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1

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

E-print Network

energy levels are derived, Twelve bands in the electronic absorption spectrum of chlorine dioxide between the wavelengths 4250 R and 5250 R were photographed and measured. Of these twelve, the vibrational energy levels calculated for nine of them... Calculation of Vibrational Energy Levels . . . . , 35 Estimation of Errors . . . , . . . . . . . . . . . 38 CONCLUSIONS Conolusions ~ ~ ~ 47 B IBLI QGRAFEZ ~ ~ ~ ~ ~ ~ ~ ~ 48 ~INTRGDUGT10 Analysis of thc rotational structure of the chlorine dioxide...

Rapp, Thomas Louis

2012-06-07

2

Ab initio study of the infrared absorption bands and their intensities for ethylene-halogen and amine-halogen complexes  

NASA Astrophysics Data System (ADS)

The infrared absorption bands and their intensities of some charge-transfer (CT) complexes, ?-? type (C 2H 4-ClF and C 2H 4-Cl 2) and n-? type (NH 3-ClF, NH 3-Cl 2, NH 2CH 3-Cl 2, NH(CH 3) 2-Cl 2 and N(CH 3) 3-Cl 2), and each isolated molecule are studied with ab initio SCF MO calculations. At the optimized geometry, the harmonic frequencies and their infrared intensities are evaluated. In the halogen complexes the halogen-halogen stretching mode is slightly shifted towards lower frequency and its infrared intensity is enhanced. In the C 2H 4 complexes the frequency shifts of the intraethylene modes are very small, while the infrared intensities of the total symmetric modes, particularly ? (C?C) at 1843 and ?(CH 3) at 1513 cm -1, are enhanced and those of the antisymmetric modes are reduced. In the NH 3 complexes the total symmetric bending mode, ? 2, is shifted towards high frequency; from 1167 to 1206 (NH 3-Cl 2) and to 1243 cm -1 (NH 3-ClF), and its infrared intensity is reduced. The N?H stretching modes, ? 1 (3699 cm -1) and ? 3 (3836 cm -1), are not changed in frequency, but their intensities are enhanced. The methylamine complexes with Cl 2 are also studied, and the results of the trimethylamine-Cl 2 complex are compared with the classical experimental work of Yada, Tanaka and Nagakura on trimethylamine-I 2.

Matsuzawa, Hidenori; Iwata, Suehiro

1992-07-01

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

Experimental and theoretical study of absorption spectrum of the (CH3)2CO⋯HF complex. Influence of anharmonic interactions on the frequency and intensity of the Cdbnd O and H-F stretching bands  

NASA Astrophysics Data System (ADS)

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?(Cdbnd O) overtone band of free acetone are reliably measured. The ?1(HF) and ?(Cdbnd O) absorption bands of the (CH3)2CO⋯HF 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 Schrödinger 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 Cdbnd 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 Cdbnd O transitions.

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

2014-01-01

5

Integrated band intensities of gaseous N/2/O/5/  

NASA Technical Reports Server (NTRS)

Values for mid-IR integrated band intensities of gaseous N2O5 were determined at room temperature. The absorptions studied were at 1720, 1246, 743, and 557/cm. The integrated intensities were 2204, 581, 685, and 699/atm cm, respectively. Implications of these results for the stratospheric detection of N(2)O(5) are discussed.

Lovejoy, R. W.; Chackerian, C., Jr.; Boese, R. W.

1980-01-01

6

Dependence of Raman and resonance Raman intensities on sample self-absorption.  

PubMed

Resonance Raman cross sections are generally larger than normal or preresonance Raman cross sections. Thus, higher Raman intensities are expected for resonance excitation, especially for backscattering measurements. However, self absorption decreases the observed Raman intensities. In the work here we examine the effect of self absorption on the observed preresonance and resonance Raman intensities. For the simplest case where a single electronic transition dominates the Raman scattering, and where the resonance enhancement scales with the square of the molar absorptivity of the absorption band, theory predicts that for close to resonance excitation the observed Raman intensities monotonically increase as resonance is approached. In the case that an impurity absorbs, the observed Raman intensities may decrease as excitation moves close to resonance for particular conditions of impurity absorption band widths and frequency offsets. Impurity absorption also causes decreases in observed Raman intensities for the more slowly increasing preresonance excitation. PMID:25506729

Hong, Zhenmin; Asher, Sanford A

2015-01-01

7

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

8

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

9

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

NASA Astrophysics Data System (ADS)

We study the porphyrin S 1?S 0 fluorescence and the photosensitized singlet oxygen 1?g? 3?g phosphorescence, both originating from absorption of photons with energy less than the porphyrin S 0?S 1 transition energy. By measuring the excitation intensity dependence of fluorescence at lowered sample temperatures, we are able to discriminate between two parallel processes of one-photon hot-band absorption (HBA) and simultaneous two-photon absorption (TPA). When the HBA and TPA contributions are comparable in magnitude, we use this new method to determine absolute TPA cross-section. We also demonstrate for the first time a singlet oxygen photosensitization via HBA in porphyrin.

Drobizhev, M.; Karotki, A.; Kruk, M.; Krivokapic, A.; Anderson, H. L.; Rebane, A.

2003-03-01

10

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

11

A Theory Attributing Optical Diffuse Interstellar Absorption Bands, ``Unidentified Infrared'' Emission Bands, and Cloud Reddening to H 2 Nonlinear Absorption  

NASA Astrophysics Data System (ADS)

A theory is described that attributes the diffuse interstellar absorption bands (DIBs) to coherently driven two-photon absorption by H2 molecules present in sheetlike clouds located near hot stars. Results from three-level nonlinear spectroscopy are used to argue that vacuum ultraviolet (VUV) photons from the star impinging on the H2-containing cloud will be primarily absorbed in simultaneous two-photon (Raman-type) transitions, resulting in the build-up of coherent VUV Stokes-wave radiation in the "plane" of the H2-containing cloud on the transitions [Cn ? X0; P(2) and P(3); n = 0-5] and on some of the transitions [Bn ? X0, P(2) and P(3)]. Via this in-plane VUV Stokes-wave radiation, parahydrogen molecules in the (X0, J" = 2) level and ortho-hydrogen molecules in the (X0, J" = 3) level are coherently excited to levels [Cn?u+); J' = 1 and 2; n = 0-5] and [Bn, J' = 1 and 2], which thus serve as the intermediate states in resonantly enhanced, coherently driven, two-photon absorption. The DIBs result from visible light from the star being simultaneously absorbed in "second step" transitions from the coherently excited (C, B)-state levels to various singlet gerade state levels. In-plane coherent VUV Stokes-wave radiation at [Cn ? X0; P(2) and P(3); n = 1-5] can also act to produce in-plane coherent IR radiation via stimulated Raman scattering processes terminating on various EF singlet gerade levels. Striking coincidences are shown to exist between frequencies of IR Stokes-wave transitions expected to be strong and those of the so-called unidentified infrared emission bands (UIBs). Assuming a common identity, assignments are offered for most of the known UIBs. More than 70 sharp DIBs are assigned to transitions from B- and C-state levels to levels of singlet gerade states. On the basis of in-plane four-wave mixing of VUV and IR-Stokes-waves radiation (i.e., four-wave parametric generation), the most prominent features seen in the emission spectrum of the Red Rectangle are also explained. It is furthermore indicated that cloud reddening should be an additional manifestation of the presence of intense, in-plane, VUV Stokes-wave radiation.

Sorokin, Peter P.; Glownia, James H.

1996-12-01

12

Correlation evaluation of intensity and color band images  

SciTech Connect

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

Carter, J.M.

1996-02-01

13

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

PubMed

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

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

2014-12-01

14

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

15

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

ERIC Educational Resources Information Center

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

Henderson, Giles

1977-01-01

16

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

SciTech Connect

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

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

2013-07-15

17

Lyman-band fluorescence intensity vs H2 pressure  

NASA Technical Reports Server (NTRS)

The fluorescence intensity of the H2 Lyman bands excited by the argon 1066 A line is found to be a linear function of the H2 pressure. The fluorescence from naturally occurring HD is linearly dependent on the HD partial pressure. The experiments described show that these fluorescence intensities can be used to measure the H2 and HD densities below 10 trillion molecules per cu cm.

Inn, E. C. Y.; Starr, W. L.

1975-01-01

18

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 0.52±0.08 and 0.88±0.13 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

19

Band intensity in the IR spectra and conformations of calix[4]arene and thiacalix[4]arene  

NASA Astrophysics Data System (ADS)

The experimental IR and Far IR spectra of the calix[4]arene, p-tert-butylcalix[4]arene, thialcalix[4]arene and p-tert-butylthiacalix[4]arene were examined at different temperatures and interpreted. The band frequencies and intensities in the IR spectra of the calix[4]arene and thialcalix[4]arene were calculated. The absorption curves of the four possible calix[4]arene conformations: cone, partial cone, 1,2- and 1,3-alternate were computed. The bands characteristic for each conformation are defined and assigned. The obtained spectra-structure correlation can be used for the characteristic of calixarenes conformation.

Furer, V. L.; Borisoglebskaya, E. I.; Kovalenko, V. I.

2005-01-01

20

Absorption of ultrashort intense lasers in laser–solid interactions  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

21

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.

Mézel, Candice; Duchateau, Guillaume; Geneste, Grégory; Siberchicot, Bruno

2013-06-01

22

A measurement of the relative intensities of some vibronic bands  

E-print Network

~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ . 1 II ~ EXPERIMENTAL ~ III ~ PROCEDURE FOR INTENSITI NEASUREHENTS . IV. EXPERINENTAL RESULTS FOR CHLORINE DIOXIDE ~ ~ ~ ~ 5 14 ~ ~ ~ ~ ~ 19 V. EXPERIHENTAL RESULTS FOR SULPHUR DIOXIDE. . . . 26 VI. CONCLUSIONS...INE DIOXIDE APPARATUS ~ . o . . . ~ 9 4. TOP VIEW OF CH1 CRINE DIOXIDE APPARATUS . 5 ~ CHLORINE DIOXIDE ABSORPTION SPECTROGRAM WITH CAI IBRATION BLANKS ~ ~ ~ e ~ ~ e ~ ~ ~ 6, CHLORINE DIOXIDE DECONPOSITION IiN PROGRESS 10 . 11 7. H AND D CURVE FOil...

Loyd, Coleman Monroe

2012-06-07

23

Infrared band intensities in ammonium hydroxide and ammonium salts  

NASA Technical Reports Server (NTRS)

We have applied Kramers-Kronig analysis to reflection spectra to determine the optical constants of ammonium hydroxide and of aqueous solutions of ammonium chloride and bromide. From considerations of the absorption indices k(nu) we conclude that ammonium hydroxide consists of a solution of NH3 in water, in which NH3 molecules are hydrogen bonded to neighboring water molecules. The spectrum of ammonium hydroxide differs from the spectra of ammonium salts, in which bands characteristic of NH4(+) ions are prominent. The existence of ammonium hydroxide as an aerosol in planetary atmospheres is briefly discussed

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

1978-01-01

24

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

25

Intense high-pressure sequence-band CO2 laser.  

PubMed

We have obtained temporally smooth, single-line megawatt output from the (0,0 degrees,2) --> [(1,0 degrees,1), (0,2 degrees,1)]1 sequence band in an 1800-Torr CO2 double-discharge laser. These lines were first observed by Reid and Siemsen in a low-pressure discharge at subwatt power outputs [Appl. Phys. Lett. 29, 250 (1976)]. The intense 10-gm region laser transitions reported here may be useful for selective molecular excitation, for nonlinear optics experiments where wavelengths of the usual C02 transitions are inappropriate, and for long-path atmospheric transmission. PMID:19680391

Feldman, B J; Fisher, R A; Pollock, C R; Simons, S W; Tercovich, R G

1978-01-01

26

Low intensity conduction states in FeS2: implications for absorption, open-circuit voltage and surface recombination.  

PubMed

Pyrite (FeS2), being a promising material for future solar technologies, has so far exhibited in experiments an open-circuit voltage (OCV) of around 0.2 V, which is much lower than the frequently quoted 'accepted' value for the fundamental bandgap of ?0.95 eV. Absorption experiments show large subgap absorption, commonly attributed to defects or structural disorder. However, computations using density functional theory with a semi-local functional predict that the bottom of the conduction band consists of a very low intensity sulfur p-band that may be easily overlooked in experiments because of the high intensity onset that appears 0.5 eV higher in energy. The intensity of absorption into the sulfur p-band is found to be of the same magnitude as contributions from defects and disorder. Our findings suggest the need to re-examine the value of the fundamental bandgap of pyrite presently in use in the literature. If the contribution from the p-band has so far been overlooked, the substantially lowered bandgap would partly explain the discrepancy with the OCV. Furthermore, we show that more states appear on the surface within the low energy sulfur p-band, which suggests a mechanism of thermalization into those states that would further prevent extracting electrons at higher energy levels through the surface. Finally, we speculate on whether misidentified states at the conduction band onset may be present in other materials. PMID:24141033

Lazi?, P; Armiento, R; Herbert, F W; Chakraborty, R; Sun, R; Chan, M K Y; Hartman, K; Buonassisi, T; Yildiz, B; Ceder, G

2013-11-20

27

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 characteristics—intensity, 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

28

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

PubMed

The computational results of the features observed in the room-temperature Q-band absorption spectrum of free-base chlorin (H2Ch) are presented. The vibrational structures of the first and second excited singlet states were calculated based on a harmonic approximation using density functional theory and its time dependent extension within the Franck-Condon and Herzberg-Teller approaches. The outcome allowed to identify the experimental bands and to assign them to the specific vibrational transitions. A very good agreement between the simulated and measured wavelengths and their relative intensities provided the opportunity to predict the origin of the S0 ? S2 transition which could not be determined experimentally. PMID:25612704

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

2015-01-21

29

Ultrafast absorption of intense x rays by nitrogen molecules.  

PubMed

We devise a theoretical description for the response of nitrogen molecules (N(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 (?SCF method). To describe the interaction with N(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(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(2)(2+), and molecular fragmentation are explained. PMID:22697546

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

30

Quantitative comparisons of absorption cross-section spectra and integrated intensities of HFC-143a  

NASA Astrophysics Data System (ADS)

The integrated absorption cross-sections of HFC-143a (CH3CF3) differ substantially in the literature. This leads to an important uncertainty on the value of the radiative efficiency of this molecule. The ambiguity on the absorption cross-sections of HFC-143a is highlighted by the existence of two significantly different datasets in the HITRAN database. To solve the issue, we performed high-resolution Fourier transform infrared laboratory measurements of HFC-13a and compared the spectra with the two HITRAN datasets and with the data from the Pacific Northwest National Laboratory (PNNL). The experimental methods and data analysis techniques are examined and typical sources of errors are discussed. The integrated intensities of the main bands are compared to other literature values. It was found that the integrated absorption cross-section values in the highest range - around 13.8 ×10-17 cm .molecule-1 in the 570-1500 cm-1 spectral band - show the most consistency between authors.

Le Bris, Karine; Graham, Laura

2015-01-01

31

INTERACTION OF LASER RADIATION WITH MATTER: Individual induced absorption bands in MgF2  

NASA Astrophysics Data System (ADS)

The absorption spectra of MgF2 samples exposed to an electron beam and laser radiation at 248, 308, and 372 nm are investigated. Fourteen individual absorption bands are separated in the spectra. The parameters of the eight spectra of them are obtained for the first time. The separated bands are assigned to the intrinsic defects of the MgF2 crystal.

Sergeev, A. P.; Sergeev, P. B.

2008-03-01

32

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

Microsoft Academic Search

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

Ryumyo Onaka; Teruhiko Mabuchi; Akira Yoshikawa

1967-01-01

33

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

PubMed

Harmonic vibrational frequencies and vibronic intensities in the first S(0)-->S(1) (pipi( *)) absorption band of free-base porphin (H(2) P) are investigated by hybrid density functional theory (DFT) with the standard B3LYP functional. The S(0)-S(1) transition probability is calculated using time-dependent DFT with account of Franck-Condon (FC) and Herzberg-Teller (HT) contributions to the electric-dipole transition moments including displacements along all 108 vibrational modes. Two weak wide bands observed in the gas phase absorption spectra of the H(2) P molecule at 626 and 576 nm are interpreted as the 0-0 band of the X(1) A(g)-->1B(3u) transition and the 0-1 band with largest contributions from the nu(10)(a(g))=1610 cm(-1) and nu(19)(b(1g))=1600 cm(-1) modes, respectively, in agreement with previous tentative assignments. Both bands are induced by the HT mechanism, while the FC contributions are negligible. A number of fine structure bands, including combination of two vibrational quanta, are obtained and compared with available spectra from supersonic jet and Shpolskij matrices. Both absorption and fluorescence spectra are interpreted on ground of the linear coupling model and a good fulfillment of the mirror-symmetry rule. PMID:16920011

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

2006-10-01

34

Measurements of small signal absorption at high temperature for the 001-100 band of CO2  

NASA Technical Reports Server (NTRS)

In the experiments an absorption cell was irradiated by a polarized CW CO2-N2-He laser. By changing the length of the laser cavity, it was possible to obtain stable oscillations on the five lines P12 through P20 in the 10.4-micron band. The power output was slightly under 10 W. Intensity measurements of the incident and the transmitted beam were conducted when the cell was filled with a nonabsorbing calibrating gas (nitrogen) and with the test gas (carbon dioxide). Data for the absorption coefficient in the temperature range from 300 K to about 600 K are presented in graphs.

Leonard, R. L.

1974-01-01

35

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

36

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

37

Enhanced light absorption of silicon in the near-infrared band by designed gold nanostructures  

NASA Astrophysics Data System (ADS)

A scheme to enhance near-infrared band absorption of a Si nanoparticle by placing the Si nanoparticle into a designed gold nanostructure is proposed. Three-dimensional (3D) finite-difference time-domain simulations are employed to calculate the absorption spectrum of the Si nanostructure and maximize it by generating alternate designs. The results show that in the near-infrared region over 700 nm, the absorption of a pure Si nanoparticle is very low, but when the same nanoparticle is placed within an optimally designed gold nanostructure, its absorption cross section can be enhanced by more than two orders of magnitude in the near-infrared band.

Liu, Ju; Zhong, Xiao-Lan; Li, Zhi-Yuan

2014-04-01

38

Measurements of Line Intensities for Some Lines of Ammonia in the ?2, 2?2 and ?4 Bands  

NASA Astrophysics Data System (ADS)

Using Fourier Transform spectra (Bruker IFS 120 HR, resolution ?0.004 cm-1) of NH3 in several branches of the ?2, 2?2 and ?4 bands, absolute line intensities have been determined at room temperature (T = 295 K) for more than 400 rovibrational lines located in the spectral range 1000-1800 cm-1. A non-linear least-squares multispectrum fitting procedure, including line mixing effects, has been used to retrieve the line intensities from eleven experimental spectra recorded at different pressures of pure ammonia. The present results are compared with previous measurements in which the collisional absorption coefficient is a Voigt profile. The line intensities determined in the present work are smaller than those determined by these authors. For example, the difference in percent between our values and the values of C. Cottaz is about 6%. For almost all lines and pressures considered in this work, it was shown that the first-order Rosenkranz absorption coefficient taking into account line-mixing effects is adequate to extract with sufficient accuracy the line intensities of NH3. An examination of these line intensities shows a pronounced J and K quantum numbers dependencies. Our results have been analyzed to obtain effective transition moments and correction parameters of symmetric and asymmetric partial bands of the fundamental ?4 band, as well as those of asymmetric partial bands of ?2 and 2?2 bands. Since these bands are affected by the rotation-vibration interactions, the zero-order theory where the Hermann-Wallis factors are not included is not able to describe the intensity anomalies in these bands. As shown by Aliev et al., it is necessary to include these interactions into theoretical line strengths expressions. These authors have developed a third-order theory of the line strengths of the vibrational transition from the ground vibrational state to the rovibrational levels of molecules with C3? symmetry using the method of contact transformation applied to the electric dipole moment operator. A suitable expression for the line strength was derived to fit the experimental intensities.

Mabrouk, K. Ben; Aroui, H.; Orphal, J.

2010-10-01

39

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

E-print Network

PHYSICAL REVIEW A 83, 043817 (2011) Observation of precursorlike behavior of femtosecond pulses in a dye with a strong absorption band Matthew M. Springer,* Wenlong Yang, Alexandre A. Kolomenski, Hans A. Schuessler, James Strohaber, George W...

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

2011-01-01

40

Narrow-Band Absorption-Enhanced Quantum Dot/J-Aggregate Conjugates  

E-print Network

We report narrow-band absorption enhancement of semiconductor nanocrystals via Förster resonance energy transfer from cyanine J-aggregates. These J-aggregated dyes associate electrostatically with short quantum-dot (QD) ...

Walker, Brian J.

41

Three-photon absorption : selection rules and line intensities G. Grynberg  

E-print Network

965 Three-photon absorption : selection rules and line intensities G. Grynberg Laboratoire d résultats théoriques concernant l'absorption à trois photons en utilisant un développement de l'opérateur de in this paper several theoretical results about three-photon absorption using an expansion of the transition

Boyer, Edmond

42

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, it seems likely that the CT band will be sensitive to the hydration of the protein. To study this premise, the protein was incorporated into trehalose/sucrose glasses and the hydration of the sugar glasses was varied

Sharp, Kim

43

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

44

Polarization-insensitive and polarization-controlled dual-band absorption in metamaterials  

NASA Astrophysics Data System (ADS)

We numerically and experimentally investigated dual-band absorption of sandwich-structure metamaterials which include periodic metal coupled rings at the front separated from the metal plane at the back by a dielectric layer. The properties are demonstrated in both GHz and mid-IR regimes of electromagnetic (EM) wave. The dual-band perfect absorber with polarization independence is observed under normal incidence. In order to understand the EM properties of dual-band perfect absorber, the plasmonic excitation was clarified for both peaks. Finally, by connecting the rings, the perfect-absorption peaks can be controlled with the polarization angle of incident EM wave.

Tuong, P. V.; Park, J. W.; Rhee, J. Y.; Kim, K. W.; Jang, W. H.; Cheong, H.; Lee, Y. P.

2013-02-01

45

Self-broadening and -shifting of very intense lines of the 1?0 band of 12C16O  

NASA Astrophysics Data System (ADS)

Absorption spectra of pure 12C16O have been recorded, at room temperature and for various pressures, in the very intense 1?0 band. This was made using a high-resolution (0.005 cm-1) Fourier transform spectrometer together with a specially designed cell that enables one to adapt the optical path from a few ?m up to several mm. Thanks to the latter, absorption by extremely intense lines is measured for the first time under adapted (non saturating transmission) absorbance conditions, even for a pure gas pressure near 1 atm. The recorded spectra, obtained for a path length of about 130 ?m, have been adjusted using Voigt line-shapes in order to retrieve the unperturbed line positions, and the self-broadening and -shifting parameters induced by pressure for the P(20) to R(19) lines. Our results for the line widths confirm the expected very small and undetected influence of vibration on the broadening and demonstrate the inaccuracy of previous high-resolution measurements made under extremely strong absorption conditions. Similarly, our study provides the first accurate self-induced line shifts for the 1?0 band.

Ngo, N. H.; Landsheere, X.; Pangui, E.; Morales, S. B.; Tran, H.; Hartmann, J.-M.

2014-12-01

46

Terahertz spectroscopy of dicyanobenzenes: Anomalous absorption intensities and spectral calculations  

NASA Astrophysics Data System (ADS)

Terahertz absorption spectra of three isomeric structures of dicyanobenzene in chloroform solution and solid phase at 298 K are reported. These spectra exhibit enhanced absorption in low THz range compared to most organic systems because of strong coupling to phonon modes. Molecular vibrational spectral calculations show strong correlation with the experiment especially for solution spectra. All intramolecular modes were assigned and intermolecular modes identified. Out-of-plane intramolecular modes at low frequency exhibit ˜75 cm -1 blue shifts as the secondary CN group moves from the para to ortho position on the benzene ring, whereas almost no frequency shift occurs for low-frequency in-plane modes.

Esenturk, O.; Evans, A.; Heilweil, E. J.

2007-07-01

47

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. PMID:25435767

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

2014-01-01

48

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

PubMed

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

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

2014-12-01

49

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

PubMed

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

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

2012-06-01

50

Acceptor-to-Band Transitions in Semiconductors: Photoluminescence, Exponential Absorption Edges, and Final-State Interactions  

Microsoft Academic Search

The effects of disorder and of final-state electron-hole interactions on acceptor-to-band absorption and photoluminescence spectra of semiconductors are treated theoretically within the effective-mass approximation. The results of the calculations are used to analyze photoluminescence spectra from lightly doped GaAs: Cd measured by Williams and Bebb. It is shown that although a proper one-electron calculation of optical absorption ?2(omega) should include

John D. Dow; Darryl Lyle Smith; Frank L. Lederman

1973-01-01

51

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

52

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

53

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

54

A laboratory Atlas of the 5 nu-1 NH3 absorption band at 6475 A with applications to Jupiter and Saturn  

NASA Technical Reports Server (NTRS)

A complete atlas of the 5 nu-1 absorption band of NH3 is presented together with measurements of the total band intensity, line intensities, and self-broadening coefficients. The spectrum, which is displayed in the interval from 6418 to 6550 A, was obtained photoelectrically at a pressure of 0.061 atm, and many more lines were seen in this spectrum than in a previous one obtained at a pressure of 0.39 atm. The band intensity is used to derive the NH3 abundance in the atmospheres of Jupiter and Saturn, and the abundances in a single vertical path are found to be about 10 m amagat for Jupiter and 2 m amagat for Saturn. These results are shown to be in agreement with previous results obtained from higher resolution photographic spectra.

Giver, L. P.; Miller, J. H.; Boese, R. W.

1975-01-01

55

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

NASA Astrophysics Data System (ADS)

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.

Picconi, David; Grebenshchikov, Sergy Yu.

2014-08-01

56

Empiric k·p Hamiltonian calculation of the band-to-band photon absorption in semiconductors  

NASA Astrophysics Data System (ADS)

The Empiric k·p Hamiltonian method is usually applied to nanostructured semiconductors. In this paper, it is applied to a homogeneous semiconductor in order to check the adequacy of the method. In this case, the solutions of the diagonalized Hamiltonian, as well as the envelope functions, are plane waves. The procedure is applied to the GaAs and the interband absorption coefficients are calculated. They result in reasonable agreement with the measured values, further supporting the adequacy of the Empiric k·p Hamiltonian method.

Luque, Antonio; Panchak, Aleksandr; Mellor, Alexander; Vlasov, Alexey; Martí, Antonio; Andreev, Viatcheslav

2015-01-01

57

Broad band enhancement of light absorption in photosystem I by metal nanoparticle antennas.  

PubMed

The photosystem I (PS I) protein is one of nature's most efficient light harvesting complexes and exhibits outstanding optoelectronic properties. Here we demonstrate how metal nanoparticles which act as artificial antennas can enhance the light absorption of the protein. This hybrid system shows an increase in light absorption and of circular dichroism over the entire absorption band of the protein rather than at the specific plasmon resonance wavelength of spherical metal nanoparticles (NPs). This is explained by broad-resonant and nonresonant field enhancements caused by metal NP aggregates, by the high dielectric constant of the metal, and by NP-PS I-NP antenna junctions which effectively enhance light absorption in the PS I. PMID:20481472

Carmeli, Itai; Lieberman, Itai; Kraversky, Leon; Fan, Zhiyuan; Govorov, Alexander O; Markovich, Gil; Richter, Shachar

2010-06-01

58

Intensity of the hydrogen peroxide v6/b/ band around 1266 cm  

NASA Technical Reports Server (NTRS)

Laboratory spectra of the V6(b) band of H2O2 at 1266/cm have been obtained at a resolution of 0.06/cm and at temperatures ranging from 278 to 294 K. A total band intensity of 375 + or - 17 per sq cm per amagat is determined from the spectra. Special techniques to handle the H2O2 samples in a way that minimizes abundance determination errors are discussed.

Valero, F. P. J.; Goorvitch, D.; Boese, R. W.; Bonomo, F. S.

1981-01-01

59

Detection of two interstellar absorption bands coincident with spectral features of C60+  

NASA Astrophysics Data System (ADS)

MORE than a hundred well-defined absorption bands, arising from diffuse gas in the interstellar medium, have been observed in the visible and near-infrared spectra of stars 1-4. The identity of the species responsible for these bands has remained unclear, although many possibilities have been suggested5,6. Carbon-based molecules ubiquitous in the interstellar medium have been widely favoured as potential carriers of some of the diffuse interstellar bands7-10,29 in particular, C60+ has been thought to be a promising candidate9,29. Here we present the results of a search for C60+ in the near-infrared spectra of seven stars, based on recent laboratory measurements of the absorption spectrum of this species11-13. We find two diffuse bands that are coincident (within 0.1%) with laboratory measurements on C60+ in a Ne matrix11. From this observation and the total absorption, we estimate that 0.3-0.9% of interstellar carbon is in the form of C60+. The molecule is very stable, which should allow it to survive in the interstellar medium for a long time14, but the inhibition of C60+ formation by hydrogen probably limits its abundance.

Foing, B. H.; Ehrenfreund, P.

1994-05-01

60

Recovery of acetylene absorption line profile basing on tunable diode laser spectroscopy with intensity modulation and photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

A novel and direct absorption line recovery technique based on tunable diode laser spectroscopy with intensity modulation is presented. Photoacoustic spectroscopy is applied for high sensitivity, zero background and efficient acoustic enhancement at a low modulation frequency. A micro-electromechanical systems (MEMS) mirror driven by an electrothermal actuator is used for generating laser intensity modulation (without wavelength modulation) through the external reflection. The MEMS mirror with 10?m thick structure material layer and 100nm thick gold coating is formed as a circular mirror of 2mm diameter attached to an electrothermal actuator and is fabricated on a chip that is wire-bonded and placed on a PCB holder. Low modulation frequency is adopted (since the resonant frequencies of the photoacoustic gas cell and the electrothermal actuator are different) and intrinsic high signal amplitude characteristics in low frequency region achieved from measured frequency responses for the MEMS mirror and the gas cell. Based on the property of photoacoustic spectroscopy and Beer's law that detectable sensitivity is a function of input laser intensity in the case of constant gas concentration and laser path length, a Keopsys erbium doped fibre amplifier (EDFA) with opto-communication C band and high output power up to 1W is chosen to increase the laser power. High modulation depth is achieved through adjusting the MEMS mirror's reflection position and driving voltage. In order to scan through the target gas absorption line, the temperature swept method is adopted for the tunable distributed feed-back (DFB) diode laser working at 1535nm that accesses the near-infrared vibration-rotation spectrum of acetylene. The profile of acetylene P17 absorption line at 1535.39nm is recovered ideally for ~100 parts-per-million (ppm) acetylene balanced by nitrogen. The experimental signal to noise ratio (SNR) of absorption line recovery for 500mW laser power was ~80 and hence the detectable sensitivity is of the order of 1ppm.

Li, Li; Thursby, Graham; Stewart, George; Arsad, Norhana; Uttamchandani, Deepak; Culshaw, Brian; Wang, Yiding

2010-04-01

61

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

62

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

63

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

E-print Network

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

Flatte, Michael E.

64

Is a pyrene-like molecular ion the cause of the 4,430-angstroms diffuse interstellar absorption band?  

PubMed

The diffuse interstellar bands (DIBs), ubiquitous absorption features in astronomical spectra, have been known since early this century and now number more than a hundred. Ranging from 4,400 angstroms to the near infrared, they differ markedly in depth, width and shape, making the concept of a single carrier unlikely. Whether they are due to gas or grains is not settled, but recent results suggest that the DIB carriers are quite separate from the grains that cause visual extinction. Among molecular candidates the polycyclic aromatic hydrocarbons (PAHs) have been proposed as the possible carriers of some of the DIBs, and we present here laboratory measurements of the optical spectrum of the pyrene cation C16H10+ in neon and argon matrices. The strongest absorption feature falls at 4,435 +/- 5 angstroms in the argon matrix and 4,395 +/- 5 angstroms in the neon matrix, both close to the strong 4,430-angstroms DIB. If this or a related pyrene-like species is responsible for this particular band, it must account for 0.2% of all cosmic carbon. The ion also shows an intense but puzzling broad continuum, extending from the ultraviolet to the visible, similar to what is seen in the naphthalene cation and perhaps therefore a common feature of all PAH cations. This may provide an explanation of how PAHs convert a large fraction of interstellar radiation from ultraviolet and visible wavelengths down to the infrared. PMID:11536498

Salama, F; Allamandola, L J

1992-07-01

65

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

NASA Astrophysics Data System (ADS)

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.; Fedorov, S. V.; Savel'ev, R. S.; Sukhorukov, A. A.; Kivshar, Yu. S.

2012-05-01

66

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

PubMed

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

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

2014-12-15

67

Spectral intensities in the nu(sub 1) band of NH3  

NASA Technical Reports Server (NTRS)

Intensities have been measured for individual transitions in the Q and R branches of the nu(sub 1) band of NH3 using a difference-frequency laser spectrometer. The data yield an integrated band strength of S(sup 0 sub v) = 219.36 +/- 1.03/sq cm/MPa at 297 K, corresponding to a transition moment of absolute value of mu(sub v) = 8.535(20) x 10(exp -32) C x m, and a Herman-Wallis correction factor,(1 + alpha(sub J)m), where alpha(sub J) = 0.0209(20). The intensities of a few lines for K greater than or equal to 7 were noticeably perturbed by a perpendicular Coriolis interaction with 2nu(sub 4)(E, l = 2), so were excluded from the fit. A small sample of nu(sub 3) band lines occurring in the nu(sub 1) band scans also yields a rough estimate of the nu(sub 3) band intensity with evident irregular perturbations.

