09-01

172

Breakdown of the mirror image symmetry in the optical absorption/emission spectra of oligo(para-phenylene)s  

E-print Network

The absorption and emission spectra of most luminescent, pi-conjugated, organic molecules are the mirror image of each other. In some cases, however, this symmetry is severely broken. In the present work, the asymmetry between the absorption and fluorescence spectra in molecular systems consisting of para-linked phenyl rings is studied. The vibronic structure of the emission and absorption bands is calculated from ab-initio quantum chemical methods and a subsequent, rigorous Franck-Condon treatment. Good agreement with experiment is achieved. A clear relation can be established between the strongly anharmonic double-well potential for the phenylene ring librations around the long molecular axis and the observed deviation from the mirror image symmetry. Consequences for related compounds and temperature dependent optical measurements are also discussed.

G. Heimel; M. Daghofer; J. Gierschner; E. J. W. List; A. C. Grimsdale; K. Müllen; D. Beljonne; J. -L. Brédas; E. Zojer

2005-12-12

173

Detection of organic compound signatures in infra-red, limb emission spectra observed by the MIPAS-B2 instrument  

Microsoft Academic Search

Organic compounds play a central role in troposphere chemistry and increasingly are a viable target for remote sensing observations. In this paper, infra-red spectral features of three organic compounds are investigated in thermal emission spectra recorded by a balloon-borne instrument, MIPAS-B2, operating at high spectral resolution. It is demonstrated, for the first time, that PAN and acetone can be detected

J. J. Remedios; G. Allen; A. M. Waterfall; H. Oelhaf; A. Kleinert

2006-01-01

174

Removing the Shock from the Thermal Emission Spectra of Shocked Terrestrial and Martian Basalts  

Microsoft Academic Search

An abundance of impact craters on the martian surface and shock effects in the martian meteorites indicate that the surface of Mars has been shocked. The thermal infrared (TIR) spectra of plagioclase feldspars experimentally shocked to various pressures have enabled the amount of shock to be correlated with changes in the TIR spectra [Johnson et al., 2002, 2003]. With these,

S. P. Wright; J. L. Bandfield; P. R. Christensen; J. R. Johnson

2004-01-01

175

[Transient emission spectra from OH, CH and C2 free radicals in the combustion reaction of n-decane].  

PubMed

Using an intensified spectroscopic detector CCD and a heated shock tube, transient emission spectra of n-decane in the combustion reaction were measured in a spectral range of 200-850 nm. Experiments were conducted at temperatures of 1100-1600 K, a pressure of 2.0 atm, an initial fuel mole fraction of 1.0% and an equivalence ratio of 1.0. Results show that the main emission bands are attributed to OH, CH and C2 radicals produced during the combustion process of n-decane. Emission intensities of the three radicals reached their maximums only after 5 micros from the onset of their ignitions. After about 30 micros had passed, the band of OH radical was still observed, but the bands of CH and C2 radicals almost disappeared. Time histories of spectral emission intensities represent the time histories of concentrations of the three radicals during the process of combustion The emission peak ratio of OH (306.4 nm)/CH(431.4 nm) is approximately 27/100 in the combustion of n-decane, which is much greater than the corresponding ratio of about 7/100 in the combustion of n-heptane. This result reveals that the two fuels have different reaction mechanisms. High resolution characteristic spectra of CH and C2 were also acquired in the present experiment, the spectra show the rotational structures of the bands clearly. Current results are valuable for understanding the property and validating the mechanism of n-decane combustion reaction PMID:22827046

Wang, Li-dong; Li, Ping; Zhang, Chang-hua; Tang, Hong-chang; Ye, Bin; Li, Xiang-yuan

2012-05-01

176

Thermoluminescence emission spectra for the LiF:Mg,Cu,Na,Si thermoluminescent materials with various concentrations of the dopants (3-D measurement).  

PubMed

The thermoluminescence (TL) emission spectra from LiF TL materials, called KLT-300 (LiF:Mg,Cu,Na,Si) with various dopant concentrations are measured and analysed. These KLT-300 materials were developed by the Korea Atomic Energy Research Institute (KAERI) to achieve an enhancement of the thermal stability in TL readings. Six types of samples are prepared with different dopant concentrations in the following ranges; Mg (0-0.20 mol%), Cu (0-0.05 mol%), Na and Si (0-0.9 mol%). The spectra measurements are carried out for the six types of samples using a TL emission spectra measurement device. The spectra measurement device consists of a monochromator, photomultiplier tube and temperature control unit to thermally stimulate the samples. The measured data shows the light emission during heating of the sample as a function of temperature and wavelength (three-dimensional TL spectra). The spectra were analysed using a method of deconvolution based on gaussian curve. The wavelength of a main peak of the emission spectra changes depending on the existence of the Cu dopant, while intensity of the spectra rapidly changes with the Cu dopant concentrations. The 385 nm emission is mainly observed in all the spectra from the samples with the Cu dopant, but in those from the samples without the Cu dopant a very weak 401 nm emission is mainly observed. However, any change in the wavelength at a main peak of the TL emission spectra from the sample materials with Na and Si dopants is not observed but that in the intensity at a peak of the spectra is observed. PMID:16644972

Lee, J I; Lee, D; Kim, J L; Chang, S Y

2006-01-01

177

Investigating Possible Departures from Maxwellian Energy Distributions in Nebulae using High-Resolution Emission Line Spectra  

NASA Astrophysics Data System (ADS)

The derivation of ionic abundance ratios from collisionally excited emission lines in gaseous nebulae requires knowledge of the physical state of the gas, particularly the electron kinetic temperature, Te, to which the resulting abundances are highly sensitive. A long-standing problem in nebular analyses has been pervasive discrepancies among values of Te obtained from different diagnostic ratios for a single nebula. Recently, Nicholls et al. (2012, ApJ, 752, 148) have suggested that the nebular electrons may not obey an equilibrium Maxwell-Boltzmann (M-B) energy distribution, but instead follow a “? distribution” seen in many solar system plasmas, a family of distributions for which the M-B distribution is the limiting case where ? ? ?. The high-energy tail of supra-thermal electrons in ? distributions have a disproportionate effect on strongly energy dependent quantities, such as Te diagnostics, for even modest departures from M-B distributions. We apply prescriptions given by Nicholls et al. (2013, ApJS, 207, 21) to high-resolution (R=36,700) optical spectra of 10 planetary nebulae obtained with the 2d-coudé echelle spectrograph on the 2.7 m Harlan J. Smith Telescope at McDonald Observatory. The advantages of these data include their broad spectral coverage and sufficiently high spectral resolution to separate blended lines and assess possible atmospheric absorption issues. The line fluxes were obtained using ROBOSPECT, an automated spectral line measurement package developed by Waters & Hollek (2013, PASP, 125, 1164). We solve both for Te under the assumption of M-B distributions, and the parameters of ? distributions consistent with the data. Our goal is to test whether the ? distribution hypothesis provides a better fit to the observed line ratios. Finally, we discuss effects on the derived ionic abundances under this alternate description of the particle energy distributions. This research was supported by NSF grant AST 0708245 and the John W. Cox Endowment for Advanced Studies in Astronomy at the University of Texas at Austin.

Turbyfill, Amanda; Dinerstein, H. L.; Sterling, N. C.

2014-01-01

178

c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines  

E-print Network

A survey of mid-IR gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer "Cores to Disks" (c2d) legacy program. The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks) and the physical processes (accretion, irradiation by UV and/or X-rays, excitation through slow and fast shocks) which take place. A key point is to spatially resolve the emission in the Spitzer-IRS spectra. An optimal extraction method is used to separate both spatially unresolved (compact, up to a few 100 AU) and spatially resolved (extended, 1000 AU or more) emission from the IRS spectra. The results are compared with the c2d disk sample and literature PDR and shock models to address the physical nature of the sources. Both compact and extended emission features are observed. Warm (Tex few 100 K) H2, observed through the pure rotatio...

Lahuis, Fred; Jørgensen, Jes K; Blake, Geoffrey A; Evans, Neal J

2010-01-01

179

A VLBA SEARCH FOR BINARY BLACK HOLES IN ACTIVE GALACTIC NUCLEI WITH DOUBLE-PEAKED OPTICAL EMISSION LINE SPECTRA  

SciTech Connect

We have examined a subset of 11 active galactic nuclei (AGNs) drawn from a sample of 87 objects that possess double-peaked optical emission line spectra, as put forward by Wang et al. and are detectable in the Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey at radio wavelengths. The double-peaked nature of the optical emission line spectra has been suggested as evidence for the existence of binary black holes in these AGNs, although this interpretation is controversial. We make a simple suggestion that direct evidence of binary black holes in these objects could be searched for in the form of dual sources of compact radio emission associated with the AGNs. To explore this idea, we have used the Very Long Baseline Array to observe these 11 objects from the Wang et al. sample. Of the 11 objects, we detect compact radio emission from two, SDSS J151709+335324 and SDSS J160024+264035. Both objects show single components of compact radio emission. The morphology of SDSS J151709+335324 is consistent with a recent comprehensive multi-wavelength study of this object by Rosario et al. Assuming that the entire sample consists of binary black holes, we would expect of order one double radio core to be detected, based on radio wavelength detection rates from FIRST and very long baseline interferometry surveys. We have not detected any double cores, thus this work does not substantially support the idea that AGNs with double-peaked optical emission lines contain binary black holes. However, the study of larger samples should be undertaken to provide a more secure statistical result, given the estimated detection rates.

Tingay, S. J.; Wayth, R. B., E-mail: s.tingay@curtin.edu.au [International Centre for Radio Astronomy Research, Curtin University, Bentley, WA (Australia)

2011-06-15

180

Deconstructing the room-temperature emission spectra of nanocrystals using Photon-Correlation Fourier Spectroscopy  

E-print Network

The photoluminescence spectrum of an ensemble of emitters is the result of the homogeneous "natural" spectra of single emitters subjected to interparticle inhomogeneities and perturbations from the environment. For ...

Cui, Jian, Ph. D. Massachusetts Institute of Technology

2014-01-01

181

On-the-fly ab initio semiclassical dynamics: Identifying degrees of freedom essential for emission spectra of oligothiophenes  

NASA Astrophysics Data System (ADS)

Vibrationally resolved spectra provide a stringent test of the accuracy of theoretical calculations. We combine the thawed Gaussian approximation (TGA) with an on-the-fly ab initio (OTF-AI) scheme to calculate the vibrationally resolved emission spectra of oligothiophenes with up to five rings. The efficiency of the OTF-AI-TGA permits treating all vibrational degrees of freedom on an equal footing even in pentathiophene with 105 vibrational degrees of freedom, thus obviating the need for the global harmonic approximation, popular for large systems. Besides reproducing almost perfectly the experimental emission spectra, in order to provide a deeper insight into the associated physical and chemical processes, we also develop a novel systematic approach to assess the importance and coupling between individual vibrational degrees of freedom during the dynamics. This allows us to explain how the vibrational line shapes of the oligothiophenes change with increasing number of rings. Furthermore, we observe the dynamical interplay between the quinoid and aromatic characters of individual rings in the oligothiophene chain during the dynamics and confirm that the quinoid character prevails in the center of the chain.

Wehrle, Marius; Šulc, Miroslav; Vaní?ek, Ji?í

2014-06-01

182

Thermal Emission Spectra of Impact Glass and Shocked Deccan Basalt from Lonar Crater, India and Implications for Remote Sensing of Mars  

Microsoft Academic Search

Sample emission spectra of Deccan basalts and impact glasses from Lonar Crater, India, a rare terrestrial crater in basalt, are examined for insight into thermal infrared data of Mars collected by orbiters and rovers.

S. P. Wright; J. R. Johnson; P. R. Christensen

2004-01-01

183

A non-LTE modeling of narrow emission components of He and Ca lines in optical spectra of CTTS  

E-print Network

A spectrum of a hot spot, produced by radiation of accretion shock at T Tauri star's surface, has been calculated taking into account non-LTE effects for HeI, HeII, CaI and CaII, using LTE-calculations of spot's atmospheric structure, calculated by Dodin & Lamzin (2012). Assuming that pre-shock gas number density N_0 and its velocity V_0 are the same across the accretion column, we calculated spectra of a system "star + round spot" for a set of N_0, V_0 values and parameters, which characterized the star and the spot. It has been shown that theoretical spectra with an appropriate choice of the parameters reproduce well observed veiling of photospheric absorption lines in optical band as well as profiles and intensities of so-called narrow components of HeII and CaI emission lines in spectra of 9 stars. We found that the accreted gas density N_0>10^{12} cm^{-3} for all considered stars except DK Tau. Observed spectra of 8 stars were succesfully fitted, asuming solar abundance of calcium, but it appeared po...

Dodin, A V; Sitnova, T M

2013-01-01

184

Pulse Profiles, Spectra and Polarization Characteristics of Non-Thermal Emissions from the Crab-Like Pulsars  

E-print Network

We discuss non-thermal emission mechanism of the Crab-like pulsars with both a two-dimensional electrodynamical study and a three-dimensional model. We investigate the emission process in the outer gap accelerator. In the two-dimensional electrodynamical study, we solve the Poisson equation of the accelerating electric field in the outer gap and the equation of motion of the primary particles with the synchrotron and the curvature radiation process and the pair-creation process. We show a solved gap structure which produces a consistent gamma-ray spectrum with EGRET observation. Based on the two-dimensional model, we conduct a three-dimensional emission model to calculate the synchrotron and the inverse-Compton processes of the secondary pairs produced outside the outer gap. We calculate the pulse profiles, the phase-resolved spectra and the polarization characteristics in optical to $\\gamma$-ray bands to compare the observation of the Crab pulsar and PSR B0540-69. For the Crab pulsar, we find that the outer gap geometry extending from near the stellar surface to near the light cylinder produces a complex morphology change of the pulse profiles as a function of the photon energy. This predicted morphology change is quite similar with that of the observations. The calculated phase-resolved spectra are consistent with the data through optical to the $\\gamma$-ray bands. We demonstrate that the 10$\\sim$20 % of the polarization degree in the optical emissions from the Crab pulsar and the Vela pulsar are explained by the synchrotron emissions with the particle gyration motion.

J. Takata; H. -K. Chang

2007-07-23

185

Infrared Emission of Normal Galaxies from 2.5 to 12 Microns: ISO Spectra, Near-Infrared Continuum and Mid-Infrared Emission Features  

E-print Network

We present ISO-PHOT spectra of the regions 2.5-4.9um and 5.8-11.6um for a sample of 45 disk galaxies from the U.S. ISO Key Project on Normal Galaxies. The spectra can be decomposed into three spectral components: (1) continuum emission from stellar photospheres, which dominates the near-infrared (2.5- 4.9um; NIR) spectral region; (2) a weak NIR excess continuum, which has a color temperature of ~ 1000K, carries a luminosity of a few percent of the total far-infrared luminosity L(FIR), and most likely arises from the ISM; and (3) the well-known broad emission features at 6.2, 7.7, 8.6 and 11.3 um, which are generally attributed to aromatic carbon particles. These aromatic features in emission (AFEs) dominate the mid-infrared (5.8-11.6 um; MIR) part of the spectrum, and resemble the so-called Type-A spectra observed in many non-stellar sources and the diffuse ISM in our own Galaxy. The relative strengths of the AFEs vary by 15-25% among the galaxies. However, little correlation is seen between these variations and either IRAS 60um-to-100um flux density ratio R(60/100) or the FIR-to-blue luminosity ratio L(FIR)/L(B), suggesting that the observed variations are not a direct consequence of the radiation field differences among the galaxies. We demonstrate that the NIR excess continuum and AFE emission are correlated, suggesting that they are produced by similar mechanisms and similar (or the same) material. On the other hand, as the current star-formation activity increases, the overall strengths of the AFEs and the NIR excess continuum drop significantly with respect to that of the far-infrared emission from large dust grains. This is likely a consequence of the preferential destruction in intense radiation fields of the small carriers responsible for the NIR/AFE emission.

Nanyao Lu; George Helou; Michael W. Werner; Harriet L. Dinerstein; Daniel A. Dale; Nancy A. Silbermann; Sangeeta Malhotra; Charles A. Beichman; Thomas H. Jarrett

2003-01-23

186

Skylab ultraviolet stellar spectra - Emission lines from the Beta Lyrae system  

NASA Technical Reports Server (NTRS)

Observations of Beta Lyr with the Skylab S-019 ultraviolet objective-prism spectrograph show numerous emission lines in the region from 1400 to 2300 A. Some variations in line strength between phases 0.25 and 0.50 are seen, which probably explain the shallowness of the OAO-2 light curve at 1910 A. Many of the emission lines are probably due to intercombination transitions, thus confirming the concept that the emission is produced by collisional excitation in low-density clouds of hot gas.

Kondo, Y.; Parsons, S. B.; Wray, J. D.; Benedict, G. F.; Henize, K. G.; Mccluskey, G. E.

1976-01-01

187

Effects of hydrogen dissociation on the infrared emission spectra of naphthalene: theoretical modeling.  

PubMed

The IR emission spectroscopy of naphthalene and its singly- and doubly-dehydrogenated radicals has been modeled using kinetic Monte Carlo simulations, taking into account the various relaxation pathways of radiative emission and hydrogen loss. Our modeling relies on quantum chemistry ingredients that were obtained from dedicated calculations based on density functional theory, including explicitly anharmonicity contributions. Our results show that the fragmentation products significantly contribute to the overall IR emission spectrum, especially to the intensity ratios between bands. Owing to the likely presence of polycyclic aromatic hydrocarbons in the interstellar medium, these findings are particularly relevant in the astrophysical context. PMID:23552801

Falvo, Cyril; Friha, Hela; Pino, Thomas; Dhaouadi, Zoubeida; Parneix, Pascal; Calvo, Florent; Bréchignac, Philippe

2013-07-01

188

Neutron Capture Cross Sections and Gamma Emission Spectra from Neutron Capture on 234,236,238U Measured with DANCE  

NASA Astrophysics Data System (ADS)

A new measurement of the 238U(n, ?) cross section using a thin 48 mg/cm2 target was made using the DANCE detector at LANSCE over the energy range from 10 eV to 500 keV. The results confirm earlier measurements. Measurements of the gamma-ray emission spectra were also made for 238U(n, ?) as well as 234,236U(n, ?). These measurements help to constrain the radiative strength function used in the cross-section calculations.

Ullmann, J. L.; Mosby, S.; Bredeweg, T. A.; Couture, A. J.; Haight, R. C.; Jandel, M.; Kawano, T.; O'Donnell, J. M.; Rundberg, R. S.; Vieira, D. J.; Wilhelmy, J. B.; Wu, C.-Y.; Becker, J. A.; Chyzh, A.; Baramsai, B.; Mitchell, G. E.; Krticka, M.

2014-05-01

189

GNASH: A preequilibrium, statistical nuclear model code for calculation of cross sections and emission spectra  

Microsoft Academic Search

A multistep Hauser--Feshbach code that includes corrections for preequilibrium effects is described. The code can calculate up to 60 decay reactions (cross sections and energy spectra) in one computation, and thereby provide considerable flexibility for handling processes with complicated reaction chains. Input parameter setup, problem output, and subroutine descriptions are given along with a sample problem calculation. A brief theoretical

P. G. Young; E. D. Arthur

1977-01-01

190

Emission spectra and intrinsic optical bistability in a two-level medium  

Microsoft Academic Search

Scattering of resonant radiation in a dense two-level medium is studied theoretically accounting for local field effects and renormalisation of the resonance frequency. Intrinsic optical bistability is viewed as switching between different spectral patterns of fluorescent light controlled by the incident field strength. Response spectra are calculated analytically for the entire hysteresis loop of atomic excitation. The equations to describe

M. G. Gladush; D. V. Kuznetsov; Vl. K. Roerich

2011-01-01

191

Plasma Emission Spectra of Opuntia Nopalea Obtained with Microsecond Laser Pulses  

SciTech Connect

Laser-induced Plasma Spectroscopy was performed during the spines ablation of Opuntia by using Nd:YAG microsecond laser pulses. The results show strong absorption in Glochids that causes the intense electronic noise on the spectra. This process is consider suitable for practical elimination of spines in alimentary products like opuntia.

Ponce, L.; Flores, T.; Arronte, A.; Flores, A. [CICATA-IPN, Unidad Altamira, Altamira 89600, Tamps (Mexico)

2008-04-15

192

Responsivity-based criterion for accurate calibration of FTIR emission spectra: theoretical  

E-print Network

. Huang, and F. A. Best, "A principal component noise filter for high spectral resolution infrared: An analytical expression for the variance of the radiance measured by Fourier-transform infrared (FTIR) emission

Walden, Von P.

193

Far Ultraviolet Emission Line Spectra of the Vela Super Nova Remnant  

Microsoft Academic Search

We present FUV emission line images at 6 different wavelengths obtained with a diffuse imaging spectrometer (SPEAR) and compare them to ROSAT and EUVE FUV maps. Spatial differences in the temperature structure are investigated.

Martin M. Sirk; J. Edelstein; K. Min; W. Han

2007-01-01

194

Emission measures derived from far ultraviolet spectra of T Tauri stars  

NASA Technical Reports Server (NTRS)

Spectroscopic diagnostics based on UV emission line observations have been developed to study the solar chromosphere, transition region, and corona. The atmospheric properties that can be inferred from observations of total line intensities include the temperature, by identifying the ionic species present; the temperature distribution of the emission measure, from the absolute intensities; and the electron density of the source, from line intensity ratios sensitive to the electron density. In the present paper, the temperature distribution of the emission measure is estimated from observations of far UV emission line fluxes of the T Tauri stars, RW Aurigae and RU Lupi, made on the IUE. A crude estimate of the electron density of one star is obtained, using density-sensitive line ratios.

Cram, L. E.; Giampapa, M. S.; Imhoff, C. L.

1980-01-01

195

Bremsstrahlung and K alpha fluorescence measurements for inferring conversion efficiencies into fast ignition relevant hot electrons  

E-print Network

The Bremsstrahlung and K-shell emission from 1×1×1 mm[superscript 3] planar targets irradiated by a short-pulse 3×10[superscript 18]–8×10[superscript 19] W/cm[superscript 2] laser were measured. The Bremsstrahlung was ...

Chen, C. D.

196

How to Collect National Institute of Standards and Technology (NIST) Traceable Fluorescence Excitation and Emission Spectra.  

PubMed

Contemporary spectrofluorimeters comprise exciting light sources, excitation and emission monochromators, and detectors that without correction yield data not conforming to an ideal spectral response. The correction of the spectral properties of the exciting and emission light paths first requires calibration of the wavelength and spectral accuracy. The exciting beam path can be corrected up to the sample position using a spectrally corrected reference detection system. The corrected reference response accounts for both the spectral intensity and drift of the exciting light source relative to emission and/or transmission detector responses. The emission detection path must also be corrected for the combined spectral bias of the sample compartment optics, emission monochromator, and detector. There are several crucial issues associated with both excitation and emission correction including the requirement to account for spectral band-pass and resolution, optical band-pass or neutral density filters, and the position and direction of polarizing elements in the light paths. In addition, secondary correction factors are described including (1) subtraction of the solvent's fluorescence background, (2) removal of Rayleigh and Raman scattering lines, as well as (3) correcting for sample concentration-dependent inner-filter effects. The importance of the National Institute of Standards and Technology (NIST) traceable calibration and correction protocols is explained in light of valid intra- and interlaboratory studies and effective spectral qualitative and quantitative analyses including multivariate spectral modeling. PMID:24108620

Gilmore, Adam Matthew

2014-01-01

197

Theoretical and experimental determination of the absorption and emission spectra of a prototypical indolenine-based squaraine dye.  

PubMed

The spectroscopy of a prototypical indolenine-based squaraine dye is analysed theoretically using state-of-the-art methodologies for the simulation of spectral lineshapes, and experimentally using optical absorption and emission spectroscopies. Density functional theory and its time-dependent extension are used to determine the stability of several conformers, to compute their excitation energies, equilibrium geometries and vibrational frequencies, both in the ground and in their first excited singlet state. Finally the generating function approach is used to simulate the vibronic lineshape of the low energy valence ??* excitation and emission spectra. Solvent effects are also computed and discussed by using the polarizable continuum model. The developed model correctly reproduces the main spectral features of the squaraine, and allows us to identify the vibrational motions that mainly contribute to the observed lineshape. PMID:24352799

Borrelli, Raffaele; Ellena, Silvano; Barolo, Claudia

2014-02-14

198

Temperature sensitivity of Cu K(alpha) imaging efficiency using a spherical Bragg reflecting crystal  

SciTech Connect

The Vulcan laser facility at the Rutherford Appleton Laboratory was used to study the interaction of a 75 J 10 ps, high intensity laser beam with low-mass solid, Cu targets. Two instruments were fielded as diagnostics of the Cu K-shell emission from the targets: A single photon counting CCD spectrometer provided the absolute K{sub {alpha}} yield and a spherically bent Bragg crystal recorded 2D monochromatic images with a spatial resolution of 10 {micro}m. Due to the shifting and broadening of the K{sub {alpha}} spectral lines with increasing temperature, there is a temperature dependence of the crystal collection efficiency. This provides a temperature diagnostic when cross calibrated against a single hit CCD spectrometer, and it affects measurements of the spatial pattern of electron transport. The experimental data showing changing collection efficiency are presented. The results are discussed in light of modeling of the temperature-dependent spectrum of Cu K-shell emission.

Akli, K U; Key, M H; Chung, H K; Hansen, S B; Freeman, R R; Chen, M H; Gregori, G; Hatchett, S; Hey, D; Izumi, N; King, J A; Kuba, J; Norreys, P; Mackinnon, A J; Murphy, C D; Snavely, R; Stepehens, R; Stoeckel, C; Theobald, W; Zhang, B

2006-08-07

199

Emission spectra and intrinsic optical bistability in a two-level medium  

Microsoft Academic Search

Scattering of resonant radiation in a dense two-level medium is studied\\u000atheoretically with account for local field effects and renormalization of the\\u000aresonance frequency. Intrinsic optical bistability is viewed as switching\\u000abetween different spectral patterns of fluorescent light controlled by the\\u000aincident field strength. Response spectra are calculated analytically for the\\u000aentire hysteresis loop of atomic excitation. The equations to

M. G. Gladush; D. V. Kuznetsov; A. A. Panteleev; Vl. K. Roerich

2010-01-01

200

Emission lines in the Near-infrared Spectra of the IR Quintuplet Stars in the Galactic Center  

NASA Astrophysics Data System (ADS)

The natures of the five infrared stars for which the Galactic center’s “Quintuplet Cluster” were named have long been a mystery, although the pinwheel morphologies of two of them suggest that those two are Wolf-Rayet colliding wind binaries. Not only does each of the five IR stars suffer the same large interstellar extinction that obscures all objects in the Galactic center, but also each is embedded within its own warm and dusty cocoon. Until recently near-infrared spectra of them have revealed only dust continua steeply rising to long wavelengths. In the J and H bands the Quintuplet stars are very faint due to the high extinction, but the continuum emission from their warm cocoons is much less than at longer wavelengths and lines arising within their dust shells should be relatively more prominent. Here we report the detection of a number of emission lines characteristic of hot and massive stars in 1.0-1.8?m spectra of four of the IR Quintuplet stars. The lines that have been detected to date allow initial classifications of most of these stars.

Geballe, Thomas R.; Najarro, F.; de la Fuente, D.; Figer, D. F.

2014-01-01

201

Direct measurement of JET local deuteron densities by neural network modelling of Balmer alpha beam emission spectra  

NASA Astrophysics Data System (ADS)

The analysis of Balmer alpha beam emission spectra represents a challenging task, both in terms of the wealth of information hidden in them, and in terms of complex spectral features. The shape of a spectrum depends on many local plasma parameters, such as magnetic field strength and direction, beam density, effective charge and deuteron density. This paper is concerned with the deduction of local plasma deuteron densities from Balmer alpha emission from plasma atoms following charge exchange with the beam atoms. The model we will use is statistical, and is based on multi-layer perceptron neural networks (Hertz et al 1991, Bishop 1995). The use of neural networks makes the deconvolution task fully automatic and fast enough for real-time calculation of complete deuteron density profiles. It is shown that the spectra themselves and local electron densities are the only data necessary for accurate inference of local deuteron densities. This result is partly inferred from a sensitivity analysis of dependences on different plasma parameters. Proper error bars for the model predictions will be derived using Bayesian probability theory.

Svensson, J.; von Hellermann, M.; König, R. W. T.

2001-04-01

202

Bremsstrahlung and K(alpha) fluorescence measurements for inferring conversion efficiencies into fast ignition relevant hot electrons  

SciTech Connect

The Bremsstrahlung and K-shell emission from 1 mm x 1 mm x 1 mm planar targets irradiated by a short-pulse 3 x 10{sup 18}-8 x 10{sup 19} W/cm{sup 2} laser were measured. The Bremsstrahlung was measured using a filter stack spectrometer with spectral discrimination up to 500 keV. K-shell emission was measured using a single photon counting charge coupled device (CCD). From Monte Carlo modeling of the target emission, conversion efficiencies into 1-3 MeV electrons of 3-12%, representing 20-40% total conversion efficiencies were inferred for intensities up to 8 x 10{sup 19} W/cm{sup 2}. Comparisons to scaling laws using synthetic energy spectra generated from the intensity distribution of the focal spot imply slope temperatures less than the ponderomotive potential of the laser. Resistive transport effects may result in potentials of a few hundred kV in the first few tens of microns in the target. This would lead to higher total conversion efficiencies than inferred from Monte Carlo modeling but lower conversion efficiencies into 1-3 MeV electrons.

Chen, C D; Patel, P K; Hey, D S; Mackinnon, A J; Key, M H; Akli, K U; Bartal, T; Beg, F N; Chawla, S; Chen, H; Freeman, R R; Higginson, D P; Link, A; Ma, T Y; MacPhee, A G; Stephens, R B; Van Woerkom, L D; Westover, B; Porkolab, M

2009-07-24

203

Plasma Modulation of Harmonic Emission Spectra from Laser-Plasma Interactions  

SciTech Connect

We report results from particle-in-cell simulations of the interaction of intense laser light with overdense plasma designed to examine the effects of plasma waves generated by pulses of fast electrons on high-order harmonic emission from the plasma. We show that the emission spectrum is modulated at the plasma frequency and identify combinations of parameters and circumstances favorable for modulation. In particular, the observed modulation is shown to depend not only on the chosen plasma electron density and intensity of the incident light but on the density profile and pulse shape.

Boyd, T. J. M. [Centre for Physics, University of Essex, Wivenhoe Park, Colchester CO4 3SQ (United Kingdom); Ondarza-Rovira, R. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, Mexico 11801, Distrito Federal (Mexico)

2007-03-09

204

Equatorial electromagnetic emission with discrete spectra near harmonics of oxygen gyrofrequency during magnetic storm  

SciTech Connect

The authors examine ELF data taken by the Akebono satellite in the low altitude plasmasphere during magnetic storms. They find that there are a set of these wave observations which are frequency related to the oxygen ion gyrofrequency. They observe emissions at frequencies closely related to the first and second harmonic of the oxygen ion gyrofrequency. The spacing between bands observed in the ELF are at the first or second oxygen ion gyrofrequency, and the frequency varies with the geomagnetic field. The authors argue that these emissions orginate from oxygen ions in the ring current region.

