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1

Relativistic iron K alpha line detection in the Suzaku spectra of IC4329a  

NASA Astrophysics Data System (ADS)

Broad iron lines are expected, and observed, to be a widespread feature in bright AGN. Still unclear is why some AGN miss a disk line component and if, as expected, the Fe K? emission is varying in a correlated way with the associated hard X-ray reflection continuum. We investigated the hypothesis of an always present broad line emitted close to the black hole and rendered indistinguishable from the continuum by relativistic effects. We also looked at a direct correlation of this component with the emission at higher energies. I will present the analysis of Suzaku observations of the bright Seyfert1 galaxy, IC4329a. The broad energy band of Suzaku allows us to constrain the continuum and better fit the Iron K? feature. A resolved peak at 6.4 keV consistent with neutral material is detected. The analysis of the spectra with a physical and self-consistent model reveals also the presence of a broad Iron K? line. This component is consistent with being produced in the inner part of the accretion disk and to be highly blurred by gravitational redshift and Doppler effects. We also detected a narrow Fe XXVI emission line peaking at 6.94 keV, consistent with being produced by distant material.

Mantovani, G.; Nandra, K.; Ponti, G.

2014-07-01

2

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

SciTech Connect

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

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

2010-07-15

3

Site determination of oxygen in B sub 6 O by oxygen K. alpha. x-ray-emission spectroscopy  

SciTech Connect

An electron-excited x-ray-emission spectrum of oxygen {ital K}{alpha} is presented for boron suboxide B{sub 6}O (isostructural with B{sub 13}C{sub 2}). The spectrum is compared with those calculated by the discrete-variation {ital X}{alpha} (DV-{ital X}{alpha}) method with various O-O distances as an adjustable parameter in the fixed icosahedral B{sub 12} framework. The observed spectrum is reproduced well when the O-O distance is in the range 2.5--3.5 A. This O-O bond length is more than twice as long as that of a free O{sub 2} molecule. The oxygen atom is located very close to the center of the boron triangle (closed three-center bond). These results support the structure determined by x-ray structural analysis.

Kawai, J.; Maeda, K.; Higashi, I.; Takami, M. (Inorganic Chemical Physics Laboratory, Institute of Physical and Chemical Research (RIKEN), Wako, Saitama 351-01 (Japan)); Hayasi, Y. (Department of Applied Physics, Tohoku University, Sendai 980 (Japan)); Uda, M. (Department of Materials Science and Engineering, School of Science Engineering, Waseda University, 3-4-1 Ohkubo, Shinjuku-ku, Tokyo 169 (Japan))

1990-09-15

4

Site determination of oxygen in B sub 6 O by oxygen K. alpha. x-ray-emission spectroscopy  

Microsoft Academic Search

An electron-excited x-ray-emission spectrum of oxygen {ital K}Îą is presented for boron suboxide BâO (isostructural with BââCâ). The spectrum is compared with those calculated by the discrete-variation {ital X}Îą (DV-{ital X}Îą) method with various O-O distances as an adjustable parameter in the fixed icosahedral Bââ framework. The observed spectrum is reproduced well when the O-O distance is in the range

J. Kawai; K. Maeda; I. Higashi; M. Takami; Y. Hayasi; M. Uda

1990-01-01

5

Elemental Absorption and Emission Spectra  

NSDL National Science Digital Library

This applet displays the periodic table of elements. Clicking on an element will show its line spectrum (as a neutral species). Both absorption and emission spectra can be observed. The cursor can be used to measure the wavelengths.

6

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

7

K{alpha} satellite transitions in elements with 12{<=}Z{<=}30 produced by electron incidence  

SciTech Connect

The emission of x-ray satellite lines in the K{alpha} region of Mg, Si, Sc, Ti, Cr, Fe, Ni, and Zn induced by electron incidence was studied by means of wavelength dispersive spectroscopy. The satellite lines studied were K{alpha}{sup '}, K{alpha}{sub 3}, K{alpha}{sub 4}, K{alpha}{sub 5}, K{alpha}{sub 6}, and two transitions denoted here as K{alpha}{sub 22} and K{alpha}{sub 12}. Energy shifts with respect to the main K{alpha}{sub 1} diagram line and transition probabilities relative to the whole K{alpha} group were determined for a number of lines through a careful spectral processing. The dependence of these parameters, as well as of the K{beta}:K{alpha} intensity ratio, on the atomic number was compared with previous experimental and theoretical determinations when available. A discussion about the different mechanisms responsible for vacancy creation involved in the production of double-ionization satellites was performed in the light of the results obtained. Finally, the behavior of the satellite intensities as a function of the incidence energy was discussed for silicon.

Limandri, Silvina P.; Carreras, Alejo C.; Trincavelli, Jorge C. [Instituto de Fisica Enrique Gaviola, Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Facultad de Matematica, Astronomia y Fisica, Universidad Nacional de Cordoba, Cordoba (Argentina); Bonetto, Rita D. [Centro de Investigacion y Desarrollo en Ciencias Aplicadas Dr. Jorge Ronco (CINDECA), Consejo Nacional de Investigaciones Cientificas y Tecnicas (Argentina); Facultad de Ciencias Exactas, Facultad de Ingenieria, Universidad Nacional de La Plata, La Plata (Argentina)

2010-09-15

8

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

9

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

10

X-ray emission in heavy-ion collisons  

Microsoft Academic Search

Results from several investigations of the X-ray emission in heavy-ion collisions are presented. Areas covered include; spectra of K alpha X-rays from 64 MeV sulfur ions traveling in solids; foil-excited K alpha X-ray transitions in few-electron sulfur ions; high resolution study of the target thickness dependence of X-ray emmision from 65 MeV sulfur ions; dynamic screening of highly stripped sulfur

R. L. Watson

1980-01-01

11

Retrieval of constituent mixing ratios from limb thermal emission spectra  

NASA Technical Reports Server (NTRS)

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.

1988-01-01

12

Extreme ultraviolet emission spectra of Gd and Tb ions  

SciTech Connect

Theoretical extreme ultraviolet emission spectra of gadolinium and terbium ions calculated with the Cowan suite of codes and the flexible atomic code (FAC) relativistic code are presented. 4d-4f and 4p-4d transitions give rise to unresolved transition arrays in a range of ions. The effects of configuration interaction are investigated for transitions between singly excited configurations. Optimization of emission at 6.775 nm and 6.515 nm is achieved for Gd and Tb ions, respectively, by consideration of plasma effects. The resulting synthetic spectra are compared with experimental spectra recorded using the laser produced plasma technique.

Kilbane, D.; O'Sullivan, G. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)

2010-11-15

13

Synthesized Spectra of Optically Thin Emission Lines  

NASA Astrophysics Data System (ADS)

In recent years realistic 3D numerical models of the solar atmosphere have become available. The models attempt to recreate the solar atmosphere and mimic observations in the best way, in order to make it possible to couple complicated observations with physical properties such as the temperatures, densities, velocities, and magnetic fields. We here present a study of synthetic spectra created using the Bifrost code in order to assess how well they fit with previously taken solar data. A study of the synthetic intensity, nonthermal line widths, Doppler shifts, and correlations between any two of these three components of the spectra first assuming statistical equilibrium is made, followed by a report on some of the effects nonequilibrium ionization will have on the synthesized spectra. We find that the synthetic intensities compare well with the observations. The synthetic observations depend on the assumed resolution and point-spread function (PSF) of the instrument, and we find a large effect on the results, especially for intensity and nonthermal line width. The Doppler shifts produce the reported persistent redshifts for the transition region (TR) lines and blueshifts for the upper TR and corona lines. The nonthermal line widths reproduce the well-known turnoff point around (2-3) × 105 K, but with much lower values than those observed. The nonthermal line widths tend to increase with decreasing assumed instrumental resolution, also when nonequilibrium ionization is included. Correlations between the nonthermal line width of any two TR line studies as reported by Chae et al. are reproduced, while the correlations of intensity to line width are reproduced only after applying a PSF to the data. Doppler shift correlations reported by Doschek for the TR lines and correlations of Doppler shift to nonthermal line width of the Fe xii19.5 line reported by Doschek et al. are reproduced.

Olluri, K.; Gudiksen, B. V.; Hansteen, V. H.; De Pontieu, B.

2015-03-01

14

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

SciTech Connect

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

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

2002-01-01

15

Spreadsheet-Based Program for Simulating Atomic Emission Spectra  

ERIC Educational Resources Information Center

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

Flannigan, David J.

2014-01-01

16

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

17

A Correlation Between Stellar Activity and Hot Jupiter Emission Spectra  

NASA Astrophysics Data System (ADS)

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 & 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 ? 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 ?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. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time has been granted by both NASA and the University of California.

Knutson, Heather A.; Howard, Andrew W.; Isaacson, Howard

2010-09-01

18

Stratospheric HBr mixing ratio obtained from far infrared emission spectra  

SciTech Connect

Emission features of HBr isotopes have been identified in high-resolution far-infrared emission spectra obtained with a balloon-born Fourier transform spectrometer in the spring of 1979 at 32{degree}N latitude. When six single-scan spectra at a zenith angle of 93.2{degree} were averaged, two features of HBr isotopes at 50.054 and 50.069 cm{sup {minus}1} were obtained with a signal-to-noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 {times} 10{sub {minus}11}, which is assumed to be constant above 28 km, with an uncertainty of 35%. 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. (NASA Langley Research Center, Hampton, VA (USA)); Carli, B. (Instituto Ricerca Onde Electromagnetiche, CNR, Firenze (Italy)); Barbis, A. (Universita di Firenze (Italy))

1989-08-01

19

K-alpha conversion efficiency measurments for x-ray scattering in inertial confinement fusion plasmas  

SciTech Connect

The conversion efficiency of ultra short-pulse laser radiation to K-{alpha} x-rays has been measured for various chlorine-containing targets to be used as x-ray scattering probes of dense plasmas. The spectral and temporal properties of these sources will allow spectrally-resolved x-ray scattering probing with picosecond temporal resolution required for measuring the plasma conditions in inertial confinement fusion experiments. Simulations of x-ray scattering spectra from these plasmas show that fuel capsule density, capsule ablator density, and shock timing information may be inferred.

Kritcher, A L; Neumayer, P; Urry, M K; Robey, H; Niemann, C; Landen, O L; Morse, E; Glenzer, S H

2006-11-21

20

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

21

Investigation of the Emission and Absorption Spectra of Water Vapor  

NASA Astrophysics Data System (ADS)

Emission and absorption spectra of water vapor are measured and analyzed for temperatures 350-2500 K in the spectral range 0.57-25 ?m. Based on the developed mathematical model of radiative transfer, the parameters of spectral transmission functions of N2O vapors are obtained at different temperatures. Practical application of the obtained radiative characteristics is considered for solving problems of radiative heat exchange in high-temperature media and designing optoelectronic systems intended for monitoring of aero carriers.

Moskalenko, N. I.; Il'in, Yu. A.; Sadykov, M. S.

2015-01-01

22

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

23

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

24

Neon Line Emission Observed in Keck/HIRES Sky Spectra  

NASA Astrophysics Data System (ADS)

Over the last three years, detailed studies of the sky spectra from the W. M. Keck (I) 10-meter telescope and the HIRES echelle spectrometer have been carried out. Many atomic and molecular emissions have been observed in the nightglow for the first time. For O2 in particular, an entire new range of molecular bands in the Atmospheric Band system has been found, following initial identifications by D.E. Osterbrock and collaborators. At the beginning co-added spectra were used, so as to optimize the identification of weak spectral features [Osterbrock et al. PASP, 110, 1499 (1998)]. We are now using individual 50-minute spectra, making it possible to use time as a variable. Of spectral lines normally associated with light pollution, by far the most prominent in Keck/HIRES sky spectra are those of neon, of which 36 have so far been identified, in the spectral range 5800-8100 Ĺ. They exhibit a great deal of variability with time, but during a given night the variation is not random. At the most intense the summed intensity of the neon lines is on the order of 30 rayleighs (R), with the strong 5852 Ĺ line having an intensity of ~ 2 R. At other times, the 5852 Ĺ line is weaker by a factor of 50. The mercury line at 5461 Ĺ is typically weaker than the Ne [5852] line, and at its maximum does not exceed 1 R. Particularly noteworthy is the fact that the neon and mercury lines are not correlated in time, as would be expected if they originate with a city source. Urban mercury radiation normally outshines that from neon by two orders of magnitude (cf. Lick Observatory observations). The highest neon intensities are observed when the telescope is pointed in a southerly direction, and no significant neon emission is observed at the azimuth of the closest city, Hilo. Approximately one-hundred 50-minute sky spectra, taken in 1993-1997, have been evaluated for this study. Continuing analysis reveals that argon and xenon lines also appear in some spectra; noteworthy is the fact that emission from the three atoms is uncorrelated in time. This work has been supported by the NSF Aeronomy program.

Cosby, P. C.; Huestis, D. L.; Slanger, T. G.

2000-12-01

25

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

PubMed Central

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

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

2009-01-01

26

Helium shells and faint emission lines from slitless flash spectra.  

PubMed

At the time of the two last solar total eclipses of August 1st, 2008 in Siberia and July 11th, 2010 in French Polynesia, high frame rate CCD flash spectra were obtained. These eclipses occurred in quiet Sun period and after. The slitless flash spectra show two helium shells, in the weak Paschen ? 4686 Ĺ line of the ionized helium HeII and in the neutral helium HeI line at 4713 Ĺ. The extensions of these helium shells are typically 3 Mm. In prominences, the extension of the interface with the corona is much more extended. The observations and analysis of these lines can properly be done only in eclipse conditions, when the intensity threshold reaches the coronal level, and the parasitic scattered light is virtually zero. Under the layers of 1 Mm above the limb, many faint low FIP lines were also seen in emission. These emission lines are superposed on the continuum containing absorption lines. The solar limb can be defined using the weak continuum appearing between the emission lines at the time of the second and third contact. The variations of the singly ionized iron line, the HeI and HeII lines and the continuum intensity are analyzed. The intensity ratio of ionized to neutral helium is studied for evaluating the ionization rate in low layers up to 2 Mm and also around a prominence. PMID:25685435

Bazin, Cyril; Koutchmy, Serge

2013-05-01

27

Helium shells and faint emission lines from slitless flash spectra  

PubMed Central

At the time of the two last solar total eclipses of August 1st, 2008 in Siberia and July 11th, 2010 in French Polynesia, high frame rate CCD flash spectra were obtained. These eclipses occurred in quiet Sun period and after. The slitless flash spectra show two helium shells, in the weak Paschen ? 4686 Ĺ line of the ionized helium HeII and in the neutral helium HeI line at 4713 Ĺ. The extensions of these helium shells are typically 3 Mm. In prominences, the extension of the interface with the corona is much more extended. The observations and analysis of these lines can properly be done only in eclipse conditions, when the intensity threshold reaches the coronal level, and the parasitic scattered light is virtually zero. Under the layers of 1 Mm above the limb, many faint low FIP lines were also seen in emission. These emission lines are superposed on the continuum containing absorption lines. The solar limb can be defined using the weak continuum appearing between the emission lines at the time of the second and third contact. The variations of the singly ionized iron line, the HeI and HeII lines and the continuum intensity are analyzed. The intensity ratio of ionized to neutral helium is studied for evaluating the ionization rate in low layers up to 2 Mm and also around a prominence. PMID:25685435

Bazin, Cyril; Koutchmy, Serge

2013-01-01

28

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

29

Emissivity spectra estimated with the MaxEnTES algorithm  

NASA Astrophysics Data System (ADS)

Temperature and Emissivity Separation (TES) applied to multispectral or hyperspectral Thermal Infrared (TIR) images of the Earth is a relevant issue for many remote sensing applications. The TIR spectral radiance can be modeled by means of the well-known Planck's law, as a function of the target temperature and emissivity. The estimation of these target's parameters (i.e. the Temperature Emissivity Separation, aka TES) is hindered by the circumstance that the number of measurements is less than the unknown number. Existing TES algorithms implement a temperature estimator in which the uncertainty is removed by adopting some a priori assumption that conditions the retrieved temperature and emissivity. Due to its mathematical structure, the Maximum Entropy formalism (MaxEnt) seems to be well suited for carrying out this complex TES operation. The main advantage of the MaxEnt statistical inference is the absence of any external hypothesis, which is instead characterizes most of the existing the TES algorithms. In this paper we describe the performance of the MaxEnTES (Maximum Entropy Temperature Emissivity Separation) algorithm as applied to ten TIR spectral channels of a MIVIS dataset collected over Italy. We compare the temperature and emissivity spectra estimated by this algorithm with independent estimations achieved with two previous TES methods (the Grey Body Emissivity (GBE), and the Model Emittance Calculation (MEC)). We show that MaxEnTES is a reliable algorithm in terms of its higher output Signal-to-Noise Ratio and the negligibility of systematic errors that bias the estimated temperature in other TES procedures.

Barducci, A.; Guzzi, D.; Lastri, C.; Nardino, V.; Pippi, I.; Raimondi, V.

2014-10-01

30

Fourier Transform Infrared Emission Spectra of MgF_2  

NASA Astrophysics Data System (ADS)

High resolution infrared emission spectra of hot MgF2 in the 700 to 1300 cm-1 region have been recorded. The molecules were generated by heating solid MgF2 to 1675 °C. Four vibrational bands were rotationally analyzed yielding band origins and rotational constants. Observed bands are: 001-000 (?u+ - ?g+), 0111 - 0110 (?g - ?u), 0221 (f parity) - 0220 (f parity) (?u - ?g), and 0331 - 0330 (?g - ?u). High level ab initio calculations were essential in making assignments and in helping to fit the data. The ?u - ?g band was only observed for f-parity because the e-parity is significantly perturbed by l-resonance.

Frohman, Daniel J.; Bernath, Peter F.; Koput, Jacek

2014-06-01

31

Interpreting the ionization sequence in AGN emission-line spectra  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

32

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

33

PUBLISHED VERSION Neutron emission profiles and energy spectra measurements at JET  

E-print Network

.1063/1.35052 Nuclear Emulsions and the Measurement of Low Energy Neutron Spectra Rev. Sci. Instrum. 21, 534 (1950); 10PUBLISHED VERSION Neutron emission profiles and energy spectra measurements at JET Giacomelli L be found at : http://dx.doi.org/10.1063/1.4894035 #12;Neutron emission profiles and energy spectra

34

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

E-print Network

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

Piana, Michele

35

Neutron emission profiles and energy spectra measurements at JET  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

36

Neutron emission profiles and energy spectra measurements at JET  

SciTech Connect

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

Giacomelli, L. [JET-EFDA, Culham Science Centre, Abingdon, 0X14 3DB, United Kingdom and Department of Physics, Universitŕ degli Studi di Milano-Bicocca, Milano (Italy); Conroy, S. [JET-EFDA, Culham Science Centre, Abingdon, 0X14 3DB, United Kingdom and Department of Physics and Astronomy, Uppsala University, Uppsala (Sweden); Belli, F.; Riva, M. [Associazione EURATOM-ENEA sulla Fusione, Roma (Italy); Gorini, G. [Department of Physics, Universitŕ degli Studi di Milano-Bicocca, Milano, Italy and Istituto di Física del Plasma Piero Caldirola, Milan (Italy); Horton, L.; Joffrin, E.; Lerche, E.; Murari, A.; Popovichev, S.; Syme, B. [JET-EFDA, Culham Science Centre, Abingdon, 0X14 3DB (United Kingdom); Collaboration: JET EFDA Contributors

2014-08-21

37

Emission spectra of an argon inductively coupled plasma in the vacuum ultraviolet: background spectra from 85 to 200 nm  

NASA Astrophysics Data System (ADS)

The background spectra emitted from an argon ICP discharge have been recorded over the spectral range 85 to 200 nm. These vacuum ultraviolet spectra were acquired by coupling the ICP to a 0.5-m Seya-Namioka vacuum monochromator, through a helium purged side-arm. Background features observed include emission from the resonance lines of ArI, and emission from gas impurities such as oxygen, nitrogen, carbon and hydrogen.

Carr, J. W.; Blades, M. W.

38

Fluorescence Emission and Excitation Spectra of Photo-Fragmented Nitrobenzene.  

NASA Astrophysics Data System (ADS)

Upon absorption of a UV photon, nitrobenzene readily dissociates into C_6H_5, NO_2, C_6H_5NO, O, C_6H_5O, and NO through three different channels. We have recorded high resolution emission and excitation spectra of the NO resulting from photo-fragmented nitrobenzene using a pulsed picosecond tunable laser and a nanosecond dye laser. Specifically, the lasers probed the A^2?^+? X^2?(1/2,3/2) NO band system between 225-260 nm using an one or two color process. In a one color process, the same energy (wavelength) photon is used to dissociate nitrobenzene and excite NO. In a two color process, photons of a particular energy are used to dissociate the nitrobenzene while photons of a different energy are used to probe the resultant NO. We have determined the rotational and vibrational temperatures of the nascent NO. And, we have examined the effect of the relative timing of the two photons on the fluorescence spectra to extract information about the photodissociation dynamics. Lin, M.-F.; Lee, Y. T.; Ni, C.-K.; Xu, S. and Lin, M. C. J. Chem. Phys., AIP, 2007, 126.

Lue, Christopher J.; Tanjaroon, Chakree; Johnson, J. Bruce; Allen, Susan D.; Reeve, Scott W.

2012-06-01

39

A K alpha dual energy x-ray source for coronary angiography.  

PubMed

The use of characteristic-line radiation from rare-earth targets bombarded by high-energy (up to 1 MeV) electron beams has been evaluated as an x-ray source for dual energy K-edge subtraction imaging of the human coronary arteries. Two characteristic-line x-ray sources, one using the split K alpha 1 and K alpha 2 lines of lanthanum excited by a high-energy electron beam and the other using the K alpha lines of barium and cerium, were studied. A Monte Carlo electron-photon simulation was used to calculate x-ray spectra and energy deposition profiles from targets of these elements bombarded by electrons in the energy range 140 keV to 1 MeV. A general dual-energy imaging model was developed that used these calculated source spectra to numerically investigate the dependence of the subtraction image signal-to-noise ratio on such factors as the ratio of K-line to x-ray continuum yield, continuum spectral shape, x-ray filtering, and detector response. A signal averaging technique for enhancing the signal-to-noise ratio was also evaluated. The results of these calculations were used to identify an optimum electron beam, target, filter, and detector configuration. A compact electron accelerator capable of providing the required electron beam parameters was designed. Calculations indicate that under ideal conditions the optimized system would be capable of imaging 2 mg/cm2 of iodine contrast agent in 20 g/cm2 of tissue with a signal-to-noise ratio of 5, a detector pixel size of 0.25 mm2, and a total image acquisition time of 10 ms. These parameters are consistent with those needed to image the human coronary arteries after an intravenous injection of iodine contrast agent. These capabilities, along with the relatively modest hardware requirements of this system, make it attractive as an x-ray source for dual energy transvenous coronary angiography. PMID:1961150

Manning, H L; Shefer, R E; Klinkowstein, R E; Mistretta, C A

1991-01-01

40

CH Hot Bands in the Near-IR Emission Spectra of the Leonids  

Microsoft Academic Search

The reported infrared (IR) emission spectra from 1999 Leonid fireballs show a 3.4mum C-H emission band and unidentified bands at longer wavelengths. Upon atmospheric entry, the Leonid meteorites were flash-heated to temperatures around 2400K, which would destroy any organics on the surface of the meteorite grains. We propose that the vcH emission hand in the Leonid emission spectra arises from

Friedemann T. Freund; John Scoville; Reimer Holm; Rudolf Seelemann; Minoru M. Freund

2002-01-01

41

Orbits and emission spectra from the 2014 Camelopardalids  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

42

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

E-print Network

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

Piana, Michele

43

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 2°C from 50°C to 320°C. Glow peaks appear at 110°C, 145°C, 235°C and 265°C. 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 145°C. 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

44

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

45

Emission spectra of a magnesium plasma created in vacuum by short laser pulses  

Microsoft Academic Search

An investigation was made of the emission spectra of a plasma formed on the surface of a magnesium barrier in a vacuum by nanosecond laser pulses of wavelengths 1.06 and 0.532 ?m. The intensity of the radiation incident on the magnesium target was (1–8)×1012 W cm-2. Photographic and photoelectric methods were used to record the emission spectra in the visible

A F Golovin

1994-01-01

46

Probing the origin of the iron K_alpha line around stellar and supermassive black holes using X-ray polarimetry  

E-print Network

Asymmetric, broad iron lines are a common feature in the X-ray spectra of both X-ray binaries (XRBs) and type-1 Active Galactic Nuclei (AGN). It was suggested that the distortion of the Fe K_alpha emission results from Doppler and relativistic effects affecting the radiative transfer close to the strong gravitational well of the central compact object: a stellar mass black hole (BH) or neutron star (NS) in the case of XRBs, or a super massive black hole (SMBH) in the case of AGN. However, alternative approaches based on reprocessing and transmission of radiation through surrounding media also attempt to explain the line broadening. So far, spectroscopic and timing analyzes have not yet convinced the whole community to discriminate between the two scenarios. Here we study to which extent X-ray polarimetric measurements of black hole X-ray binaries (BHXRBs) and type-1 AGN could help to identify the possible origin of the line distortion. To do so, we report on recent simulations obtained for the two BH flavors and show that the proposed scenarios are found to behave differently in polarization degree and polarization angle. A relativistic origin for the distortion is found to be more probable in the context of BHXRBs, supporting the idea that the same mechanism should lead the way also for AGN. We show that the discriminating polarization signal could have been detectable by several X-ray polarimetry missions proposed in the past.

Frederic Marin; Francesco Tamborra

2013-09-06

47

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

48

Laboratory technique for the measurement of thermal-emission spectra of greenhouse gases: CFC-12.  

PubMed

A new technique has been developed to make possible the laboratory study of the infrared-emission spectra of gases of atmospheric interest. The thermal-emission spectra are in local thermodynamic equilibrium, just as they are in the atmosphere, and are not chemiluminescent. Demonstration results obtained by the use of this new technique are presented for dichlorodifluoromethane (CFC-12) at a pressure of 0.5 Torr in a cell with a path length of 5 cm. The measured cell spectra have been compared with simulations with the FASCD3P radiation code. The measurements of the emission spectra of radiatively active gases may be important for the atmospheric greenhouse effect and global warming. PMID:21085268

Evans, W F; Puckrin, E

1996-03-20

49

[A new automated method to identify emission line star from massive spectra].  

PubMed

Stellar spectra are characterized by obvious absorption lines or absorption bands, while those with emission lines are usually special stars such as cataclysmic variable stars (CVs), HerbigAe/Be etc. The further study of this kind of spectra is meaningful. The present paper proposed a new method to identify emission line stars (ELS) spectra automatically. After the continuum normalization is done for the original spectral flux, line detection is made by comparing the normalized flux with the mean and standard deviation of the flux in its neighbor region The results of the experiment on massive spectra from SDSS DR8 indicate that the method can identify ELS spectra completely and accurately. Since no complex transformation and computation are involved in this method, the identifying process is fast and it is ideal for the ELS detection in large sky survey projects like LAMOST and SDSS. PMID:22870668

Pan, Jing-Chang; Zhang, Cai-Ming; Wei, Peng; Luo, A-Li; Zhao, Yong-Heng

2012-06-01

50

On the equivalent width of the Fe K$\\alpha$ line produced by a dusty absorber in active galactic nuclei  

E-print Network

Obscured AGNs provide an opportunity to study the material surrounding the central engine. Geometric and physical constraints on the absorber can be deduced from the reprocessed AGN emission. In particular, the obscuring gas may reprocess the nuclear X-ray emission producing a narrow Fe K$\\alpha$ line and a Compton reflection hump. In recent years, models of the X-ray reflection from an obscuring torus have been computed; however, although the reflecting gas may be dusty, the models do not yet take into account the effects of dust on the predicted spectrum. We study this problem by analyzing two sets of models, with and without the presence of dust, using the one dimensional photo-ionization code Cloudy. The calculations are performed for a range of column densities ($22 hydrogen densities ( $6 <{\\rm log}[n_H(\\rm cm^{-3})]< 8$). The calculations show the presence of dust can enhance the Fe K$\\alpha$ equivalent width (EW) in the reflected spectrum by factor...

Gohil, Raj

2015-01-01

51

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

NASA Technical Reports Server (NTRS)

A detailed analysis of the iron K-alpha emission spectrum covering the wavelength region from 1.840 to 1.940 A is presented. Measurements are made with a high-resolution Bragg crystal spectrometer on the Princeton Large Torus (PLT) tokamak for plasma conditions which closely resemble those of solar flares. A total of 40 features are identified, consisting of either single or multiple lines from eight charge states in iron, Fe XVIII - Fe XXV, and their wavelengths are determined with an accuracy of 0.1-0.4 mA. Many of these features are identified for the first time. In the interpretation of our observations we rely on model calculations that determine the ionic species abundances from electron density and temperature profiles measured independently with nonspectroscopic techniques and that incorporate theoretical collisional excitation and dielectronic recombination rates resulting in the excitation of the 1s2sr2ps configurations. The model calculations also include the effect of diffusive ion transport. Good overall agreement between the model calculations and the observations is obtained, which gives us confidence in our line identifications and spectral modeling capabilities. The results are compared with earlier analyses of the K-alpha emission from the Sun.

Beiersdorfer, P.; Phillips, T.; Jacobs, V. L.; Hill, K. W.; Bitter, M.; Von Goeler, S.; Kahn, S. M.

1993-01-01

52

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

53

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

54

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

55

Investigation of bound-free emission spectra of sodium-potassium  

NASA Astrophysics Data System (ADS)

This work determines relative transition dipole moment functions by fitting experimental bound-free and bound-bound emission spectra. Specifically, we use emission spectra from the 43Sigma+ ? a3Sigma+ electronic transition in the sodium-potassium, NaK, molecule. The calculations are performed using a modified version of the BCONT computer program developed by R. J. Le Roy. We examined bound-free and bound-bound emission spectra from several ro-vibrational levels of the 43Sigma+ state of NaK to the repulsive a3Sigma+ state. We considered both previously available spectra from low-lying levels and new spectra from high-lying levels. By making a slight adjustment to the inner, repulsive wall of the 43Sigma + state, we were able to improve the alignment of the peaks of the calculated spectra with those of the experimental data. Using the Inverse Perturbation Approximation (IPA) method, we determined an improved 4 3Sigma+ potential energy curve. Using this new curve, including the emission from both low-lying and high-lying 43Sigma + levels to the a3Sigma+ state, and extending our calculations to treat both bound-free and bound-bound transitions to the a3Sigma + state, we were able to determine an improved fit to the 4 3Sigma+ ? a3Sigma + transition dipole moment function that agrees very well with recent theoretical calculations.

McGeehan, Brett

56

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 ľm) 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 ľm - 14 ľm) 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 ľm - 14 ľm) 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

57

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

58

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

SciTech Connect

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

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

1996-10-25

59

Spectra  

NSDL National Science Digital Library

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

The Exploratorium

2012-06-26

60

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

61

Discernment of lint trash in raw cottton using multivariate analysis of excitation-emission luminescence spectra  

Technology Transfer Automated Retrieval System (TEKTRAN)

Excitation-Emission luminescence spectra of basic (pH 12.5) phosphate buffer solution extracts were used to distinguish among botanical components of trash within seed cotton. All components were separated from whole plants removed from a field in southern New Mexico. Unfolded Principal Component An...

62

Theory for Time Resolved Emission Spectra BYGRAHAMR. FLEMINGAND ONNOL. J. GIJZEMAN*  

E-print Network

the steady state (frequencyresolved)emissionspectrum as a function of the pressure of added buffer gas. Some to the determina- tion of dt $ba(m, f) as a function of frequency. The steady state intensity at a particular uTheory for Time Resolved Emission Spectra BYGRAHAMR. FLEMINGAND ONNOL. J. GIJZEMAN* Davy Faraday

Fleming, Graham R.

63

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

NASA Astrophysics Data System (ADS)

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

Wu, Wenpeng; Cao, Zexing; Zhao, Yi

2012-03-01

64

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

NASA Astrophysics Data System (ADS)

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

Morley, Caroline; Fortney, Jonathan; Marley, Mark

2014-11-01

65

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

NASA Astrophysics Data System (ADS)

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

Morley, Caroline; Fortney, Jonathan J.; Marley, Mark

2015-01-01

66

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

67

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

68

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

SciTech Connect

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

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

1992-11-01

69

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

SciTech Connect

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

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

1992-11-01

70

The Nuclear Region of Low Luminosity Flat Radio Spectrum Sources. II. Emission-Line Spectra  

E-print Network

We report on the spectroscopic study of 19 low luminosity Flat Radio Spectrum (LL FRS) sources selected from Marcha's et al. (1996) 200 mJy sample. In the optical, these objects are mainly dominated by the host galaxy starlight. After correcting the data for this effect, we obtain a new set of spectra clearly displaying weak emission lines; such features carry valuable information concerning the excitation mechanisms at work in the nuclear regions of LL FRS sources. We have used a special routine to model the spectra and assess the intensities and velocities of the emission lines; we have analyzed the results in terms of diagnostic diagrams. Our analysis shows that 79% of the studied objects harbour a Low Ionization Nuclear Emission-line Region (or LINER) whose contribution was swamped by the host galaxy starlight. The remaining objects display a higher ionization spectrum, more typical of Seyferts; due to the poor quality of the spectra, it was not possible to identify any possible large Balmer components. The fact that we observe a LINER-type spectrum in LL FRS sources supports the idea that some of these objects could be undergoing an ADAF phase; in addition, such a low ionization emission-line spectrum is in agreement with the black hole mass values and sub-Eddington accretion rates published for some FRS sources.

