Note: This page contains sample records for the topic absorption band intensities from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: November 12, 2013.
1

Infrared absorption spectra and integrated band intensities for gaseous methanesulphonic acid (MSA)  

NASA Astrophysics Data System (ADS)

A quantitative analysis of the infrared spectrum of gaseous methanesulphonic acid (MSA, CH 3SO 3H) has been performed in the region of 4100-700 cm -1 using in situ Fourier Transform Infrared Spectroscopy (FTIR). The influence of the temperature and the partial pressure of the diluent gas (N 2) on the measured infrared absorption coefficients and the integrated band intensities was investigated. This study represents the first report of infrared absorption coefficients and integrated band intensities for gaseous MSA.

Mihalopoulos, N.; Barnes, I.; Becker, K. H.

2

Integral intensities of absorption bands of silicon tetrafluoride in the gas phase and cryogenic solutions: Experiment and calculation  

Microsoft Academic Search

The spectral characteristics of the SiF4 molecule in the range 3100–700 cm?1, including the absorption range of the band ?3, are studied in the gas phase at P = 0.4–7 bar and in solutions in liquefied Ar and Kr. In the cryogenic solutions, the relative intensities of the vibrational\\u000a bands, including the bands of the isotopically substituted molecules, are determined.

A. P. Burtsev; V. N. Bocharov; S. K. Ignatov; T. D. Kolomiitsova; P. G. Sennikov; K. G. Tokhadze; L. A. Chuprov; D. N. Shchepkin; O. Schrems

2005-01-01

3

Rovibrational Intensities of Five Absorption Bands of (12)C(16)O2 Between 5218 and 5349/cm.  

National Technical Information Service (NTIS)

Absolute line intensities, band intensities, and Herman-Wallis parameters were measured for the (01(sup 1)2)(sub I) from (00(sup 0)0)(sub I) perpendicular band of (12)C(16)O2 centered at 5315/cm, along with the three nearby associated hot bands: (10(sup 0...

L. P. Giver L. R. Brown C. Chackerian R. S. Freedman

2002-01-01

4

Band intensities in the circular dichroism and absorption spectra and the states of d ions in absorbing media: I. Octahedrally coordinated positions of d ions  

SciTech Connect

The factors affecting the band intensity in circular dichroism (CD) and absorption spectra (selection rules, point group of structural position, and the electron density of the ground state of octahedrally coordinated d ion in absorbing medium) are considered. The intensities of CD and absorption bands are calculated and compared with the experimental data. It is shown that the differences in the spatial inversion of the electric- and magnetic-dipole moment transformations lead to a more rigorous validity of the symmetry selection rules and increase the resolution of peaks and transparency window of medium absorption in CD spectra (in contrast to absorption ones). Some criteria for estimating the valence and structural states of d ions are formulated.

Veremeichik, T. F., E-mail: tomver@online.ru [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2009-11-15

5

Ab initio and LMO studies on the integrated intensities of infrared absorption bands of polyatomic molecules. 7. The formic acid dimer. Influence of hydrogen bonding and isotopic substitution  

Microsoft Academic Search

Moderately sized (3.1 basis) ab inito SCF calculations are performed on the integrated intensities of the IR absorption bands of the formic acid dimer. A finite perturbation approach is used within the framework of the double harmonic approximation. The force field used in the normal-coordinate calculations is a refined Kishida force field yielding an average deviation of less than 1%

Didier Berckmans; Hubert P. Figeys; Yves Marechal; Paul Geerlings

1988-01-01

6

Vibrational reorganizational energies of the A-band LMCT absorption in trans-dichlorobis (triphenylphosphine) palladium (II) determined from resonance Raman intensity analysis  

NASA Astrophysics Data System (ADS)

Resonance Raman spectra including absolute resonance Raman cross section measurements have been recorded for four excitation wavelengths within the A-band ligand to metal charge transfer (LMCT) absorption at ~ 340 nm of trans-dichlorobis(triphenylphosphine) palladium (II). A relatively simple model together with time-dependent wavepacket calculations were used to simulate simultaneously the absolute absorption and resonance Raman intensities in order to get an estimate of the vibrational reorganizational energies associated with the Aband absorption plus the homogeneous and inhomogeneous broadening to the absorption bandwidth. It seems that there is significant interaction of the triphenylphosphine ligands with the Cl/Pd chromophore of the LMCT absorption band. The results for transdichlorobis(triphenylphosphine) palladium(II) are compared with those of other inorganic compounds.