Liu, H.; Kokubun, S.; Hayashi, K. (Univ. of Tokyo (Japan))

1994-02-01

205

Emission spectra of laser-produced plasmas for EUV and soft x-ray sources  

NASA Astrophysics Data System (ADS)

The plasma emission of tin, aluminum and cupper targets irradiated with laser intensities ranging from 1011 to 1016 W/cm2 has been measured beween 7nm and 18 nm. A chirped pulse amplified Ti:Sapphire laser oscillating at 790- nm with either 100 fs or 300 ps pulse duration and a Nd:YAG laser oscillating at 1064 nm with 10 ns pulse duration (fwhm) have been used. The observed plasma emission was strongest for the 300 ps laser pulse irradiation, which might be due to the additional laser plasma heating during plasma formation.

Soumagne, Georg; Abe, Tamotsu; Ikeda, Kenichi; Komori, Hiroshi; Someya, Hiroshi; Suganuma, Takashi; Nakajima, Kazuhisa; Endo, Akira

2004-06-01

206

Evaluation of Six Methods for Extracting Relative Emissivity Spectra from Thermal Infrared Images  

Microsoft Academic Search

The performance of six published methods for extracting relative spectral emissivity information from thermal infrared multispectral data has been evaluated. In the first part of this article, we recall those six methods and show mathematically that they are almost equivalent to each other. Then, using simulated data for the TIMS (Thermal Infrared Multispectral Scanner) instrument, we analyze the sensitivity of

Zhao-Liang Li; F. Becker; M. P. Stoll; Zhengming Wan

1999-01-01

207

Errors associated with fitting Gaussian profiles to noisy emission-line spectra  

NASA Technical Reports Server (NTRS)

Landman et al. (1982) developed prescriptions to predict profile fitting errors for Gaussian emission lines perturbed by white noise. We show that their scaling laws can be generalized to more complicated signal-dependent 'noise models' of common astronomical detector systems.

Lenz, Dawn D.; Ayres, Thomas R.

1992-01-01

208

Thermal Emission Spectra of Altered Tephras and Constraints on the Composition of Martian Dust  

NASA Technical Reports Server (NTRS)

We have begun to create a comprehensive set of thermal infrared (TIR, approx. 1650-200/cm, approx. 6-50 microns) spectra of palagonitic and hydrothermally altered soils that exhibit a range of mineralogical and chemical compositions for use in analyzing MGS TES data. Palagonite, a phyllosilicate-poor hydrolytically altered tephra, has been suggested as a possible component of the martian soil/dust based on visible and near infrared (VNIR) spectral similarities with martian dusty regions. The chemistry and crystallinity of altered tephras are highly variable depending on the parent material and local environmental conditions, and are important indicators of alteration processes.

Hamilton, Victoria E.; Morris, Richard V.

2003-01-01

209

Study of medical isotope production facility stack emissions and noble gas isotopic signature using automatic gamma-spectra analysis platform  

NASA Astrophysics Data System (ADS)

The nuclear industry emissions of the four CTBT (Comprehensive Nuclear-Test-Ban Treaty) relevant radioxenon isotopes are unavoidably detected by the IMS along with possible treaty violations. Another civil source of radioxenon emissions which contributes to the global background is radiopharmaceutical production companies. To better understand the source terms of these background emissions, a joint project between HC, ANSTO, PNNL and CRL was formed to install real-time detection systems to support 135Xe, 133Xe, 131mXe and 133mXe measurements at the ANSTO and CRL 99Mo production facility stacks as well as the CANDU (CANada Deuterium Uranium) primary coolant monitoring system at CRL. At each site, high resolution gamma spectra were collected every 15 minutes using a HPGe detector to continuously monitor a bypass feed from the stack or CANDU primary coolant system as it passed through a sampling cell. HC also conducted atmospheric monitoring for radioxenon at approximately 200 km distant from CRL. A program was written to transfer each spectrum into a text file format suitable for the automatic gamma-spectra analysis platform and then email the file to a server. Once the email was received by the server, it was automatically analysed with the gamma-spectrum software UniSampo/Shaman to perform radionuclide identification and activity calculation for a large number of gamma-spectra in a short period of time (less than 10 seconds per spectrum). The results of nuclide activity together with other spectrum parameters were saved into the Linssi database. This database contains a large amount of radionuclide information which is a valuable resource for the analysis of radionuclide distribution within the noble gas fission product emissions. The results could be useful to identify the specific mechanisms of the activity release. The isotopic signatures of the various radioxenon species can be determined as a function of release time. Comparison of 133mXe and 133Xe activity ratios showed distinct differences between the closed CANDU primary coolant system and radiopharmaceutical production releases. According to the concept proposed by Kalinowski and Pistner (2006), the relationship between different isotopic activity ratios based on three or four radioxenon isotopes was plotted in a log-log diagram for source characterisation (civil vs. nuclear test). The multiple isotopic activity ratios were distributed in three distinct areas: HC atmospheric monitoring ratios extended to far left; the CANDU primary coolant system ratios lay in the middle; and 99Mo stack monitoring ratios for ANSTO and CRL were located on the right. The closed CANDU primary coolant has the lowest logarithmic mean ratio that represents the nuclear power reactor operation. The HC atmospheric monitoring exhibited a broad range of ratios spreading over several orders of magnitude. In contrast, the ANSTO and CRL stack emissions showed the smallest range of ratios but the results indicate at least two processes involved in the 99Mo productions. Overall, most measurements were found to be shifted towards the reactor domain. The hypothesis is that this is due to an accumulation of the isotope 131mXe in the stack or atmospheric background as it has the longest half-life and extra 131mXe emissions from the decay of 131I. The contribution of older 131mXe to a fresh release shifts the ratio of 133mXe/131mXe to the left. It was also very interesting to note that there were some situations where isotopic ratios from 99Mo production emissions fell within the nuclear test domain. This is due to operational variability, such as shorter target irradiation times. Martin B. Kalinowski and Christoph Pistner, (2006), Isotopic signature of atmospheric xenon released from light water reactors, Journal of Environmental Radioactivity, 88, 215-235.

Zhang, Weihua; Hoffmann, Emmy; Ungar, Kurt; Dolinar, George; Miley, Harry; Mekarski, Pawel; Schrom, Brian; Hoffman, Ian; Lawrie, Ryan; Loosz, Tom

2013-04-01

210

Positronium emission spectra from self-assembled metal-organic frameworks  

NASA Astrophysics Data System (ADS)

Results of positronium (Ps) emission into vacuum from self-assembled metal-organic frameworks (MOFs) are presented and discussed in detail. Four different MOF crystals are considered, namely, MOF-5, IRMOF-8, ZnO4(FMA)3, and IRMOF-20. The measurements reveal that a fraction of the Ps is emitted into vacuum with a distinctly smaller energy than what one would expect for Ps localized in the MOFs' cells. Only calculations considering the Ps delocalized in a Bloch state can reproduce the measured Ps emission energy providing a robust demonstration of wave function delocalization in quantum mechanics. We show how the Bloch state population can be controlled by tuning the initial positron beam energy. Therefore, Ps in MOFs can be used both to simulate the dynamics of delocalized excitations in materials and to probe the MOFs for their advanced characterization.

Crivelli, P.; Cooke, D.; Barbiellini, B.; Brown, B. L.; Feldblyum, J. I.; Guo, P.; Gidley, D. W.; Gerchow, L.; Matzger, A. J.

2014-06-01

211

Thermal emission spectra of Mars (5.4-10.5 microns) - Evidence for sulfates, carbonates, and hydrates  

NASA Technical Reports Server (NTRS)

Spectra of the Martian thermal emission in the 5.4-10.5 micron region are reported. Emission features at 7.8 and 9.7 microns are attributed to surface silicates, and an emission feature at 6.1 micron is attributed to a molecular water component of the surface material. An absorption band at 8.7 micron and a possible one at 9.8 microns is attributed to sulfate or bisulfate anions probably located at a distorted crystalline site, and an absorption band at 6.7 microns is attributed to carbonate or bicarbonate anions located in a distorted crystalline site. Spectral simulations indicate that the sulfate- and carbonate-bearing minerals are contained in the same particles of airborne dust as the dominant silicate minerals, that the dust optical depth is about 0.6 at a reference wavelength of 0.3 micron over the area of the observed spots, and that sulfates and carbonates constitute 10-15 percent and 1-3 percent by volume of the airborne dust, respectively.

Pollack, James B.; Roush, Ted; Witteborn, Fred; Bregman, Jesse; Wooden, Diane; Stoker, Carol; Toon, Owen B.

1990-01-01

212

High-resolution spectra of Jupiter's northern auroral ultraviolet emission with the Hubble Space Telescope  

NASA Technical Reports Server (NTRS)

The first spectroscopic observations of planetary aurora with the Hubble Space Telescope (HST) are reported. These include spectral regions centered on the H2 Lyman and Werner bands of a region of Jupiter's northern aurora. The observations were made with the Goddard High Resolution Spectrograph (GHRS) using the Large Science Aperture as part of a campaign to study Jupiter at the time of the Ulysses flyby. The individual rotational-vibrational bands are resolved and the observed emissions are essentially all from H2. A rotational-vibrational temperature for H2 of 530 +/- 100 K is derived, a value significantly less than the 850-1100 K reported for Jovian H3(+) in the near-infrared but consistent with the temperature reported for fundamental-band quadrupole H2 emission. Comparison with the Faint Object Camera (FOC) images shows that the observed region was not one of the hot spots of the aurora. The results are interpreted in trms of electron impact excitation of H2 from secondary particles generated by primaries precipitating into Jupiter's atmsophere from the magnetosphere. In the region of the aurora observed, the homopause level is found to be significantly hotter but not necessarily higher than observed at nonauroral latitudes. The equatorial H2 dayglow spectrum was also detected; its intensity was 3.2 kR or 13% of the strength of the observed auroral emission.

Trafton, L. M.; Gerard, J. C.; Munhoven, G.; Waite, J. H., Jr.

1994-01-01

213

Modeling Optically Thick Molecular Emission Spectra of Comets Using Asymmetric Spherical Coupled Escape Probability  

NASA Astrophysics Data System (ADS)

Comets are frozen remnants from the formation of the Solar System. As such, their chemical composition is of great significance to understanding the origin of the planets and the distribution of important molecules, including water and other volatiles, throughout the Solar System. Recent observations, in particular those of the Deep Impact and EPOXI Missions, have provided better spectra of a cometary coma than were previously available. These observations include spectra with high spatial resolution very near to the nucleus. The purpose of this research is to better understand the abundances, distributions and creation mechanisms of various volatiles observed in cometary comae, in particular those of comet 9P/Tempel 1, the target of the Deep Impact Mission, and 103P/Hartley 2, the subject of the EPOXI mission. In order to do so, I have built a computer model of the spectrum of the comet's coma which includes the difficult and often ignored problem of accurately including radiative transfer to account for the potentially optically thick coma (or regions of the coma) near the nucleus. I have adapted Coupled Escape Probability, a new exact method of solving radiative transfer problems, from its original plane-parallel formulation for use in asymmetrical spherical situations. My model is designed specifically for use in modeling optically thick cometary comae, although not limited to such use. By providing for asymmetric geometry in the coma, the model is able to include the morphology of the near nucleus coma, as observed by the Deep Impact spacecraft for Tempel 1 and Hartley 2, and include this in the modeling of radiative transfer. This method enables the accurate modeling of comets' spectra even in the potentially optically thick regions nearest the nucleus, such as those seen in Deep Impact observations of 9P/Tempel 1 and EPOXI observations of 103P/Hartley 2. This model will facilitate analyzing the actual spectral data from the Deep Impact and EPOXI missions to better determine abundances of key volatile species, including CO, CO2 and H2O, as well as remote sensing data on active comets.

Gersch, Alan Michael

214

Method of Fission Product Beta Spectra Measurements for Predicting Reactor Anti-neutrino Emission  

E-print Network

The nuclear fission process that occurs in the core of nuclear reactors results in unstable, neutron rich fission products that subsequently beta decay and emit electron anti-neutrinos. These reactor neutrinos have served neutrino physics research from the initial discovery of the neutrino to current precision measurements of neutrino mixing angles. The prediction of the absolute flux and energy spectrum of the emitted reactor neutrinos hinges upon a series of seminal papers based on measurements performed in the 1970s and 1980s. The steadily improving reactor neutrino measurement techniques and recent re-considerations of the agreement between the predicted and observed reactor neutrino flux motivates revisiting the underlying beta spectra measurements. A method is proposed to use an accelerator proton beam delivered to an engineered target to yield a neutron field tailored to reproduce the neutron energy spectrum present in the core of an operating nuclear reactor. Foils of the primary reactor fissionable i...

Asner, D M; Campbell, L W; Greenfield, B; Kos, M S; Orrell, J L; Schram, M; VanDevender, B; Wood, 1 L S; Wootan, D W

2014-01-01

215

New method for measuring time-resolved spectra of lanthanide emission using square-wave excitation.  

PubMed

A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 ?s. CW Nd(3+) lasers were used as examples to present the method. Upconversion dynamic process of Ho(3+) was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb(3+) to Yb(3+) was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar(+) laser, Kr(+) laser, Ti:sapphire laser, etc. PMID:24289387

Qin, Feng; Zhao, Hua; Duan, Qianqian; Cai, Wei; Zhang, Zhiguo; Cao, Wenwu

2013-11-01

216

New method for measuring time-resolved spectra of lanthanide emission using square-wave excitation  

SciTech Connect

A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 ?s. CW Nd{sup 3+} lasers were used as examples to present the method. Upconversion dynamic process of Ho{sup 3+} was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb{sup 3+} to Yb{sup 3+} was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar{sup +} laser, Kr{sup +} laser, Ti:sapphire laser, etc.

Qin, Feng [Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin 150080 (China); Zhao, Hua; Cai, Wei, E-mail: weicai@hit.edu.cn [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China); Duan, Qianqian [College of Information Engineering, Taiyuan University of Technology, Taiyuan 030024 (China); Zhang, Zhiguo, E-mail: zhangzhiguo@hit.edu.cn [Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin 150080 (China); Laboratory of Sono- and Photo-Theranostic Technologies, Harbin Institute of Technology, Harbin 150080 (China); Cao, Wenwu, E-mail: dzk@psu.edu [Condensed Matter Science and Technology Institute, Harbin Institute of Technology, Harbin 150080 (China); Laboratory of Sono- and Photo-Theranostic Technologies, Harbin Institute of Technology, Harbin 150080 (China); Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2013-11-15

217

X-ray spectra and polarization from accreting black holes: polarization of the thermal emission  

NASA Astrophysics Data System (ADS)

Multicolour black-body emission from the accretion disc around the black hole can be polarized on its way through the atmosphere above the accretion disc. We model this effect by assuming Kerr metric for the black hole, a standard thin disc for the accretion flow and Thomson scattering in the atmosphere. We compute the expected polarization degree and the angle as they can be measured for different inclinations of the observer, optical thickness of the atmosphere and different values of the black hole spin. All relativistic effects near a compact centre are taken into account.

Dov?iak, M.; Goosmann, R. W.; Karas, V.; Matt, G.

2008-10-01

218

Emission lines of [K v] in the optical spectra of gaseous nebulae  

PubMed Central

Recent R-matrix calculations of electron impact excitation rates in K v are used to derive the nebular emission line ratio R = I(4122.6 ?)/I(4163.3 ?) as a function of electron density (Ne). This ratio is found to be very sensitive to changes in Ne over the density range 103 to 106 cm?3, but does not vary significantly with electron temperature, and hence in principle should provide an excellent optical Ne diagnostic for the high-excitation zones of nebulae. The observed value of R for the planetary nebula NGC 7027, measured from a spectrum obtained with the Hamilton Echelle spectrograph on the 3-m Shane Telescope, implies a density in excellent agreement with that derived from [Ne iv], formed in the same region of the nebula as [K v]. This observation provides observational support for the accuracy of the theoretical [K v] line ratios, and hence the atomic data on which they are based. However, the analysis of a high-resolution spectrum of the symbiotic star RR Telescopii, obtained with the University College London Echelle Spectrograph on the 3.9-m Anglo–Australian Telescope, reveals that the [K v] 4122.6 ? line in this object is badly blended with Fe ii 4122.6 ?. Hence, the [K v] diagnostic may not be used for astrophysical sources that show a strong Fe ii emission line spectrum. PMID:11904366

Keenan, Francis P.; Aller, Lawrence H.; Espey, Brian R.; Exter, Katrina M.; Hyung, Siek; Keenan, Michael T. C.; Pollacco, Don L.; Ryans, Robert S. I.

2002-01-01

219

Complex X-ray Absorption and the Fe K(alpha) Profile in NGC 3516  

NASA Technical Reports Server (NTRS)

We present data from simultaneous Chandra, XMM-Newton and BeppoSAX observations of the Seyfert 1 galaxy NGC 3516, taken during 2001 April and November. We have investigated the nature of the very flat observed X-ray spectrum. Chandra grating data show the presence of X-ray absorption lines, revealing two distinct components of the absorbing gas, one which is consistent with our previous model of the UV/X-ray absorber while the other, which is outflowing at a velocity of approximately 1100 kilometers per second, has a larger column density and is much more highly ionized. The broad-band spectral characteristics of the X-ray continuum observed with XMM during 2001 April, reveal the presence of a third layer of absorption consisting of a very large column (approximately 2.5 x 10(exp 23) per square centimeter) of highly ionized gas with a covering fraction approximately 50%. This low covering fraction suggests that the absorber lies within a few 1t-days of the X-ray source and/or is filamentary in structure. Interestingly, these absorbers are not in thermal equilibrium with one another. The two new components are too highly ionized to be radiatively accelerated, which we suggest is evidence for a hydromagnetic origin for the outflow. Applying our model to the November dataset, we can account for the spectral variability primarily by a drop in the ionization states of the absorbers, as expected by the change in the continuum flux. When this complex absorption is accounted for we find the underlying continuum to be typical of Seyfert 1 galaxies. The spectral curvature attributed to the high column absorber, in turn, reduces estimates of the flux and extent of any broad Fe emission line from the accretion disk.

Turner, T. J.; Kraemer, S. B.; George, I. M.; Reeves, J. N.; Botorff, M. C.

2004-01-01

220

Origins of PM10 determined by the micro-proton induced X-ray emission spectra of single aerosol particles  

SciTech Connect

The micro-proton induced X-ray emission (micro-PIXE) spectrum of a single aerosol particle (SAP) was considered as its fingerprint for tracing its origin. A proton microprobe was used to extract fingerprints of SAPs. Environmental monitoring samples of PM10 were collected from a heavy industrial area of Shanghai and were analyzed by proton microprobe for finding their pollution sources. In order to find the sources of SAPs collected from environmental monitoring sites, a fingerprint database of SAPS collected from various pollution Sources was established. The origins of samples collected through environmental monitoring were identified by comparison of the micro-PIXE spectra of SAPs with those of SAPs in the fingerprint database using a pattern recognition technique. The results of this study show that most of the measured PM10 is derived from metallurgic industry, soil dust, coal combustion, automobile exhaust, and motorcycle exhaust. The study also shows that the proton microprobe is an ideal tool for the analysis of SAPs. The unidentified particles of PM10 are classified into seven classes by hierarchical cluster analysis based on the element peak intensity in the spectra.

Yue, W.S.; Li, X.L.; Wan, T.M.; Liu, J.F.; Zhang, G.L.; Li, Y. [Chinese Academy of Science, Shanghai (China). Shanghai Institute of Applied Physics

2006-06-15

221

Inner valence molecular orbitals and structure of the X-ray O 4,5(Th,U) emission spectra in thorium and uranium oxides  

Microsoft Academic Search

In the present work, the possibility of an influence of the chemical environment on the structure of O4,5(Th,U) emission spectra of thorium and uranium oxides was studied. It is noted that the fine structure in such spectra is caused by the formation of inner valence molecular orbitals, involving relatively deep Th(U) 6p and O(F) 2s atomic orbitals of the neighbouring

Yu. A Teterin; V. A Terekhov; A. Yu Teterin; K. E Ivanov; I. O Utkin; A. M Lebedev; L Vukchevich

1998-01-01

222

Quantitative analysis of 77K fluorescence emission spectra in Synechocystis sp. PCC 6714 and Chlamydomonas reinhardtii with variable PS I\\/PS II stoichiometries  

Microsoft Academic Search

Low-temperature (77 K) fluorescence emission spectra of intact cells of a cyanobacterium, Synechocystis sp. PCC 6714, and a green alga, Chlamydomonas reinhardtii, were quantitatively analyzed to examine differences in PS I\\/PS II stoichiometries. Cells cultured under different spectral conditions had various PS I\\/PS II molar ratios when estimated by oxidation-reduction difference absorption spectra of P700 (for PS I) and Cyt

Akio Murakami

1997-01-01

223

Theoretical studies of electronic structures, absorption and emission spectra in cyclometalated phenylpyridine Ir(III) complex and its derivatives using density functional theory  

Microsoft Academic Search

The ground-state and electronic spectra in the Ir(III) complex Ir(ppy)3 [where ppy=2-phenylpyridine], an important phosphorescent material, and its derivatives are studied using density functional theory (DFT) B3LYP\\/LanL2dz in programme Gaussian 98. The effects of substituted groups on energies, gaps of HOMO–LUMO, absorption and emission spectra are discussed. It is found that electron-withdrawing substituent (–CN) makes both orbital energies and gaps

Xiaodong Liu; Jikang Feng; Aimin Ren; Li Yang; Bing Yang; Yuguang Ma

2006-01-01

224

Analysis of the absorption and emission spectra of poly( p-phenylene vinylene) films thermally converted at a relatively low temperature  

Microsoft Academic Search

In this work, we studied the absorption and emission spectra of spin-coated poly(p-phenylene vinylene) (PPV)–dodecylbenzenesulfonic counter-ion (DBS) films. The PPV–DBS films were obtained from a soluble precursor polymer thermally converted to PPV over a comparatively short time interval (30min), and at low temperature (110°C), conditions that yielded films with few structural defects. The line shape of the absorption spectra of

Alexandre Marletta; Débora Gonçalves

2006-01-01

225

Thermal Emission Spectra of Silica-coated Basalt and Considerations for Martian Surface Mineralogy  

NASA Technical Reports Server (NTRS)

Among the most important discoveries made during the Mars Global Surveyor (MGS) mission was that the rocky materials of Mars are broadly divisible into two distinct rock types. The geological significance of this finding is dependent on the mineralogy of these rock types as well as their geographic and stratigraphic positions. Much work has yet to be done to understand these relationships and the small-scale variability of these units. For now, it is worth considering various scenarios that could have resulted in Mars global-scale mineralogical dichotomy. Such work will make clearer what must be looked for in Thermal Emission Spectrometer (TES) and Thermal Imaging Spectrometer (THEMIS) data, what to test with other data sets, and what geological processes can be considered or ruled out as we advance with interpreting Martian geologic history. Here, we suggest that exogenic coatings of secondary silica on basaltic rocks may provide a plausible explanation for the newly discovered distribution of rock types.

Kraft, M. D.; Sharp, T. G.; Michalski, J. R.

2003-01-01

226

Ion temperatures in HIP-1 and SUMMA from charge-exchange neutral optical emission spectra  

NASA Technical Reports Server (NTRS)

Ion temperatures were obtained from observations of the H sub alpha, D sub alpha, and He 587.6 nm lines emitted from hydrogen, deuterium, and helium plasmas in the SUMMA and HIP-1 mirror devices at Lewis Research Center. Steady state discharges were formed by applying a radially inward dc electric field between cylindrical or annular anodes and hollow cathodes located at the peaks of the mirrors. The ion temperatures were found from the Doppler broadening of the charge-exchange components of spectral lines. A statistical method was developed for obtaining scaling relations of ion temperature as a function of current, voltage, and magnetic flux density. Derivations are given that take into account triangular monochromator slit functions, loss cones, and superimposed charge-exchange processes. In addition, the Doppler broadening was found to be sensitive to the influence of drift on charge-exchange cross section. The effects of finite ion-cyclotron radius, cascading, and delayed emission are reviewed.

Patch, R. W.; Lauver, M. R.

1976-01-01

227

THE LOCAL DUST FOREGROUNDS IN THE MICROWAVE SKY. I. THERMAL EMISSION SPECTRA  

SciTech Connect

Analyses of the cosmic microwave background (CMB) radiation maps made by the Wilkinson Microwave Anisotropy Probe (WMAP) have revealed anomalies not predicted by the standard inflationary cosmology. In particular, the power of the quadrupole moment of the CMB fluctuations is remarkably low, and the quadrupole and octopole moments are aligned mutually and with the geometry of the solar system. It has been suggested in the literature that microwave sky pollution by an unidentified dust cloud in the vicinity of the solar system may be the cause for these anomalies. In this paper, we simulate the thermal emission by clouds of spherical homogeneous particles of several materials. Spectral constraints from the WMAP multi-wavelength data and earlier infrared observations on the hypothetical dust cloud are used to determine the dust cloud's physical characteristics. In order for its emissivity to demonstrate a flat, CMB-like wavelength dependence over the WMAP wavelengths (3 through 14 mm), and to be invisible in the infrared light, its particles must be macroscopic. Silicate spheres of several millimeters in size and carbonaceous particles an order of magnitude smaller will suffice. According to our estimates of the abundance of such particles in the zodiacal cloud and trans-Neptunian belt, yielding the optical depths of the order of 10{sup -7} for each cloud, the solar system dust can well contribute 10 muK (within an order of magnitude) in the microwaves. This is not only intriguingly close to the magnitude of the anomalies (about 30 muK), but also alarmingly above the presently believed magnitude of systematic biases of the WMAP results (below 5 muK) and, to an even greater degree, of the future missions with higher sensitivities, e.g., Planck.

Dikarev, Valeri; Preuss, Oliver; Solanki, Sami; Krueger, Harald [Max-Planck-Institut fuer Sonnensystemforschung, 37191 Katlenburg-Lindau (Germany); Krivov, Alexander [Friedrich-Schiller Universitaet Jena (Germany)

2009-11-01

228

Demonstration of Successful X-ray Thomson Scattering Using Picosecond K-(alpha) X-ray Sources for the Characterization of Dense Heated Matter  

SciTech Connect

We discuss the first successful K-{alpha} x-ray Thomson scattering experiment from solid density plasmas for use as a diagnostic in determining the temperature, density, and ionization state of warm dense matter with picosecond resolution. The development of this source as a diagnostic and stringent requirements for successful K-{alpha} x-ray Thomson scattering are addressed. Data for the experimental techniques described in this paper [1] suggest the capability of single shot characterization of warm dense matter and the ability to use this scattering source at future Free Electron Lasers (FEL) where comparable scattering signal levels are predicted.

Kritcher, A; Neumayer, P; Lee, H J; Doeppner, T; Falcone, R; Glenzer, S; Morse, E C

2008-05-05

229

Emission from Water Vapor and Absorption from Other Gases at 5-7.5 Microns in Spitzer-IRS Spectra of Protoplanetary Disks  

E-print Network

We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph (IRS) 5-7.5 micron spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 microns due to the nu_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 seen in the spectrum of the FU Orionis star V1057 Cyg. The other six of the thirteen stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 microns, which for some is consistent with gaseous formaldehyde (H2CO) 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....

Sargent, B A; Watson, Dan M; Calvet, N; Furlan, E; Kim, K -H; Green, J; Pontoppidan, K; Richter, I; Tayrien, C

2014-01-01

230

Fluorescence excitation and emission spectra of ALA-induced protoporphyrin IX in normal and tumoral tissue of the human bladder  

NASA Astrophysics Data System (ADS)

In vivo spectrofluorometric analysis represents a tool to obtain information about fluorophore distribution in tissue. Based on a Peltier-cooled CCD we designed a fluorescence excitation and emission spectrograph which allows to obtain tissue spectra endoscopically and in a clinical environment. Clinical studies were performed on patients with positive cytology or tumor recurrence in the urinary bladder. Patients received a 50 ml instillation of 3% ALA solution at pH 5.5 during 3 to 4 hours and underwent a normal white light cystoscopic examination together with light induced fluorescence photodetection at 5 to 8 hours after the beginning of the instillation. Local fluorescence measurements with a single fiber were performed before photodetection. These showed fluorescence ratios between tumor and normal tissue of 1.5 to 20 with the strongest ratios for exophytic papillary tumors. Fluorescence excitation between 380 nm and 450 nm revealed that the higher Protoporphyrin IX (PPIX) signal on tumor tissue is accompanied by a decrease of the autofluorescence at the emission wavelength of 500 nm.

Forrer, Martin; Glanzmann, Thomas M.; Mizeret, Jerome C.; Braichotte, Daniel; Wagnieres, Georges A.; van den Bergh, Hubert; Jichlinski, Patrice; Leisinger, Hans-Juerg

1995-01-01

231

Predicting X-ray emission from wind-blown bubbles - Limitations of fits to ROSAT spectra  

E-print Network

Wind-blown bubbles, from those around massive O and Wolf-Rayet stars, to superbubbles around OB associations and galactic winds in starburst galaxies, have a dominant role in determining the structure of the Interstellar Medium. X-ray observations of these bubbles are particularly important as most of their volume is taken up with hot gas, 1E5 < T (K) < 1E8. However, it is difficult to compare X-ray observations, usually analysed in terms of single or two temperature spectral model fits, with theoretical models, as real bubbles do not have such simple temperature distributions. In this introduction to a series of papers detailing the observable X-ray properties of wind-blown bubbles, we describe our method with which we aim to solve this problem, analysing a simulation of a wind-blown bubble around a massive star. We model a wind of constant mass and energy injection rate, blowing into a uniform ISM, from which we calculate X-ray spectra as would be seen by the ROSAT PSPC. We compare the properties of the bubble as would be inferred from the ROSAT data with the true properties of the bubble in the simulation. We find standard spectral models yield inferred properties that deviate significantly from the true properties, even though the spectral fits are statistically acceptable, and give no indication that they do not represent to true spectral distribution. Our results suggest that in any case where the true source spectrum does not come from a simple single or two temperature distribution the "observed" X-ray properties cannot naively be used to infer the true properties.

David K. Strickland; Ian R. Stevens

1998-03-06

232

Ly(alpha) emission and absorption features in the spectra of galaxies  

NASA Technical Reports Server (NTRS)

The combined effects of interstellar dust absorption and of scattering by hydrogen atoms may give rise to a Ly(alpha) spectral feature of negative equivalent width, as has been observed in several star-forming galaxies. By considering the transfer of Ly(alpha) line radiation and of neighboring stellar continuum radiation within a dusty galaxy, we find that dust absorption has three effects: (1) it reduces the apparent ultraviolet continuum luminosity at all wavelengths; (2) it preferentially decreases the apparent Ly(alpha) line luminosity from H II regions; and (3) it creates an 'attenuation feature' in the continuum spectrum -- centered at the Ly(alpha) rest frequency -- which occurs because the attenuation of the stellar continuum radiation increases as the Ly(alpha) rest frequency is approached, due to the effects of scattering by hydrogen atoms. For plausible values of the galactic dust content and of the disk thickness, these effects can lead to a negative net Ly(alpha) equivalent width, even for galaxies in which the unattenuated spectrum would show a strong Ly(alpha) emission line.

Chen, W. L.; Neufeld, David A.

