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1

Propane absorption band intensities and band model parameters from 680 to 1580/cm at 296 and 200 K  

NASA Technical Reports Server (NTRS)

Band intensities and profiles have been measured for the propane absorption bands from 680 to 1580/cm at 296 and 200 K. This work was stimulated by the discovery of several propane bands in the spectrum of Titan by the Voyager 1 spacecraft. The low temperature laboratory data show that the bands become narrower and the Q branches of the bands somewhat stronger than they are at room temperature. Random band model parameters were determined over the entire region from the 42 spectra obtained at room temperature.

Giver, L. P.; Valero, F. P. J.; Varanasi, P.

1984-01-01

2

Absolute Rovibrational Intensities of C-12O2-16 Absorption Bands in the 3090-3850/ CM Spectral Region  

NASA Technical Reports Server (NTRS)

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 C-12O2-16 between 3090 and 3850/ cm. 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 resolution) were recorded at room temperature and low pressure (1 to 10 Torr) using the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak. The absorption path lengths for these spectra varied between 24.86 and 385.76 m. The first experimental determination of the intensity of the theoretically predicted 2(nu)(sub 2, sup 2) + nu(sub 3) "forbidden" band has been made. The measured line intensities obtained for each band have been analyzed to determine the vibrational band intensity, S(sub nu), in /cm/( molecule/sq cm) at 296 K, square of the rotationless transition dipole moment |R|(exp 2) in Debye, as well as the nonrigid rotor coefficients. The results are compared to the values listed in the 1996 HITRAN database which are obtained using the direct numerical diagonalization (DND) technique as well as to other published values where available.

Devi, V. Malathy; Benner, D. Chris; Rinsland, Curtis P.; Smith, Mary Ann H.

1998-01-01

3

The nu sub 9 fundamental of ethane - Integrated intensity and band absorption measurements with application to the atmospheres of the major planets  

NASA Technical Reports Server (NTRS)

Measurements of the absolute intensity and integrated band absorption have been performed for the nu sub 9 fundamental band of ethane. The intensity is found to be about 34 per sq cm per atm at STP, and this is significantly higher than previous estimates. It is shown that a Gaussian profile provides an empirical representation of the apparent spectral absorption coefficient. Employing this empirical profile, a simple expression is derived for the integrated band absorption, which is in excellent agreement with experimental values. The band model is then employed to investigate the possible role of ethane as a source of thermal infrared opacity within the atmospheres of Jupiter and Saturn, and to interpret qualitatively observed brightness temperatures for Saturn.

Varanasi, P.; Cess, R. D.; Bangaru, B. R. P.

1974-01-01

4

Band Transmittance &Band Transmittance & Absorptance Model  

E-print Network

separation d, i.e. =nd · Let the probability that line i has a line strength Si be P(Si) where 1)( dSSP 1)( 0 dSSP i · P is normally assumed to have a Poisson· P is normally assumed to have a Poisson distribution #12;Statistical Band Model (Goody)Statistical Band Model

Li, Zhanqing

5

Below band-gap optical absorption in semiconductor alloys  

Microsoft Academic Search

We have used accurate Hamiltonians and resulting wave functions to calculate the two-photon absorption coefficient and the free-carrier absorption coefficient in InAs and a HgCdTe alloy with the same band gap. Detailed results are obtained for the dependencies of the absorption on photon energy and incident intensity. Optical matrix elements are calculated from the wave number dependent wave functions. We

Srinivasan Krishnamurthy; A. Sher; A.-B. Chen

2000-01-01

6

The Rovibrational Intensities of the (40 deg 1) and (00 deg 0) Pentad Absorption Bands of 12C16O2 Between 7284 and 7921 cm(exp-1)  

NASA Technical Reports Server (NTRS)

Carbon dioxide is the major constituent of the atmospheres of both Mars and Venus. Correct interpretations of spectra of these atmospheres require accurate knowledge of a substantial number of absorption bands of this gas. This is especially true for Venus; many weak CO2 bands that are insignificant in the earth's atmosphere are prominent absorbers in Venus' hot, dense lower atmosphere. Yet, recent near-infrared spectra of Venus' nightside have discovered emission windows, which occur between CO2 absorption bands, at 4040-4550 cm(exp-1), 5700-5900 cm(exp-1), and several smaller ones between 7500 and 9400 cm(exp-1). This radiation is due to thermal emission from Venus' lower atmosphere, diminished by scattering and absorption within the sulfuric acid clouds on its way to space. Simulations of these data with radiative transfer models can provide improved information on the abundances of a number of constituents of the lower atmosphere (e.g. H2O, CO, HDO, HCl, HF, and OCS) and the optical properties of the clouds, whose spatial variation modulates the brightness of the emissions. However, the accuracy of these retrievals has been limited by insufficient knowledge of the opacity of some of the gas species, including CO2, at the large pathlengths and high temperatures and pressures that exist on Venus. In particular, modeling the emission spectrum did not produce a good fit for the emission window centered at 7830 cm(exp-1). In an ongoing effort to assist analyses of these Venus spectra, we have been making laboratory intensity measurements of several weak bands of CO2 which are significant absorbers in these Venus emission windows. The CO2 bands that are prominent in the 7830 cm(exp-1) region belong to the vibrational sequence 4v1+v3 and associated hot bands. Only 2 of the 5 bands of this sequence have been previously measured. Modeling Venus' emission spectrum in the 7830 cm(exp-1) region had to rely on calculated intensity values for the weak ground state band at 7921 cm-1 and the associated hot bands. Since the calculated intensities of ground state bands are known to have significant uncertainties, we decided to measure this (40 deg 1)I (left arrow) (00 deg 0) band with the Ames 25 meter multiple reflection absorption cell and Fourier transform spectrometer. We also measured the (40 deg 1) (sub IV) (left arrow) (00 deg 0) band at 7460 cm(exp-1), which also had not been previously measured. These measurements are reported in this article, and we also give our reanalysis of the prior measurements of the (40 deg 1) (sub III) (left arrow) (00 deg 0) bands. These measurements provide the basis for improving calculated intensities for related hot bands as well as simulations of Venus' spectrum.

Giver, L. P.; Chackerian, C., Jr.; Spencer, N.; Brown, L. R.; Wattson, R. B.; Gore, Warren J. (Technical Monitor)

1995-01-01

7

Experimental and theoretical study of absorption spectrum of the (CH3)2COHF complex. Influence of anharmonic interactions on the frequency and intensity of the C=O and H-F stretching bands.  

PubMed

IR absorption spectra of mixtures (CH3)2CO/HF and free (CH3)2CO molecules are recorded in the region of 4000-900 cm(-1) with a Bruker IFS-125 HR vacuum Fourier spectrometer at room temperature with a resolution up to 0.02 cm(-1). Spectral characteristics of the 2?(C=O) overtone band of free acetone are reliably measured. The ?1(HF) and ?(C=O) absorption bands of the (CH3)2COHF complex are obtained by subtracting the absorption bands of free HF and acetone and absorption lines of atmospheric water from the experimental spectrum of mixtures. The experimental data are compared with theoretical results obtained from variational solutions of 1D-4D vibrational Schrdinger equations. The anharmonic potential energy and dipole moment surfaces used in the calculations were computed in the MP2/6-311++G(2d,2p) approximation with corrections for the basis set superposition error. Comparison of the data derived from solutions for different combinations of vibrational degrees of freedom shows that taking the inter-mode anharmonic interactions into account has different effects on the transition frequencies and intensities. Particular attention has been given to elucidation of the influence of anharmonic coupling of the H-F and C=O stretches with the low-frequency intermolecular modes on their frequencies and intensities and the strength of resonance between the fundamental H-F and the first overtone C=O transitions. PMID:24128921

Bulychev, V P; Svishcheva, E A; Tokhadze, K G

2014-01-01

8

Intensity dependent nonlinear absorption of pyrylium chromophores  

NASA Astrophysics Data System (ADS)

The intensity dependence of nonlinear absorption (NLA) of a series of pyrylium chromophores was studied with femtosecond pulses in their two-photon absorption spectral region to assess their potential as optical limiters. The open z-scan technique using different excitation intensities was employed. Fifth-order effects appear above a critical value of the irradiance and consequently of the first excited singlet-state population. Reverse saturable absorption (RSA) based on two-photon (TPA) and excited-state absorption (ESA) was dominant in most cases. The third- and fifth-order NLA coefficients and high ESA cross-sections of the order of 10 -15 cm2 are presented at 760, 790 and 840 nm.

Fakis, Mihalis; Tsigaridas, Georgios; Polyzos, Ioannis; Giannetas, Vassilis; Persephonis, Peter; Spiliopoulos, Ioakim; Mikroyannidis, John

2001-07-01

9

Absolute integrated intensity for the nu-1 sulfur dioxide band  

NASA Technical Reports Server (NTRS)

The absolute integrated intensity of the IR vibration-rotation nu-1 SO2 band was measured using the linear portion of the curve of growth. Infrared spectroscopic-absorption cell measurements were performed on sulfur dioxide at partial pressures less than 0.15 torr with nitrogen added to give a total pressure of 705 torr, the path length being 4 mm. The absolute integrated intensity was determined to be 112.0 plus or minus 2.6/cm/sq (atm cm) at 296 K at the 95% confidence level.

Pilon, P. J.; Young, C.

1976-01-01

10

Raman band intensities of tellurite glasses.  

PubMed

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

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

2005-05-15

11

Nonlinear Absorption Processes at Half the Band Gap in GaAs Based Semiconductors.  

National Technical Information Service (NTIS)

The utility of the ultrafast nonlinearity in semiconductor waveguides operated below the band gap is limited by two photon absorption Beta (Alpha = Beta I where I is the intensity) which does not allow a nonlinear 2 Pi phase shift over one absorption leng...

A. Villeneuve, G. I. Stegeman, G. Scelsi, C. N. Ironside, J. S. Aitchison

1992-01-01

12

Nonlinera Light Absorption Saturation in Direct Band Gap Semiconductors  

NASA Astrophysics Data System (ADS)

The nonlinear light wave interaction in direct band gap semiconductor, such as InGaAsP, is theoretically investigated in the frame of pump-probe scheme. The consideration is carried out under the conditions, when the main mechanism of nonlinearity is the spectral hole burning. We consider the physical situation when the other mechanisms of optical nonlineraties, such as carrier heating, many body Coulomb effects and excitonic effects, are not important. Our calculations are based on the density matrix equation and propagation equations for pump and probe waves. Using the realistic approximation of parabolic dispersion law for carriers and assuming degenerate regime of pump-probe interaction the expressions for pump intensity dependent interband absorption coefficients (AC) of both pump and probe waves are obtained [1]. The ACs demonstrate unusual dependence on the pump intensity. Particularly, at high pump intensities both ACs decrease inverse proportionally to the fourth root of pump intensity. This result, which is a consequence of the parabolic dispersion law of carriers, implies that saturation of nonlinear wave interaction is weaker, than it follows from earlier theories. This circumstance enables to reach higher efficiencies of nonlinear processes like four-wave mixing. The propagation equations are reduced to the form, which is more convenient for numerical calculations. The calculated effective optical thickness dependence on the pump input intensity for the probe wave demonstrates good agreement with the experimental data obtained in [2]. This makes possible to obtain correct estimation for carriers intraband relaxation times, the values of which are still disputable. This work is supported by SCOPIS 2001-2003. [1] A.O.Melikyan, H.R.Minassian, Saturation of Interband Absorption in Semiconductors. Semiconductors April 2000, v.34, Issue 4, pp.386-388. [2].M.N. Islam, E.P. Ippen et al, Appl.Phys.Lett.,47,1042,(1985), M.N. Islam, E.P. Ippen et al, J.Appl.Phys.,59 (1986) 2619.

Minassian, Hayk; Melikyan, Armen

2001-03-01

13

Theory of absorption rate of carriers in fused silica under intense laser irradiation  

SciTech Connect

A quantum non-perturbation theory for phonon-assisted photon absorption of conduction band electron in intense laser was developed. By carrying out the calculation in fused silica at wavelengths from ultraviolet to infrared in terawatt intensity laser, we show that the Non-perturbation approach can make a uniform description of energy absorption rate at both short wavelengths and long wavelengths on TW / cm2 intensity laser.

Deng, Hongxiang; Xiang, Xia; Zheng, WG; Yuan, XD; Wu, SY; Jiang, XD; Gao, Fei; Zu, Xiaotao T.; Sun, Kai

2010-11-15

14

A listing of wavenumbers and intensities of carbon dioxide absorption lines between 12 and 20 micrometers  

NASA Technical Reports Server (NTRS)

A listing is given of the wavenumber, intensities at 300, 275, 250, 225, 200 and 175 k and energy of the lower state of CO2 absorption lines between 12 and 20 microns. They are ordered by wave-number and include 19 bands of C-12(O-16)2, 4 bands of C-13(O-16)2, 2 bands of C-12-O-16-O-18 and 1 band of C-12-O-16-O-17. The vibrational and rotational constants and the band intensities used to calculate the line parameters are tabulated.

Drayson, S. R.

1973-01-01

15

Structurally tunable resonant absorption bands in ultrathin broadband plasmonic absorbers.  

PubMed

Light absorption is a fundamental optical process playing significantly important role in wide variety of applications ranging from photovoltaics to photothermal therapy. Semiconductors have well-defined absorption bands with low-energy edge dictated by the band gap energy, therefore it is rather challenging to tune the absorption bandwidth of semiconductors. However, resonant absorbers based on plasmonic nanostructures and optical metamaterials emerged as alternative light absorbers due to spectrally selective absorption bands resulting from optical resonances. Recently, a broadband plasmonic absorber design was introduced by Aydin et al. with a reasonably high broadband absorption. Based on that design, here, structurally tunable, broadband absorbers with improved performance are demonstrated. This broadband absorber has a total thickness of 190 nm with 80% average measured absorption (90% simulated absorption) over the entire visible spectrum (400 - 700 nm). Moreover, the effect of the metal and the oxide thicknesses on the absorption spectra are investigated and results indicate that the shorter and the longer band-edge of broadband absorption can be structurally tuned with the metal and the oxide thicknesses, as well as with the resonator size. Detailed numerical simulations shed light on the type of optical resonances that contribute to the broadband absorption response and provide a design guideline for realizing plasmonic absorbers with structurally tunable bandwidths. PMID:25321029

Butun, Serkan; Aydin, Koray

2014-08-11

16

Saturable absorption of intense hard X-rays in iron  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

17

Saturable absorption of intense hard X-rays in iron.  

PubMed

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 10(20)?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. PMID:25270525

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

2014-01-01

18

Giant infrared absorption bands of electrons and holes in conjugated molecules  

NASA Astrophysics Data System (ADS)

Infrared (IR) absorption bands often convey identifying information about molecules, but are usually weak, having molar absorption coefficients <200?M-1?cm-1. Here we report observation of radical anions and cations of conjugated oligomers and polymers of fluorene and thiophene that possess intense mid-infrared absorption coefficients as large as 50,000?M-1?cm-1, perhaps the largest known for molecular species. For anions of fluorene oligomers, Fn, n=2-4, IR intensities increase almost linearly with n, but with a slope much larger than one, indicating that the absorptions are not extensive properties. Large intensities seem to arise from a mechanism known for charged solitons and polarons in conjugated polymers. In this mechanism, vibrations of ungerade symmetry drive substantial displacements of charge, creating the large dipole derivatives responsible for intense IR absorption. Both experiments and calculations find that pairing with counter-ions attenuates IR band intensities. The IR bands may be diagnostic for bound ion pairs and their escape to form free ions.

Zamadar, Matibur; Asaoka, Sadayuki; Grills, David C.; Miller, John R.

2013-11-01

19

Investigation of the linear polarization in infrared absorption bands  

Microsoft Academic Search

We consider the effects of the grain size, shape, structure, and chemical composition as well as the angle between the grain\\u000a rotation axis and the incident ray on the full widths at half maximum (FWHM) of the polarization bands in the two deepest\\u000a infrared absorption bands observed in the spectra of protostars, the water-ice band centered at 3.1 ?m and

T. V. Zinoveva

2008-01-01

20

Interpretation of absorption bands in airborne hyperspectral radiance data.  

PubMed

It is demonstrated that hyperspectral imagery can be used, without atmospheric correction, to determine the presence of accessory phytoplankton pigments in coastal waters using derivative techniques. However, care must be taken not to confuse other absorptions for those caused by the presence of pigments. Atmospheric correction, usually the first step to making products from hyperspectral data, may not completely remove Fraunhofer lines and atmospheric absorption bands and these absorptions may interfere with identification of phytoplankton accessory pigments. Furthermore, the ability to resolve absorption bands depends on the spectral resolution of the spectrometer, which for a fixed spectral range also determines the number of observed bands. Based on this information, a study was undertaken to determine under what circumstances a hyperspectral sensor may determine the presence of pigments. As part of the study a hyperspectral imager was used to take high spectral resolution data over two different water masses. In order to avoid the problems associated with atmospheric correction this data was analyzed as radiance data without atmospheric correction. Here, the purpose was to identify spectral regions that might be diagnostic for photosynthetic pigments. Two well proven techniques were used to aid in absorption band recognition, the continuum removal of the spectra and the fourth derivative. The findings in this study suggest that interpretation of absorption bands in remote sensing data, whether atmospherically corrected or not, have to be carefully reviewed when they are interpreted in terms of photosynthetic pigments. PMID:22574053

Szekielda, Karl H; Bowles, Jeffrey H; Gillis, David B; Miller, W David

2009-01-01

21

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

PubMed

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

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

2012-07-10

22

Millimeter Wave Absorption Bands of Silver/copper Iodides-Phosphate Glasses  

NASA Astrophysics Data System (ADS)

Millimeter wave absorption spectra of silver halides doped silver phosphate glasses were measured using an intense coherent transition radiation. Two bands were observed at 8.4cm-1 and 6.3cm-1 in AgI doped AgPO3 glass and 8.7cm-1 and 6.1cm-1 in AgBr doped one. Small difference of peak positions between these glasses suggests that these absorption bands are concerned with a large number of silver ions in dopant molecules. Cu+ conducting glasses

Awano, Teruyoshi; Takahashi, Toshiharu

2013-07-01

23

Quantitative Measurement of Integrated Band Intensities of Isoprene and Formaldehyde  

NASA Astrophysics Data System (ADS)

The OH-initiated oxidation of isoprene, which is one of the primary volatile organic compounds produced by vegetation, is a major source of atmospheric formaldehyde and other oxygenated organics. Both molecules are also known products of biomass burning. Absorption coefficients and integrated band intensities for isoprene and formaldehyde are reported in the 600 - 6500 cm^{-1} region. The pressure broadened (1 atmosphere N_2) 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 composed of a minimum of seven pressures at each temperature for both molecules. These data are part of the PNNL Spectral Database, which contains quantitative spectra of over 600 molecules. These quantitative spectra facilitate atmospheric monitoring for both remote and in situ sensing and such applications will be discussed. Timothy J. Johnson, Luisa T. M. Profeta, Robert L. Sams, David W. T. Griffith, Robert L. Yokelson Vibrational Spectroscopy {53}(1);97-102 (2010).

Brauer, Carolyn S.; Johnson, Timothy J.; Blake, Thomas A.; Sams, Robert L.

2013-06-01

24

The 3? 1+ ? 2Combination Band of HOCl: Assignments, Perturbations, and Line Intensities  

NASA Astrophysics Data System (ADS)

The high-resolution spectra (0.012 cm -1) of the 3? 1+ ? 2combination band of hypochlorous acid HO 35(37)Cl in the near infrared (11 478 cm -1) have been measured using a titanium:sapphire intracavity laser absorption (ICLA) spectrometer. Line assignments, absolute intensities, and the total band intensity for both isotopomers are reported. In the course of the band analysis two K abranches ( K a= 2,3) were found to be perturbed via low-order Fermi-type (anharmonic) resonances by a dark perturber which has been identified to be the 2? 1+ 2? 2+ 3? 3state. The data are compared with intensity predictions from simple empirical models and discussed with regard to detection limits for this molecule in the near infrared spectral region of the atmosphere.

Charvt, Ale; Deppe, Sabine F.; Hamann, Hilmar H.; Abel, Bernd

1997-10-01

25

A measurement of the relative intensities of some vibronic bands  

E-print Network

. AVERAGE RQ, ATIYE DENSITY FOR EACH PLATE WITH D AS UNITI ~ o ~ ~ ~ ~ ~ o ~ ~ X. AVERAGE a%LATIVE INTENSITY OF SEVENTEEN CHLOR1NK DIOXIDE BANDS FOR EACH OF EIGHT PLATES XI ~ MOLECULAR EXTINCTION COkTFFICIEMTS QF SO2 XII ~ RELATIVE EXTINCTION... the molecular extinction ooefficients of the band. If as in the case of chlorine dioxide the geometry of both the ground and excited state is known, then a theoretical calculation of the relative intensity can be made. This calculation will be compared...

Loyd, Coleman Monroe

2012-06-07

26

Isothermal annealing of a 620 nm optical absorption band in Brazilian topaz crystals  

NASA Astrophysics Data System (ADS)

Isothermal decay behaviors, observed at 515, 523, 562, and 693 K, for an optical absorption band at 620 nm in gamma-irradiated Brazilian blue topaz were analyzed using a kinetic model consisting of O- bound small polarons adjacent to recombination centers (electron traps). The kinetic equations obtained on the basis of this model were solved using the method of Runge-Kutta and the fit parameters describing these defects were determined with a grid optimization method. Two activation energies of 0.520.08 and 0.880.13 eV, corresponding to two different structural configurations of the O- polarons, explained well the isothermal decay curves using first-order kinetics expected from the kinetic model. On the other hand, thermoluminescence (TL) emission spectra measured at various temperatures showed a single band at 400 nm in the temperature range of 373-553 K in which the 620 nm optical absorption band decreased in intensity. Monochromatic TL glow curve data at 400 nm extracted from the TL emission spectra observed were found to be explained reasonably by using the knowledge obtained from the isothermal decay analysis. This suggests that two different structural configurations of O- polarons are responsible for the 620 nm optical absorption band and that the thermal annealing of the polarons causes the 400 nm TL emission band.

Isotani, Sadao; Matsuoka, Masao; Albuquerque, Antonio Roberto Pereira Leite

2013-04-01

27

Reversible Bleaching of a Band in the Absorption Spectrum of Diamond  

Microsoft Academic Search

When diamonds which show the absorption band in the near ultraviolet, characteristic of blue fluorescing samples, are exposed to neutron bombardment, a continuous absorption slowly rising toward shorter wavelength is superimposed upon the band. Heating such a diamond to temperatures between 300 and 600C decreases the continuous absorption and the structure of the band becomes appreciably sharper. Subsequent exposure to

Peter Pringsheim

1953-01-01

28

R&D Intensity, Technology Transfer and Absorptive Capacity  

Microsoft Academic Search

In the line of Schumpeterian fully endogenous growth theory, this study attempts to investigate whether differences in research intensity as well as absorptive capacity help to explain cross-country differences in productivity growth in a panel of 55 sample countries including 23 OECD and 32 developing economies over the period 1970 to 2004. Using several indicators of innovative activity and product

Rabiul Islam

29

Absolute intensity measurement of the 4-0 vibration-rotation band of carbon monoxide  

NASA Technical Reports Server (NTRS)

The absolute intensity of the 4-0 vibration band of CO is measured in spectra obtained using a 25-m base-path multiple-traversal absorption cell and a 5-m scanning spectrometer. The intensities of individual vibration-rotation lines in this band are determined from measurements of their equivalent widths, and absolute values for the rotationless transition moment and the vibration-rotation interaction factor are derived from the measured line strengths. The experimentally obtained vibration-rotation function is compared with a theoretical curve; agreement between theory and experiment is found to be good for the P-branch but poor for the R-branch. It is noted that numerical solutions to the radial Schroedinger equation lead to vibration-rotation function values that are in good agreement with the experiment.

Chackerian, C., Jr.; Valero, F. P. J.

1976-01-01

30

Collisionless absorption of intense laser radiation in nanoplasma  

SciTech Connect

The rate of linear collisionless absorption of an electromagnetic radiation in a nanoplasma - classical electron gas localised in a heated ionised nanosystem (thin film or cluster) irradiated by an intense femtosecond laser pulse - is calculated. The absorption is caused by the inelastic electron scattering from the self-consistent potential of the system in the presence of a laser field. The effect proves to be appreciable because of a small size of the systems. General expressions are obtained for the absorption rate as a function of the parameters of the single-particle self-consistent potential and electron distribution function in the regime linear in field. For the simplest cases, where the self-consistent field is created by an infinitely deep well or an infinite charged plane, closed analytic expressions are obtained for the absorption rate. Estimates presented in the paper demonstrate that, over a wide range of the parameters of laser pulses and nanostructures, the collisionless mechanism of heating electron subsystem can be dominant. The possibility of experimental observation of the collisionless absorption of intense laser radiation in nanoplasma is also discussed. (interaction of laser radiation with matter)

Zaretsky, D F [Russian Research Centre 'Kurchatov Institute', Moscow (Russian Federation); Korneev, Philipp A; Popruzhenko, Sergei V [Moscow Engineering Physics Institute (State University), Moscow (Russian Federation)

2007-06-30

31

A model for multiphoton absorption in dielectric materials induced by short laser pulses at moderate intensities.  

PubMed

We present a semi-analytical model for free electron production induced by multiphoton ionization in dielectric materials for short laser pulses at moderate intensities. Within this approach, the laser-induced absorption is described through the Bloch-Volkov formalism, and the electronic structure of materials is evaluated through first-principles calculations. Results obtained for NaCl and KDP (KH2PO4) materials show that significant deviations from the parabolic band approximation may occur. When the laser intensity increases, high multiphotonic orders may become the predominant mechanisms outside the centre of the Brillouin zone. PMID:23676194

Mzel, Candice; Duchateau, Guillaume; Geneste, Grgory; Siberchicot, Bruno

2013-06-12

32

A model for multiphoton absorption in dielectric materials induced by short laser pulses at moderate intensities  

NASA Astrophysics Data System (ADS)

We present a semi-analytical model for free electron production induced by multiphoton ionization in dielectric materials for short laser pulses at moderate intensities. Within this approach, the laser-induced absorption is described through the Bloch-Volkov formalism, and the electronic structure of materials is evaluated through first-principles calculations. Results obtained for NaCl and KDP (KH2PO4) materials show that significant deviations from the parabolic band approximation may occur. When the laser intensity increases, high multiphotonic orders may become the predominant mechanisms outside the centre of the Brillouin zone.

Mzel, Candice; Duchateau, Guillaume; Geneste, Grgory; Siberchicot, Bruno

2013-06-01

33

Seven broad absorption line quasars with excess broad band absorption near 2250  

E-print Network

We report the discovery of excess broad band absorption near 2250 A (EBBA) in the spectra of seven broad absorption line (BAL) quasars. By comparing with the statistical results from the control quasar sample, the significance for the detections are all above the > 4{\\sigma} level, with five above > 5{\\sigma}. The detections have also been verified by several other independent methods. The EBBAs present broader and weaker bumps at smaller wavenumbers than the Milky Way, and similar to the Large Magellanic Cloud. The EBBA bump may be related to the 2175 A bump seen in the Local Group and may be a counterpart of the 2175 A bump under different conditions in the early Universe. Furthermore, five objects in this sample show low-ionization broad absorption lines (LoBALs), such as Mg II and Al III, in addition to the high-ionization broad absorption lines (HiBALs) of C IV and Si IV. The fraction of LoBALs in our sample, ~70%, is surprisingly high compared to that of general BAL quasars, ~10%. Although the origin of...

Zhang, Shaohua; Jiang, Peng; Zhou, Hongyan; Ma, Jingzhe; Brandt, W N; York, Donald G; Noterdaeme, P; Schneider, Donald P

2014-01-01

34

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

35

Infrared line intensity measurements in the v = 0-1 band of the ClO radical  

NASA Technical Reports Server (NTRS)

Integrated line intensity measurements in the ClO-radical fundamental vibrational v = 0-1 band were carried out using a high-resolution Fourier transform spectrometer coupled to a long-path-length absorption cell. The results of a series of measurements designed to minimize systematic errors, yielded a value of the fundamental IR band intensity of the ClO-radical equal to 9.68 + or - 1.45/sq cm per atm at 296 K. This result is consistent with all the earlier published results, with the exception of measurements reported by Kostiuk et al. (1986) and Lang et al. (1988).

Burkholder, James B.; Howard, Carleton J.; Hammer, Philip D.; Goldman, Aaron

1989-01-01

36

An adiabatic model for the photodissociation of CH3SH in the first ultraviolet absorption band  

E-print Network

An adiabatic model for the photodissociation of CH3SH in the first ultraviolet absorption band; accepted 31 January 1995 The photodissociation of CH3SH in the first absorption band is studied via ab the global ground X 1 A and 1 1 A surfaces as functions of the C­S and S­H internuclear distances. The finite

Butler, Laurie J.

37

Absorption of intense regular and noise waves in relaxing media  

NASA Astrophysics Data System (ADS)

An integro-differential equation is written down that contains terms responsible for nonlinear absorption, visco-heat-conducting dissipation, and relaxation processes in a medium. A general integral expression is obtained for calculating energy losses of the wave with arbitrary characteristicsintensity, profile (frequency spectrum), and kernel describing the internal dynamics of the medium. It is shown that for weak waves, the general integral leads to well-known results of a linear approximation. Profiles of stationary solutions are constructed both for an exponential relaxation kernel and for other types of kernels. Energy losses at the front of week shock waves are calculated. General integral formulas are obtained for energy losses of intense noise, which are determined by the form of the kernel, the structure of the noise correlation function, and the mean square of the derivative of realization of a random process.

Rudenko, O. V.; Gurbatov, S. N.; Demin, I. Yu.

2014-09-01

38

Infrared absorption bands associated with native defects in ZnGeP2  

Microsoft Academic Search

An optical absorption investigation from 10 to 296 K has been performed on bulk crystals of ZnGeP2 grown by the horizontal-gradient-freeze method. We identify three broad absorption bands in the spectral range from 1 to 4 mum that are due to native defects. At low temperature, a band peaking near 1.2 mum and another band peaking near 2.2 mum have

N. C. Giles; Lihua Bai; M. M. Chirila; N. Y. Garces; K. T. Stevens; P. G. Schunemann; S. D. Setzler; T. M. Pollak

2003-01-01

39

Infrared absorption bands associated with native defects in ZnGeP2  

Microsoft Academic Search

An optical absorption investigation from 10 to 296 K has been performed on bulk crystals of ZnGeP2 grown by the horizontal-gradient-freeze method. We identify three broad absorption bands in the spectral range from 1 to 4 ?m that are due to native defects. At low temperature, a band peaking near 1.2 ?m and another band peaking near 2.2 ?m have

N. C. Giles; Lihua Bai; M. M. Chirila; N. Y. Garces; K. T. Stevens; P. G. Schunemann; S. D. Setzler; T. M. Pollak

2003-01-01

40

Ultrafast absorption of intense x rays by nitrogen molecules  

SciTech Connect

We devise a theoretical description for the response of nitrogen molecules (N{sub 2}) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations ({Delta}SCF method). To describe the interaction with N{sub 2}, a detailed investigation of intense x-ray-induced ionization and molecular fragmentation are carried out. As a figure of merit, we calculate ion yields and the average charge state measured in recent experiments at the LCLS. We use a series of phenomenological models of increasing sophistication to unravel the mechanisms of the interaction of x rays with N{sub 2}: a single atom, a symmetric-sharing model, and a fragmentation-matrix model are developed. The role of the formation and decay of single and double core holes, the metastable states of N{sub 2}{sup 2+}, and molecular fragmentation are explained.

Buth, Christian [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Argonne National Laboratory, Argonne, Illinois 60439 (United States); Liu Jicai [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany); Department of Mathematics and Physics, North China Electric Power University, 102206 Beijing (China); Chen, Mau Hsiung [Physics Division, Lawrence Livermore National Laboratory, Livermore, California 94550 (United States); Cryan, James P. [PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Physics, Stanford University, Stanford, California 94305 (United States); Fang Li; Hoener, Matthias; Berrah, Nora [Department of Physics, Western Michigan University, Kalamazoo, Michigan 49008 (United States); Glownia, James M. [PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Department of Applied Physics, Stanford University, Stanford, California 94305 (United States); Coffee, Ryan N. [PULSE Institute for Ultrafast Energy Science, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States); Linac Coherent Light Source, SLAC National Accelerator Laboratory, Menlo Park, California 94025 (United States)

2012-06-07

41

Ultrafast absorption of intense x rays by nitrogen molecules  

NASA Astrophysics Data System (ADS)

We devise a theoretical description for the response of nitrogen molecules (N2) to ultrashort and intense x rays from the free electron laser Linac Coherent Light Source (LCLS). We set out from a rate-equation description for the x-ray absorption by a nitrogen atom. The equations are formulated using all one-x-ray-photon absorption cross sections and the Auger and radiative decay widths of multiply-ionized nitrogen atoms. Cross sections are obtained with a one-electron theory and decay widths are determined from ab initio computations using the Dirac-Hartree-Slater (DHS) method. We also calculate all binding and transition energies of nitrogen atoms in all charge states with the DHS method as the difference of two self-consistent field (SCF) calculations (?SCF method). To describe the interaction with N2, a detailed investigation of intense x-ray-induced ionization and molecular fragmentation are carried out. As a figure of merit, we calculate ion yields and the average charge state measured in recent experiments at the LCLS. We use a series of phenomenological models of increasing sophistication to unravel the mechanisms of the interaction of x rays with N2: a single atom, a symmetric-sharing model, and a fragmentation-matrix model are developed. The role of the formation and decay of single and double core holes, the metastable states of N22+, and molecular fragmentation are explained.

Buth, Christian; Liu, Ji-Cai; Chen, Mau Hsiung; Cryan, James P.; Fang, Li; Glownia, James M.; Hoener, Matthias; Coffee, Ryan N.; Berrah, Nora

2012-06-01

42

Resonance Raman and density functional study of the A-band absorption of C 5H 5[WC?CPh]O 2  

Microsoft Academic Search

Resonance Raman spectra including absolute Raman cross-section measurements and density functional theory (DFT) calculations were performed to study the A-band absorption of C5H5[WC?CPh]O2. The three most intense FranckCondon active modes, the nominal W?O stretch, C?C stretch and C?C stretch, show noticeable intensity in their overtones as well as their combination bands with each other. This is consistent with the changes

Yung Fong Cheng; David Lee Phillips; Guo Zhong He; Chi-Ming Che; Yun Chi

2001-01-01

43

Experimental study of absorption band controllable planar metamaterial absorber using asymmetrical snowflake-shaped configuration  

NASA Astrophysics Data System (ADS)

In this paper, we systematically discuss a novel planar metamaterial absorber (PMA) based on asymmetrical snowflake-shaped resonators, which can exhibit two distinctly different absorption states, single- and dual-band absorptions, by controlling the branch lengths of the proposed resonators. Numerical simulations and experimental measurements are employed to investigate these two kinds of absorption characteristic in an X-band rectangular waveguide. Both results indicate that such a PMA exhibits a wide range of controllable operating frequencies for the single- and dual-band conditions. The proposed PMA is simple and easy to make, and it has wide applications in the fields of stealth technologies, thermal detectors, and imaging.

Huang, Yongjun; Tian, Yiran; Wen, Guangjun; Zhu, Weiren

2013-05-01

44

Optical Salisbury screen with design-tunable resonant absorption bands  

NASA Astrophysics Data System (ADS)

A thin-film selective absorber at visible and near infra-red wavelengths is demonstrated. The structure consists of an optically thick layer of gold, a SiO2 dielectric spacer and a partially transparent gold film on top. The optical cavity so formed traps and absorbs light at a resonance wavelength determined by the film thicknesses. Observed fundamental-resonance absorption strengths are in the range 93%-97%. The absorption red-shifts and broadens as the thickness of the top gold layer is decreased with little change in absorption strength. Thus, strong absorption with design-tunable wavelength and width is achieved easily by unstructured blanket depositions. Observed angle-dependent spectra agree well with the recent three-layer analytical model of Shu et al. [Opt. Express 21, 25307 (2013)], if effective medium approximation is used to calculate the permittivity of the top gold film when it becomes discontinuous at the lowest thicknesses.

Nath, Janardan; Smith, Evan; Maukonen, Douglas; Peale, Robert E.

2014-05-01

45

Precise Determination of the Absorption Maximum in Wide Bands  

ERIC Educational Resources Information Center

A precise method of determining absorption maxima where Gaussian functions occur is described. The method is based on a logarithmic transformation of the Gaussian equation and is suited for a mini-computer. (MR)

Eriksson, Karl-Hugo; And Others

1977-01-01

46

Wide-band perfect optical absorption and photo-thermal effect for three-tier nanogate  

NASA Astrophysics Data System (ADS)

This paper designed a perfect optical absorber based on three-tier gate nanostructure, which shows a wide-band perfect absorption in the wavelength range of 200-560 nm as a transverse wave incidents to the nanostructure with the incident angle 35< ?< 65. When ? = 45, a wide absorption band with the absorption rate more than 94% is observed, with the maximum of absorption rate reaching 99.3% at the wavelength of 430 nm. We also analyze the thermal characteristics of the perfect absorber. The band ranging from 560 nm to 1200 nm presents an increasing absorption rate with the increase of temperature. The calculation results of multi-physics analysis indicate that different cooling method causes different temperature distribution for the perfect absorber. This three-tier gate perfect absorber may find applications on broadband visible detectors, microbolometer and thermal imaging.

Cai, G. W.; Ding, P.; Wang, J. Q.; Liang, E. J.

2014-06-01

47

Wave lengths of some new absorption bands of sulfur dioxide vapor  

E-print Network

WavE LENGTHS OF SOME NEW ABSORPTION BANDS OF SUIFUR DIOXIDE VAPOR A Thesis BOBBY L. LANDRUM Approved as to style and content by: Chairman of Committee Head of Department / August 195$ LIBRARY A &III CCLLEGE OF TEXAS WAVE LENGTHS OF SOME... NEW ABSORPTION BANDS OF SULFUR DIOXIDE VAPOR Bobby L. Landrum A Thesis Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in Partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN PHYSICS...

Landrum, Bobby Lee

2012-06-07

48

Atmospheric absorption of high frequency noise and application to fractional-octave bands  

NASA Technical Reports Server (NTRS)

Pure tone sound absorption coefficients were measured at 1/12 octave intervals from 4 to 100 KHz at 5.5K temperature intervals between 255.4 and 310.9 K and at 10 percent relative humidity increments between 0 percent and saturation in a large cylindrical tube (i.d., 25.4 cm; length, 4.8 m). Special solid-dielectric capacitance transducers, one to generate bursts of sound waves and one to terminate the sound path and detect the tone bursts, were constructed to fit inside the tube. The absorption was measured by varying the transmitter receiver separation from 1 to 4 m and observing the decay of multiple reflections or change in amplitude of the first received burst. The resulting absorption was compared with that from a proposed procedure for computing sound absorption in still air. Absorption of bands of noise was numerically computed by using the pure tone results. The results depended on spectrum shape, on filter type, and nonlinearly on propagation distance. For some of the cases considered, comparison with the extrapolation of ARP-866A showed a difference as large as a factor of 2. However, for many cases, the absorption for a finite band was nearly equal to the pure tone absorption at the center frequency of the band. A recommended prediction procedure is described for 1/3 octave band absorption coefficients.

Shields, F. D.; Bass, H. E.

1977-01-01

49

Investigation of the polarization observed in infrared absorption bands in the spectra of protostars  

Microsoft Academic Search

We investigate the linear polarization in the two deepest infrared absorption bands observed in the spectra of protostars,\\u000a the water-ice band with the center near 3.1 m and the silicate band with the center near 9.7 m, using a core-mantle confocal\\u000a spheroid model with various axial ratios a\\/b and relative volumes of the core material. We consider the effect of

T. V. Zinoveva

2006-01-01

50

Investigation of the polarization observed in infrared absorption bands in the spectra of protostars  

Microsoft Academic Search

We investigate the linear polarization in the two deepest infrared absorption bands observed in the spectra of protostars, the water-ice band with the center near 3.1 m and the silicate band with the center near 9.7 m, using a core-mantle confocal spheroid model with various axial ratios a\\/b and relative volumes of the core material. We consider the effect of

T. V. Zinov'eva

2006-01-01

51

Ozone absorption bands in the 3100 A-3400 A region  

SciTech Connect

The physical processes which produce terrestrial ozone absorption are discussed deriving ozone opacities from laboratory cross sections and published ozone column densities. The ozone opacity decreases from about 1 at 3100 A to about 0.001 at 3500 A. A comparison of model DA white-dwarf spectra absorbed by ozone and actual observed spectra shows good agreement. Therefore, simulated absorbed spectra may be used to remove ozone contamination in ground-based data. 17 refs.

Schachter, J. (California, University, Berkeley (USA))

1991-05-01

52

Intensities of various bands of the molecules CN, CN/+/, and CS in comets  

NASA Astrophysics Data System (ADS)

The resonance fluorescence calculations have been carried out for the (A-X) and (B-X) bands of CN, (c-a) and (f-a) bands of CN+ and (A-X) band of CS. The expected intensities are compared with the available rocket observations.

Krishna Swamy, K. S.

1981-04-01

53

High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge absorption bands of isotopic oxygen, (O-18)2, at 79 K  

NASA Technical Reports Server (NTRS)

Cross-sections of (O-18)2 at 79 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 177.8-197.8 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 (14,0) through (2,0) are, with the exception of the (12,0) band, independent of the instrumental width. The measured cross-sections are presented graphically here and are available at wavenumber intervals of about 0.1/cm as numerical compilations stored on magnetic tape. Band oscillator strengths of those bands have been determined by direct numerical integration of the measured absolute cross-sections and are in excellent agreement with these theoretically calculated values.

