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Sample records for absorption spectra analysis

  1. Uncertainty analysis for absorption and first-derivative EPR spectra.

    PubMed

    Tseitlin, Mark; Eaton, Sandra S; Eaton, Gareth R

    2012-11-01

    Electron paramagnetic resonance (EPR) experimental techniques produce absorption or first-derivative spectra. Uncertainty analysis provides the basis for comparison of spectra obtained by different methods. In this study it was used to derive analytical equations to relate uncertainties for integrated intensity and line widths obtained from absorption or first-derivative spectra to the signal-to-noise ratio (SNR), with the assumption of white noise. Predicted uncertainties for integrated intensities and line widths are in good agreement with Monte Carlo calculations for Lorentzian and Gaussian lineshapes. Conservative low-pass filtering changes the noise spectrum, which can be modeled in the Monte Carlo simulations. When noise is close to white, the analytical equations provide useful estimates of uncertainties. For example, for a Lorentzian line with white noise, the uncertainty in the number of spins obtained from the first-derivative spectrum is 2.6 times greater than from the absorption spectrum at the same SNR. Uncertainties in line widths obtained from absorption and first-derivative spectra are similar. The impact of integration or differentiation on SNR and on uncertainties in fitting parameters was analyzed. Although integration of the first-derivative spectrum improves the apparent smoothness of the spectrum, it also changes the frequency distribution of the noise. If the lineshape of the signal is known, the integrated intensity can be determined more accurately by fitting the first-derivative spectrum than by first integrating and then fitting the absorption spectrum. Uncertainties in integrated intensities and line widths are less when the parameters are determined from the original data than from spectra that have been either integrated or differentiated.

  2. 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.

  3. Analysis of time evolution of fluorescence and absorption spectra of camptothecins

    NASA Astrophysics Data System (ADS)

    Ziomkowska, Blanka; Kruszewski, Stefan; Siuda, Ryszard; Cyrankiewicz, Michal

    2004-08-01

    Camptothecins, fluorescent anticancer agents, exhibit at neutral and physiological pH changes over time in absorption and fluorescence spectra. Analysis of these changes is a subject of this paper. Factor analysis of fluorescence spectra enabled to determine the kinetics of hydrolysis of camptothecin, i.e. the rate of converting of biologically active lactone form into inactive carboxylate. Obtained results are compared with HPLC data.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    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.

  5. 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.

  6. 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.

  7. Qualitative Analysis of Liquid Hydrocarbon Mixtures by Absorption Spectra of Their Vapors

    NASA Astrophysics Data System (ADS)

    Vesnin, V. L.

    2016-11-01

    Absorption spectra of saturated vapors of hydrocarbons and their mixtures were studied near their first overtones. Absorption spectra of hydrocarbons in the liquid and vapor states were compared. The ability to analyze qualitatively the compositions of liquid hydrocarbon mixtures using absorption spectra of their vapors was demonstrated. Indirect evidence suggested that the nonlinear absorption as a function of concentration that was seen in liquid hydrocarbon mixtures was negligible in their vapors.

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

    NASA Astrophysics Data System (ADS)

    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.

  9. [Absorption spectra analysis in the degradation process of quinoline in aqueous solution by VUV lights].

    PubMed

    Zhu, Da-Zhang; Sun, Dong-Mei; Wang, Shi-Long; Sun, Xiao-Yu; Ni, Ya-Ming

    2009-07-01

    The feasibility of monitoring the degradation progress on line by UV-Vis absorption spectra in the degradation process of quinoline in aqueous solution using the low-pressure quartz mercury lamp as vacuum ultraviolet source was evaluated by the monitoring and protracting of the UV-Vis absorption spectra at different time. The characteristic and mechanism of the change in the UV absorption spectra were analyzed by monitoring the concentration of the substrate, COD (chemical oxygen demand), TOC (total organic carbon) and pH value of the solution. It was showed that quinoline occurs in different forms under different pH conditions and consequently causes different UV-Vis absorption spectra due to the N atom in the pyridine ring. In the degradation progress, the UV-Vis absorption spectra were impacted by the degradation rate of the substrates, the production rate of the intermediates and the pH value of the solution. Proton acids were produced as intermediates and make quinoline occur in the form of its conjugated acid. When the increase in the absorption produced by the protonation was equal to the decrease induced by the degradation, the curve of the absorption at 313 nm, the characteristic absorption peak of quinoline, showed a flat in the duration of 1-3 min and then decayed continuously. In addition, the absorption at 254 nm reached a maximum at 5 min and then decayed continuously to nearly 0 at 30 min, when the absorption of the system only occurred in the region of wavelength shorter than 220 nm, indicating that the substrate was degraded completely. The research revealed that UV absorption spectra could be used to monitor the degradation process of quinoline in aqueous solution by VUV lights.

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

    NASA Astrophysics Data System (ADS)

    Penfold, T. J.; Tavernelli, I.; Milne, C. J.; Reinhard, M.; Nahhas, A. El; Abela, R.; Rothlisberger, U.; Chergui, M.

    2013-01-01

    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)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.

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

    PubMed

    Penfold, T J; Tavernelli, I; Milne, C J; Reinhard, M; El Nahhas, A; Abela, R; Rothlisberger, U; 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)(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.

  12. 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.

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

    USDA-ARS?s Scientific Manuscript database

    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. 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

    2015-07-10

    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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. On optimization of absorption-dispersion spectra

    NASA Astrophysics Data System (ADS)

    Hawranek, J. P.; Grabska, J.; Beć, K. B.

    2016-12-01

    A modified approach to the analysis of spectra of the complex electric permittivity of liquids in the Infrared region is presented. These spectra are derived from experimental spectra of the complex refractive index. Subsequently they are used to determine important secondary quantities, e.g. spectra of complex molecular polarizabilities and an integral property - the molar vibrational polarization. The accuracy of these quantities depends essentially on the accuracy of both components of the complex electric permittivity spectrum. In the proposed procedure, the spectra of the complex electric permittivity are approximated using the Classical Damped Harmonic Oscillator (CDHO) model for the description of individual bandshapes. The CDHO model defines both the real and imaginary part of the complex permittivity. The fitting procedure includes a simultaneous optimization of both the real and imaginary parts of the complex permittivity spectrum. A comparison of absorption-only curve fitting and the novel absorption-dispersion double curve fitting is presented; advantages of the new approach in accuracy, reliability and convergence time are pointed out. Due to the complexity of the problem, the choice was restricted to non-gradient methods of optimization. The performance of several gradientless algorithms was tested. Among numerous procedures the Powell General Least Squares Method Without Derivatives was found to be the most efficient. The reliability of obtained results of the band separatiovn process was tested on several simulated spectra of increasing complexity. The applicability of the developed approach to the analysis of exemplary experimental data was evaluated and discussed.

  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.

  1. Franck-Condon analysis of the S0 --> T1 absorption and phosphorescence spectra of biphenyl and bridged derivatives

    NASA Astrophysics Data System (ADS)

    Negri, Fabrizia; Zgierski, Marek Z.

    1992-11-01

    The equilibrium geometry and the vibrational force field of the ground and the lowest triplet electronic states of biphenyl and three bridged derivatives-biphenylene, fluorene and phenanthrene-are computed by using an updated version of the QCFF/PI (Quantum Chemical Force Field/π electron) Hamiltonian. The displacement parameters between T1 and S0 are obtained and used to model the S0→T1 absorption and the phosphorescence spectra. The calculated Franck-Condon envelopes are found to be in excellent agreement with the vibrational structure of the observed spectra. The common features of the phosphorescence spectra of biphenyl and fluorene are related to the same orbital nature of the lowest triplet state. The observed asymmetry between the phosphorescence and singlet-triplet absorption spectra of biphenyl is reproduced when the twisted equilibrium geometry of S0 is considered. It is shown that evidence of the nonplanarity of the ground state of biphenyl is manifested by the lower intensity of the band observed in the phosphorescence at 747 cm-1 with respect to the intensity of the same band in fluorene. The increased vibrational activity calculated in the lower frequency region for biphenylene and phenanthrene agrees with the observed spectra and reflects the different orbital nature of the lowest triplet state of the two strongly perturbed bridged derivatives with respect to biphenyl and fluorene. From the analysis of the computed vibrational frequencies, it is suggested that the false origin of the symmetry forbidden phosphorescence of biphenylene is due to the lowest out-of-plane mode of au symmetry.

  2. Practical Qβ analysis method based on the Fermi-Kurie plot for spectra measured with total absorption BGO detector

    NASA Astrophysics Data System (ADS)

    Hayashi, Hiroaki; Kojima, Yasuaki; Shibata, Michihiro; Kawade, Kiyoshi

    2010-01-01

    A practical method based on Fermi-Kurie plots was newly proposed in order to analyze β-decay energy ( Qβ) measured with a total absorption BGO detector. The detector has large efficiencies; all β-rays and subsequent γ-rays can be absorbed simultaneously, and the endpoint energy of the spectrum shows the Qβ. In the spectrum, different β-rays having maximum endpoint energies and forbiddenness are superimposed. To apply this method to the measured spectra, in addition to a simplified decay scheme that has a one-component β-ray fed to a pseudo-level Eγ, a mixed transition of the allowed and the unique-type first-forbidden transitions with a ratio of α was newly taken into account. Using the theoretical β-ray spectra, we verified that the Qβ can be deduced without information about the decay scheme, and described the dependences of the derived Qβ on Eγ and α. We also checked the reliability of this method by analyzing the spectra of fission products of 91-94Rb, 139-143Cs, 142Ba and 142,144La, which had well-determined Qβ up to 11 MeV. Consequently, we proposed that this method was applicable for analyzing spectra with a systematic uncertainty of 60 keV, when the analyzing regions were limited to about 1 MeV below the Qβ. Then, this method was also applied for re-analysis of the Qβ of neutron-rich rare earth nuclei.

  3. Stark effect spectrophone for continuous absorption spectra monitoring. [a technique for gas analysis

    NASA Technical Reports Server (NTRS)

    Kavaya, M. J. (Inventor)

    1981-01-01

    A Stark effect spectrophone using a pulsed or continuous wave laser having a beam with one or more absorption lines of a constituent of an unknown gas is described. The laser beam is directed through windows of a closed cell while the unknown gas to be modified flows continuously through the cell between electric field plates disposed in the cell on opposite sides of the beam path through the cell. When the beam is pulsed, energy absorbed by the gas increases at each point along the beam path according to the spectral lines of the constituents of the gas for the particular field strengths at those points. The pressure measurement at each point during each pulse of energy yields a plot of absorption as a function of electric field for simultaneous detection of the gas constituents. Provision for signal averaging and modulation is included.

  4. 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

  5. Assignment and rotational analysis of new absorption bands of carbon dioxide isotopologues in Venus spectra

    NASA Astrophysics Data System (ADS)

    Robert, S.; Borkov, Yu. G.; Vander Auwera, J.; Drummond, R.; Mahieux, A.; Wilquet, V.; Vandaele, A. C.; Perevalov, V. I.; Tashkun, S. A.; Bertaux, J. L.

    2013-01-01

    We present absorption bands of carbon dioxide isotopologues, detected by the Solar Occultation for the Infrared Range (SOIR) instrument on board the Venus Express Satellite. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter (AOTF) for order selection. It performs solar occultation measurements in the Venus atmosphere in the IR region (2.2-4.3 μm), at a resolution of 0.12-0.18 cm-1. The wavelength range probed by SOIR allows a detailed chemical inventory of the Venus atmosphere above the cloud layer (65-150 km) to be made with emphasis on the vertical distributions of gases. Thanks to the SOIR spectral resolution, a new CO2 absorption band was identified: the 21101-01101 band of 16O12C18O with R branch up to J=31. Two other previously reported bands were observed dispelling any doubts about their identifications: the 20001-00001 band of 16O13C18O [Villanueva G, et al. J Quant Spectrosc Radiat Transfer 2008;109:883-894] and the 01111-00001 band of 16O12C18O [Villanueva G, et al. J Quant Spectrosc Radiat Transfer 2008;109:883-894 and Wilquet V, et al. J Quant Spectrosc Radiat Transfer 2008;109:895-905]. These bands were analyzed, and spectroscopic constants characterizing them were obtained. The rotational assignment of the 20001-00001 band was corrected. The present measurements are compared with data available in the HITRAN database.

  6. 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.

  7. Artificial intelligence applied to the automatic analysis of absorption spectra. Objective measurement of the fine structure constant

    NASA Astrophysics Data System (ADS)

    Bainbridge, Matthew B.; Webb, John K.

    2017-06-01

    A new and automated method is presented for the analysis of high-resolution absorption spectra. Three established numerical methods are unified into one `artificial intelligence' process: a genetic algorithm (Genetic Voigt Profile FIT, gvpfit); non-linear least-squares with parameter constraints (vpfit); and Bayesian model averaging (BMA). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. gvpfit is also motivated by the importance of obtaining a large statistical sample of measurements of Δα/α. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. In contrast to previous methodologies, we use BMA to derive results using a large set of models and show that this procedure is more robust than a human picking a single preferred model since BMA avoids the systematic uncertainties associated with model choice. Numerical simulations provide stringent tests of the whole process and we show using both real and simulated spectra that the unified automated fitting procedure out-performs a human interactive analysis. The method should be invaluable in the context of future instrumentation like ESPRESSO on the VLT and indeed future ELTs. We apply the method to the zabs = 1.8389 absorber towards the zem = 2.145 quasar J110325-264515. The derived constraint of Δα/α = 3.3 ± 2.9 × 10-6 is consistent with no variation and also consistent with the tentative spatial variation reported in Webb et al. and King et al.

  8. Artificial intelligence applied to the automatic analysis of absorption spectra. Objective measurement of the fine structure constant.

    NASA Astrophysics Data System (ADS)

    Bainbridge, Matthew B.; Webb, John K.

    2017-01-01

    A new and automated method is presented for the analysis of high-resolution absorption spectra. Three established numerical methods are unified into one "artificial intelligence" process: a genetic algorithm (GVPFIT); non-linear least-squares with parameter constraints (VPFIT); and Bayesian Model Averaging (BMA). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. GVPFIT is also motivated by the importance of obtaining a large statistical sample of measurements of Δα/α. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. In contrast to previous methodologies, we use BMA to derive results using a large set of models and show that this procedure is more robust than a human picking a single preferred model since BMA avoids the systematic uncertainties associated with model choice. Numerical simulations provide stringent tests of the whole process and we show using both real and simulated spectra that the unified automated fitting procedure out-performs a human interactive analysis. The method should be invaluable in the context of future instrumentation like ESPRESSO on the VLT and indeed future ELTs. We apply the method to the zabs = 1.8389 absorber towards the zem = 2.145 quasar J110325-264515. The derived constraint of Δα/α = 3.3 ± 2.9 × 10-6 is consistent with no variation and also consistent with the tentative spatial variation reported in Webb et al. (2011) and King et al. (2012).

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  10. Modal-field spectra analysis of pump absorption efficiency in double-clad rare-earth doped fibers (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Koška, Pavel; Doya, Valérie; Peterka, Pavel

    2017-03-01

    High-power fiber lasers became important devices in many industrial and health care fields. The key for high-power operation of fiber lasers is the double-clad fiber technology transforming lower-brightness pumps into high-brightness laser beams. Efficient pump absorption in the active core of the double-clad fiber is crucial for reliable and economic operation of high power fiber lasers. In our recent work we extensively studied the dependence of the pump absorption efficiency on bending and twisting of the fiber. For the first time we theoretically predicted and later experimentally demonstrated significant enhancement of pump absorption efficiency by simultaneous bending and twisting of the double-clad fiber. In this contribution we provide extension of our previous theoretical studies using beam propagation model incorporating laser rate equations. The effect of bending and twisting on signal amplification in the double-clad fiber is analyzed for different input signal powers, and moreover, pump field modal spectra are evaluated. The results show that in correspondence with pump absorption efficiency the gain of the amplifier is enhanced under the conditions of simultaneously bent and twisted fiber. The key to understand the effect of bending and twisting on pump absorption efficiency consists in modal spectra of pump field propagating in the first clad of the double clad fiber. Three cases of straight, bent only, and simultaneously bent and twisted fiber are compared. The comparison shows that bending causes increase of the spectral range of propagating modes, but does not bring about mode-mixing. Substantial mode-mixing is established only in simultaneously bent and twisted fiber.

  11. Analysis of absorption spectra of purple bacterial reaction centers in the near infrared region by higher order derivative spectroscopy.

    PubMed

    Mikhailyuk, I K; Knox, P P; Paschenko, V Z; Razjivin, A P; Lokstein, H

    2006-06-20

    Reaction centers (RCs) of purple bacteria are uniquely suited objects to study the mechanisms of the photosynthetic conversion of light energy into chemical energy. A recently introduced method of higher order derivative spectroscopy [I.K. Mikhailyuk, H. Lokstein, A.P. Razjivin, A method of spectral subband decomposition by simultaneous fitting the initial spectrum and a set of its derivatives, J. Biochem. Biophys. Methods 63 (2005) 10-23] was used to analyze the NIR absorption spectra of RC preparations from Rhodobacter (R.) sphaeroides strain 2R and Blastochloris (B.) viridis strain KH, containing bacteriochlorophyll (BChl) a and b, respectively. Q(y) bands of individual RC porphyrin components (BChls and bacteriopheophytins, BPheo) were identified. The results indicate that the upper exciton level P(y+) of the photo-active BChl dimer in RCs of R. sphaeroides has an absorption maximum of 810nm. The blue shift of a complex integral band at approximately 800nm upon oxidation of the RC is caused primarily by bleaching of P(y+), rather than by an electrochromic shift of the absorption band(s) of the monomeric BChls. Likewise, the disappearance of a band peaking at 842nm upon oxidation of RCs from B. viridis indicates that this band has to be assigned to P(y+). A blue shift of an absorption band at approximately 830nm upon oxidation of RCs of B. viridis is also essentially caused by the disappearance of P(y+), rather than by an electrochromic shift of the absorption bands of monomeric BChls. Absorption maxima of the monomeric BChls, B(B) and B(A) are at 802 and 797nm, respectively, in RCs of R. sphaeroides at room temperature. BPheo co-factors H(B) and H(A) peak at 748 and 758nm, respectively, at room temperature. For B. viridis RCs the spectral positions of H(B) and H(A) were found to be 796 and 816nm, respectively, at room temperature.

  12. Optical absorption spectra of ? in ? (YGG)

    NASA Astrophysics Data System (ADS)

    Binnemans, K.; Görller-Walrand, C.

    1997-02-01

    Optical absorption spectra of trivalent europium in the rare-earth garnet 0953-8984/9/7/025/img3 (YGG) have been recorded between 4600 and 0953-8984/9/7/025/img4 at 77 and at 293 K. A total of 117 crystal-field transitions has been detected in the spectra. The symmetry of the 0953-8984/9/7/025/img5 site is 0953-8984/9/7/025/img6, so a total removal of the crystal-field degeneracy of the 0953-8984/9/7/025/img7 configuration can be expected. The energy level scheme of 0953-8984/9/7/025/img5 in YGG is parametrized in terms of 20 free-ion parameters and nine crystal-field parameters. The crystal field is strong in the garnet host, so J-mixing has to be taken into account for the crystal-field calculation.

  13. Classification and individualization of black ballpoint pen inks using principal component analysis of UV-vis absorption spectra.

    PubMed

    Adam, Craig D; Sherratt, Sarah L; Zholobenko, Vladimir L

    2008-01-15

    The technique of principal component analysis has been applied to the UV-vis spectra of inks obtained from a wide range of black ballpoint pens available in the UK market. Both the pen ink and material extracted from the ink line on paper have been examined. Here, principal component analysis characterised each spectrum within a group through the numerical loadings attached to the first few principal components. Analysis of the spectra from multiple measurements on the same brand of pen showed excellent reproducibility and clear discrimination between inks that was supported by statistical analysis. Indeed it was possible to discriminate between the pen ink and the ink line from all brands examined in this way, suggesting that the solvent extraction process may have an influence on these results. For the complete set of 25 pens, interpretation of the loadings for the first few principal components showed that both the pen inks and the extracted ink lines may be classified in an objective manner and in agreement with the results of parallel thin layer chromatography studies. Within each class almost all inks could be individualised. Further work has shown that principal component analysis may be used to identify a particular ink from a database of reference UV-vis spectra and a strategy for developing this approach is suggested.

  14. Theoretical Analysis on X-ray Absorption Spectra of Ti compounds as Catalysts in Lithium Amide-Imide reactions

    NASA Astrophysics Data System (ADS)

    Tsumuraya, Takao; Shishidou, Tatsuya; Oguchi, Tamio

    2008-03-01

    Solid-state storage is conceptually efficient approach for on-board vehicular hydrogen storage. In this context, light-element materials such as lithium amide LiNH2 and lithium imide Li2NH have been attracted much attention due to their high gravimetric densities of hydrogen. Recently, various transition-metal compounds have been examined with ball-milling technique for exploring catalysts to improve the hydrogen storage and desorption kinetics, and it is found that a small amount (1mol%) of titanium compounds revealed a superior effect in hydrogen desorption reaction LiNH2 + LiH -> Li2NH + H2 [1]. However, these catalysis mechanism and role of Ti in the reaction remain unanswered. Isobe et al. have carried out measurements of X-ray absorption spectroscopy(XAS) at Ti K-edge to see the electronic states of Ti recently [2]. In this paper, we calculate the electronic structure of Ti metal and its compounds, and obtained theoretical spectra to compare with the measured spectra by using first-principles calculations based on the all-electron FLAPW method. We discuss chemical bonding and local geometry of catalytically active states in the reaction. [1] T. Ichikawa, S. Isobe, N. Hanada and H. Fujii, J. of Alloys and Comp. 365, 271 (2004) . [2] S. Isobe, T. Ichikawa, Y. Kojima and H. Fujii, J. of Alloys and Comp. 446-447, 360 (2007).

  15. 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.

  16. Equilibria and absorption spectra of tryptophanase.

    PubMed

    Metzler, C M; Viswanath, R; Metzler, D E

    1991-05-25

    Tryptophanase (tryptophan: indole-lyase) from Escherichia coli has been isolated in the holoenzyme form and its absorption spectra and acid-base chemistry have been reevaluated. Apoenzyme has been prepared by dialysis against sodium phosphate and L-alanine and molar absorptivities of the coenzyme bands have been estimated by readdition of pyridoxal 5'-phosphate. The spectrophotometric titration curve, whose midpoint is at pH 7.6 in 0.1 M potassium phosphate buffers, indicates some degree of cooperativity in dissociation of a pair of protons. Resolution of the computed spectra of individual ionic forms of the enzyme with lognormal distribution curves shows that band shapes are similar to those of model Schiff bases and of aspartate aminotransferase. Using molar areas from the latter we estimated amounts of individual tautomeric species. In addition to ketoenamine and enolimine or covalent adduct the high pH form also appears to contain approximately 18% of a species with a dipolar ionic ring (protonated on the ring nitrogen and with phenolate -O-). We suggest that this may be the catalytically active form of the coenzyme in tryptophanase. The equilibrium between tryptophanase and L-alanine has also been reevaluated.

  17. 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.

  18. Neural Network Solutions to Optical Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Rosenbrock, Conrad

    2012-10-01

    Artificial neural networks have been effective in reducing computation time while achieving remarkable accuracy for a variety of difficult physics problems. Neural networks are trained iteratively by adjusting the size and shape of sums of non-linear functions by varying the function parameters to fit results for complex non-linear systems. For smaller structures, ab initio simulation methods can be used to determine absorption spectra under field perturbations. However, these methods are impractical for larger structures. Designing and training an artificial neural network with simulated data from time-dependent density functional theory may allow time-dependent perturbation effects to be calculated more efficiently. I investigate the design considerations and results of neural network implementations for calculating perturbation-coupled electron oscillations in small molecules.

  19. Multivariate curve resolution analysis for interpretation of dynamic Cu K-edge X-ray absorption spectroscopy spectra for a Cu doped V(2)O(5) lithium battery.

    PubMed

    Conti, Paolo; Zamponi, Silvia; Giorgetti, Marco; Berrettoni, Mario; Smyrl, William H

    2010-05-01

    Vanadium pentoxide materials prepared through sol-gel processes act as excellent intercalation hosts for lithium as well as polyvalent cations. A chemometric approach has been applied to study the X-ray absorption near-edge structure (XANES) evolution during in situ scanning of the Cu(0.1)V(2)O(5) xerogel/Li ions battery. Among the more common techniques, the fixed size windows evolving factor analysis (FSWEFA) permits the number of species involved in the experiment to be determined and the range of existence of each of them. This result, combined with the constraints of the invariance of the total concentration and non-negativity of both concentrations and spectra, enabled us to obtain the spectra of the pure components using a multivariate curve resolution refined by an alternate least squares fitting procedure. This allowed the normalized concentration profile to be understood. This data treatment evidenced the occurrence, for the first time, of three species during the battery charging. This fact finds confirmation by comparison of the pure spectra with the experimental ones. Extended X-ray absorption fine structure (EXAFS) analysis confirms the occurrence of three different chemical environments of Cu during battery charging.

  20. Broadband absorption and reduced scattering spectra of in-vivo skin can be noninvasively determined using δ-P1 approximation based spectral analysis

    PubMed Central

    Hung, Cheng-Hung; Chou, Ting-Chun; Hsu, Chao-Kai; Tseng, Sheng-Hao

    2015-01-01

    Previously, we revealed that a linear gradient line source illumination (LGLSI) geometry could work with advanced diffusion models to recover the sample optical properties at wavelengths where sample absorption and reduced scattering were comparable. In this study, we employed the LGLSI geometry with a broadband light source and utilized the spectral analysis to determine the broadband absorption and scattering spectra of turbid samples in the wavelength range from 650 to 1350 nm. The performance of the LGLSI δ-P1 diffusion model based spectral analysis was evaluated using liquid phantoms, and it was found that the sample optical properties could be properly recovered even at wavelengths above 1000 nm where μs' to μa ratios were in the range between 1 to 20. Finally, we will demonstrate the use of our system for recovering the 650 to 1350 nm absorption and scattering spectra of in-vivo human skin. We expect this system can be applied to study deep vessel dilation induced hemoglobin concentration variation and determine the water and lipid concentrations of in-vivo skin in clinical settings in the future. PMID:25780735

  1. Electronic absorption spectra from first principles

    NASA Astrophysics Data System (ADS)

    Hazra, Anirban

    Methods for simulating electronic absorption spectra of molecules from first principles (i.e., without any experimental input, using quantum mechanics) are developed and compared. The electronic excitation and photoelectron spectra of ethylene are simulated, using the EOM-CCSD method for the electronic structure calculations. The different approaches for simulating spectra are broadly of two types---Frank-Condon (FC) approaches and vibronic coupling approaches. For treating the vibrational motion, the former use the Born-Oppenheimer or single surface approximation while the latter do not. Moreover, in our FC approaches the vibrational Hamiltonian is additively separable along normal mode coordinates, while in vibronic approaches a model Hamiltonian (obtained from ab initio electronic structure theory) provides an intricate coupling between both normal modes and electronic states. A method called vertical FC is proposed, where in accord with the short-time picture of molecular spectroscopy, the approximate excited-state potential energy surface that is used to calculate the electronic spectrum is taken to reproduce the ab initio potential at the ground-state equilibrium geometry. The potential energy surface along normal modes may be treated either in the harmonic approximation or using the full one-dimensional potential. Systems with highly anharmonic potential surfaces can be treated and expensive geometry optimizations are not required, unlike the traditional FC approach. The ultraviolet spectrum of ethylene between 6.2 and 8.7 eV is simulated using vertical FC. While FC approaches for simulation are computationally very efficient, they are not accurate when the underlying approximations are unreasonable. Then, vibronic coupling model Hamiltonians are necessary. Since these Hamiltonians have an analytic form, they are used to map the potential energy surfaces and understand their topology. Spectra are obtained by numerical diagonalization of the Hamiltonians. The

  2. Determination of equilibrium structures of bromothymol blue revealed by using quantum chemistry with an aid of multivariate analysis of electronic absorption spectra.

    PubMed

    Shimada, Toru; Hasegawa, Takeshi

    2017-10-05

    The pH dependent chemical structures of bromothymol blue (BTB), which have long been under controversy, are determined by employing a combined technique of multivariate analysis of electronic absorption spectra and quantum chemistry. Principle component analysis (PCA) of the pH dependent spectra apparently reveals that only two chemical species are adequate to fully account for the color changes, with which the spectral decomposition is readily performed by using augmented alternative least-squares (ALS) regression analysis. The quantity variation by the ALS analysis also reveals the practical acid dissociation constant, pKa'. The determination of pKa' is performed for various ionic strengths, which reveals the thermodynamic acid constant (pKa=7.5) and the number of charge on each chemical species; the yellow form is negatively charged species of -1 and the blue form that of -2. On this chemical information, the quantum chemical calculation is carried out to find that BTB molecules take the pure quinoid form in an acid solution and the quinoid-phenolate form in an alkaline solution. The time-dependent density functional theory (TD-DFT) calculations for the theoretically determined chemical structures account for the peak shift of the electronic spectra. In this manner, the structures of all the chemical species appeared in equilibrium have finally been confirmed. Copyright © 2017 Elsevier B.V. All rights reserved.

  3. Determination of equilibrium structures of bromothymol blue revealed by using quantum chemistry with an aid of multivariate analysis of electronic absorption spectra

    NASA Astrophysics Data System (ADS)

    Shimada, Toru; Hasegawa, Takeshi

    2017-10-01

    The pH dependent chemical structures of bromothymol blue (BTB), which have long been under controversy, are determined by employing a combined technique of multivariate analysis of electronic absorption spectra and quantum chemistry. Principle component analysis (PCA) of the pH dependent spectra apparently reveals that only two chemical species are adequate to fully account for the color changes, with which the spectral decomposition is readily performed by using augmented alternative least-squares (ALS) regression analysis. The quantity variation by the ALS analysis also reveals the practical acid dissociation constant, pKa‧. The determination of pKa‧ is performed for various ionic strengths, which reveals the thermodynamic acid constant (pKa = 7.5) and the number of charge on each chemical species; the yellow form is negatively charged species of - 1 and the blue form that of - 2. On this chemical information, the quantum chemical calculation is carried out to find that BTB molecules take the pure quinoid form in an acid solution and the quinoid-phenolate form in an alkaline solution. The time-dependent density functional theory (TD-DFT) calculations for the theoretically determined chemical structures account for the peak shift of the electronic spectra. In this manner, the structures of all the chemical species appeared in equilibrium have finally been confirmed.

  4. APM Z >=4 QSO Survey: Spectra and Intervening Absorption Systems

    NASA Astrophysics Data System (ADS)

    Storrie-Lombardi, L. J.; McMahon, R. G.; Irwin, M. J.; Hazard, C.

    1996-09-01

    The APM multicolor survey for bright z > 4 objects, covering 2500 deg^2^ of sky to m_r_ ~ 19, resulted in the discovery of 31 quasars with z ~> 4. High signal-to-noise optical spectrophotometry at 5 A resolution has been obtained for the 28 quasars easily accessible from the northern hemisphere. These spectra have been surveyed to create new samples of high-redshift Lyman-limit systems, damped Lyα absorbers, and metal absorption systems (e.g., C IV and Mg II). In this paper we present the spectra, together with line lists of the detected absorption systems. The QSOs display a wide variety of emission- and absorption-line characteristics, with five exhibiting broad absorption lines and one with extremely strong emission lines (BR 2248 - 1242). Eleven candidate damped Lyα absorption systems have been identified covering the redshift range 2.8 <= z <= 4.4 (eight with z > 3.5). An analysis of the measured redshifts of the high-ionization emission lines with the low-ionization lines shows them to be blueshifted by 430 +/- 60 km s^-1^. In a previous paper (by Storrie-Lombardi et al.) we discussed the redshift evolution of the Lyman limit systems cataloged here. In subsequent papers we will discuss the properties of the Lyα forest absorbers and the redshift and column density evolution of the damped Lyα absorbers.

  5. A thermal broadening analysis of absorption spectra of the D1/D2/cytochrome b-559 complex in terms of Gaussian decomposition sub-bands.

    PubMed

    Cattaneo, R; Zucchelli, G; Garlaschi, F M; Finzi, L; Jennings, R C

    1995-11-21

    Absorption spectra of the isolated D1/D2/cytochrome b-559 complex have been measured in the temperature range 80-300 K. All spectra were analyzed in terms of a linear combination of Gaussian bands and the thermal broadening data interpreted in terms of a model in which the spectrum of each pigment site is broadened by (a) a homogeneous component due to linear electron-phonon coupling to a low-frequency protein vibration and (b) an inhomogeneous component associated with stochastic fluctuations at each pigment site. In order to obtain a numerically adequate description of the absorption spectra, a minimum number of five sub-bands is required. Further refinement of this sub-band description was achieved by taking into account published data from hole burning and absorption difference spectroscopy. In this way, both a six sub-band description and a seven sub-band description were generated. In arriving at the seven sub-band description, the original five sub-band wavelength positions were essentially unchanged. Thermal broadening analysis of the seven sub-band description yielded data which displayed the closest correspondence with the literature observations. The wavelength positions of the sub-bands were near 661, 667, 670, and 675 nm, with two bands near 680 and 684 nm. The two almost isoenergetic sub-bands near 680 nm, identified as P680 and pheophytin, have optical reorganization energies around 40 and 16 cm-1, respectively. All other sub-bands, identified as accessory pigments, have optical reorganization energies close to 16 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

  6. Inter-pigment interactions in the peridinin chlorophyll protein studied by global and target analysis of time resolved absorption spectra

    NASA Astrophysics Data System (ADS)

    van Stokkum, Ivo H. M.; Papagiannakis, Emmanouil; Vengris, Mikas; Salverda, Jante M.; Polívka, Tomáš; Zigmantas, Donatas; Larsen, Delmar S.; Lampoura, Stefania S.; Hiller, Roger G.; Grondelle, Rienk van

    2009-02-01

    Inter-pigment interactions define the functioning of light-harvesting protein complexes. To describe the particularly complex molecular dynamics and interactions of peridinin and chlorophyll in the peridinin chlorophyll protein of Amphidinium carterae, we applied global and target analysis to a series of ultrafast transient absorption experiments. We have created and validated a model that consistently describes and characterizes the interactions and evolution of excited and ground-state populations after excitation in all different experiments. The series of energy transfer steps that follow excitation are described by our model of cascading populations and numerous rate constants that correspond to intra-molecular thermal relaxation, fast and slow peridinin-to-chlorophyll energy transfer steps, and chlorophyll excited-state annihilation. By analyzing the spectral response of ground-state peridinins to excited chlorophylls we have identified which specific peridinin molecule is most closely coupled to the chlorophylls. No evidence was found that the intra-molecular charge transfer (ICT) state of peridinin, identified in studies of peridinin in solution, is a separate entity in the protein. The peridinin that exhibited slow peridinin-to-chlorophyll energy transfer was characterized by a difference spectrum free from ICT features, consistent with the importance of coupled ICT and S 1 states for energy transfer.

  7. 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.

  8. 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.

  9. 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.

  10. Excited state absorption spectra of dissolved and aggregated distyrylbenzene: A TD-DFT state and vibronic analysis

    NASA Astrophysics Data System (ADS)

    Oliveira, Eliezer Fernando; Shi, Junqing; Lavarda, Francisco Carlos; Lüer, Larry; Milián-Medina, Begoña; Gierschner, Johannes

    2017-07-01

    A time-dependent density functional theory study is performed to reveal the excited state absorption (ESA) features of distyrylbenzene (DSB), a prototype π-conjugated organic oligomer. Starting with a didactic insight to ESA based on simple molecular orbital and configuration considerations, the performance of various density functional theory functionals is tested to reveal the full vibronic ESA features of DSB at short and long probe delay times.

  11. 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.

  12. Two-photon absorption spectra of carotenoids compounds

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

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

  13. 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.

  14. Analysis of the near-ultraviolet absorption and circular dichroic spectra of parsley plastocyanin for the effects of pH and copper center conformation changes.

    PubMed

    Durell, S R; Gross, E L; Draheim, J E

    1988-11-15

    The absorption and circular dichroic (CD) spectra of parsley plastocyanin (PC) were measured in order to determine the effects of changes in primary amino acid sequence on both the copper center and protein components of the PC molecule. The near-ultraviolet (uv) absorption and CD spectra of parsley PC were found to be qualitatively similar to those of spinach, poplar, and lettuce PC, except for the near-uv CD spectrum of the reduced form at low pH (ca. pH 5.0). The CD spectrum of reduced parsley PC in the 250-265 nm wavelength region changes from positive to negative ellipticity upon reduction of pH, and is characterized by a pKa value of 5.7. This pKa value is the same as that for the protonation of the histidine 87 copper ligand, observed by NMR, and the change in conformation of the copper center. Similar processes are believed to occur in the other PC species at lower pH values. Thus, the pH-dependent perturbations of the near-uv CD spectra of reduced PC are interpreted as due to transitions in the reduced copper center. The increase in the near-uv absorption spectrum of reduced PC can be divided into pH-independent and pH-dependent portions. The pH-independent portion resembles the absorption spectrum of tetrahedral Cu(I) metallothionein, suggesting the presence of Cu(I)-Cys 84 and/or Cu(I)-Met 92 charge transfer transitions in the near-uv absorption spectra of reduced PC. The pH dependence of the absorption spectrum changes and the pH difference absorption spectrum indicate that tyrosine residues may contribute to at least a part of the pH-dependent portion of the absorption increase of reduced PC.

  15. Theoretical analysis of the absorption spectra of organic dyes differing by the conjugation sequence: illusion of negative solvatochromism

    NASA Astrophysics Data System (ADS)

    Manzhos, Sergei; Segawa, Hiroshi; Yamashita, Koichi

    2012-06-01

    Absorption peak maxima of two organic dyes differing by the position of the methine unit differ by 61 nm in dioxane and 128 nm in acetonnitrile. The difference is not reproduced by TDDFT using ab initio or hybrid functionals. TDDFT errors are different between the molecules due to a different albeit small extent of charge transfer, leading to a qualitative failure of TDDFT to predict relative energetics of the dyes. The TDDFT errors in non-polar solvents (such as dioxane) could be corrected based on the approach of Peach et al. (J. Chem. Phy. 128, 044118 (2008)). Here, we focus on the effect on the absorption spectrum of a polar solvent, specifically of the different between the two molecules sign of the solvatochromic shift vs. dioxane. Using the corrrection due to Peach et al, the absolute TDDFT errors can be brought within accetable ranges of 0.2-0.3 eV with the PCM solvent model, and the blue shift vs.dioxane is reporoduced, although both dyes are predicted to exhibit positive solvatochromism. The inclusion of explicit solvent molecules forming hydrogen bonds with the dye did not appreciably change neither TDDFT energies nor the correction term. These results show the importance of a more careful assessment of computational errors in the strategy of computationaly dye design by changing the conjugation order, where they are expected to be more important than in the case of an extension of the size of conjugation, and more so when polar solvents are used.

  16. A catalogue of absorption-line systems in QSO spectra

    NASA Astrophysics Data System (ADS)

    Ryabinkov, A. I.; Kaminker, A. D.; Varshalovich, D. A.

    2003-12-01

    We present a new catalog of absorption-line systems identified in the quasar spectra. It contains data on 821 QSOs and 8558 absorption systems comprising 16 139 absorption lines with measured redshifts in the QSO spectra. The catalog includes absorption-line systems consisting of lines of heavy elements, lines of neutral hydrogen, Lyman limit systems, damped Lyα absorption systems, and broad absorption-line systems. Using the data of the present catalog we also discuss redshift distributions of absorption-line systems. 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/412/707

  17. 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.

  18. Deconvolution of CPM absorption spectra: A new technique

    NASA Astrophysics Data System (ADS)

    Jensen, Pablo

    1990-12-01

    We have found a new technique for deconvoluting absorption spectra obtained with the constant photocurrent method on hydrogenated amorphous silicon samples. We have shown that our method is simpler and more accurate than those used until now. Finally, examples of spectra deconvolution for one sample after various thermal treatments are provided.

  19. Analysis of OBrO, IO, and OIO absorption signature in UV-visible spectra measured at night and at sunrise by stratospheric balloon-borne instruments

    NASA Astrophysics Data System (ADS)

    Berthet, GwenaëL.; Renard, Jean-Baptiste; Chartier, Michel; Pirre, Michel; Robert, Claude

    2003-03-01

    Absorption bands of OBrO, IO, and OIO in the visible region have been investigated in the data of the AMON ("Absorption par les Minoritaires Ozone et Nox") and SALOMON ("Spectroscopie d'Absorption Lunaire pour l'Observation des Minoritaires Ozone et Nox") balloon-borne spectrometers used to obtain measurements in the nighttime stratosphere, since 1992 and 1998 respectively. The absorption features initially detected in AMON residual spectra and attributed to OBrO are also observable in SALOMON data with better accuracy. New estimates of OBrO cross-section amplitudes taking into account recent laboratory measurements are used for the OBrO retrieval. A consequence is that previously published OBrO concentration and mixing ratio values are revised downwards of around 40%. Further tests are performed to assess the consistency of the OBrO detection. No correlation exists between OBrO and NO2 vertical profiles which practically rules out the possibility for the structures ascribed to OBrO absorption to be due to remaining NO2 contributions. It is shown that variability of OBrO quantities at high latitudes obtained from various AMON and SALOMON flights is possibly linked to the chemical processes involving the production of OClO. At midlatitudes, the exceptional and unexpected conditions of the April 28, 1999 SALOMON flight allow us to observe the drop in OBrO concentrations just after sunrise. As expected, if previous studies of stratospheric iodine species are considered, IO and OIO absorption lines are never detected in the residual spectra. The presence of unknown structures in the residual spectra in the IO and OIO absorption regions is obvious and tends to distort the retrievals. The possibility that these remaining features result from a temperature dependence effect or uncertainties of O3 and/or NO2 cross-sections is suggested. Thus, more accurate laboratory measurements and sets of cross-sections for low temperature are needed.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    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.