1994-01-01

233

Emission spectra from direct current and microwave powered Hg lamps at very high pressure  

NASA Astrophysics Data System (ADS)

Discharge lamps containing mercury at pressures above 100 bar are commercially used in data projectors and television projector systems. Due to their small size, these lamps are difficult to investigate experimentally, but spectral measurements, combined with radiation transport calculations, have provided useful information on the visible spectrum. However, classical spectral line broadening theory is inadequate to describe the UV portion of the spectrum, so self-consistent modelling of these discharges is not possible at present. This paper discusses the differences between discharges containing electrodes and discharges sustained by a microwave (mw) electromagnetic field, on the basis of the experimentally measured temperature profile in an electroded discharge, and a temperature profile computed from a 1D power balance model for a microwave discharge. A model based on the ray-tracing method is employed to simulate the radiation transport in these lamps. The model has been validated by comparing the emission spectrum from dc discharge lamps with those obtained experimentally. The output flux, luminous flux, luminous efficacy, the correlated colour temperature, the chromaticity coordinates and photometric curves of the lamp were then obtained. These results were also compared with those of a theoretically calculated temperature profile for the same lamp, excited by microwave power in the TM010 mode.

Hamady, M.; Lister, G. G.; Stafford, L.

2013-11-01

234

Electron-Electron Bremsstrahlung Emission and the Inference of Electron Flux Spectra in Solar Flares  

E-print Network

Although both electron-ion and electron-electron bremsstrahlung contribute to the hard X-ray emission from solar flares, the latter is normally ignored. Such an omission is not justified at electron (and photon) energies above $\\sim 300$ keV, and inclusion of the additional electron-electron bremsstrahlung in general makes the electron spectrum required to produce a given hard X-ray spectrum steeper at high energies. Unlike electron-ion bremsstrahlung, electron-electron bremsstrahlung cannot produce photons of all energies up to the maximum electron energy involved. The maximum possible photon energy depends on the angle between the direction of the emitting electron and the emitted photon, and this suggests a diagnostic for an upper cutoff energy and/or for the degree of beaming of the accelerated electrons. We analyze the large event of January 17, 2005 observed by RHESSI and show that the upward break around 400 keV in the observed hard X-ray spectrum is naturally accounted for by the inclusion of electron-electron bremsstrahlung. Indeed, the mean source electron spectrum recovered through a regularized inversion of the hard X-ray spectrum, using a cross-section that includes both electron-ion and electron-electron terms, has a relatively constant spectral index $\\delta$ over the range from electron kinetic energy $E = 200$ keV to $E = 1$ MeV. However, the level of detail discernible in the recovered electron spectrum is not sufficient to determine whether or not any upper cutoff energy exists.

Eduard P. Kontar; A. Gordon Emslie; Anna Maria Massone; Michele Piana; John C. Brown; Marco Prato

2007-07-28

235

Results from a Near Infrared Search for Emission-line Stars in the Inner Galaxy: Spectra of New Wolf-Rayet Stars  

E-print Network

We present follow-up spectroscopy of emission line candidates detected on near-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The filters are optimized for the detection of Wolf-Rayet stars and other objects which exhibit emission--lines in the 2 $\\mu$m region. Approximately three square degrees along the Galactic plane have been analyzed in seven narrow--filters (four emission--lines and three continuum). We have discovered 4 new Wolf-Rayet stars and present coordinates, finding charts, and K-band spectra.

N. Homeier; R. D. Blum; A. Pasquali; P. S. Conti; A. Damineli

2003-06-27

236

ULTRAVIOLET EMISSION-LINE CORRELATIONS IN HST/COS SPECTRA OF ACTIVE GALACTIC NUCLEI: SINGLE-EPOCH BLACK HOLE MASSES  

SciTech Connect

Effective methods of measuring supermassive black hole masses in active galactic nuclei (AGNs) are of critical importance to studies of galaxy evolution. While there has been much success in obtaining masses through reverberation mapping, the extensive observing time required by this method has limited the practicality of applying it to large samples at a variety of redshifts. This limitation highlights the need to estimate these masses using single-epoch spectroscopy of ultraviolet (UV) emission lines. We use UV spectra of 44 AGNs from HST/COS, the International Ultraviolet Explorer, and the Far Ultraviolet Spectroscopic Explorer of the C IV {lambda}1549, O VI {lambda}1035, O III] {lambda}1664, He II {lambda}1640, C II {lambda}1335, and Mg II {lambda}2800 emission lines and explore their potential as tracers of the broad-line region and supermassive black hole mass. The higher signal-to-noise ratio and better spectral resolution of the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) resolve AGN intrinsic absorption and produce more accurate line widths. From these, we test the viability of mass-scaling relationships based on line widths and luminosities and carry out a principal component analysis based on line luminosities, widths, skewness, and kurtosis. At L{sub 1450} {<=} 10{sup 45} erg s{sup -1}, the UV line luminosities correlate well with H{beta}, as does the 1450 A continuum luminosity. We find that C IV, O VI, and Mg II can be used as reasonably accurate estimators of AGN black hole masses, while He II and C II are uncorrelated.

Tilton, Evan M.; Shull, J. Michael, E-mail: evan.tilton@colorado.edu, E-mail: michael.shull@colorado.edu [CASA, Department of Astrophysical and Planetary Sciences, University of Colorado, 389-UCB, Boulder, CO 80309 (United States)

2013-09-01

237

X-Ray Reflected Spectra from Accretion Disk Models. II. Diagnostic Tools for X-Ray Observations  

NASA Technical Reports Server (NTRS)

We present a comprehensive study of the emission spectra from accreting sources. We use our new reflection code to compute the reflected spectra from an accretion disk illuminated by X-rays. This set of models covers different values of ionization parameter, solar iron abundance and photon index for the illuminating spectrum. These models also include the most complete and recent atomic data for the inner-shell of the iron and oxygen isonuclear sequences. We concentrate our analysis to the 2 - 10 keV energy region, and in particular to the iron K-shell emission lines. We show the dependency of the equivalent width (EW) of the Fe Ka with the ionization parameter. The maximum value of the EW is approx. 800 eV for models with log Epsilon approx. 1.5, and decreases monotonically as Epsilon increases. For lower values of Epsilon the Fe K(alpha) EW decreases to a minimum near log Epsilon approx. 0.8. We produce simulated CCD observations based on our reflection models. For low ionized, reflection dominated cases, the 2 -10 keV energy region shows a very broad, curving continuum that cannot be represented by a simple power-law. We show that in addition to the Fe K-shell emission, there are other prominent features such as the Si and S L(alpha) lines, a blend of Ar VIII-XI lines, and the Ca x K(alpha) line. In some cases the S xv blends with the He-like Si RRC producing a broad feature that cannot be reproduced by a simple Gaussian profile. This could be used as a signature of reflection.

Garcia, J.; Kallman, T. R.; Mushotzky, R. F.

2011-01-01

238

Atomic Spectra  

NSDL National Science Digital Library

In this Flash animation the user can view the atomic emission spectra (400-700nm) of eight different elements. A dragable marker allows the user to approximate the wavelength of the various spectral lines. The effect of resolution can be examined in the sodium spectrum in the region 550-600nm.

239

Spectral and spatial resolution of the 12.8 micron Ne 2 emission from the galactic center. [astronomical spectroscopy/emission spectra, radio sources (astronomy)  

NASA Technical Reports Server (NTRS)

High-resolution spectra of the Ne II 12.8 micron fine-structure line in emission from the galactic center cloud Sgr A West show a line-center LSR radial velocity of + 75 + or - 20 km/sec. and a velocity dispersion of about 200 km/sec. The line has been observed with spectral resolution as high as 0.10/cm and spatial resolution as high as 8 sec. This appears to provide a direct measurement of conditions in the 45 sec. ionized region at the galactic center. The radial velocity and dispersion are more-or-less independent of position and indicate that events as recent as the last 4 million years have given the ionized gas a systematic motion with respect to the massive stellar component of material at the galactic center. An upper limit for the mass approximately equal to four million times the solar mass was obtained from the velocity distribution, with the mass located within 0.8 parsecs of the galactic center.

Wollman, E. R.; Geballe, T. R.; Lacy, J. H.; Townes, C. H.; Rank, D. M.

1975-01-01

240

Optical spectra, energy levels, and emission intensity calculations of trivalent thulium ions in gadolinium scandium gallium garnet  

NASA Astrophysics Data System (ADS)

Absorption spectra of trivalent thulium ions in gadolinium scandium gallium garnet are reported between 1.9 and 0.25 ?m at 4 K. Laser-induced fluorescence was observed at 4 K from the 1D2, 1G4, and 3H4 (4 and 300 K) manifolds. Site-selective excitation experiments reveal large fractions of thulium ions in both regular D2 sites and alternate sites. A crystal-field splitting calculation was carried out in which a parameterized Hamiltonian (including Coulombic, spin-orbit, and crystal-field terms in D2 symmetry) was diagonalized for all multiplet manifolds of the Tm3+ (4f12) configuration. The rms deviation between 56 experimental and calculated Stark levels was 10 cm-1. Calculations were carried out to predict branching ratios for emission from the 3H4 manifold to the 3H5, 3F4, and 3H6 manifolds, as well as line-to-line transition probabilities for transitions between the 3H4 manifold and the 3H5 manifold.

Seltzer, Michael D.; Gruber, John B.; Rosenblatt, Gregg H.; Morrison, Clyde A.; Filer, Elizabeth D.

1994-01-01

241

Thorite versus huttonite: stability, electronic properties and X-ray emission spectra from first-principle calculations  

NASA Astrophysics Data System (ADS)

The structural, electronic properties and stability of thorium orthosilicate ThSiO4 polymorphs: thorite and huttonite are investigated by means of the full-potential linearized augmented-plane-wave method with the generalized gradient approximation for the exchange-correlation potential (FLAPW-GGA). The forbidden gaps of thorite and huttonite are estimated at about 7.8 and 7.6 eV, respectively. It is found that Th5f states in ThSiO4 partially overlap with occupied O2p bands. The data obtained showed that thorite is more stable than huttonite; in turn both ThSiO4 polymorphs are unstable with respect to their constituent binary oxides (thorianite ThO2 and ?-quartz SiO2) in agreement with the experiments. The theoretical shapes of X-ray emission (XES) (Si,O)K?,? spectra for thorite, huttonite as well as for SiO2 and ThO2 are calculated and discussed. We show that the XES spectroscopy near the (Si,O)K edge may be very useful technique not only for detailed investigation of the bulk-electronic structure of Th silicates but also for the phase analysis of complex mineral samples containing these species.

Shein, Igor R.; Shein, Konstantin I.; Ivanovskii, Alexander L.

2006-11-01

242

[Quantitative analysis of two food colors using excitation-emission matrix spectra coupled with parallel factor algorithm].  

PubMed

In the present paper, British Edinburgh FLS920P Steady State and Time-Resolved Fluorescence Spectrometer was applied to measure three dimensional fluorescence spectra of 12 pigment solution samples and the parallel factor algorithm was combined with the excitation-emission matrix to find a way to detect the food colors. In the experiment, making use of CORCONDIA determination method to confirm that the number of the components is 3 in mixed solution, and then by using parallel factor analysis (PARAFAC) algorithms, get the average recoveries of carminum and Allura red were 99.3% +/- 5.0% and 102.2% +/- 5.6%, and the root mean square errors of prediction (RMSEP) were 0.054 and 0.205, respectively. The results show that the method can be applied to determine carminum and Allura red in the mixed solution simultaneously even in the presence of interfering amaranth, which was simple and convenient, rapid, etc, and provides references for synthetic food pigments detection. PMID:24783544

Li, Run; Chen, Guo-Qing; Zhu, Chun; Kong, Fan-Biao

2014-01-01

243

Physical properties, transmission and emission spectra of the WASP-19 planetary system from multi-colour photometry  

NASA Astrophysics Data System (ADS)

We present new ground-based, multi-colour, broad-band photometric measurements of the physical parameters, transmission and emission spectra of the transiting extrasolar planet WASP-19b. The measurements are based on observations of eight transits and four occultations through a Gunn i filter using the 1.54-m Danish Telescope, 14 transits through an Rc filter at the Perth Exoplanet Survey Telescope (PEST) observatory and one transit observed simultaneously through four optical (Sloan g', r', i', z') and three near-infrared (J, H, K) filters, using the Gamma Ray Burst Optical and Near-Infrared Detector (GROND) instrument on the MPG/ESO 2.2-m telescope. The GROND optical light curves have a point-to-point scatter around the best-fitting model between 0.52 and 0.65 mmag rms. We use these new data to measure refined physical parameters for the system. We find the planet to be more bloated (Rb = 1.410 ± 0.017RJup; Mb = 1.139 ± 0.030MJup) and the system to be twice as old as initially thought. We also used published and archived data sets to study the transit timings, which do not depart from a linear ephemeris. We detected an anomaly in the GROND transit light curve which is compatible with a spot on the photosphere of the parent star. The starspot position, size, spot contrast and temperature were established. Using our new and published measurements, we assembled the planet's transmission spectrum over the 370-2350 nm wavelength range and its emission spectrum over the 750-8000 nm range. By comparing these data to theoretical models we investigated the theoretically predicted variation of the apparent radius of WASP-19b as a function of wavelength and studied the composition and thermal structure of its atmosphere. We conclude that: (i) there is no evidence for strong optical absorbers at low pressure, supporting the common idea that the planet's atmosphere lacks a dayside inversion; (ii) the temperature of the planet is not homogenized, because the high warming of its dayside causes the planet to be more efficient in re-radiating than redistributing energy to the night side; (iii) the planet seems to be outside of any current classification scheme.

Mancini, L.; Ciceri, S.; Chen, G.; Tregloan-Reed, J.; Fortney, J. J.; Southworth, J.; Tan, T. G.; Burgdorf, M.; Calchi Novati, S.; Dominik, M.; Fang, X.-S.; Finet, F.; Gerner, T.; Hardis, S.; Hinse, T. C.; Jørgensen, U. G.; Liebig, C.; Nikolov, N.; Ricci, D.; Schäfer, S.; Schönebeck, F.; Skottfelt, J.; Wertz, O.; Alsubai, K. A.; Bozza, V.; Browne, P.; Dodds, P.; Gu, S.-H.; Harpsøe, K.; Henning, Th.; Hundertmark, M.; Jessen-Hansen, J.; Kains, N.; Kerins, E.; Kjeldsen, H.; Lund, M. N.; Lundkvist, M.; Madhusudhan, N.; Mathiasen, M.; Penny, M. T.; Prof, S.; Rahvar, S.; Sahu, K.; Scarpetta, G.; Snodgrass, C.; Surdej, J.

2013-11-01

244

THE XMM-NEWTON X-RAY SPECTRA OF THE MOST X-RAY LUMINOUS RADIO-QUIET ROSAT BRIGHT SURVEY-QSOs: A REFERENCE SAMPLE FOR THE INTERPRETATION OF HIGH-REDSHIFT QSO SPECTRA  

SciTech Connect

We present the broadband X-ray properties of four of the most X-ray luminous (L{sub X} {>=} 10{sup 45} erg s{sup -1} in the 0.5-2 keV band) radio-quiet QSOs found in the ROSAT Bright Survey. This uniform sample class, which explores the extreme end of the QSO luminosity function, exhibits surprisingly homogenous X-ray spectral properties: a soft excess with an extremely smooth shape containing no obvious discrete features, a hard power law above 2 keV, and a weak narrow/barely resolved Fe K{alpha} fluorescence line for the three high signal-to-noise ratio (S/N) spectra. The soft excess can be well fitted with only a soft power law. No signatures of warm or cold intrinsic absorbers are found. The Fe K{alpha} centroids and the line widths indicate emission from neutral Fe (E = 6.4 keV) originating from cold material from distances of only a few light days or further out. The well-constrained equivalent widths (EW) of the neutral Fe lines are higher than expected from the X-ray Baldwin effect which has been only poorly constrained at very high luminosities. Taking into account our individual EW measurements, we show that the X-ray Baldwin effect flattens above L{sub X} {approx} 10{sup 44} erg s{sup -1} (2-10 keV band) where an almost constant (EW) of {approx}100 eV is found. We confirm the assumption of having very similar X-ray active galactic nucleus properties when interpreting stacked X-ray spectra. Our stacked spectrum serves as a superb reference for the interpretation of low S/N spectra of radio-quiet QSOs with similar luminosities at higher redshifts routinely detected by XMM-Newton and Chandra surveys.

Krumpe, M.; Markowitz, A. [University of California, San Diego, Center for Astrophysics and Space Sciences, 9500 Gilman Drive, La Jolla, CA 92093-0424 (United States); Lamer, G. [Astrophysikalisches Institut Potsdam, An der Sternwarte 16, 14482 Potsdam (Germany); Corral, A., E-mail: mkrumpe@ucsd.ed [INAF-Osservatorio Astronomico di Brera, via Brera 28, 20121 Milan (Italy)

2010-12-20

245

Time-resolved emission spectra of 4-dimethylamino-4?-cyano-stilbene and resveratrol in high viscosity solvents and silica matrices  

NASA Astrophysics Data System (ADS)

Time-resolved emission spectra of 4-dimethylamino-4?-cyano-stilbene (DMACS) and 3,5,4?-trihydroxy-stilbene (resveratrol, RSV) in propylene glycol and in rigid silica xerogel matrix at 23 °C were studied. For the polar molecule DMACS in propylene glycol, a 66 nm shift of maximum wavelength of emission spectra was observed within 1 ns after excitation, and most of the shift occurred during the first 200 ps. For resveratrol in propylene glycol no such a shift was observed. The rigid silica environment eliminates some deactivation pathways and stabilizes spectroscopic properties of both molecules. Spectral properties of nonpolar and high dipole moment molecules in viscous liquids and rigid environments are compared. Results are explained on the basis of intramolecular processes and solute-solvent relaxation, as well.

Borowiak, Ma?gorzata; Grobelna, Beata; Synak, Anna; Bojarski, Piotr; Kubicki, Aleksander A.

2013-11-01

246

Emission spectra of the cations of 1,3- and 1,4-dibromotetrafluorobenzene and of 1,3,5-tribromotrifluorobenzene in the gaseous phase  

USGS Publications Warehouse

A search was made for radiative decay of electronically excited cations of 24 bromobenzenes and of their fluoro-substituted derivatives in the gaseous phase. The only emission spectra detected were for the cations of 1,3- and 1,4-dibromotetrafluorobenzene and of 1,3,5-tribromotrifluorobenzene. The band systems, which are found between 670 and 830 nm, are assigned to the B(??-1) ??? A(??-1), X(??-1) electronic transitions of these cations. The assignments are based on the Ne(I) photoelectron spectra which are also presented for some of the studied species. The interpretation for the absence of detectable emission is that the nature of the B cationic states is ??-1, except in the case of 1,3- and 1,4-dibromobenzene cations for which B states are still formed by ??-1 processes. Possible reasons for these observations are discussed. The symmetries of the lowest three electronic states of the studied cations are given. ?? 1980.

Maier, J.P.; Marthaler, O.; Mohraz, M.; Shiley, R.H.

1980-01-01

247

Solvent effect on UV/Vis absorption and emission spectra in aqueous solution based on a modified form of solvent reorganization energy  

NASA Astrophysics Data System (ADS)

In this Letter, novel form of solvatochromic shifts for absorption and emission spectra are proposed. As a typical test, the lowest transitions of s-trans-acrolein in aqueous solution are investigated. The obtained absorption solvent shift of 0.22 eV is in good agreement with the experimental value of 0.20 eV. In addition, we predict emission solvent shift of -0.16 eV. This value seems more reasonable comparing with the value of -0.12 eV by the traditional theory. The contributions to the shift are discussed and electrostatic polarization components are found to be crucial for electronic spectra of acrolein in water.

Ren, HaiSheng; Ming, MeiJun; Zhu, Jun; Ma, JianYi; Li, XiangYuan

2013-09-01

248

DISCOVERY OF Fe K{alpha} X-RAY REVERBERATION AROUND THE BLACK HOLES IN MCG-5-23-16 AND NGC 7314  

SciTech Connect

Several X-ray observations have recently revealed the presence of reverberation time delays between spectral components in active galactic nuclei. Most of the observed lags are between the power-law Comptonization component, seen directly, and the soft excess produced by reflection in the vicinity of the black hole. NGC 4151 was the first object to show these lags in the iron K band. Here, we report the discovery of reverberation lags in the Fe K band in two other sources: MCG-5-23-16 and NGC 7314. In both objects, the 6-7 keV band, where the Fe K{alpha} line peaks, lags the bands at lower and higher energies with a time delay of {approx}1 ks. These lags are unlikely to be due to the narrow Fe K{alpha} line. They are fully consistent with reverberation of the relativistically broadened iron K{alpha} line. The measured lags, their time scale, and spectral modeling indicate that most of the radiation is emitted at {approx}5 and 24 gravitational radii for MCG-5-23-16 and NGC 7314, respectively.

Zoghbi, A.; Reynolds, C. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Cackett, E. M. [Department of Physics and Astronomy, Wayne State University, 666 W. Hancock St, Detroit, MI 48201 (United States); Miniutti, G. [Centro de Astrobiologia (CSIC-INTA), Dep. de Astrosica, P.O. Box 78, E-28691 Villanueva de la Canada, Madrid (Spain); Kara, E.; Fabian, A. C., E-mail: azoghbi@astro.umd.edu [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

2013-04-20

249

Absorption and emission spectra of ultraviolet B blocking methoxy substituted cinnamates investigated using the symmetry-adapted cluster configuration interaction method  

Microsoft Academic Search

The absorption and emission spectra of ultraviolet B (UVB) blocking cinnamate derivatives with five different substituted positions were investigated using the symmetry-adapted cluster configuration interaction (SAC-CI) method. This series included cis- and trans-isomers of ortho-, meta-, and para-monomethoxy substituted compounds and 2,4,5-(ortho-, meta-, para-) and 2,4,6-(ortho-, para-) trimethoxy substituted compounds. The ground and excited state geometries were obtained at the

Malinee Promkatkaew; Songwut Suramitr; Thitinun Monhaphol Karpkird; Supawadee Namuangruk; Masahiro Ehara; Supa Hannongbua

2009-01-01

250

Stacking Analysis of 12CO and 13CO Spectra of NGC3627: Existence of non-optically thick 12CO emission?  

E-print Network

We stacked 12CO and 13CO spectra of NGC 3627 after redefining the velocity axis of each spectrum of the mapping data so that the zero corresponds to the local mean velocity of 12CO spectra. The signal-to-noise ratios of the resulting spectra are improved by a factor of up to 3.2 compared to those obtained with normal stacking analysis. We successfully detect a weak 13CO emission from the interarm region where the emission was not detected in the individual pointings. We compare the integrated intensity ratios I12 CO/I13 CO among six characteristic regions (center, bar, bar-end, offset, arm, and interarm). We find that I12CO/I13CO in the bar and interarm are higher than those in the other regions by a factor of ~2 and I12CO/I13CO in the center is moderately high. These high I12CO/I13CO ratios in the bar and center are attributed to a high intensity ratio (T12CO/T13CO) and one in the interarm is attributed to a high ratio of the full width at half maximum of spectra (FWHM12CO/FWHM13CO). The difference between F...

Morokuma-Matsui, Kana; Watanabe, Yoshimasa; Kuno, Nario

2014-01-01

251

Neutron Emission Spectra of 104,105,106,108,110Pd Isotopes for (p,xn) Reactions at 21.6 MeV Proton Incident Energy  

NASA Astrophysics Data System (ADS)

Palladium, which is a rare and lustrous silvery-white color from precious metals, plays important role in fusion-fission reactions and different fields of nuclear technology. In addition, it is used for not only cold fusion experiments but also separation of hydrogen isotopes researches for fusion reactors. In this study, neutron-emission spectra produced by (p,xn) reactions for structural fusion material 104,105,106,108,110Pd isotopes have been investigated by a proton beam at 21.6 MeV. Moreover, multiple pre-equilibrium mean free paths constant from internal transition, and the pre-equilibrium and equilibrium level density parameters have been analyzed for some (p,xn) neutron-emission spectra calculated. New evaluated hybrid model and geometry dependent hybrid model, full exciton model and cascade exciton model were used to calculate the pre-equilibrium neutron-emission spectra. For the reaction equilibrium component, Weisskopf-Ewing model calculations were preferred. The obtained results have been discussed and compared with the available experimental data and found agreement with each other.

Büyükuslu, H.; Kaplan, A.; Tel, E.; Aydin, A.; Y?ld?r?m, G.

2010-02-01

252

Revealing discriminating power of the elements in edible sea salts: Line-intensity correlation analysis from laser-induced plasma emission spectra  

NASA Astrophysics Data System (ADS)

We have investigated the discriminating power of the elements in edible sea salts using Laser-Induced Breakdown Spectroscopy (LIBS). For the ten different sea salts from South Korea, China, Japan, France, Mexico and New Zealand, LIBS spectra were recorded in the spectral range between 190 and 1040 nm, identifying the presence of Na, Cl, K, Ca, Mg, Li, Sr, Al, Si, Ti, Fe, C, O, N, and H. Intensity correlation analysis of the observed emission lines provided a valuable insight into the discriminating power of the different elements in the sea salts. The correlation analysis suggests that the elements with independent discrimination power can be categorized into three groups; those that represent dissolved ions in seawater (K, Li, and Mg), those that are associated with calcified particles (Ca and Sr), and those that are present in soils contained in the sea salts (Al, Si, Ti, and Fe). Classification models using a few emission lines selected based on the results from intensity correlation analysis and full broadband LIBS spectra were developed based on Principal Component Analysis (PCA) and Partial Least Squares-Discriminant Analysis (PLS-DA) and their performances were compared. Our results indicate that effective combination of a few emission lines can provide a dependable model for discriminating the edible sea salts and the performance is not much degraded from that based on the full broadband spectra. This can be rationalized by the intensity correlation results.

Lee, Yonghoon; Ham, Kyung-Sik; Han, Song-Hee; Yoo, Jonghyun; Jeong, Sungho

2014-11-01

253

Emission spectra of InGaN/AlGaN/GaN quantum well heterostructures: Model of the two-dimensional joint density of states  

SciTech Connect

The luminescence spectra of light emitting diodes based on InGaN/AlGaN/GaN heterostructures with multiple quantum wells are analyzed in the context of a model of the two-dimensional density of states in the active region. The model accounts for the potential fluctuations, the statistics of occupation of the wells with charge carriers, and specific features of the extraction of radiation from the structure. The model describes the position of the maxima of the spectra and the exponential decline of the emission intensity in the short-and long-wavelength regions as well as the modification of the spectra under variations in the current. The problems of limitations of the model and the physical meaning of the parameters are discussed. The examples of approximation of the spectra of blue light emitting diodes based on InGaN/AlGaN/GaN heterostructures show the necessity of determining the temperature in the active region independently and taking into account the interference in the planar structure. The differences of the shape of the spectra from that obtained in the simple model depend not only on the properties of the quantum wells but also on the nonuniformities in the distribution of In in InGaN.

Badgutdinov, M. L.; Yunovich, A. E. [Moscow State University, Department of Physics (Russian Federation)], E-mail: yunovich@phys.msu.ru

2008-04-15

254

Simulations of the emission spectra of fac-tris(2-phenylpyridine) iridium and Duschinsky rotation effects using the Herman-Kluk semiclassical initial value representation method.  

PubMed

The phosphorescent emission spectra of fac-tris(2-phenylpyridine) iridium [fac-Ir(ppy)(3)] due to the lowest triplet T(1) and T(2) states are simulated using the harmonic oscillator approximation for the S(0), T(1), and T(2) potential energy surfaces (PESs) and taking the Duschinsky rotation into account. The simulations involve the propagation of 177-dimensional wave packets on the coupled PES according to the Herman-Kluk (HK) semiclassical (SC) initial value representation (IVR) method. The HK SC-IVR method is employed because of its accuracy for the PES with mode mixing and its efficiency in dealing with coupled degrees of freedom for large systems. The simulated emission spectrum due to T(1) reproduces the structures of the emission spectra observed experimentally, while T(2) is found very unlikely to participate in the phosphorescent emission. Although the effect of the Duschinsky mode mixing is small for the T(1) state, neglecting it blueshifts the spectrum due to the T(2) state by 800 cm(-1) and changes the relative intensities, indicating that the importance of the Duschinsky rotation is rather unpredictable and should not be overlooked. The present simulations demonstrate that the simple harmonic oscillator approximation combined with the Duschinsky rotation can adequately describe the photophysics of fac-Ir(ppy)(3) and that the HK SC-IVR method is a powerful tool in studies of this kind. PMID:19063559

Wu, Yinghua; Brédas, Jean-Luc

2008-12-01

255

New Chandra observations of the jet in 3C273. 1. Softer X-ray than radio spectra and the X-ray emission mechanism  

SciTech Connect

The jet in 3C273 is a high-power quasar jet with radio, optical and X-ray emission whose size and brightness allow a detailed study of the emission processes acting in it. We present deep Chandra observations of this jet and analyze the spectral properties of the jet emission from radio through X-rays. We find that the X-ray spectra are significantly softer than the radio spectra in all regions of the bright part of the jet except for the first bright ''knot A'', ruling out a model in which the X-ray emission from the entire jet arises from beamed inverse-Compton scattering of cosmic microwave background photons in a single-zone jet flow. Within two-zone jet models, we find that a synchrotron origin for the jet's X-rays requires fewer additional assumptions than an inverse-Compton model, especially if velocity shear leads to efficient particle acceleration in jet flows.

Jester, Sebastian; /Fermilab; Harris, D.E.; /Smithsonian Astrophys. Observ.; Marshall, H.L.; /MIT, MKI; Meisenheimer, K.; /Heidelberg, Max Planck Inst. Astron.

2006-05-01

256

Time Resolved Simulation and Measurement of Violet Emission Spectra Early in an Ar Pulsed rf Inductively Coupled Plasma During Metastable Build-Up  

NASA Astrophysics Data System (ADS)

The temporal evolution of metastable Ar within a pulsed rf inductively coupled plasma (ICP) source has been measured by tunable diode laser absorption spectroscopy (TDLAS) and combined with time-resolved Langmuir probe measurements of the EEDF and optical cross sections to simulate the evolution of the violet emission spectrum from a 5 mTorr Ar discharge. Measurements were conducted in a diffuse plasma region, 12 cm away from the rf window. Here the metastable density was found to build relatively slowly, from near zero at the beginning of the rf pulse to a maximum density over several hundred microseconds. Experimental optical emission spectra in the 410-430 nm range were found to be in good agreement with the simulations over all times. Certain emission line ratios with unique dependences on direct and step-wise excitation were shown to be good indicators of the metastable evolution. This work was supported by the Air Force Office of Scientific Research.

Adams, Steven; Dejoseph, Charles, Jr.; Demidov, Vladimir; Miles, Jared; Sawyer, Jordan

2011-11-01

257

Fluorescence of dipicolinic acid as a possible component of the observed UV emission spectra of bacterial spores  

NASA Astrophysics Data System (ADS)

Dipicolinic acid (DPA) and the Ca2+ complex of DPA (CaDPA) are well-known and are major chemical components of bacterial spores. DPA's native fluorescence is very weak and is thought to be completely masked by the fluorescence of tryptophan when this compound is presented. Thus fluorescence related to DPA in spores is assumed by many authors to be completely absent. AWe show that the fluorescence of CaDPA is substantial for excitation between about 290 nm and 310 nm with emission peaking near 400 nm. This emission is at the long wavelength tail for emission form tryptophan. We examine whether the emission of CaDPA could contribute to the total emission spectrum when bacterial spores are present in an aerosol, for excitation wavelength in the neighborhood of 310 nm. In this report we present measurements of fluorescence excitation and emission for CaDPA and compare them with that of DPA and tryptophan.