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

1988-01-01

54

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

55

Quantitative Measurement of Integrated Band Intensities of Benzene Vapor in the Mid-Infrared at 278, 298, and 323 K  

SciTech Connect

Pressure broadened (1 atm. N2) laboratory spectra of benzene vapor (in natural abundance) were recorded at 278, 298, and 323 K, covering 600-6500 cm-1. The spectra were recorded at a resolution of 0.112 cm-1 using a commercial Fourier transform spectrometer. The pressure of each benzene vapor sample was measured using high precision capacitance manometers and a minimum of nine sample pressures were recorded for each temperature. The samples were introduced into a temperature-stabilized static cell (19.94(1) cm pathlength) that was hard-mounted into the spectrometer. From these data a fit composite spectrum was calculated for each temperature. The number density for the three composite spectra was normalized to 296 K. The spectra give the absorption cross section (cm2 molecule-1, naperian units) as a function of wavenumber. From these spectra integrated band intensities (cm molecule-1 and atm-1 cm-2) for intervals corresponding to the stronger benzene bands were calculated and are compared with previously reported values. We discuss and quantify error sources and estimate our systematic (NIST Type-B) errors to be 3% for the stronger bands. The measured absorption coefficients and integrated band intensities are useful for remote sensing applications such as measurements of planetary atmospheres and assessment of the environmental impact of terrestrial oil fire emissions.

Rinsland, Curtis P.; Devi, V. M.; Blake, Thomas A.; Sams, Robert L.; Sharpe, Steven W.; Chiou, Linda

2008-10-01

56

Design of microresonator quantum well intensity modulators based on an absorption blue-shift  

NASA Astrophysics Data System (ADS)

A micro resonator quantum well intensity modulator for operation in the wavelength band around 1?m is described. High efficiency 90 bends are used to form the resonator and also provide optimal coupling to the external waveguide. The benefits are to reduce loss, to relax the lithography requirements and to provide more flexible contact designs to the modulator. The characteristics of modulator are analyzed using optical simulation tools and based on measured absorption parameters. The modulator operates with two distinctly different electrode configurations which are both based on the index change calculated using Kramers-Kronig relations. A model including parasitic is developed for HSPICE transient simulations and run in the AGILENT ADS environment. The performance parameters are determined to be an extinction ratio of 10.4dB, a bandwidth of 33GHz, and a dc power less than 1mW for device dimensions of 166?m2.

Zhang, Y.; Pile, B.; Taylor, G. W.

2011-09-01

57

A study of variations in the 787-nm ammonia absorption band in the Jupiter atmosphere  

NASA Astrophysics Data System (ADS)

During the last years the program of the spectrophotometric study of Jupiter included the measurements of the NH3 absorption band 787 nm. This band is overlapped by a broader absorption band of CH4. To detect the NH3 band we used the ratio of Jovian spectra to the spectrum of Saturn equatorial region. It was taken into account that the ammonia absorption on Saturn is significantly weaker than on Jupiter. The results of processing the spectrograms were analyzed for the years 2007-2010. Latitudinal variations of the NH3 band regularly show a depression of absorption at low and temperate latitudes of Jovian northern hemisphere. The equivalent width decreases approximately from 18-16 , to 14-12 . A more or less symmetric and steeper decrease of absorption from the disk center to limbs was obtained for the equatorial belt of Jupiter. It may be considered as evidence of the reality of that latitudinal depression but not the instrumental errors. It should be noted that the ammonia decrease in northern hemisphere was detected also from radio observations of Jupiter

Bondarenko, N. N.

2013-08-01

58

Measurement of the temperature dependence of midinfrared optical absorption spectra of germanium in intense laser fields  

SciTech Connect

We have investigated the temperature dependence of midinfrared optical absorption in germanium under intense free-electron laser fields. We observed that the absorption decreases as temperature decreases. We find that the temperature dependence of the absorption is consistent with calculations based on the Keldysh theory, in which the temperature dependence of the direct-gap energy of germanium is considered.

Furuse, H.; Mori, N.; Kubo, H.; Momose, H.; Kondow, M. [Department of Electronic Engineering, Osaka University, Suita City, Osaka 565-0871 (Japan)

2007-05-15

59

On the carriers of the 3.4-micrometer absorption and emission bands, and their evolution  

E-print Network

Based on the results of chemical analysis and simulation of kerogens and immature coals, a large number of chemical structures carrying the 3.4-mum feature were studied by means of computer simulation codes. Further selection criteria were the integrated strength of the absorption lines in the aliphatic stretchings wavelength band, weak IR activity in the aromatic stretching band and absence of notable activity outside the astronomical UIBs (Unidentified Infrared Bands). Most of the structures that were retained can be classed as branched, short and oxygen-bridged CH_{2} chains, and naphtenic chains. Combinations of their absorption spectra deliver spectra comparable to those observed in the sky. Absorption spectra were derived from Normal Mode Analysis. Emission spectra of the same structures were computed by monitoring their overall dipole moment as they vibrate freely in vacuum after excitation. These spectra were then combined in suitable proportions, together with those of aromatic structures, so as to s...

Papoular, Renaud

2014-01-01

60

Comparison of the Huggins band for six ozone isotopologues: vibrational levels and absorption cross section.  

PubMed

By use of the 3(1)A' ab initio potential energy surface (PES) of ozone and the multi-configuration time-dependent Hartree program for wavepacket propagation, we have determined numerous eigenstates of this state for six ozone isotopologues. These bound vibrational levels are the upper levels of the Huggins band, which covers the range from 27,000 to ~33,000 cm(-1). This study extends our previous work on the Hartley band, which was limited to the range ~32,000-50,000 cm(-1). Four isotopologues, (16)O(3), (16)O(17)O(16)O, (16)O(18)O(16)O, and (18)O(3) (noted hereafter 666, 676, 686, and 888), are symmetric, and two are asymmetric, (17)O(16)O(2) and (18)O(16)O(2) (noted hereafter 667 and 668). The PES of the 3(1)A' state has two equivalent minima of C(s) symmetry located at ~27,000 cm(-1) above the X(1)A(1) ground state. The equilibrium geometry of these two minima is r(e(1)) = 2.28 a(0), r(e(2)) = 3.2 a(0), and ?(e) = 107. The dissociation limit of this PES, which correlates to the O((1)D) + O(2) ((1)?) "singlet" channel, is about 4300 cm(-1) above the two minima. For the (16)O(3) isotopologue, the 120 lowest bound eigenstates have been calculated and partially assigned up to 800 cm(-1) below the dissociation limit. The 60 lower eigenstates are easily assignable in term of three normal modes, the "long" bond (?(1)), the bending (?(2)), and the "short" bond (?(3)). A new family of wave functions, aligned along the dissociation channels, appears at 3782 cm(-1) above the 3(1)A' (0,0,0) level. The 3(1)A' vibrational levels and the corresponding intensity factors from the (000), (010), (100), and (001) levels of the X(1)A(1) ground state have been calculated for the six isotopologues. The Huggins absorption cross sections of the six isotopologues have been calculated from the 3(1)A' vibrational energy levels and the corresponding intensity factors. The rotational envelope of each vibronic band has been empirically described by an ad hoc function. The ratio of the Huggins cross section of each ozone isotopologue with one of (16)O(3) provides the fractionation factor of each ozone isotopologue as a function of the photon energy. These various fractionation factors will allow predicting enrichments due to photolysis by various light sources like the actinic flux. PMID:23009265

Ndengu, Steve Alexandre; Schinke, Reinhard; Gatti, Fabien; Meyer, Hans-Dieter; Jost, Rmy

2012-12-20

61

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

PubMed Central

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.

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

2014-01-01

62

Absolute line intensities and broadening coefficients for the ?11 band of allene.  

NASA Astrophysics Data System (ADS)

Line strengths for the ?11 band of allene (352.636 cm-1) have been measured using tunable diode laser spectroscopy. The dipole moment and band strengths have been derived, and pressure broadening coefficients for self and N2 broadening were determined at temperatures representative of Titan's atmosphere (160-190 K). The absolute value for the dipole moment is 0.1093 debye giving a band intensity of 26.29 cm-2atm-1 (300 K). This band strength is about 6% lower than that inferred from the low resolution measurements performed by Koga et al. (1971) which is the only previous strength measurement for this band.

Sirota, J. M.; Reuter, D. C.; Frye, J.

1997-08-01

63

Charge-transfer absorption band in Zn1-xMxO (M: Co, Mn) investigated by means of photoconductivity, Ga doping, and optical measurements under pressure  

NASA Astrophysics Data System (ADS)

The nature of the charge-transfer absorption band in undoped and Ga-doped Zn1-xMxO (M: Co, Mn) thin films is investigated by means of photoconductivity and optical absorption measurements under pressure. Internal transitions in the crystal field split Co 3d shell do not contribute to the photoconductivity spectrum and have very low pressure coefficient. Broad absorption bands at photon energies just below the band gap in both ZnMnO and ZnCoO clearly contribute to the photoconductivity spectra, indicating that they create free carriers and are consequently charge-transfer transitions. Under pressure, charge transfer bands have a pressure coefficient close to or larger than the band gap, in contrast to the expected low or negative pressure coefficient in a valence-band-to-localized level transition. Finally, the expected Burstein-Moss shift in the fundamental edge of heavily Ga-doped samples of ZnMO is associated to a larger shift and intensity decrease in the pre-edge band, confirming that charge-transfer transitions in ZnMO should be ascribed to transitions from the Co or Mn 3d shell to the conduction band.

Gilliland, S. G.; Sans, J. A.; Snchez-Royo, J. F.; Almonacid, G.; Segura, A.

2010-06-01

64

Measurement of the absorption coefficient using the sound-intensity technique  

NASA Technical Reports Server (NTRS)

The possibility of using the sound intensity technique to measure the absorption coefficient of a material is investigated. This technique measures the absorption coefficient by measuring the intensity incident on the sample and the net intensity reflected by the sample. Results obtained by this technique are compared with the standard techniques of measuring the change in the reverberation time and the standing wave ratio in a tube, thereby, calculating the random incident and the normal incident adsorption coefficient.

Atwal, M.; Bernhard, R.

1984-01-01

65

The interband optical absorption in silicon quantum wells: Application of the 30-band k ? p model  

NASA Astrophysics Data System (ADS)

The interband optical absorption in Si/SiO2 quantum wells is calculated as function of the well width (W) and the evolution from an indirect to a direct gap material as function of the well width is investigated. In order to compute the electron states in the conduction band, the 30-band k ? p model is employed, whereas the 6-band Luttinger-Kohn model is used for the hole states. We found that the effective direct band gap in the quantum well agrees very well with the W-2 scaling result of the single-band model. The interband matrix elements for linear polarized light oscillate with the quantum well width, which agrees qualitatively with a single band calculation. Our theoretical results indicate that the absorption can be maximized by a proper choice of the well width. However, the obtained absorption coefficients are at least an order of magnitude smaller than for a typical direct semiconductor even for a well width of 2 nm.

?ukari?, Nemanja A.; Tadi?, Milan .; Partoens, Bart; Peeters, F. M.

2014-06-01

66

X-Ray Absorption Spectra Reveal the Inapplicability of the Single-Band Hubbard Model to Overdoped Cuprate Superconductors  

NASA Astrophysics Data System (ADS)

X-ray absorption spectra on the overdoped high-temperature superconductors Tl2Ba2CuO6+? and La2-xSrxCuO4? reveal a striking departure in the electronic structure from that of the underdoped regime. The upper Hubbard band, identified with strong correlation effects, is not observed on the oxygen K edge, while the lowest-energy prepeak gains less intensity than expected above ptilde 0.21. This suggests a breakdown of the Zhang-Rice singlet approximation and a loss of correlation effects or a significant shift in the most fundamental parameters of the system, rendering single-band Hubbard models inapplicable. Such fundamental changes suggest that the overdoped regime may offer a distinct route to understanding in the cuprates.

Peets, D. C.; Hawthorn, D. G.; Shen, K. M.; Kim, Young-June; Ellis, D. S.; Zhang, H.; Komiya, Seiki; Ando, Yoichi; Sawatzky, G. A.; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.

2009-08-01

67

The hybrid-type bands ?1 and ?3 of 16O16O18O: Line positions and intensities  

NASA Astrophysics Data System (ADS)

A study of 0.005-cm-1-resolution room temperature absorption spectra of 18O-enriched ozone around 10 ?m has been performed leading to a thorough analysis of the hybrid ?1 and ?3 bands of 16O16O18O. The experimental rotational energy levels of the interacting vibrational states (100) and (001) were reproduced with the aid of a Hamiltonian taking fully into account the vibration-rotation interactions. Precise vibrational energies and rotational and coupling constants were deduced. The following band centers were determined: ?1 = 1090.3541 cm-1, ?3 = 1028.1120 cm-1. Assuming the 16O18O16O line intensities calculated previously [J.-M. Flaud, C. Camy-Peyret, V. Malathy Devi, C. P Rinsland, and M. A. H. Smith, J. Mol. Spectrosc. 118, 000-000 (1986)] and a factor of 2 between the abundances of 16O16O18O and 16O18O16O, the amount of 16O16O18O in the cell was evaluated and used to determine 75 absolute intensities of ?1 and ?3 band lines of 16O16O18O. From these experimental values, the coefficients appearing in the transformed transition moment operators of these bands were derived. Finally, a complete spectrum of the ?1 and ?3 bands of 16O16O18O has been computed, which, combined with the results of our previous work on 16O18O16O (cited above), gives a detailed description of the absorption of the monosubstituted 18O isotopes of ozone in the 10-?m region.

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

1986-08-01

68

Intensity redistribution of bending and stretching Raman scattering bands in water upon degassing and crystallisation  

SciTech Connect

It is established for the first time that the intensities of deformation and valence Raman scattering (RS) bands in water vary oppositely in the processes of degassing and crystallising. Water degassing shifts the centre of a valence OH band to higher frequencies by approximately 2 cm{sup -1}, which points to a reduced contribution of structural complexes to the RS spectrum. (letters)

Pershin, Sergei M; Bunkin, Aleksei F; Luk'yanchenko, V A [Wave Research Center, A.M. Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Zakharov, S D [P N Lebedev Physical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2011-01-24

69

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

70

Observation of precursorlike behavior of femtosecond pulses in a dye with a strong absorption band  

E-print Network

absorption band and anomalous dispersion at a wavelength of approximately 800 nm. We explore this regime experimentally with sub-10-fs pulses with a central wavelength of approximately 800 nm from a Ti : sapphire oscillator. The pulses are passed through a...

Springer, Matthew M.; Yang, Wenlong; Kolomenski, Alexandre A.; Schuessler, Hans A.; Strohaber, James; Kattawar, George W.; Sokolov, Alexei V.

2011-01-01

71

Water Channel of Horseradish Peroxidase Studied by the Charge-Transfer Absorption Band of Ferric Heme  

E-print Network

connects the aqueous solution to the heme site. Ferric horseradish peroxidase has an absorption band at 640, the protein was incorporated into trehalose/sucrose glasses and the hydration of the sugar glasses was varied are narrower for the protein in glycerol/water (glass transition at 150 K) than in trehalose/sucrose (glass

Sharp, Kim

72

Ultraviolet Absorption Bands and Electronic Charge Transfers of Salicylideneanilines in Singlet Excited STATES1  

Microsoft Academic Search

Salicylideneaniline presents an electronic absorption band spectrum of complex patterns between 200 and 450 nm. However, we have successfully developed the electronic transition assignments of this molecular compound and its derivative species, substituted on the aniline ring of the salicylideneaniline structure. Thus, we have analyzed the substituent effect of the electron-acceptor groups such as ?CN, ?COCH3, and ?NO2, as well

Ral G. E. Morales; Gregorio P. Jara; Vctor Vargas

2001-01-01

73

Fully Polarimetric Differential Intensity W-band Imager  

SciTech Connect

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.

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

74

Fitting narrow-band models to temperature-dependent, spectral absorption coefficients of fuel vapors  

NASA Astrophysics Data System (ADS)

Accurate modeling of infrared radiation transport through fuel rich cores of fires and other non-premixed combustion processes requires computationally efficient processing of temperature-dependent, spectral absorption coefficients for major fuel vapor species. Spectrally resolved transmissivity band measurements in the mid-infrared and near-infrared have been taken in recent years for numerous small fuel molecules including but not limited to ethane, ethylene, and propylene for a range of temperatures relevant for combustion environments. This paper compares the spectral transmissivity measurements using FTIR for both ethane and ethylene with the HITRAN 2012 edition. Narrow band absorption coefficients and overlap parameters are derived by fitting the spectral transmissivity measurements for ethane, ethylene, and propylene with narrow band models for temperatures up to 1000 K. The resulting fits provide a basis for calculating spectrally resolved infrared radiation transport in fuel rich cores of flames and other combustion processes where these species can be prevalent.

Lecoustre, V. R.; Wakatsuki, K.; Jackson, G. S.

2014-11-01

75

Optical band-edge absorption of oxide compound SnO 2  

NASA Astrophysics Data System (ADS)

Tin oxide (SnO 2) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO 2 thin film is widely used in glass applications due to its low infra-red heat emissivity. In this work, the SnO 2 electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption ?( ?) of intrinsic SnO 2 is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO 2 qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results.

Roman, L. S.; Valaski, R.; Canestraro, C. D.; Magalhes, E. C. S.; Persson, C.; Ahuja, R.; da Silva, E. F.; Pepe, I.; da Silva, A. Ferreira

2006-05-01

76

High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge absorption bands of isotopic oxygen, (0-16)(0-18), at 79 K  

NASA Technical Reports Server (NTRS)

Cross-sections of (0-16)(0-18) at 79 K have been obtained from photoabsorption measurements on mixtures of (0-16)2, (0-18)2, and (0-16)(0-18) at various pressures throughout the wavelength region 180.5-195.3 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 (0-16)(0-18) Schumann-Runge bands (11.0)-(3.0) are independent of the instrumental width. The measured cross-sections are presented graphically.

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

1989-01-01

77

Fully polarimetric differential intensity W-band imager  

NASA Astrophysics Data System (ADS)

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 horizontal (H) and vertical (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 to 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 two input horns instead of a reference load to form signals ?H and ?V from 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 as viewed by the differential polarimetric imager.

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

2013-05-01

78

Absolute line intensities in CO2 bands near 4.8 microns  

NASA Technical Reports Server (NTRS)

Absolute intensities for 726 unblended lines in 20 bands of C-12(O-16)2, C-13(O-16)2, O-16C-12O-18, and O-16C-12O-17 in the 4.8-micron spectral region have been determined using a natural sample of ultrahigh-purity CO2. Spectral data were recorded at low pressure (less than 10 torr) and room temperature with the Fourier transform spectrometer in the McMath solar telescope complex on Kitt Peak. Derived vibrational band intensities and coefficients of the F factor for each band were compared to values of the 1982 Air Force Geophysics Laboratory line parameters compilation. The present work fills out the CO2 lines in the 5-micron band systems. Lines in the strongest of these measured bands are being used to infer atmospheric pressure from high-resolution stratospheric spectra recorded during the Spacelab 3 Atmospheric Trace Molecule Spectroscopy experiment.

Rinsland, C. P.; Benner, D. C.; Devi, V. M.

1986-01-01

79

Measurements of absolute line intensities in carbon dioxide bands near 5.2 microns  

NASA Technical Reports Server (NTRS)

A nonlinear least-squares spectral fitting procedure has been used to derive experimental absolute intensities for over 300 unblended lines belonging to twelve CO2 bands in the 5.2-micron region. The spectral data were recorded at 0.01/cm resolution and room temperature with the Fourier transform spectrometer in the McMath solar telescope complex at the National Solar Observatory on Kitt Peak and have a signal-to-rms noise ratio of 2000-4000. A natural sample of carbon dioxide was used as the sample gas. For each band, the measured line intensities have been analyzed to derive the vibrational band intensity and coefficients of the F factor. The results are compared to the values used to calculate the intensities in the 1982 Air Force Geophysics Laboratory line parameters compilation.

Rinsland, C. P.; Benner, D. C.; Devi, V. M.

1985-01-01

80

Signatures of a conical intersection in photofragment distributions and absorption spectra: photodissociation in the Hartley band of ozone.  

PubMed

Photodissociation of ozone in the near UV is studied quantum mechanically in two excited electronic states coupled at a conical intersection located outside the Franck-Condon zone. The calculations, performed using recent ab initio PESs, provide an accurate description of the photodissociation dynamics across the Hartley/Huggins absorption bands. The observed photofragment distributions are reproduced in the two electronic dissociation channels. The room temperature absorption spectrum, constructed as a Boltzmann average of many absorption spectra of rotationally excited parent ozone, agrees with experiment in terms of widths and intensities of diffuse structures. The exit channel conical intersection contributes to the coherent broadening of the absorption spectrum and directly affects the product vibrational and translational distributions. The photon energy dependences of these distributions are strikingly different for fragments created along the adiabatic and the diabatic paths through the intersection. They can be used to reverse engineer the most probable geometry of the non-adiabatic transition. The angular distributions, quantified in terms of the anisotropy parameter ?, are substantially different in the two channels due to a strong anticorrelation between ? and the rotational angular momentum of the fragment O2. PMID:25149790

Picconi, David; Grebenshchikov, Sergy Yu

2014-08-21

81

Unusual Scaling Laws of the Band Gap and Optical Absorption of Phosphorene Nanoribbons  

E-print Network

We report the electronic structure and optical absorption spectra of monolayer black phosphorus (phosphorene) nanoribbons (PNRs) via first-principles simulations. The band gap of PNRs is strongly enhanced by quantum confinement. However, differently orientated PNRs exhibit distinct scaling laws for the band gap vs the ribbon width (w). The band gaps of armchair PNRs scale as 1/(w^2), while zigzag PNRs exhibit a 1/w behavior. These distinct scaling laws reflect a significant implication of the band dispersion of phosphorene: electrons and holes behave as classical particles along the zigzag direction, but resemble relativistic particles along the armchair direction. This unexpected merging of classical and relativistic properties in a single material may produce novel electrical and magnetotransport properties of few-layer black phosphorus and its ribbon structures. Finally, the respective PNRs host electrons and holes with markedly different effective masses and optical responses, which are suitable for a wid...

Tran, Vy

2014-01-01

82

Analysis of wavelength-dependent photoisomerization quantum yields in bilirubins by fitting two exciton absorption bands  

NASA Astrophysics Data System (ADS)

The absorption spectra of bilirubins were deconvoluted by two Gaussian curves of equal width representing the exciton bands of the non-degenerate molecular system. The two bands were used to study the wavelength dependence of the (4Z, 15Z) rightarrow (4Z, 15E) configurational photoisomerization quantum yield of the bichromophoric bilirubin-IXalpha (BR-IX), the intrinsically asymmetric bile pigment associated with jaundice and the symmetrically substituted bilirubins (bilirubin-IIIalpha and mesobilirubin-XIIIalpha), when they are irradiated in aqueous solution bound to human serum albumin (HSA). The same study was performed for BR-IX in ammoniacal methanol solution (NH4OH/MeOH). The quantum yields of the configurational photoprocesses were fitted with a combination function of the two Gaussian bands normalized to the total absorption, using the proportionality coefficients and a scaling factor as parameters. The decrease of the (4Z, 15Z) rightarrow (4Z, 15E) quantum yield with increasing wavelength, which occurs for wavelengths longer than the most probable Franck-Condon transition of the molecule, did not result in a unique function of the exciton absorptions. In particular we found two ranges corresponding to different exciton interactions with different proportionality coefficients and scaling factors. The wavelength-dependent photoisomerization of bilirubins was described as an abrupt change in quantum yield as soon as the resulting excitation was strongly localized in each chromophore. The change was correlated to a variation of the interaction between the two chromophores when the short-wavelength exciton absorption became vanishingly small. With the help of the circular dichroism (CD) spectrum of BR-IX in HSA, a small band was resolved in the bilirubin absorption spectrum, delivering part of the energy required for the (4Z, 15Z) rightarrow (4Z, 15E) photoisomerization of the molecule.

Mazzoni, M.; Agati, G.; Troup, G. J.; Pratesi, R.

2003-09-01

83

Novel Cross-Band Relative Absorption (CoBRA) technique For Measuring Atmospheric Species  

NASA Astrophysics Data System (ADS)

We describe a methodology called Cross-Band Relative Absorption (CoBRA) we have implemented to significantly reduce interferences due to variations in atmospheric temperature and pressure in molecular mixing ration measurements [1-4]. The interference reduction is achieved through automatic compensation based on selecting spectral line pairs exhibiting similar evolution behavior under varying atmospheric conditions. The method is applicable to a wide range of molecules including CO2 and CH4 which can be matched with O2 or any other well-mixed atmospheric molecule. Such matching results in automatic simultaneous adjustments of the spectral line shapes at all times with a high precision under varying atmospheric conditions of temperature and pressure. We present the results of our selected CoBRA analysis based on line-by-line calculations and the Modern Era Retrospective Analysis for Research and Applications (MERRA) dataset including more recent evaluation of the error contributions due to water vapor interference effects. References: 1) N. S. Prasad, D. Pliutau, 'Cross-band relative absorption technique for the measurement of molecular mixing ratios.', Optics Express, Vol. 21, Issue 11, pp. 13279-13292 (2013) 2) D. Pliutau and N. S. Prasad, "Cross-band Relative Absorption Technique for Molecular Mixing Ratio Determination," in CLEO: 2013, OSA Technical Digest (online) (Optical Society of America, 2013), paper CW3L.4. 3) Denis Pliutau; Narasimha S. Prasad; 'Semi-empirical validation of the cross-band relative absorption technique for the measurement of molecular mixing ratios',.Proc. SPIE 8731, Laser Radar Technology and Applications XVIII, 87310L (May 20, 2013); doi:10.1117/12.2016661. 4) Denis Pliutau,; Narasimha S. Prasad; 'Comparative analysis of alternative spectral bands of CO2 and O2 for the sensing of CO2 mixing ratios' Proc. SPIE 8718, Advanced Environmental, Chemical, and Biological Sensing Technologies X, 87180L (May 31, 2013); doi:10.1117/12.2016337.

Prasad, N. S.; Pliutau, D.

2013-12-01

84

Inverse bremsstrahlung absorption with nonlinear effects of high laser intensity and non-Maxwellian distribution.  

PubMed

Inverse bremsstrahlung (IB) absorption and evolution of the electron distribution function (EDF) in a wide laser intensity range (10;{12}-10;{17} W/cm;{2}) have been studied systematically by a two velocity-dimension Fokker-Planck code. It is found that Langdon's IB operator overestimates the absorption rate at high laser intensity, consequently with an overdistorted non-Maxwellian EDF. According to the small anisotropy of EDF in the oscillation frame, we introduce an IB operator which is similar to Langdon's but without the low laser intensity limit. This operator is appropriate for self-consistently tackling the nonlinear effects of high laser intensity as well as non-Maxwellian EDF. Particularly, our operator is capable of treating IB absorption properly in the indirect and direct-drive inertial confinement fusion schemes with the National Ignition Facility and Laser MegaJoule laser parameters at focused laser intensity beyond 10;{15} W/cm;{2} . PMID:20365082

Weng, Su-Ming; Sheng, Zheng-Ming; Zhang, Jie

2009-11-01

85

Band structure and broadband compensation of absorption by amplification in layered optical metamaterials  

SciTech Connect

The frequency dependence of the gain required to compensate for absorption is determined for a layered structure consisting of alternating absorbing and amplifying layers. It is shown that the fulfillment of the same conditions is required for the existence of a band structure consisting of alternating bands allowed and forbidden for optical radiation propagation in the frequency-wave vector parametric region. Conditions are found under which the gain required for compensation is smaller than thresholds for absolute (parasitic lasing) and convective (waveguide amplification of radiation) instabilities.

Rozanov, N. N., E-mail: nrosanov@yahoo.com; Fedorov, S. V.; Savel'ev, R. S.; Sukhorukov, A. A.; Kivshar, Yu. S. [St. Petersburg State University of Information Technologies, Mechanics and Optics (Russian Federation)

2012-05-15

86

Rotational Profiles of Molecular Absorption Bands in Astrophysically Relevant Conditions: Ab-Initio Approach  

SciTech Connect

A theoretical study of rotational profiles of molecular absorption bands is essential for direct comparison with observations of diffuse interstellar bands. Applications using gaussian quantum-chemical approach within DFT are presented. Structural and vibrational properties of the polycyclic aromatic hydrocarbon ovalene cation (C32H14+) are obtained. We discuss the expected profile of the first electronic transition of such molecule, obtained with a Monte Carlo model of its rotation in the physical conditions of low temperatures and absence of collisions which are characteristic of the interstellar medium (ISM).

Malloci, Giuliano; Mulas, Giacomo; Cappellini, Giancarlo; Satta, Guido; Porceddu, Ignazio; Benvenuti, Piero

2004-05-01

87

Absolute intensity measurements of CO2 bands in the 2395-2680/cm region  

NASA Technical Reports Server (NTRS)

Absolute intensities for over 800 transitions belonging to twelve bands of (C-12)(O-16)2, (O-16)(C-12)(O-18), (O-16)(C-12)(O-17), and (O-16)(C-13)(O-18) molecules in the 2395-2680/cm spectral region have been derived using a nonlinear least-squares spectral fitting procedure. The data used in the analysis were recorded at room temperature and low pressure with the 0.01/cm resolution Fourier transform spectrometer in the McMath solar telescope complex at the National Solar Observatory. The measured intensities obtained for each band have been analyzed to derive the vibrational band intensity and F-factor coefficients. The results are compared with other published values.

Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.

1984-01-01

88

Dual-band absorption of mid-infrared metamaterial absorber based on distinct dielectric spacing layers.  

PubMed

We present the simulation, fabrication, and characterization of a dual-band metamaterial absorber in the mid-infrared regime. Two pairs of circular-patterned metal-dielectric stacks are employed to excite the dual-band absorption peaks. Dielectric characteristics of the dielectric spacing layer determine energy dissipation in each resonant stack, i.e., dielectric or ohmic loss. By controlling material parameters, both two mechanisms are introduced into our structure. Up to 98% absorption is obtained at 9.03 and 13.32 ?m in the simulation, which is in reasonable agreement with experimental results. The proposed structure holds promise for various applications, e.g., thermal radiation modulators and multicolor infrared focal plane arrays. PMID:23546265

Zhang, Nan; Zhou, Peiheng; Cheng, Dengmu; Weng, Xiaolong; Xie, Jianliang; Deng, Longjiang

2013-04-01

89

Representative wavelengths absorption parameterization applied to satellite channels and spectral bands  

NASA Astrophysics Data System (ADS)

Accurate modeling of wavelength-integrated radiative quantities, e.g. integrated over a spectral band or an instrument channel response function, requires computations for a large number of wavelengths if the radiation is affected by gas absorption which typically comprises a complex line structure. In order to increase computational speed of modeling radiation in the Earth's atmosphere, we parameterized wavelength-integrals as weighted means over representative wavelengths. We parameterized spectral bands of different widths (1 cm-1, 5 cm-1, and 15 cm-1) in the solar and thermal spectral range, as well as a number of instrument channels on the ADEOS, ALOS, EarthCARE, Envisat, ERS, Landsat, MSG, PARASOL, Proba, Sentinel, Seosat, and SPOT satellites. A root mean square relative deviation lower than 1% from a training data set was selected as the accuracy threshold for the parameterization of each band and channel. The training data set included high spectral resolution calculations of radiances at the top of atmosphere for a set of highly variable atmospheric states including clouds and aerosols. The gas absorption was calculated from the HITRAN 2004 spectroscopic data set and state-of-the-art continuum models using the ARTS radiative transfer model. Three representative wavelengths were required on average to fulfill the accuracy threshold. We implemented the parameterized spectral bands and satellite channels in the uvspec radiative transfer model which is part of the libRadtran software package. The parameterization data files, including the representative wavelengths and weights as well as lookup tables of absorption cross sections of various gases, are provided at the libRadtran webpage. In the paper we describe the parameterization approach and its application. We validate the approach by comparing modeling results of parameterized bands and channels with results from high spectral resolution calculations for atmospheric states that were not part of the training data set. Irradiances are not only compared at the top of atmosphere but also at the surface for which this parameterization approach was not optimized. It is found that the parameterized bands and channels provide a good compromise between computation time requirements and uncertainty for typical radiative transfer problems. In particular for satellite radiometer simulations the computation time requirement and the parameterization uncertainty is low. Band-integrated irradiances at any level as well as heating and cooling rates below 20 km can also be modeled with low uncertainty.

Gasteiger, J.; Emde, C.; Mayer, B.; Buras, R.; Buehler, S. A.; Lemke, O.

2014-11-01

90

Influence of Coulomb-induced band couplings on linear excitonic absorption spectra of semiconducting carbon nanotubes  

NASA Astrophysics Data System (ADS)

Starting from the extended Su-Schrieffer-Heeger model, multiband semiconductor Bloch equations are formulated in momentum space and applied to the analysis of the linear optical response of semiconducting carbon nanotubes (SCNTs). This formalism includes the coupling of electron-hole pair excitations between different valence and conduction bands, originating from the electron-hole Coulomb attraction. The influence of these couplings, which are referred to as nondiagonal interband Coulomb interaction (NDI-CI), on the linear excitonic absorption spectra is investigated and discussed for light fields polarized parallel to the tube direction. The results show that the intervalley NDI-CI leads to a significant increase of the band gap and a decrease of the exciton binding energy that results in a blueshift of the lowest-frequency excitonic absorption peak. The strength of these effects depends on the symmetry of the SCNT. Furthermore, for zigzag SCNTs with higher symmetry other nonintervalley NDI-CI terms also affect the spectral positions of excitonic absorption peaks.

Liu, Hong; Schumacher, Stefan; Meier, Torsten

2014-04-01

91

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

SciTech Connect

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.

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

92

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

NASA Astrophysics Data System (ADS)

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.

Kaur, Jagdish; Rani, Mamta; Tripathi, S. K.

2014-04-01

93

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

NASA Technical Reports Server (NTRS)

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.

Carter, Gregory A.; Spiering, Bruce A.

2000-01-01

94

Theoretical modeling of low-energy electronic absorption bands in reduced cobaloximes.  

PubMed

The reduced Co(I) states of cobaloximes are powerful nucleophiles that play an important role in the hydrogen-evolving catalytic activity of these species. In this work we analyze the low-energy electronic absorption bands of two cobaloxime systems experimentally and use a variety of density functional theory and molecular orbital ab initio quantum chemical approaches. Overall we find a reasonable qualitative understanding of the electronic excitation spectra of these compounds but show that obtaining quantitative results remains a challenging task. PMID:25113847

Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L; Gray, Harry B; Fujita, Etsuko; Muckerman, James T; Fontecave, Marc; Artero, Vincent; Arantes, Guilherme M; Field, Martin J

2014-10-01

95

Gaussian band analysis of absorption, fluorescence and photobleaching difference spectra of D1\\/D2\\/cyt b -559 complex  

Microsoft Academic Search

A study of the absorption and fluorescence characteristics of the D1\\/D2\\/cytb-559 reaction centre complex of Photosystem II has been carried out by gaussian decomposition of absorption spectra both at room temperature and 72 K and of the room temperature fluorescence spectrum. A five component fit was found in which the absorption and fluorescence sub-bands could be connected by the Stepanov

Flavio Massimo Garlaschi; Giuseppe Zucchelli; Paolo Giavazzi; Robert Charles Jennings

1994-01-01

96

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

97

Comparison of infrared absorption intensities of benzene in the liquid and gas phases  

Microsoft Academic Search

This paper presents a comparison of the absolute infrared absorption intensities in the liquid and gas phases for the four infrared active fundamentals of benzene. In Herzbergs notation these are ?12 (?3070 cm?1), and ?4 (?675 cm?1). Published data are used, including the recently published spectra of liquid benzene that have been accepted by the International Union of Pure and

John E. Bertie; C. Dale Keefe

1994-01-01

98

ABSORPTIVE CAPACITY AND INNOVATION IN THE KNOWLEDGE INTENSIVE BUSINESS SERVICE SECTOR  

Microsoft Academic Search

Innovative activity is performed to a considerable extent in the service sector, namely within the so-called knowledge intensive business services (KIBS). Particularly emphasizing the role of absorptive capacity, we analyze possible determinants of incremental and radical firm innovation using firm micro data from the KIBS Foundation Survey. The results show that access to knowledge through networking and cooperation is of

Andreas Koch; Harald Strotmann

2008-01-01

99

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

NASA Technical Reports Server (NTRS)

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.

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

1988-01-01

100

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

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

101

Nanosecond light induced, thermally tunable transient dual absorption bands in a-Ge5As30Se65 thin film.  

PubMed

In this article, we report the first observation of nanosecond laser induced transient dual absorption bands, one in the bandgap (TA1) and another in the sub-bandgap (TA2) regions of a-Ge5As30Se65 thin films. Strikingly, these bands are thermally tunable and exhibit a unique contrasting characteristic: the magnitude of TA1 decreases while that of TA2 increases with increasing temperature. Further, the decay kinetics of these bands is strongly influenced by the temperature, which signifies a strong temperature dependent exciton recombination mechanism. The induced absorption shows quadratic and the decay time constant shows linear dependence on the laser beam fluence. PMID:25300520

Khan, Pritam; Saxena, Tarun; Jain, H; Adarsh, K V

2014-01-01

102

Nanosecond light induced, thermally tunable transient dual absorption bands in a-Ge5As30Se65 thin film  

PubMed Central

In this article, we report the first observation of nanosecond laser induced transient dual absorption bands, one in the bandgap (TA1) and another in the sub-bandgap (TA2) regions of a-Ge5As30Se65 thin films. Strikingly, these bands are thermally tunable and exhibit a unique contrasting characteristic: the magnitude of TA1 decreases while that of TA2 increases with increasing temperature. Further, the decay kinetics of these bands is strongly influenced by the temperature, which signifies a strong temperature dependent exciton recombination mechanism. The induced absorption shows quadratic and the decay time constant shows linear dependence on the laser beam fluence. PMID:25300520

Khan, Pritam; Saxena, Tarun; Jain, H.; Adarsh, K. V.

2014-01-01

103

A Group Increment Scheme for Infrared Absorption Intensities of Greenhouse Gases  

NASA Technical Reports Server (NTRS)

A molecule's absorption in the atmospheric infrared (IR) window (IRW) is an indicator of its efficiency as a greenhouse gas. A model for estimating the absorption of a fluorinated molecule within the IRW was developed to assess its radiative impact. This model will be useful in comparing different hydrofluorocarbons and hydrofluoroethers contribution to global warming. The absorption of radiation by greenhouse gases, in particular hydrofluoroethers and hydrofluorocarbons, was investigated using ab initio quantum mechanical methods. Least squares regression techniques were used to create a model based on this data. The placement and number of fluorines in the molecule were found to affect the absorption in the IR window and were incorporated into the model. Several group increment models are discussed. An additive model based on one-carbon groups is found to work satisfactorily in predicting the ab initio calculated vibrational intensities.

Kokkila, Sara I.; Bera, Partha P.; Francisco, Joseph S.; Lee, Timothy J.

2012-01-01

104

Resonance Raman and density functional study of the A-band absorption of C 5H 5[WC?CPh]O 2  

NASA Astrophysics Data System (ADS)

Resonance Raman spectra including absolute Raman cross-section measurements and density functional theory (DFT) calculations were performed to study the A-band absorption of C 5H 5[WC?CPh]O 2. The three most intense Franck-Condon active modes, the nominal W?O stretch, C?C stretch and C?C stretch, show noticeable intensity in their overtones as well as their combination bands with each other. This is consistent with the changes in the HOMO-LUMO electron densities obtained from the DFT calculations. This suggests that the excited-state experiences significant structural changes simultaneously in the W?O, C?C and C?C groups and the charge transfer is delocalized in the electronic transition.

Cheng, Yung Fong; Phillips, David Lee; He, Guo Zhong; Che, Chi-Ming; Chi, Yun

2001-04-01

105

Band tail absorption saturation in CdWO4 with 100 fs laser pulses  

NASA Astrophysics Data System (ADS)

The decay kinetics of the excitonic emission of CdWO4 scintillators was studied under excitation by powerful 100 fs laser pulses in the band tail (Urbach) absorption region. A special imaging technique possessing both spatial and temporal resolution provided a unique insight into the Frster dipole-dipole interaction of self-trapped excitons, which is the main cause of the nonlinear quenching of luminescence in this material. In addition, the saturation of phonon-assisted excitonic absorption due to extremely short excitation pulses was discovered. A model describing the evolution of electronic excitations in the conditions of absorption saturation was developed and an earlier model of decay kinetics based on the Frster interaction was extended to include the saturation effect. Compared to the previous studies, a more accurate calculation yields 3.7 nm as the Frster interaction radius. It was shown that exciton-exciton interaction is the main source of scintillation nonproportionality in CdWO4. A quantitative description using a new model of nonproportionality was presented, making use of the corrected value of the Frster radius.

Laasner, R.; Fedorov, N.; Grigonis, R.; Guizard, S.; Kirm, M.; Makhov, V.; Markov, S.; Nagirnyi, V.; Sirutkaitis, V.; Vasil'ev, A.; Vielhauer, S.; Tupitsyna, I. A.

2013-06-01

106

Optical absorption of electronic Fe-Ti charge-transfer transition in natural andalusite: the thermal stability of the charge-transfer band  

NASA Astrophysics Data System (ADS)

Differently colored natural Brazilian andalusite crystals heat-treated under reducing and oxidizing conditions were analyzed by optical spectroscopy. The intensity of a broad intense band at around 20,500 cm-1 in the optical absorption spectra of all color zones of the sample is proportional to the product of Ti- and Fe-concentrations and herewith proves its attribution to electronic Fe2+/Ti4+ IVCT transition. The band is strictly E|| c-polarized, causing an intense red coloration of the samples in this polarization. The polarization of the Fe2+/Ti4+ IVCT band in andalusite, E|| c, shows that the electronic charge-transfer process takes place in Al-O octahedral groups that share edges with neighbors on either side, forming chains parallel to the c-axis of the andalusite structure. Under thermal treatments in air, the first noticeable change is some intensification of the band at 800C. However, at higher temperatures its intensity decreases until it vanishes at 1,000C in lightly colored zones and 1,100C in darkly colored ones. Under annealing in reducing conditions at 700 and 800C, the band also slightly increases and maintains its intensity at treatments at higher temperatures up to 1,000C. These results demonstrate that weakening and disappearance of the Fe2+/Ti4+ IVCT band in spectra of andalusite under annealing in air is caused by oxidization of Fe2+ to Fe3+ in IVCT Fe2+/Ti4+-pairs. Some intensification of the band at 800C is, most probably, due to thermally induced diffusion of Fe2+ and Ti4+ in the structure that leads to aggregation of "isolated" Ti4+ and Fe2+ ions into Fe2+-Ti4+-pairs. At higher temperatures, the competing process of Fe2+ ? Fe3+ oxidation overcomes such "coupling" and the band continues to decrease. The different thermal stability of the band in lightly and darkly colored zones of the samples evidence some self-stabilization over an interaction of Fe2+/Ti4+-pairs involved in IVCT process.