  2. Light absorption spectra in oligothiophene molecules

    NASA Astrophysics Data System (ADS)

    Gala, Fabrizio; Zollo, Giuseppe

    2017-08-01

    First principles calculations based on density functional theory, density functional perturbation theory and many body perturbation theory are employed to explain the optical absorption peak of a newly synthesized oligo-tiophene molecule that has been considered for bulk-heterojunction solar cells. The GW approach is used to obtain quasiparticle energies as a pre-requisite to solve the Bethe-Salpeter equation for the excitonic Hamiltonian, while density functional perturbation theory, in conjunction with the Huang-Rhys method, have been employed to calculate the vibration assisted ionization spectrum.

  3. 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.

  4. Identification of THz absorption spectra of chemicals using neural networks

    NASA Astrophysics Data System (ADS)

    Shen, Jingling; Jia, Yan; Liang, Meiyan; Chen, Sijia

    2007-09-01

    Absorption spectra in the range from 0.2 to 2.6 THz of chemicals such as illicit drugs and antibiotics obtaining from Terahertz time-domain spectroscopy technique were identified successfully by artificial neural networks. Back Propagation (BP) and Self-Organizing Feature Map (SOM) were investigated to do the identification or classification, respectively. Three-layer BP neural networks were employed to identify absorption spectra of nine illicit drugs and six antibiotics. The spectra of the chemicals were used to train a BP neural network and then the absorption spectra measured in different times were identified by the trained BP neural network. The average identification rate of 76% was achieved. SOM neural networks, another important neural network which sorts input vectors by their similarity, was used to sort 60 absorption spectra from 6 illicit drugs. The whole network was trained by setting a 20×20 and a 16×16 grid, and both of them had given satisfied clustering results. These results indicate that it is feasible to apply BP and SOM neural networks model in the field of THz spectra identification.

  5. 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.

  6. Microwave spectra of some chlorine and fluorine compounds. [spectroscopic analysis

    NASA Technical Reports Server (NTRS)

    White, W. F.

    1975-01-01

    A computer-controlled microwave spectrometer was used to catalog reference spectra for chemical analysis. Tables of absorption frequencies, peak absorption intensities, and integrated intensities are shown for 21 organic compounds which contain chlorine, fluorine, or both.

  7. Theoretical study on absorption and emission spectra of adenine analogues.

    PubMed

    Liu, Hongxia; Song, Qixia; Yang, Yan; Li, Yan; Wang, Haijun

    2014-04-01

    Fluorescent nucleoside analogues have attracted much attention in studying the structure and dynamics of nucleic acids in recent years. In the present work, we use theoretical calculations to investigate the structural and optical properties of four adenine analogues (termed as A1, A2, A3, and A4), and also consider the effects of aqueous solution and base pairing. The results show that the fluorescent adenine analogues can pair with thymine to form stable H-bonded WC base pairs. The excited geometries of both adenine analogues and WC base pairs are similar to the ground geometries. The absorption and emission maxima of adenine analogues are greatly red shifted compared with nature adenine, the oscillator strengths of A1 and A2 are stronger than A3 and A4 in both absorption and emission spectra. The calculated low-energy peaks in the absorption spectra are in good agreement with the experimental data. In general, the aqueous solution and base pairing can slightly red-shift both the absorption and emission maxima, and can increase the oscillator strengths of absorption spectra, but significantly decrease the oscillator strengths of A3 in emission spectra.

  8. Stratospheric NO and NO2 profiles at sunset from analysis of high-resolution balloon-borne infrared solar absorption spectra obtained at 33 deg N and calculations with a time-dependent photochemical model

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Boughner, R. E.; Larsen, J. C.; Goldman, A.; Murcray, F. J.; Murcray, D. G.

    1984-01-01

    Simultaneous stratospheric vertical profiles of NO and NO2 at sunset were derived from an analysis of infrared solar absorption spectra recorded from a float altitude of 33 km with an interferometer system during a balloon flight. A nonlinear least squares procedure was used to analyze the spectral data in regions of absorption by NO and NO2 lines. Normalized factors, determined from calculations of time dependent altitude profiles with a detailed photochemical model, were included in the onion peeling analysis to correct for the rapid diurnal changes in NO and NO2 concentrations with time near sunset. The CO2 profile was also derived from the analysis and is reported.

  9. Ultraviolet absorption spectra of metalorganic molecules diluted in hydrogen gas

    NASA Astrophysics Data System (ADS)

    Itoh, Hideo; Watanabe, Masanobu; Mukai, Seiji; Yajima, Hiroyoshi

    1988-12-01

    Ultraviolet absorption spectra of trimethyl gallium, triethyl gallium, and trimethyl aluminum diluted in hydrogen gas were measured as a function of the wavelength (185-350 nm) and the concentration of the molecules (4.8×10 -6 -1.6×10 -4 mol/liter). Their absorbances changed linearly with the concentration of the molecules, which allowed us to calculate the molar absorption coefficients of the molecules on the basis of the Beer-Lambert law.

  10. 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.

  11. [Ultraviolet absorption spectra of iodine, iodide ion and triiodide ion].

    PubMed

    Wei, Yong-Ju; Liu, Cui-Ge; Mo, Li-Ping

    2005-01-01

    Ultraviolet absorption spectra of iodine I2, iodide ion I(-) and triiodide ion I3(-) were studied, and molar absorptivities of these species were determined. Absorption spectrum of I2 aqueous solution appears as an absorption peak at 203 nm with a molar absorptivity of 1.96 x 10(4) L x mol(-1) x cm(-1). Absorption spectrum of I(-) appears as two absorption peaks at 193 and 226 nm with molar absorptivities of 1.42 x 10(4) and 1.34 x 10(4) L x mol(-1) x cm(-1), respectively. When I2 aqueous solution is mixed with KI solution, two absorption peaks appear at 288 and 350 nm, respectively, indicating the formation of I3(-). Using saturation method, molar absorptivities of I3(-) at 288 and 350 nm were determined to be 3.52 x 10(4) and 2.32 x 10(4) L x mol(-1) x cm(-1), respectively.

  12. Estimation of damped oscillation associated spectra from ultrafast transient absorption spectra.

    PubMed

    van Stokkum, Ivo H M; Jumper, Chanelle C; Snellenburg, Joris J; Scholes, Gregory D; van Grondelle, Rienk; Malý, Pavel

    2016-11-07

    When exciting a complex molecular system with a short optical pulse, all chromophores present in the system can be excited. The resulting superposition of electronically and vibrationally excited states evolves in time, which is monitored with transient absorption spectroscopy. We present a methodology to resolve simultaneously the contributions of the different electronically and vibrationally excited states from the complete data. The evolution of the excited states is described with a superposition of damped oscillations. The amplitude of a damped oscillation cos(ωnt)exp(-γnt) as a function of the detection wavelength constitutes a damped oscillation associated spectrum DOASn(λ) with an accompanying phase characteristic φn(λ). In a case study, the cryptophyte photosynthetic antenna complex PC612 which contains eight bilin chromophores was excited by a broadband optical pulse. Difference absorption spectra from 525 to 715 nm were measured until 1 ns. The population dynamics is described by four lifetimes, with interchromophore equilibration in 0.8 and 7.5 ps. We have resolved 24 DOAS with frequencies between 130 and 1649 cm(-1) and with damping rates between 0.9 and 12 ps(-1). In addition, 11 more DOAS with faster damping rates were necessary to describe the "coherent artefact." The DOAS contains both ground and excited state features. Their interpretation is aided by DOAS analysis of simulated transient absorption signals resulting from stimulated emission and ground state bleach.

  13. Estimation of damped oscillation associated spectra from ultrafast transient absorption spectra

    NASA Astrophysics Data System (ADS)

    van Stokkum, Ivo H. M.; Jumper, Chanelle C.; Snellenburg, Joris J.; Scholes, Gregory D.; van Grondelle, Rienk; Malý, Pavel

    2016-11-01

    When exciting a complex molecular system with a short optical pulse, all chromophores present in the system can be excited. The resulting superposition of electronically and vibrationally excited states evolves in time, which is monitored with transient absorption spectroscopy. We present a methodology to resolve simultaneously the contributions of the different electronically and vibrationally excited states from the complete data. The evolution of the excited states is described with a superposition of damped oscillations. The amplitude of a damped oscillation cos(ωnt)exp(-γnt) as a function of the detection wavelength constitutes a damped oscillation associated spectrum DOASn(λ) with an accompanying phase characteristic φn(λ). In a case study, the cryptophyte photosynthetic antenna complex PC612 which contains eight bilin chromophores was excited by a broadband optical pulse. Difference absorption spectra from 525 to 715 nm were measured until 1 ns. The population dynamics is described by four lifetimes, with interchromophore equilibration in 0.8 and 7.5 ps. We have resolved 24 DOAS with frequencies between 130 and 1649 cm-1 and with damping rates between 0.9 and 12 ps-1. In addition, 11 more DOAS with faster damping rates were necessary to describe the "coherent artefact." The DOAS contains both ground and excited state features. Their interpretation is aided by DOAS analysis of simulated transient absorption signals resulting from stimulated emission and ground state bleach.

  14. An analysis of temperature-dependent absorption and photocurrent spectra in BaAl{sub 2}Se{sub 4} layers

    SciTech Connect

    Hong, K. J.; Jeong, T. S.; Youn, C. J.; Moon, J. D.

    2015-04-28

    The temperature-dependent photoresponse behavior of BaAl{sub 2}Se{sub 4} layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by E{sub g}(T) = E{sub g}(0) − 4.39 × 10{sup −4}T{sup 2}/(T + 250), where E{sub g}(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Γ{sub 3}(A), Γ{sub 4}(B), and Γ{sub 5}(C) to the conduction band state of Γ{sub 1}, respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log J{sub ph} versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds to the activation energy for the electronic transition from the shallow donor levels to the edge of the conduction band. It is estimated that the decrease in the PC intensity is caused by trapping centers related to native defects in the BaAl{sub 2}Se{sub 4} layers. Consequently, this trap level limited the PC intensity with decreasing temperature.

  15. 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…

  16. 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…

  17. The absorption spectra of carbonates and their precursors.

    NASA Astrophysics Data System (ADS)

    Koike, C.; Chihara, H.; Suto, H.

    The carbonates calcite and dolomite have been discovered in the dust shells of evolved stars (Kemper et al. 2002) and young proto stars (Ceccarelli et al. 2002). The mechanism for carbonate formation with a aqueous or non-aqueous process were discussed in their papers. These processes have not yet been reproduced in a laboratory experiment. First of all, we measured the mass absorption spectra of varous carbonates were measured in the mid- and far-infrared region. These spectra show very strong and broad peaks in the far-infrared region. The calcite and dolomite have peaks at about 92 microns and 63 microns, respectively. The alternative process of carbonates has not yet been clear. We investigate the alternative process measuring the spectra of the precursors of carbonates. We will report the preliminary results and discuss about the alternative process comparing the measured spectra of the precursors with the observation.

  18. Kinetics of camptothecin deactivation determined by time evolution of fluorescence and absorption spectra

    NASA Astrophysics Data System (ADS)

    Ziomkowska, Blanka; Kruszewski, Stefan; Siuda, Ryszard; Cyrankiewicz, Michal

    2004-07-01

    Fluorescence and absorption spectra of camptothecin -- anticancer alkaloid, are analyzed in this paper. Camptothecin exists in two forms: lactone and carboxylate. Only lactone form is biologically active. In physiological fluids at pH 7.4 lactone form hydrolyses and converts into carboxylate form. There are some differences in shapes between fluorescence and absorption spectra of lactone and carboxylate form. In the deactivation process fluorescence and absorption spectra evaluate. Thanks to the factor analysis of series of spectra recorded during the process of hydrolysis one can follow the concentration of both forms in the solution. Described method could be useful in determining of kinetics of deactivation process and competitive with the HPLC method.

  19. In vivo absorption spectra of the two stable states of the Euglena photoreceptor photocycle.

    PubMed

    Barsanti, Laura; Coltelli, Primo; Evangelista, Valtere; Passarelli, Vincenzo; Frassanito, Anna Maria; Vesentini, Nicoletta; Santoro, Fabrizio; Gualtieri, Paolo

    2009-01-01

    Euglena gracilis possesses a simple but sophisticated light detecting system, consisting of an eyespot formed by carotenoids globules and a photoreceptor. The photoreceptor of Euglena is characterized by optical bistability, with two stable states. In order to provide important and discriminating information on the series of structural changes that Euglena photoreceptive protein(s) undergoes inside the photoreceptor in response to light, we measured the in vivo absorption spectra of the two stable states A and B of photoreceptor photocycle. Data were collected using two different devices, i.e. a microspectrophotometer and a digital microscope. Our results show that the photocycle and the absorption spectra of the photoreceptor possess strong spectroscopic similarities with a rhodopsin-like protein. Moreover, the analysis of the absorption spectra of the two stable states of the photoreceptor and the absorption spectrum of the eyespot suggests an intriguing hypothesis for the orientation of microalgae toward light.

  20. High Resolution Spectra of Low Redshift Damped Lyalpha Absorption Systems

    NASA Astrophysics Data System (ADS)

    Cohen, R. D.; Beaver, E. A.; Junkkarinen, V. T.; Lyons, R. W.; Smith, H. E.

    1998-05-01

    We have been able to form a fairly complete picture of the galaxy responsible for the z_a=0.395 absorption line system in PKS 1229--021 by combining Keck HIRES and LRIS spectroscopy with observations taken with the Hubble Space Telescope. The image of the absorber is consistent with the inclined disk of a moderately luminous spiral galaxy. We have not been able to detect the continuum from this galaxy spectroscopically, but our LRIS spectra show emission from [O II] lambda3727 which can be interpreted to be indicative of star formation at the rate of a few M_⊙ per year. The HIRES spectra clearly show an ``edge--leading'' absorption profile. Prochaska and Wolfe have predicted that the velocity of the center of mass of the absorbing galaxy should fall near one edge of the absorption profile if the damped Lyalpha systems are due to the rotating disks of spiral galaxies. The [O II] emission velocity is consistent with this, but there is some ambiguity due to the doublet nature of the [O II] emission. Although the absorption lines of the abundant elements are saturated in the components which correspond to the H I absorption, we have been able to measure accurate column densities for Ca II, Ti II, and Mn II for comparison with the H I column density determined from low resolution HST/FOS spectra. The abundances are compatible with approximately 0.1 of solar, with little or no dust, but they are also consistent with lines of sight toward zeta Oph through warm interstellar clouds. HIRES observations of the z_a=0.692 absorption line system in 3CR 286 will also be discussed, after the data are fully analyzed. This work is part of the Goddard High Resolution Spectrograph Guaranteed Time Observations and is supported by NASA grant NAG5--1858 and the NSF.

  1. Crack spectra analysis

    SciTech Connect

    Tiernan, M.

    1980-09-01

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

  2. Effect of pyridine on infrared absorption spectra of copper phthalocyanine.

    PubMed

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

    2008-02-01

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

  3. Vibrational equilibration in absorption difference spectra of chlorophyll a.

    PubMed

    Struve, W S

    1995-12-01

    We describe Franck-Condon simulations of vibrational cooling effects on absorption difference spectra in chlorophyll a (Chl a). The relative contributions of vibrational equilibration in the electronic ground and excited states depend on the pump and probe wavelengths. For Franck-Condon-active vibrational modes exhibiting small Huang-Rhys factors (S < 0.1, characteristic in Chl a pigments), vibrational thermalization causes essentially no spectral changes when the origin band is excited. Significant spectral evolution does occur for S < 0.1 when the 0-1 and 1.0 (hot) vibronic bands are excited. However, vibrational equilibration in these cases causes no spectral shifting in the empirical photobleaching/stimulated emission band maximum. This result bears on the interpretation of time-resolved absorption difference spectra of Chl a-containing antennae such as the Chl a/b light-harvesting peripheral antenna of photosystem II.

  4. 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.

  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. Absorption spectra and linear dichroism of some amphibian photoreceptors.

    PubMed

    Hárosi, F I

    1975-09-01

    Absorption spectra and linear dichroism of dark-adapted, isolated photoreceptors of mudpuppies, larval and adult tiger salamanders, and tropical toads were measured microspectrophotometrically. Spectral half-band width, dichroic ratio, and transverse specific density were determined using averaged polarized absorptance spectra and photomicrographs of seven types of rod outer segments. Two classes of cells were found, one with higher specific density and dichroic ratio, associable with the presence of rhodopsins, the other, lower in both quantities, associable with porphyropsins. Relationships were derived to calculate the product of molar concentration and extinction coefficient (CEmax) from specific density and dichroic ratio. By utilizing the hypothesis of invariance of oscillator strengths and measured half-band widths, Emax values were independently determined, permitting the calculation of C. The pigment concentration for all cells tested was about 3.5 mM. The broadness of green rod pigment spectra is correlated with reduced molar absorptivity and reduced cellular specific density. Estimation of physiological spectral sensitivities is discussed. Based on dichroic ratio considerations, a model is proposed for the orientation of retinals in situ which could account for the apparent degree of alignment of transition moments. In the chosen orientation, the ring portion of conjugation becomes primarily responsible for axial extinction. Reduced dichroism of dehydroretinal-bearing cells can thus result from the extended ring conjugation of chromophores. Some inferences derivable from the model are discussed.

  7. Implications for High Energy Blazar Spectra from Intergalactic Absorption Calculations

    NASA Technical Reports Server (NTRS)

    Stecker, F

    2008-01-01

    Given a knowledge of the density spectra intergalactic low energy photons as a function of redshift, one can derive the intrinsic gamma-ray spectra and luminosities of blazars over a range of redshifts and look for possible trends in blazar evolution. Stecker, Baring & Summerlin have found some evidence hinting that TeV blazars with harder spectra have higher intrinsic TeV gamma-ray luminosities and indicating that there may be a correlation of spectral hardness and luminosity with redshift. Further work along these lines, treating recent observations of the blazers lES02291+200 and 3C279 in the TeV and sub-TeV energy ranges, has recently been explored by Stecker & Scully. GLAST will observe and investigate many blazars in the GeV energy range and will be sensitive to blazers at higher redshifts. I examine the implications high redshift gamma-ray absorption for both theoretical and observational blazer studies.

  8. 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.

  9. 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.

  10. 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.

  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. 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.

  13. 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.

  14. Effects of compositional variation on absorption spectra of lunar pyroxenes

    NASA Technical Reports Server (NTRS)

    Hazen, R. M.; Bell, P. M.; Mao, H. K.

    1978-01-01

    Polarized absorption spectra of lunar pyroxenes with a range of iron, calcium, magnesium, titanium and chromium contents were measured on polished, oriented single crystals; spectral data on pure synthetic FeSiO3 were also recorded. The bands at 1 and 2 microns were found to vary significantly in position with composition within the pyroxene quadrilateral; wavelengths increased with increasing calcium and iron. In the visible region, a weak band at 640 nm correlates in intensity with Cr2O3, but not with titanium as had been previously suggested. The 505-nm ferrous iron peak is a sharp doublet in most low-calcium pyroxenes but a singlet in augites. A peak at 475 nm and an intense absorption edge below 700 nm correlated with titanium content.

  15. Parametric analysis of the crystal field splitting pattern of Sm(eta(5)-C(5)Me(5))(3) derived on the basis of absorption spectra of pellets or solutions and electronic raman spectra of oriented single crystals.

    PubMed

    Amberger, Hanns-Dieter; Reddmann, Hauke; Evans, William J

    2009-11-16

    By comparing the absorption spectrum of pseudo trigonal planar Sm(eta(5)-C(5)Me(5))(3) (1) (KBr pellet, methylcyclohexane solution) with the previously assigned one of Sm(eta(5)-C(5)Me(4)H)(3) (2) a truncated experimental crystal field (CF) splitting pattern of the former compound could be derived in the NIR range. Because of its dark brown color, fluorescence is not observed from complex 1, and thus the CF splitting pattern in the low energy range could not be determined on the basis of luminescence measurements. However, comparing the FIR and MIR spectra (pellets) as well as the Raman spectra of oriented single crystals of 1 with those of La(eta(5)-C(5)Me(5))(3) (3) at least two additional CF levels could be detected. The free parameters of a phenomenological Hamiltonian were fitted to the thus extended CF splitting pattern of 1, leading to a reduced rms deviation of 15.0 cm(-1) for 21 assignments. On the basis of these phenomenological CF parameters, the global CF strength experienced by the Sm(3+) central ion was estimated, and seems to be the third largest one ever encountered in Sm(III) chemistry. The obtained Slater parameter F(2) and the spin-orbit coupling parameter zeta(4f) allow the insertion of compound 1 into empirical nephelauxetic and relativistic nephelauxetic series, respectively, of Sm(III) compounds. With its low F(2) value, complex 1 is the most covalent Sm(III) compound (considering only f electrons) found to date. The experimentally based non-relativistic molecular orbital scheme (in the f range) of complex 1 was set up and compared with the results of a previous Xalpha-SW calculation on the pseudo trigonal planar model compound Sm(eta(5)-C(5)H(5))(3). In the frame of the search for f-f and electronic Raman transitions, the vibrational spectra (FIR/MIR of pellets, Raman spectra of oriented single crystals) of compound 1 were recorded too, and partly assigned on the basis of the observed coincidences and polarizations.

  16. Observational Cosmology Using Absorption Lines in Quasar Spectra

    NASA Astrophysics Data System (ADS)

    Aghaee, A.

    2016-09-01

    Distant, highly luminous quasars are important cosmological probes for a variety of astrophysical questions: the first generation of galaxies, the star formation history and metal enrichment in the early Universe, the growth of the first super massive black holes (SMBHs), the role of feedback from quasars and SMBHs in galaxy evolution, the epoch of reionization, etc. In addition, they are used as background illuminating source that reveal any object located by chance on the line of sight. I will present our group works in these issues that can be done using absorption lines in the quasar spectra.

  17. 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.

  18. Electronic absorption, vibrational spectra, nonlinear optical properties, NBO analysis and thermodynamic properties of N-(4-nitro-2-phenoxyphenyl) methanesulfonamide molecule by ab initio HF and density functional methods

    NASA Astrophysics Data System (ADS)

    Rajamani, T.; Muthu, S.; Karabacak, M.

    2013-05-01

    In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4000-100 cm-1 and 4000-400 cm-1, respectively, for N-(4-nitro-2-phenoxyphenyl) methanesulfonamide molecule. Theoretical calculations were performed by ab initio RHF and density functional theory (DFT) method using 6-31G(d,p) and 6-311G(d,p) basis sets. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The frontier orbital energy gap and dipole moment illustrates the high reactivity of the title molecule. The first order hyperpolarizability (β0) and related properties (μ, α and Δα) of the molecule were also calculated. Stability of the molecule arising from hyperconjugative interactions and charge delocalization were analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ* and π* anti-bonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded in the region 200-500 nm in ethanol and electronic properties such as excitation energies, oscillator strength and wavelength were calculated by TD-DFT/B3LYP, CIS and TD-HF methods using 6-31G(d,p) basis set. Molecular electrostatic potential (MEP) and HOMO-LUMO energy levels are also constructed. The thermodynamic properties of the title compound were calculated at different temperatures and the results reveals the heat capacity (C), and entropy (S) increases with rise in temperature.

  19. Electronic absorption, vibrational spectra, nonlinear optical properties, NBO analysis and thermodynamic properties of N-(4-nitro-2-phenoxyphenyl) methanesulfonamide molecule by ab initio HF and density functional methods.

    PubMed

    Rajamani, T; Muthu, S; Karabacak, M

    2013-05-01

    In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4000-100 cm(-1) and 4000-400 cm(-1), respectively, for N-(4-nitro-2-phenoxyphenyl) methanesulfonamide molecule. Theoretical calculations were performed by ab initio RHF and density functional theory (DFT) method using 6-31G(d,p) and 6-311G(d,p) basis sets. The complete vibrational assignments of wavenumbers were made on the basis of potential energy distribution (PED). The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The frontier orbital energy gap and dipole moment illustrates the high reactivity of the title molecule. The first order hyperpolarizability (β0) and related properties (μ, α and Δα) of the molecule were also calculated. Stability of the molecule arising from hyperconjugative interactions and charge delocalization were analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ(*) and π(*) anti-bonding orbitals and second order delocalization energies (E2) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. UV-vis spectrum of the compound was recorded in the region 200-500 nm in ethanol and electronic properties such as excitation energies, oscillator strength and wavelength were calculated by TD-DFT/B3LYP, CIS and TD-HF methods using 6-31G(d,p) basis set. Molecular electrostatic potential (MEP) and HOMO-LUMO energy levels are also constructed. The thermodynamic properties of the title compound were calculated at different temperatures and the results reveals the heat capacity (C), and entropy (S) increases with rise in temperature. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. 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.

  1. 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.

  2. Characterization and dating of blue ballpoint pen inks using principal component analysis of UV-Vis absorption spectra, IR spectroscopy, and HPTLC.

    PubMed

    Senior, Samir; Hamed, Ezzat; Masoud, Mamdouh; Shehata, Eman

    2012-07-01

    The ink of pens and ink extracted from lines on white photocopier paper of 10 blue ballpoint pens were subjected to ultraviolet-visible (UV-Vis) spectroscopy, infrared (IR), and high-performance thin-layer liquid chromatography (HPTLC). The R(f) values and color tones of the bands separated by thin-layer chromatography (TLC) analysis used to classify the writing inks into three groups. The principal component analysis (PCA) investigates the pen responsible for a piece of writing, and how time affects spectroscopy of written ink. PCA can differentiate between pen ink and ink line indicates the influence of solvent extraction process on the results. The PCA loadings are useful in individualization of a questioned ink from a database. The PCA of ink lines extracted at different times can be used to estimate the time at which a questioned document was written. The results proved that the UV-Vis spectra are effective tool to separate blue ballpoint pen ink in most cases rather than IR and HPTLC. © 2012 American Academy of Forensic Sciences.

  3. Excited state absorption spectra and intersystem crossing kinetics in diazanaphthalenes

    NASA Astrophysics Data System (ADS)

    Scott, Gary W.; Talley, Larry D.; Anderson, Robert W.

    1980-05-01

    Picosecond time-resolved, excited state absorption spectra in the visible following excitation at 355 nm are discussed for room temperature solutions of four diazanaphthalenes (DN)—quinoxaline (1,4-DN), quinazoline (1,3-DN), cinnoline (1,2-DN), and phthalazine (2,3-DN). Kinetics of singlet state decay are obtained by monitoring the decay of Sn←S1 bands. The intersystem crossing rate constant (kisc) is found to vary as kisc(1,4-DN)≳kisc(1,3-DN)≳kisc(1,2-DN). The kisc in phthalazine could not be determined from the weak, visible Sn←S1 absorption. Assuming rapid singlet vibrational relaxation and only minor effects due to energy gap variations, these experimental results agree with statistical limit predictions for the relative nonradiative rate. Calculations of the spin-orbit coupling matrix element βel= , using INDO wave functions, give the ordering βel(1,4-DN)≳βel(2,3-DN)≳βel(1,3-DN) ≳βel(1,2-DN).

  4. 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.

  5. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...: Ultraviolet/visible spectra. 796.1050 Section 796.1050 Protection of Environment ENVIRONMENTAL PROTECTION... Chemical Properties § 796.1050 Absorption in aqueous solution: Ultraviolet/visible spectra. (a... applied to measure the absorption spectra. (b) Method—(1)(i) Introduction, purpose, scope,...

  6. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...: Ultraviolet/visible spectra. 796.1050 Section 796.1050 Protection of Environment ENVIRONMENTAL PROTECTION... Chemical Properties § 796.1050 Absorption in aqueous solution: Ultraviolet/visible spectra. (a... applied to measure the absorption spectra. (b) Method—(1)(i) Introduction, purpose, scope,...

  7. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...: Ultraviolet/visible spectra. 796.1050 Section 796.1050 Protection of Environment ENVIRONMENTAL PROTECTION... Chemical Properties § 796.1050 Absorption in aqueous solution: Ultraviolet/visible spectra. (a... applied to measure the absorption spectra. (b) Method—(1)(i) Introduction, purpose, scope,...

  8. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...: Ultraviolet/visible spectra. 796.1050 Section 796.1050 Protection of Environment ENVIRONMENTAL PROTECTION... Chemical Properties § 796.1050 Absorption in aqueous solution: Ultraviolet/visible spectra. (a... applied to measure the absorption spectra. (b) Method—(1)(i) Introduction, purpose, scope,...

  9. 40 CFR 796.1050 - Absorption in aqueous solution: Ultraviolet/visible spectra.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...: Ultraviolet/visible spectra. 796.1050 Section 796.1050 Protection of Environment ENVIRONMENTAL PROTECTION... Chemical Properties § 796.1050 Absorption in aqueous solution: Ultraviolet/visible spectra. (a... applied to measure the absorption spectra. (b) Method—(1)(i) Introduction, purpose, scope,...

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    DTIC Science & Technology

    2015-05-21

    AFRL-OSR-VA-TR-2015-0134 multi-photon absorption spectra Cleber Mendonca INSTITUTO DE FISICA DE SAO CARLOS Final Report 05/21/2015 DISTRIBUTION A...multi-photon absorption spectra: a comparison between transmittance change and fluorescence methods 5a. CONTRACT NUMBER Award No: FA9550-12-1-0028...presents the progress we have made on the project Determination of multi-photon absorption spectra: a comparison between transmittance change and

  12. On the nitrogen-induced far-infrared absorption spectra

    NASA Technical Reports Server (NTRS)

    Dore, P.; Filabozzi, A.

    1987-01-01

    The rototranslational absorption spectrum of gaseous N2 is analyzed, considering quadrupolar and hexadecapolar induction mechanisms. The available experimental data are accounted for by using a line-shape analysis in which empirical profiles describe the single-line translational profiles. Thus, a simple procedure is derived that allows the prediction of the N2 spectrum at any temperature. On the basis of the results obtained for the pure gas, a procedure to compute the far-infrared spectrum of the N2-Ar gaseous mixture is also proposed. The good agreement between computed and experimental N2-Ar data indicates that it is possible to predict the far-infrared absorption induced by N2 on the isotropic polarizability of any interacting partner.

  13. 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

  14. Analyzing absorption and scattering spectra of micro-scale structures with spectroscopic optical coherence tomography.

    PubMed

    Yi, Ji; Gong, Jianmin; Li, Xu

    2009-07-20

    We demonstrate the feasibility of characterizing the absorption and scattering spectra of micron-scale structures in a turbid medium using a spectroscopic optical coherence tomography (SOCT) system with a bandwidth of 430-650 nm. SOCT measurements are taken from phantoms composed of fluorescent microspheres. The absorption and scattering spectra are recovered with proper selections of spatial window width in the post processing step. Furthermore, we present an analysis using numerical OCT simulation based on full-wave solutions of the Maxwell's Equation to elucidate the origination of the multiple peaks in the OCT image for a single microsphere. Finally, we demonstrate the possibility of identifying contrast agents concentrated in micron-sized scale in an SOCT image. Two different types of microspheres in gel phantom are discriminated based on their distinguished absorbent feature.

  15. 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.

  16. [Infrared absorption spectrum analysis and its application to blood].

    PubMed

    Wang, Le-xin; Zhao, Zhi-min; Yao, Hong-bing; Chen, Yu-ming; Shi, Lei; Gao, Yong

    2002-12-01

    The technology of infrared absorption spectrum is a branch of optical ment measurement technology, and the research on the application of infrared spectrum plays an important role in the development of technology of optical measurement. In this paper, the analysis technology of blood infrared absorption spectrum is presented. By comparison, the difference of the spectra between normal and abnormal blood samples was obtained. The infrared absorption spectra of normal blood sample and abnormal blood sample were detected, and the differences between the spectra are presented. And the analysis results of the infrared absorption spectra of normal whole blood, serum and hyperglycemia are presented also. All of these provide an experimental basis for the diagnosis of diseases, which is valuable for application. This technology features easy operation, convenient analysis and suitability for advanced experiment. The work offers a new way in the research on the application of infrared absorption spectrum.

  17. The electronic absorption spectra of pyridine azides, solvent-solute interaction.

    PubMed

    Abu-Eittah, Rafie H; Khedr, Mahmoud K

    2009-01-01

    The electronic absorption spectra of: 2-, 3-, and 4-azidopyridines have been investigated in a wide variety of polar and non-polar solvents. According to Onsager model, the studied spectra indicate that the orientation polarization of solvent dipoles affects the electronic spectrum much stronger than the induction polarization of solvent dipoles. The effect of solvent dipole moment predominates that of solvent refractive index in determining the values of band maxima of an electronic spectrum. The spectra of azidopyridines differ basically from these of pyridine or mono-substituted pyridine. Results at hand indicate that the azide group perturbs the pyridine ring in the case of 3-azidopyridine much more than it does in the case of 2-azidopyridine. This result agrees with the predictions of the resonance theory. Although the equilibrium <==> azide tetrazole is well known, yet the observed spectra prove that such an equilibrium does not exist at the studied conditions. The spectra of the studied azidopyridines are characterized by the existence of overlapping transitions. Gaussian analysis is used to obtain nice, resolved spectra. All the observed bands correspond to pi-->pi* transitions, n-->pi* may be overlapped with the stronger pi-->pi* ones.

  18. Hot Experimental Absorption Spectra of CH_4 in the Pentad and Octad Region

    NASA Astrophysics Data System (ADS)

    Hargreaves, Robert J.; Dulick, Michael; Bernath, Peter F.

    2014-06-01

    We present comprehensive line lists of CH_4 at high temperatures for the pentad and octad region (2400-5000 wn). These spectra improve on our previous emission measurements for this region by using a new quartz sample cell in conjunction with a tube furnace (pictured). Ten temperatures have been recorded from room temperature up to 1000°C and our technique involves the acquisition of four separate Fourier transform infrared spectra at each temperature, thus accounting for both the emission and absorption of the molecule and the cell. By combining these four spectra we obtain true transmission spectra of hot CH_4 in this region. Analysis of this set of spectra enables the production of a line list that includes the position, intensity and empirical lower state energy. Our spectra and line lists can be used directly to model planetary atmospheres and brown dwarfs. Hargreaves, R.J., Beale, C.A., Michaux, L., Irfan, M., & Bernath, P.F. 2012, ApJ, 757, 46

  19. Laboratory studies at high resolution of the infrared absorption spectra of a number of gases found in planetary atmospheres

    NASA Technical Reports Server (NTRS)

    Hunt, R. H.

    1983-01-01

    The infrared absorption spectra of a number of gases found in planetary atmospheres were studied at high resolution. Absorption line measurements which can be of value for the interpretation of planetary spectra in terms of molecular abundances and conditions in the planetary atmospheres were provided. The high resolution spectra have yielded measurements of individual vibration rotation line parameters including positions, strengths, pressure broadened widths and, where assignments were unknown, the temperature sensitivity of the strengths. Such information allows the determinations of the absorption of a given molecular gas under planetary conditions of temperature and pressure and at the same time it provides the data necessary if the spectra are to be understood in terms of basic molecular theory. Thus this work has included spectral analysis in the form of line assignments as well as fitting of the data to Hamiltonian models. Such fitting is very useful in that it helps to confirm and extend the assignments.

  20. 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.

  1. [Decomposition of hemoglobin UV absorption spectrum into absorption spectra of prosthetic group and apoprotein by means of an additive model].

    PubMed

    Lavrinenko, I A; Vashanov, G A; Artyukhov, V G

    2015-01-01

    The decomposition pathways of hemoglobin UV absorption spectrum into the absorption spectra of the protein and non-protein components are proposed and substantiated by means of an additive model. We have established that the heme component has an absorption band with a maximum at λ(max) = 269.2 nm (ε = 97163) and the apoprotein component has an absorption band with a maximum at λ(max) = 278.4 nm (ε = 48669) for the wavelength range from 240.0 to 320.0 nm. An integral relative proportion of absorption for the heme fraction (78.8%) and apoprotein (21.2%) in the investigating wavelength range is defined.

  2. [Absorption spectra of nucleic acids and related compounds in the spectral region 120--280 nm].

    PubMed

    Kiseleva, M N; Zarochentseva, E P; Dodonova, N Ia

    1975-01-01

    The absorption spectra of thin films of nucleic acids, nucleosides, nucleotides, D-ribose, Na3PO4 in vacuum ultraviolet region are measured. In the spectral region 280--160 nm the absorption spectra consist of the bands of nucleic acid bases. In the range shorter than 160 nm the absorption is determined by phosphate and D-ribose groups. The methods of thin films preparation are discussed.

  3. A QM/MM study of absorption spectra of uracil derivatives in aqueous solution

    NASA Astrophysics Data System (ADS)

    Nakayama, Akira

    2016-12-01

    The absorption spectra of three representative uracil derivatives (uracil, thymine, and 5-fluorouracil) in aqueous solution are investigated by the QM/MM approach, where the CASPT2 method is employed to evaluate the excitation energies. The computed absorption spectra are in good agreement with the experimental results, and in particular, the relative values of the absorption maximum between these derivatives are well reproduced in the simulations.

  4. Studies of OH - absorption and optical absorption spectra in LiNbO 3 : Mg, Ti crystals

    NASA Astrophysics Data System (ADS)

    Liu, Jianjun; Zhang, Wanlin; Zhang, Guangyin

    1996-02-01

    The OH - absorption spectra and the UV absorption edges of LiNbO 3 : Mg, Ti crystals have been measured. It is shown that Ti doping raises the Mg doping threshold level, and shifts the absorption edge towards longer wavelengths. The results can be explained by the formation of Mg Li2+Ti Nb4+ pairs after all antisite defects Nb Li have been replaced.

  5. 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).

  6. Optical spectra analysis for breast cancer diagnostics

    NASA Astrophysics Data System (ADS)

    Belkov, S. A.; Kochemasov, G. G.; Lyubynskaya, T. E.; Maslov, N. V.; Nuzhny, A. S.; da Silva, L. B.; Rubenchik, A.

    2011-11-01

    Minimally invasive probe and optical biopsy system based on optical spectra recording and analysis seem to be a promising tool for early diagnostics of breast cancer. Light scattering and absorption spectra are generated continuously as far as the needle-like probe with one emitting and several collecting optical fibers penetrates through the tissues toward to the suspicious area. That allows analyzing not only the state of local site, but also the structure of tissues along the needle trace. The suggested method has the advantages of automated on-line diagnosing and minimal tissue destruction and in parallel with the conventional diagnostic procedures provides the ground for decision-making. 165 medical trials were completed in Nizhny Novgorod Regional Oncology Centre, Russia. Independent diagnoses were the results of fine biopsy and histology. Application of wavelet expansion and clasterization techniques for spectra analysis revealed several main spectral types for malignant and benign tumors. Automatic classification algorithm demonstrated specificity ˜90% and sensitivity ˜91%. Large amount of information, fuzziness in criteria and data noisiness make neural networks to be an attractive analytic tool. The model based on three-layer perceptron was tested over the sample of 29 `cancer' and 29 `non-cancer' cases and demonstrated total separation.

  7. 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.

  8. 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.

  9. Analysis of photometric spectra of 17 meteors

    NASA Technical Reports Server (NTRS)

    Millman, P. M.

    1982-01-01

    The initial phase of the photometry which involved 17 meteor spectra consisting of eight Geminid spectra, six Orionid spectra and three Eta Aquarid spectra is discussed. Among these 17 spectra it is found that the Geminid spectra are of the best quality and are used for the identification of the atomic lines and molecular bands that normally appear on video tape spectra. The data from the Geminid records are used for developing calibration techniques in photometry. The Orionid and Eta Aquarid spectra are chosen for early analysis because of the current interest in all physical and chemical data relating to Comet Halley.

  10. Ultrafast optical nonlinearity, electronic absorption, vibrational spectra and solvent effect studies of ninhydrin.

    PubMed

    Sajan, D; Devi, T Uma; Safakath, K; Philip, Reji; Němec, Ivan; Karabacak, M

    2013-05-15

    FT-IR, FT-Raman and UV-Vis spectra of the nonlinear optical molecule ninhydrin have been recorded and analyzed. The equilibrium geometry, bonding features, and harmonic vibrational wavenumbers have been investigated with the help of B3LYP density functional theory method. A detailed interpretation of the vibrational spectra is carried out with the aid of normal coordinate analysis following the scaled quantum mechanical force field methodology. Solvent effects have been calculated using time-dependent density functional theory in combination with the polarized continuum model. Natural bond orbital analysis confirms the occurrence of strong intermolecular hydrogen bonding in the molecule. Employing the open-aperture z-scan technique, nonlinear optical absorption of the sample has been studied in the ultrafast and short-pulse excitation regimes, using 100 fs and 5 ns laser pulses respectively. It is found that ninhydrin exhibits optical limiting for both excitations, indicating potential photonic applications.

  11. Vibrational circular dichroism and IR absorption spectra of amino acids: a density functional study.

    PubMed

    Ji, Zhi; Santamaria, Rubén; Garzón, Ignacio L

    2010-03-18

    With density functional theory, vibrational circular dichroism (VCD) and infrared absorption (IR) spectra are obtained at the B3LYP/CC-pVTZ level of theory for 20 alpha-amino acids. The contribution of different vibration modes to the IR and VCD spectra is analyzed. Overall agreement between calculated results for amino acids in gas phase with the available experimental VCD data for matrix-assisted amino acid films is found. The analysis of the calculated IR and VCD spectra indicates that the functional groups in the backbones and side chains of amino acids contribute differently to the spectra line shape. It is obtained that molecular torsions are the characteristic vibrations of the amino acids at the low-frequency regime, whereas the bending of bond angles, the out-of-plane wagging of individual atoms, and some stretching modes dominate the intermediate frequency range. Specific modes like NH(2) scissoring, CO bond stretching, and the (symmetric and asymmetric) stretching of the hydrogen atoms in the NH(2) and OH groups characterize the high-frequency regime. A general trend emerging from these calculations indicates that the rho(OH) rocking and nu(C=O) stretching modes have the highest intensity in the VCD spectra of most amino acids.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  13. Quantum-chemical investigation of the structure and electronic absorption spectra of electroluminescent zinc complexes

    NASA Astrophysics Data System (ADS)

    Minaev, B. F.; Baryshnikov, G. V.; Korop, A. A.; Minaeva, V. A.; Kaplunov, M. G.