Nudelman, Raphael; Feay, Nicole; Hirsch, Mathew; Efrima, Schlomo; Bronk, Burt V.

1999-01-01

258

The Early X-ray Emission From V382 Velorum (=Nove Vel 1999): An Internal Shock Model  

NASA Technical Reports Server (NTRS)

We present the results of ASCA and RXTE observations of the early X-ray emission from the classical nova V382 Velorum. Its ASCA spectrum was hard (kT approximately 10 KeV) with a strong (10(exp 13)/sq cm) intrinsic absorption. In the subsequent RXTE data, the spectra became softer both due to a declining temperature and a diminishing column. We argue that this places the X-ray emission interior to the outermost ejecta produced by V382 Vel in 1999, and therefore must have been the result of a shock internal to the nova ejecta. The weakness of the Fe K.alpha lines probably indicates that the X-ray emitting plasmas are not in ionization equilibrium.

Mukai, Koji; Ishida, Manabu

2000-01-01

259

Dynamics of carbohydrate residues of alpha 1-acid glycoprotein (orosomucoid) followed by red-edge excitation spectra and emission anisotropy studies of Calcofluor White.  

PubMed

Dynamics studies on Calcofluor White bound to the carbohydrate residues of sialylated and asialylated alpha 1-acid glycoprotein (orosomucoid) have been performed. The interaction between the fluorophore and the protein was found to occur preferentially with the glycan residues with a dependence on their spatial conformation. In the presence of sialylated alpha 1-acid glycoprotein, excitation at the red edge of the absorption spectrum of calcofluor does not lead to a shift in the fluorescence emission maximum (440 nm) of the fluorophore. Thus, the emission of calcofluor occurs from a relaxed state. This is confirmed by anisotropy studies as a function of temperature (Perrin plot). In the presence of asialylated alpha 1-acid glycoprotein, red-edge excitation spectra show an important shift (8 nm) of the fluorescence emission maximum of the probe. This reveals that emission of calcofluor occurs before relaxation of the surrounding carbohydrate residues occurs. Emission from a non-relaxed state means that Calcofluor molecules are bound tightly to the carbohydrate residues, a result confirmed by anisotropy studies. PMID:10629951

Albani, J R; Sillen, A; Coddeville, B; Plancke, Y D; Engelborghs, Y

1999-11-23

260

From Above Threshold Ionization to Statistical Electron Emission: The Laser Pulse-Duration Dependence of C60 Photoelectron Spectra  

Microsoft Academic Search

The photoelectron spectra of C60 ionized using a 790 nm laser with pulse durations varying from 25 fs to 5 ps have been determined. For 25 fs pulses, in the absence of fragmentation, the ionization mechanism is direct multiphoton ionization with clear observation of above threshold ionization. As the pulse duration is increased, this becomes dominated by a statistical ionization

E. E. B. Campbell; K. Hansen; K. Hoffmann; G. Korn; M. Tchaplyguine; M. Wittmann; I. V. Hertel

2000-01-01

261

Ejecta patterns of Meteor Crater, Arizona derived from the linear un-mixing of TIMS data and laboratory thermal emission spectra  

NASA Technical Reports Server (NTRS)

Accurate interpretation of thermal infrared data depends upon the understanding and removal of complicating effects. These effects may include physical mixing of various mineralogies and particle sizes, atmospheric absorption and emission, surficial coatings, geometry effects, and differential surface temperatures. The focus is the examination of the linear spectral mixing of individual mineral or endmember spectra. Linear addition of spectra, for particles larger than the wavelength, allows for a straight-forward method of deconvolving the observed spectra, predicting a volume percent of each endmember. The 'forward analysis' of linear mixing (comparing the spectra of physical mixtures to numerical mixtures) has received much attention. The reverse approach of un-mixing thermal emission spectra was examined with remotely sensed data, but no laboratory verification exists. Understanding of the effects of spectral mixing on high resolution laboratory spectra allows for the extrapolation to lower resolution, and often more complicated, remotely gathered data. Thermal Infrared Multispectral Scanner (TIMS) data for Meteor Crater, Arizona were acquired in Sep. 1987. The spectral un-mixing of these data gives a unique test of the laboratory results. Meteor Crater (1.2 km in diameter and 180 m deep) is located in north-central Arizona, west of Canyon Diablo. The arid environment, paucity of vegetation, and low relief make the region ideal for remote data acquisition. Within the horizontal sedimentary sequence that forms the upper Colorado Plateau, the oldest unit sampled by the impact crater was the Permian Coconino Sandstone. A thin bed of the Toroweap Formation, also of Permian age, conformably overlays the Coconino. Above the Toroweap lies the Permian Kiabab Limestone which, in turn, is covered by a thin veneer of the Moenkopi Formation. The Moenkopi is Triassic in age and has two distinct sub-units in the vicinity of the crater. The lower Wupatki member is a fine-grained sandstone, while the upper Moqui member is a fissile siltstone. Ejecta from these units are preserved as inverted stratigraphy up to 2 crater radii from the rim. The mineralogical contrast between the units, relative lack of post-emplacement erosion and ejecta mixing provide a unique site to apply the un-mixing model. Selection of the aforementioned units as endmembers reveals distinct patterns in the ejecta of the crater.

Ramsey, Michael S.; Christensen, Philip R.

1992-01-01

262

The Effects of Side-Chain-Induced Disorder on the Emission Spectra and Quantum Yields of Oligothiophene Nanoaggregates: A Combined Experimental and MD-TDDFT Study.  

PubMed

Oligomeric thiophenes are commonly used components in organic electronics and solar cells. These molecules stack and/or aggregate readily under the processing conditions used to form thin films for these applications, significantly altering their optical and charge-transport properties. To determine how these effects depend on the substitution pattern of the thiophene main chains, nanoaggregates of three sexithiophene oligomers having different alkyl substitution patterns were formed using solvent-poisoning techniques and studied using steady-state and time-resolved emission spectroscopy. The results indicate the substantial role played by the side-chain substituents in determining the emissive properties of these species. Both the measured spectral changes and their dependence on substitution are well-modeled by combined quantum chemistry and molecular dynamics simulations. The simulations connect the side-chain-induced disorder, which determines the favorable chain-packing configurations within the aggregates, with their measured electronic spectra. PMID:24992478

Hong, Jiyun; Jeon, SuKyung; Kim, Janice J; Devi, Diane; Chacon-Madrid, Kelly; Lee, Wynee; Koo, Seung Moh; Wildeman, Jurjen; Sfeir, Matthew Y; Peteanu, Linda A; Wen, Jin; Ma, Jing

2014-11-13

263

Fluorescent excitation of Fe 2, Mn 2, Ti 2, N 1 lines by V 4, N 5, O 6: Emission lines in the spectra of symbiotic stars and Seyfert galaxies  

NASA Technical Reports Server (NTRS)

Analysis of the published IUE and ground based high resolution spectra of symbiotic stars, particularly RR Tel, shows that the dominant excitation mechanism of Fe II, Mn II, Ti II, and N I lines is the selective fluorescent excitation of some levels by the strong C IV, N V, and O VI emission lines. The same mechanism should work for the excitation of Fe II lines in the spectra of Seyfert galaxies and Q60's whose emission spectra are quite similar to those of symbiotic stars. The similarities and differences between the fluroescent excitation mechanism reported herein and the Bowen's mechanism is analyzed.

Gilra, D. P.

1984-01-01

264

HIGH-RESOLUTION ELECTRON-IMPACT EMISSION SPECTRA AND VIBRATIONAL EMISSION CROSS SECTIONS FROM 330-1100 nm FOR N{sub 2}  

SciTech Connect

Electron-impact emission cross sections for N{sub 2} were measured in the wavelength range of 330-1100 nm at 25 eV and 100 eV impact energies. Cross sections of several molecular emission bands of the first positive band system B {sup 3}{Pi}{sub g} {sup +}({nu}') {yields} A {sup 3}{Sigma}{sub g} {sup +}({nu}'') and the second positive band system C {sup 3}{Pi}{sub u} ({nu}') {yields} B {sup 3}{Pi}{sub g} ({nu}'') of N{sub 2}, the first negative band (1NB) system B {sup 2}{Sigma}{sub u} {sup +}({nu}') {yields} X {sup 2}{Sigma}{sub g} {sup +}({nu}'') and Meinel band system A {sup 2}{Pi}{sub u} ({nu}') {yields} X {sup 2}{Sigma}{sub g} {sup +}({nu}'') of N{sub 2} {sup +} ions as well as line emissions of N (N I) and N{sup +} (N II) in the visible-optical-near-IR wavelength range reported in this work were measured for the first time in a single experimental setup at high spectral resolving power ({lambda}/{Delta}{lambda} {approx} 10000) under single-collision-scattering geometry and optically thin conditions. Rotational emission lines of N{sub 2} and N{sub 2} {sup +} were observed for strong emission bands at a gas temperature of about 300 K. The absolute cross section of the strongest (0,0) vibrational band at 391.43 nm of 1NB was determined using the standard H{sub {alpha}} emission cross sections of H{sub 2} by electron impact at both 25 eV and 100 eV electron-impact energies, and the cross sections for the remainder of the emissions were determined using (0,0) 1NB value. A comparison of the present emission cross sections with the earlier published data from both electron energy loss and electron-impact-induced fluorescence emission is discussed.

Mangina, Rao S.; Ajello, Joseph M.; West, Robert A. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Dziczek, Dariusz [Institute of Physics, Nicolaus Copernicus University, Torun (Poland)

2011-09-01

265

Spectra of stable sonoluminescence  

NASA Astrophysics Data System (ADS)

The continuous emission of picosecond pulses of light has been observed to originate from a bubble trapped at the pressure antinode of a resonant sound field in water and in water/glycerin mixtures. The spectra of this light in several solutions has been measured with a scanning monochrometer/photomultiplier detector system. The spectra are broadband and show strong emission in the UV region. A comparison of this measurement to two other independently produced spectra is made. The spectra are also modeled by a blackbody radiation distribution to determine an effective blackbody temperature and a size is deduced as if Sonoluminescence were characterized by blackbody radiation.

Lewis, Stephen D.

1992-12-01

266

An analysis of the emission line spectra of AG Pegasi between phases 7.34 and 9.44  

NASA Astrophysics Data System (ADS)

The UV and optical spectra from the HST Faint Object Spectrograph and from the Fast Spectrograph for the Tillinghast Telescope (FAST) spectrograph at the Whipple Observatory reported by Kenyon, Proga & Keyes at different phases are analysed, leading to new results about the configuration of AG Pegasi. The FAST spectra contain both H? and H? lines, whose ratio changes with phase indicating that different nebulae contribute to each spectrum. In particular, the spectrum emitted from one of the nebulae must be collision dominated, in order to justify the relatively-high H?/H?. Consistent modelling by the code SUMA, which accounts for the coupled effect of the photoionization from the hot star and the shock, shows the important role of at least three nebulae: (1) the nebula between the stars, downstream of the shock created by collision of the winds, which propagates in reverse towards the white dwarf; (2) the nebula downstream of the shock expanding in the outskirts of the giant atmosphere; and (3) the shock propagating outwards from the binary system, which is not reached by the hot source radiation. The relative contributions of the three nebulae to the final spectra at different phases are calculated for all the lines. It is found that the contribution to the different lines changes with the viewing angle of the system. The relatively-low pre-shock density and magnetic field adopted in the modelling of the expanding shocks reveal that they are merging with the ISM, thus explaining the slow decline of AG Pegasi.

Contini, Marcella

2003-02-01

267

Detailed analysis of hollow ions spectra from dense matter pumped by X-ray emission of relativistic laser plasma  

NASA Astrophysics Data System (ADS)

X-ray emission from hollow ions offers new diagnostic opportunities for dense, strongly coupled plasma. We present extended modeling of the x-ray emission spectrum reported by Colgan et al. [Phys. Rev. Lett. 110, 125001 (2013)] based on two collisional-radiative codes: the hybrid-structure Spectroscopic Collisional-Radiative Atomic Model (SCRAM) and the mixed-unresolved transition arrays (MUTA) ATOMIC model. We show that both accuracy and completeness in the modeled energy level structure are critical for reliable diagnostics, investigate how emission changes with different treatments of ionization potential depression, and discuss two approaches to handling the extensive structure required for hollow-ion models with many multiply excited configurations.

Hansen, S. B.; Colgan, J.; Faenov, A. Ya.; Abdallah, J.; Pikuz, S. A.; Skobelev, I. Yu.; Wagenaars, E.; Booth, N.; Culfa, O.; Dance, R. J.; Tallents, G. J.; Evans, R. G.; Gray, R. J.; Kaempfer, T.; Lancaster, K. L.; McKenna, P.; Rossall, A. K.; Schulze, K. S.; Uschmann, I.; Zhidkov, A. G.; Woolsey, N. C.

2014-03-01

268

Broad excitation spectra and bright reddish-orange emission of transparent phosphate glass excited by sunshine for greenhouses  

NASA Astrophysics Data System (ADS)

A series of Mn2+/Sm3+ co-doped phosphate glasses have been synthesized by high temperature melting method to investigate reddish-orange emission materials for greenhouses. Experiments show that the Mn2+/Sm3+ co-doped glasses can be effectively excited by a wide spectrum (300-560 nm) and emit bright reddish-orange light. The intense emission bands for the co-doped phosphate glasses are from 590 nm to 660 nm, which exactly locate in the absorption domain of chlorophylls. Bright red-orange light emission is straightly observed by naked eyes when the sample is illuminated by sunlight without focused-lens. These improved luminescent properties show potential application in glass greenhouses.

Han, Yingdong; Song, Feng; Li, Qiong; Wang, Fengxiao; Ming, Chengguo; Tian, Jianguo

2014-11-01

269

Spectral Components in the Optical Emission of the Seyfert Galaxy NGC 5548 and the Comparison of Intrinsic Nuclear Spectra with Accreting Corona Model  

E-print Network

We study the extensively monitored Seyfert galaxy NGC 5548 and compare its nuclear emission with models of accretion disk with accreting corona. To obtain the intrinsic nuclear spectra from the observed spectra we had to estimate and subtract the contribution from circumnuclear components such as stars, the Balmer continuum and blended FeII lines, and the FC2 extended, featureless continuum. The true nuclear spectra were compared with a two parameter model of the accreting disk with an accreting corona, described by the mass of the central black hole and viscosity. The model that best fitted the data was for M_{BH}=1.4e8 solar masses and the viscosity parameter alpha=0.033. Such a low viscosity parameter was necessary to produce the sufficient amount of X-rays. The vertical outflow of mass from corona in the form of wind had to be neglected in our model in order to fit into high and low states that NGC 5548 underwent. The model also predicts the behavior of the overall opt/UV/X continuum of NGC 5548 during the whole five year campaign.

J. Kuraszkiewicz; Z. Loska; B. Czerny

1997-06-16

270

A Bulk Comptonization Model for the Prompt GRB Emission and its Relation to the Fermi GRB Spectra  

NASA Technical Reports Server (NTRS)

We present a model in which the GRB prompt emission at E E(sub peak) is due to bulk Comptonization by the relativistic blast wave motion of either its own synchrotron photons of ambient photons of the stellar configuration that gave birth to the GRB. The bulk Comptonization process then induces the production of relativistic electrons of Lorentz factor equal to that of the blast wave through interactions with its ambient protons. The inverse compton emission of these electrons produces a power law component that extends to multi GeV energies in good agreement with the LAT GRB observations.

Kazanas, Demosthenes

2010-01-01

271

The ground-based H, K, and L-band absolute emission spectra of HD 209458b  

E-print Network

Here we explore the capabilities of NASA's 3.0 meter Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 meter Hale telescope with the TripleSpec spectrometer with near-infrared H, K, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L-band indicate bright emission hypothesized to result from non-LTE CH$_{4}$ $\

Zellem, Robert T; Deroo, Pieter; Swain, Mark R; Waldmann, Ingo P

2014-01-01

272

c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines  

Microsoft Academic Search

A survey of mid-IR gas-phase emission lines of H2, H2O and various atoms\\u000atoward a sample of 43 embedded low-mass young stars in nearby star-forming\\u000aregions is presented. The sources are selected from the Spitzer \\

Fred Lahuis; Ewine F. van Dishoeck; Jes K. Jørgensen; Geoffrey A. Blake; Neal J. Evans II

2010-01-01

273

Compressed shell conditions extracted from spectroscopic analysis of Ti K-shell absorption spectra with evaluation of line self-emission  

NASA Astrophysics Data System (ADS)

Ti-doped tracer layers embedded in the shell at varying distances from the fuel-shell interface serve as a spectroscopic diagnostic for direct-drive experiments conducted at OMEGA. Detailed modeling of Ti K-shell absorption spectra produced in the tracer layer considers n = 1-2 transitions in F- through Li-like Ti ions in the 4400-4800 eV range, both including and excluding line self-emission. Testing the model on synthetic spectra generated from 1-D LILAC hydrodynamic simulations reveals that the model including self-emission best reproduces the simulation, while the model excluding self-emission overestimates electron temperature Te and density Ne to a higher degree for layers closer to the core. The prediction of the simulation that the magnitude of Te and duration of Ti absorption will be strongly tied to the distance of the layer from the core is consistent with the idea that regions of the shell close to the core are more significantly heated by thermal transport out of the hot dense core, but more distant regions are less affected by it. The simulation predicts more time variation in the observed Te, Ne conditions in the compressed shell than is observed in the experiment, analysis of which reveals conditions remain in the range Te = 400-600 eV and Ne = 3.0-10.0 × 1024 cm-3 for all but the most distant Ti-doped layer, with error bars ˜5% Te value and ˜10% Ne on average. The Te, Ne conditions of the simulation lead to a greater degree of ionization for zones close to the core than occurs experimentally, and less ionization for zones far from the core.

Johns, H. M.; Mancini, R. C.; Hakel, P.; Nagayama, T.; Smalyuk, V. A.; Regan, S. P.; Delettrez, J.

2014-08-01

274

Site-selective excitation and polarized absorption and emission spectra of trivalent thulium and erbium in strontium fluorapatite  

SciTech Connect

Polarized fluorescence spectra produced by site-selective excitation and conventional polarized absorption spectra were obtained for Tm{sup 3+} and Er{sup 3+} ions individually incorporated into single crystals of strontium fluorapatite, Sr{sub 5}(PO{sub 4}){sub 3}F. Substitution of the trivalent rare earth ion for divalent strontium was achieved by passive charge compensation during Czochralski growth of the fluorapatite crystals. Spectra were obtained between 1780 and 345 nm at temperatures from 4 K to room temperature on crystals having the hexagonal structure [P6{sub 3}/m(C{sub 6h}{sup 2})]. The polarized fluorescence spectra due to transitions from multiplet manifolds of Tm{sup 3+}(4f{sup 12}), including {sup 1}D{sub 2}, {sup 1}G{sub 4}, and {sup 3}H{sub 4} to manifolds {sup 3}H{sub 6} (the ground-state manifold), {sup 3}F{sub 4}, {sup 3}H{sub 5}, {sup 3}H{sub 4}, and {sup 3}F{sub 3} were analyzed for the details of the crystal-field splitting of the manifolds. Fluorescence lifetimes were measured for Tm{sup 3+} transitions from {sup 1}D{sub 2}, {sup 1}G{sub 4}, and {sup 3}H{sub 4} at room temperature and from {sup 1}G{sub 4} at 16 K. Results of the analysis indicate that the majority of Tm{sup 3+} ions occupy sites having C{sub s} symmetry. A point-charge lattice-sum calculation was made in which the crystal-field components, A{sub nm}, were determined assuming that trivalent thulium replaces divalent strontium in the metal site having C{sub s} symmetry. Results support the conclusion that the nearest-neighbor fluoride (F{sup {minus}}) is replaced by divalent oxygen (O{sup 2{minus}}), thus preserving overall charge neutrality and local symmetry. Crystal-field splitting calculations predict energy levels in agreement with experimental data. By varying the crystal-field parameters, B{sub nm}, we obtained a rms difference of 7cm{sup {minus}1} between 43 calculated and experimental Stark levels for Tm{sup 3+}(4f{sup 12}) in Tm:SFAP. (Abstract Truncated)

Gruber, J.B. [Department of Physics, San Jose State University, San Jose, California 95192-0106 (United States)] [Department of Physics, San Jose State University, San Jose, California 95192-0106 (United States); Wright, A.O.; Seltzer, M.D. [Research and Technology Division, Naval Air Warfare Center, Code 474230D, China Lake, California 93555-6001 (United States)] [Research and Technology Division, Naval Air Warfare Center, Code 474230D, China Lake, California 93555-6001 (United States); Zandi, B.; Merkle, L.D. [IR Optics Technology OFC, Army Research Laboratory, Ft. Belvoir, Virginia 22060-5838 (United States)] [IR Optics Technology OFC, Army Research Laboratory, Ft. Belvoir, Virginia 22060-5838 (United States); Hutchinson, J.A. [Night Vision and Electronics Sensors Directorate, The United States Army, Ft. Belvoir, Virginia 22060-5806 (United States)] [Night Vision and Electronics Sensors Directorate, The United States Army, Ft. Belvoir, Virginia 22060-5806 (United States); Morrison, C.A. [Army Research Laboratory, Adelphi, Maryland 20783-1145 (United States)] [Army Research Laboratory, Adelphi, Maryland 20783-1145 (United States); Allik, T.H. [Science Applications International Corporation, 1710 Goodridge Drive, McLean, Virginia 22102 (United States)] [Science Applications International Corporation, 1710 Goodridge Drive, McLean, Virginia 22102 (United States); Chai, B.H. [Center for Research on Electro-optics and Lasers, University of Central Florida, Orlando, Florida 32836 (United States)] [Center for Research on Electro-optics and Lasers, University of Central Florida, Orlando, Florida 32836 (United States)

1997-05-01

275

The use of the bulk properties of gamma-ray burst prompt emission spectra for the study of cosmology  

NASA Astrophysics Data System (ADS)

The study of bulk spectral properties of Gamma-Ray Bursts (GRBs) is important to understanding the physics behind these powerful explosions and may even be an aide in studying cosmology. The prompt emission spectral properties have long been studied by a growing community of researchers, and many theories have been developed since the discovery of GRBs. Even though the exact physics of these phenomena is not completely understood, GRBs have been proposed to give insight on other astrophysical phenomena from dark matter to the expansion of the universe. Obviously, using GRBs to study cosmology requires a large sample size to adequately constrain results and provide confident conjectures. For this reason, BATSE and GBM results are paramount to the study of the prompt emission of GRBs. Using results from both instruments, I study the bulk spectral properties of GRBs and describe analysis techniques that can be used to study cosmology.

Goldstein, Adam

276

Near-surface temperature gradients and their effects on thermal-infrared emission spectra of particulate planetary surfaces  

NASA Technical Reports Server (NTRS)

The infrared energy emitted from a planetary surface is generated within a finite depth determined by the material's absorption skin depth. This parameter varies significantly with wavelength in the infrared but has an average value of around 50 microns for most geologic materials. In solid rock, heat transfer is efficient enough so that this 50 micron zone of the near surface from which the radiation emanates will be more or less isothermal. In particulate materials, however, heat transfer is more complicated and occurs via a combination of mechanisms, including solid conduction within grains and across grain contacts, conduction through the interstitial gas, and thermal radiation within individual particles and across the void spaces in between grains. On planets with substantial atmospheres, the gas component dominates the heat transfer and tends to mitigate near-surface thermal gradients. However, on airless bodies, the gas component is absent and heat transfer occurs via solid conductions and radiation. If the particles are small relative to the average absorption skin depth, then the top 50-100 microns or so of the surface will be cooled by radiation to space allowing the creation of significant near-surface thermal gradients. In those regions of the spectrum where the absorption coefficient is low, the emission will come from the deeper, warmer parts of the medium, whereas in regions of high absorption, the emission will emanate from shallower, cooler parts of the medium. The resulting emission spectrum will show non-compositional features as a result of the thermal structure in the material. We have modeled the heat transfer in a particulate medium in order to determine the magnitude of near-surface thermal gradients for surfaces on airless bodies and on Mars. We use the calculated thermal structure to determine the effects it has on the infrared emission spectrum of the surface.

Henderson, B. G.; Jakosky, B. M.

1993-01-01

277

c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines  

Microsoft Academic Search

Context. A survey of mid-infrared gas-phase emission lines of H2, H2O and various atoms toward a sample of 43 embedded low-mass young stars in nearby star-forming regions is presented. The sources are selected from the Spitzer ``Cores to Disks'' (c2d) legacy program. Aims: The environment of embedded protostars is complex both in its physical structure (envelopes, outflows, jets, protostellar disks)

F. Lahuis; E. F. van Dishoeck; J. K. Jørgensen; G. A. Blake; N. J. Evans

2010-01-01

278

HST/COS SPECTRA OF DF Tau AND V4046 Sgr: FIRST DETECTION OF MOLECULAR HYDROGEN ABSORPTION AGAINST THE Ly{alpha} EMISSION LINE  

SciTech Connect

We report the first detection of molecular hydrogen (H{sub 2}) absorption in the Ly{alpha} emission line profiles of two classical T Tauri stars (CTTSs), DF Tau and V4046 Sgr, observed by the Hubble Space Telescope/Cosmic Origins Spectrograph. This absorption is the energy source for many of the Lyman-band H{sub 2} fluorescent lines commonly seen in the far-ultraviolet spectra of CTTSs. We find that the absorbed energy in the H{sub 2} pumping transitions from a portion of the Ly{alpha} line significantly differ from the amount of energy in the resulting fluorescent emission. By assuming additional absorption in the H I Ly{alpha} profile along our light of sight, we can correct the H{sub 2} absorption/emission ratios so that they are close to unity. The required H I absorption for DF Tau is at a velocity close to the radial velocity of the star, consistent with H I absorption in the edge-on disk and interstellar medium. For V4046 Sgr, a nearly face-on system, the required absorption is between +100 km s{sup -1} and +290 km s{sup -1}, most likely resulting from H I gas in the accretion columns falling onto the star.

Yang Hao; Linsky, Jeffrey L. [JILA, University of Colorado and NIST, Boulder, CO 80309-0440 (United States); France, Kevin, E-mail: haoyang@jilau1.colorado.edu, E-mail: jlinsky@jilau1.colorado.edu, E-mail: kevin.france@colorado.edu [CASA, University of Colorado, Boulder, CO 80309-0389 (United States)

2011-03-20

279

The Ground-based H-, K-, and L-band Absolute Emission Spectra of HD 209458b  

NASA Astrophysics Data System (ADS)

Here we explore the capabilities of NASA's 3.0 m Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 m Hale telescope with the TripleSpec spectrometer with near-infrared H-, K-, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L band indicate bright emission hypothesized to result from non-LTE CH4 ?3 fluorescence. We do not detect a similar bright 3.3 ?m feature to ~3?, suggesting that fluorescence does not need to be invoked to explain HD 209458b's L-band measurements. The validity of our observation and reduction techniques, which decrease the flux variance by up to 2.8 orders of magnitude, is reinforced by 1? agreement with existent Hubble/NICMOS and Spitzer/IRAC1 observations that overlap the H, K, and L bands, suggesting that both IRTF/SpeX and Palomar/TripleSpec can measure an exoplanet's emission with high precision.

Zellem, Robert T.; Griffith, Caitlin A.; Deroo, Pieter; Swain, Mark R.; Waldmann, Ingo P.

2014-11-01

280

The relativistic Iron K-alpha line from an accretion disc onto a static non-baryonic compact object  

E-print Network

This paper continues the study of the properties of an accretion disc rotating around a non-baryonic (assumed super-massive) compact object. This kind of objects, generically known as boson stars, were earlier proposed as a possible alternative scenario to the existence of super-masive black holes in the center of every galaxy. A dilute boson star has also been proposed as a large part of the non-baryonic dark matter, flattening galactic rotational velocities curves. In this contribution, we compute the profile of the emission lines of Iron; its shape has been for long known as a useful diagnosis of the space-time geometry. We compare with the case of a Schwarzschild black hole, concluding that the differences are observationally distinguishable.

Youjun Lu; Diego F. Torres

2002-05-24

281

Asymptotically-Equal-To 10 eV ionization shift in Ir K{alpha}{sub 2} from a near-coincident Lu K-edge  

SciTech Connect

Close to an x-ray filter's K-edge the transmission depends strongly on the photon energy. For a few atom pairs, the K-edge of one is only a few tens of eV higher than a K-line energy of another, so that a small change in the line's energy becomes a measurable change in intensity behind such a matching filter. Lutetium's K-edge is Asymptotically-Equal-To 27 eV above iridium's K{alpha}{sub 2} line, Asymptotically-Equal-To 63.287 keV for cold Ir. A Lu filter reduces this line's intensity by Asymptotically-Equal-To 10 % when it is emitted by a plasma, indicating an ionization shift {Delta}E Asymptotically-Equal-To 10{+-}1 eV.

Pereira, N. R. [Ecopulse, Inc, P.O. Box 528, Springfield, Virginia 22150 (United States); Weber, B. V.; Phipps, D.; Schumer, J. W. [Naval Research Laboratory, Washington, DC 20375 (United States); Seely, J. F. [Artep Inc., 2922 Excelsior Springs Ct, Ellicott City, Maryland 21042 (United States); Carroll, J. J. [Army Research Laboratory, Adelphi, Maryland 20873 (United States); VanHoy, J. R. [United States Naval Academy, Annapolis, Maryland 21402 (United States); Slabkowska, K.; Polasik, M. [Faculty of Chemistry, Nicolaus Copernicus University, Gagarina 7, 87-100 Torun (Poland)

2012-10-15

282

Markov-Chain Monte Carlo Reconstruction of Emission Measure Distributions: Application to Solar Extreme-Ultraviolet Spectra  

NASA Astrophysics Data System (ADS)

We have developed a new method for the reconstruction of differential emission measure distributions based on a Metropolis Markov-chain Monte Carlo (MCMC[M]) method. This technique allows us to (1) relax nonphysical smoothness constraints generally imposed on DEMs, (2) determine confidence bounds on the computed values, and (3) include extra information in the form of upper limits. Using the MCMC[M] algorithm, we reanalyze extreme ultraviolet spectral line fluxes obtained from Solar Extreme Ultraviolet Rocket Telescope and Spectrograph observations by Brosius et al. to obtain differential emission measure (DEM) distributions for active and quiet regions on the Sun. Both active- and quiet-region DEMs show a probable minimum near log T ~ 5.6; the quiet-region DEM drops off beyond log T = 6.4, while the active-region DEM does not show evidence of a significant downturn even at log T = 7. The most striking aspect of our results is that the latter also shows several sharp peaks (of width ~0.1 dex), notably at log T = 6 and 6.3, and a broad feature, beyond log T = 6.5. We also explore the limitations on DEM reconstruction imposed by imperfect atomic data, choice of spectral lines, uncertainties in abundances, and other systematic errors. Within these limitations, we discuss the derived emission measure distribution and comment on its implications to coronal structure. We conclude that calculation of uncertainties on the DEM are crucial in the interpretation of structure seen in reconstructions. Further, a careful selection of the spectral lines used to infer the DEM is needed in order to avoid ``artificially'' generating structure in the DEM.

Kashyap, Vinay; Drake, Jeremy J.

