Sample records for absorption band intensities

  1. ABSOLUTE ROVIBRATIONAL INTENSITIES OF 12C 16O 2 ABSORPTION BANDS IN THE 3090–3850 CM ?1 SPECTRAL REGION

    Microsoft Academic Search

    V. MALATHY DEVI; D. CHRIS BENNER; CURTIS P RINSLAND; MARY ANN H SMITH

    1998-01-01

    A multispectrum nonlinear least-squares fitting technique has been used to determine the absolute intensities for approximately 1500 spectral lines in 36 vibration–rotation bands of 12C16O2 between 3090 and 3850cm-1. A total of six absorption spectra of a high-purity (99.995% minimum) natural sample of carbon dioxide were used in the analysis. The spectral data (0.01cm-1 resolution) were recorded at room temperature

  2. Absolute rovibrational intensities of 12C16O2 absorption bands in the 3090-3850 cm-1 spectral region

    Microsoft Academic Search

    V. M. Devi; D. C. Benner; C. P. Rinsland; M. A. H. Smith

    1998-01-01

    A multispectrum nonlinear least-squares fitting technique has been used to determine the absolute intensities for approximately 1500 spectral lines in 36 vibration-rotation bands of 12C16O2 between 3090 and 3850 cm-1. A total of six absorption spectra of a high-purity (99.995% minimum) natural sample of carbon dioxide were used in the analysis. The spectral data (0.01 cm-1 resolution) were recorded at

  3. Measurement of intensities of bands in the electronic absorption spectrum of chlorine dioxide 

    E-print Network

    Rapp, Thomas Louis

    1955-01-01

    will explode instantaneously under any of the three following conditions: (a) When the gas attains a temperature of 100oC or more; (b) shen an excess of ultra- violet radiat, ion reaches the gas, 'and (c) Wnen organic particles are present anywhere... and to set the spectrograph accordingly. The spectral range used in this work was from 4850 A to 5B50 A. A filter was chosen to eliminate all ultra-violet radiation from the beam of light enter1ng the absorption cell, The f ilter used cut cff all radia...

  4. Band Transmittance &Band Transmittance & Absorptance Model

    E-print Network

    Li, Zhanqing

    AOSC 621 Band Transmittance &Band Transmittance & Absorptance Model #12;Transmittance · For monochromatic radiation the transmittance, T, is given simply bygiven simply by / );( eT /1);( and e d the transmittance, T We can also, define a beam absorptance b() , where b() =1- T · But in radiative transfer we

  5. Impurity-related nonlinear optical absorption under combined effects of intense laser field and band-edge nonparabolicity on InGaN QW

    NASA Astrophysics Data System (ADS)

    El Ghazi, Haddou; Peter, A. John

    2015-05-01

    Conduction band-edge nonparabolicity effect on linear and nonlinear optical properties related to 1s-1p intra-conduction band transition in unstrained wurtzite (In, Ga)N-GaN symmetric quantum well (QW) is investigated incorporating an additional external probe as well as the nonresonant intense laser field (ILF) effect. Using the compact density matrix approach and the iterative procedure, the analytical expressions of optical absorption coefficients (ACs) are calculated. The numerical results are obtained within the single-band effective mass and the one-parabolic-band approximations under finite potential barrier. It is found that the internal and external perturbations show an important impact on the optical spectrum. A critical value of the laser-dressed parameter (LDP) is obtained by limiting two behaviors. Moreover, the ILF can be used as a way to control the optical properties of the QW structures and to reduce the lift of the conduction band-edge.

  6. Absorption intensities of rovibronic transitions in the A-band of 16O2: Analysis and calculation of magnetic dipole and electric quadrupole contributions

    NASA Astrophysics Data System (ADS)

    Balasubramanian, T. K.; Mishra, Adya P.; Kshirsagar, R. J.

    2014-01-01

    The recently measured magnetic dipole (M1) absorption intensities of rovibronic transitions in the A-band (b?g+1-X?g-3, 030 band) of 16O2 are theoretically analyzed employing a model in which the b?g+1:X?g-3 mutual perturbations are treated to a sufficient degree of accuracy. Effects of rotational perturbations became manifest in the data analysis and rovibronic correction parameters are needed to reconcile theory and experiment. At a subtle level there is evidence of Herman-Wallis (HW) type effect arising from vibration-rotation interaction in the b and X states. The functional form for the HW correction factor is arrived at from first principles. The final calculations reproduce the measured intensities to fraction of a percent, well within the measurement accuracy. The present analysis leads to the value 0,0=0.02679(4) ?B for the M1 transition moment, and the spontaneous emission rate (Einstein-A coefficient) ?0,0=0.0874 s-1. For the sake of completeness, the electric quadrupole (E2) contribution to the observed intensities is also quantitatively assessed.

  7. Resonance Raman intensity analysis of the excited state proton transfer dynamics of 2-nitrophenol in the charge-transfer band absorption.

    PubMed

    Wang, Ya-Qiong; Wang, Hui-Gang; Zhang, Shu-Qiang; Pei, Ke-Mei; Zheng, Xuming; Lee Phillips, David

    2006-12-01

    Resonance Raman spectra were obtained for 2-nitrophenol in cyclohexane solution with excitation wavelengths in resonance with the charge-transfer (CT) proton transfer band absorption. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion along more than 15 normal modes: the nominal CCH bend+CC stretch nu(12) (1326 cm(-1)), the nominal CCC bend nu(23) (564 cm(-1)), the nominal CO stretch+NO stretch+CC stretch nu(14) (1250 cm(-1)), the nominal CCH bend+CC stretch+COH bend nu(15) (1190 cm(-1)); the nominal CCH bend+CC stretch nu(17) (1134 cm(-1)), the nominal CCC bend+CC stretch nu(22) (669 cm(-1)), the nominal CCN bend nu(27) (290 cm(-1)), the nominal NO(2) bend+CC stretch nu(21) (820 cm(-1)), the nominal CCO bend+CNO bend nu(25) (428 cm(-1)), the nominal CC stretch nu(7) (1590 cm(-1)), the nominal NO stretch nu(8) (1538 cm(-1)), the nominal CCC bend+NO(2) bend nu(20) (870 cm(-1)), the nominal CC stretch nu(6) (1617 cm(-1)), the nominal COH bend+CC stretch nu(11) (1382 cm(-1)), nominal CCH bend+CC stretch nu(9) (1472 cm(-1)). A preliminary resonance Raman intensity analysis was done and the results for 2-nitrophenol were compared to previously reported results for nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone. The authors briefly discuss the differences and similarities in the CT-band absorption excitation of 2-nitrophenol relative to those of nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone. PMID:17166032

  8. Energy levels, intensities, and linewidths of atmospheric carbon dioxide bands

    Microsoft Academic Search

    L. S. Rothman; R. L. Hawkins; R. B. Wattson; R. R. Gamache

    1992-01-01

    Spectroscopic constants are given for eight isotopic variants of carbon dioxide which provide energy levels for transitions required for terrestrial atmospheric IR absorption. A new tabulation is also furnished with bands considered for the latest HITRAN molecular database. This list provides improved band intensities and Herman-Wallis coefficients generated from recent high-resolution measurements and theoretical calculations. Rotationally-dependent air- and self-broadened halfwidths

  9. Infrared band intensities of saturated hydrocarbons

    NASA Technical Reports Server (NTRS)

    Pinkley, L. W.; Sethna, P. P.; Williams, D.

    1978-01-01

    Kramers-Kronig analysis is applied to measured values of spectral reflectance at near-normal incidence to determine the real and the imaginary parts of the complex index of refraction for methane, ethane, propane, n-butane, n-hexane, n-heptane, and n-decane in the liquid state. The results indicate that the strengths of the characteristic bands as measured by the integral of the imaginary part are roughly constant for all the liquid alkanes except for methane. The intensity of the CH valence vibration bands in the spectra of the alkanes except methane is directly proportional to the number of CH groups per unit volume. The relations for the intensity of the bands due to CH2 and CH3 deformations are examined. Characteristic band intensities of the type established for NH4(+) and SO4(2-) groups in solutions and crystals cannot be extended to the more closely coupled CH2 and CH3 groups in alkane molecules.

  10. Raman band intensities of tellurite glasses.

    PubMed

    Plotnichenko, V G; Sokolov, V O; Koltashev, V V; Dianov, E M; Grishin, I A; Churbanov, M F

    2005-05-15

    Raman spectra of TeO2-based glasses doped with WO3, ZnO, GeO2, TiO2, MoO3, and Sb2O3 are measured. The intensity of bands in the Raman spectra of MoO3-TeO2 and MoO3-WO3-TeO2 glasses is shown to be 80-95 times higher than that for silica glass. It is shown that these glasses can be considered as one of the most promising materials for Raman fiber amplifiers. PMID:15943298

  11. Saturable absorption of intense hard X-rays in iron

    NASA Astrophysics Data System (ADS)

    Yoneda, Hitoki; Inubushi, Yuichi; Yabashi, Makina; Katayama, Tetsuo; Ishikawa, Tetsuya; Ohashi, Haruhiko; Yumoto, Hirokatsu; Yamauchi, Kazuto; Mimura, Hidekazu; Kitamura, Hikaru

    2014-10-01

    In 1913, Maurice de Broglie discovered the presence of X-ray absorption bands of silver and bromine in photographic emulsion. Over the following century, X-ray absorption spectroscopy was established as a standard basis for element analysis, and further applied to advanced investigation of the structures and electronic states of complex materials. Here we show the first observation of an X-ray-induced change of absorption spectra of the iron K-edge for 7.1-keV ultra-brilliant X-ray free-electron laser pulses with an extreme intensity of 1020?W?cm?2. The highly excited state yields a shift of the absorption edge and an increase of transparency by a factor of 10 with an improvement of the phase front of the transmitted X-rays. This finding, the saturable absorption of hard X-rays, opens a promising path for future innovations of X-ray science by enabling novel attosecond active optics, such as lasing and dynamical spatiotemporal control of X-rays.

  12. Photon energy upconversion in porphyrins: one-photon hot-band absorption versus two-photon absorption

    E-print Network

    Rebane, Aleks

    Photon energy upconversion in porphyrins: one-photon hot-band absorption versus two; in final form 28 December 2002 Abstract We study the porphyrin S1 ! S0 fluorescence and the photosensitized than the porphyrin S0 ! S1 transition energy. By measuring the excitation intensity dependence

  13. The Nature of the J-band in the Absorption and Fluorescence Spectra of Cyanine Dyes

    NASA Astrophysics Data System (ADS)

    Struganova, Irina; Hazell, Mesha; Gaitor, Jacinta; McNally-Carr, Debra; Zivanovic, Sanya

    2003-05-01

    Some cyanine dyes in solutions in specific conditions show a very narrow and intense absorption band spectra and fluorescence nearly resonance with the absorption. This phenomenon was discovered by J.E. Jelley and A. Scheibe in 1936 and was later explained by formation of an excitonic state among tightly packed molecules in dye aggregates. We discovered that the addition of inorganic anions to water solutions of several cyanine dyes leads to the appearance of the J-bands in the absorption and fluorescence spectra when concentration of the dyes is extremely low (up to 10-8 mol/l). The position of the maximum and the shape of the J-band depended on the inorganic anion. Temperature dependences of the absorption spectra and other data obtained indicated on a possibility of a monomolecular, not excitonic nature of the J-band.

  14. Infrared absorption bands of alkali saturated vapors

    Microsoft Academic Search

    A. Vasilakis

    1981-01-01

    A region of absorption was observed and measured in the near infrared region of the spectrum for saturated sodium vapor and for saturated rubidium vapor (absorption beyond 0.83 microns for saturated sodium vapor, and beyond 1.20 microns in rubidium saturated vapor). In addition, earlier data taken on near infrared absorption by cesium saturated vapor beyond 1.30 microns was reexamined in

  15. Concentration measurement of NO using self-absorption spectroscopy of the ? band system in a pulsed corona discharge.

    PubMed

    Zhai, Xiaodong; Ding, Yanjun; Peng, Zhimin; Luo, Rui

    2012-07-10

    Nitric oxide (NO) concentrations were measured using the ? band system spectrum based on the strong self-absorption effect of NO in pulsed corona discharges. The radiative transitional intensities of the NO ? band were simulated based on the theory of molecular spectroscopy. The intensities of some bands, especially ?(0,0) and ?(1,0), are weakened by the self-absorption. The correlations between the spectral self-absorption intensities and NO concentration were validated using a modified Beer-Lambert law with a combined factor K relating the branching ratio and the NO concentration, and a nonlinear index ? that is applicable to the broadband system. Optical emissive spectra in pulsed corona discharges in NO and N2/He mixtures were used to evaluate the two parameters for various conditions. Good agreement between the experimental and theoretical results verifies the self-absorption behavior seen in the UV spectra of the NO ? bands. PMID:22781235

  16. Spectroscopic investigation of amber color silicate glasses and factors affecting the amber related absorption bands

    NASA Astrophysics Data System (ADS)

    Morsi, Morsi M.; El-sherbiny, Samya I.; Mohamed, Karam M.

    2015-06-01

    The effects of carbon, Fe2O3 and Na2SO4 contents on the amber color of glass with composition (wt%) 64.3 SiO2, 25.7 CaO, 10 Na2O were studied. The effect of some additives that could be found in glass batch or cullets on the amber related absorption band(s) was also studied. An amber related absorption band due to the chromophore Fe3+O3S2- was recorded at 420 nm with shoulder at 440 nm. A second amber related band recorded at 474 nm with shoulder at 483 nm was assigned to FeS. Increasing melting time at 1400 °C up to 6 h caused fainting of the amber color, decreases the intensities of the amber related bands and shifted the first band to 406 nm. Addition of ZnO, Cu2O and NaNO3 to the glass produced decolorizing effect and vanishing of the amber related bands. The effects of melting time and these additives were explained on the bases of destruction the amber chromophore and its conversion into Fe3+ in tetrahedral sites or ZnS. Addition of Se intensifies the amber related bands and may cause dark coloration due to the formation of Se° and polyselenide. Amber color can be monitored through measuring the absorption in the range 406-420 nm.

  17. Electronic Band Structure and Sub-band-gap Absorption of Nitrogen Hyperdoped Silicon

    PubMed Central

    Zhu, Zhen; Shao, Hezhu; Dong, Xiao; Li, Ning; Ning, Bo-Yuan; Ning, Xi-Jing; Zhao, Li; Zhuang, Jun

    2015-01-01

    We investigated the atomic geometry, electronic band structure, and optical absorption of nitrogen hyperdoped silicon based on first-principles calculations. The results show that all the paired nitrogen defects we studied do not introduce intermediate band, while most of single nitrogen defects can introduce intermediate band in the gap. Considering the stability of the single defects and the rapid resolidification following the laser melting process in our sample preparation method, we conclude that the substitutional nitrogen defect, whose fraction was tiny and could be neglected before, should have considerable fraction in the hyperdoped silicon and results in the visible sub-band-gap absorption as observed in the experiment. Furthermore, our calculations show that the substitutional nitrogen defect has good stability, which could be one of the reasons why the sub-band-gap absorptance remains almost unchanged after annealing. PMID:26012369

  18. Electronic Band Structure and Sub-band-gap Absorption of Nitrogen Hyperdoped Silicon.

    PubMed

    Zhu, Zhen; Shao, Hezhu; Dong, Xiao; Li, Ning; Ning, Bo-Yuan; Ning, Xi-Jing; Zhao, Li; Zhuang, Jun

    2015-01-01

    We investigated the atomic geometry, electronic band structure, and optical absorption of nitrogen hyperdoped silicon based on first-principles calculations. The results show that all the paired nitrogen defects we studied do not introduce intermediate band, while most of single nitrogen defects can introduce intermediate band in the gap. Considering the stability of the single defects and the rapid resolidification following the laser melting process in our sample preparation method, we conclude that the substitutional nitrogen defect, whose fraction was tiny and could be neglected before, should have considerable fraction in the hyperdoped silicon and results in the visible sub-band-gap absorption as observed in the experiment. Furthermore, our calculations show that the substitutional nitrogen defect has good stability, which could be one of the reasons why the sub-band-gap absorptance remains almost unchanged after annealing. PMID:26012369

  19. The effective air absorption coefficient for predicting reverberation time in full octave bands.

    PubMed

    Wenmaekers, R H C; Hak, C C J M; Hornikx, M C J

    2014-12-01

    A substantial amount of research has been devoted to producing a calculation model for air absorption for pure tones. However, most statistical and geometrical room acoustic prediction models calculate the reverberation time in full octave bands in accordance with ISO 3382-1 (International Organization for Standardization, 2009). So far, the available methods that allow calculation of air absorption in octave bands have not been investigated for room acoustic applications. In this paper, the effect of air absorption on octave band reverberation time calculations is investigated based on calculations. It is found that the approximation method, as described in the standard ANSI S1.26 (American National Standards Institute, 1995), fails to estimate accurate decay curves for full octave bands. In this paper, a method is used to calculate the energy decay curve in rooms based on a summation of pure tones within the band. From this decay curve, which is found to be slightly concave upwards, T20 and T30 can be determined. For different conditions, an effective intensity attenuation coefficient mB ;eff for the full octave bands has been calculated. This mB ;eff can be used for reverberation time calculations, if results are to be compared with T20 or T30 measurements. Also, guidelines are given for the air absorption correction of decay curves, measured in a scale model. PMID:25480055

  20. Correlation evaluation of intensity and color band images

    SciTech Connect

    Carter, J.M.

    1996-02-01

    The purpose of this project is to determine which of the three color bands--red, green, or blue--to use in providing the best possible correlation and to determine the accuracy with which these color bands correlate in comparison with the correlation of the three color bands with the intensity model. To fulfill this purpose, the correlation technique of template matching is implemented using a correlator. Correlations are implemented with each of the individual color bands and also with the corresponding intensity model. The correlation coefficient resulting from a successful correlation ranges from 0.9 to 1. A coefficient of 1 demonstrates that the feature information varies identically. When analyzing the data collected from the correlations, the following results are obtained. The color band recommended for the most accurate correlation is the green color band. The correlation of the color bands with the intensity model was not as successful in determining the better color band because the correlation coefficients were very low in comparison to the correlation of the individual color bands.

  1. Universal EUV in-band intensity detector

    DOEpatents

    Berger, Kurt W.

    2004-08-24

    Extreme ultraviolet light is detected using a universal in-band detector for detecting extreme ultraviolet radiation that includes: (a) an EUV sensitive photodiode having a diode active area that generates a current responsive to EUV radiation; (b) one or more mirrors that reflects EUV radiation having a defined wavelength(s) to the diode active area; and (c) a mask defining a pinhole that is positioned above the diode active area, wherein EUV radiation passing through the pinhole is restricted substantially to illuminating the diode active area.

  2. The Effects of Absorption and Self-Absorption Quenching on Fluorescent Intensities

    ERIC Educational Resources Information Center

    Henderson, Giles

    1977-01-01

    Describes an experiment that shows that fluorescence emission intensities are significantly modified by absorption processes and that these effects can be eliminated by positioning the sample cell such that the interrogation region corresponds to the corner of the cell. (MLH)

  3. Resonant absorption and not-so-resonant absorption in short, intense laser irradiated plasma

    SciTech Connect

    Ge, Z. Y.; Zhuo, H. B.; Ma, Y. Y.; Yang, X. H.; Yu, T. P.; Zou, D. B.; Yin, Y.; Shao, F. Q. [College of Science, National University of Defense Technology, Changsha 410073 (China)] [College of Science, National University of Defense Technology, Changsha 410073 (China); Yu, W.; Luan, S. X. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)] [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhou, C. T. [College of Science, National University of Defense Technology, Changsha 410073 (China) [College of Science, National University of Defense Technology, Changsha 410073 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Peng, X. J. [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)] [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

    2013-07-15

    An analytical model for laser-plasma interaction during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. Both the resonant absorption and not-so-resonant absorption are self-consistently included. Different from the previous theoretical works, the physics of resonant absorption is found to be valid in more general conditions as the steepening of the electron density profile is considered. Even for a relativistic intensity laser, resonant absorption can still exist under certain plasma scale length. For shorter plasma scale length or higher laser intensity, the not-so-resonant absorption tends to be dominant, since the electron density is steepened to a critical level by the ponderomotive force. The laser energy absorption rates for both mechanisms are discussed in detail, and the difference and transition between these two mechanisms are presented.

  4. Absolute intensity measurements in the ?3 band of carbon disulphide

    NASA Astrophysics Data System (ADS)

    Blanquet, Ghislain; Walrand, Jacques; Weber, Christian; Lepère, Muriel

    The aim of this paper is to determine with accuracy the band strength of the strong ?3 fundamental band of carbon disulphide CS2. By diode-laser spectroscopy, we have measured line by line the intensities for the 12C32S2 form by the equivalent width method and by the line profile fitting method. To confirm our results, we have also measured 30 lines for the 13C32S2 isotopic species using a sample of CS2 in natural abundance. We have obtained for the band strength = 1417 cm-2 atm-1 at 296 K and this value is in good agreement with the values from the literature.

  5. Valence-band photoemission and optical absorption in nickel compounds

    Microsoft Academic Search

    Atsushi Fujimori; Fujio Minami

    1984-01-01

    Photoemission, optical-absorption, and isochromat spectra of NiO and NiCl2 are studied theoretically by the consideration of configuration interactions within the metal-ligand cluster. It is shown that the satellites in the valence-band photoemission spectra contain significant d7 final-state components produced by photoemission of a d electron from the largely d8-like ground state and that final states giving the main lines are

  6. Absorption of ultrashort intense lasers in laser–solid interactions

    NASA Astrophysics Data System (ADS)

    Sheng, Zheng-Ming; Weng, Su-Ming; Yu, Lu-Le; Wang, Wei-Min; Cui, Yun-Qian; Chen, Min; Zhang, Jie

    2015-01-01

    With the advent of ultrashort high intensity laser pulses, laser absorption during the laser–solid interactions has received significant attention over the last two decades since it is related to a variety of applications of high intensity lasers, including the hot electron production for fast ignition of fusion targets, table-top bright X-ray and gamma-ray sources, ion acceleration, compact neutron sources, and generally the creation of high energy density matters. Normally, some absorption mechanisms found for nanosecond long laser pulses also appear for ultrashort laser pulses. The peculiar aspects with ultrashort laser pulses are that their absorption depends significantly on the preplasma condition and the initial target structures. Meanwhile, relativistic nonlinearity and ponderomotive force associated with the laser pulses lead to new mechanisms or phenomena, which are usually not found with nanosecond long pulses. In this paper, we present an overview of the recent progress on the major absorption mechanisms in intense laser–solid interactions, where emphasis is paid to our related theory and simulation studies. Project supported by the National Basic Research Program of China (Grant No. 2013CBA01504) and the National Natural Science Foundation of China (Grant Nos. 11421064, 11129503, 11374209, and 11374210).

  7. Are 2-micron absorptions and 11-micron emissions of M stars related. [solor and spectral band correlations with boundary temperature

    NASA Technical Reports Server (NTRS)

    Fay, T. D., Jr.

    1974-01-01

    Three properties of M stars are compared: (1) /3.5/ - /11/ colors, (2) two measures of 2.3-micron band absorption, and (3) two measures of 1.9-micron band absorption. We find that the 2.3-micron bands of 21 M giants and supergiants correlate with /3.5/ - /11/ colors at better than 99 per cent confidence. A comparable relation exists between the mean 1.9-micron bands and /3.5/ - /11/ colors of 23 M giants and Miras. The sum of the 1.9-micron + 2.3-micron band intensities correlates with /3.5/ - /11/ color at better than the 99.8 per cent level for 31 M stars. These relations are consistent with both CO and H2O cooling of M star boundaries. Binaries and Ia supergiants appear to depart from these relations.

  8. Infrared cross-sections and integrated band intensities of propylene: Temperature-dependent studies

    NASA Astrophysics Data System (ADS)

    Es-sebbar, Et-touhami; Alrefae, Majed; Farooq, Aamir

    2014-01-01

    Propylene, a by-product of biomass burning, thermal cracking of hydrocarbons and incomplete combustion of fossil fuels, is a ubiquitous molecule found in the environment and atmosphere. Accurate infrared (IR) cross-sections and integrated band intensities of propylene are essential for quantitative measurements and atmospheric modeling. We measured absolute IR cross-sections of propylene using Fourier Transform Infrared (FTIR) Spectroscopy over the wavenumber range of 400-6500 cm-1 and at gas temperatures between 296 and 460 K. We recorded these spectra at spectral resolutions ranging from 0.08 to 0.5 cm-1 and measured the integrated band intensities for a number of vibrational bands in certain spectral regions. We then compared the integrated band intensities measured at room temperature with values derived from the National Institute of Standards and Technology (NIST) and the Pacific Northwest National Laboratory (PNNL) databases. Our results agreed well with the results reported in the two databases with a maximum deviation of about 4%. The peak cross-sections for the primary bands decreased by about 20-54% when the temperature increased from 296 to 460 K. Moreover, we determined the integrated band intensities as a function of temperature for certain features in various spectral regions; we found no significant temperature dependence over the range of temperatures considered here. We also studied the effect of temperature on absorption cross-section using a Difference Frequency Generation (DFG) laser system. We compared the DFG results with those obtained from the FTIR study at certain wavenumbers over the 2850-2975 cm-1 range and found a reasonable agreement with less than 10% discrepancy.

  9. Strength of the H2O near-infrared absorption bands in hydrated minerals: Effects of measurement geometry

    NASA Astrophysics Data System (ADS)

    Pommerol, Antoine; Schmitt, Bernard

    2008-12-01

    Quantitative effects of incidence and emergence angles variations on the 1.9- and 3-?m H2O bands are experimentally investigated for two hydrated minerals: smectite and altered volcanic tuff. Near-infrared bidirectional reflectance spectra are measured with various incidence and emergence angles leading to phase angles varying between 10° and 140°. We observe a decrease of both band strengths when phase angle increases. The relationship between band strength and phase angle depends on both the absorption intensity, i.e., strong or weak band, and the particle size of the material. We compare experimental results with radiative transfer modeling with optical constants of a smectite. Numerical models can reproduce the changes in band strength with incidence and emergence angles if the value of the single particle scattering anisotropy varies over the absorption band. We attribute this wavelength-dependent scattering effect to enhanced surface scattering within the absorption bands compared to volume scattering outside the bands. Relative variations of band strength induced by measurement geometry variations can reach tens of percent at high phase angle. Therefore these effects have to be taken into account when mapping spectral parameters on a planetary surface or comparing spectral parameters between two surfaces if measurement geometries are subject to large variations.

  10. A measurement of the relative intensities of some vibronic bands

    E-print Network

    Loyd, Coleman Monroe

    1955-01-01

    values in Table VIII and Table IX, Previous values in tho literature are those by Johnston and Urey and the theoretical values obtained by Ward . Figure 9 1 8 is a curve for the values fran Table X together with Ward's theoretical curve. Ward's values... have been scaled to give his sax1am value the value obtained by' the present work, Johnston and Urey estinated the peak absorption te be at a which agrees closely with the present work. Had Johnston and Uroy taken into account underlying bands...

  11. A measurement of the relative intensities of some vibronic bands 

    E-print Network

    Loyd, Coleman Monroe

    1955-01-01

    INE DIOXIDE APPARATUS ~ . o . . . ~ 9 4. TOP VIEW OF CH1 CRINE DIOXIDE APPARATUS . 5 ~ CHLORINE DIOXIDE ABSORPTION SPECTROGRAM WITH CAI IBRATION BLANKS ~ ~ ~ e ~ ~ e ~ ~ ~ 6, CHLORINE DIOXIDE DECONPOSITION IiN PROGRESS 10 . 11 7. H AND D CURVE FOil... this uncertainty. 20 Table V RELATIVE DENSITY OF BANDS FOR EIGHT SPEOTRA FRUN PIATE 48 D7 D8 D9 D10 DII DI2 DI3 DI4 D15 D16 D17 ~ 92 . 60 . 95 1, 10 . 75 . 64 1. 09 1. 05 . 58 . 86 . 91 1, 00 . 71 . 75 o91 1. 21 88 . 57 1+07 . 97 . 75 . 71 1. 07 1, 03...

  12. New Optical Absorption Bands in Atomic Layer Superlattices

    NASA Astrophysics Data System (ADS)

    Eckstein, James

    2011-03-01

    Using atomic layer-by-layer molecular beam epitaxy, atomic layer superlattices can be constructed that exhibit new electronic, optical and lattice effects not present in the individual components. In particular, new optical transitions giving rise to sharp absorption peaks can be created by placing a layer of a material with occupied source states next to a layer of another material with unoccupied destination states. We combine atomic layers of SrTi O3 and LaMn O3 into superlattice structures with component layers as thin as single monolayer and find a new absorption band due to a transition from manganese- to titanium-derived states. The energy of the new transition depends on how the bands line up at the interface. Furthermore, a substantial shift of spectral weight occurs as well, while retaining a constant sum rule. This work was supported by the Department of Energy Basic Energy Sciences at the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana. This work was done in collaboration with Xiaofang Zhai, Mao Zheng, Amish Shah, Chandra Mohapatra, and Jian-Min Zuo. This work was supported by the Department of Energy Basic Energy Sciences at the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana.

  13. Line positions and intensities for the ?12 band of 13C12CH6

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy; Benner, D. Chris; Sung, Keeyoon; Crawford, Timothy J.; Mantz, Arlan W.; Smith, Mary Ann H.

    2014-07-01

    High-resolution, high signal-to-noise spectra of a high-purity (99%) mono-substituted 13C-enriched ethane (13C12CH6) in the ?12 fundamental band near 12.2 ?m region were recorded with a Bruker IFS 125HR Fourier transform spectrometer. The data were obtained for four sample pressures at three different temperatures (130-208 K) using a 20.38-cm long coolable absorption cell. The spectra were fitted simultaneously to retrieve individual line positions and absolute line intensities for 1660 absorption features. A multispectrum nonlinear least squares spectrum fitting technique was employed in the analysis. Constraints were used to fit each pair of doublet components arising from torsional Coriolis interaction of the excited ?12 = 1 state with the nearby excited torsional ?6 = 3 state. Line positions and absolute line intensities were retrieved by simultaneously fitting the four experimental spectra recorded at three low sample temperatures (130 K, 178 K and 208 K). The measured positions and intensities were determined for the standard reference temperature of 296 K and compared with the predicted values listed in the HITRAN database. Calculated line intensities at each of the measured spectrum temperatures are also provided as supplemental data. Integrated intensities are also reported.

  14. Wavelength dependent resonance Raman band intensity of broadband stimulated Raman spectroscopy of malachite green in ethanol.

    PubMed

    Cen, Qiongyan; He, Yuhan; Xu, Mei; Wang, Jingjing; Wang, Zhaohui

    2015-03-21

    Resonance broadband stimulated Raman spectroscopy of malachite green in ethanol has been performed. With a tuning picosecond visible laser source and a broadband Raman probe, the Raman gain and loss spectra have been measured simultaneously. By scanning the Raman pump across the first absorption band of the molecule, we found that the resonant Raman bands could be only seen when the pump laser tuned in the range of the red edge of the S1?S0 transition. Dispersive lineshapes of resonant Raman bands have been observed in the Raman loss spectra, while the line shape is normal (same as spontaneous Raman) in the Raman gain spectra. Although, the resonant bands in the loss spectrum are usually stronger than that in the gain spectrum, the band intensities of both loss and gain linearly increase with the pump energy. The relative magnitude of each corresponding resonant band in the Raman loss and gain varies with the pump wavelength. Mode specified Raman excitation profiles have been obtained through broadband stimulated Raman measurement. PMID:25796242

  15. Triple-band perfect metamaterial absorption, based on single cut-wire bar

    NASA Astrophysics Data System (ADS)

    Yoo, Y. J.; Kim, Y. J.; Hwang, J. S.; Rhee, J. Y.; Kim, K. W.; Kim, Y. H.; Cheong, H.; Chen, L. Y.; Lee, Y. P.

    2015-02-01

    In general metamaterial perfect absorber, the single meta-pattern makes the single absorption band. Therefore, the multi-absorption bands need the corresponding kinds of meta-patterns. Here, we introduce the triple-band metamaterial perfect absorber utilizing only single kind of pattern. We also demonstrate the absorption mechanism of the triple perfect absorption. The first and the second absorption bands were induced by the fundamental magnetic resonance of the major and the minor axes, respectively, of cut-wire bar. The third peak was caused by the third-harmonic magnetic resonance of the major axis. Additionally, the unexpected third band was formed, which was the overlapping of the third absorption peak with another absorption peak, which was made by pairs of antiparallel currents parallel or antiparallel to the incident electromagnetic wave.

  16. Theoretical reproduction of the Q-band absorption spectrum of free-base chlorin

    NASA Astrophysics Data System (ADS)

    Wójcik, Justyna; Ratuszna, Alicja; Peszke, Jerzy; Wrzalik, Roman

    2015-01-01

    The computational results of the features observed in the room-temperature Q-band absorption spectrum of free-base chlorin (H2Ch) are presented. The vibrational structures of the first and second excited singlet states were calculated based on a harmonic approximation using density functional theory and its time dependent extension within the Franck-Condon and Herzberg-Teller approaches. The outcome allowed to identify the experimental bands and to assign them to the specific vibrational transitions. A very good agreement between the simulated and measured wavelengths and their relative intensities provided the opportunity to predict the origin of the S0 ? S2 transition which could not be determined experimentally.

  17. Measurements of the absorption line strength of hydroperoxyl radical in the ?3 band using a continuous wave quantum cascade laser.

    PubMed

    Sakamoto, Yosuke; Tonokura, Kenichi

    2012-01-12

    Mid-infrared absorption spectroscopy has been applied to the detection of the hydroperoxyl (HO(2)) radical in pulsed laser photolysis combined with a laser absorption kinetics reactor. Transitions of the ?(3) vibrational band assigned to the O-O stretch mode were probed with a thermoelectrically cooled, continuous wave mid-infrared distributed feedback quantum cascade laser (QCL). The HO(2) radicals were generated with the photolysis of Cl(2)/CH(3)OH/O(2) mixtures at 355 nm. The absorption cross section at each pressure was determined by three methods at 1065.203 cm(-1) for the F(1), 13(1,13) ? 14(1,14) transition in the ?(3) band. From these values, the absolute absorption cross section at zero pressure was estimated. The relative line strengths of other absorptions in the feasible emitting frequency range of the QCL from 1061.17 to 1065.28 cm(-1) were also measured, and agreed with values reproduced from the HITRAN database. The ?(3) band absorption strength was estimated from the analytically obtained absolute absorption cross section and the calculated relative intensity by spectrum simulation, to be 21.4 ± 4.2 km mol(-1), which shows an agreement with results of quantum chemical calculations. PMID:22148191

  18. Enhanced dual-band infrared absorption in a Fabry-Perot cavity with subwavelength metallic grating.

    PubMed

    Kang, Guoguo; Vartiainen, Ismo; Bai, Benfeng; Turunen, Jari

    2011-01-17

    The performance of infrared (IR) dual-band detector can be substantially improved by simultaneously increasing IR absorptions for both sensor bands. Currently available methods only provide absorption enhancement for single spectral band, but not for the dual-band. The Fabry-Perot (FP) cavity generates a series of resonances in multispectral bands. With this flexibility, we introduced a novel type of dual-band detector structure containing a multilayer FP cavity with two absorbing layers and a subwavelength-period grating mirror, which is capable of simultaneously enhancing the middle wave infrared (MWIR) and the long wave infrared (LWIR) detection. Compared with the bare-absorption-layer detector (common dual-band detector), the optimized FP cavity can provide about 13 times and 17 times absorption enhancement in LWIR and MWIR bands respectively. PMID:21263618

  19. Narrow and broad band diode laser absorption spectrometry—concepts, limitations and applications

    Microsoft Academic Search

    J. Koch; A. Zybin; K. Niemax

    2002-01-01

    Implementation concepts as well as the fundamental aspects concerning the analytical capability of diode laser spectrometry with respect to narrow and broad band absorption are discussed. The applicability is illustrated by means of the element-selective analysis of flames or plasmas and the molecular analysis of liquids or turbid media. While in narrow band absorption one diode laser and different modulation

  20. Zeeman Effect of the A Absorption Bands in Tl and Pb-Doped Alkali Halides

    Microsoft Academic Search

    Ryumyo Onaka; Teruhiko Mabuchi; Akira Yoshikawa

    1967-01-01

    Zeeman effects of the A absorption bands in KBr:Tl, KI:Tl, KCl:Pb and KBr:Pb are studied by means of circular dichroism, and g-factors of the excited states relevant to these absorption bands are found to be 0.6˜0.8.

  1. Density functional theory study of vibronic structure of the first absorption Q x band in free-base porphin

    NASA Astrophysics Data System (ADS)

    Minaev, Boris; Wang, Yan-Hua; Wang, Chuan-Kui; Luo, Yi; Ågren, Hans

    2006-10-01

    Harmonic vibrational frequencies and vibronic intensities in the first S 0?S 1 ( ??) absorption band of free-base porphin (H 2 P) are investigated by hybrid density functional theory (DFT) with the standard B3LYP functional. The S 0-S 1 transition probability is calculated using time-dependent DFT with account of Franck-Condon (FC) and Herzberg-Teller (HT) contributions to the electric-dipole transition moments including displacements along all 108 vibrational modes. Two weak wide bands observed in the gas phase absorption spectra of the H 2 P molecule at 626 and 576 nm are interpreted as the 0-0 band of the X 1 A g?1B 3u transition and the 0-1 band with largest contributions from the ?10(a)=1610 cm -1 and ?19(b)=1600 cm -1 modes, respectively, in agreement with previous tentative assignments. Both bands are induced by the HT mechanism, while the FC contributions are negligible. A number of fine structure bands, including combination of two vibrational quanta, are obtained and compared with available spectra from supersonic jet and Shpolskij matrices. Both absorption and fluorescence spectra are interpreted on ground of the linear coupling model and a good fulfillment of the mirror-symmetry rule.

  2. Narrow-Band Emitting Solid Fluorescence Reference Standard with Certified Intensity Pattern.

    PubMed

    Hoffmann, Katrin; Spieles, Monika; Bremser, Wolfram; Resch-Genger, Ute

    2015-07-21

    The development of a lanthanum-phosphate glass doped with several rare-earth-ions for use as solid fluorescence standard is described. The cuvette-shaped reference material which shows a characteristic emission intensity pattern upon excitation at 365 nm consisting of a multitude of relatively narrow emission bands in the wavelength region between 450 and 700 nm is intended for the day-to-day performance validation of fluorescence measuring devices. Evaluation of the fluorescent glass includes the determination of all properties which can affect its relative emission intensity profile or contribute to the uncertainty of the certified values like absorption spectra, fluorescence anisotropy, excitation wavelength, and temperature dependence of the spectroscopic features, homogeneity of fluorophore distribution, and photo- and long-term stability. Moreover, a certification procedure was developed including the normalization of the intensity profile consisting of several narrow emission bands and the calculation of wavelength-dependent uncertainties. Criteria for the design, characterization, and working principle of the new reference material BAM-F012 are presented, and possible applications of this ready-to-use fluorescence standard are discussed. PMID:26077510

  3. Effect of treatment temperature on the intensity of the vibrational band of the SiO bonds in passivating films

    Microsoft Academic Search

    E. N. Ivanova; A. N. Latyshev; V. F. Synorov; L. E. Erokhina; M. P. Ogurtsova

    1970-01-01

    The protective properties of the films are affected strongly by these changes, so it is important to have a convenient method for monitoring the stoichiometric composition. Such a method can be based on measurement of the absorption band of the Si-O bond, which is at 9.3\\/~ for SiO 2 and near 10 # for silicon monoxide [3]. The intensity of

  4. An intensity study of the torsional bands of ethane at 35 ?m

    NASA Astrophysics Data System (ADS)

    Moazzen-Ahmadi, N.; Norooz Oliaee, J.; Ozier, I.; Wishnow, E. H.; Sung, K.; Crawford, T. J.; Brown, L. R.; Devi, V. M.

    2015-01-01

    Ethane is the second most abundant hydrocarbon detected in the outer planets. Although the torsional mode is not infrared active in the lowest order, the strongest feature in this band can be seen near 289 cm-1 in the CASSINI CIRS spectrum of Titan. Prior laboratory studies have characterized the torsional frequencies to high accuracy and measured the intensities to temperatures as low as 208 K. However, for the interpretation of the far-infrared observations of Titan, further investigation was needed to determine the intensities at lower temperatures and to higher accuracy. The spectrum of C2H6 was investigated from 220 to 330 cm-1 to obtain the band strengths of the torsional fundamental ?4 (near 289 cm-1) and the first torsional hot band (2?4 -?4). Seven laboratory spectra were obtained at resolutions of 0.01 and 0.02 cm-1 using a Bruker IFS-125 Fourier transform spectrometer at the Jet Propulsion Laboratory. The interferometer was coupled to a coolable multi-pass absorption cell set to an optical path length of 52 m. The range of temperatures was 166-292 K with the lower temperatures being most relevant to the stratosphere of Titan. The ethane sample pressures ranged from 35 to 254 Torr. The modeling of the transition intensities required the expansion of the dipole moment operator to higher order; this introduced Herman-Wallis like terms. The fitting process involved five independent dipole constants and a single self-broadening parameter. The results presented should lead to an improved understanding of the methane cycle in planetary atmospheres and permit other molecular features in the CIRS spectra to be identified.

  5. Band to band optical absorption in LPE-growth InAs0.94Sb0.06 film

    NASA Astrophysics Data System (ADS)

    Lv, Y. F.; Hu, S. H.; Zhou, W.; Xu, Y. G.; Wang, Y.; Wang, R.; Yu, G. L.; Dai, N.

    2015-07-01

    InAs1-xSbx films with x = 0.06 were grown on InAs (1 0 0) substrates by liquid phase epitaxy (LPE). Different purification procedures were applied to get InAsSb samples with different carrier concentration. The complete optical absorption spectra including absorption edge and intrinsic absorption region of InAsSb samples were extracted from the room temperature transmission spectra. The energy band gaps of InAsSb samples were obtained by fitting the intrinsic absorption spectra, giving rise to the values of 303.4-305.1 meV. The reciprocal slope (Eo) of the absorption edge related to the carrier concentration was also determined. The Eo value decreases with decrease of InAsSb epilayer carrier concentration.

  6. Observations of an Intense Field-Aligned Thermal Ion Flow and Associated Intense Narrow Band Electric Field Oscillations

    Microsoft Academic Search

    Edgar A. Bering; Michael C. Kelley; Forrest S. Mozer

    1975-01-01

    An intense downward field-aligned thermal ion flow and intense narrow band waves with frequencies just below the local ion gyrofrequency have been observed at the equatorward edge of an auroral arc. The magnitude and direction of the field-aligned current required by the measured dc electric field pattern are consistent with the ion flow measurements and with a differential drift between

  7. The ÖX˜ absorption of vinoxy radical revisited: Normal and Herzberg-Teller bands observed via cavity ringdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Thomas, Phillip S.; Chhantyal-Pun, Rabi; Kline, Neal D.; Miller, Terry A.

    2010-03-01

    The ÖX˜ electronic absorption spectrum of vinoxy radical has been investigated using room temperature cavity ringdown spectroscopy. Analysis of the observed bands on the basis of computed vibrational frequencies and rotational envelopes reveals that two distinct types of features are present with comparable intensities. The first type corresponds to "normal" allowed electronic transitions to the origin and symmetric vibrations in the à state. The second type is interpreted in terms of excitations to asymmetric à state vibrations, which are only vibronically allowed by Herzberg-Teller coupling to the B˜ state. Results of electronic structure calculations indicate that the magnitude of the Herzberg-Teller coupling is appropriate to produce vibronically induced transitions with intensities comparable to those of the normal bands.

  8. HAC: Band Gap, Photoluminescence, and Optical/Near-Infrared Absorption

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.; Ryutov, Dimitri; Furton, Douglas G.

    1996-01-01

    We report results of laboratory measurements which illustrate the wide range of physical properties found among hydrogenated amorphous carbon (HAC) solids. Within this range, HAC can match quantitatively the astronomical phenomena ascribed to carbonaceous coatings on interstellar grains. We find the optical band gap of HAC to be well correlated with other physical properties of HAC of astronomical interest, and conclude that interstellar HAC must be fairly hydrogen-rich with a band gap of E(sub g) is approx. greater than 2.0 eV.

  9. Investigation of locally resonant absorption and factors affecting the absorption band of a phononic glass

    NASA Astrophysics Data System (ADS)

    Chen, Meng; Jiang, Heng; Feng, Yafei; Wang, Yuren

    2014-12-01

    We experimentally and theoretically investigated the mechanisms of acoustic absorption in phononic glass to optimize its properties. First, we experimentally studied its locally resonant absorption mechanism. From these results, we attributed its strong sound attenuation to its locally resonant units and its broadband absorption to its networked structure. These experiments also indicated that the porosity and thickness of the phononic glass must be tuned to achieve the best sound absorption at given frequencies. Then, using lumped-mass methods, we studied how the absorption bandgaps of the phononic glass were affected by various factors, including the porosity and the properties of the coating materials. These calculations gave optimal ranges for selecting the porosity, modulus of the coating material, and ratio of the compliant coating to the stiff matrix to achieve absorption bandgaps in the range of 6-30 kHz. This paper provides guidelines for designing phononic glasses with proper structures and component materials to work in specific frequency ranges.

  10. Fe-substituted indium thiospinels: New intermediate band semiconductors with better absorption of solar energy

    NASA Astrophysics Data System (ADS)

    Chen, Ping; Chen, Haijie; Qin, Mingsheng; Yang, Chongyin; Zhao, Wei; Liu, Yufeng; Zhang, Wenqing; Huang, Fuqiang

    2013-06-01

    The indium thiospinels In2S3 and MgIn2S4 are promising host for the intermediated band (IB) photovoltaic materials due to their ideal band gap value. Here, the optical properties and electronic structure of Fe-doped In2S3 and MgIn2S4 have been investigated. All the Fe-substituted semiconductors exhibit two additional absorption bands at about 0.7 and 1.25 eV, respectively. The results of first-principles calculations revealed that the Fe substituted at the octahedral In site would introduce a partially filled IB into the band gap. Thanks to the formation of IB, the Fe-substituted semiconductors have the ability to absorb the photons with energies below the band gap. With the wide-spectrum absorption of solar energy, these materials possess potential applications in photovoltaic domain.

  11. Temperature dependence of intensities of the 8-12 micron bands of CFCl3

    NASA Technical Reports Server (NTRS)

    Nanes, R.; Silvaggio, P. M.; Boese, R. W.

    1980-01-01

    The absolute intensities of the 8-12 micron bands from Freon 11 (CFCl3) were measured at temperatures of 294 and 216 K. Intensities of the bands centered at 798, 847, 934, and 1082 per cm are all observed to depend on temperature. The temperature dependence for the 847 and 1082 per cm fundamental regions is attributed to underlying hot bands; for the nu2 + nu5 combination band (934 per cm), the observed temperature dependence is in close agreement with theoretical prediction. The implication of these results on atmospheric IR remote-sensing is briefly discussed.

  12. Spectral image analysis for the absorption bands of the ?-methallyl free radical in the vapor phase

    NASA Astrophysics Data System (ADS)

    Bayrakçeken, Fuat; Telatar, Ziya; Ar?, Fikret; Bayrak, Aykut B.

    2007-08-01

    The radicals formed in the flash photolysis of 2-methylbut-1-ene and subsequent reactions have been investigated by kinetic spectroscopy and gas liquid chromatography. Less than 10% of photo products are formed by a molecular made of fission of the excited olefin, and of the radical modes the relative probabilities of band fission, ?(C sbnd H):?(C sbnd H):?(C sbnd C) are 13:1.37:1. The extinction coefficients of ?-methallyl radical measured experimentally for all the absorption bands. The decay of the ?-methallyl radical was second order. The rate constant for the ?-methallyl radical recombination experimentally measured was 2.6 ± 0.3 × 10 10 l mol -1 s -1 at 295 ± 2 K. The spectrum image showing the absorption bands was examined by image processing techniques in order to improve the visual experience of each band by localizing to a specific region of interest. Experimental results illustrate how the exact location of absorption bands was clearly extracted from the spectral image and further improvements in the visual detection of absorption bands.

  13. Photochemical investigation of the IR absorption bands of molecular oxygen in organic and aqueous environment.

    PubMed

    Krasnovsky, A A; Kozlov, A S; Roumbal, Ya V

    2012-06-01

    It is shown that the weak IR absorption bands corresponding to the forbidden triplet-singlet transitions in oxygen molecules can be reliably studied in air-saturated solvents under ambient conditions using measurements of the photooxygenation rates of singlet oxygen traps (1,3-diphenylisobenzofuran or uric acid) upon direct excitation of oxygen molecules by IR diode lasers. The best results were obtained from comparison of the oxygenation rates upon direct and photosensitized singlet oxygen excitation. In the present paper, this method was applied to estimation of the absorbance (A(ox)) and molar absorption coefficients (?(ox)) corresponding to the oxygen absorption bands at 765 and 1273 nm in carbon tetrachloride, acetone, alcohols and water. In carbon tetrachloride, the band at 1073 nm was also investigated. Correlation of the obtained data with the luminescence spectra and radiative rate constants of singlet oxygen, contribution of oxygen dimols and biological significance of the studied effects are discussed. PMID:22307051

  14. Measurement of the depolarization ratio of Rayleigh scattering at absorption bands

    NASA Astrophysics Data System (ADS)

    Anglister, J.; Steinberg, I. Z.

    1981-01-01

    Measurements of the depolarization ratio ?v of light scattered by the pigments lycopene and ?-carotene at the red part of their absorption bands yielded values which are very close to the theoretical value 1/3 of a fully anisotropic molecular polarizability, i.e., that due to an electric dipole moment. Measurements of ?v at the blue edge of the visible absorption band of pinacyanol chloride yielded a value of 0.75 at 472.2 nm, which is the maximum value that a depolarization ratio can assume, and is attained if the average molecular polarizability is zero. This is possible only if the diagonalized polarizability tensor has at least one negative element to counterbalance the positive ones. A negative refractive index at the blue edge of the absorption band is thus experimentally demonstrated.

  15. Construct and concurrent validation of a new resistance intensity scale for exercise with thera-band® elastic bands.

    PubMed

    Colado, Juan C; Garcia-Masso, Xavier; Triplett, N Travis; Calatayud, Joaquin; Flandez, Jorge; Behm, David; Rogers, Michael E

    2014-12-01

    The construct and concurrent validity of the Thera-Band Perceived Exertion Scale for Resistance Exercise with elastic bands (EB) was examined. Twenty subjects performed two separate sets of 15 repetitions of both frontal and lateral raise exercise over two sessions. The criterion variables were myoelectric activity and heart rate. One set was performed with an elastic band grip width that permitted 15 maximum repetitions in the selected exercise, and another set was performed with a grip width 50% more than the 15RM grip. Following the final repetition of each set, active muscle (AM) and overall body (O) ratings of perceived exertion (RPE) were collected from the Thera-Band® resistance exercise scale and the OMNI-Resistance Exercise Scale of perceived exertion with Thera-Band® resistance bands (OMNI-RES EB). Construct validity was established by correlating the RPE from the OMNI-RES EB with the Thera-Band RPE scale using regression analysis. The results showed significant differences (p ? 0.05) in myoelectric activity, heart rate, and RPE scores between the low- and high-intensity sets. The intraclass correlation coefficient for active muscles and overall RPE scale scores was 0.67 and 0.58, respectively. There was a positive linear relationship between the RPE from the OMNI-RES EB and the Thera-Band scale. Validity coefficients for the RPE AM were r(2) = 0.87 and ranged from r(2) = 0.76 to 0.85 for the RPE O. Therefore, the Thera-Band Perceived Exertion Scale for Resistance Exercise can be used for monitoring elastic band exercise intensity. This would allow the training dosage to be better controlled within and between sessions. Moreover, the construct and concurrent validity indicates that the OMNI-RES EB measures similar properties of exertion as the Thera-Band RPE scale during elastic resistance exercise. Key pointsThis new resistance intensity scale is an appropriate and valid tool for assessing perceived exertion during strength training with elastic bands.This scale can be used without reducing the accuracy of the dosage prescribed during training/rehabilitation sessions and while carrying out medium and/or long-term periodization programs or therapeutic interventions.Populations with specific physical or physiological needs could have access to an easy-to-use resource that allows them to carry out their training/rehabilitation programs with greater efficacy and without any risk to health. PMID:25435767

  16. Construct and Concurrent Validation of a New Resistance Intensity Scale for Exercise with Thera-Band® Elastic Bands

    PubMed Central

    Colado, Juan C.; Garcia-Masso, Xavier; Triplett, N. Travis; Calatayud, Joaquin; Flandez, Jorge; Behm, David; Rogers, Michael E.

    2014-01-01

    The construct and concurrent validity of the Thera-Band Perceived Exertion Scale for Resistance Exercise with elastic bands (EB) was examined. Twenty subjects performed two separate sets of 15 repetitions of both frontal and lateral raise exercise over two sessions. The criterion variables were myoelectric activity and heart rate. One set was performed with an elastic band grip width that permitted 15 maximum repetitions in the selected exercise, and another set was performed with a grip width 50% more than the 15RM grip. Following the final repetition of each set, active muscle (AM) and overall body (O) ratings of perceived exertion (RPE) were collected from the Thera-Band® resistance exercise scale and the OMNI-Resistance Exercise Scale of perceived exertion with Thera-Band® resistance bands (OMNI-RES EB). Construct validity was established by correlating the RPE from the OMNI-RES EB with the Thera-Band RPE scale using regression analysis. The results showed significant differences (p ? 0.05) in myoelectric activity, heart rate, and RPE scores between the low- and high-intensity sets. The intraclass correlation coefficient for active muscles and overall RPE scale scores was 0.67 and 0.58, respectively. There was a positive linear relationship between the RPE from the OMNI-RES EB and the Thera-Band scale. Validity coefficients for the RPE AM were r2 = 0.87 and ranged from r2 = 0.76 to 0.85 for the RPE O. Therefore, the Thera-Band Perceived Exertion Scale for Resistance Exercise can be used for monitoring elastic band exercise intensity. This would allow the training dosage to be better controlled within and between sessions. Moreover, the construct and concurrent validity indicates that the OMNI-RES EB measures similar properties of exertion as the Thera-Band RPE scale during elastic resistance exercise. Key points This new resistance intensity scale is an appropriate and valid tool for assessing perceived exertion during strength training with elastic bands. This scale can be used without reducing the accuracy of the dosage prescribed during training/rehabilitation sessions and while carrying out medium and/or long-term periodization programs or therapeutic interventions. Populations with specific physical or physiological needs could have access to an easy-to-use resource that allows them to carry out their training/rehabilitation programs with greater efficacy and without any risk to health. PMID:25435767

  17. Intensity Dependent Absorption and Transit Relaxation on the Cesium D1 Line

    Microsoft Academic Search

    J. Sagle; R. K. Namiotka; J. Huennekens

    1997-01-01

    A nonlinear absorption is observed when an atomic transition is saturated. This intensity dependent absorption was measured on the D1 line in atomic cesium. The spatial cross section of the laser beam and the magnetic field applied to the vapor were controlled and varied during data collection to manipulate the transit relaxation and magnetic sublevel mixing rates, respectively. A three-level

  18. Full band structure calculation of two-photon indirect absorption in bulk silicon

    NASA Astrophysics Data System (ADS)

    Cheng, J. L.; Rioux, J.; Sipe, J. E.

    2011-03-01

    Degenerate two-photon indirect absorption in silicon is an important limiting effect on the use of silicon structures for all-optical information processing at telecommunication wavelengths. We perform a full band structure calculation to investigate two-photon indirect absorption in bulk silicon, using a pseudopotential description of the energy bands and an adiabatic bond charge model to describe phonon dispersion and polarization. Our results agree well with some recent experimental results. The transverse acoustic/optical phonon-assisted processes dominate.

  19. The absorption band at 1.128 eV of copper phthalocyanine films

    NASA Astrophysics Data System (ADS)

    Ohmukai, M.; Kubota, H.; Tsutsumi, Y.

    2007-08-01

    We deposited copper phthalocyanine (CuPc) films on (100) silicon wafers by means of a vacuum evaporation method and investigated the absorption characteristics by means of photoacoustic (PA) spectroscopy. It was verified that we excluded the PA signal originated in the silicon substrate with the chopping frequency of 200 Hz when the thickness of the CuPc film was 4.4 ?m. We then detected an absorption band at 1.128 eV (1.1 ?m). This band is possibly related to the charge transfer between Cu atoms and adsorbed oxygen molecules.

  20. Full band structure calculation of two-photon indirect absorption in bulk silicon

    SciTech Connect

    Cheng, J. L. [Department of Physics, Institute for Optical Sciences, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7 (Canada); Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Rioux, J.; Sipe, J. E. [Department of Physics, Institute for Optical Sciences, University of Toronto, 60 St. George Street, Toronto, Ontario M5S 1A7 (Canada)

    2011-03-28

    Degenerate two-photon indirect absorption in silicon is an important limiting effect on the use of silicon structures for all-optical information processing at telecommunication wavelengths. We perform a full band structure calculation to investigate two-photon indirect absorption in bulk silicon, using a pseudopotential description of the energy bands and an adiabatic bond charge model to describe phonon dispersion and polarization. Our results agree well with some recent experimental results. The transverse acoustic/optical phonon-assisted processes dominate.

  1. 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 ?m), 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.

  2. Picosecond laser induced electric field modulation of carotenoid absorption bands

    SciTech Connect

    Gosztola, D.; Yamada, Hiroko; Wasielewski, M.R.

    1994-04-01

    We present a new and unique way of forming an intense electric field near a molecule in order to induce electrochromism. We have done this by creating an electron-hole pair within close proximity to, but electronically isolated form, a polarizable molecule. The molecular system that we have utilized consists of a zinc porphyrin -- pyromellitic diimide light induced charge transfer complex held rigidly proximate to a {beta}-carotene using a calix[4]arene linkage. The formation of the charge separated state of the porphyrin-diimide results in a dipole formed by the 8.4 {Angstrom} separation of the electron-hole pair. The electric field from this dipole was found to induce electrochromism in the carotene.

  3. Diversity in the Visible-NIR Absorption Band Characteristics of Lunar and Asteroidal Plagioclase

    NASA Technical Reports Server (NTRS)

    Hiroi, T.; Kaiden, H.; Misawa, K.; Kojima, H.; Uemoto, K.; Ohtake, M.; Arai, T.; Sasaki, S.; Takeda, H.; Nyquist, L. E.; Shih, C.-Y.

    2012-01-01

    Studying the visible and near-infrared (VNIR) spectral properties of plagioclase has been challenging because of the difficulty in obtaining good plagioclase separates from pristine planetary materials such as meteorites and returned lunar samples. After an early study indicated that the 1.25 m band position of plagioclase spectrum might be correlated with the molar percentage of anorthite (An#) [1], there have been few studies which dealt with the band center behavior. In this study, the VNIR absorption band parameters of plagioclase samples have been derived using the modified Gaussian model (MGM) [2] following a pioneering study by [3].

  4. Integrated band intensities in N2O4 in the infrared range

    NASA Astrophysics Data System (ADS)

    Hurtmans, D.; Herman, M.; vander Auwera, J.

    1993-12-01

    We have measured the integrated band intensities of the nu(sub 9) and nu(sub 11) bands of N2O4 which are observed around 1757 and 1261/cm, respectively. By varying temperature and pressure, we have obtained: S(sub band)(nu (sub 9)) = 9.60(130), 9.10(24), 8.80(66) and S(sub band)(nu(sub 11)) = 5.93(64), 5.70(21) and 5.33(46) (in 10(exp -17) cm/molecule) at 293.15 (60), 277.25 (60) and 261.65 (60) K, respectively.

  5. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques.