A. C. Goncalves; M. Serote Roos

2003-09-23

71

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

72

Remote sensing of trace constituents from atmospheric infrared emission and absorption spectra  

NASA Technical Reports Server (NTRS)

Atmospheric infrared emission and absorption spectra obtained from aircraft and balloon-borne spectrometers are presented. From such spectra, mixing ratio vs altitude profiles are derived for several minor constituents. Recent results for HNO3, CF2Cl2, CFCl3, and HF are presented. In addition, the feasibility of infrared detection of other trace constituents, such as HCl, HF, NH3, NO and SO2, against the rest of the atmospheric background is studied. From this study, made on a line-by-line basis for 'state of the art' airborne spectrometers, potential spectral features for detection of the trace constituents are isolated.

Barker, D. B.; Brooks, J. N.; Goldman, A.; Kosters, J. J.; Murcray, D. G.; Murcray, F. H.; Van Allen, J.; Williams, W. J.

1976-01-01

73

Separation of Raman spectra from fluorescence emission background by principal component analysis  

NASA Astrophysics Data System (ADS)

A novel aspect of principal component analysis (PCA) which was recently revealed has been applied to the separation of a Raman signal from a strong fluorescence emission background. A Raman spectrum of indene with weak intensity that was almost hidden in the high background was readily resolved by PCA only. The resolved spectrum closely resembled the pure Raman spectrum without disturbance by the background. Another resolved spectrum by use of target testing was also very similar to the resolved spectrum by PCA alone. These results preliminarily suggest that PCA is useful to obtain Raman spectra from a collection of replicated raw spectra that are dominated by strong background signal.

Hasegawa, Takeshi; Nishijo, Jujiro; Umemura, Junzo

2000-02-01

74

Secondary electron emission characteristics of C(111) and the observation of double-peaked emission spectra  

NASA Astrophysics Data System (ADS)

Secondary electron emission spectroscopy (SEES) is used to investigate the low-energy electron emission characteristics of the C(111) surface. A negative electron affinity (NEA) is observed at hydrogenated and cesiated C(111) surfaces, and very high secondary electron yields are measured from these surfaces. The emission from both surfaces is sharply peaked at low energy, although the cesiated surface produces greater energy spread than the hydrogenated surface. Yield measurements are uniform across the hydrogenated and cesiated surfaces, but energy distribution curves (EDCs) contain emission features that depend on the measurement position on the surface. Specifically, an intense secondary emission peak centered above Ec is observed in EDCs measured at all positions while a weaker peak lying completely below Ec appears only at specific regions of the surface. The intense peak is well understood and has been observed in EDCs taken from NEA surfaces of C(100) and chemical vapor deposited diamond. However, the weaker peak has not been observed in previous SEES studies of diamond. This peak corresponds to electron emission from surface or defect electronic states in the energy gap, and it is manifested in the EDCs only when ? is sufficiently lowered by the adsorption of H or Cs. Although the origin of the surface or defect states is not known, it appears to be associated with structural properties of the C(111) surface.

Yater, J. E.; Shih, A.

2001-09-01

75

EMISSION LINES BETWEEN 1 AND 2 keV IN COMETARY X-RAY SPECTRA  

SciTech Connect

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

Ewing, Ian; Christian, Damian J. [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States)] [Department of Physics and Astronomy, California State University, 18111 Nordhoff Street, Northridge, CA 91330 (United States); Bodewits, Dennis [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)] [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Dennerl, Konrad [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany)] [Max-Planck-Institut fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching Germany (Germany); Lisse, Carey M. [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States)] [Planetary Exploration Group, Space Department, Johns Hopkins University Applied Physics Laboratory, 11100 Johns Hopkins Rd, Laurel, MD 20723 (United States); Wolk, Scott J., E-mail: ian.ewing.794@my.csun.edu, E-mail: daman.christian@csun.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

2013-01-20

76

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

77

Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics  

E-print Network

We present detuning-dependent spectral and decay-rate measurements to study the difference between spectral and dynamical properties of single quantum dots embedded in micropillar and photonic-crystal cavities. For the micropillar cavity, the dynamics is well described by the dissipative Jaynes-Cummings model, while systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to coupling of other exciton lines to the cavity and interference of different propagation paths towards the detector of the fields emitted by the quantum dot. In contrast, quantitative information about the system can readily be extracted from the dynamical measurements. In the case of photonic crystal cavities we observe an anti crossing in the spectra when detuning a single quantum dot through resonance, which is the spectral signature of strong coupling. However, time-resolved measurements reveal that the actual coupling strength is significantly smaller than anticipated from the spectral...

Madsen, K H

2012-01-01

78

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

79

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

80

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

E-print Network

Near infrared emission spectra of CoH and CoD Iouli E. Gordon a , Robert J. Le Roy b , Peter FH and CoD molecules have been recorded in the 640 nm to 3.5 lm region using a Fourier transform U4 electronic transition of CoD, and five bands for the corresponding transition of CoH. The (0

Le Roy, Robert J.

81

Chemical effects in the satellites of X-ray emission spectra  

Microsoft Academic Search

The origins of satellites in X-ray emission spectra are classified into 1) multivacancy satellite 2) charge-transfer satellite and 3) molecular-orbital splitting satellite. The multivacancy satellites are strong for ionic compounds and weak for covalent compounds. However, for ionic compounds of level crossing, the satellites are weak due to the resonance hole transfer from the X-ray emitting atom to one of

Kawai Jun

1993-01-01

82

K ? X-Ray Emission Spectra and Chemical Environments of Phosphorus in Some Selected Compounds  

NASA Astrophysics Data System (ADS)

The phosphorus K? emissionfluorescence spectra from10 selected compounds are measured with a high-resolution two-crystalvacuum spectrometer. The phosphorus compounds studied include inorganiccompounds K2HPO3, NaH2PO2ˇH2O, NaH2PO3ˇ2.5H2O, Ca2P2O7, Cu2P2O7 and (NaPO3)6; and organic compoundstri-o-tolylphosphine (o-CH3C6H4)3P,tri-m-tolylphosphine (m-CH3C6H4)3P,tri-p-tolylphosphine (p-CH3C6H4)3P andtriphenylphosphine oxide (C6H5)3PO. The measured P K?emission spectra are discussed in relation to chemical environmentsaround phosphorus atom in the compounds. It is shown that the P K?emission spectra are strongly influenced by chemical environments. Theeffect of o-, m- and p-methyl substitution at the benzene ring(position isomerism) is observed in theemission spectra of tri-o-tolylphosphine, tri-m-tolylphosphineand tri-p-tolylphosphine.

Sugiura, Chikara; Yorikawa, Hiroharu; Muramatsu, Shinji

1996-09-01

83

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

84

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

E-print Network

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

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

2014-08-21

85

Variation of Spectra Luminescence Emission of Moganite under Different Stimulation Sources  

NASA Astrophysics Data System (ADS)

This work focuses on a characterization of various type of luminescence in Moganite-rich silica minerals from Mogan (Gran Canaria, Spain). The silica minerals formed by complicated hydrous processes exhibit luminescence emissions, which depend on sample temperature and type of an irradiation for excitation such as heat, laser, ion-beam, X-ray, incident electron beam and so on. Here we examined thermoluminescence (TL), ion beam luminescence (IBL), radioluminescence (RL), cathodoluminescence (CL) of moganite aliquots combined with Raman spectroscopy for clarification of relationship between lattice defects and the spectral luminescence emissions. The spatially-resolved CL spectroscopy coupled to the environmental scanning electron microscopy (ESEM-CL) displays different luminescence spectral signals between the moganite veined core (dull emission) and the rim (bright emission) together with larger porosity and additional ions in the outer part, suggesting a later alteration process with alkali, metals and volatile ions for the moganite formation. RL and IBL spectra of silica minerals in core and rim mainly show a progressive increase in intensity of RL emission band at 470-500 nm with decrease in sample temperature, which is caused by cryogenic stress on the [AlO4]0 centers. Continuous H+ ion beam implantation on samples at room temperature produces a subtle diminishing of blue emission and a quite brightening of red emission at 700 nm assigned to Fe3+ point defects. The white turbid rim with opaline SiO2 in cavities emits bright CL emission in panchromatic CL image, and has spectral emission bands at 290 nm with high intensity (100 000 a.u.) and one at 520 nm which are probably related to H2O(Si-OH) groups, H+, Na+ and metallic ions such as Fe3+, Ti4+ and Nb4+. Moganite core zones only display emission bands at 390 nm and 670 nm (8500 a.u.) attributed to [AlO4/Na+]0 centers and silanol groups, respectively.

Garcia-Guinea, J.; Bustillo, M. A.; Crespo-Feo, E.; Tormo, L.; Finch, A. A.; Hole, D. E.; Townsend, P. D.; Correcher, V.

2009-08-01

86

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

87

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

SciTech Connect

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

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

2013-05-10

88

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

E-print Network

We conduct a comprehensive search for X-ray emission lines from sterile neutrino dark matter, motivated by recent claims of unidentified emission lines in the stacked X-ray spectra of galaxy clusters and the centers of the Milky Way and M31. Since the claimed emission lines lie around 3.5 keV, we focus on galaxies and galaxy groups (masking the central regions), since these objects emit very little radiation above ~2 keV and offer a clean background against which to detect emission lines. We develop a formalism for maximizing the signal-to-noise of sterile neutrino emission lines by weighing each X-ray event according to the expected dark matter profile. In total, we examine 81 and 89 galaxies with Chandra and XMM-Newton respectively, totaling 15.0 and 14.6 Ms of integration time. We find no significant evidence of any emission lines, placing strong constraints on the mixing angle of sterile neutrinos with masses between 4.8-12.4 keV. In particular, if the 3.57 keV feature from Bulbul et al. (2014) were due t...

Anderson, Michael E; Bregman, Joel N

2014-01-01

89

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

90

Detection and Characterisation of H-{alpha} Emission Lines from Gaia BP/RP Spectra  

SciTech Connect

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-{alpha} 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-{alpha} 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.

Jaenes, Juergen [University of Tartu, Institute of Computer Science, Tartu Observatory (Estonia); Laur, Sven [University of Tartu, Institute of Computer Science (Estonia); Kolka, Indrek [Tartu Observatory (Estonia)

2008-12-05

91

Quantitative analysis of quantum dot dynamics and emission spectra in cavity quantum electrodynamics  

NASA Astrophysics Data System (ADS)

We present detuning-dependent spectral and decay-rate measurements to study the difference between the spectral and dynamical properties of single quantum dots embedded in micropillar and photonic crystal cavities. For the micropillar cavity, the dynamics is well described by the dissipative Jaynes-Cummings model, whereas systematic deviations are observed for the emission spectra. The discrepancy for the spectra is attributed to the coupling of other exciton lines to the cavity and interference of different propagation paths toward the detector of the fields emitted by the quantum dot. In contrast, quantitative information about the system can readily be extracted from the dynamical measurements. In the case of photonic crystal cavities, we observe an anti-crossing in the spectra when detuning a single quantum dot through resonance, which is the spectral signature of a strong coupling. However, time-resolved measurements reveal that the actual coupling strength is significantly smaller than anticipated from the spectral measurements and that the quantum dot is rather weakly coupled to the cavity. We suggest that the observed Rabi splitting is due to cavity feeding by other quantum dots and/or multi-exciton complexes giving rise to collective emission effects.

Madsen, K. H.; Lodahl, P.

2013-02-01

92

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

94

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

95

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 ą 50 nm and ?emission = 475 ą 38 nm. The window of the strongest fluorescence shifted to ?excitation = 320 ą 25 nm and ?emission = 425 ą 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

96

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

NASA Astrophysics Data System (ADS)

We study the emission from H-like ions, particularly oxygen and neon, observed in ASCA spectra of low-mass X-ray binaries (LMXBs). The observed strengths of Ly? 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 × 106 K. Otherwise, the enhancement of Ly? emission with respect to the continuum may be due to (1) three-body recombination at electron densities greater than 1017 cm-3 and temperatures below 2 × 105 K, (2) contributions to the recombination spectrum from collisional excitation of the H-like ionization stage, (3) contributions to recombination Ly? 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.

Bautista, M. A.; Kallman, T. R.; Angelini, L.; Liedahl, D. A.; Smits, D. P.

1998-12-01

97

Emission spectra analysis of arc plasma for synthesis of carbon nanostructures in various magnetic conditions  

NASA Astrophysics Data System (ADS)

Arc discharge supported by the erosion of anode materials is one of the most practical and efficient methods to synthesize various high-quality carbon nanostructures. By introducing a non-uniform magnetic field in arc plasmas, high-purity single-walled carbon nanotubes (SWCNT) and large-scale graphene flakes can be obtained in a single step. In this paper, ultraviolet-visible emission spectra of arc in different spots under various magnetic conditions are analyzed to provide an in situ investigation for transformation processes of evaporated species and growth of carbon nanostructures in arc. Based on the arc spectra of carbon diatomic Swan bands, vibrational temperature in arc is determined. The vibrational temperature in arc center was measured around 6950 K, which is in good agreement with our simulation results. Experimental and simulation results suggest that SWCNT are formed in the arc periphery region. Transmission electronic microscope and Raman spectroscope are also employed to characterize the properties of carbon nanostructures.

Li, Jian; Kundrapu, Madhusudhan; Shashurin, Alexey; Keidar, Michael

2012-07-01

98

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

99

Emission spectra analysis of arc plasma for synthesis of carbon nanostructures in various magnetic conditions  

SciTech Connect

Arc discharge supported by the erosion of anode materials is one of the most practical and efficient methods to synthesize various high-quality carbon nanostructures. By introducing a non-uniform magnetic field in arc plasmas, high-purity single-walled carbon nanotubes (SWCNT) and large-scale graphene flakes can be obtained in a single step. In this paper, ultraviolet-visible emission spectra of arc in different spots under various magnetic conditions are analyzed to provide an in situ investigation for transformation processes of evaporated species and growth of carbon nanostructures in arc. Based on the arc spectra of carbon diatomic Swan bands, vibrational temperature in arc is determined. The vibrational temperature in arc center was measured around 6950 K, which is in good agreement with our simulation results. Experimental and simulation results suggest that SWCNT are formed in the arc periphery region. Transmission electronic microscope and Raman spectroscope are also employed to characterize the properties of carbon nanostructures.

Li Jian; Kundrapu, Madhusudhan; Shashurin, Alexey; Keidar, Michael [Department of Mechanical and Aerospace Engineering, George Washington University, Washington, DC 20052 (United States)

2012-07-15

100

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-François; Reale, Fabio

101

PHASE-AVERAGED SPECTRA AND LUMINOSITIES OF GAMMA-RAY EMISSIONS FROM YOUNG ISOLATED PULSARS  

SciTech Connect

We study the phase-averaged spectra and luminosities of {gamma}-ray emissions from young, isolated pulsars within a revised outer gap model. In the revised version of the outer gap, there are two possible cases for the outer gaps: the fractional size of the outer gap is estimated through the photon-photon pair process in the first case (Case I), and is limited by the critical field lines in the second case (Case II). The fractional size is described by Case I if the fractional size at the null charge surface in Case I is smaller than that in Case II, and vice versa. Such an outer gap can extend from the inner boundary, whose radial distance to the neutron star is less than that of the null charge surface to the light cylinder for a {gamma}-ray pulsar with a given magnetic inclination. When the shape of the outer gap is determined, assuming that high-energy emission at an averaged radius of the field line in the center of the outer gap, with a Gaussian distribution of the parallel electric field along the gap height, represents typical emission, the phase-averaged {gamma}-ray spectrum for a given pulsar can be estimated in the revised model with three model parameters. We apply the model to explain the phase-averaged spectra of the Vela (Case I) and Geminga (Case II) pulsars. We also use the model to fit the phase-averaged spectra of 54 young, isolated {gamma}-ray pulsars, and then calculate the {gamma}-ray luminosities and compare them with the observed data from Fermi-LAT.

Li, X.; Jiang, Z. J.; Zhang, L., E-mail: lizhang@ynu.edu.cn [Department of Physics, Yunnan University, Kunming (China)

2013-03-10

102

Emission spectra of working mixtures of a HgBr\\/HgCl excimer lamp  

Microsoft Academic Search

A study of emission spectra of a gas-discharge plasma produced in a HgBr\\/HgCl excimer lamp, which is filled with multicomponent\\u000a working mixtures at atmospheric pressure (HgBr2 and HgCl2 with additions of molecular nitrogen and xenon), are reported. A gas-discharge plasma was produced by high-frequency (pulses\\u000a ?100 ns long with a repetition rate of up to 2000 Hz) barrier and surface

A. N. Malinin; N. N. Guivan; L. L. Shimon

2000-01-01

103

Calibrated 0.1-cm(-1) IR emission spectra from 80°N.  

PubMed

Spectra from a 0.1-cm(-1) resolution absolutely calibrated emission interferometer installed near Eureka, Northwest Territories, Canada (80°N, 86°W), at the Arctic Stratospheric Observatory are presented. The Michelson-type interferometer has a maximum path difference of 10 cm and uses a liquid-N(2)-cooled HgCdTe detector, which covers the spectral region from 650 to 1250 cm(-1). Spectral intervals containing CO(2), HNO(3), and ozone have been modeled with a line-by-line radiative-transfer code and column amounts retrieved for the latter two constituents. The instrument and initial measurements are described. PMID:21085427

Olson, J R; Van Allen, J; Fogal, P F; Murcray, F J; Goldman, A

1996-06-01

104

Time evolution, Lamb shift, and emission spectra of spontaneous emission of two identical atoms  

SciTech Connect

A unitary transformation method is used to investigate the dynamic evolution of two multilevel atoms, in the basis of symmetric and antisymmetric states, with one atom being initially prepared in the first excited state and the other in the ground state. The unitary transformation guarantees that our calculations are based on the ground state of the atom-field system and the self-energy is subtracted at the beginning. The total Lamb shifts of the symmetric and antisymmetric states are divided into transformed shift and dynamic shift. The transformed shift is due to emitting and reabsorbing of virtual photons, by a single atom (nondynamic single atomic shift) and between the two atoms (quasi-static shift). The dynamic shift is due to the emitting and reabsorbing of real photons, by a single atom (dynamic single atomic shift) and between the two atoms (dynamic interatomic shift). The emitting and reabsorbing of virtual and real photons between the two atoms result in the interatomic shift, which does not exist for the one-atom case. The spectra at the long-time limit are calculated. If the distance between the two atoms is shorter than or comparable to the wavelength, the strong coupling between the two atoms splits the spectrum into two peaks, one from the symmetric state and the other from the antisymmetric state. The origin of the red or blue shifts for the symmetric and antisymmetric states mainly lies in the negative or positive interaction energy between the two atoms. In the investigation of the short time evolution, we find the modification of the effective density of states by the interaction between two atoms can modulate the quantum Zeno and quantum anti-Zeno effects in the decays of the symmetric and antisymmetric states.

Wang Dawei [Center of Optical Sciences and Department of Physics, Chinese University of Hong Kong, N.T. (Hong Kong); Li Zhenghong [Department of Physics, Hong Kong Baptist University, Kowloon Tong (Hong Kong); Zheng Hang [Department of Physics, Shanghai Jiao Tong University, Shanghai 200030 (China); Zhu Shiyao [Center of Optical Sciences and Department of Physics, Chinese University of Hong Kong, N.T. (Hong Kong); Department of Physics, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

2010-04-15

105

Super-resolution imaging of multiple fluorescent proteins with highly overlapping emission spectra in living cells  

NASA Astrophysics Data System (ADS)

Diffraction limits resolution in far field microscopy. Single molecule localization based superresolution imaging has surpassed such limitations and is rapidly gaining popularity, yet limited availability of cell-compatible photoactivatable fluorescent probes with distinct emission spectra have impeded simultaneous visualization of multiple molecular species in living cells. We introduce PAmKate, a monomeric far-red photoactivatable fluorescent protein (PAFP), which has facilitated simultaneous imaging of three PAFPs in biological samples with fluorescence photoactivation localization microscopy (FPALM). Successful probe identification was achieved by measuring the fluorescence emission intensity in two distinct spectral channels spanning approximately 100 nm of the visible spectrum. Raft-, non-raft- and cytoskeleton- associated proteins were simultaneously imaged in both live and fixed fibroblasts co-expressing Dendra2-hemagglutinin, PAmKate-transferrin receptor and PAmCherry1-?-actin chimeras, revealing evidence for specific interactions between membrane proteins and membrane-associated actin structures.

Gunewardene, Mudalige; Subach, Fedor; Gould, Travis; Penoncello, Gregory; Gudheti, Manasa; Verkhusha, Vladislav; Hess, Samuel

2011-03-01

106

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

107

``Drifting tadpoles'' in wavelet spectra of decimetric radio emission of fiber bursts  

NASA Astrophysics Data System (ADS)

Aims: The solar decimetric radio emission of fiber bursts was investigated searching for the “drifting tadpole” structures proposed by theoretical studies. Methods: Characteristic periods with the tadpole pattern were searched for in the radio flux time series by wavelet analysis methods. Results: For the first time, we have found drifting tadpoles in the wavelet spectra of the decimetric radio emission associated with the fiber bursts observed in July 11, 2005. These tadpoles were detected at all radio frequencies in the 1602-1780 MHz frequency range. The characteristic period of the wavelet tadpole patterns was found to be 81.4 s and the frequency drift of the tadpole heads is -6.8 MHz s-1. These tadpoles are interpreted as a signature of the magnetoacoustic wave train moving along a dense flare waveguide and their frequency drift as a motion of the wave train modulating the radio emission produced by the plasma emission mechanism. Using the Aschwanden density model of the solar atmosphere, only low values of the Alfvén speed and the magnetic field strength in the loop guiding this wave train were derived which indicates a neutral current sheet as the guiding structure. The present analysis supports the model of fiber bursts based on whistler waves.

Mészárosová, H.; Karlický, M.; Rybák, J.; Ji?i?ka, K.

2009-08-01

108

Detection of CO and Dust Emission in Near-Infrared Spectra of SN 1998S  

E-print Network

Near-infrared spectra (0.95 -- 2.4 micron) of the peculiar Type IIn supernova 1998S in NGC 3877 from 95 to 355 days after maximum light are presented. K-band data taken at days 95 and 225 show the presence of the first overtone of CO emission near 2.3 micron, which is gone by day 355. An apparent extended blue wing on the CO profile in the day 95 spectrum could indicate a large CO expansion velocity (~2000 -- 3000 km/s). This is the third detection of infrared CO emission in nearly as many Type II supernovae studied, implying that molecule formation may be fairly common in Type II events, and that the early formation of molecules in SN 1987A may be typical rather than exceptional. Multi-peak hydrogen and helium lines suggest that SN 1998S is interacting with a circumstellar disk, and the fading of the red side of this profile with time is suggestive of dust formation in the ejecta, perhaps induced by CO cooling. Continuum emission that rises towards longer wavelengths (J -> K) is seen after day 225 with an estimated near-infrared luminosity >~ 10^40 erg/s. This may be related to the near-infrared excesses seen in a number of other supernovae. If this continuum is due to free-free emission, it requires an exceptionally shallow density profile. On the other hand, the shape of the continuum is well fit by a 1200 +- 150 K blackbody spectrum possibly due to thermal emission from dust. Interestingly, we observe a similar 1200 K blackbody-like, near-infrared continuum in SN 1997ab, another Type IIn supernova at an even later post-maximum epoch (day 1064+). A number of dust emission scenarios are discussed, and we conclude that the NIR dust continuum is likely powered by the interaction of SN 1998S with the circumstellar medium.

Christopher L. Gerardy; Robert A. Fesen; Peter Hoeflich; J. Craig Wheeler

1999-12-20

109

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. I. Full cumulant expansions and system-bath entanglement  

NASA Astrophysics Data System (ADS)

We study the Förster resonant energy transfer rate, absorption and emission spectra in multichromophoric systems. The multichromophoric Förster theory (MCFT) is determined from an overlap integral of generalized matrices related to the donor's emission and acceptor's absorption spectra, which are obtained via a full 2nd-order cumulant expansion technique developed in this work. We calculate the spectra and MCFT rate for both localized and delocalized systems, and calibrate the analytical 2nd-order cumulant expansion with the exact stochastic path integral method. We present three essential findings: (i) The role of the initial entanglement between the donor and its bath is found to be crucial in both the emission spectrum and the MCFT rate. (ii) The absorption spectra obtained by the cumulant expansion method are nearly identical to the exact spectra for both localized and delocalized systems, even when the system-bath coupling is far from the perturbative regime. (iii) For the emission spectra, the cumulant expansion can give reliable results for localized systems, but fail to provide reliable spectra of the high-lying excited states of a delocalized system, when the system-bath coupling is large and the thermal energy is small. This paper also provides a simple golden-rule derivation of the MCFT, reviews existing methods, and motivates further developments in the subsequent papers.

Ma, Jian; Cao, Jianshu

2015-03-01

110

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. I. Full cumulant expansions and system-bath entanglement.  

PubMed

We study the Förster resonant energy transfer rate, absorption and emission spectra in multichromophoric systems. The multichromophoric Förster theory (MCFT) is determined from an overlap integral of generalized matrices related to the donor's emission and acceptor's absorption spectra, which are obtained via a full 2nd-order cumulant expansion technique developed in this work. We calculate the spectra and MCFT rate for both localized and delocalized systems, and calibrate the analytical 2nd-order cumulant expansion with the exact stochastic path integral method. We present three essential findings: (i) The role of the initial entanglement between the donor and its bath is found to be crucial in both the emission spectrum and the MCFT rate. (ii) The absorption spectra obtained by the cumulant expansion method are nearly identical to the exact spectra for both localized and delocalized systems, even when the system-bath coupling is far from the perturbative regime. (iii) For the emission spectra, the cumulant expansion can give reliable results for localized systems, but fail to provide reliable spectra of the high-lying excited states of a delocalized system, when the system-bath coupling is large and the thermal energy is small. This paper also provides a simple golden-rule derivation of the MCFT, reviews existing methods, and motivates further developments in the subsequent papers. PMID:25747060

Ma, Jian; Cao, Jianshu

2015-03-01

111

Near-infrared emission spectra of TeS, TeSe and Te2  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

112

Evaluation of potential emission spectra for the reliable classification of fluorescently coded materials  

NASA Astrophysics Data System (ADS)

The conservation and efficient use of natural and especially strategic resources like oil and water have become global issues, which increasingly initiate environmental and political activities for comprehensive recycling programs. To effectively reutilize oil-based materials necessary in many industrial fields (e.g. chemical and pharmaceutical industry, automotive, packaging), appropriate methods for a fast and highly reliable automated material identification are required. One non-contacting, color- and shape-independent new technique that eliminates the shortcomings of existing methods is to label materials like plastics with certain combinations of fluorescent markers ("optical codes", "optical fingerprints") incorporated during manufacture. Since time-resolved measurements are complex (and expensive), fluorescent markers must be designed that possess unique spectral signatures. The number of identifiable materials increases with the number of fluorescent markers that can be reliably distinguished within the limited wavelength band available. In this article we shall investigate the reliable detection and classification of fluorescent markers with specific fluorescence emission spectra. These simulated spectra are modeled based on realistic fluorescence spectra acquired from material samples using a modern VNIR spectral imaging system. In order to maximize the number of materials that can be reliably identified, we evaluate the performance of 8 classification algorithms based on different spectral similarity measures. The results help guide the design of appropriate fluorescent markers, optical sensors and the overall measurement system.

Brunner, Siegfried; Kargel, Christian

2011-06-01

113

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

E-print Network

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

Brian E. Wood; Margarita Karovska; Warren Hack

2001-07-02

114

Emissivity Spectra of Meteoritic Powders mixed with Liquid Formamide (NH2COH) at Different Temperatures  

NASA Astrophysics Data System (ADS)

We set-up an experiment at the Planetary Emissivity Laboratory (PEL) to investigate a key aspect in the prebiotic chemistry of formamide: the surface reactivity of minerals used as catalysts. The interaction of formamide and the reaction products on mineral surface, as well as, the sequestration processes in the mineral pores, can facilitate the concentration of products allowing for possible polymerization. Three meteorites, NWA2828 (PEL ID 00000887), Al Haggounia (PEL ID 00000888), and Dhofar959 (PEL ID 00000889), were used in this experiment. All the samples were reduced in the grain size fraction < 125 ?m and stored in a desiccator before measuring. Each sample was poured in one from a set of identical stainless steel cups, having 5 mm thick bottom, internal diameter 50 mm, rim thickness 2 mm, and 20 mm total height. Emissivity of the samples was measured by means of a Bruker Vertex 80V coupled to an emissivity chamber (equipped with a rotating carousel to measure several samples without breaking the vacuum), both evacuable to < 1 mbar. The dry samples were placed in the emissivity chamber, each of them having a temperature sensor in contact with the surface of the sample, reading the effective temperature of the emitting skin. The 'dry' meteorites were measured in vacuum (0.8 mbar) at 70° C on the sample surface, successively liquid formamide was vaporized on the samples surface, the cup was immediately transferred in the emissivity chamber, and evacuated. Each sample was measured at 70°, 100°, 140°, and 200° C. Then each cup was cooled in vacuum and put back in the desiccator. For each sample after this thermal processing, a small amount of heated material was used to fill a cup for reflectance measurements. Since cold reflectance measurements cannot be compared with hot emissivity, those measurements have been taken to better understand the processes happening in the moisturized soil after heating. For all of the samples, when heating at 70°C we noticed in the emissivity spectra strong signatures attributable to liquid formamide. We interpret them as being originated from a column of hot vaporized formamide, lying above the sample surface. For all the samples this effect vanished already at 100°C, probably due to complete evaporation of liquid formamide that was deposited on the meteorite sample surfaces. However, all the spectra measured at 100° and 140° C show signs of the presence of formamide, that we infer from comparing them with the 70° C dry measurement of the same sample. For 2 samples out of 3, when heating at 200°C (and only there) a new feature appears at 7.08 ?m. This band is very close to a similar band that liquid formamide has at 7.19 ?m, and that was even present in all the spectra of wet meteorites taken at 70°C. We interpret this band shift as a possible sign of interaction of formamide with the catalyst (the meteorite powder): the CH bend responsible for that is probably strengthening.

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

2013-12-01

115

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

116

Neutral Gas Temperature Estimates in an Inductively Coupled CF4 Plasma by Fitting Diatomic Emission Spectra  

NASA Technical Reports Server (NTRS)

This work examines the accuracy of plasma neutral temperature estimates by fitting the rotational band envelope of different diatomic species in emission. Experiments are performed in an inductively coupled CF4 plasma generated in a Gaseous Electronics Conference reference cell. Visible and ultraviolet emission spectra are collected at a power of 300 W (approximately 0.7 W/cc) and pressure of 30 mtorr. The emission bands of several molecules (CF, CN, C2, CO, and SiF) are fit simultaneously for rotational and vibrational temperatures and compared. Four different rotational temperatures are obtained: 1250 K for CF and CN, 1600 K for CO, 1800 K for C2, and 2300 K for SiF. The vibrational temperatures obtained vary from 1750-5950 K, with the higher vibrational temperatures generally corresponding to the lower rotational temperatures. These results suggest that the different species have achieved different degrees of equilibration between the rotational and vibrational modes and may not be equilibrated with the translational temperatures. The different temperatures are also related to the likelihood that the species are produced by ion bombardment of the surface, with etch products like SiF, CO, and C2 having higher temperatures than species expected to have formed in the gas phase.

Cruden, Brett A.; Rao, M. V. V. S.; Sharma, Surendra P.; Meyyappan, M.

2001-01-01

117

Somatic mutations in PI3K[alpha]: Structural basis for enzyme activation and drug design  

SciTech Connect

The PI3K pathway is a communication hub coordinating critical cell functions including cell survival, cell growth, proliferation, motility and metabolism. Because PI3K{alpha} harbors recurrent somatic mutations resulting in gains of function in human cancers, it has emerged as an important drug target for many types of solid tumors. Various PI3K isoforms are also being evaluated as potential therapeutic targets for inflammation, heart disease, and hematological malignancies. Structural biology is providing insights into the flexibility of the PI3Ks, and providing basis for understanding the effects of mutations, drug resistance and specificity.