Pine, A. S.; Dang-Nhu, M.

1993-01-01

68

High-resolution Fourier transform infrared absorption spectroscopy of the ?6 band of c-C3H2.  

PubMed

The gas-phase high-resolution absorption spectrum of the ?(6) band of cyclopropenylidene (c-C(3)H(2)) has been observed using a Fourier transform infrared spectrometer for the first time. The molecule has been produced by microwave discharge in an allene (3.3 Pa) and Ar (4.0 Pa) mixture inside a side arm glass tube. The observed spectrum shows a pattern of c-type ro-vibrational transitions in which the Q-branch lines strongly and distinctly stand out in the spectrum. A combined least-squares analysis of the observed 216 ro-vibrational transitions together with 28 millimeter-wave rotational transitions from the previous study has resulted in an accurate determination of the molecular constants in the ?(6) state. The band center is found to be at 776.11622(13) cm(-1) with one standard deviation in parentheses, which is 2.3% lower than the matrix isolation value. The intensity ratio I(3)(?(3))/I(6)(?(6)) obtained from the observed ?(3) and ?(6) bands, 1.90(9), is somewhat lower than the ratio estimated from ab initio (2.4-2.6) and DFT (2.8) calculations. PMID:21702474

Varadwaj, Pradeep R; Fujimori, Ryuji; Kawaguchi, Kentarou

2011-08-01

69

Detection of Near-Infrared CO Absorption Bands in R Coronae Borealis Stars  

NASA Astrophysics Data System (ADS)

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

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

2005-07-01

70

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

71

Absolute intensities of infrared-active fundamentals and combination bands of gaseous PuF6 and NpF6  

NASA Astrophysics Data System (ADS)

Results are presented for the absolute integrated molar absorption coefficients of the infrared-active fundamental and binary combination bands of PuF6 and of NpF6 between 1400 and 450 cm-1. The low resolution band contours of the combination bands ?1+?3, ?2+?3, ?3+?5, ?2+?6, and ?2+?4 are discussed. From band center positions, the six harmonic wave numbers were obtained and Coriolis constant ?i (i=3, 4, 5, and 6) estimated. For PuF6, the six normal mode vibrations appear to group into one ``local mode'' stretching at a mean value of 589±50 cm-1 and one local mode bending at 195±5 cm-1. The role of the heavy central atom and the magnitudes of the vibrational force constants are discussed in comparison with UF6. The measured intensity for ?3 is discussed in comparison with previously predicted values.

Person, W. B.; Kim, K. C.; Campbell, G. M.; Dewey, H. J.

1986-11-01

72

Nonadiabatic Ab initio multichannel quantum defect theory applied to absolute experimental absorption intensities in H(2).  

PubMed

The positions and intensities of the Q(N) (N = 1-4) X1 Sigma(g)+ --> nppi1 Pi(u)- (n = 2 to approximately 30) absorption transitions of H2 have been calculated by multichannel quantum defect theory. The computations are based on the quantum chemical ab initio clamped nuclei potential curves and absorption dipole transition moments for n = 2-4 of Wolniewicz and Staszewska (J. Mol. Spectrosc. 2003, 220, 45). The resulting Einstein spontaneous Einstein A coefficients are in good agreement with those derived from the absolute intensity measurements of Glass-Maujean et al. (Mol. Phys. 2007, 105, 1535). The results reveal widespread vibronic intensity perturbations in the Q(N) Rydberg series, whereas the line frequencies are comparatively little affected by nonadiabatic effects. PMID:19548643

Glass-Maujean, M; Jungen, Ch

2009-11-26

73

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

74

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

75

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

76

INTERACTION OF LASER RADIATION WITH MATTER: Collisionless absorption of intense laser radiation in nanoplasma  

NASA Astrophysics Data System (ADS)

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.

Zaretsky, D. F.; Korneev, Philipp A.; Popruzhenko, Sergei V.

2007-06-01

77

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

78

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

79

A new representation of the absorption by the CO2 15-microns band for a Martian general circulation model  

Microsoft Academic Search

A model for absorption by the CO2 15-microns band has been adapted from the Morcrette et al. (1986) terrestrial wide-band model for use in a general circulation model of the Martian atmosphere. The absorption model is validated by comparison with exact line-by-line integrations for a set of atmospheric profiles characteristic of Martian conditions. The Doppler effect is included in a

Frederic Hourdin

1992-01-01

80

Lunar iron abundance determination using the 2-?m absorption band parameters  

NASA Astrophysics Data System (ADS)

In this work we report the first employment of the 2-?m absorption band parameters to estimate FeO weight percentage (wt.%) abundances from high-resolution Near-Infrared (NIR) lunar data, as measured by the SIR-2 instrument on board Chandrayaan-1. Our method is based on the algorithm originally developed by Le Mouélic et al. (Le Mouélic, S., Langevin, Y., Erard, S., Pinet, P., Chevrel, S., Daydou, Y. [2000]. J. Geophys. Res. 105, 9445-9456) for assessing FeO wt.% in lunar surface materials analyzing Clementine UVVIS and NIR data. A small fresh-looking crater was selected as a test bench to understand the detrimental effect on spectral parameters caused by the prolonged exposure of surface materials to space weather. Using both 1-?m and 2-?m absorption band parameters we found a correlation of about 90% between iron abundances estimated by our method and actual laboratory-measured values (from Apollo and Luna data-sets). Also, Moon Mineralogy Mapper (M3) data collected at the same Coordinated Universal Time (UTC) were used to verify the SIR-2 data-set. Iron abundance estimations based on these instruments were compared with the Clementine iron abundance map produced by the algorithm developed by Lucey et al. (Lucey, P.G., Blewett, D.T., Hawke, B.R. [1998]. J. Geophys. Res. 103, 3679-3699). We selected crater Tycho as a case study for comparing our FeO wt.% estimates against published ones based on Clementine data and found them in good agreement. This study confirms that the 2-?m absorption band can be interrogated effectively to estimate the FeO wt.% content of exposed lunar surface materials through their NIR reflectance characteristics. Applications of this method would potentially be of great interest to those missions to the Moon and other planetary bodies carrying spectrometers ranging above the 0.9 ?m point.

Bhatt, Megha; Mall, Urs; Bugiolacchi, Roberto; McKenna-Lawlor, Susan; Banaszkiewicz, Marek; Nathues, Andreas; Ullaland, Kjetil

2012-07-01

81

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

SciTech Connect

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

2014-04-24

82

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

83

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

84

Intensity profiles of superdeformed bands in Pb isotopes in a two-level mixing model  

SciTech Connect

A recently developed two-level mixing model of the decay out of superdeformed bands is applied to examine the loss of flux from the yrast superdeformed bands in {sup 192}Pb, {sup 194}Pb, and {sup 196}Pb. Probability distributions for decay to states at normal deformations are calculated at each level. The sensitivity of the results to parameters describing the levels at normal deformation and their coupling to levels in the superdeformed well is explored. It is found that except for narrow ranges of the interaction strength coupling the states, the amount of intensity lost is primarily determined by the ratio of {gamma} decay widths in the normal and superdeformed wells. It is also found that while the model can accommodate the observed fractional intensity loss profiles for decay from bands at relatively high excitation, it cannot accommodate the similarly abrupt decay from bands at lower energies if standard estimates of the properties of the states in the first minimum are employed.

Wilson, A. N.; Szigeti, S. S.; Rogers, J. I. [Department of Nuclear Physics, Research School of Physical Sciences and Engineering Australian National University, Canberra, ACT 0200 (Australia); Department of Physics, Australian National University, Canberra, ACT 0200 (Australia); Davidson, P. M. [Department of Nuclear Physics, Research School of Physical Sciences and Engineering Australian National University, Canberra, ACT 0200 (Australia); Cardamone, D. M. [Physics Department, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6 (Canada)

2009-01-15

85

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

NASA Astrophysics Data System (ADS)

Brief bursts of third-octave bands of noise (center frequencies at 0.5, 1.0, 2.0 and 4.0 kHz) and band pass noises with different degrees of low-frequency content (0.5 to 4.0 kHz, 1.0 to 4.0 kHz and 2.0 to 4.0 kHz) were recorded binaurally from 17 different horizontal locations (90 degrees on the left to 90 degrees on the right in 11.25 degree steps) one meter from the ears of an anthropomorphic mannequin (KEMAR) in an anechoic room and a reverberant room. The recorded sounds were processed by attenuating or removing interaural intensity differences and presented to five normally hearing subjects through insert transducers (ER-3A) in a sound- source identification task. The localization accuracy of the subjects for unprocessed signals was similar to that reported in the literature for free-field listening. Auditory localization performance was not significantly degraded by reducing interaural intensity difference cues to 50% of their original value in dB. However, attenuating interaural intensity differences by 100% degraded localization performance by introducing a bias toward the center. The effect was frequency dependent, with no effect for a 0.5 kHz third octave band. Some asymmetries in localization performance were observed. Localization accuracy was similar for signals recorded in a reverberant room as for those recorded in an anechoic room.

Bakke, Matthew H.

86

Photodoping and enhanced visible light absorption in single-walled carbon nanotubes functionalized with a wide band gap oligomer.  

PubMed

Carbon nanotubes feature excellent electronic properties but narrow absorption bands limit their utility in certain optoelectronic devices, including photovoltaic cells. Here, the addition of a wide-bandgap gap oligomer enhances light absorption in the visible spectrum. Furthermore, the oligomer interacts with the carbon nanotube through a peculiar charge transfer, which provides insight into Type II heterojunctions. PMID:25367178

Bunes, Benjamin R; Xu, Miao; Zhang, Yaqiong; Gross, Dustin E; Saha, Avishek; Jacobs, Daniel L; Yang, Xiaomei; Moore, Jeffrey S; Zang, Ling

2015-01-01

87

Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities  

NASA Astrophysics Data System (ADS)

We present the first absorption measurements at laser intensity between 10^17 to 10^20 W/cm^2 using an intergrating sphere and a suite of diagnostics that measures scale length, hot electrons and laser harmonics. A much-enhanced absorption in the regime of relativestic electron heating was observed. Furthermore, we present measurements on the partitioning of absorbed laser energy into thermal and non-thermal electrons when illuminating solid targets from 10^17 to 10^19 W/cm^2. This was measured using a sub-picosecond x-ray streak camera interfaced to a dual crystal von H'amos crystal spectrograph, a spherical crystal x-ray imaging spectrometer, an electron spectrometer and optical spectrometer. Our data suggests an intensity dependent energy-coupling transition with greater energy portion into non-thermal electrons that rapidly transition to thermal electrons. The details of these experimental results and modeling simulations will be presented.

Ping, Yuan

2005-10-01

88

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

89

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

90

Absorption coefficients for the 6190-A CH sub 4 band between 290 and 100 K with application to Uranus' atmosphere  

SciTech Connect

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 CH{sub 4} 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum. 18 refs.

Smith, WM.H.; Conner, C.P.; Baines, K.H. (Washington Univ., Saint Louis, MO (USA) JPL, Pasadena, CA (USA))

1990-05-01

91

Surface-enhanced Raman scattering of 4-aminobenzenethiol in Ag sol: relative intensity of a1- and b2-type bands invariant against aggregation of Ag nanoparticles.  

PubMed

4-Aminobenzenthiol (4-ABT) is an unusual molecule, showing variable surface-enhanced Raman scattering (SERS) spectra depending upon measurement conditions. In an effort to reduce ambiguity and add clarity, we have thus conducted an ultraviolet-visible (UV-vis) extinction measurement, along with Raman scattering measurement, after adding 4-ABT into aqueous Ag sol. Upon the addition of 4-ABT, the surface plasmon absorption band of Ag at 410 nm gradually diminished and, concomitantly, a weak and broad band developed at longer wavelengths, obviously because of the aggregation of Ag nanoparticles. At the same time, the Raman scattering peaks of 4-ABT varied in intensity as the Ag particles proceeded to form aggregates. A close examination revealed that the peak intensity of the ring 7a band of 4-ABT, a typical a(1) vibrational mode, could be correlated with the UV-vis extinction of the Ag sol measured at the excitation laser wavelength. In a separate Raman measurement conducted using sedimented Ag colloidal particles, 4-ABT was found not to be subjected to any surface-induced photoreaction, implying that all of the observable Raman peaks were, in fact, solely due to 4-ABT on Ag. The intensities of the b(2)-type bands, such as the ring 3, 9b, and 19b modes of 4-ABT, were then analyzed and found to be invariant with respect to the 7a band, irrespective of the extent of Ag aggregation as far as at a fixed excitation wavelength. The intensity ratio of the b(2)-type/7a bands would then reflect the extent of the chemical enhancement that was involved in the SERS of 4-ABT in aggregated Ag sol. PMID:21405076

Kim, Kwan; Yoon, Jae Keun; Lee, Hyang Bong; Shin, Dongha; Shin, Kuan Soo

2011-04-19

92

Shallow electron traps in alkali halide crystals: Mollwo-Ivey relations of the optical absorption bands  

NASA Astrophysics Data System (ADS)

Evidences are given that two classes of the transient IR- absorption bands: (a) with max. at 0.27-0.36 eV in NaCl, KCl, KBr, KI and RbCl (due to shallow electron traps according G. Jacobs or due to bound polarons according E.V. Korovkin and T.A. Lebedkina) and (b) with max. at 0.15-0.36 eV in NaI, NaBr, NaCl:I, KCl:I, RbCl:I and RbBr:I (due to on-center STE localized at iodine dimer according M. Hirai and collaborators) are caused by the same defect- atomic alkali impurity center [M+]c0e- (electron e- trapped by a substitutional smaller size alkali cation impurity [M+]c0). The Mollwo-Ivey plots (for the transient IR-absorption bands) of the zero-phonon line energy E0 (for NaCl, KCl, KBr, RbCl and NaBr, KCl:I) and/or the low-energy edge valued E0 (for NaI, RbCl:I, RbBr:I) versus anion-cation distance (d) evidence that two types of the [M+]c0e- centers are predominant: (a) [Na+]c0e- in the KX and RbX host crystals with the relation E0approximately equals 6.15/d2.74, (b) [Li+]c03- in the NaX host crystals - E0approximately equals 29.4/d4.72. The Mollwo-Ivey relation E0approximately equals 18.36/d(superscript 2.70 is fulfilled as well for the F' band in NaCl, KCl, KBr, KI, RbCl, RbI if we use the F' center optical binding energy values E0.

Ziraps, Valters

2001-03-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

94

Theoretical calculation of absorption intensities of C2H and C2D  

NASA Astrophysics Data System (ADS)

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

Tarroni, Riccardo; Carter, Stuart

2004-01-01

95

Microwave absorption of ? /4 wave absorbers using high permeability magnetic composites in quasimicrowave frequency band  

NASA Astrophysics Data System (ADS)

For the aim of thin electromagnetic wave absorbers used in quasimicrowave frequency band, this study proposes the high-permeability magnetic composite sheets of quarter wavelength thickness (? /4 spacer) coated with resistive film of 377?/sq (impedance transformer). For the ? /4 spacer, flexible magnetic composite sheets containing Fe85Si9.5Al5.5 flake particles are used. Due to high permeability and high permittivity of the composite sheets, ? /4 thickness can be reduced as low as 0.5mm in 2GHz. By coating the conductive paste with surface resistance close to 377?/sq on the ? /4 spacer, the reflection loss can be reduced to as low as -11dB (90% power absorption). This is attributed to the wave impedance matching led by the resistive film of free-space impedance combined with a ? /4 thickness of high-permeability magnetic spacer.

Lee, Kyung-Sub; Yun, Yeo-Chun; Kim, Sang-Woo; Kim, Sung-Soo

2008-04-01

96

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

97

Long-period fiber grating inscription under high-intensity 352 nm femtosecond irradiation: Three-photon absorption  

E-print Network

-photon absorption and energy deposition in cladding Stephen A. Slattery, David N. Nikogosyan * Department of Physics-intensity 211 and 264 nm laser pulses. Three-photon absorption coefficients for pure fused silica in the fiber cladding and the core. It was shown that the deposition of the majority of the absorbed energy

Nikogosyan, David N.

98

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

99

Nonadiabatic effects in the photodissociation of H2S in the first absorption band - An ab initio study  

Microsoft Academic Search

Results are presented of extensive ab initio calculations of the photodissociation of H2S through excitation in the first absorption band (195 nm). The calculated absorption spectra for H2S and D2S were found to agree well with the measured spectra, and the calculated rotational- and vibrational-state distributions of the HS and DS fragments reproduced recent measurements. The photodissociation of H2S is

Bernd Heumann; Klaus Weide; Rudolf Dueren; Reinhard Schinke

1993-01-01

100

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

Microsoft Academic Search

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

Susanne Ohlhorst; Harald Behrens; François Holtz

2001-01-01

101

Sub-Doppler absorption narrowing in atomic vapor at two intense laser fields.  

PubMed

We have experimentally studied electromagnetically induced transparency (EIT) and absorption (EIA) in hot 85Rb atomic vapor using probe and coupling light with comparable power levels. We have shown that strong-probe EIT has different linewidth and appears in fewer configurations than does usual, weak probe EIT. In V-scheme, where optical pumping and saturation are dominant mechanisms, narrow EIT is possible only when a probe is tuned to a closed transition. The width of the EIT resonance increases with laser intensity with non-linear dependence, similar to the weak-probe EIT in Lambda- scheme. The EIT in Lambda- scheme was observed when two transitions had balanced population losses. The EIA was modified for the case of a strong probe as well: in four-level N-scheme with Zeeman sublevels the EIA was observed only for a cycling transition when F'=F+1, where F and F' are the angular momenta of the 5 2S1/2 (ground) and 5 2P3/2 (excited) state hyper-fine levels, respectively. The combination of strong probe and strong coupling laser beam intensities allows observation of an absorption dip due to three-photon resonance in a four-level scheme that involves the Raman transitions via virtual level. PMID:19495020

Krmpot, Aleksandar; Mijailovi?, Marina; Pani?, Bratimir; Luki?, Dragan; Kovacevi?, Aleksander; Panteli?, Dejan; Jelenkovi?, Branislav

2005-03-01

102

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

PubMed

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

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

2013-01-01

103

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

104

The quasi-molecular absorption bands in UV region caused by the non-symmetric ion-atom radiative processes in the solar photosphere  

NASA Astrophysics Data System (ADS)

The aim of this research is to show that the radiative processes in strongly non- symmetric ion- atom collisions significantly influence on the opacity of the solar photosphere in UV region. Within this work only the He+H+ and H+A+ ion-atom systems, where A is the atom of one of the metal (Mg, Si and Al), are taken in to account. It is caused by the fact that the needed characteristics of the corresponding molecular ions, i.e. molecular potential curves and dipole matrix elements, have been determined by now. Here the non-symmetric radiative processes are considered under the conditions characterizing the non-LTE standard model of the solar atmosphere (Vernazza J, Avrett E and Loser R 1981 ApJS 45 635), which gives the possibility to perform all needed calculations and determined the corresponding spectral absorption coefficients. It is shown that the examined processes generate rather wide quasi-molecular absorption bands in the UV and VUV regions, whose intensity is comparable and sometimes even larger than the intensity of known one's caused by the H+H+ radiative collision processes, which are included now in the solar atmosphere models. Consequently, the presented results suggest that the non-symmetric ion-atom absorption processes have to be also included in standard models of the solar atmosphere.

Mihajlov, A. A.; Sre?kovi?, V. A.; Ignjatovi?, L. J. M.; Dimitrijevi?, M. S.; Metropoulos, A.

2012-12-01

105

Photodissociation dynamics and emission spectroscopy of H2S in its first absorption band - A time dependent quantum mechanical study  

Microsoft Academic Search

A theoretical study of the photodissociation dynamics of H2S in its first absorption band is presented. The potential energy surfaces underlying the dynamics of the breakup process have been modeled so as to reproduce the principal features of all the available experimental data. The modeling is performed using time dependent quantum dynamical methods and involves the exact numerical solution of

Richard N. Dixon; C. Clay Marston; Gabriel G. Balint-Kurti

1990-01-01

106

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

107

Accurate laser measurements of ozone absorption cross-sections in the Hartley band  

NASA Astrophysics Data System (ADS)

Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 × 10-18 cm2 molecule-1 with an expanded relative uncertainty of 0.84 %. This is lower than the conventional value currently in use and measured by Hearn in 1961 with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross sections with reduced uncertainties, a system to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier Transform Infrared spectroscopy was setup. This resulted in new measurements of absolute values of ozone absorption cross sections of 9.48 × 10-18, 10.44 × 10-18, and 11.07 × 10-18 cm2 molecule-1, with relative expanded uncertainties better than 0.6%, for the wavelengths (in vacuum) of 244.062, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non UV photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

Viallon, J.; Lee, S.; Moussay, P.; Tworek, K.; Petersen, M.; Wielgosz, R. I.

2014-08-01

108

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

SciTech Connect

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

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

1994-02-04

109

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

SciTech Connect

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

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

2005-10-01

110

Line positions, intensities and self-broadening coefficients for the ?5 band of methyl chloride  

NASA Astrophysics Data System (ADS)

High resolution Fourier transform spectra have been recorded around 6.9 ?m at room temperature using a rapid scan Bruker IFS 120 HR interferometer (unapodized Bruker resolution=0.005 cm-1). Transitions of both 12CH335Cl and 12CH337Cl isotopologues belonging to the ?5 perpendicular band have been studied. Line positions, intensities, and self-broadening coefficients have been retrieved using a multispectrum fitting procedure that allowed to fit simultaneously the whole set of experimental spectra recorded at various pressures of CH3Cl. The wavenumber calibration has been performed using the frequencies of CO2 transitions. The transition dipole moments squared have been determined for each measured line and the whole set of measurements has been compared with previous measurements and with values from HITRAN and GEISA databases. The rotational J and K dependencies of the self-broadening coefficients have been clearly observed and modeled using empirical polynomial expansions. The average accuracy of the line parameters obtained in this work has been estimated to be between 0.1×10-3 and 1×10-3 cm-1 for line positions, between 2% and 5% for line intensities and between 5% and 10% for self-broadening coefficients depending on the transitions.

Barbouchi Ramchani, A.; Jacquemart, D.; Dhib, M.; Aroui, H.

2013-05-01

111

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

112

Extraordinary terahertz absorption bands observed in micro/nanostructured Au/polystyrene sphere arrays  

PubMed Central

Terahertz (THz) time-domain spectroscopy is carried out for micro/nanostructured periodic Au/dielectric sphere arrays on Si substrate. We find that the metal-insulator transition can be achieved in THz bandwidth via varying sample parameters such as the thickness of the Au shell and the diameter of the Au/dielectric sphere. The Au/polystyrene sphere arrays do not show metallic THz response when the Au shell thickness is larger than 10 nm and the sphere diameter is smaller than 500 nm. This effect is in sharp contrast to the observations in flat Au films on Si substrate. Interestingly, the Au/polystyrene sphere arrays with a 5-nm-thick Au shell show extraordinary THz absorption bands or metallic optical conductance when the diameter of the sphere is larger than 200 nm. This effect is related to the quantum confinement effect in which the electrons in the structure are trapped in the sphere potential well of the gold shell. PMID:23190688

2012-01-01

113

Synthesis and photocatalytic activity of perovskite niobium oxynitrides with wide visible-light absorption bands.  

PubMed

Photocatalytic activities of perovskite-type niobium oxynitrides (CaNbO?N, SrNbO?N, BaNbO?N, and LaNbON?) were examined for hydrogen and oxygen evolution from water under visible-light irradiation. These niobium oxynitrides were prepared by heating the corresponding oxide precursors, which were synthesized using the polymerized complex method, for 15?h under a flow of ammonia. They possess visible-light absorption bands between 600-750?nm, depending on the A-site cations in the structures. The oxynitride CaNbO?N, was found to be active for hydrogen and oxygen evolution from methanol and aqueous AgNO?, respectively, even under irradiation by light at long wavelengths (?<560?nm). The nitridation temperature dependence of CaNbO?N was investigated and 1023?K was found to be the optimal temperature. At lower temperatures, the oxynitride phase is not adequately produced, whereas higher temperatures produce more reduced niobium species (e. g., Nb³(+) and Nb?(+)), which can act as electron-hole recombination centers, resulting in a decrease in activity. PMID:21226214

Siritanaratkul, Bhavin; Maeda, Kazuhiko; Hisatomi, Takashi; Domen, Kazunari

2011-01-17

114

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

115

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 (tilde A{}^1B_1 and tilde B{}^1A_2 ) and two lowest triplet (tilde a^3 B_1 and tilde b^3 A_2 ) 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

116

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

117

Modelling vibrational-rotational interactions in intensities of v2 band of H2O by Pade approximants  

NASA Astrophysics Data System (ADS)

A semiempirical model in the form of Pade approximants, describing vibrational-rotational (VR) interactions in intensities of VR-lines of v2 water vapor (H2O) band, was developed. The corresponding to the C2v molecular symmetry group matrix elements, involved in the expansion of the transformed dipole moment, was applied to the derivation. The treatment of experimental intensities of v2 H2O band for transitions with ?K = +/-1 and ?K = +/-3 by means of obtained model results in decreasing the root mean square deviation (RMS) about two times (2.82 % instead of 6.20 %) in comparison to the traditional scheme.

Egorov, O. V.; Voitsekhovskaya, O. K.

2014-11-01

118

The absorption coefficient of the liquid N2 2.15-micron band and application to Triton  

NASA Technical Reports Server (NTRS)

The present measurements of the temperature dependence exhibited by the liquid N2 2.15-micron 2-0 collision-induced band's absorption coefficient and integrated absorption show the latter to be smaller than that of the N2 gas, and to decrease with decreasing temperature. Extrapolating this behavior to Triton's nominal surface temperature yields a new estimate of the N2-ice grain size on the Triton south polar cap; a mean N2 grain size of 0.7-3.0 cm is consistent with grain growth rate calculation results.

Grundy, William M.; Fink, Uwe

1991-01-01

119

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

120

Non-quadratic-intensity dependence of two-photon absorption induced fluorescence of organic chromophores in solution  

NASA Astrophysics Data System (ADS)

We have provided a model to interpret the non-quadratic-intensity dependence behavior commonly observed in the two-photon fluorescence (TPF) experiment excited with high laser intensity. The model also provides one with a different technique to measure the two-photon absorption cross section of an organic chromophore in solution. In contrast to the commonly used low intensity technique that depends on the quadratic-intensity law, the present technique is based on the non-quadratic-intensity dependence of two-photon fluorescence. Auxiliary data such as two-photon quantum efficiency and fluorescence collection efficiency, essential in the low intensity method, are not required in the present technique. TPF measurements of Rhodamine B in methanol are carried out to demonstrate the validity of the present method. The method is used to determine the two-photon absorption cross section of a new chromophore attached with tricyano-derivatized furan as the electron acceptor. The two-photon absorption cross section measured using this method is also compared with that using a conventional transmission technique.

Wang, C. H.; Tai, Oliver Y.-H.; Wang, Yuxiao; Tsai, Tsung-Hsiu; Chang, Nein-Chen

2005-02-01

121

Spectroscopic Determination of Leaf Biochemistry Using Band-Depth Analysis of Absorption Features and Stepwise Multiple Linear Regression  

Microsoft Academic Search

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

Raymond F. Kokaly; Roger N. Clark

1999-01-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

123

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.

124

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

125

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

126

Time-Resolved IR-Absorption Spectroscopy of Hot-Electron Dynamics in Satellite and Upper Conduction Bands in GaP  

NASA Technical Reports Server (NTRS)

The relaxation dynamics of hot electrons in the X6 and X7 satellite and upper conduction bands in GaP was directly measured by femtosecond UV-pump-IR-probe absorption spectroscopy. From a fit to the induced IR-absorption spectra the dominant scattering mechanism giving rise to the absorption at early delay times was determined to be intervalley scattering of electrons out of the X7 upper conduction-band valley. For long delay times the dominant scattering mechanism is electron-hole scattering. Electron transport dynamics of the upper conduction band of GaP has been time resolved.

Cavicchia, M. A.; Alfano, R. R.

1995-01-01

127

Interpretation of multiple Q(0,0) bands in the absorption spectrum of Mg-mesoporphyrin embedded in horseradish peroxidase.  

PubMed Central

Mg-mesoporphyrin horseradish peroxidase (MgMP-HRP) and MgMP-HRP complexed with naphtohydroxamic acid (NHA) have been studied by fluorescence line narrowing (FLN) and pressure tuning spectral hole burning (SHB) techniques. In each sample, the low temperature absorption spectra show more than one transition in the origin range of the Q band. Comparisons with broad-band fluorescence spectra and FLN studies suggest that the multiple band feature originates from the presence of different configurations of the metal-porphyrin that are subject to Qx-Qy splitting within the protein cavity. This suggestion is supported by pressure tuning SHB studies. In the uncomplexed as well as in the NHA-complexed form of MgMP-HRP, irradiation in the Q band produces photoproduct bands, which has been attributed to a species with smaller Qx-Qy splitting. In an amorphous matrix, on the other hand, only one form of MgMP could be found, and no splitting could be observed. The binding of NHA does not significantly alter the bulk parameters of the protein matrix, but it reduces the structural variety in the configuration of MgMP to a single form with a more distorted structure and thus with an enlarged Qx-Qy splitting. PMID:9199803

Balog, E; Kis-Petik, K; Fidy, J; Köhler, M; Friedrich, J

1997-01-01

128

Absolute band intensities in the nu19/nu23 (530 cm(-1)) and nu7 (777 cm(-1)) bands of acetone ((CH3)2CO) from 232 to 295 K  

NASA Technical Reports Server (NTRS)

Absolute band intensities of acetone ((CH3)2CO) in the nu19/nu23 and nu7 band systems near 530 and 777 cm(-1), respectively, were measured at temperatures of 232, 262 and 295 K, using a Fourier transform infrared (FTIR) spectrometer. No evident temperature dependence for the band intensities was observed. The dipole moments and the fundamental band intensities were derived in the harmonic oscillator approximation. The results are useful for the spectroscopic retrieval of acetone concentrations in the upper atmosphere.

Wang, W. F.; Stevenson, A.; Reuter, D. C.; Sirota, J. M.

2000-01-01

129

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

130

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

131

Experimental evidence and theoretical modeling of two-photon absorption dynamics in the reduction of intensity noise of solid-state Er:Yb lasers  

E-print Network

A theoretical and experimental investigation of the intensity noise reduction induced by two-photon absorption in a Er,Yb:Glass laser is reported. The time response of the two-photon absorption mechanism is shown to play an important role on the behavior of the intensity noise spectrum of the laser. A model including an additional rate equation for the two-photon-absorption losses is developed and allows the experimental observations to be predicted.

Amili, Abdelkrim El; Alouini, Mehdi

2013-01-01

132

Acne phototherapy with a high-intensity, enhanced, narrow- band, blue light source: an open study and in vitro investigation  

Microsoft Academic Search

The purpose of this study was to investigate the efficacy of phototherapy with a newly-developed high-intensity, enhanced, narrow-band, blue light source in patients with mild to moderate acne. An open study was performed in acne patients who were treated twice a week up to 5 weeks. Acne lesions were reduced by 64%. Two patients experienced dryness. No patient discontinued treatment

Akira Kawada; Yoshinori Aragane; Hiroko Kameyama; Yoshiko Sangen; Tadashi Tezuka

133

Eu3+-activated Y2MoO6: a narrow band red-emitting phosphor with strong near-UV absorption.  

PubMed

Near-UV excited narrow line red-emitting phosphors, Eu(3+)-activated Y2MoO6 systems, were synthesized using a simple molten salt reaction. The structure and photoluminescence characteristics were investigated using X-ray powder diffraction, UV-Vis absorption and fluorescent spectrophotometry. The excitation spectra show strong broad-band absorptions in the near-UV to blue light regions which match the radiation of near-UV light-emitting diode chips well. Under excitation of either near-UV or blue light, intense red emission with a main peak of 611 nm is observed, ascribed to the (5)D0-(7)F2 transition of Eu(3+) ions; the optimal doping concentration is 20 mol%. The chromaticity coordinates (x = 0.65, y = 0.34) of the as-obtained phosphor are very close to the National Television Standard Committee standard values (x = 0.67, y = 0.33). All these characteristics suggest that this material is a promising red-emitting phosphor candidate for white-LEDs based on near-UV LED chips. PMID:23124929

He, Xianghong; Bian, Danping; Wang, Hao; Xu, Jian

2013-01-01

134

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Excitonic optical absorption in semiconductors under intense terahertz radiation  

Microsoft Academic Search

The excitonic optical absorption of GaAs bulk semiconductors under intense terahertz (THz) radiation is investigated numerically. The method of solving initial-value problems, combined with the perfect matched layer technique, is used to calculate the optical susceptibility. In the presence of a driving THz field, in addition to the usual exciton peaks, 2p replica of the dark 2p exciton and even-THz-photon-sidebands

Tong-Yi Zhang; Wei Zhao

2008-01-01

135

Optical absorption of divalent metal tungstates: Correlation between the band-gap energy and the cation ionic radius  

E-print Network

We have carried out optical-absorption and reflectance measurements at room temperature in single crystals of AWO4 tungstates (A = Ba, Ca, Cd, Cu, Pb, Sr, and Zn). From the experimental results their band-gap energy has been determined to be 5.26 eV (BaWO4), 5.08 eV (SrWO4), 4.94 eV (CaWO4), 4.15 eV (CdWO4), 3.9-4.4 eV (ZnWO4), 3.8-4.2 eV (PbWO4), and 2.3 eV (CuWO4). The results are discussed in terms of the electronic structure of the studied tungstates. It has been found that those compounds where only the s electron states of the A2+ cation hybridize with the O 2p and W 5d states (e.g BaWO4) have larger band-gap energies than those where also p, d, and f states of the A2+ cation contribute to the top of the valence band and the bottom of the conduction band (e.g. PbWO4). The results are of importance in view of the large discrepancies existent in prevoiusly published data.