    2013-01-01

    Using the quantum chemical methods of the density functional theory and of the electron density topological analysis, we have studied the structure of two recently synthesized electroluminescent zinc complexes, one with aminoquinoline ligands and the other with a Schiff base (N,O-donor). The energies and intensities of vertical excitations for the molecules under study have been calculated in terms of the PM3 semiempirical approximation taking into account the configurational interaction between singly excited singlet excited states. Good agreement between calculation results and experimental data on the electron density topological characteristics and on the visible and UV absorption spectra has been obtained.

  14. Influence of substitution on the T-T absorption spectra in furocoumarins

    NASA Astrophysics Data System (ADS)

    Bryantseva, N. G.

    2006-11-01

    The present paper deals with compounds called photosensitizers, namely, psoralen, 3,4-phenyl-4',5'- cyclohexylpsoralen, 4'-methyl-3,4-cycloheptyl psoralen, 4',5'-dimethyl-3,4-cyclohexyl psoralen (fig. 1). The absorption spectra from excited triplets states were investigated. The computed triplet-triplet absorption spectra of research compounds have been determined using INDO method. The experimental triplet-triplet absorption spectra have been obtained using the technique of laser flash photolysis in ethanol. The compare of computed and experimental data is shows that the computed second band wavelenght throughout agree very well (0,5-6 nm) with experimental data.

  15. [Terahertz Absorption Spectra Simulation of Glutamine Based on Quantum-Chemical Calculation].

    PubMed

    Zhang, Tian-yao; Zhang, Zhao-hui; Zhao, Xiao-yan; Zhang, Han; Yan, Fang; Qian, Ping

    2015-08-01

    With simulation of absorption spectra in THz region based on quantum-chemical calculation, the THz absorption features of target materials can be assigned with theoretical normal vibration modes. This is necessary for deeply understanding the origin of THz absorption spectra. The reliabilities of simulation results mainly depend on the initial structures and theoretical methods used throughout the calculation. In our study, we utilized THz-TDS to obtain the THz absorption spectrum of solid-state L-glutamine. Then three quantum-chemical calculation schemes with different initial structures commonly used in previous studies were proposed to study the inter-molecular interactions' contribution to the THz absorption of glutamine, containing monomer structure, dimer structure and crystal unit cell structure. After structure optimization and vibration modes' calculation based on density functional theory, the calculation results were converted to absorption spectra by Lorentzian line shape function for visual comparison with experimental spectra. The result of dimmer structure is better than monomer structure in number of absorption features while worse than crystal unit cell structure in position of absorption peaks. With the most reliable simulation result from crystal unit cell calculation, we successfully assigned all three experimental absorption peaks of glutamine ranged from 0.3 to 2.6 THz with overall vibration modes. Our study reveals that the crystal unit cell should be used as initial structure during theoretical simulation of solid-state samples' THz absorption spectrum which comprehensively considers not only the intra-molecular interactions but also inter-molecular interactions.

  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. Solvent effects on the steady-state absorption and fluorescence spectra of uracil, thymine and 5-fluorouracil.

    PubMed

    Gustavsson, Thomas; Sarkar, Nilmoni; Bányász, Akos; Markovitsi, Dimitra; Improta, Roberto

    2007-01-01

    We report a comparison of the steady-state absorption and fluorescence spectra of three representative uracil derivatives (uracil, thymine and 5-fluorouracil) in alcoholic solutions. The present results are compared with those from our previous experimental and computational studies of the same compounds in water and acetonitrile. The effects of solvent polarity and hydrogen bonding on the spectra are discussed in the light of theoretical predictions. This comparative analysis provides a more complete picture of the solvent effects on the absorption and fluorescence properties of pyrimidine nucleobases, with special emphasis on the mechanism of the excited state deactivation.

  18. 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

  19. Solvatochromic behavior of the electronic absorption spectra of gallic acid and some of its azo derivatives

    NASA Astrophysics Data System (ADS)

    Masoud, Mamdouh S.; Hagagg, Sawsan S.; Ali, Alaa E.; Nasr, Nessma M.

    The electronic absorption spectra of gallic acid and its azo derivatives have been studied in various solvents of different polarities. Multiple regression techniques were applied to calculate the regression and correlation coefficients based on an equation that relates the wavenumbers of the absorption band maxima (υmax-) to the solvent parameters; refractive index (n), dielectric constant (D), empirical Kamlet-Taft solvent parameters, π*(dipolarity/polarizability), α (solvent hydrogen-bond donor acidity) and β (solvent hydrogen-bond acceptor basicity). The fitting coefficient obtained from this analysis allows estimating the contribution of each type of interactions relative to total spectral shifts in solution. The dependence of υmax- on the solvent parameters indicates that the obtained bands are affected by specific and non-specific solute-solvent interactions.

  20. Vibronic analysis of NLO spectra of PDA crystals and films

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Debasis; Soos, Zoltan G.

    1995-09-01

    A joint analysis of recent NLO spectra of polydiacetylene films and crystals is presented, using vibronic contributions in the Condon approximation and (pi) -electronic states from Pariser-Parr-Pople theory. Raman resonances are shown to be corrections to average excitations. An even-parity state above the photoconduction edge is found in two-photon absorption of PDA-PTS crystals and nondegenerate four-wave-mixing spectra of PDA- 4BCMU films. We incorporate linear and resonance Raman spectra in the joint NLO analysis and emphasize the different roles of electronic and vibrational contributions.

  1. Galactic Soft X-ray Emission Revealed with Spectroscopic Study of Absorption and Emission Spectra

    NASA Astrophysics Data System (ADS)

    Yamasaki, Noriko Y.; Mitsuda, K.; Takei, Y.; Hagihara, T.; Yoshino, T.; Wang, Q. D.; Yao, Y.; McCammon, D.

    2010-03-01

    Spectroscopic study of Oxygen emission/absorption lines is a new tool to investigate the nature of the soft X-ray background. We investigated the emission spectra of 14 fields obtained by Suzaku, and detected OVII and OVIII lines separately. There is an almost isotropic OVII line emission with 2 LU intensity. As the attenuation length in the Galactic plane for that energy is short, that OVII emission should arise within 300 pc of our neighborhood. In comparison with the estimated emission measure for the local bubble, the most plausible origin of this component is the solar wind charge exchange with local interstellar materials. Another component presented from the correlation between the OVII and OVIII line intensity is a thermal emission with an apparent temperature of 0.2 keV with a field-to-field fluctuation of 10% in temperature, while the intensity varies about a factor of 4. By the combination analysis of the emission and the absorption spectra, we can investigate the density and the scale length of intervening plasma separately. We analyzed the Chanrdra grating spectra of LMC X-3 and PKS 2155-304, and emission spectra toward the line of sight by Suzaku. In both cases, the combined analysis showed that the hot plasma is not iso-thermal nor uniform. Assuming an exponential disk distribution, the thickness of the disk is as large as a few kpc. It suggests that there is a thick hot disk or hot halo surrounding our Galaxy, which is similar to X-ray hot haloes around several spiral galaxies.

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

    PubMed

    Grante, Ilze; Actins, Andris; Orola, Liana

    2014-08-14

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

  3. Theoretical Prediction of Si2–Si33 Absorption Spectra

    DOE PAGES

    Zhao, Li -Zhen; Lu, Wen -Cai; Jilin Univ., Jilin; ...

    2017-07-07

    Here, the optical absorption spectra of Si2–Si33 clusters were systematically studied by a time-dependent density functional theory approach. The calculations revealed that the absorption spectrum becomes significantly broad with increasing cluster size, stretching from ultraviolet to the infrared region. The absorption spectra are closely related to the structural motifs. With increasing cluster size, the absorption intensity of cage structures gradually increases, but the absorption curves of the prolate and the Y-shaped structures are very sensitive to cluster size. If the transition energy reaches ~12 eV, it is noted that all the clusters have remarkable absorption in deep ultraviolet region ofmore » 100–200 nm, and the maximum absorption intensity is ~100 times that in the visible region. Further, the optical responses to doping in the Si clusters were studied.« less

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Hoepffner, Nicolas; Sathyendranath, Shubha

    1993-12-01

    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.

  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. Core-exciton absorption in the F K absorption spectra of 3d transition-metal fluorides

    SciTech Connect

    Nakai, S.; Kawata, A.; Ohashi, M.; Kitamura, M.; Sugiura, C.; Mitsuishi, T.; Maezawa, H.

    1988-06-15

    Near-edge structure in the F K absorption spectra of 3d transition-metal fluorides, MnF/sub 2/, FeF/sub 2/, CoF/sub 2/, NiF/sub 2/, CuF/sub 2/, and ZnF/sub 2/, are measured. The shoulder structures or weak peaks located at the absorption threshold are observed. The origin of these peaks is attributed to the core-exciton absorption. This core-exciton absorption is accompanied by the transition from the 1s orbitals of fluorides to the 3d orbitals of the metal ion which hybridized with the anion 2p orbitals. Chemical shifts of the first peak are clearly observed and discussed in terms of the ionization potentials of the metal ions. It is found that the F K absorption spectra of the 3d transition-metal fluorides are quite similar to the Cl K absorption spectra of the 3d transition-metal chlorides.

  10. 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.

  11. ON THE ANALYSIS OF SPECTRA IN TRANSMISSION THROUGH THIN FILMS,

    DTIC Science & Technology

    Reprint: On the analysis of spectra in transmission through thin films . A technique to investigate the adequacy of the damped harmonicoscillator...model for IR absorption in thin films . Procedure for extracting material parameters and film thickness from the transmission curve.

  12. Electronic absorption spectra of blood plasma of patients with various forms of goiter

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    The results of absorption spectra of blood plasma in the ultraviolet and visible areas of the spectrum using the technique of spherical photometer. Possibilities of using these spectra to detect the diseases - diffuse toxic goiter and nodular euthyroid goiter and to control the surgical treatment of this pathology.

  13. Electronic absorption spectra of blood plasma of patients with various forms of goiter

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

    The results of absorption spectra of blood plasma in the ultraviolet and visible areas of the spectrum using the technique of spherical photometer. Possibilities of using these spectra to detect the diseases - diffuse toxic goiter and nodular euthyroid goiter and to control the surgical treatment of this pathology.

  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. The Extragalactic Background Light and Absorption in Gamma Ray Spectra

    NASA Astrophysics Data System (ADS)

    Gilmore, Rudy C.

    2008-03-01

    Recent state-of-the-art semi-analytic models (SAMs) can now accurately model the history of galaxy formation and evolution. These SAMs utilize a 'forward evolution' approach and include all of the important processes for determining photon emission from galaxies, such as cooling and shock heating of gas, galaxy mergers, star formation and aging, supernova and AGN feedback, and the reprocessing of light by dust. I will be presenting our group's latest prediction of the extra-galactic background light based on this work and will discuss the implications for the attenuation of VHE gamma rays from distant sources due to pair-production. These results will be compared to recent limits placed on the EBL by observations of GeV and TeV blazar spectra by experiments such as H.E.S.S., MAGIC and VERITAS. The implications for reconstructing the intrinsic spectra of distant blazars will be addressed.

  16. 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.

  17. 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.

  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. 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.

  20. Absorption Spectra of High-Temperature Solid Propellant Flames

    DTIC Science & Technology

    1974-08-01

    emission, was used as the calibration parameter. A Beer -Lambert type plot of the modified absorbance versus the respective specie concentration...the flame. Where P°^ is the incident radiant power at wave- length X, and P^ is the transmitted radiant power at wavelength A. Beer -Lambert type...absorption spectroscopy is based on the use of the Beer -Lambert Law, 103 P? ^n-^-»Kxce , (1) where P*J is the Incident radiant power, P^ is the

  1. Absorption in the spectra of quasi-stellar objects and BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Perry, J. J.; Burbidge, E. M.; Burbidge, G. R.

    1978-01-01

    Observations of absorption in the spectra of 64 QSOs and two BL Lac objects are reviewed. Criteria for selecting the absorption-line objects are discussed along with line identifications, properties of identified absorption systems, the observed absence of variability in the absorption lines, the redshift distribution, line locking, and absorption shortward of the Lyman limit. The possibility of noncosmological redshifts is noted, and two interpretations of the absorption-line data are considered: (1) the 'intrinsic' hypothesis that the absorptions arise in gas associated with the QSOs and (2) the 'intervening' hypothesis that they are produced by intervening galaxies, galactic halos, or intergalactic clouds intersected by the line of sight to a QSO. Direct observational tests for the location of the absorbing hydrogen in several individual objects are described. It is concluded that no conclusive observational evidence exists which is capable of establishing whether the absorption is intrinsic or intervening.

  2. Ab-initio method for X-ray absorption spectra simulation of hydride molecular ions

    NASA Astrophysics Data System (ADS)

    Puglisi, Alessandra; Sisourat, Nicolas; Carniato, Stéphane

    2017-03-01

    Soft X-ray absorption spectra of molecular ions are important data for the modeling and understanding of laboratory and astrophysical plasma. In this work, we present an ab-initio method, based on the Configuration Interaction (CI) approach, for the calculations of energy positions and oscillator strengths of X-ray absorption spectra. Furthermore, we investigate the effects of the choice of the nature and number of spin-orbitals used in the CI expansion on the spectra. The method is applied on three hydride molecular ions, namely CH+, OH+ and SiH+. However, the approach proposed here is general and may thus be applied to any kind of molecular ions.

  3. Solvent effects on the absorption and fluorescence spectra of rhaponticin: Experimental and theoretical studies

    NASA Astrophysics Data System (ADS)

    Sun, Yang; Liang, Xuhua; Zhao, Yingyong; Fan, Jun

    2013-02-01

    Rhaponticin (RH) possesses a variety of pharmacological activities including potent antitumor, antitumor-promoting, antithrombotic, antioxidant and vasorelaxant effects. The fundamental photophysics of RH is not well understood. In this work, solvent effect on the photoluminescence behavior of RH was studied by fluorescence and absorption spectra. The bathchromic shift was observed in absorption and fluorescence spectra with the increase of solvents polarity, which implied that transition involved was π → π*. A quantitative estimation of the contribution from different solvatochromic parameters, like normalized transition energy value (ETN), was made using the linear stokes shift (Δν) relationship based on the Lippert-Suppan equation. The ground state and excited state dipole moments were calculated by quantum-mechanical second-order perturbation method as a function of the dielectric constant (ɛ) and refractive index (n). The result was found to be 2.23 and 3.67 D in ground state and excited state respectively. The density functional theory (DFT) was used to obtain the most stable structure, electronic excitation energy, dipole moments and charge distribution. The analysis revealed that the RH exhibited strong photoinduced intramolecular charge transfer (ICT), and the intermolecular hydrogen bonding ability of the solvent was the most important parameter to characterize the photophysics behavior of RH. The hydrogen bonding effect occurred at the localized electron-acceptor oxygen at the glycoside bond. The experimental and theoretical results would help us better understand the photophysical properties of RH.

  4. Total absorption spectroscopy of fission fragments relevant for reactor antineutrino spectra

    NASA Astrophysics Data System (ADS)

    Fallot, M.; Porta, A.; Meur, L. Le; Briz, J. A.; Zakari-Issoufou, A.-A.; Guadilla, V.; Algora, A.; Taìn, J.-L.; Valencia, E.; Rice, S.; Bui, V. M.; Cormon, S.; Estienne, M.; Agramunt, J.; Äystö, J.; Batist, L.; Bowry, M.; Caballero-Folch, R.; Cano-Ott, D.; Cucoanes, A.; Elomaa, V.-V.; Eronen, T.; Estévez, E.; Farrelly, G. F.; Fraile, L. M.; Fleming, M.; Ganogliu, E.; Garcia, A. R.; Gelletly, W.; Gomez-Hornillos, M. B.; Gorelov, D.; Gorlychev, V.; Hakala, J.; Jokinen, A.; Jordan, M. D.; Kankainen, A.; Karvonen, P.; Kolhinen, V. S.; Kondev, F. G.; Koponen, J.; Lebois, M.; Martinez, T.; Mason, P.; Mendoza, E.; Molina, F.; Monserrate, M.; Montaner-Pizá, A.; Moore, I.; Nácher, E.; Orrigo, S. E. A.; Penttilä, H.; Perez, A.; Podolyák, Zs.; Pohjalainen, I.; Regan, P. H.; Reinikainen, J.; Reponen, M.; Rinta-Antila, S.; Rissanen, J.; Rubio, B.; Shiba, T.; Sonnenschein, V.; Sonzogni, A. A.; Sublet, J.-C.; Vedia, V.; Voss, A.; Weber, C.; Wilson, J. N.

    2017-09-01

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

  5. [Measurement and analysis of absorption spectrum of human blood].

    PubMed

    Zhao, Zhi-Min; Xin, Yu-Jun; Wang, Le-Xin; Zhu, Wei-Hua; Zheng, Min; Guo, Xin

    2008-01-01

    The present paper puts forward a method of disease diagnosis by using the technology of spectrum analysis of human blood serum. The generation mechanism of absorption spectrum is explained and the absorption spectra of the normal blood serum and the sick blood serum are listed from the experiments of absorption spectrometry. Though the value of absorbency of the sick blood serum is almost equal to that of the normal blood serum in the most absorption spectra, there are some differences around 278 nm in the absorption spectrum. The absorbency of the blood serum with hyperglycemia is greater than that of the normal blood serum at 285 nm in the spectrum, and besides, there comes a peak shift of absorption with hyperglycemia. In the absorption spectrum of the blood serum with hypercholesterolemia, there is a clear absorption peak at 414 nm. However there is not any peak at that wavelength in the absorption spectrum of the normal blood serum. Through comparing the characters of the spectrum, we can judge if the blood sample is or not, and this blood analysis is a new method for the diagnosis of disease. Compared with other methods of blood measurements, the method of absorption spectrum analysis of blood serum presented in this paper, is more convenient for measurement, simpler for analysis, and easier to popularize.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  7. Femtosecond Transient Absorption Spectra and Relaxation Dynamics of SWNT in SDS Micellar Solutions

    NASA Astrophysics Data System (ADS)

    Nadtochenko, V. A.; Lobach, A. S.; Gostev, F. E.; Tcherbinin, D. O.; Sobennikov, A.; Sarkisov, O. M.

    2005-09-01

    Transient absorption spectra and relaxation dynamics of excited SWNT were studied by femtosecond absorption spectroscopy as a function of: the energy of excitation quanta (ℏω = 2 eV, 2.5 eV, 4 eV); the density of the excitation energy; polarizations of the pump and probe pulses. The transient absorption spectra were monitored by white supercontinuum light pulse in the spectral region of ˜ 1.2 ÷ 3.6 eV. The induced transient absorption spectra of SWNT are considered as filling of the size-quantized energy bands with nonequilibrium carriers; renormalization of the one-dimensional energy bands at high density of the induced plasma; quantum confined Stark effect and screening of excitons. The anisotropic relaxation rate is observed.

  8. Electronic structure and TDDFT optical absorption spectra of silver nanorods.

    PubMed

    Johnson, Hannah E; Aikens, Christine M

    2009-04-23

    Density functional theory calculations are employed to determine optimized geometries and excitation spectra for small pentagonal silver nanorods Ag(n), with n = 13, 19, 25, 31, 37, 43, 49, 55, 61, and 67 in various charge states. The asymptotically correct SAOP functional is utilized in the excitation calculations. Silver nanorods exhibit a sharp longitudinal excitation that results from a mixture of orbital transitions; the wavelength for this excitation depends linearly on the length of the nanorod. The broad transverse excitation arises from multiple excited states. A particle-in-a-box model is employed to explain the linear dependence of the longitudinal excitation wavelength on nanorod length.

  9. Carbon dioxide laser absorption spectra of toxic industrial compounds.

    PubMed

    Loper, G L; Sasaki, G R; Stamps, M A

    1982-05-01

    CO(2) laser absorption cross-section data are reported for acrolein, styrene, ethyl acrylate, trichloroethylene, vinyl bromide, and vinylidene chloride. These data indicate that sub parts per billion level, interference-free detection limits should be possible for these compounds by the CO(2) laser photoacoustic technique. Photoacoustic detectabilities below 40 ppb should be possible for these compounds in the presence of ambient air concentrations of water vapor and other anticipated interferences. These compounds are also found not to be important interferences in the detection of toxic hydrazine-based rocket fuels by CO(2) laser spectroscopic techniques.

  10. Near-ultraviolet absorption spectra and crystal-field analysis of Gd3+ in Na3[Gd(C4H4O5)3].2NaClO4.6H2O

    NASA Astrophysics Data System (ADS)

    Stephens, Eileen M.; Metcalf, David H.; Berry, Mary T.; Richardson, F. S.

    1991-11-01

    Optical absorption spectra between 32 000 and 41 000 cm-1 are reported for Gd3+ in trigonal Na3[Gd(oxydiacetate)3].2NaClO4.6H2O at temperatures between 10 and 298 K. Fifty-eight of the 63 crystal-field levels split out of the 6PJ(J=7/2, 5/2, and 3/2), 6IJ(J=7/2, 9/2, 17/2, 11/2, 15/2, and 13/2), and 6DJ(J=9/2, 1/2, 7/2, 3/2, and 5/2) multiplets of the Gd3+ 4f7 electronic configuration are located and assigned from the low-temperature spectra, and these energy levels are analyzed in terms of a parametrized Hamiltonian that reflects D3 site symmetry at the Gd3+ ions. Parametric fits of calculated to empirical-energy-level data yield a rms deviation of 6.3 cm-1 (between calculated and observed energies). Eigenvectors of the parametrized Hamiltonian are used in calculations of oscillator strengths for all transitions that originate from the 8S7/2 (ground) multiplet and terminate on crystal-field levels of the 6PJ, 6IJ, and 6DJ multiplet manifolds. Spectra simulations based on these calculated oscillator strengths are presented, and comparisons between the simulated spectra and experimentally observed spectra show excellent agreement with respect to intensity distributions both within and between the various multiplet-to-multiplet transition manifolds. Variable-temperature absorption measurements carried out between 10 and 298 K showed only very small changes in J-multiplet baricenter energies, crystal-field-splitting energies (within J-multiplet manifolds), and transition intensity distributions. Disparities between the energy-level structure deduced in the present study and that proposed in another recently published study of Na3[Gd(oxydiacetate)3].2NaClO4.6H2O [Phys. Rev. B 41, 10 911 (1990)] are discussed. This previous study of Kundu, Banerjee, and Chowdhury was based on two-photon luminescence excitation measurements that have special significance for elucidating two-photon-absorption intensity mechanisms of 4f-4f transitions in noncentrosymmetric lanthanide

  11. Electronic absorption spectra of hydrogenated protonated naphthalene and proflavine

    NASA Astrophysics Data System (ADS)

    Bonaca, A.; Bilalbegović, G.

    2011-09-01

    We study hydrogenated cations of two polycyclic hydrocarbon molecules as models of hydrogenated organic species that form in the interstellar medium. Optical spectra of the hydrogenated naphthalene cation Hn-C10H+8 for n= 1, 2 and 10, as well as the astrobiologically interesting hydrogenated proflavine cation Hn-C13H11N+3 for n= 1 and 14, are calculated. The pseudopotential time-dependent density functional theory is used. It is found that the fully hydrogenated proflavine cation H14-C13H11N+3 shows a broad spectrum in which the positions of individual lines are almost lost. The positions, shapes and intensities of lines change in hydronaphthalene and hydroproflavine cations, showing that hydrogen additions induce substantially different optical spectra in comparison with base polycyclic hydrocarbon cations. One calculated line in the visible spectrum of H10-C10H+8 and one in the visible spectrum of H-C13H11N+3 are close to the measured diffuse interstellar bands. We also present the positions of near-ultraviolet lines.

  12. 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.

  13. Absorption spectra of shocked liquid CS/sub 2/

    SciTech Connect

    Dallman, J.C.

    1985-01-01

    The importance of shock initiation of high explosives (HE) was understood as early as 1863 when Alfred Nobel introduced the detonator as a means of detonating nitroglycerine. The critical pressure rise times required to achieve shock initiation and steady propagation of detonation are determined by the chemical and mechanical properties of an explosive. Although progress has been made in the understanding of the effects of mechanical properties, the detailed effects of high pressures on chemical reaction mechanisms are still only poorly understood. This paper reports the results of two experiments using CS/sub 2/, which is known to undergo electronic state transitions when shocked to high pressures. The goal of these experiments was to examine the known shock-generated expansion of CS/sub 2/ absorption bands while generating the shocks with a flyer plate system driven by high explosives.

  14. 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.

  15. [Analysis of three-dimensional fluorescence overlapping spectra using differential spectra and independent component analysis].

    PubMed

    Yu, Shao-Hui; Zhang, Yu-Jun; Zhao, Nan-Jing; Xiao, Xue; Wang, Huan-Bo; Yin, Gao-Fang

    2013-01-01

    The analysis of multi-component three-dimensional fluorescence overlapping spectra is always very difficult. In view of the advantage of differential spectra and based on the calculation principle of two-dimensional differential spectra, the three-dimensional fluorescence spectra with both excitation and emission spectra is fully utilized. Firstly, the excitation differential spectra and emission differential spectra are respectively computed after unfolding the three-dimensional fluorescence spectra. Then the excitation differential spectra and emission differential spectra of the single component are obtained by analyzing the multicomponent differential spectra using independent component analysis. In this process, the use of cubic spline increases the data points of excitation spectra, and the roughness penalty smoothing reduces the noise of emission spectra which is beneficial for the computation of differential spectra. The similarity indices between the standard spectra and recovered spectra show that independent component analysis based on differential spectra is more suitable for the component recognition of three-dimensional fluorescence overlapping spectra.

  16. Simultaneous acquisition of absorption and fluorescence spectra of strong absorbers utilizing an evanescent supercontinuum.

    PubMed

    Kiefer, Johannes

    2016-12-15

    The determination of the absorption and emission spectra of strongly absorbing molecules is challenging, and the data can be biased by self-absorption of the fluorescence signal. To overcome this problem, a total internal reflection approach is proposed. The strongly absorbing sample is placed in an evanescent field of the radiation of a supercontinuum source. The collimated reflected light encodes the absorption spectrum, and the isotropic fluorescence emission is collected in a direction perpendicular to the surface at the same time. This ensures that the emitted light has a minimum possibility of self-absorption inside the sample.

  17. Solvent effect on the absorption spectra of coumarin 120 in water: A combined quantum mechanical and molecular mechanical study.

    PubMed

    Sakata, Tetsuya; Kawashima, Yukio; Nakano, Haruyuki

    2011-01-07

    The solvent effect on the absorption spectra of coumarin 120 (C120) in water was studied utilizing the combined quantum mechanical∕molecular mechanical (QM∕MM) method. In molecular dynamics (MD) simulation, a new sampling scheme was introduced to provide enough samples for both solute and solvent molecules to obtain the average physical properties of the molecules in solution. We sampled the structure of the solute and solvent molecules separately. First, we executed a QM∕MM MD simulation, where we sampled the solute molecule in solution. Next, we chose random solute structures from this simulation and performed classical MD simulation for each chosen solute structure with its geometry fixed. This new scheme allowed us to sample the solute molecule quantum mechanically and sample many solvent structures classically. Excitation energy calculations using the selected samples were carried out by the generalized multiconfigurational perturbation theory. We succeeded in constructing the absorption spectra and realizing the red shift of the absorption spectra found in polar solvents. To understand the motion of C120 in water, we carried out principal component analysis and found that the motion of the methyl group made the largest contribution and the motion of the amino group the second largest. The solvent effect on the absorption spectrum was studied by decomposing it in two components: the effect from the distortion of the solute molecule and the field effect from the solvent molecules. The solvent effect from the solvent molecules shows large contribution to the solvent shift of the peak of the absorption spectrum, while the solvent effect from the solute molecule shows no contribution. The solvent effect from the solute molecule mainly contributes to the broadening of the absorption spectrum. In the solvent effect, the variation in C-C bond length has the largest contribution on the absorption spectrum from the solute molecule. For the solvent effect on the

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  19. Breaking of symmetrical charge distribution in xanthylocyanine chromophores detecting by their absorption spectra

    NASA Astrophysics Data System (ADS)

    Vasyluk, S. V.; Viniychuk, O. O.; Poronik, Ye. M.; Kovtun, Yu. P.; Shandura, M. P.; Yashchuk, V. M.; Kachkovsky, O. D.

    2011-03-01

    A detailed experimental investigation and quantum-chemical analysis of symmetrical cyanines with xanthylium and its substituted derivatives and with different polymethine chain (containing 1 and 2 vinylene groups) have been performed with the goal of understanding the nature of the electronic transitions in molecules. It is established electronic transitions in carbocyanines are similar to that in the typical Brooker's cyanines. In contrast, the absorption spectra of dicarbocyanines demonstrate a strong solvent dependence and substantial band broadening represented by the growth of the short wavelength shoulder. Basing on the results of the quantum-chemical calculation and conception of the mobile solitonic-like charge waves, we have concluded that the dicarbocyanines exist in two charged forms in the ground state with symmetrical and unsymmetrical distributions of the charge density. These are the examples of the cationic cyanines with the shortest chain when the symmetry breaking occurs.

  20. 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.

  1. 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

  2. Separation of scattering and absorption contributions in UV/visible spectra of resonant systems.

    PubMed

    Micali, N; Mallamace, F; Castriciano, M; Romeo, A; Scolaro, L M

    2001-10-15

    Resonance light scattering (RLS) is a phenomenon due to an enhancement of the scattered light in close proximity to an absorption band. The effect is easily detectable in the case of strongly absorbing chromophores, which are able to interact, thus leading to large aggregates (Pasternack, R. F.; Collings, P. J. Science 1995, 269, 935). The measurement of absorption spectra from solutions containing such resonant systems can lead to misleading results. In this paper, a simple method is described to obtain absorption spectra of aggregated species with a fairly good correction of the scattering component. The RLS spectrum, obtained using a common spectrofluorimeter, is correlated to the extinction spectrum of the same sample, allowing for an estimation of the scattering contribution to the total extinction spectrum. The method has been successfully applied both on real samples containing aggregated chromophores, such as porphyrins, chlorophyll a and gold colloids, and by simulating extinction spectra.

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

    PubMed Central

    2012-01-01

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

  4. Research on the Terahertz Absorption Spectra of Histidine Enantiomer (L) and its Racemic Compound (DL).

    PubMed

    Zhou, Tao; Wu, Yidong; Cao, Juncheng; Zou, Liangliang; Yuan, Jie; Yao, Zhenwei; Xu, Gongjie

    2017-02-01

    Terahertz time-domain spectroscopy (THz-TDS) is used to investigate the absorption spectra of polycrystalline L- and DL-histidine in the frequency range of 10-100 cm(-1). The spectra exhibit distinct differences in peak frequencies between the enantiomer (L-histidine) and racemic compound (DL-histidine). The observed spectral differences are attributed to the intermolecular interactions. With the density function theory (DFT) method, the frequencies of vibrational modes of L-histidine and DL-histidine in the THz range are calculated and well assigned according to the measured spectra. The origin of the observed vibrational modes is found to be non-localized and of a collective (phonon-like) nature, which points to the lattice and skeleton vibrations mediated by the hydrogen bond. Furthermore, we propose and demonstrate a method for determining the composition ratio of histidine mixtures based on the THz absorption spectra.

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

    NASA Technical Reports Server (NTRS)

    Sherman, D. M.

    1985-01-01

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

  6. THE STRUCTURE OF THE ULTRAVIOLET ABSORPTION SPECTRA OF CERTAIN PROTEINS AND AMINO ACIDS

    PubMed Central

    Coulter, Calvin B.; Stone, Florence M.; Kabat, Elvin A.

    1936-01-01

    1. The absorption spectra of a number of proteins in the region 2500 to 3000 A. have been found to comprise from six to nine narrow bands. In consequence of variation in the relative intensity of these bands from protein to protein, the absorption curve has a characteristic configuration for each protein. 2. These bands correspond closely in position with the narrow bands which appear in the absorption spectra of tryptophan, tyrosin, and phenylalanine. Tryptophan and tyrosin each present three bands, phenylalanine shows nine. 3. The bands in the proteins are accordingly attributed to these amino acids. In the proteins the bands are displaced from the positions which they occupy in the uncombined amino acids, in most instances, by 10 to 35 A. toward longer wavelengths. 4. The absorption spectrum of Pneumococcus Type I antibody resembles that of normal pseudoglobulin but shows characteristic differences. PMID:19872958

  7. EMPCA and Cluster Analysis of Quasar Spectra: Application to SDSS Spectra

    NASA Astrophysics Data System (ADS)

    Leighly, Karen; Marrs, Adam; Wagner, Cassidy; Macinnis, Francis

    2017-01-01

    Accurate modeling of the quasar continuum is necessary to measure and analyze absorption lines. But quasar continua, in particular the emission lines, vary from object to object. Patterns in the variations allow a spectral principal component analysis (SPCA) approach using large samples of quasar spectra, e.g., from the SDSS. Then, a small number of the derived principal component spectra can be used to reconstruct an arbitrary quasar's continuum.A problem with this approach is that the number of principal components required to model an arbitrary quasar, usually 8 to 20 in the literature, is large. One reason why so many components are required is that SPCA implicitly assumes that spectra bins are independent. Quasar emission lines are spread over a range of spectral bins, and more importantly, can sometimes be blueshifted. So while the intrinsic variability may only be a function of a few physical parameters, the nonlinearity inherent in the variations from object to object requires a large number of prinicipal components to accurately model a quasar continuum.We present a modified approach. We perform a SPCA analysis, using an expectation-maximization algorithm by Bailey et al. 2012, which takes into account uncertainties and missing data. We project the sample spectra on the resulting eignevectors to obtain the projection coefficients. Reasoning that intriniscally similar spectra will have similar projection coefficients, we perform a cluster analysis on the projection coefficients. The results are used to divide the sample into groups of similar spectra. A second PCA analysis is then performed on each group. We find that many fewer eigenspectra are required to accurately model the spectra in each group. We apply this approach to several samples of quasars from the SDSS.

  8. Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

    SciTech Connect

    Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria; Giacobbo, Francesca; Mariani, Mari; Brambilla, Luigi; Castiglioni, Chiara; Carrara, Mauro; Pignoli, Emanuele

    2015-07-01

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

  9. The D2O absorption spectra in the treatment surfaces SiO2 airgel

    NASA Astrophysics Data System (ADS)

    Sinitsa, L.; Lugovskoi, A.

    2014-11-01

    The D2O absorption spectra adsorbed on the nanoporous airgel SiO2 walls in the spectral range 4200 ... 5400 cm-1 are recorded. Two types of sample with pores of 60 nm wide - the nitrogen gas-treated and untreated airgels were examined. The untreated sample was prolonged evacuation and filling by the D2O saturated vapor. The nitrogen gas-treated sample was short-time pumping, accompanied by treatment with dry nitrogen, and re- lapping by the saturated vapor. As a result, the recorded absorption spectra were shown the changes the hydrophilic properties of the nanopores walls by modernity surface in the presence of nitrogen.

  10. Absorption Spectra of Broadened Sodium Resonance Lines in Presence of Rare Gases

    SciTech Connect

    Chung, H-K; Shurgalin, M; Babb, J F

    2002-09-11

    The pressure broadening of alkali-metal lines is a fundamental problem with numerous applications. For example, the sodium resonance lines broadened by xenon are important in the production of broad spectra emitted in the HPS (High-Pressure Sodium) lamp and they potentially can be used for gas condition diagnostics. Broadened absorption lines of alkali-metal atoms are prominent in the optical spectra of brown dwarfs and understanding the broadening mechanism will help elucidate the chemical composition and atmospheric properties of those stars. The far-line wing spectra of sodium resonance lines broadened by rare gases are found to exhibit molecular characteristics such as satellites and hence the total absorption coefficients for vapors of Na atoms and perturbing rare gas atoms can be modeled as Na-RG (rare gas) molecular absorption spectra. In this work, using carefully chosen interatomic potentials for Na-RG molecules we carry out quantum-mechanical calculations for reduced absorption coefficients for vapors composed of Na-He, Na-Ar, and Na-Xe. Calculated spectra are compared to available experimental results and the agreement is good in the measured satellite positions and shapes.

  11. Hierarchical analysis of molecular spectra

    SciTech Connect

    Davis, M.J.

    1996-03-01

    A novel representation of molecular spectra in terms of hierarchical trees has proven to be an important aid for the study of many significant problems in gas-phase chemical dynamics. Trees are generated from molecular spectra by monitoring the changes that occur in a spectrum as resolution is changed in a continuous manner. A tree defines a genealogy among all lines of a spectrum. This allows for a detailed understanding of the assignment of features of a spectrum that may be difficult to obtain any other way as well as an understanding of intramolecular energy transfer time scales, mechanisms, and pathways. The methodology has been applied to several problems: transition state spectroscopy, intramolecular energy transfer in highly excited molecules, high-resolution overtone spectroscopy, and the nature of the classical-quantum correspondence when there is classical chaos (``quantum chaos``).

  12. 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.

  13. 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.

  14. Variability of Water and Oxygen Absorption Bands in the Disk-integrated Spectra of Earth

    NASA Astrophysics Data System (ADS)

    Fujii, Yuka; Turner, Edwin L.; Suto, Yasushi

    2013-03-01

    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 H2O and O2 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 H2O and O2 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 H2O 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.

  15. 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.

  16. Simulation of the ?-? absorption and emission spectra of the SiCCl radical

    NASA Astrophysics Data System (ADS)

    Mitrushchenkov, Alexander O.; Brites, Vincent; Léonard, Céline

    2015-07-01

    The potential energy surface of the ? state and the ? transition dipole moments of the SiCCl radical have been calculated ab initio using multireference configuration interaction approaches. The rovibrational states of the ? state have been computed with the EVEREST code and, together with the previously calculated rovibronic states of the ? electronic ground state, have been used to produce absorption and emission spectra. The simulated emission spectra compare very well with the experimental laser-induced fluorescence spectra. The assignment of the rovibronic energies of the Renner-Teller ? electronic ground state has been completed.

  17. 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.

  18. Signatures in vibrational and UV-visible absorption spectra for identifying cyclic hydrocarbons by graphene fragments.

    PubMed

    Meng, Yan; Wu, Qi; Chen, Lei; Wangmo, Sonam; Gao, Yang; Wang, Zhigang; Zhang, Rui-Qin; Ding, Dajun; Niehaus, Thomas A; Frauenheim, Thomas

    2013-12-21

    To promote possible applications of graphene in molecular identification based on stacking effects, in particular in recognizing aromatic amino acids and even sequencing nucleobases in life sciences, we comprehensively study the interaction between graphene segments and different cyclic organic hydrocarbons including benzene (C6H6), cyclohexane (C6H12), benzyne (C6H4), cyclohexene (C6H10), 1,3-cyclohexadiene (C6H8(1)) and 1,4-cyclohexadiene (C6H8(2)), using the density-functional tight-binding (DFTB) method. Interestingly, we find obviously different characteristics in Raman vibrational and ultraviolet visible absorption spectra of the small molecules adsorbed on the graphene sheet. Specifically, we find that both spectra involve clearly different characteristic peaks, belonging to the different small molecules upon adsorption, with the ones of ionized molecules being more substantial. Further analysis shows that the adsorptions are almost all due to the presence of dispersion energy in neutral cases and involve charge transfer from the graphene to the small molecules. In contrast, the main binding force in the ionic adsorption systems is the electronic interaction. The results present clear signatures that can be used to recognize different kinds of aromatic hydrocarbon rings on graphene sheets. We expect that our findings will be helpful for designing molecular recognition devices using graphene.

  19. 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.

  20. 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).

  1. Atmospheric absorption spectra near 2200 kayser and 2400 kayser. [lower tropospheric temperature sounding

    NASA Technical Reports Server (NTRS)

    Susskind, J.; Mo, T.

    1978-01-01

    Quantitative interpretation of radiometric measurements for temperature profiling requires the ability to accurately calculate the average transmittance across the sounding channel. Therefore, an accurate calculation of atmospheric absorption due to broad banded or continuum absorption features is as significant as one of features due to individual lines. The important broad banded features affecting atmospheric absorption in the 4.3 micrometer region are due to the pressure induced N2 fundamental (called the N2 continuum) and to wings of relatively nearby very saturated CO2 lines. Attention is given to the N2 continuum, the CO2 line shape, and calculated and observed line spectra.

  2. [High-order derivative spectroscopy of infrared absorption spectra of the reaction centers from Rhodobacter sphaeroides].

    PubMed

    2005-01-01

    The infrared absorption spectra of reduced and chemically oxidized reaction center preparations from the purple bacterium Rhodobacter sphaeroides were investigated by means of high-order derivative spectroscopy. The model Gaussian band with a maximum at 810 nm and a half-band of 15 nm found in the absorption spectrum of the reduced reaction center preparation is eliminated after the oxidation of photoactive bacteriochlorophyll dimer (P). This band was related to the absorption of the P(+)y excitonic band of P. On the basis of experimental results, it was concluded that the bleaching of the P(+)y absorption band at 810 nm in the oxidized reaction center preparations gives the main contribution to the blue shift of the 800 nm absorption band of Rb. sphaeroides reaction centers.

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

    NASA Astrophysics Data System (ADS)

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

    2002-07-01

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

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

    DTIC Science & Technology

    2016-06-03

    provide interpretation of absorption spectra with respect to molecular structure for excitation by electromagnetic waves at frequencies within the...IR and UV-visible ranges. The absorption spectrum corresponding to excitation states of As-H2O complexes consisting of relatively small numbers of...As emphasized previously [17], the absorption spectrum of H2O clusters should be of significance for interpretation of absorption spectra

  5. The macroscopic field in ultrathin molecular films and its manifestation in absorption and Raman spectra

    SciTech Connect

    Tyu, N.S.