Gabelli, Sandra B.; Mandelker, Diana; Schmidt-Kittler, Oleg; Vogelstein, Bert; Amzel, L. Mario (JHU); (HHMI)

2011-09-06

118

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

119

Time resolved spectra in the infrared absorption and emission from shock heated hydrocarbons  

NASA Astrophysics Data System (ADS)

We have extended the wavelength range of our previously constructed multichannel, fast recording spectrometer to the mid-infrared. With the initial configuration, using a silicon-diode (photovoltaic) array, we recorded light intensities simultaneously at 20 adjacent wavelengths, each with 20 ?s time resolution. For studies in the infrared the silicon diodes are replaced by a 20 element PbSe (photoconducting) array of similar dimensions (1×4 mm/element), cooled by a three-stage thermoelectric device. These elements have useful sensitivities over 1.0-6.7 ?m. Three interchangeable gratings in a 1/4 m monochromator cover the following spectral ranges: 1.0-2.5 ?m (resolution 33.6 cm-1) 2.5-4.5 ?m (16.8 cm-1) 4.0-6.5 ?m (16.7 cm-1). Incorporated in the new housing there are individually controlled bias-power sources for each detector, two stages of analogue amplification and a 20-line parallel output to the previously constructed digitizer, and record/hold computer. The immediate application of this system is the study of emission and absorption spectra of shock heated hydrocarbons-C2H2, C4H4 and C6H6-which are possible precursors of species that generate infrared emissions in the interstellar medium. It has been recently proposed that these radiations are due to PAH that emit in the infrared upon relaxation from highly excited states. However, it is possible that such emissions could be due to shock-heated low molecular-weight hydrocarbons, which are known to be present in significant abundances, ejected into the interstellar medium during stellar outer atmospheric eruptions. The full Swan band system appeared in time-integrated emission spectra from shock heated C2H2 (1% in Ar; T5eq~=2500K) no soot was generated. At low resolution the profiles on the high frequency side of the black body maximum show no distinctive features. These could be fitted to Planck curves, with temperatures that declined with time from an initial high that was intermediate between T5 (no conversion) and T5 (eq).

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

1990-07-01

120

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

121

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

PubMed

A detailed description of the polycyclic aromatic hydrocarbon (PAH)/unidentified infrared band (UIR) mechanism is presented in which experimental spectral bandshape functions are used to simulate IR emission spectra for individual molecules. These spectra are additively superimposed to produce a conglomerate spectrum representative of a family of PAH molecules. Ab initio vibrational frequencies and intensities for nine PAHs (neutral and cationic) as large as ovalene are used in conjunction with measured bandshape and temperature-dependent redshift data to simulate the UIR bands. The calculated spectra of cations provide a closer match to the UIRs than do those of the neutrals. However, the PAH cations used in the simulations fail to reproduce the details of the UIR emission spectra. The discrepancies are potentially alleviated if both larger PAHs and a greater number of PAHs were included in the simulation. PMID:11541733

Cook, D J; Saykally, R J

1998-02-01

122

Simulated Infrared Emission Spectra of Highly Excited Polyatomic Molecules: A Detailed Model of the PAH-UIR Hypothesis  

NASA Astrophysics Data System (ADS)

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

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

1998-01-01

123

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

124

The effects of thermal accretion disk spectra on the emission lines from active galactic nuclei  

NASA Technical Reports Server (NTRS)

Although most ratios of AGN emission lines depend primarily on global averages over the ionizing spectrum of the thermal accretion disk, there are some which behave quite differently for different spectra. Using these, it may be possible to infer the shape of the spectrum in the unobservable ultraviolet. Two classes of methods for making this inference are discussed, one based upon as many line ratios as can be observed, the other singling out those best at distinguishing different spectral shapes. Because of a variety of technical difficulties, only the first class, which uses global measures of goodness-of-fit, is practical. Application of this method to a compilation of quasar line ratios yields a weak conclusion, however, with the best fit favoring the presence of a thermal accretion disk with T(b) of roughly 20 eV.

Krolik, Julian H.; Kallman, Timothy R.

1988-01-01

125

Effects of the background environment on formation, evolution and emission spectra of laser-induced plasmas  

NASA Astrophysics Data System (ADS)

In this paper the most important features of Laser Induced Plasma (LIP) evolution were analyzed from the fundamental point of view, in order to point out the effects of background environment on the plasma emission spectra. In particular, the main differences between air and vacuum Laser-Induced Breakdown (LIBS) are discussed, as well as those arising in high-pressure gases and in liquid environment. As can be expected, the dynamics of the plasma is strongly dependent on the environment where the plasma itself expands, which can be exploited for several different applications, ranging from chemical analysis and process diagnostics to materials science. The effect of other experimental conditions, such as the state of aggregation of the irradiated target, and the effect of laser pulse duration are also briefly reviewed.

De Giacomo, A.; Dell'Aglio, M.; Gaudiuso, R.; Amoruso, S.; De Pascale, O.

2012-12-01

126

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

E-print Network

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

Moix, Jeremy; Cao, Jianshu

2015-01-01

127

Molecular phonons and their absorption/emission spectra from the far IR to microwaves  

E-print Network

Together with their fingerprint modes, molecules carry coherent vibrations of all their atoms (phonons). Phonon spectra extend from $\\sim$20 to more than $10^{4}\\,\\mu$m, depending on molecular size. These spectra are discrete but large assemblies of molecules of the same family, differing only by minor structural details, will produce continua. As such assemblies are expected to exist in regions where dust accumulates, they are bound to contribute to the observed continua underlying the Unidentified Infrared Bands and the 21-mum band of planetary nebulae as well as to the diffuse galactic emission surveyed by the Planck astronomical satellite and other means. The purpose of this work is to determine, for carbon-rich molecules, the intensity of such continua and their extent into the millimetric range, and to evaluate their detectability in this range. The rules governing the spectral distributions of phonons are derived and shown to differ from those which obtain in the solid state. Their application allow th...

Papoular, Renaud

2015-01-01

128

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

129

Detection of cervical cancer by fluorescence emission and stokes' shift spectra of blood and urine  

NASA Astrophysics Data System (ADS)

In this paper we present the results of a study to distinguish cervical cancer patients [ N=50] from healthy subjects [N=50] based on the Fluorescence Emission Spectra [FES] and Stokes' Shift Spectra [SSS] of blood and urine. FES was obtained from the cellular fraction of blood and urine by excitation at 400 nm. SSS was obtained from blood plasma and urine with ?? of 70nm. In the FES of blood cellular fraction, the ratio of intensity of the two bands due to neutral porphyrin and basic porphyrin [I630 / I580] was 1 for normal controls and 3 for cervical cancers. In the SSS of plasma, the average ratio of intensity of the two bands due to tryptophan and collagen [I305 nm / I340 nm] was 1.9 for normal controls, 1.1 for early cervical cancers and 0.9 for advanced cervical cancers In the SSS of urine, the ratio of intensity of the two bands due to flavin and NADH [I450 nm / I360 nm] was 0.2 for normal controls and 0.8 for cancer patients. A discriminant analysis combining all three parameters showed a sensitivity of 80% and specificity of 78% for this technique. In this study we show that fluorescence spectroscopy of blood and urine could develop into a promising technique for non-invasive diagnosis and screening of cervical cancers and would appropriately supplement or complement currently used techniques.

Masilamani, V.; Vijmasi, T.; AlSalhi, M.; Govindarajan, K.; VijayaRaghavan, A. P.; Rai, Ram Rathan

2011-03-01

130

Time resolved spectra in the infrared absorption and emission from shock heated hydrocarbons  

NASA Astrophysics Data System (ADS)

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

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

131

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

132

[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

133

Theoretical study on absorption and emission spectra of pyrrolo-C analogues  

NASA Astrophysics Data System (ADS)

Fluorescent nucleoside analogues have attracted much attention in studying the structure and dynamics of nucleic acids in recent years. In the present work, we use theoretical calculations to investigate the structural and optical properties of Pyrrolo-C (PyC) and its analogues which are modified via the conjugation or fusion of different aromatic ring to the PyC core. We also consider the effects of aqueous solution and base pairing. The results show that the fluorescent pyrrolo-C analogues can pair with guanosine to form stable H-bonded WC base pairs. The calculated absorption peaks of modified deoxyribonucleosides agree well with the measured data. The absorption and emission maxima of the pyrrolo-C analogues are greatly red shifted compared with nature C. The solvent effects can induce wavelength blue shift and increase the oscillator strengths in both the absorption and emission spectra. With regard to the WC base pairs, the B3LYP functional reveals that the lowest energy transitions of modified GC base pairs are charge transfer excitation while the CAM-B3LYP functional predicts that all the lowest transitions are localised on the pyrrolo-C analogues. The M062X and CAM-B3LYP functionals show good agreement with respect to both the value of the lowest energy transitions as well as the oscillator strengths.

Liu, Hongxia; Liu, Jianhua; Yang, Yan; Li, Yan; Wang, Haijun

2015-01-01

134

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

135

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

136

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

PubMed Central

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

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

2000-01-01

137

Calculations of X-ray Emission Spectra of Molecules and Surface Adsorbates by Means of Density Functional Theory  

Microsoft Academic Search

In the present study we apply density functional theory (DFT) to calculate nonresonant X-ray emission (XE) spectra of free and chemisorbed molecules. Both ground state frozen orbital and transition potential relaxed orbital procedures are investigated for the calculation of X-ray emission energies and intensities. A code implementation of these proposals has been applied to the free and surface-adsorbed carbon monoxide,

L. Triguero; L. G. M. Pettersson

1998-01-01

138

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

PubMed

A numerically exact path integral treatment of the absorption and emission spectra of open quantum systems is presented that requires only the straightforward solution of a stochastic differential equation. The approach converges rapidly enabling the calculation of spectra of large excitonic systems across the complete range of system parameters and for arbitrary bath spectral densities. With the numerically exact absorption and emission operators, one can also immediately compute energy transfer rates using the multi-chromophoric Förster resonant energy transfer formalism. Benchmark calculations on the emission spectra of two level systems are presented demonstrating the efficacy of the stochastic approach. This is followed by calculations of the energy transfer rates between two weakly coupled dimer systems as a function of temperature and system-bath coupling strength. It is shown that the recently developed hybrid cumulant expansion (see Paper II) is the only perturbative method capable of generating uniformly reliable energy transfer rates and emission spectra across a broad range of system parameters. PMID:25747062

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

2015-03-01

139

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

Microsoft Academic Search

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

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

2010-01-01

140

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

Microsoft Academic Search

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

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

2010-01-01

141

Alpha-particle emission as a probe of nuclear shapes and structure effects in proton evaporation spectra  

SciTech Connect

Emission barriers and subbarrier anisotropies from {alpha} decay of Sn* and Yb* compound nuclei are examined in the light of calculations incorporating deformation effects in the decay process. For the Yb* systems deformation which increases with spin is necessary to explain the data. For the Sn* systems the spectral shapes and anisotropies can be explained without deformation. For systems lighter than Sn this probe is not sensitive to the deformation. Energy spectra and angular correlations of evaporated protons from the {sup 52}Cr({sup 34}S, 2n2p){sup 82}Sr reaction were measured in coincidence with discrete transitions. Large shifts in proton spectra were observed when high spin states in different rotational bands are populated. They are interpreted as due to near-yrast stretched proton emission preferentially populating the yrast band by subbarrier protons. Simulations show that channel selected proton spectra cannot be used as probes of deformation.

Nicolis, N.G.; Sarantites, D.G.; Abenante, V.; Adler, L.A.; Dilmanian, F.A.; Majka, Z.; Semkow, T.M.; Stracener, D.W. (Washington Univ., St. Louis, MO (USA). Dept. of Chemistry); Baktash, C.; Beene, J.R.; Garcia-Bermudez, G.; Halbert, M.L.; Hensley, D.C.; Johnson, N.R.; Lee, I.Y.; McGowan, F.K.; Riley, M.A.; Virtanen, A. (Oak Ridge National Lab., TN (USA)); Griffin, H.C. (Michigan Univ., Ann Arbor, MI (USA). Dep

1990-01-01

142

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

SciTech Connect

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

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

2009-05-07

143

Retrieval of stratospheric ozone profiles from MIPAS/ENVISAT limb emission spectra: a sensitivity study  

NASA Astrophysics Data System (ADS)

We report on the dependance of ozone volume mixing ratio profiles, retrieved from spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), on different retrieval setups such as different a-priori profiles, regularization strengths and spectral regions used for analysis. MIPAS is a spaceborne limb-viewing Fourier transform infrared (FTIR) emission spectrometer, by which vertical profiles of various trace gases can be measured simultaneously. Purpose of this investigation is to check and to optimize the current retrieval setup. The choice of different a-priori profiles, of a different approach to retrieve the continuum radiation, and of a weaker regularization than in the reference data version (V2_O3_2) causes only small to moderate deviations of up to ą0.2, -0.3 and ą0.5 ppmv, respectively, in the retrieved ozone volume mixing ratios below 60 km altitude. Use of different microwindow sets optimized for polar, mid-latitude and tropical conditions results in deviations of up to ą1.5 ppmv in the altitude region of the ozone maximum, exceeding the total estimated retrieval error of 0.65 ppmv (polar regions) - 1.2 ppmv (tropics) in this height region. Therefore, to avoid latitudinal artefacts, one fixed set of microwindows is considered more appropriate for retrieval of a whole orbit rather than a latitude-dependent microwindow selection. For this task the microwindow set optimized for the polar atmosphere was found to be better suitable than its midlatitude and tropical counterparts. The results from the different microwindow sets, which variably cover MIPAS spectral bands A (685-970 cm-1) and AB (1020-1170 cm-1), indicated a positive bias of up to 1ppmv between the ozone maxima retrieved from the ozone emission in MIPAS band AB only and from combined analysis of MIPAS bands A and AB. Further investigations showed that this discrepancy can be caused by a bias between the radiance calibration of level-1B spectra of bands A and AB or by a bias between the spectroscopic data used in bands A and AB.

Glatthor, N.; von Clarmann, T.; Fischer, H.; Funke, B.; Gil-López, S.; Grabowski, U.; Höpfner, M.; Kellmann, S.; Linden, A.; López-Puertas, M.; Mengistu Tsidu, G.; Milz, M.; Steck, T.; Stiller, G. P.; Wang, D.-Y.

2005-11-01

144

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

145

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

146

Numerical Modeling of Multi-wavelength Spectra of M87 Core Emission  

NASA Astrophysics Data System (ADS)

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 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 × 107 cm-3, equivalent to horizon accretion rates between \\dot{m} = \\dot{M}/\\dot{M}_{Edd} \\approx 2\\times 10^{-6} and 1 × 10-5 (with \\dot{M}_{Edd} defined assuming a radiative efficiency ? = 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.

2012-02-01

147

Forbidden emission lines of NE IV in the optical and ultraviolet spectra of gaseous nebulae  

NASA Astrophysics Data System (ADS)

Recent R-matrix calculations of electron impact excitation rates in Ne IV are used to calculate emission line ratio-ratio diagrams involving both the UV (1602, 2422 and 2424 A) and optical (4714, 4716, 4724 and 4726 A) forbidden Ne IV transitions, for a range of electron temperatures and electron densities appropriate to gaseous nebulae. These diagrams should, in principle, allow the simultaneous determination of T(e) and N(e) from measurements of the forbidden Ne IV lines in a spectrum. Plasma parameters deduced for a sample of high-excitation planetary nebulae, using a combination of observational data obtained with the IUE satellite and the Hamilton Echelle Spectrograph (HES) on the 3-m Shane Telescope at the Lick Observatory, are found to show generally excellent internal consistency. In addition, they are in good agreement with the values of T(e) and N(e) estimated from other high-excitation line ratios in the HES spectra, and by previous authors using IR and UV transitions in forbidden O IV and Ne V. These results provide observational support for the accuracy of the theoretical forbidden Ne IV ratios, and hence the atomic data adopted in their derivation.

Keenan, F. P.; Aller, L. H.; Bell, K. L.; Espey, B. R.; Feibelman, W. A.; Hyung, S.; McKenna, F. C.; Ramsbottom, C. A.

1998-04-01

148

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

149

[Study on stable process of hexagon pattern in dielectric barrier discharge by optical emission spectra].  

PubMed

The effect of plasma parameters and excited states on the stable process of the hexagon pattern in a dielectric barrier discharge was studied by using optical emission spectra. It was found that the diameter of the discharge filament increases, the pattern gets more stable, and the color of the pattern changes from purple to gray with the increase in the voltage in dielectric barrier discharge in argon and air mixture. It indicates that the plasma excited states and parameters may be changed. To this end, the relative intensity of N2 and Ar spectral lines with respect to Ar I 763.51 nm, the molecular vibration temperature, and the electron excitation temperature were measured with the change in the applied voltage. The results show that the relative intensity of N2 spectral lines decreases and that of Ar spectral lines increases with the increase in the voltage. And both the molecular vibration temperature and the electron excitation temperature increase. These phenomena indicate that the electron energy increases with the increase in the voltage. The increase of the stimulated argon atoms excited by higher energy electron leads to the increase in the diameters of the discharge filaments. Correspondingly, the areas of the wall charges deposited on the dielectric increase, which results in the enhancement of the interactions between filaments, and therefore the hexagon pattern becomes stable. PMID:24555348

Dong, Li-Fang; Zhang, Chao; Zhang, Xin-Pu; Zhao, Long-Hu

2013-11-01

150

Analysis of arc emission spectra of stainless steel electric arc furnace slag affected by fluctuating arc voltage.  

PubMed

Control of chromium oxidation in the electric arc furnace (EAF) is a significant problem in stainless steel production due to variations of the chemical compositions in the EAF charge. One potential method to control chromium oxidation is to analyze the emission spectrum of the electric arc in order to find indicators of rising chromium content in slag. The purpose of this study was to determine if slag composition can be gained by utilizing electric arc emission spectra in the laboratory environment, despite electric arc voltage fluctuations and varying slag composition. The purpose of inducing voltage fluctuation was to simulate changes in the industrial EAF process. The slag samples were obtained from Outokumpu Stainless Oy Tornio Works, and three different arc currents were used. The correlation analysis showed that the emission spectra offer numerous peak ratios with high correlations to the X-ray fluorescence-measured slag CrO(x)/FeO(x) and MnO/SiO2 ratios. These ratios are useful in determining if the reduction agents have been depleted in the EAF. The results suggest that analysis of laboratory-scale electric arc emission spectra is suitable for indicating the high CrO(x) or MnO content of the slag despite the arc fluctuations. Reliable analysis of other slag components was not successful. PMID:24405950

Aula, Matti; Mäkinen, Ari; Fabritius, Timo

2014-01-01

151

(??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

152

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

SciTech Connect

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

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

2013-11-10

153

Mid-infrared Atomic Fine-structure Emission-line Spectra of Luminous Infrared Galaxies: Spitzer/IRS Spectra of the GOALS Sample  

NASA Astrophysics Data System (ADS)

We present the data and our analysis of mid-infrared atomic fine-structure emission lines detected in Spitzer/Infrared Spectrograph high-resolution spectra of 202 local Luminous Infrared Galaxies (LIRGs) observed as part of the Great Observatories All-sky LIRG Survey (GOALS). We readily detect emission lines of [S IV], [Ne II], [Ne V], [Ne III], [S III]18.7 ?m, [O IV], [Fe II], [S III]33.5 ?m, and [Si II]. More than 75% of these galaxies are classified as starburst-dominated sources in the mid-infrared, based on the [Ne V]/[Ne II] line flux ratios and equivalent width of the 6.2 ?m polycyclic aromatic hydrocarbon feature. We compare ratios of the emission-line fluxes to those predicted from stellar photo-ionization and shock-ionization models to constrain the physical and chemical properties of the gas in the starburst LIRG nuclei. Comparing the [S IV]/[Ne II] and [Ne III]/[Ne II] line ratios to the Starburst99-Mappings III models with an instantaneous burst history, the emission-line ratios suggest that the nuclear starbursts in our LIRGs have ages of 1-4.5 Myr, metallicities of 1-2 Z ?, and ionization parameters of 2-8 × 107 cm s-1. Based on the [S III]33.5 ?m/[S III]18.7 ?m ratios, the electron density in LIRG nuclei is typically one to a few hundred cm-3, with a median electron density of ~300 cm-3, for those sources above the low density limit for these lines. We also find that strong shocks are likely present in 10 starburst-dominated sources of our sample. A significant fraction of the GOALS sources (80) have resolved neon emission-line profiles (FWHM >=600 km s-1) and five show clear differences in the velocities of the [Ne III] or [Ne V] emission lines, relative to [Ne II], of more than 200 km s-1. Furthermore, six starburst and five active galactic nucleus dominated LIRGs show a clear trend of increasing line width with ionization potential, suggesting the possibility of a compact energy source and stratified interstellar medium in their nuclei. We confirm a strong correlation between the sum of the [Ne II]12.8 ?m and [Ne III]15.5 ?m emission, as well as [S III]33.5 ?m, with both the infrared luminosity and the 24 ?m warm dust emission measured from the spectra, consistent with all three lines tracing ongoing star formation. Finally, we find no correlation between the hardness of the radiation field or the emission-line width and the ratio of the total infrared to 8 ?m emission (IR8), a measure of the strength of the starburst and the distance of the LIRGs from the star-forming main sequence. This may be a function of the fact that the infrared luminosity and the mid-infrared fine-structure lines are sensitive to different timescales over the starburst, or that IR8 is more sensitive to the geometry of the region emitting the warm dust than the radiation field producing the H II region emission.

Inami, H.; Armus, L.; Charmandaris, V.; Groves, B.; Kewley, L.; Petric, A.; Stierwalt, S.; Díaz-Santos, T.; Surace, J.; Rich, J.; Haan, S.; Howell, J.; Evans, A. S.; Mazzarella, J.; Marshall, J.; Appleton, P.; Lord, S.; Spoon, H.; Frayer, D.; Matsuhara, H.; Veilleux, S.

2013-11-01

154

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

155

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

156

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

157

Faint Object Spectrograph Spectra of the UV Emission Lines in NGC 5558: Detection of Strong Narrow Components  

NASA Technical Reports Server (NTRS)

Ultraviolet spectra of the Seyfert 1 galaxy NGC 5548 were obtained with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope on 1992 July 5, when the UV continuum and broad emission lines were at their lowest ever observed level. The high resolution of the spectra, relative to previous UV observations, and the low state of NGC 5548 allow the detection and accurate measurement of strong narrow components of the emission lines of Ly alpha, C IV 1549, and C III 1909. Isolation of the UV narrow components enables a detailed comparison of narrow-line region (NLR) properties in Seyfert 1 and 2 galaxies, and removal of their contribution is important for studies of the broad-line region (BLR). Relative to the other narrow lines, C IV 1549 is much stronger in NGC 5548 than in Seyfert 2 galaxies, and Mg II 2798 is very weak or absent.

Crenshaw, D. Michael; Boggess, Albert; Wu, Chi-Chao

1993-01-01

158

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

159

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

160

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

161

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

162

Oxygen emission lines in the high resolution spectra of 9P/Tempel 1 following the Deep Impact event  

NASA Astrophysics Data System (ADS)

Context: On 2005 July 4, the NASA spacecraft Deep Impact delivered an impactor on the comet 9P/Tempel 1 to study the material ejected from the nucleus. A worldwide observation campaign accompanied the mission, to characterize the activity of 9P/Tempel 1 before and after the impact. Aims: At La Palma (Canary Islands), the comet was observed from July 2 to July 9 using the echelle spectrograph SARG on the Telescopio Nazionale Galileo (TNG). Fifteen spectra were obtained with a resolving power of R=29 000 in the spectral range 4620-7920 Ĺ. Many interesting emission lines can be found in this range, in particular the [OI] lines at 5577 Ĺ ("green line”) and at 6300 and 6364 Ĺ ("red doublet”). From the analysis of these lines it is possible to derive information on the processes that produce these emissions. Methods: The three atomic oxygen lines are clearly visible in most of the spectra. The intensity ratio between the green line and the sum of the red lines, indicative of the parent of these lines, was computed for 9 of the 15 spectra. The value of the intensity ratio for the night of July 5 was compared with the model results obtained from a coupled chemistry transport model. Results: The intensity ratio of green to red oxygen lines obtained from the observed spectra and the one derived from the model suggest water is the main parent of the [OI] emissions on comet 9P/Tempel 1. Based on observations collected at the Italian Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de Los Muchachos of the Instituto de Astrofisica de Canarias.

Capria, M. T.; Cremonese, G.; Bhardwaj, A.; de Sanctis, M. C.; Mazzotta Epifani, E.

2008-02-01

163

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

E-print Network

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

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

2014-01-01

164

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

165

The Case for General Relativistic Effects in the Fe K(alpha) Profile of an Active Galaxy  

NASA Technical Reports Server (NTRS)

We present results from a simultaneous Chandra HETG (High Energy Transmission Grating) and XMM (X-ray Multi-mirror Mission)-Newton observation of NGC 3516. We find evidence for several narrow components of Fe K(alpha) along with a broad line. We consider the possibility that the lines arise in a blob of material ejected from the nucleus with velocity of approximately 0.25c. We also consider an origin in a neutral accretion disk, suffering enhanced illumination at 35 and 175 R(sub g), perhaps due to magnetic reconnection. The presence of these narrow features indicates there is no Comptonizing region along the line-of-sight to the nucleus. This in turn is compelling support for the hypothesis that broad Fe K(alpha) components are, in general, produced by strong gravity.

Turner, T. J.; Mushotzky, R.; Yaqoob, T.; George, I. M.; Snowden, S. L.; Netzer, H.; Kraemer, S. B.; Nandra, K.; Chelouche, D.; White, Nicholas E. (Technical Monitor)

2002-01-01

166

Effects of Incident Electron Fluence and Energy on the Election Yield Curves and Emission Spectra of Dielectrics  

NASA Technical Reports Server (NTRS)

We present an experimental study of evolution of electron emission yields and spectra as a result of internal charge build up due to electron dose. Reliable total, backscattered and secondary yield curves and electron emission spectra for un-charged insulators using a low fluence, pulsed electron beam (= or < 5 microsec at = or < 3 nA/sq mm or = or < 10(exp 5) e/sq mm per pulse) with low energy electron and UV flooding to neutralize the charging between pulses. Quantifiable changes in yield curves are observed due to < 100 fC/sq mm fluences for several excellent dielectric thin film materials. We find good agreement with a phenomenological argument based on insulator charging predicted by the yield curve; this includes an approximately linear decrease in the magnitude of the yield as incident energies approach the crossover energies and an exponential decrease in yield as accumulated internal charge reduces the landing energy to asymptotically approach a steady state surface charge and unity yield. We also find that the exponential decay of yield curves with fluence exhibit an energy dependent decay constant, alpha(E), over a broad range of incident energies below, between and above the crossover energies. Finally, we present some preliminary physics-based models for this energy dependence and attempt to relate our charging measurements to knowledge of how charge is deposited within the insulator, the mechanisms for charge trapping and transport, and how the profile of trapped charge affects the transport and emission of charges from insulators.

Sim, Alec; Dennison, J. R.; Thomson, Clint

2005-01-01

167

On the Early Time X-ray Spectra of Swift Afterglows I: Evidence for Anomalous Soft X-ray Emission  

E-print Network

We have conducted a thorough and blind search for emission lines in >70 Swift X-ray afterglows of total exposure ~10^7s. We find that most afterglows are consistent with pure power-laws plus extinction. Significant outliers to the population exist at the 5-10% level and have anomalously soft, possibly thermal spectra. Four bursts are singled out via detections of 2-5 lines: GRBs 060218, 060202, 050822, and 050714B. The most significant soft component detections in the full data set of ~2000 spectra correspond to GRB060218/SN2006aj, with significances ranging up to ~20sigma. A thermal plasma model fit to the data indicates that the flux is primarily due to L-shell transitions of Fe at ~solar abundance. We associate (>4sigma significant) line emission from the 3 other events with K-shell transitions in light metals. We favor a model where the line emission in these afterglows arises from the mildly relativistic cocoon of matter surrounding the GRB jet as it penetrates and exits the surface of the progenitor sta...

Butler, N R

2006-01-01

168

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Emission spectra of a magnesium plasma created in vacuum by short laser pulses  

Microsoft Academic Search

An investigation was made of the emission spectra of a plasma formed on the surface of a magnesium barrier in a vacuum by nanosecond laser pulses of wavelengths 1.06 and 0.532 mum. The intensity of the radiation incident on the magnesium target was (1-8)×1012 W cm-2. Photographic and photoelectric methods were used to record the emission spectra in the visible

A. F. Golovin

1994-01-01

169

X-ray emission spectra and gaps of CuFeO2 with the modified Becke-Johnson potential  

NASA Astrophysics Data System (ADS)

We investigate the electronic structures of CuFeO2 by using Tran and Blaha's modified Becke and Johnson exchange potential. The calculated X-ray emission spectra of CuFeO2 for O-K and Fe-L are quite compatible with experimental data. The calculated energy band gap and optical band gap are 0.15 eV and 1.03 eV, respectively, and the theoretical magnetic moment for Fe atom is 4.11?B, which is very close to experimental value 4.2 ą 0.1?B.

Guo, San-Dong

2015-03-01

170

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

171

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

172

Calculation of emission spectra in terms of a stochastic relaxation model: Fe3+ in LiNbO3  

NASA Astrophysics Data System (ADS)

Mössbauer emission spectra of LiNbO3:57Co single crystals at 100 K in a magnetic field of 4 T show Fe3+ line intensities corresponding to a nearly Boltzmann population of the6A1g Zeeman sublevels. Supposing that this is due to a spin-lattice relaxation in the ground state, no relaxation matrix can reproduce the shape of the spectrum. We conclude that the initial populations are temperature dependent due to spin-lattice relaxation within the? _6 ^T excited doublet.

Gruber, W.; Nagy, D. L.; Ritter, G.; Szücs, I. S.

1988-02-01

173

A theoretical study of the emission spectra of indole and its analogs: indene, benzimidazole, and 7-azaindole  

NASA Astrophysics Data System (ADS)

The complete active space (CAS) SCF method and multiconfigurational second-order perturbation theory (CASPT2) have been used to study the electronic spectra of indole, indene, benzimidazole, and 7-azaindole. The paper is focused on the study of the low-lying valence triplet and singlet electronic states at the optimized geometries of the excited states. The geometries have been optimized by using analytic CASSCF derivatives. CASPT2 point calculations have been performed in order to obtain band origins and relaxed emission energies. The results are analyzed in the context of the complex emission processes, both fluorescence and phosphorescence, displayed by the title compounds, which can be used as biochemical probes in the characterization of protein properties and activity.

Serrano-Andrés, Luis; Borin, Antonio Carlos

2000-12-01

174

Fourier transform emission spectra of the A2? ? X2?+ and B2?+ ? X2?+ transitions of CaD  

NASA Astrophysics Data System (ADS)

Emission spectra of the A2? ? X2?+ and B2?+ ? X2?+ transitions of CaD were produced in a discharge-furnace emission source and recorded with a high resolution Fourier transform spectrometer. The ?v = 0 and ?v = -1 sequences up to v' = 3 of the A2? state and v' = 2 of the B2?+ state have been observed and rotationally analyzed. Empirical band constants and Dunham-type constants were determined for all electronic states using N2 Hamiltonians. The equilibrium constants Te, ?e and ?exe were determined to be 14407.604(2), 957.330(4) and 10.415(2) cm-1 for the A2? state, and 15751.570(2), 925.840(4) and 12.417(2) cm-1 for the B2?+ state, respectively. The equilibrium bond lengths (re) of the A2? and B2?+ states are 1.977495(3) and 1.963467(6) Ĺ, respectively.

GharibNezhad, Ehsan; Shayesteh, Alireza; Bernath, Peter F.

2012-11-01

175

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

NASA Technical Reports Server (NTRS)

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

Roesler, Collin S.; Pery, Mary Jane

1995-01-01

176

Analysis of emission spectra of Ho{sup 3+}:LFBCd glasses  

SciTech Connect

In the present paper, we report on the absorption and emission properties of (0.1-1.5 mol %) Ho{sup 3+} doped LFBCd (Li{sub 2}O{sub ?}LiF{sub ?}B{sub 2}O{sub 3?}CdO) glasses prepared via melt quenching method. On exciting these glasses at (?{sub exci}) = 452 nm, two emissions at 556 nm ({sup 5}S{sub 2}?{sup 5}I{sub 8}; Green), 655 nm ({sup 5}F{sub 5}?{sup 5}I{sub 8}; Red) have been obtained. Upon exciting these glasses with a 980 nm diode laser, NIR emissions at 1195 nm ({sup 5}I{sub 6}?{sup 5}I{sub 8}), 1951 nm ({sup 5}I{sub 7}?{sup 5}I{sub 8}) have been measured for 1 mol % Ho{sup 3+}:LFBCd glass. For higher concentration beyond 1.0 mol %, emission quenching of Ho{sup 3+} 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 % Ho{sup 3+}:LFBCd glass.

