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1

DETECTION OF IRON K{alpha} EMISSION FROM A COMPLETE SAMPLE OF SUBMILLIMETER GALAXIES  

SciTech Connect

We present an X-ray stacking analysis of a sample of 38 submillimeter galaxies (SMGs) with (z) = 2.6 discovered at {>=}4{sigma} significance in the Lockman Hole North with the MAMBO array. We find a 5{sigma} detection in the stacked soft band (0.5-2.0 keV) image, and no significant detection in the hard band (2.0-8 keV). We also perform rest-frame spectral stacking based on spectroscopic and photometric redshifts and find a {approx}4{sigma} detection of Fe K{alpha} emission with an equivalent width of EW {approx}> 1 keV. The centroid of the Fe K{alpha} emission lies near 6.7 keV, indicating a possible contribution from highly ionized Fe XXV or Fe XXVI; there is also a slight indication that the line emission is more spatially extended than the X-ray continuum. This is the first X-ray analysis of a complete, flux-limited sample of SMGs with statistically robust radio counterparts.

Lindner, Robert R.; Baker, Andrew J. [Rutgers, State University of New Jersey, 136 Frelinghuysen Road, Piscataway, NJ 08854-8019 (United States); Beelen, Alexandre [Institut d'Astrophysique Spatiale, Universite Paris Sud 11 and CNRS, F-91405 Orsay (France); Owen, Frazer N. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Polletta, Maria, E-mail: lindner@physics.rutgers.edu, E-mail: ajbaker@physics.rutgers.edu, E-mail: alexandre.beelen@ias.u-psud.fr, E-mail: fowen@nrao.edu, E-mail: polletta@iasf-milano.inaf.it [INAF-IASF Milano, via E. Bassini, I-20133 Milan (Italy)

2012-09-20

2

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

3

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

4

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

5

Simulations of spatially resolved K-alpha emission as a tool to measure the divergence of fast electrons relevant to Fast Ignition  

NASA Astrophysics Data System (ADS)

The Fast Ignition (FI) concept of Inertial Confinement Fusion relies on fast electrons created from the laser-matter interaction to deposit their energy into the compressed target core and start the fusion burn. Divergence of those electrons is one of the most crucial parameters in FI. Spatially resolved, time-integrated K-alpha x-ray imagers have been used in the past as a way to measure the divergence of fast electrons. Since any electron with energy above some threshold could produce a K-alpha photon, the K-alpha emission distribution can be quite different from that of the fast electrons. We present the results of 2D simulations using the hybrid PIC code LSP on the study of spatially resolved K-alpha emission as a tool to measure fast electron divergence. Among our results, we find that the K-alpha images evolve with time due to refluxing electrons, well after the laser pulse has stopped, giving rise to K-alpha images that suggest a larger electron beam size than is actually present for the FI relevant electrons.

Ovchinnikov, V. M.; Schumacher, D. W.; Kemp, G. E.; Link, A.; Freeman, R. R.; van Woerkom, L. D.

2010-11-01

6

Multiconfiguration Dirac-Fock calculations in open-shell atoms: Convergence methods and satellite spectra of the copper K{alpha} photoemission spectrum  

SciTech Connect

The copper K{alpha} photoemission spectra is one of the most widely studied. Recent Dirac-Fock calculations have produced transition energies in good agreement with experiment, though they have relied on approximations that may not be transferable to other complex atoms in which uncertainties in theoretical results are dominated by poor convergence. Through a detailed examination of convergence issues in the copper spectrum, we consider the accuracy obtainable with the multiconfiguration Dirac-Fock (MCDF) method, provide the first determination of fine structure contributions to the spectrum, and demonstrate reliable techniques for modeling spectator states with vacancies in the 3p, 3d, and 4s shells.

Chantler, C. T.; Lowe, J. A.; Grant, I. P. [School of Physics, University of Melbourne, Victoria 3101 (Australia); Mathematical Institute, Oxford University, Oxford (United Kingdom)

2010-11-15

7

X-ray back-lighter characterization for iron opacity measurements using laser-produced aluminium K-alpha emission  

Microsoft Academic Search

Aluminium Kalpha emission (1.5 keV) produced by an 8 J, 500 ps, Nd:glass laser incident at 45 onto a layered target of 0.8 m thick aluminium (front side) and 1 m thick iron (backside) has been used to probe the opacity of iron plasma. Source broadened spectroscopy and continuum emission analysis show that whole beam self-focusing within the aluminium plasma

A. K. Rossall; L. M. R. Gartside; S. Chaurasia; S. Tripathi; D. S. Munda; N. K. Gupta; L. J. Dhareshwar; J. Gaffney; S. J. Rose; G. J. Tallents

2010-01-01

8

Study of the broad Fe K-alpha emission line in the bright source GX 17+2  

NASA Astrophysics Data System (ADS)

We propose to observe the Z source GX 17+2 with XMM-Newton for 40 ks, to perform a detailed study of the iron K-shell feature to assess its origin. A broad emission feature compatible with a highly ionized iron line has been detected both in BeppoSAX and in Chandra observations of the source. The Chandra spectrum suggests that the line might be of relativistic origin, but the large collecting area of XMM-Newton is needed to resolve unambiguously the line profile, which can give important information on the dynamics of accretion and on the structure of neutron stars. Use of the modified timing mode will allow to maximize the time efficiency of the observation and to perform high-statistics timing analysis.

Lavagetto, Giuseppe

2007-10-01

9

Thermal Emission Spectra of Mercury  

NASA Technical Reports Server (NTRS)

The emission spectrum of Mercury may hold clues as to the mineral composition of the surface from reststrahlen bands. Unfortunately, these bands are very weak in finely powdered materials, such as are expected on the mercurian surface, and they lie in a region of the spectrum where there are substantial atmospheric absorptions. We have been measuring the 8-14-micron spectra of Mercury and the Sun at a resolution of about 0.03 wavenumbers, using the Fourier Transform Spectrometer (FTS) located at the National Solar Observatory, Kitt Peak, Arizona. The objective of using such a high resolution for the measurement is to be able to look between atmospheric absorption lines as much as possible. The atmospheric effects are largely cancelled by ratioing Mercury spectra to Sun spectra taken at nearly the same airmass, although small differences in airmass produce some residual atmospheric absorptions in the ratio spectra. We expect that spectral features of Mercury, if any, should appear in the ratio spectra, since the 8-14 micron spectrum of the Sun approximates a black body.

Potter, A. E.; Cooper, B. L.; Killen, R. M.; Morgan, T. H.

1999-01-01

10

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

11

Investigation of nonequilibrium hydroxyl emission spectra  

NASA Astrophysics Data System (ADS)

Ultraviolet nonequilibrium OH emission spectra in flames are measured and analyzed. Spectra of nonequilibrium coefficients are recorded for an optically thin jet, and spectral absorption coefficients and electronic absorption band intensities are determined. Based on the developed mathematical radiative transfer model in a nonequilibrium radiating media, the OH contribution to radiative jet cooling is estimated, and practical applications of the nonequilibrium emission process to the development of optoelectronic systems of observation over aero carriers are considered.

Moskalenko, N. I.; Zaripov, A. V.; Il'in, Yu. A.

2010-07-01

12

Emission Spectra as a Combustion Diagnostic Tool  

Microsoft Academic Search

In the present work, spontaneous emission spectra of Liquefied Petroleum Gas (LPG) flames were used for combustion diagnostics. CH* and C2 * radicals were chosen as flame probe because these species shown a large optical emission in the visible spectrum region. Additionally, the occurrence of these radicals is strongly dependent of the flame composition. In rich flames, for which the

Dermeval Carinhana Junior; Juliana C. de Oliveira; Marcelo G. Destro; Alberto M. dos Santos

13

Investigation of nonequilibrium hydroxyl emission spectra  

Microsoft Academic Search

Ultraviolet nonequilibrium OH emission spectra in flames are measured and analyzed. Spectra of nonequilibrium coefficients are recorded for an optically\\u000a thin jet, and spectral absorption coefficients and electronic absorption band intensities are determined. Based on the developed\\u000a mathematical radiative transfer model in a nonequilibrium radiating media, the OH contribution to radiative jet cooling is estimated, and practical applications of the

N. I. Moskalenko; A. V. Zaripov; Yu. A. Ilin

2010-01-01

14

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

15

Soil emissivity and reflectance spectra measurements  

SciTech Connect

We present an analysis of the laboratory reflectance and emissivity spectra of 11 soil samples collected on different field campaigns carried out over a diverse suite of test sites in Europe, North Africa, and South America from 2002 to 2008. Hemispherical reflectance spectra were measured from 2.0 to 14 {mu}m with a Fourier transform infrared spectrometer, and x-ray diffraction analysis (XRD) was used to determine the mineralogical phases of the soil samples. Emissivity spectra were obtained from the hemispherical reflectance measurements using Kirchhoff's law and compared with in situ radiance measurements obtained with a CIMEL Electronique CE312-2 thermal radiometer and converted to emissivity using the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) temperature and emissivity separation algorithm. The CIMEL has five narrow bands at approximately the same positions as the ASTER. Results show a root mean square error typically below 0.015 between laboratory emissivity measurements and emissivity measurements derived from the field radiometer.

Sobrino, Jose A.; Mattar, Cristian; Pardo, Pablo; Jimenez-Munoz, Juan C.; Hook, Simon J.; Baldridge, Alice; Ibanez, Rafael

2009-07-01

16

Determination of Particle Temperature from Emission Spectra  

Microsoft Academic Search

This paper discusses the fundamental possibility of determining the temperature of nanooxides in flames using thermal emission spectra. It is found that experimentally determined temperatures can be close to the real temperatures of particles only in the case of a high concentration of structural defects in the particles. It is shown that the energy accumulated in these defects should be

I. S. Altman

2004-01-01

17

Engineering upconversion emission spectra using plasmonic nanocavities.  

PubMed

We show that the upconversion emission spectra of Tm3+ and Yb3+ codoped ?-NaYF4-NaYF4 core-shell nanoparticles can be judiciously modified by means of plasmonic nanocavities. Our analysis indicates that more than a 30-fold increase in conversion efficiency to the UV spectral band can be expected by engineering the NIR absorption and the local density of states. The effect of the nanocavity on the resulting radiation patterns is discussed. Our results are exemplified in cylindrical cavity geometries. PMID:24978717

Lantigua, Christopher; He, Sha; Bouzan, Milad Akhlaghi; Hayenga, William; Johnson, Noah J J; Almutairi, Adah; Khajavikhan, Mercedeh

2014-07-01

18

Comparison of experimental and simulated K{alpha} yield for 400 nm ultrashort pulse laser irradiation  

SciTech Connect

Ti K{alpha} emission yields from foils irradiated with {approx}45 fs, p-polarized pulses of a frequency-doubled Ti:sapphire laser are presented. A simple model invoking vacuum heating to predict absorption and hot electron temperature was coupled with the cross section for K-shell ionization of Ti and the Bethe-Bloch stopping power equation for electrons. The peak predicted K{alpha} emission was in generally good agreement with experiment. This contrasts strongly with previous work at the fundamental frequency. Similar predictions using particle-in-cell (PIC) code simulation to estimate the number and temperature of hot electrons also gave good agreement for yield.

Khattak, F. Y.; Percie du Sert, O. A. M. B.; Riley, D.; Foster, P. S.; Divall, E. J.; Hooker, C. J.; Langley, A. J.; Smith, J.; Gibbon, P. [School of Mathematics and Physics, Queen's University of Belfast, University Road, Belfast BT7 1NN (United Kingdom); Central Laser Facility, CLRC Rutherford Appleton Laboratory, Chilton, Didcot, Oxon OX11 0QX (United Kingdom); John von Neumann Institute for Computing, Central Institute for Applied Mathematics (ZAM), Computer Simulations Division, Research Centre Juelich, D-52425 Juelich (Germany)

2006-08-15

19

SCIENTIFIC NOTE: A method for estimation of thermoluminescence emission spectra  

Microsoft Academic Search

A simple apparatus including oven and camera is described. The method involves colour-slide photography during heating and the subsequent conversion of the colour of the developed film into the emission spectra using a common absorption spectrometer.

Z. Spurny; J. Hruska

1976-01-01

20

Retrieval of constituent mixing ratios from limb thermal emission spectra  

NASA Astrophysics Data System (ADS)

An onion-peeling iterative, least-squares relaxation method to retrieve mixing ratio profiles from limb thermal emission spectra is presented. The method has been tested on synthetic data, containing various amounts of added random noise for O3, HNO3, and N2O. The retrieval method is used to obtain O3 and HNO3 mixing ratio profiles from high-resolution thermal emission spectra. Results of the retrievals compare favorably with those obtained previously.

Shaffer, William A.; Kunde, Virgil G.; Conrath, Barney J.

1988-08-01

21

Polarization Angular Spectra of Galactic Synchrotron Emission on Arcminute Scales  

Microsoft Academic Search

We study the angular power spectra of the polarized component of the Galactic synchrotron emission in the 28 deg2 test region of the Southern Galactic Plane Survey at 1.4 GHz. These data were obtained by the Australia Telescope Compact Array and allow us to investigate angular power spectra down to arcminute scales. We find that, at this frequency, the polarization

M. Tucci; E. Carretti; S. Cecchini; L. Nicastro; R. Fabbri; B. M. Gaensler; J. M. Dickey; N. M. McClure-Griffiths

2002-01-01

22

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

23

Emission and absorption spectra of the HgZn excimer  

NASA Astrophysics Data System (ADS)

Extensive and previously unknown fluorescence and excitation spectra of the HgZn excimer have been observed and correlated with a potential energy (PE) diagram. The spectra were excited in a HgZn mixture contained in a quartz vapor cell by successive pulses from two dye lasers using pump-and-probe methods. A vibrational analysis of the spectra yield the frequencies and anharmonicities for the states involved in the absorption and emission processes.

Supronowicz, J.; Hegazi, E.; Chambaud, G.; Atkinson, J. B.; Baylis, W. E.; Krause, L.

1988-10-01

24

Spectra of Stellar Flares. Continuum Emission  

NASA Astrophysics Data System (ADS)

Spectral studies of stellar flares are discussed in this article. It is shown that at least during strong flares the continuum emission plays a vital role, especially in the blue part of the spectrum. This may explain the fact that the H? emission line is suppressed much more strongly than the H? line during flare maxima. The distribution of the flare energy in the 4600-7200 range is obtained during a flare of the star WX UMa. The delays in the maximum values of the equivalent widths of the emission lines relative to the flare maximum are also obtained, as well as the increase in these lines to a maximum when the star is in a quiescent state. While the post-maximum evolution of the equivalent widths can be explained by recombination emission in lines, the pre-flare increase in the line intensities remains incomprehensible. Slow and flare-like variations in the emission lines are also recorded. The spectral classes of three Orion flare stars are determined.

Melikian, N. D.

2014-03-01

25

Observation of infrared emission spectra from silicon combustion products  

NASA Astrophysics Data System (ADS)

The combustion of silicon based pyrotechnic compositions is observed with time resolved infrared spectrometry. This revealed the build up of strong emission at 9.1 0.1 ?m, which is associated with condensed silicon dioxide particulates. Time averaged spectra for compositions containing different oxidants or binders illustrate the dependence of SiO 2 emission intensity on composition.

Smit, Kenneth J.; De Yong, Leo V.; Gray, Rodney

1996-05-01

26

Observation and analysis of emission spectra of tungsten hydride  

Microsoft Academic Search

The authors report in this paper the first observation of electronic emission spectra from the tungsten monohydride radical. This emission originates from the plasma generated by a dc discharge through hydrogen flowing between a tungsten anode rod and a tungsten cathode nozzle of a hydrogen atom beam source. By analysis of this spectrum, rotational constants and bond distances have been

James F. Garvey; Aron Kuppermann

1988-01-01

27

High-resolution studies of atmospheric IR emission spectra  

NASA Technical Reports Server (NTRS)

Atmospheric emission spectra obtained with two different spectrometer systems are presented. The first system (the BOMEM Michelson interferometer) is designed for emission work. Spectra were obtained under adverse conditions in the Antarctic, and are still of good absolute accuracy. The second system (a modified Bruker Instruments IFS120 very high spectral resolution interferometer) demonstrates the sensitivity that can be achieved even at higher spectral resolution. This system shows that mid-IR atmospheric emission spectra can be obtained with a good SNR in a reasonable length of time at a relatively high resolution. A properly designed high resolution system should achieve high accuracy, sensitivity, and resolution, thereby permitting measurements of many atmospheric constituents when solar spectra cannot be obtained.

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

1991-01-01

28

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

29

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

30

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

31

Thermal emission spectra from individual suspended carbon nanotubes.  

PubMed

We study the thermal emission spectra of individual suspended carbon nanotubes induced by electrical heating. Semiconducting and metallic devices exhibit different spectra, based on their distinctive band structures. These spectra are compared with the ideal blackbody emission spectrum. In the visible wavelength range, the thermal emission spectra of semiconducting devices agree well with Planck's law, while the spectra of metallic devices show an additional peak between 1.5 and 1.9 eV. In the near-infrared wavelength range, the semiconducting nanotubes exhibit a peak around 1 eV. These additional peaks are attributed to the E11M and E22SC transitions that are thermally driven under these high applied bias voltages. These peaks show a strong polarization dependence, while the blackbody tail is unpolarized, which provides further evidence for electron-hole recombination in thermal emission. For semiconducting devices, the temperature of the nanotube is fit to Planck's law and compared with the temperatures obtained from the G band and 2D band Raman downshifts, as well as the anti-Stokes/Stokes intensity ratio. For devices showing thermal non-equilibrium, the electron temperature agrees well with G+ downshift but deviates from G_ downshift. PMID:21545117

Liu, Zuwei; Bushmaker, Adam; Aykol, Mehmet; Cronin, Stephen B

2011-06-28

32

Production of copper(I) halide emission spectra by MECA  

Microsoft Academic Search

THE introduction of copper (II) salts into most commonly used flames gives a green emission. Copper halides give a particularly intense emission, which is used in the well-known Beilstein test for halogens. The spectra from all copper salts, however, are very similar, and consist mainly of diffuse CuOH bands in the region 535-555 nm, a CuH band centred around 429

R. Belcher; S. L. Bogdanski; S. A. Ghonaim; A. Townshend

1974-01-01

33

Emission spectra of burning iron in high-pressure oxygen  

Microsoft Academic Search

Emission spectra of burning vertical iron rods in high-pressure oxygen were taken and correlated with the different stages of the burn evolution. By applying the least squares method to the spectral curves, the corresponding equivalent blackbody temperatures were computed. Based on the assumption of a wavelength-independent emissivity between 495 and 780 nm, it was found that the surface-averaged temperatures of

Theodore A. Steinberg

1996-01-01

34

Energy-dispersive measurements of the K. alpha. /sub 3/, KM/sub 1/, K. beta. /sub 1/, and K. beta. /sub 2/ x-ray intensities relative to the K. alpha. /sub 1/ intensity in lead and uranium  

SciTech Connect

Lead and uranium K x-ray spectra recorded with a specially designed Ge detector have been fitted using an accurately determined line-shape model. This provides the first accurate Ge measurements of the K..alpha../sub 3/ relative intensity and the first reported measurement of the KM/sub 1/ relative intensity. Measurements of the transition probabilities of K..beta../sub 1/ and K..beta../sub 2/ relative to the K..alpha../sub 1/ line provide a much more stringent test of calculated overlap and exchange effects than earlier ratios of gross line groups.

Campbell, J.L.; McGhee, P.L.; Maxwell, J.A.; Ollerhead, R.W.; Whittaker, B.

1986-02-01

35

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

36

In-Guide - Far Field Emission Spectra Measurements and Correlations.  

National Technical Information Service (NTIS)

This report describes tests conducted with the purpose of correlating In-Guide (AN/GPM-59) and Far Field emission spectra measurements. The report discusses both In-Guide and conventional Far Field measurement techniques, and identifies the error sources ...

E. W. Taylor E. F. Hjort

1967-01-01

37

Downshifted maximum features in stimulated electromagnetic emission spectra  

Microsoft Academic Search

New and detailed experimental and theoretical results concerning the prominant downshifted maximum (DM) feature in spectra of stimulated electromagnetic emissions are reported. The experimental results were obtained at the Sura ionospheric modification facility in Russia by transmitting a powerful high-frequency ordinary mode pump wave into the ionospheric F region. We present detailed experimental results of the dependence of the DM

T. B. Leyser; B. Thide; M. Waldenvik; E. Veszelei; V. L. Frolov; S. M. Grach; G. P. Komrakov

1994-01-01

38

Ponderomotive narrow continuum (NCp) component in stimulated electromagnetic emission spectra  

Microsoft Academic Search

We present experimental results concerning the ponderomotive narrow continuum (NCp) in stimulated electromagnetic emission spectra, generated in the ionospheric F region plasma by a powerful O mode electromagnetic wave. It is found that the generation of the NCp is determined by the development of the parametric decay instability in the initial stage of the interaction of the HF pump wave

V. L. Frolov; E. N. Sergeev; G. P. Komrakov; P. Stubbe; B. Thid; M. Waldenvik; E. Veszelei; T. B. Leyser

2004-01-01

39

Potential For Qualitative Analysis Using Organic Emission Spectra In Flames  

Microsoft Academic Search

A preliminary investigation into the potential of using the emission spectra of organic molecules arising from a hydrogen-entrained air flame to obtain structural information has been made. Results for several alcohols show that the technique can be used to distinguish between geometrical isomers.

Michael L. Parsons

1969-01-01

40

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

41

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

42

SMM observations of K-alpha radiation from fluorescence of photospheric iron by solar flare X-rays  

NASA Technical Reports Server (NTRS)

High-resolution Fe K-alpha spectra near 1.94 A observed during solar flares with the Bent Crystal Spectrometer on the Solar Maximum Mission are presented. The evidence for two possible excitation mechanisms, electron impact and fluorescence, is examined. It is found that the fluorescence mechanism satisfactorily describes the results, while the observations do not support electron collisional excitation of the Fe K-alpha transitions in low ionization stages (II-XII) of iron. Using Bai's model of the fluorescent excitation process, the photospheric iron abundance relative to that of hydrogen is estimated to be 5-6 x 10 to the -5th. The mean height of the soft X-ray source producing the K-alpha fluorescence is calculated on the basis of this model for about 40 large flares. The solar K-alpha lines are found to be about 25 percent wider than those measured in the laboratory. Weak line features observed at wavelengths shorter than that of the K-alpha lines are discussed.

Parmar, A. N.; Culhane, J. L.; Rapley, C. G.; Wolfson, C. J.; Acton, L. W.; Phillips, K. J. H.; Dennis, B. R.

1984-01-01

43

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

44

Modelling broad Fe K-alpha reverberation in AGN  

NASA Astrophysics Data System (ADS)

The recent detection of X-ray reverberation lags, especially in the Fe K-alpha line region, around Active Galactic Nuclei (AGN) has opened up the possibility of studying the time-resolved response (reflection) of hard X-rays from the accretion disk around supermassive black holes. Here, we use general relativistic transfer functions for reflection of X-rays from a point source located at some height above the black hole to study the time lags expected as a function of frequency and energy in the Fe K-alpha line region. We explore the models and the dependence of the lags on key parameters such as the height of the X-ray source, accretion disk inclination, black hole spin and black hole mass. We then compare these models with the observed frequency and energy dependence of the Fe K-alpha line lag in NGC 4151. Assuming the optical reverberation mapping mass of 4.6E7 M(solar) we get a best fit to the lag profile across the Fe K-alpha line in the frequency range 1E-5 - 2E-5 Hz for an X-ray source located at a height h = 7 (+2.9,-2.6) R_G with a maximally spinning black hole and an inclination i < 30 degrees.

Cackett, Edward; Zoghbi, Abderahmen; Reynolds, Christopher S.; Fabian, Andrew c; Kara, Erin; Uttley, Phil; Wilkins, Dan

2014-08-01

45

Stratospheric HBr mixing ratio obtained from far infrared emission spectra  

NASA Technical Reports Server (NTRS)

Emission features of HBr isotopes have been identified in high-resolution FIR emission spectra obtained with a balloon-borne Fourier-transform spectrometer in the spring of 1979 at 32 deg N latitude. When six single-scan spectra at a zenith angle of 93.2 deg were averaged, two features of HBr isotopes at 50.054 and 50.069/cm were obtained with a signal-to-noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 x 10 to the -11th, which is assumed to be constant above 28 km, with an uncertainty of 35 percent. This stratospheric amount of HBr is about the same as the current level of tropospheric organic bromine compounds, 25 pptv. Thus HBr could be the major stratospheric bromine species.

Park, J. H.; Carli, B.; Barbis, A.

1989-01-01

46

New downshifted maximum in stimulated electromagnetic emission spectra  

Microsoft Academic Search

A new spectral maximum in spectra of stimulated electromagnetic emission of the ionosphere (SEE, [1]) was detected in experiments at the SURA facility in 2008 for the pump frequencies f0 4.4-4.5 MHz, most stably for f0 = 4.3 MHz, the lowest possible pump frequency at the SURA facility. The new maximum is situated at frequency shifts ?f -6 kHz from

Evgeny Sergeev; Savely Grach

2010-01-01

47

Modeling of the emission spectra of tungsten plasma  

Microsoft Academic Search

A model of nonequilibrium radiating multicharge ion plasma, which takes into account the radiation transport and level kinetics\\u000a of electrons, is constructed. The model allows one to obtain the properties of plasma with arbitrary optical thickness. On\\u000a the basis of this model, emission spectra of tungsten plasma were calculated, which are of interest in connection with studying\\u000a high-current multiwire liners.

I. Yu. Vichev; V. G. Novikov; A. D. Solomyannaya

2009-01-01

48

Emission spectra of pyrotechnic mixtures of heat flux simulators  

NASA Astrophysics Data System (ADS)

Comprehensive optical spectroscopic studies of the combustion process of solid-state pyrotechnic mixtures based on Mg and Sr(NO3)2 have been carried out. Emission spectra of the mixtures in the ultraviolet, visible, and infrared wavelength regions have been studied under various atmospheric conditions taking into account radiation transfer in air along an optical path of observation up to 5 km long.

Azharonok, V. V.; Kratsko, L. E.; Chubryk, N. I.; Goncharik, S. V.; Miatselskaya, N. S.; Yakshonak, P. P.; Hamayunau, V. I.

2012-01-01

49

DISCOVERY OF STRONG IRON K{alpha} EMITTING COMPTON THICK QUASARS AT z = 2.5 AND 2.9  

SciTech Connect

We report the detection of the 6.4 keV iron K{alpha} emission line in two infrared-luminous, massive, star-forming BzK galaxies at z = 2.578 and z = 2.90 in the CDF-S. The Chandra 4 Ms spectra of BzK 4892 and BzK 8608 show a reflection-dominated continuum with strong iron lines, with rest-frame equivalent widths EW {approx} 2.3 keV and 1.2 keV, respectively, demonstrating Compton thick (CT) obscuration of the central active galactic nucleus (AGN). For BzK 8608, the line identification closely matches the existing photometric redshift derived from the stellar emission. We use the observed luminosities of the iron K{alpha} line, of the rest-frame mid-IR continuum and of the UV rest-frame narrow emission lines to infer intrinsic L{sub 2-10}{sub keV} {approx}> 10{sup 44} erg s{sup -1}, about 1.0-2.5 dex larger than the observed ones, hence confirming the presence of an absorber with N{sub H}>10{sup 24} cm{sup -2}. The two BzK galaxies have stellar masses of 5 x 10{sup 10} M{sub sun} and, based on Very Large Array 1.4 GHz and submillimeter 870 {mu}m observations, they appear to host vigorous starburst activity with star formation rate {approx} 300-700 M{sub sun} yr{sup -1} that is also optically thick. We estimate that the AGN might also conceivably account for an important fraction of the bolometric far-IR emission of the galaxies. The implied volume density of CT AGN with L{sub 2-10}{sub keV}>10{sup 44} erg s{sup -1} is in agreement with predictions from X-ray background synthesis models. These sources provide one of the first clear-cut observations of the long-sought phase of simultaneous, heavily obscured quasar and star formation activity, predicted by models of massive galaxy evolution at high redshifts.

Feruglio, C.; Daddi, E. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d'Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex (France); Fiore, F.; Piconcelli, E. [INAF-Osservatorio Astronomico di Roma, via Frascati 33, 00040 Monteporzio Catone (Italy); Alexander, D. M. [Department of Physics, Durham University, South Road, DH1 3LE (United Kingdom); Malacaria, C., E-mail: chiara.feruglio@cea.fr [Universita' La Sapienza, Piazzale Aldo Moro 5, 00185 Roma (Italy)

2011-03-01

50

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

51

Terrestrial FeO Continuum Emission Observed in Sky Spectra  

NASA Astrophysics Data System (ADS)

The terrestrial continuum emission in the visible spectral region has often been studied by both astronomers and aeronomers, in order to clarify backgrounds and the nature of the emissions. New observations from the ESI spectrograph on the Keck II telescope, as well as from the OSIRIS/Odin spectrograph and orbiter, have established that a major component of the emission originates with the FeO molecule [Evans et al., 2010]. This quasi-continuum peaks at 5950 A and extends from 5000 A well into the infrared. The identity has been demonstrated by comparison with meteor trains and laboratory measurements [Jenniskens et al., 2000]. Early studies of the continuum show consistency with the FeO emission as presently observed [Gadsden and Marovich, 1973]. Analysis of spectra from Kitt Peak [Neugent and Massey, 2010] demonstrates the great similarity between FeO emission in a clean atmosphere and high pressure sodium lamp emission in a polluted atmosphere. This research was supported by NSF Aeronomy under Grant ATM-0637433 . Evans, W.F.J., et al., Geophys. Res. Lett. [in press, 2010] Gadsden, M. and E. Marovich, J. Atm. Terr. Phys., 35, 1601-1614 [1973] Jenniskens, P., et al., Earth, Moon and Planets, 82-83, 429-434 [2000] Neugent, K.F. and P. Massey, PASP [in press, 2010

Slanger, Tom G.; Melchiorri, R.; Saran, D. V.

2011-01-01

52

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

53

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

54

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

55

Modeling the PAH Emission Spectra of Protoplanetary and Debris Disks  

NASA Astrophysics Data System (ADS)

The 3.3, 6.2, 7.7, 8.6 and 11.3 micron emission features of polycyclic aromatic hydrocarbon (PAH) molecules have been detected in protoplanetary disks around Herbig Ae/Be stars and T Tauri stars and in debris disks around main-sequence stars. PAHs play an important role in the thermal budget and chemistry of the gas in the disk, by providing photoelectrons for heating the gas and large surface areas for chemical reactions. Stochastically heated by a single UV/visible photon, the PAH emission is spatially more extended than large grains and therefore, the disks can be more easily resolved at the PAH emission bands. We propose to model the PAH emission spectra of protoplanetary and debris disks obtained by Spitzer and ISO. We will first calculate the temperature probability distribution functions dP/dT for both neutral and ionized PAHs of a wide range of sizes, at a wide range of radial distances (from the central star) in disks illuminated by stars of a wide range of spectral types. By modeling the PAH emission of dust disks, we will be able (1) to derive the abundance, size and spatial distributions of PAHs; (2) to derive the PAH photoelectric heating rates which dominate the gas heating in the disk surface layers; and (3) to see how the abundance and properties of the PAHs vary among disks at different evolutionary stages and illuminated by stars of different parameters (e.g. luminosity, spectral type). This program will create a web-based ``library'' of the temperature distribution functions dP/dT of PAHs (and their emission spectra and photoelectric heating rates) as a function of size, charge state, and radial distance in disks illuminated by stars of different spectral types. This library, a useful tool for interpreting the PAH emission features of dust disks obtained by Spitzer and for understanding the disk chemistry, will be made publicly available by April 2007 via the WWW at http://www.missouri.edu/~lia/.

Li, Aigen; Lunine, J. I.

2006-05-01

56

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

57

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

58

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

59

Fe II emission lines. I - Chromospheric spectra of red giants  

NASA Astrophysics Data System (ADS)

A 'difference filtering' algorithm developed by Ayers (1979) is used to construct high-quality high-dispersion long-wavelength IUE spectra of three giant stars. Measurements of all the emission lines seen between 2230 and 3100 A are tabulated. The emission spectrum of Fe II is discussed in comparison with other lines whose formation mechanisms are well understood. Systematic changes in the Fe II spectrum are related to the different physical conditions in the three stars, and examples are given of line profiles and ratios which can be used to determine conditions in the outer atomspheres of giants. It is concluded that most of the Fe II emission results from collisional excitation and/or absorption of photospheric photons at optical wavelengths, but some lines are formed by fluorescence, being photoexcited by other strong chromospheric lines. Between 10 and 20 percent of the radiative losses of Fe II arise from 10 eV levels radiatively excited by the strong chromospheric H Ly-alpha line.

Judge, P. G.; Jordan, C.

1991-09-01

60

Absorption and emission spectra of Ce3+ in elpasolite lattices.  

PubMed

The experimental determination of the electronic energy levels for Ce(3+) in some chloroelpasolite hosts for both the ground 4f(1) and the excited 5d(1) configurations is described. High-resolution f-f absorption and f-(2)T(2g) d absorption and emission spectra have been recorded at low temperatures for Ce(3+) diluted into various hexachloroelpasolite lattices. A fluorescence spectrum at approximately 50 000 cm(-1) is tentatively assigned to the emission from the highest 5d crystal field level, (2)E(g), of a Ce(3+) impurity in Cs(2)NaErCl(6), enabling the values of all the energy levels of both the 4f(1) and 5d(1) configurations to be given for Ce(3+) in elpasolite hosts. Vibronic structure superimposed on the electronic transitions is analyzed in terms of a simple configurational coordinate model involving the ground and excited configurations. It is found that the difference in the Ce-Cl bond length between the 4f(1) and 5d(1) configurations is approximately 0.04 A. Ab initio model potential calculations on the (CeCl(6))(3-) cluster embedded in a reliable representation of the Cs(2)NaYCl(6) host support these conclusions. PMID:14570498

Tanner, Peter A; Mak, Chris S K; Edelstein, Norman M; Murdoch, Keith M; Liu, Guokiu; Huang, Jin; Seijo, Luis; Barandiarn, Zoila

2003-10-29

61

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

62

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

Plek, Jaromr; Dostl, Marek; Gkov, Dana

2012-07-01

63

Fe X Emission Lines in Solar and Stellar Spectra  

NASA Astrophysics Data System (ADS)

Theoretical electron density sensitive emission line ratios involving Fe X 3s23p5-3s23p43d transitions in the 170-190 wavelength range are compared with observational data for a solar active region and flares, obtained during the Skylab mission, and Cen and Procyon observations from the Extreme Ultraviolet Explorer (EUVE) satellite. Electron densities derived from the majority of the ratios are consistent for the events but are in poor agreement with the values of Ne estimated from diagnostic lines in other species observed in the spectra, casting doubt on the accuracy of the theoretical line ratio calculations and, hence, the atomic data of Mohan et al. used in their derivation. At low Ne, the present ratios are significantly different from those of Young et al., while the latter imply densities that are in somewhat better agreement with densities derived from other diagnostics. This would appear to indicate that the electron impact excitation rates of Bhatia & Doschek adopted by Young et al. are to be preferred over the Mohan et al. results.

Foster, V. J.; Mathioudakis, M.; Keenan, F. P.; Drake, J. J.; Widing, K. G.

1996-12-01

64

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

65

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

66

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

SciTech Connect

We have performed angle-resolved measurements of spontaneous-emission spectra from laser dyes and quantum dots in opal and inverse opal photonic crystals. Pronounced directional dependencies of the emission spectra are observed: angular ranges of strongly reduced emission adjoin with angular ranges of enhanced emission. It appears that emission from embedded light sources is affected both by the periodicity and by the structural imperfections of the crystals: the photons are Bragg diffracted by lattice planes and scattered by unavoidable structural disorder. Using a model comprising diffuse light transport and photonic band structure, we quantitatively explain the directional emission spectra. This work provides detailed understanding of the transport of spontaneously emitted light in real photonic crystals, which is essential in the interpretation of quantum optics in photonic-band-gap crystals and for applications wherein directional emission and total emission power are controlled.

Nikolaev, Ivan S.; Lodahl, Peter; Vos, Willem L. [Complex Photonic Systems (COPS), Department of Science and Technology, and MESA Institute of Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

2005-05-15

67

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

68

Method for the analysis of nonselective spectra of optically stimulated electron emission from irradiated dielectrics  

Microsoft Academic Search

A method has been proposed and substantiated for processing of nonselective optically stimulated electron emission (OSEE) spectra of irradiated crystalline and amorphous dielectrics. This method allows the separation of the emission contribution of discrete centers taking into account effects of radiation-induced electrization of materials and the unsteady state of the electron emission. Separation of OSEE selective bands facilitates the establishment

A. F. Zatsepin; D. Yu. Biryukov; V. S. Kortov

2005-01-01

69

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

70

Near-threshold multielectronic effects in the Cu K{alpha}{sub 1,2} x-ray spectrum  

SciTech Connect

The variation with excitation energy of the line shapes of the Cu K{alpha}{sub 1,2} x-ray spectrum was measured with high energy resolution near the K-shell threshold. Fits with ab initio Dirac-Fock calculated spectra allow us to estimate separately the magnitudes and energy variations of the 3d electron shakeup and shakeoff probabilities from threshold to saturation. The Thomas model is found to account well for the intensity evolution, in contrast with shakeoff from deeper shells. A suggested, yet unexplained, strong dependence of the shakeoff intensity saturation range on the shell number is confirmed.

Galambosi, S.; Sutinen, H.; Mattila, A.; Haemaelaeinen, K. [Division of X-Ray Physics, Department of Physical Sciences, P.O. Box 64, FIN-00014 University of Helsinki (Finland); Sharon, R.; Deutsch, M. [Physics Department, Bar-Ilan University, Ramat-Gan 52900 (Israel); Kao, C.C. [NSLS, Brookhaven National Laboratory, Upton, New York 11973 (United States)

2003-02-01

71

On the thermoluminescence emission spectra of CaF 2: Tm  

NASA Astrophysics Data System (ADS)

Thermoluminescence (TL) emission spectra in the visible and near infrared region of TLD-300 (CaF 2: Tm) commonly used for TL dosimetry were studied at exposures 286 and 7300 R. The TL emission spectra from 300 to 900 nm are observed every 2C from 50C to 320C. Glow peaks appear at 110C, 145C, 235C and 265C. Emission bands in the spectra were measured at 357, 460, 655 and 805 nm. Discussion is given about a possibility of using the infrared emission band 805 nm as well as the visible emission bands in the routine work of radiation detector dosimetry at a temperature of around 145C. Further we discuss the change of the integral glow curve for each of these emission bands for the exposure radiation at 286 and 7300 R.