    PubMed

    Limaye, Mukta V; Chen, S C; Lee, C Y; Chen, L Y; Singh, Shashi B; Shao, Y C; Wang, Y F; Hsieh, S H; Hsueh, H C; Chiou, J W; Chen, C H; Jang, L Y; Cheng, C L; Pong, W F; Hu, Y F

    2015-01-01

    The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S(2-) (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S(2-) species, but significantly increases the concentration of larger S clusters [polysulfides (Sn(2-), n?>?2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples. PMID:26098075

  6. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

    PubMed Central

    Limaye, Mukta V.; Chen, S. C.; Lee, C. Y.; Chen, L. Y.; Singh, Shashi B.; Shao, Y. C.; Wang, Y. F.; Hsieh, S. H.; Hsueh, H. C.; Chiou, J. W.; Chen, C. H.; Jang, L. Y.; Cheng, C. L.; Pong, W. F.; Hu, Y. F.

    2015-01-01

    The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2? (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2? species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2?, n?>?2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples. PMID:26098075

  7. Infrared absorption cross-sections and integrated absorption intensities of HFC-134 and HFC-143a vapour.

    NASA Astrophysics Data System (ADS)

    Smith, K.; Newnham, D.; Page, M.; Ballard, J.; Duxbury, G.

    1998-05-01

    Infrared absorption cross-sections and integrated absorption intensities of HFC-134 (1,1,2,2-tetrafluoroethane) and HFC-143a (1,1,1-trifluoroethane) vapour have been determined from laboratory measurements at six temperatures (203, 213, 233, 253, 273 and 297 K) for the region 560-1900 cm-1 (5.3-17.9 ?m) at 0.03 cm-1 instrument resolution, by Fourier transform infrared spectroscopy. In addition, air-broadened spectra have been recorded at 297 K and pressures of 5, 20 and 100 kPa air. Inter-comparisons between this work and previous studies have been made where possible.

  8. Fully Polarimetric Differential Intensity W-band Imager

    SciTech Connect

    Bernacki, Bruce E.; Tedeschi, Jonathan R.; Kelly, James F.; Sheen, David M.; Hall, Thomas E.; Valdez, Patrick LJ; Lechelt, Wayne M.; McMakin, Douglas L.

    2013-05-31

    We present a novel architecture based upon a Dicke-switched heterodyne radiometer architecture employing two identical input sections consisting of horn and orthomode transducer to detect the difference between the H and V polarization states of two separate object patches imaged by the radiometer. We have constructed and described previously a fully polarimetric W-band passive millimeter wave imager constructed to study the phenomenology of anomaly detection using polarimetric image exploitation of the Stokes images. The heterodyne radiometer used a PIN diode switch between the input millimeter wave energy and that of a reference load in order to eliminate the effects of component drifts and reduce the effects of 1/f noise. The differential approach differs from our previous work by comparing H and V polarization states detected by each of the two input horns instead of a reference load to form signals delta H and delta V from closely adjacent paired object patches. This novel imaging approach reduces common mode noise and enhances detection of small changes between the H and V polarization states of two object patches, now given as difference terms of the fully polarimetric radiometer. We present the theory of operation, initial proof of concept experimental results, and extension of the differential radiometer to a system with a binocular fore optics that allow adjustment of the convergence or shear of the object patches viewed by the differential polarimetric imager.

  9. Effect of Sn on the optical band gap determined using absorption spectrum fitting method

    NASA Astrophysics Data System (ADS)

    Heera, Pawan; Kumar, Anup; Sharma, Raman

    2015-05-01

    We report the preparation and the optical studies on tellurium rich glasses thin films. The thin films of Se30Te70-x Snx system for x= 0, 1.5, 2.5 and 4.5 glassy alloys prepared by melt quenching technique are deposited on the glass substrate using vacuum thermal evaporation technique. The analysis of absorption spectra in the spectral range 400nm-4000 nm at room temperature obtained from UV-VIS-NIR spectrophotometer [Perkin Elmer Lamda-750] helps us in the optical characterization of the thin films under study. The absorption spectrum fitting method is applied by using the Tauc's model for estimating the optical band gap and the width of the band tail of the thin films. The optical band gap is calculated and is found to decrease with the Sn content.

  10. Intelligent information extraction from reflectance spectra Absorption band positions. [application to laboratory and earth-based telescope spectra

    NASA Technical Reports Server (NTRS)

    Huguenin, R. L.; Jones, J. L.

    1986-01-01

    A multiple high-order derivative analysis algorithm has been developed which can automatically extract absorption band positions from low-quality reflectance spectra with little degredation of accuracy. Overlapping bands with comparable widths and intensities can be resolved whose centers are as close as 0.3-0.5 W, with safer resolution limits of 0.6-1.0 W band center separations suggested for overlapping bands that are dissimilar. The segment length for smoothing is continually adjusted to about 0.5 W to minimize signal distortion, and a spectral pattern recognition algorithm predicts the signal spectrum and calculates approximate W across the spectrum using its second derivative. A single-pass cubic spline is applied to the smoothed data, and a sliding segment sixth-order polynomial is fit to the spectrum, with the length of the segment being continuously locally adjusted to 1.0 W across the spectrum. Good reliability and consistency of the algorithm is demonstrated with application to laboratory and earth-based telescope spectra.

  11. Exploration of faint absorption bands in the reflectance spectra of the asteroids by method of optimal smoothing: Vestoids

    Microsoft Academic Search

    D. I. Shestopalov; L. A. McFadden; L. F. Golubeva

    2007-01-01

    An optimization method of smoothing noisy spectra was developed to investigate faint absorption bands in the visual spectral region of reflectance spectra of asteroids and the compositional information derived from their analysis. The smoothing algorithm is called ``optimal'' because the algorithm determines the best running box size to separate weak absorption bands from the noise. The method is tested for

  12. Exploration of faint absorption bands in the reflectance spectra of the asteroids by method of optimal smoothing: Vestoids

    Microsoft Academic Search

    D. I. Shestopalov; L. A. McFadden; L. F. Golubeva

    2007-01-01

    An optimization method of smoothing noisy spectra was developed to investigate faint absorption bands in the visual spectral region of reflectance spectra of asteroids and the compositional information derived from their analysis. The smoothing algorithm is called “optimal” because the algorithm determines the best running box size to separate weak absorption bands from the noise. The method is tested for

  13. Photonic band-engineering absorption enhancement of amorphous silicon for solar cells

    NASA Astrophysics Data System (ADS)

    El Daif, Ounsi; Drouard, Emmanuel; Gomard, Guillaume; Park, Yeonsang; Kaminski, Anne; Fave, Alain; Lemiti, Mustapha; Letartre, Xavier; Viktorovitch, Pierre; Ahn, Sungmo; Jeon, Heonsu; Seassal, Christian

    2009-08-01

    We report on enhancement of thin layer absorption through photonic band-engineering of a photonic crystal structure. We realized amorphous silicon (aSi) photonic crystals, where slow light modes improve absorption efficiency. We show through simulation that an increase of the absorption by a factor of 1.5 is expected for a model film of 100nm of aSi. The proposal is then validated by an experimental demonstration, showing a 50% increase of the absorption of a demonstrator layer of 1?m thick aSi over a spectral range of 0.32 -- 0.76?m. This shows new possibilities of increasing the efficiency of thin film photovoltaic cells. Photonic crystal based architecture are proposed and discussed.

  14. The cause of absorption and luminescence band shift of disperse Red-13 in silica spheres

    NASA Astrophysics Data System (ADS)

    Kim, Byoung-Ju; Kang, Kwang-Sun

    2014-02-01

    Optical absorption and luminescence band shifts have been observed for a disperse red-13 (DR-13) attached on silica spheres. A covalent bond is formed between an isocyanatopropyl triethoxysilane (ICPTES) and a DR-13 prior to DR-13 being incorporated inside the spheres. The Stöber synthesis process was performed with the synthesized ICPTES-DR-13 (ICPDR), tetraethoxy orthosilane (TEOS), 2-propanol and NH4OH solution. The final silica spheres with ICPDR (ICPDRSS) were analyzed with Fourier transform infrared, UV-visible and fluorescence spectrometers. Characteristic absorption peaks at 1700 and 1704 cm-1 representing -C=O stretching vibrations for ICPDR and ICPDRSS indicate the formation of urethane linkages. Although the absorption band at 502 nm did not shift with increasing concentration of DR-13 in methanol, the absorption band for the ICPDRSS shifted 28 nm toward shorter wavelength due to the antiparallel geometry of the azochromophores. A broad luminescence was observed for ICPDRSS and shifted toward the blue with increasing excitation wavelength, which was due to a transformation of the DR-13 in silica spheres from a trans-form to a cis-form.

  15. Absorption of Narrow-Gap HgCdTe Near the Band Edge Including Nonparabolicity and the Urbach Tail

    E-print Network

    Flatte, Michael E.

    Absorption of Narrow-Gap HgCdTe Near the Band Edge Including Nonparabolicity and the Urbach Tail, USA. 6.--e-mail: yonchang@uic.edu An analytical model describing the absorption behavior of Hg1-x. This model smoothly fits experimental absorption coefficients over energies ranging from the Urbach tail

  16. Phase Angle Effects on 3-micron Absorption Band on Ceres: Implications for Dawn Mission

    E-print Network

    Takir, Driss; Sanchez, Juan A; Corre, Lucille Le; Hardersen, Paul S; Nathues, Andreas

    2015-01-01

    Phase angle-induced spectral effects are important to characterize since they affect spectral band parameters such as band depth and band center, and therefore skew mineralogical interpretations of planetary bodies via reflectance spectroscopy. Dwarf planet (1) Ceres is the next target of NASA's Dawn mission, which is expected to arrive in March 2015. The visible and near-infrared mapping spectrometer (VIR) onboard Dawn has the spatial and spectral range to characterize the surface between 0.25-5.0 microns. Ceres has an absorption feature at 3.0 microns due to hydroxyl- and/or water-bearing minerals (e.g. Lebofsky et al. 1981, Rivkin et al. 2003). We analyzed phase angle-induced spectral effects on the 3-micron absorption band on Ceres using spectra measured with the long-wavelength cross-dispersed (LXD: 1.9-4.2 microns) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility (IRTF). Ceres LXD spectra were measured at different phase angles ranging from 0.7o to 22o. We found that the band...

  17. Detection of Near-IR CO Absorption Bands in R Coronae Borealis Stars

    E-print Network

    Emily D. Tenenbaum; Geoffrey C. Clayton; Martin Asplund; C. W. Engelbracht; Karl D. Gordon; M. M. Hanson; Richard J. Rudy; David K. Lynch; S. Mazuk; Catherine C. Venturini; R. C. Puetter

    2005-03-23

    R Coronae Borealis (RCB) stars are hydrogen-deficient, carbon-rich pulsating post-AGB stars that experience massive irregular declines in brightness caused by circumstellar dust formation. The mechanism of dust formation around RCB stars is not well understood. It has been proposed that CO molecules play an important role in cooling the circumstellar gas so that dust may form. We report on a survey for CO in a sample of RCB stars. We obtained H- and K-band spectra including the first and second overtone CO bands for eight RCB stars, the RCB-like star, DY Per and the final-helium-flash star, FG Sge. The first and second overtone CO bands were detected in the cooler (T(eff)6000 K) RCB stars, R CrB, RY Sgr, SU Tau, XX Cam. In addition, first overtone bands are seen in FG Sge, a final-helium-flash star that is in an RCB-like phase at present. Effective temperatures of the eight RCB stars range from 4000 to 7250 K. The observed photospheric CO absorption bands were compared to line-blanketed model spectra of RCB stars. As predicted by the models, the CO bands are strongest in the coolest RCB stars and not present in the warmest. No correlation was found between the presence or strength of the CO bands and dust formation activity in the stars.

  18. Parallel LC circuit model for multi-band absorption and preliminary design of radiative cooling.

    PubMed

    Feng, Rui; Qiu, Jun; Liu, Linhua; Ding, Weiqiang; Chen, Lixue

    2014-12-15

    We perform a comprehensive analysis of multi-band absorption by exciting magnetic polaritons in the infrared region. According to the independent properties of the magnetic polaritons, we propose a parallel inductance and capacitance(PLC) circuit model to explain and predict the multi-band resonant absorption peaks, which is fully validated by using the multi-sized structure with identical dielectric spacing layer and the multilayer structure with the same strip width. More importantly, we present the application of the PLC circuit model to preliminarily design a radiative cooling structure realized by merging several close peaks together. This omnidirectional and polarization insensitive structure is a good candidate for radiative cooling application. PMID:25607485

  19. Phase Angle Effects on 3 ?m Absorption Band on Ceres: Implications for Dawn Mission

    NASA Astrophysics Data System (ADS)

    Takir, D.; Reddy, V.; Sanchez, J. A.; Le Corre, L.; Hardersen, P. S.; Nathues, A.

    2015-05-01

    Phase angle-induced spectral effects are important to characterize since they affect spectral band parameters such as band depth and band center, and therefore skew mineralogical interpretations of planetary bodies via reflectance spectroscopy. Dwarf planet (1) Ceres is the next target of NASA’s Dawn mission, which is expected to arrive in 2015 March. The visible and near-infrared mapping spectrometer (VIR) on board Dawn has the spatial and spectral range to characterize the surface between 0.25–5.0 ?m. Ceres has an absorption feature at 3.0 ?m due to hydroxyl- and/or water-bearing minerals. We analyzed phase angle-induced spectral effects on the 3 ?m absorption band on Ceres using spectra measured with the long-wavelength cross-dispersed (LXD: 1.9–4.2 ?m) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility. Ceres LXD spectra were measured at different phase angles ranging from 0.°7 to 22°. We found that the band center slightly increases from 3.06 ?m at lower phase angles (0.°7 and 6°) to 3.07 ?m at higher phase angles (11° and 22°), the band depth decreases by ?20% from lower phase angles to higher phase angles, and the band area decreases by ?25% from lower phase angles to higher phase angles. Our results will have implications for constraining the abundance of OH on the surface of Ceres from VIR spectral data, which will be acquired by Dawn starting spring 2015.

  20. The IR spectra of 2-haloethylamines V. The intensity of the CCl and CBr stretching vibration bands in Kbr disks

    Microsoft Academic Search

    L. V. Sennitskaya; Yu. A. Pentin

    1973-01-01

    In the present paper the dependence of the intensity of the above-mentioned bands on the structure of the molecule has been investigated with the aim of comparing the v(C-C1) and v(C-Br) band intensities for the gauche and trans conformations. The intensities of the v(C-C1) and v(C-Br) bands of the majority of the compotmds previously studied have also been measured in

  1. A new k-interval optimization technique for atmospheric upwelling radiance calculation in infrared absorption bands

    NASA Astrophysics Data System (ADS)

    Zhang, Yin; Hao, Shijing; Yu, Kun; Cong, Mingyu

    2015-07-01

    A new optimization technique is proposed to generate the k-interval parameters including the quadrature weights and their corresponding equivalent absorption coefficients when using correlated k-distribution method for computations of spectrally integrated atmospheric upwelling radiances in infrared absorption bands. The main feature of this technique is the introduction of the upwelling contribution function (UCF) both in expressing the atmospheric upwelling radiance and in constructing the merit function for fitting, so that the optimization for the band radiance smoothly turns into the optimization for the band UCF of each atmospheric sublayer. The performance of the proposed technique is illustrated by comparing with the ?log(k) technique and the Gauss-Legendre quadrature technique at three different band settings in both the US standard atmosphere and the tropical atmosphere, and the line-by-line results are treated as the reference. Results show that there are less relative errors by the proposed optimization technique than by the other two techniques under the same number of k-intervals. In most cases, the computational efficiency can be improved by more than 10% under the same precision requirement in upwelling radiance calculations, and even 80% in some preferable conditions.

  2. Linear and nonlinear optical absorption in different graded quantum wells modulated by intense laser field

    NASA Astrophysics Data System (ADS)

    Ozturk, E.; Sokmen, I.

    2012-11-01

    The laser field dependence of the linear and nonlinear intersubband optical absorption in different graded quantum wells (GQWs) is investigated in the effective mass approximation. Results obtained show that the position and the magnitude of the linear and total absorption coefficients depend on the laser parameter and the shape of GQW. The resonant peak of total absorption coefficient can be bleached at sufficiently high incident optical intensities. Such a dependence of the exciting optical intensity on the external field strengths in different GQWs can be very useful for several potential device applications. It should point out that by applying the laser field we can obtain a blue shift or a red shift in the intersubband optical transitions.

  3. Sensitivity analysis of oxygen absorption lines in the 1.26-1.27 micron spectral band

    NASA Astrophysics Data System (ADS)

    Edwards, W. C.; Prasad, N.; Browell, E. V.

    2009-12-01

    In the Decadal Survey prepared by the National Research Council (Reference: Earth Science and Applications from Space: National Imperatives for the Next Decade and Beyond), the ASCENDS mission (Active Sensing of CO2 Emissions over Nights, Days and Seasons), requires simultaneous laser remote sensing of CO2 and O2 in order to convert CO2 atmospheric concentrations to mixing ratios. As the mission is envisioned, the CO2 mixing ratio needs to be measured to a precision of 0.5 percent of background or better (slightly less than 2 ppm) at 100-km horizontal length scale overland and at 200-km scale over open oceans. While the O2 measurement could be made at 0.765 µm (the oxygen A band), the absorption cross section is substantially higher and the scattering is lower in the 1.26-1.27 µm wavelength band, and as such it is anticipated that better accuracies could be accomplished. Hence, NASA Langley Research Center is developing oxygen lidar technology in the 1.26-1.27 micron band for surface pressure measurements. One or more wavelengths for differential absorption lidar operation have to be carefully chosen to eliminate ambient influences on them. The model optical depth calculation is very sensitive to knowledge of the transmitted wavelengths and to the choice of Voigt input parameters. Uncertainties in atmospheric profiles of temperature, pressure and relative humidity can cause ~0.5 % errors in model optical depths. In order to select candidate wavelengths in the 1.26 micron spectral band, wavelength uncertainties due to temperature and pressure have to be determined. Uncertainties at line center and offset wavelengths have to be known precisely to reduce uncertainties in oxygen concentration measurements from airborne and space based platforms. In this paper, based on HITRAN database and absorption line measurements, we evaluate systematic relative errors and their sources of pressure shift and atmospheric temperature influences for selected O2 lines suitable for making high precision measurements.

  4. Electronic absorption band broadening and surface roughening of phthalocyanine double layers by saturated solvent vapor treatment

    SciTech Connect

    Kim, Jinhyun [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of)] [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of); Yim, Sanggyu, E-mail: sgyim@kookmin.ac.kr [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of)] [Department of Chemistry, Kookmin University, Seoul 136-702 (Korea, Republic of)

    2012-10-15

    Variations in the electronic absorption (EA) and surface morphology of three types of phthalocyanine (Pc) thin film systems, i.e. copper phthalocyanine (CuPc) single layer, zinc phthalocyanine (ZnPc) single layer, and ZnPc on CuPc (CuPc/ZnPc) double layer film, treated with saturated acetone vapor were investigated. For the treated CuPc single layer film, the surface roughness slightly increased and bundles of nanorods were formed, while the EA varied little. In contrast, for the ZnPc single layer film, the relatively high solubility of ZnPc led to a considerable shift in the absorption bands as well as a large increase in the surface roughness and formation of long and wide nano-beams, indicating a part of the ZnPc molecules dissolved in acetone, which altered their molecular stacking. For the CuPc/ZnPc film, the saturated acetone vapor treatment resulted in morphological changes in mainly the upper ZnPc layer due to the significantly low solubility of the underlying CuPc layer. The treatment also broadened the EA band, which involved a combination of unchanged CuPc and changed ZnPc absorption.

  5. Frequency and intensity analysis of the nu3, nu4, and nu6 bands of formaldehyde

    NASA Technical Reports Server (NTRS)

    Reuter, D. C.; Nadler, S.; Daunt, S. J.; Johns, J. W. C.

    1989-01-01

    The infrared spectra of the nu3, nu4, and nu6 bands of formaldehyde in the region from 890/cm to 1580/cm have been obtained at high resolution using tunable diode laser and Fourier transform-infrared spectroscopy. The transition frequencies have been analyzed using a Hamiltonian including terms through sextic in centrifugal distortion and including five interstate vibration-rotation coupling terms. Excited-state pure rotational transitions are also included in the data, and their frequencies are reproduced well. Individual measured line intensities are used to determine dipole derivatives and band strengths using the fully coupled, asymmetric top eigenvectors.

  6. Absorption and x-ray measurements from ultra-intense laser-plasma interactions

    SciTech Connect

    Klem, D.E.; Darrow, C.; Lane, S.; Perry, M.D.

    1993-03-01

    The interaction of subpicosecond 1.06 mm laser light at intensities up to 10{sup 18} W/cm{sup 2} with dense performed plasmas is investigated by measurements of the absorption of the laser light in the plasma and by measurements of the production of bremsstrahlung x-rays. Absorption measurements are made by collecting the scattered light in an Ulbricht sphere. Light scattered in the backward and specular directions is collected separately. Measurements are presented for both high and low Z targets. X-ray production is measured using a nine channel filter/scintillator spectrometer.

  7. Ultra-narrow band perfect absorbers based on plasmonic analog of electromagnetically induced absorption.

    PubMed

    He, Jinna; Ding, Pei; Wang, Junqiao; Fan, Chunzhen; Liang, Erjun

    2015-03-01

    A novel plasmonic metamaterial consisting of the solid (bar) and the inverse (slot) compound metallic nanostructure for electromagnetically induced absorption (EIA) is proposed in this paper, which is demonstrated to achieve an ultra-narrow absorption peak with the linewidth less than 8 nm and the absorptivity exceeding 97% at optical frequencies. This is attributed to the plasmonic EIA resonance arising from the efficient coupling between the magnetic response of the slot (dark mode) and the electric resonance of the bar (bright mode). To the best of our knowledge, this is the first time that the plasmonic EIA is used to realize the narrow-band perfect absorbers. The underlying physics are revealed by applying the two-coupled-oscillator model. The near-perfect-absorption resonance also causes an enhancement of about 50 times in H-field and about 130 times in E-field within the slots. Such absorber possesses potential for applications in filter, thermal emitter, surface enhanced Raman scattering, sensing and nonlinear optics. PMID:25836832

  8. The gamma 1 and gamma 3 bands of (16)O3: Line positions and intensities

    NASA Technical Reports Server (NTRS)

    Flaud, J.-M.; Camy-Peyret, C.; Devi, V. Malathy; Rinsland, C. P.; Smith, M. A. H.

    1988-01-01

    Using 0.005/cm-resolution Fourier transform spectra of samples of ozone, the gamma 1 and gamma 3 bands of (16)O3 have been reanalyzed to obtain accurate line positions and an extended set of upper state rotational levels (J up to 69, K sub a up to 20). Combined with the available microwave data, these upper state rotational levels were satisfactorily fitted using a Hamiltonian which takes explicitly into account the strong Coriolis interaction affecting the rotational levels of these two interacting states. In addition, 350 relative line intensities were measured from which the rotational expansions of the transition moment operators for the gamma 1 and gamma 3 states have been deduced. Finally, a complete listing of line positions, intensities, and lower state energies of the gamma 1 and gamma 3 bands of (16)O3 has been generated.

  9. 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.

  10. Entire band absorption enhancement in double-side textured ultrathin solar cells by nanoparticle imprinting

    NASA Astrophysics Data System (ADS)

    Cai, Boyuan; Jia, Baohua; Fang, Jia; Hou, Guofu; Zhang, Xiaodan; Zhao, Ying; Gu, Min

    2015-06-01

    Entire band light management is crucial for amorphous silicon (a-Si) solar cells, especially when the absorbing layer becomes ultrathin. Here, we propose and demonstrate a double-side texture strategy to effectively manage light in ultrathin solar cells via a simple and scalable nanoparticle imprinting technique. SiO2 nanoparticles are half embedded into the top surface of the solar cells to introduce the double-side texture. Using a solar cell with a 150 nm thick a-Si layer as an example, we observe significant enhancement over the entire absorption band of a-Si both theoretically and experimentally. A maximum short circuit current density enhancement as high as 43.9% has been achieved experimentally compared with a flat solar cell.

  11. Study of sub band gap absorption of Sn doped CdSe thin films

    SciTech Connect

    Kaur, Jagdish; Rani, Mamta [Department of Physics, Panjab University, Chandigarh- 160014 (India); Tripathi, S. K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Panjab University, Chandigarh- 160014 (India)

    2014-04-24

    The nanocrystalline thin films of Sn doped CdSe at different dopants concentration are prepared by thermal evaporation technique on glass substrate at room temperature. The effect of Sn doping on the optical properties of CdSe has been studied. A decrease in band gap value is observed with increase in Sn concentration. Constant photocurrent method (CPM) is used to study the absorption coefficient in the sub band gap region. Urbach energy has been obtained from CPM spectra which are found to increase with amount of Sn dopants. The refractive index data calculated from transmittance is used for the identification of oscillator strength and oscillator energy using single oscillator model which is found to be 7.7 and 2.12 eV, 6.7 and 2.5 eV for CdSe:Sn 1% and CdSe:Sn 5% respectively.

  12. Optimal Reflectance, Transmittance, and Absorptance Wavebands and Band Ratios for the Estimation of Leaf Chlorophyll Concentration

    NASA Technical Reports Server (NTRS)

    Carter, Gregory A.; Spiering, Bruce A.

    2000-01-01

    The present study utilized regression analysis to identify: wavebands and band ratios within the 400-850 nm range that could be used to estimate total chlorophyll concentration with minimal error; and simple regression models that were most effective in estimating chlorophyll concentrations were measured for two broadleaved species, a broadleaved vine, a needle-leaved conifer, and a representative of the grass family.Overall, reflectance, transmittance, and absorptance corresponded most precisely with chlorophyll concentration at wavelengths near 700 nm, although regressions were strong as well in the 550-625 nm range.

  13. Infrared spectrum of solid isocyanic acid (HNCO): vibrational assignments and integrated band intensities

    NASA Astrophysics Data System (ADS)

    Lowenthal, M. S.; Khanna, R. K.; Moore, Marla H.

    2002-01-01

    Infrared spectra of thin films of solid HNCO condensed from the gas phase are characterized in terms of their vibrational frequencies, mode assignments, and integrated band intensities at low temperatures (˜20-145 K). Isocyanic acid is shown to react with water (H 2O) and ammonia (NH 3) even at low temperatures; consequently, it may be an important species in the chemistry of interstellar ices and comets.

  14. Absolute Rovibrational Intensities for the Chi(sup 1)Sigma(sup +) v=3 <-- 0 Band of (12)C(16)O Obtained with Kitt Peak and BOMEM FTS Instruments

    NASA Technical Reports Server (NTRS)

    Chackerian, Charles, Jr.; Kshirsagar, R. J.; Giver, L. P.; Brown, L. R.; Condon, Estelle P. (Technical Monitor)

    1999-01-01

    This work was initiated to compare absolute line intensities retrieved with the Kitt Peak FTS (Fourier Transform Spectrometer) and Ames BOMEM FTS. Since thermal contaminations can be a problem using the BOMEM instrument if proper precautions are not taken it was thought that measurements done at 6300 per cm would more easily result in satisfactory intercomparisons. Very recent measurements of the CO 3 <-- 0 band fine intensities confirms results reported here that the intensities listed in HITRAN (High Resolution Molecular Absorption Database) for this band are on the order of six to seven percent too low. All of the infrared intensities in the current HITRAN tabulation are based on the electric dipole moment function reported fifteen years ago. The latter in turn was partly based on intensities for the 3 <-- 0 band reported thirty years ago. We have, therefore, redetermined the electric dipole moment function of ground electronic state CO.

  15. Effects of soot absorption and scattering on LII intensities in laminar coflow diffusion flames

    Microsoft Academic Search

    Fengshan Liu; Kevin A. Thomson; Gregory J. Smallwood

    2008-01-01

    Absorption and scattering of laser-induced incandescence (LII) intensities by soot particles present between the measurement volume and the detector were numerically investigated at detection wavelengths of 400 and 780nm in a laminar coflow ethylene\\/air flame. The radiative properties of aggregated soot particles were calculated using the Rayleigh–Debye–Gans polydisperse fractal aggregate theory. The radiative transfer equation in emitting, absorbing, and scattering

  16. Measurements of Lorentz air-broadening coefficients and relative intensities in the H2O-16 pure rotational and nu2 bands from long horizontal path atmospheric spectra

    NASA Technical Reports Server (NTRS)

    Rinsland, Curtis P.; Smith, Mary Ann H.; Goldman, Aaron; Malathy Devi, V.

    1991-01-01

    Lorentz air-broadening coefficients and relative intensities have been measured for forty-three lines in the pure rotational band and twenty lines in the nu2 band of H2O-16 between 800 and 1150/cm. The results were derived from analysis of nine 0.017/cm-resolution atmospheric absorption spectra recorded over horizontal paths of 0.5-1.5 km with the McMath Fourier transform spectrometer and main solar telescope operated on Kitt Peak by the National Solar Observatory. A nonlinear least-squares spectral fitting technique was used in the spectral analysis. The results are compared with previous measurements and calculations. In most cases, the measured pressure-broadening coefficients and intensities are significantly different from the values in the 1986 HITRAN line parameters compilation.

  17. Absorption coefficients for the 6190-A CH4 band between 290 and 100 K with application to Uranus' atmosphere

    NASA Technical Reports Server (NTRS)

    Smith, Wm. Hayden; Conner, Charles P.; Baines, Kevin H.

    1990-01-01

    A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH4 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum.

  18. Determination of Strong Absorption Band Profiles of Low-Temperature Liquids from Reflection Spectra: The ?3 Band of Liquefied Tetrafluoromethane (CF4).

    PubMed

    Sergeev, Pavel K; Shchepkin, Dmitriy N; Kolomiitsova, Tatiana D; Bertsev, Vladimir V; Asfin, Ruslan E

    2015-04-01

    An experimental unit for recording the combined reflection-absorption spectra of low-temperature liquids was designed and manufactured and an algorithm for obtaining the extinction coefficient was developed. The manufactured experimental unit and the algorithm were tested by recording, for the first time, the absorption spectrum of liquefied CF4. The band parameters derived from the experimental data are compared with estimates available in the literature. PMID:25742364

  19. Structure in the visible absorption bands of jet-cooled phenylperoxy radicals.

    PubMed

    Freel, Keith A; Sullivan, Michael N; Park, J; Lin, M C; Heaven, Michael C

    2013-08-15

    The visible absorption bands of the phenylperoxy radical in the gas phase have been investigated using cavity ring-down spectroscopy. Jet-cooling was used to reduce the spectral congestion. Structured spectra spanning the range from 17,500 to 19,000 cm(-1) are reported for the first time. Analyses of these data have been guided by the results from time-dependent density functional calculations. The observed spectrum was found to be dominated by the bands of the B?(2)A?-X?(2)A? transition. An analysis of the rotational contour for the origin band yielded a homogeneous line width of 2.2 cm(-1), corresponding to a decay rate of 4.1 × 10(11) s(-1). The results provide a rationale for the lack of structure in room temperature spectra that have been previously attributed to phenylperoxy. They also indicate that the lower energy region of the spectrum may show resolvable structure at room temperature. If so, this would provide a more definitive signature for monitoring phenylperoxy in kinetic measurements. PMID:23590572

  20. Propagation and absorption of high-intensity femtosecond laser radiation in diamond

    NASA Astrophysics Data System (ADS)

    Kononenko, V. V.; Konov, V. I.; Gololobov, V. M.; Zavedeev, E. V.

    2014-12-01

    Femtosecond interferometry has been used to experimentally study the photoexcitation of the electron subsystem of diamond exposed to femtosecond laser pulses of intensity 1011 to 1014 W cm-2. The carrier concentration has been determined as a function of incident intensity for three harmonics of a Ti : sapphire laser (800, 400 and 266 nm). The results demonstrate that, in a wide range of laser fluences (up to those resulting in surface and bulk graphitisation), a well-defined multiphoton absorption prevails. We have estimated nonlinear absorption coefficients for pulsed radiation at ? = 800 nm (four-photon transition) and at 400 and 266 nm (indirect and direct two-photon transitions, respectively). It has also been shown that, at any considerable path length of a femtosecond pulse in diamond (tens of microns or longer), the laser beam experiences a severe nonlinear transformation, determining the amount of energy absorbed by the lattice, which is important for the development of technology for diamond photostructuring by ultrashort pulses. The competition between wave packet self-focusing and the plasma defocusing effect is examined as a major mechanism governing the propagation of intense laser pulses in diamond.

  1. Theoretical calculation of absorption intensities of C2H and C2D

    NASA Astrophysics Data System (ADS)

    Tarroni, Riccardo; Carter, Stuart

    2004-01-01

    The theory of dipole-allowed absorption intensities in triatomic molecules is presented for systems with three close-lying electronic states of doublet multiplicity. Its derivation is within the framework of a recently developed variational method [CARTER, S., HANDY, N. C., PUZZARINI, C., TARRONI, R., and PALMIERI, P., 2000, Molec. Phys., 98, 1967]. The method has been applied to the calculation of the infrared absorption spectrum of the C2H radical and its deuterated isotopomer for energies up to 10 000 cm-1 above the ground state, using highly accurate ab initio diabatic potential energy and dipole moment surfaces. The calculated spectra agree very well with those recorded experimentally in a neon matrix [FORNEY, D., JACOX, M. E., and THOMPSON, W. E., 1995, J. molec. Spectrosc., 170, 178] and assignments in the high energy region of the IR spectra are proposed for the first time.

  2. A simple method of absorption and decay correction in intensities measured by area-detector X-ray diffractometer

    E-print Network

    Takusagawa, Fusao

    1987-01-01

    A simple numerical method has been developed to correct for absorption and decay effects in the intensities measured by area-detector X-ray diffractometers. Application of this method improves not only the internal consistency of symmetry...

  3. The 5-0 Overtone Band of HCl by Intracavity Laser Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

    O'Brien, James J.; Ryan, Steven A.; O'Brien, Leah C.

    2011-06-01

    The 5-0 overtone band of HCl was recorded using intracavity laser absorption spectroscopy. The experimental conditions provided an effective pathlength of 23.6 km for the 1.81 m long intracavity compartment that contained the HCl gas. Most lines were recorded at 12-22 torr pressure: no noticeable pressure broadening or pressure shifts were observed in the spectra at the HCl pressures used in these experiments. Unblended lines could be determined to an accuracy of better than 0.005 wn, with a precision of better than 0.002 wn as indicated by the fit. Data from the two isotopologues were fit separately and the molecular constants compare favorably with previous literature values.

  4. First CRDS-measurements of water vapour continuum in the 940 nm absorption band

    NASA Astrophysics Data System (ADS)

    Reichert, L.; Andrés Hernández, M. D.; Burrows, J. P.; Tikhomirov, A. B.; Firsov, K. M.; Ptashnik, I. V.

    2007-06-01

    Measurements of near-infrared water vapour continuum using continuous wave cavity ring down spectroscopy (cw-CRDS) have been performed at around 10611.6 and 10685.2cm. The continuum absorption coefficients for N2-broadening have been determined to be CF296K=(1.0±0.2)×10cmmolatm and CF278K=(1.8±0.4)×10cmmolatm at 10611.6cm, and CF296K=(1.6±0.5)×10cmmolatm and CF278K=(2.1±0.4)×10cmmolatm at 10685.2cm, respectively. These results represent the first near-IR continuum laboratory data determined within the complex spectral environment in the 940 nm water vapour band and are in reasonable agreement with simulations using the semiempirical CKD formulation.

  5. VARIABILITY OF WATER AND OXYGEN ABSORPTION BANDS IN THE DISK-INTEGRATED SPECTRA OF EARTH

    SciTech Connect

    Fujii, Yuka; Suto, Yasushi [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Turner, Edwin L., E-mail: yuka.fujii@utap.phys.s.u-tokyo.ac.jp [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    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.

  6. Direct Observation of Two-Step Photon Absorption in an InAs/GaAs Single Quantum Dot for the Operation of Intermediate-Band Solar Cells.

    PubMed

    Nozawa, Tomohiro; Takagi, Hiroyuki; Watanabe, Katsuyuki; Arakawa, Yasuhiko

    2015-07-01

    We present the first direct observation of two-step photon absorption in an InAs/GaAs single quantum dot (QD) using photocurrent spectroscopy with two lasers. The sharp peaks of the photocurrent are shifted due to the quantum confined Stark effect, indicating that the photocurrent from a single QD is obtained. In addition, the intensity of the peaks depends on the power of the secondary laser. These results reveal the direct demonstration of the two-step photon absorption in a single QD. This is an essential result for both the fundamental operation and the realization of ultrahigh solar-electricity energy conversion in quantum dot intermediate-band solar cells. PMID:26099362

  7. Self-absorption theory applied to rocket measurements of the nitric oxide (1, 0) gamma band in the daytime thermosphere

    NASA Technical Reports Server (NTRS)

    Eparvier, F. G.; Barth, C. A.

    1992-01-01

    Observations of the UV fluorescent emissions of the NO (1, 0) and (0, 1) gamma bands in the lower-thermospheric dayglow, made with a sounding rocket launched on March 7, 1989 from Poker Flat, Alaska, were analyzed. The resonant (1, 0) gamma band was found to be attenuated below an altitude of about 120 km. A self-absorption model based on Holstein transmission functions was developed for the resonant (1, 0) gamma band under varying conditions of slant column density and temperature and was applied for the conditions of the rocket flight. The results of the model agreed with the measured attenuation of the band, indicating the necessity of including self-absorption theory in the analysis of satellite and rocket limb data of NO.

  8. Compositional dependence of molar absorptivities of near-infrared OH and H 2O bands in rhyolitic to basaltic glasses

    Microsoft Academic Search

    Susanne Ohlhorst; Harald Behrens; François Holtz

    2001-01-01

    Molar absorption coefficients (molar absorptivities) of the near infrared combination bands at 4500 and 5200 cm?1 assigned to OH groups and H2O molecules, respectively, were determined for glasses of dacitic, andesitic and basaltic compositions. Total water contents (range 1.5–6.3 wt.%) of the samples used in the calibration were determined by pyrolysis and subsequent Karl–Fischer Titration. Different combinations of baseline types

  9. Photodissociation of water in the first absorption band: A prototype for dissociation on a repulsive potential energy surface

    Microsoft Academic Search

    V. Engel; V. Staemmler; R. L. Vander Wal; F. F. Crim; R. J. Sension; B. Hudson; P. Andresen; S. Hennig; K. Weide; R. Schinke

    1992-01-01

    The photodissociation of water in the first absorption band, HâO(X) + âÏ â HâO(A¹Bâ) â H(²S) + OH(²II), is a prototype of fast and direct bond rupture in an excited electronic state. It has been investigated from several perspectives-absorption spectrum, final state distributions of the products, dissociation of vibrationally excited states, isotope effects, and emission spectroscopy. The availability of a

  10. Saturable absorption of highly stacked InAs quantum dot layer in 1.5 ?m band

    NASA Astrophysics Data System (ADS)

    Inoue, Jun; Isu, Toshiro; Akahane, Kouichi; Tsuchiya, Masahiro

    2006-10-01

    The authors examined 1.5?m band absorption saturation properties of 150 stacked InAs quantum dot layers on InP substrate. The transmission change at the vertical incidence based on the saturable absorption of the quantum dots was as much as 1%. Theoretical prediction shows that the transmission change could be greatly increased by removing the InP substrate. After grinding the substrate and antireflection coating on both surfaces, transmittance change was build up to 3%. It is thus concluded that highly stacked quantum dot layers are potentially applicable to a planar-type mode locker for short optical pulse generation in the 1.5?m band.

  11. Rotation-tunneling analysis of the origin band in the tropolone pi(*)<--pi absorption system.

    PubMed

    Bracamonte, Alfredo E; Vaccaro, Patrick H

    2004-03-01

    The tunneling-split origin band of the tropolone A (1)B(2)-X (1)A(1) (pi(*)<--pi) absorption system was interrogated under ambient, bulk-gas conditions by exploiting high-resolution degenerate four-wave mixing techniques. The inherent complexity of this spectral region was alleviated by performing polarization-resolved measurements, with judicious selection of transverse characteristics for the incident and detected electromagnetic fields enabling rovibronic transitions to be discriminated according to their attendant changes in rotational angular momentum, DeltaJ. Quantitative simulation of recorded data sets showed the vibrationless level of the electronically excited state to be bifurcated by Delta(0) (A)=19.846(25) cm(-1), representing a factor of 20 increase in proton-transfer efficiency over the corresponding level of the ground electronic state. Spectroscopic parameters extracted for the 0(+) and 0(-) manifolds of A (1)B(2) tropolone yield unexpectedly large values of the inertial defect, DeltaI(0(+) ) (A)=-0.802(86) amu A(2) and DeltaI(0(-) ) (A)=-0.882(89) amu A(2), strongly suggesting that a loss of molecular planarity accompanies the pi(*)<--pi electron promotion. These results, as well as complementary information deduced for interloping hot-band resonances, are discussed in terms of the unique structural and dynamical properties exhibited by tropolone and related proton-transfer species. PMID:15267323

  12. Determination of the Rb atomic number density in dense rubidium vapors by absorption measurements of Rb 2 triplet bands

    Microsoft Academic Search

    Vlasta Horvatic; Damir Veza; Kay Niemax; Cedomil Vadla

    2008-01-01

    A simple and accurate way of determining atom number densities in dense rubidium vapors is presented. The method relies on the experimental finding that the reduced absorption coefficients of the Rb triplet satellite bands between 740 nm and 750 nm and the triplet diffuse band between 600 nm and 610 nm are not temperature dependent in the range between 600 K and 800 K. Therefore, the

  13. Two-Photon Absorption in GaAs1 -x -yPyNx Intermediate-Band Solar Cells

    NASA Astrophysics Data System (ADS)

    Jussila, H.; Kivisaari, P.; Lemettinen, J.; Tanaka, T.; Sopanen, M.

    2015-05-01

    We demonstrate that a two-photon absorption process occurs in a GaAs1 -x -yPyNx -based solar cell in which a GaAs0.31P0.68N0.01 layer is implemented in the heterostructure and the E- energy band is isolated using an AlP blocking layer. The observed transition energies in external quantum-efficiency spectra correspond to the E- and E+ energy bands of the GaAs0.31P0.68N0.01 alloy and agree with the photoreflectance results. With photon energy smaller than the transition between the valence band and the E- band, the absorption of IR light increases the quantum efficiency by over 10% at room temperature and significantly more at lower temperatures due to the suppression in the thermionic emission. The effects of two-photon absorption on the I -V characteristics and output power of the fabricated GaAs1 -x -yPyNx solar cell are studied by current transport simulations. We show how doping of the intermediate band and current transport between the intermediate band and surrounding regions affect the operation of GaAs1 -x -yPyNx solar cells. Simulations under 1 Sun illumination result in an enhancement of 6% in the power density compared to a corresponding reference single-junction cell.

  14. Theoretical study of firefly luciferin pKa values--relative absorption intensity in aqueous solutions.

    PubMed

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

    2013-01-01

    Ground-state vibrational analyses of firefly luciferin and its conjugate acids and bases are performed. The Gibbs free energies obtained from these analyses are used to estimate pKa values for phenolic hydroxy and carboxy groups and the N-H(+) bond in the N-protonated thiazoline or benzothiazole ring of firefly luciferin. The theoretical pKa values are corrected using the experimental values. The concentrations of these chemical species in solutions with different pH values are estimated from their corrected pKa values, and the pH dependence of their relative absorption intensities is elucidated. With the results obtained we assign the experimental spectra unequivocally. Especially, the small peak near 400 nm at pH 1-2 in experimental absorption spectra is clarified to be due to the excitation of carboxylate anion with N-protonated thiazoline ring of firefly luciferin. Our results show that the pKa values of chemical species, which are contained in the aqueous solutions, are effective to assign experimental absorption spectra. PMID:23360188

  15. Photonic band gap structures of obliquely incident electromagnetic wave propagation in a one-dimension absorptive plasma photonic crystal

    SciTech Connect

    Guo Bin [Department of Physical Science and Technology, Wuhan University of Technology, Wuhan 430070 (China)

    2009-04-15

    The photonic band gap structures of obliquely incident electromagnetic waves propagating in a one-dimension plasma photonic crystal with collision have been studied on the basis of electromagnetic theory and transfer matrix approach. The dispersion relations for both the transverse electric wave case and the transverse magnetic wave case are deduced. And the photonic band gap structures, with their function dependence on the microplasma layer density, microplasma width, collision frequency, background material dielectric constant, and incident angle, are computed. The results show that there exist two photonic band gap structures in an adsorptive plasma photonic crystal: one is a normal photonic band gap structure and the other is an absorption photonic band gap structure. Parameter dependence of the effects is calculated and discussed.

  16. Effect of interdiffusion on band structure and intersubband absorption coefficient of GaAs\\/GaAlAs double quantum well

    Microsoft Academic Search

    V. L. Aziz Aghchegala; V. N. Mughnetsyan; A. A. Kirakosyan

    2011-01-01

    The influence of Ga and Al atoms interdiffusion on the band structure and absorption coefficient of coupled double quantum wells are investigated on the basis of a potential composed of four modified Wood–Saxon potentials. Wave functions of the real potential are expressed as a superposition of the stationary state wave functions of the “basal” potential. It is shown that interdiffusion

  17. Effect of interdiffusion on band structure and intersubband absorption coefficient of GaAs\\/GaAlAs double quantum well

    Microsoft Academic Search

    V. L. Aziz Aghchegala; V. N. Mughnetsyan; A. A. Kirakosyan

    2011-01-01

    The influence of Ga and Al atoms interdiffusion on the band structure and absorption coefficient of coupled double quantum wells are investigated on the basis of a potential composed of four modified Wood-Saxon potentials. Wave functions of the real potential are expressed as a superposition of the stationary state wave functions of the ``basal'' potential. It is shown that interdiffusion

  18. Enhanced light absorption of TiO2 in the near-ultraviolet band by Au nanoparticles

    E-print Network

    Wang, Wei Hua

    Enhanced light absorption of TiO2 in the near-ultraviolet band by Au nanoparticles Shu-Ya Du1, 2010 We proposea schemeto enhancenear-UVbandabsorptionof a rutileTiO2 nanoparticle by placing spectrum of pure rutile TiO2 and that of TiO2 mixed with Au nanoparticles. The results indicate that pure

  19. Below gap optical absorption in GaAs driven by intense, single-cycle coherent transition radiation

    DOE PAGESBeta

    Goodfellow, J.; Fuchs, M.; Daranciang, D.; Ghimire, S.; Chen, F.; Loos, H.; Reis, D. A.; Fisher, A. S.; Lindenberg, A. M.

    2014-01-01

    Single-cycle terahertz fields generated by coherent transition radiation from a relativistic electron beam are used to study the high field optical response of single crystal GaAs. Large amplitude changes in the sub-band-gap optical absorption are induced and probed dynamically by measuring the absorption of a broad-band optical beam generated by transition radiation from the same electron bunch, providing an absolutely synchronized pump and probe geometry. This modification of the optical properties is consistent with strong-field-induced electroabsorption. These processes are pertinent to a wide range of nonlinear terahertz-driven light-matter interactions anticipated at accelerator-based sources.

  20. High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge bands of oxygen at 79 K

    Microsoft Academic Search

    K. Yoshino; D. E. Freeman; J. R. Esmond; W. H. Parkinson

    1987-01-01

    Cross sections of O2 at 79 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 179.3-198.0 nm with a 6.65-m photoelectric scanning spectrometer equipped with a 2400-lines\\/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross sections of the Schumann-Runge bands (12,0) through (2,0) are independent of the instrumental width.

  1. Band gap tuning and optical absorption in type-II InAs/GaSb mid infrared short period superlattices: 14 bands K Dot-Operator p study

    SciTech Connect

    AbuEl-Rub, Khaled M. [Department of Applied Physical Sciences, Jordan University of Science and Technology Irbid, 21141 (Jordan)

    2012-09-06

    The MBE growth of short-period InAs/GaSb type-II superlattice structures, varied around 20.5 A InAs/24 A GaSb were [J. Applied physics, 96, 2580 (2004)] carried out by Haugan et al. These SLs were designed to produce devices with an optimum mid-infrared photoresponse and a sharpest photoresponse cutoff. We have used a realistic and reliable 14-band k.p formalism description of the superlattice electronic band structure to calculate the absorption coefficient in such short-period InAs/GaSb type-II superlattices. The parameters for this formalism are known from fitting to independent experiments for the bulk materials. The band-gap energies are obtained without any fitting parameters, and are in good agreement with experimental data.

  2. Absorption of high-contrast, intense short laser pulses on solids

    NASA Astrophysics Data System (ADS)

    Kemp, Andreas; Divol, Laurent

    2014-10-01

    We study the interaction of a 10 J / 100 fs intense laser pulse with solid aluminum using 1D and 2D kinetic / collisional particle simulations. In particular we are interested in an accurate description of the early phase of the interaction where the target is still cold, assuming that no plasma formation has set in before the arrival of the pulse. While most of the laser pulse is reflected, penetration of light into the skin layer and collisional heating lead to fast heating of the skin layer, and an increasing absorption of light into several groups of energetic electrons. We discuss details of the resulting electron spectrum, and plasma conditions expected immediately behind the interaction region under realistic conditions. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  3. Axial segregation in high intensity discharge lamps measured by laser absorption spectroscopy

    SciTech Connect

    Flikweert, A.J.; Nimalasuriya, T.; Groothuis, C.H.J.M.; Kroesen, G.M.W.; Stoffels, W.W. [Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven (Netherlands)

    2005-10-01

    High intensity discharge lamps have a high efficiency. These lamps contain rare-earth additives (in our case dysprosium iodide) which radiate very efficiently. A problem is color separation in the lamp because of axial segregation of the rare-earth additives, caused by diffusion and convection. Here two-dimensional atomic dysprosium density profiles are measured by means of laser absorption spectroscopy; the order of magnitude of the density is 10{sup 22} m{sup -3}. The radially resolved atomic density measurements show a hollow density profile. In the outer parts of the lamp molecules dominate, while the center is depleted of dysprosium atoms due to ionization. From the axial profiles the segregation parameter is determined. It is shown that the lamp operates on the right-hand side of the Fischer curve [J. Appl. Phys. 47, 2954 (1976)], i.e., a larger convection leads to less segregation.

  4. Influence of ion mass on laser-energy absorption and synchrotron radiation at ultrahigh laser intensities.

    PubMed

    Capdessus, R; d'Humières, E; Tikhonchuk, V T

    2013-05-24

    The role of ions in the energy absorption of a short and ultraintense laser pulse and in the synchrotron radiation generated by accelerated electrons is revisited. For laser intensities above 10(22) W/cm(2) and plasma densities more than 10 times the critical density, the ion-to-electron mass ratio strongly affects the energy repartition between the electrons, ions, and radiation. This phenomenon is studied with a one-dimensional relativistic particle-in-cell code, taking into account the radiation reaction force. The choice of the ion mass strongly affects the energy and angular distribution of the photon emission and the electron energy distribution. This effect may be important for laboratory modeling of radiation dominated relativistic astrophysical events. It can be verified in experiments with solid hydrogen targets. PMID:23745889

  5. Absorption of intense microwaves and ion acoustic turbulence due to heat transport

    SciTech Connect

    De Groot, J.S.; Liu, J.M. [California Univ., Davis, CA (United States); Matte, J.P. [INRS-Energie (Canada)] [and others

    1994-02-04

    Measurements and calculations of the inverse bremsstrahlung absorption of intense microwaves are presented. The isotropic component of the electron distribution becomes flat-topped in agreement with detailed Fokker-Planck calculations. The plasma heating is reduced due to the flat-topped distributions in agreement with calculations. The calculations show that the heat flux at high microwave powers is very large, q{sub max} {approx} 0.3 n{sub e}v{sub e}T{sub e}. A new particle model to, calculate the heat transport inhibition due to ion acoustic turbulence in ICF plasmas is also presented. One-dimensional PIC calculations of ion acoustic turbulence excited due to heat transport are presented. The 2-D PIC code is presently being used to perform calculations of heat flux inhibition due to ion acoustic turbulence.

  6. Study of molecular iodine, iodate ions, iodide ions, and triiodide ions solutions absorption in the UV and visible light spectral bands

    NASA Astrophysics Data System (ADS)

    Kireev, S. V.; Shnyrev, S. L.

    2015-07-01

    The paper reports on experimental studies concerning the absorption spectra of molecular iodine and its \\text{IO}3- , I?, \\text{I}3- anions in the spectral band of 180–600?nm. Values of the absorption cross-sections of the above mentioned substances have been measured, and relations of absorption coefficients to concentrations have been studied. The results obtained demonstrate that the spectral band under consideration is likely to be successfully used for simultaneous real-time detection of substances containing iodine with an absorption method using laser emission sources in the UV and visible light spectral bands.

  7. Transient reduction of tinnitus intensity is marked by concomitant reductions of delta band power

    PubMed Central

    Kahlbrock, Nina; Weisz, Nathan

    2008-01-01

    Background Tinnitus is an auditory phantom phenomenon characterized by the sensation of sounds without objectively identifiable sound sources. To date, its causes are not well understood. Previous research found altered patterns of spontaneous brain activity in chronic tinnitus sufferers compared to healthy controls, yet it is unknown whether these abnormal oscillatory patterns are causally related to the tinnitus sensation. Partial support for this notion comes from a neurofeedback approach developed by our group, in which significant reductions in tinnitus loudness could be achieved in patients who successfully normalized their patterns of spontaneous brain activity. The current work attempts to complement these studies by scrutinizing how modulations of tinnitus intensity alter ongoing oscillatory activity. Results In the present study the relation between tinnitus sensation and spontaneous brain activity was investigated using residual inhibition (RI) to reduce tinnitus intensity and source-space projected magnetencephalographic (MEG) data to index brain activity. RI is the sustained reduction (criteria: 50% for at least 30 s) in tinnitus loudness after cessation of a tonal tinnitus masker. A pilot study (n = 38) identified 10 patients who showed RI. A significant reduction of power in the delta (1.3–4.0 Hz) frequency band was observed in temporal regions during RI (p ? 0.001). Conclusion The current results suggest that changes of tinnitus intensity induced by RI are mediated by alterations in the pathological patterns of spontaneous brain activity, specifically a reduction of delta activity. Delta activity is a characteristic oscillatory activity generated by deafferented/deprived neuronal networks. This implies that RI effects might reflect the transient reestablishment of balance between excitatory and inhibitory neuronal assemblies, via reafferentation, that have been perturbed (in most tinnitus individuals) by hearing damage. As enhancements have been reported in the delta frequency band for tinnitus at rest, this result conforms to our assumption that a normalization of oscillatory properties of cortical networks is a prerequisite for attenuating the tinnitus sensation. For RI to have therapeutic significance however, this normalization would have to be stabilized. PMID:18199318

  8. Quantum-mechanical description of the intensity distribution in two-photon absorption spectra of dihalogenated benzenes

    NASA Astrophysics Data System (ADS)

    Burova, T. G.; Kucherova, V. V.

    2003-01-01

    Using molecules of dihalogenated benzenes as an example, the verification of an earlier proposed method of direct quantum-mechanical calculation of the relative intensities of lines in the two-photon absorption spectra of polyatomic molecules is continued. The method of calculation is based on the adiabatic model in the context of the Herzberg-Teller approximation. A comparative analysis of the intensity distribution in the two-photon absorption spectra of dihalogenated and monosubstituted benzenes is carried out, and the vibrational characteristics of these molecules in the lowest singlet excited electronic states are determined. A satisfactory agreement with experimental values, along with the analysis of the possibilities of the method, confirms the expediency of its use for gaining information about the intensity distribution in two-photon absorption spectra of polyatomic molecules.

  9. Multi-Band Absorption Properties and Near-Field Enhancement in Mid-Infrared Based on the Interference Theory

    NASA Astrophysics Data System (ADS)

    Heng, Hang; Yang, Li

    2014-05-01

    We numerically study the multi-band absorption properties and near-field enhancement inside the microcavity based on the interference theory. The compact single unit cell consists of a gold square patch placed on the top of a metallic ground plane, separated by a dielectric layer. At the normal incidence of electromagnetic radiation, four bands of a maximum absorption of 98% are accomplished by appropriate sizes of the square patch. Furthermore, we demonstrate that the four bands, which are corresponding to the fundamental mode and higher modes of the standing wave, can be readily tuned in the mid-infrared region and associated with the near-field enhancement in the cuboid microcavity. Since chemical and biological fingerprints of the common functional groups can be found in the mid-infrared region, we may readily tune the multi-bands of interest in the mid-infrared range and identify the molecular stretches of groups. Moreover, the proposed structure is insensitive to the polarization of the incident wave due to the complete rotational symmetry (C4 symmetry). The unique properties of the optical metamaterial indicate that this approach is a promising strategy for surface-enhanced infrared absorption spectroscopy and for the tracking of characteristic molecular vibrational modes

  10. Line intensities and collisional-broadening parameters for the nu4 and nu6 bands of carbonyl fluoride

    NASA Technical Reports Server (NTRS)

    May, Randy D.

    1992-01-01

    Line intensities, air- and self-broadening parameters have been measured for selected lines in the nu4 (1243/cm) and nu6 (774/cm) bands of carbonyl fluoride at 296 and 215 K using a tunable diode-laser spectrometer. Measured line intensities are in good agreement +/- 6 percent with recently reported values derived from rotational analyses of the nu4 and nu6 bands. The measured average air-broadening coefficient at 296 K also agrees well (+/- 5 percent) with N2-broadening coefficients determined from microwave studies, while the average self-broadening coefficient reported here is smaller than a previously reported value by 45 percent.

  11. Higher Order Mode Absorption in TTF Modules in the Frequency Range of the 3rd Dipole Band

    Microsoft Academic Search

    M. Dohlus; V. Kaljuzhny; S. G. Wipf

    2002-01-01

    One of the sources of transverse emittance dilution in the superconducting e+e? linear collider TESLA are transverse wakefields of higher frequency modes (HOM) excited in the accelerating cavities by long trains of intense bunches. Traditionally HOM couplers (HOMC) have been designed to damp modes from the 1st and 2nd dipole bands, however measurements have shown that modes with unexpectedly high

  12. The absorption spectrum of 13CH4 in the region of the 2?3 band at 1.66 ?m: Empirical line lists and temperature dependence

    NASA Astrophysics Data System (ADS)

    Campargue, A.; Segovia, J. Lopez; Béguier, S.; Kassi, S.; Mondelain, D.

    2015-02-01

    The absorption spectrum of 13CH4 has been recorded at 296 K and 80 K by differential absorption spectroscopy (DAS) in the high energy part of the tetradecad (5853-6201 cm-1) dominated by the 2?3 band near 5988 cm-1. The achieved noise equivalent absorption of the spectra (?min?1×10-7 cm-1) allowed us to double the number of 13CH4 lines previously measured in the region (our lists include about 7200 and 3700 lines at 296 and 80 K, respectively). Empirical values of the lower state energy level, Eemp, were systematically derived from the intensity ratios of the lines measured at 80 K and 296 K. Overall 2782 Eemp values were determined extending significantly the previous set of about 1200 Eemp values available in the literature. The corresponding empirical values of the rotational quantum number, Jemp, show a clear propensity to be close to an integer, illustrating the validity of the method. The line lists at 296 K and 80 K, provided as Supplementary material, are discussed in relation with line lists and rovibrational assignments available in the literature.

  13. [Preparation and SERS activity studies on substrate of nano-silver film with broad plasma absorption band].

    PubMed

    Zhang, De-Qing; Si, Min-Zhen; Liu, Ren-Ming; Liu, Zhen-Quan

    2012-09-01

    A highly reproducible and broad plasma absorption band nano-silver film was prepared by electrostatic self-assembly technology. The size of nano-silver particles on the surface of silver film, in the scanning electron microscopy (SEM) micrograph, is in a wide distribution from 18 to 200 nm. At the same time, the ultraviolet-visible spectrophotometer was employed to detect the nano-silver film. There is a broad plasma absorption band in the UV-Vis spectrum. To test the SERS activity of the nano-silver film, crystal violet and serum of healthy person were used as probe molecules and the high quality SERS spectra were obtained. PMID:23240413

  14. Detection of metal stress in boreal forest species using the 0.67-micron chlorophyll absorption band

    NASA Technical Reports Server (NTRS)

    Singhroy, Vernon H.; Kruse, Fred A.