Naresh, V., E-mail: varna.naresh@gmail.com; Buddhudu, S., E-mail: varna.naresh@gmail.com [Department of Physics, Sri Venkateswara University, Tirupati-517502 (India)

2014-04-24

177

Spectra of Stimulated Electromagnetic Emission of the Ionosphere Upon Sweeping of the Pump Wave Frequency Near Gyroharmonics. I. Experimental Results  

NASA Astrophysics Data System (ADS)

We present the results of experimental studies of the spectra of the stimulated electromagnetic emission excited in the ionosphere by powerful radio waves during the pump wave frequency sweeping near the forth ( n = 4) and fifth ( n = 5) harmonics of the electron cyclotron frequency nf ce. The frequency sweep was carried out for long (continuous) pumping in vertical and inclined directions (at 14° and 18° south of the zenith), as well as for the pulse diagnostic wave both with and without additional pumping far from the gyroharmonics. The dependences of the spectral features of the stimulated electromagnetic emission on the ratio between the pump-wave frequency f 0 (or on the diagnostic-wave frequency fDW) and nf ce were analyzed. It is found that near the multiple gyroresonance, different spectral features of the stimulated emission are quenched at the same frequency for different pump-wave frequencies. For a sufficiently large inclination of the pump wave beam from the vertical direction, the intensity of the stimulated electromagnetic emission is notably decreased for f 0 ? nf ce as compared with f 0 > nf ce.

Kotov, P. V.; Sergeev, E. N.; Grach, S. M.

2008-06-01

178

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

NASA Astrophysics Data System (ADS)

We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming region showing emission in Spitzer Space Telescope Infrared Spectrograph 5-7.5 ?m spectra from water vapor and absorption from other gases in these stars' protoplanetary disks. Seven stars' spectra show an emission feature at 6.6 ?m due to the ?2 = 1-0 bending mode of water vapor, with the shape of the spectrum suggesting water vapor temperatures >500 K, though some of these spectra also show indications of an absorption band, likely from another molecule. This water vapor emission contrasts with the absorption from warm water vapor seen in the spectrum of the FU Orionis star V1057 Cyg. The other 6 of the 13 stars have spectra showing a strong absorption band, peaking in strength at 5.6-5.7 ?m, which for some is consistent with gaseous formaldehyde (H2CO) and for others is consistent with gaseous formic acid (HCOOH). There are indications that some of these six stars may also have weak water vapor emission. Modeling of these stars' spectra suggests these gases are present in the inner few AU of their host disks, consistent with recent studies of infrared spectra showing gas in protoplanetary disks.

Sargent, B. A.; Forrest, W.; Watson, Dan M.; D'Alessio, P.; Calvet, N.; Furlan, E.; Kim, K. H.; Green, J.; Pontoppidan, K.; Richter, I.; Tayrien, C.

2014-09-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

180

Broadband Emission Spectra from the Cygnus X-3 Jet in the Soft Spectral State  

NASA Astrophysics Data System (ADS)

In order to understand the main observational characteristics of the Galactic X-ray binary Cygnus X-3, we propose a radiation model in which high-energy electrons accelerate in the dissipation zone of a jet and produce nonthermal broadband emissions. Broadband spectral energy distributions are computed to compare the AGILE and Fermi LAT data with the multi-band data during soft X-ray spectral states. By fitting observations at different locations of the jet, we find that the emission region is rather compact and should be located at a distance of about one orbital radius. Our results can explain the current multi-frequency observations and also predict the TeV band emission. The model could be tested by a polarization measurement at IR band, and/or by a correlation study between the GeV and TeV bands once very-high-energy observations are available.

Zhang, Jian-Fu; Lu, Ju-Fu

2015-02-01

181

Effects of temporal laser profile on the emission spectra for underwater laser-induced breakdown spectroscopy: Study by short-interval double pulses with different pulse durations  

NASA Astrophysics Data System (ADS)

We investigate the effects of temporal laser profile on the emission spectra of laser ablation plasma in water. We use short-interval (76 ns) double pulses with different pulse durations of the composing two pulses for the irradiation of underwater target. Narrow atomic spectral lines in emission spectra are obtained by the irradiation, where the two pulses are wide enough to be merged into a single-pulse-like temporal profile, while deformed spectra are obtained when the two pulses are fully separated. The behavior of the atomic spectral lines for the different pulse durations is consistent with that of the temporal profiles of the optical emission intensities of the plasma. All these results suggest that continuous excitation of the plasma during the laser irradiation for ˜100 ns is a key to obtain narrow emission spectral lines.

Tamura, Ayaka; Matsumoto, Ayumu; Nakajima, Takashi; Fukami, Kazuhiro; Ogata, Yukio H.; Nishi, Naoya; Sakka, Tetsuo

2015-01-01

182

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

183

Designer emission spectra through tailored energy transfer in nanoparticle-doped silica preforms.  

PubMed

This Letter provides a qualitative proof of concept for purposefully tailoring the emission spectrum of glass by spatially localizing dissimilar dopants to control the degree of energy transfer. More specifically, modified-chemical-vapor-deposition-derived silica preforms were solution doped with either a solution of individually Eu(3+)- or Tb(3+)-doped nanoparticles or a solution of Eu(3+)/Tb(3+)-codoped nanoparticles. The preform prepared using the codoped nanoparticles exhibited energy transfer from the Tb(3+) to the Eu(3+) ions, whereas the preform containing individually doped nanoparticles yielded only discretely Tb(3+) or Eu(3+) emissions. The extension of this work to broadband amplifiers and lasers is discussed. PMID:19649090

Kucera, Courtney; Kokuoz, Baris; Edmondson, Dale; Griese, David; Miller, Michael; James, Andrew; Baker, William; Ballato, John

2009-08-01

184

Experimental Studies of Low-Pressure Plasma Jet by Means of Langmuir Probes and Emission Spectra  

Microsoft Academic Search

An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and

Lei Liu; Jinxiang Cao; Tianye Niu; Liang Wang; Gang Meng; Xin Liu; Lei Yuan; Runhui Wu; Shengjun Zhang; Aimin Ren

2009-01-01

185

DERIVING CHLOROPHYLL FLUORESCENCE EMISSIONS OF VEGETATION CANOPIES FROM HIGH RESOLUTION FIELD REFLECTANCE SPECTRA  

Technology Transfer Automated Retrieval System (TEKTRAN)

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 (Chlorophyll fluorescence) peaks centered at 685"10 nm and 735"5 nm. Methods ha...

186

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

187

On the Early Time X-ray Spectra of Swift Afterglows I: Evidence for Anomalous Soft X-ray Emission  

E-print Network

We have conducted a thorough and blind search for emission lines in >70 Swift X-ray afterglows of total exposure ~10^7s. We find that most afterglows are consistent with pure power-laws plus extinction. Significant outliers to the population exist at the 5-10% level and have anomalously soft, possibly thermal spectra. Four bursts are singled out via possible detections of 2-5 lines: GRBs 060218, 060202, 050822, and 050714B. Alternatively, a blackbody model with kT~0.1-0.5 keV can describe the soft emission in each afterglow. The most significant soft component detections in the full data set of ~2000 spectra correspond to GRB060218/SN2006aj, with line significances ranging up to \\~20-sigma. A thermal plasma model fit to the data indicates that the flux is primarily due to L-shell transitions of Fe at ~ solar abundance. We associate (>4-sigma significant) line triggers in the 3 other events with K-shell transitions in light metals. We favor a model where the possible line emission in these afterglows arises from the mildly relativistic cocoon of matter surrounding the GRB jet as it penetrates and exits the surface of the progenitor star. The emitting material in each burst is at a similar distance \\~10^12--10^13 cm, a similar density ~10^17 cm^-3, and subject to a similar flux of ionizing radiation. The lines may correlate with the X-ray flaring. For the blackbody interpretation, the soft flux may arise from break out of the GRB shock or plasma cocoon from the progenitor stellar wind, as recently suggested for GRB060218 (Campana et al. 2006). Due to the low z of GRB060218, bursts faint in Gamma-rays with fluxes dominated by this soft X-ray component could outnumber classical GRBs 100-1.

Nathaniel R. Butler

2006-11-03

188

X-ray Emission from Charge Exchange in the Cygnus Loop SNR  

E-print Network

The Cygnus Loop has been the focus of substantial debate concerning the contribution of charge exchange (CX) to supernova remnant (SNR) X-ray emission. We take advantage of a distinct feature of CX, enhanced K{\\alpha} forbidden line emission, and employ the energy centroid of the OVII K{\\alpha} triplet as a diagnostic. Based on X-ray spectra extracted from an extensive set of Suzaku observations, we measure the energy centroid shifts of the triplet on and off the shock rim of the remnant. We find that enhanced forbidden to resonance line emission exists throughout much of the rim and this enhancement azimuthally correlates with non-radiative H{\\alpha} filaments, a tracer of strong neutral-plasma interaction in the optical. We also show that alternative mechanisms cannot explain the enhancement observed. These results demonstrate the need to model the CX contribution to the X-ray emission of SNRs, particularly for shocks propagating in a partially neutral medium. Such modeling may be critically important to th...

Roberts, Shawn R

2015-01-01

189

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

190

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

NASA Astrophysics Data System (ADS)

A method using modulated continuous wave (CW) visible laser to measure time-resolved fluorescence spectra of trivalent rare-earth ions has been developed. Electro-optic modulator was used to modulate the CW pumping laser with a rise time of 2 ?s. CW Nd3+ lasers were used as examples to present the method. Upconversion dynamic process of Ho3+ was studied utilizing a 532 nm CW laser. Quantum cutting dynamic process from Tb3+ to Yb3+ was analyzed by a 473 nm CW laser. This method can be applied to any CW laser such as He-Ne laser, Ar+ laser, Kr+ laser, Ti:sapphire laser, etc.

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

2013-11-01

191

Light emission and excitonic effect of boron nitride nanotubes observed by photoluminescent spectra  

Microsoft Academic Search

Photoluminescent (PL) and optical absorption spectra of high-yield multi-wall BN nanotubes (BNNTs) were systematically investigated at room temperature in comparison with commercial hexagonal BN (h-BN) powder. The direct band gap of the BNNTs was determined to be 5.75eV, just slightly narrower than that of h-BN powder (5.82eV). Two Frenkel excitons with the binding energy of 1.27 and 1.35eV were also

Hua Chen; Ying Chen; Yun Liu; Chao-Nan Xu; Jim S. Williams

2007-01-01

192

EARLY RESULTS FROM THE GALACTIC O-STAR SPECTROSCOPIC SURVEY: C III EMISSION LINES IN Of SPECTRA  

SciTech Connect

On the basis of an extensive new spectroscopic survey of Galactic O stars, we introduce the Ofc category, which consists of normal spectra with C III {lambda}{lambda}4647-4650-4652 emission lines of comparable intensity to those of the Of defining lines N III {lambda}{lambda}4634-4640-4642. The former feature is strongly peaked to spectral type O5, at all luminosity classes, but preferentially in some associations or clusters and not others. The relationships of this phenomenon to the selective C III {lambda}5696 emission throughout the normal Of domain, and to the peculiar, variable Of?p category, for which strong C III {lambda}{lambda}4647-4650-4652 emission is a defining characteristic, are discussed. Magnetic fields have recently been detected on two members of the latter category. We also present two new extreme Of?p stars, NGC 1624-2 and CPD -28 deg. 2561, bringing the number known in the Galaxy to five. Modeling of the behavior of these spectral features can be expected to better define the physical parameters of both normal and peculiar objects, as well as the atomic physics involved.

Walborn, Nolan R. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Sota, Alfredo; MaIz Apellaniz, Jesus; Alfaro, Emilio J. [Instituto de Astrofisica de AndalucIa-CSIC, Glorieta de la Astronomia s/n, 18008 Granada (Spain); Morrell, Nidia I. [Las Campanas Observatory, Observatories of the Carnegie Institution of Washington, Casilla 601, La Serena (Chile); Barba, Rodolfo H.; Arias, Julia I. [Departamento de Fisica, Universidad de La Serena, Cisternas 1200 Norte, La Serena (Chile); Gamen, Roberto C. [Instituto de Astrofisica de La Plata-CONICET and Facultad de Ciencias Astronomicas y GeofIsicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata (Argentina)], E-mail: walborn@stsci.edu, E-mail: sota@iaa.es, E-mail: jmaiz@iaa.es, E-mail: emilio@iaa.es, E-mail: nmorrell@lco.cl, E-mail: rbarba@dfuls.cl, E-mail: julia@dfuls.cl, E-mail: rgamen@fcaglp.unlp.edu.ar

2010-03-10

193

Early Results from the Galactic O-Star Spectroscopic Survey: C III Emission Lines in Of Spectra  

NASA Astrophysics Data System (ADS)

On the basis of an extensive new spectroscopic survey of Galactic O stars, we introduce the Ofc category, which consists of normal spectra with C III ??4647-4650-4652 emission lines of comparable intensity to those of the Of defining lines N III ??4634-4640-4642. The former feature is strongly peaked to spectral type O5, at all luminosity classes, but preferentially in some associations or clusters and not others. The relationships of this phenomenon to the selective C III ?5696 emission throughout the normal Of domain, and to the peculiar, variable Of?p category, for which strong C III ??4647-4650-4652 emission is a defining characteristic, are discussed. Magnetic fields have recently been detected on two members of the latter category. We also present two new extreme Of?p stars, NGC 1624-2 and CPD -28° 2561, bringing the number known in the Galaxy to five. Modeling of the behavior of these spectral features can be expected to better define the physical parameters of both normal and peculiar objects, as well as the atomic physics involved.

Walborn, Nolan R.; Sota, Alfredo; Maíz Apellániz, Jesús; Alfaro, Emilio J.; Morrell, Nidia I.; Barbá, Rodolfo H.; Arias, Julia I.; Gamen, Roberto C.

2010-03-01

194

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

195

Experimental Studies of Low-Pressure Plasma Jet by Means of Langmuir Probes and Emission Spectra  

NASA Astrophysics Data System (ADS)

An investigation was made into the argon plasma jet that expanded in a low-pressure vacuum chamber. The spatial distributions of the parameters of the plasma jet with different supplied powers were measured using a ten-channel Langmuir probe array. The chemical species in the plasma jet were identified by emission spectroscopy. The electron excitation temperatures at two positions, 10 cm and 50 cm downstream from the nozzle exit were calculated, respectively, by the Boltzmann plot method.

Liu, Lei; Cao, Jinxiang; Niu, Tianye; Wang, Liang; Meng, Gang; Liu, Xin; Yuan, Lei; Wu, Runhui; Zhang, Shengjun; Ren, Aimin

2009-06-01

196

VizieR Online Data Catalog: 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 0.80Ĺ/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 3.2Ĺ and 4.8Ĺ, 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 (-1.5Ĺ) and Ha5 and 6 (both -2.2Ĺ); 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 6250Ĺ and 7600Ĺ, 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

197

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. II. Hybrid cumulant expansion  

NASA Astrophysics Data System (ADS)

We develop a hybrid cumulant expansion method to account for the system-bath entanglement in the emission spectrum in the multi-chromophoric Förster transfer rate. In traditional perturbative treatments, the emission spectrum is usually expanded with respect to the system-bath coupling term in both real and imaginary time. This perturbative treatment gives a reliable absorption spectrum, where the bath is Gaussian and only the real-time expansion is involved. For the emission spectrum, the initial state is an entangled state of the system plus bath. Traditional perturbative methods are problematic when the excitations are delocalized and the energy gap is larger than the thermal energy, since the second-order expansion cannot predict the displacement of the bath. In the present method, the real-time dynamics is carried out by using the 2nd-order cumulant expansion method, while the displacement of the bath is treated more accurately by utilizing the exact reduced density matrix of the system. In a sense, the hybrid cumulant expansion is based on a generalized version of linear response theory with entangled initial states.

Ma, Jian; Moix, Jeremy; Cao, Jianshu

2015-03-01

198

Notes on the radial velocities of 14 O stars and the emission lines in their spectra  

NASA Astrophysics Data System (ADS)

Radial-velocity observations of 10 Of stars of various subtypes and of four O stars are presented. Two of the stars appear to have a constant velocity, one is known to be a spectroscopic binary, three are suspected spectroscopic binaries, and eight show a variable velocity of small range. The sharp Of emission lines are stationary with respect to the atmospheric layer in which the absorption lines are formed in all of the Of stars except one peculiar Of star, HD 108, and two supergiants. It is inferred that the purely emission lines in the spectrum of HD 108 are formed in plasma contained in arcades of magnetically supported loops which are attached to the photosphere of the star. The purely absorption lines and the lines with P-Cygni-type profiles in the spectrum of HD 108 are formed in a wind which originates in the photosphere. It is argued that the average radial velocity of the purely emission lines of HD 108 represents the true line-of-sight component of the stellar motion.

Underhill, A. B.; Gilroy, K. K.

1990-12-01

199

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

200

Förster resonance energy transfer, absorption and emission spectra in multichromophoric systems. II. Hybrid cumulant expansion.  

PubMed

We develop a hybrid cumulant expansion method to account for the system-bath entanglement in the emission spectrum in the multi-chromophoric Förster transfer rate. In traditional perturbative treatments, the emission spectrum is usually expanded with respect to the system-bath coupling term in both real and imaginary time. This perturbative treatment gives a reliable absorption spectrum, where the bath is Gaussian and only the real-time expansion is involved. For the emission spectrum, the initial state is an entangled state of the system plus bath. Traditional perturbative methods are problematic when the excitations are delocalized and the energy gap is larger than the thermal energy, since the second-order expansion cannot predict the displacement of the bath. In the present method, the real-time dynamics is carried out by using the 2nd-order cumulant expansion method, while the displacement of the bath is treated more accurately by utilizing the exact reduced density matrix of the system. In a sense, the hybrid cumulant expansion is based on a generalized version of linear response theory with entangled initial states. PMID:25747061

Ma, Jian; Moix, Jeremy; Cao, Jianshu

2015-03-01

201

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

202

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

SciTech Connect

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

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

2013-11-15

203

Optical cavity temperature measurement based on the first overtones spontaneous emission spectra for HF chemical laser  

NASA Astrophysics Data System (ADS)

An optical cavity temperature test method has been established for the HF chemical laser. This method assumes that in HF optical cavity the rotational distribution of vibrationally excited HF molecules meets the statistical thermodynamic distribution, the first overtones (v = 3-1 and 2-0) spontaneous emission spectral intensity distribution is obtained by using OMA V, the optical cavity temperature is calculated by linear fitting the rotational thermal equilibrium distribution formula for each HF vibrationally excited state. This method is simple, reliable, and repeatable. This method can be used to test the optical cavity temperature not only without lasing, but also with lasing.

Tang, Shukai; Li, Liucheng; Duo, Liping; Wang, Yuanhu; Yu, Haijun; Jin, Yuqi; Sang, Fengting

2015-02-01

204

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

NASA Astrophysics Data System (ADS)

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

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

2008-10-01

205

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

206

Theoretical Emission Spectra of Atmospheres of Hot Rocky Super-Earths  

NASA Astrophysics Data System (ADS)

Motivated by recent detection of transiting high-density super-Earths, we explore the detectability of hot rocky super-Earths orbiting very close to their host stars. In an environment hot enough for their rocky surfaces to be molten, they would have an atmosphere composed of gas species from the magma oceans. In this study, we investigate the radiative properties of the atmosphere that is in gas/melt equilibrium with the underlying magma ocean. Our equilibrium calculations yield Na, K, Fe, Si, SiO, O, and O2 as the major atmospheric species. We compile the radiative absorption line data of those species available in the literature and calculate their absorption opacities in the wavelength region of 0.1–100 ?m. Using them, we integrate the thermal structure of the atmosphere. Then, we find that thermal inversion occurs in the atmosphere because of the UV absorption by SiO. In addition, we calculate the ratio of the planetary to stellar emission fluxes during secondary eclipse, and we find prominent emission features induced by SiO at 4 ?m detectable by Spitzer, and those at 10 and 100 ?m detectable by near-future space telescopes.

Ito, Yuichi; Ikoma, Masahiro; Kawahara, Hajime; Nagahara, Hiroko; Kawashima, Yui; Nakamoto, Taishi

2015-03-01

207

PARAFAC modeling of fluorescence excitation-emission spectra for rapid assessment of compost maturity.  

PubMed

Assessment of compost maturity is crucial for achieving high quality compost in order to guarantee its marketability. In this context, a novel technique that combines fluorescence excitation-emission matrices (EEMs) with parallel factor (PARAFAC) analysis to assess compost maturity is presented. A total of 60 fluorescence EEMs of composts were successfully decomposed into a three-factor model using PARAFAC analysis. Components 1 [excitation/emission (Ex/Em) wavelengths=(230, 330)/410] and 2 [Ex/Em wavelengths=(250, 350)/450] were attributable to humic-like and fulvic-like substances, whereas component 3 [Ex/Em wavelengths=(220, 280)/340] belonged to protein-like substances. Pearson correlation analysis between the common maturity indices and log scores of three components demonstrated that components 1 and 3 are more suitable to assess compost maturity than component 2. These results reveal that EEM-PARAFAC could be applied as a valuable tool for assessing compost maturity, given its high sensitivity and selectivity. PMID:20598876

Yu, Guang-Hui; Luo, Yi-Hong; Wu, Min-Jie; Tang, Zhu; Liu, Dong-Yang; Yang, Xing-Ming; Shen, Qi-Rong

2010-11-01

208

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

PubMed Central

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

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

2002-01-01

209

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

210

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

211

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

SciTech Connect

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

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

2009-07-24

212

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

E-print Network

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

David K. Strickland; Ian R. Stevens

1998-03-06

213

COS Spectra of High-Redshift AGN: Probing Deep into the Rest-Frame Ionizing Continuum and Broad Emission Lines  

NASA Astrophysics Data System (ADS)

The order-of-magnitude improvement in sensitivity of COS over previous spectrographs has increased the number of AGN available for far-UV spectroscopy covering the rest-frame EUV. In archival work, we have enlarged our composite spectrum from 22 to 150 AGN, but the maximum redshift is z_max = 1.47. We request COS/G140L observations of 11 bright AGN {z = 1.45 to 2.13} to extend the composite below 400 A and greatly improve the statistics. At these redshifts, the G140L {1105 A setting} covers 1120-2000 A, probing the rest-frame continuum and emission lines down to 360-450 A. We will observe the Lyman continuum {LyC} below the He I edge {504 A} as it approaches the He II Lya break {304 A}. Obtaining 11 well-exposed QSO spectra will greatly increase our knowledge in the EUV beyond the few AGN currently observed in this band. These LyC photons are responsible for ionizing hydrogen, helium, and many metal ions, for ionizing QSO broad emission-line regions {BELR}, and for heating the IGM. Characterizing the AGN spectrum in the far-UV and ionizing EUV is also a crucial ingredient for studies of accretion disk structure and QSO outflows. We will also measure {or limit} the He I continuum edge {504 A} expected in some models of accretion disks, and will identify and characterize the key QSO broad emission lines in the FUV and EUV {Ne II, Ne III, Ne V, Ne VI, Ne VIII, O II, O III, O IV, O V, O VI}. Detecting multiple ions from the same element {Ne and O} will yield more accurate diagnostics of BELR temperatures and metallicities.

Shull, J.

2013-10-01

214

The retrieval of vertical profiles of chlorine source gases and N2O5 from MIPAS-B-92 limb emission spectra  

SciTech Connect

During the European Arctic Stratospheric Ozone Experiment (EASOE) the balloon-borne cryogenic Fourier transform spectrometer MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) recorded several sequences of mid-infrared limb emission spectra, which were used for the retrieval of vertical profiles of CFC-11, CFC-12, HCFC-22, CF4, and N2O5. These gases are characterized by very dense emission bands of unresolved lines. Results are consistent with the current theories of stratospheric dynamics and chemistry.

Clarmann, T.V.; Linden, A.; Wetzel, G.; Oelhaf, H.

1995-01-01

215

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

216

Effect of annealing treatment on K{beta}-to-K{alpha} x-ray intensity ratios of 3d transition-metal alloys  

SciTech Connect

The influence of heat annealing treatment on the K{beta}-to-K{alpha} x-ray intensity ratios of 3d transition metal was carried out by x-ray fluorescence studies of various alloy compositions. K{beta}-to-K{alpha} x-ray intensity ratios of Fe, Ni, Ti, Co, and Cu in Fe{sub x}Ni{sub 1-x}, Ti{sub x}Ni{sub 1-x}, and Co{sub x}Cu{sub 1-x} alloys unannealed and thermally annealed at different temperatures have been measured following excitation by 22.69-keV x rays from a 10-mCi {sup 109}Cd radioactive point source. The experimental data obtained after annealing treatment indicate deviations of K{beta}-to-K{alpha} x-ray intensity ratios for 3d transition metals in different alloy compositions from the corresponding ratios for unannealed samples. The present investigation makes it possible to perform reliable interpretation of experimental K{beta}-to-K{alpha} x-ray intensity ratios for various 3d transition metals in their alloys and can also provide quantitative information about the changes of the K{beta}-to-K{alpha} x-ray intensity ratios of these metals with annealing treatment in considered systems.

Han, I. [Faculty of Arts and Sciences, Department of Physics, Agri Ibrahim Cecen University, TR-04100 Agri (Turkey); Demir, L. [Faculty of Sciences, Department of Physics, Atatuerk University, TR-25240 Erzurum (Turkey)

2010-06-15

217

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

E-print Network

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

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

2007-07-28

218

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

219

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

SciTech Connect

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

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

2013-09-01

220

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

SciTech Connect

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

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

2008-05-05

221

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

222

Measurements of the Temperature of Subsonic CO{sub 2} Induction Plasma Flows by Analyzing Their Emission Spectra  

SciTech Connect

Results are presented from measurements of the temperature characteristics of subsonic CO{sub 2} 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{sub a} and the population temperature T{sub e} of the electronic states of C{sub 2} molecules (both averaged over the jet diameter) were measured from the absolute intensities of the atomic spectral lines and the spectrum of C{sub 2} 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{sub r} and T{sub 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 C{sub 2} 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{sub e} , T{sub v} , and T{sub r} was examined.

Bykova, N.G. [Institute for Problems of Mechanics, Russian Academy of Sciences, pr. Vernadskogo 101, Moscow, 117526 (Russian Federation); Kuznetsova, L.A. [Moscow State University, Vorob'evy Gory, Moscow, 119899 (Russian Federation)

2004-11-15

223

Research as a guide for curriculum development: An example from introductory spectroscopy. II. Addressing student difficulties with atomic emission spectra  

NASA Astrophysics Data System (ADS)

This is the second of two closely related articles (Paper I and Paper II) that together illustrate how research in physics education has helped guide the design of instruction that has proved effective in improving student understanding of atomic spectroscopy. Most of the more than 1000 students who participated in this four-year investigation were science majors enrolled in the introductory calculus-based physics course at the University of Washington (UW) in Seattle, WA, USA. The others included graduate and undergraduate teaching assistants at UW and physics majors in introductory and advanced physics courses at the University of Zagreb, Zagreb, Croatia. About half of the latter group were preservice high school physics teachers. Paper I describes how several conceptual and reasoning difficulties were identified among university students as they tried to relate a discrete line spectrum to the energy levels of atoms in a light source. This second article (Paper II) illustrates how findings from this research informed the development of a tutorial that led to improvement in student understanding of atomic emission spectra.

Ivanjek, L.; Shaffer, P. S.; McDermott, L. C.; Planinic, M.; Veza, D.

2015-02-01

224

Research as a guide for curriculum development: An example from introductory spectroscopy. I. Identifying student difficulties with atomic emission spectra  

NASA Astrophysics Data System (ADS)

This is the first of two closely related articles (Paper I and Paper II) that together illustrate how research in physics education has helped guide the design of instruction that has proved effective in improving student understanding of atomic spectroscopy. Most of the more than 1000 students who participated in this four-year investigation were science majors enrolled in the introductory calculus-based physics course at the University of Washington (UW) in Seattle, WA, USA. The others included graduate and undergraduate teaching assistants at UW and physics majors in introductory and advanced physics courses at the University of Zagreb, Zagreb, Croatia. About half of the latter group were preservice high school physics teachers. This article (Paper I) describes how several serious conceptual and reasoning difficulties were identified among students as they tried to relate a discrete line spectrum to the energy levels of atoms in a light source. Paper II illustrates how findings from this research informed the development of a tutorial that led to significant improvement in student understanding of atomic emission spectra.

Ivanjek, L.; Shaffer, P. S.; McDermott, L. C.; Planinic, M.; Veza, D.

2015-01-01

225

Diagnosis of lubricating oil by evaluating cyanide and carbon molecular emission lines in laser induced breakdown spectra  

NASA Astrophysics Data System (ADS)

To prevent engine failure it is essential to change lubricating oil regularly before it loses its protective properties. It is also necessary to monitor the physical and chemical conditions of the oil to reliably determine the optimum oil-change intervals. The present work focuses on studying evolution of the cyanide (CN) and carbon (C 2) molecular spectral emission lines in the laser induced breakdown spectra of lubricating oil as a function of its consumption. The intensities of these molecular bands have been taken as indicator of engine oil degradation at certain mileage. Furthermore, the percentage of decay of CN and C 2 integral intensity values at the corresponding mileage was calculated in order to relate it to the degree of consumption of the motor oil. Such percentage decay of the CN and C 2 integral intensities have been found to increase gradually with increasing mileage which is accompanied with increasing depletion of engine oil. The results of using LIBS technique in the present measurements proved that it is possible to have a direct, straightforward and easy method for prediction of lubricating oil degree of consumption. This may facilitate scheduling the proper time and/or mileage intervals for changing the oil to avoid any possibility of engine failure.

Elnasharty, I. Y.; Kassem, A. K.; Sabsabi, M.; Harith, M. A.

2011-08-01

226

Vibrationally resolved absorption, emission and resonance Raman spectra of diamondoids: a study based on time-dependent correlation functions.  

PubMed

The time-dependent approach to electronic spectroscopy, as popularized by Heller and coworkers in the 1980's, is applied here in conjunction with linear-response, time-dependent density functional theory to study vibronic absorption, emission and resonance Raman spectra of several diamondoids. Two-state models, the harmonic and the Condon approximations, are used for the calculations, making them easily applicable to larger molecules. The method is applied to nine pristine lower and higher diamondoids: adamantane, diamantane, triamantane, and three isomers each of tetramantane and pentamantane. We also consider a hybrid species "Dia = Dia" - a shorthand notation for a recently synthesized molecule comprising two diamantane units connected by a C=C double bond. We resolve and interpret trends in optical and vibrational properties of these molecules as a function of their size, shape, and symmetry, as well as effects of "blending" with sp(2)-hybridized C-atoms. Time-dependent correlation functions facilitate the computations and shed light on the vibrational dynamics following electronic transitions. PMID:24226411

Banerjee, Shiladitya; Saalfrank, Peter

2014-01-01

227

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

228

Application of a radiometric calibration method to lunar Fourier transform IR spectra by using a liquid-nitrogen-cooled high-emissivity blackbody.  

PubMed

Since winter 1994/1995 the Moon has been used in addition to the Sun as an IR source of radiation to measure atmospheric absorption spectra with a Bruker IR Fourier transform spectrometer IFS 120M located near Kiruna, Sweden. A two-point radiometric calibration method with blackbody references was applied to lunar spectra in the long-wave detector channel to improve the accuracy of evaluation of the column amounts of different atmospheric trace gases. A new liquid-nitrogen-cooled high-emissivity blackbody without an entrance window is described that is used for this calibration method. PMID:18264352

Schreiber, J; Blumenstock, T; Hase, F

1997-11-01

229

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

SciTech Connect

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

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

2010-12-20

230

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

231

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

232

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

USGS Publications Warehouse

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

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

1980-01-01

233

A frequent kinase domain mutation that changes the interaction between PI3K[alpha] and the membrane  

SciTech Connect

Mutations in oncogenes often promote tumorigenesis by changing the conformation of the encoded proteins, thereby altering enzymatic activity. The PIK3CA oncogene, which encodes p110{alpha}, the catalytic subunit of phosphatidylinositol 3-kinase alpha (PI3K{alpha}), is one of the two most frequently mutated oncogenes in human cancers. We report the structure of the most common mutant of p110{alpha} in complex with two interacting domains of its regulatory partner (p85{alpha}), both free and bound to an inhibitor (wortmannin). The N-terminal SH2 (nSH2) domain of p85{alpha} is shown to form a scaffold for the entire enzyme complex, strategically positioned to communicate extrinsic signals from phosphopeptides to three distinct regions of p110{alpha}. Moreover, we found that Arg-1047 points toward the cell membrane, perpendicular to the orientation of His-1047 in the WT enzyme. Surprisingly, two loops of the kinase domain that contact the cell membrane shift conformation in the oncogenic mutant. Biochemical assays revealed that the enzymatic activity of the p110{alpha} His1047Arg mutant is differentially regulated by lipid membrane composition. These structural and biochemical data suggest a previously undescribed mechanism for mutational activation of a kinase that involves perturbation of its interaction with the cellular membrane.

Mandelker, Diana; Gabelli, Sandra B.; Schmidt-Kittler, Oleg; Zhu, Jiuxiang; Cheong, Ian; Huang, Chuan-Hsiang; Kinzler, Kenneth W.; Vogelstein, Bert; Amzel, L. Mario; (JHU-MED); (HHMI)

2009-12-01

234

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

235

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

SciTech Connect

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

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

2006-05-01

236

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

237

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

238

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

239

A CCD-OMA device for the measurement of complete chlorophyll fluorescence emission spectra of leaves during the fluorescence induction kinetics.  