Lacomba-Perales, R; Errandonea, D; Martinez-Garcia, D; Segura, A

2008-01-01

136

Hydration of the hydrogen ion in aqueous solutions from intensity of the OD band of HDO  

NASA Astrophysics Data System (ADS)

The OD band of HDO has been studied in partly deuterated aqueous solutions of acids: hydrochloric, sulfuric, nitric, trifluoroacetic, and perchloric. Composition of the hydrogen ion is determined. Observations are made on hydration of the perchlorate and trifluoroacetate ions.

Zawada, K.; Dryjañski, P.

2001-01-01

137

Iron-absorption band analysis for the discrimination of iron-rich zones  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Analysis of ERTS-1 images of Nevada has followed two courses: comparative lineament mapping and spectral reflectance evaluation. The comparative lineament mapping was conducted by mapping lineaments on 9 x 9 inch prints of MSS bands 5 and 7, transferring the data to a base map, and comparing the results with existing geologic maps. The most significant results are that lineaments are more numerous on the band 7 images, and approximately 100 percent more were mapped than appear on existing maps. Geologic significance of these newly mapped lineaments will not be known until they are checked in the field: many are probably faults. Spectral analysis has been limited to visual comparison among the four MSS bands. In general, higher scene contrast is shown in the near infrared bands (6 and 7) than in the visible wavelength bands (4 and 5). The economic implications of these results derive chiefly from the greater efficiency that can be obtained by using near infrared as well as visible wavelength images.

Rowan, L. C. (principal investigator)

1972-01-01

138

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

PubMed

Absorption coefficients in the bending ?2 and stretching 2?3 bands of OCS perturbed by He at high pressures up to 300 atm have been measured and analyzed in the impact-approximation region by two theoretical models accounting for the line mixing. In the first approach, the frequency-independent relaxation operator is treated semi-classically [N. N. Filippov and M. V. Tonkov, J. Quant. Spectrosc. Radiat. Transf. 50, 111 (1993)] with adiabatic corrections. To characterize the strength of collisions and the line mixing efficiency a single parameter G is used and its value is estimated from the intermolecular interaction potential. The adiabaticity of collisions and the corresponding correction to the collisional cross sections amplitude are taken into account by two other parameters ?(corr) and ? deduced from fitting to experimental line widths. In the second approach, the symmetrized non-Markovian relaxation operator of Energy-Corrected Sudden type developed for rototranslational Raman spectra of linear rotators [J. Buldyreva and L. Bonamy, Phys. Rev. A 60, 370 (1999)] and satisfying all the basic properties (in particular, the detailed balance relation and the double-sided sum rules) is adapted to absorption spectra for the first time. Its off-diagonal elements are determined via the common adiabaticity factor and the basic transition rates whose parameters are adjusted on experimental values of isolated line widths. Both models provide a very consistent description of OCS-He 2?3 and ?2 band intensities up to the maximal experimentally studied pressure, with a slightly more realistic picturing of the inter-branch exchange by the second approach. PMID:23635121

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

2013-04-28

139

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

140

Laser-power measurement technique using the relationship between intensities of photoluminescence bands  

Microsoft Academic Search

We experimentally established that the dependence of ratio between luminescence intensities of two centers on excitation power was determined by, besides the concentrations of these centers, the inverse ratio of their radiative lifetimes. This effect can be used to measure a power of laser excitation by relationship of luminescence intensities, corresponding to two centers with different radiative lifetime. We propose

V. Y. Degoda; A. A. Artamonova; V. E. Rodionov

1995-01-01

141

Electromagnetic wave absorption properties of amorphous alloy-ferrite-epoxy composites in quasi-microwave band  

Microsoft Academic Search

Reports on the electromagnetic wave absorption properties of amorphous alloy-ferrite-epoxy composites with various amorphous alloy fractions in the frequency range from 1 to 5 GHz. We varied the fraction of amorphous alloy in amorphous alloy-ferrite-epoxy composites from 0 to 50 vol.% at a fixed 50 vol.% fraction of epoxy resin polymer. We measured the complex permeability ? and permittivity ?

K. M. Lim; M. C. Kim; K. A. Lee; C. G. Park

2003-01-01

142

Ultrawide Band Microwave Absorption Properties of Ultrasound Processed CrO2-Paraffin Wax Composites  

NASA Astrophysics Data System (ADS)

The microwave absorption properties of ultrasound processed CrO2-paraffin wax composites are investigated in the frequency range of 0.1-18 GHz by the coaxial method. By analysis and comparison between ultrasound processed sample and the unprocessed sample, we discovered that the ultrasound treatment will induce a thin insulating Cr2O3 shell over the CrO2 rods to form a core/shell structure that performs excellent in microwave absorption. An optimum reflection loss of -50.9 dB was found at 5.2 GHz with a matching thickness of 3.4 mm for 70 wt % CrO2-paraffin wax composite. Moreover, the frequency range of which the reflection loss is less than -20 dB spreads from 4.0 to 8.7 GHz with the corresponding absorption thickness ranges from 2.3 to 4.0 mm. The comparison among our result and other reported ones indicates that, in addition to its common applications, the CrO2 after certain process may have potential in microwave absorption. More profoundly, the technique of ultrasound process employed in this report may suggest a new method to induce, according to different needs, crystalline phase transition for a various range of metastable chemicals.

Xi, Li; Yang, Yikai

2011-03-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

144

Orientation of chromophores in reaction centers of Rhodopseudomonas sphaeroides. Evidence for two absorption bands of the dimeric primary electron donor.  

PubMed

Chromatophores from Rhodopseudomonas sphaeroides were oriented by allowing aqueous suspensions to dry on glass plates. Orientation of reaction center pigments was investigated by studying the linear dichroism of chromatophores in which the absorption by antenna bacteriochlorophyll had been attenuated through selective oxidation. Alternatively the light-induced absorbance changes, in the ranges 550-650 and 700-950nm, were studied in untreated chromatophores. The long wave transition moment of reaction center bacteriochlorophyll (P-870) was found to be nearly parallel to the plane of the membrane, whereas the long wave transition moments of bacteriopheophytin are polarized out of this plane. For light-induced changes the linear dichroic ratios, defined as deltaav/deltaah, are nearly the same for untreated and for oxidized chromatophores. Typical values are 1.60 at 870 nm, 0.80 at 810nm, 1.20 at 790 nm, 0.70 at 765 nm, 0.30 at 745 nm , and 0.50 at 600 nm. The different values for the absorbance decrease at 810 nm (0.80) and the increase at 790 nm (1.20) are incompatible with the hypothesis that these changes are due to the blue-shift of a single band. We propose that the decreases at 870 and 810 nm reflect bleaching of the two components of a bacteriochlorophyll dimer, the "special pair" that shares in the photochemical donation of a single electron. The increase at 790 nm then represents the appearance of a monomer band in place of the dimer spectrum, as a result of electron donation. This hypothesis is consistent with available data on circular dichroism. It is confirmed by the presence of a shoulder at 810 nm in the absorption spectrum of reaction centers at low temperature; this band disappears upon photooxidation of the reaction centers. For the changes near 760 nm, associated with bacteriopheophytin, the polarization and the shape of the "light-dark" difference spectrum (identical to the first derivative of the absorption spectrum) show that the 760 nm band undergoes a light-induced shift to greater wavelengths. PMID:1087160

Vermeglio, A; Clayton, R K

1976-12-01

145

Capacity bounds for power- and band-limited optical intensity channels corrupted by Gaussian noise  

Microsoft Academic Search

We determine upper and lower bounds on the channel capacity of power- and bandwidth-constrained optical intensity channels corrupted by white Gaussian noise. These bounds are shown to converge asymptotically at high optical signal-to-noise ratios (SNRs). Unlike previous investigations on low-intensity Poisson photon counting channels, such as some fiber optic links, this channel model is realistic for indoor free space optical

Steve Hranilovic; Frank R. Kschischang

2004-01-01

146

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

SciTech Connect

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

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

2011-03-15

147

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

Microsoft Academic Search

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

F. D. Shields; H. E. Bass

1977-01-01

148

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

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

149

Unusual stripes in emission and absorption in solar radio bursts: Ropes of fibers in the meter wave band  

NASA Astrophysics Data System (ADS)

Based on data from the spectrographs of IZMIRAN and Tremsdorf station (Astronomical Institute, Potsdam), we analyze the ropes of narrow-band fibers in the spectra of solar radio bursts in the meter wave band by invoking events of satellite data (SOHO/LASCO, EIT, MDI) for the analysis. We consider in detail basic properties of the ropes in four events in comparison with previously known data. The fibers in ropes are more commonly observed with an overlap in time and frequency, but occasionally (more often at the end of the ropes) they can follow with a separation in time. The fiber duration and recurrence period seldom remain stable and, in general, increase from 0.3 0.5 s at the beginning to several seconds at the end of the rope. The relative values of the instantaneous and total fiber frequency bandwidths change only slightly in different events; ? f / f ? 0.003 0.005 and ? f / f ? 0.02 0.03. Most of the ropes exhibit a low-frequency absorption. The fibers in ropes are similar to ordinary intermediate drift bursts (fiber bursts), but they drift in a narrow frequency band and have a more frequent recurrence in some events. The ropes of fibers are usually observed in the time interval when the shock front catches up with the leading edge of a coronal mass ejection. Under the condition of a unified approach to interpreting the ropes of fibers in all events, their basic properties can be explained in terms of the model of fiber bursts. The connection of fibers with the developed zebra pattern is shown within the framework of a unified approach to the formation theory of stripes in emission and absorption in the model on whistlers.

Chernov, G. P.

2008-07-01

150

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

151

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

152

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

153

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

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

2014-11-21

154

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 (8.2–12.4 GHz) with minimal RL of ?35.0 dB at 9.2 GHz).

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

2014-09-01

155

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

156

Depolarisation of light scattered by disperse systems of low-dimensional potassium polytitanate nanoparticles in the fundamental absorption band  

NASA Astrophysics Data System (ADS)

The results of experimental studies of depolarising properties of disperse systems on the basis of potassium polytitanate nanoplatelets and nanoribbons in the visible and near-UV spectral regions are presented. It is shown that in the fundamental absorption band of the nanoparticle material the increase in the depolarisation factor takes place for the radiation scattered perpendicularly to the direction of the probing beam. For nanoribbons a pronounced peak of depolarisation is observed, which is caused by the essential anisotropy of the particles shape and the peculiarities of the behaviour of the material dielectric function. The empirical data are compared with the theoretical results for 'nanodiscs' and 'nanoneedles' with the model dielectric function, corresponding to that obtained from optical constants of the titanium dioxide dielectric function.

Zimnyakov, D. A.; Yuvchenko, S. A.; Pravdin, A. B.; Kochubey, V. I.; Gorokhovsky, A. V.; Tretyachenko, E. V.; Kunitsky, A. I.

2014-07-01

157

Study of the H-F stretching band in the absorption spectrum of (CH3)2O...HF in the gas phase.  

PubMed

The absorption spectra of the (CH3)2O...HF complex in the range of 4200-2800 cm(-1) were recorded in the gas phase at a resolutions of 0.1 cm(-1) at T = 190-340 K. The spectra obtained were used to analyze their structure and to determine the temperature dependencies of the first and second spectral moments. The band shape of the (CH3)2O...HF complex in the region of the nu1(HF) stretching mode was reconstructed nonempirically. The nu1 and nu3 stretching vibrations and four bending vibrations responsible for the formation of the band shape were considered. The equilibrium geometry and the 1D-4D potential energy surfaces were calculated at the MP2 6-311++G(2d,2p) level with the basis set superposition error taken into account. On the basis of these surfaces, a number of one- and multidimensional anharmonic vibrational problems were solved by the variational method. Solutions of auxiliary 1D and 2D vibrational problems showed the strong coupling between the modes. The energy levels, transition frequencies and intensities, and the rotational constants for the combining vibrational states necessary to reconstruct the spectrum were obtained from solutions of the 4D problem (nu1, nu3, nu5(B2), nu6(B2)) and the 2D problem (nu5(B1), nu6(B1)). The theoretical spectra reconstructed for different temperatures as a superposition of rovibrational bands associated with the fundamental, hot, sum, and difference transitions reproduce the shape and separate spectral features of the experimental spectra. The calculated value of the nu1 frequency is 3424 cm(-1). Along with the frequencies and absolute intensities, the calculation yields the vibrationally averaged values of the separation between the centers of mass of the monomers Rc.-of-m., R(O...F), and r(HF) for different states. In particular, upon excitation of the nu1 mode, Rc.-of-m. becomes shorter by 0.0861 A, and r(HF) becomes longer by 0.0474 A. PMID:18211040

Bulychev, V P; Gromova, E I; Tokhadze, K G

2008-02-14

158

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

159

Absorption  

NSDL National Science Digital Library

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

Katherine M Knudson (Polson Middle School)

1998-04-01

160

A Density-Functional Study on the Change of Q/B-Band Intensity Ratio of Zinc Tetraphenylporphyrin in Solvents  

NASA Astrophysics Data System (ADS)

We study the Q/B-band intensity ratio (IQ/B) of zinc tetraphenylporphyrin (ZnTPP) in various solvents from its electronic structure by utilizing the polarizable continuum model and density functional theory (DFT). The selected solvents are benzene, chloroform, dichloromethane, pyridine and methanol. The Q/B-band intensity ratio is simplified by dipole strength of HOMO ? LUMO and HOMO?1 ? LUMO from a two-level system, or fQ/B. The results show the linear correlation between the calculated fQ/B and the experimental IQ/B. This suggests that IQ/B of ZnTPP in solvents can be studied from dipole strength ratio from a two-level system, where the orbitals are determined by DFT. The change of fQ/B is due to the change of frontier molecular orbital shape of ZnTPP which are dominantly constructed by pz-orbital. In the core part of ZnTPP, the change of pz-orbital shape is inversely proportional to the solvent dielectric constant, ?.

Rusydi, Febdian; Gandaryus Saputro, Adhitya; Kasai, Hideaki

2014-08-01

161

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

162

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

163

Nonlinear polarization spectroscopy in the frequency domain of light-harvesting complex II: absorption band substructure and exciton dynamics.  

PubMed Central

Spectral substructure and ultrafast excitation dynamics have been investigated in the chlorophyll (Chl) a and b Qy region of isolated plant light-harvesting complex II (LHC II). We demonstrate the feasibility of Nonlinear Polarization Spectroscopy in the frequency domain, a novel photosynthesis research laser spectroscopic technique, to determine not only ultrafast population relaxation (T1) and dephasing (T2) times, but also to reveal the complex spectral substructure in the Qy band as well as the mode(s) of absorption band broadening at room temperature (RT). The study gives further direct evidence for the existence of up to now hypothetical "Chl forms". Of particular interest is the differentiated participation of the Chl forms in energy transfer in trimeric and aggregated LHC II. Limits for T2 are given in the range of a few ten fs. Inhomogeneous broadening does not exceed the homogeneous widths of the subbands at RT. The implications of the results for the energy transfer mechanisms in the antenna are discussed. PMID:8534824

Lokstein, H; Leupold, D; Voigt, B; Nowak, F; Ehlert, J; Hoffmann, P; Garab, G

1995-01-01

164

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

165

Nonadiabatic approach for resonant molecular multiphoton absorption processes in intense infrared laser fields  

E-print Network

, including state?to?state multiquantum transitions and transitions from initially thermally distributed states as a whole. Results are presented for the case of IR laser intensity 50 GW/cm2 and frequencies ranging from 2115 to 2165 cm? 1. Excellent agreement...

Ho, Tak-San; Chu, Shih-I

1983-07-14

166

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

NASA Technical Reports Server (NTRS)

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

Zheng, Chunguang; Borysow, Aleksandra

1995-01-01

167

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

168

Controlling spin polarized band-structure by variation of vacancy intensity in nanostructures.  

PubMed

In this study, the magnetic properties of FeAl alloys with different grain sizes produced by high-pressure torsion were probed by means of magnetic Compton scattering. The measurements were performed at 300 and 10 K. Magnetic Compton profiles of nanocrystalline (35 nm) and ultrafine-grained (160 nm) FeAl alloys were analyzed in terms of the integral area, the width, and the distinctive dip intensity at low momenta. The changes in total magnetic moment and the strength of spin-polarization of itinerant electrons are assumed to be caused by vacancies induced during the preparation of the samples. Despite local disordering due to interfacial regions and deviations in perfect stoichiometry for B2 structure, the effect of vacancies is considered as the major magnetic state contributor. PMID:25646271

Kamali, S; Kilmametov, A; Ghafari, M; Itou, M; Hahn, H; Sakurai, Y

2015-02-25

169

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

170

Insulator-metal transition in TiGePt: A combined photoelectron spectroscopy, x-ray absorption spectroscopy, and band structure study  

NASA Astrophysics Data System (ADS)

We present a combined experimental and theoretical study of the electronic structure of the intermetallic compound TiGePt by means of photoelectron spectroscopy, x-ray absorption spectroscopy, and full potential band structure calculations. It was recently shown [S.-V. Ackerbauer , Chemistry - a European Journal10.1002/chem.201102401 18, 6272 (2012)] that TiGePt undergoes a structural phase transition by heating which is accompanied by a large volume contraction and a drastic change of physical properties, in particular a large decrease of the electrical resistivity. The present study revealed substantial differences in the electronic structure for the two TiGePt modifications, although they have the same nominal composition and show similar electron counts for particular valence band states. Our photoemission experiments and band structure calculations establish that an insulator-to-metal transition occurs with an appreciable band broadening and closing of the band gap.

Gegner, J.; Gam?a, M.; Ackerbauer, S.-V.; Hollmann, N.; Hu, Z.; Hsieh, H.-H.; Lin, H.-J.; Chen, C. T.; Ormeci, A.; Leithe-Jasper, A.; Rosner, H.; Grin, Yu.; Tjeng, L. H.

2012-06-01

171

Narrow-band imaging of fields around optically-thick absorption systems: The line-of-sight towards Q 0000-2619  

NASA Astrophysics Data System (ADS)

In this paper we describe deeper observations, both imaging and spectroscopy, of the most distant radio-quiet Ly-alpha galaxy known so far, at redshift of z = 3.428 (galaxy G2) and of other faint objects in the field around the QSO 0000 - 2619. Galaxy G2, which we discovered in the field around the damped absorber of the QSO with narrow-band imaging tuned to detect Ly-alpha emission at the redshift of the absorption system, is the best primaeval galaxy candidate identified so far. Here we report measurements of its restframe UV spectral energy distribution in the interval lambda lambda 1000, 1700 A, in particular the depression of the continuum due to the blanketing of the intervening Ly-alpha forest and the Ly-alpha emission line, and give better upper limits for the high-ionization emission lines, such as NV and CIV. We conclude that this object is very likely a primaeval galaxy observed during a major episode of star formation and in which dust does not extinguish the Ly-alpha emission. We also present Ly-alpha narrow-band imaging of the galaxy which causes the damped absorber in the spectrum of the QSO. No emission is detected, down to a 3 sigma upper limit of 1.2 x 10-17 erg/s/sq cm in an aperture of 2 arcsec in diameter. A corresponding upper limit to the rest-frame equivalent width is 6 A. Similar limits apply also to other 13 flat-spectrum z greater than 3 galaxy candidates identified in the same field by Steidel & Hamilton, if their redshift is such that their Ly-alpha emission falls within our narrow-band filter. However, from their rest-frame UV continuum luminosity, we estimate that the star formation rates for these galaxies are in the range 30 to 100 solar mass/yr. This would suggest that radioquiet primaeval galaxies, though in a star-forming phase, are not characterized by the intense Ly-alpha emission and large star formation rates (SFRs) typical of radio-galaxies. If these candidates are confirmed to be at similar redshifts than those of G2 and the galaxy responsible for the damped system of the QSO, then this association of galaxies would be the most distant cluster observed so far, with a total stellar mass of the order of 1013 solar mass (throughout this paper we assume H0 = 50 km/s/Mpc and Omega = 0, unless differently stated).

Giavalisco, M.; Macchetto, F. D.; Sparks, W. B.

1994-08-01

172

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

173

Acetylene weak bands at 2.5 $?$m from intracavity Cr2+:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy  

E-print Network

The spectral dynamics of a mid-infrared multimode Cr^2+:ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C_2H_2 in natural isotopic abundance are recorded around 4000 cm^-1 with kilometric absorption path lengths and sensitivities better than 3 10^-8 cm-1. Two cold bands are newly identified and assigned to the n_1+n_4^1 and n_3+n_5^1 transitions of ^12C^13CH_2. The n_1+n_5^1 band of ^12C_2HD and fourteen ^12C_2H_2 bands are observed, among which for the first time n_2+2n_4^2+n_5^-1.

Véronique Girard; Robert Farrenq; Evgeni Sorokin; Irina T. Sorokina; Guy Guelachvili; Nathalie Picqué

2006-12-01

174

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

175

Intense duskside lower band chorus waves observed by Van Allen Probes: Generation and potential acceleration effect on radiation belt electrons  

NASA Astrophysics Data System (ADS)

Local acceleration driven by whistler mode chorus waves largely accounts for the enhancement of radiation belt relativistic electron fluxes, whose favored region is usually considered to be the plasmatrough with magnetic local time approximately from midnight through dawn to noon. On 2 October 2013, the Van Allen Probes recorded a rarely reported event of intense duskside lower band chorus waves (with power spectral density up to 10-3nT2/Hz) in the low-latitude region outside of L=5. Such chorus waves are found to be generated by the substorm-injected anisotropic suprathermal electrons and have a potentially strong acceleration effect on the radiation belt energetic electrons. This event study demonstrates the possibility of broader spatial regions with effective electron acceleration by chorus waves than previously expected. For such intense duskside chorus waves, the occurrence probability, the preferential excitation conditions, the time duration, and the accurate contribution to the long-term evolution of radiation belt electron fluxes may need further investigations in future.

Su, Zhenpeng; Zhu, Hui; Xiao, Fuliang; Zheng, Huinan; Wang, Yuming; He, Zhaoguo; Shen, Chao; Shen, Chenglong; Wang, C. B.; Liu, Rui; Zhang, Min; Wang, Shui; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Spence, H. E.; Reeves, G. D.; Funsten, H. O.; Blake, J. B.; Baker, D. N.; Wygant, J. R.

2014-06-01

176

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

177

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. PMID:25435927

LIN, YANG; WANG, BENZHONG

2015-01-01

178

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

PubMed

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. PMID:25435927

Lin, Yang; Wang, Benzhong

2015-01-01

179

The effect of intense laser light on the absorption-edge region of the spectrum of a CdCr 2 Se 4 ferromagnetic semiconductor  

Microsoft Academic Search

The effect of intense incident laser light on the spectral dependence of the absorption of circularly polarized light is investigated\\u000a in single crystals of CdCr2Se4 in the neighborhood of the absorption edge for temperatures in the range 100–130 K. The observed large changes in the shape\\u000a of the edge are related to peaking of the exciton resonance, which is caused

L. L. Golik; Z. É. Kun’kova

1999-01-01

180

Analysis of Mars surface hydration through the MEx/OMEGA observation of the 3 ?m absorption band.  

NASA Astrophysics Data System (ADS)

The near infrared Mars surface global mapping done by OMEGA gives the first opportunity to study the global and detailed characteristics of the 3µm hydration absorption band on Mars surface. This feature is indistinctly due to bending and stretching vibrations of water bound in minerals or adsorbed at their surface, and of hydroxyl groups (for a review, see e.g. [1] or [2]). Its study may give new elements to determine the geologic and climatic past of Mars, and may put new constrain about the current water cycle of Mars. OMEGA data are processed in a pipeline that converts raw data to radiance, removes atmospheric effects and gets I/F. Specific data reduction scheme has been developed to assess temperature of OMEGA spectra at 5 µm and to remove their thermal part so as to get the albedo from 1.µm to 5.1µm ([2]). Two methods, the Integrated Band Depth and the water content based on comparison with laboratory measures of Yen et al. ([3]), have been used to assess the 3µm band depth. These two methods where applied to OMEGA spectra acquired at a nominal calibration level and not exhibiting water ice features. This corresponds to approximately 35 million spectra ([2]). The data processed show the presence of this absorption feature overall the Martian surface, which could be explained by the presence of adsorbed water up to 1% water mass percentage ([4]) and by rinds or coating resulting from weathering (see e.g. [5] or [6]). A possible increase of hydration with albedo is discussed so as to discriminate between the albedo-dependence of the method and hydration variations. Terrains enriched in phyllosilicates ([7]), sulfates ([8]) or hydroxides exhibit an increased hydration at 3 µm. This terrains show that the 3 µm band can bring additional information about composition, for example by observing a variation in the shape of the band. A decrease of hydration with elevation is observed on the processed data independently of the value of albedo. This correlation may be explained by a decrease of pressure with altitude so that less water can adsorb on minerals. Study of global maps reveals a strong increase of hydration with high latitudes (over 60°N), maybe due to a change in composition [9]. Careful analysis also shows seasonal variations of the hydration of soils with the decrease of hydration between spring and summer for mid latitudes regions (from 40°N to 60°N). This hydration enrichment is not due to instrumental effect or to the presence of aerosols or water ice. It is associated to an increase of hydration with latitude in spring, increase that has disappeared in summer. This temporal variation may be explained by the presence of frost in winter. Frost is in contact with minerals and imposes a high water vapor pressure, which makes water to fix on minerals during winter. Then the hydration of the surface returns to equilibrium with the atmosphere by releasing water. These variations seem to confirm the important role of regolith on water cycle, which was predicted from numerical simulations (e.g. [10]). [1] Cooper C.D. and Mustard J.F. (1999) Icarus 142, 557-570. [2] Jouglet D.et al., article in preparation. [3] Yen A.S. et al (1998) JGR E5, 103, 11,125-11,133. [4] Zent A.P. and Quinn R.C.(1997) JGR E4, 102, 9085-9095. [5] Yen A.S. et al (2005), Nature 436, 49-54. [6] Hurowitz J.A. et al (2006) JGR, 111, E02S19, doi:10.1029/2005JE002515. [7] Poulet F. et al (2005) Nature 438, 623-627. [8] Gendrin A. et al. (2005) Science 307, 1587-1591. [9] Milliken et al, article in preparation. [10] Böttger H.M.et al. (2005) Icarus 177, 174-189. 2

Jouglet, D.; Poulet, F.; Bibring, J. P.; Langevin, Y.; Gondet, B.; Milliken, R. E.; Mustard, J. F.

181

The absorption spectrum of D2: Ultrasensitive cavity ring down spectroscopy of the (2-0) band near 1.7 ?m and accurate ab initio line list up to 24 000 cm-1  

NASA Astrophysics Data System (ADS)

Eleven very weak electric quadrupole transitions Q(2), Q(1), S(0)-S(8) of the first overtone band of D2 have been measured by very high sensitivity CW-cavity ring down spectroscopy (CRDS) between 5850 and 6720 cm-1. The noise equivalent absorption of the recordings is on the order of ?min ? 3 × 10-11 cm-1. By averaging a high number of spectra, the noise level was lowered to ?min ? 4 × 10-12 cm-1 in order to detect the S(8) transition which is among the weakest transitions ever detected in laboratory experiments (line intensity on the order of 1.8 × 10-31 cm/molecule at 296 K). A Galatry profile was used to reproduce the measured line shape and derive the line strengths. The pressure shift and position at zero pressure limit were determined from recordings with pressures ranging between 10 and 750 Torr. A highly accurate theoretical line list was constructed for pure D2 at 296 K. The intensity threshold was fixed to a value of 1 × 10-34 cm/molecule at 296 K. The obtained line list is provided as supplementary material. It extends up to 24 000 cm-1 and includes 201 transitions belonging to ten v-0 cold bands (v = 0-9) and three v-1 hot bands (v = 1-3). The energy levels include the relativistic and quantum electrodynamic corrections as well as the effects of the finite nuclear mass. The quadrupole transition moments are calculated using highly accurate adiabatic wave functions. The CRDS line positions and intensities of the first overtone band are compared to the corresponding calculated values and to previous measurements of the S(0)-S(3) lines. The agreement between the CRDS and theoretical results is found within the claimed experimental uncertainties (on the order of 1 × 10-3 cm-1 and 2% for the positions and intensities, respectively) while the previous S(0)-S(3) measurements showed important deviations for the line intensities.

Kassi, Samir; Campargue, Alain; Pachucki, Krzysztof; Komasa, Jacek

2012-05-01

182

The absorption spectrum of D2: ultrasensitive cavity ring down spectroscopy of the (2-0) band near 1.7 ?m and accurate ab initio line list up to 24,000 cm(-1).  

PubMed

Eleven very weak electric quadrupole transitions Q(2), Q(1), S(0)-S(8) of the first overtone band of D(2) have been measured by very high sensitivity CW-cavity ring down spectroscopy (CRDS) between 5850 and 6720 cm(-1). The noise equivalent absorption of the recordings is on the order of ?(min) ? 3 × 10(-11) cm(-1). By averaging a high number of spectra, the noise level was lowered to ?(min) ? 4 × 10(-12) cm(-1) in order to detect the S(8) transition which is among the weakest transitions ever detected in laboratory experiments (line intensity on the order of 1.8 × 10(-31) cm/molecule at 296 K). A Galatry profile was used to reproduce the measured line shape and derive the line strengths. The pressure shift and position at zero pressure limit were determined from recordings with pressures ranging between 10 and 750 Torr. A highly accurate theoretical line list was constructed for pure D(2) at 296 K. The intensity threshold was fixed to a value of 1 × 10(-34) cm/molecule at 296 K. The obtained line list is provided as supplementary material. It extends up to 24,000 cm(-1) and includes 201 transitions belonging to ten v-0 cold bands (v = 0-9) and three v-1 hot bands (v = 1-3). The energy levels include the relativistic and quantum electrodynamic corrections as well as the effects of the finite nuclear mass. The quadrupole transition moments are calculated using highly accurate adiabatic wave functions. The CRDS line positions and intensities of the first overtone band are compared to the corresponding calculated values and to previous measurements of the S(0)-S(3) lines. The agreement between the CRDS and theoretical results is found within the claimed experimental uncertainties (on the order of 1 × 10(-3) cm(-1) and 2% for the positions and intensities, respectively) while the previous S(0)-S(3) measurements showed important deviations for the line intensities. PMID:22583289

Kassi, Samir; Campargue, Alain; Pachucki, Krzysztof; Komasa, Jacek

2012-05-14

183

Microwave magnetic and absorption properties of M-type ferrite BaCoxTixFe12-2xO19 in the Ka band  

NASA Astrophysics Data System (ADS)

In this study, microwave magnetic and absorption properties were investigated for BaCoxTixFe12-2xO19 (x=0.3, 0.4 and 0.5). M-type barium ferrite can be used as high frequency absorber by Co-Ti substitution because of the strong uniaxial anisotropy and high saturated magnetization. The X-ray diffraction and magnetic hysteresis loops of the samples show that the c-axis anisotropy of BaCoxTixFe12-2xO19 decreases with the substitution, resulting in the decrease of coercivity. The frequency dependence of complex permeability, permittivity and microwave absorption of BaCoxTixFe12-2xO19 has been studied in the Ka band (26.5-40 GHz), respectively. The results show that the natural resonance frequency decreases with the substitution. The complex permeability increases as the sintering temperature increases in the range from 1280 °C to 1310 °C with 10 °C as a step. The imaginary part of permeability value obtained here is the highest value among the reported ferrite millimeter wave absorbers in the Ka band. The microwave absorption bandwidth at -10 dB of BaCoxTixFe12-2xO19 is effectively broadened compared with other ferrites. Therefore, BaCoxTixFe12-2xO19 may be a good candidate for electromagnetic materials with low reflectivity in the Ka band.