1998-08-01

283

Palagonitic (Not Andesitic) Mars: Evidence from Thermal Emission and VNIR Spectra of Palgonitic Alteration Rinds on Basaltic Rock  

NASA Technical Reports Server (NTRS)

Visible and near-IR (VNIR) spectra of both Martian bright and dark regions are characterized by a ferric absorption edge extending from approx. 400 to 750 nm, with bright regions having about twice the reflectivity at 750 nm as dark regions. Between 750 nm to beyond 2000 nm, bright and dark regions have nearly constant and slightly negative spectral slopes, respectively. Depending on location, bright regions have shallow reflectivity minima in the range 850-910 nm that are attributed to ferric oxides. Similarly, dark regions have shallow reflectivity minima near approx. 950 and 1700-2000 nm that are attributed to ferrous silicate minerals (pyroxene). Among terrestrial geologic materials, the best spectral analogues for Martian bright regions are certain palagonitic tephras from Mauna Kea Volcano (Hawaii). By definition, palagonite is a "yellow or orange isotropic mineraloid formed by hydration and devitrification of basaltic glass". The ferric pigment in palagonite is nanometer-sized ferric oxide particles (np-Ox) dispersed throughout the hydrated basaltic glass matrix. The hydration state of the np-Ox particles is not known, but the best Martian spectral analogues contain allophane-like materials and not crystalline phyllosilicates.

Morris, R. V.; Graff, T. G.; Mertzman, S. A.; Lane, M. D.; Christensen, P. R.

2003-01-01

284

Effects of thermal annealing on photoluminescence spectra in ?-conjugated polymer film: evidence for dual emission by temperature dependent measurements  

NASA Astrophysics Data System (ADS)

Various spectroscopy techniques such as absorption, photoluminescence and photoinduced absorption (PIA) spectroscopy, were used to study the photophysics in poly [2-methoxy-5-(20-ethyl-hexyloxy)-1, 4-phenylenevinylene] (MEH-PPV) films, which were dropped cast on glass substrates using its toluene solution and being annealed at various temperatures. With the analysis of temperature dependence PL intensities, we conclude that PL emission around 680 nm at low temperature is due to intertain excimers instead of intrachain excitons for 450 K annealed film. On the other hand, this relative intensity difference is much smaller in both unannealed and 500 K annealed films, in which the morphology is amorphous and microcrystalline, respectively. We conclude that the interchain photoexcitations play crucial roles in the photophysics of MEH-PPV films. The further measurements on PIA spectrum of MEH-PPV films suggest that the interchain photoexciation is also important for the generation of triplet excitons.

Wang, R. Z.; Yang, X.; Wang, Y. C.; Sheng, C.-X.; Chen, Q.

2014-09-01

285

Signal-to-noise ratios in IUE SWP-LO spectra of chromospheric emission-line sources  

NASA Technical Reports Server (NTRS)

The short-wavelength-prime (SWP) detector of the International Ultraviolet Explorer should operate near the photon-counting limit, but the noise levels in flat-field images are several times higher. The exaggerated noise can be traced to the incomplete removal of the pixel-to-pixel granularity of the television frames by the prevailing spectral image processing system. An empirical noise model for the current-epoch photometric linearization strategy and one for a hypothetical processing system that achieves complete flat fielding of the raw images are derived. A formula is then proposed to predict the signal-to-noise ratio in the measured flux of an emission line (possibly superimposed on a smooth continuum) in an IUE low-dispersion (5 A resolution) far-ultraviolet (1150 A-1950 A) spectrum as recorded with the SWP camera. For illustration, the formula is specialized to the important C IV 1549 A feature of F-K stars. The S/N relation permits one to determine sensitivity limits, upper limits in faint exposures, and optimum exposure times.

Ayres, Thomas R.

1990-01-01

286

Core-Hole Effect in the Ce L3 X-Ray Absorption Spectra of CeO2 and CeFe2: New Examination by Using Resonant X-Ray Emission Spectroscopy  

NASA Astrophysics Data System (ADS)

We consider two different resonant X-ray emission spectra for Ce compounds: Ce 3d to 2p X-ray emission (denoted by 3d-RXES) and valence to 2p X-ray emission (v-RXES), both of which follow the Ce 2p to 5d resonant excitation. We propose that the comparison of the 3d- and v-RXES spectra is a new powerful method of directly detecting the core-hole effect in the final state of Ce L3 X-ray absorption spectra (XAS). We applied this method to recent experimental RXES spectra for CeO2 and CeFe2, and showed unambiguously that the core-hole effect should be essential in the XAS of both materials. This result is confirmed by theoretical calculations, which reproduce well the experimental RXES and XAS spectra. We conclude that the ground state of CeO2 is in the mixed state of 4f0 and 4f1_{L} configurations, where _{L} is a ligand hole, instead of a pure 4f0 configuration which was proposed recently by first-principles energy band calculations. Also, we conclude that the double peaks observed in L3 XAS of CeFe2 are caused by the 4f0 and 4f1 configurations, which are mixed in the ground state but separated in energy by the large core-hole potential in the final state of XAS.

Kotani, A.

2013-06-01

287

The Galactic plane at faint X-ray fluxes - II. Stacked X-ray spectra of a sample of serendipitous XMM-Newton sources  

E-print Network

We have investigated the X-ray spectral properties of a sample of 138 X-ray sources detected serendipitously in $XMM-Newton$ observations of the Galactic plane, at an intermediate to faint flux level. We divide our sample into 5 subgroups according to the spectral hardness of the sources, and stack (i.e. co-add) the individual source spectra within each subgroup. As expected these stacked spectra show a softening trend from the hardest to the softest subgroups, which is reflected in the inferred line-of-sight column density. The spectra of the three hardest subgroups are characterized by a hard continuum plus superimpose Fe-line emission in the 6--7 keV bandpass. The average equivalent width (EW) of the 6.7-keV He-like Fe-K$\\alpha$ line is 170$^{+35}_{-32}$ eV, whereas the 6.4-keV Fe-K fluorescence line from neutral iron and the 6.9-keV H-like Fe-Ly$\\alpha$ line have EWs of 89$^{+26}_{-25}$ eV and 81$^{+30}_{-29}$ eV respectively, i.e. roughly half that of the 6.7-keV line. The remaining subgroups exhibit sof...

Warwick, R S; Pérez-Ramírez, D

2014-01-01

288

Combining Single-Molecule Optical Trapping and Small-Angle X-Ray Scattering Measurements to Compute the Persistence Length of a Protein ER/K [alpha]-Helix  

SciTech Connect

A relatively unknown protein structure motif forms stable isolated single {alpha}-helices, termed ER/K {alpha}-helices, in a wide variety of proteins and has been shown to be essential for the function of some molecular motors. The flexibility of the ER/K {alpha}-helix determines whether it behaves as a force transducer, rigid spacer, or flexible linker in proteins. In this study, we quantify this flexibility in terms of persistence length, namely the length scale over which it is rigid. We use single-molecule optical trapping and small-angle x-ray scattering, combined with Monte Carlo simulations to demonstrate that the Kelch ER/K {alpha}-helix behaves as a wormlike chain with a persistence length of 15 nm or 28 turns of {alpha}-helix. The ER/K {alpha}-helix length in proteins varies from 3 to 60 nm, with a median length of 5 nm. Knowledge of its persistence length enables us to define its function as a rigid spacer in a translation initiation factor, as a force transducer in the mechanoenzyme myosin VI, and as a flexible spacer in the Kelch-motif-containing protein.

Sivaramakrishnan, S.; Sung, J.; Ali, M.; Doniach, S.; Flyvbjerg, H.; Spudich, J.A.; (Stanford); (Danmarks)

2010-01-12

289

Inner valence molecular orbitals and the structure of X-ray O{sub 4,5}(U) emission spectra of uranium in oxides UO{sub 2} and {gamma}-UO{sub 3}  

SciTech Connect

The efficient participation of the relatively low-lying U6p, 6s and Lns atomic orbitals (AOs) of the neighboring ions and ligands (L) in the formation of outer valence and inner valence molecular orbitals (OVMOs and IVMOs, respectively) was first found when interpreting the fine structure of the X-ray photoelectron spectra. However, the first X-ray O{sub 4,5}(U) emission spectra of uranium in oxides, which could prove the formation of IVMO in them, were low-resolution. In this work, the authors obtained, for the first time, high-resolution emission spectra for uranium in dioxide UO{sub 2} and trioxide {gamma}-UO{sub 3} with the aim of interpreting the fine structure using the results of X-ray photoelectron spectroscopy on the IVMOs in these oxides.

Teterin, Yu.A.; Ivanov, K.E. [Kurchatov Institute Russian Research Center, Moscow (Russian Federation); Terekhov, V.A. [Voronezh State Univ. (Russian Federation)

1995-11-01

290

Discovery of a ~2 hr high frequency X-ray QPO and iron K alpha reverberation in the active galaxy MS 2254.9-3712  

E-print Network

We report the discovery of a $\\sim 1.5 \\times 10^{-4}$ Hz ($\\sim 2$ hr) X-ray quasi-periodic oscillation (QPO) in the active galaxy MS 2254.9-3712, using a $\\sim 70$ ks XMM-Newton observation. The QPO is significantly detected in the $1.2 - 5.0$ keV band only, connecting its origin with the primary X-ray power-law continuum. We detect a highly coherent soft lag between the $0.3 - 0.7$ keV and $1.2 - 5.0$ keV energy bands at the QPO and harmonic frequencies, with a 3:2 frequency ratio. An iron K$\\alpha$ reverberation lag is found at the harmonic frequency, indicating the reflecting material subtends some angle to the primary continuum, which is modulated by the QPO mechanism. The coherence at the QPO and harmonic frequencies is ~ unity, whereas the coherence in the broadband noise is decreasing with increasing frequency. Frequency resolved spectroscopy reveals the QPO and harmonic to have a hard energy dependence. These properties of the QPO variability, together with the current black hole mass estimate, $M_{...

Alston, W N; Markeviciute, J; Fabian, A C; Middleton, M; Lohfink, A; Kara, E; Pinto, C

2014-01-01

291

Relativistically Skewed Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288  

NASA Technical Reports Server (NTRS)

We report evidence for an Fe K-alpha fluorescence line feature in the Very High, High, and Low state X-ray spectra of the galactic microquasar XTE JI748-288 during its June 1998 outburst. Spectral analyses were made on observations spread across the outburst, gathered with the Rossi X-ray Timing Explorer. Gaussian line. disk emission line, relativistic disk emission line, and disk reflection models are fit to the data. In the Very High State, the line profile is strongly redshifted and consistent with emission from the innermost radius of a maximally rotating Kerr black hole, 1.235 R(sub g). The line profile is less redshifted in the High State, but increasingly prominent. In the Low State, the line profile is very strong and centered af approx. 6.7 keV; disk line emission models constrain the inner edge of the disk to fluctuate between approx.20 and approx.59 R(sub g). We trace the disk reflection fraction across the full outburst of this source, and find well-constrained fractions below those observed in AGN in the Very High and High States, but consistent with other galactic sources in the Low State. We discuss the possible implications for black hole X-ray binary system dynamics and accretion flow geometry.

Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Kouveliotou, C.; Lewin, W. H. G.

2000-01-01

292

The Infrared Spectra of Polycyclic Aromatic Hydrocarbons with Excess Peripheral H atoms (H n -PAHs) and Their Relation to the 3.4 and 6.9 ?m PAH Emission Features  

NASA Astrophysics Data System (ADS)

Polycyclic aromatic hydrocarbons (PAHs) are likely responsible for the family of infrared emission features seen in a wide variety of astrophysical environments. A potentially important subclass of these materials are PAHs whose edges contain excess H atoms (H n -PAHs). This type of compound may be present in space, but it has been difficult to assess this possibility because of a lack of suitable laboratory spectra to assist with analysis of astronomical data. We present 4000-500 cm-1 (2.5-20 ?m) infrared spectra of 23 H n -PAHs and related molecules isolated in argon matrices under conditions suitable for interpretation of astronomical data. Spectra of molecules with mixed aromatic and aliphatic domains show characteristics that distinguish them from fully aromatic PAH equivalents. Two major changes occur as PAHs become more hydrogenated: (1) aromatic C-H stretching bands near 3.3 ?m weaken and are replaced with stronger aliphatic bands near 3.4 ?m, and (2) aromatic C-H out-of-plane bending mode bands in the 11-15 ?m region shift and weaken concurrent with growth of a strong aliphatic -CH2- deformation mode near 6.9 ?m. Implications for interpreting astronomical spectra are discussed with emphasis on the 3.4 and 6.9 ?m features. Laboratory data is compared with emission spectra from IRAS 21282+5050, an object with normal PAH emission features, and IRAS 22272+5435 and IRAS 0496+3429, two protoplanetary nebulae with abnormally large 3.4 ?m features. We show that "normal" PAH emission objects contain relatively few H n -PAHs in their emitter populations, but less evolved protoplanetary nebulae may contain significant abundances of these molecules.

Sandford, Scott A.; Bernstein, Max P.; Materese, Christopher K.

2013-03-01

293

Non-LTE modeling of narrow emission components of He and Ca lines in optical spectra of classical T Tauri stars  

NASA Astrophysics Data System (ADS)

Using LTE calculations of the structure of T Tauri stellar atmospheres heated by radiation from an accretion shock (Dodin and Lamzin 2012), we have calculated the spectrum of the hot spot emerging on the stellar surface by taking into account non-LTE effects for He I, He II, Ca I, and Ca II. Assuming the pre-shock gas density N 0 and velocity V 0 to be the same at all points of the accretion stream cross section, we have calculated the spectrum of the star+circular spot system at various N 0, V 0, and parameters characterizing the star and the spot. Using nine stars as an example, we show that the theoretical optical spectra reproduce well the observed veiling of photospheric absorption lines as well as the profiles and intensities of the so-called narrow components of He II and Ca I emission lines with an appropriate choice of parameters. The accreted gas density in all of the investigated stars except DK Tau has been found to be N 0 > 1012 cm-3. We have managed to choose the parameters for eight stars at a calcium abundance in the accreted gas ? Ca equal to the solar one, but we have been able to achieve agreement between the calculations and observations for TW Hya only by assuming ? Ca to be approximately a factor of 3 lower than the solar one. The estimated parameters do not depend on interstellar extinction, because they have been determined from the spectra normalized to the continuum level. The calculated intensity of Ca II lines has turned out to be lower than the observed one, but this contradiction can be eliminated by assuming that, in addition to the accreted gas with a high density N 0, a more rarefied gas also falls onto the star. The theoretical equivalent widths and relative intensities of the subordinate He I lines disagree significantly with the observations. This is apparently because non-LTE effects should be taken into account when calculating the structure of the upper layers of the hot spot, the accuracy of the cross sections for collisional processes from upper levels is insufficient, and the spot inhomogeneity should probably be taken into account.

Dodin, A. V.; Lamzin, S. A.; Sitnova, T. M.

2013-05-01

294

Iron K-shell emission from NGC 1068  

NASA Technical Reports Server (NTRS)

The X-ray iron line emission from NGC 1068 is modeled using the new multiline, multilevel, non-LTE radiative transport code Altair and a detailed atomic model for Ne-like through-stripped iron. The X-rays passing through the ionized gas induce iron K-alpha line emission. The atomic model was constructed to describe in detail the K-shell ionization and K-alpha line emission, as well as to calculate the ionization state properly. A greater equivalent width than previously predicted is found because the observed K-alpha line is produced not only by fluorescence but also by line scattering of the continuum into the line of sight. The K-alpha equivalent width and energy are functions not only of the ionization parameter, but also of the column depth and temperature. For a likely model of NGC 1068, it is found that the iron abundance is about twice solar, but that modifications of this model may permit a smaller abundance.

Band, David L.; Klein, Richard I.; Castor, John I.; Nash, J. K.

1990-01-01

295

Possible Charge-Exchange X-Ray Emission in the Cygnus Loop Detected with Suzaku  

NASA Technical Reports Server (NTRS)

X-ray spectroscopic measurements of the Cygnus Loop supernova remnant indicate that metal abundances throughout most of the remnant s rim are depleted to approx.0.2 times the solar value. However, recent X-ray studies have revealed in some narrow regions along the outermost rim anomalously "enhanced" abundances (up to approx. 1 solar). The reason for these anomalous abundances is not understood. Here, we examine X-ray spectra in annular sectors covering nearly the entire rim of the Cygnus Loop using Suzaku (21 pointings) and XMM-Newton (1 pointing). We find that spectra in the "enhanced" abundance regions commonly show a strong emission feature at approx.0.7 keV. This feature is likely a complex of He-like O K(gamma + delta + epsilon), although other possibilities cannot be fully excluded. The intensity of this emission relative to He-like O K(alpha) appears to be too high to be explained as thermal emission. This fact, as well as the spatial concentration of the anomalous abundances in the outermost rim, leads us to propose an origin from charge-exchange processes between neutrals and H-like O. We show that the presence of charge-exchange emission could lead to the inference of apparently "enhanced" metal abundances using pure thermal emission models. Accounting for charge-exchange emission, the actual abundances could be uniformly low throughout the rim. The overall abundance depletion remains an open question. Subject headings: ISM: abundances ISM: individual objects (Cygnus Loop) ISM: supernova remnants X-rays: ISM atomic processes

Katsuda, Satoru; Tsunemi, Hiroshi; Mori, Koji; Uchida, Hiroyuki; Kosugi, Hiroko; Kimura, Masashi; Nakajima, Hiroshi; Takakura, Satoru; Petre, Robert; Hewitt. John W.; Yamaguchi, Hiroya

2011-01-01

296

F-GAMMA program: Unification and physical interpretation of the radio spectra variability patterns in Fermi blazars and detection of radio jet emission from NLSY1 galaxies  

NASA Astrophysics Data System (ADS)

The F-GAMMA program aims at understanding the physics at work in AGN via a multi-frequency monitoring approach. A number of roughly 65 Fermi-GST detectable blazars are being monitored monthly since January 2007 at radio wavelengths. The core program relies on the 100-m Effelsberg telescope operating at 8 frequencies between 2.6 and 43 GHz, the 30-m IRAM telescope observing at 86, 145 and 240 GHz and the APEX 12-m telescope at 345 GHz. For the targeted sources the LAT instrument onboard Fermi-GST provides gamma-ray light curves sampled daily. Here we discuss two recent findings: A). On the basis of their variability pattern, the observed quasi-simultaneous broad-band spectra can be classified to merely 5 classes. The variability for the first 4 is clearly dominated by spectral-evolution. Sources of the last class vary self-similarly with almost no apparent shift of the peak frequency. The former classes can be attributed to a two-component principal system made of a quiescent optically thin spectrum and a super-imposed flaring event. The later class must be interpreted in terms of a completely different mechanism. The apparent differences among the classes are explained in terms of a redshift modulus and an intrinsic-source/flare parameters modulus. Numerical simulations have shown that a shock-in-jet model can very well describe the observed behavior. It is concluded therefore that only two mechanisms seem to be producing variability. None of the almost 90 sources used for this study show a switch of class indicating that the variability mechanism is either (a) a finger-print of the source, or (b) remains stable on timescales far longer than the monitoring period of almost 4 years. B). Recently it has been disclosed that Narrow Line Seyfert 1 galaxies show gamma-ray emission. Within the F-GAMMA program radio jet emission has been detected from 3 such sources challenging the belief that jets are associated with elliptical galaxies. The recent findings in this area will be discussed.

Angelakis, E.

2012-01-01

297

Sm M/sub 4,5/ emission spectra of Sm metal and SmB/sub 6/ with fluorescence-excitation and near-threshold electron-excitation methods  

SciTech Connect

The Sm M/sub 4,5/ fluorescent emission and characteristic isochromat spectra of Sm metal and SmB/sub 6/ were measured to obtain information on the valence mixing of SmB/sub 6/. It was found that the fluorescent spectra do not exhibit resonant emission, which had been observed in the electron-excited spectra measured with relatively low electron-beam energy. The fluorescent spectrum of SmB/sub 6/ is quite similar to that of Sm metal and the fluorescent and characteristic isochromat spectra of SmB/sub 6/ show no distinct indication of the spectrum corresponding to the Sm/sup 2+/ ion. The characteristic isochromat spectra at the photon energy of the resonant peak of these materials show that an electron-beam energy beyond 1085 eV is required for the generation of the resonant emission (3d/sub 5/2//sup -1/4f/sup n+1/..-->..3d/sup 10/4f /sup n/), where n is equal to 5 for the Sm/sup 3+/ ion. This is ascribed to the formation of the transient state 3d/sup 9/4f/sup n+2/, which is caused by both the electron excited from the 3d level and the incident electron losing the initial energy. The possibility of a valence change from divalent to trivalent is discussed as the reason no distinct indication of the spectrum corresponding to the Sm/sup 2+/ ion in SmB/sub 6/ is observed.

Aita, O.; Ichikawa, K.; Okusawa, M.; Tsutsumi, K.

1986-12-15

298

Lipid raft facilitated ligation of K-{alpha}1-tubulin by specific antibodies on epithelial cells: Role in pathogenesis of chronic rejection following human lung transplantation  

SciTech Connect

Research highlights: {yields} Addition of KAT Abs (+) sera to NHBE culture causes upregulation of growth factors. {yields} Cholesterol depletion causes down regulation of growth factor expression. {yields} Cholesterol depletion is accompanied by loss of membrane bound caveolin. {yields} Thus, we demonstrate lipid raft are critical for efficient ligation of the KAT Abs. -- Abstract: Long term function of human lung allografts is hindered by development of chronic rejection manifested as Bronchiolitis Obliterans Syndrome (BOS). We have previously identified the development of antibodies (Abs) following lung transplantation to K-{alpha}1-tubulin (KAT), an epithelial surface gap junction cytoskeletal protein, in patients who develop BOS. However, the biochemical and molecular basis of the interactions and signaling cascades mediated by KAT Abs are yet to be defined. In this report, we investigated the biophysical basis of the epithelial cell membrane surface interaction between KAT and its specific Abs. Towards this, we analyzed the role of the lipid raft-domains in the membrane interactions which lead to cell signaling and ultimately increased growth factor expression. Normal human bronchial epithelial (NHBE) cells, upon specific ligation with Abs to KAT obtained either from the serum of BOS(+) patients or monoclonal KAT Abs, resulted in upregulation of growth factors VEGF, PDGF, and bFGF (6.4 {+-} 1.1-, 3.2 {+-} 0.9-, and 3.4 {+-} 1.1-fold increase, respectively) all of which are important in the pathogenesis of BOS. To define the role for lipid raft in augmenting surface interactions, we analyzed the changes in the growth factor expression pattern upon depletion and enrichment with lipid raft following the ligation of the epithelial cell membranes with Abs specific for KAT. NHBE cells cultured in the presence of {beta}-methyl cyclodextran ({beta}MCD) had significantly reduced growth factor expression (1.3 {+-} 0.3, vs {beta}MCD untreated being 6.4 {+-} 1.1-fold increase) upon stimulation with KAT Abs. Depletion of cholesterol on NHBE cells upon treatment with {beta}MCD also resulted in decreased partitioning of caveolin in the membrane fraction indicating a decrease in raft-domains. In conclusion, our results demonstrate an important role for lipid raft-mediated ligation of Abs to KAT on the epithelial cell membrane, which results in the upregulation of growth factor cascades involved in the pathogenesis of BOS following human lung transplantation.

Tiriveedhi, Venkataswarup; Angaswamy, Nataraju [Department of Surgery, Pathology and Immunology, Washington University School of Medicine, St. Louis, MO (United States)] [Department of Surgery, Pathology and Immunology, Washington University School of Medicine, St. Louis, MO (United States); Weber, Joseph [Department of Medicine, Washington University School of Medicine, St. Louis, MO (United States)] [Department of Medicine, Washington University School of Medicine, St. Louis, MO (United States); Mohanakumar, T., E-mail: kumart@wustl.edu [Department of Surgery, Pathology and Immunology, Washington University School of Medicine, St. Louis, MO (United States)

2010-08-20

299

Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288  

NASA Technical Reports Server (NTRS)

We report evidence for an Fe K-alpha fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748 - 288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20R(sub g) and - approx. 100R(sub g) in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748 - 288.

Miller, J. M.; Fox, D. W.; DiMatteo, T.; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

2001-01-01

300

Relativistic Iron Emission and Disk Reflection in Galactic Microquasar XTE J1748-288  

NASA Technical Reports Server (NTRS)

We report evidence for an Fe K(alpha) fluorescence line feature and disk reflection in the very high, high-, and low-state X-ray spectra of the Galactic microquasar XTE J1748-288 during its 1998 June outburst. Spectral analyses are made on data gathered throughout the outburst by the Rossi X-Ray Timing Explorer Proportional Counter Array. Gaussian line, relativistic disk emission line, and ionized disk reflection models are fitted to the data. In the very high state the line profile appears strongly redshifted, consistent with disk emission from the innermost stable orbits around a maximally rotating Kerr black hole. In the high state the line profile is less redshifted and increasingly prominent. The low-state line profile is very strong (approx. 0.5 keV equivalent width) and centered at 6.7 +/- 0.10 keV; disk line emission model fits indicate that the inner edge of the disk fluctuates between approx. 20Rg and approx. 100Rg in this state. The disk reflection fraction is traced through the outburst; reflection from an ionized disk is preferred in the very high and high states, and reflection from a relatively neutral disk is preferred in the low state. We discuss the implications of our findings for the binary system dynamics and accretion flow geometry in XTE J1748-288.

Miller, J. M.; Fox, D. W.; Matteo, T. DI; Wijnands, R.; Belloni, T.; Pooley, D.; Kouveliotou, C.; Lewin, W. H. G.

2001-01-01

301

The arrangement of chloroplasts in cells influences the reabsorption of chlorophyll fluorescence emission. The effect of desiccation on the chlorophyll fluorescence spectra of Rhizomnium punctatum leaves  

Microsoft Academic Search

Chlorophyll fluorescence spectra measured with leaves are distorted by the effect of fluorescence reabsorption. A heterogeneous theoretical model simulating the effect of chloroplast arrangement in a cell on the distortion of chlorophyll fluorescence spectra due to reabsorption was formulated. Desiccation of leaves of the moss Rhizomnium punctatum was carried out as a simple model experiment. The parameters entering the model

Hana Bartošková; Jan Nauš; Martin Výkruta

1999-01-01

302

Suzaku Detection of Super-hard X-ray Emission from the Classical Nova V2491 Cygni  

E-print Network

We report the detection of super-hard (>10 keV) X-ray emission extending up to 70 keV from the classical nova V2491 Cygni using the Suzaku observatory. We conducted two ~20 ks target-of-opportunity observations 9 and 29 days after the outburst on 2008 April 11, yielding wide energy range spectra by combining the X-ray Imaging Spectrometer and the Hard X-ray Detector. On day 9, a spectrum was obtained at 1.0-70 keV with the Fe XXV K\\alpha line feature and a very flat continuum, which is explained by thermal plasma with a 3 keV temperature and power-law emission with a photon index of 0.1 attenuated by a heavy extinction of 1.4x10^{23} cm^{-2}. The 15-70 keV luminosity at 10.5 kpc is 6x10^{35} ergs s^{-1}. The super-hard emission was not present on day 29. This is the highest energy at which X-rays have been detected from a classical nova. We argue a non-thermal origin for the emission, which suggests the presence of accelerated charged particles in the nova explosion.

Takei, D; Kitamoto, S; Ness, J -U; Drake, J J; Takahashi, H; Mukai, K

2009-01-01

303

X-RAY SPECTRA FROM MAGNETOHYDRODYNAMIC SIMULATIONS OF ACCRETING BLACK HOLES  

SciTech Connect

We present the results of a new global radiation transport code coupled to a general relativistic magnetohydrodynamic simulation of an accreting, non-rotating black hole. For the first time, we are able to explain from first principles in a self-consistent way all the components seen in the X-ray spectra of stellar-mass black holes, including a thermal peak and all the features associated with strong hard X-ray emission: a power law extending to high energies, a Compton reflection hump, and a broad iron line. Varying only the mass accretion rate, we are able to reproduce a wide range of X-ray states seen in most galactic black hole sources. The temperature in the corona is T{sub e} {approx} 10 keV in a boundary layer near the disk and rises smoothly to T{sub e} {approx}> 100 keV in low-density regions far above the disk. Even as the disk's reflection edge varies from the horizon out to Almost-Equal-To 6M as the accretion rate decreases, we find that the shape of the Fe K{alpha} line is remarkably constant. This is because photons emitted from the plunging region are strongly beamed into the horizon and never reach the observer. We have also carried out a basic timing analysis of the spectra and find that the fractional variability increases with photon energy and viewer inclination angle, consistent with the coronal hot spot model for X-ray fluctuations.

Schnittman, Jeremy D. [NASA Goddard Space Flight Center Greenbelt, MD 20771 (United States); Krolik, Julian H. [Department of Physics and Astronomy, Johns Hopkins University Baltimore, MD 21218 (United States); Noble, Scott C., E-mail: jeremy.schnittman@nasa.gov, E-mail: jhk@pha.jhu.edu, E-mail: scn@astro.rit.edu [Center for Computational Relativity and Gravitation, Rochester Institute of Technology Rochester, NY 14623 (United States)

2013-06-01

304

Continuum Fitting HST QSO Spectra  

NASA Technical Reports Server (NTRS)

The Principal Component Analysis (PCA) method which we are using to fit and describe QSO spectra relies upon the fact that QSO continuum are generally very smooth and simple except for emission and absorption lines. To see this we need high signal-to-noise (S/N) spectra of QSOs at low redshift which have relatively few absorption lines in the Lyman-a forest. We need a large number of such spectra to use as the basis set for the PCA analysis which will find the set of principal component spectra which describe the QSO family as a whole. We have found that too few HST spectra have the required S/N and hence we need to supplement them with ground based spectra of QSOs at higher redshift. We have many such spectra and we have been working to make them suitable for this analysis. We have concentrated on this topic since 12/15/01.

Tytler, David; Oliversen, Ronald J. (Technical Monitor)

2002-01-01

305

Near-field investigation of spatial variations of (202xAF1xAF) InGaN quantum well emission spectra  

NASA Astrophysics Data System (ADS)

Scanning near-field optical spectroscopy was applied to semipolar (202¯1¯) InGaN/GaN quantum wells (QWs) to evaluate spatial homogeneity of QW band gap and its dependence on the growth conditions. In the most uniform QW, photoluminescence (PL) spectra were found to be narrow with small peak wavelength and spectral width variations. A QW grown at reduced temperature showed sub-micrometer size PL features aligned along the a axis and caused by nonuniform In incorporation at surface undulations. At extended defects, complex and strongly varying near-field spectra were observed and tentatively assigned to QW segments of different orientations around these defects.

Marcinkevi?ius, S.; Zhao, Y.; Kelchner, K. M.; Nakamura, S.; DenBaars, S. P.; Speck, J. S.