PubMed

A new device for the measurement of complete laser induced fluorescence emission spectra (maxima near 690 and 735 nm) of leaves during the induction of the chlorophyll fluorescence is described. In this the excitation light (cw He/Ne laser, 632.8 nm) is switched on by a fast electro-mechanical shutter which provides an opening time of 1 ms. The emitted fluorescence is imaged onto the entrance slit of a multichannel spectrograph through a red cut-off filter (greater than 645 nm). A charge coupled device (CCD) sensor with 2048 elements simultaneously detects the complete chlorophyll fluorescence emission spectrum in the 650-800 nm wavelength range. Scanning is accomplished electronically and the integration time for a complete fluorescence emission spectrum can be selected from 10 ms up to 260 ms. Shutter, detector system and data acquisition are controlled by an IBM-PC/AT compatible computer. A maximum of 32 spectra can be measured at selected times during the fluorescence induction kinetics with the shortest time resolution of 10 ms. The instrument permits the determination of various fluorescence parameters: a) the rise-time of the fluorescence to the maximum level fm, b) the changes in the shape of the fluorescence emission spectra during the induction kinetics, c) the induction kinetics in the fluorescence ratio F690/F735 as well as d) the fluorescence decrease ratio Rfd at any wavelength between 650 to 800 nm. These fluorescence parameters provide information about the functioning of photosynthesis. The ratio F690/F735 allows the non-destructive determination of the chlorophyll content of leaves. The application of this instrument in ecophysiological research and stress physiology of plants is outlined. PMID:1609060

Szabó, K; Lichtenthaler, H K; Kocsányi, L; Richter, P

1992-01-01

240

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

PubMed

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(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. PMID:19044555

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

2008-10-01

241

A time-dependent density-functional theory and complete active space self-consistent field method study of vibronic absorption and emission spectra of coumarin  

NASA Astrophysics Data System (ADS)

Time-dependent density-functional theory (TD-DFT) and complete active space multiconfiguration self-consistent field (CASSCF) calculations have been used to determine equilibrium structures and vibrational frequencies of the ground state and several singlet low-lying excited states of coumarin. Vertical and adiabatic transition energies of S1, S2, and S3 have been estimated by TD-B3LYP and CASSCF/PT2. Calculations predict that the dipole-allowed S1 and S3 states have a character of 1(??*), while the dipole-forbidden 1(n?*) state is responsible for S2. The vibronic absorption and emission spectra of coumarin have been simulated by TD-B3LYP and CASSCF calculations within the Franck-Condon approximation, respectively. The simulated vibronic spectra show good agreement with the experimental observations available, which allow us to reasonably interpret vibronic features in the S0?S1 and S0?S3 absorption and the S0?S1 emission spectra. Based on the calculated results, activity, intensity, and density of the vibronic transitions and their contribution to the experimental spectrum profile have been discussed.

Li, Junfeng; Rinkevicius, Zilvinas; Cao, Zexing

2014-07-01

242

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

243

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

244

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

245

Optical emission spectra and crystal field analysis of Eu3 + in the cubic Cs2NaYCl6 host  

NASA Astrophysics Data System (ADS)

Unpolarized and magnetic-field-induced circularly polarized luminescence spectra are reported for Eu3+ doped into the cubic Cs2NaYCl6 host. These spectra were obtained at high resolution under variable temperature conditions, and they span the 5DJ(J = 0-3)?7FJ(J = 0-5) transition regions of Eu3+. A detailed analysis of the spectra leads to a nearly complete location and assignment of the crystal field levels split out of the 7FJ(J = 0-5) and 5DJ(J = 0-3) term levels of Eu3+. Essential to the spectral analysis are crystal field energy level calculations and intensity calculations for both the magnetic dipole origin transitions and the electric dipole (one-phonon) vibronic transitions. The dominant contributions to the vibronic structure in the spectra are assigned to vibronically induced electric dipole transitions which involve coupling between the 4f electrons and the three ungerade vibrational modes localized within the EuCl3-6 chromophoric moiety. Lesser contributions are made by vibronic transitions involving vibrational modes not localized within the EuCl3-6 cluster (e.g., low-frequency lattice modes). Excellent agreement between theory and experiment is achieved for the luminescence intensities and the magnetic-field-induced circularly polarized luminescence spectra associated with the magnetic dipole allowed origin transitions. Very good agreement is also achieved between the calculated and observed vibronic intensity spectra. The latter were calculated using a theoretical model for vibronically induced electric dipole transition intensities which includes contributions from both the static-coupling and dynamic-coupling Eu3+-ligand interaction mechanisms.

Morley, J. P.; Faulkner, T. R.; Richardson, F. S.

1982-08-01

246

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

247

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.; Özkorucuklu, S.; Büyükuslu, H.; Y?ld?r?m, G.

2010-08-01

248

On the origin of the absorption and emission line components in the spectra of PHL 293B  

E-print Network

From the structure of PHL 293B and the physical properties of its ionizing cluster and based on results of hydrodynamic models, we point at the various events required to explain in detail the emission and absorption components seen in its optical spectrum. We ascribe the narrow and well centered emission lines, showing the low metallicity of the galaxy, to an HII region that spans through the main body of the galaxy. The broad emission line components are due to two off-centered supernova remnants evolving within the ionizing cluster volume and the absorption line profiles are due to a stationary cluster wind able to recombine at a close distance from the cluster surface, as originally suggested by Silich et al. (2004). Our numerical models and analytical estimates confirm the ionized and neutral column density values and the inferred X-ray emission derived from the observations.

Tenorio-Tagle, Guillermo; Martinez-Gonzalez, Sergio; Terlevich, Roberto; Terlevich, Elena

2015-01-01

249

On the Origin of the Absorption and Emission Line Components in the Spectra of PHL 293B  

NASA Astrophysics Data System (ADS)

From the structure of PHL 293B and the physical properties of its ionizing cluster and based on results of hydrodynamic models, we point at the various events required to explain in detail the emission and absorption components seen in its optical spectrum. We ascribe the narrow and well centered emission lines, showing the low metallicity of the galaxy, to an H II region that spans through the main body of the galaxy. The broad emission line components are due to two off-centered supernova remnants evolving within the ionizing cluster volume and the absorption line profiles are due to a stationary cluster wind that is able to recombine at a close distance from the cluster surface, as originally suggested by Silich et al. Our numerical models and analytical estimates confirm the ionized and neutral column density values and the inferred X-ray emission derived from the observations.

Tenorio-Tagle, Guillermo; Silich, Sergiy; Martínez-González, Sergio; Terlevich, Roberto; Terlevich, Elena

2015-02-01

250

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

NASA Technical Reports Server (NTRS)

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

Gilra, D. P.

1984-01-01

251

Excimer Emission Properties on Pyrene-Labeled Protein Surface: Correlation between Emission Spectra, Ring Stacking Modes, and Flexibilities of Pyrene Probes.  

PubMed

The excimer emission of pyrene is popularly employed for investigating the association between pyrene-labeled biomolecules or between pyrene-labeled places in a biomolecule. The property of pyrene excimer emission is affected by the fluctuation in ring stacking modes, which originates from the structural flexibilities of pyrene probes and/or of labeled places. Investigations of the excimer emission in terms of dynamics of pyrene stacking modes provide the detailed spatial information between pyrene-labeled places. In order to evaluate the effects of probe structures and fluctuation in pyrene-pyrene association modes on their emission properties on protein surface, three types of pyrene probe with different linker lengths were synthesized and conjugated to two cysteine residues in the A55C/C77S/V169C mutant of adenylate kinase (Adk), an enzyme that shows a structural transition between OPEN and CLOSED forms. In the CLOSED form of Adk labeled by a pyrene probe with a short linker, excimer emission was found to be predominated by the ground-state association of pyrenes. The pyrene stacking structure on the protein surface was successfully determined by an X-ray crystallographic analysis. However, the emission decay in the protein suggested the existence of several stacking orientations in solution. With the increase in the linker length, the effect of fluctuation in pyrene association modes on the spectral properties distinctly emerged at both ground and excited states. The combination of steady-state and time-resolved spectroscopic analyses is useful for differentiation in the origin of the excimer emission, which is essential for precisely understanding the interaction fashions between pyrene-labeled biomolecules. PMID:25646669

Fujii, Akira; Sekiguchi, Yutaka; Matsumura, Hiroyoshi; Inoue, Tsuyoshi; Chung, Wen-Sheng; Hirota, Shun; Matsuo, Takashi

2015-03-18

252

Cassini UVIS Observations of Titan Ultraviolet Airglow Spectra with Laboratory Modeling from Electron- and Proton-Excited N2 Emission Studies  

NASA Astrophysics Data System (ADS)

Joseph M. Ajello, Robert A. West, Rao S. Mangina Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 Charles P. Malone Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 & Department of Physics, California State University, Fullerton, CA 92834 Michael H. Stevens Space Science Division, Naval Research Laboratory, Washington, DC 20375 Jacques Gustin Laboratoire de Physique Atmosphérique et Planétaire, Université de Ličge, Ličge, Belgium A. Ian F. Stewart, Larry W. Esposito, William E. McClintock, Gregory M. Holsclaw Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 E. Todd Bradley Department of Physics, University of Central Florida, Orlando, FL 32816 The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed photon emissions of Titan's day and night limb-airglow and disk-airglow on multiple occasions, including three eclipse observations from 2009 through 2010. The 77 airglow observations analyzed in this paper show EUV (600-1150 Ĺ) and FUV (1150-1900 Ĺ) atomic multiplet lines and band emissions (lifetimes less than ~100 ?s), including the Lyman-Birge-Hopfield (LBH) band system, arising from photoelectron induced fluorescence and solar photo-fragmentation of molecular nitrogen (N2). The altitude of peak UV emission on the limb of Titan during daylight occurred inside the thermosphere/ionosphere (near 1000 km altitude). However, at night on the limb, the same emission features, but much weaker in intensity, arise in the lower atmosphere below 1000 km (lower thermosphere, mesosphere, haze layer) extending downwards to near the surface at ~300 km, possibly resulting from proton- and/or heavier ion-induced emissions as well as secondary-electron-induced emissions. The eclipse observations are unique. UV emissions were observed during only one of the three eclipse events, and no Vegard-Kaplan (VK) or LBH emissions were seen. Through regression analysis using laboratory spectra, we have analyzed the intensity and identified each spectral feature from the limb or disk emission spectrum. The strongest dipole-allowed transitions of N2 occur in the EUV. The electronic transitions proceed from the X 1?g+ ground-state to about seven closely spaced (~12-15 eV) Rydberg-valence (RV) states, which are the source of the molecular emissions in the EUV observed by spacecraft and have recently been studied in our laboratory at medium-to-high spectral resolution (delta-? = 0.1 Ĺ FWHM). Three of these RV states (b 1?u, b' 1?u+, and c4' 1?u+) are highly-perturbed, weakly-to-strongly predissociated, and have significant emission cross sections, which will be summarized in this paper. We will also discuss our recently published proton and electron impact emission cross sections for the LBH (a 1?g - X 1?g+) band system of N2, and their significance to the modeling of the day and night FUV spectra of the atmospheres of Earth and Titan.

Ajello, J. M.; West, R. A.; Malone, C. P.; Gustin, J.; Esposito, L. W.; McClintock, W. E.; Holsclaw, G. M.; Stevens, M. H.

2011-12-01

253

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

SciTech Connect

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

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

2011-09-01

254

Stacking analysis of 12CO and 13CO spectra of NGC 3627: Existence of non-optically thick 12CO emission?  

NASA Astrophysics Data System (ADS)

We stacked 12CO and 13CO spectra of NGC 3627 after redefining the velocity axis of each spectrum of the mapping data so that the zero corresponds to the local mean velocity of the 12CO spectra. The signal-to-noise ratios of the resulting spectra are improved by a factor of up to 3.2 compared to those obtained with normal stacking analysis. We successfully detect a weak 13CO emission from the interarm region where the emission was not detected in the individual pointings. We compare the integrated intensity ratios I_{^{12}{CO}}/I_{^{13}CO} among six characteristic regions (center, bar, bar-end, offset, arm, and interarm). We find that I_{^{12}{CO}}/I_{^{13}CO} in the bar and interarm are higher than those in the other regions by a factor of ˜ 2 and I_{^{12}{CO}}/I_{^{13}CO} in the center is moderately high. These high I_{^{12}{CO}}/I_{^{13}CO} ratios in the bar and center are attributed to a high intensity ratio (T_{^{12}{CO}}/T_{^{13}CO}), and that in the interarm is attributed to a high ratio of the full width at half maximum of spectra (FWHM_{^{12}{CO}}/FWHM_{^{13}CO}). The difference between FWHM_{^{12}CO} and FWHM_{^{13}CO} of the interarm indicates the existence of two components, one with a narrow line width (˜ FWHM_^{13CO}) and the other with a broad line width (˜ FWHM_^{12CO}). Additionally, the T_{^{12}{CO}}/T_{^{13}CO} ratio in the broad-line-width component of the interarm is higher than the other regions. The high T_{^{12}{CO}}/T_{^{13}CO} in the center and bar and of the broad-line-width component in the interarm suggest the existence of non-optically thick 12CO components. We find that more than half of the 12CO emissions of the interarm are likely to be radiated from the diffuse component. Our result suggests that the use of a universal CO-to-H2 conversion factor might lead to an overestimation of molecular gas mass and underestimation of star-formation efficiency in the interarm by a factor of a few.

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

2015-02-01

255

Analysis of Extreme-Ultraviolet Off-Limb Spectra Obtained with SUMER/SOHO: Ne VI-Mg VI Emission Lines  

NASA Astrophysics Data System (ADS)

We present results from a study of extreme-ultraviolet (EUV) off-limb spectra. These were obtained on 1996 June 20 with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) instrument on the Solar and Heliospheric Observatory (SOHO). With the capabilities of SUMER, we rastered the emitting source from 40" off the limb outward, and secured a unique, high-quality set of high-resolution EUV spectra. The scientific objective of this observing sequence was to record Ne VI and Mg VI intercombination/forbidden lines, which provide good possibilities to study the relative element abundance of Ne (high FIP) and Mg (low FIP) in transition-region emission in the corona, and the electron density in the solar atmosphere. While this observing sequence produced excellent spectra of the Ne VI and Mg VI lines, the occurrence of a dynamic event in the corona is an added bonus of the program. We also observed several other bright, as yet unidentified lines. Among these are lines that have been observed for the first time. Using the new data, we have been able to deduce the plasma density and relative element abundance in the source. In addition, improved values of the wavelengths of the Ne VI and Mg VI intercombination/forbidden lines have been obtained. Possible identifications of the bright lines not previously observed, along with their measured intensities, are discussed. Paper presented at the JD-19/IAU, Kyoto, 1997 August 26-27.

Dwivedi, Bhola N.; Curdt, Werner; Wilhelm, Klaus

1999-05-01

256

Prediction of the hydrophilic antioxidant capacity of tomato pastes from the IR and fluorescence excitation-emission spectra of extracts and intact samples.  

PubMed

The performance of the recently proposed excitation-emission fluorescence method was compared to the method using infrared measurements for the evaluation of the antioxidant properties of intact samples and extracts that had been obtained from tomato pastes. The oxygen radical absorbance capacity assay (ORAC) was applied in order to estimate the antioxidant capacity of the extracts, while the Folin-Ciocalteu reagent was adopted for the evaluation of the total phenolic content. The optimal extraction conditions for tomato pastes (three minutes of sonication under 80°C) were determined using the central composite design. Chemometric models such as the partial least squares regression and its N-way variant were further constructed in order to predict the antioxidant capacity or total phenolic content of the samples using either the IR or fluorescence spectra. The prediction errors that were obtained for the total antioxidant content were evaluated as the Trolox equivalents from the ORAC assay and were found to be equal to 2.011 (14.21%) for the fluorescence and 2.426 (17.15%) for the IR spectra, respectively. The prediction errors of the total phenolic content expressed as gallic acid equivalents were 0.067 (10.78%) for the fluorescence and 0.033 (5.36%) for the IR spectra, which were used as independent variables in the regression models. PMID:25863373

Orzel, Joanna; Stanimirova, Ivana; Czarnik-Matusewicz, Boguslawa; Daszykowski, Michal

2015-06-01

257

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

E-print Network

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

J. Kuraszkiewicz; Z. Loska; B. Czerny

1997-06-16

258

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

259

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

SciTech Connect

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

Hansen, S. B., E-mail: sbhanse@sandia.gov, E-mail: anatolyf@hotmail.com [Sandia National Laboratories, Albuquerque, New Mexico 87123 (United States); Colgan, J.; Abdallah, J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Faenov, A. Ya., E-mail: sbhanse@sandia.gov, E-mail: anatolyf@hotmail.com [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation); Quantum Beam Science Directorate, Japan Atomic Energy Agency, Kyoto 619-0215 (Japan); Pikuz, S. A.; Skobelev, I. Yu. [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation)] [Joint Institute for High Temperatures, Russian Academy of Sciences, Moscow 125412 (Russian Federation); Wagenaars, E.; Culfa, O.; Dance, R. J.; Tallents, G. J.; Rossall, A. K.; Woolsey, N. C. [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom)] [York Plasma Institute, Department of Physics, University of York, York YO10 5DD (United Kingdom); Booth, N.; Lancaster, K. L. [Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom)] [Central Laser Facility, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX (United Kingdom); Evans, R. G. [Department of Physics, Imperial College, London SW7 2AZ (United Kingdom)] [Department of Physics, Imperial College, London SW7 2AZ (United Kingdom); Gray, R. J.; McKenna, P. [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 ONG (United Kingdom)] [SUPA, Department of Physics, University of Strathclyde, Glasgow G4 ONG (United Kingdom); Kaempfer, T.; Schulze, K. S. [Helmholtzinstitut Jena, Jena D-07743 (Germany)] [Helmholtzinstitut Jena, Jena D-07743 (Germany); Uschmann, I. [Helmholtzinstitut Jena, Jena D-07743 (Germany) [Helmholtzinstitut Jena, Jena D-07743 (Germany); Institut für Optik und Quantenelektronic, Friedrich-Schiller-Universität Jena, Max-Wien Platz 1, Jena, D-07743 (Germany); and others

2014-03-15

260

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

261

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

SciTech Connect

Ti-doped tracer layers embedded in the shell at varying distances from the fuel-shell interface serve as a spectroscopic diagnostic for direct-drive experiments conducted at OMEGA. Detailed modeling of Ti K-shell absorption spectra produced in the tracer layer considers n?=?1–2 transitions in F- through Li-like Ti ions in the 4400–4800?eV range, both including and excluding line self-emission. Testing the model on synthetic spectra generated from 1-D LILAC hydrodynamic simulations reveals that the model including self-emission best reproduces the simulation, while the model excluding self-emission overestimates electron temperature T{sub e} and density N{sub e} to a higher degree for layers closer to the core. The prediction of the simulation that the magnitude of T{sub e} and duration of Ti absorption will be strongly tied to the distance of the layer from the core is consistent with the idea that regions of the shell close to the core are more significantly heated by thermal transport out of the hot dense core, but more distant regions are less affected by it. The simulation predicts more time variation in the observed T{sub e}, N{sub e} conditions in the compressed shell than is observed in the experiment, analysis of which reveals conditions remain in the range T{sub e}?=?400–600?eV and N{sub e}?=?3.0–10.0?×?10{sup 24} cm{sup ?3} for all but the most distant Ti-doped layer, with error bars ?5% T{sub e} value and ?10% N{sub e} on average. The T{sub e}, N{sub e} conditions of the simulation lead to a greater degree of ionization for zones close to the core than occurs experimentally, and less ionization for zones far from the core.

Johns, H. M.; Mancini, R. C.; Hakel, P.; Nagayama, T. [Physics Department, University of Nevada, Reno, 1664 N. Virginia St., Reno, Nevada 89557 (United States); Smalyuk, V. A.; Regan, S. P.; Delettrez, J. [Laboratory for Laser Energetics, University of Rochester, 250 E. River Road, Rochester, New York 14623 (United States)

2014-08-15

262

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

263

On the Early-Time X-Ray Spectra of Swift Afterglows. I. Evidence for Anomalous Soft X-Ray Emission  

NASA Astrophysics Data System (ADS)

We have conducted a thorough and blind search for emission lines in >70 Swift X-ray afterglows of total exposure ~107 s. We find that most afterglows are consistent with pure power laws plus extinction. Significant outliers to the population exist at the 5%-10% level and have anomalously soft, possibly thermal spectra. Four bursts are singled out via possible detections of two to five lines: GRB 060218, GRB 060202, GRB 050822, and GRB 050714B. Alternatively, a blackbody model with kT~0.1-0.5 keV can describe the soft emission in each afterglow. The most significant soft-component detections in the full data set of ~2000 spectra correspond to GRB 060218/SN 2006aj, with line significances ranging up to ~20 ?. A thermal plasma model fit to the data indicates that the flux is primarily due to L-shell transitions of Fe at roughly solar abundance. We associate (>4 ? significant) line triggers in the three other events with K-shell transitions in light metals. We favor a model where the possible line emission in these afterglows arises from the mildly relativistic cocoon of matter surrounding the GRB jet as it penetrates and exits the surface of the progenitor star. The emitting material in each burst is at a similar distance ~1012-1013 cm, a similar density ~1017 cm-3, and subject to a similar flux of ionizing radiation. The lines may correlate with the X-ray flaring. For the blackbody interpretation, the soft flux may arise from breakout of the GRB shock or plasma cocoon from the progenitor stellar wind, as recently suggested for GRB 060218 (Campana et al. 2006). Due to the low z of GRB 060218, bursts faint in gamma rays with fluxes dominated by this soft X-ray component could outnumber classical GRBs 100 to 1.

Butler, N. R.

2007-02-01

264

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 García, S.; Kitzmann, D.; Patzer, B.; Rauer, H.; Trautmann, T.

2013-01-01

265

Cospatial Longslit UV-Optical Spectra of Ten Galactic Planetary Nebulae with HST STIS: Description of observations, global emission-line measurements, and empirical CNO abundances  

NASA Astrophysics Data System (ADS)

This poster describes details of HST Cycle 19 (program GO 12600), which was awarded 32 orbits of observing time with STIS to obtain the first cospatial UV-optical spectra of 10 Galactic planetary nebulae (PNe). The observational goal was to measure the UV emission lines of carbon and nitrogen with unprecedented S/N and wavelength and spatial resolution along the disk of each object over a wavelength range 1150-10270 Ang . The PNe were chosen such that each possessed a near-solar metallicity but the group together spanned a broad range in N/O. This poster concentrates on describing the observations, emission-line measurements integrated along the entire slit lengths, ionic abundances, and estimated total elemental abundances using empirical ionization correction factors and the ELSA code. Related posters by co-authors in this session concentrate on analyzing CNO abundances, progenitor masses and nebular properties of the best-observed targets using photoionization modeling of the global emission-line measurements [Henry et al.] or detailed analyses of spatial variations in electron temperatures, densities, and abundances along the sub arcsecond resolution slits [Miller et al. & Shaw et al.]. We gratefully acknowledge AURA/STScI for the GO 12600 program support, both observational and financial.

Dufour, R. J.; Kwitter, K. B.; Shaw, R. A.; Balick, B.; Henry, R. B. C.; Miller, T. R.; Corradi, R. L. M.

2015-01-01

266

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

267

Effects of the self-emission of an IR Fourier-transform spectrometer on measured absorption spectra.  

PubMed

Up to now the effect of the modulated thermal self-emission of Fourier-transform spectrometers has been investigated for emission measurements only. But this instrumental radiation also influences Fourier-transform absorption spectroscopy in the mid-IR when the Moon, a hot blackbody, or even the Sun is taken as a radiation source, e.g., by causing small negative radiance values in the center of saturated absorption lines. For our experimental investigations, a blackbody that can be cooled down to liquid-nitrogen temperature was constructed. Measurements at different temperatures of the blackbody and for different optical configurations in the detector port of the Fourier spectrometer as well as transmission measurements of gas cells are used to examine the statements above. PMID:21127641

Schreiber, J; Blumenstock, T; Fischer, H

1996-11-01

268

Application of PARAFAC for calibration with excitation-emission matrix fluorescence spectra of three classes of environmental pollutants  

Microsoft Academic Search

SUMMARY Parallel factor analysis (PARAFAC) is applied to three calibrations of a field-portable, cuvette-based, single- measurement, excitation-emission matrix fluorometer. In the first example the fluorometer is calibrated based on interactions between a non-fluorescent DDT-type pesticide and a fluorescent dye. PARAFAC is employed to deconvolve the fluorescence profiles of dissociated and complexed dye states. Calibration is performed based on the intensity

Greger G. Andersson; Karl S. Booksh

2000-01-01

269

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

270

An iterative method in a probabilistic approach to the spectral inverse problem. Differential emission measure from line spectra and broadband data  

NASA Astrophysics Data System (ADS)

Context. Inverse problems are of great importance in astrophysics, e.g., for deriving information about the physical characteristics of hot optically thin plasma sources from their extreme ultraviolet and X-ray spectra. Aims: We describe and test an iterative method developed within the framework of a probabilistic approach to the spectral inverse problem for determining the thermal structures of the emitting plasma. We also demonstrate applications of this method to both high resolution line spectra and broadband imaging data. Methods: Our so-called Bayesian iterative method (BIM) is an iterative procedure based on Bayes' theorem and is used to reconstruct differential emission measure (DEM) distributions. Results: To demonstrate the abilities of the BIM, we performed various numerical tests and model simulations establishing its robustness and usefulness. We then applied the BIM to observable data for several active regions (AR) previously analyzed with other DEM diagnostic techniques: both SUMER/SOHO (Landi & Feldman 2008, ApJ, 672, 674) and SPIRIT/CORONAS-F (Shestov et al. 2010, Astron. Lett., 36, 44) line spectra data, and XRT/Hinode (Reale et al. 2009, ApJ, 698, 756) broadband imaging data. The BIM calculations confirmed the main results for SUMER/SOHO data showing very good quantitative agreement between both DEMs at log T ? 6.5 (T is the temperature in units of Kelvin) and a slight shift for two maxima at lower temperatures with ?30-50% difference in the DEM values for the coolest peak. For the SPIRIT data, we revised and validated AR DEM results including the inference of hot plasma in ARs with an emission measure (EM) at temperatures ?9-15 MK comparable to the EM at ?2-4 MK. In the case of XRT broadband data, the BIM solutions provided evidence of hot plasma at temperatures ?4-6 MK with EM up to ~30% as compared to that at ?2-4 MK in a non-flaring AR on 2006 November 12. Conclusions: The BIM results show that this method is an effective tool for determining the thermal structure of emitting plasma and can be successfully used for the DEM analysis of both line spectra and broadband imaging data. The BIM calculations correlate with recent studies confirming the existence of hot plasma in solar ARs. The BIM results also indicate that the coronal plasma may have the continuous distributions predicted by the nanoflare paradigm.

Goryaev, F. F.; Parenti, S.; Urnov, A. M.; Oparin, S. N.; Hochedez, J.-F.; Reale, F.

2010-11-01

271

Unification and physical interpretation of the radio spectra variability patterns in Fermi blazars and jet emission from NLSy1s  

E-print Network

The F-GAMMA program is among the most comprehensive programs that aim at understanding the physics in active galactic nuclei through the multi-frequency monitoring of Fermi blazars. Here we discuss monthly sampled broad-band radio spectra (2.6 - 142 GHz). Two different studies are presented. (a) We discuss that the variability patterns traced can be classified into two classes: (1) to those showing intense spectral-evolution and (2) those showing a self-similar quasi-achromatic behaviour. We show that a simple two-component model can very well reproduce the observed phenomenologies. (b) We present the cm-to-mm behaviour of three gamma-ray bright Narrow Line Seyfert 1 galaxies over time spans varying between ~1.5 and 3 years and compare their variability characteristics with typical blazars.

Angelakis, E; Nestoras, I; Fromm, C M; Schmidt, R; Zensus, J A; Marchili, N; Krichbaum, T P; Perucho, M; Ungerechts, H; Sievers, A; Riquelme, D; Foschini, L

2012-01-01

272

Emission spectra of a plasma observed upon irradiation of solid targets by high-intensity ultrashort laser pulses  

SciTech Connect

The spectral radiative losses are investigated in a plasma under conditions typical of a plasma produced upon irradiation of solid targets by high-intensity (up to 10{sup 17} W cm{sup -2} ultrashort (10{sup -13}-10{sup -9} s) laser pulses. The comparison of the calculated X-ray spectra with the experimental data for aluminum and carbon plasmas shows their satisfactory agreement. These studies made it possible to test the methods in use and to conclude that it is necessary to introduce supplements into the collision - radiation model for calculating the optical characteristics of a nonequilibrium plasma of complex chemical composition. (special issue devoted to the 80th anniversary of academician n g basov's birth)

Vergunova, G A; Rozanov, Vladislav B [P.N. Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Ivanov, E M [Institute of Mathematical Modelling, Russian Academy of Sciences, Moscow (Russian Federation)

2003-02-28

273

On the Early Time X-ray Spectra of Swift Afterglows I: Evidence for Anomalous Soft X-ray Emission  

Microsoft Academic Search

We have conducted a thorough and blind search for emission lines in >70 Swift\\u000aX-ray afterglows of total exposure ~10^7s. We find that most afterglows are\\u000aconsistent with pure power-laws plus extinction. Significant outliers to the\\u000apopulation exist at the 5-10% level and have anomalously soft, possibly thermal\\u000aspectra. Four bursts are singled out via possible detections of 2-5 lines:

Nathaniel R. Butler

2006-01-01

274

Analysis of transmission spectra for large ratio of emission-to-absorber linewidths: extension of differential absorption lidar analysis for finite laser linewidths.  

PubMed

A simple algorithm is presented for the analysis of transmission spectra provided by a lidar with an emission linewidth that is comparable with or larger than the absorption features of interest. The spreading of line shapes as seen by the lidar precludes use of the classical differential absorption lidar (DIAL) approach. However, it is assumed that, as with the DIAL method, small spectral intervals exist where single absorbers are dominant, and an inversion process for the transmission over such intervals is carried out for the absorber concentration. A second-stage algorithm based on singular-value decomposition is also provided to improve further the concentration estimates. An example situation for use of the algorithms is included wherein the objective is to estimate the concentration of a known trace gas in a composite transmission spectrum in the mid-infrared, where the dominant absorbers are water vapor and methane. PMID:16045223

Klett, James D

2005-07-10

275

Analysis of transmission spectra for large ratio of emission-to-absorber linewidths: extension of differential absorption lidar analysis for finite laser linewidths  

NASA Astrophysics Data System (ADS)

A simple algorithm is presented for the analysis of transmission spectra provided by a lidar with an emission linewidth that is comparable with or larger than the absorption features of interest. The spreading of line shapes as seen by the lidar precludes use of the classical differential absorption lidar (DIAL) approach. However, it is assumed that, as with the DIAL method, small spectral intervals exist where single absorbers are dominant, and an inversion process for the transmission over such intervals is carried out for the absorber concentration. A second-stage algorithm based on singular-value decomposition is also provided to improve further the concentration estimates. An example situation for use of the algorithms is included wherein the objective is to estimate the concentration of a known trace gas in a composite transmission spectrum in the mid-infrared, where the dominant absorbers are water vapor and methane.

Klett, James D.

2005-07-01

276

Bounds on the inner radius of emission around supermassive black holes  

NASA Astrophysics Data System (ADS)

Observations of iron K-alpha fluorescence lines in Seyfert galaxies provide strong evidence for an accretion disk around a supermassive black hole as the source of the line emission. Here we consider a diagnostic of a disk line profile, based on the minimum and maximum frequency of emission, to robustly constrain the inner radius of the disk. This diagnostic is applied to spectra from Seyfert I galaxies (Iwasawa et al. 1996 [1] Nandra et al. 1997 [2]), and a composite Seyfert II spectrum (Turner et al. 1997 [3]). We are able to place firm bounds on the inner radius of emission from the bright nucleus in MCG-6-30-15 we find that the disk extends to within 6.2 Rg of the central black hole, independent of inclination angle (Rg is GM/c2 for a black hole of mass M). With inclination angle constraints-we find 29+/-5° from frequency extrema of the [1] data-the inner radius bounded by 5.2+/-0.6 Rg. The frequency extrema of composite Seyfert I and II spectra both show inner radii below about 20 Rg and are consistent with modest inclination angles (i<45 degrees). Hence, at the present noise level, the data do not support Seyfert unification models based on orientation effects.

Bromley, Benjamin C.; Miller, Warner A.; Pariev, Vladimir I.

1998-04-01

277

The kinetics of in vivo state transitions in mesophyll and guard cell chloroplasts monitored by 77 k fluorescence emission spectra.  