Taran, Michail N.; Koch-Mller, Monika

2011-03-01

107

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

NASA Astrophysics Data System (ADS)

The interaction of subpicosecond 1.06 micrometers laser light at intensities up to 1018 W/cm2 with dense preformed 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.

Klem, Daniel E.; Darrow, Christopher B.; Lane, Stephen M.; Perry, Michael D.

1993-07-01

108

Anomalously Broad Diffuse Interstellar Bands and Excited CH+ Absorption in the Spectrum of Herschel 36  

NASA Astrophysics Data System (ADS)

Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 are found in absorption along the line of sight to Herschel 36, an O star system next to the bright Hourglass nebula of the Hii region Messier 8. Excited lines of CH and CH+ are seen as well. We show that the region is very compact and itemize other anomalies of the gas. An infrared-bright star within 400 AU is noted. The combination of these effects produces anomalous DIBs, interpreted by Oka et al. (2013, see also this volume) as being caused predominantly by infrared pumping of rotational levels of relatively small molecules.

York, D. G.; Dahlstrom, J.; Welty, D. E.; Oka, T.; Hobbs, L. M.; Johnson, S.; Friedman, S. D.; Jiang, Z.; Rachford, B. L.; Snow, T. P.; Sherman, R.; Sonnentrucker, P.

2014-02-01

109

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)

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.

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

1999-01-01

110

Line mixing and speed dependence in CO 2 at 6227.9 cm -1: Constrained multispectrum analysis of intensities and line shapes in the 30013 ? 00001 band  

NASA Astrophysics Data System (ADS)

Line position, intensity and line shape parameters (Lorentz widths, pressure shifts, line mixing, speed dependence) are reported for transitions of the 30013 ? 00001 band of 16O 12C 16O ( ?0 = 6227.9 cm -1). The results are determined from 26 high-resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath-Pierce Fourier transform spectrometer. To minimize the systematic errors of the retrieved parameters, we constrained the multispectrum nonlinear least squares retrieval technique to use quantum mechanical expressions for the rovibrational energies and intensities rather than retrieving the individual positions and intensities line by line. Self- and air-broadened Lorentz width and pressure-induced shift, speed dependence and line mixing (off-diagonal relaxation matrix elements) coefficients were adjusted individually. Errors were further reduced by simultaneously fitting the interfering absorptions from the weak 30012 ? 00001 band of 16O 13C 16O as well as the weak hot bands 31113 ? 01101, 32213 ? 02201, 40014 ? 10002 and 40013 ? 10001 of 16O 12C 16O in this spectral window. This study complements our previous work on line mixing and speed dependence in the 30012 ? 00001 band ( ?0 = 6347.8 cm -1) [V.M. Devi, D.C. Benner, L.R. Brown, C.E. Miller, R.A. Toth, J. Mol. Spectrosc. 242 (2007) 90-117] and provides key data needed to improve atmospheric remote sensing of CO 2.

Devi, V. Malathy; Benner, D. Chris; Brown, L. R.; Miller, C. E.; Toth, R. A.

2007-09-01

111

0.9 eV Absorption Band of Polyaniline: A Morphologically Sensitive Electronic Absorption. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

In this paper, a comparative study of different bands viz. 0.9 eV, 2.9 eV and 1.5 eV has been made for polyaniline samples of different morphology. It is found that although the 0.9 eV band is like the other two bands, due to the existence of polarons, it...

D. Zhang, J. H. Hwang, S. C. Yang

1990-01-01

112

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

SciTech Connect

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.

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

113

Intense square-flash source for time-resolved absorption spectroscopy  

NASA Astrophysics Data System (ADS)

This paper describes a compact xenon flash source and associated circuit designed as an absorption background source for time-resolved spectroscopic measurements. The output is a square wave of nearly constant intensity for a period of 250 ?s. Its spectral emissivity is roughly equivalent to a blackbody of 12 000 K, depending on the voltage used, except for a cutoff in the far ultraviolet by the quartz envelope. The lamp jacket is simple and inexpensive to replace and refill.

Paur, Richard J.; Dorsett, John L.; Bair, Edward J.

1982-03-01

114

Study of the effect of Cu heavy doping on band gap and absorption spectrum of ZnO  

NASA Astrophysics Data System (ADS)

Contradictory experimental absorption spectra blue shift and red shift results have been reported in the literatures. To solve this problem, this study investigates the electronic structure and absorption spectra of Zn1-xCuxO (x = 0, 0.0313 and 0.0625, respectively) and Zn32CuO32 supercells employing first-principles calculations with GGA+U method. By increasing the Cu substitutional doping concentration from 3.13% to 6.25%, the following results are obtained: increased magnetic properties, narrower band gaps, and a significant red shift in the absorption spectrum. These findings are in good agreement with the experimental results. The changes of band gap and absorption spectrum for interstitial doping and substitutional doping are opposite.

Guo, Shaoqiang; Hou, Qingyu; Zhao, Chunwang; Zhang, Yue

2014-10-01

115

Intensities, broadening and narrowing parameters in the ?3 band of methane  

NASA Astrophysics Data System (ADS)

The P-branch of methane's ?3 band is probed to carry out an extensive study of the 2905-2908 cm-1 infrared spectral region. Absolute line intensities as well as N2-, O2-, H2-, He-, Ar- and CO2-broadening coefficients are determined for nine transitions at room temperature. Narrowing parameters due to the Dicke effect have also been investigated. A narrow emission line-width (~0.0001 cm-1) difference-frequency-generation (DFG) laser system is used as the tunable light source. To retrieve the CH4 spectroscopic parameters, Voigt and Galatry profiles were used to simulate the measured line shape of the individual transitions.

Es-sebbar, Et-touhami; Farooq, Aamir

2014-12-01

116

Measurements of Band Intensities, Herman-Wallis Parameters, and Self-Broadening Line-Widths of the 30011 - 00001 and 30014 - 00001 Bands of CO2 at 6503 cm(exp -1) and 6076 cm(exp -1)  

NASA Technical Reports Server (NTRS)

Rotationless band intensities and Herman-Wallis parameters are listed in HITRAN tabulations for several hundred CO2 overtone-combination bands. These parameters are based on laboratory measurements when available, and on DND calculations for the unmeasured bands. The DND calculations for the Fermi interacting nv(sub 1) + v(sub 3) polyads show the a(sub 2) Herman-Wallis parameter varying smoothly from a negative value for the first member of the polyad to a positive value for the final member. Measurements of the v(sub 1) + v(sub 3) dyad are consistent with the DND calculations for the a(sub 2) parameter, as are our recent measurements of the 4v(sub 1) + v(sub 3) pentad. However, the measurement-based values in the HITRAN tables for the 2v(sub 1) + v(sub 3) triad and the 3v(sub 1) + v(sub 3) tetrad do not support the DND calculated values for the a(sub 2) parameters. We therefore decided to make new measurements to improve some of these intensity parameters. With the McMath FTS at Kitt Peak National Observatory/National Solar Observatory we recorded several spectra of the. 4000 to 8000 cm(exp -1) region of pure CO2 at 0.011 cm(exp -1) resolution using the 6 meter White absorption cell. The signal/noise and absorbance of the first and fourth bands of the 3v(sub 1) + v(sub 3) tetrad of C-12O-16 were ideal on these spectra for measuring line intensities and broadening widths. Our selfbroadening results agree with the HITRAN parameterization, while our measurements of the rotationless band intensities are about 15% less than the HITRAN values. We find a negative value of a(sub 2) for the 30011-00001 band and a positive value for the 30014-00001 band, whereas the HITRAN values of a(sub 2) are positive for all four tetrad bands. Our a(sub 1) and a(sub 2) Herman-Wallis parameters are closer to DND calculated values than the 1992 HITRAN values for both the 30011-00001 and the 30014-00001 band.

Giver, L. P.; Brown, L. R.; Wattson, R. B.; Spencer, M. N.; Chackerian, C., Jr.; Strawa, Anthony W. (Technical Monitor)

1995-01-01

117

Low-Intensity Pump-Probe Measurements on the B800 Band of Rhodospirillum molischianum  

PubMed Central

We have measured low-intensity, polarized one-color pump-probe traces in the B800 band of the light-harvesting complex LH2 of Rhodospirillum molischianum at 77 K. The excitation/detection wavelength was tuned through the B800 band. A single-wavelength and a global target analysis of the data were performed with a model that accounts for excitation energy transfer among the B800 molecules and from B800 to B850. By including the anisotropy of the signals into the fitting procedure, both transfer processes could be separated. It was estimated in the global target analysis that the intra-B800 energy transfer, i.e., the hopping of the excitation from one B800 to another B800 molecule, takes ?0.5 ps at 77 K. This transfer time increases with the excitation/detection wavelength from 0.3 ps on the blue side of the B800 band to ?0.8 ps on the red side. The residual B800 anisotropy shows a wavelength dependence as expected for energy transfer within an inhomogeneously broadened cluster of weakly coupled pigments. In the global target analysis, the transfer time from B800 to B850 was determined to be ?1.7 ps at 77 K. In the single-wavelength analysis, a speeding-up of the B800 ? B850 energy transfer rate toward the blue edge of the B800 band was found. This nicely correlates with the proposed position of the suggested high-exciton component of the B850 band acting as an additional decay channel for B800 excitations. PMID:12524297

Wendling, Markus; Mourik, Frank van; van Stokkum, Ivo H. M.; Salverda, Jante M.; Michel, Hartmut; Grondelle, Rienk van

2003-01-01

118

Correlation of the 5.0- and 7.6eV absorption bands in SiO2 with oxygen vacancy  

Microsoft Academic Search

Various uv and vacuum-uv optical-absorption bands found in as-manufactured high-purity SiO2 glass were studied. Two types of absorption bands were found near 5.0 eV, one of which is attributed to the oxygen vacancy (Si-Si). The absorption band at 7.6 eV is also found to be caused by the same oxygen vacancy. Observation of the decay lifetime of photoluminescence and calculations

Ryoichi Tohmon; Hiroyasu Mizuno; Yoshimichi Ohki; Kotoku Sasagane; Kaya Nagasawa; Yoshimasa Hama

1989-01-01

119

Optical bandshape theory of Voigt profiles and approximate analytical calculation of broadening parameters for observed spectral absorption bands  

NASA Astrophysics Data System (ADS)

We have derived an analytical bandshape expression for the Voigt profile for optical absorption. The Voigt profile is a convolution of a gaussian and a lorentzian and is representative of a variety of optical processes. The analytical expression has the form of a rapidly converging and numerically easily tractable sum. It reduces to simpler and transparent forms close to the absorption maximum where the gaussian character dominates, far from the maximum where the band approaches a lorentzian, and in a broad intermediate frequency range. We also provide two simple procedures for calculation of the Voigt bandshape parameters from experimental absorption data.

Zakaraya, Merab G.; Ulstrup, Jens

1988-09-01

120

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

Microsoft Academic Search

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.

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

1987-01-01

121

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

SciTech Connect

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.

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

2009-04-15

122

Multiwavelength diode-laser absorption spectroscopy using external intensity modulation by semiconductor optical amplifiers.  

PubMed

A novel opto-electronic scheme for line-of-sight Near-IR gas absorption measurement based on direct absorption spectroscopy (DAS) is reported. A diode-laser-based, multiwavelength system is designed for future application in nonintrusive, high temporal resolution tomographic imaging of H2O in internal combustion engines. DAS is implemented with semiconductor optical amplifiers (SOAs) to enable wavelength multiplexing and to induce external intensity modulation for phase-sensitive detection. Two overtone water transitions in the Near-IR have been selected for ratiometric temperature compensation to enable concentration measurements, and an additional wavelength is used to account for nonabsorbing attenuation. A wavelength scanning approach was used to evaluate the new modulation technique, and showed excellent absorption line recovery. Fixed-wavelength, time-division-multiplexing operation with SOAs has also been demonstrated. To the best of our knowledge this is the first time SOAs have been used for modulation and switching in a spectroscopic application. With appropriate diode laser selection this scheme can be also used for other chemical species absorption measurements. PMID:23207374

Karagiannopoulos, Solon; Cheadle, Edward; Wright, Paul; Tsekenis, Stylianos; McCann, Hugh

2012-12-01

123

Electric quadrupole transitions and collision-induced absorption in the region of the first overtone band of H2 near 1.25 ?m  

NASA Astrophysics Data System (ADS)

The Q(1)-Q(4) electric quadrupole transitions of the first overtone band of H2 have been recorded for six pressure values up to 640 Torr, by CW-Cavity Ring Down Spectroscopy near 8000 cm-1. The noise equivalent absorption of the spectra is on the order of ?min ? 5 10-12 cm-1. Line intensities derived from a profile fit accounting for Dicke narrowing effects, range from 1.0 10-29 to 2.6 10-27 cm/molecule for the Q(4) and Q(1) line, respectively. The claimed absolute uncertainty on the derived line positions and on the line strengths are of the order of 0.001 cm-1 and 1%, respectively. The pressure line shifts of the four lines were derived allowing for an accurate determination of the position at zero pressure limit. The obtained positions and intensities agree within the experimental uncertainty with the most recent theoretical calculations including non-adiabatic, relativistic and quantum electrodynamical effects. The present frequency determinations confirm the high accuracy of these calculations. From the pressure dependence of the baseline of the CRDS spectra, the self continuum cross section of the collision induced absorption band of H2 is determined in the vicinity of the Q(1) line. The derived cross section is found in good agreement with recent theoretical values.

Kassi, Samir; Campargue, Alain

2014-06-01

124

Conduction-band electronic states of YbInCu4 studied by photoemission and soft x-ray absorption spectroscopies  

NASA Astrophysics Data System (ADS)

We have studied conduction-band (CB) electronic states of a typical valence-transition compound YbInCu4 by means of temperature-dependent hard x-ray photoemission spectroscopy (HX-PES) of the Cu 2p3/2 and In 3d5/2 core states taken at h?=5.95 keV, soft x-ray absorption spectroscopy (XAS) of the Cu 2p3/2 core absorption region around h?935 eV, and soft x-ray photoemission spectroscopy (SX-PES) of the valence band at the Cu 2p3/2 absorption edge of h?=933.0 eV. With decreasing temperature below the valence transition at TV=42 K, we have found that (1) the Cu 2p3/2 and In 3d5/2 peaks in the HX-PES spectra exhibit the energy shift toward the lower binding-energy side by 40 and 30 meV, respectively, (2) an energy position of the Cu 2p3/2 main absorption peak in the XAS spectrum is shifted toward higher photon-energy side by 100 meV, with an appearance of a shoulder structure below the Cu 2p3/2 main absorption peak, and (3) an intensity of the Cu L3VV Auger spectrum is abruptly enhanced. These experimental results suggest that the Fermi level of the CB-derived density of states is shifted toward the lower binding-energy side. We have described the valence transition in YbInCu4 in terms of the charge transfer from the CB to Yb 4f states.

Utsumi, Yuki; Sato, Hitoshi; Kurihara, Hidenao; Maso, Hiroyuki; Hiraoka, Koichi; Kojima, Kenichi; Tobimatsu, Komei; Ohkochi, Takuo; Fujimori, Shin-Ichi; Takeda, Yukiharu; Saitoh, Yuji; Mimura, Kojiro; Ueda, Shigenori; Yamashita, Yoshiyuki; Yoshikawa, Hideki; Kobayashi, Keisuke; Oguchi, Tamio; Shimada, Kenya; Namatame, Hirofumi; Taniguchi, Masaki

2011-09-01

125

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

NASA Technical Reports Server (NTRS)

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. The measured cross-sections are presented graphically here and are available at wavenumber intervals of about 0.1/cm as numerical compilations stored on magnetic tape from the National Space Science Data Center, NASA/Goddard. Band oscillator strengths of these bands have been determined by direct numerical integration of the measured cross sections.

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

1987-01-01

126

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

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.

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

2012-09-06

127

Line Positions, Intensities, - and N_2-BROADENING Parameters in the ?_9 Band of Ethane (C_2H_6)  

NASA Astrophysics Data System (ADS)

High-resolution infrared spectra of ethane have been recorded using the Bruker IFS 120 HR Fourier transform spectrometer (FTS) at the Pacific Northwest National Laboratory (PNNL), in Richland, Washington. Several spectra of pure ethane and ethane in N_2 mixtures were obtained with absorption paths of 20 cm and 3.2 m. Room temperature spectra were obtained in both 20 cm and 3.2 m paths while cold spectra were obtained using only the 20 cm path cell. The spectra were obtained at 0.0028 cm^{-1} resolution with sample pressures ranging from 0.3 to 36 torr for pure ethane and 11 to 180 torr in ethane-N_2 mixtures. The volume mixing ratios of ethane in the ethane-N_2 mixtures varied between 0.01 and 0.2. The gas temperatures varied from -66^C to 24^C. Positions, intensities, self- and N_2-broadening parameters were determined by processing 16 or 17 room temperature spectra using the multispectrum nonlinear least squares spectrum fitting technique. The results obtained for transitions in a few select ^PQ and ^RQ sub-bands will be reported at this time. D. Chris Benner, C.P. Rinsland, V. Malathy Devi, M.A.H. Smith, and D. Atkins, J. Quant. Spectrosc. Radiat. Transfer 53, 705-721 (1995)

Rinsland, Curtis P.; Devi, V. Malathy; Benner, D. Chris; Sams, Robert L.; Blake, Thomas A.

2009-06-01

128

Redshift of the purple membrane absorption band and the deprotonation of tyrosine residues at high pH  

PubMed Central

At high pH (> 8) the 570 nm absorption band of all-trans bacteriorhodopsin (bR) in purple membrane undergoes a small (1.5 nm) shift to longer wavelengths, which causes a maximal increase in absorption at 615 nm. The pK of the shift is 9.0 in the presence of 167 mM KCl, and its intrinsic pK is ?8.3. The red shift of the trans-bR absorption spectrum correlates with the appearance of the fast component in the light-induced L to M transition, and absorption increases at 238 and 297 nm which are apparently caused by the deprotonation of a tyrosine residue and red shift of the absorption of tryptophan residues. This suggests that the deprotonation of a tyrosine residue with an exceptionally low pK (pKa ? 8.3) is responsible for the absorption shift of the chromophore band and fast M formation. The pH and salt dependent equilibrium between the two forms of bR, neutral and alkaline, bR ? bRa, results in two parallel photocycles of trans-bR at high pH, differing in the rate of the L to M transition. In the pH range 10-11.8 deprotonation of two more tyrosine residues is observed with pK's ? 10.3 and 11.3 (in 167 mM KCL). Two simple models discussing the role of the pH induced tyrosine deprotonation in the photocycle and proton pumping are presented. It is suggested that the shifts of the absorption bands at high pH are due to the appearance of a negatively charged group inside the protein (tyrosinate) which causes electrochromic shifts of the chromophore and protein absorption bands due to the interaction with the dipole moments in the ground and excited states of bR (Stark effect). This effect gives evidence for a significant change in the dipole moment of the chromophore of bR upon excitation. Under illumination alkaline bR forms, besides the usual photocycle intermediates, a long-lived species with absorption maximum at 500 nm (P500). P500 slowly converts into bRa in the dark. Upon illumination P500 is transformed into an intermediate having an absorption maximum at 380 nm (P380). P380 can be reconverted to P500 by blue light illumination or by incubation in the dark. PMID:19431801

Balashov, S. P.; Govindjee, R.; Ebrey, T. G.

1991-01-01

129

Comparative analysis of the H-F stretching band in absorption spectra of gas-phase complexes of HF with water, dimethyl ether, and acetone  

NASA Astrophysics Data System (ADS)

Comparative analysis of the ?1(H-F) stretching band shapes in the absorption spectra of complexes of HF with water, dimethyl ether, and acetone and the mechanisms of formation of this band is performed by comparing the experimental spectra and results of nonempirical quantum-mechanical calculations. The experimental spectra of complexes considered were obtained by subtracting the spectra of monomers from the experimental spectra of gaseous mixtures recorded at different temperatures in the region of the ?1(H-F) band at a high resolution with Bruker IFS-113v and ?ruker IFS-125 HR vacuum Fourier spectrometers. These spectra are compared with the band shapes reconstructed theoretically with the use of electro-optical parameters obtained from variational solutions of multidimensional anharmonic vibrational problems. The equilibrium geometries of the complexes, their potential energy and dipole moment surfaces necessary for solving these problems were calculated ab initio at a high level of theory. In this approach the internal anharmonicity of the ?1(H-F) mode and its interaction with all low-frequency intermolecular modes are considered explicitly. Anharmonic interactions between different intermolecular motions are also analyzed in detail. The inter-mode interactions are found to have different effects on the frequency and absolute intensity of the ?1(H-F) fundamental transition. Comparison of the data for different complexes shows that the resulting spectral manifestations of the anharmonic effects depend on the interplay between the H-bond strength, the barrier height for tunneling, the magnitudes of frequencies of intermolecular vibrations, rotational constants, etc. The reconstruction of spectra as a superposition of rovibrational bands of the fundamental, hot, and combination transitions with calculated values of absolute intensities can reproduce the shape and separate details of the experimental spectra. Analysis of the experimental and calculated data provides reliable values of the fundamental ?1(H-F) transition frequency, indicates its position in the spectrum, and elucidates the nature of different structural features.

Bulychev, V. P.; Tokhadze, K. G.

2010-07-01

130

Determining Limits on the Intensity of the O2 0-0 Atmospheric Band Emission in the Venus Nightglow  

NASA Astrophysics Data System (ADS)

Recombination of oxygen atoms is the source of excited O2 states in the nighttime mesospheres of the terrestrial planets - Venus, Earth, and Mars. Emission in the O2 Atmospheric 0-0 band at 762 nm is one of the strongest features in the terrestrial visible/near-IR spectral region, with a typical intensity of 5 kR, although this emission does not reach the ground due to self-absorption. We inquire as to what intensity is expected at Venus, although there are no published spectra for either Venus or Mars in this spectral region. A recent estimated upper limit of 200 R for Venus has been given [Krasnopolsky, 2011]. The calculation requires knowledge of the temperature-dependent rate coefficients for three-body oxygen atom recombination in CO2 and for O2(b, v = 0) removal by CO2, as well as an estimate for the fraction of stabilized excited O2 molecules that reach b(v = 0). The resultant nadir intensity depends on [O(3P)]2, and for a value of [O(3P)] = 1.5 1011 cm-3, the 95-km intensity is of the order of 2 R, probably accurate to within a factor of two. Such a value is consistent with the lack of detection in recent Venus Express VIRTIS spectra, which include the 762 nm region. Measurements of the Venus nightglow with the 3.5-m telescope at Apache Point Observatory in December, 2010 also show no 762 nm emission, where in principle the 0.03 nm Doppler shift in the emission due to the relative velocities of Earth and Venus could have made observation possible. The principal differences between the Venus and Earth cases are (1) quenching of O2(b, v = 0) is more than two orders of magnitude faster by CO2 than by N2 (the terrestrial quencher) and (2) the densities in the ~95 km mesospheric nightglow region are two orders of magnitude higher at Venus. TGS acknowledge support for this work from the NASA Planetary Astronomy Program, Grant NNX08A0276. AM acknowledges ASI for support. Krasnopolsky, V.A., Planet. Space Sci. 59, 754-766, 2011.

Slanger, T. G.; Migliorini, A.; Gray, C.

2011-12-01

131

Ab initio determination of potential energy surfaces for the first two UV absorption bands of SO2  

NASA Astrophysics Data System (ADS)

Three-dimensional potential energy surfaces for the two lowest singlet (A~1B1 and B~1A2) and two lowest triplet (a~3B1 and b~3A2) states of SO2 have been determined at the Davidson corrected internally contracted multi-reference configuration interaction level with the augmented correlation-consistent polarized triple-zeta basis set (icMRCI+Q/AVTZ). The non-adiabatically coupled singlet states, which are responsible for the complex Clements bands of the B band, are expressed in a 2 2 quasi-diabatic representation. The triplet state potential energy surfaces, which are responsible for the weak A band, were constructed in the adiabatic representation. The absorption spectrum spanning both the A and B bands, which is calculated with a three-state non-adiabatic coupled Hamiltonian, is in good agreement with experiment, thus validating the potential energy surfaces and their couplings.

Xie, Changjian; Hu, Xixi; Zhou, Linsen; Xie, Daiqian; Guo, Hua

2013-07-01

132

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

NASA Astrophysics Data System (ADS)

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

Heng, Hang; Yang, Li

2014-05-01

133

Evolution of isolated G-band bright points: size, intensity and velocity  

NASA Astrophysics Data System (ADS)

We study the evolution pattern of isolated G-band bright points (GBPs) in terms of their size, intensity and velocity. Using a high resolution image sequence taken with the Hinode/Solar Optical Telescope (SOT), we detect GBPs in each image by the Laplacian and Morphological Dilation algorithm, and track their evolutions by a 26-adjacent method in a three-dimensional space-time cube. For quantifying the evolution, we propose a quantification method based on lifetime normalization which aligns the different lifetimes to common stages. The quantification results show that, on average, the diameter of isolated GBPs changes from 173 to 166 km, then down to 165 km; the maximum intensity contrast changes from 1.012 to 1.027, then down to 1.011; however, the velocity changes from 1.709 to 1.593 km s-1, then up to 1.703 km s-1. The results indicate that the evolution follows a pattern such that the GBP is small, faint and fast-moving at the birth stage, becomes big, bright and slow-moving at the middle stage, then gets small, faint and fast-moving at the decay stage until disappearance. Although the differences are very small, a two-sample t-test is used to demonstrate there are significant differences in means between the distributions of the different stages. Furthermore, we quantify the relationship between the lifetimes of GBPs and their properties. It is found that there are positive correlations between the lifetimes and their sizes and intensities with correlation coefficients of 0.83 and 0.65, respectively; however, there is a negative correlation between the lifetimes and velocities with a correlation coefficient of -0.49. In summary, the longer the GBP persists, the bigger, brighter and slower it will be.

Yang, Yun-Fei; Lin, Jia-Ben; Feng, Song; Ji, Kai-Fan; Deng, Hui; Wang, Feng

2014-06-01

134

Temperature behavior of the fundamental optical absorption band in quasi-two-dimensional crystalline MnPS3  

NASA Astrophysics Data System (ADS)

Optical absorption spectra of the layered semiconductor MnPS3 are measured in the temperature range 12-160 K, which covers the magnetic ordering temperature. It is shown that the interband optical absorption coefficient is well described by a model for direct allowed transitions in three-dimensional compounds, while temperature increases lead to an effective reduction in the band gap. A theoretical model is proposed for optical transitions in crystalline MnPS3. A comparison of experimental data with the theory indicates that the chosen model is adequate.

Piryatinskaya, V. G.; Kachur, I. S.; Slavin, V. V.; Yeremenko, A. V.; Vysochanskii, Yu. M.

2012-09-01

135

Optical absorption and x-ray diffraction in narrow-band-gap InAs\\/GaSb superlattices  

Microsoft Academic Search

We report on the optical transmission properties of narrow-band-gap (Eg<0.1 eV) InAs\\/GaSb superlattices grown by molecular-beam epitaxy. Energy band gaps of 0.15 and 0.085 eV at 4.8 K are determined for a 102-A?-period and a 124-A?-period superlattice, respectively. The absorption edge is extremely soft due to the spatial mismatch of hole and electron wave functions. In addition we show the

D. K. Arch; G. Wicks; Tom Tonaue; Jean-Louis Staudenmann

1985-01-01

136

A new computation of the infrared absorption by H2 pairs in the fundamental band at temperatures from 600 to 5000 K. [in stellar atmospheres  

NASA Technical Reports Server (NTRS)

A new computation of the absorption spectrum of H2 pairs in the fundamental band is given for temperatures from 600 to 5000 K. It is based on advanced interaction potentials and recent induced dipole components which were shown to be consistent with the existing laboratory measurements of low-temperature absorption spectra. The absorption is greater by factors of 2-3 than previous estimates and show a different band profile at the higher temperatures.

Borysow, Aleksandra; Frommhold, Lothar

1990-01-01

137

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

138

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

NASA Technical Reports Server (NTRS)

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.

Singhroy, Vernon H.; Kruse, Fred A.

1991-01-01

139

Manifestation of protein conformations in the B850 absorption band of light-harvesting complex LH2  

NASA Astrophysics Data System (ADS)

As experimentally established the absorption bands corresponding to the B850 ring of LH2 complexes from Rhodoblastus acidophilus and Rhodobacter sphaeroides broaden and shift by changing the temperature. The peak shift with the temperature cannot be explained in terms of the conventional disordered exciton model, therefore the modified (dichotomous) exciton model is formulated. The modified exciton model, which assumes the presence of two conformational states for every bacteriochlorophyll molecule constituting the B850 ring, is postulated. Since the conformational states are characterized by their free energies, the population ratio of the conformational states is temperature dependent. As the result, the disorder becomes also temperature dependent and, thus, both the broadening and the shift of the B850 absorption bands are explained within the frame of the modified exciton model.

Meldaikis, Julius; Zerlauskiene, Oksana; Abramavicius, Darius; Valkunas, Leonas

2013-09-01

140

The 217.5 nm band, infrared absorption and infrared emission features in hydrogenated amorphous carbon nanoparticles  

E-print Network

We report on the preparation of hydrogenated amorphous carbon nano-particles 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 nano-particles having an sp2/sp3 ratio = 0.4. Spectroscopic analysis of particle composition indicates that naphthalene and naphthalene derivatives are important constituents of this material. We suggest that carbon nano-particles with similar composition are responsible for the appearance of the interstellar 217.5 nm band and outline how t...

Duley, W W

2012-01-01

141

Picosecond kinetic confirmation of overlapping Ca cluster and MNa absorption bands in UV grade CaF2  

NASA Astrophysics Data System (ADS)

The ArF laser induced absorption feature between 450 and 700 nm observed in the bulk of mono crystalline calcium fluoride (CaF2) upon prolonged 193 nm irradiation is shown to have two origins: The first band at 530 nm is revealed by a transient femtosecond (fs) laser transparency spectrum and attributed to Ca clusters (colloid). The second band at 600 nm originates from MNa centers as identified by their laser induced fluorescence excitation spectrum, emission wavelength, and fluorescence lifetime. The analysis of the absorption feature by fs pump-probe techniques benefits from the different lifetimes of the transient transparency (excited states of the Ca clusters) and the fluorescing MNa centers of about 5 ps and 22 ns, respectively.

Zeuner, T.; Paa, W.; Triebel, W.; Mhlig, C.; Stafast, H.

2011-09-01

142

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

NASA Technical Reports Server (NTRS)

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.

May, Randy D.

1992-01-01

143

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

E-print Network

T S o ere I D~aphragri Aeeoenv rorr Ceil Fiktae Rota. ting Sec+on Coir irene&or Skit lon& The light source used was a clear, ribbon filament, incandescent lamp. The ribbon f ilament type wae used be- cause of its close approximation...T S o ere I D~aphragri Aeeoenv rorr Ceil Fiktae Rota. ting Sec+on Coir irene&or Skit lon& The light source used was a clear, ribbon filament, incandescent lamp. The ribbon f ilament type wae used be- cause of its close approximation...

Rapp, Thomas Louis

2012-06-07

144

Calculation of radiowave absorption and field intensity for oblique incidence on the ionosphere based on vertical sounding data  

NASA Technical Reports Server (NTRS)

A graphical method is proposed for calculating the field intensity, LUF, and minimum required power with account for antenna parameters at distances for which the ionosphere can be considered constant along the path. The method is based on data from vertical sounding of the ionosphere (nomograms and absorption measurement by the pulse method). This method takes into account directly multipath transmission in calculating the field intensity, which makes it possible to select the radiowave propagation mode which is most effective for each specific case. A method is proposed for quantitative estimation of the absorption (and also the field intensity and required transmitter power) along the radio path during disturbances from cosmic radio emission absorption measurement (riometer) data.

Pushkin, Y. R.; Fligel, M. D.

1973-01-01

145

Absorption  

NSDL National Science Digital Library

The process of absorption is a cellular process (microscopic). Absorption cells line the stomach and intestine walls and allow small nutrients (broken down from the food we eat) to pass through and into our blood. The process of absorption is much like a leaking balloon filled with water. The balloon is the stomach or intestine, the tiny holes are the absorption cells, and the water is nutrients leaving.

Katie Hale (CSUF;)

2002-09-26

146

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

NASA Technical Reports Server (NTRS)

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.

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

1989-01-01

147

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)

Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 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 ) 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 m 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.

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

148

Semi-Empirical Validation of the Cross-Band Relative Absorption Technique for the Measurement of Molecular Mixing Ratios  

NASA Technical Reports Server (NTRS)

Studies were performed to carry out semi-empirical validation of a new measurement approach we propose for molecular mixing ratios determination. The approach is based on relative measurements in bands of O2 and other molecules and as such may be best described as cross band relative absorption (CoBRA). . The current validation studies rely upon well verified and established theoretical and experimental databases, satellite data assimilations and modeling codes such as HITRAN, line-by-line radiative transfer model (LBLRTM), and the modern-era retrospective analysis for research and applications (MERRA). The approach holds promise for atmospheric mixing ratio measurements of CO2 and a variety of other molecules currently under investigation for several future satellite lidar missions. One of the advantages of the method is a significant reduction of the temperature sensitivity uncertainties which is illustrated with application to the ASCENDS mission for the measurement of CO2 mixing ratios (XCO2). Additional advantages of the method include the possibility to closely match cross-band weighting function combinations which is harder to achieve using conventional differential absorption techniques and the potential for additional corrections for water vapor and other interferences without using the data from numerical weather prediction (NWP) models.

Pliutau, Denis; Prasad, Narasimha S

2013-01-01

149

Semi-empirical validation of the cross-band relative absorption technique for the measurement of molecular mixing ratios  

NASA Astrophysics Data System (ADS)

Studies were performed to carry out semi-empirical validation of a new measurement approach we propose for molecular mixing ratios determination. The approach is based on relative measurements in bands of O2 and other molecules and as such may be best described as cross band relative absorption (CoBRA). The current validation studies rely upon well verified and established theoretical and experimental databases, satellite data assimilations and modeling codes such as HITRAN, line-by-line radiative transfer model (LBLRTM), and the modern-era retrospective analysis for research and applications (MERRA). The approach holds promise for atmospheric mixing ratio measurements of CO2 and a variety of other molecules currently under investigation for several future satellite lidar missions. One of the advantages of the method is a significant reduction of the temperature sensitivity uncertainties which is illustrated with application to the ASCENDS mission for the measurement of CO2 mixing ratios (XCO2). Additional advantages of the method include the possibility to closely match cross-band weighting function combinations which is harder to achieve using conventional differential absorption techniques and the potential for additional corrections for water vapor and other interferences without using the data from numerical weather prediction (NWP) models.

Pliutau, Denis; Prasad, Narasimha S.

2013-05-01

150

Multispectrum analysis of the v9 band of 12C2H6: Positions, intensities, self- and N2-broadened half-width coefficients  

SciTech Connect

Line positions, intensities, Lorentz self- and N2-broadened half-width coefficients have been measured for PQ3, PQ2, PQ1, RQ0,RQ1, RQ2, and RQ3 sub-band transitions in the 9 fundamental band of 12C2H6. A multispectrum nonlinear least-squares fitting technique was used to fit up to 17 high-resolution (~0.00156 cm-1), room temperature absorption spectra of pure (99.99% chemical purity) natural sample of ethane and lean mixtures of the high-purity ethane diluted with N2. A Bruker IFS 120HR Fourier transform spectrometer located at the Pacific Northwest National Laboratory (PNNL), in Richland, Washington was used to record the data. A standard Voigt line shape was assumed to fit all the data since no line mixing or other non Voigt line shapes were required to fit any of the spectra used in the analysis. Short spectral intervals (~2 to 2.5 cm-1) of all 17 spectra covering a specific PQ or RQ sub band were fit simultaneously. For the first time in an ethane band, pressure-broadened half-width coefficients were determined for each of the torsional-split components. Constraints were used such that the half-width coefficients of both torsional-split components were identical for a specific broadening gas. No pressure-induced shift coefficients were necessary to fit the spectra to their noise level. The present study revealed for the first time the dependence of self- and N2-broadened half-width coefficients upon the J, K quantum numbers of the transitions in ethane. A number of transitions belonging to the 9+ 4- 4 and the 9+2 4-2 4 hot bands were also observed in the fitted regions and measurements were made when possible.

Devi, V. Malathy; Rinsland, Curtis P.; Benner, D. C.; Sams, Robert L.; Blake, Thomas A.

2010-06-01

151

Near resonant absorption by atoms in intense fluctuating laser fields. Final report  

SciTech Connect

The objective of this program was to make quantitative measurements of the effects of higher-order phase/frequency correlations in a laser beam on nonlinear optical absorption processes in atoms. The success of this program was due in large part to a unique experimental capability for modulating the extracavity beam of a stabilized ({approx_lt}200 kHz) continuous-wave laser with statistically-well-characterized stochastic phase (or frequency) fluctuations, in order to synthesize laser bandwidths to {approximately}20 MHz (depending on noise amplitude), with profiles variable between Gaussian and Lorentzian (depending on noise bandwidth). Laser driven processes investigated included the following: (1) the optical Autler-Towns effect in the 3S{sub 1/2} (F = 2, M{sub F} = 2) {yields} 3P{sub 3/2} (F = 3, M{sub F} = 3) two- level Na resonance, using a weak probe to the 4D{sub 5/2} level; (2) the variance and spectra of fluorescence intensity fluctuations in the two-level Na resonance; (3) the Hanle effect in the {sup 1}S{sub 0} {minus} {sup 3}P{sub 1}, transition at {lambda} = 555.6 nm in {sup 174} Yb; (4) absorption (and gain) of a weak probe, when the probe is a time-delayed replica of the resonant (with the two-level Na transition) pump laser; and (5) four-wave-mixing in a phase-conjugate geometry, in a sodium cell, and, finally, in a diffuse atomic sodium beam. The experimental results from these several studies have provided important confirmation of advanced theoretical methods.

Smith, S.J.

1994-01-01

152

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

DOE Data Explorer

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.

Greenwood, R.E.

153

Theoretical modeling of deuteration-induced shifts of the 0-0 bands in absorption spectra of selected aromatic amines: the role of the double-well potential.  

PubMed

The harmonic approximation fails for inversion of the NH2 group in the ground state of aromatic amines as this vibration is characterized by a symmetric double-well potential with relatively small energy barrier. In such cases, the standard harmonic vibrational analysis is inapplicable: the inversion frequency calculated for the bottom of the potential well is strongly overestimated, while it attains imaginary values for the planar conformation of the molecule. The model calculations are discussed taking explicitly into account the presence of the double-well potential. The study is initially focused on reproduction of the deuteration-induced shifts of the 0-0 absorption band for anthranilic acid. The (incorrect) harmonic frequency of the NH2 inversion is replaced by a better one, obtained from numerical calculations employing a simple, quartic-quadratic model for the double-well potential, which is parametrized using just the harmonic frequency of the inversion and the height of the energy barrier. This operation brings theoretical results to qualitative agreement with experiment. A still better match is achieved with a modified version of the model that accounts for mixing of the NH2 inversion mode with other normal modes while retaining the initial simplicity of one-dimensional approach. The corrected results show surprisingly good accuracy, with deviations of the calculated shifts from the experimental values reduced to less than 5 cm(-1). In order to test the performance of the model for systems with higher energy barrier for the NH2 inversion, we have measured the LIF excitation spectra of three different amminobenzonitriles. Partial assignment of the 0-0 bands has been achieved based on their relative intensities for samples with different isotopic exchange ratios. Calculated shifts are in excellent agreement with experimental values for the identified bands. Theoretical predictions are used to complete the assignment of the 0-0 bands in the spectra of the studied amminobenzonitriles. PMID:24219819

Andrzejak, Marcin; Kolek, Przemys?aw

2013-12-01

154

Extracting interstellar diffuse absorption bands from cool star spectra. Application to bulge clump giants in Baade's window  

NASA Astrophysics Data System (ADS)

Aims: Interstellar (IS) absorption lines or diffuse bands are usually extracted from early-type star spectra because they are characterized by smooth continua. However, this introduces a strong limitation on the number of available targets, and reduces potential studies of the IS matter and the use of absorptions for cloud mapping. Methods: We have developed a new and automated fitting method appropriate to interstellar (IS) absorptions in the spectra of cool stars that possess stellar atmospheric parameters. We applied this method to the extraction of three diffuse interstellar bands (DIBs) in high resolution VLT FLAMES/GIRAFFE spectra of red-clump stars from the bulge. By combining all stellar synthetic spectra, HITRAN-LBLRTM atmospheric transmission spectra and diffuse band empirical absorption profiles, we determined the 6196.0, 6204.5, and 6283.8 DIB strength toward the 219 target stars and discuss the sources of uncertainties. To test the sensitivity of the DIB extraction, we compared all three results and compared the DIB equivalent widths (EWs) with the reddening derived from an independent extinction map based on OGLE photometric data. We also derived the three independent color excess estimates based on the DIB strengths and average linear correlation coefficients previously established in the solar neighborhood and compared with the OGLE photometric results. Results: Most stellar spectra could be reproduced well by the composite stellar, atmospheric, and IS models. Measurement uncertainties on the EWs are smaller for the broad and strong 6283.8 DIB, and are in the range 10-15%. Uncertainties on the two narrow and weaker DIBs are larger, as expected, and found to be highly variable from one target to the next. They strongly depend on the star's radial velocity. DIB-DIB correlations among the three bands demonstrate that a meaningful signal is extracted. For the 6284 and 6204 DIBs, the star-to-star variability of the EW also reflects features of the OGLE extinction map. The three independent extinction estimates deduced from the EWs and solar neighborhood correlation coefficients agree with each other within 20%, a value which probably reflects that they belong to different families. The estimated average color excess is also compatible with the photometric determination. Conclusions: This work demonstrates the feasibility of the method of ISM DIB extraction in cool star spectra, based on synthetic spectra. It confirms that DIB measurements and local DIB-extinction calibrations can provide rough, first-order estimates of the towards distant targets.