    1991-01-01

    Several recent studies have shown that a shift of the red-edge inflection near 0.70 micron in vegetation reflectance spectra is an indicator of metal stress, partially attributable to changes in chlorophyll concentration. This 'red-edge shift', however, is difficult to detect and has been reported both toward longer (red) and shorter (blue) wavelengths. Our work demonstrates that direct measurement of the depth and width of the chlorophyll absorption band at 0.67 micron using digital feature extraction and absorption band characterization procedures developed for the analysis of mineral spectra is a more consistent indicator of metal stress. Additionally, the magnitude of these parameters is generally greater than that of the red edge shift and thus should be more amenable to detection and mapping using field and aircraft spectrometers.

  15. Dual-band perfect absorption and field enhancement by interaction between localized and propagating surface plasmons in optical metamaterials

    NASA Astrophysics Data System (ADS)

    Ding, Pei; Liang, Erjun; Cai, Genwang; Hu, Weiqin; Fan, Chunzhen; Xue, Qianzhong

    2011-07-01

    Dual-band perfect absorbers involving an array of gold nanoellipsoids or nanoellipsoid dimers near a gold film are designed and their resonance absorptions and field enhancements are numerically investigated. It is shown that the multilayer structures combining gold nanoparticles and gold film enable dual-band higher absorption and larger field enhancement than the structures without the metal film, due to the strong coupling between the localized surface plasmon resonance from the particles or particle dimers and the surface plasmon polaritons from the gold film. A field enhancement factor (|E|/|E0|) of more than 102 is achieved at the positions of 2.5 nm from the particle tip at two distinct wavelengths in the surface-plasmon-coupled nanoellipsoid dimer structure. The results suggest that the coupling of the localized surface plasmon resonance and the surface plasmon polaritons excited in the plasmonic metamaterials may have potential applications for multifrequency absorbers, emitters and SERS substrates as well as sensing.

  16. Analysis of the influence of O2 A-band absorption on atmospheric correction of ocean-color imagery

    NASA Astrophysics Data System (ADS)

    Ding, Kuiyuan; Gordon, Howard R.

    1995-04-01

    Two satellite-borne ocean-color sensors scheduled for launch in the mid 1990's each have a spectral band (nominally 745-785 nm) that completely encompasses the O2 A band at 762 nm. These spectral bands are to be used in atmospheric correction of the color imagery by assessment of the aerosol contribution to the total radiance at the sensor. The effect of the O 2 band on the radiance measured at the satellite is studied with a line-by-line backward Monte Carlo radiative transfer code. As expected, if the O2 absorption is ignored, unacceptably large errors in the atmospheric correction result. The effects of the absorption depend on the vertical profile of the aerosol. By assuming an aerosol profile-the base profile-we show that it is possible to remove most of the O 2-absorption effects from atmospheric correction in a simple manner. We also investigate the sensitivity of the results to the details of the assumed base profile and find that, with the exception of situations in which there are significant quantities of aerosol in the stratosphere, e.g., following volcanic eruptions or in the presence of thin cirrus clouds, the quality of the atmospheric correction depends only weakly on the base profile. Situations with high concentrations of stratospheric aerosol require additional information regarding vertical structure for this spectral band to be used in atmospheric correction; however, it should be possible to infer the presence of such aerosol by a failure of the atmospheric correction to produce acceptable water-leaving radiance in the red. An important feature of our method for removal of

  17. Total Absorption Gamma-ray Spectrometer (TAGS) Intensity Distributions from INL's Gamma-Ray Spectrometry Center

    DOE Data Explorer

    Greenwood, R. E.

    A 252Cf fission-product source and the INL on-line isotope separator were used to supply isotope-separated fission-product nuclides to a total absorption -ray spectrometer. This spectrometer consisted of a large (25.4-cm diameter x 30.5-cm long) NaI(Tl) detector with a 20.3-cm deep axial well in which is placed a 300-mm2 x 1.0-mm Si detector. The spectra from the NaI(Tl) detector are collected both in the singles mode and in coincidence with the B-events detected in the Si detector. Ideally, this detector would sum all the energy of the B- rays in each cascade following the population of daughter level by B- decay, so that the event could be directly associated with a particular daughter level. However, there are losses of energy from attenuation of the rays before they reach the detector, transmission of rays through the detector, escape of secondary photons from Compton scattering, escape of rays through the detector well, internal conversion, etc., and the measured spectra are thus more complicated than the ideal case and the analysis is more complex. Analysis methods have been developed to simulate all of these processes and thus provide a direct measure of the B- intensity distribution as a function of the excitation energy in the daughter nucleus. These data yield more accurate information on the B- distribution than conventional decay-scheme studies for complex decay schemes with large decay energies, because in the latter there are generally many unobserved and observed but unplaced rays. The TAGS data have been analyzed and published [R. E. Greenwood et al., Nucl Instr. and metho. A390(1997)] for 40 fission product-nuclides to determine the B- intensity distributions. [Copied from the TAGS page at http://www.inl.gov/gammaray/spectrometry/tags.shtml]. Those values are listed on this page for quick reference.

  18. Line positions and intensities for the gamma 1 + gamma 2 and gamma 2 + gamma 3 bands of (16)O3

    NASA Technical Reports Server (NTRS)

    Devi, V. Malathy; Flaud, J.-M.; Canypeyret, C.; Rinsland, C. P.; Smith, M. A. H.

    1988-01-01

    Using 0.005 cm-resolution Fourier transform spectra of (16)O3, generated by electric discharge from a greater than 99.98 percent pure sample of (16)O3, an extensive analysis of the gamma 1 + gamma 2 and the gamma 2 + gamma 3 bands in the 5.7 micron region was performed. The rotational energy levels of the upper (110) and (011) vibrational states of (16)O3 were reproduced within their experimental uncertainties using a Hamiltonian which takes explicitly into account the Coriolis-type interaction occurring between the rotational energy levels of both states. Improved vibrational energies and rotational and coupling constants were also derived for the (110) and (011) states. Precise transition moment constants for these two bands were deduced from analysis of 220 measured line intensities. Finally, a complete list of line positions, intensities, and lower state energies for both bands has been generated.

  19. Analysis of airborne imaging spectrometer data for the Ruby Mountains, Montana, by use of absorption-band-depth images

    NASA Technical Reports Server (NTRS)

    Brickey, David W.; Crowley, James K.; Rowan, Lawrence C.

    1987-01-01

    Airborne Imaging Spectrometer-1 (AIS-1) data were obtained for an area of amphibolite grade metamorphic rocks that have moderate rangeland vegetation cover. Although rock exposures are sparse and patchy at this site, soils are visible through the vegetation and typically comprise 20 to 30 percent of the surface area. Channel averaged low band depth images for diagnostic soil rock absorption bands. Sets of three such images were combined to produce color composite band depth images. This relative simple approach did not require extensive calibration efforts and was effective for discerning a number of spectrally distinctive rocks and soils, including soils having high talc concentrations. The results show that the high spectral and spatial resolution of AIS-1 and future sensors hold considerable promise for mapping mineral variations in soil, even in moderately vegetated areas.

  20. Anomalous Diffuse Interstellar Bands in the Spectrum of Herschel 36. I. Observations of Rotationally Excited CH and CH+ Absorption and Strong, Extended Redward Wings on Several DIBs

    NASA Astrophysics Data System (ADS)

    Dahlstrom, Julie; York, Donald G.; Welty, Daniel E.; Oka, Takeshi; Hobbs, L. M.; Johnson, Sean; Friedman, Scott D.; Jiang, Zihao; Rachford, Brian L.; Sherman, Reid; Snow, Theodore P.; Sonnentrucker, Paule

    2013-08-01

    Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 Å are found in absorption along the line of sight to Herschel 36, the star illuminating the bright Hourglass region of the H II region Messier 8. Interstellar absorption from excited CH+ in the J = 1 level and from excited CH in the J = 3/2 level is also seen. To our knowledge, neither those excited molecular lines nor such strongly extended DIBs have previously been seen in absorption from interstellar gas. These unusual features appear to arise in a small region near Herschel 36 which contains most of the neutral interstellar material in the sight line. The CH+ and CH in that region are radiatively excited by strong far-IR radiation from the adjacent infrared source Her 36 SE. Similarly, the broadening of the DIBs toward Herschel 36 may be due to radiative pumping of closely spaced high-J rotational levels of relatively small, polar carrier molecules. If this picture of excited rotational states for the DIB carriers is correct and applicable to most DIBs, the 2.7 K cosmic microwave background may set the minimum widths (about 0.35 Å) of known DIBs, with molecular processes and/or local radiation fields producing the larger widths found for the broader DIBs. Despite the intense local UV radiation field within the cluster NGC 6530, no previously undetected DIBs stronger than 10 mÅ in equivalent width are found in the optical spectrum of Herschel 36, suggesting that neither dissociation nor ionization of the carriers of the known DIBs by this intense field creates new carriers with easily detectable DIB-like features. Possibly related profile anomalies for several other DIBs are noted. Based in part on data obtained from the ESO Science Archive Facility by user DWELTY.

  1. Distortion of the amide-I and -II bands of an ?-helical membrane protein, pharaonis halorhodopsin, depends on thickness of gold films utilized for surface-enhanced infrared absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Guo, Hao; Kimura, Tetsunari; Furutani, Yuji

    2013-06-01

    Surface-enhanced infrared absorption with attenuated total reflection (ATR-SEIRA) is a powerful tool for exploring molecular mechanisms of membrane proteins at the monolayer level. However, the band intensity, position, and direction can be largely influenced by the presence of a thin gold film, as observed for small molecules existing in close proximity to the surface. Here we investigated influence on the band shapes of an ?-helical membrane protein, pharaonis halorhodopsin (pHR), attached on the gold surface through a complex formation between a six-histidines tag and a Ni-nitrilotriacetic acid (Ni-NTA) linker. Normal, bipolar, and inverted shapes of amide-I and -II bands were observed with an increase in film thickness, although pHR molecules would locate relatively far from the surface. The physical origin of this interesting phenomenon has been identified by changing incident angle, polarization, and film deposition rate. We find that the observed absorption anomalies are due to the influence of perpendicularly polarized light. Furthermore, it is shown that the band shapes are normal below the percolation threshold, and bipolar ones occur when an anomalous absorption by the films is strong, while the inverted ones develop with films in which surface scattering is predominant.

  2. 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.

  3. The 4750-Å band system of chlorine dioxide. Rotational analysis, force field and intensity calculations

    Microsoft Academic Search

    J. C. D. Brand; R. W. Redding; A. W. Richardson

    1970-01-01

    The structure of the nu1 vibronic band in the 2A2 <-- 2B1 electronic band system of chlorine dioxide has been rotationally analyzed as an A-type (parallel) band of a near-prolate asymmetric rotor. Excited state constants nu0, A, B, C, tauaaaa, taubbbb, tauaabb, and tauabab were obtained by a least-squares term value analysis based on about 730 assignments in the (100)

  4. Quantitative IR spectrophotometry of peptide compounds in water (H2O) solutions. II. Amide absorption bands of polypeptides and fibrous proteins in alpha-, beta-, and random coil conformations.

    PubMed

    Venyaminov SYu; Kalnin, N N

    1990-01-01

    Infrared spectra of poly(D,L-alanine), poly(L-glutamic acid), poly(L-lysine), silk fibroin, and tropomyosin have been registered for various conformations of the polypeptide chain. Assuming additivity of the main- and side-chain absorption, spectral parameters of amide I and II absorption bands corresponding to alpha-, beta-, and random coil conformations have been derived. The amide I band parameters for H2O and D2O have been compared. PMID:1707690

  5. Modeling of intensity-modulated continuous-wave laser absorption spectrometer systems for atmospheric CO(2) column measurements.

    PubMed

    Lin, Bing; Ismail, Syed; Wallace Harrison, F; Browell, Edward V; Nehrir, Amin R; Dobler, Jeremy; Moore, Berrien; Refaat, Tamer; Kooi, Susan A

    2013-10-10

    The focus of this study is to model and validate the performance of intensity-modulated continuous-wave (IM-CW) CO(2) laser absorption spectrometer (LAS) systems and their CO(2) column measurements from airborne and satellite platforms. The model accounts for all fundamental physics of the instruments and their related CO(2) measurement environments, and the modeling results are presented statistically from simulation ensembles that include noise sources and uncertainties related to the LAS instruments and the measurement environments. The characteristics of simulated LAS systems are based on existing technologies and their implementation in existing systems. The modeled instruments are specifically assumed to be IM-CW LAS systems such as the Exelis' airborne multifunctional fiber laser lidar (MFLL) operating in the 1.57 ?m CO(2) absorption band. Atmospheric effects due to variations in CO(2), solar radiation, and thin clouds, are also included in the model. Model results are shown to agree well with LAS atmospheric CO(2) measurement performance. For example, the relative bias errors of both MFLL simulated and measured CO(2) differential optical depths were found to agree to within a few tenths of a percent when compared to the in situ observations from the flight of 3 August 2011 over Railroad Valley (RRV), Nevada, during the summer 2011 flight campaign. In addition, the horizontal variations in the model CO(2) differential optical depths were also found to be consistent with those from MFLL measurements. In general, the modeled and measured signal-to-noise ratios (SNRs) of the CO(2) column differential optical depths (?d) agreed to within about 30%. Model simulations of a spaceborne IM-CW LAS system in a 390 km dawn/dusk orbit for CO(2) column measurements showed that with a total of 42 W of transmitted power for one offline and two different sideline channels (placed at different locations on the side of the CO(2) absorption line), the accuracy of the ?d measurements for surfaces similar to the playa of RRV, Nevada, will be better than 0.1% for 10 s averages. For other types of surfaces such as low-reflectivity snow and ice surfaces, the precision and bias errors will be within 0.23% and 0.1%, respectively. Including thin clouds with optical depths up to 1, the SNR of the ?d measurements with 0.1 s integration period for surfaces similar to the playa of RRV, Nevada, will be greater than 94 and 65 for sideline positions placed +3 and +10??pm, respectively, from the CO(2) line center at 1571.112 nm. The CO(2) column bias errors introduced by the thin clouds are ?0.1% for cloud optical depth ?0.4, but they could reach ?0.5% for more optically thick clouds with optical depths up to 1. When the cloud and surface altitudes and scattering amplitudes are obtained from matched filter analysis, the cloud bias errors can be further reduced. These results indicate that the IM-CW LAS instrument approach when implemented in a dawn/dusk orbit can make accurate CO(2) column measurements from space with preferential weighting across the mid to lower troposphere in support of a future ASCENDS mission. PMID:24217721

  6. Wideband enhancement of infrared absorption in a direct band-gap semiconductor by using nonabsorptive pyramids

    E-print Network

    Dai, Weitao

    Efficient trapping of the light in a photon absorber or a photodetector can improve its performance and reduce its cost. In this paper we investigate two designs for light-trapping in application to infrared absorption. ...

  7. Band-edge absorption coefficients from photoluminescence in semiconductor multiple quantum wells

    NASA Technical Reports Server (NTRS)

    Kost, Alan; Zou, Yao; Dapkus, P. D.; Garmire, Elsa; Lee, H. C.

    1989-01-01

    A novel approach to determining absorption coefficients in thin films using luminescence is described. The technique avoids many of the difficulties typically encountered in measurements of thin samples, Fabry-Perot effects, for example, and can be applied to a variety of materials. The absorption edge for GaAs/AlGaAs multiple quantum well structures, with quantum well widths ranging from 54 to 193 A is examined. Urbach (1953) parameters and excitonic linewidths are tabulated.

  8. Microscopic theory of gain, absorption, and refractive index in semiconductor laser materials-influence of conduction-band nonparabolicity and Coulomb-induced intersubband coupling

    Microsoft Academic Search

    J. Hader; J. V. Moloney; S. W. Koch

    1999-01-01

    The influence of the conduction-band nonparabolicity and Coulomb coupling between different electronic subbands and different hole subbands on gain, absorption, and refractive index in semiconductor heterostructures is investigated. We implement these features into a fully microscopic approach. At low carrier densities, the nonparabolicity leads to a steeper increase of the absorption for increasing transition energy. In this regime, the Coulomb

  9. Line-mixing in absorption bands of linear molecules diluted in high-density rare gases: Measurements and modeling for OCS-He

    NASA Astrophysics Data System (ADS)

    Buldyreva, Jeanna V.; Gennadiev, Nikolai A.; Filippov, Nikolai N.

    2013-04-01

    Absorption coefficients in the bending ?2 and stretching 2?3 bands of OCS perturbed by He at high pressures up to 300 atm have been measured and analyzed in the impact-approximation region by two theoretical models accounting for the line mixing. In the first approach, the frequency-independent relaxation operator is treated semi-classically [N. N. Filippov and M. V. Tonkov, J. Quant. Spectrosc. Radiat. Transf. 50, 111 (1993), 10.1016/0022-4073(93)90134-4] with adiabatic corrections. To characterize the strength of collisions and the line mixing efficiency a single parameter G is used and its value is estimated from the intermolecular interaction potential. The adiabaticity of collisions and the corresponding correction to the collisional cross sections amplitude are taken into account by two other parameters ?corr and ? deduced from fitting to experimental line widths. In the second approach, the symmetrized non-Markovian relaxation operator of Energy-Corrected Sudden type developed for rototranslational Raman spectra of linear rotators [J. Buldyreva and L. Bonamy, Phys. Rev. A 60, 370 (1999), 10.1103/PhysRevA.60.370] and satisfying all the basic properties (in particular, the detailed balance relation and the double-sided sum rules) is adapted to absorption spectra for the first time. Its off-diagonal elements are determined via the common adiabaticity factor and the basic transition rates whose parameters are adjusted on experimental values of isolated line widths. Both models provide a very consistent description of OCS-He 2?3 and ?2 band intensities up to the maximal experimentally studied pressure, with a slightly more realistic picturing of the inter-branch exchange by the second approach.

  10. Crystalline sulfur dioxide: Crystal field splittings, absolute band intensities and complex refractive indices derived from infrared spectra

    NASA Technical Reports Server (NTRS)

    Khanna, R. K.; Zhao, Guizhi

    1986-01-01

    The infrared absorption spectra of thin crystalline films of sulfur dioxide at 90 K are reported in the 2700 to 450/cm region. The observed multiplicity of the spectral features in the regions of fundamentals is attributed to factor group splittings of the modes in a biaxial crystal lattice and the naturally present minor S-34, S-36, and O-18 isotopic species. Complex refractive indices determined by an iterative Kramers-Kronig analysis of the extinction data, and absolute band strengths derived from them, are also reported in this region.

  11. Application of surface pressure measurements of O2-band differential absorption radar system in three-dimensional data assimilation on hurricane: Part II - A quasi-observational study

    NASA Astrophysics Data System (ADS)

    Min, Qilong; Gong, Wei; Lin, Bing; Hu, Yongxiang

    2015-01-01

    This is the second part on assessing the impacts of assimilating various distributions of sea-level pressure (SLP) on hurricane simulations, using the Weather and Research Forecast (WRF) three dimensional variational data assimilation system (3DVAR). One key purpose of this series of study is to explore the potential of using remotely sensed sea surface barometric data from O2-band differential absorption radar system currently under development for server weather including hurricane forecasts. In this part II we further validate the conclusions of observational system simulation experiments (OSSEs) in the part I using observed SLP for three hurricanes that passed over the Florida peninsula. Three SLP patterns are tested again, including all available data near the Florida peninsula, and a band of observations either through the center or tangent to the hurricane position. Before the assimilation, a vortex SLP reconstruction technique is employed for the use of observed SLP as discussed in the part I. In agreement with the results from OSSEs, the performance of assimilating SLP is enhanced for the two hurricanes with stronger initial minimum SLP, leading to a significant improvement in the track and position relative to the control where no data are assimilated. On the other hand, however, the improvement in the hurricane intensity is generally limited to the first 24-48 h of integration, while a high resolution nested domain simulation, along with assimilation of SLP in the coarse domain, shows more profound improvement in the intensity. A diagnostic analysis of the potential vorticity suggests that the improved track forecasts are attributed to the combined effects of adjusting the steering wind fields in a consistent manner with having a deeper vortex, and the associated changes in the convective activity.

  12. On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

    SciTech Connect

    Chattopadhyay, P.; Karim, B.; Guha Roy, S. [Department of Electronic Science, University of Calcutta, 92, A.P.C. Road, Kolkata 700009 (India)

    2013-12-28

    The sub-band gap optical absorption in chemical bath deposited cadmium sulphide thin films annealed at different temperatures has been critically analyzed with special reference to Urbach relation. It has been found that the absorption co-efficient of the material in the sub-band gap region is nearly constant up to a certain critical value of the photon energy. However, as the photon energy exceeds the critical value, the absorption coefficient increases exponentially indicating the dominance of Urbach rule. The absorption coefficients in the constant absorption region and the Urbach region have been found to be sensitive to annealing temperature. A critical examination of the temperature dependence of the absorption coefficient indicates two different kinds of optical transitions to be operative in the sub-band gap region. After a careful analyses of SEM images, energy dispersive x-ray spectra, and the dc current-voltage characteristics, we conclude that the absorption spectra in the sub-band gap domain is possibly associated with optical transition processes involving deep levels and the grain boundary states of the material.

  13. The nature of the bands in the electronic absorption spectrum of trans-chalcone

    Microsoft Academic Search

    A. A. Sukhorukov; B. A. Zadorozhnyi; V. F. Lavrushin

    1973-01-01

    The present paper examines the ground and excited states of the ~-electron system of trans-chalcone within the framework of the semiempirical MO theory. The results of the theory are compared with more accurate experimental data on the vibronic absorption spectra. EXPERIMENTAL For the spectrophotometr ic measurements we used trans-chalcone with mp =58~ The solvents (noctane and ethanol) were purified by

  14. THE 217.5 nm BAND, INFRARED ABSORPTION, AND INFRARED EMISSION FEATURES IN HYDROGENATED AMORPHOUS CARBON NANOPARTICLES

    SciTech Connect

    Duley, W. W. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada)] [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada); Hu, Anming, E-mail: wwduley@uwaterloo.ca, E-mail: a2hu@uwaterloo.ca [Department of Mechanical and Mechatronics Engineering, Centre for Advanced Material Joining, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada)] [Department of Mechanical and Mechatronics Engineering, Centre for Advanced Material Joining, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1 (Canada)

    2012-12-20

    We report on the preparation of hydrogenated amorphous carbon nanoparticles whose spectral characteristics include an absorption band at 217.5 nm with the profile and characteristics of the interstellar 217.5 nm feature. Vibrational spectra of these particles also contain the features commonly observed in absorption and emission from dust in the diffuse interstellar medium. These materials are produced under ''slow'' deposition conditions by minimizing the flux of incident carbon atoms and by reducing surface mobility. The initial chemistry leads to the formation of carbon chains, together with a limited range of small aromatic ring molecules, and eventually results in carbon nanoparticles having an sp {sup 2}/sp {sup 3} ratio Almost-Equal-To 0.4. Spectroscopic analysis of particle composition indicates that naphthalene and naphthalene derivatives are important constituents of this material. We suggest that carbon nanoparticles with similar composition are responsible for the appearance of the interstellar 217.5 nm band and outline how these particles can form in situ under diffuse cloud conditions by deposition of carbon on the surface of silicate grains. Spectral data from carbon nanoparticles formed under these conditions accurately reproduce IR emission spectra from a number of Galactic sources. We provide the first detailed fits to observational spectra of Type A and B emission sources based entirely on measured spectra of a carbonaceous material that can be produced in the laboratory.

  15. Spectroscopic determination of leaf biochemistry using band-depth analysis of absorption features and stepwise multiple linear regression

    USGS Publications Warehouse

    Kokaly, R.F.; Clark, R.N.

    1999-01-01

    We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ??m, 2.10 ??m, and 2.30 ??m that were highly correlated with the chemistry of samples from eastern U.S. forests. Band depths of absorption features at these wavelengths were found to also be highly correlated with the chemistry of four other sites. A subset of data from the eastern U.S. forest sites was used to derive linear equations that were applied to the remaining data to successfully estimate their nitrogen, lignin, and cellulose concentrations. Correlations were highest for nitrogen (R2 from 0.75 to 0.94). The consistent results indicate the possibility of establishing a single equation capable of estimating the chemical concentrations in a wide variety of species from the reflectance spectra of dried leaves. The extension of this method to remote sensing was investigated. The effects of leaf water content, sensor signal-to-noise and bandpass, atmospheric effects, and background soil exposure were examined. Leaf water was found to be the greatest challenge to extending this empirical method to the analysis of fresh whole leaves and complete vegetation canopies. The influence of leaf water on reflectance spectra must be removed to within 10%. Other effects were reduced by continuum removal and normalization of band depths. If the effects of leaf water can be compensated for, it might be possible to extend this method to remote sensing data acquired by imaging spectrometers to give estimates of nitrogen, lignin, and cellulose concentrations over large areas for use in ecosystem studies.We develop a new method for estimating the biochemistry of plant material using spectroscopy. Normalized band depths calculated from the continuum-removed reflectance spectra of dried and ground leaves were used to estimate their concentrations of nitrogen, lignin, and cellulose. Stepwise multiple linear regression was used to select wavelengths in the broad absorption features centered at 1.73 ??m, 2.10 ??m, and 2.301 ??m that were highly correlated with the chemistry of samples from eastern U.S. forests. Band depths of absorption features at these wavelengths were found to also be highly correlated with the chemistry of four other sites. A subset of data from the eastern U.S. forest sites was used to derive linear equations that were applied to the remaining data to successfully estimate their nitrogen, lignin, and cellulose concentrations. Correlations were highest for nitrogen (R2 from 0.75 to 0.94). The consistent results indicate the possibility of establishing a single equation capable of estimating the chemical concentrations in a wide variety of species from the reflectance spectra of dried leaves. The extension of this method to remote sensing was investigated. The effects of leaf water content, sensor signal-to-noise and bandpass, atmospheric effects, and background soil exposure were examined. Leaf water was found to be the greatest challenge to extending this empirical method to the analysis of fresh whole leaves and complete vegetation canopies. The influence of leaf water on reflectance spectra must be removed to within 10%. Other effects were reduced by continuum removal and normalization of band depths. If the effects of leaf water can be compensated for, it might be possible to extend this method to remote sensing data acquired by imaging spectrometers to give estimates of nitrogen, lignin, and cellulose concentrations over large areas for use in ecosystem studies.

  16. Experimental demonstrations of record high REAM intensity modulator-enabled 19.25Gb/s real-time end-to-end dual-band optical OFDM colorless transmissions over 25km SSMF IMDD systems.

    PubMed

    Zhang, Q W; Hugues-Salas, E; Giddings, R P; Wang, M; Tang, J M

    2013-04-01

    Record-high 19.25Gb/s real-time end-to-end dual-band optical OFDM (OOFDM) colorless transmissions across the entire C-band are experimentally demonstrated, for the first time, in reflective electro-absorption modulator (REAM)-based 25km standard SMF systems using intensity modulation and direct detection. Adaptively modulated baseband (0-2GHz) and passband (6.125 ± 2GHz) OFDM RF sub-bands, supporting signal line rates of 9.75Gb/s and 9.5Gb/s respectively, are independently generated and detected with FPGA-based DSP clocked at only 100MHz as well as DACs/ADCs operating at sampling speeds as low as 4GS/s. The two OFDM sub-bands are electrically multiplexed for intensity modulation of a single optical carrier by an 8GHz REAM. The REAM colorlessness is experimentally characterized, based on which optimum REAM operating conditions are identified. To maximize and balance the signal transmission performance of each sub-band, on-line adaptive transceiver optimization functions and live performance monitoring are fully exploited to optimize key OOFDM transceiver and system parameters. For different wavelengths within the C-band, corresponding minimum received optical powers at the FEC limit vary in a range of <0.5dB and bit error rate performances for both baseband and passband signals are almost identical. Furthermore, detailed investigations are also undertaken of the maximum aggregated signal line rate sensitivity to electrical sub-band power variation. It is shown that the aforementioned system has approximately 3dB tolerance to RF sub-band power variation. PMID:23572005

  17. Infrared, visible and ultraviolet absorptions of transition metal doped ZnS crystals with spin-polarized bands

    SciTech Connect

    Zhang, J.H. [Department of Physics and Institute for Nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan 411105 (China); Ding, J.W., E-mail: jwding@xtu.edu.c [Department of Physics and Institute for Nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan 411105 (China); Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan University, Xiangtan, Hunan 411105 (China); Cao, J.X. [Department of Physics and Institute for Nanophysics and Rare-earth Luminescence, Xiangtan University, Xiangtan 411105 (China); Key Laboratory of Low Dimensional Materials and Application Technology, Xiangtan University, Xiangtan, Hunan 411105 (China); Zhang, Y.L. [Department of Physics, Zhejiang University, Hangzhou 310027 (China)

    2011-03-15

    The formation energies, electronic structures and optical properties of TM:ZnS systems (TM=Cr{sup 2+}, Mn{sup 2+}, Fe{sup 2+}, Co{sup 2+} and Ni{sup 2+}) are investigated by using the first principles method. It is found that the wurtzite and zinc-blende structures have about the same stability, and thus can coexist in the TM:ZnS system. From the wurtzite TM:ZnS, especially, a partially filled intermediate band (IB) is obtained at TM=Cr{sup 2+}, Ni{sup 2+} and Fe{sup 2+}, while it is absent at TM=Mn{sup 2+} and Co{sup 2+}. The additional absorptions are obtained in infrared, visible and ultraviolet (UV) regions, due to the completely spin-polarized IB at Fermi level. The results are very helpful for both the designs and applications of TM:ZnS opto-electronics devices, such as solar-cell prototype. -- Graphical abstract: Absorption coefficients of w-TM{sub x}Zn{sub 1-x}S crystals (TM=Cr{sup 2+}, Mn{sup 2+}, Fe{sup 2+}, Co{sup 2+} and Ni{sup 2+}) at x=0.028. The results may be helpful for the design and applications of TM:ZnS devices, especially for the new high efficiency solar-cell prototype, UV detector and UV LEDs. Display Omitted Research highlights: > It is found that the wurtzite and zinc-blende structures can coexist in TM:ZnS. > An intermediate band is obtained in TM:ZnS at TM=Cr{sup 2+}, Ni{sup 2+} and Fe{sup 2+}. > The absorption coefficients are obtained in infrared, visible and ultraviolet regions.

  18. Band offsets and chemical bonding states in N-plasma-treated HfSiON gate stacks studied by photoelectron spectroscopy and x-ray absorption spectroscopy

    SciTech Connect

    Oshima, M.; Takahashi, H.; Okabayashi, J.; Toyoda, S.; Kumigashira, H.; Inoue, M.; Mizutani, M.; Yugami, J. [Department of Applied Chemistry, University of Tokyo, Bunkyo-ku, Tokyo 113-8656 (Japan); Renesas Technology Corporation, Itami, Hyogo 664-0005 (Japan)

    2006-08-01

    We have investigated valence band and conduction band electronic structures and interfacial chemical bonding states of nitrogen-plasma-treated HfSiON/SiON gate stacks on Si substrates with and without rapid thermal annealing by photoelectron spectroscopy and x-ray absorption spectroscopy to correlate them with electrical properties. We have found that the N3 component in N 1s can be correlated with electron trapping. Photoelectron spectra and O K-edge absorption spectra confirm the existence of the SiO{sub 2}-rich phase-separated area in HfSiON films. Band offsets for the HfSiON/Si and the SiO{sub 2}-rich HfSiON/Si are determined to be 2.5 and 4.2 eV for valence band and 1.7 and 3.6 eV for conduction band, respectively.

  19. Hydrogen-Saturated Saline Protects Intensive Narrow Band Noise-Induced Hearing Loss in Guinea Pigs through an Antioxidant Effect

    PubMed Central

    Chen, Liwei; Yu, Ning; Lu, Yan; Wu, Longjun; Chen, Daishi; Guo, Weiwei; Zhao, Lidong; Liu, Mingbo; Yang, Shiming; Sun, Xuejun; Zhai, Suoqiang

    2014-01-01

    The purpose of the current study was to evaluate hydrogen-saturated saline protecting intensive narrow band noise-induced hearing loss. Guinea pigs were divided into three groups: hydrogen-saturated saline; normal saline; and control. For saline administration, the guinea pigs were given daily abdominal injections (1 ml/100 g) 3 days before and 1 h before narrow band noise exposure (2.5–3.5 kHz 130 dB SPL, 1 h). The guinea pigs in the control group received no treatment. The hearing function was assessed by the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recording. The changes of free radicals in the cochlea before noise exposure, and immediately and 7 days after noise exposure were also examined. By Scanning electron microscopy and succinate dehydrogenase staining, we found that pre-treatment with hydrogen-saturated saline significantly reduced noise-induced hair cell damage and hearing loss. We also found that the malondialdehyde, lipid peroxidation, and hydroxyl levels were significantly lower in the hydrogen-saturated saline group after noise trauma, indicating that hydrogen-saturated saline can decrease the amount of harmful free radicals caused by noise trauma. Our findings suggest that hydrogen-saturated saline is effective in preventing intensive narrow band noise-induced hearing loss through the antioxidant effect. PMID:24945316

  20. Broad-band polarization-independent absorption of electromagnetic waves by an overdense plasma

    SciTech Connect

    Bliokh, Y. P.; Brodsky, Yu. L.; Chashka, Kh. B.; Felsteiner, J.; Slutsker, Ya. Z. [Department of Physics, Technion, 32000 Haifa (Israel)

    2010-08-15

    Surface plasmon-polaritons can be efficiently excited on a plasma-vacuum interface by an electromagnetic wave when a subwavelength diffraction grating is placed in front of the plasma boundary. The excitation efficiency depends strongly on the wave frequency (or plasma density, when the frequency is fixed) and polarization. We show both experimentally and theoretically that this sensitivity can be essentially suppressed. A nonzero angle of incidence and an axially symmetric diffraction grating ensure near-total absorption of the incident wave in a broad range of wave frequencies (or plasma densities, when the frequency is fixed). Direct detection of surface plasmon-polaritons has been achieved for the first time using a miniature antenna embedded in the plasma. A new absorption mechanism which is not associated with surface plasma wave excitation is revealed.

  1. Non-linear optical response of bulk chalcogenide glasses near the fundamental absorption band edge

    NASA Astrophysics Data System (ADS)

    Romanova, E. A.; Konyukhov, A. I.; Kochubey, V. I.; Benson, T. M.; Barney, E.; Abdel-Moneim, N.; Furniss, D.; Seddon, A. B.; Guizard, S.

    2015-06-01

    Magnitudes of the non-linear coefficients of absorption and refraction have been evaluated near the bandgap wavelengths of chalcogenide glasses of the system As-S-Se by using the interferometric pump-probe method and are compared with literature data. Photoexcited plasma dynamics and long-time scale variation of the dielectric constant have been studied by comparison with the results of numerical modelling of the behaviour of the glasses when heated by the ultra-short laser pulses.

  2. The contribution of interaural intensity differences to the horizontal auditory localization of narrow bands of noise

    Microsoft Academic Search

    Matthew H. Bakke

    1999-01-01

    Brief bursts of third-octave bands of noise (center frequencies at 0.5, 1.0, 2.0 and 4.0 kHz) and band pass noises with different degrees of low-frequency content (0.5 to 4.0 kHz, 1.0 to 4.0 kHz and 2.0 to 4.0 kHz) were recorded binaurally from 17 different horizontal locations (90 degrees on the left to 90 degrees on the right in 11.25

  3. Laser photochemistry of DNA: Two-photon absorption and optical breakdown using high-intensity, 532-nm radiation

    SciTech Connect

    Hefetz, Y.; Dunn, D.A.; Deutsch, T.F.; Buckley, L.; Kochevar, I.E. (Harvard Medical School, Boston, MA (United States)); Hillenkamp, F. (Univ. of Muenster (West Germany))

    1990-11-07

    Formation of cyclobutylpyrimidine dimers and strand breaks in double-stranded DNA was investigated by using 532-nm, 28-ps pulses from a frequency-doubled, mode-locked Nd:YAG laser at intensities below and above the threshold for optical breakdown. Two-photon absorption by DNA was detected in the absence of optical breakdown by measuring the yields of cyclobutylpyrimidine dimers formed in supercoiled pBR322 DNA. The yield of cyclobutylpyrimidine dimers per laser pulse was measured at seven peak intensities between 1.03 and 8.04 GW/cm{sup 2}. A plot of the ln (dimer yield/pulse) versus ln (photon flux) was linear with a slope of 1.88 {plus minus} 0.26. The two-photon cross section for absorption at 532 nm was calculated to be 0.5 ({plus minus}0.2) {times}{sup {minus}52} cm{sup 4} s photon{sup {minus}1} per nucleotide. Experiments performed by using intensities above the threshold for optical breakdown caused breaks in the DNA strands but no cyclobutylpyrimidine dimers. The free-radical quencher, mannitol, partially inhibited formation of the strand breaks, indicating that the mechanical processes initiated by the plasma also contribute to the creation of DNA strand breaks.

  4. Correlations of instantaneous transition energy and intensity of absorption peaks during molecular vibration: toward potential hyper-surface

    NASA Astrophysics Data System (ADS)

    Kobayashi, Takayoshi; Wang, Zhuan

    2008-06-01

    Time-resolved spectrum after ultrashort pulse excitation revealed fine structure of instantaneous vibronic absorption spectra in a thiophene derivative. The probe photon energy-dependent amplitudes of molecular vibration coupled to the induced absorption were composed of several peaks. An absorbance-change peak-tracking method revealed four vibronic transitions buried in the time-integrated spectra over several vibrational periods of typical molecular vibration. Four vibronic transitions located at 2.024, 1.921, 1.818 and 1.731 eV were found to be correlated among themselves with respect to the photon energies and intensities of the peaks in the difference absorbance change spectra. From the size and sign of the correlation strengths the mechanism of the vibronic coupling was related to non-Condon mechanism and Herzberg Teller vibronic coupling.

  5. Comparative study of UV absorption changes induced in germanosilicate glass by high-intensity femtosecond

    E-print Network

    Nikogosyan, David N.

    to the UV absorption changes, we observed small-scale damage due to self-focusing. This dam- age appears pulses with different wavelengths (267, 400 and 800 nm). The accompanying glass damage due to self-focusing a , Stephen A. Slattery b , David N. Nikogosyan b,* a Laser Research Center, Vilnius University, Sauletikio

  6. Band gap hierarchy of single crystal CoFe2O4 thin films from optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Holinsworth, Brian; Sims, Hunter; Mazumdar, Dipanjan; Sun, Qi; Yurtisigi, Mehmet; Sarker, Sanjoy; Gupta, Arun; Butler, Bill; Musfeldt, Janice

    2013-03-01

    Thin film materials have a wide variety of applications and also serve as an useful bridge between bulk single crystals and the nanoscale. In this work, we report temperature-dependent optical absorption spectroscopy of single crystal CoFe2O4 thin-films along with complimentary electronic structure analysis. This magnetic insulator has one of the highest Curie temperature among complex oxides and potentially useful in areas such as spintronics. Similar to its Nickel analogue, our work reveals CoFe2O4 to be an indirect band gap material (1.2 eV) with a direct gap much higher (2.8eV) at 300K. These gap values are robust down to 4.2K. Electronically, both chemical tuning and inversion fraction are found to be important factors in lowering of the band gap compared to NiFe2O4. Thin film materials have a wide variety of applications and also serve as an useful bridge between bulk single crystals and the nanoscale. In this work, we report temperature-dependent optical absorption spectroscopy of single crystal CoFe2O4 thin-films along with complimentary electronic structure analysis. This magnetic insulator has one of the highest Curie temperature among complex oxides and potentially useful in areas such as spintronics. Similar to its Nickel analogue, our work reveals CoFe2O4 to be an indirect band gap material (1.2 eV) with a direct gap much higher (2.8eV) at 300K. These gap values are robust down to 4.2K. Electronically, both chemical tuning and inversion fraction are found to be important factors in lowering of the band gap compared to NiFe2O4. Q.C. Sun, H. Sims, D.Mazumdar, J.X.Ma, B. Holinswoth, K.O'Neal, G.Kim, W.H.Butler, A.Gupta, and J.Musfeldt (accepted to Phys. Rev. B).

  7. Molecular dynamics simulations for CO2 spectra. II. The far infrared collision-induced absorption band

    NASA Astrophysics Data System (ADS)

    Hartmann, J.-M.; Boulet, C.; Jacquemart, D.

    2011-03-01

    Classical molecular dynamics simulations have been carried out for gaseous CO2 starting from various anisotropic intermolecular potential energy surfaces. Through calculations for a large number of molecules treated as rigid rotors, the time evolution of the interaction-induced electric dipole vector is obtained and the Laplace transform of its autocorrelation function gives the collision-induced absorption rototranslational spectrum. The results are successfully compared with those of previous similar calculations before studies of the influences of the intermolecular potential and induced-dipole components are made. The calculated spectra show a significant sensitivity to anisotropic forces consistently with previous analyses limited to the spectral moments. The present results also demonstrate the importance of vibrational and back-induction contributions to the induced dipole. Comparisons between measured far infrared (0-250 cm-1) spectra at different temperatures and results calculated without the use of any adjustable parameter are made. When the best and more complete input data are used, the quality of our predictions is similar to that obtained by Gruszka et al. [Mol. Phys. 93, 1007 (1998)] after the introduction of ad hoc short-range overlap contributions. Our results thus largely obviate the need for such contributions the magnitudes of which remain questioned. Nevertheless, problems remain since, whereas good agreements with measurements are obtained above 50 cm-1, the calculations significantly underestimate the absorption below, a problem which is discussed in terms of various possible error sources.

  8. Organic dyes with intense light absorption especially suitable for application in thin-layer dye-sensitized solar cells.

    PubMed

    Dessì, Alessio; Calamante, Massimo; Mordini, Alessandro; Peruzzini, Maurizio; Sinicropi, Adalgisa; Basosi, Riccardo; Fabrizi de Biani, Fabrizia; Taddei, Maurizio; Colonna, Daniele; Di Carlo, Aldo; Reginato, Gianna; Zani, Lorenzo

    2014-11-21

    Three new thiazolo[5,4-d]thiazole-based organic dyes have been designed and synthesized for employment as DSSC sensitizers. Alternation of the electron poor thiazolothiazole unit with two propylenedioxythiophene (ProDOT) groups ensured very intense light absorption in the visible region (? up to 9.41 × 10(4) M(-1) cm(-1) in THF solution). The dyes were particularly suitable for application in transparent and opaque thin-layer DSSCs (TiO2 thickness: 5.5-6.5 ?m, efficiencies up to 7.71%), thus being good candidates for production of solar cells under simple fabrication conditions. PMID:25264863

  9. Analytical approach to optical absorption in carbon nanotubes

    Microsoft Academic Search

    Ermin Malic; Matthias Hirtschulz; Frank Milde; Andreas Knorr; Stephanie Reich

    2006-01-01

    We derive an analytic expression for the optical matrix elements of carbon nanotubes and calculate their optical absorption spectra within the tight-binding approximation. For zigzag nanotubes we present an analytical result for the absorption coefficient. Metallic nanotubes have an optical band gap regardless of their chiral angle. The optical absorption intensity increases by up to 10% from zigzag to armchair

  10. Performance of ultrathin silicon solar microcells with nanostructures of relief formed by soft imprint lithography for broad band absorption enhancement.

    PubMed

    Shir, Dan; Yoon, Jongseung; Chanda, Debashis; Ryu, Jae-Ha; Rogers, John A

    2010-08-11

    Recently developed classes of monocrystalline silicon solar microcells can be assembled into modules with characteristics (i.e., mechanically flexible forms, compact concentrator designs, and high-voltage outputs) that would be impossible to achieve using conventional, wafer-based approaches. This paper presents experimental and computational studies of the optics of light absorption in ultrathin microcells that include nanoscale features of relief on their surfaces, formed by soft imprint lithography. Measurements on working devices with designs optimized for broad band trapping of incident light indicate good efficiencies in energy production even at thicknesses of just a few micrometers. These outcomes are relevant not only to the microcell technology described here but also to other photovoltaic systems that benefit from thin construction and efficient materials utilization. PMID:20583751

  11. Performance of Ultrathin Silicon Solar Microcells with Nanostructures of Relief Formed by Soft Imprint Lithography for Broad Band Absorption Enhancement

    SciTech Connect

    Shir, Daniel J.; Yoon, Jongseung; Chanda, Debashis; Ryu, Jae-Ha; Rogers, John A.

    2010-01-01

    Recently developed classes of monocrystalline silicon solar microcells can be assembled into modules with characteristics (i.e., mechanically flexible forms, compact concentrator designs, and high-voltage outputs) that would be impossible to achieve using conventional, wafer-based approaches. This paper presents experimental and computational studies of the optics of light absorption in ultrathin microcells that include nanoscale features of relief on their surfaces, formed by soft imprint lithography. Measurements on working devices with designs optimized for broad band trapping of incident light indicate good efficiencies in energy production even at thicknesses of just a few micrometers. These outcomes are relevant not only to the microcell technology described here but also to other photovoltaic systems that benefit from thin construction and efficient materials utilization.

  12. Band Gap Energy of Chalcopyrite Thin Film Solar Cell Absorbers Determined by Soft X-Ray Emission and Absorption Spectroscopy

    SciTech Connect

    Bar, M.; Weinhardt, L.; Pookpanratana, S.; Heske, C.; Nishiwaki, S.; Shafarman, W.; Fuchs, O.; Blum, M.; Yang, W.; Denlinger, J.D.

    2008-05-11

    The chemical and electronic structure of high efficiency chalcopyrite thin film solar cell absorbers significantly differs between the surface and the bulk. While it is widely accepted that the absorber surface exhibits a Cu-poor surface phase with increased band gap (Eg), a direct access to the crucial information of the depth-dependency of Eg is still missing. In this paper, we demonstrate that a combination of x-ray emission and absorption spectroscopy allows a determination of Eg in the surface-near bulk and thus complements the established surface- and bulk-sensitive techniques of Eg determination. As an example, we discuss the determination of Eg for a Cu(In,Ga)Se2 absorber [(1.52 +- 0.20) eV].

  13. Multilayer Cloud Detection with the MODIS Near-Infrared Water Vapor Absorption Band

    NASA Technical Reports Server (NTRS)

    Wind, Galina; Platnick, Steven; King, Michael D.; Hubanks, Paul A,; Pavolonis, Michael J.; Heidinger, Andrew K.; Yang, Ping; Baum, Bryan A.

    2009-01-01

    Data Collection 5 processing for the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the NASA Earth Observing System EOS Terra and Aqua spacecraft includes an algorithm for detecting multilayered clouds in daytime. The main objective of this algorithm is to detect multilayered cloud scenes, specifically optically thin ice cloud overlying a lower-level water cloud, that presents difficulties for retrieving cloud effective radius using single layer plane-parallel cloud models. The algorithm uses the MODIS 0.94 micron water vapor band along with CO2 bands to obtain two above-cloud precipitable water retrievals, the difference of which, in conjunction with additional tests, provides a map of where multilayered clouds might potentially exist. The presence of a multilayered cloud results in a large difference in retrievals of above-cloud properties between the CO2 and the 0.94 micron methods. In this paper the MODIS multilayered cloud algorithm is described, results of using the algorithm over example scenes are shown, and global statistics for multilayered clouds as observed by MODIS are discussed. A theoretical study of the algorithm behavior for simulated multilayered clouds is also given. Results are compared to two other comparable passive imager methods. A set of standard cloudy atmospheric profiles developed during the course of this investigation is also presented. The results lead to the conclusion that the MODIS multilayer cloud detection algorithm has some skill in identifying multilayered clouds with different thermodynamic phases

  14. Comparison of line-by-line and band models of near-IR methane absorption applied to outer planet atmospheres

    NASA Astrophysics Data System (ADS)

    Sromovsky, L. A.; Fry, P. M.; Boudon, V.; Campargue, A.; Nikitin, A.

    2012-03-01

    Recent improvements in high spectral resolution measurements of methane absorption at wavenumbers between 4800 cm-1 and 7919 cm-1 have greatly increased the number of lines with known lower state energies, the number of weak lines, and the number of lines observed at low temperatures (Campargue, A., Wang, L., Kassi, S., Mašát, M., Votava, O. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1141-1151; Campargue, A., Wang, L., Liu, A.W., Hu, S.M., Kassi, S. [2010]. Chem. Phys. 373, 203-210; Mondelain, D., Kassi, S., Wang, L.C. [2011]. Phys. Chem. Chem. Phys. 13, 7985-7996; Nikitin, A.V. et al. [2011a]. J. Mol. Spectrosc. 268, 93-106; Nikitin, A.V. et al. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 2211-2224; Wang, L., Kassi, S., Campargue, A. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1130-1140; Wang, L., Kassi, S., Liu, A.W., Hu, S.M., Campargue, A. [2011]. J. Quant. Spectrosc. Radiat. Trans. 112, 937-951), making it possible to fit near-IR spectra of Titan using line-by-line calculations instead of band models (Bailey, J., Ahlsved, L., Meadows, V.S. [2011]. Icarus 213, 218-232; de Bergh, C. et al. [2011]. Planet. Space Sci. doi:10.1016/j.pss.2011.05.003). Using these new results, we compiled an improved line list relative that used by Bailey et al. by updating several spectral regions with either calculated or more recently measured line parameters, revising lower state energy estimates for lines lacking them, and adding room temperature lines to make the list applicable over a wider range of temperatures. We compared current band models with line-by-line calculations using this new line list, both to assess the behavior of band models, and to identify remaining issues with line-by-line calculations when applied to outer planet atmospheres and over a wider range of wavelengths. Comparisons were made for a selection of uniform paths representing outer planet conditions and for representative non-uniform paths within the atmospheres of Uranus, Saturn, and Jupiter, as well as comparisons with 77 K lab measurements of McKellar (McKellar, A.R.W. [1989]. Can. J. Phys. 67, 1027-1035). At room temperatures and pressures band models and new line-by-line calculations generally agree within 1.6-3% RMS between 1800 cm-1 and 7919 cm-1, but disagree more significantly near 3200-3500 cm-1 and in the region where CH3D line data are missing between 5200 cm-1 and 5600 cm-1, and also at band edges near 3250 cm-1 and 5600 cm-1, where far wing line shapes may need improvement. For intermediate temperatures and methane paths, the Irwin et al. (Irwin, P.G.J., Sromovsky, L.A., Strong, E.K., Sihra, K., Bowles, N., Calcutt, S.B., Remedios, J.J. [2006]. Icarus 181, 309-319) band model agrees best with the line-by-line calculations at wavenumbers less than 5000 cm-1. At low temperatures and long path lengths the band models diverge more seriously, with that of Karkoschka and Tomasko (Karkoschka, E., Tomasko, M. [2010]. Icarus 205, 309-319) providing the best agreement with line-by-line calculations. Model spectra computed from the band and line-by-line models were also compared with a Keck/NIRC2 H-band spectrum of Uranus (Sromovsky, L.A., Fry, P.M. [2008]. Icarus 193, 252-266), which could be fit well with either of the two band models, but the main aerosol layer required an optical depth five times smaller using the Irwin et al. band model than for either line-by-line calculations or the Karkoschka and Tomasko band model. By far the best fit to the Uranus H-band spectrum was obtained using line-by-line absorption calculations with a far wing line shape intermediate between that of Hartmann et al. (Hartmann, J.-M., Boulet, C., Brodbeck, C., van Thanh, N., Fouchet, T., Drossart, P. [2002]. J. Quant. Spectrosc. Radiat. Trans. 72, 117-122) and that of de Bergh et al. (de Bergh, C. et al. [2011]. Planet. Space Sci. doi:10.1016/j.pss.2011.05.003).

  15. Absorption

    NSDL National Science Digital Library

    Katherine M Knudson (Polson Middle School)

    1998-04-01

    This activity can be used to allow students to explore the concept of absorption using a variety of materials. Extensions include exploring how Native Americans used absorbtion in a number of ways. This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÂ?s 1998 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

  16. Picosecond Studies of Transient Absorption Induced by BandGap Excitation of CsI and CsI:Tl at Room Temperature

    Microsoft Academic Search

    Richard T. Williams; Kamil B. Ucer; Joel Quedar Grim; Kyle C. Lipke; Larysa M. Trefilova; William W. Moses

    2010-01-01

    Abstract-We report picosecond time-resolved measurements of optical absorption induced by a sub-picosecond pulse of light producing two-photon bandgap excitation of Csl and CsI:Tl at room temperature. The transient spectrum of undoped Csl reveals for the first time strong infrared absorption rising through the 0.8-eV limit of present measurements. We suggest that this infrared band is due to transitions of the

  17. Three-pulse femtosecond spectroscopy of PbSe nanocrystals: 1S bleach nonlinearity and sub-band-edge excited-state absorption assignment.

    PubMed

    Gdor, Itay; Shapiro, Arthur; Yang, Chunfan; Yanover, Diana; Lifshitz, Efrat; Ruhman, Sanford

    2015-02-24

    Above band-edge photoexcitation of PbSe nanocrystals induces strong below band gap absorption as well as a multiphased buildup of bleaching in the 1Se1Sh transition. The amplitudes and kinetics of these features deviate from expectations based on biexciton shifts and state filling, which are the mechanisms usually evoked to explain them. To clarify these discrepancies, the same transitions are investigated here by double-pump-probe spectroscopy. Re-exciting in the below band gap induced absorption characteristic of hot excitons is shown to produce additional excitons with high probability. In addition, pump-probe experiments on a sample saturated with single relaxed excitons prove that the resulting 1Se1Sh bleach is not linear with the number of excitons per nanocrystal. This finding holds for two samples differing significantly in size, demonstrating its generality. Analysis of the results suggests that below band edge induced absorption in hot exciton states is due to excited-state absorption and not to shifted absorption of cold carriers and that 1Se1Sh bleach signals are not an accurate counter of sample excitons when their distribution includes multiexciton states. PMID:25629237

  18. Anomalous band gap behavior in mixed Sn and Pb perovskites enables broadening of absorption spectrum in solar cells.

    PubMed

    Hao, Feng; Stoumpos, Constantinos C; Chang, Robert P H; Kanatzidis, Mercouri G

    2014-06-01

    Perovskite-based solar cells have recently been catapulted to the cutting edge of thin-film photovoltaic research and development because of their promise for high-power conversion efficiencies and ease of fabrication. Two types of generic perovskites compounds have been used in cell fabrication: either Pb- or Sn-based. Here, we describe the performance of perovskite solar cells based on alloyed perovskite solid solutions of methylammonium tin iodide and its lead analogue (CH3NH3Sn(1-x)Pb(x)I3). We exploit the fact that, the energy band gaps of the mixed Pb/Sn compounds do not follow a linear trend (the Vegard's law) in between these two extremes of 1.55 and 1.35 eV, respectively, but have narrower bandgap (<1.3 eV), thus extending the light absorption into the near-infrared (~1,050 nm). A series of solution-processed solid-state photovoltaic devices using a mixture of organic spiro-OMeTAD/lithium bis(trifluoromethylsulfonyl)imide/pyridinium additives as hole transport layer were fabricated and studied as a function of Sn to Pb ratio. Our results show that CH3NH3Sn(0.5)Pb(0.5)I3 has the broadest light absorption and highest short-circuit photocurrent density ~20 mA cm(-2) (obtained under simulated full sunlight of 100 mW cm(-2)). PMID:24823301

  19. Transient magneto-photoinduced absorption study of singlet fission in low band gap copolymers

    NASA Astrophysics Data System (ADS)

    Huynh, Uyen; Vardeny, Z. Valy

    2015-03-01

    We have observed the existence of singlet fission in thin films of low band gap (LBG) copolymers, PDTP-DFBT and PTB7, using the ultrafast optical pump/probe spectroscopy, probed at the energy range from IR to MIR. The singlet fission is the dissociation of a singlet exciton into two triplets through an intermediate triplet pair state (TT pair) in an overall singlet configuration; in the studied copolymers, it was observed to be very fast, in femtosecond time domain. The intermediate TT state, which dissociates into two separated triplets at later time, or recombines to the ground state appears instantaneously with the singlet exciton formation using our laser system that has ~ 150 fs time resolution. The interplay between the rate of singlet fission into sTT pairs, triplet fusion back to singlet excitons and relaxation between the TT spin sublevels explains the obtained opposite pattern of the transient magnetic field response on the dynamics of singlet excitons and TT pairs.

  20. CS band intensity and column densities and production rates of 15 comets

    NASA Astrophysics Data System (ADS)

    Sanzovo, G. C.; Singh, P. D.; Huebner, W. F.

    1993-09-01

    An accurate fluorescence efficiency of the CS(0,0) band and the lifetime of CS have been calculated at 1 AU heliocentric distance. Model-independent CS column densities and production rates are determined from derived fluorescent emission rates (g-factors) and lifetimes for 15 comets: Austin (1982g), Borrelly (1980i), Bradfield (1979X), Crommelin (1983n), Encke (1980), Encke (1984), Giacobini-Zinner (1984e), Halley (1982i), IRAS-Araki-Alcock (1983d), Meier (1980q), Panther (1980u), Stephan-Oterma (1980g), Tuttle (1980h), West (1975n), and Wilson (1986l).

  1. Intensity Variations of Narrow Bands of Solar UV Radiation during Descending Phases of SACs 21-23

    NASA Astrophysics Data System (ADS)

    Gigolashvili, M.; Kapanadze, N.

    2014-12-01

    The study of variations of four narrow bands of solar spectral irradiance (SSI) in the ultraviolet (UV) range for period 1981-2008 is presented. Observational data obtained by space-flight missions SORCE, UARS, SME and daily meanings of international sunspot number (ISN) have been used. The investigated data cover the decreasing phases of the solar activity cycles (SACs) 21, 22 and 23. We have revealed a peculiar behavior of intensity variability of some solar ultraviolet spectral lines originated in the solar chromospheres for period corresponding to the declining phase of the solar cycle 23. It is found that variability of emission of different solar spectral narrow bands (289.5 nm, 300.5 nm) does not agree equally well with ISN variability during decreasing phase of the solar activity cycle 23. The negative correlations between total solar irradiance and the solar spectral narrow bands of UV emission (298.5 nm, 300.5 nm) had been revealed. The existence of the negative correlation can be explained by the sensitivity of SSI of some emission lines to the solar global magnetic field.

  2. Intensity Calculation of Some Optical Absorption Lines in Hydrated Manganous Salts

    Microsoft Academic Search

    S. Koide; M. H. L. Pryce

    1958-01-01

    The ligand field theory is applied to the hydrated manganous salts. The splitting of the degenerate levels of A1g and Eg is first investigated, and then the intensities of the transitions from the ground sextet Alg to these levels are calculated. The properties of the odd vibrations responsible for these transitions are also discussed. It is found that the calculated

  3. Modeled and empirical approaches for retrieving columnar water vapor from solar transmittance measurements in the 0.72, 0.82, and 0.94 ?m absorption bands

    NASA Astrophysics Data System (ADS)

    Ingold, T.; Schmid, B.; MäTzler, C.; Demoulin, P.; KäMpfer, N.

    2000-01-01

    A Sun photometer (18 channels between 300 and 1024 nm) has been used for measuring the columnar content of atmospheric water vapor (CWV) by solar transmittance measurements in absorption bands with channels centered at 719, 817, and 946 nm. The observable is the band-weighted transmittance function defined by the spectral absorption of water vapor and the spectral features of solar irradiance and system response. The transmittance function is approximated by a three-parameter model. Its parameters are determined from MODTRAN and LBLRTM simulations or empirical approaches using CWV data of a dual-channel microwave radiometer (MWR) or a Fourier transform spectrometer (FTS). Data acquired over a 2-year period during 1996-1998 at two different sites in Switzerland, Bern (560 m above sea level (asl)) and Jungfraujoch (3580 m asl) were compared to MWR, radiosonde (RS), and FTS retrievals. At the low-altitude station with an average CWV amount of 15 mm the LBLRTM approach (based on recently corrected line intensities) leads to negligible biases at 719 and 946 nm if compared to an average of MWR, RS, and GPS retrievals. However, at 817 nm an overestimate of 2.7 to 4.3 mm (18-29%) remains. At the high-altitude station with an average CWV amount of 1.4 mm the LBLRTM approaches overestimate the CWV by 1.0, 1.4, and 0.1 mm (58, 76, and 3%) at 719, 817, and 946 nm, compared to the FTS instrument. At the low-altitude station, CWV estimates, based on empirical approaches, agree with the MWR within 0.4 mm (2.5% of the mean); at the high-altitude site with a factor of 10 less water vapor the agreement of the SPM with the FTS is 0.0 to 0.2 mm (1 to 9% of the mean CWV there). Sensitivity analyses show that for the conditions met at the two stations with CWV ranging from 0.2 to 30 mm, the retrieval errors are smallest if the 946 nm channel is used.