Rasheedy, Mahmoud Said; Nishimura, Fumio; Ichimori, Toshihiro

1991-07-01

72

Emission Spectra of Particulate Silicates under Simulated Lunar Conditions.  

National Technical Information Service (NTIS)

Infrared spectra have been acquired under simulated lunar conditions that demonstrate that, contrary to popular belief, features of high spectral contrast are available for small-particle-size samples. The spectral information occurs in the form of emissi...

G. R. Hunt L. M. Logan

1970-01-01

73

On the interpretation of tungsten emission spectra in fusion devices  

NASA Astrophysics Data System (ADS)

Atomic spectra emitted by fusion plasmas are generally contaminated by ions originating from plasma erosion of material walls. These ions may be present in several charge states and the radiation they emit falls in the x-ray to vacuum ultraviolet regions, making them atomic fingerprints used as a diagnostic tool. This work reports on recent achievements on the interpretation of specific tungsten spectra from the Axially Symmetric Divertor Experiment (ASDEX) Upgrade tokamak and the Large Helical Device (LHD) stellarator.

Madeira, T. I.; Amorim, P.; Parente, F.; Indelicato, P.; Marques, J. P.

2013-09-01

74

Chemometric analysis of infrared emission spectra for quantitative analysis of BPSG films on silicon.  

National Technical Information Service (NTIS)

Infrared emission spectra of 21 borophosphosilicate glass (BPSG) thin films on silicon wafers were collected with the samples held at constant temperature between 125--400(degree)C using a heating stage designed for precise temperature control ((plus minu...

J. E. Franke C. S. Chen S. Zhang T. M. Niemczyk D. M. Haaland

1993-01-01

75

Equilibrium excited state and emission spectra of molecular aggregates from the hierarchical equations of motion approach.  

PubMed

The hierarchical equations of motion (HEOM) method was applied to calculate the emission spectra of molecular aggregates using the Frenkel exciton model. HEOM equations for the one-exciton excited state were first propagated until equilibration. The reduced density operator and auxiliary density operators (ADOs) were used to characterize the coupled system-bath equilibrium. The dipole-dipole correlation functions were then calculated to obtain the emission spectra of model dimers, and the B850 band of light-harvesting complex II (LH2) in purple bacteria. The effect of static disorder on equilibrium excited state and the emission spectra of LH2 was also explicitly considered. Several approximation schemes, including the high temperature approximation (HTA) of the HEOM, a modified version of the HTA, the stochastic Liouville equation approach, the perturbative time-local and time-nonlocal generalized quantum master equations, were assessed in the calculation of the equilibrium excited state and emission spectra. PMID:23387623

Jing, Yuanyuan; Chen, Liping; Bai, Shuming; Shi, Qiang

2013-01-28

76

Equilibrium excited state and emission spectra of molecular aggregates from the hierarchical equations of motion approach  

NASA Astrophysics Data System (ADS)

The hierarchical equations of motion (HEOM) method was applied to calculate the emission spectra of molecular aggregates using the Frenkel exciton model. HEOM equations for the one-exciton excited state were first propagated until equilibration. The reduced density operator and auxiliary density operators (ADOs) were used to characterize the coupled system-bath equilibrium. The dipole-dipole correlation functions were then calculated to obtain the emission spectra of model dimers, and the B850 band of light-harvesting complex II (LH2) in purple bacteria. The effect of static disorder on equilibrium excited state and the emission spectra of LH2 was also explicitly considered. Several approximation schemes, including the high temperature approximation (HTA) of the HEOM, a modified version of the HTA, the stochastic Liouville equation approach, the perturbative time-local and time-nonlocal generalized quantum master equations, were assessed in the calculation of the equilibrium excited state and emission spectra.

Jing, Yuanyuan; Chen, Liping; Bai, Shuming; Shi, Qiang

2013-01-01

77

Velocity spectra of emission and absorption in electron-cyclotron radiation.  

National Technical Information Service (NTIS)

Selective electron-cyclotron processes are investigated using the phase-space spectra of emission and absorption for arbitrary momentum distribution functions. It is shown that, in general, for a system of electrons a sharp resonant velocity does not exis...

I. Fidone G. Giruzzi G. Chiozzi V. Krivenski

1989-01-01

78

Extreme Ultraviolet Emission Spectra of Core-Excited Levels in Sodium and Magnesium.  

National Technical Information Service (NTIS)

Using a pulsed-hollow-cathode discharge, we have observed the emission spectra of core-excited levels of Na I and Mg II. Line identifications and implications for extreme ultraviolet lasers are discussed. Keywords: Extreme Ultraviolet Radiation; Sodium; M...

K. D. Pedrotti A. J. Mendelsohn R. W. Falcone J. F. Young S. E. Harris

1985-01-01

79

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

80

Quantitative analysis of remote gas temperatures and concentrations from their infrared emission spectra  

Microsoft Academic Search

Techniques for obtaining quantitative values of the temperatures and concentrations of remote hot gaseous effluents from their measured passive emission spectra have been examined in laboratory experiments and on field trials. These emission spectra were obtained using an adapted FTIR spectrometer with 0.25 cm-1 spectral resolution. The CO2 and H2O vapour content in the plume from a 55 m smoke

M. Hilton; A. H. Lettington; I. M. Mills

1995-01-01

81

The Influence of Water Vapour on the Emission Spectra of Flames  

Microsoft Academic Search

The infrared emission spectra of a variety of small diffusion flames was studied in the laboratory. Ethylene, acetylene, matchwood and the pyrolysis products of Eucalypt forest litter gave qualitatively similar spectra consisting largely of non-specific black body radiation from carbon particles, with narrow radiation bands due to water vapour and, especially, carbon dioxide. Addition of water to the fuels had

N. K. KING

1973-01-01

82

Analysis of emission spectra of Ho3+:LFBCd glasses  

NASA Astrophysics Data System (ADS)

In the present paper, we report on the absorption and emission properties of (0.1-1.5 mol %) Ho3+ doped LFBCd (Li2O-LiF-B2O3-CdO) glasses prepared via melt quenching method. On exciting these glasses at (?exci) = 452 nm, two emissions at 556 nm (5S2?5I8; Green), 655 nm (5F5?5I8; Red) have been obtained. Upon exciting these glasses with a 980 nm diode laser, NIR emissions at 1195 nm (5I6?5I8), 1951 nm (5I7?5I8) have been measured for 1 mol % Ho3+:LFBCd glass. For higher concentration beyond 1.0 mol %, emission quenching of Ho3+ glass has been noticed and which has successfully been explained in terms of an energy level diagram. From absorption cross-section data, stimulated emission cross-section has been evaluated by applying McCumber's theory and further cross-sectional gain has also been computed for the emissions at 1195 nm (1.20 ?m) and 1951 nm (2.0 ?m) of 1 mol % Ho3+:LFBCd glass.

Naresh, V.; Buddhudu, S.

2014-04-01

83

HULLCA-Based Simulations of Non-LTE Emission Spectra.  

National Technical Information Service (NTIS)

This document describes the calculations I have carried out to synthesize spectra for test cases Ar1, Ge1, Ba1 and Au1. First, a brief description of how HULLAC generates atomic data is presented. Next, the implementation of those data in a collisional-ra...

K. B. Fournier

2001-01-01

84

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

85

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

NASA Astrophysics Data System (ADS)

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 by a temperature-controlled hot plate rather than from above by a solar lamp in order to separate infrared surface cooling from solar heating effects. Our spectra show prominent emission peaks which are attributed to the presence of near-surface thermal gradients created by infrared cooling of the uppermost layer of the material. The contrast of the emission peak is maximized under vacuum conditions, for which it is estimated that a temperature difference of at least 40 K existed within the top emission skin depth. The wavelength location of the emission peak occurs near the Christiansen wavelength at 7.35 ?m but has been shifted by approximately 0.2 ?m to shorter wavelengths. This result is in agreement with the earlier results of Logan et al. [1973] and points out that the existence of a thermal gradient violates the conditions required by Kirchoff's law, and therefore care should be taken when spectra of surfaces on airless bodies are interpreted using emissivity spectra converted from reflectance data. Increasing the atmospheric pressure in the chamber increased the conductivity of the soil, mitigating the thermal gradient and decreasing the contrast of the emission maxima. Although thermal gradients complicate the interpretation of emission spectra of airless bodies, they tend to enhance certain spectral features, and therefore emission spectroscopy should be useful for remote sensing of the surfaces of the Moon and Mercury.

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

86

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

Microsoft Academic Search

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

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

2009-01-01

87

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

Microsoft Academic Search

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=0.10.3) 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

T. P. Surkova; V. R. Galakhov; E. Z. Kurmaev

2009-01-01

88

Hydrocarbon emission features in the IR spectra of warm supergiants  

NASA Technical Reports Server (NTRS)

Observations in the 3-13 micron range are presented for two objects possessing the unidentified 21-micron feature, IRAS 22272 and IRAS 07134, which were obtained in the course of search for circumstellar aromatic hydrocarbon (PAH) emission bands. The 3.3 and 6.2 micron bands are attributed to circumstellar PAH molecules, and the 6-9 micron plateau and the 12- and 6.9-micron lines are attributed to larger, aromatic hydrocarbon clusters. These are the coolest stars known to exhibit the IR emission bands. The 21-micron feature is conjectured to also originate in a carbonaceous carrier.

Buss, R. H., Jr.; Cohen, M.; Tielens, A. G. G. M.; Werner, M. W.; Bregman, J. D.

1990-01-01

89

Chemiluminescent emission spectra of tin mono- and di-halides  

Microsoft Academic Search

Chemiluminescent emission from flames of tin halides burning at low pressure in potassium vapor is found to include vibronic bands of mono- and di-halides. The emitters are, quite certainly, electrically neutral species. Bands from SnCl2 are analyzed with the aid of a Deslandres scheme and some vibrational constants are assigned to the upper and lower states.

David Naegeli; Howard B. Palmer

1966-01-01

90

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

91

Effect of Molecular Oxygen on the Emission Spectra of Atomic Oxygen-Acetylene Flames  

Microsoft Academic Search

Studies have been made of the emission spectra (3000 to 6000 A) obtained from low-pressure atomic oxygen-acetylene flames diluted with varying amounts of molecular oxygen and molecular nitrogen. Added molecular oxygen greatly increased the OH emission while reducing CH and C2 emission. It also had an effect on the rotational intensity distribution of OH and on the vibrational intensity distribution

S. L. N. G. Krishnamachari; H. P. Broida

1961-01-01

92

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

93

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

94

Identifying plant species using MIR and TIR (2 - 14 ?m) emissivity spectra  

NASA Astrophysics Data System (ADS)

Tittle: Identifying plant species using MIR and TIR (2 - 14 m) emissivity spectra Identification plant species using remote sensing is generally limited by the similarity of their reflectance spectra in the visible, NIR and SWIR domains. Laboratory measured emissivity spectra in the mid to thermal infrared (MIR-TIR; 2 m - 14 m) shows significant differences. The laboratory emissivity spectra of thirteen common broad leaved species, comprising 3024 spectral bands in the MIR and TIR, were analyzed. For each wavelength the differences between the species were tested for significance using the one way analysis of variance (ANOVA) with the post-hoc Tukey HSD test. The emissivity spectra of the analysed species were found to be statistically different at various wavebands. Subsequently, six spectral bands were selected (based on the histogram of separable pairs of species for each waveband) to quantify the separability between each species pair based on the Jefferies Matusita (JM) distance. Out of 78 combinations, 76 pairs had a significantly different JM distance. Using the selected six wavebands for multiple plant species, overall classification accuracy of 92 % was achieved. This means that careful selection of hyperspectral bands in the MIR and TIR (2.5 m - 14 m) results in reliable species discrimination. Keywords: Spectral emissivity, J-M distance, ANOVA, Tukey HSD, spectral separability, Kirchhoff law

Ullah, S.; Schlerf, M.; Skidmore, A. K.; Hecker, C.

2012-04-01

95

Fluorine-K? and Chlorine-K? Emission Spectra from Alkali Fluorides and Chlorides  

NASA Astrophysics Data System (ADS)

The fluorine-K? and chlorine-K? emission spectra in fluorescence from a series of alkali halides MX (M=Li, Na, K, Rb and Cs; X=F and Cl) are measured with a high-resolution two-crystal spectrometer. Solid-state effects are observed on the intensities of the K1L1 and K?x satellite peaks in the K? and K? emission spectra, respectively. An anomalously low intensity of the K1L1 satellite peak is observed for KF. The measured emission spectra are presented along with the UPS spectra of the F- 2p and Cl- 3p valence bands obtained by Poole et al., the fluorine K absorption-edge spectra by Nakai et al. and the chlorine K absorption-edge spectra by the author. By using these spectra, the first shoulder at the K absorption edge is identified as being due to a core exciton, the energy level of which is formed below the bottom of the conduction band. The binding energy of the exciton is estimated.

Sugiura, Chikara

1991-04-01

96

Shaping Emission Spectra of Fluorescent Molecules with Single Plasmonic Nanoresonators  

SciTech Connect

We show that plasmonic nanoresonators composed of two gold nanoparticles change not only the intensity but also the spectral shape of the emission of fluorescent molecules. The plasmonic resonance frequency can be tuned by varying the distance between the nanoparticles, which allows us to selectively favor transitions of a fluorescent molecule to a specific vibrational ground state. Experimental data from correlated scattering and fluorescence microscopy agree well with calculations in the framework of generalized Mie theory. Our results show that the widely used description of a dye molecule near a metal surface as a mere two-level system is inadequate.

Ringler, M.; Schwemer, A.; Wunderlich, M.; Feldmann, J. [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet Muenchen, Amalienstrasse 54, 80799 Munich (Germany); Nichtl, A.; Kuerzinger, K. [Roche Diagnostics GmbH, Nonnenwald 2, 82372 Penzberg (Germany); Klar, T. A. [Photonics and Optoelectronics Group, Physics Department and CeNS, Ludwig-Maximilians-Universitaet Muenchen, Amalienstrasse 54, 80799 Munich (Germany); Institute of Physics and Institute of Micro- and Nanotechnologies, Technical University of Ilmenau, 98684 Ilmenau (Germany)

2008-05-23

97

Amplified spontaneous emission spectra from the superexciplex of coumarin 138  

NASA Astrophysics Data System (ADS)

In this report the dual amplified spontaneous emission (ASE) characteristics of coumarin 138 (C138) had been studied, under different solvent environments. The results obtained were compared with coumarin 461 (C461) and coumarin 450 (C450), which have closely related structure. The results showed that all these dyes could produce ASE from superexciplex - a new molecular species - formed only under high inversion densities, obtainable by pulsed laser excitation. We have strong indication that a superexciplex with TICT conformation is capable of producing strong ASE.

Ibnaouf, K. H.; Prasad, S.; Aldwayyan, A. S.; AlSalhi, Mohammad S.; Masilamani, V.

2012-11-01

98

NOISE AND SIGNAL FOR SPECTRA OF INTERMITTENT NOISELIKE EMISSION  

SciTech Connect

We show that intermittency of noiselike emission, after propagation through a scattering medium, affects the distribution of noise in the observed correlation function. Intermittency also affects correlation of noise among channels of the spectrum, but leaves the average spectrum, average correlation function, and distribution of noise among channels of the spectrum unchanged. Pulsars are examples of such sources: intermittent and affected by interstellar propagation. We assume that the source emits Gaussian white noise, modulated by a time envelope. Propagation convolves the resulting time series with an impulse-response function that represents effects of dispersion, scattering, and absorption. We assume that this propagation kernel is shorter than the time for an observer to accumulate a single spectrum. We show that rapidly varying intermittent emission tends to concentrate noise near the central lag of the correlation function. We derive mathematical expressions for this effect, in terms of the time envelope and the propagation kernel. We present examples, discuss effects of background noise, and compare our results with observations.

Gwinn, C. R.; Johnson, M. D., E-mail: cgwinn@physics.ucsb.edu, E-mail: michaeltdh@physics.ucsb.edu [Department of Physics, University of California, Santa Barbara, California 93106 (United States)

2011-05-20

99

A new emission feature in IRAS spectra and the polycyclic aromatic hydrocarbon spectrum  

NASA Technical Reports Server (NTRS)

IRAS spectra of those sources which show strong 7.7 and 11.3 micron emission features also show a plateau of emission extending from 11.3 to about 13.0 microns. Like the 11.3 micron feature, this new feature is attributed to the CH out-of-plane bending mode in polycyclic aromatic hydrocarbons (PAHs). Its discovery reinforces the identification of the 'unidentified infrared emission features' as emission from PAHs. The wavelength of this new feature suggests that interstellar PAHs are not as partially hydrogenated as hitherto thought. It also constrains their molecular structure.

Cohen, M.; Tielens, A. G. G. M.; Allamandola, L. J.

1985-01-01

100

Chemometric analysis of infrared emission spectra for quantitative analysis of BPSG films on silicon  

Microsoft Academic Search

Infrared emission spectra of 21 borophosphosilicate glass (BPSG) thin films on silicon wafers were collected with the samples held at constant temperature between 125--400°C using a heating stage designed for precise temperature control (±°C). Partial test squares calibrations applied to the BPSG infrared emittance spectra allowed four BPSG thin-film properties to be simultaneously quantified with precisions of 0.1 wt. %

J. E. Franke; Chuenyuan S. Chen; Songbaio Zhang; T. M. Niemczyk; D. M. Haaland

1993-01-01

101

Analysis of optical emission spectra from ICP of ArSiH 4CH 4 system  

Microsoft Academic Search

An inductively coupled plasma flame of ArSiH4CH4 system was analyzed in situ by spectroscopic method during chemical vapor deposition of ultrafine SiC particles. In the region of 200550nm, optical emission spectra of neutral Si, C, Ar, H, H2 and C2 were observed. As CH4\\/SiH4 ratio of the reactant gases was increased from 1.0 to 5.0, Si atomic spectra became weak.

A. Okada; K. Kijima

2002-01-01

102

Temperature-Dependent Total Emission Spectra of Azulene in Polymers: Modeling Using Spectral Densities  

Microsoft Academic Search

Narrowband excited, temperature dependent (1.4-150 K) emission spectra of the S1-S0 transition of azulene in different amorphous polymers are used to explore the matrix modes that contribute to dephasing of the electronic transition. The low- temperature spectra in all polymers consist of sharp zero-phonon lines (ZPL) whose frequencies represent the ground state vibrations of azulene, and broad phonon wings (PW)

Vinita Gupta; Anne B. Myers

1998-01-01

103

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

104

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

105

Resonant emission in the X-ray spectra. I. transition 3d metal dioxides  

Microsoft Academic Search

The calculations of the electronic structure and X-ray spectra of the MO68- (M = Ti, V, Cr, Mn) clusters, which were used as models for respective solid state dioxides, have been performed by the Xalpha-DV method. The one-electron model for resonant emission (reemission) was used. The calculations show, that X-ray resonant emission significantly affects the shape of the ML2,3 and

N. V. Dobrodey; A. V. Kondratenko; G. L. Gutsev; V. P. Krivitsky; Yu A. Nosatschov

1993-01-01

106

Resonant emission in the X-ray spectra. I. transition 3d metal dioxides  

Microsoft Academic Search

The calculations of the electronic structure and X-ray spectra of the MO68? (M = Ti, V, Cr, Mn) clusters, which were used as models for respective solid state dioxides, have been performed by the X?-DV method. The one-electron model for resonant emission (reemission) was used. The calculations show, that X-ray resonant emission significantly affects the shape of the ML2,3 and

N V Dobrodey; A V Kondratenko; G L Gutsev; V P Krivitsky; Yu A Nosatschov

1993-01-01

107

Emission and absorption spectra of InBr in low pressure discharges  

Microsoft Academic Search

This paper studies heated inductively driven rf-discharges using emission and absorption spectroscopy. The dependence on parameters such as pressure, heating temperature and amount of InBr in different background gases has been investigated. The measured spectra are compared to simulations of the InBr emission based on molecular constants, Franck-Condon factors and transition probabilities, providing information about rotational, vibrational and electronic population

S. Briefi; U. Fantz

2008-01-01

108

The 15-20 ?m Spitzer Spectra of Interstellar Emission Features in NGC 7023  

NASA Astrophysics Data System (ADS)

We present 15-20 ?m long-slit spectra of NGC 7023 from the Infrared Spectrograph (IRS) on Spitzer. We observe recently discovered interstellar emission features at 15.9, 16.4, 17.0, 17.4, 17.8, and 18.9 ?m, throughout the reflection nebula. The 16.4 ?m emission feature peaks near the photodissociation front northwest of the star, as the aromatic emission features (AEFs) at 3.3, 6.2, and 11.3 ?m do. The 16.4 ?m emission feature is thus likely related to the AEFs and radiates by nonequilibrium emission. The new 18.9 ?m emission feature, by contrast, decreases monotonically with stellar distance. We consider candidate species for the 18.9 ?m feature, including polycyclic aromatic hydrocarbons, fullerenes, and diamonds. We describe future laboratory and observational research needed to identify the 18.9 ?m feature carrier.

Sellgren, K.; Uchida, K. I.; Werner, M. W.

2007-04-01

109

Characteristics of high energy K{alpha} and Bremsstrahlung sources generated by short pulse petawatt lasers  

SciTech Connect

We have measured the characteristics of high energy K{alpha} sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at Lawrence Livermore National Laboratory. High energy x-ray backlighters will be essential for radiographing high energy-density experimental science targets for NIF projects especially to probe implosions and high areal density planar samples. Hard K{alpha} x-ray photons are created through relativistic electron plasma interactions in the target material after irradiated by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator charge coupled device (CCD) camera for imaging and a CCD camera for single photon counting. We have directly measured the 22 keV Ag K{alpha} source size using the RAL petawatt laser and performed knife-edge measurements of a 40 keV Sm K{alpha} source using the JanUSP laser. The measured source sizes are both {approx}60 {mu}m full width half maximum. We have also measured the Ag K{alpha} conversion efficiencies. At laser intensities of 1x10{sup 18} W/cm{sup 2} range, the conversion efficiency at 22 keV is {approx}1x10{sup -4}.

Park, H.-S.; Izumi, N.; Key, M.H.; Koch, J.A.; Landen, O.L.; Patel, P.K.; Phillips, T.W.; Zhang, B.B. [University of California, Lawrence Livermore National Laboratory, Livermore, California 94551 (United States); University of California, Davis, California 95616 (United States)

2004-10-01

110

Remote gas detection and quantitative analysis from infrared emission spectra obtained by Fourier transform infrared spectroscopy  

Microsoft Academic Search

Techniques for obtaining quantitative values of the temperatures and concentrations of remote hot gaseous effluents from their measured passive emission spectra have been examined in laboratory experiments. The high sensitivity of the spectrometer in the vicinity of the 2397 cm-1 band head region of CO2 has allowed the gas temperature to be calculated from the relative intensity of the observed

Moira Hilton; Alan H. Lettington; Ian M. Mills

1994-01-01

111

Ultraviolet-Visible and Infrared Emission Spectra of Propagating Methane-Coal-Dust Inhibitor Flames.  

National Technical Information Service (NTIS)

Ultraviolet-visible and infrared emission spectra from propagating methane-coal-dust-inhibitor mixtures have been obtained in a 0.2-by 0.2-by 5.3-m vertical duct over a range of flame speeds from 2 to 100 m/sec. Results serve as a basis for the design and...

Z. J. Fink L. E. Dalverny J. Grumer

1974-01-01

112

Identification of a specific type of PD from acoustic emission frequency spectra  

Microsoft Academic Search

The paper presents an attempt to apply spectral analysis tools in processing acoustic emission (AE) pulses generated by partial discharge (FD). The experimental part of the paper describes spark gaps generating four types of PD and specifies parameters of measured acoustic signals and recalls the system used for measurement and analysis of the frequency spectra. Also, a spectral analysis procedure

T. Boczar

2001-01-01

113

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

114

Influence of Clouds on the Emission Spectra of Earth-like Extrasolar Planets  

NASA Astrophysics Data System (ADS)

The climate of Earth-like planets results from the energy balance between absorbed starlight and radiative losses of heat from the surface and atmosphere to space. Clouds reflect sunlight back towards space, reducing the stellar energy available for heating the atmosphere (albedo effect), but also reduce radiative losses to space (greenhouse effect). Clouds also have a large effect on the emission spectra of planetary atmospheres, by either concealing the thermal emission from the surface or dampening the spectral features of molecules, which is, of course, also true for biomarkers (e.g., N2O and O3). We present first results on the impact of multi-layered clouds in the atmospheres of Earth-like extrasolar planets orbiting different types of central stars on the planetary IR emission spectra.

Kitzmann, D.; Patzer, A. B. C.; von Paris, P.; Godolt, M.; Grenfell, J. L.; Rauer, H.

2010-10-01

115

Emission spectra of nitrous oxide supported acetylene flames at atmospheric pressure.  

PubMed

The emission spectra of a premixed flame of acetylene supported by nitrous oxide have been recorded under different fuel-gas mixture conditions. The emission spectra in these flames of a series of metals, for which it is difficult to obtain a significant population of ground state atoms for atomic absorption spectroscopy in more conventional flames, have also been studied. The red secondary zone which is present in the fuel-rich flames shows emission attributable to long-lived CN and NH species which form a strongly reducing atmosphere to inhibit refractory oxide formation from elements such as molybdenum, titanium and aluminium introduced into the flame. An attempt has also been made to explain some of the reactions which may occur between the flame species above the primary reaction zone. PMID:18960164

Kirkbright, G F; Peters, M K; West, T S

1967-07-01

116

Package for Interactive Analysis of Line Emission (Analysis of UV-X-Ray High-Resolution Emission Spectra)  

NASA Technical Reports Server (NTRS)

The Package for Interactive Analysis of Line Emission (PINTofALE) is a suite of IDL routines designed to carry out spectroscopic analysis of high-resolution X-ray spectra. The current version is 1.5, and will shortly be upgraded to v2. A detailed description of the package, together with detailed documentation, example walk-throughs, science threads, and downloadable tar files, are available on-line.

Hunter, Paul (Technical Monitor); Kashyap, Vinay

2004-01-01

117

Chemiluminescent emission spectra of lead, chromium, ruthenium, iron, manganese, rhenium, osmium and tungsten in the reactive flow detector  

Microsoft Academic Search

Spectra have been measured of the chemiluminescent emissions produced by various organometallic compounds passing through the reactive flow detector (RFD). The RFD spectra of osmium, rhenium and tungsten each display a broad continuum from approximately 400 to 800 nm, whose emitting species remain unidentified. The luminescence spectra of lead, chromium, ruthenium, iron and manganese in the reactive flow are each

Kevin B. Thurbide; Walter A. Aue

2002-01-01

118

Chemometric analysis of infrared emission spectra for quantitative analysis of BPSG films on silicon  

SciTech Connect

Infrared emission spectra of 21 borophosphosilicate glass (BPSG) thin films on silicon wafers were collected with the samples held at constant temperature between 125--400{degree}C using a heating stage designed for precise temperature control ({plus_minus}{degree}C). Partial test squares calibrations applied to the BPSG infrared emittance spectra allowed four BPSG thin-film properties to be simultaneously quantified with precisions of 0.1 wt. % for boron and phosphorus, 35 {Angstrom} for film thickness, and 1.2{degree}C for temperature.

Franke, J.E.; Chen, Chuenyuan S.; Zhang, Songbaio; Niemczyk, T.M. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Chemistry; Haaland, D.M. [Sandia National Labs., Albuquerque, NM (United States)

1993-11-01

119

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

120

Rotational and vibrational temperatures measured in a chemiluminescent flame from FTIR Bi 2 emission spectra  

Microsoft Academic Search

Rotational and vibrational temperatures of the Bi2 dimer have been measured in a chemiluminescent flame. Emission spectra of the Bi2 a3?u+(a11u)?X1?g+(X0g+) transition in the near-infrared region were recorded with a FTIR spectrometer. High-resolution spectra of the 0-3, 0-8, 0-9, 2-3, 4-1, 6-0, 6-1, and 7-1 bands served for the determination of the rotational temperature. It was observed that both rotational

J. Borkowska-Burnecka; W. ?yrnicki; K. D. Setzer; E. H. Fink

2004-01-01

121

Laboratory simulation of infrared astrophysical features. Ph.D. Thesis; [emission spectra of comets  

NASA Technical Reports Server (NTRS)

Intermediate resolution emission spectroscopy was used to study a group of 9 terrestrial silicates, 1 synthetic silicate, 6 meteorites and 2 lunar soils; comparisons were made with the intermediate resolution spectra of Comet Kohoutek in order to determine which materials best simulate the 10um astrophysical feature. Mixtures of silicates which would yield spectra matching the spectrum of the comet in the 10um region include: (1) A hydrous layer lattice silicate in combination with a high temperature condensate; (2) an amorphous magnesium silicate in combination with a high temperature condensate and (3) glassy olivine and glassy anorthite in approximately equal proportions.

Rose, L. A.

1977-01-01

122

High-energy K{alpha} radiography using high-intensity, short-pulse lasers  

SciTech Connect

The characteristics of 22-40 keV K{alpha} x-ray sources are measured. These high-energy sources are produced by 100 TW and petawatt high-intensity lasers and will be used to develop and implement workable radiography solutions to probe high-Z and dense materials for the high-energy density experiments. The measurements show that the K{alpha} source size from a simple foil target is larger than 60 {mu}m, too large for most radiography applications. The total K{alpha} yield is independent of target thicknesses, verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. One-dimensional radiography experiments using small-edge-on foils resolved 10 {mu}m features with high contrast. Experiments were performed to test a variety of small volume two-dimensional point sources such as cones, wires, and embedded wires, measured photon yields, and compared the measurements with predictions from hybrid-particle-in-cell simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the high-energy range. An initial look at some of these detector issues is also presented.

Park, H.-S.; Chung, H.-K.; Izumi, N.; Key, M.H.; King, J.A.; Koch, J.A.; Landen, O.L.; Patel, P.K.; Price, D.F.; Remington, B.A.; Robey, H.F.; Snavely, R.A.; Tabak, M.; Town, R.P.J.; Wickersham, J.E. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Chambers, D.M.; Eagleton, R.; Goldsack, T. [Atomic Weapons Establishment, Aldermaston, Reading, RG7 4PR (United Kingdom); Clarke, R.J.; Heathcote, R. [Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX (United Kingdom)] (and others)

2006-05-15

123

High Energy K(alpha) Radiography Using High-intensity, Short-pulse Lasers  

SciTech Connect

We have performed experiments using Callisto, the Vulcan 100 TW and the Vulcan Petawatt high intensity lasers to understand the characteristics of high energy, K{alpha} x-ray sources and to implement workable radiography solutions at 20-100 keV. Our measurements show that the K{alpha} size from a simple foil target is larger than 60 {micro}m, far larger than the experiment resolution requirement. The total K{alpha} yield is independent of target thicknesses verifying that refluxing plays a major role in photon generation. Smaller radiating volumes emit brighter K{alpha} radiation. 1-D radiography experiments using small-edge-on foils resolved 10 {micro}m features with high contrast. We tested a variety of small volume 2-D point sources such as cones, wires, and embedded wires, measuring photon yields and comparing our measurements with predictions from hybrid-PIC LSP simulations. In addition to high-energy, high-resolution backlighters, future experiments will also need imaging detectors and diagnostic tools that are workable in the 20-100 keV energy range. An initial look at some of these detector issues is also presented.

Park, H; Izumi, N; Key, M H; King, J A; Koch, J A; Landen, O L; Patel, P K; Price, D F; Remington, B A; Robey, H F; Snavely, R A; Tabak, M; Town, R J; Wickersham, J E; Stoeckl, C; Storm, M; Theobald, W; Chambers, D M; Eagelton, R; Goldsack, T; Clarke, R J; Heathcote, R; Giraldez, E; Nikroo, A; Steinman, D A; Stephens, R B; Zhang, B B

2005-11-16

124

THE EMISSION-LINE SPECTRA OF MAJOR MERGERS: EVIDENCE FOR SHOCKED OUTFLOWS  

SciTech Connect

Using a spectral decomposition technique, we investigate the physical origin of the high-velocity emission-line gas in a sample of 39 gas-rich, ultraluminous infrared galaxy mergers. Regions with shock-like excitation were identified in two kinematically distinct regimes, characterized by broad ({sigma} > 150 km s{sup -1}) and narrow linewidths ({sigma} {<=} 150 km s{sup -1}). Here, we investigate the physical origin of the broad emission, which we show is predominantly excited by shocks with velocities of 200-300 km s{sup -1}. Considering the large amount of extinction in these galaxies, the blueshift of the broad emission suggests an origin on the near side of the galaxy and therefore an interpretation as a galactic outflow. The large spatial extent of the broad, shocked emission component is generally inconsistent with an origin in the narrow-line region of an active galactic nucleus. The kinetic energy in the mass loss as well as the luminosity of the emission lines is consistent with the fraction of the supernova energy attributed to these mechanisms by shocked stellar winds. Since some shocks can be recognized in moderately high resolution, integrated spectra of nearby ultraluminous starbursts, the spectral fitting technique introduced in Soto and Martin may therefore be used to improve the accuracy of the physical properties measured for high-redshift galaxies from their (observed frame) infrared spectra.

Soto, Kurt T.; Martin, C. L.; Prescott, M. K. M. [Physics Department, University of California, Santa Barbara, CA 93106-9530 (United States); Armus, L. [Spitzer Science Center, California Institute of Technology, Pasadena, CA (United States)

2012-09-20

125

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

126

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

127

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

NASA Astrophysics Data System (ADS)

The authors present 8.0 - 13.0 micron spectra (??/? = 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.

1983-12-01

128

InP quantum dots in pillar microcavities - mode spectra and single-photon emission  

NASA Astrophysics Data System (ADS)

We have investigated mode spectra and single-photon emission from InP quantum dots in a pillar microcavity. Micropillars are fabricated by milling a planar AlAs/AlGaAs cavity with a focused ion beam, containing self assembled InP quantum dots embedded in AlGaInP barriers as the active medium. We performed micro-photoluminescence measurements to characterize the mode spectra and compared them with a theoretical model revealing excellent agreement. Quality factors up to 3700 were achieved. Furthermore almost background-free single-photon emission was verified by second-order photon auto-correlation measurements under pulsed excitation, yielding g(2)(0) values of 0.15.

Bommer, M.; Schulz, W.-M.; Thomay, T.; Tomas, M.; Robach, R.; Jetter, M.; Leitenstorfer, A.; Bratschitsch, R.; Michler, P.

2010-02-01

129

Chemical effects in the K? X-ray emission spectra of sulfur  

NASA Astrophysics Data System (ADS)

In this work our previous study about chemical effects in the K? spectra of S compounds employing high-resolution X-ray spectroscopy has been extended to the K? emission spectra. The measurements were performed with a wavelength dispersive single crystal spectrometer operated in the von Hamos geometry having an energy resolution comparable to the natural linewidth of the measured K? X-ray lines. The target fluorescence was produced by irradiating the samples with the bremsstrahlung from an X-ray tube. The energies and widths of the main components in the K? emission spectrum are given for different sulfur compounds (sulfide, sulfite, sulfate). The measured energy shifts between the K? lines of the compounds and elemental sulfur are presented as a function of the sulfur oxidation state and compared with the results obtained from the former K? measurements.

Kav?i?, M.; Dousse, J.-Cl.; Szlachetko, J.; Cao, W.

2007-07-01

130

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

131

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

132

Emission Spectra of the CuTe and AuTe Molecules  

Microsoft Academic Search

Emission spectra from a King's furnace containing mixtures of Cu-Te and Au-Te respectively have been recorded. New bands appear with the Cu-Te mixture at about 1800 C in the region lambdalambda6965-6110, and with the Au-Te mixture they appear at about 2100 C in the range lambdalambda6940-6155. In both cases the bands are degraded to the red. They are attributed to

R. C. Maheshwari; D. Sharma

1963-01-01

133

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

134

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

135

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

136

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

137

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, . Z.

2009-01-01

138

Proposal for Predictive Expressions of Emissivity Spectra for Powdery Coal Ash  

NASA Astrophysics Data System (ADS)

The calculation expressions for the emissivity spectra of powdery coal ashes have been derived by fitting the measured emissivity spectra to improve the accuracy with which the radiative heat transfer rate can be estimated with a calculation tool for pulverized coal-fired boilers. The expressions are defined in three bands. First, in band 1, which corresponds to wavelengths ranging from 2 to 4 micrometers, and in band 3, which corresponds to wavelengths ranging from 8 to 16 micrometers, the expressions are formulated into the linear function of the weight ratio of five chemical compositions, which correspond to silica, alumina, calcium oxide, ferric oxide and magnesia, and the temperature of the coal ash and the wavelengths. Second, the expression in band 2, with the wavelengths ranging from 4 to 8 micrometers, is formulated into the cubic function of the wavelength. The expression predicts the emissivity spectra of powdery coal ash, whose raw coals range from 0.6 to 2.4 (-) in a fuel ratio (=mass ratio of fixed carbon to volatile matter in coal), with 0.050 (-) to 0.170 (-) predictability. The proposed expression has widespread predictability of powdery coal ashes that range from 2 to 16 micrometers in wavelength.

Tsuda, Shinji; Okazaki, Teruyuki; Gwosdz, Alfred

139

Doppler effects on 3-D non-LTE radiation transport and emission spectra.  

SciTech Connect

Spatially and temporally resolved X-ray emission lines contain information about temperatures, densities, velocities, and the gradients in a plasma. Extracting this information from optically thick lines emitted from complex ions in dynamic, three-dimensional, non-LTE plasmas requires self-consistent accounting for both non-LTE atomic physics and non-local radiative transfer. We present a brief description of a hybrid-structure spectroscopic atomic model coupled to an iterative tabular on-the-spot treatment of radiative transfer that can be applied to plasmas of arbitrary material composition, conditions, and geometries. The effects of Doppler line shifts on the self-consistent radiative transfer within the plasma and the emergent emission and absorption spectra are included in the model. Sample calculations for a two-level atom in a uniform cylindrical plasma are given, showing reasonable agreement with more sophisticated transport models and illustrating the potential complexity - or richness - of radially resolved emission lines from an imploding cylindrical plasma. Also presented is a comparison of modeled L- and K-shell spectra to temporally and radially resolved emission data from a Cu:Ni plasma. Finally, some shortcomings of the model and possible paths for improvement are discussed.

Giuliani, J. L. (Naval Research Laboratory, Washington, DC); Davis, J. (Naval Research Laboratory, Washington, DC); DasGupta, A. (Naval Research Laboratory, Washington, DC); Apruzese, John P. (Naval Research Laboratory, Washington, DC); Jennings, Christopher A.; Clark, R. W. (Naval Research Laboratory, Washington, DC); Ampleford, David J.; Bailey, James E.; Thornhill, Joseph W. (Naval Research Laboratory, Washington, DC); Cuneo, Michael Edward; Rochau, Gregory Alan; Coverdale, Christine Anne; Jones, Brent Manley; Hansen, Stephanie B.