Chen, H.-C.; Lallement, R.; Babusiaux, C.; Puspitarini, L.; Bonifacio, P.; Hill, V.

2013-02-01

155

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

PubMed

We present the design, numerical simulations and experimental measurements of terahertz metamaterial absorbers with a broad and flat absorption top over a wide incidence angle range for either transverse electric or transverse magnetic polarization depending on the incident direction. The metamaterial absorber unit cell consists of two sets of structures resonating at different but close frequencies. The overall absorption spectrum is the superposition of individual components and becomes flat at the top over a significant bandwidth. The experimental results are in excellent agreement with numerical simulations. PMID:22854451

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

2012-01-15

156

Spectroscopic effects resulting from interacting singlet and triplet excited states: vibronic structure involving the O-H stretching mode in d-d absorption bands of Ni(H2O)6(2+).  

PubMed

The ligand-field absorption spectrum of the Ni(H2O)6(2+) cation has been thoroughly measured and analyzed over the past sixty years, often on crystals with low symmetry at the metal site, and its absorption band maxima have been used as a benchmark for increasingly sophisticated electronic structure calculations over the last decades. We present variable-temperature absorption spectra measured on crystals with cubic Th symmetry at the site of the nickel(ii) cation. This high site symmetry is confirmed for CsNi(H2O)6PO4 by X-ray diffraction and allows for a direct comparison with ligand-field calculations in Th symmetry, at the basis of an analysis of the vibronic structure in the energy range of the lowest-energy spin-forbidden transition, the "red" or middle band of the spectrum. This spectroscopic region displays effects of strong interactions between singlet and triplet excited states, influencing intensities and vibronic structure. A particular feature that has not been analyzed in detail is a clearly discernible vibronic progression involving the O-H stretching mode on the high-energy side of the absorption band. A quantitative model is presented and applied in order to rationalize this unusual effect, originating from coupling between normal coordinates, to the best of our knowledge the first analysis of this distinct spectroscopic feature arising from interacting excited states. PMID:25311941

Dobe, Christopher; Gonzlez, Emmanuel; Tregenna-Piggott, Philip L W; Reber, Christian

2014-11-12

157

Airborne Measurements of Air Mass from O2 A-Band Absorption Spectra  

Microsoft Academic Search

Airborne experiments to assess the feasibility of remote sensing surface pressure from a space platform are described. The data are high-resolution spectra in the O 2 A band (759-771 nm) of sunlight reflected from the sea surface, measured by a grating spectrograph directed toward sunglint from a research aircraft. It is shown that in the first approximation the reflected radiance

D. M. OBrien; R. M. Mitchell; S. A. English; G. A. Da Costa

1998-01-01

158

Infrared Absorption Bands of Enamel and Dentin Tissues from Human and Bovine Teeth  

Microsoft Academic Search

The chemical components present in the hard tissue such as water, phosphate, carbonate and organic material strongly absorb infrared radiation. The research in dentistry area has a fundamental interest in identifying the chemical origin of all the bands present in the infrared region to study the chemical and thermal action on the hard dental tissues. To improve this technique it

Luciano Bachmann; Rolf Diebolder; Raimund Hibst; Denise Maria Zezell

2003-01-01

159

What is the best DFT functional for vibronic calculations? A comparison of the calculated vibronic structure of the S1-S0 transition of phenylacetylene with cavity ringdown band intensities.  

PubMed

The sensitivity of vibronic calculations to electronic structure methods and basis sets is explored and compared to accurate relative intensities of the vibrational bands of phenylacetylene in the S(1)(A(1)B(2)) ? S(0)(X(1)A(1)) transition. To provide a better measure of vibrational band intensities, the spectrum was recorded by cavity ringdown absorption spectroscopy up to energies of 2000 cm(-1) above the band origin in a slit jet sample. The sample rotational temperature was estimated to be about 30 K, but the vibrational temperature was higher, permitting the assignment of many vibrational hot bands. The vibronic structure of the electronic transition was simulated using a combination of time-dependent density functional theory (TD-DFT) electronic structure codes, Franck-Condon integral calculations, and a second-order vibronic model developed previously [Johnson, P. M.; Xu, H. F.; Sears, T. J. J. Chem. Phys. 2006, 125, 164331]. The density functional theory (DFT) functionals B3LYP, CAM-B3LYP, and LC-BLYP were explored. The long-range-corrected functionals, CAM-B3LYP and LC-BLYP, produced better values for the equilibrium geometry transition moment, but overemphasized the vibronic coupling for some normal modes, while B3LYP provided better-balanced vibronic coupling but a poor equilibrium transition moment. Enlarging the basis set made very little difference. The cavity ringdown measurements show that earlier intensities derived from resonance-enhanced multiphoton ionization (REMPI) spectra have relative intensity errors. PMID:22616733

Lopez, Gary V; Chang, Chih-Hsuan; Johnson, Philip M; Hall, Gregory E; Sears, Trevor J; Markiewicz, Beatrice; Milan, Mariana; Teslja, Alexey

2012-06-28

160

High-Resolution Fourier-Transform Intracavity Laser Absorption Spectroscopy of D 2O in the Region of the 4? 1+? 3 Band  

NASA Astrophysics Data System (ADS)

The high-resolution absorption spectrum of the D 2O molecule was recorded with the Fourier-transform intracavity laser absorption spectrometer in the region 12 570-12 820 cm -1 where the band 4? 1+? 3 is located. Transitions belonging to the 4? 1+? 3 band, and the bands 3? 1+2? 3 and 3? 1+2? 2+? 3, of which the up states are strongly interacted with that of the 4? 1+? 3, were assigned in the recorded spectrum. Up state energy levels were fitted to derive effective spectroscopic parameters, which reproduce majority of the assigned transitions within the experimental accuracy.

Hu, Shui-Ming; Ulenikov, O. N.; Bekhtereva, E. S.; Onopenko, G. A.; He, Sheng-Gui; Lin, Hai; Cheng, Ji-Xin; Zhu, Qing-Shi

2002-03-01

161

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

SciTech Connect

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.

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

2010-08-15

162

Preparation and oscillation of absorption bands of ZnS clusters  

Microsoft Academic Search

Electric-field-induced transient pore formation (electroporation) in DOPC vesicles is used for the preparation of molecular ZnS clusters. The absence of caps permits (a) continued growth of the ZnS clusters formed, (b) the assessment of their true absorption spectra unaltered by stabilizing ligands, and (c) the previously inaccessible live observation of the growth of the clusters in the molecular-size regime. The

Xinshou Wang; Hongtao Xu; Hongzeng Liu; Zoltan A. Schelly; Sixin Wu

2007-01-01

163

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

USGS Publications Warehouse

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.

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

1999-01-01

164

Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs  

NASA Astrophysics Data System (ADS)

Room temperature absorption spectra of low temperature molecular beam epitaxy grown GaAs (LT-GaAs) and AlGaAs (LT-AlGaAs) are reported. We performed measurements in an extended spectral range from 0.8 eV to photon energies of 2.8 eV far above the band gap. For as-grown LT-materials, the absorption coefficients at the band gap are twice as high as for high temperature grown materials. By annealing the samples, we obtained a drastic reduced absorption coefficient below as well as above the band gap. We observed absorption changes up to 17 000 cm-1 for LT-GaAs and 9000 cm-1 for LT-AlGaAs taking place in a two phase process.

Dankowski, S. U.; Streb, D.; Ruff, M.; Kiesel, P.; Kneissl, M.; Knpfer, B.; Dhler, G. H.; Keil, U. D.; Srenson, C. B.; Verma, A. K.

1996-01-01

165

Exciton exciton annihilation dynamics in chromophore complexes. II. Intensity dependent transient absorption of the LH2 antenna system  

NASA Astrophysics Data System (ADS)

Using the multiexciton density matrix theory of excitation energy transfer in chromophore complexes developed in a foregoing paper [J. Chem. Phys. 118, 746 (2003)], the computation of ultrafast transient absorption spectra is presented. Beside static disorder and standard mechanisms of excitation energy dissipation the theory incorporates exciton exciton annihilation (EEA) processes. To elucidate signatures of EEA in intensity dependent transient absorption data the approach is applied to the B850 ring of the LH2 found in rhodobacter sphaeroides. As main indications for two-exciton population and resulting EEA we found (i) a weakening of the dominant single-exciton bleaching structure in the transient absorption, and (ii) an intermediate suppression of long-wavelength and short-wavelength shoulders around the bleaching structure. The suppression is caused by stimulated emission from the two-exciton to the one-exciton state and the return of the shoulders follows from a depletion of two-exciton population according to EEA. The EEA-signature survives as a short-wavelength shoulder in the transient absorption if orientational and energetic disorder are taken into account. Therefore, the observation of the EEA-signatures should be possible when doing frequency resolved transient absorption experiments with a sufficiently strongly varying pump-pulse intensity.

Brggemann, B.; May, V.

2004-02-01

166

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

NASA Astrophysics Data System (ADS)

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.

Chattopadhyay, P.; Karim, B.; Guha Roy, S.

2013-12-01

167

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

SciTech Connect

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.

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

168

Assignment of aluminum corroles absorption bands to electronic transitions by femtosecond polarization resolved VIS-pump IR-probe spectroscopy.  

PubMed

We combine femtosecond polarization resolved VIS-pump IR-probe spectroscopy with DFT and TD-DFT calculations to identify and assign absorption bands to electronic transitions for corroles. These macrocycles and their corresponding metal complexes are receiving great attention because of their utility in many fields, while many of their spectroscopic features have not yet been fully described. Analysis of the perturbed free induction decay provides information about the bleaching signal at time zero and allows for determination of overlapping excited state and bleaching signal amplitudes. The S(0) ? S(1) and S(0) ? S(2) transitions in the Q-band of the hexacoordinated Al(tpfc)(py)(2) and Br(8)Al(tpfc)(py)(2) absorption spectra are explicitly assigned. Angles between these electronic transition dipole moments (tdms) with a single vibrational transition dipole moment of (53 2) and (34 2) when excited at 580 and 620 nm for hexacoordinated Al(tpfc)(py)(2) and (51 2) and (43 2) when excited at 590 and 640 nm for hexacoordinated Br(8)Al(tpfc)(py)(2) were determined. The relative angles between the two lowest electronic tdms are (90 8) and (94 3) for Al(tpfc)(py)(2) and Br(8)Al(tpfc)(py)(2), respectively. Angles are determined before time zero by polarization resolved perturbed free induction decay and after time zero by polarization resolved transients. Comparison of corrole's wave functions with those of porphine show that the reduced symmetry in the corrole molecules results in lifting of Q-band degeneracy and major reorientation of the electronic transition dipole moments within the molecular scaffold. This information is necessary in designing optimal corrole-based electron and energy transfer complexes. PMID:22201283

Yang, Yang; Jones, Dagmar; von Haimberger, Theodore; Linke, Martin; Wagnert, Linn; Berg, Alexander; Levanon, Haim; Zacarias, Angelica; Mahammed, Atif; Gross, Zeev; Heyne, Karsten

2012-01-26

169

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

NASA Technical Reports Server (NTRS)

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.

Khanna, R. K.; Zhao, Guizhi

1986-01-01

170

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

PubMed

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

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

171

Application of BWO for excitation of intensive chaotic oscillations of millimeter wave band  

Microsoft Academic Search

Radioelectronic systems using a random signals are distinguished by a high electromagnetic compatibility, sensitivity, quantity of information. That is why a problem of excitation of random signals is very important. Especially it refers to millimeter wave band. In this paper a method of creation of millimeter random signal sources using dynamic properties of backward wave oscillators is considered. Causes are

K. A. Lukin; V. A. Rakityansky

1993-01-01

172

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

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

173

Highly luminescent S, N co-doped graphene quantum dots with broad visible absorption bands for visible light photocatalysts  

NASA Astrophysics Data System (ADS)

A facile hydrothermal synthesis route to N and S, N co-doped graphene quantum dots (GQDs) was developed by using citric acid as the C source and urea or thiourea as N and S sources. Both N and S, N doped GQDs showed high quantum yield (78% and 71%), excitation independent under excitation of 340-400 nm and single exponential decay under UV excitation. A broad absorption band in the visible region appeared in S, N co-doped GQDs due to doping with sulfur, which alters the surface state of GQDs. However, S, N co-doped GQDs show different color emission under excitation of 420-520 nm due to their absorption in the visible region. The excellent photocatalytic performance of the S, N co-doped GQD/TiO2 composites was demonstrated by degradation of rhodamine B under visible light. The apparent rate of S, N:GQD/TiO2 is 3 and 10 times higher than that of N:GQD/TiO2 and P25 TiO2 under visible light irradiation, respectively.A facile hydrothermal synthesis route to N and S, N co-doped graphene quantum dots (GQDs) was developed by using citric acid as the C source and urea or thiourea as N and S sources. Both N and S, N doped GQDs showed high quantum yield (78% and 71%), excitation independent under excitation of 340-400 nm and single exponential decay under UV excitation. A broad absorption band in the visible region appeared in S, N co-doped GQDs due to doping with sulfur, which alters the surface state of GQDs. However, S, N co-doped GQDs show different color emission under excitation of 420-520 nm due to their absorption in the visible region. The excellent photocatalytic performance of the S, N co-doped GQD/TiO2 composites was demonstrated by degradation of rhodamine B under visible light. The apparent rate of S, N:GQD/TiO2 is 3 and 10 times higher than that of N:GQD/TiO2 and P25 TiO2 under visible light irradiation, respectively. Electronic supplementary information (ESI) available: More XPS and UV-Vis spectra. See DOI: 10.1039/c3nr04402e

Qu, Dan; Zheng, Min; Du, Peng; Zhou, Yue; Zhang, Ligong; Li, Di; Tan, Huaqiao; Zhao, Zhao; Xie, Zhigang; Sun, Zaicheng

2013-11-01

174

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

PubMed Central

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 (2.53.5 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

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

175

Turbulent Fluctuations in G-band and K-line Intensities Observed with the Rapid Oscillations in the Solar Atmosphere (ROSA) Instrument  

NASA Astrophysics Data System (ADS)

Using the Rapid Oscillation in the Solar Atmosphere (ROSA) instrument at the Dunn Solar Telescope we have found that the spectra of fluctuations of the G-band (cadence 1.05 s) and Ca II K-line (cadence 4.2 s) intensities show correlated fluctuations above white noise out to frequencies beyond 300 mHz and up to 70 mHz, respectively. The noise-corrected G-band spectrum presents a scaling range (Ultra High Frequency UHF) for f = 25-100 mHz, with an exponent consistent with the presence of turbulent motions. The UHF power, is concentrated at the locations of magnetic bright points in the intergranular lanes, it is highly intermittent in time and characterized by a positive kurtosis ?. Combining values of G-band and K-line intensities, the UHF power, and ?, reveals two distinct states of the internetwork solar atmosphere. State 1, with ? ? 6, which includes almost all the data, is characterized by low intensities and low UHF power. State 2, with ? ? 3, including a very small fraction of the data, is characterized by high intensities and high UHF power. Superposed epoch analysis shows that for State 1, the K-line intensity presents 3.5 min chromospheric oscillations with maxima occurring 21 s after G-band intensity maxima implying a 150-210 km effective height difference. For State 2, the G-band and K-line intensity maxima are simultaneous, suggesting that in the highly magnetized environment sites of G-band and K-line emission may be spatially close together. Analysis of observations obtained with Hinode/SOT confirm a scaling range in the G-band spectrum up to 53 mHz also consistent with turbulent motions as well as the identification of two distinct states in terms of the H-line intensity and G-band power as functions of G-band intensity.

Cadavid, A. C.; Lawrence, J. K.; Christian, D. J.; Jess, D. B.; Mathioudakis, M.

2012-12-01

176

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

SciTech Connect

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].

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

2008-05-11

177

Preparation of Ni-B Coating on Carbonyl Iron and Its Microwave Absorption Properties in the X Band  

NASA Astrophysics Data System (ADS)

Ni-B coated carbonyl iron particles (CI@Ni-B) are prepared by the electroless plating technique. The structure, morphology, and antioxidant properties of the CI@Ni-B particles are analyzed. The results demonstrate that the CI particles have been coated with intact spherical-shell Ni-B coating, indicating the core-shell structure of CI@Ni-B particles, and the Ni-B coating can prevent the further oxidation of the CI particles. Compared with the raw CI particles/paraffin coatings with the same coating thickness of 2.0 mm and particles content of 70%, the CI@Ni-B particles/paraffin coatings possess higher microwave absorption (the RL exceeding ?10 dB is obtained in the whole X band (8.212.4 GHz) with minimal RL of ?35.0 dB at 9.2 GHz).

Li, Rong; Zhou, Wan-Cheng; Qing, Yu-Chang

2014-09-01

178

Exciton exciton annihilation dynamics in chromophore complexes. II. Intensity dependent transient absorption  

E-print Network

an intermediate suppression of long-wavelength and short-wavelength shoulders around the bleaching structure as a short-wavelength shoulder in the transient absorption if orientational and energetic disorder are taken

Röder, Beate

179

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

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

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

2013-04-01

180

Near field enhancement and absorption properties of the double cylindrical microcavities based on triple-band metamaterial absorber  

NASA Astrophysics Data System (ADS)

We numerically study the near field enhancement and absorption properties inside the double cylindrical microcavities based on triple-band metamaterial absorber. The compact single unit cell consists of concentric gold rings each with a gold disk in the center, and a metallic ground plane separated by a dielectric layer. At the normal incidence of electromagnetic radiation, the obtained reflection spectra show that the resonance frequencies of the double microcavities are 16.65 THz, 20.65 THz, and 25.65THz, respectively. We also calculate the values of contrast C (C = 1 - Rmin), which can reach 95%, 97%, and 95% at the corresponding frequencies by optimizing the geometry parameters of structure. Moreover, we demonstrate that the multilayer structure with subwavelength electromagnetic confinement allows 104 ~105-fold enhancement of the electromagnetic energy density inside the double cavities, which contains the most energy of the incoming electromagnetic radiation. Moreover, the proposed structure will be insensitive to the polarization of the incident wave due to the symmetry of the double cylindrical microcavities. The proposed optical metamaterial is a promising candidate as an absorbing element in scientific and technical applications because of its extreme confinement, multiband absorptions, and polarization insensitivity.

Heng, Hang; Yang, Li

2014-06-01

181

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

PubMed

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

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

2014-06-01

182

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

NASA Astrophysics Data System (ADS)

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,footnotetextQ.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). 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.

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

2013-03-01

183

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

NASA Technical Reports Server (NTRS)

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).

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

1993-01-01

184

Determination of vibration-rotation lines intensities from absorption Fourier spectra  

NASA Technical Reports Server (NTRS)

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

Mandin, J. Y.

1979-01-01

185

Modelling of Collision Induced Absorption Spectra Of H2-H2 Pairs for the Planetary Atmospheres Structure: The Second Overtone Band  

NASA Technical Reports Server (NTRS)

The main objective of the proposal was to model the collision induced, second overtone band of gaseous hydrogen at low temperatures. The aim of this work is to assist planetary scientists in their investigation of planetary atmospheres, mainly those of Uranus and Neptune. The recently completed extended database of collision induced dipole moments of hydrogen pairs allowed us, for the first time, to obtain dipole moment matrix elements responsible for the roto-vibrational collision induced absorption spectra of H2-H2 in the second overtone band. Despite our numerous attempts to publish those data, the enormous volume of the database did not allow us to do this. Instead, we deposited the data on a www site. The final part of this work has been partially supported by NASA, Division for Planetary Atmospheres. In order to use our new data for modelling purpose, we first needed to test how well we can reproduce the existing experimental data from theory, when using our new input data. Two papers resulted from this work. The obtained agreement between theoretical results and the measurements appeared to be within 10-30%. The obviously poorer agreement than observed for the first H2 overtone, the fundamental, and the rototranslational bands can be attributed to the fact that dipole moments responsible for the second overtone are much weaker, therefore susceptible to larger numerical uncertainties. At the same time, the intensity of the second overtone band is much weaker and therefore it is much harder to be measured accurately in the laboratory. We need to point out that until now, no dependable model of the 2nd overtone band was available for modelling of the planetary atmospheres. The only one, often referred to in previous works on Uranian and Neptune's atmospheres, uses only one lineshape, with one (or two) parameter(s) deduced at the effective temperature of Uranus (by fitting the planetary observation). After that, the parameter(s) was(were) made temperature dependent according to some very simple relation. Summarizing, no reliable temperature-dependent model has been available yet. Our approach was a bit different from similar attempts done earlier, on account of the poorer agreement of theory with experiment. We needed to resort to some semi-empirical procedure. While we were in a favourable position to be able to rely on the physical input data, these, apparently, did not supply the most dependable predictions (simply because the results did not agree well enough with experimental data). On the other hand, the relative deviations between the theory and experiment were comparable at 77 and at 298 K. That fact indicated that theory is capable of predicting the temperature dependence of the absorption spectra well. We have thus chosen the "middle way". We have fitted the existing measurements with many 3- parameter lineshapes, in order to achieve the closest fit.

Borysow, Aleksandra; Borysow, Jacek I.

1998-01-01

186

The determination of minority carrier lifetimes in direct band-gap semiconductors by monitoring intensity-modulated luminescence radiation  

NASA Technical Reports Server (NTRS)

When an extrinsic, direct band-gap semiconductor sample is irradiated by photons of an energy higher than the energy of the band gap between valence and conduction bands, excess electron-hole pairs are generated which, while diffusing through the sample, produce luminescence via radiative recombination. If, furthermore, the intensity of the impinging beam of photons is modulated sinusoidally, the luminescence radiation escaping from the sample will be phase shifted with respect to the original photon beam in a characteristic way. It will be shown that by measuring the phase shift at different modulation frequencies, the Shockley-Read-Hall lifetime of minority carriers may be ascertained. The method is nondestructive inasmuch as there is no need to fabricate p-n junctions or Ohmic contacts, nor is it necessary to remove already existing Ohmic contacts of angle lap the surface, etc., procedures often needed when determining lifetimes with the scanning electron microscope (in which case a p-n junction must be present).

Von Roos, O.

1985-01-01

187

Determination of integrated intensities of overlapped IR bands by curve-fitting, Fourier self-deconvolution and a combination of both methods  

NASA Astrophysics Data System (ADS)

Curve-fitting, Fourier self-deconvolution, and a combination of these methods have been applied to determine integrated intensities of the bands arising from the C=O stretching mode of n-octanoic acid. When these bands are separated by more than an average band width, the most reliable results are supplied by curve-fitting. However, simple functions (Gauss or Lorentz) do not satisfactorily describe shapes of experimental bands, and more complex profiles should be used such as the sum or product of the Gauss and Lorentz functions or their convolution (Voigt profile). The applied Fourier self-deconvolution procedure assumes Lorentzian band shapes; therefore the determined intensities of the bands that deviate from this profile are always higher than the true values. An analysis combining the two methods mentioned above did not improve the results. The output bands from curve-fitting, with a high Lorentzian fraction, might have overestimated the band areas. Thus, the integration should be done over a limited wavenumber range. Our results clearly show that the band-shape function plays an important role during the determination of the integrated intensities using curve-fitting, Fourier self-deconvolution or a combination of both methods (referred to in this paper as the "combined method").

Czarnecki, Miros?aw A.; Ozaki, Yukihiro

1996-11-01

188

Ultra intense laser/plasma interaction at normal incidence: Relativistic mirrors effects, high harmonics generation and absorption  

NASA Astrophysics Data System (ADS)

An analytical study of the relativistic interaction of a linearly-polarized laser-field of ? frequency with highly overdense plasma is presented. Very intense high harmonics are generated produced by relativistic mirrors effects due to the relativistic electron plasma oscillation. Also, in agreement with 1D Particle-In-Cell Simulations (PICS), the model self-consistently explains the transition between the sheath inverse bremsstrahlung (SIB) absorption regime and the JB heating (responsible for the 2? electron bunches), as well as the mean electron energy.

Sanz, Javier; Debayle, Arnaud; Mima, K.

2012-11-01

189

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

PubMed

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

Dess, 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

2014-10-16

190

Collision-Induced Absorption by H2 Pairs in the Second Overtone Band at 298 and 77.5 K: Comparison between Experimental and Theoretical Results  

NASA Technical Reports Server (NTRS)

The collision-induced spectra of hydrogen in the region of the second overtone at 0.8 microns have been recorded at temperatures of 298 and 77.5 K and for gas densities ranging from 100 to 800 amagats. The spectral profile defined by the absorption coefficient per squared density varies significantly with the density, so that the binary absorption coefficient has been determined by extrapolations to zero density of the measured profiles. Our extrapolated measurements and our recent ab initio quantum calculation are in relatively good agreement with one another. Taking into account the very weak absorption of the second overtone band, the agreement is, however, not as good as it has become (our) standard for strong bands.

Brodbeck, C.; Bouanich, J.-P.; van-Thanh, Nguyen; Fu, Y.; Borysow, A.

1999-01-01

191

Linear and nonlinear intra-conduction band optical absorption in (In,Ga)N/GaN spherical QD under hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Linear, third-order nonlinear and total optical absorption coefficients of intra-conduction band 1s-1p transition with hydrogenic shallow-donor impurity in wurtzite (In,Ga)N/GaN spherical quantum dot are reported. Hydrostatic pressure effect is investigated within the framework of single band effective-mass approximation using a combination of Quantum Genetic Algorithm (QGA) and Hartree-Fock-Roothaan (HFR) method. The results show that the pressure has a great influence on optical absorption coefficients of QDs. A blue-shift of the resonant peak is observed while the maximum of the amplitude of optical absorption coefficients decreases under hydrostatic pressure effect. A good agreement is shown compared with results of the finding.

El Ghazi, Haddou; Jorio, Anouar; Zorkani, Izeddine

2014-11-01

192

High resolution absorption cross sections in the transmission window region of the Schumann-Runge bands and Herzberg continuum of O2  

NASA Technical Reports Server (NTRS)

Results are presented on measurements, conducted in the wavelength region 180-195 nm, and at different pressures of oxygen (between 2.5-760 torr) in order to separate the pressure-dependent absorption from the main cross sections, of the absorption cross sections of the Schumann-Runge bands in the window region between the rotational lines of S-R bands of O2. The present cross sections supersede the earlier published cross sections (Yoshino et al., 1983). The combined cross sections are presented graphically; they are available at wavenumber intervals of about 0.1/cm from the National Space Science Data Center. The Herzberg continuum cross sections are derived after subtracting calculated contributions from the Schumann-Runge bands. These are significantly smaller than any previous measurements.

Yoshino, K.; Esmond, J. R.; Cheung, A. S.-C.; Freeman, D. E.; Parkinson, W. H.

1992-01-01

193

Spectral moments for the collision-induced rotovibrational absorption bands of nonpolar gases and mixtures (H2-He)  

NASA Astrophysics Data System (ADS)

Expressions for the zeroth, first, and second translational spectral moments are reported for the rotovibrational collision-induced absorption (RVCIA) spectra of atom-diatom pairs, which take into account the dependence of the intermolecular interaction potential on the vibrational excitation of the molecule involved. From these, numerical results are obtained for the fundamental CIA band of H2He. Consistency with a previous ab initio line-shape computation is observed which has also accounted for this dependence. However, especially at the higher temperatures considered (150-300 K), the first and second moments differ significantly, by up to 30%, from values calculated from existing, commonly used sum formulas which neglect the vibrational-state dependence of the interaction potential. The work thus corrects an existing inexactitude of the moment expressions in general use. When these expressions are combined with suitable model profile functions, a simple and yet very accurate modeling of RVCIA spectra is possible, with rms deviations from exact quantum profiles of no more than a few percent.

Moraldi, Massimo; Borysow, Jacek; Frommhold, Lothar

1987-11-01

194

The Effects of Light Intensity and Color Absorption of Diurnal Leaf Movements of Malva parviflora  

Microsoft Academic Search

Our group measured the heliotropic response rate of the Malva parviflora under various light environments in order to see the effect that light color and intensity had on daily leaf movement. In our experiment we measured the leaf angle of plants under white, blue, red and green light, as well as plants under shade, over a specific duration of time

Amy Lawrence; Ben Young; Matthew Yarborough

2009-01-01

195

A model of gastric emptying using paracetamol absorption in intensive care patients  

Microsoft Academic Search

Objectives: To describe the range and factors which may affect gastric emptying in the ICU patient. Design: Validation sample. Setting: The adult Intensive Care Unit (ICU) of a teaching hospital. Patients: Twenty-seven ICU patients, aged 1865 years were studied within 3 days of their ICU admission. All patients had normal hepatic\\u000a and renal chemistry and had no contraindications to enteral

M. M. Tarling; C. C. Toner; P. S. Withington; M. K. Baxter; R. Whelpton; D. R. Goldhill

1997-01-01

196

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

SciTech Connect

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)

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

2010-06-23

197

Photo response of the EL2 absorption band and of the As+Ga ESR signal in B. Dischler and U. Kaufmann  

E-print Network

779 Photo response of the EL2 absorption band and of the As+Ga ESR signal in GaAs B. Dischler and U'absorption de EL2 et du spectre paramagnétique du As+Ga dans GaAs sont décrites et comparées avec les propriétés résultats avec ceux du défaut As+Ga montre que les deux défauts possèdent les mêmes propriétés optiques et

Boyer, Edmond

198

The J- and H-bands of organic dye aggregates  

NASA Astrophysics Data System (ADS)

Certain molecular aggregates consisting of organic dyes are remarkable in exhibiting an intense and very narrow absorption peak, known as a J-band, which is red-shifted away from the region of monomer absorption. Apart from those dyes showing the J-band on aggregation, there are also dyes where the absorption maximum is shifted to higher energies. The width of the resulting absorption band (called an H-band) is comparable to that of the monomeric dyes and shows a complicated vibrational structure. Following our analysis of the J-band spectra of polymer aggregates using the CES approximation [A. Eisfeld, J.S. Briggs, Chem. Phys. 281 (2002) 61], a theory that includes vibrations explicitly, we show that the same approximation can account for measured H-band spectra. Using simple analytical forms of the monomer spectrum the origin of the widely different shapes of H- and J-bands is explained within the CES approximation.

Eisfeld, A.; Briggs, J. S.

2006-05-01

199

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)

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 m. Recent studies established empirical relationships between the strength of the 3 m 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 m. 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 m bands strength, especially for the finest particles (less than 200 m). 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 m bands. The discussion will especially focus on the case of Mars and the results of the OMEGA instrument.

Pommerol, A.; Schmitt, B.

200

Dosimetric absorption of intensity-modulated radiotherapy compared with conventional radiotherapy in breast-conserving surgery  

PubMed Central

The aim of this study was to investigate the dosimetric benefits between intensity-modulated radiotherapy (IMRT) and conventional radiotherapy (CR) among patients receiving breast-conserving surgery. A dosimetric comparison of IMRT and CR was evaluated in 20 patients with early-stage breast cancer using a three-dimensional treatment planning system. The prescribed mammary gland dose was completed in 25 fractions with a total dose of 5,000 cGy. Homogeneity of the planning target volume (PTV), irradiation dose and volume of organs at risk (OARs) were evaluated through a dose-volume histogram. For the homogeneity of PTV, the average volume receiving 95% of the prescribed dose in the IMRT plan was similar to that in the CR plan (97 vs. 96%, respectively). With regard to normal tissue sparing in OARs, the ipsilateral lung V20 in the IMRT and CR plans was 27.8 and 20.8%, respectively. The mean dose and V30 of the heart for five patients were 598.4 versus 348.3 cGy and 10.06 versus 5.3%, respectively. The mean dose sparing the heart or lung was markedly reduced in the IMRT plan compared with the CR plan. The results of the current study demonstrated that whole breast IMRT improves PTV dose distribution and improves normal tissue sparing in OARs.

LIN, YANG; WANG, BENZHONG

2015-01-01

201

Optical absorption and band gap reduction in (Fe1-xCrx)2O3 solid solutions: A first-principles study  

SciTech Connect

We provide a detailed theoretical analysis of the character of optical transitions and band gap reduction in (Fe1-xCrx)2O3 solid solutions using extensive periodic model and embedded cluster calculations. Optical absorption bands for x = 0.0, 0.5, and 1.0 are assigned on the basis of timedependent density functional theory (TDDFT) calculations. A band-gap reduction of as much as 0.7 eV with respect to that of pure ?-Fe2O3 is found. This result can be attributed to predominantly two effects: (i) the higher valence band edge for x ? 0.5, as compared to those in pure ?-Fe2O3 and ?-Cr2O3, and, (ii) the appearance of Cr ? Fe dd transitions in the solid solutions. Broadening of the valence band due to hybridization of the O 2p states with Fe and Cr 3d states also contributes to band gap reduction.

Wang, Yong; Lopata, Kenneth A.; Chambers, Scott A.; Govind, Niranjan; Sushko, Petr V.

2013-12-02

202

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)

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.

Dufrchou, Grgory; Granjean, Gilles; Bourguignon, Anne

2014-05-01

203

PHOTOLUMINESCENT SIGNATURE OF ABSORBING MEDIUM WITH DEEP LEVELS BASED UPON ABSORPTION COEFFICIENTS DERIVED FROM PARABOLIC-BAND APPROXIMATIONS  

E-print Network

, yet with distinct absorption characteristics, distinct temperatures, and distinct lengths. The authors to be investigated. Therefore, properties of an absorber that are relevant to photovoltaic solar energy conversion. There, specific details of the absorption characteristics of the IB absorber are highlighted

Honsberg, Christiana

204

FTIR spectroscopy reveals lipid droplets in drug resistant laryngeal carcinoma cells through detection of increased ester vibrational bands intensity.  

PubMed

The major obstacle to successful chemotherapy of cancer patients is drug resistance. Previously we explored the molecular mechanisms of curcumin cross-resistance in carboplatin resistant human laryngeal carcinoma 7T cells. Following curcumin treatment we found a reduction in curcumin accumulation, and reduced induction of reactive oxygen species (ROS) and their downstream effects, compared to parental HEp-2 cells. In order to shed more light on mechanisms involved in drug resistance of 7T cells, in the present study we applied Fourier transform infrared (FTIR) spectroscopy, a technique that provides information about the nature and quantities of all molecules present in the cell. By comparing the spectra from parental HEp-2 cells and their 7T subline, we found an increase in the intensity of ester vibrational bands in 7T cells. This implied an increase in the amount of cholesteryl esters in resistant cells, which we confirmed by an enzymatic assay. Since cholesteryl esters are localized in lipid droplets, we confirmed their higher quantity and serum dependency in 7T cells compared to HEp-2 cells. Moreover, treatment with oleic acid induced more lipid droplets in 7T when compared to HEp-2 cells, as shown by flow cytometry. We can conclude that along with previously determined molecular mechanisms of curcumin resistance in 7T cells, these cells exhibit an increased content of cholesteryl esters and lipid droplets, suggesting an alteration in cellular lipid metabolism as a possible additional mechanism of drug resistance. Furthermore, our results suggest the use of FTIR spectroscopy as a promising technique in drug resistance research. PMID:24834449

Rak, Sanjica; De Zan, Tihana; Stefulj, Jasminka; Kosovi?, Marin; Gamulin, Ozren; Osmak, Maja

2014-07-01

205

ANOMALOUS DIFFUSE INTERSTELLAR BANDS IN THE SPECTRUM OF HERSCHEL 36. I. OBSERVATIONS OF ROTATIONALLY EXCITED CH AND CH{sup +} ABSORPTION AND STRONG, EXTENDED REDWARD WINGS ON SEVERAL DIBs  

SciTech Connect

Anomalously broad diffuse interstellar bands (DIBs) at 5780.5, 5797.1, 6196.0, and 6613.6 A 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{sup +} 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{sup +} 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 A) 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 mA 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.

Dahlstrom, Julie [Carthage College, 2001 Alford Park Dr., Kenosha, WI 53140 (United States); York, Donald G.; Welty, Daniel E.; Oka, Takeshi; Johnson, Sean; Jiang Zihao; Sherman, Reid [University of Chicago, Astronomy and Astrophysics Center, 5640 S. Ellis Avenue, Chicago, IL 60637 (United States); Hobbs, L. M. [University of Chicago, Yerkes Observatory, Williams Bay, WI 53191 (United States); Friedman, Scott D.; Sonnentrucker, Paule [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Rachford, Brian L. [Department of Physics, Embry-Riddle Aeronautical University, 3700 Willow Creek Road, Prescott, AZ 86301 (United States); Snow, Theodore P., E-mail: jdahlstrom1@carthage.edu [University of Colorado, CASA-Campus Box 389, Boulder, CO 80309 (United States)

2013-08-10

206

Tentative Identification of the 780/cm nu(sub 4) Band Q Branch of Chlorine Nitrate in High-Resolution Solar Absorption Spectra of the Stratosphere  

NASA Technical Reports Server (NTRS)

Absorption by the Q branch of the nu(sub 4), band of ClONO2 at 780.2/cm has been tentatively identified in a series of 0.02/cm resolution balloon-borne solar absorption spectra of the stratosphere. The spectral data were recorded at sunset from a flot altitude of 33.5 km during a balloon flight from Holloman Air Force Base (32.8deg N, 106.0 deg W) near Alamogordo, New Mexico, on March 23 1998. A preliminary ClONO2 vertical profile has been determined from the stratospheric spectra by using the technique of nonlinear least squares spectral curve fitting and new spectroscopic parameters deduced from high-resolution laboratory spectra of ClONO2 and O3.

Rinsland, C. P.; Goldman, A.; Murcray, D. G.; Murcray, F. J.; Bonomo, F. S.; Blatherwick, R. D.; Devi, V. Malathy; Smith, M. A. H.; Rinsland, P. L.

1985-01-01

207

Chemoselectivity-induced multiple interfaces in MWCNT/Fe3O4@ZnO heterotrimers for whole X-band microwave absorption.  

PubMed

A chemoselective route to induce Fe3O4@ZnO core-shell nanoparticles decorating carbon nanotubes to form MWCNT/Fe3O4@ZnO heterotrimers has been developed. Charges are redistributed in the heterotrimers through C-O-Zn, C-O-Fe and Fe-O-Zn bondings, giving rise to multiple electronic phases. The generated significant interfacial polarization and synergetic interaction between dielectric and magnetic absorbers result in the MWCNT/Fe3O4@ZnO heterotrimers with high-performance microwave absorption in an entire X band. PMID:25080205

Wang, Zhijiang; Wu, Lina; Zhou, Jigang; Jiang, Zhaohua; Shen, Baozhong

2014-10-01

208

Evolution of dielectric function of Al-doped ZnO thin films with thermal annealing: effect of band gap expansion and free-electron absorption.  

PubMed

Evolution of dielectric function of Al-doped ZnO (AZO) thin films with annealing temperature is observed. It is shown that the evolution is due to the changes in both the band gap and the free-electron absorption as a result of the change of free-electron concentration of the AZO thin films. The change of the electron concentration could be attributed to the activation of Al dopant and the creation/annihilation of the donor-like defects like oxygen vacancy in the thin films caused by annealing. PMID:25321779

Li, X D; Chen, T P; Liu, Y; Leong, K C

2014-09-22

209

Imaging the stereodynamics of methyl iodide photodissociation in the second absorption band: fragment polarization and the interplay between direct and predissociation.  

PubMed

The stereochemistry of methyl iodide photodissociation in the onset of the second absorption B-band has been studied using slice imaging of the CH3(? = 0) and I*((2)P1/2) photoproducts. The stereodynamical data have been crucial to disentangle the photochemistry of methyl iodide in terms of the competition between direct dissociation and electronic predissociation. The origin of the B-band has been established with high accuracy at 201.11 0.12 nm and a depolarization factor due to parent molecule rotation during predissociation has been found to be 0.29 0.06. Analysis of the semiclassical Dixon's bipolar moments extracted from the CH3(? = 0) sliced images indicates that direct excitation to the A-band (3)A1 repulsive state in the vicinity of the origin of the B-band is remarkably enhanced by vibrational coupling between the electronic states involved at the conical intersection through in-plane vibrational motion of the molecule. PMID:25367399

Gonzlez, Marta G; Rodrguez, Javier D; Rubio-Lago, Luis; Baares, Luis

2014-12-21

210

A heuristic approach to precisely represent optical absorption and refractive index data for photon energies below, at, and above the band gap of semiconductors: The case of high-purity GaAs. Part I  

Microsoft Academic Search

The existence of band tails even in nominally undoped and uncompensated GaAs, and the nonparabolic absorption shape above the band gap are the prime examples for the discrepancy between theory and experiments. To overcome this difficulty, we propose a heuristic approach that is guided by the fundamental theoretical aspects and the experimental facts. For this reason, we fit the available

F. K. Reinhart

2005-01-01

211

Chemoselectivity-induced multiple interfaces in MWCNT/Fe3O4@ZnO heterotrimers for whole X-band microwave absorption  

NASA Astrophysics Data System (ADS)

A chemoselective route to induce Fe3O4@ZnO core-shell nanoparticles decorating carbon nanotubes to form MWCNT/Fe3O4@ZnO heterotrimers has been developed. Charges are redistributed in the heterotrimers through C-O-Zn, C-O-Fe and Fe-O-Zn bondings, giving rise to multiple electronic phases. The generated significant interfacial polarization and synergetic interaction between dielectric and magnetic absorbers result in the MWCNT/Fe3O4@ZnO heterotrimers with high-performance microwave absorption in an entire X band.A chemoselective route to induce Fe3O4@ZnO core-shell nanoparticles decorating carbon nanotubes to form MWCNT/Fe3O4@ZnO heterotrimers has been developed. Charges are redistributed in the heterotrimers through C-O-Zn, C-O-Fe and Fe-O-Zn bondings, giving rise to multiple electronic phases. The generated significant interfacial polarization and synergetic interaction between dielectric and magnetic absorbers result in the MWCNT/Fe3O4@ZnO heterotrimers with high-performance microwave absorption in an entire X band. Electronic supplementary information (ESI) available: Experimental details and Fig. S1-S7 as mentioned in the text. See DOI: 10.1039/c4nr03040k

Wang, Zhijiang; Wu, Lina; Zhou, Jigang; Jiang, Zhaohua; Shen, Baozhong

2014-10-01

212

Oscillation of absorption bands of Zn1?xMnxS clusters: an experimental and theoretical study  

Microsoft Academic Search

Electroporation of synthetic vesicles is utilized for the preparation of molecular size uncapped Zn1?xMnxS clusters. The absence of caps permits (i) continued growth of the Zn1?xMnxS clusters formed, (ii) the assessment of their true absorption spectra unaltered by stabilizing ligands, and (iii) the previously inaccessible live observation of the growth of the clusters in the molecular size regime. Upon cluster

Sixin Wu; HeYing Chu; Hongtao Xu; Xinshou Wang; Na Yuan; Yuncai Li; Zhishen Wu; Zuliang Du; Zoltan A Schelly

2008-01-01

213

Two-dimensional correlation analysis to study variation of near-infrared water absorption bands in the presence of inorganic acids  

NASA Astrophysics Data System (ADS)

Two-dimensional (2D) correlation analysis has been utilized to investigate NIR water bands perturbed by the presence of four different inorganic acids individually: HCl, H2SO4, H3PO4, and HNO3. The observed spectral variation in the 9000-7700 cm-1 range was mainly due to interaction of dissociated H3O+ and corresponding anions with the vibration of water in a hydrogen bonding network. 2D correlation analysis of NIR spectra acquired from sample solutions (concentration range: 0.2-1.0 M) showed that individual acids differently influenced water vibration. In addition, unforeseen spectral variations under the water band that were difficult to identify with corresponding raw NIR spectra were clearly observed. Based on the asynchronous correlation analysis, three underlying individual variations occurred for HCl under the 8718 cm-1 band. Only two asynchronous correlations were observed for H2SO4 and H3PO4. The 2D correlation features of HNO3 were distinctly different from those of the other three acids due to an additional spectral feature caused by direct absorption by NO3-. The dissimilar influence of the selected acids on water vibration was confirmed by NIR spectroscopy combined with 2D correlation analysis. Partial least squares (PLS) loadings from each case were compared to examine the difference in weights that were constructed to follow the corresponding concentration changes.