  4. Modeled and Empirical Approaches for Retrieving Columnar Water Vapor from Solar Transmittance Measurements in the 0.72, 0.82, and 0.94 Micrometer Absorption Bands

    NASA Technical Reports Server (NTRS)

    Ingold, T.; Schmid, B.; Maetzler, C.; Demoulin, P.; Kaempfer, N.

    2000-01-01

    A Sun photometer (18 channels between 300 and 1024 nm) has been used for measuring the columnar content of atmospheric water vapor (CWV) by solar transmittance measurements in absorption bands with channels centered at 719, 817, and 946 nm. The observable is the band-weighted transmittance function defined by the spectral absorption of water vapor and the spectral features of solar irradiance and system response. The transmittance function is approximated by a three-parameter model. Its parameters are determined from MODTRAN and LBLRTM simulations or empirical approaches using CWV data of a dual-channel microwave radiometer (MWR) or a Fourier transform spectrometer (FTS). Data acquired over a 2-year period during 1996-1998 at two different sites in Switzerland, Bern (560 m above sea level (asl)) and Jungfraujoch (3580 m asl) were compared to MWR, radiosonde (RS), and FTS retrievals. At the low-altitude station with an average CWV amount of 15 mm the LBLRTM approach (based on recently corrected line intensities) leads to negligible biases at 719 and 946 nm if compared to an average of MWR, RS, and GPS retrievals. However, at 817 nm an overestimate of 2.7 to 4.3 mm (18-29%) remains. At the high-altitude station with an average CWV amount of 1.4 mm the LBLRTM approaches overestimate the CWV by 1.0, 1.4. and 0.1 mm (58, 76, and 3%) at 719, 817, and 946 nm, compared to the ITS instrument. At the low-altitude station, CWV estimates, based on empirical approaches, agree with the MWR within 0.4 mm (2.5% of the mean); at the high-altitude site with a factor of 10 less water vapor the agreement of the sun photometers (SPM) with the ITS is 0.0 to 0.2 mm (1 to 9% of the mean CWV there). Sensitivity analyses show that for the conditions met at the two stations with CWV ranging from 0.2 to 30 mm, the retrieval errors are smallest if the 946 nm channel is used.

  5. Infrared energy levels and intensities of carbon dioxide

    Microsoft Academic Search

    L. S. Rothman; W. S. Benedict

    1978-01-01

    Updated tables of vibrational energy levels, molecular constants, band origins, and intensities for carbon dioxide in the infrared region of the spectrum are presented. These tables are references for the AFGL Atmospheric Absorption Line Parameters Compilation.

  6. Infrared energy levels and intensities of carbon dioxide.

    PubMed

    Rothman, L S; Benedict, W S

    1978-08-15

    Updated tables of vibrational energy levels, molecular constants, band origins, and intensities for carbon dioxide in the infrared region of the spectrum are presented. These tables are references for the AFGL Atmospheric Absorption Line Parameters Compilation. PMID:20203829

  7. Vibrational characteristic features and band intensities in solving two-dimensional inverse vibrational problems

    NASA Astrophysics Data System (ADS)

    Nikolova, B. M.

    1993-10-01

    An iterative approach to solving the inverse vibrational problem is used for two-dimensional molecular force field species and all their multiple solutions are obtained. Two methods, one of isotopic molecular force constant invariance and another of differential increments of the force constants, are applied to methane, silane, germane, stannane, ammonia, phosphine, arsine, stibine and their deuterium isotopes, as well as to tetrafluoromethane and its carbon-13 isotope, Criteria for physical significance of each solution based on the characteristic features of the normal vibrations are utilized in discriminating between the multiple solutions. The vibrational intensities are used in an attempt to determine the sign combination for the dipole moment derivatives with respect to the normal coordinates. The force constant results agree very well with those obtained by the parametric approach to the two-dimensional inverse vibrational problem solved for the same molecules [B.M. Nikolova, J. Mol. Struct., 291 (1993) 123].

  8. Light absorption in blood during low-intensity laser irradiation of skin

    SciTech Connect

    Barun, V V; Ivanov, A P [B.I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    2010-06-23

    An analytical procedure is proposed for describing optical fields in biological tissues inhomogeneous in the depth direction, such as human skin, with allowance for multiple scattering. The procedure is used to investigate the depth distribution of the optical power density in homogeneous and multilayer dermis when the skin is exposed to a laser beam. We calculate the absorbed laser power spectra for oxy- and deoxyhaemoglobin at different depths in relation to the absorption selectivity of these haemoglobin derivatives and the spectral dependence of the optical power density and demonstrate that the spectra vary considerably with depth. A simple exponential approximation is proposed for the depth distribution of the power density in the epidermis and dermis. (laser methods in medicine)

  9. Microwave-assisted synthesis of graphene-Ni composites with enhanced microwave absorption properties in Ku-band

    NASA Astrophysics Data System (ADS)

    Zhu, Zetao; Sun, Xin; Li, Guoxian; Xue, Hairong; Guo, Hu; Fan, Xiaoli; Pan, Xuchen; He, Jianping

    2015-03-01

    Recently, graphene has been applied as a new microwave absorber because of its high dielectric loss and low density. Nevertheless, the high dielectric constant of pristine graphene has caused unbalanced electromagnetic parameters and results in a bad impedance matching characteristic. In this study, we report a facile microwave-assisted heating approach to produce reduced graphene oxide-nickel (RGO-Ni) composites. The phase and morphology of as-synthesized RGO-Ni composites are characterized by XRD, Raman, FESEM and TEM. The results show that Ni nanoparticles with a diameter around 20 nm are grown densely and uniformly on the RGO sheets. In addition, enhanced microwave absorption properties in Ku-band of RGO-Ni composites is mainly due to the synergistic effect of dielectric loss and magnetic loss and the dramatically electron polarizations caused by the formation of large conductive network. The minimum reflection loss of RGO-Ni-2 composite with the thickness of 2 mm can reaches -42 dB at 17.6 GHz. The RGO-Ni composite is an attractive candidate for the new type of high performance microwave absorbing material.

  10. Protein Normal Modes: Calculations of Amide Band Positions and Infrared Intensities for Helical Polypeptides and Proteins

    NASA Astrophysics Data System (ADS)

    Reisdorf, William Charles, Jr.

    To understand protein function requires input from a wide variety of techniques. The ability of diffraction and magnetic resonance studies to provide structural models with high atomic resolution are particularly crucial. Increasingly, information on protein dynamics is also sought. Vibrational spectroscopy can contribute information on the conformations of peptides and proteins, but the complexity of proteins makes interpretation of their spectra difficult. For this reason, computational models of protein vibrational modes are expected to play a major role in aiding our comprehension of protein dynamics. A set of FORTRAN programs referred to as 'POLYPEP' has been designed for computing the frequencies (eigenvalues) and normal modes (eigenvectors) of polypeptides of any structure. Model structures can be generated by specifying the backbone dihedral angles and using standard peptide group geometry. Alternatively one can use cartesian coordinates from experimental structures as input. The side chains are modeled as point masses, except for cysteine residues which may participate in disulfide linkages. Hydrogen bonding interactions between backbone groups are also included. The force fields adopted have been developed and refined to accurately reproduce the vibrational modes of alpha-helical and beta -sheet conformations of poly-L-alanine. Preliminary attempts have also been made for modifying selected force constants according to variations in hydrogen bond strength. Dipole derivatives for the peptide group are taken from an ab initio study of hydrogen-bonded N-methylacetamide. Those values, in combination with the calculated eigenvectors and frequencies, allow determination of infrared intensities for selected spectral regions, and the use of transition dipole coupling theory to obtain better frequencies. The present work involves application of this model to studies of model helical polypeptides and proteins. For the model structures (alpha-helix, 3 _{10}-helix, coiled coil, etc.) we examine the effects of helix length, hydrogen bond strength, side chain mass, dihedral angle irregularity, and other structural defects. Additionally, calculations have been done for the experimental structures of melittin and myoglobin. This is the first instance of a normal mode analysis using a spectroscopically-derived force field applied to a protein as large as myoglobin.

  11. Influence of temperature and light intensity on absorption, translocation, and phytotoxicity of fenoxaprop-ethyl and imazamethabenz-methyl in Avena fatua

    Microsoft Academic Search

    H. S. Xie; A. I. Hsiao; W. A. Quick

    1996-01-01

    The absorption and translocation of fenoxaprop-ethyl and imazamethabenz-methyl were investigated in wild oat (Avena fatua L.) plants grown under different temperature and light intensity conditions by using 14C tracer techniques. The phytotoxicity of both herbicides, applied as individual droplets, was also determined under similar\\u000a environments. The absorption of fenoxaprop-ethyl and imazamethabenz-methyl was increased by high temperature (30\\/20°C) and\\u000a to a

  12. Ground-state ?--branching intensities of several fission-product isotopes measured using a total absorption ?-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Greenwood, R. C.; Putnam, M. H.; Watts, K. D.

    1996-02-01

    The final set of results of "ground-state" ?--branching intensities obtained in a program of systematic study of those regions of the fission-product nuclides accessible to investigation using the 252Cf-based INEL ISOL facility are presented. A total absorption ?-ray spectrometer, operating in a 4??-? coincidence mode, was used to obtain these "ground-state" ?--branching intensities; where here the "ground-state" is defined to include all states below a selected ?-ray discriminator level. Results obtained for 89Rb, 90gRb, 91Rb, 93Rb, 93Sr, 94Sr, 94Y, 95Sr, 95Y, 140Cs, 142La, 143Ba, 143La, 144Ba, 144La, 145Ba, 145La, 146Ce, 146Pr, 147Ce, 147Pr, 148Ce, 148Pr, (2.27 min), 149Pr, 149Nd, 151Pr, 151Nd, 152Pm (4.1 min), 153Nd, 155Nd, 157Pm, 157Sm, 158Sm and 158Eu are presented and compared with existing published data.

  13. Measurement of ? --decay intensity distributions of several fission-product isotopes using a total absorption ?-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Greenwood, R. C.; Helmer, R. G.; Putnam, M. H.; Watts, K. D.

    1997-02-01

    A total absorption ?-ray spectrometer coupled to the 252Cf-based INEL ISOL facility has been used in a program of systematic study of the distributions of ? --decay intensities of fission-product radionuclides. Cascade-summed ?-ray spectra measured with the system have been compared with the spectrum simulated from the corresponding decay schemes, as a test of the completeness and correctness of these schemes. New ? --decay intensity distributions have been deduced for the decay of these radionuclides. Radionuclides which have been studied in this manner include 89Rb, 90gRb, 90mRb, 91Rb, 93Rb, 93Sr, 94Sr, 94Y, 95Sr, 95Y, 138gCs, 138mCs, 139Cs, 140Cs, 141Cs, 141Ba, 142Ba, 142La, 143Ba, 143La, 144Ba, 144La, 145Ba, 145La, 145Ce, 146Ce, 146Pr, 147Ce, 147Pr, 148Ce, 148Pr (2.0 min), 148Pr (2.27 min), 149Pr, 149Nd, 151Pr, 151Nd, 152Nd - 152Pm (4.1 min.), 153Nd, 153Pm, 154Nd, 154Pm (1.7 min), 155Nd, 155Pm, 156Pm, 157Pm, 157Sm, 158Sm, and 158Eu.

  14. Indirect optical absorption and origin of the emission from {beta}-FeSi{sub 2} nanoparticles: Bound exciton (0.809 eV) and band to acceptor impurity (0.795 eV) transitions

    SciTech Connect

    Lang, R.; Amaral, L. [Programa de Pos-Graduacao em Ciencias dos Materiais, PGCIMAT, Instituto de Fisica, UFRGS, Porto Alegre, 15051/91501-970 Rio Grande do Sul (Brazil); Meneses, E. A. [Instituto de Fisica Gleb Wataghin, UNICAMP, Campinas, 13083-970 Sao Paulo (Brazil)

    2010-05-15

    We investigated the optical absorption of the fundamental band edge and the origin of the emission from {beta}-FeSi{sub 2} nanoparticles synthesized by ion-beam-induced epitaxial crystallization of Fe{sup +} implanted SiO{sub 2}/Si(100) followed by thermal annealing. From micro-Raman scattering and transmission electron microscopy measurements it was possible to attest the formation of strained {beta}-FeSi{sub 2} nanoparticles and its structural quality. The optical absorption near the fundamental gap edge of {beta}-FeSi{sub 2} nanoparticles evaluated by spectroscopic ellipsometry showed a step structure characteristic of an indirect fundamental gap material. Photoluminescence spectroscopy measurements at each synthesis stage revealed complex emissions in the 0.7-0.9 eV spectral region, with different intensities and morphologies strongly dependent on thermal treatment temperature. Spectral deconvolution into four transition lines at 0.795, 0.809, 0.851, and 0.873 eV was performed. We concluded that the emission at 0.795 eV may be related to a radiative direct transition from the direct conduction band to an acceptor level and that the emission at 0.809 eV derives from a recombination of an indirect bound exciton to this acceptor level of {beta}-FeSi{sub 2}. Emissions 0.851 and 0.873 eV were confirmed to be typical dislocation-related photoluminescence centers in Si. From the energy balance we determined the fundamental indirect and direct band gap energies to be 0.856 and 0.867 eV, respectively. An illustrative energy band diagram derived from a proposed model to explain the possible transition processes involved is presented.

  15. Analysis of the two-photon absorption spectrum of benzonitrile based on the direct quantum-mechanical calculation of the intensity distribution

    NASA Astrophysics Data System (ADS)

    Burova, T. G.; Anashkin, A. A.

    2007-11-01

    A direct quantum-mechanical calculation of the intensity distribution in the two-photon absorption spectrum of benzonitrile is performed taking into account the Herzberg-Teller effect. The excitation mechanism of all the observed lines, including lines corresponding to the excitation of single-quantum nontotally symmetric vibrations and their combinations with totally symmetric modes, is analyzed. The results of the calculation, performed taking into account the frequency effect and the Duschinsky effect, agree satisfactorily with experimental data. This indicates that it is worthwhile to apply the quantum-mechanical method in calculations of the intensity distribution in the two-photon absorption spectra of cyclic molecules.

  16. Indicator kriging applied to absorption band analysis in hyperspectral imagery: A case study from the Rodalquilar epithermal gold mining area, SE Spain

    NASA Astrophysics Data System (ADS)

    Meer, Freek van der

    2006-01-01

    A new approach to the analysis of hyperspectral data for the purpose of surface compositional mapping is presented in this paper. We use an interpolated value of the absorption band position and the absorption band depth for the diagnostic of mineral absorption features. Using thresholds for this depth and position, the data is transformed to indicator [0,1] values. By kriging these values, we obtain the probability of exceeding certain absorption depth and the probability of a pixel exhibiting absorption features within a specified wavelength region. Using Bayesian statistics, the indicator kriging derived probabilities are used to produce a hard classification result. By adapting the prior probabilities to the dominant mineralogy in the various alteration facies mapped, data stratification is achieved. The classification results are compared to results derived using the spectral angle mapper and maximum likelihood classification. In addition, the results are statistically compared to field spectral data classified into dominant mineralogy. The indicator approach and the spectral angle mapper produce favourable results relative to field data and in comparison to the maximum likelihood classifier. A data set from the Rodalquilar high-sulfidation epithermal gold system in SE Spain, consisting of HyMAP airborne imaging spectrometer data and ASD field spectra focusing on the key minerals alunite, kaolinite, illite and chlorite, is used to illustrate the methodology.

  17. Effects of surface texture and measurement geometry on the near infrared water-of-hydration absorption bands. Implications for the Martian regolith water content.

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Schmitt, B.

    Near-IR reflectance spectroscopy is widely used to detect mineral hydration on Solar System surfaces by the observation of absorption bands at 1.9 and 3 µm. Recent studies established empirical relationships between the strength of the 3 µm band and the water content of the studied minerals (Milliken et al., 2005). These results have especially been applied to the OMEGA dataset to derive global maps of the Martian regolith water content (Jouglet et al., 2006 and Milliken et al., 2006). However, parameters such as surface texture and measurement geometry are known to have a strong effect on reflectance spectra but their influence on the hydration bands is poorly documented. The aim of this work is the determination of the quantitative effects of particle size, mixing between materials with different albedo and measurement geometry on the absorption bands at 1.9 and 3 µm. We used both an experimental and a modeling approach to study these effects. Bidirectional reflectance spectra were measured for series of well characterized samples (smectite, volcanic tuff and coals, pure and mixed) and modeled with optical constants of a smectite (Roush, 2005). Criteria commonly used to estimate the strength of the bands were then calculated on these spectra. We show that particle size has a strong effect on the 1.9 and 3 µm bands strength, especially for the finest particles (less than 200 µm). Mixing between a fine smectite powder and anthracite powders with various particle sizes (modeled by a synthetic neutral material) highlights the strong effect of the materials albedo on the hydration band estimation criteria. Measurement geometry has a significant effect on the bands strength for high phase angles. Furthermore, the relative variations of band strength with measurement geometry appear very dependent on the surface texture. We will present in details the relationships between these physical parameters and various criteria chosen to estimate the hydration bands strength. We will then discuss the implications of these results in terms of uncertainties on the quantification of water-of-hydration and in terms of detection limit of mineral hydration through the identification of the 1.9 and 3 µm bands. The discussion will especially focus on the case of Mars and the results of the OMEGA instrument.

  18. An Analysis of the High-Resolution Spectrum of the Weak v 1 +v 2 +v 3 Absorption Band of the SO2 Molecule

    NASA Astrophysics Data System (ADS)

    Belova, A. S.; Bolotova, I. B.; Gromova, O. V.; Bekhtereva, E. S.; Ulenikov, O. N.

    2015-03-01

    The v 1 +v 2 +v 3 absorption band of the SO2 molecule is recorded and analyzed for the first time on the basis of the specially developed procedure for assignment of superweak high-resolution spectra. The spectral line positions obtained from an analysis of the experimental spectrum are used for the determination of rotational and centrifugal distortion parameters of the (111) state.

  19. Effects of rapid thermal annealing conditions on GaInNAs band gap blueshift and photoluminescence intensity

    SciTech Connect

    Liverini, V.; Rutz, A.; Keller, U.; Schoen, S. [ETH Zurich, Physics Department, Institute of Quantum Electronics, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland); ETH Zurich, FIRST Center for Micro- and Nanoscience, Wolfgang-Pauli-Strasse 10, CH-8093 Zurich (Switzerland)

    2006-06-01

    We have studied the effects of various conditions of rapid thermal annealing (RTA) on 10 nm GaInNAs/GaAs single quantum wells (SQWs) with fixed indium concentration and increasing nitrogen content to obtain photoluminescence (PL) in the telecom wavelength regime of 1.3 and 1.5 {mu}m. Specifically, we analyzed the results of annealing for a fixed short time but at different temperatures and for longer times at a fixed temperature. In all experiments, InGaAs SQWs with the same In concentration were used as references. For both RTA conditions, the well-known blueshift of the band gap energy and the PL intensity improvement show trends that reveal that these are unrelated effects. At high RTA temperatures the PL efficiency reaches a maximum and then drops independently of N content. On the contrary, the blueshift experiences a rapid increase up to 700 deg. C (strong blueshift regime) and it saturates above this temperature (weak blueshift regime). Both these blueshift regimes are related to the nitrogen content in the SQWs but in different ways. In the strong blueshift regime, we could obtain activation energy for the blueshift process in the range of 1.25 eV, which increases with N content. Analysis with high-resolution x-ray diffraction (HRXRD) shows that the blueshift experienced in this regime is not due to a stoichiometric change in the QW. In the weak blueshift regime, the blueshift, which is only partly due to In outdiffusion, saturates more slowly the higher the N content. Annealing at the same temperature (600 deg. C) for a longer time shows that the blueshift saturates earlier than the PL intensity and that samples with higher nitrogen experience a larger blueshift. Only a small In outdiffusion for annealing at high temperatures (>650 deg. C) and long duration was observed. However, this modest stoichiometric change does not explain the large blueshift experienced by the GaInNAs SQWs. We conclude that the mechanism responsible for the drastic blueshift after annealing is related to the N content in the QW, while the improvement in PL integrated intensity is uniquely related to the annealing conditions.

  20. Cavity enhanced absorption spectroscopy of molecular carbon dioxide near IR region with a DFB diode laser

    Microsoft Academic Search

    Shixin Pei; Xiaoming Gao; Fenping Cui; Wei Huang; Jie Shao; Teng Huang; Weixiong Zhao; Weijun Zhang

    2005-01-01

    This paper is about cavity enhanced absorption spectroscopy (CEAS) experiment with a tunable narrow line width continuous wave DFB diode laser and it was used to measure the weak absorption band of carbon dioxide in the near infrared region. The absorption spectrum was extracted from the measurement of light intensity that leaks out of an optical cavity which was consisted

  1. Evaluation of intensity and energy interaction parameters for the complexation of Pr(III) with selected nucleoside and nucleotide through absorption spectral studies

    NASA Astrophysics Data System (ADS)

    Bendangsenla, N.; Moaienla, T.; David Singh, Th.; Sumitra, Ch.; Rajmuhon Singh, N.; Indira Devi, M.

    2013-02-01

    The interactions of Pr(III) with nucleosides and nucleotides have been studied in different organic solvents employing absorption difference and comparative absorption spectrophotometry. The magnitudes of the variations in both energy and intensity interaction parameters were used to explore the degree of outer and inner sphere co-ordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Various electronic spectral parameters like Slater-Condon (Fk), Racah (Ek), Lande parameter (?4f), Nephelauxatic ratio (?), bonding (b1/2), percentage covalency (?) and intensity parameters like oscillator strength (P) and Judd Ofelt electronic dipole intensity parameter (T?, ? = 2, 4, 6) have been evaluated. The variation of these evaluated parameters were employed to interpret the nature of binding of Pr(III) with different ligands i.e. Adenosine/ATP in presence and absence of Ca2+.

  2. Clay composition and swelling potential estimation of soils using depth of absorption bands in the SWIR (1100-2500 nm) spectral domain

    NASA Astrophysics Data System (ADS)

    Dufréchou, Grégory; Granjean, Gilles; Bourguignon, Anne

    2014-05-01

    Swelling soils contain clay minerals that change volume with water content and cause extensive and expensive damage on infrastructures. Presence of clay minerals is traditionally a good estimator of soils swelling and shrinking behavior. Montmorillonite (i.e. smectite group), illite, kaolinite are the most common minerals in soils and are usually associated to high, moderate, and low swelling potential when they are present in significant amount. Characterization of swelling potential and identification of clay minerals of soils using conventional analysis are slow, expensive, and does not permit integrated measurements. SWIR (1100-2500 nm) spectral domain are characterized by significant spectral absorption bands related to clay content that can be used to recognize main clay minerals. Hyperspectral laboratory using an ASD Fieldspec Pro spectrometer provides thus a rapid and less expensive field surface sensing that permits to measure soil spectral properties. This study presents a new laboratory reflectance spectroscopy method that used depth of clay diagnostic absorption bands (1400 nm, 1900 nm, and 2200 nm) to compare natural soils to synthetic montmorillonite-illite-kaolinite mixtures. We observe in mixtures that illite, montmorillonite, and kaolinite content respectively strongly influence the depth of absorption bands at 1400 nm (D1400), 1900 nm (D1900), and 2200 nm (D2200). To attenuate or removed effects of abundance and grain size, depth of absorption bands ratios were thus used to performed (i) 3D (using D1900/D2200, D1400/D1900, and D2200/D1400 as axis), and (ii) 2D (using D1400/D1900 and D1900/D2200 as axis) diagrams of synthetic mixtures. In this case we supposed that the overall reduction or growth of depth absorption bands should be similarly affected by the abundance and grain size of materials in soil. In 3D and 2D diagrams, the mixtures define a triangular shape formed by two clay minerals as external envelop and the three clay minerals mixtures are located inside of the triangular shape. Clay composition of natural soils were estimated using 3D and 2D diagrams used as standard template from: (i) the average clay composition of the three closer mixtures when soil samples were plotted inside the triangular distribution of mixtures; and (ii) the closer mixture when the soil sample were plotted outside of the triangular distribution of mixtures. Comparison with X-ray diffraction analysis show reliable prediction of montmorillonite content that were used to estimate the swelling potential of soils. This method allows a simple, fast, and low cost method that classes soils into four swelling classes based on comparison with Methylene Blue test, and could be used as complementary or alternative method to traditional geotechnical analysis.

  3. Slow-Reduction Synthesis of a Thiolate-Protected One-Dimensional Gold Cluster Showing an Intense Near-Infrared Absorption.

    PubMed

    Takano, Shinjiro; Yamazoe, Seiji; Koyasu, Kiichirou; Tsukuda, Tatsuya

    2015-06-10

    Slow reduction of Au ions in the presence of 4-(2-mercaptoethyl)benzoic acid (4-MEBA) gave Au76(4-MEBA)44 clusters that exhibited a strong (3 × 10(5) M(-1) cm(-1)) near-infrared absorption band at 1340 nm. Powder X-ray diffraction studies indicated that the Au core has a one-dimensional fcc structure that is elongated along the {100} direction. PMID:26020460

  4. Intensive visible-light photoactivity of Bi- and Fe-containing pyrochlore nanoparticles

    NASA Astrophysics Data System (ADS)

    Bencina, Metka; Valant, Matjaz; Pitcher, Michael W.; Fanetti, Mattia

    2013-12-01

    Bi-Fe-Nb-O pyrochlore nanoparticles were synthesized by a facile coprecipitation reaction. They exhibit intense visible-light absorption due to a narrow band gap and high visible-light photocatalytic activity for degradation of methyl orange.

  5. The effect of external magnetic field on the bremsstrahlung nonlinear absorption mechanism in the interaction of high intensity short laser pulse with collisional underdense plasma

    NASA Astrophysics Data System (ADS)

    Sedaghat, M.; Ettehadi-Abari, M.; Shokri, B.; Ghorbanalilu, M.

    2015-03-01

    Laser absorption in the interaction between ultra-intense femtosecond laser and solid density plasma is studied theoretically here in the intensity range I ? 2 ? 10 14 - 10 16 Wcm - 2 ? m 2 . The collisional effect is found to be significant when the incident laser intensity is less than 10 16 Wcm - 2 ? m 2 . In the current work, the propagation of a high frequency electromagnetic wave, for underdense collisional plasma in the presence of an external magnetic field is investigated. It is shown that, by considering the effect of the ponderomotive force in collisional magnetized plasmas, the increase of laser pulse intensity leads to steepening of the electron density profile and the electron bunches of plasma makes narrower. Moreover, it is found that the wavelength of electric and magnetic fields oscillations increases by increasing the external magnetic field and the density distribution of electrons also grows in comparison with the unmagnetized collisional plasma. Furthermore, the spatial damping rate of laser energy and the nonlinear bremsstrahlung absorption coefficient are obtained in the collisional regime of magnetized plasma. The other remarkable result is that by increasing the external magnetic field in this case, the absorption coefficient increases strongly.

  6. Ultraviolet absorption spectrum of HOCl

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.

    1993-01-01

    The room temperature UV absorption spectrum of HOCl was measured over the wavelength range 200 to 380 nm with a diode array spectrometer. The absorption spectrum was identified from UV absorption spectra recorded following UV photolysis of equilibrium mixtures of Cl2O/H2O/HOCl. The HOCl spectrum is continuous with a maximum at 242 nm and a secondary peak at 304 nm. The measured absorption cross section at 242 nm was (2.1 +/- 0.3) x 10 exp -19/sq cm (2 sigma error limits). These results are in excellent agreement with the work of Knauth et al. (1979) but in poor agreement with the more recent measurements of Mishalanie et al. (1986) and Permien et al. (1988). An HOCl nu2 infrared band intensity of 230 +/- 35/sq cm atm was determined based on this UV absorption cross section. The present results are compared with these previous measurements and the discrepancies are discussed.

  7. Intensive two-photon absorption induced decay pathway in a ZnO crystal: Impact of light-induced defect state

    SciTech Connect

    Li, Zhong-guo; Wei, Tai-Huei [Department of Physics, Harbin Institute of Technology, Harbin 15001 (China)] [Department of Physics, Harbin Institute of Technology, Harbin 15001 (China); Yang, Jun-yi [School of Physical Science and Technology, Soochow University, Suzhou 215006 (China)] [School of Physical Science and Technology, Soochow University, Suzhou 215006 (China); Song, Ying-lin, E-mail: ylsong@hit.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 15001 (China) [Department of Physics, Harbin Institute of Technology, Harbin 15001 (China); School of Physical Science and Technology, Soochow University, Suzhou 215006 (China)

    2013-12-16

    Using the pump-probe with phase object technique with 20 ps laser pulses at 532?nm, we investigated the carrier relaxation process subsequent to two-photon absorption (TPA) in ZnO. As a result, we found that an additional subnanosecond decay pathway is activated when the pump beam intensity surpasses 0.4?GW/cm{sup 2}. We attributed this intensity-dependent pathway to a TPA induced bulk defect state and our results demonstrate that this photo induced defect state has potential applications in ZnO based optoelectronic and spintronic devices.

  8. Intensities and N2 collision-broadening coefficients measured for selected H2O absorption lines between 715 and 732 nm

    NASA Technical Reports Server (NTRS)

    Wilkerson, T. D.; Schwemmer, G.; Gentry, B.; Giver, L. P.

    1979-01-01

    Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.

  9. Visible-light absorption and large band-gap bowing of GaN1-xSbx from first principles

    DOE PAGESBeta

    Sheetz, R. Michael; Richter, Ernst; Andriotis, Antonis N.; Lisenkov, Sergey; Pendyala, Chandrashekhar; Sunkara, Mahendra K.; Menon, Madhu

    2011-08-01

    Applicability of the Ga(Sbx)N1-x alloys for practical realization of photoelectrochemical water splitting is investigated using first-principles density functional theory incorporating the local density approximation and generalized gradient approximation plus the Hubbard U parameter formalism. Our calculations reveal that a relatively small concentration of Sb impurities is sufficient to achieve a significant narrowing of the band gap, enabling absorption of visible light. Theoretical results predict that Ga(Sbx)N1-x alloys with 2-eV band gaps straddle the potential window at moderate to low pH values, thus indicating that dilute Ga(Sbx)N1-x alloys could be potential candidates for splitting water under visible light irradiation.

  10. Quasi-random narrow-band model FITS to near-infrared low-temperature laboratory methane spectra and derived exponential-sum absorption coefficients

    NASA Astrophysics Data System (ADS)

    Baines, K. H.; West, R. A.; Giver, L. P.; Moreno, F.

    1993-03-01

    Near-infrared 10/cm resolution spectra of methane obtained at various temperatures, pressures, and abundances are fit to a quasi-random narrow-band model. Exponential-sum absorption coefficients for three temperatures (112, 188, and 295 K), and 20 pressures from 0.0001 to 5.6 bars, applicable to the cold environments of the major planets, are then derived from the band model for the 230 wavelengths measured from 1.6 to 2.5 microns. RMS deviations between the laboratory and the exponential-sum synthetic transmissions are reported for the best fitting 50 wavelengths. Deviations relevant to broadband, 1-percent spectral resolution observations are also presented. The validity of exponential-sum coefficients derived from broadband (10/cm) transmission data is demonstrated via direct comparison with line-by-line calculations. The complete atlas of coefficients is available from the Planetary Data System-Planetary Atmospheres Discipline Node.

  11. High-resolution spectra and photoabsorption coefficients for carbon monoxide absorption bands between 94.0 nm and 100.4 nm

    NASA Technical Reports Server (NTRS)

    Yoshino, K.; Stark, G.; Smith, P. L.; Parkinson, W. H.; Ito, K.

    1988-01-01

    Photoabsorption coefficients have been measured for the CO in interstellar clouds at a resolving power more than 20 times greater than previously obtainable. In order to facilitate comparisons, these data have been integrated over the same wavelength ranges as used in Letzelter et al. (1987). It is found that most of the results obtained for bands between 94.0 and 100.4 nm are larger than those of Letzelter; the discrepancy may be attributable to the difference between the resolving powers of the spectrometers used, because the saturation effects associated with low resolution can underestimate absorption coefficient values.

  12. Infrared line intensities of chlorine monoxide

    NASA Technical Reports Server (NTRS)

    Kostiuk, T.; Faris, J. L.; Mumma, M. J.; Deming, D.; Hillman, J. J.

    1986-01-01

    Absolute infrared line intensities of several ClO lines in the rotational-vibrational (1-0) band were measured using infrared heterodyne spectroscopy near 12 microns. A measurement technique using combined ultraviolet absorption and infrared line measurements near 9.5 microns and 12 microns permitted an accurate determination of the column densities of O3 and ClO in the absorption cell and thus improved ClO line intensities. Results indicate ClO line and band intensities approximately 2.4 times lower than previous experimental results. Effects of possible failure of local thermodynamic equilibrium conditions in the absorption cell and the implication of the results for stratospheric ClO measurements in the infrared are discussed.

  13. 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

  14. Infrared energy levels and intensities of carbon dioxide. III

    Microsoft Academic Search

    L. S. Rothman

    1986-01-01

    New and improved spectroscopic constants for calculating the transition frequences and intensities of carbon dioxide and its significant isotopic variants in telluric atmospheric paths in the infrared are reported. This empirically based, self-consistent set of constants reproduces the majority of transitions significant in atmospheric absorption experiments to within 0.001\\/cm. New band intensity observations and calculations improve many of the band

  15. Water absorption lines, 931-961 nm - Selected intensities, N2-collision-broadening coefficients, self-broadening coefficients, and pressure shifts in air

    NASA Technical Reports Server (NTRS)

    Giver, L. P.; Gentry, B.; Schwemmer, G.; Wilkerson, T. D.

    1982-01-01

    Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.

  16. A narrow-band tunable diode laser system with grating feedback, and a saturated absorption spectrometer for Cs and Rb

    Microsoft Academic Search

    K. B. MacAdam; A. Steinbach; C. Wieman

    1992-01-01

    Detailed instructions for the construction and operation of a diode laser system with optical feedback are presented. This system uses feedback from a diffraction grating to provide a narrow-band continuously tuneable source of light at red or near-IR wavelengths. These instructions include machine drawings for the parts to be constructed, electronic circuit diagrams, and prices and vendors of the items

  17. Light absorption and X-ray emission measurements from 100 femtosecond laser produced plasmas

    SciTech Connect

    Price, D.F.; Guethlein, G.; Shepherd, R.L.; White, W.E.; Stewart, R.E.; Walling, R.S.; More, R.M. (Lawrence Livermore National Laboratory, P.O. Box 808, L-43, Livermore, California 94550 (United States))

    1994-10-05

    Total reflected and scattered light measurements are used to define the net absorption for a 100 femtosecond, 400 nm laser pulse's interaction with a wide range of solid density target materials. Absorption is determined over the intensity range of 10[sup 13] to 10[sup 18] W/cm[sup 2]. This range is sufficiently broad to observe the transition in absorption from a low intensity region dominated by the cold material's electronic band structure, to an absorption at the highest intensities marked by a convergence to a nearly universal, material independent value. [copyright] 1994 [ital American] [ital Institute] [ital of] [ital Physics

  18. Nasogastric Aspiration as an Indicator for Feed Absorption in Model-Based Glycemic Control in Neonatal Intensive Care

    PubMed Central

    Gunn, Cameron A.; Dickson, Jennifer L.; Hewett, James N.; Lynn, Adrienne; Rose, Hamish J.; Clarkson, Sooji H.; Shaw, Geoffrey M.; Geoffrey Chase, J.

    2013-01-01

    Background STAR (stochastic targeted) is a glycemic control model-based framework for critically ill neonates that has shown benefits in reducing hypoglycemia and hyperglycemia. STAR uses a stochastic matrix method to forecast future changes in a patient’s insulin sensitivity and then applies this result to a physiological model to select an optimal insulin treatment. Nasogastric aspiration may be used as an indicator to suggest periods of care when enteral feed absorption is compromised, improving the performance of glycemic control. An analysis has been carried out to investigate the effect of poorly absorbed feeds on glycemic control. Method Clinical data were collected from eight patients on insulin therapy and enteral feed, which included large or significantly milky aspirates. Patients had a median gestational age of 25 weeks and postnatal age of 5.5 days. Virtual patients were created using the NICING model, and insulin sensitivity (SI) profiles were fit. Alternative feed profiles were generated whereby enteral feed absorption was redistributed with time to account for poor feed absorption. The effect of poor feed absorption, as indicated by aspirates, is investigated. Results The average percentage change of SI 4 h before a significant aspirate was 1.16%, and 1.49% in the 4 h following the aspirate. No distinct relationship was found between the fractional change in SI and the volume of the aspirate. Accounting for aspirates had a clinically negligible impact on glycemic control in virtual trials. Conclusion Accounting for aspirates by manipulating enteral feed profiles had a minimal influence on both modeling and controlling glycemia in neonates. The impact of this method is clinically insignificant, suggesting that a population constant for the rate of glucose absorption in the gut adequately models feed absorption within the STAR framework. J Diabetes Sci Technol 2013;7(3):717–726 PMID:23759405

  19. The effect of the ionosphere on remote sensing of sea surface salinity from space: absorption and emission at L band

    Microsoft Academic Search

    David M. Le Vine; Saji Abraham

    2002-01-01

    The purpose of this work is to examine the effects of Faraday rotation and attenuation\\/emission in the ionosphere in the context of a future remote sensing system in space to measure salinity. Sea surface salinity is important for understanding ocean circulation and for modeling energy exchange with the atmosphere. A passive microwave sensor in space operating near 1.4 GHz (L-band)

  20. Absorption intensities and complex refractive indices of crystalline HCN, HC3N, and C4N2 in the infrared region

    NASA Astrophysics Data System (ADS)

    Masterson, C. M.; Khanna, R. K.

    1990-01-01

    IR absorption intensities are presented for thin crystalline films of HCN, HC3N, and C4N2, together with n and k complex refractive indices determined on the basis of an iterative program for the Kramers-Konig integral via a least-squares, point-by-point fitting of the experimental transmission data. It is established that the transmission spectra generated by means of these n and k values can reproduce the experimental transmission observation values to within + or - 2 percent.

  1. Efficient tissue ablation using a laser tunable in the water absorption band at 3 microns with little collateral damage

    NASA Astrophysics Data System (ADS)

    Nierlich, Alexandra; Chuchumishev, Danail; Nagel, Elizabeth; Marinova, Kristiana; Philipov, Stanislav; Fiebig, Torsten; Buchvarov, Ivan; Richter, Claus-Peter

    2014-03-01

    Lasers can significantly advance medical diagnostics and treatment. At high power, they are typically used as cutting tools during surgery. For lasers that are used as knifes, radiation wavelengths in the far ultraviolet and in the near infrared spectral regions are favored because tissue has high contents of collagen and water. Collagen has an absorption peak around 190 nm, while water is in the near infrared around 3,000 nm. Changing the wavelength across the absorption peak will result in significant differences in laser tissue interactions. Tunable lasers in the infrared that could optimize the laser tissue interaction for ablation and/or coagulation are not available until now besides the Free Electron Laser (FEL). Here we demonstrate efficient tissue ablation using a table-top mid-IR laser tunable between 3,000 to 3,500 nm. A detailed study of the ablation has been conducted in different tissues. Little collateral thermal damage has been found at a distance above 10-20 microns from the ablated surface. Furthermore, little mechanical damage could be seen in conventional histology and by examination of birefringent activity of the samples using a pair of cross polarizing filters.

  2. Numerical investigation of intense rainfall effects on coherent and incoherent slant-path propagation at K-band and above

    Microsoft Academic Search

    Frank Silvio Marzano; Laura Roberti

    2003-01-01

    A model investigation is carried out to analyze the impact of intense rainfall on slant-path microwave propagation, using a rainfall microphysical model. The effects are evaluated both for path attenuation, undergone by coherent radiation, and for multiple scattering phenomena, originating incoherent radiation along the path. Atmospheric spatial inhomogeneity is taken into account. The EM propagation model is formulated by means

  3. Determination of vibrational energy levels and parallel band intensities of 12C16O2 by Direct Numerical Diagonalization

    Microsoft Academic Search

    Richard B. Wattson; Laurence S. Rothman

    1986-01-01

    The Direct Numerical Diagonalization (DND) technique has been applied to the principal symmetric species of carbon dioxide. A three-dimensional formulation of the DND method has been implemented as a first step in using the method to calculate properties of simple polyatomic molecules. Recent high-resolution observations of both line positions and intensities have been incorporated into the method to yield new

  4. Acne phototherapy using UV-free high-intensity narrow-band blue light: a three-center clinical study

    NASA Astrophysics Data System (ADS)

    Shalita, Alan R.; Harth, Yoram; Elman, Monica; Slatkine, Michael; Talpalariu, Gerry; Rosenberg, Yitzhak; Korman, Avner; Klein, Arieh

    2001-05-01

    Propionibacterium. acnes is a Gram positive, microaerophilic bacterium which takes a part in the pathogenesis of inflammatory acne. P. acnes is capable to produce high amounts endogenic porphyrins with no need of any trigger molecules. Light in the violet-blue range (407-420 nm) has been shown to exhibit a phototoxic effect on Propionibacterium acnes when irradiated in vitro. The purpose of our study was to test the clinical effects of a high intensity narrowband blue light source on papulo pustular acne. A total of 35 patients in 3 centers were treated twice a week with a high intensity metal halide lamp illuminating the entire face (20x20 cm2) or the back with visible light in the 407-420 nm range at an intensity of 90 mW/cm2 (CureLight Ltd.) for a total of 4 weeks. UV is totally cut off. In each treatment the patient was exposed to light for 8-15 minutes. After 8 treatments, 80% of the patients with mild to moderate papulo-pustular acne showed significant improvement at reducing the numbers of non- inflammatory, inflammatory and total facial lesions. Inflammatory lesion count decrease by a mean of 68%. No side effects to the treatment were noticed. In conclusion, full face or back illumination with the high intensity pure blue light we used exhibits a rapid significant decrease in acne lesions counts in 8 biweekly treatments.

  5. Molecular dynamics simulations for CO2 absorption spectra. I. Line broadening and the far wing of the ?3 infrared band

    NASA Astrophysics Data System (ADS)

    Hartmann, J.-M.; Boulet, C.; Tran, H.; Nguyen, M. T.

    2010-10-01

    Classical molecular dynamics simulations (CMDS) have been carried out for gaseous CO2 starting from the intermolecular potential energy surface. Through calculations for a large number of molecules treated as rigid rotors, various autocorrelation functions (ACFs) are obtained together with probabilities of rotational changes. Those used in the present paper are the ACFs of the center of mass velocity and of the molecular orientation, and the conditional probability of a change of the angular speed. They enable calculations, respectively, of the mass diffusion coefficient, of the infrared (dipolar) band shape including the wings, and of individual line-broadening coefficients. It is shown that these calculations, free of any adjustable parameter, lead to good agreement with measured values. This is expected from previous studies for the mass diffusion coefficient and line-broadening coefficients, but it is, to our knowledge, the first demonstration of the interest of CMDS for the prediction of band wings. The present results thus open promising perspectives for the theoretical treatment of the difficult problem of far wings profiles.

  6. Cavity Ringdown Absorption Spectrum of the T_1(n,?*) ? S_0 Transition of Acrolein: Analysis of the 0^0_0 Band Rotational Contour

    NASA Astrophysics Data System (ADS)

    Hlavacek, Nikolaus C.; McAnally, Michael O.; Drucker, Stephen

    2012-06-01

    Acrolein (propenal, CH_2=CH---CH=O) is the simplest conjugated enal molecule and serves as a prototype for investigating the photochemical properties of larger enals and enones. Acrolein has a coplanar arrangement of heavy atoms in its ground electronic state. Much of the photochemistry is mediated by the T_1(?,?*) state, which has a CH_2--twisted equilibrium structure. In solution, the T_1(?,?*) state is typically accessed via intersystem crossing from an intially prepared planar S_1(n,?*) state. An intermediate in this photophysical transformation is the lowest ^3 (n,?*) state, a planar species with adiabatic excitation energy below S_1 and above T_1(?,?*). The present work focuses on this ^3 (n,?*) intermediate state; it is designated T_1(n,?*) as the lowest-energy triplet state of acrolein having a planar equilibrium structure. The T_1(n,?*) ? S_0 band system, with origin near 412 nm, was first recorded in the 1970s at medium (0.5 cm-1) resolution using a long-path absorption cell. Here we report the cavity ringdown spectrum of the 0^0_0 band, recorded using a pulsed dye laser with 0.1 cm-1 spectral bandwidth. The spectrum was measured under both bulk-gas (room-temperature) and jet-cooled conditions. The band contour in each spectrum was analyzed by using a computer program developed for simulating and fitting the rotational structure of singlet-triplet transitions. The assignment of several resolved sub-band heads in the room-temperature spectrum permitted approximate fitting of the inertial constants for the T_1(n,?*) state. The determined values (cm-1) are A=1.662, B=0.1485, C=0.1363. For the parameters A and (B+C)/2, estimated uncertainties of ± 0.003 cm-1 and ± 0.0004 cm-1, respectively, correspond to a range of values that produce qualitatively satisfactory global agreement with the observed room-temperature contour. The fitted inertial constants were used to simulate the rotational contour of the 0^0_0 band under jet-cooled conditions. Agreement with the observed jet-cooled spectrum was optimized by varying the homogeneous linewidth of the rovibronic transitions as well as the rotational temperature. The optimal FWHM was about 0.20 cm-1, leading to an estimate of 25 ps for the lifetime of the T_1(n,?*) state of acrolein (v=0) under isolated-molecule conditions. R. H. Judge et al., J. Chem. Phys. 103, 5343 (1995).

  7. 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.

  8. Optimization of absorption bands of dye-sensitized and perovskite tandem solar cells based on loss-in-potential values.

    PubMed

    Sobu?, Jan; Zió?ek, Marcin

    2014-07-21

    A numerical study of optimal bandgaps of light absorbers in tandem solar cell configurations is presented with the main focus on dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). The limits in efficiency and the expected improvements of tandem structures are investigated as a function of total loss-in-potential (V(L)), incident photon to current efficiency (IPCE) and fill factor (FF) of individual components. It is shown that the optimal absorption onsets are significantly smaller than those derived for multi-junction devices. For example, for double-cell devices the onsets are at around 660 nm and 930 nm for DSSCs with iodide based electrolytes and at around 720 nm and 1100 nm for both DSSCs with cobalt based electrolytes and PSCs. Such configurations can increase the total sunlight conversion efficiency by about 35% in comparison to single-cell devices of the same VL, IPCE and FF. The relevance of such studies for tandem n-p DSSCs and for a proposed new configuration for PSCs is discussed. In particular, it is shown that maximum total losses of 1.7 V for DSSCs and 1.4 V for tandem PSCs are necessary to give any efficiency improvement with respect to the single bandgap device. This means, for example, a tandem n-p DSSC with TiO2 and NiO porous electrodes will hardly work better than the champion single DSSC. A source code of the program used for calculations is also provided. PMID:24901747

  9. Using OMEGA Data to Determine the Optical Depths of Water Vapor Absorption Bands in the Martian Atmosphere Earth and Environmental Sciences, The University of Texas at San Antonio, San

    E-print Network

    Texas at San Antonio, University of

    Using OMEGA Data to Determine the Optical Depths of Water Vapor Absorption Bands in the Martian atmosphere. Recently, OMEGA data has also been used to study water vapor abundance [7], in which the water.56, SPICAM-1.38, OMEGA-2.56) have similar pattern from southern hemisphere to northern hemisphere, though

  10. TAKING ANOTHER LOOK AT THE 3-MICRON ABSORPTION BAND ON ASTEROIDS. E. S. Howell, Arecibo Obser-vatory, HC 3 Box 53995, Arecibo PR 00612, USA, (ehowell@naic.edu), A. S. Rivkin, Department of Earth, Atmospheric, and

    E-print Network

    Cohen, Barbara Anne

    TAKING ANOTHER LOOK AT THE 3-MICRON ABSORPTION BAND ON ASTEROIDS. E. S. Howell, Arecibo Obser asteroids have hydrated minerals on the surface. This has been interpreted as evidence of aqueous alteration, and suggests that these asteroids may be related to meteorites rich in serpentine and/or saponite. However

  11. Cost-effective 33-Gbps intensity modulation direct detection multi-band OFDM LR-PON system employing a 10-GHz-based transceiver

    NASA Astrophysics Data System (ADS)

    Hsu, Dar-Zu; Wei, Chia-Chien; Chen, Hsing-Yu; Li, Wei-Yuan; Chen, Jyehong

    2011-08-01

    We develop a dynamic multi-band OFDM subcarrier allocation scheme to fully utilize the available bandwidth under the restriction of dispersion- and chirp-related power fading. The experimental results successfully demonstrate an intensity-modulation-direct-detection 34.78-Gbps OFDM signal transmissions over 100-km long-reach (LR) passive-optical networks (PONs) based on a cost-effective 10-GHz EAM and a 10-GHz PIN. Considering 0--100-km transmission bandwidth of a 10-GHz EAM, the narrowest bandwidth is theoretically evaluated to occur at ~40 km, instead of 100 km. Consequently, the performances of 20--100-km PONs are experimentally investigated, and at least 33-Gbps capacity is achieved to support LR-PONs of all possible 20--100-km radii.

  12. Infrared absorption mechanisms of black silicon

    NASA Astrophysics Data System (ADS)

    Cheng, Zhengxi; Chen, Yongping; Ma, Bin

    2014-09-01

    Black silicon has a wide spectrum of non-spectral characteristics high absorption from visible to long wave infrared band .Based on semi-empirical impurity band model, free carrier absorption, radiation transitions between the valence band and the impurity band, radiation transitions between the impurity band and the conduction band were calculated, and absorption coefficients for each process were got. The results showed that the transitions from valence band to the impurity band induced absorption in the near-infrared waveband, but it has a rapid decay with wavelength. In the shortwave mid-wave and long-wave IR bands, transitions from the impurity band to the conduction band caused a huge absorption, and the absorption coefficient was slowly decreased with increasing wavelength. The free carrier absorption dominates in long-wave band. The calculation results agreed well with the test results of plant black silicon in magnitude and trends.

  13. Reduction of timing jitter and intensity noise in normal-dispersion passively mode-locked fiber lasers by narrow band-pass filtering.

    PubMed

    Qin, Peng; Song, Youjian; Kim, Hyoji; Shin, Junho; Kwon, Dohyeon; Hu, Minglie; Wang, Chingyue; Kim, Jungwon

    2014-11-17

    Fiber lasers mode-locked with normal cavity dispersion have recently attracted great attention due to large output pulse energy and femtosecond pulse duration. Here we accurately characterized the timing jitter of normal-dispersion fiber lasers using a balanced cross-correlation method. The timing jitter characterization experiments show that the timing jitter of normal-dispersion mode-locked fiber lasers can be significantly reduced by using narrow band-pass filtering (e.g., 7-nm bandwidth filtering in this work). We further identify that the timing jitter of the fiber laser is confined in a limited range, which is almost independent of cavity dispersion map due to the amplifier-similariton formation by insertion of the narrow bandpass filter. The lowest observed timing jitter reaches 0.57 fs (rms) integrated from 10 kHz to 10 MHz Fourier frequency. The rms relative intensity noise (RIN) is also reduced from 0.37% to 0.02% (integrated from 1 kHz to 5 MHz Fourier frequency) by the insertion of narrow band-pass filter. PMID:25402069

  14. Proposal of high efficiency solar cells with closely stacked InAs/In{sub 0.48}Ga{sub 0.52}P quantum dot superlattices: Analysis of polarized absorption characteristics via intermediate–band

    SciTech Connect

    Yoshikawa, H., E-mail: yoshikawa-hirofumi@sharp.co.jp; Kotani, T.; Kuzumoto, Y.; Izumi, M.; Tomomura, Y.; Hamaguchi, C. [Advanced Technology Research Laboratories, Sharp Corporation Tenri, Nara 632-8567 (Japan)

    2014-07-07

    We present a theoretical study of the electronic structures and polarized absorption properties of quantum dot superlattices (QDSLs) using wide–gap matrix material, InAs/In{sub 0.48}Ga{sub 0.52}P QDSLs, for realizing intermediate–band solar cells (IBSCs) with two–step photon–absorption. The plane–wave expanded Burt–Foreman operator ordered 8–band k·p theory is used for this calculation, where strain effect and piezoelectric effect are taken into account. We find that the absorption spectra of the second transitions of two–step photon–absorption can be shifted to higher energy region by using In{sub 0.48}Ga{sub 0.52}P, which is lattice–matched material to GaAs substrate, as a matrix material instead of GaAs. We also find that the transverse magnetic polarized absorption spectra in InAs/In{sub 0.48}Ga{sub 0.52}P QDSL with a separate IB from the rest of the conduction minibands can be shifted to higher energy region by decreasing the QD height. As a result, the second transitions of two–step photon–absorption by the sunlight occur efficiently. These results indicate that InAs/In{sub 0.48}Ga{sub 0.52}P QDSLs are suitable material combination of IBSCs toward the realization of ultrahigh efficiency solar cells.

  15. X-ray relative intensities at incident photon energies across the Li (i=1-3) absorption edges of elements with 35?Z?92

    NASA Astrophysics Data System (ADS)

    Puri, Sanjiv

    2014-07-01

    The intensity ratios, ILk/IL?1 (k=l,?,?2,?1,?2,15,?3,?4,?5,7,?6,?9,10,?1,5,?6,8,?2,3,?4) and ILj/IL? (j=?,?), have been evaluated at incident photon energies across the Li (i=1-3) absorption edge energies of all the elements with 35?Z?92. Use is made of what are currently considered to be more reliable theoretical data sets of different physical parameters, namely, the Li (i=1-3) sub-shell photoionization cross sections based on the relativistic Hartree-Fock-Slater (RHFS) model, the X-ray emission rates based on the Dirac-Fock model, and the fluorescence and Coster-Kronig yields based on the Dirac-Hartree-Slater model. In addition, the L?1 X-ray production cross sections for different elements at various incident photon energies have been tabulated so as to facilitate the evaluation of production cross sections for different resolved L X-ray components from the tabulated intensity ratios. Further, to assist evaluation of the prominent (Li-Sj) (Sj=Mj, Nj and i=1-3, j=1-7) resonant Raman scattered (RRS) peak energies for an element at a given incident photon energy (below the Li sub-shell absorption edge), the neutral-atom electron binding energies based on the relaxed orbital RHFS calculations are also listed so as to enable identification of the RRS peaks, which can overlap with the fluorescent X-ray lines.

  16. A combined resonance enhanced multiphoton ionization and ab initio study of the first absorption band of 1,2,4,5-tetrafluorobenzene, pentafluorobenzene, and hexafluorobenzene

    NASA Astrophysics Data System (ADS)

    Ridley, Trevor; Rogers, David M.; Lawley, Kenneth P.

    2014-10-01

    The resonance enhanced multiphoton ionization (REMPI) spectra of jet-cooled penta- and hexafluorobenzene when excited in the region ?ex = 265-253 nm of the first absorption band and observed only in the CF+ mass channel is dominated by rotational structure in the A?X transition of CF. However, structure in the CF+ channel for ?ex > 265 nm is not a continuation of this CF spectrum and is assigned to vibrational activity in two low-frequency modes of a distorted excited state of the parent molecule. The vibrational structure is assigned to the lowest ??* state from a comparison with the equivalent spectrum of 1,2,4,5-tetrafluorobenzene. Ab initio calculations at the CIS level of theory of the ??* state of the penta- and hexafluorobenzene reveal a much more distorted equilibrium geometry (C1 symmetry) than that of 1,2,4,5-tetrafluorobenzene. Long progressions observed in the ?ex > 265 nm REMPI spectra of C6HF5 and C6F6 are assigned to two very low frequency (˜30 and 80 cm-1) modes. The role of the close-lying ??* and ??* states in determining the energy redistribution of the initially excited state by internal conversion is discussed. Both the fluorescent yield and the direct production of CF(X) are associated with transfer to the lower-lying ??* state.

  17. Absorption spectroscopic study of EDA complexes of.

    PubMed

    Bhattacharya, S; Nayak, S K; Chattopadhyay, S K; Banerjee, M; Mukherjee, A K

    2001-02-01

    [70]Fullerene has been shown to form 1:1 molecular complexes with toluene, p-xylene, m-xylene, 1,2,4,5-tetramethyl benzene (durene) and pentamethyl benzene (PMB) in CCl4 medium by absorption spectroscopic method. Isosbestic points have been detected in case of complexes with PMB and durene. Charge transfer absorption band could not be detected but the intensity of the broad absorption band of C70 in CCl4 decreases systematically with increase in the concentration of the added methylbenzenes. From this trend the formation constants (Kc) of the complexes have been determined at three different wavelengths. The constancy of Kc with respect to change in the wavelength of measurement supports the view that complex of a single stoichiometry (1:1) is formed in each case. PMID:11206565

  18. The infrared spectrum and vibrational intensity of gaseous dioxygen difluoride (foof)

    NASA Astrophysics Data System (ADS)

    Kim, K. C.; Campbell, G. M.

    1985-07-01

    A complete absorption spectrum of gaseous dioxygen difluoride (FOOF) was obtained using a very long pathlength, temperature-programmable cell and an FT-IR spectrometer. All six fundamental vibrational frequencies were deduced from three fundamental bands and four binary combination bands. A significant deviation of the v frequency is observed from the matrix studies of solid FOOF. The absolute vibrational intensities of observed bands are reported.

  19. 100 Femtosecond laser absorption in solid density targets

    SciTech Connect

    Price, D.F.; More, R.M.; Walling, R.S.; Stewart, R.E.

    1996-10-08

    Experimental short pulse lasers are rapidly approaching energy levels where target irradiances exceeding 10{sup 20} W/CM{sup 2} are routinely achievable. These high intensity levels will open up a new class of solid target interaction physics where relativistic effects must be included and non-traditional absorption mechanisms become significant. However much remains to be understood of the absorption physics at lower intensities where classical absorption is dominated by collisional and resonance absorption. If attention is paid to producing clean laser pulses that do not significantly pre-pulse interact with the target, it is possible to produce plasmas of sufficiently short scale length that near-solid density interactions are observable at intensities exceeding 10{sup 18} W/CM{sup 2} for 100 fs laser irradiation. We report here extensions to our previous efforts at normal incidence that expand our observations to non-normal angles including the effect of polarization for several target materials. Between 10{sup 13} W/CM{sup 2} and 10{sup 14} W/CM{sup 2} we observe that the target absorption retains a signature of the intra-band atomic transitions. At higher intensities a more material independent ion-electron collisional absorption and short scale length resonance absorption dominate. P - polarized absorption in short scale length plasmas has been observed to exceed 60 percent.

  20. A neural network-based four-band model for estimating the total absorption coefficients from the global oceanic and coastal waters

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Cui, Tingwei; Quan, Wenting

    2015-01-01

    this study, a neural network-based four-band model (NNFM) for the global oceanic and coastal waters has been developed in order to retrieve the total absorption coefficients a(?). The applicability of the quasi-analytical algorithm (QAA) and NNFM models is evaluated by five independent data sets. Based on the comparison of a(?) predicted by these two models with the field measurements taken from the global oceanic and coastal waters, it was found that both the QAA and NNFM models had good performances in deriving a(?), but that the NNFM model works better than the QAA model. The results of the QAA model-derived a(?), especially in highly turbid waters with strong backscattering properties of optical activity, was found to be lower than the field measurements. The QAA and NNFM models-derived a(?) could be obtained from the MODIS data after atmospheric corrections. When compared with the field measurements, the NNFM model decreased by a 0.86-24.15% uncertainty (root-mean-square relative error) of the estimation from the QAA model in deriving a(?) from the Bohai, Yellow, and East China seas. Finally, the NNFM model was applied to map the global climatological seasonal mean a(443) for the time range of July 2002 to May 2014. As expected, the a(443) value around the coastal regions was always larger than the open ocean around the equator. Viewed on a global scale, the oceans at a high latitude exhibited higher a(443) values than those at a low latitude.