Dong, Changshun; Wang, Xin; Zhou, Peiheng; Liu, Tao; Xie, Jianliang; Deng, Longjiang

2014-03-01

184

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

185

Application of surface pressure measurements from O2-band differential absorption radar system in three-dimensional data assimilation on hurricane: Part I - An observing system simulation experiments study  

NASA Astrophysics Data System (ADS)

Sea level pressure (SLP) is an important variable in regulating hurricane motion. However, SLP generally cannot be measured in open oceans due to limited buoys. Because of the potential availability of an O2-band differential absorption radar for sea surface barometry, we investigate the value of assimilating various patterns of SLP from such a system on hurricane prediction using the Weather Research and Forecasting (WRF) three-dimensional variational data assimilation system (3DVAR) based on Observing System Simulation Experiments (OSSEs). An important objective of this series of study is to explore the potential to use space and airborne sea surface air pressure measurements from an O2-band differential absorption radar currently under development for server weather including hurricane forecasts. The surface pressure patterns include an area of SLP, and a band of SLP either through the center or tangent to the hurricane position; the latter two distributions are similar to what could be obtained from the differential absorption radar system, which could be installed on spaceborne satellites and/or mounted on reconnaissance aircraft. In the banded pressure cases, we propose a vortex reconstruction technique based on surface pressure field. Assimilating observations from the reconstructed surface pressure leads to a better representation of initial SLP and vertical cross-section of wind, relative to the control where no data is assimilated and to the assimilation without vortex reconstruction. In eight of the nine OSSEs simulations on three hurricanes with three leading times of integration, which cover a wide range of initial minimum SLP from 951 to 1011 hPa, substantial improvements are found not only in the hurricane track and position, but also in the hurricane intensity, in terms of the SLP and maximum surface wind. The only case without significant improvement is resulted from the very weak initial condition (SLP 1011 hPa), which had no clear indication of tropical disturbance at the stage for initialization. The improvements of assimilation are generally enhanced for the stronger hurricanes whose differences in initial minimum SLP between nature run and control are larger.

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

2015-01-01

186

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

187

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

NASA Astrophysics Data System (ADS)

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/cm2. 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; Yang, Jun-yi; Wei, Tai-Huei; Song, Ying-lin

2013-12-01

188

Infrared band intensities and global warming potentials of CFâ, CâFâ, CâFâ, CâFââ, CâFââ, and CâFââ  

Microsoft Academic Search

The authors report infrared band intensity measurements for a series of fluorocarbons, expected to be decay products of new substitutes for freons, and based on these data perform radiative forcing calculations to study the global warming potential of these compounds. The compounds studied include CFâ, CâFâ, CâFâ, CâFââ, CâFââ, and CâFââ. Only the first two have been measured in atmospheric

C. M. Roehl; D. Boglu; C. Bruehl

1995-01-01

189

The effect of mid-infrared and far-infrared emission, generated at NH3 excitation by intense radiation of a TEA CO2 laser, on ammonia absorption  

Microsoft Academic Search

The effect of Mid-InfraRed (MIR) (lambda ? 12 mum) and Far-InfraRed (FIR) (lambda ≽ 100 mum) emission from excited ammonia on the absorption of intense radiation of a TEA CO2 laser has been studied experimentally under collisional and collisionless excitation conditions with ammonia pressures from 0.5 to 0.03 Torr. The energy of MIR and FIR emission was studied as a

R. S. Karve; V. N. Lokhman; G. N. Makarov

1996-01-01

190

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

NASA Astrophysics Data System (ADS)

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

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

1993-03-01

191

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

NASA Technical Reports Server (NTRS)

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

Baines, Kevin H.; West, Robert A.; Giver, Lawrence P.; Moreno, Fernando

1993-01-01

192

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

2014-11-01

193

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

194

Shifts of H2O absorption lines in the nu1 + 3nu3 band induced by H2, CO2, and H2O pressure  

NASA Astrophysics Data System (ADS)

Results of measurements and calculations of H2O absorption line widths and shifts in the nu1 + 3nu3 band induced by H2O pressure and also by H2 and CO2 pressure are reported. The measurements have been carried out using a two-channel optoacoustic spectrometer with a frequency-tunable ruby laser. The calculations of the shift and broadening coefficients have been performed using the Anderson-Tsao-Curnutte-Frost method. Possible physical mechanisms which can account for the nonlinear change of the measured H2O line shift with H2 pressure are examined.

Lazarev, V. V.; Ponomarev, Iu. N.; Stroinova, V. N.; Tikhomirov, B. A.

1992-09-01

195

Yb(3+)-doped GeS(2)-Ga2S(3)-CsCl glass with broad and adjustable absorption/excitation band for near-infrared luminescence.  

PubMed

The luminescent property of Yb(3+) ions in GeS(2)-Ga(2)S(3)-CsCl glasses with different CsCl contents has been studied. All the samples demonstrate a broad excitation band in the UV or/and visible range, depending on the composition, which is attributed to the charge transfer of the Yb(3+)-S(2-)/Cl(-) couple. The width of the excitation/absorption band can be as large as 150 nm. Moreover, with the increase of CsCl content, the peak position of the band can be continuously adjusted from 458 to 380 nm, due to the increase of the local average electronegativity around Yb(3+) ions. The broad and adjustable excitation band makes the Yb(3+)doped GeS(2)-Ga(2)S(3)-CsCl glass interesting for modifying the solar spectrum by absorbing strongly in the UV/blue region for emission around 1 ?m. This kind of material is the key to adapting the solar spectrum to the response of silicon photovoltaic solar cells. PMID:23811902

Fan, Bo; Xue, Bai; Zhang, Xianghua; Adam, Jean-Luc; Fan, Xianping

2013-07-01

196

Water-vapor absorption line measurements in the 940-nm band by using a Raman-shifted dye laser.  

PubMed

We report water-vapor absorption line measurements that are made by using the first Stokes radiation (930-982 nm) with HWHM 0.015 cm(-1) generated by a narrow-linewidth, tunable dye laser. Forty-five absorption line strengths are measured with an uncertainty of 6% and among them are fourteen strong lines that are compared with previous measurements for the assessment of spectral purity of the light source. Thirty air-broadened linewidths are measured with 8% uncertainty at ambient atmospheric pressure with an average of 0.101 cm(-1). The lines are selected for the purpose of temperature-sensitive or temperature-insensitive lidar measurements. Results for these line strengths and linewidths are corrected for broadband radiation and finite laser linewidth (0.015 cm(-1) HWHM) broadening effects and compared with the high-resolution transmission molecular absorption. PMID:20802779

Chu, Z; Wilkerson, T D; Singh, U N

1993-02-20

197

N-annulated perylene-substituted and fused porphyrin dimers with intense near-infrared one-photon and two-photon absorption.  

PubMed

Fusion of two N-annulated perylene (NP) units with a fused porphyrin dimer along the S0 -S1 electronic transition moment axis has resulted in new near-infrared (NIR) dyes 1?a/1?b with very intense absorption (?>1.3×10(5) ?M(-1) ?cm(-1) ) beyond 1250?nm. Both compounds displayed moderate NIR fluorescence with fluorescence quantum yields of 4.4×10(-6) and 6.0×10(-6) for 1?a and 1?b, respectively. The NP-substituted porphyrin dimers 2?a/2?b have also been obtained by controlled oxidative coupling and cyclodehydrogenation, and they showed superimposed absorptions of the fused porphyrin dimer and the NP chromophore. The excited-state dynamics of all of these compounds have been studied by femtosecond transient absorption measurements, which revealed porphyrin dimer-like behaviour. These new chromophores also exhibited good nonlinear optical susceptibility with large two-photon absorption cross-sections in the NIR region due to extended ?-conjugation. Time-dependent density functional theory calculations have been performed to aid our understanding of their electronic structures and absorption spectra. PMID:25606849

Luo, Jie; Lee, Sangsu; Son, Minjung; Zheng, Bin; Huang, Kuo-Wei; Qi, Qingbiao; Zeng, Wangdong; Li, Gongqiang; Kim, Dongho; Wu, Jishan

2015-02-23

198

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

199

Infrared intensities. Use of the CH-stretching band intensity as a tool for evaluating the acidity of hydrogen atoms in hydrocarbons  

NASA Astrophysics Data System (ADS)

The accurate study of the infrared spectra (both frequencies and intensities) of a large number of molecules and the decodification of their intensities in terms of parameters representing changes of charge distribution with vibration have provided standards that, at least in the case of molecules with an appreciable presence of CH bonds, may now be used to give information on the acidity of the hydrogen atoms even based only on the qualitative aspects of the infrared spectrum in the CH-stretching region. The charge on the hydrogen atom of a CH bond may change by hybridization of the carbon atom, by induction of polarization in the CH bond by a close electronegative atom, by backdonation into the CH bond of negative charge from any lone pair of an electronegative atom and with hyperconjugation of CH 3 and CH 2 with the electrons of double and triple bonds. The variation of the hydrogen charge is also accompanied by a change in the CH stretching frequencies, as reported in several works by McKean and coworkers. It has to be pointed out that the change in the CH stretching intensities is almost always more noticeable and often so large that it can be detected by the simple qualitative examination of the spectrum. We present here examples of such a qualitative analysis.

Gussoni, M.; Castiglioni, C.

2000-03-01

200

Band-gap variation in RScO3 (R=Pr, Nd, Sm, Eu, Gd, Tb, and Dy): X-ray absorption and O K-edge x-ray emission spectroscopies  

NASA Astrophysics Data System (ADS)

The electronic structure of rare-earth scandates RScO3 (R: newly studied Pr, Nd, Eu, and Tb, compared with previously studied Sm, Gd, and Dy) was analyzed by a combined use of O K absorption and emission spectroscopies and Sc L-edge absorption spectroscopy. This permitted the estimation of band gaps by use of a method that differed from optical measurements. The band-gap variation over the series in dependence on the rare-earth ion is analyzed, and a correlation between the Sc-O mean distance and the band gap is found and discussed.

Derks, C.; Kuepper, K.; Raekers, M.; Postnikov, A. V.; Uecker, R.; Yang, W. L.; Neumann, M.

2012-10-01

201

Evaluation of minority and majority spin band energies of ferromagnetic GdN thin film using optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Temperature dependent optical Tauc plots of AlN/GdN/AlN heterostructures have showed two optically induced transitions, and those optical transitions could be attributed to the minority and majority spin band energy. In contrast, temperature dependent magnetization measurements of GdN thin film provide direct evidence of spin ordering below 39 K, and which is also evidenced by Arrott plots.

Vidyasagar, R.; Yoshitomi, H.; Kitayama, S.; Kita, T.; Ohta, H.; Sakurai, T.

2013-12-01

202

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

203

LINE ABSORPTION OSCILLATOR STRENGTHS FOR THE c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3)-X{sup 1}{Sigma}{sup +}{sub g}(0-5) BANDS IN N{sub 2}  

SciTech Connect

Theoretical absorption oscillator strengths and emission branching ratios for rotational lines of the c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3)-X{sup 1}{Sigma}{sup +}{sub g}(0-5) bands of molecular nitrogen are reported. The calculations have been performed with the molecular quantum defect orbital method, which has proved to be reliable in previous studies of rovibronic transitions in diatomic molecules. The strong interaction between c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3) and b' {sup 1}{Sigma}{sup +}{sub u}(10) states has been analyzed through an interaction matrix that includes rotational terms. Owing to the perturbation, the c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3)-X{sup 1}{Sigma}{sup +}{sub g}(0), c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3)-X{sup 1}{Sigma}{sup +}{sub g}(1), and c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3)-X{sup 1}{Sigma}{sup +}{sub g}(5) bands are not weak, in contrast to what would be expected on the basis of the Franck-Condon principle. Moreover, the intensity distribution of the rotational lines within each of the vibronic bands deviates from considerations based on Hoenl-London factors. In this work, we provide data that may be useful to interpret spectra from atmospheres of the Earth, Titan, and Triton, in which transitions from the c'{sub 4}{sup 1}{Sigma}{sup +}{sub u}(3) level have been detected.

Lavin, C.; Velasco, A. M., E-mail: clavin@qf.uva.es [Departamento de Quimica Fisica y Quimica Inorganica, Facultad de Ciencias, Universidad de Valladolid, E-47005 Valladolid (Spain)

2011-09-20

204

Activation of an intense near band edge emission from ZnTe/ZnMgTe core/shell nanowires grown on silicon.  

PubMed

The absence of luminescence in the near band edge energy region of Te-anion based semiconductor nanowires grown by gold catalyst assisted molecular beam epitaxy has strongly limited their applications in the field of photonics. In this paper, an enhancement of the near band edge emission intensity from ZnTe/ZnMgTe core/shell nanowires grown on Si substrates is reported. A special role of the use of Si substrates instead of GaAs substrates is emphasized, which results in an increase of the near band edge emission intensity by at least one order of magnitude accompanied by a simultaneous reduction of the defect related luminescence. A possible explanation of this effect relies on the presence of Ga-related deep level defects in structures grown on GaAs substrates, which are absent when Si substrates are used. Monochromatic mapping of the cathodoluminescence clearly confirms that the observed emission originates, indeed, from the ZnTe/ZnMgTe core/shell nanowires, whereas individual objects are studied by means of microphotoluminescence. PMID:23960005

Wojnar, P; Szymura, M; Zaleszczyk, W; K?opotowski, L; Janik, E; Wiater, M; Baczewski, L T; Kret, S; Karczewski, G; Kossut, J; Wojtowicz, T

2013-09-13

205

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 (HF···HF, HCl···HCl, HCN···HCN, HNC···HNC, HCN···HF, HF···HCl and H2O···HF) 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

2014-12-01

206

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

207

Large acceptance magnetic focussing horns for production of a high intensity narrow band neutrino beam at the AGS  

SciTech Connect

A set of two large acceptance (20 to 140 mrad) horns have been designed and built to form a parallel beam of 3 GeV/c pions and kaons for the production of an intense, dichromatic neutrino beam. A set of beam plugs and collimators determined the momentum of the particles which pass through the horns. The cooling and maintenance of the horns and target was a particular concern since they were operated with an incident intensity of over 10/sup 13/ proton/sec. These systems were designed for simplicity, reliability, and easy replacement.

Carroll, A.; Chimienti, L.; Leonhardt, W.; Monaghan, R.; Ryan, G.; Sandberg, J.; Sims, W.; Smith, G.; Stillman, P.; Thorwarth, H.

1985-10-01

208

Large acceptance magnetic focussing horns for production of a high intensity narrow band neutrino beam at the AGS  

SciTech Connect

A set of two large acceptance (20 to 140 mrad) horns have been designed and built to form a parallel beam of 3 GeV/c pions and kaons for the production of an intense, dichromatic neutrino beam. A set of beam plugs and collimators determined the momentum of the particles which pass through the horns. The cooling and maintenance of the horns and target was a particular concern since they were operated with an incident intensity of over 10/sup 13/ proton/sec. These systems were designed for simplicity, reliability, and easy replacement.

Carroll, A.; Chimienti, L.; Leonhardt, W.; Monaghan, R.; Ryan, G.; Sandberg, J.; Sims, W.; Smith, G.; Stillman, P.; Thorwarth, H.

1985-01-01

209

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

210

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

NASA Astrophysics Data System (ADS)

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

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

2001-05-01

211

Laboratory absorption strengths and line shape parameters in the 4-0, 5-0, and 6-0 vibration bands of HD  

NASA Technical Reports Server (NTRS)

Experimental values for the visible vibration-dipole bands of HD are improved through a study of weak, unsaturated absorption lines of HD against a well-defined white light continuum at low gas densities between 0.3 and 1.7 amagats. Spectral resolution was high enough to allow recovery of line profiles with only minor corrections for instrumental effects, so line strengths and shapes are determined directly without recourse to theoretical assumptions regarding the curve of growth, and the unusual phenomenon of collision narrowing in HD is directly observed in the line shape for the first time. Accurate line strengths are reported, the behavior of spectral profiles as a function of gas density is discussed, and the pressure shift coefficients are determined. These are compared with previous laboratory work done either at lower spectral resolving power or at higher gas densities.

Trauger, J. T.; Mickelson, M. E.

1983-01-01

212

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

213

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_...

Junkkarinen, V T; Beaver, E A; Burbidge, Eleanor Margaret; Lyons, R W; Madejski, G

2004-01-01

214

Iron-absorption band analysis for the discrimination of iron-rich zones. [infrared spectral reflectance of Nevada iron deposits  

NASA Technical Reports Server (NTRS)

The author has identified the following significant results. Most major rock units and unaltered and altered areas in the study area can be discriminated on the basis of visible and near-infrared spectral reflectivity differences recorded from satellite altitude. These subtle spectral differences are detectable by digital ratioing of the MSS bands and subsequent stretching to increase the contrast to enhance spectral differences. Hydrothermally altered areas appear as anomalous color patches within the volcanic-rock areas. A map has been prepared which can be regarded as an excellent reconnaissance exploration map, for use in targeting areas for more detailed geological, geochemical, and geophysical studies. Mafic and felsic rock types are easily discriminated on the color stretched-ratio composite. The ratioing process minimizes albedo effects, leaving only the recorded characteristic spectral response. The spectra of unaltered rocks appear different from those of altered rocks, which are typically dominated by limonite and clay minerals. It seems clear that differences in spectral shape can provide a basis for discrimination of geologic material, although the relations between visible and near-infrared spectral reflectivity and mineralogical composition are not yet entirely understood.

Rowan, L. C. (principal investigator)

1974-01-01

215

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

PubMed

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

Sobu?, Jan; Zió?ek, Marcin

2014-07-21

216

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

217

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

NASA Astrophysics Data System (ADS)

Exposure to loud sounds is one of the leading causes of hearing loss in the United States. The purpose of the current research was to measure the sound pressure levels generated within a university concert band and determine if those levels exceeded permissible sound limits for exposure according to criteria set by the Occupational Safety and Health Administration (OSHA) and the National Institute of Occupational Safety and Health (NIOSH). Time-weighted averages (TWA) were obtained via a dosimeter during six rehearsals for nine members of the ensemble (plus the conductor), who were seated in frontal proximity to "instruments of power" (trumpets, trombones, and percussion; (Backus, 1977). Subjects received audiometer tests prior to and after each rehearsal to determine any temporary threshold shifts (TTS). Single sample t tests were calculated to compare TWA means and the maximum sound intensity exposures set by OSHA and NIOSH. Correlations were calculated between TWAs and TTSs, as well as TTSs and the number of semesters subjects reported being seated in proximity to instruments of power. The TWA-OSHA mean of 90.2 dBA was not significantly greater than the specified OSHA maximum standard of 90.0 dBA (p > .05). The TWA-NIOSH mean of 93.1 dBA was, however, significantly greater than the NIOSH specified maximum standard of 85.0 dBA (p < .05). The correlation between TWAs and TTSs was considered weak (r = .21 for OSHA, r = .20 for NIOSH); the correlation between TTSs and semesters of proximity to instruments of power was also considered weak (r = .13). TWAs cumulatively exceeded both association's sound exposure limits at 11 specified locations (nine subjects and both ears of the conductor) throughout the concert band's rehearsals. In addition, hearing acuity, as determined by TTSs, was substantially affected negatively by the intensities produced in the concert band. The researcher concluded that conductors, as well as their performers, must be aware of possible damaging sound intensities in rehearsals or performances.

Holland, Nicholas Vedder, III

218

Intersubband optical absorption coefficients and refractive index changes in a graded quantum well under intense laser field: Effects of hydrostatic pressure, temperature and electric field  

NASA Astrophysics Data System (ADS)

The effects of hydrostatic pressure, temperature, and electric field on the optical absorption coefficients and refractive index changes associated with intersubband transition in a typical GaAs/Ga0.7Al0.3As graded quantum well under intense laser field have been investigated theoretically. The electron energy eigenvalues and the corresponding eigenfunctions of the graded quantum well are calculated within the effective mass approximation and envelope wave function approach. The analytical expressions of the optical properties are obtained using the compact density-matrix approach and the iterative method. The numerical results show that the linear and nonlinear optical properties depend strongly on the intense laser field and electric field but weakly on the hydrostatic pressure and temperature. Additionally, it has been found that the electronic and optical properties in a GaAs/Ga0.7Al0.3As graded quantum well under the intense laser field can be tuned by changing these external inputs. Thus, these results give a new degree of freedom in the devices applications.

Ungan, F.; Restrepo, R. L.; Mora-Ramos, M. E.; Morales, A. L.; Duque, C. A.

2014-02-01

219

Simultaneous suppression of laser relative intensity noise: second- and third-order distortions using a balanced electro-absorption modulator  

NASA Astrophysics Data System (ADS)

Balanced electroabsorption modulators (B-EAM) are an attractive alternative to the cross-coupled Mach-Zehnder modulator. The B-EAM enables bias independent suppression of even-order distortions, relative intensity noise (RIN), and common amplified spontaneous emission noise. By biasing the B-EAM at the 3rd order null, a 5th order distortion limited spurious free dynamic range can be achieved. We report on the experimental demonstration of the simultaneous suppression of laser RIN, 2nd and 3rd order distortions using a 300 micrometers long B-EAM.

Mathai, Sagi; Capelluti, Federica; Jung, Thomas; Novak, Dalma; Waterhouse, Rod; Sivco, Deborah L.; Cho, Alfred Y.; Ghione, Giovanni; Wu, Ming C.

2001-12-01

220

Positions and Intensities in the 3v2/v2+v4 Vibrational System of 14NH3 Near 4 micron meters  

NASA Technical Reports Server (NTRS)

Ammonia is the fourth most abundant constituent in the atmospheres of Jupiter and Saturn, after hydrogen, helium and methane. This relative abundance is attested by the presence in the infrared planetary spectra of many absorption features observed in the range of fundamental bands and also in the higher bands. Reported are experimental line positions and intensities of selected ammonia bands.

Kleiner, I.; Tarrago, G.; Brown, L. R.

1995-01-01

221

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

222

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

SciTech Connect

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

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

2014-07-07

223

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

224

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

225

[Quantitative analysis of absorption spectra and spectra of magneto-optical rotatory dispersion of hemoproteins with reference to zero-field splitting. I. Analysis of the divalentcation of deuteroporphyrin in the Q-band region].  

PubMed

I. Analysis of the dication of deuteroporphyrin in the Q-band region. Methods for quantitative analysis of absorption spectra and magneto-optical rotatory dispersion with regard to zero-field splitting of a nearly degenerated term for the latter are described. The methods are based on adaptation of band-form functions to the spectrum using the principle of least squares. Calculation of the zero-field splitting utilizes the formalism evolved by Stephens for strictly degenerated terms (A-terms in the magneto-optical spectrum) which has been further developed to a band-form function depending on zero-field splitting. The curve-form function of the modified A-term contains 4 parameters (zero-field splitting, rotational strength, band width, and the maximum of the band) which have been determined by a computer program. The oscillator and the dipole strength of absorption bands to be calculated simultaneously with the program allows the determination of the magnetic orbital moments of the terms. Exemplified by the dication of deuteroporphyrindimethylester, the significance of zero-field splitting for the recognition of the exact molecule symmetry is demonstrated, and a model of the molecular structure is proposed. PMID:1028327

Ristau, O; Rein, H

1976-01-01

226

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

227

High-resolution spectroscopy of cool K and M stars through the telluric water vapor absorption band near 9360 A. 1: Methodology and first results  

Microsoft Academic Search

An observational program has been undertaken for the study of stellar spectra within telluric water vapor lines absorption region near 9360 A. This program has been developed in the future context of a European Space Agency's (ESAs) environment-dedicated experiment designed to probe atmospheric water vapor absorption with cool star spectrophotometry. With ground observations presented here, we determine absorption levels and

T. Widemann; J.-L. Bertaux; M. Querci; F. Querci

1994-01-01

228

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

229

A method to accurately quantitate intensities of (32)P-DNA bands when multiple bands appear in a single lane of a gel is used to study dNTP insertion opposite a benzo[a]pyrene-dG adduct by Sulfolobus DNA polymerases Dpo4 and Dbh.  

PubMed

Quantitating relative (32)P-band intensity in gels is desired, e.g., to study primer-extension kinetics of DNA polymerases (DNAPs). Following imaging, multiple (32)P-bands are often present in lanes. Though individual bands appear by eye to be simple and well-resolved, scanning reveals they are actually skewed-Gaussian in shape and neighboring bands are overlapping, which complicates quantitation, because slower migrating bands often have considerable contributions from the trailing edges of faster migrating bands. A method is described to accurately quantitate adjacent (32)P-bands, which relies on having a standard: a simple skewed-Gaussian curve from an analogous pure, single-component band (e.g., primer alone). This single-component scan/curve is superimposed on its corresponding band in an experimentally determined scan/curve containing multiple bands (e.g., generated in a primer-extension reaction); intensity exceeding the single-component scan/curve is attributed to other components (e.g., insertion products). Relative areas/intensities are determined via pixel analysis, from which relative molarity of components is computed. Common software is used. Commonly used alternative methods (e.g., drawing boxes around bands) are shown to be less accurate. Our method was used to study kinetics of dNTP primer-extension opposite a benzo[a]pyrene-N(2)-dG-adduct with four DNAPs, including Sulfolobus solfataricus Dpo4 and Sulfolobus acidocaldarius Dbh. Vmax/Km is similar for correct dCTP insertion with Dpo4 and Dbh. Compared to Dpo4, Dbh misinsertion is slower for dATP (?20-fold), dGTP (?110-fold) and dTTP (?6-fold), due to decreases in Vmax. These findings provide support that Dbh is in the same Y-Family DNAP class as eukaryotic DNAP ? and bacterial DNAP IV, which accurately bypass N(2)-dG adducts, as well as establish the scan-method described herein as an accurate method to quantitate relative intensity of overlapping bands in a single lane, whether generated from (32)P-signals or by other means (e.g., staining). PMID:25497330

Sholder, Gabriel; Loechler, Edward L

2015-01-01

230

Mechanism for strong nonlinearities in the Faraday rotation and absorption in the ferromagnetic semiconductor CdCr2Se4  

Microsoft Academic Search

At high laser radiation intensities a strong nonlinear Faraday rotation (FR) may be observed in a relatively narrow energy band near the absorption edge of CdCr2Se4. To study the nature of this effect, we investigated the influence of the incident radiation intensity on the spectral properties of the FR and the circularly polarized light absorption, and studied the dynamics of

L. L. Golik; Z. E. Kun'kova; C. Heide

2000-01-01

231

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

2014-11-28

232

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

Microsoft Academic Search

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

C. M. Roehl; D. Boglu; C. Brühl; G. K. Moortgat

1995-01-01

233

Technical Note: A novel parameterization of the transmissivity due to ozone absorption in the k-distribution method and correlated-k approximation of Kato et al. (1999) over the UV band  

NASA Astrophysics Data System (ADS)

The k-distribution method and the correlated-k approximation of Kato et al. (1999) is a computationally efficient approach originally designed for calculations of the broadband solar radiation at ground level by dividing the solar spectrum in 32 specific spectral bands from 240 to 4606 nm. Compared to a spectrally-resolved computation, its performance in the UV band appears to be inaccurate, especially in the spectral intervals #3 [283, 307] nm and #4 [307, 328] nm because of inaccuracy in modelling the transmissivity due to ozone absorption. Numerical simulations presented in this paper indicate that a single effective ozone cross section is insufficient to accurately represent the transmissivity over each spectral interval. A novel parameterization of the transmissivity using more quadrature points yields maximum error of respectively 0.0006 and 0.0041 for interval #3 and #4. How to practically implement this new parameterization in a radiative transfer model is discussed for the case of libRadtran.

Wandji Nyamsi, W.; Arola, A.; Blanc, P.; Lindfors, A. V.; Cesnulyte, V.; Pitkänen, M. R. A.; Wald, L.

2015-01-01

234

Absorption of surface acoustic waves by topological insulator thin films  

NASA Astrophysics Data System (ADS)

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

Li, L. L.; Xu, W.

2014-08-01

235

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

NASA Technical Reports Server (NTRS)

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

Mustel, E. R.

1979-01-01

236

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

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

2013-01-01

237

Electromagnetic and microwave absorption properties of the Nickel/Ti3SiC2 hybrid powders in X-band  

NASA Astrophysics Data System (ADS)

The electromagnetic (EM) characteristics and microwave absorption properties of the Nickel/Ti3SiC2 hybrid powders are studied in 8.2-12.4 GHz.With the enhancement of Ti3SiC2 content, the dielectric loss of the hybrid powders increases while the magnetic loss decreases compared with the pure Ni powders. A favorable microwave absorption property can be obtained by changing the Ti3SiC2 content to tailor the EM parameters. The composite with 30 wt% Ni and 30 wt% Ti3SiC2 powders presents the optimum microwave absorption property. For the composite of 2.2 mm thickness, a reflection loss (RL) below -10 dB is obtained in the frequency range of 8.2-12 GHz with a minimum RL of -41.2 dB at the matching frequency 9.7 GHz. This study contributes to exploring the absorber with broad absorption bandwidth, low density and thin thickness.

Liu, Yi; Luo, Fa; Su, Jinbu; Zhou, Wancheng; Zhu, Dongmei

2014-09-01

238

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

NASA Astrophysics Data System (ADS)

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

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

1997-12-01

239

On the state of the emitter of the 3.3 micron unidentified infrared band - Absorption spectroscopy of polycyclic aromatic hydrocarbon species  

NASA Technical Reports Server (NTRS)

Results of absorption measurements indicate that the PAH species responsible for the UIR (unidentified infrared) emission probably exist in a condensed form rather than as isolated molecules. It is shown that the peak absorption of the C-H stretch feature of vapor-phase PAHs occurs at a higher frequency than that of the condensed-phase PAHs and does not match the 3.289-micron interstellar feature. The vapor-phase experiments duplicate the phenomenon of the 3.3-micron profile simplification of PAH in KBr at elevated temperature. This confirms that the change of the profile with temperature is an intrinsic molecular effect, and is not a consequence of matrix (KBr) or condensed state interactions.

Flickinger, Gregory C.; Wdowiak, Thomas J.; Gomez, Percy L.

1991-01-01

240

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

241

440 Biophysical Journal Volume 84 January 2003 440449 Low-Intensity Pump-Probe Measurements on the B800 Band of  

E-print Network

harvesting, all photosynthetic organisms have so-called antennae or light- harvesting complexes. The function-color pump-probe traces in the B800 band of the light-harvesting complex LH2 of Rhodospirillum molischianum for B800 excitations. INTRODUCTION Photosynthesis is the synthesis of organic compounds by the use

van Stokkum, Ivo

242

Intrinsic absorptive optical bistability in CdS  

NASA Astrophysics Data System (ADS)

An intrinsic absorptive optical bistability is observed in the transmission of high intensity, nanosecond laser pulses through thin CdS platelets at liquid helium temperature. The bistability is due to a renormalization of the band gap which is caused by the formation of an electron hole plasma and occurs in a broad spectral range below the excitonic resonances. The switching times are in the subnanosecond range. The dependence on photon energy is investigated and discussed.

Bohnert, K.; Kalt, H.; Klingshirn, C.

1983-12-01

243

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

Microsoft Academic Search

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

Neil S. Sadick; Cynthia Magro; Alison Hoenig

2007-01-01

244

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

245

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

SciTech Connect

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

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

2014-02-07

246

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

247

H + O3 Fourier-transform infrared emission and laser absorption studies of OH(X2Pi) radical - An experimental dipole moment function and state-to-state Einstein A coefficients  

NASA Technical Reports Server (NTRS)

FTIR emission/absorption spectroscopy is used to measure the relative intensities of 88 pairs of rovibrational transitions of OH(X2Pi) distributed over 16 vibrational bands. The experimental technique used to obtain the Einstein A ratios is discussed. The dipole moment function which follows from the intensity ratios along with Einstein A coefficients calculated from mu(r) is presented.

Nelson, David D., Jr.; Schiffman, Aram; Nesbitt, David J.; Orlando, John J.; Burkholder, James B.

1990-01-01

248

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

249

A method for precomputing effective absorption coefficients from satellite measurements of backscattered UV radiation  

NASA Astrophysics Data System (ADS)

This paper presents a method for computing the effective absorption coefficients for ozone and Rayleigh scattering from satellite measurements of backscattered UV solar radiation. Values of the effective absorption coefficients for ozone and Rayleigh scattering were calculated for polar-zone summer, moderate-zone winter, moderate-zone summer, and the tropics for 12 different wavelength channels. Using these coefficients, the calculations of solar UV radiation (backscattered by the terrestrial atmosphere within the ozone absorption band and measured with SBUV/TOMS instruments) are reduced to calculations of the intensity of monochromatic radiation.

Ishov, A. G.; Kozina, T. V.

1990-10-01

250

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

251

Fourier transform spectra of overtone bands of HCN from 5400 to 15100 cm -1  

NASA Astrophysics Data System (ADS)

The absolute intensities and vibration-rotation constants of 26 overtone and combination bands of HCN are reported. The dynamic range for the absolute intensity measurements is nearly one million to one. Absorption spectra of HCN from 5400 to 15100 cm -1 were obtained using the Fourier transform spectrometer at the Kitt Peak National Solar Observatory with optical path lengths up to 432 m. The frequencies of 1346 assigned HCN lines were used to derive vibration-rotation constants for 23 bands (14 ?-?, 4 ?-?, 4 ?-?, and 1 ?-?) of H 12C 14N, 3 bands (?-?) of H 13C 14N, and 2 bands (?-?) of H 12C 15N. These new band origin and rotational constant data have been combined with existing data given in the literature to derive an improved set of vibrational (?, x, and y) constants and rovibrational (? and ?) constants for HCN. The vibrational dependence of the centrifugal distortion constants has also been examined. One thousand thirtysix derived line areas were used to determine absolute intensities for all 28 bands. Four weak stretch-only bands were observed for the first time: the (300)-(000), the (201)-(000), the (301)-(000) and the (202)-(000). Such data should be an important aid in accurately determining the CN contribution to the potential and dipole moment functions. Finally, we present a comparison of 13 of the measured absolute overtone intensities (stretching states only) with recent ab initio results.

Smith, Alice M.; Coy, Stephen L.; Klemperer, William; Lehmann, Kevin K.