    1995-12-01

    Optical properties of an ultrathin molecular film placed in a dielectric medium are considered. A macroscopic field is calculated and a spectrum of Coulomb excitons is found. The features of their manifestation in absorption and Raman spectra are studied. 15 refs., 2 figs.

  6. Excited states and absorption spectra of β-diketonate complexes of boron difluoride with aromatic substituents

    NASA Astrophysics Data System (ADS)

    Vovna, V. I.; Kazachek, M. V.; L'vov, I. B.

    2012-04-01

    In the approximation of the time-dependent electron density functional theory, we have studied using the quantum-chemical method the nature of excited states of boron difluoride acetylacetonate F2BAA and its substituted derivatives that contain aromatic groups with one or two benzene cycles in the β-position. Optimization of the geometry of complexes show coplanar positions of cycles for all compounds, except for that with the substituent C6H3(CH3)2. Based on the calculated transition energies and oscillator strengths, we have simulated the absorption spectra in the prevacuum range. The calculated absorption spectra have been compared with the experimental spectra in the gas phase or in solutions. We show that, in the absorption spectra of complexes that contain substituents with one benzene cycle, the first three bands are caused by the transition of π electrons of the substituent to the LUMO of the chelate cycle. In complexes with two cycles in the substituent, the number of these transitions increases to five. As the π system becomes more extended, a bathochromic shift of the first absorption band and an increase in the transition probability are observed.

  7. 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.

  8. 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).

  9. Absorption and fluorescence spectra of poly(p-phenylenevinylene) (PPV) oligomers: an ab initio simulation.

    PubMed

    Cardozo, Thiago M; Aquino, Adélia J A; Barbatti, Mario; Borges, Itamar; Lischka, Hans

    2015-03-05

    The absorption and fluorescence spectra of poly(p-phenylenevinylene) (PPV) oligomers with up to seven repeat units were theoretically investigated using the algebraic diagrammatic construction method to second order, ADC(2), combined with the resolution-of-the-identity (RI) approach. The ground and first excited state geometries of the oligomers were fully optimized. Vertical excitation energies and oscillator strengths of the first four transitions were computed. The vibrational broadening of the absorption and fluorescence spectra was studied using a semiclassical nuclear ensemble method. After correcting for basis set and solvent effects, we achieved a balanced description of the absorption and fluorescence spectra by means of the ADC(2) approach. This fact is documented by the computed Stokes shift along the PPV series, which is in good agreement with the experimental values. The experimentally observed band width of the UV absorption and fluorescence spectra is well reproduced by the present simulations showing that the nuclear ensemble generated should be well suitable for consecutive surface hopping dynamics simulations.

  10. Comparison of x-ray absorption spectra between water and ice: New ice data with low pre-edge absorption cross-section

    SciTech Connect

    Sellberg, Jonas A.; Nilsson, Anders; Kaya, Sarp; Segtnan, Vegard H.; Chen, Chen; Tyliszczak, Tolek; Ogasawara, Hirohito; Nordlund, Dennis; Pettersson, Lars G. M.

    2014-07-21

    The effect of crystal growth conditions on the O K-edge x-ray absorption spectra of ice is investigated through detailed analysis of the spectral features. The amount of ice defects is found to be minimized on hydrophobic surfaces, such as BaF{sub 2}(111), with low concentration of nucleation centers. This is manifested through a reduction of the absorption cross-section at 535 eV, which is associated with distorted hydrogen bonds. Furthermore, a connection is made between the observed increase in spectral intensity between 544 and 548 eV and high-symmetry points in the electronic band structure, suggesting a more extended hydrogen-bond network as compared to ices prepared differently. The spectral differences for various ice preparations are compared to the temperature dependence of spectra of liquid water upon supercooling. A double-peak feature in the absorption cross-section between 540 and 543 eV is identified as a characteristic of the crystalline phase. The connection to the interpretation of the liquid phase O K-edge x-ray absorption spectrum is extensively discussed.

  11. Solvent and structural effects on the UV absorption spectra of N-(substituted phenyl)-2-cyanoacetamides.

    PubMed

    Matijević, Borko M; Vaštag, Đenđi Đ; Perišić-Janjić, Nada U; Apostolov, Suzana Lj; Milčić, Miloš K; Živanović, Lidija; Marinković, Aleksandar D

    2014-01-03

    UV absorption spectra of N-(substituted phenyl)-2-cyanoacetamides have been recorded in the range 200-400 nm in the set of selected solvents. The solute-solvent interactions were analyzed on the basis of linear solvation energy relationships (LSER) concept proposed by Kamlet and Taft. The effects of substituents on the absorption spectra were interpreted by correlation of absorption frequencies with Hammett substituent constant, σ. It was found that substituents significantly change the extent of conjugation. Furthermore, the experimental findings were interpreted with the aid of ab initio B3LYP/6-311G(d,p) method. Electronic energies was calculated by the use of 6-311++G(3df,3pd) methods with standard polarized continuum model (PCM) for inclusion of the solvent effect.

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  15. 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.

  16. Delta bilirubin: absorption spectra, molar absorptivity, and reactivity in the diazo reaction.

    PubMed

    Doumas, B T; Wu, T W; Jendrzejczak, B

    1987-06-01

    Delta bilirubin (B delta), isolated from serum, has an absorption maximum near 440 nm and a molar absorptivity of 72,000 L mol-1cm-1 in either Tris HCl (0.1 mol/L, pH 8.5) or phosphate (0.13 mol/L, pH 7.4) buffer. This absorptivity exceeds by approximately 50% and 59%, respectively, that of unconjugated bilirubin in the same buffers. This finding suggests that substantial errors can be incurred in direct spectrophotometry of bilirubins in serum. In the total diazo (TBIL) assay (Clin Chem 1985;31:1779-89), the color yield from B delta increases by 10% as the final diazo concentration is increased from 0.27 to 0.81 mmol/L. In the direct (DBIL) assay, if done in HCl (50 mmol/L), B delta yields approximately 15% more color as the diazo concentration is increased from 0.51 to 1.53 mmol/L, whereas in acetate buffer (0.4 mol/L, pH 4.7) the corresponding color yield is 25% greater. However, the absolute color yield for the reaction in HCl exceeds that in acetate buffer. In both the TBIL and the DBIL assay, B delta reacts slowly, nearly complete reaction requiring 10 min. Thus, B delta may be seriously underestimated in diazo (especially DBIL) methods in which short reaction times (20 s to 1 min) are used.

  17. PCA: Principal Component Analysis for spectra modeling

    NASA Astrophysics Data System (ADS)

    Hurley, Peter D.; Oliver, Seb; Farrah, Duncan; Wang, Lingyu; Efstathiou, Andreas

    2012-07-01

    The mid-infrared spectra of ultraluminous infrared galaxies (ULIRGs) contain a variety of spectral features that can be used as diagnostics to characterize the spectra. However, such diagnostics are biased by our prior prejudices on the origin of the features. Moreover, by using only part of the spectrum they do not utilize the full information content of the spectra. Blind statistical techniques such as principal component analysis (PCA) consider the whole spectrum, find correlated features and separate them out into distinct components. This code, written in IDL, classifies principal components of IRS spectra to define a new classification scheme using 5D Gaussian mixtures modelling. The five PCs and average spectra for the four classifications to classify objects are made available with the code.

  18. Effects of solvent and substituent on the electronic absorption spectra of some substituted Schiff bases: a chemometrics study.

    PubMed

    Hemmateenejad, Bahram; Yazdani, Mahdieh; Sharghi, Hashem

    2012-06-01

    A series of Schiff bases were studied for their delicate changes in absorption electronic spectra by changing substituents and solvents. UV/vis absorbance spectra of Schiff base derivatives of different substituents ranging from electron withdrawing to electron donating (Br, CF(3), Cl, CN, CO(2)H, F, Me, NO(2), OH, OMe, H) were studied in different solvents (acetonitrile, chloroform, cyclohexane, dioxane, dimethylsulfoxide and methanol). Linear relationships were established to investigate the effect of solute structure and solvatochromic parameters of solvents on the absorbance spectra. Meaningful chemical factors and then regression models were provided utilizing factor analysis (FA) and multiple linear regression (MLR). It was found that the frequency of maximum absorbance was mainly controlled by the solvent's dipolarity/polarizability. The λ(max) of the ortho-nitro derivative represented the largest dependency on solvents' polarity/polarizability so that it can be used as a solvatochromic probe. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Infrared absorption and Raman scattering spectra of water under pressure via first principles molecular dynamics.

    PubMed

    Ikeda, Takashi

    2014-07-28

    From both the polarized and depolarized Raman scattering spectra of supercritical water a peak located at around 1600 cm(-1), attributed normally to bending mode of water molecules, was experimentally observed to vanish, whereas the corresponding peak remains clearly visible in the measured infrared (IR) absorption spectrum. In this computational study a theoretical formulation for analyzing the IR and Raman spectra is developed via first principles molecular dynamics combined with the modern polarization theory. We demonstrate that the experimentally observed peculiar behavior of the IR and Raman spectra for water are well reproduced in our computational scheme. We discuss the origins of a feature observed at 1600 cm(-1) in Raman spectra of ambient water.

  20. 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.

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

    SciTech Connect

    Lewandowski, Wojciech; Rożko, Karolina; Kijak, Jarosław; Melikidze, George I.

    2015-07-20

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

  2. SimBAL: A Spectral Synthesis Approach to Analyzing Broad Absorption Line Quasar Spectra

    NASA Astrophysics Data System (ADS)

    Terndrup, Donald M.; Leighly, Karen; Gallagher, Sarah; Richards, Gordon T.

    2017-01-01

    Broad Absorption Line quasars (BALQSOs) show blueshifted absorption lines in their rest-UV spectra, indicating powerful winds emerging from the central engine. These winds are essential part of quasars: they can carry away angular momentum and thus facilitate accretion through a disk, they can distribute chemically-enriched gas through the intergalactic medium, and they may inject kinetic energy to the host galaxy, influencing its evolution. The traditional method of analyzing BALQSO spectra involves measuring myriad absorption lines, computing the inferred ionic column densities in each feature, and comparing with the output of photonionization models. This method is inefficient and does not handle line blending well. We introduce SimBAL, a spectral synthesis fitting method for BALQSOs, which compares synthetic spectra created from photoionization model results with continuum-normalized observed spectra using Bayesian model calibration. We find that we can obtain an excellent fit to the UV to near-IR spectrum of the low-redshift BALQSO SDSS J0850+4451, including lines from diverse ionization states such as PV, CIII*, SIII, Lyalpha, NV, SiIV, CIV, MgII, and HeI*.

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

    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.

  5. 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.

  6. Multivariate analysis of endometrial tissue fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Vaitkuviene, Aurelija; Auksorius, E.; Fuchs, D.; Gavriushin, V.

    2002-10-01

    Background and Objective: The detailed multivariate analysis of endometrial tissue fluorescence spectra was done. Spectra underlying features and classification algorithm were analyzed. An effort has been made to determine the importance of neopterin component in endometrial premalignization. Study Design/Materials and Methods: Biomedical tissue fluorescence was measured by excitation with the Nd YAG laser third harmonic. Multivariate analysis techniques were used to analyze fluorescence spectra. Biomedical optics group at Vilnius University analyzed the neopterin substance supplied by the Institute of Medical Chemistry and Biochemistry of Innsbruck University. Results: Seven statistically significant spectral compounds were found. The classification algorithm classifying samples to histopathological categories was developed and resulted in sensitivity of 80% and specificity 93% for malignant vs. hyperplastic and normal. Conclusions: Fluorescence spectra could be classified with high accuracy. Spectral variation underlying features can be extracted. Neopterin component might play an important role in endometrial hyperplasia development.

  7. Vibrational dynamics of DNA. II. Deuterium exchange effects and simulated IR absorption spectra

    NASA Astrophysics Data System (ADS)

    Lee, Chewook; Cho, Minhaeng

    2006-09-01

    In Paper I, we studied vibrational properties of normal bases, base derivatives, Watson-Crick base pairs, and multiple layer base pair stacks in the frequency range of 1400-1800cm-1. However, typical IR absorption spectra of single- and double-stranded DNA have been measured in D2O solution. Consequently, the more relevant bases and base pairs are those with deuterium atoms in replacement with labile amino hydrogen atoms. Thus, we have carried out density functional theory vibrational analyses of properly deuterated bases, base pairs, and stacked base pair systems. In the frequency range of interest, both aromatic ring deformation modes and carbonyl stretching modes appear to be strongly IR active. Basis mode frequencies and vibrational coupling constants are newly determined and used to numerically simulate IR absorption spectra. It turns out that the hydration effects on vibrational spectra are important. The numerically simulated vibrational spectra are directly compared with experiments. Also, the O18-isotope exchange effect on the poly(dG):poly(dC) spectrum is quantitatively described. The present calculation results will be used to further simulate two-dimensional IR photon echo spectra of DNA oligomers in the companion Paper III.

  8. Low Temperature Absorption Spectra of Chlorophyll a in Polar and Nonpolar Solvents

    PubMed Central

    Brody, S. S.; Broyde, S. B.

    1968-01-01

    Absorption spectra of chlorophyll a were measured in polar and non-polar solvents, as a function of temperature from 298° to 77°K. Both dilute and concentrated solutions were examined. In both types of solvents at room temperature, the absorption spectra of concentrated solutions differ from dilute ones in that the half width of the main red absorption band is greater, and all bands are shifted to longer wavelengths. These differences are largely due to the presence of dimers when the pigment concentration is high. In dilute ethanol solutions, where the chlorophyll is unassociated, cooling causes a red shift in all bands which is due to the increased polarity of the solvent at low temperature. On cooling at high concentrations in ethanol and EPA, a new band appears near 700 nm. This band is attributed to dimers present prior to cooling, but absorbing at shorter wavelengths at room temperature. In nonpolar solvents, a band near 700 nm appears at the solvent freezing point. In these solvents, the “700” nm absorption is attributed to dimers, and/or small polymers, partly formed by cooling. A change in aggregate geometry when the solvent becomes viscous or frozen can account for the appearance of this “700” nm absorption band at low temperature, in polar and nonpolar media. PMID:5713456

  9. 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.

  10. Theoretical simulations for vibrationally-resolved absorption spectra of naphthalenediimide cyclophane derivatives

    NASA Astrophysics Data System (ADS)

    Song, Ce; Li, Li; Duan, Sai; Luo, Yi; Tian, Guangjun

    2017-08-01

    In the present work we systematically investigated the vibrationally-resolved absorption spectra of three core substituted naphthalenediimide cyclophane derivatives. It has been performed by time-dependent density functional theory calculations using three different exchange-correlation functionals, including the conventional B3LYP functional and two long-range corrected functionals: CAM-B3LYP and ωB97XD. The solvent effects were also considered with the polarizable continuum model. Calculation results showed that long range corrections are needed to correctly describe the optical properties of the three molecules because of the strong charge transfer characteristic of the excited states. The core substitution induced red shift to the first absorption band is nicely explained by the theoretical calculations. It is found that this band mainly involves the transitions within the core substituted naphthalenediimide chromophore. The high energy absorption band, on the other hand, is generated mainly from the un-substituted chromophore. These characters result in different substitution dependence for those two main absorption bands. Furthermore, the simulated vibrational profiles of the first two absorption bands nicely reproduce the observed vibrational features in the measured spectra. The accuracy of the calculated results from different functionals and basis sets has been discussed.

  11. Optical Absorption Spectra of Ternary Complex of Praseodymium in Different Environment

    NASA Astrophysics Data System (ADS)

    Gupta, Anup Kumar; Ujjwal, Shri Kishan

    The optical absorption spectra of complex of Praseodymium in different solvents i.e water, Methanol, Ethanol & Acetic Acid have been recorded in visible region (360-620 nm for Pr3+) using amino acid as primary ligand and diol as secondary ligand. The value of energies & intensities of various transitions have been calculated using Judd-Ofelt relation is in good agreement with experimental result. The study of complex found it to be covalent in nature. The spectra in visible region have been recorded on model uv-2601 Rayleigh analytical instrument corp.

  12. Absorption, fluorescence, and SERS spectra of sanguinarine at different pH values

    NASA Astrophysics Data System (ADS)

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

    2007-09-01

    We have studied the absorption, fluorescence, and surface-enhanced Raman scattering (SERS) spectra of sanguinarine using a silver hydrosol and an electrochemical cell with a silver working electrode for different pH values in the medium. We carried out quantum chemical calculations in order to interpret the electronic and vibrational spectra and to establish their correlations with the structure of the molecules. We optimized the structure and determined the spectral characteristics of the cationic and neutral forms of the sanguinarine molecules in solution and adsorbed on the surface of an anodized Ag electrode for different potentials.

  13. Near-IR Absorption Spectra for the C70 Fullerene Anions

    DTIC Science & Technology

    1992-07-20

    were prepared in benzonitrile that was 0.1M in Bu 4 NPF6 support- ing electrolyte. Spectra of the various C70 species were obtained at room temperature...we note that the near-IR transition observed for C701 " appears at the same wavelength in benzonitrile and dichloromethane solutions. Furthermore...1. UV-visible-near-IR absorption spectra for (A) C70 and (B) C70 1- obtained in benzonitrile /0.1M Bu 4NPF6. A blank sample of the supporting

  14. Density-functional calculations of structures and absorption spectra of sulfur cluster S-6

    NASA Astrophysics Data System (ADS)

    Zhu, J.; Cheng, Y.; Bai, Y. L.; Chen, X. R.

    2005-01-01

    A finite-difference pseudopotential density-functional theory in real space and the Langevin molecular dynamics annealing technique as well as the adiabatic time-dependent density functional theory within the time-dependent local density approximation (TDLDA) are applied to the descriptions of structures and optical absorption spectra of sulfur cluster S-6. It is found that the ground-state structure of S-6 belongs to either a boat-shaped C-2v or chair-shaped D-3d symmetry structure and the calculated spectra exhibit a variety of features that can be used for comparison against future experimental investigations.

  15. 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.

  16. Intervening Mg II absorption systems from the SDSS DR12 quasar spectra

    NASA Astrophysics Data System (ADS)

    Raghunathan, Srinivasan; Clowes, Roger G.; Campusano, Luis E.; Söchting, Ilona K.; Graham, Matthew J.; Williger, Gerard M.

    2016-12-01

    We present the catalogue of the Mg II absorption systems detected at a high significance level using an automated search algorithm in the spectra of quasars from the 12th data release of the Sloan Digital Sky Survey. A total of 266,433 background quasars were searched for the presence of absorption systems in their spectra. The continuum modelling for the quasar spectra was performed using a mean filter. A pseudo-continuum derived using a median filter was used to trace the emission lines. The absorption system catalogue contains 39,694 Mg II systems detected at a 6.0, 3.0σ level respectively for the two lines of the doublet. The catalogue was constrained to an absorption line redshift of 0.35 ≤ z2796 ≤ 2.3. The rest-frame equivalent width of the λ2796 line ranges between 0.2 ≤ Wr ≤ 6.2 Å. Using Gaussian noise-only simulations, we estimate a false positive rate of 7.7 per cent in the catalogue. We measured the number density ∂N2796/∂z of Mg II absorbers and find evidence for steeper evolution of the systems with Wr ≥ 1.2 Å at low redshifts (z2796 ≤ 1.0), consistent with other earlier studies. A suite of null tests over the redshift range 0.5 ≤ z2796 ≤ 1.5 was used to study the presence of systematics and selection effects like the dependence of the number density evolution of the absorption systems on the properties of the background quasar spectra. The null tests do not indicate the presence of any selection effects in the absorption catalogue if the quasars with spectral signal-to-noise level less than 5.0 are removed. The resultant catalogue contains 36,981 absorption systems. The Mg II absorption catalogue is publicly available and can be downloaded from the link http://srini.ph.unimelb.edu.au/mgii.php.

  17. In vivo low-coherence spectroscopic measurements of local hemoglobin absorption spectra in human skin

    NASA Astrophysics Data System (ADS)

    Bosschaart, Nienke; Faber, Dirk J.; van Leeuwen, Ton G.; Aalders, Maurice C. G.

    2011-10-01

    Localized spectroscopic measurements of optical properties are invaluable for diagnostic applications that involve layered tissue structures, but conventional spectroscopic techniques lack exact control over the size and depth of the probed tissue volume. We show that low-coherence spectroscopy (LCS) overcomes these limitations by measuring local attenuation and absorption coefficient spectra in layered phantoms. In addition, we demonstrate the first in vivo LCS measurements of the human epidermis and dermis only. From the measured absorption in two distinct regions of the dermal microcirculation, we determine total hemoglobin concentration (3.0+/-0.5 g/l and 7.8+/-1.2 g/l) and oxygen saturation.

  18. In vivo low-coherence spectroscopic measurements of local hemoglobin absorption spectra in human skin.

    PubMed

    Bosschaart, Nienke; Faber, Dirk J; van Leeuwen, Ton G; Aalders, Maurice C G

    2011-10-01

    Localized spectroscopic measurements of optical properties are invaluable for diagnostic applications that involve layered tissue structures, but conventional spectroscopic techniques lack exact control over the size and depth of the probed tissue volume. We show that low-coherence spectroscopy (LCS) overcomes these limitations by measuring local attenuation and absorption coefficient spectra in layered phantoms. In addition, we demonstrate the first in vivo LCS measurements of the human epidermis and dermis only. From the measured absorption in two distinct regions of the dermal microcirculation, we determine total hemoglobin concentration (3.0±0.5 g∕l and 7.8±1.2 g∕l) and oxygen saturation.

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

    PubMed

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

    2003-01-01

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

  20. 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.

  1. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-07-01

    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.

  3. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Three-dimensional time-dependent wave-packet calculations of OBrO absorption spectra

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Sun, Zhigang; Cong, Shu-Lin; Lou, Nanquan

    2005-08-01

    The absorption spectra of the C(A22)←X(B12) transition of the OBrO molecule are calculated using three-dimensional time-dependent wave-packet method in Radau coordinates for a total angular momentum J =0. The wave packet is propagated using the split operator technique associated with fast Fourier transform. Employing the basis functions obtained by one-dimensional Fourier grid Hamiltonian method, the initial wave packet is calculated directly on the three-dimensional Fourier grid. The numerical model is characterized by simplicity and efficiency. The ab initio potential surfaces for the C(A22) and X(B12) states are used in the calculation. The calculated absorption spectra of the C(A22)←X(B12) transition of OBrO molecule agree well with the experimental results.

  5. 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.

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

    DTIC Science & Technology

    2013-08-20

    the calculated absorption spectra of isolated molecules can help to identify intramolecular vibrational modes of various materials. A series of...Transformation A molecule in 3-dimensions has a total of 3N-6 normal mode vibrations . The Schrodinger equation for the harmonic...oscillations of these normal modes has known solutions. The quantum mechanical spectrum of each of these vibrations is given in the harmonic approximation

  7. Ab initio study of optical absorption spectra of semiconductors and conjugated polymers

    SciTech Connect

    Tiago, M.L.; Chang, Eric K.; Rohlfing, Michael; Louie, Steven G.

    2000-04-30

    The effects of electron-hole interaction on the optical properties of a variety of materials have been calculated using an ab initio method based on solving the Bethe-Salpeter equation. Results on selected semiconductors, insulators, and semiconducting polymers are presented. In the cases of alpha-quartz (SiO2) and poly-phenylene-vinylene, resonant excitonic states qualitatively alter the absorption spectra.

  8. Multifractal Analysis of Expoplanetary Spectra

    NASA Astrophysics Data System (ADS)

    Agarwal, S.; Sordo, F. D.; Wettlaufer, J. S.

    2016-12-01

    Owing to technological advances the number of exoplanets discovered has risen dramatically in the last few years. However, the false detection rate is still high. We have developed a new approach to the analysis of exoplanetary spectral observations based on temporal multifractality, which focuses on identifying time scales that characterize planetary orbital motion around the host star. With no fitting of spectral data to stellar models, we show how the planetary signal can be robustly detected from the noisy data using stochasticity as a source of information. Combining this with simple geometry allows us to relate the time scales obtained to primary transit and secondary eclipse of the exoplanets. Making use of publicly available data obtained with ground-based and space-based observations we have tested our approach on HD 189733b. We have also investigated the use of this technique in measuring planetary orbital motion via doppler shift detection. We have analyzed data obtained with the SOAP 2.0 tool, that simulates a stellar spectrum and how it can be affected by the presence of a planet or a spot across one orbital period. We have demonstrated that our approach reconstructs the planetary orbital period, as well as the rotation period of a spot on the stellar surface as long as the signal-to-noise-ratio ≥ 100.

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

    PubMed

    Mosquera, Martín A; Jackson, Nicholas E; Fauvell, Thomas J; Kelley, Matthew S; Chen, Lin X; Schatz, George C; Ratner, Mark A

    2017-03-15

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

  10. High-resolution Absorption Spectra of Acetylene in 142.8-152.3 nm

    NASA Astrophysics Data System (ADS)

    Hu, Ya-hua; Zhen, Chen; Dai, Jing-hua; Zhou, Xiao-guo; Liu, Shi-lin

    2008-10-01

    The absorption spectra of acetylene molecules was measured under jet-cooled conditions in the wavelength range of 142.8-152.3 nm, with a tunable and highly resolved vacuum ultraviolet (VUV) laser generated by two-photon resonant four wave difference frequency mixing processes. Due to the sufficient vibrational and rotational cooling effect of the molecular beam and the higher resolution VUV laser, the observed absorption spectra exhibit more distinct spectral features than the previous works measured at room temperature. The major three vibrational bands are assigned as a C-C symmetry stretching vibrational progress (u2 = 0-2) of the tilde C1 IIu state of acetylene. The observed shoulder peak at 148.2 nm is assigned to the first overtone band of the trans-bending mode u4 of the tilde C1 IIustate of acetylene. Additionally, the two components, 4o2(μ1IIu) and 4o2(κ1 IIuare suggested to exhibit in the present absorption spectra, due to their Renner-Teller effect and transition selection rule. All band origins and bandwidths are obtained subsequently, and it is found that bandwidths are broadened and lifetimes decrease gradually with the excitation of vibration.

  11. 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

    2011-11-03

    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.

  12. 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.

  13. The use of commercial glass as a potential gamma accidental dosimeter through the absorption spectra

    NASA Astrophysics Data System (ADS)

    Kharita, M. H.; Yousef, S.; Bakr, S.

    2012-05-01

    Various types of commercial glass (ordinary windows, cathode ray tubes, glass kitchenware) have been studied as potential accidental radiation dosimeters. The proposed method utilizes the changes in the glasses' absorption spectra as a result of irradiation. A 60Co gamma irradiation cell has been used to irradiate samples with doses ranging from 5 to 200 Gy. The transmittance was measured using a photospectrometer (UV-visible spectrometry). The results demonstrate that the transmittance spectra of most of the glass samples change in linear proportion to the exposure dose. Moreover, the study considers the fading effect on the absorption spectra of the irradiated samples for fading times up to 100 days at room temperature. The results of this work demonstrate that several widely used types of glass can be used as high-dose accidental dosimeters for doses ranging between 8 and 200 Gy. A reasonable calibration line can be established for any irradiated glass sample by heating, re-irradiating with standard doses and measuring the related absorption coefficient. Further investigations are needed to decrease the minimum detectable dose of the proposed method and to study the effect of glass composition on radiation response.

  14. 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%.

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

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

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

  16. [Wavelet property analysis of near infrared spectra].

    PubMed

    Tian, Gao-You; Yuan, Hong-Fu; Liu, Hui-Ying

    2006-08-01

    Wavelet analysis (WT) was conducted on the simulated near infrared spectra (NIR) obtained by adding simulated background and simulated noise into diesel NIR Results show that the background components are mainly located in the low frequency region, while noise in the high frequency region, and useful signal in the middle frequency region. Background and noise components can be simultaneously subtracted from the spectra by WT. The WT coefficients in mid-frequency details can be selected as variables to build the multivariate calibration model, which can improve analytic accuracy and reduce the analysis time.

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

    NASA Astrophysics Data System (ADS)

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

    2006-09-01

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

  18. 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.

  19. Time-resolved Absorption Spectra of the Laser-dressed Hydrogen Atom

    NASA Astrophysics Data System (ADS)

    Murakami, Mitsuko; Chu, Shih-I.

    2013-05-01

    A theoretical study of the transient absorption spectra for the laser-dressed hydrogen atom based on the accurate numerical solution of the time-dependent Schrödinger equation is presented. The timing of absorption is controlled by the time delay between an isolated extreme ultraviolet (XUV) pulse and a dressing infrared (IR) field. We identify two different kinds of physical processes in the spectra. One is the formation of dressed states, signified by the appearance of sidebands between the XUV absorption lines separated by one IR-photon energy. We show that their population is maximized when the XUV pulse coincides with the zero-crossing of the IR field, and that their energy can be manipulated by using a chirped IR field. The other process is the dynamical AC Stark shift induced by the IR field and probed by the XUV pulse. Our calculations indicate that the accidental degeneracy of the hydrogen atom leads to the multiple splittings of each XUV absorption line whose separations change in response to a slowly-varying IR envelope. Furthermore, we observe the Autler-Townes doublets for the n=2 and 3 states using the 656 nm dressing field, but their separation does not agree with the prediction by the conventional 3-level model that neglects the dynamical AC Stark effects.

  20. 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.

  1. 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.

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

    PubMed

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

    2012-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  4. Dynamical analysis of highly excited molecular spectra

    SciTech Connect

    Kellman, M.E.

    1993-12-01

    The goal of this program is new methods for analysis of spectra and dynamics of highly excited vibrational states of molecules. In these systems, strong mode coupling and anharmonicity give rise to complicated classical dynamics, and make the simple normal modes analysis unsatisfactory. New methods of spectral analysis, pattern recognition, and assignment are sought using techniques of nonlinear dynamics including bifurcation theory, phase space classification, and quantization of phase space structures. The emphasis is chaotic systems and systems with many degrees of freedom.

  5. Principal component analysis of synthetic galaxy spectra

    NASA Astrophysics Data System (ADS)

    Ronen, Shai; Aragon-Salamanca, Alfonso; Lahav, Ofer

    1999-02-01

    We analyse synthetic galaxy spectra from the evolutionary models of Bruzual & Charlot and Fioc & Rocca-Volmerange using the method of principal component analysis (PCA). We explore synthetic spectra with different ages, star formation histories and metallicities, and identify the principal components (PCs) of variance in the spectra resulting from these different model parameters. The PCA provides a more objective and informative alternative to diagnostics by individual spectral lines. We discuss how the PCs can be used to estimate the input model parameters, and explore the impact of dust and noise in this inverse problem. We also discuss how changing the sampling of the ages and other model parameters affects the resulting PCs. Our first two synthetic PCs agree with a similar analysis on observed spectra obtained by Kennicutt and the 2dF redshift survey. We conclude that with a good enough signal-to-noise ratio (S/N> > 10) it is possible to derive age, star formation history and metallicity from observed galaxy spectra using PCA.

  6. Principal component analysis of phenolic acid spectra

    USDA-ARS?s Scientific Manuscript database

    Phenolic acids are common plant metabolites that exhibit bioactive properties and have applications in functional food and animal feed formulations. The ultraviolet (UV) and infrared (IR) spectra of four closely related phenolic acid structures were evaluated by principal component analysis (PCA) to...

  7. Composite Spectra of Broad Absorption Line Quasars in SDSS-III BOSS

    NASA Astrophysics Data System (ADS)

    Herbst, Hanna; Hamann, Fred; Paris, Isabelle; Capellupo, Daniel M.

    2017-01-01

    We present preliminary results from a study of broad absorption line (BAL) quasars in the SDSS-III BOSS survey. We’re particularly interested in BALs because they arise from quasar outflows, which may be a source of feedback to the host galaxy. We analyze median composite spectra for BOSS QSOs in the redshift range 2.1 to 3.4 sorted by the strength of the BAL absorption troughs, parameterized by the Balnicity Index (BI), to study trends in the emission and absorption properties of BAL quasars. The wavelength coverage and high number of quasars observed in the BOSS survey allow us to examine BALs in the Lyman forest. Our main preliminary results when sorting the quasars by BI are 1) doublet absorption lines such as P V 1128A show a 1:1 ratio across all BI, indicating large column densities at all BI. This suggests that weaker BAL troughs result from smaller covering fractions rather than lower column densities. 2) The He II emission line, which is a measure of the far-UV/near-UV hardness of the ionizing continuum, is weaker in the larger BI composite spectra, indicating a far-UV spectral softening correlated with BI. This is consistent with the radiatively-driven BAL outflows being helped by intrinsically weaker ionizing continuum shapes (e.g., Baskin, Laor, and Hamann 2013). We also find a trend for slightly redder continuum slopes in the larger BI composite spectra, suggesting that the slope differences in the near-UV are also intrinsic.

  8. 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.

  9. [The absorption and fluorescence spectra of the cyanobacterial phycobilins of cryptoendolithic lichens in the high-polar region of Antarctica].

    PubMed

    Erokhina, L G; Shatilovich, A V; Kaminskaia, O P; Gilichinskiĭ, D A

    2002-01-01

    The algologically pure cultures of the green-brown cyanobacterium Chroococcidiopsis sp. and three cyanobacteria of the genus Gloeocapsa, the blue-green Gloeocapsa sp.1, the brown Gloeocapsa sp.2, and the red-orange Gloeocapsa sp.3, were isolated from sandstones and rock fissures in the high-polar regions of Antarctica. These cyanobacteria are the most widespread phycobionts of cryptoendolithic lichens in these regions. The comparative analysis of the absorption and the second-derivative absorption spectra of the cyanobacteria revealed considerable differences in the content of chlorophyll a and in the content and composition of carotenoids and phycobiliproteins. In addition to phycocyanin, allophycocyanin, and allophycocyanin B, which were present in all of the cyanobacteria studied, Gloeocapsa sp.2 also contained phycoerythrocyanin and Gloeocapsa sp.3 phycoerythrocyanin and C-phycoerythrin (the latter pigment is typical of nitrogen-fixing cyanobacteria). The fluorescence spectra of Gloeocapsa sp.2 and Gloeocapsa sp.3 considerably differed from the fluorescence spectra of the other cyanobacteria as well. The data obtained suggest that various zones of the lichens may be dominated either by photoheterotrophic or photoautotrophic cyanobacterial phycobionts, which differ in the content and composition of photosynthetic pigments.

  10. Harmonic and anharmonic features of IR and NIR absorption and VCD spectra of chiral 4-X-[2.2]paracyclophanes.

    PubMed

    Abbate, Sergio; Castiglioni, Ettore; Gangemi, Fabrizio; Gangemi, Roberto; Longhi, Giovanna; Ruzziconi, Renzo; Spizzichino, Sara

    2007-08-02

    The vibrational absorption spectra and vibrational circular dichroism (VCD) spectra of both enantiomers of 4-X-[2.2]paracyclophanes (X = COOCD3, Cl, I) have been recorded for a few regions in the range of 900-12000 cm(-1). The analysis of the VCD spectra for the two IR regions, 900-1600 cm(-1) and 2800-3200 cm(-1), is conducted by comparing with DFT calculations of the corresponding spectra; the latter region reveals common motifs of vibrational modes for the three molecules for aliphatic CH stretching fundamentals, whereas in the mid-IR region, one is able to identify specific signatures arising from the substituent groups X. In the CH stretching region between 2900 and 2800 cm(-1), we identify and interpret a group of three IR VCD bands due to HCH bending overtone transitions in Fermi resonance with CH stretching fundamental transitions. The analysis of the NIR region between approximately 8000 and approximately 9000 cm(-1) for X = COOCD3 reveals important features of the aromatic CH stretching overtones that are of value since the aromatic CH stretching fundamentals are almost silent. The intensifying of such overtones is attributed to electrical anharmonicity terms, which are evaluated here by ab initio methods and compared with literature data.

  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. Ultraviolet and Visible Absorption Spectra of Potassium and Potassium-Xenon Mixtures

    NASA Astrophysics Data System (ADS)

    Johnson, Daniel Enoch

    1985-12-01

    The visible absorption spectrum of the potassium dimer has been studied using a new type of optical cell designed specifically for the alkali vapors or alkali-rare gas mixtures. Particular emphasis has been placed on examining the diffuse K(,2) bands lying at 722 nm, 575 nm, 478 nm and 402 nm. Measurements of the reduced absorption coefficient for each feature are presented, and band assignments are made in light of ab initio potential energy level calculations for K(,2) that were recently made by Konowalow and Fish. The 575 nm band is found to arise from the free-bound (excimer) 2('3)(PI)(,g) (<---) 1('3)(SIGMA)(,u)('+) transition of the molecule, and the band peaking near 722 nm, which has been previously attributed to the 1('3)(PI)(,g) (<---) 1('3)(SIGMA)(,u)('+) transition, has been reexamined. The blue and violet features are shown to probably arise from the C('1)(PI)(,u) (<---) X('1)(SIGMA)(,g)('+) transition of K(,2). The ultraviolet and visible absorption spectra of potassium vapor - xenon mixtures have been studied for K and Xe as large as 7(.)10('17) cm('-3) and 4(.)10('19) cm('-3), respectively. Collision -induced absorption is observed inthe ultraviolet (285 (LESSTHEQ) (lamda) < 370 nm) for the 4S (--->) nF, nD (4 (LESSTHEQ) n (LESSTHEQ) 8) transitions as well as for the 4S (--->) 5S transition in the visible, but peak absorption lies an average of (TURN)0.6 nm to the red side of the position of the electric dipole forbidden line. The 4S (--->) 4F, 5F transitions, in particular, are quite strong, having peak reduced absorption coefficients measured (within a factor of 2) to be 1.1(.)10('-39) cm('5) and 2.6(.)10(' -40) cm('5), respectively. The KXe (C('2)(SIGMA)) excimer has been observed in absorption for the first time. Absorption at the band peak (reduced absorption coeffi- cient of (TURN)2(.)10(' -40) cm('5) at (lamda) = 507 nm) is roughly two orders of magnitude weaker than that for the analogous bands of CsXe and RbXe and is displaced at least 5 nm

  13. EMPCA and Cluster Analysis of Quasar Spectra: Sample Preparation and Validation

    NASA Astrophysics Data System (ADS)

    Wagner, Cassidy; Leighly, Karen; Macinnis, Francis; Marrs, Adam; Richards, Gordon T.

    2017-01-01

    All quasars are fundamentally similar, powered by accretion of matter onto a super massive black hole. However, patterns of differences can be identified through the emission lines. Quasar broad absorption lines have been postulated to be responsible for feedback in galaxy evolution. Principal component analysis (PCA) quantifies trends in emission lines of quasars that can be used to predict and reconstruct the underlying continuum in broad absorption line quasars.Richards et al. 2011 hypothesized that emission-line variance across the rest-UV spectrum is correlated with C IV blueshift and equivalent width. We fit their composite spectra, constructed based on these properties, to identify trends for the purpose of creating simulated spectra to test the weighted Expectation Maximization PCA (EMPCA; Bailey 2012) and cluster analysis method discussed in adjacent poster by Marrs et al.More than 800 SDSS spectra from Allen et al. 2011, with a redshift range of z = 2.2 - 2.3, were selected for analysis, particularly spectra with high signal to noise ratios, without broad absorption lines, and without numerous narrow absorption lines. Interstellar and intergalactic absorption lines add variance that contaminates the principal components. To remove these lines, we smoothed the spectra using a Fourier transform and a low-pass filter. We then used a line-finding and -removal program to remove or flag narrow absorption lines. From the principal components that resulted from the PCA analysis we were able to reconstruct the continua of a small sample of BAL QSOs.

  14. A comparative study of the phenyl ring motion in styrene oligomers and polystyrene using FIR absorption and depolarized Rayleigh wing spectra

    NASA Astrophysics Data System (ADS)

    Zoidis, E.; Borsdorf, Ch.; Strehle, F.; Dorfmüller, Th.

    1992-12-01

    FIR absorption and depolarized Rayleigh wing spectra of styrene oligomer model compounds and polystyrene standards with a narrow molecular weight distribution were recorded at various temperatures below and above the glass transition point. For a comparative discussion of the spectral properties we have used the reduced depolarized Rayleigh spectrum RVH( overlineν). In the case of cumene, 2,4-diphenylpentane and 2,4,6-triphenylheptane we were able to fit the well-known Mori function, which is often used to describe FIR absorption spectra of dipolar simple liquids, on the experimental data points. The analysis of the theoretical and band shape parameters obtained from the spectra measured as a function of chain length and temperature allows us to assume that the phenyl ring librational motion may be considered as the main dynamical process shaping the low-frequency part in the FIR absorption spectrum as well as in the depolarized Rayleigh wing of polystyrene.

  15. A new algorithm to retrieve chromophoric dissolved organic matter (CDOM) absorption spectra in the UV from ocean color

    NASA Astrophysics Data System (ADS)

    Cao, Fang; Miller, William L.

    2015-01-01

    Accurate estimation of the absorption coefficient (ag) for chromophoric dissolved organic matter (CDOM) over ultraviolet (UV) and short visible radiation wavelengths (with λ = 275-450 nm) is crucial to provide a robust assessment of the biogeochemical significance of UV in the global ocean. Using a training data set spanning a variety of water types from the clearest open ocean to dynamic inshore waters, a novel algorithm to accurately resolve CDOM absorption spectra from ocean color is presented. Employing a suite of multivariate statistical approaches (principal component analysis, cluster analysis, and multiple linear regression), this new algorithm was developed with matched field data for CDOM spectra and remote sensing reflectance (Rrs) at Sea-viewing Wide Field-of-view Sensor (SeaWiFS) bands. Freed from any presupposition about CDOM spectral shape or conventional spectral extrapolations from visible data, our algorithm allows direct retrieval of a fully resolved CDOM absorption spectrum over UV wavelengths from visible Rrs and further enables a global scale view of the dynamics of CDOM over different water types. Accuracy of ag retrieval is good, with a mean absolute percent difference for ag in the UV of ˜25%. With fully resolved spectra, maps of calculated CDOM spectral slopes (S275-295, S350-400) and slope ratios (SR) are presented with the potential to provide new information about the chemical composition (e.g., molecular weight and aromaticity), sources, transformation, and cycling pathways of CDOM on global as well as regional scales. The new algorithm will contribute to improved accuracy for photochemical and photobiological rate calculations from ocean color.