Chang, Kyeol; Jung, Young Mee; Chung, Hoeil

2014-07-01

214

Measurement of atmospheric precipitable water using a solar radiometer. [water vapor absorption effects  

NASA Technical Reports Server (NTRS)

A technique is described and tested that allows the determination of atmospheric precipitable water from two measurements of solar intensity: one in a water-vapor absorption band and another in a nearby spectral region unaffected by water vapor.

Pitts, D. E.; Dillinger, A. E.; Mcallum, W. E.

1974-01-01

215

Defect Band Luminescence Intensity Reversal as Related to Application of Anti-Reflection Coating on mc-Si PV Cells: Preprint  

SciTech Connect

Photoluminescence (PL) imaging is widely used to identify defective regions within mc-Si PV cells. Recent PL imaging investigations of defect band luminescence (DBL) in mc-Si have revealed a perplexing phenomenon. Namely, the reversal of the DBL intensity in various regions of mc-Si PV material upon the application of a SiNx:H anti-reflective coating (ARC). Regions with low DBL intensity before ARC application often exhibit high DBL intensity afterwards, and the converse is also true. PL imaging alone cannot explain this effect. We have used high resolution cathodoluminescence (CL) spectroscopy and electron beam induced current (EBIC) techniques to elucidate the origin of the DBL intensity reversal. Multiple sub-bandgap energy levels were identified that change in peak position and intensity upon the application of the ARC. Using this data, in addition to EBIC contrast information, we provide an explanation for the DBL intensity reversal based on the interaction of the detected energy levels with the SiNx:H ARC application. Multiple investigations have suggested that this is a global problem for mc-Si PV cells. Our results have the potential to provide mc-Si PV producers a pathway to increased efficiencies through defect mitigation strategies.

Guthrey, H.; Johnston, S.; Yan, F.; Gorman, B.; Al-Jassim, M.

2012-06-01

216

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

SciTech Connect

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.

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

217

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

218

Dust and Diffuse Interstellar Bands in the z_a = 0.524 Absorption System toward AO 0235+164  

E-print Network

We present new HST STIS NUV-MAMA and STIS CCD observations of the BL Lac object AO 0235+164 and the intervening damped Ly alpha (DLA) line at z_a = 0.524. The line profile gives N(H I) = 5 +/- 1 x 10^{21} cm^{-2} and, combined with the H I 21 cm absorption data leads to a spin temperature of T_s = 220 K +/- 60 K. Those spectra also show a strong, broad feature at the expected position of the 2175 Angstrom graphitic dust feature at z_a = 0.524. Assuming a Galactic type dust extinction curve at z_a = 0.524 gives a dust-to-gas ratio of 0.19 Galactic, but the fit, assuming the underlying, un-reddened spectrum is a single power-law, is poor in the far-UV. A dust-to-gas ratio of 0.19 Galactic is similar to the LMC, but the AO 0235+164 spectrum does not fit the LMC extinction curve, or the SMC extinction curve (which has practically no 2175 Angstrom feature). A possible interpretation includes dust similar to Galactic, but with less of the small particles that produce the far-UV extinction. The metallicity of the z_a = 0.524 absorber, estimated from the observed N(H I) and excess X-ray absorption (beyond Galactic) derived from contemporaneous and archival ASCA and ROSAT X-ray data, is Z = 0.72 +/- 0.28 Z_sun, implying in turn the dust-to-metals ratio of 0.27 Galactic. If the dust mass density is the same in the z_a = 0.524 DLA system as in our Galaxy, only 14% (+/- 6%) of the metals (by mass) are in dust compared with 51%, 36%, and 46% for the Galaxy, LMC, and SMC respectively. Such a dusty z_a = 0.524 AO 0235+164 absorption system is a good example of the kind of DLA system that will be missed due to selection effects, which in turn can bias the measurement of the co-moving density of interstellar gas (in units of the closure density), Omega_g, as a function of z.

V. T. Junkkarinen; Ross D. Cohen; E. A. Beaver; E. M. Burbidge; R. W. Lyons; G. Madejski

2004-07-14

219

Theoretical study of band gap engineering and optical absorption in InGaN/GaN superlattices with short periodicity  

NASA Astrophysics Data System (ADS)

We have carried out a theoretical study for calculating the electronic and optical properties of {In}x {Ga}_{1 - x} {N}/{GaN} (001) superlattices with short periodicity, while In composition is altered from 0 to 100 %. These appealing systems have been simulated using ab initio method in the framework of full-potential linearized augmented plane wave scheme. In this respect, a modified Becke-Johnson for the exchange and correlation potential term is included for describing adequately the energy gap of these promising low-dimensional materials. Exclusively, we computed the density of states, imaginary part of dielectric function, refractive index and absorption coefficient. However, it is viable to control the optical properties of these superlattices which may be useful for optoelectronic devices application.

Laref, A.; Altujar, A.; Luo, S. J.

2014-06-01

220

L(alpha)-induced two-photon absorption of visible light emitted from an O-type star by H2(+) ions located near the surface of the Stromgren sphere surrounding the star: A possible explanation for the diffuse interstellar absorption bands (DIDs)  

NASA Technical Reports Server (NTRS)

In this paper, a new model is proposed to account for the DIB's (Diffuse Interstellar Bands). In this model, the DIB's result from a non-linear effect: resonantly-enhanced two-photon absorption of H(2+) ions located near the surface of the Stromgren sphere that surrounds an O- or B- type star. The strong light that is required to 'drive' the two-photon transition is provided by L(alpha) light emerging from the Stromgren sphere that bounds the H II region surrounding the star. A value of approximately 100 micro W/sq cm is estimated for the L(alpha) flux at the Stromgren radius, R(s), of a strong (O5) star. It is shown that a c.w. L(alpha) flux of this intensity should be sufficient to induce a few percent absorption for visible light radiated by the same star at a frequency (omega2) that completes an allowed two-photon transition, provided (1) the L(alpha) radiation happens to be nearly resonant with the frequency of a fully-allowed absorber transition that effectively represents the first step in the two-photon transition, and (2) an effective column density approximately 10(sup18)/sq cm of the absorber is present near the Stromgren sphere radius, R(sub s).

Glownia, James H.; Sorokin, Peter P.

1994-01-01

221

An atom in molecules study of infrared intensity enhancements in fundamental donor stretching bands in hydrogen bond formation.  

PubMed

Vibrational modes ascribed to the stretching of X-H bonds from donor monomers (HXdonor) in complexes presenting hydrogen bonds (HFHF, HClHCl, HCNHCN, HNCHNC, HCNHF, HFHCl and H2OHF) exhibit large (4 to 7 times) infrared intensity increments during complexation according to CCSD/cc-pVQZ-mod calculations. These intensity increases are explained by the charge-charge flux-dipole flux (CCFDF) model based on multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) as resulting from a reinforcing interaction between two contributions to the dipole moment derivatives with respect to the vibrational displacements: charge and charge flux. As such, variations that occur in their intensity cross terms in hydrogen bond formation correlate nicely with the intensity enhancements. These stretching modes of HXdonor bonds can be approximately modeled by sole displacement of the positively charged hydrogens towards the acceptor terminal atom with concomitant electronic charge transfers in the opposite direction that are larger than those occurring for the H atom displacements of their isolated donor molecules. This analysis indicates that the charge-charge flux interaction reinforcement on H-bond complexation is associated with variations of atomic charge fluxes in both parent molecules and small electronic charge transfers between them. The QTAIM/CCFDF model also indicates that atomic dipole flux contributions do not play a significant role in these intensity enhancements. PMID:25325528

Terrabuio, Luiz A; Richter, Wagner E; Silva, Arnaldo F; Bruns, Roy E; Haiduke, Roberto L A

2014-10-22

222

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

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

223

Imaging the photodissociation of CH3SH in the first and second absorption bands: the CH3(X2A1)+SH(X2Pi) channel.  

PubMed

The CH3(X2A1)+SH(X2Pi) channel of the photodissociation of CH3SH has been investigated at several wavelengths in the first 1 1A"<--X 1A' and second 2 1A"<--X1A' absorption bands by means of velocity map imaging of the CH3 fragment. A fast highly anisotropic (beta=-1+/-0.1) CH3(X2A1) signal has been observed in the images at all the photolysis wavelengths studied, which is consistent with a direct dissociation process from an electronically excited state by cleavage of the C-S bond in the parent molecule. From the analysis of the CH3 images, vibrational populations of the SH(X2Pi) counterfragment have been extracted. In the second absorption band, the SH fragment is formed with an inverted vibrational distribution as a consequence of the forces acting in the crossing from the bound 2 1A" second excited state to the unbound 1 1A" first excited state. The internal energy of the SH radical increases as the photolysis wavelength decreases. In the case of photodissociation via the first excited state, the direct production of CH3 leaves the SH counterfragment with little internal excitation. Moreover, at the longer photolysis wavelengths corresponding to excitation to the 1 1A" state, a slower anisotropic CH3 channel has been observed (beta=-0.8+/-0.1) consistent with a two step photodissociation process, where the first step corresponds to the production of CH3S(X2E) radicals via cleavage of the S-H bond in CH3SH, followed by photodissociation of the nascent CH3S radicals yielding CH3(X2A1)+S(X3P0,1,2). PMID:17228948

Amaral, G A; Ausfelder, F; Izquierdo, J G; Rubio-Lago, L; Baares, L

2007-01-14

224

Microwave absorption in X and Ku band frequency of cotton fabric coated with Ni-Zn ferrite and carbon formulation in polyurethane matrix  

NASA Astrophysics Data System (ADS)

The present study highlights various microwave properties, i.e. reflection, transmission, absorption and reflection loss, of the coated cotton fabric [formulation: Ni-Zn ferrite (Ni 0.5Zn0.5Fe2O4) and carbon black (acetylene black) at concentrations of 30, 40, 50, 60 and70 g of ferrite and 5 g carbon in each 100 ml polyurethane] evaluated at 8-18 GHz frequency. The uniform density of filling materials in coated fabrics (dotted marks in SEM micrograph) indicates homogeneous dispersion of conducting fillers in polyurethane and the density of filling material cluster increases with increase in ferrite concentration. SEM images also show uniform coating of conducting fillers/resin system over individual fibers and interweave spaces. The important parameters governing the microwave properties of coated fabrics i.e. permittivity and permeability, S-parameters, reflection loss, etc. were studied in a HVS free space microwave measurement system. The lossy character of coated fabric is found to increase with increase of ferrite content; the ferrite content decreases the impedance and increases the permittivity and permeability values. The 1.6-1.8 mm thick coated fabric sample (40 wt% ferrite, 3 wt% carbon and 57 wt% PU) has shown about 40% absorption, 20% transmission and 40% reflectance in X (8.2-12.4 GHz) and Ku (12-18 GHz) frequency bands. The reflection loss at 13.5 GHz has shown the highest peak value (22.5 dB) due to coated sample optical thickness equal to ?/4 and more than 7.5 dB in entire Ku band. Owing to its thin and flexible nature, the coated fabric can be used as apparel in protecting human being from hazardous microwaves and also as radar camouflage covering screen in defense.

Gupta, K. K.; Abbas, S. M.; Goswami, T. H.; Abhyankar, A. C.

2014-08-01

225

Highly efficient reversible Z-E photoisomerization of a bridged azobenzene with visible light through resolved S(1)(n pi*) absorption bands.  

PubMed

The reversible Z-E photoswitching properties of the (Z) and (E) isomers of the severely constrained bridged azobenzene derivative 5,6-dihydrodibenzo[c,g][1,2]diazocine (1) were investigated quantitatively by UV/vis absorption spectroscopy in solution in n-hexane. In contrast to normal azobenzene (AB), 1 has well separated S(1)(n pi*) absorption bands, peaking at lambda(Z) = 404 nm and lambda(E) = 490 nm. Using light at lambda = 385 nm, it was found that 1Z can be switched to 1E with very high efficiency, Gamma = 92 +/- 3%. Conversely, 1E can be switched back to 1Z using light at lambda = 520 nm with approximately 100% yield. The measured quantum yields are Phi(Z-->E) = 72 +/- 4% and Phi(E-->Z) = 50 +/- 10%. The thermal lifetime of the (E) isomer is 4.5 +/- 0.1 h at 28.5 degrees C. The observed photochromic and photoswitching properties of 1 are much more favorable than those for normal AB, making our title compound a promising candidate for interesting applications as a molecular photoswitch especially at low temperatures. The severe constraints by the ethylenic bridge apparently do not hinder but favor the Z-E photoisomerization reactions. PMID:19827776

Siewertsen, Ron; Neumann, Hendrikje; Buchheim-Stehn, Bengt; Herges, Rainer; Nther, Christian; Renth, Falk; Temps, Friedrich

2009-11-01

226

Electromagnetic properties and microwave absorption properties of BaTiO 3-carbonyl iron composite in S and C bands  

NASA Astrophysics Data System (ADS)

BaTiO3 powders are prepared by sol-gel method. The carbonyl iron powder is prepared via thermal decomposition of iron pentacarbonyl. Then BaTiO3-carbonyl iron composite with different mixture ratios was prepared using the as-prepared material. The structure, morphology, and properties of the composites are characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, scanning electron microscopy (SEM), and a network analyzer. The complex permittivity and reflection loss of the composites have been measured at different microwave frequencies in S- and C-bands employing vector network analyzer model PNA 3629D vector. The effect of the mass ratio of BaTiO3/carbonyl iron on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO3-carbonyl iron composite has been proposed. The BaTiO3-carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.

Rui-gang, Yang

2011-07-01

227

Self-broadening coefficients and improved line intensities for the ?7 band of ethylene near 10.5 ?m, and impact on ethylene retrievals from Jungfraujoch solar spectra  

NASA Astrophysics Data System (ADS)

Relying on high-resolution Fourier transform infrared (FTIR) spectra, the present work involved extensive measurements of individual line intensities and self-broadening coefficients for the ?7 band of 12C2H4. The measured self-broadening coefficients exhibit a dependence on both J and Ka. Compared to the corresponding information available in the latest edition of the HITRAN spectroscopic database, the measured line intensities were found to be higher by about 10% for high J lines in the P branch and lower by about 5% for high J lines of the R branch, varying between these two limits roughly linearly with the line positions. The impact of the presently measured line intensities on retrievals of atmospheric ethylene in the 949.0-952.0 cm-1 microwindow was evaluated using a subset of ground-based high-resolution FTIR solar spectra recorded at the Jungfraujoch station. The use of HITRAN 2012 with line intensities modified to match the present measurements led to a systematic reduction of the measured total columns of ethylene by -4.10.1%.

Vander Auwera, J.; Fayt, A.; Tudorie, M.; Rotger, M.; Boudon, V.; Franco, B.; Mahieu, E.

2014-11-01

228

DIFFUSE SOUND ABSORPTION COEFFICIENT DETERMINATION FROM IN SITU SPECIFIC BOUNDARY IMPEDANCE MEASUREMENTS BY THE SOUND INTENSITY TECHNIQUE  

Microsoft Academic Search

At present, the most part of errors on acoustic prediction and modelling of acoustic designs are as a result of the use of low precision sound absorption coefficients. To predict the acoustic performance of a material, within the infinity possible forms of assembly and constructive terminations, is mathematically complex. On the other hand, the most used method for the sound

Adrin Montoya; Ricardo Pesse

229

Enhancement of intensity-dependent absorption in InP and GaAs at 1.9 microns by doping  

NASA Technical Reports Server (NTRS)

It is pointed out that the study of intensity-dependent absorption (IDA) in general, and two-photon absorption (TPA), in particular, has suffered from experimental difficulties and inadequate theoretical models. Bass et al. (1979) could improve the experimental situation by making use of laser calorimetry to obtain directly the TPA coefficient of a medium with a high degree of sensitivity. In the present investigation, the employed technique has been used to study the effect of deep level dopants on IDA in InP and GaAs. It is found that the coefficient for IDA is strongly dependent on the presence of Fe in InP and Cr in GaAs. The conducted investigation had the objective to examine the effect of deep level impurities on IDA processes in InP and GaAs. Fe-doped InP and Cr-doped GaAs were compared with undoped crystals.

Li, N.-L.; Bass, M.; Swimm, R.

1985-01-01

230

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)

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.

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

1984-01-01

231

A Search for Formic Acid in the Upper Troposphere: A Tentative Identification of the 1105-cm(exp -1) nu(sub 6) Band Q Branch in High-Resolution Balloon-Borne Solar Absorption Spectra  

NASA Technical Reports Server (NTRS)

Infrared solar absorption spectra recorded at 0.02/cm resolution during a balloon flight from Alamogordo, N.M. (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/ cm has been tentatively identified in upper tropospheric spectra as due to the nu(sub 6) band Q branch. A preliminary analysis indicates a concentration of approx. = 0.6 ppbv and approx. = 0.4 ppbv near 8 and 10 km, respectively.

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

1984-01-01

232

Inhomogeneous broadening and peak shift of the 7.6 eV optical absorption band of oxygen vacancies in SiO2  

NASA Astrophysics Data System (ADS)

The peak parameters of radiation-induced 7.6 eV optical absorption band of oxygen vacancies (Si-Si bonds) were examined for high-purity synthetic ?-quartz and amorphous SiO2 (a-SiO2) exposed to 60Co ?-rays. The peak shape is asymmetric with the steeper edge at the lower energy side both in ?-quartz and a-SiO2, and the peak energy is larger for ?-quartz than that for a-SiO2. The full width at half maximum for a-SiO2 is larger by 40-60% than that for ?-quartz, and it increases with an increase in the disorder of the a-SiO2 network, which is enhanced by raising the temperature of preannealing before irradiation, i.e., fictive temperature. These data are interpreted from the viewpoint of the site-to-site distribution of the Si-Si bond length in a-SiO2.

Kajihara, Koichi; Skuja, Linards; Hosono, Hideo

2014-10-01

233

Cavity enhanced absorption spectroscopy measurements of pressure-induced broadening and shift coefficients in the ? 1+ ? 3 combination band of ammonia  

NASA Astrophysics Data System (ADS)

Cavity enhanced absorption spectroscopy is performed using an external cavity diode laser operating around 1516 nm. We demonstrate a sensitivity of 610-8 cm-1 Hz-1/2 and utilise a simple method to measure pressure-induced broadening and shift coefficients. The broadening and shift coefficients for six gases (helium, neon, argon, xenon, oxygen and nitrogen) have been determined at room temperature for four transitions in the ? 1+ ? 3 combination band of ammonia. Comparisons of the broadening coefficients with previous work in this region, where it exists, show good agreement. The broadening and shift coefficients of nitrogen and oxygen are also in good agreement with calculated values using the Robert and Bonamy theory. Both the broadening and shift coefficients show a clear trend through the rare gases, which can be explained in terms of the varying magnitude of the long range attractive forces operating between the colliding partners. We also demonstrate the application of the Parmenter-Seaver formalism to estimate the potential well depth of the ammonia dimer from the obtained broadening coefficients. The obtained well depth agrees well with theoretical calculations.

Bell, C. L.; Dhib, M.; Hancock, G.; Ritchie, G. A. D.; van Helden, J. H.; van Leeuwen, N. J.

2009-02-01

234

Proposal of high efficiency solar cells with closely stacked InAs/In0.48Ga0.52P quantum dot superlattices: Analysis of polarized absorption characteristics via intermediate-band  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the electronic structures and polarized absorption properties of quantum dot superlattices (QDSLs) using wide-gap matrix material, InAs/In0.48Ga0.52P 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 In0.48Ga0.52P, 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/In0.48Ga0.52P 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/In0.48Ga0.52P QDSLs are suitable material combination of IBSCs toward the realization of ultrahigh efficiency solar cells.

Yoshikawa, H.; Kotani, T.; Kuzumoto, Y.; Izumi, M.; Tomomura, Y.; Hamaguchi, C.

2014-07-01

235

Tuned intensity-dependent refractive index n2 and two-photon absorption in oxide glasses: Role of non-bridging oxygen bonds in optical nonlinearity  

NASA Astrophysics Data System (ADS)

Several nonlinear glass parameters such as second-order refractive index, n2, third-order susceptibility ?(3), the imaginary part of ?(3) and two-photon absorption coefficient are calculated for five different oxide glass systems. The glasses exhibit considerable optical nonlinearities. It has been found that the decrease in band gap energy and Fermi energy increases the glass nonlinear optical properties. Glasses contain either chromium oxide, magnesium or barium oxide exhibit considerable nonlinearity comparing with titanium-containing glasses. The origin of this nonlinearity and the ability to tune it has been discussed based on the glass linear refractive indices, nonbridging oxygen bonds, hyperpolarizability of modifier cations and on the rule of these cations on the creation of nonbridging oxygen bonds.

El-Diasty, Fouad; Abdel-Baki, Manal; Abdel-Wahab, F. A.

2008-10-01

236

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

PubMed

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

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

2014-11-17

237

Coupling of narrow and wide band-gap semiconductors on uniform films active in bacterial disinfection under low intensity visible light: implications of the interfacial charge transfer (IFCT).  

PubMed

This study reports the design, preparation, testing and surface characterization of uniform films deposited by sputtering Ag and Ta on non-heat resistant polyester to evaluate the Escherichia coli inactivation by TaON, TaN/Ag, Ag and TaON/Ag polyester. Co-sputtering for 120 s Ta and Ag in the presence of N? and O? led to the faster E. coli inactivation by a TaON/Ag sample within ?40 min under visible light irradiation. The deconvolution of TaON/Ag peaks obtained by X-ray photoelectron spectroscopy (XPS) allowed the assignment of the Ta?O? and Ag-species. The shifts observed for the XPS peaks have been assigned to AgO to Ag?O and Ag(0), and are a function of the applied sputtering times. The mechanism of interfacial charge transfer (IFCT) from the Ag?O conduction band (cb) to the lower laying Ta?O? (cb) is discussed suggesting a reaction mechanism. The optical absorption of the TaON and TaON/Ag samples found by diffuse reflectance spectroscopy (DRS) correlated well with the kinetics of E. coli inactivation. The TaON/Ag sample microstructure was characterized by contact angle (CA) and by atomic force microscopy (AFM). Self-cleaning of the TaON/Ag polyester after each disinfection cycle enabled repetitive E. coli inactivation. PMID:23867967

Rtimi, S; Sanjines, R; Pulgarin, C; Houas, A; Lavanchy, J-C; Kiwi, J

2013-09-15

238

Infrared absorption mechanisms of black silicon  

NASA Astrophysics Data System (ADS)

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.

Cheng, Zhengxi; Chen, Yongping; Ma, Bin

2014-09-01

239

Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu5Ta11O30 materials.  

PubMed

We present a joint theoretical and experimental investigation of the optoelectronic properties of CuVO3, CuNbO3 and Cu5Ta11O30 materials for potential photocatalytic and solar cell applications. In addition to the experimental results obtained by powder X-ray diffraction and UV-Vis spectroscopy of the materials synthesized under flowing N2 gas at atmospheric pressure via solid-state reactions, the electronic structure and the UV-Vis optical absorption coefficient of these compounds are predicted with high accuracy using advanced first-principles quantum methods based on DFT (including the perturbation theory approach DFPT) within the screened coulomb hybrid HSE06 exchange-correlation formalism. The calculated density of states are found to be in agreement with the UV-Vis diffuse reflectance spectra, predicting a small indirect band gap of 1.4 eV for CuVO3, a direct band gap of 2.6 eV for CuNbO3, and an indirect (direct) band gap of 2.1 (2.6) eV for Cu5Ta11O30. It is confirmed that the Cu(I)-based multi-metal oxides possess a strong contribution of filled Cu(I) states in the valence band and of empty d(0) metal states in the conduction band. Interestingly, CuVO3 with its predicted small indirect band gap of 1.4 eV shows the highest absorption coefficient in the visible range with a broad absorption edge extending to 886 nm. This novel result offers a great opportunity for this material to be an excellent candidate for solar cell applications. PMID:25055167

Harb, Moussab; Masih, Dilshad; Takanabe, Kazuhiro

2014-09-14

240

Theory of the J-band: From the Frenkel exciton to charge transfer  

Microsoft Academic Search

This review concerns the current status of the theory of formation of the so-called J-band (Jelley, Scheibe, 1936), an abnormally narrow, high-intensity, red-shifted optical absorption band arising from the aggregation of polymethine dyes. Two opposite approaches to explaining the physical nature of the J-band are given special attention. In the first of these, the old one based on Frenkels statistical

Vladimir V. Egorov

2009-01-01

241

Collision-induced absorption spectra of hydrogen in the first overtone region and the fundamental band of deuterium in binary mixtures: Deuterium-nitrogen, deuterium-carbon monoxide, deuterium-helium, deuterium-argon and deuterium-krypton  

NASA Astrophysics Data System (ADS)

The present research project consisted of three distinct spectral regions of study. First there was a refinement to the spectral analysis of the collision-induced absorption (CIA) spectra of the first overtone band of hydrogen. This consisted primarily of an investigation of the density dependence of the so-called "fudge factor" by use of various semi-empirical line shapes. The second part was an analysis of the CIA of the fundamental band of D2 in D2-N2 and D2-CO mixtures. The absorption coefficients were determined using appropriate statistical methods applied to a density expansion of the integrated absorption of the spectra, as well as calculation of the characteristic parameters of various semi-empirical line shapes applied to the experimental data. The third part of the thesis consisted of a systematic study of the CIA spectra of the fundamental band of D2 enhanced by He, Ar, and Kr at room temperature. The absorption coefficients were determined using appropriate statistical methods applied to a density expansion of the integrated absorption of the spectra, and the characteristic parameters of various semi-empirical line shapes were deduced from a nonlinear fitting procedure applied to the experimental data. During the course of the above work, the FORTRAN programs used to transform the raw data into the desired numerical quantities and complete the necessary analysis were updated and as necessary completely rewritten to advance the data analysis. This work was commenced in earnest during the author's M.Sc. thesis with the goal being to maximize the robust nature of the analysis and propagation of errors throughout all calculations to obtain maximum reliability in the results.

Stamp, Clifford Francis Joseph

242

Electronic structure of InN studied using soft x-ray emission, soft x-ray absorption, and quasiparticle band structure calculations  

E-print Network

, and quasiparticle band structure calculations L. F. J. Piper,* Leyla Colakerol, Timothy Learmonth, Per-Anders Glans within the GW framework of many body perturbation theory. Good agreement between the experimental spectra theory DFT calculations of the valence band structure of single crystalline wurtzite InN have been

243

Fast, narrow-band computer model for radiation calculations  

SciTech Connect

A fast, narrow-band computer model, FASTNB, which predicts the radiation intensity in a general nonisothermal and nonhomogeneous combustion environment, has been developed. The spectral absorption coefficients of the combustion products, including carbon dioxide, water vapor, and soot, are calculated based on the narrow-band model. FASTNB provides an accurate calculation at reasonably high speed. Compared with Grosshandler`s narrow-band model, RADCAL, which has been verified quite extensively against experimental measurements, FASTNB is more than 20 times faster and gives almost exactly the same results.

Yan, Z.; Holmstedt, G. [Lund Univ. (Sweden). Dept. of Fire Safety Engineering

1997-01-01

244

REVIEWS OF TOPICAL PROBLEMS: Theory of the J-band: from the Frenkel exciton to charge transfer  

Microsoft Academic Search

This review concerns the current status of the theory of formation of the so-called J-band (Jelley, Scheibe, 1936), an abnormally narrow, high-intensity, red-shifted optical absorption band arising from the aggregation of polymethine dyes. Two opposite approaches to explaining the physical nature of the J-band are given special attention. In the first of these, the old one based on Frenkel's statistical

V. V. Egorov; M. V. Alfimov

2007-01-01

245

Absolute Rovibrational Intensities, Self-Broadening and Self-Shift Coefficients for the X(sup 1) Sigma(+) V=3 (left arrow) V=0 Band (C-12)(O-16)  

NASA Technical Reports Server (NTRS)

The rotationless transition moment squared for the x(sup 1) sigma (sup +) v=3 (left arrow) v=0 band of CO is measured to be the absolute value of R (sub 3-0) squared = 1.7127(25)x 10(exp -7) Debye squared. This value is about 8.6 percent smaller than the value assumed for HITRAN 2000. The Herman-Wallis intensity factor of this band is F=1+0.01168(11)m+0.0001065(79)m squared. The determination of self-broadening coefficients is improved with the inclusion of line narrowing; self-shifts are also reported.

Chackerian, Charles, Jr.; Freedman, R.; Giver, L. P.; Brown, L. R.

2001-01-01

246

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)

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.

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

1982-01-01

247

Band gap engineering of FeS2 under biaxial strain: a first principles study.  

PubMed

The promising photovoltaic activity of pyrite (FeS2) is attributed to its excellent optical absorptivity and earth abundance, but its band gap, 0.95 eV, is slightly lower than the optimum value of 1.3 eV. Here we report the first investigation of strained FeS2, whose band gap can be increased by ?0.3 eV. The influence of uniaxial and biaxial strains on the atomic structure as well as the electronic and optical properties of bulk FeS2 is systematically examined by the first principles calculations. We found that the biaxial strain can effectively increase the band gap with respect to uniaxial strain. Our results indicate that the band gap increases with increasing tensile strain to its maximum value at 6% strain, but under the increasing compressive strain, the band gap decreases almost linearly. Moreover, the low intensity states at the bottom of the conduction band disappear and a sharp increase in the intensity appears at the lower energy level under the tensile strain, which causes the red shift of the absorption edge and enhances the overall optical absorption. With the increase of the band gap and enhanced optical absorption, FeS2 will make a better photovoltaic material. PMID:25308322

Xiao, Pin; Fan, Xiao-Li; Liu, Li-Min; Lau, Woon-Ming

2014-10-21

248

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

PubMed Central

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 pumpIR 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 644nm (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

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

2013-01-01

249

A novel red emitting phosphor CaIn 2O 4:Eu 3+, Sm 3+ with a broadened near-ultraviolet absorption band for solid-state lighting  

Microsoft Academic Search

Red phosphor of CaIn2O4:Eu3+, Sm3+ is synthesized by solid state reaction. The 5D0?7F2 transition of Eu3+ is dominantly observed in the photoluminescence spectrum, leading to a red emission of the phosphor. The doped Sm3+ is found to be efficient to sensitize the emission of Eu3+ and be effective to extend and strengthen the absorption of near-UV light with wavelength of

Xiaosong Yan; Wanwan Li; Kang Sun

250

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

NASA Technical Reports Server (NTRS)

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, more than 20 times greater than that used in previous work.

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

1991-01-01

251

Band gap energy determination by photoacoustic absorption and optical analysis of Cd 1? x Zn x Te for low zinc concentrations  

Microsoft Academic Search

In this paper we present a study of the optical properties of CdZnTe single crystal for low Zn concentrations at room temperature using photoacoustic spectroscopy and photoreflectance (PR) measurements. The photoreflectance measurements were carried out in order to determine the Eg value at room temperature of the CdTe sample to validate the criterion for the photoacoustic absorption measurements. The closed

J. J. Pras-Barragn; L. Tirado-Meja; H. Ariza-Caldern; L. Baos; J. J. Perez-Bueno; M. E. Rodrguez

2006-01-01

252

An integrated computational tool to model the broadening of the absorption bands of flexible dyes in solution: cationic chromophores as test cases.  

PubMed

This paper is devoted to the development and application of an effective computational approach for the prediction of band broadening in the electronic spectra of semi-flexible organic molecules in solution. The protocol is based on DFT, TD-DFT, and PCM computational techniques and attempts to take into account the three main contributions tuning electronic spectra, namely vibronic transitions, conformational equilibria, and solvent relaxation. The whole procedure has been implemented in the Gaussian code and has been tested for the interpretation of the spectroscopic behaviour of a betainic dye and a series of charged dyes, containing one methyl-pyridinium or quinolinium group and a flexible moiety. The results provide a comprehensive picture of solvatochromic effects and offer a reliable answer to the open problem of the origin of band broadening in the target semi-flexible dyes. PMID:25377174

Benassi, Enrico; Cappelli, Chiara; Carlotti, Benedetta; Barone, Vincenzo

2014-11-19

253

Absolute IR Band Intensities of CH 2N 2, CH 3N 3, and CH 3NC in the 250-4300 cm -1Region and Upper Limits of Abundance in Titan's Stratosphere  

NASA Astrophysics Data System (ADS)

In the frame of a program of systematic studies to determine or reassess the absolute intensities of gas phase organics of interest to Titan, we have experimentally studied the IR spectra in the gas phase of diazomethane, methyl azide, and methyl isocyanide, at room temperature, in the 250-4300 cm -1region. The absolute intensities, S?, of the most intense vibrational bands of these compounds were determined experimentally together with the associated uncertainties. In order to estimate the detectability of the selected compounds by infrared spectroscopy in Titan's atmosphere, our data were compared with Voyager IRIS spectra of Titan. Upper limits of, respectively, 5, 5.4, and 1.3 ppb on the mean stratospheric abundances are inferred. These values are consistent with photochemical modeling of Titan's atmosphere. They appear auspicious for possible detection in Titan using upcoming space missions.

Khlifi, Mohammed; Paillous, Pierre; Bruston, Paul; Raulin, Franois; Guillemin, Jean Claude

1996-11-01

254

STUDIES ON PURE ELEMENT INTENSITIES, MASS ABSORPTION COEFFICIENTS AND PARAMETERS (n AND no FOR ENERGY-DISPERSIVE X-RAY FLUORESCENCE ANALYSIS  

Microsoft Academic Search

Determination of pure element intensities is important in EDS (energy-dispersive X-ray fluorescence analysis) analysis. In a previous paper, we have studied three determination methods of pure element intensities: the pure thick metal foil, oxide, and low concentration methods. The pure element intensities of Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Br, Rb, Sr, Y, Zr, Nb, and

Hua Younan

2001-01-01

255

Phonon side bands in the absorption spectra of Ni2+ and Co2+ in CdI2 and PbI2  

Microsoft Academic Search

The absorption and magnetic circular dichroism spectra of the 3A2g-->1Eg electronic transition of CdI2: Ni2+ and PbI2: Ni2+ and of the a4T1g-->b2T1g, 2A1g transition of CdI2: Co2+ have been measured. The spectra show a complicated fine structure caused by the coupling with nonlocalized vibrational modes of the host lattice. The theory of this effect is presented. It is shown that

S. R. Kuindersma; P. R. Boudewijn; C. Haas; J. Bethlehem; A. Meetsma

1982-01-01

256

The NLTE problem of radiative transfer in the near-infrared CO2 and CO bands in the Martian atmosphere taking account for scattering and absorption of radiation by aerosol  

NASA Astrophysics Data System (ADS)

Heating of the Martian atmosphere due to the radiative transfer in the nearinfrared (NIR) ro-vibrational CO2 bands is one of the most important mechanisms which control the structural and dynamical properties throughout the entire atmosphere of Mars. Also, the emissions in some of these bands are used for remote sensing of the atmosphere of Mars. So, a development of more sophisticated models for estimating the values of the Martian atmosphere emissions in the NIR bands of CO2 molecules is required. A high rate of absorption of solar NIR radiation by CO2 molecules and a low density of the Martian atmosphere result in that the non-local thermodynamic equilibrium (NLTE) takes place in large altitude intervals for populations of the excited CO2 vibrational states. On other hand, dust and water ice aerosols permanently exist in the atmosphere of Mars. The aerosol optical depth of the Martian atmosphere varies from less than 0.1 for the condition of transparent atmosphere up to about 5 during global dust storms. Thus, the values of aerosol optical depth are comparable to the ones of some NIR bands of CO2 . The extinction of the NIR radiation by the aerosol particles makes an important influence on the radiative heating and, thus, on the dynamics of the Martian atmosphere. In the paper [1] the model used for solving the NLTE problem of radiative transfer in the CO2 bands in the Martian atmosphere included the 321 excited vibrational states belonging to 7 isotopologues of CO2 and 779 radiative vibrational transitions (about 100000 lines). The most upper state is 200 3 of the principal isotopologue with energy of about 9500 cm-1 . In the present study, this model has been further developed. The main improvements are following. 1) The 10 bands rising between 8 vibrational states of 2 isotopologues of the CO molecules have been included. 2) The radiative transfer in all the bands of CO2 and CO within the 15-1.02 m spectral interval is taken into account with an exact treatment of overlapping of the spectral lines in frequency. 3) The processes of aerosol scattering and absorption of radiation at the frequencies of the NIR bands of CO2 and CO molecules were taken into account for the first time. 4) A reflection of the NIR radiation by the Martian surface is also taken into account. The accelerated lambda-iteration technique used for solving the NLTE radiative transfer problem has been modified for the case of the aerosol extinction presence. The dependence of non-equilibrium populations of high excited CO2 and CO vibrational states on adopted optical properties of the Martian aerosol particles and on their vertical distribution as well as the effect of reflectance properties of the Martian surface on these vibrational state populations have been investigated. The spectra of slant and limb emission of the Martian atmosphere with and without taking account for the aerosol extinction of the NIR radiation are simulated. The research was supported by the Russian Foundation for Basic Research (grant 07-05-00899a). [1] Ogibalov, V.P., and Shved, G.M. // Solar System Res., 37, No. 1, pp. 23-33, 2003.

Ogibalov, Vladimir

257

Coloration and oxygen vacancies in wide band gap oxide semiconductors: Absorption at metallic nanoparticles induced by vacancy clusteringA case study on indium oxide  

NASA Astrophysics Data System (ADS)

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 In2O3 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.

Albrecht, M.; Schewski, R.; Irmscher, K.; Galazka, Z.; Markurt, T.; Naumann, M.; Schulz, T.; Uecker, R.; Fornari, R.; Meuret, S.; Kociak, M.

2014-02-01

258

High-resolution study of some doubly excited vibrational states of PH 2D: the ?1+ ?2, ?2+ ?5, ?2+ ?3, and ?2+ ?6 bands  

NASA Astrophysics Data System (ADS)

The absorption bands ?1+ ?2, ?2+ ?3, and ?2+ ?6 of PH 2D have been recorded for the first time using a high-resolution Bruker 120 HR interferometer, and rotationally analyzed. Some transitions belonging to the very weak band ?2+ ?5 and enhanced in intensity by strong interactions with the ?1+ ?2 band were also assigned. Sets of parameters obtained from the fit reproduce experimental line position of the bands ?1+ ?2 and ?2+ ?3 with about the experimental accuracy. The residuals of the ro-vibrational energies of the ?2+ ?6 band are about 10 times larger. Reasons for the poorer reproduction of the latter data are given.

Ulenikov, O. N.; Bekhtereva, E. S.; Grebneva, S. V.; Brger, H.; Jerzembeck, W.; Leroy, C.

2004-07-01

259

Calculation of electric dipole intensity parameter to explore some interaction between hard metal ions Pr(III) and Nd(III) with pi-electron density of butene-1,4 and butyne-1,4-diols in non-aqueous solutions: an absorption spectral study.  

PubMed

Pr(III) and Nd(III) are hard acceptors in HSAB (hard and soft acid base) sense and hence are known to exhibit practically a little affinity towards electrons. At the same time these metal ions show strong preference for oxygen donor chelating ligands. The ligands chosen for this study are structurally related diols, viz. butane-1,4, butene-1,4 and butyne-1,4-diols which form identical seven membered chelate ring by coordinating to metals in a bidentate manner through oxygen on 1 and 4 positions of the diol molecules. Complexation of these diols with Pr(III) and Nd(III) was carried out in DMF, CH3OH, CH3CN and their equimolar binary mixtures using comparative absorption spectrophotometry of 4f-4f transitions. The variation of oscillator strengths (P) of different 4f-4f bands as well as the magnitude and variation of Judd-Ofelt electric dipole intensity parameters (T lambda, lambda = 2, 4, 6) was discussed. They correlate the interaction between the metal 4f-orbitals of Pr(III) and Nd(III) with the pi-electron densities of the double and triple bonds present in butene-1,4 and butyne-1,4-diols, respectively. The value of empirical intensity parameter [T lambda(complex)/T lambda (aquo)] was calculated and its plot against oscillator strength (P) is drawn. PMID:16344248

Singh, Th David; Sumitra, Ch; Bag, G C; Devi, M Indira; Singh, N Rajmuhon

2006-01-01

260

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

PubMed

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

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

2014-01-21

261

Laser supported solid state absorption fronts in silica  

SciTech Connect

We develop a model based on simulation and experiment that explains the behavior of solid-state laser-supported absorption fronts generated in fused silica during high intensity (up to 5GW/cm{sup 2}) laser exposure. We find that the absorption front velocity is constant in time and is nearly linear in laser intensity. Further, this model can explain the dependence of laser damage site size on these parameters. This behavior is 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. The regime of parameter space critical to this problem spans and extends that measured by other means. It serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

Carr, C W; Bude, J D

2010-02-09

262

Controlling absorption spectra of strained graphene nanoribbon by magnetic modulation  

NASA Astrophysics Data System (ADS)

This study shows that the optical absorption spectra of strained graphene nanoribbons can be effectively tuned by a spatially modulated magnetic field. The absorption spectra exhibit many asymmetric square-root divergent peaks structure due to the oscillatory parabolic subbands. These absorption peaks can be classified into primary and secondary ones. The number, spectral intensity, and frequency of the absorption peaks depend sensitively on the strength and period of the modulated field. The transition channels of the absorption peaks are identified and the optical selection rule is analyzed. There exists an optical selection rule for the primary absorption peaks. Such rule is originated from the orthogonal properties of the quasi-Landau level wave functions. A uniaxial stress changes the band-edge state energy and subband curvature, in turn modifying the optical absorption spectra. The evolution of the frequencies of the absorption peaks with the field strength is explored. They first show linear, then square-root dependence on the field strength. These theoretical predictions can be validated by absorption spectroscopy experiments.