2013-09-01

306

Intraoperative detection of 18F-FDG-avid tissue sites using the increased probe counting efficiency of the K-alpha probe design and variance-based statistical analysis with the three-sigma criteria  

PubMed Central

Background Intraoperative detection of 18F-FDG-avid tissue sites during 18F-FDG-directed surgery can be very challenging when utilizing gamma detection probes that rely on a fixed target-to-background (T/B) ratio (ratiometric threshold) for determination of probe positivity. The purpose of our study was to evaluate the counting efficiency and the success rate of in situ intraoperative detection of 18F-FDG-avid tissue sites (using the three-sigma statistical threshold criteria method and the ratiometric threshold criteria method) for three different gamma detection probe systems. Methods Of 58 patients undergoing 18F-FDG-directed surgery for known or suspected malignancy using gamma detection probes, we identified nine 18F-FDG-avid tissue sites (from amongst seven patients) that were seen on same-day preoperative diagnostic PET/CT imaging, and for which each 18F-FDG-avid tissue site underwent attempted in situ intraoperative detection concurrently using three gamma detection probe systems (K-alpha probe, and two commercially-available PET-probe systems), and then were subsequently surgical excised. Results The mean relative probe counting efficiency ratio was 6.9 (± 4.4, range 2.2–15.4) for the K-alpha probe, as compared to 1.5 (± 0.3, range 1.0–2.1) and 1.0 (± 0, range 1.0–1.0), respectively, for two commercially-available PET-probe systems (P?K-alpha probe (P?=?0.05). Conclusions Our results suggest that the improved probe counting efficiency of the K-alpha probe design used in conjunction with the three-sigma statistical threshold criteria method can allow for improved detection of 18F-FDG-avid tissue sites when a low in situ T/B ratio is encountered. PMID:23496877

2013-01-01

307

Results from a Near Infrared Search for Emission-line Stars in the Inner Galaxy: Spectra of New Wolf-Rayet Stars  

Microsoft Academic Search

We present follow-up spectroscopy of emission line candidates detected on\\u000anear-infrared narrow band images in the inner Galaxy (Homeier et al. 2003). The\\u000afilters are optimized for the detection of Wolf-Rayet stars and other objects\\u000awhich exhibit emission--lines in the 2 $\\\\mu$m region. Approximately three\\u000asquare degrees along the Galactic plane have been analyzed in seven\\u000anarrow--filters (four emission--lines and

Nicole L. Homeier; Robert D. Blum; Anna Pasquali; Peter S. Conti; Augusto Damineli

2003-01-01

308

Measurement of the 238U neutron-capture cross section and gamma-emission spectra from 10 eV to 100 keV using the DANCE detector at LANSCE  

SciTech Connect

A careful new measurement of the {sup 238}U(n,{gamma}) cross section from 10 eV to 100 keV has been made using the DANCE detector at LANSCE. DANCE is a 4{pi} calorimetric scintillator array consisting of 160 BaF{sub 2} crystals. Measurements were made on a 48 mg/cm{sup 2} depleted uranium target. The cross sections are in general good agreement with previous measurements. The gamma-ray emission spectra, as a function of gamma multiplicity, were also measured and compared to model calculations.

Ullmann, John L [Los Alamos National Laboratory; Couture, A J [Los Alamos National Laboratory; Keksis, A L [Los Alamos National Laboratory; Vieira, D J [Los Alamos National Laboratory; O' Donnell, J M [Los Alamos National Laboratory; Jandel, M [Los Alamos National Laboratory; Haight, R C [Los Alamos National Laboratory; Rundberg, R S [Los Alamos National Laboratory; Kawano, T [Los Alamos National Laboratory; Chyzh, A [NORTH CAROLINA STATE UNIV; Baramsai, B [NORTH CAROLINA STATE UNIV; Wu, C Y [LLNL; Mitchell, G E [NORTH CAROLINA STATE UNIV; Becker, J A [LLNL; Krticka, M [CHARLES UNIV

2010-01-01

309

Atomic Spectra  

NSDL National Science Digital Library

This page from Hyperphysics contains images depicting the light emitted by several elements and their respective spectra. The page also provides a description of how the size of a holographic image scales with the wavelength of the light used to observe it.

Nave, Carl R.

2010-03-12

310

Atomic Spectra  

NSDL National Science Digital Library

This well-illustrated page from Hyperphysics contains the light emitted by several elements and their respective spectra as well. The page also provides a description of how the size of a holographic image scales with the wavelength of the light used to observe it.

Nave, Carl R.

2007-12-20

311

Gas Lamp Emission  

NSDL National Science Digital Library

This resource, part of the Spectroscopy Lab Suite, simulates optical transitions in gasses. Spectra from gas emission tubes are shown, along with a tool for students to create bound state energy levels and electronic transitions to match the observed spectra.

Group, Kansas S.; Zollman, Dean A.

2004-03-05

312

Studies of electronic configurations in the emission spectra of lanthanides and actinides: application to the interpretation of Es I and Es II, predictions for Fm I  

SciTech Connect

The interpretation of the spectra of free atoms and gaseous ions in the 4f{sup N} and 5f{sup N} periods became less active after critical compilations of energy levels appeared. However, several spectra are still under study and the application of the Racah-Slater and HFR methods to extended sets of configurations leads to revisions and additions. In doubly charged ions of lanthanides, the treatment of configuration interaction by means of effective parameters and by extension of the basis of states are both important. Concerning actinides, calculations of several observables (Lande factors and isotope shifts in Pu I, hyperfine constants, transition probabilities) prove the quality of eigenfunctions. The classification of Es I and Es II has been extended and radial parameters for fine and hyperfine structures have been derived. Level predictions for the next element fermium are supported by parameter extrapolations.

Wyart, Jean-Francois [Laboratoire Aime Cotton, CNRS, Batiment 505, Centre Universitaire, FR-91405 Orsay Cedex (France)]. E-mail: jean-francois.wyart@lac.u-psud.fr; Blaise, Jean [Laboratoire Aime Cotton, CNRS, Batiment 505, Centre Universitaire, FR-91405 Orsay Cedex (France); Worden, Earl F. [Physics and Advanced Technologies Directorate, Lawrence Livermore National Laboratory, L-044, Livermore, CA 94550 (United States)

2005-02-15

313

Observation of high-N hydroxyl pure rotation lines in atmospheric emission spectra by the Cirris 1A Space Shuttle experiment  

NASA Astrophysics Data System (ADS)

Pure rotation line emissions from highly rotationally excited OH have been observed between 80 and 110 km tangent height under both nighttime and daytime quiescent conditions. Data were obtained using the cryogenic CIRRIS 1A interferometer, operated on the Space Shuttle. Transitions from OH were identified between 400 and 1000 per cm, corresponding to states with energies as high as 23,000 per cm. These are the first definitive observations of OH pure rotation transitions in the airglow, and by far the highest N levels observed in any type of OH airglow emission spectrum.

Smith, D. R.; Blumberg, W. A. M.; Nadile, R. M.; Lipson, S. J.; Huppi, E. R.; Wheeler, N. B.

1992-03-01

314

atomic spectra 1 Atomic Spectra  

E-print Network

. Eisberg and Resnick: Quantum Physics of Atoms, Molecules, Solids, Nuclei and Particles, pp. 95-119, p286 Physics, pp. 88-93 (Rutherford nuclear model), 93-106 (atomic structure and electron spectra) 2. D. W. Preston and E. R. Dietz: The Art of Experimental Physics, pp. 397- 399, resolution of optical instruments

Glashausser, Charles

315

Observation of high-N hydroxyl pure rotation lines in atmospheric emission spectra by the Cirris 1A Space Shuttle experiment  

Microsoft Academic Search

Pure rotation line emissions from highly rotationally excited OH have been observed between 80 and 110 km tangent height under both nighttime and daytime quiescent conditions. Data were obtained using the cryogenic CIRRIS 1A interferometer, operated on the Space Shuttle. Transitions from OH were identified between 400 and 1000 per cm, corresponding to states with energies as high as 23,000

D. R. Smith; W. A. M. Blumberg; R. M. Nadile; S. J. Lipson; E. R. Huppi; N. B. Wheeler

1992-01-01

316

Observation of high-N hydroxyl pure rotation lines in atmospheric emission spectra by the CIRRIS 1A Space Shuttle Experiment  

Microsoft Academic Search

Pure rotation line emissions from highly rotationally excited OH have been observed between 80 and 110 km tangent height under both nighttime and daytime quiescent conditions. Data were obtained using the cryogenic CIRRIS 1A interferometer, operated on the Space Shuttle. Transitions from OH(v=0–2, N??33) were identified between 400 and 1000 cm?1, corresponding to states with energies as high as 23000

D. R. Smith; W. A. M. Blumberg; R. M. Nadile; S. J. Lipson; E. R. Huppi; N. B. Wheeler; J. A. Dodd

1992-01-01

317

A search for iron emission lines in the Chandra X-ray spectra of neutron star low-mass X-ray binaries  

E-print Network

While iron emission lines are well studied in black hole systems, both in X-ray binaries and Active Galactic Nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad asymmetric iron line profiles in 4 neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in 6 neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at 2 separate epochs, allowing for both a high resolution spectrum, as well as broadband spectral coverage. Out of the six objects in the survey, we only find significant iron lines in two of the objects, GX 17+2 and GX 349+2. However, we cannot rule out that there are weak, broad lines present in the other sources. The equivalent width of the line in GX 17+2 is consistent between the 2 epochs, while in GX 349+2 the line equivalent width increases by a factor of ~3 between epochs as the source flux decreases by a factor of 1.3. This suggests that the disk is highly ionized, and the line is dominated by recombination emission. We find that there appears to be no specific locations in the long-term hardness-intensity diagrams where iron emission lines are formed, though more sources and further observations are required.

E. M. Cackett; J. M. Miller; J. Homan; M. van der Klis; W. H. G. Lewin; M. Mendez; J. Raymond; D. Steeghs; R. Wijnands

2008-09-18

318

High K-alpha X-ray Conversion Efficiency From Extended Source Gas Jet Targets Irradiated by Ultra Short Laser Pulses  

SciTech Connect

The absolute laser conversion efficiency to K{sub {alpha}}-like inner shell x-rays (integrated from K{sub {alpha}} to K{sub {beta}}) is observed to be an order of magnitude higher in argon gas jets than in solid targets due to enhanced emission from higher ionization stages following ultra short pulse laser irradiation. Excluding the higher ionization stages, the conversion efficiency to near-cold K{sub {alpha}} is the same in gas jets as in solid targets. These results demonstrate that gas jet targets are bright, high conversion efficiency, high repetition rate, debris-free multi-keV x-ray sources for spectrally resolved scattering and backlighting of rapidly evolving dense matter.

Kugland, N L; Constantin, C; Collette, A; Dewald, E; Froula, D; Glenzer, S H; Kritcher, A; Neumayer, P; Ross, J S; Niemann, C

2007-11-01

319

Analysis of the absorption spectra of gas emission of patients with lung cancer and chronic obstructive pulmonary disease by laser optoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

It is important to identify patients with chronic obstructive pulmonary disease (COPD) and lung cancer in the early stages of the disease. The method of laser opto-acoustic gas analysis, in this case, can act as a promising tool for diagnostics. The material for this study were the gas emission samples collected from patients and healthy volunteers - samples of exhaled air, swabs from teeth and cheeks. A set of material was formed three groups: healthy volunteers, patients with COPD, lung cancer patients. The resulting samples were analyzed by means of laser opto-acoustic gas analyzers: with intracavity location detector (ILPA-1), with extracavity location detector (LGA-2). Presentation of the results in an easy to visual form was performed using the method of elastic maps, based on the principal component analysis. The results of analysis show potentialities of usage of laser optoacoustic spectroscopy application to assess the status of patients with chronic obstructive pulmonary disease and lung cancer.

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

2013-02-01

320

Local and Nonlocal Excitations in Cu 4p-1s Resonant X-Ray Emission Spectra of Nd 2CuO 4  

NASA Astrophysics Data System (ADS)

Theoretical study for Cu 4p-1s resonant X-ray emission spectroscopy (RXES) of Nd2CuO4 is given in the context of local and nonlocal natures of electronic excitations. Detailed analyses with an impurity Anderson model and multi-Cu models are presented, based on exact diagonalization technique. By investigating partial densities of states, basic characters of each excited state are clarified. It is demonstrated that a disagreement with experimental data is unavoidable with the impurity model. The key concept to solve the difficulty is Zhang-Rice singlet formation in the intermediate state of RXES. We find that it survives in the final state of RXES as the lowest charge-transfer excitation. The limitation of the impurity model and the essential role of nonlocal excitations in RXES are stressed.

Idé, Tsuyoshi; Kotani, Akio

1999-09-01

321

High resolution emission Fourier transform infrared spectra of the 4p-5s and 5p-6s bands of ArH  

NASA Astrophysics Data System (ADS)

In the 2500-8500cm-1 region several strong emission bands of ArH40 were observed by Fourier transform spectroscopy through a dc glow discharge in a mixture of argon and hydrogen. Rotational-electronic transitions of the two previously unstudied 4p-5s and 5p-6s,v=0-0, bands of ArH40 were measured and assigned in the 6060 and 3770cm-1 regions, respectively. A simultaneous fit of the emission transitions of the 4p-5s and 5p-6s bands and an extended set of transitions of the 6s-4p band observed by Dabrowski, Tokaryk, and Watson [J. Mol. Spectrosc. 189, 95 (1998)] and remeasured in the present work yielded consistent values of the spectroscopic parameters of the electronic states under investigation. In the branch of the 4p-5s band with transitions of type Qf3eQ we observed a narrowing in the linewidths with increasing rotational quantum number N. The rotational dependence of the linewidth is caused by predissociation of the 5s state by the repulsive ground 4s state through homogeneous coupling and changes in overlap integrals of the vibrational wave functions with the rotational level. Analysis was based on the Fermi's golden rule approximation model. In the 4p-5s band region a vibrational sequence ofv'-v?=1-1, 2-2, and 3-3 were recorded and a number of transitions belonging to the strongest Qf3eQ form branch of the 1-1 band were analyzed.

Baskakov, O. I.; Civiš, S.; Kawaguchi, K.

2005-03-01

322

Theoretical spectra of terrestrial exoplanet surfaces  

E-print Network

We investigate spectra of airless rocky exoplanets with a theoretical framework that self-consistently treats reflection and thermal emission. We find that a silicate surface on an exoplanet is spectroscopically detectable ...

Hu, Renyu

323

Photobleaching Response of Different Sources of Chromophoric Dissolved Organic Matter Exposed to Natural Solar Radiation Using Absorption and Excitation-Emission Matrix Spectra  

PubMed Central

CDOM biogeochemical cycle is driven by several physical and biological processes such as river input, biogeneration and photobleaching that act as primary sinks and sources of CDOM. Watershed-derived allochthonous (WDA) and phytoplankton-derived autochthonous (PDA) CDOM were exposed to 9 days of natural solar radiation to assess the photobleaching response of different CDOM sources, using absorption and fluorescence (excitation-emission matrix) spectroscopy. Our results showed a marked decrease in total dissolved nitrogen (TDN) concentration under natural sunlight exposure for both WDA and PDA CDOM, indicating photoproduction of ammonium from TDN. In contrast, photobleaching caused a marked increase in total dissolved phosphorus (TDP) concentration for both WDA and PDA CDOM. Thus TDN?TDP ratios decreased significantly both for WDA and PDA CDOM, which partially explained the seasonal dynamic of TDN?TDP ratio in Lake Taihu. Photobleaching rate of CDOM absorption a(254), was 0.032 m/MJ for WDA CDOM and 0.051 m/MJ for PDA CDOM from days 0–9, indicating that phototransformations were initially more rapid for the newly produced CDOM from phytoplankton than for the river CDOM. Extrapolation of these values to the field indicated that 3.9%–5.1% CDOM at the water surface was photobleached and mineralized every day in summer in Lake Taihu. Photobleaching caused the increase of spectral slope, spectral slope ratio and molecular size, indicating the CDOM mean molecular weight decrease which was favorable to further microbial degradation of mineralization. Three fluorescent components were validated in parallel factor analysis models calculated separately for WDA and PDA CDOM. Our study suggests that the humic-like fluorescence materials could be rapidly and easily photobleached for WDA and PDA CDOM, but the protein-like fluorescence materials was not photobleached and even increased from the transformation of the humic-like fluorescence substance to the protein-like fluorescence substance. Photobleaching was an important driver of CDOM and nutrients biogeochemistry in lake water. PMID:24204852

Zhang, Yunlin; Liu, Xiaohan; Osburn, Christopher L.; Wang, Mingzhu; Qin, Boqiang; Zhou, Yongqiang

2013-01-01

324

Characterizing the heavy metal-complexing potential of fluorescent water-extractable organic matter from composted municipal solid wastes using fluorescence excitation–emission matrix spectra coupled with parallel factor analysis.  

PubMed

To investigate the effect of organic matter evolution on heavy metal sorption, fluorescence excitation–emission matrix (EEM) spectra combined with parallel factor (PARAFAC) analysis were employed to characterize the evolution and metal-complexing potential of fluorescent water-extractable organic matter (WEOM) from composted municipal solid wastes (MSWs). The WEOMs examined comprised humic-, fulvic-, tryptophan-, and tyrosine-like substances. Composting treatment increased the content of humic- and fulvic-like matter, and changed the existence pattern of tryptophan- and tyrosine-like substances (i.e., the tryptophan- and tyrosine-like substances from uncomposted MSWs were mainly bound in protein-like matter, whereas those from composted MSWs were primarily bound in humic- and fulvic-like substances). Furthermore, composting treatment increased the polar functional group, aromaticity, and humification degree of the WEOMs, but decreased the aliphatic and hydroxyl group. These evolutions decreased the Cu(II) affinities of fulvic- and humic-like substances and the Pb(II) affinities and complexing capacities of fulvic-like substances, but increased the Cu(II) complexing capacities of fulvic- and humic-like substances. These results reveal that mature composts from the MSWs can be used for the remediation of Cu- and Pb-contaminated soils in situ, whereas immature composts can enhance the metal transferability from soil to plant. PMID:24659406

He, Xiao-Song; Xi, Bei-Dou; Pan, Hong-Wei; Li, Xiang; Li, Dan; Cui, Dong-Yu; Tang, Wen-Bin; Yuan, Ying

2014-07-01

325

Thermal infrared spectra of the Moon  

NASA Technical Reports Server (NTRS)

Contrary to recent assertions in the literature, lunar emission spectra obtained at an altitude of 32 km with a balloon-borne telescope are virtually undistorted by atmospheric absorption, except in the ozone region. These spectra have been found to correlate closely with laboratory emission spectra of returned lunar samples measured in a simulated lunar environment. Thus, lunar spectra obtained with the balloon-borne telescope system are the standards against which groundbased spectral measurements of the Moon should be compared. Comparison of balloon-borne measurements with recent groundbased spectral measurements suggests that the latter suffer from some source of systematic error. When high-quality lunar spectra are available, they will be best interpreted by comparison with returned lunar samples, rather than terrestrial minerals or rocks, because of subtle spectral differences between lunar and terrestrial minerals perhaps associated with incipient alteration of the latter.

Salisbury, John W.; Murcray, D. G.; Williams, W. J.; Blatherwick, R. D.

1995-01-01

326

Galaxy and Stellar Spectra  

NSDL National Science Digital Library

In this activity students learn that galaxies shine on the basis of their intergrated stellar population, therefore, adding together different stellar spectra should reproduce the spectra of a galaxy. This activity contains an applet which allows one to add spectra of up to four different stars to produce a resultant spectra. To reproduce qualitatively a spectra of a galaxy one can add together and F main sequence star and a K Giant. The spectra are normalized by V-band luminosity.

Department, University O.

2005-06-17

327

Phonon emission spectra of thin metallic films  

Microsoft Academic Search

Thin metallic films evaporated on an Al2O3-single crystal and cooled to liquid helium temperatures are heated by short electric current pulses. The high frequency part\\u000a of the emitted phonons is detected by calibrated superconductive tunneling junctions on the opposite surface of the substrate.\\u000a The observed phonon detector signal amplitude is compared with theoretical models taking account of the boundary conditions

Wolfgang Frick; Dieter Waldmann; Wolfgang Eisenmenger

1975-01-01

328

Digital filtering of plume emission spectra  

NASA Technical Reports Server (NTRS)

Fourier transformation and digital filtering techniques were used to separate the superpositioned spectral phenomena observed in the exhaust plumes of liquid propellant rocket engines. Space shuttle main engine (SSME) spectral data were used to show that extraction of spectral lines in the spatial frequency domain does not introduce error, and extraction of the background continuum introduces only minimal error. Error introduced during band extraction could not be quantified due to poor spectrometer resolution. Based on the atomic and molecular species found in the SSME plume, it was determined that spectrometer resolution must be 0.03 nm for SSME plume spectral monitoring.

Madzsar, George C.

1990-01-01

329

The First Reported Observations on Emission Spectra  

Microsoft Academic Search

The first person to use a prism to examine the light from colored flames was a young Scot named Thomas Melvill. He announced his results in a paper read before a philosophical society in Edinburgh early in 1752, less than two years before his death at the early age of twenty-seven. This paper, which was not published until 1756, is

E. C. Watson

1952-01-01

330

Cosmology from quasar spectra  

NASA Astrophysics Data System (ADS)

High resolution spectroscopy of high redshift quasar spectra enables us to investigate the properties of the intergalactic medium (IGM) and measure cosmological parameters from the Lya forest. Toward high precision cosmology, this dissertation presents the following four topics. (1) Principal Component Analysis (PCA) on quasar spectrum: We introduce the PCA to describe quasar emission lines and continua quantitatively, and we attempt to make a prediction of the continuum shape in the Lya forest using wavelengths redward of Lya emission. (2) Flux calibration of Keck HIRES data: On our way to achieve high accuracy measurement, it was necessary to develop new calibration schemes and explore the origin of systematic errors. My contribution includes the following and is discussed throughout the thesis: (i) the development of the flux calibration scheme, (ii) the discovery of three emission lines in the Lya forest, (iii) the establishment of high resolution standard star spectra, and (iv) the identification of ozone lines in the spectrum. (3) D/H measurement: We present precise measurements of the primordial deuterium to hydrogen ratio (D/ H) toward two quasars, HS0105+1619 and Q1243+3047, which constrains the baryon to photon ratio e = 5.9 +/- 0.5 x 10 -10 or the baryon density O b h 2 = 0.0214 +/- 0.0020 via the Big Bang Nucleosynthesis theory. (4) Studies of the Lya forest at z ~ 2: We also present the measurements of the total amount of neutral hydrogen absorption in the IGM. We compare our observed data with hydrodynamic simulations and find good agreement when we use the following cosmological parameters: H o = 71 kin s -1 Mpc -1 , O L = 0.73, O m = 0.27, O b = 0.044, the amplitude of the power spectrum s 8 = 0.9, and the photoinization rate G 912 = (1.44 +/- 0.11) x 10 -12 s -1 . We conclude that the measurements of the cosmological parameters from our primordial D/H measurements, recent WMAP satellite observation of the cosmic microwave background, and our the total amount of neutral hydrogen in the IGM at z ~ 2 are in a concordance with the LCDM model.

Suzuki, Nao

2005-11-01

331

Ab initio calculations on SnCl2 and Franck-Condon factor simulations of its ã-X and B-X absorption and single-vibronic-level emission spectra.  

PubMed

Minimum-energy geometries, harmonic vibrational frequencies, and relative electronic energies of some low-lying singlet and triplet electronic states of stannous dichloride, SnCl(2), have been computed employing the complete-active-space self-consistent-field/multireference configuration interaction (CASSCF/MRCI) and/or restricted-spin coupled-cluster single-double plus perturbative triple excitations [RCCSD(T)] methods. The small core relativistic effective core potential, ECP28MDF, was used for Sn in these calculations, together with valence basis sets of up to augmented correlation-consistent polarized-valence quintuple-zeta (aug-cc-pV5Z) quality. Effects of outer core electron correlation on computed geometrical parameters have been investigated, and contributions of off-diagonal spin-orbit interaction to relative electronic energies have been calculated. In addition, RCCSD(T) or CASSCF/MRCI potential energy functions of the X(1)A(1), ã(3)B(1), and B(1)B(1) states of SnCl(2) have been computed and used to calculate anharmonic vibrational wave functions of these three electronic states. Franck-Condon factors between the X (1)A(1) state, and the ã (3)B(1) and B (1)B(1) states of SnCl(2), which include anharmonicity and Duschinsky rotation, were then computed, and used to simulate the ã-X and B-X absorption and corresponding single-vibronic-level emission spectra of SnCl(2) which are yet to be recorded. It is anticipated that these simulated spectra will assist spectroscopic identification of gaseous SnCl(2) in the laboratory and/or will be valuable in in situ monitoring of SnCl(2) in the chemical vapor deposition of SnO(2) thin films in the semiconductor gas sensor industry by laser induced fluorescence and/or ultraviolet absorption spectroscopy, when a chloride-containing tin compound, such as tin dichloride or dimethyldichlorotin, is used as the tin precursor. PMID:17640129

Lee, Edmond P F; Dyke, John M; Mok, Daniel K W; Chow, Wan-ki; Chau, Foo-tim

2007-07-14

332

THE SPECTRA OF THE DOUBLY AND TRIPLY IONIZED RARE EARTHS  

Microsoft Academic Search

The present status of the knowledge of the structure of the spectra of ; the doubly and triply ionized spectra of the rare earths is derived partly from ; experimental data of the emission spectra of the free ions which provide the ; energy level scheme in great detail but are difficuit and laborious to analyze. ; For the lower

G. H. Dieke; H. M. Crosswhite

1963-01-01

333

Infrared reflectance spectra (4-12 micron) of lunar samples  

NASA Technical Reports Server (NTRS)

Presented here are infrared reflectance spectra of a typical set of Apollo samples to illustrate spectral character in the mid-infrared (4 to 12 microns) of lunar materials and how the spectra varies among three main forms: soil, breccia, and igneous rocks. Reflectance data, to a close approximation, are the inverse of emission spectra; thus, for a given material the spectral reflectance (R) at any given wavelength is related to emission (E) by 1 - R equals E. Therefore, one can use reflectance spectra of lunar samples to predict how emission spectra of material on the lunar surface will appear to spectrometers on orbiting spacecraft or earthbound telescopes. Spectra were measured in the lab in dry air using a Fourier Transform Infrared spectrometer. Shown here is only the key portion (4 to 12 microns) of each spectrum relating to the principal spectral emission region for sunlit lunar materials and to where the most diagnostic spectral features occur.

Nash, Douglas B.

1991-01-01

334

K{beta} spectra of heliumlike iron from TFTR plasmas  

SciTech Connect

K{beta} spectra of helium-like iron, Fe XXV, have been observed from TFTR plasmas with a high-resolution crystal spectrometer. The wavelength range of the Fe K{beta} spectrum partially overlaps the spectrum of helium-like nickel (Ni XXVII), which is used on TFTR and JET for ion temperature measurements. The experimental arrangement made it possible to observe the Fe XXV K{beta} lines and their satellite transitions of the type 1s2l{prime}31{double_prime} {yields} 1s{sup 2}21{prime}, as well as the entire satellite spectrum of the Ni XXVII K {alpha} line simultaneously. In order to identify the features of the K{beta} spectra and to study their possible interference with the Ni XXVII spectrum, the intensity of the K{beta} spectrum was enhanced by injection of iron into the plasma. Accurate wavelengths and intensities have been obtained and compared with different theoretical calculations.

Smith, A.J. [Lock Haven University, Lock Haven, PA (United States); Bitter, M.; Hsuan, H.; Hill, K.W.; von Goeler, S.; Timberlake, J. [Princeton Univ., NJ (United States). Plasma Physics Lab.; Beiersdorfer, P.; Osterheld, A. [Lawrence Livermore National Lab., CA (United States)

1992-12-01

335

K[beta] spectra of heliumlike iron from TFTR plasmas  

SciTech Connect

K[beta] spectra of helium-like iron, Fe XXV, have been observed from TFTR plasmas with a high-resolution crystal spectrometer. The wavelength range of the Fe K[beta] spectrum partially overlaps the spectrum of helium-like nickel (Ni XXVII), which is used on TFTR and JET for ion temperature measurements. The experimental arrangement made it possible to observe the Fe XXV K[beta] lines and their satellite transitions of the type 1s2l[prime]31[double prime] [yields] 1s[sup 2]21[prime], as well as the entire satellite spectrum of the Ni XXVII K [alpha] line simultaneously. In order to identify the features of the K[beta] spectra and to study their possible interference with the Ni XXVII spectrum, the intensity of the K[beta] spectrum was enhanced by injection of iron into the plasma. Accurate wavelengths and intensities have been obtained and compared with different theoretical calculations.

Smith, A.J. (Lock Haven University, Lock Haven, PA (United States)); Bitter, M.; Hsuan, H.; Hill, K.W.; von Goeler, S.; Timberlake, J. (Princeton Univ., NJ (United States). Plasma Physics Lab.); Beiersdorfer, P.; Osterheld, A. (Lawrence Livermore National Lab., CA (United States))

1992-12-01

336

Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-Heated Corona  

E-print Network

We investigate the iron K$\\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk photoelectrically absorb X-ray photons and radiate K$\\alpha$ line photons. Therefore, the activity of corona is responsible to the iron line emission from the underlying disk. In previous studies, oversimplified X-ray photon sources are often assumed above the disk in order to compute the iron line profile or power-law line emissivity profiles are assumed with an index being a free parameter. We adopt the more realistic corona model constructed by Liu et al. in which the corona is heated by magnetic energy released through the reconnection of magnetic flux loops and which has no free parameter. Then the accretion energy is dominantly dissipated in the corona, in which X-ray photons are efficiently produced and irradiate the underlying disk. We find the local emmisivity of iron line on the disk is approximated as $F_{{\\rm K}\\alpha}(r)\\propto r^{-5}$. The iron line profiles derived from this model give excellent fits to the observational data of MCG-6-30-15 with the profiles derived theoretically for $i\\sim 30^{\\circ}$ for energy band 4-7keV. Possible origins of line variability are briefly discussed.

N. Kawanaka; S. Mineshige; K. Iwasawa

2005-08-24

337

Discriminating the Progenitor Type of Supernova Remnants with Iron K-Shell Emission  

E-print Network

Supernova remnants (SNRs) retain crucial information about both their parent explosion and circumstellar material left behind by their progenitor. However, the complexity of the interaction between supernova ejecta and ambient medium often blurs this information, and it is not uncommon for the basic progenitor type (Ia or core-collapse) of well-studied remnants to remain uncertain. Here we present a powerful new observational diagnostic to discriminate between progenitor types and constrain the ambient medium density of SNRs solely using Fe K-shell X-ray emission. We analyze all extant Suzaku observations of SNRs and detect Fe K alpha emission from 23 young or middle-aged remnants, including five first detections (IC 443, G292.0+1.8, G337.2-0.7, N49, and N63A). The Fe K alpha centroids clearly separate progenitor types, with the Fe-rich ejecta in Type Ia remnants being significantly less ionized than in core-collapse SNRs. Within each progenitor group, the Fe K alpha luminosity and centroid are well correlate...

Yamaguchi, Hiroya; Petre, Robert; Nakano, Toshio; Castro, Daniel; Enoto, Teruaki; Hiraga, Junko S; Hughes, John P; Maeda, Yoshitomo; Nobukawa, Masayoshi; Safi-Harb, Samar; Slane, Patrick O; Smith, Randall K; Uchida, Hiroyuki

2014-01-01

338

Fe K Emission and Absorption in the Bright Seyfert IC 4329a  

NASA Astrophysics Data System (ADS)

We present a re-analysis of the XMM-EPIC long-look of the X-ray bright Seyfert AGN IC 4329a, complementary to the RGS/EPIC analysis of Steenbrugge et al (2005). The Fe K bandpass is dominated by emission consistent with moderately-broadened Fe K alpha and beta. We detect, at high significance (confirmed with Monte Carlo simulations), a narrow absorption feature at 7.7 keV; one possible candidate for this feature's origin is highly blueshifted Fe K XXVI. Time-resolved spectrscopy of the XMM data as well as RXTE monitoring data, covering time scales from minutes to 2 years, show there is little variability in continuum flux or photon index on any time scale. There is no evidence for variability of the Fe K alpha line on any time scale, consistent with an origin far from the black hole (e.g., as discussed by previous works).