1989-03-01

252

Temperature dependence of the ratio of intensities of up-conversion fluorescence bands of YVO4 and YGdVO4 crystals and lead fluoride nano glass ceramics activated with erbium ions  

NASA Astrophysics Data System (ADS)

Up-conversion fluorescence spectra of YVO4 and YGdVO4 crystals and lead fluoride nano glass ceramics coactivated with erbium and ytterbium ions have been studied in the wavelength range of 520-560 nm under 967-nm pumping. The ratio of intensities of fluorescence bands in the ranges of 520-530 and 540-550 nm has been measured in the temperature range of from room temperature to 150°C. It is shown that the considered materials can be used for preparing a sensing element of optical fluorescent temperature sensors; the sensitivity of measuring the temperature of nano glass-ceramics can be close to that of crystal samples.

Varaksa, Yu. A.; Sinitsyn, G. V.; Khodasevich, M. A.; Aseev, V. A.; Kolobkova, E. V.; Yasyukevich, A. S.

2015-01-01

253

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; Sundström, V; Freiberg, A; Timpmann, K; van Grondelle, R

1994-01-01

254

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

255

A study of the absorption features of Makemake  

NASA Astrophysics Data System (ADS)

Most transneptunian objects do not show prominent absorption features due to the size and location [1]. Nevertheless, absorption due to water ice and volatile ices do appear on a few large objects, particularly those that have good signal-to-noise-ratio spectra. In particular, methane appears in three dwarf planets (Pluto, Eris, and Makemake), as well as in some smaller objects, such as Quaoar and probably Sedna, and in Neptune's satellite Triton. Methane has such intense absorption features that even small amounts of methane on the surface dominate the reflectance spectra in the visible and near-infrared range, making it a great tool to probe surfaces, especially, considering that the depth of the bands could be used as a proxy for physical depths and that shifts in the bands with respect to laboratory measurements could point to possible dilutions (as seen in Pluto and Eris; for instance [3] and references therein). Aiming at gaining a deeper insight into Makemake's surface through its methane absorption bands, we have observed it with X-Shooter at the VLT with a medium spectral resolution in the range of 0.4--1.8 microns. In this work, we present the results of comparing these features with those of methane in the laboratory and the same features in Eris and Pluto, within the context of methane-dominated spectra of dwarf planets.

Alvarez-Candal, A.; Pinilla-Alonso, N.; Ortiz, J.; Duffard, R.; Carvano, J.; de Pra, M.

2014-07-01

256

Ice absorption features in the 5-8 ?m region toward embedded protostars  

NASA Astrophysics Data System (ADS)

We have obtained 5-8 ?m spectra towards 10~embedded protostars using the Short Wavelength Spectrometer on board the Infrared Space Observatory (ISO-SWS) with the aim of studying the composition of interstellar ices. The spectra are dominated by absorption bands at 6.0 ?m and 6.85 ?m. The observed peak positions, widths and relative intensities of these bands vary dramatically along the different lines of sight. On the basis of comparison with laboratory spectra, the bulk of the 6.0 ?m absorption band is assigned to amorphous H2O ice. Additional absorption, in this band, is seen toward 5 sources on the short wavelength wing, near 5.8 ?m, and the long wavelength side near 6.2 ?m. We attribute the short wavelength absorption to a combination of formic acid (HCOOH) and formaldehyde (H2CO), while the long wavelength absorption has been assigned to the C-C stretching mode of aromatic structures. From an analysis of the 6.85 ?m band, we conclude that this band is composed of two components: a volatile component centered near 6.75 ?m and a more refractory component at 6.95 ?m. From a comparison with various temperature tracers of the thermal history of interstellar ices, we conclude that the two 6.85 ?m components are related through thermal processing. We explore several possible carriers of the 6.85 ?m absorption band, but no satisfactory identification can be made at present. Finally, we discuss the possible implications for the origin and evolution of interstellar ices that arise from these new results. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA.

Keane, J. V.; Tielens, A. G. G. M.; Boogert, A. C. A.; Schutte, W. A.; Whittet, D. C. B.

2001-09-01

257

Quasi-Molecular K-H[2 ]Absorption As An Alternative To The Resurgence Of CaH Bands In The Spectra Of T-Type Dwarfs: Is The Cloud-Clearing Scheme At Stake?  

NASA Astrophysics Data System (ADS)

As brown dwarfs cool off with time, their atmospheres become denser and more transparent, allowing the emitted thermal flux to escape from deeper atmospheric layers. Burgasser et al. (2002) have investigated and classified the red spectra of T dwarfs in a spectral sequence where a resurgence of the hydride bands, after disappearing in the M to L spectral transition, occur between the late L to T before disappearing again in the late T dwarfs. CaH for example is identified in mid-T dwarfs at around 0.7?m (Burgassser 2003). The authors explain this resurgence by a cloud-clearing scheme where holes would allow to see the CaH from deeper enriched layers, while it is settled out from the uppermost atmospheric layers seen on the rest of the brown dwarf surface. We present the first synthetic spectra of T dwarfs including a semi-classical modelling of the pressure broadening of alkalis lines (Na I D, Li I, K I, Rb I, and Cs I fundamental resonance doublets) by molecular hydrogen and helium, the most important species in these atmospheres. We compare the models to the T dwarfs red optical spectra of Burgasser et al. (2003) and we find that the 0.7?m feature has been wrongly identified to CaH. In particular, the very strong KI resonance transition doublet at 0.77?m explains by itself this absorption feature by producing a quasi-molecular satellite absorption feature at this wavelength. The strength of this satellite is very sensitive to the density of perturbers in the lower photosphere and to the background opacity provided by the Na I D red wing, which explains naturally both its apparition in late L dwarfs and its vanishing in late T dwarfs. We find in conclusion that no cloud-clearing scheme or non-equilibrium processes is necessary to explain this absorption feature, and the evolution of the red optical spectrum of T dwarfs. And this should teach us caution about these atmospheres often too enthusiastly considered planetary. MHR 3D convection models are nevertheless underway to estimate the likelihood of cloud-clearings in late L and T dwarfs.

Allard, F.; Allard, N. F.; Johnas, C. M. S.; Hauschildt, P. H.; Homeier, D.; Kielkopf, J. K.; Spiegelman, F.

2007-08-01

258

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

PubMed Central

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. PMID:25073935

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

2014-01-01

259

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

PubMed

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?cm(2)). We present a simple method for producing crystalline silicon nanohole arrays of up to 5 × 5?cm(2) 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. PMID:25073935

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

2014-01-01

260

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

261

A search for diffuse bands in fullerene planetary nebulae: evidence of diffuse circumstellar bands  

NASA Astrophysics Data System (ADS)

Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some planetary nebulae (PNe) now enable us to study the DIBs towards fullerene-rich space environments. We search DIBs in the optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC 418). Special attention is given to DIBs which are found to be unusually intense towards these fullerene sources. In particular, an unusually strong 4428 Å absorption feature is a common charateristic of fullerene PNe. Similar to Tc 1, the strongest optical bands of neutral C60 are not detected towards IC 418. Our high-quality (S/N > 300) spectra for PN Tc 1, together with its large radial velocity, permit us to search for the presence of diffuse bands of circumstellar origin, which we refer to as diffuse circumstellar bands (DCBs). We report the first tentative detection of two DCBs at 4428 and 5780 Å in the fullerene-rich circumstellar environment around the PN Tc 1. Laboratory and theoretical studies of fullerenes in their multifarious manifestations (carbon onions, fullerene clusters, or even complex species formed by fullerenes and other molecules like PAHs or metals) may help solve the mystery of some of the diffuse band carriers. Appendix A is available in electronic form at http://www.aanda.org

Díaz-Luis, J. J.; García-Hernández, D. A.; Kameswara Rao, N.; Manchado, A.; Cataldo, F.

2015-01-01

262

Extinction and PAH intensity variations across the HII region IRAS 12063-6259  

NASA Astrophysics Data System (ADS)

The spatial variations in polycyclic aromatic hydrocarbon (PAH) band intensities are generally attributed to variations of the physical conditions in the environment hosting the emitting PAH molecules. 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 HII region IRAS 12063-6259. We use these data to construct multiple independent extinction maps and to measure the main PAH feature intensities (6.2, 7.7, 8.6 and 11.2 µ m). Three extinction maps are derived: the first using the NIR hydrogen lines and case B recombination theory; the second combining the NIR data, radio data and case B recombination; and the third making use of the Spitzer/IRS MIR observations to measure the 9.8 µ m silicate absorption feature intensity using the Spoon method and PAHFIT. We conclude that different areas of IRAS 12063-6259 possess markedly different extinction properties, with some regions displaying both silicate absorption and corresponding NIR extinction, and other regions displaying NIR extinction and no corresponding silicate absorption. While such breakdowns of the relationship between the NIR extinction and the silicate absorption strength have been observed in molecular clouds, they have never been observed for HII regions. We then compare the PAH intensity variations in the Spitzer/IRS data after dereddening to those found in the original data. Generally it was found that 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.; Peeters, E.; Tielens, X.; Otaguro, J.; Bik, A.

263

Bird Banding  

USGS Multimedia Gallery

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

264

The 506 nm absorption feature in pyroxene spectra: Nature and implications for spectroscopy-based studies of pyroxene-bearing targets  

NASA Astrophysics Data System (ADS)

High-resolution (0.34 nm) reflectance spectra of a suite of terrestrial ortho- and clinopyroxenes were characterized in the 506-nm region. This region exhibits absorption bands attributed to spin-forbidden transitions in Fe 2+ located in the M2, and possibly M1, crystallographic site(s). The most intense absorption bands (up to 3.8% deep in <45 ?m fractions) are present in low Ca-content orthopyroxene spectra. This region exhibits two (spectral Group I) or more (spectral Group II) absorption bands in the 500-515 nm interval. Group I spectra are associated with the lowest Ca-content samples. For orthopyroxenes, the number of constituent absorption bands and band depths vary as a function of Ca content; increasing Ca content results the appearance of more than two absorption bands and a general reduction in band depths, offsetting an expected increase in band depth with increasing Fe 2+ content; band depths may also be reduced due to the long wavelength wing of ultraviolet region Fe-O charge transfer absorptions. Band depths and shapes in this region are also a function of grain size, with the strongest bands appearing for larger grain sizes - in the 90-250 ?m range. The number and position of constituent absorption bands can be used to constrain factors such as cooling rates, as expressed in the formation of Guinier-Preston zones versus coarser-grained augite exsolution lamellae. Band depths in the spectra of fine-grained (<45 ?m) clinopyroxenes do not exceed 1% and are generally lowest for spectral type A clinopyroxenes, where most of the Fe 2+ is present in the M1 crystallographic site. The appearance of the 506 nm band in the spectra of pyroxene-bearing asteroids can be used to constrain pyroxene composition and structure. The results of this study suggest that detailed analysis of absorption features in the 506 nm region is a powerful tool for determining the composition and structure of pyroxenes. The spectral resolution of the VIR-MS spectrometer aboard the Dawn spacecraft - which will examine Asteroid 4 Vesta, a body possessing surficial pyroxenes - will be sufficient to provide some constraints on pyroxene composition.

Cloutis, Edward A.; Klima, Rachel L.; Kaletzke, Lindsay; Coradini, A.; Golubeva, L. F.; McFadden, L. A.; Shestopalov, D. I.; Vilas, F.

2010-05-01

265

Origin of coherent G -band phonon spectra in single-wall carbon nanotubes  

NASA Astrophysics Data System (ADS)

Coherent phonons in single-wall carbon nanotubes (SWNTs) are observed as oscillations of the differential absorption coefficient as a function of time by means of pump-probe spectroscopy. For the radial breathing mode (RBM) of a SWNT, the coherent phonon signal is understood to be a result of the modulated diameter-dependent energy gaps due to the coherent RBM phonon oscillations. However, this mechanism might not be the dominant contribution to other phonon modes in the SWNT. In particular, for the G -band phonons, which correspond to bond-stretching motions, we find that the modulation of the interatomic optical dipole (electron-photon) matrix element gives rise to a strong coherent G -band phonon intensity comparable to the coherent RBM phonon intensity. We also further discuss the dependence of coherent G -band and RBM phonon amplitudes on the laser excitation pulse width.

Nugraha, A. R. T.; Hasdeo, E. H.; Sanders, G. D.; Stanton, C. J.; Saito, R.

2015-01-01

266

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

267

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

PubMed

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. PMID:25362294

Huang, Yu-Hsuan; Lee, Yuan-Pern

2014-10-28

268

Relative intensity calculations for nitrous oxide.  

NASA Technical Reports Server (NTRS)

A tabulation of calculated rotational line intensities, relative to the integrated intensity of a vibration-rotation band, is given for Sigma-Sigma, Pi-Sigma, Sigma-Pi, Pi-Pi, and Delta-Pi transitions of nitrous oxide. These calculations were made for temperatures of 250 K and 300 K. A summary of band-intensity measurements is also presented.

Young, L. D. G.

1972-01-01

269

A search of diffuse bands in fullerene planetary nebulae: evidence for diffuse circumstellar bands  

E-print Network

Large fullerenes and fullerene-based molecules have been proposed as carriers of diffuse interstellar bands (DIBs). The recent detection of the most common fullerenes (C60 and C70) around some Planetary Nebulae (PNe) now enable us to study the DIBs towards fullerene-rich space environments. We search DIBs in the optical spectra towards three fullerene-containing PNe (Tc 1, M 1-20, and IC 418). Special attention is given to DIBs which are found to be unusually intense towards these fullerene sources. In particular, an unusually strong 4428A absorption feature is a common charateristic to fullerene PNe. Similarly to Tc 1, the strongest optical bands of neutral C60 are not detected towards IC 418. Our high-quality (S/N > 300) spectra for PN Tc 1 together with its large radial velocity permits us to search for the presence of diffuse bands of circumstellar origin which we refer to as diffuse circumstellar bands (DCBs). We report the first tentative detection of two DCBs at 4428 and 5780 A in the fullerene-rich ci...

Diaz-Luis, J J; Rao, N Kameswara; Manchado, A; Cataldo, F

2014-01-01

270

Resolving the forbidden band of SF6.  

PubMed

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

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

2014-01-28

271

Quantitative infrared absorption cross sections of isoprene for atmospheric measurements  

SciTech Connect

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

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

2014-11-19

272

Absolute intensities and foreign gas broadening coefficients of the 11(sub 1,10) from 11(sub 2,10) and 18(sub 0,18) from 18(sub 1,18) lines in the nu(sub 7) band of C2H4  

NASA Technical Reports Server (NTRS)

Absolute intensities and foreign gas broadening coefficients of the 18(sub 0,18) from 18(sub 1,18) and 11(sub 1,10) from 11(sub 2,10) transitions in the nu(sub 7) band of C2H4 near 948/cm have been measured at a spectral resolution of approximately 5 x 10(exp -4)/cm using tunable diode laser spectrometry. Ar, He, N2, O2 were used as the broadening gases. In order to determine the temperature dependence of the broadening coefficient, data were obtained at temperatures ranging from 150 to 296 K. The absolute intensity of the 5(sub 0,5) from 5(sub 1,5) transition was also found at 296 K. A band strength of 330 +/- 10/sq cm/atm was obtained from weighted averages of the individual line intensities and a rigid asymmetric top calculation.

Reuter, Dennis C.; Sirota, J. Marcos

1993-01-01

273

The 890 nm Band of Methane  

NASA Astrophysics Data System (ADS)

The near infrared bands of methane were the first observed in the outer planets and Titan. With the very long paths of rays in this spectral region within the atmospheres of these objects, scattering and pressure and temperature inhomogeneities are important. Here the spectrum is very complex and long absorption paths in the laboratory are difficult to cool to outer solar system temperatures. Many significant spectral lines appear per Doppler width, so the absorption is usually modeled statistically. The problem with these statistical models is that violations of the modeling assumptions can cause the extrapolation of laboratory parameters to predict absorption that diverges from the actual. These models generally do not provide transmissions that are multiplicative, so scattering and inhomogeneous atmospheres cannot be properly modeled. The intracavity laser spectrometer of the University of Missouri-St. Louis was used to obtain low temperature (99-161K), low pressure (0.12-7.13 Torr), long path (3.14-5.65 km) and high resolution ( 0.01 cm-1 HWHM) spectra of methane covering the entire 890nm feature (10925-11500 cm-1), the deepest band in the CCD spectral region. At these temperatures the spectral lines originating from higher energy levels are not visible and the Doppler width is decreased substantially from room temperature. The result is a dense, but manageable spectrum from which line positions, intensities and lower state energies are derived on a line by line basis by the William and Mary multispectrum nonlinear least squares fitting program, allowing for the simulation of the spectrum at infinite resolution for any physical conditions with temperature less than 160K. Support for the work at William and Mary was provided by NASA through grant NNX08AF06G. Support for the work at UM-St. Louis provided by NASA through grant NAG5-12013, from NSF through grant CHE-0213356 and by the University of Missouri Research Board.

Benner, D. Chris; O'Brien, J. J.; Shaji, S.; Spickler, P. T.; Houck, C. P.; Coakley, J. A.; Malathy Devi, V.

2009-09-01

274

The 890 nm Band of Methane  

NASA Astrophysics Data System (ADS)

The near infrared bands of methane were the first observed in the outer planets and Titan. With the very long paths of rays in this spectral region within the atmospheres of these objects, scattering and pressure and temperature inhomogeneities are important. Here the spectrum is very complex and long absorption paths in the laboratory are difficult to cool to outer solar system temperatures. Many significant spectral lines appear per Doppler width, so the absorption is usually modeled statistically. The problem with these statistical models is that violations of the modeling assumptions can cause the extrapolation of laboratory parameters to predict absorption that diverges from the actual. These models generally do not provide transmissions that are multiplicative, so scattering and inhomogeneous atmospheres cannot be properly modeled. The intracavity laser spectrometer of the University of Missouri-St. Louis was used to obtain low temperature (99-161K), low pressure (0.12-7.13 Torr), long path (3.14-5.65 km) and high resolution ( 0.01 cm-1 HWHM) spectra of methane covering the entire 890nm feature (10925-11500 cm-1), the deepest band in the CCD spectral region. At these temperatures the spectral lines originating from higher energy levels are not visible and the Doppler width is decreased substantially from room temperature. The result is a dense, but manageable spectrum from which line positions, intensities and lower state energies are derived on a line by line basis by the William and Mary multispectrum nonlinear least squares fitting program, allowing for the simulation of the spectrum at infinite resolution for any physical conditions with temperature less than 160K. A sample spectrum will be shown. Support for work at William and Mary provided by NASA through grant NNX08AF06G. Support for work at UM-St. Louis provided by NASA through grant NAG5-12013, from NSF through grant CHE-0213356 and by the University of Missouri Research Board.

Spickler, Philip T.; Benner, D.; O'Brien, J.; Devi, V.; Shaji, S.; Houck, C.; Coakley, J.

2010-01-01

275

Silicate absorption in heavily obscured galaxy nuclei  

E-print Network

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

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

2006-10-19

276

Optical absorption spectra of deoxy- and oxyhemoglobin in the temperature range 300-20 K. Relation with protein dynamics.  

PubMed

We have studied the optical absorption spectra of human deoxy- and oxyhemoglobin in the temperature range 300-20 K and in the wavelength range 350-1350 nm. By lowering the temperature, a narrowing and a shift of all bands were observed together with a sizeable increase of the integrated intensities of the charge-transfer bands of deoxyhemoglobin. At all temperatures the spectra are in full agreement with the band assignment previously suggested in the literature and no new relevant bands have been detected for both deoxy- and oxyhemoglobin. Analysis of the first and second moment of the bands, within the framework of the harmonic Franck-Condon approximation, gave information on the dynamic properties of the heme in the heme pocket. PMID:3768470

Cordone, L; Cupane, A; Leone, M; Vitrano, E

1986-08-01

277

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

278

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

PubMed Central

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

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

2013-01-01

279

Nonlinear Faraday effect near the fundamental absorption edge in the ferromagnetic semiconductor CdCr 2 Se 4  

Microsoft Academic Search

A sharp increase of the Faraday rotation with increasing incident radiation power is observed in a band near the fundamental\\u000a absorption edge of the ferromagnetic semiconductor CdCr2 Se4. The magnitude of the effect is a nonmonotonic function of the radiation intensity. The effect is explained by narrowing\\u000a of an excitonic resonance as a result of screening of the internal electric

L. L. Golik; Z. E. Kun’kova

1997-01-01

280

Studies on Hyperspectral Face Recognition in Visible Spectrum With Feature Band Selection  

Microsoft Academic Search

This correspondence paper studies face recognition by using hyperspectral imagery in the visible light bands. The spectral measurements over the visible spectrum have different discriminatory information for the task of face identification, and it is found that the absorption bands related to hemoglobin are more discriminative than the other bands. Therefore, feature band selection based on the physical absorption characteristics

Wei Di; Lei Zhang; David Zhang; Quan Pan

2010-01-01

281

Optical absorption of isotopically enriched Li 2B 4O 7 single crystals irradiated by thermal neutrons  

Microsoft Academic Search

Induced absorption spectra in the range 200–900nm at 77 and 290K for Li2B4O7 single crystals, isotopically Li and B enriched are presented after irradiation of these crystals by thermal neutrons with fluence 1.8×1016cm?2. The dependence of induced absorption spectra on the isotope composition was revealed: for 6Li210B4O7 and 7Li210B4O7 crystals intensive band in the region of 280–294nm was observed. Under

Ya. V. Burak; V. T. Adamiv; I. M. Teslyuk; V. M. Shevel

2004-01-01

282

EPR and optical absorption spectral studies of Cu 2+ ions doped in alkali lead tetraborate glasses  

NASA Astrophysics Data System (ADS)

Electron paramagnetic resonance and optical absorption spectra of Cu 2+ ions in 90R 2B 4O 7+(10- x) PbO + xCuO (where R=Li, Na and K; 0.25 ? x ? 1.5 mol% of CuO) glasses have been studied. EPR spectra of all glasses show resonance peaks characteristic of Cu 2+ ions. From the observed EPR spectra, the spin-Hamiltonian parameters have been evaluated. The values of spin-Hamiltonian parameters indicate that Cu 2+ ions in alkali lead tetraborate glasses have octahedral coordination with a strong tetragonal distortion. The number of spins participating in resonance is measured as a function of temperature and the activation energy is calculated. The paramagnetic susceptibility is also calculated from the EPR data at various temperatures. From the plot of temperature versus 1/ ?, the Curie constant and the Curie temperature values have been evaluated. The optical absorption spectra of all the glass samples show two bands. One broad band at low-energy side is assigned to 2B 1g? 2B 2g transition of Cu 2+ ion and the intense band at high-energy side is assigned to charge transfer band. By correlating EPR and optical absorption data, the molecular orbital coefficients have been evaluated.

Lakshmana Rao, J.; Sivaramaiah, G.; Gopal, N. O.

2004-06-01

283

A novel green phosphor for three band white LEDs  

NASA Astrophysics Data System (ADS)

Current technology of lighting is Solid state lighting using LED's (SSL-LED). The aim of the present study is to find the critical concentration of Eu2+ for high emission intensity and also the role of Ce3+ co-doping on the absorption and emission properties in the host BaMgSiO4. Photoluminescence emission of Eu2+ in BaMgSiO4 when excited with 370 nm shows a broad band in the region 450 to 550 nm with a maximum at 502 nm and a shoulder at ~480 nm and one more band at ~ 400nm. The three emissions are due to Eu2+ in three different Ba sites in the lattice. Studies on Ba1 xEuxMgSiO4 [x = 0.0025 - 0.1 in steps of 0.0025] show that the emission intensity is maximum for x = 0.075 and a decrease in emission intensity is observed for higher x values. Ce3+ luminescence is studied for the first time in BaMgSiO4. Ce3+ emission occurs as a broad band with maximum at 430 nm when excited with 356 nm. The Eu2+ excitation that occurs in the region 250 - 420 nm covers both the Ce3+ absorption and emission. Hence Ce3+ to Eu2+ energy transfer is possible in BaMgSiO4. In the case of Ba0.99 xEu0.01CexMgSiO4 [ x = 0.0025 - 0.1 ], it is observed that the emission intensity of Eu2+ increases with increasing Ce3+ content up to 0.01. This result proves the energy transfer from Ce3+ to Eu2+. Thus, the co-doping of Ce3+ also enhances the absorption of Eu2+ in the near UV to blue region where the LED emission occurs. BaMgSiO4:Eu2+, Ce3+ with bright green emission can find potential application as a green phosphor for SSL-LED technology.

Vaidyanathan, Sivakumar; Upadhyayula, Varadaraju

2005-09-01

284

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

NASA Technical Reports Server (NTRS)

Two independent, extensive theoretical calculations are reported for the relative band strengths of the AlO (B2Sigma + - X2Sigma +) blue-green system and for the radiative lifetimes of the lowest few vibrational levels of the B2Sigma(+) state. The theoretical lifetimes, which include a small (less than -.5 percent) contribution from bound-bound transitions into the A2Pi state, are in excellent agreement with laser fluorescence studies. The theoretical lifetimes increase monotonically and very slowly with increasing vibrational quantum number. The relative band strengths for the blue-green system derived from the two theoretical calculations are in excellent agreement, but differ systematically from the relative band strengths of Linton and Nicholls (1969). The present results suggest that their self-absorption corrections are not large enough, resulting in relative intensities that are too large, especially for the weak bands with r centroids less than 1.5 A.

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

1983-01-01

285

Density functional calculation of the electronic absorption spectrum of Cu+ and Ag+ aqua ions.  

PubMed

The UV absorption of aqueous Cu+ and Ag+ 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+ 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+ 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+ 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-->s transitions. PMID:15634150

Bernasconi, Leonardo; Blumberger, Jochen; Sprik, Michiel; Vuilleumier, Rodolphe

2004-12-15

286

Phase shift cavity ring down and Fourier transform infrared measurements of C-H vibrational transitions, energy levels, and intensities of (CH3)3Si-C?C-H  

NASA Astrophysics Data System (ADS)

Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (?? = 1-5) and methyl (?? = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi?CH] at 295 K. Harmonic frequencies ?(?1), ?a, and ?s and anharmonicities x(?1), ?axa, ?sxs were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds. A hot band, assigned as ??1 + ?24 - ?24 is observed for transitions with ?? = 1-5 in a region near the acetylenic stretch. The intensity of the hot band is reduced considerably at 240 K. The strength of a Fermi resonance between C-Ha transition (??a) and the combination band ((?-1)?a + 2?bend) with (? = 3-6) was calculated using the experimental perturbed energies and relative intensities. The main bands are separated by computer deconvolution and are integrated at each level to get the experimental band strengths. For methyl absorptions, the dipole moment function is expanded as a function of two C-H stretching coordinates and the intensities are calculated in terms of the HCAO model where only the C-H modes are considered. Acetylenic intensities are derived with a one dimensional dipole moment function. The expansion coefficients are obtained from molecular orbital calculations. The intensities are calculated without using adjustable parameters and they are of the same order of magnitude of the experimental intensities for all C-H transitions.

Barroso, Jenny Z.; Perez-Delgado, Yasnahir; Manzanares, Carlos E.

2013-07-01

287

Optical absorption of silicon nanowires  

SciTech Connect

We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

Xu, T. [Key Laboratory of Advanced Display and System Application, Shanghai University, 149 Yanchang Road, Shanghai 200072 (China); Institut d'Electronique et de Microelectronique et de Nanotechnologies, IEMN (CNRS, UMR 8520), Groupe de Physique, Cite scientifique, avenue Poincare, 59652 Villeneuve d'Ascq (France); Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B. [Institut d'Electronique et de Microelectronique et de Nanotechnologies, IEMN (CNRS, UMR 8520), Groupe de Physique, Cite scientifique, avenue Poincare, 59652 Villeneuve d'Ascq (France)

2012-08-01

288

Absorption spectroscopic probe to investigate the interaction between Nd(III) and calf-thymus DNA.  

PubMed

The interaction between Nd(III) and Calf Thymus DNA (CT-DNA) in physiological buffer (pH 7.4) has been studied using absorption spectroscopy involving 4f-4f transition spectra in different aquated organic solvents. Complexation with CT-DNA is indicated by the changes in absorption intensity following the subsequent changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity (T(?)) parameters. The other spectral parameters namely Slator-Condon (F(k)'s), nephelauxetic effect (?), bonding (b(1/2)) and percent covalency (?) parameters are computed to correlate with the binding of Nd(III) with DNA. The absorption spectra of Nd(III) exhibited hyperchromism and red shift in the presence of DNA. The binding constant, K(b) has been determined by absorption measurement. The relative viscosity of DNA decreased with the addition of Nd(III). Thermodynamic parameters have been calculated according to relevant absorption data and Van't Hoff equation. The characterisation of bonding mode has been studied in detail. The results suggested that the major interaction mode between Nd(III) and DNA was external electrostatic binding. PMID:21247794

Devi, Ch Victory; Singh, N Rajmuhon

2011-03-01

289

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

290

VOLUME 78, NUMBER 16 P H Y S I C A L R E V I E W L E T T E R S 21 APRIL 1997 High Intensity Laser Absorption by Gases of Atomic Clusters  

E-print Network

high .95% , indicating that substantial laser energy is deposited per particle in the plasma. IonVOLUME 78, NUMBER 16 P H Y S I C A L R E V I E W L E T T E R S 21 APRIL 1997 High Intensity Laser of high intensity, picosecond laser pulses in low density gases composed of large atomic clusters. We find

Ditmire, Todd

291

Band gap enhancement of glancing angle deposited TiO{sub 2} nanowire array  

SciTech Connect

Vertically oriented TiO{sub 2} nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters {approx}80 nm and {approx}40 nm TiO{sub 2} NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO{sub 2}. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm{sup -1} of anatase E{sub g}) and blue (7.4 cm{sup -1} of rutile E{sub g}, 7.8 cm{sup -1} of rutile A{sub 1g}) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and {approx}3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

Chinnamuthu, P.; Mondal, A.; Singh, N. K.; Dhar, J. C. [National Institute of Technology Agartala, Department of Electronics and Communication Engineering, Jirania, Tripura (West) 799055 (India); Chattopadhyay, K. K. [Jadavpur University, Department of Physics, Kolkata 700032 (India); Bhattacharya, Sekhar [SSN Research Centre, Tamil Nadu 603110 (India)

2012-09-01

292

High-resolution Fourier-transform intra-cavity laser absorption spectroscopy: application to 12C2H2 near 12 300 cm -1  

NASA Astrophysics Data System (ADS)

The capabilities of intra-cavity laser absorption spectroscopy associated with a high-resolution Fourier-transform spectrometer (FT-ICLAS) are investigated with a Ti:Sapphire laser. Weak absorption lines of atmospheric water were used to test the accuracy of absolute intensity measurements by FT-ICLAS leading to an excellent agreement (a few %) with the HITRAN data. The performances in terms of spectral resolution (0.028 cm -1) and sensitivity ( 2×10 -9 cm-1) are illustrated by the spectroscopic study of the overtone spectrum of 12C2H2 between 12 250 and 12 400 cm -1 which allowed for a significant improvement of recent cavity ring-down measurements. Among the three ?-? bands rotationally analyzed, one is newly observed. The absolute intensity values of the bands are given.

Hu, Shui-Ming; Campargue, Alain; Wu, Zhi-Yong; Ding, Yun; Liu, An-Wen; Zhu, Qing-Shi

2003-05-01

293

APPLICATIONS OF LASERS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Simultaneous influence of quantum fluctuations of the intensity and of spatial inhomogeneities on the emission dynamics of wide-band lasers and on the sensitivity of intracavity spectroscopy  

NASA Astrophysics Data System (ADS)

Rate equations are used to show that the combination of fluctuations and inhomogeneities can have a significant influence on the dynamics of emission of multimode wide-band lasers even when the lasing duration is ~ 1 ms. The sensitivity of intracavity spectroscopy is then limited to ~ 10 - 8 cm - 1.

Kovalenko, S. A.; Semin, S. P.

1989-01-01

294

Line Intensities of Isotopic Carbonyl Sulfide (ocs) at 2.5 Micrometer  

NASA Astrophysics Data System (ADS)

We have measured line intensities of ^{16}O^{12}C^{32}S, ^{16}O^{13}C^{32}S, ^{16}O^{12}C^{33}S, ^{16}O^{12}C^{34}S, and ^{18}O^{12}C^{32}S in the 2.5 ?m region for the first time to support planetary studies of the Venus atmosphere. Laboratory absorption spectra of OCS were recorded at 0.0033 cm^{-1} resolution at room temperature using a Bruker IFS 125-HR Fourier transform spectrometer at the Jet Propulsion Laboratory. Normal samples of OCS were used in this study, and sample impurities and isotopic abundances were determined from mass spectrum analysis. Optical densities sufficient to observe isotopic bands and weaker hot bands were achieved by using a multi-pass White cell and single pass gas cells in various path lengths, which were validated by analyzing near-IR CO_2 spectra. We present line intensities for almost 30 bands of the OCS isotopes excluding ground state bands of ^{16}O^{12}C^{32}S, which we have reported recently. We have Herman-Wallis factors determined for the individual bands. In some cases, it has been observed that band intensities normalized to 100% isotopic species show a significant deviation from that of the primary isotopic species (up to by 12.5%). No earlier measurements have been reported for these bands. Measurement precision and accuracies will be discussed. Research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration. We thank Drs. Stojan Madzunkov, John A. MacAskill, and Murray R. Darrach from the Atomic and Molecular Collision Group at Jet Propulsion Laboratory for recording mass spectrum of the OCS sample used in this work.

Toth, Robert A.; Sung, Keeyoon; Brown, Linda R.; Crawford, Timothy J.