  16. Calculation of UV attenuation and colored dissolved organic matter absorption spectra from measurements of ocean color

    NASA Astrophysics Data System (ADS)

    Johannessen, S. C.; Miller, W. L.; Cullen, J. J.

    2003-09-01

    The absorption of ultraviolet and visible radiation by colored or chromophoric dissolved organic matter (CDOM) drives much of marine photochemistry. It also affects the penetration of ultraviolet radiation (UV) into the water column and can confound remote estimates of chlorophyll concentration. Measurements of ocean color from satellites can be used to predict UV attenuation and CDOM absorption spectra from relationships between visible reflectance, UV attenuation, and absorption by CDOM. Samples were taken from the Bering Sea and from the Mid-Atlantic Bight, and water types ranged from turbid, inshore waters to the Gulf Stream. We determined the following relationships between in situ visible radiance reflectance, Lu/Ed (λ) (sr-1), and diffuse attenuation of UV, Kd(λ) (m-1): Kd(323nm) = 0.781[Lu/Ed(412)/Lu/Ed(555)]-1.07; Kd(338nm) = 0.604[Lu/Ed(412)/Lu/Ed(555)]-1.12; Kd(380 nm) = 0.302[Lu/Ed(412)/Lu/Ed(555)]-1.24. Consistent with published observations, these empirical relationships predict that the spectral slope coefficient of CDOM absorption increases as diffuse attenuation of UV decreases. Excluding samples from turbid bays, the ratio of the CDOM absorption coefficient to Kd is 0.90 at 323 nm, 0.86 at 338 nm, and 0.97 at 380 nm. We applied these relationships to SeaWiFS images of normalized water-leaving radiance to calculate the CDOM absorption and UV attenuation in the Mid-Atlantic Bight in May, July, and August 1998. The images showed a decrease in UV attenuation from May to August of approximately 50%. We also produced images of the areal distribution of the spectral slope coefficient of CDOM absorption in the Georgia Bight. The spectral slope coefficient increased offshore and changed with season.

  17. 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

  18. 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

  19. Sticking to (first) principles: quantum molecular dynamics and Bayesian probabilistic methods to simulate aquatic pollutant absorption spectra.

    PubMed

    Trerayapiwat, Kasidet; Ricke, Nathan; Cohen, Peter; Poblete, Alex; Rudel, Holly; Eustis, Soren N

    2016-08-10

    This work explores the relationship between theoretically predicted excitation energies and experimental molar absorption spectra as they pertain to environmental aquatic photochemistry. An overview of pertinent Quantum Chemical descriptions of sunlight-driven electronic transitions in organic pollutants is presented. Second, a combined molecular dynamics (MD), time-dependent density functional theory (TD-DFT) analysis of the ultraviolet to visible (UV-Vis) absorption spectra of six model organic compounds is presented alongside accurate experimental data. The functional relationship between the experimentally observed molar absorption spectrum and the discrete quantum transitions is examined. A rigorous comparison of the accuracy of the theoretical transition energies (ΔES0→Sn) and oscillator strength (fS0→Sn) is afforded by the probabilistic convolution and deconvolution procedure described. This method of deconvolution of experimental spectra using a Gaussian Mixture Model combined with Bayesian Information Criteria (BIC) to determine the mean (μ) and standard deviation (σ) as well as the number of observed singlet to singlet transition energy state distributions. This procedure allows a direct comparison of the one-electron (quantum) transitions that are the result of quantum chemical calculations and the ensemble of non-adiabatic quantum states that produce the macroscopic effect of a molar absorption spectrum. Poor agreement between the vertical excitation energies produced from TD-DFT calculations with five different functionals (CAM-B3LYP, PBE0, M06-2X, BP86, and LC-BLYP) suggest a failure of the theory to capture the low energy, environmentally important, electronic transitions in our model organic pollutants. However, the method of explicit-solvation of the organic solute using the quantum Effective Fragment Potential (EFP) in a density functional molecular dynamics trajectory simulation shows promise as a robust model of the hydrated organic

  20. 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.

  1. Specific effects of a polar solvent in optical absorption spectra of 1,2-naphthoquinone

    NASA Astrophysics Data System (ADS)

    Tseplin, E. E.; Tseplina, S. N.; Khvostenko, O. G.

    2016-02-01

    The optical absorption spectra of 1,2-naphthoquinone in polar (methanol) and nonpolar ( n-hexane) solvents are recorded. It is found that the specific effect of a polar solvent, which manifests itself in a hypsochromic shift of the first nπ* band and in a bathochromic shift of the second and third ππ* bands, is caused by the formation of hydrogen bonds between solvent molecules and the molecule under study and, as a result, by a change in the energy gap between the corresponding occupied and unoccupied molecular orbitals. This result is obtained by TDDFT B3LYP/6-311+G(d, p) calculations of electronic spectra, which, in the case of an isolated 1,2-naphthoquinone molecule, reproduce its experimental optical absorption spectra in n-hexane and, in the case of the same molecule forming a complex with methanol molecules by means of hydrogen bonds, reproduce the spectrum of 1,2-naphthoquinone in methanol.

  2. 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.

  3. 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.

  4. Infrared absorption spectra, radiative efficiencies, and global warming potentials of perfluorocarbons: Comparison between experiment and theory

    NASA Astrophysics Data System (ADS)

    Bravo, IváN.; Aranda, Alfonso; Hurley, Michael D.; Marston, George; Nutt, David R.; Shine, Keith P.; Smith, Kevin; Wallington, Timothy J.

    2010-12-01

    Experimentally and theoretically determined infrared spectra are reported for a series of straight-chain perfluorocarbons: C2F6, C3F8, C4F10, C5F12, C6F14, and C8F18. Theoretical spectra were determined using both density functional (DFT) and ab initio methods. Radiative efficiencies (REs) were determined using the method of Pinnock et al. (1995) and combined with atmospheric lifetimes from the literature to determine global warming potentials (GWPs). Theoretically determined absorption cross sections were within 10% of experimentally determined values. Despite being much less computationally expensive, DFT calculations were generally found to perform better than ab initio methods. There is a strong wavenumber dependence of radiative forcing in the region of the fundamental C-F vibration, and small differences in wavelength between band positions determined by theory and experiment have a significant impact on the REs. We apply an empirical correction to the theoretical spectra and then test this correction on a number of branched chain and cyclic perfluoroalkanes. We then compute absorption cross sections, REs, and GWPs for an additional set of perfluoroalkenes.

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

    PubMed

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

    2014-09-08

    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.

  6. 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.

  7. Comparison between IR absorption and raman scattering spectra of liquid and supercritical 1-butanol.

    PubMed

    Sokolova, Maia; Barlow, Stephen J; Bondarenko, Galina V; Gorbaty, Yuri E; Poliakoff, Martyn

    2006-03-23

    Raman spectra of 1-butanol have been obtained at a constant pressure of 500 bar up to 350 degrees C and along isotherms 250, 300, and 350 degrees C up to 600 bar. The purpose of the experiment was to compare responses of Raman and IR absorption spectroscopy to the forming of O-H...O bonds in alcohols. As a result, some important inferences were drawn from the experiment. In particular, it has been estimated quantitatively how the intensity of Raman scattering in the region of the OH band depends on the extent of hydrogen bonding. As might be expected, the dependence is much weaker than in the case of the IR absorption. As was shown, the ratio of integrated intensities of bonded molecules in the absorption and scattering spectra is a constant and does not depend on temperature and density. The effect of cooperativity of hydrogen bonds is confirmed. It was also found that even at high pressures, a noticeable amount of nonbonded molecules exists at room temperature.

  8. Absorption spectra of electronic-homoeopathic copies of homoeopathic nosodes and placebo have essential differences.

    PubMed

    Korenbaum, Vladimir I; Chernysheva, Tatyana N; Apukhtina, Tatyana P; Sovetnikova, Lyudmila N

    2006-10-01

    Electronic-homoeopathic copies (EHC), i.e. preparations made by 'imprinting' the parent substance onto water (or other carriers) with the help of M. Rae devices, have gained certain acceptance in some fields of alternative medicine as homoeopathic nosodes. To verify the electronic-homoeopathic copying effect with the use of absorption spectroscopy. In a double-blind randomized procedure 7 homoeopathic nosodes and a blank placebo were 'imprinted' onto ampoules with saline solution by means of a 'simulator' apparatus by Metabolics Ltd (Wiltshire, UK). There were 63 ampoules of the EHC (9 of each nosode) and 27 ampoules of the placebo (3 groups). The absorption spectra of the preparations were determined by a UV-2101 PC (Shimadzu, Kyoto, Japan) double-beam spectrometer in the wave band 800-600 nm at an interval of 0.5 nm. The values of optical density - log (1/transmission coefficient) - were written. The absorption spectra of 3 EHC of the 7 homoeopathic nosodes investigated showed regions marked by statistically significant differences (p < 0.05 for 2 adjacent wavelengths) in the band of 800-700 nm in 2 (as a minimum) out of 3 independent placebo groups. When compared in independent groups of placebo, the spectral regions - for which the significant differences between the EHC and the placebo were evident - are close to each other (in the range of 0.5-7.0 nm). The result obtained supports the existence of an electronic-homoeopathic copying effect.

  9. DFT assessment of the spectroscopic constants and absorption spectra of neutral and charged diatomic species of group 11 and 14 elements.

    PubMed

    Tsipis, Athanassios C

    2014-09-15

    The spectroscopic constants and absorption spectra of neutral and charged diatomic molecules of group 11 and 14 elements formulated as [M(2)](+/0/-) (M = Cu, Ag, Au), and [E(2)](+/0/-) (E = C, Si, Ge, Sn, Pb) have been calculated at the PBE0/Def2-QZVPP level of theory. The electronic and bonding properties of the diatomics have been analyzed by natural bond orbital analysis approach and topology analysis by the atoms in molecules method. Particular emphasis was given on the absorption spectra of the diatomic species, which were simulated by time-dependent density functional theory calculations employing the hybrid Coulomb-attenuating CAM-B3LYP density functional. The simulated absorption spectra of the [M(2)](+/0/-) (M = Cu, Ag, Au) and [E(2)](+/0/-) (E = C, Si, Ge, Sn, Pb) species are in close resemblance with the experimentally observed spectra whenever available. The neutral M(2) and E(2) diatomics strongly absorb in the ultraviolet region, given rise to UVC, UVA and in a few cases UVB absorptions. In a few cases, weak absorbion bands also occur in the visible region. The absorption bands have thoroughly been analyzed and assignments of the contributing principal electronic transitions associated to individual excitations have been made. © 2014 Wiley Periodicals, Inc.

  10. 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).

  11. Principal Component Analysis of Arctic Solar Irradiance Spectra

    NASA Technical Reports Server (NTRS)

    Rabbette, Maura; Pilewskie, Peter; Gore, Warren J. (Technical Monitor)

    2000-01-01

    During the FIRE (First ISCPP Regional Experiment) Arctic Cloud Experiment and coincident SHEBA (Surface Heat Budget of the Arctic Ocean) campaign, detailed moderate resolution solar spectral measurements were made to study the radiative energy budget of the coupled Arctic Ocean - Atmosphere system. The NASA Ames Solar Spectral Flux Radiometers (SSFRs) were deployed on the NASA ER-2 and at the SHEBA ice camp. Using the SSFRs we acquired continuous solar spectral irradiance (380-2200 nm) throughout the atmospheric column. Principal Component Analysis (PCA) was used to characterize the several tens of thousands of retrieved SSFR spectra and to determine the number of independent pieces of information that exist in the visible to near-infrared solar irradiance spectra. It was found in both the upwelling and downwelling cases that almost 100% of the spectral information (irradiance retrieved from 1820 wavelength channels) was contained in the first six extracted principal components. The majority of the variability in the Arctic downwelling solar irradiance spectra was explained by a few fundamental components including infrared absorption, scattering, water vapor and ozone. PCA analysis of the SSFR upwelling Arctic irradiance spectra successfully separated surface ice and snow reflection from overlying cloud into distinct components.

  12. Principal Component Analysis of Arctic Solar Irradiance Spectra

    NASA Technical Reports Server (NTRS)

    Rabbette, Maura; Pilewskie, Peter; Gore, Warren J. (Technical Monitor)

    2000-01-01

    During the FIRE (First ISCPP Regional Experiment) Arctic Cloud Experiment and coincident SHEBA (Surface Heat Budget of the Arctic Ocean) campaign, detailed moderate resolution solar spectral measurements were made to study the radiative energy budget of the coupled Arctic Ocean - Atmosphere system. The NASA Ames Solar Spectral Flux Radiometers (SSFRs) were deployed on the NASA ER-2 and at the SHEBA ice camp. Using the SSFRs we acquired continuous solar spectral irradiance (380-2200 nm) throughout the atmospheric column. Principal Component Analysis (PCA) was used to characterize the several tens of thousands of retrieved SSFR spectra and to determine the number of independent pieces of information that exist in the visible to near-infrared solar irradiance spectra. It was found in both the upwelling and downwelling cases that almost 100% of the spectral information (irradiance retrieved from 1820 wavelength channels) was contained in the first six extracted principal components. The majority of the variability in the Arctic downwelling solar irradiance spectra was explained by a few fundamental components including infrared absorption, scattering, water vapor and ozone. PCA analysis of the SSFR upwelling Arctic irradiance spectra successfully separated surface ice and snow reflection from overlying cloud into distinct components.

  13. Analysis of spectra using correlation functions

    NASA Technical Reports Server (NTRS)

    Beer, Reinhard; Norton, Robert H.

    1988-01-01

    A novel method is presented for the quantitative analysis of spectra based on the properties of the cross correlation between a real spectrum and either a numerical synthesis or laboratory simulation. A new goodness-of-fit criterion called the heteromorphic coefficient H is proposed that has the property of being zero when a fit is achieved and varying smoothly through zero as the iteration proceeds, providing a powerful tool for automatic or near-automatic analysis. It is also shown that H can be rendered substantially noise-immune, permitting the analysis of very weak spectra well below the apparent noise level and, as a byproduct, providing Doppler shift and radial velocity information with excellent precision. The technique is in regular use in the Atmospheric Trace Molecule Spectroscopy (ATMOS) project and operates in an interactive, realtime computing environment with turn-around times of a few seconds or less.

  14. Theoretical studies on the vibrationally-resolved absorption and fluorescence spectra of H-Pyrene+ and H-Coronene+

    NASA Astrophysics Data System (ADS)

    Li, JunFeng; Tian, GuanJun; Luo, Yi; Cao, ZeXing

    2015-11-01

    H-Pyrene+ and H-Coronene+ are important carrier candidates for the diffuse interstellar band. In order to understand the observed absorption and fluorescence emission spectra of H-Pyrene+ and H-Coronene+, time-dependent density functional theory (TD-DFT) method and Franck-Condon approximation have been employed to simulate the corresponding vibrationally-resolved optical spectra. For H-Pyrene+, the calculated absorption, emission and 0-0 band energies are in good agreement with the experimental values. The strong absorption and emission vibrational peaks near the 0-0 band match well with the experiment peaks. A noticeable deviation for several weak peaks far away from the origin band is observed, as a result of the vibronic coupling with other excited states. For H-Coronene+, the predicted vibrationally resolved electronic absorption and emission spectra resemble very well their experimental counterparts spectra, allowing to fully assign the observed vibronic peaks.

  15. 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.

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

    PubMed

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

    2016-02-15

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

  17. 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.

  18. Multiple-scattering approach to the x-ray-absorption spectra of 3d transition metals

    NASA Astrophysics Data System (ADS)

    Kitamura, Michihide; Muramatsu, Shinji; Sugiura, Chikara

    1986-04-01

    The x-ray-absorption near-edge structure (XANES) has been calculated for the 3d transition metals Cr, Fe, Ni, and Cu from a multiple-scattering approach within the muffin-tin-potential approximation, as a first step to studying the XANES for complicated materials. The muffin-tin potential is constructed via the Mattheiss prescription using the atomic data of Herman and Skillman. It is found that the XANES is sensitive to the potential used and that the calculated XANES spectra reproduce the number of peaks and their separations observed experimentally. The final spectra, including the lifetime-broadening effect, show the general features of each material. We emphasize that the multiple-scattering theory which can be applied to the disordered systems as well as the ordered ones may be promising as a tool to analyze the XANES of complicated materials.

  19. Modelling long-range wavelength distortions in quasar absorption echelle spectra

    NASA Astrophysics Data System (ADS)

    Dumont, V.; Webb, J. K.

    2017-06-01

    Spectra observed with the Ultraviolet and Visual Echelle Spectrograph on the European Southern Observatory's VLT exhibit long-range wavelength distortions. These distortions impose a systematic error on high-precision measurements of the fine-structure constant, α, derived from intervening quasar absorption systems. If the distortion is modelled using a model that is too simplistic, the resulting bias in Δα/α away from the true value can be larger than the statistical uncertainty on the α measurement. If the effect is ignored altogether, the same is true. If the effect is modelled properly, accounting for the way in which final spectra are generally formed from the co-addition of exposures made at several different instrumental settings, the effect can be accurately removed and the correct Δα/α recovered.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  1. Paradoxical solvent effects on the absorption and emission spectra of amino-substituted perylene monoimides.

    PubMed

    Zoon, Peter D; Brouwer, Albert M

    2005-08-12

    In N-(2,5-di-tert-butylphenyl)-9-pyrrolidinoperylene-3,4-dicarboximide (5PI) the absorption and emission spectra display large solvatochromic shifts, but, remarkably, the Stokes shift is practically independent of solvent polarity. This unique behavior is caused by the extraordinarily large ground-state dipole moment of 5PI, which further increases upon increasing the solvent polarity, whereas the excited-state dipole moment is less solvent dependent. In the corresponding piperidine compound, 6PI, this effect is much less important owing to the weaker coupling between the amino group and the aromatic imide moiety, and in the corresponding naphthalimide, 5NI, it is absent. The latter shows the conventional solvatochromic behavior of a push-pull substituted conjugated system, that is, minor shifts in absorption and a larger change in the emission energy with solvent polarity.

  2. [Study on absorption spectra and optical limiting properties of soluble polymer/multi-walled carbon nanotube composites].

    PubMed

    Qiu, Xue-Qiong; Wu, Hui-Xia; Tong, Rui; Qian, Shi-Xiong; Lin, Yang-Hui; Cai, Rui-Fang

    2008-07-01

    Three kinds of soluble polymer grafted multi-walled carbon nanotubes (MWNTs), including poly(N-vinylcarbazole)-MWNTs (MWNTs-PVK), polystyrene-MWNTs (MWNTs-PSt) and poly(methyl methacrylate)-MWNTs (MWNTs-PMMA) were synthesized. The TEM images of these samples show that polymers are coated outside the carbon nanotubes. The UV-Vis absorption spectra of the samples in CHCl3 were taken on a HP8452 spectrophotometer at room temperature. Compared with that of MWNTs suspension, there is a characteristic absorption peak in the ultraviolet region, which can be attributed to the polymers linked covalently with MWNTs. Their nonlinear optical properties and optical limiting (OL) performances were investigated by Z-scan method with 527 nm nanosecond laser pulses. These MWNTs dissolved in chloroform possess similar optical limiting properties, which are better than that of raw MWNT suspension and C60 in toluene solution. Nonlinear refraction, nonlinear absorption and nonlinear scattering mechanism were taken into consideration for explaining the observed results. The analysis of the experimental results shows that nonlinear absorption is the dominant mechanism behind the OL performance of these samples.

  3. Effects of domain size on x-ray absorption spectra of boron nitride doped graphenes

    NASA Astrophysics Data System (ADS)

    Li, Xin; Hua, Weijie; Wang, Bo-Yao; Pong, Way-Faung; Glans, Per-Anders; Guo, Jinghua; Luo, Yi

    2016-08-01

    Doping is an efficient way to open the zero band gap of graphene. The control of the dopant domain size allows us to tailor the electronic structure and the properties of the graphene. We have studied the electronic structure of boron nitride doped graphenes with different domain sizes by simulating their near-edge X-ray absorption fine structure (NEXAFS) spectra at the N K-edge. Six different doping configurations (five quantum dot type and one phase-separated zigzag-edged type) were chosen, and N K-edge NEXAFS spectra were calculated with large truncated cluster models by using the density functional theory with hybrid functional and the equivalent core hole approximation. The opening of the band gap as a function of the domain size is revealed. We found that nitrogens in the dopant boundary contribute a weaker, red-shifted π* peak in the spectra as compared to those in the dopant domain center. The shift is related to the fact that these interfacial nitrogens dominate the lowest conduction band of the system. Upon increasing the domain size, the ratio of interfacial atom decreases, which leads to a blue shift of the π* peak in the total NEXAFS spectra. The spectral evolution agrees well with experiments measured at different BN-dopant concentrations and approaches to that of a pristine h-BN sheet.

  4. Resonant Photoemission and M_{2,3}-Absorption Spectra in Nickel Dichloride

    NASA Astrophysics Data System (ADS)

    Igarashi, J.

    Ni 3p-resonant photoemission and Ni M_{2,3}-absorption spectra are calculated in detail on a cluster of (NiCl_6)^{4-} with the use of the transition matrix elements evaluated on the Herman-Skillman potential in Ni atom. Overall spectral shape agrees well with experiment, allowing a determination of the parameters which characterize Ni 3d and Cl 3p states. Resonance behavior is discussed near the Ni 3p-core level photothreshold. The resonant enhancement is found to be larger for the peak with higher binding energy in the d^7-multiplets.

  5. Extended spin-polarized x-ray absorption near-edge spectra of MnO

    SciTech Connect

    Hayashi, Hisashi; Kawata, Masaki; Udagawa, Yasuo; Kawamura, Naomi; Nanao, Susumu

    2004-10-01

    We present Mn K{beta}(3p{yields}1s) emission data as a contour map over wide energy ranges in both excitation and emission. It is demonstrated that spin-polarized x-ray absorption near edge structure (SPXANES) can be deduced by analyzing the data in terms of a formula derived from the Kramers-Heisenberg equation. The SPXANES spectra thus obtained are considerably different from those by conventional method, but are consistent with an anticipation from Hund's rule, and the overall spectral shapes as well as peak positions agree well with a theoretical calculation.

  6. A ubiquitous absorption feature in the X-ray spectra of BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Madejski, Greg M.; Mushotzky, Richard F.; Weaver, Kimberly A.; Arnaud, Keith A.; Urry, C. Megan

    1991-01-01

    The paper presents the broadband (0.5-20-keV) X-ray spectra of five X-ray bright BL Lac objects observed with the Einstein Observatory Solid State Spectrometer (SSS) and Monitor Proportional Counter (MPC) detectors. The combination of moderate energy resolution and broad spectral coverage makes it possible to confirm the presence of an absorption feature at an energy of 650 eV in the BL Lac object PKS 2155-304, originally reported by Canizares and Kruper (1984) based on higher resolution Einstein Objective Grating Spectrometer (OGS) data.

  7. The energy calibration of x-ray absorption spectra using multiple-beam diffraction

    SciTech Connect

    Hagelstein, M.; Cunis, S. ); Frahm, R. ); Rabe, P. )

    1992-01-01

    A new method for calibrating the energy scale of x-ray absorption spectra from an energy dispersive spectrometer has been developed. Distinct features in the diffracted intensity of the curved silicon crystal monochromator have been assigned to multiple-beam diffraction. The photon energies of these structures can be calculated if the precise spacing of the diffracting planes and the orientation of the crystal relative to the incident synchrotron radiation are known. The evaluation of Miller indices of operative reflections and the calculation of the corresponding photon energy is presented. The assignment of operative reflexes is simplified if the monochromator crystal can be rotated around the main diffracting vector {bold H}.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  9. A Survey for Intervening CIV Absorption-Line Systems Using SDSS Quasar Spectra

    NASA Astrophysics Data System (ADS)

    Monier, Eric M.; Nestor, D. B.; Daino, M. M.; Quider, A. M.; Rao, S. M.; Turnshek, D. A.

    2006-06-01

    Intervening CIV absorption-line systems are readily found in Sloan Digital Sky Survey (SDSS) quasar spectra at redshifts z > 1.5. Given the large number of absorbers, high statistical accuracy is possible in comparison to what was possible in the past. Here we present preliminary results on the incidence and evolution of the CIV systems as a function of CIV rest equivalent width. The absorber incidence is proportional to the product of gas cross-section and co-moving number density of absorbers, while the rest equivalent width is related to their kinematic spread. We discuss the interpretation of our results.

  10. Gain and Absorption Spectra of Quantum Wire Lasers Diodes Grown on Nonplanar Substrates

    DTIC Science & Technology

    1992-04-01

    SIMMJ^ COMPONENT PART NOTICE THIS PAPER IS A COMPONENT PART OF THE FOLLOWING COMPILATION REPORT: TTT1F: Integrated Photonics Research. Volume 10...i’t’y Co" .,.*» Dist kl Avji. :.;;fl,’or Spital ulll’MAR85Mb:> OPI: DTIC-TID Integrated Photonics Research -1 Gain and Absorption Spectra of...modulators and switches. 92-31749 Integrated Photonics Research 59 MC2-2 References: 1. E. Kapon, D.M. Hwang and R. Bhat, Phys. Rev. Lett. 63, 430 (1989

  11. Solvent effects on the electronic absorption spectra and acid strength of some substituted pyridinols

    NASA Astrophysics Data System (ADS)

    Hashem, Elham Y.; Saleh, Magda S.

    2002-01-01

    The electronic absorption spectra of some substituted pyridinols in organic solvents of different polarities are studied. Also, the solvent effects on the intramolecular charge transfer bands are discussed using various solvent parameters. The acid-base equilibria of the compounds used are studied spectrophotometrically in various mixed aqueous solvents at 25 °C and 0.1 M ionic strength (NaClO 4). Furthermore, the influence of the solvents on the dissociation constants and tautomeric equilibria of a pyridinol derivatives are discussed. The effect of molecular structure of the pyridinols on the p K's is also examined.

  12. Modulated microwave absorption spectra from Josephson junctions on a scratched niobium wire

    SciTech Connect

    Rubins, R.S. |; Hutton, S.L.; Ravindran, K.; Subbaraman, K.; Drumheller, J.E.

    1997-05-01

    Modulated microwave absorption (MMA) spectra from Josephson junction formations on a scratched Nb wire have been studied at 9.3 GHz and 4 K. The peak-to-peak separation, {delta}H of the Josephson lines was found to vary linearly with P{sup 1/2}, where P is the applied microwave power, in contrast to a recent interpretation of junction formation in pressed lead pieces by Rubins, Drumheller, and Trybula. The interpretation of the MMA data on Nb are given in terms of the theory of Vichery, Beuneu, and Lejay for superconducting loops containing weak links. {copyright} {ital 1997} {ital The American Physical Society}

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-11-01

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

  15. 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.

  16. Automated analysis of slitless spectra - Stars

    NASA Astrophysics Data System (ADS)

    Beauchemin, M.; Borra, E. F.; Levesque, S.

    1991-09-01

    The stellar spectral classification that can be achieved with very low-dispersion spectroscopy is examined. Several methods are applied to slitless spectra taken from the automated grens plates analysis project undertaken at Laval University. It is suggested that an accuracy in B - V of about 0.1 mag at B approximating 19 for stars bluer than B - V below 0.8 mag or better for redder stars can be obtained by probing the continuum. Results from DDO-like photometry show that grens data behave similarly to the Gunn and Stryker library of standard stars for many indices. Results of multivariate analysis are coherent with the stellar spectral classification and provide a powerful and objective means of cataloging spectra of the same spectral shape.

  17. Simulation of Vacuum UV Absorption and Electronic Circular Dichroism Spectra of Methyl Oxirane: the Role of Vibrational Effects

    PubMed Central

    Hodecker, Manuel; Biczysko, Malgorzata; Dreuw, Andreas; Barone, Vincenzo

    2017-01-01

    Vibrationally resolved one-photon absorption and electronic circular dichroism spectra of (R)-methyl oxirane were calculated with different electronic and vibronic models selecting, through an analysis of the convergence of the results, the best compromise between reliability and computational cost. Linear-response TD-DFT/CAM-B3LYP/SNST electronic computations in conjunction with the simple vertical gradient vibronic model were chosen and employed for systematic comparison with the available experimental data. Remarkable agreement between simulated and experimental spectra was achieved for both one photon absorption and circular dichroism concerning peak positions, relative intensities, and general spectral shapes considering the computational efficiency of the chosen theoretical approach. The significant improvement of the results with respect to smearing of vertical electronic transitions by phenomenological Gaussian functions and the possible inclusion of solvent effects by polarizable continuum models at a negligible additional cost paves the route toward the simulation and analysis of spectral shapes of complex molecular systems in their natural environment. PMID:27159495

  18. Computed and Experimental Absorption Spectra of the Perovskite CH3NH3PbI3.

    PubMed

    Zhu, Xi; Su, Haibin; Marcus, Rudolph A; Michel-Beyerle, Maria E

    2014-09-04

    Electronic structure and light absorption properties of the perovskite CH3NH3PbI3 are investigated by relativistic density functional theory with quasiparticle GW corrections and many-body interactions. The nature of the Wannier exciton is studied by solving the Bethe-Salpeter equation augmented with the analysis of a conceptual hydrogen-like model. The computed absorption spectrum unravels a remarkable absorption "gap" between the first two absorption peaks. This discontinuity is maintained in the calculated tetragonal structure that, however, is not stable at low temperature. Most importantly, the discontinuity is also observed in the experimental absorption spectrum of the orthorhombic single crystal at low temperature (4 K). However, in contrast to the single crystal, in a polycrystalline perovskite film at 5 K the "gap" is filled by a monotonously increasing absorption throughout the visible range. This feature of thin films points to the potential significance of defect absorption for the excellent light harvesting properties of perovskite-based solar cells.

  19. 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.

  20. Role of non-Condon vibronic coupling and conformation change on two-photon absorption spectra of green fluorescent protein

    NASA Astrophysics Data System (ADS)

    Ai, Yuejie; Tian, Guangjun; Luo, Yi

    2013-07-01

    Two-photon absorption spectra of green fluorescent proteins (GFPs) often show a blue-shift band compared to their conventional one-photon absorption spectra, which is an intriguing feature that has not been well understood. We present here a systematic study on one- and two-photon spectra of GFP chromophore by means of the density functional response theory and complete active space self-consistent field (CASSCF) methods. It shows that the popular density functional fails to provide correct vibrational progression for the spectra. The non-Condon vibronic coupling, through the localised intrinsic vibrational modes of the chromophore, is responsible for the blue-shift in the TPA spectra. The cis to trans isomerisation can be identified in high-resolution TPA spectra. Our calculations demonstrate that the high level ab initio multiconfigurational CASSCF method, rather than the conventional density functional theory is required for investigating the essential excited-state properties of the GFP chromophore.

  1. 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…

  2. 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…

  3. 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

  4. 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

  5. Absorption spectra of e-beam-excited Ne, Ar, and Kr, pure and in binary mixtures.

    PubMed

    Levchenko, A O; Ustinovskii, N N; Zvorykin, V D

    2010-10-21

    A technique using the broadband emission of a laser plume as probe radiation is applied to record UV-visible (190-510 nm) absorption spectra of Ne, Ar, and Kr, pure and in binary mixtures under moderate e-beam excitation up to 1 MW/cm(3). In all the rare gases and mixtures, the absorption spectra show continuum related to Rg(2) (+) homonuclear ions [peaking at λ∼285, 295, and 320 nm in Ne, Ar, and Kr(Ar/Kr), respectively] and a number of atomic lines related mainly to Rg(∗)(ms) levels, where m is the lowest principal quantum number of the valence electron. In argon, a continuum related to Ar(2) (∗) (λ∼325 nm) is also recorded. There are also trains of narrow bands corresponding to Rg(2) (∗)(npπ (3)Π(g))←Rg(2) (∗)(msσ (3)Σ(u) (+)) transitions. All the spectral features mentioned above were reported in literature but have never been observed simultaneously. Although charge transfer to a homonuclear ion of the heavier additive is commonly believed to dominate in binary rare-gas mixtures, it is found in this study that in Ne/Kr mixture, the charge is finally transferred from the buffer gas Ne(2) (+) ion not to Kr(2) (+) but to heteronuclear NeKr(+) ion.

  6. Multi-State Extrapolation of Uv/vis Absorption Spectra with Qm/qm Hybrid Methods

    NASA Astrophysics Data System (ADS)

    Ren, Sijin; Caricato, Marco

    2017-06-01

    In this work, we present a simple approach to obtain absorption spectra from hybrid QM/QM calculations. The goal is to obtain reliable spectra for compounds that are too large to be treated entirely at a high level of theory. The 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.

  7. K-edge x-ray absorption spectra of Cs and Xe

    SciTech Connect

    Gomilsek, J. Padeznik; Kodre, A.; Arcon, I.; Hribar, M.

    2003-10-01

    X-ray absorption spectrum of cesium vapor in the K-edge region is measured in a stainless steel cell. The spectrum is free of the x-ray absorption fine structure signal and shows small features analogous to those in the spectrum of the neighbor noble gas Xe. Although the large natural width of the K vacancy (>10 eV) washes out most of the details, fingerprints of multielectron excitations can be recognized at energies close to Dirac-Fock estimates of doubly excited states 1s4(d,p,s) and 1s3(d,p). Among these, the 1s3p excitation 1000 eV above the K edge in both spectra is the deepest double excitation observed so far. Within the K-edge profile, some resolution is recovered with numerical deconvolution of the spectra, revealing the coexcitation of the 5(p,s) electrons, and even the valence 6s electron in Cs. As in homologue elements, three-electron excitations, either as separate channels or as configuration admixtures are required to explain some spectral features in detail.

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

    SciTech Connect

    Baishya, K.; Idrobo, J. C.; Ogut, S.; Yang, M.; Jackson, K. A.; Jellinek, J.

    2011-06-17

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

  9. Analysis of positron lifetime spectra in polymers

    NASA Technical Reports Server (NTRS)

    Singh, Jag J.; Mall, Gerald H.; Sprinkle, Danny R.

    1988-01-01

    A new procedure for analyzing multicomponent positron lifetime spectra in polymers was developed. It requires initial estimates of the lifetimes and the intensities of various components, which are readily obtainable by a standard spectrum stripping process. These initial estimates, after convolution with the timing system resolution function, are then used as the inputs for a nonlinear least squares analysis to compute the estimates that conform to a global error minimization criterion. The convolution integral uses the full experimental resolution function, in contrast to the previous studies where analytical approximations of it were utilized. These concepts were incorporated into a generalized Computer Program for Analyzing Positron Lifetime Spectra (PAPLS) in polymers. Its validity was tested using several artificially generated data sets. These data sets were also analyzed using the widely used POSITRONFIT program. In almost all cases, the PAPLS program gives closer fit to the input values. The new procedure was applied to the analysis of several lifetime spectra measured in metal ion containing Epon-828 samples. The results are described.

  10. Diagnosis of core-shell mixing with absorption and emission spectra of a doped layer. Final technical report

    SciTech Connect

    1998-04-01

    Shell-core mixing which can occur during the deceleration phase of laser-driven implosion is believed to be the major limitation on target performance. The authors proposed a diagnostic method for detecting core-shell mixing based on the comparison of absorption and emission spectra due to a signature layer embedded in the target shell. Experimentally the method is simple as it does not require backlighting nor imaging. They have developed a mixing and radiation transport model used here to demonstrate the proposed diagnostic method. The proposal consists of target experiments on OMEGA as well as the interpretation and analysis of these experiments. They show that a signature layer of a high-Z dopant can be placed within the shell such that, in the absence of mixing, the emergent spectrum will only show absorption lines (of L-shell ionic species). Mixing causes the appearance of K-shell lines in emission. The more severe the mixing, the higher is the intensity of emission lines, as compared with that of the absorption lines. Modeling results are presented to demonstrate a numerical analysis of doped target experiments carried out on OMEGA.

  11. Nucleic acid vibrational circular dichroism, absorption, and linear dichroism spectra. I. A DeVoe theory approach.

    PubMed Central

    Self, B D; Moore, D S

    1997-01-01

    Infrared (IR) vibrational circular dichroism (VCD), absorption, and linear dichroism (LD) spectra of four homopolyribonucleotides, poly(rA), poly(rG), poly(rC), and poly(rU), have been calculated, in the 1750-1550 cm-1 spectral region, using the DeVoe polarizability theory. A newly derived algorithm, which approximates the Hilbert transform of imaginaries to reals, was used in the calculations to obtain real parts of oscillator polarizabilities associated with each normal mode. The calculated spectra of the polynucleotides were compared with previously measured solution spectra. The good agreement between calculated and measured polynucleotide spectra indicates, for the first time, that the DeVoe theory is a useful means of calculating the VCD and IR absorption spectra of polynucleotides. For the first time, calculated DeVoe theory VCD and IR absorption spectra of oriented polynucleotides are presented. The calculated VCD spectra for the oriented polynucleotides are used to predict the spectra for such measurements made in the future. The calculated IR spectra for the oriented polynucleotides are useful in interpreting the linear dichroism of the polynucleotides. PMID:9199798

  12. 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.

  13. Spectral and luminescent properties of forsterite single crystals heavily doped with chromium: I. Absorption spectra

    SciTech Connect

    Lebedev, V F; Gaister, A V; Zharikov, Evgeny V; Tenyakov, S Yu; Levchenko, A E; Dianov, Evgenii M

    2003-03-31

    The polarisation absorption spectra of forsterite single crystals grown from a melt containing from 0.015 to 0.97 wt% of chromium are studied. Most of the crystals were grown by the Czochralski method under standard oxidation conditions (1.4-2.4 vol % of oxygen). Some crystals were grown in the atmosphere with a higher content of oxygen ({approx}12 vol %) or in the neutral atmosphere (100% of Ar). Crystals grown from a melt containing more than 0.6 wt % of chromium exhibited the saturation of absorption of Cr{sup 4+} ions. The maximum absorption coefficient of Cr{sup 4+} ions at 1064 nm was {approx}3.2 cm{sup -1}. The relative content of Cr{sup 3+} ions also increased (approximately by 70% in the range studied) with increasing the doping level. The relative content of Cr{sup 3+} ions in a crystal grown in the atmosphere with a high content of oxygen ({approx}12 vol %) was approximately lower by a factor of 1.5 than that in a crystal grown in the standard oxidation atmosphere. (active media)

  14. [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.

  15. Absorption-mode Fourier transform mass spectrometry: the effects of apodization and phasing on modified protein spectra.

    PubMed

    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.

  16. Multivariate calibration applied to the quantitative analysis of infrared spectra

    SciTech Connect

    Haaland, D.M.

    1991-01-01

    Multivariate calibration methods are very useful for improving the precision, accuracy, and reliability of quantitative spectral analyses. Spectroscopists can more effectively use these sophisticated statistical tools if they have a qualitative understanding of the techniques involved. A qualitative picture of the factor analysis multivariate calibration methods of partial least squares (PLS) and principal component regression (PCR) is presented using infrared calibrations based upon spectra of phosphosilicate glass thin films on silicon wafers. Comparisons of the relative prediction abilities of four different multivariate calibration methods are given based on Monte Carlo simulations of spectral calibration and prediction data. The success of multivariate spectral calibrations is demonstrated for several quantitative infrared studies. The infrared absorption and emission spectra of thin-film dielectrics used in the manufacture of microelectronic devices demonstrate rapid, nondestructive at-line and in-situ analyses using PLS calibrations. Finally, the application of multivariate spectral calibrations to reagentless analysis of blood is presented. We have found that the determination of glucose in whole blood taken from diabetics can be precisely monitored from the PLS calibration of either mind- or near-infrared spectra of the blood. Progress toward the non-invasive determination of glucose levels in diabetics is an ultimate goal of this research. 13 refs., 4 figs.

  17. Atomic absorption background of Ba in EXAFS analysis of BaFe(12)O(19) nanoparticles.

    PubMed

    Padeznik Gomilšek, Jana; Kodre, Alojz; Arčon, Iztok; de Panfilis, Simone; Makovec, Darko

    2011-07-01

    The approximate barium X-ray atomic absorption in the energy region of L-edges is reconstructed from the absorption spectrum of an aqueous solution of BaCl(2). The result is corroborated by comparison with pure atomic absorption spectra of neighbour elements Xe and Cs. The application of the atomic absorption signal as a proper EXAFS background is demonstrated and discussed in the analysis of Ba hexaferrite nanoparticles with a very weak structural signal. The essential gain is found in the decrease of uncertainty intervals of structural parameters and their correlations. A simple analytical model of the absorption background for the practical EXAFS analysis is demonstrated.

  18. Sensitivity of absorption spectra to surface segregation in InGaN/GaN quantum well structures

    SciTech Connect

    Klymenko, M. V.; Shulika, O. V.; Sukhoivanov, I. A.

    2014-05-15

    We investigate the influence of the indium surface segregation on absorption spectra in InGaN/GaN quantum well structures having different indium amount. Results of the mathematical modeling show that such influence is more pronounced in quantum well structures with high indium amounts. The origin of this effect is related to the interplay between the indium surface segregation and internal electrostatic fields. Our theoretical analysis is performed using semiconductor Bloch equations within the Hartree-Fock approximation including into consideration excitonic effects. Results of the global sensitivity analysis evidence that the influence of the indium surface segregation is less than one order of magnitude in comparison with the impact of the quantum-well width and indium molar fraction. Also, the influence of the indium surface segregation is not the same for each interface of the quantum well.

  19. [Prediction the octane number of gasoline by near infrared spectra analysis].