  1. Development and study of a 1.5 ?m optical frequency standard referenced to the P(16) saturated absorption line in the ( ? 1+ ? 3) overtone band of 13C 2H 2

    Microsoft Academic Search

    A. Czajkowski; A. A. Madej; P. Dubé

    2004-01-01

    We describe a recently developed saturated absorption spectrometer realizing an optical frequency standard based on the P(16) transition of the (?1+?3) band of 13C2H2. Studies of stability, reproducibility and sensitivity to various parameters were performed. The current stability of the system has been measured to reach 4×10?13 for an averaging time of 100 s. To our knowledge, we report the

  2. Investigation of OH absorption cross sections of rotational transitions in the A2Sigma+, v'=0<-X2Pi, v`=0 band under atmospheric conditions: Implications for tropospheric long-path absorption measurements

    Microsoft Academic Search

    H.-P. Dorn; R. Neuroth; A. Hofzumahaus

    1995-01-01

    The accuracy of tropospheric hydroxyl radical measurements by long-path absorption spectroscopy is ultimately limited by the uncertainty of the effective OH absorption cross sections. The latter were determined from calculated spectra for the Q1(2), Q1(3), and P1(1) rotational lines of the OH A2Sigma+, (v'=0)X2Pi, (v`=0) transition at 308 nm. The calculations took into account Doppler broadening, measured data of the

  3. Absorption of surface acoustic waves by topological insulator thin films

    SciTech Connect

    Li, L. L., E-mail: lllihfcas@foxmail.com [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Xu, W., E-mail: wenxu-issp@aliyun.com [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China); Department of Physics, Yunnan University, Kunming 650091 (China)

    2014-08-11

    We present a theoretical study on the absorption of the surface acoustic waves (SAWs) by Dirac electrons in topological insulator (TI) thin films (TITFs). We find that due to momentum and energy conservation laws, the absorption of the SAWs in TITFs can only be achieved via intra-band electronic transitions. The strong absorption can be observed up to sub-terahertz frequencies. With increasing temperature, the absorption intensity increases significantly and the cut-off frequency is blue-shifted. More interestingly, we find that the absorption of the SAWs by the TITFs can be markedly enhanced by the tunable subgap in the Dirac energy spectrum of the TI surface states. Such a subgap is absent in conventional two-dimensional electron gases (2DEGs) and in the gapless Dirac 2DEG such as graphene. This study is pertinent to the exploration of the acoustic properties of TIs and to potential application of TIs as tunable SAW devices working at hypersonic frequencies.

  4. Absorption of surface acoustic waves by topological insulator thin films

    NASA Astrophysics Data System (ADS)

    Li, L. L.; Xu, W.

    2014-08-01

    We present a theoretical study on the absorption of the surface acoustic waves (SAWs) by Dirac electrons in topological insulator (TI) thin films (TITFs). We find that due to momentum and energy conservation laws, the absorption of the SAWs in TITFs can only be achieved via intra-band electronic transitions. The strong absorption can be observed up to sub-terahertz frequencies. With increasing temperature, the absorption intensity increases significantly and the cut-off frequency is blue-shifted. More interestingly, we find that the absorption of the SAWs by the TITFs can be markedly enhanced by the tunable subgap in the Dirac energy spectrum of the TI surface states. Such a subgap is absent in conventional two-dimensional electron gases (2DEGs) and in the gapless Dirac 2DEG such as graphene. This study is pertinent to the exploration of the acoustic properties of TIs and to potential application of TIs as tunable SAW devices working at hypersonic frequencies.

  5. Estimation of Aromatic Structure Contents in Hardwood Lignins from IR Absorption Spectra

    NASA Astrophysics Data System (ADS)

    Derkacheva, O. Yu.

    2013-11-01

    Results of an in-depth analysis of Fourier-transform IR absorption spectra of hardwood and softwood dioxane lignins were reported. Correlations between absorption band intensities in initial and second-derivative spectra and 13C NMR spectroscopic data on the contents of guaiacyl and syringyl structural units were found. The found linear dependences enabled the contents of two types of phenylpropane units to be estimated in the range 0-100% with a relative error of ?5%.

  6. The two-photon absorptivity of rotational transitions in the A2 Sigma hyperon + (v prime = O) - X-2 pion (v prime prime = O) gamma band of nitric oxide

    NASA Technical Reports Server (NTRS)

    Gross, K. P.; Mckenzie, R. L.

    1982-01-01

    A predominantly single-mode pulsed dye laser system giving a well characterized spatial and temporal output suitable for absolute two-photon absorptivity measurements was used to study the NO gamma(0,0) S11 + R21 (J double prime = 7-1/2) transition. Using a calibrated induced-fluorescence technique, an absorptivity parameter of 2.8 + or - 1.4 x 10 to the minus 51st power cm to the 6th power was obtained. Relative strengths of other rotational transitions in the gamma(0,0) band were also measured and shown to compare well with predicted values in all cases except the O12 (J double prime = 10-1/2) transition.

  7. ESR and optical absorption of bound-small polarons in YAlO3

    Microsoft Academic Search

    O. F. Schirmer; K. W. Blazey; W. Berlinger; R. Diehl

    1975-01-01

    Nominally undoped YAlO3 shows broad intense absorption bands in the visible after irradiation with visible and near uv light at 77 K; they become especially strong after subsequent irradiation with near ir. The bands could be correlated with an ESR spectrum arising from holes, which are trapped at O2- ions near unidentified defects or are possibly self-trapped. A similar spectrum

  8. Propane gas leak detection by infrared absorption using carbon infrared emitter and infrared camera

    Microsoft Academic Search

    Naoya Kasai; Chihiro Tsuchiya; Takabumi Fukuda; Kazuyoshi Sekine; Takeru Sano; Tatsumi Takehana

    2011-01-01

    The present study investigated the ability of a system using a carbon infrared emitter (CIE) and an infrared (IR) camera to detect a combustible gas, propane. The CIE transmitted infrared at wavelengths ranging from 1 to 5?m, and the infrared absorption band of propane gas (3.37?m) was obtained using a bandpass filter to remove other infrared wavelengths. The intensity of

  9. Intensive visible-light photoactivity of Bi- and Fe-containing pyrochlore nanoparticles.

    PubMed

    Bencina, Metka; Valant, Matjaz; Pitcher, Michael W; Fanetti, Mattia

    2014-01-21

    Bi-Fe-Nb-O pyrochlore nanoparticles were synthesized by a facile coprecipitation reaction. They exhibit intense visible-light absorption due to a narrow band gap and high visible-light photocatalytic activity for degradation of methyl orange. PMID:24306495

  10. Matrix-assisted laser desorption and ionization in the O---H and C=O absorption bands of aliphatic and aromatic matrices: dependence on laser wavelength and temporal beam profile

    NASA Astrophysics Data System (ADS)

    Cramer, Rainer; Haglund, Richard F.; Hillenkamp, Franz

    1997-12-01

    A tunable free-electron laser (FEL) was used to initiate infrared (IR) matrix-assisted laser desorption and ionization (MALDI) of small proteins in aliphatic and aromatic matrices. The laser wavelength was scanned from 2.65 to 4.2 [mu]m and from 5.5 to 6.5 [mu]m, covering the absorption bands of the O---H and C=O stretching vibrations found in such commonly used IR matrices as succinic, fumaric and nicotinic acids. The temporal profile of the laser pulse was also varied using a broadband electro-optic switch (Pockels cell) to study the effects of fluence and irradiance. Although there are absorption peaks at 3.3 [mu]m for succinic acid and fumaric acid, and at 4.1 [mu]m for nicotinic acid, the lowest threshold-fluence for IR MALDI in this region was around 2.94 [mu]m for all matrices. Moreover, the threshold-fluence increased with increasing absorption up to a value five times that of the 2.94 [mu]m value. This result raises questions about the relative contributions of the different sample constitutents to the absorption and the role of resonant absorption in IR MALDI. The threshold-fluences are typically one order of magnitude higher than those for ultraviolet (UV) MALDI, while extinction coefficients of the IR matrices are 100-1000 times smaller than for UV matrices. Therefore, the absorbed energies per unit volume at the MALDI threshold are 10-100 times smaller than in UV MALDI. All these facts clearly indicate that a different desorption/ionization process must be operative in IR MALDI. Variations in temporal profile of the FEL pulse also revealed that ion desorption depends on laser irradiance rather than laser fluence, a result which cannot be explained simply by energy loss due to heat conduction. Two possible models for IR desorption are suggested based on these observations.

  11. Fine structure of 6A 1g ? 4A 1g, 4E g ( 4G) absorption band in MnF 2

    NASA Astrophysics Data System (ADS)

    Darwish, S.; Al-Tel, S. Y.; Abu-Teir, M. M.; Kitanah, R. M.-L.; Legrouze, A. A.; Saleh, A. M.

    2009-02-01

    Systematic spectroscopic measurements of the spectral lines in MnF 2 have been carried out in the temperature range 10-300 K. Observations of exciton and exciton-magnon sidebands in the fine structures of the 6A 1g ? 4A 1g, 4E g ( 4G) state of Mn +2 ions are reported at low temperatures for MnF 2. The fine structure of the C-band is mainly attributed to spin multiplicity in the ordered state. In addition, the pure exciton bands have been identified and the ratios for the separation energies between these lines are fitted with the ratios expected form Lande interval rule.

  12. Electronic transitions and heterogeneity of the bacteriophytochrome Pr absorption band: An angle balanced polarization resolved femtosecond VIS pump-IR probe study.

    PubMed

    Linke, Martin; Yang, Yang; Zienicke, Benjamin; Hammam, Mostafa A S; von Haimberger, Theodore; Zacarias, Angelica; Inomata, Katsuhiko; Lamparter, Tilman; Heyne, Karsten

    2013-10-15

    Photoisomerization of biliverdin (BV) chromophore triggers the photoresponse in native Agp1 bacteriophytochrome. We discuss heterogeneity in phytochrome Pr form to account for the shape of the absorption profile. We investigated different regions of the absorption profile by angle balanced polarization resolved femtosecond VIS pump-IR probe spectroscopy. We studied the Pr form of Agp1 with its natural chromophore and with a sterically locked 18Et-BV (locked Agp1). We followed the dynamics and orientations of the carbonyl stretching vibrations of ring D and ring A in their ground and electronically excited states. Photoisomerization of ring D is reflected by strong signals of the ring D carbonyl vibration. In contrast, orientational data on ring A show no rotation of ring A upon photoexcitation. Orientational data allow excluding a ZZZasa geometry and corroborates a nontwisted ZZZssa geometry of the chromophore. We found no proof for heterogeneity but identified a new, to our knowledge, electronic transition in the absorption profile at 644 nm (S0?S2). Excitation of the S0?S2 transition will introduce a more complex photodynamics compared with S0?S1 transition. Our approach provides fundamental information on disentanglement of absorption profiles, identification of chromophore structures, and determination of molecular groups involved in the photoisomerization process of photoreceptors. PMID:24138851

  13. Optical absorption and determination of band offset in strain-balanced GaInP/InAsP multiple quantum wells grown by low-pressure metalorganic vapour phase epitaxy

    NASA Astrophysics Data System (ADS)

    Ababou, Y.; Desjardins, P.; Chennouf, A.; Masut, R. A.; Yelon, A.; Beaudoin, M.; Bensaada, A.; Leonelli, R.; L'Espérance, G.

    1997-05-01

    We report on optical absorption of the interband transitions in zero-net strained 0268-1242/12/5/006/img12 multiple quantum wells (MQW) grown by low-pressure metalorganic vapour phase epitaxy (LP-MOVPE), using tertiarybutylarsine as a group V source. Sharp interfaces are obtained using a growth interruption procedure. Analysis of this procedure with different interruption times leads to the same optimal times as those obtained for InP/InAsP superlattices grown in the same reactor. We have achieved the growth of modulation-free strain-balanced heterostructures, as indicated by cross-sectional transmission electron microscopy. High-resolution x-ray diffraction and optical absorption analysis demonstrate the high crystallographic and optical quality of these structures. The absorption spectrum of an x = 0.06, y = 0.14 sample was accurately fitted using the Bastard/Marzin model, and a strained conduction band offset of 0268-1242/12/5/006/img13 was deduced. This corresponds to about 0268-1242/12/5/006/img14 of the total strained bandgap difference.

  14. Facial Rejuvenation and Other Clinical Applications of Intense Pulsed Light

    Microsoft Academic Search

    Peter Bjerring; Kaare Christiansen

    \\u000a Nonablative optical rejuvenation of facial skin targeting ectatic vessels, mottled pigmentation, and fine wrinkling can be\\u000a safely performed with intense pulsed light (IPL) systems, which produce broad band visible and near infrared light. IPL systems\\u000a use several optical filtering techniques, matching the emitted light spectrum to principal light absorption wavelengths of\\u000a the major skin chromophores: hemoglobin and melanin. Besides skin

  15. Developments for vegetation fluorescence retrieval from spaceborne high-resolution spectrometry in the O2-A and O2B absorption bands

    Microsoft Academic Search

    L. Guanter; L. Alonso; L. Gómez-Chova; M. Meroni; R. Preusker; J. Fischer; J. Moreno

    2010-01-01

    Solar-induced chlorophyll fluorescence is a weak electromagnetic signal emitted in the red and far-red spectral regions by vegetation chlorophyll under excitation by solar radiation. Chlorophyll fluorescence has been demonstrated to be a close proxy to vegetation physiological functioning. The basis for fluorescence retrieval from passive space measurements is the exploitation of the O2-A and O2-B atmospheric absorption features to isolate

  16. High-resolution absorption cross sections of carbon monoxide bands at 295 K between 91.7 and 100.4 nanometers

    Microsoft Academic Search

    G. Stark; K. Yoshino; Peter L. Smith; K. Ito; W. H. Parkinson

    1991-01-01

    Theoretical descriptions of the abundance and excitation of carbon monoxide in interstellar clouds require accurate data on the vacuum-ultraviolet absorption spectrum of the molecule. The 6.65 m spectrometer at the Photon Factory synchrotron light source was used to measure photoabsorption cross sections of CO features between 91.2 and 100.4 nm. These data were recorded at a resolving power of 170,000,

  17. Mapping sound intensities by seating position in a university concert band: A risk of hearing loss, temporary threshold shifts, and comparisons with standards of OSHA and NIOSH

    Microsoft Academic Search

    Nicholas Vedder Holland III

    2004-01-01

    Exposure to loud sounds is one of the leading causes of hearing loss in the United States. The purpose of the current research was to measure the sound pressure levels generated within a university concert band and determine if those levels exceeded permissible sound limits for exposure according to criteria set by the Occupational Safety and Health Administration (OSHA) and

  18. Molecular Reorganization Energy as a Key Determinant of J-Band Formation in J-Aggregates of Polymethine Dyes.

    PubMed

    Petrenko, Alexander; Stein, Matthias

    2015-07-01

    This work demonstrates the feasibility of the theory of extended multiphonon electron transitions for the description of optical spectra of polymethine dyes and J-aggregates using quantum chemistry. The formation of a strong absorption band in dye monomers and a J-band in their aggregates is uniformly explained from the electron-nuclear resonance condition. The redistribution of optical band intensities among cyanine dyes with the solvent is also explained. The dependence of the possibility of J-band formation in aggregates on the dye structure is successfully predicted. The results presented provide an insight for rational molecular design and application of polymethine dyes. PMID:26091059

  19. Atmospheric correction of ENVISAT\\/MERIS data over case II waters: the use of black pixel assumption in oxygen and water vapour absorption bands

    Microsoft Academic Search

    Jingjing Zhu; Jin Chen; Bunkei Matsushita; Wei Yang; Takehiko Fukushima

    2012-01-01

    The Medium Resolution Imaging Spectrometer (MERIS) sensor, with its good physical design, can provide excellent data for water colour monitoring. However, owing to the shortage of shortwave-infrared (SWIR) bands, the traditional near-infrared (NIR)–SWIR algorithm for atmospheric correction in inland turbid case II waters cannot be extended to the MERIS data directly, which limits its applications. In this study, we developed

  20. Relation of molecular structure to Franck-Condon bands in the visible-light absorption spectra of symmetric cationic cyanine dyes.

    PubMed

    Lin, Katrina Tao Hua; Silzel, John W

    2015-05-01

    A Franck-Condon (FC) model is used to study the solution-phase absorbance spectra of a series of seven symmetric cyanine dyes having between 22 and 77 atoms. Electronic transition energies were obtained from routine visible-light absorbance and fluorescence emission spectra. Harmonic normal modes were computed using density functional theory (DFT) and a polarizable continuum solvent model (PCM), with frequencies corrected using measured mid-infrared spectra. The model predicts the relative energies of the two major vibronic bands to within 5% and 11%, respectively, and also reproduces structure-specific differences in vibronic band shapes. The bands themselves result from excitation of two distinct subsets of normal modes, one with frequencies between 150 and 625cm(-1), and the other between 850 and 1480cm(-1). Vibronic transitions excite symmetric in-plane bending of the polymethine chain, in-plane bends of the polymethine and aromatic C-H bonds, torsions and deformations of N-alkyl substituents, and in the case of the indocyanines, in-plane deformations of the indole rings. For two dyes, the model predicts vibronic coupling into symmetry-breaking torsions associated with trans-cis photoisomerization. PMID:25703366

  1. Relation of molecular structure to Franck-Condon bands in the visible-light absorption spectra of symmetric cationic cyanine dyes

    NASA Astrophysics Data System (ADS)

    Lin, Katrina Tao Hua; Silzel, John W.

    2015-05-01

    A Franck-Condon (FC) model is used to study the solution-phase absorbance spectra of a series of seven symmetric cyanine dyes having between 22 and 77 atoms. Electronic transition energies were obtained from routine visible-light absorbance and fluorescence emission spectra. Harmonic normal modes were computed using density functional theory (DFT) and a polarizable continuum solvent model (PCM), with frequencies corrected using measured mid-infrared spectra. The model predicts the relative energies of the two major vibronic bands to within 5% and 11%, respectively, and also reproduces structure-specific differences in vibronic band shapes. The bands themselves result from excitation of two distinct subsets of normal modes, one with frequencies between 150 and 625 cm-1, and the other between 850 and 1480 cm-1. Vibronic transitions excite symmetric in-plane bending of the polymethine chain, in-plane bends of the polymethine and aromatic C-H bonds, torsions and deformations of N-alkyl substituents, and in the case of the indocyanines, in-plane deformations of the indole rings. For two dyes, the model predicts vibronic coupling into symmetry-breaking torsions associated with trans-cis photoisomerization.

  2. Gastric Banding

    MedlinePLUS

    ... Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco ... of Gastric Banding Lifestyle Changes after Gastric Banding Surgery Gastric banding is a weight loss option for ...

  3. Can sample treatments based on advanced oxidation processes assisted by high-intensity focused ultrasound be used for toxic arsenic determination in human urine by flow-injection hydride-generation atomic absorption spectrometry?

    Microsoft Academic Search

    A. Correia; M. Galesio; H. Santos; R. Rial-Otero; C. Lodeiro; A. Oehmen; Antonio C. L. Conceição; J. L. Capelo

    2007-01-01

    Two advanced oxidation processes (AOPs), based on high-intensity focused ultrasound (HIFU), namely, KMnO4\\/HCl\\/HIFU and H2O2\\/HCl\\/HIFU are studied and compared for the determination of toxic arsenic in human urine [As(III)+As(V)+MMA+DMA] by flow-injection hydride-generation atomic absorption spectrometry (FI-HG-AAS). The KMnO4\\/HCl\\/HIFU procedure was found to be adequate for organic matter degradation in human urine. l-cysteine (letra minuscula) was used for As reduction to

  4. Comparison of HITRAN Calculated Spectra with Laboratory Measurements of the 820, 940, 1130, and 1370 nm Water Vapor Bands

    NASA Technical Reports Server (NTRS)

    Giver, Lawrence P.; Pilewskie, P.; Gore, Warren J.; Freedman, R. S.; Chackerian, C., Jr.; Varanasi, P.

    2001-01-01

    Several groups have recently been working to improve the near-infrared spectrum of water vapor on HITRAN. The unit-conversion errors found by Giver, et al have now been corrected on the recently released HITRAN-2000. The most important aspect of this article for atmospheric absorption was increasing all the HITRAN-1996 intensities of the 940 nm band by nearly 15%. New intensity measurements of this band by Brown, et al (submitted to J. Mol. Spec.) have now been included in the latest HITRAN. However, Belmiloud, et al discuss new data in the 633-1175 nm region which they expect will substantially increase the calculated absorption of solar radiation by water vapor. They suggest the 4 bands at 725, 820, 940, and 1130 nm are all stronger than the sum of the line intensities currently on HITRAN. For the 725 and 820 nm bands, their recommended intensity increases are 10% and 15%, about the same as previously noted by Grossmann and Browell and Ponsardin and Browell. Belmiloud, et al only suggest a 6% increase for the 940 nm. band over the corrected HITRAN-1996 intensities, but a large 38% increase for the 1130 nm band. The new data discussed by Belmiloud, et al have now been published in greater detail by Schermaul, et al. The intensity increase for the 1130 nm band discussed by Belmiloud, et al is very substantial; it is important to quickly determine if the HITRAN intensity values are in error by as much as they claim. Only intensity errors for the strong lines could result in the total band intensity being in error by such a large amount. To quickly get a number of spectra of the entire near-infrared region from 650 to 1650 nm, we used the Solar Spectral Flux Radiometer with our 25-meter base path White absorption cell. This moderate resolution spectrometer is a flight instrument that has flown on the Sandia Twin Otter for the ARESE 11 experiment. The measured band profiles were then compared to calculated spectra using the latest HITRAN line intensities, convolved with the instrumental resolution. Our spectra for the 725 and 820 nm bands show somewhat more absorption than the HITRAN simulations, about as expected by Belmiloud, el al. The total absorption for our spectra of the 940 nm band agrees well with the HITRAN simulations; this HITRAN spectral region now has the new measurements of Brown, et al. Our spectra of the 1130 nm band have somewhat more absorption than the HITRAN simulations, but not as much as the 38% intensity increase for this band suggested by Belmiloud, et al. An intensity increase of about 20% on average would be more compatible with our data. Finally, our spectra of the 1370 nm band are fairly well modeled by the HITRAN simulations, despite the known problems of the older HITRAN data in this region.

  5. Prospective clinical and histological study to evaluate the efficacy and safety of a targeted high?intensity narrow band UVB\\/UVA1 therapy for striae alba

    Microsoft Academic Search

    Neil S. Sadick; Cynthia Magro; Alison Hoenig

    2007-01-01

    Objective: The purpose of this study was to determine the efficacy and safety of a targeted narrow band UVB\\/UVA1 therapy for the treatment of striae alba. Methods: Fourteen individuals with skin types II-VI were enrolled in this 22-week trial that consisted of up to 10 treatments with a combination of UVB\\/UVA1 (MultiClear2, Curelight Ltd, Israel). Participants were treated with a

  6. Absorption and photoluminescence of ternary nanostructured Ge-S-Ga(In)glassy semiconductor systems

    SciTech Connect

    Babaev, A. A., E-mail: babaev-arif@mail.ru [Russian Academy of Sciences, Amirkhanov Institute of Physics, Dagestan Scientific Center (Russian Federation); Kudoyarova, V. Kh. [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation)

    2013-07-15

    The photoluminescence and luminescence excitation spectra and the edge and IR absorption of Ge-S-Ga(In) glassy semiconductor systems are studied. The observed shifts of the optical-absorption edge, photoluminescence spectra (a decrease in their full width at half-maximum), and luminescence excitation spectra to lower energies upon the introduction of Ga or In into Ge-S binary systems are due to the fact that Ga or In tend to interact with sulfur, rather than with germanium. As the content of Ga(In) in the system increases, the intensity of the absorption band associated with vibrations of the Ge-S bond decreases.

  7. Coloration and oxygen vacancies in wide band gap oxide semiconductors: Absorption at metallic nanoparticles induced by vacancy clustering—A case study on indium oxide

    SciTech Connect

    Albrecht, M., E-mail: martin.albrecht@ikz-berlin.de; Schewski, R.; Irmscher, K.; Galazka, Z.; Markurt, T.; Naumann, M.; Schulz, T.; Uecker, R.; Fornari, R. [Leibniz-Institut für Kristallzüchtung, Max-Born-Straße 2, 12489 Berlin (Germany); Meuret, S.; Kociak, M. [CNRS, Laboratoire de Physique des Solides, Université Paris-Sud XI, 91405 Orsay (France)

    2014-02-07

    In this paper, we show by optical and electron microscopy based investigations that vacancies in oxides may cluster and form metallic nanoparticles that induce coloration by extinction of visible light. Optical extinction in this case is caused by generation of localized surface plasmon resonances at metallic particles embedded in the dielectric matrix. Based on Mie's approach, we are able to fit the absorption due to indium nanoparticles in In{sub 2}O{sub 3} to our absorption measurements. The experimentally found particle distribution is in excellent agreement with the one obtained from fitting by Mie theory. Indium particles are formed by precipitation of oxygen vacancies. From basic thermodynamic consideration and assuming theoretically calculated activation energies for vacancy formation and migration, we find that the majority of oxygen vacancies form just below the melting point. Since they are ionized at this temperature they are Coulomb repulsive. Upon cooling, a high supersaturation of oxygen vacancies forms in the crystal that precipitates once the Fermi level crosses the transition energy level from the charged to the neutral charge state. From our considerations we find that the ionization energy of the oxygen vacancy must be higher than 200?meV.

  8. Band models and correlations for infrared radiation

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.

    1975-01-01

    Absorption of infrared radiation by various line and band models are briefly reviewed. Narrow band model relations for absorptance are used to develop 'exact' formulations for total absorption by four wide band models. Application of a wide band model to a particular gas largely depends upon the spectroscopic characteristic of the absorbing-emitting molecule. Seven continuous correlations for the absorption of a wide band model are presented and each one of these is compared with the exact (numerical) solutions of the wide band models. Comparison of these results indicate the validity of a correlation for a particular radiative transfer application. In radiative transfer analyses, use of continuous correlations for total band absorptance provides flexibilities in various mathematical operations.

  9. First-principles study of direct and narrow band gap semiconducting ?-CuGaO2

    NASA Astrophysics Data System (ADS)

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-04-01

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the ?-CuGaO2 phase. Our calculations show that the ?-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the ? point of Brillouin zone. The optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.

  10. Electron densities during winter anomalous absorption of different intensity observed at 37.1 deg N, 6.73 deg W, during winter 1975\\/76. I, II

    Microsoft Academic Search

    H. U. Widdel; G. Rose; K. Spenner; M. Friedrich; K. M. Torkar

    1979-01-01

    The paper describes in situ measurements of electron concentration in the D-region of the ionosphere obtained with various probe techniques during the Western European Winter Anomaly Campaign in 1975\\/76. Electron density profiles were measured when the amount of absorption was low, medium, or winter-anomalous at time of launch. The electron density increased at heights between 75 and 95 km when

  11. Acoustic power absorption and enhancement generated by slow and fast MHD waves. Evidence of solar cycle velocity/intensity amplitude changes consistent with the mode conversion theory

    NASA Astrophysics Data System (ADS)

    Simoniello, R.; Finsterle, W.; García, R. A.; Salabert, D.; Jiménez, A.; Elsworth, Y.; Schunker, H.

    2010-06-01

    We used long duration, high quality, unresolved (Sun-as-a star) observations collected by the ground based network BiSON and by the instruments GOLF and VIRGO on board the ESA/NASA SOHO satellite to search for solar-cycle-related changes in mode characteristics in velocity and continuum intensity for the frequency range between 2.5 mHz intensity data between 2.5 mHz intensity observations. Over the range of 4.5 mHz intensity amplitudes. At still higher frequencies, in the so called High-frequency Interference Peaks (HIPs) between 5.8 mHz intensity observations we found a rather smaller enhancement of about 5 ± 2 per cent in the same interval. There is evidence that the frequency dependence of solar-cycle velocity amplitude changes is consistent with the theory behind the mode conversion of acoustic waves in a non-vertical magnetic field, but there are some problems with the intensity data, which may be due to the height in the solar atmosphere at which the VIRGO data are taken.

  12. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

    A nonlinear aspect of the acousto-optic interaction that is analogous to multi-photon absorption is discussed. An experiment is described in which the second-order acousto-optically scattered intensity is measured and found to scale with the square of the acoustic intensity. This experiment using a commercially available acousto-optic modulator is…

  13. Negative nonlinear absorption effect in glasses containing a large amount of erbium oxide

    NASA Astrophysics Data System (ADS)

    Hashima, Hidekazu; Konishi, Akio; Wakabayashi, Hajimu; Yamada, Toshikazu; Maeda, Yoshinobu

    1999-04-01

    Compositions which vitrify by means of a conventional glass melting method, containing a large amount of erbium ion were investigated in aluminosilicate, phosphate, borate, borosilicate, telluride and fluoride systems. As a result of melting test, we obtain some glasses which contain higher than 20 mol% erbium. In transparent materials containing erbium an anomalous optical absorption phenomena have been reported by Maeda et al. With increasing in an incident laser light intensity, the transmitted one through the transparency such as the glass decreases, that is called negative nonlinear absorption (NNA) effect. With a particular modulation degree of an incident laser light, the transmitted waveform were reversed in phase to an incident one. The NNA effect in these glasses was observed over a wide band of the wavelength, while in erbium doped yttrium aluminum garnet and erbium doped lutetium aluminum garnet crystals were observed at a narrow band. The discrepancy of the NNA effect between the glasses and the crystals might be explained in the term of absorption spectrum associated with erbium. Namely, the absorption spectra of erbium doped yttrium aluminum garnet crystal have a narrow absorption band of 788 nm, while that of the glasses have broad absorption band of about 800 nm.

  14. Self-consistent band structures, charge distributions, and optical-absorption spectra in MgO,. alpha. -Al sub 2 O sub 3 , and MgAl sub 2 O sub 4

    SciTech Connect

    Xu, Y.; Ching, W.Y. (University of Missouri, Kansas City, MO (USA). Department of Physics)

    1991-02-15

    The electronic structures, the charge-density distributions, and the optical-absorption spectra in MgO, {alpha}-Al{sub 2}O{sub 3}, and MgAl{sub 2}O{sub 4} crystals are studied by means of the first-principles self-consistent orthogonalized linear combination of atomic orbitals method. The calculated band structures of MgO and {alpha}-Al{sub 2}O{sub 3} are compared with experimental data and previous calculations. It is concluded that the electronic structure and optical properties of the spinel MgAl{sub 2}O{sub 4} cannot be taken as a simple average of that of MgO and {alpha}-Al{sub 2}O{sub 3}. By direct space integration of the calculated charge, it is shown that the ionic nature of these crystals should be best described by the formulas Mg{sup 1.83+}O{sup 1.83{minus}}, Al{sub 2}{sup 2.63+}O{sub 3}{sup 1.75{minus}}, and Mg{sup 1.79+}Al{sub 2}{sup 2.63+}O{sub 4}{sup 1.76{minus}}. The charge-density maps also reveal that there are open channels of very low electron density in MgAl{sub 2}O{sub 4}, which may be important in ionic conductivity. The calculated optical dielectric functions for the three crystals are compared with recent vacuum ultraviolet data for an energy range up to 40 eV and show good overall agreement. The existence of an excitonic peak near the absorption edge tends to sharpen the edge, thereby increasing the gap as compared with the one-electron local-density calculations. For absorption spectra beyond the excitonic peak, most of the experimentally resolved structures are reproduced by the calculations without the need of an adjustment to widen the gap. It appears that the high conduction-band states in these three crystals, calculated by using the local-density approximation, are reasonably accurate.

  15. Nonlinear absorption in polydiacetylene waveguides

    Microsoft Academic Search

    William A. Pender; Adrian J. Boyle; Paul Lambkin; Werner J. Blau; Kourosh Mazaheri; Duncan J. Westland; Vladimir Skarda; Massimo Sparpaglione

    1995-01-01

    We have observed nonlinear absorption in spin-coated poly(4,6-decadiyne-1, 10-diolbis {[(n-butoxycarbonyl)methyl]urethane}) [poly(3BCMU)] polydiacetylene channel waveguides at different wavelengths in the near-infrared. Intensity dependent absorption coefficients, ?2 and ?3, have been determined by measurements of the intensity dependent transmission. The implications of nonlinear absorption for all-optical device applications in this material are discussed.

  16. Two-acceptor levels in the band gap of boron-doped diamondsemiconductors analyzed by soft x-ray absorption spectroscopy and dv-xalpha calculations

    SciTech Connect

    Muramatsu, Y.; Takebe, T.; Sawamura, A.; Iihara, J.; Nanba, A.; Imai, T., Denlinger, J.D.; Perera, R.C.C.

    2007-01-10

    To clarify the electronic structure of semiconductingboron-doped diamond, especially the two-acceptor levels observed in thesoft x-ray absorption spectra in the C K region, the density of states(DOS) of a B-doped diamond cluster model, BC146H148, were calculatedusing discrete variational (DV)-X MO methods. The results were comparedto the measured x-ray spectra. In the calculations, the localizedacceptor levels (lowest unoccupied molecular orbitals: (LUMOs)) appearedjust above the highest occupied molecular orbitals (HOMOs) of the C atomthat was directly bonded to the B atom, and the other C atoms that werebonded to the C atoms next to the B atom. However, a chemical shift ofthe LUMOs was not observed between the C atoms. On the other hand, achemical shift of the occupied C 1s orbitals was observed between these Catoms. Therefore, it is concluded that the two-acceptor levels in the Catoms result from the chemical shift of the inner C 1s orbitals due tothe local structure differences between the C atoms in B-dopeddiamond.

  17. Cosmological parameters sigma_8, the baryon density, and the UV background intensity from a calibrated measurement of H I Lyman-alpha absorption at z = 1.9

    E-print Network

    David Tytler; David Kirkman; John M. O'Meara; Nao Suzuki; Adam Orin; Dan Lubin; Pascal Paschos; Tridivesh Jena; Wen-Ching Lin; Michael L. Norman

    2004-03-31

    We identify a concordant model for the intergalactic medium (IGM) at redshift z=1.9 that uses popular values for cosmological and astrophysical parameters and accounts for all baryons with an uncertainty of 6%. We have measured the amount of absorption, DA, in the Ly-alpha forest at redshift 1.9 in spectra of 77 QSO from the Kast spectrograph. We calibrated the continuum fits with realistic artificial spectra, and we found that averaged over all 77 QSOs the mean continuum level is within 1-2% of the correct value. Absorption from all lines in the Ly-alpha forest at z=1.9 removes DA=15.1 +/- 0.7% of the flux between 1070 and 1170 (rest) Angstroms. This is the first measurement using many QSOs at this z, and the first calibrated measurement at any redshift. Metal lines absorb 2.3 +/- 0.5%, and LLS absorb 1.0 +/- 0.4% leaving 11.8 +/- 1.0% from the lower density bulk of the IGM. Averaging over Delta z=0.1 or 154 Mpc, the dispersion is 6.1 +/- 0.3% including LLS and metal lines, or 3.9 (+0.5, -0.7)% for the lower density IGM alone, consistent with the usual description of large scale structure. LLS and metal lines are major contributors to the variation in the mean flux, and they make the flux field significantly non-Gaussian. We find that a hydrodynamic simulation on a 1024 cubed grid in a 75.7 Mpc box reproduces the observed DA from the low density IGM with parameters values H_o=71 km/s/Mpc, Omega_Lambda=0.73, Omega_m=0.27, Omega_b=0.044, sigma_8=0.9 and a UV background that has an ionization rate that is 1.08 +/- 0.08 times the prediction by Madau, Haardt & Rees (1999).

  18. Neuron absorption study and mid-IR optical excitations

    NASA Astrophysics Data System (ADS)

    Guo, Dingkai; Chen, Xing; Vadala, Shilpa; Leach, Jennie; Kostov, Yordan; Bewley, William W.; Kim, Chul-Soo; Kim, Mijin; Canedy, Chadwick L.; Merritt, Charles D.; Vurgaftman, Igor; Meyer, Jerry R.; Choa, Fow-Sen

    2012-02-01

    Neuronal optical excitation can provide non-contacting tools to explore brain circuitry and a durable stimulation interface for cardiac pacing and visual as well as auditory sensory neuronal stimulation. To obtain accurate absorption spectra, we scan the transmission of neurons in cell culture medium, and normalize it by subtracting out the absorption spectrum of the medium alone. The resulting spectra show that the main neuronal absorption peaks are in the 3000- 6000nm band, although there is a smaller peak near 1450nm. By coupling the output of a 3?m interband cascade laser (ICL) into a mid-IR fluorozirconate fiber, we can effectively deliver more than 1J/cm2 photon intensity to the excitation site for neuronal stimulation.

  19. Determination of interstitial oxygen concentration in germanium by infrared absorption

    SciTech Connect

    Litvinov, V. V.; Svensson, B. G.; Murin, L. I.; Lindstroem, J. L.; Markevich, V. P.; Peaker, A. R. [Physics Faculty, Belarussian State University, F. Scorina Avenue 4, 220050 Minsk (Belarus); Department of Physics and Center for Materials Science and Nanotechnology, University of Oslo, N0371 Oslo (Norway); Joint Institute of Solid State and Semiconductor Physics, 220072 Minsk (Belarus); Division of Solid State Physics, Lund University, S-22100 Lund (Sweden); Centre for Electronic Materials, Devices and Nanostructures, School of Electrical and Electronic Engineering, University of Manchester, Manchester M60 1QD (United Kingdom)

    2006-08-01

    The intensities of infrared absorption due to the asymmetric stretching vibrations of interstitial oxygen atoms in Ge crystals enriched with {sup 16}O and {sup 18}O isotopes have been compared with oxygen concentrations determined by means of secondary ion mass spectrometry. For Ge samples with oxygen content less than 5x10{sup 17} cm{sup -3}, a good correlation has been found between the values of oxygen concentration and the values of the absorption coefficient at the maximum of the {sup 16}O{sub i} related absorption band at 855.6 cm{sup -1} with a proportionality coefficient C{sub O}=1.05x10{sup 17} cm{sup -2}.

  20. High Resolution Infrared Studies of the v2, v4 Bands of 34S16O3, Including Both Intensity and Wavenumber Perturbations

    SciTech Connect

    Barber, Jeffrey B.; Masiello, Tony; Chrysostom, Engelene; Nibler, Joseph W.; Maki, Arthur; Weber, Alfons; Blake, Thomas A.; Sams, Robert L.

    2003-06-15

    The infrared spectrum of the v2, v4 bending mode region of 34S-substituted sulfur trioxide, 34S16O3, has been recorded at a resolution of 0.0025 cm-1. The v2 and v4 levels are coupled by a Coriolis interaction, yielding significant spectral shifts that have been successfully analyzed to obtain rovibrational constants for the ground state and both fundamentals. Comparisons are made with 32S16O3 parameters and the Bo rotational constant is found to be 0.348 556 04(28) cm-1, only very slightly larger than the corresponding value of 0.348 543 33(5) cm-1 for 32S16O3. Coriolis and l-type resonance interactions between the v2 and v4 levels produce frequency shifts and strong intensity perturbations in the spectra that are considered for both 34S16O3 and 32S16O3. The resulting analysis yields an average value of+0.62(8) for the dipole derivative ratio (?x/?Q4x) (?z/?Q2) and a positive sign for the product of this ratio with the?y2,4 Coriolis constant, for which experiment gives+0.5940(15) . Ab initio calculations indicate that the signs of?x/?Q4x and?z/?Q2 are both positive and hence?y2,4 is also positive, in agreement with earlier calculations. These signs indicate that the effective charge movement in the xz plane has the same sense of rotation as Q2, Q4x atom motion in this plane that produces a py vibrational angular momentum component, correlated motion that is confirmed by ab initio calculations.

  1. Photodissociation of carbon dioxide in singlet valence electronic states. II. Five state absorption spectrum and vibronic assignment

    E-print Network

    Grebenshchikov, Sergy Yu

    2013-01-01

    The absorption spectrum of CO$_2$ in the wavelength range 120\\,nm --- 160\\,nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled PESs of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T=190\\,K via Boltzmann averaging of optical transitions from many initial rotational states, accurtely reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that...

  2. Absorption spectroscopic study of EDA complexes of [70] fullerene with a series of methyl benzenes

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sumanta; Nayak, Sandip K.; Chattopadhyay, Subrata K.; Banerjee, Manas; Mukherjee, Asok K.

    2001-02-01

    [70]Fullerene has been shown to form 1:1 molecular complexes with toluene, p-xylene, m-xylene, 1,2,4,5-tetramethyl benzene (durene) and pentamethyl benzene (PMB) in CCl 4 medium by absorption spectroscopic method. Isosbestic points have been detected in case of complexes with PMB and durene. Charge transfer absorption band could not be detected but the intensity of the broad absorption band of C 70 in CCl 4 decreases systematically with increase in the concentration of the added methylbenzenes. From this trend the formation constants ( Kc) of the complexes have been determined at three different wavelengths. The constancy of Kc with respect to change in the wavelength of measurement supports the view that complex of a single stoichiometry (1:1) is formed in each case.

  3. A reward band study of mallards to estimate band reporting rates

    USGS Publications Warehouse

    Henny, C.J.; Burnham, K.P.

    1976-01-01

    Reward bands ($10) were placed on 2,122 hatching-year mallards (Anas platyrhynchos), and an additional 11,490 received conventional bands (controls) to estimate band reporting rates. An analysis of band recoveries indicated that the reporting rate was dependent primarily upon three factors: (1) the distance banded birds were recovered from the banding site, (2) band collecting activities of conservation agencies (usually near banding sites), and ( 3) the intensity of banding effort in the region (frequency of banded birds in the population of the region). Reporting rates were uniformly depressed near the banding sites, but they showed an east-west cline at distances greater than 80 km from the banding sites. The reporting rate was highest in the west. Limited data on historical band reporting rates were compiled. Recommendations are given for adjusting band recoveries to account for the nonreporting of bands for 1957-73.

  4. Infrared band strengths: Laboratory techniques and applications to astronomical observations

    NASA Astrophysics Data System (ADS)

    Gerakines, P. A.

    2002-09-01

    Whenever an abundance measurement is derived by way of infrared spectroscopy, it will typically make use of a laboratory-obtained conversion factor between the size of an IR absorption feature and the (column) density of the molecule under study. This factor is usually called the "absolute absorption intensity" by a chemist or the "band strength" by a typical IR astronomer. Band strengths have been studied in chemistry since the 1950s, and the commonly quoted "accuracy to with a factor of ten" historically required of astronomical calculations has not required much new input into this area. Today, however, astronomical measurements require much higher precision, and it is time for IR astronomers to ask more of laboratory measurements and to understand when and why to use IR band strengths in a more appropriate manner. The history, interpretation, measurement, and common astrophysical applications of infrared band strengths will be discussed. The "secrets" of the laboratory techniques involved in their measurement are described, and a compilation of results from the literature is given along with some new results. Typical astrophysical applications and appropriate uses will also be discussed. Common misconceptions are confronted and two challenges are presented: (i) to the laboratory astrophysics community to produce and advertise accurate values with caveats when necessary, and (ii) to the observational community to use the most appropriate results for the environment under study.

  5. Absorption spectroscopy using quantum cascade laser

    Microsoft Academic Search

    Simin Cai

    1999-01-01

    Characteristic molecular and atomic absorption spectra in the middle infrared region are extensively used for chemical analysis and spectroscopic detection of gases. The absorption of electromagnetic radiation in this so- called ``fingerprint'' spectral region is due to the vibration-rotational bands of molecular structures. Various techniques have been developed for high resolution and high sensitivity absorption spectroscopic detection. In this dissertation,

  6. Electron paramagnetic resonance and low-field microwave absorption in the manganese-gallium oxide

    NASA Astrophysics Data System (ADS)

    Montiel, H.; Alvarez, G.; Conde-Gallardo, A.; Zamorano, R.

    2015-07-01

    Microwave absorption measurements in MnGa2O4 powders are carried out at X-band (8.8-9.8 GHz) in 92-296 K temperature range. For all temperatures, the electron paramagnetic resonance (EPR) spectra show a single broad line due to Mn2+ ions. Temperature dependence of the EPR parameters: the peak-to-peak linewidth (?Hpp), the integrated intensity (IEPR) and the g-factor, suggests the presence of magnetic fluctuations that precede to antiferromagnetic ordering at low temperature. Additionally, the low-field microwave absorption (LFMA) is used to give further information on this material, giving also evidence of these magnetic fluctuations.

  7. Absorption spectroscopy of surfactant-dispersed carbon nanotube film: Modulation of electronic structures

    NASA Astrophysics Data System (ADS)

    Geng, Hong-Zhang; Lee, Dae Sik; Kim, Ki Kang; Han, Gang Hee; Park, Hyeon Ki; Lee, Young Hee

    2008-04-01

    The effect of surfactant in dispersing single-walled carbon nanotubes (SWCNTs) to form conducting films were examined using UV-vis-NIR absorption spectroscopy. The distinctive sub-band transition peaks of sodium dodecyl sulfate (SDS)-dispersed SWCNTs in water were severely suppressed in the film due to the presence of residual SDS interacting strongly with SWCNTs. The recovery of electronic structures of SWCNTs could be monitored systematically using a simple acid treatment through the peak intensities and peak positions of the corresponding transition energies of absorption spectrum. The changes in electrical and optical conductivity of SWCNT film before and after acid treatment were discussed.

  8. Bird Banding

    USGS Multimedia Gallery

    Bird Banding - Elizabeth Sellers points out identification characteristics in the plumage of a male common yellowthroat to John P. Mosesso during a capture-recapture study at a Monitoring Avian Productivity and Survivorship (MAPS) program bird banding station....

  9. Resolving the forbidden band of SF6.

    PubMed

    Boudon, V; Manceron, L; Kwabia Tchana, F; Loëte, M; Lago, L; Roy, P

    2014-01-28

    Sulfur hexafluoride is an important molecule for modeling thermophysical and polarizability properties. It is also a potent greenhouse gas of anthropogenic origin, whose concentration in the atmosphere, although very low is increasing rapidly; its global warming power is mostly conferred by its strong infrared absorption in the ?3 S-F stretching region near 948 cm(-1). This heavy species, however, features many hot bands at room temperature (at which only 31% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6 = 1 vibrational state. Unfortunately, the ?6 band itself (near 347 cm(-1)), in the first approximation, is both infrared- and Raman-inactive, and no reliable spectroscopic information could be obtained up to now and this has precluded a correct modeling of the hot bands. It has been suggested theoretically and experimentally that this band might be slightly activated through Coriolis interaction with infrared-active fundamentals and appears in high pressure measurements as a very faint, unresolved band. Using a new cryogenic multipass cell with 93 m optical path length and regulated at 163 ± 2 K temperature, coupled to synchrotron radiation and a high resolution interferometer, the spectrum of the ?6 far-infrared region has been recorded. Low temperature was used to avoid the presence of hot bands. We are thus able to confirm that the small feature in this region, previously viewed at low-resolution, is indeed ?6. The fully resolved spectrum has been analyzed, thanks to the XTDS software package. The band appears to be activated by faint Coriolis interactions with the strong ?3 and ?4 fundamental bands, resulting in the appearance of a small first-order dipole moment term, inducing unusual selection rules. The band center (?6 = 347.736707(35) cm(-1)) and rovibrational parameters are now accurately determined for the v6 = 1 level. The ?6 perturbation-induced dipole moment is estimated to be 33 ± 3 ?D and the ?6 integrated intensity to be 0.0035 km mol(-1). PMID:24297100

  10. Method and apparatus for aerosol-particle absorption spectroscopy. [DOE patent application

    SciTech Connect

    Campillo, A.J.; Lin, H.B.

    1981-06-25

    A method and apparatus are described for determining the absorption spectra, and other properties, of aerosol particles. A heating beam source provides a beam of electromagnetic energy which is scanned through the region of the spectrum which is of interest. Particles exposed to the heating beam which have absorption bands within the band width of the heating beam absorb energy from the beam. The particles are also illuminated by light of a wave length such that the light is scattered by the particles. The absorption spectra of the particles can thus be determined from an analysis of the scattered light since the absorption of energy by the particles will affect the way the light is scattered. Preferably the heating beam is modulated to simplify the analysis of the scattered light. In one embodiment the heating beam is intensity modulated so that the scattered light will also be intensity modulated when the particles absorb energy. In another embodiment the heating beam passes through an interferometer and the scattered light reflects the Fourier Transform of the absorption spectra.

  11. Optical absorption and fluorescence properties of Dy3+: SFB glasses

    Microsoft Academic Search

    D. Uma Maheswari; J. Suresh Kumar; T. Sasikala; A. Mohan Babu; K. Pavani; Kiwan Jang; L. Rama Moorthy

    2009-01-01

    This paper presents the preparation and spectroscopic characterization of Dy3+-doped sodium fluoroborate (SFB) glasses of the type (50-x) B2O3 + 25 Na2O + 10 CaF2 + 10 AlF3 + 5 LaF3 + x DyF3 (x = 0.01, 0.1, 0.5,1.0, 2.0 and 4.0 mol%). By measuring the area under absorption bands, the experimental oscillator strengths are determined. The Judd-Ofelt (J-O) intensity

  12. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    SciTech Connect

    Brauer, Carolyn S.; Blake, Thomas A.; Guenther, Alex B.; Sharpe, Steven W.; Sams, Robert L.; Johnson, Timothy J.

    2014-11-19

    The OH- and O3- initiated oxidations of isoprene, which is one of the primary volatile organic compounds produced by vegetation, are a major source of atmospheric formaldehyde and other oxygenated organics, yet little quantitative IR data exists for isoprene. We thus report absorption coefficients and integrated band intensities for isoprene in the 600 - 6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298 and 323 K in a 19.96 cm path length cell at 0.112 cm-1 resolution, using a Bruker 66V FTIR. Composite spectra are derived from a minimum of seven pressures at each temperature.

  13. Fluid absorption in endoscopic surgery

    Microsoft Academic Search

    R. G. Hahn

    2005-01-01

    Fluid absorption is an unpredictable complication of endoscopic surgery. Absorption of small amounts of fluid (1-2 litre) occurs in 5-10% of patients undergoing transurethral prostatic resection and results in an easily overlooked mild transurethral resection (TUR) syndrome. Large-scale fluid absorption is rare but leads to symptoms severe enough to require intensive care. Pathophysiological mechanisms consist of pharmacological effects of the

  14. Light absorption efficiencies of photosynthetic pigments: the dependence on spectral types of central stars

    NASA Astrophysics Data System (ADS)

    Komatsu, Yu; Umemura, Masayuki; Shoji, Mitsuo; Kayanuma, Megumi; Yabana, Kazuhiro; Shiraishi, Kenji

    2015-07-01

    For detecting life from reflection spectra on extrasolar planets, trace of photosynthesis is one of the indicators. However, it is not yet clear what kind of radiation environments is acceptable for photosynthesis. Light absorption in photosystems on the Earth occurs using limited photosynthetic pigments such as chlorophylls (Chls) and bacteriochlorophylls (BChls). Efficiencies of light absorption for the pigments were evaluated by calculating the specific molecular absorption spectra at the high accuracy-quantum mechanical level. We used realistic stellar radiation spectra such as F, G, K and M-type stars to investigate the efficiencies. We found that the efficiencies are increased with the temperature of stars, from M to F star. Photosynthetic pigments have two types of absorption bands, the Q y and Soret. In higher temperature stars like F star, contributions from the Soret region of the pigments are dominant for the efficiency. On the other hand, in lower temperature stars like M stars, the Q y band is crucial. Therefore, differences on the absorption intensity and the wavelength between the Q y and Soret band are the most important to characterize the photosynthetic pigments. Among photosynthetic pigments, Chls tend to be efficient in higher temperature stars, while BChls are efficient for M stars. Blueward of the 4000 Å break, the efficiencies of BChls are smaller than Chls in the higher temperature stars.

  15. Banded matrices with banded inverses

    E-print Network

    Srinivasa Gopala Raghavan, Venugopalan

    2010-01-01

    We discuss the conditions that are necessary for a given banded matrix to have a banded inverse. Although a generic requirement is known from previous studies, we tend to focus on the ranks of the block matrices that are ...

  16. Band energies of nanoparticle semiconductor electrodes determined by spectroelectrochemical measurements of free electrons.

    PubMed

    Mandal, Dhritabrata; Hamann, Thomas W

    2015-05-01

    Nanostructured semiconductor electrodes have garnered intense recent interest for use in various solar energy conversion systems since they offer the possibilities of circumventing low efficiencies associated with short diffusion length bulk materials as well as optimizing light absorption in dye-sensitized solar cells. In such context, knowledge of the conduction (ECB) and valence band (EVB) edge positions are the most important electronic properties in order to optimize performance and obtain a detailed understanding of relevant electron-transfer processes. However, there is no reliable direct method to measure the band edges in nanostructured semiconductor electrodes. Spectroeletrochemical methods have been utilized, but the nature of the absorbing species and interpretation of results are unsettled issues. Herein we describe a new simple spectroelectrochemical method which simultaneously produces the conduction band energy and the extinction coefficient, ?, of free conduction band electrons in nanoparticle TiO2 electrodes. PMID:25864683

  17. Effect of temperature on electron spectra in the region of the intrinsic-absorption edge of CdGa{sub 2}Se{sub 4}

    SciTech Connect

    Kerimova, T. G., E-mail: ktaira@physics.ab.az; Guliyev, R. A. [Academy of Sciences of Azerbajan, Institute of Physics (Azerbaijan)

    2011-03-15

    The results of investigation of the temperature dependence of CdGa{sub 2}Se{sub 4} absorption coefficient in the polarized radiation at 5-300 K and that of the emission intensity at 4.2-77 K are presented. The changes observed for the polarization dependence of absorption coefficient and the radiation intensity with decreasing temperature are attributed to a different velocity of motion of states of the valence-band top {Gamma}{sub 3} + {Gamma}{sub 4} and {Gamma}{sub 2} with changing tetragonal compression.

  18. Monochromatic calculations of atmospheric radiative transfer due to molecular line absorption

    NASA Technical Reports Server (NTRS)

    Chou, M.-D.; Kouvaris, L.

    1986-01-01

    Sensitivity studies related to the effects of line cutoff, spectral resolution, and temperature and pressure interpolations in radiative transfer have been performed so that a data set of absorption coefficients for water vapor, CO2, and O3 may be created efficiently. Results show that computations of absorption coefficients are affected only slightly by cutting a line off at a wave number 190 times the Lorentz half width from the center, or equivalently, cutting off 0.33 percent of the line intensity from the wings. To achieve a relative cooling rate error smaller than 2 percent, it is sufficient to precompute the absorption coefficient at three temperatures (210, 250, and 290 K) and 19 pressures with Delta (log 10 p) = 0.2. The absorption coefficient at other conditions can be interpolated linearly with pressure and exponentially with a quadratic in temperature. For the spectral resolution the absorption coefficients can be adequately computed at 0.01, 0.002, 0.005, and 0.025/cm intervals in the thermal water vapor, the CO2 and O3 bands, and the solar water vapor bands, respectively, which limits the error to only a few percent in the cooling and heating rates. Using the precomputed absorption coefficients, repeated monochromatic calculations of atmospheric heating/cooling rates for radiation model developments and for comparison with less detailed calculations are no longer difficult.

  19. Silicate absorption in heavily obscured galaxy nuclei

    E-print Network

    P. F. Roche; C. Packham; D. K. Aitken; R. E. Mason

    2006-10-19

    Spectroscopy at 8-13 microns with T-ReCS on Gemini-S is presented for 3 galaxies with substantial silicate absorption features, NGC 3094, NGC 7172 and NGC 5506. In the galaxies with the deepest absorption bands, the silicate profile towards the nuclei is well represented by the emissivity function derived from the circumstellar emission from the red supergiant, mu Cephei which is also representative of the mid-infrared absorption in the diffuse interstellar medium in the Galaxy. There is spectral structure near 11.2 microns in NGC 3094 which may be due to a component of crystalline silicates. In NGC 5506, the depth of the silicate absorption increases from north to south across the nucleus, suggestive of a dusty structure on scales of 10s of parsecs. We discuss the profile of the silicate absorption band towards galaxy nuclei and the relationship between the 9.7 micron silicate and 3.4 micron hydrocarbon absorption bands.

  20. Thermodynamic derivatives of infrared absorptance

    NASA Technical Reports Server (NTRS)

    Broersma, S.; Walls, W. L.

    1974-01-01

    Calculation of the concentration, pressure, and temperature dependence of the spectral absorptance of a vibrational absorption band. A smooth thermodynamic dependence was found for wavelength intervals where the average absorptance is less than 0.65. Individual rotational lines, whose parameters are often well known, were used as bases in the calculation of medium resolution spectra. Two modes of calculation were combined: well-separated rotational lines plus interaction terms, or strongly overlapping lines that were represented by a compound line of similar shape plus corrections. The 1.9- and 6.3-micron bands of H2O and the 4.3-micron band of CO2 were examined in detail and compared with experiment.

  1. Optical and infrared absorption spectra of 3d transition metal ions-doped sodium borophosphate glasses and effect of gamma irradiation.

    PubMed

    Abdelghany, A M; ElBatal, F H; Azooz, M A; Ouis, M A; ElBatal, H A

    2012-12-01

    Undoped and transition metals (3d TM) doped sodium borophosphate glasses were prepared. UV-visible absorption spectra were measured in the region 200-900nm before and after gamma irradiation. Experimental optical data indicate that the undoped sodium borophosphate glass reveals before irradiation strong and broad UV absorption and no visible bands could be identified. Such UV absorption is related to the presence of unavoidable trace iron impurities within the raw materials used for preparation of this base borophosphate glass. The TMs-doped glasses show absorption bands within the UV and/or visible regions which are characteristic to each respective TM ion in addition to the UV absorption observed from the host base glass. Infrared absorption spectra of the undoped and TMs-doped glasses reveal complex FTIR consisting of extended characteristic vibrational bands which are specific for phosphate groups as a main constituent but with the sharing of some vibrations due to the borate groups. This criterion was investigated and approved using DAT (deconvolution analysis technique). The effects of different TMs ions on the FTIR spectra are very limited due to the low doping level (0.2%) introduced in the glass composition. Gamma irradiation causes minor effect on the FTIR spectra specifically the decrease of intensities of some bands. Such behavior is related to the change of bond angles and/or bond lengths of some structural building units upon gamma irradiation. PMID:22995547

  2. Optical and infrared absorption spectra of 3d transition metal ions-doped sodium borophosphate glasses and effect of gamma irradiation

    NASA Astrophysics Data System (ADS)

    Abdelghany, A. M.; ElBatal, F. H.; Azooz, M. A.; Ouis, M. A.; ElBatal, H. A.

    2012-12-01

    Undoped and transition metals (3d TM) doped sodium borophosphate glasses were prepared. UV-visible absorption spectra were measured in the region 200-900 nm before and after gamma irradiation. Experimental optical data indicate that the undoped sodium borophosphate glass reveals before irradiation strong and broad UV absorption and no visible bands could be identified. Such UV absorption is related to the presence of unavoidable trace iron impurities within the raw materials used for preparation of this base borophosphate glass. The TMs-doped glasses show absorption bands within the UV and/or visible regions which are characteristic to each respective TM ion in addition to the UV absorption observed from the host base glass. Infrared absorption spectra of the undoped and TMs-doped glasses reveal complex FTIR consisting of extended characteristic vibrational bands which are specific for phosphate groups as a main constituent but with the sharing of some vibrations due to the borate groups. This criterion was investigated and approved using DAT (deconvolution analysis technique). The effects of different TMs ions on the FTIR spectra are very limited due to the low doping level (0.2%) introduced in the glass composition. Gamma irradiation causes minor effect on the FTIR spectra specifically the decrease of intensities of some bands. Such behavior is related to the change of bond angles and/or bond lengths of some structural building units upon gamma irradiation.