Phillips, Chi Leung Choi David Lee

7

Analysis and prediction of absorption band shapes, fluorescence band shapes, resonance Raman intensities, and excitation profiles using the time-dependent theory of electronic spectroscopy  

Microsoft Academic Search

A general method for the simulation of absorption (ABS) and fluorescence band shapes, resonance-Raman (rR) spectra, and excitation profiles based on the time-dependent theory of Heller is discussed. The following improvements to Heller's theory have been made: (a) derivation of new recurrence relations for the time-dependent wave packet overlap in the case of frequency changes between the ground and electronically

Taras Petrenko; Frank Neese

2007-01-01

8

Ab initio and LMO studies on the integrated intensities of infrared absorption bands of polyatomic molecules. 7. The formic acid dimer. Influence of hydrogen bonding and isotopic substitution  

SciTech Connect

Moderately sized (3.1 basis) ab inito SCF calculations are performed on the integrated intensities of the IR absorption bands of the formic acid dimer. A finite perturbation approach is used within the framework of the double harmonic approximation. The force field used in the normal-coordinate calculations is a refined Kishida force field yielding an average deviation of less than 1% between theoretical and experimental frequencies. The overall agreement between theoretical and gas-phase experimental intensity values is very satisfactory; an average deviation of 1.3, i.e., almost the same value as for the monomer in the preceding paper, is found. The experimental dimer/monomer intensity ratios are also accounted for in our calculations, the increase in the OH(D) stretching intensity being one order of magnitude larger than the two other stretching modes for which experimental data exist, namely the C=O and CH(D) stretching modes. A vibrational origin is attributed to the experimentally found large deviation from the localized harmonic value for the isotopic intensity ratio A/sub CD//A/sub CH.

Berckmans, D.; Figeys, H.P.; Marechal, Y.; Geerlings, P.

1988-01-14

9

Ab initio calculation of band absolute intensities in IR spectra  

NASA Astrophysics Data System (ADS)

Ab initio calculations in a harmonic approximation of absorption band absolute intensities in infrared spectra were carried out for 3 hydrocarbons and 14 halogenated hydrocarbons. The calculated data were compared with experimental values of the absolute absorption intensities. It is shown that a Hartree-Fock calculation method overestimates significantly (by an average of 66%) the integrated absolute intensities of the fundamental bands in the region 575-4000 cm-1. The deviation is reduced to 32% in the case of the MP2 method of accounting for electron correlations. Most of the overestimation occurs for bands corresponding to vibrations involving halogen atoms.

Pavlyuchko, A. I.; Vasilyev, E. V.; Gribov, L. A.

2012-01-01

10

Infrared Absorption Bands of Methane  

Microsoft Academic Search

The fine structure of the infrared bands of methane in the region 1-2mu has been observed, and four new bands located at 1.135, 1.187, 1.330 and 1.734mu. The 1.66mu band observed by Moorhead was re-observed with the result that some 14 new lines were added to it. The line spacing in all the bands in this region is of the

Will V. Norris; Hilbert J. Unger

1933-01-01

11

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

PubMed

IR absorption spectra of mixtures (CH3)2CO/HF and free (CH3)2CO molecules are recorded in the region of 4000-900cm(-1) with a Bruker IFS-125 HR vacuum Fourier spectrometer at room temperature with a resolution up to 0.02cm(-1). Spectral characteristics of the 2?(CO) overtone band of free acetone are reliably measured. The ?1(HF) and ?(CO) 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 CO 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 CO transitions. PMID:24128921

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

2013-09-27

12

Absolute absorption intensities of liquids: the determination of secondary infrared absorption intensity standards; absorption intensities of benzene, chlorobenzene and toluene  

Microsoft Academic Search

The presentation of absorption intensities in infrared spectra is usually limited to relative intensities, instead of absolute intensities. The measurement of absolute intensities would be facilitated by the existence of accepted secondary intensity standards that could be used to calibrate the path length of a transmission cell or the number of reflections in an attenuated total reflection cell. Under the

John E. Bertie; R. N. Jones; Yoram Apelblat; C. D. Keefe

1994-01-01

13

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

NASA Astrophysics Data System (ADS)

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

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

1992-12-01

14

Deconvolution of Mineral Absorption Bands: An Improved Approach  

Microsoft Academic Search

Although visible and near-infrared reflectance spectra contain absorption bands that are characteristic of the composition and structure of the absorbing species, deconvolving a complex spectrum is nontrivial. An improved approach to spectral deconvolution is presented here that accurately represents absorption bands as discrete mathematical distributions and resolves composite absorption features into individual absorptions bands. The frequently used Gaussian model of

Jessica M. Sunshine; Carle M. Pieters; Stephen F. Pratt

1990-01-01

15

Measurement of the sound absorption coefficient of materials with a new sound intensity technique  

Microsoft Academic Search

The paper presents a completely new measurement technique of the sound absorption properties of materials, based on the measurements of active intensity and sound energy density. It allows one to measure the absorption coefficient with a wide band excitation, to use frequency bands of any width and to make measurements both inside a tube or in situ. The intensity technique

