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Sample records for absorption spectra demonstrate

  1. 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…

  2. 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.

  3. 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)

  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. Short-range demonstrations of monocular passive ranging using O2 (X3Σg- → b1Σg+) absorption spectra.

    PubMed

    Hawks, Michael R; Vincent, R Anthony; Martin, Jacob; Perram, Glen P

    2013-05-01

    The depth of absorption bands in observed spectra of distant, bright sources can be used to estimate range to the source. Experimental results are presented based on observations of the O2 X(v" = 0) → b(v' = 0) absorption band centered around 762 nm and the O2 X(v" = 0) → b(v' = 1) band around 689 nm. Range is estimated by comparing observed values of band-average absorption against predicted curves derived from either historical data or model predictions. Accuracy of better than 0.5% was verified in short-range (up to 3 km), static experiments using a high-resolution (1 cm(-1)) spectroradiometer. This method was also tested against the exhaust plume of a Falcon 9 rocket launched from Cape Canaveral, Florida. The rocket was launched from an initial range of 13 km and tracked for 90 s after ignition. Range error was below 2% for the first 30 s and consistent with predicted error throughout the track.

  6. 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.

  7. Terahertz absorption spectra of highly energetic chemicals

    NASA Astrophysics Data System (ADS)

    Slingerland, E. J.; Vallon, M. K.; Jahngen, E. G. E.; Giles, R. H.; Goyette, T. M.

    2010-04-01

    Research into absorption spectra is useful for detecting chemicals in the field. Each molecule absorbs a set of specific frequencies, which are dependent on the molecule's structure. While theoretical models are available for predicting the absorption frequencies of a particular molecule, experimental measurements are a more reliable method of determining a molecule's actual absorption behavior. The goal of this research is to explore chemical markers (absorption frequencies) that can be used to identify highly energetic molecules of interest to the remote sensing community. Particular attention was paid to the frequency ranges located within the terahertz transmission windows of the atmosphere. In addition, theoretical derivations, with the purpose of calculating the detection limits of such chemicals, will also be presented.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Computed survey spectra of 2-5 micron atmospheric absorption

    NASA Astrophysics Data System (ADS)

    Leslie, D. H.; Lebow, P. S.

    1983-08-01

    Computed high resolution survey spectra of atmospheric absorption coefficient vs wavenumber are presented covering the wavelength region 2-5 micrometers. The 1980 AFGL atmospheric absorption parameter compilation was employed with a mid-latitude, sea-level atmospheric model.

  15. Anomalous atmospheric absorption spectra due to water dimer

    NASA Astrophysics Data System (ADS)

    Cai, Peipei; Zhang, Hansheng; Shen, Shanxiong; Cheng, I.-Shan

    1986-11-01

    The anomalous atmospheric absorption spectra in the window wavelength region of 8-14 microns have been suggested due to the water dimer. Based on laboratory measurements, water continuum CO2 laser absorption spectra and a resonance absorption line due to the weak local wave vapor pure rotational transition have been reported. The equilibrium concentration of water dimers in the atmosphere, the electronic binding energy and the theoretical calculations for absorption attenuation have been obtained in agreement with published data.

  16. 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.

  17. Taped Random Spectra for Reliability Demonstration Testing

    DTIC Science & Technology

    1981-04-01

    undertaken to develop an economical test technique for Reliability Demonstration tests in accord- ance with MIL- STD -78 IC. This has been accomplished...Demonstrotion tests in accordance with MIL-- STD -781C. In order td accomplish the above, two different methods were evaluated: * Multiplex System...user with the necessary information to perform Reliability Demonstration Tests in accordance with MIL- STD -781C. Appendix A describes the Multiplex

  18. 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

  19. Absorption-Edge-Modulated Transmission Spectra for Water Contaminant Monitoring

    DTIC Science & Technology

    2016-03-31

    Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6390--16-9675 Absorption-Edge-Modulated Transmission Spectra for Water Contaminant...ABSTRACT c. THIS PAGE 18. NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Absorption-Edge-Modulated Transmission Spectra for Water Contaminant Monitoring...Unlimited Unclassified Unlimited 35 Samuel G. Lambrakos (202) 767-2601 Monitoring of contaminants associated with specific water resources using

  20. 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.

  1. 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.

  2. Mid-infrared FEL absorption spectra

    NASA Astrophysics Data System (ADS)

    Kozub, John A.; Feng, Bibo; Gabella, William E.

    2002-04-01

    The Vanderbilt Mark III FEL is a tunable source of high- intensity coherent mid-infrared radiation occurring as a train of picosecond pulses spaced 350ps apart. The laser beam is transported to each laboratory under vacuum, but is typically transmitted through some distance of atmosphere before reaching the target. Losses due to absorption by water vapor and CO2 can be large, and since the bandwidth of the FEL is several percent of the wavelength, the spectrum can be altered by atmospheric absorptions. In order to provide an accurate representation of the laser spectrum delivered to the target, and to investigate any non-linear effects associated with transport of the FEL beam, we have recorded the spectrum of the FEL output using a vacuum spectrometer positioned after measured lengths of atmosphere. The spectrometer is equipped with a linear pyroelectric array which provides the laser spectrum for each pulse. Absorption coefficients are being measured for laboratory air, averaged over the bandwidth of the FEL. The high peak powers of this Fel have induced damage in common infrared-transparent materials; we are also measuring damage thresholds for several materials at various wavelengths.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. [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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Scalar and vector collisional interference in the vibration-rotation absorption spectra of H2 and HD

    NASA Technical Reports Server (NTRS)

    Herman, R. M.

    1987-01-01

    The only atomic or molecular spectra known to exhibit 'collisional interference' effects are those of H2 and its isotopes. Attention is presently given to the sharp absorption spectra of HD, which demonstrate collisional interference effects is a fashion that while surprising has been experimentally verified and theoretically characterized in detail. Collisional interference can dramatically alter the line shapes usually encountered in dipole absorption spectra, while nevertheless remaining narrow.

  16. 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.

  17. 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.

  18. Demonstrations of Optical Spectra with a Video Camera

    ERIC Educational Resources Information Center

    Kraftmakher, Yaakov

    2012-01-01

    The use of a video camera may markedly improve demonstrations of optical spectra. First, the output electrical signal from the camera, which provides full information about a picture to be transmitted, can be used for observing the radiant power spectrum on the screen of a common oscilloscope. Second, increasing the magnification by the camera…

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

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

    NASA Technical Reports Server (NTRS)

    Roesler, Collin S.; Pery, Mary Jane

    1995-01-01

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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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).

  16. 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.

  17. 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.

  18. 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.

  19. 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

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  2. 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.

  3. 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.

  4. A mixed quantum-classical description of pheophorbide a linear absorption spectra: Quantum-corrections of the Qy- and Qx-absorption vibrational satellites

    NASA Astrophysics Data System (ADS)

    Megow, Jörg; Kulesza, Alexander; May, Volkhard

    2016-01-01

    The ground-state classical path approximation is utilized to compute molecular absorption spectra in a mixed quantum-classical frame. To improve the description for high-frequency vibrational satellites, related quantum correction factors are introduced. The improved method is demonstrated for the Qy- and Qx-bands of pheophorbide a.

  5. [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.

  6. [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.

  7. 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.

  8. 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.

  9. 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.

  10. Gas suspension absorption demonstrated for flue gas desulfurization

    SciTech Connect

    1994-03-01

    The first U.S. demonstration of gas suspension absorption (GSA), a flue gas desulfurization (FGD) technology developed in Europe, has been conducted at the Tennessee Valley Authority`s National Center for Emissions Research (NCER) in Paducah, Kentucky. The technology was developed by the Danish company FLS miljo a/s. GSA is an attractive FGD candidate technology because, unlike conventional wet scrubbing, GSA requires no chemical analyses as part of its routine operation and maintenance. The 10-MW GSA demonstration plant was constructed by AirPol, Inc. (Teterboro, New Jersey), a U.S. subsidiary of FLS miljo a/s. The project was partially funded by the U.S. Department of Energy (DOE) through its clean coal technology program. GSA technology and results of the demonstration project are discussed in this paper in brief. The factorial tests conducted on the GSA demonstration plant at NCER showed that, using a modest Ca/S ratio, the system can achieve high SO{sub 2} removal efficiencies, low particulate emissions, and a low-moisture solid waste by-product. 1 ref., 3 figs., 1 tab.

  11. 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

  12. 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

  13. 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.

  14. 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.

  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. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  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. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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).

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. 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)

  16. 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.

  17. 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.

  18. 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.

  19. [Study on the effect of solar spectra on the retrieval of atmospheric CO2 concentration using high resolution absorption spectra].

    PubMed

    Hu, Zhen-Hua; Huang, Teng; Wang, Ying-Ping; Ding, Lei; Zheng, Hai-Yang; Fang, Li

    2011-06-01

    Taking solar source as radiation in the near-infrared high-resolution absorption spectrum is widely used in remote sensing of atmospheric parameters. The present paper will take retrieval of the concentration of CO2 for example, and study the effect of solar spectra resolution. Retrieving concentrations of CO2 by using high resolution absorption spectra, a method which uses the program provided by AER to calculate the solar spectra at the top of atmosphere as radiation and combine with the HRATS (high resolution atmospheric transmission simulation) to simulate retrieving concentration of CO2. Numerical simulation shows that the accuracy of solar spectrum is important to retrieval, especially in the hyper-resolution spectral retrieavl, and the error of retrieval concentration has poor linear relation with the resolution of observation, but there is a tendency that the decrease in the resolution requires low resolution of solar spectrum. In order to retrieve the concentration of CO2 of atmosphere, the authors' should take full advantage of high-resolution solar spectrum at the top of atmosphere.

  20. Search for CO absorption bands in IUE far-ultraviolet spectra of cool stars

    NASA Technical Reports Server (NTRS)

    Gessner, Susan E.; Carpenter, Kenneth G.; Robinson, Richard D.

    1994-01-01

    Observations of the red supergiant (M2 Iab) alpha Ori with the Goddard High Resolution Spectrograph (GHRS) on board the Hubble Space Telescope (HST) have provided an unambiguous detection of a far-ultraviolet (far-UV) chromospheric continuum on which are superposed strong molecular absorption bands. The absorption bands have been identified by Carpenter et al. (1994) with the fourth-positive A-X system of CO and are likely formed in the circumstellar shell. Comparison of these GHRS data with archival International Ultraviolet Explorer (IUE) spectra of alpha Ori indicates that both the continuum and the CO absorption features can be seen with IUE, especially if multiple IUE spectra, reduced with the post-1981 IUESIPS extraction procedure (i.e., with an oversampling slit), are carefully coadded to increase the signal to noise over that obtainable with a single spectrum. We therefore initiated a program, utilizing both new and archival IUE Short Wavelength Prime (SWP) spectra, to survey 15 cool, low-gravity stars, including alpha Ori, for the presence of these two new chromospheric and circumstellar shell diagnostics. We establish positive detections of far-UV stellar continua, well above estimated IUE in-order scattered light levels, in spectra of all of the program stars. However, well-defined CO absorption features are seen only in the alpha Ori spectra, even though spectra of most of the program stars have sufficient signal to noise to allow the dectection of features of comparable magnitude to the absorptions seen in alpha Ori. Clearly if CO is present in the circumstellar environments of any of these stars, it is at much lower column densities.

  1. 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).

  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. 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.

  4. 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.

  5. 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.

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

    ERIC Educational Resources Information Center

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

    2004-01-01

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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Computer Simulation of the far Infrared Collision Induced Absorption Spectra of Gaseous CO2

    NASA Technical Reports Server (NTRS)

    Gruszka, Marcin; Borysow, Aleksandra

    1998-01-01

    Far infrared collision induced absorption spectra of gaseous CO2 were computed using molecular dynamics simulations. The quadrupole and hexadecapole multipolar induction, through the trace, and the anisotropy of the molecular polarizability were found to be insufficient to represent properly the dipole induction mechanism. For a detailed analysis of the induction process the spectra obtained were decomposed into components resulting from different terms of the induced dipole. Based on this decomposition, all additional overlap contribution for each term was proposed. When spectra were recomputed including such overlap, good agreement between experiment and simulation was achieved over the temperature range at which measurements exist (233-400 K). The use of an anisotropic intermolecular potential was found to be of critical importance for obtaining the right shape of the far wings of the spectra.

  16. On the origin of a very close similarity between the spectra of the supernova type 1 in NGC 3198 and the absorption of DQ HeR

    NASA Technical Reports Server (NTRS)

    Mustel, E. R.

    1979-01-01

    The type 1 supernova discovered late in 1966 in NGC 3198 has broad minima in its spectrum break down into a number of significantly narrower absorption bands. The broad minima of tau, sigma and mu, which usually show no details in the spectra of type supernovas, contain a number of narrow absorption bands. The reality of most of these absorption bands is demonstrated by comparison of recordings of spectra of the supernova presented for two moments in time. These minima (particularly of tau and mu,) are a result of blending of several broad absorption bands. The minimum of tau should be a blend of intensive and very broad Fe absorption lines, in which the lower level is metastable. The wavelengths of these line are: 5169, 5198, 5235, 5276, 5317, 5363A.

  17. 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*.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  3. 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.

  4. Identification of acetylene (C2H2) in infrared atmospheric absorption spectra

    NASA Astrophysics Data System (ADS)

    Goldman, A.; Murcray, F. J.; Blatherwick, R. D.; Gillis, J. R.; Bonomo, F. S.; Murcray, F. H.; Murcray, D. G.; Cicerone, R. J.

    1981-12-01

    Infrared atmospheric absorption spectra at ˜0.02 cm-1 resolution obtained during a balloon flight made on March 23, 1981, show absorption features attributable to C2H2. These features are used to derive a preliminary mixing ratio of ˜25 pptv near 9 km. This mixing ratio falls into the range of values we calculate for upper tropospheric C2H2 in a photochemical/transport model but well below values measured previously in samples collected by other researchers.

  5. Identification of acetylene /C2H2/ in infrared atmospheric absorption spectra

    NASA Technical Reports Server (NTRS)

    Goldman, A.; Murcray, F. J.; Blatherwick, R. D.; Gillis, J. R.; Bonomo, F. S.; Murcray, F. H.; Murcray, D. G.; Cicerone, R. J.

    1981-01-01

    Infrared atmospheric absorption spectra at 0.02/cm resolution were obtained during a balloon flight on March 23, 1981 from the Holloman AFB, New Mexico. The absorption features, attributed to C2H2, were used to derive a preliminary mixing ratio of about 25 pptv near 9 km, accurate to + or - 40%. This mixing ratio falls into the range of values calculated for the upper troposphere C2H2 in a photochemical/transport model. However, previous measurements from aircraft grab sampling (Cronn and Robinson, 1979) show four to twelve times this C2H2 concentration 1.5 km below the tropopause.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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...5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Instituto de Fisica de Sao Carlos - Universidade de Sao Paulo Av...Trabalhador Saocarlense 400 Sao Carlos, SP, 13566-590 Brazil 8. PERFORMING ORGANIZATION REPORT NUMBER Report 3 - Final 9. SPONSORING/MONITORING AGENCY

  13. 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.

  14. 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

  15. 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.

  16. 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%.

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

    PubMed

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

    2011-11-03

    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.

  18. 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.

  19. 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

  20. 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.

  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. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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).

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  18. 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.

  19. Simulations of X-ray absorption spectra: the effect of the solvent.

    PubMed

    Penfold, Thomas J; Curchod, Basile F E; Tavernelli, Ivano; Abela, Rafael; Rothlisberger, Ursula; Chergui, Majed

    2012-07-14

    We perform quantum mechanics/molecular mechanics molecular dynamics simulations on the [Pt(2)(P(2)O(5)H(2))(4)](4-) (abbreviated PtPOP) complex; in water, dimethylformamide and ethanol. These are used to calculate the ground state X-ray absorption spectrum of the complex. The structural parameters from X-ray spectra are usually extracted using a fit of the experimental data. In such simulations the solvent is neglected meaning that any effect of the local environment will be compensated for by structural changes of the solute, leading to possible discrepancies in the extracted structural parameters. Our simulations show a significant solvent effect on the spectra, which has important implications for the structural analysis of molecules in solution.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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}.

  13. 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.

  14. 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.

  15. 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.

  16. 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}

  17. 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.

  18. 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.

  19. 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.

  20. Long-Range Chemical Sensitivity in the Sulfur K-Edge X-ray Absorption Spectra of Substituted Thiophenes

    PubMed Central

    2015-01-01

    Thiophenes are the simplest aromatic sulfur-containing compounds and are stable and widespread in fossil fuels. Regulation of sulfur levels in fuels and emissions has become and continues to be ever more stringent as part of governments’ efforts to address negative environmental impacts of sulfur dioxide. In turn, more effective removal methods are continually being sought. In a chemical sense, thiophenes are somewhat obdurate and hence their removal from fossil fuels poses problems for the industrial chemist. Sulfur K-edge X-ray absorption spectroscopy provides key information on thiophenic components in fuels. Here we present a systematic study of the spectroscopic sensitivity to chemical modifications of the thiophene system. We conclude that while the utility of sulfur K-edge X-ray absorption spectra in understanding the chemical composition of sulfur-containing fossil fuels has already been demonstrated, care must be exercised in interpreting these spectra because the assumption of an invariant spectrum for thiophenic forms may not always be valid. PMID:25116792

  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. Experimental demonstration of coherent perfect absorption in a silicon photonic racetrack resonator.

    PubMed

    Rothenberg, Jacob M; Chen, Christine P; Ackert, Jason J; Dadap, Jerry I; Knights, Andrew P; Bergman, Keren; Osgood, Richard M; Grote, Richard R

    2016-06-01

    We present the first experimental demonstration of coherent perfect absorption (CPA) in an integrated device using a silicon racetrack resonator at telecommunication wavelengths. Absorption in the racetrack is achieved by Si+-ion-implantation, allowing for phase controllable amplitude modulation at the resonant wavelength. The device is measured to have an extinction of 24.5 dB and a quality-factor exceeding 3000. Our results will enable integrated CPA devices for data modulation and detection.

  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. 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.

  5. Removal of Mars atmospheric gas absorption from Phobos-2/ISM spectra

    NASA Astrophysics Data System (ADS)

    Castronuovo, M. M.; Ulivieri, C.

    Infrared imaging spectrometer (ISM) is an imaging spectrometer in the range of the near infrared that flew onboard of Soviet probe Phobos 2 in 1989. Its first objective was to obtain information about the mineralogic composition of the soil of Mars and its satellite Phobos, and about the spatial and temporal variability of the Martian atmosphere. In the spectral range of the instrument 0.76-3.16 microns, the radiation emerging from Mars' atmosphere is almost entirely due to the solar radiation reflected by the soil. Therefore, independent knowledge of the spectral transmittance of the atmosphere allows us to eliminate the atmospheric effect from the ISM data and so to obtain the spectral signature of the planet soil. In the present work the Martian atmospheric transmittance has been computed using FASCODE and the spectral lines atlas HITRAN of AFGL. The atmospheric profile has been defined on the basis of the work of Moroz et al. Then, the convolution of the computed transmittance with the response functions of ISM has been carried out to obtain the atmospheric absorption from the measurements it is necessary to renormalize the transmittance computed with FASCODE so that the depth of the absorption bands is the same as that of the bands measured by ISM. Finally, dividing the measured spectra by the computed ones we obtain the spectra signature of Martian soil from which it is possible to deduce the mineralogical composition of the observed zones.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. [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.

  12. 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.

  13. 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.

  14. Franck-Condon factors perturbed by damped harmonic oscillators: Solvent enhanced X 1Ag ↔ A1B1u absorption and fluorescence spectra of perylene

    NASA Astrophysics Data System (ADS)

    Wang, Chen-Wen; Yang, Ling; Zhu, Chaoyuan; Yu, Jian-Guo; Lin, Sheng-Hsien

    2014-08-01

    Damped harmonic oscillators are utilized to calculate Franck-Condon factors within displaced harmonic oscillator approximation. This is practically done by scaling unperturbed Hessian matrix that represents local modes of force constants for molecule in gaseous phase, and then by diagonalizing perturbed Hessian matrix it results in direct modification of Huang-Rhys factors which represent normal modes of solute molecule perturbed by solvent environment. Scaling parameters are empirically introduced for simulating absorption and fluorescence spectra of an isolated solute molecule in solution. The present method is especially useful for simulating vibronic spectra of polycyclic aromatic hydrocarbon molecules in which hydrogen atom vibrations in solution can be scaled equally, namely the same scaling factor being applied to all hydrogen atoms in polycyclic aromatic hydrocarbons. The present method is demonstrated in simulating solvent enhanced X 1Ag ↔ A1B1u absorption and fluorescence spectra of perylene (medium-sized polycyclic aromatic hydrocarbon) in benzene solution. It is found that one of six active normal modes v10 is actually responsible to the solvent enhancement of spectra observed in experiment. Simulations from all functionals (TD) B3LYP, (TD) B3LYP35, (TD) B3LYP50, and (TD) B3LYP100 draw the same conclusion. Hence, the present method is able to adequately reproduce experimental absorption and fluorescence spectra in both gas and solution phases.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. Comparison of absorption spectra of adenocarcinoma and squamous cell carcinoma cervical tissue

    NASA Astrophysics Data System (ADS)

    Peresunko, O. P.; Zelinska, N. V.; Prydij, O. G.; Zymnyakov, D. A.; Ushakova, O. V.

    2013-12-01

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

  20. The "Chocolate Experiment"--A Demonstration of Radiation Absorption by Different Colored Surfaces

    ERIC Educational Resources Information Center

    Fung, Dennis

    2015-01-01

    In the typical "cookbook" experiment comparing the radiation absorption rates of different colored surfaces, students' hands are commonly used as a measurement instrument to demonstrate that dull black and silvery surfaces are good and poor absorbers of radiation, respectively. However, college students are often skeptical about using…

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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).

  10. 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.

  11. 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.

  12. 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+.

  13. 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.

  14. 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.

  15. 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.

  16. Performance Enhancement of Polymer Solar Cells by Using Two Polymer Donors with Complementary Absorption Spectra.

    PubMed

    Lu, Heng; Zhang, Xuejuan; Li, Cuihong; Wei, Hedi; Liu, Qian; Li, Weiwei; Bo, Zhishan

    2015-07-01

    Performance enhancement of polymer solar cells (PSCs) is achieved by expanding the absorption of the active layer of devices. To better match the spectrum of solar radiation, two polymers with different band gaps are used as the donor material to fabricate ternary polymer cells. Ternary blend PSCs exhibit an enhanced short-circuit current density and open-circuit voltage in comparison with the corresponding HD-PDFC-DTBT (HD)- and DT-PDPPTPT (DPP)-based binary polymer solar cells, respectively. Ternary PSCs show a power conversion efficiency (PCE) of 6.71%, surpassing the corresponding binary PSCs. This work demonstrates that the fabrication of ternary PSCs by using two polymers with complementary absorption is an effective way to improve the device performance.

  17. [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.

  18. 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.

  19. 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.

  20. Field demonstration of the combined effects of absorption and evapotranspiration on septic system drainfield capacity.