2009-06-01

295

Infrared laser absorption spectroscopy of the nu4 (sigma u) fundamental and associated nu11(pi u) hot band of C7 - Evidence for alternating rigidity in linear carbon clusters  

NASA Technical Reports Server (NTRS)

The first characterization of the bending potential of the C7 cluster is reported via the observation of the v = 1(1) and v = 2 deg levels of the nu11 (pi u) bend as hot bands associated with the nu4 (sigma u) antisymmetric stretch fundamental. The lower state hot band rotational constants are measured to be 1004.4(1.3) and 1123.6(9.0) MHz, constituting a 9.3 and 22 percent increase over the ground state rotational constant, 918.89 (41) MHz. These large increases are strong quartic and sextic centrifugal distortion constants determined for the ground and nu 4 = 1 states are found to be anomalously large and negative, evidencing strong perturbations between stretching and bending modes.

Heath, J. R.; Saykally, R. J.

1991-01-01

296

Liquid water absorption and scattering effects in DOAS retrievals over oceans  

NASA Astrophysics Data System (ADS)

Spectral effects of liquid water are present in absorption (differential optical absorption spectroscopy - DOAS) measurements above the ocean and, if insufficiently removed, may interfere with trace gas absorptions, leading to wrong results. Currently available literature cross sections of liquid water absorption are provided in coarser resolution than DOAS applications require, and vibrational Raman scattering (VRS) is mostly not considered, or is compensated for using simulated pseudo cross sections from radiative transfer modeling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS (Multi-AXis differential optical absorption spectroscopy) measurements of light penetrating very clear natural waters were performed, achieving average underwater light paths of up to 50 m. From these measurements, the retrieval of a correction spectrum (H2Ocorr) is presented, compensating simultaneously for insufficiencies in the liquid water absorption cross section and broad-banded VRS structures. Small-banded structures caused by VRS were found to be very efficiently compensated for by the intensity offset correction included in the DOAS fit. No interference between the H2Ocorr spectrum and phytoplankton absorption was found. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality, and performed better than using a liquid water cross section in combination with a simulated VRS spectrum. The decrease in the residual root mean square (rms) of the DOAS fit depends on the measurement's contamination with liquid water structures, and ranges from ? 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ocorr spectrum was found to prevent misfits of NO2 slant columns, especially for very low NO2 scenarios, and thus increases the reliability of the fit. In test fits on OMI satellite data, the H2Ocorr spectrum was found selectively above ocean surfaces, where it decreases the rms by up to ? 11 %.

Peters, E.; Wittrock, F.; Richter, A.; Alvarado, L. M. A.; Rozanov, V. V.; Burrows, J. P.

2014-12-01

297

A band-to-band Coulomb interaction model for refractive index spectra of ternary semiconductors  

NASA Astrophysics Data System (ADS)

A band-to-band Coulomb interaction model for the refractive index spectra is presented of AlxGa1-xAs for 0band gap. An accurate absorption model is used to calculate the contribution on the refractive index near band-edge region through a complete closed-form Kramers-Kronig transform. In addition, a Sellmeier-type single-oscillator representation provides all the additional absorption at higher energies due to nonparabolicity and higher-energy bands. The refractive index spectra are extended beyond the band-gap energy and are in excellent agreement with the available experimental data. The refractive index spectra of ternary compounds are fully parametrized by interpolation of the fitting parameters. The results will be important for the detailed design of photonic devices, such as electroabsorption modulators and semiconductor optical amplifiers.

Lin, E. Y.; Lay, T. S.

2009-01-01

298

Temperature dependence of amino acid side chain IR absorptions in the amide I' region.  

PubMed

Amide I' IR spectra are widely used for studies of structural changes in peptides and proteins as a function of temperature. Temperature dependent absorptions of amino acid side-chains that overlap the amide I' may significantly complicate the structural analyses. While the side-chain IR spectra have been investigated previously, thus far their dependence on temperature has not been reported. Here we present the study of the changes in the IR spectra with temperature for side-chain groups of aspartate, glutamate, asparagine, glutamine, arginine, and tyrosine in the amide I' region (in D2 O). Band fitting analysis was employed to extract the temperature dependence of the individual spectral parameters, such as peak frequency, integrated intensity, band width, and shape. As expected, the side-chain IR bands exhibit significant changes with temperature. The majority of the spectral parameters, particularly the frequency and intensity, show linear dependence on temperature, but the direction and magnitude vary depending on the particular side-chain group. The exception is arginine, which exhibits a distinctly nonlinear frequency shift with temperature for its asymmetric CN3 H5 (+) bending signal, although a linear fit can account for this change to within ~1/3 cm(-1) . The applicability of the determined spectral parameters for estimations of temperature-dependent side-chain absorptions in peptides and proteins are discussed. © 2013 Wiley Periodicals, Inc. Biopolymers 101: 536-548, 2014. PMID:24122549

Anderson, Benjamin A; Literati, Alex; Ball, Borden; Kubelka, Jan

2014-05-01

299

Temperature and multi-species measurements by supercontinuum absorption spectroscopy for IC engine applications.  

PubMed

The first supercontinuum (SC) absorption spectroscopy measurements showing the feasibility of quantitative temperature evaluation are presented to the best of the authors' knowledge. Temperature and multi-species measurements were carried out at a detection rate of ~2 MHz in a high-temperature flow cell within a temperature range from 450 K to 750 K at 0.22 MPa, representing conditions during the suction and compression stroke in an internal combustion (IC) engine. The broadband SC pulses were temporally dispersed into fast wavelength sweeps, covering the overtone absorption bands 2?(1), 2?(3), ?(1) + ?(3) of H2O and 3?(3) of CO2 in the near-infrared region from 1330 nm to 1500 nm. The temperature information is inferred from the peak ratio of a temperature sensitive (1362.42 nm) and insensitive (1418.91 nm) absorption feature in the ?(1) + ?(3) overtone bands of water. The experimental results are in very good agreement with theoretical intensity ratios calculated from absorption spectra based on HiTran data. PMID:23736618

Werblinski, Thomas; Engel, Sascha R; Engelbrecht, Rainer; Zigan, Lars; Will, Stefan

2013-06-01

300

Optical Absorption, Stability and Structure of NpO2+ Complexeswith Dicarboxylic Acids  

SciTech Connect

Complexation of NpO2+ with oxalic acid (OX),2,2'-oxydiacetic acid (ODA), 2,2'-iminodiacetic acid (IDA) and 2,2'-thiodiacetic acid (TDA), has been studied using spectrophotometry in1 M NaClO4. Both the position and the intensity of the absorption band of NpO2+ at 980 nm are affected by the formation of NpO2+/dicarboxylate complexes, providing useful information on the complexation strength, the coordination mode and the structure of the complexes.

Guoxin Tian; Linfeng Rao

2006-01-04

301

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

302

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 Å) region at an average resolution of 1.2 Å 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

303

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

304

EPR and optical absorption studies of VO 2+ doped L-alanine (C 3H 7NO 2) single crystals  

NASA Astrophysics Data System (ADS)

VO 2+ doped L-alanine (C 3H 7NO 2) single crystals and powders are examined by electron paramagnetic resonance (EPR) and optical absorption spectroscopy. Three magnetically different sites are resolved from angular variations of L-alanine single crystal EPR spectra. In some specific orientations each VO 2+ line splits into three superhyperfine lines with intensities of 1:2:1 and maximum splitting value of 2.23 mT. The local symmetries of VO 2+ complex sites are nearly axial. The optical absorption spectra show three bands. Spin Hamiltonian parameters are measured and molecular orbital coefficients are calculated by correlating EPR and optical absorption data for the central vanadyl ion.

B?y?k, Recep

2009-11-01

305

Q-band splitting and relaxation of aluminum phthalocyanine tetrasulfonate  

NASA Astrophysics Data System (ADS)

The doublet band structure evident in the fluorescence excitation and absorption spectra of aluminum phthalocyanine tetrasulfonate in various hyperquenched glassy solvents is attributed to splitting of the Q-band transition into x and y components. The splitting is caused by the ligation of water molecules to the aluminum atom which decreases the molecular symmetry. Picosecond relaxation from the Q y band to the Q x band is evident in the hole burned spectra.

Reinot, T.; Hayes, J. M.; Small, G. J.; Zerner, M. C.

1999-01-01

306

Propionaldehyde infrared cross-sections and band strengths  

NASA Astrophysics Data System (ADS)

The use of oxygenated biofuels reduces the greenhouse gas emissions; however, they also result in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propionaldehyde. These aldehydes are carcinogenic and/or toxic and therefore it is important to understand their formation and destruction pathways in combustion and atmospheric systems. Accurate information about their infrared cross-sections and integrated strengths are crucially needed for development of quantitative detection schemes and modeling tools. Critical to the development of such diagnostics are accurate characterization of the absorption features of these species. In this study, the gas phase infrared spectra of propionaldehyde (also called propanal, CH3-CH2-CHO), a saturated three carbon aldehyde found in the exhaust emissions of biodiesel or diesel fuels, was studied using high resolution Fourier Transform Infrared (FTIR) spectroscopy over the wavenumber range of 750-3300 cm-1 and at room temperature 295 K. The absorption cross sections of propionaldehyde were recorded at resolutions of 0.08 and 0.096 cm-1 and at seven different pressures (4-33 Torr). The calculated band-strengths were reported and the integrated band intensity results were compared with values taken from the Pacific Northwest National Laboratory (PNNL) database (showing less than 2% discrepancy). The peak positions of the 19 different vibrational bands of propionaldehyde were also compared with previous studies taken at a lower resolution of 1 cm-1. To the best of our knowledge, the current FTIR measurements provide the first highest resolution infrared cross section data for propionaldehyde.

Köro?lu, Batikan; Loparo, Zachary; Nath, Janardan; Peale, Robert E.; Vasu, Subith S.

2015-02-01

307

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'Éclairage). (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 = ƒ(t°C) 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.; ChayéD'Albissin, M.; Gouet, G.; Visocekas, R.

1982-11-01

308

Quantum numbers and band topology of nanotubes  

NASA Astrophysics Data System (ADS)

Nanotubes as well as polymers and quasi-1D subsystems of 3D crystals have line group symmetry. This allows two types of quantum numbers: roto-translational and helical. The roto-translational quantum numbers are linear and total angular (not conserved) momenta, while the helical quantum numbers are helical and complementary angular momenta. Their mutual relations determine some topological properties of energy bands, such as systematic band sticking or van Hove singularities related to parities. The importance of these conclusions is illustrated by the optical absorption in carbon nanotubes: parity may prevent absorption peaks at van Hove singularities.

Damnjanovic, M.; Milosevic, I.; Vukovic, T.; Maultzsch, J.

2003-05-01

309

Improvement of two-photon absorption lithography  

Microsoft Academic Search

Recently, a novel Resolution Enhancement Technology (RET) have been proposed to overcome the Rayleigh resolution limit by using both entangled photon pair and two-photon absorption resist. However, the illumination intensity is not enough to attain the reasonable throughput. We propose a new method which enables to enhance the resolution over the Rayleigh limit with more strong intensity source by using

Masato Shibuya; Hiromi Ezaki

2002-01-01

310

Laser isotope separation by multiple photon absorption  

DOEpatents

Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, is the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO[sub 2] laser light may be used to highly enrich [sup 34]S in natural SF[sub 6] and [sup 11]B in natural BCl[sub 3]. 8 figs.

Robinson, C.P.; Rockwood, S.D.; Jensen, R.J.; Lyman, J.L.; Aldridge, J.P. III.

1987-04-07

311

Laser isotope separation by multiple photon absorption  

DOEpatents

Multiple photon absorption from an intense beam of infrared laser light may be used to induce selective chemical reactions in molecular species which result in isotope separation or enrichment. The molecular species must have a sufficient density of vibrational states in its vibrational manifold that, is the presence of sufficiently intense infrared laser light tuned to selectively excite only those molecules containing a particular isotope, multiple photon absorption can occur. By this technique, for example, intense CO.sub.2 laser light may be used to highly enrich .sup.34 S in natural SF.sub.6 and .sup.11 B in natural BCl.sub.3.

Robinson, C. Paul (Los Alamos, NM); Rockwood, Stephen D. (Los Alamos, NM); Jensen, Reed J. (Los Alamos, NM); Lyman, John L. (Los Alamos, NM); Aldridge, III, Jack P. (Los Alamos, NM)

1987-01-01

312

Interpretation of the Minkowski bands in Grw + 70 deg 8247.  

NASA Technical Reports Server (NTRS)

Demonstration on the basis of the spectral structure of circular polarization in Grw + 70 deg 8247, that the absorption bands are at least in part molecular in origin. The spectrum of molecular helium has strong bands coincident with several of the Minkowski bands and, in particular, at high temperature shows a strong band head at about 4125 A. Helium molecules could be formed in sufficient density to give the absorption features in the star if it has a pure helium atmosphere. The Zeeman effect in molecular helium can explain in general the observed spectral features in the polarization and also may be responsible for the continuum polarization.

Angel, J. R. P.

1972-01-01

313

Resonance Absorption of Microwaves by the Human Skull  

Microsoft Academic Search

Resonance absorption of microwaves by the human skull is examined by making computerized calculations of theoretical models of the skull. The calculated relative absorption versus frequency is plotted and compared for homogeneous and inhomogeneous skull models. At a frequency of maximum power absorption, the spatial distribution of intracranial field intensity (based upon the theoretical model) is also calculated and plotted.

William T. Joines; Ronald J. Spiegel

1974-01-01

314

Quasi-Fermi level splitting and sub-bandgap absorptivity from semiconductor photoluminescence  

NASA Astrophysics Data System (ADS)

A unified model for the direct gap absorption coefficient (band-edge and sub-bandgap) is developed that encompasses the functional forms of the Urbach, Thomas-Fermi, screened Thomas-Fermi, and Franz-Keldysh models of sub-bandgap absorption as specific cases. We combine this model of absorption with an occupation-corrected non-equilibrium Planck law for the spontaneous emission of photons to yield a model of photoluminescence (PL) with broad applicability to band-band photoluminescence from intrinsic, heavily doped, and strongly compensated semiconductors. The utility of the model is that it is amenable to full-spectrum fitting of absolute intensity PL data and yields: (1) the quasi-Fermi level splitting, (2) the local lattice temperature, (3) the direct bandgap, (4) the functional form of the sub-bandgap absorption, and (5) the energy broadening parameter (Urbach energy, magnitude of potential fluctuations, etc.). The accuracy of the model is demonstrated by fitting the room temperature PL spectrum of GaAs. It is then applied to Cu(In,Ga)(S,Se)2 (CIGSSe) and Cu2ZnSn(S,Se)4 (CZTSSe) to reveal the nature of their tail states. For GaAs, the model fit is excellent, and fitted parameters match literature values for the bandgap (1.42 eV), functional form of the sub-bandgap states (purely Urbach in nature), and energy broadening parameter (Urbach energy of 9.4 meV). For CIGSSe and CZTSSe, the model fits yield quasi-Fermi leveling splittings that match well with the open circuit voltages measured on devices made from the same materials and bandgaps that match well with those extracted from EQE measurements on the devices. The power of the exponential decay of the absorption coefficient into the bandgap is found to be in the range of 1.2 to 1.6, suggesting that tunneling in the presence of local electrostatic potential fluctuations is a dominant factor contributing to the sub-bandgap absorption by either purely electrostatic (screened Thomas-Fermi) or a photon-assisted tunneling mechanism (Franz-Keldysh). A Gaussian distribution of bandgaps (local Eg fluctuation) is found to be inconsistent with the data. The sub-bandgap absorption of the CZTSSe absorber is found to be larger than that for CIGSSe for materials that yield roughly equivalent photovoltaic devices (8% efficient). Further, it is shown that fitting only portions of the PL spectrum (e.g., low energy for energy broadening parameter and high energy for quasi-Fermi level splitting) may lead to significant errors for materials with substantial sub-bandgap absorption and emission.

Katahara, John K.; Hillhouse, Hugh W.

2014-11-01

315

Band gap effects of hexagonal boron nitride using oxygen plasma  

SciTech Connect

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; Leong Chow, Wai [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Yingjie Tay, Roland [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Hon Tsang, Siu [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Mallick, Govind [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); Tong Teo, Edwin Hang, E-mail: htteo@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

2014-04-21

316

A model for the spectral dependence of optically induced absorption in amorphous silicon  

NASA Technical Reports Server (NTRS)

A model based on transitions from localized band tail states to states above the mobility edge is used to explain the broad band induced absorptions observed in recent pump-probe experiments. The model gives the observed decrease of absorption with frequency at subband gap photo energies and high carrier densities (of about 10 to the 20th/cu cm). At lower carrier densities, the absorption has a maximun which is sensitive to the spatial extent of the band tail states.

Lawandy, N. M.

1990-01-01

317

The application of differential optical absorption spectroscopy (DOAS) from space  

NASA Astrophysics Data System (ADS)

Trace gas measurements by absorptions spectroscopy make use of the attenuation of radiation by molecules. The central idea of Differential Optical Absorption Spectroscopy (DOAS) is to analyse strongly structured (fingerprint) absorptions of visible, UV, or near IR radiation by atmospheric trace gases. In contrast to traditional spectroscopic methods relying on measuring the attenuation of the radiation intensity at a few, selected wavelengths (typically pairs of `on line' and `off line' wavelengths) only, DOAS typically uses intensity measurements at hundreds or even thousands of wavelengths. The strength of DOAS lies in the excellent specificity, inherent calibration, the potential for real time measurements, and its remote sensing capabilities. Since its introduction in the late 1970's by Platt and Perner significant advances have been made in the DOAS technique, including the development of reliable evaluation techniques based and new methods allowing a realistic estimate of the resulting errors, also techniques to compensate for instrumental effects, like residual spectra, were developed. Most importantly the range of application of DOAS was greatly enhanced to include observations using scattered sunlight, multi axis observ ation (MAX-DOAS), vertical trace gas -concentration profiles, and measurements from satellites (e.g. the GOME, SCIAMACHY, GOME-2, and OMI instruments). At the same time the palette of species measurable by DOAS was expanded from the original SO2, NO2, CH2O, and O3 to include many free radicals (e.g. OH, NO3, IO, OIO, BrO, ClO, OClO), nitrous acid (HONO), and a large set of aromatic compounds (e.g. benzene, toluene, xylenes, phenols, benzaldehyde). In addition it is now possible to determine the photon path-length distribution in clouds by ground based observation of O2 and O4 bands. Here the new approaches, specific requirements and sample applications for space- borne DOAS instruments are described. Recent advances and directions of future development are dis c u s s e d .

Platt, U.

318

Titanium-silicon oxide film structures for polarization-modulated infrared reflection absorption spectroscopy  

PubMed Central

We present a titanium-silicon oxide film structure that permits polarization modulated infrared reflection absorption spectroscopy on silicon oxide surfaces. The structure consists of a ~6 nm sputtered silicon oxide film on a ~200 nm sputtered titanium film. Characterization using conventional and scanning transmission electron microscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and X-ray reflectometry is presented. We demonstrate the use of this structure to investigate a selectively protein-resistant self-assembled monolayer (SAM) consisting of silane-anchored, biotin-terminated poly(ethylene glycol) (PEG). PEG-associated IR bands were observed. Measurements of protein-characteristic band intensities showed that this SAM adsorbed streptavidin whereas it repelled bovine serum albumin, as had been expected from its structure. PMID:20418963

Dunlop, Iain E.; Zorn, Stefan; Richter, Gunther; Srot, Vesna; Kelsch, Marion; van Aken, Peter A.; Skoda, Maximilian; Gerlach, Alexander; Spatz, Joachim P.; Schreiber, Frank

2010-01-01

319

Ultrafast band-gap oscillations in iron pyrite  

E-print Network

With its combination of favorable band gap, high absorption coefficient, material abundance, and low cost, iron pyrite, FeS[subscript 2], has received a great deal of attention over the past decades as a promising material ...

Kolb, Brian

320

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

PubMed

The effect of crystal growth conditions on the O K-edge x-ray absorption spectra of ice is investigated through detailed analysis of the spectral features. The amount of ice defects is found to be minimized on hydrophobic surfaces, such as BaF2(111), with low concentration of nucleation centers. This is manifested through a reduction of the absorption cross-section at 535 eV, which is associated with distorted hydrogen bonds. Furthermore, a connection is made between the observed increase in spectral intensity between 544 and 548 eV and high-symmetry points in the electronic band structure, suggesting a more extended hydrogen-bond network as compared to ices prepared differently. The spectral differences for various ice preparations are compared to the temperature dependence of spectra of liquid water upon supercooling. A double-peak feature in the absorption cross-section between 540 and 543 eV is identified as a characteristic of the crystalline phase. The connection to the interpretation of the liquid phase O K-edge x-ray absorption spectrum is extensively discussed. PMID:25053326

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

2014-07-21

321

Attosecond band-gap dynamics in silicon  

NASA Astrophysics Data System (ADS)

Electron transfer from valence to conduction band states in semiconductors is the basis of modern electronics. Here, attosecond extreme ultraviolet (XUV) spectroscopy is used to resolve this process in silicon in real time. Electrons injected into the conduction band by few-cycle laser pulses alter the silicon XUV absorption spectrum in sharp steps synchronized with the laser electric field oscillations. The observed ~450-attosecond step rise time provides an upper limit for the carrier-induced band-gap reduction and the electron-electron scattering time in the conduction band. This electronic response is separated from the subsequent band-gap modifications due to lattice motion, which occurs on a time scale of 60 ± 10 femtoseconds, characteristic of the fastest optical phonon. Quantum dynamical simulations interpret the carrier injection step as light-field–induced electron tunneling.

Schultze, Martin; Ramasesha, Krupa; Pemmaraju, C. D.; Sato, S. A.; Whitmore, D.; Gandman, A.; Prell, James S.; Borja, L. J.; Prendergast, D.; Yabana, K.; Neumark, Daniel M.; Leone, Stephen R.

2014-12-01

322

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

323

Amniotic constriction bands  

MedlinePLUS

Pseudo-ainhum; Streeter's dysplasia; Amniotic band sequence; Amniotic band syndrome ... Amniotic constriction bands are caused by damage to a part of the placenta called the amnion. The placenta carries ...

324

Photoluminescence of charged CdSe/ZnS quantum dots in the gas phase: effects of charge and heating on absorption and emission probabilities.  

PubMed

Gas phase spectral measurements for CdSe/ZnS core/shell nanocrystal quantum dots (QDs) before and after heating with both infrared (CO2) and visible lasers are reported. As-trapped QDs are spectrally similar to the same QDs in solution; however their photoluminescence (PL) intensities are very low, at least partly due to low absorption cross sections. After heating, the PL intensities brighten by factors ranging from ?4 to 1800 depending on the QD size and pump laser wavelength. The emission spectra no longer resemble solution spectra and are similar, regardless of the QD diameter. Emission extends from the pump laser wavelength into the near-IR, with strong emission features above the band gap energy, between 645 and 775 nm, and in the near-infrared. Emission spectra from brightened QD ensembles, single QD aggregates, and single QD monomers are similar, showing that even single QDs support PL from a wide variety of states. The heating and cooling processes for QDs in this environment are analyzed, providing limits on the magnitudes of the absorption cross sections before and after thermal brightening. A model, based on absorption bleaching by extra electrons in the conduction band, appears to account for the changes in absorption and emission behavior induced by charging and heating. PMID:25427008

Howder, Collin R; Long, Bryan A; Bell, David M; Furakawa, Kevin H; Johnson, Ryan C; Fang, Zhiyuan; Anderson, Scott L

2014-12-23

325

Self-broadening of 16O12C16O ?3-band lines  

NASA Astrophysics Data System (ADS)

Absorption spectra of pure 16O12C16O have been recorded, at room temperature and for five pressures between 0.2 and 1 atm, in the very intense ?3 band. As recently done for CO, this was achieved using a high resolution (0.005 cm-1) Fourier transform spectrometer together with a specially designed cell. With the latter, set to a path length of about 20 ?m, the absorption by extremely intense lines is measured under appropriate (non saturating transmission) absorption conditions, regardless of the gas pressure. The recorded spectra have been adjusted one-by-one using Voigt line-shapes in order to retrieve the line positions and the Lorentz widths for the P(40) to R(40) lines. The results show that accurate self-broadening coefficients ? are obtained but that experimental uncertainties forbid any reliable determinations of the pressure-induced shifts ? due to the fact that they are about two order of magnitude smaller than ?. The present values of ? show the limited accuracy of previous determinations for the exact same lines. They are in very good agreement with those in the HITRAN database if the latter, which are for a speed-dependent Voigt profile, are properly corrected to correspond to a Voigt profile.

Ngo, N. H.; Landsheere, X.; Pangui, E.; Morales, S. B.; Hartmann, J.-M.

2014-12-01

326

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

SciTech Connect

A generalized theory is developed to study inter-band optical absorption coefficient (IOAC) and material gain (MG) in quantum dot structures of narrow gap III-V compound semiconductor considering the wave-vector (k{sup ?}) dependence of the optical transition matrix element. The band structures of these low band gap semiconducting materials with sufficiently separated split-off valance band are frequently described by the three energy band model of Kane. This has been adopted for analysis of the IOAC and MG taking InAs, InSb, Hg{sub 1?x}Cd{sub x}Te, and In{sub 1?x}Ga{sub x}As{sub y}P{sub 1?y} lattice matched to InP, as example of III–V compound semiconductors, having varied split-off energy band compared to their bulk band gap energy. It has been found that magnitude of the IOAC for quantum dots increases with increasing incident photon energy and the lines of absorption are more closely spaced in the three band model of Kane than those with parabolic energy band approximations reflecting the direct the influence of energy band parameters. The results show a significant deviation to the MG spectrum of narrow-gap materials having band nonparabolicity compared to the parabolic band model approximations. The results reflect the important role of valence band split-off energies in these narrow gap semiconductors.

Dey, Anup, E-mail: a-dey2002@yahoo.com [Electronics and Communication Engineering Department, Kalyani Government Engineering College, Kalyani 741235 (India); Maiti, Biswajit [Physics Department, Kalyani Government Engineering College, Kalyani 741235 (India); Chanda, Debasree [Department of Engineering and Technological Studies, Kalyani University, Kalyani 741235 (India)

2014-04-14

327

Converting Sabine absorption coefficients to random incidence absorption coefficients.  

PubMed

Absorption coefficients measured by the chamber method are referred to as Sabine absorption coefficients, which sometimes exceed unity due to the finite size of a sample and non-uniform intensity in the reverberation chambers under test. In this study, conversion methods from Sabine absorption coefficients to random incidence absorption coefficients are proposed. The overestimations of the Sabine absorption coefficient are investigated theoretically based on Miki's model for porous absorbers backed by a rigid wall or an air cavity, resulting in conversion factors. Additionally, three optimizations are suggested: An optimization method for the surface impedances for locally reacting absorbers, the flow resistivity for extendedly reacting absorbers, and the flow resistance for fabrics. With four porous type absorbers, the conversion methods are validated. For absorbers backed by a rigid wall, the surface impedance optimization produces the best results, while the flow resistivity optimization also yields reasonable results. The flow resistivity and flow resistance optimization for extendedly reacting absorbers are also found to be successful. However, the theoretical conversion factors based on Miki's model do not guarantee reliable estimations, particularly at frequencies below 250 Hz and beyond 2500?Hz. PMID:23742349

Jeong, Cheol-Ho

2013-06-01

328

Analysis of the visible absorption spectrum of I2 in inert solvents using a physical model.  

PubMed

Absorption spectra of I(2) dissolved in n-heptane and CCl(4) are analyzed with a quantum gas-phase model, in which spectra at four temperatures between 15° and 50 °C are least-squares fitted by bound-free spectral simulations to obtain estimates of the excited-state potential energy curves and transition moment functions for the three component bands--A ? X, B ? X, and C ? X. Compared with a phenomenological band-fitting model used previously on these spectra, the physical model (1) is better statistically, and (2) yields component bands with less variability. The results support the earlier tentative conclusion that most of the ~20% gain in intensity in solution is attributable to the C ? X transition. The T-dependent changes in the spectrum are accounted for by potential energy shifts that are linear in T and negative (giving red shifts in the spectra) and about twice as large for CCl(4) as for heptane. The derived upper potentials resemble those in the gas phase, with one major exception: In the statistically best convergence mode, the A potential is much lower and steeper, with a strongly varying transition moment function. This observation leads to the realization that two markedly different potential curves can give nearly identical absorption spectra. PMID:22128887

Tellinghuisen, Joel

2012-01-12

329

Heteroleptic cationic iridium(iii) complexes bearing naphthalimidyl substituents: synthesis, photophysics and reverse saturable absorption.  

PubMed

Three heteroleptic cationic iridium(iii) complexes containing a cyclometalating 2-[3-(7-naphthalimidylfluoren-2'-yl)phenyl]pyridine ligand and different diimine (N^N) ligands (N^N = 2,2'-bipyridine (bpy, ), 1,10-phenanthroline (phen, ), and 5,5'-bis[7-(benzothiazol-2'-yl)fluoren-2'-yl]-2,2'-bipyridine (BTF-bpy, )) were synthesized and characterized. The photophysics of these complexes was systematically investigated via spectroscopic methods and by time-dependent density functional theory (TDDFT). All complexes possess a very weak charge-transfer tail at ca. 450-570 nm; and two intense absorption bands in the region of 290-350 nm and 350-450 nm, respectively. The emission of in CH2Cl2 emanates predominantly from the C^N ligand-localized (3)?,?* state. These emitting excited states also give rise to broadband triplet excited-state absorption in the visible to the near-IR region (i.e. 420-800 nm for and , and 460-800 nm for ). The kinetics of fs transient absorption (TA) reveals that the lowest singlet excited-state lifetimes of these complexes vary from 1.43 ps to 142 ps. The stronger excited-state absorption of compared to their respective ground-state absorption in the visible spectral range leads to strong reverse saturable absorption (RSA) at 532 nm for ns laser pulses. The trend of transmission signal decrease follows > > . Extending the ?-conjugation of the N^N ligand increases the strength of RSA. In addition, the naphthalimidyl (NI) substitution at the cyclometalating ligand dramatically increases the triplet excited-state lifetimes and broadens the triplet excited-state absorption to the NIR region compared to the respective Ir(iii) complexes with a benzothiazolyl substituent on the cyclometalating ligand. PMID:25512315

Pei, Chengkui; Cui, Peng; McCleese, Christopher; Kilina, Svetlana; Burda, Clemens; Sun, Wenfang

2015-01-20

330

Ice absorption toward background stars  

NASA Astrophysics Data System (ADS)

We present results of ice absorption between 5-20 ?m toward background stars as part of the Cores to Disks (c2d) Legacy program (Evans et al. 2003). Molecules such as H2O, CO2, HCOOH, NH3, CH3OH, and NH4+ have bands in this wavelength region. Absorption from H2O bands at 6 and 13 ?m is observed toward all sources. We detect strong CO2 absorption toward CK 2, a background star with high extinction in the Serpens dark cloud. The abundance of CO2 with respect to H2O is 30-40%, similar to what is observed toward protostars. Also, at 6.8 ?m, CK 2 shows a feature which may be due to NH4+ . Other sources with lower extinction, such as Elias 13 and Elias 16 in the Taurus dark cloud, do not show this feature. By probing different lines of sight, we can learn how ice composition varies with extinction. The abundances found toward background stars are then compared to abundances observed toward protosatars.

Knez, Claudia; Boogert, A. C. Adwin; Pontoppidan, Klaus M.; Kessler-Silacci, Jacqueline; Evans, Neal J., II; Augereau, Jean-Charles; van Dishoeck, Ewine F.; Blake, Geoffrey A.; Brown, Joanna; Geers, Vincent; Jørgensen, Jes K.; Lahuis, Fred

331

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

332

Band gap narrowing in BaTiO{sub 3} nanoparticles facilitated by multiple mechanisms  

SciTech Connect

In the present work, BaTiO{sub 3} 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{sup ?1}. The higher surface charge density is expected in case of enhanced surface optical Raman modes (638?cm{sup ?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{sup ?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. [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046 (India); James Raju, K. C., E-mail: kcjrsp@uohyd.ernet.in [Advanced Centre of Research in High Energy Materials (ACRHEM), University of Hyderabad, Hyderabad 500046 (India); School of Physics, University of Hyderabad, Hyderabad 500046 (India)

2014-05-07

333

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

334

Photodegradation of polycarbonate under narrow band irradiation at 172 nm  

NASA Astrophysics Data System (ADS)

Photostability of polymers is an important issue since most polymers tend to loose their original properties upon exposure to light, especially to ultraviolet radiation. Polycarbonates are widely used industrial materials because of their excellent properties, which includes transparency, high tensile strength, impact resistance and rigidity. In this paper, we present results on 172 nm photodegradation of polycarbonate (PC) films. PC films of 50 ?m thickness were irradiated for up to 20 min using a Xe2? excimer lamp system. Ex situ UV visible spectroscopic investigation of the treated films revealed the appearance of two strong absorption bands at 279 and 317 nm and a third broad band centred around 380 nm whose intensity increased linearly with illumination time. The morphological changes were characterised by atomic force microscopy and resulted in a gradually increasing roughness, being a linear function of irradiation time. The interpretation of the observed chemical degradation is based on attenuated total reflection IR and X-ray photoelectron spectroscopic measurements which show cleavage of the aromatic C-C and carboxylic CO-O bonds together with some nitrogen incorporation into the surface layer of the irradiated films.