    PubMed

    Cao, D; Tan, J; Chen, Z; Hu, Y; Han, S

    1999-06-01

    The feasibility of predicting the octane number by the near infrared spectra analysis technique in the quantitative analysis was investigated. 12 calibration gasoline samples and 4 prediction samples were collected and their absorption spectra were measured with a high precision model Lambda 19 scanning spectrophotometer. Based on the multivariate statistic model, stagewise regression and partial least squares were selected. A model of the correlation behavior between the spectra and octane number was established and calibrated, and then the prediction of octane number is made. The prediction error is +/-1.0 octane number in the best analysis results.

  20. pH-Induced changes in electronic absorption and fluorescence spectra of phenazine derivatives

    NASA Astrophysics Data System (ADS)

    Ryazanova, O. A.; Voloshin, I. M.; Makitruk, V. L.; Zozulya, V. N.; Karachevtsev, V. A.

    2007-04-01

    The visible electronic absorption and fluorescence spectra as well as fluorescence polarization degrees of imidazo-[4,5-d]-phenazine (F1), 2-methylimidazo-[4,5-d]-phenazine (F2), 2-trifluoridemethylimidazo-[4,5-d]-phenazine (F3), 1,2,3-triazole-[4,5-d]-phenazine (F4) and their glycosides, imidazo-[4,5-d]-phenazine-N1-β- D-ribofuranoside (F1rib), 1,2,3-triazole-[4,5-d]-phenazine-N1-β- D-glucopyranoside (F4gl), were investigated in aqueous buffered solutions over the pH range of 0-12, where the spectral transformations were found to be reversible. The effects of protonation and deprotonation on spectral properties of these dyes were studied. We have determined the ranges of pH, where individual ionic species are predominant. In aqueous buffered solutions the fluorescence was found only for neutral species of F1, F1rib, F2, and F4gl dyes, whereas for the ionic forms of these dyes, as well as for F3 and F4 ones, the fluorescence has not been detected. The concentrational deprotonation p Ka values were evaluated from experimental data. It was shown that donor-acceptor properties of the substituent group in the second position of the pentagonal ring substantially affect the values of the deprotonation constants and the character of protonation for chromophore. The substitution of a hydrogen atom in the NH-group by the sugar residue blocks the formation of the anionic species, and results in enhancement of the dye emission intensity. The steep emission dependence for F1 and F1rib over pH range of 0-7 with intensities ratio of IpH 7/ IpH 1 = 60 allows us to propose them as possible indicator dyes in luminescence based pH sensors for investigation of processes accompanied by acidification, e.g. as gastric pH-sensors. A comparative analysis of the studied dyes has shown that F4gl is the most promising compound to be used as a fluorescent probe for investigation of molecular hybridization of nucleic acids.

  1. The UV absorption of nucleobases: semi-classical ab initio spectra simulations.

    PubMed

    Barbatti, Mario; Aquino, Adelia J A; Lischka, Hans

    2010-05-21

    Semi-classical simulations of the UV-photoabsorption cross sections of adenine, guanine, cytosine, thymine, and uracil in gas phase were performed at the resolution-of-identity coupled cluster to the second-order (RI-CC2) level. With the exception of cytosine, the spectra of the other four nucleobases show a two band pattern separated by a low intensity region. The spectrum of cytosine is shaped by a sequence of three bands of increasing intensity. The first band of guanine is composed by two pipi* transitions of similar intensities. The analysis of individual contributions to the spectra allows a detailed assignment of bands. It is shown that the semi-classical simulations are able to predict general features of the experimental spectra, including their absolute intensities.

  2. Extraction of pigment information from near-UV vis absorption spectra of extra virgin olive oils.

    PubMed

    Domenici, Valentina; Ancora, Donatella; Cifelli, Mario; Serani, Andrea; Veracini, Carlo Alberto; Zandomeneghi, Maurizio

    2014-09-24

    This work reports a new approach to extract the maximum chemical information from the absorption spectrum of extra virgin olive oils (EVOOs) in the 390-720 nm spectral range, where "oil pigments" dominate the light absorption. Four most important pigments, i.e., two carotenoids (lutein and β-carotene) and two chlorophylls (pheophytin-a and pheophytin-b), are chosen as reference oil pigments, being present in all the reported analytical data regarding pigments of EVOOs. The method allows the quantification of the concentration values of these four pigments directly from the deconvolution of the measured absorption spectrum of EVOOs. Advantages and limits of the method and the reliability of the pigment family quantification are discussed. The main point of this work is the description of a fast and simple method to extract of such information in less than a minute, through the mathematical analysis of the UV-vis spectrum of untreated samples of oil.

  3. 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

  4. 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.

  5. Error reduction in retrievals of atmospheric species from symmetrically measured lidar sounding absorption spectra.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2014-10-20

    We report new methods for retrieving atmospheric constituents from symmetrically-measured lidar-sounding absorption spectra. The forward model accounts for laser line-center frequency noise and broadened line-shape, and is essentially linearized by linking estimated optical-depths to the mixing ratios. Errors from the spectral distortion and laser frequency drift are substantially reduced by averaging optical-depths at each pair of symmetric wavelength channels. Retrieval errors from measurement noise and model bias are analyzed parametrically and numerically for multiple atmospheric layers, to provide deeper insight. Errors from surface height and reflectance variations are reduced to tolerable levels by "averaging before log" with pulse-by-pulse ranging knowledge incorporated.

  6. 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.

  7. Complex Investigation of the Absorption and Emission Spectra of Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Moskalenko, N. I.; Zotov, O. V.; Il'in, Yu. A.; Parzhin, S. N.; Khamidullina, M. S.

    2017-04-01

    Absorption and emission spectra of carbon dioxide are measured and analyzed for temperatures 220-2500 K in the spectral range 1-25 μm. Intensities and half-widths of the spectral lines are determined and hightemperature atlas of the spectral lines' parameters is compiled. Based on the developed mathematical model, the parameters of spectral transmission functions of CO2 are obtained at different temperatures in the vibration-rotation and pressure-induced bands of CO2. Practical application of the obtained radiative characteristics is considered for solving problems of radiative heat exchange in planetary atmospheres and high-temperature media and designing optoelectronic systems intended for aero carriers monitoring.

  8. Electronic absorption spectra of cresyl violet acetate in anisotropic and isotropic solvents

    NASA Astrophysics Data System (ADS)

    Jafari, A.; Ghanadzadeh, A.; Tajalli, H.; Yeganeh, M.; Moghadam, M.

    2007-03-01

    The isotropic and anisotropic solvation characteristics of cresyl violet acetate (CVA) were investigated in isotropic liquid solutions and in polar nematic matrices as a function of the solvent type and concentration. The interaction of the ionic dye with the anisotropic surrounding and with that of the isotropic solvents was investigated and compared. The experimental result suggests that the nematic liquid crystalline solvents might create stronger solvation than the isotropic solvents. The spectral shifts were correlated by the solvent permittivity and Kamlet-Taft parameters. The polarized absorption spectra of cresyl violet acetate were measured between 400 and 800 nm and the dichroic ratio R and degree of anisotropy S of this dye in the liquid crystalline host determined.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  11. 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.

  12. Specific absorption spectra of hemoglobin at different PO2 levels: potential noninvasive method to detect PO2 in tissues.

    PubMed

    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.

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

    NASA Astrophysics Data System (ADS)

    Kong, Lingzhu; Car, Roberto

    2013-03-01

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

  14. Progress in the Theory and Interpretation of X-ray Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Rehr, J. J.

    2002-03-01

    There has been dramatic progress in recent years in the understanding of x-ray absorption spectra (XAS) [1]. For example, modern real space multiple scattering theory has yielded a quantitative treatment of the extended fine structure in XAS. Crucial in the theory is a treatment of electronic excited states including many-body effects such as inelastic losses and Debye-Waller factors. These developments have led to ab initio codes which permit an interpretation of the spectra in terms of geometrical and electronic properties of materials [2]. Indeed, the availability of such codes has revolutionized experimental investigations based on synchrotron radiation x-ray sources. Algorithmic improvements have recently made possible fast, parallel calculations of the near edge structure (XANES) [3], and approximate treatments of local field effects and many-body amplitude factors. Related techniques have been applied to several other spectroscopies, e.g., anomalous x-ray scattering, x-ray magnetic circular dichroism, and photoelectron diffraction [4]. [1] J. J. Rehr and R. C. Albers, Rev. Mod. Phys. 72, 621 (2000); [2] A. L. Ankudinov, B. Ravel, J.J. Rehr, and S. Conradson, Phys. Rev. B 58, 7565 (1998); [3] A. L. Ankudinov, C. E. Bouldin, J. J. Rehr, J. Sims, and H. Hung, Phys. Rev. B, in press (2002); [4] F. J. Garcia de Abajo, M. A. Van Hove, C. S. Fadley, Phys. Rev. B 63, 075404 (2001).

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Ultraviolet spectra of quenched carbonaceous composite derivatives: Comparison to the '217 nanometer' interstellar absorption feature

    NASA Astrophysics Data System (ADS)

    Sakata, Akira; Wada, Setsuko; Tokunaga, Alan T.; Narisawa, Takatoshi; Nakagawa, Hidehiro; Ono, Hiroshi

    1994-07-01

    QCCs (quenched carbonaceous composite) are amorphous 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 resembles 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 filmy 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.

  20. 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.

  1. C-13 NMR chemical shifts and visible absorption spectra of unsymmetrical fluoran dye by MO calculations

    NASA Astrophysics Data System (ADS)

    Hoshiba, T.; Ida, T.; Mizuno, M.; Otsuka, T.; Takaoka, K.; Endo, K.

    2002-01-01

    An unsymmetrical fluoran dye, 3-diethylamino-6-methyl-7-chlorofluoran (DEAMCF) is one of the leuco dyes which shows the coloring-to-decoloring reversible reaction with acidity. We calculated the 13C chemical shieldings of the DEAMCF with the frame model compounds using ab initio gauge invariant atomic orbital methods, and compared it with the experimental shifts. The calculated values of the frame compounds are in good agreement with the experimental ones in the error range of -4.9-16.7 ppm. The calculated ones for the decolored-form of the DEAMCF reflected the observed ones, although the errors range from -13.4 to 23.1 ppm. Furthermore, we analyzed the UV-Visible absorption spectra of the decolored and colored forms of DEAMCF by a semiempirical ZINDO MO method. For the colored form, the observed absorption peaks at 550 and 510 nm correspond to the excitation from π-bonding HOMO (π-electrons which conjugated in xanthene ring) and π-bonding nearest HOMO (π-electrons concentrated in benzene-ring with methyl and Cl groups of xanthene) to π ∗-antibonding LUMO (π ∗-electrons of xanthene), respectively.

  2. K edge absorption spectra of sulphur in vapour, molecular and polymerized solid phases

    NASA Astrophysics Data System (ADS)

    Durand, J. M.; Olivier-Fourcade, J.; Jumas, J. C.; Womes, M.; Teodorescu, C. M.; Elafif, A.; Esteva, J. M.; Karnatak, R. C.

    1996-12-01

    X-ray K absorption spectra of sulphur have been studied in its vapour, molecular and polymerized solid phases. The vapour phase of sulphur containing 0953-4075/29/23/019/img11 molecules yields a K spectrum which is similar to that of the 0953-4075/29/23/019/img12 molecule. This observation suggests a 0953-4075/29/23/019/img13 ground state of 0953-4075/29/23/019/img11, which is in agreement with that obtained from optical spectra. Different line splittings in the spectra of these molecules are discussed in the light of the p orbital and s - p orbital energy differences of some second- and third-period elements. While the condensed phase spectrum of 0953-4075/29/23/019/img12 remains unchanged, the observed K spectrum of condensed 0953-4075/29/23/019/img11 differs considerably from its vapour phase. This abrupt change in the bonding between the S atoms in the condensed phase is typical behaviour of sulphur and indicates the formation of two directional covalent bonds and creation of 0953-4075/29/23/019/img17 and 0953-4075/29/23/019/img18 lone pairs. This behaviour is, in fact, a clear distinction between the chemistries of sulphur and that of its homologue oxygen. The cyclic and chain forms of sulphur show some similarity in 0953-4075/29/23/019/img19 line structure and a marked difference in their near-edge structure due to a different number of S atoms surrounding a central atom in these allotropic forms.

  3. A combination spectrophotometer for measuring electronic absorption, natural circular dichroism, and magnetic circular dichroism spectra

    NASA Astrophysics Data System (ADS)

    Policke, Timothy A.; Schreiner, Anton F.; Trexler, Jack W.; Knopp, James A.

    1990-08-01

    The design, construction, and evaluation of a combination spectrometer for measuring electronic absorption (EA), natural circular dichroism (CD), and magnetic circular dichroism (MCD) are described. Around the optical components of a JASCO ORD/UV-5 spectropolarimeter, a new EA/CD/MCD instrument was built with the realized intentions of increasing sensitivity and upgrading the analog tube type circuitry to a solid-state digitally, computer-controlled spectrophotometer. It is a flexible, dynamic, and user-controllable system, interfaced to an Apple II Plus computer, for studying instrument and signal parameters. The monochromator (M), photoelastic modulator (PEM), photomultiplier tube applied voltage (PMHV), and photomultiplier tube dc output current (PMdc) are under complete and independent software control. Our system has two unique aspects for obtaining the circular dichroism. First, the ac signal is measured with a voltage-to-frequency (V/f) converter; and, second, both the ac and the dc are independently recorded and their ratio is digitally calculated. This design has several advantages which include the elimination of voltage divider integrated circuits or division electronics, a wide dynamic range, a greater precision of ac values at low percentages of full scale, and the capability of continuous integration over long time periods. Also, both types of spectra, EA and CD or MCD, are obtained from the current output of the PM. This paper not only describes the design of the instrument for obtaining the two types of spectra but also compares four methods of obtaining the circular dichroism. Sensitivities of ˜1×10-7ΔA units are achievable as determined by measuring CD spectra of the well-known enantiomer (+)-[Co(en)3]3+.

  4. The role of Hartree-Fock exchange in the simulation of X-ray absorption spectra: A study of photoexcited [

    NASA Astrophysics Data System (ADS)

    Capano, G.; Penfold, T. J.; Besley, N. A.; Milne, C. J.; Reinhard, M.; Rittmann-Frank, H.; Glatzel, P.; Abela, R.; Rothlisberger, U.; Chergui, M.; Tavernelli, I.

    2013-08-01

    We present a theoretical analysis for the K- and L2/3-edge static and picosecond X-ray absorption spectra of [. Simulations of the pre-edge region at the Fe K-edge using time-dependent density functional theory demonstrate the importance of Hartree-Fock exchange within the exchange-correlation functional, especially when describing charge transfer and 1s→3d transitions. This becomes particularly relevant for range separated functionals, for which the incorporation of Hartree-Fock exchange at short range decreases the absolute error in the excitation energy usually observed using TD-DFT. Finally, we compute and interpret the L2/3-edge spectrum using the Restricted Open-Shell Configuration Interaction Singles method.

  5. Modeling of collision induced absorption spectra of CO2-CO2 pairs for planetary atmosphere of Venus

    NASA Technical Reports Server (NTRS)

    Borysow, Aleksandra

    1995-01-01

    The objective of the proposal was to model the rototranslational and rotovibrational collision induced absorption spectral bands of importance for the radiative transfer analysis of the atmosphere of Venus. Our main task has involved CO2 pairs. The approach is not straightforward: whereas computational techniques to compute CIA spectra of small linear molecules exist, and were successfully applied to molecules like H2 or N2, they fail when applied to large molecules like CO2. For small molecules one can safely assume that the interaction potential is isotropic. The same approximation does not work for CO2, and when employed, it gives an incorrect band shape and only 50 percent of the CIA intensity.

  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. Soft X-ray absorption spectra in the 0 K region of microporous carbon and some reference aromatic compounds

    SciTech Connect

    Muramatsu, Yasuji; Kuramoto, Kentaro; Gullikson, Eric M.; Perera, Rupert C.C.

    2003-06-01

    To analyze the oxidation states of the graphitic surface of microporous carbon, soft X-ray absorption spectra in the 0 K region have been obtained for microporous carbon and various aromatic compounds. The aromatic molecules studied are substituted with one or more of the following oxygenated functional groups: hydroxy (-OH), carboxy (-COOH), carbonyl (>C=O), formyl (-CH=O), and ether (-O-). From comparison of the soft X-ray absorption spectra of microporous carbon and of reference aromatic compounds, the most probable chemical bonding states of oxygen in microporous carbon are found to be -COOH and >C(H)=O. Spectral features in the soft X-ray absorption spectra of microporous carbon are well explained by the O2p density of states in these oxygenated functional groups from discrete variational (DV)-X{alpha} molecular orbital calculations.

  8. Calculation of One-Photon and Two-Photon Absorption Spectra of Porphyrins Using Time-Dependent Density Functional Theory.

    PubMed

    Day, Paul N; Nguyen, Kiet A; Pachter, Ruth

    2008-07-01

    Time-dependent density functional theory has been used to calculate the one-photon and two-photon absorption spectra of free-base porphyrin, a substituted zinc porphyrin, and a zinc porphyrin dimer, in order to assess the validity of the method to reproduce the large increase in the two-photon absorption (TPA) cross-section for the dimer. Three hybrid functionals with varying amounts of exact exchange were tested, and the calculated one-photon absorption spectra for each of the molecular systems were shown to be in qualitative agreement with the measured spectra. All three functionals predict a large enhancement in the TPA cross-section for the dimer relative to the monomer, in agreement with experimental results. However, because of the sensitivity of the resonance enhancement factor to small differences in the relevant state energies, quantitative prediction of the TPA cross-section by this method is still a challenge.

  9. Microwave spectra of some sulfur and nitrogen compounds. [for chemical analysis

    NASA Technical Reports Server (NTRS)

    White, W. F.

    1974-01-01

    A computer-controlled microwave spectrometer was used to catalog reference spectra for chemical analysis. The apparatus, software, and experimental procedures are described. Tables of absorption frequencies, peak absorption coefficients, and integrated intensities are included for 13 sulfur compounds, 14 nitrogen compounds, and 1 compound containing both sulfur and nitrogen. The frequency range covered was 26,500 to 40,000 MHz for most compounds and 18,000 to 40,000 MHz for some.

  10. Rotary spectra analysis applied to static stabilometry.

    PubMed

    Chiaramello, E; Knaflitz, M; Agostini, V

    2011-01-01

    Static stabilometry is a technique aimed at quantifying postural sway during quiet standing in the upright position. Many different models and many different techniques to analyze the trajectories of the Centre of Pressure (CoP) have been proposed. Most of the parameters calculated according to these different approaches are affected by a relevant intra- and inter-subject variability or do not have a clear physiological interpretation. In this study we hypothesize that CoP trajectories have rotational characteristics, therefore we decompose them in clockwise and counter-clockwise components, using the rotary spectra analysis. Rotary spectra obtained studying a population of healthy subjects are described through the group average of spectral parameters, i.e., 95% spectral bandwidth, mean frequency, median frequency, and skewness. Results are reported for the clockwise and the counter-clockwise components and refer to the upright position maintained with eyes open or closed. This study demonstrates that the approach is feasible and that some of the spectral parameters are statistically different between the open and closed eyes conditions. More research is needed to demonstrate the clinical applicability of this approach, but results so far obtained are promising.

  11. 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.

  12. [Characteristics of the absorption spectra of the mixtures of C42(Al), C32 (Si) and so on].

    PubMed

    Chen, W

    1998-12-01

    The mixtures containing C42 (A1), C32 (Si), C30 (Ca) and C28 (Fe) are produced by means of arc discharge and He gas convection. The spectra are measured and compared with the absorption spectra of all carbon molecules. The result shows that after imbeded in all carbon molecules, the Al, Si, Ca and Fe atoms do not change the positions of the absorption peak of original molecules, but only change the probability of pi --> pi* transition and n --> pi* transition of these molecules.

  13. 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.

  14. [Study on absorption spectra of cell substrate for Hep-2 cell after being radiated by X-ray].

    PubMed

    Tang, Wei-Yue; Liu, Ren-Ming; Zhang, Feng-Qiu; Hu, Xiao-Bo; Diao, Zhen-Qi; Li, Yun-Tao

    2007-09-01

    UV-absorption spectra of the Hep-2 cell's culture medium RPMI1640 (10% Foetal Calf Serum) were collected by UV-3101 spectrophotometer after the Hep-2 cell was radiated by X-ray and cultivated for 24, 48 and 72 h, and the absorbability of the proteins in the substrate was analyzed. From these results it was found that there were visible differences among these absorption spectra. In particular, the absorption peaks of the RPMI1640 culture medium during the cultivation shifted from 233 to 235 nm, while the absorption peak at 278 nm became more and more smooth and even finally disappeared with the cultivation time. On the other hand, the absorption intensity of the different-dose groups rose greatly with the time, and were all lower than the control group until the cells were cultivated for 72 h after being radiated by X-ray. It was showed that the content of each amino acid has already changed. That is, during the growing course of the cancer cells, the tryptophan and casein were not depleted equivalently. And there were some important relations between the absorption spectra and the cells' apoptosis and necrosis induced by X-ray. This will be a foundation for the study of the best X-ray dose for the larynx carcinoma.

  15. Moment analysis of hydrated electron cluster spectra : surface or internal states?

    SciTech Connect

    Bartels, D. M.; Chemistry

    2001-09-01

    Moment analysis is applied to the absorption spectra of size-selected water anion clusters measured by Ayotte and Johnson, to extract the radius of gyration and the kinetic energy for the unpaired electron. Implications for the surface versus interior binding model controversy are discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  17. 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.

  18. Synthesis, DFT calculations, electronic structure, electronic absorption spectra, natural bond orbital (NBO) and nonlinear optical (NLO) analysis of the novel 5-methyl-8H-benzo[h]chromeno[2,3-b][1,6] naphthyridine-6(5H),8-dione (MBCND)

    NASA Astrophysics Data System (ADS)

    Halim, Shimaa Abdel; Ibrahim, Magdy A.

    2017-02-01

    New derivative of heteroannulated chromone identified as 5-methyl-8H-benzo[h]chromeno[2,3-b][1,6]naphthyridine-6(5H),8-dione (5, MBCND) was easily and efficiently synthesized from DBU catalyzed condensation reaction of 2-aminochromone-3-carboxaldehyde (1) with 4-hydroxy-1-methylquinolin-2(1H)-one (2). The same product 5 was isolated from condensation reaction of aldeyde 1 with 3-(4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinolin-3-yl)-3-oxopropanoic acid (3) or ethyl 4-(4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinolin-3-yl)-2,4-dioxobutanoate (4). Structure of compound (5, MBCND) was deduced based on their elemental analyses and spectral data (IR, 1H NMR and mass spectra). Density Functional Theory (DFT) calculations at the B3LYP/6-311G (d,p) level of theory have been carried out to investigate the equilibrium geometry of the novel compound (5, MBCND). Moreover, total energy, energy of HOMO and LUMO and Mullikan atomic charges were calculated. In addition, the dipole moment, theoretical study of the electronic structure, nonlinear optical properties (NLO), and natural bonding orbital (NBO) analysis and orientation have been performed and discussed. Also the electronic absorption spectra were measured in polar (methanol) as well as non polar (dioxane) solvents and the assignment of the observed bands has been discussed by TD-DFT calculations. The correspondences between calculated and experimental transitions energies are satisfactory.

  19. ALIEN: A nebular spectra analysis software

    NASA Astrophysics Data System (ADS)

    Cook, R.; Vazquez, R.

    2000-11-01

    A new C-coded software, designed to analyze nebular spectra, is presented. T his software is able to read the fluxes of the most important ions directly from IRAF's output file (splot.log). Spectra can be dereddened using the Balmer lines ratio and the Seaton's extinction law. Electron temperature and density, as well as ionic abundances by number are estimated by means of numeric calculations based on the five-level atom model. The dereddened spectra and the table containing the ionic abundances can be saved in a LaTex formatted file. This software has been initially designed to work with a low dispersion spectra.

  20. Spectroscopic and DFT study of solvent effects on the electronic absorption spectra of sulfamethoxazole in neat and binary solvent mixtures.

    PubMed

    Almandoz, M C; Sancho, M I; Blanco, S E

    2014-01-24

    The solvatochromic behavior of sulfamethoxazole (SMX) was investigated using UV-vis spectroscopy and DFT methods in neat and binary solvent mixtures. The spectral shifts of this solute were correlated with the Kamlet and Taft parameters (α, β and π(*)). Multiple lineal regression analysis indicates that both specific hydrogen-bond interaction and non specific dipolar interaction play an important role in the position of the absorption maxima in neat solvents. The simulated absorption spectra using TD-DFT methods were in good agreement with the experimental ones. Binary mixtures consist of cyclohexane (Cy)-ethanol (EtOH), acetonitrile (ACN)-dimethylsulfoxide (DMSO), ACN-dimethylformamide (DMF), and aqueous mixtures containing as co-solvents DMSO, ACN, EtOH and MeOH. Index of preferential solvation was calculated as a function of solvent composition and non-ideal characteristics are observed in all binary mixtures. In ACN-DMSO and ACN-DMF mixtures, the results show that the solvents with higher polarity and hydrogen bond donor ability interact preferentially with the solute. In binary mixtures containing water, the SMX molecules are solvated by the organic co-solvent (DMSO or EtOH) over the whole composition range. Synergistic effect is observed in the case of ACN-H2O and MeOH-H2O, indicating that at certain concentrations solvents interact to form association complexes, which should be more polar than the individual solvents of the mixture.

  1. Spectroscopic and DFT study of solvent effects on the electronic absorption spectra of sulfamethoxazole in neat and binary solvent mixtures

    NASA Astrophysics Data System (ADS)

    Almandoz, M. C.; Sancho, M. I.; Blanco, S. E.

    2014-01-01

    The solvatochromic behavior of sulfamethoxazole (SMX) was investigated using UV-vis spectroscopy and DFT methods in neat and binary solvent mixtures. The spectral shifts of this solute were correlated with the Kamlet and Taft parameters (α, β and π*). Multiple lineal regression analysis indicates that both specific hydrogen-bond interaction and non specific dipolar interaction play an important role in the position of the absorption maxima in neat solvents. The simulated absorption spectra using TD-DFT methods were in good agreement with the experimental ones. Binary mixtures consist of cyclohexane (Cy)-ethanol (EtOH), acetonitrile (ACN)-dimethylsulfoxide (DMSO), ACN-dimethylformamide (DMF), and aqueous mixtures containing as co-solvents DMSO, ACN, EtOH and MeOH. Index of preferential solvation was calculated as a function of solvent composition and non-ideal characteristics are observed in all binary mixtures. In ACN-DMSO and ACN-DMF mixtures, the results show that the solvents with higher polarity and hydrogen bond donor ability interact preferentially with the solute. In binary mixtures containing water, the SMX molecules are solvated by the organic co-solvent (DMSO or EtOH) over the whole composition range. Synergistic effect is observed in the case of ACN-H2O and MeOH-H2O, indicating that at certain concentrations solvents interact to form association complexes, which should be more polar than the individual solvents of the mixture.

  2. Physical Properties of the Interstellar Medium Using High-resolution Chandra Spectra: O K-edge Absorption

    NASA Astrophysics Data System (ADS)

    Gatuzz, E.; García, J.; Mendoza, C.; Kallman, T. R.; Bautista, M. A.; Gorczyca, T. W.

    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 O = 0.70. The latter is given relative to the standard by Grevesse & 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 O = 9.2 × 1017 cm-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.

  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 spectra of garnet films between 1. 0 and 1. 8. mu. m by guided-wave optical spectroscopy

    SciTech Connect

    Olivier, M.; Peuzin, J.; Danel, J.; Challeton, D.

    1981-01-15

    Continuous recording of the absorption spectra of thin films by an optical guided-wave technique is demonstrated. In the case of a garnet thin film of compositoin (YSmLuCa)/sub 3/(FeGe)/sub 5/O/sub 12/ it is shown that the near-infrared Sm/sup 3 +/ absorption bands are clearly visible in contrast with conventional transmission measurement. Comparison with the absorption spectrum of bulk Sm/sub 3/Fe/sub 5/O/sub 12/ garnet allows the determination of an Sm concentration in the film.

  5. Specdata: Automated Analysis Software for Broadband Spectra

    NASA Astrophysics Data System (ADS)

    Oliveira, Jasmine N.; Martin-Drumel, Marie-Aline; McCarthy, Michael C.

    2017-06-01

    With the advancement of chirped-pulse techniques, broadband rotational spectra with a few tens to several hundred GHz of spectral coverage are now routinely recorded. When studying multi-component mixtures that might result, for example, with the use of an electrical discharge, lines of new chemical species are often obscured by those of known compounds, and analysis can be laborious. To address this issue, we have developed SPECdata, an open source, interactive tool which is designed to simplify and greatly accelerate the spectral analysis and discovery. Our software tool combines both automated and manual components that free the user from computation, while giving him/her considerable flexibility to assign, manipulate, interpret and export their analysis. The automated - and key - component of the new software is a database query system that rapidly assigns transitions of known species in an experimental spectrum. For each experiment, the software identifies spectral features, and subsequently assigns them to known molecules within an in-house database (Pickett .cat files, list of frequencies...), or those catalogued in Splatalogue (using automatic on-line queries). With suggested assignments, the control is then handed over to the user who can choose to accept, decline or add additional species. Data visualization, statistical information, and interactive widgets assist the user in making decisions about their data. SPECdata has several other useful features intended to improve the user experience. Exporting a full report of the analysis, or a peak file in which assigned lines are removed are among several options. A user may also save their progress to continue at another time. Additional features of SPECdata help the user to maintain and expand their database for future use. A user-friendly interface allows one to search, upload, edit or update catalog or experiment entries.

  6. Analysis of Phytoplankton Communities Using Hyperspectral Absorption Measurements

    NASA Astrophysics Data System (ADS)

    Wollschläger, J.; Röttgers, R.

    2016-02-01

    Methods based on optical measurements are well suited for phytoplankton observation. They are rapid, require comparably low effort, and are often automatable. Besides fluorescence, also the absorption of the water is influenced by the concentration and type of the phytoplankton present. With instruments based on integrating cavities like the point source integrating cavity absorption meter (PSICAM), it is possible to analyze natural water samples in situ. Due to its design, the PSICAM has a long optical path length and the sample has not to be concentrated on a filter prior to analysis. Additionally, light scattered by particles present in the sample has no effect on the absorption measurements. Since the hyperspectral measurements are of high quality, efforts have been made to adapt this approach also for continuous and automated measurement (flow-through-PSICAM). Absorption coefficient data were obtained using both instruments on research cruises in the German Bight and along the Norwegian coast. In case of the discrete measurements, the water samples were filtered through various pore sizes to separate the bulk absorption into the absorption of the different phytoplankton size classes (micro-, nano-, and picophytoplankton). A proxy for chl-a concentration was derived from the data which was used to characterize phytoplankton biomass distributions in the area of investigation. Furthermore, in order to obtain additional information about the phytoplankton community beyond biomass distributions, also the spectral shape of the absorption spectra was analyzed. Attempts were made to attribute different spectral shapes to different phytoplankton groups and find similarities or differences between the cruises stations, respectively.

  7. Transient absorption and luminescence spectra of K9 glass at sub-damage site by ultraviolet laser irradiation

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Huang, J.; Geng, F.; Zhou, X. Y.; Feng, S. Q.; Cheng, X. L.; Jiang, X. D.; Wu, W. D.; Zheng, W. G.; Tang, Y. J.

    2014-01-01

    Transient absorption and luminescence spectra at sub-damage site of K9 glass by laser irradiation at 355 nm are presented. The dependence of transient absorption on laser energy and number of pulses was investigated. As the energy density increases to 2.54 and 3.18 J/cm2, the transient absorption intensity reaches to about 0.20 range from 400 to 480 nm. With the increase of number of pulses the process of residual absorption appears, which can be used to explain the fatigue effect of K9 glass. The defects in K9 glass were investigated by fluorescence and Raman spectra. The fluorescence band centered at about 410 nm is attributed to oxygen deficiency centers. The mechanism of two-photon ionization plays a critical role at sub-damage site. Compared to the Raman spectra of pristine site, intensity of Raman spectra is very high at a lower energy density, while it decreased at a higher energy density.

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

    Ke, Yaling; Zhao, Yi

    2017-05-01

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

  11. Free-energy predictions and absorption spectra calculations for supramolecular nanocarriers and their photoactive cargo.

    PubMed

    Pietropaolo, Adriana; Tang, Sicheng; Raymo, Françisco M

    2017-04-13

    We reconstructed the free-energy landscape for supramolecular nanoparticles of amphiphilic methacrylated-based co-polymers. Their self-assembly in aqueous solution and encapsulation of borondipyrromethene (BODIPY) derivatives were enforced through atomistic free-energy simulations. The BODIPY binding modes detected in each of the free-energy basins were validated through a comparison of theoretical absorption spectra, calculated at the TD-DFT level, to their experimental counterparts. The nanoparticle distribution is controlled within a thermodynamic regime, with free-energy barriers approaching 8 kcal mol(-1), enabling the existence of different-sized nanoparticles in aqueous solution at room temperature. Two types of supramolecular morphologies were identified. One is compact and spherical in shape and the other is large and donut-like, with the former more stable than the latter by 4 kcal mol(-1). The morphology of the supramolecular host affects the binding mode of the BODIPY guests. Stacked BODIPY aggregates are encapsulated in the spherical nanocarriers, whereas isolated chromophores associate with the donut-shaped assemblies.

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

    PubMed

    Derricotte, Wallace D; Evangelista, Francesco A

    2015-06-14

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

  13. Dielectronic Recombination Of Iron M-shell Ions Motivated By Absorption Features In AGN Spectra

    NASA Astrophysics Data System (ADS)

    Lukic, Dragan; Schnell, M.; Savin, D. W.; Brandau, C.; Schmidt, E. W.; Yu, D.; Bernhardt, D.; Schippers, S.; Müller, A.; Lestinsky, M.; Orlov, D.; Sprenger, F.; Grieser, M.; Repnow, R.; Hoffmann, J.; Wolf, A.

    2006-09-01

    XMM-Newton and Chandra observations of active galactic nuclei (AGN) show spectra rich with X-ray absorption features. These observations have detected a broad unresolved transition array (UTA) between 15-17 Å. This is attributed to inner-shell photoexcitation of M-shell iron ions. Modeling these UTA features is currently limited by uncertainties in the low-temperature dielectronic recombination (DR) data for M-shell iron. In order to resolve this issue, and to provide reliable iron M-shell DR data for plasma modeling, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring (TSR) at the Max-Plank-Institute for Nuclear Physics in Heidelberg, Germany. We use the DR data obtained at TSR, to calculate rate coefficients for plasma modeling. We are also providing our data to atomic theorist to benchmark their DR calculations. Here we report our recent experimental results for DR for several iron M-shell ions and plans for future work. This work has been supported in part by NASA, the German Federal Ministry for Education and Research, and the German Research Council

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Pascal, Tod; Prendergast, David

    2014-03-01

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

  16. 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.

  17. Calibration-free absolute quantification of optical absorption coefficients using acoustic spectra in 3D photoacoustic microscopy of biological tissue.

    PubMed

    Guo, Zijian; Hu, Song; Wang, Lihong V

    2010-06-15

    Optical absorption is closely associated with many physiological important parameters, such as the concentration and oxygen saturation of hemoglobin, and it can be used to quantify the concentrations of nonfluorescent molecules. We propose a method to use acoustic spectra of photoacoustic signals to quantify the absolute optical absorption. This method is self-calibrating and thus insensitive to variations in the optical fluence. Factors such as system bandwidth and acoustic attenuation can affect the quantification but can be canceled by dividing the acoustic spectra measured at two optical wavelengths. Using optical-resolution photoacoustic microscopy, we quantified the absolute optical absorption of black ink samples with various concentrations. We also quantified both the concentration and oxygen saturation of hemoglobin in a live mouse in absolute units.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  19. Spectral investigations of 2,5-difluoroaniline by using mass, electronic absorption, NMR, and vibrational spectra

    NASA Astrophysics Data System (ADS)

    Kose, Etem; Karabacak, Mehmet; Bardak, Fehmi; Atac, Ahmet

    2016-11-01

    One of the most significant aromatic amines is aniline, a primary aromatic amine replacing one hydrogen atom of a benzene molecule with an amino group (NH2). This study reports experimental and theoretical investigation of 2,5-difluoroaniline molecule (2,5-DFA) by using mass, ultraviolet-visible (UV-vis), 1H and 13C nuclear magnetic resonance (NMR), Fourier transform infrared and Raman (FT-IR and FT-Raman) spectra, and supported with theoretical calculations. Mass spectrum (MS) of 2,5-DFA is presented with their stabilities. The UV-vis spectra of the molecule are recorded in the range of 190-400 nm in water and ethanol solvents. The 1H and 13C NMR chemical shifts are recorded in CDCl3 solution. The vibrational spectra are recorded in the region 4000-400 cm-1 (FT-IR) and 4000-10 cm-1 (FT-Raman), respectively. Theoretical studies are underpinned the experimental results as described below; 2,5-DFA molecule is optimized by using B3LYP/6-311++G(d,p) basis set. The mass spectrum is evaluated and possible fragmentations are proposed based on the stable structure. The electronic properties, such as excitation energies, oscillator strengths, wavelengths, frontier molecular orbitals (FMO), HOMO and LUMO energies, are determined by time-dependent density functional theory (TD-DFT). The electrostatic potential surface (ESPs), density of state (DOS) diagrams are also prepared and evaluated. In addition to these, reduced density gradient (RDG) analysis is performed, and thermodynamic features are carried out theoretically. The NMR spectra (1H and 13C) are calculated by using the gauge-invariant atomic orbital (GIAO) method. The vibrational spectra of 2,5-DFA molecule are obtained by using DFT/B3LYP method with 6-311++G(d,p) basis set. Fundamental vibrations are assigned based on the potential energy distribution (PED) of the vibrational modes. The nonlinear optical properties (NLO) are also investigated. The theoretical and experimental results give a detailed description of

  20. Discriminating the Mineralogical Composition in Drill Cuttings Based on Absorption Spectra in the Terahertz Range.

    PubMed

    Miao, Xinyang; Li, Hao; Bao, Rima; Feng, Chengjing; Wu, Hang; Zhan, Honglei; Li, Yizhang; Zhao, Kun

    2017-02-01

    Understanding the geological units of a reservoir is essential to the development and management of the resource. In this paper, drill cuttings from several depths from an oilfield were studied using terahertz time domain spectroscopy (THz-TDS). Cluster analysis (CA) and principal component analysis (PCA) were employed to classify and analyze the cuttings. The cuttings were clearly classified based on CA and PCA methods, and the results were in agreement with the lithology. Moreover, calcite and dolomite have stronger absorption of a THz pulse than any other minerals, based on an analysis of the PC1 scores. Quantitative analyses of minor minerals were also realized by building a series of linear and non-linear models between contents and PC2 scores. The results prove THz technology to be a promising means for determining reservoir lithology as well as other properties, which will be a significant supplementary method in oil fields.

  1. Absorption spectra of viral components of Sendai virus in the wavelength region from 130 to 320 nm.

    PubMed

    Megumi, T; Nishikawa, R; Fujita, S; Saito, M; Ito, T

    1991-07-01

    Using synchrotron radiation as a light source, the absorption spectra of purified viral components of the Sendai virus, i.e. messenger RNA, lipids, spike (envelope) proteins, reconstructed envelopes, core proteins and whole virions, were obtained in the wavelength region 130-320 nm by measuring the transmission of thin films. Viral (messenger) RNA two peaks at 260 and 190 nm, and a large increase below 160 nm. The absorption spectrum of lipids exhibited a broad peak at 190 nm and a very sharp increase below 160 nm. With spike proteins, a slight peak at 280 nm and a shoulder at 230 nm were observed in addition to a sharper peak at 190 nm and a rather slow increasing absorption below 160 nm. Reconstructed envelopes showed the features of a combination of lipids and proteins. The absorption spectra of core proteins and whole virions exhibited similar characteristics to spike proteins. Conventional UV data were also obtained in the wavelength range 210-320 nm with RNA and lipids. The UV and synchrotron radiation data were in good agreement in terms of the mass absorption coefficients. The molecular splitting of spike proteins was also examined. Proteins gave more diffuse reflection than their subunits, causing a reduction in absorption. This was explained by a loss of transparency with increasing molecular weight.

  2. An analysis of middle ultraviolet dayglow spectra

    NASA Astrophysics Data System (ADS)

    Walden, Billie S.

    1991-12-01

    Middle ultraviolet spectra from 1800 to 3400A are analyzed. These spectra were obtained from the March 1990 rocket flight of the NPS MUSTANG instrument over the altitudes 105km to 315km. The data were compared with computer generated synthetic spectra. A least squares fitting procedure was developed for this purpose. Each data point was weighted using the standard deviation of the means. Synthetic spectra were generated for the following emissions: N2 Vegard-Kaphan; N2 Lyman-Birge-Hopfield; NO gamma, delta, and epsilon; OI 2972A, OII 2470A; and NII 2143A. Altitude profiles for the emissions were obtained. Tentative identification was made of the OIII 2853A emission. A comparison of VK and LBH profiles demonstrates the process of N2 A-state quenching by atomic oxygen.

  3. Testing Accretion Disk Wind Models of Broad Absorption Line Quasars with SDSS Spectra

    NASA Astrophysics Data System (ADS)

    Lindgren, Sean; Gabel, Jack

    2017-06-01

    We present an investigation of a large sample of broad absorption line (BAL) quasars (QSO) from the Sloan Digital Sky Survey (SDSS) Data Release 5 (DR5). Properties of the BALs, such as absorption equivalent width, outflow velocities, and depth of BAL, are obtained from analysis by Gibson et al. We perform correlation analysis on these data to test the predictions made by the radiation driven, accretion disk streamline model of Murray and Chiang. We find the CIV BAL maximum velocity and the continuum luminosity are correlated, consistent with radiation driven models. The mean minimum velocity of CIV is lower in low ionization BALs (LoBALs), than highly ionized BALs (HiBALS), suggesting an orientation effect consistent with the Murray and Chiang model. Finally, we find that HiBALs greatly outnumber LoBALs in the general BAL population, supporting prediction of the Murray and Chiang model that HiBALs have a greater global covering factor than LoBALs.