2010-10-01

140

Thermal Emission Spectra of Phobos, Vesta, Ceres, and Pallas: A Comparison  

NASA Technical Reports Server (NTRS)

Ultraviolet, visual, and near-infrared spectra of Phobos, obtained by Mariner 9 and Viking Orbiters, were interpreted to suggest a compositional similarity with carbonaceous chrondrites. Such a composition would be inconsistent with the moon's origin in the proto-Mars region, as Mars is composed chiefly of differentiated silicates. This interpretation was used to suggest that the moons originated in the main-asteroid belt, with subsequent capture and orbital evolution into their current locations. Interpretations of more recent visual and near-infrared spectra, obtained by Phobos-2 and Mars Pathfinder, have demonstrated that the Phobos spectrum is more similar to spectra of other classes of asteroids and lunar soils. If lunar mare soil is the correct analogy, then such a composition suggests a formation of Phobos from materials similar to that on Mars, i.e. basalts, and would not require a dynamically difficult capture and orbital evolution. During the science phasing orbits of the Mars Global Surveyor mission Thermal Emission Spectrometer (TES) observations of Phobos were acquired at each of four encounters. The spectral variability observed for localized surface regions on Phobos has been previously reported and is greatest near the northern wall of Stickney crater. Interpretation of the thermal infrared spectra of airless bodies, based upon most existing laboratory measurements, is complicated by the absence of interstitial gases on the celestial objects that would act to minimize potential thermal gradients in the upper layers of the surface. As an aid to interpretation of the TES Phobos spectra are compared to telescopic and airborne thermal infrared spectra of asteroids from several classes, including Ceres (G), Pallas (B), and Vesta (V). The asteroid spectra provide a direct analogy to the physical situation encountered at the surface of Phobos, albeit different thermal gradients may exist for each surface. This work is supported by NASA RTOP's 344-30-30-01 and 344-34-21-08.

Roush, Ted; DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

141

Influence of the surface band structure on electron emission spectra from metal surfaces  

NASA Astrophysics Data System (ADS)

Electron distributions produced by grazing impact of fast protons on Mg(0001), Cu(111), Ag(111), and Au(111) surfaces are investigated, focusing on the effects of the electronic band structure. The process is described within the band-structure-based approximation, which is a perturbative method that includes an accurate representation of the electron-surface interaction, incorporating information of the electronic band structure of the solid. For all the studied surfaces, the presence of partially occupied surface electronic states produces noticeable structures in double-differentialenergy- and angle-resolvedelectron emission probabilities from the valence band. For Mg, Cu, and Ag these structures remain visible in electron emission spectra after adding contributions coming from core electrons, which might make possible their experimental detection, but for Au they are hidden by inner-shell emission.

Archubi, C. D.; Faraggi, M. N.; Silkin, V. M.; Gravielle, M. S.

2014-04-01

142

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

143

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

144

Detection and Characterisation of H-? Emission Lines from Gaia BP/RP Spectra  

NASA Astrophysics Data System (ADS)

The Gaia probe, set to launch in 2011, will measure an estimated billion astronomical objects, producing an enormous amount of data. One of the data analysis tasks will be the identification and classification of measured objects. A vast majority of them will be ``ordinary'' stars from our Galaxy but a certain percentage will belong to ``peculiar'' objects. We are interested in detecting emission line stars (ELS). The characteristic feature of most ELS is the presence of a H-? emission line in their spectra. In the case of Gaia measurements, the influence of this line could be detected in low resolution prismatic spectra which will be recorded both in blue (BP) and red (RP) spectral region. In this work, we compare different algorithms for detecting and characterising H-? lines in Gaia spectra. These include a simple, integrated flux ratio-based algorithm and several machine learning algorithms, such as neural networks, support vector machines and support vector regression. We study line detection both from single-transit and over-sampled end-of-mission data.

Jnes, Jrgen; Laur, Sven; Kolka, Indrek

2008-12-01

145

Temperature-Dependent Total Emission Spectra of Azulene in Polymers: Modeling Using Spectral Densities  

NASA Astrophysics Data System (ADS)

Narrowband excited, temperature dependent (1.4-150 K) emission spectra of the S1-S0 transition of azulene in different amorphous polymers are used to explore the matrix modes that contribute to dephasing of the electronic transition. The low- temperature spectra in all polymers consist of sharp zero-phonon lines (ZPL) whose frequencies represent the ground state vibrations of azulene, and broad phonon wings (PW) on the lower-energy side of the ZPL which carry information about optically active matrix modes. As the temperature is raised the ratio of ZPL to PW intensity decreases and the PW broadens until the spectrum resembles that in room temperature liquids, with sharp Raman-like peaks on a broad fluorescence background. The temperature-dependent emission spectra are simulated by modeling the azulene vibrations as undamped, displaced harmonic oscillators while the effect of the matrix is incorporated as a spectral density function that represents the optically active modes weighted by their coupling strengths. Spectral densities extracted from other experiments in the same polymers are used to evaluate the dependence of the relevant spectral density on the chromophore and the type of measurement.

Gupta, Vinita; Myers, Anne B.

1998-03-01

146

K-alpha X-ray Thomson Scattering From Dense Plasmas  

Microsoft Academic Search

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 1.71023 cm-3, were determined from the plasmon frequency shift

Andrea L. Kritcher; Paul Neumayer; John Castor; Tilo Doeppner; Roger W. Falcone; Otto L. Landen; Hae Ja Lee; Richard W. Lee; Edward C. Morse; Andrew Ng; Steve Pollaine; Dwight Price; Siegfried H. Glenzer

2009-01-01

147

Excitation and emission spectra of rubidium in rare-gas thin-films.  

PubMed

To understand the optical properties of atoms in solid state matrices, the absorption, excitation, and emission spectra of rubidium doped thin-films of argon, krypton, and xenon were investigated in detail. A two-dimensional spectral analysis extends earlier reports on the excitation and emission properties of rubidium in rare-gas hosts. We found that the doped crystals of krypton and xenon exhibit a simple absorption-emission relation, whereas rubidium in argon showed more complicated spectral structures. Our sample preparation employed in the present work yielded different results for the Ar crystal, but our peak positions were consistent with the prediction based on the linear extrapolation of Xe and Kr data. We also observed a bleaching behavior in rubidium excitation spectra, which suggests a population transfer from one to another spectral feature due to hole-burning. The observed optical response implies that rubidium in rare-gas thin-films is detectable with extremely high sensitivity, possibly down to a single atom level, in low concentration samples. PMID:22779665

Gerhardt, Ilja; Sin, Kyungseob; Momose, Takamasa

2012-07-01

148

Excitation and emission spectra of rubidium in rare-gas thin-films  

SciTech Connect

To understand the optical properties of atoms in solid state matrices, the absorption, excitation, and emission spectra of rubidium doped thin-films of argon, krypton, and xenon were investigated in detail. A two-dimensional spectral analysis extends earlier reports on the excitation and emission properties of rubidium in rare-gas hosts. We found that the doped crystals of krypton and xenon exhibit a simple absorption-emission relation, whereas rubidium in argon showed more complicated spectral structures. Our sample preparation employed in the present work yielded different results for the Ar crystal, but our peak positions were consistent with the prediction based on the linear extrapolation of Xe and Kr data. We also observed a bleaching behavior in rubidium excitation spectra, which suggests a population transfer from one to another spectral feature due to hole-burning. The observed optical response implies that rubidium in rare-gas thin-films is detectable with extremely high sensitivity, possibly down to a single atom level, in low concentration samples.

Gerhardt, Ilja; Sin, Kyungseob; Momose, Takamasa [Department of Chemistry, Low Temperature Group, University of British Columbia, Vancouver, B.C. V6T 1Z1 (Canada)

2012-07-07

149

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

150

Plagioclase compositions derived from thermal emission spectra of compositionally complex mixtures: Implications for Martian feldspar mineralogy  

NASA Astrophysics Data System (ADS)

The compositions of plagioclase, the most abundant mineral in the Martian crust, reflect changing conditions during magmatic evolution. Plagioclase contains spectral features at thermal infrared wavelengths that permit its detection by thermal emission spectrometers (Thermal Emission Spectrometer (TES), Thermal Emission Imaging System (THEMIS), and Miniature TES (Mini-TES)) on Mars spacecraft. Previous studies have determined the accuracy with which average plagioclase compositions can be modeled in simple two-component sand mixtures and terrestrial volcanic rocks. Studies of terrestrial rock analogs suffer from difficulties in accurately determining the average plagioclase composition for comparison with the spectrally modeled composition. Sand mixtures, however, provide a means of controlling plagioclase compositions for direct comparison to those modeled by linear deconvolution. This has allowed us to address how compositional complexity may affect our ability to derive average plagioclase compositions from thermal emission data. In this study, we examine the accuracy with which average plagioclase compositions can be modeled from emission spectra of complex mixtures of three, four, and five compositions of coarse (500-850 ?m) plagioclase sand. Additionally, we examine multiphase mixtures of plagioclase with pyroxene, olivine, magnetite, and ilmenite that are analogous to selected Martian surface materials. Increasing the number of plagioclase compositions or introducing additional mineral phases does not affect the accuracy previously reported for modeling average plagioclase compositions. Plagioclase can be modeled to within 6 An of measured compositions at laboratory, TES, THEMIS, and Mini-TES resolution (within 1? standard deviation).

Milam, Keith A.; McSween, Harry Y.; Christensen, Philip R.

2007-10-01

151

Modelling of emission spectra of Pr I by summarizing hyperfine patterns of overlapping spectral lines  

NASA Astrophysics Data System (ADS)

We present studies of the the hyperfine (hf) structure of spectral lines of Praseodymium (Pr) by laser spectroscopic investigations as well as by analyzing Fourier Transform (FT) spectra. The experimental part of our work is done with the technique of laser-induced fluorescence (LIF) spectroscopy in a hollow cathode lamp. We present detailed studies of the very small region of 1.5 (from 5810.5 to 5812.0 ) in the visible area of the FT spectrum where at least 14 spectral lines are overlapping. In the investigated region we discovered two new even levels and three new odd levels and could classify 11 new spectral lines. The final goal is to model the emission spectrum by a sum of the hf profiles of all spectral lines in a certain region. Application of such modelling may be found in analyzing highly resolved stellar spectra.

Gamper, B.; Khan, S.; Siddiqui, I.; Windholz, L.

2013-10-01

152

Differential emission measure for line spectra and broadband data from the Bayesian iterative method  

NASA Astrophysics Data System (ADS)

Inverse problems techniques allow deriving physical characteristics of hot optically thin so-lar and stellar plasma from their extreme ultraviolet and X-ray spectra. One of them, called Bayesian iterative method (BIM), relies on a probabilistic Bayesian framework for the spec-tral inverse problem, and reconstructs differential emission measure (DEM) distributions. We present here the application of BIM to both high resolution solar line spectra as well as to broadband imaging data. To demonstrate its abilities, we present various numerical tests and model simulations establishing robustness and usefulness. We then apply BIM to several so-lar non flaring active regions data previously analyzed with other techniques and instruments (SOHO-SUMER, CORONAS/F-SPIRIT, and HINODE-XRT).

Goryaev, Farid; Parenti, Susanna; Urnov, Alexander; Oparin, S. N.; Hochedez, Jean-Franois; Reale, Fabio

153

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

154

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

155

Emission features in the 4-13 micron spectra of the reflection nebulae NGC 7023 and NGC 2023  

NASA Technical Reports Server (NTRS)

Spectroscopy from 4 to 13 microns of the visual reflection nebulae NGC 7023 and NGC 2023 has been obtained. These data, together with previous work from 1 to 4 microns, show that the spectra of these sources consist of a relatively flat continuum from 1 to 13 microns and six emission features at 3.3, 3.4, 6.2, 7.7, 8.6, and 11.3 microns. The observations rule out equilibrium thermal emission for the features and continuum in reflection nebulae, and point toward a nonequilibrium emission mechanism such as thermal emission from thermally fluctuating small grains or fluorescence from large molecules. The similarity of the emission feature spectra in reflection nebulae to those in other sources suggests a universal emission mechanism, thus implying nonequilibrium emission mechanisms in other sources.

Sellgren, K.; Allamandola, L. J.; Bregman, J. D.; Werner, M. W.; Wooden, D. H.

1985-01-01

156

Temperature determination of N2 discharge plasma by computational simulation of its emission spectra  

NASA Astrophysics Data System (ADS)

The emission spectra of N2 hollow cathode and pulsed discharges were investigated and computational simulations have been made for the determination of the rotational and vibrational temperatures. A calibration curve was obtained by rotational simulation and was applied to study the space-resolved temperature in the pulsed discharge plasma. The rotational temperature was found to decrease rapidly along the radial axis of the plasma. The vibrational temperature in the pulsed discharge plasma was estimated by spectral simulation and was found to be more than three times higher than the rotational temperature.

Mi, Lan; Xu, Peng; Wang, Pei-Nan

2005-11-01

157

New analysis of the C2 Ballik-Ramsay system from flame emission spectra  

Microsoft Academic Search

The C2 b3Sigmag- --> a3Piu Ballik-Ramsay system has been studied through emission flame spectra recorded with a Fourier transform interferometer. The 14 bands 0-0, 1-0, 1-1, 2-0, 2-1, 3-0, 3-1, 3-2, 4-1, 4-2, 5-2, 5-3, 6-3, and 7-4 were identified in the 4850- 9900-cm-1 spectral range. They have been reduced to molecular constants using an iterative, nonlinear, least-squares method. Rotational

C. Amiot; J. Chauville; J.-P. Maillard

1979-01-01

158

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, Jrn; Rossi, Manuela; Nestola, Fabrizio; D'Amore, Mario; Hiesinger, Harald

2014-05-01

159

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

160

[Optimization of optical parametric amplification on femtosecond fluorescence spectra by referring to cone emission].  

PubMed

Femtosecond time-resolved fluorescence spectra technique based on non-collinear optical parametric amplification is a new method for ultrafast spectroscopy research In the present report, the authors discuss the dynamic range for amplifying fluorescence. The supercontinuum seed can be amplified linearly to its transient intensity. Due to large amplification ratio up to 10(7), small instability in pump pulse energy produces large fluctuation in final output amplitude. Here the authors introduce a method using cone emission as reference to overcome this difficulty. The results show significant improvement in fluorescence dynamics curve. PMID:21800583

Li, Feng-ming; Wang, Shu-feng; Gong, Qi-huang

2011-05-01

161

Thermal emission from particulate surfaces: A comparison of scattering models with measured spectra  

NASA Technical Reports Server (NTRS)

Emissivity spectra of particulate mineral samples are highly dependent on particle size when that size is comparable to the wavelength of light emitted (5-50 micrometers for the midinfrared). Proper geologic interpretation of data from planetary infrared spectrometers will require that these particle size effects be well understood. To address this issue, samples of quartz powders were produced with narrow, well-characterized particle size distributions. Mean particle diameters in these samples ranged from 15 to 227 micrometers. Emission spectra of these powders allow the first detailed comparison of the complex spectral variations with particle size observed in laboratory data with the predictions of radiative transfer models. Four such models are considered here. Hapke's relectance theory (converted to emissivity via Kirchoff's law) is the first model tested. Hapke's more recently published emission theory is also employed. The third model, the 'Mie/Conel' model, uses Mie single scattering with a two-stream approximation for multiple scattering. This model, like the first, is a converted reflec- tance model. Mie scattering assumes particles are both spherical and well separated, which is not true for the quartz powders, but includes diffraction effects. The fourth model uses the Mie solution for single scattering by spheres and inputs those results into the multiple scattering formalism of Hapke's emission theory. The results of the four models are considered in relation to the values of the optical constants n and k. We have grouped these as class 1 (k large), class 2 (k moderate, n is approximately 2), class 3 (k small, n is approximately 2), and class 4 (k small, n is approximately 1). In general, the Mie/Hapke hybrid model does best at predicting variations with grain size. In particular, it predicts changes of the correct pattern, although incorrect magnitude, for class 1 bands, where large increases in emissivity with decreasing grain size are observed. This model also does an excellent job on moderate (class 2) and very weak and intraband (class 3) regions, and correctly predicts the emission maximum and its invariance with grain size near the Christiansen frequency (class 4). The Mie/Hapke hybrid model also has the fewest free parameters of the four models examined, while maintaining the most physical treatment of the radiative transfer. The Mie/Conel model performs as well as the Mie/Hapke hybrid model in strong bands (class 1) but does not accurately model the behavior of moderate (class 2) and very weak (class 3) bands.

Moersch, J. E.; Christensen, P. R.

1995-01-01

162

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

163

Effects of Clouds on High Resolution Thermal Emission Spectra of Terrestrial Exo-Planets  

NASA Astrophysics Data System (ADS)

For an investigation of the potential habitability of terrestrial exo-planets the spectroscopic characterization of the planetary atmosphere and the identification of biomarker signatures is crucial. The radiative transfer is critically dependent on atmospheric (pressure, temperature, composition) and surface conditions. In particular, clouds can have a large impact on the planetary spectra (intensities and shapes) due to extinction events. Here the effects of the presence of clouds in Earth-like planetary atmosphere are studied with a high resolution radiative transfer model and compared to low and moderate resolution spectra. Infrared transmission and emission spectra are modeled using a combination of a line-by-line (lbl) molecular absorption code with a multiple scattering radiative transfer solver. Temperature profiles and low resolution spectra for Earth-like planets around different types of central stars have been taken from a radiative-convective climate model with a parametrized cloud description (see Kitzmann et al. 2010, AA, Vol 511, A66). The new lbl-multiple scattering code was tested successfully with respect to consistency to a low resolution radiative transfer code and by comparisions with Venus observations. The dependency of biomarker signatures on the presence of low-level water and high-level ice clouds is studied, e.g. for the thermal infrared band of ozone at 9.6 micrometer. Results indicate the important impact of clouds on the detectability of biomarker molecules by dampening their spectral signatures. Furthermore, biosignatures may be lost in low resolution spectra leading to false negative classification, i.e. high resolution lbl modeling is mandatory for an assessment of detection feasibility. Hence systematic high resolution studies have to be pursued covering other (UV, Vis, NIR) spectral ranges of interest (other biomolecules). Acknowlegements: This work has been supported by the Research Alliance Planetary Evolution and Life of the Helmholtz Association.

Vasquez, M.; Schreier, F.; Kitzmann, D.; Patzer, B.; Rauer, H.; Gimeno Garcia, S.; Trautmann, T.

2012-04-01

164

The Gas-Phase Spectra of Resonance-Stabilized Radicals and the Red Rectangle Emission  

NASA Astrophysics Data System (ADS)

Alpha aromatic radicals may explain some of the emission features of Red Rectangle (RR), a nearby protoplanetary nebulae. Erosion of amorphous hydrogenated carbon may lead to resonance-stabilized products by breaking aliphatic side-chains to aromatic ``islands''. The resulting radicals may be excited by starlight to give rise to the characteristic emissions. As a part of the ongoing Research and in order to investigate this hypothesis, the gas-phase excitation and emission spectra of some of these radicals have been identified in a molecular beam using laser induced fluorescence (LIF) spectroscopy. Resonance-stabilized 1-naphthylmethyl, 2-naphthylmethyl and acenaphthenyl radicals were produced from the discharge of 1-methylnaphthalene, 2-methylnaphthalene and acenaphthene precursors in argon, respectively. In order to determine the ground state vibrational energies of these species, their fluorescence bands were dispersed. The results are consistent with the Density Functional Theory (DFT) calculated ground state frequencies. As a complementary experiment, and to further confirm the identity of the spectral carriers, resonant two color two photon ionization (R2C2PI) spectra were also recorded. The origin bands of all these three molecules show up in the 5790 - 5840 range of the spectrum, the well-known RR emission region. N. J. Reilly, D. L. Kokkin, M. Nakajima, K. Nauta, S. H. Kable, and T. W. Schmidt J. Am. Chem. Soc., 130(10), 3137 (2009). T. P. Troy, M. Nakajima, N. Chalyavi, R. G. C. R. Clady, K. Nauta, S. H. Kable, and T. W. Schmidt J. Phys. Chem. A, 113, 10279 (2009).

Chalyavi, Nahid; Troy, Tyler P.; Nakajima, Masakazu; Nauta, Klaas; Kable, Scott H.; Schmidt, Timothy W.

2010-06-01

165

Ionic absorption and emission features in X-ray spectra of active galactic nuclei  

NASA Astrophysics Data System (ADS)

I present a comprehensive study of ionic absorption and emission features observed in high-resolution X-ray spectra of active galactic nuclei (AGN). AGN are galaxies that harbor a central, actively-accreting supermassive black hole. Through accretion, gravitational energy is converted into radiation, spread roughly equally (in logarithmic intervals) over the entire electromagnetic spectrum. A simple model of a cone of material irradiated by a variable, featureless power-law spectrum produced at the nucleus plus an additional constant, hard component due to reflection in distant Compton-thick material is sufficient to fit the X-ray spectra of several different AGN. Depending on the orientation of the cone to the observer, the spectrum appears either as ionic absorption of the power law (for lines of sight directly down the cone to the nucleus) or as reprocessed emission in the irradiated material (for lines of sight transverse to the cone and for which the nucleus is highly obscured by some other medium). The hard reflection component is observed in both orientations. A broad density distribution (over several orders of magnitude) at each position in the ionic absorber is also observed. For observations down the cone to the nucleus, I argue that the observed broad spectral features are more likely artifacts of absorption of the featureless power-law spectrum plus some contribution from the constant reflection component rather than relativistically-broadened emission lines arising from the inner regions of an accretion disk. In our model, all discrete and continuous ionic absorption and emission features are based on atomic data calculated using the Flexible Atomic Code (FAC).

Kinkhabwala, Ali Amir

2003-12-01

166

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

NASA Astrophysics Data System (ADS)

Recently, chlorophyll fluorescence (ChlF) retrievals in narrow spectral regions (< 1 nm, between 750-770 nm) of the near infrared (NIR) region of Earth's reflected radiation have been achieved from satellites, including the Japanese GOSAT and the European Space Agency's Sciamachy/Envisat. However, these retrievals sample the total full-spectrum ChlF and are made at non-optimal wavelengths since they are not located at the peak fluorescence emission features. We wish to estimate the total full-spectrum ChlF based on emissions obtained at selected wavelengths. For this, we drew upon leaf emission spectra measured on corn leaves obtained from a USDA experimental cornfield in MD (USA). These emission spectra were determined for the adaxial and abaxial (i.e., top and underside) surfaces of leaves measured throughout the 2008 and 2011 growing seasons (n>400) using a laboratory instrument (Fluorolog-3, Horiba Scientific, USA), recorded in either 1 nm or 5 nm increments with monochromatic excitation wavelengths of either 532 or 420 nm. The total ChlF signal was computed as the area under the continuous spectral emission curves, summing the emission intensities (counts per second) per waveband. The individual narrow (1 or 5 nm) waveband emission intensities were linearly related to full emission values, with variable success across the spectrum. Equations were developed to estimate total ChlF from these individual wavebands. Here, we report the results for the average adaxial/abaxial emissions. Very strong relationships were achieved for the relatively high fluorescence intensities at the red chlorophyll peak, centered at 685 nm (r2= 0.98, RMSE = 5.53 x 107 photons/s) and in the nearby O2-B atmospheric absorption feature centered at 688 nm (r2 = 0.94, RMSE = 4.04 x 107), as well as in the far-red peak centered at 740 nm (r2=0.94, RMSE = 5.98 x107). Very good retrieval success occurred for the O2-A atmospheric absorption feature on the declining NIR shoulder centered at 760 nm (r2 = 0.88, RMSE = 7.54 x 107). When perfect retrievals were assumed (0% noise), retrievals remained good in the low emission regions on either side of the peaks-- those associated with the H alpha line at 655 nm (r2 = 0.83, RMSE =8.87 x 107) and the far-NIR wavelengths recently utilized for satellite retrievals: a K line at 770 nm (r2 = 0.85, RMSE = 8.36 x 107) and the 750-770 nm interval (r2 = 0.88, RMSE = 6.92 x 107). However, the atmosphere and satellite observations are expected to add noise to retrievals. Adding 5% random error to these relationships did not seriously impair the retrieval successes in the red and far-red peaks (r2 ~ 0.85, RMSEs = 6.31 x 107). A greater impact occurred (reducing retrieval success by ~10%) when adding 5% noise for the far-NIR narrow band at 770 nm (r2 ~ 0.70, RMSE ~ 8.5 x 107). When a 10% random error was added, the retrieval successes fell to ~68 7% for all retrieval wavebands, and RMSEs increased by a factor of 10. This laboratory approach will be critical to calibrate space borne retrievals, but additional information across plant species is needed. Furthermore, this experiment indicates that ChlF retrievals from space should include information from the red and far-red peak emission regions, since the true total fluorescence signal is the desired parameter for Earth carbon and energy budgets.

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

2012-12-01

167

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

168

Correction of emission spectra in microspectrofluorimetry using a reference lamp: computations.  

PubMed

Accurate correction of emission spectra in microspectrofluorimetry, using a reference lamp, may require that a factor for the emissivity of tungsten be introduced. This is only possible provided that the true temperature of the lamp filament is known. A method is given for obtaining the true temperature from the knowledge of the colour temperature. Also, the values of the spectral concentration of the radiance of the black body, either computed according to Planck's equation or taken from available published tables, have to be converted from energetic units to units of quanta since the photomultiplier is linear not to absorbed power but to units of quanta. When the fluorescence spectra to be corrected extend into the far red it is preferable to use a lower temperature (by lowering the supply voltage) than that for which the lamp is certified. It is possible to determine the new temperature (and then the corresponding spectral distribution) by taking a few pairs of measurements at different wavelengths both at the lower voltage and at the voltage for which the lamp is certified and then introducing these values in a non-linear regression soluble on a PC with a curve fitting program. The microscope tungsten halogen lamp can conveniently be used as a reference, thanks to its small size and its steady spectral characteristics. When high accuracy is required, however, the halogen lamp should be calibrated against a certified ribbon filament lamp. PMID:1380859

Galassi, L

1992-01-01

169

Computation of AlO B 2? + ? X 2? + emission spectra  

NASA Astrophysics Data System (ADS)

Application of molecular spectroscopy to analytical chemistry usually requires accurate description of the particular transition of interest. In this communication we describe the creation of a list of spectral lines. Following the introduction and definition of the line strength, we present a recipe for computation of diatomic-line-strengths, including the Hnl-London factor and electric dipole line strength for each spectral line. The diatomic eigenfunction is discussed including Hund's case basis functions. In our data tables we prefer use of Hund's case (a) basis, and we apply the usual Born-Oppenheimer approximation for the electronic-vibrational strengths. This allows us to generate the table of line strengths that we frequently apply for spectroscopic temperature determination. Using these line-strength tables, we present theoretical AlO emission spectra for the B-X system of AlO. These emission spectra are computed for temperatures of 3000 and 6000 K and for typical spectroscopic resolution used in laser-induced optical breakdown studies.

Parigger, Christian G.; Hornkohl, James O.

2011-10-01

170

Influence of femtosecond superradiant pulses on spontaneous emission spectra of GaAs/AlGaAs heterostructures  

SciTech Connect

The spectra of spontaneous emission accompanying the generation of femtosecond superradiant pulses in GaAs/AlGaAs heterostructures are studied. It is clearly demonstrated that spontaneous emission spectra of electron-hole pairs, which have been left in the semiconductor after the formation of a coherent collective e-h state, correspond to the strong overheating of carriers. This phenomenon can be explained by the effect of dynamic cooling and nonequilibrium condensation of collectively paired carriers at the bottoms of the bands during the superradiant emission, which was observed earlier. (lasers)

Vasil'ev, P P [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Kan, H; Hiruma, T [Central Research Lab, Hamamatsu Photonics K.K. (Japan)

2007-11-30

171

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

172

Mineralogy of Natural Basalt Weathering Rinds With Application to Thermal Emission Spectra of Mars  

NASA Astrophysics Data System (ADS)

Mineralogy of Natural Basalt Weathering Rinds With Application to Thermal Emission Spectra of Mars M.D. Kraft, J.R. Michalski, T.G. Sharp, (and P.R. Christensen?) Chemically weathered rocks have been suggested to cover a significant portion of the Martian surface based on orbiter observations, and rocks investigated by the Mars Exploration Rover at the Gusev landing site show evidence of chemical alteration and weathering rinds. To understand remote mineralogical and chemical measurements of altered rock surfaces, whether in situ or from orbit, it is important to understand the general characteristics of weathering rinds (e.g., secondary mineralogy and microstructure in rinds) and how these characteristics affect remote observations. We are investigating a suite of weathered rocks of the Columbia River Basalt Group (CRBG) to identify chemical, mineralogical, and micro-structural changes associated with weathering and determine how these changes influence thermal emission measurements. Preliminary work shows that thermal emission spectra of weathered surfaces can vary substantially from spectra of fresh rocks despite rather low degrees of alteration in weathered surfaces. In rocks studied thus far, the predominant difference between the unweathered rock and weathering rind is an increase in porosity in the rind due to dissolution and/or volume expansion, causing a substantial increase in the volume density of micron-scale cracks. Mineralogical differences are imparted in the rind by the (partial) infilling of cracks by secondary materials that are Si, Al, and Fe-rich. A previous investigation by Colman (1982) showed that secondary silicates in basalt weathering rinds were dominantly X-ray amorphous. High-resolution secondary electron imaging of crack-filling products reveals spheroid-shaped materials, 10s of nm in diameter, which are consistent with short-range order allophane. We are currently performing additional analyses using XRD and TEM to constrain the mineralogy of secondary phases in CRGB weathering rinds, including the crystallinity of secondary silicates. Assessing chemical weathering on Mars may rely largely on the ability to detect and constrain the mineralogy of short-range order silicates, which may be the dominant Martian weathering products. Thermal emission spectroscopic data of Mars, with the detailed understanding that we intend to provide with this study, provides a unique and excellent means of constraining the nature of silicate weathering on Mars.

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

2004-12-01

173

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

174

Changes of chlorophyll fluorescence emission spectra of different stages and different position rice leaves during progressive senescence  

NASA Astrophysics Data System (ADS)

Changes of chlorophyll fluorescence emission spectra of different position leaves were investigated during the later growth stages of rice leaves. Results showed that natural illumination induced a shift change of fluorescence emission intensity (both in P685 and P735) during the progressive senescence of rice leaves. These data suggested that changes of chlorophyll fluorescence emission spectra of different position leaves were possible due to the declined of energy and electron transport activities of PSII reaction center. On the other hand, different position leaves of rice were treated with 3-(3,4 dichlorophenyl)-1,1-dimethyl-urea (DCMU), the results showed that DCMU had a significant effect on Chl fluorescence emission spectra (both in P685 and P735) under room temperature and different position leaves had a different sensibility of DCMU. It is concluded that natural illumination plays an important role in the progressive senescence process of rice leaves.

Chen, Zhi-qiang; Chen, Wen-li; Liao, Ling-Yan; Zhou, Quan; Xing, Da

2008-03-01

175

Modeling of the EUV and X-Ray Emission Spectra Induced by the Solar Winds Ions in the Heliosphere  

NASA Technical Reports Server (NTRS)

We have carried out investigation of the EUV and X-ray emission spectra induced in interaction between the Solar Wind (SW) and interstellar neutral gas. The spectra of most important SW ions have been computed for the charge-exchange mechanism of X-ray emission using new accurate spectroscopic data from recent laboratory measurements and theoretical calculations. Total spectra have been constructed as a sum of spectra induced in the charge-exchange collisions by individual O(exp q+), C(exp q+), N(exp q+), Ne(exp q+), Mg (exp q+) and Fe(exp q+) ions. Calculations have been performed for X-ray emission from the heliospheric hydrogen and helium gas. X-ray maps of the heliosphere have been computed. The power density of X-ray sources in the heliospheric ecliptic plane is shown for the H gas and for the He gas. Distances from the Sun (0,0) are given in AU. The helium cone is clear seen in the X-ray map of the charge-exchange emission induced by the solar wind. X-ray emission spectra detected by the Chandra X-ray telescope from the "dark" side of Moon has been identified as a X-ray background emission induced by the solar wind from the geocorona. Spectra and intensities of this charge-exchange X-rays have been compared with the heliospheric component of the X-ray background. Observations and modeling of the SW spectra induced from the geocorona indicate a strong presence of emission lines of highly charged oxygen ions. Anisotropy in distribution of heliospheric X-rays has been predicted and calculated for the regions of the fast and slow solar winds.

Kharchenko, Vasili

2005-01-01

176

Hydrogen-like Ion Emission in the Spectra of Low-Mass X-Ray Binaries  

SciTech Connect

We study the emission from H-like ions, particularly oxygen and neon, observed in {ital ASCA} spectra of low-mass X-ray binaries (LMXBs). The observed strengths of Ly{alpha} emission lines relative to the recombination continua differ from the classical recombination model. This suggests a different excitation mechanism for the lines. Various mechanisms are considered, which include three-body recombination, collisional excitation, recombination satellite line emission, and resonant fluorescent excitation. We find that the detection of Lyman recombination continuum implies that the plasma is photoionized, in agreement with previous studies by Hatchett, Buff, & McCray and Liedahl & Paerels. Under collisional ionization conditions, on the other hand, the Lyman continuum should be negligible unless the temperature were greater than 3 {times} 10{sup 6} K. Otherwise, the enhancement of Ly{alpha} emission with respect to the continuum may be due to (1) three-body recombination at electron densities greater than 10{sup 17} cm{sup {minus}3} and temperatures below 2 {times} 10{sup 5} K, (2) contributions to the recombination spectrum from collisional excitation of the H-like ionization stage, (3) contributions to recombination Ly{alpha} emission from satellite lines due to recombination onto the He-like ionization stage, and (4) contributions to the recombination spectrum from resonant fluorescence excitation of the H-like ionization stage. Further observations of higher order Lyman series lines and lines from other ionization stages are suggested to discriminate between the various excitation mechanisms. In addition, the implications of the different spectral formation mechanisms to the hydrodynamic accretion model of LMXBs are discussed. {copyright} {ital {copyright} 1998.} {ital The American Astronomical Society}

Bautista, M.A.; Kallman, T.R.; Angelini, L. [Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)] [Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Liedahl, D.A. [Department of Physics and Space Technology, Lawrence Livermore National Laboratory, P.O. Box 808, L-41, Livermore, CA 94550 (United States)] [Department of Physics and Space Technology, Lawrence Livermore National Laboratory, P.O. Box 808, L-41, Livermore, CA 94550 (United States); Smits, D.P. [HartRAO, P.O. Box 443, Krugersdorp 1740 (South Africa)] [HartRAO, P.O. Box 443, Krugersdorp 1740 (South Africa)

1998-12-01

177

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

178

Random mixtures of polycyclic aromatic hydrocarbon spectra match interstellar infrared emission  

NASA Astrophysics Data System (ADS)

The mid-infrared (mid-IR; 5-15 ?m) spectrum of a wide variety of astronomical objects exhibits a set of broad emission features at 6.2, 7.7, 8.6, 11.3, and 12.7 ?m. About 30 years ago it was proposed that these signatures are due to emission from a family of UV heated nanometer-sized carbonaceous molecules known as polycyclic aromatic hydrocarbons (PAHs), causing them to be referred to as aromatic IR bands (AIBs). Today, the acceptance of the PAH model is far from settled, as the identification of a single PAH in space has not yet been successful, and physically relevant theoretical models involving true PAH cross sections do not reproduce the AIBs in detail. In this paper, we use the NASA Ames PAH IR Spectroscopic Database, which contains over 500 quantum-computed spectra, in conjunction with a simple emission model, to show that the spectrum produced by any random mixture of at least 30 PAHs converges to the same kernel-spectrum. This kernel-spectrum captures the essence of the PAH emission spectrum and is highly correlated with observations of AIBs, strongly supporting PAHs as their source. Furthermore, the fact that a large number of molecules are required implies that spectroscopic signatures of the individual PAHs contributing to the AIBs spanning the visible, near-IR, and far-IR spectral regions are weak, explaining why they have not yet been detected. An improved effort, joining laboratory, theoretical, and observational studies of the PAH emission process, will support the use of PAH features as a probe of physical and chemical conditions in the near and distant Universe. Appendices are available in electronic form at http://www.aanda.org

Rosenberg, Marissa J. F.; Bern, Olivier; Boersma, Christiaan

2014-06-01

179

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

180

K-(alpha) Radiography at 20-100 keV Using Short-Pulse Lasers  

SciTech Connect

X-ray radiography is an important tool for diagnosing and imaging planar and convergent hydrodynamics phenomena for laser experiments. Until now, hydrodynamics experiments at Omega and NIF utilize E{sub x-ray} < 9 keV backlighter x-rays emitted by thermal plasmas. However, future experiments will need to diagnose larger and denser targets and will require x-ray probes of energies from 20-100 keV and possibly up to 1 MeV. Hard K-{alpha} x-ray photons can be created through high-energy electron interactions in the target material after irradiation by petawatt-class high-intensity-short-pulse lasers with > 10{sup 17} W/cm{sup 2}. We have performed several experiments on the JanUSP, and the Vulcan 100TW, and Vulcan Petawatt lasers to understand K-{alpha} sources and to test radiography concepts. 1-D radiography using an edge-on foil and 2-D radiography using buried wires and cone-fiber targets were tested. We find that 1-D thin edge-on foils can have imaging resolution better than 10 {micro}m. Micro volume targets produce bright sources with measured conversion efficiency from laser energy to x-ray photons of {approx} 1 x 10{sup -5}. This level of conversion may not be enough for 2-D point projection radiography. A comparison of our experimental measurements of small volume sources with the LSP/PIC simulation show similar K-{alpha} creation profiles but discrepancy in absolute yields.

Park, H S; Chambers, D; Clarke, R; Eagleton, R; Giraldez, E; Goldsack, T; Heathcote, R; Izumi, N; Key, M; King, J; Koch, J; Landen, O L; Mackinnon, A; Nikroo, A; Patel, P; Pasley, J; Remington, B; Robey, H; Snavely, R; Steinman, D; Stephenson, R; Stoeckl, C; Storm, M; Tabak, M; Theobald, W; Town, R J

2005-08-29

181

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

182

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

183

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 0.80/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 3.2 and 4.8, 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 (-1.5) and Ha5 and 6 (both -2.2); 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 6250 and 7600, 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

184

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

185

[Application study of the thermal infrared emissivity spectra in the estimation of salt content of saline soil].  