PubMed

Fluorescence emission spectral peaks at 685, 695 and 730 nanometers (F685, F695, and F730) were recorded 77 K from diluted leaf tissue and epidermal powders prepared from Saxifraga cernua. The time course for state 1 to state 2 transitions was monitored as changes in the ratios of the three emission peaks. During illumination with light 2 (580 nm) the F730/F695 and F730/F685 ratios increased within minutes to establish a condition characteristic of state 2. A major difference between the two chloroplast types was the more rapid establishment of state 2 by mesophyll chloroplasts. An increase in light 2 intensity caused an increase in the magnitude of the F730/F695 ratio for both chloroplast types and, for guard cell chloroplasts, a decrease in the time required to establish the new ratio. The role of reversible phosphorylation of the light-harvesting chlorophyll a/b protein complex in regulating state transitions for both mesophyll and guard cell chloroplasts was assessed using DCMU and sodium fluoride, a specific phosphatase inhibitor. DCMU-treated mesophyll and epidermal tissues failed to show a state 1-state 2 transition. NaF-treated tissues attained state 2 but lacked the ability to revert back to state 1. PMID:16665160

Mawson, B T; Cummins, W R

1986-12-01

278

Retrieval of atmospheric O(3), HNO(3), CFC-11, and CFC-12 profiles from MIPAS-B-89 limb emission spectra.  

PubMed

During the night from May 17 to May 18, 1989, the first of four flights of the Michelson Interferometer for Passive Atmospheric Sounding, Balloon-borne version (MIPAS-B) instrument took place from the Centre National d'Etudes Spatiales balloon-launching site at Aire-sur-l'Adour (France, 44° N latitude). From approximately 33 km float altitude, stratospheric and tropospheric limb infrared emission spectra have been recorded by this novel type of fast-scanning interferometer. Although the measured spectra did not reach the expected quality and the a priori information on the corresponding viewing directions was coarse, the data were processed successfully with a retrieval algorithm specially adapted for application to noisydata. Mixingratio profiles of ozone, nitric acid, CFC-11, and CFC-12 havebeen retrieved from limb sequences of wide spectral intervals by nonlinear least-squares fitting in combination with a layer-bylayer onion-peeling approach. A rigorous error analysis has been carried out by means of Monte Carlo calculations. PMID:20856534

Clarmann, T V; Oelhaf, H; Fischer, H

1993-11-20

279

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

280

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

281

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 García, S.; Kitzmann, D.; Patzer, B.; Rauer, H.; Trautmann, T.

2013-09-01

282

Study of iron dimers reveals angular dependence of valence-to-core X-ray emission spectra.  

PubMed

Transition-metal K? X-ray emission spectroscopy (XES) is a developing technique that probes the occupied molecular orbitals of a metal complex. As an element-specific probe of metal centers, K? XES is finding increasing applications in catalytic and, in particular, bioinorganic systems. For the continued development of XES as a probe of these complex systems, however, the full range of factors which contribute to XES spectral modulations must be explored. In this report, an investigation of a series of oxo-bridged iron dimers reveals that the intensity of valence-to-core features is sensitive to the Fe-O-Fe bond angle. The intensity of these features has a well-known dependence on metal-ligand bond distance, but a dependence upon bond angle has not previously been documented. Herein, we explore the angular dependence of valence-to-core XES features both experimentally and computationally. Taken together, these results show that, as the Fe-O-Fe angle decreases, the intensity of the K?? feature increases and that this effect is modulated by increasing amounts of Fe np mixing into the O 2s orbital at smaller bond angles. The relevance of these findings to the identification of oxygenated intermediates in bioinorganic systems is highlighted, with special emphasis given to the case of soluble methane monooxygenase. PMID:25211540

Pollock, Christopher J; Lancaster, Kyle M; Finkelstein, Kenneth D; DeBeer, Serena

2014-10-01

283

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

284

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

285

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

286

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

SciTech Connect

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

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

2012-10-15

287

Line-shape analyses of XVV Auger spectra of p(1×1)-V3Si(100): Evidence for autoionization emission  

NASA Astrophysics Data System (ADS)

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, V3Si. We report for clean p(1×1)-V3Si(100) Auger spectra that include the region of the vanadium M2,3VV and M1VV and the Si L2,3VV 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(L2,3M2,3M2,3) and the V dd(M2,3M4,5M4,5) peak positions between experiment and calculation verified that the final-state hole-hole repulsion for Si (Upp) and V (Udd) are both ~0 eV. Also, the Si L2,3VV 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 M2,3VV threshold possesses a broad (~30-eV-wide) intense feature that is not amenable to conventional interpretation in terms of the M1VV transition or M2,3VV 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 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 (0-20 L) (1 langmuir = 1 L = 10-6 Torr sec) indicate dramatic Si L2,3VV line-shape changes associated with oxidation, similar to that observed previously for Pd4Si. The initial oxidation rate is ~102 faster than that for elemental Si. We hypothesize that the dissociation of O2 is a rate-determining step in the oxidation of elemental Si, but is rapid at transition-metal sites in the silicides. Atomic oxygen then rapidly spills over to the neighboring silicon sites where oxidation subsequently occurs.

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

1983-06-01

288

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

289

Parallel factor analysis of excitation-emission matrix fluorescence spectra of water soluble soil organic matter as basis for the determination of conditional metal binding parameters.  

PubMed

Organic matter-metal complexes in soil solution and aquatic systems are involved in important environmental and ecological processes such as plant nutrient availability and the solubilization and transport of metals. Our work presented here extends the use of fluorescence spectrometry for determining conditional stability constants for such complexes. We combine the use of excitation-emission matrix (EEM) fluorescence spectrometry and parallel factor analysis (PARAFAC) to determine the stability constants of the chemically meaningful components modeled by PARAFAC. Water-soluble organic matter (WSOM) from O-horizon soils of deciduous and coniferous forest stands were extracted and titrated at pH = 4.7 with iron(lll) (Fe) and aluminum (Al) which are important metals in acid soil systems. The EEM spectra were then recorded and PARAFAC analysis showed that the WSOM contained three humic-substance-like components. Fe titration led to fluorescence quenching of the three components, while Al titration enhanced fluorescence for two components and quenched one of the components. The average Ryan-Weber stability constants at pH 4.7 ranged from log K of 4.28 to 4.91 for Fe and 4.84 to 5.96 for Al. The conditional stability constants were similar for Fe binding for deciduous and coniferous stand-derived WSOM, while they were stronger for Al binding with coniferous stand-derived WSOM. This difference in binding strengths for Al may affect the chemical behavior of Al in soil and aquatic systems. Determining the individual binding parameters of organic matter components with metals represents a significant advance over current approaches that utilize fluorescence quenching at a single excitation-emission wavelength pair to characterize organic matter-metal interactions. PMID:18350895

Ohno, Tsutomu; Amirbahman, Aria; Bro, Rasmus

2008-01-01

290

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

291

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

292

XANES spectra of sesqui-oxides of Al, Cr and Fe  

SciTech Connect

Oxygen X-ray absorption near edge (XANES) spectra obtainedfrom alpha-Al2O3, Cr2O3 and alpha-Fe2O3 were found to be clearlydistinguishable. The energy distributions of the XANES spectra werereproduced here fairly well by the DV-X alpha molecular orbitalcalculation On the other hand, O K alpha spectra emitted from theseoxides showed no significant difference. This indicates that the XANES isa very promising candidate to study the chemical environment of anions intypical ionic compounds.

Uda, Masayuki; Yamashita, D.; Terashi, D.; Yamamoto, T.; Osawa,H.; Kanai, K.; Nakamatsu, H.; Perera, Rupert C.C.

2000-08-07

293

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

294

atomic spectra 1 Atomic Spectra  

E-print Network

Physics, pp. 88-93 (Rutherford nuclear model), 93-106 (atomic structure and electron spectra) 2. D. Watomic spectra 1 Atomic Spectra '96, THK-MRM Object To become familiar with the construction and interpret spin-orbit doublets and triplets in alkali spectra. References 1. Serway, Moses and Moyer: Modern

Glashausser, Charles

295

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

296

An analysis of the X-ray emission from the supernova remnant 3C397  

E-print Network

The ASCA SIS and the ROSAT PSPC spectral data of the SNR 3C397 are analysed with a two-component non-equilibrium ionization model. Besides, the ASCA SIS0 and SIS1 spectra are also fitted simultaneously in an equilibrium case. The resulting values of the hydrogen column density yield a distance of $\\sim8\\kpc$ to 3C397. It is found that the hard X-ray emission, containing S and Fe K$\\alpha$ lines, arises primarily from the hot component, while most of the soft emission, composed mainly of Mg, Si, Fe L lines, and continuum, is produced by the cool component. The emission measures suggest that the remnant evolves in a cloudy medium and imply that the supernova progenitor might not be a massive early-type star. The cool component is approaching ionization equilibrium. The ages estimated from the ionization parameters and dynamics are all much greater than the previous determination. We restore the X-ray maps using the ASCA SIS data and compare them with the ROSAT HRI and the NRAO VLA Sky Survey (NVSS) 20 cm maps. The morphology with two bright concentrations suggests a bipolar remnant encountering a denser medium in the west.

Yang Chen; Ming Sun; Zhen-Ru Wang; Q. F. Yin

1999-03-04

297

X-RAY SPECTRA FROM MAGNETOHYDRODYNAMIC SIMULATIONS OF ACCRETING BLACK HOLES  

SciTech Connect

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

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

2013-06-01

298

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

Microsoft Academic Search

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

Hana Bartošková; Jan Nauš; Martin Výkruta

1999-01-01

299

X-ray and soft gamma-ray spectra of Broad-Line Radio Galaxies  

E-print Network

We study X-ray and soft gamma-ray spectral properties of BLRGs using data from Ginga, ASCA, OSSE and EXOSAT. The X-ray spectra are well fitted by an intrinsic power-law continuum with an energy index of alpha ~ 0.7, moderately absorbed by a cold medium. In addition, the Ginga spectra show Fe K-alpha lines with an average equivalent width of ~ 100 eV, and, in some cases, Compton reflection humps. However, the latter components are significantly weaker than both those seen in radio-quiet Seyferts and those expected if the Fe K-alpha lines were due to reflection. Some ASCA and EXOSAT spectra show soft X-ray excesses below ~ 3 keV. When that component is taken into account, the Fe K-alpha lines in the ASCA data become unresolved with equivalent widths 10^23 cm^-2. Such a medium is in the line-of-sight in 3C 445 but it has to be out of it in other objects, in which the observed N_H are substantially lower. Thus, a cold medium with that N_H and covering a large solid angle is out of the line-of-sight in most objects. The spectra of BLRGs break and become softer above ~ 100 keV, as shown by a simultaneous ASCA/OSSE observation of 3C 120 and by the OSSE spectra being on average much softer than the X-ray spectra. Finally, we find the X-ray and gamma-ray spectral properties of Cen A intrinsically very similar to BLRGs studied here.

Przemyslaw R. Wozniak; Andrzej A. Zdziarski; David Smith; Greg M. Madejski; W. Neil Johnson

1998-05-12

300

A gas-tight Cu K alpha x-ray transparent reaction chamber for high-temperature x-ray diffraction analyses of halide gas/solid reactions.  

PubMed

An externally heated, x-ray transparent reaction chamber has been developed to enable the dynamic high temperature x-ray diffraction (HTXRD) analysis of a gas/solid [TiF(4)(g)/SiO(2)(s)] reaction involving a halide gas reactant formed at elevated temperatures (up to 350 degrees C) from a condensed source (TiF(4) powder) sealed within the chamber. The reaction chamber possessed x-ray transparent windows comprised of a thin (13 microm) internal layer of Al foil and a thicker (125 microm) external Kapton film. After sealing the SiO(2) specimens (diatom frustules or Stober spheres) above TiF(4) powder within the reaction chamber, the chamber was heated to a temperature in the range of 160-350 degrees C to allow for internal generation of TiF(4)(g). The TiF(4)(g) underwent a metathetic reaction with the SiO(2) specimen to yield a TiOF(2)(s) product. HTXRD analysis, using Cu K alpha x rays passed through the Kapton/Al windows of the chamber, was used to track the extent of SiO(2) consumption and/or TiOF(2) formation with time. The Al foil inner layer of the windows protected the Kapton film from chemical attack by TiF(4)(g), whereas the thicker, more transparent Kapton film provided the mechanical strength needed to contain this gas. By selecting an appropriate combination of x-ray transparent materials to endow such composite windows with the required thermal, chemical, and mechanical performance, this inexpensive reaction chamber design may be applied to the HTXRD analyses of a variety of gas/solid reactions. PMID:19947758

Shian, Samuel; Sandhage, Kenneth H

2009-11-01

301

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

302

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

303

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

SciTech Connect

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

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

2010-08-20

304

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

SciTech Connect

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

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

2010-01-01

305

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

SciTech Connect

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

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

2005-02-15

306

The dependence of emission spectra of rare earth ion on the band-gap energy of Mg x Zn 1? x O alloy  

Microsoft Academic Search

Rare-earth (RE) Tb3+ ion doped ZnO and Mg0.15Zn0.85O thin films were successfully fabricated by the sol–gel deposition method. The Tb3+ ion was substituted for the Zn2+ ion in the host material, as revealed by X-ray diffraction and optical absorption spectra. The cathodoluminescence properties of the doped samples were also studied. The RE3+ luminescence mechanism is discussed.

Dongxu Zhao; Yichun Liu; Dezhen Shen; Jiying Zhang; Youming Lu; Xiwu Fan

2003-01-01

307

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

308

Investigation of soft X-ray emission and K-edge absorption spectra of V2O5 and LixV2O5 electrodes  

NASA Astrophysics Data System (ADS)

The investigation of electrode materials based on Li-V2O5/MoO3 was performed by V L? soft X-ray emission, V K-absorption, and photoelectron spectroscopies. During the discharge process lithium is inserted into the electrodes accompanied by a surface enrichment of LiO- groups. As the X-ray absorption spectrum obtained by excitation with synchrotron radiation, the emission band recorded with a laboratory spectrometer is also sensitive to reduction processes of the vanadium atom and to changes of bond lengths in the first coordination sphere.

Meisel, A.; Hallmeier, K. H.; Szargan, R.; Müller, J.; Schneider, W.

1990-04-01

309

A SEARCH FOR IRON EMISSION LINES IN THE CHANDRA X-RAY SPECTRA OF NEUTRON STAR LOW-MASS X-RAY BINARIES  

E-print Network

While iron emission lines are well studied in black hole systems, both in X-ray binaries and active galactic nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, ...

Cackett, E. M.

310

Atomic Spectra  

NSDL National Science Digital Library

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

Nave, Carl R.

311

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

PubMed Central

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

2013-01-01

312

SpectraFactory.net: A Database of Molecular Model Spectra  

NASA Astrophysics Data System (ADS)

We present a homogeneous database of synthetic molecular absorption and emission spectra from the optical to mm wavelengths for a large range of temperatures and column densities relevant for various astrophysical purposes, but in particular for the analysis, identification, and first-order analysis of molecular bands in spectroscopic observations. All spectra are calculated in the LTE limit from several molecular line lists, and are presented at various spectral resolving powers corresponding to several specific instrument simulations. The database is available online at http://www.spectrafactory.net, where users can freely browse, search, display, and download the spectra. We describe how additional model spectra can be requested for (automatic) calculation and inclusion. The database already contains over half a million model spectra for 39 molecules (96 different isotopologues) over the wavelength range 350 nm-3 mm (?3-30000 cm-1).

Cami, J.; van Malderen, R.; Markwick, A. J.

2010-04-01

313

A search for iron emission lines in the Chandra X-ray spectra of neutron star low-mass X-ray binaries  

E-print Network

While iron emission lines are well studied in black hole systems, both in X-ray binaries and Active Galactic Nuclei, there has been less of a focus on these lines in neutron star low-mass X-ray binaries (LMXBs). However, recent observations with Suzaku and XMM-Newton have revealed broad asymmetric iron line profiles in 4 neutron star LMXBs, confirming an inner disk origin for these lines in neutron star systems. Here, we present a search for iron lines in 6 neutron star LMXBs. For each object we have simultaneous Chandra and RXTE observations at 2 separate epochs, allowing for both a high resolution spectrum, as well as broadband spectral coverage. Out of the six objects in the survey, we only find significant iron lines in two of the objects, GX 17+2 and GX 349+2. However, we cannot rule out that there are weak, broad lines present in the other sources. The equivalent width of the line in GX 17+2 is consistent between the 2 epochs, while in GX 349+2 the line equivalent width increases by a factor of ~3 between epochs as the source flux decreases by a factor of 1.3. This suggests that the disk is highly ionized, and the line is dominated by recombination emission. We find that there appears to be no specific locations in the long-term hardness-intensity diagrams where iron emission lines are formed, though more sources and further observations are required.

E. M. Cackett; J. M. Miller; J. Homan; M. van der Klis; W. H. G. Lewin; M. Mendez; J. Raymond; D. Steeghs; R. Wijnands

2008-09-18

314

Palagonitic Mars from Rock Rinds to Dust: Evidence from Visible, Near-IR, and Thermal Emission Spectra of Poorly Crystalline Materials  

NASA Technical Reports Server (NTRS)

Visible and near-IR (VNIR) spectral data for Martian bright regions are characterized by a general shape consisting of a ferric absorption edge extending from about 400 to 750 nm and relatively constant reflectivity extending from about 750 nm to beyond 2000 nm . Among terrestrial geologic materials, the best spectral analogues are certain palagonic 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, and the best Martian spectral analogues contain allophane-like materials and not crystalline phyllosilicates. We show here that laboratory VNIR and TES spectra of palagonitic alteration rinds developed on basaltic rocks are spectral endmembers that provide a consistent explanation for both VNIR and TES data of Martian dark regions.

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

2003-01-01

315

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

SciTech Connect

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 [Supercomputing Applications and Innovation, CINECA, Via dei Tizii, 6, 00185 Rome (Italy) [Supercomputing Applications and Innovation, CINECA, Via dei Tizii, 6, 00185 Rome (Italy); Dipartimento di Chimica, Universitá Sapienza, P.le Aldo Moro, 5, 00185, Rome (Italy); Aschi, Massimiliano [Department of Physical and Chemical Sciences, University of Aquila, via Vetoio (Coppito 1), 67010 Aquila (Italy)] [Department of Physical and Chemical Sciences, University of Aquila, via Vetoio (Coppito 1), 67010 Aquila (Italy); Amadei, Andrea, E-mail: andrea.amadei@uniroma2.it [Dipartimento di Scienze e Tecnologie Chimiche Universita’ di Roma, Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy)] [Dipartimento di Scienze e Tecnologie Chimiche Universita’ di Roma, Tor Vergata, via della Ricerca Scientifica 1, I-00133 Roma (Italy)

2014-04-28

316

The Kinetics of in Vivo State Transitions in Mesophyll and Guard Cell Chloroplasts Monitored by 77 K Fluorescence Emission Spectra 1  

PubMed Central

Fluorescence emission spectral peaks at 685, 695 and 730 nanometers (F685, F695, and F730) were recorded 77 K from diluted leaf tissue and epidermal powders prepared from Saxifraga cernua. The time course for state 1 to state 2 transitions was monitored as changes in the ratios of the three emission peaks. During illumination with light 2 (580 nm) the F730/F695 and F730/F685 ratios increased within minutes to establish a condition characteristic of state 2. A major difference between the two chloroplast types was the more rapid establishment of state 2 by mesophyll chloroplasts. An increase in light 2 intensity caused an increase in the magnitude of the F730/F695 ratio for both chloroplast types and, for guard cell chloroplasts, a decrease in the time required to establish the new ratio. The role of reversible phosphorylation of the light-harvesting chlorophyll a/b protein complex in regulating state transitions for both mesophyll and guard cell chloroplasts was assessed using DCMU and sodium fluoride, a specific phosphatase inhibitor. DCMU-treated mesophyll and epidermal tissues failed to show a state 1-state 2 transition. NaF-treated tissues attained state 2 but lacked the ability to revert back to state 1. PMID:16665160

Mawson, Bruce T.; Cummins, W. Raymond

1986-01-01

317

Firefly luciferase has two nucleotide binding sites: effect of nucleoside monophosphate and CoA on the light-emission spectra.  

PubMed Central

A laboratory-made spectroluminometer was used to analyse the light emitted by firefly (Photinus pyralis) luciferase reacting with several nucleotide derivatives. The analysis of the light emission in the presence of ATP or dATP provides some evidence that the enzyme has two nucleotide binding sites, each one leading to the formation of a complex emitting mainly at 575 nm (ATP) or 610 nm (dATP). AMP is able to displace dATP from the second site (610 nm) to the first one. Photoaffinity labelling of the second site by 8-azido-AMP gives similar results. The amplification effect of CoA and acetyl-CoA is also reconsidered according to this model. PMID:9806891

Steghens, J P; Min, K L; Bernengo, J C

1998-01-01

318

Distribution of Water Vapor in the Stratosphere as Determined from Balloon Measurements of Atmospheric Emission Spectra in the 24-29-microm Region.  

PubMed

The stratospheric water vapor mixing ratio altitude profile has been derived from spectral observations of the downward night emission from the pure rotation water vapor lines in the 24-29-microm region of the spectrum. The data were obtained during two balloon flights, made on 22 February 1971 and on 29 June 1971, using a balloon-borne spectral radiometer with ~2 cm(-1) resolution. The observed radiances have been fitted to line-by-line, layer-by-layer radiance calculations, from which the water vapor mixing ratio between 10 km and 30 km has been flights show a broad minimum around of 6 x 10(-7)g/g to 4 x 10(-6) g/g. PMID:20125466

Goldman, A; Murcray, D G; Murcray, F H; Williams, W J; Brooks, J N

1973-05-01

319

Analysis of the absorption spectra of gas emission of patients with lung cancer and chronic obstructive pulmonary disease by laser optoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

It is important to identify patients with chronic obstructive pulmonary disease (COPD) and lung cancer in the early stages of the disease. The method of laser opto-acoustic gas analysis, in this case, can act as a promising tool for diagnostics. The material for this study were the gas emission samples collected from patients and healthy volunteers - samples of exhaled air, swabs from teeth and cheeks. A set of material was formed three groups: healthy volunteers, patients with COPD, lung cancer patients. The resulting samples were analyzed by means of laser opto-acoustic gas analyzers: with intracavity location detector (ILPA-1), with extracavity location detector (LGA-2). Presentation of the results in an easy to visual form was performed using the method of elastic maps, based on the principal component analysis. The results of analysis show potentialities of usage of laser optoacoustic spectroscopy application to assess the status of patients with chronic obstructive pulmonary disease and lung cancer.

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

2013-02-01

320

Co-spatial Long-slit UV/Optical AL Spectra of 10 Galactic Planetary Nebulae with HST/STIS. I. Description of the Observations, Global Emission-line Measurements, and CNO Abundances  

NASA Astrophysics Data System (ADS)

We present observations and initial analysis from a Hubble Space Telescope (HST) Cycle 19 program using STIS to obtain the first co-spatial, UV–optical spectra of 10 Galactic planetary nebulae (PNs). Our primary objective was to measure the critical emission lines of carbon and nitrogen with unprecedented signal-to-noise ratio (S/N) and spatial resolution over the wavelength range 1150–10270 Ĺ, with the ultimate goal of quantifying the production of these elements in low- and intermediate-mass stars. Our sample was selected from PNs with a near-solar metallicity, but spanning a broad range in N/O based on published ground-based and IUE spectra. This study, the first of a series, concentrates on the observations and emission-line measurements obtained by integrating along the entire spatial extent of the slit. We derived ionic and total elemental abundances for the seven PNs with the strongest UV line detections (IC 2165, IC 3568, NGC 2440, NGC 3242, NGC 5315, NGC 5882, and NGC 7662). We compare these new results with other recent studies of the nebulae and discuss the relative merits of deriving the total elemental abundances of C, N, and O using ionization correction factors (ICFs) versus summed abundances. For the seven PNs with the best UV line detections, we conclude that summed abundances from direct diagnostics of ions with measurable UV lines give the most accurate values for the total elemental abundances of C and N (although ICF abundances often produced good results for C). In some cases where significant discrepancies exist between our abundances and those from other studies, we show that the differences can often be attributed to their use of fluxes that are not co-spatial. Finally, we examined C/O and N/O versus O/H and He/H in well-observed Galactic, LMC, and SMC PNs and found that highly accurate abundances are essential for properly inferring elemental yields from their progenitor stars. Future papers will discuss photoionization modeling of our observations, of both the integrated spectra and spatial variations of the UV versus optical lines along the STIS slit lengths, which are unique to our observations. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

Dufour, Reginald J.; Kwitter, Karen B.; Shaw, Richard A.; Henry, Richard B. C.; Balick, Bruce; Corradi, Romano L. M.

2015-04-01

321

Co-spatial Long-slit UV/Optical Spectra of Ten Galactic Planetary Nebulae with HST/STIS I. Description of the Observations, Global Emission-line Measurements, and CNO Abundances  

E-print Network

We present observations and initial analysis from an HST/STIS program to obtain the first co-spatial, UV-optical spectra of ten Galactic planetary nebulae (PNe). Our primary objective was to measure the critical emission lines of carbon and nitrogen with unprecedented S/N and spatial resolution over UV-optical range, with the ultimate goal of quantifying the production of these elements in low- and intermediate-mass stars. Our sample was selected from PNe with a near-solar metallicity, but spanning a broad range in N/O. This study, the first of a series, concentrates on the observations and emission-line measurements obtained by integrating along the entire spatial extent of the slit. We derived ionic and total elemental abundances for the seven PNe with the strongest UV line detections (IC~2165, IC~3568, NGC~2440, NGC~3242, NGC~5315, NGC~5882, and NGC~7662). We compare these new results with other recent studies of the nebulae, and discuss the relative merits of deriving the total elemental abundances of C, ...

Dufour, Reginald J; Shaw, Richard A; Henry, Richard B C; Balick, Bruce; Corradi, Romano L M

2015-01-01

322

Detailed non-LTE calculations of the iron emission from NGC 1068  

NASA Technical Reports Server (NTRS)

The X-ray iron line emission from NGC 1068 observed by the Ginga satellite 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 parameter space of the obscured type 1 Seyfert nucleus model for this object is studied. The equivalent width is greater than previously predicted. It is found that detailed radiative transfer can have a significant effect on the observed line flux both for the K alpha line and for the L-shell emission. The ionization of the iron increases with temperature. Therefore the K alpha equivalent width and energy is a function 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.

1989-01-01

323

Photobleaching response of different sources of chromophoric dissolved organic matter exposed to natural solar radiation using absorption and excitation-emission matrix spectra.  

PubMed

CDOM biogeochemical cycle is driven by several physical and biological processes such as river input, biogeneration and photobleaching that act as primary sinks and sources of CDOM. Watershed-derived allochthonous (WDA) and phytoplankton-derived autochthonous (PDA) CDOM were exposed to 9 days of natural solar radiation to assess the photobleaching response of different CDOM sources, using absorption and fluorescence (excitation-emission matrix) spectroscopy. Our results showed a marked decrease in total dissolved nitrogen (TDN) concentration under natural sunlight exposure for both WDA and PDA CDOM, indicating photoproduction of ammonium from TDN. In contrast, photobleaching caused a marked increase in total dissolved phosphorus (TDP) concentration for both WDA and PDA CDOM. Thus TDN:TDP ratios decreased significantly both for WDA and PDA CDOM, which partially explained the seasonal dynamic of TDN:TDP ratio in Lake Taihu. Photobleaching rate of CDOM absorption a(254), was 0.032 m/MJ for WDA CDOM and 0.051 m/MJ for PDA CDOM from days 0-9, indicating that phototransformations were initially more rapid for the newly produced CDOM from phytoplankton than for the river CDOM. Extrapolation of these values to the field indicated that 3.9%-5.1% CDOM at the water surface was photobleached and mineralized every day in summer in Lake Taihu. Photobleaching caused the increase of spectral slope, spectral slope ratio and molecular size, indicating the CDOM mean molecular weight decrease which was favorable to further microbial degradation of mineralization. Three fluorescent components were validated in parallel factor analysis models calculated separately for WDA and PDA CDOM. Our study suggests that the humic-like fluorescence materials could be rapidly and easily photobleached for WDA and PDA CDOM, but the protein-like fluorescence materials was not photobleached and even increased from the transformation of the humic-like fluorescence substance to the protein-like fluorescence substance. Photobleaching was an important driver of CDOM and nutrients biogeochemistry in lake water. PMID:24204852

Zhang, Yunlin; Liu, Xiaohan; Osburn, Christopher L; Wang, Mingzhu; Qin, Boqiang; Zhou, Yongqiang

2013-01-01

324

[Excitation-emission matrix fluorescence spectra characteristics of DOM in a subsurface constructed wetland for advanced treatment of municipal sewage plant effluent].  

PubMed

Composition and dynamics of dissolved organic matter (DOM) were analyzed in a horizontal subsurface constructed wetland for advanced treatment of municipal sewage plant effluent using three-dimensional excitation emission matrix fluores cence spectroscopy (3D-EEM). The results indicate that the two subsurface constructed wetlands performed excellent purification of organic substances, and the removal rates of COD(cr), and DOC were 61.6% and 70.1%, respectively. The constructed wetland system filled with ceramsite showed slightly greater removal efficiency of organic substance than that with zeolite substrate. Four different types of peaks such as aromatic protein-like compounds (S), soluble microbial byproducts (T), fulvic acid-like compounds, visible fulvic-like (M) and UV fulvic-like compounds (A) were found in DOM from inflow and outflow of the subsurface wetlands based on the three-dimensional fluorescence spectroscopy analysis. The fluorescence intensity of the four peaks was significantly decreased in the effluent after purification by the subsurface constructed wetlands. Especially, the visible fulvic-like compounds and soluble microbial byproducts were effectively removed from the sewage plant effluent by the subsurface constructed wetland with fluorescence intensity reduction percentages of 16.4% and 11.7%. Aromatic structures of humic-like compounds were weakened and organic compounds with benzene rings were decreased in the outflow of the subsurface constructed wetland. This indicates that the subsurface constructed wetlands can decompose the chemically stable and biorefractory humic-like compounds. The fluorescence intensity of M and T peaks decreased along distance, while the fluorescence intensity of S peaks firstly increased, then decreased along the distance of the subsurface constructed wetlands. As compared to zeolite substrate constructed wetland system, the constructed wetland system filled with ceramsite was more effective to reduce the fluorescence intensity of characterized peaks of DOM from the sewage plant effluent. PMID:22582638

Yang, Chang-ming; Wang, Meng-meng; Ma, Rui; Li, Jian-hua

2012-03-01

325

Photobleaching Response of Different Sources of Chromophoric Dissolved Organic Matter Exposed to Natural Solar Radiation Using Absorption and Excitation–Emission Matrix Spectra  

PubMed Central

CDOM biogeochemical cycle is driven by several physical and biological processes such as river input, biogeneration and photobleaching that act as primary sinks and sources of CDOM. Watershed-derived allochthonous (WDA) and phytoplankton-derived autochthonous (PDA) CDOM were exposed to 9 days of natural solar radiation to assess the photobleaching response of different CDOM sources, using absorption and fluorescence (excitation-emission matrix) spectroscopy. Our results showed a marked decrease in total dissolved nitrogen (TDN) concentration under natural sunlight exposure for both WDA and PDA CDOM, indicating photoproduction of ammonium from TDN. In contrast, photobleaching caused a marked increase in total dissolved phosphorus (TDP) concentration for both WDA and PDA CDOM. Thus TDN?TDP ratios decreased significantly both for WDA and PDA CDOM, which partially explained the seasonal dynamic of TDN?TDP ratio in Lake Taihu. Photobleaching rate of CDOM absorption a(254), was 0.032 m/MJ for WDA CDOM and 0.051 m/MJ for PDA CDOM from days 0–9, indicating that phototransformations were initially more rapid for the newly produced CDOM from phytoplankton than for the river CDOM. Extrapolation of these values to the field indicated that 3.9%–5.1% CDOM at the water surface was photobleached and mineralized every day in summer in Lake Taihu. Photobleaching caused the increase of spectral slope, spectral slope ratio and molecular size, indicating the CDOM mean molecular weight decrease which was favorable to further microbial degradation of mineralization. Three fluorescent components were validated in parallel factor analysis models calculated separately for WDA and PDA CDOM. Our study suggests that the humic-like fluorescence materials could be rapidly and easily photobleached for WDA and PDA CDOM, but the protein-like fluorescence materials was not photobleached and even increased from the transformation of the humic-like fluorescence substance to the protein-like fluorescence substance. Photobleaching was an important driver of CDOM and nutrients biogeochemistry in lake water. PMID:24204852

Zhang, Yunlin; Liu, Xiaohan; Osburn, Christopher L.; Wang, Mingzhu; Qin, Boqiang; Zhou, Yongqiang

2013-01-01

326

ADAS analysis of the differential emission measure structure of the inner solar corona. II. A study of the `quiet Sun' inhomogeneities from SOHO CDS-NIS spectra  

E-print Network

We present a study of the differential emission measure (DEM) of a `quiet Sun' area observed in the extreme ultraviolet at normal incidence by the Coronal Diagnostic Spectrometer (CDS) on the SOHO spacecraft. The data used for this work were taken using the NISAT_S observing sequence. This takes the full wavelength ranges from both the NIS channels (308-381 Angtr. and 513-633 Angst.) with the 2 arcsec by 240 arcsec slit, which is the narrowest slit available, yielding the best spectral resolution. In this work we contrast the DEM from subregions of 2 by 80 arcsec$^2$ with that obtained from the mean spectrum of the whole raster (20 by 240 arcsec$^2$). We find that the DEM maintains essentially the same shape in the subregions, differing by a constant factor between 0.5 and 2 from the mean DEM, except in areas were the electron density is below $2 \\times 10^7$ cm$^{-3}$ and downflow velocities of 50 km/s are found in the transition region. Such areas are likely to contain plasma departing from ionisation equilibrium, violating the basic assumptions underlying the DEM method. The comparison between lines of Li-like and Be-like ions may provide further evidence of departure from ionisation equilibrium. We find also that line intensities tend to be lower where velocities of the order of 30 km/s or higher are measured in transition region lines. The DEM analysis is also exploited to improve the line identification performed by Brooks et al (1999) and to investigate possible elemental abundance variations from region to region. We find that the plasma has composition close to photospheric in all the subregions examined.