  4. Density functional calculations of the vibronic structure of electronic absorption spectra.

    PubMed

    Dierksen, Marc; Grimme, Stefan

    2004-02-22

    Calculations of the vibronic structure in electronic spectra of large organic molecules based on density functional methods are presented. The geometries of the excited states are obtained from time-dependent density functional (TDDFT) calculations employing the B3LYP hybrid functional. The vibrational functions and transition dipole moment derivatives are calculated within the harmonic approximation by finite difference of analytical gradients and the transition dipole moment, respectively. Normal mode mixing is taken into account by the Duschinsky transformation. The vibronic structure of strongly dipole-allowed transitions is calculated within the Franck-Condon approximation. Weakly dipole-allowed and dipole-forbidden transitions are treated within the Franck-Condon-Herzberg-Teller and Herzberg-Teller approximation, respectively. The absorption spectra of several organic pi systems (anthracene, pentacene, pyrene, octatetraene, styrene, azulene, phenoxyl) are calculated and compared with experimental data. For dipole-allowed transitions in general a very good agreement between theory and experiment is obtained. This indicates the good quality of the optimized geometries and harmonic force fields. Larger errors are found for the weakly dipole-allowed S0 --> S1 transition of pyrene which can tentatively be assigned to TDDFT errors for the relative energies of excited states close to the target state. The weak bands of azulene and phenoxyl are very well described within the Franck-Condon approximation which can be explained by the large energy gap (>1.2 eV) to higher-lying excited states leading to small vibronic couplings. Once corrections are made for the errors in the theoretical 0-0 transition energies, the TDDFT approach to calculate vibronic structure seems to outperform both widely used ab initio methods based on configuration interaction singles or complete active space self-consistent field wave functions and semiempirical treatments regarding accuracy

  5. Electronic Absorption Spectra and Phosphorescence of Oxygen-Containing Molybdenum(IV) Complexes.

    PubMed

    Isovitsch, Ralph A.; Beadle, A. Scott; Fronczek, Frank R.; Maverick, Andrew W.

    1998-08-24

    Electronic absorption and emission spectra are reported for salts of two oxomolybdenum(IV) cations, [MoOCl(CN-t-Bu)(4)](+) and [MoOCl(Ph(2)PCH(2)CH(2)PPh(2))(2)](+), and for the new Mo(IV) complex [trans-Mo(OCH(3))(2)(CN-t-Bu)(4)](2+). All three ions show absorption bands (lambda(max,abs) 550-570 nm; epsilon 45-120 M(-)(1) cm(-)(1)) attributable to the (1)A(1)[(d(xy)())(2)] --> (1)E[(d(xy)())(1)(d(xz)()(,)(yz)())(1)] (C(4)(v)()) transition, and the last two show weak shoulders in the 700-750 nm range due to the analogous spin-forbidden ((1)A(1) --> (3)E) transition. Phosphorescence (lambda(max,em) 850-960 nm) occurs in the solid state for all three compounds at both room temperature and 77 K, and for [MoOCl(CN-t-Bu)(4)](+) in CH(2)Cl(2) at room temperature. These are the first phosphorescences recorded for molybdenum(IV) complexes. [MoOCl(CN-t-Bu)(4)](BPh(4)) precipitates quickly if NaBPh(4) is added to the Mo(IV) solution prepared from MoCl(5) and tert-butyl isocyanide in CH(3)OH. However, if NaPF(6) is used instead, [trans-Mo(OCH(3))(2)(CN-t-Bu)(4)](PF(6))(2) (formed by reaction of [MoOCl(CN-t-Bu)(4)](+) with methanol) crystallizes over a period of ca. 24 h. The crystal structure of [trans-Mo(OCH(3))(2)(CN-t-Bu)(4)](PF(6))(2) has been determined: C(22)H(42)F(12)MoN(4)O(2)P(2), monoclinic; space group P2(1)/c; a = 9.1538(8) Å, b = 15.709(2) Å, c = 13.456(2) Å; beta = 103.31(1) degrees; Z = 2; R(F) = 0.063, R(w)(F) = 0.056 for 2719 reflections with I > sigma(I).

  6. 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.

  7. 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.

  8. Multiple pre-edge structures in Cu K -edge x-ray absorption spectra of high- Tc cuprates revealed by high-resolution x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Gougoussis, C.; Rueff, J.-P.; Calandra, M.; D'Astuto, M.; Jarrige, I.; Ishii, H.; Shukla, A.; Yamada, I.; Azuma, M.; Takano, M.

    2010-06-01

    Using high-resolution x-ray absorption spectroscopy and state-of-the-art electronic structure calculations we demonstrate that the pre-edge region at the Cu K edge of high- Tc cuprates is composed of several excitations invisible in standard x-ray absorption spectra. We consider in detail the case of Ca2-xCuO2Cl2 and show that the many pre-edge excitations (two for c -axis polarization, four for in-plane polarization and out-of-plane incident x-ray momentum) are dominated by off-site transitions and intersite hybridization. This demonstrates the relevance of approaches beyond the single-site model for the description of the pre edges of correlated materials. Finally, we show the occurrence of a doubling of the main edge peak that is most visible when the polarization is along the c axis. This doubling, that has not been seen in any previous absorption data in cuprates, is not reproduced by first-principles calculations. We suggest that this peak is due to many-body charge-transfer excitations while all the other visible far-edge structures are single particle in origin. Our work indicates that previous interpretations of the Cu K -edge x-ray absorption spectra in high- Tc cuprates can be profitably reconsidered.

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

    PubMed

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

    2012-04-01

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

  10. Electronic absorption spectra of rare earth (III) species in NaCl-2CsCl eutectic based melts

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Ivanov, A. B.; Yakimov, S. M.; Tsarevskii, D. V.; Golovanova, O. A.; Sukhikh, V. V.; Griffiths, T. R.

    2016-09-01

    Electronic absorption spectra of ions of trivalent rare earth elements were measured in the melts based on NaCl-2CsCl eutectic in the wavelength ranges of 190-1350 and 1450-1700 nm. The measurements were performed at 550-850 °C. The EAS of Y, La, Ce and Lu containing melts have no absorption bands in the studied regions. For the remaining REEs (Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) the absorption bands in the EAS were assigned to the corresponding f-f electron transitions. The Stark effect was observed for Yb(III) F5/2 excited state. Increasing temperature leads to decreasing intensity of the absorption bands, except for the bands resulting from hypersensitive transitions. Beer's law was confirmed up to 0.4 M solutions of REE.

  11. 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.

  12. 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.

  13. Low-temperature absorption spectra and electron structure of HoFe3(BO3)4 single crystal

    NASA Astrophysics Data System (ADS)

    Malakhovskii, A. V.; Gnatchenko, S. L.; Kachur, I. S.; Piryatinskaya, V. G.; Gudim, I. A.

    2017-05-01

    Polarized absorption spectra of HoFe3(BO3)4 single crystal in the range of 8500-24 500 cm-1 were studied as a function of temperature beginning from 2 K. The ground and excited electron states of Ho3+ were identified. The abrupt changes of the spectra at the reorientation phase transition at 4.7 K were observed. The exchange splitting of some excited states were revealed and measured. They changed at the reorientation phase transition. Several vibronic transitions were observed. The splitting of absorption lines corresponding to the C2 local symmetry of the Ho ion was not observed. Moreover, spectra of some absorption bands correspond to splitting in the cubic crystal field. There are some absorption lines, whose polarization cannot be explained both in D3 and C2 local symmetries. Some lines appear or disappear as a result of the transition from the easy axis to the easy plane state of the crystal. All these observations testify to the substantial changes of the local magnetic and structural properties in the excited states of the Ho3+ ion and to the strong influence of the magnetic moments orientation on the polarization of the electron transitions.

  14. A Census of Intrinsic Narrow Absorption Lines in the Spectra of Quasars at z = 2-4

    NASA Astrophysics Data System (ADS)

    Misawa, Toru; Charlton, Jane C.; Eracleous, Michael; Ganguly, Rajib; Tytler, David; Kirkman, David; Suzuki, Nao; Lubin, Dan

    2007-07-01

    We use Keck HIRES spectra of 37 optically bright quasars at z=2-4 to study narrow absorption lines that are intrinsic to the quasars (intrinsic NALs, produced in gas that is physically associated with the quasar central engine). We identify 150 NAL systems, which contain 124 C IV, 12 N V, and 50 Si IV doublets, of which 18 are associated systems (within 5000 km s-1 of the quasar redshift). We use partial coverage analysis to separate intrinsic NALs from NALs produced in cosmologically intervening structures. We find 39 candidate intrinsic systems (28 reliable determinations and 11 that are possibly intrinsic). We estimate that 10%-17% of C IV systems at blueshifts of 5000-70,000 km s-1 relative to quasars are intrinsic. At least 32% of quasars contain one or more intrinsic C IV NALs. Considering N V and Si IV doublets showing partial coverage as well, at least 50% of quasars host intrinsic NALs. This result constrains the solid angle subtended by the absorbers to the background source(s). We identify two families of intrinsic NAL systems, those with strong N V absorption and those with negligible absorption in N V but with partial coverage in the C IV doublet. We discuss the idea that these two families represent different regions or conditions in accretion disk winds. Of the 26 intrinsic C IV NAL systems, 13 have detectable low-ionization absorption lines at similar velocities, suggesting that these are two-phase structures in the wind rather than absorbers in the host galaxy. We also compare possible models for quasar outflows, including radiatively accelerated disk-driven winds, magnetocentrifugally accelerated winds, and pressure-driven winds, and we discuss ways of distinguishing between these models observationally. The data presented here were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration

  15. Ultrafast Time-Resolved Emission and Absorption Spectra of meso-Pyridyl Porphyrins upon Soret Band Excitation Studied by Fluorescence Up-Conversion and Transient Absorption Spectroscopy.

    PubMed

    Venkatesh, Yeduru; Venkatesan, M; Ramakrishna, B; Bangal, Prakriti Ranjan

    2016-09-08

    A comprehensive study of ultrafast molecular relaxation processes of isomeric meso-(pyridyl) porphyrins (TpyPs) has been carried out by using femtosecond time-resolved emission and absorption spectroscopic techniques upon pumping at 400 nm, Soret band (B band or S2), in 4:1 dichloromethane (DCM) and tetrahydrofuran (THF) solvent mixture. By combined studies of fluorescence up-conversion, time-correlated single photon counting, and transient absorption spectroscopic techniques, a complete model with different microscopic rate constants associated with elementary processes involved in electronic manifolds has been reported. Besides, a distinct coherent nuclear wave packet motion in Qy state is observed at low-frequency mode, ca. 26 cm(-1) region. Fluorescence up-conversion studies constitute ultrafast time-resolved emission spectra (TRES) over the whole emission range (430-710 nm) starting from S2 state to Qx state via Qy state. Careful analysis of time profiles of up-converted signals at different emission wavelengths helps to reveal detail molecular dynamics. The observed lifetimes are as indicated: A very fast decay component with 80 ± 20 fs observed at ∼435 nm is assigned to the lifetime of S2 (B) state, whereas being a rise component in the region of between 550 and 710 nm emission wavelength pertaining to Qy and Qx states, it is attributed to very fast internal conversion (IC) occurring from B → Qy and B → Qx as well. Two distinct components of Qy emission decay with ∼200-300 fs and ∼1-1.5 ps time constants are due to intramolecular vibrational redistribution (IVR) induced by solute-solvent inelastic collisions and vibrational redistribution induced by solute-solvent elastic collision, respectively. The weighted average of these two decay components is assigned as the characteristic lifetime of Qy, and it ranges between 0.3 and 0.5 ps. An additional ∼20 ± 2 ps rise component is observed in Qx emission, and it is assigned to the formation time of

  16. Artificial intelligence analysis of paraspinal power spectra.

    PubMed

    Oliver, C W; Atsma, W J

    1996-10-01

    OBJECTIVE: As an aid to discrimination of sufferers with back pain an artificial intelligence neural network was constructed to differentiate paraspinal power spectra. DESIGN: Clinical investigation using surface electromyography. METHOD: The surface electromyogram power spectra from 60 subjects, 33 non-back-pain sufferers and 27 chronic back pain sufferers were used to construct a back propagation neural network that was then tested. Subjects were placed on a test frame in 30 degrees of lumbar forward flexion. An isometric load of two-thirds maximum voluntary contraction was held constant for 30 s whilst surface electromyograms were recorded at the level of the L(4-5). Paraspinal power spectra were calculated and loaded into the input layer of a three-layer back propagation network. The neural network classified the spectra into normal or back pain type. RESULTS: The back propagation neural was shown to have satisfactory convergence with a specificity of 79% and a sensitivity of 80%. CONCLUSIONS: Artificial intelligence neural networks appear to be a useful method of differentiating paraspinal power spectra in back-pain sufferers.

  17. Quantitative analysis of planetary reflectance spectra with principal components analysis

    NASA Technical Reports Server (NTRS)

    Johnson, P. E.; Smith, M. O.; Adams, J. B.

    1985-01-01

    A technique is presented for quantitative analysis of planetary reflectance spectra as mixtures of particles on microscopic and macroscopic scales using principal components analysis. This technique allows for determination of the endmembers being mixed, their abundance, and the scale of mixing, as well as other physical parameters. Eighteen lunar telescopic reflectance spectra of the Copernicus crater region, from 600 nm to 1800 nm in wavelength, are modeled in terms of five likely endmembers: mare basalt, mature mare soil, anorthosite, mature highland soil, and clinopyroxene. These endmembers were chosen from a similar analysis of 92 lunar soil and rock samples. The models fit the data to within 2 percent rms. It is found that the goodness of fit is marginally better for intimate mixing over macroscopic mixing.

  18. Quantitative analysis of planetary reflectance spectra with principal components analysis

    NASA Astrophysics Data System (ADS)

    Johnson, P. E.; Smith, M. O.; Adams, J. B.

    1985-02-01

    A technique is presented for quantitative analysis of planetary reflectance spectra as mixtures of particles on microscopic and macroscopic scales using principal components analysis. This technique allows for determination of the endmembers being mixed, their abundance, and the scale of mixing, as well as other physical parameters. Eighteen lunar telescopic reflectance spectra of the Copernicus crater region, from 600 nm to 1800 nm in wavelength, are modeled in terms of five likely endmembers: mare basalt, mature mare soil, anorthosite, mature highland soil, and clinopyroxene. These endmembers were chosen from a similar analysis of 92 lunar soil and rock samples. The models fit the data to within 2 percent rms. It is found that the goodness of fit is marginally better for intimate mixing over macroscopic mixing.

  19. Absorption spectra and photovoltaic characterization of chlorophyllins as sensitizers for dye-sensitized solar cells.

    PubMed

    Calogero, Giuseppe; Citro, Ilaria; Crupi, Cristina; Di Marco, Gaetano

    2014-11-11

    Dye-sensitized solar cells (DSSCs) based on Chlorine-e6 (Chl-e6), a Chlorophyll a derivative, and Chl-e6 containing Cu, have been investigated by carrying out incident photon to current efficiency (IPCE) and current-voltage (I-V) measurements. The effect of the metallic ion and the influence of the solvent polarity on the dye aggregation and their absorption bands have been analysed by performing electronic absorption measurements. The dependence of the photoelectrochemical parameters of these DSSCs on the electrolyte by the addition of pyrimidine and/or pyrrole has been discussed in details. For the first time I-V curves for a DSSC based on copper Chl-e6 dye have been shown and compared with Zn based chlorophyllin. Furthermore, the performance of a Cu-Chl-e6 based DSSC has been deeply improved by a progressive optimization of the TiO2 multilayer photoanode overcoming the best data reported in literature so far for this dye. It's worth to emphasize that, the analysis reported in this paper supplies very useful information which paves the way to further detailed studies turned to the employment of natural pigments as sensitizers for solar cells.

  20. Analysis of the excited-state absorption spectral bandshape of oligofluorenes

    NASA Astrophysics Data System (ADS)

    Hayes, Sophia C.; Silva, Carlos

    2010-06-01

    We present ultrafast transient absorption spectra of two oligofluorene derivatives in dilute solution. These spectra display a photoinduced absorption band with clear vibronic structure, which we analyze rigorously using a time-dependent formalism of absorption to extract the principal excited-state vibrational normal-mode frequencies that couple to the electronic transition, the configurational displacement of the higher-lying excited state, and the reorganization energies. We can model the excited-state absorption spectrum using two totally symmetric vibrational modes with frequencies 450 (dimer) or 400 cm-1 (trimer), and 1666 cm-1. The reorganization energy of the ground-state absorption is rather insensitive to the oligomer length at 230 meV. However, that of the excited-state absorption evolves from 58 to 166 meV between the oligofluorene dimer and trimer. Based on previous theoretical work [A. Shukla et al., Phys. Rev. B 67, 245203 (2003)], we assign the absorption spectra to a transition from the 1Bu excited state to a higher-lying mAg state, and find that the energy of the excited-state transition with respect to the ground-state transition energy is in excellent agreement with the theoretical predictions for both oligomers studied here. These results and analysis permit profound understanding of the nature of excited-state absorption in π-conjugated polymers, which are the subject of general interest as organic semiconductors in the solid state.

  1. The use of visible absorption spectra to evaluate different color reactions for the detection of cyclic ureides.

    PubMed

    Meusel, M; Frizler, M; Ottersbach, P; Peters, L; Gütschow, M

    2007-06-01

    Modifications of the Zwikker- and Parri color detection tests were investigated and compared according to their ability to distinguish between nine different barbituric acids and hydantoins. Solutions of the resulting complexes in 50% DMSO were analyzed spectrophotometrically. 350 spectra have been analyzed and criteria for their assessment have been defined. The evaluation based upon the occurrence of a peak in the visible absorption spectra, in comparison with the spectrum of the blank solution. The results were in accordance to those obtained in the visual assessment using a color palette formerly introduced. Cobalt(II) nitrate and methanolic solution of piperidine, or cyclohexylamine, respectively, were the suitable components to get unmistakable results.

  2. Engineering the ground- and excited-state absorption spectra of broadband reverse saturable absorbers

    NASA Astrophysics Data System (ADS)

    Pritchett, Timothy M.; Ferry, Michael J.; Shensky, William M.; Mott, Andrew G.; Pei, Chengkui; Sun, Wenfang

    2014-10-01

    We exploit the strong spin-orbit coupling in iridium to modify the linear absorption spectrum of a novel iridium(III) complex so as to broaden the spectral region over which it exhibits reverse saturable absorption. We discuss the design of the new chromophore, present its ground-state absorption spectrum, and report values of its singlet excited-state lifetime and singlet and triplet excited-state absorption cross sections, determined from femtosecond transient difference absorption measurements and nanosecond and picosecond open-aperture Z scans.

  3. Effects of positional disorder on optical absorption spectra of light-harvesting antenna complexes in photosynthetic bacteria

    NASA Astrophysics Data System (ADS)

    Mukai, Koichiro; Abe, Shuji

    2001-03-01

    We study theoretically the influence of both diagonal and off-diagonal disorder on the absorption spectra of the light-harvesting antenna complex LH2 consisting of two circular aggregates, B850 and B800, of bacteriochlorophyll pigments in photosynthetic purple bacteria. Off-diagonal disorder, i.e., randomness in excitonic couplings between molecules, is introduced by a model of disorder in the position of each pigment molecule embedded in proteins. We demonstrate that a large contribution of positional disorder provides a natural explanation for the experimental fact that the excitonic B850 absorption peak is broader than that of monomeric B800 in spite of motional narrowing.

  4. EMPCA and Cluster Analysis of Quasar Spectra: Construction and Application to Simulated Spectra

    NASA Astrophysics Data System (ADS)

    Marrs, Adam; Leighly, Karen; Wagner, Cassidy; Macinnis, Francis

    2017-01-01

    Quasars have complex spectra with emission lines influenced by many factors. Therefore, to fully describe the spectrum requires specification of a large number of parameters, such as line equivalent width, blueshift, and ratios. Principal Component Analysis (PCA) aims to construct eigenvectors-or principal components-from the data with the goal of finding a few key parameters that can be used to predict the rest of the spectrum fairly well. Analysis of simulated quasar spectra was used to verify and justify our modified application of PCA.We used a variant of PCA called Weighted Expectation Maximization PCA (EMPCA; Bailey 2012) along with k-means cluster analysis to analyze simulated quasar spectra. Our approach combines both analytical methods to address two known problems with classical PCA. EMPCA uses weights to account for uncertainty and missing points in the spectra. K-means groups similar spectra together to address the nonlinearity of quasar spectra, specifically variance in blueshifts and widths of the emission lines.In producing and analyzing simulations, we first tested the effects of varying equivalent widths and blueshifts on the derived principal components, and explored the differences between standard PCA and EMPCA. We also tested the effects of varying signal-to-noise ratio. Next we used the results of fits to composite quasar spectra (see accompanying poster by Wagner et al.) to construct a set of realistic simulated spectra, and subjected those spectra to the EMPCA /k-means analysis. We concluded that our approach was validated when we found that the mean spectra from our k-means clusters derived from PCA projection coefficients reproduced the trends observed in the composite spectra.Furthermore, our method needed only two eigenvectors to identify both sets of correlations used to construct the simulations, as well as indicating the linear and nonlinear segments. Comparing this to regular PCA, which can require a dozen or more components, or to

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  6. APPLICATION OF ABSORPTION SPECTROSCOPY TO ACTINIDE PROCESS ANALYSIS AND MONITORING

    SciTech Connect

    Lascola, R.; Sharma, V.

    2010-06-03

    The characteristic strong colors of aqueous actinide solutions form the basis of analytical techniques for actinides based on absorption spectroscopy. Colorimetric measurements of samples from processing activities have been used for at least half a century. This seemingly mature technology has been recently revitalized by developments in chemometric data analysis. Where reliable measurements could formerly only be obtained under well-defined conditions, modern methods are robust with respect to variations in acidity, concentration of complexants and spectral interferents, and temperature. This paper describes two examples of the use of process absorption spectroscopy for Pu analysis at the Savannah River Site, in Aiken, SC. In one example, custom optical filters allow accurate colorimetric measurements of Pu in a stream with rapid nitric acid variation. The second example demonstrates simultaneous measurement of Pu and U by chemometric treatment of absorption spectra. The paper concludes with a description of the use of these analyzers to supplement existing technologies in nuclear materials monitoring in processing, reprocessing, and storage facilities.

  7. Atmospheric lifetimes and global warming potentials of hydrofluoroethers: Reactivity toward OH, UV spectra, and IR absorption cross sections

    SciTech Connect

    Orkin, V.L.; Villenave, E.; Huie, R.E.; Kurylo, M.J.

    1999-12-02

    The rate constants for the reactions of OH radicals with the fluorinated ethers, CHF{sub 2}-O-CHF{sub 2} (HFOC-134) and CF{sub 3}CH{sub 2}-O-CH{sub 2}CF{sub 3} (HFOC-356mff), were measured using the flash photolysis resonance fluorescence technique over the temperature range 277--370 K to give the following Arrhenius expressions: k{sub HFOC-356mff}(T) = (2.32{sub {minus}0.41}{sup +0.46}) x 10{sup {minus}12} exp{l{underscore}brace}{minus}(790 {+-} 47)/T{r{underscore}brace} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. On the basis of the analysis of the available experimental results, the following Arrhenius expression can be recommended for the rate constant of the reaction between OH and HFOC-134: k{sub HFOC-134}(T) = (0.82{sub {minus}0.24}{sup +0.34}) x 10{sup {minus}12} exp{l{underscore}brace}{minus}(1,730 {+-} 110)/T{r{underscore}brace} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Atmospheric lifetimes were estimated to be 24.8 years for HFOC-134 (23.8 years based on the results of this study alone) and 0.3 years for HFOC-356mff. Infrared absorption cross sections of HFOC-134, HFOC-356mff, and HFOC-125 (CHF{sub 2}-O-CF{sub 3}) were measured at T = 295 K from 500 to 1,600 cm{sup {minus}1} and the global warming potentials of the three compounds were estimated. Ultraviolet absorption spectra of the ethers were measured between 160 and 220 nm. The general pattern of reactivity of hydrofluoroethers toward OH is discussed.

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

    USGS Publications Warehouse

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

    2014-01-01

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

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

    USGS Publications Warehouse

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

    2011-01-01

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

  10. Linear absorption and two-dimensional infrared spectra of N-methylacetamide in chloroform revisited: polarizability and multipole effects.

    PubMed

    Jansen, Thomas L C

    2014-07-17

    The effect of solvent polarizability and multipole effects on the amide I vibrational spectra of a peptide unit is investigated. Four molecular dynamics force fields of increasing complexity for the solvent are used to model both the linear absorption and two-dimensional infrared spectra. It is observed that, at least in chloroform solution, the predicted solvent shift is considerably improved when accounting for the polarizabiltiy and multipole effects. The latter are typically connected with halogen bonding. Significant deviations are still observed for more sensitive line shape parameters such as the spectral width and line skewness. However, the findings demonstrate that previously observed deviations have an origin in the force field treatment rather than in the electrostatic mapping procedure frequently employed to simulate linear absorption and two-dimensional infrared spectroscopy.

  11. Electronic structure and optical absorption spectra of CdSe covered with ZnSe and ZnS epilayers

    NASA Astrophysics Data System (ADS)

    Yun, So Jeong; Lee, Geunsik; Kim, Jai Sam; Shin, Seung Koo; Yoon, Young-Gui

    2006-02-01

    Using the first-principles methods we compute the electronic structure and the absorption spectra for a wurtzite CdSe (0001) slab covered with zincblende ZnSe and ZnS epilayers. For each structure we compute the DOS and the imaginary part of the dielectric function. We find that the semiconductor passivation shifts the 'near Fermi-level' states of the bare CdSe slab down to lower energy levels. The migration suggests the decrease of surface effects and energy loss. We observe the substantial reduction of the abnormal peaks in the absorption spectra of the bare CdSe slab, which seems to be a consequence of the DOS migration. This is consistent with the experimental results that a proper passivation enhance the luminescence efficiency. We also study the case that the epilayer surface is terminated with PH 3 and find the PH 3 passivation also reduces the surface state to some extent.

  12. The structure of the absorption spectra of the quasars Q 0420-388 and Q 1101-264

    NASA Astrophysics Data System (ADS)

    Chernomordik, V. V.

    1988-08-01

    The spectra of the quasars Q 0420-388 and Q 1101-264 are studied in the framework of the shock-wave model of the Lyman-alpha forest in the spectra of distant quasars, in which the origin of Lyman-alpha absorption lines is related to absorption zones in the shells of metagalactic shock waves. It is shown that more that 50 percent of the narrow Lyman-alpha abosrption lines are components of doublets, or pairs of nearby lines with the same equivalent widths. This is in good agreement with the predictions of the shock-wave model. The expected H I column density distribution of the Lyman-alpha lines is calculated and is found to be in agreement with the findings of Atwood et al. (1985).

  13. First-principles calculation of principal Hugoniot and K-shell X-ray absorption spectra for warm dense KCl

    SciTech Connect

    Zhao, Shijun; Zhang, Shen; Kang, Wei; Li, Zi; Zhang, Ping; He, Xian-Tu

    2015-06-15

    Principal Hugoniot and K-shell X-ray absorption spectra of warm dense KCl are calculated using the first-principles molecular dynamics (FPMD) method. Evolution of electronic structures as well as the influence of the approximate description of ionization on pressure (caused by the underestimation of the energy gap between conduction bands and valence bands) in the first-principles method are illustrated by the calculation. It is shown that approximate description of ionization in FPMD has small influence on Hugoniot pressure due to mutual compensation of electronic kinetic pressure and virial pressure. The calculation of X-ray absorption spectra shows that the band gap of KCl persists after the pressure ionization of the 3p electrons of Cl and K taking place at lower energy, which provides a detailed understanding to the evolution of electronic structures of warm dense matter.

  14. Using high-resolution laboratory and ground-based solar spectra to assess CH4 absorption coefficient calculations

    NASA Astrophysics Data System (ADS)

    Mendonca, J.; Strong, K.; Sung, K.; Devi, V. M.; Toon, G. C.; Wunch, D.; Franklin, J. E.

    2017-03-01

    A quadratic-speed-dependent Voigt line shape (qSDV) with line mixing (qSDV+LM), together with spectroscopic line parameters from Devi et al. [1,2] for the 2v3 band of CH4, was used to retrieve total columns of CH4 from atmospheric solar absorption spectra. The qSDV line shape (Tran et al., 2013) [3] with line mixing (Lévy et al., 1992) [4] was implemented into the forward model of GFIT (the retrieval algorithm that is at the heart of the GGG software (Wunch et al., 2015) [5]) to calculate CH4 absorption coefficients. High-resolution laboratory spectra of CH4 were used to assess absorption coefficients calculated using a Voigt line shape and spectroscopic parameters from the atm line list (Toon, 2014) [6]. The same laboratory spectra were used to test absorption coefficients calculated using the qSDV+LM line shape with spectroscopic line parameters from Devi et al. [1,2] for the 2v3 band of CH4 and a Voigt line shape for lines that don't belong to the 2v3 band. The spectral line list for lines that don't belong to the 2v3 band is an amalgamation of multiple spectral line lists. We found that for the P, Q, and R branches of the 2v3 band, the qSDV+LM simulated the laboratory spectra better than the Voigt line shape. The qSDV+LM was also used in the spectral fitting of high-resolution solar absorption spectra from four ground-based remote sensing sites and compared to spectra fitted with a Voigt line shape. The average root mean square (RMS) residual for 131,124 solar absorption spectra fitted with absorption coefficients calculated using the qSDV+LM for the 2v3 band of CH4 and the new spectral line list for lines for lines that don't belong to the 2v3 band, was reduced in the P, Q, and R branches by 5%, 13%, and 3%, respectively when compared with spectra fitted using a Voigt line shape and the atm line list. We found that the average total column of CH4 retrieved from these 131,124 spectra, with the qSDV+LM was 1.1±0.3% higher than the retrievals performed using a

  15. Interacting He and Ar atoms: Revised theoretical interaction potential, dipole moment, and collision-induced absorption spectra

    SciTech Connect

    Meyer, Wilfried; Frommhold, Lothar

    2015-09-21

    Coupled cluster quantum chemical calculations of the potential energy surface and the induced dipole surface are reported for the He–Ar van der Waals collisional complex. Spectroscopic parameters are derived from global analytical fits while an accurate value for the long-range dipole coefficient D{sub 7} is obtained by perturbation methods. Collision-induced absorption spectra are computed quantum mechanically and compared with existing measurements.

  16. Simulation of FREE→FREE Absorption Spectra and the Calculation of Interaction Potentials for Alkali-Rare Gas Atom Pairs

    NASA Astrophysics Data System (ADS)

    Hewitt, J. Darby; Spinka, Thomas M.; Readle, Jason. D.; Eden, J. Gary

    2013-06-01

    We have simulated free→free (X^2Σ^+_{1/2}→B^2Σ^+_{1/2}) absorption spectra for alkali-rare gas pairs. By comparing simulation results with experimental data, we have been able to iteratively determine the form for the B^2Σ^+_{1/2} interaction potential for the system for a range in internuclear separation of 1.5-20 Å. Simulation methods will be presented, as will our results pertaining to Cs-Ar.

  17. Polarized absorption spectra of aromatic radicals in stretched polymer film. 3. Radical ions of acridine and phenazine

    SciTech Connect

    Sekigucki, K.; Hiratsuka, H.; Tanizaki, Y.; Hatano, Y.

    1980-02-21

    Radical anions and cations of acridine and phenazine have been prepared in polymer film by ..gamma..-ray irradiation at 77 K. For the preparation of radical anions the sample was incorporated into polyethylene film by sec-butylamine, while for radical cations poly(vinyl chloride) film and sec-butyl chloride were used. Polarized absorption spectra of these radical ions have been measured in stretched polymer film and analyzed qualitatively in terms of molecular orbital calculations.

  18. Interacting He and Ar atoms: Revised theoretical interaction potential, dipole moment, and collision-induced absorption spectra.

    PubMed

    Meyer, Wilfried; Frommhold, Lothar

    2015-09-21

    Coupled cluster quantum chemical calculations of the potential energy surface and the induced dipole surface are reported for the He-Ar van der Waals collisional complex. Spectroscopic parameters are derived from global analytical fits while an accurate value for the long-range dipole coefficient D7 is obtained by perturbation methods. Collision-induced absorption spectra are computed quantum mechanically and compared with existing measurements.

  19. Real-Time Analysis of Raman Spectra for Temperature Field Characterization in Aircraft Exhaust Noise Studies

    NASA Astrophysics Data System (ADS)

    Wormhoudt, J.; Nelson, D. D.; Annen, K.; Locke, R. J.; Wernet, M.

    2009-06-01

    Raman scattering has long been used as a non-intrusive diagnostic of temperatures in combustion exhaust flows, using a variety of spectral analysis techniques. As part of their ongoing program of experiments to support development of computer codes that calculate exhaust flow fields and predict jet noise, NASA Glenn Research Center is developing a laser Raman diagnostic system that will measure mean temperatures and temperature fluctuations in hot and cold jet flows. We describe a software package, ART (Analysis for Raman Temperatures), that analyzes Raman spectra of air for temperature and density using vibrational or resolved or unresolved rotational bands, presenting results in a variety of real-time displays. Each analysis technique presents its own challenges in obtaining the most precise and accurate values, and we will comment on these issues by exhibiting example spectra of each type. The ART program is closely related to another Aerodyne software package (TDLWintel) which automates the acquisition and analysis of tunable laser absorption spectra.

  20. Xgremlin: Interferograms and spectra from Fourier transform spectrometers analysis

    NASA Astrophysics Data System (ADS)

    Nave, G.; Griesmann, U.; Brault, J. W.; Abrams, M. C.

    2015-11-01

    Xgremlin is a hardware and operating system independent version of the data analysis program Gremlin used for Fourier transform spectrometry. Xgremlin runs on PCs and workstations that use the X11 window system, including cygwin in Windows. It is used to Fourier transform interferograms, plot spectra, perform phase corrections, perform intensity and wavenumber calibration, and find and fit spectral lines. It can also be used to construct synthetic spectra, subtract continua, compare several different spectra, and eliminate ringing around lines.

  1. Chemomertical analysis of endometrial tissue fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Vaitkuviene, Aurelija; Auksorius, E.; Fuchs, D.; Gavriushin, V.

    2002-10-01

    An effort has been made to detect neopterin spectrum in fluorescence of premalignant endometrial tissue and to estimate the number of fluorophores naturally existing in the tissue with fluorescence present above the noise level. Endometrial Tissue fluorescence was measured in vitro by excitation with the third harmonic of Nd YAG laser. Multivariate curve resolution was used for testing neopterin presence in endometrial tissue. Fluorescence spectra ofneopterin was measured and used as a target spectrum for testing. Seven factors -fluorescence ofnatural fluorophores ofendometrial tissue were found to be present above the noise level in the overall autofluorescence. Neopterin concentration may be too low in endometrial tissue to make its fluorescence above the noise level because neopterin spectrum was not found to be among the spectra resolved by multivariate curve resolution. An intensity increase in the neopterin spectrum spectral region in hyperplastic endometrial samples might be associated with neopterin concentration increase.

  2. Application of Video Spectral Comparator (absorption spectra) for establishing the chronological order of intersecting printed strokes and writing pen strokes.

    PubMed

    Kaur, Ridamjeet; Saini, Komal; Sood, N C

    2013-06-01

    The sequence of intersecting strokes of laser printers (black, blue, red and green) and typewriter ink (black) with the strokes of gel pen ink, ballpoint pen ink and fountain pen ink (black, blue, red and green) has been determined by studying their absorption spectra. The absorption spectra have been generated for each of the two pure inks (i.e. A and B) and points of their intersections (i.e. A over B and B over A) by using Video Spectral Comparator (VSC-2000-HR). The study was carried out with an assumption that the peak characteristics of spectra from the point of intersection should correspond to the peak characteristics of pure ink which was executed later. It was observed that the absorption spectrum of intersection corresponds with either the laser printer or the typewriter ink stroke, whether these strokes were executed earlier or later than the writing instrument strokes. As the results obtained from the study were negative, the FDEs are advised against the practice of this technique in the examination of the sequence of intersecting strokes for these specified inks.

  3. Research program in nuclear and solid state physics. [including pion absorption spectra and muon spin precession

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The survey of negative pion absorption reactions on light and medium nuclei was continued. Muon spin precession was studied using an iron target. An impulse approximation model of the pion absorption process implied that the ion will absorb almost exclusively on nucleon pairs, single nucleon absorption being suppressed by energy and momentum conservation requirements. For measurements on both paramagnetic and ferromagnetic iron, the external magnetic field was supplied by a large C-type electromagnet carrying a current of about 100 amperes.

  4. A search for diffuse absorption bands in the spectra of two PPN candidate stars: HD 179821 and SAO 34504

    NASA Astrophysics Data System (ADS)

    Začs, Laimons; Schmidt, Mirek R.; Szczerba, Ryszard

    1999-07-01

    High-resolution spectra and spectral-synthesis methods have been used to search for diffuse absorption bands in two protoplanetary nebulae candidate stars HD 179821 and SAO 34504. We have found strong evidence for eight diffuse bands (5780, 5797, 5850, 6196, 6270, 6614, 6660, 6699) in HD 179821. The mean value of the heliocentric velocity (V_solar) of these bands is -11.5kms^-1, which may be compared to V_solar ~= -11kms^-1 obtained for the Nai D12 interstellar component. A feature on the red wing of the diffuse interstellar band at 5780Å is likely to have a circumstellar origin. Its Doppler velocity is close to that for one of the Nai D12 absorption components. No significant interstellar absorption bands are detected in SAO 34504. However, we have found a number of unidentified absorption features. Those at 6196, 6597 and 5780Å may be diffuse circumstellar bands blueshifted with respect to the stellar velocity derived from the photospheric absorption lines, V_solar = -39.7kms^-1, in agreement with the expansion velocity of the circumstellar remnant derived from the radio observations, V_exp ~= 10kms^-1. The Nai D12 lines for SAO34504 consist of two absorption components at V_solar ~= -13 and -49kms^-1.

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

    PubMed

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

    2015-03-07

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

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

    SciTech Connect

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

    2015-03-07

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

  7. 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.

  8. pH-dependent absorption spectra of rhodopsin mutant E113Q: On the role of counterions and protein

    NASA Astrophysics Data System (ADS)

    Xie, Peng; Zhou, Panwang; Alsaedi, Ahmed; Zhang, Yan

    2017-03-01

    The absorption spectra of bovine rhodopsin mutant E113Q in solutions were investigated at the molecular level by using a hybrid quantum mechanics/molecular mechanics (QM/MM) method. The calculations suggest the mechanism of the absorption variations of E113Q at different pH values. The results indicate that the polarizations of the counterions in the vicinity of Schiff base under protonation and unprotonation states of the mutant E113Q would be a crucial factor to change the energy gap of the retinal to tune the absorption spectra. Glu-181 residue, which is close to the chromophore, cannot serve as the counterion of the protonated Schiff base of E113Q in dark state. Moreover, the results of the absorption maximum in mutant E113Q with the various anions (Cl-, Br-, I- and NO3-) manifested that the mutant E113Q could have the potential for use as a template of anion biosensors at visible wavelength.

  9. Electric field effect on the nonlinear and linear intersubband absorption spectra in CdTe/ZnTe spherical quantum dot

    NASA Astrophysics Data System (ADS)

    Kostić, Radmila; Stojanović, Dušanka

    2012-01-01

    Linear and nonlinear absorption spectra of neutral (D0) hydrogenic impurity located at the center of the CdTe/ZnTe spherical quantum dot (QD) were investigated after assuming a spherically symmetric confining potential of finite depth. Calculations were performed under the effective mass approximation on the basis of exact solution of the Schrödinger and Poisson equations. Eigenfunctions were expressed in terms of the Whittaker and Coulomb wave functions. Results for D0 impurity energies of ground 1s, and excited 2p, 3d, and 2s states strongly depend on QD radius if it does not exceed a few effective Bohr radius. Wave functions and Stark shift energy levels in external electric field were determined from a variational-calculus approach for states labeled m=0. The absorption spectra for intersubband transitions were found to depend strongly on the QD radius. Whether or not the impurity is present, the peak energy of absorption decreases with increasing QD radius. An external electric field increases the transition energy but does not significantly change absorption characteristics.

  10. Analysis of IUE spectra using the interactive data language

    NASA Technical Reports Server (NTRS)

    Joseph, C. L.

    1981-01-01

    The Interactive Data Language (IDL) is used to analyze high resolution spectra from the IUE. Like other interactive languages, IDL is designed for use by the scientist rather than the professional programmer, allowing him to conceive of his data as simple entities and to operate on this data with minimal difficulty. A package of programs created to analyze interstellar absorption lines is presented as an example of the graphical power of IDL.

  11. Covariance Analysis of Gamma Ray Spectra

    SciTech Connect

    Trainham, R.; Tinsley, J.

    2013-01-01

    The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

  12. Covariance analysis of gamma ray spectra

    SciTech Connect

    Trainham, R.; Tinsley, J.

    2013-01-15

    The covariance method exploits fluctuations in signals to recover information encoded in correlations which are usually lost when signal averaging occurs. In nuclear spectroscopy it can be regarded as a generalization of the coincidence technique. The method can be used to extract signal from uncorrelated noise, to separate overlapping spectral peaks, to identify escape peaks, to reconstruct spectra from Compton continua, and to generate secondary spectral fingerprints. We discuss a few statistical considerations of the covariance method and present experimental examples of its use in gamma spectroscopy.

  13. Variability in the Intrinsic UV Absorption in Mrk 279 based on HST/COS Spectra

    NASA Astrophysics Data System (ADS)

    Schmachtenberger, Benjamin R.; Gabel, Jack; Crenshaw, D. Michael; Kraemer, Steven B.