PubMed

Studying of soil salinization is of great significance for agricultural production in arid area oasis, thermal infrared remote sensing technology provides a new technology and method in this field. Authors used Fourier transform infrared spectrometer to measure the oasis saline soil in field, employed iterative spectrally smooth temperature/emissivity separation algorithm (ISSTES) to separate temperature and emissivity, and acquired the thermal infrared emissivity data of the saline soil. Through researching the emissivity spectral feature of saline soil, and concluded that soil emissivity will reduce with the increasing of salt content from 8 to 13 microm, so emissivity spectra is more sensitive to salt factor from 8 to 9.5 microm. Then, analyzed the correlation between original emissivity spectra and its first derivative, second derivative and normalized ratio with salt content, the result showed that they have a negative correlation relationship between soil emissivity and salt content, and the correlation between emissivity first derivative and salt content is highest, reach to 0.724 2, the corresponding bands are from 8.370 745-8.390 880 microm. Finally, established the quadratic function regression model, its determination coefficient is 0.741 4, and root mean square error is 0.235 5, the result explained that the approach of using thermal infrared emissivity to retrieve the salt content of saline soil is feasible. PMID:23387157

Xia, Jun; Tashpolat, Tiyip; Mamat, Sawut; Zhang, Fei; Han, Gui-Hong

2012-11-01

186

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

NASA Astrophysics Data System (ADS)

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 this technique, the SCB plasma electron density was measured well and accurately. Moreover, the electron density distribution Vs time was acquired from one SCB discharge. The individual result from the broadening of the Al I 394.4 nm Stark width and Saha equation was all in the range of 1015 cm-3 to 1016 cm-3. Finally the presumption of the local thermodynamic equilibrium (LTE) condition was validated.

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

2010-02-01

187

Remote gas detection and quantitative analysis from infrared emission spectra obtained by Fourier transform infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Techniques for obtaining quantitative values of the temperatures and concentrations of remote hot gaseous effluents from their measured passive emission spectra have been examined in laboratory experiments. The high sensitivity of the spectrometer in the vicinity of the 2397 cm-1 band head region of CO2 has allowed the gas temperature to be calculated from the relative intensity of the observed rotational lines. The spatial distribution of the CO2 in a methane flame has been reconstructed tomographically using a matrix inversion technique. The spectrometer has been calibrated against a black body source at different temperatures and a self absorption correction has been applied to the data avoiding the need to measure the transmission directly. Reconstruction artifacts have been reduced by applying a smoothing routine to the inversion matrix.

Hilton, Moira; Lettington, Alan H.; Mills, Ian M.

1994-06-01

188

Expected gamma-ray emission spectra from the lunar surface as a function of chemical composition  

NASA Technical Reports Server (NTRS)

The gamma rays emitted from the moon or any similar body carry information on the chemical composition of the surface layer. The elements most easily measured are K, U, Th and major elements such as O, Si, Mg, and Fe. The expected fluxes of gamma ray lines were calculated for four lunar compositions and one chondritic chemistry from a consideration of the important emission mechanisms: natural radioactivity, inelastic scatter, neutron capture, and induced radioactivity. The models used for cosmic ray interactions were those of Reedy and Arnold and Lingenfelter. The areal resolution of the experiment was calculated to be around 70 to 140 km under the conditions of the Apollo 15 and 16 experiments. Finally, a method was described for recovering the chemical information from the observed scintillation spectra obtained in these experiments.

Reedy, R. C.; Arnold, J. R.; Trombka, J. I.

1973-01-01

189

Theoretical study of absorption and emission spectra of the monomer of PFBT  

NASA Astrophysics Data System (ADS)

Conjugated polymers (CPs) have been used as highly responsive optical sensors for chemical and biological targets. The density functional theory (DFT), the time-dependent density functional theory (TDDFT) and the singly excited configuration interaction (CIS) approach were employed to simulate the absorption and emission spectra of a model monomer unit of the typical CP, poly[9,9'-bis-(6'- N, N, N-trimethylammonium)hexyl]fluorene-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT). Various basis sets were applied in the calculations and their effects on the predictions for the optical properties of FBT are discussed. The results suggest that the TD-B3LYP method with basis sets larger than 6-311G(d,p) provides a suitable approach for investigations of the studied system.

Wang, Jing; Gu, Jiande; Leszczynski, Jerzy

2008-05-01

190

Extreme Ultraviolet Emission Lines of Fe XIII in Solar and Stellar Spectra  

NASA Astrophysics Data System (ADS)

Recent R-matrix calculations of electron impact excitation rates for Fe XIII are used to derive the theoretical electron density sensitive emission line ratios R1 = I(3s23p2 1D-3s3p3 1D)/I(3s23p2 3P2-3s3p3 3P2) = I(318.12 )/I(320.80 ) and R2 = I(3s23p2 1D-3s3p3 1P)/I(3s22p2 3P2-3s3p3 3S) = 1(256.42 )/I(251.95 ), which are found to be up to 70% different from earlier diagnostics. A comparison of the current line ratios with both solar flare and active region observations, obtained by the Naval Research Laboratory's S082A spectrograph on board Skylab, reveals generally good agreement between densities deduced from Fe XIII and those estimated from diagnostic line ratios in species formed at similar temperatures, such as I(219.12 )/I(211.32 ) in Fe XIV. This provides experimental support for the accuracy of the line ratio calculations, and hence the atomic data adopted in their derivation. In Extreme Ultraviolet Explorer satellite (EUVE) spectra the Fe XIII emission lines are found to be severely blended. However, an analysis of these lines measured in the spectra of Procyon and ? Cen demonstrates that they still allow very approximate values of the electron density to be inferred. Moreover, it should be possible to increase the accuracy of the measured line fluxes, and hence of the inferred densities, if longer exposures of the stars concerned can be obtained.

Keenan, F. P.; Foster, V. J.; Drake, J. J.; Tayal, S. S.; Widing, K. G.

1995-11-01

191

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

192

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

193

Determination of two-photon excitation and emission spectra of fluorescent molecules in single living cells  

NASA Astrophysics Data System (ADS)

Modelocked Ti:Sapphire lasers are widely used in two-photon microscopes (TPM), partly due to their tunability over a broad range of wavelengths (between 700 nm and 1000 nm). Many biophysical applications, including quantitative Frster Resonance Energy Transfer (FRET) and photoswitching of fluorescent proteins between dark and bright states, require wavelength tuning without optical realignment, which is not easily done in tunable Ti:Sapphire lasers. In addition, for studies of dynamics in biological systems the time required for tuning the excitation should be commensurate with the shortest of the time scales of the processes investigated. A set-up in which a modelocked Ti:Sapphire oscillator providing broad-bandwidth (i.e., short) pulses with fixed center wavelength is coupled to a pulse shaper incorporating a spatial light modulator placed at the Fourier plane of a zero-dispersion two-grating setup, represents a faster alternative to the tunable laser. A pulse shaping system and a TPM with spectral resolution allowed us to acquire two-photon excitation and emission spectra of fluorescent molecules in single living cells. Such spectra may be exploited for mapping intracellular pH and for quantitative studies of protein localization and interactions in vivo.

Raicu, Valeric?; Chaturvedi, Anurag; Stoneman, Michael; Petrov, Giorgi; Fung, Russell; Saldin, Dilano; Gillman, Devin

2008-03-01

194

Electron dynamics and harmonics emission spectra due to electron oscillation driven by intense laser pulses  

NASA Astrophysics Data System (ADS)

The dynamics and harmonics emission spectra due to electron oscillation driven by intense laser pulses have been investigated considering a single electron model. The spectral and angular distributions of the harmonics radiation are numerically analyzed and demonstrate significantly different characteristics from those of the low-intensity field case. Higher-order harmonic radiation is possible for a sufficiently intense driving laser pulse. A complex shifting and broadening structure of the spectrum is observed and analyzed for different polarization. For a realistic pulsed photon beam, the spectrum of the radiation is redshifted for backward radiation and blueshifted for forward radiation, and spectral broadening is noticed. This is due to the changes in the longitudinal velocity of the electron during the laser pulse. These effects are much more pronounced at higher laser intensities giving rise to even higher-order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that broadening of the high harmonic radiation can be limited by increasing the laser pulse width. The complex shifting and broadening of the spectra can be employed to characterize the ultrashort and ultraintense laser pulses and to study the ultrafast dynamics of the electrons.

Tian, Youwei; Yu, Wei; He, Feng; Xu, Han; Senecha, Vinod; Deng, Degang; Wang, Yi; Li, Ruxin; Xu, Zhizhan

2006-12-01

195

Extremely hard GRB spectra prune down the forest of emission models  

NASA Astrophysics Data System (ADS)

We consider the evidence for very hard low energy spectra during the prompt phase of Gamma-Ray Bursts (GRB). In particular we examine the spectral evolution of GRB 980306 together with the detailed analysis of some other bursts already presented in the literature (GRB 911118, GRB 910807, GRB 910927 and GRB 970111), and check for the significance of their hardness (i.e. extremely steep spectral slopes below the EFE peak) by applying different tests. These bursts, detected by the Burst And Transient Source Experiment (BATSE) in the ~ 30 keV-2 MeV energy range, are sufficiently bright to allow time resolved spectral studies on time intervals of the order of tenths of a second. We discuss the hard spectra of these bursts and their evolution in the context of several non-thermal emission models, which all appear inadequate to account for these cases. The extremely hard spectra, which are detected in the early part of the BATSE light curve, are also compared with a black body spectral model: the resulting fits are remarkably good, except for an excess at high energies (in several cases) which could be simply accounted for by the presence of a supra-thermal component. The findings on the possible thermal character of the evolving spectrum and the implications on the GRB physical scenario are considered in the frameworks of photospheric models for a fireball which is becoming optically thin, and of Compton drag models, in which the fireball boosts ``ambient" seed photons by its own bulk motion. Both models, according to simple estimates, appear to be qualitatively and quantitatively consistent with the found spectral characteristics, although their possible caveats are discussed.

Ghirlanda, G.; Celotti, A.; Ghisellini, G.

2003-08-01

196

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

197

Visible and ultra-violet emission and absorption spectra of MgAl2O4:Cr  

Microsoft Academic Search

Information is presented on the emission and absorption spectra at room and low temperatures of chromium activated MgAl2O4 single crystals. These crystals had been grown by a flux-melt technique, and have been shown to be structurally perfect and of high chemical purity. A systematic study of the changes in the spectra with impurity concentration has been made. The appearance of

F H Lou; D W G Ballentyne

1968-01-01

198

Tomographic reconstruction of FT-IR emission and transmission spectra in a sooting laminar diffusion flame; Species concentrations and temperatures  

Microsoft Academic Search

This paper reports on tomographic reconstruction techniques applied to line-of-sight Fourier Transform infrared (FT-IR) emission and transmission measurements to derive spectra corresponding to small volumes within an ethylene diffusion flame. From these spectra, point values for species temperatures and relative concentrations have been determined for CO, HO, alkanes, alkenes, alkynes, and soot. In this article the methods that were used

P. E. Best; P. L. Chien; R. M. Carangelo; P. R. Solomon; M. Danchak; I. Ilovici

1991-01-01

199

New emission features in the infrared spectra of two IRAS sources  

SciTech Connect

Observations of IRAS 21282 + 5050 and IRAS 03055 + 5819 (AFGL 437) obtained at 7.7-22.5 microns using the IRAS LRS during 1983 and at 3.1-3.8 microns using the 3.75-m UKIRT in September 1985, are reported and analyzed. The data are presented graphically, and the significance of three new nonatomic emission features at 3.46, 3.51, and 3.56 microns; the known emission features at 3.3, 3.40, 7.7, 8.6, and 11.3 microns; and the plateaus at 3.4-3.6 and above 11.5 microns is discussed in detail. It is suggested that the plateau and narrow features between 3.4 and 3.6 microns may be due to polycyclic aromatic hydrocarbons with attached molecular subgroups such as -CH/sub 3/ or -C/sub 2/H/sub 5/, a hypothesis developed by analogy to that proposed by Cohen et al. (1985), and Puget et al. (1985) for the 12-micron plateaus seen in many IRAS spectra. 26 references.

De Muizon, M.; Geballe, T.R.; Dhendecourt, L.B.; Baas, F.

1986-07-01

200

[Analysis of optical emission spectra from ICP of Ar in the vicinity of plasma sheath].  

PubMed

In order to control the ion density and energy distribution in the vicinity of plasma sheath independently, the inductively coupled plasma and its glow discharge mechanism in the vicinity of plasma sheath were studied by means of optical emission spectroscopy (OES) under different RF power, different discharge and different substrate DC bias voltage. It was shown that the ion density is higher and the electron temperature is lower in the vicinity of inductively coupled plasma sheath according to the ionic line and atomic line. With changing the discharge pressure and RF power, the spectral characteristics analysis shows that the ion density in the vicinity of plasma sheath linearly increases with the RF power and rises with the pressure under the low pressure. The atomic spectral intensity of low excitation states increases rapidly. The atomic spectral intensity of high excitation states rises slowly and the intensity of ion spectrum increases not obviously. By applying the DC bias voltage to substrate, the intensity of emission spectroscopy was analyzed. The result shows that the intensity of spectra rises with the increase in positive bias voltage, while first reduces then increases with the increase in negative bias voltage, and is the weakest in the case of DC bias at -30 V. This shows that the fast ions and the electrons are the main source of energy for Ar ionization and excitation. PMID:20102002

Zhao, Wen-Feng; Chen, Jun-Fang; Meng, Ran

2009-11-01

201

Package for Interactive Analysis of Line Emission (Analysis of UV-X-Ray High-Resolution Emission Spectra)  

NASA Technical Reports Server (NTRS)

PINTofALE is an IDL based package to analyze high-resolution grating spectra. The first version was made available to the public on 3 February 2001. Since then we have carried out numerous changes, and the current release is version 1.5, released on 9 October 2002. The changes include upgrades to handle higher versions of IDL, the new version of the CHIANTI database (v4), major enhancements in user-friendliness, improved handling of response matrices, the ability to handle 24-bit color, access to the Atomic Plasma Emission Database (APED), and beta releases of Markov Chain Monte Carlo (MCMC) based DEM fitting routines. Plans for the future include: inclusion of MCMC techniques in the fitting programs, enhanced graphics capabilities, an overhaul of the line and continuum database structure, and bug fixes. In September 2002, we hired a data analyst (LiWei Lin) to work on PINTofALE. Mr.Lin is concentrating on incorporating MCMC as well as simpler Monte-Carlo techniques, fast RMF convolution, etc., into the code base, as well as reviewing the existing documentation and searching for bugs. A detailed description of the package, together with fairly detailed documentation, example walks-throughs, and downloadable tar files, are available on-line from http://hea-www. harvard.edu/PINTofALE/

Kashyap, Vinay; Hunter, Paul (Technical Monitor)

2003-01-01

202

EMISSION FROM HOT DUST IN THE INFRARED SPECTRA OF GAMMA-RAY BRIGHT BLAZARS  

SciTech Connect

A possible source of {gamma}-ray photons observed from the jets of blazars is inverse Compton scattering by relativistic electrons of infrared seed photons from a hot, dusty torus in the nucleus. We use observations from the Spitzer Space Telescope to search for signatures of such dust in the infrared spectra of four {gamma}-ray bright blazars, the quasars 4C 21.35, CTA102, and PKS 1510-089, and the BL Lacertae object ON231. The spectral energy distribution (SED) of 4C 21.35 contains a prominent infrared excess indicative of dust emission. After subtracting a non-thermal component with a power-law spectrum, we fit a dust model to the residual SED. The model consists of a blackbody with temperature {approx}1200 K, plus a much weaker optically thin component at {approx}660 K. The total luminosity of the thermal dust emission is 7.9 {+-} 0.2 x 10{sup 45} erg s{sup -1}. If the dust lies in an equatorial torus, the density of infrared photons from the torus is sufficient to explain the {gamma}-ray flux from 4C 21.35 as long as the scattering occurs within a few parsecs of the central engine. We also report a tentative detection of dust in the quasar CTA102, in which the luminosity of the infrared excess is 7 {+-} 2 x 10{sup 45} erg s{sup -1}. However, in CTA102 the far-infrared spectra are too noisy to detect the 10 {mu}m silicate feature. Upper limits to the luminosity from thermal emission from dust in PKS 1510-089, and ON231, are 2.3 x 10{sup 45}, and 6.6 x 10{sup 43} erg s{sup -1}, respectively. These upper limits do not rule out the possibility of inverse Compton upscattering of infrared photons to {gamma}-ray energies in these two sources. The estimated covering factor of the hot dust in 4C 21.35, 22%, is similar to that of non-blazar quasars; however, 4C 21.35 is deficient in cooler dust.

Malmrose, Michael P.; Marscher, Alan P.; Jorstad, Svetlana G. [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Nikutta, Robert; Elitzur, Moshe [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506-0055 (United States)

2011-05-10

203

FeII emission in a sample of AGN spectra (Kovacevic+, 2010)  

NASA Astrophysics Data System (ADS)

We present a study of optical FeII emission in 302 active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey. We group the strongest FeII multiplets into three groups according to the lower term of the transition (b4F, a6S, and a4^G terms). These approximately correspond to the blue, central, and red parts, respectively, of the "iron shelf" around H?. We calculate an FeII 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 FeII template gives a more precise fit of the FeII lines in broad-line AGNs than other templates. We extract FeII, H?, H?, [OIII], and [NII] emission parameters and investigate correlations between them. We find that FeII 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?, the velocity shift of FeII, and the H?/H? flux ratio. We examine the dependence of the well-known anti-correlation between the equivalent widths of FeII and [OIII] on continuum luminosity. We find that there is a Baldwin effect for [OIII] but an inverse Baldwin effect for the FeII emission. The [OIII]/FeII ratio thus decreases with L?5100. Since the ratio is a major component of the Boroson & 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? FWHMs greater and less than ~3000km/s, and that there are different correlation coefficients between the parameters. (1 data file).

Kovacevic, J.; Popovic, L. C.; Dimitrijevic, M. S.

2010-09-01

204

Fluorescence excitation-emission matrix regional integration to quantify spectra for dissolved organic matter.  

PubMed

Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the > 10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (phi(i,n)). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (phi(T,n) = sigma phi(i,n)) was observed for hydrophobic neutral DOM fractions, followed by lower phi(T,n) values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM. PMID:14717183

Chen, Wen; Westerhoff, Paul; Leenheer, Jerry A; Booksh, Karl

2003-12-15

205

Fluorescence Excitation-Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter  

USGS Publications Warehouse

Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (??i,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (??T,n = ????i,n) was observed for hydrophobic neutral DOM fractions, followed by lower ??T,n values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

Chen, W.; Westerhoff, P.; Leenheer, J. A.; Booksh, K.

2003-01-01

206

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.

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

2000-01-01

207

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 1.7x10{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, Andrea L. [Nuclear Engineering Department, University of California Berkeley, Berkeley, CA 94709 (United States); Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States); Neumayer, Paul; Castor, John; Doeppner, Tilo; Landen, Otto L.; Ng, Andrew; Pollaine, Steve; Price, Dwight; Glenzer, Siegfried H. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States); Falcone, Roger W.; Ja Lee, Hae [Physics Department, University of California Berkeley, Berkeley, CA 94709 (United States); Lee, Richard W. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, CA 94551 (United States); Physics Department, University of California Berkeley, Berkeley, CA 94709 (United States); Morse, Edward C. [Nuclear Engineering Department, University of California Berkeley, Berkeley, CA 94709 (United States)

2009-09-10

208

Analysis of terrestrial and Martian volcanic compositions using thermal emission spectroscopy 2. Application to Martian surface spectra from the Mars Global Surveyor Thermal Emission Spectrometer  

Microsoft Academic Search

Atmospherically corrected thermal infrared spectra of large regions of the Martian surface from the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES) previously have been interpreted to represent two general spectral classes. One class represents a basalt to basaltic andesite composition, and the other class represents a basaltic andesite to andesite composition. We have performed new linear deconvolutions of the

Victoria E. Hamilton; Michael B. Wyatt; Harry Y. McSween Jr; Philip R. Christensen

2001-01-01

209

Development of a high-efficiency high-resolution particle-induced x-ray emission system for chemical state analysis of environmental samples  

SciTech Connect

We have developed a high-efficiency high-resolution particle-induced x-ray emission (PIXE) system employing a von Hamos-type crystal spectrometer for a chemical state identification of trace elements in environmental samples. The energy resolution of the system was determined to be about 0.05% through the observation of Si K{alpha}{sub 1,2} x rays (1.74 keV) from elemental silicon. The throughput efficiency of the system was also evaluated quasitheoretically to be 1.6x10{sup -7} counts/incident proton for Si K{alpha}{sub 1,2} emission. To demonstrate a chemical state analysis using the high-resolution PIXE system, Si K{alpha}{sub 1,2} and K{beta} x-ray spectra for SiC, Si{sub 3}N{sub 4}, and SiO{sub 2} were measured and compared. The observed chemical shifts of the Si K{alpha}{sub 1,2} peaks for SiC, Si{sub 3}N{sub 4}, and SiO{sub 2} relative to elemental silicon were 0.20, 0.40, and 0.55 eV, respectively. The tendency of these shifts were well explained by the effective charges of the silicon atoms calculated by a molecular orbital method.

Hasegawa, J.; Tada, T.; Oguri, Y.; Hayashi, M.; Toriyama, T.; Kawabata, T.; Masai, K. [Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550 (Japan); Musashi Institute of Technology, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 (Japan)

2007-07-15

210

Spectra and modeling of laser-induced emission from multiple-photon (?=248.4 nm) irradiation of UF6  

NASA Astrophysics Data System (ADS)

The laser-induced emission from KrF-laser irradiation of gaseous, room temperature UF6 has been studied as a function of time, wavelength, pressure, and laser fluence. Spectra in the 200-900 nm region are presented at several sampling times. One group of 17 emission peaks in the 650-900 nm range has been assigned to the 3?6-->1?7 transition in UF5. A possible kinetic mechanism is presented that is qualitatively consistent with the time-resolved emission data over the experimental pressures and laser fluences investigated.

Rice, W. W.; Wampler, F. B.; Oldenborg, R. C.; Lewis, W. B.; Tiee, J. J.; Pack, R. T.

1980-03-01

211

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

212

Comprehensive analysis of Barkhausen emission spectra using pulse height analysis, frequency spectrum, and pulse wave form analysis  

SciTech Connect

The dependence of magnetic Barkhausen emissions (MBE) upon both field excitation and detection frequencies and excitation wave form was studied in order to investigate two of several crucial factors which affect the emissions. Sinusoidal, triangular, and square wave forms were used to generate the MBE and the pulse height spectra, frequency spectra, and pulse wave forms of these signals were analyzed. The frequency spectra of sinusoidal and triangular alternating field excitations showed similar behavior but the spectrum under square wave excitation was different due to the existence of high frequency components during square wave switching. As yet, no common standard has been agreed upon for parameterization and representation of Barkhausen signals. It appears from this work that field excitation wave form and frequency should define the inputs, while detection frequency range, pulse height spectrum, frequency spectrum, and emitted pulse wave form analysis should be used to quantify the output.

Sipahi, L.B. (Physics Department, Ames Laboratory, and Center for Nondestructive Evaluation, Iowa State University, Ames, Iowa 50011 (United States)); Jiles, D.C. (Ames Laboratory, Center for Nondestructive Evaluation, Department of Materials Science and Engineering, and Department of Electrical Engineering, Iowa State University, Ames, Iowa 50011 (United States)); Chandler, D. (Ames Laboratory, Iowa State University, Ames, Iowa 50011 (United States))

1993-05-15

213

High-resolution spectra of distant compact narrow emission line galaxies: Progrenitors of spheroidal galaxies  

NASA Technical Reports Server (NTRS)

Emission-line velocity widths have been determined for 17 faint (B approximately 20-23) very blue, compact galaxies whose redshifts range from z = 0.095 to 0.66. The spectra have a resolution of 8 Km/s and were taken with the HIRES echelle spectrograph of the Keck 10 m telescope. The galaxies are luminous with all but two within 1 mag of M(sub B) approximately -21. Yet they exhibit narrow velocity widths between sigma = 28-157 km/s, more consistent with typical values of extreme star-forming galaxies than with those of nearby spiral galaxies of similar luminosity. In particular, objects with sigma is less than or equal to 65 km/s follow the same correlations between sigma and both blue and H beta luminosities as those of nearby H II galaxies. These results strengthen the identification of H II glaxies as thier local counterparts. The blue colors and strong emission lines suggest these compact galaxies are undergoing a recent, strong burst of star formation. Like those which characterize some H II galaxies, this burst could be a nuclear star-forming event within a much larger, older stellar population. If the burst is instead a major episode in the total star-forming history, these distant galaxies could fade enough to match the low luminosities and surface brightnesses typical of nearby spheroidals like NGC 185 or NGC 205. Together with evidence for recent star formation, exponential light profiles, and subsolar metallicities, the postfading correlations between luminosity and velocity width and bewtween luminosity and surface brightness suggest that among the low-sigma galaxies, we may be witnessing, in situ, the progenitors of today's spheroidal galaxies.

Koo, David C.; Guzman, Rafael; Faber, S. M.; Illingworth, Garth D.; Bershady, Matthew A.; Kron, Richard G.; Takamiya, Marianne

1995-01-01

214

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

215

Time-space distribution of laser-induced plasma parameters and its influence on emission spectra of the laser plumes  

NASA Astrophysics Data System (ADS)

A physical model is developed accounting for dynamics and radiation of plasma plumes induced by nanosecond laser pulses on surface of solid samples. The model has been applied to simulate emission spectra of the laser erosion plasma at the elemental analysis of metals using single- and double-pulse excitation modes. Dynamics of the sample heating and expansion of the erosion products are accounted for by the thermal conductivity and gas dynamic equations, respectively, supposing axial symmetry. Using the resulting time-space distributions of the plasma parameters, emission spectra of the laser plumes are evaluated by solving the radiation transfer equation. Particle concentration in consecutive ionization stages is described by the Saha equation in the Debye approximation. The population of excited levels is determined according to Boltzmann distribution. Local characteristics determining spectral emission and absorption coefficients are obtained point-by-point along an observation line. Voigt spectral line profiles are considered with main broadening mechanisms taken into account. The plasma dynamics and plume emission spectra have been studied experimentally and by the model. A Q-switched Nd:YAG laser at 1064 nm wavelength has been used to irradiate Al sample with the pulses of 15 ns and 50 mJ duration and energy, respectively. It has resulted in maximum power density of 0.8 MW/cm 2 on the sample surface. The laser plume emission spectra have been recorded at a side-on observation. Problems of the spectra contrast and of the elemental analysis efficiency are considered relying on a comparative study of the measurement and simulation results at the both excitation modes.

Ershov-Pavlov, E. A.; Katsalap, K. Yu.; Stepanov, K. L.; Stankevich, Yu. A.

2008-10-01

216

Emission spectra of CF3 radicals. III. Spectra and quenching of CF3 emission bands produced in the VUV photolyses of CF3Cl and CF3Br  

Microsoft Academic Search

Fluorescence in the photolysis of CF3Cl and CF3Br was investigated using various vacuum ultraviolet light sources of atomic lines (Ar, Kr, H, and O). Both UV and visible emission bands of CF3 were observed as in the case of the photolysis of CF3H. Lower v? levels of the emission bands were excited when CF3X was photolyzed by the lower energy

Masako Suto; Nobuaki Washida; Hajime Akimoto; Masatoshi Nakamura

1983-01-01

217

Ar +-induced silicon Auger spectra: a probe for the sputter-related collisional and emission processes  

NASA Astrophysics Data System (ADS)

We performed a detailed, angle resolved study of the Ar +-induced Si LMM Auger electron emission from silicon single crystals in the 1-15 keV ion energy range. Attention has been focused on the Doppler shift of the atomic Unes, which arises from the motion of the decaying atoms with respect to the analyzer. It has been found to be a powerful tool to investigate the spatial and energy distribution of sputter-ejected atoms. The Doppler shifted contributions have been up to now associated with an anisotropic "spike" of fast atoms which originates from projectile-target collisions, superimposed on the nearly isotropic distribution of slow atoms which originate from collisions between target particles in the cascade. We report on new features in the shifted spectrum, whose behaviour vs ion energy suggests a more complex picture of the surface collisional processes and of the consequent fast particle ejection. The total yield, the relative weight of the atomic and bulk contributions to the SiL 23 derived Auger spectra and the behaviour of the asymmetric projectile-target collisions have been investigated as a function of the ion energy at different incident angles.

Valeri, S.; Verucchi, R.

1991-07-01

218

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

219

Measurements of the temperature of subsonic CO2 induction plasma flows by analyzing their emission spectra  

NASA Astrophysics Data System (ADS)

Results are presented from measurements of the temperature characteristics of subsonic CO2 plasma flows generated by a 100-kW induction plasmatron at the Institute for Problems of Mechanics, Russian Academy of Sciences. The atomic excitation temperature T a and the population temperature T e of the electronic states of C2 molecules (both averaged over the jet diameter) were measured from the absolute intensities of the atomic spectral lines and the spectrum of C2 molecules in different generation regimes at gas pressures of 25 140 hPa and anode supply powers of 29 72 kW. The longitudinal and radial profiles of the temperatures were determined for some of these regimes and compared to those obtained from numerical calculations of equilibrium induction plasma flows in the discharge channel. For some generation regimes, the dependences of the averaged (over the line of sight) rotational and vibrational temperatures ( T r and T v) on the discharge parameters, as well as the radial profiles of these temperatures, were determined from the best fit of the measured and calculated spectra of C2 molecules (Swan bands). The self-absorption of molecular emission was observed at sufficiently high temperatures and gas pressures, and its influence on the measured values of the molecular temperatures T e, T v, and T r was examined.

Bykova, N. G.; Kuznetsova, L. A.

2004-11-01

220

Features of the broad upshifted structure in stimulated electromagnetic emission spectra  

NASA Astrophysics Data System (ADS)

We present experimental results concerning features of the broad upshifted structure (BUS) in stimulated electromagnetic emission spectra, generated in the ionospheric F region plasma by a powerful electromagnetic wave. The BUS is observed for pump frequencies far from electron cyclotron harmonics. Modification experiments, using O-mode HF pump waves, were conducted at the SURA heating facility (56N, 44E, Nizhny Novgorod, Russia). We investigated the BUS properties for pump frequencies ranging from the third to the sixth electron cyclotron harmonic, concentrating on the dependence of (1) the BUS spectral features on pump frequency and power and (2) the BUS temporal evolution under different ionospheric conditions with and without additional heating of the ionosphere by another pump wave. We find (1) that the frequency range of BUS generation depends on the gyroharmonic mode number, becoming narrower with increasing mode number, and (2) that the BUS is produced in the vicinity of the upper hybrid resonance layer, located typically a few kilometers below the pump wave reflection height. An important result is that small-scale striations, being produced concurrently with the upper hybrid plasma waves due to the thermal parametric instability, do not play a crucial role for the BUS evolution. A possible relationship of the BUS to gyroharmonic features is discussed.

Frolov, V. L.; Ermakova, E. N.; Kagan, L. M.; Komrakov, G. P.; Sergeev, E. N.; Stubbe, P.

2000-09-01

221

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

222

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

223

Ti K{alpha} radiography of Cu-doped plastic microshell implosions via spherically bent crystal imaging  

SciTech Connect

We show that short pulse laser generated Ti K{alpha} radiation can be used effectively as a backlighter for radiographic imaging. This method of x-ray radiography features high temporal and spatial resolution, high signal to noise ratio, and monochromatic imaging. We present here the Ti K{alpha} backlit images of six-beam driven spherical implosions of thin-walled 500-{mu}m Cu-doped deuterated plastic (CD) shells and of similar implosions with an included hollow gold cone. These radiographic results were used to define conditions for the diagnosis of fast ignition relevant electron transport within imploded Cu-doped coned CD shells.

King, J.A.; Akli, K.; Zhang, B.; Freeman, R.R.; Key, M.H.; Chen, C.D.; Hatchett, S.P.; Koch, J. A.; MacKinnon, A. J.; Patel, P. K.; Snavely, R.; Town, R. P. J.; Borghesi, M.; Romagnani, L.; Zepf, M.; Cowan, T.; Habara, H.; Kodama, R.; Toyama, Y.; Karsch, S. [Department of Applied Sciences, University of California, Davis, Davis, California 95616 (United States); College of Mathematical and Physical Sciences, Ohio State University, Columbus, Ohio 43210 (United States); Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); The Queens University of Belfast, Belfast, Northern Ireland, BT7 1NN (United Kingdom); Department of Physics, University of Nevada Reno, Reno, Nevada 89557 (United States); Institute of Laser Engineering, Osaka University, Osaka 565 (Japan); Max Planck Institute for Quantum Optics, D-85748 Garching (Germany); Rutherford Appleton Laboratory, Chilton, Oxon, OX11 OQX (United Kingdom); General Atomics, San Diego, California 92186 (United States); Laboratory for Laser Energetics, University of Rochester, Rochester, New York 14623 (United States)] [and others

2005-05-09

224

Practical retrieval of land surface emissivity spectra in 8-14 ?m from hyperspectral thermal infrared data.  

PubMed

A practical physics-based regression method was developed and evaluated for nearly real time estimate of land surface emissivity spectra in 8-14 ?m from hyperspectral thermal infrared data. Two spectral emissivity libraries and one atmospheric profile database fully covering all the possible situations for clear sky conditions were elaborately selected to simulate the radiances at the top of the atmosphere (TOA). The regression coefficients were determined by the main principal components of emissivity spectra and those of simulated brightness temperature at TOA using a ridge regression method. The experience with the simulated Interferometer Atmospheric Sounding Instrument (IASI) data showed that the emissivity spectra could be retrieved under clear sky conditions with root mean square errors of 0.015 and 0.03 for 714-970 cm(-1) (10.3-14.0 ?m) and 970-1250 cm(-1) (8.0-10.3 ?m), respectively, for various land surface and atmospheric conditions. This indicates the proposed method may be robust and applicable for all hyperspectral infrared sensors. PMID:23187241

Wu, Hua; Wang, Ning; Ni, Li; Tang, Bo-Hui; Li, Zhao-Liang

2012-10-22

225

(??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

226

Do s-Process Enhanced Planetary Nebulae Have Unusual Dust Emission Spectra?  

NASA Astrophysics Data System (ADS)

We propose to obtain IRS observations of the mid-infrared dust emission of a sample of Galactic planetary nebulae (PNs) which are known to have enrichments of elements produced in the precursor star by slow neutron-capture nucleosynthesis (the "s-process"). These enhanced abundances result from captures of free neutrons by Fe-peak nuclei following by convective mixing during the AGB; this "third dredge-up" is also responsible for increasing the surface abundance of carbon. Since PNs are the descendants of AGB stars and are often C-rich, it is not surprising that we find substantial enrichments of s-process products such as Ge, Se, and Kr in some PNs. Despite their low initial abundances, 1e-9 to 1e-10 times H, modest enrichments of neutron-capture elements can have observable effects. The spectral type S, a transitional class between O-rich and C-rich AGB stars, is characterized by prominent ZrO bands; Zr is produced in the s-process. We have attempted, without success, to detect gas-phase Zr in PNs. However, Zr is highly refractory. It can condense into ZrO2 or be incorporated into high-temperature rocky condensates in O-rich environments, while in C-rich environments it may form metallic carbides (i.e. ZrC, an analog of TiC). Indeed, Zr-Mo carbide inclusions found in some meteoritic presolar grains are thought to originate in the atmospheres of C-rich AGB stars. Other refractory s-process products (e.g. Sr, Ba) may also be incorporated into grains. High-quality Spitzer spectra of the dust emission in a set of PNs with known s-process enhancements - determined by us from gas-phase measurements of undepleted elements - will be valuable for comparison with laboratory spectroscopy of grain analogs. These comparisons will help determine whether the dredge-up of n-capture products affects the dust chemistry of PNs and may offer some new insights into the dust composition.

Dinerstein, Harriet; Sellgren, Kris; Sterling, Nicholas

2006-05-01

227

Chemical Environment Effects on K[beta]/K[alpha] Intensity Ratio: An X-Ray Fluorescence Experiment on Periodic Trends  

ERIC Educational Resources Information Center

X-ray fluorescence (XRF) data from an energy-dispersive XRF instrument were used to investigate the chlorine K[alpha] and K[beta] peaks in several group 1 salts. The ratio of the peak intensity is sensitive to the local chemical environment of the chlorine atoms studied in this experiment and it shows a periodic trend for these salts. (Contains 1

Durham, Chaney R.; Chase, Jeffery M.; Nivens, Delana A.; Baird, William H.; Padgett, Clifford W.

2011-01-01

228

Effect of heat treatment on the far-infrared emission spectra and fine structures of black tourmaline.  

PubMed

Mineral black tourmaline powders were heat-treated at different temperatures. Their crystal structure was studied by X-ray diffractometer. Their infrared absorption and emission spectra before and after the heat treatment were analyzed by the Fourier transform infrared spectrometer. The corresponding fine structures were discussed in detail. The results showed that the powders possessed higher infrared emissivity at the band where they showed stronger infrared absorption. However, there is no certain correlation between the peak intensity of infrared absorption and emissivity values at the same frequency. Because of the crystal shrinkage of c-axis, the electronic transitions were stimulated between different energy levels, and the abilities of infrared absorption and emission were enhanced with increasing the temperature of heat treatment. PMID:24734598

Meng, Junping; Liang, Jinsheng; Liu, Jie; Ding, Yan; Gan, Kun

2014-05-01

229

Ultrafast K-(alpha) X-ray Thomson Scattering from Shock Compressed Lithium Hydride  

SciTech Connect

Spectrally and temporally resolved x ray Thomson scattering using ultrafast Ti K-{alpha} x-rays has provided experimental validation for modeling of the compression and heating of shocked matter. The coalescence of two shocks launched into a solid density LiH target by a shaped 6 nanosecond heater beam was observed from rapid heating to temperatures of 2.2 eV, enabling tests of shock timing models. Here, the temperature evolution of the target at various times during shock progression was characterized from the intensity of the elastic scattering component. The observation of scattering from plasmons, electron plasma oscillations, at shock coalescence indicates a transition to a dense metallic plasma state in LiH. From the frequency shift of the measured plasmon feature the electron density was directly determined with high accuracy, providing a material compression of a factor of three times solid density. The quality of data achieved in these experiments demonstrates the capability for single-shot dynamic characterization of dense shock compressed matter. The conditions probed in this experiment are relevant for the study of the physics of planetary formation and to characterize inertial confinement fusion targets for experiments such as on the National Ignition Facility (NIF), LLNL.