    PubMed

    Rainwater, Ken; Jackson, Andrew; Ingram, Wesley; Lee, Chang Yong; Thompson, David; Mollhagen, Tony; Ramsey, Heyward; Urban, Lloyd

    2005-01-01

    Drainfields for disposal of septic tank effluents are typically designed by considering the loss of water by either upward evapotranspiration into the atmosphere or lateral and downward absorption into the adjacent soil. While this approach is appropriate for evapotranspiration systems, absorption systems allow water loss by both mechanisms. It was proposed that, in areas where high evapotranspiration rates coincide with permeable soils, drainfield sizes could be substantially reduced by accounting for both mechanisms. A two-year field demonstration was conducted to determine appropriate design criteria for areas typical of the Texas High Plains. The study consisted of evaluating the long-term acceptance rates for three different drainfield configurations: evapotranspiration only, absorption only, and combined conditions. A second field demonstration repeated the experiments for additional observation of the combined evapotranspiration and absorption and achieved similar results as the first study. The field tests indicated that the current design loading criteria may be increased by at least a factor of two for the Texas High Plains region and other Texas areas with similar soil composition and evapotranspiration rates, while still retaining a factor of safety of two.

  1. 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.

  2. 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.

  3. The Clean Coal Technology Program 100 MWe demonstration of gas suspension absorption for flue gas desulfurization

    SciTech Connect

    Hsu, F.E.; Hedenhag, J.G.; Marchant, S.K.; Pukanic, G.W.; Norwood, V.M.; Burnett, T.A.

    1997-12-31

    AirPol Inc., with the cooperation of the Tennessee Valley Authority (TVA) under a Cooperative Agreement with the United States Department of Energy, installed and tested a 10 MWe Gas Suspension Absorption (GSA) Demonstration system at TVA`s Shawnee Fossil Plant near Paducah, Kentucky. This low-cost retrofit project demonstrated that the GSA system can remove more than 90% of the sulfur dioxide from high-sulfur coal-fired flue gas, while achieving a relatively high utilization of reagent lime. This paper presents a detailed technical description of the Clean Coal Technology demonstration project. Test results and data analysis from the preliminary testing, factorial tests, air toxics texts, 28-day continuous demonstration run of GSA/electrostatic precipitator (ESP), and 14-day continuous demonstration run of GSA/pulse jet baghouse (PJBH) are also discussed within this paper.

  4. 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.

  5. Analysis of atmospheric trace constituents from high resolution infrared balloon-borne and ground-based solar absorption spectra

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Results of ongoing studies of high-resolution solar absorption spectra aimed at the identification and quantification of trace constituents of importance in the chemistry of the stratosphere and upper troposphere are presented. An analysis of balloon-borne and ground-based spectra obtained at 0.0025/cm covering the 700-2200/cm interval is presented. The 0.0025/cm spectra, along with corresponding laboratory spectra, improves the spectral line parameters, and thus the accuracy of quantifying trace constituents. Results for COF2, F22, SF6, and other species are presented. The retrieval methods used for total column density and altitude distribution for both ground-based and balloon-borne spectra are also discussed.

  6. 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.

  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. 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

  9. 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.

  10. Modeling of IR absorption spectra of the mixture CO2-He at moderate and high pressures

    NASA Astrophysics Data System (ADS)

    Golovko, Vladimir F.

    2004-02-01

    The He-broadened spectra of carbon dioxide are calculated within the pressure range 2-800 atm in the absorption regions of the bands v2, v3, and 3v3 that are positioned from 590 to 7020 cm-1. The main difficulty is consideration of the line shape narrowing at relatively high pressures. For Q-branches, this effect is observed at atmospheric conditions and, therefore, it is important for remote sounding of the gas atmosphere. The mixtures of the mentioned gases are well studied in experiments and it can serve as a good test for validating the simulating techniques developing. The line by line method is used with modeling of the single line shape without the conventional interference of lines. The problem is focused on the order and disorder in arrangement of the rotational lines with P-, R-, and Q-branches of vibrational bands. A database CDSD-1000 in the HITRAN format is reformatted with adding supplement four parameters for every entry. The physical meaning of the phenomena known as the line and branch mixing is discussed.

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. Detection of nanoscale electron spin resonance spectra demonstrated using nitrogen-vacancy centre probes in diamond

    PubMed Central

    Hall, L. T.; Kehayias, P.; Simpson, D. A.; Jarmola, A.; Stacey, A.; Budker, D.; Hollenberg, L. C. L.

    2016-01-01

    Electron spin resonance (ESR) describes a suite of techniques for characterizing electronic systems with applications in physics, chemistry, and biology. However, the requirement for large electron spin ensembles in conventional ESR techniques limits their spatial resolution. Here we present a method for measuring ESR spectra of nanoscale electronic environments by measuring the longitudinal relaxation time of a single-spin probe as it is systematically tuned into resonance with the target electronic system. As a proof of concept, we extracted the spectral distribution for the P1 electronic spin bath in diamond by using an ensemble of nitrogen-vacancy centres, and demonstrated excellent agreement with theoretical expectations. As the response of each nitrogen-vacancy spin in this experiment is dominated by a single P1 spin at a mean distance of 2.7 nm, the application of this technique to the single nitrogen-vacancy case will enable nanoscale ESR spectroscopy of atomic and molecular spin systems. PMID:26728001

  17. Simulating One-Photon Absorption and Resonance Raman Scattering Spectra Using Analytical Excited State Energy Gradients within Time-Dependent Density Functional Theory

    SciTech Connect

    Silverstein, Daniel W.; Govind, Niranjan; van Dam, Hubertus J. J.; Jensen, Lasse

    2013-12-10

    A parallel implementation of analytical time-dependent density functional theory gradients is presented for the quantum chemistry program NWChem. The implementation is based on the Lagrangian approach developed by Furche and Ahlrichs. To validate our implementation, we first calculate the Stokes shifts for a range of organic dye molecules using a diverse set of exchange-correlation functionals (traditional density functionals, global hybrids, and range-separated hybrids) followed by simulations of the one-photon absorption and resonance Raman scattering spectrum of the phenoxyl radical, the well-studied dye molecule rhodamine 6G, and a molecular host–guest complex (TTFcCBPQT4+). The study of organic dye molecules illustrates that B3LYP and CAM-B3LYP generally give the best agreement with experimentally determined Stokes shifts unless the excited state is a charge transfer state. Absorption, resonance Raman, and fluorescence simulations for the phenoxyl radical indicate that explicit solvation may be required for accurate characterization. For the host–guest complex and rhodamine 6G, it is demonstrated that absorption spectra can be simulated in good agreement with experimental data for most exchange-correlation functionals. Finally, however, because one-photon absorption spectra generally lack well-resolved vibrational features, resonance Raman simulations are necessary to evaluate the accuracy of the exchange-correlation functional for describing a potential energy surface.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Clean coal technology III 10 MW demonstration of gas suspension absorption. Final public design report

    SciTech Connect

    1995-06-01

    This report provides the nonproprietary design information for the ``10 MW Demonstration of Gas Suspension Absorption (GSA)`` Demonstration Project at Tennessee Valley Authority`s (TVA) Shawnee Power Station, Center for Emission Research (CER). The 10 MW Demonstration of GSA program is designed to demonstrate the performance of the GSA system in treating the flue gas from a boiler burning high sulfur coal. This project involves design, manufacturing, construction and testing of a retrofitted GSA system. This report presents a nonproprietary description of the technology and overall process performance requirements, plant location and plant facilities. The process, mechanical, structural and electrical design of the GSA system as well as project cost information are included. It also includes a description the modification or alterations made during the course of construction and start-up. Plant start-up provisions, environmental considerations and control, monitoring and safety considerations are also addressed for the process. This report, initially drafted in 1993, covers design information available prior to startup of the demonstration project. It does not reflect the results obtained in that project, which is now complete.

  10. 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.

  11. 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).

  12. 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.

  13. 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

  14. Presence of monovalent oxygen anions in oxides demonstrated using X-ray photoelectron spectra

    SciTech Connect

    Wu, L. Q.; Li, Z. Z.; Tang, G. D. Qi, W. H.; Xue, L. C.; Ding, L. L.; Ge, X. S.; Li, S. Q.; Li, Y. C.

    2016-01-11

    The oxygen vacancy model has been used to explain the magnetic and electrical transport properties of dilute magnetic semiconductors and resistive switching. In particular, some authors have claimed that they found a symmetric peak corresponding to the oxygen vacancies in O1s photoelectron spectra. In this paper, using X-ray photoelectron spectra with argon ion etching, it is shown that this symmetric peak may also be interpreted as being related to O{sup 1−} anions, rather than to oxygen vacancies.

  15. 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.

  16. 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.

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

    DTIC Science & Technology

    2016-06-03

    of Arsenic- Water Complexes Using Density Functional Theory June 3, 2016 Approved for public release; distribution is unlimited. L. Huang S.g...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Calculation of Vibrational and Electronic Excited-State Absorption Spectra of Arsenic- Water Complexes Using... water molecules should be associated with response features that are intermediate between that of isolated molecules and that of a bulk system. DFT and

  20. 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.

  1. 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.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. The `Chocolate Experiment' - A Demonstration of Radiation Absorption by Different Colored Surfaces

    NASA Astrophysics Data System (ADS)

    Fung, Dennis

    2015-12-01

    In the typical "cookbook" experiment comparing the radiation absorption rates of different colored surfaces, students' hands are commonly used as a measurement instrument to demonstrate that dull black and silvery surfaces are good and poor absorbers of radiation, respectively. However, college students are often skeptical about using their bare hands in this experiment because they learned in early science lessons that skin is not a reliable detector of heat transfer. Moreover, when the experiment is conducted in a school laboratory, it is often difficult for students to perceive the slight differences in heat transfer on the dull black and silvery aluminum leaves attached to their hands. Rather than replacing students' bare hands with such sophisticated apparatus as a data logger and temperature probe, I suggest using a simple (and delicious!) low-cost instrument, i.e., chocolate, which simply melts when it receives radiation.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. [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.

  15. 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).

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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}.

  1. [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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Predicting the Shifts of Absorption Maxima of Azulene Derivatives Using Molecular Modeling and ZINDO CI Calculations of UV-Vis Spectra

    ERIC Educational Resources Information Center

    Patalinghug, Wyona C.; Chang, Maharlika; Solis, Joanne

    2007-01-01

    The deep blue color of azulene is drastically changed by the addition of substituents such as CH[subscript 3], F, or CHO. Computational semiempirical methods using ZINDO CI are used to model azulene and azulene derivatives and to calculate their UV-vis spectra. The calculated spectra are used to show the trends in absorption band shifts upon…

  8. Two-photon absorption spectra of a near-infrared 2-azaazulene polymethine dye: solvation and ground-state symmetry breaking.

    PubMed

    Hu, Honghua; Przhonska, Olga V; Terenziani, Francesca; Painelli, Anna; Fishman, Dmitry; Ensley, Trenton R; Reichert, Matthew; Webster, Scott; Bricks, Julia L; Kachkovski, Alexey D; Hagan, David J; Van Stryland, Eric W

    2013-05-28

    Polymethine dyes (PDs) with absorption bands in the near-infrared region undergo symmetry breaking in polar solvents. To investigate how symmetry breaking affects nonlinear optical responses of PDs, an extensive and challenging experimental characterization of a cationic 2-azaazulene polymethine dye, including linear absorption, fluorescence, two-photon absorption and excited-state absorption, has been performed in two solvents with different polarity. Based on this extensive set of experimental data, a three-electronic-state model, accounting for the coupling of electronic degrees of freedom to molecular vibrations and polar solvation, has been reliably parameterized and validated for this dye, fully rationalizing optical spectra in terms of spectral position, intensities and bandshapes. In low-polarity solvents where the dye is mainly in its symmetric form, a nominally forbidden two-photon absorption band is observed, due to a vibronic activation mechanism. Inhomogeneous broadening plays a major role in polar solvents: absorption spectra represent the weighted sum of contributions from states with a variable amount of symmetry breaking, leading to a complex evolution of linear and nonlinear optical spectra with solvent polarity. In more polar solvents, the dominant role of the asymmetric form leads to the activation of two-photon absorption as a result of the symmetry lowering. The subtle interplay between the two mechanisms for two-photon absorption activation, vibronic coupling and polar solvation, can be fully accounted for within the proposed microscopic model allowing a detailed interpretation of the optical spectra of PDs.

  9. Electronic Absorption Spectra from MM and ab initio QM/MM Molecular Dynamics: Environmental Effects on the Absorption Spectrum of Photoactive Yellow Protein

    PubMed Central

    Isborn, Christine M.; Götz, Andreas W.; Clark, Matthew A.; Walker, Ross C.; Martínez, Todd J.

    2012-01-01

    We describe a new interface of the GPU parallelized TeraChem electronic structure package and the Amber molecular dynamics package for quantum mechanical (QM) and mixed QM and molecular mechanical (MM) molecular dynamics simulations. This QM/MM interface is used for computation of the absorption spectra of the photoactive yellow protein (PYP) chromophore in vacuum, aqueous solution, and protein environments. The computed excitation energies of PYP require a very large QM region (hundreds of atoms) covalently bonded to the chromophore in order to achieve agreement with calculations that treat the entire protein quantum mechanically. We also show that 40 or more surrounding water molecules must be included in the QM region in order to obtain converged excitation energies of the solvated PYP chromophore. These results indicate that large QM regions (with hundreds of atoms) are a necessity in QM/MM calculations. PMID:23476156

  10. 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.

  11. Simultaneous infrared and UV-visible absorption spectra of matrix-isolated carbon vapor

    NASA Technical Reports Server (NTRS)

    Kurtz, Joe; Huffman, Donald R.

    1989-01-01

    Carbon molecules were suggested as possible carriers of the diffuse interstellar bands. In particular, it was proposed that the 443 nm diffuse interstellar band is due to the same molecule which gives rise to the 447 nm absorption feature in argon matrix-isolated carbon vapor. If so, then an associated C-C stretching mode should be seen in the IR. By doing spectroscopy in both the IR and UV-visible regions on the same sample, the present work provides evidence for correlating UV-visible absorption features with those found in the IR. Early data indicates no correlation between the strongest IR feature (1997/cm) and the 447 nm band. Correlation with weaker IR features is being investigated.

  12. Study of absorption spectra of gasolines and other hydrocarbon mixtures in the second overtone region of the CH3, CH2, CH groups

    NASA Astrophysics Data System (ADS)

    Muradov, V. G.; Sannikov, D. G.

    2007-03-01

    We have obtained experimental and model absorption spectra for individual hydrocarbons (toluene, benzene, n-heptane, and iso-octane) and their mixtures in the near IR range (λ = 1080 1220 nm). We model the spectra of nonsynthetic gasolines obtained under the same conditions by combining the spectra of three pure hydrocarbons. We show that the octane number of the studied gasoline is linearly related to the toluene (or benzene) concentrations in the model mixture.

  13. Absorption spectra of Fe I in the 1550-3215-A region

    NASA Technical Reports Server (NTRS)

    Brown, C. M.; Ginter, M. L.; Johansson, S.; Tilford, S. G.

    1988-01-01

    The high-dispersion absorption spectrum of Fe I is reported in the 1550-3215-A region. Included are wavelengths of about 3000 observed spectral features, improved spectral assignments, 248 new energy levels, and a value for the ionization potential of 63 737/cm obtained from extrapolation of Rydberg series. Improved wavelengths for several hundred V I and Ti I spectral lines determined on the same spectrograms as the iron data also are presented.

  14. TD-DFT Study of Absorption and Emission Spectra of 2-(2'-Aminophenyl)benzothiazole Derivatives in Water.

    PubMed

    Manojai, Natthaporn; Daengngern, Rathawat; Kerdpol, Khanittha; Kungwan, Nawee; Ngaojampa, Chanisorn

    2017-03-01

    Reduction of aromatic azides to amines is an important property of hydrogen sulphide (H2S) which is useful in fluorescence microscopy and H2S probing in cells. The aim of this work is to study the substituent effect on the absorption and emission spectra of 2-(2'-aminophenyl)benzothiazole (APBT) in order to design APBT derivatives for the use of H2S detection. Absorption and emission spectra of APBT derivatives in aqueous environment were calculated using density functional theory (DFT) and time-dependent DFT (TD-DFT) at B3LYP/6-311+G(d,p) level. The computed results favoured the substitution of strong electron-donating group on the phenyl ring opposite to the amino group for their large Stokes' shifts and emission wavelengths of over 600 nm. Also, three designed compounds were suggested as potential candidates for the fluorescent probes. Such generalised guideline learnt from this work can also be useful in further designs of other fluorescent probes of H2S in water.

  15. Dataset on absorption spectra and bulb concentration of phenolic compounds that may interfere with onion pyruvate determinations.

    PubMed

    Beretta, Vanesa H; Bannoud, Florencia; Insani, Marina; Galmarini, Claudio R; Cavagnaro, Pablo F

    2017-04-01

    We present data on absorption spectra (400-540 nm) and concentration of phenolic compounds quercetin, myricetin, kaempferol, rutin, catechin, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), in yellow, red and white onions. These data are related to the article entitled "Variability in spectrophotometric pyruvate analyses for predicting onion pungency and nutraceutical value" (Beretta et al., 2017) [1]. Given the relevance of pyruvate determinations for estimating onion pungency and functional value, it is important to identify compounds that can interfere with pyruvate determinations when using two previously published analytical procedures, namely Schwimmer and Weston (1961) (SW) [2] and Anthon and Barret (2002) (AB) [3], which are based on spectrophotometry and light-absorbance at 420 nm and 515 nm, respectively. The data presented in this article are absorption spectra for 7 onion phenolic compounds in the range 400-540 nm, which include wavelengths used by the two pyruvate analytical methods (Schwimmer and Weston, 1961; Anthon and Barret, 2002) [2,3] that were compared in our reference article (Beretta et al., 2017) [1]. Additionally, bulb content data for these 7 phenolic compounds in onion cultivars and F2 progenies with different bulb color were included to allow further analyses.

  16. X-ray Absorption Spectra of Dissolved Polysulfides in Lithium-Sulfur Batteries from First-Principles.

    PubMed

    Pascal, Tod A; Wujcik, Kevin H; Velasco-Velez, Juan; Wu, Chenghao; Teran, Alexander A; Kapilashrami, Mukes; Cabana, Jordi; Guo, Jinghua; Salmeron, Miquel; Balsara, Nitash; Prendergast, David

    2014-05-01

    The X-ray absorption spectra (XAS) of lithium polysulfides (Li2Sx) of various chain lengths (x) dissolved in a model solvent are obtained from first-principles calculations. The spectra exhibit two main absorption features near the sulfur K-edge, which are unambiguously interpreted as a pre-edge near 2471 eV due to the terminal sulfur atoms at either end of the linear polysulfide dianions and a main-edge near 2473 eV due to the (x - 2) internal atoms in the chain, except in the case of Li2S2, which only has a low-energy feature. We find an almost linear dependence between the ratio of the peaks and chain length, although the linear dependence is modified by the delocalized, molecular nature of the core-excited states that can span up to six neighboring sulfur atoms. Thus, our results indicate that the ratio of the peak area, and not the peak intensities, should be used when attempting to differentiate the polysulfides from XAS.

  17. Calculations of One- and Two-Photon Absorption Spectra for Molecular Metal Chalcogenide Clusters with Electron-Acceptor Ligands.

    PubMed

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

    2017-03-02

    We present calculated one- and two-photon absorption (OPA, TPA) spectra for molecular neutral, cation, and anion cadmium chalcogenide nonstoichiometric clusters [CdnE'm'(ER)m, E = S and Se, R = hydrogen, methyl, phenyl, para-nitrophenyl, para-cyanophenyl], ranging from less than 1 nm to more than 2 nm in size with well-defined structures. A systematic treatment of the clusters is carried out to assess the effects of size and ligand on their linear and nonlinear optical properties. Ligands and cluster size were found to have a large influence on the color and intensity of the electronic absorption spectra. TPA cross sections were found to increase linearly with cluster size. Electron-accepting ligands were also found to induce linear enhancement in TPA cross sections. Blue shifts of TPA maxima were observed for the first band with reduced molecular size. The effects of phenyl, para-nitrophenyl, and para-cyanophenyl substitutions, as well as changes in the chalcogenide atom, have been analyzed in detail.

  18. Arylperoxyl radicals. Formation, absorption spectra, and reactivity in aqueous alcohol solutions

    SciTech Connect

    Alfassi, Z.B.; Khaikin, G.I.; Neta, P. )

    1995-01-05

    Aryl radicals (phenyl, 4-biphenylyl, 2-naphthyl, 1-naphthyl, and 9-phenanthryl) were produced by the reaction of the corresponding aryl bromide with solvated electrons and reacted rapidly with oxygen to produce the arylperoxyl radicals. These radicals exhibit optical absorptions in the visible range, with [lambda][sub max] at 470, 550, 575, 650, and 700 nm, respectively. Arylperoxyl radicals react with 2,2[prime]-azinobis(3-ethylbenzothiazoiine-6-sulfonate ion) (ABTS), chlorpromazine, and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox C) by one-electron oxidation. The rate constants k for these reactions, determined from the rate of formation of the one-electron oxidation products as a function of substrate concentration, vary between 4 [times] 10[sup 6] and 2 [times] 10[sup 9] L mol[sup [minus]1] s[sup [minus]1] and increase in the order phenyl-, 4-biphenyl-, 2-naphthyl-, 1-naphthyl-, and 9-phenanthrylperoxyl, the same order as the absorption peaks of these radicals. Good correlation was found between log k and the energy of the absorption peak. 16 refs., 2 figs., 2 tabs.

  19. Quantitative spectroscopic and theoretical study of the optical absorption spectra of H2O, HOD, and D2O in the 125-145 nm region.

    PubMed

    Cheng, Bing-Ming; Chung, Chao-Yu; Bahou, Mohammed; Lee, Yuan-Pern; Lee, L C; van Harrevelt, Rob; van Hemert, Marc C

    2004-01-01

    The room temperature absorption spectra of water and its isotopomers D2O and HOD have been determined in absolute cross section units in the 125 to 145 nm wavelength region using synchrotron radiation. The experimental results for these B band spectra are compared with results from quantum mechanical calculations using accurate diabatic ab initio potentials. A Monte Carlo sampling over the initial rotational states of the molecules is applied in order to calculate the cross sections at a temperature of 300 K. The overall rotation of the water molecule is treated exactly. Both for the experimental and for the theoretical spectrum an analysis is made in terms of a component attributed to rapid direct dissociation processes and a component attributed to longer-lived resonances. The agreement between the results from experiment and theory is excellent for H2O and D2O. In the case of HOD in the results of theory two more resonances are found at low energy. It is demonstrated that the width of the resonances of 0.04 eV is the result of overlapping and somewhat narrower resonances in the spectra of molecules differing in rotational ground state.

  20. 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

  1. Carbon X-ray absorption spectra of fluoroethenes and acetone: a study at the coupled cluster, density functional, and static-exchange levels of theory.