  3. Multiplasmon Absorption in Graphene

    NASA Astrophysics Data System (ADS)

    Jablan, Marinko; Chang, Darrick E.

    2015-06-01

    We show that graphene possesses a strong nonlinear optical response in the form of multiplasmon absorption, with exciting implications in classical and quantum nonlinear optics. Specifically, we predict that graphene nanoribbons can be used as saturable absorbers with low saturation intensity in the far-infrared and terahertz spectrum. Moreover, we predict that two-plasmon absorption and extreme localization of plasmon fields in graphene nanodisks can lead to a plasmon blockade effect, in which a single quantized plasmon strongly suppresses the possibility of exciting a second plasmon.

  4. Ultra-violet Absorption of Sea Water

    Microsoft Academic Search

    F. A. J. ARMSTRONG; G. T. BOALCH

    1961-01-01

    The intensity of submarine daylight is of such importance to the growth of marine plants that much attention has been given to measurements of the absorption of solar radiation by sea water. It has long been known that absorption is least in the blue green in the visible spectrum, and Tsukamoto (1927) showed that the absorption of ultra-violet radiation increased

  5. Q BAND CHROMOSOMAL POLYMORPHISMS IN LAKE TROUT (SALVELINUS NAMAYCUSH)

    Microsoft Academic Search

    RUTH B. PHILLIPS; KERRY D. ZAJICEK

    Q banding of chromosome preparations from lake trout revealed the presence of heteromorphic quinacrine bright bands on several chromosomes. All of the metacentric chromosome pairs can be distinguished on the basis of number, position and intensity of the quinacrine bright bands and chromosome size. These bands appear to represent heterochromatin, since they are darkly staining with the C band technique.

  6. Excited states and absorption spectra of 2-?-diketonato-1,3,2-benzodioxaborol with aromatic substituents: Quantum-chemistry modeling.

    PubMed

    Kazachek, M V; Svistunova, I V

    2015-09-01

    The nature of excited states of 2-?-diketonato-1,3,2-benzodioxaborol compounds with aromatic substituent have been studied by the quantum-chemical method in the approximation of the time-dependent electron density functional theory. We have measured the absorption spectra of these compounds in acetonitrile solution and compared them with the model spectra constructed on the basis of calculations. The calculations give two long-wavelength transitions with small oscillator strengths, caused by ?-? transitions with the charge transfer from the benzodioxo-group to the chelate fragment. Observed long-wavelength shoulders of the spectra bands correlate with the mentioned transitions. Typical high intensity bands for ?-? transitions in the ultra-violet range are caused by transitions of ?-electrons in the fragments. Increasing extension of ?-system gives the batochromic shift of these absorption bands and the growth of the probabilities of the transition. PMID:25863460

  7. Assignment of the Q-Bands of the Chlorophylls: Coherence Loss via Qx ? Qy Mixing

    PubMed Central

    Reimers, Jeffrey R.; Cai, Zheng-Li; Kobayashi, Rika; Rätsep, Margus; Freiberg, Arvi; Krausz, Elmars

    2013-01-01

    We provide a new and definitive spectral assignment for the absorption, emission, high-resolution fluorescence excitation, linear dichroism, and/or magnetic circular dichroism spectra of 32 chlorophyllides in various environments. This encompases all data used to justify previous assignments and provides a simple interpretation of unexplained complex decoherence phenomena associated with Qx ? Qy relaxation. Whilst most chlorophylls conform to the Gouterman model and display two independent transitions Qx (S2) and Qy (S1), strong vibronic coupling inseparably mixes these states in chlorophyll-a. This spreads x-polarized absorption intensity over the entire Q-band system to influence all exciton-transport, relaxation and coherence properties of chlorophyll-based photosystems. The fraction of the total absorption intensity attributed to Qx ranges between 7% and 33%, depending on chlorophyllide and coordination, and is between 10% and 25% for chlorophyll-a. CAM-B3LYP density-functional-theory calculations of the band origins, relative intensities, vibrational Huang-Rhys factors, and vibronic coupling strengths fully support this new assignment. PMID:24067303

  8. UV-visible luminescence properties of the broad-band Yb:CALGO laser crystal

    NASA Astrophysics Data System (ADS)

    Jaffres, A.; Sharma, S. K.; Loiseau, P.; Viana, B.; Doualan, J. L.; Moncorgé, R.

    2015-03-01

    Yb:CALGO is now recognized to exhibit outstanding properties for the production of high-power and ultra-short laser pulses in the near infrared spectral range. However, various UV-visible absorption bands can be also observed due to different types of charge transfer mechanisms. Some of them are assigned to the formation of color centers due to small polarons and others to O2-?Yb3+ ligand-to-metal charge transfer (LMCT) transitions. The former can be removed by using adequate thermal treatments. The latter are intrinsic and they are very intense with cross sections of about two orders of magnitude larger that the near infrared ones. In fact, such LMCT absorption bands are responsible for relatively large changes of ionic polarizabilities and to non-negligible pseudo-nonlinear changes of refractive indices which should certainly affect the laser properties of Yb:CALGO at high pump power levels.

  9. Fabrication of sol gel 70GeO2 30SiO2 thick films from TEOG and DEOS and investigation of the 5 eV band

    NASA Astrophysics Data System (ADS)

    Jing, Chengbin; Hou, Jinxia; Zhang, Yongheng

    2006-03-01

    Crack-free germanosilicate films, 3.6 µm-thick and containing up to 70 mol% germanium dioxide, which are inaccessible through the conventional sol-gel process, were fabricated using tetraethyl orthogermanate (TEOG) and diethylorthosilicate (DEOS) as precursors for germania and silica, respectively. The studies using viscosity, TEM and SEM revealed that DEOS contributed largely to stabilizing the GeO2-SiO2 sol and suppressing crack formation in thick films. XRD study showed that the films remained amorphous after being sintered at 600 °C in air for 60 min and annealed at 550 °C under a flowing H2/N2 atmosphere for 120 min. An intense absorption band at around 241 nm was distinctly observed in the films. The intensity of this absorption band was found to be effectively bleached by UV illumination. Weak photoluminescence emission bands which originated from the neutral oxygen di-vacancy were detected near 375 and 275 nm. Therefore, the 5 eV absorption band observed in this work was mainly caused by the neutral oxygen monovacancy. A saturated absorptivity change of the UV-bleachable band after prolonged illumination was found to be 389 cm-1 for 70GeO2-30SiO2 films.

  10. Simultaneous Effects of External Electric Field and Conduction Band Nonparabolicity on Optical Properties of a GaAs Quantum Dot Embedded at the Center of a GaAlAs Nano-Wire

    NASA Astrophysics Data System (ADS)

    Gh., Safarpour; M. A., Izadi; Novzari, M.; Niknam, E.; M. M., Golshan

    2014-06-01

    An investigation of the optical properties of a GaAs spherical quantum dot which is located at the center of a Ga1-xAlxAs cylindrical nano-wire has been performed in the presence of an external electric held. The band nonparabolicity effect is also considered using the energy dependent effective mass approximation. The energy eigenvalues and corresponding wave functions are calculated by finite difference approximation and the reliability of calculated wave functions is checked by computing orthogonality. Using computed energy eigenvalues and wave functions, the linear, third-order nonlinear and total optical absorption coefficients and refractive index changes are examined in detail. It is found that (i) Presence of electric field causes both blue and red shifts in absorption spectrum; (ii) The absorption coefficients shift toward lower energies by taking into account the conduction band nonparabolicity; (iii) For large values of electric field the effect of conduction band nonparabolicity is less dominant and parabolic band is estimated correctly; (iv) In the presence of electric field and conduction band nonparabolicity the nonlinear term of absorption coefficient rapidly increases by increasing incident optical intensity. In other words, the saturation in optical spectrum occurs at lower incident optical intensities.

  11. Two-step photon absorption in InAs/GaAs quantum-dot superlattice solar cells

    NASA Astrophysics Data System (ADS)

    Kada, T.; Asahi, S.; Kaizu, T.; Harada, Y.; Kita, T.; Tamaki, R.; Okada, Y.; Miyano, K.

    2015-05-01

    We studied the two-step photon absorption (TSPA) process in InAs/GaAs quantum-dot superlattice (QDSL) solar cells. TSPA of subband-gap photons efficiently occurs when electrons are pumped from the valence band to the states above the inhomogeneously distributed fundamental states of QDSLs. The photoluminescence (PL)-excitation spectrum demonstrates an absorption edge attributed to the higher excited states of the QDSLs in between the InAs wetting layer states and the fundamental states of QDSLs. When the absorption edge of the excited state was resonantly excited, the superlinear excitation power dependence of the PL intensity demonstrated that the electron and hole created by the interband transition separately relax into QDSLs. Furthermore, time-resolved PL measurements demonstrated that the electron lifetime is extended by thereby inhibiting recombination with holes, enhancing the second subband-gap absorption.

  12. Complementary cavity-enhanced spectrometers to investigate the OH + CH combination band in trans-formic acid.

    PubMed

    Golebiowski, D; Földes, T; Vanfleteren, T; Herman, M; Perrin, A

    2015-07-01

    We have used continuous-wave cavity ring-down and femto-Fourier transform-cavity-enhanced absorption spectrometers to record the spectrum of the OH-stretching + CH-stretching (?1 + ?2) combination band in trans-formic acid, with origin close to 6507 cm(-1). They, respectively, allowed resolving and simplifying the rotational structure of the band near its origin under jet-cooled conditions (Trot = 10 K) and highlighting the overview of the band under room temperature conditions. The stronger B-type and weaker A-type subbands close to the band origin could be assigned, as well as the main B-type Q branches. The high-resolution analysis was hindered by numerous, severe perturbations. Rotational constants are reported with, however, limited physical meaning. The ?1 + ?2 transition moment is estimated from relative intensities to be 24° away from the principal b-axis of inertia. PMID:26156476

  13. Theoretical study of the AlO blue-green (B2Sigma + - X2Sigma +) band system

    NASA Technical Reports Server (NTRS)

    Partridge, H.; Langhoff, S. R.; Lengsfield, B. H., III; Liu, B.

    1983-01-01

    Two independent, extensive theoretical calculations are reported for the relative band strengths of the AlO (B2Sigma + - X2Sigma +) blue-green system and for the radiative lifetimes of the lowest few vibrational levels of the B2Sigma(+) state. The theoretical lifetimes, which include a small (less than -.5 percent) contribution from bound-bound transitions into the A2Pi state, are in excellent agreement with laser fluorescence studies. The theoretical lifetimes increase monotonically and very slowly with increasing vibrational quantum number. The relative band strengths for the blue-green system derived from the two theoretical calculations are in excellent agreement, but differ systematically from the relative band strengths of Linton and Nicholls (1969). The present results suggest that their self-absorption corrections are not large enough, resulting in relative intensities that are too large, especially for the weak bands with r centroids less than 1.5 A.

  14. Phase shift cavity ring down and Fourier transform infrared measurements of C-H vibrational transitions, energy levels, and intensities of (CH3)3Si-C?C-H

    NASA Astrophysics Data System (ADS)

    Barroso, Jenny Z.; Perez-Delgado, Yasnahir; Manzanares, Carlos E.

    2013-07-01

    Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (?? = 1-5) and methyl (?? = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi?CH] at 295 K. Harmonic frequencies ?(?1), ?a, and ?s and anharmonicities x(?1), ?axa, ?sxs were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. A hot band, assigned as ??1 + ?24 - ?24 is observed for transitions with ?? = 1-5 in a region near the acetylenic stretch. The intensity of the hot band is reduced considerably at 240 K. The strength of a Fermi resonance between C-Ha transition (??a) and the combination band ((?-1)?a + 2?bend) with (? = 3-6) was calculated using the experimental perturbed energies and relative intensities. The main bands are separated by computer deconvolution and are integrated at each level to get the experimental band strengths. For methyl absorptions, the dipole moment function is expanded as a function of two C-H stretching coordinates and the intensities are calculated in terms of the HCAO model where only the C-H modes are considered. Acetylenic intensities are derived with a one dimensional dipole moment function. The expansion coefficients are obtained from molecular orbital calculations. The intensities are calculated without using adjustable parameters and they are of the same order of magnitude of the experimental intensities for all C-H transitions.

  15. Phase shift cavity ring down and Fourier transform infrared measurements of C-H vibrational transitions, energy levels, and intensities of (CH3)3Si-C?C-H.

    PubMed

    Barroso, Jenny Z; Perez-Delgado, Yasnahir; Manzanares, Carlos E

    2013-07-01

    Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (?? = 1-5) and methyl (?? = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi?CH] at 295 K. Harmonic frequencies ?(?1), ?(a), and ?(s) and anharmonicities x(?1), ?(a)x(a), ?(s)x(s) were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. A hot band, assigned as ??1 + ?24 - ?24 is observed for transitions with ?? = 1-5 in a region near the acetylenic stretch. The intensity of the hot band is reduced considerably at 240 K. The strength of a Fermi resonance between C-Ha transition (??(a)) and the combination band ((?-1)?(a) + 2?(bend)) with (? = 3-6) was calculated using the experimental perturbed energies and relative intensities. The main bands are separated by computer deconvolution and are integrated at each level to get the experimental band strengths. For methyl absorptions, the dipole moment function is expanded as a function of two C-H stretching coordinates and the intensities are calculated in terms of the HCAO model where only the C-H modes are considered. Acetylenic intensities are derived with a one dimensional dipole moment function. The expansion coefficients are obtained from molecular orbital calculations. The intensities are calculated without using adjustable parameters and they are of the same order of magnitude of the experimental intensities for all C-H transitions. PMID:23822307

  16. Surface-Enhanced Infrared Absorption

    Microsoft Academic Search

    Masatoshi Osawa

    2001-01-01

    Molecules adsorbed on metal island films or particles exhibit 10-1000 times more intense infrared absorption than would be\\u000a expected from conventional measurements without the metal. This effect is referred to as surface-enhanced infrared absorption\\u000a (SEIRA) to emphasize the similarities with surface-enhanced Raman scattering (SERS). The electromagnetic interactions of the\\u000a incident photon field with the metal and molecules play predominant roles

  17. Absorption of surface acoustic waves by graphene

    Microsoft Academic Search

    S. H. Zhang; W. Xu

    2011-01-01

    We present a theoretical study on interactions of electrons in graphene with surface acoustic waves (SAWs). We find that owing to momentum and energy conservation laws, the electronic transition accompanied by the SAW absorption cannot be achieved via inter-band transition channels in graphene. For graphene, strong absorption of SAWs can be observed in a wide frequency range up to terahertz

  18. Design of resonant-cavity-enhanced multi-band photodetectors

    Microsoft Academic Search

    Yan-Feng Lao; Gamini Ariyawansa; A. G. Unil Perera

    2011-01-01

    A theoretical analysis to improve the quantum efficiency of detectors sensing in multiple spectral bands is presented. The effective coupling between the incoming light and multiple absorbing regions for simultaneously improving the multi-band absorption efficiency is obtained by using resonant-cavity structures. An optimized cavity with only a Au bottom reflector gives rise to an enhancement factor of 11 in absorption

  19. Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts

    SciTech Connect

    Carr, C W; Bude, J D; Shen, N; Demange, P

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

  20. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T. [Key Laboratory of Advanced Display and System Application, Shanghai University, 149 Yanchang Road, Shanghai 200072 (China); Institut d'Electronique et de Microelectronique et de Nanotechnologies, IEMN (CNRS, UMR 8520), Groupe de Physique, Cite scientifique, avenue Poincare, 59652 Villeneuve d'Ascq (France); Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B. [Institut d'Electronique et de Microelectronique et de Nanotechnologies, IEMN (CNRS, UMR 8520), Groupe de Physique, Cite scientifique, avenue Poincare, 59652 Villeneuve d'Ascq (France)

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  1. Nonlinear ionization mechanism dependence of energy absorption in diamond under femtosecond laser irradiation

    SciTech Connect

    Wang Cong; Jiang Lan; Li Xin; Wang Feng; Yuan Yanping [Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081 (China); Qu Liangti [Key Laboratory of Cluster Science, Ministry of Education, School of Chemistry, Beijing Institute of Technology, Beijing 100081 (China); Lu Yongfeng [Department of Electrical Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska 68588-0511 (United States)

    2013-04-14

    We present first-principles calculations for nonlinear photoionization of diamond induced by the intense femtosecond laser field. A real-time and real-space time-dependent density functional theory with the adiabatic local-density approximation is applied to describe the laser-material interactions in the Kohn-Sham formalism with the self-interaction correction. For a certain laser wavelength, the intensity dependence of energy absorption on multiphoton and/or tunnel ionization mechanisms is investigated, where laser intensity regions vary from 10{sup 12} W/cm{sup 2} to 10{sup 16} W/cm{sup 2}. In addition, the effect of laser wavelength on energy absorption at certain ionization mechanism is discussed when the Keldysh parameter is fixed. Theoretical results show that: (1) at the fixed laser wavelength, the relationship between the energy absorption and laser intensity shows a good fit of E = c{sub M}I{sup N} (N is the number of photons absorbed to free from the valence band) when multiphoton ionization dominates; (2) while when tunnel ionization becomes significant, the relationship coincides with the expression of E = c{sub T}I{sup n} (n < N).

  2. Near-infrared studies of glucose and sucrose in aqueous solutions: water displacement effect and red shift in water absorption from water-solute interaction

    E-print Network

    Jung, Youngeui

    2013-01-01

    We use near infrared spectroscopy to obtain concentration dependent glucose absorption spectra in their aqueous solutions in the near-infrared range (3800 - 7500 cm^{-1}). We introduce a new method to obtain reliable glucose absorption bands from aqueous glucose solutions without measuring the water displacement coefficients of glucose separately. Additionally, we are able to extract the water displacement coefficients of glucose, and this may give a new general method using spectroscopy techniques applicable to other water soluble materials. We also observe red shifts in the absorption bands of water in the hydration shell around solute molecules, which comes from contribution of the interacting water molecules around the glucose molecules in solutions. The intensity of the red shift get larger as the concentration increases, which indicates that as the concentration increases more water molecules are involved in the interaction. However, the red shift in frequency does not seem to depend significantly on th...

  3. Infrared spectra and molar absorption coefficients of the 20 alpha amino acids in aqueous solutions in the spectral range from 1800 to 500 cm -1

    NASA Astrophysics Data System (ADS)

    Wolpert, Martina; Hellwig, Petra

    2006-07-01

    In this work, we present the absorption spectra and molar coefficients of all 20 amino acids in aqueous solutions down to 500 cm -1. The spectral region between 1200 and 500 cm -1 was yet disregarded for protein infrared spectroscopy, mainly due to the strong H 2O absorption. Absorption spectra were obtained mainly for physiological relevant pH region. Intense bands for aromatic amino acids, histidine and such with OH group could clearly be identified throughout the given spectral region. For sulfur-containing amino acids cysteine and methionine some strong bands besides the weak carbon-sulfur stretching vibration was shown. Effects of aqueous solution environment, pH, protonation states were discussed, together with previously reported data from theoretical approaches. With this complete set of spectral information application to proteins in the whole mid infrared region could be described precise and the potential of the lower spectral region to study typical cofactor ligands like histidine, shown.

  4. Band gap enhancement of glancing angle deposited TiO{sub 2} nanowire array

    SciTech Connect

    Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C. [National Institute of Technology Agartala, Department of Electronics and Communication Engineering, Jirania, Tripura (West) 799055 (India); Chattopadhyay, K. K. [Jadavpur University, Department of Physics, Kolkata 700032 (India); Bhattacharya, Sekhar [SSN Research Centre, Tamil Nadu 603110 (India)

    2012-09-01

    Vertically oriented TiO{sub 2} nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters {approx}80 nm and {approx}40 nm TiO{sub 2} NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO{sub 2}. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm{sup -1} of anatase E{sub g}) and blue (7.4 cm{sup -1} of rutile E{sub g}, 7.8 cm{sup -1} of rutile A{sub 1g}) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and {approx}3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

  5. Photodissociation of carbon dioxide in singlet valence electronic states. II. Five state absorption spectrum and vibronic assignment

    NASA Astrophysics Data System (ADS)

    Grebenshchikov, Sergy Yu.

    2013-06-01

    The absorption spectrum of CO2 in the wavelength range 120-160 nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled potential energy surfaces of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T = 190 K via Boltzmann averaging of optical transitions from many initial rotational states, accurately reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that the main progressions in the high energy band correspond to consecutive excitations of the pseudorotational motion along the closed loop of the CI seam, and progressions differ in the number of nodes along the radial mode perpendicular to the closed seam. Irregularity of the diffuse peaks in the low energy band is interpreted as a manifestation of the carbene-type "cyclic" OCO minimum.

  6. Effect of host glass on the optical absorption properties of Nd3+, Sm3+, and Dy3+ in lead borate glasses

    Microsoft Academic Search

    M. B. Saisudha; J. Ramakrishna

    1996-01-01

    The effect of host glass composition on the optical absorption spectra of Nd3+, Sm3+, and Dy3+ in lead borate glasses, with PbO contents varying from 30 to 70 mol %, has been analyzed using Judd-Ofelt theory and the compositional dependence has been determined for the hypersensitive bands. Judd-Ofelt intensity parameters Omegat (t=2,4,6), and the radiative transition probabilities. The variation of

  7. 4f–4f absorption spectra and hypersensitivity in nine-coordinate Ho(III) and Er(III) complexes in different environments

    Microsoft Academic Search

    Azad A Khan; H. A Hussain; K Iftikhar

    2004-01-01

    The effect of change in the environment upon 4f–4f absorption spectra of nine-coordinate Ho(III) and Er(III) complexes with thiocyanate and 2,2?-bipyridyl in methanol, DMSO, DMF and pyridine have been investigated. The oscillator strength for hypersensitive and non-hypersensitive transitions have been calculated and variation in the intensity and band shape with respect to solvent type is rationalized in terms of solvent

  8. Absorptivity of vibrationally nonequilibrium carbon dioxide in 15-micron Q branches - Determination of populations of discrete vibration levels and vibrational temperatures of CO2

    Microsoft Academic Search

    S. I. Kriuchkov; N. N. Kudriavtsev; S. S. Novikov

    1985-01-01

    The absorptivity of the intense Q branches of the 15-micron band of CO2 is studied numerically within a broad range of parameters of the vibrationally nonequilibrium gas. The range of parameters includes the conditions in the resonators of CO2 lasers operating in the spectral regions 9-11 and 16-19 microns. The computations are used to develop methods for determining the vibrational

  9. New assignments in the 2 ?m transparency window of the 12CH4 Octad band system

    NASA Astrophysics Data System (ADS)

    Daumont, L.; Nikitin, A. V.; Thomas, X.; Régalia, L.; Von der Heyden, P.; Tyuterev, Vl. G.; Rey, M.; Boudon, V.; Wenger, Ch.; Loëte, M.; Brown, L. R.

    2013-02-01

    This paper reports new assignments of rovibrational transitions of 12CH4 bands in the range 4600-4887 cm-1 which is usually referred to as a part of the 2 ?m methane transparency window. Several experimental data sources for methane line positions and intensities were combined for this analysis. Three long path Fourier transform spectra newly recorded in Reims with 1603 m absorption path length and pressures of 1, 7 and 34 hPa for samples of natural abundance CH4 provided new measurements of 12CH4 lines. Older spectra for 13CH4 (90% purity) from JPL with 73 m absorption path length were used to identify the corresponding lines. Most of the lines in this region belong to the Octad system of 12CH4. The new spectra allowed us to assign 1014 new line positions and to measure 1095 line intensities in the cold bands of the Octad. These new line positions and intensities were added to the global fit of Hamiltonian and dipole moment parameters of the Ground State, Dyad, Pentad and Octad systems. This leads to a noticeable improvement of the theoretical description in this methane transparency window and a better global prediction of the methane spectrum.

  10. Oral cancer detection using diffuse reflectance spectral ratio R540/R575 of oxygenated hemoglobin bands

    NASA Astrophysics Data System (ADS)

    Subhash, N.; Mallia, J. R.; Thomas, S. S.; Mathews, A.; Sebastian, P.; Madhaven, J.

    2006-01-01

    A low-cost, fast, and noninvasive method for early diagnosis of malignant lesions of oral mucosa based on diffuse reflectance spectral signatures is presented. In this technique, output of a tungsten halogen lamp is guided to the tissue through the central fiber of a reflection probe whose surrounding six fibers collects tissue reflectance. Ex vivo diffuse reflectance spectra in the 400 to 600-nm region is measured from surgically removed oral cavity lesions using a miniature fiber optic spectrometer connected to a computer. Reflectance spectral intensity is higher in malignant tissues and shows dips at 542 and 577 nm owing to absorption from oxygenated hemoglobin (HbO2). Measurements carried out, within an hour of surgical excision, on malignant lesion and adjoining uninvolved mucosa show that these absorption features are more prominent in neoplastic tissues owing to increased microvasculature and blood content. It is observed that reflectance intensity ratio of hemoglobin bands, R540/R575, from malignant sites are always lower than that from normal sites and vary according to the histological grade of malignancy. The diffuse reflectance intensity ratio R540/R575 of the hemoglobin bands appears to be a useful tool to discriminate between malignant lesions and normal mucosa of the oral cavity in a clinical setting.

  11. Analysis of several high-resolution infrared bands of spiropentane, C5H8

    NASA Astrophysics Data System (ADS)

    Maki, A.; Price, J. E.; Harzan, J.; Nibler, J. W.; Weber, A.; Masiello, T.; Blake, T. A.

    2015-06-01

    The high-resolution infrared absorption spectrum of spiropentane (C5H8) has been measured from 200 to 4000 cm-1, and a detailed analysis is presented for eight bands in the region from 700 to 2200 cm-1. Two fundamental perpendicular bands were analyzed, ?22 and ?24 near 1050 and 780 cm-1, respectively, along with two fundamental parallel bands, ?14 and ?16 near 1540 and 990 cm-1, respectively. Two other fundamentals, ?17 and ?23, are seen as intense overlapping bands near 880 cm-1 and are Coriolis-coupled, producing a complex mixture in which only P-branch transitions could be tentatively assigned for ?17. In addition, three binary combination bands were fit at about 1570, 2082, and 2098 cm-1 which are assigned as either 2?24 or ?5 + ?16 in the first case, ?4 + ?22 in the second case, and 2?22 in the latter case. The two l-type resonance constants, q+ and q-, were determined for each of the two perpendicular fundamentals ?22 and ?24. Those two constants were also responsible for splittings observed in the K = 3 levels of ?24. For the ground state the order of the split K = 2 B1/B2 levels has been reversed from that reported previously, based on the measurements and assignments for the ?24 band. Rovibrational parameters deduced from the analyses are compared with those obtained from density functional Gaussian calculations at the anharmonic level.

  12. Nutrient absorption.

    PubMed

    Siddiqi, S A; Kumar, N S; St Hilaire, R J; Nutting, D F; Mansbach, C M

    2000-03-01

    Some key advances occurred last year in understanding mechanisms involved in nutrient absorption. A novel "prechylomicron transport vesicle" was identified; its movement to the Golgi is the rate-limiting step for triacylglycerol absorption. A scavenger receptor (type BI) in the brush border membrane appears to facilitate cholesterol uptake. Several studies define mechanisms for gastrointestinal peptide hormone stimulation of glucose uptake. An oligopeptide transporter, PepT1, is transcriptionally upregulated by certain dietary amino acids and dipeptides. Surprisingly, both insulin and fasting double the maximum velocity for dipeptide uptake (via PepT1), but they act by different mechanisms. Three transporters, SMVT (sodium-dependent multivitamin transporter for biotin and pantothenate), SVCT (for vitamin C), and CaT1 (for Ca uptake from the lumen) have been cloned and are active when expressed in various cells. Additional studies provide insights on Ca absorption and vitamin D action in aging, estrogen deficiency, and adaptation to a low Ca diet. Nramp2, also called DMT1 (divalent metal ion transporter), seems to be a major regulator of transferrin-independent, nonheme iron uptake. Finally, the protein HFE associates with the transferrin receptor and is part of an iron-sensing mechanism that regulates iron absorption. It is defective in hereditary hemochromatosis. HFE and Nramp2 (DMT1) genes are reciprocally regulated. PMID:17024033

  13. Pioneer 11 observations of trapped particle absorption by the Jovian ring and the satellites 1979, J1, J2, and J3

    NASA Technical Reports Server (NTRS)

    Pyle, K. R.; Mckibben, R. B.; Simpson, J. A.

    1983-01-01

    Pioneer 11 low energy telescope observation of charged particles around the Jovian satellites Amalthea, 1979 J1, J2, and J3, and the Jupiter ring are examined in the light of Voyager optical data from the same region. Good agreement was found in the absorption features of 0.5-8.7 MeV protons, electrons with energies of 3.4 MeV or more, and medium-Z nuclei. The heavier nuclei are suggested to be oxygen and sulfur particles with energies exceeding 70 MeV/nucleon. The observed intensity features in the regularly spaced radiation bands are interpreted as ring and satellite absorption.

  14. Vibronic bands in the HOMO-LUMO excitation of linear polyyne molecules

    NASA Astrophysics Data System (ADS)

    Wakabayashi, Tomonari; Wada, Yoriko; Iwahara, Naoya; Sato, Tohru

    2013-04-01

    Hydrogen-capped linear carbon chain molecules, namely polyynes H(C?C)nH (n>=2), give rise to three excited states in the HOMO-LUMO excitation. Electric dipole transition from the ground state is fully allowed to one of the three excited states, while forbidden for the other two low-lying excited states. In addition to the strong absorption bands in the UV for the allowed transition, the molecules exhibit weak absorption and emission bands in the near UV and visible wavelength regions. The weak features are the vibronic bands in the forbidden transition. In this article, symmetry considerations are presented for the optical transitions in the centrosymmetric linear polyyne molecule. The argument includes Herzberg-Teller expansion for the state mixing induced by nuclear displacements along the normal coordinate of the molecule, intensity borrowing from fully allowed transitions, and inducing vibrational modes excited in the vibronic transition. The vibronic coupling considered here includes off-diagonal matrix elements for second derivatives along the normal coordinate. The vibronic selection rule for the forbidden transition is derived and associated with the transition moment with respect to the molecular axis. Experimental approaches are proposed for the assignment of the observed vibronic bands.

  15. Near-infrared absorptions of monomethylhydrazine

    NASA Technical Reports Server (NTRS)

    Murray, Mark; Kurtz, Joe

    1993-01-01

    The peak absorption coefficients for two near-infrared absorptions of monomethylhydrazine, CH3-N2H3, (MMH) were measured. Absorption bands located at 1.524 micrometers (6560/cm), 1.557 micrometers (6423/cm), and 1.583 micrometers (6316/cm) are assigned to the Delta upsilon = 2 overtones of the infared N-H stretching fundamentals at 3317, 3245 and 3177/cm. An absorption band located at 1.04 micrometers (9620 +/- 100/cm) is assigned to the Delta upsilon = 3 overtone of one of these fundamentals. The peak absorption coefficients (alpha(sub 10)) at 1.524 micrometers (6560 +/- 20/cm) and 1.04 micrometers (9620 +/- 100/cm) are 31 x 10(exp -3) and 0.97 x 10(exp -3)/(cm atm), respectively. Uncertainties in these coefficients were estimated to be less than +/- 20% due primarily to uncertainties in the partial vapor pressure of MMH.

  16. Temperature and multi-species measurements by supercontinuum absorption spectroscopy for IC engine applications.

    PubMed

    Werblinski, Thomas; Engel, Sascha R; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

    2013-06-01

    The first supercontinuum (SC) absorption spectroscopy measurements showing the feasibility of quantitative temperature evaluation are presented to the best of the authors' knowledge. Temperature and multi-species measurements were carried out at a detection rate of ~2 MHz in a high-temperature flow cell within a temperature range from 450 K to 750 K at 0.22 MPa, representing conditions during the suction and compression stroke in an internal combustion (IC) engine. The broadband SC pulses were temporally dispersed into fast wavelength sweeps, covering the overtone absorption bands 2?(1), 2?(3), ?(1) + ?(3) of H2O and 3?(3) of CO2 in the near-infrared region from 1330 nm to 1500 nm. The temperature information is inferred from the peak ratio of a temperature sensitive (1362.42 nm) and insensitive (1418.91 nm) absorption feature in the ?(1) + ?(3) overtone bands of water. The experimental results are in very good agreement with theoretical intensity ratios calculated from absorption spectra based on HiTran data. PMID:23736618

  17. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, Michael E. (Bedford, MA); Bien, Fritz (Concord, MA); Bernstein, Lawrence S. (Bedford, MA)

    1986-01-01

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.

  18. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, M.E.; Bien, F.; Bernstein, L.S.

    1986-12-09

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

  19. Optical Absorption, Stability and Structure of NpO2+ Complexeswith Dicarboxylic Acids

    SciTech Connect

    Guoxin Tian; Linfeng Rao

    2006-01-04

    Complexation of NpO2+ with oxalic acid (OX),2,2'-oxydiacetic acid (ODA), 2,2'-iminodiacetic acid (IDA) and 2,2'-thiodiacetic acid (TDA), has been studied using spectrophotometry in1 M NaClO4. Both the position and the intensity of the absorption band of NpO2+ at 980 nm are affected by the formation of NpO2+/dicarboxylate complexes, providing useful information on the complexation strength, the coordination mode and the structure of the complexes.

  20. Artifacts in femtosecond transient absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Lorenc, M.; Ziolek, M.; Naskrecki, R.; Karolczak, J.; Kubicki, J.; Maciejewski, A.

    The paper discusses three different artifacts related to two-photon absorption (TPA), stimulated Raman amplification (SRA) and cross-phase modulation (XPM), all intrinsic to transient absorption measurements with femtosecond time resolution. Certain properties of these signals are analysed and shown to superimpose onto measured transient absorption spectra. Ways of reducing the influence of the artifacts discussed are suggested. A simple correcting procedure based on the linear intensity dependence of the artifacts discussed is proposed.

  1. Infrared laser absorption spectroscopy of the nu4 (sigma u) fundamental and associated nu11(pi u) hot band of C7 - Evidence for alternating rigidity in linear carbon clusters

    NASA Technical Reports Server (NTRS)

    Heath, J. R.; Saykally, R. J.

    1991-01-01

    The first characterization of the bending potential of the C7 cluster is reported via the observation of the v = 1(1) and v = 2 deg levels of the nu11 (pi u) bend as hot bands associated with the nu4 (sigma u) antisymmetric stretch fundamental. The lower state hot band rotational constants are measured to be 1004.4(1.3) and 1123.6(9.0) MHz, constituting a 9.3 and 22 percent increase over the ground state rotational constant, 918.89 (41) MHz. These large increases are strong quartic and sextic centrifugal distortion constants determined for the ground and nu 4 = 1 states are found to be anomalously large and negative, evidencing strong perturbations between stretching and bending modes.

  2. Photoluminescence investigation of the indirect band gap and shallow impurities in icosahedral B12As2

    NASA Astrophysics Data System (ADS)

    Klein, P. B.; Nwagwu, Ugochukwu; Edgar, J. H.; Freitas, J. A.

    2012-07-01

    The indirect band gap of icosahedral B12As2 (IBA) has been determined by variable temperature photoluminescence measurements (8 K-294 K) on solution-grown bulk samples. In addition, evidence of three shallow acceptor levels and one shallow donor level is reported. The low-temperature spectra were characterized by broad and intense deep defect emission, donor-acceptor pair (DAP) bands, and exciton recombination. The appearance of DAP emission verifies the incorporation of a donor in IBA, which has not been reported previously. The temperature dependence of the free exciton (FE) intensity reflected a FE binding energy of 45 meV. The variation of the FE peak position with temperature was fitted with both Varshni and Pässler models to determine an expression for the temperature dependence of the indirect band gap. The resulting low and room temperature band gaps are Eg(0) = 3.470 eV and Eg(294 K) = 3.373 eV, respectively. The latter is not consistent with previous reports of the room temperature band gap, 3.20 eV and 3.47 eV, derived from band structure calculations and optical absorption, respectively. The origin of these discrepancies is discussed. The DAP spectra reveal three relatively shallow acceptors with binding energies of ?175, 255, and 291 meV, and a shallow donor with binding energy ?25 meV. Although the identity of the individual acceptors is not known, they appear to be associated with the light-hole band. The small donor binding energy is suggestive of an interstitial donor impurity, which is suspected to be Ni.

  3. FIRE DETECTION IN IMAGING SPECTROMETER DATA USING ATMOSPHERIC CARBON DIOXIDE ABSORPTION

    E-print Network

    1 FIRE DETECTION IN IMAGING SPECTROMETER DATA USING ATMOSPHERIC CARBON DIOXIDE ABSORPTION P (CIBR) was used to measure the relative depth of the 2000 nm carbon dioxide absorption band. Low CIBR and reflected radiance within a shortwave infrared carbon dioxide absorption band. Methods The SWIR radiance

  4. Determination of the content of rare-earth elements in yttrium-aluminum garnet crystals by the method of absorption spectrophotometry

    SciTech Connect

    Meil'man, M.L.; Bagdasarov, K.S.; Baskakova, Z.M.; Kevorkov, A.M.; Kolomiitsev, A.I.

    1986-05-01

    The method of absorption spectrophotometric analysis is used to determine the relative and absolute content of impurity trivalent ions of the remaining REE (rare-earth elements) in YAG (Yttrium-aluminum garnet) single crystals. This method enables measuring the content of REE impurities in YAG single crystals using the peak intensities of the characteristic absorption lines of trivalent ions of these elements in the concentration range about 1.10/sup -3/-5 mass% with an accuracy of not worse than 20% and a sample thickness of -1 cm. The sensitivity with which many REE are determined can be raised by at least two orders of magnitude by using wide absorption bands, associated with the allowed interconfigurational transitions of the impurity ions. The values of the absorption coefficients of REE impurities in YAG crystals enable the determination of the absolute concentrations of these impurities, including situations when several REE are present simultaneously in one sample.

  5. Excited singlet state and photoionization of 8-methoxypsoralen. Picosecond transient absorption study.

    PubMed

    Gurzadyan, Gagik G

    2002-10-01

    Time-resolved pico- and nanosecond transient absorption measurements of 8-methoxypsoralen (8-MOP) were performed in different solvents at room temperature. The excited singlet state has two strong absorption bands with maxima at 430 and 630-690 nm. The lifetime of the first excited singlet state, tau(s), ranges from <10 ps up to 2.7 ns, being shorter in low-polar solvents (toluene, THF) and longer in highly polar water, TFE and HFIP. The rate of the singlet depopulation decreases exponentially with increasing solvent polarity as expressed by the Dimroth-Reichardt (ET(N)) or Gutmann solvent acceptor number (AN). In aqueous ethanol solution (H2O: EtOH 10:1), addition of the synthetic nucleobase 2-aminopurine slightly decreased the lifetime tau(s). The long-time (t > 5 ns) absorption spectrum remaining after the complete decay of the S1 state is due to the hydrated electron e(aq) and the radical cation 8-MOPF.+. Ionization is due to both, one and two-quantum excitation. In the intensity range I = 10(6)-10(9) W cm(-2) the quantum yield of electron ejection (ionization) phi(i) does not depend on the intensity of radiation, therefore the ionization is monophotonic, phi(i) = 0.03. At intensities 1> 5 x 10(9) W cm(-2) phi1 becomes larger due to two-quantum excitation followed by ionization. PMID:12656475

  6. Band Structures of Plasmonic Polarons

    NASA Astrophysics Data System (ADS)

    Caruso, Fabio; Lambert, Henry; Giustino, Feliciano

    2015-03-01

    In angle-resolved photoemission spectroscopy (ARPES), the acceleration of a photo-electron upon photon absorption may trigger shake-up excitations in the sample, leading to the emission of phonons, electron-hole pairs, and plasmons, the latter being collective charge-density fluctuations. Using state-of-the-art many-body calculations based on the `GW plus cumulant' approach, we show that electron-plasmon interactions induce plasmonic polaron bands in group IV transition metal dichalcogenide monolayers (MoS2, MoSe2, WS2, WSe2). We find that the energy vs. momentum dispersion relations of these plasmonic structures closely follow the standard valence bands, although they appear broadened and blueshifted by the plasmon energy. Based on our results we identify general criteria for observing plasmonic polaron bands in the angle-resolved photoelectron spectra of solids.

  7. The Fourier transform absorption spectrum of acetylene between 7000 and 7500 cm-1

    NASA Astrophysics Data System (ADS)

    Lyulin, O. M.; Vander Auwera, J.; Campargue, A.

    2015-07-01

    High resolution (0.011 cm-1) room temperature (295 K) Fourier transform absorption spectra (FTS) of acetylene have been recorded between 7000 and 7500 cm-1. Line parameters (positions, intensities and self broadening coefficients) have been measured using a multispectrum treatment of three FTS spectra, recorded at 3.84, 8.04 and 56.6 hPa. As a result, a list of 3788 lines was constructed with intensities ranging between about 10-26 and 10-22 cm/molecule. Comparison with accurate predictions provided by a global effective operator model (Lyulin OM, Perevalov VI, Teffo JL, Proc. SPIE 2004;5311:134-43) led to the assignment of 2471 of these lines to 12C2H2. The assigned lines belong to 29 12C2H2 bands, 12 of them being newly reported. Spectroscopic parameters of the upper vibrational levels were derived from band-by-band fits of the line positions (typical rms values are on the order of 0.001 cm-1). About half of the analyzed bands were found to be affected by rovibrational perturbations. Line parameters obtained in this work were compared with those available for about 350 transitions in the HITRAN 2012 database. The large set of new data will be valuable to refine the parameters of the global effective Hamiltonian and dipole moments of 12C2H2.

  8. Not-so-resonant, resonant absorption

    SciTech Connect

    Brunel, F.

    1987-07-06

    When an intense electromagnetic wave is incident obliquely on a sharply bounded overdense plasma, strong energy absorption can be accounted for by the electrons that are dragged into the vacuum and sent back into the plasma with velocities vapprox. =v/sub osc/. This mechanism is more efficient than usual resonant absorption for v/sub osc//..omega..>L, with L being the density gradient length. In the very high-intensity CO/sub 2/-laser--target interaction, this mechanism may account for most of the energy absorption.

  9. Propionaldehyde infrared cross-sections and band strengths

    NASA Astrophysics Data System (ADS)

    Köro?lu, Batikan; Loparo, Zachary; Nath, Janardan; Peale, Robert E.; Vasu, Subith S.

    2015-02-01

    The use of oxygenated biofuels reduces the greenhouse gas emissions; however, they also result in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propionaldehyde. These aldehydes are carcinogenic and/or toxic and therefore it is important to understand their formation and destruction pathways in combustion and atmospheric systems. Accurate information about their infrared cross-sections and integrated strengths are crucially needed for development of quantitative detection schemes and modeling tools. Critical to the development of such diagnostics are accurate characterization of the absorption features of these species. In this study, the gas phase infrared spectra of propionaldehyde (also called propanal, CH3-CH2-CHO), a saturated three carbon aldehyde found in the exhaust emissions of biodiesel or diesel fuels, was studied using high resolution Fourier Transform Infrared (FTIR) spectroscopy over the wavenumber range of 750-3300 cm-1 and at room temperature 295 K. The absorption cross sections of propionaldehyde were recorded at resolutions of 0.08 and 0.096 cm-1 and at seven different pressures (4-33 Torr). The calculated band-strengths were reported and the integrated band intensity results were compared with values taken from the Pacific Northwest National Laboratory (PNNL) database (showing less than 2% discrepancy). The peak positions of the 19 different vibrational bands of propionaldehyde were also compared with previous studies taken at a lower resolution of 1 cm-1. To the best of our knowledge, the current FTIR measurements provide the first highest resolution infrared cross section data for propionaldehyde.

  10. Resonance Absorption

    Microsoft Academic Search

    Peter Mulser; Dieter Bauer

    \\u000a The most familiar absorption process of laser radiation is inverse bremsstrahlung. As the electron temperature increases Coulomb\\u000a collisions become less effective and, in the absence of other conversion processes, a plasma becomes highly transparent to\\u000a the laser radiation when the electron density n\\u000a \\u000a e\\u000a is below its critical value n\\u000a \\u000a c\\u000a ; alternatively, in case an overdense layer exists, i.e.,

  11. A theoretical and experimental study of pressure broadening of the oxygen A-band by helium

    NASA Astrophysics Data System (ADS)

    Grimminck, Dennis L. A. G.; Spiering, Frans R.; Janssen, Liesbeth M. C.; van der Avoird, Ad; van der Zande, Wim J.; Groenenboom, Gerrit C.

    2014-05-01

    The rotationally resolved magnetic dipole absorption spectrum of the oxygen A-band b{^1? _g^+}(v=0)leftarrow X{^3? _g^-}(v=0) perturbed by collisions with helium was studied theoretically using the impact approximation. To calculate the relaxation matrix, scattering calculations were performed on a newly computed helium-oxygen (b{^1? _g^+}) interaction potential as well as on a helium-oxygen (X{^3? _g^-}) interaction potential from the literature. The calculated integrated line cross sections and broadening coefficients are in good agreement with experimental results from the literature. Additionally, cavity ring-down experiments were performed in the wings of the spectral lines for a quantitative study of line-mixing, i.e., the redistribution of rotational line intensities by helium-oxygen collisions. It is shown that inclusion of line-mixing in the theory is required to reproduce the experimentally determined absolute absorption strengths as a function of the density of the helium gas.

  12. Perceiving the Intensity of Light

    ERIC Educational Resources Information Center

    Purves, Dale; Williams, S. Mark; Nundy, Surajit; Lotto, R. Beau

    2004-01-01

    The relationship between luminance (i.e., the photometric intensity of light) and its perception (i.e., sensations of lightness or brightness) has long been a puzzle. In addition to the mystery of why these perceptual qualities do not scale with luminance in any simple way, "illusions" such as simultaneous brightness contrast, Mach bands

  13. Generation of intense ultrashort x-ray pulses

    SciTech Connect

    Eder, D.C.; London, R.A.; Rosen, M.D. [Lawrence Livermore National Lab., CA (United States); Strobel, G.L. [Georgia Univ., Macon, GA (United States)

    1993-08-01

    Modeling of x-ray emission from targets heated by an ultrashort-pulse high-intensity optical laser is discussed. One application, using the emitted x rays, is pumping inner-shell photo-ionized x-ray lasers. Short wavelength lasing ({lambda} {le} 15 {Angstrom}) requires fast rise-time 1--3 key x rays to ionize inner K-shell electrons. It has been shown that structured targets, consisting of grooves on a solid material or a composite of clusters, have high absorption. We model grooved targets as an ensemble of exploding foils finding that the rise time of x rays is rapid enough for pumping inner-shell x-ray lasers. We show that simple atomic models can overestimate the energy in x-ray emission bands. High-Z materials are found to have the highest conversion efficiency but mid-Z materials can be used to provide a band of emission at a particular energy. We show that the pondermotive inhibition of expansion has only a small effect on the x-ray emission. The emission of a Au plasma is found to be appropriate for pumping inner-shell lasing at 14.6 {Angstrom} in Ne. The required optical laser intensity is of order 10{sup 17} W/cm{sup 2} using a 100 fsec FWHM duration pulse. To produce a laser with a gain-length product of order 10 requires 5--15 J of optical energy.

  14. Ultra Wide Band ULTRA WIDE BAND

    E-print Network

    Dobigeon, Nicolas

    Ultra Wide Band ULTRA WIDE BAND Martial COULON ENSEEIHT - 3 ann´ee T´el´ecom-R´eseaux - option Mobilit´e ann´ee 2007-2008 1/ 108 #12;Ultra Wide Band Plan du cours Introduction D´efinition Historique et;Ultra Wide Band Plan du cours Introduction D´efinition Historique et R´eglementations Applications Sp

  15. Hot Band Spectroscopy of the Formyl Cation, H12C16O+

    NASA Astrophysics Data System (ADS)

    Neese, Christopher F.; Kreynin, Peter S.; Oka, Takeshi

    2013-10-01

    Midinfrared spectra of the formyl cation, HCO+, were recorded by direct absorption in a glow discharge (composition CO, 50 mTorr; H2, 50 mTorr; He, 7 Torr) using a color center laser spectrometer and velocity modulation with heterodyne detection. The bands measured were 1000-0000, 1110-0110, 1200-0200, 1220-0220, 1001-0001, 1111-0111, 2000-1000, and 1002-0002. These bands were analyzed and fitted together with all other available rotationally resolved spectra to arrive at a new set of spectroscopic constants for HCO+. The relative intensities were fit to obtain a rotational temperature, Trot = 434 ± 7 K, and vibrational temperatures for each mode, T1 = 3300 ± 240 K, T2 = 841 ± 15 K, and T3 = 3157 ± 68 K.

  16. Efficient laser heating of transparent liquids using multiphoton absorption

    Microsoft Academic Search

    Jon P. Longtin; Chang-Lin Tien

    1997-01-01

    At high laser intensities, otherwise transparent liquids can absorb strongly by the mechanism of multiphoton absorption, resulting in heating and temperature increases orders of magnitude greater than that from classical, low-intensity mechanisms. The use of multiphoton absorption provides a new mechanism for significant, controlled energy deposition in transparent liquids, which is important for a variety of laser-liquid technologies. This work

  17. Gaia broad band photometry

    NASA Astrophysics Data System (ADS)

    Jordi, C.; Gebran, M.; Carrasco, J. M.; de Bruijne, J.; Voss, H.; Fabricius, C.; Knude, J.; Vallenari, A.; Kohley, R.; Mora, A.

    2010-11-01

    Aims: The scientific community needs to be prepared to analyse the data from Gaia, one of the most ambitious ESA space missions, which is to be launched in 2012. The purpose of this paper is to provide data and tools to predict how Gaia photometry is expected to be. To do so, we provide relationships among colours involving Gaia magnitudes (white light G, blue GBP, red GRP and GRVS bands) and colours from other commonly used photometric systems (Johnson-Cousins, Sloan Digital Sky Survey, Hipparcos and Tycho). Methods: The most up-to-date information from industrial partners has been used to define the nominal passbands, and based on the BaSeL3.1 stellar spectral energy distribution library, relationships were obtained for stars with different reddening values, ranges of temperatures, surface gravities and metallicities. Results: The transformations involving Gaia and Johnson-Cousins V - IC and Sloan DSS g - z colours have the lowest residuals. A polynomial expression for the relation between the effective temperature and the colour GBP - GRP was derived for stars with Teff ? 4500 K. For stars with Teff < 4500 K, dispersions exist in gravity and metallicity for each absorption value in g - r and r - i. Transformations involving two Johnson or two Sloan DSS colours yield lower residuals than using only one colour. We also computed several ratios of total-to-selective absorption including absorption AG in the G band and colour excess E(GBP - GRP) for our sample stars. A relationship involving AG/AV and the intrinsic (V - IC) colour is provided. The derived Gaia passbands have been used to compute tracks and isochrones using the Padova and BASTI models. Finally, the performances of the predicted Gaia magnitudes have been estimated according to the magnitude and the celestial coordinates of the star. Conclusions: The provided dependencies among colours can be used for planning scientific exploitation of Gaia data, performing simulations of the Gaia-like sky, planning ground-based complementary observations and for building catalogues with auxiliary data for the Gaia data processing and validation. Tables 11-13 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/523/A48

  18. Effects of CO2 on H2O band profiles and band strengths in mixed H2O:CO2 ices

    E-print Network

    Karin I. Oberg; Helen J. Fraser; A. C. Adwin Boogert; Suzanne E. Bisschop; Guido W. Fuchs; Ewine F. van Dishoeck; Harold Linnartz

    2006-10-25

    H2O is the most abundant component of astrophysical ices. In most lines of sight it is not possible to fit both the H2O 3 um stretching, the 6 um bending and the 13 um libration band intensities with a single pure H2O spectrum. Recent Spitzer observations have revealed CO2 ice in high abundances and it has been suggested that CO2 mixed into H2O ice can affect relative strengths of the 3 um and 6 um bands. We used laboratory infrared transmission spectroscopy of H2O:CO2 ice mixtures to investigate the effects of CO2 on H2O ice spectral features at 15-135 K. We find that the H2O peak profiles and band strengths are significantly different in H2O:CO2 ice mixtures compared to pure H2O ice. In all H2O:CO2 mixtures, a strong free-OH stretching band appears around 2.73 um, which can be used to put an upper limit on the CO2 concentration in the H2O ice. The H2O bending mode profile also changes drastically with CO2 concentration; the broad pure H2O band gives way to two narrow bands as the CO2 concentration is increased. This makes it crucial to constrain the environment of H2O ice to enable correct assignments of other species contributing to the interstellar 6 um absorption band. The amount of CO2 present in the H2O ice of B5:IRS1 is estimated by simultaneously comparing the H2O stretching and bending regions and the CO2 bending mode to laboratory spectra of H2O, CO2, H2O:CO2 and HCOOH.

  19. Theoretical model of absorption of laser light by a plasma

    Microsoft Academic Search

    Patrick Mora

    1982-01-01

    A simple model of laser light absorption is described. The absorption mechanism is mainly inverse bremsstrahlung, but a crude description of resonance absorption is also included. The intensity and the wavelength dependence are emphasized, but the model takes into account the target material composition, the laser pulse length, and the focal spot radius. Plane and spherical expansion are treated. Results

  20. Resonance Absorption of Microwaves by the Human Skull

    Microsoft Academic Search

    William T. Joines; Ronald J. Spiegel

    1974-01-01

    Resonance absorption of microwaves by the human skull is examined by making computerized calculations of theoretical models of the skull. The calculated relative absorption versus frequency is plotted and compared for homogeneous and inhomogeneous skull models. At a frequency of maximum power absorption, the spatial distribution of intracranial field intensity (based upon the theoretical model) is also calculated and plotted.

  1. Characterization of photon-counting detector responsivity for nonlinear two-photon absorption process

    Microsoft Academic Search

    S. E. Sburlan; W. H. Farr

    2011-01-01

    Sub-band absorption at 1550 nm has been demonstrated and characterized on silicon Geiger mode detectors, which normally would be expected to have no response at this wavelength. We compare responsivity measurements to single-photon absorption for wavelengths slightly above the band gap wavelength of silicon (~1100 mum). One application for this low efficiency sub-band absorption is in deep space optical communication

  2. Resonant photoemission study of ScF3 at the Sc 2p and F 1s absorption edges: Observation of the satellite structure due to the strong hybridization effect

    Microsoft Academic Search

    M. Umeda; Y. Tezuka; S. Shin; A. Yagishita

    1996-01-01

    The electronic structure of ScF3 has been investigated by resonant photoemission at the Sc 2p and F 1s absorption edges. At off-resonant photoemission, a charge-transfer-type satellite is found with an energy separation of about 13 eV below main peaks in valence-band and various core-energy regions. Another satellite is found with an energy separation of about 9-10 eV and its intensity

  3. Titanium-silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy

    PubMed Central

    Dunlop, Iain E.; Zorn, Stefan; Richter, Gunther; Srot, Vesna; Kelsch, Marion; van Aken, Peter A.; Skoda, Maximilian; Gerlach, Alexander; Spatz, Joachim P.; Schreiber, Frank

    2010-01-01

    We present a titanium-silicon oxide film structure that permits polarization modulated infrared reflection absorption spectroscopy on silicon oxide surfaces. The structure consists of a ~6 nm sputtered silicon oxide film on a ~200 nm sputtered titanium film. Characterization using conventional and scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and X-ray reflectometry is presented. We demonstrate the use of this structure to investigate a selectively protein-resistant self-assembled monolayer (SAM) consisting of silane-anchored, biotin-terminated poly(ethylene glycol) (PEG). PEG-associated IR bands were observed. Measurements of protein-characteristic band intensities showed that this SAM adsorbed streptavidin whereas it repelled bovine serum albumin, as had been expected from its structure. PMID:20418963

  4. Defect generation, d- d transition, and band gap reduction in Cu-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Choudhury, Biswajit; Dey, Munmun; Choudhury, Amarjyoti

    2013-04-01

    TiO2 doped with Cu2+ initiates the formation of brookite phase along with anatase. Doping of Cu2+ introduces structural defects into TiO2. The direct evidence is the low intense and broad diffraction peaks. Raman peaks of doped TiO2 are also broad and are blueshifted. Pure TiO2 exhibits an absorption in the UV region, the position of which is shifted towards the visible region on incorporation of Cu into it. The visible absorption peaks arise due to the d- d transition of Cu2+ in the crystalline environment of TiO2. Incorporation of Cu2+ distorts the local structure of TiO2, resulting in the loss of octahedral symmetry surrounding Cu2+. The Jahn-Teller distortion splits the 2 E g and 2 T 2g state of Cu2+ into several d states. Interaction of light excites the electron from ground to several of the excited states and gives the visible absorption peaks in the framework of TiO2. These Cu2+ d states and oxygen defects create band states, thereby favoring electronic transition to these levels and resulting in lowering of band gap of TiO2. A direct confirmation is the increase in the magnitude of Urbach energy with the reduction in the band gap of doped TiO2.

  5. Band gap effects of hexagonal boron nitride using oxygen plasma

    SciTech Connect

    Sevak Singh, Ram; Leong Chow, Wai [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Yingjie Tay, Roland [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Hon Tsang, Siu [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Mallick, Govind [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); Tong Teo, Edwin Hang, E-mail: htteo@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    2014-04-21

    Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6?eV of pristine h-BN to 4.31?eV when exposed to oxygen plasma for 12?s. The narrowing of band gap causes the reduction in electrical resistance by ?100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

  6. Quantitative treatment of coarsely binned low-resolution recordings in molecular absorption spectroscopy.

    PubMed

    Spietz, Peter; Martín, Juan Carlos Gómez; Burrows, John P

    2006-06-01

    Optical multichannel detectors like photodiode arrays or CCD cameras combined with grating spectrometers are commonly used as detection systems in quantitative absorption spectroscopy. As a trade-off to broad spectral coverage, banded spectral features are sometimes recorded with insufficient spectral resolution and/or insufficiently fine detector binning. This renders the true physical spectrum of recorded intensities changed by instrumental and spectrum specific artefacts thus impeding comparability between results from different set-ups. In this work, it is demonstrated that in the case of a "well-behaved"--i.e. free of ro-vibronic structure--absorption band like the iodine monoxide IO(4<--0) transition, these effects can easily change the apparent peak absorption by up to 50%. Also deviations from the strict linearity (Beer-Lambert's law) between absorber concentration and apparent, i.e. pixelwise optical density occur. This can be critical in studies of chemical kinetics. It is shown that the observed non-linearity can cause errors of up to 50% in the determination of a second order rate coefficient for the IO self reaction. To overcome the problem, a consistent and rigorous integral approach for the treatment of intensity recordings is developed. Linearity between optical density and absorber concentration thereby is re-established. The method is validated using artificial test data as well as experimental data of the IO(4<--0) absorption transition, obtained in the context of I2/O3 photochemistry studies. The agreement is accurate to within +/-2% (test data) and +/-3% (experimental data) supporting the validity of the approach. Possible consequences for other spectroscopic work are indicated. PMID:16387540

  7. Quantitative treatment of coarsely binned low-resolution recordings in molecular absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Spietz, Peter; Martín, Juan Carlos Gómez; Burrows, John P.

    2006-06-01

    Optical multichannel detectors like photodiode arrays or CCD cameras combined with grating spectrometers are commonly used as detection systems in quantitative absorption spectroscopy. As a trade-off to broad spectral coverage, banded spectral features are sometimes recorded with insufficient spectral resolution and/or insufficiently fine detector binning. This renders the true physical spectrum of recorded intensities changed by instrumental and spectrum specific artefacts thus impeding comparability between results from different set-ups. In this work, it is demonstrated that in the case of a "well-behaved" - i.e. free of ro-vibronic structure - absorption band like the iodine monoxide IO(4 ? 0) transition, these effects can easily change the apparent peak absorption by up to 50%. Also deviations from the strict linearity (Beer-Lambert's law) between absorber concentration and apparent, i.e. pixelwise optical density occur. This can be critical in studies of chemical kinetics. It is shown that the observed non-linearity can cause errors of up to 50% in the determination of a second order rate coefficient for the IO self reaction. To overcome the problem, a consistent and rigorous integral approach for the treatment of intensity recordings is developed. Linearity between optical density and absorber concentration thereby is re-established. The method is validated using artificial test data as well as experimental data of the IO(4 ? 0) absorption transition, obtained in the context of I 2/O 3 photochemistry studies. The agreement is accurate to within ±2% (test data) and ±3% (experimental data) supporting the validity of the approach. Possible consequences for other spectroscopic work are indicated.

