Science.gov

Sample records for absorption line spectra

  1. Oscillator strength measurements of atomic absorption lines from stellar spectra

    NASA Astrophysics Data System (ADS)

    Lobel, Alex

    2011-05-01

    Herein we develop a new method to determine oscillator strength values of atomic absorption lines with state-of-the-art detailed spectral synthesis calculations of the optical spectrum of the Sun and of standard spectral reference stars. We update the log(gf) values of 911 neutral lines observed in the KPNO-FTS flux spectrum of the Sun and high-resolution echelle spectra (R = 80 000) of Procyon (F5 IV-V) and Eps Eri (K2 V) observed with large signal-to-noise (S/N) ratios of 2000 using the new Mercator-Hermes spectrograph at La Palma Observatory (Spain). We find for 483 Fe I, 85 Ni I, and 51 Si I absorption lines in the sample a systematic overestimation of the literature log(gf) values with central line depths below 15%. We employ a curve-of-growth analysis technique to test the accuracy of the new oscillator strength values and compare calculated equivalent line widths to the Moore, Minnaert, and Houtgast atlas of the Sun. The online SpectroWeb database at http://spectra.freeshell.org interactively displays the observed and synthetic spectra and provides the new log(gf) values together with important atomic line data. The graphical database is under development for stellar reference spectra of every spectral sub-class observed with large spectral resolution and S/N ratios.

  2. Monitoring the variability of intrinsic absorption lines in quasar spectra , ,

    SciTech Connect

    Misawa, Toru; Charlton, Jane C.; Eracleous, Michael

    2014-09-01

    We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 yr (1-3.5 yr in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems or in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable BALs. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density ∼10{sup 3}-10{sup 5} cm{sup –3} and upper limits on the distance of the absorbers from the central engine of the order of a few kiloparsecs. Motivated by the observed variability properties, we suggest that mini-BALs can vary because of fluctuations of the ionizing continuum or changes in partial coverage while NALs can vary primarily because of changes in partial coverage.

  3. Monitoring the Variability of Intrinsic Absorption Lines in Quasar Spectra

    NASA Astrophysics Data System (ADS)

    Misawa, Toru; Charlton, Jane C.; Eracleous, Michael

    2014-09-01

    We have monitored 12 intrinsic narrow absorption lines (NALs) in five quasars and seven mini-broad absorption lines (mini-BALs) in six quasars for a period of 4-12 yr (1-3.5 yr in the quasar rest-frame). We present the observational data and the conclusions that follow immediately from them, as a prelude to a more detailed analysis. We found clear variability in the equivalent widths (EWs) of the mini-BAL systems but no easily discernible changes in their profiles. We did not detect any variability in the NAL systems or in narrow components that are often located at the center of mini-BAL profiles. Variations in mini-BAL EWs are larger at longer time intervals, reminiscent of the trend seen in variable BALs. If we assume that the observed variations result from changes in the ionization state of the mini-BAL gas, we infer lower limits to the gas density ~103-105 cm-3 and upper limits on the distance of the absorbers from the central engine of the order of a few kiloparsecs. Motivated by the observed variability properties, we suggest that mini-BALs can vary because of fluctuations of the ionizing continuum or changes in partial coverage while NALs can vary primarily because of changes in partial coverage. Based on data collected at Subaru telescope, which is operated by the National Astronomical Observatory of Japan. Based on observations obtained at the European Southern Observatory at La Silla, Chile in programs 65.O-0063(B), 65.O-0474(A), 67.A-0078(A), 68.A-0461(A), 69.A-0204(A), 70.B-0522(A), 072.A-0346(A), 076.A-0860(A), 079.B-0469(A), and 166.A-0106(A).

  4. Radiatively driven winds for different power law spectra. [for explaining narrow and broad quasar absorption lines

    NASA Technical Reports Server (NTRS)

    Beltrametti, M.

    1980-01-01

    The analytic solutions for radiatively driven winds are given for the case in which the winds are driven by absorption of line and continuum radiation. The wind solutions are analytically estimated for different parameters of the central source and for different power law spectra. For flat spectra, three sonic points can exist; it is shown, however, that only one of these sonic points is physically realistic. Parameters of the central source are given which generate winds of further interest for explaining the narrow and broad absorption lines in quasars. For the quasar model presented here, winds which could give rise to the narrow absorption lines are generated by central sources with parameters which are not realistic for quasars.

  5. Common lines in the rest-frame absorption-line spectra of QSOs?

    NASA Astrophysics Data System (ADS)

    Varshni, Y. P.; Singh, D.

    1985-02-01

    Libby et al. (1984) have studied the absorption-line data for 13 QSOs in the rest-frames of the QSOs. It is shown that the number of groups in which 5 lines or more lie within a wavelength interval of 1.0 Å found by these authors is insignificantly different from that that would be expected from chance coincidences. Consequently, there is no evidence that the rest-frame wavelengths at which these groups occur have any special significance.

  6. Time variations of narrow absorption lines in high resolution quasar spectra

    NASA Astrophysics Data System (ADS)

    Boissé, P.; Bergeron, J.; Prochaska, J. X.; Péroux, C.; York, D. G.

    2015-09-01

    Aims: We have searched for temporal variations of narrow absorption lines in high resolution quasar spectra. A sample of five distant sources were assembled, for which two spectra are available, either VLT/UVES or Keck/HIRES, which were taken several years apart. Methods: We first investigate under which conditions variations in absorption line profiles can be detected reliably from high resolution spectra and discuss the implications of changes in terms of small-scale structure within the intervening gas or intrinsic origin. The targets selected allow us to investigate the time behaviour of a broad variety of absorption line systems by sampling diverse environments: the vicinity of active nuclei, galaxy halos, molecular-rich galaxy disks associated with damped Lyα systems, as well as neutral gas within our own Galaxy. Results: Intervening absorption lines from Mg ii, Fe ii, or proxy species with lines of lower opacity tracing the same kind of (moderately ionised) gas appear in general to be remarkably stable (1σ upper limits as low as 10% for some components on scales in the range 10-100 au), even for systems at zabs ≈ ze. Marginal variations are observed for Mg ii lines towards PKS 1229-021 at zabs = 0.83032; however, we detect no systems that display any change as large as those reported in low resolution SDSS spectra. The lack of clear variations for low β Mg ii systems does not support the existence of a specific population of absorbers made of swept-up gas towards blazars. In neutral or diffuse molecular media, clear changes are seen for Galactic Na i lines towards PKS 1229-02 (decrease in N by a factor of four for one of the five components over 9.7 yr), corresponding to structure on a scale of about 35 au, in good agreement with known properties of the Galactic interstellar medium. Tentative variations are detected for H2J = 3 lines towards FBQS J2340-0053 at zabs = 2.05454 (≃35% change in column density, N, over 0.7 yr in the rest frame), suggesting

  7. Measurability of Kinetic Temperature from Metal Absorption-Line Spectra Formed in Chaotic Media

    NASA Astrophysics Data System (ADS)

    Levshakov, Sergei A.; Takahara, Fumio; Agafonova, Irina I.

    1999-06-01

    We present a new method for recovering the kinetic temperature of the intervening diffuse gas to an accuracy of 10%. The method is based on the comparison of unsaturated absorption-line profiles of two species with different atomic weights. The species are assumed to have the same temperature and bulk motion within the absorbing region. The computational technique involves the Fourier transform of the absorption profiles and the consequent entropy-regularized χ2-minimization (ERM) to estimate the model parameters. The procedure is tested using synthetic spectra of C+, Si+, and Fe+ ions. The comparison with the standard Voigt fitting analysis is performed, and it is shown that the Voigt deconvolution of the complex absorption-line profiles may result in estimated temperatures that are not physical. We also successfully analyze Keck telescope spectra of C II λ1334 and Si II λ1260 lines observed at the redshift z=3.572 toward the quasar Q1937-1009 by Tytler et al. Based in part on data obtained at the W. M. Keck Observatory, which is jointly operated by the University of California and the California Institute of Technology.

  8. [Laser induced breakdown spectra of coal sample and self-absorption of the spectral line].

    PubMed

    Zhang, Gui-yin; Ji, Hui; Jin, Yi-dong

    2014-12-01

    The LIBS of one kind of household fuel coal was obtained with the first harmonic output 532 nm of an Nd·YAG laser as radiation source. With the assignment of the spectral lines, it was found that besides the elements C, Si, Mg, Fe, Al, Ca, Ti, Na and K, which are reported to be contained in coal, the presented sample also contains trace elements, such as Cd, Co, Hf, Ir, Li, Mn, Ni, Rb, Sr, V, W, Zn, Zr etc, but the spectral lines corresponding to O and H elements did not appear in the spectra. This is owing to the facts that the transition probability of H and O atoms is small and the energy of the upper level for transition is higher. The results of measurement also show that the intensity of spectral line increases with the laser pulse energy and self-absorption of the spectral lines K766.493 nm and K769.921 nm will appear to some extent. Increasing laser energy further will make self-absorption more obvious. The presence of self-absorption can be attributed to two factors. One is the higher transition rate of K atoms, and the other is that the increase in laser intensity induces the enhancement of the particle number density in the plasma. PMID:25881446

  9. Synthetic Spectra of H Balmer and HE I Absorption Lines. I. Stellar Library

    NASA Astrophysics Data System (ADS)

    González Delgado, Rosa M.; Leitherer, Claus

    1999-12-01

    We present a grid of synthetic profiles of stellar H Balmer and He I lines at optical wavelengths with a sampling of 0.3 Å. The grid spans a range of effective temperature 50,000 K>=Teff>=4000 K, and gravity 0.0<=logg<=5.0 at solar metallicity. For Teff>=25,000 K, non-LTE stellar atmosphere models are computed using the code TLUSTY (Hubeny). For cooler stars, Kurucz LTE models are used to compute the synthetic spectra. The grid includes the profiles of the high-order hydrogen Balmer series and He I lines for effective temperatures and gravities that have not been previously synthesized. The behavior of H8 to H13 and He I λ3819 with effective temperature and gravity is very similar to that of the lower terms of the series (e.g., Hβ) and the other He I lines at longer wavelengths; therefore, they are suited for the determination of the atmospheric parameters of stars. These lines are potentially important to make predictions for these stellar absorption features in galaxies with active star formation. Evolutionary synthesis models of these lines for starburst and poststarburst galaxies are presented in a companion paper. The full set of the synthetic stellar spectra is available for retrieval at our website or on request from the authors.

  10. Gravitationally redshifted absorption lines in the X-ray burst spectra of a neutron star.

    PubMed

    Cottam, J; Paerels, F; Mendez, M

    2002-11-01

    The fundamental properties of neutron stars provide a direct test of the equation of state of cold nuclear matter, a relationship between pressure and density that is determined by the physics of the strong interactions between the particles that constitute the star. The most straightforward method of determining these properties is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere. The equation of state implies a mass-radius relation, while a measurement of the gravitational redshift at the surface of a neutron star provides a direct constraint on the mass-to-radius ratio. Here we report the discovery of significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO0748-676. We identify the most significant features with the Fe XXVI and XXV n = 2-3 and O VIII n = 1-2 transitions, all with a redshift of z = 0.35, identical within small uncertainties for the respective transitions. For an astrophysically plausible range of masses (M approximately 1.3-2.0 solar masses; refs 2-5), this value is completely consistent with models of neutron stars composed of normal nuclear matter, while it excludes some models in which the neutron stars are made of more exotic matter. PMID:12422210

  11. Determination of vibration-rotation lines intensities from absorption Fourier spectra

    NASA Technical Reports Server (NTRS)

    Mandin, J. Y.

    1979-01-01

    The method presented allows the line intensities to be calculated from either their equivalent widths, heights, or quantities deduced from spectra obtained by Fourier spectrometry. This method has proven its effectiveness in measuring intensities of 60 lines of the molecule H2O with a precision of 10%. However, this method cannot be applied to isolated lines.

  12. The determination of absorption cross sections and line profiles in vibrational overtone spectra with the use of intracavity absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Bettermann, H.; Kleist, E.; Kok, R.

    1993-03-01

    This contribution presents quantitative absorption data concerning the 7 th CH overtone stretching vibrations of n-hexane and of methylcyclopentane. The transitions are adapted to Lorentzian and Gaussian line shapes. The bank shape analyses yield the spectral positions, absorption cross sections and linewidths of the investigated transitions.

  13. First detection of ionized helium absorption lines in infrared K band spectra of O-type stars

    NASA Technical Reports Server (NTRS)

    Conti, Peter S.; Block, David L.; Geballe, T. R.; Hanson, Margaret M.

    1993-01-01

    We have obtained high SNR, moderate-resolution K band spectra of two early O-type main sequence stars, HD 46150 O5 V, and HD 46223 O4 V, in the Rosette Nebula. We report the detection, for the first time, of the 2.189 micron He II line in O-type stars. Also detected is the 2.1661 micron Br-gamma line in absorption. The 2.058 micron He I line appears to be present in absorption in both stars, although its appearance at our resolution is complicated by atmospheric features. These three lines can form the basis for a spectral classification system for hot stars in the K band that may be used at infrared wavelengths to elucidate the nature of those luminous stars in otherwise obscured H II and giant H II regions.

  14. Effect of a progressive sound wave on the profiles of spectral lines. 2: Asymmetry of faint Fraunhofer lines. [absorption spectra

    NASA Technical Reports Server (NTRS)

    Kostyk, R. I.

    1974-01-01

    The absorption coefficient profile was calculated for lines of different chemical elements in a medium with progressive sound waves. Calculations show that (1) the degree and direction of asymmetry depend on the atomic ionization potential and the potential of lower level excitation of the individual line; (2) the degree of asymmetry of a line decreases from the center toward the limb of the solar disc; and (3) turbulent motions 'suppress' the asymmetry.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  16. Searching for narrow absorption and emission lines in XMM-Newton spectra of gamma-ray bursts

    NASA Astrophysics Data System (ADS)

    Campana, S.; Braito, V.; D'Avanzo, P.; Ghirlanda, G.; Melandri, A.; Pescalli, A.; Salafia, O. S.; Salvaterra, R.; Tagliaferri, G.; Vergani, S. D.

    2016-08-01

    We present the results of a spectroscopic search for narrow emission and absorption features in the X-ray spectra of long gamma-ray burst (GRB) afterglows. Using XMM-Newton data, both EPIC and RGS spectra, of six bright (fluence > 10-7 erg cm-2) and relatively nearby (z = 0.54-1.41) GRBs, we performed a blind search for emission or absorption lines that could be related to a high cloud density or metal-rich gas in the environ close to the GRBs. We detected five emission features in four of the six GRBs with an overall statistical significance, assessed through Monte Carlo simulations, of ≲ 3.0σ. Most of the lines are detected around the observed energy of the oxygen edge at ~ 0.5 keV, suggesting that they are not related to the GRB environment but are most likely of Galactic origin. No significant absorption features were detected. A spectral fitting with a free Galactic column density (NH) testing different models for the Galactic absorption confirms this origin because we found an indication of an excess of Galactic NH in these four GRBs with respect to the tabulated values.

  17. Quasar broad absorption line variability measurements using reconstructions of unabsorbed spectra

    NASA Astrophysics Data System (ADS)

    Wildy, C.; Goad, M. R.; Allen, J. T.

    2014-01-01

    We present a two-epoch Sloan Digital Sky Survey and Gemini/GMOS+William Herschel Telescope/ISIS variability study of 50 broad absorption line (BAL) quasars of redshift range 1.9 < z < 4.2, containing 38 Si IV and 59 C IV BALs and spanning rest-frame time intervals of ≈10 months to 3.7 years. We find that 35/50 quasars exhibit one or more variable BALs, with 58 per cent of Si IV and 46 per cent of C IV BALs showing variability across the entire sample. On average, Si IV BALs show larger fractional change in BAL pseudo-equivalent width than C IV BALs, as referenced to an unabsorbed continuum+emission line spectrum constructed using non-negative matrix factorization. No correlation is found between BAL variability and quasar luminosity, suggesting that ionizing continuum changes do not play a significant role in BAL variability (assuming the gas is in photoionization equilibrium with the ionizing continuum). A subset of 14 quasars have one variable BAL from each of Si IV and C IV with significant overlap in velocity space and for which variations are in the same sense (strengthening or weakening) and which appear to be correlated (98 per cent confidence). We find examples of both appearing and disappearing BALs in weaker/shallower lines with disappearance rates of 2.3 per cent for C IV and 5.3 per cent for Si IV, suggesting average lifetimes of 142 and 43 years, respectively. We identify five objects in which the BAL is coincident with the broad emission line, but appears to cover only the continuum source. Assuming a clumpy inhomogeneous absorber model and a typical size for the continuum source, we infer a maximum cloud radius of 1013 to 1014 cm, assuming Eddington limited accretion.

  18. Bounds on the fine structure constant variability from Fe ii absorption lines in QSO spectra

    NASA Astrophysics Data System (ADS)

    Molaro, P.; Reimers, D.; Agafonova, I. I.; Levshakov, S. A.

    2008-10-01

    The Single Ion Differential α Measurement (SIDAM)method for measuring Δα/α and its figures of merit are illustrated together withthe results produced by means of Fe ii absorption linesof QSO intervening systems. The method providesΔα/α = -0.12 ±1.79 ppm (parts-per-million) at zabs = 1.15towards HE 0515-4414 and Δα/α = 5.66±2.67 ppm at zabs = 1.84towards Q 1101-264, which are so far the most accurate measurementsfor single systems. SIDAM analysis for 3 systems from the Chand et al. [1]sample provides inconsistent results which we interpret as due tocalibration errors of the Chand et al. data at the level ≈10 ppm.In one system evidence for photo-ionization Dopplershift between Mg ii and Fe ii lines is found.This evidence has important bearings on the Many Multipletmethod where the signal for Δα/αvariabilityis carried mainly by systems involving Mg ii absorbers.Some correlations are also found in the Murphy et al. [10] sample which suggestlarger errors than previously reported.Thus, we consider unlikely that both the Chand et al.and Murphy et al. datasets could providean estimate of Δα/α with an accuracy at the level of 1 ppm.A new spectrograph like the ESPRESSO projectwill be crucial to make progress in the astronomical determination of Δα/α.

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

    SciTech Connect

    Yang Hao; Linsky, Jeffrey L.; France, Kevin E-mail: jlinsky@jilau1.colorado.edu

    2011-03-20

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

  20. Line Coupling in Atmospheric Spectra

    NASA Technical Reports Server (NTRS)

    Tipping, R. H.

    1996-01-01

    The theoretical modeling of atmospheric spectra is important for a number of different applications: for instance, in the determination of minor atmospheric constituents such as ozone, carbon dioxide, CFC's etc.; in monitoring the temperature profile for climate studies; and in measuring the incoming and outgoing radiation to input into global climate models. In order to accomplish the above mentioned goal, one needs to know the spectral parameters characterizing the individual spectral lines (frequency, width, strength, and shape) as well as the physical parameters of the atmosphere (temperature, abundances, and pressure). When all these parameters are known, it is usually assumed that the resultant spectra and concomitant absorption coefficient can then be calculated by a superposition of individual profiles of appropriate frequency, strength and shape. However, this is not true if the lines are 'coupled'. Line coupling is a subtle effect that takes place when lines of a particular molecule overlap in frequency. In this case when the initial states and the final states of two transitions are connected by collisions, there is a quantum interference resulting in perturbed shapes. In general, this results in the narrowing of Q-branches (those in which the rotational quantum number does not change), and vibration-rotational R- and P branches (those in which the rotational quantum number changes by +/- 1), and in the spectral region beyond band heads (regions where the spectral lines pile up due to centrifugal distortion). Because these features and spectral regions are often those of interest in the determination of the abundances and pressure-temperature profiles, one must take this effect into account in atmospheric models.

  1. Gravitationally Redshifted Absorption Lines in the Burst Spectra of the Neutron Star in the X-Ray Binary EXO 0748-676

    NASA Technical Reports Server (NTRS)

    Cottoam, J.; Paerels, F.; Mendez, M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    The most straightforward manner of determining masses and radii of neutron stars is by measuring the gravitational redshift of spectral lines produced in the neutron star photosphere; such a measurement would provide direct constraints on the mass-to-radius ratio of the neutron star, and therefore on the equation of state for neutron star matter. Using data taken with the Reflection Grating Spectrometer on board the XMM-Newton observatory we identify, for the first time, significant absorption lines in the spectra of 28 bursts of the low-mass X-ray binary EXO 0748-676. The most significant features are consistent with the Fe XXVI and XXV n=2-3 and O VIII n=1-2 transitions, with a redshift of z=0.35, identical within small uncertainties for the different transitions. This constitutes the first direct and unambiguous measurement of the gravitational redshift in a neutron star.

  2. Errarum: Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655-40

    NASA Astrophysics Data System (ADS)

    Ueda, Y.; Inoue, H.; Tanaka, Y.; Ebisawa, K.; Nagase, F.; Kotani, T.; Gehrels, N.

    1998-06-01

    In the paper ``Detection of Absorption-Line Features in the X-Ray Spectra of the Galactic Superluminal Source GRO J1655-40'' by Y. Ueda, H. Inoue, Y. Tanaka, K. Ebisawa, F. Nagase, T. Kotani, and N. Gehrels (ApJ, 492, 782 [1998]), there is an error in the curve of growth for the Kα absorption line (Fig. 4). The revised version of Figure 4 given here replaces Figure 4 in the paper. Several numbers derived from the figure should be corrected accordingly, but the conclusion of the paper is not affected. In the third paragraph of the discussion section (page 786), the iron column density of the plasma should be 1019-1020 cm-2, which corresponds to a hydrogen column density of 3 × 1023-3 × 1024 cm-2. The final limit on the hydrogen column density of the line-absorbing plasma should be changed to 3 × 1023 cm-2 < NH < 1024 cm-2.

  3. Determination of mass loss and mass transfer rates of Algol (Beta Persei) from the analysis of absorption lines in the UV spectra obtained by the IUE satellite

    NASA Astrophysics Data System (ADS)

    Wecht, Kristen

    The International Ultraviolet Explorer (IUE) archive of high-resolution ultraviolet spectra of the eclipsing semi-detached binary star, Algol ([beta] Persei, HD 19356), taken from September 1978 to September 1989, is analyzed in order to characterize the movement of gas within and from this system. Light curves are constructed, using a total of 1647 continuum level measurements. These results support the semidetached status of this interacting binary star. Radial velocities, residual intensities, full width half maxima (FWHM), line asymmetries, and equivalent widths of UV absorption lines for aluminum, magnesium, iron, and silicon in a range of ionization states are determined and analyzed. For selected epochs, we were able to isolate gas stream and photospheric contributions by an examination of the differences between spectral line shapes. We observed variations in line shape and strength, with orbital phase and epoch, indicating the presence of stable gas streams and circumstellar gas, and periods of increased mass-transfer activity associated with transient gas streams. The 1989 data indicates moderate activity. This epoch was examined most closely since it provides the greatest phase coverage. Spectral line profiles in 1978 and 1984 have the strongest gas-flow absorption components, indicating that these are the epochs of the greatest activity. The dense phase coverage in September 1989 allows us to measure the mass loss rate from Algol B into Algol A which is of order ~10 -14 [Special characters omitted.] /yr. Since the highest gas-flow velocities are in the 100 kilometer per second range, well below escape velocity, we conclude that systemic mass loss due to gas flow is small for the Algol system.

  4. On the statistics of quasar absorption lines

    NASA Astrophysics Data System (ADS)

    Zuiderwijk, E. J.

    1984-12-01

    The distribution of absorption lines in 13 quasar spectra is analyzed and shown to be fully consistent with the hypothesis of randomly, but not uniformly, distributed absorption features. The analysis by Libby et al. (1984), in which it is claimed that the number of wavelength coincidences among absorption lines in different quasar spectra (as measured in the rest frame of the quasars) is much larger than expected, implying absorbers in the quasars themselves, is totally invalid. Instead, the number of these coincidences is fully commensurate with the expected one on the assumption of randomness.

  5. Filling in of Fraunhofer and gas-absorption lines in sky spectra as caused by rotational Raman scattering.

    PubMed

    Sioris, C E; Evans, W F

    1999-04-20

    A line-by-line radiative-transfer model to quantify the Ring effect as caused by rotational Raman scattering has been developed for the 310-550-nm spectral interval. The solar zenith angle and the resolution are key input parameters, as is the sky spectrum (excluding inelastic atmospheric scattering), which was modeled with MODTRAN 3.5. The filling in is modeled for ground-based viewing geometry and includes surface reflection and single inelastic scattering. It is shown that O2 contributes half of the filling in of N2. A strong inverse relationship with wavelength is noted in the filling in. A comparison with observations shows moderate agreement. The largest filling in occurs in the Ca II K and H lines. PMID:18319844

  6. Radio HI and optical absorption-line spectra of an intermediate-velocity cloud in the general direction of the M15 globular cluster

    NASA Astrophysics Data System (ADS)

    Kennedy, D. C.; Bates, B.; Keenan, F. P.; Kemp, S. N.; Ryans, R. S. I.; Davies, R. D.; Sembach, K. R.

    1998-07-01

    Using HI spectra obtained with the Lovell telescope (FWHM ~ 12 arcmin) we present maps showing the HI distribution and velocity structure of an intermediate-velocity cloud (IVC; v_LSR~70 km s^-1) which is observed in the general direction of the globular cluster M15. The gas is shown to be clumpy in nature and we examine its position and velocity structure. The IVC is detected in absorption in the CaII K line towards five cluster stars in intermediate resolution spectra obtained with ISIS/WHT and in high resolution UES/WHT NaI D line spectra of two cluster stars (II-75; IV-38). The clumpy nature of the gas is indicated by the NaI and KI spectra obtained in the II-75 and IV-38 sightlines, which have angular separation ~ 3.5 arcmin. The IVC is detected in KI in the higher column density II-75 sightline; this appears to be the first detection of IVC or HVC gas in KI. The IVC gas towards M15 has a similar velocity to that observed towards HD 203664, some 3.1 deg away from the cluster. Similarities in the IVC gas velocity suggest a gas structure that extends across both sightlines, although gas column densities are considerably higher towards M15. For a common feature, this would place the M15 IVC at a height above the Galactic plane (z-distance) of <~1.5 kpc based on the Little et al. estimate of the HD 203664 distance. From the fine-scale structure and column density observations, estimates are made of the space density of the small-scale concentrations. However, these remain uncertain and the present observations emphasize the need for higher spatial and spectral resolution studies to provide firmer estimates of cloud properties. We report also on a radio HI and CaII line survey towards a sample of 24 stars over a wider field. This was carried out in an attempt to detect any wider distribution of the IVC gas and to place better limits on its distance. Although these observations are of sufficient spectral quality, no new optical detections are reported.

  7. Atlas of Infrared Absorption Lines

    NASA Technical Reports Server (NTRS)

    Park, J. H.

    1977-01-01

    This atlas of infrared absorption line contains absorption line parameters (line strength vs. wavenumber) from 500 to 7000 cm(exp-1) for 15 gases: H2O, CO2, O3, N2O, CO, CH4, O2, SO2, NO, NO2, NH3, HCl, HF, HNO3 and CH3Cl.

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

    SciTech Connect

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

    2014-08-15

    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.

  9. The Hubble Space Telescope quasar absorption line key project. v. redshift evolution of lyman limit absorption in the spectra of a large sample of quasars

    NASA Astrophysics Data System (ADS)

    Stengler-Larrea, Erik A.; Boksenberg, Alec; Steidel, Charles C.; Sargent, W. L. W.; Bahcall, John N.; Bergeron, Jacqueline; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.; Schneider, Donald P.; Turnshek, David A.; Weymann, Ray J.

    1995-05-01

    Using a sample of 119 QSOs, containing objects we have selected having previously available high quality ground-based and IUE spectral observations, together with Hubble Space Telescope (HST) observations of 26 QSOs from Bahcall et al. (1993, 1995) and Impey et al. (1995) and new optical observations of 41 objects by Steidel & Sargent (1995), we study the redshift evolution of Lyman limit absorption systems (LLSs; tau greater than 1.0) over the reshift range 0.32 less than or equal to zLLS less than or equal to 4.11. The HST observations significantly improve the determination of the low redshift (0.4 less than or equal to zLLS less than or equal to 1.4) distribution. We find the effect which may have been responsible for the apparent strong evolution at aLLS greater than or equal to 2.5 found by Lanzetta (1991), which led him to consider a broken, not single power law as a better description of the redshift distribution of LLSs. After removing objects which may bias our sample, leaving a total of 169 QSOs, we find the distribution is well described by a single power law, and obtain for the number density as a function of redshift the form N(z) = N0(1 + z)gamma with gamma = 1.50 =/- 0.39 and N0 = 0.25-0.10+0.17, consistent with a constant comoving density of absorbers in a Firedmann universe with q0 = 0 but indicating evolution if q0 = 1/2.

  10. The Hubble Space Telescope quasar absorption line key project. v. redshift evolution of lyman limit absorption in the spectra of a large sample of quasars

    NASA Technical Reports Server (NTRS)

    Stengler-Larrea, Erik A.; Boksenberg, Alec; Steidel, Charles, C.; Sargent, W. L. W.; Bacall, John N.; Bergeron, Jacqueline; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Savage, Blair D.

    1995-01-01

    Using a sample of 119 QSOs, containing objects we have selected having previously available high quality ground-based and IUE spectral observations, together with Hubble Space Telescope (HST) observations of 26 QSOs from Bahcall et al. (1993, 1995) and Impey et al. (1995) and new optical observations of 41 objects by Steidel & Sargent (1995), we study the redshift evolution of Lyman limit absorption systems (LLSs; tau greater than 1.0) over the reshift range 0.32 less than or equal to z(sub LLS) less than or equal to 4.11. The HST observations significantly improve the determination of the low redshift (0.4 less than or equal to z(sub LLS) less than or equal to 1.4) distribution. We find the effect which may have been responsible for the apparent strong evolution at a(sub LLS) greater than or equal to 2.5 found by Lanzetta (1991), which led him to consider a broken, not single power law as a better description of the redshift distribution of LLSs. After removing objects which may bias our sample, leaving a total of 169 QSOs, we find the distribution is well described by a single power law, and obtain for the number density as a function of redshift the form N(z) = N(sub 0)(1 + z)(exp gamma) with gamma = 1.50 =/- 0.39 and N(sub 0) = 0.25(sup -0.10)(sub +0.17), consistent with a constant comoving density of absorbers in a Firedmann universe with q(sub 0) = 0 but indicating evolution if q(sub 0) = 1/2.

  11. Demonstrating Absorption Spectra Using Commercially Available Incandescent Light Bulbs

    NASA Astrophysics Data System (ADS)

    Birriel, Jennifer J.

    In introductory astronomy courses, I typically introduce the three types of spectra: continuous, absorption line, and emission line. It is standard practice to use an ordinary incandescent light bulb to demonstrate the production of a continuous spectrum, and gas discharge tubes to demonstrate the production of an emission line spectrum. The concept of an absorption spectrum is more difficult for students to grasp. A variety of commercially available light bulbs can be used to demonstrate absorption spectra. Here I discuss the use of specialty incandescent light bulbs to demonstrate the phenomenon of absorption of the continuous spectrum produced by a hot tungsten filament. The bulbs examined include the GE Reveal bulb, yellow anti-insect lights, colored party bulbs, and an incandescent "black light" bulb. The bulbs can be used in a lecture or laboratory setting.

  12. Creating semiconductor metafilms with designer absorption spectra

    PubMed Central

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  13. Creating semiconductor metafilms with designer absorption spectra

    NASA Astrophysics Data System (ADS)

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L.

    2015-07-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells.

  14. Creating semiconductor metafilms with designer absorption spectra.

    PubMed

    Kim, Soo Jin; Fan, Pengyu; Kang, Ju-Hyung; Brongersma, Mark L

    2015-01-01

    The optical properties of semiconductors are typically considered intrinsic and fixed. Here we leverage the rapid developments in the field of optical metamaterials to create ultrathin semiconductor metafilms with designer absorption spectra. We show how such metafilms can be constructed by placing one or more types of high-index semiconductor antennas into a dense array with subwavelength spacings. It is argued that the large absorption cross-section of semiconductor antennas and their weak near-field coupling open a unique opportunity to create strongly absorbing metafilms whose spectral absorption properties directly reflect those of the individual antennas. Using experiments and simulations, we demonstrate that near-unity absorption at one or more target wavelengths of interest can be achieved in a sub-50-nm-thick metafilm using judiciously sized and spaced Ge nanobeams. The ability to create semiconductor metafilms with custom absorption spectra opens up new design strategies for planar optoelectronic devices and solar cells. PMID:26184335

  15. Nebular UV Absorption Lines in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet

    We propose to continue our Cycle 1 program of studying the Lyman and Werner bands of H_2, seen in absorption against the UV continua of planetary nebula central stars, which arise within neutral-molecular envelopes surrounding the ionized gas. These are the pump lines for a fluorescent cascade of near-infrared emission lines which are observed in many planetary nebulae. By observing the UV lines we can probe the chemical and thermal structure of the envelopes, as well as measure molecular column densities and clarify the excitation processes for the infrared lines. In Cycle 1 we were granted time for three targets, one of which was successfully observed shortly before submission of this proposal. Although the data were not yet available for examination, similar target observed by the project team revealed a rich set of H_2 circumstellar absorption features, demonstrating the feasibility of our program. FUSE spectra also include absorption features from atomic species such as O I and C II, which give rise to important far-infrared fine-structure cooling lines that likewise have been observed from planetary nebulae. In Cycle 2, we add as a secondary goal a search for nebular components of the O VI 032, 1038 AA absorption lines, which trace the presence of hot shocked gas, in nebulae with anomalously strong optical recombination lines of ions of oxygen and nitrogen. This will test a plausible hypothesis for the origin of this anomaly.

  16. Calculated Hanle transmission and absorption spectra of the {sup 87}Rb D{sub 1} line with residual magnetic field for arbitrarily polarized light

    SciTech Connect

    Noh, Heung-Ryoul; Moon, Han Seb

    2010-09-15

    This paper reports a theoretical study on the transmission spectra of an arbitrarily polarized laser beam through a rubidium cell with or without a buffer gas in Hanle-type coherent population trapping (CPT). This study examined how laser polarization, transverse magnetic field, and collisions with buffer gas affects the spectrum. The transmission spectrum due to CPT and the absorption spectrum due to the level crossing absorption (LCA) were calculated according to the laser polarization. The results show that the LCA is strongly dependent on the transverse magnetic field and interaction time of the atoms with a laser light via collisions with the buffer gas. In addition, the spectral shape of the calculated Hanle spectrum is closely related to the direction between the (stray) transverse magnetic field and polarization of the laser.

  17. Non-Voigt Lyalpha Absorption Line Profiles.

    PubMed

    Outram; Carswell; Theuns

    2000-02-01

    Recent numerical simulations have lead to a paradigm shift in our understanding of the intergalactic medium and the loss of a physical justification for Voigt profile fitting of the Lyalpha forest. Many individual lines seen in simulated spectra have significant departures from the Voigt profile, yet could be well fitted by a blend of two or more such lines. We discuss the expected effect on the line profiles due to ongoing gravitational structure formation and Hubble expansion. We develop a method to detect departures from Voigt profiles of the absorption lines in a statistical way and apply this method to simulated Lyalpha forest spectra, confirming that the profiles seen do statistically differ from Voigt profiles. PMID:10622758

  18. Absorption spectra of cold dilute solid solutions

    SciTech Connect

    Holland, R.F.; Maier, W.B. II; Freund, S.; Beattie, W.H.

    1983-06-01

    Infrared absorption spectra have been obtained for some compounds trapped in crystalline solids by freezing liquid Xe, Kr, Ar, or CH/sub 4/ solutions. The optical quality of the solid solutions is good, and they have been cooled to approx.80 K in 1.35 cm sample thicknesses to study the absorption in fundamental vibrational bands of the solutes. In the cases discussed, the bands are narrow, with observed full widths at half-maximum absorbance 0.05--0.30 cm/sup -1/ greater than the instrumental resolution (0.18--0.29 cm/sup -1/). The spectra appear to be free of ''multiple site'' and solute aggregate absorptions. Spectra displaying isotropic splitting in bands of natural BCl/sub 3/, SeF/sub 6/, OsO/sub 4/, TiCl/sub 4/, and MoF/sub 6/ are presented, and band frequencies are compared with some results obtained in evaporative matrices, in the gas phase, and in liquid solutions. For this comparison we have obtained some spectra of SeF/sub 6/ and BCl/sub 3/ gas.

  19. Mars Ozone Absorption Line Shapes from Infrared Heterodyne Spectra Applied to GCM-Predicted Ozone Profiles and to MEX/SPICAM Column Retrievals

    NASA Astrophysics Data System (ADS)

    Fast, Kelly Elizabeth; Kostiuk, T.; Hewagama, T.; Livengood, T. A.; Delgado, J. D.; Annen, J.; Lefèvre, F.

    2008-09-01

    We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry Mars’ atmosphere, serving as an observable with which to test predictions of photochemistry-coupled GCMs. Infrared heterodyne spectroscopy at 9.5 μm with spectral resolving power >1,000,000 is the only technique that can directly measure fully-resolved line shapes of Martian ozone features from the surface of the Earth. Measurements were made with Goddard Space Flight Center's Heterodyne Instrument for Planetary Wind And Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai'i on February 21-24 2008 UT at Ls=35°, on or near the MEX orbital path. The HIPWAC observations were used to test GCM predictions. For example, a GCM-generated ozone profile for 60°N 112°W was scaled so that a radiative transfer calculation of its absorption line shape matched an observed HIPWAC absorption feature at the same areographic position, local time, and season. The RMS deviation of the model from the data was slightly smaller for the GCM-generated profile than for a line shape produced by a constant-with-height profile, even though the total column abundances were the same, showing potential for testing and constraining GCM ozone profiles. The resulting ozone column abundance from matching the model to the HIPWAC line shape was 60% higher than that observed by SPICAM at the same areographic position one day earlier and 2.5 hours earlier in local time. This could be due to day-to-day, diurnal, or north polar region variability, or to measurement sensitivity to the ozone column and its distribution, and these possibilities will be explored. This work was supported by NASA's Planetary Astronomy Program.

  20. Mars Ozone Absorption Line Shapes from Infrared Heterodyne Spectra Applied to GCM-Predicted Ozone Profiles and to MEX/SPICAM Column Retrievals

    NASA Technical Reports Server (NTRS)

    Fast, Kelly E.; Kostiuk, T.; Annen, J.; Hewagama, T.; Delgado, J.; Livengood, T. A.; Lefevre, F.

    2008-01-01

    We present the application of infrared heterodyne line shapes of ozone on Mars to those produced by radiative transfer modeling of ozone profiles predicted by general circulation models (GCM), and to contemporaneous column abundances measured by Mars Express SPICAM. Ozone is an important tracer of photochemistry Mars' atmosphere, serving as an observable with which to test predictions of photochemistry-coupled GCMs. Infrared heterodyne spectroscopy at 9.5 microns with spectral resolving power >1,000,000 is the only technique that can directly measure fully-resolved line shapes of Martian ozone features from the surface of the Earth. Measurements were made with Goddard Space Flight Center's Heterodyne instrument for Planetary Wind And Composition (HIPWAC) at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii on February 21-24 2008 UT at Ls=35deg on or near the MEX orbital path. The HIPWAC observations were used to test GCM predictions. For example, a GCM-generated ozone profile for 60degN 112degW was scaled so that a radiative transfer calculation of its absorption line shape matched an observed HIPWAC absorption feature at the same areographic position, local time, and season. The RMS deviation of the model from the data was slightly smaller for the GCM-generated profile than for a line shape produced by a constant-with-height profile, even though the total column abundances were the same, showing potential for testing and constraining GCM ozone-profiles. The resulting ozone column abundance from matching the model to the HIPWAC line shape was 60% higher than that observed by SPICAM at the same areographic position one day earlier and 2.5 hours earlier in local time. This could be due to day-to-day, diurnal, or north polar region variability, or to measurement sensitivity to the ozone column and its distribution, and these possibilities will be explored. This work was supported by NASA's Planetary Astronomy Program.

  1. Absorption Features in Soil Spectra Assessment.

    PubMed

    Vašát, Radim; Kodešová, Radka; Borůvka, Luboš; Jakšík, Ondřej; Klement, Aleš; Drábek, Ondřej

    2015-12-01

    From a wide range of techniques appropriate to relate spectra measurements with soil properties, partial least squares (PLS) regression and support vector machines (SVM) are most commonly used. This is due to their predictive power and the availability of software tools. Both represent exclusively statistically based approaches and, as such, benefit from multiple responses of soil material in the spectrum. However, physical-based approaches that focus only on a single spectral feature, such as simple linear regression using selected continuum-removed spectra values as a predictor variable, often provide accurate estimates. Furthermore, if this approach extends to multiple cases by taking into account three basic absorption feature parameters (area, width, and depth) of all occurring features as predictors and subjecting them to best subset selection, one can achieve even higher prediction accuracy compared with PLS regression. Here, we attempt to further extend this approach by adding two additional absorption feature parameters (left and right side area), as they can be important diagnostic markers, too. As a result, we achieved higher prediction accuracy compared with PLS regression and SVM for exchangeable soil pH, slightly higher or comparable for dithionite-citrate and ammonium oxalate extractable Fe and Mn forms, but slightly worse for oxidizable carbon content. Therefore, we suggest incorporating the multiple linear regression approach based on absorption feature parameters into existing working practices. PMID:26555184

  2. Millimeter wave absorption spectra of biological samples

    SciTech Connect

    Gandhi, O.P.; Hagmann, M.J.; Hill, D.W.; Partlow, L.M.; Bush, L.

    1980-01-01

    A solid-state computer-controlled system has been used to make swept-frequency measurements of absorption of biological specimens from 26.5 to 90.0 GHz. A wide range of samples was used, including solutions of DNA and RNA, and suspensions of BHK-21/C13 cells, Candida albicans, C krusei, and Escherichia coli. Sharp spectra reported by other workers were not observed. The strong absorbance of water (10--30 dB/mm) caused the absorbance of all aqueous preparations that we examined to have a water-like dependence on frequency. Reduction of incident power (to below 1.0 microW), elimination of modulation, and control of temperature to assure cell viability were not found to significantly alter the water-dominated absorbance. Frozen samples of BHK-21/C13 cells tested at dry ice and liquid nitrogen temperatures were found to have average insertion loss reduced to 0.2 dB/cm but still showed no reproducible peaks that could be attributed to absorption spectra. It is concluded that the special resonances reported by others are likely to be in error.

  3. Preliminary optical design of a varied line-space spectrograph for the multi-channel detection of near-edge X-ray absorption fine structure (NEXAFS) spectra in the 280-550 eV energy range

    SciTech Connect

    Wheeler, B.S.; McKinney, W.R.; Hussain, Z.; Padmore, H.

    1996-07-01

    The optical design of a varied line-space spectrograph for the multi-channel recording of NEXAFS spectra in a single {open_quotes}snapshot{close_quotes} is proposed. The spectrograph is to be used with a bending magnet source on beamline 7.3.2 at the Advanced Light Source (ALS). Approximately 20 volts of spectra are simultaneously imaged across a small square of material sample at each respective K absorption edge of carbon, nitrogen, and oxygen. Photoelectrons emitted from the material sample will be collected by an electron imaging microscope, the view field of which determines the sampling size. The sample also forms the exit slit of the optical system. This dispersive method of NEXAFS data acquisition is three to four orders of magnitude faster than the conventional method of taking data point-to-point using scanning of the grating. The proposed design is presented along with the design method and supporting SHADOW raytrace analysis.

  4. Optical-absorption spectra, crystal-field energy levels, and transition line strengths of holmium in trigonal Na3[Ho(C4H4O5)3].2NaClO4.6H2O

    NASA Astrophysics Data System (ADS)

    Moran, D. M.; de Piante, Anne; Richardson, F. S.

    1990-08-01

    Locations and assignments of 105 crystal-field levels are reported for Ho3+ in the trigonal Na3[Ho(oxydiacetate)3].2NaClO4.6H2O system. These levels were located and assigned from transitions observed in axial and σ- and π-polarized orthoaxial absorption spectra obtained on single-crystal samples at temperatures between 5 and 295 K. The absorption measurements spanned the 8000-37 000-cm-1 spectral region, and the assigned energy levels derive from 23 different [SL]J multiplet manifolds of the 4f10 electronic configuration of Ho3+, with principal SL parentages derived from nine different Russell-Saunders terms (5I, 5F, 5S, 3K, 5G,3H, 3L, 3M, and 5D). The empirical energy-level data are analyzed in terms of a parametrized model Hamiltonian for the 4f10 electronic configuration, assumed to be perturbed by a crystal field of trigonal dihedral (D3) symmetry. Parametric fits of calculated-to-empirical energy-level data yield a rms deviation of ~9 cm-1 (between calculated and observed energies). The Hamiltonian parameter values obtained from these energy-level analyses are compared with results obtained from similar analyses of Ho3+ in other crystals and of other lanthanide (M3+) ions in the Na3[M(oxydiacetate)3].2NaClO4.6H2O system. In addition to energy-level locations and assignments, quantitatively determined line strengths are reported for 42 transitions observed in the axial absorption spectra at 10 K, and for 19 transitions observed in the π-polarized orthoaxial absorption spectra at 10 K. Fifty of these transitions originate from the ground crystal-field level of the 5I8 (ground) multiplet, and eleven originate from the second crystal-field level (located 14 cm-1 above ground) of 5I8.

  5. A study of ultraviolet absorption lines through the complete Galactic halo by the analysis of HST faint object spectrograph spectra of active Galactic nuclei, 1

    NASA Technical Reports Server (NTRS)

    Burks, Geoffrey S.; Bartko, Frank; Shull, J. Michael; Stocke, John T.; Sachs, Elise R.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Harms, Richard J.; Massa, Derck

    1994-01-01

    The ultraviolet (1150 - 2850 A) spectra of a number of active galactic nuclei (AGNs) observed with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) have been used to study the properties of the Galactic halo. The objects that served as probes are 3C 273, PKS 0454-220, Pg 1211+143, CSO 251, Ton 951, and PG 1351+640. The equivalent widths of certain interstellar ions have been measured, with special attention paid to the C IV/C II and Si IV/Si II ratios. These ratios have been intercompared, and the highest values are found in the direction of 3C 273, where C IV/C II = 1.2 and Si IV/Si II greater than 1. These high ratios may be due to a nearby supernova remnant, rather than to ionized gas higher up in the Galactic halo. Our data give some support to the notion that QSO metal-line systems may arise from intervening galaxies which contain high supernova rates, galactic fountains, and turbulent mixing layers.

  6. Optical absorption spectra of dications of carotenoids

    SciTech Connect

    Jeevarajan, J.A.; Wei, C.C.; Jeevarajan, A.S.; Kispert, L.D.

    1996-04-04

    Quantitative optical absorption spectra of the cation radicals and the dications of canthaxanthin (I), {beta}carotene (II), 7`-cyano-7`-ethoxycarbonyl-7`-apo-{beta}-carotene (III), and 7`,7`-dimethyl-7`-apo-{beta}-carotene (IV) in dichloromethane solution are reported. Exclusive formation of dications occurs when the carotenoids are oxidized with ferric chloride. Addition of neutral carotenoid to the dications results in equilibrium formation of cation radicals. Oxidation with iodine in dichloromethane affords only cation radicals; electrochemical oxidation under suitable conditions yields both dications and cation radicals. Values of the optical parameters depend on the nature of the oxidative medium. The oscillator strengths calculated for gas phase cation radicals and dications of I-IV using the INDO/S method show the same trend as the experimental values. 31 refs., 4 figs., 2 tabs.

  7. Absorption spectra of irradiated XRCT radiochromic film

    NASA Astrophysics Data System (ADS)

    Butson, Martin J.; Cheung, Tsang; Yu, Peter K. N.

    2006-06-01

    Gafchromic XRCT radiochromic film is a self-developing high sensitivity radiochromic film product which can be used for assessment of delivered radiation doses which could match applications such as computed tomography (CT) dosimetry. The film automatically changes colour upon irradiation changing from a yellow to green/brown colour. The absorption spectra of Gafchromic XRCT radiochromic film as measured with reflectance spectrophotometry have been investigated to analyse the dosimetry characteristics of the film. Results show two main absorption peaks produced from irradiation located at 636 nm and 585 nm. This is similar to EBT Gafchromic film. A high level of sensitivity is found for this film with a 1 cGy applied dose producing an approximate net optical density change of 0.3 at 636 nm. This high sensitivity combined with its relatively energy independent nature around the 100 kVp to 150 kVp x-ray energy range provides a unique enhancement in dosimetric measurement capabilities over currently available dosimetry films for CT applications.

  8. Determination of phytoplankton composition using absorption spectra.

    PubMed

    Martínez-Guijarro, R; Romero, I; Pachés, M; Del Río, J G; Martí, C M; Gil, G; Ferrer-Riquelme, A; Ferrer, J

    2009-05-15

    Characterisation of phytoplankton communities in aquatic ecosystems is a costly task in terms of time, material and human resources. The general objective of this paper is not to replace microscopic counts but to complement them, by fine-tuning a technique using absorption spectra measurements that reduces the above-mentioned costs. Therefore, the objective proposed in this paper is to assess the possibility of achieving a qualitative determination of phytoplankton communities by classes, and also a quantitative estimation of the number of phytoplankton cells within each of these classes, using spectrophotometric determination. Samples were taken in three areas of the Spanish Mediterranean coast. These areas correspond to estuary systems that are influenced by both continental waters and Mediterranean Sea waters. 139 Samples were taken in 7-8 stations per area, at different depths in each station. In each sample, the absorption spectrum and the phytoplankton classes (Bacyllariophyceae (diatoms), Cryptophyceae, Clorophyceae, Chrysophyceae, Prasynophyceae, Prymnesophyceae, Euglenophyceae, Cyanophyceae, Dynophyceae and the Synechococcus sp.) were determined. Data were analysed by means of the Partial Least Squares (PLS) multivariate statistical technique. The absorbances obtained between 400 and 750 nm were used as the independent variable and the cell/l of each phytoplankton class was used as the dependent variable, thereby obtaining models which relate the absorbance of the sample extract to the phytoplankton present in it. Good results were obtained for diatoms (Bacillarophyceae), Chlorophyceae and Cryptophyceae. PMID:19269434

  9. Absorption-line measurements of AGN outflows

    NASA Astrophysics Data System (ADS)

    Fields, Dale L.

    Investigations into the elemental abundances in two nearby active galaxies, the narrow-line Seyfert 1 Markarian 1044 and the Seyfert 1 Markarian 279, are reported. Spectra from three space-based observatories HST, FUSE, and CHANDRA, are used to measure absorption lines in material outflowing from the nucleus. I make multi-wavelength comparisons to better convert the ionic column densities into elemental column densities which can then be used to determine abundances (metallicities). Narrow-line Seyfert 1 galaxies are known to have extreme values of a number of properties compared to active galactic nuclei (AGNs) as a class. In particular, emission-line studies have suggested that NLS1s are unusually metal-rich compared to broad-line AGNs of comparable luminosity. To test these suggestions I perform absorption-line studies on the NLS1 Markarian 1044, a nearby and bright AGN. I use lines of H I, C IV, N V, and O VI to properly make the photoionization correction through the software Cloudy and determine abundances of Carbon, Nitrogen and Oxygen. I find two results. The first is that Markarian 1044 has a bulk metallicity greater than five times solar. The second is that the N/C ratio in Markarian 1044 is consistent with a solar mixture. This is in direct contradiction of extrapolations from local H II regions which state N/ C should scale with bulk metallicity. This implies a different enrichment history in Markarian 1044 than in the Galactic disk. I also report discovery of three new low-redshift Lya forest lines with log N HI >= 12:77 in the spectrum of Markarian 1044. This number is consistent with the 2.6 expected Lya forest lines in the path length to Markarian 1044. I also investigate the CHANDRA X-ray spectrum of Markarian 279, a broad-line Seyfert 1. I use a new code, PHASE, to self-consistently model the entire absorption spectrum simultaneously. Using solely the X-ray spectrum I am able to determine the physical parameters of this absorber to a degree only

  10. X-Ray Absorption Spectra of Uranium by Synchrotron Radiation

    NASA Astrophysics Data System (ADS)

    Adachi, Hirohiko; Fujima, Kazumi; Taniguchi, Kazuo; Miyake, Chie; Imoto, Shosuke

    1981-08-01

    The X-ray absorption spectra of U, UO2 and UCl4 near the U OIV and OV thresholds have been measured by use of synchrotron radiation. The absorption peaks at about 100 eV and 110 eV are observed for all of these materials. However, the detailed structure of the spectra depend on the chemical state.

  11. Absorption line CW EPR using an amplitude modulated longitudinal field.

    PubMed

    Fedin, Matvey; Gromov, Igor; Schweiger, Arthur

    2004-11-01

    In standard continuous wave electron paramagnetic resonance (CW-EPR) experiments, the first derivative of absorption lines is detected. This type of a line shape is caused by the magnetic field modulation and is usually an undesired feature, since the sensitivity of CW-EPR drastically decreases with increasing linewidth. A new approach is introduced, which allows for the measurement of absorption line EPR spectra in systems with broad inhomogeneous lines. The method makes use of multiple-photon transitions that are induced in spin systems when a transverse microwave and a longitudinal radio frequency field are simultaneously applied. The absorption lines are obtained by using amplitude modulation of the radio frequency field and slight saturation of the spectral lines. The basics of the new approach are discussed and experimental examples are given. PMID:15504685

  12. Do Atoms Really "Emit" Absorption Lines?

    ERIC Educational Resources Information Center

    Brecher, Kenneth

    1991-01-01

    Presents three absorption line sources that enhance student understanding of the phenomena associated with the interaction of light with matter and help dispel the misconception that atoms "emit" absorption lines. Sources include neodymium, food coloring and other common household liquids, and fluorescent materials. (MDH)

  13. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    NASA Astrophysics Data System (ADS)

    Scaringi, Simone; Cottis, Christopher E.; Knigge, Christian; Goad, Michael R.

    2008-12-01

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

  14. Broad Absorption Line Quasar catalogues with Supervised Neural Networks

    SciTech Connect

    Scaringi, Simone; Knigge, Christian; Cottis, Christopher E.; Goad, Michael R.

    2008-12-05

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

  15. Interstellar absorption lines in the galaxy NGC 1705

    SciTech Connect

    York, D.G.; Caulet, A.; Rybski, P.M.; Gallagher, J.S.; Blades, J.C. Lowell Observatory, Flagstaff, AZ Space Telescope Science Institute, Baltimore, MD )

    1990-03-01

    The possibility is considered, and shown to be plausible, that the strong C IV and Si IV absorption lines in low-resolution ultraviolet spectra of gas-rich dwarf galaxies are primarily interstellar, not stellar as has been supposed. The argument is based on analogies with H II regions in the Local Group, on low-resolution equivalent width measurements of gas-rich dwarf galaxies from the literature and on high-resolution UV spectra of NGC 1705. 48 refs.

  16. Interstellar absorption lines in the galaxy NGC 1705

    NASA Technical Reports Server (NTRS)

    York, Donald G.; Caulet, Adeline; Rybski, Paul M.; Gallagher, John S.; Blades, J. Chris

    1990-01-01

    The possibility is considered, and shown to be plausible, that the strong C IV and Si IV absorption lines in low-resolution ultraviolet spectra of gas-rich dwarf galaxies are primarily interstellar, not stellar as has been supposed. The argument is based on analogies with H II regions in the Local Group, on low-resolution equivalent width measurements of gas-rich dwarf galaxies from the literature and on high-resolution UV spectra of NGC 1705.

  17. Active Galactic Nuclei Probed by QSO Absorption Lines

    NASA Astrophysics Data System (ADS)

    Misawa, Toru

    2007-07-01

    Quasars are the extremely bright nuclei found in about 10% of galaxies. A variety of absorption features (known collectively as quasar absorption lines) are detected in the rest-frame UV spectra of these objects. While absorption lines that have very broad widths originate in gas that is probably physocally related to the quasars, narrow absorption lines (NALs) were thought to arise in galaxies and/or in the intter-alacttic medium between the quasars and us. Using high-resolution spectra of quasars, it is found that a substantial fraction of NALs arise in gas in the immediate vicinity of the quasars. A dramatically variable, moderately-broad absorption line in the spectrum of the quasar HS 1603+3820l is also found. The variability of this line is monitored in a campaign with Subaru telescope. These observational results are compared to models for outflows from the quasars, specifically, models for accretion disk winds and evaporating obscuring tori. It is quite important to determine the mechanism of outflow because of its cosmological implications. The outflow could expel angular momentum from the accretion disk and enable quasars to accrete and shine. In addition, the outflow may also regulate star formation in the early stages of the assembly of the host galaxy and enrich the interstellar and intergalactic medium with metals.

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

    NASA Astrophysics Data System (ADS)

    Grante, Ilze; Actins, Andris; Orola, Liana

    2014-08-01

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

  19. Absorption Spectra of Magnesium Sulphite Hexahydrate Doped with Nickel

    NASA Astrophysics Data System (ADS)

    Petkova, Petya N.; Bunzarov, Zhelyu I.; Iliev, Ilia A.; Dimov, Todor N.

    2007-04-01

    In the work are presented absorption spectra of MgSO3.6H2O monocrystals doped with Ni. The spectra are measured in a wide spectral range (200 - 1200nm) at room temperature with polarized light. The impurity of Ni changes essentially the absorption of MgSO3.6H2O because it causes the appearance of additional spectral structures.

  20. Variable interstellar lines in spectra of HD 73882

    NASA Astrophysics Data System (ADS)

    Galazutdinov, G.; Krełowski, J.; Beletsky, Y.; Valyavin, G.

    2013-11-01

    We report a detection of variability in interstellar absorption lines of Cai at 4227 Å and Fei at 3860 Å in very high signal-to-noise ratio (>1000) UVES and MIKE spectra of HD 73882 (NX Vel) carried out with the aid of 8-m telescope UT2 at Paranal and 6.5-m Magellan Telescope Clay at Las Campanas Observatory, Chile. The spectra, acquired in 2006 January and 2012 January, respectively, clearly show that the intensity and profile shapes of the Cai and Fei lines had dramatically changed within the 6 year period. Other interstellar features, observed along the same line of sight, do not demonstrate strong changes. It is likely that a high velocity CaFe cloud obscured the star between the two observations.

  1. Extreme Variability in a Broad Absorption Line Quasar

    NASA Astrophysics Data System (ADS)

    Stern, Daniel; Graham, Matthew; Arav, Nahum; Djorgovski, Stanislav G.; Chamberlain, Carter; Barth, Aaron J.; Donalek, Ciro; Drake, Andrew J.; Glikman, Eilat; Jun, Hyunsung David; Mahabal, Ashish A.; Steidel, Charles C.

    2016-01-01

    We report on extreme spectral variability seen in a broad absorption line quasar over the past decade, initially identified from the Catalina Real-time Transient Survey (CRTS). Photometrically, the source had a visual magnitude of V = 17.3 between 2002 and 2008. Then, over the following 5 years, the source slowly brightened by approximately one magnitude, to V = 16.2. A combination of archival and newly acquired spectra reveal the source to be an iron low-ionization broad absorption line (Fe-LoBAL) quasar with extreme changes in its absorption spectrum. Some absorption features completely disappear over the 9 years of optical spectra, while other features remain essentially unchanged. Absorption systems separated by several 1000 km/s in velocity show coordinated changes in the depths of their troughs, correlated with the flux changes. Therefore, we interpret the variability in the absorption troughs to be due to changes in photoionization, rather than due to motion of material into our line of sight. This source highlights the sort of rare transition objects that astronomy will now be finding through dedicated time domain surveys.

  2. Helium shells and faint emission lines from slitless flash spectra

    NASA Astrophysics Data System (ADS)

    Bazin, Cyril; Koutchmy, Serge

    2013-05-01

    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 α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. 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.

  3. Helium shells and faint emission lines from slitless flash spectra

    PubMed Central

    Bazin, Cyril; Koutchmy, Serge

    2013-01-01

    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 α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. 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

  4. Helium shells and faint emission lines from slitless flash spectra.

    PubMed

    Bazin, Cyril; Koutchmy, Serge

    2013-05-01

    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 α 4686 Å line of the ionized helium HeII and in the neutral helium HeI line at 4713 Å. 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

  5. An investigation of a mathematical model for atmospheric absorption spectra

    NASA Technical Reports Server (NTRS)

    Niple, E. R.

    1979-01-01

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

  6. Optical Absorption Spectra of Sodium Borate Cobalt Doped Glasses

    SciTech Connect

    Elokr, M. M.; Hassan, M. A.; Yaseen, A. M.; Elokr, R.

    2007-02-14

    Glassy system: xNa2O-(100-x-y)B2O3-yCo3O4 has been prepared by conventional melt quenching technique. Optical absorption spectra have been obtained in the range 300 - 2500 nm at room temperature. An absorption edge was observed in the near UV range, the analysis of which reveals that indirect transition is the dominant absorption mechanism. All prepared samples exhibit blue color, indicating that the Co ions are acted upon by tetrahedral ligand field. Obtained spectra were used to estimate some ligand field parameters.