    PubMed

    Fransson, Thomas; Coriani, Sonia; Christiansen, Ove; Norman, Patrick

    2013-03-28

    Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger π-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to π∗-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate π∗-peak separations due to spectral compressions, a characteristic which is inherent to this

  2. Carbon X-ray absorption spectra of fluoroethenes and acetone: A study at the coupled cluster, density functional, and static-exchange levels of theory

    SciTech Connect

    Fransson, Thomas; Norman, Patrick; Coriani, Sonia; Christiansen, Ove

    2013-03-28

    Near carbon K-edge X-ray absorption fine structure spectra of a series of fluorine-substituted ethenes and acetone have been studied using coupled cluster and density functional theory (DFT) polarization propagator methods, as well as the static-exchange (STEX) approach. With the complex polarization propagator (CPP) implemented in coupled cluster theory, relaxation effects following the excitation of core electrons are accounted for in terms of electron correlation, enabling a systematic convergence of these effects with respect to electron excitations in the cluster operator. Coupled cluster results have been used as benchmarks for the assessment of propagator methods in DFT as well as the state-specific static-exchange approach. Calculations on ethene and 1,1-difluoroethene illustrate the possibility of using nonrelativistic coupled cluster singles and doubles (CCSD) with additional effects of electron correlation and relativity added as scalar shifts in energetics. It has been demonstrated that CPP spectra obtained with coupled cluster singles and approximate doubles (CC2), CCSD, and DFT (with a Coulomb attenuated exchange-correlation functional) yield excellent predictions of chemical shifts for vinylfluoride, 1,1-difluoroethene, trifluoroethene, as well as good spectral features for acetone in the case of CCSD and DFT. Following this, CPP-DFT is considered to be a viable option for the calculation of X-ray absorption spectra of larger {pi}-conjugated systems, and CC2 is deemed applicable for chemical shifts but not for studies of fine structure features. The CCSD method as well as the more approximate CC2 method are shown to yield spectral features relating to {pi}*-resonances in good agreement with experiment, not only for the aforementioned molecules but also for ethene, cis-1,2-difluoroethene, and tetrafluoroethene. The STEX approach is shown to underestimate {pi}*-peak separations due to spectral compressions, a characteristic which is inherent to this

  3. Ultraviolet-visible absorption spectra of chromophoric dissolved organic matter (CDOM) in waters throughout the Kolyma River basin, East Siberia

    NASA Astrophysics Data System (ADS)

    Frey, K. E.; Bulygina, E. B.; Bunn, A. G.; Chandra, S.; Davydov, S.; Holmes, R. M.; Schade, J. D.; Sobczak, W. V.; Spektor, V. V.; Zimov, S. A.

    2009-12-01

    The Kolyma River in East Siberia is among the six largest Arctic rivers and drains a region underlain by vast deposits of Pleistocene loess known as yedoma, most of which are currently stored in ice-rich permafrost throughout the region. These yedoma deposits are important sources of dissolved organic matter to terrestrial waters that in turn play a significant role in the transport and ultimate mineralization of organic carbon to atmospheric CO2 and CH4. In order to determine the concentrations and characteristics of this dissolved organic matter, we measured the ultraviolet-visible absorption spectra (200-800 nm) of chromophoric dissolved organic matter (CDOM) from a broad collection of waters throughout a ~250 km transect of the northern Kolyma River basin. 124 samples were collected during July 2008 and 2009 and include soil pore waters, lakes, streams, rivers, and the Kolyma River mainstem. Absorbance values are highly positively correlated with dissolved organic carbon concentrations, with the highest values in soil pore waters and lowest values in the Kolyma River mainstem. Spectral slopes (at 275-295 nm and 350-400 nm, calculated within log-transformed absorption spectra) are also used to investigate contrasting water types and are found to be useful indicators of the bioavailability of dissolved organic matter. With ongoing and future permafrost degradation, yedoma deposits throughout the East Siberian region will become more hydrologically active and have the potential to be even greater sources of dissolved organic matter to soil pore waters, lakes, streams, rivers, and ultimately to the Arctic Ocean. As such, the ability to easily and comprehensively monitor the quantity and quality of dissolved organic matter across the landscape through methods such as ultraviolet-visible absorption is becoming critical for understanding the global significance of the Arctic carbon cycle.

  4. Resonance Raman and vibronic absorption spectra with Duschinsky rotation from a time-dependent perspective: Application to β-carotene

    NASA Astrophysics Data System (ADS)

    Banerjee, Shiladitya; Kröner, Dominik; Saalfrank, Peter

    2012-12-01

    The time-dependent approach to electronic spectroscopy, as popularized by Heller and co-workers in the 1980s, is applied here in conjunction with linear-response, time-dependent density functional theory to study vibronic absorption and resonance Raman spectra of β-carotene, with and without a solvent. Two-state models, the harmonic and the Condon approximations are used in order to do so. A new code has been developed which includes excited state displacements, vibrational frequency shifts, and Duschinsky rotation, i.e., mode mixing, for both non-adiabatic spectroscopies. It is shown that Duschinsky rotation has a pronounced effect on the resonance Raman spectra of β-carotene. In particular, it can explain a recently found anomalous behaviour of the so-called ν1 peak in resonance Raman spectra [N. Tschirner, M. Schenderlein, K. Brose, E. Schlodder, M. A. Mroginski, C. Thomsen, and P. Hildebrandt, Phys. Chem. Chem. Phys. 11, 11471 (2009)], 10.1039/b917341b, which shifts with the change in excitation wavelength.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  6. Reflectance Spectra of Ureilites: Nature of the Mafic Silicate Absorption Features

    NASA Technical Reports Server (NTRS)

    Cloutis, E. A.; Hudon, P.

    2004-01-01

    Ureilites are unique carbon-bearing achondrites. They are composed primarily of olivine and pyroxene with minor amounts of finely dispersed matrix material consisting mostly of carbon, metal, sulfides and fine-grained silicates. As is the case with many classes of meteorites, no clear chain of evidence exists which can relate them to specific asteroidal parent bodies. In order to provide insights into parent body connections, visible and near-IR (VNIR) reflectance spectra of a number of ureilites have been measured and analyzed in light of their mineralogy.

  7. Multiple-scattering approach to the x-ray-absorption spectra of perovskite-type compounds

    NASA Astrophysics Data System (ADS)

    Kitamura, Michihide; Muramatsu, Shinji; Sugiura, Chikara

    1988-04-01

    The metal K x-ray-absorption near-edge structure has been calculated for the first time from a multiple-scattering formalism for the perovskite-type compounds KMnF3, KFeF3, KCoF3, KNiF3, and KZnF3. The calculation includes the effects of a core hole and of Madelung corrections for crystal potentials. It is shown that the results including the lifetime-broadening effect are in good agreement with the experiment of Shulman et al.

  8. Franck-Condon factors perturbed by damped harmonic oscillators: Solvent enhanced X {sup 1}A{sub g} ↔ A{sup 1}B{sub 1u} absorption and fluorescence spectra of perylene

    SciTech Connect

    Wang, Chen-Wen; Zhu, Chaoyuan Lin, Sheng-Hsien; Yang, Ling; Yu, Jian-Guo

    2014-08-28

    Damped harmonic oscillators are utilized to calculate Franck-Condon factors within displaced harmonic oscillator approximation. This is practically done by scaling unperturbed Hessian matrix that represents local modes of force constants for molecule in gaseous phase, and then by diagonalizing perturbed Hessian matrix it results in direct modification of Huang–Rhys factors which represent normal modes of solute molecule perturbed by solvent environment. Scaling parameters are empirically introduced for simulating absorption and fluorescence spectra of an isolated solute molecule in solution. The present method is especially useful for simulating vibronic spectra of polycyclic aromatic hydrocarbon molecules in which hydrogen atom vibrations in solution can be scaled equally, namely the same scaling factor being applied to all hydrogen atoms in polycyclic aromatic hydrocarbons. The present method is demonstrated in simulating solvent enhanced X {sup 1}A{sub g} ↔ A{sup 1}B{sub 1u} absorption and fluorescence spectra of perylene (medium-sized polycyclic aromatic hydrocarbon) in benzene solution. It is found that one of six active normal modes v{sub 10} is actually responsible to the solvent enhancement of spectra observed in experiment. Simulations from all functionals (TD) B3LYP, (TD) B3LYP35, (TD) B3LYP50, and (TD) B3LYP100 draw the same conclusion. Hence, the present method is able to adequately reproduce experimental absorption and fluorescence spectra in both gas and solution phases.

  9. The Infrared Spectra and Absorption Intensities of Amorphous Ices: Methane and Carbon Dioxide

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

    Our research group is carrying out new IR measurements of icy solids relevant to the outer solar system and the interstellar medium, with an emphasis on amorphous and crystalline ices below ~70 K. Our goal is to 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 two of the simplest and most abundant components of icy bodies in the solar system - methane (CH4) and carbon dioxide (CO2). 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 70 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.

  10. 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.

  11. Experimental demonstration of terahertz metamaterial absorbers with a broad and flat high absorption band.

    PubMed

    Huang, Li; Chowdhury, Dibakar Roy; Ramani, Suchitra; Reiten, Matthew T; Luo, Sheng-Nian; Taylor, Antoinette J; Chen, Hou-Tong

    2012-01-15

    We present the design, numerical simulations and experimental measurements of terahertz metamaterial absorbers with a broad and flat absorption top over a wide incidence angle range for either transverse electric or transverse magnetic polarization depending on the incident direction. The metamaterial absorber unit cell consists of two sets of structures resonating at different but close frequencies. The overall absorption spectrum is the superposition of individual components and becomes flat at the top over a significant bandwidth. The experimental results are in excellent agreement with numerical simulations.

  12. 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.

  13. Comparative theoretical study of the UV/Vis absorption spectra of styrylpyridine compounds using TD-DFT calculations.

    PubMed

    Castro, Maria Eugenia; Percino, M Judith; Chapela, Victor M; Soriano-Moro, Guillermo; Ceron, Margarita; Melendez, Francisco J

    2013-05-01

    This study examined absorption properties of 2-styrylpyridine, trans-2-(m-cyanostyryl)pyridine, trans-2-[3-methyl-(m-cyanostyryl)]pyridine, and trans-4-(m-cyanostyryl)pyridine compounds based on theoretical UV/Vis spectra, with comparisons between time-dependent density functional theory (TD-DFT) using B3LYP, PBE0, and LC-ωPBE functionals. Basis sets 6-31G(d), 6-31G(d,p), 6-31+G(d,p), and 6-311+G(d,p) were tested to compare molecular orbital energy values, gap energies, and maxima absorption wavelengths. UV/Vis spectra were calculated from fully optimized geometry in B3LYP/6-311+G(d,p) in gas phase and using the IEFPCM model. B3LYP/6-311+G(d,p) provided the most stable form, a planar structure with parameters close to 2-styrylpyridine X-ray data. Isomeric structures were evaluated by full geometry optimization using the same theory level. Similar energetic values were found: ~4.5 kJ mol(-1) for 2-styrylpyridine and ~1 kJ mol(-1) for derivative compound isomers. The 2-styrylpyridine isomeric structure differed at the pyridine group N-atom position; structures considered for the other compounds had the cyano group attached to the phenyl ring m-position equivalent. The energy difference was almost negligible between m-cyano-substituted molecules, but high energy barriers existed for cyano-substituted phenyl ring torsion. TD-DFT appeared to be robust and accurate approach. The B3LYP functional with the 6-31G(d) basis set produced the most reliable λmax values, with mean errors of 0.5 and 12 nm respect to experimental values, in gas and solution, respectively. The present data describes effects on the λmax changes in the UV/Vis absorption spectra of the electron acceptor cyano substituent on the phenyl ring, the electron donor methyl substituent, and the N-atom position on the electron acceptor pyridine ring, causing slight changes respect to the 2-styrylpyridine title compound.

  14. Photosensitivity spectra of Schottky barriers in the region of strong absorption

    NASA Astrophysics Data System (ADS)

    Borkovskaia, O. Iu.; Dmitruk, N. L.; Ziuganov, A. N.

    Spectral characteristics of the photocurrent of metal-semiconductor contacts with a Schottky barrier are calculated for analytically determined boundary conditions. The expression obtained for the photocurrent of a quasi-monopolar semiconductor is shown to reduce, in the limiting cases, to the known formulas of Gartner (1959), Caywood-Mead (1969), and Gutkin-Sedov (1975). On the basis of generalized formulas for the photocurrent spectra and relative sensitivity, a method is proposed for determining the surface recombination velocities and transport velocities of holes and electrons for Schottky barriers. The predictions of the theory developed here are shown to be in good agreement with experimental results for Au-GaAs Schottky barriers.

  15. 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

  16. Electronic absorption spectra of protonated pyrene and coronene in neon matrixes.

    PubMed

    Garkusha, Iryna; Fulara, Jan; Sarre, Peter J; Maier, John P

    2011-10-13

    Protonated pyrene and coronene have been isolated in 6 K neon matrixes. The cations were produced in the reaction of the parent aromatics with protonated ethanol in a hot-cathode discharge source, mass selected, and co-deposited with neon. Three electronic transitions of the most stable isomer of protonated pyrene and four of protonated coronene were recorded. The strongest, S(1) ← S(0) transitions, are in the visible region, with onset at 487.5 nm for protonated pyrene and 695.6 nm for protonated coronene. The corresponding neutrals were also observed. The absorptions were assigned on the basis of ab initio coupled-cluster and time-dependent density functional theory calculations. The astrophysical relevance of protonated polycyclic aromatic hydrocarbons is discussed.

  17. Electronic absorption spectra and energy gap studies of Er3+ ions in different chlorophosphate glasses.

    PubMed

    Ratnakaram, Y C; Reddy, A Viswanadha; Chakradhar, R P Sreekanth

    2002-06-01

    Spectroscopic properties of Er3+ ions in different chlorophosphate glasses 50P2O5-30Na2HPO4-19.8RCl (R = Li, Na, K, Ca and Pb) are studied. The direct and indirect optical band gaps (Eopt) and the various spectroscopic parameters (E1, E2, E3, and zeta4f and alpha) are reported. The oscillator strengths of the transitions in the absorption spectrum are parameterized in terms of three Judd-Ofelt intensity parameters (omega2, omega4 and omega6). These intensity parameters are used to predict the transition probabilities (A), radiative lifetimes (tauR), branching ratios (beta) and integrated cross sections (sigma) for stimulated emission. Attention has been paid to the trend of the intensity parameters over hypersensitive transitions and optical band gaps. The lifetimes and branching ratios of certain transitions are compared with other glass matrices.

  18. 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.

  19. 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.

  20. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2013-01-01

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

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

    SciTech Connect

    Gatuzz, E.; Mendoza, C.; Garcia, J.; Lohfink, A.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Palmeri, P.; Quinet, P. E-mail: claudio@ivic.gob.ve E-mail: alohfink@astro.umd.edu E-mail: michael.c.witthoeft@nasa.gov E-mail: palmeri@umons.ac.be

    2013-05-01

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

  4. 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.

  5. 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.

  6. Zn K edge and O K edge x-ray absorption spectra of ZnO surfaces: implications for nanorods.

    PubMed

    Šipr, O; Rocca, F

    2011-08-10

    Zn K edge and O K edge x-ray absorption near-edge structure (XANES) spectra of ZnO surfaces are calculated. The difference between theoretical XANES for ZnO surfaces and ZnO bulk is then compared to the earlier observed differences between experimental XANES for ZnO nanostructures and ZnO bulk as taken from the literature. It follows from our calculations that the differences between the experimental XANES of bulk ZnO and nanocrystalline ZnO is not due to the enhanced role of the surfaces in nanostructures. Rather, the difference in XANES has to reflect differences in the local geometry around the photoabsorbing sites. The dependence of XANES of ZnO surfaces on the polarization of the incoming radiation is also investigated theoretically and found to be similar as in the bulk.

  7. Vibronic fine structure in high-resolution x-ray absorption spectra from ion-bombarded boron nitride nanotubes

    SciTech Connect

    Petravic, Mladen; Peter, Robert; Varasanec, Marijana; Li Luhua; Chen Ying; Cowie, Bruce C. C.

    2013-05-15

    The authors have applied high-resolution near-edge x-ray absorption fine structure measurements around the nitrogen K-edge to study the effects of ion-bombardment on near-surface properties of boron nitride nanotubes. A notable difference has been observed between surface sensitive partial electron yield (PEY) and bulk sensitive total electron yield (TEY) fine-structure measurements. The authors assign the PEY fine structure to the coupling of excited molecular vibrational modes to electronic transitions in NO molecules trapped just below the surface. Oxidation resistance of the boron nitride nanotubes is significantly reduced by low energy ion bombardment, as broken B-N bonds are replaced by N-O bonds involving oxygen present in the surface region. In contrast to the PEY spectra, the bulk sensitive TEY measurements on as-grown samples do not exhibit any fine structure while the ion-bombarded samples show a clear vibronic signature of molecular nitrogen.

  8. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  10. 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.

  11. Collisional Processing of Comet and Asteroid Surfaces: Velocity Effects on Absorption Spectra

    NASA Technical Reports Server (NTRS)

    Lederer, S. M.; Jensen, E. A.; Wooden, D. H.; Lindsay, S. S.; Smith, D. C.; Nakamura-Messenger, K.; Keller, L. P.; Cintala, M. J.; Zolensky, M. E.

    2012-01-01

    A new paradigm has emerged where 3.9 Gyr ago, a violent reshuffling reshaped the placement of small bodies in the solar system (the Nice model). Surface properties of these objects may have been affected by collisions caused by this event, and by collisions with other small bodies since their emplacement. These impacts affect the spectrographic observations of these bodies today. Shock effects (e.g., planar dislocations) manifest in minerals allowing astronomers to better understand geophysical impact processing that has occurred on small bodies. At the Experimental Impact Laboratory at NASA Johnson Space Center, we have impacted forsterite and enstatite across a range of velocities. We find that the amount of spectral variation, absorption wavelength, and full width half maximum of the absorbance peaks vary non-linearly with the velocity of the impact. We also find that the spectral variation increases with decreasing crystal size (single solid rock versus granular). Future analyses include quantification of the spectral changes with different impactor densities, temperature, and additional impact velocities. Results on diopside, fayalite, and magnesite can be found in Lederer et al., this meeting.

  12. Absorption Spectra and Photoreactivity of p-Aminobenzophenone by Time-dependent Density Functional Theory

    NASA Astrophysics Data System (ADS)

    Cheng, Xue-mei; Huang, Yao; Ma, Jian-yi; Li, Xiang-yuan

    2007-06-01

    The absorption spectral properties of para-aminobenzophenone (p-ABP) were investigated in gas phase and in solution by time-dependent density functional theory. Calculations suggest that the singlet states vary greatly with the solvent polarities. In various polar solvents, including acetonitrile, methanol, ethanol, dimethyl sulfoxide, and dimethyl formamide, the excited S1 states with charge transfer character result from π → π* transitions. However, in nonpolar solvents, cyclohexane, and benzene, the S1 states are the result of n → π* transitions related to local excitation in the carbonyl group. The excited T1 states were calculated to have ππ* character in various solvents. From the variation of the calculated excited states, the band due to π → π* transition undergoes a redshift with an increase in solvent polarity, while the band due to n → π* transition undergoes a blueshift with an increase in solvent polarity. In addition, the triplet yields and the photoreactivities of p-ABP in various solvents are discussed.

  13. Electronic absorption and resonance Raman spectra of large linear carbon clusters isolated in solid argon.

    PubMed

    Szczepanski, J; Fuller, J; Ekern, S; Vala, M

    2001-03-15

    Neutral and anionic carbon clusters have been generated via a laser-induced graphite-based plasma and deposited in a solid argon matrix. Anionic clusters were formed from neutral clusters by using crossed electron/carbon cluster beams. Thermal annealing (to 36 K) resulted in the aggregation of the smaller carbon species, leading to the formation of long chain neutral and anionic clusters. Spectroscopic measurements in the ultraviolet, visible, near-infrared and infrared regions revealed a series of bands attributable to a homologous set of odd-numbered C5-C29 neutral clusters and even-numbered C6(-)-C36- anionic clusters. Good agreement is found for the band positions of carbon chains containing odd C15-C21 neutrals and even C6(-)-C22- anions, with species previously identified by Maier and coworkers using mass selection or laser vaporization, followed by neon matrix isolation. Resonance Raman frequencies for the neutral C17, C21 and C23 species are shown to be consistent with the above attributions. Density functional theory calculations agree well with the observed bands. It is found that certain low frequency Raman stretching frequencies decrease in a predictable way with increasing chain length. Comparison of the 0(0)0 absorption transitions of the even C18(-)-C36- anionic clusters with the 'unidentified' infrared (UIR) interstellar emission bands suggests that the electronic emission from specific long chain carbon anions may contribute to the some of the UIR bands.

  14. Collisional Processing Of Comet And Asteroid Surfaces: Velocity Effects On Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Jensen, Elizabeth; Lederer, S. M.; Wooden, D. H.; Lindsay, S. S.; Nakamura-Messenger, K.; Keller, L. P.; Cintala, M. J.; Zolensky, M. E.

    2012-10-01

    A new paradigm has emerged where 3.9 Gyr ago, a violent reshuffling reshaped the placement of small bodies in the solar system (the Nice model). Surface properties of these objects may have been affected by collisions caused by this event, and by collisions with other small bodies since their emplacement. These impacts affect the spectroscopic observations of these bodies today. Shock effects (e.g., planar dislocations) manifest in minerals allowing astronomers to better understand geophysical impact processing that has occurred on small bodies. At the Experimental Impact Laboratory at NASA Johnson Space Center, we have impacted forsterite and enstatite across a range of velocities. We find that the amount of spectral variation, absorption wavelength, and full width half maximum of the absorbance peaks vary non-linearly with the velocity of the impact. We also find that the spectral variation increases with decreasing crystal size (single solid rock versus granular). Future analyses include quantification of the spectral changes with different impactor densities, temperature, and additional impact velocities. Results on diopside, fayalite, and magnesite can be found in Lederer et al., this meeting. Funding was provided by the NASA PG&G grant 09-PGG09-0115, NSF grant AST-1010012, and a Cottrell College Scholarship through the Research Corporation.

  15. Dressing effects in the attosecond transient absorption spectra of doubly excited states in helium

    NASA Astrophysics Data System (ADS)

    Argenti, L.; Jiménez-Galán, Á.; Marante, C.; Ott, C.; Pfeifer, T.; Martín, F.

    2015-06-01

    Strong-field manipulation of autoionizing states is a crucial aspect of electronic quantum control. Recent measurements of the attosecond transient absorption spectrum (ATAS) of helium dressed by a few-cycle visible pulse [C. Ott et al., Nature (London) 516, 374 (2014), 10.1038/nature14026] provide evidence of the inversion of Fano profiles. With the support of accurate ab initio calculations that reproduce the results of the latter experiment, here we investigate the new physics that arise from ATAS when the laser intensity is increased. In particular, we show that (i) previously unnoticed signatures of the dark 2 p21S doubly excited state are observed in the experimental spectrum, (ii) inversion of Fano profiles is predicted to be periodic in the laser intensity, and (iii) the ac Stark shift of the higher terms in the s p2,n + autoionizing series exceeds the ponderomotive energy, which is the result of a genuine two-electron contribution to the polarization of the excited atom.

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

    SciTech Connect

    Ma, Jian; Cao, Jianshu

    2015-03-07

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

  17. 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).

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

    SciTech Connect

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

    1989-03-01

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

  19. 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.

  20. 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.