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

2008-12-10

230

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

231

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

232

Ultrafast K{alpha} x-ray Thomson scattering from shock compressed lithium hydride  

SciTech Connect

Spectrally and temporally resolved x-ray Thomson scattering using ultrafast Ti K{alpha} x rays has provided experimental validation for modeling of the compression and heating of shocked matter. The coalescence of two shocks launched into a solid density LiH target by a shaped 6 ns heater beam was observed from rapid heating to temperatures of 2.2 eV, enabling tests of shock timing models. Here, the temperature evolution of the target at various times during shock progression was characterized from the intensity of the elastic scattering component. The observation of scattering from plasmons, electron plasma oscillations, at shock coalescence indicates a transition to a dense metallic plasma state in LiH. From the frequency shift of the measured plasmon feature the electron density was directly determined with high accuracy, providing a material compression of a factor of 3 times solid density. The quality of data achieved in these experiments demonstrates the capability for single shot dynamic characterization of dense shock compressed matter. The conditions probed in this experiment are relevant for the study of the physics of planetary formation and to characterize inertial confinement fusion targets for experiments such as on the National Ignition Facility, Lawrence Livermore National Laboratory.

Kritcher, A. L. [L-399, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Nuclear Engineering Department, University of California Berkeley, Berkeley, California 94709 (United States); Neumayer, P.; Castor, J.; Doeppner, T.; Landen, O. L.; Ng, A.; Pollaine, S.; Price, D.; Glenzer, S. H. [L-399, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Falcone, R. W.; Lee, H. J. [Physics Department, University of California Berkeley, Berkeley, California 94709 (United States); Lee, R. W. [L-399, Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States); Physics Department, University of California Berkeley, Berkeley, California 94709 (United States); Holst, B.; Redmer, R. [Institut fuer Physik, Universitaet Rostock, D-18051 Rostock (Germany); Morse, E. C. [Nuclear Engineering Department, University of California Berkeley, Berkeley, California 94709 (United States)

2009-05-15

233

Effect of nearest-neighbor ions on excited ionic states, emission spectra, and line profiles in hot and dense plasmas  

NASA Technical Reports Server (NTRS)

The effect of the cylindrical symmetry imposed by the nearest-neighbor ions on the ionic levels and the emission spectra of a Li-like Kr ion immersed in hot and dense plasmas is investigated using the Stein et al. (1989) two-centered model extended to include computations of the line profiles, shifts, and widths, as well as the energy-level mixing and the forbidden transition probabilities. It is shown that the cylindrical symmetry mixes states with different orbital quantum numbers l, particularly for highly excited states, and, thereby, gives rise to forbidden transitions in the emission spectrum. Results are obtained for the variation of the ionic level shifts and mixing coefficients with the distance to the nearest neighbor. Also obtained are representative computed spectra that show the density effects on the spectral line profiles, shifts, and widths, and the forbidden components in the spectrum.

Salzmann, D.; Stein, J.; Goldberg, I. B.; Pratt, R. H.

1991-01-01

234

Ab initio quantum-chemical study on emission spectra of bioluminescent luciferases by fragment molecular orbital method  

NASA Astrophysics Data System (ADS)

Bioluminescence spectra of firefly Luciola cruciata were theoretically analyzed on the basis of the fragment molecular orbital (FMO) method. The CIS(D) and PR-CIS(Ds) methods were employed for the calculations of emission energies of wild-type and mutant luciferase-oxyluciferin systems, and various multi-layer FMO calculations were performed changing the sizes of the luciferase protein and of the chromophore to which the excited-state calculations were applied. We have thus reproduced the experimental emission energies of wild-type and mutant luciferase systems with good accuracy, which provides useful information concerning the roles of protein environment for the color tuning of the bioluminescence spectra of firefly.

Tagami, Ayumu; Ishibashi, Nobuhiro; Kato, Dai-ichiro; Taguchi, Naoki; Mochizuki, Yuji; Watanabe, Hirofumi; Ito, Mika; Tanaka, Shigenori

2009-04-01

235

The effect of Fe, Cu, and Si impurities on the formation of emission spectra in bulk ZnO crystals  

SciTech Connect

On the basis of the results of complex investigations (photoluminescence, x-ray fluorescence, and infrared spectroscopy), the features of emission-spectra formation are shown under the change in the type (Fe, Cu, and Si) and concentration of background impurities appearing during both growth and treatment of bulk crystals by grinding and polishing. Special attention is given to the concentration and types of bonds with hydrogen-the basic impurity preventing the formation of crystals with the p-type conductivity.

Mezdrogina, M. M., E-mail: margaret.m@mail.ioffe.ru; Danilevskii, E. Yu.; Kuz'min, R. V.; Poletaev, N. K.; Trapeznikova, I. N. [Ioffe Physicotechnical Institute (Russian Federation); Chukichev, M. V. [Moscow State University (Russian Federation); Bordovskii, G. A.; Marchenko, A. V. [Russian State Pedagogical University (Russian Federation); Eremenko, M. V. [St. Petersburg State Polytechnical University (Russian Federation)

2010-04-15

236

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

237

Time-resolved measurements of near infrared emission spectra from explosions: Pure pentaerythritol tetranitrate and its mixtures containing silver and aluminum particles  

NASA Astrophysics Data System (ADS)

Measurements of chemical transients and thermodynamic conditions are difficult to obtain yet fundamentally important in understanding the behavior of explosives. We have constructed a fast near infrared (NIR) spectrometer and have made temporally and spectrally-resolved emission measurements during postdetonation combustion of pure pentaerythritol tetranitrate (PETN) charges and PETN charges doped with 10 wt % microparticles composed of silver (Ag) and aluminum (Al). We have observed postdetonation PETN emission spectra between 750 and 1500 nm at rates up to 46 992 spectra/s. The instrument captures the highly structured spectra immediately following breakout as well as the longer-lived broadband NIR emission signals from hot particles. The early spectra reveal spectral signatures related to PETN and the reacting constituents of the particles. The later spectra provide a means to infer the gray-body temperature history of the particles.

Koch, Jon D.; Piecuch, Scott; Lightstone, James M.; Carney, Joel R.; Hooper, Joe

2010-08-01

238

Field emission spectra of single-atom tips with thermodynamically stable structures  

Microsoft Academic Search

Energy spectra of field emitted electrons from well-characterized tungsten nanoemitters covered with different metals have been measured in detail while changing the electric field and the topmost atomic structure. At very high electric fields, additional humps appear in the spectra of a single-atom tip. Their energy positions depend on both the coated material and structure termination but not on the

E. Rokuta; H.-S. Kuo; T. Itagaki; K. Nomura; T. Ishikawa; B.-L. Cho; I.-S. Hwang; T. T. Tsong; C. Oshima

2008-01-01

239

Chemiluminescent emission spectra and possible upper-state potentials of KCl and KBr  

Microsoft Academic Search

Chemiluminescent optical spectra of potassium chloride and potassium bromide have been observed in dilute flames. In the KCl spectra 56 ``fluctuation bands'' could be resolved. A table of 66 such bands were measured for KBr, extending the observed spectral range by about 1000 to the red for this molecule. Possible upper-state potential curves accounting for the observations are proposed.

Kenneth J. Kaufmann; James L. Kinsey; Howard B. Palmer; Archibald Tewarson

1974-01-01

240

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-coud 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

241

X-RAY REFLECTED SPECTRA FROM ACCRETION DISK MODELS. II. DIAGNOSTIC TOOLS FOR X-RAY OBSERVATIONS  

SciTech Connect

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 on the 2-10 keV energy region and in particular on the iron K-shell emission lines. We show the dependency of the equivalent width (EW) of the Fe K{alpha} on the ionization parameter. The maximum value of the EW is {approx}800 eV for models with log {xi} {approx} 1.5 and decreases monotonically as {xi} increases. For lower values of {xi}, the Fe K{alpha} EW decreases to a minimum near log {xi} {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 radiative recombination continua producing a broad feature that cannot be reproduced by a simple Gaussian profile. This could be used as a signature of reflection.

GarcIa, J. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Kallman, T. R. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Mushotzky, R. F., E-mail: javier.garcia@wmich.edu, E-mail: timothy.r.kallman@nasa.gov, E-mail: richard@astro.umd.edu [Department of Astronomy, University of Maryland, College Park, MD (United States)

2011-04-20

242

Low-Energy Electron Emission Spectra in F^q+Ne Collisions for Well Defined Emission Multiplicity  

Microsoft Academic Search

In swift collisions of highly charged ions with atoms it is well established that recoiling target ions with high charge states are created profusely. Using electron-recoil coincidence spectroscopy, creation of highly excited He-like Ne was identified via its Auger emission.(S. Hagmann et al., Phys. Rev. A\\\\underbar34), 2897 (1986). In this collision process leading to such a highly ionized ion, many

T. Zaepfel; S. Hagmann

1996-01-01

243

Ab-initio modeling of an iron laser-induced plasma: Comparison between theoretical and experimental atomic emission spectra  

NASA Astrophysics Data System (ADS)

We report on efforts to model the Fe emission spectrum generated from laser-induced breakdown spectroscopy (LIBS) measurements on samples of pure iron oxide (Fe2O3). Our modeling efforts consist of several components. We begin with ab-initio atomic structure calculations performed by solving the Hartree-Fock equations for the neutral and singly ionized stages of Fe. Our energy levels are then adjusted to their experimentally known values. The atomic transition probabilities and atomic collision quantities are also computed in an ab-initio manner. We perform LTE or non-LTE calculations that generate level populations and, subsequently, an emission spectrum for the iron plasma for a range of electron temperatures and electron densities. Such calculations are then compared to the experimental spectrum. We regard our work as a preliminary modeling effort that ultimately strives towards the modeling of emission spectra from even more complex samples where less atomic data are available.

Colgan, J.; Judge, E. J.; Kilcrease, D. P.; Barefield, J. E.

2014-07-01

244

Strong Calcite-Like Spectra Cathodoluminescence Emission from Allende Meteorite Cai Phases  

Microsoft Academic Search

Calciumaluminum-rich inclusions (CAIs) of Allende CV3 chondrite were studied by Environmental Scanning Electron Microscopy (ESEM), Energy Dispersive Spectrometry (EDS), Backscattering (BS), and Spectra Cathodoluminescence (CL). CAI minerals show spectra CL curves exceeding the 450,000a.u. with a large homogeneity along the white inclusions. CL curve features fit perfectly with terrestrial patterns of stressed specimens of weathered marble and limestone in which

Javier Garcia-Guinea; Laura Tormo; Oscar Azumendi; Javier Ruiz; Virgilio Correcher

2011-01-01

245

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

PubMed

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. PMID:24985625

Wehrle, Marius; Sulc, Miroslav; Van?ek, Ji?

2014-06-28

246

Imaging and blackbody emission spectra of hot particulates generated during laser ablation.  

National Technical Information Service (NTIS)

Blackbody emission from particulates generated during KrF-laser ablation of Y(sub 1)Ba(sub 2)Cu(sub 3)O(sub 7-x) (YBCO) and BN has been recorded for the first time by sensitive photography and emission spectroscopy in order to study the velocity, temperat...

D. B. Geohegan

1993-01-01

247

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

248

Infrared spectra of protonated coronene and its neutral counterpart in solid parahydrogen: implications for unidentified interstellar infrared emission bands.  

PubMed

Large protonated polycyclic aromatic hydrocarbons (H(+) PAHs) are possible carriers of unidentified infrared (UIR) emission bands from interstellar objects, but the characterization of infrared (IR) spectra of large H(+) PAHs in the laboratory is challenging. IR absorption spectra of protonated coronene (1-C24 H13 (+) ) and mono-hydrogenated coronene (1-C24 H13 (.) ), which were produced upon electron bombardment of parahydrogen containing a small proportion of coronene (C24 H12 ) during matrix deposition, were recorded. The spectra are of a much higher resolution than those obtained by IR multiphoton dissociation by Dopfer and co-workers. The IR spectra of protonated pyrene and coronene collectively appear to have the required chromophores for features of the UIR bands, and the spectral shifts on an increase in the number of benzenoid rings point in the correct direction towards the positions of the UIR bands. Larger protonated peri-condensed PAHs might thus be key species among the carriers of UIR bands. PMID:24310834

Bahou, Mohammed; Wu, Yu-Jong; Lee, Yuan-Pern

2014-01-20

249

Abundance determination from global emission-line SDSS spectra: exploring objects with high N/O ratios  

NASA Astrophysics Data System (ADS)

We have compared the oxygen and nitrogen abundances derived from global emission-line Sloan Digital Sky Survey (SDSS) spectra of galaxies using (1) the Te method and (2) two recent strong-line calibrations: the ON and NS calibrations. Using the Te method, anomalously high N/O abundance ratios have been found in some SDSS galaxies. To investigate this, we have Monte Carlo simulated the global spectra of composite nebulae by a mix of spectra of individual components, based on spectra of well-studied H II regions in nearby galaxies. We found that the Te method results in an underestimated oxygen abundance (and hence in an overestimated nitrogen-to-oxygen ratio) if H II regions with different physical properties contribute to the global spectrum of composite nebulae. This effect is somewhat similar to the small-scale temperature fluctuations in H II regions discussed by Peimbert. Our work thus suggests that the high Te-based N/O abundance ratios found in SDSS galaxies may not be real. However, such an effect is not expected to be present in dwarf galaxies since they generally have a uniform chemical composition. The ON and NS calibrations give O and N abundances in composite nebulae which agree with the mean luminosity-weighted abundances of their components to within 0.2 dex.

Pilyugin, L. S.; Vlchez, J. M.; Mattsson, L.; Thuan, T. X.

2012-04-01

250

Tomographic reconstruction of FT-IR emission and transmission spectra in a sooting laminar diffusion flame; Species concentrations and temperatures  

SciTech Connect

This paper reports on tomographic reconstruction techniques applied to line-of-sight Fourier Transform infrared (FT-IR) emission and transmission measurements to derive spectra corresponding to small volumes within an ethylene diffusion flame. From these spectra, point values for species temperatures and relative concentrations have been determined for CO{sub 2}, H{sub 2}O, alkanes, alkenes, alkynes, and soot. In this article the methods that were used are described, and the results are reported and compared with previous determinations on similar flames. There is strong evidence that the soot temperature differs from the gas temperature at the same location, over large regions of the flame, with a maximum difference of 360 K ({plus minus} 60 K) being observed.

Best, P.E.; Chien, P.L.; Carangelo, R.M.; Solomon, P.R. (Advanced Fuel Research, Inc., East Hartford, CT (US)); Danchak, M.; Ilovici, I. (Hartford Graduate Center, Hartford, CT (US))

1991-06-01

251

Effects of reactive admixtures on the near-IR emission spectra of hydrogen and deuterium oxidation flames  

Microsoft Academic Search

The emission spectra of hydrogen-oxygen and hydrogen-air flames at 0.11 atm exhibit a system of bands between 852 and 880\\u000a nm, which is assigned to the H2O2 molecule vibrationally excited into the overtone region. This molecule results from the reaction HO\\u000a 2\\u000a \\u000a + HO\\u000a 2\\u000a \\u000a ? H2O\\u000a 2\\u000a v\\u000a + O2. The overtone region also contains bands at 670 and

N. M. Rubtsov; G. I. Tsvetkov; V. I. Chernysh; V. V. Azatyan

2007-01-01

252

Torsional broadening in absorption and emission spectra of bithiophene as calculated by time-dependent density functional theory  

NASA Astrophysics Data System (ADS)

The optimized geometries of bithiophene in the electronic ground and excited state have been calculated by time-dependent density functional theory using the hybrid functional B3-LYP. The dependence of the singlet excitation energies and transition dipoles on the torsion between the two thienyl groups has been determined and compared with the torsional potential curve previously found for biphenyl. Based on these data the torsional progressions in absorption and emission have been computed quantum-mechanically in order to show their contribution to the inhomogeneous broadening in the respective spectra of bithiophene.

Beenken, Wichard J. D.

2008-06-01

253

Autoionization emission for x-ray-excited Auger spectra in the Compton-scattering process  

SciTech Connect

Autoionization emission in the 3d transition-metal series is observed for the x-ray-excited Auger electrons in the Compton-scattering process. Kinematical analysis of Compton scattering shows that such emission becomes possible only when the x rays have sufficiently high energy to lift the bound 3p electrons into the conduction band. With the tuning capabilities of synchrotron sources, this should open a new channel in autoionization experiments.

Brener, R.; Felsteiner, J.; Tyk, R.; Zak, J.

1988-01-15

254

The Origin of MN II Emission in the Spectra of Chemically Peculiar Stars  

NASA Astrophysics Data System (ADS)

Emission from Mn II multiplet 13 (??6122-6132) in the spectrum of the 3He star 3 Centauri A and the hot, mild, HgMn star 46 Aquilae can be naturally explained by interlocked non-LTE effects. However, reproduction of the strength of the Mn II emission in both stars requires vertical stratification of the manganese abundance, with manganese concentrated high in the photosphere (column mass <~10-2 g cm-2). If this formation picture is correct, several additional transitions of Mn II with ?>8000 should also be present in emission in the spectrum of 3 Cen A. The wide range in the strength of Mn II multiplet 13 among upper main-sequence stars (ranging from absorption to emission) is made possible by the interplay in the non-LTE radiative transfer solution of the stellar Teff, manganese abundance, and manganese stratification profile. In particular, emission is strongly suppressed by a large manganese overabundance in the photosphere. This explains why the hot, mild, HgMn star 46 Aql, which has only a modest manganese enhancement, is detected in emission in Mn II multiplet 13 while other HgMn stars of similar Teff but with large photospheric manganese overabundances, such as ? Cancri, present Mn II multiplet 13 in absorption.

Sigut, T. A. A.

2001-01-01

255

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

256

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

257

A new non-LTE retrieval method for atmospheric parameters from mipas-envisat emission spectra  

Microsoft Academic Search

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution limb sounder on board the European polar platform ENVISAT, scheduled to be launched in 2001. A large number of atmospheric trace gases relevant to stratospheric ozone chemistry and global change are expected to be retrieved from the IR spectra covering a wide spectral range. While operational data analysis under

B. Funke; M. Lpez-Puertas; G. Stiller; T. V. Clarmann; M. Hpfner

2001-01-01

258

Plasma Emission Spectra of Opuntia Nopalea Obtained with Microsecond Laser Pulses  

Microsoft Academic Search

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.

L. Ponce; T. Flores; A. Arronte; A. Flores

2008-01-01

259

L{beta}1 and L{beta}2 Satellites in the X-ray Emission Spectra  

SciTech Connect

The X-ray satellites L{beta}{sub 1}{sup I}, L{beta}{sub 1}{sup II}, L{beta}{sub 1}{sup III}, L{beta}{sub 1}{sup IV}, L{beta}{sub 2}{sup I}, L{beta}{sub 2}{sup (b)}, L{beta}{sub 2}{sup II} and L{beta}{sub 2}{sup (c)} observed in the L-emission spectra in elements with Z = 26 to 92, have been calculated. The energies of various transitions have been calculated by available Hartree-Fock-Slater (HFS) data using the semi-empirical Auger transition energies in the doubly ionized atoms and their relative intensities have been estimated by considering cross - sections of singly ionized 2x-1 (x {identical_to} s, p) states and then of subsequent Coster-Kronig and shake off processes. The calculated spectra have been compared with the measured satellite energies in the L emission spectra. Their intense peaks have been identified as the observed satellite lines. The one to one correspondence between the peaks in calculated spectra and the satellites in measured spectra has been established on the basis of the agreement between the separations in the peak energies and those in the measured satellite energies. Group of transitions under the transition schemes L2Mx-MxM4,5 and L3Mx-MxN4,5 (x {identical_to} 1-5), which give rise to these satellites have been identified. It is observed that the satellite L{beta}{sub 2}{sup (b)} in all these spectra can be assigned to the superposition of 3F4-3G5 and 3F4-3D3 transitions and that this must be most intense one out of all these satellites, contributing in order of decreasing intensity. Each of the remaining satellites is found to have different origin in different elements. The possible contributions of the suitable transitions to all these lines have also been discussed.

Poonia, Surendra [Division of Natural Resources and Environment, Central Arid Zone Research Institute, Jodhpur - 342 003, Rajasthan (India)

2005-10-26

260

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

261

Angular Dependence of Secondary Electron Emission Spectra from a Polycrystalline Au Surface  

Microsoft Academic Search

The angle dependence of emitted electron spectra from a polycrystalline Au surface has been measured at several incident electron beam energies. The range of incident energies ( 100 eV to 3000 eV) extends from below the first crossover energy, through Emax, to above the second crossover energy. The traditional distinction between secondary electrons (50 eV)is found to be inconsistent with

Jason Kite; J. R. Dennison; R. E. Davies

2002-01-01

262

Plasma modulation of harmonic emission spectra from laser-plasma interactions.  

PubMed

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. PMID:17358542

Boyd, T J M; Ondarza-Rovira, R

2007-03-01

263

Simulation of neutron emission spectra from neutral beam-heated plasmas in the EAST tokamak  

NASA Astrophysics Data System (ADS)

The neutron emission spectrum from neutral beam-heated plasmas of the Experimental Advanced Superconducting Tokamak (EAST) is investigated based on first-principles simulations of the fast deuteron energy distribution. Parametrized plasma profiles are used to determine the beam deposition and fast deuteron distribution function using the NUBEAM code. The deuteron distribution is also interpreted with the help of empirical models and the components in the neutron energy spectrum are computed for different viewing lines using a Monte Carlo method. The resulting observational possibilities are discussed for the case of a time-of-flight neutron emission spectrometer optimized for EAST.

Chen, Z.; Nocente, M.; Tardocchi, M.; Fan, T.; Gorini, G.

2013-06-01

264

Constraining thermal dust emission in distant galaxies with number counts and angular power spectra  

NASA Astrophysics Data System (ADS)

We perform a joint fit to differential number counts from Spitzer's Multiband Imaging Photometer for Spitzer and Herschel's Spectral and Photometric Imaging Receiver (SPIRE) instruments, and angular power spectra of cosmic infrared background (CIB) anisotropies from SPIRE, Planck, the Atacama Cosmology Telescope and the South Pole Telescope, which together span 220 ? ? /GHz ? 4300 (70 ? ?/? m ? 1400). We simultaneously constrain the dust luminosity function, thermal dust spectral energy distribution (SED) and clustering properties of CIB sources, and the evolution of these quantities over cosmic time. We find that the data strongly require redshift evolution in the thermal dust SED. In our adopted parametrization, this evolution takes the form of an increase in greybody dust temperature at high redshift, but it may also be related to a temperature - dust luminosity correlation or evolution in dust opacity. The counts and spectra together constrain the evolution of the thermal dust luminosity function up to z 2.5-3, complementing approaches relying on rest-frame mid-infrared observations of the rarest bright objects. We are able to fit the power spectra without requiring a complex halo model approach, and show that neglecting scale-dependent halo bias may be impairing analyses that do use this framework.

Addison, G. E.; Dunkley, J.; Bond, J. R.

2013-12-01

265

Emission lines of FeXV in spectra obtained with the Solar Extreme-Ultraviolet Research Telescope and Spectrograph  

NASA Astrophysics Data System (ADS)

Recent R-matrix calculations of electron impact excitation rates in Mg-like FeXV are used to derive theoretical emission-line ratios involving transitions in the 243-418 wavelength range. A comparison of these with a data set of solar active region, subflare and off-limb spectra, obtained during rocket flights by the Solar Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS), reveals generally very good agreement between theory and observation, indicating that most of the FeXV emission lines may be employed with confidence as electron density diagnostics. In particular, the 312.55-line of FeXV is not significantly blended with a CoXVII transition in active region spectra, as suggested previously, although the latter does make a major contribution in the subflare observations. Most of the FeXV transitions which are blended have had the species responsible clearly identified, although there remain a few instances where this has not been possible. We briefly address the long-standing discrepancy between theory and experiment for the intensity ratio of the 3s21S-3s3p 3P1 intercombination line at 417.25 to the 3s21S-3s3p 1P resonance transition at 284.16 .

Keenan, F. P.; Aggarwal, K. M.; Milligan, R. O.; Ryans, R. S. I.; Bloomfield, D. S.; Srigengan, V.; O'Mullane, M. G.; Lawson, K. D.; Msezane, A. Z.; Brosius, J. W.; Davila, J. M.; Thomas, R. J.

2005-02-01

266

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

NASA Astrophysics Data System (ADS)

The fluorine K? emission spectra in fluorescence from a series of 3d transition-metal difluorides MF2 (M=Mn, Fe, Co, Ni, Cu and Zn) have been measured with a high-resolution two-crystal vacuum spectrometer. It is shown that the observed FWHM of the K?1,2 emission band is closely related to the difference in the electronegativity between the metal and fluorine atoms. The measured emission spectra are presented along with the UPS or XPS spectra of the valence bands and the fluorine K absorption spectra of the metal difluorides, reported previously. The structures at the fluorine K absorption edges are interpreted in terms of a molecular orbital (MO) model.

Sugiura, Chikara

1991-08-01

267

The effect of zinc ion on the absorption and emission spectra of glutathione derivative: Predication by ab initio and DFT methods  

NASA Astrophysics Data System (ADS)

Relying on the reaction of o-phthalaldehyde (OPA) with glutathione (GSH) to form a highly fluorescence derivative GSH-OPA has been widely used to measure reduced glutathione. In order to better understand spectra property of the GSH-OPA and the effect of zinc ion on it, the ground and the lowest singlet excited state properties, the electronic absorption and emission spectra are predicted by ab initio and DFT methods. The absorption spectra are simulated using time dependent DFT method (TD-DFT) whereas the emission spectra are approximated by optimizing the lowest singlet excited state by HF/CI-Singles and then subsequently using this geometry for the TD-DFT calculations. The solvent effects on transition energies have been described within the conductor-like polarizable continuum model (CPCM). The calculated transition energies (absorption and emission) are in agreement with available experimental information.

Liu, Jianhua; Ma, Jie; Zhang, Hua; Wang, Haijun

2012-06-01

268

Measurement of Neutron Emission Spectra in Li(d,xn) Reaction with Thick and Thin Targets for 40-MeV Deuterons  

SciTech Connect

To improve the data accuracy of the neutron emission spectra of the {sup nat}Li(d,xn) reaction that will be used as the neutron source in the International Fusion Materials Irradiation Facility, the authors have measured the neutron emission spectra from thick and thin lithium targets bombarded by 40-MeV deuterons at the AVF cyclotron (K = 110) facility of Tohoku University. The neutron spectra were measured at nine laboratory angles between 0 and 110 deg with the time-of-flight method using a beam-swinger system and a well-collimated neutron flight channel, obtained over almost the entire energy range of secondary neutrons using a two-gain method. The data obtained revealed the shape and angular dependence of emission spectra up to the high-energy region called a 'high-energy tail'. The experimental results are compared with other experimental data and calculations.

Hagiwara, M. [Tohoku University Cyclotron and Radioisotope Center (Japan); Itoga, T. [Tohoku University Cyclotron and Radioisotope Center (Japan); Kawata, N. [Tohoku University Cyclotron and Radioisotope Center (Japan); Hirabayashi, N. [Tohoku University Cyclotron and Radioisotope Center (Japan); Oishi, T. [Tohoku University Cyclotron and Radioisotope Center (Japan); Yamauchi, T. [Tohoku University Cyclotron and Radioisotope Center (Japan); Baba, M. [Tohoku University Cyclotron and Radioisotope Center (Japan); Sugimoto, M. [Japan Atomic Energy Research Institute (Japan); Muroga, T. [National Institute for Fusion Science (Japan)

2005-11-15

269

Analysis of (030),(110), and (011) interacting states of D II 16O from hot temperature emission spectra  

NASA Astrophysics Data System (ADS)

This study is the continuation of our analysis of emission spectra of pure D II0. The spectra have been recorded in the 320 - 860 and 1750 - 4300 cm -1 spectral regions at different pressures and temperatures. The measurements were performed in an alumina cell with an effective length of hot gas of about 50 cm. All spectra have been recorded by using the Bruker IFS 120 spectrometer at the Physikalisch-Chemisches-Institut, Justus-Liebig-Universitat Giessen, Germany). More than 5600 lines have been assigned to the second triad {(030), (110), (011)} of interacting states of the D II 160 molecule. These transitions were assigned to 24 vibration-rotation and rotational bands. An extended set of more than 1500 experimental rovibrational levels for the (030), (110), and (011) interacting states has been obtained. The maximum values of rotational quantum numbers are J max = 30 and K a max = 21 with E max = 10568 cm -1 for the (011) state; J max = 29 and K a max = 21 with E max= 10540 cm -1 for the (030) state, and Jm 26 and Ka max 22 with Eniax 10488 cm1 for the (110) state. A comparison of the observed energy levels with the best available values from literature and with the global prediction is discussed.

Starikova, Eugeniya N.; Mikhailenko, Semen N.; Mellau, Georg Ch.; Tyuterev, Vladimir G.

2006-12-01

270

Using Hot Emission Spectra in Generating Line Lists of Molecules (NH3, CH4) for Astrophysical Applications  

NASA Astrophysics Data System (ADS)

Spectra of cool stars, brown dwarfs and extrasolar planets (exoplanets) contain a dense forest of lines from hot molecules. Examples include CH4 and NH3 in brown dwarfs and CH4 in `hot Jupiter' exoplanets. These observations present challenges to astronomers, who typically use databases such as HITRAN intended for room-temperature applications, to model the spectral energy distributions. We have used a novel technique to combine `hot' emission spectra recorded for a range of sample temperatures (300 -- 1400C) in order to deduce empirical lower state energies of the emitted lines. We have applied this method to NH3 in the 740 -- 2100 cm-1 range which includes the ?2 and the ?4 fundamental modes and in the 1650 -- 4000 cm-1 range which includes the ?1 and ?3 fundamental modes. We have estimated empirical lower state energies and our values have been incorporated into the line lists along with line positions and calibrated line intensities. This method is currently being extended to CH4. Our results can be used directly for the simulation of astronomical spectra. Hargreaves, R. J., Li, G., and Bernath, P. F. Astrophys. J. 735 (2011) 111. Hargreaves, R. J., Li, G., and Bernath, P. F. J. Quant. Spectrosc. Radiat. Transfer, (2012) in press.

Hargreaves, R. J.; Michaux, L.; Li, G.; Beale, C.; Irfan, M.; Bernath, P. F.

2012-06-01

271

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

272

Integrated fluxes for emission lines in the ultraviolet spectra of several planetaries  

NASA Technical Reports Server (NTRS)

The IUE satellite observatory was used to obtain absolutely-calibrated emission line fluxes for diagnostic lines of multiply-ionized C, N, O, Si, Ne, and Ar which occur in the ultraviolet spectral region of planetary nebulae. These data, when combined with data from the blue, visual, and near infrared, provide improved estimates of ionic concentrations, plasma temperatures and densities, and elemental abundances.

Carpenter, K. G.; Czyzak, S. J.

1981-01-01

273

Temperature Dependence of Vibrational Spectra in Calcite by Means of Emissivity Measurement  

Microsoft Academic Search

The emissivities at various temperatures from 500 to 1200 K, together with the reflectivity at 300 K in calcite, were measured on the spectral region 200-4000 cm-1. It was found by the measurements that conspicuous changes with temperature occurred in the reststrahlen bands of the lattice and molecular vibrations. By analyzing the reststrahlen bands, the temperature dependences of vibration parameters

Takemaro Sakurai; Tsutomu Sato

1971-01-01

274

Tuning the emission spectra of pyrromethene doped polycarbonate by light confinement  

Microsoft Academic Search

Spectrophotometry and photoluminescence (PL) are used to investigate the optical properties and photodegradation of thin films of pyrromethene 580 dispersed in polycarbonate (PC). The films spin-coated on glass act as asymmetric planar waveguides and excited with blue light yield a linearly polarized emission whose color changes according to the film thickness. .

M. Allegrini; A. Arena; E. Cefali; C. Pace; S. Patan; G. Saitta

2000-01-01

275

PCI Effects on Coincidence Spectra Associated with the Emission of Two Auger Electrons  

Microsoft Academic Search

Experimental investigation of the threshold electron \\/ fast electron coincidences allows one to select lines which are associated with two Auger electron emission. Such an investigation carried out for near threshold photoionization of Xe 4d shell reveals a considerable distortion of the lineshapes due to Post Collision Interaction (PCI). Analysis of the PCI influence on the Auger lineshapes allows us

S. Sheinerman; P. Lablanquie; F. Penent; R. I. Hall; M. Ahmad; Y. Hikosaka; K. Ito

2003-01-01

276

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

277

Errors Associated with Fitting Gaussian Profiles to Noisy Emission-Line Spectra  

NASA Astrophysics Data System (ADS)

Landman, Roussel-Dupre, and Tanigawa 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. (SECTION: Instrumentation and Data Analysis)

Lenz, Dawn D.; Ayres, Thomas R.

1992-11-01

278

1-2.5 mu m spectra of jets from young stars: Strong Fe II emission in HH111, HH240-241 and HH120  

Microsoft Academic Search

As part of a 1-2.5 mu m spectroscopic survey of jets and molecular outflows, we present the spectra of three Herbig Haro chains (HH111, HH240\\/241, HH120) characterized by strong emission from several Fe Ii, transitions originating from the first 13 fine structure levels. Such emission is correlated with optical S Ii emission and appears to decrease moving away from the

B. Nisini; A. Caratti o Garatti; T. Giannini; D. Lorenzetti

2002-01-01

279

Broadening and splitting of emission spectra of a GaInAs/AlInAs quantum cascade laser in a quantising magnetic field  

SciTech Connect

We have studied the effect of a relatively weak quantising magnetic field on emission spectra of a GaInAs/AlInAs quantum cascade laser near 10 K. The results demonstrate that, as the magnetic field induction increases to 7 T, the spectra broaden (to 5 meV) and split into three emission bands. As a result, we observe simultaneously up to 80 longitudinal lasing modes in the three bands and the integrated laser output intensity increases 70 times. The presence of bands in the emission spectra can be accounted for in terms of the magnetic quantisation of the laser levels into spinsplit Landau levels. The increase in emission intensity is attributable primarily to phonon resonance adjustment in a magnetic field. (lasers)

Zasavitskii, I I; Pashkeev, D A; Bushuev, E V; Mikaelyan, G T

2013-02-28

280

Infrared Emission of Normal Galaxies from 2.5 to 12 Micron: Infrared Space Observatory Spectra, Near-Infrared Continuum, and Mid-Infrared Emission Features  

NASA Astrophysics Data System (ADS)

We present ISOPHOT spectra of the regions 2.5-4.9 ?m and 5.8-11.6 ?m for a sample of 45 disk galaxies from the US Infrared Space Observatory Key Project on Normal Galaxies. The galaxies were selected to span the range in global properties of normal, star-forming disk galaxies in the local universe. The spectra can be decomposed into three spectral components: (1) continuum emission from stellar photospheres, which dominates the near-infrared (NIR; 2.5-4.9 ?m) spectral region; (2) a weak NIR excess continuum, which has a color temperature of ~103 K, carries a luminosity of a few percent of the total far-infrared (FIR) dust luminosity LFIR and most likely arises from the interstellar medium (ISM); and (3) the well-known broad emission features at 6.2, 7.7, 8.6, and 11.3 ?m, which are generally attributed to aromatic carbon particles. These aromatic features in emission (AFEs) dominate the mid-infrared (MIR; 5.8-11.6 ?m) part of the spectrum and resemble the so-called type A spectra observed in many nonstellar sources and the diffuse ISM in our own Galaxy. The few notable exceptions include NGC 4418, where a dust continuum replaces the AFEs in MIR, and NGC 1569, where the AFEs are weak and the strongest emission feature is [S IV] 10.51 ?m. The relative strengths of the AFEs vary by 15%-25% among the galaxies. However, little correlation is seen between these variations and either IRAS 60 ?m/100 ?m flux density ratio R(60/100) or the FIR/blue luminosity ratio LFIR/LB, two widely used indicators of the current star formation activity, suggesting that the observed variations are not a 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 FIR emission from large dust grains. In particular, the summed luminosity of the AFEs falls from ~0.2 LFIR for the most ``IR-quiescent'' galaxies to ~0.1 LFIR for the most ``IR-active'' galaxies. This is likely a consequence of the preferential destruction in intense radiation fields of the small carriers responsible for the NIR/AFE emission. Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries, France, Germany, the Netherlands, and the United Kingdom) and with the participation of ISAS and NASA.

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

2003-05-01

281

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

282

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

283

Study of supra-thermal electrons and {ital K}-{alpha} x-rays from high intensity 500 fs laser-produced plasmas  

SciTech Connect

We describe recent laser-solid interaction experiments using the 500 fs Janus Nd:glass (1053 nm) laser presently at 1.5 TW power level. The laser beam path is enclosed in vacuum from the compressor to the target and is focused using an off-axis paraboloid. Optical diagnostics monitor the near field pattern, focal spot, spectrum, temporal shape and pre-pulse level. A 12 {mu}m diameter (FWHM) focal spot is achieved (2.5{times}diffraction limit) corresponding to a peak irradiance of 8{times}10{sup 17} Wcm{sup {minus}2} on target. A suite of x-ray diagnostics characterize the x-ray emission from the plasma. We present results for normal incidence irradiation of high-Z (Zn, Ge, Mo, Sn) solid targets. The supra-thermal electrons produced in the short scale length plasma have temperature {ital T}{sub {ital H}}{gt}100 keV and can efficiently fluoresce the cold {ital K}-{alpha} lines in the 8{endash}30 keV energy range. {copyright} {ital 1996 American Institute of Physics.}

Dunn, J.; Young, B.K.; Hankla, A.K.; Conder, A.D.; White, W.E.; Stewart, R.E. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)

1996-05-01

284

Study of supra-thermal electrons and K-{alpha} x-rays from high intensity 500 fs laser-produced plasmas  

SciTech Connect

We describe recent laser-solid interaction experiments using the 500 fs Janus Nd:glass (1053 nm) laser presently at 1.5 TW power level. The laser beam path is enclosed in vacuum from the compressor to the target and is focused using an off-axis paraboloid. Optical diagnostics monitor the near field pattern, focal spot, spectrum, temporal shape and pre-pulse level. A 12 {mu}m diameter (FWHM) focal spot is achieved (2.5 {times} diffraction limit) corresponding to a peak irradiance of 8 {times} 1017 W cm{sup {minus}2} on target. A suite of x-ray diagnostics characterize the x-ray emission from the plasma. We present results for normal incidence irradiation of high-Z (Zn, Ge, Mo, Sn) solid targets. The supra-thermal electrons produced in the short scale length plasma have temperature T{sub H} > 100 keV and can efficiently fluoresce the cold K-{alpha} lines in the 8--30 keV energy range.

Dunn, J.; Young, B.K.F.; Hankla, A.K.; Conder, A.D.; White, W.E.; Stewart, R.E.