  7. Terahertz absorption spectra and potential energy distribution of liquid crystals.

    PubMed

    Chen, Zezhang; Jiang, Yurong; Jiang, Lulu; Ma, Heng

    2016-01-15

    In this work, the terahertz (THz) absorption spectra of a set of nematic liquid crystals were studied using the density functional theories (DFT). An accurate assignment of the vibrational modes corresponding to absorption frequencies were performed using potential energy distribution (PED) in a frequency range of 0-3 THz. The impacts of different core structures on THz absorption spectra were discussed. The results indicate that scope of application must be considered in the LC-based THz device designing. This proposed work may give a useful suggestion on the design of novel liquid crystal material in THz wave. PMID:26476072

  8. Abundances in 8 QSO Absorption Line Systems

    NASA Astrophysics Data System (ADS)

    Lauroesch, James Thomas

    1995-01-01

    An analysis is given of high resolution observations of metal-absorption line systems in the spectra of 4 QSOs made with the echelle spectrograph on the Mayall 4-meter telescope at Kitt Peak National Observatory. High spectral -resolution (9 to 18 km cdot s^{ -1}) observations were obtained for the QSOs S5 0014 + 813, H 0913 + 072, B2 1225 + 317, and HS 1946 + 7658; column densities were derived for the heavy element line systems. Abundances and/or abundance ratios have been determined for 8 systems and a variety of H I column densities in the redshift range 1-3.4 are probed. The systems studies are generally relatively poor in heavy elements, and appear to be similar in heavy element abundances to the gas out of which the Galactic halo stars of similar metallicity formed. Indications of the halo star-abundance sample include the observed ratios of (N/Si), (Al/Si), and (Mn/Fe). The existence of associated H II regions is inferred for a number of damped systems, and it is suggested that the possibly significant amount of gas in H II regions in damped Lyman-alpha systems can be constrained by the comparison of the column densities of O I, N I, N II, Si II, and S II in these systems. The ratio of N(Al II)/N(Al III) is shown to be a poor indicator of the amount of ionized gas in some cases. The abundances of Si as determined from N(Si II)/N(H I) suggest that there is a relatively rapid decrease in abundances in these systems at z _sp{ ~}> 2. Such a decrease in abundances is what would be expected if the galactic (thin) disks did not form before redshifts of z {~} 2. The use of Si II is important, since the weakness of the Zn II lines at low abundances (due to the low relative abundance of Zn compared to elements such as Si) will result in few detections, and in upper limits that are difficult to interpret. The observed drop in abundances is consistent with the decrease in number of heavy-element absorption systems at high redshifts, a result that is found in

  9. Ultraviolet absorption spectra of mercuric halides.

    NASA Technical Reports Server (NTRS)

    Templet, P.; Mcdonald, J. R.; Mcglynn, S. P.; Kendrow, C. H.; Roebber, J. L.; Weiss, K.

    1972-01-01

    The gas phase transitions of the mercuric halides were observed in the UV region by operating at temperatures above 400 K and at vapor pressures on the order of 0.5 mm. Spectral features exhibited by the chloride, bromide, and iodide of mercury correlate energetically with bands previously designated as intermolecular charge transfer transitions. The solution spectra of mercuric iodide and deep color of the crystals (if not due to some solid state interactions) indicate that this molecule may also have longer wavelength transitions.

  10. Constraining The Reionization History With QSO Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Gallerani, S.; Choudhury, T. R.; Ferrara, A.

    2006-08-01

    We use a semi-analytical approach to simulate absorption spectra of QSOs at high redshifts with the aim of constraining the cosmic reionization history. We consider two physically motivated and detailed reionization histories: (i) an Early Reionization Model (ERM) in which the intergalactic medium is reionized by PopIII stars at z~14, and (ii) a more standard Late Reionization Model (LRM) in which overlapping, induced by QSOs and normal galaxies, occurs at z~6. An example of simulated spectra is provided by FIG.1. From the analysis of current Lyα forest data at z<6, we conclude that it is impossible to disentangle the two scenarios, which fit equally well the observed Gunn-Peterson optical depth, flux probability distribution function and dark gap width distribution. At z>6, however, clear differences start to emerge which are best quantified by the dark gap width distribution. We find that 35 (zero) per cent of the lines of sight within 5.750Å in the rest frame of the QSO if re-ionization is not (is) complete at z>~6 (FIG.2). Similarly, the ERM predicts peaks of width ~1Å in 40 per cent of the lines of sight in the redshift range 6.0-6.6; in the same range, LRM predicts no peaks of width >0.8Å (FIG.3). We conclude that the dark gap and peak width statistics represent superb probes of cosmic reionization if about ten QSOs can be found at z>6.

  11. Statistical Analysis of Spectra with Many Lines

    NASA Astrophysics Data System (ADS)

    van Dyk, D. A.; Kang, H. S.; Connors, A.; Kashyap, V. L.; Siemiginowska, A.

    2001-12-01

    Please join us in our wider effort to engage the strengths of modern computational statistics methods in solving challenging stellar and solar data analysis problems. As just one example (of a great breadth of possibilities) consider analyzing a spectrum with a very large number of lines. Some of these may be faint, merged, indistinguishable from each other and the underlying smooth continuum. The ensemble of line intensities follows a predictable distribution. The shape of this distribution depends on the properties of the source, e.g., its temperature, abundances, and emission measure. Hence, a better understanding of the distribution of line fluxes in a particular source may tighten our inference for other model parameters such as temperature---even when very few lines are actually easy to distinguish. To take advantage of this structure, we directly model the distribution of the line fluxes rather than fitting each line flux directly or ``investing'' the emissivities to get a DEM. Statistically, this strategy reduces the number of free parameters, which we expect will lead to improved statistical properties. We believe this method holds much promise for improved analysis, especially for low count sources. For example, we expect this method to correctly account for the ``pseudo-continuum'' that results from the large number of faint, unresolvable lines in X-ray grating spectra. Moreover, our statistical methods should apply directly to other settings involving a multitude of lines such as timing data. We hope that these methods will increase our statistical power to set the continuum level in the presence of a multitude of lines and to distinguish weak lines from fluctuations in the continuum. Funding for this project partially provided by NSF grant and DMS-01-04129 and by NASA Contract NAS8-39073 (CXC).

  12. Probing molecular chirality by coherent optical absorption spectra

    SciTech Connect

    Jia, W. Z.; Wei, L. F.

    2011-11-15

    We propose an approach to sensitively probe the chirality of molecules by measuring their coherent optical-absorption spectra. It is shown that quantum dynamics of the cyclic three-level chiral molecules driven by appropriately designed external fields is total-phase dependent. This will result in chirality-dependent absorption spectra for the probe field. As a consequence, the charality-dependent information in the spectra (such as the locations and relative heights of the characteristic absorption peaks) can be utilized to identify molecular chirality and determinate enantiomer excess (i.e., the percentages of different enantiomers). The feasibility of the proposal with chiral molecules confined in hollow-core photonic crystal fiber is also discussed.

  13. Pressure dependence of Se absorption lines in AlSb

    SciTech Connect

    Hsu, L. |; Haller, E.E.; Ramdas, A.K.

    1996-09-01

    Using far infrared absorption spectroscopy, the authors have investigated electronic transition spectra of Se donors in AlSb as a function of hydrostatic pressure. At least two distinct ground to bound excited state transition lines, which depend quadratically on the pressure, can be seen. At pressures between 30 and 50 kbar, evidence of an anti-crossing between one of the electronic transitions and a peak which they attribute to the 2 zone center LO phonon mode can be seen.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  15. IR absorption spectra of cellulose obtained from ozonated wood

    NASA Astrophysics Data System (ADS)

    Mamleeva, N. A.; Autlov, S. A.; Kharlanov, A. N.; Bazarnova, N. G.; Lunin, V. V.

    2015-08-01

    The kinetic curves of ozone absorption by aspen wood were obtained. Processing of wood with peracetic acid gave cellulose samples. The yields of ozonated wood, water-soluble compounds, and cellulose were determined for the samples corresponding to different consumptions of ozone. The IR absorption spectra of wood and cellulose isolated from ozonated wood were analyzed. The supramolecular structure of cellulose can be changed by varying the conditions of wood ozonation.

  16. Cyclotron scattering lines in gamma-ray burst spectra

    NASA Technical Reports Server (NTRS)

    Harding, Alice K.; Preece, Robert D.

    1989-01-01

    If cyclotron scattering, rather than absorption, is responsible for the line features observed recently in two gamma-ray burst spectra (Murakami et al., 1988), then the second and higher harmonics are due to resonant scattering events that excite the electron to Landau levels above the ground state. Here, relativistic Compton scattering cross sections are used to estimate the expected ratio of third to second harmonics in the presence of Doppler broadening. At the field strength (1.7 TG) required to give first and second harmonics at 19 keV and 38 keV, there should be no detectable third harmonic in the spectrum.

  17. A Simple Demonstration of Absorption Spectra Using Tungsten Holiday Lights

    ERIC Educational Resources Information Center

    Birriel, Jennifer J.

    2009-01-01

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

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

    PubMed

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

    2012-06-01

    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

  19. Observationally determined Fe II oscillator strengths. [interstellar and quasar absorption spectra

    NASA Technical Reports Server (NTRS)

    Van Steenberg, M.; Shull, J. M.; Seab, C. G.

    1983-01-01

    Absorption oscillator strengths for 21 Fe II resonance lines, have been determined using a curve-of-growth analysis of interstellar data from the Copernicus and International Ultraviolet Explorer (IUE) satellites. In addition to slight changes in strengths of the far-UV lines, new f-values are reported for wavelength 1608.45, a prominent line in interstellar and quasar absorption spectra, and for wavelength 2260.08, a weak, newly identified linen in IUE interstellar spectra. An upper limit on the strength of the undetected line at 2366.867 A (UV multiplet 2) is set. Using revised oscillator strengths, Fe II column densities toward 13 OB stars are derived. The interstellar depletions, (Fe/H), relative to solar values range between factors of 10 and 120.

  20. A SURVEY OF ALKALI LINE ABSORPTION IN EXOPLANETARY ATMOSPHERES

    SciTech Connect

    Jensen, Adam G.; Redfield, Seth; Endl, Michael; Cochran, William D.; Koesterke, Lars; Barman, Travis S. E-mail: sredfield@wesleyan.edu E-mail: wdc@astro.as.utexas.edu E-mail: barman@lowell.edu

    2011-12-20

    We obtained over 90 hr of spectroscopic observations of four exoplanetary systems with the Hobby-Eberly Telescope. Observations were taken in transit and out of transit, and we analyzed the differenced spectra-i.e., the transmission spectra-to inspect it for absorption at the wavelengths of the neutral sodium (Na I) doublet at {lambda}{lambda}5889, 5895 and neutral potassium (K I) at {lambda}7698. We used the transmission spectrum at Ca I {lambda}6122-which shows strong stellar absorption but is not an alkali metal resonance line that we expect to show significant absorption in these atmospheres-as a control line to examine our measurements for systematic errors. We use an empirical Monte Carlo method to quantify these systematic errors. In a reanalysis of the same data set using a reduction and analysis pipeline that was derived independently, we confirm the previously seen Na I absorption in HD 189733b at a level of (- 5.26 {+-} 1.69) Multiplication-Sign 10{sup -4} (the average value over a 12 A integration band to be consistent with previous authors). Additionally, we tentatively confirm the Na I absorption seen in HD 209458b (independently by multiple authors) at a level of (- 2.63 {+-} 0.81) Multiplication-Sign 10{sup -4}, though the interpretation is less clear. Furthermore, we find Na I absorption of (- 3.16 {+-} 2.06) Multiplication-Sign 10{sup -4} at <3{sigma} in HD 149026b; features apparent in the transmission spectrum are consistent with real absorption and indicate this may be a good target for future observations to confirm. No other results (Na I in HD 147506b and Ca I and K I in all four targets) are significant to {>=}3{sigma}, although we observe some features that we argue are primarily artifacts.

  1. The OH - absorption spectra of low doped lithium niobate crystals

    NASA Astrophysics Data System (ADS)

    Kong, Yongfa; Zhang, Wanlin; Xu, Jingjun; Yan, Wenbo; Liu, Hongde; Xie, Xiang; Li, Xiaochun; Shi, Lihong; Zhang, Guangyin

    2004-07-01

    The OH - absorption spectra of low doped lithium niobate (LiNbO 3) crystals have been investigated. Though no apparent band shift is observed in these absorption spectra, their shapes are quite different. In order to analyze the information on the defect structure underlying these OH - absorption bands, the normalization and difference methods were employed. It was found that although the doping concentrations are under the thresholds the doping ions have apparent affect to the site occupation of OH - ions. The OH - vibrations related to Mg Li+ (Mg 2+ occupying Li-site) and In Li2+ are 3483 and 3484 cm -1 in LiNbO 3:Mg and LiNbO 3:In crystals, respectively. The absorption peak of LiNbO 3:Ti (2.5 mol%) crystal at 3487 cm -1 is mainly related to Ti Li3+-OH - and the 3489 cm -1 peak of LiNbO 3:Mg (5.0 mol%), Ti (10.0 mol%) related to Mg Li+-OH -, Ti Nb--OH - and Ti Li3+-OH -. Doping with Na improves the peak intensity near 3466 cm -1 and induces a new absorption peak at 3470 cm -1. The absorption bands of LiNbO 3 crystals codoped with trivalent ions are associated with the co-effect of the doped ions and have some different characteristics from mono-doped crystals.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  3. A computer code to calculate line by line atmospheric transmission spectra on a microcomputer

    NASA Astrophysics Data System (ADS)

    Safren, H. G.

    1987-07-01

    A computer program is described which calculates line by line atmospheric transmission spectra on a microcomputer. Radiance calculations are not included. The program is written in FORTRAN and could be modified to run on a microcomputer other than the one on which it was implemented, except that the plotting routine would have to be replaced. The program is based on the 1978 Air Force Geophysics Laboratory LASER routine, and uses absorption line data from the 1982 update of the AFGL Atmospheric Absorption Line Parameters Compilation; segments of needed line data are taken from the tape, preprocessed into the form used by the program and stored on floppy disks. The program calculates transmission spectra over a variety of paths and spanning an arbitrarily chosen wavelength or frequency range; the path may be chosen to be horizontal, vertical or slanted at any zenith angle, and may extend between any two altitudes between 0 and 15 km. Aerosol effects are included, presently based on the 1976 Shettle and Fenn models, plus some molecular continuum effects and Rayleigh scattering.

  4. Constraining the reionization history with QSO absorption spectra

    NASA Astrophysics Data System (ADS)

    Gallerani, S.; Choudhury, T. Roy; Ferrara, A.

    2006-08-01

    We use a semi-analytical approach to simulate absorption spectra of QSOs at high redshifts with the aim of constraining the cosmic reionization history. We consider two physically motivated and detailed reionization histories: (i) an early reionization model (ERM) in which the intergalactic medium is reionized by Pop III stars at z ~ 14, and (ii) a more standard late reionization model (LRM) in which overlapping, induced by QSOs and normal galaxies, occurs at z ~ 6. From the analysis of current Lyα forest data at z < 6, we conclude that it is impossible to disentangle the two scenarios, which fit equally well the observed Gunn-Peterson optical depth, flux probability distribution function and dark gap width distribution. At z > 6, however, clear differences start to emerge which are best quantified by the dark gap and peak width distributions. We find that 35 (0) per cent of the lines of sight (LOS) within 5.7 < z < 6.3 show dark gaps of widths >50Å in the rest frame of the QSO if reionization is not (is) complete at z >~ 6. Similarly, the ERM predicts peaks of width ~1Å in 40 per cent of the LOS in the redshift range 6.0-6.6 in the same range, LRM predicts no peaks of width >0.8Å. We conclude that the dark gap and peak width statistics represent superb probes of cosmic reionization if about ten QSOs can be found at z > 6. We finally discuss strengths and limitations of our method.

  5. Infrared absorption spectra of metal carbides, nitrides and sulfides

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  6. EPR and electronic absorption spectra of copper bearing turquoise mineral

    NASA Astrophysics Data System (ADS)

    Sharma, K. B. N.; Moorthy, L. R.; Reddy, B. J.; Vedanand, S.

    1988-10-01

    Electron paramagnetic resonance and optical absorption spectra of turquoise have been studied both at room and low temperatures. It is concluded from the EPR spectra that the ground state of Cu 2+ ion in turquoise is 2A g(d x2- y2) and it is sited in an elongated rhombic octahedron (D 2π). The observed absorption bands at 14970 and 18354 cm -1 are assigned at 2A g→ 2B 1 g( dx2- y2→ xy) and 2A g→[ su2B 3g(d x 2-y 2→d yz) respectively assuming D 2π symmetry which are inconsistent with EPR studies. The three bands in the NIR region are attributed to combinations of fundamental modes of the H 2O molecule present in the sample.

  7. Modeling absorption spectra for detection of the combustion products of jet engines by laser remote sensing.

    PubMed

    Voitsekhovskaya, Olga K; Kashirskii, Danila E; Egorov, Oleg V; Shefer, Olga V

    2016-05-10

    The absorption spectra of exhaust gases (H2O, CO, CO2, NO, NO2, and SO2) and aerosol (soot and Al2O3) particles were modeled at different temperatures for the first time and suitable spectral ranges were determined for conducting laser remote sensing of the combustion products of jet engines. The calculations were conducted on the basis of experimental concentrations of the substances and the sizes of the aerosol particles. The temperature and geometric parameters of jet engine exhausts were also taken from the literature. The absorption spectra were obtained via the line-by-line method, making use of the spectral line parameters from the authors' own high-temperature databases (for NO2 and SO2 gases) and the HITEMP 2010 database, and taking into account atmospheric transmission. Finally, the theoretical absorption spectra of the exhaust gases were plotted at temperatures of 400, 700, and 1000 K, and the impact of aerosol particles on the total exhaust spectra was estimated in spectral ranges suitable for remote sensing applications. PMID:27168298

  8. Theoretical investigations of absorption and fluorescence spectra of protonated pyrene.

    PubMed

    Chin, Chih-Hao; Lin, Sheng Hsien

    2016-05-25

    The equilibrium geometry and 75 vibrational normal-mode frequencies of the ground and first excited states of protonated pyrene isomers were calculated and characterized in the adiabatic representation by using the complete active space self-consistent field (CASSCF) method. Electronic absorption spectra of solid neon matrixes in the wavelength range 495-415 nm were determined by Maier et al. and they were analyzed using time-dependent density functional theory calculations (TDDFT). CASSCF calculations and absorption and emission spectra simulations by one-photon excitation equations were used to optimize the excited and ground state structures of protonated pyrene isomers. The absorption band was attributed to the S0 → S1 electronic transition in 1H-Py(+), and a band origin was used at 20580.96 cm(-1). The displaced harmonic oscillator approximation and Franck-Condon approximation were used to simulate the absorption spectrum of the (1) (1)A' ← X[combining tilde](1)A' transition of 1H-Py(+), and the main vibronic transitions were assigned for the first ππ* state. It shows that the vibronic structures were dominated by one of the eight active totally symmetric modes, with ν15 being the most crucial. This indicates that the electronic transition of the S1((1)A') state calculated in the adiabatic representation effectively includes a contribution from the adiabatic vibronic coupling through Franck-Condon factors perturbed by harmonic oscillators. The present method can adequately reproduce experimental absorption and fluorescence spectra of a gas phase. PMID:27181017

  9. Optical absorption spectra of palladium doped gold cluster cations

    SciTech Connect

    Kaydashev, Vladimir E.; Janssens, Ewald Lievens, Peter

    2015-01-21

    Photoabsorption spectra of gas phase Au{sub n}{sup +} and Au{sub n−1}Pd{sup +} (13 ≤ n ≤ 20) clusters were measured using mass spectrometric recording of wavelength dependent Xe messenger atom photodetachment in the 1.9–3.4 eV photon energy range. Pure cationic gold clusters consisting of 15, 17, and 20 atoms have a higher integrated optical absorption cross section than the neighboring sizes. It is shown that the total optical absorption cross section increases with size and that palladium doping strongly reduces this cross section for all investigated sizes and in particular for n = 14–17 and 20. The largest reduction of optical absorption upon Pd doping is observed for n = 15.

  10. Infrared absorption spectra of methylidene radicals in solid neon.

    PubMed

    Lu, Hsiao-Chi; Lo, Jen-Iu; Lin, Meng-Yeh; Peng, Yu-Chain; Chou, Sheng-Lung; Cheng, Bing-Ming; Ogilvie, J F

    2014-07-28

    Infrared absorption lines of methylidene--(12)C(1)H, (13)C(1)H, and (12)C(2)H--dispersed in solid neon at 3 K, recorded after photolysis of methane precursors with vacuum-ultraviolet light at 121.6 nm, serve as signatures of these trapped radicals. PMID:24912563

  11. Real-time atmospheric absorption spectra for in-flight tuning of an airborne dial system

    NASA Technical Reports Server (NTRS)

    Dombrowski, M.; Walden, H.; Schwemmer, G. K.; Milrod, J.; Korb, C. L.

    1986-01-01

    Real-time measurements of atmospheric absorption spectra are displayed and used to precisely calibrate and fix the frequency of an Alexandrite laser to specific oxygen absorption features for airborne Differential Absorption Lidar (DIAL) measurements of atmospheric pressure and temperature. The DIAL system used contains two narrowband tunable Alexandrite lasers: one is electronically scanned to tune to oxygen absorption features for on-line signals while the second is used to obtain off-line (nonabsorbed) atmospheric return signals. The lidar operator may select the number of shots to be averaged, the altitude, and altitude interval over which the signals are averaged using single key stroke commands. The operator also determines exactly which oxygen absorption lines are scanned by comparing the line spacings and relative strengths with known line parameters, thus calibrating the laser wavelength readout. The system was used successfully to measure the atmospheric pressure profile on the first flights of this lidar, November 20, and December 9, 1985, aboard the NASA Wallops Electra aircraft.

  12. Absorption Features in Spectra of Magnetized Neutron Stars

    SciTech Connect

    Suleimanov, V.; Hambaryan, V.; Neuhaeuser, R.; Potekhin, A. Y.; Pavlov, G. G.; Adelsberg, M. van; Werner, K.

    2011-09-21

    The X-ray spectra of some magnetized isolated neutron stars (NSs) show absorption features with equivalent widths (EWs) of 50-200 eV, whose nature is not yet well known.To explain the prominent absorption features in the soft X-ray spectra of the highly magnetized (B{approx}10{sup 14} G) X-ray dim isolated NSs (XDINSs), we theoretically investigate different NS local surface models, including naked condensed iron surfaces and partially ionized hydrogen model atmospheres, with semi-infinite and thin atmospheres above the condensed surface. We also developed a code for computing light curves and integral emergent spectra of magnetized neutron stars with various temperature and magnetic field distributions over the NS surface. We compare the general properties of the computed and observed light curves and integral spectra for XDINS RBS 1223 and conclude that the observations can be explained by a thin hydrogen atmosphere above the condensed iron surface, while the presence of a strong toroidal magnetic field component on the XDINS surface is unlikely.We suggest that the harmonically spaced absorption features in the soft X-ray spectrum of the central compact object (CCO) 1E 1207.4-5209 (hereafter 1E 1207) correspond to peaks in the energy dependence of the free-free opacity in a quantizing magnetic field, known as quantum oscillations. To explore observable properties of these quantum oscillations, we calculate models of hydrogen NS atmospheres with B{approx}10{sup 10}-10{sup 11} G(i.e., electron cyclotron energy E{sub c,e}{approx}0.1-1 keV) and T{sub eff} = 1-3 MK. Such conditions are thought to be typical for 1E 1207. We show that observable features at the electron cyclotron harmonics with EWs {approx_equal}100-200 eV can arise due to these quantum oscillations.

  13. Transient absorption spectra of the laser-dressed hydrogen atom

    NASA Astrophysics Data System (ADS)

    Murakami, Mitsuko; Chu, Shih-I.

    2013-10-01

    We present a theoretical study of transient absorption spectra of laser-dressed hydrogen atoms, based on numerical solutions of the time-dependent Schrödinger equation. The timing of absorption is controlled by the delay between an extreme ultra violet (XUV) pulse and an infrared (IR) laser field. The XUV pulse is isolated and several hundred attoseconds in duration, which acts as a pump to drive the ground-state electron to excited p states. The subsequent interaction with the IR field produces dressed states, which manifest as sidebands between the 1s-np absorption spectra separated by one IR-photon energy. We demonstrate that the population of dressed states is maximized when the timing of the XUV pulse coincides with the zero crossing of the IR field, and that their energies can be manipulated in a subcycle time scale by adding a chirp to the IR field. An alternative perspective to the problem is to think of the XUV pulse as a probe to detect the dynamical ac Stark shifts. Our results indicate that the accidental degeneracy of the hydrogen excited states is removed while they are dressed by the IR field, leading to large ac Stark shifts. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 levels using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional three-level model that neglects the dynamical ac Stark shifts.

  14. Optical Absorption Spectra of Hydrous Wadsleyite to 32 GPa

    NASA Astrophysics Data System (ADS)

    Thomas, S.; Goncharov, A. F.; Jacobsen, S. D.; Bina, C. R.; Frost, D. J.

    2009-05-01

    Optical absorption spectra of high-pressure minerals can be used as indirect tools to calculate radiative conductivity of the Earth's interior [e.g., 1]. Recent high-pressure studies show that e.g. ringwoodite, γ-(Mg,Fe)2SiO4, does not become opaque in the near infrared and visible region, as previously assumed, but remains transparent to 21.5 GPa [2]. Therefore, it has been concluded that radiative heat transfer does not necessarily become blocked at high pressures of the mantle and ferromagnesian minerals actually could contribute to the heat flow in the Earth's interior [2]. In this study we use gem-quality single-crystals of hydrous Fe-bearing wadsleyite, β-(Mg,Fe)2SiO4, that were synthesized at 18 GPa and 1400 °C in a multianvil apparatus. Crystals were analyzed by Mössbauer and Raman spectroscopy, electron microprobe analysis and single-crystal X-ray diffraction. For absorption measurements a double-polished 50 μm sized single-crystal of wadsleyite was loaded in a diamond-anvil cell with neon as pressure medium. Optical absorption spectra were recorded at ambient conditions as well as up to 32 GPa from 400 to 50000 cm-1. At ambient pressure the absorption spectrum reveals two broad bands at - 10000 cm-1 and -15000 cm-1, and an absorption edge in the visible-ultraviolet range. With increasing pressure the absorption spectrum changes, both bands continuously shift to higher frequencies as has been observed for ringwoodite [2], but is contrary to earlier presumptions for wadsleyite [3]. Here, we will discuss band assignment along with the influence of iron, compare our results to previous absorption studies of mantle materials [2], and analyze possible implications for radiative conductivity of the transition zone. References: [1] Goncharov et al. (2008), McGraw Yearbook Sci. Tech., 242-245. [2] Keppler & Smyth (2005), Am. Mineral., 90 1209-1212. [3] Ross (1997), Phys. Chem. Earth, 22 113-118.

  15. The x-ray absorption spectra of water and ice

    NASA Astrophysics Data System (ADS)

    Kong, Lingzhu; Wu, Xifan; Car, Roberto

    2012-02-01

    We calculate the x-ray absorption spectra of liquid water at STP, hexagonal ice and amorphous low- and high-density ice at T=269K, using the static Coulomb-hole and screened exchange self energy approach ootnotetextW. Chen, X. Wu and R. Car, PRL 105, 017802 (2008) . We take the nuclear quantum effects into account by averaging over the Feynman path-integral replicas. We find that quantum disorder is particularly important in liquid water where it substantially improves the structure ootnotetextJ. Morrone and R. Car, PRL 101, 017801 (2008) Compared to Ref. 2, we use an improved screening model that includes the approximate local field correction ootnotetextM. Hybertsen and S. G. Louie, PRB 37, 2733 (1988). The resulting spectra are in significantly better agreement with experiments than in previous calculations.

  16. Optical absorption and scattering spectra of pathological stomach tissues

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  17. Absorption Spectra and Absorption Coefficients for Methane in the 750-940 nm region obtained by Intracavity Laser Spectroscopy

    NASA Astrophysics Data System (ADS)

    O'Brien, J. J.; Cao, H.

    2000-10-01

    Methane spectral features are prominent in the reflected sunlight spectra from the outer planets and some of their major satellites and can provide useful information on the atmospheres of those bodies. Methane bands occurring in the visible to near-IR region are particularly important because for many of these planetary bodies, methane bands occurring in the IR are saturated. Spectral observations of these bodies also are being made at increasingly higher resolution. In order to interpret the planetary spectra, laboratory data for methane obtained at appropriate sample conditions and spectral resolution are required. Since the visible to near-IR spectrum of methane is intrinsically weak, sensitive techniques are required to perform the laboratory measurements. We have employed the intracavity laser spectroscopy (ILS) technique to record methane spectrum in the visible to near-IR region. New results for room temperature methane in the 10,635 - 13,300 cm-1 region and for liquid nitrogen temperature (77 K) methane in the 10,860 - 11,605 cm-1 region will be presented. Spectra throughout the more strongly absorbing sections will be shown. These spectra are acquired at a resolution of 400,000 - 500,000 and are calibrated using iodine reference spectra acquired from an extra-cavity cell at nearly the same time as when the methane data are recorded. From the spectra, absorption coefficients are determined and these are presented as averages over 1 Å and 1 cm-1 intervals. In order to obtain the results, spectra are deconvolved for the instrument function using a Fourier transform technique. The validity of the approach is verified from studies of isolated oxygen lines in the A band occurring around 760 nm. Good agreement is observed between the intensity values determined from the FT deconvolution and integration method and those derived by fitting the observed line profiles to Voigt line-shapes convoluted with the instrument function. The methane results are compared

  18. Modelling telluric line spectra in the optical and infrared with an application to VLT/X-Shooter spectra

    NASA Astrophysics Data System (ADS)

    Rudolf, N.; Günther, H. M.; Schneider, P. C.; Schmitt, J. H. M. M.

    2016-01-01

    Context. Earth's atmosphere imprints a large number of telluric absorption and emission lines on astronomical spectra, especially in the near infrared, that need to be removed before analysing the affected wavelength regions. Aims: These lines are typically removed by comparison to A- or B-type stars used as telluric standards that themselves have strong hydrogen lines, which complicates the removal of telluric lines. We have developed a method to circumvent that problem. Methods: For our IDL software package tellrem we used a recent approach to model telluric absorption features with the line-by-line radiative transfer model (LBLRTM). The broad wavelength coverage of the X-Shooter at VLT allows us to expand their technique by determining the abundances of the most important telluric molecules H2O, O2, CO2, and CH4 from sufficiently isolated line groups. For individual observations we construct a telluric absorption model for most of the spectral range that is used to remove the telluric absorption from the object spectrum. Results: We remove telluric absorption from both continuum regions and emission lines without systematic residuals for most of the processable spectral range; however, our method increases the statistical errors. The errors of the corrected spectrum typically increase by 10% for S/N ~ 10 and by a factor of two for high-quality data (S/N ~ 100), i.e. the method is accurate on the percent level. Conclusions: Modelling telluric absorption can be an alternative to the observation of standard stars for removing telluric contamination. Based on observations collected at the European Southern Observatory, Paranal, Chile, 085.C-0764(A) and 60.A-9022(C).The tellrem package is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A113

  19. Ultraviolet observations of interstellar absorption lines toward SN 1987A

    NASA Technical Reports Server (NTRS)

    Savage, Blair D.; Jenkins, Edward B.; Joseph, Charles L.; De Boer, Klass S.

    1989-01-01

    High-dispersion IUE echelle spectra of SN 1987A were averaged in order to obtain UV absorption-line profiles of the highest possible quality in the direction of SN 1987A. The profiles for Si IV and C IV are quite similar and have much less structure than the Al III profile. On relating column densities, while the C IV and Si IV ratio is relatively constant over the 0-100 km/s velocity range, the C IV to Al III and Si IV to Al III ratios vary by nearly a factor of 10. This suggests that the C IV and Si IV along this sight line in the Galaxy and its halo may have a common origin which differs from that for Al III.

  20. NOTE: Visible absorption spectra of radiation exposed SIRAD dosimeters

    NASA Astrophysics Data System (ADS)

    Butson, Martin J.; Cheung, Tsang; Yu, Peter K. N.

    2006-12-01

    SIRAD badge dosimeters are a new type of personal dosimeter designed to measure radiation exposure up to 200 R and give a visual qualitative measurement of exposure. This is performed using the active dosimeter window, which contains a radiochromic material amalgamated in the badge assembly. When irradiated, the badges active window turns blue, which can be matched against the given colour chart for a qualitative assessment of the exposure received. Measurements have been performed to analyse the absorption spectra of the active window, and results show that the window automatically turns a blue colour upon irradiation and produces two peaks in the absorption spectra located at 617 nm and 567 nm. When analysed with a common computer desktop scanner, the optical density response of the film to radiation exposure is non-linear but reproducible. The net OD of the film was 0.21 at 50 R exposure and 0.31 at 200 R exposure when irradiated with a 6 MV x-ray energy beam. When compared to the calibration colour strips at 6 MV x-ray energy the film's OD response matches relatively well within 3.5%. An approximate 8% reduction in measured OD to exposure was seen for 250 kVp x-rays compared to 6 MV x-rays. The film provides an adequate measurement and visually qualitative assessment of radiation exposure for levels in the range of 0 to 200 R.

  1. Detection of significant differences between absorption spectra of neutral helium and low temperature photoionized helium plasmas

    SciTech Connect

    Bartnik, A.; Wachulak, P.; Fiedorowicz, H.; Fok, T.; Jarocki, R.; Szczurek, M.

    2013-11-15

    In this work, spectral investigations of photoionized He plasmas were performed. The photoionized plasmas were created by irradiation of helium stream, with intense pulses from laser-plasma extreme ultraviolet (EUV) source. The EUV source was based on a double-stream Xe/Ne gas-puff target irradiated with 10 ns/10 J Nd:YAG laser pulses. The most intense emission from the source spanned a relatively narrow spectral region below 20 nm, however, spectrally integrated intensity at longer wavelengths was also significant. The EUV radiation was focused onto a gas stream, injected into a vacuum chamber synchronously with the EUV pulse. The long-wavelength part of the EUV radiation was used for backlighting of the photoionized plasmas to obtain absorption spectra. Both emission and absorption spectra in the EUV range were investigated. Significant differences between absorption spectra acquired for neutral helium and low temperature photoionized plasmas were demonstrated for the first time. Strong increase of intensities and spectral widths of absorption lines, together with a red shift of the K-edge, was shown.

  2. An iron absorption model of gamma-ray burst spectra

    NASA Technical Reports Server (NTRS)

    Liang, Edison P.; Kargatis, Vincent E.

    1994-01-01

    Most gamma-ray bursts (GRBs) exhibit deficits of X-rays below approximately 200 keV. Here we consider a spectral model in which the burst source is shielded by an optically thick layer of circumburster material (CBM) rich in iron-group elements whose photoelectric absorption opacity exceeds the Thomson opacity below approximately 120 keV. For power-law distributions of absorption depths along the lines of sight the absorbed spectrum can indeed mimic the typial GRB spectrum. This model predicts that (a) the spectrum should evolve monotonically from hard to soft during each energy release, which is observed in most bursts, especially in fast rise exponential decay bursts; (b) Fe spectral features near 7 keV may be present in some bursts; and (c) the ratio of burst distances to the CBM and to Earth should be approximately 10(exp -11) if the spectral evolution is purely due to Fe stripping by the photons.

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

    SciTech Connect

    Hidalgo, Paola Rodriguez; Eracleous, Michael; Charlton, Jane; Hamann, Fred; Murphy, Michael T.; Nestor, Daniel

    2013-09-20

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    We report the discovery of a high-ionization broad absorption line system at a redshift of z(sub abs) = 0.695 in the spectrum of the z(sub em) = 1.052 radio-quiet quasar PG 2302+029. Broad absorption with FWHM from 3000 to 5000 km/s is detected from C iv, N v, and O vi in Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the quasar. A narrow-line system (FWHM approx. 250 km/s) at z(sub abs) = 0.7016 is resolved from the broad blend and includes absorption by Ly alpha and the C iv, N v, and O vi doublets. No absorption by low-ionization metal species (e.g., Si II and Mg II) is detected in the HST or ground-based spectra for either the broad or the narrow system. The centroids of the broad system lines are displaced by approx. 56,000 km/s to the blue of the quasar's broad emission lines. The reddest extent of the broad-line absorption is more than 50,000 km/s from the quasar. The properties of this system are unprecedented, whether it is an intervening or an ejected system.

  5. Absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissues

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  6. X-ray Emission and Absorption Lines During the SSS Phase of RS Ophiuchi

    NASA Astrophysics Data System (ADS)

    Schönrich, R. A.; Ness, J.-U.

    2008-12-01

    The high-resolution X-ray spectra of the sixth outburst of RS Ophiuchi revealed P Cygni-like line profiles. We use the column densities of selected isolated absorption lines to derive the nitrogen-to-oxygen abundance ratio. We next discuss the origin of the emission lines, which may originate from the shock, and the absorption and emission lines may thus have a different formation history. Finally, we discuss the correlation of high-amplitude variability detected during the early SSS phase with variability in the hardness ratio that follows the same pattern but is shifted by 1000~sec.

  7. Absorption and electroabsorption spectra of carotenoid cation radical and dication

    NASA Astrophysics Data System (ADS)

    Krawczyk, Stanisław

    1998-05-01

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

  8. A Parallel Iterative Method for Computing Molecular Absorption Spectra.

    PubMed

    Koval, Peter; Foerster, Dietrich; Coulaud, Olivier

    2010-09-14

    We describe a fast parallel iterative method for computing molecular absorption spectra within TDDFT linear response and using the LCAO method. We use a local basis of "dominant products" to parametrize the space of orbital products that occur in the LCAO approach. In this basis, the dynamic polarizability is computed iteratively within an appropriate Krylov subspace. The iterative procedure uses a matrix-free GMRES method to determine the (interacting) density response. The resulting code is about 1 order of magnitude faster than our previous full-matrix method. This acceleration makes the speed of our TDDFT code comparable with codes based on Casida's equation. The implementation of our method uses hybrid MPI and OpenMP parallelization in which load balancing and memory access are optimized. To validate our approach and to establish benchmarks, we compute spectra of large molecules on various types of parallel machines. The methods developed here are fairly general, and we believe they will find useful applications in molecular physics/chemistry, even for problems that are beyond TDDFT, such as organic semiconductors, particularly in photovoltaics. PMID:26616067

  9. Stratospheric N2O mixing ratio profile from high-resolution balloon-borne solar absorption spectra and laboratory spectra near 1880/cm

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Goldman, A.; Murcray, F. J.; Murcray, D. G.; Smith, M. A. H.; Seals, R. K., Jr.; Larsen, J. C.; Rinsland, P. L.

    1982-01-01

    A nonlinear least-squares fitting procedure is used to derive the stratospheric N2O mixing ratio profile from balloon-borne solar absorption spectra and laboratory spectra near 1880/cm. The atmospheric spectra analyzed here were recorded during sunset from a float altitude of 33 km with the University of Denver's 0.02/cm resolution interferometer near Alamogordo, N.M. (33 deg N) on Oct. 10, 1979. The laboratory data are used to determine the N2O line intensities. The measurements suggest an N2O mixing ratio of 264 ppbv near 15 km, decreasing to 155 ppbv near 28 km.

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

    NASA Astrophysics Data System (ADS)

    Duari, Debiprosad; Narlikar, Jayant V.

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

  11. Determination of phosphorus using high-resolution diphosphorus molecular absorption spectra produced in the graphite furnace

    NASA Astrophysics Data System (ADS)

    Huang, Mao Dong; Becker-Ross, Helmut; Okruss, Michael; Geisler, Sebastian; Florek, Stefan

    2016-01-01

    Molecular absorption of diphosphorus was produced in a graphite furnace and evaluated in view of its suitability for phosphorus determination. Measurements were performed with two different high-resolution continuum source absorption spectrometers. The first system is a newly in-house developed simultaneous broad-range spectrograph, which was mainly used for recording overview absorption spectra of P2 between 193 nm and 245 nm. The region covers the main part of the C 1Σu+ ← X 1Σg+ electronic transition and shows a complex structure with many vibrational bands, each consisting of a multitude of sharp rotational lines. With the help of molecular data available for P2, an assignment of the vibrational bands was possible and the rotational structure could be compared with simulated spectra. The second system is a commercial sequential continuum source spectrometer, which was used for the basic analytical measurements. The P2 rotational line at 204.205 nm was selected and systematically evaluated with regard to phosphorus determination. The conditions for P2 generation were optimized and it was found that the combination of a ZrC modified graphite tube and borate as a chemical modifier were essential for a good production of P2. Serious interferences were found in the case of nitrate and sulfuric acid, although the nitrate interference can be eliminated by a higher pyrolysis temperature. The reliability of the method was proved by analysis of certified samples. Using standard tubes, a characteristic mass of 10 ng and a limit of detection of 7 ng were found. The values could further be improved by a factor of ten using a miniaturized tube with an internal diameter of 2 mm. Compared to the conventional method based on the phosphorus absorption line at 213.618 nm, the advantages of using P2 are the gentle temperature conditions and the potential of performing a simultaneous multi-line evaluation to further improve the limit of detection.

  12. Atomic lines in infrared spectra for ultracool dwarfs

    NASA Astrophysics Data System (ADS)

    Lyubchik, Y.; Jones, H. R. A.; Pavlenko, Y. V.; Viti, S.; Pickering, J. C.; Blackwell-Whitehead, R.

    2004-03-01

    We provide a set of atomic lines which are suitable for the description of ultracool dwarf spectra from 10 000 to 25 000 Å. This atomic linelist was made using both synthetic spectra calculations and existing atlases of infrared spectra of Arcturus and Sunspot umbra. We present plots which show the comparison of synthetic spectra and observed Arcturus and Sunspot umbral spectra for all atomic lines likely to be observable in high resolution infrared spectra. Figure 1 is only available in electronic form at http://www.edpsciences.org Tables 1 and 2 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/416/655

  13. LINE-BY-LINE CALCULATION OF SPECTRA FROM DIATOMIC MOLECULES AND ATOMS ASSUMING A VOIGT LINE PROFILE

    NASA Technical Reports Server (NTRS)

    Whiting, E. E.

    1994-01-01

    This program predicts the spectra resulting from electronic transitions of diatomic molecules and atoms in local thermodynamic equilibrium. The program produces a spectrum by accounting for the contribution of each rotational and atomic line considered. The integrated intensity of each line is distributed in the spectrum by an approximate Voigt profile. The program can produce spectra for optically thin gases or for cases where simultaneous emission and absorption occurs. In addition, the program can compute the spectrum resulting from the absorption of incident radiation by a column of cold gas or the high-temperature, self-absorbed emission spectrum from a nonisothermal gas. The computed spectrum can be output directly or combined with a slit function and sensitivity calibration to predict the output of a grating spectrograph or a fixed wavelength radiometer. Specifically, the program has the capability to include the following features in any computations: (1) Parallel transitions, in which spin splitting and lambda doubling are ignored (ignoring spin splitting and/or lambda doubling means that the total multiple strength is assumed to reside in a single "effective" line), (2) Perpendicular transitions, in which spin splitting and lambda doubling are ignored, (3) Sigma Pi transitions, in which lambda doubling is ignored, (4) Atomic lines, (5) Option to terminate rotational line calculations when the molecule dissociates due to rotation, (6) Option to include the alternation of line intensities for homonuclear molecules, (7) Use of an approximate Voigt profile for the line shape, and (8) Radiative energy transport in a nonisothermal gas. The output options available in the program are: (1) Tabulation of the spontaneous emission spectrum (i.e., optically thin spectrum) for a 1.0 cm path length, (2) Tabulation of the "true" spectrum, which incorporates spontaneous emission, induced emission, absorption, and externally incident radiation through the equation of

  14. Absorption Line Profiles for 39 Rapidly Rotating Stars

    NASA Astrophysics Data System (ADS)

    Stoeckley, T. R.; Carroll, R. W.; Miller, R. D.

    1984-05-01

    Absorption lines of He II, HeI, MgII and other ions have been measured in 169 photographic coude spectra for 39 rapidly rotating B-type stars on the main sequence. All 1500 separate line profiles have been analysed with a procedure of differential corrections by least-squares to yield the following parameters and their error estimates: half-width, central depth, equivalent width and shape parameter. The shape parameter includes Voigt profiles and also `super-Gaussian' and `super-damping' profiles. Up to 15 separately measured line profiles in each star have been superimposed to yield better composite profiles with point scatter as small as 0.5 per cent. In addition, a preliminary value of V sin i is derived for each line of each star, and a mean value (including error bars) is derived for each star. Results are compared and discussed, with reference to forthcoming work incorporating stellar distortion, gravity darkening, and other second-order effects, which will allow determinations of axial inclination and differential rotation of individual stars, using the data sets presented here and elsewhere.

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

    PubMed

    Chandran, Satheesh; Varma, Ravi

    2016-01-15

    1, 4-Dioxane (DX) is a commonly found ether in industrially polluted atmosphere. The near infrared absorption spectra of this compound has been recorded in the region 5900-8230 cm(-1) with a resolution of 0.08 cm(-1) using a novel Fourier transform incoherent broadband cavity-enhanced absorption spectrometer (FT-IBBCEAS). All recorded spectra were found to contain regions that are only weakly perturbed. The possible combinations of fundamental modes and their overtone bands corresponding to selected regions in the measured spectra are tabulated. Two interesting spectral regions were identified as 5900-6400 cm(-1) and 8100-8230 cm(-1). No significant spectral interference due to presence of water vapor was observed suggesting the suitability of these spectral signatures for spectroscopic in situ detection of DX. The technique employed here is much more sensitive than standard Fourier transform spectrometer measurements on account of long effective path length achieved. Hence significant enhancement of weaker absorption lines above the noise level was observed as demonstrated by comparison with an available measurement from database. PMID:26474242

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

    NASA Astrophysics Data System (ADS)

    Chandran, Satheesh; Varma, Ravi

    2016-01-01

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

  17. Modeling of multi-exciton transient absorption spectra of protochlorophyllide aggregates in aqueous solution.

    PubMed

    Sytina, Olga A; Novoderezhkin, Vladimir I; van Grondelle, Rienk; Groot, Marie Louise

    2011-11-01

    Protochlorophyllide (Pchlide) is a natural porphyrin, a precursor of chlorophyll, synthesized by plants for its photosynthetic apparatus. The pigment spontaneously forms aggregates when dissolved in neat water solution. We present here calculations of the transient absorption spectra and its comprising components (ground-state bleach, stimulated emission, and excited-state absorption) for a strongly excitonically coupled linear chain of four Pchlide chromophores, using exciton theory with phenomenological Gaussian line shapes and without energetic disorder. A refined multiexciton model that includes static disorder is applied to fit the experimental power-dependent transient absorption spectra of aqueous protochlorophyllide and the kinetics for delay times up to 20 ps after photoexcitation. We show that population up to the 4-exciton manifold is sufficient to explain the pronounced saturation of the bleaching and the shape changes in the instantaneous, t = 0.2 ps transient spectra when the pulse energy is increased from 10 to 430 nJ per pulse. The decay of the multiexciton manifold is relatively slow and is preceded by a spectroscopically distinct process. We suggest that the exciton states in the Pchlide aggregates are mixed with charge-transfer states (CTS) and that the population and repopulation of the CTS coupled to the exciton states explains the relatively slow decay of the multiexciton manifold. The relevance of our results to the optical properties and dynamics of natural photosynthetic complexes and the possible physical origin of CTS formation are discussed. PMID:21936513

  18. Spectra extraction for wavelength-modulation spectroscopy of intra-cavity absorption gas sensor

    NASA Astrophysics Data System (ADS)

    Han, Wennian; Wang, Yan; Liu, Kun; Jia, Dagong; Liu, Tiegen

    2010-11-01

    Low-frequency wavelength modulation is introduced to increase sensitivity of intra-cavity absorption gas sensor (ICAGS) system. ICAGS system including erbium-doped fiber amplifier (EDFA), pump laser, tunable fiber Fabry-Perot (F-P) optical filter and gas cell is set up. Using virtual instrument technique, modulation function is generated by LabVIEW software and outputted through the AO ports of data acquisition card to tune the driving voltage of optical filter. The AI ports collect the laser power signals in a synchronous mode. Harmonic spectra can be computed by adopting the method of the Discrete Fourier Transform (DFT). According to the characteristics of different order harmonic, even harmonics and odd harmonics are analyzed respectively. Here, second harmonic is used to determine the spectral intensity, and third harmonic is mainly used to locate the position of spectral lines. With optimum 10 Hz frequency modulation, acetylene absorption experiments were carried out. The pump current of EDFA is 60 mA and the acetylene concentration in the gas cell is 1%. After spectra extraction, in the 1526 nm to 1537 nm wavelength range, 17 absorption lines of acetylene were achieved. The results indicated that the error of wavelength position is less than 0.1 nm and the minimum detection limit of acetylene is about 120x10-6. It is possible to realize the recognition of measured gas type and multi-component gas detection for ICAGS system.

  19. Laboratory verification of on-line lithium analysis using ultraviolet absorption spectrometry

    SciTech Connect

    Beemster, B.J.; Schlager, K.J.; Schloegel, K.M.; Kahle, S.J.; Fredrichs, T.L.

    1992-12-31

    Several laboratory experiments were performed to evaluate the capability of absorption spectrometry in the ultraviolet-visible wavelength range with the objective of developing methods for on-line analysis of lithium directly in the primary coolant of Pressurized Water Reactors using optical probes. Although initial laboratory tests seemed to indicate that lithium could be detected using primary absorption (detection of natural spectra unassisted by reagents), subsequent field tests demonstrated that no primary absorption spectra existed for lithium in the ultraviolet-visible wavelength range. A second series of tests that were recently conducted did, however, confirm results reported in the literature to the effect that reagents were available that will react with lithium to form chelates that possess detectable absorption and fluorescent signatures. These results point to the possible use of secondary techniques for on-line analysis of lithium.

  20. Infra-red absorption lines by molecules in grain mantles

    NASA Astrophysics Data System (ADS)

    Hagen, W.; Allamandola, L. J.; Greenberg, J. M.

    1980-06-01

    The laboratory spectrum of a solid mixture of H2O, CO, CH3OH, and NH3 at a temperature of 10 K reproduces the shape and peak positions of interstellar features. It is shown that the broad absorption features evident in the MIR spectra of some astronomical objects associated with interstellar dust can be explained by absorptions of molecules in grain mantles.

  1. An Inverse Modeling Approach to Estimating Phytoplankton Pigment Concentrations from Phytoplankton Absorption Spectra

    NASA Technical Reports Server (NTRS)

    Moisan, John R.; Moisan, Tiffany A. H.; Linkswiler, Matthew A.

    2011-01-01

    Phytoplankton absorption spectra and High-Performance Liquid Chromatography (HPLC) pigment observations from the Eastern U.S. and global observations from NASA's SeaBASS archive are used in a linear inverse calculation to extract pigment-specific absorption spectra. Using these pigment-specific absorption spectra to reconstruct the phytoplankton absorption spectra results in high correlations at all visible wavelengths (r(sup 2) from 0.83 to 0.98), and linear regressions (slopes ranging from 0.8 to 1.1). Higher correlations (r(sup 2) from 0.75 to 1.00) are obtained in the visible portion of the spectra when the total phytoplankton absorption spectra are unpackaged by multiplying the entire spectra by a factor that sets the total absorption at 675 nm to that expected from absorption spectra reconstruction using measured pigment concentrations and laboratory-derived pigment-specific absorption spectra. The derived pigment-specific absorption spectra were further used with the total phytoplankton absorption spectra in a second linear inverse calculation to estimate the various phytoplankton HPLC pigments. A comparison between the estimated and measured pigment concentrations for the 18 pigment fields showed good correlations (r(sup 2) greater than 0.5) for 7 pigments and very good correlations (r(sup 2) greater than 0.7) for chlorophyll a and fucoxanthin. Higher correlations result when the analysis is carried out at more local geographic scales. The ability to estimate phytoplankton pigments using pigment-specific absorption spectra is critical for using hyperspectral inverse models to retrieve phytoplankton pigment concentrations and other Inherent Optical Properties (IOPs) from passive remote sensing observations.

  2. Molecular structures and absorption spectra assignment of corrole NH tautomers.

    PubMed

    Beenken, Wichard; Presselt, Martin; Ngo, Thien H; Dehaen, Wim; Maes, Wouter; Kruk, Mikalai

    2014-02-01

    The individual absorption spectra of the two NH tautomers of 10-(4,6-dichloropyrimidin-5-yl)-5,15-dimesitylcorrole are assigned on the basis of the Gouterman four-orbital model and a quantum chemical TD-DFT study. The assignment indicates that the red-shifted T1 tautomer is the one with protonated pyrrole nitrogen atoms N(21), N(22) and N(23), whereas the blue-shifted T2 tautomer has pyrrole nitrogen atoms N(21), N(22) and N(24) protonated. A wave-like nonplanar distortion of the macrocycle in the ground state is found for both NH tautomers, with the wave axis going through the pyrroles containing N(22) and N(24). The 7C plane determined by the least-squares distances to the carbon atoms C1, C4, C5, C6, C9, C16, and C19 is suggested as a mean corrole macrocycle plane for the analysis of out-of-plane distortions. The magnitude of these distortions is distinctly different for the two NH tautomers, leading to substantial perturbations of their acid-base properties, which are rationalized by the interplay of the degree of out-of-plane distortion of the macrocycle as a whole and the tendency of the pyrrole nitrogen atoms toward pyramidalization, with the former leading to a basicity increase whereas the latter enhances the acidity. PMID:24432802

  3. The Hubble Space Telescope quasar absorption line key project. III - First observational results on Milky Way gas

    NASA Technical Reports Server (NTRS)

    Savage, Blair D.; Lu, Limin; Bahcall, John N.; Bergeron, Jacqueline; Boksenberg, Alec; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Lockman, Felix J.; Sargent, W. L. W.

    1993-01-01

    Absorption lines found near zero redshift due to Milky Way disk and halo gas in the spectra of 15 quasars observed with the Faint Object Spectrograph (FOS) of the HST at a resolution of about 230 km/s are reported. Results show that Milky Way absorption lines comprise about 44 percent of all absorption lines seen in the first group of Key Project FOS spectra. Milky Way lines were observed for 3C 273 and H1821 + 643. Limits to the Mg-to-H abundance ratio obtained for very high velocity Mg II absorption detections imply gas-phase Mg abundances for the very high velocity gas ranging from more than 0.059 to more than 0.32 times the solar abundance. In all cases where high-velocity H I emission is seen, corresponding high-velocity metal-line absorption is observed.

  4. Quasar Outflow Constraints using Broad Absorption Line Variability Studies

    NASA Astrophysics Data System (ADS)

    McGraw, Sean; Shields, Joseph C.; Hamann, Fred; Capellupo, Daniel M.; Gallagher, Sarah; Brandt, W. Niel; Herbst, Hanna

    2016-01-01

    Quasar outflows are plausible candidates for AGN feedback processes influencing the host galaxy and may explain the established correlations between the supermassive black hole (SMBH) and the surrounding bulge. In order to better understand feedback and the physical conditions of the outflowing gas, observational constraints on absorber kinematics and energetics are needed. We are utilizing multiple epoch, rest frame UV quasar spectra to establish limits on outflow locations and total column densities for the purpose of estimating wind kinetic energies and momenta. We are also investigating the variability patterns of broad absorption lines (BALs) and mini-BALs across a range of ionization states to probe underlying connections between the various classes of absorbers. This work employs observations from the Sloan Digital Sky Survey, Hobby Eberly Telescope, and MDM observatory. We detect BAL variability in 3 out of 12 FeLoBAL quasars over multiple year timescales and conclude that the variable absorbers lie within tens of parsecs of the SMBH based on interpretations of the Fe II and Mg II BALS. We also measure significant BAL changes across daily to yearly timescales in a sample of 71 quasars with plausible detections of the P V 1117,1128 BAL. Detecting phosphorus in absorption is notable because it traces high column density outflows and is therefore relevant for studying AGN feedback. Constraints on outflow energetics and other selected results will be presented.

  5. Discovery of Broad Soft X-ray Absorption Lines from the Quasar Wind in PDS 456

    NASA Astrophysics Data System (ADS)

    Reeves, J. N.; Braito, V.; Nardini, E.; Behar, E.; O’Brien, P. T.; Tombesi, F.; Turner, T. J.; Costa, M. T.

    2016-06-01

    High-resolution soft X-ray spectroscopy of the prototype accretion disk wind quasar, PDS 456, is presented. Here, the XMM-Newton reflection grating spectrometer spectra are analyzed from the large 2013–2014 XMM-Newton campaign, consisting of five observations of approximately 100 ks in length. During the last observation (OBS. E), the quasar is at a minimum flux level, and broad absorption line (BAL) profiles are revealed in the soft X-ray band, with typical velocity widths of {σ }{{v}}˜ {{10,000}} km s‑1. During a period of higher flux in the third and fourth observations (OBS. C and D, respectively), a very broad absorption trough is also present above 1 keV. From fitting the absorption lines with models of photoionized absorption spectra, the inferred outflow velocities lie in the range ˜ 0.1{--}0.2c. The absorption lines likely originate from He and H-like neon and L-shell iron at these energies. A comparison with earlier archival data of PDS 456 also reveals a similar absorption structure near 1 keV in a 40 ks observation in 2001, and generally the absorption lines appear most apparent when the spectrum is more absorbed overall. The presence of the soft X-ray BALs is also independently confirmed by an analysis of the XMM-Newton EPIC spectra below 2 keV. We suggest that the soft X-ray absorption profiles could be associated with a lower ionization and possibly clumpy phase of the accretion disk wind, where the latter is known to be present in this quasar from its well-studied iron K absorption profile and where the wind velocity reaches a typical value of 0.3c.

  6. Dielectric tensor of tetracene single crystals: the effect of anisotropy on polarized absorption and emission spectra.

    PubMed

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

    2008-04-21

    The full UV-visible dielectric tensor and the corresponding directions of the principal axes of triclinic tetracene crystals are reported as deduced either by polarized absorption and ellipsometry measurements or by calculations based on the molecular and crystallographic data. The results allow the attribution of the polarized bands observed in both absorption and photoluminescence emission spectra. In particular, the spectral line shape and polarization of the emission are found to depend on the sample thickness, and the effect is attributed to the modification of the state of polarization of the emitted light during its propagation inside the crystal. Indeed, the directions of polarization of the lowest optical transitions and the directions of the principal axes of the dielectric tensor are demonstrated not to coincide, in contrast to the assumptions typically made in the literature, thus causing the mixed transverse/longitudinal character of light propagation. PMID:18433260

  7. QSO Lyalpha Absorption Lines in Galaxy Superclusters and Voids

    NASA Astrophysics Data System (ADS)

    Stocke, J. T.; Shull, J. M.; Penton, S.; Burks, G.; Donahue, M.

    1993-12-01

    We have used the Hubble Space Telescope (HST) Goddard High Resolution Spectrograph (GHRS) to search for Lyalpha absorption clouds in nearby galaxy voids (cz <= 10,000 km s(-1) ). Thus far, we have obtained GHRS spectra (G160M, 1225 -- 1255 Angstroms, 0.25 Angstroms resolution) of three very bright Active Galactic Nuclei, Mrk 501, I Zw I, and Mrk 335, at V <= 14.5. We find 4 probable (4.0 sigma - 4.5 sigma ) and 4 definite (5 sigma - 16 sigma ) Lyalpha absorption lines, with equivalent widths W_λ = 50 - 200 m Angstroms, corresponding to column densities N(H I) = 10(13) -- 10(14) cm(-2) , assuming a typical Doppler parameter of b = 25 km s(-1) . Based on an updated version of the CfA redshift survey (Huchra and Clemens, private communication), most of these Lyalpha systems appear to be associated with supercluster - sized ``strings'' of galaxies similar to the ``Great Wall''. Toward Mrk 501, the nearest bright galaxy at the redshift of the strongest (200 m Angstroms) Lyalpha cloud lies 500 h75(-1) kpc off the line of sight. Models of H I disks exposed to the intergalactic ionizing radiation field (Dove & Shull 1994, ApJ, 423, in press) show that the N(H I) = 10(13) cm(-2) contour in a typical spiral galaxy is reached at 100 kpc radial extent. Thus, the Lyalpha absorbers associated with galaxy-string systems may be the result of H I in an extended halo, in dwarf satellite galaxies (M_B > -15), or in tidally-stripped gas. Most importantly for cosmological origins of baryons, one (4.3 sigma ) Lyalpha absorption line in the spectrum of Mrk 501 lies within the galaxy void in the foreground of the ``Great Wall''. The nearest bright galaxy, to a level M_B <= -18.5 for H_0 = 75 km s(-1) Mpc(-1) , is more than 5 Mpc away. A pencil-beam survey of faint galaxies to M_B = -16.0 finds no galaxy within 100 h75(-1) kpc of the line of sight, at or near the absorber redshift.

  8. The effect of ionization on the infrared absorption spectra of PAHs: A preliminary report

    NASA Technical Reports Server (NTRS)

    Defrees, Doug J.; Miller, M. D.

    1989-01-01

    The emission lines observed in many interstellar IR sources at 3.28, 6.2, 7.7, 8.7, and 11.3 microns are theorized to originate from polycyclic aromatic hydrocarbons (PAHs). These assignments are based on analyses of lab IR spectra of neutral PAHs. However, it is likely that in the interstellar medium that PAHs are ionized, i.e., are positively charged. Besides, as pointed out by Allamandola et al., although the IR emission band spectrum resembles what one might expect from a mixture of PAHs, it does not match in details such as frequency, band profile, or relative intensities predicted from the absorption spectra of any known PAH molecule. One source of more information to test the PAH theory is ab initio molecular orbital theory. It can be used to compute, from first principles, the geometries, vibrational frequencies, and vibrational intensities for model PAH compounds which are difficult to study in the lab. The Gaussian 86 computer program was used to determine the effect of ionization on the infrared absorption spectra of several small PAHs: naphthalene and anthracene. A preliminary report is presented of the results of these calculations.

  9. Evidence for Active Galactic Nucleus Feedback in the Broad Absorption Lines and Reddening of Mrk 231

    NASA Astrophysics Data System (ADS)

    Leighly, Karen M.; Terndrup, Donald M.; Baron, Eddie; Lucy, Adrian B.; Dietrich, Matthias; Gallagher, Sarah C.

    2014-06-01

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

  10. Line shape studies in CW dye laser intracavity absorption

    NASA Astrophysics Data System (ADS)

    Kumar, P.; Brink, G. O.; Spence, S.; Lakkaraju, H. S.

    1980-01-01

    The line shape of the signals observed by intracavity absorption in an atomic beam of barium is studied as a function of absorber density. Complex structure is observed consisting of both absorption and enhancement features. Comparison is made with models of intracavity absorption, and it is concluded that the rate equation model in its present form does not explain the structure. On the other hand the super-regen model does seem able to partially account for the observed structure. The complexity of the line shape will directly affect those workers who are using intracavity absorption as a spectroscopic technique.

  11. CRIRES spectroscopy and empirical line-by-line identification of FeH molecular absorption in an M dwarf

    NASA Astrophysics Data System (ADS)

    Wende, S.; Reiners, A.; Seifahrt, A.; Bernath, P. F.