  1. Excited S 1 state dipole moments of nitrobenzene and p-nitroaniline from thermochromic effect on electronic absorption spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-11-01

    The effect of temperature on the absorption spectra of nitrobenzene (NB) and p-nitroaniline (NA) in 1,2-dichloroethane was studied for temperature ranging from 295 K to 378 K and from 296 K to 408 K, respectively. With temperature increase the absorption bands of both compounds are blue shifted, which is caused by the decrease of permittivity ɛ and refractive index n. From the band shifts and by using the Bilot and Kawski theory [ L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621] the dipole moments in the excited singlet state μe = 6.59 D of NB and μe = 13.35 D of NA were determined. The influence of polarizability α, the Onsager cavity radius a and dipole moment in the ground state μg on the determined values of μe are discussed. A comparison of the obtained μe values with those of other authors is given. In the case of p-NA a strong intramolecular charge transfer (ICT) was confirmed.

  2. Excited state dipole moments of N, N-dimethylaniline from thermochromic effect on electronic absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Kukliński, B.; Bojarski, P.

    2006-01-01

    The effect of temperature on absorption and fluorescence spectra of N, N-dimethylaniline (DMA) in ethyl acetate has been studied for temperature ranging from 293 to 388 K. The permittivity ɛ and refractive index n of the solvent decrease with temperature increase and the absorption and fluorescence bands are blue shifted (so-called "thermochromic shift"). Based on this phenomenon, the dipole moment μe in the excited singlet state and the Onsager interaction radius a for DMA were determined using the Bilot and Kawski theory [L. Bilot, A. Kawski, Z. Naturforsch. 17a (1962) 621; 18a (1963) 10, 256]. For the known dipole moment in the ground state μg = 1.61 D and for α/ a3 = 0.54 ( α is the polarizability of the solute) the average value of μe = 3.55 D and a = 3.1 Å were determined. The obtained values for DMA are compared with the experimental values determined by other authors.

  3. 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.

  4. 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.

  5. 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.

  6. Pure absorption electron spin echo envelope modulation spectra by using the filter-diagonalization method for harmonic inversion.

    PubMed

    Jeschke, G; Mandelshtam, V A; Shaka, A J

    1999-03-01

    Harmonic inversion of electron spin echo envelope (ESEEM) time-domain signals by filter diagonalization is investigated as an alternative to Fourier transformation. It is demonstrated that this method features enhanced resolution compared to Fourier-transform magnitude spectra, since it can eliminate dispersive contributions to the line shape, even if no linear phase correction is possible. Furthermore, instrumental artifacts can be easily removed from the spectra if they are narrow either in time or frequency domain. This applies to echo crossings that are only incompletely eliminated by phase cycling and to spurious spectrometer frequencies, respectively. The method is computationally efficient and numerically stable and does not require extensive parameter adjustments or advance knowledge of the number of spectral lines. Experiments on gamma-irradiated methyl-alpha-d-glucopyranoside show that more information can be obtained from typical ESEEM time-domain signals by filter-diagonalization than by Fourier transformation.

  7. Potential chlorofluorocarbon replacements: OH reaction rate constants between 250 and 315 K and infrared absorption spectra

    SciTech Connect

    Garland, N.L.; Medhurst, L.J.; Nelson, H.H.

    1993-12-20

    The authors measured the rate constant for reactions of the OH radical with several potential chlorofluorocarbon replacements over the temperature range 251-314 K using laser photolysis laser-induced fluorescence techniques. The compounds studied and Arrhenius parameters determined from fits to the measured rate constants are as follows: CHF{sub 2}OCHF{sub 2} (E 134), k(T) = (5.4 {+-} 3.5) x 10{sup {minus}13} cm{sup 3} s{sup {minus}1} exp [({minus}3.1 {+-} 0.4 kcal mol{sup {minus}1})/RT]; CF{sub 3}CH{sub 2}CF{sub 3} (FC 236fa), k(T) = (2.0 {+-} 1.0) x 10{sup {minus}14} cm{sup 3} s{sup {minus}1} exp [({minus}1.8 {+-} 0.3 kcal mol{sup {minus}1})/RT]; CF{sub 3}CHFCHF{sub 2} (FC 236ea), k(T) = (2.0 {+-} 0.9) x 10{sup {minus}13} cm{sup 3} s{sup {minus}1} exp [({minus}2.0 {+-} 0.3 kcal mol{sup {minus}1})/RT]; and CF{sub 3}CF{sub 2}CH{sub 2}F (FC 236cb), k(T) = (2.6 {+-} 1.6) x 10{sup {minus}13} cm{sup 3} s{sup {minus}1} exp [({minus}2.2 {+-} 0.4 kcal mol{sup {minus}1})/RT]. The measured activation energies (2-3 kcal mol{sup {minus}1}) are consistent with a mechanism of H atom abstraction. The tropospheric lifetimes, estimated from the measured OH reaction rates, and measured integrated infrared absorption cross sections over the range 770 to 1430 cm{sup {minus}1} suggest that E 134 and FC 236fa may have significant global warming potential, while FC 236ea and FC 236cb do not. 17 refs., 4 figs., 3 tabs.

  8. Monomeric C-phycocyanin at room temperature and 77 K. Resolution of the absorption and fluorescence spectra of the individual chromophores and the energy-transfer rate constants

    SciTech Connect

    Debreczeny, M.P.; Sauer, K. Univ. of California, Berkeley, CA ); Zhou, J.; Bryant, D.A. )

    1993-09-23

    At both room temperature (RT) and 77 K, the absorption and fluorescence spectra of the three individual chromophore types ([alpha][sub 84], [beta][sub 84], and [beta][sub 155]) found in monomeric C-phycocyanin ([alpha][sup PC][beta][sup PC]), isolated from the cyanobacterium Synechococcus sp. PCC 7002, were resolved along with the rates of energy transfer between the chromophores. The cpcB/C155S mutant, whose PC is missing the [beta][sub 155] chromophore, was useful in effecting this resolution. At RT, the single broad peak in the visible region of the absorption spectrum of ([alpha][sup PC][beta][sup PC]) was resolved into its three-component spectra by comparing the steady-state absorption spectra of the isolated wild-type [alpha] subunit of PC ([alpha][sup PC]) (containing only the [alpha][sub 84] chromophore) with those of the monomeric PCs isolated from the mutant strain ([alpha][sup PC][beta]*) and the wild-type strain ([alpha][sup PC][beta][sup PC]). At 77 K, the visible region of the absorption spectrum of ([alpha][sup PC][beta][sup PC]) splits into two peaks. This partial resolution at 77 K of the chromophore spectra of ([alpha][sup PC][beta][sup PC]) when compared with the 77 K absorption spectra of [alpha][sup PC], [beta][sup PC], and ([alpha][sup PC][beta]*) provided a confirmation of our RT assignments of the chromophore absorption spectra. 38 refs., 9 figs., 6 tabs.

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

    SciTech Connect

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

    2015-02-28

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

  10. 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

  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. 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.

  13. 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.

  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. How Accurately Can Extended X-ray Absorption Spectra Be Predicted from First Principles? Implications for Modeling the Oxygen-Evolving Complex in Photosystem II.

    PubMed

    Beckwith, Martha A; Ames, William; Vila, Fernando D; Krewald, Vera; Pantazis, Dimitrios A; Mantel, Claire; Pécaut, Jacques; Gennari, Marcello; Duboc, Carole; Collomb, Marie-Noëlle; Yano, Junko; Rehr, John J; Neese, Frank; DeBeer, Serena

    2015-10-14

    First principle calculations of extended X-ray absorption fine structure (EXAFS) data have seen widespread use in bioinorganic chemistry, perhaps most notably for modeling the Mn4Ca site in the oxygen evolving complex (OEC) of photosystem II (PSII). The logic implied by the calculations rests on the assumption that it is possible to a priori predict an accurate EXAFS spectrum provided that the underlying geometric structure is correct. The present study investigates the extent to which this is possible using state of the art EXAFS theory. The FEFF program is used to evaluate the ability of a multiple scattering-based approach to directly calculate the EXAFS spectrum of crystallographically defined model complexes. The results of these parameter free predictions are compared with the more traditional approach of fitting FEFF calculated spectra to experimental data. A series of seven crystallographically characterized Mn monomers and dimers is used as a test set. The largest deviations between the FEFF calculated EXAFS spectra and the experimental EXAFS spectra arise from the amplitudes. The amplitude errors result from a combination of errors in calculated S0(2) and Debye-Waller values as well as uncertainties in background subtraction. Additional errors may be attributed to structural parameters, particularly in cases where reliable high-resolution crystal structures are not available. Based on these investigations, the strengths and weaknesses of using first-principle EXAFS calculations as a predictive tool are discussed. We demonstrate that a range of DFT optimized structures of the OEC may all be considered consistent with experimental EXAFS data and that caution must be exercised when using EXAFS data to obtain topological arrangements of complex clusters.

  16. Modeling of collision-induced infrared absorption spectra of H2-H2 pairs in the fundamental band at temperatures from 20 to 300 K. [Planetary atmospheres

    SciTech Connect

    Borysow, A. )

    1991-08-01

    The 20-300 K free-free rotovibrational collision-induced absorption (RV CIA) spectra of H2-H2 pairs are presently obtained by a numerical method which, in addition to closely matching known CIA spectra of H2-H2, can reproduce the results of the quantum-mechanical computations to within a few percent. Since the spectral lineshape parameters are derivable by these means from the lowest three quantum-mechanical spectral moments, these outer-planet atmosphere-pertinent model spectra may be computed on even small computers. 35 refs.

  17. Harmonic Models in Cartesian and Internal Coordinates to Simulate the Absorption Spectra of Carotenoids at Finite Temperatures.

    PubMed

    Cerezo, Javier; Zúñiga, José; Requena, Alberto; Ávila Ferrer, Francisco J; Santoro, Fabrizio

    2013-11-12

    When large structural displacements take place between the ground state (GS) and excited state (ES) minima of polyatomic molecules, the choice of a proper set of coordinates can be crucial for a reliable simulation of the vibrationally resolved absorption spectrum. In this work, we study two carotenoids that undergo structural displacements from GS to ES minima of different magnitude, from small displacements for violaxanthin to rather large ones for β-carotene isomers. Their finite-temperature (77 and 300 K) spectra are simulated at the harmonic level, including Duschinsky effect, by time-dependent (TD) and time-independent (TI) approaches, using (TD)DFT computed potential energy surfaces (PES). We adopted two approaches to construct the harmonic PES, the Adiabatic (AH) and Vertical Hessian (VH) models and, for AH, two reference coordinate frames: Cartesian and valence internal coordinates. Our results show that when large displacements take place, Cartesian coordinates dramatically fail to describe curvilinear displacements and to account for the Duschinsky matrix, preventing a realistic simulation of the spectra within the AH model, where the GS and ES PESs are quadratically expanded around their own equilibrium geometry. In contrast, internal coordinates largely amend such deficiencies and deliver reasonable spectral widths. As expected, both coordinate frames give similar results when small displacements occur. The good agreement between VH and experimental line shapes indicates that VH model, in which GS and ES normal modes are both evaluated at the GS equilibrium geometry, is a good alternative to deal with systems exhibiting large displacements. The use of this model can be, however, problematic when imaginary frequencies arise. The extent of the nonorthogonality of the Dushinsky matrix in internal coordinates and its correlation with the magnitude of the displacement of the GS and ES geometries is analyzed in detail.

  18. 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 (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.

  19. 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).

  20. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution.

    PubMed

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-08-07

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5'-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5'-monophosphate, and adenosine 5'-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  1. Study on erythrosine-phen-Cd(II) systems by resonance Rayleigh scattering, absorption spectra and their analytical applications.

    PubMed

    Tian, Jing; Zhang, Qiqi; Liu, Shaopu; Yang, Jidong; Teng, Ping; Zhu, Jinghui; Qiao, Man; Shi, Ying; Duan, Ruilin; Hu, Xiaoli

    2015-04-05

    In pH 7.0-8.0 KH2PO4-Na2HPO4 buffer solution, Cd(II) reacted with 1,10-phenanthroline to form chelate cation [Cd(phen)3]2+, which further reacted with anion of erythrosine to form ternary ion-association complex through electrostatic attraction and hydrophobic effect. This process could result in remarkable absorption spectra change and produce obvious fading reaction at 528 nm. Absorbance change (ΔA) of system was directly proportional to the concentration of Cd(II). Hereby, a highly sensitive spectrophotometric method for the determination of Cd(II) was established. The molar absorption coefficient was 2.29×10(5) L mol(-1) cm(-1) and the detection limit of Cd(II) was 26.5 ng mL(-1). Furthermore, the resonance Rayleigh scattering (RRS) of this system with two peaks located at 371 and 590 nm enhanced significantly, and second-order scattering (SOS) and frequence doubling scattering (FDS) of this system changed notably at 640 and 350 nm, respectively. Under the optimum conditions, the scattering intensities (ΔIRRS, ΔIDWO-RRS, ΔISOS and ΔIFDS) had good linear relationship with the concentration of Cd(II) in certain ranges. The detection limits of Cd(II) were 1.27 ng mL(-1), 1.39 ng mL(-1), 4.03 ng mL(-1), 5.92 ng mL(-1) and 14.7 ng mL(-1) for dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS), RRS (371 nm), RRS (590 nm), SOS and FDS, respectively. In addition, the suitable reaction conditions and effects of coexisting substances were investigated. The methods had been successfully applied to the determination of Cd(II) in environmental water samples. The recovery range was between 93.0% and 103.0% and the relative standard deviation (RSD) was between 2.5% and 4.3%. The results were in agreement with those obtained from atomic absorption spectroscopy.

  2. Study on erythrosine-phen-Cd(II) systems by resonance Rayleigh scattering, absorption spectra and their analytical applications

    NASA Astrophysics Data System (ADS)

    Tian, Jing; Zhang, Qiqi; Liu, Shaopu; Yang, Jidong; Teng, Ping; Zhu, Jinghui; Qiao, Man; Shi, Ying; Duan, Ruilin; Hu, Xiaoli

    2015-04-01

    In pH 7.0-8.0 KH2PO4-Na2HPO4 buffer solution, Cd(II) reacted with 1,10-phenanthroline to form chelate cation [Cd(phen)3]2+, which further reacted with anion of erythrosine to form ternary ion-association complex through electrostatic attraction and hydrophobic effect. This process could result in remarkable absorption spectra change and produce obvious fading reaction at 528 nm. Absorbance change (ΔA) of system was directly proportional to the concentration of Cd(II). Hereby, a highly sensitive spectrophotometric method for the determination of Cd(II) was established. The molar absorption coefficient was 2.29 × 105 L mol-1 cm-1 and the detection limit of Cd(II) was 26.5 ng mL-1. Furthermore, the resonance Rayleigh scattering (RRS) of this system with two peaks located at 371 and 590 nm enhanced significantly, and second-order scattering (SOS) and frequence doubling scattering (FDS) of this system changed notably at 640 and 350 nm, respectively. Under the optimum conditions, the scattering intensities (ΔIRRS, ΔIDWO-RRS, ΔISOS and ΔIFDS) had good linear relationship with the concentration of Cd(II) in certain ranges. The detection limits of Cd(II) were 1.27 ng mL-1, 1.39 ng mL-1, 4.03 ng mL-1, 5.92 ng mL-1 and 14.7 ng mL-1 for dual-wavelength overlapping resonance Rayleigh scattering (DWO-RRS), RRS (371 nm), RRS (590 nm), SOS and FDS, respectively. In addition, the suitable reaction conditions and effects of coexisting substances were investigated. The methods had been successfully applied to the determination of Cd(II) in environmental water samples. The recovery range was between 93.0% and 103.0% and the relative standard deviation (RSD) was between 2.5% and 4.3%. The results were in agreement with those obtained from atomic absorption spectroscopy.

  3. Signs of the Biological Effect of ~2 μm Low-Intensity Laser Radiation in Raman and Absorption Spectra of Blood

    NASA Astrophysics Data System (ADS)

    Batay, L. E.; Khodasevich, I. A.; Khodasevich, M. A.; Gorbunova, N. B.; Manina, E. Yu.

    2016-09-01

    Local exposure of experimental animals to low-intensity emission from a thulium laser (λ = 1.96 μm) leads to changes in the Raman and IR absorption spectra of blood. This indicates development of systemic effects caused by direct excitation of water molecules by radiation with wavelength ~2 μm, in particular modifi cation of the hemoglobin molecule.

  4. Anharmonic Franck-Condon simulation of the absorption and fluorescence spectra for the low-lying S1 and S2 excited states of pyridine.

    PubMed

    Wang, Huan; Zhu, Chaoyuan; Yu, Jian-Guo; Lin, Sheng Hsien

    2009-12-31

    Anharmonic effects of the absorption and fluorescence spectra of pyridine molecule are studied and analyzed for the two-low lying singlet excited states S(1)((1)B(1)) and S(2)((1)B(2)). The complete active space self-consistent field (CASSCF) method is utilized to compute equilibrium geometries and all 27 vibrational normal-mode frequencies for the ground state and the two excited states. The present calculations show that the frequency differences between the ground and two excited states are small for the ten totally symmetric vibrational modes so that the displaced oscillator approximation can be used for spectrum simulations. The Franck-Condon factors within harmonic approximation basically grasp the main features of molecular spectra, but simulated 0-0 transition energy position and spectrum band shapes are not satisfactorily good for S(1)((1)B(1)) absorption and fluorescence spectra in comparison with experiment observation. As the first-order anharmonic correction added to Franck-Condon factors, both spectrum positions and band shapes can be simultaneously improved for both absorption and fluorescence spectra. It is concluded that the present anharmonic correction produces a significant dynamic shifts for spectrum positions and improves spectrum band shapes as well. The detailed structures of absorption spectrum of S(2)((1)B(2)) state observed from experiment can be also reproduced with anharmonic Franck-Condon simulation, and these were not shown in the harmonic Franck-Condon simulation with either distorted or Duschinsky effects in the literature.

  5. Human and mouse tissue-engineered small intestine both demonstrate digestive and absorptive function.

    PubMed

    Grant, Christa N; Mojica, Salvador Garcia; Sala, Frederic G; Hill, J Ryan; Levin, Daniel E; Speer, Allison L; Barthel, Erik R; Shimada, Hiroyuki; Zachos, Nicholas C; Grikscheit, Tracy C

    2015-04-15

    Short bowel syndrome (SBS) is a devastating condition in which insufficient small intestinal surface area results in malnutrition and dependence on intravenous parenteral nutrition. There is an increasing incidence of SBS, particularly in premature babies and newborns with congenital intestinal anomalies. Tissue-engineered small intestine (TESI) offers a therapeutic alternative to the current standard treatment, intestinal transplantation, and has the potential to solve its biggest challenges, namely donor shortage and life-long immunosuppression. We have previously demonstrated that TESI can be generated from mouse and human small intestine and histologically replicates key components of native intestine. We hypothesized that TESI also recapitulates native small intestine function. Organoid units were generated from mouse or human donor intestine and implanted into genetically identical or immunodeficient host mice. After 4 wk, TESI was harvested and either fixed and paraffin embedded or immediately subjected to assays to illustrate function. We demonstrated that both mouse and human tissue-engineered small intestine grew into an appropriately polarized sphere of intact epithelium facing a lumen, contiguous with supporting mesenchyme, muscle, and stem/progenitor cells. The epithelium demonstrated major ultrastructural components, including tight junctions and microvilli, transporters, and functional brush-border and digestive enzymes. This study demonstrates that tissue-engineered small intestine possesses a well-differentiated epithelium with intact ion transporters/channels, functional brush-border enzymes, and similar ultrastructural components to native tissue, including progenitor cells, whether derived from mouse or human cells.

  6. A census of quasar-intrinsic absorption in the Hubble Space Telescope archive: systems from high-resolution echelle spectra

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Lynch, Ryan S.; Charlton, Jane C.; Eracleous, Michael; Tripp, Todd M.; Palma, Christopher; Sembach, Kenneth R.; Misawa, Toru; Masiero, Joseph R.; Milutinovic, Nikola; Lackey, Benjamin D.; Jones, Therese M.

    2013-10-01

    We present a census of zabs ≲ 2 intrinsic (those showing partial coverage) and associated (zabs ˜ zem) quasar absorption-line systems detected in the Hubble Space Telescope archive of Space Telescope Imaging Spectrograph echelle spectra. This work complements the Misawa et al. survey of 2 < zem < 4 quasars that selects systems using similar techniques. We confirm the existence of so-called strong N V intrinsic systems (where the equivalent width of H I Lyα is small compared to N V λ1238) presented in that work, but find no convincing cases of `strong C IV' intrinsic systems at low redshift/luminosity. Moreover, we also report on the existence of `strong O VI' systems. From a comparison of partial coverage results as a function of ion, we conclude that systems selected by the N V ion have the highest probability of being intrinsic. By contrast, the C IV and O VI ions are poor selectors. Of the 30 O VI systems tested, only two of the systems in the spectrum on 3C 351 show convincing evidence for partial coverage. However, there is an ˜3σ excess in the number of absorbers near the quasar redshift (|Δv| ≤ 5000 km s-1) over absorbers at large redshift differences. In at least two cases, the associated O VI systems are known not to arise close to the accretion disc of the quasar.

  7. Quantitative description of the absorption spectra of the coenzyme in glycogen phosphorylases based on log-normal distribution curves.

    PubMed Central

    Donoso, J; Muñoz, F; Garcia Blanco, F

    1993-01-01

    The absorption spectra of the coenzyme [pyridoxal 5'-phosphate (PLP)] in glycogen phosphorylase a (GPha), glycogen phosphorylase b (GPhb) and of the latter bound to various effectors and substrates were analysed on the basis of log-normal distribution curves. The results obtained showed that the ionization state of the PLP and GPha environment differs from that of GPhb. This divergence was interpreted in terms of tautomeric equilibria between some forms of the Schiff base of PLP and enzymic Lys-679. The ionic forms are slightly more predominant in GPha than they are in GPhb, so ionic and/or hydrogen-bonding interactions between the aromatic ring of PLP and GPha must be stronger than with GPhb. This confirms the purely structural role of the aromatic ring of the coenzyme. Binding of GPhb to AMP and Mg2+ results in the coenzyme adopting a similar state as in GPha. On the other hand, binding to IMP gives rise to no detectable changes in the tautomeric equilibrium of the coenzyme. PMID:8503849

  8. Prediction of High-Valent Iron K-edge Absorption Spectra by Time-Dependent Density Functional Theory

    PubMed Central

    Chandrasekaran, P.; Stieber, S. Chantal E.; Collins, Terrence J.; Que, Lawrence; Neese, Frank; DeBeer, Serena

    2011-01-01

    In recent years a number of high-valent iron intermediates have been identified as reactive species in iron-containing metalloproteins. Inspired by the interest in these highly reactive species, chemists have synthesized Fe(IV) and Fe(V) model complexes with terminal oxo or nitrido groups, as well as a rare example of an Fe(VI)-nitrido species. In all these cases, X-ray absorption spectroscopy has played a key role in the identification and characterization of these species, with both the energy and intensity of the pre-edge features providing spectroscopic signatures for both the oxidation state and the local site geometry. Here we build on a time-dependent DFT methodology for the prediction of Fe K- pre-edge features, previously applied to ferrous and ferric complexes, and extend it to a range of Fe(IV), Fe(V) and Fe(VI) complexes. The contributions of oxidation state, coordination environment and spin state to the spectral features are discussed. These methods are then extended to calculate the spectra of the heme active site of P450 Compound II and the non-heme active site of TauD. The potential for using these methods in a predictive manner is highlighted. PMID:21956429

  9. Solvent Effects on the Electronic Absorption and Fluorescence Spectra of HNP: Estimation of Ground and Excited State Dipole Moments.