1995-07-01

285

Helium Emissions Observed in Ground-Based Spectra of Solar Prominences  

NASA Astrophysics Data System (ADS)

The only prominent line of singly ionized helium in the visible spectral range, He ii 4686 , is observed together with the He i 5015 singlet and the He i 4471 triplet line in solar prominences. The Na D2 emission is used as a tracer for He ii emissions which are sufficiently bright to exceed the noise level near 10-6 of the disk-center intensity. The prominences thus selected are characterized by small non-thermal line broadening and almost absent velocity shifts, yielding narrow line profiles without wiggles. The reduced widths [? ? D/ ?] of He ii 4686 are 1.5 times broader than those of the He i 4471 triplet and 1.65 times broader than those of the He i 5015 singlet. This indicates that the He lines originate in a prominence-corona transition region with outwards increasing temperature.

Ramelli, R.; Stellmacher, G.; Wiehr, E.; Bianda, M.

2012-12-01

286

Infrared, X-ray, and XUV astrophysics. [emission spectra/galaxies  

NASA Technical Reports Server (NTRS)

An observational program covering wavelengths from the near infrared to 1 millimeter is reviewed. The program of millimeter observations largely consisted of analyzing previous observations since the summer humidity was too high for new observations. Maps of millimeter emission from W3, Sgr B2, W49 and M42 were made. Five extragalactic sources were detected and are discussed. Energy distributions of several of the discrete sources at the Galactic Center were studied. A 5-year visual/infrared program on Markarian galaxies is discussed which showed the presence of both thermal and nonthermal infrared radiation sources and established correlations between the infrared sources and the emission line regions. The Nova Cygnus 1975, caught during its rise as well as subsequent dimming, is also discussed. Several other continuing programs are described, including studies of dark clouds and CO maser sources.

1975-01-01

287

Fluorescence properties of twenty fluorescein derivatives: lifetime, quantum yield, absorption and emission spectra.  

PubMed

The fluorescence lifetime (?f), emission quantum yield (?f), absorption and emission spectral data of 20 fluorescein derivatives were measured under the same conditions by using time-correlated single photon counting, steady state fluorescence and absorption methods to get comparable data. Based on the results, the factors and mechanism that control the fluorescence properties of the fluorescein dyes are discussed. Both ?f and ?f are remarkably dependent on the substitution on either xanthene or phenyl rings, but their ratio (?f/?f), i.e. rate constant of radiation process, is a constant value (0.20 10(9) s(-1)). The rate constant of nonradiation process, on the other hand, is varied with both the structure and the solvent used. PMID:24510430

Zhang, Xian-Fu; Zhang, Jianlong; Liu, Limin

2014-05-01

288

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

289

Demonstration of x-ray Thomson scattering using picosecond K-alpha x-ray sources in the characterization of dense heated matter  

Microsoft Academic Search

We present K-alpha x-ray Thomson scattering from shock compressed matter for use as a diagnostic in determining the temperature, density, and ionization state with picosecond resolution. The development of this source as a diagnostic as well as stringent requirements for successful K-alpha x-ray Thomson scattering are addressed. Here, the first elastic and inelastic scattering measurements on a medium size laser

A. L. Kritcher; P. Neumayer; H. J. Lee; T. Dppner; R. W. Falcone; S. H. Glenzer; E. C. Morse

2008-01-01

290

Study Of Titanium Emission Spectra In N2 - H2 Abnormal DC Glow Discharge  

NASA Astrophysics Data System (ADS)

In this paper we tried to answer why small amount of hydrogen (3 %) in a nitrogen abnormal glow discharge so strongly reduce Ti I spectral line intensities. Decreasing of Ti I line intensities in N2 - H2 discharge are compared with less pronounced decreasing of N I line intensities. Using emission spectroscopy we have observed that line intensity changes are correlated to variations in electron energy distribution function (EEDF) and change of metastable density.

Obradovic, B. M.; Cvetanovic, N.; Kuraica, M. M.

2010-07-01

291

The Visible Emission Spectra of Iodine and Bromine Monofluorides and their Dissociation Energies  

Microsoft Academic Search

A new emission band spectrum has been observed in the iodine-fluorine flame of reaction and has been assigned to the IF molecule. A similar type of spectrum is emitted by the bromine-fluorine flame and is shown to be an extension of the BrF system already known in absorption. Both these systems probably arise from a 3Pi 0+-> 1Sigma transition. Vibrational

R. A. Durie

1951-01-01

292

Edge excitation geometry for studying intrinsic emission spectra of bulk n-InP  

NASA Astrophysics Data System (ADS)

The shape of the photoluminescence line excited at an edge face of InP wafer and recorded from the broadside is used to investigate the intrinsic emission spectrum. The procedure is much less sensitive to the surface properties and the carrier kinetics than the conventional methods used with the reflection or transmission geometry of photoluminescence. Our method provides a tool for studying the effects of non-equilibrium distribution of minority carriers in doped direct-band semiconductors.

Semyonov, Oleg; Subashiev, Arsen; Chen, Zhichao; Luryi, Serge

2014-03-01

293

Radial profiles of the emission spectra of dc glow discharge sustained in molecular gases at medium pressures  

NASA Astrophysics Data System (ADS)

The results of a study of the radial dependence of the emission spectra of the active dc glow discharge sustained in pure oxygen and in mixtures of CO2, N2 and He are presented. Optical emission spectroscopy has been employed to determine parameters such as rotational and vibrational temperature. Considering the CO2N2He mixtures, we were also able to determine the [CO]/[N2] relative concentration using the method of optical emission actinometry. The dc glow discharge in pure oxygen has been studied for pressures of 200400 Pa and for discharge currents 20 and 40 mA. The profile was found to be flat, independent of the discharge parameters and an increase in the rotational temperature with increasing pressure and discharge current was observed. The radial profile of the vibrational temperature of nitrogen in the CO2N2He mixture was flat for all studied pressures (4001330 Pa) and all discharge currents (1040 mA). The radial profile of the [CO] relative concentration exhibited a local maximum at approximately half the radius of the discharge tube for 400 Pa. It increased uniformly from the centre to the wall of the tube at a pressure of 1330 Pa.

Morvek, M. J.; Schmiedt, L.; Laca, M.; Ka?ka, A.; Hrachov, V.

2014-05-01

294

Modeling of high-resolution K? emission spectra from Fe XVIII through Fe XXIV  

NASA Astrophysics Data System (ADS)

Results for K? x-ray emission from highly charged iron ions, which were obtained from a detailed and systematic spectral model, are presented in the wavelength range from 1.84 to 1.94 . Account has been taken of the fundamental atomic radiative-emission processes associated with inner-shell electron collisional excitation, inner-shell electron collisional ionization, as well as dielectronic recombination. Particular emphasis has been directed at the identification of spectral features that can serve as diagnostics of extreme nonequilibrium or transient-ionization conditions, which can occur in stellar flares and supernova remnants, as well as in tokamak plasmas. In order to investigate the fundamental K? line-formation processes that can play a dominant role under these conditions, theoretical predictions have been compared with spectral observations of the EBIT-II x-ray emission from highly charged Fe ions in the electron-beam ion trap at the Lawrence Livermore National Laboratory. The observed spectroscopic features are found to be well represented by our theoretical calculations, validating earlier theoretical work on transient-ionization phenomena. We have identified spectral features that can serve as diagnostics of the electron density, the line-formation mechanism, and the charge-state distribution.

Decaux, V.; Jacobs, V. L.; Beiersdorfer, P.; Liedahl, D. A.; Kahn, S. M.

2003-07-01

295

Bayesian model selection and parameter estimation of nuclear emission spectra using RJMCMC  

NASA Astrophysics Data System (ADS)

This paper addresses the general problem of estimating parameters in nuclear spectroscopy. We present a unified Bayesian formulation to tackle the various aspects of this problem. This includes deconvolution and modelling of both the peaks and background. The peaks are modelled with Gaussian or Lorentz-type functions and the background with cubic B-splines. The Bayesian model allows us to define a posterior probability in the parameter space upon which all subsequent Bayesian inference is based. Direct evaluation of this distribution or its derived features such as the conditional expectation is, unfortunately, not possible on account of the need to evaluate high-dimension integrals. As such we resort to a stochastic numerical Bayesian technique, the reversible-jump Markov-chain Monte-Carlo method. We have carried out simulations on both artificial and real data. Our results on the 1995 IAEA ?-ray test spectra shows that our program performs better than those previously reported.

Gulam Razul, S.; Fitzgerald, W. J.; Andrieu, C.

2003-02-01

296

Peak flux density spectra of large solar radio bursts and proton emission from flares  

NASA Astrophysics Data System (ADS)

Castelli et al. (1967) proposed that the 'U-shaped' peak flux density radio spectrum with high flux densities at meter and centimeter wavelengths and a minimum in the decimeter range is the 'preferred spectrum' for major solar proton flares. Evidence was presented indicating that the U-shaped spectrum was a necessary or almost necessary condition for a solar flare to produce a polar cap absorption (PCA) event. The present study is concerned with a classification of the peak flux density spectra of all large radio bursts observed from 1965-1979, taking into account also a comparison of the associations of bursts of different spectral classes with interplanetary proton events and type II/IV bursts. In addition an examination is conducted of the nature of the low-frequency branch of the U-shaped spectrum. A search is performed regarding the necessary conditions in the radio domain for the occurrence of a significant proton event.

Cliver, E. W.; McNamara, L. F.; Gentile, L. C.

1985-07-01

297

Anomaly in the P- and R- Branches in the Spectra of Hydrogen Fulcher Band Emission  

NASA Astrophysics Data System (ADS)

Anomalies in the Fulcher-band (d3?u-a3?+g) spectra, which are widely used for the purpose of measuring ro-vibronic structure of the hydrogen molecule, are investigated using the hollow cathode glow discharge of 230V - 70 mA at 30 Pa. By making use of the recently developed analyzing scheme and experimentally determined lifetime of the state involved, the historical data in the Ginsburg and Dieke's publication are reanalyzed and compared with our present data. Populations of the vibronic state (v'?4 in the Q branch can be corrected to a considerable extent by taking into account the lifetime of the states, while those of any v' the P and R branches cannot. However, the average values of the upper-Fulcher populations deduced from the P and R branches coincide with those from Q branch by taking into consideration the difference in the excitation from the ground electronic state.

Kado, Shinichiro; Yamasaki, Daisuke; Iida, Yohei; Xiao, Bingjia

298

Characterization of potentially habitable planets: Retrieval of atmospheric and planetary properties from emission spectra  

NASA Astrophysics Data System (ADS)

Context. An increasing number of potentially habitable terrestrial planets and planet candidates are found by ongoing planet search programs. The search for atmospheric signatures to establish planetary habitability and the presence of life might be possible in the future. Aims: We want to quantify the accuracy of retrieved atmospheric parameters (composition, temperature, pressure) that might be obtained from infrared emission spectroscopy. Methods: We use synthetic observations of the atmospheres of hypothetical potentially habitable planets. These were constructed with a parametrized atmosphere model, a high-resolution radiative transfer model and a simplified noise model. The simulated observations were used to fit the model parameters. Furthermore, classic statistical tools such as ?2 statistics and least-square fits were used to analyze the simulated observations. Results: When adopting the design of currently planned or proposed exoplanet characterization missions, we find that emission spectroscopy could provide weak limits on the surface conditions of terrestrial planets, hence their potential habitability. However, these mission designs are unlikely to allow the composition of the atmosphere of a habitable planet to be characterized, even though CO2 is detected. Upon increasing the signal-to-noise ratios by about a factor of 2-5 (depending on spectral resolution) compared to current mission designs, the CO2 content could be characterized to within two orders of magnitude. The detection of the O3 biosignature remains marginal. The atmospheric temperature structure could not be constrained. Therefore, a full atmospheric characterization seems to be beyond the capabilities of such missions when using only emission spectroscopy during secondary eclipse or target visits. Other methods such as transmission spectroscopy or orbital photometry are probably needed in order to give additional constraints and break degeneracies.

von Paris, P.; Hedelt, P.; Selsis, F.; Schreier, F.; Trautmann, T.

2013-03-01

299

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

300

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 AngloAustralian 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.

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

301

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

PubMed

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 A)/I(4163.3 A) as a function of electron density (N(e)). This ratio is found to be very sensitive to changes in N(e) over the density range 10(3) to 10(6) cm(-3), but does not vary significantly with electron temperature, and hence in principle should provide an excellent optical N(e) 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 A line in this object is badly blended with Fe ii 4122.6 A. 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

2002-04-01

302

Fluorescence excitation-emission matrix spectra coupled with parallel factor and regional integration analysis to characterize organic matter humification.  

PubMed

The present several humification indexes cannot provide the whole fluorescence information on organic matter composition and the evaluation results from them are inconsistent sometimes. In this study, fluorescence excitation-emission matrix spectra coupled with parallel factor analysis and fluorescence regional integration analysis were utilized to investigate organic matter humification, and the projection pursuit cluster (PPC) model was applied to form a suitable index for overcoming the difficulties in multi-index evaluation. The result showed that the ratio between the volume of humic- and fulvic-like fluorescence region and the volume of protein-like fluorescence region not only revealed the heterogeneity of organic matter, but also provided more accurate information on organic matter humification. In addition, the results showed that the PPC model could be used to characterize integrally the humification, and the projected characteristic value calculated from the PPC model could be used as the integrated humification evaluation index. PMID:23706894

He, Xiao-Song; Xi, Bei-Dou; Li, Xiang; Pan, Hong-Wei; An, Da; Bai, Shuo-Guo; Li, Dan; Cui, Dong-Yu

2013-11-01

303

Theoretical emission line ratios for [Fe III] and [Fe VII] applicable to the optical and infrared spectra of gaseous nebulae  

PubMed Central

Recent calculations of electron impact excitation rates and Einstein A-coefficients for transitions among the 3d6 levels of Fe III and among the 3d2 levels of Fe VII are used to derive theoretical emission line ratios applicable to the optical and infrared spectra of gaseous nebulae. Results for [Fe III] are generated for electron temperatures Te = 7,00020,000 K and densities Ne = 102-108 cm?3, whereas those for [Fe VII] are provided for Te = 10,00030,000 K and Ne = 102-108 cm?3. The theoretical line ratios are significantly different in some instances from earlier calculations and resolve discrepancies between theory and observation found for the planetary nebulae IC 4997 and NGC 7027.

Keenan, Francis P.; Aller, Lawrence H.; Ryans, Robert S. I.; Hyung, Siek

2001-01-01

304

Theoretical emission line ratios for [Fe III] and [Fe VII] applicable to the optical and infrared spectra of gaseous nebulae.  

PubMed

Recent calculations of electron impact excitation rates and Einstein A-coefficients for transitions among the 3d(6) levels of Fe III and among the 3d(2) levels of Fe VII are used to derive theoretical emission line ratios applicable to the optical and infrared spectra of gaseous nebulae. Results for [Fe III] are generated for electron temperatures T(e) = 7,000-20,000 K and densities N(e) = 10(2)-10(8) cm(-3), whereas those for [Fe VII] are provided for T(e) = 10,000-30,000 K and N(e) = 10(2)-10(8) cm(-3). The theoretical line ratios are significantly different in some instances from earlier calculations and resolve discrepancies between theory and observation found for the planetary nebulae IC 4997 and NGC 7027. PMID:11493676

Keenan, F P; Aller, L H; Ryans, R S; Hyung, S

2001-08-14

305

Fourier Transform Emission Spectra of the (000)-(000) Band of the ?4051.6 Band of C3  

NASA Astrophysics Data System (ADS)

The (000)-(000) band of the 4051.6 group (A1?u-X1?+g) of C3 was recorded in emission with a Bruker IFS 120HR Fourier transform (FT) spectrometer at the University of Waterloo. The band was excited by a microwave discharge in isopropanol (less than a few mtorr) diluted in helium (2 torr). Our new FT data provide more reliable and accurately calibrated transition wavenumbers than those from the grating spectra given by Gausset and coworkers. Analysis of our new spectrum combined with the data by McCall and coworkers confirmed that the lower J levels in the A state were strongly perturbed, as reported by Gausset and coworkers. The unidentified lines observed by McCall and coworkers could be attributed to extra transitions to an unknown perturbing state.

Tanabashi, A.; Hirao, T.; Amano, T.; Bernath, P. F.

2005-05-01

306

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

307

Using violet laser-induced chlorophyll fluorescence emission spectra for crop yield assessment of cowpea (Vigna unguiculata (L) Walp) varieties  

NASA Astrophysics Data System (ADS)

The use of violet laser-induced chlorophyll fluorescence (LICF) emission spectra to monitor the growth of five varieties of cowpea in the University of Cape Coast Botanical Garden is presented. Radiation from a continuous-wave violet laser diode emitting at 396 nm through a fibre is closely incident on in vivo leaves of cowpea to excite chlorophyll fluorescence, which is detected by an integrated spectrometer with CCD readout. The chlorophyll fluorescence spectra with peaks at 683 and 731 nm were used for growth monitoring of the cowpea plants over three weeks and analysed using Gaussian spectral functions with curve fitted parameters to determine the peak positions, area under the spectral curve and the intensity ratio F683/F731. The variation in the intensity ratio of the chlorophyll bands showed sensitive changes indicating the photosynthetic activity of the cowpea varieties. A discussion of the fluorescence result as compared to conventional assessment is presented with regard to discrimination between the cowpea varieties in terms of crop yield performance.

Anderson, Benjamin; Buah-Bassuah, Paul K.; Tetteh, Jonathan P.

2004-07-01

308

Interpretation of the Emission Spectra of Trivalent Chromium-Doped Garnet Crystals Using Tanabe-Sugano Diagrams  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to provide an example of a real-world application in which Tanabe-Sugano diagrams can be used to relate the optical properties and performance of a material to its physical and chemical properties. Tanabe-Sugano diagrams illustrate the effect of the strength of the octahedral ligand field on the relative positions of the various energy level components that arise as a result of the splitting of the degenerate free-ion states. The application of these diagrams can also be extended to the spectra of transition metal ions found in solid state matrices where the predominant external force is the crystal field. In insulating materials, transition metal ions occupy sites with six anions as nearest-neighbors, forming a coordination sphere characterized as a distorted octahedron. Although the actual site symmetry is lower than Oh in most cases, an octahedral approximation is qualitatively sufficient for the present application involving an analysis and interpretation of the emission spectra of chromium-doped garnets.

Seltzer, Michael D.

1995-10-01

309

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

PubMed

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 PM(10) 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 PM(10) 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 PM(10) are classified into seven classes by hierarchical cluster analysis based on the element peak intensity in the spectra. PMID:16808872

Yue, Weisheng; Li, Xiaolin; Wan, Tianmin; Liu, Jiangfeng; Zhang, Guilin; Li, Yan

2006-06-01

310

BROADBAND X-RAY SPECTRA OF TWO LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI NGC 1566 AND NGC 4941 OBSERVED WITH SUZAKU  

SciTech Connect

We report the first broadband X-ray spectra of the low-luminosity active galactic nuclei (LLAGNs), NGC 1566 (type 1.5) and NGC 4941 (type 2), observed with Suzaku and Swift/BAT covering the 0.5-195 keV band. Both targets have hard X-ray luminosities of {approx}10{sup 41-42} erg s{sup -1} in the 15-55 keV band. The spectra of the nucleus are well reproduced by a sum of partially or fully covered transmitted emission and its reflection from the accretion disk, reprocessed emission from the torus accompanied by a strong narrow iron-K{alpha} line, and a scattered component (for NGC 4941). We do not significantly detect a broad iron-K{alpha} line from the inner accretion disk in both targets, and obtain an upper limit on the corresponding solid angle of {Omega}/2{pi} < 0.3 in NGC 1566. The reflection strength from the torus is moderate, {Omega}/2{pi}=0.45{sup +0.13}{sub -0.10} in NGC 1566 and {Omega}/2{pi}=0.64{sup +0.69}{sub -0.27} in NGC 4941. Comparison of the equivalent width of the narrow iron-K{alpha} line with a model prediction based on a simple torus geometry constrains its half-opening angle to be {theta}{sub oa} {approx_equal} 60 Degree-Sign -70 Degree-Sign in NGC 4941. These results agree with the obscured AGN fraction obtained from hard X-ray and mid-infrared selected samples at similar luminosities. Our results support the implication that the averaged covering fraction of AGN tori is peaked at L {approx} 10{sup 42-43} erg s{sup -1} but decreases toward lower luminosities.

Kawamuro, Taiki; Ueda, Yoshihiro; Tazaki, Fumie [Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan); Terashima, Yuichi [Department of Physics, Ehime University, Matsuyama 790-8577 (Japan)

2013-06-20

311

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

312

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

313

Frequency Doubling of Interference Structures in Electron Emission Spectra of H2 from Heavy Ion Impact  

NASA Astrophysics Data System (ADS)

The ionization of molecules with identical atomic centers gives rise to interference effects due to coherent electron emission from the identical centers. In measurements conducted at GANIL for 68 MeV/u Kr^33+ ions, electron interference structures have been observed with an oscillation frequency that depends on the electron observation angle. Detailed analysis indicates that the primary interference structures exhibit secondary oscillations, with slightly more than twice the frequency of the main oscillations, superimposed on the main oscillatory structure. A formulation based on wave optics indicates that the frequency doubling is a second-order effect, in which the electron wave emitted at one center interferes with the wave backscattered at the other center. *Supported by U.S. DOE, NSF, PROCOPE, OTKA, and the German-Hungarian S Collab.

Tanis, J. A.; Hossain, S.; Sulik, B.; Chesnel, J.-Y.; Fremont, F.; Hennecart, D.; Cassimi, A.; Adoui, L.; Skogvall, B.; Stolterfoht, N.

2004-05-01

314

Optical emission spectra of a copper plasma produced by a metal vapour vacuum arc plasma source  

NASA Astrophysics Data System (ADS)

Optical emission spectroscopy in the range 200-800 nm was applied for investigation of the copper plasma produced by a metal vapour vacuum arc plasma source. The experiments were conducted for the cases when the plasma was guided by straight and ?-shaped curved solenoids as well as without solenoids, and also for different vacuum conditions. It was found that, besides singly- and doubly-charged ions, a relatively high concentration of excited neutral copper atoms was present in the plasma. The relative fraction of excited atoms was much higher in the region close to the cathode surface than in the plasma column inside the solenoid. The concentration of excited neutral, singly- and doubly-ionized atoms increased proportionally when the arc current was increased to 400 A. Some weak lines were attributed to more highly ionized copper species and impurities in the cathode material.

Yotsombat, B.; Davydov, S.; Poolcharuansin, P.; Vilaithong, T.; Brown, I. G.

2001-06-01

315

Stratospheric minor constituent distributions from far-infrared thermal emission spectra  

NASA Technical Reports Server (NTRS)

We retrieve mixing ratio profiles of O3, H2(O-16), H2(O-17), H2(O-18), HF, and HCl from far-infrared thermal emission observations of the limb in the 80-220 cm/sec spectral region. The observations were made with a balloon-borne Fourier transform spectrometer as a part of the 1983 Balloon Intercomparison Campaign (BIC-2). A subset of the data was analyzed previously using the method in the work of Traub et al. (1982, 1991); in the present paper we use an alternative method of calibration and analysis, given by Abbas et al. (1985). The retrieved constituent profiles are compared with the measurements made with other instruments on the BIC-2 flights. The results for the concentrations of H2(O-17) and H2(O-18) obtained in this study indicate no isotopic enhancement or depletion with a standard deviation of about 20 percent.

Abbas, Mian M.; Traub, Wesley A.

1992-01-01

316

Seasonal variations of Saturn's auroral acceleration region deduced from spectra of auroral radio emissions  

NASA Astrophysics Data System (ADS)

Multi-instrumental surveys of Saturn's magnetosphere by Cassini have indicated that auroral radio emissions (Saturnian Kilometric Radiation, SKR), aurorae at UV and IR wavelengths and Energetic Neutral Atoms (ENA) from the inner magnetosphere exhibit periodic behavior at around Saturn's rotational period with the north-south asymmetry and seasonal variations [e.g., Gurnett et al., 2010; Mitchell et al., 2009; Nichols et al., 2010]. These rotationally periodic phenomena are suggestive of distinct magnetosphere-ionosphere coupling current systems, rotating at different periods in the northern and southern hemispheres [e.g., Andrews et al., 2010]. These phenomena suggest that the magnetosphere-ionosphere coupling process and associated energy dissipation process (aurora & SKR) are dynamically dependent on both magnetospheric rotations and long-term conditions of the magnetosphere/ionosphere.

Kimura, T.; Lamy, L.; Tao, C.; Badman, S. V.; Cecconi, B.; Zarka, P.; Morioka, A.; Miyoshi, Y.; Kasaba, Y.; Maruno, D.; Fujimoto, M.

2012-09-01

317

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

318

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; Mizeret, Jerome; Braichotte, Daniel; Wagnieres, Georges; van den Bergh, Hubert; Jichlinski, Patrice; Leisinger, Hans J.

1995-01-01

319

Spontaneous emission spectra and quantum light-matter interactions from a strongly coupled quantum dot metal-nanoparticle system  

NASA Astrophysics Data System (ADS)

We investigate the quantum optical properties of a quantum-dot dipole emitter coupled to a finite-size metal nanoparticle using a photon Green-function technique that rigorously quantizes the electromagnetic fields. We first obtain pronounced Purcell factors and photonic Lamb shifts for both a 7- and 20-nm-radius metal nanoparticle, without adopting a dipole approximation. We then consider a quantum-dot photon emitter positioned sufficiently near the metal nanoparticle so that the strong-coupling regime is possible. Accounting for nondipole interactions, quenching, and photon transport from the dot to the detector, we demonstrate that the strong-coupling regime should be observable in the far-field spontaneous emission spectrum, even at room temperature. The vacuum-induced emission spectra show that the usual vacuum Rabi doublet becomes a rich spectral triplet or quartet with two of the four peaks anticrossing, which survives in spite of significant nonradiative decays. We discuss the emitted light spectrum and the effects of quenching for two different dipole polarizations.

van Vlack, C.; Kristensen, Philip Trst; Hughes, S.

2012-02-01

320

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

321

Continuous electron spectra from 150keV\\/u C++He, Ne, Ar collisions at electron emission angles from 0 deg to 180 deg  

Microsoft Academic Search

Electron spectra in the 20-550eV energy range and in the full angular range of 0-180 deg were measured by the impact of 150keV\\/u C+ ions on He, Ne and Ar atoms. Double differential cross sections for electron emission have been determined. We observed an unexpected, broad structure around 300eV electron energy at backward emission angles relative to the beam direction.

B. Sulik; Cs. Koncz; K. Tkesi; . Kvr; S. Ricz; Gy. Vkor; J.-Y. Chesnel; N. Stolterfoht; D. Bernyi

1999-01-01

322

Advances in High-Resolution Studies of the Chemical Effects in the Molybdenum L Heavy-Ion-Induced X-Ray Satellite Emission (HIXSE) Spectra.  

National Technical Information Service (NTIS)

High-resolution measurements of the molybdenum L heavy-ion-induced x-ray satellite emission (HIXSE) spectra of a series of Mo alloys and compounds have been obtained with a new, high-efficiency, high-resolution Bragg crystal spectrometer in the von Hamos ...

T. M. Rosseel J. M. Dale L. D. Hulett P. L. Pepmiller C. R. Vane

1986-01-01

323

Near-surface thermal gradients and mid-IR emission spectra: A new model including scattering and application to real data  

Microsoft Academic Search

We model the radiative and conductive heat transfer in the top few millimeters of a particulate medium in order to investigate near-surface thermal gradients and their effects on mid-IR emission spectra for different planetary environments. The model extends our previous work by including scattering in the radiative heat transfer. Our results show that significant thermal gradients will form in the

Bradley G. Henderson; Bruce M. Jakosky

1997-01-01

324

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

325

Fluorine K? X-Ray Emission Spectra of MgF2, CaF2, SrF2 and BaF2  

NASA Astrophysics Data System (ADS)

The fluorine K? emission spectra in fluorescence from a series of alkaline-earth fluorides MF2 (M=Mg, Ca, Sr and Ba) are measured with a high-resolution two-crystal vacuum spectrometer. An anomalously low intensity of the K1L1 satellite peak arising from 1s-1(2s2p)-1 initial states is observed for SrF2. The measured emission spectra are presented along with the UPS spectra of the F- 2p valence bands obtained by Poole et al. and the fluorine K absorption-edge spectra by Oizumi et al. By using these spectra, the first peak or shoulder in the fluorine K absorption-edge spectra is identified as being due to a core exciton which is formed below the bottom of the conduction band. The binding energy of the exciton is estimated to be 1.3( 0.3), 1.1( 0.2), 1.0( 0.2) and 1.7( 0.2) eV for MgF2, CaF2, SrF2 and BaF2, respectively.

Sugiura, Chikara; Konishi, Wataru; Shoji, Shizuko; Kojima, Shinjiro

1990-11-01

326

X-ray emission spectra of the plasma produced by an ultrashort laser pulse in cluster targets  

SciTech Connect

The first observation of x-ray emission spectra of multiply charged ions in the plasma produced by a 35-fs laser pulse with an intensity up to 10{sup 17} W cm{sup -2} in CO{sub 2} and Kr gas jet targets is reported. The emission in the wavelength ranges of the 1snp-1s{sup 2}(n=3-6) transitions of O VII ions and the Ly{sub {alpha}} line of O VIII ions, as well as of the (2s{sub 1/2}2p{sup 6}3p{sub 3/2}){sub 1}-2s{sup 2}2p{sup 6} {sup 1}S{sub 0} and (2s{sub 1/2}2p{sup 6}3p{sub 1/2}){sub 1}-2s{sup 2}2p{sup 6} {sup 1}S{sub 0} lines of Ne-like KrXXVII ions testifies that the highly ionised plasma is formed by collision processes in clusters. Modelling the shape of the spectral lines of oxygen ions by including the principal mechanisms of broadening and absorption in optically dense plasmas reveals that the main contribution to the time-integrated intensity is made by the plasma with the parameters N{sub e}=(2-20)x10{sup 20} cm{sup -3} and T{sub e}=100 - 115 eV. (interaction of laser radiation with matter. laser plasma)

Stenz, C; Bagnoud, V; Blasco, F; Roche, J R; Salin, F [Centre Laser Intenses et Applications, Universite Bordeaux, Talence (France); Faenov, A Ya; Skobelev, I Yu [Multicharged Ion Spectra Data Center, All-Russia Research Institute of Psysicotechnical and Radio Enginering Measurments, Mendeleevo, Moscow Region (Russian Federation); Magunov, A I [A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Pikuz, T A [N.E. Bauman Moscow State Technical University, Moscow (Russian Federation)

2000-08-31

327

Ultraviolet Emission-line Correlations in HST/COS Spectra of Active Galactic Nuclei: Single-epoch Black Hole Masses  

NASA Astrophysics Data System (ADS)

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 ?1549, O VI ?1035, O III] ?1664, He II ?1640, C II ?1335, and Mg II ?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 1450 <= 1045 erg s-1, the UV line luminosities correlate well with H?, as does the 1450 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. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Tilton, Evan M.; Shull, J. Michael

2013-09-01

328

Experimental and PCM/TD-DFT investigation on the absorption and emission spectra of a light emitting material in various solvents  

NASA Astrophysics Data System (ADS)

The ground (S 0) and lowest singlet excited state (S 1) as well as the absorption and emission properties of a donor- ?-acceptor structure molecule, 3-(dicyanomethylene)-5,5-dimethyl-1(4-[(2-hydroxy-ethyl)-methyl-amino]-styryl)cyclohexene (DCDHC), are investigated. The experimental emission spectra in four solvents of different polarity are obtained. The optimization of the geometries for S 0 and S 1 states are computed by density functional theory (DFT) and time-dependent (TD) DFT. The absorption and emission spectra in solvents are calculated at the TDDFT methods in combination with the polarized continuum model. The performance of ten exchange-correlation functionals is discussed and it turns out that, within the selected TDDFT framework, M06 and PBE0 emerge as the most efficient hybrids for DCDHC molecule.

Liu, Xiaojun; Yang, Dan; Ju, Haidong; Teng, Feng; Hou, Yanbing; Lou, Zhidong

2011-02-01

329

[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

330

Redshifts of high-temperature emission lines in the far-ultraviolet spectra of late-type stars  

NASA Technical Reports Server (NTRS)

High-dispersion IUE spectra of six late-type stars exhibit small but statistically significant differential redshifts of high-temperature emission lines, like Si IV and C IV, with respect to low-temperature lines like S I and O I. A well-exposed, small-aperture spectrum of the active chromosphere binary Capella (Alpha Aurigae A: G6 II+F9 III) establishes that the high-temperature lines are redshifted in an absolute sense with respect to the accurately determined photospheric velocity of the system at single-line phase 0.50. Several possible explanations for the stellar redshifts are discused, including a warm wind (100,000 K) in which aparent redshifts are produced in optically thick lines by an accelerating outfow, and the downflowing component of a vertical circulation system for which the up-leg portion of the flow is too cool, too hot, or too tenuous to be visible in Si IV and C IV. If the second scenario is true, the stellar redshifts may provide an important phenomenological link to the downflows observed in 100,000 K species over magnetic active regions in the sun.

Ayres, T. R.; Stencel, R. E.; Linsky, J. L.; Simon, T.; Jordan, C.; Brown, A.; Engvold, O.

1983-01-01

331

Absolute, time-resolved emission of non-LTE L-shell spectra from Ti-doped aerogels  

NASA Astrophysics Data System (ADS)

Outstanding discrepancies between data and calculations of laser-produced plasmas in recombination have been observed since the 1980s. Although improvements in hydrodynamic modeling may reduce the discrepancies, there are indications that non-LTE atomic kinetics may be the dominant cause. Experiments to investigate non-LTE effects were recently performed at the NIKE KrF laser on low-density Ti-doped aerogels. The laser irradiated a 2 mm diameter, cylindrical sample of various lengths with a 4-ns square pulse to create a volumetrically heated plasma. Ti L-shell spectra spanning a range of 0.47 3 keV were obtained with a transmission grating coupled to Si photodiodes. The diagnostic can be configured to provide 1-dimensional spatial resolution at a single photon energy, or 18 discrete energies with a resolving power, ?/?? of 3 20. The data are examined and compared to calculations to develop absolute emission measurements that can provide new tests of the non-LTE physics.

Back, C. A.; Feldman, U.; Weaver, J. L.; Seely, J. F.; Constantin, C.; Holland, G.; Lee, R. W.; Chung, H.-K.; Scott, H. A.

2006-05-01

332

Absolute Time-Resolved Emission of Non-LTE L-Shell Spectra from Ti-Doped Aerogels  

SciTech Connect

Outstanding discrepancies between data and calculations of laser-produced plasmas in recombination have been observed since the 1980s. Although improvements in hydrodynamic modeling may reduce the discrepancies, there are indications that non-LTE atomic kinetics may be the dominant cause. Experiments to investigate non-LTE effects were recently performed at the NIKE KrF laser on low-density Ti-doped aerogels. The laser irradiated a 2 mm diameter, cylindrical sample of various lengths with a 4-ns square pulse to create a volumetrically heated plasma. Ti L-shell spectra spanning a range of 0.47-3 keV were obtained with a transmission grating coupled to Si photodiodes. The diagnostic can be configured to provide 1-dimensional spatial resolution at a single photon energy, or 18 discrete energies with a resolving power, {gamma}/{delta}{gamma} of 3-20. The data are examined and compared to calculations to develop absolute emission measurements that can provide new tests of the non-LTE physics.

Back,C.; Feldman, U.; Weaver, J.; Seely, J.; Constantin, C.; Holland, G.; Lee, R.; Chung, H.; Scott, H.

2006-01-01

333

Complex organic matter in space: about the chemical composition of carriers of the Unidentified Infrared Bands (UIBs) and protoplanetary emission spectra recorded from certain astrophysical objects.  

PubMed

In this communication we present the basic concept that the pure PAHs (Polycyclic Aromatic Hydrocarbons) can be considered only the ideal carriers of the UIBs (Unidentified Infrared Bands), the emission spectra coming from a large variety of astronomical objects. Instead we have proposed that the carriers of UIBs and of protoplanetary nebulae (PPNe) emission spectra are much more complex molecular mixtures possessing also complex chemical structures comparable to certain petroleum fractions obtained from the petroleum refining processes. The demonstration of our proposal is based on the comparison between the emission spectra recorded from the protoplanetary nebulae (PPNe) IRAS 22272+ 5435 and the infrared absorption spectra of certain 'heavy' petroleum fractions. It is shown that the best match with the reference spectrum is achieved by highly aromatic petroleum fractions. It is shown that the selected petroleum fractions used in the present study are able to match the band pattern of anthracite coal. Coal has been proposed previously as a model for the PPNe and UIBs but presents some drawbacks which could be overcome by adopting the petroleum fractions as model for PPNe and UIBs in place of coal. A brief discussion on the formation of the petroleum-like fractions in PPNe objects is included. PMID:14979641

Cataldo, Franco; Keheyan, Yeghis; Heymann, Dieter

2004-02-01

334

State-of-the art comparability of corrected emission spectra. 2. Field laboratory assessment of calibration performance using spectral fluorescence standards.  

PubMed

In the second part of this two-part series on the state-of-the-art comparability of corrected emission spectra, we have extended this assessment to the broader community of fluorescence spectroscopists by involving 12 field laboratories that were randomly selected on the basis of their fluorescence measuring equipment. These laboratories performed a reference material (RM)-based fluorometer calibration with commercially available spectral fluorescence standards following a standard operating procedure that involved routine measurement conditions and the data evaluation software LINKCORR developed and provided by the Federal Institute for Materials Research and Testing (BAM). This instrument-specific emission correction curve was subsequently used for the determination of the corrected emission spectra of three test dyes, X, QS, and Y, revealing an average accuracy of 6.8% for the corrected emission spectra. This compares well with the relative standard uncertainties of 4.2% for physical standard-based spectral corrections demonstrated in the first part of this study (previous paper in this issue) involving an international group of four expert laboratories. The excellent comparability of the measurements of the field laboratories also demonstrates the effectiveness of RM-based correction procedures. PMID:22376144

Resch-Genger, Ute; Bremser, Wolfram; Pfeifer, Dietmar; Spieles, Monika; Hoffmann, Angelika; DeRose, Paul C; Zwinkels, Joanne C; Gauthier, Franois; Ebert, Bernd; Taubert, R Dieter; Voigt, Jan; Hollandt, Jrg; Macdonald, Rainer

2012-05-01

335

Correcting for variable laser-target distances of laser-induced breakdown spectroscopy measurements with ChemCam using emission lines of Martian dust spectra  

NASA Astrophysics Data System (ADS)

As part of the Mars Science Laboratory, the ChemCam instrument acquires remote laser induced breakdown spectra at distances that vary between 1.56 m and 7 m. This variation in distance affects the intensities of the measured LIBS emission lines in non-trivial ways. To determine the behavior of a LIBS emission line with distance, it is necessary to separate the effects of many parameters such as laser energy, laser spot size, target homogeneity, and optical collection efficiency. These parameters may be controlled in a laboratory on Earth but for field applications or in space this is a challenge. In this paper, we show that carefully selected ChemCam LIBS emission lines acquired from the Martian dust can be used to build an internal proxy spectroscopic standard. This in turn, allows for a direct measurement of the effects of the distance of various LIBS emission lines and hence can be used to correct ChemCam LIBS spectra for distance variations. When tested on pre-launch LIBS calibration data acquired under Martian-like conditions and with controlled and well-calibrated targets, this approach yields much improved agreement between targets observed at various distances. This work lays the foundation for future implementation of automated routines to correct ChemCam spectra for differences caused by variable distance.