    2010-11-01

    Molecular FeH provides a large number of sharp and isolated absorption lines that can be used to measure radial velocity, rotation, or magnetic field strength with high accuracy. Our aim is to provide an FeH atlas for M-type stars in the spectral region from 986 nm to 1077 nm (Wing-Ford band). To identify these lines in CRIRES spectra of the magnetically inactive, slowly rotating, M5.5 dwarf GJ1002, we calculated model spectra for the selected spectral region with theoretical FeH line data. In general this line list agrees with the observed data, but several individual lines differ significantly in position or in line strength. After identification of as many as possible FeH lines, we corrected the line data for position and line strength to provide an accurate atlas of FeH absorption lines for use in high precision spectroscopy of low mass stars. For all lines, we used a Voigt function to obtain their positions and equivalent widths. Identification with theoretical lines was done by hand. For confirmation of the identified lines, we used statistical methods, cross-correlation techniques, and line intensities. Eventually, we were able to identify FeH lines from the (0,0), (1,0), (1,1), (2,1), (2,2), (3,2), and (4,3) vibrational bands in the observed spectra and correct the positions of the lines if necessary. The deviations between theoretical and observed positions follow a normal distribution approximately around zero. In order to empirically correct the line strength, we determined Teff, instrumental broadening (rotational broadening) and a van der Waals enhancement factor for the FeH lines in GJ1002. We also give the scaling factors for the Einstein A values to correct the line strengths. With the identified lines, we derived rotational temperatures from the line intensities for GJ1002. We conclude that FeH lines can be used for a wide variety of applications in astrophysics. With the identified lines it will be possible for example to characterize magnetically

  12. Outflow and hot dust emission in broad absorption line quasars

    SciTech Connect

    Zhang, Shaohua; Zhou, Hongyan; Wang, Huiyuan; Wang, Tinggui; Xing, Feijun; Jiang, Peng; Zhang, Kai E-mail: whywang@mail.ustc.edu.cn

    2014-05-01

    We have investigated a sample of 2099 broad absorption line (BAL) quasars with z = 1.7-2.2 built from the Sloan Digital Sky Survey Data Release Seven and the Wide-field Infrared Survey. This sample is collected from two BAL quasar samples in the literature and is refined by our new algorithm. Correlations of outflow velocity and strength with a hot dust indicator (β{sub NIR}) and other quasar physical parameters—such as an Eddington ratio, luminosity, and a UV continuum slope—are explored in order to figure out which parameters drive outflows. Here β{sub NIR} is the near-infrared continuum slope, which is a good indicator of the amount of hot dust emission relative to the accretion disk emission. We confirm previous findings that outflow properties moderately or weakly depend on the Eddington ratio, UV slope, and luminosity. For the first time, we report moderate and significant correlations of outflow strength and velocity with β{sub NIR} in BAL quasars. It is consistent with the behavior of blueshifted broad emission lines in non-BAL quasars. The statistical analysis and composite spectra study both reveal that outflow strength and velocity are more strongly correlated with β{sub NIR} than the Eddington ratio, luminosity, and UV slope. In particular, the composites show that the entire C IV absorption profile shifts blueward and broadens as β{sub NIR} increases, while the Eddington ratio and UV slope only affect the high and low velocity part of outflows, respectively. We discuss several potential processes and suggest that the dusty outflow scenario, i.e., that dust is intrinsic to outflows and may contribute to the outflow acceleration, is most likely.

  13. Shape of the absorption and fluorescence spectra of condensed phases and transition energies.

    PubMed

    Lagos, Miguel; Paredes, Rodrigo

    2014-11-13

    General integral expressions for the temperature-dependent profile of the spectral lines of photon absorption and emission by atomic or molecular species in a condensed environment are derived with no other hypothesis than: (a) The acoustic vibrational modes of the condensed host medium constitute the thermodynamic energy reservoir at a given constant temperature, and local electronic transitions modifying the equilibrium configuration of the surroundings are multiphonon events, regardless of the magnitude of the transition energy. (b) Electron-phonon coupling is linear in the variations of the bond length. The purpose is to develop a theoretical tool for the analysis of the spectra, allowing us to grasp highly accurate information from fitting the theoretical line shape function to experiment, including those spectra displaying wide features. The method is illustrated by applying it to two dyes, Lucifer Yellow CH and Coumarin 1, which display fluorescence maxima of 0.41 and 0.51 eV fwhm. Fitting the theoretical curves to the spectra indicates that the neat excitation energies are 2.58 eV ± 2.5% and 3.00 eV ± 2.0%, respectively. PMID:25321927

  14. Radio line and continuum observations of quasar-galaxy pairs and the origin of low reshift quasar absorption line systems

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Vangorkom, J. H.; Hauxthausen, E. M.; Stocke, J. T.; Salzer, J.

    1990-01-01

    There are a number of known quasars for which our line of sight to the high redshift quasar passes within a few Holmberg radii of a low redshift galaxy. In a few of these cases, spectra of the quasar reveal absorption by gas associated with the low redshift galaxy. A number of these pairs imply absorption by gas which lies well outside the optical disk of the associated galaxy, leading to models of galaxies with 'halos' or 'disks' of gas extending to large radii. The authors present observations of 4 such pairs. In three of the four cases, they find that the associated galaxy is highly disturbed, typically due to a gravitational interaction with a companion galaxy, while in the fourth case the absorption can be explained by clouds in the optical disk of the associated galaxy. They are led to an alternative hypothesis concerning the origin of the low redshift absorption line systems: the absorption is by gas clouds which have been gravitationally stripped from the associated galaxy. These galaxies are rapidly evolving, and should not be used as examples of absorption by clouds in halos of field spirals. The authors conclude by considering the role extended gas in interacting systems plays in the origin of higher redshift quasar absorption line systems.

  15. The η Car Campaign with UVES at the ESO VLT II. Interstellar and circumstellar absorption lines

    NASA Astrophysics Data System (ADS)

    Weis, K.; Bomans, D. J.; Stahl, O.; Davidson, K.; Humphreys, R. M.; Gull, T. R.

    2005-09-01

    We monitored η Car and the Homunculus using the ESO VLT UVES spectrograph between 2002 and 2004 (see Weis et al., this proceedings). In these high dispersion spectra practically all interstellar absorption features known in the 3000 Å to 10000 Å regime are present (e.g. 4 Ti II lines, 3 Fe I lines, the Ca I line, both Na I doublets, the two K I doublets, and the Ca II doublets, several molecular lines, and a number of diffuse interstellar bands). Near-UV STIS spectra show many low ionization absorption lines (e.g. Gull et al., this proceedings), but there are several differences in the velocity structure and line strengths between these lines of sight, e.g. we do not detect multiple absorption components between -350 to -550 km s-1 in the UVES spectra. Changes over time are present in e.g. the Ca II lines, with small column density changes in the (probably interstellar) +80 km s-1 component and large changes in the -510 km s-1 component, which is most probably located in the outer shell of the Homunculus (see e.g. Nielsen et al., this proceedings). Similar changes in the Ti II 3384 Å component at -147 km s-1 are present, too. With the data set, we not only follow the temporal evolution of the circumstellar absorption components (presumably originating near η Car and in the Homunculus) before, during and after the event, but also search for changes along our long-slits centered on the star and on FOS4. Indeed, the -147 km s-1 component of the Ti II 3384 Å lines shows line strength variations over the southeast lobe of the Homunculus. A preliminary search for very high velocity absorption lines from the outer ejected using only one of our spectra already yielded a possible detection at -1500 km s-1. Clearly a detailed analysis of the absorption lines in the UVES data will provide many new insights into the structure and physics of η Car's ejecta.

  16. Photon interference effect in x-ray absorption spectra over a wide energy range

    NASA Astrophysics Data System (ADS)

    Nishino, Y.; Ishikawa, T.; Suzuki, M.; Kawamura, N.; Kappen, P.; Korecki, P.; Haack, N.; Materlik, G.

    2002-09-01

    We consider fundamental structures in x-ray absorption spectra over a wide energy range. We formulate the elastic scattering in addition to the photoelectric absorption in recently reported photon interference x-ray absorption fine structure (πXAFS). The simulations show excellent agreement with experimental x-ray absorption spectra for platinum and tungsten powders far above and below the L absorption edges. πXAFS can be as big as in the order of 10% of XAFS, and cannot be easily neglected in detailed analysis of XAFS and related phenomena.

  17. PG 1700 + 518 - a low-redshift, broad absorption line QSO

    SciTech Connect

    Pettini, M.; Boksenberg, A.

    1985-07-01

    The first high-resolution optical spectra and lower resolution UV spectra of PG 1700 + 518, the only known broad-absorption-line (BAL) QSO at low emission redshift (0.288) are presented. The optical data were obtained with the Isaac Newton Telescope on the island of La Palma and the UV data with the International Ultraviolet Explorer satellite. The outstanding feature of the optical spectrum is a strong, broad Mg II absorption trough, detached from the Mg II emission line and indicative of ejection velocities of between 7000 and 18,000 km/s. Also detected were narrow (FWHM = 350 km/s) Mg II absorption lines at absolute z = 0.2698, which are probably related to the mass ejection phenomenon. It is concluded that the emission-line spectrum is similar to that of other low-redshift QSOs although there are some obvious differences from typical BAL QSOs, most notably in the unusually low level of ionization of both emission-line and broad absorption line gas. 21 references.

  18. Spectro web: oscillator strength measurements of atomic absorption lines in the sun and procyon

    NASA Astrophysics Data System (ADS)

    Lobel, A.

    2008-10-01

    We update the online SpectroWeb database of spectral standard reference stars with 1178 oscillator strength values of atomic absorption lines observed in the optical spectrum of the Sun and Procyon (α CMi A). The updated line oscillator strengths are measured with best fits to the disk-integrated KPNO-FTS spectrum of the Sun observed between 4000 Å and 6800 Å using state-of-the-art detailed spectral synthesis calculations. A subset of 660 line oscillator strengths is validated with synthetic spectrum calculations of Procyon observed with ESO-UVES between 4700 Å and 6800 Å. The new log(gf)-values in SpectroWeb are improvements upon the values offered in the online Vienna Atomic Line Database (VALD). We find for neutral iron-group elements, such as Fe I, Ni I, Cr I, and Ti I, a statistically significant over-estimation of the VALD log((gf)-values for weak absorption lines with normalized central line depths below 15 %. For abundant lighter elements (e.g. Mg I and Ca I) this trend is statistically not significantly detectable, with the exception of Si I for which the log(gf)-values of 60 weak and medium-strong lines are substantially decreased to best fit the observed spectra. The newly measured log(gf)-values are available in the SpectroWeb database at http://spectra.freeshell.org, which interactively displays the observed and computed stellar spectra, together with corresponding atomic line data.

  19. The relativistic Doppler broadening of the line absorption profile

    NASA Astrophysics Data System (ADS)

    Kichenassamy, S.; Krikorian, R.; Nikogosian, A.

    1982-06-01

    The classical results of Doppler broadening of the line absorption profile are generalized to a relativistic gas in thermal equilibrium by taking into account the relativistic variance of the volume absorption coefficients of the gas, as derived by L. H. Thomas. This variance produces a small correction, even in the non-relativistic approximation.

  20. Low-Cost Elimination of Plasma Lines in Raman Spectra.

    ERIC Educational Resources Information Center

    Behlow, Herbert W., Jr.; Petersen, John D.

    1985-01-01

    Describes a low-cost ($120) device which eliminates plasma lines in Raman spectra. The device consists of two prisms and two mirrors which are held in a symmetrical relationship to one another so that a particular position will allow only one wavelength to pass through on a given axis. (JN)

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

    PubMed

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

    2014-05-14

    Time-dependent density functional theory (TDDFT) has been used to predict the absorption spectra of cation-π complexes of benzene and borazine. Both polarized continuum model (PCM) and discrete solvation model (DSM) and a combined effect of PCM and DSM on the absorption spectra have been elucidated. With decrease in size of the cation, the π → π* transitions of benzene and borazine are found to undergo blue and red shift, respectively. A number of different substituents (both electron-withdrawing and electron-donating) and a range of solvents (nonpolar to polar) have been considered to understand the effect of substituent and solvents on the absorption spectra of the cation-π complexes of benzene and borazine. Red shift in the absorption spectra of benzene cation-π complexes are observed with both electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). The same trend has not been observed in the case of substituted borazine cation-π complexes. The wavelength of the electronic transitions corresponding to cation-π complexes correlates well with the Hammet constants (σp and σm). This correlation indicates that the shifting of spectral lines of the cation-π complexes on substitution is due to both resonance and inductive effect. On incorporation of solvent phases, significant red or blue shifting in the absorption spectra of the complexes has been observed. Kamlet-Taft multiparametric equation has been used to explain the effect of solvent on the absorption spectra of complexes. Polarity and polarizability are observed to play an important role in the solvatochromism of the cation-π complexes. PMID:24801959

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

    NASA Astrophysics Data System (ADS)

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

    1993-03-01

    effective methods for eliminating contamination of Martian surface spectra by absorption in the solar, terrestrial, and Martian atmospheres. Both methods involve the use of very-high-resolution spectra that completely resolve the narrow atmospheric absorption lines.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    effective methods for eliminating contamination of Martian surface spectra by absorption in the solar, terrestrial, and Martian atmospheres. Both methods involve the use of very-high-resolution spectra that completely resolve the narrow atmospheric absorption lines.

  4. Broad absorption line variability in radio-loud quasars

    NASA Astrophysics Data System (ADS)

    Welling, C. A.; Miller, B. P.; Brandt, W. N.; Capellupo, D. M.; Gibson, R. R.

    2014-05-01

    We investigate C IV broad absorption line (BAL) variability within a sample of 46 radio-loud quasars (RLQs), selected from Sloan Digital Sky Survey (SDSS)/Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) data to include both core-dominated (39) and lobe-dominated (7) objects. The sample consists primarily of high-ionization BAL quasars, and a substantial fraction have large BAL velocities or equivalent widths; their radio luminosities and radio-loudness values span ˜2.5 orders of magnitude. We have obtained 34 new Hobby-Eberly Telescope spectra of 28 BAL RLQs to compare to earlier SDSS data, and we also incorporate archival coverage (primarily dual-epoch SDSS) for a total set of 78 pairs of equivalent width measurements for 46 BAL RLQs, probing rest-frame time-scales of ˜80-6000 d (median 500 d). In general, only modest changes in the depths of segments of absorption troughs are observed, akin to those seen in prior studies of BAL radio-quiet quasars (RQQs). Also similar to previous findings for RQQs, the RLQs studied here are more likely to display BAL variability on longer rest-frame time-scales. However, typical values of |{Δ}EW| and |{Δ}EW|/ are ˜40 ± 20 per cent lower for BAL RLQs when compared with those of a time-scale-matched sample of BAL RQQs. Optical continuum variability is of similar amplitude in BAL RLQs and BAL RQQs; for both RLQs and RQQs, continuum variability tends to be stronger on longer time-scales. BAL variability in RLQs does not obviously depend upon their radio luminosities or radio-loudness values, but we do find tentative evidence for greater fractional BAL variability within lobe-dominated RLQs. Enhanced BAL variability within more edge-on (lobe-dominated) RLQs supports some geometrical dependence to the outflow structure.

  5. The Hubble Space Telescope quasar absorption line key project. II - Data calibration and absorption-line selection

    NASA Technical Reports Server (NTRS)

    Schneider, Donald P.; Hartig, George F.; Jannuzi, Buell T.; Kirhakos, Sofia; Saxe, David H.; Weymann, Ray J.; Bahcall, John N.; Bergeron, Jacqueline; Boksenberg, Alec; Sargent, W. L. W.

    1993-01-01

    We present the observational and data processing aspects of the Hubble Space Telescope Quasar Absorption Line Key Project. Topics discussed include the observational technique, calibration of the data, software that simulates the data, the automated procedure used to identify and characterize the absorption features, and the determination of the sensitivity limits of the survey.

  6. Interpretation of NO2 absorption in twilight sky spectra

    NASA Astrophysics Data System (ADS)

    McMahon, B. B.

    1984-07-01

    A multiple scattering model has been developed to calculate nitrogen dioxide (NO2) absorption in the light from the zenith sky during twilight. Model studies show that this absorption is not very sensitive to the atmospheric temperature profile or to tropospheric NO2. The model was used to interpret some ground-based measurements of NO2 sky absorption. Values for the total stratospheric column amount vary from 2 to 12 x 10 to the 15th molec/sq cm, and the mean altitude of the stratospheric concentration profile is around 35 km. These observations are in broad agreement with those of other workers.

  7. Intracavity absorption line shape and the super-regen model

    NASA Astrophysics Data System (ADS)

    Lewellen, L. R.; Brink, G. O.

    1981-10-01

    Intracavity absorption has been observed in a short lived excited state of helium produced in an RF discharge inside the dye laser cavity. The line shape consists of an absorption feature with two symmetric enhancement wings. The central absorption feature is considerably broadened over the natural width, and this is shown to be in agreement with the superregen model. It is also shown that under certain conditions the ICA signal inverts so that the central feature becomes enhanced and the symmetric wings appear as absorption. This result is also in agreement with predictions of the model.

  8. The bispectrum of the Lyman α forest at z~ 2-2.4 from a large sample of UVES QSO absorption spectra (LUQAS)

    NASA Astrophysics Data System (ADS)

    Viel, M.; Matarrese, S.; Heavens, A.; Haehnelt, M. G.; Kim, T.-S.; Springel, V.; Hernquist, L.

    2004-01-01

    We present a determination of the bispectrum of the flux in the Lyman α forest of quasi-stellar object (QSO) absorption spectra obtained from a large sample of Ultraviolet Echelle Spectrograph (UVES) QSO absorption spectra (LUQAS), which consists of spectra observed with the high-resolution UVES. Typical errors on the observed bispectrum as obtained from a jack-knife estimator are ~ 50 per cent. For wavenumbers in the range 0.03 < k < 0.1 s km-1 the observed bispectrum agrees within the errors with that of the synthetic absorption spectra obtained from numerical hydro-simulations of a ΛCDM model with and without feedback from star formation. Including galactic feedback changes the bispectrum by less than 10 per cent. At smaller wavenumbers, the associated metal absorption lines contribute about 50 per cent to the bispectrum and the observed bispectrum exceeds that of the simulations. At wavenumbers k < 0.03 s km-1, second-order perturbation theory applied to the flux spectrum gives a reasonable (errors smaller than 30 per cent) approximation to the bispectra of observed and simulated absorption spectra. The bispectrum of the observed absorption spectra also agrees, within the errors, with that of a randomized set of absorption spectra where a random shift in wavelength has been added to absorption lines identified with VPFIT. This suggests that for a sample of the size presented here, the errors on the bispectrum are too large to discriminate between models with very different 3D distribution of Lyman α absorption. If it were possible to substantially reduce these errors for larger samples of absorption spectra, the bispectrum might become an important statistical tool for probing the growth of gravitational structure in the Universe at redshift z>~ 2.

  9. SIMPLE MODELS OF METAL-LINE ABSORPTION AND EMISSION FROM COOL GAS OUTFLOWS

    SciTech Connect

    Prochaska, J. Xavier; Rubin, Kate

    2011-06-10

    We analyze the absorption and emission-line profiles produced by a set of simple, cool gas wind models motivated by galactic-scale outflow observations. We implement Monte Carlo radiative transfer techniques that track the propagation of scattered and fluorescent photons to generate one-dimensional spectra and two-dimensional spectral images. We focus on the Mg II {lambda}{lambda}2796, 2803 doublet and Fe II UV1 multiplet at {lambda} {approx} 2600 A, but the results are applicable to other transitions that trace outflows (e.g., Na I, H I Ly{alpha}, Si II). By design, the resonance transitions show blueshifted absorption but one also predicts strong resonance and fine-structure line emission at roughly the systemic velocity. This line-emission 'fills in' the absorption, reducing the equivalent width by up to 50%, shifting the absorption-line centroid by tens of km s{sup -1}, and reducing the effective opacity near systemic. Analysis of cool gas outflows that ignores this line emission may incorrectly infer that the gas is partially covered, measure a significantly lower peak optical depth, and/or conclude that gas at systemic velocity is absent (e.g., an interstellar or slowly infalling component). Because the Fe II lines are connected by optically thin transitions to fine-structure levels, their profiles more closely reproduce the intrinsic opacity of the wind. Together these results naturally explain the absorption and emission-line characteristics observed for star-forming galaxies at z < 1. We also study a scenario promoted to describe the outflows of z {approx} 3 Lyman break galaxies and find profiles inconsistent with the observations due to scattered photon emission. Although line emission complicates the analysis of absorption-line profiles, the surface brightness profiles offer a unique means of assessing the morphology and size of galactic-scale winds. Furthermore, the kinematics and line ratios offer powerful diagnostics of outflows, motivating deep

  10. Simple Models of Metal-line Absorption and Emission from Cool Gas Outflows

    NASA Astrophysics Data System (ADS)

    Prochaska, J. Xavier; Kasen, Daniel; Rubin, Kate

    2011-06-01

    We analyze the absorption and emission-line profiles produced by a set of simple, cool gas wind models motivated by galactic-scale outflow observations. We implement Monte Carlo radiative transfer techniques that track the propagation of scattered and fluorescent photons to generate one-dimensional spectra and two-dimensional spectral images. We focus on the Mg II λλ2796, 2803 doublet and Fe II UV1 multiplet at λ ≈ 2600 Å, but the results are applicable to other transitions that trace outflows (e.g., Na I, H I Lyα, Si II). By design, the resonance transitions show blueshifted absorption but one also predicts strong resonance and fine-structure line emission at roughly the systemic velocity. This line-emission "fills in" the absorption, reducing the equivalent width by up to 50%, shifting the absorption-line centroid by tens of km s-1, and reducing the effective opacity near systemic. Analysis of cool gas outflows that ignores this line emission may incorrectly infer that the gas is partially covered, measure a significantly lower peak optical depth, and/or conclude that gas at systemic velocity is absent (e.g., an interstellar or slowly infalling component). Because the Fe II lines are connected by optically thin transitions to fine-structure levels, their profiles more closely reproduce the intrinsic opacity of the wind. Together these results naturally explain the absorption and emission-line characteristics observed for star-forming galaxies at z < 1. We also study a scenario promoted to describe the outflows of z ~ 3 Lyman break galaxies and find profiles inconsistent with the observations due to scattered photon emission. Although line emission complicates the analysis of absorption-line profiles, the surface brightness profiles offer a unique means of assessing the morphology and size of galactic-scale winds. Furthermore, the kinematics and line ratios offer powerful diagnostics of outflows, motivating deep, spatially extended spectroscopic

  11. THE VIEWING ANGLES OF BROAD ABSORPTION LINE VERSUS UNABSORBED QUASARS

    SciTech Connect

    DiPompeo, M. A.; Brotherton, M. S.; De Breuck, C.

    2012-06-10

    It was recently shown that there is a significant difference in the radio spectral index distributions of broad absorption line (BAL) quasars and unabsorbed quasars, with an overabundance of BAL quasars with steeper radio spectra. This result suggests that source orientation does play into the presence or absence of BAL features. In this paper, we provide more quantitative analysis of this result based on Monte Carlo simulations. While the relationship between viewing angle and spectral index does indeed contain a lot of scatter, the spectral index distributions are different enough to overcome that intrinsic variation. Utilizing two different models of the relationship between spectral index and viewing angle, the simulations indicate that the difference in spectral index distributions can be explained by allowing BAL quasar viewing angles to extend about 10 Degree-Sign farther from the radio jet axis than non-BAL sources, though both can be seen at small angles. These results show that orientation cannot be the only factor determining whether BAL features are present, but it does play a role.

  12. Absolute absorption on the potassium D lines: theory and experiment

    NASA Astrophysics Data System (ADS)

    Hanley, Ryan K.; Gregory, Philip D.; Hughes, Ifan G.; Cornish, Simon L.

    2015-10-01

    We present a detailed study of the absolute Doppler-broadened absorption of a probe beam scanned across the potassium D lines in a thermal vapour. Spectra using a weak probe were measured on the 4S \\to 4P transition and compared to the theoretical model of the electric susceptibility detailed by Zentile et al (2015 Comput. Phys. Commun. 189 162-74) in the code named ElecSus. Comparisons were also made on the 4S \\to 5P transition with an adapted version of ElecSus. This is the first experimental test of ElecSus on an atom with a ground state hyperfine splitting smaller than that of the Doppler width. An excellent agreement was found between ElecSus and experimental measurements at a variety of temperatures with rms errors ˜ {10}-3. We have also demonstrated the use of ElecSus as an atomic vapour thermometry tool, and present a possible new measurement technique of transition decay rates which we predict to have a precision of ˜3 {kHz}.

  13. Absorption spectra of graphene nanoribbons in a composite magnetic field

    NASA Astrophysics Data System (ADS)

    Li, T. S.; Wu, M. F.; Hsieh, C. T.

    2015-10-01

    The low-frequency optical absorption properties of graphene nanoribbons in a composite magnetic field are investigated by using the gradient approximation. The spectral function exhibits symmetric delta-function like prominent peaks structure in a uniform magnetic field, and changes to asymmetric square-root divergent peaks structure when subjecting to a composite field. These asymmetric divergent peaks can be further classified into principal and secondary peaks. The spectral intensity and frequency of the absorption peaks depend sensitively on the strength and modulation period of the composite field. The transition channels of the absorption peaks are also analyzed. There exists an optical selection rule which is caused by the orthogonal properties of the sublattice wave functions. The evolution of the spectral frequency of the absorption peaks with the field strength is explored.

  14. NEW Fe I LEVEL ENERGIES AND LINE IDENTIFICATIONS FROM STELLAR SPECTRA

    SciTech Connect

    Peterson, Ruth C.; Kurucz, Robert L.

    2015-01-01

    The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond. Measurements of the energies of its high-lying levels remain woefully incomplete, however, despite extensive laboratory and solar analysis. In this work, we use high-resolution archival absorption-line ultraviolet and optical spectra of stars whose warm temperatures favor moderate Fe I excitation. We derive the energy for a particular upper level in Kurucz's semiempirical calculations by adopting a trial value that yields the same wavelength for a given line predicted to be about as strong as that of a strong unidentified spectral line observed in the stellar spectra, then checking the new wavelengths of other strong predicted transitions that share the same upper level for coincidence with other strong observed unidentified lines. To date, this analysis has provided the upper energies of 66 Fe I levels. Many new energy levels are higher than those accessible to laboratory experiments; several exceed the Fe I ionization energy. These levels provide new identifications for over 2000 potentially detectable lines. Almost all of the new levels of odd parity include UV lines that were detected but unclassified in laboratory Fe I absorption spectra, providing an external check on the energy values. We motivate and present the procedure, provide the resulting new energy levels and their uncertainties, list all the potentially detectable UV and optical new Fe I line identifications and their gf values, point out new lines of astrophysical interest, and discuss the prospects for additional Fe I energy level determinations.

  15. Phase speed spectra of transient eddy fluxes and critical layer absorption

    NASA Technical Reports Server (NTRS)

    Randel, William J.; Held, Isaac M.

    1991-01-01

    Tropospheric zonal mean eddy fluxes of heat and momentum, and the divergence of the Eliassen-Palm flux, are decomposed into contributions from different zonal phase speeds. Data analyzed are the European Center for Medium Range Weather Forecasts operational global analyses covering 1980-1987. Eastward moving medium-scale waves (zonal waves 4-7) dominate the spectra of lower tropospheric heat fluxes in both hemispheres and all seasons. Upper tropospheric wave flux spectra are similar to the low level spectra in midlatitudes, but shift to slower zonal phase speeds as low latitudes are approached. The cause of this shift is the selective absorption of faster moving components in midlatitudes as the waves propagate meridionally. Latitude-phase speed distributions of eddy fluxes are constructed and compared to the zonal mean wind structure. These results demonstrate that upper tropospheric eddies break and decelerate the zonal mean flow approximately 10-20 deg in latitude away from their critical line (where phase speed equals zonal wind speed). Comparisons are also made with results from the middle stratosphere.

  16. Assignment of benzodiazepine UV absorption spectra by the use of photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Khvostenko, O. G.; Tzeplin, E. E.; Lomakin, G. S.

    2002-04-01

    Correlations between singlet transition energies and energy gaps of corresponding pairs of occupied and unoccupied molecular orbitals were revealed in a series of benzodiazepines. The occupied orbital energies were taken from the photoelectron spectra of the compound investigated, the unoccupied ones were obtained from MNDO/d calculations, and the singlet energies were taken from the UV absorption spectra. The correspondence of the singlet transitions to certain molecular orbitals was established using MNDO/d calculations and comparing between UV and photoelectron spectra. It has been concluded that photoelectron spectroscopy can be applied for interpretation of UV absorption spectra of various compounds on the basis of similar correlations.

  17. Narrow absorption lines with two observations from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Fu; Gu, Qiu-Sheng; Chen, Yan-Mei; Cao, Yue

    2015-07-01

    We assemble 3524 quasars from the Sloan Digital Sky Survey (SDSS) with repeated observations to search for variations of the narrow C IV λ λ 1548,1551 and Mg II λ λ 2796,2803 absorption doublets in spectral regions shortward of 7000 Å in the observed frame, which corresponds to time-scales of about 150-2643 d in the quasar rest frame. In these quasar spectra, we detect 3580 C IV absorption systems with zabs = 1.5188-3.5212 and 1809 Mg II absorption systems with zabs = 0.3948-1.7167. In term of the absorber velocity (β) distribution in the quasar rest frame, we find a substantial number of C IV absorbers with β < 0.06, which might be connected to absorption of quasar outflows. The outflow absorption peaks at υ ≈ 2000 km s^{-1} and drops rapidly below this peak value. Among 3580 C IV absorption systems, 52 systems (˜1.5 per cent) show obvious variations in equivalent widths in the absorber rest frame (Wr): 16 enhanced, 16 emerged, 12 weakened and 8 disappeared systems, respectively. We find that changes in Wrλ1548 are related neither to the time-scales of the two SDSS observations nor to absorber velocities in the quasar rest frame. Variable absorption in low-ionization species is important to constrain the physical conditions of the absorbing gas. There are two variable Mg II absorption systems measured from SDSS spectra detected by Hacker et al. However, in our Mg II absorption sample, we find that neither shows variable absorption with confident levels of >4σ for λ2796 lines and >3σ for λ2803 lines.

  18. Effects of lowly ionized ions on silicon K-shell absorption spectra

    NASA Astrophysics Data System (ADS)

    Wei, H. G.; Shi, J. R.; Liang, G. Y.; Wang, F. L.; Zhong, J. Y.; Zhao, G.

    2016-05-01

    Context. In both astrophysical and laboratory plasmas, K-shell absorption spectra have become powerful diagnostic tools to investigate electron density and temperature. These spectra are also widely used to verify the opacity codes in laboratory settings. Aims: We report the effects of the low ionization silicon ions, namely from Si I to Si V, which have rarely been considered in previous models, on the K-shell silicon absorption spectra. Methods: The Si K-shell atomic data were calculated with the flexible atomic code, which is a fully relativistic atomic program with configuration interaction taken into consideration. Detailed level accounting models were employed to calculate the absorption spectra. Results: We calculate the Si absorption spectra in local thermodynamic equilibrium conditions with temperature and density ranges of 20-70 eV and ~1020 cm-3 to ~1022 cm-3, respectively, and show the contributions of the lowly ionized ions to the K-shell absorption spectra of silicon. We also investigate the effects of the different atomic data on the absorption spectra. We find good agreement between our results and these from OPLIB. Conclusions: We find that the contributions from these lowly ionized ions cannot be neglected at relative low temperatures. Accurate experimental measurements are needed to benchmark the theoretical calculations.

  19. Optical absorption spectra and energy levels of Er3+ ions in glassy lithium tetraborate matrix

    NASA Astrophysics Data System (ADS)

    Danilyuk, P. S.; Popovich, K. P.; Puga, P. P.; Gomonai, A. I.; Primak, N. V.; Krasilinets, V. N.; Turok, I. I.; Puga, G. D.; Rizak, V. M.

    2014-11-01

    The optical absorption spectra of Er:Li2B4O7 glasses are studied in the range 200-800 nm. The lines corresponding to the direct f-f parity-forbidden intraconfigurational transitions from the ground 4 I 15/2 state to the levels of the excited 4 F 9/2, 4 S 3/2, 2 H 9/2, 2 H 11/2, 4 F 7/2, 4 F 5/2, 4 F 3/2, 2 H 9/2, 4 G 11/2, 4 D 3/2, 4 D 1/2, and 2 D 3/2 states are found.

  20. Line by Line Analysis of Carbon Dioxide Absorption for Predicting Global Warming

    NASA Astrophysics Data System (ADS)

    Smith, D. C.

    2010-12-01

    The anthropologic cause of global warming rests on the impact of CO2 on the green house effect. Previous derivations of the increase in the CO2 Forcing Function caused by doubling of atmospheric CO2 from 320 ppm to 640 ppm reported a value of 4 W/M2( Ramananathan,V,et al, J.of Geophysical Research Vol 84, C8,p4949, Aug.1979) This value leads to a calculated temperature rise of 1 deg.K (Charney,J. et al,”Carbon Dioxide and Climate: A Scientific Assessment”, National Academy of Science, Washington D.C., 1979). This increase in global temperature leads to an increase in water vapor if it is assumed that the relative humidity is constant. This ampflication leads to a calculated temperature rise of an additional 2 deg.K. Different arguments as to the effects of the earth’s albido change, clouds, and the oceans also impact the earths global warming with predictions of total temperature rise of as high as 6 deg.K { IPCC,2007 Summary for Policymakers. In: Climate Change 2007: The Physical Sciences Basis. Contributions of Working Group 1 to the Fourth Assessment Report of the IPCC [ Solomon,S,D. et al (eds)] Cambridge University Press, NY,USA}. Regardless of the other effects, the only way that man can be held responsible for global warming is by CO2 emissions and the resulting increase in the Forcing Function. This paper challenges the magnitude of the 4 W/M2 Forcing Function. The earth radiates in the 4 to 30 micron wavelength range. CO2 has absorption bands in the 4, 10, and 15 micron wavelengths (Hertzberg G. Molecular Spectra & Molecular Structure,Norstrand Co.,1960). McClatchey has tabulated the line stengths for all CO2 transitions and they are used to calculate the atmospheric absorption (McClatchey,R, et al “AFCRL Atmospheric Absorption Line Parameter Compilation”,AFCRL-TR-0096,1973). Detailed calculations of the CO2 line absorption in the 8 to 12 micron atmospheric window shows an increase of 0.3 W/M2 for CO2 doubling. The increase in absorbed fluence in

  1. How Van der Waals Interactions Influence the Absorption Spectra of Pheophorbide a Complexes: A Mixed Quantum-Classical Study.

    PubMed

    Megow, Jörg

    2015-10-01

    The computation of dispersive site energy shifts due to van der Waals interaction (London dispersion forces) was combined with mixed quantum-classical methodology to calculate the linear optical absorption spectra of large pheophorbide a (Pheo) dendrimers. The computed spectra agreed very well with the measurements considering three characteristic optical features occurring with increasing aggregate size: a strong line broadening, a redshift, and a low-energy shoulder. The improved mixed quantum-classical methodology is considered a powerful tool in investigating molecular aggregates. PMID:26275373

  2. A method for normalization of X-ray absorption spectra

    SciTech Connect

    Weng, T.-C.; Waldo, G.S.; Penner-Hahn, J.E.

    2010-07-20

    Accurate normalization of X-ray absorption data is essential for quantitative analysis of near-edge features. A method, implemented as the program MBACK, to normalize X-ray absorption data to tabulated mass absorption coefficients is described. Comparison of conventional normalization methods with MBACK demonstrates that the new normalization method is not sensitive to the shape of the background function, thus allowing accurate comparison of data collected in transmission mode with data collected using fluorescence ion chambers or solid-state fluorescence detectors. The new method is shown to have better reliability and consistency and smaller errors than conventional normalization methods. The sensitivity of the new normalization method is illustrated by analysis of data collected during an equilibrium titration.

  3. Systematic view of optical absorption spectra in the actinide series

    SciTech Connect

    Carnall, W.T.

    1985-01-01

    In recent years sufficient new spectra of actinides in their numerous valence states have been measured to encourage a broader scale analysis effort than was attempted in the past. Theoretical modelling in terms of effective operators has also undergone development. Well established electronic structure parameters for the trivalent actinides are being used as a basis for estimating parameters in other valence states and relationships to atomic spectra are being extended. Recent contributions to our understanding of the spectra of 4+ actinides have been particularly revealing and supportive of a developing general effort to progress beyond a preoccupation with modelling structure to consideration of the much broader area of structure-bonding relationships. We summarize here both the developments in modelling electronic structure and the interpretation of apparent trends in bonding. 60 refs., 9 figs., 1 tab.

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

    NASA Technical Reports Server (NTRS)

    Hoepffner, Nicolas; Sathyendranath, Shubha

    1993-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  6. Catalog of Narrow C IV Absorption Lines in BOSS. II. For Quasars with Z em > 2.4

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Fu; Qin, Yi-Ping; Qin, Ming; Pan, Cai-Juan; Pan, Da-Sheng

    2014-11-01

    As the second work in a series of papers aiming to detect absorption systems in the quasar spectra of the Baryon Oscillation Spectroscopic Survey, we continue the analysis of Paper I by expanding the quasar sample to those quasars with z em > 2.4. This yields a sample of 21,963 appropriate quasars to search for narrow C IV λλ1548, 1551 absorptions with Wr >= 0.2 Å for both lines. There are 9708 quasars with at least one appropriate absorption system imprinted on their spectra. From these spectra, we detect 13,919 narrow C IV absorption systems whose absorption redshifts cover a range of z abs = 1.8784-4.3704. In this paper and Paper I, we have selected 37,241 appropriate quasars with median S/N >= 4 and 1.54 <~ z em <~ 5.16 to visually analyze narrow C IV λλ1548, 1551 absorption doublets one by one. A total of 15,999 quasars are found to have at least one appropriate absorption system imprinted on their spectra. From these 15,999 quasar spectra, we have detected 23,336 appropriate C IV λλ1548, 1551 absorption systems with Wr >= 0.2 Å whose absorption redshifts cover a range of z abs = 1.4544-4.3704. The largest values of Wr are 3.19 Å for the λ1548 absorption line and 2.93 Å for the λ1551 absorption line, respectively. We find that only a few absorbers show large values of Wr . About 1.1% of the total absorbers have Wr λ1548 >= 2.0 Å.

  7. Vibronic Structures in Absorption and Fluorescence Spectra of Firefly Oxyluciferin in Aqueous Solutions.

    PubMed

    Hiyama, Miyabi; Noguchi, Yoshifumi; Akiyama, Hidefumi; Yamada, Kenta; Koga, Nobuaki

    2015-01-01

    To elucidate the factors determining the spectral shapes and widths of the absorption and fluorescence spectra for keto and enol oxyluciferin and their conjugate bases in aqueous solutions, the intensities of vibronic transitions between their ground and first electronic excited states were calculated for the first time via estimation of the vibrational Franck-Condon factors. The major normal modes, overtones and combination tones in absorption and fluorescence spectra are similar for all species. The theoretical full widths at half maximum of absorption spectra are 0.4-0.7 eV and those for the fluorescence spectra are 0.4-0.5 eV, except for phenolate-keto that exhibits exceptionally sharp peak widths due to the dominance of the 0-0' or 0'-0 band. These spectral shapes and widths explain many relevant features of the experimentally observed spectra. PMID:25946599

  8. The FTS atomic spectrum tool (FAST) for rapid analysis of line spectra

    NASA Astrophysics Data System (ADS)

    Ruffoni, M. P.

    2013-07-01

    The FTS Atomic Spectrum Tool (FAST) is an interactive graphical program designed to simplify the analysis of atomic emission line spectra obtained from Fourier transform spectrometers. Calculated, predicted and/or known experimental line parameters are loaded alongside experimentally observed spectral line profiles for easy comparison between new experimental data and existing results. Many such line profiles, which could span numerous spectra, may be viewed simultaneously to help the user detect problems from line blending or self-absorption. Once the user has determined that their experimental line profile fits are good, a key feature of FAST is the ability to calculate atomic branching fractions, transition probabilities, and oscillator strengths-and their uncertainties-which is not provided by existing analysis packages. Program SummaryProgram title: FAST: The FTS Atomic Spectrum Tool Catalogue identifier: AEOW_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEOW_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 3 No. of lines in distributed program, including test data, etc.: 293058 No. of bytes in distributed program, including test data, etc.: 13809509 Distribution format: tar.gz Programming language: C++. Computer: Intel x86-based systems. Operating system: Linux/Unix/Windows. RAM: 8 MB minimum. About 50-200 MB for a typical analysis. Classification: 2.2, 2.3, 21.2. Nature of problem: Visualisation of atomic line spectra including the comparison of theoretical line parameters with experimental atomic line profiles. Accurate intensity calibration of experimental spectra, and the determination of observed relative line intensities that are needed for calculating atomic branching fractions and oscillator strengths. Solution method: FAST is centred around a graphical interface, where a user may view sets of experimental line profiles and compare

  9. Probing low-redshift galaxies using quasar absorption lines with an emphasis on Ca II absorption

    NASA Astrophysics Data System (ADS)

    Sardane, Gendith M.

    We searched for intervening CaII absorption in nearly 95,000 quasar spectra with i≤20 from the Sloan Digital Sky Survey(SDSS) data releases DR7+DR9. Our identification of >400 CaII systems is the largest compilation of CaII absorbers in a blind search. (Abstract shortened by ProQuest.).

  10. The spatial and kinematic structure of QSO metal-line absorption systems

    NASA Technical Reports Server (NTRS)

    Lanzetta, Kenneth M.

    1992-01-01

    Recent attempts to infer the spatial and kinematic distributions of the material responsible for absorption lines observed in the spectra of background QSOs are presented. Current models of the absorbing regions are compared, and initial observational results are described. This research is expected to lead eventually to a detailed picture of the extended gaseous halo regions of galaxies at early evolutionary stages and to an understanding of the physical processes at work in these halos.

  11. Multiple Velocity Components in the C IV Absorption Line of NGC 5548

    NASA Technical Reports Server (NTRS)

    Mathur, Smita; Elvis, Martin; Wilkes, Belinda

    1999-01-01

    We have observed the much-studied Seyfert 1 galaxy NGC 5548 with the Goddard High-Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST). Our 14 ks observation covers the C IV emission line at a resolution of greater than 20,000. Our purpose was to study the absorption line found at lower resolution by IUE and the HST Faint Object Spectrograph. We found that the C IV absorption line resolves into six separate doublets with equivalent widths of 0.07-0.38 Angstrom. The absorption lines have blueshifts relative to the systemic velocity of the galaxy of 380-1250 km s(exp -1), except for one, which has a redshift of 250 km s(exp -1), suggesting both inflow and outflow. The inflowing component may be related to the accretion flow into the nuclear black hole. All the doublet lines are resolved by the GHRS. Three doublets are narrow, with FWHM greater than or approximately 100 km s(exp -1), and three are broad, FWHM approximately 160-290 km s(exp -1). We find evidence of partial covering by the narrow absorption lines. Either (but not both) of the two strongest broad doublets could be from the same material that produces the X-ray ionized absorber seen in soft X-rays. The remaining five systems must be at least 10 times less ionized (and so of lower total column density) to remain consistent with the X-ray spectra.

  12. The low-ion QSO absorption-line systems

    SciTech Connect

    Lanzetta, K.M.

    1988-01-01

    Various techniques are used to investigate the class of QSO absorption-line systems that exhibit low-ion absorption lines. Four separate investigations are conducted as follows: Spectroscopy of 32 QSOs at red wavelengths is presented and used to investigate intermediate-redshift MgII absorption. A total of 22 Mg II doublets are detected, from which properties of the Mg II absorbers are derived. Marginal evidence for intrinsic evolution of the number density of the Mg II absorbers with redshift is found. The data are combined with previous observations of C IV and C II seen in the same QSOs at blue wavelengths, and the properties of Mg II- and C IV-selected systems are compared. A sample is constructed of 129 QSOs for which are available published data suitable for detecting absorption-line systems that are optically thick to Lyman continuum radiation. A total of 53 such Lyman-limit systems are found, from which properties of the Lyman-limit systems are derived. It is found that the rate of incidence of the systems does not strongly evolved with redshift. This result is contrasted with the evolution found previously for systems selected on the basis of Mg II absorption. Spectroscopy at red wavelengths of eight QSOs with known damped Ly{alpha} absorption systems is presented. Spectroscopic and spectrophotometric observations aimed at detecting molecular hydrogen and dust in the z = 2.796 damped Ly{alpha} absorber toward Q1337 + 113 are presented.

  13. Analysis of absorption and scattering spectra for assessing apple fruit internal quality after harvest and storage

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical absorption and scattering properties are useful for quantifying light interaction with plant tissue, as well as for quality assessment of horticultural products. The aim of this research was to measure the absorption and reduced scattering coefficient spectra of two cultivars of apple (Malus...

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

    USGS Publications Warehouse

    Feinstein, H.I.

    1956-01-01

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

  15. Data processing of absorption spectra from photoionized plasma experiments at Za)

    NASA Astrophysics Data System (ADS)

    Hall, I. M.; Durmaz, T.; Mancini, R. C.; Bailey, J. E.; Rochau, G. A.

    2010-10-01

    We discuss the processing of x-ray absorption spectra from photoionized plasma experiments at Z. The data was recorded with an imaging spectrometer equipped with two elliptically bent potassium acid phthalate (KAP) crystals. Both time-integrated and time-resolved data were recorded. In both cases, the goal is to obtain the transmission spectra for quantitative analysis of plasma conditions.

  16. Determining neutrino absorption spectra at ultra-high energies

    SciTech Connect

    Scholten, O; Van Vliet, A R E-mail: A.R.van.Vliet@student.rug.nl

    2008-06-15

    A very efficient method for measuring the flux of ultra-high energy (UHE) neutrinos is through the detection of radio waves which are emitted by the particle shower in the lunar regolith. The highest acceptance is reached for radio waves in the frequency band of 100-200 MHz which can be measured with modern radio telescopes. In this work we investigate the sensitivity of this detection method to structures in the UHE neutrino spectrum caused by their absorption on the low energy relic anti-neutrino background through the Z boson resonance. The position of the absorption peak is sensitive to the neutrino mass and the redshift of the source. A new generation of low frequency digital radio telescopes will provide excellent detection capabilities for measuring these radio pulses, thus making our consideration here very timely.

  17. Electronic absorption spectra of some arylidene pyrazolone derivatives

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. R.; El-Kashef, H. S.; El-Hamide, R. Abd

    The u.v. and visible spectra of some 1 - phenyl - 3 - methyl - 4 - arylidene - 2 - pyrazolin - 5 - one derivatives are investigated in pure and mixed organic solvents as well as in aqueous buffer solutions. Electronic transitions have been identified as either locally excited or predominantly charge transfer states. Moreover, the spectra of the hydroxy derivatives in proton acceptor solvents (DMF, DMSO, ethanol) are characterized by an extra band located at longer wavelengths, which is ascribed to an intermolecular CT transition. This involves an electron transfer from the lone pair of electrons of the oxygen atom of the solvent molecules (ψ ol) to the antibonding orbital of the substituent OH group. The spectral shifts are discussed in terms of medium effects and in relation to molecular structure. The variation of absorbance with pH is utilized for the determination of p K a for the dimethylamino and hydroxy derivatives.

  18. Infrared absorption spectra of human malignant tumor tissues

    NASA Astrophysics Data System (ADS)

    Skornyakov, I. V.; Tolstorozhev, G. B.; Butra, V. A.

    2008-05-01

    We used infrared spectroscopy methods to study the molecular structure of tissues from human organs removed during surgery. The IR spectra of the surgical material from breast, thyroid, and lung are compared with data from histological examination. We show that in malignant neoplasms, a change occurs in the hydrogen bonds of protein macromolecules found in the tissue of the studied organs. We identify the spectral signs of malignant pathology.

  19. Temperature-insensitive laser frequency locking near absorption lines

    NASA Astrophysics Data System (ADS)

    Kostinski, Natalie; Olsen, Ben A.; Marsland, Robert; McGuyer, Bart H.; Happer, William

    2011-03-01

    Combined magnetically induced circular dichroism and Faraday rotation of an atomic vapor are used to develop a variant of the dichroic atomic vapor laser lock that eliminates lock sensitivity to temperature fluctuations of the cell. Operating conditions that eliminate first-order sensitivity to temperature fluctuations can be determined by low-frequency temperature modulation. This temperature-insensitive gyrotropic laser lock can be accurately understood with a simple model, that is in excellent agreement with observations in potassium vapor at laser frequencies in a 2 GHz range about the 770.1 nm absorption line. The methods can be readily adapted for other absorption lines.

  20. Temperature-insensitive laser frequency locking near absorption lines

    SciTech Connect

    Kostinski, Natalie; Olsen, Ben A.; Marsland, Robert III; McGuyer, Bart H.; Happer, William

    2011-03-15

    Combined magnetically induced circular dichroism and Faraday rotation of an atomic vapor are used to develop a variant of the dichroic atomic vapor laser lock that eliminates lock sensitivity to temperature fluctuations of the cell. Operating conditions that eliminate first-order sensitivity to temperature fluctuations can be determined by low-frequency temperature modulation. This temperature-insensitive gyrotropic laser lock can be accurately understood with a simple model, that is in excellent agreement with observations in potassium vapor at laser frequencies in a 2 GHz range about the 770.1 nm absorption line. The methods can be readily adapted for other absorption lines.

  1. AFGL atmospheric absorption line parameters compilation - 1982 edition

    NASA Technical Reports Server (NTRS)

    Rothman, L. S.; Gamache, R. R.; Barbe, A.; Goldman, A.; Gillis, J. R.; Brown, L. R.; Toth, R. A.; Flaud, J.-M.; Camy-Peyret, C.

    1983-01-01

    The latest edition of the AFGL atmospheric absorption line parameters compilation for the seven most active infrared terrestrial absorbers is described. Major modifications to the atlas for this edition include updating of water-vapor parameters from 0 to 4300 per cm, improvements to line positions for carbon dioxide, substantial modifications to the ozone bands in the middle to far infrared, and improvements to the 7- and 2.3-micron bands of methane. The atlas now contains about 181,000 rotation and vibration-rotation transitions between 0 and 17,900 per cm. The sources of the absorption parameters are summarized.

  2. Electronic and oscillation absorption spectra of blood plamsa at surgical diseases of thyroid gland

    NASA Astrophysics Data System (ADS)

    Guminetskiy, S. G.; Motrich, A. V.; Poliansky, I. Y.; Hyrla, Ya. V.

    2012-01-01

    The results of investigating the absorption spectra of blood plasma in the visible and infrared parts of spectra obtained using the techniques of spherical photometer and spectrophotometric complex "Specord IR75" are presented. The possibility of using these spectra for diagnoses the cases of diffuse toxic goiter and nodular goiter and control of treatment process in postsurgical period in the cases of thyroid gland surgery is estimated.

  3. Electronic and oscillation absorption spectra of blood plamsa at surgical diseases of thyroid gland

    NASA Astrophysics Data System (ADS)

    Guminetskiy, S. G.; Motrich, A. V.; Poliansky, I. Y.; Hyrla, Ya. V.

    2011-09-01

    The results of investigating the absorption spectra of blood plasma in the visible and infrared parts of spectra obtained using the techniques of spherical photometer and spectrophotometric complex "Specord IR75" are presented. The possibility of using these spectra for diagnoses the cases of diffuse toxic goiter and nodular goiter and control of treatment process in postsurgical period in the cases of thyroid gland surgery is estimated.

  4. Laser plasma diagnostics and self-absorption measurements of the Hβ Balmer series line

    NASA Astrophysics Data System (ADS)

    Gautam, Ghaneshwar; Parigger, Christian G.; Surmick, David M.; EL Sherbini, Ashraf M.

    2016-02-01

    In this work, the peak-separation of the Balmer series hydrogen beta line was measured to determine the electron density of laser-induced plasma from spatially and temporally resolved spectra collected in laboratory air at standard ambient temperature and pressure. The self-absorption phenomenon is investigated by using a mirror that retro-reflects the emitted radiation through the plasma. The experimental data with and without the mirror were analyzed with available hydrogen beta computer simulations. Hardly any self-absorption was found as indicated by the correction factors that only marginally differ from unity. The obtained electron density values are also compared with the electron densities from nearby nitrogen lines. The hydrogen beta Hβ peak-separation method yields reliable results for an electron density of the order of 1 ×1017cm-3 for time delays of 5 μs from plasma generation, which confirms that self-absorption is insignificant for such electron densities.

  5. Polarized absorption spectra of (2,2) carbon nanotubes aligned in channels of an AEL crystal

    NASA Astrophysics Data System (ADS)

    Chen, Yanping; Zhai, Jianpang; Li, Irene Ling; Ruan, Shuangchen; Tang, Zikang

    2015-11-01

    We report polarized absorption spectra for the (2,2) tubes arrayed in the one-dimensional channels of an AlPO4-11 (AEL) single crystal. Strong polarization dependence is observed indicating a preferential optical dipole along the axis of carbon nanotubes. By correlating with the absorption spectra and First-principles local density function (LDA) calculation, the absorption peak at 2.95 eV is uniquely assigned to semiconducting type (2,2) tubes, and peaks at 2.67 and 2.40 eV are corresponding to metallic type (2,2) tubes.

  6. Infrared absorption spectra of pure and doped YAl3(BO3)4 single crystals

    NASA Astrophysics Data System (ADS)

    Kovács, L.; Mazzera, M.; Beregi, E.; Capelletti, R.

    2009-02-01

    Several weak absorption bands have been observed in the optical absorption spectra of pure and rare-earth-doped YAl3(BO3)4 single crystals in the 3350- 3650 cm-1 wave number region. Two of them, peaking at about 3377 cm-1 and 3580 cm-1 in the 8 K spectra, appear in most of the samples. They are tentatively attributed to the stretching mode of OH- ions incorporated in the crystal during the growth. An additional absorption band at about 5250 cm-1 at 8 K has also been detected in almost all samples. The temperature and polarization dependences of these bands, and their possible origin, are discussed.

  7. Influence of electric fields on absorption spectra of AAB-stacked trilayer graphene

    NASA Astrophysics Data System (ADS)

    Chiu, Chih-Wei; Chen, Rong-Bin

    2016-06-01

    The tight-binding model and gradient approximation are, respectively, used to calculate the band structures and the absorption spectra of AAB-stacked trilayer graphene (AAB-TLG). AAB stacking, the lowest symmetric geometric structure in trilayer systems, induces the most atomic interactions, and thus, complicates the energy dispersions and the joint density of states. AAB stacking enriches the optical absorption spectra [A(ω)], which dictate the characteristics of the electronic structure. A(ω) are changed by the static electric field, such as the intensity, frequency, and number of absorption structures. These results contrast sharply with those for TLG in other stacking configurations.

  8. Theory and interpretation of L-shell X-ray absorption spectra

    NASA Astrophysics Data System (ADS)

    Nesvizhskii, Alexey I.

    X-ray absorption near edge structure (XANES) directly reflects the electronic structure in a material. However, despite significant progress in XANES theory, the quantitative analysis of XANES is not fully developed and remains a challenge. In this work, a detailed analysis of the L2,3 edge XANES in transition metals was performed using relativistic, self-consistent real space Green's function code FEFFS. Several prescriptions for taking into account core hole in calculations of x-ray absorption spectra (XAS) were discussed. It was found that in most cases of L2,3 edge XANES in transition metals, the initial state (ground state) calculations were in the best agreement with experimental data. A procedure was developed for quantitative applications of the sum rules for XAS, e.g., for x-ray magnetic circular dichroism and for obtaining hole counts. The approach is based on theoretical atomic calculations of transformations relating various experimental spectra to corresponding operator-spectral densities. This approach overcomes the difficulties of background subtraction and hole-count normalization of other sum rule analysis methods and yields quantitative values for spin- and orbital-moments from experimental absorption spectra. The developed approach was theoretically tested and applied to experimental XAS data in Cu, Ni, Co, Fe, and other materials. Hole counts obtained from XAS are often interpreted in terms of free-atom occupation numbers or Mulliken counts. We demonstrated that renormalized-atom (RA) counts are a better choice to characterize the configuration of occupied electron states in molecules and condensed matter. A projection-operator approach was introduced to subtract delocalized states and to determine such hole counts from XAS quantitatively. Theoretical tests for the s- and d-electrons in transition metals showed that the approach works well. A formalism was developed based on time dependent local density approximation (TDLDA) theory that takes

  9. Artifacts in Absorption Measurements of Organometal Halide Perovskite Materials: What Are the Real Spectra?

    PubMed

    Tian, Yuxi; Scheblykin, Ivan G

    2015-09-01

    Organometal halide (OMH) perovskites have attracted lots of attention over the last several years due to their very promising performance as the materials for solar cells and light-emitting devices. Photophysical processes in these hybrid organic-inorganic semiconductors are still heavily debated. To know precise absorption spectra is absolutely necessary for quantitative understanding of the fundamental properties of OMH perovskites. We show that to measure the absorption of perovskite materials correctly is a difficult task which could be easily overlooked by the community. Many of the published absorption spectra exhibit a characteristic step-like featureless shape due to light scattering, high optical density of individual perovskite crystals and poor coverage of the substrate. We show how to recognize these artifacts, to avoid them, and to use absorption spectra of films for estimation of the surface coverage ratio. PMID:27120683

  10. Analysis of the collision-induced absorption spectra in the second overtone region of H2-H2 at 298 K

    NASA Astrophysics Data System (ADS)

    Abu-Kharma, M.

    2015-02-01

    The collision-induced absorption (CIA) spectra of the second overtone band of normal hydrogen in a pure gas were recorded for a number of gas densities up to 750 amagat (1 amagat = 44.614981 mol/m3) with a two meter stainless steel absorption cell at 298 K. The profile analyses of these spectra were carried out using the Birnbaum-Cohen line shape function for the quadrupolar vibrational transitions and the Levine-Birnbaum line shape function for the overlap transitions.

  11. C IV LINE-WIDTH ANOMALIES: THE PERILS OF LOW SIGNAL-TO-NOISE SPECTRA

    SciTech Connect

    Denney, K. D.; Vestergaard, M.; Pogge, R. W.; Kochanek, C. S.; Peterson, B. M.; Assef, R. J.

    2013-09-20

    Comparison of six high-redshift quasar spectra obtained with the Large Binocular Telescope with previous observations from the Sloan Digital Sky Survey shows that failure to correctly identify absorption and other problems with accurate characterization of the C IV λ1549 emission line profile in low signal-to-noise (S/N) data can severely limit the reliability of single-epoch mass estimates based on the C IV emission line. We combine the analysis of these new high-quality data with a reanalysis of three other samples based on high-S/N spectra of the C IV emission line region. We find that a large scatter between the Hβ- and C IV-based masses remains even for this high-S/N sample when using the FWHM to characterize the broad-line region velocity dispersion and the standard virial assumption to calculate the mass. However, we demonstrate that using high-quality data and the line dispersion to characterize the C IV line width leads to a high level of consistency between C IV- and Hβ-based masses, with <0.3 dex of observed scatter and an estimated ∼0.2 dex intrinsic scatter, in the mass residuals.

  12. Absorption spectra and speciation of plutonium(VI) with phosphate

    SciTech Connect

    Weger, H.T.; Reed, D.

    1996-02-01

    Plutonium(VI)-phosphate species in aqueous solution, at pH < 2.4, formed two species: PuO{sub 2}H{sub 2}PO{sub 4}{sup +} (characterized by an 835 nm absorption band) and the solid phase PuO{sub 2}(H{sub 2}PO{sub 4}){sub 2}. The stability constant {beta} for the PuO{sub 2}H{sub 2}PO{sub 4}{sup +} species was determined to be log {beta} = 2.1 {+-} 0.1 (ionic strength = 0.6--0.9 M) and log {beta}{sup T} = 2.6 {+-} 0.15 (zero ionic strength). Four Pu(VI)-phosphate species (absorption bands at 842, 846, 857, and 866 nm) formed at pH = 2.4 to 12.2 and are characterized by polynuclear behavior, the formation of precipitates, and colloidal properties. The 842 and 846 nm species are believed to be [PuO{sub 2}(HPO{sub 4}){sub m}]{sub n} and [PuO{sub 2}(NaPO{sub 4}){sub m}]{sub n}. The 857 and 866 nm species area as yet unidentified. The speciation of plutonium with phosphate is of interest to radionuclide migration studies because phosphate is present in many groundwaters and may be used as an actinide getter in nuclear waste disposal. An actinide getter is a complexing agent that forms insoluble phases with actinides, thereby reducing their migration.

  13. The Infrared Spectra and Absorption Intensities of Amorphous Ices

    NASA Astrophysics Data System (ADS)

    Gerakines, Perry A.; Hudson, Reggie L.; Loeffler, Mark

    2016-06-01

    Our research group is carrying out new IR measurements of icy solids relevant to the outer solar system and to the interstellar medium, with an emphasis on amorphous and crystalline ices below ~ 120 K. Our goal is to update and add to the relatively meager literature on this subject and to provide electronic versions of state-of-the-art data, since the abundances of such molecules cannot be deduced without accurate reference spectra and IR band strengths. In the past year, we have focused on three of the simplest and most abundant components of interstellar and solar-system ices: methane (CH4), carbon dioxide (CO2), and methanol (CH3OH). Infrared spectra from ∼ 4500 to 500 cm-1 have been measured for each of these molecules in μm-thick films at temperatures from 10 to 120 K. All known amorphous and crystalline phases have been reproduced and, for some, presented for the first time. We also report measurements of the index of refraction at 670 nm and the mass densities for each ice phase. Comparisons are made to earlier work where possible. Electronic versions of our new results are available at http://science.gsfc.nasa.gov/691/cosmicice/ constants.html.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  15. On the Origin of the Wide HI Absorption Line Towards Sgr A *

    NASA Astrophysics Data System (ADS)

    Dwarakanath, K. S.; Goss, W. M.; Zhao, J. H.; Lang, C. C.

    2004-09-01

    We have imaged a region of ~5 extent surrounding Sgr A* in the HI 21 cm-line absorption using the Very Large Array. A Gaussian decomposition of the optical depth spectra at positions within ~2(~5 pcat 8.5 kpc) of Sgr A* detects a wide linw underlying the many narrow absorption lines. The wide line has a mean peak optical depth of 0.32 ± 0.12 centered at a mean velocity of Vlsr = -4 ± 15 km s-1. The mean full width half maximum is 119 ± 42 km s-1. Such a wide line is absent in the spectra at positions beyond ~2 from Sgr A*. The position-velocity diagrams do not reveal any diffuse feature which could be attributed to a large number of HI clouds along the line of sight to Sgr A*. Consequently, the wide line has no implications either to a global population of shocked HI clouds in the Galaxy or to the energetics of the interstellar medium as was earlier thought.