    PubMed

    Desai, Vani R; Hunagund, Shirajahammad M; Basanagouda, Mahantesha; Kadadevarmath, Jagadish S; Sidarai, Ashok H

    2016-07-01

    We report the effect of solvents on absorption and fluorescence spectra of biologically active 3(2H)-pyridazinone namely 5-(2-hydroxy-naphthalen-1-yl)-2-phenyl-2H-pyridazin-3-one (HNP) in different solvents at room temperature. The ground and the excited state dipole moments of HNP molecule was estimated from Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations using the solvatochromic shift method. The ground state dipole moment (μ g ) was also estimated by Guggenheim and Higasi method using the dielectric constant and refractive index of solute at different concentrations, the μ g value obtained from these two methods are comparable to the μ g value obtained by the solvatochromic shift method. The excited state dipole moment (μ e ) is greater than the ground state dipole moment (μ g ), which indicates that the excited state is more polar than the ground state. Further, we have evaluated the change in dipole moment (Δμ) from the solvatochromic shift method and on the basis of molecular-microscopic solvent polarity parameter[Formula: see text], later on the values were compared.

  10. Artificial neural networks for retrieving absorption and reduced scattering spectra from frequency-domain diffuse reflectance spectroscopy at short source-detector separation.

    PubMed

    Chen, Yu-Wen; Chen, Chien-Chih; Huang, Po-Jung; Tseng, Sheng-Hao

    2016-04-01

    Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm.

  11. Artificial neural networks for retrieving absorption and reduced scattering spectra from frequency-domain diffuse reflectance spectroscopy at short source-detector separation

    PubMed Central

    Chen, Yu-Wen; Chen, Chien-Chih; Huang, Po-Jung; Tseng, Sheng-Hao

    2016-01-01

    Diffuse reflectance spectroscopy (DRS) based on the frequency-domain (FD) technique has been employed to investigate the optical properties of deep tissues such as breast and brain using source to detector separation up to 40 mm. Due to the modeling and system limitations, efficient and precise determination of turbid sample optical properties from the FD diffuse reflectance acquired at a source-detector separation (SDS) of around 1 mm has not been demonstrated. In this study, we revealed that at SDS of 1 mm, acquiring FD diffuse reflectance at multiple frequencies is necessary for alleviating the influence of inevitable measurement uncertainty on the optical property recovery accuracy. Furthermore, we developed artificial neural networks (ANNs) trained by Monte Carlo simulation generated databases that were capable of efficiently determining FD reflectance at multiple frequencies. The ANNs could work in conjunction with a least-square optimization algorithm to rapidly (within 1 second), accurately (within 10%) quantify the sample optical properties from FD reflectance measured at SDS of 1 mm. In addition, we demonstrated that incorporating the steady-state apparatus into the FD DRS system with 1 mm SDS would enable obtaining broadband absorption and reduced scattering spectra of turbid samples in the wavelength range from 650 to 1000 nm. PMID:27446671

  12. Applicability of the Kubelka-Munk theory for the evaluation of reflectance spectra demonstrated for haemoglobin-free perfused heart tissue.

    PubMed

    Hoffmann, J; Lübbers, D W; Heise, H M

    1998-12-01

    Reflectance spectrometry is a useful tool for studying in vivo kinetic changes in the oxygen saturation of haemoglobin and myoglobin as well as the redox state of cytochromes. A method is given which allows the quantification of tissue reflectance spectra using multicomponent analysis. This method utilizes the Kubelka-Munk theory for modelling the measured tissue spectra. To test this approach, reflectance spectra of a haemoglobin-free perfused guinea pig heart were measured by a fast scanning spectrophotometer (100 spectra/s, spectral resolution 1.0 nm) and evaluated using the component absorbance spectra measured separately. A relative mean spectral residual error of 0.15% was achieved by least-squares fitting. Using statistical error propagation, oxygenation of myoglobin is obtained within a relative precision of 1%, and the redox state of cytochromes aa3 and c are determined simultaneously within a margin of 3%; the results for the redox-state of cytochrome b, however, are less precise. Special component error functions are presented to provide a reliability measure for the concentration prediction using this multicomponent assay. The consistency of the theory and the component absorptivity data is tested by regressing the actual concentrations obtained for each of the redox pair components during the various states of tissue oxygenation. A method is described for the recognition and reduction of systematic errors.

  13. 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.

  14. DEMONSTRATION OF TUMOR-SPECIFIC ANTIGENS IN HUMAN COLONIC CARCINOMATA BY IMMUNOLOGICAL TOLERANCE AND ABSORPTION TECHNIQUES

    PubMed Central

    Gold, Phil; Freedman, Samuel O.

    1965-01-01

    Two methods were used to demonstrate the presence of tumor-specific antigens in adenocarcinomata of the human colon: (a) rabbits were immunized with extracts of pooled colonic carcinomata, and the antitumor antisera thus produced were absorbed with a pooled extract of normal human colon and with human blood components; (b) newborn rabbits were made immunologically tolerant to normal colonic tissue at birth, and were then immunized with pooled tumor material in adult life. Normal and tumor tissues were obtained from the same human donors in order to avoid misinterpretation of results due to individual-specific antigenic differences. The antisera prepared by both methods were tested against normal and tumor antigens by the techniques of agar gel diffusion, immunoelectrophoresis, hemagglutination, PCA, and immunofluorescence. Distinct antibody activity directed against at least two qualitatively tumor-specific antigens, or antigenic determinants, was detected in the antisera prepared by both methods and at least two additional tumor antigens were detected exclusively in antisera prepared by the tolerance technique. Whether these additional antigens were qualitatively different from normal tissue antigens, or merely present in tumor tissue in higher concentrations than in normal tissue has not as yet been determined. Furthermore, it was shown that the tumor-specific antibodies were not directed against bacterial contaminants or against the unusually high concentrations of fibrin found in many neoplastic tissues. It was concluded from these results that the pooled tumor extracts contained tumor-specific antigens not present in normal colonic tissue. Identical tumor-specific antigens were also demonstrated in a number of individual colonic carcinomata obtained from different human donors. PMID:14270243

  15. Clean Coal Technology III: 10 MW Demonstration of Gas Suspension Absorption final project performance and economics report

    SciTech Connect

    Hsu, F.E.

    1995-08-01

    The 10 MW Demonstration of the Gas Suspension Absorption (GSA) program is a government and industry co-funded technology development. The objective of the project is to demonstrate the performance of the GSA system in treating a 10 MW slipstream of flue gas resulting from the combustion of a high sulfur coal. This project involves design, fabrication, construction and testing of the GSA system. The Project Performance and Economics Report provides the nonproprietary information for the ``10 MW Demonstration of the Gas Suspension Absorption (GSA) Project`` installed at Tennessee Valley Authority`s (TVA) Shawnee Power Station, Center for Emissions Research (CER) at Paducah, Kentucky. The program demonstrated that the GSA flue-gas-desulfurization (FGD) technology is capable of achieving high SO{sub 2} removal efficiencies (greater than 90%), while maintaining particulate emissions below the New Source Performance Standards (NSPS), without any negative environmental impact (section 6). A 28-day test demonstrated the reliability and operability of the GSA system during continuous operation. The test results and detailed discussions of the test data can be obtained from TVA`s Final Report (Appendix A). The Air Toxics Report (Appendix B), prepared by Energy and Environmental Research Corporation (EERC) characterizes air toxic emissions of selected hazardous air pollutants (HAP) from the GSA process. The results of this testing show that the GSA system can substantially reduce the emission of these HAP. With its lower capital costs and maintenance costs (section 7), as compared to conventional semi-dry scrubbers, the GSA technology commands a high potential for further commercialization in the United States. For detailed information refer to The Economic Evaluation Report (Appendix C) prepared by Raytheon Engineers and Constructors.

  16. Influence of the pH value of a colloidal gold solution on the absorption spectra of an LSPR-assisted sensor

    SciTech Connect

    Zhu, Jin; Li, Wenbin; Zhu, Mao; Zhang, Wei; Niu, Wencheng; Liu, Guohua

    2014-03-15

    The localized surface plasmon resonances (LSPRs) of gold particles assembled on a crystal plate are a powerful tool for biological sensors. Here, we prepare gold colloids in different pH solutions. We monitor the effects of the particle radius and particle coverage on the absorption spectra of AT-cut (r-face dihedral angle of about 3°) crystal plates supporting gold nanoparticles. The surface morphologies were monitored on silicon dioxide substrates using ultraviolet and visible (UV-vis) spectroscopy, and atomic force microscopy (AFM). The results showed that the gold particle coverage decreases with increasing pH value of the gold colloid solution. This phenomenon demonstrates that self-assembled gold surfaces were formed via the electrostatic adsorption of gold particles on the positively charged, ionized amino groups on the crystal plates in the acidic solution. The spectrum of gold nanoparticles with different coverage degree on the crystal plates showed that the LSPR properties are highly dependent on pH.

  17. Bound excitons and many-body effects in x-ray absorption spectra of azobenzene-functionalized self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Cocchi, Caterina; Draxl, Claudia

    2015-11-01

    We study x-ray absorption spectra of azobenzene-functionalized self-assembled monolayers (SAMs), investigating excitations from the nitrogen K edge. Azobenzene with H-termination and functionalized with CF3 groups is considered. The Bethe-Salpeter equation is employed to compute the spectra, including excitonic effects, and to determine the character of the near-edge resonances. Our results indicate that core-edge excitations are intense and strongly bound: their binding energies range from about 6 to 4 eV, going from isolated molecules to densely-packed SAMs. Electron-hole correlation rules these excitations, while the exchange interaction plays a negligible role.

  18. FIRST ULTRAVIOLET REFLECTANCE SPECTRA OF PLUTO AND CHARON BY THE HUBBLE SPACE TELESCOPE COSMIC ORIGINS SPECTROGRAPH: DETECTION OF ABSORPTION FEATURES AND EVIDENCE FOR TEMPORAL CHANGE

    SciTech Connect

    Stern, S. A.; Spencer, J. R.; Shinn, A.; Cunningham, N. J.; Hain, M. J.

    2012-01-15

    We have observed the mid-UV spectra of both Pluto and its large satellite, Charon, at two rotational epochs using the Hubble Space Telescope (HST) Cosmic Origins Spectrograph (COS) in 2010. These are the first HST/COS measurements of Pluto and Charon. Here we describe the observations and our reduction of them, and present the albedo spectra, average mid-UV albedos, and albedo slopes we derive from these data. These data reveal evidence for a strong absorption feature in the mid-UV spectrum of Pluto; evidence for temporal change in Pluto's spectrum since the 1990s is reported, and indirect evidence for a near-UV spectral absorption on Charon is also reported.

  19. Difference in effect of temperature on absorption and Raman spectra between all-trans-β-carotene and all-trans-retinol

    NASA Astrophysics Data System (ADS)

    Qu, Guan-Nan; Li, Shuo; Sun, Cheng-Lin; Liu, Tian-Yuan; Wu, Yong-Ling; Sun, Shang; Shan, Xiao-Ning; Men, Zhi-Wei; Chen, Wei; Li, Zuo-Wei; Gao, Shu-Qin

    2012-12-01

    Temperature dependencies (81 °C-18 °C) ofvisible absorption and Raman spectra of all-trans-β-carotene and all-trans-retinol extremely diluted in dimethyl sulfoxide are investigated in order to clarify temperature effects on different polyenes. Their absorption spectra are identified to be redshifted with temperature decreasing. Moreover, all-trans-β-carotene is more sensitive to temperature due to the presence of a longer length of conjugated system. The characteristic energy responsible for the conformational changes in all-trans-β-carotene is smaller than that in all-trans-retinol. Both of the Raman scattering cross sections increase with temperature decreasing. The results are explained with electron—phonon coupling theory and coherent weakly damped electron—lattice vibrations model.

  20. FTIR measurements of mid-IR absorption spectra of gaseous fatty acid methyl esters at T=25-500 °C

    NASA Astrophysics Data System (ADS)

    Campbell, M. F.; Freeman, K. G.; Davidson, D. F.; Hanson, R. K.

    2014-09-01

    Gas-phase mid-infrared (IR) absorption spectra (2500-3400 cm-1) for eleven fatty acid methyl esters (FAMEs) have been quantitatively measured at temperatures between 25 and 500 °C using an FTIR spectrometer with a resolution of 1 cm-1. Using these spectra, the absorption cross section at 3.39 μm, corresponding to the monochromatic output of a helium-neon laser, is reported for each of these fuels as a function of temperature. The data indicate that the 3.39 μm cross section values of saturated FAMEs vary linearly with the logarithm of the number of Csbnd H bonds in the molecule.

  1. Mid and Near-IR Absorption Spectra of PAH Neutrals and Ions in H20 Ice to Facilitate their Astronomical Detection

    NASA Technical Reports Server (NTRS)

    Bernstein, Max P.; Sandford, Scott A.; Allamandola, Louis J.

    2004-01-01

    Polycyclic aromatic hydrocarbons (PAHs) are believed to be the most abundant and widespread class of organic compounds in the universe, having been observed in emission towards energetic regions and absorption towards colder ones.We will present IR spectra of PAHs and their cations in H20 ice measured in the laboratory in the hopes that this will facilitate the detection of these features in the interstellar medium.

  2. Polarization angle dependence of stark absorption spectra of spirilloxanthin bound to the reconstituted LH1 complexes using LH1-subunits isolated from the purple photosynthetic bacterium Rhodospirillum rubrum.

    PubMed

    Horibe, Tomoko; Nakagawa, Katsunori; Kusumoto, Toshiyuki; Fujii, Ritsuko; Cogdell, Richard J; Nango, Mamoru; Hashimoto, Hideki

    2012-01-01

    Reconstituted LH1 complexes were prepared using the LH1 subunit-type complexes, isolated from the purple photosynthetic bacterium Rhodospirillum (Rs.) rubrum, and purified all-trans spirilloxanthin. Stark absorption spectra of spirilloxanthin bound to both the native and reconstituted LH1 complexes were compared in different polarization angles (χ) against the external electric field. From the polarization angle dependence of the Stark absorption spectra, two angles were determined in reference to the direction of transition dipole moment (m) of spirilloxanthin: one is the change in polarizability upon photoexcitation (Δα), θ(Δα) and the other is the change in static dipole moment upon photoexcitation (Δμ), θ(Δμ). Despite the symmetric molecular structure of all-trans spirilloxanthin, its Stark absorption spectra show pronounced values of Δμ. This large Δμ values essentially caused by the effect of induced dipole moment through Δα both in the cases for native and reconstituted LH1 complexes. However, slightly different values of θ(Δα) and θ(Δμ) observed for the native LH1 complex suggest that spirilloxanthin is asymmetrically distorted when bound to the native LH1 complex and gives rise to intrinsic Δμ value.

  3. Determining CDOM Absorption Spectra in Diverse Coastal Environments Using a Multiple Pathlength, Liquid Core Waveguide System. Measuring the Absorption of CDOM in the Field Using a Multiple Pathlength Liquid Waveguide System

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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, a(sub CDOM), 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 (r > 0.99) and showed a linear response across all four pathlengths. Values of a(sub CDOM) measured using the MPLCW were virtually identical to spectrophotometer values over a wide range of concentrations. The dynamic range of a(sub CDOM) for MPLCW measurements was 0.002 - 231.5/m. At low CDOM concentrations (a(sub 370) < 0.1/m) spectrophotometric a(sub CDOM) 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. The maximum deviation in replicate MPLCW spectra was less than 0.001 absorbance units. The portability, sampling, and optical characteristics of a MPLCW system provide significant enhancements for routine CDOM absorption measurements in a broad range of natural waters.

  4. Infrared measurements of atmospheric ethane (C2H6) from aircraft and ground-based solar absorption spectra in the 3000/cm region

    NASA Technical Reports Server (NTRS)

    Coffey, M. T.; Mankin, W. G.; Goldman, A.; Rinsland, C. P.; Harvey, G. A.; Devi, V. M.; Stokes, G. M.

    1985-01-01

    A number of prominent Q-branches of the nu-7 band of C2H6 have been identified near 3000/cm in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The ground-based spectra yield a column of 9.0 x 10 to the 15th molecules/sq cm above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv.

  5. Infrared Measurements of Atmospheric Ethane (C2H6) From Aircraft and Ground-Based Solar Absorption Spectra in the 3000/ cm Region

    NASA Technical Reports Server (NTRS)

    Coffey, M. T.; Mankin, W. G.; Goldman, A.; Rinsland, C. P.; Harvey, G. A.; Devi, V. Malathy; Stokes, G. M.

    1985-01-01

    A number or prominent Q-branches or the upsilon(sub 7) band or C2H6 have been identified near 3000/ cm in aircraft and ground-based infrared solar absorption spectra. The aircraft spectra provide the column amount above 12 km at various altitudes. The column amount is strongly correlated with tropopause height and can be described by a constant mixing ratio of 0.46 ppbv in the upper troposphere and a mixing ratio scale height of 3.9 km above the tropopause. The, ground-based spectra yield a column of 9.0 x 10(exp 15) molecules/sq cm above 2.1 km; combining these results implies a tropospheric mixing ratio of approximately 0.63 ppbv.

  6. Absolute absorption coefficient of C6H2 in the mid-UV range at low temperature; implications for the interpretation of Titan atmospheric spectra.

    PubMed

    Bénilan, Y; Bruston, P; Raulin, F; Courtin, R; Guillemin, J C

    1995-01-01

    The interpretation of mid-UV albedo spectra of planetary atmospheres, especially that of Titan, is the main goal of the SIPAT (Spectroscopie uv d'Interet Prebiologique dans l'Atmosphere de Titan) research program. This laboratory experiment has been developed in order to systematically determine the absorption coefficients of molecular compounds which are potential absorbers of scattered sunlight in planetary atmospheres, with high spectral resolution, and at various temperatures below room temperature. From photochemical modelling and experimental simulations, we may expect triacetylene (C6H2) to be present in the atmosphere of Titan, even though it has not yet been detected. We present here the first determination of the absolute absorption coefficient of that compound in the 200-300 nm range and at two temperatures (296 K and 233 K). The temperature dependence of the C6H2 absorption coefficient in that wavelength range is compared to that previously observed in the case of cyanoacetylene (HC3N). We then discuss the implications of the present results for the interpretation of Titan UV spectra, where it appears that large uncertainities can be introduced either by the presence of trace impurities in laboratory samples or by the variations of absorption coefficients with temperature.

  7. 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.

  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. Ultraviolet and infrared absorption spectra of Cr2O3 doped-sodium metaphosphate, lead metaphosphate and zinc metaphosphate glasses and effects of gamma irradiation: a comparative study.

    PubMed

    Marzouk, M A; ElBatal, F H; Abdelghany, A M

    2013-10-01

    The effects of gamma irradiation on spectral properties of Cr2O3-doped phosphate glasses of three varieties, namely sodium metaphosphate, lead metaphosphate and zinc metaphosphate have been investigated. Optical spectra of the undoped samples reveal strong UV absorption bands which are attributed to the presence of trace iron impurities in both the sodium and zinc phosphate glasses while the lead phosphate glass exhibits broad UV near visible bands due to combined absorption of both trace iron impurities and divalent lead ions. The effect of chromium oxide content has been investigated. The three different Cr2O3-doped phosphate glasses reveal spectral visible bands varying in their position and intensity and splitting due to the different field strengths of the Na(+), Pb(2+), Zn(2+) cations, together with the way they are housed in the network and their effects on the polarisability of neighboring oxygens ligands. The effects of gamma irradiation on the optical spectral properties of the various glasses have been compared. The different effects for lead and zinc phosphate are related to the ability of Pb(2+), and Zn(2+) to form additional structural units causing stability of the network towards gamma irradiation. Also, the introduction of the transition metal chromium ions reveals some shielding behavior towards irradiation. Infrared absorption spectra of the three different base phosphate glasses show characteristic vibrations due to various phosphate groups depending on the type of glass and Cr2O3 is observed to slightly affect the IR spectra. Gamma irradiation causes minor variations in some of the intensities of the IR spectra but the main characteristic bands due to phosphate groups remain in their number and position.

  10. Nitrogen K-edge X-ray absorption near edge structure (XANES) spectra of purine-containing nucleotides in aqueous solution

    SciTech Connect

    Shimada, Hiroyuki; Fukao, Taishi; Minami, Hirotake; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

    2014-08-07

    The N K-edge X-ray absorption near edge structure (XANES) spectra of the purine-containing nucleotide, guanosine 5{sup ′}-monophosphate (GMP), in aqueous solution are measured under various pH conditions. The spectra show characteristic peaks, which originate from resonant excitations of N 1s electrons to π* orbitals inside the guanine moiety of GMP. The relative intensities of these peaks depend on the pH values of the solution. The pH dependence is explained by the core-level shift of N atoms at specific sites caused by protonation and deprotonation. The experimental spectra are compared with theoretical spectra calculated by using density functional theory for GMP and the other purine-containing nucleotides, adenosine 5{sup ′}-monophosphate, and adenosine 5{sup ′}-triphosphate. The N K-edge XANES spectra for all of these nucleotides are classified by the numbers of N atoms with particular chemical bonding characteristics in the purine moiety.

  11. Ultraviolet Spectra of Two Magnetic White Dwarfs and Ultraviolet Spectra of Subluminous Objects Found in the Kiso Schmidt Survey and Ultraviolet Absorptions in the Spectra of DA White Dwarfds

    NASA Technical Reports Server (NTRS)

    Wegner, Gary A.

    1988-01-01

    Research under NASA Grant NAG5-287 has carried out a number of projects in conjunction with the International Ultraviolet Explorer (IUE) satellite. These include: (1) studies of the UV spectra of DA white dwarfs which show quasi-molecular bands of H2 and H2(+); (2) the peculiar star HR6560; (3) the UV spectra of two magnetic white dwarfs that also show the quasi-molecular features; (4) investigations of the UV spectra of subluminous stars, primarily identified from visual wavelength spectroscopy in the Kiso survey of UV excess stars, some of which show interesting metal lines in their UV spectra; and (5) completion of studies of UV spectra of DB stars. The main result of this research has been to further knowledge of the structure and compositions of subluminous stars which helps cast light on their formation and evolution.

  12. Energy Spectrum and Optical Absorption Spectra of Fullerene C76 Isomers and Endohedral Metal Complexes on Their Basis Within the Limits of the Concept of a Strongly Correlated State

    NASA Astrophysics Data System (ADS)

    Lebedev, Yu. A.; Lobanov, B. V.; Murzashev, A. I.