Melikechi, N.; Mezzacappa, A.; Cousin, A.; Lanza, N. L.; Lasue, J.; Clegg, S. M.; Berger, G.; Wiens, R. C.; Maurice, S.; Tokar, R. L.; Bender, S.; Forni, O.; Breves, E. A.; Dyar, M. D.; Frydenvang, J.; Delapp, D.; Gasnault, O.; Newsom, H.; Ollila, A. M.; Lewin, E.; Clark, B. C.; Ehlmann, B. L.; Blaney, D.; Fabre, C.

2014-06-01

336

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

337

Updated summary of measurements and calculations of neutron and gamma-ray emission spectra from spheres pusled with 14-MeV neutrons: Revision 1  

SciTech Connect

New measurements of the neutron and gamma-ray emission spectra from materials of interest to thermonuclear reactors with a 14 MeV neutron source were done during 1986 and 1987. These measurements characterized by better resolution than those reported in the Summary published in 1982, were performed using the pulsed sphere and time-of-flight techniques. The detector used in these measurements was a NE-213 cylinder, 5.08 cm in diameter by 5.08 cm thick. The new measurements include the following materials: Be, C, N, H/sub 2/O, C/sub 2/F/sub 4/ (teflon), Al, Si, Ti, Fe, Cu, Ta, W, Au, Pb, /sup 232/Th, and /sup 238/U. For all these materials, both the neutron and gamma emission spectra were measured. A complete tabulation of all the measurements done under the Pulse Sphere Program is presented. 37 refs., 1 tab.

Hansen, L.F.; Goldberg, E.; Howerton, R.J.; Komoto, T.T.; Pohl, B.A.

1989-01-19

338

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

339

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: Percolation and emission spectra of a laser plasma upon ablation of silicon and silicon-containing composites  

NASA Astrophysics Data System (ADS)

The emission spectra of plasmas produced near the surface of silicon and sulphur samples and their mixtures by nanosecond and millisecond laser pulses are studied in a broad range of pressures of buffer gases. The percolation dependences are obtained for composite SiS, SiSiO2, and SiO2S targets. It is found that experimental percolation thresholds coincide with the typical threshold for three-dimensional continual percolation.

Kask, Nikolai E.; Michurin, Sergei V.; Fedorov, Gennadii M.

2006-05-01

340

The relation between AGN hard X-ray emission and mid-infrared continuum from ISO spectra: Scatter and unification aspects  

Microsoft Academic Search

We use mid-infrared spectral decomposition to separate the 6 mum mid-infrared AGN continuum from the host emission in the ISO low resolution spectra of 71 active galaxies and compare the results to observed and intrinsic 2-10 keV hard X-ray fluxes from the literature. We find a correlation between mid-infrared luminosity and absorption corrected hard X-ray luminosity, but the scatter is

D. Lutz; R. Maiolino; H. W. W. Spoon; A. F. M. Moorwood

2004-01-01

341

Detection of organic compound signatures in infra-red, limb emission spectra observed by the MIPAS-B2 balloon 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 on a flight on 8 May 1998 near Aire sur l'Adour by a balloon-borne instrument, MIPAS-B2, operating at high spectral resolution. It is demonstrated,

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

2007-01-01

342

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra  

NASA Astrophysics Data System (ADS)

We examine volume mixing ratios (vmr) retrieved from limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). In level 2 (L2) data products of three different retrieval processors, which perform one dimensional (1-D) retrievals, we find significant differences between species' profiles from ascending and descending orbit parts. The relative differences vary systematically with time of the year, latitude, and altitude. In the lower stratosphere their monthly means can reach maxima of 20% for CFC-11, CFC-12, HNO3, H2O, 10% for CH4 and N2O. Relative differences between monthly means of 1-D retrieval results and of the true atmospheric state can be expected to reach half of these percentage values, while relative differences in single vmr profiles might well exceed those numbers. Often there are no physical or chemical reasons for these differences, so they are an indicator for a problem in the data processing. The differences are generally largest at locations where the meridional temperature gradient of the atmosphere is strong. On the contrary, when performing the retrieval with a tomographic two dimensional (2-D) retrieval, L2 products generally do not show these differences. This implies that inhomogeneities in the temperature field, and possibly in the species' fields, which are accounted for in the 2-D algorithm and not in standard 1-D processors, may cause significant deviations in the results. Inclusion of an externally given adequate temperature gradient in the forward model of a 1-D processor helps to reduce the observed differences. However, only the full tomographic approach is suitable to resolve the horizontal inhomogeneities. Implications for the use of the 1-D data, e.g. for validation, are discussed. The dependence of the ascending/descending differences on the observation strategy suggests that this problem is to be expected to affect in general 1-D retrievals of infrared limb sounders, if the line of sight of the instrument has a significant component in the direction of the horizontal temperature variation.

Kiefer, M.; Arnone, E.; Dudhia, A.; Carlotti, M.; Castelli, E.; von Clarmann, T.; Dinelli, B. M.; Kleinert, A.; Linden, A.; Milz, M.; Papandrea, E.; Stiller, G.

2010-04-01

343

Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra  

NASA Astrophysics Data System (ADS)

We examine volume mixing ratios (vmr) retrieved from limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board Envisat. In level 2 (L2) data products of three different retrieval processors, which perform one dimensional (1-D) retrievals, we find significant differences between species' profiles from ascending and descending orbit parts. The relative differences vary systematically with time of the year, latitude, and altitude. In the lower stratosphere their monthly means can reach maxima of 20% for CFC-11, CFC-12, HNO3, H2O, 10% for CH4 and N2O. Relative differences between monthly means of 1-D retrieval results and of the true atmospheric state can be expected to reach half of these percentage values, while relative differences in single vmr profiles might well exceed those numbers. Often there are no physical or chemical reasons for these differences, so they are an indicator for a problem in the data processing. The differences are generally largest at locations where the meridional temperature gradient of the atmosphere is strong. On the contrary, when performing the retrieval with a tomographic two dimensional (2-D) retrieval, L2 products generally do not show these differences. This suggests that inhomogeneities in the temperature field, and possibly in the species' fields, which are accounted for in the 2-D algorithm and not in standard 1-D processors, may cause significant deviations in the results. Inclusion of an externally given adequate temperature gradient in the forward model of a 1-D processor helps to reduce the observed differences. However, only the full tomographic 2-D approach is suitable to resolve the horizontal inhomogeneities. Implications for the use of the 1-D data, e.g. for validation, are discussed. The dependence of the ascending/descending differences on the observation strategy suggests that this problem may affect 1-D retrievals of infrared limb sounders, if the line of sight of the instrument has a significant component in the direction of the horizontal temperature variation.

Kiefer, M.; Arnone, E.; Dudhia, A.; Carlotti, M.; Castelli, E.; von Clarmann, T.; Dinelli, B. M.; Kleinert, A.; Linden, A.; Milz, M.; Papandrea, E.; Stiller, G.

2010-10-01

344

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; Brdas, Jean-Luc

2008-12-01

345

Extracting ion emission lines from femtosecond-laser plasma x-ray spectra heavily contaminated by spikes  

NASA Astrophysics Data System (ADS)

Nowadays charged-coupled device (CCD) detectors are widely used for the registration of multicharged ions x-ray spectra. These spectra are generated in a plasma during interaction of ultrashort, ultraintense laser pulses with solid targets. Strong parasitic radiation from the plasma affects CCD detectors and contaminates resulting spectra, so that spectral features can be completely covered by noise even during measurements with a very short accumulation time. In this work we propose a ``mean to median'' (M2M) algorithm for noise suppression in femtosecond laser plasma x-ray spectra. Series of spectra is necessary for the identification of corrupted data points by the developed method. The algorithm was tested with model spectra which reflect main features of experimental data. In practice we used it for extracting information about spectral lines of Ne-like Fe ions and He-like Al ions which allowed us to calculate plasma parameters. It is demonstrated that M2M method is able to clean spectra with more than 10% of corrupted pixels. Fluctuations in intensity of spectral lines induced by laser instability do not affect validity of the proposed method.

Gasilov, S. V.; Faenov, A. Ya.; Pikuz, T. A.; Villoresi, P.; Poletto, L.; Stagira, S.; Calegari, F.; Vozzi, C.; Nisoli, M.

2007-09-01

346

Demonstration of x-ray Thomson scattering using picosecond K-{alpha} x-ray sources in the characterization of dense heated matter  

SciTech Connect

We present K-{alpha} x-ray Thomson scattering from shock compressed matter for use as a diagnostic in determining the temperature, density, and ionization state with picosecond resolution. The development of this source as a diagnostic as well as stringent requirements for successful K-{alpha} x-ray Thomson scattering are addressed. Here, the first elastic and inelastic scattering measurements on a medium size laser facility have been observed. We present scattering data from solid density carbon plasmas with >1x10{sup 5} photons in the elastic peak that validate the capability of single shot characterization of warm dense matter and the ability to use this scattering source at future free electron lasers and for fusion experiments at the National Ignition Facility (NIF), LLNL.

Kritcher, A. L. [L-399, Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States); Nuclear Engineering Department, University of California Berkeley, Berkeley, California 94709 (United States); Neumayer, P.; Doeppner, T.; Glenzer, S. H. [L-399, Lawrence Livermore National Laboratory, University of California, P.O. Box 808, Livermore, California 94551 (United States); Lee, H. J.; Falcone, R. W. [Physics Department, University of California Berkeley, Berkeley, California 94709 (United States); Morse, E. C. [Nuclear Engineering Department, University of California Berkeley, Berkeley, California 94709 (United States)

2008-10-15

347

Role of modifier oxide in emission spectra and kinetics of Er-Ho codoped Na 2SO 4-MO-P 2O 5 glasses  

NASA Astrophysics Data System (ADS)

The glasses of the composition 19Na 2SO 4-20MO-60P 2O 5: 1.0Ho 2O 3/1.0Er 2O 3 (M = Mg, Ca, and Ba) have been synthesized. Optical absorption and fluorescence spectra (in the spectral range 350-2100 nm were studied at ambient temperature. The spectra were characterized using Judd-Ofelt theory. From the luminescence spectra, various radiative properties like transition probability A, branching ratio ? and the radiative life time ? for blue (B), green (G) and red (R) emission levels of these glasses have been evaluated. The energy transfer between the two rare earth ions (Ho 3+ and Er 3+) in co-doped Na 2SO 4-MO-P 2O 5 glass systems in the visible and NIR regions has also been investigated. Highest intensity, the highest quantum efficiency and maximum energy transfer with low phonon losses of B, G, and R lines has been observed in BaO mixed glasses. The reasons for such higher values of these parameters have been discussed in the light of varying field strengths at the rare earths ion site due to replacement of one modifier oxide with the other. The enhanced intensity of NIR emission (at 2.0 ?m) has also been discussed in terms of cross relaxation of Er 3+ ions from 4I 13/2 level to 5I 7 of Ho 3+ ions.

Rao, P. Raghava; Venkatramaiah, N.; Gandhi, Y.; Kumar, V. Ravi; Kityk, I. V.; Veeraiah, N.

2012-02-01

348

The Broad Iron K-alpha line of Cygnus X-1 as Seen by XMM-Newton in the EPIC-pn Modified Timing Mode  

NASA Technical Reports Server (NTRS)

We present the analysis of the broadened, flourescent iron K(alpha) line in simultaneous XMM-Newton and RXTE data from the black hole Cygnus X-I. The XMM-Newton data were taken in a modified version of the Timing Mode of the EPIC-pn camera. In this mode the lower energy threshold of the instrument is increased to 2.8 keV to avoid telemetry drop outs due to the brightness of the source, while at the same time preserving the signal to noise ratio in the Fe K(alpha) band. We find that the best-fit spectrum consists of the sum of an exponentially cut-off power-law and relativistically smeared, ionized reflection. The shape of the broadened Fe K(alpha) feature is due to strong Compton broadening combined with relativistic broadening. Assuming a standard, thin accretion disk, the black hole is close to maximally rotating. Key words. X-rays: binaries - black hole physics - gravitation

Duro, Refiz; Dauser, Thomas; Wilms, Jorn; Pottschmidt, Katja; Nowak, Michael A.; Fritz, Sonja; Kendziorra, Eckhard; Kirsch, Marcus G. F.; Reynolds, Christopher S.; Staubert, Rudiger

2011-01-01

349

Implications of heavy-ion-induced satellite x-ray emission. III. Chemical effects in high resolution sulfur K/sub. cap alpha. / x-ray spectra  

SciTech Connect

High resolution (approx. 7 eV at 2.3 keV) sulfur K/sub ..cap alpha../ x-ray spectra have been obtained for a series of sulfur compound targets under heavy ion impact at the Holified Heavy Ion Facility. The spectra observed are dominated by a series of satellite peaks arising from varying degrees of L-shell ionization at the time of x-ray emission. Each spectral profile has been parameterized by a single variable p/sub L/, the apparent average L-shell ionization probability. Correlations are evident between p/sub L/ and the corresponding sulfur atom chemical environment. Much stronger correlations are however found for variations of some individual peak intensities with specific chemical parameters. Comparison of results for Ar/sup q+/ and Kr/sup q+/ projectiles shows that while L-shell ionization probability has increased, chemical sensitivity has apparently saturated.

Vane, C.R.; Hulett, L.D. Jr.; Kahane, S.; McDaniel, F.D.; Milner, W.T.; Raman, S.; Rosseel, T.M.; Slaughter, G.G.; Varghese, S.L.; Young, J.P.

1983-01-01

350

Near-field investigation of spatial variations of (2021) InGaN quantum well emission spectra  

NASA Astrophysics Data System (ADS)

Scanning near-field optical spectroscopy was applied to semipolar (2021) 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

351

Structural defects and the electronic structure of zirconium hydrides: x-ray emission spectra and quantum chemical calculations  

Microsoft Academic Search

X-ray emission spectroscopy and the Green function LMTO band method was used to study the effect of structural defects in the hydrogen sublattice on the electronic structure and chemical bonding in ZrH2.

A. L. Ivanovskii; Yu. M. Yarmoshenko; A. Ya. Kupryazhkin; V. I. Anisimov; V. A. Gubanov; . Z. Kurmaev; V. P. Antropov

1989-01-01

352

Experimental and theoretical investigations of absorption and emission spectra of the light-emitting polymer MEH-PPV in solution  

Microsoft Academic Search

We report the absorption and photoluminescence spectra of the MEH-PPV polymer in a chloroform solvent. In the analysis, we assume that the polymer consists of short conjugated segments which are called oligomers with different lengths. The appearance of each chain length is controlled by a distribution function. Based on the conformational disorder caused by torsional motion, we found that the

R. Chang; J. H. Hsu; W. S. Fann; K. K. Liang; C. H. Chang; M. Hayashi; J. Yu; S. H. Lin; E. C. Chang; K. R. Chuang; S. A. Chen

2000-01-01

353

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

354

The Equilibrium and Pre-equilibrium Triton Emission Spectra of Some Target Nuclei for ( n, xt) Reactions up to 45 MeV Energy  

NASA Astrophysics Data System (ADS)

Although there have been significant research and development studies on the inertial and magnetic fusion reactor technology, there is still a long way to go to penetrate commercial fusion reactors to the energy market. Tritium self-sufficiency must be maintained for a commercial power plant. For self-sustaining (D-T) fusion driver tritium breeding ratio should be greater than 1.05. So, working out the systematics of ( n,t) reaction cross sections and triton emission differential data are important for the given reaction taking place on various nuclei at different energies. In this study, ( n,xt) reactions for some target nuclei as 16O, 27Al, 59Co and 209Bi have been investigated up to 45 MeV incident neutron energy. In the calculations of the triton emission spectra, the pre-equilibrium and equilibrium effects have been used. The calculated results have been compared with the experimental data taken from the literature.

Tel, E.; Kaplan, A.; Ayd?n, A.; zkorucuklu, S.; Bykuslu, H.; Y?ld?r?m, G.

2010-08-01

355

The influence of visible light and inorganic pigments on fluorescence excitation emission spectra of egg-, casein- and collagen-based painting media  

NASA Astrophysics Data System (ADS)

Spectrofluorimetric analysis of proteinaceous binding media is particularly promising because proteins employed in paintings are often fluorescent and media from different sources have significantly different fluorescence spectral profiles. Protein-based binding media derived from eggs, milk and animal tissue have been used for painting and for conservation, but their analysis using non-destructive techniques is complicated by interferences with pigments, their degradation and their low concentration. Changes in the fluorescence excitation emission spectra of films of binding media following artificial ageing to an equivalent of 50 and 100 years of museum lighting include the reduction of bands ascribed to tyrosine, tryptophan and Maillard reaction products and an increase in fluorescent photodegradation. Fluorescence of naturally aged paint is dependent on the nature of the pigment present and, with egg-based media, in comparison with un-pigmented films, emissions ascribed to amino acids are more pronounced.

Nevin, A.; Anglos, D.; Cather, S.; Burnstock, A.

2008-07-01

356

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

357

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

358

Spectrometer IRIS: Investigation of the Time Structure and Energy Spectra of X-Ray Emission from Solar Flares  

NASA Astrophysics Data System (ADS)

The research program underlying the IRIS experiment (Russian acronym for Investigation of Solar X-Ray Emission) encompasses investigation of the characteristics of X-ray emission from solar flares and of their precursors in the 2-200-keV range, which would form a basis for development of physical models describing the process of buildup and explosive release of energy in a solar flare, as well as accumulation of experimental data to serve in devising techniques for forecasting the solar flare activity

Matveev, G. A.; Dmitriev, P. B.; Kudryavtsev, I. V.; Lazutkov, V. P.; Savchenko, M. I.; Skorodumov, D. V.; Charikov, Yu. E.

359

The application and comparison of several chemometric methods of excitation-emission matrix spectra in studying the interactions of metal complexes with DNA.  

PubMed

The interactions of fs DNA and two metal complexes [Cu(phen)SO4] x 2 H2O and [Ni(phen)SO4] x 2 H2O were explored by several chemometric methods, including parallel factor (PARAFAC), singular value decomposition-least squares (SVD-LS), and singular value decomposition-nonnegative least squares (SVD-NNLS) of excitation-emission matrix spectra (EEMs). The applications of SVD-LS and SVD-NNLS in this domain have been discussed. Rayleigh scatter part is avoided by ordered zero and reconstructed by linear interpolation. The importance of avoiding Rayleigh scatter has also been discussed. All the three methods do well in qualitative analysis. SVD-LS does best in present small changes of ethidium bromide (EB). In order to get accurate results, PARAFAC and SVD-NNLS can be utilized together in quantitative analysis. All the three chemometric methods indicate that the DNA binding modes of [Cu(phen)SO4] x 2 H2O are hydrogen bond effect and intercalation, while intercalation is the only DNA binding mode for [Ni(phen)SO4] x 2 H2O. These results are verified by the electronic absorption and emission fluorescence spectra. Just like PARAFAC, both SVD-LS and SVD-NNLS are proven to be convenient and convincing in studying the interactions between nucleic acids and complexes. PMID:17870282

Zhang, Fang; Zhang, Qian-Qian; Wang, Wei-Guo; Zhu, Chen-Jian; Wang, Xiu-Lin

2007-09-19

360

Ab initio simulation of photoemission spectroscopy in solids: Plane-wave pseudopotential approach with applications to normal-emission spectra of Cu(001) and Cu(111)  

NASA Astrophysics Data System (ADS)

We develop a method for simulating photoemission spectra from bulk crystals in the ultraviolet energy range within a three-step model. Our method explicitly accounts for transmission and matrix-element effects, as calculated from state-of-the-art plane-wave pseudopotential techniques within the density-functional theory. Transmission effects, in particular, are included by extending to the present problem a technique previously employed with success to deal with ballistic conductance in metal nanowires. The spectra calculated for normal emission in Cu(001) and Cu(111) are in fair agreement with previous theoretical results and with experiments, including a recently determined experimental spectrum. The residual discrepancies between our results and the latter are mainly due to the well-known deficiencies of the density-functional theory in accounting for correlation effects in quasiparticle spectra. A significant improvement is obtained by the LDA+U method. Further improvements are obtained by including surface-optics corrections, as described by Snells law and Fresnels equations.

Stoji?, Nataa; Dal Corso, Andrea; Zhou, Bo; Baroni, Stefano

2008-05-01

361

The electronic spectrum of the fluoroborane free radical. II. Analysis of laser-induced fluorescence and single vibronic level emission spectra  

NASA Astrophysics Data System (ADS)

Subsequent to our spectroscopic detection of the HBX (X=F, Cl, Br) free radicals (S.-G. He, F. X. Sunahori, and D. J. Clouthier, J. Am. Chem. Soc. 127, 10814 (2005)), the electronic spectrum of the A~ 2A''?-X~ 2A' system of the fluoroborane (HBF) radical in the 600-745 nm region has been studied in detail using the pulsed discharge jet technique. The band system involves a linear-bent transition between the two Renner-Teller components of what would be a 2? state at linearity. Using the results of our theoretical study of the ground and excited state vibrational energy levels and 11B-10B isotope shifts (see the companion paper), the vibrational quantum numbers of the bands in the laser-induced fluorescence (LIF) spectra have been assigned. Rotational and vibrational analyses of the LIF and wavelength resolved emission spectra have been carried out, from which the linear excited state and the bent ground state equilibrium configurations have been confirmed. The ground state molecular geometry of HBF has been determined as r0(BH)=1.214(2) A?, r0(BF)=1.303 4(5) A?, and ?=120.7(1). Based on high-level ab initio calculations and symmetry considerations, predissociation of the excited state into H(2S)+BF(1?+) on the ground state potential energy surface is identified as the cause of the breaking off of fluorescence in the LIF spectra.

Sunahori, Fumie X.; Clouthier, Dennis J.

2009-04-01

362

Effect of precursor mineralogy on the thermal infrared emission spectra of hematite: Application to Martian hematite mineralization  

Microsoft Academic Search

Observations from the Thermal Emission Spectrometer (TES) instrument aboard the Mars Global Surveyor (MGS) spacecraft led to the discovery of two isolated deposits of gray, crystalline hematite located in Meridiani Planum and Aram Chaos and several smaller deposits in Valles Marineris. Several pathways for formation of these hematite deposits have been proposed, involving both aqueous and nonaqueous processes. This work

T. D. Glotch; R. V. Morris; P. R. Christensen; T. G. Sharp

2004-01-01

363

Simultaneous X-ray and Far-Ultraviolet Spectra of AGN with ASCA and HUT  

NASA Technical Reports Server (NTRS)

We obtained ASCA spectra of the Seyfert 1 galaxy NGC 3516 in March 1995. Simultaneous far-UV observations were obtained with the Hopkins Ultraviolet Telescope on the Astro-2 shuttle mission. The ASCA spectrum shows a lightly absorbed power law of energy index 0.78. The low energy absorbing column is significantly less than previously seen. Prominent 0 VII and 0 VIII absorption edges are visible, but, consistent with the much lower total absorbing column, no Fe K absorption edge is detectable. A weak, narrow Fe K(alpha) emission line from cold material is present as well as a broad Fe K(alpha) line. These features are similar to those reported in other Seyfert 1 galaxies. A single warm absorber model provides only an imperfect description of the low energy absorption. In addition to a highly ionized absorber with ionization parameter U = 1.66 and a total column density of 1.4 x 10(exp 22)/sq cm, adding a lower ionization absorber with U = 0.32 and a total column of 6.9 x 10(exp 21)/sq cm significantly improves the fit. The contribution of resonant line scattering to our warm absorber models limits the Doppler parameter to less than 160 km/s at 90% confidence. Turbulence at the sound speed of the photoionized gas provides the best fit. None of the warm absorber models fit to the X-ray spectrum can match the observed equivalent widths of all the UV absorption lines. Accounting for the X-ray and UV absorption simultaneously requires an absorbing region with a broad range of ionization parameters and column densities.

Kriss, Gerard A.

1997-01-01

364

Analysis of neutron emission spectra for 30 50 MeV ?-particle induced reactions in thick targets  

NASA Astrophysics Data System (ADS)

Comparisons of calculated neutron yield distributions from ?-particle induced reactions on thick targets are made with measured data to analyze the initial reaction process in the framework of the exciton (hybrid) model code ALICE91 (M. Blann, Lawrence Livermore National Laboratory Report UCID 19614, 1982). We have considered two reaction mechanisms: dissolution of the ? in the nuclear field, and preequilibrium processes initiated by ?-nucleon collisions. Both these processes seem to contribute to the emitted neutron spectra in varying proportions depending on the incident ? energy and possibly on the target nucleus. Contributions from other processes appear to be non-negligible.

Dhar, D.; Roy, S. N.; Nandy, Maitreyee; Sarkar, P. K.

2003-06-01

365

Vibronic transitions in the excitation and emission spectra of hexakis(antipyrine)europium(III) tri-iodide and tri-perchlorate crystals  

NASA Astrophysics Data System (ADS)

Optical emission and emission excitation spectra are reported for crystals of Eu(AP)6I3 and Eu(AP)6(ClO4)3 (where AP denotes an antipyrine ligand molecule). Emission results are reported for the 7F0,1,2 ? 5D0 (luminescent) transition regions, and emission excitation results are reported for the 7F0 ? 5D0,1,2 (absorptive) transition regions. Particular attention is focused on vibronic transitions occurring between crystal-field (electronic) levels with the simultaneous excitation (or de-excitation) of a phonon or vibrational mode. The 7F0 ? 5D2 excitation and 7F2 ? 5D0 emission regions exhibit large numbers of resolved vibronic lines with displacement-from-origin frequencies ranging from 22 to 1613 cm-1. Vibronic transitions characterized by at least 48 different vibrational (or discrete phonon) frequencies are observed. Several intense vibronic lines are assigned to relatively low-frequency (< 200 cm-1) vibrational modes associated with the octahedral EuO6 coordination clusters, but the great majority of vibronic lines are assigned to vibrational modes associated with internal ligand (antipyrine) atomic motions. Several of the vibronic transitions promoted by internal ligand vibrations are nearly as intense as those promoted by EuO6 moiety modes. The Eu(AP)6I3 and Eu(AP)6(ClO4)3 systems exhibit identical vibronic structure in their spectra, and this structure is essentially independent of temperature between 295 and 10K (except for line narrowing and redistributions of relative line intensities attributable to changes in relative energy-level populations). However, loss of inversion symmetry at the europium sites appears to occur at T < 100 K in each system. No-phonon (origin) lines in the 7F0 ? 5D0, 7F0 ? 5D2, and 7F2 ? 5D0 transition regions gradually exhibit (weak) electric-dipole intensity as sample temperature is lowered from 100 K to 10 K.

Berry, M. T.; Kirby, A. F.; Richardson, F. S.

366

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

367

Argon and copper optical emission spectra in a Grimm glow discharge source: mathematical simulations and comparison with experiment  

Microsoft Academic Search

discharge optical emission spectrometry. The calculations were based on the Einstein transition probabilities for radiative decay and on the level populations of excited levels of the CALCULATION PROCEDURE argon atoms and copper atoms and ions, which were computed A comprehensive three-dimensional modeling network has previously in a comprehensive self-consistent modeling network been developed before,3-17 consisting of diVerent sub-models for the

Annemie Bogaerts; Renaat Gijbels

1998-01-01

368

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

369

Flame Emission Spectra in the Region 400600 nm during Low-Pressure Silane and Dichlorosilane Oxidation  

Microsoft Academic Search

The flame emission in the region 400600 nm during monosilane and dichlorosilane oxidation (initial pressures of 320 torr; T = 300 K) is caused by radical luminescence processes on the surface of aerosol microparticles of the SiO2 formed. The generation of energy by the interaction of gas-phase species with the SiO2 surface at the initial stages of the phase formation

V. I. Chernysh; N. M. Rubtsov; G. I. Tsvetkov

2002-01-01

370

CONTROL OF LASER RADIATION PARAMETERS: Phase-polarization control of the emission spectra of ring dye lasers  

NASA Astrophysics Data System (ADS)

A ring dye laser with a three-mirror resonator and phase-polarization control of the emission spectrum was constructed and investigated. A resonator mirror performed the function of a nonresonant rotator of the plane of polarization of the light wave. Such a system subjected to single-pulse laser pumping was capable of generating narrow-band radiation with a spectral width 2-4 pm and a high signal/noise ratio in a fairly wide range of pump energies.

Smirnov, A. Ya; Teplyashin, L. L.

1988-05-01

371

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars. I. Clear-sky thermal emission spectra and weighting functions  

NASA Astrophysics Data System (ADS)

Context. The atmosphere of Earth-like extrasolar planets orbiting different types of stars is influenced by the spectral dependence of the incoming stellar radiation. The changes in structure and composition affect atmospheric radiation, hence the spectral appearance of these exoplanets. Aims: We provide a thorough investigation of infrared radiative transfer in cloud-free exoplanets atmospheres by not only analyzing the planetary spectral appearance but also discussing the radiative processes behind the spectral features in detail and identifying the regions in the atmosphere that contribute most at a given wavelength. Methods: Using cloud-free scenarios provided by a one-dimensional radiative-convective steady-state atmospheric model, we computed high-resolution infrared transmission and emission spectra, as well as weighting functions for exoplanets located within the habitable zone of F, G, K, and M stars by means of a line-by-line molecular absorption model and a Schwarzschild solver for the radiative transfer. The monochromatic spectra were convolved with appropriate spectral response functions to study the effects of finite instrument resolution. Results: Spectra of the exoplanets of F, G, K, and M stars were analyzed in the 4.5 ?m N2O band, the 4.3 ?m and 15 ?m CO2 bands, the 7.7 ?m CH4 band, the 6.3 ?m H2O band, and the 9.6 ?m O3 band. Differences in the state of the atmosphere of the exoplanets clearly show up in the thermal infrared spectra; absorption signatures known from Earth can be transformed to emission features (and vice versa). Weighting functions show that radiation in the absorption bands of the uniformly mixed gases (CO2, CH4, N2O) and (to some extent) ozone comes from the stratosphere and upper troposphere, and also indicate that changes in the atmospheres can shift sources of thermal radiation to lower or higher altitudes. Molecular absorption and/or emission features can be identified in the high-resolution spectra of all planets and in most reduced resolution spectra. Conclusions: Insight into radiative transfer processes is essential for analyzing exoplanet spectral observations; for instance, understanding the impact of the temperature profile (nb. non-existence of an inversion) on the CO2 bands facilitates their interpretation and can help avoid false positive or negative estimates of O3. The detailed analysis of the radiation source and sink regions could even help give an indication about the feasibility of identifying molecular signatures in cloud-covered planets, i.e. radiation mainly coming from the upper atmosphere is less likely to be hidden by clouds. Infrared radiative transfer and biomarker detectability in cloud-covered exoplanets will be presented in a companion paper. Appendix is available in electronic form at http://www.aanda.org

Vasquez, M.; Schreier, F.; Gimeno Garca, S.; Kitzmann, D.; Patzer, B.; Rauer, H.; Trautmann, T.

2013-01-01

372

High-resolution KMM radiative Auger x-ray emission spectra of calcium induced by synchrotron radiation  

NASA Astrophysics Data System (ADS)

The KMM radiative Auger (RA) x-ray spectra of solid Ca were induced by monochromatic synchrotron radiation and measured with a high-resolution von Hamos bent crystal spectrometer. Two excitation energies were employed, one in the near K threshold region and the second well above the K absorption edge. The KMM RA spectral structure and relative intensity with respect to the diagram K?1,3 (K-M3,2) line are found to be independent of the excitation energy. The overall RA structure resembles the density of unoccupied s, p, and d states. Due to solid-state effects, however, spectral features resulting from the major discrete shake-up transitions could not be resolved. For the total KMM RA to K?1,3 yield ratio, a value of 0.053(3) is obtained. The latter is compared to theoretical predictions and available experimental data obtained by various types of target excitation.

Cao, W.; Kav?i?, M.; Dousse, J.-Cl.; Berset, M.; Bu?ar, K.; Budnar, M.; Fennane, K.; Hoszowska, J.; Maillard, Y.-P.; Szlachetko, J.; Szlachetko, M.; itnik, M.

2011-04-01

373

Analysis of secondary electron emission spectra of equal-LET protons and alpha particles for purposes of radiation quality and spaceflight hazard assessment.  

PubMed

Amongst the great variety of heavy particles present in the galactic and solar cosmic ray spectra, hydrogen and helium nuclei are significantly more abundant than all other heavier ions and, as such, represent a major radiation hazard to humans in space. Experimental data have suggested that differences in relative biological effectiveness (RBE) exist between the two species at the same value of linear energy transfer (LET). This has consequences for heavily ionising radiation protection procedures, which currently still assume a simple dependence of radiation quality on LET. By analysing the secondary electron (delta-ray) emission spectra of protons and alpha particles, in terms of the spatial characteristics of energy deposition in cellular targets and the likelihood of complex lesion formation, a numerical quantity representing biological effectiveness is generated. When expressed relative to a reference radiation, this quantity is found to differ for protons and a particles of the same LET, demonstrating not only the ion-specific nature of RBE but also the inadequacy of specifying radiation quality as a function of LET only. Such a method for numerically assessing radiation quality may have implications for procedures for heavy ion protection in space at low doses and for understanding the initial mechanisms of radiation action. PMID:15934210

Craven, P A; Rycroft, M J

2005-01-01

374

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

375

Four micron high-resolution spectra of Jupiter in the North Equatorial Belt: H3(+) emissions and the C-12/C-13 ratio  

NASA Technical Reports Server (NTRS)

Spectra of the North Equatorial Belt of Jupiter were obtained in March 1992 at an unapodized resolution of 0.1/cm between 2450 and 2600/cm with the Fourier Transform Spectrometer at the 3.6 m Canada-France-Hawaii Telescope (CFHT) on Mauna Kea. Several emissions from the nu(sub 2) band of H3(+) were detected. The excitation temperature derived from the relative intensities of these emissions averaged over a wide range of longitudes is 800 +/- 100 K, and the H3(+) column density is 1.56(sup +1.0)(sub -0.5) x 10(exp 11)/sq. cm. In addition, several strong absorption features due to (13)CH4 were observed. A comparison between (12)CH4 and (13)CH4 absorptions allowed us to obtain a new measurement of the C-12/C-13 ratio. We found that this ratio, estimated for the first time in this spectral range, is 89 (+/- 25), in agreement with the terrestrial value.

Marten, A.; De Bergh, C.; Owen, T.; Gautier, D.; Maillard, J. P.; Drossart, P.; Lutz, B. L.; Orton, G. S.

1994-01-01

376

INTERACTION OF LASER RADIATION WITH MATTER. LASER PLASMA: X-ray emission spectra of the plasma produced by an ultrashort laser pulse in cluster targets  

NASA Astrophysics Data System (ADS)

The first observation of x-ray emission spectra of multiply charged ions in the plasma produced by a 35-fs laser pulse with an intensity up to 1017 W cm-2 in CO2 and Kr gas jet targets is reported. The emission in the wavelength ranges of the 1snp1s2(n=3-6) transitions of O VII ions and the Ly? line of O VIII ions, as well as of the (2s1/22p63p3/2)12s22p6 1S0 and (2s1/22p63p1/2)12s22p6 1S0 lines of Ne-like KrXXVII ions testifies that the highly ionised plasma is formed by collision processes in clusters. Modelling the shape of the spectral lines of oxygen ions by including the principal mechanisms of broadening and absorption in optically dense plasmas reveals that the main contribution to the time-integrated intensity is made by the plasma with the parameters Ne=(2-20)1020 cm-3 and Te=100 115 eV.

Stenz, C.; Bagnoud, V.; Blasco, F.; Roche, J. R.; Salin, F.; Faenov, A. Ya; Magunov, A. I.; Pikuz, T. A.; Skobelev, I. Yu

2000-08-01

377

X-ray emission-line spectra of photoionized plasmas - Density sensitivity of the Fe L-shell series  

NASA Technical Reports Server (NTRS)

The circumsource environments of accretion-powered X-ray sources are likely to support relatively dense (greater than 10 exp 11/cu cm) photoionized X-ray emission-line regions. The Fe L-shell ions provide a versatile class of plasma diagnostics in this regime, their multielectron structures resulting in diverse spectral phenomena. Attention is given to the spectral response of Fe L-shell ions to variations in electron density over the range 10 exp 11 to 10 exp 16/cu cm. It is found that density-sensitive line ratios exist in the wavelength interval 12-17 A for the ions Fe XVII-XXI. The prominent role of radiative recombination in the population kinetics distinguishes the density-sensitive Fe lines in photoionized plasmas from those which operate in coronal equilibrium plasmas. The results of detailed atomic modeling of these ions are presented and applications to spectroscopic observations of accretion-driven X-ray sources are discussed.

Liedahl, Duane A.; Kahn, Steven M.; Osterheld, Albert L.; Goldstein, William H.

1992-01-01

378

Effects of chemical combination on x-ray K? and K?1,3 emission spectra of Co  

NASA Astrophysics Data System (ADS)

Chemical shift, differences of full width at half maximum (?FWHM) and full width at half maximum (FWHM) of K? and K?1,3 x-ray emission lines were measured for the following Co compounds: Co, CoO, Co2O3, CoSO4.7H2O, Co(NO3)2.6H2O, CoCr2O4, Co(ClO4)2.6H2O, Co(C2H3O2), CoCl2.6H2O, CoCl2, CoF2, CoF2.4H2O and CoF3. The measurements were performed with wavelength-dispersive x-ray fluorescence spectrometry (WDXRF). It was found that the calculated results for Co compounds are strongly correlated with the oxidation state. At the same time, chemical shift for F compounds is generally more than that for Cl compounds. Larger chemical shifts and FWHM were also found for K?1,3 lines than K? ones. It should be noted that the magnitude of chemical shifts increases with the increasing number of ligand atoms.

Bayda?, E.; z, E.