  16. Detection of water vapour absorption around 363nm in measured atmospheric absorption spectra and its effect on DOAS evaluations

    NASA Astrophysics Data System (ADS)

    Lampel, Johannes; Polyansky, Oleg. L.; Kyuberis, Alexandra A.; Zobov, Nikolai F.; Tennyson, Jonathan; Lodi, Lorenzo; Pöhler, Denis; Frieß, Udo; Platt, Ulrich; Beirle, Steffen; Wagner, Thomas

    2016-04-01

    Water vapour is known to absorb light from the microwave region to the blue part of the visible spectrum at a decreasing magnitude. Ab-initio approaches to model individual absorption lines of the gaseous water molecule predict absorption lines until its dissociation limit at 243 nm. We present first evidence of water vapour absorption at 363 nm from field measurements based on the POKAZATEL absorption line list by Polyansky et al. (2016) using data from Multi-Axis differential optical absorption spectroscopy (MAX-DOAS) and Longpath (LP)-DOAS measurements. The predicted absorptions contribute significantly to the observed optical depths with up to 2 × 10‑3. Their magnitude correlates well (R2 = 0.89) to simultaneously measured well-established water vapour absorptions in the blue spectral range from 452-499 nm, but is underestimated by a factor of 2.6 ± 0.6 in the ab-initio model. At a spectral resolution of 0.5nm this leads to a maximum absorption cross-section value of 5.4 × 10‑27 cm2/molec at 362.3nm. The results are independent of the employed cross-section data to compensate for the overlayed absorption of the oxygen dimer O4. The newly found absorption can have a significant impact on the spectral retrieval of absorbing trace-gas species in the spectral range around 363 nm. Its effect on the spectral analysis of O4, HONO and OClO are discussed.

  17. Intermediate-redshift galaxy halos - Results from QSO absorption lines

    SciTech Connect

    Lanzetta, K.M.; Bowen, D. Royal Greenwich Observatory, Cambridge )

    1990-07-01

    For a sample of Mg II-selected QSO absorption-line systems for which the absorbing galaxies have been successfully identified, the rest-frame equivalent widths of the Mg II 2796-A absorption lines are examined as a function of the known impact parameters between the background QSOs and the absorbing galaxies. There appears to exist a relationship between the equivalent widths and the impact parameters, in the sense that larger equivalent widths occur at smaller impact parameters. No trend of the doublet ratio is found with impact parameter, and neither the equivalent widths nor the doublet ratios are correlated with the absolute luminosities or redshifts of the absorbing galaxies. These results apparently indicate that the main factor that determines the equivalent width of a particular absorption system is the impact parameter between the background QSO and the absorbing galaxy. 32 refs.

  18. Interstellar MG II Absorption Lines from Low-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Bowen, David V.; Blades, J. Chris; Pettini, Max

    1995-08-01

    We have used the GHRS aboard HST to search for interstellar Mg II 2796, 2803 absorption from the disks and halos of 17 low-redshift galaxies, using as probes QSOs and extragalactic supernovae whose sight lines pass close to, or through, intervening galaxies. The galaxies studied are of diverse morphological type, reside in different environments, and lie at separations of p' ≃ 2-113 h-1 kpc from a QSO line of sight. Ten of 11 galaxies at separations 31-113 h-1 kpc show no absorption to equivalent width limits of W(λ2796) <40-90 mÅ, which corresponds to N(Mg II) ≃1-4 × 1012 cm-2. Six galaxies lie at p' ≤ 9 kpc, and of these, four (NGC 4319, the LMC, M81, and the Milky Way) show absorption. Two early-type galaxies (NGC 1380 and Leo I) show no absorption at p' < 9 kpc: these nondetections are surprising because the separations are small and point to the possibility that the existence of extended absorbing halos may be a function of galaxy type. All of the galaxies which produce absorption are plausibly members of interacting systems. For absorbing galaxies probed below 9 kpc, the sight line passes within the optical radius of the galaxy, where the interstellar medium (ISM) is expected to have a high covering factor, and we do not attribute the absorption to the interactions. However, we do find that the environment of the absorbing galaxies affects the characteristics of the absorption detected the strength of lines, the complexity of line components, the ionization state of the gas and we warn of the dangers inherent in constructing models of generic halos based on statistical properties of QSO absorption-line surveys. Our data suggest that the covering factor of Mg II absorption is high for galaxies within ≍10 kpc, but very small beyond ≍30 h-1 kpc, a result consistent with the size found of Mg II halos deduced for galaxies at redshifts z > 0.2. The low-redshift galaxies observed in this study which show Mg II absorption are probably drawn from the same

  19. Fine-structure Constancy Measurements in QSO Absorption Lines

    NASA Astrophysics Data System (ADS)

    Whitmore, Jonathan B.

    2013-01-01

    The ESO Large Programme 185.A-0745 has awarded 10 nights on the VLT-UVES spectrograph for the study of the possible variation in the fine structure constant. We will present the fine-structure measurements from two lines of sight and several absorption systems. We will also present updated systematic error analyses.

  20. Influence of laser radiation on induced absorption spectra of pure quartz glass optical fibers

    NASA Astrophysics Data System (ADS)

    Dianov, Y. M.; Karpechev, V. N.; Korniyenko, L. S.; Rybaltovskiy, A. O.; Chernov, P. V.

    1986-01-01

    The influence of laser radiation on radiation color centers and their associated induced absorption in the spectra of irradiated glass optical fibers is investigated. The glass fiber specimens employed had 40 to 50 micron diameter cores made of day pure quartz glass. The optical fibers were 6 to 20 meters long, produced by chemical precipitation from the gaseous phase and clad with reflecting borosilicate glass. Spectral measurements of the induced absorption in the ultraviolet region were made using an FEU-71 photodetector and a sounding radiation source. The stimulated laser emission power in the cross section of the optical fiber was measured by a photodiode; the absorption spectra were recorded by the fragment method. Eight different types of color centers were isolated whose bands cover practically the entire observed absorption spectra. The connection found between color centers and a 340 nm absorption band, and color center with absorption in the infrared band, indicate that absorption in the ultraviolet band can have a significant influence on the amount of induced absorption in the infrared band.

  1. Linewidths in excitonic absorption spectra of cuprous oxide

    NASA Astrophysics Data System (ADS)

    Schweiner, Frank; Main, Jörg; Wunner, Günter

    2016-02-01

    We present a theoretical calculation of the absorption spectrum of cuprous oxide (Cu2O ) based on the general theory developed by Y. Toyozawa. An inclusion not only of acoustic phonons but also of optical phonons and of specific properties of the excitons in Cu2O like the central-cell corrections for the 1 S exciton allows us to calculate the experimentally observed linewidths in experiments by T. Kazimierczuk et al. [T. Kazimierczuk, D. Fröhlich, S. Scheel, H. Stolz, and M. Bayer, Nature (London) 514, 343 (2014), 10.1038/nature13832] within the same order of magnitude, which demonstrates a clear improvement in comparison to earlier work on this topic. We also discuss a variety of further effects, which explain the still observable discrepancy between theory and experiment but can hardly be included in theoretical calculations.

  2. Measurement and feature analysis of absorption spectra of four algal species

    NASA Astrophysics Data System (ADS)

    Zhu, Jianhua; Zhou, Hongli; Han, Bing; Li, Tongji

    2016-04-01

    Two methods for particulate pigments (i.e., quantitative filter technique, QFT, and in vivo measurement, InVivo, respectively) and two methods for dissolved pigments (i.e., Acetone Extracts, AceEx, and high-performance liquid chromatography, HPLC, respectively) were used to obtain the optical absorption coefficient spectra for cultures of four typical algal species. Through normalization and analysis of the spectra, it is shown that (1) the four methods are able to measure optical absorption spectra of particulate and/or dissolved pigments; (2) that the optical absorption spectra of particulate and dissolved pigments were consistent in terms of the peak position in the blue wavelength, and the difference of the peak position in the near infrared wavelength was ~10 nm between each other; and (3) that the leveling effect of the absorption spectra of particulate pigments was significant. These four methods can all effectively measure the absorption coefficients of phytoplankton pigments, while each one has its unique advantages in different applications. Therefore, appropriate method should be carefully selected for various application due to their intrinsic difference.

  3. Simultaneous Fitting of Absorption Spectra and Their Second Derivatives for an Improved Analysis of Protein Infrared Spectra.

    PubMed

    Baldassarre, Maurizio; Li, Chenge; Eremina, Nadejda; Goormaghtigh, Erik; Barth, Andreas

    2015-01-01

    Infrared spectroscopy is a powerful tool in protein science due to its sensitivity to changes in secondary structure or conformation. In order to take advantage of the full power of infrared spectroscopy in structural studies of proteins, complex band contours, such as the amide I band, have to be decomposed into their main component bands, a process referred to as curve fitting. In this paper, we report on an improved curve fitting approach in which absorption spectra and second derivative spectra are fitted simultaneously. Our approach, which we name co-fitting, leads to a more reliable modelling of the experimental data because it uses more spectral information than the standard approach of fitting only the absorption spectrum. It also avoids that the fitting routine becomes trapped in local minima. We have tested the proposed approach using infrared absorption spectra of three mixed α/β proteins with different degrees of spectral overlap in the amide I region: ribonuclease A, pyruvate kinase, and aconitase. PMID:26184143

  4. SPECTROPOLARIMETRY OF RADIO-SELECTED BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    DiPompeo, M. A.; Brotherton, M. S.; Becker, R. H.; Gregg, M. D.; Tran, H. D.; White, R. L.; Laurent-Muehleisen, S. A.

    2010-07-15

    We report spectropolarimetry of 30 radio-selected broad absorption line (BAL) quasars with the Keck Observatory, 25 from the sample of Becker et al. Both high- and low-ionization BAL quasars are represented, with redshifts ranging from 0.5 to 2.5. The spectropolarimetric properties of radio-selected BAL quasars are very similar to those of radio-quiet BAL quasars: a sizeable fraction (20%) shows large continuum polarization (2%-10%) usually rising toward short wavelengths; emission lines are typically less polarized than the continuum; and absorption line troughs often show large polarization jumps. There are no significant correlations between polarization properties and radio properties, including those indicative of system orientation, suggesting that BAL quasars are not simply normal quasars seen from an edge-on perspective.

  5. Absorption spectra of typical space materials in the vacuum ultraviolet

    NASA Astrophysics Data System (ADS)

    Muscari, J. A.

    1981-01-01

    In order to develop a data base for potential optical degradation of space vacuum ultraviolet instruments, the collected volatile condensed material (CVCM) transmittance was measured in the wavelength region from 115 nm to 300 nm. The parent outgassing materials included: the adhesives, Ablebond 36-2, Trabond BB-2116, EA-9309, and Scotchweld 2216; the paints, Chemglaze Z-306, Z-306 over 9922 primer, Z-306 over AP-131 primer, Cat-A-Lac 463-3-8, 463-3-8 over primer, 3M Nextel 401-C10, and 401-C10 over 901-P1 primer; the resins, Fiberite 934, Solithane 113/C113-300 Formulation no. 1, and 113/C113-300 Formulation no. 8; the lubricants, Lube-Lok 4306 and RT/Duroid 5813; and the double-sided adhesive tape 3M-415. The effect of thermal vacuum conditioning of selected materials was also studied. The transmittance measurements were used to calculate the absorption coefficient for each of 28 different source materials versus wavelength.

  6. Modeling the double-trough structure observed in broad absorption line QSOs using radiative acceleration

    NASA Technical Reports Server (NTRS)

    Arav, Nahum; Begelman, Mitchell C.

    1994-01-01

    We present a model explaining the double trough, separated by delta v approximately = 5900 km/s, observed in the C IV lambda-1549 broad absorption line (BAL) in a number of BALQSOs. The model is based on radiative acceleration of the BAL outflow, and the troughs result from modulations in the radiative force. Specifically, where the strong flux from the Lyman-alpha lambda-1215 broad emission line is redshifted to the frequency of the N V lambda-1240 resonance line, in the rest frame of the accelerating N V ions, the acceleration increases and the absorption is reduced. At higher velocities the Lyman-alpha emission is redshifted out of the resonance and the N V ions experience a declining flux which causes the second absorption trough. A strongly nonlinear relationship between changes in the flux and the optical depth in the lines is shown to amplify the expected effect. This model produces double troughs for which the shallowest absorption between the two troughs occurs at v approximately = 5900 km/s. Indeed, we find that a substantial number of the observed objects show this feature. A prediction of the model is that all BALQSOs that show a double-trough signature will be found to have an intrinsic sharp drop in their spectra shortward of approximately 1200 A.

  7. P Cygni profiles in zeta Ophiuchi and zeta Puppis. [far UV absorption lines

    NASA Technical Reports Server (NTRS)

    Morton, D. C.

    1976-01-01

    Detailed P Cygni profiles are plotted using data from selected regions of the far-UV spectra of zeta OPh and zeta Pup obtained by the Copernicus satellite. Equivalent widths and velocity shifts of both emission and absorption features are also presented. For zeta Oph, it is found that only the C IV and N V resonance lines exhibit the P Cygni phenomenon; for zeta Pup, the resonance lines of C III, N III, Si IV, C IV, P V, S VI, N V, and O VI all show strong P Cygni lines, although the emission component seems to be absent in N III. For both stars, it is shown that parts of most absorption profiles exceed the escape velocity, indicating mass ejection. The short-wavelength edges of the resonance lines are found to average about -1590 km/s in zeta Oph and about -2660 km/s in zeta Pup, with no significant dependence on ionization potential. It is noted that the equivalent width of the emission component is always considerably less than that of the absorption component, suggesting that absorption occurs close to the stellar surface.

  8. H{beta} LINE WIDTHS AS AN ORIENTATION INDICATOR FOR LOW-IONIZATION BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    Punsly, Brian; Zhang Shaohua E-mail: brian.punsly@comdev-usa.co

    2010-12-20

    There is evidence from radio-loud quasars to suggest that the distribution of the H{beta} broad emission line (BEL) gas is arranged in a predominantly planar orientation, and this result may well also apply to radio-quiet quasars. This would imply that the observed FWHM of the H{beta} BELs is dependent on the orientation of the line of sight to the gas. If this view is correct then we propose that the FWHM can be used as a surrogate, in large samples, to determine the line of sight to the H{beta} BELs in broad absorption line quasars (BALQSOs). The existence of broad UV absorption lines (BALs) means that the line of sight to BALQSOs must also pass through the BAL out-flowing gas. It is determined that there is a statistically significant excess of narrow-line profiles in the SDSS DR7 archival spectra of low-ionization broad absorption line quasars (LoBALQSOs), indicating that BAL gas flowing close to the equatorial plane does not commonly occur in these sources. We also find that the data is not well represented by random lines of sight to the BAL gas. Our best fit indicates two classes of LoBALQSOs, the majority ({approx}2/3) are polar outflows that are responsible for the enhanced frequency of narrow-line profiles, and the remainder are equatorial outflows. We further motivated the line of sight explanation of the narrow-line excess in LoBALQSOs by considering the notion that the skewed distribution of line profiles is driven by an elevated Eddington ratio in BALQSOs. We constructed a variety of control samples comprised of non-LoBALQSOs matched to a de-reddened LoBALQSO sample in redshift, luminosity, black hole mass, and Eddington ratio. It is demonstrated that the excess of narrow profiles persists within the LoBALQSO sample relative to each of the control samples with no reduction of the statistical significance. Thus, we eliminate the possibility that the excess narrow lines seen in the LoBALQSOs arise from an enhanced Eddington ratio.

  9. Theoretical analysis of electronic absorption spectra of vitamin B12 models

    NASA Astrophysics Data System (ADS)

    Andruniow, Tadeusz; Kozlowski, Pawel M.; Zgierski, Marek Z.

    2001-10-01

    Time-dependent density-functional theory (TD-DFT) is applied to analyze the electronic absorption spectra of vitamin B12. To accomplish this two model systems were considered: CN-[CoIII-corrin]-CN (dicyanocobinamide, DCC) and imidazole-[CoIII-corrin]-CN (cyanocobalamin, ImCC). For both models 30 lowest excited states were calculated together with transition dipole moments. When the results of TD-DFT calculations were directly compared with experiment it was found that the theoretical values systematically overestimate experimental data by approximately 0.5 eV. The uniform adjustment of the calculated transition energies allowed detailed analysis of electronic absorption spectra of vitamin B12 models. All absorption bands in spectral range 2.0-5.0 eV were readily assigned. In particular, TD-DFT calculations were able to explain the origin of the shift of the lowest absorption band caused by replacement of the-CN axial ligand by imidazole.

  10. A novel acoustic sensor approach to classify seeds based on sound absorption spectra.

    PubMed

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

    2010-01-01

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

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

    PubMed Central

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

    2010-01-01

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

  12. Rich magneto-absorption spectra of AAB-stacked trilayer graphene.

    PubMed

    Do, Thi-Nga; Shih, Po-Hsin; Chang, Cheng-Peng; Lin, Chiun-Yan; Lin, Ming-Fa

    2016-06-29

    A generalized tight-binding model is developed to investigate the feature-rich magneto-optical properties of AAB-stacked trilayer graphene. Three intragroup and six intergroup inter-Landau-level (inter-LL) optical excitations largely enrich magneto-absorption peaks. In general, the former are much higher than the latter, depending on the phases and amplitudes of LL wavefunctions. The absorption spectra exhibit single- or twin-peak structures which are determined by quantum modes, LL energy spectra and Fermion distribution. The splitting LLs, with different localization centers (2/6 and 4/6 positions in a unit cell), can generate very distinct absorption spectra. There exist extra single peaks because of LL anti-crossings. AAB, AAA, ABA, and ABC stackings considerably differ from one another in terms of the inter-LL category, frequency, intensity, and structure of absorption peaks. The main characteristics of LL wavefunctions and energy spectra and the Fermi-Dirac function are responsible for the configuration-enriched magneto-optical spectra. PMID:27305856

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

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, E.

    1981-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

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

  15. Fe X Emission Lines in Solar and Stellar Spectra

    NASA Astrophysics Data System (ADS)

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

    1996-12-01

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

  16. Quantum mechanical calculation of the collision-induced absorption spectra of N2-N2 with anisotropic interactions.

    PubMed

    Karman, Tijs; Miliordos, Evangelos; Hunt, Katharine L C; Groenenboom, Gerrit C; van der Avoird, Ad

    2015-02-28

    We present quantum mechanical calculations of the collision-induced absorption spectra of nitrogen molecules, using ab initio dipole moment and potential energy surfaces. Collision-induced spectra are first calculated using the isotropic interaction approximation. Then, we improve upon these results by considering the full anisotropic interaction potential. We also develop the computationally less expensive coupled-states approximation for calculating collision-induced spectra and validate this approximation by comparing the results to numerically exact close-coupling calculations for low energies. Angular localization of the scattering wave functions due to anisotropic interactions affects the line strength at low energies by two orders of magnitude. The effect of anisotropy decreases at higher energy, which validates the isotropic interaction approximation as a high-temperature approximation for calculating collision-induced spectra. Agreement with experimental data is reasonable in the isotropic interaction approximation, and improves when the full anisotropic potential is considered. Calculated absorption coefficients are tabulated for application in atmospheric modeling. PMID:25725730

  17. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Astrophysics Data System (ADS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2002-12-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127-22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg II, Fe II, V II, etc observed in STIS/E230H spectra (see accompanying posters by Gull, Vieira, and Danks). The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-1 above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30x30 arcsec for FUSE, 0.2x0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic miniumum in 2003.

  18. High-Velocity Absorption Features in FUSE Spectra of Eta Carinae

    NASA Technical Reports Server (NTRS)

    Sonneborn, G.; Iping, R. C.; Gull, T. R.; Vieira, G.

    2003-01-01

    Numerous broad (200 to 1000 km/sec) features in the FUSE spectrum (905-1187 A) of eta Carinae are identified as absorption by a forest of high-velocity narrow lines formed in the expanding circumstellar envelope. These features were previously thought to be P-Cygni lines arising in the wind of the central star. The features span a heliocentric velocity range of -140 to -580 km/sec and are seen prominently in low-ionization ground-state transitions (e.g. N I 1134-35, Fe II 1145-42, 1133, 1127- 22, P II 1153, C I 1158) in addition to C III] 1176 A. The high-velocity components of the FUSE transitions have depths about 50% below the continuum. The identifications are consistent with the complex velocity structures seen in ground- and excited-state transitions of Mg I, Mg 11, Fe II, V II, etc observed in STIS/E230H spectra. The origin of other broad features of similar width and depth in the FUSE spectrum, but without low-velocity ISM absorption, are unidentified. However, they are suspected of being absorption of singly-ionized iron-peak elements (e.g. Fe II, V II, Cr II) out of excited levels 1,000 to 20,000 cmE-l above the ground state. The high-velocity features seen in Fe II 1145 are also present in Fe II 1608 (STIS/E140M), but are highly saturated in the latter. Since these transitions have nearly identical log (flambda) (1.998 vs. 2.080), the differences in the profiles are attributable to the different aperture sizes used (30 x 30 arcsec for FUSE, 0.2 x 0.2 arcsec for STIS/E140M). The high-velocity gas appears to be very patchy or has a small covering factor near the central star. Eta Carinae has been observed several times by FUSE over the past three years. The FUSE flux levels and spectral features in eta Car are essentially unchanged over the 2000 March to June 2002 period, establishing a baseline far-UV spectrum in advance of the predicted spectroscopic minimum in 2003.

  19. Ultraviolet Fe VII absorption lines in planetary nebula nuclei, hot subdwarfs, and hot degenerate objects

    NASA Technical Reports Server (NTRS)

    Feibelman, Walter A.; Bruhweiler, Frederick C.

    1990-01-01

    Results are reported from a search for Fe VII absorption lines in data from high-dispersion IUE-SWP observations of PN nuclei (PNN), hot subdwarfs (HSDs), and hot white dwarfs (HWDs). The data-reduction techniques employed are outlined, and the results are presented in extensive tables and sample spectra and characterized in detail. Absorption in at least one of the four Fe VII lines above 120 nm wavelength is found in 22 of 51 PNN, and possibly in 10 HSDs, in the pulsating HWD PG 1159 - 035, and in the PNN K1 - 16. It is concluded that Fe VII is more common in WD progenitors such as PNN than previously predicted and is especially typical of the more luminous low-gravity stars.

  20. The interstellar absorption-line spectrum of Mu Ophiuchi

    NASA Technical Reports Server (NTRS)

    Cardelli, J.; Boehm-Vitense, E.

    1982-01-01

    UV interstellar lines have been measured on high-resolution, long- and short-wavelength IUE spectra of the B8 V star Mu Oph. Column densities for the observed atoms and ions have been determined as well as turbulent velocities. The interstellar spectrum of Mu Oph is similar to the ones for Rho Oph and Zeta Oph. The ionization equilibria of several elements give consistent limits for the electron density. The C I line arising from different fine-structure levels are studied to yield estimates on the physical conditions in the cloud. Relative depletion of elements in the cloud seen in the interstellar spectrum of Mu Oph follows the same pattern as seen in the interstellar spectra of Zeta Oph and six other stars in the Rho Oph cloud complex.

  1. The missing UV absorption lines of NGC 4151

    NASA Technical Reports Server (NTRS)

    Leech, K. J.; Penston, M. V.; Snijders, M. A. J.; Ward, M. J.; Gull, T. R.

    1990-01-01

    Near simultaneous high dispersion long and short wavelength International Ultraviolet Explorer (IUE) observations of the Seyfert galaxy NGC 4151 are discussed. Previous observations revealed a narrow absorption system in Mg II not present in Ly alpha or C IV. The new observations confirm the presence of this system in Mg II and its absence in the other lines. Possible reasons for this are discussed. Future Hubble Space Telescope studies of NGC 4151 are discussed.

  2. Line shape analysis of two-dimensional infrared spectra

    PubMed Central

    Guo, Qi; Pagano, Philip; Li, Yun-Liang; Kohen, Amnon; Cheatum, Christopher M.

    2015-01-01

    Ultrafast two-dimensional infrared (2D IR) spectroscopy probes femtosecond to picosecond time scale dynamics ranging from solvation to protein motions. The frequency-frequency correlation function (FFCF) is the quantitative measure of the spectral diffusion that reports those dynamics and, within certain approximations, can be extracted directly from 2D IR line shapes. A variety of methods have been developed to extract the FFCF from 2D IR spectra, which, in principle, should give the same FFCF parameters, but the complexity of real experimental systems will affect the results of these analyses differently. Here, we compare five common analysis methods using both simulated and experimental 2D IR spectra to understand the effects of apodization, anharmonicity, phasing errors, and finite signal-to-noise ratios on the results of each of these analyses. Our results show that although all of the methods can, in principle, yield the FFCF under idealized circumstances, under more realistic experimental conditions they behave quite differently, and we find that the centerline slope analysis yields the best compromise between the effects we test and is most robust to the distortions that they cause. PMID:26049447

  3. Absorption spectra and spectral-kinetic characteristics of the fluorescence of Sanguinarine in complexes with polyelectrolytes and DNA

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

    The absorption spectra and stationary and time resolved fluorescence spectra of the isoquinoline alkaloid sanguinarine are studied in aqueous media and during interactions with synthetic polyelectrolytes (polystyrene sulfonate and polyallylamine) and a natural polyelectrolyte (DNA).

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

    SciTech Connect

    Leighly, Karen M.; Baron, Eddie; Lucy, Adrian B.; Terndrup, Donald M.; Dietrich, Matthias; Gallagher, Sarah C.

    2014-06-20

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

  5. Oxygen K-edge absorption spectra of small molecules in the gas phase

    SciTech Connect

    Yang, B.X.; Kirz, J.; Sham, T.K.

    1986-01-01

    The absorption spectra of O/sub 2/, CO, CO/sub 2/ and OCS have been recorded in a transmission mode in the energy region from 500 to 950 eV. Recent observation of EXAFS in these molecules is confirmed in this study. 7 refs., 3 figs.

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

    ERIC Educational Resources Information Center

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

    2004-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Roesler, Collin S.; Pery, Mary Jane

    1995-01-01

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

  8. Optical absorption of nanoporous silicon: quasiparticle band gaps and absorption spectra

    NASA Astrophysics Data System (ADS)

    Shi, Guangsha; Kioupakis, Emmanouil

    2013-03-01

    Silicon is an earth-abundant material of great importance in semiconductors electronics, but its photovoltaic applications are limited by the low absorption coefficient in the visible due to its indirect band gap. One strategy to improve the absorbance is to perforate silicon with nanoscale pores, which introduce carrier scattering that enables optical transitions across the indirect gap. We used density functional and many-body perturbation theory in the GW approximation to investigate the electronic and optical properties of porous silicon for various pore sizes, spacings, and orientations. Our calculations include up to 400 atoms in the unit cell. We will discuss the connection of the band-gap value and absorption coefficient to the underlying nanopore geometry. The absorption coefficient in the visible range is found to be optimal for appropriately chosen nanopore size, spacing, and orientation. Our work allows us to predict porous-silicon structures that may have optimal performance in photovoltaic applications. This research was supported as part of CSTEC, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science. Computational resources were provided by the DOE NERSC facility.

  9. THE PHYSICAL CONDITIONS OF THE INTRINSIC N V NARROW ABSORPTION LINE SYSTEMS OF THREE QUASARS

    SciTech Connect

    Wu Jian; Charlton, Jane C.; Misawa, Toru; Eracleous, Michael; Ganguly, Rajib E-mail: misawatr@shinshu-u.ac.j

    2010-10-20

    We employ detailed photoionization models to infer the physical conditions of intrinsic narrow absorption line systems found in high-resolution spectra of three quasars at z = 2.6-3.0. We focus on a family of intrinsic absorbers characterized by N V lines that are strong relative to the Ly{alpha} lines. The inferred physical conditions are similar for the three intrinsic N V absorbers, with metallicities greater than 10 times the solar value (assuming a solar abundance pattern), and with high ionization parameters (log U {approx} 0). Thus, we conclude that the unusual strength of the N V lines results from a combination of partial coverage, a high ionization state, and high metallicity. We consider whether dilution of the absorption lines by flux from the broad emission line region can lead us to overestimate the metallicities and we find that this is an unlikely possibility. The high abundances that we infer are not surprising in the context of scenarios in which metal enrichment takes place very early on in massive galaxies. We estimate that the mass outflow rate in the absorbing gas (which is likely to have a filamentary structure) is less than a few M{sub sun} yr{sup -1} under the most optimistic assumptions, although it may be embedded in a much hotter, more massive outflow.

  10. Asymmetry between absorption and photoluminescence line shapes of TPD: spectroscopic fingerprint of the twisted biphenyl core.

    PubMed

    Scholz, Reinhard; Gisslén, Linus; Himcinschi, Cameliu; Vragović, Igor; Calzado, Eva M; Louis, Enrique; San Fabián Maroto, Emilio; Díaz-García, María A

    2009-01-01

    We analyze absorption, photoluminescence (PL), and resonant Raman spectra of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), with the aim of providing a microscopic interpretation of a significant Stokes shift of about 0.5 eV that makes this material suitable for stimulated emission. The optical spectra were measured for TPD dissolved in toluene and chloroform, as well as for polystyrene films doped with varying amounts of TPD. In addition, we measured preresonant and resonant Raman spectra, giving direct access to the vibrational modes elongated in the relaxed excited geometry of the molecule. The experimental data are interpreted with calculations of the molecular geometry in the electronic ground state and the optically excited state using density functional theory. Several strongly elongated high-frequency modes within the carbon rings results in a vibronic progression with a calculated spacing of 158 meV, corroborated by the observation of vibrational sidebands in the PL spectra. The peculiarities of the potential energy surfaces related to a twisting around the central bond in the biphenyl core of TPD allow to quantify the asymmetry between the line shapes observed in absorption and emission. PMID:19086796

  11. High-Resolution Ultraviolet Spectra of the Dwarf Seyfert 1 Galaxy NGC 4395: Evidence for Intrinsic Absorption

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Kraemer, S. B.; Gabel, J. R.; Schmitt, H. R.; Filippenko, A. V.; Ho, L. C.; Shields, J. C.; Turner, T. J.

    2004-09-01

    We present ultraviolet spectra of the dwarf Seyfert 1 nucleus of NGC 4395, obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Hubble Space Telescope Space Telescope Imaging Spectrograph at velocity resolutions of 7-15 km s-1. We confirm our earlier claim of C IV absorption in low-resolution UV spectra and detect a number of other absorption lines with lower ionization potentials. In addition to the Galactic lines, we identify two kinematic components of absorption that are likely to be intrinsic to NGC 4395. We consider possible origins of the absorption, including the interstellar medium (ISM) of NGC 4395, the narrow-line region, the outflowing UV absorbers, and the X-ray ``warm absorbers.'' Component 1, at a radial velocity of -770 km s-1 with respect to the nucleus, is only identified in the C IV λ1548.2 line. It most likely represents an outflowing UV absorber, similar to those seen in a majority of Seyfert 1 galaxies, although additional observations are needed to confirm the reality of this feature. Component 2, at -114 km s-1, most likely arises in the ISM of NGC 4395; its ionic column densities cannot be matched by photoionization models with a power-law continuum. Our models of the highly ionized X-ray absorbers claimed for this active galactic nucleus indicate that they would have undetectable C IV absorption, but large O VI and H I columns should be present. We attribute our lack of detection of the O VI and Lyβ absorption from the X-ray absorbers to a combination of noise and dilution of the nuclear spectrum by hot stars in the large FUSE aperture. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555 these observations are associated with proposal GO-9362. Also based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer

  12. Possible spinel absorption bands in S-asteroid visible reflectance spectra

    NASA Technical Reports Server (NTRS)

    Hiroi, T.; Vilas, F.; Sunshine, J. M.

    1994-01-01

    Minor absorption bands in the 0.55 to 0.7 micron wavelength range of reflectance spectra of 10 S asteroids have been found and compared with those of spinel-group minerals using the modified Gaussian model. Most of these S asteroids are consistently shown to have two absorption bands around 0.6 and 0.67 micron. Of the spinel-group minerals examined in this study, the 0.6 and 0.67 micron bands are most consistent with those seen in chromite. Recently, the existence of spinels has also been detected from the absorption-band features around 1 and 2 micron of two S-asteroid reflectance spectra, and chromite has been found in a primitive achondrite as its major phase. These new findings suggest a possible common existence of spinel-group minerals in the solar system.

  13. Theoretical collision-induced rototranslational absorption spectra for the outer planets - H2-CH4 pairs

    NASA Astrophysics Data System (ADS)

    Borysow, A.; Frommhold, L.

    1986-05-01

    Computations of the rototranslational absorption spectra of H2-CH4 molecular complexes are presented which are based on the classical multipole expansion; spectral profiles are obtained from an exact quantum formalism. The interaction potential is based on laboratory measurements of H2-CH4 pairs at 195 and 297K. The computed spectra provide the most reliable temperature dependence of the absorption coefficient as a function of frequency that can be made under the present circumstances. A theoretical description of the H2CH4 dimer features is given in the isotropic potential approximation. This work is significant for the modeling of the far-infrared absorption of the outer planets' atmospheres, where H2 and CH4 are present.

  14. Local environment of metal ions in phthalocyanines: K-edge X-ray absorption spectra.

    PubMed

    Rossi, G; d'Acapito, F; Amidani, L; Boscherini, F; Pedio, M

    2016-09-14

    We report a detailed study of the K-edge X-ray absorption spectra of four transition metal phthalocyanines (MPc, M = Fe, Co, Cu and Zn). We identify the important single and multiple scattering contributions to the spectra in the extended energy range and provide a robust treatment of thermal damping; thus, a generally applicable model for the interpretation of X-ray absorption fine structure spectra is proposed. Consistent variations of bond lengths and Debye Waller factors are found as a function of atomic number of the metal ion, indicating a variation of the metal-ligand bond strength which correlates with the spatial arrangement and occupation of molecular orbitals. We also provide an interpretation of the near edge spectral features in the framework of a full potential real space multiple scattering approach and provide a connection to the local electronic structure. PMID:27510989

  15. Calibration and analysis of spatially resolved x-ray absorption spectra from a nonuniform plasma

    SciTech Connect

    Knapp, P. F.; Hansen, S. B.; Pikuz, S. A.; Shelkovenko, T. A.; Hammer, D. A.

    2012-07-15

    We report here the calibration and analysis techniques used to obtain spatially resolved density and temperature measurements of a pair of imploding aluminum wires from x-ray absorption spectra. A step wedge is used to measure backlighter fluence at the film, allowing transmission through the sample to be measured with an accuracy of {+-}14% or better. A genetic algorithm is used to search the allowed plasma parameter space and fit synthetic spectra with 20 {mu}m spatial resolution to the measured spectra, taking into account that the object plasma nonuniformity must be physically reasonable. The inferred plasma conditions must be allowed to vary along the absorption path in order to obtain a fit to the spectral data. The temperature is estimated to be accurate to within {+-}25% and the density to within a factor of two. This information is used to construct two-dimensional maps of the density and temperature of the object plasma.

  16. Calibration and analysis of spatially resolved x-ray absorption spectra from a nonuniform plasma.

    PubMed

    Knapp, P F; Hansen, S B; Pikuz, S A; Shelkovenko, T A; Hammer, D A

    2012-07-01

    We report here the calibration and analysis techniques used to obtain spatially resolved density and temperature measurements of a pair of imploding aluminum wires from x-ray absorption spectra. A step wedge is used to measure backlighter fluence at the film, allowing transmission through the sample to be measured with an accuracy of ±14% or better. A genetic algorithm is used to search the allowed plasma parameter space and fit synthetic spectra with 20 μm spatial resolution to the measured spectra, taking into account that the object plasma nonuniformity must be physically reasonable. The inferred plasma conditions must be allowed to vary along the absorption path in order to obtain a fit to the spectral data. The temperature is estimated to be accurate to within ±25% and the density to within a factor of two. This information is used to construct two-dimensional maps of the density and temperature of the object plasma. PMID:22852690

  17. WAVELENGTH MEASUREMENTS OF K TRANSITIONS OF OXYGEN, NEON, AND MAGNESIUM WITH X-RAY ABSORPTION LINES

    SciTech Connect

    Liao Jinyuan; Zhang Shuangnan; Yao Yangsen

    2013-09-10

    Accurate atomic transition data are important in many astronomical research areas, especially for studies of line spectroscopy. Whereas transition data of He-like and H-like ions (i.e., ions in high-charge states) have been accurately calculated, the corresponding data of K transitions of neutral or low-ionized metal elements are still very uncertain. Spectroscopy of absorption lines produced in the interstellar medium (ISM) has been proven to be an effective way to measure the central wavelengths of these atomic transitions. In this work, we analyze 36 Chandra High Energy Transmission Grating observations to search for and measure the ISM absorption lines along sight lines to 11 low-mass X-ray binaries. We correct the Galactic rotation velocity to the rest frame for every observation and then use two different methods to merge all the corrected spectra to a co-added spectrum. However, the co-added spectra obtained by this method exhibit biases, toward to either observations with high counts or lines with high signal-to-noise ratios. We do a Bayesian analysis of several significantly detected lines to obtain the systematic uncertainty and the bias correction for other lines. Compared to previous studies, our results improve the wavelength accuracy by a factor of two to five and significantly reduce the systematic uncertainties and biases. Several weak transitions (e.g., 1s-2p of Mg IV and Mg V; 1s-3p of Mg III and Mg V) are also detected for the first time, albeit with low significance; future observations with improved accuracy are required to confirm these detections.

  18. IMPROVED AND QUALITY-ASSESSED EMISSION AND ABSORPTION LINE MEASUREMENTS IN SLOAN DIGITAL SKY SURVEY GALAXIES

    SciTech Connect

    Oh, Kyuseok; Yi, Sukyoung K.; Sarzi, Marc; Schawinski, Kevin

    2011-08-01

    We present a new database of absorption and emission-line measurements based on the entire spectral atlas from the Sloan Digital Sky Survey (SDSS) 7th data release of galaxies within a redshift of 0.2. Our work makes use of the publicly available penalized pixel-fitting (pPXF) and gas and absorption line fitting (gandalf) IDL codes, aiming to improve the existing measurements for stellar kinematics, the strength of various absorption-line features, and the flux and width of the emissions from different species of ionized gas. Our fit to the stellar continuum uses both standard stellar population models and empirical templates obtained by combining a large number of stellar spectra in order to fit a subsample of high-quality SDSS spectra for quiescent galaxies. Furthermore, our fit to the nebular spectrum includes an exhaustive list of both recombination and forbidden lines. Foreground Galactic extinction is implicitly treated in our models, whereas reddening in the SDSS galaxies is included in the form of a simple dust screen component affecting the entire spectrum that is accompanied by a second reddening component affecting only the ionized gas emission. In order to check for systematic departures from the rather standard set of assumptions that enters our models, we provide a quality assessment for our fit to the SDSS spectra in our sample, for both the stellar continuum and the nebular emissions and across different wavelength regions. This quality assessment also allows the identification of objects with either problematic data or peculiar features. We hope to foster the discovery potential of our database; therefore, our spectral fit is available to the community. For example, based on the quality assessment around the H{alpha} and [N II] {lambda}6584 lines, approximately 1% of the SDSS spectra classified as 'galaxies' by the SDSS pipeline do in fact require additional broad lines to be matched, even though they do not show a strong continuum from an active

  19. Improved and Quality-assessed Emission and Absorption Line Measurements in Sloan Digital Sky Survey Galaxies

    NASA Astrophysics Data System (ADS)

    Oh, Kyuseok; Sarzi, Marc; Schawinski, Kevin; Yi, Sukyoung K.

    2011-08-01

    We present a new database of absorption and emission-line measurements based on the entire spectral atlas from the Sloan Digital Sky Survey (SDSS) 7th data release of galaxies within a redshift of 0.2. Our work makes use of the publicly available penalized pixel-fitting (pPXF) and gas and absorption line fitting (gandalf) IDL codes, aiming to improve the existing measurements for stellar kinematics, the strength of various absorption-line features, and the flux and width of the emissions from different species of ionized gas. Our fit to the stellar continuum uses both standard stellar population models and empirical templates obtained by combining a large number of stellar spectra in order to fit a subsample of high-quality SDSS spectra for quiescent galaxies. Furthermore, our fit to the nebular spectrum includes an exhaustive list of both recombination and forbidden lines. Foreground Galactic extinction is implicitly treated in our models, whereas reddening in the SDSS galaxies is included in the form of a simple dust screen component affecting the entire spectrum that is accompanied by a second reddening component affecting only the ionized gas emission. In order to check for systematic departures from the rather standard set of assumptions that enters our models, we provide a quality assessment for our fit to the SDSS spectra in our sample, for both the stellar continuum and the nebular emissions and across different wavelength regions. This quality assessment also allows the identification of objects with either problematic data or peculiar features. We hope to foster the discovery potential of our database; therefore, our spectral fit is available to the community. For example, based on the quality assessment around the Hα and [N II] λ6584 lines, approximately 1% of the SDSS spectra classified as "galaxies" by the SDSS pipeline do in fact require additional broad lines to be matched, even though they do not show a strong continuum from an active nucleus, as

  20. An Atlas of Far-ultraviolet Spectra of the Zeta Aurigae Binary 31 Cygni with Line Identifications

    NASA Astrophysics Data System (ADS)

    Hagen Bauer, Wendy; Bennett, Philip D.

    2014-04-01

    The ζ Aurigae system 31 Cygni (K4 Ib + B4 V) was observed by the FUSE satellite during total eclipse and at three phases during chromospheric eclipse. We present the coadded, calibrated spectra and atlases with line identifications. During total eclipse, emission from high ionization states (e.g., Fe III and Cr III) shows asymmetric profiles redshifted from the systemic velocity, while emission from lower ionization states (e.g., Fe II and O I) appears more symmetric and is centered closer to the systemic velocity. Absorption from neutral and singly ionized elements is detected during chromospheric eclipse. Late in chromospheric eclipse, absorption from the K star wind is detected at a terminal velocity of ~80 km s-1. These atlases will be useful for interpreting the far-UV spectra of other ζ Aur systems, as the observed FUSE spectra of 32 Cyg, KQ Pup, and VV Cep during chromospheric eclipse resemble that of 31 Cyg.

  1. AN ATLAS OF FAR-ULTRAVIOLET SPECTRA OF THE ZETA AURIGAE BINARY 31 CYGNI WITH LINE IDENTIFICATIONS

    SciTech Connect

    Bauer, Wendy Hagen; Bennett, Philip D.

    2014-04-01

    The ζ Aurigae system 31 Cygni (K4 Ib + B4 V) was observed by the FUSE satellite during total eclipse and at three phases during chromospheric eclipse. We present the coadded, calibrated spectra and atlases with line identifications. During total eclipse, emission from high ionization states (e.g., Fe III and Cr III) shows asymmetric profiles redshifted from the systemic velocity, while emission from lower ionization states (e.g., Fe II and O I) appears more symmetric and is centered closer to the systemic velocity. Absorption from neutral and singly ionized elements is detected during chromospheric eclipse. Late in chromospheric eclipse, absorption from the K star wind is detected at a terminal velocity of ∼80 km s{sup –1}. These atlases will be useful for interpreting the far-UV spectra of other ζ Aur systems, as the observed FUSE spectra of 32 Cyg, KQ Pup, and VV Cep during chromospheric eclipse resemble that of 31 Cyg.

  2. Asymmetric and symmetric absorption peaks observed in infrared spectra of CO2 adsorbed on TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Yamakawa, Koichiro; Sato, Yoshinori; Fukutani, Katsuyuki

    2016-04-01

    Infrared spectra of CO2 physisorbed on titania nanotubes (TiNTs), predominantly in the anatase polymorph, were measured at 81 K. Asymmetric and symmetric absorption peaks due to the antisymmetric stretch vibration (ν3) of CO2 were observed at 2340 cm-1 and 2350 cm-1, respectively. On the basis of the exposure- and time-dependence of the spectrum, the 2340 cm-1 peak was attributed to CO2 at the defective sites related to subsurface O vacancies (Vos) while the 2350 cm-1 peak was assigned to that at the fivefold coordinated Ti4+ sites. It was found that the generalized Fano line shape was well fitted to the 2340 cm-1 peak. We also observed an absorption peak at 2372 cm-1, which was attributed to the combination band of ν3 and the external mode of CO2 at Ti4+.

  3. Measurements of self-broadening of infrared absorption lines of ozone

    NASA Technical Reports Server (NTRS)

    Smith, M. A. H.; Rinsland, C. P.; Devi, V. M.

    1991-01-01

    Lorentz self-broadening coefficients have been determined for 355 spectral lines belonging to five different infrared vibration-rotation bands of O3 in the spectral region from 4.8 to 17 microns. Six ozone absorption spectra, recorded at room temperature using a Fourier transform spectrometer, were analyzed. The half-width values were obtained through a nonlinear least-squares spectral fitting procedure. The results are compared with previous measurements, and the vibration of the half-widths with vibrational and rotational quantum numbers is examined.

  4. Observation of Fano line shapes in infrared vibrational spectra of CO2 adsorbed on Cu(997) and Cu(111).

    PubMed

    Koitaya, Takanori; Shiozawa, Yuichiro; Mukai, Kozo; Yoshimoto, Shinya; Yoshinobu, Jun

    2016-02-01

    Adsorption states of carbon dioxide on the Cu(997) and Cu(111) surfaces were investigated by infrared reflection absorption spectroscopy, temperature programmed desorption, and X-ray photoelectron spectroscopy. CO2 molecules are physisorbed on the Cu(997) surface at temperatures below 70 K; neither chemisorption nor dissociation of CO2 occurs on the Cu(997) surface at this low temperature. However, the vibrational spectra of adsorbed CO2 depend significantly on the substrate temperature and coverage. IR spectra of CO2 vibrational modes at 70 K show asymmetric Fano line shapes, while only normal absorption bands are observed when CO2 is adsorbed at 20 K. Fano line shapes are also observed for CO2 on Cu(111) at 85 K. The observation of Fano effect indicates the coupling between the electronic continuum states of the Cu surface and the internal vibrational modes of CO2 even in such physisorbed system. PMID:26851930

  5. Observation of Fano line shapes in infrared vibrational spectra of CO2 adsorbed on Cu(997) and Cu(111)

    NASA Astrophysics Data System (ADS)

    Koitaya, Takanori; Shiozawa, Yuichiro; Mukai, Kozo; Yoshimoto, Shinya; Yoshinobu, Jun

    2016-02-01

    Adsorption states of carbon dioxide on the Cu(997) and Cu(111) surfaces were investigated by infrared reflection absorption spectroscopy, temperature programmed desorption, and X-ray photoelectron spectroscopy. CO2 molecules are physisorbed on the Cu(997) surface at temperatures below 70 K; neither chemisorption nor dissociation of CO2 occurs on the Cu(997) surface at this low temperature. However, the vibrational spectra of adsorbed CO2 depend significantly on the substrate temperature and coverage. IR spectra of CO2 vibrational modes at 70 K show asymmetric Fano line shapes, while only normal absorption bands are observed when CO2 is adsorbed at 20 K. Fano line shapes are also observed for CO2 on Cu(111) at 85 K. The observation of Fano effect indicates the coupling between the electronic continuum states of the Cu surface and the internal vibrational modes of CO2 even in such physisorbed system.

  6. Computational study of collision-induced dipole moments and absorption spectra of H

    NASA Astrophysics Data System (ADS)

    Zheng, Chunguang

    1997-08-01

    H2-H2 collision-induced absorption (CIA) spectra are computed for the first over-tone band at temperatures from 20 to 500 K, and for the rototranslational band at temperatures from 600 to 7,000 K. The theoretical results are based on simple model line shapes. The parameters of the model functions are obtained from the three lowest translational spectral moments, which are computed from the H2-H2 collision-induced dipole moments of Meyer et al. (1) using the sum formulae (2, 3). Ab initio computations of H2-H2 collision- induced dipole moments are performed using the Gaussian 92 program (4). The computations extend the previous work of Meyer et al. (1). Four internuclear distances of H2 molecule 1.111, 1.449, 1.787 and 2.150 a.u., and eleven intermolecular distances of H2-H2 from 2.5 to 9.0 a.u. are included in the computations. The radial transition matrix elements of the collision- induced dipole components are obtained for vibrational transitions /Delta v = (v1' - v1) + (v2' - v2) = 0, 1, 2, 3 and v1,/ v2 = 0, 1, 2. where v1 and v2 are the vibrational quantum numbers of the two interacting H2 molecules, and primes denote final states. The dependences of these matrix elements on the rotational quantum numbers of the two H2 molecules j1j1'j2j2' are obtained for j1j1'j2j2' up to 10. These matrix elements are suitable for high temperature H2-H2 CIA computations. The second overtone band H2-H2 CIA spectra are computed for the first time at temperatures from 20 to 500 K employing the newly developed H2-H2 collision-induced dipole moments. The computations are based on the three lowest translational spectral moments and simple model line shapes.

  7. An absorption line in the ultraviolet spectrum of 40 Eridani B

    NASA Technical Reports Server (NTRS)

    Greenstein, J. L.

    1980-01-01

    Two excellent low-resolution spectra show an absorption line of equivalent width 3 A, near 1391 A, in the typical DA (hydrogen atmosphere) white dwarf 40 Eri B. The line is confirmed by a high-resolution spectrum and is the first seen in any DA star. Ultraviolet fluxes and the profile of Lyman-alpha confirm an effective temperature near 17,000 K. If the line is Si IV, it requires a temperature near 40,000 K. Unattractive possibilities are a hot circumstellar absorbing envelope dependent on accretion from companions, or formation at large optical depth in a transparent atmosphere with high Si/H. A suggestion that H2 should be considered leads to the possible interpretation as the (0, 5) transition of the Lyman band, formed at small optical depth. The band should be stronger in cooler DAs.

  8. VERY LARGE TELESCOPE SPECTROPOLARIMETRY OF BROAD ABSORPTION LINE QSOs

    SciTech Connect

    DiPompeo, M. A.; Brotherton, M. S.; De Breuck, C.

    2011-03-15

    We present spectropolarimetry of 19 confirmed and four possible bright, southern broad absorption line (BAL) quasars from the European Southern Observatory Very Large Telescope. A wide range of redshifts is covered in the sample (from 0.9 to 3.4), and both low- and high-ionization quasars are represented, as well as radio-loud and radio-quiet BALQSOs. We continue to confirm previously established spectropolarimetric properties of BALQSOs, including the generally rising continuum polarization with shorter wavelengths and comparatively large fraction with high broadband polarization (6 of 19 with polarizations >2%). Emission lines are polarized less than or similar to the continuum, except in a few unusual cases, and absorption troughs tend to have higher polarizations. A search for correlations between polarization properties has been done, identifying two significant or marginally significant correlations. These are an increase in continuum polarization with decreasing optical luminosity (increasing absolute B magnitude) and decreasing C IV emission-line polarization with increased continuum polarization.

  9. High resolution infrared absorption spectra of various trace gases present in the upper atmosphere of the Earth

    NASA Technical Reports Server (NTRS)

    Hunt, Robert H.

    1988-01-01

    The objective of NASA Grant NsG 7473 was to obtain and analyze high resolution infrared absorption spectra of various trace gases present in the Earth's upper atmosphere. The goal of the spectral analysis was to obtain values of absorption line strengths, widths and frequencies of sufficient accuracy for use in upper atmosphere trace gas monitoring. During the early phase of the grant, high resolution spectra were obtained from two instruments. One was the 0.02/cm resolution vacuum grating spectrometer at the Florida State University and the other was the 0.01/cm resolution Fourier transform spectrometer at the McMath solar telescope at the Kitt Peak Observatory. Using these instruments, a considerable amount of spectra of methane and hydrogen peroxide were obtained and analyzed. During the latter years of the project, data taking was halted while efforts were devoted to building a new 0.0025/cm resolution vacuum Fourier transform spectrometer. Progress during this phase of the grant then became greatly slowed due to a lack of suitable graduate students in the program. However, the instrument was completed and brought to the point of producing interferograms.

  10. ``Ultimate'' information content in solar and stellar spectra. Photospheric line asymmetries and wavelength shifts

    NASA Astrophysics Data System (ADS)

    Dravins, Dainis

    2008-12-01

    Context: Spectral-line asymmetries (displayed as bisectors) and wavelength shifts are signatures of the hydrodynamics in solar and stellar atmospheres. Theory may precisely predict idealized lines, but accuracies in real observed spectra are limited by blends, few suitable lines, imprecise laboratory wavelengths, and instrumental imperfections. Aims: We extract bisectors and shifts until the “ultimate” accuracy limits in highest-quality solar and stellar spectra, so as to understand the various limits set by (i) stellar physics (number of relevant spectral lines, effects of blends, rotational line broadening); by (ii) observational techniques (spectral resolution, photometric noise); and by (iii) limitations in laboratory data. Methods: Several spectral atlases of the Sun and bright solar-type stars were examined for those thousands of “unblended” lines with the most accurate laboratory wavelengths, yielding bisectors and shifts as averages over groups of similar lines. Representative data were obtained as averages over groups of similar lines, thus minimizing the effects of photometric noise and of random blends. Results: For the solar-disk center and integrated sunlight, the bisector shapes and shifts were extracted for previously little-studied species (Fe II, Ti I, Ti II, Cr II, Ca I, C I), using recently determined and very accurate laboratory wavelengths. In Procyon and other F-type stars, a sharp blueward bend in the bisector near the spectral continuum is confirmed, revealing line saturation and damping wings in upward-moving photospheric granules. Accuracy limits are discussed: “astrophysical” noise due to few measurable lines, finite instrumental resolution, superposed telluric absorption, inaccurate laboratory wavelengths, and calibration noise in spectrometers, together limiting absolute lineshift studies to ≈50-100 m s-1. Conclusions: Spectroscopy with resolutions λ/Δλ ≈ 300 000 and accurate wavelength calibration will enable

  11. A Passive Method for Detecting Vegetation Stress from Orbit: Chlorophyll Fluorescence Spectra from Fraunhofer Lines

    NASA Technical Reports Server (NTRS)

    Theisen, Arnold F.

    2000-01-01

    Solar-stimulated chlorophyll fluorescence measured with the Fraunhofer line depth method has correlated well with vegetation stress in previous studies. However, the instruments used in those studies were limited to a single solar absorption line (e.g. 656.3 nm), obviating the red/far-red ratio (R/FR) method. Optics and detector technology have reached the level whereby multiple, very narrow Fraunhofer lines are resolvable. Thirteen such lines span the visible spectrum in the red to far-red region where chlorophyll fluorescence occurs. Fluorescence intensities at the 13 Fraunhofer line wavelengths were used to model emission spectra. The source data were collected for summer and fall bean crops (Phaseolus vulgaris L.) subjected to various levels of nitrogen fertilization. The intensities were adjusted to account for Fraunhofer line depth and atmospheric transmittance. Multiple R/FR fluorescence ratios, calculated from the modeled fluorescence spectra, correlated strongly with leaf chlorophyll concentration and well with applied nitrogen. The ratio yielding the best correlation with chlorophyll utilized red fluorescence at the 694.5 nm Fraunhofer line and farred fluorescence at the 755.6 nm Fraunhofer line. Twenty R/FR ratios, each evaluated for the maximum differential between low and high (optimal) nitrogen treatments, ranked higher in some cases and lower in others, possibly related to the time of year the crops were grown and the stage of growth of the crops. Ratios with 728.9 nm and 738.9 nm in the denominator consistently ranked in the lowest and next lowest quartile, respectively. Ratios of the 656.3 nm Fraunhofer line and the 755.6 nm line consistently ranked highest for the summer crop. Ratios with 755.6 nm in the denominator ranked in the upper quartile for 10 out of 12 measurement dates. Differences in ratio ranking indicate that physiological conditions may be estimated using selected ratios of Fraunhofer lines within the context of R/FR analysis. A

  12. Quantum mechanical calculation of the collision-induced absorption spectra of N{sub 2}–N{sub 2} with anisotropic interactions

    SciTech Connect

    Karman, Tijs; Groenenboom, Gerrit C.; Avoird, Ad van der; Miliordos, Evangelos; Hunt, Katharine L. C.

    2015-02-28

    We present quantum mechanical calculations of the collision-induced absorption spectra of nitrogen molecules, using ab initio dipole moment and potential energy surfaces. Collision-induced spectra are first calculated using the isotropic interaction approximation. Then, we improve upon these results by considering the full anisotropic interaction potential. We also develop the computationally less expensive coupled-states approximation for calculating collision-induced spectra and validate this approximation by comparing the results to numerically exact close-coupling calculations for low energies. Angular localization of the scattering wave functions due to anisotropic interactions affects the line strength at low energies by two orders of magnitude. The effect of anisotropy decreases at higher energy, which validates the isotropic interaction approximation as a high-temperature approximation for calculating collision-induced spectra. Agreement with experimental data is reasonable in the isotropic interaction approximation, and improves when the full anisotropic potential is considered. Calculated absorption coefficients are tabulated for application in atmospheric modeling.

  13. High-resolution spectroscopy of V854 Cen in decline - absorption and emission lines of C2 molecules

    NASA Astrophysics Data System (ADS)

    Kameswara Rao, N.; Lambert, David L.

    2000-04-01

    High-resolution optical spectra of the R Coronae Borealis (RCB) star V854 Centauri in the early stages of a decline show, in addition to the features reported for other RCBs in decline, narrow absorption lines from the C2 Phillips system. The low rotational temperature, Trot=1150K, of the C2 ground electronic state suggests the cold gas is associated with the developing shroud of carbon dust. These absorption lines were not seen at a fainter magnitude on the rise from minimum light, nor at maximum light. This is the first detection of cold gas around an RCB star.

  14. Communication: On the difficulty of reproducibly measuring PbCl2 X-ray absorption spectra

    NASA Astrophysics Data System (ADS)

    Schwartz, Craig P.; Prendergast, David

    2015-09-01

    Previous measurements of the X-ray absorption spectra of PbCl2 at the chlorine K-edge have shown significant variation between different studies. Herein, using first principles simulations of X-ray absorption spectroscopy, we show that the observed spectral variations are due to the generation of Cl2 gas and depletion of chlorine from PbCl2, consistent with what is observed during ultraviolet absorption for the same compound. We note that Cl2 gas generation can also be initiated using higher resonant X-ray energies, including Pb X-ray absorption edges. While this casts doubt on previous interpretations of certain measurements, it does indicate a means of generating chlorine gas during in situ experiments by passing high energy x-rays through a hard x-ray transparent medium and onto PbCl2.

  15. Communication: On the difficulty of reproducibly measuring PbCl2 X-ray absorption spectra.

    PubMed

    Schwartz, Craig P; Prendergast, David

    2015-09-21

    Previous measurements of the X-ray absorption spectra of PbCl2 at the chlorine K-edge have shown significant variation between different studies. Herein, using first principles simulations of X-ray absorption spectroscopy, we show that the observed spectral variations are due to the generation of Cl2 gas and depletion of chlorine from PbCl2, consistent with what is observed during ultraviolet absorption for the same compound. We note that Cl2 gas generation can also be initiated using higher resonant X-ray energies, including Pb X-ray absorption edges. While this casts doubt on previous interpretations of certain measurements, it does indicate a means of generating chlorine gas during in situ experiments by passing high energy x-rays through a hard x-ray transparent medium and onto PbCl2. PMID:26395677

  16. IR absorption and Raman spectra of single crystals of stable germanium isotopes

    NASA Astrophysics Data System (ADS)

    Gavva, V. A.; Kotereva, T. V.; Lipskiy, V. A.; Nezhdanov, A. V.

    2016-02-01

    The Raman and IR absorption spectra of single crystals of germanium isotopes 72Ge, 73Ge, 74Ge, and 76Ge in the region of phonon absorption and interband electronic transitions are studied at room temperature. The dependence of the Raman peak position on the atomic mass has the form ν ~ M -1/2. The shifts of the phonon absorption peaks of individual isotopes with respect to germanium of natural isotopic composition natGe are determined. With increasing average atomic mass of germanium, these peaks shift to longer wavelengths. In the region of interband electronic transitions, the intrinsic absorption edge of 76Ge is observed to shift by 1 meV to higher energies with respect to Ge of natural isotopic composition. For isotopes with atomic masses close to that of natural germanium (72Ge,73Ge, 74Ge), we found no significant difference in the band gap width at room temperature.

  17. High-dispersion absorption-line spectroscopy of AE Aqr

    NASA Astrophysics Data System (ADS)

    Echevarría, J.; Smith, Robert Connon; Costero, R.; Zharikov, S.; Michel, R.

    2008-07-01

    High-dispersion time-resolved spectroscopy of the unique magnetic cataclysmic variable AE Aqr is presented. A radial velocity analysis of the absorption lines yields K2 = 168.7 +/- 1kms-1. Substantial deviations of the radial velocity curve from a sinusoid are interpreted in terms of intensity variations over the secondary star's surface. A complex rotational velocity curve as a function of orbital phase is detected which has a modulation frequency of twice the orbital frequency, leading to an estimate of the binary inclination angle that is close to 70°. The minimum and maximum rotational velocities are used to indirectly derive a mass ratio of q = 0.6 and a radial velocity semi-amplitude of the white dwarf of K1 = 101 +/- 3kms-1. We present an atmospheric temperature indicator, based on the absorption-line ratio of FeI and CrI lines, whose variation indicates that the secondary star varies from K0 to K4 as a function of orbital phase. The ephemeris of the system has been revised, using more than 1000 radial velocity measurements, published over nearly five decades. From the derived radial velocity semi-amplitudes and the estimated inclination angle, we calculate that the masses of the stars are M1 = 0.63 +/- 0.05Msolar M2 = 0.37 +/- 0.04Msolar, and their separation is a = 2.33 +/- 0.02Rsolar. Our analysis indicates the presence of a late-type star whose radius is larger, by a factor of nearly 2, than the radius of a normal main-sequence star of the same mass. Finally, we discuss the possibility that the measured variations in the rotational velocity, temperature and spectral type of the secondary star as functions of orbital phase may, like the radial velocity variations, be attributable to regions of enhanced absorption on the star's surface.

  18. Constraining the variation of the fine-structure constant with observations of narrow quasar absorption lines

    SciTech Connect

    Songaila, A.; Cowie, L. L.