Li, T. S.; Hsieh, C. T.; Yang, S. P.; Chang, S. C.

2014-12-01

263

Temperature-Dependent Infrared Absorption Cross Sections of Methyl Cyanide (Acetonitrile)  

SciTech Connect

Pressure broadened (1 atm. N2) absorption cross sections and integrated band intensities have been derived from laboratory spectra of CH3CN, recorded at 276,298, and 323 K, covering 600-6500 cm-1. The spectra were recorded at a resolution of 0.112cm-1 using a commercial Fourier transform spectrometer and a custom flowing sample delivery system. We report integrated absorption cross sections for intervals corresponding to the most prominent bands, compare the results with previously reported values, and discuss error sources, which are estimated as ~7% with systematic error the largest error source.

Rinsland, Curtis P.; Sharpe, Steven W.; Sams, Robert L.

2005-12-01

264

Observation of intense two-beam positron diffraction and the precise determination of the positron band gap in rare-gas crystals  

SciTech Connect

We have measured the energy dependence of the elastic specular reflection of positrons from the (111) surfaces of solid rare-gas crystals. For each sample we observe an intense first-order Bragg peak with a profile closely resembling the ideal ''top-hat shaped'' profile first derived by Darwin. The well-defined width and center of the peak enables us to determine the positron-energy gap and inner potential as a sensitive test of the positron--gas-atom interaction in the solid.

Gullikson, E.M.; Mills A.P. Jr.; McRae, E.G.

1988-01-01

265

Method and apparatus for aerosol particle absorption spectroscopy  

DOEpatents

A method and apparatus 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.

Campillo, Anthony J. (Nesconset, NY); Lin, Horn-Bond (Manorville, NY)

1983-11-15

266

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

NASA Technical Reports Server (NTRS)

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.

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

2001-01-01

267

Saturation of intervalence-band transitions in p-type semiconductors  

SciTech Connect

We present a theory of the saturation of heavy-hole to light-hole band absorption in p-type semiconductors with the diamond or zinc-blende crystal structure by high-intensity light with a wavelength near 10 ..mu..m. The absorption coefficient is found to decrease with intensity in a manner closely approximated by an inhomogeneously broadened two-level model. For temperatures and hole concentrations where hole-phonon scattering dominates hole-impurity and hole-hole scattering, the saturation intensity is independent of the hole concentration. We calculate the saturation intensity as a function of excitation wavelength and temperature for p-Ge and p-GaAs. We find that the saturation intensity increases with photon energy and with temperature. The calculated results are compared with the available experimental data and good agreement is found.

James, R.B.; Smith, D.L.

1980-04-15

268

On the red giant titanium oxide bands  

NASA Astrophysics Data System (ADS)

The dependence of TiO absorption in cool oxygen-sequence giant stars on the Teff and log g of their atmospheres is investigated theoretically on the basis of spectra simulated using the computer program described by Hanni (1983) and the giant model atmospheres of Johnson et al. (1980). The temperature dependence of the intensity jumps at the head of the alpha(1.0) band is determined from simulated spectra, and the jumps are related to spectral types using the calibration of Ridgway et al. (1980). The results are presented in tables and graphs and shown to be in good agreement with the empirical Teff/intensity-jump correlation of Boyarchuk (1969).

Hanni, L.; Sitska, J.

1985-12-01

269

SF_6: the Forbidden Band Unveiled  

NASA Astrophysics Data System (ADS)

Sulfur hexafluoride (SF_6) is a greenhouse gas of anthropogenic origin, whose strong infrared absorption in the ?_3 S-F stretching region near 948 cm^{-1} induces a global warming potential 23900 times bigger than CO_2. This heavy species features many hot bands at room temperature (at which the ground state population is only 30 %), especially those originating from the v_6=1 state. Unfortunately, the ?_6 band itself (near 347 cm^{-1}) being, in first approximation, both infrared and Raman inactive, no reliable information could be obtained about it up to now. A long time ago, some authors suggested that this band may be slightly activated through Coriolis interaction and may appear as a very faint band, with an integrated intensity about 2 millionths of that of ?_3. Using a new cryogenic multipass cell with 93 m optical path length and regulated at 165 2 K temperature, we recorded a spectrum of the ?_6 far-infrared region thanks to the performances of the AILES Beamline at the SOLEIL french synchrotron facility. Low temperature was used to avoid the presence of the 2?_6-?_6 hot band and to reduce the neighboring, stronger ?_4-?_2 difference band. We are thus able to confirm that the small feature in this region, previously viewed at low-resolution is indeed ?_6. We present its fully resolved spectrum. It appears to be activated thanks to unidentified faint interactions resulting in the presence of a first-order dipole moment term that induces unusual selection rules. This spectrum was analyzed thanks to the XTDS software package, leading to accurate molecular spectroscopic parameters that should be useful to model the hot bands of SF_6. W. B. Person, B. J. Krohn, J. Mol. Spectrosc. {98}, 229-257 (1983), C. Chappados, G. Birnbaum, J. Mol. Spectrosc. {105}, 206-214 (1984). Ch. Wenger, V. Boudon, M. Rotger, M. Sanzharov and J.-P. Champion, J. Mol. Spectrosc., {251} 102-113 (2008).

Boudon, V.; Manceron, L.; Kwabia-Tchana, F.; Roy, P.

2013-06-01

270

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

SciTech Connect

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.

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

271

Optical nonlinear absorption characteristics of crystalline Ge2Sb2Te5 thin films  

NASA Astrophysics Data System (ADS)

In this work, the optical nonlinear absorption characteristics of the crystalline Ge2Sb2Te5 thin films were investigated by performing z-scan measurements with nanosecond laser pulse. The experimental results showed that the nonlinear saturable absorption coefficient was as large as -10-2 m/W for the excitation intensity lower than 0.17 GW/m2. The nonlinear saturable absorption changed to the nonlinear reverse-saturable absorption with a coefficient of about + 10-2 at the excitation intensity of above 0.17 GW/m2. To explore the internal mechanisms, the first-principle theory was employed to calculate the electronic structure, and a five-level structure suitable for explanation of nonlinear absorption reversal was suggested. The theoretical calculation and analysis indicated that for the excitation intensity smaller than 0.17 GW/m2, the contribution to the nonlinear saturable absorption is mainly from band-filling effect; for the excitation intensity larger than 0.17 GW/m2, the nonlinear reverse saturable absorption results from the thermal-induced nonlinearity, which is further confirmed by picosecond laser pulse z-scan measurement and the variable-temperature spectroscopy ellipsometric analysis.

Liu, Shuang; Wei, Jingsong; Gan, Fuxi

2011-08-01

272

Infrared band intensities and global warming potentials of CF4, C2F6, C3F8, C4F10, C5F12, and C6F14  

NASA Astrophysics Data System (ADS)

IR band intensities have been measured for the species: CF4, C2F6, C3F8, C4F10, C5F12, and C6F14 via Fourier transform spectroscopy and compared to previous literature values if available. Relative radiative forcing calculations have been performed using these data in order to determine the global warming potential of the particular species. The relative forcing (compared to CFC11, per volume) increases with molecular weight in the above series from 0.47 to 2.1, the GWP for a time horizon of 100 yrs from 1.1 to 4.7. This corresponds to a GWP on CO2 basis per mass of about 5000.

Roehl, C. M.; Boglu, D.; Brhl, C.; Moortgat, G. K.

1995-04-01

273

Intensive (up to 1015 W/cm2) Laser Light Absorption and Energy Transfer in Subcritical Media with or Without High-Z Dopants  

SciTech Connect

Fabrication methods for low-density fine-structure (cell size <1 {mu}m) 3-D networks of cellulose triacetate (TAC) are developed. Target densities ranged 4-20 mg/cc, similar polymer structures were produced both with no load and with high-Z cluster dopant with concentration up to 30%. Foams of varying density down to 0.25 plasma critical density at the third harmonic of iodine laser wavelength are supplied for laser shots. Experiments with underdense foam targets with and without clusters irradiated on the PALS laser facility are analyzed preliminary, showing strong influence of target structure on process of laser light absorption. Heat and radiation transport in such targets are considered.

Borisenko, N. G.; Akimova, I. V.; Gromov, A. I.; Khalenkov, A. M.; Merkuliev, Yu. A. [P.N. Lebedev Physical Institute of RAS, Leninskyi Pr-t. 53, 117924 Moscow (Russian Federation); Kondrashov, V. N. [Troitsk Institute of Innovation and Thermonuclear Research, 142190 Troitsk (Russian Federation); Limpouch, J. [Institute of Physics, AS CR, Na Slovance 2, 18221 Prague 8 (Czech Republic); Pimenov, V. G. [Zelinsky Institute of Organic Chemistry, 49 Leninskiy Pr-t. 119991, Moscow (Russian Federation)

2006-08-03

274

Energy transfer in the inhomogeneously broadened core antenna of purple bacteria: a simultaneous fit of low-intensity picosecond absorption and fluorescence kinetics.  

PubMed Central

The excited state decay kinetics of chromatophores of the purple photosynthetic bacterium Rhodospirillum rubrum have been recorded at 77 K using picosecond absorption difference spectroscopy under strict annihilation free conditions. The kinetics are shown to be strongly detection wavelength dependent. A simultaneous kinetic modeling of these experiments together with earlier fluorescence kinetics by numerical integration of the appropriate master equation is performed. This model, which accounts for the spectral inhomogeneity of the core light-harvesting antenna of photosynthetic purple bacteria, reveals three qualitatively distinct stages of excitation transfer with different time scales. At first a fast transfer to a local energy minimum takes place (approximately 1 ps). This is followed by a much slower transfer between different energy minima (10-30 ps). The third component corresponds to the excitation transfer to the reaction center, which depends on its state (60 and 200 ps for open and closed, respectively) and seems also to be the bottleneck in the overall trapping time. An acceptable correspondence between theoretical and experimental decay kinetics is achieved at 77 K and at room temperature by assuming that the width of the inhomogeneous broadening is 10-15 nm and the mean residence time of the excitation in the antenna lattice site is 2-3 ps. PMID:8130341

Pullerits, T; Visscher, K J; Hess, S; Sundstrom, V; Freiberg, A; Timpmann, K; van Grondelle, R

1994-01-01

275

Rotational Analysis of the 0-0 Band of the ^2A_1-^2B_1 Electronic Transition of PH_2  

Microsoft Academic Search

The long wavelength bands of the visible absorption spectrum of PH_2 have been rephotographed with much greater intensity than in the earlier work of Ramsay. A detailed rotational analysis has been carried out for the 0-0 band. The transition is of the type ^2A_1-^2B_1 and the rotational constants lead to the following molecular parameters: ground state, r''_0 = 1.429 ,

R. N. Dixon; G. Duxbury; D. A. Ramsay

1967-01-01

276

Hemorrhoidal banding  

Microsoft Academic Search

Band ligation of symptomatic internal hemorrhoids is a well-established and accepted outpatient procedure. The purpose of\\u000a this paper is to alert the medical profession to potential complications and death following this procedure. Each of the four\\u000a patients described in this report experienced pain and inability to urinate following banding. This report does not condemn\\u000a banding but, rather, focuses on problems

Thomas R. Russell; John H. Donohue

1985-01-01

277

5 5 cm2 silicon photonic crystal slabs on glass and plastic foil exhibiting broadband absorption and high-intensity near-fields  

NASA Astrophysics Data System (ADS)

Crystalline silicon photonic crystal slabs are widely used in various photonics applications. So far, the commercial success of such structures is still limited owing to the lack of cost-effective fabrication processes enabling large nanopatterned areas (>> 1 cm2). We present a simple method for producing crystalline silicon nanohole arrays of up to 5 5 cm2 size with lattice pitches between 600 and 1000 nm on glass and flexible plastic substrates. Exclusively up-scalable, fast fabrication processes are applied such as nanoimprint-lithography and silicon evaporation. The broadband light trapping efficiency of the arrays is among the best values reported for large-area experimental crystalline silicon nanostructures. Further, measured photonic crystal resonance modes are in good accordance with light scattering simulations predicting strong near-field intensity enhancements greater than 500. Hence, the large-area silicon nanohole arrays might become a promising platform for ultrathin solar cells on lightweight substrates, high-sensitive optical biosensors, and nonlinear optics.

Becker, C.; Wyss, P.; Eisenhauer, D.; Probst, J.; Preidel, V.; Hammerschmidt, M.; Burger, S.

2014-07-01

278

C60 and C70 electronic absorption spectra in different solvents and matrices.  

PubMed

The electronic absorption spectra of C60 and C70 molecules have been reported in various solvents viz., polar, aliphatic and aromatic. In addition the electronic absorption spectra of C60 and C70 also recorded in different matrices viz., sol-gel, polymer and thin film. The solvent effect has been observed in polar, aliphatic and aromatic solvents. The aromatic solvent shows larger red shift as compared to other solvents. The solution form electronic absorption spectra C60 and C70 show the conjugation effect and compared with the absorption spectra reported in different matrices like sol-gel, polymer and thin film. In the case of sol-gel, polymer and thin film matrices of C60 and C70, it is found that the broader absorption bands with less intensity suffer from intermolecular interaction. PMID:21485869

Bansal, Sonia; Kumar, Niranjan

2011-02-01

279

High-temperature UV absorption of methyl radicals behind shock waves  

NASA Astrophysics Data System (ADS)

The absorption of ultraviolet narrow-line laser radiation by methyl radicals (CH3) in the BA1??XA2? electronic system has been studied at high temperatures behind shock waves. Methyl radicals at high temperatures were generated by the shock heating of methyl precursors: azomethane, methyl iodide, and ethane. The spectral shape and intensity of the broadband BA1??XA2?CH3 absorption feature from 211.5 to 220 nm at high temperature (1565 K) has been measured. The absorption coefficient of CH3 at 216.62 nm, the wavelength of peak absorption at high temperatures in the P+Q band, has been determined from 1200 to 2500 K. Additionally, the absorption coefficients of several interfering UV-absorbing combustion species (C2H2,C2H4, and C3H6) have been determined at 216.62 nm.

Oehlschlaeger, Matthew A.; Davidson, David F.; Hanson, Ronald K.

2005-06-01

280

The multimode Jahn-Teller effect in one-phonon side-band of optical absorption spectrum ?8(4A2 e4t3) -> ?8(?) (4T1 e3t4) of the CdTe:Co2+ system (in English)  

NASA Astrophysics Data System (ADS)

Complicated fine structure in the low-temperature optical absorption band of the impurity d ? d transition ?_{8}({}^{4}A_{2} e^{4}t^{3})??_{8}^{(?)} ({}^{4}T_{1} e^{3}t^{4}) for semiconductor crystal CdTe doped by impurity Co^{2+} ions substituting tetrahedral Cd sites was studied experimentally and interpreted theoretically in terms of multimode Jahn-Teller effect for the excited term ?_{8}^{(?)} ({}^{4}T_{1} e^{3}t^{4}) coupled to trigonal and tetragonal modes. An attempt to use the old classical theory of impurity absorption ignoring the Jahn-Teller effect and treating the optical band in terms of phonon replicas turned out to fail. The one phonon side-band of the optical band in question has nothing in common with the projected phonon densities calculated for the defect crystal using the RIM-11 model. The multimode Jahn-Teller effect ?_{8}bigotimes(e+t_{2}) considered in terms of second-order perturbation theory resulted in a considerable redistribution of the projected densities of states and in appearance of new resonant vibronic modes. The experimental spectral line in the region of one-phonon side-band fitted well with the theoretical curve obtained by the adjustment of vibronic constants.

Polinger, V. Z.; Gnatenko, Yu. P.; Bukivsky, P. N.; Melnichuk, S. V.; Yurijchuk, I. M.

281

Infrared absorption of defects in quartz  

Microsoft Academic Search

A number of sharp absorption bands in the infrared spectrum of ; crystalline alpha -quartz between 3200 and 3655 cm⁻¹ were assigned to ; defects in the lattice. Defects containing water may cause a broad absorption ; through this region of the spectrum in very imperfect parts of certain crystals, ; but it does not contribute to the sharp bands

D. Wood

1960-01-01

282

Optical conductivity of ABA stacked graphene trilayer: mid-IR resonance due to band nesting  

NASA Astrophysics Data System (ADS)

The band structure and the optical conductivity of an ABA (Bernal-type) stacked graphene trilayer are calculated. It is shown that, under appropriate doping, a strong resonant peak develops in the optical conductivity, located at the frequency corresponding to approximately 1.4 times the interlayer hopping energy and caused by the nesting of two nearly parabolic bands in the electronic spectrum. The intensity of this resonant absorption can be controlled by adjusting the gate voltage. The effect is robust with respect to increasing temperature.

Rashidian, Zeinab; Bludov, Yuliy V.; Ribeiro, Ricardo M.; Peres, N. M. R.; Vasilevskiy, Mikhail I.

2014-10-01

283

An Accurate Method for Computing the Absorption of Solar Radiation by Water Vapor  

NASA Technical Reports Server (NTRS)

The method is based upon molecular line parameters and makes use of a far wing scaling approximation and k distribution approach previously applied to the computation of the infrared cooling rate due to water vapor. Taking into account the wave number dependence of the incident solar flux, the solar heating rate is computed for the entire water vapor spectrum and for individual absorption bands. The accuracy of the method is tested against line by line calculations. The method introduces a maximum error of 0.06 C/day. The method has the additional advantage over previous methods in that it can be applied to any portion of the spectral region containing the water vapor bands. The integrated absorptances and line intensities computed from the molecular line parameters were compared with laboratory measurements. The comparison reveals that, among the three different sources, absorptance is the largest for the laboratory measurements.

Chou, M. D.

1980-01-01

284

Absorption Spectra of Astaxanthin Aggregates  

E-print Network

Carotenoids in hydrated polar solvents form aggregates characterized by dramatic changes in their absorption spectra with respect to monomers. Here we analyze absorption spectra of aggregates of the carotenoid astaxanthin in hydrated dimethylsulfoxide. Depending on water content, two types of aggregates were produced: H-aggregates with absorption maximum around 390 nm, and J-aggregates with red-shifted absorption band peaking at wavelengths >550 nm. The large shifts with respect to absorption maximum of monomeric astaxanthin (470-495 nm depending on solvent) are caused by excitonic interaction between aggregated molecules. We applied molecular dynamics simulations to elucidate structure of astaxanthin dimer in water, and the resulting structure was used as a basis for calculations of absorption spectra. Absorption spectra of astaxanthin aggregates in hydrated dimethylsulfoxide were calculated using molecular exciton model with the resonance interaction energy between astaxanthin monomers constrained by semi-e...

Olsina, Jan; Minofar, Babak; Polivka, Tomas; Mancal, Tomas

2012-01-01

285

Gastric Banding  

MedlinePLUS

... received gastric banding have reported the following benefits: Weight-loss Decreased waist and hip circumference Improvements in obesity-related conditions, like diabetes, hypertension, and sleep apnea Improvements in general health Improvements in quality ...

286

A mid-infrared laser absorption sensor for carbon monoxide and temperature measurements  

Microsoft Academic Search

A mid-infrared (mid-IR) absorption sensor based on quantum cascade laser (QCL) technology has been developed and demonstrated for high-temperature thermometry and carbon monoxide (CO) measurements in combustion environments. The sensor probes the high-intensity fundamental CO ro-vibrational band at 4.6 mum enabling sensitive measurement of CO and temperature at kHz acquisition rates. Because the sensor operates in the mid-IR CO fundamental

Jeremy Vanderover; Matthew A. Oehlschlaeger

2010-01-01

287

Infrared absorption of gaseous CH2BrOO detected with a step-scan Fourier-transform absorption spectrometer  

NASA Astrophysics Data System (ADS)

CH2BrOO radicals were produced upon irradiation, with an excimer laser at 248 nm, of a flowing mixture of CH2Br2 and O2. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record temporally resolved infrared (IR) absorption spectra of reaction intermediates. Transient absorption with origins at 1276.1, 1088.3, 961.0, and 884.9 cm-1 are assigned to ?4 (CH2-wagging), ?6 (O-O stretching), ?7 (CH2-rocking mixed with C-O stretching), and ?8 (C-O stretching mixed with CH2-rocking) modes of syn-CH2BrOO, respectively. The assignments were made according to the expected photochemistry and a comparison of observed vibrational wavenumbers, relative IR intensities, and rotational contours with those predicted with the B3LYP/aug-cc-pVTZ method. The rotational contours of ?7 and ?8 indicate that hot bands involving the torsional (?12) mode are also present, with transitions 7_0^1 12_v^v and 8_0^1 12_v^v, v = 1-10. The most intense band (?4) of anti-CH2BrOO near 1277 cm-1 might have a small contribution to the observed spectra. Our work provides information for directly probing gaseous CH2BrOO with IR spectroscopy, in either the atmosphere or laboratory experiments.

Huang, Yu-Hsuan; Lee, Yuan-Pern

2014-10-01

288

Absorptance of infrared radiation by methane at elevated temperatures  

SciTech Connect

In large-scale fires and flames, radiative transport can be an important factor determining the rate of fuel volatilization and flame spread in condensed fuels, and in general can affect the amount of soot that is produced by the flame. The radiant flux can be significantly attenuated by core hydrocarbon gases that have absorption features in the infrared. The spectral absorptance of the {upsilon}{sub 3} (centered at approximately 3020 cm{sup -1}) and {upsilon}{sub 4} (centered at approximately 1306 cm{sup -1}) fundamental bands of methane were measured at elevated temperatures. The measurements were made using a FTIR spectrometer coupled to a gas cell that was maintained at a constant temperature in a furnace. The partial pressure of the methane was varied between 5 and 95 percent, yielding pressure path lengths between 1.14 and 21.74 atm-cm. The total pressure was maintained at 1 atm. Measurements were made at temperatures between 296 and 900 K. The effect of spectral resolution on the measurements and derived parameters was examined. Spectral resolutions between 4 and 32 cm{sup -1} were used. The spectral mean parameters of line strength and line shape were determined for the Elsasser narrow band radiation model using the data taken at a resolution of 4 cm{sup -1}. The band model parameters were incorporated into RADCAL, a narrow band model used to predict spectral intensity and transmittance. 13 refs., 10 figs., 1 tab.

Fuss, S.P.; Ezekoye, O.A.; Hall, M.J. [Univ. of Texas, Austin, TX (United States)

1996-11-01

289

Q BAND CHROMOSOMAL POLYMORPHISMS IN LAKE TROUT (SALVELINUS NAMAYCUSH)  

Microsoft Academic Search

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.

RUTH B. PHILLIPS; KERRY D. ZAJICEK

290

The shape of the J-band of pseudoisocyanine  

NASA Astrophysics Data System (ADS)

We show that, within the coherent exciton scattering (CES) approximation, both the measured exponential band-tail and the detailed shape of the J-band region of the absorption spectrum of pseudoisocyanine aggregates can be reproduced with high accuracy, using only a single free parameter. Our numerical studies confirm analytical results that the J-band width depends crucially on the monomer absorption strength in the energy region where the J-band peak occurs.

Eisfeld, A.; Briggs, J. S.

2007-10-01

291

Light-induced chloroplast rearrangements and their action spectra as measured by absorption spectrophotometry.  

PubMed

A new combination technique of using both dual-wavelength and opalglas methods for scanning translucent biological samples was applied to leaves of terrestrial plants in order to observe their absorption changes by irradiation and the action spectra for the absorption changes. The measurements of true absorption, free from various effects of scattering, by this technique showed an increase of absorption by weak blue light and a decrease of absorption by strong blue light for almost all of the leaves of 20 plant species examined. These weak- and strong-light responses in absorption were reversible. The fractional increase and decrease of absorbance at 678 nm by weak and strong light were highest, +20% and -31%, for leaves of Begonia semperflorens Link et Otto, and +12% and -13% for leaves of foxtail, Setaria viridis (L.) Beauv., the species examined in further experiments. The response to strong light proceeded to completion earlier than did that to weak light. The strong-light response could be observed separately from the weak-light response by using a leaf pre-irradiated with weak blue light. The responses were measured as a function of light intensity by scanning a single leaf irradiated locally at different intensities, and the action spectra for these responses were measured by scanning a leaf irradiated locally at different wavelengths but at identical intensities. The action spectra for these opposite responses were similar, and showed a band at 450 nm with shoulders but no band in the red region. Microscopic observations of chloroplasts in leaves during irradiation indicated that these changes in absorption are mostly due to rearrangements of chloroplasts in cells caused by irradiation. PMID:24458792

Inoue, Y; Shibata, K

1973-12-01

292

In situ measurements of the optical absorption of dioxythiophene-based conjugated polymers  

E-print Network

Conjugated polymers can be reversibly doped by electrochemical means. This doping introduces new subband-gap optical absorption bands in the polymer while decreasing the band-gap absorption. To study this behavior, we have ...

Hwang, J.

293

Triple band polarization-independent metamaterial absorber with bandwidth enhancement at X-band  

NASA Astrophysics Data System (ADS)

In this paper, we propose a triple band polarization-independent metamaterial absorber using square-shaped closed ring resonators over wide angle of incidence. The unit cell consisting of various square loops is designed by using the parametric analysis so that it exhibits a triple band absorption response with two bands lying in C-band and one in X-band for airborne and surveillance radar signal absorption applications. Furthermore, in X-band, the absorber exhibits a broadband response with full width at half maxima bandwidth of 940 MHz (9.43%). The structure exhibits bandwidth enhanced properties for any angle of polarization under normal incidence. It also shows high absorption for wide angle of incidence up to 60. The proposed structure is fabricated and experimental results show proper matching with the simulated responses.

Bhattacharyya, Somak; Ghosh, Saptarshi; Vaibhav Srivastava, Kumar

2013-09-01

294

Absorption cross-section measurements of methane, ethane, ethylene and methanol at high temperatures  

NASA Astrophysics Data System (ADS)

Mid-IR absorption cross-sections are measured for methane, ethane, ethylene and methanol over 2800-3400 cm-1 (2.9-3.6 ?m) spectral region. Measurements are carried out using a Fourier-Transform-Infrared (FTIR) spectrometer with temperatures ranging 296-1100 K and pressures near atmospheric. As temperature increases, the peak cross-sections decrease but the wings of the bands increase as higher rotational lines appear. Integrated band intensity is also calculated over the measured spectral region and is found to be a very weak function of temperature. The absorption cross-sections of the relatively small fuels studied here show dependence on the bath gas. This effect is investigated by studying the variation of absorption cross-sections at 3.392 ?m using a HeNe laser in mixtures of fuel and nitrogen, argon, or helium. Mixtures of fuel with He have the highest value of absorption cross-sections followed by Ar and N2. Molecules with narrow absorption lines, such as methane and methanol, show strong dependence on bath gas than molecules with relatively broader absorption features i.e. ethane and ethylene.

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

2014-09-01

295

Enhanced band edge luminescence from stress and defect free GaN nanowall network morphology  

NASA Astrophysics Data System (ADS)

We report on very high brightness of high quality, dislocation free GaN nanowall network. The GaN nanowall network sample was grown by plasma assisted molecular beam epitaxy and the optical properties were investigated by photoluminescence (PL) and absorption spectroscopy. Other nanostructures and flat structures were grown for comparison and a standard epilayer was used as a reference sample. The PL intensity of the nanowall network structure was observed to be a hundred times more than nanostructures consisting of tubes, as well as flat films. To explain the broadness and the peak position values, strain was calculated by X-ray diffraction studies and a band diagram was proposed to elucidate the structure of these films using PL, absorption and XPS valence band values.

Thakur, Varun; Kesaria, Manoj; Shivaprasad, S. M.

2013-10-01

296

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

297

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

PubMed

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

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

2012-12-01

298

Indication for dominating surface absorption in crystalline silicon test masses at 1550 nm  

NASA Astrophysics Data System (ADS)

The sensitivity of future gravitational wave (GW) observatories will be limited by thermal noise in a wide frequency band. To reduce thermal noise, the European GW observatory Einstein GW Telescope (ET) is suggested to use crystalline silicon test masses at cryogenic temperature and a laser wavelength of 1550?nm. Here, we report a measurement of the optical loss in a prototype high-resistivity crystalline silicon test mass as a function of optical intensity at room temperature. The total loss from both the bulk crystal and the surfaces was determined in a joint measurement. The characterization window ranged from small intensities below 1?W?cm-2, as planned to be used in ET, up to 21?kW?cm-2. A nonlinear absorption was observed for intensities above a few kW?cm-2. In addition, we have observed an intensity-independent offset that possibly arises from absorption in the crystal surfaces. This absorption was estimated to ?surf ? 800??ppm/surface, which might be too high for a cryogenic operation of a fiber-suspended silicon test mass. Such an offset was not observed in other recent measurements that were insensitive to surface absorption. Finally, a set of further characterization measurements is proposed to clearly separate the contributions from the surfaces and the bulk crystal.

Khalaidovski, Alexander; Steinlechner, Jessica; Schnabel, Roman

2013-08-01

299

Neural network cloud screening algorithm Part II: global synthetic cases using high resolution spectra in O2 and CO2 near infrared absorption bands in nadir and sun glint  

NASA Astrophysics Data System (ADS)

In Part I a set of two layer feed-forward neural networks, trained via back propagation of sensitivities, was applied to a synthetic set of radiances in micro-windows of the near-infrared to make predictions of cloud water (cw), cloud ice (ci), effective scattering heights of cloud water and ice, (pcw and pci, respectively) and the column water vapor (w). A threshold test, using 2 g/m-2 for cloud water and 10 g/m-2 for cloud ice, was applied to the retrieved values to distinguish clear from cloudy scenes. In that work the discussion was limited to the nadir viewing geometry, and was applied only to land surfaces, excluding desert and snow and ice fields. Part II describes the extension to a set of high resolution radiances, as might be measured by a grating spectrometer from space, in both nadir and sun glint viewing geometries. Furthermore, results are given for all land surface types as well as scenes over ocean. Prior to neural network training, a Principal Component Analysis (PCA) is applied to the high resolution spectra, which consist of three bands centered at 0.76?m (O2 A-band), 1.61?m (weak CO2 band) and 2.06?m (strong CO2 band), each with 1016 channels. Analysis shows that the five leading EOFs together capture 99.9% of the variance in each band, reducing the data size by more than two orders of magnitude. Application of the trained neural networks to an independent data set, generated using CloudSat and Calipso cloud and aerosol profiles, as well as carbon dioxide profiles from a chemical transport model, were used to quantify the skill in the retrieval. The results vary significantly with surface type, viewing mode and cloud properties. Accuracies range from 7% to 100% (typically close to 75%), with confidence levels almost always greater than 90%.

Taylor, Thomas E.; O'Brien, D. M.

2010-03-01

300

Radiation Induced Optical Absorption of Cubic Lead Fluoride Crystals and the Effect of Annealing  

NASA Astrophysics Data System (ADS)

Transparent and colorless lead fluoride crystals with sizes of 20 20 20 (mm3) are irradiated with several doses of ?-rays from a 60 Co source. Their transmittance spectra before and after irradiation are measured, and a new parameter ?T = Tb - Ta is defined to evaluate the irradiation damage. Three optical absorption bands peaking at 270 nm, 370 nm and 500 nm are found in the plots of ?T versus wavelength, and their intensities increase with the irradiation dose. These optical absorption bands, except the one at 270 nm, can recover spontaneously with time. Thermal annealing treatment can enhance this recovery of the transmittance, while the optimum annealing temperature for different samples depends on the irradiation dose.

Ren, Guo-Hao; Chen, Xiao-Feng; Li, Huan-Ying; Wu, Yun-Tao; Shi, Hong-Sheng; Qin, Lai-Shun

2014-08-01

301

Surface-Enhanced Infrared Absorption  

Microsoft Academic Search

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

Masatoshi Osawa

2001-01-01

302

Infrared- and millimeter-wavelength absorption in the atmospheric windows by water vapor and nitrogen - Measurements and models  

NASA Astrophysics Data System (ADS)

The current knowledge of the water vapor window regions from 10 to 1000 GHz, 8 to 12 microns, 3 to 5 microns, and 2 to 2.5 microns is reviewed with emphasis on the continuum absorption observed in each window region. The observed frequency dependence in each window is consistent with the concept of far wings emanating from the bordering water vapor absorption bands, which provides a promising basis for modeling continuum absorption. Theoretical line-shape models predict the observed frequency and pressure dependence of absorption but thus far not the temperature dependence. A model for the integrated intensity of the nitrogen continuum is developed as a function of density and temperature.

Thomas, Michael E.

1988-01-01

303

Thermoluminescence, electron paramagnetic resonance and optical absorption in natural and synthetic rhodonite crystals  

NASA Astrophysics Data System (ADS)

Thermoluminescence, electron paramagnetic resonance and optical absorption properties of rhodonite, a natural silicate mineral, have been investigated and compared to those of synthetic crystal, pure and doped. The TL peaks grow linearly for radiation dose up to 4 kGy, and then saturate. In all the synthetic samples, 140 and 340C TL peaks are observed; the difference occurs in their relative intensities, but only 340C peak grows strongly for high doses. Al2O3 and Al2O3 + CaO-doped synthetic samples presented several decades intenser TL compared to that of synthetic samples doped with other impurities. A heating rate of 4C/s has been used in all the TL readings. The EPR spectrum of natural rhodonite mineral has only one huge signal around g = 2.0 with width extending from 1,000 to 6,000 G. This is due to Mn dipolar interaction, a fact proved by numerical calculation based on Van Vleck dipolar broadening expression. The optical absorption spectrum is rich in absorption bands in near-UV, visible and near-IR intervals. Several bands in the region from 540 to 340 nm are interpreted as being due to Mn3+ in distorted octahedral environment. A broad and intense band around 1,040 nm is due to Fe2+. It decays under heating up to 900C. At this temperature it is reduced by 80% of its original intensity. The pink, natural rhodonite, heated in air starts becoming black at approximately 600C.

Paio, J. R. B.; Watanabe, S.

2008-10-01

304

Band gap enhancement of glancing angle deposited TiO2 nanowire array  

NASA Astrophysics Data System (ADS)

Vertically oriented TiO2 nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters 80 nm and 40 nm TiO2 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 TiO2. 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-1 of anatase Eg) and blue (7.4 cm-1 of rutile Eg, 7.8 cm-1 of rutile A1g) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and 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.

Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C.; Chattopadhyay, K. K.; Bhattacharya, Sekhar

2012-09-01

305

Temperature activated absorption during laser-induced damage: The evolution of laser-supported solid-state absorption fronts  

SciTech Connect

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.

Carr, C W; Bude, J D; Shen, N; Demange, P

2010-10-26

306

Ionic-to-neutral phase transformation induced by photoexcitation of the charge-transfer band in tetrathiafulvalene-p-chloranil crystals  

NASA Astrophysics Data System (ADS)

The transformation from ionic to neutral phases in tetrathiafulvalene-p-chloranil crystals is induced by exciting the charge-transfer absorption band below the transition temperature. The transformation takes place only above a threshold intensity of excitation, and the efficiency of generating neutral-phase domains is lower than the case induced by the excitation in intramolecular optical transitions of tetrathiafulvalene molecules. The mechanism of the photoinduced phase transition in this crystal is discussed based on these results.

Suzuki, T.; Sakamaki, T.; Tanimura, K.; Koshihara, S.; Tokura, Y.

1999-09-01

307

Collision-induced absorption and anisotropy of the intermolecular potential  

NASA Astrophysics Data System (ADS)

A scheme is developed for quantum mechanical calculations of binary collision-induced spectra which permits full inclusion of rotovibrational molecular degrees of freedom. A close-coupling scheme which includes the radiation in the Hamiltonian is used. The collision- induced absorption spectra of interacting atom-diatom and diatom-diatom pairs are investigated. The inclusion of the anisotropy of the inter-molecular potential introduces couplings among the rotational levels of the diatomic molecules. Previous calculations of collision- induced spectra have almost exclusively been done using the isotropic potential approximation and we present an extensive investigation of the validity of that approximation. Absorption spectra in the rotational and fundamental bands of H 2, induced by collisions with He, H, Ar, and H2 are calculated for various temperatures. In all of these, except for H2- H, the anisotropy of the intermolecular potential affect the absorption by 5 10% in certain parts of the spectra. Comparisons with the available measurements show very good agreement of the shapes of the spectral profiles, although the absolute intensities differ by up to 10% in some cases. These remaining differences between theory and measurements appear to be random and are generally smaller than the differences among comparable measurements. In the H 2-H spectra the effect of the anisotropy of the potential turns out to be almost negligible at the temperature for which a full coupled quantum calculation was done. This is supported by spectral moment calculations. The smallness of the effect is believed to stern from the short range character of the anisotropy potential components for H2-H. Collision-induced absorption spectra of gaseous mixtures of deuterium hydride and helium in the rotational and fundamental bands of HD are calculated at a temperature of 77 K. The computed absorption profile agree with a measurement taken in the HD fundamental band. We also consider the interference phenomena of the HD permanent dipole with the HD-He interaction-induced dipole by computing the wings of various R(j) lines and of the P1(1) line in the single, binary collision limit. Agreement between theory and measurements is observed in the low-helium-density limit of the measured absorption line shapes.

Gustafsson, Magnus Sven

308

Clear atmospheric effects on insolation illustrated by broad-band radiometer measurements  

SciTech Connect

Spectral measurements from the Solar Energy Meteorological Research and Training Site - Region II monitoring station - are used to determine some of the effects of the cloudless atmosphere on the surface insolation. The effects illustrated are aerosol scattering and absorption, attenuation by volcanic dust clouds, and water vapor absorption. Parameters determined from the measurements are also compared to the results from a radiative transfer model. The direct and global solar infrared spectrum decreases with increasing dew point. A linear regression between dew point and the direct and global intensities under clear skies resulted in predictive errors less than 10%. The visible portions of the spectrum were not effected. The measured aerosol optical depths were compared to the results of a radiative transfer model. The diffuse-to-direct ratio increased with increasing optical depth in a similar fashion in both the radiative transfer model and measurements. The El Chichon dust cloud reduced the solar direct intensity in late summer of 1982. The effect was most pronounced in the 620-690 nm spectral band, although all bands were reduced. The global intensity was not measurably affected. The Mt. St. Helens dust cloud produced a dramatic insolation reduction over several days, but had no measurable long-term effect.

Spencer, D.W.

1983-01-01

309

Multi-band, highly absorbing, microwave metamaterial structures  

NASA Astrophysics Data System (ADS)

A further example of multi-band absorption using ultra-thin, polarization-insensitive, wide-angled metamaterial absorbers that operate in multi-frequency bands within the microwave regime is presented in this work. The basic structure geometry is utilised to create multi-band highly absorbing structures by incorporating the scalability property of the metamaterials. Simulation results verify the structure's ability for high absorption. The multi-band absorbers are promising candidates as absorbing elements in scientific and technical applications because of its multi-band absorption, polarization insensitivity, and wide-angle response. Finally, the current distributions for those structures are presented to gain a better insight into the physics behind the multiple absorption mechanism.

Kollatou, T. M.; Dimitriadis, A. I.; Assimonis, S. D.; Kantartzis, N. V.; Antonopoulos, C. S.

2014-05-01

310

Nonlinear absorption and excited state dynamics in Rhodamine B studied using Z-scan and degenerate four wave mixing techniques  

Microsoft Academic Search

We report our experimental results of nonlinear absorption and excited state dynamics in Rhodamine B solutions at 532 nm, on resonance of the absorption band and 600 nm at the absorption edge, studied using the standard Z-scan and degenerate four wave mixing techniques. We observed saturable absorption at 532 nm and a transition from saturable absorption to reverse saturable absorption

S. Venugopal Rao; N. K. M. Naga Srinivas; D. Narayana Rao

2002-01-01

311

EXTINCTION AND POLYCYCLIC AROMATIC HYDROCARBON INTENSITY VARIATIONS ACROSS THE H II REGION IRAS 12063-6259  

SciTech Connect

The spatial variations in polycyclic aromatic hydrocarbon (PAH) band intensities are normally attributed to the physical conditions of the emitting PAHs, however in recent years it has been suggested that such variations are caused mainly by extinction. To resolve this question, we have obtained near-infrared (NIR), mid-infrared (MIR), and radio observations of the compact H II region IRAS 12063-6259. We use these data to construct multiple independent extinction maps and also to measure the main PAH features (6.2, 7.7, 8.6, and 11.2 {mu}m) in the MIR. Three extinction maps are derived: the first using the NIR hydrogen lines and case B recombination theory; the second combining the NIR data with radio data; and the third making use of the Spitzer/IRS MIR observations to measure the 9.8 {mu}m silicate absorption feature using the Spoon method and PAHFIT (as the depth of this feature can be related to overall extinction). The silicate absorption over the bright, southern component of IRAS 12063-6259 is almost absent while the other methods find significant extinction. While such breakdowns of the relationship between the NIR extinction and the 9.8 {mu}m absorption have been observed in molecular clouds, they have never been observed for H II regions. We then compare the PAH intensity variations in the Spitzer/IRS data after dereddening to those found in the original data. It was found that in most cases, the PAH band intensity variations persist even after dereddening, implying that extinction is not the main cause of the PAH band intensity variations.