Markowitz, A.; Reeves, J.

2005-12-01

339

Degree Spectra of Alexandra A.  

E-print Network

Degree Spectra of Structures Alexandra A. Soskova DEGREE SPECTRA OF STRUCTURES CO-SPECTRA OF STRUCTURES PROPERTIES OF THE DEGREE SPECTRA AND CO-SPECTRA RELATIVE SPECTRA OF STRUCTURES PROPERTIES OF RELATIVE SPECTRA Degree Spectra of Structures Alexandra A. Soskova Faculty of Mathematics and Computer

Haase, Markus

340

Night Spectra Quest.  

ERIC Educational Resources Information Center

Presents the Night Spectra Quest, a pocket-sized chart that identifies in color the spectra of all the common night lights and has an integrally mounted, holographic diffraction grating to look through. (JRH)

Jacobs, Stephen

1995-01-01

341

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES  

E-print Network

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES MINIMAL PAIRS QUASI-MINIMAL DEGREE Minimal for Joint Spectra #12;DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES MINIMAL PAIRS QUASI-MINIMAL DEGREE DEGREE SPECTRA OF STRUCTURES Degree Spectra of Structures Let A = (N; R1, . . . , Rk

Soskova, Alexandra A.

342

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES  

E-print Network

DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES PROPERTIES OF JOINT SPECTRA Properties of the Joint Spectra of Sequence of Structures Alexandra A. Soskova Department of Mathematics and Computer of Structures #12;DEGREE SPECTRA OF STRUCTURES JOINT SPECTRA OF STRUCTURES PROPERTIES OF JOINT SPECTRA

Soskova, Alexandra A.

343

IUE spectra of flares on AU Mic  

NASA Technical Reports Server (NTRS)

Some IUE spectra were obtained in August 1980 through a substantial part of the optical cycle of the BY Draconis-type, spotted M dwarf star, AU Mic. No modulation of the ultraviolet emission line fluxes in antiphase with the optical curve is detected. Simultaneous optical photometry of AU Mic shows remarkably poor correlation of optical flare strength and ultraviolet emission-line enhancements. The flares detected on AU Mic show considerable variety in the degree of enhancement in the various emission lines and optical continuum.

Butler, C. J.; ion lines and optical continuum.

1986-01-01

344

DEGREE SPECTRA OF STRUCTURES RELATIVE SPECTRA OF STRUCTURES  

E-print Network

DEGREE SPECTRA OF STRUCTURES RELATIVE SPECTRA OF STRUCTURES PROPERTIES OF RELATIVE SPECTRA Degree Spectra of Structures Alexandra A. Soskova Faculty of Mathematics and Computer Science Sofia University Leeds Logic Seminar Alexandra A. Soskova Degree Spectra of Structures #12;DEGREE SPECTRA OF STRUCTURES

Soskova, Alexandra A.

345

K-Shell Diagram and Hypersatellite Spectra of 4D Transition Elements  

SciTech Connect

The K-shell diagram (K{alpha}{sub 1,2} and K{beta}{sub 1,3}) and hypersatellite (HS) (K{sup h}{alpha}{sub 1,2}) spectra of Y, Zr, Mo, and Pd have been measured with high energy-resolution using photoexcitation by 90 keV synchrotron radiation. Comparison of the measured and ab initio calculated HS spectra demonstrates the importance of quantum electrodynamical (QED) effects for the HS spectra. Phenomenological fits of the measured spectra by Voigt functions yield accurate values for the shift of the HS from the diagram lines, the splitting of the HS lines, and their intensity ratio. Good agreement with theory was found for all quantities except for the intensity ratio, which is dominated by the intermediacy of the coupling of the angular momenta. The observed deviations imply that our current understanding of the variation of the coupling scheme from LS to jj across the periodic table may require some revision.

Diamant, R.; Kao, C.; Huotari, S.; Hamalainen, K.; Sharon, R.; Honkimaki, V.; Buslaps, T.; Deutsch, M.

2009-07-25

346

The angular power spectra of polarized Galactic synchrotron  

Microsoft Academic Search

We derive the angular power spectra of intensity and polarization of Galactic synchrotron emission in the range 36???103 from the Parkes survey mapping the southern Galactic plane at 2.4 GHz. The polarization spectra of both electric and magnetic parity up to ??103 are approximated very well by power laws with slope coefficients ?1.4, quite different from the CMB spectra. We

M. Tucci; E. Carretti; S. Cecchini; R. Fabbri; M. Orsini; E. Pierpaoli

2000-01-01

347

Resonant Compton scattering and gamma-ray burst continuum spectra  

NASA Technical Reports Server (NTRS)

The Thomson limit of resonant inverse Compton scattering in the strong magnetic fields of neutron stars is considered as a mechanism for producing gamma-ray burst continuum spectra. Photon production spectra and electron cooling rates are presented using the full magnetic Thomson cross-section. Model emission spectra are obtained as self-consistent solutions of a set of photon and electron kinetic equations, displaying spectral breaks and other structure at gamma-ray energies.

Baring, M. G.

1995-01-01

348

Spectra Luminescence of Extraterrestrial Calcium Phosphates in Mexican Chondrites  

Microsoft Academic Search

Merrillite and apatite crystals from four historical Mexican chondrites were studied by Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive Spectrometry (EDS), Back-scattering (BS), Spectra cathodoluminescence (CL), and Micro-Raman Spectroscopy (MRS). CL is a powerful technique for exciting light emission from intrinsic relaxations, impurities, and imperfections in the outer few microns of the surface of minerals. The spectra CL patterns of

Leticia Alba Aldave; Javier García Guinea; Laura Tormo

2011-01-01

349

Spectra from Space  

NSDL National Science Digital Library

This site from the Exploratorium provides information on telescopes and observatories such as the Hubble Space Telescope that are being used to study spectra from space. Gamma-ray, x-ray, ultraviolet, and infrared spectra are all examined. The purpose and discoveries made by each observatory are included along with related hands-on activities like a liquid crystal IR detector activity.

Felter, Neil

2008-05-13

350

Libraries of Stellar Spectra  

NSDL National Science Digital Library

This is a guide to online and abstract libraries of stellar spectra. This reference list also includes information about the spectra of Late-M, L, and T Dwarf stars, Morgan-Keenan spectral classification, the solar spectrum, spectrophotometric atlases, and automated and neural network classification.

2005-04-25

351

Output Tube Emission Characteristics of Operational Radars.  

National Technical Information Service (NTIS)

This report contains the emission spectra of 19 different types of radars, selected to show the different emission spectrum characteristics produced by a variety of radar output tube technologies. The radars include examples of ground-based search, airpor...

R. J. Matheson, J. D. Smilley, G. D. Falcon, V. S. Lawrence

1982-01-01

352

Action spectra again?  

PubMed

Action spectroscopy has a long history and is of central importance to photobiological studies. Action spectra were among the first assays to point to chlorophyll as the molecule most responsible for plant growth and to DNA as the genetic material. It is useful to construct action spectra early in the investigation of new areas of photobiological research in an attempt to determine the wavelength limits of the radiation region causing the studied response. But due to the severe absorption of ultraviolet (UV) radiation by biological samples, UV action spectra were first limited to small cells (bacteria and fungi). Advances in techniques (e.g. single cell culture) and analysis allowed accurate action spectra to be reported even for mammalian cells. But precise analytical action spectra are often difficult to obtain when large, pigmented, or groups of cells are investigated. Here some action spectra are limited in interpretation and merely supply a wavelength vs effect curve. When polychromatic sources are employed, the interpretation of action spectra is even more complex and formidable. But such polychromatic action spectra can be more directly related to ambient responses. Since precise action spectra usually require the completion of a relatively large number of careful experiments using somewhat sophisticated equipment over a range of at least six wavelengths, they are often not pursued. But they remain central to the elucidation of the effect being studied. The worldwide community has agreed that stratospheric ozone is depleting, with the possibility of a consequent rise in the amount of UV-B (290-320 nm) reaching the earth's surface. It is therefore essential that new action spectra be completed for UV-B effects on a large variety of responses of human, animal, and aquatic plant systems. Combining these action spectra with the known amounts of UV-B reaching the biosphere can give rise to solar UV effectiveness spectra that, in turn, can give rise to estimates of effect. Preliminary estimates suggest that ozone layer depletion may seriously impact such important biological end-points as skin cancer, cataracts, the immune system, crop yields, and oceanic phytoplankton. So action spectra continue to play a central role in important photobiological research. PMID:1798760

Coohill, T P

1991-11-01

353

The ultraviolet spectra of the Jovian aurora  

SciTech Connect

The ultraviolet spectra of molecular hydrogen H{sub 2} due to electron impact excitation are calculated and compared with the high-resolution (0.56 A) spectra of the Jovian aurora obtained with the {ital Hubble} {ital Space} {ital Telescope} Goddard High-Resolution Spectrograph. All the observed features are reproduced by electron impact excitation emissions of H{sub 2}, and the predicted intensities agree well with the observed intensities. Accurate molecular parameters are used, and effects of secondary electrons are included. The auroral emissions are reproduced by energetic electron impact excitation of H{sub 2} with a temperature of 400{endash}600 K. Large temperature gradients occur with respect to altitude within the auroral emission regions. The auroral spectra contain a cascade contribution to the Lyman band emission from high-lying {ital E} and {ital F} states that are populated by the low-energy secondary electrons produced as the energetic auroral electrons slow down. {copyright} {ital 1996 The American Astronomical Society.}

Liu, W.; Dalgarno, A. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)] [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, Massachusetts 02138 (United States)

1996-08-01

354

Spectra over complex terrain  

SciTech Connect

Spectra have been measured over land downwind of a water surface, over hilltops and escarpments, and over rolling farmland. The following hypotheses can be used to explain the differences between these spectra. (1) For wavelengths short compared to the fetch over the new terrain, spectral densities are in equilibrium with the new terrain. (2) For wavelengths long compared to this fetch, spectral densities remain unchanged if the ground is horizontal. If the flow is over a steep hill, the low-frequency structure is modified by distortion of the mean flow, with the longitudinal component losing energy relative to the lateral and vertical components. Because vertical-velocity spectra contain relatively less low-frequency energy than horizontal-velocity spectra, energetic vertical-velocity fluctuations tend to be in equilibrium with local terrain.

Panofsky, H.A.; Larko, D.; Lipschutz, R.; Stone, G.

1981-01-01

355

8- to 13-micron spectra of asteroids  

NASA Astrophysics Data System (ADS)

It is pointed out that thermal emission from asteroids reaches a maximum in the 10- to 20-micron region. In connection with the present investigation, a uniform set of spectra was obtained in the 8- to 13-micron region for 12 asteroids (together with additional observations of 19 Fortuna). These spectra provide a potentially valuable data set for future use (e.g., with IRAS data). The main conclusion from the obtained results is that diagnostic emission features of the type observed by Feierberg et al. (1983) are not common in C- and M-type asteroids. Optical studies of 19 Fortuna do not reveal any unusual properties which distinguish it from other C-type asteroids observed.

Green, S. F.; Eaton, N.; Aitken, D. K.; Roche, P. F.; Meadows, A. J.

1985-05-01

356

HOTSPUR: gamma ray emission from spheres pulsed with D-T neutrons. I. Calibration of improved NE213 detector assembly. II. Comparison of TART/SANDYL electron recoil spectra to experiment; preliminary results  

SciTech Connect

The NE213 scintillator detector was modified so that the pulse height would be linear with electron energy over the full range of interest - up to 7.1 MeV. Absolute calibration was done with four different calibrated gamma sources. An average correction factor is obtained which normalizes SANDYL calculations with respect to the calibration experiments. The procedure for calculating neutron-induced gamma-ray output and electron recoil spectra is described, and experimental data from a number of spherical assemblies are given and compared to TART/SANDYL calculations. (LEW)

Goldberg, E.; Hansen, L.F.; Komoto, T.T.; Pohl, B.A.

1986-09-01

357

Multifrequency spectra of BL Lac objects  

NASA Technical Reports Server (NTRS)

A program to obtain simultaneous multifrequency spectra of BL Lacertae objects that are known X-ray sources is discussed. The IUE spectra are generally featureless and well-fitted by power law models. For the faintest exposures, Gaussian extraction of the spectrum can greatly impove the signal-to-noise. Most program objects vary in the ultraviolet, although the time scales are not known because of limited observing time. The broadband spectra of BL Lacs exhibit a range of characteristics but the curvature is always downward and the shape is generally smooth. This can be interpreted as synchrotron emission from a relativistic jet; different jet models are possible, and each allows a range of values for the bulk velocity, magnetic field strength, and electron density. Synchrotron models are not required, however an accretion disk model also gives a good fit to the ultraviolet-through-X-ray continuum.

Urry, C. M.; Kondo, Y.; Mufson, S. L.; Wandel, A.

1988-01-01

358

Near infrared and ultraviolet spectra of TLEs  

NASA Astrophysics Data System (ADS)

We have found that sprites, beads and halos have similar optical spectra, but measurable differences in the near IR and near UV spectra. In particular, near infrared (NIR) and ultraviolet (UV) spectra of sprites, halos and beads corresponding to the first (1PG) and second positive (2PG) bands of N2 have been calculated for different observation altitudes from mountains (3.25 km) to airplanes (14 km), balloons (35 km) and space (nadir) platforms. The calculated non-equilibrium vibrational distribution functions (VDF) of the N2(B3?g) states in halos and beads show that the calculated NIR emissions produced through strong N2-1PG (B3?g ? A3?u+) transitions differ from the calculated sprite spectral emission patterns at ˜888 nm but particularly pronounced differences are found in the NIR spectral region at ˜1046 nm and ˜1231 nm corresponding to the N2-1PG (0,0) and (0,1) transitions, respectively. The blue - near UV spectra from N2-2PG (C3?u ? B3?g) transitions in halos and beads also exhibits slightly different spectral features when compared to the blue - near UV spectrum of sprites for bands originating from higher v-levels (v > 0) although they might not be above electronic noise level to be distinguished.

Gordillo-Vázquez, F. J.; Luque, A.; Simek, M.

2012-05-01

359

Low energy X-ray spectra measured with a mercuric iodide energy dispersive spectrometer in a scanning electron microscope  

NASA Technical Reports Server (NTRS)

A mercuric iodide energy dispersive X-ray spectrometer, with Peltier cooling provided for the detector and input field effect transistor, has been developed and tested in a scanning electron microscope. X-ray spectra were obtained with the 15 keV electron beam. An energy resolution of 225 eV (FWHM) for Mn-K(alpha) at 5.9 keV and 195 eV (FWHM) for the Mg-K line at 1.25 keV has been measured. Overall system noise level was 175 eV (FWHM). The detector system characterization with a carbon target demonstrated good energy sensitivity at low energies and lack of significant spectral artifacts at higher energies.

Iwanczyk, J. S.; Dabrowski, A. J.; Huth, G. C.; Bradley, J. G.; Conley, J. M.

1986-01-01

360

WebSpectra  

NSDL National Science Digital Library

This site, created by Barry C. Fam and Craig A. Merlic of the University of California - Los Angeles, was established to provide chemistry students with a library of spectroscopy problems. Interpretation of spectra is a technique that requires practice - this site provides 1H NMR and 13C NMR, DEPT, COSY and IR spectra of various compounds for students to interpret. Hopefully, these problems will provide a useful resource to better understand spectroscopy. The page was given a "Top 5% Chemistry Site" award for its usefulness and content. This is a great resource for anyone interested in either biochemistry or chemistry.

Fam, Barry C.; Merlic, Craig A.

2009-05-07

361

Camera artifacts in IUE low-dispersion spectra  

NASA Technical Reports Server (NTRS)

Sky-background images obtained by the International Ultraviolet Explorer (IUE) were analyzed to study artificial spectral features (camera artifacts) in low-dispersion spectra. The artifacts mimic emission features and have been present in long-exposure spectra since the launch of the IUE satellite. The camera artifacts are strong in spectra characterized by long exposure times because they scale in time-integrated flux with the background level, which increases during the exposure due to camera phosphorescence. The artifacts cannot be detected in spectra obtained from short, direct exposures of flat-field lamps or standard stars. Plots of average sky-background spectra for the three operational IUE cameras (SWP, LWP, and LWR) are given to aid scientists in the identification of artifacts in their spectra.

Crenshaw, D. Michael; Norman, Dara J.; Bruegman, Otto W.

1990-01-01

362

Fluorescence bands in the FT-Raman spectra of some calcium minerals  

Microsoft Academic Search

FT-Raman spectra of some calcium phosphates, calcium carbonate and calcium hydroxide are reported. Comparing with dispersive Raman spectra, it is shown that some strong bands in the FT-Raman spectra of these compounds which have been erroneously assigned to Raman bands, are in fact fluorescence emission bands. The origin of these fluorescence bands have been discussed in terms of rare earth

A. Aminzadeh

1997-01-01

363

Disk-averaged synthetic spectra of Mars.  

PubMed

The principal goal of the NASA Terrestrial Planet Finder (TPF) and European Space Agency's Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earthsized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of a Mars-like planet to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra. We explore the detectability as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPFC) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model. This model uses observational data as input to generate a database of spatially resolved synthetic spectra for a range of illumination conditions and viewing geometries. The model was validated against spectra recorded by the Mars Global Surveyor-Thermal Emission Spectrometer and the Mariner 9-Infrared Interferometer Spectrometer. Results presented here include disk-averaged synthetic spectra, light curves, and the spectral variability at visible and mid-infrared wavelengths for Mars as a function of viewing angle, illumination, and season. We also considered the differences in the spectral appearance of an increasingly ice-covered Mars, as a function of spectral resolution, signal-to-noise and integration time for both TPF-C and TPFI/ Darwin. PMID:16078866

Tinetti, Giovanna; Meadows, Victoria S; Crisp, David; Fong, William; Velusamy, Thangasamy; Snively, Heather

2005-08-01

364

Cirrus Spectra of Low Surface Brightness Regions  

NASA Astrophysics Data System (ADS)

We have studied the galactic cirrus in low surface brightness regions using ISOPHOT raster maps at 90 microns, 150 microns and 180 microns. Observations are used to determine dust emission spectra and dust temperatures. The data extend to longer wavelengths than the IRAS observations. Compared with DIRBE data, the resolution and the sensitivity are better and this makes it possible to study faint cirrus emission in individual fields. We will discuss the calibration of the observations and present results of a comparison between ISOPHOT and DIRBE surface brightness values. The correspondence was found to be better than ~30%. At 90 microns the ISOPHOT surface brightnesses tend to be slightly higher than the DIRBE values while at longer wavelength the situation is reversed. Surface brightness variations caused by cirrus fluctuations make it possible to determine the spectrum of the dust emission. Cirrus spectra were obtained for six fields with surface brightnesses in the range 1--2 MJy sr-1 after the Zodiacal light and the contribution of extra-galactic sources have been subtracted. Assuming ?2 emissivity law the dust temperatures are in the range 18--20 K. Temperature variations can be seen even within individual fields. These values are higher than values from DIRBE but this can be explained by differences in the calibration.

Juvela, M.; Mattila, K.; Lemke, D.

365

Cassini UVIS observations of Titan nightglow spectra  

NASA Astrophysics Data System (ADS)

In this paper we present the first nightside EUV and FUV airglow limb spectra of Titan showing molecular emissions. The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed photon emissions of Titan's day and night limb-airglow and disk-airglow on multiple occasions, including during an eclipse observation. The 71 airglow observations analyzed in this paper show EUV (600-1150 Å) and FUV (1150-1900 Å) atomic multiplet lines and band emissions arising from either photoelectron induced fluorescence and solar photo-fragmentation of molecular nitrogen (N2) or excitation by magnetosphere plasma. The altitude of the peak UV emissions on the limb during daylight occurred inside the thermosphere at the altitude of the topside ionosphere (near 1000 km altitude). However, at night on the limb, a subset of emission features, much weaker in intensity, arise in the atmosphere with two different geometries. First, there is a twilight photoelectron-excited glow that persists with solar depression angle up to 25-30 degrees past the terminator, until the solar XUV shadow height passes the altitude of the topside ionosphere (1000-1200 km). The UV twilight glow spectrum is similar to the dayglow but weaker in intensity. Second, beyond 120° solar zenith angle, when the upper atmosphere of Titan is in total XUV darkness, there is indication of weak and sporadic nightside UV airglow emissions excited by magnetosphere plasma collisions with ambient thermosphere gas, with similar N2 excited features as above in the daylight or twilight glow over an extended altitude range.

Ajello, Joseph M.; West, Robert A.; Gustin, Jacques; Larsen, Kristopher; Stewart, A. Ian F.; Esposito, Larry W.; McClintock, William E.; Holsclaw, Gregory M.; Bradley, E. Todd

2012-12-01

366

Observed Barium Emission Rates  

NASA Technical Reports Server (NTRS)

The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.

Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.

1993-01-01

367

Temperature effect on single chain MEH-PPV spectra  

NASA Astrophysics Data System (ADS)

We report single molecule photoluminescence spectra of poly[2-methoxy-5-(2 '-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) in PMMA-matrix at 293 and 20 K with 90 s acquisition time. All spectra at 293 K are very similar, contrary to literature results with acquisition times <5 s. We propose that fluctuations of conformations with distinct emission properties cause broadening of the spectra and reduce the differences in fluorescence spectra between separate chains. At 20 K the spectrum from a single chain consists of a few narrow peaks with absence of major spectral evolution within tens-of-minutes. The emission from distinct chains is spread over 3000 cm -1 characterizing different frozen conformations.

Rønne, C.; Trägårdh, J.; Hessman, D.; Sundström, V.

2004-04-01

368

Parmeterization of spectra  

NASA Technical Reports Server (NTRS)

Following reception and analog to digital conversion (A/D) conversion, atmospheric radar backscatter echoes need to be processed so as to obtain desired information about atmospheric processes and to eliminate or minimize contaminating contributions from other sources. Various signal processing techniques have been implemented at mesosphere-stratosphere-troposphere (MST) radar facilities to estimate parameters of interest from received spectra. Such estimation techniques need to be both accurate and sufficiently efficient to be within the capabilities of the particular data-processing system. The various techniques used to parameterize the spectra of received signals are reviewed herein. Noise estimation, electromagnetic interference, data smoothing, correlation, and the Doppler effect are among the specific points addressed.

Cornish, C. R.

1983-01-01

369

Band structure and CK ? emission of ultrathin nanotubes  

Microsoft Academic Search

An attempt is made to calculate the energy bands and spectra of the characteristic CK\\u000a ? emission of small-diameter carbon nanotubes. The calculated spectra for the nanotubes are compared with similar spectra for\\u000a graphite monolayers used as a test object and with known experimental results for nanotubes. It is concluded that the x-ray\\u000a emission spectra can be used to identify

M. M. Brzhezinskaya; E. M. Baitinger; V. I. Kormilets

2000-01-01

370

Nuclear-structure effects in proton evaporation spectra  

NASA Astrophysics Data System (ADS)

Energy spectra and angular distributions of evaporated protons from the reaction 52Cr(34S, 2p2n)82Sr at 130 MeV were measured in coincidence with discrete ? transitions. Large shifts and changes in the shape of the proton spectra were observed when high-spin states in different rotational bands are populated. They are interpreted as due to near-yrast stretched proton emission, which preferentially populates the yrast band by subbarrier protons.

Sarantites, D. G.; Baktash, C.; Nicolis, N. G.; Garcia-Bermudez, G.; Abenante, V.; Beene, J. R.; Johnson, N. R.; Halbert, M. L.; Hensley, D. C.; McGowan, F. K.; Griffin, H. C.; Lee, I. Y.; Majka, Z.; Riley, M. A.; Semkow, T. M.; Stracener, D. W.; Virtanen, A.

1990-04-01

371

The ultraviolet spectra of R and N type stars  

NASA Technical Reports Server (NTRS)

Low dispersion long wave radiation spectra of three early N-type carbon stars (BL Orionis, TX Piscium and T Indi) obtained with the IUE are discussed. N-star spectra were compared with IUE observations of late M-type stars and several differences were noted. The Mg II and C II chromospheric emission lines reported are the first convincing detection of a 10,000-20,000 K chromosphere in the N stars.

Obrien, G. T.; Johnson, H. R.

1982-01-01

372

Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra  

E-print Network

We investigate the signature of the photospheric albedo contribution in solar flare hard X-ray spectra, the effect of low energy cutoffs in electron spectra, and the directivity of hard X-ray emission. Using Ramaty High Energy Solar Spectroscopic Imager (RHESSI) flare data we perform a statistical analysis of spatially integrated spectra and positions of solar flares. We demonstrate clear centre-to-limb variation of photon spectral indices in the 15-20 keV energy range and a weaker dependency in the 20-50 keV range which is consistent with photospheric albedo as the cause. The results also suggest that low-energy cutoffs sometimes inferred in mean electron spectra are an artefact of albedo. We also derive the anisotropy (ratio of downward/observer directed photons) of hard X-ray emission in the 15-20 keV range for various heliocentric angles.

J. Kasparova; E. P. Kontar; J. C. Brown

2007-01-30

373

Infrared spectra of protostellar collapse  

NASA Technical Reports Server (NTRS)

Theoretical models of the formation of low mass stars by cloud collapse predict that OI(63 micrometers) and IR rotational lines of CO and H2O dominate the cooling in the freefalling region 10-1000 AU from the protostar. The freefalling gas supersonically hits the protoplanetary disk orbiting the protostar, forming an accretion shock with strong IR emission in rotational lines of H2O and OH, and OI(63 microns). The accretion shock spectra and line profiles depend on the mass flux through the shock and the typical distance r-bar at which the freefalling gas strikes the disk. The line widths are of order the Keplerian speed, or approx. 10(r-bar/10AU)(exp -0.5) km/s, for the accretion shock lines, and less for the lines from the infalling gas. Measurements of the IR line fluxes and profiles from the freefalling gas and the accretion shock diagnoses how a protostar and disk are formed and requires high sensitivity and high spectral and spatial resolving power. SOFIA will be the optimum observatory for many of these lines, although ISO will contribute and the KAO may make a few pioneering detections.

Hollenbach, David J.; Ceccarelli, Cecilia; Neufeld, David A.; Tielens, Alexander G. G. M.

1995-01-01

374

Spectra of Gas Discharges  

NSDL National Science Digital Library

This resource provides pictures of the emission spectrum of range of atomic elements. These elements consist of: hydrogen, helium, lithium, oxygen, carbon, nitrogen, neon, magnesium, silicon, sulfur, iron, aluminum, calcium, argon, sodium, krypton, xenon, barium and strontium. Displays include instrumental and intrinsic broadening. The data from which the pictures are created is also available.

Talbot, John; Varashni, Yatendra

2009-03-26

375

X-ray Grating Spectra of Classical and Recurrent Novae  

NASA Astrophysics Data System (ADS)

We present high resolution XMM-Newton RGS grating spectra of recent recurrent novae of the last 5 years, taken after the outburst in the supersoft X-ray phase. We show cases that can be fitted with white dwarf static atmospheric models and cother examples that should be fitted with white dwarf "wind" atmospheric models. We also show how to disentagle emission line spectra produced in he ejecta from the hot and luminous white dwarf atmosphere. We discuss innovative ways to examine the spectra taking into account the secular evolution, the accretion history, and optical observations done immediately after the outburst.

Orio, M.; Behar, E.; Polina, Z.

2014-07-01

376

Measurements and parameterization of neutron energy spectra from targets bombarded with 120 GeV protons  

NASA Astrophysics Data System (ADS)

The energy spectra of neutrons were measured by a time-of-flight method for 120 GeV protons on thick graphite, aluminum, copper, and tungsten targets with an NE213 scintillator at the Fermilab Test Beam Facility. Neutron energy spectra were obtained between 25 and 3000 MeV at emission angles of 30°, 45°, 120°, and 150°. The spectra were parameterized as neutron emissions from three moving sources and then compared with theoretical spectra calculated by PHITS and FLUKA codes. The yields of the theoretical spectra were substantially underestimated compared with the yields of measured spectra. The integrated neutron yields from 25 to 3000 MeV calculated with PHITS code were 16-36% of the experimental yields and those calculated with FLUKA code were 26-57% of the experimental yields for all targets and emission angles.

Kajimoto, T.; Shigyo, N.; Sanami, T.; Iwamoto, Y.; Hagiwara, M.; Lee, H. S.; Soha, A.; Ramberg, E.; Coleman, R.; Jensen, D.; Leveling, A.; Mokhov, N. V.; Boehnlein, D.; Vaziri, K.; Sakamoto, Y.; Ishibashi, K.; Nakashima, H.

2014-10-01

377

Novel insights into anoxic/aerobic(1)/aerobic(2) biological fluidized-bed system for coke wastewater treatment by fluorescence excitation-emission matrix spectra coupled with parallel factor analysis.  

PubMed

Fluorescence spectroscopy coupled with parallel factor analysis (PARAFAC) was applied to investigate the contaminant removal efficiency and fluorescent characteristic variations in a full scale coke wastewater (CWW) treatment plant with a novel anoxic/aerobic(1)/aerobic(2) (A/O(1)/O(2)) process, which combined with internal-loop fluidized-bed reactor. Routine monitoring results indicated that primary contaminants in CWW, such as phenols and free cyanide, were removed efficiently in A/O(1)/O(2) process (removal efficiency reached 99% and 95%, respectively). Three-dimensional excitation-emission matrix fluorescence spectroscopy and PARAFAC identified three fluorescent components, including two humic-like fluorescence components (C1 and C3) and one protein-like component (C2). Principal component analysis revealed that C1 and C2 correlated with COD (correlation coefficient (r)=0.782, p<0.01 and r=0.921, p<0.01), respectively) and phenols (r=0.796, p<0.01 and r=0.914, p<0.01, respectively), suggesting that C1 and C2 might be associated with the predominating aromatic contaminants in CWW. C3 correlated with mixed liquor suspended solids (r=0.863, p<0.01) in fluidized-bed reactors, suggesting that it might represent the biological dissolved organic matter. In A/O(1)/O(2) process, the fluorescence intensities of C1 and C2 consecutively decreased, indicating the degradation of aromatic contaminants. Correspondingly, the fluorescence intensity of C3 increased in aerobic(1) stage, suggesting an increase of biological dissolved organic matter. PMID:25065804

Ou, Hua-Se; Wei, Chao-Hai; Mo, Ce-Hui; Wu, Hai-Zhen; Ren, Yuan; Feng, Chun-Hua

2014-10-01

378

The high energy emission line spectrum of NGC 1068  

NASA Astrophysics Data System (ADS)

We present and discuss the high energy (E>4 keV) XMM-Newton spectrum of the Seyfert 2 galaxy, NGC 1068. Possible evidence for flux variability in both the neutral and ionized reflectors with respect to a BeppoSAX observation taken 3.5 years before is found. Several Fe and Ni emission lines, from both neutral and highly ionized material, are detected. The intensity of the iron K\\alpha Compton shoulder implies that the neutral reflector is Compton-thick, likely the visible inner wall of the N_H > 1025 cm-2 absorber. From the equivalent width of the ionized iron lines a column density of a few × 1021 cm-2 is deduced for the hot ionized reflector. Finally, an iron (nickel) overabundance, when compared to solar values, of about 2 (4) with respect to lower Z elements, is found.