    2014-10-01

    The unequivocal demonstration of temporal or spatial variability in a fundamental constant of nature would be of enormous significance. Recent attempts to measure the variability of the fine-structure constant α over cosmological time, using high-resolution spectra of high-redshift quasars observed with 10 m class telescopes, have produced conflicting results. We use the many multiplet (MM) method with Mg II and Fe II lines on very high signal-to-noise, high-resolution (R = 72, 000) Keck HIRES spectra of eight narrow quasar absorption systems. We consider both systematic uncertainties in spectrograph wavelength calibration and also velocity offsets introduced by complex velocity structure in even apparently simple and weak narrow lines and analyze their effect on claimed variations in α. We find no significant change in α, Δα/α = (0.43 ± 0.34) × 10{sup –5}, in the redshift range z = 0.7-1.5, where this includes both statistical and systematic errors. We also show that the scatter in measurements of Δα/α arising from absorption line structure can be considerably larger than assigned statistical errors even for apparently simple and narrow absorption systems. We find a null result of Δα/α = (– 0.59 ± 0.55) × 10{sup –5} in a system at z = 1.7382 using lines of Cr II, Zn II, and Mn II, whereas using Cr II and Zn II lines in a system at z = 1.6614 we find a systematic velocity trend that, if interpreted as a shift in α, would correspond to Δα/α = (1.88 ± 0.47) × 10{sup –5}, where both results include both statistical and systematic errors. This latter result is almost certainly caused by varying ionic abundances in subcomponents of the line: using Mn II, Ni II, and Cr II in the analysis changes the result to Δα/α = (– 0.47 ± 0.53) × 10{sup –5}. Combining the Mg II and Fe II results with estimates based on Mn II, Ni II, and Cr II gives Δα/α = (– 0.01 ± 0.26) × 10{sup –5}. We conclude that spectroscopic measurements of

  19. Constraining the Variation of the Fine-structure Constant with Observations of Narrow Quasar Absorption Lines

    NASA Astrophysics Data System (ADS)

    Songaila, A.; Cowie, L. L.

    2014-10-01

    The unequivocal demonstration of temporal or spatial variability in a fundamental constant of nature would be of enormous significance. Recent attempts to measure the variability of the fine-structure constant α over cosmological time, using high-resolution spectra of high-redshift quasars observed with 10 m class telescopes, have produced conflicting results. We use the many multiplet (MM) method with Mg II and Fe II lines on very high signal-to-noise, high-resolution (R = 72, 000) Keck HIRES spectra of eight narrow quasar absorption systems. We consider both systematic uncertainties in spectrograph wavelength calibration and also velocity offsets introduced by complex velocity structure in even apparently simple and weak narrow lines and analyze their effect on claimed variations in α. We find no significant change in α, Δα/α = (0.43 ± 0.34) × 10-5, in the redshift range z = 0.7-1.5, where this includes both statistical and systematic errors. We also show that the scatter in measurements of Δα/α arising from absorption line structure can be considerably larger than assigned statistical errors even for apparently simple and narrow absorption systems. We find a null result of Δα/α = (- 0.59 ± 0.55) × 10-5 in a system at z = 1.7382 using lines of Cr II, Zn II, and Mn II, whereas using Cr II and Zn II lines in a system at z = 1.6614 we find a systematic velocity trend that, if interpreted as a shift in α, would correspond to Δα/α = (1.88 ± 0.47) × 10-5, where both results include both statistical and systematic errors. This latter result is almost certainly caused by varying ionic abundances in subcomponents of the line: using Mn II, Ni II, and Cr II in the analysis changes the result to Δα/α = (- 0.47 ± 0.53) × 10-5. Combining the Mg II and Fe II results with estimates based on Mn II, Ni II, and Cr II gives Δα/α = (- 0.01 ± 0.26) × 10-5. We conclude that spectroscopic measurements of quasar absorption lines are not yet capable of

  20. Plant phenolics and absorption features in vegetation reflectance spectra near 1.66 μm

    NASA Astrophysics Data System (ADS)

    Kokaly, Raymond F.; Skidmore, Andrew K.

    2015-12-01

    Past laboratory and field studies have quantified phenolic substances in vegetative matter from reflectance measurements for understanding plant response to herbivores and insect predation. Past remote sensing studies on phenolics have evaluated crop quality and vegetation patterns caused by bedrock geology and associated variations in soil geochemistry. We examined spectra of pure phenolic compounds, common plant biochemical constituents, dry leaves, fresh leaves, and plant canopies for direct evidence of absorption features attributable to plant phenolics. Using spectral feature analysis with continuum removal, we observed that a narrow feature at 1.66 μm is persistent in spectra of manzanita, sumac, red maple, sugar maple, tea, and other species. This feature was consistent with absorption caused by aromatic Csbnd H bonds in the chemical structure of phenolic compounds and non-hydroxylated aromatics. Because of overlapping absorption by water, the feature was weaker in fresh leaf and canopy spectra compared to dry leaf measurements. Simple linear regressions of feature depth and feature area with polyphenol concentration in tea resulted in high correlations and low errors (% phenol by dry weight) at the dry leaf (r2 = 0.95, RMSE = 1.0%, n = 56), fresh leaf (r2 = 0.79, RMSE = 2.1%, n = 56), and canopy (r2 = 0.78, RMSE = 1.0%, n = 13) levels of measurement. Spectra of leaves, needles, and canopies of big sagebrush and evergreens exhibited a weak absorption feature centered near 1.63 μm, short ward of the phenolic compounds, possibly consistent with terpenes. This study demonstrates that subtle variation in vegetation spectra in the shortwave infrared can directly indicate biochemical constituents and be used to quantify them. Phenolics are of lesser abundance compared to the major plant constituents but, nonetheless, have important plant functions and ecological significance. Additional research is needed to advance our understanding of the spectral influences

  1. THE PITTSBURGH SLOAN DIGITAL SKY SURVEY Mg II QUASAR ABSORPTION-LINE SURVEY CATALOG

    SciTech Connect

    Quider, Anna M.; Nestor, Daniel B.; Turnshek, David A.; Rao, Sandhya M.; Weyant, Anja N.; Monier, Eric M.; Busche, Joseph R.

    2011-04-15

    We present a catalog of intervening Mg II quasar absorption-line systems in the redshift interval 0.36 {<=} z {<=} 2.28. The catalog was built from Sloan Digital Sky Survey Data Release Four (SDSS DR4) quasar spectra. Currently, the catalog contains {approx}17, 000 measured Mg II doublets. We also present data on the {approx}44, 600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available online. A careful second search of 500 random spectra indicated that, for every 100 spectra searched, approximately one significant Mg II system was accidentally rejected. Current plans to expand the catalog beyond DR4 quasars are discussed. Many Mg II absorbers are known to be associated with galaxies. Therefore, the combination of large size and well understood statistics makes this catalog ideal for precision studies of the low-ionization and neutral gas regions associated with galaxies at low to moderate redshift. An analysis of the statistics of Mg II absorbers using this catalog will be presented in a subsequent paper.

  2. The Pittsburgh Sloan Digital Sky Survey Mg II Quasar Absorption-line Survey Catalog

    NASA Astrophysics Data System (ADS)

    Quider, Anna M.; Nestor, Daniel B.; Turnshek, David A.; Rao, Sandhya M.; Monier, Eric M.; Weyant, Anja N.; Busche, Joseph R.

    2011-04-01

    We present a catalog of intervening Mg II quasar absorption-line systems in the redshift interval 0.36 <= z <= 2.28. The catalog was built from Sloan Digital Sky Survey Data Release Four (SDSS DR4) quasar spectra. Currently, the catalog contains ~17, 000 measured Mg II doublets. We also present data on the ~44, 600 quasar spectra which were searched to construct the catalog, including redshift and magnitude information, continuum-normalized spectra, and corresponding arrays of redshift-dependent minimum rest equivalent widths detectable at our confidence threshold. The catalog is available online. A careful second search of 500 random spectra indicated that, for every 100 spectra searched, approximately one significant Mg II system was accidentally rejected. Current plans to expand the catalog beyond DR4 quasars are discussed. Many Mg II absorbers are known to be associated with galaxies. Therefore, the combination of large size and well understood statistics makes this catalog ideal for precision studies of the low-ionization and neutral gas regions associated with galaxies at low to moderate redshift. An analysis of the statistics of Mg II absorbers using this catalog will be presented in a subsequent paper.

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

    NASA Astrophysics Data System (ADS)

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

    2007-05-01

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

  4. FTIR spectrometer with 30 m optical cell and its applications to the sensitive measurements of selective and nonselective absorption spectra

    NASA Astrophysics Data System (ADS)

    Ponomarev, Yu. N.; Solodov, A. A.; Solodov, A. M.; Petrova, T. M.; Naumenko, O. V.

    2016-07-01

    A description of the spectroscopic complex at V.E. Zuev Institute of Atmospheric Optics, SB RAS, operating in a wide spectral range with high threshold sensitivity to the absorption coefficient is presented. Measurements of weak lines and nonselective spectra of CO2 and H2O were performed based on the built setup. As new application of this setup, positions and intensities of 152 weak lines of H2O were measured between 2400 and 2560 cm-1 with threshold sensitivity of 8.6×10-10 cm-1, and compared with available calculated and experimental data. Essential deviations between the new intensity measurements and calculated data accepted in HITRAN 2012 and GEISA 2015 forthcoming release are found.

  5. Studies on external electric field effects on absorption and fluorescence spectra of NADH

    NASA Astrophysics Data System (ADS)

    Nakabayashi, Takakazu; Islam, Md. Serajul; Li, Liming; Yasuda, Masahide; Ohta, Nobuhiro

    2014-03-01

    Electric field effects on absorption and fluorescence spectra have been investigated for NADH that is a representative autofluorescent chromophore in cells. The change in electric dipole moment following absorption is significant in the electroabsorption spectrum, indicating charge transfer character in the excited state. The fluorescence intensity decreases in the presence of an electric field, which arises from the field-induced increase in the rate of the non-radiative process. The blue shift of the fluorescence spectrum and the increase in the fluorescence lifetime of NADH are measured in yeast cells, which is discussed in terms of a local electric field around NADH.

  6. Absorption spectra of monolayer MoS2 in high magnetic field

    NASA Astrophysics Data System (ADS)

    Yang, Hung-Duen; Her, Jim-Long; Takeyama, Shojiro; Matsuda, Yasuhiro; Wang, Kai-Hsuan

    2015-03-01

    We have measured the absorption spectra of monolayer MoS2 film at several temperatures in pulsed high magnetic fields up to 52 T. At room temperature, the observed spectrum dominated by two main peaks, which are located at 660 nm and 606 nm. These peaks are ascribed to excition and trion absorption peaks respectively [1]. At low temperature (4.2 K), two peaks show the blue shift to 633 nm and 588 nm, respectively. Irrespective of the temperature, applying magnetic field does not show pronounced influence on the peaks even in 52 T.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  8. Dust depletion of Ca and Ti in QSO absorption-line systems

    NASA Astrophysics Data System (ADS)

    Guber, C. R.; Richter, P.

    2016-06-01

    Aims: To explore the role of titanium- and calcium-dust depletion in gas in and around galaxies, we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. Methods: We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope (VLT) and spectroscopically analyze 34 absorption-line systems at z ≤ 0.5 to measure column densities (or limits) for Ca ii and Ti ii. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z ~ 3.8. Our absorber sample contains 110 absorbers including damped Lyman α systems (DLAs), sub-DLAs, and Lyman-Limit systems (LLS). We compare our Ti/Ca findings with results from the Milky Way and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems. Results: Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca] ≈ 1. While the calcium-dust depletion in most of the absorbers appears to be severe, the titanium depletions are mild in systems with high Ti/Ca ratios. The derived trend indicates that absorbers with high Ti/Ca ratios have dust-to-gas ratios that are substantially lower than in the Milky Way. We characterize the overall nature of the absorbers by correlating Ti/Ca with other observables (e.g., metallicity, velocity-component structure) and by modeling the ionization properties of singly-ionized Ca and Ti in different environments. Conclusions: We conclude that Ca ii and Ti ii bearing absorption-line systems trace predominantly neutral gas in the disks and inner halo regions of galaxies, where the abundance of Ca and Ti reflects the local metal and dust content of the gas. Our study suggests that the Ti/Ca ratio represents a useful measure for the gas-to-dust ratio and overall metallicity in intervening absorption-line systems.

  9. The orientation and polarization of broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    DiPompeo, M. A.; Brotherton, M. S.; De Breuck, C.

    2013-01-01

    We present new spectropolarimetric observations of eight radio-loud broad absorption line (BAL) quasars, and combine these new data with our previous spectropolarimetric atlases (of both radio-loud and radio-quiet objects; DiPompeo et al. 2010, DiPompeo et al. 2011a) in order to investigate the polarization properties of BAL quasars as a group. The total (radio-selected) sample includes 36 (26) high-ionization and 22 (15) low-ionization BAL quasars (HiBALs and LoBALs, respectively). On average, we confirm that broad emission lines are polarized at a level similar to or less than the continuum and broad absorption troughs are more highly polarized, but we note that these properties are not true for all individual objects. Of the whole sample, 18 (31 per cent) have high (>2 per cent) continuum polarization, including 45 per cent of the LoBALs and 22 per cent of the HiBALs. We identify a few correlations between polarization and other quasar properties, as well as some interesting non-correlations. In particular, continuum polarization does not correlate with radio spectral index, which suggests that the polarization is not due to a standard geometry and preferred viewing angle to BAL quasars. The polarization also does not correlate with the amount of intrinsic dust reddening, indicating that the polarization is not solely due to direct light attenuation either. Polarization does appear to depend on the minimum BAL outflow velocity, confirming the results of previous studies and it may correlate with the maximum outflow velocity. We also find that continuum polarization anticorrelates with the polarization in the C iv broad emission and broad absorption. These results suggest that the polarization of BAL quasars cannot be described by one simple model, and that the scatterer location and geometry can vary significantly from object to object.

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

    NASA Technical Reports Server (NTRS)

    Du, Ping

    1993-01-01

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

  11. Impact of different visible light spectra on oxygen absorption and surface discoloration of bologna sausage.

    PubMed

    Böhner, Nadine; Rieblinger, Klaus

    2016-11-01

    The objective of this study was to evaluate the influence of several visible light spectra in various intensities on the oxygen absorption and surface color of sliced bologna. Sausage samples were stored in a gastight model packaging system and illuminated at 5°C with six single-colored LEDs covering the main part of the visible light spectrum. The initial oxygen level was set at 0.5% in order to simulate common residual oxygen amounts in conventional packaging. The oxygen absorption and the discoloration measured as changes in CIE a*-value were dependent from the applied light intensity. The color stability of bologna was differently affected by light of various wavelengths. The results show that the use of suitable LEDs with specific spectra for display illumination can help to reduce the light induced deterioration of cured sausages in retail markets. PMID:27343458

  12. Spectroscopic Parameters for Ozone and its Isotopes: Current Status, Prospects for Improvement, and the Identification of 16O16O17O and O-16O-16O-17 and O-16O-17O-16 Lines in Infrared Ground-Based and Stratospheric Solar Absorption Spectra

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Flaud, J.-M.; Goldman, A.; Perrin, A.; Camy-Peyret, C.; Smith, M. A. H.; Devi, V. Malathy; Benner, D. C.; Barbe, A.; Stephens, T. M.; Murcray, F. J.

    1998-01-01

    We describe the updates to the spectroscopic parameters of ozone and its isotopes in the 1996 HITRAN compilation. Recent published studies not included in HITRAN are also summarized. Finally, we report the identification of infrared lines of the v(sub 3) bands of O-16O-16O-17 and O-16O-17O-16 in high-resolution solar spectra recorded by stratospheric balloon-borne and ground-based Fourier transform spectrometers.

  13. The JHU-SDSS Metal Absorption Line Catalog: Redshift Evolution and Properties of Mg II Absorbers

    NASA Astrophysics Data System (ADS)

    Zhu, Guangtun; Ménard, Brice

    2013-06-01

    We present a generic and fully automatic method aimed at detecting absorption lines in the spectra of astronomical objects. The algorithm estimates the source continuum flux using a dimensionality reduction technique and nonnegative matrix factorization, and then detects and identifies metal absorption lines. We apply it to a sample of ~105 quasar spectra from the Sloan Digital Sky Survey and compile a sample of ~40,000 Mg II- and Fe II-absorber systems, spanning the redshift range 0.4 < z < 2.3. The corresponding catalog is publicly available. We study the statistical properties of these absorber systems and find that the rest equivalent width distribution of strong Mg II absorbers follows an exponential distribution at all redshifts, confirming previous studies. Combining our results with recent near-infrared observations of Mg II absorbers, we introduce a new parameterization that fully describes the incidence rate of these systems up to z ~ 5. We find the redshift evolution of strong Mg II absorbers to be remarkably similar to the cosmic star formation history over 0.4 < z < 5.5 (the entire redshift range covered by observations), suggesting a physical link between these two quantities.

  14. THE JHU-SDSS METAL ABSORPTION LINE CATALOG: REDSHIFT EVOLUTION AND PROPERTIES OF Mg II ABSORBERS

    SciTech Connect

    Zhu Guangtun; Menard, Brice

    2013-06-20

    We present a generic and fully automatic method aimed at detecting absorption lines in the spectra of astronomical objects. The algorithm estimates the source continuum flux using a dimensionality reduction technique and nonnegative matrix factorization, and then detects and identifies metal absorption lines. We apply it to a sample of {approx}10{sup 5} quasar spectra from the Sloan Digital Sky Survey and compile a sample of {approx}40,000 Mg II- and Fe II-absorber systems, spanning the redshift range 0.4 < z < 2.3. The corresponding catalog is publicly available. We study the statistical properties of these absorber systems and find that the rest equivalent width distribution of strong Mg II absorbers follows an exponential distribution at all redshifts, confirming previous studies. Combining our results with recent near-infrared observations of Mg II absorbers, we introduce a new parameterization that fully describes the incidence rate of these systems up to z {approx} 5. We find the redshift evolution of strong Mg II absorbers to be remarkably similar to the cosmic star formation history over 0.4 < z < 5.5 (the entire redshift range covered by observations), suggesting a physical link between these two quantities.

  15. Empirical calibrations of optical absorption-line indices based on the stellar library MILES

    NASA Astrophysics Data System (ADS)

    Johansson, Jonas; Thomas, Daniel; Maraston, Claudia

    2010-07-01

    Stellar population models of absorption-line indices are an important tool for the analysis of stellar population spectra. They are most accurately modelled through empirical calibrations of absorption-line indices with the stellar parameters such as effective temperature, metallicity and surface gravity, which are the so-called fitting functions. Here we present new empirical fitting functions for the 25 optical Lick absorption-line indices based on the new stellar library Medium resolution INT Library of Empirical Spectra (MILES). The major improvements with respect to the Lick/IDS library are the better sampling of stellar parameter space, a generally higher signal-to-noise ratio and a careful flux calibration. In fact, we find that errors on individual index measurements in MILES are considerably smaller than in Lick/IDS. Instead, we find the rms of the residuals between the final fitting functions and the data to be dominated by errors in the stellar parameters. We provide fitting functions for both Lick/IDS and MILES spectral resolutions and compare our results with other fitting functions in the literature. A FORTRAN 90 code is available online in order to simplify the implementation in stellar population models. We further calculate the offsets in index measurements between the Lick/IDS system to a flux-calibrated system. For this purpose, we use the three libraries MILES, ELODIE and STELIB. We find that offsets are negligible in some cases, most notably for the widely used indices Hβ, Mgb, Fe5270 and Fe5335. In a number of cases, however, the difference between the flux-calibrated library and Lick/IDS is significant with the offsets depending on index strengths. Interestingly, there is no general agreement between the three libraries for a large number of indices, which hampers the derivation of a universal offset between the Lick/IDS and flux-calibrated systems.

  16. Emission and absorption spectra of some bridged 1,5-benzodiazepines

    NASA Astrophysics Data System (ADS)

    Mellor, J. M.; Pathirana, R. N.; Stibbard, J. H. A.

    Absorption spectra in neutral and acidic media are reported for a series of bridged 1,5-benzodiazepines, which are unable to tautomerize. Comparison is made with non-bridged 1,5-benzodiazepines capable of tautomeric rearrangement. Both bridged and non-bridged 1,5-benzodiazepines are essentially non-fluorescent due to the "proximity effect" of interaction between singlet ηπ* and ππ* states of similar energy, a phenomenon previously recognised in six-membered nitrogen heterocycles.

  17. Absorption features in the 3 micron spectra of highly obscured objects

    NASA Technical Reports Server (NTRS)

    Smith, Robert G.; Sellgren, Kris; Tokunaga, Alan T.

    1989-01-01

    Using the IRTF cooled-grating spectrometer moderate resolution 2.4 to 3.8 micron spectra of a selection of IR protostars and one object located behind the Taurus dark cloud were obtained. Two examples of the spectra are presented. It is clear that the absorption near 3.07 micron is dominated by H2O ice and a comparison between the spectra and a simple H2O ice model allows a temperature estimate for the hottest ice-coated grains in these sources. Higher resolution observations showed no indication of the absorption due to the N-H stretching vibration of NH3 near 2.963 micron. The most plausible explanation for the 3.3 and 3.45 micron features appears to be absorption by the mixture of hydrocarbons, although they cannot be identified with features already attributed to hydrocarbons in the ISM, reflection nebulae and Comets. However these features appear the same for all sources in the sample, including Elias 16, thus implying a very similar mixture of molecules in each source.

  18. Algae (Microcystis and Scenedesmus) absorption spectra and its application on Chlorophyll a retrieval

    NASA Astrophysics Data System (ADS)

    Wu, Di; Chen, Maosi; Wang, Qiao; Gao, Wei

    2013-12-01

    Blue algae and green algae are the dominant phytoplankton groups that contribute to the eutrophication and the water bloom in inland water of China. The absorption coefficients (spectra) of the algae, which do not change with its intrinsic optical characteristics and the observation geometry, are strictly additive quantities. The characteristics of the absorption spectra of the two algae are presented. The pure blue algae and the pure green algae cultured in the laboratory environment are diluted and mixed at ten volume ratios. The Quantitative Filter Technique was applied to measure their absorption spectra. The "hot-ethanol extraction" method was chosen to calculate their concentration of Chlorophyll a. The retrieval algorithm developed in this study extracts the mapping information between each individual alga and their Chlorophyll a concentration via Continuous Wavelet Transform, and retrieves the Chlorophyll a concentration of each alga in their mixture using a trust region optimizer. The results show that the retrieved and the measured Chlorophyll a concentrations of the blue algae and the green algae components in the ten mixture match well with the average relative error of 5.55%.

  19. UV Absorption and Luminescence Spectra of [2.2]Paracyclophane Phenyl Derivatives

    NASA Astrophysics Data System (ADS)

    Nurmukhametov, R. N.; Shapovalov, A. V.; Antonov, D. Yu.

    2016-03-01

    UV absorption, fluorescence emission and excitation, and fluorescence excitation synchronous scanning spectra at 298 K and fluorescence and phosphorescence spectra at 77 K were measured for solutions of 4-phenyl- ( I) and 4,12-( II), 4,15- ( III), and 4,16-diphenyl derivatives ( IV) of [2.2]paracyclophane. Analysis of absorption spectra shows that they are determined by two types of chromophores (biphenyl and paracyclophane). It was shown that their weak long wavelength band (310-340 nm) and fluorescence band are governed by the same electron transition from the ground to an excimer-like excited state, as in the case of the unsubstituted macrocycle. Phenyl substitution shows only a weak influence on the energy of this transition. Strong absorption bands of I- IV at 230-310 nm originate from electronic transitions of biphenyl groups in these molecules. The strong bands of isomeric II- IV (with two biphenyl chromophores) differ significantly. It was supposed that this phenomenon was caused by different resonance interaction between electron oscillators (transitions) of the two biphenyl chromophores leading to different splitting of their excited states.

  20. Theoretical interpretation of the vacuum ultraviolet reflectance of liquid helium and of the absorption spectra of helium microbubbles in aluminum

    NASA Astrophysics Data System (ADS)

    Lucas, A. A.; Vigneron, J. P.; Donnelly, S. E.; Rife, J. C.

    1983-09-01

    The position and width of the helium resonance line 11S0-->21P1 are calculated for a high-density helium fluid. The theory aims at understanding the reflectivity data of Surko et al. for the low-temperature liquid-vapor interface and the absorption data of Rife et al. for room-temperature, high-pressure helium bubbles in aluminum. The theoretical ingredients of the model are (i) the long-range dipole interaction of an excited 2P atom with the rest of the fluid and with the metal substrate; (ii) the short-range Pauli pseudorepulsion arising from orthogonalization of the 2p-electron wave function with the 1s ground-state orbital of neighboring atoms; (iii) a statistical treatment of the high-density fluid based either on the experimentally measured radial pair distribution function of low-T liquid He, or on the Percus-Yevick distribution function of hard spheres and the theoretical equation of state of Young et al. for the He fluid in the bubbles; (iv) the standard static line-broadening theory to calculate the effect of Pauli repulsion on the line shapes. The theory provides a reasonably accurate understanding of the observed spectra in both the liquid and high-density gas, and can serve as a sound basis for interpretation of vacuum ultraviolet spectra in other gas-metal combinations.

  1. Twin-peaks absorption spectra of excess electron in ionic liquids

    NASA Astrophysics Data System (ADS)

    Musat, Raluca M.; Kondoh, Takafumi; Yoshida, Yoichi; Takahashi, Kenji

    2014-07-01

    The solvated electron in room temperature ionic liquids (RTILs) has been the subject of several investigations and several reports exist on its nature and absorption spectrum. These studies concluded that the solvated electron exhibits an absorption spectrum peaking in the 1000-1400 nm region; a second absorption band peaking in the UV region has been assigned to the hole or dication radicals simultaneously formed in the system. Here we report on the fate of the excess electron in the ionic liquid 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, P14+/NTf2- using nanosecond pulse radiolysis. Scavenging experiments allowed us to record and disentangle the complex spectrum measured in P14+/NTf2-. We identified a bi-component absorption spectrum, due to the solvated electron, the absorption maxima located at 1080 nm and around 300 nm, as predicted by previous ab-initio molecular dynamics simulations for the dry excess electron. We also measured the spectra using different ionic liquids and confirmed the same feature of two absorption peaks. The present results have important implications for the characterization of solvated electrons in ionic liquids and better understanding of their structure and reactivity.

  2. In vivo determination of the absorption and scattering spectra of the human prostate during photodynamic therapy

    PubMed Central

    Finlay, Jarod C.; Zhu, Timothy C; Dimofte, Andreea; Stripp, Diana; Malkowicz, S. Bruce; Whittington, Richard; Miles, Jeremy; Glatstein, Eli; Hahn, Stephen M.

    2015-01-01

    A continuing challenge in photodynamic therapy is the accurate in vivo determination of the optical properties of the tissue being treated. We have developed a method for characterizing the absorption and scattering spectra of prostate tissue undergoing PDT treatment. Our current prostate treatment protocol involves interstitial illumination of the organ via cylindrical diffusing optical fibers (CDFs) inserted into the prostate through clear catheters. We employ one of these catheters to insert an isotropic white light point source into the prostate. An isotropic detection fiber connected to a spectrograph is inserted into a second catheter a known distance away. The detector is moved along the catheter by a computer-controlled step motor, acquiring diffuse light spectra at 2 mm intervals along its path. We model the fluence rate as a function of wavelength and distance along the detector’s path using an infinite medium diffusion theory model whose free parameters are the absorption coefficient µa at each wavelength and two variables A and b which characterize the reduced scattering spectrum of the form µ’s = Aλ−b. We analyze our spectroscopic data using a nonlinear fitting algorithm to determine A, b, and µa at each wavelength independently; no prior knowledge of the absorption spectrum or of the sample’s constituent absorbers is required. We have tested this method in tissue simulating phantoms composed of intralipid and the photosensitizer motexafin lutetium (MLu). The MLu absorption spectrum recovered from the phantoms agrees with that measured in clear solution, and µa at the MLu absorption peak varies linearly with concentration. The µ’s spectrum reported by the fit is in agreement with the known scattering coefficient of intralipid. We have applied this algorithm to spectroscopic data from human patients sensitized with MLu (2 mg kg−1) acquired before and after PDT. Before PDT, the absorption spectra we measure include the characteristic

  3. Systematic trend of water vapour absorption in red giant atmospheres revealed by high resolution TEXES 12 μm spectra

    NASA Astrophysics Data System (ADS)

    Ryde, N.; Lambert, J.; Farzone, M.; Richter, M. J.; Josselin, E.; Harper, G. M.; Eriksson, K.; Greathouse, T. K.

    2015-01-01

    Context. The structures of the outer atmospheres of red giants are very complex. Recent interpretations of a range of different observations have led to contradictory views of these regions. It is clear, however, that classical model photospheres are inadequate to describe the nature of the outer atmospheres. The notion of large optically thick molecular spheres around the stars (MOLspheres) has been invoked in order to explain spectro-interferometric observations and low- and high-resolution spectra. On the other hand high-resolution spectra in the mid-IR do not easily fit into this picture because they rule out any large sphere of water vapour in LTE surrounding red giants. Aims: In order to approach a unified scenario for these outer regions of red giants, more empirical evidence from different diagnostics are needed. Our aim here is to investigate high-resolution, mid-IR spectra for a range of red giants, spanning spectral types from early K to mid M. We want to study how the pure rotational lines of water vapour change with effective temperature, and whether we can find common properties that can put new constraints on the modelling of these regions, so that we can gain new insights. Methods: We have recorded mid-IR spectra at 12.2 - 12.4 μm at high spectral resolution of ten well-studied bright red giants, with TEXES mounted on the IRTF on Mauna Kea. These stars span effective temperatures from 3450 K to 4850 K. Results: We find that all red giants in our study cooler than 4300 K, spanning a wide range of effective temperatures (down to 3450 K), show water absorption lines stronger than expected and none are detected in emission, in line with what has been previously observed for a few stars. The strengths of the lines vary smoothly with spectral type. We identify several spectral features in the wavelength region that are undoubtedly formed in the photosphere. From a study of water-line ratios of the stars, we find that the excitation temperatures, in the

  4. Absorption spectra and photoresponse observation of Cu2O thin film photoanodes

    NASA Astrophysics Data System (ADS)

    Mani, Endri; Garuthara, Rohana

    2014-03-01

    Electrodeposition was used to deposit Cu2O thin films on ITO substrates. The deposited Cu2O films were characterized by photocurrent, absorption and reflectance spectroscopy. Photoresponse of the film clearly indicated n-type behavior of Cu2O in photoelectrochemical cells. The effects of chlorine doped photoanodes deposited in different solution pH on the magnitude of their photocurrent are studied. The low temperature absorption spectra of chlorine doped Cu2O films are found to depend on the solution pH in the range 10.0-7.5. Optical absorption spectra of Cu2O films were measured in the temperature range 79K - 295K. The Urbach's tail was observed for n-type conductive Cu2O films in the temperature range 79K to 295K. The Urbach's energy as a function of temperature for Cu2O films were studied. The results will be discussed with emphasis on the reflectance, absorption and photoresponse observation.

  5. TDDFT prediction of UV-vis absorption and emission spectra of tocopherols in different media.

    PubMed

    Bakhouche, Kahina; Dhaouadi, Zoubeida; Lahmar, Souad; Hammoutène, Dalila

    2015-06-01

    We use the TDDFT/PBE0/6-31+G* method to determine the electronic absorption and emission energies, in different media, of the four forms of tocopherol, which differ by the number and the position of methyl groups on the chromanol. Geometries of the ground state S0 and the first singlet excited state S1 were optimized in the gas phase, and various solvents. The solvent effect is evaluated using an implicit solvation model (IEF-PCM). Our results are compared to the experimental ones obtained for the vitamin E content in several vegetable oils. For all forms of tocopherols, the HOMO-LUMO first vertical excitation is a π-π* transition. Gas phase and non-polar solvents (benzene and toluene) give higher absorption wavelengths than polar solvents (acetone, ethanol, methanol, DMSO, and water); this can be interpreted by a coplanarity between the O-H group and the chroman, allowing a better electronic resonance of the oxygen lone pairs and the aromatic ring, and therefore giving an important absorption wavelength, whereas the polar solvents give high emission wavelengths comparatively to gas phase and non-polar solvents. Fluorescence spectra permit the determination, the separation, and the identification of the four forms of tocopherols by a large difference in emission wavelength values. Graphical Abstract Scheme from process methodological to obtain the absorption and emission spectra for tocopherols. PMID:26026299

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  7. Photon-photon absorption and the uniqueness of the spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    1984-01-01

    The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon-photon absorption of its own radiation was examined. Under the assumption of continuous electron injection with a power law spectrum E to the minus gamma power and Compton losses only, it is shown that for gamma 2 the steady state electron distribution function has a unique form independent of the primary injection spectrum. This electron distribution function can, by synchrotron emission, reproduce the general characteristics of the observed radio to optical active galactic nuclei spectra. Inverse Compton scattering of the synchrotron photons by the same electron distribution can account for their X-ray spectra, and also implies gamma ray emission from these objects. This result is invoked to account for the similarity of these spectra, and it is consistent with observations of the diffuse gamma ray background.

  8. pH-dependent x-ray absorption spectra of aqueous boron oxides

    NASA Astrophysics Data System (ADS)

    Duffin, Andrew M.; Schwartz, Craig P.; England, Alice H.; Uejio, Janel S.; Prendergast, David; Saykally, Richard J.

    2011-04-01

    Near edge x-ray absorption fine structure (NEXAFS) spectra at the boron K-edge were measured for aqueous boric acid, borate, and polyborate ions, using liquid microjet technology, and compared with simulated spectra calculated from first principles density functional theory in the excited electron and core hole (XCH) approximation. Thermal motion in both hydrated and isolated molecules was incorporated into the calculations by sampling trajectories from quantum mechanics/molecular mechanics simulations at the experimental temperature. The boron oxide molecules exhibit little spectral change upon hydration, relative to mineral samples. Simulations reveal that water is arranged nearly isotropically around boric acid and sodium borate, but the calculations also indicate that the boron K-edge NEXAFS spectra are insensitive to hydrogen bonding, molecular environment, or salt interactions.

  9. Spectra of polarized thermal radiation in a cloudy atmosphere: Line-by-Line and Monte Carlo model for passive remote sensing of cirrus and polar clouds

    NASA Astrophysics Data System (ADS)

    Fomin, Boris; Falaleeva, Victoria

    2016-07-01

    A polarized high-resolution 1-D model has been presented for TIR (Thermal Infrared) remote sensing application. It is based on the original versions of MC (Monte Carlo) and LbL (Line-by-Line) algorithms, which have shown their effectiveness when modelling the thermal radiation atmospheric transfer, taking into account, the semi-transparent Ci-type and polar clouds scattering, as well as the direct consideration of the spectra of molecular absorption. This model may be useful in the planning of satellite experiments and in the validation of similar models, which use the "k-distribution" or other approximations, to account for gaseous absorption. The example simulations demonstrate that, the selective gas absorption does not only significantly affect the absorption and emission of radiation, but also, its polarization in the Ci-type clouds. As a result, the spectra of polarized radiation contain important information about the clouds, and a high-resolution polarized limb sounding in the TIR, seems to be a useful tool in obtaining information on cloud types and their vertical structures.

  10. Broad Balmer-Line Absorption in SDSS J172341.10+555340.5

    NASA Astrophysics Data System (ADS)

    Aoki, Kentaro

    2010-10-01

    We present the discovery of Balmer-line absorption from Hα to H9 in an iron low-ionizaton broad absorption line (FeLoBAL) quasar, SDSS J172341.10+555340.5, by near-infrared spectroscopy with the Cooled Infrared Spectrograph and Camera for OHS (CISCO) attached to the Subaru Telescope. The redshift of the Balmer-line absorption troughs is 2.0530±0.0003, and it is blueshifted by 5370 km s-1 from the Balmer emission lines. It is more than 4000 km s-1 blueshifted from the previously known UV absorption lines. We detected relatively strong (EWrest = 20 Å) [OIII] emission lines that are similar to those found in other broad absorption line quasars with Balmer-line absorption. We also derived the column density of neutral hydrogen of 5.2 × 1017 cm-2 by using the curve of growth and taking account of Lyα trapping. We searched for UV absorption lines that had the same redshift with Balmer-line absorption, and found Ali III and Fe III absorption lines at z = 2.053 that correspond to previously unidentified absorption lines, and the presence of other blended troughs that were difficult to identify.

  11. SPECTRAL POLARIZATION OF THE REDSHIFTED 21 cm ABSORPTION LINE TOWARD 3C 286

    SciTech Connect

    Wolfe, Arthur M.; Jorgenson, Regina A.; Robishaw, Timothy; Heiles, Carl; Xavier Prochaska, J. E-mail: raj@ast.cam.ac.uk E-mail: heiles@astro.berkeley.edu

    2011-05-20

    A reanalysis of the Stokes-parameter spectra obtained of the z = 0.692 21 cm absorption line toward 3C 286 shows that our original claimed detection of Zeeman splitting by a line-of-sight magnetic field, B{sub los} = 87 {mu}G, is incorrect. Because of an insidious software error, what we reported as Stokes V is actually Stokes U: the revised Stokes V spectrum indicates a 3{sigma} upper limit of B{sub los}< 17 {mu}G. The correct analysis reveals an absorption feature in fractional polarization that is offset in velocity from the Stokes I spectrum by -1.9 km s{sup -1}. The polarization position-angle spectrum shows a dip that is also significantly offset from the Stokes I feature, but at a velocity that differs slightly from the absorption feature in fractional polarization. We model the absorption feature with three velocity components against the core-jet structure of 3C 286. Our {chi}{sup 2} minimization fitting results in components with differing (1) ratios of H I column density to spin temperature, (2) velocity centroids, and (3) velocity dispersions. The change in polarization position angle with frequency implies incomplete coverage of the background jet source by the absorber. It also implies a spatial variation of the polarization position angle across the jet source, which is observed at frequencies higher than the 839.4 MHz absorption frequency. The multi-component structure of the gas is best understood in terms of components with spatial scales of {approx}100 pc comprised of hundreds of low-temperature (T {<=} 200 K) clouds with linear dimensions of <<100 pc. We conclude that previous attempts to model the foreground gas with a single uniform cloud are incorrect.

  12. Determination of molecular line parameters for acrolein (C 3H 4O) using infrared tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Harward, Charles N.; Thweatt, W. David; Baren, Randall E.; Parrish, Milton E.

    2006-04-01

    Acrolein (C 3H 4O) molecular line parameters, including infrared (IR) absorption positions, strengths, and nitrogen broadened half-widths, must be determined since they are not included in the high resolution transmission (HITRAN) molecular absorption database of spectral lines. These parameters are required for developing a quantitative analytical method for measuring acrolein in a single puff of cigarette smoke using tunable diode laser absorption spectroscopy (TDLAS). The task is complex since acrolein has many highly overlapping infrared absorption lines in the room temperature spectrum and the cigarette smoke matrix contains thousands of compounds. This work describes the procedure for estimating the molecular line parameters for these overlapping absorption lines in the wavenumber range (958.7-958.9 cm -1) using quantitative reference spectra taken with the infrared lead-salt TDLAS instrument at different pressures and concentrations. The nitrogen broadened half-width for acrolein is 0.0937 cm -1 atm -1 and to our knowledge, is the first time it has been reported in the literature.

  13. Radio Structures of Compact Quasars with Broad Absorption Lines

    NASA Astrophysics Data System (ADS)

    Kunert-Bajraszewska, Magdalena; Gawroński, Marcin P.

    2010-05-01

    Broad absorption lines (BALs), seen in a small fraction of both the radio-quiet and radio-loud quasar populations, are probably caused by the outflow of gas with high velocities and are part of the accretion process. The presence of BALs is due to a geometrical effect and/or it is connected with the quasar evolution. Using the final release of FIRST survey combined with a catalog of BAL QSOs from SDSS/DR3, we have constructed a new sample of compact radio-loud BAL QSOs, which constitutes the majority of radio-loud BAL QSOs. The main goal of this project is to study the origin of BALs by analysis of the BAL QSOs radio morphology, orientation, and jet evolution using the European VLBI Network (EVN) at 1.6 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz.

  14. The intrinsic fraction of broad-absorption line quasars

    NASA Astrophysics Data System (ADS)

    Knigge, Christian; Scaringi, Simone; Goad, Michael R.; Cottis, Christopher E.

    2008-05-01

    We carefully reconsider the problem of classifying broad-absorption line quasars (BALQSOs) and derive a new, unbiased estimate of the intrinsic BALQSO fraction from the Sloan Digital Sky Survey (SDSS) DR3 quasi-stellar object (QSO) catalogue. We first show that the distribution of objects selected by the so-called `absorption index' (AI) is clearly bimodal in logAI, with only one mode corresponding to definite BALQSOs. The surprisingly high BALQSO fractions that have recently been inferred from AI-based samples are therefore likely to be overestimated. We then present two new approaches to the classification problem that are designed to be more robust than the AI, but also more complete than the traditional `balnicity index' (BI). Both approaches yield observed BALQSO fractions around 13.5 per cent, while a conservative third approach suggests an upper limit of 18.3 per cent. Finally, we discuss the selection biases that affect our observed BALQSO fraction. After correcting for these biases, we arrive at our final estimate of the intrinsic BALQSO fraction. This is fBALQSO = 0.17 +/- 0.01(stat) +/- 0.03(sys) with an upper limit of fBALQSO ~= 0.23. We conclude by pointing out that the bimodality of the logAI distribution may be evidence that the BAL-forming region has clearly delineated physical boundaries.

  15. Quasar Broad Absorption Line Variability on Multiyear Timescales

    NASA Astrophysics Data System (ADS)

    Gibson, Robert R.; Brandt, W. N.; Schneider, Donald P.; Gallagher, S. C.

    2008-03-01

    We use quantitative metrics to characterize the variation of C IV λ1549 broad absorption lines (BALs) over 3-6 (rest-frame) years in a sample of 13 quasars at 1.7 <= z<= 2.8 and compare the results to previous studies of BAL variability on shorter timescales. The strong BALs in our study change in complex ways over 3-6 yr. Variation occurs in discrete regions only a few thousand kilometers per second wide, and the distribution of the change in absorption equivalent width broadens over time. We constrain the typical C IV BAL lifetime to be at least a few decades. While we do not find evidence to support a scenario in which the variation is primarily driven by photoionization on multiyear timescales, there is some indication that the variation is produced by changes in outflow geometry. We do not observe significant changes in the BAL onset velocity, indicating that the absorber is either far from the source or is being continually replenished and is azimuthally symmetric. It is not possible in a human lifetime to expand the timescales in our study by more than a factor of a few using optical spectroscopy. However, the strong variation we have observed in some BALs indicates that future studies of large numbers of BAL QSOs will be valuable to constrain BAL lifetimes and the physics of variation.

  16. Progress in Identifying Fe I Level Energies and Lines from Stellar Spectra

    NASA Astrophysics Data System (ADS)

    Peterson, Ruth

    2015-08-01

    The spectrum of the Fe I atom is critical to many areas of astrophysics and beyond, the vital input necessary to characterize the spectral absorption and emission of the atomic and molecular systems that pervade stars, stellar nebulae, exploding supernovae, and the interstellar and intergalactic medium, from the local environment to the highest redshifts. Yet measurements of the energies of its high-lying levels remain seriously incomplete, despite extensive efforts incorporating both laboratory sources and the solar spectrum. Peterson & Kurucz (2015, ApJS, 216, 1) reported the first results from a new approach, one which uses the spectra of sharp-lined stars of near-solar temperature to identify level energies. By matching predicted to observed stellar line wavelengths and strengths transition by transition, the upper energies of 66 Fe I levels were established. Many new levels are at higher energies than can be determined in the laboratory, including several that lie above the Fe I ionization energy. However, many more unidentified levels remain, especially those levels whose strongest lines fall in wavelength regions where stellar data is marginal or missing. Here we update the progress in this effort, and outline where new data are most urgently required and why.

  17. Identification of isolated NO lines in balloon-borne infrared solar spectra

    NASA Technical Reports Server (NTRS)

    Murcray, F. J.; Goldman, A.; Murcray, D. G.; Cook, G. R.; Van Allen, J. W.; Blatherwick, R. D.

    1980-01-01

    Ballon-borne infrared solar spectra at about 0.02/cm resolution show a number of atmospheric NO lines isolated from other atmospheric and solar lines in the 1830-1930/cm region. Typical spectra are presented and NO total column values are derived.

  18. NOTE: Absorption spectra variations of EBT radiochromic film from radiation exposure

    NASA Astrophysics Data System (ADS)

    Butson, M. J.; Cheung, T.; Yu, P. K. N.

    2005-07-01

    Gafchromic EBT radiochromic film is one of the newest radiation-induced auto-developing x-ray analysis films available for therapeutic radiation dosimetry in radiotherapy applications. The spectral absorption properties in the visible wavelengths have been investigated and results show two main peaks in absorption located at 636 nm and 585 nm. These absorption peaks are different to many other radiochromic film products such as Gafchromic MD-55 and HS film where two peaks were located at 676 nm and 617 nm respectively. The general shape of the absorption spectra is similar to older designs. A much higher sensitivity is found at high-energy x-rays with an average 0.6 OD per Gy variation in OD seen within the first Gy measured at 636 nm using 6 MV x-rays. This is compared to approximately 0.09 OD units for the first Gy at the 676 nm absorption peak for HS film at 6 MV x-ray energy. The film's blue colour is visually different from older varieties of Gafchromic film with a higher intensity of mid-range blue within the film. The film provides adequate relative absorbed dose measurement for clinical radiotherapy x-ray assessment in the 1 2 Gy dose range which with further investigation may be useful for fractionated radiotherapy dose assessment.

  19. Rest-frame optical properties of luminous, radio-selected broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Runnoe, Jessie C.; Ganguly, R.; Brotherton, M. S.; DiPompeo, M. A.

    2013-08-01

    We have obtained Infrared Telescope Facility/SpeX spectra of eight moderate-redshift (z = 0.7-2.4), radio-selected (log R* ≈ 0.4-1.9) broad absorption line (BAL) quasars. The spectra cover the rest-frame optical band. We compare the optical properties of these quasars to those of canonically radio-quiet (log R* ≲ 1) BAL quasars at similar redshifts and to low-redshift quasars from the Palomar-Green catalogue. As with previous studies of BAL quasars, we find that [O III] λ5007 is weak, and optical Fe II emission is strong, a rare combination in canonically radio-loud (log R* ≳ 1) quasars. With our measurements of the optical properties, particularly the Balmer emission-line widths and the continuum luminosity, we have used empirical scaling relations to estimate black hole masses and Eddington ratios. These lie in the range (0.4-2.6) × 109 M⊙ and 0.1-0.9, respectively. Despite their comparatively extreme radio properties relative to most BAL quasars, their optical properties are quite consistent with those of radio-quiet BAL quasars and dissimilar to those of radio-loud non-BAL quasars. While BAL quasars generally appear to have low values of [O III] λ5007/Fe II an extreme of `Eigenvector 1', the Balmer line widths and Eddington ratios do not appear to significantly differ from those of unabsorbed quasars at similar redshifts and luminosities.

  20. Unlocking the secrets of absorption line complexes in the intergalactic medium

    NASA Astrophysics Data System (ADS)

    O'Shea, Brian

    2013-10-01

    It is well-established that the fraction of baryons in the Universe that are observable drops from nearly 100% at z 3 to less than 50% by z 0. Simulations predict that most of the missing baryons are located in the IGM at moderate densities and at temperatures of 10^5-10^7 K - gas that is generally in the filaments of the cosmic web and in circumgalactic regions. This gas is typically detected in the low-z Lyman alpha forest by measuring UV absorption lines of highly ionized metals, such as CIV and OVI. However, significant uncertainties exist relating to the physical conditions of the gas associated with these lines {such as temperature, metallicity, and ionization state}, which severely limits our ability to understand the physical environment of these absorbers. We propose to clarify the relationship between the multi-species absorption line complexes seen in QSO spectra and the physical conditions of the corresponding absorbing gas. We will do this using synthetic observing tools and the largest, most detailed simulations of the IGM to date, which include a new sophisticated treatment of non-equilibrium gas chemistry. We will create catalogs that enable conversion between specific combinations of observed absorption lines and the equivalent physical gas distribition, will calculate the total baryon content that is traceable with each ion, and will devise tests to distinguish between the circumgalactic and truly intergalactic medium. This work will be critical to the interpretation of previous and ongoing HST studies of the IGM - particularly those using the Cosmic Origins Spectrograph - and directly addresses the HST Cycle 21 Ultraviolet Initiative.

  1. On the origins of C IV absorption profile diversity in broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Baskin, Alexei; Laor, Ari; Hamann, Fred

    2015-05-01

    There is a large diversity in the C IV broad absorption line (BAL) profile among BAL quasars (BALQs). We quantify this diversity by exploring the distribution of the C IV BAL properties, full width at half-maximum (FWHM), maximum depth of absorption and its velocity shift (vmd), using the Sloan Digital Sky Survey DR7 quasar catalogue. We find the following: (i) Although the median C IV BAL profile in the quasar rest-frame becomes broader and shallower as the UV continuum slope (αUV at 1700-3000 Å) gets bluer, the median individual profile in the absorber rest-frame remains identical, and is narrow (FWHM = 3500 km s-1) and deep. Only 4 per cent of BALs have FWHM > 10 000 km s-1. (ii) As the He II emission equivalent width (EW) decreases, the distributions of FWHM and vmd extend to larger values, and the median maximum depth increases. These trends are consistent with theoretical models in which softer ionizing continua reduce overionization, and allow radiative acceleration of faster BAL outflows. (iii) As αUV becomes bluer, the distribution of vmd extends to larger values. This trend may imply faster outflows at higher latitudes above the accretion disc plane. (iv) For non-BALQs, the C IV emission line decreases with decreasing He II EW, and becomes more asymmetric and blueshifted. This suggests an increasing relative contribution of emission from the BAL outflow to the C IV emission line as the ionizing spectral energy distribution (SED) gets softer, which is consistent with the increasing fraction of BALQs as the ionizing SED gets softer.

  2. Investigating the radio-loud phase of broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Bruni, G.; González-Serrano, J. I.; Pedani, M.; Benn, C. R.; Mack, K.-H.; Holt, J.; Montenegro-Montes, F. M.; Jiménez-Luján, F.

    2014-09-01

    Context. Broad absorption lines (BALs) are present in the spectra of ~20% of quasars (QSOs); this indicates fast outflows (up to 0.2c) that intercept the observer's line of sight. These QSOs can be distinguished again into radio-loud (RL) BAL QSOs and radio-quiet (RQ) BAL QSOs. The first are very rare, even four times less common than RQ BAL QSOs. The reason for this is still unclear and leaves open questions about the nature of the BAL-producing outflows and their connection with the radio jet. Aims: We explored the spectroscopic characteristics of RL and RQ BAL QSOs with the aim to find a possible explanation for the rarity of RL BAL QSOs. Methods: We identified two samples of genuine BAL QSOs from SDSS optical spectra, one RL and one RQ, in a suitable redshift interval (2.5 < z < 3.5) that allowed us to observe the Mg ii and Hβ emission lines in the adjacent near-infrared (NIR) band. We collected NIR spectra of the two samples using the Telescopio Nazionale Galileo (TNG, Canary Islands). By using relations known in the literature, we estimated the black-hole mass, the broad-line region radius, and the Eddington ratio of our objects and compared the two samples. Results: We found no statistically significant differences from comparing the distributions of the cited physical quantities. This indicates that they have similar geometries, accretion rates, and central black-hole masses, regardless of whether the radio-emitting jet is present or not. Conclusions: These results show that the central engine of BAL QSOs has the same physical properties with and without a radio jet. The reasons for the rarity of RL BAL QSOs must reside in different environmental or evolutionary variables. Figure 3 is available in electronic form at http://www.aanda.org

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  5. Plant phenolics and absorption features in vegetation reflectance spectra near 1.66 μm

    USGS Publications Warehouse

    Kokaly, Raymond F.; Skidmore, Andrew K

    2015-01-01

    Past laboratory and field studies have quantified phenolic substances in vegetative matter from reflectance measurements for understanding plant response to herbivores and insect predation. Past remote sensing studies on phenolics have evaluated crop quality and vegetation patterns caused by bedrock geology and associated variations in soil geochemistry. We examined spectra of pure phenolic compounds, common plant biochemical constituents, dry leaves, fresh leaves, and plant canopies for direct evidence of absorption features attributable to plant phenolics. Using spectral feature analysis with continuum removal, we observed that a narrow feature at 1.66 μm is persistent in spectra of manzanita, sumac, red maple, sugar maple, tea, and other species. This feature was consistent with absorption caused by aromatic C-H bonds in the chemical structure of phenolic compounds and non-hydroxylated aromatics. Because of overlapping absorption by water, the feature was weaker in fresh leaf and canopy spectra compared to dry leaf measurements. Simple linear regressions of feature depth and feature area with polyphenol concentration in tea resulted in high correlations and low errors (% phenol by dry weight) at the dry leaf (r2 = 0.95, RMSE = 1.0%, n = 56), fresh leaf (r2 = 0.79, RMSE = 2.1%, n = 56), and canopy (r2 = 0.78, RMSE = 1.0%, n = 13) levels of measurement. Spectra of leaves, needles, and canopies of big sagebrush and evergreens exhibited a weak absorption feature centered near 1.63 μm, short ward of the phenolic compounds, possibly consistent with terpenes. This study demonstrates that subtle variation in vegetation spectra in the shortwave infrared can directly indicate biochemical constituents and be used to quantify them. Phenolics are of lesser abundance compared to the major plant constituents but, nonetheless, have important plant functions and ecological significance. Additional research is needed to advance our understanding of the

  6. Line shape of 57Co sources exhibiting self absorption

    NASA Astrophysics Data System (ADS)

    Spiering, H.; Ksenofontov, V.; Leupold, O.; Kusz, J.; Deák, L.; Németh, Z.; Bogdán, C.; Bottyán, L.; Nagy, D. L.

    2016-12-01

    The effect of selfabsorption in Mössbauer sources is studied in detail. Spectra were measured using an old 57 C o/ R h source of 74 M B q activity with an original activity of ca. 3.7 G B q and a 0.15 G B q 57 C o/ α - F e source magnetized by an in-plane magnetic field of 0.2 T. The 57 C o/ α - F e source of a thickness of 25 μ was used both from the active and the inactive side giving cause to very different selfabsorption effects. The absorber was a single crystal of ferrous ammonium sulphate hexahydrate (FAS). Its absorption properties were taken over from a detailed study (Bull et al., Hyperfine Interact. 94(1-3), 1; Spiering et al. 2). FAS (space group P21/c) crystallizes as flat plates containing the (overline {2}01) plane. The γ-direction was orthogonal to the crystal plate. The 57 C o atoms of the 57 C o/ R h source were assumed to be homogeneously distributed over a 6 μ thick Rh foil and to follow a one dimensional diffusion profile in the 25 μ Fe-foil. The diffusion length was fitted to 10 μ. The theory follows the Blume-Kistner equations for forward scattering (Blume and Kistner, Phys. Rev. 171, 417, 3) by integrating over the source sampled up to 128 layers.

  7. The Physical Nature of Polar Broad Absorption Line Quasars

    NASA Technical Reports Server (NTRS)

    Ghost, Kajal; Punsly, Brian

    2007-01-01

    It has been shown based on radio variability arguments that some BALQSOs (broad absorption line quasars) are viewed along the polar axis (o rthogonal to accretion disk) in the recent article of Zhou et a. Thes e arguments are based on the brightness temperature, T(sub b) exceedi ng 10(exp 12) K which leads to the well-known inverse Compton catastr ophe unless the radio jet is relativistic and is viewed along its axi s. In this letter, we expand the Zhou et al sample of polar BALQSOs u sing their techniques applied to SDSS DR5. In the process, we clarify a mistake in their calculation of brightness temperature. The expanded sample of high T(sub b) BALQSOS, has an inordinately large fraction of LoBALQSOs (low ionization BALQSOs). We consider this an important clue to understanding the nature of the polar BALQSOs. This is expec ted in the polar BALQSO analytical/numerical models of Punsly that pr edicted that LoBALQSOs occur when the line of sight is very close to the polar axis, where the outflow density is the highest.

  8. Line broadening, line shifting, and line coupling effects on N sub 2 --H sub 2 O stimulated Raman spectra

    SciTech Connect

    Bonamy, J.; Robert, D. ); Hartmann, J.M. ); Gonze, M.L.; Saint-Loup, R.; Berger, H. )

    1989-11-15

    In order to understand the influence of H{sub 2}O on the stimulated Raman {ital Q}-branch spectra of nitrogen in combusting media, an exhaustive theoretical and experimental study has been carried out. Starting from a semiclassical model, particularly convenient at high temperature, the {ital Q}-line broadening and shifting coefficients have been calculated over a wide temperature range and for a large number of lines. Stimulated Raman Spectra (SRS) measurements have allowed us to test these calculated line broadening coefficients and thus establish the high accuracy of semiclassical values. The theoretical broadening coefficients have been inverted to deduce state-to-state rotational relaxation rates by using two types of fitting laws. A partial test of the resulting {ital Q}-branch profiles has been realized at moderate pressures leading to a discrimination between these two laws. Furthermore, the effect of rotational energy transfers on collisionally narrowed profiles at higher densities has been simulated and compared with the pure N{sub 2} case.

  9. Interplay between structural and electronic properties of various fullerene derivatives, and their absorption spectra

    NASA Astrophysics Data System (ADS)

    Park, Sora; Ahn, Jeung Sun; Kwon, Young-Kyun

    2011-03-01

    Using density functional theory (DFT), we investigate the geometrical structures and electronic properties of various fullerene derivatives formed by attaching several kinds of addends on C60 through [2+2] cycloaddition. Various forms of such derivatives are modeled by considering different kinds, different positions and different numbers of addends to study how structural configurations will affect their electronic structures. Our results reveal that some derivatives with certain symmetries determined by the configuration of addends may have wider energy gap than that of pristine C60 . This suggests that absorption properties could be adjusted by controlling the addends configurations. To describe the excited state properties, such as absorption spectra, of various C60 derivatives more accurately, we performed time-dependent (TD) DFT calculations. We find the position and the intensity of the peak of absorption spectra of derivatives are affected by the specific symmetry of the derivatives defined by the configurations of the addends. To explore such peculiar effects, we analyze the charge distribution and orbital mixing characters.

  10. Effects of Spectralon absorption on reflectance spectra of typical planetary surface analog materials.

    PubMed

    Zhang, Hao; Yang, Yazhou; Jin, Weidong; Liu, Chujian; Hsu, Weibiao

    2014-09-01

    Acquiring accurate visible and near-infrared (VisNIR) reflectance values of atmosphereless celestial bodies is very important in inferring the physical and geological properties of their surficial materials. When a calibration target with inherent non-trivial absorption features is used, the calibrated reflectance would essentially always contain spurious spectral features and the spectroscopic data may easily be misinterpreted if the artifact is not properly taken care of. We demonstrate with laboratory reflectance measurements that the VisNIR spectra of three typical planetary surface analog materials, lunar simulant JSC-1A, olivine and pyroxene grains, have an artificial peak at 2.1 µm when Spectralon-type plaque made of polytetrafluoroethylene is used as the calibration target in the NIR region. The degree of severity of this artifact is dependent on the strength of the 2.0 µm absorption feature of the mineral. Empirical methods are proposed to remove this artifact to bring the spectra close to that calibrated by a gold mirror which does not have any conspicuous absorption features in the NIR region. The correction methods may be applied to reflectance data acquired by the VisNIR imaging spectrometer onboard the Yutu Rover of the Chinese Chang'E 3 lunar mission which employed an onboard Spectralon-type calibration target. PMID:25321507

  11. Vibronic bandshape of the absorption spectra of dibenzoylmethanatoboron difluoride derivatives: analysis based on ab initio calculations.

    PubMed

    Rukin, Pavel S; Freidzon, Alexandra Ya; Scherbinin, Andrei V; Sazhnikov, Vyacheslav A; Bagaturyants, Alexander A; Alfimov, Michael V

    2015-07-14

    The nature of absorption bandshapes of dibenzoylmethanatoboron difluoride (DBMBF2) dye substituted in ortho-, meta-, and para-positions of the phenyl ring is investigated using DFT and TDDFT with the range-separated hybrid CAM-B3LYP functional and the 6-311G(d,p) basis set. The solvent effects are taken into account within the polarized continuum model. The vibronic bandshape is simulated using a time-dependent linear coupling model with a vertical gradient approach through an original code. For flexible chromophores, the spectra of individual conformers are summed up with Boltzmann factors. It is shown that the long-wavelength absorption bandshape of DBMBF2 derivatives is determined by three factors: the relative statistical weights of conformers with different electronic absorption patterns, the relative position and intensity of the second low-energy electronic transition, and the vibronic structure of individual electronic peaks. The latter is governed by the relationship between the hard vibrational modes, which contribute to vibronic progression, and soft modes, which provide broadening of the peaks. The simulated spectra of the dyes in the study are generally consistent with the available experimental data and explain the observed spectral features. PMID:26062782

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

    SciTech Connect

    Liu, W. L.; Zheng, Z. R.; Liu, Z. G.; Zhu, R. B.; Wu, W. Z.; Li, A. H.; Yang, Y. Q.; Dai, Z. F.; Su, W. H.

    2008-03-28

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

  13. Rototranslational absorption spectra of H/sub 2/-H/sub 2/ pairs in the far infrared

    SciTech Connect

    Meyer, W.; Frommhold, L.; Birnbaum, G.

    1989-03-01

    For the computation of the induced dipole moments, the collisional H/sub 2/-H/sub 2/ complex is treated as a molecule in the self-consistent field and size-consistent, coupled electron pair approximations. The basis set accounts for 95% of the correlation energies and separates correctly at distant range. The average of the induced dipole components is obtained for the case of both H/sub 2/ molecules in the vibrational groundstate (v = v' = 0) and recast in a simple but accurate analytical form. The analytical dipole expression is used for computations of the spectral moments (sum rules) and line shapes of the collision-induced rototranslational absorption spectra of molecular hydrogen in the far infrared, over a range of frequencies from 0 to 2200 cm/sup -1/, and for temperatures from 77 to 300 K, using a quantum formalism. Proven isotropic potential models are input. Numerical consistency of the line-shape calculations with the sum rules is observed at the 1% level. The comparison of the computational results with the available measurements shows agreement within the estimated uncertainties of the measurements of typically better than 10%. This fact suggests that the theory is capable of predicting these spectra reliably at temperatures for which no measurements exist.

  14. Measurement of Gas and Aerosol Phase Absorption Spectra across the Visible and Near-IR Using Supercontinuum Photoacoustic Spectroscopy.