Angelo Farina; Anna Torelli

16

Ab initio and LMO studies on the integrated intensities of infrared absorption bands of polyatomic molecules. 6. The formic acid monomer. Influence of isotopic substitution  

Microsoft Academic Search

Ab initio calculations are performed on the integrated intensities of the in-plane vibrations of the four H,D isotope combinations of the formic acid monomer. Within the framework of the double harmonic approximation and the finite difference approach for calculating the (delta..mu..\\/deltaQ\\/sub i\\/)â derivatives, the STO-3G minimal basis yields intensity results which deviate a factor 6.7 from the experimental values, known

Didier Berckmans; Hubert P. Figeys; Paul Geerlings

1988-01-01

17

Ab initio and LMO studies on the integrated intensities of infrared absorption bands of polyatomic molecules. 6. The formic acid monomer. Influence of isotopic substitution  

SciTech Connect

Ab initio calculations are performed on the integrated intensities of the in-plane vibrations of the four H,D isotope combinations of the formic acid monomer. Within the framework of the double harmonic approximation and the finite difference approach for calculating the (delta..mu../deltaQ/sub i/)/sub 0/ derivatives, the STO-3G minimal basis yields intensity results which deviate a factor 6.7 from the experimental values, known for the C=O, CH(D), and OH(D) stretching vibrations. Consequently this basis is inadequate for further work in this direction (influence of dimerization). The moderately sized 3.1 basis yields highly satisfactory results (average deviation factor 1.2) even better than the extended DTZPD basis (deviation factor 1.6). The CH(D) and OH(D) stretching intensities are analyzed in detail. Both theory and experiment indicate a A/sub CD/A/sub CH/ ratio of about 1.5 whereas the A/sub OD/A/sub OH/ ratio is of the order of 0.5, the value expected on the basis of a perfectly localized oscillator. The reason for the large deviation from this value in the CH(D) vibration is found to be related to the much larger vibrational impurity of the CH(D) mode as compared to the OH(D) case, the effects in the L/sup -1/ or L/sup tau/ matrices being reinforced in the intensity calculations as seen when the (delta..mu../deltaQ/sub i/)/sub 0/ is decomposed in terms of the contributions of the various internal coordinates (delta..mu../deltaR/sub j/)/sub 0/. A LMO decomposition of (delta..mu../deltaQ/sub OH(D)/)/sub 0/ shows that the most important contributions to the intensity of this mode originate from electronic rearrangements in the OH bond, where an incomplete orbital following effect upon stretching can be observed.

Berckmans, D.; Figeys, H.P.; Geerlings, P.

1988-01-14

18

Diode laser absorption spectrum of cold bands of C2HD at 6500 cm-1  

NASA Astrophysics Data System (ADS)

The absorption spectrum of acetylene-d has been observed at high resolution between 6470 and 6630 cm-1 using an external cavity diode laser. Three cold bands have been observed: the strong 2?1 band, the weaker ?1 + ?2 + 2?5 band, and the (?1 + ?3 + ?5)1 band, which gains its intensity through Coriolis resonance with 2?1. Centers of unblended lines are determined with an accuracy of approximately 10 MHz.

Hardwick, J. L.; Martin, Z. T.; Schoene, E. A.; Tyng, V.; Wolf, E. N.

2006-10-01

19

Raman band intensities of tellurite glasses  

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

20

Raman band intensities of tellurite glasses.  

PubMed

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

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

2005-05-15

21

Nonlinera Light Absorption Saturation in Direct Band Gap Semiconductors  

NASA Astrophysics Data System (ADS)

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

Minassian, Hayk; Melikyan, Armen

2001-03-01

22

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

SciTech Connect

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

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

2010-11-15

23

Plasmon band gap generated by intense ion acoustic waves  

SciTech Connect

In the presence of an intense ion acoustic wave, the energy-momentum dispersion relation of plasmons is strongly modified to exhibit a band gap structure. The intensity of an ion acoustic wave might be measured from the band gap width. The plasmon band gap can be used to block the nonlinear cascading channel of the Langmuir wave decay.