  8. The Absorption Spectrum of Chlorine Dioxide

    Microsoft Academic Search

    Harold C. Urey; Helen Johnston

    1931-01-01

    The wave-lengths of 134 absorption bands of ClO2 have been measured with the Hilger E-1 and E-185 quartz instruments. The bands have been arranged in progressions and the energy levels deduced. Five vibrational levels of the normal electronic state have been found; the vibrational levels of the excited electronic state can be described with the use of two vibrational quantum

  9. Visible to deep ultraviolet range optical absorption of electron irradiated borosilicate glass

    NASA Astrophysics Data System (ADS)

    Wang, Tie-Shan; Duan, Bing-Huang; Tian, Feng; Peng, Hai-Bo; Chen, Liang; Zhang, Li-Min; Yuan, Wei

    2015-07-01

    To study the room-temperature stable defects induced by electron irradiation, commercial borosilicate glasses were irradiated by 1.2 MeV electrons and then ultraviolet (UV) optical absorption (OA) spectra were measured. Two characteristic bands were revealed before irradiation, and they were attributed to silicon dangling bond (E’-center) and Fe3+ species, respectively. The existence of Fe3+ was confirmed by electron paramagnetic resonance (EPR) measurements. After irradiation, the absorption spectra revealed irradiation-induced changes, while the content of E’-center did not change in the deep ultraviolet (DUV) region. The slightly reduced OA spectra at 4.9 eV was supposed to transform Fe3+ species to Fe2+ species and this transformation leads to the appearance of 4.3 eV OA band. By calculating intensity variation, the transformation of Fe was estimated to be about 5% and the optical absorption cross section of Fe2+ species is calculated to be 2.2 times larger than that of Fe3+ species. Peroxy linkage (POL, ?Si–O–O–Si?), which results in a 3.7 eV OA band, is speculated not to be from Si–O bond break but from Si–O–B bond, Si–O–Al bond, or Si–O–Na bond break. The co-presence defect with POL is probably responsible for 2.9-eV OA band. Project supported by the Fundamental Research Funds for the Central Universities of China (Grant No. lzujbky-2014-16).

  10. Ultraviolet absorption and luminescence of matrix-isolated adenine

    SciTech Connect

    Polewski, K.; Sutherland, J.; Zinger, D.; Trunk, J.

    2011-10-01

    We have investigated the absorption, the fluorescence and phosphorescence emission and the fluorescence lifetimes of adenine in low-temperature argon and nitrogen matrices at 15 K. Compared to other environments the absorption spectrum shows higher intensity at the shortest wavelengths, and a weak apparent absorption peak is observed at 280 nm. The resolved fluorescence excitation spectrum has five peaks at positions corresponding to those observed in the absorption spectrum. The position of the fluorescence maximum depends on the excitation wavelength. Excitation below 220 nm displays a fluorescence maximum at 305 nm, while for excitations at higher wavelengths the maximum occurs at 335 nm. The results suggest that multiple-emission excited electronic states are populated in low-temperature gas matrices. Excitation at 265 nm produces a phosphorescence spectrum with a well-resolved vibrational structure and a maximum at 415 nm. The fluorescence decays corresponding to excitation at increasing energy of each resolved band could be fit with a double exponential, with the shorter and longer lifetimes ranging from 1.7 to 3.3 ns and from 12 to 23 ns, respectively. Only for the excitation at 180 nm one exponential is required, with the calculated lifetimes of 3.3 ns. The presented results provide an experimental evidence of the existence of multiple site-selected excited electronic states, and may help elucidate the possible deexcitation pathways of adenine. The additional application of synchrotron radiation proved to result in a significant enhancement of the resolution and spectral range of the phenomena under investigation.

  11. Study of Optical Absorption in Gamma Irradiated Glass for Radiation Dosimetry Purpose

    SciTech Connect

    Farah, K.; Mejri, A. [Laboratoire de Radiotraitement, Centre National des Sciences et Technologies Nucleaires. 2020 Sidi-Thabet (Tunisia); Ben Ouada, H. [Laboratoire de Physique et Chimie des Interfaces, Faculte des Sciences de Monastir, 5000 (Tunisia)

    2007-09-19

    Optical absorption investigation in a silicate glass before and after gamma irradiation was performed in the range 350-800 nm to study the induced colour centres to evaluate this potential as radiation-sensitive material for dose measurements. The radiation induced bands are observed around 410 and 600 nm leading. The intensities of the overall absorption spectra are observed to increase progressively with increasing doses between 1 and 1200 kGy. The influence of isothermal annealing on the formation and the decay of the induced colour centres has been investigated. The activation energy characteristic of the annealing process was calculated from Arrhenius equation. The obtained values are equal to 0.251 and 0.310 eV for the 410 nm band and 0.261 and 0.353 eV for the 600 nm one. The similarity of these values for both bands suggests that the related optical transitions correspond to the same type of Non-Bridging-Oxygen Hole Centres (NBOHCs): ({identical_to}Si-O deg.) in different configurations.

  12. Absorption and scattering in photo-thermo-refractive glass induced by UV-exposure and thermal development

    NASA Astrophysics Data System (ADS)

    Lumeau, Julien; Glebova, Larissa; Glebov, Leonid B.

    2014-01-01

    Photo-thermo-refractive (PTR) glass is a multicomponent photosensitive silicate glass that, after successive UV-exposure and thermal treatment, exhibits a refractive index change that results from the precipitation of nano-crystalline NaF. This glass is successfully used for the fabrication of holographic optical elements (volume Bragg gratings) that dramatically enhance properties of numerous laser systems and spectrometers. In this paper, induced absorption and scattering that determine efficiency of such elements were studied. It is found that the main contribution to induced absorption is produced by several types of silver containing particles having absorption bands with maxima in the blue-green region with exponential tails extending to the near IR spectral region. Evolution of all absorption bands was studied for different conditions of UV exposure and thermal development. Complex mechanisms of interconversion of silver containing particles is demonstrated as well as the fact that some of these particles can be associated with catalyzers of the nucleation process. It is also found that induced scattering obeys the classic Rayleigh law with an intensity depending on the conditions of UV exposure and thermal development. For short development times, scattering increases with dosage because of increased volume fraction of crystalline phase. For long development times, scattering decreases with dosage because of decreased size of individual crystals.

  13. Intermediate band solar cells

    Microsoft Academic Search

    Antonio Marti

    2010-01-01

    Intermediate band (IB)solar cells aim to exploit the energy of below bandgap energy photons in solar cells. They are based in a material that, in addition to the conventional conduction and valence bands, have an electronic band (named intermediate band) located inside the bandgap and separated from the conduction and valence band by a null density of states. The theoretical

  14. Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors

    SciTech Connect

    Dey, Anup, E-mail: a-dey2002@yahoo.com [Electronics and Communication Engineering Department, Kalyani Government Engineering College, Kalyani 741235 (India); Maiti, Biswajit [Physics Department, Kalyani Government Engineering College, Kalyani 741235 (India); Chanda, Debasree [Department of Engineering and Technological Studies, Kalyani University, Kalyani 741235 (India)

    2014-04-14

    A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k{sup ?}) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg{sub 1?x}Cd{sub x}Te, and In{sub 1?x}Ga{sub x}As{sub y}P{sub 1?y} lattice matched to InP, as example of III–V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

  15. Interpretation of preedge features in the Ti and S K-edge x-ray-absorption near-edge spectrain the layered disulfides TiS2 and TaS2

    NASA Astrophysics Data System (ADS)

    Wu, Z. Y.; Ouvrard, G.; Moreau, P.; Natoli, C. R.

    1997-04-01

    The electronic structure of the layered titanium and tantalum disulfides TiS2 and TaS2 is investigated by the experimental sulfur and titanium K-edge x-ray-absorption near-edge structures, full multiple-scattering theory, and tight-binding linear muffin-tin orbital band-structure method. Good agreement between experimental data and theoretical calculations is obtained, especially in preedge regions that are interpreted in terms of mixing between the central atom p and higher-neighboring metal d orbitals. The variation of width and intensity of the prepeak is associated with the occupation of the d band and linked with metal site symmetry.

  16. Single-crystal electronic absorption spectroscopy of synthetic chromium-, cobalt-, and vanadium-bearing pyropes at different temperatures and pressures

    Microsoft Academic Search

    M. N. Taran; K. Langer; C. A. Geiger

    2002-01-01

    Single crystals of synthetic vanadium-, chromium- and cobalt-bearing garnets, Pyr:V0.06, Pyr:V0.13, Pyr:Cr0.04, Pyr:Co0.10,\\u000a and Gt:Co3.00, and a natural vanadium-bearing grossular, Gross:V0.07 (Cr3+ ?1 under ambient conditions and at temperatures up to 600 K and pressures up to 8 GPa. The T and P behavior of the absorption band energies and intensities shows the following for the different transition metal-bearing garnets:

  17. J. Phys. B: At. Mol. Opt. Phys. 29 (1996) 26292643. Printed in the UK Measurement and modelling of intensity dependent

    E-print Network

    Huennekens, John

    1996-01-01

    showing intensity dependent absorption on the cesium D1 line. We compare these data with a three of intensity dependent absorption and transit relaxation on the cesium D1 line J Sagle, R K Namiotka and J 18 December 1995 Abstract. The intensity dependent absorption was measured on the D1 line (6S1/2 6P1

  18. Ice absorption toward background stars

    NASA Astrophysics Data System (ADS)

    Knez, Claudia; Boogert, A. C. Adwin; Pontoppidan, Klaus M.; Kessler-Silacci, Jacqueline; Evans, Neal J., II; Augereau, Jean-Charles; van Dishoeck, Ewine F.; Blake, Geoffrey A.; Brown, Joanna; Geers, Vincent; Jørgensen, Jes K.; Lahuis, Fred

    We present results of ice absorption between 5-20 ?m toward background stars as part of the Cores to Disks (c2d) Legacy program (Evans et al. 2003). Molecules such as H2O, CO2, HCOOH, NH3, CH3OH, and NH4+ have bands in this wavelength region. Absorption from H2O bands at 6 and 13 ?m is observed toward all sources. We detect strong CO2 absorption toward CK 2, a background star with high extinction in the Serpens dark cloud. The abundance of CO2 with respect to H2O is 30-40%, similar to what is observed toward protostars. Also, at 6.8 ?m, CK 2 shows a feature which may be due to NH4+ . Other sources with lower extinction, such as Elias 13 and Elias 16 in the Taurus dark cloud, do not show this feature. By probing different lines of sight, we can learn how ice composition varies with extinction. The abundances found toward background stars are then compared to abundances observed toward protosatars.

  19. Intermediate Band Properties of Femtosecond-Laser Hyperdoped Silicon

    E-print Network

    Mazur, Eric

    incorporation and the IB properties. First, we study dopant incorporation with a gas-phase dopant precursor (SF6 use Fourier transform infrared spectroscopy to study light iii #12;absorption. The absorption extends at concentrations below the insulator- to-metal transition. Using a two-band model, we obtain the location

  20. Perfect and broad absorption by the active control of electric resonance in metamaterial

    NASA Astrophysics Data System (ADS)

    Dung, N. V.; Tuong, P. V.; Yoo, Y. J.; Kim, Y. J.; Tung, B. S.; Lam, V. D.; Rhee, J. Y.; Kim, K. W.; Kim, Y. H.; Chen, L. Y.; Lee, Y. P.

    2015-04-01

    Anti-oscillating plasmas have been the key to perfect absorption induced by magnetic resonance. This is an achievement in recent research on metamaterials (MMs), especially in GHz and the lower-frequency regions of electromagnetic waves. Here, a comprehensive view of perfect absorption is introduced by means of both magnetic resonance and electric resonance in meta molecules. A conventional metal-dielectric-metal MM absorber is proposed to obtain dual-band perfect absorption. It is clarified that the mechanism of dual-band absorption is due to fundamental (at 7.2 GHz) and third-order (at 18.7 GHz) magnetic resonances. Finally, we develop triple-band absorption by integrating resistors in to the MM absorber. The electric resonance, under the presence of resistors, matches the impedance of the MM absorber with the air at 13 GHz and gives rise to the new absorption band, with absorption higher than 90%.

  1. Temperature Measurement of Liquids by Differential Absorption of Two Diode Lasers: Application of Contactless Optical Detection in Isotachophoresis

    Microsoft Academic Search

    B. Graß; R. Hergenröder; M. Bolshov; K. Niemax; A. Zybin; V. Krivtzun

    2001-01-01

    A modié cation of the wavelength modulation diode laser (DL) ab- sorption technique for detection of broad-band molecular absorp- tion lines is proposed. The method based on the detection of differ- ential absorption of two narrow-band DLs at specially selected wavelengths within the molecular absorption band enables the mea- surement of the temperature changes of a sample. These cause shifts

  2. Theoretical model of absorption of laser light by a plasma

    SciTech Connect

    Mora, P.

    1982-06-01

    A simple model of laser light absorption is described. The absorption mechanism is mainly inverse bremsstrahlung, but a crude description of resonance absorption is also included. The intensity and the wavelength dependence are emphasized, but the model takes into account the target material composition, the laser pulse length, and the focal spot radius. Plane and spherical expansion are treated. Results range from short-wavelength, low-intensity regime, where inverse bremsstrahlung absorption is total, to long-wavelength high-intensity regime, where inverse bremsstrahlung absorption is negligible. Scaling laws concerning absorption, electron temperature, and electron kinetic pressure are given in the two limiting regimes. A characteristic flux Phi(, or, alternatively, a characteristic wavelength lambda( is defined which separates the two regimes, the other parameters being held constant.

  3. Electromagnetically induced absorption via incoherent collisions

    SciTech Connect

    Yang Xihua [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States); Department of Physics, Shanghai University, Shanghai 200444 (China); Sheng Jiteng; Xiao Min [Department of Physics, University of Arkansas, Fayetteville, Arkansas 72701 (United States)

    2011-10-15

    We conduct theoretical studies on electromagnetically induced absorption via incoherent collisions in an inhomogeneously broadened ladder-type three-level system with the density-matrix approach. The effects of the collision-induced coherence decay rates as well as the probe laser field intensity on the probe field absorption are examined. It is shown that with the increase of the collisional decay rates in a moderate range, a narrow dip due to electromagnetically induced transparency superimposed on the Doppler-broadened absorption background can be turned into a narrow peak under the conditions that the probe field intensity is not very weak as compared to the pump field, which results from the enhancement of constructive interference and suppression of destructive interference between one-photon and multiphoton transition pathways. The physical origin of the collision-assisted electromagnetically induced absorption is analyzed with a power-series solution of the density-matrix equations.

  4. UV absorption cross sections for SO3

    Microsoft Academic Search

    James B. Burkholder; Stuart McKeen

    1997-01-01

    Room temperature gas phase absorption cross sections for SO3 have been measured over the wavelength range 195 to 330 nm using a diode array spectrometer. The SO3 spectrum is continuous with weak diffuse vibrational band structure in the 225 to 295 nm region. Atmospheric photolysis rate calculations show that photolysis of SO3 in the 190 to 230 nm actinic window

  5. Satellite Bands in the Emission Spectrum of Cesium

    Microsoft Academic Search

    Joel A. Gwinn; Paul M. Thomas; John F. Kielkopf

    1968-01-01

    Satellite bands near the atomic lines of the emission spectrum of cesium in the presence of heavy noble gases were observed and their positions measured. For the series which also appear in absorption, the measured positions of the band maxima are in general agreement with those previously reported. Several interesting regularities in the data are noted and a simple interpretation

  6. Measurement of Temperature and Absorptance for Laser Processing Applications

    Microsoft Academic Search

    S. Ramanathan; M. F. Modest

    1994-01-01

    The use of CO[sub 2] lasers has been successfully demonstrated for several manufacturing processes such as cutting, drilling, scribing, etc., of a wide range of materials. The absorptance of a material at the laser wavelength and at the material removal temperature substantially affect the efficiency of the laser machining process. Some materials have absorption bands in the mid-infrared and the

  7. Absorption properties of carbon black\\/silicon carbide microwave absorbers

    Microsoft Academic Search

    Xiangxuan Liu; Zeyang Zhang; Youpeng Wu

    2011-01-01

    An absorbing medium is prepared using nanosize carbon black (CB) blended with nanosize silicon carbide (SiC). The medium improves the wave absorption properties and the wave band of the single CB absorbent. The microstructure, conductivity, dielectric property, and microwave absorption of the material are studied by means of field emission scanning electron microscopy, trielectrode method, and vector network analyzer respectively.

  8. Characterization of the UV absorption feature in asteroid 1 Ceres

    Microsoft Academic Search

    Jian-Yang Li

    2007-01-01

    We propose to obtain the UV spectrum of asteroid 1 Ceres from 120 nm to 200 nm with ACS\\/SBC objective prism to characterize the broad and deep absorption feature within this wavelength range as reported by ACS observations of Ceres in 2003\\/04 Li et al. 2006. Our scientific goals include, 1 to characterize the absorption band, 2 to determine the

  9. Trimethylated chitosan as polymeric absorption enhancer for improved peroral delivery of peptide drugs

    Microsoft Academic Search

    S. M. van der Merwe; J. C. Verhoef; J. H. M. Verheijden; A. F. Kotzé; H. E. Junginger

    2004-01-01

    The absorption enhancing effects of chitosan and its derivatives have been intensively studied in recent years. It has been shown that these compounds are potent absorption enhancers. Chitosan is only soluble in acidic environments and is therefore incapable of enhancing absorption in the small intestine, the main absorption area in the gastrointestinal tract. Special emphasis has been placed on the

  10. Polarization control of intermediate state absorption in resonance-mediated multi-photon absorption process

    NASA Astrophysics Data System (ADS)

    Xu, Shuwu; Huang, Yunxia; Yao, Yunhua; Jia, Tianqing; Ding, Jingxin; Zhang, Shian; Sun, Zhenrong

    2015-07-01

    We theoretically and experimentally demonstrate the control of the intermediate state absorption in an (n + m) resonance-mediated multi-photon absorption process by the polarization-modulated femtosecond laser pulse. An analytical solution of the intermediate state absorption in a resonance-mediated multi-photon absorption process is obtained based on the time-dependent perturbation theory. Our theoretical results show that the control efficiency of the intermediate state absorption by the polarization modulation is independent of the laser intensity when the transition from the intermediate state to the final state is coupled by the single-photon absorption, but will be affected by the laser intensity when this transition is coupled by the non-resonant multi-photon absorption. These theoretical results are experimentally confirmed via a two-photon fluorescence control in (2 + 1) resonance-mediated three-photon absorption of Coumarin 480 dye and a single-photon fluorescence control in (1 + 2) resonance-mediated three-photon absorption of IR 125 dye.

  11. Parameterization of near infrared absorption by atmospheric gases

    NASA Technical Reports Server (NTRS)

    Ridgway, W. L.; Arking, A.

    1986-01-01

    An absorption coefficient (k) distribution model is presented for fast calculation of atmospheric transmittances based solely on essential data from line-by-line (LBL) calculations. The absorption at any site is summed over the spectra obtained by LBL calculations. Application of the scaling model is illustrated with sample calculations for 0.72 micron emissions and the 1.36 micron water vapor band. LBL absorption spectra are calculated for the pressure levels 260 mb, 400 mb and 1000 mb.

  12. Electronic absorption spectra of heterocyclic analogs of trans-chalcone

    Microsoft Academic Search

    M. Reinkhardt; A. A. Sukhorukov; V. F. Lavrushin

    1977-01-01

    Thiophene, furan, and pyrrole analogs of trans-chalcone have UV spectra consisting of bands belonging to the spectra of the corresponding 2-acetylhetaryls and 2-hetarylideneacetones that are shifted bathochromically as a result of mutual perturbation of these two crossconjugated fragments. The absorption curves of 10 chalcones in hexane solution were measured up to 190 nm, the bands of the individual transitions were

  13. UV/VUV high sensitivity absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Goyette, A. N.; Anderson, L. W.; Mullman, K. L.; Lawler, J. E.

    1998-09-01

    High sensitivity absorption spectroscopy is a powerful diagnostic technique for reactive glow discharges plasmas. Absolute column densities of many chemical radicals have been measured in both deposition and etching plasmas. Modern photodiode or charge-coupled device (CCD) detector arrays vastly increase the sensitivity of traditional absorption experiments enabling one to observe fractional absorptions of ultraviolet (UV) and vacuum ultraviolet (VUV) radiation less than 0.0001. Stable arc lamps provide a continuum source in some experiments, but experiments at very high spectral resolution or at VUV wavelengths require the greater spectral radiance of synchrotron radiation. High sensitivity absorption spectroscopy has been applied to intense glow discharges used for lighting, for diamond film deposition, and for both depositing and etching Si films. Absorption spectroscopy provides absolute column densities, is useful for transitions that do not fluoresce, and approaches the sensitivity of laser-induced fluorescence (LIF) in glow discharges under some conditions.

  14. The Effects of Light Intensity and Spectral Quality on Growth and Shoot Initiation in Tobacco Callus

    PubMed Central

    Seibert, Michael; Wetherbee, Phyllis J.; Job, Donald D.

    1975-01-01

    The effects of eight different narrow band-emitting fluorescent lamps (371-750 nm) and four commercial broad band-emitting fluorescent sources upon growth and shoot initiation in tobacco callus (Nicotiana tabacum var. Wisconsin 38) have been characterized. Wavelength and intensity are equally important parameters in determining morphogenic changes. Near ultraviolet light (371 nm) was found to stimulate (0.024 mw/cm2) or inhibit (above 0.15 mw/cm2) callus growth and shoot initiation, depending on the light intensity. Stimulation of growth and shoot production occurs also in blue light region, but at higher intensity than in the near ultraviolet. Red and far red light (up to 1.7 mw/cm2) do not appear to affect callus growth or stimulate shoot initiation. The enhancement of callus growth and the stimulation of shoot initiation are controlled by the same near ultraviolet-absorbing photoreceptor system present in a small enough concentration that it cannot be recognized in the absorption spectrum of the intact tissue. Carotenoids, porphyrins, and phytochrome associated with the high irradiance response do not appear to qualify as the photoreceptor. Flavonoids are possible candidates. Radiation emitted by fluorescent lamps outside the near visible region was determined, and we concluded that energy levels were not sufficient to affect the reported results. The spectral output of several commercial lamps in the visible and near visible regions is such that there could be different effects on growth and development of tissue cultures. Images PMID:16659243

  15. Temperature dependence of C-terminal carboxylic group IR absorptions in the amide I? region

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin A.; Literati, Alex; Ball, Borden; Kubelka, Jan

    2015-01-01

    Studies of structural changes in peptides and proteins using IR spectroscopy often rely on subtle changes in the amide I? band as a function of temperature. However, these changes can be obscured by the overlap with other absorptions, namely the side-chain and terminal carboxylic groups. The former were the subject of our previous report (Anderson et al., 2014). In this paper we investigate the IR spectra of the asymmetric stretch of ?-carboxylic groups for amino acids representing all major types (Gly, Ala, Val, Leu, Ser, Thr, Asp, Glu, Lys, Asn, His, Trp, Pro) as well as the C-terminal groups of three dipeptides (Gly-Gly, Gly-Ala, Ala-Gly) in D2O at neutral pH. Experimental temperature dependent IR spectra were analyzed by fitting of both symmetric and asymmetric pseudo-Voigt functions. Qualitatively the spectra exhibit shifts to higher frequency, loss in intensity and narrowing with increased temperature, similar to that observed previously for the side-chain carboxylic groups of Asp. The observed dependence of the band parameters (frequency, intensity, width and shape) on temperature is in all cases linear: simple linear regression is therefore used to describe the spectral changes. The spectral parameters vary between individual amino acids and show systematic differences between the free amino acids and dipeptides, particularly in the absolute peak frequencies, but the temperature variations are comparable. The relative variations between the dipeptide spectral parameters are most sensitive to the C-terminal amino acid, and follow the trends observed in the free amino acid spectra. General rules for modeling the ?-carboxylic IR absorption bands in peptides and proteins as the function of temperature are proposed.

  16. Calibration-free self-absorption model for measuring nitric oxide concentration in a pulsed corona discharge.

    PubMed

    Du, Yanjun; Ding, Yanjun; Liu, Yufeng; Lan, Lijuan; Peng, Zhimin

    2014-08-01

    The effect of self-absorption on emission intensity distributions can be used for species concentration measurements. A calculation model is developed based on the Beer-Lambert law to quantify this effect. And then, a calibration-free measurement method is proposed on the basis of this model by establishing the relationship between gas concentration and absorption strength. The effect of collision parameters and rotational temperature on the method is also discussed. The proposed method is verified by investigating the nitric oxide emission bands (A²???X²?) that are generated by a pulsed corona discharge at various gas concentrations. Experiment results coincide well with the expectations, thus confirming the precision and accuracy of the proposed measurement method. PMID:25090323

  17. An analysis of temperature-dependent absorption and photocurrent spectra in BaAl2Se4 layers

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    The temperature-dependent photoresponse behavior of BaAl2Se4 layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by Eg(T) = Eg(0) - 4.39 × 10-4T2/(T + 250), where Eg(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states ?3(A), ?4(B), and ?5(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of ?3(A), ?4(B), and ?5(C) to the conduction band state of ?1, respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log Jph versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds to the activation energy for the electronic transition from the shallow donor levels to the edge of the conduction band. It is estimated that the decrease in the PC intensity is caused by trapping centers related to native defects in the BaAl2Se4 layers. Consequently, this trap level limited the PC intensity with decreasing temperature.

  18. Complete decay out of the superdeformed band in [sup 133]Nd

    SciTech Connect

    Bazzacco, D.; Brandolini, F.; Burch, R.; Lunardi, S.; Maglione, E.; Medina, N.H.; Pavan, P.; Rossi-Alvarez, C. (Dipartimento di Fisica and INFN, Sezione di Padova, Padova (Italy)); de Angelis, G.; De Acuna, D.; De Poli, M.; Rico, J. (INFN, Laboratori Nazionali di Legnaro, Legnaro (Italy)); Bucurescu, D.; Ur, C. (Institute of Physics and Nuclear Engineering, Bucharest (Romania))

    1994-05-01

    Ten transitions linking the superdeformed band to the normal deformed states have been identified in [sup 133]Nd. These transitions drain the full band intensity into the different band structures established at lower spin. The major part of the decay out of the superdeformed band is understood in terms of mixing of levels which involve orbitals differing by two major oscillator quantum numbers.

  19. X-ray absorption spectroscopy of photoionised plasmas at Z

    NASA Astrophysics Data System (ADS)

    Mancini, R. C.

    2011-06-01

    Photoionised plasmas are found in astrophysical environments such as x-ray binaries, active galactic nuclei, and in the accretion disks of compact objects. The Z facility at Sandia National Laboratories is a powerful source of x-rays that enables us to produce and study in the laboratory photoionised plasmas relevant for astrophysics under well characterized conditions. We discuss an experimental and theory/modeling effort in which the intense x-ray flux emitted at the collapse of a z-pinch experiment conducted at Z is employed to produce a neon photoionized plasma. The broad-band x-ray radiation flux from the z-pinch is used to both create the neon photoionised plasma and provide a source of backlighting photons to study the atomic kinetics through K-shell line absorption spectroscopy. The plasma is contained in a cm-scale gas cell located at about 5 cm from the z-pinch, and the filling pressure is carefully monitored all the way to shot time since it determines the particle number density of the plasma. Time-integrated and gated transmission spectra are recorded with a TREX spectrometer equipped with two elliptically-bent crystals and a set of slits to record up to six spatially-resolved spectra per crystal in the same shot. The spectral resolution is approximately 1000. The transmission data shows line absorption transitions in several ionization stages of neon including Be-, Li-, He- and H-like Ne ions. Detailed modeling calculations of the absorption spectra are used to interpret and model the high-resolution transmission spectra recorded in the Z experiments with the goal of extracting the ion population distribution of the plasma. Furthermore, the analysis of the gated data provides a window into the dynamics of the photoionized plasma. The data analysis is performed with the aid of a novel application of genetic algorithms to plasma spectroscopy.

  20. Influence of Duschinsky and Herzberg-Teller effects on S0 ? S1 vibrationally resolved absorption spectra of several porphyrin-like compounds

    NASA Astrophysics Data System (ADS)

    Yang, Pan; Qi, Dan; You, Guojian; Shen, Wei; Li, Ming; He, Rongxing

    2014-09-01

    The S0 ? S1 (Q band) high-resolved absorption spectra of three porphyrin-like compounds, porphycene, magnesium porphyrin, and zinc tetraazaporphyrin, were simulated in the framework of the Franck-Condon approximation including the Duschinsky and Herzberg-Teller (HT) contributions. Substitution of meso-aza on porphyrin macrocycle framework could change severely the absorption energy, vibrational intensity, and spectral profile of Q band. Therefore, we focused attention on the spectral similarities and contrasts among the three compounds based on the density functional theory and its time-dependent extension calculations. The simulated spectra agreed well with the experimental ones and further confirmed that the HT and Duschinsky effects have significant influence on the weakly allowed or forbidden transition of sizable organic molecules. The pure HT and Duschinsky effects were explored separately to clarify their contributions on changing vibrational intensities of different modes. Moreover, we tentatively assigned most of the vibrational modes which appeared in the experimental spectra but corresponding assignments were not given. The present work provided a useful method to simulate and interpret the absorption spectra of porphyrin-like compounds.

  1. Lap Band® adjustable gastric banding system

    Microsoft Academic Search

    L. Angrisani; F. Furbetta; S. B. Doldi; N. Basso; M. Lucchese; F. Giacomelli; M. Zappa; L. Cosmo; A. Veneziani; G. U. Turicchia; M. Alkilani; P. Forestieri; G. Lesti; F. Puglisi; M. Toppino; F. Campanile; F. D. Capizzi; C. D'Atri; L. Sciptoni; C. Giardiello; N. Lorenzo; S. Lacitignola; N. Belvederesi; B. Marzano; P. Bernate; A. Iuppa; V. Borrelli; M. Lorenzo

    2003-01-01

    Background: The Lap Band system procedure is currently the most common bariatric surgical procedure worldwide. This is an interim report of the experience of the 27 Italian centers participating in the national collaborative study group for Lap Band® (GILB). Methods: An electronic database was specifically created. It was mailed and e-mailed to all of the surgeons now performing the laparoscopic

  2. Transient picosecond studies of singlet fission in PDTP-DFBT low band gap polymer

    NASA Astrophysics Data System (ADS)

    Huynh, Uyen; Vardeny, Valy; Li, Gang; Yang, Yang

    2014-03-01

    We measured picoseconds transient mid-IR photoinduced absorption (PA) spectra in PDTP-DFBT low band-gap polymer. With 800 nm pumping the PA spectrum at t =0 in pristine film and isolated polymer chain in polystyrene shows two prominent PA bands: PA1 at 0.4eV and Pa2 at 0.8eV. PA1 is assigned to absorption from singlet excitons (transition from 1Bu to mAg) , whereas PA2 is due to a state of triplet-pair, which is formed via singlet fission in the sub-ps time domain. We found that PA2 lifetime strongly depends on the excitation intensity, showing non linear recombination process in both pristine film and in polystyrene. We also found that the triplet-pair recombines with no trace of fusion back to the singlet exciton; we thus conclude that singlet fission is an exothermic process in this polymer. We therefore do not find any magnetic field effect on the transient dynamics of the triplet-pair within our experimental sensitivity (0.2%). Supported by DOE and NSF-MRSEC.

  3. Design of resonant-cavity-enhanced multi-band photodetectors

    NASA Astrophysics Data System (ADS)

    Lao, Yan-Feng; Ariyawansa, Gamini; Unil Perera, A. G.

    2011-08-01

    A theoretical analysis to improve the quantum efficiency of detectors sensing in multiple spectral bands is presented. The effective coupling between the incoming light and multiple absorbing regions for simultaneously improving the multi-band absorption efficiency is obtained by using resonant-cavity structures. An optimized cavity with only a Au bottom reflector gives rise to an enhancement factor of 11 in absorption compared to the conventional detector without the cavity. Further improvement, by a factor of 26, can be attained with the aid of a dual-band Bragg reflector placed at the top. The resulting multi-band resonant-cavity detector increases the response in three out of four detection bands contributing to the spectral range from visible to long-wave infrared (IR). The optimized detector is capable of serving multiple purposes, such as regular IR detection for atmospheric windows, gas sensing, and for optical communications.

  4. Infrared Absorptions of Interstitial Hydrogen Atoms in Solid Argon and Krypton

    Microsoft Academic Search

    Vladimir E. Bondybey; George C. Pimentel

    1972-01-01

    Infrared absorptions are reported in the spectra of inert gas-hydrogen matrix samples which were deposited after the gas mixture passed through a glow discharge. For hydrogen in argon, absorption is recorded at 905 cm?1. This band shifts to 644 cm?1 for deuterium in argon and no new bands are observed with hydrogen-deuterium mixtures. With krypton matrix, similar absorptions are observed

  5. 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. PMID:23816486

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

    NASA Astrophysics Data System (ADS)

    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+, Pb2+, Zn2+ 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 Pb2+, and Zn2+ 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.

  7. Absorption spectra of gamma-irradiation TM-doped cabal glasses

    Microsoft Academic Search

    Samir Y. Marzouk; Fatma H. Elbatal; A. M. Salem; S. M. Abo-Naf

    2007-01-01

    The UV visible absorption spectra of nominally pure and transition metals-doped (Ti --> Cu 0.1%) cabal glasses were measured from 200 to 1000 nm before and after successive gamma irradiation. The absorption spectra of the undoped glass exhibit charge transfer bands due to iron trace impurities which eventually affect the induced absorption due to some transition metals and that due

  8. Intracavity Dye-Laser Absorption Spectroscopy (IDLAS) for application to planetary molecules

    NASA Technical Reports Server (NTRS)

    Lang, Todd M.; Allen, John E., Jr.

    1990-01-01

    Time-resolved, quasi-continuous wave, intracavity dye-laser absorption spectroscopy is applied to the investigation of absolute absorption coefficients for vibrational-rotational overtone bands of water at visible wavelengths. Emphasis is placed on critical factors affecting detection sensitivity and data analysis. Typical generation-time dependent absorption spectra are given.

  9. Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption

    E-print Network

    Javey, Ali

    Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption Zhiyong Fan,,,§ Rehan control to achieve the optimal absorption efficiency. Increasing the Ge materials filling ratio is shown a strong diameter dependency. To enhance the broad band optical absorption efficiency, a novel dual

  10. Mid-infrared FEL absorption spectra

    Microsoft Academic Search

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

    2002-01-01

    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,

  11. The Noisiness of Low Frequency Bands of Noise

    NASA Technical Reports Server (NTRS)

    Lawton, B. W.

    1975-01-01

    The relative noisiness of low frequency 1/3-octave bands of noise was examined. The frequency range investigated was bounded by the bands centered at 25 and 200 Hz, with intensities ranging from 50 to 95 db (SPL). Thirty-two subjects used a method of adjustment technique, producing comparison band intensities as noisy as 100 and 200 Hz standard bands at 60 and 72 db. The work resulted in contours of equal noisiness for 1/3-octave bands, ranging in intensity from approximately 58 to 86 db (SPL). These contours were compared with the standard equal noisiness contours; in the region of overlap, between 50 and 200 Hz, the agreement was good.

  12. Vibrational overtone spectroscopy, energy levels, and intensities of (CH3)3C-C?C-H.

    PubMed

    Perez-Delgado, Yasnahir; Barroso, Jenny Z; Garofalo, Lauren A; Manzanares, Carlos E

    2012-03-01

    The vibrational overtone spectra of the acetylenic (?? = 4, 5) and methyl (?? = 5, 6) C-H stretch transitions of tert-butyl acetylene [(CH(3))(3)C-C?C-H] were obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The C-H stretch fundamental and overtone absorptions of the acetylenic (?? = 2 and 3) and methyl (?? = 2-4) C-H bonds have been obtained using a Fourier transform infrared and near-infrared spectrophotometer. Harmonic frequency ?(?(1)) and anharmonicities x(?(1)) and x(?(1), ?(24)) are reported for the acetylenic C-H bond. Molecular orbital calculations of geometry and vibrational frequencies were performed. A harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. Band strength values were obtained experimentally and compared with intensities calculated in terms of the HCAO model where only the C-H modes are considered. No adjustable parameters were used to get order of magnitude agreement with experimental intensities for all pure local mode C-H transitions. PMID:22263573

  13. Multiplex-bands spectral characteristics of infrared perfect absorber metamaterials

    NASA Astrophysics Data System (ADS)

    Li, Yongqian; Su, Lei; Wang, Binbin; Guo, Yongjun; Zhu, Zhenyu; Zhou, Zili

    2013-09-01

    The multiplex-bands absorption of sandwich-structure metamaterials based metal- dielectric- metal scheme are investigated numerically and experimentally. The optical properties of cross-shape antenna perfect absorber metamaterials are demonstrated in mid-IR electromagnetic (EM) wave. The dual-band perfect absorber with polarization independence is observed under normal incidence. In order to understand the EM properties of dual-band perfect absorber, the plasmonic excitation and the induced current distribution were clarified for both peaks. The simulation results clearly show that the absorption bands are independently governed by the size of each part of the patterned nanostructure. The repositioning of two near-perfect absorption peaks possesses a linear relationship. This allows for a flexible reconfigurability over the entire near-infrared regime. Furthermore, in order to obtain multiplex-bands spectral absorption response, two cross-shape antennas are connected to form one dumbbell antenna. The three perfect-absorption peaks can be controlled by the individual dipole antenna elements in the conditions of polarization incident EM wave.

  14. Resonance in scattering and absorption from large noble gas clusters.

    PubMed

    Zweiback, J S; Ditmire, T; Perry, M

    2000-06-01

    Light scattering in large noble gas clusters irradiated by intense laser pulses was studied and compared to absorption measurements. The scattering signal shows the presence of a peak, when the pulse width was varied, similar to one previously reported in absorption measurements. The peak of the scattering, however, occurs at a longer pulse width than for absorption. This result disagrees with a simple simulation and may be due to propagation or non-linear effects not included in the model. PMID:19404356

  15. Focused optical and acoustic beams in media with nonlinear absorption

    Microsoft Academic Search

    O. V. Rudenko; A. A. Sukhorukov

    1996-01-01

    Optical and acoustic beams are known to be useful for medical and biological applications, such as diagnostics, surgery, etc. At high intensities both nonlinear lens effects and nonlinear absorption can be significant for the beams. The nonlinear absorption arises due to two-photon optical processes or acoustic shock wave formation. The present work is devoted to the theoretical description of nonlinear

  16. Spectral dependence of aerosol light absorption over the Amazon Basin

    Microsoft Academic Search

    L. V. Rizzo; A. L. Correia; P. Artaxo; A. S. Procópio; M. O. Andreae

    2011-01-01

    In this study, we examine the spectral dependence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pasture site (Fazenda Nossa Senhora, Rondônia) and at a primary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two

  17. Optical absorption and luminescence of LiTaO3:Cr and LiTaO3:Cr,Nd crystals

    NASA Astrophysics Data System (ADS)

    Golab, Stanislaw; Sokolska, I.; Dominiak-Dzik, Grazyna; Palatnikov, M. N.; Sidorov, N. V.; Biryukova, I.; Kalinnikov, V. T.; Ryba-Romanowski, Witold

    1999-03-01

    In this work we investigate spectroscopic properties of Cr3+ and Cr3+ - Nd3+ interaction in LiTaO3 using optical absorption, luminescence and luminescence decay times at temperatures between 5 K and 300 K. Some preliminary data obtained with singly doped LiTaO3:Cr at low activator concentration are given in our previous work. Recorded spectra indicate that both the Cr3+ and Nd3+ are located in several non- equivalent sites which differ in the strength of the crystal field. Luminescence spectrum of Cr3+ consists of a broad band whose maximum and intensity depend on temperature. Below about 50 K an additional sharp band with four distinct components appears in the spectrum. The broad band attributed to the spin allowed 4T2 - 4A2 transition of Cr3+ ions overlaps two absorption bands of Nd3+ ions at about 810 nm and 890 nm making the Cr3+ - Nd3+ energy transfer process feasible. Results of measurements are discussed and compared to those obtained with LiNbO3:Cr.

  18. Rubber Band Racers

    NSDL National Science Digital Library

    2013-08-30

    In this activity, learners explore the design of rubber band powered cars. Learners work in teams of "engineers" to design and build their own rubber band cars out of everyday items. They test their rubber band cars, evaluate their results, and present to the group.

  19. Detection of metal vapour in the high-current phase of a pseudospark switch by resonance absorption of laser light

    NASA Astrophysics Data System (ADS)

    Lins, Günter; Verleger, Jobst

    1996-03-01

    The electron emission mechanism which is active at the cathode of a pseudospark switch leads to thermal overloading of emission sites followed by the evaporation of cathode material. As a consequence, metal vapour should be present very shortly after the beginning of current flow. However, it has never been possible to observe metal vapour by laser-induced fluorescence (LIF) prior to the cessation of current. In the present work resonance absorption of laser light was used to detect molybdenum vapour from the cathode during the high-current phase of a pseudospark switch. To observe the narrow-band absorption the laser light which had passed the switch was introduced into a molybdenum hollow cathode lamp where it caused fluorescence from molybdenum vapour. The intensity of the fluorescence light from the hollow cathode lamp was proportional to the intensity of the laser light left after the absorption process in the pseudospark. For a current amplitude of 12 kA and a pulse duration of 0022-3727/29/3/040/img1, it is shown that molybdenum vapour is definitely present shortly after the current maximum, well before the current stops flowing. The neutral vapour density in the high-current phase is estimated to amount to at least 0022-3727/29/3/040/img2. It is concluded that LIF fails to detect metal vapour prior to the cessation of current, mainly because the fluorescence process is severely disturbed by electronic collisions which deplete the upper fluorescence level.

  20. Compatibility of infrared band models with scattering

    Microsoft Academic Search

    R. A. Reed; D. G. Brown; R. S. Hiers III; B. K. Cromwell; V. A. Zaccardi

    1994-01-01

    Techniques for the computation of radiative heating from aluminized solid propellant rocket exhaust plumes must account for infrared emission and absorption by hot H2O and CO2 in the presence of strong three-dimensional aerosol scattering by micron-sized Al2O3 droplets and particles. Radiative heating computations are usually performed over wide spectral intervals using infrared band models. However, no rigorous extension to infrared

  1. D-xylose absorption

    MedlinePLUS

    D-xylose absorption is a laboratory test to determine how well the intestines absorb a simple sugar (D-xylose). The test ... test is primarily used to determine if nutrient absorption problems are due to a disease of the ...

  2. Ultrathin flexible dual band terahertz absorber

    NASA Astrophysics Data System (ADS)

    Shan, Yan; Chen, Lin; Shi, Cheng; Cheng, Zhaoxiang; Zang, Xiaofei; Xu, Boqing; Zhu, Yiming

    2015-09-01

    We propose an ultrathin and flexible dual band absorber operated at terahertz frequencies based on metamaterial. The metamaterial structure consists of periodical split ring resonators with two asymmetric gaps and a metallic ground plane, separated by a thin-flexible dielectric spacer. Particularly, the dielectric spacer is a free-standing polyimide film with thickness of 25 ?m, resulting in highly flexible for our absorber and making it promising for non-planar applications such as micro-bolometers and stealth aircraft. Experimental results show that the absorber has two resonant absorption frequencies (0.41 THz and 0.75 THz) with absorption rates 92.2% and 97.4%, respectively. The resonances at the absorption frequencies come from normal dipole resonance and high-order dipole resonance which is inaccessible in the symmetrical structure. Multiple reflection interference theory is used to analyze the mechanism of the absorber and the results are in good agreement with simulated and experimental results. Furthermore, the absorption properties are studied under various spacer thicknesses. This kind of metamaterial absorber is insensitive to polarization, has high absorption rates (over 90%) with wide incident angles range from 0° to 45° and the absorption rates are also above 90% when wrapping it to a curved surface.

  3. HII Absorption Bill Erickson

    E-print Network

    Ellingson, Steven W.

    HII Absorption Bill Erickson November 10, 2006 It would make all of the drift curve simulations.8 dB above the data. One reason for this might be HII absorption which is not modeled in simulations. There are a number of ways that one might try to estimate the absorption. One might use optical maps of HII

  4. Deep-UV absorption study of nonlinear optical crystal KBe2BO3F2

    NASA Astrophysics Data System (ADS)

    Wang, Xiaolong; Liu, Lijuan; Xu, Bo; Wang, Xiaoyang; Chen, Chuangtian

    2014-10-01

    KBe2BO3F2 (KBBF) crystals have some extrinsic absorption in the deep-UV region around 150-160 nm and the reason was unknown. In this paper, undoped KBBF and Cu2+-doped KBBF crystals were grown for the investigation of the extrinsic deep-UV absorption behaviors. The samples were characterized by the transmission spectra, electron paramagnetic resonance (EPR) and photoluminescence spectra (PL). The impurity contents were measured by the inductively coupled plasma-atomic emission spectrometry (ICP-AES). Transmission spectra showed a red shift of about 5 nm in Cu2+-doped KBBF crystals compared with undoped ones. EPR signals only occurred in the spectra of Cu2+-doped KBBF crystals. Photoluminescence spectra showed emission bands at 416 nm and 441 nm which were identified as emission of Cu2+ions with an excitation wavelength of 380 nm. The fluorescence intensity of the Cu2+-doped samples is about 3-4 times higher than that of undoped ones. The above results reveal that Cu2+ ions are possible to enter into the crystal lattice and cause the deep-UV absorption.

  5. The optical band gap and surface free energy of polyethylene modified by electron beam irradiations

    NASA Astrophysics Data System (ADS)

    Abdul-Kader, A. M.

    2013-04-01

    In this study, investigations have been carried out on electron beam irradiated ultra high molecular weight polyethylene (UHMWPE). Polyethylene samples were irradiated with 1.5 MeV electron beam at doses ranging from 50 to 500 kGy. Modifications in optical properties and photoluminescence behavior of the polymer were evaluated by UV-vis and photoluminescence techniques. Changes of surface layer composition of UHMWPE produced by electron irradiations were studied by Rutherford back scattering spectrometry (RBS). The change in wettability and surface free energy induced by irradiations was also investigated. The optical absorption studies reveal that both optical band gap and Urbach's energy decreases with increasing electron dose. A correlation between energy gap and the number of carbon atoms in clusters is discussed. Photoluminescence spectra were reveal remarkable decrease in the integrated luminescence intensity with increasing irradiation dose. Contact angle measurements showed that wettability and surface free energy increases with increasing the irradiation dose.

  6. Dual-band optics

    NASA Astrophysics Data System (ADS)

    Nevo, Yitzhak

    2013-05-01

    A dual-band optics design for disjoint spectral bands and for a cooled FPA sensor, sensitive to both bands, is presented. The use of special optical splitting mechanisms enables matching the optical paths of both bands to the same sensor. Reasonable optical performance and good registration were achieved for dual bands such as 8 to 12 ?m together with 3.6 to 4.2 ?m, and for the 3.6 to 4.2 ?m band with various monochromatic laser bands in the 1.06 to 1.8 ?m spectral range. Regular IR materials were used with aspheric and diffractive surfaces. Both single-objective designs and zoomed-objective designs are presented.

  7. Band-selective radiofrequency pulses

    NASA Astrophysics Data System (ADS)

    Geen, Helen; Freeman, Ray

    A theoretical treatment is given of the general problem of designing amplitude-modulated radiofrequency pulses that will excite a specified band of frequencies within a high-resolution NMR spectrum with uniform intensity and phase but with negligible excitation elsewhere. First a trial pulse envelope is defined in terms of a finite Fourier series and its frequency-domain profile calculated through the Bloch equations. The result is compared with the desired target profile to give a multidimensional error surface. The method of simulated annealing is then used to find the global minimum on this surface and the result refined by standard gradient-descent optimization. In this manner, a family of new shaped radio-frequency pulses, known as BURP ( band-selective, uniform response, pure-phase) pulses, has been created. These are of two classes—pulses that excite or invert z magnetization and those that act as general-rotation ?r/2 or ? pulses irrespective of the initial condition of the nuclear magnetization. It was found convenient to design the latter class as amplitude-modulated time-symmetric pulses. Tables of Fourier coefficients and pulse-shape ordinates are given for practical implementation of BURP pulses, together with the calculated frequency-domain responses and experimental verifications. Examples of the application of band-selective pulses in conventional and multidimensional spectroscopy are given. Pure-phase pulses of this type should also find applications in magnetic resonance imaging where refocusing schemes are undesirable.

  8. Impact of atmospheric molecular absorption on the temporal and spatial evolution of ultra-short optical pulses.

    PubMed

    Gebhardt, Martin; Gaida, Christian; Stutzki, Fabian; Hädrich, Steffen; Jauregui, Cesar; Limpert, Jens; Tünnermann, Andreas

    2015-06-01

    We present a rigorous study on the impact of atmospheric molecular absorption on the linear propagation of ultrashort pulses in the mid-infrared wavelength region. An ultrafast thulium-based fiber laser was employed to experimentally investigate ultrashort-pulse propagation through the atmosphere in a spectral region containing several strong molecular absorption lines. The atmospheric absorption profile causes a significant degradation of the pulse quality in the time domain as well as a distortion of the transverse beam profile in the spatial domain. Numerical simulations carried out in the small signal limit accurately reproduce the experimental observations in the time domain and reveal that the relative loss in peak power after propagation can be more than twice as high as the relative amount of absorbed average power. Although their nature is purely linear (i.e. the intensities considered are sufficiently low) the discussed effects represent significant challenges to performance-scaling of mid-infrared ultrafast lasers operating in spectral regions with molecular absorption bands. Guidelines for an efficient mitigation of the pulse quality degradation and the beam profile distortion are discussed. PMID:26072749

  9. The interstellar 4.62 micron band

    NASA Technical Reports Server (NTRS)

    Pendleton, Y. J.; Tielens, A. G.; Tokunaga, A. T.; Bernstein, M. P.

    1999-01-01

    We present new 4.5-5.1 micron (2210-1970 cm-1) spectra of embedded protostars, W33 A, AFGL 961 E, AFGL 2136, NGC 7538 IRS 9, and Mon R2 IRS 2, which contain a broad absorption feature located near 4.62 micron (2165 cm-1), commonly referred to in the literature as the "X-C triple bond N" band. The observed peak positions and widths of the interstellar band agree to within 2.5 cm-1 and 5 cm-1, respectively. The strengths of the interstellar 4.62 micrometers band and the ice absorption features in these spectra are not correlated, which suggests a diversity of environmental conditions for the ices we are observing. We explore several possible carriers of the interstellar band and review possible production pathways through far-ultraviolet photolysis (FUV), ion bombardment of interstellar ice analog mixtures, and acid-base reactions. Good fits to the interstellar spectra are obtained with an organic residue produced through ion bombardment of nitrogen-containing ices or with the OCN- ion produced either through acid-base reactions or FUV photolysis of NH3-containing ices.

  10. Effect of electrolytes and temperature on dications and radical cations of carotenoids: Electrochemical, optical absorption, and high-performance liquid chromatography studies

    SciTech Connect

    He, Z.; Kispert, L.D.

    1999-11-25

    The effect of supporting electrolytes and temperature on the behavior of dications and radical cations of carotenoids is studied. Cyclic voltammograms (CVs) of canthaxanthin (I) at 23 and {minus}25 C show that Car{sup sm{underscore}bullet+} of I has similar stability during the time of the CV scan, when using tetrabutylammonium perchlorate (TBAPC), tetrabutylammonium tetrafluoroborate (TBATFB), or tetrabutylammonium hexafluorophosphate (TBAHFP) as supporting electrolyte. However, the stability of Car{sup 2+} decreases when using TBAPC or TBATFB; {beta}-carotene (II) shows similar behavior. The CV of I at {minus}25 C shows a strong cathodic wave (wave 6) near {minus}0.15 V (vs Ag) with an intensity about half that of the neutral oxidation wave when TBAPC or TBATFB is the supporting electrolyte. When TBAHFP is used, wave 6 (ca. {minus}0.05 V vs Ag) is ca. 8 times weaker than when TBAPC or TBATFB is used. This wave results from the reduction of a species that may be a decay product of Car{sup 2+} of I. Results show that these electrolytes commonly used in electrochemical studies may affect the studied systems to different extents. In simultaneous bulk electrolysis (BE) and optical absorption spectroscopic measurements, the absorption band of Car{sup 2+} of I in the presence of 0.1 M TBAHFP can be observed by lowering the BE temperature to {minus}20 C. In the presence of 0.1 M TBAPC or TBATFB, this band is not observed, even at {minus}50 C. Isomerization of neutral I (as shown by HPLC and its blue absorption band shift) is observed only when the Car{sup 2+} absorption band is absent during BE. This observation, along with an increase of the neutral absorption band after stopping BE, suggests that the equilibrium Car + Car{sup 2+} {r{underscore}equilibrium} 2Car{sup {sm{underscore}bullet}+} is shifted to the left because Car{sup 2+} decays more quickly than Car{sup {sm{underscore}bullet}+} in the presence of electrolyte and this is a major path for formation of cis neutral species from cis Car{sup {sm{underscore}bullet}+}. The optical absorption of Car{sup 2+} of I at 18 C in the presence of 0.1 M TBAHFP is obtained, which suggests that Car{sup 2+} of I is not as unstable at room temperature in the presence of TBAHFP as was thought before.

  11. Impedance Matched Absorptive Thermal Blocking Filters

    NASA Technical Reports Server (NTRS)

    Wollack, E. J.; Chuss, D. T.; Rostem, K.; U-Yen, K.

    2014-01-01

    We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match 50O and its response has been validated from 0-to-50GHz. The observed return loss in the 0-to-20GHz design band is greater than 20 dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.

  12. Two Photon Absorption Spectroscopy of Polydiacetylene PTS

    Microsoft Academic Search

    J. M. Leng; Z. V. Vardeny; B. A. Hooper; K. D. Straub; J. M. J. Madey; G. L. Baker

    1994-01-01

    We have studied two photon absorption (TPA) of single crystal polydiacetylene-toluene-sulfonate (PTS) using the Mark III Free Electron Laser (FEL) in the spectrum range of 0.95–1.5 ?m. We observed two features in the TPA spectrum at two photon energies of 1.85 eV and 2.35 eV, respectively. We discuss the assignment of the two bands in terms of TPA allowed excitons

  13. Impedance Matched Absorptive Thermal Blocking Filters

    NASA Technical Reports Server (NTRS)

    Wollack, E. J.; Chuss, D. T.; U-Yen, K.; Rostem, K.

    2014-01-01

    We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match 50 Omega and its response has been validated from 0-to-50GHz. The observed return loss in the 0-to-20GHz design band is greater than 20 dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.

  14. Synthesis and nonlinear optical absorption of novel chalcone derivative compounds

    NASA Astrophysics Data System (ADS)

    Rahulan, K. Mani; Balamurugan, S.; Meena, K. S.; Yeap, G.-Y.; Kanakam, Charles C.

    2014-03-01

    3-(4-(dimethylamino)phenyl)-1-(4-(4-(hydroxymethyl)-1H-1,2,3-triazol-1-yl)phenyl)prop-2-en-1-one was synthesized and its third order nonlinear optical properties have been investigated using a z-scan technique with nanosecond laser pulses at 532 nm. The nonlinear absorption behavior of the compound in chloroform presents a distinct difference at different laser intensity. Interestingly, the compound showed a switchover from saturable absorption (SA) to reverse saturable absorption (RSA) with the increase of excitation intensity. Our studies suggest that compound could be used as a potential candidate for optical device applications such as optical limiters.

  15. Electronic states of DNA and M-DNA studied by optical absorption

    NASA Astrophysics Data System (ADS)

    Tsuburaya, Makoto; Sakamoto, Hirokazu; Mizoguchi, Kenji

    2014-02-01

    To unveil the electronic states of divalent metal ion incorporated M-DNAs, where M is Mg, Mn, Ni, Co, or Fe, optical absorption spectra have been studied in aqueous solutions of single-stranded (SS) 30mer DNA of poly(dA) (adenine), poly(dG) (guanine), poly(dT) (thymine), poly(dC) (cytosine), salmon-sperm DNA (B-DNA), and M-DNA. The absorption spectrum of the double-stranded (DS) B-DNA can be reproduced with the sum of the four absorption spectra of the SS oligo-DNAs in the ratio corresponding to the composition of B-DNA. This observation suggests that the interactions between complementary strands of DS DNA are negligibly weaker than the bandwidths of the optical spectra. In the metal-incorporated M-DNAs, except for Fe-DNA, the absorption spectra show no significant qualitative change from that of B-DNA. Quantitatively, however, the absorption intensity decreases by ?15% uniquely in a DS poly(dA)-poly(dT) solution with adding MCl2, while nothing happens quantitatively and qualitatively in any SS oligo-DNA and DS poly(dG)-poly(dC) solutions, suggesting some suppression of the electronic excitation only in the Adenine-M-Thymine complex. In contrast, remarkable differences have been observed in Fe-DNA, prepared with FeCl2 and B-DNA. New absorption bands appear in the intragap energy of Fe-DNA, in addition to the suppression of the interband absorption peak of DNA at 4.8 eV. The intragap absorption is attributed to the appearance of Fe3+ species with the same spectral feature as that of FeCl3, that is, purely ionic Fe3+ species. This observation suggests that FeCl2+B-DNA forms Fe-DNA with hydrated Fe3+ ions with ionic bonds. Thus, it is concluded that the charge transfer from Fe2+ to DNA has occurred in Fe-DNA and that the transferred charges are expected to be located in the nearby bases.

  16. Single-junction solar cells with the optimum band gap for terrestrial concentrator applications

    DOEpatents

    Wanlass, Mark W. (Golden, CO)

    1994-01-01

    A single-junction solar cell having the ideal band gap for terrestrial concentrator applications. Computer modeling studies of single-junction solar cells have shown that the presence of absorption bands in the direct spectrum has the effect of "pinning" the optimum band gap for a wide range of operating conditions at a value of 1.14.+-.0.02 eV. Efficiencies exceeding 30% may be possible at high concentration ratios for devices with the ideal band gap.

  17. X-ray absorption of Ba1 - xKxBiO3 and BaPb1 - yBiyO3: Competition between bipolaronic and charge-density wave states

    NASA Astrophysics Data System (ADS)

    Merz, M.; Nücker, N.; Schuppler, S.; Arena, D.; Dvorak, J.; Idzerda, Y. U.; Ustinovich, S. N.; Soldatov, A. G.; Shiryaev, S. V.; Barilo, S. N.

    2005-10-01

    Bulk-sensitive O 1s near-edge X-ray absorption spectroscopy on Ba1 - xKxBiO3 and BaPb1 - yBiyO3 single crystals shows for undoped BaBiO3 a distinct charge-density wave derived band slightly above the Fermi level; upon K doping it is effectively reduced and competes with bipolaronic hole states whose spectral weight increases with K content. For Pb doping, on the other hand, a wide Pb-O band is formed near EF while the intensity of the bipolaronic hole band remains unaffected. The data suggest a crucial role of hole bipolarons for bismuthate superconductivity.

  18. Development of near-infrared absorption spectrometry system by using NIR wideband glass phosphor LED

    NASA Astrophysics Data System (ADS)

    Uemura, H.; Fuchi, S.; Kato, R.; Amano, K.; Hiraizumi, K.; Hayase, H.; Takeda, Y.