    PubMed

    Radney, James G; Zangmeister, Christopher D

    2015-07-21

    We demonstrate a method to measure the absorption spectra of gas and aerosol species across the visible and near-IR (500 to 840 nm) using a photoacoustic (PA) spectrometer and a pulsed supercontinuum laser source. Measurements of gas phase absorption spectra were demonstrated using H2O(g) as a function of relative humidity (RH). The measured absorption intensities and peak shapes were able to be quantified and compared to spectra calculated using the 2012 High Resolution Transmission (HITRAN2012) database. Size and mass selected nigrosin aerosol was used to measure absorption spectra across the visible and near-IR. Spectra were measured as a function of aerosol size/mass and show good agreement to Mie theory calculations. Lastly, we measured the broadband absorption spectrum of flame generated soot aerosol at 5% and 70% RH. For the high RH case, we are able to quantifiably separate the soot and water absorption contributions. For soot, we observe an enhancement in the mass specific absorption cross section ranging from 1.5 at 500 nm (p < 0.01) to 1.2 at 840 nm (p < 0.2) and a concomitant increase in the absorption Ångström exponent from 1.2 ± 0.4 (5% RH) to 1.6 ± 0.3 (70% RH). PMID:26098142

  15. Absolute calibration and atmospheric versus mineralogic origin of absorption features in 2.0 to 2.5 micron Mars spectra obtained during 1993

    NASA Technical Reports Server (NTRS)

    Bell, James F., III; Pollack, James B.; Geballe, Thomas R.; Cruikshank, Dale P.; Freedman, Richard

    1994-01-01

    We obtained new high resolution reflectance spectra of Mars during the 1993 opposition from Mauna Kea Observatory using the UKIRT CGS4 spectrometer. Fifty spectra of 1600-2000 km surface regions and a number of standard star spectra were obtained in the 2.04 to 2.44 micron wavelength region on 4 February 1993 UT. Near-simultaneous observations of bright standard stars were used to perform terrestrial atmospheric corrections and an absolute flux calibration. Using the known magnitude of the stars and assuming blackbody continuum behavior, the flux from Mars could be derived. A radiative transfer model and the HITRAN spectral line data base were used to compute atmospheric transmission spectra for Mars and the Earth in order to simulate the contributions of these atmospheres to our observed data. Also, we examined the ATMOS solar spectrum in the near-IR to try to identify absorption features in the spectrum of the Sun that could be misinterpreted as Mars features. Eleven absorption features were detected in our Mars spectra. Our data provide no conclusive identification of the mineralogy responsible for the absorption features we detected. However, examination of terrestrial spectral libraries and previous high spectral resolution mineral studies indicates that the most likely origin of these features is either CO3(sup 2-), HCO3(-), or HSO4(-) anions in framework silicates or possibly (Fe, Mg)-OH bonds in sheet silicates.

  16. Infrared absorption and vibrational circular dichroism spectra of poly(vinyl ether) containing diastereomeric menthols as pendants

    NASA Astrophysics Data System (ADS)

    McCann, Jennifer L.; Rauk, Arvi; Wieser, Hal

    1997-06-01

    The absorption and vibrational circular dichroism (VCD) spectra in the 1700 to 830 cm -1 region are reported and qualitatively interpreted for poly(vinyl ether) with (+)-menthol (I), (+)-isomenthol (II) and (+)-neomenthol (III) as pendants.

  17. First-principles calculation of ground and excited-state absorption spectra of ruby and alexandrite considering lattice relaxation

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinta; Sasaki, Tomomi; Taniguchi, Rie; Ishii, Takugo; Ogasawara, Kazuyoshi

    2009-02-01

    We performed first-principles calculations of multiplet structures and the corresponding ground-state absorption and excited-state absorption spectra for ruby (Cr3+:α-Al2O3) and alexandrite (Cr3+:BeAl2O4) which included lattice relaxation. The lattice relaxation was estimated using the first-principles total energy and molecular-dynamics method of the CASTEP code. The multiplet structure and absorption spectra were calculated using the configuration-interaction method based on density-functional calculations. For both ruby and alexandrite, the theoretical absorption spectra, which were already in reasonable agreement with experimental spectra, were further improved by consideration of lattice relaxation. In the case of ruby, the peak positions and peak intensities were improved through the use of models with relaxations of 11 or more atoms. For alexandrite, the polarization dependence of the U band was significantly improved, even by a model with a relaxation of only seven atoms.

  18. Index of Refraction and Absorption Coefficient Spectra of Paratellurite in the Terahertz Region

    NASA Astrophysics Data System (ADS)

    Unferdorben, Márta; Buzády, Andrea; Hebling, János; Kiss, Krisztián; Hajdara, Ivett; Kovács, László; Péter, Ágnes; Pálfalvi, László

    2016-07-01

    Index of refraction and absorption coefficient spectra of pure paratellurite (α-TeO2) crystal as a potential material for terahertz (THz) applications were determined in the 0.25-2 THz frequency range at room temperature by THz time domain spectroscopy (THz-TDS). The investigation was performed with beam polarization both parallel (extraordinary polarization) and perpendicular (ordinary polarization) to the optical axis [001] of the crystal. Similarly to the visible spectral range, positive birefringence was observed in the THz range as well. It was shown that the values of the refractive index for extraordinary polarization are higher and show significantly larger dispersion than for the ordinary one. The absorption coefficient values are also larger for extraordinary polarization. The measured values were fitted by theoretical curves derived from the complex dielectric function containing independent terms of Lorentz oscillators due to phonon-polariton resonances. The results are compared with earlier publications, and the observed significant discrepancies are discussed.

  19. Radiolytically induced formation and optical absorption spectra of colloidal silver nanoparticles in supercritical ethane.

    SciTech Connect

    Dimitrijevic, N. M.; Bartels, D. M.; Jonah, C. D.; Takahashi, K.; Rajh, T.; Chemistry

    2001-02-08

    Colloidal silver nanoparticles were synthesized in supercritical ethane at 80 {sup o}C and 80-120 bar, with methanol as cosolvent. Solvated electrons, produced by a pulse of 20 MeV electrons, reduced the silver ions. The time-resolved technique of pulse radiolysis was employed to characterize the reduction products and colloidal metallic particles. The absorption spectra of small silver clusters (Ag{sub 2}{sup +}, Ag{sub 3}{sup +}, Ag{sub 4}{sup 2+}, etc.) were detected at short times after the pulse. Colloidal metallic silver particles were identified by their characteristic plasmon absorption at 1-10 s after the pulse. Colloidal particles are stable for hours in supercritical ethane. The particles are less than 10 nm in diameter. Their size was determined using transmission electron microscope after precipitation from the solution.

  20. Pressure dependence of Hexanitrostilbene Raman/ electronic absorption spectra to validate DFT EOS

    NASA Astrophysics Data System (ADS)

    Farrow, Darcie; Alam, Kathleen; Martin, Laura; Fan, Hongyou; Kay, Jeffrey; Wixom, Ryan

    2015-06-01

    Due to its thermal stability and low vapor pressure, Hexanitrostilbene (HNS) is often used in high-temperature or vacuum applications as a detonator explosive or in mild detonating fuse. Toward improving the accuracy of the equation of state used in hydrodynamic simulations of the performance of HNS, we have measured the Raman and electronic absorption spectra of this material under static pressure in a diamond anvil cell. Density functional theory calculations were used to simulate the pressure dependence of the Raman/Electronic spectra along the Hugoniot and 300K isotherm for comparison and to aid in interpreting the data. We will discuss changes in the electronic structure of HNS under pressure, validation of a DFT predicted equation of state (EOS), and using this data as a basis for understanding future pulsed Raman measurements on dynamically compressed HNS samples.

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

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

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

  2. Atomic calculations and search for variation of the fine-structure constant in quasar absorption spectra

    NASA Astrophysics Data System (ADS)

    Dzuba, V. A.; Flambaum, V. V.

    A brief review of the search for variation of the fine structure constant in quasar absorption spectra is presented. Special consideration is given to the role of atomic calculations in the analysis of the observed data. A range of methods which allow to perform calculations for atoms or ions with different electron structure and which cover practically all periodic table of elements is discussed. Critical compilation of the results of the calculations as well as a review of the most recent results of the analysis are presented.

  3. Decay heat and anti-neutrino energy spectra in fission fragments from total absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Rykaczewski, Krzysztof

    2015-10-01

    Decay studies of over forty 238U fission products have been studied using ORNL's Modular Total Absorption Spectrometer. The results are showing increased decay heat values, by 10% to 50%, and the energy spectra of anti-neutrinos shifted towards lower energies. The latter effect is resulting in a reduced number of anti-neutrinos interacting with matter, often by tens of percent per fission product. The results for several studied nuclei will be presented and their impact on decay heat pattern in power reactors and reactor anti-neutrino physics will be discussed.

  4. Water vapor absorption spectra of the upper atmosphere /45-185 per cm/

    NASA Technical Reports Server (NTRS)

    Augason, G. C.; Mord, A. J.; Witteborn, F. C.; Erickson, E. F.; Swift, C. D.; Caroff, L. J.; Kunz, L. W.

    1975-01-01

    The far IR nighttime absorption spectrum of the earth's atmosphere above 14 km is determined from observations of the bright moon. The spectra were obtained using a Michelson interferometer attached to a 30-cm telescope aboard a high-altitude jet aircraft. Comparison with a single-layer model atmosphere implies a vertical column of 3.4 plus or minus 0.4 microns of precipitable water on 30 August 1971 and 2.4 plus or minus 0.3 microns of precipitable water on 6 January 1972.-

  5. Water vapor absorption spectra of the upper atmosphere (45-185 cm(-1)).

    PubMed

    Augason, G C; Mord, A J; Witteborn, F C; Erickson, E F; Swift, C D; Caroff, L J; Kunz, L W

    1975-09-01

    The far ir nighttime absorption spectrum of the earth's atmosphere above 14 km is determined from observations of the bright moon. The spectra were obtained using a Michelson interferometer attached to a 30-cm telescope aboard a high-altitude jet aircraft. Comparison with a single-layer model atmosphere implies a vertical column of 3.4 +/- 0.4 mum of percipitable water on 30 August 1971 and 2.4 +/- 0.3 mum of precipitable water on 6 January 1972. PMID:20154976

  6. The Hubble Space Telescope Quasar Absorption Line Key Project. XIV. The Evolution of Lyα Absorption Lines in the Redshift Interval z = 0-1.5

    NASA Astrophysics Data System (ADS)

    Weymann, Ray J.; Jannuzi, Buell T.; Lu, Limin; Bahcall, John N.; Bergeron, Jacqueline; Boksenberg, Alec; Hartig, George F.; Kirhakos, Sofia; Sargent, W. L. W.; Savage, Blair D.; Schneider, Donald P.; Turnshek, David A.; Wolfe, Arthur M.

    1998-10-01

    We present the results of an analysis of the rate of evolution of the Lyα absorption lines in the redshift interval 0.0 to ~1.5 based upon a sample of 987 Lyα absorption lines identified in the spectra of 63 QSOs obtained with the Faint Object Spectrograph (FOS) of the Hubble Space Telescope (HST). These spectra were obtained as part of the QSO Absorption Line Survey, an HST Key Project during the first four years of observations with the telescope. Fits to the evolution of the number of absorbers per unit redshift (dN/dz) of the form dN/dz = A × (1 + z)γ continue to yield values of γ in the range 0.1-0.3, decidedly flatter than results from ground-based data pertaining to the redshift range z > 1.7. These results are consistent with our previous results based on a much smaller sample of lines, but the uncertainties in the fit have been greatly reduced. The combination of the HST and ground-based data suggest a marked transition in the rate of evolution of the Lyα lines at a redshift of about 1.7. The 19 Lyα lines from an additional higher redshift QSO from our sample for which tentative line identifications are available (UM 18; zem = 1.89) support the suggestion of a rapid increase at around this redshift. We derive the cumulative distribution of the full sample of Lyα lines and show that the distribution in redshift can indeed be well represented by a power law of the form (1 + z)γ. For this same sample, the distribution of equivalent widths of the Lyα absorbers above a rest equivalent width of 0.1 Å is fit quite well by an exponential. Comparing samples of Lyα lines, one set of which has redshifts the same as, or very near to, the redshifts of ions from heavy elements and another set in which no ions from heavy elements have been identified, we find that the Lyα systems with heavy element detections have a much steeper slope than the high rest equivalent width portion of the Lyman-only sample. We argue that this result is not likely to be due to

  7. Absorption spectra of riboflavin--a difficult case for computational chemistry.

    PubMed

    Wu, Min; Eriksson, Leif A

    2010-09-23

    Computing accurate absorption spectra of riboflavin (RBF) has proven a difficult task for computational chemistry. Time-dependent density functional theory have herein been employed using a wide range of recent range-separated and hybrid meta functionals to investigate ultraviolet and visible spectra of RBF to determine if any progress has been made through recent developments. It is concluded that B3LYP and PBE0 perform the best throughout the entire test set. However, since all methods deviate from experimental results by at least 40 nm when computing the spectra in vacuum, two approaches to describe aqueous solution are implemented together with the MPWB1K, B3LYP, and PBE0 functionals: implicitly using integral equation formulation of the polarized continuum model (minor improvement) and explicitly through molecular dynamics (MD) simulations of the molecule embedded in a water cluster whereafter snapshots of RBF-water clusters are extracted and time-dependent density functional theory calculations performed. The resulting averaged spectra from the MD-simulated clusters show a constant blue-shift for all peaks by ∼20 nm compared to experimental data at the TD-B3LYP/6-31+G(d,p) level. PMID:20718485

  8. The X-shooter sample of GRB afterglow spectra: Properties of the absorption features

    NASA Astrophysics Data System (ADS)

    de Ugarte Postigo, Antonio

    2015-08-01

    Since its commissioning at ESO's Very Large Telescope in 2009, the X-shooter spectrograph has become the reference instrument in gamma-ray burst (GRB) afterglow spectroscopy. During this time our collaboration has collected more than 70 spectra of GRB afterglows, with redshifts ranging from 0.06 to 6.3. Thanks to their extreme luminosity and simple intrinsic shape, GRB spectra are optimal tools for the study of galactic environments at basically any redshift. Being produced by the death of short-lived massive stars, they are also tracers of star formation.I will present the sample of absorption spectral features identified in X-shooter's GRB spectra describing observation and analysis techniques. The different features are compared with the characteristics of the explosion (duration, spectral shape, energetics, etc.) and with the properties of the host galaxy (mass, age, etc.) to improve our understanding of the nature of the explosions and how they interact with their environments. Using the large redshift range of the spectra collection we perform studies of the evolution of GRB environments across the history of the Universe and their relation with the evolution of star formation.

  9. Appraisal of Surface Hopping as a Tool for Modeling Condensed Phase Linear Absorption Spectra.

    PubMed

    Petit, Andrew S; Subotnik, Joseph E

    2015-09-01

    Whereas surface hopping is usually used to study populations and mean-field dynamics to study coherences, in two recent papers, we described a procedure for calculating dipole-dipole correlation functions (and therefore absorption spectra) directly from ensembles of surface hopping trajectories. We previously applied this method to a handful of one-dimensional model problems intended to mimic the gas phase. In this article, we now benchmark this new procedure on a set of multidimensional model problems intended to mimic the condensed phase and compare our results against other standard semiclassical methods. By comparison, we demonstrate that methods that include only dynamical information from one PES (the standard Kubo approaches) exhibit large discrepancies with the results of exact quantum dynamics. Furthermore, for model problems with nonadiabatic excited state dynamics but no quantized vibrational structure in the spectra, our surface hopping approach performs comparably to using Ehrenfest dynamics to calculate the electronic coherences. That being said, however, when quantized vibrational structures are present in the spectra but the electronic states are uncoupled, performing the dynamics on the mean PES still outperforms our present method. These benchmark results should influence future studies that use ensembles of independent semiclassical trajectories to model linear as well as multidimensional spectra in the condensed phase. PMID:26575927

  10. Deriving the Extinction to Young Stellar Objects using [Fe II] Near-infrared Emission Lines: Prescriptions from GIANO High-resolution Spectra

    NASA Astrophysics Data System (ADS)

    Pecchioli, T.; Sanna, N.; Massi, F.; Oliva, E.

    2016-07-01

    The near-infrared (NIR) emission lines of Fe+ at 1.257, 1.321, and 1.644 μm share the same upper level; their ratios can then be exploited to derive the extinction to a line emitting region once the relevant spontaneous emission coefficients are known. This is commonly done, normally from low-resolution spectra, in observations of shocked gas from jets driven by Young Stellar Objects. In this paper we review this method, provide the relevant equations, and test it by analyzing high-resolution (R ∼ 50,000) NIR spectra of two young stars, namely the Herbig Be star HD 200775 and the Be star V1478 Cyg, which exhibit intense emission lines. The spectra were obtained with the new GIANO echelle spectrograph at the Telescopio Nazionale Galileo. Notably, the high-resolution spectra allowed checking the effects of overlapping telluric absorption lines. A set of various determinations of the Einstein coefficients are compared to show how much the available computations affect extinction derivation. The most recently obtained values are probably good enough to allow reddening determination within 1 visual mag of accuracy. Furthermore, we show that [Fe ii] line ratios from low-resolution pure emission-line spectra in general are likely to be in error due to the impossibility to properly account for telluric absorption lines. If low-resolution spectra are used for reddening determinations, we advice that the ratio 1.644/1.257, rather than 1.644/1.321, should be used, being less affected by the effects of telluric absorption lines.

  11. Statistics of electric-quadrupole lines in atomic spectra

    NASA Astrophysics Data System (ADS)

    Pain, Jean-Christophe; Gilleron, Franck; Bauche, Jacques; Bauche-Arnoult, Claire

    2012-07-01

    In hot plasmas, a temperature of a few tens of eV is sufficient for producing highly stripped ions where multipole transitions become important. At low density, the transitions from tightly bound inner shells lead to electric-quadrupole (E2) lines which are comparable in strength with electric-dipole ones. In this work, we propose analytical formulas for the estimation of the number of E2 lines in a transition array. Such expressions rely on statistical descriptions of electron states and J-levels. A generalized ‘J-file’ sum rule for E2 lines and the strength-weighted shift and variance of the line energies of a transition array nℓN + 1 → nℓNn‧ℓ‧ of inter-configuration E2 lines are also presented.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; Garcia, J.; Lohfink, A.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Palmeri, P.; Quinet, P. E-mail: claudio@ivic.gob.ve E-mail: alohfink@astro.umd.edu E-mail: michael.c.witthoeft@nasa.gov E-mail: palmeri@umons.ac.be

    2013-05-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 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.

  15. Metal-line absorption at Z(sub abs) approximately Z(sub em) from associated galaxies

    NASA Technical Reports Server (NTRS)

    Ellingson, E.; Yee, H. K. C.; Bechtold, Jill; Dobrzycki, Adam

    1994-01-01

    For a preliminary study of whether C IV absorption at Z(sub abs) approximately Z(sub em) is related to associated galaxy companions, we have collected data from a sample of 10 quasars with 0.15 less than z less than 0.65 for which high-resolution optical and UV spectroscopy is available from the literature, and for which we have deep optical images and limited spectroscopy. We also present new optical spectra for two of our samples. Four of these quasars have associated C IV absorption systems. In thes four fields, there are eight galaxies with M(sub r) less than -19.0 mag within 35 kpc of the quasar (projected distance, assuming they are at the quasar redshift), which may be candidates for the associated C IV absorption. This observed density of galaxies near quasars with associated C IV absorption is significantly greater than that for a control sample of quasars chosen from the literature. This result suggests that galaxies near the quasar line of sight may be linked with associated C IV absorption. None of these quasars show associated Mg II absorption, despite the presence of galaxies very near the line of sight, suggesting a Mg II 'proximity effect,' where ionizing flux from the quasar destroys the Mg(+) from at least the outer parts of the galaxies. Three quasars are located in rich galaxy clusters, but none of these quasars are found to have associated C IV absorption. This suggests that galaxies in rich clusters associated with quasars are less likely to be metal-line absorbers. It is plausible that the extended galaxy halos which may be responsible for the absorptions are stripped from galaxies in these dense environments. While it seems that at Z approximately 0.6 rich clusters do not cause them, associated C IV absorption systems at higher redshift may be explained by associated clusters if there has been evolution in the properties of galaxy halos in dense environments.

  16. Metallic Line Doubling and van hoof Effect in the Spectra of the Variable Star RR Lyrae

    NASA Astrophysics Data System (ADS)

    Sefyani Lakrizi, Fouad; Benhida, Abdelmjid; Gillet, Denis; Mathias, phillipe; de France, Thibault; Benkhaldoun, Zouhair; Lazrek, Mohamed; Daassou, Ahmed

    2015-08-01

    The Oukaïmeden observatory is situated at an altitude of 2700m in the High Atlas mountain range, 78km south of Marrakech 7°52’52’’ west and 31°12’32’’ north. The quality of the sky is considered exceptional, not only for imaging but also for photometry. Indeed, the average measured seeing is of the order of 1 arc second which ensures high quality spectrum recording with a good signal-to-noise ratio. In this communication, we will present our observations of the phenomenon of metallic absorption lines, doubling in the spectra of the variable star RR Lyrae on Fe II (l4923.921 Å), as well as of sodium D lines. In emission, we observed the lines of hydrogen Hα, Hβ and Hγ with a very strong intensity (50 % above the continuum). We also observed the Van Hoof effect which consists of a difference between the radial velocity of the line of the Fe II (λ4923.921 Å) and that of the line Hβ. These observations were carried out with a small spectrograph of approximately 12000 resolution, installed on a 14 inch telescope, during the night of October 12th 2013. This date corresponded to the maximal phase of the Blazhko cycle. The doubling of the lines was interpreted by Schwarzschild on the basis of an atmosphere in two layers. Based on this interpretation we were able to measure the radial velocity of the shock wave deducted from the difference between both red and blue spectral components on the lines Hα of hydrogen, D of the sodium and the Fe II during the doubling of observed lines. The shock wave reached the maximal speed of 160 kms-1 so confirming the hypersonic regime to which atmosphere is submitted during this maximum phase of the Blazhko cycle. We will also present a comparison of our results with those obtained with high resolution spectrographs and thus confirm the validity of our results.

  17. Line-Parameter Measurements and Stringent Tests of Line-Shape Models Based on Cavity-Enhanced Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    Bielska, Katarzyna; Fleisher, Adam J.; Hodges, Joseph T.; Lin, Hong; Long, David A.; Reed, Zachary D.; Sironneau, Vincent; Truong, Gar-Wing; Wójtewicz, Szymon

    2014-06-01

    Laser methods that are based on cavity-enhanced absorption spectroscopy (CEAS) are well-suited for measuring molecular line parameters under conditions of low optical density, and as such they are complementary to broadband Fourier-transform spectroscopy (FTS) techniques. Attributes of CEAS include relatively low detection limits, accurate and precise detuning axes and high fidelity measurements of line shape. In many cases these performance criteria are superior to those obtained using direct laser absorption spectroscopy and FTS-based systems. In this presentation we will survey several examples of frequency-stabilized cavity ring-down spectroscopy (FS-CRDS)1 measurements obtained with laser spectrometers developed at the National Institute of Standards and Technology (NIST) in Gaithersburg Maryland. These experiments, which are motivated by atmospheric monitoring and remote-sensing applications that require high-precision and accuracy, involve nearinfrared transitions of carbon dioxide, water, oxygen and methane. We discuss spectra with signal-to-noise ratios exceeding 106, frequency axes with absolute uncertainties in the 10 kHz to 100 kHz range and linked to a Cs clock, line parameters with relative uncertainties at the 0.2 % level and isotopic ratios measured with a precision of 0.03 %. We also present FS-CRDS measurements of CO2 line intensities which are measured at atmospheric concentration levels and linked to gravimetric standards for CO2 in air, and we quantify pressure-dependent deviations between various theoretical line profiles and measured line shapes. Finally we also present recent efforts to increase data throughput and spectral coverage in CEAS experiments. We describe three new high-bandwidth CEAS techniques including frequency-agile, rapid scanning spectroscopy (FARS)2, which enables continuous-wave measurements of cavity mode linewidth and acquisition of ringdown decays with no dead time during laser frequency tuning, heterodyne

  18. Picosecond kinetics and Sn <-- S1 absorption spectra of retinoids and carotenoids

    NASA Astrophysics Data System (ADS)

    Bondarev, Stanislav L.; Tikhomirov, S. A.; Bachilo, Sergei M.

    1991-05-01

    Light energy absorption, as well as the subsequent photochemical and photophysical processes of cis -+trans isomerisation (vision and bacteriorhodopsin photosynthesis) and energy transfer (photosynthesis in green plants and micro organisms) take place in a pigment-protein complex including polyene chromophors, retinoids and carotenoids. Picosecond and subpicosecond studies of the spectral and kinetic characteristics of these processes are carried out in both complex photoreceptor and photosynthetic ms'2 and model systems with the use of solutions of retinoids and carotenoids.36 The lifetimes of the lower singlet-exited states S (21A; ) ofsome carotenoids in toluene at room temperature have been measured by the method of picosecond photolysis and amount to 8.6+/- 0.5 for all-trans-fl -carotene1 and 5.2 0.6 PS for canthaxanthin.5 /3 -carotene fluorescence at room temperature is practically absent, its yield being less than iO (Ref. 7). /1 -carotene fluorescence at 77 and 4.2 K in isopentane discovered by us8 is characterized by yields of (4+/-2) .iO and (8+/-3) . i0- and lifetimes of(4+/-2) .iO' and (8+/-3) .iO' and is due to the transitions from the higher S(1' B) state. The picosecond transient S -S absorption of/I - carotene in different solvents at 293 K is characterized by spectra in the 550-600 nm range.8 For retinoids, there is one work (Ref. 4) which gives the S, +-Si absorption spectrum of the Schiff base (aldimine) of retinal with amaz 465 mn in n-hexane at 290 K. The duration of transient absorption was 21 5 ps, although the fluorescence kinetics measured in this work (Ref. 4) at 298 K were characterized by two-component decay with r1 = 22 and r2 = 265 ps. The transient picosecond absorption spectra for retinal are absent in the literature and the lifetimes of its singlet-excited state at room temperature, measured by absorption and fluorescence, amount to 20+/-10 Ps in n-hexane3 and 17 Ps in ethanol,'9 respectively.

  19. Search for infrared absorption lines of atmospheric chlorine monoxide (ClO)

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Goldman, Aaron

    1992-01-01

    A search for features of the ClO (1-0) vibration-rotation band has been conducted based on a 5000 signal-to-rms noise ratio IR spectrum derived by coadding 39 high-quality 0.0053/cm resolution solar spectra recorded with the McMath Fourier transform spectrometer on Kitt Peak. Evidence for absorption has been found at the locations of several of the stronger ClO P-branch lines with minimal interference. Detailed results are presented for the P(8.5) and P(7.5) 2Pi3/2-2Pi3/2 lines of Cl-35O at 833.2974 and 834.6249/cm, respectively. If ClO is present in the stratosphere at the concentrations indicated by other methods, our analysis indicates that modest improvements in signal-to-noise ratio and spectral resolution would permit a definitive detection of ClO in IR ground-based spectra.

  20. Absolute Transition Probabilities of Lines in the Spectra of Astrophysical Atoms, Molecules, and Ions

    NASA Technical Reports Server (NTRS)

    Parkinson, W. H.; Smith, P. L.; Yoshino, K.

    1984-01-01

    Progress in the investigation of absolute transition probabilities (A-values or F values) for ultraviolet lines is reported. A radio frequency ion trap was used for measurement of transition probabilities for intersystem lines seen in astronomical spectra. The intersystem line at 2670 A in Al II, which is seen in pre-main sequence stars and symbiotic stars, was studied.

  1. X-Ray Continua of Broad Absorption Line Quasars

    NASA Technical Reports Server (NTRS)

    Mathur, S.

    1999-01-01

    The targets for this program, PG1416-129 and LBQS 2212-1759 were known to be Broad Absorption Line Quasars (BALQSOs). BALQSOs are highly absorbed in soft X-rays. Good high energy response of Rossi-XTE made them ideal targets for observation. We observed LBQS 2212-1759 with PCA. We have now analyzed the data and found that the source was not detected. Since our target was expected to be faint, reliable estimate of background was very important. With the release of new FTOOLS (version 4.1) we were able to do so. We also analyzed a well known bright object and verified our results with the published data. This gave us confidence in the non-detection of our target LBQS 2212-1759. We are currently investigating the implications of this non-detection. Due to some scheduling problems, our second target PG1416-129 was not observed in A01. It was observed on 06/26/98. This target was detected with RXTE. We are now working on the spectral analysis with XSPEC.

  2. Absorption in X-ray spectra of high-redshift quasars

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

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

    ERIC Educational Resources Information Center

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

    2016-01-01

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

  4. Stratospheric and mesospheric pressure-temperature profiles from rotational analysis of CO2 lines in atmospheric trace molecule spectroscopy/ATLAS 1 infrared solar occultation spectra

    NASA Technical Reports Server (NTRS)

    Stiller, G. P.; Gunson, M. R.; Lowes, L. L.; Abrams, M. C.; Raper, O. F.; Farmer, C. B.; Zander, R.; Rinsland, C. P.

    1995-01-01

    A simple, classical, and expedient method for the retrieval of atmospheric pressure-temperature profiles has been applied to the high-resolution infrared solar absorption spectra obtained with the atmospheric trace molecule spectroscopy (ATMOS) instrument. The basis for this method is a rotational analysis of retrieved apparent abundances from CO2 rovibrational absorption lines, employing existing constituent concentration retrieval software used in the analysis of data returned by ATMOS. Pressure-temperature profiles derived from spectra acquired during the ATLAS 1 space shuttle mission of March-April 1992 are quantitatively evaluated and compared with climatological and meteorological data as a means of assessing the validity of this approach.

  5. Stratospheric and mesospheric pressure-temperature profiles from rotational analysis of CO2 lines in atmospheric trace molecule spectroscopy/ATLAS 1 infrared solar occultation spectra

    SciTech Connect

    Stiller, G.P.; Gunson, M.R.; Lowes, L.L.; Abrams, M.C.; Raper, O.F.; Farmer, C.B.; Zander, R.; Rinsland, C.P. |||

    1995-02-01

    A simple, classical, and expedient method for the retrieval of atmospheric pressure-temperature profiles has been applied to the high-resolution infrared solar absorption spectra obtained with the atmospheric trace molecule spectroscopy (ATMOS) instrument. The basis for this method is a rotational analysis of retrieved apparent abundances from CO2 rovibrational absorption lines, employing existing constituent concentration retrieval software used in the analysis of data returned by ATMOS. Pressure-temperature profiles derived from spectra acquired during the ATLAS 1 space shuttle mission of March-April 1992 are quantitatively evaluated and compared with climatological and meteorological data as a means of assessing the validity of this approach.

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

    PubMed

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

    2014-10-15

    We describe here the effects of aprotic solvents on the spectroscopic characteristics of bixin. Bixin was dissolved in dimethyl sulfoxide, acetone, dichloromethane, ethyl acetate, chloroform, dimethyl carbonate, cyclohexane and hexane, separately, and its spectra in the resulting solutions were determined by UV-visible spectrophotometry at normal pressure and room temperature. We analyzed the effect of aprotic solvents on λmax according to Onsager cavity model and Hansen theory, and determined the approximate absorption coefficient with the Beer-Lambert law. We found that the UV-visible absorption spectra of bixin were found to be solvent dependent. The S0→S2 transition energy of bixin in solution was dependent principally on the refractive index of the solvents and the bixin-solvent dispersion interaction. There was a small influence of the solvents dielectric constant, permanent dipole interaction and hydrogen bonding occurred between bixin and solvents. The absorbance of bixin in various solvents, with the exception of hexane, increased linearly with concentration. PMID:24840486

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

    SciTech Connect

    Penfold, T. J.; Tavernelli, I.; Rothlisberger, U.; Milne, C. J.; Abela, R.; Reinhard, M.; Nahhas, A. El; Chergui, M.

    2013-01-07

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

  8. Understanding the absorption and emission spectra of borondipyrromethene dye and its substituted analogues

    NASA Astrophysics Data System (ADS)

    Nithya, R.; Kolandaivel, P.; Senthilkumar, K.

    2012-04-01

    Borondipyrromethene (BODIPY) dye possesses a bright and long wavelength emitting fluorescent character with a wide spectral range from visible to near infrared region. In the present work, the spectral properties of BODIPY dyes were analyzed using ab intio and density functional theory methods. The ground and excited state geometries of BODIPY and its substituted analogues in chloroform medium, were optimized using the density functional theory (DFT) and singly excited configuration interaction (CIS) methods. Based on the ground and excited state geometries, the absorption and emission spectra have been calculated using time-dependent density functional theory (TDDFT) method. The TDDFT calculations have been performed using hybrid exchange correlation functionals B3LYP and M06-HF and long-range separated functionals LC-BLYP, LC-BOP, LC-PBE, LC-PBE0 and CAM-B3LYP. The solvent phase calculations were carried out using polarizable continuum model (PCM). The TDDFT investigation reveals that the substitution of acceptor, donor-donor, donor-acceptor-donor and phenyl group in BODIPY dye influence the absorption and emission spectra significantly.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  10. Multi-state extrapolation of UV/Vis absorption spectra with QM/QM hybrid methods

    NASA Astrophysics Data System (ADS)

    Ren, Sijin; Caricato, Marco

    2016-05-01

    In this work, we present a simple approach to simulate absorption spectra from hybrid QM/QM calculations. The goal is to obtain reliable spectra for compounds that are too large to be treated efficiently at a high level of theory. The present approach is based on the extrapolation of the entire absorption spectrum obtained by individual subcalculations. Our program locates the main spectral features in each subcalculation, e.g., band peaks and shoulders, and fits them to Gaussian functions. Each Gaussian is then extrapolated with a formula similar to that of ONIOM (Our own N-layered Integrated molecular Orbital molecular Mechanics). However, information about individual excitations is not necessary so that difficult state-matching across subcalculations is avoided. This multi-state extrapolation thus requires relatively low implementation effort while affording maximum flexibility in the choice of methods to be combined in the hybrid approach. The test calculations show the efficacy and robustness of this methodology in reproducing the spectrum computed for the entire molecule at a high level of theory.

  11. Multi-state extrapolation of UV/Vis absorption spectra with QM/QM hybrid methods.

    PubMed

    Ren, Sijin; Caricato, Marco

    2016-05-14

    In this work, we present a simple approach to simulate absorption spectra from hybrid QM/QM calculations. The goal is to obtain reliable spectra for compounds that are too large to be treated efficiently at a high level of theory. The present approach is based on the extrapolation of the entire absorption spectrum obtained by individual subcalculations. Our program locates the main spectral features in each subcalculation, e.g., band peaks and shoulders, and fits them to Gaussian functions. Each Gaussian is then extrapolated with a formula similar to that of ONIOM (Our own N-layered Integrated molecular Orbital molecular Mechanics). However, information about individual excitations is not necessary so that difficult state-matching across subcalculations is avoided. This multi-state extrapolation thus requires relatively low implementation effort while affording maximum flexibility in the choice of methods to be combined in the hybrid approach. The test calculations show the efficacy and robustness of this methodology in reproducing the spectrum computed for the entire molecule at a high level of theory. PMID:27179466

  12. Absorption and spectra of optical parameters in amorphous solid solutions of the Se-S system

    SciTech Connect

    Djalilov, N. Z.; Damirov, G. M.

    2011-04-15

    A study of the optical properties of the Se-S system has revealed a correlation between the dependences of optical absorption coefficient {alpha}, effective concentration of charged defects N{sub t}, and characteristic energy E{sub 0} corresponding to the Urbach optical absorption in the spectral region where the Urbach rule works for the Se-S system on the S concentration. These optical properties are controlled by charged defects. It is shown that concentrations of intrinsic charged defects can be changed by variation in composition of the Se-S system. Reflectance spectra of amorphous solid solutions of the Se-S system are studied within the energy range 1-6 eV. Using the Kramers-Kronig method, spectral dependences of optical constants and derivative optical and dielectric functions are calculated. Variation in the spectra of optical parameters with composition of the Se-S system are explained within a cluster model in which the density of electron states is a function of atomic configurations in clusters, i.e., of the character of a short-range order.

  13. Plasmonic resonance absorption spectra in mid-infrared in an array of graphene nanoresonators

    NASA Astrophysics Data System (ADS)

    Abeysinghe, Don C.; Myers, Joshua; Nader Esfahani, Nima; Hendrickson, Joshua R.; Cleary, Justin W.; Walker, Dennis E.; Chen, Kuei-Hsien; Chen, Li-Chyong; Mou, Shin

    2013-12-01

    We experimentally demonstrated graphene plasmon resonant absorption in mid-IR by utilizing an array of graphene nanoribbon resonators on SiO2 substrate. By tuning resonator width we probed the graphene plasmons with λp <= λ0/100 and plasmon resonances as high as 0.240 eV (2100 cm-1) for 40 nm wide nanoresonators. Resonant absorption spectra revealed plasmon dispersion as well as plasmon damping due to the interaction of graphene plasmons with the surface polar phonons in SiO2 substrate and intrinsic graphene optical phonons. Graphene nanoribbons with varying widths enabled us to identify the damping mechanisms of graphene plasmons and much reduced damping was observed when the plasmon resonance frequencies were close to the substrate polar phonon frequencies. Then, by direct ebeam exposure of graphene nanoresonators, we effectively changed the carrier density and caused red-shift of the plasmon spectra. This work will provide insight into light-sensitive, frequency-tunable photodetectors based on graphene's plasmonic excitations.

  14. Catalog of Narrow Mg II Absorption Lines in the Baryon Oscillation Spectroscopic Survey

    NASA Astrophysics Data System (ADS)

    Chen, Zhi-Fu; Gu, Qiu-Sheng; Chen, Yan-Mei

    2015-12-01

    Using the Data Release 9 Quasar spectra from the Baryonic Oscillation Spectroscopic Survey, which does not include quasar spectra from the Sloan Digital Sky Survey Data Release 7, we detect narrow Mg ii λλ2796, 2803 absorption doublets in the spectral data redward of 1250 Å (quasar rest frame) until the red wing of the Mg ii λ2800 emission line. Our survey is limited to quasar spectra with a median signal-to-noise ratio < {{S}}/{{N}}> ≥slant 4 pixel-1 in the surveyed spectral region, resulting in a sample that contains 43,260 quasars. We have detected a total of 18,598 Mg ii absorption doublets with 0.2933 ≤ zabs ≤ 2.6529. About 75% of absorbers have an equivalent width at rest frame of {W}rλ 2796≥slant 1 \\mathringA . About 75% of absorbers have doublet ratios ({DR}={W}rλ 2796/{W}rλ 2803) in the range of 1 ≤ DR ≤ 2, and about 3.2% lie outside the range of 1 - σDR ≤ DR ≤ 2 + σDR. We characterize the detection false positives/negatives by the frequency of detected Mg ii absorption doublets in the limits of the S/N of the spectral data. The S/N = 4.5 limit is assigned a completeness fraction of 53% and tends to be complete when the S/N is greater than 4.5. The redshift number densities of all of the detected Mg ii absorbers moderately increase from z ≈ 0.4 to z ≈ 1.5, which parallels the evolution of the cosmic star formation rate density. Limiting our investigation to those quasars whose emission redshift can be determined from narrow emission lines, the relative velocities (β) of Mg ii absorbers have a complex distribution which probably consists of three classes of Mg ii absorbers: (1) cosmologically intervening absorbers; (2) environmental absorbers that reside within the quasar host galaxies or galaxy clusters; (3) quasar outflow absorbers. After subtracting contributions from cosmologically intervening absorbers and environmental absorbers, the β distribution of the Mg iiabsorbers might mainly be contributed by the quasar outflow

  15. THE STELLAR INITIAL MASS FUNCTION IN EARLY-TYPE GALAXIES FROM ABSORPTION LINE SPECTROSCOPY. II. RESULTS

    SciTech Connect

    Conroy, Charlie; Van Dokkum, Pieter G.

    2012-11-20

    The spectral absorption lines in early-type galaxies contain a wealth of information regarding the detailed abundance pattern, star formation history, and stellar initial mass function (IMF) of the underlying stellar population. Using our new population synthesis model that accounts for the effect of variable abundance ratios of 11 elements, we analyze very high quality absorption line spectra of 38 early-type galaxies and the nuclear bulge of M31. These data extend to 1 {mu}m and they therefore include the IMF-sensitive spectral features Na I, Ca II, and FeH at 0.82 {mu}m, 0.86 {mu}m, and 0.99 {mu}m, respectively. The models fit the data well, with typical rms residuals {approx}< 1%. Strong constraints on the IMF and therefore the stellar mass-to-light ratio, (M/L){sub stars}, are derived for individual galaxies. We find that the IMF becomes increasingly bottom-heavy with increasing velocity dispersion and [Mg/Fe]. At the lowest dispersions and [Mg/Fe] values the derived IMF is consistent with the Milky Way (MW) IMF, while at the highest dispersions and [Mg/Fe] values the derived IMF contains more low-mass stars (is more bottom-heavy) than even a Salpeter IMF. Our best-fit (M/L){sub stars} values do not exceed dynamically based M/L values. We also apply our models to stacked spectra of four metal-rich globular clusters in M31 and find an (M/L){sub stars} that implies fewer low-mass stars than a MW IMF, again agreeing with dynamical constraints. We discuss other possible explanations for the observed trends and conclude that variation in the IMF is the simplest and most plausible.

  16. Temperature measurement of wood flame based on the double line method of atomic emission spectra

    NASA Astrophysics Data System (ADS)

    Hao, Xiaojian; Liu, Zhenhua; Sang, Tao

    2016-01-01

    Aimed at the testing requirement of the transient high temperature in explosion field and the bore of barrel weapon, the temperature measurement system of double line of atomic emission spectrum was designed, the method of flame spectrum testing system were used for experimental analysis. The experimental study of wood burning spectra was done with flame spectrum testing system. The measured spectra contained atomic emission spectra of the elements K, Na, and the excitation ease of two kinds atomic emission spectra was analyzed. The temperature was calculated with two spectral lines of K I 766.5nm and 769.9nm. The results show that, compared with Na, the excitation temperature of K atomic emission spectra is lower. By double line method, the temperature of wood burning is 1040K, and error is 3.7%.

  17. Exciton-Like Behavior in Low-Energy Absorption Spectra of Simple Alloys

    NASA Astrophysics Data System (ADS)

    Bakshi, Mira Hemendraray

    The valence excitation (ns('2) (--->) nsnp) spectra of Mg, Zn, and Ca impurities at various concentrations in Li have been measured. Polarization modulation ellipsometry was used to determine the impurity-induced changes in real and imaginary parts of the dielectric function simultaneously, together with the differential reflectivity, in the energy range 1.5 - 4.5 eV. The most important result at sufficiently dilute alloy compositions, is that the system investigated display a distinct absorption peak above the Drude background. The height of this peak varies linearly with impurity content. The impurity-specific character of these spectral features points to exciton-like behavior at low-energy, arising from atomic-like excitations in which the electron and the hole linger together at the impurity site. Existing theories of alloy spectra do not explain these effects, because they do not include the Coulomb correlations between the interacting quasiparticles created in the optical event, or the way in which the interacting pair is confined to the impurity site by the mutual field. A remarkable added result of this research is that the exciton-like behavior can be followed with increasing impurity content, all the way to the pure Mg response, when it becomes the interband transition. This has led Kunz and Flynn to reformulate the theory of optical absorption including excited state interactions; and to apply the theory to the spectrum of pure Mg. The Coulomb interaction causes striking effects which are in generally good agreement with experiment. Zn-Li alloys behave differently. At an alloy composition for which Zn-Zn interactions become prevalent, the local, impurity-specific character of the spectrum disappears, leaving only a featureless Drude-like absorption. These results have provoked cluster calculations by Boisvert and Kunz, which predict the spectral shifts, and exhibit qualitatively similar persistence for Mg-Li, and broadening for Zn-Li.

  18. Excitation dynamics in Phycoerythrin 545: modeling of steady-state spectra and transient absorption with modified Redfield theory.

    PubMed

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

    2010-07-21

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

  19. Infrared absorption spectra of a Nd0.5Ho0.5Fe3(BO3)4 crystal

    NASA Astrophysics Data System (ADS)

    Gerasimova, Yu. V.; Sofronova, S. N.; Gudim, I. A.; Oreshonkov, A. S.; Vtyurin, A. N.; Ivanenko, A. A.

    2016-01-01

    Infrared absorption spectra of a Nd0.5Ho0.5Fe3(BO3)4 crystal in the spectral range of 30-1700 cm-1 have been measured at temperatures from 6 to 300 K. The experimental spectra have been analyzed based on the semiempirical calculation of the lattice dynamics and the analysis of correlation diagrams of borate complexes. No changes associated with structural phase transitions have been detected in the temperature range of measurements; the effect of magnetic ordering on the infrared absorption spectra has not been observed.

  20. Orthogonal spectra and cross sections: Application to optimization of multi-spectral absorption and fluorescence lidar

    SciTech Connect

    Shokair, I.R.

    1997-09-01

    This report addresses the problem of selection of lidar parameters, namely wavelengths for absorption lidar and excitation fluorescence pairs for fluorescence lidar, for optimal detection of species. Orthogonal spectra and cross sections are used as mathematical representations which provide a quantitative measure of species distinguishability in mixtures. Using these quantities, a simple expression for the absolute error in calculated species concentration is derived and optimization is accomplished by variation of lidar parameters to minimize this error. It is shown that the optimum number of wavelengths for detection of a species using absorption lidar (excitation fluorescence pairs for fluorescence lidar) is the same as the number of species in the mixture. Each species present in the mixture has its own set of optimum wavelengths. There is usually some overlap in these sets. The optimization method is applied to two examples, one using absorption and the other using fluorescence lidar, for analyzing mixtures of four organic compounds. The effect of atmospheric attenuation is included in the optimization process. Although the number of optimum wavelengths might be small, it is essential to do large numbers of measurements at these wavelengths in order to maximize canceling of statistical errors.

  1. Plastocyanin conformation: an analysis of its near ultraviolet absorption and circular dichroic spectra

    SciTech Connect

    Draheim, J.E.; Anderson, G.P.; Duane, J.W.; Gross, E.L.

    1986-04-01

    The near-ultraviolet absorption and circular dichroic spectra of plastocyanin are dependent upon the redox state, solution pH, and ammonium sulfate concentration. This dependency was observed in plastocyanin isolated from spinach, poplar, and lettuce. Removal of the copper atom also perturbed the near-ultraviolet spectra. Upon reduction there are increases in both extinction and ellipticity at 252 nm. Further increases at 252 nm were observed upon formation of apo plastocyanin eliminating charge transfer transitions as the cause. The spectral changes in the near-ultraviolet imply a flexible tertiary conformation for plastocyanin. There are at least two charge transfer transitions at approx.295-340 nm. One of these transitions is sensitive to low pH's and is attributed to the His 87 copper ligand. The redox state dependent changes observed in the near-ultraviolet spectra of plastocyanin are attenuated either by decreasing the pH to 5 or by increasing the ammonium sulfate concentration to 2.7 M. This attenuation cannot be easily explained by simple charge screening. Hydrophobic interactions probably play an important role in this phenomenon. The pH and redox state dependent conformational changes may play an important role in regulating electron transport.

  2. Phase-dependent absorption features in X-ray spectra of XDINSs

    NASA Astrophysics Data System (ADS)

    Borghese, A.; Rea, N.

    2016-06-01

    A detailed pulse phase spectroscopy using all the available XMM-Newton observations of X-ray dim isolated neutron stars (XDINSs) have revealed the presence of narrow and strongly phase-dependent absorption X-ray features. The first discovered was in the X-ray spectrum of the nearby XDINS RX J0720.4-3125. The line seems to be stable in time over a timespan of 12 years and is present in 20% of the pulsar rotation. Because of its narrow width and its strong dependency on the rotational phase, the spectral line is probably due to proton cyclotron absorption in a ˜10^{14} G confined magnetic structure (with a field strength about 7 times the dipolar field of this pulsar). Performing the same analysis to all archival XDINS data, a new possible candidate was found in the X-ray spectrum of RX J1308.6+2127. This absorption feature shows the same phase dependency and energy as the first one, revealing the presence of a high-B structure close to the stellar surface. This result supports the proposed scenario of XDINSs being aged magnetars, having still a strong non-dipolar crustal B-field component.

  3. Physical properties of the interstellar medium using high-resolution Chandra spectra: O K-edge absorption

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; García, J.; Kallman, T. R.; Bautista, M. A.; Gorczyca, T. W. E-mail: claudio@ivic.gob.ve E-mail: manuel.bautista@wmich.edu E-mail: timothy.r.kallman@nasa.gov

    2014-08-01

    Chandra high-resolution spectra toward eight low-mass Galactic binaries have been analyzed with a photoionization model that is capable of determining the physical state of the interstellar medium. Particular attention is given to the accuracy of the atomic data. Hydrogen column densities are derived with a broadband fit that takes into account pileup effects, and in general are in good agreement with previous results. The dominant features in the oxygen-edge region are O I and O II Kα absorption lines whose simultaneous fits lead to average values of the ionization parameter of log ξ = –2.90 and oxygen abundance of A{sub O} = 0.70. The latter is given relative to the standard by Grevesse and Sauval, but rescaling with the revision by Asplund et al. would lead to an average abundance value fairly close to solar. The low average oxygen column density (N{sub O} = 9.2 × 10{sup 17} cm{sup –2}) suggests a correlation with the low ionization parameters, the latter also being in evidence in the column density ratios N(O II)/N(O I) and N(O III)/N(O I) that are estimated to be less than 0.1. We do not find conclusive evidence for absorption by any other compound but atomic oxygen in our oxygen-edge region analysis.

  4. Absorption-Mode Fourier Transform Mass Spectrometry: The Effects of Apodization and Phasing on Modified Protein Spectra

    NASA Astrophysics Data System (ADS)

    Qi, Yulin; Li, Huilin; Wills, Rebecca H.; Perez-Hurtado, Pilar; Yu, Xiang; Kilgour, David P. A.; Barrow, Mark P.; Lin, Cheng; O'Connor, Peter B.

    2013-06-01

    The method of phasing broadband Fourier transform ion cyclotron resonance (FT-ICR) spectra allows plotting the spectra in the absorption-mode; this new approach significantly improves the quality of the data at no extra cost. Herein, an internal calibration method for calculating the phase function has been developed and successfully applied to the top-down spectra of modified proteins, where the peak intensities vary by 100×. The result shows that the use of absorption-mode spectra allows more peaks to be discerned within the recorded data, and this can reveal much greater information about the protein and modifications under investigation. In addition, noise and harmonic peaks can be assigned immediately in the absorption-mode.

  5. Absorption-Mode Fourier Transform Mass Spectrometry: the Effects of Apodization and Phasing on Modified Protein Spectra

    PubMed Central

    Qi, Yulin; Li, Huilin; Wills, Rebecca H.; Perez-Hurtado, Pilar; Yu, Xiang; Kilgour, David. P. A.; Barrow, Mark P.; Lin, Cheng; O’Connor, Peter B.

    2014-01-01

    The method of phasing broadband FT-ICR spectra allows plotting the spectra in the absorption-mode; this new approach significantly improves the quality of the data at no extra cost. Herein, an internal calibration method for calculating the phase function has been developed, and successfully applied to the top-down spectra of modified proteins, where the peak intensities vary by >100×. The result shows that the use of absorption-mode spectra allows more peaks to be discerned within the recorded data, and this can reveal much greater information about the protein and modifications under investigation. In addition, noise and harmonic peaks can be assigned immediately in the absorption-mode. PMID:23568027

  6. Tracing inflows and outflows with absorption lines in circumgalactic gas

    NASA Astrophysics Data System (ADS)

    Ford, Amanda Brady; Davé, Romeel; Oppenheimer, Benjamin D.; Katz, Neal; Kollmeier, Juna A.; Thompson, Robert; Weinberg, David H.

    2014-10-01

    We examine how H I and metal absorption lines within low-redshift galaxy haloes trace the dynamical state of circumgalactic gas, using cosmological hydrodynamic simulations that include a well-vetted heuristic model for galactic outflows. We categorize inflowing, outflowing, and ambient gas based on its history and fate as tracked in our simulation. Following our earlier work, showing that the ionization level of absorbers was a primary factor in determining the physical conditions of absorbing gas, we show here that it is also a governing factor for its dynamical state. Low-ionization metal absorbers (e.g. Mg II) tend to arise in gas that will fall on to galaxies within several Gyr, while high-ionization metal absorbers (e.g. O VI) generally trace material that was deposited by outflows many Gyr ago. Inflowing gas is dominated by enriched material that was previously ejected in an outflow; hence, accretion at low redshifts is typically substantially enriched. Recycling wind material is preferentially found closer to galaxies, and is more dominant in lower mass haloes since high-mass haloes have more hot gas that is able to support itself against infall. Low-mass haloes also tend to re-eject more of their accreted material, owing to our outflow prescription that employs higher mass loading factors for lower mass galaxies. Typical H I absorbers trace unenriched ambient material that is not participating in the baryon cycle, but stronger H I absorbers arise in cool, enriched inflowing gas. Instantaneous radial velocity measures of absorbers are generally poor at distinguishing between inflowing and outflowing gas, except in the case of very recent outflows. These results suggest that probing halo gas using a range of absorbers can provide detailed information about the amount and physical conditions of material that is participating in the baryon cycle.

  7. Polarized electronic absorption spectra of Cr2SiO4 single crystals

    NASA Astrophysics Data System (ADS)

    Furche, A.; Langer, K.

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  9. XMM-Newton/Reflection Grating Spectrometer detection of the missing interstellar O VII Kα absorption line in the spectrum of Cyg X-2

    NASA Astrophysics Data System (ADS)

    Cabot, Samuel H. C.; Wang, Q. Daniel; Yao, Yangsen

    2013-05-01

    The hot interstellar medium is an important part of the Galactic ecosystem and can be effectively characterized through X-ray absorption line spectroscopy. However, in a study of the hot medium using the accreting neutron star X-ray binary, Cyg X-2, as a background light source, a mystery came about when the putatively strong O VII Kα line was not detected in Chandra grating observations, while other normally weaker lines such as O VII Kβ as well as O VI and O VIII Kα are clearly present. We have investigated the grating spectra of Cyg X-2 from 10 XMM-Newton observations, in search of the missing line. We detect it consistently in nine of these observations, but the line is absent in the remaining one observation or is inconsistent with the detection in others at a ˜4σ confidence level. This absence of the line resembles that seen in the Chandra observations. Similarly, the O VI Kα line is found to disappear occasionally, but not in concert with the variation of the O VII Kα line. All these variations are most likely due to the presence of changing O VII and O VI Kα emission lines of Cyg X-2, which are blurred together with the absorption ones in the X-ray spectra. A re-examination of the Chandra grating data indeed shows evidence for a narrow emission line slightly off the O VI Kα absorption line. We further show that narrow N V emission lines with varying centroids and fluxes are present in far-ultraviolet spectra from the Cosmic Origins Spectrograph aboard the Hubble Space Telescope. These results provide new constraints on the accretion around the neutron star and on the X-ray-heating of the stellar companion. The understanding of these physical processes is also important to the fidelity of using such local X-ray binaries for interstellar absorption line spectroscopy.

  10. Accurate modeling of fluorescence line narrowing difference spectra: Direct measurement of the single-site fluorescence spectrum

    NASA Astrophysics Data System (ADS)

    Reppert, Mike; Naibo, Virginia; Jankowiak, Ryszard

    2010-07-01

    Accurate lineshape functions for modeling fluorescence line narrowing (FLN) difference spectra (ΔFLN spectra) in the low-fluence limit are derived and examined in terms of the physical interpretation of various contributions, including photoproduct absorption and emission. While in agreement with the earlier results of Jaaniso [Proc. Est. Acad. Sci., Phys., Math. 34, 277 (1985)] and Fünfschilling et al. [J. Lumin. 36, 85 (1986)], the derived formulas differ substantially from functions used recently [e.g., M. Rätsep et al., Chem. Phys. Lett. 479, 140 (2009)] to model ΔFLN spectra. In contrast to traditional FLN spectra, it is demonstrated that for most physically reasonable parameters, the ΔFLN spectrum reduces simply to the single-site fluorescence lineshape function. These results imply that direct measurement of a bulk-averaged single-site fluorescence lineshape function can be accomplished with no complicated extraction process or knowledge of any additional parameters such as site distribution function shape and width. We argue that previous analysis of ΔFLN spectra obtained for many photosynthetic complexes led to strong artificial lowering of apparent electron-phonon coupling strength, especially on the high-energy side of the pigment site distribution function.

  11. The Hubble Space Telescope Quasar Absorption Line Key Project. 10: Galactic H I 21 centimeter emission toward 143 quasars and active Galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lockman, Felix J.; Savage, Blair D.

    1995-01-01

    Sensitive H I 21 cm emission line spectra have been measured for the directions to 143 quasars and active galactic nuclei (AGNs) chosen from the observing lists for the Hubble Space Telescope (HST) Quasar Absorption Line Key Project. Narrow-band and wide-band data were obtained with the National Radio Astronomy Observatory (NRAO) 43 m radio telescope for each object. The narrow-band data have a velocity resolution of 1 km/s, extend from -220 to +170 km/s, and are corrected for stray 21 cm radiation. The wide-band data have a resolution of 4 km/s and extend from -1000 to +1000 km/s. The data are important for the interpretation of ultraviolet absorption lines near zero redshift in Key Project spectra. Twenty-two percent of the quasars lie behind Galactic high-velocity H I clouds with absolute value of V(sub LSR) greater than 100 km/s whose presence can increase the equivalent width of interstellar absorption lines significantly. This paper contains the emission spectra and measures of the H I velocities and column densities along the sight line to each quasar. We discuss how the measurements can be used to estimate the visual and ultraviolet extinction toward each quasar and to predict the approximate strength of the strong ultraviolet resonance lines of neutral gas species in the HST Key Project spectra.

  12. Polarization-dependent spectra of x-ray dielectronic satellite lines of Be-like Fe

    SciTech Connect

    Shlyaptseva, A.S.; Mancini, R.C.; Neill, P.; Beiersdorfer, P.; Crespo Lopez-Urrutia, J.R.; Widmann, K.

    1998-02-01

    We have studied the polarization properties of dielectronic satellite lines in Be-like Fe ions excited through resonant electron capture by an electron beam. Using the photon density-matrix formalism, we have calculated the degree of polarization and polarization-dependent spectra of dielectronic satellite lines, i.e., the spectral intensity distribution of lines associated with a given polarization state. Theoretical results have been compared with experiments performed at the Lawrence Livermore National Laboratory electron-beam ion trap where dielectronic satellite line emission from Fe ions produced at different energies of the electron beam was simultaneously recorded with two crystal spectrometers. These spectrometers had different polarization sensitivities. The experimental spectra recorded by the two spectrometers are reproduced by the theory. This ability to model the polarization dependence of x-ray line spectra is important for the diagnosis of electron beams in plasmas. {copyright} {ital 1998} {ital The American Physical Society}

  13. Multicomponent Analysis of the UV Si IV and C IV Broad Absorption Troughs in BALQSO Spectra: The Examples of J01225 + 1339 and J02287 + 0002

    NASA Astrophysics Data System (ADS)

    Stathopoulos, D.; Danezis, E.; Lyratzi, E.; Antoniou, A.; Tzimeas, D.

    2015-12-01

    Broad Absorption Line QSOs (BALQSOs) are a subtype of radio-quite QSOs that exhibit complex and unusually broad (FWHM ≥ 2,000 km/s) absorption lines. The existence of these lines in BALQSO spectra raises some questions with respect to the properties, the physical conditions and kinematics of the BAL material as well as the morphology of BAL troughs. In this study, taking into consideration the clumpy structure of the AGN outflow winds, we propose a physical model in order to explain the formation of BAL troughs and we give the mathematical description of this model. We also propose a method for analyzing spectroscopically the BAL profiles in the UV region of the electromagnetic spectrum. This method consists of the criteria we set during the fitting process of BAL troughs. The purpose of these criteria is to enable us to determine the exact number of components needed to simulate accurately the BAL troughs and guarantee the uniqueness of the fit. We give an application of the model and the method for Si IV and C IV resonance lines in the case of two BALQSOs. From the analysis, we conclude that the BAL material is in the form of clouds (density enhancements) that move radially and intercept the line-of-sight to the central continuum source. Using our method, we find the number of absorption components needed to simulate the BAL profiles, which means the number of clouds in the line-of-sight. We calculate the velocity shifts, the FWHM and the optical depths of the absorption components of BALs and we propose an internal structure for these clouds. Finally, we give some correlations between the properties of absorption components of Si IV and C IV.

  14. Breit-Wigner-Fano line shapes in Raman spectra of graphene

    NASA Astrophysics Data System (ADS)

    Hasdeo, Eddwi H.; Nugraha, Ahmad R. T.; Dresselhaus, Mildred S.; Saito, Riichiro

    2014-12-01

    Excitation of electron-hole pairs in the vicinity of the Dirac cone by the Coulomb interaction gives rise to an asymmetric Breit-Wigner-Fano line shape in the phonon Raman spectra in graphene. This asymmetric line shape appears due to the interference effect between the phonon spectra and the electron-hole pair excitation spectra. The calculated Breit-Wigner-Fano asymmetric factor 1 /qBWF as a function of the Fermi energy shows a V-shaped curve with a minimum value at the charge neutrality point and gives good agreement with the experimental results.

  15. Electrochromism in the near-infrared absorption spectra of bridged ruthenium mixed-valence complexes

    SciTech Connect

    Oh, D.H.; Boxer, S.G. )

    1990-10-24

    Many experimental and theoretical approaches have been developed to characterize the chemical and physical properties of mixed-valence complexes. These molecules may possess metals in differing oxidation states which participate in intervalence charge-transfer transitions. In principle, these transitions should be strongly affected by an external electric field. Such electrochromism can provide a direct and sensitive approach to investigating the electronic properties of molecules. The authors report the first measurements of the effects of an externally applied electric field on the near-infrared absorption spectra of ((NH{sub 3}){sub 5}Ru){sub 2}L{sup 5+} (L = pyrazine or 4,4{prime}-bipyridine). Significant differences are observed between the two complexes, illustrating the range of electronic interactions between the metal centers.

  16. kspectrum: an open-source code for high-resolution molecular absorption spectra production

    NASA Astrophysics Data System (ADS)

    Eymet, V.; Coustet, C.; Piaud, B.