A. C. Lanzafame; D. H. Brooks; J. Lang

2004-12-06

327

Tracking variations in fluorescent-dissolved organic matter in an aerobic submerged membrane bioreactor using excitation-emission matrix spectra combined with parallel factor analysis.  

PubMed

In this study, the variations in the fluorescent components of dissolved organic matter (DOM) were tracked for an aerobic submerged membrane bioreactor (MBR) at three different operation stages (cake layer formation, condensation, and after cleaning). The fluorescent DOM was characterized using excitation-emission matrix (EEM) spectroscopy combined with parallel factor analysis (PARAFAC). Non-aromatic carbon structures appear to be actively involved in the membrane fouling for the cake layer formation stage as revealed by much higher UV-absorbing DOM per organic carbon found in the effluent versus those inside the reactor. Four fluorescent components were successfully identified from the reactor and the effluent DOMs by EEM-PARAFAC modeling. Among those in the reactor, microbial humic-like fluorescence was the most abundant component at the cake layer formation stage and tryptophan-like fluorescence at the condensation stage. In contrast to the reactor, relatively similar composition of the PARAFAC components was exhibited for the effluent at all three stages. Tryptophan-like fluorescence displayed the largest difference between the reactor and the effluent, suggesting that this component could be a good tracer for membrane fouling. It appears that the fluorescent DOM was involved in membrane fouling by cake layer formation rather than by internal pore adsorption because its difference between the reactor and the effluent was the highest among all the four components, even after the membrane cleaning. Our study provided an insight into the fate and the behavior fluorescent DOM components for an MBR system, which could be an indicator of the membrane fouling. PMID:24390578

Hur, Jin; Shin, Jaewon; Kang, Minsun; Cho, Jinwoo

2014-08-01

328

Spectra of Irradiated Giant Planets  

NASA Astrophysics Data System (ADS)

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 and atmospheres. We are now entering a new era of planet discovery and measurement. This contribution is meant to communicate some of the excitement in the astronomical community as the hunt for these exotic and remarkable objects accelerates.

Burrows, Adam; Sudarsky, David

2002-11-01

329

C NMR Spectra C NMR Spectra  

E-print Network

S16 1 H and 13 C NMR Spectra (see p S3) Me N-i-Pr #12;S17 1 H and 13 C NMR Spectra (see p S3) Me NBn #12;S18 1 H and 13 C NMR Spectra (see p S4) NBn #12;S19 1 H and 13 C NMR Spectra (see p S4) NBn Me Me Me #12;S20 1 H and 13 C NMR Spectra (see p S4) N-n-Bu Me Me Me #12;S21 1 H and 13 C NMR Spectra

Collum, David B.

330

Cooling effect in emissions of 103mRh excited by bremsstrahlung  

E-print Network

Nonlinear characteristic emissions of K alpha, K beta and gamma with a significant triplet splitting at room temperature are observed from the long-lived nuclear state of 103mRh excited by bremsstrahlung irradiation. A pronounced phase-transition-like narrowing of the emission profiles occurs immediately after the sample is cooled down to 77 K. The room temperature profiles reappear again abruptly and almost reversibly as the temperature drifts freely back to approximately the ice point after the filling of liquid nitrogen is stopped. These emission properties at 300 K and at low temperature may indicate that the 103mRh nuclei are in collective states.

Yao Cheng; Bing Xia; Chinping Chen

2009-04-29

331

Mid-Infrared Spectra of Be Stars  

E-print Network

We present the first medium-resolution ($R\\sim 600$) mid-infrared (8-13.3\\micron) spectra of 11 Be stars. A large number of lines are observed and identified in these spectra, including, as an example, 39 hydrogen recombination lines in the spectrum of $\\gamma$ Cas. In the majority of our spectra, all of the observed lines are attributable to hydrogen recombination. Two of the sources, $\\beta$ Lyr and MWC 349 also show emission from other species. Both of these objects show evidence of [Ne II] emission, and $\\beta$ Lyr also shows evidence of He I emission. We tabulate the effective line strength and line widths for the observed lines, and briefly discuss the physical implications of the observed line series. We also use a simple model of free-free emission to characterize the disks around these sources.

S. A. Rinehart; J. R. Houck; J. D. Smith

1999-10-11

332

Digital filtering of plume emission spectra  

NASA Technical Reports Server (NTRS)

Fourier transformation and digital filtering techniques were used to separate the superpositioned spectral phenomena observed in the exhaust plumes of liquid propellant rocket engines. Space shuttle main engine (SSME) spectral data were used to show that extraction of spectral lines in the spatial frequency domain does not introduce error, and extraction of the background continuum introduces only minimal error. Error introduced during band extraction could not be quantified due to poor spectrometer resolution. Based on the atomic and molecular species found in the SSME plume, it was determined that spectrometer resolution must be 0.03 nm for SSME plume spectral monitoring.

Madzsar, George C.

1990-01-01

333

THE SPECTRA OF THE DOUBLY AND TRIPLY IONIZED RARE EARTHS  

Microsoft Academic Search

The present status of the knowledge of the structure of the spectra of ; the doubly and triply ionized spectra of the rare earths is derived partly from ; experimental data of the emission spectra of the free ions which provide the ; energy level scheme in great detail but are difficuit and laborious to analyze. ; For the lower

G. H. Dieke; H. M. Crosswhite

1963-01-01

334

Iron Fluorescent Line Emission from Black Hole Accretion Disks with Magnetic Reconnection-Heated Corona  

E-print Network

We investigate the iron K$\\alpha$ fluorescent line produced by hard X-ray photons from magnetic reconnection-heated corona. The hot corona with temperature being about $10^9$K can irradiate the underlying disk with a continuum X-ray spectrum produced via thermal Comptonization. Then the iron atoms in the disk photoelectrically absorb X-ray photons and radiate K$\\alpha$ line photons. Therefore, the activity of corona is responsible to the iron line emission from the underlying disk. In previous studies, oversimplified X-ray photon sources are often assumed above the disk in order to compute the iron line profile or power-law line emissivity profiles are assumed with an index being a free parameter. We adopt the more realistic corona model constructed by Liu et al. in which the corona is heated by magnetic energy released through the reconnection of magnetic flux loops and which has no free parameter. Then the accretion energy is dominantly dissipated in the corona, in which X-ray photons are efficiently produced and irradiate the underlying disk. We find the local emmisivity of iron line on the disk is approximated as $F_{{\\rm K}\\alpha}(r)\\propto r^{-5}$. The iron line profiles derived from this model give excellent fits to the observational data of MCG-6-30-15 with the profiles derived theoretically for $i\\sim 30^{\\circ}$ for energy band 4-7keV. Possible origins of line variability are briefly discussed.

N. Kawanaka; S. Mineshige; K. Iwasawa

2005-08-24

335

The Theory of Spectra and Atomic Constitution  

NASA Astrophysics Data System (ADS)

Part I. On the Spectrum of Hydrogen: 1. Empirical spectral laws; 2. Laws of temperature radiation; 3. The nuclear theory of the atom; 4. Quantum theory of spectra; 5. Hydrogen spectrum; 6. The Pickering lines; 7. Other spectra; Part II. On the Series Spectra of the Elements; Section 1. Introduction; Section 2. General Principles of the Quantum Theory of Spectra: 8. Hydrogen spectrum; 9. The correspondence principle; 10. General spectral laws; 11. Absorption and excitation of radiation; Section 3. Development of the Quantum Theory of Spectra: 12. Effect of external forces on the hydrogen spectrum; 13. The Stark effect; 14. The Zoeman effect; 15. Central pertubations; 16. Relativity effect of hydrogen lines; 17. Theory of series spectra; 18. Correspondence principle and conservation of angular momentum; 19. The spectra of helium and lithium; 20. Complex structure of series lines; Section 4. Conclusion; Part III. The Structure of the Atom and the Physical and Chemical Properties of the Elements; Section 5. Preliminary: 21. The nuclear atom; 22. The postulates of the quantum theory; 23. Hydrogen atom; 24. Hydrogen spectrum and x-ray spectra; 25. The fine structure of the hydrogen lines; 26. Periodic table; 27. Recent atomic models; Section 6. Series Spectra and the Capture of Electrons by Atoms: 28. Arc and spark spectra; 29. Series diagram; 30. Correspondence principle; Section 7. Formation of Atoms and the Periodic Table: 31. First period. Hydrogen-helium; 32. Second period. Lithium-neon; 33. Third period. Sodium-argon; 34. Fourth period. Potassium-Krypton; 35. Fifth period. Rubidium-xenon; 36. Sixth period. Caesium-niton; 37. Seventh period; 38. Survey of the periodic table; Section 8. Reorganization of Atoms and X-Ray SPectra: 39. Absorption and emission of x-rays and correspondence principle; 40. X-ray spectra and atomic structure; 41. Classification of x-ray spectra; 42. Conclusion; Appendix.

Bohr, Niels

2011-06-01

336

IRAS low-resolution spectra of galaxies  

NASA Technical Reports Server (NTRS)

The spectra of external galaxies are selected and extracted from the IRAS LRS database. Twenty-one objects present viable spectra. One is a peculiar star-forming E-S0 galaxy. The remainder are all starburst or H II region galaxies. Their average spectrum demonstrates the importance of the PAH emission bands in the 8-23-micron region and reinforces the conclusion reached from ground-based spectra, that there is a strong correlation between the PAH bands and the starburst or H II region character of a galaxy.

Cohen, Martin; Volk, Kevin

1989-01-01

337

Transient infrared emission spectroscopy  

Microsoft Academic Search

Transient infrared emission spectroscopy (TIRES) is a new method that produces analytically useful emission spectra from optically thick, solid samples by greatly reducing self-absorption of emitted radiation. The method reduces self-absorption by creating a thin, short-lived, heated layer at the sample surface and collecting the transient emission from this layer. The technique requires no sample preparation and may be applied

J. F. McClelland

1989-01-01

338

New LRS spectra for 356 bright IRAS sources  

NASA Technical Reports Server (NTRS)

The low-resolution spectra of all IRAS point sources with F(nu) (12 microns) greater than 40 Jy that were not included in the Atlas of Low-Resolution Spectra are presented. These have been classified into eight groups based upon the spectral morphology. Silicate emission spectra and red-continuum spectra associated with H II region sources form about 60 percent of this sample. All types of spectra in the LRS Atlas are represented in the sample except for emission-line sources. The sample is used to test a recent classification scheme for IRAS sources based on broadband colors. The spectra is used to test a recent classification scheme for IRAS sources based on broadband colors. The spectra are consistent with the classifications from the colors in most cases.

Volk, Kevin; Cohen, Martin

1989-01-01

339

Optical Spectra of Supernovae  

E-print Network

Supernova flux and polarization spectra bring vital information on the geometry, physical conditions, and composition structure of the ejected matter. For some supernovae the circumstellar matter is also probed by the observed spectra. Some of this information can be inferred directly from the observed line profiles and fluxes, but because of the Doppler broadening and severe line blending, interpretation often involves the use of synthetic spectra. The emphasis in this Chapter is on recent results obtained with the help of synthetic spectra.

David Branch; E. Baron; David J. Jeffery

2001-11-30

340

Shape effects on asteroid spectra  

NASA Astrophysics Data System (ADS)

The objective of this work is to probe how the shape of a body like an asteroid could be modifying its observed spectra and the derived mineralogical interfaces based on spectral modeling. To model this effect, we construct an oblate ellipsoid with triangular facets, where each facet contributes to the overall reflectance. The synthetic spectra is generated by the isotropic multiple-scattering approximation (IMSA) reflectance model of Hapke (1993). First, we obtained optical constants by inverting the spectra of meteorites, obtained from the RELAB spectral database. These optical constants were found inverting the reflectance bidirectional equation of Hapke; this is made in two steps: (i) The first inversion is to find the single-scattering albedo ? (ii) in the model of Hapke, this albedo is found under the regime of the geometric optics, where the particle size is much larger than the wavelength of the incident radiation. Here we assumed a constant value for the real part of the optical constant n=1.5. With these optical constants, we can construct synthetic spectra for any particle size. The phase function used is the double Henyey-Greenstein phase function and an accurate expression for the H-functions. We started with the ellipsoidal shape a=1.0, b=c=0.5 for two particle size 50 and 250 ? m, in this part, we found good differences in the BAR parameter between the two geometric models, this was done for 100 Eucrite meteorites spectra. In this first study, we found that the BAR parameter between the two models is bigger when the particle size increases. In the second part, we started with different ellipsoidal shapes and produced synthetic spectra for material with eucrite and diogenite composition with a phase angle of 20 degrees, incidence and emission angles of 10 degrees, and particle size at 250 ? m. All spectra was generated for four parameters of phase angle b=[0.2,0.4,0.6,0.8] taking the empirical relation between the phase constants of Hapke (2012), where, for the ellipsoidal model, we set the rotational phase at 0 degrees. We observed significant differences between the two models for the band-I area and the band-II area but, we did not find significant differences for the BAR parameter. For the spectral slope, we have meaningful differences between the two models, where the variation of the spectral slope is in the first decimal place, and this difference is bigger when we increase the phase parameter b.

Davalos, J.; Carvano, J.

2014-07-01

341

Quantum synchrotron spectra from semirelativistic electrons in teragauss magnetic fields  

NASA Technical Reports Server (NTRS)

Synchrotron spectra are calculated from quantum electrodynamic transition rates for thermal and power-law electron distributions. It is shown that quantum effects appear in thermal spectra when the photon energy is greater than the electron temperature, and in power-law spectra when the electron energy in units of the electron rest mass times the magnetic field strength in units of the critical field strength is of order unity. These spectra are compared with spectra calculated from the ultrarelativistic approximation for synchrotron emission. It is found that the approximation for the power-law spectra is good, and the approximation for thermal spectra produces the shape of the spectrum accurately but fails to give the correct normalization. Single photon pair creation masks the quantum effects for power-law distributions, so only modifications to thermal spectra are important for gamma-ray bursts.

Brainerd, J. J.

1987-01-01

342

Mineralogy of Martian atmospheric dust inferred from thermal infrared spectra of aerosols  

Microsoft Academic Search

We have utilized optical constants derived from thermal infrared spectra acquired by the Mariner 9 Infrared Interferometer Spectrometer (M9 IRIS) and Mars Global Surveyor Thermal Emission Spectrometer (MGS TES), during periods of relatively high dust\\/low water ice opacity, to generate synthetic transmission and emission spectra of the atmospheric dust. Using libraries of transmission and emission spectra of common rock-forming minerals

Victoria E. Hamilton; Harry Y. McSween Jr; Bruce Hapke

2005-01-01

343

Oscillating field model in the theory of optical spectra  

Microsoft Academic Search

Usually, broad-band spectra of transition-metal ions are explained as a result of vibrational quanta's emission or absorption. In this paper optical spectra are interpreted as a result of oscillator position detecting by absorption or emission of light quantum. The basis of coherent oscillator states is then used in averaging procedure to obtain spectrum lineshape. Such formalism is useful in high-temperature

A. G. Avanesov; V. V. Zhorin; V. F. Pisarenko

1996-01-01

344

Resonant Compton scattering and gamma-ray burst continuum spectra  

NASA Technical Reports Server (NTRS)

The Thomson limit of resonant inverse Compton scattering in the strong magnetic fields of neutron stars is considered as a mechanism for producing gamma-ray burst continuum spectra. Photon production spectra and electron cooling rates are presented using the full magnetic Thomson cross-section. Model emission spectra are obtained as self-consistent solutions of a set of photon and electron kinetic equations, displaying spectral breaks and other structure at gamma-ray energies.

Baring, M. G.

1995-01-01

345

The width of gamma-ray burst spectra  

NASA Astrophysics Data System (ADS)

The emission processes active in the highly relativistic jets of gamma-ray bursts (GRBs) remain unknown. In this paper, we propose a new measure to describe spectra: the width of the EFE spectrum, a quantity dependent only on finding a good fit to the data. We apply this to the full sample of GRBs observed by Fermi/Gamma-ray Burst Monitor (GBM) and Compton Gamma-ray Observatory/Burst and Transient Source Experiment (BATSE). The results from the two instruments are fully consistent. We find that the median widths of spectra from long and short GRBs are significantly different (chance probability <10-6). The width does not correlate with either duration or hardness, and this is thus a new, independent distinction between the two classes. Comparing the measured spectra with widths of spectra from fundamental emission processes - synchrotron and blackbody radiation - the results indicate that a large fraction of GRB spectra are too narrow to be explained by synchrotron radiation from a distribution of electron energies: for example, 78 per cent of long GRBs and 85 per cent of short GRBs are incompatible with the minimum width of standard slow cooling synchrotron emission from a Maxwellian distribution of electrons, with fast cooling spectra predicting even wider spectra. Photospheric emission can explain the spectra if mechanisms are invoked to give a spectrum much broader than a blackbody.

Axelsson, Magnus; Borgonovo, Luis

2015-03-01

346

Crack spectra analysis  

SciTech Connect

Crack spectra derived from velocity data have been shown to exhibit systematics which reflect microstructural and textural differences between samples (Warren and Tiernan, 1980). Further research into both properties and information content of crack spectra have yielded the following: Spectral features are reproducible even at low pressures; certain observed spectral features may correspond to non-in-situ crack populations created during sample retrieval; the functional form of a crack spectra may be diagnostic of the sample's grain texture; hysteresis is observed in crack spectra between up and down pressure runs - it may be due to friction between the faces of closed crack populations.

Tiernan, M.

1980-09-01

347

Characteristics of energetic solar flare electron spectra  

NASA Technical Reports Server (NTRS)

A 55 event survey of energy spectra of 0.1-100 MeV interplanetary electrons originating from solar flares as measured by two spectrometers onboard the ISEE 3 (ICE) spacecraft for the years 1978-1982 has been completed. Spectra generated using the maximum flux of a given event in each energy channel were restricted to events with a well-defined flux rise time. Two broad groups of electron spectra are considered. In one group, the spectra are well represented by a single power law in rigidity with spectral index in the range 3-4.5. The spectra in the other group deviate from a power law in rigidity systematically in that they harden with increasing rigidity. Events with near power-law spectra are found to be correlated with long-duration soft X-ray events, whereas those with hardening spectra are correlated with short-duration events. The possible variation of acceleration and propagation processes with the properties of the flare site is discussed, using the duration of the soft X-ray flare emission as an indicator of the physical parameters of the flare site (flare volume, density, coronal height, and magnetic field geometry).

Moses, Dan; Droege, Wolfgang; Meyer, Peter; Evenson, Paul

1989-01-01

348

Near-Infrared Spectra of Supernovae  

NASA Astrophysics Data System (ADS)

We present results from a survey of the near-infrared properties of all types of supernovae. Near-infrared spectra of the subluminous Type Ia SN 1999by taken 5 days before to two weeks after maximum light have been analysed using self-consistent SN Ia explosion models. The data generally agree with 1D delayed-detonation models, indicate a near Chandrasekhar-mass WD progenitor, and show low yield of iron-peak elements confined to the innermost layers of the ejecta. This puts strong constraints on the mixing of large iron blobs into the outer layers due to Rayleigh-Taylor instabilities during the deflagration phase. NIR spectra of Type IIP SNe are relatively line-free during the plateau phase, showing largely hydrogen emission with only a handful of other lines, mostly in the 1-1.2 micron region. After the plateau phase, Type IIP spectra become much richer, showing many overlapping emission features throughout the near-infrared. It appears that CO emission is a common feature of core-collapse supernovae, as several detections of first overtone CO emission near 2.3 microns have been made, including SN 1998S (IIn), SN 1999em, SN 1999gi (IIP) and SN 2000ew (Ic). Finally, we find that Type IIn supernovae often exhibit extraordinary infrared excesses at late times. This is probably thermal emission from hot dust, most likely in the dense circumstellar gas surrounding the progenitor star. The infrared luminosity can reach 1041-42 erg s-1, and can last for several years. A possible scenario is that the dust emission is an ``infrared echo'' powered not by the flash of the SN explosion, but rather by UV/X-ray emission from the strong shock interaction with the dense circumstellar material.

Gerardy, C. L.; Fesen, R. A.; Hoflich, P.; Nomoto, K.; Garnavich, P. M.; Jha, S.; Challis, P. M.; Kirshner, R. P.; Wheeler, J. C.; Sakai, S.

2001-12-01

349

Optical Spectra of Supernovae  

Microsoft Academic Search

The temporal evolution of the optical spectra of various types of supernovae (SNe) is illustrated, in part to aid observers classifying supernova candidates. Type II SNe are defined by the presence of hydrogen, and they exhibit a very wide variety of photometric and spectroscopic properties. Among hydrogen-deficient SNe (Type I), three subclasses are now known: those whose early-time spectra show

Alexei V. Filippenko

1997-01-01

350

Emission Line Galaxies The Data Set  

E-print Network

Emission Line Galaxies The Data Set The Sloan Digital Sky Survey (http://www.sdss.org, also http://skyserver.sdss.org) has taken spectra of roughly 800,000 galaxies. Galaxy spectra can be divided into two, types: those galaxies. By studying the strength and shape of various emission lines we can classify these galaxies

Johnson, Andrew

351

Signatures of hot electrons and fluorescence in Mo K? emission on Z  

SciTech Connect

Recent experiments on the Z accelerator have produced high-energy (17?keV) inner-shell K-alpha emission from molybdenum wire array z-pinches. Extensive absolute power and spectroscopic diagnostics along with collisional-radiative modeling enable detailed investigation into the roles of thermal, hot electron, and fluorescence processes in the production of high-energy x-rays. We show that changing the dimensions of the arrays can impact the proportion of thermal and non-thermal K-shell x-rays.

Hansen, S. B.; Ampleford, D. J.; Cuneo, M. E.; Jones, B.; Jennings, C. A.; Coverdale, C. A.; Rochau, G. A.; Dunham, G. [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States)] [Sandia National Laboratories, Albuquerque, New Mexico 87185 (United States); Ouart, N.; Dasgupta, A.; Giuliani, J. L. [Naval Research Laboratory, Washington, DC 20375 (United States)] [Naval Research Laboratory, Washington, DC 20375 (United States); Apruzese, J. P. [Consultant to NRL through Engility Corp., Chantilly, Virginia 20151 (United States)] [Consultant to NRL through Engility Corp., Chantilly, Virginia 20151 (United States)

2014-03-15

352

High-energy thermal synchrotron emission  

NASA Technical Reports Server (NTRS)

It is shown how the thermal synchrotron emission spectrum is modified when the photon energy is greater than the mean energy of the radiating particles. The effect if applying this energy conservation constraint is to produce spectra which have less high-energy photon emission than had been previously estimated. The thermal synchrotron spectra provide satisfactory fits to recently observed very high energy gamma ray spectra of certain burst sources.

Imamura, J. N.; Epstein, R. I.; Petrosian, V.

1985-01-01

353

Cathodoluminescence spectra of gallium nitride nanorods  

PubMed Central

Gallium nitride [GaN] nanorods grown on a Si(111) substrate at 720°C via plasma-assisted molecular beam epitaxy were studied by field-emission electron microscopy and cathodoluminescence [CL]. The surface topography and optical properties of the GaN nanorod cluster and single GaN nanorod were measured and discussed. The defect-related CL spectra of GaN nanorods and their dependence on temperature were investigated. The CL spectra along the length of the individual GaN nanorod were also studied. The results reveal that the 3.2-eV peak comes from the structural defect at the interface between the GaN nanorod and Si substrate. The surface state emission of the single GaN nanorod is stronger as the diameter of the GaN nanorod becomes smaller due to an increased surface-to-volume ratio. PMID:22168896

2011-01-01

354

Discrimination of phytoplankton classes using characteristic spectra of 3D fluorescence spectra  

NASA Astrophysics Data System (ADS)

The discrimination of phytoplankton classes using the characteristic fluorescence spectra extracted from three-dimensional fluorescence spectra was investigated. Single species cultures of 11 phytoplankton species, representing 5 major phytoplankton divisions, were used. The 3D fluorescence spectra of the cultures grown at different temperatures (20 and 15 °C) and illumination intensities (140, 80 and 30 ?M m -2 s -1) were measured and their feature extraction methods were explored. Ordering Rayleigh and Raman scattering data as zero, the obtained excitation-emission matrices were processed by both singular value decomposition (SVD) and trilinear decomposition methods. The resulting first principal component can be regarded as the characteristic spectrum of the original 3D fluorescence spectrum. The analysis shows that such characteristic spectra have a discriminatory capability. At different temperatures, the characteristic spectra of Isochrysis galbana, Platymonas helgolanidica and Skeletonema costatuma have high degrees of similarity to their own species samples, while the spectra similarities of Alexandrium tamarense, Prorocentrum dentatum, Pseudo-nitzschia pungens, Chaetoceros curvisetus, Ch. Debilis, Ch. Didymus and Synechococcus sp. are not as significant as the other three species. C. curvisetus, Ch. Debilis and Ch. Didymus, belonging to genus Chaetoceros, have identical spectra and cannot be discriminated at all. Regarding all six diatom species as one class, the average discriminant error rate is below 9%. It is worth mentioning that the diatom class can be distinguished from A. tamarense and P. dentatum, which belong to Dinophyta.

Zhang, Qian-Qian; Lei, Shu-He; Wang, Xiu-Lin; Wang, Lei; Zhu, Chen-Jian

2006-02-01

355

Observed Barium Emission Rates  

NASA Technical Reports Server (NTRS)

The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.

Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.

1993-01-01

356

Disk-averaged synthetic spectra of Mars.  

PubMed

The principal goal of the NASA Terrestrial Planet Finder (TPF) and European Space Agency's Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earthsized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of a Mars-like planet to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra. We explore the detectability as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPFC) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model. This model uses observational data as input to generate a database of spatially resolved synthetic spectra for a range of illumination conditions and viewing geometries. The model was validated against spectra recorded by the Mars Global Surveyor-Thermal Emission Spectrometer and the Mariner 9-Infrared Interferometer Spectrometer. Results presented here include disk-averaged synthetic spectra, light curves, and the spectral variability at visible and mid-infrared wavelengths for Mars as a function of viewing angle, illumination, and season. We also considered the differences in the spectral appearance of an increasingly ice-covered Mars, as a function of spectral resolution, signal-to-noise and integration time for both TPF-C and TPFI/ Darwin. PMID:16078866

Tinetti, Giovanna; Meadows, Victoria S; Crisp, David; Fong, William; Velusamy, Thangasamy; Snively, Heather

2005-08-01

357

Disk-averaged synthetic spectra of Mars  

NASA Technical Reports Server (NTRS)

The principal goal of the NASA Terrestrial Planet Finder (TPF) and European Space Agency's Darwin mission concepts is to directly detect and characterize extrasolar terrestrial (Earthsized) planets. This first generation of instruments is expected to provide disk-averaged spectra with modest spectral resolution and signal-to-noise. Here we use a spatially and spectrally resolved model of a Mars-like planet to study the detectability of a planet's surface and atmospheric properties from disk-averaged spectra. We explore the detectability as a function of spectral resolution and wavelength range, for both the proposed visible coronograph (TPFC) and mid-infrared interferometer (TPF-I/Darwin) architectures. At the core of our model is a spectrum-resolving (line-by-line) atmospheric/surface radiative transfer model. This model uses observational data as input to generate a database of spatially resolved synthetic spectra for a range of illumination conditions and viewing geometries. The model was validated against spectra recorded by the Mars Global Surveyor-Thermal Emission Spectrometer and the Mariner 9-Infrared Interferometer Spectrometer. Results presented here include disk-averaged synthetic spectra, light curves, and the spectral variability at visible and mid-infrared wavelengths for Mars as a function of viewing angle, illumination, and season. We also considered the differences in the spectral appearance of an increasingly ice-covered Mars, as a function of spectral resolution, signal-to-noise and integration time for both TPF-C and TPFI/ Darwin.

Tinetti, Giovanna; Meadows, Victoria S.; Crisp, David; Fong, William; Velusamy, Thangasamy; Snively, Heather

2005-01-01

358

Component analysis of the fluorescence spectra of a lignin model compound.  

PubMed

In order to test whether lignin fluorescence originates from discrete fluorophores, fluorescence emission spectra of the lignin model dehydrogenative polymer (DHP) were analyzed by the band deconvolution method and time-resolved analysis of both the excitation and emission spectra. Two series of 22 fluorescence emission spectra of DHP in chloroform/methanol (3:1, v/v) solution, and as a solid suspension in water, were deconvoluted into three fluorescence and one Raman Gaussian components. Emission spectra were obtained by stepwise variation of the excitation wavelength from 360 to 465 nm. Deconvolution was performed by nonlinear fitting of all three Gaussian parameters: area, width and position. Position of all components in a series was treated as a random variable and its approximate probability distribution (APD) calculated from a series of histograms with increasing number of abscissa intervals. A five peak multimodal APD profile was obtained for both series of DHP emission spectra. The mean fluorescence lifetime varied with wavelength both in the emission and the excitation decay-associated spectra (DAS), where four kinetic components were resolved. The shapes of the excitation spectra of the four components were quite different and gradually shifted bathochromically. The multicomponent nature of the DHP emission spectra along with the changes in the mean fluorescence lifetime and the form of the excitation DAS of the four components give evidence of the heterogeneous origin of fluorescent species emitting in the visible. PMID:16406801

Radoti?, Ksenija; Kalauzi, Aleksandar; Djikanovi?, Daniela; Jeremi?, Milorad; Leblanc, Roger M; Cerovi?, Zoran G

2006-04-01

359

Atomic Spectra Database (ASD)  

National Institute of Standards and Technology Data Gateway

SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

360

Spectra of coronae  

Microsoft Academic Search

We introduce a new invariant, the coronal of a graph, and use it to compute the spectrum of the corona G?H of two graphs G and H. In particular, we show that this spectrum is completely determined by the spectra of G and H and the coronal of H. Previous work has computed the spectrum of a corona only in

Cam McLeman; Erin McNicholas

2011-01-01

361

The high energy emission line spectrum of NGC 1068  

NASA Astrophysics Data System (ADS)

We present and discuss the high energy (E>4 keV) XMM-Newton spectrum of the Seyfert 2 galaxy, NGC 1068. Possible evidence for flux variability in both the neutral and ionized reflectors with respect to a BeppoSAX observation taken 3.5 years before is found. Several Fe and Ni emission lines, from both neutral and highly ionized material, are detected. The intensity of the iron K\\alpha Compton shoulder implies that the neutral reflector is Compton-thick, likely the visible inner wall of the N_H > 1025 cm-2 absorber. From the equivalent width of the ionized iron lines a column density of a few × 1021 cm-2 is deduced for the hot ionized reflector. Finally, an iron (nickel) overabundance, when compared to solar values, of about 2 (4) with respect to lower Z elements, is found.

Matt, G.; Bianchi, S.; Guainazzi, M.; Molendi, S.

2004-01-01

362

Evaluation of fission neutron spectra for minor actinides  

SciTech Connect

A method of evaluation of fission neutron spectra was developed and applied to minor actinides. The method is based on the Madland-Nix model of fission neutron emission, combined with the Ignatyuk model of the level density, the Moriyama-Ohnishi model of fission fragment mass distribution and the mass formula of Tachibana et al. It was found that the neutron spectra tend to be harder with increasing fissility of the compound nucleus.

Ohsawa, Takaaki; Shibata, Toshikazu [Kinki Univ., Osaka (Japan)

1994-12-31

363

Hard X-ray Spectra and Positions of Solar Flares observed by RHESSI: photospheric albedo, directivity and electron spectra  

E-print Network

We investigate the signature of the photospheric albedo contribution in solar flare hard X-ray spectra, the effect of low energy cutoffs in electron spectra, and the directivity of hard X-ray emission. Using Ramaty High Energy Solar Spectroscopic Imager (RHESSI) flare data we perform a statistical analysis of spatially integrated spectra and positions of solar flares. We demonstrate clear centre-to-limb variation of photon spectral indices in the 15-20 keV energy range and a weaker dependency in the 20-50 keV range which is consistent with photospheric albedo as the cause. The results also suggest that low-energy cutoffs sometimes inferred in mean electron spectra are an artefact of albedo. We also derive the anisotropy (ratio of downward/observer directed photons) of hard X-ray emission in the 15-20 keV range for various heliocentric angles.