    2015-06-01

    We developed a NIR absorption spectrometry system for detection of toxic substances by using a glass phosphor based LED. Using this NIR absorption spectrometry system, phosphoric acid solution samples were measured by molybdenum-blue method. Absorption band around 900 nm and that around 960 nm were observed. The absorption band around 900 nm increased with increasing of the phosphoric acid concentration. Partial least squares (PLS) analysis was revealed that a lower phosphoric acid concentration limit of 0.01 ppm. Furthermore, Cu dilute solutions were measured. Although there was no clear absorption band related to Cu, PLS analysis was revealed that a lower Cu concentration limit of 0.1 ppm. These results indicated that this NIR absorption spectrometry system is useful for practical applications.

  19. 6.3-micron water-vapor-band derivatives

    NASA Technical Reports Server (NTRS)

    Hendrickson, P. E.; Walls, W. L.; Broersma, S.

    1974-01-01

    Measurement of the absorptance in the 6.3-micron band of a 1-m column of water vapor as a function of concentration c, pressure p, and temperature T. From the measured absorptance, the first derivatives with respect to c, p, and T, as well as the second derivatives with respect to cc, pp, cp, and pT have been obtained. These experimental results have been compared with values calculated from the line parameters of the 720 strongest rotational lines in the band.

  20. An extremely broad band metamaterial absorber based on destructive interference.

    PubMed

    Sun, Jingbo; Liu, Lingyun; Dong, Guoyan; Zhou, Ji

    2011-10-24

    We propose a design of an extremely broad frequency band absorber based on destructive interference mechanism. Metamaterial of multilayered SRRs structure is used to realize a desirable refractive index dispersion spectrum, which can induce a successive anti-reflection in a wide frequency range. The corresponding high absorptance originates from the destructive interference of two reflection waves from the two surfaces of the metamaterial. A strongly absorptive bandwidth of almost 60 GHz is demonstrated in the range of 0 to 70 GHz numerically. This design provides an effective and feasible way to construct broad band absorber in stealth technology, as well as the enhanced transmittance devices. PMID:22108966

  1. Laboratory Investigation of the Airglow Bands

    NASA Astrophysics Data System (ADS)

    Drouin, Brian; Yu, Shanshan; Crawford, Timothy J.; Miller, Charles E.; Yee, Jeng-Hwa

    2013-06-01

    We report the first high spectral resolution laboratory measurements of oxygen A-band night glow simulated using a static discharge cell. Our static discharge system reproduces the conditions of the mesospheric oxygen night glow - suggesting O(^1D) + O_2 as the primary source of the emission. Additionally, use of the static cell has enabled us to collect spectra for rare molecular oxygen isotopologues using isotopically enriched samples. The (0,0), (0,1), and (1,1) b-Xvibrational bands were observed with a Bruker 125 HR for all six isotopologues. The (1,2) and (2,2) bands were observed also for the main isotopologue. The frequencies of the observed (0,1) transitions resolved discrepancies in Raman data for (16-17, 17-17, and 17-18), enabling us to improve the vibrational parameterization of the ground electronic state in the global fit of Yu et al. Rotationally resolved intensities were determined for the (0,0), (0,1) and (1,1) bands. The experimental band intensity ratios I(0,0)/I(0,1) = 13.6 and I(0,0)/I(1,1) = 60 are in excellent agreement with the recent mesospheric remote sensing data. S. Yu, C.E. Miller, B.J. Drouin, H.S.P. Müller, J. Chem. Phys. 136, 024304, 2012

  2. Dead pixel correction techniques for dual-band infrared imagery

    NASA Astrophysics Data System (ADS)

    Nguyen, Chuong T.; Mould, Nick; Regens, James L.

    2015-07-01

    We present two new dead pixel correction algorithms for dual-band infrared imagery. Specifically, we address the problem of repairing unresponsive elements in the sensor array using signal processing techniques to overcome deficiencies in image quality that are present following the nonuniformity correction process. Traditionally, dead pixel correction has been performed almost exclusively using variations of the nearest neighbor technique, where the value of the dead pixel is estimated based on pixel values associated with the neighboring image structure. Our approach differs from existing techniques, for the first time we estimate the values of dead pixels using information from both thermal bands collaboratively. The proposed dual-band statistical lookup (DSL) and dual-band inpainting (DIP) algorithms use intensity and local gradient information to estimate the values of dead pixels based on the values of unaffected pixels in the supplementary infrared band. The DSL algorithm is a regression technique that uses the image intensities from the reference band to estimate the dead pixel values in the band undergoing correction. The DIP algorithm is an energy minimization technique that uses the local image gradient from the reference band and the boundary values from the affected band to estimate the dead pixel values. We evaluate the effectiveness of the proposed algorithms with 50 dual-band videos. Simulation results indicate that the proposed techniques achieve perceptually and quantitatively superior results compared to existing methods.

  3. Probing the sensitivity of polarimetric O2 A-band measurements to clouds with emphasis on potential OCO-2 and GOSAT retrievals

    NASA Astrophysics Data System (ADS)

    Sanghavi, S.; Lebsock, M.; Stephens, G.

    2014-09-01

    Clouds play a crucial role in the Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O2 A-band, such as the GOSAT and OCO-2 satellites, could make it possible to simultaneously retrieve several cloud parameters that play a vital role in the Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. In this work, the hyperspectral, polarimetric response of the O2 A-band to mainly three important cloud parameters, viz., optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A-band. Cloud optical thickness finds greatest sensitivity in both intensity and polarization measurements at non-absorbing wavelengths. Cloud height had a negligible effect on intensity measurements at non-absorbing wavelengths, but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness, except that the sensitivity is weaker. Sensitivity to droplet size is generally weaker than to cloud optical thickness to top height at non-absorbing wavelengths and diminishes further with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multiangular measurements. Our results show that, in the absence of sunglint, the backscatter direction is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that I and Q generally have differing sensitivities to cloud parameters. Thus, accurate measurements of both orthogonal components Ih and Iv (as in GOSAT) are expected to contain more information than measurements of only I, Ih or Iv (as in the case of OCO-2).

  4. Probing the sensitivity of polarimetric O2 A-band measurements to clouds with emphasis on potential OCO-2 and GOSAT retrievals

    NASA Astrophysics Data System (ADS)

    Sanghavi, S.; Lebsock, M. D.; Stephens, G. L.

    2014-12-01

    Clouds play a crucial role in the Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O2 A-band, such as the GOSAT and OCO-2 satellites, could make it possible to simultaneously retrieve several cloud parameters that play a vital role in the Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. The hyperspectral, polarimetric response of the O2 A-band to optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A-band. Cloud optical thickness finds greatest sensitivity in both intensity and polarization measurements at non-absorbing wavelengths. Cloud height had a negligible effect on intensity measurements at non-absorbing wavelengths, but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness, except that the sensitivity is weaker. Sensitivity to droplet size is generally weaker than to cloud optical thickness to top height at non-absorbing wavelengths and diminishes further with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multiangular measurements. Our results show that, in the absence of sunglint, the backscatter direction is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that I and Q generally have differing sensitivities to cloud parameters. Thus, accurate measurements of both orthogonal components Ih and Iv (as in GOSAT) are expected to contain more information than measurements of only I, Ih or Iv (as in the case of OCO-2).

  5. Upconverting-nanoparticle-assisted photochemistry induced by low-intensity near-infrared light: how low can we go?

    PubMed

    Chen, Zhijun; Sun, Wen; Butt, Hans-Jürgen; Wu, Si

    2015-06-15

    Upconverting nanoparticles (UCNPs) convert near-infrared (NIR) light into UV or visible light that can trigger photoreactions of photosensitive compounds. In this paper, we demonstrate how to reduce the intensity of NIR light for UCNP-assisted photochemistry. We synthesized two types of UCNPs with different emission bands and five photosensitive compounds with different absorption bands. A ?=974?nm laser was used to induce photoreactions in all of the investigated photosensitive compounds in the presence of the UCNPs. The excitation thresholds of the photoreactions induced by ?=974?nm light were measured. The lowest threshold was 0.5?W?cm(-2) , which is lower than the maximum permissible exposure of skin (0.726?W?cm(-2) ). We demonstrate that low-intensity NIR light can induce photoreactions after passing through a piece of tissue without damaging the tissue. Our results indicate that the threshold for UCNP- assisted photochemistry can be reduced by using highly photosensitive compounds that absorb upconverted visible light. Low excitation intensity in UCNP-assisted photochemistry is important for biomedical applications because it minimizes the overheating problems of NIR light and causes less photodamage to biomaterials. PMID:25965187

  6. Subpicosecond Time-Resolved Absorption and Transient Gratings in Gallium-Arsenide

    NASA Astrophysics Data System (ADS)

    Katz, Alvin I.

    Carrier-carrier and intervalley scattering has been studied in submicron thick GaAs under intense photoexcitation by time resolved absorption and four wave mixing techniques using a femtosecond laser and amplifier system which was constructed as part of this thesis. The laser oscillator is a colliding pulse ring cavity passively modelocked (cpm) Rhodamine 6G dye laser. The saturable absorber is DODCI (3,3^' -diethyloxodicarbocyanine iodide). The oscillator produces pulses of 100 femtosecond duration and pulse energies of 50 picojoules at 620 nm and 115 megahertz repetition rate. The oscillator is pumped by a cw argon ion laser operating at a single line (514.5 nm). The amplifier system is a four stage amplifier pumped by a frequency doubled Q-switch Nd Yag laser. The electronics were constructed so as to allow the dye laser to trigger the pockel's cell of the Nd:Yag laser. The amplifier has a gain of 5 times 10^6; with an output pulse energy of 500 microjoules and a pulse width of 450 fs at a 20 hertz repetition rate. Pump and probe absorption techniques were used to measure the time evolution of the photoexcited carrier distribution function in GaAs. These measurements show that the electrons and holes do not achieve a Fermi-Dirac distribution until 800 femtoseconds after excitation. Time resolved four wave mixing techniques were used to study intervalley scattering in GaAs. Both the dispersive (real part of n) and absorption saturation (imaginary part of n) of the free carrier contributions to the dielectric function is included to correctly explain the data. For energies high above the band gap, the interband (bleaching) contribution is strongly dependent on the distribution of electrons among the different valleys (Gamma , L or X) of the conduction band and is opposite in sign from the intraband (dispersive) term. By using a three pulse transient grating experiment under the conditions of high pump intensity and probe energy (2.0 eV) much greater than the band gap (1.424 eV at room temperature), the effective time for intervalley scattering of electrons from the L -valleys back to the Gamma-valley is directly measured. From the grating decay time of ~9 picoseconds, a L to Gamma time of 3 ps is estimated which is in good agreement with other recent work using time resolved photoluminescence.

  7. Multi-plasmon absorption in graphene

    E-print Network

    Marinko Jablan; Darrick E. Chang

    2015-01-21

    We show that graphene possesses a strong nonlinear optical response in the form of multi-plasmon absorption, with exciting implications in classical and quantum nonlinear optics. Specifically, we predict that graphene nano-ribbons can be used as saturable absorbers with low saturation intensity in the far-infrared and terahertz spectrum. Moreover, we predict that two-plasmon absorption and extreme localization of plasmon fields in graphene nano-disks can lead to a plasmon blockade effect, in which a single quantized plasmon strongly suppresses the possibility of exciting a second plasmon.

  8. Infrared absorption in amorphous selenium

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazuma; Ikawa, Atushi

    2001-12-01

    The infrared (IR) absorption spectrum of amorphous selenium (a-Se) are calculated for the atomic structure constructed by a molecular dynamics with recently proposed chain model using an semiempirical electronic structure calculation. Its microscopic mechanism is investigated with an IR formula for chains in terms of bond and induced current correlations. The stretching band in the IR spectrum has two peaks, which are related to the intermediate range order that dihedral angle sequences with the signs of (+,-,+,-) and (-,+,-,+) hardly occur due to steric hindrance. The result urges us to modify the conventional picture that a-Se consists of the polymer chains with completely random sequences of the signs of the dihedral angles.

  9. Survey analysis of chorus intensity at Saturn

    NASA Astrophysics Data System (ADS)

    Menietti, J. D.; Averkamp, T. F.; Groene, J. B.; Horne, R. B.; Shprits, Y. Y.; Woodfield, E. E.; Hospodarsky, G. B.; Gurnett, D. A.

    2014-10-01

    In order to conduct theoretical studies or modeling of pitch angle scattering of electrons by whistler mode chorus emission at Saturn, a knowledge of chorus occurrence and magnetic intensity levels, PB, as well as the distribution of PB relative to frequency and spatial parameters is essential. In this paper an extensive survey of whistler mode magnetic intensity levels at Saturn is carried out, and Gaussian fits of PB are performed. We fit the spectrum of wave magnetic intensity between the lower hybrid frequency and fceq/2 and for frequencies in the interval fceq/2 < f < 0.9 fceq, where fceq is the cyclotron frequency mapped to the equator. Saturn chorus is observed over most local times, but is dominant on the nightside in the range of 4.5 < L <7.5, with minimum power at the equator and peak power in the range of 5° < ? < 10°. Saturn wave magnetic intensity averaged in frequency bins peaks in the range of 10-5 < PB < 10-4 nT2 for 0.4 < ? < 0.5 (? = f/fceq). Gaussian fits of PB with frequency and latitude are obtained for lower band chorus. Plasma injection regions are occasionally encountered with significant chorus power levels. Upper band chorus is seen almost exclusively within plasma injection regions, and the number of events is very limited, but when present, the average levels of PB can be higher than the lower band chorus. The overall magnetic intensity contribution of the upper band, however, is insignificant relative to the lower band.

  10. Parametric distortion of the optical absorption edge of a magnetic semiconductor by a strong laser field

    SciTech Connect

    Nunes, O.A.C.

    1985-09-15

    The influence of a strong laser field on the optical absorption edge of a direct-gap magnetic semiconductor is considered. It is shown that as the strong laser intensity increases the absorption coefficient is modified so as to give rise to an absorption tail below the free-field forbidden gap. An application is made for the case of the EuO.

  11. Band gap bowing parameter of In1-xAlxN

    NASA Astrophysics Data System (ADS)

    Jones, R. E.; Broesler, R.; Yu, K. M.; Ager, J. W.; Haller, E. E.; Walukiewicz, W.; Chen, X.; Schaff, W. J.

    2008-12-01

    We report a band gap bowing parameter for In1-xAlxN of 4.7 eV from a study of high quality and homogenous samples with x =0.017-0.60. Optical absorption data were modeled to extract the band gaps in order to consider the complications of the band structure of In-rich InAlN, including the Burstein-Moss shift, nonparabolic conduction band, and broadening of the absorption edge. The alloy compositions were accurately determined using Rutherford backscattering spectrometry and the sample quality was evaluated using x-ray diffraction and channeling-RBS.

  12. Relative Band Oscillator Strengths for Carbon Monoxide: Alpha (1)Pi-Chi (1)Sigma(+) Transitions

    NASA Technical Reports Server (NTRS)

    Federman, S. R.; Menningen, K. L.; Lee, Wei; Stoll, J. B.

    1997-01-01

    Band oscillator strengths for CO transitions between the electronic states A (l)Pi and X(1)Sigma(+) were measured via absorption with a synchrotron radiation source. When referenced to the well-characterized (5,0) band oscillator strength, our relative values for the (7,0) to (11,0) bands are most consistent with the recent experiments of Chan et al. and the theoretical predictions of Kirby & Cooper. Since the results from various laboratory techniques and theory now agree, analyses of interstellar CO based on absorption from A-X bands are no longer hindered by uncertainties in oscillator strength.

  13. Atmospheric pressure and temperature profiling using near IR differential absorption lidar

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Weng, C. Y.

    1983-01-01

    The present investigation is concerned with differential absorption lidar techniques for remotely measuring the atmospheric temperature and pressure profile, surface pressure, and cloud top pressure-height. The procedure used in determining the pressure is based on the conduction of high-resolution measurements of absorption in the wings of lines in the oxygen A band. Absorption with respect to these areas is highly pressure sensitive in connection with the mechanism of collisional line broadening. The method of temperature measurement utilizes a determination of the absorption at the center of a selected line in the oxygen A band which originates from a quantum state with high ground state energy.

  14. An intensive study on the optical, rheological, and electrokinetic properties of polyvinyl alcohol-capped nanogold

    NASA Astrophysics Data System (ADS)

    Behera, Manoranjan

    2015-05-01

    Low-temperature-assisted wet chemical synthesis of nanogold (NG) using gold hydroxide, a new precursor salt in the presence of a macroscopic ligand poly(vinyl alcohol) PVA in water in the form of nanofluid, is reported for the first time in this article. In the absorption spectra, the surface Plasmon resonance absorption band in the range of 520-545 nm signifies the formation of NG via a controlled Au3+ + 3e ? Au reaction grafted in small assemblies with polymer. Absorption maximum increases nonlinearly with Au-contents up to 100 µM Au in Au-PVA charge-transfer complex. Marked enhancement in the peak intensity of some of the vibration bands of PVA polymer such as C-H stretching, C=O stretching, CH2 bending, and C-C in-plane bending in the presence of NG reveals an interfacial interaction between NG and oxidized PVA via C=O group. Execution of shear thinning behavior regardless of the Au-content strongly suggests that crosslinking exists between NG and PVA in Au-PVA rheo-optical nanofluids. Hydrodynamic diameter and polydispersity index draw a nonlinear path with the Au doping with 30.0 g/L PVA in water over a wide region of 5-100 ?M Au covered in this study. Enhancement in the zetapotential of Au-PVA nanofluid over bare PVA in water is ascribed to buildup of nonbonding electrons of "-C=O" moieties from the oxidized PVA on the NG surface. Displaying of lattice fringes in the microscopic image of core-shell Au-PVA nanostructure confirms that crystalline nature of NG core with inter planar spacing 0.235 nm corresponds to Au (111) plane.

  15. Methane absorption variations in the spectrum of Pluto

    Microsoft Academic Search

    M. W. Buie; U. Fink

    1987-01-01

    The lightcurve phases of 0.18, 0.35, 0.49, and 0.98 covered by 5600-10,500 A absolute spectrophotometry of Pluto during four nights include minimum (0.98) light and one near-maximum (0.49) light. The spectra are noted to exhibit significant methane band absorption depth variations at 6200, 7200, 7900, 8400, 8600, 8900, and 10,000 A, with the minimum absorption occurring at minimum light and

  16. Optical absorption of twisted bilayer graphene with interlayer potential asymmetry

    NASA Astrophysics Data System (ADS)

    Moon, Pilkyung; Son, Young-Woo; Koshino, Mikito

    2014-10-01

    We investigate the band structure and the optical absorption spectrum of twisted bilayer graphenes with changing interlayer bias and Fermi energy simultaneously. We show that the interlayer bias lifts the degeneracy of the superlattice Dirac point, while the amount of the Dirac point shift is significantly suppressed in small rotation angles, and even becomes opposite to the applied bias. We calculate the optical absorption spectrum in various asymmetric potentials and Fermi energies, and associate the characteristic spectral features with the band structure. The spectroscopic features are highly sensitive to the interlayer bias and the Fermi energy, and widely tunable by the external field effect.

  17. Mg-induced increase of bandgap in Zn1-xMgxO nanorods revealed by x-ray absorption and emission spectroscopy

    SciTech Connect

    Pong, Way-Faung; Chiou, J. W.; Tsai, H. M.; Pao, C. W.; Chien, F. Z.; Pong, W. F.; Chen, C. W.; Tsai, M.-H.; Wu, J. J.; Ko, C. H.; Chiang, H. H.; Lin, H.-J.; Lee, J. F.; Guo, J.-H.

    2008-07-10

    X-ray absorption near-edge structure (XANES) and x-ray emission spectroscopy (XES) measurements were used to investigate the effect of Mg doping in ZnO nanorods. The intensities of the features in the O K-edge XANES spectra of Zn{sub 1-x}Mg{sub x}O nanorods are lower than those of pure ZnO nanorods, suggesting that Mg doping increases the negative effective charge of O ions. XES and XANES spectra of O 2p states indicate that Mg doping raises (lowers) the conduction-band-minimum (valence-band-maximum) and increases the bandgap. The bandgap is found to increase linearly with the Mg content, as revealed by photoluminescence and combined XANES and XES measurements.

  18. Far-field diffraction patterns by a thin nonlinear absorptive nonlocal media.

    PubMed

    Martinez Irivas, B A; Arroyo Carrasco, M L; Mendez Otero, M M; Ramos García, R; Iturbe Castillo, M D

    2015-06-01

    In this work we present numerical results of the far field intensity distributions obtained for a Gaussian beam after crossing a thin nonlinear nonlocal material that exhibit nonlinear refraction and absorption. The distributions are obtained for different positions along the Z axis and different signs of the nonlinear absorption. The results demonstrate that the far field intensity patterns obtained for strong nonlocal media are more affected by the presence of the nonlinear absorption than weak nonlocal media. PMID:26072773

  19. Effect of Laser Wavelength and Pulse Duration on Laser-Light Absorption and Back Reflection

    NASA Astrophysics Data System (ADS)

    Garban-Labaune, C.; Fabre, E.; Max, C. E.; Fabbro, R.; Amiranoff, F.; Virmont, J.; Weinfeld, M.; Michard, A.

    1982-04-01

    Absorption efficiency has been measured in laser-irradiated plane-target experiments with various laser wavelengths (1.06, 0.53, and 0.26 ?m), pulse durations (100 ps, 2 ns), and intensities (1010-2×1015 W/cm). Results show a strong increase of absorption for long pulses, low intensities, and short wavelengths which favor inverse bremsstrahlung absorption. A one-dimensional Lagrangian hydrocode (film) is used to interpret these results.

  20. High temperature measurement of water vapor absorption

    NASA Technical Reports Server (NTRS)

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  1. Optical absorption and fluorescence properties of Dy3+: SFB glasses

    NASA Astrophysics Data System (ADS)

    Maheswari, D. Uma; Kumar, J. Suresh; Sasikala, T.; Mohan Babu, A.; Pavani, K.; Jang, Kiwan; Rama Moorthy, L.

    2009-07-01

    This paper presents the preparation and spectroscopic characterization of Dy3+-doped sodium fluoroborate (SFB) glasses of the type (50-x) B2O3 + 25 Na2O + 10 CaF2 + 10 AlF3 + 5 LaF3 + x DyF3 (x = 0.01, 0.1, 0.5,1.0, 2.0 and 4.0 mol%). By measuring the area under absorption bands, the experimental oscillator strengths are determined. The Judd-Ofelt (J-O) intensity parameters ?? (? = 2, 4, 6) are evaluated by the least square fit method. These phenomenological parameters are used to predict luminescence properties of the lanthanide ions in SFB glasses. Photoluminescence spectra and lifetimes of 4F9/2 level of Dy3+ ions in these glasses have been measured by exciting with 348 nm line of xenon flash lamp. The measured decay curves exhibit single exponential at lower concentrations of 0.01, 0.1, 0.5 and 1.0 mol% and non-exponential at higher concentrations of 2.0 and 4.0 mol%. The predicted ?R and (?R values of 4F9/2 transition are compared with the experimentally measured values. From the magnitude of stimulated emission cross sections (?e), branching ratios (?m), multiphonon relaxation rates (WMP), the most potential laser transitions are identified and the utility of these glasses as laser active material is discussed.

  2. Quantitative infrared absorption cross sections of isoprene for atmospheric measurements

    NASA Astrophysics Data System (ADS)

    Brauer, C. S.; Blake, T. A.; Guenther, A. B.; Sharpe, S. W.; Sams, R. L.; Johnson, T. J.

    2014-11-01

    Isoprene (C5H8, 2-methyl-1,3-butadiene) is a volatile organic compound (VOC) and is one of the primary contributors to annual global VOC emissions. Isoprene is produced primarily by vegetation as well as anthropogenic sources, and its OH- and O3-initiated oxidations are a major source of atmospheric oxygenated organics. Few quantitative infrared studies have been reported for isoprene, limiting the ability to quantify isoprene emissions via remote or in situ infrared detection. We thus report absorption cross sections and integrated band intensities for isoprene in the 600-6500 cm-1 region. The pressure-broadened (1 atmosphere N2) spectra were recorded at 278, 298, and 323 K in a 19.94 cm path-length cell at 0.112 cm-1 resolution, using a Bruker IFS 66v/S Fourier transform infrared (FTIR) spectrometer. Composite spectra are derived from a minimum of seven isoprene sample pressures, each at one of three temperatures, and the number densities are normalized to 296 K and 1 atm.

  3. Unfolding polyhedral bands

    Microsoft Academic Search

    Greg Aloupis; Erik D. Demaine; Stefan Langerman; Pat Morin; Joseph O'rourke; Ileana Streinu; Godfried T. Toussaint

    2004-01-01

    Abstract: A band is dened as the intersection of the surface of aconvex polyhedron with the space between two parallelplanes, as long as this space does not contain any verticesof the polyhedron. An unfolding of a given bandis obtained by cutting along exactly one edge and placingall faces of the band into the plane, without causingintersections. We prove that for

  4. Stretch Band Exercise Program

    ERIC Educational Resources Information Center

    Skirka, Nicholas; Hume, Donald

    2007-01-01

    This article discusses how to use stretch bands for improving total body fitness and quality of life. A stretch band exercise program offers a versatile and inexpensive option to motivate participants to exercise. The authors suggest practical exercises that can be used in physical education to improve or maintain muscular strength and endurance,…

  5. Infrared radiation parameterizations for the minor CO2 bands and for several CFC bands in the window region

    NASA Technical Reports Server (NTRS)

    Kratz, David P.; Chou, Ming-Dah; Yan, Michael M.-H.

    1993-01-01

    Fast and accurate parameterizations have been developed for the transmission functions of the CO2 9.4- and 10.4-micron bands, as well as the CFC-11, CFC-12, and CFC-22 bands located in the 8-12-micron region. The parameterizations are based on line-by-line calculations of transmission functions for the CO2 bands and on high spectral resolution laboratory measurements of the absorption coefficients for the CFC bands. Also developed are the parameterizations for the H2O transmission functions for the corresponding spectral bands. Compared to the high-resolution calculations, fluxes at the tropopause computed with the parameterizations are accurate to within 10 percent when overlapping of gas absorptions within a band is taken into account. For individual gas absorption, the accuracy is of order 0-2 percent. The climatic effects of these trace gases have been studied using a zonally averaged multilayer energy balance model, which includes seasonal cycles and a simplified deep ocean. With the trace gas abundances taken to follow the Intergovernmental Panel on Climate Change Low Emissions 'B' scenario, the transient response of the surface temperature is simulated for the period 1900-2060.

  6. Detailed analysis of absorption data for indium nitride

    Microsoft Academic Search

    K. S. A. Butcher; M. Wintrebert-Fouquet; P. P.-T. Chen; H. Timmers; S. K. Shrestha

    2003-01-01

    It is shown that the 0.7eV band gap recently announced for InN is actually due to a sub band gap deep level trap with |s? like symmetry. This level had been known in the literature, but was previously misinterpreted as a deep level trap with |p? like symmetry. It is also shown that proper interpretation of the absorption data for

  7. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  8. Hole-induced transient bandgap renormalization: A mechanism for photo-induced absorption in defect-engineered semiconductors

    Microsoft Academic Search

    Paul W. Juodawlkis; Stephen E. Ralph

    2000-01-01

    In semiconductors, photoexcitation often results in a transient band edge-absorption bleaching due to the dominance of conduction-band filling over bandgap renormalization. In this letter, we show that the presence of electron traps can act to reverse this behavior so that photoexcitation results in an absorption increase in these same semiconductors. We associate this photo-induced absorption with bandgap renormalization caused by

  9. Dual-band ultraviolet-short-wavelength infrared imaging via luminescent downshifting with colloidal quantum dots

    E-print Network

    Geyer, Scott M.

    The performance of short-wavelength infrared (SWIR) cameras in the visible and ultraviolet (UV) regions is limited by the absorption of high-energy photons in inactive regions of the imaging array. Dual-band UV-SWIR imaging ...

  10. High absorption efficiency of AlGaAs/GaAs superlattice solar cells

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kawaharazuka, Atsushi; Horikoshi, Yoshiji

    2015-05-01

    The effects of excitonic absorption on the solar cell efficiency have been investigated in solar cells with AlGaAs/GaAs superlattice absorption layers. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption coefficient. The excitonic absorption shows strong peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of superlattice solar cells at room temperature are reasonably well reproduced by simulations taking excitonic effects into account. The superlattice solar cells are confirmed to have a high absorbance and good temperature stability. The theoretical analysis of the experimental results confirms that the enhanced excitonic absorption in the superlattice absorption layers survives even at 100 °C, which is considered as the actual device temperature under realistic device operations.

  11. [Influence of light wavelength and intensity on the reduction of divalent mercury in aquatic system].

    PubMed

    Li, Xi-Jia; Zhong, Zi-Xuan; Sun, Rong-Guo; Yang, Kun; Wang, Ding-Yong

    2014-05-01

    Laboratory experiments were conducted to investigate the photo-reduction of HgCI2, under various light wavelengths and intensities. The whole process was tracked by changing Hg0 concentrations in argon and Hg0 flux was calculated for qualitative and quantitative analysis; the rate order was determined by both differential and integral methods. The principal results indicated: Higher mercury emission flux was observed under shorter light wavelength and stronger intensity, which shows the important role of photoenergy in the reaction. The degree of mercury reduction was determined by radiation wavelength and intensity, and it was also influenced by solution volume and the flow rate of carrier gas. Under different light conditions, Hg0 concentrations in argon all increased at the beginning and decreased after a specific time period, since the main reactions in rising period were the photo-reduction of Hg2+ and the emission of Hg0 while the reaction in decreasing period was the emission of Hg0 only. The rate order under visible light was the first order while it was the second order under UVA and UVB, which attributes to the fact that coordination complex has certain light absorption band, which is related with the available light wavelength provided by experimental lamps. PMID:25055667

  12. Polarized electronic absorption spectra of Cr2SiO4 single crystals

    NASA Astrophysics Data System (ADS)

    Furche, A.; Langer, K.

    Polarized electronic absorption spectra, E?a(?X), E?b(?Y) and E?c(?Z), in the energy range 3000-5000 cm-1 were obtained for the orthorhombic thenardite-type phase Cr2SiO4, unique in its Cr2+-allocation suggesting some metal-metal bonding in Cr2+Cr2+ pairs with Cr-Cr distance 2.75 Å along [001]. The spectra were scanned at 273 and 120 K on single crystal platelets ?(100), containing optical Y and Z, and ?(010), containing optical X and Z, with thicknesses 12.3 and 15.6 ?m, respectively. Microscope-spectrometric techniques with a spatial resolution of 20 ?m and 1 nm spectral resolution were used. The orientations were obtained by means of X-ray precession photographs. The xenomorphic, strongly pleochroic crystal fragments (X deeply greenish-blue, Y faint blue almost colourless, Z deeply purple almost opaque) were extracted from polycrystalline Cr2SiO4, synthesized at 35 kbar, above 1440 °C from high purity Cr2O3, Cr (10% excess) and SiO2 in chromium capsules. The Cr2SiO4-phase was identified by X-ray diffraction (XRD). Four strongly polarized bands, at about 13500 (I), 15700 (II), 18700 (III) and 19700 (IV) cm-1, in the absorption spectra of Cr2SiO4 single crystals show properties (temperature behaviour of linear and integral absorption coefficients, polarization behaviour, molar absorptivities) which are compatible with an assignment to localized spin-allowed transitions of Cr2+ in a distorted square planar coordination of point symmetry C2. The crystal field parameter of Cr2+ is estimated to be 10 Dq =10700 cm-1. A relatively intense, sharp band at 18400 cm-1 and three other minor features can, from their small half widths, be assigned to spin-forbidden dd-transitions of Cr2+. The intensity of such bands strongly decreases on decreasing temperature. The large half widths, near 5000 cm-1 of band III are indicative of some Cr-Cr interactions, i.e. ?-?* transitions of Cr24+, whereas the latter alone would be in conflict with the strong polarization of bands I and II parallel [100]. Therefore, it is concluded that the spectra obtained can best be interpreted assuming both dd-transitions of localized d-electrons at Cr2+ as well as ?-?* transitions of Cr24+ pairs with metal-metal interaction. To explain this, a dynamic exchange process 2 Crloc2+?Cr2, cpl4+ is suggested wherein the half life times of the ground states of both exchanging species are significantly longer than those of the respective optically excited states, such that the spectra show both dd- and ?-?*-transitions.

  13. The 890 nm Methane Band: Line by Line Parameters for the Outer Solar System

    NASA Astrophysics Data System (ADS)

    Benner, D. Chris; O'Brien, J. J.; Shaji, S.; Malathy Devi, V.; Spickler, P. T.; Houck, C. P.; Coakley, J. A.; Haga, K. J.; Dolph, J. D.

    2010-10-01

    The near infrared bands of methane were the first observed in the outer planets and Titan. With the very long paths of rays within the atmospheres of these objects, scattering, pressure and temperature inhomogeneities are important. The spectrum of methane is very complex and long laboratory gas cells are difficult to cool to outer solar system temperatures. The absorption is usually modeled statistically. Violations of the modeling assumptions cause poor extrapolations of simulations based upon laboratory parameters. These band models generally do not provide transmissions that are multiplicative, so proper modeling of scattering and inhomogeneous atmospheres is not possible. The Intra Cavity Laser Spectrometer of the University of Missouri, St. Louis obtained low temperature (99-161K), low pressure ( few Torr), long path (few km) and high resolution ( 0.01 cm-1 HWHM) spectra of methane covering the entire 890 nm feature (10925-11500 cm-1), the deepest band below 1.1 µm. At these temperatures fewer spectral lines are visible and the Doppler width is substantially smaller than at room temperature. The result is a dense, but manageable spectrum from which line positions, intensities and lower state energies are derived on a line by line basis by the William and Mary multispectrum nonlinear least squares fitting technique. For temperatures less than 160K, simulation of the spectrum at infinite resolution is possible. Simulations at various physical conditions will be shown and compared to band models and other laboratory spectra. Support at William and Mary was provided by NASA through grant NNX08AF06G. Support at UM, St. Louis provided by NASA through grant NAG5-12013, from NSF through grant CHE-0213356 and by the University of Missouri Research Board. Partial support at Bridgewater College was provided by its Martin Science Research Institute and from an AAS Small Research Grant.

  14. PHOSPHATE ABSORPTION IN EELGRASS

    Microsoft Academic Search

    C. Peter McRoy; Robert J. Barsdate

    The absorption of phosphate by eelgrass (Zostera marina L. ) was studied using 32P in a partitioned container where leaves were separated from roots and rhizomes. Absorption, which was greatest in the light, occurred through both leaves and roots, and the absorbed phosphorus was transported rapidly to all parts of the plant. It therefore appears that eelgrass can use phosphate

  15. Electronic absorption spectra of chromium-bearing sapphirine

    NASA Astrophysics Data System (ADS)

    Langer, K.; Platonov, A. N.; Matsuk, S. S.; Andrut, M.

    1994-05-01

    Violet, non-pleochroic and greenish-blue, pleochroic chromium-substituted sapphirines were found in corundum-bearing spinel-websterite xenolites from the Yakutian kimberlite pipes Noyabrskaya (N) and Sludyanka (Sl), respectively. The crystallochemical formulae of sapphirine crystals from such xenolites were determined by EMP to be (Mg3.40Fe0.23Al3.25Cr0.16)[6] Al{1.00/[6]}[O2/Al4.53Si1.47O18] (N) and (Mg2.53Fe0.55 Mn0.04Ti{0.03/4+}Al3.55Cr{0.08/3+})[6]Al{1.00/[16]}[O2/Al4.28Si1.73O18] (Sl). Single crystal spectra in the range 35000 6000 cm1- showed a slightly polarization dependent absorption edge near 3200 cm1- (N) or 30000 cm1- (Sl) and unpolarized bands at 25300 and 17300 cm1-, typical of spin-allowed transitions, derived from 4A2g?4T1g and 4A2g?4T2g, of Cr3+ in octahedral sites, with point symmetry C1, of the structure. Another weak band at 23000 cm-1 in the sapphirine-N spectra is attributed to low symmetry splitting of the excited 4T1 (F)-State of Cr3+. These assignments lead to crystal field parameters Dq=1730cm-1 and B= 685cm-1 of Cr3+ in sapphirine. Crystallochemical and spectroscopic arguments suggest that Cr3+ subsitutes for Al in the M(1) or M(8) sites of the sapphirine structure. In addition to Cr3+-transitions, spectra of Sl exhibit weak dd-bands of Fe2+ at 10000 and 7700 cm1-, which are unpolarized in consistency with the C1 site symmetry of the octahedra in the structure. Spectra of Sl show also prominent, broad bands (?v1/2˜-5000 cm1-) at 15000 and 11000 cm1-, which occur in E//Y(//b) and E//Z(//c=12°) only and exhibit an intensity ratio ?Y??z close to 1?3. This result, the large half width, as well as band energy — MM distance considerations suggest that these bands originate from Fe2+[6]-Fe3+[6] charge-transfer transitions in wall octahedra M(1)M(2), M(6)M(7) etc., forming MM vectors of 30° with the c-axis. The lack of Fe2+-Fe3+ charge-transfer bands in sapphirine N might indicate a lower oxygen fugacity during the formation of the websterite from the Noyabrskaya pipe compared to that from the Sludyanka pipe.

  16. Fast transforms: Banded matrices with banded inverses

    PubMed Central

    Strang, Gilbert

    2010-01-01

    It is unusual for both A and A-1 to be banded—but this can be a valuable property in applications. Block-diagonal matrices F are the simplest examples; wavelet transforms are more subtle. We show that every example can be factored into A = F1…FN where N is controlled by the bandwidths of A and A-1 (but not by their size, so this extends to infinite matrices and leads to new matrix groups). PMID:20615937

  17. Wedge absorption remote sensor

    NASA Astrophysics Data System (ADS)

    Watkins, Wendell R.; White, Kenneth O.

    1981-11-01

    Remote detection of gases, especially methane, is important in several fields including coal mining, natural gas storage, and pollution monitoring. Near real-time remote sensing of atmospheric gases can already be performed by using differential absorption lidar or transmission techniques. A new system called the wedge absorption remote sensor has been developed which improves integrated path detection of atmospheric gases. The wedge absorption remote sensor utilizes an emission spike train of short-time duration as is found in the long-pulse output mode of a solid-state laser to define the on- and off-line absorption of an atmospheric gas and, hence, its concentration. The wedge absorption remote sensor has performed well as a remote sensor of methane concentrations with an erbium:ytterbium-aluminum-garnet laser as the source.

  18. Study of the formation equilibria of electron donor-acceptor complexes between [60]fullerene and methylbenzenes by absorption spectrometric method

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sumanta; Banerjee, Manas; Mukherjee, Asok K.

    2001-06-01

    The electron donor-acceptor (EDA) interaction between [60]fullerene and three methylbenzenes, viz., durene, pentamethylbenzene and hexamethylbenzene has been studied in carbon tetrachloride medium at a number of temperatures. It has been found that these methylbenzenes form stable 1:1 EDA complexes with [60]fullerene. Charge transfer (CT) absorption bands of the complexes in the 410-460 nm region are more intense than the usual 420-700 nm absorption band of C60. The CT transition energies ( h?CT) of the complexes change systematically with change in the number and position of the methyl groups in the donor molecules (methylbenzenes) and also with the donor ionisation potentials. From an analysis of this variation the electron affinity of C60 has been found to be 2.30 eV and also an inductive effect Hückel parameter of the methyl group has been determined. Formation constants ( K) have been determined at three different temperatures from which the enthalpies and entropies of formation of the complexes have been determined.

  19. Study of the formation equilibria of electron donor-acceptor complexes between [60]fullerene and methylbenzenes by absorption spectrometric method.

    PubMed

    Bhattacharya, S; Banerjee, M; Mukherjee, A K

    2001-06-01

    The electron donor-acceptor (EDA) interaction between [60]fullerene and three methylbenzenes, viz., durene, pentamethylbenzene and hexamethylbenzene has been studied in carbon tetrachloride medium at a number of temperatures. It has been found that these methylbenzenes form stable 1:1 EDA complexes with [60]fullerene. Charge transfer (CT) absorption bands of the complexes in the 410-460 nm region are more intense than the usual 420-700 nm absorption band of C60. The CT transition energies (hvCT) of the complexes change systematically with change in the number and position of the methyl groups in the donor molecules (methylbenzenes) and also with the donor ionisation potentials. From an analysis of this variation the electron affinity of C60 has been found to be 2.30 eV and also an inductive effect Hückel parameter of the methyl group has been determined. Formation constants (K) have been determined at three different temperatures from which the enthalpies and entropies of formation of the complexes have been determined. PMID:11446701

  20. A study of electron paramagnetic resonance and optical absorption spectra of VO 2+ ions in alkali calcium borate glasses

    NASA Astrophysics Data System (ADS)

    Sreekanth Chakradhar, R. P.; Murali, A.; Rao, J. Lakshmana

    2000-12-01

    Electron paramagnetic resonance (EPR) and optical absorption spectra of VO 2+ ions in different alkali calcium borate glasses have been studied. The spin-Hamiltonian parameters ( g and A), bonding parameter ( ?2?2), Fermi contact interaction parameter ( k) and crystal field parameters have been evaluated. The values of spin-Hamiltonian parameters confirm that vanadyl ions are present in the glasses as VO 2+ molecular ions in an octahedral site with a tetragonal compression. At high concentrations of vanadyl ions, the intensity of the EPR resonance signals decreases which has been attributed to the change of oxidation state from V 4+ to V 5+. The EPR spectra have also been studied at different temperatures for VO 2+ ions in sodium calcium borate glasses. The spin-Hamiltonian parameters are found to be independent of temperature. The magnetic susceptibility ? is calculated from the EPR data. It is observed that as the temperature is decreased the susceptibility increases in accordance with the Curie's law. The theoretical values of optical basicity (? th) of glasses have been evaluated. The optical absorption spectrum exhibits two bands characteristic of VO 2+ ions in tetragonal symmetry. The two bands have been assigned to the transitions 2B2 g? 2B1 g and 2B2 g? 2Eg in the decreasing order of energy. The octahedral field parameter (Dq) and the tetragonal field parameters Ds and Dt have been evaluated.

  1. Anomalous electromagnetically induced transparency in photonic-band-gap materials

    SciTech Connect

    Singh, Mahi R. [Department of Physics and Astronomy, University of Western Ontario, London, Ontario, N6A 3K7 (Canada)

    2004-09-01

    The phenomenon of electromagnetically induced transparency has been studied when a four-level atom is located in a photonic band gap material. Quantum interference is introduced by driving the two upper levels of the atom with a strong pump laser field. The top level and one of the ground levels are coupled by a weak probe laser field and absorption takes place between these two states. The susceptibility due to the absorption for this transition has been calculated by using the master equation method in linear response theory. Numerical simulations are performed for the real and imaginary parts of the susceptibility for a photonic band gap material whose gap-midgap ratio is 21%. It is found that when resonance frequencies lie within the band, the medium becomes transparent under the action of the strong pump laser field. More interesting results are found when one of the resonance frequencies lies at the band edge and within the band gap. When the resonance frequency lies at the band edge, the medium becomes nontransparent even under a strong pump laser field. On the other hand, when the resonance frequency lies within the band gap, the medium becomes transparent even under a weak pump laser field. In summary, we found that the medium can be transformed from the transparent state to the nontransparent state just by changing the location of the resonance frequency. We call these two effects anomalous electromagnetically induced transparency.

  2. Absorption coefficient instrument for turbid natural waters.

    PubMed

    Friedman, E; Poole, L; Cherdak, A; Houghton, W

    1980-05-15

    An instrument has been developed that directly measures the multispectral absorption coefficient of turbid natural water. The design incorporates methods for compensation of variation in the internal light source intensity, correction of the spectrally dependent nature of the optical elements, and correction for variation in background light level. When used in conjunction with a spectrally matched total attenuation instrument, the spectrally dependent scattering coefficient can also be derived. Systematic errors associated with multiple scattering have been estimated using Monte Carlo techniques. PMID:20221099

  3. Photonic band gap materials

    NASA Astrophysics Data System (ADS)

    Cassagne, D.

    Photonic band gap materials Photonic band gap materials are periodic dielectric structures that control the propagation of electromagnetic waves. We describe the plane wave method, which allows to calculate the band structures of photonic crystals. By symmetry analysis and a perturbative approach, we predict the appearance of the low energy photonic band gaps of hexagonal structures. We propose new two-dimensional structures called graphite and boron nitride. Using a transfer matrix method, we calculate the transmission of the graphite structure and we show the crucial role of the coupling with external modes. We study the appearance of allowed modes in the photonic band gap by the introduction of localized defects in the periodicity. Finally, we discuss the properties of opals formed by self-organized silica microspheres, which are very promising for the fabrication of three-dimensional photonic crystals. Les matériaux à bandes interdites photoniques sont des structures diélectriques périodiques qui contrôlent la propagation des ondes électromagnétiques. Nous décrivons la méthode des ondes planes qui permet de calculer les structures de bandes des cristaux photoniques. Par une analyse de la symétrie et une approche perturbative, nous précisons les conditions d'existence des bandes interdites de basse énergie. Nous proposons de nouvelles structures bidimensionnelles appelées graphite et nitrure de bore. Grâce à une méthode de matrices de transfert, nous calculons la transmission de la structure graphite et nous mettons en évidence le rôle fondamental du couplage avec les modes extérieurs. Nous étudions l'apparition de modes permis dans la bande interdite grâce à l'introduction de défauts dans la périodicité. Enfin, nous discutons les propriétés des opales constituées de micro-billes de silice auto-organisées, qui sont très prometteuses pour la fabrication de cristaux photoniques tridimensionnels.

  4. Band-gap changes in shocked gallium nitride

    NASA Astrophysics Data System (ADS)

    Peng, H. Y.; McCluskey, M. D.; Gupta, Y. M.

    2001-06-01

    The band gap shift in GaN for uniaxial strain compression along the c-axis was determined using time-resolved, optical absorption measurements in shock wave, plate impact experiments. N-type GaN films, grown on c-cut sapphire, were subjected to instantaneous stresses between 4.5 and 14 GPa. An abrupt increase of the band gap was observed upon shock wave arrival, followed by a slower increase. The stress dependence of the abrupt band gap shift is approximately 0.02 eV/GPa, which is higher than that predicted by ab inito calculations. The results suggest that GaN unit cell may undergo a deformation that contains uniaxial and isotropic components. To determine the effect of carrier concentration, the band gap shift of semi-insulating GaN:Mg was also measured. The influence of piezoelectric fields on the measured band gap (Franz-Keldysh effect) will be discussed.

  5. Photoacoustic imaging of human coronary atherosclerosis in two spectral bands?

    PubMed Central

    Jansen, Krista; Wu, Min; van der Steen, Antonius F.W.; van Soest, Gijs

    2013-01-01

    Spectroscopic intravascular photoacoustic imaging (sIVPA) has shown promise to detect and distinguish lipids in atherosclerotic plaques. sIVPA generally utilizes one of the two high absorption bands in the lipid absorption spectrum at 1.2 ?m and 1.7 ?m. Specific absorption signatures of various lipid compounds within the bands in either wavelength range can potentially be used to differentiate between plaque lipids and peri-adventitial lipids. With the aim to quantify any differences between the two bands, we performed combined sIVPA imaging in both absorption bands on a vessel phantom and an atherosclerotic human coronary artery ex vivo. Lipid detection in a human atherosclerotic lesion with sIVPA required lower pulse energy at 1.7 ?m than at 1.2 ?m (0.4 mJ versus 1.2 mJ). The imaging depth was twice as large at 1.2 ?m compared to 1.7 ?m. Adequate differentiation between plaque and peri-adventitial lipids was achieved at 1.2 ?m only. PMID:25302152

  6. Surface Science Letters Structure, band offsets and photochemistry at

    E-print Network

    Pennycook, Steve

    Surface Science Letters Structure, band offsets and photochemistry at epitaxial a-Cr2O3/a-Fe2O3 that electron­hole pair separation following light absorption enhances photochemistry at oxide- ally been avoided. Thiel et al. [3] investigated the role of surface vibrations on the photochemistry

  7. Infrared cavity ringdown spectroscopy of water clusters: OD stretching bands

    E-print Network

    Cohen, Ronald C.

    interest in the study of gaseous water clusters by modern laser spectroscopy methods,1­3 as such studies of the novel and more general cavity ringdown laser absorption spectroscopy CRLAS technique for the firstInfrared cavity ringdown spectroscopy of water clusters: O­D stretching bands J. B. Paul, R. A

  8. Plasmonic absorption enhancement in periodic cross-shaped graphene arrays.

    PubMed

    Ke, Shaolin; Wang, Bing; Huang, He; Long, Hua; Wang, Kai; Lu, Peixiang

    2015-04-01

    We present a wavelength tunable absorber composed of periodically patterned cross-shaped graphene arrays in the far-infrared and THz regions. The absorption of the single-layer array can essentially exceed the continuous graphene sheet by increasing the cross-arm width, even for small graphene filling ratio. As chemical potential and relaxation time increase, the absorption can be significantly enhanced. The complementary structure shows higher absorption compared to the original graphene array. Moreover, the wavelength of absorption maximum is angle-insensitive for both TE and TM polarizations. The absorption efficiency can be further improved with double layers of the cross-shaped graphene arrays, which are helpful to design dual-band and broadband absorbers. PMID:25968726

  9. Luminescence efficiency growth in wide band gap semiconducting Bi2O3 doped Cd0.4Pb0.1B0.5 glasses and effect of ?-irradiation

    NASA Astrophysics Data System (ADS)

    Marzouk, M. A.; Ibrahim, S.; Hamdy, Y. M.

    2014-11-01

    Cadmium lead borate glasses together with other glasses containing different Bi2O3-doping concentrations (2.5, 5, 7.5, 10 mol%) were prepared by conventional melt annealing method. The density and molar volume values were calculated to obtain some insight on the packing density and arrangement in the network. Also their optical and structural properties have been characterized by means of X-ray diffraction, UV-visible spectroscopy, luminescence spectroscopy and FTIR spectroscopy. Optical measurements have been used to determine the optical band gap (Eg), Urbach energy (?E) and the refractive index (n). The results demonstrate the effective rule of Bi2O3 on the studied glasses. The undoped and Bi2O3 doped - glass show strong extended UV-near visible absorption bands which are attributed to the collective presence of both trace iron impurities from raw materials and also the sharing of bismuth Bi+3 ions. Furthermore, the luminescence intensity strongly increases with increasing Bi2O3 content which may be attributed to transfer of energy from transitions in its energy levels. It has been revealed that the decreasing values of optical band gap and band tail can be understood and related in terms of the structural changes that are taking place in the glass samples. The infrared absorption spectra of the prepared glasses show characteristic absorption bands related to the borate network (BO3, BO4 groups) together with vibrational modes due to Bi-O groups upon the introduction of Bi2O3. The prepared samples reveal a very limited response towards of gamma irradiation which reflects its shielding behavior towards the effect of such type of irradiation.

  10. Adjustable gastric banding (image)

    MedlinePLUS

    Restrictive gastric operations, such as an adjustable gastric banding procedure, serve only to restrict and decrease food intake and do not interfere with the normal digestive process. In this procedure, a hollow ...

  11. 18 Ghz propagation and rainfall intensity

    NASA Astrophysics Data System (ADS)

    Kuehn, U.

    1988-07-01

    Comparisons between the depth of the absorption fading at 18 Ghz and rainfall intensity along a 21 km path revealed information on how to reduce point rainfall intensity over a radio path in order to predict fading probability from point rainfall data. Simultaneous studies of 18 Ghz propagation on two radio paths, one running in the east-west and the other in the north-south direction, have been performed to get information about the influence of rain cells moving mostly from west to east in central Europe. Six rain recorders of the water-wheel type made it possible to distinguish between absorption and multipath fading. The fading probability was found to be higher on the east-west path as the rain cells remain over the radio link for a longer time compared with a north-south running path.

  12. Supersymmetry and Identical Bands

    NASA Astrophysics Data System (ADS)

    von Brentano, P.

    2004-04-01

    Supersymmetry as applied to identical bands is discussed. A review of the work of the Koeln-Dubna group on this topic is given and examples in 171,172Yb , 173,174Hf and 195,194pt are discussed. The role of pseudo-spin in the supersymmetry is investigated. A recent precision lifetime measurement for identical bands in 171,172Yb is discussed.

  13. A theoretical and experimental study of pressure broadening of the oxygen A-band by helium.

    PubMed

    Grimminck, Dennis L A G; Spiering, Frans R; Janssen, Liesbeth M C; van der Avoird, Ad; van der Zande, Wim J; Groenenboom, Gerrit C

    2014-05-28

    The rotationally resolved magnetic dipole absorption spectrum of the oxygen A-band b(1)?(g)(+)(v=0) <- X(3)?(g)(-)(v=0) perturbed by collisions with helium was studied theoretically using the impact approximation. To calculate the relaxation matrix, scattering calculations were performed on a newly computed helium-oxygen (b(1)?(g)(+)) interaction potential as well as on a helium-oxygen (X(3)?(g)(-)) interaction potential from the literature. The calculated integrated line cross sections and broadening coefficients are in good agreement with experimental results from the literature. Additionally, cavity ring-down experiments were performed in the wings of the spectral lines for a quantitative study of line-mixing, i.e., the redistribution of rotational line intensities by helium-oxygen collisions. It is shown that inclusion of line-mixing in the theory is required to reproduce the experimentally determined absolute absorption strengths as a function of the density of the helium gas. PMID:24880287

  14. A theoretical and experimental study of pressure broadening of the oxygen A-band by helium

    SciTech Connect

    Grimminck, Dennis L. A. G.; Spiering, Frans R.; Janssen, Liesbeth M. C.; Avoird, Ad van der; Zande, Wim J. van der; Groenenboom, Gerrit C., E-mail: Gerritg@theochem.ru.nl [Institute for Molecules and Materials, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands)

    2014-05-28

    The rotationally resolved magnetic dipole absorption spectrum of the oxygen A-band b{sup 1}?{sub g}{sup +}(v=0)?X{sup 3}?{sub g}{sup ?}(v=0) perturbed by collisions with helium was studied theoretically using the impact approximation. To calculate the relaxation matrix, scattering calculations were performed on a newly computed helium-oxygen (b{sup 1}?{sub g}{sup +}) interaction potential as well as on a helium-oxygen (X{sup 3}?{sub g}{sup ?}) interaction potential from the literature. The calculated integrated line cross sections and broadening coefficients are in good agreement with experimental results from the literature. Additionally, cavity ring-down experiments were performed in the wings of the spectral lines for a quantitative study of line-mixing, i.e., the redistribution of rotational line intensities by helium-oxygen collisions. It is shown that inclusion of line-mixing in the theory is required to reproduce the experimentally determined absolute absorption strengths as a function of the density of the helium gas.

  15. Intermediate band properties of femtosecond-laser hyperdoped silicon

    NASA Astrophysics Data System (ADS)

    Sher, Meng-Ju

    This thesis explores using femtosecond-laser pulses to hyperdope silicon with chalcogen dopants at concentrations above the maximum equilibrium solubility. Hyperdoped silicon is promising for improving efficiencies of solar cells: the material exhibits broad-band light absorption to wavelengths deep below the corresponding bandgap energy of silicon. The high concentration of dopants forms an intermediate band (IB), instead of discrete energy levels, and the IB enables sub-bandgap light absorption. This thesis is divided into two primary studies: the dopant incorporation and the IB properties. First, we study dopant incorporation with a gas-phase dopant precursor (SF6) using secondary ion mass spectrometry. By varying the pressure of SF6, we find that the surface adsorbed molecules are the dominant source of the dopant. Furthermore, we show the hyperdoped layer is single crystalline. The results demonstrate that the dopant incorporation depth, concentration, and crystallinity are controlled respectively by the number of laser pulses, pressure of the dopant precursor, and laser fluence. Second, we study the IB properties of hyperdoped silicon using optical and electronic measurements. We use Fourier transform infrared spectroscopy to study light absorption. The absorption extends to wavelengths as far as 6 mum before thermal annealing and we find the upper bound of the IB location at 0.2 eV below the conduction band edge. For electronic measurements, we anneal the samples to form a diode between the hyperdoped layer and the substrate, allowing us to probe the IB using temperature-dependent electronic transport measurements. The measurement data indicate that these samples form a localized IB at concentrations below the insulator-to-metal transition. Using a two-band model, we obtain the location of the localized IB at >0.07 eV below the conduction band edge. After femtosecond-laser hyperdoping, annealing is necessary to reduce the laser-induced defects; however annealing decreases the sub-bandgap absorption. As we are interested in the IB that contributes to sub-bandgap absorption, we explore methods to reactivate the sub-bandgap absorption. We show that the sub-bandgap absorption is reactivated by annealing at high temperatures between 1350 and 1550 K followed by fast cooling (>50 K/s). Our results demonstrate an ability to control sub-bandgap absorption using thermal processing.

  16. Circular Intensity Differential Scattering of chiral molecules

    SciTech Connect

    Bustamante, C.J.

    1980-12-01

    In this thesis a theory of the Circular Intensity Differential Scattering (CIDS) of chiral molecules as modelled by a helix oriented with respect to the direction of incidence of light is presented. It is shown that a necessary condition for the existence of CIDS is the presence of an asymmetric polarizability in the scatterer. The polarizability of the scatterer is assumed generally complex, so that both refractive and absorptive phenomena are taken into account.

  17. Flexible metamaterial absorbers with multi-band infrared response

    NASA Astrophysics Data System (ADS)

    Dayal, Govind; Ramakrishna, S. Anantha

    2015-01-01

    A flexible metamaterial with a tri-layer metal-dielectric-metal structure is fabricated by combining Excimer laser micromachining of a polyimide sheet and oblique angle physical vapour deposition methods. Excimer laser micromachining is used to generate an array of micro-disks on the flexible polymer sheet followed by physical vapour deposition at normal incidence to produce continuous metal and dielectric layers while oblique angle deposition of metal vapour is used to finally form discrete oblate ellipsoids on top of the micro-disks. The fabricated metamaterial shows multi-band metamaterial absorption exceeding 90% simultaneously over infrared bands centred at 3 µm, 5 µm, and 13.85 µm. The multi-band absorption arises due to multipole resonances of the disk structure and is accurately modelled by electromagnetic simulation as well. A theoretical model of a perfect absorber as an array of optimally impedance matched antennas is also presented.

  18. Hot band spectroscopy of the formyl cation, H12C16O+.

    PubMed

    Neese, Christopher F; Kreynin, Peter S; Oka, Takeshi

    2013-10-01

    Midinfrared spectra of the formyl cation, HCO(+), were recorded by direct absorption in a glow discharge (composition CO, 50 mTorr; H2, 50 mTorr; He, 7 Torr) using a color center laser spectrometer and velocity modulation with heterodyne detection. The bands measured were 10(0)0-00(0)0, 11(1)0-01(1)0, 12(0)0-02(0)0, 12(2)0-02(2)0, 10(0)1-00(0)1, 11(1)1-01(1)1, 20(0)0-10(0)0, and 10(0)2-00(0)2. These bands were analyzed and fitted together with all other available rotationally resolved spectra to arrive at a new set of spectroscopic constants for HCO(+). The relative intensities were fit to obtain a rotational temperature, Trot = 434 ± 7 K, and vibrational temperatures for each mode, T1 = 3300 ± 240 K, T2 = 841 ± 15 K, and T3 = 3157 ± 68 K. PMID:23488795

  19. Electronic absorption spectra dibenzotetraazaannulenes: Effect of periphery substituents

    Microsoft Academic Search

    B. A. Snopok; Ya D. Lampeka

    1992-01-01

    We resolved the electronic absorption spectra of three tetraazaannulenes of different symmetry measured in solution at 298 and 77 K. The results obtained allow us to assign the bands observed in the visible region to n yields gamma(sup *) transitions and to vibronic components of two gamma yields gamma(sup *) transitions. The efficiency of vibronic interaction is shown to depend

  20. On the Absorption Spectra of Complex Ions. I

    Microsoft Academic Search

    Yukito Tanabe; Satoru Sugano

    1954-01-01

    In order to explain the origin of both absorption bands and lines of the octahedral normal complex ions in which the central metal ions belong to iron group elements, the crystalline field approximation interpreted in somewhat generalized sense is adopted. For this purpose the calculation of the energy matrix elements for dn (n{=}1, 2, \\\\ldots, 9) electron configuration in cubic