2010-01-01

379

H-Bonding vs Non-H-Bonding in 100% Pyrene Methacrylate Comb Polymers: Self-Assembly Probed by Time-Resolved Emission Spectra and Temperature Dependent Fluorescence.  

PubMed

The differences in self-organization behavior in novel 100% pyrene labeled comb methacrylate polymers probed as a function of their varied origins of excimer formation are presented. The different structural variations in the polymers included the presence or absence of hydrogen bonding interactions in the form of urethane linkages, short or long alkyl spacer segments separating the pyrene units from the polymer backbone and linear versus kinked urethane linkage. The effect of variable concentration and temperature on the chemical shift of the NH proton of the urethane linkage was probed using (1)H NMR experiments conducted at temperatures varying from 25 to 70 C at two different concentrations (2.5 and 25 mmol) in DMSO-d6 as solvent. The photophysical properties of the polymers in dilute DMF solutions were investigated by steady state emission, fluorescence decay studies, time-resolved emission spectra (TRES), and variable temperature emission studies. It was observed that the polymer poly(PBH) having a non-hydrogen-bondable ester linkage in the pendant chains formed an excimer completely via a static mechanism and the ground state aggregate species were not broken even at higher temperatures. The polymer poly(PIC) having a short hydrogen-bondable urethane linkage formed an excimer via a static as well as dynamic mechanism. The other hydrogen-bondable urethane methacrylate polymers having a linear linker poly(PHH) and kinked linker (PIHP) formed excimer mostly via a dynamic mechanism with a very small contribution from the static route. The TRES studies carried out for the polymers provided significant insight into the excimer formation mechanism in these polymers. The variable temperature fluorescence studies highlighted the differences in the H-bonded vs non-H-bonded polymer as a function of their excimer recovery upon cooling. PMID:24734783

Kaushlendra, K; Asha, S K

2014-05-01

380

Infrared radiative transfer in atmospheres of Earth-like planets around F, G, K, and M stars. II. Thermal emission spectra influenced by clouds  

NASA Astrophysics Data System (ADS)

Context. Clouds play an important role in the radiative transfer of planetary atmospheres because of the influence they have on the different molecular signatures through scattering and absorption processes. Furthermore, they are important modulators of the radiative energy budget affecting surface and atmospheric temperatures. Aims: We present a detailed study of the thermal emission of cloud-covered planets orbiting F-, G-, K-, and M-type stars. These Earth-like planets include planets with the same gravity and total irradiation as Earth, but can differ significantly in the upper atmosphere. The impact of single-layered clouds is analyzed to determine what information on the atmosphere may be lost or gained. The planetary spectra are studied at different instrument resolutions and compared to previously calculated low-resolution spectra. Methods: A line-by-line molecular absorption model coupled with a multiple scattering radiative transfer solver was used to calculate the spectra of cloud-covered planets. The atmospheric profiles used in the radiation calculations were obtained with a radiative-convective climate model combined with a parametric cloud description. Results: In the high-resolution flux spectra, clouds changed the intensities and shapes of the bands of CO2, N2O, H2O, CH4, and O3. Some of these bands turned out to be highly reduced by the presence of clouds, which causes difficulties for their detection. The most affected spectral bands resulted for the planet orbiting the F-type star. Clouds could lead to false negative interpretations for the different molecular species investigated. However, at low resolution, clouds were found to be crucial for detecting some of the molecular bands that could not be distinguished in the cloud-free atmospheres. The CO2 bands were found to be less affected by clouds. Radiation sources were visualized with weighting functions at high resolution. Conclusions: Knowledge of the atmospheric temperature profile is essential for estimating the composition and important for avoiding false negative detection of biomarkers, in both cloudy and clear-sky conditions. In particular, a pronounced temperature contrast between the ozone layer and surface or cloud is needed to detect the molecule. Fortunately, the CO2 bands allow temperature estimation from the upper stratosphere down to the troposphere even in the presence of clouds.

Vasquez, M.; Schreier, F.; Gimeno Garca, S.; Kitzmann, D.; Patzer, B.; Rauer, H.; Trautmann, T.

2013-09-01

381

Estimation of Mass-Loss Rates from Emission Line Profiles in the UV Spectra of Cool Stars  

NASA Technical Reports Server (NTRS)

The photon-scattering winds of cool, low-gravity stars (K-M giants and supergiants) produce absorption features in the strong chromospheric emission lines. This provides us with an opportunity to assess important parameters of the wind, including flow and turbulent velocities, the optical depth of the wind above the region of photon creation, and the star's mass-loss rate. We have used the Lamers et al. Sobolev with Exact Integration (SEI) radiative transfer code along with simple models of the outer atmospheric structure to compute synthetic line profiles for comparison with the observed line profiles. The SEI code has the advantage of being computationally fast and allows a great number of possible wind models to be examined. We therefore use it here to obtain initial first-order estimates of the wind parameters. More sophisticated, but more time-consuming and resource intensive calculations will be performed at a later date, using the SEI-deduced wind parameters as a starting point. A comparison of the profiles over a range of wind velocity laws, turbulence values, and line opacities allows us to constrain the wind parameters, and to estimate the mass-loss rates. We have applied this analysis technique (using lines of Mg II, 0 I, and Fe II) so far to four stars: the normal K5-giant alpha Tau, the hybrid K-giant gamma Dra, the K5 supergiant lambda Vel, and the M-giant gamma Cru. We present in this paper a description of the technique, including the assumptions which go into its use, an assessment of its robustness, and the results of our analysis.

Carpenter, K. G.; Robinson, R. D.; Harper, G. M.

1999-01-01

382

Modeling K- and L-shell Spectra from Cu Wire Array Implosions on ZR  

NASA Astrophysics Data System (ADS)

We will examine K- and L-shell data obtained from the copper nested wire-array SNL shot Z1975, and compare it with data obtained from a simulation using the 1-D DZAPP radiation-hydrodynamics code. In addition to Cu, lines of Ni, Fe and Cr were observed in the experimental spectra, and we performed the calculations with an appropriate mixture of these elements. In the present analysis, we find support for an alternative K-alpha model which competes with the better known e-beam generation mechanism, wherein K-shell photons from hot plasma on or near the axis are absorbed in a dense, cool annular envelope via inner-shell photoionization. The resulting electronic relaxation of the absorbing ions produces the K-alpha radiation. By generating radially resolved synthetic spectra from self-consistent calculations of K-shell vacancy formation, and characterizing the energies of the resulting K-alpha radiation, diagnostics are obtained which can help differentiate between beam generated and photon driven K-alpha radiation.

Clark, R. W.; Dasgupta, A.; Giuliani, J. L.; Ouart, N. D.; Jones, B.; Ampleford, D. J.; Coverdale, C. A.

2012-10-01

383

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

384

Line-shape analyses of XVV Auger spectra of p(1 x 1)-V/sub 3/Si(00): Evidence for autoionization emission  

SciTech Connect

In the light of recent advances in understanding the Auger process, the local electronic structural origins of selected core-valence-valence (XVV) Auger line shapes are analyzed for a transition-metal silicide prototype, V/sub 3/Si. We report for clean p(1 x 1)-V/sub 3/Si(100) Auger spectra that include the region of the vanadium M/sub 2,3/VV and M/sub 1/VV and the Si L/sub 2,3/VV transitions. We compare the measured line shapes to spectra we generated based on the muffin-tin local density of states (DOS) calculated self-consistently by Klein et al. Good agreement in both the Si pp(L/sub 2,3/M/sub 2,3/M/sub 2,3/) and the V dd(M/sub 2,3/M/sub 4,5/M/sub 4,5/) peak positions between experiment and calculation verified that the final-state hole-hole repulsion for Si (U/sub p/p) and V (U/sub d/d) are both approx.0 eV. Also, the Si L/sub 2,3/VV spectrum resembles that of elemental Si in that the line shape is predominantly a self-fold of the Si 3p DOS. However, an unexpected result is that the V spectral region above the M/sub 2,3/VV threshold possesses a broad (approx.30-eV-wide) intense feature that is not amenable to conventional interpretation in terms of the M/sub 1/VV transition or M/sub 2,3/VV double-ionization or plasmon-gain satellites. We attribute this observation to the presence of Fano autoionization emission associated with deexcitation of the resonant 3p..-->..3d transition. Supporting evidence comes from a comparison of our p x-ray- and electron-stimulated Auger spectra, and to the line shape of the 3p loss spectrum. In addition, oxygen-dosing Auger and x-ray photoelectron spectroscopy experiments p (0--20 L) (1 langmuir = 1 L = 10/sup -6/ Torr sec) indicate dramatic Si L/sub 2,3/VV line-shape changes associated with oxidation, similar to that observed previously for Pd/sub 4/Si. The initial oxidation rate is approx.10/sup 2/ faster than that for elemental Si.

Zajac, G.; Zak, J.; Bader, S.D.

1983-06-01

385

Monitoring Disinfection Byproduct Forming Potential with Simultaneous Absorbance Spectra and Fluorescence Excitation-Emission Mapping: Supporting Stage 2 EPA Regulation Monitoring Compliance  

NASA Astrophysics Data System (ADS)

Water treatment plants in the United States will soon (by 2013 to 2013) be required to initialize enhanced monitoring for reducing disinfection by-products (DBPs) to meet the Stage 2 levels enforced by the EPA. The key to successfully meeting these requirements lies in the treatment plant's ability to deal with often dramatic source-water variations in natural organic matter (NOM) content. Whereas the regulated levels of NOM must be determined by measuring total organic carbon (TOC) often this parameter does not provide rapid or cost-effective qualitative or quantitative assessment of the various humic, fulvic and other aromatic NOM components. However, 2 main optical techniques namely UV absorbance and fluorescence excitation-emission mapping can be used for rapid assessment with precise identification of humic and fulvic components. This study presents data from a new type of instrument which simultaneously measures the UV-VIS absorbance spectrum and EEM. The rapid absorbance-EEM is facilitated by a single system that is more than 100 time faster than conventional scanning absorbance and fluoresence optical benches. The new system can continuously collect EEMs and absorbance spectra at a rate often greater than 1 per min with the extra capacity to monitor the UV254 absorbance and fluorescence emission spectrum excited at 254 nm in 4 ms intervals (an equivalent scan rate of 5.5 million nm/min). The EEM spectral data is corrected for all instrumental response factors including concentration dependent inner-filter effects. The accumulated EEM data sets can be modeled using conventional peak identification, PARAFAC and or PCA analysis of the fractionated samples to predict the trihalomethane forming potential (THMFP). This study compares the effectiveness of THFMP predictive models based on these three techniques and explains how these can be readily employed to facilitate the Stage 2 regulation compliance for DBP monitoring.

Gilmore, A. M.

2011-12-01

386

Comparison of calculated spectra for the interaction of photons in a liquid scintillator. Example of 54Mn 835 keV emission.  

PubMed

The CIEMAT/NIST and TDCR methods in liquid scintillation counting, initially developed for the activity standardization of pure-beta radionuclides, have been extended to the standardization of electron capture and beta-gamma radionuclides. Both methods require the calculation of the energy spectrum absorbed by the liquid scintillator. For radionuclides emitting X-rays or gamma-rays, when the energy is greater than a few tens of keV the Compton interaction is important and the absorption is not total. In this case, the spectrum absorbed by the scintillator must be calculated using analytical or stochastic models. An illustration of this problem is the standardization of 54Mn, which is a radionuclide decaying by electron capture. The gamma transition, very weakly converted, leads to the emission of an 835 keV photon. The calculation of the detection efficiency of this radionuclide requires the calculation of the energy spectrum transferred to the scintillator after the absorption of the gamma ray and the associated probability of absorption. The validity of the method is thus dependent on the correct calculation of the energy transferred to the scintillator. In order to compare the calculation results obtained using various calculation tools, and to provide the metrology community with some information on the choice of these tools, the LS working group of the ICRM organised a comparison of the calculated absorbed spectra for the 835 keV photon of 54Mn. The result is the spectrum of the energy absorbed by the scintillator per emission of an 835 keV gamma ray. This exercise was proposed for a standard 20 ml LS glass vial and for LS cocktail volumes of 10 and 15 ml. The calculation was done for two different cocktails: toluene and a widely used commercial cocktail, Ultima Gold. The paper describes the results obtained by nine participants using a total of 12 calculation codes. PMID:16600600

Cassette, P; Ahn, G H; Alzitzoglou, T; Aubineau-Lanice, I; Bochud, F; Garcia Torano, E; Grau Carles, A; Grau Malonda, A; Kossert, K; Lee, K B; Laedermann, J P; Simpson, B R S; van Wyngaardt, W M; Zimmerman, B E

2006-01-01

387

Effect of PCBM concentration on photoluminescence properties of composite MEH-PPV/PCBM nanoparticles investigated by a Franck-Condon analysis of single-particle emission spectra.  

PubMed

The emission of composite conjugated polymer (MEH-PPV)/fullerene (PCBM) nanoparticles is investigated by single particle spectroscopy (SPS), and changes in vibronic structure with nanoparticle composition are evaluated by means of a detailed Franck-Condon analysis. Consistent with previous reports we find that the emission spectra can be modeled as the superposition of two types of emitters, one with aggregate character and one with molecular character. Major findings from the fitting of the SPS data to a Franck-Condon model are that 1) the occurrence of each of the two types of emitters changes with nanoparticle composition to the point that no aggregate emitters are detected (at 50 wt% PCBM), 2) at the highest PCBM doping levels (75 wt% PCBM) aggregate emitters reappear due to nanoscale phase separation in the composite nanoparticles, 3) the molecular emitters show small Huang-Rhys factors that increase with PCBM doping, indicative of extensive delocalization and exciton migration that is reduced by the disorder introduced in the polymer material by PCBM doping and 4) the aggregate emitters show large Huang-Rhys factors, indicative of the localized nature of these energy trap sites, with a broad distribution of values of these Huang-Rhys factors. The latter observation suggests a broad heterogeneous distribution of aggregate morphologies in blended conducting polymer materials, which can be attributed to variations in polymer chain folding and stacking at the aggregate sites. The reported results obtained by the SPS approach show how blending conjugated polymers with fullerenes at various doping levels induces changes in interchain interactions and aggregate site density even at length scales below a few tens of nanometers that affect conjugated polymer material properties, an observation that has gone unnoticed in bulk studies of blended conjugated polymer films. PMID:19787692

Tenery, Daeri; Gesquiere, Andre J

2009-10-01

388

The relation between AGN hard X-ray emission and mid-infrared continuum from ISO spectra: Scatter and unification aspects  

NASA Astrophysics Data System (ADS)

We use mid-infrared spectral decomposition to separate the 6 ?m mid-infrared AGN continuum from the host emission in the ISO low resolution spectra of 71 active galaxies and compare the results to observed and intrinsic 2-10 keV hard X-ray fluxes from the literature. We find a correlation between mid-infrared luminosity and absorption corrected hard X-ray luminosity, but the scatter is about an order of magnitude, significantly larger than previously found with smaller statistics. Main contributors to this scatter are likely variations in the geometry of absorbing dust, and AGN variability in combination with non-simultaneous observations. There is no significant difference between type 1 and type 2 objects in the average ratio of mid-infrared and hard X-ray emission, a result which is not consistent with the most simple version of a unified scheme in which an optically and geometrically thick torus dominates the mid-infrared AGN continuum. Most probably, significant non-torus contributions to the AGN mid-IR continuum are masking the expected difference between the two types of AGN. Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/465 Based on observations with ISO, an ESA project with instruments funded by ESA member states (especially the PI countries: France, Germany, The Netherlands, and the UK) with the participation of ISAS and NASA.

Lutz, D.; Maiolino, R.; Spoon, H. W. W.; Moorwood, A. F. M.

2004-05-01

389

A combined optical and X-ray study of unobscured type 1 active galactic nuclei - II. Relation between X-ray emission and optical spectra  

NASA Astrophysics Data System (ADS)

In this second paper in a series of three, we study the properties of the various emission features and underlying continuum in the optical spectra of type 1 active galactic nuclei (AGNs) by using the unobscured hard X-ray emission as a diagnostic. We introduce the use of the 'correlation spectrum technique' (CST) for the first time. We use this to show the strength of the correlation between the hard X-ray luminosity and each wavelength of the optical spectrum. This shows that for broad-line Seyfert 1 galaxies all the strong emission lines (the broad component of H? and H?, [Ne III] ??3869/3967, [O I] ??6300/6364, [O II] ??3726/3729 and [O III] ??4959/5007) and the optical underlying continuum all strongly correlate with the hard X-ray emission. In contrast, the narrow-line Seyfert 1 galaxies show a stronger correlation in the optical continuum but a weaker correlation in the lines. A cross-correlation with luminosity between the various Balmer line components and the broad-band spectral energy distribution (SED) components shows that the best correlation exists between the hard X-ray component and the broad component (BC) of the Balmer lines. Such a correlation is weaker for the intermediate (IC) and narrow components, which supports the view that the broad-line region (BLR) has the closest link with the AGN's compact X-ray emission. The equivalent widths of the Balmer line IC and BC are found to correlate with ?, ?, Balmer line full width at half-maximum (FWHM) and black hole mass. There is a non-linear dependence of the Balmer line IC and BC luminosities with ? and L5100, which suggests that a second-order factor such as the intermediate-line region (ILR) and BLR covering factors affect the Balmer line component luminosities. The Balmer decrement is found to decrease from 5 in the line core to 2 in the extended wings, with mean decrements of 2.1 in the BLR and 4.8 in the ILR. This suggests different physical conditions in these regions, such as variations in electron density and dust abundance. The [O III] line is composed of a narrow core together with a blueshifted component with an average outflow velocity of ?. The total luminosity of [O III] ?5007 shows the best correlation with the luminosity of hard X-ray emission, and so can be used to estimate the intrinsic X-ray luminosity of obscured AGNs. We use the CST to show the correlation of the [O III] ?5007 luminosity with each wavelength of the full continuum SED. This shows as before that not only does the [O III] ?5007 luminosity strongly correlate with a power-law tail, but it also correlates almost as strongly with the optical continuum from the disc, but not with the soft excess.

Jin, Chichuan; Ward, Martin; Done, Chris

2012-06-01

390

Emission-Line Spectra of Ar IX-Ar XVI in the Soft X-Ray Region 20-50  

NASA Astrophysics Data System (ADS)

As part of a larger project to complete a comprehensive catalog of astrophysically relevant emission lines in support of new-generation X-ray observatories using the Lawrence Livermore electron beam ion traps EBIT-I and EBIT-II, we present observations of argon lines in the extreme-ultraviolet region. Our database includes wavelength measurements with standard errors, relative intensities, and line assignments for Ar IX-Ar XVI between 20 and 50 . The experimental data are complemented with a full set of calculations using the Hebrew University Lawrence Livermore Atomic Code (HULLAC). Despite differences in calculated and measured wavelengths, we find the calculated lines to be of great utility in analyzing our laboratory spectra. The calculated line intensities are generally sufficient to identify the strongest transitions in each charge state. We note, however, an underestimation by theory of the strength of the 3s-->2p lines relative to the 3d-->2p lines in Ar IX, Ar X, and Ar XI. The laboratory data are compared with Chandra observations of Procyon, resulting in the identification of an Ar IX line that was previously thought to be from S IX.

Lepson, J. K.; Beiersdorfer, P.; Behar, E.; Kahn, S. M.

2003-06-01

391

STUDYING THE WARM-HOT INTERGALACTIC MEDIUM IN EMISSION  

SciTech Connect

We assess the possibility of detecting the warm-hot intergalactic medium in emission and characterizing its physical conditions and spatial distribution through spatially resolved X-ray spectroscopy, in the framework of the recently proposed DIOS, EDGE, Xenia, and ORIGIN missions, all of which are equipped with microcalorimeter-based detectors. For this purpose, we analyze a large set of mock emission spectra, extracted from a cosmological hydrodynamical simulation. These mock X-ray spectra are searched for emission features showing both the O VII K{alpha} triplet and O VIII Ly{alpha} line, which constitute a typical signature of the warm-hot gas. Our analysis shows that 1 Ms long exposures and energy resolution of 2.5 eV will allow us to detect about 400 such features per deg{sup 2} with a significance {>=}5{sigma} and reveals that these emission systems are typically associated with density {approx}100 above the mean. The temperature can be estimated from the line ratio with a precision of {approx}20%. The combined effect of contamination from other lines, variation in the level of the continuum, and degradation of the energy resolution reduces these estimates. Yet, with an energy resolution of 7 eV and all these effects taken into account, one still expects about 160 detections per deg{sup 2}. These line systems are sufficient for tracing the spatial distribution of the line-emitting gas, which constitute an additional information, independent from line statistics, to constrain the poorly known cosmic chemical enrichment history and the stellar feedback processes.

Takei, Y.; Mitsuda, K. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Ursino, E.; Branchini, E. [Dipartimento di Fisica, Universita degli Studi 'Roma Tre' via della Vasca Navale 84, I-00146 Roma (Italy); Ohashi, T.; Kawahara, H. [Department of Physics, School of Science, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397 (Japan); Piro, L.; Corsi, A. [INAF-Istituto di Astrofisica Spaziale Fisica Cosmica, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Amati, L. [INAF-Istituto di Astrofisica Spaziale e Fisica Cosmica Bologna, via P. Gobetti 101, I-40129 Bologna (Italy); Den Herder, J. W.; Kaastra, J. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht (Netherlands); Galeazzi, M. [Physics Department of University of Miami, 319 Knight Physics Building, Coral Gables, FL 33164 (United States); Moscardini, L.; Roncarelli, M. [Dipartimento di Astronomia, Universita di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Nicastro, F. [INAF-Osservatorio Astronomico di Roma, via Frascati 33, I00040 Monteporzio-Catone (RM) (Italy); Paerels, F. [Columbia Astrophysics Laboratory and Department of Astronomy, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Viel, M., E-mail: takei@astro.isas.jaxa.jp [INAF-Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste (Italy)

2011-06-20

392

High-resolution X-ray spectra of solar flares. III - General spectral properties of X1-X5 type flares  

NASA Technical Reports Server (NTRS)

High-resolution X-ray spectra of six class X1-X5 solar flares are discussed. The spectra were recorded by spaceborne Bragg crystal spectrometers in the ranges 1.82-1.97, 2.98-3.07 and 3.14-3.24 A. Electron temperatures derived from dielectronic satellite line to resonance line ratios for Fe XXV and Ca XIX are found to remain fairly constant around 22,000,000 and 16,000,000 K respectively during the rise phase of the flares, then decrease by approximately 6,000,000 K during the decay phase. Nonthermal motions derived from line widths for the April 27, 1979 event are found to be greatest during the rise phase (approximately 130 km/sec) and decrease to about 60 km/sec during decay. Volume emission measures for Fe XXV, Ca XIX and Ca XX are derived from photon fluxes as a function of temperature, and examination of the intensity behavior of the Fe K alpha emission as a function of time indicates that it is a result of fluorescence. Differences between the present and previous observations of temperature variation are discussed, and it is concluded that the flare plasmas are close to ionization equilibrium for the flares investigated.

Doschek, G. A.; Feldman, U.; Kreplin, R. W.; Cohen, L.

1980-01-01

393

SUZAKU OBSERVATION OF STRONG FLUORESCENT IRON LINE EMISSION FROM THE YOUNG STELLAR OBJECT V1647 ORI DURING ITS NEW X-RAY OUTBURST  

SciTech Connect

The Suzaku X-ray satellite observed the young stellar object (YSO) V1647 Ori on 2008 October 8 during the new mass accretion outburst reported in 2008 August. During the 87 ks observation with a net exposure of 40 ks, V1647 Ori showed a high level of X-ray emission with a gradual decrease in flux by a factor of 5 and then displayed an abrupt flux increase by an order of magnitude. Such enhanced X-ray variability was also seen in XMM-Newton observations in 2004 and 2005 during the 2003-2005 outburst, but has rarely been observed for other YSOs. The spectrum clearly displays emission from Helium-like iron, which is a signature of hot plasma (kT {approx} 5 keV). It also shows a fluorescent iron K{alpha} line with a remarkably large equivalent width (EW) of {approx}600 eV. Such a large EW suggests that a part of the incident X-ray emission that irradiates the circumstellar material and/or the stellar surface is hidden from our line of sight. XMM-Newton spectra during the 2003-2005 outburst did not show a strong fluorescent iron K{alpha} line, so that the structure of the circumstellar gas very close to the stellar core that absorbs and re-emits X-ray emission from the central object may have changed in between 2005 and 2008. This phenomenon may be related to changes in the infrared morphology of McNeil's nebula between 2004 and 2008.

Hamaguchi, Kenji [CRESST and X-ray Astrophysics Laboratory NASA/GSFC, Greenbelt, MD 20771 (United States); Grosso, Nicolas [Universite de Strasbourg, Observatoire Astronomique de Strasbourg, 11 rue de l'universite, 67000 Strasbourg (France); Kastner, Joel H.; Richmond, Michael [Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Weintraub, David A. [Vanderbilt University, Nashville, TN 37235 (United States)], E-mail: Kenji.Hamaguchi@nasa.gov

2010-05-01

394

The effect of high temperatures on the mid-to-far-infrared emission and near-infrared reflectance spectra of phyllosilicates and natural zeolites: Implications for martian exploration  

NASA Astrophysics Data System (ADS)

Most phyllosilicates on Mars appear to be associated with ancient terrains. As such, they may have experienced shock heating produced by impacts and could have been significantly altered or melted. We characterized the effects of high temperatures on the mid-to-far-infrared (mid-to-far-IR) emission (100-1400 cm-1; 7.1-100 ?m) and near-infrared (NIR) reflectance (1.2-2.5 ?m) spectra of phyllosilicates by measuring experimentally calcined (100-900 C) phyllosilicates and also two zeolites. Correlated differential scanning calorimetry (DSC) measurements were also performed on each sample to provide insight into the thermal activities of the phyllosilicates and natural zeolites. Our results indicate that all phyllosilicates exhibit characteristic degradations in both NIR and mid-to-far-IR spectral properties between 400 and 800 C, mainly attributable to the dehydroxylation and recrystallization processes as temperature increases. Spectral features of natural zeolites persist to higher temperatures compared to features of phyllosilicates during heating treatments. The thermal behaviors of phyllosilicate infrared (IR) properties are greatly influenced by the compositions of the octahedral cations: (1) changes in both the NIR and mid-to-far-IR spectra of phyllosilicates tend to occur at lower temperatures (300-400 C) in the Fe3+-rich samples as compared to the Al3+-rich types (400-600 C); (2) Mg2+-trioctahedral phyllosilicates hectorite, saponite, and sepiolite all display major mid-to-far-IR spectral changes at 700 C, corresponding to the formation of enstatite; (3) phyllosilicates that have minor replacement of Mg2+ for Al3+ in octahedral positions (e.g. cheto-type montmorillonite and palygorskite) show an absorption band at 920 cm-1 that becomes strong at 900 C. Inconsistency between spectral behaviors in the mid-to-far-IR and NIR regions is also discussed for phyllosilicates. Results from this study have provided suggestive evidence for the scenario that some phyllosilicates could lose all original spectral features in mid-to-far-IR region while maintaining their characteristic hydration bands in NIR region in the same temperature range.

Che, Congcong; Glotch, Timothy D.

2012-03-01

395

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

396

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

397

Auroral Colors and Spectra  

NSDL National Science Digital Library

This site, co-produced by the NCAR High Altitude Observatory and the COMET Program, provides an explanation of how auroral colors are produced. The emission of specific colors of light is discussed in relation to oxygen and nitrogen emission spectra. Numerous images, graphs, and a video of an aurora are included. The site is part of "Physics of the Aurora: Earth Systems," an interactive learning module about the aurora.

2007-01-26

398

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

399

Characterization of bound parts of the b30u+(53P1), c 31 u(5 3P2) and X10g+ states of Cd 2 revisited: Bound-bound excitation and dispersed emission spectra  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence excitation and dispersed emission spectra of Cd 2 recorded using the c31(53P2)?X10g+ and b30u+(53P1)?X10g+ transitions, respectively are reported. In the excitation to the c 31 u state, red-shaded vibrational components of several ?' ? ?? = 0, 1, 2, 3 progressions and ? ? = 0,1 sequences were identified. In the emission from the b30u+ state, well resolved ?' = 0,1,2,3,4 ? ?? transitions were recorded using a spectrograph with CCD camera. Analyses of the spectra provided an improved characterization of the b30u+, c 31 u and X10g+ states involved in the transitions. The results were compared with our ab initio calculations and those obtained experimentally in earlier studies.

M.; | M., Strojecki; | P., Kro?nicki; | J., Zgoda; Koperski

2010-04-01

400

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

401

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

402

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

403

Ab initio potential energy surfaces for both the ground (X (1)A') and excited (A (1)A") electronic states of HGeCl and the absorption and emission spectra of HGeCl/DGeCl.  

PubMed

Potential energy surfaces for the ground (X (1)A(')) and excited (A (1)A(")) electronic states of HGeCl and the transition dipole moment surface were obtained using an internally contracted multireference configuration interaction method with the Davidson correction and an augmented correlation-consistent polarized valence quadruple zeta basis set. Calculated vibrational energy levels of HGeCl and DGeCl on both the ground and excited electronic states are in excellent agreement with available experimental data. In addition, the absorption and emission spectra of both HGeCl and DGeCl were obtained using an efficient single Lanczos propagation method and the agreement with experimental spectra is also excellent. PMID:19045199

Lin, Sen; Xie, Daiqian; Guo, Hua

2008-10-21

404

Observation of ionization shifts in K-shell emission from short-pulse laser irradiated micro-dot targets  

NASA Astrophysics Data System (ADS)

X-ray Thomson scattering using short pulse laser generated intense line radiation has a great potential as a time-resolved temperature and density diagnostic for high-energy density states of matter. We present recent results characterizing Chlorine K-alpha and K-beta line emission obtained by irradiating Saran foil with 50 Terawatt laser pulses from the Callisto laser (Jupiter Laser Facility, Lawrence Livermore National Laboratory). Spectra from front and rear side emission are recorded simultaneously with high resolution HOPG spectrometers employing imaging plate detectors. Conversion efficiencies of laser pulse energy into x-ray line emission of several 10-5 are achieved and are maintained throughout up to 7 J of laser energy, thus constituting a short pulsed narrow band x-ray source of more than 10^11 photons. When the target size is reduced to 50 micrometer (``micro-dot'') a significant blue-shift of up to 5 eV is clearly observed. This can be attributed to higher ionization states of the target atoms indicating achievement of a high-temperature solid density state. This work was performed under the auspices of the U.S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48 and LDRD 05-ERI-003.

Neumayer, Paul; Kritcher, Andrea; Landen, Otto; Lee, Haeja; Offerman, Dustin; Shipton, Eric; Glenzer, Siegfried

2006-10-01

405

Ab initio simulation of photoemission spectroscopy in solids: Plane-wave pseudopotential approach with applications to normal-emission spectra of Cu(001) and Cu(111)  

Microsoft Academic Search

We develop a method for simulating photoemission spectra from bulk crystals in the ultraviolet energy range within a three-step model. Our method explicitly accounts for transmission and matrix-element effects, as calculated from state-of-the-art plane-wave pseudopotential techniques within the density-functional theory. Transmission effects, in particular, are included by extending to the present problem a technique previously employed with success to deal

Natasa Stojic; Andrea Dal Corso; Bo Zhou; Stefano Baroni

2008-01-01

406

PAH Spectra for Everyone  

NASA Astrophysics Data System (ADS)

The Ames Astrochemistry Laboratory now has PAH IR spectra of more than 220 laboratory measured and over 600 theoretically calculated IR spectra of polycyclic aromatic hydrocarbons (PAHs) in a multitude of forms. The vast majority of these spectra are not readily accessible to the public. We propose to make the full collection of the Ames experimental and computational collection of PAH IR spectra available to the entire Spitzer community and accessible via the World Wide Web (WWW). The laboratory measured mid-IR spectral collection includes over 220 neutral, cationic, and anionic PAHs, PAHs with deuterium in place of hydrogen, PAHs containing oxygen, and PAHs containing nitrogen (PANHs). The formulae of the PAHs in the experimental data collection range from C10H8 to C50H22. Unfortunately, it is not possible to obtain physical samples of all of the types of PAHs that are of astrophysical interest for experimental study. We also have an extensive collection of accurate computational spectra to fill in gaps in the experimentally available spectra. Our theoretical PAH spectral collection includes very large PAHs, PAHs containing 40 to 132 carbon atoms which are comparable to the size of the PAHs thought to dominate the interstellar emission spectrum. Large PAHs might be multiply charged and these are also represented in the theoretical database. There is also observational evidence for PAH cations with nitrogen in the inner rings (PANHs) and interest in the spectroscopy of aromatic species containing oxygen and deuterium as well as PAH metal clusters. All of these types of PAHs are represented in the Ames computational PAH IR spectroscopic collection. If funded, we plan to make our entire inventory of the lab spectra available to the Spitzer community within the next two years.

Allamandola, Louis; Bauschlicher, Charlie, Jr.; Mattioda, Andrew

2007-05-01

407

An investigation of FeXVI emission lines in solar and stellar extreme-ultraviolet and soft X-ray spectra  

NASA Astrophysics Data System (ADS)

New fully relativistic calculations of radiative rates and electron impact excitation cross-sections for FeXVI are used to determine theoretical emission-line ratios applicable to the 251-361 and 32-77 portions of the extreme-ultraviolet (EUV) and soft X-ray spectral regions, respectively. A comparison of the EUV results with observations from the Solar Extreme-Ultraviolet Research Telescope and Spectrograph (SERTS) reveals excellent agreement between theory and experiment. However, for emission lines in the 32-49 portion of the soft X-ray spectral region, there are large discrepancies between theory and measurement for both a solar flare spectrum obtained with the X-Ray Spectrometer/Spectrograph Telescope (XSST) and for observations of Capella from the Low-Energy Transmission Grating Spectrometer (LETGS) on the Chandra X-ray Observatory. These are probably due to blending in the solar flare and Capella data from both first-order lines and from shorter wavelength transitions detected in second and third order. By contrast, there is very good agreement between our theoretical results and the XSST and LETGS observations in the 50-77 wavelength range, contrary to previous results. In particular, there is no evidence that the FeXVI emission from the XSST flare arises from plasma at a much higher temperature than that expected for FeXVI in ionization equilibrium, as suggested by earlier work.

Keenan, F. P.; Drake, J. J.; Aggarwal, K. M.

2007-11-01

408

Time-Resolved keV Emission Spectra from Hot, Dense Buried Layer K-Shell and L-Shell Targets  

NASA Astrophysics Data System (ADS)

We report new time-resolved measurements for 50 nm thick Al and Ge buried layer targets. The top-coat thickness of carbon is varied between 0 and 100 nm. A single beam of the Compact Multipulse Terawatt (COMET) laser is frequency doubled, at 527 nm wavelength, up to 1 J energy in a 500 fs (FWHM) pulse and focused to a maximum of 7 x 1017 W cm-2 with an off-axis parabola. An RbAP (001) von Hamos curved crystal spectrometer with an 500 fs x-ray streak camera is fielded to measure the time history of the Al n = 2 - 1 K-shell emission and the Ge n = 3 - 2 L-shell emission in the 7 - 10 waveband. The main objective is to generate and study hot, Te ~ 100 - 200 eV, dense, ne ~ 1023 cm-3, thermal plasmas in tamped optically thin targets under a range of laser irradiance conditions. We observe short-lived emission lasting a few picoseconds and indications of cooler, denser plasmas with increasing thickness of the tamping carbon layers.

Dunn, J.; Widmann, K.; Shepherd, R.; Booth, R.; Fournier, K. B.; Eng, C. D.; Hansen, B. B.

409

Spectra of Irradiated Giant Planets  

Microsoft Academic Search

As many as 101 extrasolar giant planets (EGPs) have been detected by radial-velocity techniques, but none has been detected directly by its own emission or by reflection of the light from its parent star. We review the current state-of-the-art in the theoretical modeling of the spectra of giant planets outside the solar system and the basic theory of EGP spectra

Adam Burrows; David Sudarsky

2002-01-01

410

Fluorescence Spectra  

NSDL National Science Digital Library

This experiment uses the Tracker video analysis and modeling tool to explore the phenomenon of fluorescence and its application in fluorescent lamps. For each of five different visible spectra, students (a) observe the spectrum directly, (b) measure its brightness versus wavelength in Tracker, and (c) answer both qualitative and quantitative questions about it. The spectra include a fluorescent dye with laser and UV illumination, a mercury lamp and two fluorescent lamps, all with red and green laser spots added for easy calibration. For more information, see the AAPT presentation. The zip file includes the lab instructions, spectrum images and Tracker data files. This requires Tracker version 4.62 or higher. Tracker installers are available for Windows, Mac and Linux from ComPADRE or the Tracker web site (http://www.cabrillo.edu/~dbrown/tracker/).

Brown, Douglas

2012-01-17

411

Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: Explicit treatment of the vibronic transitions  

NASA Astrophysics Data System (ADS)

Here, we extend a recently introduced theoretical-computational procedure [M. D'Alessandro, M. Aschi, C. Mazzuca, A. Palleschi, and A. Amadei, J. Chem. Phys. 139, 114102 (2013)] to include quantum vibrational transitions in modelling electronic spectra of atomic molecular systems in condensed phase. The method is based on the combination of Molecular Dynamics simulations and quantum chemical calculations within the Perturbed Matrix Method approach. The main aim of the presented approach is to reproduce as much as possible the spectral line shape which results from a subtle combination of environmental and intrinsic (chromophore) mechanical-dynamical features. As a case study, we were able to model the low energy UV-vis transitions of pyrene in liquid acetonitrile in good agreement with the experimental data.

D'Abramo, Marco; Aschi, Massimiliano; Amadei, Andrea

2014-04-01

412

Theoretical modeling of UV-Vis absorption and emission spectra in liquid state systems including vibrational and conformational effects: Explicit treatment of the vibronic transitions.  

PubMed

Here, we extend a recently introduced theoretical-computational procedure [M. D'Alessandro, M. Aschi, C. Mazzuca, A. Palleschi, and A. Amadei, J. Chem. Phys. 139, 114102 (2013)] to include quantum vibrational transitions in modelling electronic spectra of atomic molecular systems in condensed phase. The method is based on the combination of Molecular Dynamics simulations and quantum chemical calculations within the Perturbed Matrix Method approach. The main aim of the presented approach is to reproduce as much as possible the spectral line shape which results from a subtle combination of environmental and intrinsic (chromophore) mechanical-dynamical features. As a case study, we were able to model the low energy UV-vis transitions of pyrene in liquid acetonitrile in good agreement with the experimental data. PMID:24784250

D'Abramo, Marco; Aschi, Massimiliano; Amadei, Andrea

2014-04-28

413