    2016-01-01

    We present the kspectrum, scientific code that produces high-resolution synthetic absorption spectra from public molecular transition parameters databases. This code was originally required by the atmospheric and astrophysics communities, and its evolution is now driven by new scientific projects among the user community. Since it was designed without any optimization that would be specific to any particular application field, its use could also be extended to other domains. kspectrum produces spectral data that can subsequently be used either for high-resolution radiative transfer simulations, or for producing statistic spectral model parameters using additional tools. This is a open project that aims at providing an up-to-date tool that takes advantage of modern computational hardware and recent parallelization libraries. It is currently provided by Méso-Star (http://www.meso-star.com) under the CeCILL license, and benefits from regular updates and improvements.

  17. Absorption and luminescence excitation spectra of ClF in the Vac UV region

    NASA Astrophysics Data System (ADS)

    Alekseev, Vadim A.; Schwentner, Nikolaus

    2010-07-01

    Absorption and luminescence excitation spectra of ClF are recorded in the vacuum ultraviolet employing synchrotron radiation. A broad band (120-130 nm) due to transition to the ion-pair state E(0 +) and sparse transitions to Rydberg states are observed. All Rydberg states are predissociated and their excitation yields no luminescence. Perturbations by the 4 sσ1Π 1 and 4p π1Σ + Rydberg states result in characteristic dips in the E(0 +) state luminescence excitation spectrum. Excitation above the Cl∗ + F dissociation threshold results in luminescence from ion-pair states of ClF or Cl 2 populated in reaction of Cl∗ with ClF or Cl 2.

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. Optical absorption and energy-loss spectra of aligned carbon nanotubes

    NASA Astrophysics Data System (ADS)

    García-Vidal, F. J.; Pitarke, J. M.

    2001-07-01

    Optical-absorption cross-sections and energy-loss spectra of aligned multishell carbon nanotubes are investigated, on the basis of photonic band-structure calculations. A local graphite-like dielectric tensor is assigned to every point of the tubules, and the effective transverse dielectric function of the composite is computed by solving Maxwell's equations in media with tensor-like dielectric functions. A Maxwell-Garnett-like approach appropriate to the case of infinitely long anisotropic tubules is also developed. Our full calculations indicate that the experimentally measured macroscopic dielectric function of carbon nanotube materials is the result of a strong electromagnetic coupling between the tubes. An analysis of the electric-field pattern associated with this coupling is presented, showing that in the close-packed regime the incident radiation excites a very localized tangential surface plasmon.

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

    PubMed Central

    Derricotte, Wallace D.; Evangelista, Francesco A.

    2015-01-01

    Orthogonality constrained density functional theory (OCDFT) is a variational time-independent approach for the computation of electronic excited states. In this work we extend OCDFT to compute core-excited states and generalize the original formalism to determine multiple excited states. Benchmark computations on a set of 13 small molecules and 40 excited states show that unshifted OCDFT/B3LYP excitation energies have a mean absolute error of 1.0 eV. Contrary to time-dependent DFT, OCDFT excitation energies for first- and second-row elements are computed with near-uniform accuracy. OCDFT core excitation energies are insensitive to the choice of the functional and the amount of Hartree–Fock exchange. We show that OCDFT is a powerful tool for the assignment of X-ray absorption spectra of large molecules by simulating the gas-phase near-edge spectrum of adenine and thymine. PMID:25690350

  2. DETECTION OF A TRANSIENT X-RAY ABSORPTION LINE INTRINSIC TO THE BL LACERTAE OBJECT H 2356-309

    SciTech Connect

    Fang Taotao; Buote, David A.; Humphrey, Philip J.; Canizares, Claude R.

    2011-04-10

    Since the launch of the Einstein X-ray Observatory in the 1970s, a number of broad absorption features have been reported in the X-ray spectra of BL Lac objects. These features are often interpreted as arising from high-velocity outflows intrinsic to the BL Lac object, therefore providing important information about the inner environment around the central engine. However, such absorption features have not been observed more recently with high-resolution X-ray telescopes such as Chandra and XMM-Newton. In this paper, we report the detection of a transient X-ray absorption feature intrinsic to the BL Lac object H 2356-309 with the Chandra X-ray Telescope. This BL Lac object was observed during XMM-Newton cycle 7 and Chandra cycles 8 and 10, as part of our campaign to investigate X-ray absorption produced by the warm-hot intergalactic medium residing in the foreground large-scale superstructure. During one of the 80 ks Chandra cycle 10 observations, a transient absorption feature was detected at 3.3{sigma} (or 99.9% confidence level, accounting for the number of 'trials), which we identify as the O VIII K{alpha} line produced by an absorber intrinsic to the BL Lac object. None of the other 11 observations showed this line. We constrain the ionization parameter (25 {approx}< {Xi} {approx}< 40) and temperature (10{sup 5} K absorption line; however, the derived properties of the emission material are very different from those of the absorption material, implying it is unlikely a typical P Cygni-type profile.

  3. VARIABILITY OF WATER AND OXYGEN ABSORPTION BANDS IN THE DISK-INTEGRATED SPECTRA OF EARTH

    SciTech Connect

    Fujii, Yuka; Suto, Yasushi; Turner, Edwin L.

    2013-03-10

    We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H{sub 2}O and O{sub 2} bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H{sub 2}O and O{sub 2} bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H{sub 2}O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    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 “κ distribution” seen in many solar system plasmas, a family of distributions for which the M-B distribution is the limiting case where κ → ∞. The high-energy tail of supra-thermal electrons in κ 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 κ distributions consistent with the data. Our goal is to test whether the κ 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

  5. Automated decomposition algorithm for Raman spectra based on a Voigt line profile model.

    PubMed

    Chen, Yunliang; Dai, Liankui

    2016-05-20

    Raman spectra measured by spectrometers usually suffer from band overlap and random noise. In this paper, an automated decomposition algorithm based on a Voigt line profile model for Raman spectra is proposed to solve this problem. To decompose a measured Raman spectrum, a Voigt line profile model is introduced to parameterize the measured spectrum, and a Gaussian function is used as the instrumental broadening function. Hence, the issue of spectral decomposition is transformed into a multiparameter optimization problem of the Voigt line profile model parameters. The algorithm can eliminate instrumental broadening, obtain a recovered Raman spectrum, resolve overlapping bands, and suppress random noise simultaneously. Moreover, the recovered spectrum can be decomposed to a group of Lorentzian functions. Experimental results on simulated Raman spectra show that the performance of this algorithm is much better than a commonly used blind deconvolution method. The algorithm has also been tested on the industrial Raman spectra of ortho-xylene and proved to be effective. PMID:27411136

  6. MOSFIRE ABSORPTION LINE SPECTROSCOPY OF z > 2 QUIESCENT GALAXIES: PROBING A PERIOD OF RAPID SIZE GROWTH

    SciTech Connect

    Belli, Sirio; Ellis, Richard S.; Konidaris, Nick P.; Newman, Andrew B.

    2014-06-20

    Using the MOSFIRE near-infrared multi-slit spectrograph on the Keck 1 Telescope, we have secured high signal-to-noise ratio absorption line spectra for six massive galaxies with redshift 2 < z < 2.5. Five of these galaxies lie on the red sequence and show signatures of passive stellar populations in their rest-frame optical spectra. By fitting broadened spectral templates we have determined stellar velocity dispersions and, with broad-band Hubble Space Telescope and Spitzer photometry and imaging, stellar masses and effective radii. Using this enlarged sample of galaxies, we confirm earlier suggestions that quiescent galaxies at z > 2 have small sizes and large velocity dispersions compared to local galaxies of similar stellar mass. The dynamical masses are in very good agreement with stellar masses (log M {sub *}/M {sub dyn} = –0.02 ± 0.03), although the average stellar-to-dynamical mass ratio is larger than that found at lower redshift (–0.23 ± 0.05). By assuming evolution at fixed velocity dispersion, not only do we confirm a surprisingly rapid rate of size growth but we also consider the necessary evolutionary track on the mass-size plane and find a slope α = dlog R{sub e} /dlog M {sub *} ≳ 2 inconsistent with most numerical simulations of minor mergers. Both results suggest an additional mechanism may be required to explain the size growth of early galaxies.

  7. Variability of 188 broad absorption lines QSOs from the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Bian, Weihao

    2015-08-01

    The variability of broad absorption lines is investigated for a sample of 188 BAL QSOs (Z > 1.7) from the SDSS DR7, covering a timescale of about 0.001 - 3 years in the rest frame. 79 variable regions in the C iv BAL troughs are identified in 47 two-epoch different spectra. For 188 BAL QSOs with two-epoch spectra, it is found that there is no significant correlation between ∆L1500 and ∆α, and about half BAL QSOs appear redder during their brighter phases. It is consistent with the result for non-BAL QSOs by Bian et al. For a subsample of BAL QSOs with variable regions in BAL toughs, it is found that there is a mediate correlation between the ∆L1500 and ∆α, about 70% BAL QSOs appear bluer during their brighter phases. A larger proportion of BAL QSOs with variable BAL-trough regions show bluer during their brighter phases, which implies that the origin of variable BAL-trough regions is related to the central accretion processing. There is a weak correlation between ∆EW and ∆L1500. It suggests that the BAL-trough variation is not dominated by photoionization.

  8. The compact structure of radio-loud broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Jiang, D. R.; Wang, T. G.; Xie, F. G.

    2008-11-01

    We present the results of EVN+MERLIN very long baseline interferometry (VLBI) polarization observations of eight broad absorption line (BAL) quasars at 1.6 GHz, including four low-ionization BAL quasars (LoBALs) and four high-ionization BAL quasars (HiBALs) with either steep or flat spectra on Very Large Array (VLA) scales. Only one steep-spectrum source, J1122+3124, shows two-sided structure on the scale of 2 kpc. The other four steep-spectrum sources and three flat-spectrum sources display either an unresolved image or a core-jet structure on scales of less than 300 pc. In all cases, the marginally resolved core is the dominant radio component. Linear polarization in the cores has been detected in the range of a few to 10 per cent. Polarization, together with high brightness temperatures (from 2 × 109 to 5 × 1010K), suggests a synchrotron origin for the radio emission. There is no apparent difference in the radio morphologies or polarization between low-ionization and high-ionization BAL quasi-stellar objects (QSOs) or between flat- and steep-spectrum sources. We discuss the orientation of BAL QSOs with both flat and steep spectra, and consider a possible evolutionary scenario for BAL QSOs. In this scenario, BAL QSOs are probably a young population of radio sources that are compact steep spectrum or GHz peaked radio source analogues at the low end of radio power.

  9. Studying Velocity Turbulence from Doppler-broadened Absorption Lines: Statistics of Optical Depth Fluctuations

    SciTech Connect

    Lazarian, A.; Pogosyan, D.

    2008-10-10

    We continue our work on developing techniques for studying turbulence with spectroscopic data. We show that Doppler-broadened absorption spectral lines, in particular, saturated absorption lines, can be used within the framework of the previously introduced technique termed the velocity coordinate spectrum (VCS). The VCS relates the statistics of fluctuations along the velocity coordinate to the statistics of turbulence; thus, it does not require spatial coverage by sampling directions in the plane of the sky. We consider lines with different degree of absorption and show that for lines of optical depth less than one, our earlier treatment of the VCS developed for spectral emission lines is applicable, if the optical depth is used instead of intensity. This amounts to correlating the logarithms of absorbed intensities. For larger optical depths and saturated absorption lines, we show that only wings of the line are available for the analysis. In terms of the VCS formalism, this results in introducing an additional window, whose size decreases with the increase of the optical depth. As a result, strongly saturated absorption lines only carry the information about the small-scale turbulence. Nevertheless, the contrast of the fluctuations corresponding to the small-scale turbulence increases with the increase of the optical depth, which provides advantages for studying turbulence by combining lines with different optical depths. By combining different absorption lines one can develop a tomography of the turbulence in the interstellar gas in all its complexity.

  10. Specific absorption spectra of hemoglobin at different PO2 levels: potential noninvasive method to detect PO2 in tissues

    NASA Astrophysics Data System (ADS)

    Liu, Peipei; Zhu, Zhirong; Zeng, Changchun; Nie, Guang

    2012-12-01

    Hemoglobin (Hb), as one of main components of blood, has a unique quaternary structure. Its release of oxygen is controlled by oxygen partial pressure (PO2). We investigate the specific spectroscopic changes in Hb under different PO2 levels to optimize clinical methods of measuring tissue PO2. The transmissivity of Hb under different PO2 levels is measured with a UV/Vis fiber optic spectrometer. Its plotted absorption spectral curve shows two high absorption peaks at 540 and 576 nm and an absorption valley at 560 nm when PO2 is higher than 100 mm Hg. The two high absorption peaks decrease gradually with a decrease in PO2, whereas the absorption valley at 560 nm increases. When PO2 decreases to approximately 0 mm Hg, the two high absorption peaks disappear completely, while the absorption valley has a hypochromic shift (8 to 10 nm) and forms a specific high absorption peak at approximately 550 nm. The same phenomena can be observed in visible reflectance spectra of finger-tip microcirculation. Specific changes in extinction coefficient and absorption spectra of Hb occur along with variations in PO2, which could be used to explain pathological changes caused by tissue hypoxia and for early detection of oxygen deficiency diseases in clinical monitoring.

  11. N2O vertical profiles retrieved from ground-based solar absorption spectra taken at McMurdo station during austral spring of 1989

    SciTech Connect

    Liu, X.; Murcray, F.J.

    1995-01-01

    N2O can be a tracer of atmospheric air motion due to its long life time. Ground-based FTIR solar spectra contain information on the vertical distributions of N2O due to pressure broadening of absorption lines. The authors have combined the Chahine-Twomey` relaxation method with a line-by-line layer-by-layer radiative transfer code to retrieve N2O VMR profiles from ground based solar absorption spectra. The spectra were taken at McMurdo station during the austral spring of 1989 with a 0.02 wavenumber resolution FTIR spectrometer. Since N2O is released from troposphere and is photolyzed in the stratosphere, the line shape of its absorption is mainly due Lorentz broadening. The 0.02 wavenumber resolution is high enough for the authors to retrieve N2O VMR profiles up to 25 kilometers. Figures show a typical observed N2O solar spectrum near 1993.15 wavenumber and a calculated spectrum using the authors profile retrieval program. The best fit is obtained by iteratively adjusting N20 VMR profile according to the formulation of Chahine and Twomey. The lower tropospheric N2O VMR`s have an average value around 310 ppb. Correlations of the N2O contour with that of temperature shows interesting features of tropospheric and lower stratospheric air motions. The authors have also compared the total N2O column amounts retrieved from this profile retrieval method and from the PC version of the non-linear least square spectral fitting algorithm (SFIT). The temporal variations of the N2O total column amounts retrieved from the two methods show excellent correlation.

  12. A computer program for a line-by-line calculation of spectra from diatomic molecules and atoms assuming a Voight line profile

    NASA Technical Reports Server (NTRS)

    Arnold, J. O.; Lyle, G. C.; Whiting, E. E.

    1969-01-01

    Computer program predicts the spectra resulting from electronic transitions of diatomic molecules and atoms in local thermodynamic equilibrium. The program produces a spectrum by accounting for the contribution of each rotational and atomic line considered.

  13. What Drives the Outflows in Broad Absorption Line QSOs?

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.

    1997-01-01

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

  14. Broad Balmer Absorption Line Variability: Evidence of Gas Transverse Motion in the QSO SDSS J125942.80+121312.6

    NASA Astrophysics Data System (ADS)

    Shi, Xiheng; Zhou, Hongyan; Shu, Xinwen; Zhang, Shaohua; Ji, Tuo; Pan, Xiang; Sun, Luming; Zhao, Wen; Hao, Lei

    2016-03-01

    We report on the discovery of broad Balmer absorption lines variability in the QSO SDSS J125942.80+121312.6, based on the optical and near-infrared spectra taken from the SDSS-I, SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), and TripleSpec observations over a timescale of 5.8 years in the QSO's rest-frame. The blueshifted absorption profile of Hβ shows a variation of more than 5σ at a high velocity portion (\\gt 3000 {km} {{{s}}}-1) of the trough. We perform a detailed analysis for the physical conditions of the absorber using Balmer lines as well as metastable He i and optical Fe ii absorptions (λ4233 from b4P5/2 level and λ5169 from a6S5/2) at the same velocity. These Fe ii lines are identified in the QSO spectra for the first time. According to the photoionization simulations, we estimate a gas density of n({{H}})≈ {10}9.1 {{cm}}-3 and a column density of {N}{col}({{H}})≈ {10}23 {{cm}}-2 for the BOSS data, but the model fails to predict the variations of ionic column densities between the SDSS and BOSS observations if changes in ionizing flux are assumed. We thus propose transverse motion of the absorbing gas being the cause of the observed broad Balmer absorption line variability. In fact, we find that the changes in covering factors of the absorber can well-reproduce all of the observed variations. The absorber is estimated ∼0.94 pc away from the central engine, which is where the outflow likely experiences deceleration due to the collision with the surrounding medium. This scheme is consistent with the argument that LoBAL QSOs may represent the transition from obscured star-forming galaxies to classic QSOs.

  15. Linewidth Extraction From the THz Absorption Spectra Using a Modified Lorentz Model

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Zhang, Zhaohui; Zhao, Xiaoyan; Su, Haixia; Zhang, Han; Lan, Jinhui

    2013-10-01

    Identification of specific materials is one of the most promising THz applications. It is commonly achieved by comparing the experimental peak central frequencies of the transmission or absorption spectra with a database for known materials while neglecting the linewidths. However, due to the restriction of the signal-to-noise ratio, only a narrow band, extending from several hundred GHz to several THz, can be used. It is difficult to distinguish two materials from each other if their peaks' central frequencies are similar. In this paper, we present a modified Lorentz model by taking the scattering effect into account. The modified Lorentz model can be used for the extraction of reliable absorption peak parameters, i.e. the central frequency and linewidth. On comparison with our experiments, we observed that the parameters extracted using the modified Lorentz model in glutamine samples of different concentrations exhibited a better agreement than those obtained using the traditional model. Therefore, the utilization of the narrow THz band to identify materials can be improved by comparing both the central frequency and linewidth obtained from this method.

  16. Ab initio optical absorption spectra of size-expanded xDNA base assemblies.

    PubMed

    Varsano, Daniele; Garbesi, Anna; Di Felice, Rosa

    2007-12-20

    We present the results of time-dependent density functional theory calculations of the optical absorption spectra of synthetic nucleobases and of their hydrogen-bonded and stacked base pairs. We focus on size-expanded analogues of the natural nucleobases obtained through the insertion of a benzene ring bonded to the planar heterocycles (x-bases), according to the protocol designed and realized by the group of Eric Kool (e.g., see: Gao, J.; Liu, H.; Kool, E.T. Angew. Chem., Int. Ed. 2005, 44, 3118, and references therein). We find that the modifications of the frontier electron orbitals with respect to natural bases, which are induced by the presence of the aromatic ring, also affect the optical response. In particular, the absorption onset is pinned by the benzene component of the HOMO of each x-base (xA, xG, xT, xC). In addition, the main trait of the H-bonding interbase coupling is a conspicuous red shift of spectral peaks in the low-energy range. Finally, the hypochromicity, a well-known fingerprint of stacking, is more pronounced in stacked xG-C and xA-T pairs than that in stacked G-C and A-T pairs, an index of enhanced stacking. PMID:18034470

  17. The influence of thermolysis time on the absorption spectra of polyvinyl chloride in acetophenone

    NASA Astrophysics Data System (ADS)

    Rasmagin, S. I.; Krasovskii, V. I.; Vlasov, D. V.; Apresyan, L. A.; Vlasova, T. V.; Kryshtoba, V. I.; Feofanov, I. N.; Kazaryan, M. A.

    2015-12-01

    The influence of thermolysis time on the absorption spectra of partially thermally dehydrochlorinated polyvinyl chloride in acetophenone solution is studied. Strong increase in the optical density Dλ of the dehydrochlorinated PVC samples is caused by the increasing amount N-C=C- and the length of chains of conjugated double bonds of carbon -C = C-. It is noted that the optical density Dλ first increases linearly with dehydrochlorination time and then reaches saturation. The estimation of amount of double conjugated carbon bonds in 1ml versus thermolysis time t is given, which varies between N-C=C- = 4.1017 - 7.4.1018 for t from 40 to 420 minutes. The effective capture cross section of a photon on conjugated double bonds of carbon for dehydrochlorinated PVC solution in acetophenone is estimated, which was about 10-17 cm2 . The analysis is done of the absorption curves «red» shift to longer wavelengths with growth of N-C=C- upon increase of thermolysis time. It is noted that the dependence of the optical density on the wavelength in this range is well described by a simple exponential function.

  18. Ultraviolet spectra of quenched carbonaceous composite derivatives: Comparison to the '217 nanometer' interstellar absorption feature

    NASA Technical Reports Server (NTRS)

    Sakata, Akira; Wada, Setsuko; Tokunaga, Alan T.; Narisawa, Takatoshi; Nakagawa, Hidehiro; Ono, Hiroshi

    1994-01-01

    QCCs (quenched carbonaceous composite) are amorphus carbonaceous material formed from a hydrocarbon plasma. We present the UV-visible spectra of 'filmy QCC; (obtained outside of the beam ejected from the hydrocarbon plasma) and 'dark QCC' (obtained very near to the beam) for comparison to the stellar extinction curve. When filmy QCC is heated to 500-700 C (thermally altered), the wavelength of the absorption maximum increases form 204 nm to 220-222 nm. The dark QCC has an absorption maximum at 217-222 nm. In addition, the thermally altered filmy QCC has a slope change at about 500 nm which resmbles that in the interstellar extinction curve. The resemblance of the extinction curve of the QCCs to that of the interstellar medium suggests that QCC derivatives may be representative of the type of interstellar material that produces the 217 nm interstellar medium feature. The peak extinction of the dark QCC is higher than the average interstellar extinction curve while that of the thermally altered filmy QCC is lower, so that a mixture of dark and thermally altered filmy QCC can match the peak extinction observed in the interstellar medium. It is shown from electron micrographs that most of the thermally altered flimy QCC is in the form of small grainy structure less than 4 nm in diameter. This shows that the structure unit causing the 217-222 nm feature in QCC is very small.

  19. Solvent effects on the resonance Raman and electronic absorption spectra of bacteriochlorophyll a cation radical

    SciTech Connect

    Misono, Yasuhito; Itoh, Koichi; Limanatara, Leenawaty; Koyama, Yasushi

    1996-02-08

    Resonance Raman and electronic absorption spectra of bacteriocholrophyll a cation radical (BChl a{sup .+}) were recorded in 14 different kinds of solvents. The frequency of the ring-breathing Raman band of BChl a{sup .+} was in the region of 1596-1599 cm{sup -1} in solvents forming the pentacoordinated state in neutral bacteriochlorophyll a (BChl a), while it was in the region of 1584-1588 cm{sup -1} in solvents forming the hexacoordinated state. BChl a{sup .+} exhibited a key absorption band in the regions 546-554 and 557-563 nm in the above penta- and hexa-coordinating solvents. Therefore, it has been concluded that the penta- and hexa-coordinated states are retained even after conversion of BChl a into BChl a{sup .+} (one-electron oxidization). Application of this rule to the case of 2-propanol solution showed transformation from the penta- to the hexa-coordinated state upon one-electron oxidation in this particular solution. The coordination states of BChl a{sup .+} could be correlated with the donor number(DN) and the Taft parameters, {Beta} and {pi}{sup *}, of the solvent: The hexacoordinated state was formed in solvents with DN >= 18 or {Beta} > 0.5 showing higher electron donating power, while the pentacoordinated state was formed in solvents with {pi}{sup *} > 0.65 showing higher dielectric stabilization. 27 refs., 8 figs., 3 tabs.

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

    NASA Astrophysics Data System (ADS)

    Aydarous, Abdulkadir

    2016-05-01

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

  1. Time-Dependent Density Functional Calculations of Ligand K-Edge X-Ray Absorption Spectra

    SciTech Connect

    DeBeer George, S.; Petrenko, T.; Neese, F.

    2007-07-10

    X-ray absorption spectra (XAS) at the Cl and S K edge and Mo L edge have been calculated at the TDDFT level for a series of dioxomolybdenum complexes LMoO{sub 2}X (L = hydrotris(3,5-dimethyl-1-pyrazolyl)borate, X = Cl, SCH{sub 2}Ph, OPh), which play an important role in modeling the catalytic cycle of the sulfite oxidase enzyme. Also, the XAS spectra of model molecules of the Mo complexes have been simulated and interpreted in terms of the Mo 4d orbital splitting, in order to find possible correlations with the spectral pattern of the complexes. Comparison with the available experimental data allows us to assess the performances of the present computational scheme to describe the core excitations in large bioinorganic systems. The theoretical interpretation of the spectral features of both the metal and ligand core excitations in terms of the oscillator strength distribution provides important insight into the covalency of the metal-ligand bond.

  2. Polarized absorption spectra of single crystals of lunar pyroxenes and olivines.

    NASA Technical Reports Server (NTRS)

    Burns, R. G.; Huggins, F. E.; Abu-Eid, R. M.

    1972-01-01

    Measurements have been made of the polarized absorption spectra (360-2200 nm) of compositionally zoned pyroxene minerals in rocks 10045, 10047 and 10058 and olivines in rocks 10020 and 10022. The Apollo 11 pyroxenes with relatively high Ti/Fe ratios were chosen initially to investigate the presence of crystal field spectra of Fe(2+) and Ti(3+) ions in the minerals. Broad intense bands at about 1000 and 2100 nm arise from spin-allowed, polarization-dependent transitions in Fe(2+) ions in pyroxenes. Several weak sharp peaks occur in the visible region. Peaks at 402, 425, 505, 550, and 585 nm represent spin-forbidden transitions in Fe(2+) ions, while broader bands at 460-470 nm and 650-660 nm are attributed to Ti(3+) ions. Charge transfer bands, which in terrestrial pyroxenes often extend into the visible region, are displaced to shorter wavelengths in lunar pyroxenes. This feature correlates with the absence of Ti(3+) ions in these minerals.

  3. Total Absorption Spectroscopy of Fission Fragments Relevant for Reactor Antineutrino Spectra and Decay Heat Calculations

    NASA Astrophysics Data System (ADS)

    Porta, A.; Zakari-Issoufou, A.-A.; Fallot, M.; Algora, A.; Tain, J. L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; Äystö, J.; Bowry, M.; Briz, J. A.; Caballero-Folch, R.; Cano-Ott, D.; Cucouanes, A.; Elomaa, V.-V.; Eronen, T.; Estévez, E.; Farrelly, G. F.; Garcia, A. R.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Karvonen, P.; Kolhinen, V. S.; Kondev, F. G.; Martinez, T.; Mendoza, E.; Molina, F.; Moore, I.; Perez-Cerdán, A. B.; Podolyák, Zs.; Penttilä, H.; Regan, P. H.; Reponen, M.; Rissanen, J.; Rubio, B.; Shiba, T.; Sonzogni, A. A.; Weber, C.

    2016-03-01

    Beta decay of fission products is at the origin of decay heat and antineutrino emission in nuclear reactors. Decay heat represents about 7% of the reactor power during operation and strongly impacts reactor safety. Reactor antineutrino detection is used in several fundamental neutrino physics experiments and it can also be used for reactor monitoring and non-proliferation purposes. 92,93Rb are two fission products of importance in reactor antineutrino spectra and decay heat, but their β-decay properties are not well known. New measurements of 92,93Rb β-decay properties have been performed at the IGISOL facility (Jyväskylä, Finland) using Total Absorption Spectroscopy (TAS). TAS is complementary to techniques based on Germanium detectors. It implies the use of a calorimeter to measure the total gamma intensity de-exciting each level in the daughter nucleus providing a direct measurement of the beta feeding. In these proceedings we present preliminary results for 93Rb, our measured beta feedings for 92Rb and we show the impact of these results on reactor antineutrino spectra and decay heat calculations.

  4. Deconvolution of C-phycocyanin beta-84 and beta-155 chromophore absorption and fluorescence spectra of cyanobacterium Mastigocladus laminosus.

    PubMed Central

    Demidov, A A; Mimuro, M

    1995-01-01

    Absorption and fluorescence spectra of the C-phycocyanin beta-subunit were quantitatively deconvoluted into component spectra of the beta-84 and beta-155 chromophores. The deconvolution procedure was based on a theoretical treatment of polarization properties. Four kinds of spectra (absorption, emission, emission polarization, and excitation polarization) measured on C-phycocyanin isolated from the cyanobacterium Mastigocladus laminosus were used as the experimental data set. Without any assumption of spectral shape, the absorption and fluorescence spectra of both chromophores were unambiguously resolved and their fluorescence quantum yields were evaluated. By combining the spectra of the alpha-subunit, independently measured, with the resolved spectra of the beta-subunit, the fluorescence and fluorescence polarization spectra and the fluorescence quantum yield of the monomer were estimated; they agree with experimental values to within an acceptable error. Further, the matrix of energy transfer rates in the monomer was estimated; it gave a significantly different result (by up to 40%) from previously estimated ones. PMID:7787035

  5. Absorption spectra and photolysis of methyl peroxide in liquid and frozen water.

    PubMed

    Epstein, Scott A; Shemesh, Dorit; Tran, Van T; Nizkorodov, Sergey A; Gerber, R Benny

    2012-06-21

    Methyl peroxide (CH(3)OOH) is commonly found in atmospheric waters and ices in significant concentrations. It is the simplest organic peroxide and an important precursor to hydroxyl radical. Many studies have examined the photochemical behavior of gaseous CH(3)OOH; however, the photochemistry of liquid and frozen water solutions is poorly understood. We present a series of experiments and theoretical calculations designed to elucidate the photochemical behavior of CH(3)OOH dissolved in liquid water and ice over a range of temperatures. The molar extinction coefficients of aqueous CH(3)OOH are different from the gas phase, and they do not change upon freezing. Between -12 and 43 °C, the quantum yield of CH(3)OOH photolysis is described by the following equation: Φ(T) = exp((-2175 ± 448)1/T) + 7.66 ± 1.56). We use on-the-fly ab initio molecular dynamics simulations to model structures and absorption spectra of a bare CH(3)OOH molecule and a CH(3)OOH molecule immersed inside 20 water molecules at 50, 200, and 220 K. The simulations predict large sensitivity in the absorption spectrum of CH(3)OOH to temperature, with the spectrum narrowing and shifting to the blue under cryogenic conditions because of constrained dihedral motion around the O-O bond. The shift in the absorption spectrum is not observed in the experiment when the CH(3)OOH solution is frozen suggesting that CH(3)OOH remains in a liquid layer between the ice grains. Using the extinction coefficients and photolysis quantum yields obtained in this work, we show that under conditions with low temperatures, in the presence of clouds with a high liquid-water content and large solar zenith angles, the loss of CH(3)OOH by aqueous photolysis is responsible for up to 20% of the total loss of CH(3)OOH due to photolysis. Gas phase photolysis of CH(3)OOH dominates under all other conditions. PMID:22217262

  6. Absorption spectra of isomeric OH adducts of 1,3,7-trimethylxanthine

    SciTech Connect

    Vinchurkar, M.S.; Rao, B.S.M.; Mohan, H.; Mittal, J.P.; Schmidt, K.H.; Jonah, C.D.

    1997-04-17

    The reactions of OH{sup .}, O{sup .-}, and SO{sub 4}{sup .-} with 1,3,7-trimethylxanthine (caffeine) were studied by pulse radiolysis with optical and conductance detection techniques. The absorption spectra of transients formed in OH{sup .} reaction in neutral solutions exhibited peaks at 310 and 335 nm, as well as a broad absorption maximum at 500 nm, which decayed by first-order kinetics. The rate (k = (4.0 {+-} 0.5) x 10{sup 4} s{sup -1}) of this decay is independent of pH in the range 4-9 and is in agreement with that determined from the conductance detection (k = 4 x 10{sup 4} s{sup -1}). The spectrum in acidic solutions has only a broad peak around 330 nm with no absorption in the higher wavelength region. The intermediates formed in reaction of O{sup .-} absorb around 310 and at 350 nm, and the first-order decay at the latter wavelength was not seen. The OH radical adds to C-4 (X-40H{sup .}) and C-8 (X-80H{sup .}) positions of caffeine in the ratio 1:2 as determined from the redox titration and conductivity measurements. H abstraction from the methyl group is an additional reaction channel in O{sup .-} reaction. Dehydroxylation of the X-40H{sup .} adduct occurs, whereas the X-80H{sup .} adduct does not undergo ring opening. The spectrum obtained for OH{sup .} reaction in oxygenated solutions is similar to that observed in SO{sub 4}{sup .-} reaction in basic solutions. 25 refs., 5 figs., 1 tab.

  7. Ionization states of metallic absorption-line systems in continua of quasars

    NASA Technical Reports Server (NTRS)

    Denda, Kiyomi; Ikeuchi, Satoru

    1993-01-01

    Ionization states of metallic absorption-line systems in continua of quasars (QSO's) are studied, assuming that the metallic lines arise in gaseous halos of high-redshift galaxies in photoionization equilibrium under the background UV radiation, and constraints on the intensity and spectral shape of the UV radiation are obtained. Then a structure of absorbers suitable for all of the metallic absorption line systems are discussed.

  8. Multi-harmonic measurements of line shape under low absorption conditions

    NASA Astrophysics Data System (ADS)

    Lan, L. J.; Ding, Y. J.; Peng, Z. M.; Du, Y. J.; Liu, Y. F.; Li, Z.

    2014-06-01

    We propose a method that employs the ratios of the 2nd and 4th harmonics at the line center to measure line shape under low absorption conditions. To verify this method, the transition of CO2 at 6,982.0678 cm-1 is selected to measure line shape by using the proposed method and direct absorption spectroscopy in laboratory conditions. The results from both methods have a high degree of consistency. This satisfactory agreement indicates the validity of the proposed method.

  9. Unidentified line in x-ray spectra of the Andromeda galaxy and Perseus galaxy cluster.

    PubMed

    Boyarsky, A; Ruchayskiy, O; Iakubovskyi, D; Franse, J

    2014-12-19

    We report a weak line at 3.52±0.02  keV in x-ray spectra of the Andromeda galaxy and the Perseus galaxy cluster observed by the metal-oxide-silicon (MOS) and p-n (PN) CCD cameras of the XMM-Newton telescope. This line is not known as an atomic line in the spectra of galaxies or clusters. It becomes stronger towards the centers of the objects; is stronger for Perseus than for M31; is absent in the spectrum of a deep "blank sky" data set. Although for each object it is hard to exclude that the feature is due to an instrumental effect or an atomic line, it is consistent with the behavior of a dark matter decay line. Future (non-)detections of this line in multiple objects may help to reveal its nature. PMID:25554871

  10. The 13CH4 absorption spectrum in the Icosad range (6600-7692 cm-1) at 80 K and 296 K: Empirical line lists and temperature dependence

    NASA Astrophysics Data System (ADS)

    Campargue, A.; Béguier, S.; Zbiri, Y.; Mondelain, D.; Kassi, S.; Karlovets, E. V.; Nikitin, A. V.; Rey, M.; Starikova, E. N.; Tyuterev, Vl. G.

    2016-08-01

    The 13CH4 absorption spectrum has been recorded at 296 K and 80 K in the Icosad range between 6600 and 7700 cm-1. The achieved noise equivalent absorption of the spectra recorded by differential absorption spectroscopy (DAS) is about αmin ≈ 1.5 × 10-7 cm-1. Two empirical line lists were constructed including 17,792 and 24,139 lines at 80 K and 296 K, respectively. For comparison, the HITRAN database provides only 1040 13CH4 lines in the region determined from methane spectra with natural isotopic abundance. Empirical values of the lower state energy level, Eemp, were systematically derived from the intensity ratios of the lines measured at 80 K and 296 K. Overall 10,792 Eemp values were determined providing accurate temperature dependence for most of the 13CH4 absorption in the region (93% and 82% at 80 K and 296 K, respectively). The quality of the derived empirical values of the lower state rotational quantum number, Jemp, is illustrated by their clear propensity to be close to an integer. A good agreement is achieved between our small Jemp values, with previous accurate determinations obtained by applying the 2T method to jet and 80 K spectra. The line lists at 296 K and 80 K which are provided as Supplementary material will be used for future rovibrational assignments based on accurate variational calculations.

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

    NASA Astrophysics Data System (ADS)

    Kriss, Gerard A.; Agn Storm Team

    2015-01-01

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

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

    PubMed

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

    2016-09-13

    The optical spectra of 5-methylcytidine in three different solvents (tetrahydrofuran, acetonitrile, and water) is measured, showing that both the absorption and the emission maximum in water are significantly blue-shifted (0.08 eV). The absorption spectra are simulated based on CAM-B3LYP/TD-DFT calculations but including solvent effects with three different approaches: (i) a hybrid implicit/explicit full quantum mechanical approach, (ii) a mixed QM/MM static approach, and (iii) a QM/MM method exploiting the structures issuing from molecular dynamics classical simulations. Ab-initio Molecular dynamics simulations based on CAM-B3LYP functionals have also been performed. The adopted approaches all reproduce the main features of the experimental spectra, giving insights on the chemical-physical effects responsible for the solvent shifts in the spectra of 5-methylcytidine and providing the basis for discussing advantages and limitations of the adopted solvation models. PMID:27529792

  13. A strong redshift dependence of the broad absorption line quasar fraction

    NASA Astrophysics Data System (ADS)

    Allen, James T.; Hewett, Paul C.; Maddox, Natasha; Richards, Gordon T.; Belokurov, Vasily

    2011-01-01

    We describe the application of non-negative matrix factorization to generate compact reconstructions of quasar spectra from the Sloan Digital Sky Survey (SDSS), with particular reference to broad absorption line quasars (BALQSOs). BAL properties are measured for Si IVλ1400, C IVλ1550, Al IIIλ1860 and Mg IIλ2800, resulting in a catalogue of 3547 BALQSOs. Two corrections, based on extensive testing of synthetic BALQSO spectra, are applied in order to estimate the intrinsic fraction of C IV BALQSOs. First, the probability of an observed BALQSO spectrum being identified as such by our algorithm is calculated as a function of redshift, signal-to-noise ratio and BAL properties. Secondly, the different completenesses of the SDSS target selection algorithm for BALQSOs and non-BAL quasars are quantified. Combining the detection probabilities with an intrinsic E(B-V) distribution capable of reproducing the observed increase in mean E(B-V) with increasing redshift, the intrinsic C IV BALQSO fraction is 41 ± 5 per cent. Our analysis of the selection effects allows us to measure the dependence of the intrinsic C IV BALQSO fraction on luminosity and redshift. We find a factor of 3.5 ± 0.4 decrease in the intrinsic fraction from the highest redshifts, z≃ 4.0, down to z≃ 2.0. The redshift dependence implies that an orientation effect alone is not sufficient to explain the presence of BAL troughs in some but not all quasar spectra. Our results are consistent with the intrinsic BALQSO fraction having no strong luminosity dependence, although with 3σ limits on the rate of change of the intrinsic fraction with luminosity of -6.9 and 7.0 per cent dex-1 we are unable to rule out such a dependence.

  14. First principle studies on the electronic structures and absorption spectra in KMgF 3 crystal with fluorine vacancy

    NASA Astrophysics Data System (ADS)

    Cheng, Fang; Liu, Tingyu; Zhang, Qiren; Qiao, Hailin; Zhou, Xiuwen

    2010-08-01

    The experiments indicate that the perfect KMgF 3 crystal has no absorption in the visible range, however the electron irradiation induces a complex absorption spectrum. The absorption spectra can be decomposed by five Gaussian bands peaking at 2.5 eV (488 nm), 3.4 eV (359 nm), 4.2 eV (295 nm), 4.6 eV (270 nm) and 5.2 eV (239 nm), respectively. The purpose of this paper is to seek the origins of the absorption bands. The electronic structures and absorption spectra either for the perfect KMgF 3 or for KMgF 3: VF+ with electrical neutrality have been studied by using density functional theory code CASTEP with the lattice structure optimized. The calculation results predicate that KMgF 3: VF+ also exhibits five absorption bands caused by the existence of the fluorine ion vacancy VF+ and the five absorption bands well coincide with the experimental results. It is believable that the five absorption bands are related to VF+ in KMgF 3 crystal produced by the electron irradiation.

  15. Prediction of induction motor line current spectra from design data

    NASA Astrophysics Data System (ADS)

    Guldemir, Hanifi

    The thesis concentrates on the estimation of the magnitude and frequency of the spectral components of line current that may be used for sensorless speed detection. The prediction method uses a mixture of permeance-mmf, finite element and reluctance mesh techniques to establish the air gap magnetic field. This traditional type of approach is chosen to maintain a visible link between cause and effect so enhancing understanding. The approach is enhanced by the use of slot permanence effects calculated by finite element techniques where saturation due to the current carrying conductors in the slots is incorporated. This is essential for closed slots. Further enhancements include examining slot permeance effects over one or more poles so that the influence of the spatial distribution of slot currents, and slot top saturation can be incorporated. The harmonic chain equivalent circuit is extensively modified to provide a vehicle for predicting the correct saturation conditions in a skewed machine and the correct winding currents for the field solutions. Rotor pole aliasing is introduced to explain the large number of independent speed harmonic terms found experimentally. Special equivalent circuits are introduced to enable these current harmonic to be predicted. A thorough experimental validation is then conducted of the model using a 30 kW experimental machine with adjustable eccentricity with rotors of different slotting form, slot number and skew to determine their effect on the speed dependent harmonic components. Very good agreement is demonstrated. Finally, the improved prediction model is used to provide information on the significance of saturation, skew, slot number and rotor eccentricity on the level of speed dependent harmonic signals. All of this information helps formulate important rules to assist in the choice of motors for satisfactory operation with sensorless speed control of drives using RSH. This in itself is an important extension to the knowledge

  16. Magnetic Turbulence and Line Broadening in Simulations of Lyman-Alpha Absorption

    NASA Astrophysics Data System (ADS)

    Gurvich, Alex; Burkhart, Blakesley K.; Bird, Simeon

    2016-01-01

    We use the Illustris cosmological AREPO simulations to study the effects of gas turbulence and magnetic fields on measurements from the Lyman-Alpha forest. We generate simulated Lyman-Alpha spectra and plot the distributions of Column Density (CDD) and Doppler Width (b) both by adhering to the canonical method of fitting Voigt profiles to absorption lines and by directly measuring the column density and equivalent widths from snapshot data .We investigate the effects of additional unresolved gas turbulence in Illustris by adding an additional broadening term to the line profiles to mimic turbulent broadening. When we do this, we find a measurable effect in the CDD and an offset in the mean of the b distribution corresponding to the additional turbulence. We also compare different MHD runs in AREPO we find that the CDD can measurably differentiate between magnetic seed field at redshifts as low as z=0.1, but we do not find that the b distribution is affected at a detectable level. Our work suggests that the effects of turbulence and magnetic fields from z=2-0.1 can potentially be measured with these diagnostics. This work was supported in part by the NSF REU and DoD ASSURE programs under NSF grant no. 1262851 and by the Smithsonian Institution.

  17. C IV Broad Absorption Line Acceleration in Sloan Digital Sky Survey Quasars

    NASA Astrophysics Data System (ADS)

    Grier, C. J.; Brandt, W. N.; Hall, P. B.; Trump, J. R.; Filiz Ak, N.; Anderson, S. F.; Green, Paul J.; Schneider, D. P.; Sun, M.; Vivek, M.; Beatty, T. G.; Brownstein, Joel R.; Roman-Lopes, Alexandre

    2016-06-01

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

  18. Optical Absorption Spectra and Excitons of Dye-Substrate Interfaces: Catechol on TiO2(110).

    PubMed

    Mowbray, Duncan John; Migani, Annapaola

    2016-06-14

    Optimizing the photovoltaic efficiency of dye-sensitized solar cells (DSSC) based on staggered gap heterojunctions requires a detailed understanding of sub-band gap transitions in the visible from the dye directly to the substrate's conduction band (CB) (type-II DSSCs). Here, we calculate the optical absorption spectra and spatial distribution of bright excitons in the visible region for a prototypical DSSC, catechol on rutile TiO2(110), as a function of coverage and deprotonation of the OH anchoring groups. This is accomplished by solving the Bethe-Salpeter equation (BSE) based on hybrid range-separated exchange and correlation functional (HSE06) density functional theory (DFT) calculations. Such a treatment is necessary to accurately describe the interfacial level alignment and the weakly bound charge transfer transitions that are the dominant absorption mechanism in type-II DSSCs. Our HSE06 BSE spectra agree semiquantitatively with spectra measured for catechol on anatase TiO2 nanoparticles. Our results suggest deprotonation of catechol's OH anchoring groups, while being nearly isoenergetic at high coverages, shifts the onset of the absorption spectra to lower energies, with a concomitant increase in photovoltaic efficiency. Further, the most relevant bright excitons in the visible region are rather intense charge transfer transitions with the electron and hole spatially separated in both the [110] and [001] directions. Such detailed information on the absorption spectra and excitons is only accessible via periodic models of the combined dye-substrate interface. PMID:27183273

  19. Is there a connection between broad absorption line quasars and narrow-line Seyfert 1 galaxies?

    SciTech Connect

    Grupe, Dirk; Nousek, John A.

    2015-02-01

    We consider whether broad absorption line quasars (BAL QSOs) and narrow-line Seyfert 1 galaxies (NLS1s) are similar, as suggested by Brandt and Gallagher and Boroson. For this purpose, we constructed a sample of 11 BAL QSOs from existing Chandra and Swift observations. We found that BAL QSOs and NLS1s both operate at high Eddington ratios L/L{sub Edd}, although BAL QSOs have slightly lower L/L{sub Edd}. BAL QSOs and NLS1s in general have high Fe ii/Hβ and low [O iii]/Hβ ratios following the classic “Boroson and Green” eigenvector 1 relation. We also found that the mass accretion rates M-dot of BAL QSOs and NLS1s are more similar than previously thought, although some BAL QSOs exhibit extreme mass accretion rates of more than 10 M{sub ⊙} yr{sup −1}. These extreme mass accretion rates may suggest that the black holes in BAL QSOs are relativistically spinning. Black hole masses in BAL QSOs are a factor of 100 larger than NLS1s. From their location on a M−σ plot, we find that BAL QSOs contain fully developed black holes. Applying a principal component analysis to our sample, we find eigenvector 1 to correspond to the Eddington ratio L/L{sub Edd}, and eigenvector 2 to black hole mass.

  20. Is There a Connection between Broad Absorption Line Quasars and Narrow-Line Seyfert 1 Galaxies?

    NASA Astrophysics Data System (ADS)

    Grupe, Dirk; Nousek, John. A.

    2015-02-01

    We consider whether broad absorption line quasars (BAL QSOs) and narrow-line Seyfert 1 galaxies (NLS1s) are similar, as suggested by Brandt & Gallagher and Boroson. For this purpose, we constructed a sample of 11 BAL QSOs from existing Chandra and Swift observations. We found that BAL QSOs and NLS1s both operate at high Eddington ratios L/{{L}Edd}, although BAL QSOs have slightly lower L/{{L}Edd}. BAL QSOs and NLS1s in general have high Fe ii/Hβ and low [O iii]/Hβ ratios following the classic “Boroson & Green” eigenvector 1 relation. We also found that the mass accretion rates \\dot{M} of BAL QSOs and NLS1s are more similar than previously thought, although some BAL QSOs exhibit extreme mass accretion rates of more than 10 {{M}⊙ } yr-1. These extreme mass accretion rates may suggest that the black holes in BAL QSOs are relativistically spinning. Black hole masses in BAL QSOs are a factor of 100 larger than NLS1s. From their location on a M-σ plot, we find that BAL QSOs contain fully developed black holes. Applying a principal component analysis to our sample, we find eigenvector 1 to correspond to the Eddington ratio L/{{L}Edd}, and eigenvector 2 to black hole mass.

  1. The D2O absorption spectra in SiO2 airgel pores: technical features of treatment

    NASA Astrophysics Data System (ADS)

    Lugovskoi, A.; Duchko, A.

    2015-11-01

    The dynamic of the D2O in silica airgel absorption spectra in 4000…6000 cm-1 were recorded using Fourier Transform spectrometer FS-125M at room temperature and pressure of 23.4 mbar with spectral resolution of 0.03 cm-1. It is shown that the D2O dimers to make a significant contribution into absorption when nanopores filled with gas molecules is small. Is present a detailed description of techniques for processing the primary experimental data.

  2. A variable P v broad absorption line and quasar outflow energetics

    NASA Astrophysics Data System (ADS)

    Capellupo, D. M.; Hamann, F.; Barlow, T. A.

    2014-10-01

    Broad absorption lines (BALs) in quasar spectra identify high-velocity outflows that might exist in all quasars and could play a major role in feedback to galaxy evolution. The viability of BAL outflows as a feedback mechanism depends on their kinetic energies, as derived from the outflow velocities, column densities, and distances from the central quasar. We estimate these quantities for the quasar, Q1413+1143 (redshift ze = 2.56), aided by the first detection of P V λλ1118, 1128 BAL variability in a quasar. In particular, P V absorption at velocities where the C IV trough does not reach zero intensity implies that the C IV BAL is saturated and the absorber only partially covers the background continuum source (with characteristic size <0.01 pc). With the assumption of solar abundances, we estimate that the total column density in the BAL outflow is log NH ≳ 22.3 cm-2. Variability in the P V and saturated C IV BALs strongly disfavours changes in the ionization as the cause of the BAL variability, but supports models with high column density BAL clouds moving across our lines of sight. The observed variability time of 1.6 yr in the quasar rest frame indicates crossing speeds >750 km s-1 and a radial distance from the central black hole of ≲ 3.5 pc, if the crossing speeds are Keplerian. The total outflow mass is ˜4100 M⊙, the kinetic energy ˜4 × 1054 erg, and the ratio of the outflow kinetic energy luminosity to the quasar bolometric luminosity is ˜0.02 (at the minimum column density and maximum distance), which might be sufficient for important feedback to the quasar's host galaxy.

  3. Estimation of calcified tissues hardness via calcium and magnesium ionic to atomic line intensity ratio in laser induced breakdown spectra

    NASA Astrophysics Data System (ADS)

    Abdel-Salam, Z. A.; Galmed, A. H.; Tognoni, E.; Harith, M. A.

    2007-12-01

    Calcified tissues representing three different matrices, namely enamel of human teeth, shells and eggshell, have been studied via Laser Induced Breakdown Spectroscopy (LIBS) technique. The experimental CaII/CaI and MgII/MgI ratios have been measured, in view of the expected correlation between the extent of ionization caused by the laser induced shock wave (SW) and the hardness of the target. The ratio CaII/CaI between the ionic calcium line at 373.69 nm and the neutral line at 428.9 nm is obtained for enamel, shells and eggshell spectra, as well as the ratio MgII/MgI between the ionic magnesium line at 280.26 nm and the neutral line at 285.22 nm. The results show that such spectral lines intensities ratio differs for different matrices and is indeed related to the target materials hardness. It is also found that the MgII/MgI ratio is preferable as an indicator of hardness since these lines are less affected by self absorption. The SW front speed has been measured in the three cases and the obtained values confirm the proportionality to the target hardness. The results here obtained suggest the feasibility of the quantitative estimation of hardness for any other calcified tissues.

  4. The mystery of spectral breaks: Lyman continuum absorption by photon-photon pair production in the Fermi GeV spectra of bright blazars

    SciTech Connect

    Stern, Boris E.; Poutanen, Juri E-mail: juri.poutanen@utu.fi

    2014-10-10

    We re-analyze Fermi/LAT γ-ray spectra of bright blazars using the new Pass 7 version of the detector response files and detect breaks at ∼5 GeV in the rest-frame spectra of 3C 454.3 and possibly also 4C +21.35, associated with the photon-photon pair production absorption by the He II Lyman continuum (LyC). We also detect significant breaks at ∼20 GeV associated with hydrogen LyC in both the individual spectra and the stacked redshift-corrected spectrum of several bright blazars. The detected breaks in the stacked spectra univocally prove that they are associated with atomic ultraviolet emission features of the quasar broad-line region (BLR). The dominance of the absorption by the hydrogen Ly complex over He II, a small detected optical depth, and break energy consistent with head-on collisions with LyC photons imply that the γ-ray emission site is located within the BLR, but most of the BLR emission comes from a flat disk-like structure producing little opacity. Alternatively, the LyC emission region size might be larger than the BLR size measured from reverberation mapping, and/or the γ-ray emitting region is extended. These solutions would resolve the long-standing issue of how the multi-hundred GeV photons can escape from the emission zone without being absorbed by softer photons.

  5. Foreign-gas broadening of nitrous oxide absorption lines.

    NASA Technical Reports Server (NTRS)

    Tubbs, L. D.; Williams, D.

    1972-01-01

    We have measured the foreign-gas broadening coefficients for collisional broadening of lines in the nu-3 fundamental of N2O by He, Ne, Ar, Kr, Xe, H2, D2, and CH4. These coefficients, which give the ratio of the line-broadening ability of these gases to the line-broadening ability of N2, can be used with recent measurements and calculations of N2 broadening to obtain optical collision cross sections.

  6. Efficient algorithm for generating spectra using line-by-lne methods

    SciTech Connect

    Sonnad, V; iglesias, C A

    2010-11-01

    A method is presented for efficient generation of spectra using line-by-line approaches. The only approximation is replacing the line shape function with an interpolation procedure, which makes the method independent of the line profile functional form. The resulting computational savings for large number of lines is proportional to the number of frequency points in the spectral range. Therefore, for large-scale problems the method can provide speedups of two orders of magnitude or more. A method was presented to generate line-by-line spectra efficiently. The first step was to replace the explicit calculation of the profile by the Newton divided-differences interpolating polynomial. The second step is to accumulate the lines effectively reducing their number to the number of frequency points. The final step is recognizing the resulting expression as a convolution and amenable to FFT methods. The reduction in computational effort for a configuration-to-configuration transition array with large number of lines is proportional to the number of frequency points. The method involves no approximations except for replacing the explicit profile evaluation by interpolation. Specifically, the line accumulation and convolution are exact given the interpolation procedure. Furthermore, the interpolation makes the method independent of the line profile functional form contrary to other schemes using FFT methods to generate line-by-line spectra but relying on the analytic form of the profile Fourier transform. Finally, the method relies on a uniform frequency mesh. For non-uniform frequency meshes, however, the method can be applied by using a suitable temporary uniform mesh and the results interpolated onto the final mesh with little additional cost.

  7. ABSORPTION-LINE PROBES OF THE PREVALENCE AND PROPERTIES OF OUTFLOWS IN PRESENT-DAY STAR-FORMING GALAXIES

    SciTech Connect

    Chen Yanmei; Kauffmann, Guinevere; Wang Jing; Tremonti, Christy A.; Heckman, Timothy M.; Weiner, Benjamin J.; Brinchmann, Jarle

    2010-08-15

    We analyze star-forming galaxies drawn from SDSS DR7 to show how the interstellar medium (ISM) Na I {lambda}{lambda}5890, 5896 (Na D) absorption lines depend on galaxy physical properties, and to look for evidence of galactic winds. We combine the spectra of galaxies with similar geometry/physical parameters to create composite spectra with signal-to-noise {approx}300. The stellar continuum is modeled using stellar population synthesis models, and the continuum-normalized spectrum is fit with two Na I absorption components. We find that (1) ISM Na D absorption lines with equivalent widths EW > 0.8 A are only prevalent in disk galaxies with specific properties-large extinction (A{sub V} ), high star formation rates (SFR), high SFR per unit area ({Sigma}{sub SFR}), or high stellar mass (M{sub *}); (2) the ISM Na D absorption lines can be separated into two components: a quiescent disk-like component at the galaxy systemic velocity and an outflow component; (3) the disk-like component is much stronger in the edge-on systems, and the outflow component covers a wide angle but is stronger within 60{sup 0} of the disk rotation axis; (4) the EW and covering factor of the disk component correlate strongly with dust attenuation, highlighting the importance that dust shielding may play in the survival of Na I; (5) the EW of the outflow component depends primarily on {Sigma}{sub SFR} and secondarily on A{sub V} ; and (6) the outflow velocity varies from {approx}120 to 160 km s{sup -1} but shows little hint of a correlation with galaxy physical properties over the modest dynamic range that our sample probes (1.2 dex in log {Sigma}{sub SFR} and 1 dex in log M{sub *}).

  8. Improving atmospheric CO2 retrievals using line mixing and speed-dependence when fitting high-resolution ground-based solar spectra

    NASA Astrophysics Data System (ADS)

    Mendonca, J.; Strong, K.; Toon, G. C.; Wunch, D.; Sung, K.; Deutscher, N. M.; Griffith, D. W. T.; Franklin, J. E.

    2016-05-01

    A quadratic speed-dependent Voigt spectral line shape with line mixing (qSDV + LM) has been included in atmospheric trace-gas retrievals to improve the accuracy of the calculated CO2 absorption coefficients. CO2 laboratory spectra were used to validate absorption coefficient calculations for three bands: the strong 20013 ← 00001 band centered at 4850 cm-1, and the weak 30013 ← 00001 and 30012 ← 00001 bands centered at 6220 cm-1 and 6340 cm-1 respectively, and referred to below as bands 1 and 2. Several different line lists were tested. Laboratory spectra were best reproduced for the strong CO2 band when using HITRAN 2008 spectroscopic data with air-broadened widths divided by 0.985, self-broadened widths divided by 0.978, line mixing coefficients calculated using the exponential power gap (EPG) law, and a speed-dependent parameter of 0.11 used for all lines. For the weak CO2 bands, laboratory spectra were best reproduced using spectroscopic parameters from the studies by Devi et al. in 2007 coupled with line mixing coefficients calculated using the EPG law. A total of 132,598 high-resolution ground-based solar absorption spectra were fitted using qSDV + LM to calculate CO2 absorption coefficients and compared to fits that used the Voigt line shape. For the strong CO2 band, the average root mean square (RMS) residual is 0.49 ± 0.22% when using qSDV + LM to calculate the absorption coefficients. This is an improvement over the results with the Voigt line shape, which had an average RMS residual of 0.60 ± 0.21%. When using the qSDV + LM to fit the two weak CO2 bands, the average RMS residual is 0.47 ± 0.19% and 0.51 ± 0.20% for bands 1 and 2, respectively. These values are identical to those obtained with the Voigt line shape. Finally, we find that using the qSDV + LM decreases the airmass dependence of the column averaged dry air mole fraction of CO2 retrieved from the strong and both weak CO2 bands when compared to the retrievals obtained using the Voigt

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

    NASA Astrophysics Data System (ADS)

    Bromová P.; Bařina, D.; Škoda, P.; Vážný, J.; Zendulka, J.

    2014-05-01

    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 Hα 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.

  10. Line shapes in CP/MAS NMR spectra of half-integer quadrupolar nuclei

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenobu; Hayamizu, Kikuko

    1993-02-01

    Cross polarization (CP) from 1H to quadrupolar nuclei with S = 3/2 has been carried out under magic-angle-spinning (MAS) conditions for powder samples of Na 2B 4O 7·10H 2O and H 3BO 3. The line shapes in the CP/MAS NMR spectra are different from those in the spectra measured with the single pulse sequence combined with 1H dipolar decoupling. Furthermore, the line shapes are found to be dependent on the measuring conditions such as the pulse amplitude for the quadrupolar nuclei. The spin-locking experiments demonstrate that line shapes in CP/MAS NMR spectra are largely dependent on the spin-locking efficiency.

  11. Soft X-ray absorption spectra of aqueous salt solutions with highly charged cations in liquid microjets

    SciTech Connect

    Schwartz, Craig P.; Uejio, Janel S.; Duffin, Andrew M.; Drisdell, Walter S.; Smith, Jared D.; Saykally, Richard J.

    2010-03-11

    X-ray absorption spectra of 1M aqueous solutions of indium (III) chloride, yttrium (III) bromide, lanthanum (III) chloride, tin (IV) chloride and chromium (III) chloride have been measured at the oxygen K-edge. Relatively minor changes are observed in the spectra compared to that of pure water. SnCl{sub 4} and CrCl{sub 3} exhibit a new onset feature which is attributed to formation of hydroxide or other complex molecules in the solution. At higher energy, only relatively minor, but salt-specific changes in the spectra occur. The small magnitude of the observed spectral changes is ascribed to offsetting perturbations by the cations and anions.

  12. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...

  13. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...

  14. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...

  15. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...

  16. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... by both molar absorption coefficient (molar extinction coefficient) and band width. However, the..., expressed in cm; and the molar absorption (extinction) coefficient,εi, of each species. The...

  17. Absorption spectra of Q 0000-263 and Q 1442+101

    NASA Technical Reports Server (NTRS)

    Frye, B. L.; Bechtold, J.; Moustakas, L. A.; Dobrzycki, A.

    1993-01-01

    Studying the Lyman-alpha forest allows us to trace the cosmological distribution of matter through time, and may reveal insights into important questions such as the onset of galaxy formation. An equation for determining the number of Lyman-alpha absorption lines per redshift per rest equivalent in the Lyman-alpha forest is given. For a nonevolving population of clouds gamma = 1 for q(sub 0) = 0, and gamma = 0.5 for q(sub 0) = 0.5. A detailed study of the Lyman-alpha forests of Q 1442+101 at z(sub em) = 3.54 and Q 0000-263 at z(sub em) = 4.11.

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

    PubMed

    Karpf, Andreas; Rao, Gottipaty N

    2015-07-01

    We describe and demonstrate a highly sensitive trace gas sensor based on a simplified design that is capable of measuring sub-ppb concentrations of NO2 in tens of milliseconds. The sensor makes use of a relatively inexpensive Fabry-Perot diode laser to conduct off-axis cavity enhanced spectroscopy. The broad frequency range of a multimode Fabry-Perot diode laser spans a large number of absorption lines, thereby removing the need for a single-frequency tunable laser source. The use of cavity enhanced absorption spectroscopy enhances the sensitivity of the sensor by providing a pathlength on the order of 1 km in a small volume. Off-axis alignment excites a large number of cavity modes simultaneously, thereby reducing the sensor's susceptibility to vibration. Multiple-line integrated absorption spectroscopy (where one integrates the absorption spectra over a large number of rovibronic transitions of the molecular species) further improves the sensitivity of detection. Relatively high laser power (∼400  mW) is used to compensate for the low coupling efficiency of a broad linewidth laser to the optical cavity. The approach was demonstrated using a 407 nm diode laser to detect trace quantities of NO2 in zero air. Sensitivities of 750 ppt, 110 ppt, and 65 ppt were achieved using integration times of 50 ms, 5 s, and 20 s respectively. PMID:26193156

  19. A census of quasar-intrinsic absorption in the Hubble Space Telescope archive: systems from high-resolution echelle spectra

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Lynch, Ryan S.; Charlton, Jane C.; Eracleous, Michael; Tripp, Todd M.; Palma, Christopher; Sembach, Kenneth R.; Misawa, Toru; Masiero, Joseph R.; Milutinovic, Nikola; Lackey, Benjamin D.; Jones, Therese M.