Matt, G.; Bianchi, S.; Guainazzi, M.; Molendi, S.

2004-01-01

379

Ultraviolet spectra and chromospheres of cool carbon stars  

NASA Technical Reports Server (NTRS)

The authors assemble and discuss all available low-resolution IUE spectra of N-type carbon stars - including TW Hor, BL Ori, UU Aur, NP Pup, U Hya, T Ind, and TX Psc. Identification of spectral features is aided by a composite spectrum. Shortward of 2850 A only emission lines of C II, Mg II, Al II, and Fe II are seen, while the spectrum longward of 2850 A appears to be a photospheric absorption spectrum with a few superposed emission lines of Fe II. The most prominent absorption features are due to Fe I, CH, and CaCl. The emission feature at 2325 A, second only to Mg II in strength, is conclusively identified as C II (UV 0.01). Ultraviolet spectra of N-type carbon stars are similar to, though the emission-line fluxes are generally weaker than, those of the coolest M-giant stars available, such as HD 18191 (M6 III).

Johnson, Hollis R.; Luttermoser, Donald G.

1987-01-01

380

Spectra From Space : Main Menu  

NSDL National Science Digital Library

On-line science lesson (grades 7 - 9) - students learn about satellite spectra research, electromagnetic spectrum, do hands-on activities. In this lesson students investigate satellite missions operating in four electromagnetic bands. Students learn about spectra and why satellites gather certain kinds of spectra from space by using the Internet and doing hands-on activities. From the University of California, Berkeley.

1997-01-01

381

Two-photon spectra of quantum emitters  

NASA Astrophysics Data System (ADS)

We apply our recently developed theory of frequency-filtered and time-resolved N-photon correlations (del Valle et al 2012 Phys. Rev. Lett. 109 183601) to study the two-photon spectra of a variety of systems of increasing complexity: single-mode emitters with two limiting statistics (one harmonic oscillator or a two-level system) and the various combinations that arise from their coupling. We consider both the linear and nonlinear regimes under incoherent excitation. We find that even the simplest systems display a rich dynamics of emission, not accessible by simple single-photon spectroscopy. In the strong coupling regime, two-photon emission processes involving virtual states are revealed. Furthermore, two general results are unravelled by two-photon correlations with narrow linewidth detectors: (i) filtering-induced bunching and (ii) breakdown of the semi-classical theory. We show how to overcome the latter in a fully quantized picture.

Gonzalez-Tudela, Alejandro; Laussy, Fabrice P.; Tejedor, Carlos; Hartmann, Michael J.; del Valle, Elena

2013-03-01

382

The radio spectra of galactic nuclei  

E-print Network

We present a model for the inverted radio spectra of active active galactic nuclei as well as the central regions of normal galaxies. The model is based on the unified scenario for active galaxies, stating that the central engines of active galaxies consists of a supermassive black hole surrounded by an accretion disk and a radio jet. The nuclei of normal (i. e. less active) galaxies are supposed to be scaled-down versions of the same phenomenon. We show that the radio emission of a jet component, becoming optically thin to the radio emission of a monoenergetic pair plasma at decreasing frequencies as it moves outward and expands, is well suited to explain the observational results. We present a model calculation for the special case of the nucleus of M~81.

M. Boettcher; H. -P. Reuter; H. Lesch

1997-07-31

383

AKN 564: An Unusual Component in the X-ray Spectra of NLSy1 Galaxies  

NASA Technical Reports Server (NTRS)

We present an ASCA observation of the narrow-line Seyfert l (NLSyl) Arakelian 564. The X-ray light curve shows rapid variability, but no evidence for energy-dependence to these variations, within the 0.6 - 10 keV bandpass. A strong (EW approximately 70 eV) spectral feature is observed close to 1 keV. A similar feature has been observed in TON S180, another member of the NLSyl class of objects, but has not been observed in broad-line Seyfert galaxies. The feature energy suggests a large contribution from Fe L-shell lines but its intensity is difficult to explain in terms of emission and/or absorption from photoionized gas. The models which predict most emission at 1 keV are characterized by extreme values of column density, Fe abundance and ionization parameter. Models based on gas in thermal equilibrium with kT approximately l keV provide an alternative parameterization of the soft spectrum. The latter may be interpreted as the hot intercloud medium, undergoing rapid cooling and producing strong Fe L-shell recombination lines. In all cases the physical conditions are rather different from those observed in broad-line Seyferts. The hard X-ray spectrum shows a broad and asymmetric Fe K(alpha) line of large equivalent width (approximately 550 eV) suggestive of significant emission from the inner accretion disk. The profile can be explained by a neutral disk viewed at approximately 60 deg to the line-of-sight, contrary to the hypothesis that NLSyls are viewed pole-on. The large EW of this line, the strong 1 keV emission and the strong optical Fe emission lines all suggest an extreme Fe abundance in this and perhaps other NLSyls.

Turner, T. J.; George, I. M.; Netzer, Hagai

1999-01-01

384

Inelastic scattering effects on photoelectron spectra and ionospheric electron temperature  

Microsoft Academic Search

Three sets of inelastic scattering cross sections have been used by various investigators in energy degradation computations of photoelectrons. The effects of the three sets upon photoelectron spectra in the ionosphere, electron heating rates and temperature, and dayglow emissions are examined for solar minimum and solar maximum conditions. Comparison of individual cross sections shows large differences among the three sets

K. Stamnes; M. H. Rees

1983-01-01

385

Titan's atmospheric structure from Voyager 2 infrared spectra  

Microsoft Academic Search

Voyager 2 flew by Titan 9 months after Voyager 1 at a distance from its centre 100 times greater at closest approach (27 August 1981). A total of 115 infrared spectra are analysed here (taken mainly between 15 deg S and 60 deg N of latitude at emission angles less than 50 deg). The projected field of view of IRIS

B. Letourneur; A. Coustenis

1993-01-01

386

Non-thermal radiative pair plasmas: processes and spectra  

E-print Network

We study the emission and absorption spectra due to various photon and pair processes in a non-equilibrium pair plasma containing a significant density of photons. We present here some preliminary results from Monte-Carlo simulations. These investigations are likely to be useful in understanding the radiation and relaxation mechanisms in non-thermal gamma-ray sources in astrophysics.

Ravi P. Pilla; Jacob Shaham

1995-05-17

387

The Physical Interpretation of Optical Spectra of High Redshift Galaxies  

E-print Network

by the stellar population and the surrounding neutral hydrogen. The emitted photons ionize the neutral gas and red spectra correspond to emission line, intermediate and early-type galaxies respectively. But galaxy, resulting in absorption features, and then when the gas recombines a photon is re-emitted, resulting

Tittley, Eric

388

Dust Spectra from Above and Below  

NASA Technical Reports Server (NTRS)

Spectra of martian dust taken by the Mars Exploration Rover Spirit's mini-thermal emission spectrometer are compared to that of the orbital Mars Global Surveyor's thermal emission spectrometer. The graph shows that the two instruments are in excellent agreement.

Rover Senses Carbon Dioxide [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data acquired on Mars from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signature of carbon dioxide. Carbon dioxide makes up the bulk of the thin martian atmosphere.

Rover Senses Silicates [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data acquired on Mars by the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signature of silicates - a group of minerals that form the majority of Earth's crust. Minerals called feldspars and zeolites are likely candidates responsible for this feature.

Rover Senses Bound Water [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data acquired on Mars from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signature of an as-of-yet unidentified mineral that contains bound water in its crystal structure. Minerals such as gypsum and zeolites are possible candidates.

Rover Senses Carbonates [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signatures of carbonates - minerals common to Earth that form only in water. The detection of trace amounts of carbonates on Mars may be due to an interaction between the water vapor in the atmosphere and minerals on the surface.

2004-01-01

389

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

NASA Technical Reports Server (NTRS)

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.

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

1998-01-01

390

SPECTRA OF CEMENTED, HEMATITE-RICH MATERIAL AND TES SPECTRA OF SINUS MERIDIANI, MARS. L. E. Kirkland1  

E-print Network

.g. duricrust and desert varnish) in order to determine whether they may match the spectra recorded of Mars called "reststrahlen bands." In the case of emission, the surface of a body reflects radiance inward. This occurs for smooth-surfaced cemented, fine particles (e.g. as can occur in duricrust and desert varnish

Kirkland, Laurel

391

THERMAL NEUTRON SPECTRA IN GRAPHITE  

Microsoft Academic Search

A pulsed, high-current, electron linear accelerator is used to excite ; thermal-neutron spectra in a graphite asemmbly. The steady-state energy spectra ; of neutrons are measured at several temperatures by pulsed-beam time-of-flight ; techniques. The measured spectra are compared with theoretical predictions which ; use free- and bound-carbon scattering kernels. The scattering kernel for carbon ; bound in graphite is

D. E. Parks; J. R. Beyster; N. F. Wikner

1962-01-01

392

Ion Signatures in Supernova Spectra  

E-print Network

A systematic survey of ions that could be responsible for features in the optical spectra of supernovae is carried out. Six different compositions that could be encountered in supernovae are considered. For each composition, the LTE optical depth of one of the strongest optical lines of each ion is plotted against temperature. For each ion that can realistically be considered as a candidate to produce identifiable features in supernova spectra, a sample synthetic spectrum is displayed. The optical depth plots and the synthetic spectra can provide guidance to studies of line identifications in the optical spectra of all types of supernovae during their photospheric phases.

K. Hatano; D. Branch; A. Fisher; J. Deaton; E. Baron

1998-09-18

393

Interpreting Chromosome Aberration Spectra  

NASA Technical Reports Server (NTRS)

Ionizing radiation can damage cells by breaking both strands of DNA in multiple locations, essentially cutting chromosomes into pieces. The cell has enzymatic mechanisms to repair such breaks; however, these mechanisms are imperfect and, in an exchange process, may produce a large-scale rearrangement of the genome, called a chromosome aberration. Chromosome aberrations are important in killing cells, during carcinogenesis, in characterizing repair/misrepair pathways, in retrospective radiation biodosimetry, and in a number of other ways. DNA staining techniques such as mFISH ( multicolor fluorescent in situ hybridization) provide a means for analyzing aberration spectra by examining observed final patterns. Unfortunately, an mFISH observed final pattern often does not uniquely determine the underlying exchange process. Further, resolution limitations in the painting protocol sometimes lead to apparently incomplete final patterns. We here describe an algorithm for systematically finding exchange processes consistent with any observed final pattern. This algorithm uses aberration multigraphs, a mathematical formalism that links the various aspects of aberration formation. By applying a measure to the space of consistent multigraphs, we will show how to generate model-specific distributions of aberration processes from mFISH experimental data. The approach is implemented by software freely available over the internet. As a sample application, we apply these algorithms to an aberration data set, obtaining a distribution of exchange cycle sizes, which serves to measure aberration complexity. Estimating complexity, in turn, helps indicate how damaging the aberrations are and may facilitate identification of radiation type in retrospective biodosimetry.

Levy, Dan; Reeder, Christopher; Loucas, Bradford; Hlatky, Lynn; Chen, Allen; Cornforth, Michael; Sachs, Rainer

2007-01-01

394

Analysis of Jovian Auroral H Ly-? Emission (1981–1991)  

Microsoft Academic Search

We present a new analysis of jovian auroral IUE spectra covering the period from 1981 to 1991. To extract integrated auroral H Ly-? emission from these spectra we have developed a new extraction method that bins signal with wavelength while preserving the spatial information provided by the IUE imaging spectrograph. This separates auroral emission from background sources including the jovian

Walter Harris; John T. Clarke; Melissa A. McGrath; Gilda E. Ballester

1996-01-01

395

HEAO 1 observations of X-ray emission from flares on dMe stars  

NASA Technical Reports Server (NTRS)

The paper reports the detection of two X-ray flares from each of the nearby dMe stars, AT Mic and AD Leo, with the A-2 experiment on board HEAO 1. A spectrum obtained during the brighter AT Mic flare, the first X-ray spectrum of a stellar flare, is well matched by a thermal model with a temperature 3 x 10 to the 7 K and an iron K-alpha emission line. The X-ray luminosities derived are in the range 1.3-16 x 10 to the 30th ergs/s, while emission measures are in the range 1.1-14 x 10 to the 53rd/cu cm. The estimated Lx/Lopt ratios exceed unity and are inconsistent with Mullan's flare model. Several scenarios to explain this discrepancy are proposed.

Kahn, S. M.; Mason, K. O.; Bowyer, C. S.; Linsky, J. L.; Haisch, B. M.; White, N. E.; Pravdo, S. H.

1979-01-01

396

EFFECTS OF FORSTERITE GRAIN SHAPE ON INFRARED SPECTRA  

SciTech Connect

The Infrared Space Observatory (ISO) detected several sharp infrared features around young stars, comets, and evolved stars. These sharp features were identified as Mg-rich crystalline silicates of forsterite and enstatite by comparison with spectra from laboratory data. However, certain infrared emission bands in the observed spectra cannot be identified because they appear at slightly shorter wavelengths than the peaks in forsterite laboratory spectra, where the shapes of forsterite particles are irregular. To solve this problem, we measured infrared spectra of forsterite grains of various shapes (irregular, plate-like with no sharp edges, elliptical, cauliflower, and spherical) in the infrared spectral region between 5 and 100 mum. The spectra depend on particle shape. The spectra of the 11, 19, 23, and 33 mum bands, in particular, are extremely sensitive to particle shape, whereas some peaks such as the 11.9, 49, and 69 mum bands remained almost unchanged despite different particle shapes. This becomes most evident from the spectra of near-spherical particles produced by annealing an originally amorphous silicate sample at temperature from 600 to 1150 deg. C. The spectra of these samples differ strongly from those of other ones, showing peaks at much shorter wavelengths. At a higher annealing temperature of 1200 deg. C, the particle shapes changed drastically from spherical to irregular and the spectra became similar to those of forsterite particles with irregular shapes. Based on ISO data and other observational data, the spectra of outflow sources and disk sources may correspond to differences in forsterite shape, and further some unidentified peaks, such as those at 32.8 or 32.5 mum, may be due to spherical or spherical-like forsterite.

Koike, C.; Imai, Y.; Chihara, H.; Murata, K.; Tsuchiyama, A. [Department of Earth and Space Science, Osaka University, Toyonaka 560-0043 (Japan); Suto, H. [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI (United States); Tachibana, S. [Department of Earth and Planetary Science, University of Tokyo, Tokyo 113-0033 (Japan); Ohara, S., E-mail: koike@astroboy.ess.sci.osaka-u.ac.j [Joining and Welding Research Institute, Osaka University, Ibaraki 567-0047 (Japan)

2010-02-01

397

Polarization effects in cutaneous autofluorescent spectra  

NASA Astrophysics Data System (ADS)

Used polarized light for fluorescence excitation one could obtain response related to the anisotropy features of extracellular matrix. The fluorophore anisotropy is attenuated during lesions' growth and level of such decrease could be correlated with the stage of tumor development. Our preliminary investigations are based on in vivo point-by-point measurements of excitation-emission matrices (EEM) from healthy volunteers skin on different ages and from different anatomical places using linear polarizer and analyzer for excitation and emission light detected. Measurements were made using spectrofluorimeter FluoroLog 3 (HORIBA Jobin Yvon, France) with fiber-optic probe in steady-state regime using excitation in the region of 280-440 nm. Three different situations were evaluated and corresponding excitation-emission matrices were developed - with parallel and perpendicular positions for linear polarizer and analyzer, and without polarization of excitation and fluorescence light detected from a forearm skin surface. The fluorescence spectra obtained reveal differences in spectral intensity, related to general attenuation, due to filtering effects of used polarizer/analyzer couple. Significant spectral shape changes were observed for the complex autofluorescence signal detected, which correlated with collagen and protein cross-links fluorescence, that could be addressed to the tissue extracellular matrix and general condition of the skin investigated, due to morphological destruction during lesions' growth. A correlation between volunteers' age and the fluorescence spectra detected was observed during our measurements. Our next step is to increase developed initial database and to evaluate all sources of intrinsic fluorescent polarization effects and found if they are significantly altered from normal skin to cancerous state of the tissue, this way to develop a non-invasive diagnostic tool for dermatological practice.

Borisova, E.; Angelova, L.; Jeliazkova, Al.; Genova, Ts.; Pavlova, E.; Troyanova, P.; Avramov, L.

2014-05-01

398

How Astronomers Use Spectra to Learn About the Sun and Other Stars  

NSDL National Science Digital Library

This is a booklet about spectra and their usefulness to astronomers. Learners will read about the electromagnetic spectrum, how atomic physics is used to obtain information out of stellar spectra, and how the Doppler effect is used to measure stellar motions. An activity at the end allows learners to analyze and identify several emission lines in the spectrum of the Sun.

399

Emission reduction  

NASA Technical Reports Server (NTRS)

Control of the gaseous pollutant emissions of aircraft engines is considered in terms of the emission standards for six classes of aircraft engines. Emphasis is placed on combustor design concepts to significantly reduce emissions levels and lean-burning techniques to lower flame temperature, to reduce the oxides of nitrogen in the gaseous emissions.

Petrash, D. A.; Diehl, L. A.; Jones, R. E.; Mularz, E. J.

1979-01-01

400

Projecting Spectra for Classroom Investigations.  

ERIC Educational Resources Information Center

Describes an inexpensive spectrum projector that makes high-dispersion, high-efficiency diffraction gratings using a holographic process. Discusses classroom applications such as transmission spectra, absorption spectra, reflection characteristics of materials, color mixing, florescence and phosphorescence, and break up spectral colors. (MDH)

Sadler, Philip

1991-01-01

401

Two components in meteor spectra  

Microsoft Academic Search

Through an analysis of fireball spectra it was found that meteor heads consist of two parts with quite different temperatures. The spectra of both parts can be fitted with a simple thermal equilibrium model. The temperature of the main spectrum is about 4000 K, and that of the second spectrum is about 10,000 K. There is little evidence for a

Jiri Borovicka

1994-01-01

402

The Ultraviolet Emission Spectra of AN HII Region  

NASA Astrophysics Data System (ADS)

ONE OF THE ADVANTAGES OF THE NEW INSTRUMENTS SUCH AS THE HUBBLE SPACE TELESCOPE IS TO BE ABLE TO STUDY THE UNIVERSE AT WAVELENGTHS PREVIOUSLY UNOBSERVABLE FROM UNDER THE EARTH'S ATMOSPHERE. ONE THE THESE IS THE UV REGION OF THE STECTRUM. USING HST'S FOS, I WOULD LIKE TO TAKE A UV SPETRUM OF AN HII REGION, M8, THE LAGOON NEBULA (HOURGLASS REGION). HII REGIONS ARE AREAS OF STARBIRTH AND ARE SAMPLES OF THE INTERSTELLAR MATTER OUT OF WHICH STARS ARE BEING BORN. HOT, YOUNG O STARS WHICH RADIATE STRONGLY IN THE UV ARE EMBEDDED IN M8. MANY EMSSION LINES ARE EXPECTED BETWEEN 912-3300 ANGTROMS. USING WF/PC, AN IMAGE OF THE HOURGALSS WILL BE TAKEN LOOKING FOR FILIMENTARY STRUCTURE AND NEW BORN STARS.

Cox, Nancy

1991-07-01

403

The Ultraviolet Emission Spectra of AN HII Region  

Microsoft Academic Search

ONE OF THE ADVANTAGES OF THE NEW INSTRUMENTS SUCH AS THE HUBBLE SPACE TELESCOPE IS TO BE ABLE TO STUDY THE UNIVERSE AT WAVELENGTHS PREVIOUSLY UNOBSERVABLE FROM UNDER THE EARTH'S ATMOSPHERE. ONE THE THESE IS THE UV REGION OF THE STECTRUM. USING HST'S FOS, I WOULD LIKE TO TAKE A UV SPETRUM OF AN HII REGION, M8, THE LAGOON NEBULA

Nancy Cox

1992-01-01

404

RELATIONSHIP BETWEEN THE ABSORPTION AND EMISSION SPECTRA AND  

E-print Network

(see equation 3 in text) to suspensions of Chlorella, Porphyridium, and Anacystis and to chlorophyll with frequency. In Chlorella (green alga) a sharp drop of '(iv) is indicated towards the lower frequencies

Govindjee

405

Orbits and emission spectra from the 2014 Camelopardalids  

E-print Network

We have analyzed the meteor activity associated with meteoroids of fresh dust trails of Comet 209P/LINEAR, which produced an outburst of the Camelopardalid meteor shower (IAU code #451, CAM) in May 2014. With this aim, we have employed an array of high-sensitivity CCD video devices and spectrographs deployed at 10 meteor observing stations in Spain in the framework of the Spanish Meteor Network (SPMN). Additional meteoroid flux data were obtained by means of two forward-scatter radio systems. The observed peak zenithal hourly rate (ZHR) was much lower than expected, of around 20 meteors h-1. Despite of the small meteor flux in the optical range, we have obtained precise atmospheric trajectory, radiant and orbital information for 11 meteor and fireball events associated with this stream. The ablation behaviour and low tensile strength calculated for these particles reveal that Camelopardalid meteoroids are very fragile, mostly pristine aggregates with strength similar to that of the Orionids and the Leonids. T...

Madiedo, José M; Zamorano, Jaime; Izquierdo, Jaime; de Miguel, Alejandro Sánchez; Ocaña, Francisco; Ortiz, José L; Espartero, Francisco; Morillas, Lorenzo G; Cardeñosa, David; Moreno-Ibáñez, Manuel; Urzáiz, Marta

2014-01-01

406

Depleted uranium ({sub 92}U{sup 238}) induced preionization for enhanced and reproducible x-ray emission from plasma focus  

SciTech Connect

The effect of preionization induced by depleted uranium ({sub 92}U{sup 238}) around the insulator sleeve on the x-ray emission of (2.3-3.9 kJ) plasma focus device is investigated by employing Quantrad Si p-i-n diodes and a multipinhole camera. X-ray emission in 4{pi} geometry is measured as a function of charging voltage with and without preionization. It is found that the preionization enhances Cu K{alpha} and total x-ray yield about 100%, broadens the x-ray emission pressure range and x-ray pulse width, and improves shot to shot reproducibility of plasma focus operation. The pinhole images of x-ray emitting zones indicate that dominant x-ray emission is from the anode tip.

Ahmad, S.; Shafiq, M.; Zakaullah, M.; Waheed, A. [Department of Physics, Quaid-i-Azam University, 45320 Islamabad (Pakistan); PINSTECH, P.O. Box 1331, 44000 Islamabad (Pakistan)

2006-08-07

407

The Berlin emissivity database (BED)  

NASA Astrophysics Data System (ADS)

Remote-sensing infrared spectroscopy is the principal field of investigation for planetary surfaces composition. Past, present and future missions to the solar system bodies include in their payload, instruments measuring the emerging radiation in the infrared range. Apart from measuring the reflected radiance, more and more spacecrafts are equipped with instruments measuring directly the emitted radiation from the planetary surface. The emitted radiation is not only a function of the composition of the material but also of its texture and especially the grain size distribution. For the interpretation of the measured data an emissivity spectral library of planetary analogue materials in grain size fractions appropriate for planetary surfaces is needed. The Berlin emissivity database (BED) presented here is focused on relatively fine-grained size separates, providing thereby a realistic basis for the interpretation of thermal emission spectra of planetary regoliths. The BED is therefore complimentary to existing thermal emission libraries, like the ASU library for example. BED currently contains emissivity spectra of plagioclase and potassium feldspars, low Ca and high Ca pyroxenes, olivine, elemental sulfur, Martian analogue minerals and volcanic soils, and a lunar highland soil sample measured in the wavelength range from 7 to 22 ?m as a function of particle size. For each sample we measured the spectra of four particle size separates ranging from <25 to 250 ?m. The device we used is built at DLR (Berlin) and is coupled to a Fourier-transform infrared spectrometer Bruker IFS 88 purged with dry air and equipped with a nitrogen-cooled MCT detector. All spectra were acquired with a spectral resolution of 4 cm -1. We are currently working on upgrading our emissivity facility. A new spectrometer (Bruker VERTEX 80 V) and new detectors will allow us to measure the emissivity of samples in the wavelength range from 1 to 50 ?m in a vacuum environment. This will be particularly important for the interpretation of the MERcury Thermal Infrared Imaging Spectrometer (MERTIS) data.

Maturilli, A.; Helbert, J.; Moroz, L.

2008-03-01

408

Composite Spectra in Merging U/LIRGs Caused by Shocks  

NASA Astrophysics Data System (ADS)

We present a key result from our optical integral field spectroscopic survey of 27 nearby ultraluminous and luminous infrared galaxies (U/LIRGs) from the Great Observatory All-Sky LIRG Survey. Using spatially resolved multi-component emission line fitting to trace the emission line ratios and velocity dispersion of the ionized gas, we quantify for the first time the widespread shock ionization in gas-rich merging U/LIRGs. Our results show a fractional contribution to the total observed H? flux from radiative shocks increasing from a few percent during early merger stages to upward of 60% of the observed optical emission line flux in late-stage mergers. We compare our resolved spectroscopy to nuclear spectra and find that 3/4 of the galaxies in our sample that would be classified as "composite" based on optical spectroscopy are primarily characterized by a combination of star formation and merger-driven shocks. Our results have important implications for the interpretation of "composite" rest-frame optical spectra of U/LIRGs as starburst+active galactic nucleus (AGN), as the shock emission combined with star formation can mimic "composite" optical spectra in the absence of any contribution from an AGN.

Rich, J. A.; Kewley, L. J.; Dopita, M. A.

2014-01-01

409

IntrAst2 (Petrovay) Spectra STELLAR SPECTRA  

E-print Network

. This is the spectrum (lat. spectrum = apparition -- cf. "ghost image") For an extended object these images overlap) Spectra Kirchhoff's laws of spectroscopy (1860): 1. The spectrum of a hot body (solid body or opaque

Petrovay, Kristóf

410

Effects of Microwave Desert Surface Emissivity on AMSU-A Data Assimilation  

Microsoft Academic Search

A microwave land emissivity library has been de- veloped from the Advanced Microwave Sounding Unit (AMSU) data for improving satellite data assimilation. Over the desert, surface emissivity is classified according to soil type into several spectra. For sand, loamy sand, and sandy loam, which contain some large mineral particles, the emissivity spectra generally decrease with frequency. For other desert types

Banghua Yan; Fuzhong Weng

2011-01-01

411

A spectroscopic temperature measurement of converging detonations by the emission spectral matching method  

Microsoft Academic Search

The emission of CN violet bands from a converging point is analyzed using a microdensitometer. To determine the temperature at the converging point of a detonation, a method of matching the entire emission spectra is utilized. The anticipated emission spectra of the observed band can be calculated theoretically with a combination of the gasdynamic quantities, assuming Boltzmann distributions for rotational,

T. Sugimura; T. Fujiwara

1981-01-01

412

[Selective excitation spectra and energy level structure of Dy3+:ThO2 crystal].  

PubMed

Dy3+:ThO2 crystal was grown by the flux technique for the first time. The emission spectra, excitation spectra and fluorescence decay curves were measured and discussed. By using emission spectra obtained under selective dye laser excitation at 12 K, together with the crystal-field theory, the site symmetry of Dy3+ ions in ThO2 was determined as C3 nu and its energy level structure was tabulated. The lifetime of radiative level 4F9/2 was also determined as 0.40 ms. PMID:12945248

Yin, M; Krupa, J C

2001-08-01

413

Thermionic emission and work function of multiwalled carbon nanotube yarns  

Microsoft Academic Search

Thermionic emission from multiwalled carbon nanotubes (MWNTs) was investigated by using MWNT yarns. The work function of MWNT and thermionic emission constant of the yarn sample were both calculated from the thermionic emission data. The measured work function of MWNT is about 4.54-4.64eV . The emission constant is larger than conventional thermionic cathode. Thermionic emission electron energy spectra at various

Peng Liu; Yang Wei; Kaili Jiang; Qin Sun; Xiaobo Zhang; Shoushan Fan; Shufeng Zhang; Chuangang Ning; Jingkang Deng

2006-01-01

414

Line emission from gamma-ray burst environments  

E-print Network

The time and angle dependent line and continuum emission from a dense torus around a cosmological gamma-ray burst source is simulated, taking into account photoionization, collisional ionization, recombination, and electron heating and cooling due to various processes. The importance of the hydrodynamical interaction between the torus and the expanding blast wave is stressed. Due to the rapid deceleration of the blast wave as it interacts with the dense torus, the material in the torus will be illuminated by a drastically different photon spectrum than observable through a low-column-density line of sight, and will be heated by the hydrodynamical interaction between the blast wave and the torus. A model calculation to reproduce the Fe K-alpha line emission observed in the X-ray afterglow of GRB 970508 is presented. The results indicate that ~ 10^{-4} solar masses of iron must be concentrated in a region of less than 10^{-3} pc. The illumination of the torus material due to the hydrodynamic interaction of the blast wave with the torus is the dominant heating and ionization mechanism leading to the formation of the iron line. These results suggest that misaligned GRBs may be detectable as X-ray flashes with pronounced iron emission line features.

M. Boettcher

1999-12-01

415

PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330  

SciTech Connect

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 A 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 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 Multiplication-Sign 10{sup 21} cm{sup -2}; an ionization parameter of log {xi} = -2.70 {+-} 0.023; an oxygen abundance of A{sub O}= 0.689{sup +0.015}{sub -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 results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A{sub O}=0.952{sup +0.020}{sub -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-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 > 2 associated with ISM cold absorption.

Gatuzz, E.; Mendoza, C. [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); Garcia, J.; Lohfink, A. [Department of Astronomy and Maryland Astronomy Center for Theory and Computation, University of Maryland, College Park, MD 20742 (United States); Kallman, T. R.; Witthoeft, M. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bautista, M. A. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Palmeri, P.; Quinet, P., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@astro.umd.edu, E-mail: alohfink@astro.umd.edu, E-mail: timothy.r.kallman@nasa.gov, E-mail: michael.c.witthoeft@nasa.gov, E-mail: manuel.bautista@wmich.edu, E-mail: palmeri@umons.ac.be, E-mail: quinet@umons.ac.be [Astrophysique et Spectroscopie, Universite de Mons-UMONS, B-7000 Mons (Belgium)

2013-05-01

416

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

NASA Technical Reports Server (NTRS)

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.

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

2013-01-01

417

Absorption Spectra of Astaxanthin Aggregates  

E-print Network

Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption maximum of monomeric astaxanthin (470-495 nm depending on solvent) are caused by excitonic interaction between aggregated molecules. We applied molecular dynamics simulations to elucidate structure of astaxanthin dimer in water, and the resulting structure was used as a basis for calculations of absorption spectra. Absorption spectra of astaxanthin aggregates in hydrated dimethylsulfoxide were calculated using molecular exciton model with the resonance interaction energy between astaxanthin monomers constrained by semi-e...

Olsina, Jan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

2012-01-01

418

Skyshine spectra of gamma rays  

Microsoft Academic Search

A study of the spectra of gamma photons back-scattered in vertical direction by infinite air above ground (skyshine) is presented. The source for these measurements is a 650 Ci Cobalt-60 point-source and the skyshine spectra are reported for distances from 150 m to 325 m from the source, measured with a 5 cm NaI(T1) detector collimated with collimators of 12

J. Swarup

1980-01-01

419

Mutational spectra of human cancer  

Microsoft Academic Search

The purpose of this review is to summarize the evidence that can be used to reconstruct the etiology of hu