J. Kasparova; E. P. Kontar; J. C. Brown

2007-01-30

364

Activity: Graphing Spectra  

NSDL National Science Digital Library

This activity introduces two different representations of spectra: the photographic representation, such as the rainbow, and the graphical representation used more often by astronomers. A rainbow is often given as an everyday example of a spectrum. Most students have seen a rainbow, so this example is used to help make the unfamiliar more familiar. However, the spectra that scientists use, which students will see in this lesson plan, appear very different than a rainbow. In this activity, students will explore for themselves two different representations of the same spectrum, noting advantages and disadvantages of each. They will explore the differences and similarities of both these representations, and will develop a more intuitive feel for a graphical representation, which may not yet be familiar to them.

2007-02-03

365

Rock Outcrop Spectra  

NASA Technical Reports Server (NTRS)

The color image on the lower left shows a rock outcrop at Meridiani Planum, Mars. This image was taken by the panoramic camera on the Mars Exploration Rover Opportunity, looking north, and was acquired on the 4th sol, or martian day, of the rover's mission (Jan. 27, 2004). The yellow box outlines an area detailed in the top left image, which is a monochrome (single filter) image from the rover's panoramic camera. The top image uses solid colors to show several regions on or near the rock outcrop from which spectra were extracted: the dark soil above the outcrop (yellow), the distant horizon surface (aqua), a bright rock in the outcrop (green), a darker rock in the outcrop (red), and a small dark cobblestone (blue). Spectra from these regions are shown in the plot to the right.

2004-01-01

366

Leading neutron spectra  

E-print Network

It is shown that the observation of the spectra of leading neutrons from proton beams can be a good probe of absorptive and migration effects. We quantify how these effects modify the Reggeized pion-exchange description of the measurements of leading neutrons at HERA. We are able to obtain a satisfactory description of all the features of these data. We also briefly discuss the corresponding data for leading baryons produced in hadron-hadron collisions.

A. B. Kaidalov; V. A. Khoze; A. D. Martin; M. G. Ryskin

2006-05-27

367

Infrared spectra of Venus  

NASA Technical Reports Server (NTRS)

A historical account of observations of Venus and their interpretation is given. The major constituent of the atmosphere on Venus (CO2) was detected spectroscopically forty years ago, and minor constituents (CO, HF, HCl) have been found more recently. The infrared spectra also provide a means of studying the motions of her cloudly atmosphere. The composition of the clouds has been sought in the reflection spectrum of Venus, and some of the evidence for their nature is discussed.

Young, L. G.

1974-01-01

368

Pluto and Charon's UV spectra from IUE to New Horizons  

NASA Astrophysics Data System (ADS)

We compare Mid-Ultraviolet (MUV) spectra of Pluto taken over a period of 20 years by the International Ultraviolet Explorer, the HST-Faint Object Spectrograph, and the HST-Cosmic Origins Spectrograph. We extract Pluto-only spectra from the IUE data and associate them with corrected longitudes when necessary. Comparing them with HST spectra provides further evidence of temporal changes in Pluto's geometric albedo between 2000 and 3200 Ĺ. These various spectra are used to explore the contributions of atmospheric or surface changes to Pluto's reflectance. We also provide predictions for the Far-Ultraviolet (FUV) surface reflectance and atmospheric emission spectra of Pluto that will be measured by the Alice spectrograph (Stern, S.A. et al. [2008]. Space Sci. Rev. 140, 155-187) during the New Horizons flyby of Pluto in 2015. FUV surface reflectance predictions are also made for Charon, Hydra, and Nix.

Schindhelm, Eric; Stern, S. Alan; Gladstone, Randy; Zangari, Amanda

2015-01-01

369

Slovak video meteor network --- meteor spectra  

NASA Astrophysics Data System (ADS)

After the great success of the All-Sky Meteor Orbit System (AMOS) [1,2], we upgraded the system by adding the AMOS-Spec camera for recording meteor spectra. The long-term AMOS-Spec program aims to measure the main element abundances of meteors detected by AMOS. Installed at the Modra Observatory station, the camera is based on the AMOS camera, equipped with 30~mm f/3.5 lens and 500 grooves/mm grating. Having the trajectory and orbit from AMOS and merging it with the simultaneously measured spectrum from AMOS-Spec allows us to identify the source of the meteoroid. Here, we report on preliminary results from a sample of meteor spectra collected by the AMOS-Spec camera since November 2013. The figure shows an example emission spectrum produced by the sigma Hydrid captured by the AMOS-Spec camera on December 4, 2013.

Rudawska, R.; Tóth, J.; Kalman?ok, D.; Zigo, P.

2014-07-01

370

Spectra of Gas Discharges  

NSDL National Science Digital Library

This resource provides pictures of the emission spectrum of range of atomic elements. These elements consist of: hydrogen, helium, lithium, oxygen, carbon, nitrogen, neon, magnesium, silicon, sulfur, iron, aluminum, calcium, argon, sodium, krypton, xenon, barium and strontium. Displays include instrumental and intrinsic broadening. The data from which the pictures are created is also available.

Talbot, John

371

Spitzer/IRS Spectra of GOODS AGN  

NASA Astrophysics Data System (ADS)

IRS Spectra of GOODS AGN Infrared emission from AGN comes from dust heated by black hole accretion and/or star-formation. Separating the contributions in optical/UV light can be difficult, particularly when obscuration is high; mid-infrared spectra are less affected by obscuration and thus offer diagnostics of the underlying power source(s). We present Spitzer IRS spectra of 10 IR-bright, hard X-ray-selected AGN from the GOODS-North field, spanning the redshift range 0.485Spectra were obtained with the deep Long and Short-Low modules, in exposures of 4-8 hours duration, resulting in a S/N ratio of 8-10 per pixel. The observed PAH features, silicate absorption, and infrared continua offer clues to distinguish reprocessed torus emission from the stellar-heated dust component. Combining with extensive GOODS imaging data at radio, sub-mm, infrared, optical and X-ray wavelengths, we place limits on the star-formation rates, Eddington ratios, and bolometric luminosities of the sample, and compare with lower-redshift samples to probe the evolution of the dust-enshrouded phase of AGN activity. This work was supported by NASA JPL/Spitzer grant RSA 177278. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA JPL/Spitzer grant RSA 177278.

Van Duyne, Jeffrey; Urry, C. M.

2006-12-01

372

Theoretical Studies of Molecular Spectra  

NASA Technical Reports Server (NTRS)

This summary describes the research activities of the principal investigator during the reporting period. The research includes spectroscopy, management of molecular databases, and generation of spectral line profiles and opacity data. The spectroscopy research includes oxygen broadening of nitric oxide (NO), analysis of CO2 spectra, analysis of HNO3 spectra, and analysis of CO spectra.

McKay, Christopher (Technical Monitor); Freedman, Richard S.

2002-01-01

373

IUE archived spectra  

NASA Technical Reports Server (NTRS)

The International Ultraviolet Explorer (IUE) Satellite has been in continuous operation since January 26, 1978. To date, approximately 65,000 spectra have been stored in an archive at Goddard Space Flight Center in Greenbelt, MD. A number of procedures have been generated to facilitate access to the data in the IUE spectral archive. This document describes the procedures which include on-line quick look of the displays, search of an observation data base for selected observations, and several methods for ordering data from the archive.

Sullivan, Edward C.; Bohlin, Ralph C.; Heap, Sara R.; West, Donald K.; Schmitz, Marion

1988-01-01

374

[Raman spectra of pyroxene].  

PubMed

By testing the Raman spectra of megacryst pyroxene, enstatite and diopside in terms of location, shape and intensity, the symmetries of the main spectral band of pyroxene and the vibration modes of Raman shift were identified. The spectral bands of corresponding ionic groups such as non-bridge oxygen Si-O- and bridge oxygen Si-O0, O-Si-O and M-O were assigned for vibrational mode. Through the change in the intensity of the spectral band in different section direction and the deficiency of some spectral bands, the orientation problem in mineral crystallography was preliminarily studied. PMID:20384128

Wang, Rong; Zhang, Bao-Min

2010-02-01

375

Stars and their Spectra  

NASA Astrophysics Data System (ADS)

1. Stars; 2. Atoms and spectra; 3. The spectral sequence; 4. The M stars: red supergiants to dwarfs; 5. Descending the staircase: class L; 6. The wet basement: class T; 7. The K stars: orange giants and brighter dwarfs; 8. Our Sun and its cousins: the G stars; 9. Class F: stars in transition; 10. The white stars of class A; 11. The B stars: beacons of the skies; 12. Class O: the head of the spectral sequence; 13. Extraordinary classes; 14. Journeys on the HR diagram; Star index; Subject index.

Kaler, James B.

2011-07-01

376

Twenty southern peculiar emission-line stars  

NASA Technical Reports Server (NTRS)

Observational data for 20 southern stars having emission-line spectra that suggest a significant degree of mass ejection are given in order to present an atlas of their spectra and to give a quantitative description of their appearance during the 1961-62 epoch. Most of the stars are P Cygni stars; others include nova-like, peculiar Be, and symbiotic stars, as well as stellar planetary nebulae and emission-line binaries, all of whose spectra were obtained with the Newtonian two-prism Zeiss Spectrograph and the 74-inch reflector at Mount Stromlo Observatory. It is noted that among the P Cygni stars, there is a strong correlation between the a-e expansion velocity and the strength of Balmer emission, while in both the P Cygni and the Bep stars, there is positive dependence of Fe II and negative dependence of (Fe II) emission strengths on Balmer emission strength.

Carlson, E. D.; Henize, K. G.

1979-01-01

377

Catalog of total excitation-emission and total synchronous fluorescence maps with synchronous fluorescence spectra of homologated fluorescent pesticides in large use in Morocco: development of a spectrometric low cost and direct analysis as an alert method in case of massive contamination of soils and waters by fluorescent pesticides.  

PubMed

The purpose of this research is to develop a direct spectrometric approach to monitor soils and waters, at a lower cost than the widely used chromatographic techniques; a spectrometric approach that is effective, reliable, fast, easy to implement, and without any use of organic solvents whose utilization is subject to law limitation. It could be suitable at least as an alert method in case of massive contamination. Here, we present for the first time a catalog of excitation-emission and total synchronous fluorescence maps that may be considered as fingerprints of a series of homologated pesticides, in large use in Morocco, aiming at a direct detection of their remains in agricultural soils and neighboring waters. After a large survey among farmers, agricultural workers and product distributors in two important agricultural regions of Morocco (Doukkala-Abda and Sebou basin), 48 commercial pesticides, which are fluorescent, were chosen. A multi-component spectral database of these targeted commercial pesticides was elaborated. For each pesticide, dissolved in water at the lowest concentration giving a no-noise fluorescence spectrum, the total excitation-emission matrix (TEEM), the total synchronous fluorescence matrix (TSFM) in addition to synchronous fluorescence spectra (SFS) at those offsets giving the highest fluorescence intensity were recorded. To test this preliminary multi-component database, two real soil samples, collected at a wheat field and at a vine field in the region of Doukkala, were analyzed. Remains of the commercial Pirimor (Carbamate) and Atlantis (Sulfonylurea) were identified by comparison of the recorded TEEM, TSFM, and SFS to those of the preliminary catalog at one hand, and on the basis of the results of a field pre-survey. The developed approach seems satisfactory, and the fluorimetric fingerprint database is under extension to a higher number of fluorescent pesticides in common use among the Moroccan agricultural regions. PMID:25424031

Foudeil, S; Hassoun, H; Lamhasni, T; Ait Lyazidi, S; Benyaich, F; Haddad, M; Choukrad, M; Boughdad, A; Bounakhla, M; Bounouira, H; Duarte, R M B O; Cachada, A; Duarte, A C

2014-11-27

378

Non-thermal radiative pair plasmas: processes and spectra  

E-print Network

We study the emission and absorption spectra due to various photon and pair processes in a non-equilibrium pair plasma containing a significant density of photons. We present here some preliminary results from Monte-Carlo simulations. These investigations are likely to be useful in understanding the radiation and relaxation mechanisms in non-thermal gamma-ray sources in astrophysics.

Ravi P. Pilla; Jacob Shaham

1995-05-17

379

Determining the modal mineralogy of mafic and ultramafic igneous rocks using thermal emission spectroscopy  

Microsoft Academic Search

The modal mineralogies of 20 mafic and ultramafic igneous rocks were determined from their thermal infrared emission spectra using a linear deconvolution approach, which uses a library of end-member mineral spectra to model a bulk rock spectrum. Over 90% of the modes obtained from thermal emission spectra agree with modes obtained by traditional optical analyses to within the stated error

Victoria E. Hamilton; Philip R. Christensen

2000-01-01

380

The X-ray spectra of symbiotic stars  

E-print Network

Symbiotic stars are thought to show distinct X-ray emission from the accreting object and from the colliding winds of the two stars. I show that the colliding wind component is unnecessary. Instead, the spectra can be interpreted as emission only from the compact object that is strongly absorbed by the partially-ionised wind of the red giant. There remains no evidence of any X-ray emission from colliding winds, and thus no need for a substantial wind from the compact object.

Peter J. Wheatley

1999-10-29

381

EUV spectra from highly charged terbium ions in optically thin and thick plasmas  

NASA Astrophysics Data System (ADS)

We have observed extreme ultraviolet (EUV) spectra from terbium (Tb) ions in optically thin and thick plasmas for a comparative study. The experimental spectra are recorded in optically thin, magnetically confined torus plasmas and dense laser-produced plasmas (LPPs). The main feature of the spectra is quasicontinuum emission with a peak around 6.5-6.6 nm, the bandwidth of which is narrower in the torus plasmas than in the LPPs. A comparison between the two types of spectra also suggests strong opacity effects in the LPPs. A comparison with the calculated line strength distributions gives a qualitative interpretation of the observed spectra.

Suzuki, C.; Koike, F.; Murakami, I.; Tamura, N.; Sudo, S.; Long, E.; Sheil, J.; White, E.; O'Reilly, F.; Sokell, E.; Dunne, P.; O'Sullivan, G.

2015-01-01

382

Dust Spectra from Above and Below  

NASA Technical Reports Server (NTRS)

Spectra of martian dust taken by the Mars Exploration Rover Spirit's mini-thermal emission spectrometer are compared to that of the orbital Mars Global Surveyor's thermal emission spectrometer. The graph shows that the two instruments are in excellent agreement.

Rover Senses Carbon Dioxide [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data acquired on Mars from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signature of carbon dioxide. Carbon dioxide makes up the bulk of the thin martian atmosphere.

Rover Senses Silicates [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data acquired on Mars by the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signature of silicates - a group of minerals that form the majority of Earth's crust. Minerals called feldspars and zeolites are likely candidates responsible for this feature.

Rover Senses Bound Water [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data acquired on Mars from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signature of an as-of-yet unidentified mineral that contains bound water in its crystal structure. Minerals such as gypsum and zeolites are possible candidates.

Rover Senses Carbonates [figure removed for brevity, see original site] Click on image for larger view

This graph, consisting of data from the Mars Exploration Rover Spirit's mini-thermal emission spectrometer, shows the light, or spectral, signatures of carbonates - minerals common to Earth that form only in water. The detection of trace amounts of carbonates on Mars may be due to an interaction between the water vapor in the atmosphere and minerals on the surface.

2004-01-01

383

Reviewing Pulsar Spectra  

E-print Network

Problems solved? Pulsar research must be considered - 35 years after the detection of pulsars - a mature science, where the basic questions have been raised and discussed. One would hope that many if not all generic and important problems have found some kind of answer and that scientific work can concentrate now on specific details requiring more in depth investigation. We know, however, that this picture is not true. Even well studied areas did in the past not always lead to a general accepted model and some were investigated at the beginning with enthusiasm but left behind. This paper will concentrate on one narrow topic, pulsar radio spectra. It is the attempt to work out, what features are now generally accepted, but also what features are still in discussion after so many years of pulsar research. In this sense the paper will enlighten in a personal view those aspects which are still under discussion.

W. Sieber

2002-08-30

384

TDS spectra analysis  

NASA Astrophysics Data System (ADS)

Methods of TDS spectra analysis start usually from the Polanyi-Wigner desorption rate equation. The Redhead approximative solution of the equation can be rearranged into a reduced form in which it serves as an analytical expression for the desorption rate versus time or temperature. Fitting the analytical form to an experimental curve we can confirm or deny the invariability of kinetic parameters — a desorption energy Ed and a preexponential factor ?l — and determine their values. If the parameters depend on surface coverage ? the application of the reduced form allows us to determine their values at ??0 and ?? ?0 and estimate the dependence Ed( ?), ?(?) from a single TDS spectrum. The method proposed in this paper is valid for the first-order kinetics of desorption; for the estimation mentioned above an assumption is made that desorption sites are identical and that E d as well as ?l changes with ? monotonously.

Tomková, E.

1996-05-01

385

A temperature and emissivity separation algorithm for Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images  

Microsoft Academic Search

The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) scanner on NASA's Earth Observing System (EOS)-AM1 satellite (launch scheduled for 1998) will collect five bands of thermal infrared (TIR) data with a noise equivalent temperature difference (NE?T) of ⩽0.3 K to estimate surface temperatures and emissivity spectra, especially over land, where emissivities are not known in advance. Temperature\\/emissivity separation (TES)

Alan Gillespie; Shuichi Rokugawa; Tsuneo Matsunaga; J. Steven Cothern; Simon Hook; Anne B. Kahle

1998-01-01

386

CLASSIFICATION OF STELLAR SPECTRA WITH LOCAL LINEAR EMBEDDING  

SciTech Connect

We investigate the use of dimensionality reduction techniques for the classification of stellar spectra selected from the Sloan Digital Sky Survey. Using local linear embedding (LLE), a technique that preserves the local (and possibly nonlinear) structure within high-dimensional data sets, we show that the majority of stellar spectra can be represented as a one-dimensional sequence within a three-dimensional space. The position along this sequence is highly correlated with spectral temperature. Deviations from this 'stellar locus' are indicative of spectra with strong emission lines (including misclassified galaxies) or broad absorption lines (e.g., carbon stars). Based on this analysis, we propose a hierarchical classification scheme using LLE that progressively identifies and classifies stellar spectra in a manner that requires no feature extraction and that can reproduce the classic MK classifications to an accuracy of one type.

Daniel, Scott F.; Connolly, Andrew; Vanderplas, Jake [Astronomy Department, University of Washington, Box 351580, U.W. Seattle, WA 98195-1580 (United States); Schneider, Jeff; Xiong Liang [School of Computer Science, Carnegie Mellon University, Pittsburgh, PA 15213 (United States)

2011-12-15

387

Attenuation-corrected fluorescence spectra unmixing for spectroscopy and microscopy.  

PubMed

In fluorescence measurements, light is often absorbed and scattered by a sample both for excitation and emission, resulting in the measured spectra to be distorted. Conventional linear unmixing methods computationally separate overlapping spectra but do not account for these effects. We propose a new algorithm for fluorescence unmixing that accounts for the attenuation-related distortion effect on fluorescence spectra. Using a matrix representation, we derive forward measurement formation and a corresponding inverse method; the unmixing algorithm is based on nonnegative matrix factorization. We also demonstrate how this method can be extended to a higher-dimensional tensor form, which is useful for unmixing overlapping spectra observed under the attenuation effect in spectral imaging microscopy. We evaluate the proposed methods in simulation and experiments and show that it outperforms a conventional, linear unmixing method when absorption and scattering contributes to the measured signals, as in deep tissue imaging. PMID:25321030

Ikoma, Hayato; Heshmat, Barmak; Wetzstein, Gordon; Raskar, Ramesh

2014-08-11

388

Nuclear temperatures from the evaporation fragment spectra and observed anomalies  

E-print Network

The extreme back-angle evaporation spectra of alpha, lithium, beryllium, boron and carbon from different compound nuclei near A=100 (EX=76-210 MeV) have been compared with the predictions of standard statistical model codes such as 'CASCADE' and 'GEMINI'. It was found that the shapes of the alpha spectra agree well with the predictions of the statistical models. However the spectra of lithium, beryllium, boron and carbon show significantly gentler slopes implying higher temperature of the residual nuclei, even though the spectra satisfy all other empirical criteria of statistical emissions. The observed slope anomaly was found to be largest for lithium and decreases at higher excitation energy. These results could not be understood by adjusting the parameters of the statistical models or from reaction dynamics and might require examining the statistical model from a quantum mechanical perspective.

A. Ray; A. De; A. Chatterjee; S. Kailas; S. R. Banerjee; K. Banerjee; S. Saha

2013-06-16

389

Stability of the IRSL Spectra of Alkali Feldspars  

NASA Astrophysics Data System (ADS)

Measurements of infrared stimulated luminescence (IRSL) emission spectra are presented for detrital potassium-rich feldspars separated from sands and for museum specimens of low albite and intermediate microcline. The samples show common emission bands at 335, 400 and 550 nm and a thermally unstable emission band at 290 nm which is associated with sodic phases in the crystal structure. Rapid preheating and room temperature storage causes a decrease in emission from the 290 nm centre with a corresponding increase in the other emission centres, with potential problems for pulse annealing routines. This may be due to charge transfer or structural transformations in the defect. A sustained preheat regime is essential if detrital potassium-rich feldspars are to be used for IRSL dating.

Clarke, M. L.; Rendell, H. M.

1997-02-01

390

Photoreflectance spectra of excitonic polaritons in GaN substrate prepared by lateral epitaxial overgrowth  

Microsoft Academic Search

Photoreflectance (PR) spectra of high-purity, nearly free-standing GaN substrate were compared with emission and reflectance spectra, which were analyzed based on a model exciton-polariton picture in which A, B, and C free excitons couple simultaneously to an electromagnetic wave. The GaN substrate with reduced dislocation density was prepared by lateral epitaxial overgrowth technique and it exhibited predominant excitonic emissions with

S. F. Chichibu; K. Torii; T. Deguchi; T. Sota; A. Setoguchi; H. Nakanishi; T. Azuhata; S. Nakamura

2000-01-01

391

VizieR Online Data Catalog: H? spectra of ? Aqr (Zharikov+, 2013)  

NASA Astrophysics Data System (ADS)

Table 1: Dates of observations of pi Aqr (HJD), the source (ID), and results of V/R and EW measurements of the Halpha emission line. spectra/* : Archive of all presented spectra in FITS format. The wavelength is given in Angstrom. The continuum is normalized to unit. (3 data files).

Zharikov, S.; Miroshnichenko, A. S.; Pollmann, E.; Danford, S.; Bjorkman, K. S.; Morrison, N. D.; Favaro, A.; Guarro Flo, J.; Terry, J. N.; Desnoux, V.; Garrel, T.; Martineau, G.; Buchet, Y.; Ubaud, S.; Mauclaire, B.; Kalbermatten, H.; Buil, C.; Sawicky, C. J.; Blank, T.; Garde, O.

2013-11-01

392

How Astronomers Use Spectra to Learn About the Sun and Other Stars  

NSDL National Science Digital Library

This is a booklet about spectra and their usefulness to astronomers. Learners will read about the electromagnetic spectrum, how atomic physics is used to obtain information out of stellar spectra, and how the Doppler effect is used to measure stellar motions. An activity at the end allows learners to analyze and identify several emission lines in the spectrum of the Sun.

2012-08-03

393

4 -STELLAR SPECTRA The spectra of most stars are approximately  

E-print Network

classification criteria have been developed. For stars heavily obscured by dust, near-IR (1-2.5 Âľm) features1 4 - STELLAR SPECTRA The spectra of most stars are approximately blackbodies. The presence features indicated the luminosity L of the star, and Roman numerals were appended to indicate

Sitko, Michael L.

394

Polarization effects in cutaneous autofluorescent spectra  

NASA Astrophysics Data System (ADS)

Used polarized light for fluorescence excitation one could obtain response related to the anisotropy features of extracellular matrix. The fluorophore anisotropy is attenuated during lesions' growth and level of such decrease could be correlated with the stage of tumor development. Our preliminary investigations are based on in vivo point-by-point measurements of excitation-emission matrices (EEM) from healthy volunteers skin on different ages and from different anatomical places using linear polarizer and analyzer for excitation and emission light detected. Measurements were made using spectrofluorimeter FluoroLog 3 (HORIBA Jobin Yvon, France) with fiber-optic probe in steady-state regime using excitation in the region of 280-440 nm. Three different situations were evaluated and corresponding excitation-emission matrices were developed - with parallel and perpendicular positions for linear polarizer and analyzer, and without polarization of excitation and fluorescence light detected from a forearm skin surface. The fluorescence spectra obtained reveal differences in spectral intensity, related to general attenuation, due to filtering effects of used polarizer/analyzer couple. Significant spectral shape changes were observed for the complex autofluorescence signal detected, which correlated with collagen and protein cross-links fluorescence, that could be addressed to the tissue extracellular matrix and general condition of the skin investigated, due to morphological destruction during lesions' growth. A correlation between volunteers' age and the fluorescence spectra detected was observed during our measurements. Our next step is to increase developed initial database and to evaluate all sources of intrinsic fluorescent polarization effects and found if they are significantly altered from normal skin to cancerous state of the tissue, this way to develop a non-invasive diagnostic tool for dermatological practice.

Borisova, E.; Angelova, L.; Jeliazkova, Al.; Genova, Ts.; Pavlova, E.; Troyanova, P.; Avramov, L.

2014-05-01

395

The Ultraviolet Emission Spectra of AN HII Region  

NASA Astrophysics Data System (ADS)

ONE OF THE ADVANTAGES OF THE NEW INSTRUMENTS SUCH AS THE HUBBLE SPACE TELESCOPE IS TO BE ABLE TO STUDY THE UNIVERSE AT WAVELENGTHS PREVIOUSLY UNOBSERVABLE FROM UNDER THE EARTH'S ATMOSPHERE. ONE THE THESE IS THE UV REGION OF THE STECTRUM. USING HST'S FOS, I WOULD LIKE TO TAKE A UV SPETRUM OF AN HII REGION, M8, THE LAGOON NEBULA (HOURGLASS REGION). HII REGIONS ARE AREAS OF STARBIRTH AND ARE SAMPLES OF THE INTERSTELLAR MATTER OUT OF WHICH STARS ARE BEING BORN. HOT, YOUNG O STARS WHICH RADIATE STRONGLY IN THE UV ARE EMBEDDED IN M8. MANY EMSSION LINES ARE EXPECTED BETWEEN 912-3300 ANGTROMS. USING WF/PC, AN IMAGE OF THE HOURGALSS WILL BE TAKEN LOOKING FOR FILIMENTARY STRUCTURE AND NEW BORN STARS.

Cox, Nancy

1991-07-01

396

RELATIONSHIP BETWEEN THE ABSORPTION AND EMISSION SPECTRA AND  

E-print Network

(see equation 3 in text) to suspensions of Chlorella, Porphyridium, and Anacystis and to chlorophyll with frequency. In Chlorella (green alga) a sharp drop of '(iv) is indicated towards the lower frequencies

Govindjee

397

Projecting Spectra for Classroom Investigations.  

ERIC Educational Resources Information Center

Describes an inexpensive spectrum projector that makes high-dispersion, high-efficiency diffraction gratings using a holographic process. Discusses classroom applications such as transmission spectra, absorption spectra, reflection characteristics of materials, color mixing, florescence and phosphorescence, and break up spectral colors. (MDH)

Sadler, Philip

1991-01-01

398

Two components in meteor spectra  

Microsoft Academic Search

Through an analysis of fireball spectra it was found that meteor heads consist of two parts with quite different temperatures. The spectra of both parts can be fitted with a simple thermal equilibrium model. The temperature of the main spectrum is about 4000 K, and that of the second spectrum is about 10,000 K. There is little evidence for a

Jiri Borovicka

1994-01-01

399

FHILs in Seyferts and Liners in the optical spectra  

NASA Astrophysics Data System (ADS)

We present the main results from a selection of optical spectra of Seyfert and LINER galaxies taken from the 9^{th} release of the SDSS with detectable emission of forbidden high ionization lines (FHILs), better known as coronal lines. A catalog of 345 Seyfert 1 (Sy1) and Seyfert 2 (Sy2) galaxies with FHILs emission is presented. By analyzing their spectra and utilizing data from the literature we found the following results: (1) The flux ratios between FHILs suggests anisotropy of emission between Sy1 and Sy2 galaxies, which agrees with the results found by Nagao et al. (2002) and Portilla (2012). Sy1 seems to emit more FHILs than Sy2. (2) This anisotropy suggests the idea that an important, but not the majority, of the emission of FHILs comes from the inner part of the obscuring torus. (3) We present diagnostic diagrams between FHILs lines which indicate clear correlations between the flux ratios. (4) It is observed that the ratio of Ne V/Fe VII is of the order of 3 to 10, while the ratios between iron lines (i.e., Fe VII, Fe X, Fe XI) are roughly around the unity. (5) At least in the optical spectra, the present study continues to support the general idea that LINERs are not energetic enough to present FHILs. A complete version of this study including the catalog with the objects of study, and diagnosis diagrams using only this kind of lines can be found in Vera & Portilla (in prep).

Vera, R. J. C.; Rodriguez, A. M.; Portilla, J. G.

2014-10-01

400

Analysis of chemiluminescence spectra in oxidative degradation of oleic acid  

NASA Astrophysics Data System (ADS)

We studied chemiluminescence spectroscopy to develop an evaluation method for organic material degradation. The thermal oxidation of oleic acid as a monounsaturated fatty acid was investigated using chemiluminescence measurements. The obtained spectra indicated that the luminescence consisted of several peaks, including peaks for singlet oxygen and excited carbonyls. A detailed analysis of the nuclear magnetic resonance and infrared absorption spectra allowed us to determine the probable structures of the oxidative products. The relationship between the spectrum and the analyzed structure implied that the wavelength of the carbonyl group emission peak shifted as a result of the structure.

Sago, Tomohiro; Ishii, Hiroshi; Hagihara, Hideaki; Takada, Noriyuki; Suda, Hiroyuki

2013-04-01

401

Experimental and Computational Studies of Electric Thruster Plasma Radiation Emission  

E-print Network

thrusters and plasma sources. First, the BHT-200 Hall thruster emission spectra measurements are pre- sented type laboratory mini-Hall thruster, MHT-9, were presented. Third, radiation emission measurementsExperimental and Computational Studies of Electric Thruster Plasma Radiation Emission Murat Celik

402

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

403

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

404

PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330  

SciTech Connect

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

Gatuzz, E.; Mendoza, C. [Centro de Fisica, Instituto Venezolano de Investigaciones Cientificas (IVIC), P.O. Box 20632, Caracas 1020A (Venezuela, Bolivarian Republic of); Garcia, J.; Lohfink, A. [Department of Astronomy and Maryland Astronomy Center for Theory and Computation, University of Maryland, College Park, MD 20742 (United States); Kallman, T. R.; Witthoeft, M. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Bautista, M. A. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Palmeri, P.; Quinet, P., E-mail: egatuzz@ivic.gob.ve, E-mail: claudio@ivic.gob.ve, E-mail: javier@astro.umd.edu, E-mail: alohfink@astro.umd.edu, E-mail: timothy.r.kallman@nasa.gov, E-mail: michael.c.witthoeft@nasa.gov, E-mail: manuel.bautista@wmich.edu, E-mail: palmeri@umons.ac.be, E-mail: quinet@umons.ac.be [Astrophysique et Spectroscopie, Universite de Mons-UMONS, B-7000 Mons (Belgium)

2013-05-01

405

Particle abundances and spectra in the hydrodynamical description of relativistic nuclear collisions with light projectiles  

E-print Network

We show that a hydrodynamical model with continuous particle emission instead of sudden freeze out may explain both the observed strange particle and pion abundances and transverse mass spectra for light projectile at SPS energy. We found that the observed enhancement of pion production corresponds, within the context of continuous emission, to the maximal entropy production.

F. Grassi; Y. Hama; T. Kodama; O. Socolowski Jr

2003-07-24

406

Spectra of Herbig Ae/Be stars in the region of the Ca II infrared triplet.  

NASA Astrophysics Data System (ADS)

Near-infrared spectra of 9 Herbig Ae/Be stars and 3 Be stars of ? Cas-type were obtained on an infrared image tube. Strong Ca II, P11-P20 and O I 8446 emission lines were identified, similar to the emission spectrum of T Tauri-type stars.

Kotyshev, V. V.

407

Thermal Emission Spectroscopy of 1 Ceres: Evidence for Olivine  

NASA Technical Reports Server (NTRS)

Thermal emission spectra of the largest asteroid, 1 Ceres, obtained from the Kuiper Airborne Observatory display features that may provide information about its surface mineralogy. The emissivity, obtained by dividing the spectra by a standard thermal model, is compared with emissivity spectra of olivines and phyllosilicates deduced via Kirchoff's law from reflectivity measurements. The spectra provide a fairly good match to fine grained olivines (0 to 5 micrometer size range). The smoothness of the spectrum beyond 18 micrometers is an indication of particles smaller than 50 micrometers. While the abrupt rise in emissivity near 8 micrometers matches many silicates, the distinct emissivity minimum centered near 12.8 micrometers is consistant with iron-poor olivines, but not with phyllosilicates. It suggests the presence of opaques and does not exclude a mixture with organics and fine-grained phyllosilicates.

Witteborn, Fred. C.