    2013-10-01

    We present a census of zabs ≲ 2 intrinsic (those showing partial coverage) and associated (zabs ˜ zem) quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. survey of 2 < zem < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called strong N V intrinsic systems (where the equivalent width of H I Lyα is small compared to N V λ1238) presented in that work, but find no convincing cases of `strong C IV' intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of `strong O VI' systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is an ˜3σ excess in the number of absorbers near the quasar redshift (|Δv| ≤ 5000 km s-1) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disc of the quasar.

  20. Hydrodynamical simulations of the jet in the symbiotic star MWC 560. I. Structure, emission and synthetic absorption line profiles

    NASA Astrophysics Data System (ADS)

    Stute, M.; Camenzind, M.; Schmid, H. M.

    2005-01-01

    We performed hydrodynamical simulations with and without radiative cooling of jet models with parameters representative of the symbiotic system MWC 560. For symbiotic systems we have to perform jet simulations of a pulsed underdense jet in a high density ambient medium. We present the jet structure resulting from our simulations and calculate emission plots which account for expected radiative processes. In addition, our calculations provide expansion velocities for the jet bow shock, the density and temperature structure in the jet, and the propagation and evolution of the jet pulses. In MWC 560 the jet axis is parallel to the line of sight so that the outflowing jet gas can be seen as blue shifted, variable absorption lines in the continuum of the underlying jet source. Based on our simulations we calculate and discuss synthetic absorption profiles. Based on a detailed comparison between model spectra and observations we discuss our hydrodynamical calculations for a pulsed jet in MWC 560 and suggest improvements for future models. Figures \\ref{skizze}, \\ref{modi_det}, \\ref{slice_cool_p}, \\ref{NV_3.0_synch}, \\ref{modelicool_greyscale}, \\ref{line_rem}-\\ref{line_dv} and \\ref{line_zmax} are only available in electronic form at http://www.edpsciences.org

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

    NASA Technical Reports Server (NTRS)

    Smith, S. M.

    1977-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  3. Effects of velocity averaging on the shapes of absorption lines

    NASA Technical Reports Server (NTRS)

    Pickett, H. M.

    1980-01-01

    The velocity averaging of collision cross sections produces non-Lorentz line shapes, even at densities where Doppler broadening is not apparent. The magnitude of the effects will be described using a model in which the collision broadening depends on a simple velocity power law. The effect of the modified profile on experimental measures of linewidth, shift and amplitude will be examined and an improved approximate line shape will be derived.

  4. Multiple Velocity Components of Narrow-lined Absorption Arising from the Ejecta of AG Car, P Cyg, and Eta Car.

    NASA Astrophysics Data System (ADS)

    Vieira Kober, Gladys; Gull, T. R.; Bruhweiler, F.; Nielsen, K. E.; Hill, G.

    2007-12-01

    Luminous Blue Variables (LBVs) are a small group of massive objects, with a past characterized by occasional outbursts. Well known members in our galaxy are Eta Car, AG Car, HR Car and P Cyg. HST/STIS observations of Eta Car show a very complex and rich circumstellar absorption spectrum. Of the 20 distinct absorption systems, the ionized strong absorber at -146 km/s (Little Homunculus) shows lines from transitions originating from mainly singly ionized iron-group elements. Curve-of-growth analysis for Fe II lines plus photo-ionization and statistical equilibrium modeling indicated a temperature Te = 6400 K and density n 5x107 cm-3. AG Car and P Cyg have, like Eta Car, circumstellar nebulae which likely are remnants of typical LBV mass loss events. Spectral analysis of high resolution VLT/UVES data for AG Car and Keck/HIRES data for P Cyg also reveal multiple narrow absorption components with excitation and velocities similar to Eta Car's Little Homunculus. In this poster we present curve-of-growth analysis for Fe II lines for the narrow components around AG Car and P Cyg, and temperature estimates based on level populations for these absorbers. We compare the absorbing features around these three LBVs, providing clues to wind structures and ejections for these massive stars. We thank NASA, STScI, Keck and ESO for providing resources and spectra analyzed in this poster, recorded with HST/STIS, Keck/HIRES and VLT/UVES.

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

    SciTech Connect

    George, S.DeBeer; Petrenko, T.; Neese, F.

    2009-05-14

    Iron K-edge X-ray absorption pre-edge features have been calculated using a time-dependent density functional approach. The influence of functional, solvation, and relativistic effects on the calculated energies and intensities has been examined by correlation of the calculated parameters to experimental data on a series of 10 iron model complexes, which span a range of high-spin and low-spin ferrous and ferric complexes in O{sub h} to T{sub d} geometries. Both quadrupole and dipole contributions to the spectra have been calculated. We find that good agreement between theory and experiment is obtained by using the BP86 functional with the CP(PPP) basis set on the Fe and TZVP one of the remaining atoms. Inclusion of solvation yields a small improvement in the calculated energies. However, the inclusion of scalar relativistic effects did not yield any improved correlation with experiment. The use of these methods to uniquely assign individual spectral transitions and to examine experimental contributions to backbonding is discussed.

  6. Novel Techniques and Approaches to Unravel the Nature of X-Ray Absorption Spectra

    SciTech Connect

    Groot, F. M. F. de

    2007-02-02

    This paper discusses the role of resonant inelastic X-ray scattering (RIXS) to unravel the nature of the states that are visible in the pre-edge region of the 3d metal K edges. The traditional pre-edge analysis into quadrupole transitions to the 3d-states plus dipole transitions to the 4p states is outlined, with special attention to the situation of TiO2. The general possibilities of RIXS are described, including the various possible cross-sections through the 2D RIXS plane. Recent developments in High-Energy Resolution Fluorescence Detection (HERFD) are discussed, that yield XANES-like spectra with unprecedented resolution. Using the 1s2p RIXS of LiCoO2 as example, the presence of an extra peak due to non-local dipole transitions is explained. The non-local nature of this dipole pre-edge peak is proven from its behavior in the 2D RIXS plane. The paper also discusses a range of selective X-ray absorption experiments, where the selectivity is towards (a) the spin-state, (b) the valence, (c) the neighbor atom and (d) the edge. In the outlook, a number of additional experimental routes is suggested, which shows that the use of RIXS, HERFD and selective XAS techniques is only just starting.

  7. Strong anisotropy in the THz absorption spectra of stretch-aligned single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Iwasa, Y.; Akima, N.; Matsui, H.; Toyota, N.; Brown, S.; Barbour, A. M.; Cao, J.; Musfeldt, J. L.; Shiraishi, M.; Shimoda, H.; Zhou, O.

    2006-03-01

    Polarized THz spectroscopy is crucial for understanding the low-energy electronic structure and carrier dynamics in single walled carbon nanotubes (SWNTs), as well as for exploring polarization-sensitive THz applications. We prepared stretch-aligned SWNT/polymer composites, and measured the polarized absorption spectra from the THz through the visible region. The low-frequency electronic excitations are predominantly polarized parallel to the tube direction. The peak centered near 100 cm-1 is discussed in terms of a curvature-induced gap and a plasmon resonance due to a finite size/wavelength effects in the SWNTs. The broad middle infrared structure that is observed in unoriented films with spaghetti-like morphology disappears in stretch-aligned samples, suggesting that this middle infrared feature may be due to in-gap states in the semiconducting tubes caused by the highly disordered morphology of the unoriented films. Hole doping effects were also investigated, and conversion of semiconducting tubes to more conducting ones is demonstrated.

  8. Absorption spectra and sunlight conversion efficiency in fullerene bonded supramolecules on nanostructured ZnO

    NASA Astrophysics Data System (ADS)

    Zakhidov, Erkin; Kokhkharov, Abdumutallib; Kuvondikov, Vakhobjon; Nematov, Sherzod; Nusretov, Rafael

    2015-10-01

    The efficiency of solar radiation conversion in a model system of artificial photosynthesis, the porphyrin-fullerene assembly, is analyzed. A study of the optical absorption spectra of the porphyrin and the fullerene molecules, as well as their assembly in organic solutions, made it possible to estimate the energy efficiency of the conversion. Numerical values of the energy efficiency, defined as the fraction of the light quantum energy converted to the chemical potential of separated charges, are calculated for low- and high-concentration solutions of such a supramolecular system. The possibility of the efficient utilization of long-wavelength solar radiation in the high-concentration porphyrin-fullerene assembly solution in toluene and benzene is shown. In the photovoltaic system consisting of such a supramolecular active element, a thin ZnO film with a nanostructured surface may be introduced as a secondary acceptor of electrons from fullerene molecules. An enhancement of the transformation of separated charges of the porphyrin-fullerene assembly into electrical current by means of the ZnO film deposited on the surface of the anode electrode in such a heterogenic photovoltaic unit is proposed.

  9. Time-dependent excitation and ionization modelling of absorption-line variability due to GRB 080310

    NASA Astrophysics Data System (ADS)

    Vreeswijk, P. M.; Ledoux, C.; Raassen, A. J. J.; Smette, A.; De Cia, A.; Woźniak, P. R.; Fox, A. J.; Vestrand, W. T.; Jakobsson, P.

    2013-01-01

    We model the time-variable absorption of Fe II, Fe III, Si II, C II and Cr II detected in Ultraviolet and Visual Echelle Spectrograph (UVES) spectra of gamma-ray burst (GRB) 080310, with the afterglow radiation exciting and ionizing the interstellar medium in the host galaxy at a redshift of z = 2.42743. To estimate the rest-frame afterglow brightness as a function of time, we use a combination of the optical VRI photometry obtained by the RAPTOR-T telescope array, which is presented in this paper, and Swift's X-Ray Telescope (XRT) observations. Excitation alone, which has been successfully applied for a handful of other GRBs, fails to describe the observed column density evolution in the case of GRB 080310. Inclusion of ionization is required to explain the column density decrease of all observed Fe II levels (including the ground state 6D9/2) and increase of the Fe III 7S3 level. The large population of ions in this latter level (up to 10% of all Fe III) can only be explained through ionization of Fe II, as a large fraction of the ionized Fe II ions (we calculate 31% using the Flexible Atomic and Cowan codes) initially populate the 7S3 level of Fe III rather than the ground state. This channel for producing a significant Fe III 7S3 level population may be relevant for other objects in which absorption lines from this level, the UV34 triplet, are observed, such as broad absorption line (BAL) quasars and η Carinae. This provides conclusive evidence for time-variable ionization in the circumburst medium, which to date has not been convincingly detected. However, the best-fit distance of the neutral absorbing cloud to the GRB is 200-400 pc, i.e. similar to GRB-absorber distance estimates for GRBs without any evidence for ionization. We find that the presence of time-varying ionization in GRB 080310 is likely due to a combination of the super-solar iron abundance ([Fe/H] = +0.2) and the low H I column density (log N(H i) = 18.7) in the host of GRB 080310. Finally

  10. Bethe-Salpeter calculation of optical-absorption spectra of In2O3 and Ga2O3

    NASA Astrophysics Data System (ADS)

    Varley, Joel B.; Schleife, André

    2015-02-01

    Transparent conducting oxides keep attracting strong scientific interest not only due to their promising potential for ‘transparent electronics’ applications but also due to their intriguing optical absorption characteristics. Materials such as In2O3 and Ga2O3 have complicated unit cells and, consequently, are interesting systems for studying the physics of excitons and anisotropy of optical absorption. Since currently no experimental data is available, for instance, for their dielectric functions across a large photon-energy range, we employ modern first-principles computational approaches based on many-body perturbation theory to provide theoretical-spectroscopy results. Using the Bethe-Salpeter framework, we compute dielectric functions and we compare to spectra computed without excitonic effects. We find that the electron-hole interaction strongly modifies the spectra and we discuss the anisotropy of optical absorption that we find for Ga2O3 in relation to existing theoretical and experimental data.

  11. Vibrationally Resolved Absorption and Fluorescence Spectra of Firefly Luciferin: A Theoretical Simulation in the Gas Phase and in Solution.

    PubMed

    Cheng, Yuan-Yuan; Liu, Ya-Jun

    2016-07-01

    Firefly bioluminescence has been applied in several fields. However, the absorption and fluorescence spectra of the substrate, luciferin, have not been observed at the vibrational level. In this study, the vibrationally resolved absorption and fluorescence spectra of firefly luciferin (neutral form LH2 , phenolate ion form LH(-) and dianion form L(2-) ) are simulated using the density functional method and convoluted by a Gaussian function, with displacement, distortion and Duschinsky effects in the framework of the Franck-Condon approximation. Both neutral and anionic forms of the luciferin are considered in the gas phase and in solution. The simulated spectra have desired band maxima with the experimental ones. The vibronic structure analysis reveals that the features of the most contributive vibrational modes coincide with the key geometry-changing region during transition between the ground state and the first singlet excited state. PMID:27165852

  12. Identifying student and teacher difficulties in interpreting atomic spectra using a quantum model of emission and absorption of radiation

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Our study sets out to identify the difficulties that high school students, teachers, and university students encounter when trying to explain atomic spectra. To do so, we identify the key concepts that any quantum model for the emission and absorption of electromagnetic radiation must include to account for the gas spectra and we then design two questionnaires, one for teachers and the other for students. By analyzing the responses, we conclude that (i) teachers lack a quantum model for the emission and absorption of electromagnetic radiation capable of explaining the spectra, (ii) teachers and students share the same difficulties, and (iii) these difficulties concern the model of the atom, the model of radiation, and the model of the interaction between them.

  13. The hydration dependence of CaCO3 absorption lines in the Far IR

    NASA Astrophysics Data System (ADS)

    Powell, Johnny; Emery, Logan P

    2014-06-01

    The far infrared (FIR) absorption lines of CaCO3 have been measured at a range of relative humidities (RH) between 33 and 92% RH using a Bruker 66v/S spectrometer. Hydration measurements on CaCO3 have been made in the mid-infrared (MIR) by [Al-Hosney, H.A. and Grassian, V.H., 2005, Phys. Chem. Chem. Phys., 7, 1266], and astrophysically-motivated temperature-dependent FIR measurements of CaCO3 in vacuum have also been reported [Posch, T., et al., 2007, Ap. J., 668, 993]. The custom sample cell constructed for these hydrated-FIR spectra is required because the 66v/S bench is under vacuum (3 mbar) during typical measurements. Briefly, the sample cell consists of two Thalium Bromoiodide (KRS-5) windows, four O-rings, a plastic ring for separating the windows and providing a volume for the saturated atmosphere. CaCO3 was deposited on KRS-5 windows using doubly-distilled water as an intermediary. The KRS-5 window with sample and assembled sample cell were placed in a desiccator with the appropriated saturated salt solution [Washburn, E.W. (Ed.), International Critical Tables of Numerical Data, Physics Chemistry and Technology, Vol. 1, (McGraw-Hill, New York, 1926), p. 67-68] and allowed to hydrate for 23 hours. For spectroscopy the desiccator was quickly opened and the second KRS-5 window placed in the cell to seal the chamber. A spectrum was then taken of the sample at the appropriate RH. The spectra taken characterize the adsorption of water vapor and CaCO3 that might occur in circumstellar environments [Melnick, G.J., et al. 2001, Nature, 412, 160].The MIR and FIR reflectance spectra of calcite (CaCO3) have been thoroughly studied by [Hellwege, K.H., et al., 1970, Z. Physik, 232, 61]. Five Lorentzian curves were fit to our data in the range from 378-222 cm-1/SUP> and each was able to be assigned to a known mode of CaCO3. The data does not support the conclusion of a hydration effect on these modes of CaCO3, but it does suggest a possible broadening of three modes

  14. Iron Emission Lines in the Spectra of Classical T Tauri Stars

    NASA Astrophysics Data System (ADS)

    Beristain, G.; Edwards, S.; Hartigan, P.

    1993-05-01

    The optical and infrared continuum emission excesses in classical T Tauri stars are frequently attributed to accretion disks with characteristic mass accretion rates of 10(-7) Msun yr(-1) . The spectra of classical T Tauri stars are also rich in emission lines, arising from both permitted and forbidden atomic species, which have been attributed to formation in regions as diverse as chromospheres, boundary layers, winds and collimated jets. We have conducted a high resolution spectroscopic survey of 48 T Tauri stars in the Tau-Aur star formation complex covering the wavelength range 3900{\\kern.2em Angstroms} to 7000{\\kern.2em Angstroms} with the aim of determining the origin of the various emission lines and report here on the most prominent metallic species present in the T Tauri spectra, Fe I and Fe II. From our spectra we have both 1) determined the level of optical continuum emission, expressed as the ratio of `veiling' to photospheric flux, and 2) extracted residual Fe emission line profiles, free of contamination from underlying photospheric features. We find that Fe I, II emission is seen only in T Tauri stars which have infrared and optical continuum emission excesses attributed to accretion disks; none of the `weak-line' T Tauri stars, with photospheric IR colors and no optical veiling, have detectable Fe emission. Correlations of Fe emission equivalent widths with both K-L and the ratio of veiling to photospheric flux, r, suggest that the Fe lines arise as a result of accretion related activity. DR Tau's rich emission line spectra permit study of the largest number of unblended Fe I,II profiles, for which we have spectra covering 5 different nights. Multiplet line ratios indicate the Fe lines are optically thick, and line luminosities imply emitting areas covering a few percent of the stellar surface. The lines are typically broad and symmetric, although inverse P Cygni structure in Fe II is seen on one night. For 4 nights, the Fe I and Fe II lines

  15. Electronic absorption spectra of U3+ and U4+ in molten LiCl-RbCl eutectic

    NASA Astrophysics Data System (ADS)

    Nagai, T.; Uehara, A.; Fujii, T.; Sato, N.; Yamana, H.

    2010-03-01

    In the non-aqueous reprocessing process of spent nuclear fuels by the pyro-electrochemical method, a spent fuel is dissolved into molten LiCl-KCl and NaCl-CsCl eutectics and dissolved uranium and plutonium are collected as either metal or oxide. However, the binary alkali chloride mixture with the lowest melting point is the LiCl-RbCl eutectic. In this study, electronic absorption spectra of U3+ and U4+ in molten LiCl-RbCl eutectic at various temperatures between 673 and 973 K were measured by the UV/Vis/NIR spectrophotometry. We confirmed that these spectra were similar to those in molten LiCl-KCl and NaCl-CsCl eutectics. The sensitive absorption bands of U4+ in LiCl-RbCl eutectic were found at 22000, 16500, 14900, 8600, and 4950 cm-1. The large absorption bands of U4+ over 25000 cm-1 increased with increasing melt temperature, while absorption peaks at 15500-4000 cm-1 decreased. The large absorption bands of U3+ in LiCl-RbCl eutectic were observed over 14000 cm-1. The sensitive absorption bands of U3+ at Vis/NIR region were found at 13300, 11500-11200, 9800-9400, and 8250 cm-1, and these peaks decreased with increasing temperature.

  16. On-Line Wavelength Calibration of Pulsed Laser for CO2 Differential Absorption LIDAR

    NASA Astrophysics Data System (ADS)

    Xiang, Chengzhi; Ma, Xin; Han, Ge; Liang, Ailin; Gong, Wei

    2016-06-01

    Differential absorption lidar (DIAL) remote sensing is a promising technology for atmospheric CO2 detection. However, stringent wavelength accuracy and stability are required in DIAL system. Accurate on-line wavelength calibration is a crucial procedure for retrieving atmospheric CO2 concentration using the DIAL, particularly when pulsed lasers are adopted in the system. Large fluctuations in the intensities of a pulsed laser pose a great challenge for accurate on-line wavelength calibration. In this paper, a wavelength calibration strategy based on multi-wavelength scanning (MWS) was proposed for accurate on-line wavelength calibration of a pulsed laser for CO2 detection. The MWS conducted segmented sampling across the CO2 absorption line with appropriate number of points and range of widths by using a tunable laser. Complete absorption line of CO2 can be obtained through a curve fitting. Then, the on-line wavelength can be easily found at the peak of the absorption line. Furthermore, another algorithm called the energy matching was introduced in the MWS to eliminate the backlash error of tunable lasers during the process of on-line wavelength calibration. Finally, a series of tests was conducted to elevate the calibration precision of MWS. Analysis of tests demonstrated that the MWS proposed in this paper could calibrate the on-line wavelength of pulsed laser accurately and steadily.

  17. Doppler wavelength shifts of transition zone lines measured in Skylab solar spectra

    NASA Technical Reports Server (NTRS)

    Doschek, G. A.; Bohlin, J. D.; Feldman, U.

    1976-01-01

    Wavelengths of lines of the transition-zone ions Si IV, C IV, O IV, N V, and O V are observed to be redshifted relative to the wavelengths of chromospheric lines in XUV spectra obtained from the normal-incidence spectrograph on Skylab. The spectra cover the wavelength range from 1200 to 1565 A and were obtained with the slit positioned over chromospheric network and cell regions, on coronal holes, and above the limb. The network-area and coronal-hole spectra were obtained near the disk center. Only some of the spectra show redshifted transition-zone lines. The observed shifts are between 0.03 and 0.08 A, implying velocities of 15 km/s or less. The amount of wavelength shift does not always appear to be the same for lines of different ions. The shifts imply that descending plasma in the solar atmosphere produces more emission than ascending plasma at temperatures between approximately 70,000 and 200,000 K.

  18. Enhancement of ammonia gas detection by integrating wavelength-modulated spectra across the line 992.69 cm-1

    NASA Astrophysics Data System (ADS)

    Dallah, Mohammad; Salloum, Akil

    2016-05-01

    A rapid tunable diode laser (TDL) absorption sensor was developed for real-time measurements of ammonia concentration by using wavelength modulation spectroscopy (WMS) at 992.698 cm-1 of the ν2 vibrational band. This line has patterns free from interference with other species in the atmosphere, and can be used for open-path detection. The 1f signal was used to normalize the 2f signal thereby eliminating the need for calibration and explaining the laser transmission variations. Using WMS with a large modulation depth and integrating the absolute value of the resulting spectra increased the limit of detection (LOD) of the sensor by a factor of seven, compared with the LOD achieved by using the maximum value of the WMS 2f signal. Furthermore, an increase by a factor of 25 compared with the direct absorption spectroscopy was achieved, which allowed obtaining LOD ∼ 1 ppb with a resolution time of <2 s for the detection of NH3 in the atmosphere using a short-path cell (a 60-cm absorption cell with four passes).

  19. General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra

    SciTech Connect

    Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

    2012-10-08

    Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

  20. Quantitative analysis of deconvolved X-ray absorption near-edge structure spectra: a tool to push the limits of the X-ray absorption spectroscopy technique.

    PubMed

    D'Angelo, Paola; Migliorati, Valentina; Persson, Ingmar; Mancini, Giordano; Della Longa, Stefano

    2014-09-15

    A deconvolution procedure has been applied to K-edge X-ray absorption near-edge structure (XANES) spectra of lanthanoid-containing solid systems, namely, hexakis(dmpu)praseodymium(III) and -gadolinium(III) iodide. The K-edges of lanthanoids cover the energy range 38 (La)-65 (Lu) keV, and the large widths of the core-hole states lead to broadening of spectral features, reducing the content of structural information that can be extracted from the raw X-ray absorption spectra. Here, we demonstrate that deconvolution procedures allow one to remove most of the instrumental and core-hole lifetime broadening in the K-edge XANES spectra of lanthanoid compounds, highlighting structural features that are lost in the raw data. We show that quantitative analysis of the deconvolved K-edge XANES spectra can be profitably used to gain a complete local structural characterization of lanthanoid-containing systems not only for the nearest neighbor atoms but also for higher-distance coordination shells. PMID:25171598

  1. Variability of broad absorption lines in QSO SDSS J022844.09+000217.0 on multiyear time-scales

    NASA Astrophysics Data System (ADS)

    He, Zhi-Cheng; Bian, Wei-Hao; Jiang, Xiao-Lei; Wang, Yue-Feng

    2014-09-01

    The variability of broad absorption lines is investigated for a broad-absorption-line (BAL) quasar (QSO), SDSS J022844.09+000217.0 (z = 2.719), with 18 Sloan Digital Sky Survey (SDSS)/Baryon Oscillation Spectroscopic Survey (BOSS) spectra covering 4128 d in the observed frame. Using the ratio of the root-mean-square (rms) spectrum to the mean spectrum, the relative flux change of the BAL trough is larger than that of the emission lines and the continuum. Fitting a power-law continuum and the emission-line profiles of C IV λ1549 and Si IVλ1399, we calculate the equivalent width (EW) for different epochs, as well as the continuum luminosity and the spectral index. It is found that there is a strong correlation between the BAL-trough EW and the spectral index and a weak negative correlation between the BAL-trough EW and the continuum luminosity. The strong correlation between the BAL-trough EW and the spectral index for this particular QSO suggests that dust is intrinsic to outflows. The weak correlation between the BAL variability and the continuum luminosity for this particular QSO implies that the BAL-trough variation is not dominated by photoionization.

  2. X-ray line polarization spectroscopy of Li-like satellite line spectra

    SciTech Connect

    Sherrill, Manolo Edgar; Abdallah, Joseph; Zhang, Honglin; Hakel, Peter; Mancini, Roberto C

    2008-01-01

    We apply the magnetic-sublevel atomic kinetics model POLAR to the calculation of polarization properties of satellite lines in Li-like Si driven by subpicosecond-duration laser pulses. We identify spectral lines whose polarization can serve as a marker of plasma anisotropy due to anisotropy in the electron distribution function. We also discuss the utility and limitations of ur current theoretical approach and point out possible future improvements and directions.

  3. Analysis of Gain and Absorption Spectra of Gallium Nitride-based Laser Diodes

    NASA Astrophysics Data System (ADS)

    Melo, Thiago

    Laser diodes (LDs) based on the III-Nitride material system, (Al,In,Ga)N, stand to satisfy a number of application needs, and their huge market segment has been further growing with the use of LDs for full color laser projection. All commercially available GaN-based devices are based on the conventional c-plane (polar) orientation of this material. However, strong polarization fields caused by strained quantum-well (QW) layers on c-plane induce the quantum-confined Stark effect (QCSE), which leads to reduced radiative recombination rate and are aggravated when more indium is added into the QW(s) in order to achieve longer wavelengths. A promising solution for this is the use of nonpolar and semipolar crystal growth orientations. Elimination or mitigation of polarization-related fields within the QWs grown along these novel orientations is observed and one expects increased radiative recombination rate and stabilization of the wavelength emission with respect to the injection current. In order to have more insights on the advantages of using the novel crystal orientations of the III-Nitride material system, we compare the gain of LD structures fabricated from c-plane, nonpolar and semipolar GaN substrates. Using thesegmented contact method, single-pass gain spectra of LD epitaxial structures at wafer level are compared for the different crystal orientations as well as the single-pass absorption coefficient spectrum of the active region material and its dependence on reversed bias. Experimental gain spectra under continuous-wave (CW) operation of actual industry LDs fabricated from c-plane and nonpolar/semipolar GaN-based materials emitting wavelengths in the visible are then presented, using the Hakki-Paoli technique at high resolution. Measurements of the transparency current density, total losses and differential modal gain curves up to threshold are analyzed and compared between nonpolar/semipolar and c-plane LDs in violet and blue spectral regions regions. In a

  4. Intensities and N2 collision-broadening coefficients measured for selected H2O absorption lines between 715 and 732 nm

    NASA Technical Reports Server (NTRS)

    Wilkerson, T. D.; Schwemmer, G.; Gentry, B.; Giver, L. P.

    1979-01-01

    Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.

  5. The centre-to-limb variations of solar Fraunhofer lines imprinted upon lunar eclipse spectra. Implications for exoplanet transit observations

    NASA Astrophysics Data System (ADS)

    Yan, F.; Fosbury, R. A. E.; Petr-Gotzens, M. G.; Zhao, G.; Pallé, E.

    2015-02-01

    The atmospheres of exoplanets are commonly studied by observing the transit of the planet passing in front of its parent star. The obscuration of part of the stellar disk during a transit will reveal aspects of its surface structure resulting from general centre-to-limb variations (CLVs). These become apparent when forming the ratio between the stellar light in and out of transit. These phenomena can be seen particularly clearly during the progress of a penumbral lunar eclipse, where the Earth transits the solar disk and masks different regions of the solar disk as the eclipse progresses. When inferring the properties of the planetary atmosphere, it is essential that this effect originating at the star is properly accounted for. Using the data observed from the 2014-April-15 lunar eclipse with the ESPaDOnS spectrograph mounted on the Canada France Hawaii Telescope (CFHT), we have obtained for the first time a time sequence of the penumbral spectra. These penumbral spectra enable us to study the centre-to-limb variations of solar Fraunhofer lines when the Earth is transiting Sun. The Na i and Ca ii absorption features reported from previous lunar eclipse observations are demonstrated to be CLV features, which dominate the corresponding line profiles and mask possible planetary signal. Detecting atmospheric species in exoplanets via transit spectroscopy must account for the CLV effect.

  6. Effect of Ionization on Infrared and Electronic Absorption Spectra of Methyl and Ethyl Formate in the Gas Phase and in Astrophysical H2O Ice: A Computational Study

    NASA Astrophysics Data System (ADS)

    Naganathappa, Mahadevappa; Chaudhari, Ajay

    2011-04-01

    This work reports infrared and electronic absorption spectra of trans and gauche conformers of neutral ethyl formate, trans and cis conformers of neutral methyl formate, their ions in the gas phase, and neutral ethyl and methyl formate in astrophysical H2O ice. The second-order Møller-Plesset perturbation (MP2) method with TZVP basis set has been used to obtain ground-state geometries. An influence of ice on vibrational frequencies of neutral ethyl and methyl formate was obtained using integral equation formalism polarizable continnum model (IEFPCM). Significant shift in vibrational frequencies for neutral methyl and ethyl formate when studied in H2O ice and upon ionization is observed. Rotational and distortion constants for neutral ethyl and methyl formate from this work are in excellent agreement with the available experimental values. Electronic absorption spectra of conformers of ethyl and methyl formate and their ions are obtained using time-dependent density functional method (TDDFT). The nature of electronic transitions is also identified. We suggested lines especially good to detect these molecules in interstellar medium. Using these lines, we can identify the conformers of ethyl and methyl formate in gas phase and H2O ice in interstellar medium. This comparative study should provide useful guidelines to detect conformers of ethyl and methyl formate and their ions in gas phase and neutral molecules in H2O ice in different astronomical environment.

  7. Detectability of cold streams into high-redshift galaxies by absorption lines

    NASA Astrophysics Data System (ADS)

    Goerdt, Tobias; Dekel, Avishai; Sternberg, Amiel; Gnat, Orly; Ceverino, Daniel

    2012-08-01

    Cold gas streaming along the dark matter filaments of the cosmic web is predicted to be the major source of fuel for disc buildup, violent disc instability and star formation in massive galaxies at high redshift. We investigate to what extent such cold gas is detectable in the extended circumgalactic environment of galaxies via Lyα absorption and selected low-ionization metal absorption lines. We model the expected absorption signatures using high-resolution zoom-in adaptive mesh refinement cosmological simulations. In the post-processing, we distinguish between self-shielded gas and unshielded gas. In the self-shielded gas, which is optically thick to Lyman continuum radiation, we assume pure collisional ionization for species with an ionization potential greater than 13.6 eV. In the optically-thin, unshielded gas, these species are also photoionized by the metagalactic radiation. In addition to absorption of radiation from background quasars, we compute the absorption line profiles of radiation emitted by the galaxy at the centre of the same halo. We predict the strength of the absorption signal for individual galaxies without stacking. We find that the Lyα absorption profiles produced by the streams are consistent with observations of absorption and emission Lyα profiles in high-redshift galaxies. Due to the low metallicities in the streams, and their low covering factors, the metal absorption features are weak and difficult to detect.

  8. Photodynamic cancer therapy: fluorescence localization and light absorption spectra of chlorophyll-derived photosensitizers inside cancer cells

    NASA Astrophysics Data System (ADS)

    Moser, Joerg G.; Rueck, Angelika C.; Schwarzmaier, Hans-Joachim; Westphal-Frosch, Christel

    1992-07-01

    The first prerequisite for an optimum effect of photodynamic therapy with chlorophyll- derived photosensitizers is irradiation at the S1 absorption maximum in the red spectral region. This absorption maximum changes its position due to molecular association by 20 to 100 nm depending on the subcellular environment, and must be determined by direct absorption spectrometry in the region of subcellular sensitizer localization. Fluorescence- intensifying video microscopy allows for localization of the sensitizer storage site at or near the Galgi apparatus of OAT 75 small-cell lung carcinoma cells. The absorption maximum at 760 nm taken from spectra of single cells and cell layers determines the postulated optimum condition for dye laser irradiation with bacteriopheophorbide-a-methyl-ester as the sensitizer.

  9. Solvent dependence of two-photon absorption spectra of the enhanced green fluorescent protein (eGFP) chromophore

    NASA Astrophysics Data System (ADS)

    Hosoi, Haruko; Tayama, Ryo; Takeuchi, Satoshi; Tahara, Tahei

    2015-06-01

    Two-photon absorption spectra of 4‧-hydroxybenzylidene-2,3-dimethylimidazolinone, a model chromophore of enhanced green fluorescent protein (eGFP), were measured in various solvents. The two-photon absorption band of its anionic form is markedly blue-shifted from the corresponding one-photon absorption band in all solvents. Moreover, the magnitude of the blue shift varies largely depending on the solvent, which does not accord with the assignment of the two-photon absorption band to the transitions to the vibrationally excited S1 state. Our finding is readily rationalized by considering overlapping contributions of the S1 ← S0 and S2 ← S0 transitions, suggesting the involvement of the S2 state also in two-photon fluorescence of eGFP.

  10. Absorption spectra of CdSe-ZnS core-shell quantum dots at high photon energies: Experiment and modeling

    NASA Astrophysics Data System (ADS)

    Mukherjee, Amlan; Ghosh, Sandip

    2014-11-01

    Absorption spectra of CdSe-ZnS core-shell quantum dot (QD) ensembles, with average core diameters ranging from 2.6 nm to 7.2 nm have been obtained using both transmission and photoluminescence excitation measurements. In agreement with previous reports, the absorption coefficient at energies ≃1 eV above the effective bandgap increases monotonically as in bulk solids. A simple effective-mass spherical core-shell potential model cannot explain the relatively high absorption at higher energies. The calculated electron and hole radial envelope wavefunctions show asymmetry due to the core-shell structure. It leads to normally symmetry-disallowed transitions acquiring a weak oscillator strength, with their number and strength increasing with energy. A phenomenological model that invokes normally disallowed transitions in general is shown to reproduce the absorption spectrum at higher energies quite well. The oscillator strength scaling factor for such transitions increases with decrease in QD size, consistent with expectations.

  11. Broadening of infrared absorption lines at reduced temperatures - Carbon dioxide.

    NASA Technical Reports Server (NTRS)

    Tubbs, L. D.; Williams, D.

    1972-01-01

    An evacuated high-resolution Czerny-Turner spectrograph, which is described in this paper, has been used to determine the strengths S and self-broadening parameters for lines in the R branch of the nu (sub 3) fundamental of carbon dioxide at 298 and at 207 K. The values of self-broadening parameters at 207 K are greater than those to be expected on the basis of a fixed collision cross section.

  12. Invisible Active Galactic Nuclei. II. Radio Morphologies and Five New H i 21cm Absorption Line Detectors

    NASA Astrophysics Data System (ADS)

    Yan, Ting; Stocke, John T.; Darling, Jeremy; Momjian, Emmanuel; Sharma, Soniya; Kanekar, Nissim

    2016-03-01

    This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Paper I. In this paper, we present both high-resolution radio continuum images for all of these sources and H i 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.″5 and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ∼three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H i 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral “window” (i.e., the percentage of H i 21 cm absorption-line detections could be as high as ∼90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H i detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H i absorption may well be present but is masked by

  13. Collison-induced rototranslational absorption spectra of H/sub 2/-He pairs at temperatures from 40 to 3000 K

    SciTech Connect

    Borysow, J.; Frommhold, L.; Birnbaum, G.

    1988-03-01

    The zeroth, first, and second spectral moments of the rototranslational collision-induced absorption (RT CIA) spectra of hydrogen-helium mixtures are calculated from the fundamental theory, for temperatures from 40 to 3000 K. With the help of simple analytical functions of three parameters and the information given, the RT CIA spectra of H/sub 2/-He pairs can be generated on computers of small capacity, with rms deviations from exact quantum profiles of not more than a few percent. Such representations of the CIA spectra are of interest for work related to the atmospheres of the outer planets and cool stars. The theoretical spectra are in close agreement with existing laboratory measurements at various temperatures from about 77 to 3000 K. 28 references.

  14. On-the-Fly ab Initio Semiclassical Dynamics of Floppy Molecules: Absorption and Photoelectron Spectra of Ammonia.

    PubMed

    Wehrle, Marius; Oberli, Solène; Vaníček, Jiří

    2015-06-01

    We investigate the performance of on-the-fly ab initio (OTF-AI) semiclassical dynamics combined with the thawed Gaussian approximation (TGA) for computing vibrationally resolved absorption and photoelectron spectra. Ammonia is used as a prototype of floppy molecules, whose potential energy surfaces display strong anharmonicity. We show that despite complications due to the presence of large amplitude motion, the main features of the spectra are captured by the OTF-AI-TGA, which—by definition—does not require any a priori knowledge of the potential energy surface. Moreover, the computed spectra are significantly better than those based on the popular global harmonic approximation. Finally, we probe the limit of the TGA to describe higher-resolution spectra, where long time dynamics is required. PMID:25928833

  15. Collison-induced rototranslational absorption spectra of H2-He pairs at temperatures from 40 to 3000 K

    NASA Technical Reports Server (NTRS)

    Borysow, Jacek; Frommhold, Lothar; Birnbaum, George

    1988-01-01

    The zeroth, first, and second spectral moments of the rototranslational collision-induced absorption (RT CIA) spectra of hydrogen-helium mixtures are calculated from the fundamental theory, for temperatures from 40 to 3000 K. With the help of simple analytical functions of three parameters and the information given, the RT CIA spectra of H2-He pairs can be generated on computers of small capacity, with rms deviations from exact quantum profiles of not more than a few percent. Such representations of the CIA spectra are of interest for work related to the atmospheres of the outer planets and cool stars. The theoretical spectra are in close agreement with existing laboratory measurements at various temperatures from about 77 to 3000 K.

  16. Broadening and collisional interference of lines in the IR spectra of ammonia. Theory

    NASA Astrophysics Data System (ADS)

    Cherkasov, M. R.

    2016-06-01

    The general theory of relaxation spectral shape parameters in the impact approximation (M. R. Cherkasov, J. Quant. Spectrosc. Radiat. Transfer 141, 73 (2014)) is adapted to the case of line broadening of infrared spectra of ammonia. Specific features of line broadening of parallel and perpendicular bands are discussed. It is shown that in both cases the spectrum consists of independently broadened singlets and doublets; however, the components of doublets can be affected by collisional interference. The paper is the first part of a cycle of studies devoted to the problems of spectral line broadening of ammonia.

  17. Study of electron transition energies between anions and cations in spinel ferrites using differential UV-vis absorption spectra

    NASA Astrophysics Data System (ADS)

    Xue, L. C.; Wu, L. Q.; Li, S. Q.; Li, Z. Z.; Tang, G. D.; Qi, W. H.; Ge, X. S.; Ding, L. L.

    2016-07-01

    It is very important to determine electron transition energies (Etr) between anions and different cations in order to understand the electrical transport and magnetic properties of a material. Many authors have analyzed UV-vis absorption spectra using the curve (αhν)2 vs E, where α is the absorption coefficient and E(=hν) is the photon energy. Such an approach can give only two band gap energies for spinel ferrites. In this paper, using differential UV-vis absorption spectra, dα/dE vs E, we have obtained electron transition energies (Etr) between the anions and cations, Fe2+ and Fe3+ at the (A) and [B] sites and Ni2+ at the [B] sites for the (A)[B]2O4 spinel ferrite samples CoxNi0.7-xFe2.3O4 (0.0≤x≤0.3), CrxNi0.7Fe2.3-xO4 (0.0≤x≤0.3) and Fe3O4. We suggest that the differential UV-vis absorption spectra should be accepted as a general analysis method for determining electron transition energies between anions and cations.

  18. Interpretation of unexpected behavior of infrared absorption spectra of ScF3 beyond the quasiharmonic approximation

    NASA Astrophysics Data System (ADS)

    Piskunov, Sergei; Žguns, Pjotrs A.; Bocharov, Dmitry; Kuzmin, Alexei; Purans, Juris; Kalinko, Aleksandr; Evarestov, Robert A.; Ali, Shehab E.; Rocca, Francesco

    2016-06-01

    Scandium fluoride (ScF3), having cubic ReO3-type structure, has attracted much scientific attention due to its rather strong negative thermal expansion (NTE) in the broad temperature range from 10 to 1100 K. Here we use the results of diffraction and extended x-ray absorption fine-structure (EXAFS) spectroscopy to interpret the influence of NTE on the temperature dependence of infrared absorption spectra of ScF3. Original infrared absorption and EXAFS experiments in a large temperature range are presented and interpreted using ab initio lattice dynamics simulations within and beyond quasiharmonic approximations. We demonstrate that ab initio electronic structure calculations, based on the linear combination of atomic orbitals method with hybrid functionals, are able to reproduce well the experimental values of lattice parameter a0, band gap Eg, and lattice dynamics in ScF3. However, the simulations performed within quasiharmonic approximation fail to reproduce the temperature dependence of two infrared active bands due to the F-Sc-F bending (at 220 cm-1) and Sc-F stretching (at 520 cm-1) modes present in the infrared absorption spectra. To overcome this problem, an approach beyond the quasiharmonic approximation is proposed: It accounts for the negative thermal expansion of the lattice and for fluorine atom displacements due to strong F vibrational motion perpendicular to the cubic axes and allows us to explain qualitatively the temperature behavior of infrared spectra of ScF3.

  19. Electronic Absorption Spectra of Tetrapyrrole-Based Pigments via TD-DFT: A Reduced Orbital Space Study.

    PubMed

    Shrestha, Kushal; Virgil, Kyle A; Jakubikova, Elena

    2016-07-28

    Tetrapyrrole-based pigments play a crucial role in photosynthesis as principal light absorbers in light-harvesting chemical systems. As such, accurate theoretical descriptions of the electronic absorption spectra of these pigments will aid in the proper description and understanding of the overall photophysics of photosynthesis. In this work, time-dependent density functional theory (TD-DFT) at the CAM-B3LYP/6-31G* level of theory is employed to produce the theoretical absorption spectra of several tetrapyrrole-based pigments. However, the application of TD-DFT to large systems with several hundreds of atoms can become computationally prohibitive. Therefore, in this study, TD-DFT calculations with reduced orbital spaces (ROSs) that exclude portions of occupied and virtual orbitals are pursued as a viable, computationally cost-effective alternative to conventional TD-DFT calculations. The effects of reducing orbital space size on theoretical spectra are qualitatively and quantitatively described, and both conventional and ROS results are benchmarked against experimental absorption spectra of various tetrapyrrole-based pigments. The orbital reduction approach is also applied to a large natural pigment assembly that comprises the principal light-absorbing component of the reaction center in purple bacteria. Overall, we find that TD-DFT calculations with proper and judicious orbital space reductions can adequately reproduce conventional, full orbital space, TD-DFT results of all pigments studied in this work. PMID:27392135

  20. Interconfigurational absorption and two-photon excitation spectra of PtCl sub 6 sub 2 minus -containing crystals

    SciTech Connect

    Yoo, Ryong, K.; Keiderling, T.A. )

    1990-10-18

    Low-temperature absorption and two-photon excitation spectra of complexes containing PtCl{sub 6}{sup 2{minus}} are presented and discussed. One-photon absorption spectra with moderately well resolved vibronic structure were obtained for PtCl{sub 6}{sup 2{minus}} in dilute mixed crystals. The data show that a transition to a low-lying interconfigurational state is located at {approximately} 18,000 cm{sup {minus}1} in the spectral frequency region below the first absorption transition previously assigned by others. This transition cannot be unambiguously assigned. If it corresponds to the same excited state responsible for the PtCl{sub 6}{sup 2{minus}} emission spectrum, this would lead to a partial reassignment of the excited states from that of earlier work. Ligand field calculations consistent with such a reassignment are presented. The two-photon excitation (TPE) spectra of the mixed Cs{sub 2}ZrCl{sub 6}:PtCl{sub 6}{sup 2{minus}} and pure K{sub 2}PtCl{sub 6} (at 77 K), measured with an improved spectrometer, show a noticeable improvement in signal-to-noise ratio compared to the previously reported TPE spectra of K{sub 2}PtCl{sub 6} and are assigned to higher energy d-d transitions.

  1. Stratospheric HNO3 measurements from 0.002/cm resolution solar occultation spectra and improved spectroscopic line parameters in the 5.8-micron region

    NASA Technical Reports Server (NTRS)

    Goldman, A.; Murcray, F. J.; Blatherwick, R. D.; Kosters, J. J.; Murcray, D. G.; Rinsland, C. P.; Flaud, J.-M.; Camy-Peyret, C.

    1992-01-01

    Very-high-resolution FWHM solar-occultation spectra are investigated with a balloon-borne interferometer using revised spectroscopic line parameters for HNO3, O3, and H2O. The O3 and H2O data are evaluated to determine their capacity for interference in the HNO3 line which is studied in the nu sub 2 band at 5.8 microns. The line parameters developed with the stratospheric data are compared to data based on a HITRAN compilation as well as laboratory spectra with a 0.002/cm resolution. The line list is calculated and shown to include J and Ka transitions which improve the line parameters for HNO3 by accounting for the weaker absorption features in the stratospheric spectra. The stratospheric HNO3 profile developed analytically is compared to those based on reported measurements, and the one developed with the stratospheric solar spectra is found to be consistent with the measurements and confirm inherent measurement biases.

  2. Stratospheric HNO3 measurements from 0.002/cm resolution solar occultation spectra and improved spectroscopic line parameters in the 5.8-micron region

    NASA Astrophysics Data System (ADS)

    Goldman, A.; Murcray, F. J.; Blatherwick, R. D.; Kosters, J. J.; Murcray, D. G.; Rinsland, C. P.; Flaud, J.-M.; Camy-Peyret, C.

    1992-02-01

    Very-high-resolution FWHM solar-occultation spectra are investigated with a balloon-borne interferometer using revised spectroscopic line parameters for HNO3, O3, and H2O. The O3 and H2O data are evaluated to determine their capacity for interference in the HNO3 line which is studied in the nu sub 2 band at 5.8 microns. The line parameters developed with the stratospheric data are compared to data based on a HITRAN compilation as well as laboratory spectra with a 0.002/cm resolution. The line list is calculated and shown to include J and Ka transitions which improve the line parameters for HNO3 by accounting for the weaker absorption features in the stratospheric spectra. The stratospheric HNO3 profile developed analytically is compared to those based on reported measurements, and the one developed with the stratospheric solar spectra is found to be consistent with the measurements and confirm inherent measurement biases.

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

    SciTech Connect

    Jaenes, Juergen; Laur, Sven; Kolka, Indrek

    2008-12-05

    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.

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

    SciTech Connect

    Bar-Shalon, A.; Oreg, J. . Nuclear Research Center-Negev); Goldstein, W.H. )

    1991-01-11

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

  5. Variability, absorption features, and parent body searches in "spectrally featureless" meteorite reflectance spectra: Case study - Tagish Lake

    NASA Astrophysics Data System (ADS)

    Izawa, M. R. M.; Craig, M. A.; Applin, D. M.; Sanchez, J. A.; Reddy, V.; Le Corre, L.; Mann, P.; Cloutis, E. A.

    2015-07-01

    Reflectance spectra of many asteroids and other Solar System bodies are commonly reported as "featureless". Here, we show that weak but consistently detectable absorption bands are observable in 200-2500 nm spectra of the Tagish Lake meteorite, a likely compositional and spectral analogue for low-albedo, "spectrally-featureless" asteroids. Tagish Lake presents a rare opportunity to study multiple lithologies within a single meteorite. Reflectance spectra of Tagish Lake display significant variation between different lithologies. The spectral variations are due in part to mineralogical variations between different Tagish Lake lithologies. Ultraviolet reflectance spectra (200-400 nm), few of which have been reported in the literature to date, reveal albedo and spectral ratio variations as a function of mineralogy. Similarly visible-near infrared reflectance spectra reveal variations in albedo, spectral slope, and the presence of weak absorption features that persist across different lithologies and can be attributed to various phases present in Tagish Lake. These observations demonstrate that significant spectral variability may exist between different lithologies of Tagish Lake, which may affect the interpretation of potential source body spectra. It is also important to consider the spectral variability within the meteorite before excluding compositional links between possible parent bodies in the main belt and Tagish Lake. Tagish Lake materials may also be spectral-compositional analogues for materials on the surfaces of other dark asteroids, including some that are targets of upcoming spacecraft missions. Tagish Lake has been proposed as a spectral match for 'ultra-primitive' D or P-type asteroids, and the variability reported here may be reflected in spatially or rotationally-resolved spectra of possible Tagish Lake parent bodies and source objects in the Near-Earth Asteroid population. A search for objects with spectra similar to Tagish Lake has been carried

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

    SciTech Connect

    Tilton, Evan M.; Shull, J. Michael E-mail: michael.shull@colorado.edu

    2013-09-01

    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.

  7. Low-density laboratory spectra near the He ii λ304 line

    NASA Astrophysics Data System (ADS)

    Träbert, Elmar; Beiersdorfer, Peter; Brickhouse, Nancy S.; Golub, Leon

    2016-02-01

    Aims: To interpret the EUV spectra of the solar corona, one hopes for laboratory data of specific chemical elements obtained under coronal conditions. Methods: EUV spectra of He, C, N, O, F, Ne, S, Ar, Fe, and Ni in a 40 Å wide wavelength interval near λ304 were excited in an electron beam ion trap. Results: We observe some two hundred lines about half of which are not yet identified and included in spectral models. Conclusions: Our data provide a check on the atomic data bases underlying the spectral models that are used to interpret solar corona data. However, a multitude of mostly weak additional lines taken together represent a flux that is comparable to that of various primary lines. Research supported by the Solar and Heliospherical Physics Program of the National Aeronautics and Space Administration under award NNH10AN31I.

  8. On the line profiles in the spectra of the zodiacal light.

    NASA Astrophysics Data System (ADS)

    Clarke, D.; Matthews, S. A.; Mundell, C. G.; Weir, A. S.

    1996-04-01

    The model proposed by Hong (1985) describing the surface brightness variation with elongation of the Zodiacal Light has been applied to predict the spectral line profiles produced by Doppler effects associated with scattering from interplanetary dust for the simple case of prograde Keplerian orbits. Over the greater elongation range, the predictions are substantially the same as for previous models but with shallower line depths and more pronounced asymmetries. At elongations ~30deg and less, however, Hong's mixture of phase angle scattering functions predicts bifurcation of the lines so providing an alternative explanation to the two dust stream model of Beavers et al. (1980) proposed as the interpretation of their spectra of the F corona. The work also highlights a general problem of using radial velocity correlation masks for investigations of Zodiacal Light spectra.

  9. [A Method to Estimate Metal Abundance from Stellar Spectra Using Ca Line Index].

    PubMed

    Pan, Jing-chang; Luo, A-li; Li, Xiang-ru; Wei, Peng

    2015-09-01

    This paper presents a method to estimate stellar metallicity based on BP neural network and Ca line index. This method trains a BP ANN model from SDSS/SEGUE stellar spectra and parameters provided by SSPP. The values of Teff and the line index of Ca lines are the input of network while the [Fe/H] values are the oputput of the network. A set of samples are resampled from the set of all and then a network model is trained. The network can be used to predict the stellar metallicity from low-resolution spsectra. The experiment shows that the proposed method can accurately and effectively measure the [Fe/H] from the stellar spectra. PMID:26669184

  10. The Milky Way's Hot Gas Kinematics: Signatures in Current and Future OVII Absorption Line Observations

    NASA Astrophysics Data System (ADS)

    Miller, Matthew J.; Hodges-Kluck, Edmund J.; Bregman, Joel N.

    2016-02-01

    Detections of z ≈ 0 oxygen absorption and emission lines indicate the Milky Way hosts a hot (˜ {10}6 K), low-density plasma extending ≳ 50 {{kpc}} into the Mily Way’s halo. Current X-ray telescopes cannot resolve the line profiles, but the variation of their strengths on the sky constrains the radial gas distribution. Interpreting the O vii Kα absorption line strengths has several complications, including optical depth and line of sight velocity effects. Here, we present model absorption line profiles accounting for both of these effects to show the lines can exhibit asymmetric structures and be broader than the intrinsic Doppler width. The line profiles encode the hot gas rotation curve, the net inflow or outflow of hot gas, and the hot gas angular momentum profile. We show how line of sight velocity effects impact the conversion between equivalent width and the column density, and provide modified curves of growth accounting for these effects. As an example, we analyze the LMC sight line pulsar dispersion measure and O vii equivalent width to show the average gas metallicity is ≳ 0.6{Z}⊙ and b ≳ 100 km s-1. Determining these properties offers valuable insights into the dynamical state of the Milky Way’s hot gas, and improves the line strength interpretation. We discuss future strategies to observe these effects with an instrument that has a spectral resolution of about 3000, a goal that is technically possible today.

  11. Superresolution and other mathematical techniques for quantitative analysis of infrared absorption and emission spectra of gases

    NASA Astrophysics Data System (ADS)

    Davies, Nicholas M.; Lettington, Alan H.; Hilton, Moira

    1997-05-01

    Fourier transform IR (FTIR) spectroscopy has become a powerful analytical tool for the detection and measurement of atmospheric pollutant gases. This work describes the application of concentration analysis techniques to data recorded with a versatile FTIR spectroscopy system, developed at the University of Reading PHysics Department. Spectra were recorded at three separate sites, each possessing a distinct source of atmospheric pollution gases. The two sites monitored in the active mode were a traffic congested town center at rush hour and a dairy farm cow shed. The site monitored passively contained three 5 m high methane burners. The analysis techniques have been designed to provide rapid and accurate analysis of the spectrometer data, without the need for high computing power, thus making analysis possible in the field using a laptop PC. In an attempt to enhance the resolution of the spectral data, and therefore resolve overlapping spectral lines, a super- resolution algorithm has been tested on part of the recorded data. The results of applying the algorithm has been tested on part of the recorded data. The results of applying the algorithm, predominantly an image processing technique, are shown and improvements to the algorithm are discussed. Results from the urban and agricultural sites show that CO, CH4, and NH3 can be measured to a ppm level with a maximum uncertainly of 8 percent.

  12. Ca II AND Na I QUASAR ABSORPTION-LINE SYSTEMS IN AN EMISSION-SELECTED SAMPLE OF SDSS DR7 GALAXY/QUASAR PROJECTIONS. I. SAMPLE SELECTION

    SciTech Connect

    Cherinka, B.; Schulte-Ladbeck, R. E.

    2011-10-15

    The aim of this project is to identify low-redshift host galaxies of quasar absorption-line systems by selecting galaxies that are seen in projection onto quasar sightlines. To this end, we use the Seventh Data Release of the Sloan Digital Sky Survey to construct a parent sample of 97,489 galaxy/quasar projections at impact parameters of up to 100 kpc to the foreground galaxy. We then search the quasar spectra for absorption-line systems of Ca II and Na I within {+-}500 km s{sup -1} of the galaxy's velocity. This yields 92 Ca II and 16 Na I absorption systems. We find that most of the Ca II and Na I systems are sightlines through the Galactic disk, through high-velocity cloud complexes in our halo, or Virgo Cluster sightlines. Placing constraints on the absorption line rest equivalent width significance ({>=}3.0{sigma}), the local standard of rest velocity along the sightline ({>=}345 km s{sup -1}), and the ratio of the impact parameter to the galaxy optical radius ({<=}5.0), we identify four absorption-line systems that are associated with low-redshift galaxies at high confidence, consisting of two Ca II systems (one of which also shows Na I) and two Na I systems. These four systems arise in blue, {approx}L*{sub r} galaxies. Tables of the 108 absorption systems are provided to facilitate future follow-up.

  13. Intermolecular interaction as the origin of red shifts in absorption spectra of zinc-phthalocyanine from first-principles.

    PubMed

    Yanagisawa, Susumu; Yasuda, Taiga; Inagaki, Kouji; Morikawa, Yoshitada; Manseki, Kazuhiro; Yanagida, Shozo

    2013-11-01

    We investigate electronic origins of a redshift in absorption spectra of a dimerized zinc phthalocyanine molecule (ZnPc) by means of hybrid density functional theoretical calculations. In terms of the molecular orbital (MO) picture, the dimerization splits energy levels of frontier MOs such as the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the constituent molecules. Consequently, the absorption wavelength seems to become longer than the monomer as the overlap between the monomers becomes larger. However, for a ZnPc dimer configuration with its cofacially stacked monomer arrangement, the calculated absorption spectra within the time-dependent density functional theory indicates no redshift but blueshift in the Q-band absorption spectrum, i.e., a typical H-aggregate. The origin of the apparently contradictory result is elucidated by the conventional description of the interaction between monomer transition dipoles in molecular dimers [Kasha, M. Radiat. Res. 1963, 20, 55]. The redshift is caused by an interaction between the two head-to-tail transition dipoles of the monomers, while the side-by-side arranged transition dipoles result in a blueshift. By tuning the dipole-dipole interaction based on the electronic natures of the HOMO and the LUMO, we describe a slipped-stacked ZnPc dimer configuration in which the Q-band absorption wavelength increases by as large as 144 nm relative to the monomer Q-band. PMID:24106753

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    PubMed Central

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

    2016-01-01

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

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

    PubMed

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

    2016-01-01

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

  17. Understanding the symmetric line shape in the 17O MAS spectra for hexagonal ice

    NASA Astrophysics Data System (ADS)

    Yamada, Kazuhiko; Oki, Shinobu; Deguchi, Kenzo; Shimizu, Tadashi

    2016-06-01

    Solid-state 17O Magic-Angle Spinning (MAS) nuclear magnetic resonance (NMR) spectra of 17O-enriched hexagonal ice, [17O]-Ih, between 173 and 253 K were presented. Marked changes in the line shape were clearly observed, indicating water molecular reorientation in the crystal structure. At 173 K, molecular motions were considered to be frozen and analysis of the 1D MAS spectrum yielded the following parameters: quadrupole coupling constant (CQ) = 6.6 ± 0.2 MHz and asymmetry parameter (ηQ) = 0.95 ± 0.05. At 232 K and above, contrary to the conventional explanation, pseudo-symmetric line shapes appeared in the 17O MAS NMR spectra arising from the contribution of second-order quadrupole interactions. As a chemical exchange model to describe these isotropic 17O MAS NMR spectra, a modified Ratcliffe model, which consider the effects of proton disorder, was proposed, and the resulting theoretical spectra could well reproduce the experimental spectra.

  18. Quasi-random narrow-band model fits to near-infrared low-temperature laboratory methane spectra and derived exponential-sum absorption coefficients

    NASA Technical Reports Server (NTRS)

    Baines, Kevin H.; West, Robert A.; Giver, Lawrence P.; Moreno, Fernando

    1993-01-01

    Near-infrared 10/cm resolution spectra of methane obtained at various temperatures, pressures, and abundances are fit to a quasi-random narrow-band model. Exponential-sum absorption coefficients for three temperatures (112, 188, and 295 K), and 20 pressures from 0.0001 to 5.6 bars, applicable to the cold environments of the major planets, are then derived from the band model for the 230 wavelengths measured from 1.6 to 2.5 microns. RMS deviations between the laboratory and the exponential-sum synthetic transmissions are reported for the best fitting 50 wavelengths. Deviations relevant to broadband, 1-percent spectral resolution observations are also presented. The validity of exponential-sum coefficients derived from broadband (10/cm) transmission data is demonstrated via direct comparison with line-by-line calculations. The complete atlas of coefficients is available from the Planetary Data System-Planetary Atmospheres Discipline Node.

  19. Time-resolved K-shell line spectra measurement of z-pinch plasmas

    NASA Astrophysics Data System (ADS)

    Yang, Qingguo; Zhou, Shaotong; Chen, Guanhua; Huang, Xianbin; Cai, Hongchun; Li, Zeren

    2013-11-01

    A Johann-type crystal spectrometer integrated with x-ray PIN diodes has been developed for measuring the time-resolved K-shell line spectra of the imploding Al wire array. In this spectrometer, the PIN diodes are mounted on the Rowland circle of the cylindrical bent crystal with an appointed position to collect the line emissions from z-pinch plasmas. The spectrometer with four typical channels, which are keyed to the Al ion hydrogen-like (Hα, 0.7171 nm and Hβ, 0.6052 nm) and helium-like (Heα, 0.7757 nm and Heβ, 0.6634 nm) resonance lines is designed and fabricated. Example data from the experiment on the Yang accelerator are shown and the time-dependent electron temperature is determined from the signal ratios of Al ion Hα line to Heα line using the collisional and radiative model.

  20. Terbium chloride--aluminum chloride vapor system. I. Absorption and excitation spectra

    SciTech Connect

    Caird, J.A.; Carnall, W.T.; Hessler, J.P.; Williams, C.W.

    1981-01-15

    The absorption spectrum of the vapor complex formed at elevated temperatures between TbCl/sub 3/ and AlCl/sub 3/ has been measured in the region 20 000--50 000 cm/sup -1/. Oscillator strengths of f--f absorption bands below 37 000 cm/sup -1/ were determined. Strong absorption due to opposite parity 4f/sup 7/5d states was observed in the 37 000 to 50 000 cm/sup -1/ region with a peak molar absorptivity of approximately 500 l/mol cm. Significant additional absorption attributed to a molecular complex was also observed in this region. By measuring the excitation spectrum it was found that the molecular absorption does not appear to lead to fluorescence of the /sup 5/D/sub 4/ state. In contrast, absorption by the 4f/sup 7/5d states does result in strong /sup 5/D/sub 4/ fluorescence.