Stock, D. J.; Peeters, E.; Otaguro, J. N. [Department of Physics and Astronomy, University of Western Ontario, London, ON N6A 3K7 (Canada); Tielens, A. G. G. M. [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 RA Leiden (Netherlands); Bik, A. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, D-69117 Heidelberg (Germany)

2013-07-01

312

Suppression of thermal carrier escape and efficient photo-carrier generation by two-step photon absorption in InAs quantum dot intermediate-band solar cells using a dot-in-well structure  

NASA Astrophysics Data System (ADS)

We investigated the effects of an increase in the barrier height on the enhancement of the efficiency of two-step photo-excitation in InAs quantum dot (QD) solar cells with a dot-in-well structure. Thermal carrier escape of electrons pumped in QD states was drastically reduced by sandwiching InAs/GaAs QDs with a high potential barrier of Al0.3Ga0.7As. The thermal activation energy increased with the introduction of the barrier. The high potential barrier caused suppression of thermal carrier escape and helped realize a high electron density in the QD states. We observed efficient two-step photon absorption as a result of the high occupancy of the QD states at room temperature.

Asahi, S.; Teranishi, H.; Kasamatsu, N.; Kada, T.; Kaizu, T.; Kita, T.

2014-08-01

313

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

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...

Jung, Youngeui

2013-01-01

314

Flat-band potentials of GaN and InGaN\\/GaN QWs by bias-dependent photoluminescence in electrolyte solution  

Microsoft Academic Search

Flat-band potentials of n-GaN and selectively doped n-In0.17Ga0.83N\\/GaN quantum wells (QWs) grown by metalorganic vapor phase epitaxy are determined by measuring the bias dependence of photoluminescence intensity in electrolyte solutions for different pHs. The In0.17Ga0.83N\\/GaN QWs with the absorption edge of 430nm in the photocurrent spectrum, has a lower flat-band potential (?0.86V vs. AgAgCl ) than that of n-GaN (?1.07V),

Naoki Kobayashi; Ryusuke Morita; Toru Narumi; Jun Yamamoto; Yuzaburo Ban; Kiyohide Wakao

2007-01-01

315

Computation of energy interaction parameters as well as electric dipole intensity parameters for the absorption spectral study of the interaction of Pr(III) with L-phenylalanine, L-glycine, L-alanine and L-aspartic acid in the presence and absence of Ca 2+ in organic solvents  

NASA Astrophysics Data System (ADS)

Studying the absorption difference and comparative absorption spectra of the interaction of Pr(III) and Nd(III) with L-phenylalanine, L-glycine, L-alanine and L-aspartic acid in the presence and absence of Ca 2+ in organic solvents, various energy interaction parameters like Slater-Condon ( FK), Racah ( Ek), Lande factor ( ?4f), nephelauxetic ratio ( ?), bonding ( b1/2), percentage-covalency ( ?) have been evaluated applying partial and multiple regression analysis. The values of oscillator strength ( P) and Judd-Ofelt electric dipole intensity parameter T? ( ? = 2, 4, 6) for different 4f-4f transitions have been computed. On analysis of the variation of the various energy interaction parameters as well as the changes in the oscillator strength ( P) and T? values reveal the mode of binding with different ligands.

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

2009-10-01

316

Molecular simulation of the complexation effects on conformations and electronic absorption spectra of crown ether styryl dyes  

NASA Astrophysics Data System (ADS)

The structure and spectra of new styryl dyes containing a crown ether moiety and a sulfoalkyl group along with their complexes with metal cations are investigated using spectroscopic methods and computer simulation. Large differences between the absorption spectra of the cis form and its complexes with alkaline earth metals are found. The absorption maximum of the high intensity longwave band is at 429 nm for the cis form and at 321-328 nm for the complexes. We show that this difference results from a large distortion of the chromophore geometry, which arises from the formation of an intramolecular coordination bond between the sulfo group and the metal cation captured in the crown cavity. For the distorted geometry, the first electronic transition is symmetry forbidden. The disappearance of the longwave band results in a large hypsochromic shift, observed experimentally.

Baskin, I. I.; Burshtein, K. Ya.; Bagatur'yants, A. A.; Gromov, S. P.; Alfimov, M. V.

1992-11-01

317

Unified picture of the photoexcitations in phenylene-based conjugated polymers: Universal spectral and dynamical features in subpicosecond transient absorption  

SciTech Connect

Using subpicosecond transient absorption spectroscopy, we investigate the primary photoexcitations in thin films and solutions of several phenylene-based conjugated polymers and an oligomer. We identify several features in the transient absorption spectra and dynamics that are common to all of the materials which we studied from this family. The first spectral feature is a photoinduced absorption (PA) band peaking near 1 eV that has intensity-dependent dynamics that match the stimulated emission dynamics exactly over two orders of magnitude in excitation density. This band is associated with singlet intrachain excitons. The second spectral feature (observed only in thin films and aggregated solutions) is a PA band peaking near 1.8 eV, that is longer lived than the 1 eV exciton PA band, and that has dynamics that are independent (or weakly dependent) on excitation density. This feature is attributed to polarons, generated through a mechanism that is sample dependent. In pristine samples, polarons are generated via a mechanism that is quadratic in exciton density, whereas in photodegraded samples or samples doped with electron acceptors, the generation mechanism becomes linear in exciton density. (c) 2000 The American Physical Society.

Kraabel, B. [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Klimov, V. I. [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Kohlman, R. [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Xu, S. [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Wang, H-L. [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); McBranch, D. W. [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Chemical Science and Technology Division, CST-6, MS-J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2000-03-15

318

Angle-resolved resonant photoemission at the MIII absorption threshold of Co and Fe metal  

NASA Astrophysics Data System (ADS)

We report on an angle-resolved resonant photoemission study of Co and Fe metal at the MIII absorption threshold. The intensity of the various spectral components was measured as a function of the electron emission angle relative to the E vector of the incident light. On MIII resonance, the main valence-band photoemission (PE) intensity of Co and Fe metal, located between EF and 3 eV, follows a cos2? behavior, as is expected for a photoemission process. However, the intensity of the enhanced feature located at ~5 eV is found to be almost independent of the emission angle, as expected for an incoherent Auger process. This clearly shows that the enhancement of the 5 eV PE signal is mainly caused by an incoherent Auger decay and not by a resonant PE process.

Gutirrez, A.; Lpez, M. F.

1997-07-01

319

Microwave radiation absorption: Behavioral effects  

SciTech Connect

The literature contains much evidence that absorption of microwave energy will lead to behavioral changes in man and laboratory animals. The changes include simple perturbations or outright stoppage of ongoing behavior. On one extreme, intense microwave absorption can result in seizures followed by death. On the other extreme, man and animals can hear microwave pulses at very low rates of absorption. Under certain conditions of exposure, animals will avoid microwaves, while under other conditions, they will actively work to obtain warmth produced by microwaves. Some research has shown behavioral effects during chronic exposure to low-level microwaves. The specific absorption rates that produce behavioral effects seem to depend on microwave frequency, but controversy exists over thresholds and mechanism of action. In all cases, however, the behavioral disruptions cease when chronic microwave exposure is terminated. Thermal changes in man and animals during microwave exposure appear to account for all reported behavioral effects. 66 refs.

D'Andrea, J.A. (Naval Aerospace Medical Research Laboratory, Naval Air Station, Pensacola, FL (USA))

1991-07-01

320

Laparoscopic gastric banding  

MedlinePLUS

Lap-Band; LAGB; Laparoscopic adjustable gastric banding; Bariatric surgery - laparoscopic gastric banding ... J, Welch G, Zagarins S, Kuhn J, Romanelli J. Bariatric surgery for the treatment of morbid obesity: a meta- ...

321

Band gap effects of hexagonal boron nitride using oxygen plasma  

NASA Astrophysics Data System (ADS)

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.

Sevak Singh, Ram; Yingjie Tay, Roland; Leong Chow, Wai; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

2014-04-01

322

Effects of CO2 on H2O band profiles and band strengths in mixed H2O:CO2 ices  

E-print Network

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.

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

323

Effects of ?-ray irradiation on optical absorption and laser damage performance of KDP crystals containing arsenic impurities.  

PubMed

The effects of ?-irradiation on potassium dihydrogen phosphate crystals containing arsenic impurities are investigated with different optical diagnostics, including UV-VIS absorption spectroscopy, photo-thermal common-path interferometer and photoluminescence spectroscopy. The optical absorption spectra indicate that a new broad absorption band near 260 nm appears after ?-irradiation. It is found that the intensity of absorption band increases with the increasing irradiation dose and arsenic impurity concentration. The simulation of radiation defects show that this absorption is assigned to the formation of AsO4 4- centers due to arsenic ions substituting for phosphorus ions. Laser-induced damage threshold test is conducted by using 355 nm nanosecond laser pulses. The correlations between arsenic impurity concentration and laser induced damage threshold are presented. The results indicate that the damage performance of the material decreases with the increasing arsenic impurity concentration. Possible mechanisms of the irradiation-induced defects formation under ?-irradiation of KDP crystals are discussed. PMID:25402141

Guo, D C; Jiang, X D; Huang, J; Wang, F R; Liu, H J; Xiang, X; Yang, G X; Zheng, W G; Zu, X T

2014-11-17

324

Photo-absorption studies on carbonyl sulphide in 30,000-91,000 cm-1 region using synchrotron radiation  

NASA Astrophysics Data System (ADS)

Photo-absorption spectrum of carbonyl sulphide (OCS) is recorded in 30,000-91,000 cm-1 (3300-1050 ) region at an average resolution of 1.2 using Photo-physics beamline on the 450 MeV Indus-1 synchrotron radiation source at RRCAT Indore, India. Owing to significant absorption cross section dependence, spectra of OCS are recorded at various pressures (0.001-5 mbar) to optimize the S/N ratio for band systems appearing at different energy regions. The spectral region below 70,000 cm-1 has contributions from dissociation mechanism of the ground state of OCS and three valence band systems arising from promotion of a 3? electron to 4? and 10? orbital. Improved S/N ratio helped in unambiguous assignment of the valence band progressions at 42,000-48,000 cm-1, 53,000-62,000 cm-1 and 63,500-70,000 cm-1 regions to the 1??X1?+ transition, the relatively intense and sharp bands of 1??X1?+ transition and intense but broad bands of 1?+?X1?+ transition, respectively, and obtain the vibrational frequencies. Above 70,000 cm-1 Rydberg series arising from s, p, d and f orbitals converging to the ionic ground state X2? of OCS+ (90,121 cm-1) are identified. Long progression in the first few members of the Rydberg series is suggestive of mixed valence character. Quantum defects are evaluated and used to discuss the nature of the molecular orbital. The present study provides a unifying picture of the VUV photo-absorption spectrum of OCS up to its first ionization limit.

Sunanda, K.; Rajasekhar, B. N.; Saraswathy, P.; Jagatap, B. N.

2012-01-01

325

Franck-Condon simulation of the B-A bands of BO  

NASA Astrophysics Data System (ADS)

Franck-Condon simulation of the emission B-A band system of boron monoxide are given. The computed band origin wavenumbers are found to be in good agreement with those derived from measured band head positions. In the absence of intensity measurements for the B-A bands, the simulated intensities were tested by calculation of the relative intensities of the well known A-X bands under the assumption that the electronic transition moment function is constant. The resulting good agreement between the simulated and experimentally obtained intensity patterns for A-X bands supports the reliability of our simulated B-A spectrum.

Anti?-Jovanovi?, A.; Kuzmanovi?, M.; Khakoo, M. A.; Laher, R. R.

2013-12-01

326

Absorption spectra of crystalline limestones experimentally deformed or tectonised  

NASA Astrophysics Data System (ADS)

Diffuse-reflectance spectra have been measured for a series of samples of Carrara marble experimentally deformed under different cylindrical stress ( P = 0, 100, 250, 500, 980 bars). The creation of point defects that results has been shown up classically by irradiation with ? rays (40 krads), thus producing a typical blue coloration linked with the formation of colour centres. The diffuse-reflectance spectra, measured on powders with a microscope-spectrometer in the visible range (400-800 nm), allow the determination of the absorption spectra by means of the Kubelka-Munk function. These absorption spectra have been measured for each of the deformed samples, as well as for different fractions of a very deformed specimen subsequently heated at temperatures between 100 and 500 C for a fixed time. In the same way, tectonised crystalline limestones, of various origins, were studied without any other treatment than the irradiation with ? rays. From this study the following preliminary conclusions have been drawn: (1) The absorption spectrum of an undeformed but merely irradiated specimen of crystalline limestone is practically monotonous, but in the deformed specimens a broad band of absorption appears, having a maximum at 620 nm with several shoulders, the chief of which is at 520 nm. (2) This absorption band shows the existence of colour centres, the density of which can be estimated relatively by means of the chromaticity coordinates x and y of the C.I.E. obtained from the diffuse-reflectance spectra (C.I.E. = Commission Internationale de l'clairage). (3) An overgrinding of calcite generates defects that have the same spectra as those produced during the experimental deformation. Consequently, in obtaining the powders of grain size 50-80 ?m needed for the diffuse spectrometry, great care must be exercised. (4) For a given confining pressure, the defect density is proportional to the deformation rate. (5) One can calibrate the effect of the annealing of crystalline limestone deformed at 1000 bars by means of the ratio Q of the intensities of the absorption peaks at 510 and 620 nm. The curve Q = (tC) is exponential. The experimental curves show the density of the point defects created by the deformation on the one hand and on the other their healing as a function of the temperature. Further studies are being carried out in order to determine how far the plotting (on these experimental calibrations) of the chromaticity coordinates x and y and of the ratio Q of natural tectonised crystalline limestones allows the estimation of the latest orogenic pressures to which they have been subjected, as well as the temperatures reached since the last tectonic phase.

Cervelle, B.; ChayD'Albissin, M.; Gouet, G.; Visocekas, R.

1982-11-01

327

Inter-band optoelectronic properties in quantum dot structure of low band gap III-V semiconductors  

NASA Astrophysics Data System (ADS)

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?) 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, Hg1-xCdxTe, and In1-xGaxAsyP1-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.

Dey, Anup; Maiti, Biswajit; Chanda Sarkar, Debasree

2014-04-01

328

Density functional calculation of the electronic absorption spectrum of Cu{sup +} and Ag{sup +} aqua ions  

SciTech Connect

The UV absorption of aqueous Cu{sup +} and Ag{sup +} has been studied using Time Dependent Density Functional Theory (TDDFT) response techniques. The TDDFT electronic spectrum was computed from finite temperature dynamical trajectories in solution generated using the Density Functional Theory (DFT) based Ab Initio Molecular Dynamics (AIMD) method. The absorption of the two ions is shown to arise from similar excitation mechanisms, namely transitions from d orbitals localized on the metal center to a rather delocalized state originating from hybridization of the metal s orbital to the conduction band edge of the solvent. The ions differ in the way the spectral profile builds up as a consequence of solvent thermal motion. The Cu{sup +} absorption is widely modulated, both in transition energies and intensities by fluctuations in the coordination environment which is characterized by the formation of strong coordination bonds to two water molecules in an approximately linear geometry. Though, on average, absorption intensities are typical of symmetry forbidden transitions of metal ions in the solid state, occasionally very short (<100 fs) bursts in intensity are observed, associated with anomalous Cu-H interactions. Absorption by the Ag{sup +} complex is in comparison relatively stable in time, and can be interpreted in terms of the energy splitting of the metal 4d manifold in an average crystal field corresponding to a fourfold coordination in a distorted tetrahedral arrangement. Whereas the spectral profile of the Ag{sup +} aqua ion is in good agreement with experiment, the overall position of the band is underestimated by 2 eV in the BLYP approximation to DFT. The discrepancy with experiment is reduced to 1.3 eV when a hybrid functional (PBE0) is used. The remaining inaccuracy of TDDFT in this situation is related to the delocalized character of the target state in d{yields}s transitions.

Bernasconi, Leonardo; Blumberger, Jochen; Sprik, Michiel; Vuilleumier, Rodolphe [Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW (United Kingdom); Laboratoire de Physique Theorique des Liquides, Universite P. et M. Curie, 4 Place Jussieu, 75005 Paris (France)

2004-12-15

329

Gas in scattering media absorption spectroscopy - GASMAS  

Microsoft Academic Search

An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many

Sune Svanberg

2008-01-01

330

Optical absorption in paired correlated random lattices  

NASA Astrophysics Data System (ADS)

Optical absorption in a random one-dimensional lattice in the presence of paired correlated disorder is studied. The absorption line shape is evaluated by solving the microscopic equations of motion of the Frenkel-exciton problem in the lattice. We find that paired correlation causes the occurrence of well-defined characteristic lines in the absorption spectra which clearly differ from the case of unpaired correlation. The behavior of the absorption lines as a function of defect concentration is studied in detail. We also show how exciton dynamics can be inferred from experimental data by deriving an analytical expression relating the energy and intensity of lines to the model parameters.

Domnguez-Adame, Francisco; Maci, Enrique; Snchez, Angel

1994-09-01

331

Deep Searches for High Redshift Molecular Absorption  

E-print Network

Millimetre-band scans of the frequency space towards optically dim quasars is potentially a highly efficient method for detecting new high redshift molecular absorption systems. Here we describe scans towards 7 quasars over wide bandwidths (up to 23 GHz) with sensitivity limits sufficient to detect the 4 redshifted absorbers already known. With wider frequency bands, highly efficient searches of large numbers of possibly obscured objects will yield many new molecular absorbers.

S. J. Curran; J. K. Webb; M. T. Murphy; N. Kuno

2003-10-21

332

Perceiving the Intensity of Light  

ERIC Educational Resources Information Center

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,

Purves, Dale; Williams, S. Mark; Nundy, Surajit; Lotto, R. Beau

2004-01-01

333

High-Frequency Absorption Properties of Three Kinds of Hollow Multiphase Ceramic Microspheres  

NASA Astrophysics Data System (ADS)

Al-TiO2-Fe2O3-MnO2-Fe-Sucrose-Epoxy Resin as reaction system and self-reactive quenching technology which combines flame thermal spraying, self-propagating high-temperature synthesis and rapid solidification, were used to prepare three kinds of hollow multiphase ceramic microspheres (HMCMs) in different feeding gas (N2, O2) and dimension (coarse, fine). The characteristic results of three kinds of HMCMs indicated that various process parameters containing feeding gas and initial agglomerate size in this study can result in the change of surface organization, composition, morphology, and dimension. Investigation of microwave electromagnetic (EM) characteristics of three kinds of HMCMs showed that intrinsic characteristics play an important role in the determining the resulting properties. At 10-14.5 GHz, No. 3 HMCMs possess weak absorption intensity and narrow effective bandwidth (<-10 dB) owing to smaller dimension, but in higher-frequency band (14.5-17 GHz), an obvious absorption peak appears due to good EM match and nano-effects. Compared with No. 1 (O2 coarse) and No. 3 (O2 fine) HMCMs, enhanced absorption intensity and effective bandwidth (<-10 dB) were observed in No. 2 (N2 coarse) HMCMs. Enhancements of absorption intensity and effective bandwidth are associated with extra nitride (AlN, FeN), partial open microspheres, M-hexagonal crystal and micro-nano thick dendrite. No. 2 HMCMs presented excellent microwave-absorption property, with the minimum reflectivity ( R L) of -27.7 dB at 12.9 GHz. The effective bandwidth (<-10 dB) could reach to 4.1 GHz (10.9-15 GHz). This may be ascribed to the increased conductance loss, multiple scattering, magnetocrystalline anisotropy, and shape anisotropy.

Lou, Hongfei; Wang, Jianjiang; Hou, Yongshen; He, Ming; Zhao, Zhining

2014-02-01

334

Inverse bremsstrahlung absorption in spherical laser targets  

NASA Astrophysics Data System (ADS)

Inverse bremsstrahlung has been incorporated into an analytical model of the expanding corona of a laser-irradiated spherical target. Absorption decreases slowly with increasing intensity, in agreement with some numerical simulations, and contrary to estimates from simple models in use up to now, which are optimistic at low values of intensity and very pessimistic at high values. Present results agree well with experimental data from many laboratories; substantial absorption (of up to 0.5) is found up to moderate intensities, say below 10 to the 15th W per sq cm for light of 1.06 microns wavelength light. Anomalous absorption, when included in the analysis, leaves practically unaffected the ablation pressure and mass ablation rate, for given absorbed intensity. Universal results are given in dimensionless form.

Nicolas, J. A.; Sanmartin, J. R.

1985-03-01

335

Band gap narrowing in BaTiO3 nanoparticles facilitated by multiple mechanisms  

NASA Astrophysics Data System (ADS)

In the present work, BaTiO3 nanoparticles of four different size ranges were prepared by sol-gel method. The optical band gap of these particles at some size ranges has come down to 2.53 eV from 3.2 eV, resulting in substantial increase in optical absorption by these ferroelectric nanoparticles making them potential candidates for light energy harvesting. XRD results show the presence of higher compressive strain in 23 nm and 54 nm size particles, they exhibit a higher band gap narrowing, whereas tensile strain is observed in 31 nm and 34 nm particles, and they do not show the marginal band gap narrowing. The 23 nm and 54 nm particles also show a coupling of free carriers to phonons by increasing the intensity of LO phonon mode at 715 cm-1. The higher surface charge density is expected in case of enhanced surface optical Raman modes (638 cm-1) contained in 31 and 34 nm size particles. In addition to this, the red shift in an LO mode Raman spectral line at 305 cm-1 with decrease in particle size depicts the presence of phonon confinement in it. The enhanced optical absorption in 23 nm and 54 nm size particles with a narrowed band gap of 3 eV and 2.53 eV is due to exchange correlation interactions between the carriers present in these particles. In 31 nm and 34 nm range particles, the absorption got bleached exhibiting increased band gaps of 3.08 eV and 3.2 eV, respectively. It is due to filling up of conduction band resulting from weakening of exchange correlation interactions between the charge carriers. Hence, it is concluded that the band gap narrowing in the nanoparticles of average size 23 nm/54 nm is a consequence of multiple effects like strain, electron-phonon interaction, and exchange correlation interactions between the carriers which is subdued in some other size ranges like 31 nm/34 nm.

Ramakanth, S.; James Raju, K. C.

2014-05-01

336

Effect of solvents on the electronic absorption spectra of some salicylidene thioschiff bases  

NASA Astrophysics Data System (ADS)

The electronic absorption spectra of some salicylidine-2-aminothiophenol schiff bases are studied in nine solvents of different polarities. The spectra comprise five absorption bands: their wavelength maxima ' ?max' and the molar absorptivities '? max' are given. Band assignments of the observed absorption bands are given and correlated with the possible electronic transitions. The effect of solvents on the intranolecular CT bands is studied using the unified scale of solvent polarities for specific and non-specific interactions ( ECW model) in comparison with the ?- ?* scale.

Soliman, A. A.

1997-04-01

337

Computational search for direct band gap silicon crystals  

NASA Astrophysics Data System (ADS)

Due to its abundance, silicon is the preferred solar-cell material despite the fact that current silicon materials have indirect band gaps. Although the band gap properties of silicon have been studied intensively, until now, no direct band gap silicon-based material has been found or suggested. We report here the discovery of direct band gap silicon crystals. By using conformational space annealing, we optimize various crystal structures containing multiple (10 to 20) silicon atoms per unit cell so that their electronic structures become direct band gap. Through first-principles calculations, we identify many direct and quasidirect band gap crystal structures, which exhibit excellent photovoltaic efficiency.

Lee, In-Ho; Lee, Jooyoung; Oh, Young Jun; Kim, Sunghyun; Chang, K. J.

2014-09-01

338

Absorption dynamics of a femtosecond laser pulse at the surface of dielectrics  

NASA Astrophysics Data System (ADS)

We study numerically the propagation of an ultrashort laser pulse (sub-100 fs) ionizing a dielectric material (e.g. fused silica). Helmholtz equation for the electric field is integrated in time, coupled to a plasma model taking into account basic processes in the conduction band like nonlinear photoionization, impact ionization, self-trapped exciton relaxation, electron collisions in the conduction band and inverse bremsstrahlung. A detailed model of the critical surface (ne = ncr) reflecting a high intensity laser pulse is crucial for understanding the excitation of the material, and thus the absorption of the radiation, potentially leading to optical breakdown. Finally, we link our results to recent experimental findings about ultrafast ablation of fused silica in order to optimize the energy deposition for micromachining processes.

Lebugle, M.; Sanner, N.; Pierrot, S.; Utza, O.

2012-07-01

339

Interpretation of two photon absorption driven nonlinear absorption  

NASA Astrophysics Data System (ADS)

Extensive measurements and modeling of several two photon absorbing materials are described. These are used to elucidate the relative significance of various relaxation and excitation processes that come into play in nonlinear transmission (NLT) and two photon absorption cross section measurements. A reliable measurement of the one photon absorption cross sections at energies 0.5 to ~1.7 eV below the fundamental transition are presented with Voigt function fits that enable the determination of the Gaussian and Lorentzian line widths. Both a numerical model and an analytical model are developed neither of which use any adjustable parameters in comparing calculated NLT results to data. Both models fit the data relatively well over the full range of the experiment. The analytical model captures the primary causes of the nonlinear absorption in the low intensity regime and demonstrates that the nonlinear transmittance can be estimated as a simple effective three-photon process. The numerical model calculates the spatial and time dependence of three state populations and all of the transitions between these states. This model improves the quality of the nonlinear transmission fit which is due to the inclusion of the ground state absorption. Additionally an observation of a strong, long lived transient which is quenched by oxygen suggests multiphoton ionization is happening at low intensities. Thus the full range of constraints applicable to all measurements of the two photon cross section are presented.

McLean, Daniel G.; Sutherland, Richard L.; Rogers, Joy E.; Slagle, Jonathan E.; Brant, Mark C.; Fleitz, Paul A.

2005-08-01

340

Strong terahertz absorption using thin metamaterial structures  

SciTech Connect

Metamaterial absorbers with nearly 100% absorption in the terahertz (THz) spectral band have been designed and fabricated using a periodic array of aluminum (Al) squares and an Al ground plane separated by a thin silicon dioxide (SiO{sub 2}) dielectric film. The entire structure is less than 1.6 mm thick making it suitable for the fabrication of microbolometers or bi-material sensors for THz imaging. Films with different dielectric layer thicknesses exhibited resonant absorption at 4.1, 4.2, and 4.5 THz with strengths of 98%, 95%, and 88%, respectively. The measured absorption spectra are in good agreement with simulations using finite element modeling.

Alves, Fabio [Naval Postgraduate School, Monterey, CA; Kearney, Brian [Naval Postgraduate School, Monterey, CA; Grbovic, Dragoslav [ORNL; Lavrik, Nickolay V [ORNL; Karunasiri, Gamani [Naval Postgraduate School, Monterey, CA

2012-01-01

341

Temperature dependence of absorption and fluorescence spectra of bacteriochlorophylls in vivo and in vitro  

Microsoft Academic Search

The short wave far-red absorption bands (795825 nm) of bacteriochlorophyll in photosynthetic red bacteria are sharpened but not shifted upon cooling, the long wave far-red bands (840890 nm) are sharpened less but shifted appreciably towards longer wavelengths. The fluorescence bands are shifted about as much as the corresponding long wave absorption bands. Warming results in changes in the opposite direction.

J. C. Goedheer

1972-01-01

342

Identification Of Chiral Bands In 135Ce  

SciTech Connect

High spin states in 135Ce were studied following the 124Sn(16O, 5n)135Ce reaction with an array of 8 Compton suppressed clover detectors and a multiplicity filter consisting of 14 NaI(T1) detectors. The decay scheme of 135Ce shows a pair of {delta}I = 1 bands which have nearly degenerate energies. The levels in two bands cross each other near the band head spin and again close to the highest spin. Both these bands have similar intensity and moment of inertia. Inter-band transitions have been observed in both directions. Both the bands have also similar (B(M1)/B(E2)) ratios with increasing rotational frequency. Lifetimes of levels up to a spin of 41/2({Dirac_h}/2{pi}) have been measured to obtain inband B(M1), B(E2) values and the ratios of the infra band and inter band B(M1) values. It has been concluded from the present observations that these bands may form a 'Chiral doublet' in 135Ce.

Jain, H.C.; Lakshmi, S.; Joshi, P.K. [Tata Institute of Fundamental Research, Mumbai (India)

2005-04-05

343

Water-related absorption in fibrous diamonds  

NASA Astrophysics Data System (ADS)

Cubic and coated diamonds from several localities (Brasil, Canada, Yakutia) were investigated using spectroscopic techniques. Special emphasis was put on investigation of water-related features of transmission Infra-red and Raman spectra. Presence of molecular water is inferred from broad absorption bands in IR at 3420 and 1640 cm-1. These bands were observed in many of the investigated samples. It is likely that molecular water is present in microinclusions in liquid state, since no clear indications of solid H_2O (ice VI-VII, Kagi et al., 2000) were found. Comparison of absorption by HOH and OH vibrations shows that diamonds can be separated into two principal groups: those containing liquid water (direct proportionality of OH and HOH absorption) and those with stronger absorption by OH group. Fraction of diamonds in every group depends on their provenance. There might be positive correlation between internal pressure in microinclusions (determined using quartz barometer, Navon et al., 1988) and affiliation with diamonds containing liquid water. In many cases absorption by HOH vibration is considerably lower than absorption by hydroxyl (OH) group. This may be explained if OH groups are partially present in mineral and/or melt inclusions. This hypothesis is supported by following fact: in diamonds with strong absorption by silicates and other minerals shape and position of the OH band differs from that in diamonds with low absorption by minerals. Moreover, in Raman spectra of individual inclusions sometimes the broad band at 3100 cm-1 is observed. This band is OH-related. In some samples water distribution is not homogeneous. Central part of the diamond usually contains more water than outer parts, but this is not a general rule for all the samples. Water absorption usually correlated with absorption of other components (carbonates, silicates and others). At that fibrous diamonds with relatively high content of silicates are characterized by molecular water. OH-enriched diamonds contain more carbonatitic material. This was supported by JSPS and grant of University of Russia (No. 09.01.054).

Zedgenizov, D. A.; Shiryaev, A. A.; Kagi, H.; Navon, O.

2003-04-01

344

Intestinal apoproteins during fat absorption.  

PubMed Central

To compare the roles of apolipoprotein (Apo) A-I, B, and E (or arginine-rich apoprotein, ARP) in the intracellular production of intestinal chylomicrons (and/or VLDL), these apoproteins were localized in rat intestinal mucosa by the light microscope method of indirect immunofluorescence. In addition, tissue levels of ApoA-I and ApoB were measured during fat absorption by radioimmunoassay. Antisera were produced using ApoA-I isolated from rat plasma high density lipoprotein, and ApoB and ARP from plasma VLDL by column chromatography. The apoproteins yielded single bands on polyacrylamide disc gel electrophoresis in urea and in sodium dodecyl sulfate. Anti-apoprotein antisera were produced in rabbits. These antisera appeared to be monospecific on double-antibody immunoprecipitation of 125I-labeled apoproteins. In fasted animals granular staining of ApoA-I was noted in the supranuclear (Golgi) regions of epithelial cells in the top third of the villus. At 30 min, when fat droplets were seen in the supranuclear cytoplasm of the cells along the top two-thirds of the villus, intense ApoA-I staining surrounded droplets in the cytoplasm. At later times when epithelial cells and lamina propria both contained fat droplets, bright ApoA-I stain surrounded many droplets in the supranuclear cytoplasm of cells and in the lamina propria. Over the same period of time, tissue levels of ApoA-I rose 10-fold. The distribution and time-course of ApoB staining was nearly identical with that of ApoA-I. Concomitantly, tissue ApoB levels doubled. By contrast, in fasting rat intestine, staining of ARP was sparse, punctate, and confined to the lower quarter of the villus. After fat feeding, stained droplets were seen only in the lamina propria near the base of the villus even though abundant ARP was found in cells along most of this length of the villus. Stain was never seen to surround any droplets inside cells. Thus, ApoA-I and ApoB appeared to participate in the intracellular assemply of lipoproteins in gut, whereas ARP did not, although ARP was found within mucosal cells. Liver and intestine differed in their stainable contents of ApoA-I and ARP. Whereas intestine stained heavily for ApoA-I and lightly for ARP, liver stained heavily for ARP and lightly for ApoA-I. Both organs stained for ApoB. These findings suggest that there may be some quantitative "specialization" of the two organs which secrete lipoproteins. Images PMID:350901

Schonfeld, G; Bell, E; Alpers, D H

1978-01-01

345

Electric field induced optical absorption and refractive index changes in a diluted magnetic quantum well  

NASA Astrophysics Data System (ADS)

Binding energy of a confined exciton is investigated in a CdMnTe/CdMnTe/CdMnTe diluted magnetic quantum well in the influence of electric field. Calculations are performed for various Mn incorporation in Cd1-xMnxTe material within a single band effective mass approximation using variational method. Spin polaronic shifts are estimated using mean field theory for different Mn concentration and the well sizes. A theoretical study of diluted magnetic semiconductors treating local sp-d exchange interaction J between the itinerant carriers and the Mn electrons is treated within a realistic band structure. The optical absorption and the refractive index changes as a function of normalized photon energy in the presence of electric field strength and the Mn ion content are analysed. Our results show that the occurred red shift of the absorption resonant peak due to the electric field gives the information about the variation of two energy levels in the quantum well. The optical absorption coefficients and the refractive index changes strongly depend on the incident optical intensity, the electric field strength and Mn content.

Leonora, J. Merciline; Peter, A. John; Yoo, ChangKyoo

2013-01-01

346

Band filling effects on temperature performance of intermediate band quantum wire solar cells  

NASA Astrophysics Data System (ADS)

Detailed studies of solar cell efficiency as a function of temperature were performed for quantum wire intermediate band solar cells grown on the (311)A plane. A remotely doped one-dimensional intermediate band made of self-assembled In0.4Ga0.6As quantum wires was compared to an undoped intermediate band and a reference p-i-n GaAs sample. These studies indicate that the efficiencies of these solar cells depend on the population of the one-dimensional band by equilibrium free carriers. A change in this population by free electrons under various temperatures affects absorption and carrier transport of non-equilibrium carriers generated by incident light. This results in different efficiencies for both the doped and undoped intermediate band solar cells in comparison with the reference GaAs p-i-n solar cell device.

Kunets, Vas. P.; Furrow, C. S.; Ware, M. E.; de Souza, L. D.; Benamara, M.; Mortazavi, M.; Salamo, G. J.

2014-08-01

347

Tricarbonyls of Low-Coordinated Au(0) Atoms in Zeolite-Supported Gold Nanoparticles: Evidence from Infrared and X-ray Absorption Spectroscopies  

SciTech Connect

Mononuclear gold complexes in zeolite NaY were synthesized from initially physisorbed Au(CH{sub 3}){sub 2}(C{sub 5}H{sub 7}O{sub 2}) and characterized by X-ray absorption and infrared spectra recorded as the samples were exposed to flowing CO. X-ray absorption spectra demonstrate the formation of zero-valent gold nanoparticles during the CO treatment. Three new {nu}{sub CO} bands grew in during this treatment, at 2070, 2033, and 2000 cm{sup -1}, characteristic of carbonyls of Au{sup 0}. Because the relative intensities of these bands decreased monotonically when the flow of CO was replaced by flowing He, it is inferred that they correspond to a single Au{sup 0}(CO){sub 3} species, on low-coordinated Au atoms. This is the first example of an Au{sup 0}(CO){sub 3} species.

Anderson,B.; Fierro-Gonzalez, J.; Ramesh, K.; Vinod, C.; Niemantsverdriet, J.; Gates, B.

2006-01-01

348

Absorption and scattering in photo-thermo-refractive glass induced by UV-exposure and thermal development  

NASA Astrophysics Data System (ADS)

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.

Lumeau, Julien; Glebova, Larissa; Glebov, Leonid B.

2014-01-01

349

Rubber Band Racers  

NSDL National Science Digital Library

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.

Ieee

2013-08-30

350

Development of gold induced surface plasmon enhanced CIGS absorption layer on polyimide substrate  

NASA Astrophysics Data System (ADS)

Localized surface plasmon resonance (LSPR) with metal nanoparticles is the promising phenomenon to increase light absorption by trapping light in thin film solar cells. In this study we demonstrate a successful LSPR effect with gold (Au) nanoparticles onto the Cu(In,Ga)Se2 (CIGS) absorption layer. First, the CIGS absorber layers is fabricated onto the Mo coated polyimide (PI) substrate by using two stage process as DC sputtering of CIG thin film followed by the selenization at 400 C. Finally, the Au nanoparticles are deposited onto the CIGS layer with increasing particles size from 4-15 nm by using sputter coater for 10-120 s. The X-ray diffraction (XRD) patterns confirm the formation of CIGS/Au nanocomposite structure with prominent peak shift of CIGS reflections and increasing intensity for Au phase. The CIGS/Au nanocomposite morphologies with Au particle size distribution uniformity and surface coverage is examined under ultra-high resolution field effect scanning electron microscope (UHR-FESEM). A peak at 176 cm-1 in Raman spectra, associated with the A1 mode of lattice vibration for the attributed to the pure chalcopyrite structure. The secondary ion mass spectroscopy (SIMS) showed ?200 nm depth converge of Au nanoparticles into the CIGS absorption layer. The optical properties as transmittance, reflectance and absorbance of CIGS/Au layers were found to expand in the infrared region and the LSPR effect is the most prominent for Au particles (5-7 nm) deposited for 60 s. The absorption coefficient and band gap measurement also confirms that the LSPR effect for 5-7 nm Au particles with band gap improvement from 1.31 to 1.52 eV for CIGS/Au layer as the defect density decreases due to the deposition of Au nanoparticles onto the CIGS layer. Such LSPR effect in CIGS/Au nanocomposite absorption layer will be a key parameter to further improve performance of the solar cell.

Park, Seong-Un; Sharma, Rahul; Sim, Jae-Kwan; Baek, Byung Joon; Ahn, Haeng-Kwun; Kim, Jin Soo; Lee, Cheul-Ro

2013-09-01

351

Radiation Absorption between the Ultraviolet and X-ray Bands.  

PubMed

The recent initial exploration of photoabsorption in a previously unmapped portion of the spectrum, photon energies between approximately 20 and 500 electron volts or wavelengths between 20 and 600 angstroms, is reviewed. PMID:17830365

Fano, U

1966-07-29

352

Electron hopping interactions in amorphous ZnO films probed by x-ray absorption near edge structure analysis  

NASA Astrophysics Data System (ADS)

The x-ray absorption near edge structures of amorphous ZnO (a-ZnO) films were examined. The near-edge structure, which reflects the virtual electron hopping interactions in the photoabsorption final states, increased in intensity compared to crystalline ZnO. Theoretical path-by-path analyses revealed that this reflects the extinction of the multiple hopping processes found in paths such as Zn?O?O'?Zn or Zn?O?Zn'?Zn while the Zn-(O or Zn) hopping interactions remain. This suggests that the structural disorders in a-ZnO can induce the localization of the conduction band through the limited hopping interactions.

Cho, Deok-Yong; Kim, Jeong Hwan; Hwang, Cheol Seong

2011-05-01

353

Mesoscale Banded Precipitation  

NSDL National Science Digital Library

Precipitation frequently falls and accumulates in discrete bands with accumulations that vary markedly over short distances. This module examines several mechanisms that result in mesoscale banded precipitation, focusing primarily on processes at work in midlatitude cyclones. The module starts with a review of the Norwegian and conveyor belt cyclone models. Then several banding processes are examined in detail, including deformation/frontogenesis, the Trowal (Trough of Warm Air Aloft), frontal merger, CSI/slantwise convection, and melting/evaporation-induced circulations. The module concludes with discussions of the representation of banded precipitation by NWP models and the detection of banded precipitation with satellite sensors.

Comet

2005-06-24

354

Electromagnetically induced absorption via incoherent collisions  

SciTech Connect

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.

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

355

X-ray Absorption Study of Colloidal Ge Quantum Dots  

NASA Astrophysics Data System (ADS)

X-ray absorption measurements at the L-edge in chemically prepared Germanium nanoclusters show a blue shift of the conduction band edge consistent with quantum confinement theory. Additionally the effects of the surface termination on the electronic properties are probed with x-ray absorption processes.

van Buuren, Tony; Bostedt, Christoph; Taylor, Boyd R.; Willey, Trevor M.; Hope-Weeks, Louisa; Weeks, Brandon L.; Terminello, L. J.

2002-11-01

356

Enormous enhancements of the Kerr nonlinearity at C-band telecommunication wavelength in an Er3+-doped YAG crystal  

NASA Astrophysics Data System (ADS)

A novel solid configuration is proposed to achieve a giant Kerr nonlinearity with reduced absorption under conditions of slow light levels. It is shown that an enhanced Kerr nonlinearity accompanied with negligible absorption can be obtained just through the proper tuning of intensity of coherent driving field at C-band telecommunication wavelength which is practical for communication applications. Moreover, the impact of incoherent pump field as well as frequency detuning of coherent field on manipulating the linear and nonlinear optical properties of the yttrium-aluminum-garnet (YAG) crystal medium is discussed. The presented results may be of interest to researchers in the field of all-optical signal processing and solid-state quantum information science.

Hamedi, Hamid Reza

2014-06-01

357

Production of photocurrent due to intermediate-to-conduction-band transitions: a demonstration of a key operating principle of the intermediate-band solar cell.  

PubMed

We present intermediate-band solar cells manufactured using quantum dot technology that show for the first time the production of photocurrent when two sub-band-gap energy photons are absorbed simultaneously. One photon produces an optical transition from the intermediate-band to the conduction band while the second pumps an electron from the valence band to the intermediate-band. The detection of this two-photon absorption process is essential to verify the principles of operation of the intermediate-band solar cell. The phenomenon is the cornerstone physical principle that ultimately allows the production of photocurrent in a solar cell by below band gap photon absorption, without degradation of its output voltage. PMID:17280325

Mart, A; Antoln, E; Stanley, C R; Farmer, C D; Lpez, N; Daz, P; Cnovas, E; Linares, P G; Luque, A

2006-12-15

358

Tunable, narrow-band, all-metallic microwave absorber  

NASA Astrophysics Data System (ADS)

We exploit the metamaterial properties of a thick metallic grating with extreme sub-wavelength slits on a metallic slab to achieve complete absorption of transverse magnetic polarized microwaves. We measure narrow bands of total absorption (up to 99.9999%) from normal to grazing incidence that can be tuned by varying an air gap between the grating and the slab. Unlike typical absorbers, the structure is mostly metallic with a 97% filling factor, and no absorptive material beside the metal itself is employed. We access the absorption properties of metals in the microwave where they are commonly believed to be perfect reflectors.