    2016-11-01

    The energy spectra of five fullerene C76 isomers are calculated for the Hubbard model in the static fluctuation approximation. Based on the spectra obtained, the optical absorption spectra of pure fullerene C76 represented by the isomer of symmetry D2 and endohedral Lu2@C76, Sm@C76, and DySc2N@C76 metal complexes are calculated. The calculated optical absorption spectra agree qualitatively well with the available experimental data, thereby indicating a need to consider the strong Coulomb interactions in the study of the π-electron fullerene subsystem.

  13. General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra

    SciTech Connect

    Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

    2012-10-08

    Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

  14. Effects of solvent polarity on the absorption and fluorescence spectra of chlorogenic acid and caffeic acid compounds: determination of the dipole moments.

    PubMed

    Belay, Abebe; Libnedengel, Ermias; Kim, Hyung Kook; Hwang, Yoon-Hwae

    2016-02-01

    The effects of solvent polarity on absorption and fluorescence spectra of biologically active compounds (chlorogenic acid (CGA) and caffeic acids (CA)) have been investigated. In both spectra pronounced solvatochromic effects were observed with shift of emission peaks larger than the corresponding UV-vis electronic absorption spectra. From solvatochromic theory the ground and excited-state dipole moments were determined experimentally and theoretically. The differences between the excited and ground state dipole moment determined by Bakhshiev, Kawski-Chamma-Viallet and Reichardt equations are quite similar. The ground and excited-state dipole moments were determined by theoretical quantum chemical calculation using density function theory (DFT) method (Gaussian 09) and were also similar to the experimental results. The HOMO-LUMO energy band gaps for CGA and CFA were calculated and found to be 4.1119 and 1.8732 eV respectively. The results also indicated the CGA molecule is more stable than that of CFA. It was also observed that in both compounds the excited state possesses a higher dipole moment than that of the ground state. This confirms that the excited state of the hydroxycinnamic compounds is more polarized than that of the ground state and therefore is more sensitive to the solvent.

  15. Demonstration of a portable near-infrared CH4 detection sensor based on tunable diode laser absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Zheng, Chuan-Tao; Huang, Jian-Qiang; Ye, Wei-Lin; Lv, Mo; Dang, Jing-Min; Cao, Tian-Shu; Chen, Chen; Wang, Yi-Ding

    2013-11-01

    A portable near-infrared (NIR) CH4 detection sensor based on a distributed feedback (DFB) laser modulated at 1.654 μm is experimentally demonstrated. Intelligent temperature controller with an accuracy of -0.07 to +0.09 °C as well as a scan and modulation module generating saw-wave and cosine-wave signals are developed to drive the DFB laser, and a cost effective lock-in amplifier used to extract the second harmonic signal is integrated. Thorough experiments are carried out to obtain detection performances, including detection range, accuracy, stability and the minimum detection limit (MDL). Measurement results show that the absolute detection error relative to the standard value is less than 7% within the range of 0-100%, and the MDL is estimated to be about 11 ppm under an absorption length of 0.2 m and a noise level of 2 mVpp. Twenty-four hours monitoring on two gas samples (0.1% and 20%) indicates that the absolute errors are less than 7% and 2.5%, respectively, suggesting good long term stability. The sensor reveals competitive characteristics compared with other reported portable or handheld sensors. The developed sensor can also be used for the detection of other gases by adopting other DFB lasers with different center-wavelength using the same hardware and slightly modified software.

  16. [Formation of maxima in the absorption spectrum of carotenoids in the region around 370 nm; consequences for the interpretation of certain action spectra].

    PubMed

    Hager, A

    1970-03-01

    similarity of some action spectra to certain 4-peak, carotenoid spectra is striking. This is true particularly for the action spectrum of the first positive curvature of Avena coleoptile (Fig. 10). On the basis of the described abilities of the carotenoids to form an absorption peak in the wave uv, the appearance of such a maximum in an action spectrum (in the region about 370 nm) can no longer be considered to be sufficient proof for the participation of a flavin as light-acceptor.

  17. 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.

  18. Retrieval of vertical trace gas profiles from ground-based infrared absorption spectra inside and outside the Antarctic vortex using SFIT2

    NASA Astrophysics Data System (ADS)

    Wood, S. W.; Jones, N. B.; Rinsland, C. P.; Goldman, A.; Connor, B. J.; Stephen, T. M.; Lawrence, B. N.; Murcray, F. J.

    2001-05-01

    SFIT2 has been developed by NIWA, NASA Langley and the University of Denver for the retrieval of vertical trace-gas profiles from high-resolution ground-based infrared absorption spectra measured with Fourier transform spectrometers. Such measurements are made at a number of sites around the world as part of the Network for the Detection of Stratospheric Change (NDSC). The vertical profile information in the measurement is due to the pressure broadening of atmospheric absorption lines in the spectra. The retrieval method is optimal estimation, which uses information from the measurement and supplied a priori information to construct an optimal solution based on the assumed uncertainties of these two information sources. We have used SFIT2 to analyse high spectral resolution (0.0035 cm-1) infrared solar absorption spectra recorded at Arrival Heights in Antarctica (78o S), from shortly after sunrise (day 240) to the end of the year in 1999. The motion of the Antarctic vortex, and the chemical processes within it, cause large changes in the vertical profiles of most of the trace gases measured over the site. We have made use of analyses of scaled potential vorticity (sPV) from UKMO data to classify measurements as inside or outside the vortex. This information has been incorporated into the selection of a priori profile information for the analyses of a number of trace gases that are chemically active or act as tracers, including O3, HNO3, N2O, CH4, HCl and ClONO2. The retrieved mixing ratios of these gases in the lower stratosphere show that the station sampled primarily vortex air during the spring period while the vortex existed, but had brief periods outside the vortex near day 290 and again close to vortex breakdown. Comparison with independent measurements, such as the sPV calculations, satellite temperature measurements and correlative TOMS total ozone measurements, are consistent with these retrievals.

  19. Multiconfigurational and DFT analyses of the electromeric formulation and UV-vis absorption spectra of the superoxide adduct of ferrous superoxide reductase.

    PubMed

    Attia, Amr A A; Cioloboc, Daniela; Lupan, Alexandru; Silaghi-Dumitrescu, Radu

    2016-12-01

    The putative initial adduct of ferrous superoxide reductase (SOR) with superoxide has been alternatively formulated as ferric-peroxo or ferrous-superoxo. The ~600-nm UV-vis absorption band proposed to be assigned to this adduct (either as sole intermediate in the SOR catalytic cycle, or as one of the two intermediates) has recently been interpreted as due to a ligand-to-metal charge transfer, involving thiolate and superoxide in a ferrous complex, contrary to an alternative assignment as a predominantly cysteine thiolate-to-ferric charge transfer in a ferric-peroxo electromer. In an attempt to clarify the electromeric formulation of this adduct, we report a computational study using a multiconfigurational complete active space self-consistent field (MC-CASSCF) wave function approach as well as modelling the UV-vis absorption spectra with time-dependent density functional theory (TD-DFT). The MC-CASSCF calculations disclose a weak interaction between iron and the dioxygenic ligand and a dominant configuration with an essentially ferrous-superoxo character. The computed UV-vis absorption spectra reveal a marked dependence on the choice of density functional - both in terms of location of bands and in terms of orbital contributors. For the main band in the visible region, besides the recently reported thiolate-to-superoxide charge transfer, a more salient, and less functional-dependent, feature is a thiolate-to-ferric iron charge transfer, consistent with a ferric-peroxo electromer. By contrast, the computed UV-vis spectra of a ferric-hydroperoxo SOR model match distinctly better (and with no qualitative dependence on the DFT methodology) the 600-nm band as due to a mainly thiolate-to-ferric character - supporting the assignment of the SOR "600-nm intermediate" as a S=5/2 ferric-hydroperoxo species.

  20. 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)

  1. Demonstration of on-sky calibration of astronomical spectra using a 25 GHz near-IR laser frequency comb.

    PubMed

    Ycas, Gabriel G; Quinlan, Franklyn; Diddams, Scott A; Osterman, Steve; Mahadevan, Suvrath; Redman, Stephen; Terrien, Ryan; Ramsey, Lawrence; Bender, Chad F; Botzer, Brandon; Sigurdsson, Steinn

    2012-03-12

    We describe and characterize a 25 GHz laser frequency comb based on a cavity-filtered erbium fiber mode-locked laser. The comb provides a uniform array of optical frequencies spanning 1450 nm to 1700 nm, and is stabilized by use of a global positioning system referenced atomic clock. This comb was deployed at the 9.2 m Hobby-Eberly telescope at the McDonald Observatory where it was used as a radial velocity calibration source for the fiber-fed Pathfinder near-infrared spectrograph. Stellar targets were observed in three echelle orders over four nights, and radial velocity precision of ∼10 m/s (∼6 MHz) was achieved from the comb-calibrated spectra.

  2. The Be K-edge in beryllium oxide and chalcogenides: soft x-ray absorption spectra from first-principles theory and experiment.

    PubMed

    Olovsson, W; Weinhardt, L; Fuchs, O; Tanaka, I; Puschnig, P; Umbach, E; Heske, C; Draxl, C

    2013-08-07

    We have carried out a theoretical and experimental investigation of the beryllium K-edge soft x-ray absorption fine structure of beryllium compounds in the oxygen group, considering BeO, BeS, BeSe, and BeTe. Theoretical spectra are obtained ab initio, through many-body perturbation theory, by solving the Bethe-Salpeter equation (BSE), and by supercell calculations using the core-hole approximation. All calculations are performed with the full-potential linearized augmented plane-wave method. It is found that the two different theoretical approaches produce a similar fine structure, in good agreement with the experimental data. Using the BSE results, we interpret the spectra, distinguishing between bound core-excitons and higher energy excitations.

  3. Study of the absorption spectra of the 4f electron transitions of the praseodymium complex with ciprofloxacin and its analytical application.

    PubMed

    Wei, J; Naixing, W; Quanjie, M; Zhikun, S; Xiuqin, X; Fuxiang, L

    2001-08-01

    Ciprofloxacin (CPFX) is proposed as a reagent for the derivative spectrophotometric determination of praseodymium in mixed rare earths. The absorption spectra of 4f electron transitions of the praseodymium complex with CPFX was studied by normal and derivative spectrophotometry. The stoichiometry of the praseodymium-CPFX complex was calculated by the molar ratio and continuous variations methods. A ratio of Pr to CPFX of 1:3 was found. The absorption bands of the 4f electron transitions of the complex were enhanced markedly. Using the third derivative spectrum. Beer's law was obeyed up to 35 microg cm(-3) of praseodymium. The relative standard deviation is 0.62% for 14 microg cm(-3) of praseodymium. The detection and quantification limits were 0.17 and 0.56 microg cm(-3) of praseodymium, respectively. A method for the direct determination of praseodymium in mixtures of rare earths with good accuracy and selectivity is described.

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

    SciTech Connect

    Noh, Heung-Ryoul; Moon, Han Seb

    2010-09-15

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

  5. The effect of temperature and pressure on optical absorption spectra of transition zone minerals - Implications for the radiative conductivity of the Earth's interior

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    Optical absorption spectra of high-pressure minerals can be used as indirect tools to calculate radiative conductivities of the Earth’s interior [e.g., 1]. Recent high-pressure studies imply 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 might contribute to the heat flow in the Earth’s interior [2]. However, experimental results on temperature effects on radiative heat transfer are not available. We studied the effect of both, pressure and temperature, on the optical absorption of hydrous Fe-bearing ringwoodite, γ-(Mg,Fe)2SiO4, and hydrous Fe-bearing wadsleyite, β-(Mg,Fe)2SiO4, which are the main components of the Earth’s transition zone. Gem-quality single-crystals were synthesized at 18 GPa and 1400 °C in a 5000t multianvil apparatus. Crystals were analyzed by Mössbauer and Raman spectroscopy, electron microprobe analysis and single-crystal X-ray diffraction. For optical absorption measurements in the IR - VIS - UV spectral range (400 - 50000 cm-1) 50 µm sized single-crystals of ringwoodite and wadsleyite were double polished to thicknesses of 13 µm and 18 µm, respectively, and loaded in resistively heated diamond-anvil cells with argon as pressure medium. After taking measurements at high pressure and room temperature, ringwoodite was studied at 26 GPa up to 650 °C and wadsleyite spectra were recorded at 16 GPa up to 450 °C. At ambient pressure the absorption spectrum of ringwoodite reveals a crystal field band (Fe2+) at 12075 cm-1, an intervalence charge transfer band (Fe2+ to Fe3+) at 16491 cm-1, and an absorption edge due to ligand-metal charge transfer close to 30000 cm-1. The wadsleyite spectrum is characterized by a similar absorption edge in the VIS-UV range

  6. First-principles calculation of optical absorption spectra in conjugated polymers: Role of electron-hole interaction

    SciTech Connect

    Rohlfing, Michael; Tiago, M.L.; Louie, Steven G.

    2000-03-20

    Experimental and theoretical studies have shown that excitonic effects play an important role in the optical properties of conjugated polymers. The optical absorption spectrum of trans-polyacetylene, for example, can be understood as completely dominated by the formation of exciton bound states. We review a recently developed first-principles method for computing the excitonic effects and optical spectrum, with no adjustable parameters. This theory is used to study the absorption spectrum of two conjugated polymers: trans-polyacetylene and poly-phenylene-vinylene(PPV).

  7. Modeling of collision-induced infrared absorption spectra of H2 pairs in the first overtone band at temperatures from 20 to 500 K

    NASA Technical Reports Server (NTRS)

    Zheng, Chunguang; Borysow, Aleksandra

    1995-01-01

    A simple formalism is presented that permits quick computations of the low-resolution, rotovibrational collision-induced absorption (RV CIA) spectra of H2 pairs in the first overtone band of hydrogen, at temperatures from 20 to 500 K. These spectra account for the free-free transitions. The sharp dimer features, originating from the bound-free, free-bound, and bound-bound transitions are ignored, though their integrated intensities are properly accounted for. The method employs spectral model line- shapes with parameters computed from the three lowest spectral moments. The moments are obtained from first principles expressed as analytical functions of temperature. Except for the sharp dimer features, which are absent in this model, the computed spectra reproduce closely the results of exact quantum mechanical lineshape computations. Comparisons of the computed spectra with existing experimental data also show good agreement. The work interest for the modeling of the atmospheres of the outer planets in the near-infrared region of the spectrum. The user-friendly Fortran program developed here is available on request from the authors.

  8. DFT/TDDFT investigation on the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of 1-butoxy-4-methoxybenzenepillar[5]arene constitutional isomers.

    PubMed

    Zhang, Jian; Ren, Shuqing

    2016-09-01

    We investigate the chemical reactivities, aromatic properties, and UV-Vis absorption spectra of four constitutional isomers of 1-butoxy-4-methoxybenzenepillar[5]arene with the DFT and TDDFT methods. These characteristics in the gas and solvent phases are discussed on the basis of electronic energy, the highest occupied molecular orbital energy, electrophilicity, global hardness, chemical potential, and nucleus-independent chemical shift. The out-of-plane component of the NICS values reveals that there is a great contrast between aromatic rings of the isomer and benzene. The most intense wavelengths of BMpillar[5]arenes are all made up of delocalized-delocalized π → π* transition.

  9. The Production of Polycyclic Aromatic Hydrocarbon Anions in Inert Gas Matrices Doped with Alkali Metals. Electronic Absorption Spectra of the Pentacene Anion (C22H14(-))

    NASA Technical Reports Server (NTRS)

    Halasinski, Thomas M.; Hudgins, Douglas M.; Salama, Farid; Allamandola, Louis J.; Mead, Susan (Technical Monitor)

    1999-01-01

    The absorption spectra of pentacene (C22H14) and its radical cation (C22H14(+)) and anion (C22H14(-)) isolated in inert-gas matrices of Ne, Ar, and Kr are reported from the ultraviolet to the near-infrared. The associated vibronic band systems and their spectroscopic assignments are discussed together with the physical and chemical conditions governing ion (and counterion) production in the solid matrix. In particular, the formation of isolated pentacene anions is found to be optimized in matrices doped with alkali metal (Na and K).

  10. Quantum-chemical investigation of the structure and electronic absorption spectra of symmetric triphenylamine oligomers conjugated to vinylene, imine, azine, and ethynylene groups

    NASA Astrophysics Data System (ADS)

    Stromylo, E. V.; Baryshnikov, G. V.; Minaev, B. F.; Grigoras, M.

    2015-05-01

    Based on the density functional theory (DFT) and using the B3LYP and BMK hybrid exchange-correlation functionals, we have studied the structure and electronic-spectral properties of some triphenylamine oligomers that contain various π-electron spacers of end groups and that are of interest as electro- and photoactive materials. Good agreement between calculation results and experimental data on absorption spectra in the visible and UV ranges has been obtained. The nature of visible spectral bands has been elucidated based on interrelations with structural changes of oligomer molecules.

  11. Estimation of ground- and excited-state dipole moments of Nile Red dye from solvatochromic effect on absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Bojarski, P.; Kukliński, B.

    2008-10-01

    The effect of various nonpolar and polar solvents on the location of absorption and fluorescence of Nile Red at room temperature was investigated. Based on the batochromic shift of electronic spectra of Nile Red and Bilot-Kawski theory the following values of ground- and excited-state dipole moments μg = 8.2 ± 1.0 D and μe = 10.0 ± 1.0 D were found. The reasons of high discrepancy between the literature results were discussed.

  12. Molecular dynamics simulation and TDDFT study of the structures and UV-vis absorption spectra of MCT-β-CD and its inclusion complexes.

    PubMed

    Lu, Huijuan; Wang, Yujiao; Xie, Xiaomei; Chen, Feifei; Li, Wei

    2015-01-01

    In this research, the inclusion ratios and inclusion constants of MCT-β-CD/PERM and MCT-β-CD/CYPERM inclusion complexes were measured by UV-vis and fluorescence spectroscopy. The inclusion ratios are both 1:1, and the inclusion constants are 60 and 342.5 for MCT-β-CD/PERM and MCT-β-CD/CYPERM, respectively. The stabilities of inclusion complexes were investigated by MD simulation. MD shows that VDW energy plays a vital role in the stability of inclusion complex, and the destruction of inclusion complex is due to the increasing temperature. The UV-vis absorption spectra of MCT-β-CD and its inclusion complexes were studied by time-dependent density functional theory (TDDFT) method employing BLYP-D3, B3LYP-D3 and M06-2X-D3 functionals. BLYP-D3 well reproduces the UV-vis absorption spectrum and reveals that the absorption bands of MCT-β-CD mainly arise from n→π(∗) and n→σ(∗) transition, and those of inclusion complexes mainly arise from intramolecular charge transfer (ICT). ICT results in the shift of main absorption bands of MCT-β-CD.

  13. 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.

  14. Review of the absorption spectra of solid O2 and N2 as they relate to contamination of a cooled infrared telescope

    NASA Technical Reports Server (NTRS)

    Smith, S. M.

    1977-01-01

    During contamination studies for the liquid helium cooled shuttle infrared telescope facility, a literature search was conducted to determine the absorption spectra of the solid state of homonuclear molecules of O2 and N2, and ascertain what laboratory measurements of the solid have been made in the infrared. With the inclusion of one unpublished spectrum, the absorption spectrum of the solid oxygen molecule has been thoroughly studied from visible to millimeter wavelengths. Only two lines appear in the solid that do not also appear in the gas or liquid. A similar result is implied for the solid nitrogen molecule because it also is homonuclear. The observed infrared absorption lines result from lattice modes of the alpha phase of the solid, and disappear at the warmer temperatures of the beta, gamma, and liquid phases. They are not observed from polycrystalline forms of O2, while strong scattering is. Scattering, rather than absorption, is considered to be the principal natural contamination problem for cooled infrared telescopes in low earth orbit.

  15. Assessment of mode-mixing and Herzberg-Teller effects on two-photon absorption and resonance hyper-Raman spectra from a time-dependent approach.

    PubMed

    Ma, HuiLi; Zhao, Yi; Liang, WanZhen

    2014-03-07

    A time-dependent approach is presented to simulate the two-photon absorption (TPA) and resonance hyper-Raman scattering (RHRS) spectra including Duschinsky rotation (mode-mixing) and Herzberg-Teller (HT) vibronic coupling effects. The computational obstacles for the excited-state geometries, vibrational frequencies, and nuclear derivatives of transition dipole moments, which enter the expressions of TPA and RHRS cross sections, are further overcome by the recently developed analytical excited-state energy derivative approaches in the framework of time-dependent density functional theory. The excited-state potential curvatures are evaluated at different levels of approximation to inspect the effects of frequency differences, mode-mixing and HT on TPA and RHRS spectra. Two types of molecules, one with high symmetry (formaldehyde, p-difluorobenzene, and benzotrifluoride) and the other with non-centrosymmetry (cis-hydroxybenzylidene-2,3-dimethylimidazolinone in the deprotonated anion state (HDBI(-))), are used as test systems. The calculated results reveal that it is crucial to adopt the exact excited-state potential curvatures in the calculations of TPA and RHRS spectra even for the high-symmetric molecules, and that the vertical gradient approximation leads to a large deviation. Furthermore, it is found that the HT contribution is evident in the TPA and RHRS spectra of HDBI(-) although its one- and two-photon transitions are strongly allowed, and its effect results in an obvious blueshift of the TPA maximum with respect to the one-photon absorption maximum. With the HT and solvent effects getting involved, the simulated blueshift of 1291 cm(-1) agrees well with the experimental measurement.

  16. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies

    PubMed Central

    El-Shishtawy, Reda M.; Elroby, Shaaban A.; Asiri, Abdullah M.; Müllen, Klaus

    2016-01-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1–SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (−4.26 eV) of the conduction band of TiO2 nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO2 in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices. PMID:27043556

  17. Optical Absorption Spectra and Electronic Properties of Symmetric and Asymmetric Squaraine Dyes for Use in DSSC Solar Cells: DFT and TD-DFT Studies.

    PubMed

    El-Shishtawy, Reda M; Elroby, Shaaban A; Asiri, Abdullah M; Müllen, Klaus

    2016-04-01

    The electronic absorption spectra, ground-state geometries and electronic structures of symmetric and asymmetric squaraine dyes (SQD1-SQD4) were investigated using density functional theory (DFT) and time-dependent (TD-DFT) density functional theory at the B3LYP/6-311++G** level. The calculated ground-state geometries reveal pronounced conjugation in these dyes. Long-range corrected time dependent density functionals Perdew, Burke and Ernzerhof (PBE, PBE1PBE (PBE0)), and the exchange functional of Tao, Perdew, Staroverov, and Scuseria (TPSSh) with 6-311++G** basis set were employed to examine optical absorption properties. In an extensive comparison between the optical data and DFT benchmark calculations, the BEP functional with 6-311++G** basis set was found to be the most appropriate in describing the electronic absorption spectra. The calculated energy values of lowest unoccupied molecular orbitals (LUMO) were 3.41, 3.19, 3.38 and 3.23 eV for SQD1, SQD2, SQD3, and SQD4, respectively. These values lie above the LUMO energy (-4.26 eV) of the conduction band of TiO₂ nanoparticles indicating possible electron injection from the excited dyes to the conduction band of the TiO₂ in dye-sensitized solar cells (DSSCs). Also, aromaticity computation for these dyes are in good agreement with the data obtained optically and geometrically with SQD4 as the highest aromatic structure. Based on the optimized molecular geometries, relative positions of the frontier orbitals, and the absorption maxima, we propose that these dyes are suitable components of photovoltaic DSSC devices.