Geretovszky, Zs.; Hopp, B.; Bertóti, I.; Boyd, I. W.

2002-01-01

335

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

336

Excitons and fundamental absorption in quantum wells  

Microsoft Academic Search

We present an accurate theory for the excitonic absorption in quantum-well structures which yields very good agreement with a wide range of experimental data. Our approach is based on an expansion of the exciton wave function in terms of multicomponent envelope functions of electron and hole states. It is rather general with respect to band-structure effects and potential profiles. In

R. Winkler

1995-01-01

337

Band gap engineering of TiO2 through hydrogenation  

NASA Astrophysics Data System (ADS)

The band gap of rutile TiO2 is reduced remarkably through high-temperature annealing in hydrogen atmosphere, and the absorption of visible light of the hydrogenated-TiO2 can be enhanced. These modifications of hydrogenated-TiO2 become more evident with the increase in annealing hydrogen pressure. A defect band arises near the valence band upon hydrogenation while the conduction band remains almost unchanged, which helps for meeting the requirements for hydrogen production through water splitting. This method could be also indicative for the band gap adjustment of other oxide semiconductors.

Mo, Li-Bin; Bai, Yang; Xiang, Qing-Yun; Li, Qun; Wang, Jia-Ou; Ibrahim, Kurash; Cao, Jiang-Li

2014-11-01

338

Q Band Chromosomal Polymorphisms in Lake Trout (SALVELINUS NAMAYCUSH)  

PubMed Central

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. Since all of the fish examined had consistent heteromorphisms at several of the quinacrine bright bands, these chromosome markers should be useful in genetic comparisons between different trout stocks and populations. PMID:7173603

Phillips, Ruth B.; Zajicek, Kerry D.

1982-01-01

339

Infrared radiation parameterizations for the minor CO[sub 2] bands and for several CFC bands in the window region  

SciTech Connect

Fast and accurate parameterizations have been developed for the transmission functions of the CO[sub 2] 9.4- and 10.4-[mu]m bands, as well as the CFC-11, CFC-12, and CFC-22 bands located in the 8-12[mu]m region. The parameterizations are based on line-by-line calculations of transmission functions for the CO[sub 2] bands on high spectral resolution laboratory measurements of the absorption coefficients for the CFC bands. Also developed are the parameterizations for the H[sub 2]O transmission functions for the corresponding spectral bands. Compared to the high-resolution calculations, fluxes at the tropopause computed with the parameterizations are accurate to within 10% when overlapping of gas absorptions within a band is taken into account. For individual gas absorption, the accuracy is of order 0%-2%. The climate effects of these trace gases have been studied using a zonally averaged multilayer energy balance model, which includes seasonal cycles and a simplified deep ocean. With the trace gas abundances taken to follow the Intergovernmental Panel on Climate Change Low Emissions [open quotes]B[close quotes] scenario, the transient response of the surface temperature is simulated for the period 1900-2060. The minor CO[sub 2] and CFC bands contribute about 20%-25% of the total warming at the surface, which is comparable to the contribution from the CH[sub 4] and N[sub 2] bands. Collectively these minor absorption band account for 40%-45% of the total surface temperature increases. Thus, the climate warming due to absorption in these bands is comparable to that in the 15 [mu]m CO[sub 2] band. 41 refs., 2 figs., 11 tabs.

Kratz, D.P. (Lockheed Engineering and Sciences Company, Hampton, VA (United States)); Chou, M.D. (NASA/Goddard Space Flight Center, Greenbelt, MD (United States)); Yan, M.M.H. (Science Systems Applications, Inc., Lanham, MD (United States))

1993-07-01

340

Infrared absorption properties of KTN single crystals  

Microsoft Academic Search

We report the results of a Fourier transform infrared absorption study of two samples of KTa1?x NbxO3 as a function of temperature from 350 to 7 K and for x-value of 0.187 and 0.344. A group of absorption peaks in the vicinity of 3500 cm which display an intensity reversal with decreasing temperature for x = 0.344 and no reversal

B. C. Covington; Zhongji Zou; R. K. Pandey; K. W. Goeking

1989-01-01

341

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, Bärbel

2012-12-01

342

Intensity studies  

SciTech Connect

The May 2 earthquake was felt over an area of 205,000 km{sup 2} and generated a maximum modified Mercalli intensity (MMI) of VIII in the city of Coalinga (approx 12 km southwest of the epicenter) and at Pacific Gas and Electric Substation 2 (1 km southwest of the epicenter). The main shock also generated an MMI of VII at Avenal (30 km southeast of the epicenter). Field investigation of the damage showed that 75% of the old (pre-1945) unreinforced-brick structures in the central business district of Coalinga were severely damaged, whereas newer masonry buildings in the same area sustained no damage or only nonstructural damage. About 15% of the single-family dwellings in Coalinga were thrown off their foundations, and more than half of the chimneys were damaged. An MMI of VIII was assigned to the main shock because of the toppling of many chimneys, the partial collapse of old, unreinforced-masonry buildings, and the absence of serious damage to substantial masonry structures. Coalinga underwent many strong aftershocks through August 1983. A strong aftershock on July 25 caused extensive damage, primarily to structures that had been weakened by effects of the main shock.

Highland, L.M.; Stover, C.W.; Hopper, M.G.; Thenhaus, P.C.; Algermissen, S.T.

1990-01-01

343

The band structure of WO3 and non-rigid-band behaviour in Na0.67WO3 derived from soft x-ray spectroscopy and density functional theory.  

PubMed

The electronic structure of single-crystal WO3 and Na0.67WO3 (a sodium-tungsten bronze) has been measured using soft x-ray absorption and resonant soft x-ray emission oxygen K-edge spectroscopies. The spectral features show clear differences in energy and intensity between WO3 and Na0.67WO3. The x-ray emission spectrum of metallic Na0.67WO3 terminates in a distinct Fermi edge. The rigid-band model fails to explain the electronic structure of Na0.67WO3 in terms of a simple addition of electrons to the conduction band of WO3. Instead, Na bonding and Na 3s-O 2p hybridization need to be considered for the sodium-tungsten bronze, along with occupation of the bottom of the conduction band. Furthermore, the anisotropy in the band structure of monoclinic ?-WO3 revealed by the experimental spectra with orbital-resolved geometry is explained via density functional theory calculations. For ?-WO3 itself, good agreement is found between the experimental O K-edge spectra and the theoretical partial density of states of O 2p orbitals. Indirect and direct bandgaps of insulating WO3 are determined from extrapolating separations between spectral leading edges and accounting for the core-hole energy shift in the absorption process. The O 2p non-bonding states show upward band dispersion as a function of incident photon energy for both compounds, which is explained using the calculated band structure and experimental geometry. PMID:23553445

Chen, B; Laverock, J; Piper, L F J; Preston, A R H; Cho, S W; DeMasi, A; Smith, K E; Scanlon, D O; Watson, G W; Egdell, R G; Glans, P-A; Guo, J-H

2013-04-24

344

The band structure of WO3 and non-rigid-band behaviour in Na0.67WO3 derived from soft x-ray spectroscopy and density functional theory  

NASA Astrophysics Data System (ADS)

The electronic structure of single-crystal WO3 and Na0.67WO3 (a sodium-tungsten bronze) has been measured using soft x-ray absorption and resonant soft x-ray emission oxygen K-edge spectroscopies. The spectral features show clear differences in energy and intensity between WO3 and Na0.67WO3. The x-ray emission spectrum of metallic Na0.67WO3 terminates in a distinct Fermi edge. The rigid-band model fails to explain the electronic structure of Na0.67WO3 in terms of a simple addition of electrons to the conduction band of WO3. Instead, Na bonding and Na 3s-O 2p hybridization need to be considered for the sodium-tungsten bronze, along with occupation of the bottom of the conduction band. Furthermore, the anisotropy in the band structure of monoclinic ?-WO3 revealed by the experimental spectra with orbital-resolved geometry is explained via density functional theory calculations. For ?-WO3 itself, good agreement is found between the experimental O K-edge spectra and the theoretical partial density of states of O 2p orbitals. Indirect and direct bandgaps of insulating WO3 are determined from extrapolating separations between spectral leading edges and accounting for the core-hole energy shift in the absorption process. The O 2p non-bonding states show upward band dispersion as a function of incident photon energy for both compounds, which is explained using the calculated band structure and experimental geometry.

Chen, B.; Laverock, J.; Piper, L. F. J.; Preston, A. R. H.; Cho, S. W.; DeMasi, A.; Smith, K. E.; Scanlon, D. O.; Watson, G. W.; Egdell, R. G.; Glans, P.-A.; Guo, J.-H.

2013-04-01

345

Femtosecond optical absorption in poly(3-alkyl thienylene)s  

NASA Astrophysics Data System (ADS)

We report transient absorption measurements on poly(3-hexyl thienylene) and poly(3-dodecyl thienylene). In both materials we observe a transient absorption followed by a transient bleaching, and oscillations with a period of 120 fs. We propose that the oscillatory features are due to coupling between vibrational modes of the polymer chains and the ?-electronic structure, and that the unusual initial absorption is due, at least in part, to electromodulation of the band edge produced by separation of electrons and holes.

Samuel, I. D. W.; Meyer, K. E.; Graham, S. C.; Friend, R. H.; Rühe, J.; Wegner, G.

1991-11-01

346

The electronic states of isothiazole studied by VUV absorption spectroscopy and ab initio configuration interaction methods  

NASA Astrophysics Data System (ADS)

The isothiazole VUV absorption spectrum over the range 5-12 eV shows (broad) intense bands centred near 5.17, 6.11, 7.37, 7.75, 9.18 and 10.43 eV. The lowest Rydberg states relating to the first ionisation energy are difficult to identify, but higher members are particularly numerous on the region from 8.4 to 9.6 eV. Electronic excitation energies for valence (singlet and triplet) and Rydberg-type states have been computed using ab initio multi-reference multi-root CI methods. These studies used a triple zeta + double polarisation basis set, augmented by diffuse (Rydberg) orbitals. The theoretical study shows the nature of the more intense Rydberg state types, and positions of the main valence and Rydberg bands. By study of the excitation energies to specific upper states, the vertical ionisation energies (IE) are confirmed as ?4-1intensities and the experimental envelope. The ground state atomic and molecular properties are in good agreement with experiment.

Palmer, Michael H.; Gordon, Agnieszka J.

2007-12-01

347

Theory of excited-state absorption in phenylene-based ?-conjugated polymers  

NASA Astrophysics Data System (ADS)

Within a rigid-band correlated electron model for oligomers of poly-(paraphenylene) (PPP) and poly-(paraphenylenevinylene) (PPV), we show that there exist two fundamentally different classes of two-photon Ag states in these systems to which photoinduced absorption (PA) can occur. At relatively lower energies there occur Ag states which are superpositions of one electron one hole (1e 1h) and two electron two hole (2e 2h) excitations, that are both comprised of the highest delocalized valence-band and the lowest delocalized conduction-band states only. The dominant PA is to one specific member of this class of states (the mAg). In addition to the above class of Ag states, PA can also occur to a higher energy kAg state whose 2e 2h component is different and has significant contributions from excitations involving both delocalized and localized bands. Our calculated scaled energies of the mAg and the kAg agree reasonably well to the experimentally observed low- and high-energy PA’s in PPV. The calculated relative intensities of the two PA’s are also in qualitative agreement with experiment. In the case of ladder-type PPP and its oligomers, we predict from our theoretical work an intense PA at an energy considerably lower than the region where PA’s have been observed currently. Based on earlier work that showed that efficient charge-carrier generation occurs upon excitation to odd-parity states that involve both delocalized and localized bands, we speculate that it is the characteristic electronic nature of the kAg that leads to charge generation subsequent to excitation to this state, as found experimentally.

Shukla, Alok; Ghosh, Haranath; Mazumdar, Sumit

2003-06-01

348

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

349

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

350

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

351

Temperature dependence of C-terminal carboxylic group IR absorptions in the amide I? region  

NASA Astrophysics Data System (ADS)

Studies of structural changes in peptides and proteins using IR spectroscopy often rely on subtle changes in the amide I? band as a function of temperature. However, these changes can be obscured by the overlap with other absorptions, namely the side-chain and terminal carboxylic groups. The former were the subject of our previous report (Anderson et al., 2014). In this paper we investigate the IR spectra of the asymmetric stretch of ?-carboxylic groups for amino acids representing all major types (Gly, Ala, Val, Leu, Ser, Thr, Asp, Glu, Lys, Asn, His, Trp, Pro) as well as the C-terminal groups of three dipeptides (Gly-Gly, Gly-Ala, Ala-Gly) in D2O at neutral pH. Experimental temperature dependent IR spectra were analyzed by fitting of both symmetric and asymmetric pseudo-Voigt functions. Qualitatively the spectra exhibit shifts to higher frequency, loss in intensity and narrowing with increased temperature, similar to that observed previously for the side-chain carboxylic groups of Asp. The observed dependence of the band parameters (frequency, intensity, width and shape) on temperature is in all cases linear: simple linear regression is therefore used to describe the spectral changes. The spectral parameters vary between individual amino acids and show systematic differences between the free amino acids and dipeptides, particularly in the absolute peak frequencies, but the temperature variations are comparable. The relative variations between the dipeptide spectral parameters are most sensitive to the C-terminal amino acid, and follow the trends observed in the free amino acid spectra. General rules for modeling the ?-carboxylic IR absorption bands in peptides and proteins as the function of temperature are proposed.

Anderson, Benjamin A.; Literati, Alex; Ball, Borden; Kubelka, Jan

2015-01-01

352

Temperature dependence of C-terminal carboxylic group IR absorptions in the amide I' region.  

PubMed

Studies of structural changes in peptides and proteins using IR spectroscopy often rely on subtle changes in the amide I' band as a function of temperature. However, these changes can be obscured by the overlap with other absorptions, namely the side-chain and terminal carboxylic groups. The former were the subject of our previous report (Anderson et al., 2014). In this paper we investigate the IR spectra of the asymmetric stretch of ?-carboxylic groups for amino acids representing all major types (Gly, Ala, Val, Leu, Ser, Thr, Asp, Glu, Lys, Asn, His, Trp, Pro) as well as the C-terminal groups of three dipeptides (Gly-Gly, Gly-Ala, Ala-Gly) in D?O at neutral pH. Experimental temperature dependent IR spectra were analyzed by fitting of both symmetric and asymmetric pseudo-Voigt functions. Qualitatively the spectra exhibit shifts to higher frequency, loss in intensity and narrowing with increased temperature, similar to that observed previously for the side-chain carboxylic groups of Asp. The observed dependence of the band parameters (frequency, intensity, width and shape) on temperature is in all cases linear: simple linear regression is therefore used to describe the spectral changes. The spectral parameters vary between individual amino acids and show systematic differences between the free amino acids and dipeptides, particularly in the absolute peak frequencies, but the temperature variations are comparable. The relative variations between the dipeptide spectral parameters are most sensitive to the C-terminal amino acid, and follow the trends observed in the free amino acid spectra. General rules for modeling the ?-carboxylic IR absorption bands in peptides and proteins as the function of temperature are proposed. PMID:25036456

Anderson, Benjamin A; Literati, Alex; Ball, Borden; Kubelka, Jan

2015-01-01

353

Optical absorption in “quarter-filled band” TCNQ salts  

NASA Astrophysics Data System (ADS)

We have studied the infrared and optical properties of a group of TCNQ salts which contain on average 0.5 electrons per TCNQ: MTPP(TCNQ) 2, MNEB(TCNQ) 2, and (NMP) x(Phen) 1-xTCNQ. In the cases of MTPP(TCNQ) 2 and MNEB(TCNQ) 2 the crystals were sufficiently large that spectra could be obtained from up to six different crystllographic faces. The spectra are complicated by the presence of a strong localized exciton (observed for most polarization directions) in the energy range where the charge-transfer excitation from anion to anion occurs. The charge transfer excitation is present but rather weak. These results are compared with calculations using an extended Hubbard model of short chains and small rings.

Tanner, D. B.; Hamberg, Ivar; Jacobsen, C. S.; Almeida, M.; Carneiro, K.; Epstein, A. J.; Miller, Joel S.

1986-11-01

354

Ultraviolet absorption spectroscopy in optically dense fireballs using broadband second-harmonic generation of a pulsed modeless dye laser.  

PubMed

Broadband frequency doubling of a modeless dye laser pulse is used to enable single-shot absorption spectroscopy in the ultraviolet for optically dense, energetic-materials fireball applications. Band widths of approximately 1-3 nm are generated in the 226 and 268 nm regions using a doubling crystal. Strong focusing of the fundamental beam onto the crystal is found to be sufficient to achieve 1-5% conversion efficiency with a pulse intensity sufficient to saturate the array detector even after 75% attenuation through the fireball. The technique is demonstrated with nitric oxide (NO) absorption in a gas cell and is then used to perform the first detection and temperature fitting of aluminum monofluoride (AlF) and magnesium monofluoride (MgF) in a fireball environment. PMID:25014593

Soo, Michael; Glumac, Nick

2014-01-01

355

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

356

Device simulation of intermediate band solar cells  

NASA Astrophysics Data System (ADS)

To realize high efficiency solar cells, new concepts beyond the Shockley-Queisser limit are widely investigated. The intermediate band solar cell (IBSC) is one of the candidate concepts. From the importance of device physics, we have developed a device simulator for IBSCs. For device simulation of IBSC, the Poisson equation, carrier continuity equations of electrons in the conduction band (CB) and the valance band (VB) and balanced equation of IB state electrons must be solved self-consistently. The simulation methods can clarify the intrinsic device behavior of IBSCs which cannot be investigated by the detailed balance model. For example, by the existence of electrons trapped in IB states, electrostatic potential along the depth direction of the solar cells is strongly modified from the equilibrium under illumination of sunlight. This potential change is strongly related to its absorption property of sunlight. And the doping to IB region can enhance short circuit current density via IB states. Under larger concentration, this doping effect is decreased by the photofilling effects in the radiative limit. Absorption coefficients of each band-to-band transition are decided by the semiconductor materials and fundamental physics. These limitations make the different spectra and values from ideal treatments and decide the maximum efficiency of the IBSC. In this work, we present the fundamental properties and suggestions to approach the high efficiency IBSC operations as a device.

Yoshida, K.; Okada, Y.; Sano, N.

2012-02-01

357

Absorption in Extended Inhomogeneous Clouds  

NASA Technical Reports Server (NTRS)

The launch of several different sensors, including CloudSat, into the A-train constellation of satellites allows us for the first time to compute absorption that can occur in realistic vertically inhomogeneous clouds including multiple cloud decks. CloudSat data show that these situations are common. Therefore, understanding vertically inhomogeneous clouds is important from both climate and satellite atmospheric composition remote sensing perspectives. Satellite passive sensors that operate from the near IR to the UV often rely on radiative cloud pressures derived from absorption in oxygen bands (A, B, gamma, or O2-O2 bands) or from rotational-Raman scattering in order to retrieve information about atmospheric trace gases. The radiative cloud pressure is distinct from the physical cloud top derived from thermal infrared measurements. Therefore, the combination of information from different passive sensors yields some information about the cloud vertical profile. When either or both the clouds or atmospheric absorbers (trace gases and aerosols) are vertically inhomogeneous, the use of an effective cloud pressure derived from these approaches may lead to errors. Here, we focus on several scenarios (deep convective clouds and distinct two layer clouds) based on realistic cloud optical depth vertical profiles derived from the CloudSatfMODIS combination. We focus on implications for trace-gas column amount retrievals (specifically ozone and NO2) and derived surface UV irradiance from the Ozone Monitoring Instrument (OMI) on the Atrain Aura platform.

Joiner, Joanna; Vasilkov, Alexander; Spurr, Robert; Bhartia, P. K.; Krotkov, Nick

2008-01-01

358

Liquid water absorption and scattering effects in DOAS retrievals over oceans  

NASA Astrophysics Data System (ADS)

It is well-known that spectral effects of liquid water are present in absorption (DOAS) measurements above the ocean and insufficiently removed liquid water structures may interfere with trace gas absorptions leading to wrong (sometimes even non-physical) results. Currently available literature cross-sections of liquid water absorption are provided in coarser resolution than hyperspectral DOAS applications require and Vibrational Raman Scattering (VRS) is mostly unconsidered or compensated for using simulated pseudo cross-sections from radiative transfer modelling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS measurements were performed into very clear natural waters achieving underwater light paths of up to 50 m. From these measurements, the retrieval of a residual (H2Ores) spectrum is presented compensating simultaneously for insufficiencies of the liquid water absorption cross-section and broad-banded VRS structures. Small-banded (Ring) structures caused by VRS were found to be very efficiently compensated for by the intensity offset (straylight) correction included in the DOAS fit. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality. This was not achieved using a liquid water cross-section in combination with a simulated VRS spectrum. Typical values of improvement depend on the measurement's contamination with liquid water structures and range from ? 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ores spectrum was found to prevent misfits of NO2 slant columns especially for very low NO2 scenarios and thus increase the reliability of the fit. In test fits on OMI satellite data, the H2Ores spectrum was found selectively above ocean surfaces where it leads to fit quality improvements of up to 6-18%.

Peters, E.; Wittrock, F.; Richter, A.; Alvarado, L. M. A.; Rozanov, V. V.; Burrows, J. P.

2014-05-01

359

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

360

The Absorption Refrigerator as a Thermal Transformer  

ERIC Educational Resources Information Center

The absorption refrigerator can be considered a thermal transformer, that is, a device that is analogous to the electric transformer. The analogy is based on the correspondence between the extensive quantities, entropy and electric charge and the intensive variables, temperature and electric potential. (Contains 1 footnote and 6 figures.)

Herrmann, F.

2009-01-01

361

Mid-infrared FEL absorption spectra  

Microsoft Academic Search

The Vanderbilt Mark III FEL is a tunable source of high- intensity coherent mid-infrared radiation occurring as a train of picosecond pulses spaced 350ps apart. The laser beam is transported to each laboratory under vacuum, but is typically transmitted through some distance of atmosphere before reaching the target. Losses due to absorption by water vapor and CO2 can be large,

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

2002-01-01

362

An aerosol absorption remote sensing algorithm  

NASA Astrophysics Data System (ADS)

Aerosol absorption plays an important role in the climate by modulating atmospheric radiative forcing processes. Unfortunately aerosol absorption is very difficult to obtain via satellite remote sensing techniques. In this work we have built an algorithm to obtain aerosol absorption optical depth using both measurements from a passive O2 A-band spectrometer and an active lidar. The instrument protocols for these two satellite instruments are the O2 A-band spectrometer onboard the Orbiting Carbon Observatory (OCO-2) and the CALIOP onboard CALIPSO. The aerosol height and typing information is obtained from the CALIOP measurement. The aerosol extinction and absorption optical depths are then retrieved by fitting the forward model simulations to the O2 A-band spectrometer measurements. The forward model simulates the scattering and absorption of solar light at high spectral resolution in the O2 A-band region. The O2 and other gas absorption coefficients near 0.76 micron are calculated by either the line-by-line code (for instance, the Atmospheric Radiative Transfer Simulator) or the OCO2 ABSCO Look-Up-Table. The line parameters used are from the HITRAN 2008 database (http://www.cfa.harvard.edu/hitran/). The multiple light scattering by molecules, aerosols, and clouds is handled by the radiative transfer model based on the successive order of scattering method (Zhai et al, JQSRT, Vol. 111, pp. 1025-1040, 2010). The code is parallelized with Message Passing Interface (MPI) for better efficiency. The aerosol model is based on Shettle and Fenn (AFGL-TR 790214, 1979) with variant relative humidity. The vertical distribution of the aerosols and clouds will be read in from the CALIPSO product (http://www-calipso.larc.nasa.gov). The surface albedo is estimated by the continuum of the three bands of OCO2 payloads. Sensitivity study shows that the Gaussian quadrature (stream) number should be at least 12 to ensure the reflectance error is within 0.5% at the top of the atmosphere (TOA). The Fourier expansion number for the radiance field can be as small as 6. The fitting process is based on the Levenberg-Marquardt least squares fitting algorithm. Based on preliminary tests using the synthetic simulation data, the algorithm provides promising results for aerosol absorption retrievals.

Zhai, P.; Winker, D. M.; Hu, Y.; Trepte, C. R.; Lucker, P. L.

2013-12-01

363

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

364

Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption  

E-print Network

Ordered Arrays of Dual-Diameter Nanopillars for Maximized Optical Absorption Zhiyong Fan,,,§ Rehan control to achieve the optimal absorption efficiency. Increasing the Ge materials filling ratio is shown a strong diameter dependency. To enhance the broad band optical absorption efficiency, a novel dual

Javey, Ali

365

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL  

E-print Network

Characterizing Absorption Spectrum of Natural Rubidium by Using a Directly Modulated VCSEL Ido Ben in the absorption profile of a medium containing system atoms. Moreover, the change leads to a very narrow spectra: the VCSEL output and the absorption. Two modulation side bands, separated by fhfs owe to coincide

Eisenstein, Gadi

366

Preparation of amorphous calcium-magnesium phosphates at pH 7 and characterization by x-ray absorption and fourier transform infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Amorphous calcium-magnesium phosphates were prepared by precipitation from moderately supersaturated aqueous solutions at pH 7. Chemical analysis of the samples by ion chromatography showed that up to about 50% of the phosphate ions were protonated, the proportion increasing with the magnesium to calcium ion activity ratio in the solution. When left it contact with the supernatant, the amorphous precipitates matured to form the crystalline calcium phosphate brushite (CaHPO 4·2H 2O). The amorphous phases were characterized by X-ray absorption spectroscopy and by Fourier transform infrared spectroscopy and their properties compared with those of a basic amorphous tricalcium phosphate precipitated at pH 10. The X-ray absorption spectra near the K edge of calcium were very similar for all samples but there were differences in the infrared spectra between the basic and the more acidic salts. In the phosphate stretching region, the main band of the more acidic materials occured at higher wavenumber and was broader. Also there was a broad band of medium intensity at about 890 cm -1 whereas there was virtually no absorption band in this region in the spectrum of the amorphous tricalcium phosphate. The acidic amorphous calcium phosphates may be useful as model compounds in describing some complex biological calcium phosphates that form near neutral pH.

Holt, C.; van Kemenade, M. J. J. M.; Harries, J. E.; Nelson, L. S.; Bailey, R. T.; Hukins, D. W. L.; Hasnain, S. S.; De Bruyn, P. L.

1988-10-01

367

Multiplex-bands spectral characteristics of infrared perfect absorber metamaterials  

NASA Astrophysics Data System (ADS)

The multiplex-bands absorption of sandwich-structure metamaterials based metal- dielectric- metal scheme are investigated numerically and experimentally. The optical properties of cross-shape antenna perfect absorber metamaterials are demonstrated in mid-IR electromagnetic (EM) wave. The dual-band perfect absorber with polarization independence is observed under normal incidence. In order to understand the EM properties of dual-band perfect absorber, the plasmonic excitation and the induced current distribution were clarified for both peaks. The simulation results clearly show that the absorption bands are independently governed by the size of each part of the patterned nanostructure. The repositioning of two near-perfect absorption peaks possesses a linear relationship. This allows for a flexible reconfigurability over the entire near-infrared regime. Furthermore, in order to obtain multiplex-bands spectral absorption response, two cross-shape antennas are connected to form one dumbbell antenna. The three perfect-absorption peaks can be controlled by the individual dipole antenna elements in the conditions of polarization incident EM wave.

Li, Yongqian; Su, Lei; Wang, Binbin; Guo, Yongjun; Zhu, Zhenyu; Zhou, Zili

2013-09-01

368

Aerosol Absorption Measurements in MILAGRO.  

NASA Astrophysics Data System (ADS)

During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due to carbonyl- and nitro- functional groups on conjugated and aromatic organic structures (e.g. PAH, and terpene derived products). Using 12-hour fine (0.1-1.0 micron) aerosol samples collected in the field on quartz filters, uv/vis and infrared spectra were obtained in the laboratory using integrating spheres and diffuse reflectance spectroscopy, respectively. An inter-comparison of the "real-time" measurements made by the photo-acoustic, aethalometer and MAAP techniques have been described. In addition, the in situ aethalometer (seven-channel) results are compared with continuous integrating sphere uv-visible spectra to examine the angstrom absorption coefficient variance. These results will be briefly overviewed and the specific posters detailing these results will be highlighted highlighted. This work was performed as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City under the support of the Atmospheric Science Program. "This researchwas supported by the Office of Science (BER), U. S. Department of Energy, Grant No. DE-FG02-07ER64329.

Gaffney, J. S.; Marley, N. A.; Arnott, W. P.; Paredes-Miranda, L.; Barnard, J. C.

2007-12-01

369

Excitonic contribution to the optical absorption in zinc-blende III-V semiconductors  

Microsoft Academic Search

The imaginary part of the dielectric function of zinc-blende III-V semiconductors in the vicinity of the direct absorption edge was calculated using the kp model of the band structure and the Elliott's theory of excitonic absorption. From comparison to the experimental data, we found that the excitonic contribution is to be weighted in favor of the band-to-band transitions by a

S. Shokhovets; G. Gobsch; O. Ambacher

2006-01-01

370

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

NASA Astrophysics Data System (ADS)

The effects of gamma irradiation on spectral properties of Cr2O3-doped phosphate glasses of three varieties, namely sodium metaphosphate, lead metaphosphate and zinc metaphosphate have been investigated. Optical spectra of the undoped samples reveal strong UV absorption bands which are attributed to the presence of trace iron impurities in both the sodium and zinc phosphate glasses while the lead phosphate glass exhibits broad UV near visible bands due to combined absorption of both trace iron impurities and divalent lead ions. The effect of chromium oxide content has been investigated. The three different Cr2O3-doped phosphate glasses reveal spectral visible bands varying in their position and intensity and splitting due to the different field strengths of the Na+, Pb2+, Zn2+ cations, together with the way they are housed in the network and their effects on the polarisability of neighboring oxygens ligands. The effects of gamma irradiation on the optical spectral properties of the various glasses have been compared. The different effects for lead and zinc phosphate are related to the ability of Pb2+, and Zn2+ to form additional structural units causing stability of the network towards gamma irradiation. Also, the introduction of the transition metal chromium ions reveals some shielding behavior towards irradiation. Infrared absorption spectra of the three different base phosphate glasses show characteristic vibrations due to various phosphate groups depending on the type of glass and Cr2O3 is observed to slightly affect the IR spectra. Gamma irradiation causes minor variations in some of the intensities of the IR spectra but the main characteristic bands due to phosphate groups remain in their number and position.

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

2013-10-01

371

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.

2014-09-14

372

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

373

Compatibility of infrared band models with scattering  

Microsoft Academic Search

Techniques for the computation of radiative heating from aluminized solid propellant rocket exhaust plumes must account for infrared emission and absorption by hot H2O and CO2 in the presence of strong three-dimensional aerosol scattering by micron-sized Al2O3 droplets and particles. Radiative heating computations are usually performed over wide spectral intervals using infrared band models. However, no rigorous extension to infrared

R. A. Reed; D. G. Brown; R. S. Hiers III; B. K. Cromwell; V. A. Zaccardi

1994-01-01

374

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

375

Linear optical absorption and photoluminescence emission properties of gold nanoparticles prepared by laser ablation technique  

NASA Astrophysics Data System (ADS)

Gold nanoparticles of average size varying between 1.1 and 3.3 nm are prepared by 1064 nm Nd:YAG laser ablation of solid gold target kept in ethylene glycol medium. The measured UV-Visible absorption spectra showed the presence of sharp absorption peaks in the UV and in the visible regions due to the interband transition and surface plasmon resonance (SPR) oscillations in Au nanoparticles, respectively. The increase in linewidth of the SPR peaks with the reduction in particle sizes is observed due to intrinsic size effects. The prepared samples exhibit photoluminescence (PL) emissions in the UV-Visible region peaked at ˜354 nm due to the recombination of electrons with holes from sp conduction band to d-band of Au. The peak PL intensity in the sample prepared with 60 minutes of laser ablation time is enhanced by a factor of ˜2.5 compared to that obtained in the sample prepared with a laser-ablation time duration of 15 minutes.

Desarkar, H. S.; Kumbhakar, P.; Mitra, A. K.

2012-07-01

376

HII Absorption Bill Erickson  

E-print Network

HII Absorption Bill Erickson November 10, 2006 It would make all of the drift curve simulations.8 dB above the data. One reason for this might be HII absorption which is not modeled in simulations. There are a number of ways that one might try to estimate the absorption. One might use optical maps of HII

Ellingson, Steven W.