Mattiucci, N.; Trimm, R.; D'Aguanno, G.; Akzbek, N.; Bloemer, M. J.

2012-10-01

359

Photoinduced ?-?* band gap renormalization in graphite.  

PubMed

As is well-known, the character of the ? orbitals is of paramount importance for the chemical properties of the carbon allotropes and their derived compounds. While at equilibrium the nature of these orbitals is well understood, their photoinduced nonequilibrium behavior is under investigation. Here, we demonstrate that when a UV-laser pulse excites a carrier density larger than 10% of the ?* density of state in graphite, a renormalization of the ?-?* band gap takes place. This result has been achieved by detecting the transient reflectivity and the associated decay time of an infrared probe following the excitation of a UV pump pulse tuned across the ?-?* absorption resonance. The pump photon energy at which both the transient reflectivity and the decay time are maximum is downshifted by 500 meV with respect to the relative absorption maximum at equilibrium. This finding is interpreted as a transient ?-?* band gap shrinking of similar magnitude, near the M point of the Brillouin zone. PMID:21452870

Pagliara, S; Galimberti, G; Mor, S; Montagnese, M; Ferrini, G; Grandi, M S; Galinetto, P; Parmigiani, F

2011-04-27

360

A Novel Approach for the Evaluation of Band Gap Energy in Semiconductors  

Microsoft Academic Search

On the basis of absorption nature of semiconductors, we present a novel and simple method to determine the band gap energies of semiconductors directly from their absorption spectra at any temperatures, without any fitting processes and restrictions of sample thickness. The key point of the approach is the different dependence of the absorption coefficient derivative on the photon energy at

W. Z. Shen

2002-01-01

361

Band profiles and band strengths in mixed H2O:CO ices  

E-print Network

A laboratory study on the band profiles and band strengths of H2O in CO ice, and vice versa, is presented and interpreted in terms of two models. The results show that a mutual interaction takes place between the two species in the solid, which alters the band positions and band strengths. It is found that the band strengths of the H2O bulk stretch, bending and libration vibrational bands decrease linearly by a factor of up to 2 when the CO concentration is increased from 0 to 80%. By contrast, the band strength of the free OH stretch increases linearly. The results are compared to a recently performed quantitative study on H2O:CO2 ice mixtures. It is shown that for mixing ratios of 1:0.5 H2O:X and higher, the H2O bending mode offers a good tracer to distinguish between CO2 or CO in H2O ice. Additionally, it is found that the band strength of the CO fundamental remains constant when the water concentration is increased in the ice. The integrated absorbance of the 2152 cm-1 CO feature, with respect to the total integrated CO absorption feature, is found to be a good indicator of the degree of mixing of CO in the H2O:CO laboratory ice system. From the change in the H2O absorption band strength in laboratory ices upon mixing we conclude that astronomical water ice column densities on various lines of sight can be underestimated by up to 25% if significant amounts of CO and CO2 are mixed in.

Jordy Bouwman; Wiebke Ludwig; Zainab Awad; Karin I. Oberg; Guido W. Fuchs; Ewine F. van Dishoeck; Harold Linnartz

2007-12-13

362

Band-gap enhancement in core-excited metals  

NASA Astrophysics Data System (ADS)

Through analyses of the density-matrix equations of motion for electrons in metals, we show that the energy band gap is enhanced when many electrons are excited from core to valence bands, indicating a tendency opposite to the band-gap reduction observed in the valence-electron excitation of semiconductors; it is a consequence of inhomogeneous excitation from highly localized core to delocalized valence bands. Such a band-gap enhancement suggests a blue shift of the photoabsorption edge, leading to a possibility of demonstrating saturable absorber switching by means of intense EUV or X-ray free-electron-laser pulses.

Kitamura, Hikaru

2011-04-01

363

The Noisiness of Low Frequency Bands of Noise  

NASA Technical Reports Server (NTRS)

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.

Lawton, B. W.

1975-01-01

364

Enhanced absorption cycle computer model  

NASA Astrophysics Data System (ADS)

Absorption heat pumps have received renewed and increasing attention in the past two decades. The rising cost of electricity has made the particular features of this heat-powered cycle attractive for both residential and industrial applications. Solar-powered absorption chillers, gas-fired domestic heat pumps, and waste-heat-powered industrial temperature boosters are a few of the applications recently subjected to intensive research and development. The absorption heat pump research community has begun to search for both advanced cycles in various multistage configurations and new working fluid combinations with potential for enhanced performance and reliability. The development of working absorption systems has created a need for reliable and effective system simulations. A computer code has been developed for simulation of absorption systems at steady state in a flexible and modular form, making it possible to investigate various cycle configurations with different working fluids. The code is based on unit subroutines containing the governing equations for the system's components and property subroutines containing thermodynamic properties of the working fluids. The user conveys to the computer an image of his cycle by specifying the different subunits and their interconnections. Based on this information, the program calculates the temperature, flow rate, concentration, pressure, and vapor fraction at each state point in the system, and the heat duty at each unit, from which the coefficient of performance (COP) may be determined. This report describes the code and its operation, including improvements introduced into the present version. Simulation results are described for LiBr-H2O triple-effect cycles, LiCl-H2O solar-powered open absorption cycles, and NH3-H2O single-effect and generator-absorber heat exchange cycles. An appendix contains the user's manual.

Grossman, G.; Wilk, M.

1993-09-01

365

Electron dynamics in transparent materials under high-intensity laser irradiation  

NASA Astrophysics Data System (ADS)

The energy of a laser beam irradiating a surface is primarily absorbed by electrons within the solid. In actual transparent materials, absorption is low. High-intensity lasers may, however, be absorbed by initially bounded electrons through nonlinear processes. The increase of free-electron density leads eventually to dielectric breakdown, and the material becomes highly absorbing. We present theoretical studies on the dynamics of electrons in dielectrics under irradiation with a visible high-intensity laser pulse. We consider microscopic processes determining absorption, redistribution of the energy among electrons, and transfer of energy to the crystal lattice. We review different aspects of electronic excitation, studied with time-resolved models as the Boltzmann kinetic approach and the time and spatial resolved multiple rate equation. Furthermore, we investigate criteria for damage thresholds. Two concepts are compared, namely a critical free-electron density and the melting threshold of the lattice. We show that in dielectrics both criteria are fulfilled simultaneously. Optical parameters depend on the density of free electrons in the conduction band of the solid, so the free-electron density directly leads to an increased energy absorption causing material modification. We present results on the spatial dependence of dielectric breakdown.

Brenk, Oliver; Rethfeld, Brbel

2012-12-01

366

Absorption spectra reconstruction using Voigt profiles  

NASA Astrophysics Data System (ADS)

The identification of the components of algal absorption spectra can be made mathematically through either derivative or spectral deconvolution analyses. This work establishes a methodology for identifying phytoplankton pigments from absorption spectra by combining the derivative and spectral deconvolution methods and interpreting the results with the knowledge of the major light absorbing pigments. This was achieved a) by locating the position of the absorption peaks present in the spectra of different algal groups through the derivative analysis, b) by fitting a combination of Gaussian-Lorentzian or Voigt shaped bands, centered at these peaks, to the original spectra and c) by using pigment analysis via HPLC to provide the biological background for identifying these bands and peaks. The results of this study show that the derivative method can be used successfully in monocultures and natural populations to identify pigments by their individual absorption peaks. Secondly, a good agreement has been found between the original spectra and the reconstructed spectra which were a Voigt combination. The HPLC analysis provided the objective platform for the biological interpretation of the bands.

Aguirre-Gomez, R.; Weeks, Alison R.; Boxall, Simon R.

1997-02-01

367

Absorption spectra of cold dilute solid solutions  

SciTech Connect

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

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

1983-06-01

368

X-ray absorption spectroscopy of photoionised plasmas at Z  

NASA Astrophysics Data System (ADS)

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.

Mancini, R. C.

2011-06-01

369

Nitric oxide gamma and delta band emission at twilight  

NASA Technical Reports Server (NTRS)

Nitric oxide twilight emission above 140 km in the gamma- and delta-bands was observed with a rocket-borne spectrophotometer. The relative intensity of the two band systems indicates that the emission is produced predominantly by the chemiluminescent preassociation of oxygen and nitrogen atoms.

Feldman, P. D.; Takacs, P. Z.

1974-01-01

370

Calibration-free self-absorption model for measuring nitric oxide concentration in a pulsed corona discharge.  

PubMed

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 (A???X?) 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

Du, Yanjun; Ding, Yanjun; Liu, Yufeng; Lan, Lijuan; Peng, Zhimin

2014-08-01

371

Effects of two-photon absorption on terahertz radiation generated by femtosecond-laser excited photoconductive antennas.  

PubMed

Terahertz (THz) radiation can be generated more efficiently from a low-temperature-grown GaAs (LT-GaAs) photoconductive (PC) antenna by considering the two-photon absorption (TPA) induced photo-carrier in the photoconductor. A rate-equation-based approach using the Drude-Lorentz model taking into account the band-diagram of LT-GaAs is used for the theoretical analysis. The use of transform-limited pulses at the PC antenna is critical experimentally. Previously unnoticed THz pulse features and anomalously increasing THz radiation power rather than saturation were observed. These are in good agreement with the theoretical predictions. The interplay of intensity dependence and dynamics of generation of photoexcited carriers by single-photon absorption and TPA for THz emission is discussed. PMID:22109395

Lee, Chao-Kuei; Yang, Chan-Shan; Lin, Sung-Hui; Huang, Shiuan-Hua; Wada, Osamu; Pan, Ci-Ling

2011-11-21

372

Swift heavy ion irradiation induced modifications in the optical band gap and Urbach's tail in polyaniline nanofibers  

NASA Astrophysics Data System (ADS)

Optical band gap and Urbach tail width of HCl and CSA doped polyaniline (PAni) nanofibers and the ion beam induced modifications in the band gap and Urbach's tail of the samples have been studied employing UV-Vis absorption spectroscopy. All the major bands appearing in the FTIR spectra exhibit a decrease in intensity and broadening in their band widths upon interaction with the highly energetic ion beams. This suggests that SHI irradiation induces chain-scissioning events in the PAni nanofibers. An interesting result that comes out from the FTIR analysis is a transition from the benzenoid to quinoid states in the PAni chains, which reveals that there is a decrease in the degree of conjugation in the polymer upon irradiation. Optical absorption studies indicate three direct allowed transitions at 2.64, 3.61 and 4.08 eV for HCl doped PAni nanofibers and at 2.62, 3.49 and 4.02 eV for the CSA doped PAni nanofibers. The optical band gap is found to increase with increasing ion fluence which may be attributed to the reduction in the fiber diameters upon irradiation, which is corroborated by TEM analysis. Increase in the optical band gap also points out to a decrease in the conjugation length due to the larger torsion angles between the adjacent phenyl rings of the polymer with respect to the plane of the nitrogen atoms, which is also supported by FTIR results. The Urbach tail width decreases with increasing ion fluence indicating that structural disorders are annealed out of the PAni nanofibers which is also observed from the plots of (? h?) 2 against photon energy ( h?) for HCl doped PAni nanofibers. The quantum confinement effect is confirmed by fact that a band gap exhibits a linear dependence on the inverse of the square of the radius of the PAni nanofibers. Infact, the increase in the optical band gap may be a combined effect of the decrease in the Urbach band width and the quantum confinement effect.

Banerjee, Somik; Kumar, A.

2011-12-01

373

The correlation between f-f absorption and sensitized visible light emission of luminescent Pr(III) complexes: role of solvents and ancillary ligands on sensitivity.  

PubMed

The electronic absorption, excitation and sensitized visible light emission studies of three praseodymium (III) complexes: [Pr(fod)(3)(bpy)], [Pr(fod)(3)(phen)] and [Pr(fod)(3)(bpm)](n) (fod = anion of 6,6,7,7,8,8,8- heptafluoro-2,2-dimethyl-3,5-octanedione; bpy=2,2'-bipyridyl, phen=1,10-phenanthroline, bpm=2,2'-bipyrimidine) in a series of non-aqueous solvents is presented. The f-f absorption transitions of Pr(III) are environment sensitive which is reflected by the change in the intensity (oscillator strength) and band shape (stark splitting) upon change in the solvent and/or the ligands. The sensitization of intense Pr(III) emission, in the visible region, of the complexes in solution upon excitation into the ligand centered ???* absorption band is remarkable. The planar phen has pronounced impact and increases considerably the emission intensity of Pr(III) luminescence than the flexible bpy while bpm has been found least effective in promoting the emission intensity. The intensity of the f-f absorption and sensitized emission are correlated with the nature of the solvents. The donor solvent pyridine enhances the emission intensity of the [Pr(fod)(3)(phen)] drastically and of [Pr(fod)(3)(bpy)] marginally while the luminescent intensity of [Pr(fod)(3)(bpm)](n) is decreased. The combined photophysical studies demonstrate that entry of the solvent molecule(s) to inner coordination sphere (complex-solvent interaction) is governed by the structure and basicity of the ancillary heterocyclic ligand attached to the Pr(III) complex. The strong donor DMSO transforms the three complexes into a similar species, [Ln(fod)(3)(DMSO)(2)], which results in similar electronic absorption and emission properties of the complexes in this solvent. The results demonstrate that highly luminescent praseodymium chelates can be designed with ligands containing suitable energy levels and their emission properties can be further modulated through suitable ancillary ligands and donor solvents, thus opening perspectives for applications in electroluminescent devices and luminescent probes. PMID:21046438

Irfanullah, Mir; Iftikhar, Khalid

2011-03-01

374

Intermediate band solar cells based on indium arsenide quantum dots embedded in indium gallium arsenide quantum well  

NASA Astrophysics Data System (ADS)

Intermediate band solar cells based on quantum dots and quantum wells with anti-reflection coating are investigated in this thesis. The demand for high efficient solar cells as an alternate source of energy is the main motivation for this research project. Intermediate band solar cells based on quantum dots were the subject of intensive research in recent years. High power conversion efficiency was predicted from InAs/GaAs intermediate band solar cells as the presence of InAs quantum dots increased the absorption below the band gap of the host material. In this thesis, an attempt has been made to further increase the absorption of GaAs solar cells by embedding InAs quantum dots in InxGa 1-xAs quantum wells. The quantum efficiency and spectral response measurements of quantum dots embedded in quantum well devices exhibit an extended response till 1280 nm in the near infrared region of the electromagnetic spectrum. The interband transition peaks associated with the InxGa 1-xAs quantum well exhibit a red shift as In mole fraction (x) in In xGa1-xAs quantum well is increased above 0%. The short circuit current density increased, while open circuit voltage decreased, as x is increased. In addition, the use of inexpensive anti-reflection coating (ARC) on these intermediate band solar cells has been studied. Anti-reflection coating based on Zinc oxide (ZnO) has significantly improved the power conversion efficiency of the solar cells. The ZnO synthesized using sol-gel technique was spin coated on the solar cells and subsequently annealed. The short circuit current density was significantly increased after the deposition of the ARC. Enhancement of the order of 42 % in the power conversion efficiency was obtained. Around 43% enhancement in quantum efficiency and 44% enhancement in spectral response measurements were also observed.

Vasan, Ramesh

375

Singing with the Band  

ERIC Educational Resources Information Center

Usually band, orchestra, and choir directors work independently. However, the authors--one a choral director, the other a band director--have learned that making music together makes friends. Not only can ensemble directors get along, but joint concerts may be just the way to help students see how music can reach the heart. Combined instrumental

Altman, Timothy Meyer; Wright, Gary K.

2012-01-01

376

Stretch Band Exercise Program  

ERIC Educational Resources Information Center

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,

Skirka, Nicholas; Hume, Donald

2007-01-01

377

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

NASA Technical Reports Server (NTRS)

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

Borysow, Aleksandra

1995-01-01

378

Methane overtone absorption by intracavity laser spectroscopy  

NASA Technical Reports Server (NTRS)

Interpretation of planetary methane (CH4) visible-near IR spectra, used to develop models of planetary atmospheres, has been hampered by a lack of suitable laboratory spectroscopic data. The particular CH4 spectral bands are due to intrinsically weak, high overtone-combination transitions too complex for classical spectroscopic analysis. The traditional multipass cell approach to measuring spectra of weakly absorbing species is insufficiently sensitive to yield reliable results for some of the weakest CH4 absorption features and is difficult to apply at the temperatures of the planetary environments. A time modulated form of intracavity laser spectroscopy (ILS), has been shown to provide effective absorption pathlengths of 100 to 200 km with sample cells less than 1 m long. The optical physics governing this technique and the experimental parameters important for obtaining reliable, quantitative results are now well understood. Quantitative data for CH4 absorption obtained by ILS have been reported recently. Illustrative ILS data for CH4 absorption in the 619.7 nm and 681.9 nm bands are presented. New ILS facilities at UM-St. Louis will be used to measure CH4 absorption in the 700 to 1000 nm region under conditions appropriate to the planetary atmospheres.

Obrien, James J.

1990-01-01

379

Transient absorption spectroscopy of radical ions of rigid anti- and syn-tetrasilane  

Microsoft Academic Search

Transient absorption spectra of ion radicals were observed for tetrasilanes with rigid syn or anti Si units by electron beam pulse radiolysis. Two transient absorption bands at 4.1 and 2.8 eV were clearly resolved for the anion radical of syn-tetrasilane, while for anti-tetrasilane, the anion radical produced a broad absorption band at 4.4 eV. Cation radicals of the tetrasilanes gave

Shu Seki; Kazumasa Okamoto; Yoshinori Matsui; Seiichi Tagawa; Hayato Tsuji; Akio Toshimitsu; Kohei Tamao

2003-01-01

380

Excited-state absorption spectroscopy in oxidized Cytochrome c  

NASA Astrophysics Data System (ADS)

This work reports on the excited-state absorption spectrum of oxidized Cytochrome c (Fe 3+) dissolved in water, measured with the Z-scan technique with femtosecond laser pulses. The excited-state absorption cross-sections between 460 and 560 nm were determined with the aid of a three-energy-level model. Reverse saturable absorption was observed below 520 nm, while a saturable absorption process occurs in the Q-band, located around 530 nm. Above 560 nm, a competition between saturable absorption and two-photon absorption was inferred. These results show that Cytochrome c presents distinct nonlinear behaviors, which may be useful to study electron transfer chemistry in proteins by one- and two-photon absorption. In addition, owing to these nonlinear optical features, this molecule may be employed in applications involving photodynamics therapy and saturable absorbers.

De Boni, L.; Andrade, A. A.; Misoguti, L.; Zlio, S. C.; Mendona, C. R.

2010-02-01

381

Progressive Band Selection  

NASA Technical Reports Server (NTRS)

Progressive band selection (PBS) reduces spectral redundancy without significant loss of information, thereby reducing hyperspectral image data volume and processing time. Used onboard a spacecraft, it can also reduce image downlink time. PBS prioritizes an image's spectral bands according to priority scores that measure their significance to a specific application. Then it uses one of three methods to select an appropriate number of the most useful bands. Key challenges for PBS include selecting an appropriate criterion to generate band priority scores, and determining how many bands should be retained in the reduced image. The image's Virtual Dimensionality (VD), once computed, is a reasonable estimate of the latter. We describe the major design details of PBS and test PBS in a land classification experiment.

Fisher, Kevin; Chang, Chein-I

2009-01-01

382

The Effects of Light Intensity and Spectral Quality on Growth and Shoot Initiation in Tobacco Callus  

PubMed Central

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

Seibert, Michael; Wetherbee, Phyllis J.; Job, Donald D.

1975-01-01

383

Infrared absorption of CH3OSO detected with time-resolved Fourier-transform spectroscopy  

NASA Astrophysics Data System (ADS)

A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to detect temporally resolved infrared absorption spectra of CH3OSO produced upon irradiation of a flowing gaseous mixture of CH3OS(O)Cl in N2 or CO2 at 248 nm. Two intense transient features with origins near 1152 and 994 cm-1 are assigned to syn-CH3OSO; the former is attributed to overlapping bands at 1154 +/- 3 and 1151 +/- 3 cm-1, assigned to the S=O stretching mixed with CH3 rocking (?8) and the S=O stretching mixed with CH3 wagging (?9) modes, respectively, and the latter to the C-O stretching (?10) mode at 994 +/- 6 cm-1. Two weak bands at 2991 +/- 6 and 2956 +/- 3 cm-1 are assigned as the CH3 antisymmetric stretching (?2) and symmetric stretching (?3) modes, respectively. Observed vibrational transition wavenumbers agree satisfactorily with those predicted with quantum-chemical calculations at level B3P86/aug-cc-pVTZ. Based on rotational parameters predicted at that level, the simulated rotational contours of these bands agree satisfactorily with experimental results. The simulation indicates that the S=O stretching mode of anti-CH3OSO near 1164 cm-1 likely makes a small contribution to the observed band near 1152 cm-1. A simple kinetic model of self-reaction is employed to account for the decay of CH3OSO and yields a second-order rate coefficient k = (4 +/- 2)10-10 cm3 molecule-1 s-1.

Chen, Jin-Dah; Lee, Yuan-Pern

2011-03-01

384

Infrared absorption of CH3OSO detected with time-resolved Fourier-transform spectroscopy.  

PubMed

A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to detect temporally resolved infrared absorption spectra of CH(3)OSO produced upon irradiation of a flowing gaseous mixture of CH(3)OS(O)Cl in N(2) or CO(2) at 248 nm. Two intense transient features with origins near 1152 and 994 cm(-1) are assigned to syn-CH(3)OSO; the former is attributed to overlapping bands at 1154 3 and 1151 3 cm(-1), assigned to the S=O stretching mixed with CH(3) rocking (?(8)) and the S=O stretching mixed with CH(3) wagging (?(9)) modes, respectively, and the latter to the C-O stretching (?(10)) mode at 994 6 cm(-1). Two weak bands at 2991 6 and 2956 3 cm(-1) are assigned as the CH(3) antisymmetric stretching (?(2)) and symmetric stretching (?(3)) modes, respectively. Observed vibrational transition wavenumbers agree satisfactorily with those predicted with quantum-chemical calculations at level B3P86?aug-cc-pVTZ. Based on rotational parameters predicted at that level, the simulated rotational contours of these bands agree satisfactorily with experimental results. The simulation indicates that the S=O stretching mode of anti-CH(3)OSO near 1164 cm(-1) likely makes a small contribution to the observed band near 1152 cm(-1). A simple kinetic model of self-reaction is employed to account for the decay of CH(3)OSO and yields a second-order rate coefficient k=(4 2)10(-10) cm(3)molecule(-1)s(-1). PMID:21384966

Chen, Jin-Dah; Lee, Yuan-Pern

2011-03-01

385

Temperature and density dependence of the light and heavy water ultraviolet absorption edge  

Microsoft Academic Search

Characteristics of the ultraviolet absorption band edge of high-pressure light and heavy water are reported over the temperature range of 25-400 C, extending into the supercritical regime. A gradual redshift in the absorption band edge of ?0.6 eV is observed with increasing temperature. This shift cannot be explained by vibrational hot band growth or changes in the degree of Rayleigh

Timothy W. Marin; Kenji Takahashi; David M. Bartels

2006-01-01

386

Temperature and density dependence of the light and heavy water ultraviolet absorption edge  

Microsoft Academic Search

Characteristics of the ultraviolet absorption band edge of high-pressure light and heavy water are reported over the temperature range of 25-400 C, extending into the supercritical regime. A gradual redshift in the absorption band edge of ~0.6 eV is observed with increasing temperature. This shift cannot be explained by vibrational hot band growth or changes in the degree of Rayleigh

Timothy W. Marin; Kenji Takahashi; David M. Bartels

2006-01-01

387

Characterization of Novel Semiconductor Alloys for Band Gap Engineering  

NASA Astrophysics Data System (ADS)

The novel semiconductor alloys, In1-xAlx N, GaN1-xAsx, and ZnSe1-xOx, are promising materials for low-cost and high-efficiency solar cells and efficient solid-state lighting. The band gap of all of the alloys can be controlled through the visible electromagnetic energy spectrum by varying x. In-rich InAlN tends to be degenerately n-type due to the high electron affinity of InN and the conduction band and light hole band are non-parabolic due to the narrow band gap and the interaction of the conduction band and valence bands. The absorption spectra can be blue shifted due to the Burstein-Moss Shift. GaNAs and ZnSeO are highly mismatched alloys, where the alloying involves elements that are very dissimilar in terms of electronegativity and size. The band anticrossing model, which treats the interaction of a localized defect level with the extended states of the conduction and valence bands, quantitatively describes the properties of highly mismatched alloys. The band gap bowing parameter, which quantifies the band gap dependence on composition, of InAlN is determined while accounting for the effects of degenerate electron concentrations and non-parabolic bands on the absorption spectra. The composition is independently determined by two complimentary methods. The band gap and temperature dependence of the band gap of ZnSe 1-xOx are determined by optical spectroscopy and can be understood in terms of the band anticrossing model. The exciton kinetics is quantified through time-resolved photoluminescence and is found to cause a low temperature enhancement of the photoluminescence. The band gaps of GaNAs are determined for the full composition range for both crystalline and amorphous phases. The composition dependence of the band gap can be quantified by the band anticrossing model across the full composition range through a linear interpolation of the conduction band and valence band anticrossing models.

Broesler, Robert Joseph, Jr.

388

Intracavity Dye-Laser Absorption Spectroscopy (IDLAS) for application to planetary molecules  

NASA Technical Reports Server (NTRS)

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.

Lang, Todd M.; Allen, John E., Jr.

1990-01-01

389

Subbarrier absorption in a stationary superlattice  

NASA Technical Reports Server (NTRS)

The calculation of the interband absorption coefficient was carried out in the classical case, when the frequency of light was assumed to bind two miniband subbarrier states of different bands. The influence of two dimensional Mott excitons on this absorption was studied and a comparison was made with the experiment. All of these considerations were done taking into account the photon wave vector (the phase spatial heterogeneity). The basic traits of the energy spectra of superlattice semiconductors, their kinetic and optical properties, and possible means of electromagnetic wave intensification were examined. By the density matrix method, a theory of electrical and electromagnetic properties of superlattices was suggested.

Arutyunyan, G. M.; Nerkararyan, K. V.

1984-01-01

390

IR absorption spectroscopic study of mixed cobalt substituted lithium ferrites  

NASA Astrophysics Data System (ADS)

The IR spectra of Li0.5-(x/2)CoxFe2.5-(x/2)O4 ferrite samples (0?x?0.6) prepared by solution combustion method have been reported. The influence of Co substitution is verified. XRD studies confirm the spinel phase formation of ferrites. Lattice constant varies linearly from 8.31 (x=0) to 8.35 (x=0.6) with composition. Evidence of two absorption bands in the IR spectra (below 800 cm-1) reveals the characteristic feature of spinel ferrite. The IR spectra featured additional three absorption bands around 550, 670 and 705 cm-1 for the samples x=0.1 and x=0.6. Absence of bands splitting specifies that Fe ions do not exist in excess form. It is found that high frequency band (?1), due to tetrahedral (A) group, lies at around 600 cm-1 and low frequency band (?2), due to octahedral (B) group, around 450 cm-1. The positions of bands are found to be composition dependent. The IR bands due to tetrahedral complexes shift slightly towards high frequency side with composition upto x=0.4 where as that due to octahedral complexes shift towards lower frequency side with x. Based on the data of absorption bands, force constants (kt, ko) and bond lengths (RA, RB) were estimated. Compositional dependence of force constants is explained on the basis of cation-oxygen bond distances of respective sites and cation distribution.

Sawant, V. S.; Bagade, A. A.; Mohite, S. V.; Rajpure, K. Y.

2014-10-01

391

Influence of Duschinsky and Herzberg-Teller effects on S0 ? S1 vibrationally resolved absorption spectra of several porphyrin-like compounds  

NASA Astrophysics Data System (ADS)

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.

Yang, Pan; Qi, Dan; You, Guojian; Shen, Wei; Li, Ming; He, Rongxing

2014-09-01

392

New CW-CRDS measurements and global modeling of 12C 16O 2 absolute line intensities in the 1.6 ?m region  

NASA Astrophysics Data System (ADS)

Line intensities of 12C 16O 2 transitions have been measured by CW-Cavity Ring Down Spectroscopy in four wavenumber intervals near 1.6 ?m. Intensity values of 952 transitions ranging from 1.10 10 -28 to 4.94 10 -25 cm/molecule were retrieved with an average accuracy of 4%. These transitions belong to a total of 30 bands corresponding to the ? P = 9 series of transitions. The achieved sensitivity (noise equivalent absorption ?min 3 10 -10 cm -1) allows lowering by more than two orders of magnitude the lower intensity values measured in the region. Comparison with the values included in the JPL database [R.A. Toth, L.R. Brown, C.E. Miller, V. Malathi Devi, D.C. Benner, J. Quant. Spectrosc. Radiat. Transf. 109 (2008) 906-921] shows residuals exceeding one order of magnitude for weak lines. The measured intensities together with a selection of experimental intensities available in the literature were used to extend and refine the set of effective dipole moment parameters for the ? P = 9 series of transitions of the principal isotopologue of carbon dioxide. The refined parameters allow reproducing, within the experimental uncertainties, the whole set of intensity measurements which extends over nearly six orders of magnitude (1.10 10 -28-6.12 10 -23 cm/molecule). Combining the CW-CRDS line positions with the calculated line intensities, a line list has been generated for the whole 5851-7045 cm -1 region and is provided as Supplementary Material. The obtained effective dipole moment parameters have also been used to generate the ? P = 9 series of transitions included in the new version of the CDSD database. The comparison of the CDSD line intensities with the values provided by the HITRAN-2004 database shows discrepancies up to 80% for some of the bands while discrepancies up to three orders of magnitude are noted for the weakest bands included in the JPL database.

Perevalov, B. V.; Campargue, A.; Gao, B.; Kassi, S.; Tashkun, S. A.; Perevalov, V. I.

2008-12-01

393

Sapphire fiber evanescent wave absorption in turbid media.  

PubMed

The influence of particulates on sapphire fiber evanescent wave absorption by water has been studied. Suspensions containing micro-sized graphite flakes and glassy carbon powder were used. Conventional free-space transmittance measurements of these samples showed strong absorption and scattering, which severely screened the absorption by water. However, the absorption on the water band determined from the evanescent wave interaction was unaffected by the presence of the graphite flakes. These results indicate that fiber-optic evanescent wave chemical sensors may be suitable for process control applications involving turbid reactor streams. PMID:19678991

Zhang, Jian; Xiong, Feibing; Djeu, Nicholas

2009-08-01

394

Infrared and millimeter-wavelength absorption by atmospheric water vapor  

NASA Astrophysics Data System (ADS)

An account is given of the current understanding of the atmospheric water vapor window regions from 10 to 1000 GHz, 8-12 microns, and 2-2.5 microns, with attention to the continuum absorption observable in each window region. The observed frequency-dependence in each window is consistent with the concept of far wings that emanate from the bordering water vapor absorption bands; this connection is considered the most prominent basis for the modeling of continuum absorption. It is judged that absorption behavior beyond experimentally measured conditions can be predicted with reasonable confidence.

Thomas, Michael E.

1987-12-01

395

Band Gap Fluorescence from Individual Single-Walled Carbon Nanotubes  

NASA Astrophysics Data System (ADS)

Fluorescence has been observed directly across the band gap of semiconducting carbon nanotubes. We obtained individual nanotubes, each encased in a cylindrical micelle, by ultrasonically agitating an aqueous dispersion of raw single-walled carbon nanotubes in sodium dodecyl sulfate and then centrifuging to remove tube bundles, ropes, and residual catalyst. Aggregation of nanotubes into bundles otherwise quenches the fluorescence through interactions with metallic tubes and substantially broadens the absorption spectra. At pH less than 5, the absorption and emission spectra of individual nanotubes show evidence of band gap-selective protonation of the side walls of the tube. This protonation is readily reversed by treatment with base or ultraviolet light.

O'Connell, Michael J.; Bachilo, Sergei M.; Huffman, Chad B.; Moore, Valerie C.; Strano, Michael S.; Haroz, Erik H.; Rialon, Kristy L.; Boul, Peter J.; Noon, William H.; Kittrell, Carter; Ma, Jianpeng; Hauge, Robert H.; Weisman, R. Bruce; Smalley, Richard E.

2002-07-01

396

An extremely broad band metamaterial absorber based on destructive interference.  

PubMed

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

Sun, Jingbo; Liu, Lingyun; Dong, Guoyan; Zhou, Ji

2011-10-24

397

The optical band gap and surface free energy of polyethylene modified by electron beam irradiations  

NASA Astrophysics Data System (ADS)

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.

Abdul-Kader, A. M.

2013-04-01

398

North American Bird Banding Program  

USGS Publications Warehouse

The new Chief will cover the status of key elements of the Bird Banding Laboratory as well as review highlights over the past year. These will include: the upcoming Oracle-based database system, band supply, banding requests, band data requests, Band Manager, the Reward Band program, the I-800-Mexico program, the partnership with Canada's Bird Banding Office, the strategic planning process, the budget, the Federal Advisory Committee, and a look to the future.

Tomosy, M.

2005-01-01

399

Weak morphology dependent valence band structure of boron nitride  

NASA Astrophysics Data System (ADS)

We report a hard X-ray photoelectron spectroscopy (HX-PES) investigation on valence band structure of Boron Nitrides (BN) having different morphologies, including nanosheets, nanotubes, and micro-sized particles. Very weak morphology/valence band structure dependence was observed. For each case, the B-N ?-band overlapping with ?-band between 0 to -12.5 eV and the s-band below -15 eV were identified. No obvious morphology-induced band shifts and intensity variations were observed. First-principles calculations based on density functional theory were performed and the results were compared with the experimental data. This theoretical analysis well explains the weak morphology dependent valence band spectra of BN nanomaterials obtained during HX-PES measurements.

Zhi, Chunyi; Ueda, Shigenori; Zeng, Haibo; Wang, Xuebin; Tian, Wei; Wang, Xi; Bando, Yoshio; Golberg, Dmitri

2013-08-01

400

The Pennsylvania State University Marching Blue Band Blue Band Office  

E-print Network

The Pennsylvania State University Marching Blue Band Press Kit Blue Band Office 101 Blue Band Director vcc2@psu.edu orb1@psu.edu gad157@psu.edu (814) 865 - 3982 #12;History of the Blue Band The Marching Blue Band numbers 310 members which includes: 260 instrumentalists, 34 silks, 14 Touch of Blue

Maroncelli, Mark

401

CIRCULAR INTENSITY DIFFERENTIAL SCATTERING OF LIGHT BY HELICAL STRUCTURES. III. A GENERAL POLARIZABILITY TENSOR AND ANOMALOUS SCATTERING  

SciTech Connect

Numerical calculations of the circular intensity differential scattering of light by oriented helical structures made of units with general polarizability tensors are presented. The effects on the scattering patterns of both absorptive and dispersive properties of the units are illustrated. The differential scattering and the total scattering both show anomalous scattering phenomena; the differential scattering pattern is asymmetric when the wavelength of incident light is within an absorption band. Equations for bi-axial polarizabilities are used to derive the symmetry properties of the differential scattering pattern and to show how this symmetry can be used to determine the right- or left-handed sense of the helical structure. The wavelength dependence of the scattering pattern is obtained for a Lorentzian polarizability.

Bustamante, Carlos; Maestre, Marcos F.; Tinoco, Jr., Ignacio

1980-11-01

402

Optical absorption and EPR studies on enargite  

NASA Astrophysics Data System (ADS)

The behaviour of transition metal ions in enargite has been studied by electron paramagnetic resonance and absorption spectroscopy in the UV-VIS and near-IR regions. The ground state of Cu(II) ions in enargite is confirmed as 2B1g since g11>g? (2.54>2.11). Three characteristic bands observed in the optical absorption spectra at 8275, 13105 and 18420 cm-1 are assigned to the transitions, 2B1g?2A1g, 2B1g?2B2 and 2B1g?2Eg, respectively, of Cu(II) ion in the tetragonal field. The presence of Fe(II) bands is an evidence for iron impurities in the mineral.

Reddy, S. Lakshmi; Reddy, N. C. Gangi; Reddy, G. Siva; Reddy, B. Jagannadha; Frost, R. L.

403

Electrodynamics of an Omega-Band Determined With the Local KRM Method  

NASA Astrophysics Data System (ADS)

We investigate an Omega-band event that took place above northern Scandinavia around 02:00 - 02:30 UT on 9.3.1999. The Omega-band event occurred in the recovery phase of a moderate substorm. We examine the electrodynamic structure of the Omega-band using a local variant of the well-known KRM method, introduced by Vanhamki and Amm in 2007. We use ground magnetic measurements together with estimates of ionospheric Hall and Pedersen conductances as input in the calculation method. The first conductance data set is derived from UV images produced with the UVI instrument onboard the POLAR satellite. Together with data from the IMAGE magnetometer network this gives us an over-all picture of the Omega-band event. The second conductance data set is obtained by combining riometer absorption data and all-sky camera pictures of auroral brightness at 557 nm. This gives us a detailed view of the Omega-band as it propagates directly over the observational area. Previously the ionospheric electric field of Omega-bands has mostly been studied with coherent scatter radars, which may have trouble in resolving small electric fields, such as those that are present in the highly conductive luminous "tongues" of the Omega-band. Both the riometer- and optical image -based conductance estimates used in this study should have their best accuracy in the luminous areas, where electron precipitation is intense and conductances are high. Consequently, high resolution conductance estimates and magnetometer measurements allow us to asses the electric field structure of the whole Omega-band, including the luminous tongues, thus complementing the previous studies. The local KRM method is a new data analysis tool, and this is the first time it is used in event analysis. Although the method has been validated using several synthetic models of typical meso-scale phenomena in the auroral ionosphere, we wish to asses its performance also using real observational data. For this effect we compared the electric field calculated using the local KRM method with line-of-sight velocities measured by the CUTLASS radar at Hankasalmi. We find good qualitative agreement between the calculated and measured plasma velocities, demonstrating that the local KRM method is a practical tool for studying ionospheric electrodynamics.

Vanhamki, H.; Kauristie, K.; Amm, O.; Senior, A.; Lummerzheim, D.; Milan, S.

2009-04-01

404

Splitting of the F 2 bands in ion implanted LiF  

NASA Astrophysics Data System (ADS)

Optical absorption studies of ion-implanted LiF, after annealing, show the growth of a band at 414 nm (3 eV), whose behaviour is similar to that of the F 2 band at 445 nm (2.8 eV). This band is attributed to the association of F 2 centres with an impurity, deforming the normal F 2 centre structure. Details of the deformation are presented. In situ measurements during implantation at 77 or 300 K do not show this new absorption feature, but the implant temperature influences the subsequent 414 nm band production.

Wood, R. A.; Townsend, P. D.

1991-07-01

405

Enhancement Of Free Exciton Peak Intensity In Reactively Sputtered ZnO Thin Films On (0001) Al2O3  

SciTech Connect

Wide bandgap materials such as GaN with its direct bandgap structure have been developed rapidly for applications in short wavelength light emission. ZnO, II-VI oxide semiconductor, is also promising for various technological applications, especially for optoelectronic light emitting devices in the visible and ultraviolet (UV) range of the electromagnetic spectrum. Above-band-edge absorption spectra of reactively sputtered Zn- and O-rich samples exhibit free exciton (FX) and neutral acceptor bound exciton (A deg. X) features. It is shown that the residual acceptors which bind excitons with an energy of 75 meV reside about 312 meV above the valence band, according to effective mass theory. An intra-bandgap absorption feature peaking at 2.5 eV shows correlation with the characteristically narrow A-free exciton peak intensity. Relevant annealing processes are presented as a function of time and temperature dependently for both Zn- and O- rich thin films. Enhancement of the free exciton peak intensity is observed without disturbing the residual shallow acceptor profile which is necessary for at least background p-type conductivity.

Tuezemen, S.; Guer, Emre; Yildirim, T.; Xiong, G.; Williams, R. T. [Department of Physics, Faculty of Arts and Sciences, Atatuerk University, 25240 Erzurum (Turkey); Department of Physics, Wake Forest University, Winston-Salem, NC 27109 (United States)

2007-04-23

406

Deep-UV absorption study of nonlinear optical crystal KBe2BO3F2  

NASA Astrophysics Data System (ADS)

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.

Wang, Xiaolong; Liu, Lijuan; Xu, Bo; Wang, Xiaoyang; Chen, Chuangtian

2014-10-01

407

Pixel-based absorption correction for dual-tracer fluorescence imaging of receptor binding potential  

PubMed Central

Ratiometric approaches to quantifying molecular concentrations have been used for decades in microscopy, but have rarely been exploited in vivo until recently. One dual-tracer approach can utilize an untargeted reference tracer to account for non-specific uptake of a receptor-targeted tracer, and ultimately estimate receptor binding potential quantitatively. However, interpretation of the relative dynamic distribution kinetics is confounded by differences in local tissue absorption at the wavelengths used for each tracer. This study simulated the influence of absorption on fluorescence emission intensity and depth sensitivity at typical near-infrared fluorophore wavelength bands near 700 and 800 nm in mouse skin in order to correct for these tissue optical differences in signal detection. Changes in blood volume [1-3%] and hemoglobin oxygen saturation [0-100%] were demonstrated to introduce substantial distortions to receptor binding estimates (error > 30%), whereas sampled depth was relatively insensitive to wavelength (error < 6%). In response, a pixel-by-pixel normalization of tracer inputs immediately post-injection was found to account for spatial heterogeneities in local absorption properties. Application of the pixel-based normalization method to an in vivo imaging study demonstrated significant improvement, as compared with a reference tissue normalization approach. PMID:25360349

Kanick, Stephen C.; Tichauer, Kenneth M.; Gunn, Jason; Samkoe, Kimberley S.; Pogue, Brian W.

2014-01-01