  18. Amorphous solid dispersion of berberine with absorption enhancer demonstrates a remarkable hypoglycemic effect via improving its bioavailability.

    PubMed

    Zhaojie, Meng; Ming, Zhang; Shengnan, Wei; Xiaojia, Bi; Hatch, Grant M; Jingkai, Gu; Li, Chen

    2014-06-05

    Low oral bioavailability of berberine due to poor solubility and membrane permeability limits its clinical use for treatment of diabetes. We developed an amorphous solid dispersion of berberine with absorption enhancer sodium caprate, referred to as Huang-Gui Solid Dispersion (HGSD) preparations, and examined them for improvement of dissolution and oral bioavailability. HGSDs were prepared by solvent evaporation, and the formulations of amorphous solid dispersions were characterized by X-ray diffraction, differential scanning calorimetry and scanning electron microscopy. According to in vitro solubility and dissolution studies, P9, the 9th production of HGSDs based on orthogonal test, was sorted out. Then pharmacokinetic behavior of P9 was evaluated by in vitro membrane permeation, in situ intestinal perfusion, and in vivo bioavailability in rats. Furthermore, the anti-diabetic effect of P9 was examined in a type 2 diabetic rat model. It was found that majority of berberine in P9 existed in an amorphous form, and its solubility and dissolution rate were significantly increased. Pharmacokinetic studies demonstrated a 3-fold increase in in vitro membrane permeation, a 4-fold increase in in situ intestinal perfusion and a 5-fold increase in vivo bioavailability of P9 compared to berberine or berberine tablets. In addition, oral administration of P9 (100mg/kg) improved glucose and lipid metabolism in diabetic rats compared to pure berberine (100mg/kg), berberine tablets (100mg/kg) or metformin (300 mg/kg) treatment. These findings indicate that P9 enhances oral bioavailability of berberine and may be a potential candidate drug for treatment of diabetes.

  19. Excitations, optical absorption spectra, and optical excitonic gaps of heterofullerenes: I. C60, C59N+ and C48N12

    SciTech Connect

    Xie, R; Bryant, G W; Sun, G; C.Nicklaus, M; Heringer, D; Frauenheim, T; Manaa, M R; Smith, Jr., V H; Araki, Y; Ito, O

    2003-10-02

    Low-energy excitations and optical absorption spectrum of C{sub 60} are computed by using time-dependent (TD) Hartree-Fock (HF), TD-density functional theory (TD-DFT), TD-DFT-based tight-binding (TD-DFT-TB) and a semiempirical ZINDO method. A detailed comparison of experiment and theory for the excitation energies, optical gap and absorption spectrum of C{sub 60} is presented. It is found that electron correlations and collective effects of exciton pairs play important roles in assigning accurately the spectral features of C{sub 60} and the TD-DFT method with non-hybrid functionals or a local spin density approximation leads to more accurate excitation energies than with hybrid functionals. The level of agreement between theory and experiment for C{sub 60} justifies similar calculations of the excitations and optical absorption spectrum of a monomeric azafullerene cation C{sub 59}N{sup +} exhibits distinguishing spectral features different from C{sub 60}: (1) the first singlet is dipole-allowed and the optical gap is redshifted by 1.44 eV; (2) several weaker absorption maxima occur in the visible region; (3) the transient triplet-triplet absorption at 1.60 eV (775 nm) is much broader and the decay of the triplet state is much faster. The calculated spectra of C{sub 59}N{sup +} characterize and explain well our measured ultraviolet-visible (UV-vis) and transient absorption spectra of the carborane anion salt [C{sub 59}N][Ag(CB{sub 11}H{sub 6}Cl{sub 6}){sub 2}]. For the most stable isomer of C{sub 48}N{sub 12}, we predict that the first singlet is dipole-allowed, the optical gap is redshifted by 1.22 eV relative to that of C{sub 60}, and optical absorption maxima occur at 585, 528, 443, 363, 340, 314 and 303 nm. We point out that the characterization of the UV-vis and transient absorption spectra of C{sub 48}N{sub 12} isomers is helpful in distinguishing the isomer structures required for applications in molecular electronics. For C{sub 59}N{sup +} and C{sub 48}N

  20. The origin of the absorption spectra of porphyrin N- and dithiaporphyrin S-oxides in their neutral and protonated states.

    PubMed

    Bruhn, Torsten; Brückner, Christian

    2015-02-07

    meso-Tetraphenylporphyrin N-oxide (1) and meso-tetraphenyl-21,23-dithiaporphyrin S-oxide (3) possess optical spectra that are distinctly different from their parent porphyrins, meso-tetraphenylporphyrin (2) and meso-tetraphenyl-21,23-dithiaporphyrin (4), respectively. The hyperporphyrin spectra were reproduced and classified using TD CAM-B3LYP and SCS-CC2 computational methods. Calculations revealed the electronic and conformational influences of the N- and S-oxide functionalities. While the N-oxide under acidic conditions forms a dication with a UV-vis spectrum that is nearly indistinguishable from that of the diprotonated parent porphyrin, the diprotonated S-oxide possesses a much different UV-vis spectrum from diprotonated parent dithiaporphyrin. A computational study of the protonation events revealed the site and degree of protonation and rationalized the regular and hyperporphyrin UV-vis spectra of the neutral and protonated species, respectively. The study illuminates the electronic effects of the relatively rare modification of the inner porphyrin heteroatoms. It also illustrates a case in which TD CAM-B3LYP reaches its limits to make reliable predictions about the optical properties of a porphyrinoid, making the use of higher methods essential.

  1. 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.

  2. Absorption spectra of vanadyl ion doped in MgNH 4PO 4·6H 2O (struvite) crystal

    NASA Astrophysics Data System (ADS)

    Agarwal, O. P.; Chand, Prem

    1984-10-01

    Results of Electron Paramagnetic Resonance (EPR) and optical absorption studies of VO 2+ ion doped in struvite at room liquid nitrogen temperatures are reported. Three preferential V= O bond directions in the crystal have been identified. The optical and EPR data have shown the formation of NH 4(PO 4VO(H 2O) 5 complex in the crystal as a result of VO 2+ doping. Correlating the optical and EPR data the molecular orbital coefficients are also obtained and discussed.

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

    NASA Technical Reports Server (NTRS)

    Kostyk, R. I.

    1974-01-01

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

  4. Spectral response of the intrinsic region of a GaAs-InAs quantum dot solar cell considering the absorption spectra of ideal cubic dots

    NASA Astrophysics Data System (ADS)

    Biswas, Sayantan; Chatterjee, Avigyan; Biswas, Ashim Kumar; Sinha, Amitabha

    2016-10-01

    Recently, attempts have been made by some researchers to improve the efficiency of quantum dot solar cells by incorporating different types of quantum dots. In this paper, the photocurrent density has been obtained considering the absorption spectra of ideal cubic dots. The effects of quantum dot size dispersion on the spectral response of the intrinsic region of a GaAs-InAs quantum dot solar cell have been studied. The dependence of the spectral response of this region on the size of quantum dots of such solar cell has also been investigated. The investigation shows that for smaller quantum dot size dispersion, the spectral response of the intrinsic region of the cell increases significantly. It is further observed that by enlarging the quantum dot size it is possible to enhance the spectral response of such solar cells as it causes better match between absorption spectra of the quantum dots and the solar spectrum. These facts indicate the significant role of quantum dot size and size dispersion on the performance of such devices. Also, the power conversion efficiency of such solar cell has been studied under 1 sun, AM 1.5 condition.

  5. Solvatochromic effect in absorption and emission spectra of star-shaped bipolar derivatives of 1,3,5-triazine and carbazole. A time-dependent density functional study.

    PubMed

    Baryshnikov, Gleb V; Bondarchuk, Sergey V; Minaeva, Valentina A; Ågren, Hans; Minaev, Boris F

    2017-02-01

    A series of three star-shaped compounds containing both donor (carbazole) and acceptor (2,4,6-triphenyl-1,3,5-triazine) moieties linked through various linking bridges was studied theoretically at the linear response TD-DFT level of theory to describe their absorption and fluorescence spectra. The concept of a localized charge-transfer excited state has been applied successfully to explain the observed strong solvatochromic effect in the emission spectra of the studied molecules, which can be utilized for the fabrication of color tunable solution-processable OLEDs. The concept is in particularly applicable to donor-acceptor species with a C 3 symmetry point group where the static dipole moment changes dramatically upon electronic excitation. An important peculiarity of the studied molecules is that they are characterized by non-zero values of the HOMO and LUMO orbitals in the same common part of molecular space that provides a large electric dipole transition moment for both light absorption and emission. Graphical abstract Star-shaped C 3 symmetry point group derivatives for color tunable OLEDs.

  6. A 2A2<--X 2B1 absorption and Raman spectra of the OClO molecule: A three-dimensional time-dependent wave packet study

    NASA Astrophysics Data System (ADS)

    Sun, Zhigang; Lou, Nanquan; Nyman, Gunnar

    2005-02-01

    Time-dependent wave packet calculations of the (A 2A2←X 2B1) absorption and Raman spectra of the OClO molecule are reported. The Fourier grid Hamiltonian method in three dimensions is employed. The X 2B1 ground state ab initio potential energy surface reported by Peterson [J. Chem. Phys. 109, 8864 (1998)] is used together with his corresponding A 2A2 state surface or the revised surface of the A 2A2 state by Xie and Guo [Chem. Phys. Lett. 307, 109 (1999)]. Radau coordinates are used to describe the vibrations of a nonrotating OClO molecule. The split-operator method combined with fast Fourier transform is applied to propagate the wave function. We find that the ab initio A 2A2 potential energy surface better reproduces the detailed structures of the absorption spectrum at long wavelength, while the revised surface of the A 2A2 state, consistent with the work of Xie and Guo, better reproduces the overall shape and the energies of the vibrational levels. Both surfaces of the A 2A2 state can reasonably reproduce the experimental Raman spectra but neither does so in detail for the numerical model employed in the present work.

  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. Tailored pump-probe transient spectroscopy with time-dependent density-functional theory: controlling absorption spectra

    NASA Astrophysics Data System (ADS)

    Walkenhorst, Jessica; De Giovannini, Umberto; Castro, Alberto; Rubio, Angel

    2016-05-01

    Recent advances in laser technology allow us to follow electronic motion at its natural time-scale with ultra-fast time resolution, leading the way towards attosecond physics experiments of extreme precision. In this work, we assess the use of tailored pumps in order to enhance (or reduce) some given features of the probe absorption (for example, absorption in the visible range of otherwise transparent samples). This type of manipulation of the system response could be helpful for its full characterization, since it would allow us to visualize transitions that are dark when using unshaped pulses. In order to investigate these possibilities, we perform first a theoretical analysis of the non-equilibrium response function in this context, aided by one simple numerical model of the hydrogen atom. Then, we proceed to investigate the feasibility of using time-dependent density-functional theory as a means to implement, theoretically, this absorption-optimization idea, for more complex atoms or molecules. We conclude that the proposed idea could in principle be brought to the laboratory: tailored pump pulses can excite systems into light-absorbing states. However, we also highlight the severe numerical and theoretical difficulties posed by the problem: large-scale non-equilibrium quantum dynamics are cumbersome, even with TDDFT, and the shortcomings of state-of-the-art TDDFT functionals may still be serious for these out-of-equilibrium situations.

  9. Ultraviolet-visible absorption spectra of N-doped TiO2 film deposited on sapphire

    NASA Astrophysics Data System (ADS)

    Park, Jaewon; Lee, Jung-Yup; Cho, Jun-Hyung

    2006-12-01

    The optical-response properties of nitrogen(N)-doped titanium dioxide (TiO2) films are investigated by means of a combination of ultraviolet-visible absorption spectroscopy and first-principles density-functional calculations. The TiO2 films were epitaxially grown on the sapphire substrate by the pulsed laser deposition method. The doping of N atoms was achieved by 70keV of N+ ion implantation, followed by postirradiation heat treatment at 550°C for 2h in air. We find that when 5×1016 (1×1017)Nions/cm2 were implanted into the epitaxially grown TiO2 film, the absorption edge is reproducibly shifted to lower energy by about 0.06 (0.12)eV together with a significant optical absorption extending into the visible-light region. These experimental data can be explained by our calculated band structure of N-doped TiO2, where the bands originating from N 2p states locate above the valence band edge, while the band gap narrowing due to the mixing of N with O 2p states is 0.04eV.

  10. Ab Initio Study of the Effects of Surface Chemistry and Size on Xray Absorption Spectra of CdSe Nanoparticles

    NASA Astrophysics Data System (ADS)

    Whitley, Heather; Prendergast, David; Ogitsu, Tadashi; Schwegler, Eric

    2009-03-01

    The specificity of their opto-electronic properties with respect to size, shape, and surface chemistry, as well as cost-effective solution based methods of synthesis, make CdSe nanoparticles a material of choice for use in novel opto-electronic devices, such as photovoltaics and field effect transistors. Developing methods by which these nanomaterials can be systematically engineered to meet specific device goals is largely dependent on understanding how surface passivation and reconstruction affect the properties of a given nanomaterial. Xray absorption spectroscopy (XAS) is an ideal method for structural analysis, but its application to studying nanomaterial surfaces is nontrivial due to the convolution of the absorption of surface atoms with those within the nanomaterial. We utilize ab initio methods to investigate the dependence of the Cd L-edge xray absorption cross-section on the size and passivation for Cd atoms both at the surface and within the core of CdSe nanomaterials. We aim to enable routine surface characterization of CdSe nanomaterials via XAS. Prepared by LLNL under Contract DE-AC52 07NA27344.

  11. 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.

  12. Simulating the absorption spectra of helium clusters (N = 70, 150, 231, 300) using a charge transfer correction to superposition of fragment single excitations.

    PubMed

    Ge, Qinghui; Mao, Yuezhi; White, Alec F; Epifanovsky, Evgeny; Closser, Kristina D; Head-Gordon, Martin

    2017-01-28

    Simulations of the n = 2 absorption spectra of HeN (N = 70, 150, 231, 300) clusters are reported, with nuclear configurations sampled by path integral molecular dynamics. The electronic structure is treated by a new approach, ALMO-CIS+CT, which is a formulation of configuration interaction singles (CIS) based on absolutely localized molecular orbitals (ALMOs). The method generalizes the previously reported ALMO-CIS model [K. D. Closser et al. J. Chem. Theory Comput. 11, 5791 (2015)] to include spatially localized charge transfer (CT) effects. It is designed to recover large numbers of excited states in atomic and molecular clusters, such as the entire n = 2 Rydberg band in helium clusters. ALMO-CIS+CT is shown to recover most of the error caused by neglecting charge transfer in ALMO-CIS and has comparable accuracy to standard CIS for helium clusters. For the n = 2 band, CT stabilizes states towards the blue edge by up to 0.5 eV. ALMO-CIS+CT retains the formal cubic scaling of ALMO-CIS with respect to system size. With improvements to the implementation over that originally reported for ALMO-CIS, ALMO-CIS+CT is able to treat helium clusters with hundreds of atoms using modest computing resources. A detailed simulation of the absorption spectra associated with the 2s and 2p bands of helium clusters up to 300 atoms is reported, using path integral molecular dynamics with a spherical boundary condition to generate atomic configurations at 3 K. The main features of experimentally reported fluorescence excitation spectra for helium clusters are reproduced.

  13. Simulating the absorption spectra of helium clusters (N = 70, 150, 231, 300) using a charge transfer correction to superposition of fragment single excitations

    NASA Astrophysics Data System (ADS)

    Ge, Qinghui; Mao, Yuezhi; White, Alec F.; Epifanovsky, Evgeny; Closser, Kristina D.; Head-Gordon, Martin

    2017-01-01

    Simulations of the n = 2 absorption spectra of HeN (N = 70, 150, 231, 300) clusters are reported, with nuclear configurations sampled by path integral molecular dynamics. The electronic structure is treated by a new approach, ALMO-CIS+CT, which is a formulation of configuration interaction singles (CIS) based on absolutely localized molecular orbitals (ALMOs). The method generalizes the previously reported ALMO-CIS model [K. D. Closser et al. J. Chem. Theory Comput. 11, 5791 (2015)] to include spatially localized charge transfer (CT) effects. It is designed to recover large numbers of excited states in atomic and molecular clusters, such as the entire n = 2 Rydberg band in helium clusters. ALMO-CIS+CT is shown to recover most of the error caused by neglecting charge transfer in ALMO-CIS and has comparable accuracy to standard CIS for helium clusters. For the n = 2 band, CT stabilizes states towards the blue edge by up to 0.5 eV. ALMO-CIS+CT retains the formal cubic scaling of ALMO-CIS with respect to system size. With improvements to the implementation over that originally reported for ALMO-CIS, ALMO-CIS+CT is able to treat helium clusters with hundreds of atoms using modest computing resources. A detailed simulation of the absorption spectra associated with the 2s and 2p bands of helium clusters up to 300 atoms is reported, using path integral molecular dynamics with a spherical boundary condition to generate atomic configurations at 3 K. The main features of experimentally reported fluorescence excitation spectra for helium clusters are reproduced.

  14. Two-channel opto-acoustic diode laser spectrometer and fine structure of methane absorption spectra in 6070-6180 cm-1 region.

    PubMed

    Kapitanov, V A; Ponomarev, Yu N; Tyryshkin, I S; Rostov, A P

    2007-04-01

    We describe the hardware and software of the high-sensitive two-channel opto-acoustic spectrometer with a near infrared diode laser. A semiconductor TEC-100 laser with outer resonator generates a continuous single-frequency radiation in the range of 6040-6300 cm-1 with spectral resolution better that 10 MHz. The newly designed model of photo-acoustic cells in the form of a ring type resonator was used in the spectrometer, and the system allows the measurement of a weak absorption coefficient equal to 1.4x10(-7) cm-1 Hz-1/2 with a laser radiation power of 0.003 W. The methane absorption spectra within a range of 6080-6180 cm-1 were measured with a spectral resolution of 10 MHz and the signal to noise ratio more than 10(3). Six hundred absorption lines were recorded, which is twice as many as in HITRAN-2004. The accurate measurements of the half-width and shift of methane unresolved triplet R3 of 2nu3 band permit us to determine values of the broadening and shift coefficients for CH4-air, CH4-N2, and CH4-SF6 mixtures.

  15. Absorption spectra and nonlinear transmission (at λ = 2940 nm) of a diffusion-doped Fe{sup 2+}:ZnSe single crystal

    SciTech Connect

    Bufetova, G A; Gulyamova, E S; Il'ichev, N N; Pashinin, P P; Shapkin, P V; Nasibov, A S

    2015-06-30

    Transmission spectra of a ZnSe sample diffusion-doped with Fe{sup 2+} ions have been measured in the wavelength range 500 – 7000 nm. A broad absorption band in the range 500 – 1500 nm has been observed in both doped and undoped regions of the sample. This band is possibly due to deviations from stoichiometry in the course of diffusion doping. The transmission of the Fe{sup 2+}:ZnSe sample at a wavelength of 2940 nm has been measured at various dopant concentrations and high peak pulse intensities (up to 8 MW cm{sup -2}). The samples have been shown to be incompletely bleached: during a laser pulse, the transmission first increases, reaches a maximum, and then falls off. Our results suggest that the incomplete bleaching cannot be accounted for by excited-state absorption. The incomplete bleaching (as well as the transmission maximum) is due to the heating of the sample, which leads to a reduction in upper level lifetime and, accordingly, to an increase in absorption saturation intensity. (nonlinear optical phenomena)

  16. A model predicting the evolution of ice particle size spectra and radiative properties of cirrus clouds. Part 2: Dependence of absorption and extinction on ice crystal morphology

    NASA Technical Reports Server (NTRS)

    Mitchell, David L.; Arnott, W. Patrick

    1994-01-01

    geometrical properties of ice crystals before the influence of ice crystal shape on cirrus radiative properties can be adequately understood. This study provides a way of coupling the radiative properties of absorption, extinction, and single scatter albedo to the microphysical properties of cirrus clouds. The dependence of extinction and absorption on ice crystal shape was not just due to geometrical differences between crystal types, but was also due to the effect these differences had on the evolution of ice particle size spectra. The ice particle growth model in Part 1 and the radiative properties treated here are based on analytical formulations, and thus represent a computationally efficient means of modeling the microphysical and radiative properties of cirrus clouds.

  17. Visible spectral dependence of the scattering and absorption coefficients of pigmented coatings from inversion of diffuse reflectance spectra.

    PubMed

    Curiel, Fernando; Vargas, William E; Barrera, Rubén G

    2002-10-01

    A spectral-projected gradient method and an extension of the Kubelka-Munk theory are applied to obtain the relevant parameters of the theory from measured diffuse reflectance spectra of pigmented samples illuminated with visible diffuse radiation. The initial estimate of the spectral dependence of the parameters, required by a recursive spectral-projected gradient method, was obtained by use of direct measurements and up-to-date theoretical estimates. We then tested the consistency of the Kubelka-Munk theory by repeating the procedure with samples of different thicknesses.

  18. Modeling of pressure-induced far-infrared absorption spectra Molecular hydrogen pairs. [in outer planets atmospheres

    NASA Technical Reports Server (NTRS)

    Borysow, J.; Trafton, L.; Frommhold, L.; Birnbaum, G.

    1985-01-01

    Meyer et al. (1985) have calculated the accurate induced dipole moment function of H2-H2 from first principles, using highly correlated wave functions for the first time in such work. The present paper is concerned with the collision-induced translational-rotational absorption coefficient for molecular hydrogen pairs, taking into account computations on the basis of the fundamental theory considered by Meyer et al. Data have been obtained for temperatures in the range from 40 to 300 K. Criteria are developed for choosing among various model line shapes. It is found that certain models are capable of approximating the quantum profiles closely, with rms errors of only a few percent.

  19. A Novel Method for Characterizing the Diameter of Single-Wall Carbon Nanotubes by Optical Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Saito, Takeshi; Ohmori, Shigekazu; Shukla, Bikau; Yumura, Motoo; Iijima, Sumio

    2009-09-01

    The potentiality of optical absorption spectroscopy (OAS) for the estimation of mean diameter of single-wall carbon nanotubes (SWCNTs) from electronic transition energies has been explored. The observed dependence of electronic transition energies of both metallic and semiconducting SWCNTs on their mean diameters clearly showed that transition energies scale inversely with the tube diameter. In the present study, the applicability of this estimation method has been experimentally confirmed for the diameter range of 1-2 nm and is expected to be useful for the characterization of wide range of diameters of SWNCTs.

  20. Modelling the Emission And/or Absorption Features in the High Resolution Spectra of the Southern Binary System: HH Car

    NASA Astrophysics Data System (ADS)

    Koseoglu, Dogan; Bakış, Hicran

    2016-07-01

    High-resolution spectra (R=48000) of the southern close binary system, HH Car, has been analyzed with modern analysis techniques. Precise absolute parameters were derived from the simultaneous solution of the radial velocity, produced in this study and the light curves, published. According to the results of these analyses, the primary component is an O9 type main sequence star while the secondary component is a giant/subgiant star with a spectral type of B0. Hα emissions can be seen explicitly in the spectra of HH Car. These features were modelled using the absolute parameters of the components. Since components of HH Car are massive early-type stars, mass loss through stellar winds can be expected. This study revealed that the components of HH Car have stellar winds and the secondary component loses mass to the primary. Stellar winds and the gas stream between the components were modelled as a hot shell around the system. It is determined that the interaction between the winds and the gas stream leads to formation of a high temperature impact region.