377

Nonlinear absorption and photoluminescence emission in nanocomposite films of Fuchsine Basic dye–polymer system  

Microsoft Academic Search

Fuchsine Basic dye–polyvinyl alcohol composite films were fabricated and their structure, nonlinear absorption as well as linear absorption and photoluminescence properties were investigated. Switchover from saturable absorption to two-photon assisted excited state absorption with increase in intensity was observed in the open aperture Z-scan study (Nd:YAG, 532nm, 7ns). The effective two-photon absorption coefficient ? was found to be several orders

G. Sreekumar; P. G. Louie Frobel; S. Sreeja; S. R. Suresh; S. Mayadevi; C. I. Muneera; C. S. Suchand Sandeep; Reji Philip; Chandrachur Mukharjee

2011-01-01

378

Mixed Valence and Hybridization Effects in the Early Rare Earths as Studied by X-Ray Absorption and Photoelectron Spectroscopies  

NASA Astrophysics Data System (ADS)

The general motivation for this work was to better understand the anomalous behavior of Ce-based systems by applying XPS, resonant photoemission and X-ray absorption spectroscopies. L(,III) absorption measurements on a number of Ce-based systems together with their La and/or Pr isomorphs, show that the double peaked Ce-edge is not caused by final state shakeup processes. Shakedown satellites have been identified in the absorption edges of LaNi(,5) and LaPd(,3) by comparing to isomorphs of heavier rare earths. The observed smallness of final state effects implies that the method of L(,III) absorption is both a convenient and reliable method for measuring the mixed valent quotient. XPS and L(,III) absorption measurements have been performed in a system where the electronic bandstructure can be varied continuously; namely Ce(Pd(,1-x)T(,x))(,3) where T = Rh or Ag. The shakedown intensities in the Ce 3d core-levels have been correlated with the mixed valent behavior in this system. The two peaks in the 4f-derived photoemission in Ce-based systems have been a major puzzle in the understanding of these mixed valent effects. Several theories have tried to explain this phenomenon. Resonant valence-band photoelectron measurements have been performed on the systems REAl(,2), RERu(,2) and REPd(,3) (RE = La, Ce, Pr, and Nd). One observes the bimodal 4f spectrum in PrAl(,2), PrPd(,3) and NdPd(,3) as well as in the Ce-isomorphs. This lends support to the theory of Liu and Ho and especially to the generalization of this theory to include hybridization effects by Riseborough, which envisions two different screening channels in the final state; one itinerant and one in which the screening is provided by a state pulled off the bottom of the conduction band.

Raaen, Steinar

1984-06-01

379

Quality evaluation of polarization-modulation infrared reflection-absorption spectra of a Langmuir monolayer on water dependent on angle of incidence and molecular orientation.  

PubMed

Quality analysis of polarization-modulation infrared reflection-absorption spectrometry (PM-IRRAS) for measurements of a Langmuir (L) monolayer film on water is presented. The spectral quality represented by the signal-to-noise ratio is evaluated by taking into account both the band intensity and the electrical signal throughput led out from the Fourier transform infrared (FT-IR) spectrometer. The product of the two parameters, which is named the quality evaluation function, theoretically reveals the optimal angle of incidence for the L film measurements. In addition, the PM-IRRAS-specific surface selection rule with respect to the spectral quality is also presented. PMID:21144155

Itoh, Yuki; Muro, Maiko; Hasegawa, Takeshi

2010-12-01

380

On the origins of the absorption spectroscopy of pterin and Re(CO)3(pterin)(H2O) aqueous solutions. A combined theoretical and experimental study  

NASA Astrophysics Data System (ADS)

The origins of the absorption spectroscopy of pterin and Re(CO)3(pterin)(H2O) complex as a function of pH is studied using the hybrid functional B3LYP and PBE0 in combination with 6-311++G(d,p) and LanL2TZ(f) basis sets. A natural bond analysis was performed to the principal molecular orbitals involved in the electronic transitions of the studied compounds. The low energy band of pterin, which is described as a H ? L electronic transition, can be interpreted as an admixture of ? ? ?*, n ? ?* and n ? n electronic transitions involving ?(C2-N1, C6-N5, C9-C10) and n(C2) orbitals of the HOMO and ?*(C6-N5, C7-N8) and n(C4) orbitals of the LUMO. The low energy band of Re(CO)3(pterin)(H2O) can be described as a combination of different MLLCT transitions where electron density residing on different ? orbitals of carbonyl-Re bonds and lone pairs of Re is transferred to pterin moiety. Besides MLLCT transitions, IL, LLCT and LLMCT transitions contribute the absorptions of the Re(I) complex in the wavelength region corresponding to the high energy bands. The calculated electronic spectra of the acid and base forms of pterin and Re(CO)3(pterin)(H2O) were simulated from the theoretical results and compared to the experimental absorption spectra with great accuracy both in position and relative intensities of the absorption bands.

Wolcan, Ezequiel

2014-08-01

381

The metabolism of intense sweeteners.  

PubMed

Three organic acids (saccharin, acesulfame-K and cyclamate) are used or have been used extensively as intense sweeteners. Once absorbed from the gut they are eliminated, largely in the urine, without undergoing metabolism. Early studies using radiolabelled saccharin indicated the existence of limited metabolism, but this was not confirmed by later more extensive studies using highly purified compound. Metabolism could not be induced by a variety of pretreatments. Following an initial report of the presence of traces of cyclohexylamine in the urines of subjects given cyclamate, it was shown that chronic administration of the sweetener caused the induction of extensive metabolism. The metabolism, which showed wide inter- and intra-individual variability was performed the gut microflora. The peptide sweeteners (aspartame and thaumatin) are metabolized to their constituent amino acids in the gastro intestinal tract, prior to absorption. As such they are incorporated into normal intermediary metabolism and their low-calorie applications derive from their intense sweetness. PMID:3541395

Renwick, A G

1986-01-01

382

Incomplete relaxation and plasmon formation in the K emission band of copper  

NASA Astrophysics Data System (ADS)

A method of calculating the effect of self-absorption in X-ray emission spectra and which is suitable for non-adiabatic excitation processes is presented. The Fermi-level EF and the "true" profile of the electron-excited (20-40keV) Cu K? 2,5 band are determined. A deviation from the calvulated one-electron spectrum in the energy interval [-12 eV, -7 eV] below EF is interpreted as a result of plasmon formation and Auger broadening. A pronounced disagreement is found also in the range [-1 eV, + 10eV]. Above EF, a part of the intensity may be due to incomplete electron relaxation.

Bremer, J.

1983-09-01

383

Band gap, CIE and trap depth parameters of rare earth molybdate phosphors for optoelectronic applications  

NASA Astrophysics Data System (ADS)

This paper reports on the comparative investigation of optical, luminescence and dielectric properties of Tb doped lanthanum and gadolinium molybdate phosphors. The crystal structures of the prepared phosphors were identified from XRD studies. The emission spectra of both the phosphors show the most intense peak at 545 nm due to 5D4 ? 7F5 transition. The optical absorption and diffuse reflectance spectra of both the phosphors show the main peak at 210 nm due to the band gap. Thermoluminescence studies were carried out after irradiating the phosphors by ?-rays. Trap depth associated with different trap levels was calculated from thermoluminescence data using various glow curve analysis techniques. The dielectric properties such as permittivity and dielectric loss were studied as a function of frequency.

Dutta, S.; Som, S.; Priya, J.; Sharma, S. K.

2013-04-01

384

Longwave Band-by-band Cloud Radiative Effect and its Application in GCM Evaluation  

NASA Technical Reports Server (NTRS)

The cloud radiative effect (CRE) of each longwave (LW) absorption band of a GCM fs radiation code is uniquely valuable for GCM evaluation because (1) comparing band-by-band CRE avoids the compensating biases in the broadband CRE comparison and (2) the fractional contribution of each band to the LW broadband CRE (f(sub CRE)) is sensitive to cloud top height but largely insensitive to cloud fraction, presenting thus a diagnostic metric to separate the two macroscopic properties of clouds. Recent studies led by the first author have established methods to derive such band ]by ]band quantities from collocated AIRS and CERES observations. We present here a study that compares the observed band-by-band CRE over the tropical oceans with those simulated by three different atmospheric GCMs (GFDL AM2, NASA GEOS-5, and CCCma CanAM4) forced by observed SST. The models agree with observation on the annual ]mean LW broadband CRE over the tropical oceans within +/-1W/sq m. However, the differences among these three GCMs in some bands can be as large as or even larger than +/-1W/sq m. Observed seasonal cycles of f(sub CRE) in major bands are shown to be consistent with the seasonal cycle of cloud top pressure for both the amplitude and the phase. However, while the three simulated seasonal cycles of f(sub CRE) agree with observations on the phase, the amplitudes are underestimated. Simulated interannual anomalies from GFDL AM2 and CCCma CanAM4 are in phase with observed anomalies. The spatial distribution of f(sub CRE) highlights the discrepancies between models and observation over the low-cloud regions and the compensating biases from different bands.

Huang, Xianglei; Cole, Jason N. S.; He, Fei; Potter, Gerald L.; Oreopoulos, Lazaros; Lee, Dongmin; Suarez, Max; Loeb, Norman G.

2012-01-01

385

nBn and pBp infrared detectors with graded barrier layer, graded absorption layer, or chirped strained layer super lattice absorption layer  

NASA Technical Reports Server (NTRS)

An nBn detector is described where for some embodiments the barrier layer has a concentration gradient, for some embodiments the absorption layer has a concentration gradient, and for some embodiments the absorption layer is a chirped strained layer super lattice. The use of a graded barrier or absorption layer, or the use of a chirped strained layer super lattice for the absorption layer, allows for design of the energy bands so that the valence band may be aligned across the device. Other embodiments are described and claimed.

Gunapala, Sarath D. (Inventor); Ting, David Z. (Inventor); Hill, Cory J. (Inventor); Bandara, Sumith V. (Inventor)

2010-01-01

386

What band rocks the MTB? (Invited)  

NASA Astrophysics Data System (ADS)

Magnetotactic bacteria (MTB) are a polyphyletic group of bacteria that have been found in marine and lacustrine environments and soils [e.g. 1]. The hallmark of MTB is their intracellular formation of magnetosomes, single-domain ferrimagnetic particles that are aligned in chains. The chain configuration generates a strong magnetic dipole, which is used as magnetic compass to move the MTB into their favorable habit. The term band corresponds to a frequency window of microwaves in the gigahertz (GHz) range. Ferromagnetic resonance (FMR) spectroscopy uses the microwave absorption in a magnetic field to analyze the anisotropy properties and the domain state of magnetic materials. Specific microwave frequency causes absorption in a characteristic magnetic field range. For the investigation of MTB we use S-band (4.02 GHz), X-band (9.47 GHz), and Q-band (34.16 GHz). Experiments on cultured MTB and on sediment samples of Holocene age showed that absorption in X- and Q-band occurs when the sample is in a saturated or nearly saturated state [2, 3]. By contrast, absorption in the S-band appears in lower magnetic fields, where the sample is far from saturation. All FMR spectra show two distinct low-field features that can be assigned to magnetite particles in chains, aligned parallel and perpendicular to the external magnetic field. The detailed separation of the parallel and perpendicular components in the bulk samples is hampered, because of the random orientation of the chains in the sample. The comparison of S-, X-, and Q-band shows that the lower the frequency the better the separation of the components. In the S-band FMR spectroscopy, the separation of chains parallel to the external magnetic field is supported by the internal field of the sample. This field is caused by the remanence that contributes to the external magnetic field to fulfill the resonance condition [3,4]. Considering the different FMR responses, it can be postulated that a lower microwave frequency generally leads to a better resolution of the chain configuration. Finally, for the investigation of geological samples, the application of S-band can be a powerful tool to complement the commonly used X-band FMR spectroscopy, i.e. multiple band rock the MTB. [1] Blakemore R.P., 1975, Magnetotactic bacteria, Science, 190, 377-379 [2] Mastogiacomo G., Fischer H., Garcia-Rubio I., and Gehring A. U., 2010, Ferromagnetic resonance spectroscopic response of magnetic chains in a biological matrix, J. Magn. Magn. Matter, 322, 661-663, doi: 10.1016/j.jmmm.2009.10.035 [3] Gehring A. U., Kind. J., Charilaou M., Garcia-Rubio I., 2011, S-band ferromagnetic resonance spectroscopy and the detection of magnetofossils, J. R. Soc. Interface, 10(80), doi: 10.1098/rsif.2012.0790 [4] Kind J., van Raden U., Garcia-Rubio I., and Gehring A. U., 2012, Rock magnetic techniques complemented by ferromagnetic resonance spectroscopy to analyse a sediment record, Geophys. J. Int., 191, 51-61, doi: 10.1111/j.1365-246X.2012.05620.x

Kind, J.; García-Rubio, I.; Gehring, A. U.

2013-12-01

387

Impedance Matched Absorptive Thermal Blocking Filters  

NASA Technical Reports Server (NTRS)

We have designed, fabricated and characterized absorptive thermal blocking filters for cryogenic microwave applications. The transmission line filter's input characteristic impedance is designed to match 50O and its response has been validated from 0-to-50GHz. The observed return loss in the 0-to-20GHz design band is greater than 20 dB and shows graceful degradation with frequency. Design considerations and equations are provided that enable this approach to be scaled and modified for use in other applications.

Wollack, E. J.; Chuss, D. T.; Rostem, K.; U-Yen, K.

2014-01-01

388

Two Photon Absorption Spectroscopy of Polydiacetylene PTS  

Microsoft Academic Search

We have studied two photon absorption (TPA) of single crystal polydiacetylene-toluene-sulfonate (PTS) using the Mark III Free Electron Laser (FEL) in the spectrum range of 0.95–1.5 ?m. We observed two features in the TPA spectrum at two photon energies of 1.85 eV and 2.35 eV, respectively. We discuss the assignment of the two bands in terms of TPA allowed excitons

J. M. Leng; Z. V. Vardeny; B. A. Hooper; K. D. Straub; J. M. J. Madey; G. L. Baker

1994-01-01

389

The role of cellulose acetate as a matrix for aggregation of pseudoisocyanine iodide: absorption and emission studies.  

PubMed

Films of pseudoisocyanine iodide in a cellulose acetate matrix were prepared by spin coating and characterized by UV/Vis absorption and fluorescence spectroscopies. The comparison with self-supported films of the same dye enabled analysing the role of the matrix in the aggregation of pseudoisocyanine iodide ([PIC]I). It was proved that cellulose acetate is a suitable support for [PIC]I J-aggregates, which form during spinning, as shown by a very sharp J-band in the absorption spectra. This indicates a perfect coherence between stacked monomers in the supported J-aggregates. It was possible to individualize the emission spectrum of [PIC]I J-aggregates in cellulose acetate, by decomposition of the steady-state fluorescence spectra of the films. The dependence on the excitation wavelength of the relative emission intensities of monomers and J-aggregates, for lambda(em) = 587 nm, lead to confirm that the latter species have an absorption maximum at approximately 500 nm in cellulose acetate. Finally, polarised absorption spectra of films obtained by the vertical spin coating technique showed that cellulose acetate allows a partial orientation of J-aggregates. PMID:11506031

Brito de Barros, R; Ilharco, L M

2001-08-01

390

Laboratory Investigation of the Airglow Bands  

NASA Astrophysics Data System (ADS)

We report the first high spectral resolution laboratory measurements of oxygen A-band night glow simulated using a static discharge cell. Our static discharge system reproduces the conditions of the mesospheric oxygen night glow - suggesting O(^1D) + O_2 as the primary source of the emission. Additionally, use of the static cell has enabled us to collect spectra for rare molecular oxygen isotopologues using isotopically enriched samples. The (0,0), (0,1), and (1,1) b-Xvibrational bands were observed with a Bruker 125 HR for all six isotopologues. The (1,2) and (2,2) bands were observed also for the main isotopologue. The frequencies of the observed (0,1) transitions resolved discrepancies in Raman data for (16-17, 17-17, and 17-18), enabling us to improve the vibrational parameterization of the ground electronic state in the global fit of Yu et al. Rotationally resolved intensities were determined for the (0,0), (0,1) and (1,1) bands. The experimental band intensity ratios I(0,0)/I(0,1) = 13.6 and I(0,0)/I(1,1) = 60 are in excellent agreement with the recent mesospheric remote sensing data. S. Yu, C.E. Miller, B.J. Drouin, H.S.P. Müller, J. Chem. Phys. 136, 024304, 2012

Drouin, Brian; Yu, Shanshan; Crawford, Timothy J.; Miller, Charles E.; Yee, Jeng-Hwa

2013-06-01

391

Single-junction solar cells with the optimum band gap for terrestrial concentrator applications  

SciTech Connect

A single-junction solar cell having the ideal band gap for terrestrial concentrator applications. Computer modeling studies of single-junction solar cells have shown that the presence of absorption bands in the direct spectrum has the effect of "pinning" the optimum band gap for a wide range of operating conditions at a value of 1.14.+-.0.02 eV. Efficiencies exceeding 30% may be possible at high concentration ratios for devices with the ideal band gap.

Wanlass, Mark W. (Golden, CO)

1994-01-01

392

Wide Band to ''Double Band'' upgrade  

SciTech Connect

The Wide Band beam currently uses electrons obtained from secondary photon conversions to produce the photon beam incident on the experimental targets. By transporting the positrons produced in these conversions as well as the electrons it is possible to almost double the number of photons delivered to the experiments per primary beam proton. 11 figs.

Kasper, P.; Currier, R.; Garbincius, P.; Butler, J.

1988-06-01

393

Electronic states of DNA and M-DNA studied by optical absorption  

NASA Astrophysics Data System (ADS)

To unveil the electronic states of divalent metal ion incorporated M-DNAs, where M is Mg, Mn, Ni, Co, or Fe, optical absorption spectra have been studied in aqueous solutions of single-stranded (SS) 30mer DNA of poly(dA) (adenine), poly(dG) (guanine), poly(dT) (thymine), poly(dC) (cytosine), salmon-sperm DNA (B-DNA), and M-DNA. The absorption spectrum of the double-stranded (DS) B-DNA can be reproduced with the sum of the four absorption spectra of the SS oligo-DNAs in the ratio corresponding to the composition of B-DNA. This observation suggests that the interactions between complementary strands of DS DNA are negligibly weaker than the bandwidths of the optical spectra. In the metal-incorporated M-DNAs, except for Fe-DNA, the absorption spectra show no significant qualitative change from that of B-DNA. Quantitatively, however, the absorption intensity decreases by ?15% uniquely in a DS poly(dA)-poly(dT) solution with adding MCl2, while nothing happens quantitatively and qualitatively in any SS oligo-DNA and DS poly(dG)-poly(dC) solutions, suggesting some suppression of the electronic excitation only in the Adenine-M-Thymine complex. In contrast, remarkable differences have been observed in Fe-DNA, prepared with FeCl2 and B-DNA. New absorption bands appear in the intragap energy of Fe-DNA, in addition to the suppression of the interband absorption peak of DNA at 4.8 eV. The intragap absorption is attributed to the appearance of Fe3+ species with the same spectral feature as that of FeCl3, that is, purely ionic Fe3+ species. This observation suggests that FeCl2+B-DNA forms Fe-DNA with hydrated Fe3+ ions with ionic bonds. Thus, it is concluded that the charge transfer from Fe2+ to DNA has occurred in Fe-DNA and that the transferred charges are expected to be located in the nearby bases.

Tsuburaya, Makoto; Sakamoto, Hirokazu; Mizoguchi, Kenji

2014-02-01

394

Surface-enhanced infrared absorption (SEIRA) of adsorbates on copper nanoparticles synthesized by galvanic displacement.  

PubMed

Copper nanoparticles (Cu NPs) were made by electroless deposition on Ge disks as substrates for surface-enhanced infrared absorption (SEIRA). Previous X-ray photoelectron spectra had shown that elemental copper is deposited on the Ge substrate and that the nanoparticulate film remains resistant to oxidation even after several days of air exposure at room temperature. SEIRA spectra of p-nitrothiophenol (p-NTP) adsorbed on the copper nanoparticles were measured. Freshly made substrates made by electroless deposition gave higher enhancements than both the 12-day-old oxidized substrates and substrates made by physical vapor deposition. The intensity of the antisymmetric NO(2) stretching band of p-NTP relative to that of the symmetric stretch was significantly higher for p-NTP adsorbed on copper than on silver nanofilms, indicating that the C(2) axis of the aromatic ring is tilted with respect to the copper surface. PMID:21740636

Fasasi, Ayuba; Griffiths, Peter R; Scudiero, Louis

2011-07-01

395

Franz-Keldysh effect of band states in polydiacetylene  

Microsoft Academic Search

Electroabsorption spectra of polydioacetylene single crystals with well ordered chains show 0.5 eV above the excitonic absorption edge a strong signal from states which contribute little to absorption. While the strongly absorbing excitons respond to an external field by a quadratic Stark effect this particular signal is attributed to the Franz-Keldysh effect, the response of a free carrier band. The

Gerhard Weiser; A. Horvath; H. J. Kolbe

1997-01-01

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

Spatial variations of methane absorption on Jupiter according to the results of quasicontinuous CCD spectrophotometry  

NASA Astrophysics Data System (ADS)

Spectrophotometry observations of Jupiter were carried out during four nights in November-December 1999. Three hundred and eighty eight CCD-spectrograms of the central meridian of the planet were obtained and processed with doubly overlapped longitudes with a step of 1.8°. Latitudinal variations in central depths of methane absorption bands were studied corresponding to the wavelengths of 619, 725, 798, and 887 nm. It has been shown that these variations are mainly present at all longitudes, but for different absorption bands the positions of maxima and minima do not coincide. Zonal differences do not correlate with positions of dark and bright cloud belts in absorption, with one exception for the band 887 nm, which for a long time shows a well-expressed minimum in the equatorial zone of Jupiter. The 798 nm band reveals great dispersion of the depths at low latitudes as compared to other bands, which can be related with the presence of the ammonium absorption band. Comparison of the latitudinal absorption band variability at wave-lengths 619 and 725 nm shows a "loop-like" form of the relation between the depths of these bands in the low-latitude zone of Jupiter. Indicative estimates of the effective optical depth formation and absorption and their difference in the framework of simple two-layer model indicate the existence of vertical heterogeneity of the cloud cover varying with latitude.

Tejfel, V. G.; Kharitonova, G. A.

2014-11-01

398

Infrared spectrum of 4-methoxypicolinic acid N-oxide: computation of asymmetric O-H stretching band.  

PubMed

In this article we studied the strong intramolecularly hydrogen-bonded system 4-methoxypicolinic acid N-oxide. The potential energy surface V = V(rOH,rOO) and the corresponding dipole moment function were calculated using the DFT B3LYP/6-31+G(d,p) level of approximation. The time-independent vibrational Schrödinger equation was solved using a rectangular grid basis set and shifted Gaussian basis set. The vibrational spectrum and metric parameters were also calculated. Effects of deuteration were considered. The calculated vibrational spectra were compared with the experimental spectra. The vibrational transition corresponding to asymmetric O-H stretching that occurs at about 1400 cm-1 compares well with the experimentally assigned O-H asymmetric stretching band centered at 1380 cm-1. The corresponding asymmetric O-D stretching band was predicted to be at 1154 cm-1, while the experimental O-D band was not assigned due to its very low intensity. Several overtones and hot transitions of significant intensities were located in the vicinity of the fundamental O-H stretching frequency, effectively broadening the infrared absorption attributed to the O-H stretching mode. This is in a good agreement with the observed broad protonic absorptions found in the infrared spectra of the title compound and its analogs. We have shown that the Gaussian basis set is the method of choice for a two-dimensional vibrational problem that requires several hundreds of vibrational basis functions and when high accuracy of the eigenvalues is required or when extending the calculations to more vibrational degrees of freedom. We have also demonstrated that for a large number of basis functions the Gramm-Schmidt orthogonalization procedure outperforms symmetric and canonical orthogonalization schemes. PMID:17469813

Balazic, Katja; Stare, Jernej; Mavri, Janez

2007-01-01

399

Intestinal magnesium absorption.  

PubMed

Available data on the mechanism of Mg absorption is mainly descriptive in nature. There is data to support the existence of both gradient-driven and saturable Mg absorption. It is not clear, however, which process predominates under normal conditions. Evidence for a saturable process is based on a curvilinear relationship between dietary or luminal [Mg] and Mg uptake. Whether this is due to a carrier-mediated mechanism or due to alterations in absorption through the paracellular route remains to be determined. A careful review of the literature indicates that the predominate site of Mg absorption is the distal small intestine. Most of these studies, however, have been done in isolated segments which may not adequately reflect absorption in an undisturbed gastrointestinal tract. Future work will need to focus on identifying and characterizing Mg transport at the cellular and paracellular level as well as developing more sophisticated strategies for examining Mg absorption in the whole animal. PMID:8264506

Kayne, L H; Lee, D B

1993-01-01

400

Multi-plasmon absorption in graphene  

E-print Network

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

Marinko Jablan; Darrick E. Chang

2015-01-21

401

Absorption Changes in Bacterial Chromatophores  

PubMed Central

The magnitude and kinetics of photo-induced absorption changes in bacterial chromatophores (R. rubrum, R. spheroides and Chromatium) have been studied as a function of potential, established by added redox couples. No photochanges can be observed above +0.55 v or below -0.15 v. The loss of signal at the higher potential is centered at +0.439 v and follows a one-electron change. The loss of signal at the lower potential is centered at -0.044 v and is also consistent with a one-electron change. Both losses are reversible. A quantitative relationship exists between light-minus-dark and oxidized-minus-reduced spectra in the near infrared from +0.30 to +0.55 v. Selective treatment of the chromatophores with strong oxidants irreversibly bleaches the bulk pigments but appears to leave intact those pigments responsible for the photo- and chemically-induced absorption changes. Kinetic studies of the photochanges in deaerated samples of R. rubrum chromatophores revealed the same rise time for bands at 433, 792, and 865 m? (t½ = 50 msec.). However, these bands had different decay rates (t½ = 1.5, 0.5, 0.15 sec., respectively), indicating that they belong to different pigments. Analysis of the data indicates, as the simplest interpretation, a first-order (or pseudo first-order) forward reaction and two parallel first-order (or pseudo first-order) decay reactions at each wavelength. These results imply that all pigments whose kinetics are given are photooxidized and the decay processes are dark reductions. These experiments are viewed as supporting and extending the concept of a bacterial photosynthetic unit, with energy migration within it to specific sites of electron transfer. PMID:14185583

Kuntz, Irwin D.; Loach, Paul A.; Calvin, Melvin

1964-01-01

402

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

403

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

404

A joint band prioritization and band-decorrelation approach to band selection for hyperspectral image classification  

Microsoft Academic Search

Band selection for remotely sensed image data is an effective means to mitigate the curse of dimensionality. Many criteria have been suggested in the past for optimal band selection. In this paper, a joint band-prioritization and band-decorrelation approach to band selection is considered for hyperspectral image classification. The proposed band prioritization is a method based on the eigen (spectral) decomposition

Chein-I. Chang; Qian Du; Tzu-Lung Sun; M. L. G. Althouse

1999-01-01

405

Collision parameters of N2-broadened methane lines in R5 multiplet of 2 ? 3 band. Multispectrum fitting of overlapping spectral lines  

NASA Astrophysics Data System (ADS)

The results of the investigation of absorption spectra of the methane R5 multiplet of 2 ? 3 band, broadened by nitrogen, are presented. The absorption spectra of the methane-nitrogen mixture (CH4:N2 = 1:113.36) were recorded, using a two-channel photometric spectrometer, based on a tunable diode laser. The multispectrum least-squares fitting procedure was applied to all experimental spectra, recorded at different pressures, using the program, developed at IAO SB RAS (Protasevich, 2011). The program is based on a relatively simple line-profile model proposed in Pine (J. Quant. Spectrosc. Radiat. Transf. 57:145, 1997) and linear pressure dependence of the line-profile parameters. The line center positions, intensities, broadening, shifting, and mixing coefficients were determined for four lines of the methane R5 multiplet. The results have been compared with other available data.

Osipov, K. Y.; Protasevich, A. E.; Kapitanov, V. A.; Ponurovskii, Y. Y.

2012-03-01

406

Absorption technology for solar and waste heat utilization  

NASA Astrophysics Data System (ADS)

Absorption heat pumps, first developed in the 19th century, have received renewed and growing attention in the past two decades. With the increasing cost of oil and electricity, the particular features of this heat-powered cycle have made it attractive for both residential and industrial applications. Solar-powered temperature boosters are among the applications on which intensive research was conducted. The operation of absorption systems is described and several practical applications are discussed. It surveys recent advances in absorption technology, including the selection of working fluids, cycle improvements and multi-staging, and fundamentals of the combined heat and mass transfer in absorption processes.

Grossman, G.

1991-05-01

407

Electronic absorption spectra of B3 and B3- in neon matrices and ab initio analysis of the vibronic structure  

NASA Astrophysics Data System (ADS)

Mass selected B3- ions have been isolated in 6 K neon matrices and their absorption spectra measured. A band system with origin at 467 nm is assigned as the 1E'?X 1A1' electronic transition of the cyclic anion. After photobleaching, the 1 2E'?X 2A1' and 2 2E'?X 2A1' band systems of neutral cyclic B3 are observed which start around 736 and 458 nm, respectively. Large scale ab initio calculations have provided potential energy surfaces for a variational treatment of the vibrational motion. Calculated band origins leave no doubt about the electronic symmetry assignments. The complex vibrational structure in the 1 2E' state, which is due to relatively strong Jahn-Teller distortions, appears to be closely reproduced by the calculated vibrational energies and intensities, if the first observed stronger line is identified with the first vibrationally excited state, placing the "true" band origin of the 1 2E' state at 775 nm where no signal with significant strength is apparent. The 2 2E' state undergoes only a relatively weak Jahn-Teller distortion and shows a short progression with an observed frequency of 981(10) cm-1 that compares favorably with the theoretical frequency of 973 cm-1. The 1E' system of B3- shows a Jahn-Teller activity comparable to that of the 1 2E' state of B3.

Wyss, Muriel; Riaplov, Evgueni; Batalov, Anton; Maier, John P.; Weber, Thomas; Meyer, Wilfried; Rosmus, Pavel

2003-11-01

408

Planning of Axiom Absorptions  

E-print Network

Abstract. Absorptions are generally employed in Description Logics (DL) reasoners in a uniform way regardless of the structure of an input knowledge base. In this paper we present an approach to encode some state-of-the-art absorption techniques into a state space planner, aiming to achieve a better solution. The planner applies appropriate operators to general axioms and produces a solution with a minimized cost to automatically organize these absorptions in a certain sequence to facilitate DL reasoning. Compared to predetermined or fixed applications of established absorptions, such a solution is more flexible and probable to absorb more general axioms into an unfoldable TBox. 1

unknown authors

409

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

410

Probing the sensitivity of polarimetric O2 A-band measurements to clouds with emphasis on potential OCO-2 and GOSAT retrievals  

NASA Astrophysics Data System (ADS)

Clouds play a crucial role in the Earth's radiative budget, yet their climate feedbacks are poorly understood. The advent of space-borne high resolution spectrometers probing the O2 A-band, such as the GOSAT and OCO-2 satellites, could make it possible to simultaneously retrieve several cloud parameters that play a vital role in the Earth's radiative budget, thereby allowing a reduction of the corresponding uncertainty due to clouds. In this work, the hyperspectral, polarimetric response of the O2 A-band to mainly three important cloud parameters, viz., optical thickness, top height and droplet size has been studied, revealing a different sensitivity to each for the varying atmospheric absorption strength within the A-band. Cloud optical thickness finds greatest sensitivity in both intensity and polarization measurements at non-absorbing wavelengths. Cloud height had a negligible effect on intensity measurements at non-absorbing wavelengths, but finds maximum sensitivity at an intermediate absorption strength, which increases with cloud height. The same is found to hold for cloud geometric thickness, except that the sensitivity is weaker. Sensitivity to droplet size is generally weaker than to cloud optical thickness to top height at non-absorbing wavelengths and diminishes further with increasing absorption strength. It has been shown that significantly more information on droplet size can be drawn from multiangular measurements. Our results show that, in the absence of sunglint, the backscatter direction is richer in information on droplet size, especially in the glory and rainbow regions. It has been shown that I and Q generally have differing sensitivities to cloud parameters. Thus, accurate measurements of both orthogonal components Ih and Iv (as in GOSAT) are expected to contain more information than measurements of only I, Ih or Iv (as in the case of OCO-2).

Sanghavi, S.; Lebsock, M.; Stephens, G.

2014-09-01

411

Analysis of spectral absorption features in hyperspectral imagery  

NASA Astrophysics Data System (ADS)

Spectral reflectance in the visible and near-infrared wavelengths provides a rapid and inexpensive means for determining the mineralogy of samples and obtaining information on chemical composition. Absorption-band parameters such as the position, depth, width, and asymmetry of the feature have been used to quantitatively estimate composition of samples from hyperspectral field and laboratory reflectance data. The parameters have also been used to develop mapping methods for the analysis of hyperspectral image data. This has resulted in techniques providing surface mineralogical information (e.g., classification) using absorption-band depth and position. However, no attempt has been made to prepare images of the absorption-band parameters. In this paper, a simple linear interpolation technique is proposed in order to derive absorption-band position, depth and asymmetry from hyperspectral image data. AVIRIS data acquired in 1995 over the Cuprite mining area (Nevada, USA) are used to demonstrate the technique and to interpret the data in terms of the known alteration phases characterizing the area. A sensitivity analysis of the methods proposed shows that good results can be obtained for estimating the absorption wavelength position, however the estimated absorption-band-depth is sensitive to the input parameters chosen. The resulting parameter images (depth, position, asymmetry of the absorption) when carefully examined and interpreted by an experienced remote sensing geologist provide key information on surface mineralogy. The estimates of depth and position can be related to the chemistry of the samples and thus allow to bridge the gap between field geochemistry and remote sensing.

van der Meer, Freek

2004-02-01

412

Optical absorption from an indirect transition in bismuth nanowires M. R. Black,1,  

E-print Network

Optical absorption from an indirect transition in bismuth nanowires M. R. Black,1, * P. L; published 30 December 2003 Simulations of the optical absorption in bismuth nanowires resulting from size dependence of the high intensity absorption peak observed in bismuth nanowires at 1000 cm 1 can

Cronin, Steve