    2015-01-01

    We present an analysis of the variability of the mass outflow systems in the Seyfert 1 galaxy Mrk 279 based on spectra obtained with the Cosmic Origin Spectrograph (COS) aboard the Hubble Space Telescope in 2011, compared with observations in 2002 and 2003 obtained with the Space Telescope Imaging Spectrograph (STIS). The continuum flux dropped by a factor of fifteen in 2011 compared to 2003, similar to the low flux level observed in 2002. We measure covering factors and ionic column densities for the outflow systems, treating three distinct emission components - continuum, broad line region (BLR) and intermediate line region (ILR). We find that the column densities of C IV and N V have increased in both the low and high velocity kinematic components (radial velocities -265 km/s and -460 km/s), and Si IV has appeared in the former. Based on photoionization models using CLOUDY, we find the column density variations in both components are consistent with a response of the outflow to the drop in ionizing flux. We also find that the covering factor of the ILR in the low velocity component has increased in the 2011 spectrum, while the covering factors in the high velocity component are stable across the three epochs. We use these results to constrain the geometry and physical conditions of the outflows in Mrk 279.

  14. Predicting X-ray absorption spectra of semiconducting polymers for electronic structure and morphology characterization

    NASA Astrophysics Data System (ADS)

    Su, Gregory; Patel, Shrayesh; Pemmaraju, C. Das; Kramer, Edward; Prendergast, David; Chabinyc, Michael

    2015-03-01

    Core-level X-ray absorption spectroscopy (XAS) reveals important information on the electronic structure of materials and plays a key role in morphology characterization. Semiconducting polymers are the active component in many organic electronics. Their electronic properties are critically linked to device performance, and a proper understanding of semiconducting polymer XAS is crucial. Techniques such as resonant X-ray scattering rely on core-level transitions to gain materials contrast and probe orientational order. However, it is difficult to identify these transitions based on experiments alone, and complementary simulations are required. We show that first-principles calculations can capture the essential features of experimental XAS of semiconducting polymers, and provide insight into which molecular model, such as oligomers or periodic boundary conditions, are best suited for XAS calculations. Simulated XAS can reveal contributions from individual atoms and be used to visualize molecular orbitals. This allows for improved characterization of molecular orientation and scattering analysis. These predictions lay the groundwork for understanding how chemical makeup is linked to electronic structure, and to properly utilize experiments to characterize semiconducting polymers.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    Matrix isolation techniques are used to investigate the spectra of lead molecules and, in particular, to obtain resonance Raman spectra of lead vapors isolated in solid xenon matrices. The presence of Pb2 is confirmed by the visible adsorption, and Raman spectra yield a vibrational frequency for the ground state of 108 per cm and a dissociation energy of 8200 per cm. A second resonance Raman progression indicates a Pb3 species of D3h symmetry. Finally, two additional Raman features at approximately 111 per cm spacing are evidence for a third species, tentatively identified as Pb4.

  16. Structural characterization of astaxanthin aggregates as revealed by analysis and simulation of optical spectra

    NASA Astrophysics Data System (ADS)

    Lu, Liping; Hu, Taoping; Xu, Zhigang

    2017-10-01

    Carotenoids can self-assemble in hydrated polar solvents to form J- or H-type aggregates, inducing dramatic changes in photophysical properties. Here, we measured absorption and emission spectra of astaxanthin in ethanol-water solution using ultraviolet-visible and fluorescence spectrometers. Two types of aggregates were distinguished in mixed solution at different water contents by absorption spectra. After addition of water, all probed samples immediately formed H-aggregates with maximum blue shift of 31 nm. In addition, J-aggregate was formed in 1:3 ethanol-water solution measured after an hour. Based on Frenkel exciton model, we calculated linear absorption and emission spectra of these aggregates to describe aggregate structures in solution. For astaxanthin, experimental results agreed well with the fitted spectra of H-aggregate models, which consisted of tightly packed stacks of individual molecules, including hexamers, trimers, and dimers. Transition moment of single astaxanthin in ethanol was obtained by Gaussian 09 program package to estimate the distance between molecules in aggregates. Intermolecular distance of astaxanthin aggregates ranges from 0.45 nm to 0.9 nm. Fluorescence analysis showed that between subbands, strong exciton coupling induced rapid relaxation of H-aggregates. This coupling generated larger Stokes shift than monomers and J-aggregates.

  17. [Near infrared Raman spectra analysis of rhizoma dioscoreae].

    PubMed

    Lin, Wen-Shuo; Chen, Rong; Li, Yong-Zeng; Feng, Shang-Yuan; Huang, Zu-Fang; Xie, Bing-Xian

    2008-05-01

    A novel and compact near-infrared (NIR) Raman system was developed using 785 nm diode laser, volume-phase technology holographic system, and NIR intensified charge-coupled device (CCD). The Raman spectra and first derivative spectra of rhizoma dioscoreae were obtained. The Raman spectra of rhizoma dioscoreae showed three strong characteristic peaks at 477, 863 and 936 cm(-1), respectively. The major ingredients are protein, amino acid, starch, polysaccharides and so on, matching the known basic biochemical composition of rhizoma dioscoreae. In the first derivative spectra of rhizoma dioscoreae, the distinguishing characteristic peaks appeared at 467, 484, 870 and 943 cm(-1). Contrasted with rhizoma dioscoreae Raman spectra in the ranges of 600 to 800 cm(-1) and 1 000 to 1 400 cm(-1), the changes in rhizoma dioscoreae Raman first derivative spectra are represented more clearly than the rhizoma dioscoreae Raman spectra. So the rhizoma dioscoreae Raman first derivative spectra can be an accurate supplementary analysis method to the rhizoma dioscoreae Raman spectra.

  18. Automatic continuum analysis of reflectance spectra

    NASA Technical Reports Server (NTRS)

    Clark, Roger N.; King, Trude V. V.

    1987-01-01

    A continuum algorithm based on a Segmented Upper Hull method (SUH) is described. An upper hull is performed on segments of a spectrum defined by local minima and maxima. The segments making a complete spectrum are then combined. The definition of the upper hull allows the continuum to be both concave and/or convex, adapting to the shape of the spectrum. The method performs multiple passes on a spectrum by segmenting each local maximum to minimum and performing an upper hull. The algorithm naturally adapts to the widths of absorption features, so that all features are found, including the nature of doublets, triplets, etc. The algorithm is also reasonably fast on common minicomputers so that it might be applied to the large data sets from imaging spectrometers.

  19. The UV/visible absorption spectra of shocked nitromethane - amine mixtures

    NASA Astrophysics Data System (ADS)

    Constantinou, C. P.; Gupta, Y. M.

    1994-07-01

    Time-resolved optical absorption spectroscopy has been used to examine the response of a mixture of nitromethane with ethylenediamine (0.1% by weight) to stepwise shock compression up to a pressure of 14 GPa. Unlike pure nitromethane, the mixture shows an irreversible time-dependent shift in the absorption edge of up to 100 nm towards longer wavelengths. This provides evidence for the chemical nature of the mechanism by which nitromethane is sensitized in the presence of amines.

  20. A sensitive continuum analysis method for gamma ray spectra

    NASA Technical Reports Server (NTRS)

    Thakur, Alakh N.; Arnold, James R.

    1993-01-01

    In this work we examine ways to improve the sensitivity of the analysis procedure for gamma ray spectra with respect to small differences in the continuum (Compton) spectra. The method developed is applied to analyze gamma ray spectra obtained from planetary mapping by the Mars Observer spacecraft launched in September 1992. Calculated Mars simulation spectra and actual thick target bombardment spectra have been taken as test cases. The principle of the method rests on the extraction of continuum information from Fourier transforms of the spectra. We study how a better estimate of the spectrum from larger regions of the Mars surface will improve the analysis for smaller regions with poorer statistics. Estimation of signal within the continuum is done in the frequency domain which enables efficient and sensitive discrimination of subtle differences between two spectra. The process is compared to other methods for the extraction of information from the continuum. Finally we explore briefly the possible uses of this technique in other applications of continuum spectra.

  1. Ti K-edge X-ray absorption spectra of spray pyrolysis synthesized TiO2-x and TiO2-x Nx thin films

    NASA Astrophysics Data System (ADS)

    Sahoo, Madhusmita; Yadav, Ashok Kumar; Jha, S. N.; Bhattacharyya, Dibyendu; Mathews, Tom; Dash, S.

    2017-05-01

    Oxygen deficient TiO2 and N-TiO2 anatase thin films were synthesized by employing a two step process. First TiO2 and N-TiO2 films were synthesized by using a cost effective spray pyrolysis method. Subsequently, these films were reduced under H2 to create oxygen vacancies. Formation of oxygen vacancies was confirmed by using synchrotron source X-ray Absorption Spectroscopy (XAS). Effect of oxygen vacancies on electronic and structural properties were deduced from the near edge and extended region analysis of the X-ray absorption spectra. It is inferred that reduction time plays a crucial role in creating oxygen vacancies and number of oxygen vacancies increases with increase in reduction time. Substrate effect was delineated by using Si and FTO (Fluorine doped tin oxide coated glass) as substrates for film deposition.

  2. Theoretical UV absorption spectra of hydrodynamically escaping O{sub 2}/CO{sub 2}-rich exoplanetary atmospheres

    SciTech Connect

    Gronoff, G.; Mertens, C. J.; Norman, R. B.; Maggiolo, R.; Wedlund, C. Simon; Bell, J.; Bernard, D.; Parkinson, C. J.; Vidal-Madjar, A.

    2014-06-20

    Characterizing Earth- and Venus-like exoplanets' atmospheres to determine if they are habitable and how they are evolving (e.g., equilibrium or strong erosion) is a challenge. For that endeavor, a key element is the retrieval of the exospheric temperature, which is a marker of some of the processes occurring in the lower layers and controls a large part of the atmospheric escape. We describe a method to determine the exospheric temperature of an O{sub 2}- and/or CO{sub 2}-rich transiting exoplanet, and we simulate the respective spectra of such a planet in hydrostatic equilibrium and hydrodynamic escape. The observation of hydrodynamically escaping atmospheres in young planets may help constrain and improve our understanding of the evolution of the solar system's terrestrial planets' atmospheres. We use the dependency of the absorption spectra of the O{sub 2} and CO{sub 2} molecules on the temperature to estimate the temperature independently of the total absorption of the planet. Combining two observables (two parts of the UV spectra that have a different temperature dependency) with the model, we are able to determine the thermospheric density profile and temperature. If the slope of the density profile is inconsistent with the temperature, then we infer the hydrodynamic escape. We address the question of the possible biases in the application of the method to future observations, and we show that the flare activity should be cautiously monitored to avoid large biases.

  3. Vibrational absorption spectra from vibrational coupled cluster damped linear response functions calculated using an asymmetric Lanczos algorithm

    NASA Astrophysics Data System (ADS)

    Thomsen, Bo; Hansen, Mikkel Bo; Seidler, Peter; Christiansen, Ove

    2012-03-01

    We report the theory and implementation of vibrational coupled cluster (VCC) damped response functions. From the imaginary part of the damped VCC response function the absorption as function of frequency can be obtained, requiring formally the solution of the now complex VCC response equations. The absorption spectrum can in this formulation be seen as a matrix function of the characteristic VCC Jacobian response matrix. The asymmetric matrix version of the Lanczos method is used to generate a tridiagonal representation of the VCC response Jacobian. Solving the complex response equations in the relevant Lanczos space provides a method for calculating the VCC damped response functions and thereby subsequently the absorption spectra. The convergence behaviour of the algorithm is discussed theoretically and tested for different levels of completeness of the VCC expansion. Comparison is made with results from the recently reported [P. Seidler, M. B. Hansen, W. Györffy, D. Toffoli, and O. Christiansen, J. Chem. Phys. 132, 164105 (2010)] vibrational configuration interaction damped response function calculated using a symmetric Lanczos algorithm. Calculations of IR spectra of oxazole, cyclopropene, and uracil illustrate the usefulness of the new VCC based method.

  4. a Theoretical Model for Wide-Band Infrared-Absorption Molecular Spectra at any Pressure: Fiction or Reality?

    NASA Astrophysics Data System (ADS)

    Buldyreva, Jeanna; Vander Auwera, Jean

    2014-06-01

    Various atmospheric applications require modeling of infrared absorption by the main atmospheric species in wide ranges of frequencies, pressures and temperatures. For different pressure regimes, different mechanisms are responsible for the observed intensities of vibration-rotation line manifolds, and the structure of the bands changes drastically when going from low to high densities. Therefore, no universal theoretical model exists presently to interpret simultaneously collapsed band-shapes observed at very high pressures and isolated-line shapes recorded in sub-atmospheric regimes. Using CO_2 absorption spectra as an example, we introduce some improvements in the non-Markovian Energy-Corrected Sudden model, developed for high-density spectra of arbitrary tensorial rank and generalized recently to parallel and perpendicular infrared absorption bands, and test the applicability of this approach for the case of nearly Doppler pressure regime via comparisons with recently recorded experimental intensities. J.V. Buldyreva and L. Bonamy, Phys. Rev. A 60(1), 370-376 (1999). J. Buldyreva and L. Daneshvar, J. Chem. Phys. 139, 164107 (2013). L. Daneshvar, T. Földes, J. Buldyreva, J. Vander Auwera, J. Quant. Spectrosc. Radiat. Transfer 2014 (to be submitted).

  5. SYNCHROTRON POLARIZATION AND SYNCHROTRON SELF-ABSORPTION SPECTRA FOR A POWER-LAW PARTICLE DISTRIBUTION WITH FINITE ENERGY RANGE

    SciTech Connect

    Fouka, M.; Ouichaoui, S. E-mail: souichaoui@usthb.dz

    2011-12-10

    We have derived asymptotic forms for the degree of polarization of the optically thin synchrotron and for synchrotron self-absorption (SSA) spectra assuming a power-law particle distribution of the form N({gamma}) {approx} {gamma}{sup -p} with {gamma}{sub 1} < {gamma} < {gamma}{sub 2}, especially for a finite high-energy limit, {gamma}{sub 2}, in the case of an arbitrary pitch angle. The new results inferred concern more especially the high-frequency range x >> {eta}{sup 2} with parameter {eta} = {gamma}{sub 2}/{gamma}{sub 1}. The calculated SSA spectra concern instantaneous photon emission where cooling effects are not considered. They have been obtained by also ignoring likely effects such as Comptonization, pair creation and annihilation, as well as magnetic photon splitting. To that aim, in addition to the two usual absorption frequencies, a third possible one has been derived and expressed in terms of the Lambert W function based on the analytical asymptotic form of the absorption coefficient, {alpha}{sub {nu}}, for the high-frequency range {nu} >> {nu}{sub 2} (with {nu}{sub 2} the synchrotron frequency corresponding to {gamma}{sub 2}). We have shown that the latter frequency may not have realistic applications in astrophysics, except in the case of an adequate set of parameters allowing one to neglect Comptonization effects. More detailed calculations and discussions are presented.

  6. Synchrotron Polarization and Synchrotron Self-absorption Spectra for a Power-law Particle Distribution with Finite Energy Range

    NASA Astrophysics Data System (ADS)

    Fouka, M.; Ouichaoui, S.

    2011-12-01

    We have derived asymptotic forms for the degree of polarization of the optically thin synchrotron and for synchrotron self-absorption (SSA) spectra assuming a power-law particle distribution of the form N(γ) ~ γ-p with γ1 < γ < γ2, especially for a finite high-energy limit, γ2, in the case of an arbitrary pitch angle. The new results inferred concern more especially the high-frequency range x Gt η2 with parameter η = γ2/γ1. The calculated SSA spectra concern instantaneous photon emission where cooling effects are not considered. They have been obtained by also ignoring likely effects such as Comptonization, pair creation and annihilation, as well as magnetic photon splitting. To that aim, in addition to the two usual absorption frequencies, a third possible one has been derived and expressed in terms of the Lambert W function based on the analytical asymptotic form of the absorption coefficient, αν, for the high-frequency range ν Gt ν2 (with ν2 the synchrotron frequency corresponding to γ2). We have shown that the latter frequency may not have realistic applications in astrophysics, except in the case of an adequate set of parameters allowing one to neglect Comptonization effects. More detailed calculations and discussions are presented.

  7. Study on the interaction between fluoroquinolones and erythrosine by absorption, fluorescence and resonance Rayleigh scattering spectra and their application

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Liu, Zhongfang; Liu, Jiangtao; Liu, Shaopu; Shen, Wei

    2008-03-01

    In pH 4.4-4.5 Britton-Robinson (BR) buffer solution, fluoroquinolone antibiotics (FLQs) including ciprofloxacin (CIP), norfloxacin (NOR), levofloxacin (LEV) and lomefloxacin (LOM) could react with erythrosine (Ery) to form 1:1 ion-association complexes, which not only resulted in the changes of the absorption spectra and the quenching of fluorescence, but also resulted in the great enhancement of resonance Rayleigh scattering (RRS). These offered some indications of the determination of fluoroquinolone antibiotics by spectrophotometric, fluorescence and resonance Rayleigh scattering methods. The detection limits for fluoroquinolone antibiotics were in the range of 0.097-0.265 μg/mL for absorption methods, 0.022-0.100 μg/mL for fluorophotometry and 0.014-0.027 μg/mL for RRS method, respectively. Among them, the RRS method had the highest sensitivity. In this work, the spectral characteristics of the absorption, fluorescence and RRS, the optimum conditions of the reactions and the properties of the analytical chemistry were investigated. The methods have been successfully applied to determination of some fluoroquinolone antibiotics in human urine samples and tablets. Taking CIP-Ery system as an example, the charge distribution, the enthalpy of formation and the mean polarizability were calculated by density function theory (DFT) method. In addition, the reasons for the enhancement of scattering spectra were discussed.

  8. Vibrational absorption spectra from vibrational coupled cluster damped linear response functions calculated using an asymmetric Lanczos algorithm.

    PubMed

    Thomsen, Bo; Hansen, Mikkel Bo; Seidler, Peter; Christiansen, Ove

    2012-03-28

    We report the theory and implementation of vibrational coupled cluster (VCC) damped response functions. From the imaginary part of the damped VCC response function the absorption as function of frequency can be obtained, requiring formally the solution of the now complex VCC response equations. The absorption spectrum can in this formulation be seen as a matrix function of the characteristic VCC Jacobian response matrix. The asymmetric matrix version of the Lanczos method is used to generate a tridiagonal representation of the VCC response Jacobian. Solving the complex response equations in the relevant Lanczos space provides a method for calculating the VCC damped response functions and thereby subsequently the absorption spectra. The convergence behaviour of the algorithm is discussed theoretically and tested for different levels of completeness of the VCC expansion. Comparison is made with results from the recently reported [P. Seidler, M. B. Hansen, W. Györffy, D. Toffoli, and O. Christiansen, J. Chem. Phys. 132, 164105 (2010)] vibrational configuration interaction damped response function calculated using a symmetric Lanczos algorithm. Calculations of IR spectra of oxazole, cyclopropene, and uracil illustrate the usefulness of the new VCC based method.

  9. Studying the complex absorption profiles of Si IV in 21 HiBALQSO spectra

    NASA Astrophysics Data System (ADS)

    Stathopoulos, D.; Danezis, E.; Lyratzi, E.; Antoniou, A.; Popović, L. Č.; Tzimeas, D.; Dimitrijević, M. S.

    2014-12-01

    We investigate the physical conditions and kinematics of broad absorption line region clouds of Si IV in 21 HiBAL Quasars. We use the Danezis et al. method [1], [2], [3] in order to fit and analyze the broad absorption troughs of Si IV resonance lines in the UV region of the electromagnetic spectrum. We find that the BAL flow is not smooth but instead plasma clouds are formed in it. BAL troughs present multicomponent structure which indicates the existence of more than one absorbing cloud in the line of sight, where every absorbing cloud produces a Si IV doublet. We show that the blending of these doublets produces the apparent broad absorption troughs we observe. One of our main achievements is that we managed to decompose and deblend each complex absorption trough to the individual doublets that it consists of. Apart from that, we succeeded in deblending the resonance lines of every doublet. By achieving accurate fits to the BAL troughs we calculated some physical and kinematical parameters that describe the plasma clouds in the line of sight. These parameters are: the radial outflow velocities of the clouds, the random velocities of ions inside each plasma cloud, the apparent optical depth in the center of every absorption component, the FWHM and the equivalent width. As a final step we correlate these physical parameters in order to draw useful conclusions.

  10. Analysis of Nearby Supernova Factory Type Ia Spectra with SYNAPPS: Maximum-Light Sample

    NASA Astrophysics Data System (ADS)

    Sofiatti, Caroline; Thomas, R.; Aldering, G. S.; Bailey, S.; Birchall, D.; Childress, M.; Fakhouri, H.; Hayden, B.; Kim, A. G.; Nordin, J.; Nugent, P. E.; Perlmutter, S.; Rubin, D.; Runge, K.; Saunders, C.; Suzuki, N.; Weaver, B.; Pecontal, E.; Buton, C.; Copin, Y.; Chotard, N.; Gangler, E.; Pereira, R.; Rigault, M.; Smadja, G.; Cellier-Holzem, F.; Canto, A.; Antilogus, P.; Bongard, S.; Fleury, M.; Guy, J.; Pain, R.; Chen, J.; Tao, C.; Feindt, U.; Greskovic, P.; Kowalski, M.; Lombardo, S.; Baltay, C.; Rabinowitz, D. L.

    2014-01-01

    We present a preliminary study of absorption features in the maximum-light spectra of 68 Type Ia supernovae. These spectra are a subset of spectrophotometric time series obtained by the Nearby Supernovae Factory using the SuperNova Integral Field Spectrograph (SNIFS). To extract ion signatures - strengths and velocities - from these absorption features we use the automated parameterized direct spectroscopic analysis code SYNAPPS. Trends in ion signatures as a function of spectroscopic sub-classification, photometric properties, and host galaxy stellar environment are considered. A new and experimental aspect of our approach is uncertainty quantification for SYNAPPS and calibration of its model inadequacy as a function of wavelength (for Type Ia supernovae near maximum light) using the Nearby Supernova Factory as a training sample. With further development and extension to other phases, this information could be used as a pre-processing step for SYNAPPS fitting, or it could be directly incorporated into SYNAPPS itself.

  11. Optical absorption spectra and structures of Ag{6/+} and Ag{8/+}

    NASA Astrophysics Data System (ADS)

    Shayeghi, A.; Götz, D. A.; Johnston, R. L.; Schäfer, R.

    2015-06-01

    This work presents optical photodissociation spectra of the Ag{6/+} and the Ag{8/+} clusters in the photon energy range ħω = 1.9-4.4 eV. Experimental spectra are interpreted by means of range separated TDDFT using the LC- ωPBEh and HSE06 functionals, where putative global minimum structures are obtained by the new pool-based Birmingham Cluster Genetic Algorithm, coupled with density functional theory. Structural assignment is facilitated by additionally taking data from previous ion mobility experiments into account. Both functionals reproduce the measured spectra very well, whereas HSE06 shows an almost quantitative agreement, questioning the importance of Hartree-Fock exchange in the long-range part of the range separated functional.

  12. All-electron first-principles GW+Bethe-Salpeter calculation for optical absorption spectra of sodium clusters

    SciTech Connect

    Noguchi, Yoshifumi; Ohno, Kaoru

    2010-04-15

    The optical absorption spectra of sodium clusters (Na{sub 2n}, n{<=} 4) are calculated by using an all-electron first-principles GW+Bethe-Salpeter method with the mixed-basis approach within the Tamm-Dancoff approximation. In these small systems, the excitonic effect strongly affects the optical properties due to the confinement of exciton in the small system size. The present state-of-the-art method treats the electron-hole two-particle Green's function by incorporating the ladder diagrams up to the infinite order and therefore takes into account the excitonic effect in a good approximation. We check the accuracy of the present method by comparing the resulting spectra with experiments. In addition, the effect of delocalization in particular in the lowest unoccupied molecular orbital in the GW quasiparticle wave function is also discussed by rediagonalizing the Dyson equation.

  13. The effect of absorption and coherent interference in the photoluminescence and electroluminescence spectra of SRO/SRN MIS capacitors.

    PubMed

    Juvert, Joan; González-Fernández, Alfredo Abelardo; Llobera, Andreu; Domínguez, Carlos

    2013-04-22

    In this paper we present a technique that can be used to study the effect of absorption and coherent interference in the luminescence of multilayer structures. We apply the technique to the measured photoluminescence and electroluminescence spectra of MIS capacitors where the insulator is composed of a silicon rich oxide (SRO)/silicon rich nitride (SRN) bilayer structure. We remove the effect of the multilayer stack on the measured photoluminescence spectrum of the samples without the metal contact to find the intrinsic spectrum. Then we apply the effect of the MIS structure on the intrinsic spectrum in order to calculate the electroluminescence spectrum. Good agreement with the experimentally measured EL spectrum is found. We discuss which parameters affect the spectra most significantly.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  15. On the time-dependent calculation of angular averaged vibronic absorption spectra with an application to molecular aggregates

    NASA Astrophysics Data System (ADS)

    Brüning, Christoph; Engel, Volker

    2017-01-01

    We introduce an efficient method to determine angular averaged absorption spectra for cases where electronic transitions take place to a manifold of N coupled excited states. The approach rests on the calculation of time-dependent auto-correlation functions which, upon Fourier-transform yield the spectrum. Assuming the Condon-approximation, it is shown that three wave-packet propagations are sufficient to calculate the spectrum. This is in contrast to a direct approach where it is necessary to perform N propagations to arrive at N2 cross-correlation functions. The reduction in computation time is of importance for larger molecular aggregates where the number N is determined by the aggregate size. We provide an example by determining spectra for macrocyclic dyes in different dipole-geometries.

  16. Theory of x-ray-absorption spectra in PrO2 and some other rare-earth compounds

    NASA Astrophysics Data System (ADS)

    Ogasawara, H.; Kotani, A.; Okada, K.; Thole, B. T.

    1991-01-01

    We analyze rare-earth 3d-core x-ray-absorption spectra (3d XAS) in PrO2, as well as in CeO2, using the impurity Anderson model. It is shown that the interplay between the atomic multiplet coupling and the solid-state hybridization between rare-earth 4f and oxygen 2p states is essential in determining the spectral shape. The calculated spectra are in fair agreement with experimental data which supports the theory that there is a strong mixing between 4f1 and 4f2v in the ground state of PrO2, where v denotes a hole in the oxygen 2p valence band. A theoretical prediction of Pr 4d XAS of PrO2 is also given. Because it contains much structure, experimental determination of this spectrum would be very valuable for the study of mixed-valence compounds.

  17. Ab initio calculations of electronic structures, polarizabilities, Raman and infrared spectra, optical gaps, and absorption spectra of M@Si16 (M=Ti and Zr) clusters

    NASA Astrophysics Data System (ADS)

    Kumar, Vijay; Briere, Tina M.; Kawazoe, Yoshiyuki

    2003-10-01

    Ab initio calculations have been performed using density-functional theory with the B3PW91 hybrid exchange-correlation functional and the Gaussian method to obtain the electronic and vibrational properties of the fullerene (f) and Frank-Kasper (FK) isomers of the metal-encapsulated silicon clusters M@Si16, M=Ti and Zr. The electron affinities of the two isomers are found to differ significantly and our result for FK-Ti@Si16 is in good agreement with recent experiments. The Raman and infrared vibrational spectra of the f and FK isomers show marked differences, due to their distinct bonding natures and structural features, that can be used unambiguously to identify the structures of these clusters experimentally. The polarizabilities, however, have similar values and lie above the bulk limit of silicon. The optical gaps and absorption spectra have been calculated using time-dependent density-functional theory. The lowest electronic excitation for the FK isomer lies in the deep blue region, while the one for the f isomer lies in the red region, making them attractive for optoelectronic applications.

  18. Electronic absorption spectra of C60+ -L (L = He, Ne, Ar, Kr, H2, D2, N2) complexes

    NASA Astrophysics Data System (ADS)

    Holz, Mathias; Campbell, Ewen Kyle; Rice, Corey Allen; Maier, John Paul

    2017-02-01

    Electronic spectra in the near infrared of C60+ with He, Ne, Ar, Kr, H2, D2 and N2 attached have been recorded below 10 K in a cryogenic radio frequency ion trap. Additional absorption bands are observed compared to the spectrum of C60+ -He. In the case of C60+ -N2, the strongest one of these shifts to lower energies by 21.3 cm-1 compared to the origin band of C60+ -He at 10378.5 cm-1. The pattern in the spectrum is dependent on the attached ligand. The gas-phase observations on C60+ -Ne allow a rationalization of the relative intensities of the absorptions of C60+ in a neon matrix.

  19. Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction

    PubMed Central

    2015-01-01

    We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Δm is mainly caused by dispersion effects and depends sensitively on the molecule’s specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Δm= −QWm in two factors, where Q depends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion while Wm is a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI). PMID:25834658

  20. Calculating Optical Absorption Spectra of Thin Polycrystalline Organic Films: Structural Disorder and Site-Dependent van der Waals Interaction.

    PubMed

    Megow, Jörg; Körzdörfer, Thomas; Renger, Thomas; Sparenberg, Mino; Blumstengel, Sylke; Henneberger, Fritz; May, Volkhard

    2015-03-12

    We propose a new approach for calculating the change of the absorption spectrum of a molecule when moved from the gas phase to a crystalline morphology. The so-called gas-to-crystal shift Δ[Formula: see text] m is mainly caused by dispersion effects and depends sensitively on the molecule's specific position in the nanoscopic setting. Using an extended dipole approximation, we are able to divide Δ[Formula: see text] m = -QWm in two factors, where Q depends only on the molecular species and accounts for all nonresonant electronic transitions contributing to the dispersion while Wm is a geometry factor expressing the site dependence of the shift in a given molecular structure. The ability of our approach to predict absorption spectra is demonstrated using the example of polycrystalline films of 3,4,9,10-perylenetetracarboxylic diimide (PTCDI).

  1. Cooperative enhancement of TPA in cruciform double-chain DSB derivation: a femtosecond transient absorption spectra study

    NASA Astrophysics Data System (ADS)

    He, X.; Wang, Y.; Yang, Z.; Ma, Y.; Yang, Y.

    2010-09-01

    Femtosecond time-resolved transient absorption (TA) spectra study was adopted to study the mechanism of the cooperative enhancement of two-photon absorption (TPA) cross section from the linear structure 1,4-di(4'-N,N-diphenylaminostyryl)benzene (DPA-DSB) to its cruciform double-chain dimer DPA-TSB. The results suggested that a non-emissive intramolecular charge-transfer (ICT) state, ICT’, was present upon excitation in the dimer, which was absent in the monomer. The existence of this non-emissive state, indicating the enhancement of the intramolecular charge-transfer of the dimer, should be the reason for the cooperative enhancement of the TPA cross section of the dimer compared to the monomer.

  2. 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.

  3. 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.

  4. Combined experimental and computational investigation of the absorption spectra of E- and Z-cinnamic acids in solution: The peculiarity of Z-cinnamics.

    PubMed

    Salum, María L; Arroyo Mañez, Pau; Luque, F Javier; Erra-Balsells, Rosa

    2015-07-01

    Cinnamic acids are present in all kinds of plant tissues and hence in herbs and derived medicines, cosmetics and foods. The interest in their role in plants and their therapeutic applications has grown exponentially. Because of their molecular structure they can exist in E- and Z-forms, which are both found in plants. However, since only the E-forms are commercially available, very few in vitro and in vivo studies of the Z-form have been reported. In this work the physico-chemical properties of Z-cinnamic acids in solution have been examined by means of UV-absorption spectroscopy and high-level quantum mechanical computations. For each isomer similar absorption spectra were obtained in methanol and acetonitrile. However, distinct trends were found for Z- and E forms of cinnamic acids in water, where a higher hypsochromic shift of the Z-isomer relative to the E-form was observed. In general the wavelength of maximal absorption of the Z-form is dramatically blue shifted (-30 to -40 nm) to λ<280 nm, while a slightly blue shift of the absorption maxima for the corresponding E-form (+3 to -4 nm) was observed. This difference is associated with the non-planar, largely distorted, Z-structure and to the almost complete flat structure of the E-form. The results provide a basis for the study of functional and biotechnological roles of cinnamic acids and for the analysis of samples containing mixture of both geometric isomers.

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

    PubMed

    Marković, Svetlana; Tošović, Jelena

    2015-09-03

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

  6. A search for weak ultraviolet interstellar absorption features in IUE spectra of Rho Ophiuchi and Zeta Ophiuchi

    NASA Technical Reports Server (NTRS)

    Welty, D. E.; Thorburn, J. A.; Hobbs, L. M.; York, D. G.

    1992-01-01

    We have applied procedures designed to reduce substantially the nonrandom, so-called 'fixed-pattern' noise present in IUE spectra to archival long-wavelength high-dispersion spectra of Rho Ophiuchi and Zeta Ophiuchi. Substantial elimination of the fixed-pattern noise via flat fielding can yield 2sigma equivalent width limits of 5-10 mA from the sum of a small number (about less than 5) of well-exposed archival spectra, and increases confidence in the reality of any weak features found. Examination of complete long-wavelength (about 2200-3250 A) spectra of these two stars has revealed, in addition to many known strong absorption lines, several lines of Fe I and Si I which had not previously been reported, as well as a small number of possible unidentified lines. We also present substantially improved upper limits to the equivalent widths of a number of other weak lines; limits an order of magnitude smaller, now achievable with the HST GHRS, should produce detections of some of these.

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

    PubMed

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

    2014-09-28

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

  8. Doublet structure of bands of low-frequency IR absorption spectra of some aromatic compounds

    NASA Astrophysics Data System (ADS)

    Demchuk, Yu. S.; Vandyukov, A. E.; Vandyukov, E. A.

    2000-12-01

    To increase the efficiency of identifying the complex aromatic compounds, the present paper gives the results of investigating the low-frequency region of the IR absorption and recorded doublet structure of absorption bands of the deformation(al) vibrations of naphtalene-, anthracene-, phenantrene-, pyrene- and coronene molecules in a fine- disperse state in matrices of KBr, polyethylene and in a vaseline oil. Parameters of changing the position of the centers of doublet components and the relationship of their intensities in changing the temperature are determined. Parameters of doublet components in dependence on the concentration of aromatic molecules in KBr tablets are investigated.

  9. Microhydration effects on geometric properties and electronic absorption spectra of ortho-aminobenzoic acid.

    PubMed

    Olivier, Danilo da Silva; Ito, Amando Siuiti; Galembeck, Sergio Emanuel

    2015-08-05

    TD-DFT and a combination of polarized continuum model (PCM) and microhydration methods helped to simulate the optical electronic absorption spectrum of ortho-aminobenzoic acid (o-Abz). The microhydration method involved the use of different numbers, from 1 to 5, of first solvation layer water molecules. We examined how implicit and explicit water affected the energies of the HOMO-LUMO transition in the o-Abz/water systems. Adding until five water molecules, the theoretical spectrum becomes closer to the experimental data. Microhydration combined with the PCM method leads to agreement between the theoretical result for five water molecules and the experimentally measured absorption bands.

  10. Electronic properties and absorption spectra of ZnSnP{sub 2} using mBJ potential

    SciTech Connect

    Joshi, Ritu Ahuja, B. L.

    2015-06-24

    We present the energy bands and density of states of ZnSnP{sub 2} using full potential linearized augmented plane wave method with modified Becke Johnson potential. It is found that this compound has a direct band gap of about 2.01 eV at Γ point, which originates from the energy difference between P-3p and Sn-5s states. In addition, we have also calculated absorption spectra in the solar energy range and compared it with that of bulk Si to explore the applicability of ZnSnP{sub 2} in photovoltaic and optoelectronic devices.

  11. Room temperature and low-temperature absorption and emission spectra of some polypyridylruthenium(II) 3.2.1 complexes

    NASA Astrophysics Data System (ADS)

    Silva, M. I.; Burrows, H. D.; Formosinho, S. J.; Miguel, M. da G.

    2001-05-01

    Electronic absorption and luminescence spectra are reported for a series of complexes of type [Ru(tpy)(L-L)(py)] 2+, where tpy and py are 2,2',2″-terpyridine and pyridine, and L-L represents the bidentate ligands bipyridyl, 4,4'-dimethylbipyridyl, 4-nitrobipyridyl, oxalate and acetylacetonate. The effect of solvent polarity and temperature on their spectral and light emission properties is studied. Energies are reported for the lowest-energy 3MLCT ∗ excited state, and on the basis of these it is suggested that the complexes may make good triplet energy acceptors for use in organic and polymeric light emitting devices.

  12. Impact of broadened laser line-shape on retrievals of atmospheric species from lidar sounding absorption spectra.

    PubMed

    Chen, Jeffrey R; Numata, Kenji; Wu, Stewart T

    2015-02-09

    We examine the impact of broadened laser line-shape on retrievals of atmospheric species from lidar-sounding absorption spectra. The laser is assumed to be deterministically modulated into a stable, nearly top-hat frequency comb to suppress the stimulated Brillouin scattering, allowing over 10-fold pulse energy increase without adding measurement noise. Our model remains accurate by incorporating the laser line-shape factor into the effective optical depth. Retrieval errors arising from measurement noise and model bias are analyzed parametrically and numerically to provide deeper insight. The stable laser line-shape broadening minimally degrades the column-averaged retrieval, but can significantly degrade the multiple-layer retrievals.

  13. Multiplet structures of the inner core absorption spectra of KMnF 3 and KCoF 3 measured by synchrotron radiation

    NASA Astrophysics Data System (ADS)

    Shin, S.; Suga, S.; Kanzaki, H.; Shibuya, S.; Yanaguchi, T.

    1981-06-01

    Absorption spectra resulting from the inner 3 p shell of the transition metal ion in KMnF 3 and KCoF 3 perovskites have been measured in the energy range from 35 to 80 eV by synchrotron radiation. On the basis of a ligand field theory, we have analyzed the multiplet structures of the inner core absorption spectra and quantitatively evaluated the final state interactions in these transition metal compounds.

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

    SciTech Connect

    Picconi, David; Grebenshchikov, Sergy Yu.

    2014-08-21

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

  15. Effects of crossed electric and magnetic fields on the interband optical absorption spectra of variably spaced semiconductor superlattices

    NASA Astrophysics Data System (ADS)

    Zuleta, J. N.; Reyes-Gómez, E.

    2016-05-01

    The interband optical absorption spectra of a GaAs-Ga1-xAlxAs variably spaced semiconductor superlattice under crossed in-plane magnetic and growth-direction applied electric fields are theoretically investigated. The electronic structure, transition strengths and interband absorption coefficients are analyzed within the weak and strong magnetic-field regimes. A dramatic quenching of the absorption coefficient is observed, in the weak magnetic-field regime, as the applied electric field is increased, in good agreement with previous experimental measurements performed in a similar system under growth-direction applied electric fields. A decrease of the resonant tunneling in the superlattice is also theoretically obtained in the strong magnetic-field regime. Moreover, in this case, we found an interband absorption coefficient weakly dependent on the applied electric field. Present theoretical results suggest that an in-plane magnetic field may be used to tune the optical properties of variably spaced semiconductor superlattices, with possible future applications in solar cells and magneto-optical devices.

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

    NASA Astrophysics Data System (ADS)

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

    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 Å 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 Å) 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 H = 1.38 ± 0.01 × 1021 cm-2 an ionization parameter of log ξ = -2.70 ± 0.023; an oxygen abundance of A_O= 0.689^{+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 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_O=0.952^{+0.020}_{-0.013}, a value close to solar that reinforces the new standard. We identify several atomic absorption lines—Kα, Kβ, and Kγ in O I and O II and Kα 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.

  17. 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.

  18. The SLUGGS survey: globular cluster stellar population trends from weak absorption lines in stacked spectra

    NASA Astrophysics Data System (ADS)

    Usher, Christopher; Forbes, Duncan A.; Brodie, Jean P.; Romanowsky, Aaron J.; Strader, Jay; Conroy, Charlie; Foster, Caroline; Pastorello, Nicola; Pota, Vincenzo; Arnold, Jacob A.

    2015-01-01

    As part of the SAGES Legacy Unifying Globulars and GalaxieS (SLUGGS) survey, we stack 1137 Keck DEIMOS (Deep Imaging Multi-Object Spectrograph) spectra of globular clusters from 10 galaxies to study their stellar populations in detail. The stacked spectra have median signal-to-noise ratios of ˜90 Å-1. Besides the calcium triplet, we study weaker sodium, magnesium, titanium and iron lines as well as the Hα and higher order Paschen hydrogen lines. In general, the stacked spectra are consistent with old ages and a Milky Way-like initial mass function. However, we see different metal line index strengths at fixed colour and magnitude, and differences in the calcium triplet-colour relation from galaxy to galaxy. We interpret this as strong evidence for variations in the globular cluster colour-metallicity relation between galaxies. Two possible explanations for the colour-metallicity relation variations are that the average ages of globular clusters vary from galaxy to galaxy or that the average abundances of light elements (i.e. He, C, N and O) differ between galaxies. Stacking spectra by magnitude, we see that the colours become redder and metal line indices stronger with brighter magnitudes. These trends are consistent with the previously reported `blue tilts' being mass-metallicity relations.

  19. Near-IR Absorption Spectra for the Buckminsterfullerene Anions: An Experimental and Theoretical Study

    DTIC Science & Technology

    1992-05-08

    0.15 mM) were prepared in benzonitrile which was O.1M in Bu4NPF 6 (supporting electrolyte) (13). Spectra for the various C6 0 species were obtained by...Hale, P. J. Am. Chem. Soc. 1986, 108, 6087. 13. Benzonitrile was doubly vacuum distilled over sodium; Bu4NPF 6 was triply recrystallized from ethanol

  20. A Simple Experiment Demonstrating the Relationship between Response Curves and Absorption Spectra.

    ERIC Educational Resources Information Center

    Li, Chia-yu

    1984-01-01

    Describes an experiment for recording two individual spectrophotometer response curves. The two curves are directly related to the power of transmitted beams that pass through a solvent and solution. An absorption spectrum of the solution can be constructed from the calculated rations of the curves as a function of wavelength. (JN)