  1. Prediction of the Ultraviolet-Visible Absorption Spectra of Polycyclic Aromatic Hydrocarbons (Dibenzo and Naphtho) Derivatives of Fluoranthene.

    PubMed

    Oña-Ruales, Jorge O; Ruiz-Morales, Yosadara

    2016-09-26

    The annellation theory method has been used to predict the locations of maximum absorbance (LMA) of the ultraviolet-visible (UV-Vis) spectral bands in the group of polycyclic aromatic hydrocarbons (PAHs) C24H14 (dibenzo and naphtho) derivatives of fluoranthene (DBNFl). In this group of 21 PAHs, ten PAHs present a sextet migration pattern with four or more benzenoid rings that is potentially related to a high molecular reactivity and high mutagenic conduct. This is the first time that the locations of maximum absorbance in the UV-Vis spectra of naphth[1,2-a]aceanthrylene, dibenz[a,l]aceanthrylene, indeno[1,2,3-de]naphthacene, naphtho[1,2-j]fluoranthene, naphth[2,1-e]acephenanthrylene, naphth[2,1-a]aceanthrylene, dibenz[a,j]aceanthrylene, naphth[1,2-e]acephenanthrylene, and naphtho[2,1-j]fluoranthene have been predicted. Also, this represents the first report about the application of the annellation theory for the calculation of the locations of maximum absorbance in the UV-Vis spectra of PAHs with five-membered rings. Furthermore, this study constitutes the premier investigation beyond the pure benzenoid classical approach toward the establishment of a generalized annellation theory that will encompass not only homocyclic benzenoid and non-benzenoid PAHs, but also heterocyclic compounds.

  2. 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.

  3. Integrated intensity of continuous absorption in infrared spectra of complexes with medium-strong and strong hydrogen bonds

    NASA Astrophysics Data System (ADS)

    Dega-Szafran, Zofia; Hrynio, Andrej; Szafran, Miroslaw

    A simple, nongraphical and reproducible method of separation of the complex absorption due to strong hydrogen bonds from that due to the skeleton is proposed. The method has been tested on 17 complexes of pyridine N-oxide, triphenylphosphine oxide and DMSO- d6 with dichloroacetic acid in dry dichloromethane and acetonitrile. The integrated intensity ( ACPA) and the centre of gravity (mathtype1) of complex absorption due to protonic vibration were measured and correlated with p Ka values of bases and chemical shifts of the hydrogen-bonded protons (δ), and discussed with respect to hydrogen bond strength variations. The ACPA values vary from 17.5 to 46 x 10 4 cm mmol -1 and were reproducible to within ± 1 x 10 4 cm mmol -1 (5-15 %). A nonlinear correlation between A CPA and (mathtype2) has been found in wide region of data; (mathtype3) varies from 500 to 2300 cm -1. A gradual proton transfer has been considered from the acid to pyridine N-oxides via strengthening intermolecular H-bonds, AH⋯ON, and further via weakening interionic H-bonds, A -⋯ HON +. The obtained correlations suggest that variations of hydrogen bond strength caused similar changes of A CPA and (mathtype4) both in molecular (A-H⋯B) and ionic (A -⋯H-B +) species.

  4. Absorption, Fluorescence and Emission Anisotropy Spectra of 4-Cyano-N,N-dimethylaniline in Different Media and at Different Temperatures

    NASA Astrophysics Data System (ADS)

    Kawski, A.; Piszczek, G.

    1997-05-01

    The effect of temperature on fluorescence and emission anisotropy spectra of 4-cyano-N,N-dimethylaniline (CDMA) was investigated in viscous (glycerol and paraffin oil) and rigid (polyvinyl alcohol) PVA and polyvinyl chloride) PVC) media. A strong effect of temperature on the intensity of a and b emission bands was observed. It was also found that the emission anisotropy, r, does not vary in the longwave emission band a at a fixed temperature but decreases in the emission band b together with the decreasing wavelength. The latter effect is due to the fact that the transition moment in this band is perpendicular to the long axis of the CDMA molecule. For CDMA in paraffin oil, a normal b band with negative emission anisotropy only occurs. In all other media used, the emission anisotropy has lower values, approaching zero, which results from the considerable covering of band b with a broad emission band a.

  5. Simulations of iron K pre-edge X-ray absorption spectra using the restricted active space method.

    PubMed

    Guo, Meiyuan; Sørensen, Lasse Kragh; Delcey, Mickaël G; Pinjari, Rahul V; Lundberg, Marcus

    2016-01-28

    The intensities and relative energies of metal K pre-edge features are sensitive to both geometric and electronic structures. With the possibility to collect high-resolution spectral data it is important to find theoretical methods that include all important spectral effects: ligand-field splitting, multiplet structures, 3d-4p orbital hybridization, and charge-transfer excitations. Here the restricted active space (RAS) method is used for the first time to calculate metal K pre-edge spectra of open-shell systems, and its performance is tested against on six iron complexes: [FeCl6](n-), [FeCl4](n-), and [Fe(CN)6](n-) in ferrous and ferric oxidation states. The method gives good descriptions of the spectral shapes for all six systems. The mean absolute deviation for the relative energies of different peaks is only 0.1 eV. For the two systems that lack centrosymmetry [FeCl4](2-/1-), the ratios between dipole and quadrupole intensity contributions are reproduced with an error of 10%, which leads to good descriptions of the integrated pre-edge intensities. To gain further chemical insight, the origins of the pre-edge features have been analyzed with a chemically intuitive molecular orbital picture that serves as a bridge between the spectra and the electronic structures. The pre-edges contain information about both ligand-field strengths and orbital covalencies, which can be understood by analyzing the RAS wavefunction. The RAS method can thus be used to predict and rationalize the effects of changes in both the oxidation state and ligand environment in a number of hard X-ray studies of small and medium-sized molecular systems.

  6. Solvent Effects on the Absorption Spectra of the para-Coumaric Acid Chromophore in Its Different Protonation Forms.

    PubMed

    García-Prieto, Francisco F; Galván, Ignacio Fdez; Muñoz-Losa, Aurora; Aguilar, Manuel A; Martín, M Elena

    2013-10-08

    The effects of the solvent and protonation state on the electronic absorption spectrum of the para-coumaric acid (pCA), a model of the photoactive yellow protein (PYP), have been studied using the ASEP/MD (averaged solvent electrostatic potential from molecular dynamics) method. Even though, in the protein, the chromophore is assumed to be in its phenolate monoanionic form, when it is found in water solution pH control can favor neutral, monoanionic, and dianionic species. As the pCA has two hydrogens susceptible of deprotonation, both carboxylate and phenolate monoanions are possible. Their relative stabilities are strongly dependent on the medium. In gas phase, the most stable isomer is the phenolate while in aqueous solution it is the carboxylate, although the population of the phenolate form is not negligible. The s-cis, s-trans, syn, and anti conformers have also been included in the study. Electronic excited states of the chromophore have been characterized by SA-CAS(14,12)-PT2/cc-pVDZ level of theory. The bright state corresponds, in all the cases, to a π → π* transition involving a charge displacement in the system. The magnitude and direction of this displacement depends on the protonation state and on the environment (gas phase or solution). In the same way, the calculated solvatochromic shift of the absorption maximum depends on the studied form, being a red shift for the neutral, carboxylate monoanion, and dianionic chromophores and a blue shift for the phenolate monoanion. Finally, the contribution that the solvent electronic polarizability has on the solvent shift was analyzed. It represents a very important part of the total solvent shift in the neutral form, but its contribution is completly negligible in the mono- and dianionic forms.

  7. Resonance Raman and temperature-dependent electronic absorption spectra of cavity and noncavity models of the hydrated electron

    PubMed Central

    Casey, Jennifer R.; Larsen, Ross E.; Schwartz, Benjamin J.

    2013-01-01

    Most of what is known about the structure of the hydrated electron comes from mixed quantum/classical simulations, which depend on the pseudopotential that couples the quantum electron to the classical water molecules. These potentials usually are highly repulsive, producing cavity-bound hydrated electrons that break the local water H-bonding structure. However, we recently developed a more attractive potential, which produces a hydrated electron that encompasses a region of enhanced water density. Both our noncavity and the various cavity models predict similar experimental observables. In this paper, we work to distinguish between these models by studying both the temperature dependence of the optical absorption spectrum, which provides insight into the balance of the attractive and repulsive terms in the potential, and the resonance Raman spectrum, which provides a direct measure of the local H-bonding environment near the electron. We find that only our noncavity model can capture the experimental red shift of the hydrated electron’s absorption spectrum with increasing temperature at constant density. Cavity models of the hydrated electron predict a solvation structure similar to that of the larger aqueous halides, leading to a Raman O–H stretching band that is blue-shifted and narrower than that of bulk water. In contrast, experiments show the hydrated electron has a broader and red-shifted O–H stretching band compared with bulk water, a feature recovered by our noncavity model. We conclude that although our noncavity model does not provide perfect quantitative agreement with experiment, the hydrated electron must have a significant degree of noncavity character. PMID:23382233

  8. Effects of excess oxygen on the 4.5-6.3 eV absorption spectra of oxygen-rich high purity silica

    NASA Astrophysics Data System (ADS)

    Magruder, R. H.; Robinson, S. J.

    2016-05-01

    Type III silica samples were implanted with O using a multi-energy process that produced a layer of constant concentration to within ±5% beginning ∼80 nm from the surface and extending to ∼640 nm below the surfaces of the samples. The concentrations of excess oxygen in the layer ranged from 0.035 to ∼2.1at.%. In these samples we show that E‧ centers and NBOHCs, as well as the normal cadre of ODC (II) centers, were suppressed, and the optical absorption from 4.7 to 6.4 eV was primarily due to oxygen excess defects. Using Gaussian fitting techniques to examine the optical difference spectra, we have been able to identify four defect centers that are related to excess oxygen defect bands at 4.76 eV, 5.42 eV, 5.75 eV and 6.25 eV.

  9. Tentative identification of the 780/cm nu-4 band Q branch of chlorine nitrate in high-resolution solar absorption spectra of the stratosphere

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Goldman, A.; Murcray, D. G.; Murcray, F. J.; Malathy Devi, V.

    1985-01-01

    According to models of the photochemistry of the stratosphere, chlorine nitrate (ClONO2) is an important temporary reservoir of stratospheric chlorine. At night, ClO is believed to combine in a three-body reaction with NO2 to form chlorine nitrate. During daylight, chlorine nitrate is destroyed by photolysis to form free chlorine and NO3. Infrared spectroscopy has the potential to provide a technique for conducting important quantitative measurements of stratospheric chlorine nitrate. The present paper reports a detailed study of spectra in the 780/cm region. This study has led to the tentative identification of the nu-4 band Q branch of ClONO2 as a significant contributor to the observed stratospheric absorption near 780.21 per cm.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  11. Li K-edge X-ray absorption near edge structure spectra for a library of lithium compounds applied in lithium batteries

    NASA Astrophysics Data System (ADS)

    Wang, Dongniu; Zuin, Lucia

    2017-01-01

    Lithium ion batteries (LIB) have achieved great success as energy supply systems in portable devices and in electrical vehicles. Identifying the local chemical structures of elemental lithium in lithium compounds is beneficial for improving understanding of battery components and performance. Herein, a library of Li K-edge X-ray absorption near edge structure (XANES) of lithium compounds relevant to Li-ion batteries is reported. Materials described include lithium metals (anode), Li-containing cathodes, electrolytes and solid electrolyte interphase (SEI). The results illustrate the characteristic spectral features stemming from the various electronic structures and chemical environment of lithium atoms for each and every possible battery component. XANES spectra of Sn based anode after discharging reveal the appearance of Li2CO3 on electrode surface. X-ray damage on sensitive lithium species is also assessed; the results reveal that more attention should be paid to irradiation effects to conduct XANES measurements for battery materials properly.

  12. Structural relaxation around Cr3+ in YAlO3-YCrO3 perovskites from electron absorption spectra.

    PubMed

    Cruciani, Giuseppe; Ardit, Matteo; Dondi, Michele; Matteucci, Francesco; Blosi, Magda; Dalconi, Maria Chiara; Albonetti, Stefania

    2009-12-10

    The structural relaxation around Cr(3+) in YAl(1-x)Cr(x)O(3) perovskites was investigated and compared with analogous Cr-Al joins (corundum, spinel, garnet). Eight compositions (x(Cr)((3+)) from 0 to 1) were prepared by sol-gel combustion and were analyzed by a combined X-ray diffraction (XRD) and electron absorption spectroscopy (EAS) approach. The unit cell parameters and the XRD averaged octahedral (Cr,Al)-O and ([VIII])Y-O bond distances scale linearly with the chromium fraction. The optical parameters show an expected decrease of crystal field strength (10Dq) and an increase of covalency (B(35)) and polarizability (B(55)) toward YCrO(3), but a nonlinear trend outlines some excess 10Dq below x(Cr)((3+)) approximately 0.4. The local Cr-O bond lengths, as calculated from EAS, indicate a compression from 1.98 A (x(Cr)((3+)) = 1.0) down to 1.95 A (x(Cr)((3+)) = 0.035) so that the relaxation coefficient of perovskite (epsilon = 0.54) is the lowest in comparison with garnet (epsilon = 0.74), spinel (epsilon = 0.68), and corundum (epsilon = 0.58) in contrast with its structural features. The enhanced covalent character of the Cr(3+)-O-Cr(3+) bond in the one-dimensional arrangement of corner-sharing octahedra can be invoked as a factor limiting the perovskite polyhedral network flexibility. The increased probability of Cr-O-Cr clusters for x(Cr)((3+)) greater than approximately 0.4 is associated to diverging trends of nonequivalent interoctahedral angles. The relatively low relaxation degree of Y(Al,Cr)O(3) can be also understood by considering an additional contribution to 10Dq because of the electrostatic potential of the rest of the lattice ions upon the localized electrons of the CrO(6) octahedron. Such an "excess" of 10Dq increases when the point symmetry of the Cr site is low, as in perovskite, and would be affected by the change of yttrium effective coordination number observed by XRD for x(Cr)((3+)) greater than approximately 0.4. This would justify the

  13. Rigid rod-like dinuclear Ru(II)/Os(II) terpyridine-type complexes. Electrochemical behavior, absorption spectra, luminescence properties, and electronic energy transfer through phenylene bridges

    SciTech Connect

    Barigelletti, F.; Flamigni, L.; Balzani, V. ||

    1994-08-24

    The absorption spectra, the luminescence properties (at 293 and 77 K), and the electrochemical behavior of six dinuclear heterometallic compounds have been investigated. The compounds are made of Ru(tpy){sub 2}{sup 2+}- and Os(tpy){sub 2}{sup 2+}-type components (tpy = 2,2{prime}:6{prime},2 inches-terpyridine, which in some cases carries p-tolyl (Meph) or methylsulphone (MeO{sub 2}S) substituents in the 4{prime} position), connected by n phenylene (ph) spacers (n=0,1, and 2). In the resulting rigid rod-like structures of general formula (X{sub 1}tpy)Ru(tpy(ph){sub n}tpy)Os(tpyX{sub 2}){sup 4+} the metal-to-metal distance varies form 11 to 20 {Angstrom}. The absorption spectra of the two components are slightly perturbed in the dinuclear compounds, and metal-metal and ligand-ligand interactions are evidenced by the trends of the oxidation and reduction potentials. The luminescence of the Ru-based unit is quenched by the connected Os-based unit with practically unitary efficiency, regardless of the number of interposed phenylene spacers. Quenching is accompanied by quantitative sensitization of the Os-based luminescence. The rate of energy transfer at 293 K is larger than 10{sup 10} s{sup -1} in all cases. The Foerster (Coulombic) mechanism does not satisfactorily account for such a fast rate, particularly for the species with n=2. It is concluded that the observed energy-transfer processes take place most likely via a Dexter (electron exchange) mechanism. This is consistent with the strong electronic coupling of the Ru-based units in the compound with n=0, and with the relatively small insulating effect expected for the phenylene spacers. 37 refs., 7 figs., 3 tabs.

  14. The Very Young Type Ia Supernova 2013dy: Discovery, and Strong Carbon Absorption in Early-time Spectra

    NASA Astrophysics Data System (ADS)

    Zheng, WeiKang; Silverman, Jeffrey M.; Filippenko, Alexei V.; Kasen, Daniel; Nugent, Peter E.; Graham, Melissa; Wang, Xiaofeng; Valenti, Stefano; Ciabattari, Fabrizio; Kelly, Patrick L.; Fox, Ori D.; Shivvers, Isaac; Clubb, Kelsey I.; Cenko, S. Bradley; Balam, Dave; Howell, D. Andrew; Hsiao, Eric; Li, Weidong; Marion, G. Howie; Sand, David; Vinko, Jozsef; Wheeler, J. Craig; Zhang, JuJia

    2013-11-01

    The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ≈ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 ± 0.05 days (2.4 ± 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R 0 <~ 0.25 R ⊙, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 days after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of MB = -18.72 ± 0.03 mag ~17.7 days after first light.

  15. THE VERY YOUNG TYPE Ia SUPERNOVA 2013dy: DISCOVERY, AND STRONG CARBON ABSORPTION IN EARLY-TIME SPECTRA

    SciTech Connect

    Zheng, WeiKang; Filippenko, Alexei V.; Nugent, Peter E.; Graham, Melissa; Kelly, Patrick L.; Fox, Ori D.; Shivvers, Isaac; Clubb, Kelsey I.; Li, Weidong; Silverman, Jeffrey M.; Howie Marion, G.; Kasen, Daniel; Wang, Xiaofeng; Valenti, Stefano; Howell, D. Andrew; Ciabattari, Fabrizio; Cenko, S. Bradley; Balam, Dave; Hsiao, Eric; Sand, David; and others

    2013-11-20

    The Type Ia supernova (SN Ia) 2013dy in NGC 7250 (d ≈ 13.7 Mpc) was discovered by the Lick Observatory Supernova Search. Combined with a prediscovery detection by the Italian Supernova Search Project, we are able to constrain the first-light time of SN 2013dy to be only 0.10 ± 0.05 days (2.4 ± 1.2 hr) before the first detection. This makes SN 2013dy the earliest known detection of an SN Ia. We infer an upper limit on the radius of the progenitor star of R {sub 0} ≲ 0.25 R {sub ☉}, consistent with that of a white dwarf. The light curve exhibits a broken power law with exponents of 0.88 and then 1.80. A spectrum taken 1.63 days after first light reveals a C II absorption line comparable in strength to Si II. This is the strongest C II feature ever detected in a normal SN Ia, suggesting that the progenitor star had significant unburned material. The C II line in SN 2013dy weakens rapidly and is undetected in a spectrum 7 days later, indicating that C II is detectable for only a very short time in some SNe Ia. SN 2013dy reached a B-band maximum of M{sub B} = –18.72 ± 0.03 mag ∼17.7 days after first light.

  16. 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.

  17. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra

    NASA Astrophysics Data System (ADS)

    Basavaraja, Jana; Suresh Kumar, H. M.; Inamdar, S. R.; Wari, M. N.

    2016-02-01

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π → π* transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μe). It is observed that dipole moment value of excited state (μe) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.

  18. Estimation of ground and excited state dipole moment of laser dyes C504T and C521T using solvatochromic shifts of absorption and fluorescence spectra.

    PubMed

    Basavaraja, Jana; Kumar, H M Suresh; Inamdar, S R; Wari, M N

    2016-02-05

    The absorption and fluorescence spectra of laser dyes: coumarin 504T (C504T) and coumarin 521T (C521T) have been recorded at room temperature in a series of non-polar and polar solvents. The spectra of these dyes showed bathochromic shift with increasing in solvent polarity indicating the involvement of π→π⁎ transition. Kamlet-Taft and Catalan solvent parameters were used to analyze the effect of solvents on C504T and C521T molecules. The study reveals that both general solute-solvent interactions and specific interactions are operative in these two systems. The ground state dipole moment was estimated using Guggenheim's method and also by quantum mechanical calculations. The solvatochromic data were used to determine the excited state dipole moment (μ(e)). It is observed that dipole moment value of excited state (μ(e)) is higher than that of the ground state in both the laser dyes indicating that these dyes are more polar in nature in the excited state than in the ground state.

  19. Diffuse Reflectance Spectroscopy of Hidden Objects, Part I: Interpretation of the Reflection-Absorption-Scattering Fractions in Near-Infrared (NIR) Spectra of Polyethylene Films.

    PubMed

    Pomerantsev, Alexey L; Rodionova, Oxana Ye; Skvortsov, Alexej N

    2017-01-01

    Investigation of a sample covered by an interfering layer is required in many fields, e.g., for process control, biochemical analysis, and many other applications. This study is based on the analysis of spectra collected by near-infrared (NIR) diffuse reflectance spectroscopy. Each spectrum is a composition of a useful, target spectrum and a spectrum of an interfering layer. To recover the target spectrum, we suggest using a new phenomenological approach, which employs the multivariate curve resolution (MCR) method. In general terms, the problem is very complex. We start with a specific problem of analyzing a system, which consists of several layers of polyethylene (PE) film and underlayer samples with known spectral properties. To separate information originating from PE layers and the target, we modify the system versus both the number of the PE layers as well as the reflectance properties of the target sample. We consider that the interfering spectrum of the layer can be modeled using three components, which can be tentatively called transmission, absorption, and scattering contributions. The novelty of our approach is that we do not remove the reflectance and scattering effects from the spectra, but study them in detail aiming to use this information to recover the target spectrum.

  20. Optical absorption spectra of boron clusters Bn (n = 2-5) for application in nano scintillator - a time dependent density functional theory study

    NASA Astrophysics Data System (ADS)

    Shivade, Rajendra K.; Chakraborty, Brahmananda

    2016-09-01

    Boron nano-clusters of various shapes and sizes have potential applications as scintillating detector and hydrogen storage material. Using time dependent density functional theory (TDDFT) as implemented in CASIDA we have studied the linear optical absorption spectra for boron clusters B n ( n = 2-5) and compared with previously reported results using Hatree-Fock (H-F) based method where the spectrum is limited to 8 eV due to exclusion of excitation into very high energy unoccupied orbital. The optical spectra fall in the visible and near UV region and are very much dependent on the shape of the isomer. We have obtained additional peaks for B2 linear, B3 triangular, B4 rhombus and square shaped isomers beyond 8 eV which were missing in the previous H-F based study and has significance as they fall below the ionization potential. We correlate the optical spectrum with the shape of the Kohn-Sham orbitals and HUMO-LUMO gap and assess comparative stability of various B n ( n = 2-5) clusters in terms of HUMO-LUMO gap, bond-length and relative energy. TDDFT computed optical spectroscopy correlated with Kohn-Sham orbitals and HUMO-LUMO gap and its comparison with H-F based method may give significant knowledge regarding geometry and optical properties of B n ( n = 2-5) clusters enabling to distingush between various isomers of B n clusters.