Son, S.; Ku, S. [Courant Institute of Mathematical Sciences, New York University, New York 10012 (United States)

2010-02-15

24

Interpretation of Absorption Bands in Airborne Hyperspectral Radiance Data  

PubMed Central

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

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

2009-01-01

25

Constraints on the absorption band model of Q  

NASA Astrophysics Data System (ADS)

First order models for the combined depth and frequency dependence of Q are derived and tested using several independent constraints. (1) Using a microphysics approach, the adoption of an absorption band as a first-order model for the frequency dependence of Q is justified, and the expected depth behavior of relaxation times in the earth is derived. The significant new parameter in this model of Q is ?2, the period at the half-amplitude point of the high frequency end of the absorption band. (2) Using observed body-wave spectra, the existence of a frequency dependence in Q is proved, and the average location of that frequency dependence (i.e., ?2) is estimated to be in the range 1 to 2.5 Hz. (3) Under the constraints of Q model ratios, the depth dependence of ?2 is estimated by assuming that a free-oscillation and a body-wave Q model both measure Q from the same absorption band. The resulting ?2 is about 0.04 s in the upper 200 km and then increases exponentially with depth in the mantle to about 1.9 at the core mantle boundary. The Q model ratios are better satisfied if a second absorption band is hypothesized to operate in the depth range of the asthenosphere. In that case, ?2 for the mantle absorption band varies from about 0.09 s in the first 200 km to 4.0 s at 2886 km, and ?2 for the asthenosphere absorption band is about 0.005 s in the depth range 35-220 km. (4) Both classes of Q models are tested in the time domain using synthetic seismograms of Russian and American nuclear explosions. Although trade-offs between source and mantle transfer functions preclude further refinement of the models at this time, a compatibility is demonstrated between the double absorption band model and time domain constraints, including arrival time and pulse shape.

Lundquist, Gary M.; Cormier, Vernon C.

1980-10-01

26

A radiation source developed for broad band optical absorption spectroscopy measurements  

Microsoft Academic Search

In order to investigate the post-arc period and the hot gas regions surrounding the electrical arc in circuit breakers, a broad band radiation source has been developed to perform absorption spectroscopy measurements. The source consists of a Z-pinch electrical discharge in which the high temperature and the high density argon plasma obtained at maximum compression produces an extremely intense continuous

D. Hong; G. Sandolache; K. Lan; J. M. Bauchire; E. LeMenn; C. Fleurier

2003-01-01

27

Intensity of the v2 Infrared Band of Methane  

Microsoft Academic Search

An expression for the absolute intensity of the v2 infrared ``forbidden'' fundamental band of methane-type molecules has been obtained and the observed intensity of the methane band has been quantitatively explained. The expression, in principle, allows one to decide on the sign of the ratio of the bond moment of the molecule to its bond moment derivative. For the methane

J. Herranz

1962-01-01

28

Imaging Breathing Rate in the CO2Absorption Band  

Microsoft Academic Search

Following up on our previous work, we have developed one more non-contact method to measure human breathing rate. We have retrofitted our mid-wave infra-red (MWIR) imaging system with a narrow band-pass filter in the CO2 absorption band (4.3 mum). This improves the contrast between the foreground (i.e., expired air) and background (e.g., wall). Based on the radiation information within the

Jin Fei; Zhen Zhu; Ioannis Pavlidis

2005-01-01

29

Optical spin orientation in ruby by Zeeman-selective U-band absorption  

NASA Astrophysics Data System (ADS)

Optically induced magnetization in ruby at room temperature has been observed by excitation of the U-absorption band. Optically induced Zeeman coherence associated with different pairs of Zeeman sublevels has also been observed as free induction decay signals. Zeeman-selectivity in the U-band transition is derived by assuming a spin-orbit coupling which provides a small fraction of the intensity of the U-band. Calculation of the relative transition probability yields different Zeeman population distributions depending on the types of irreducible representations used for the spin-orbit coupling.

Takagi, Y.; Fukuda, Y.; Hashi, T.

1985-08-01

30

Absorption coefficient of luminescent bodies in the emission band  

NASA Astrophysics Data System (ADS)

Einstein's theory associating the coefficients of absorption, induced emission and spontaneous emission cannot be applied to luminescent systems, because the radiative transitions occur with the absorption or emission of phonons. It may be generalised to include luminescent systems by the use of a hollow sphere whose internal walls are covered with a substance irradiated by a Wood lamp, placed at the centre of the sphere. From this we determine the absorption coefficient of the luminescent substance in the emission band. Work performed in part at Groupe de Physique du Solide de l'Ecole Normale Superieure.

Alexic', A.; Nikoli?, K.; Buri?, J.; Magnant, D.; de La Garanderie, H. Payen

1982-02-01

31

Peculiarities of vertical atmosphere absorption in the millimeter wave band  

Microsoft Academic Search

One complete year of continuous observations of vertical radiation of the atmosphere in two points of millimeter wave band (94 and 38 GHz) was conducted. The total vertical absorption, liquid and vapor water content of atmosphere, and average (effective) temperature of clouds are restored on the basis of these two-frequency radiometric data. Numerous cases of abnormal differences between experimental and

Nikolay V. Ruzhentsev

2003-01-01

32

Wide-Band Ultrasonic Transducers: Design, Calibration, Radiation Intensity Measurement.  

National Technical Information Service (NTIS)

Transducers for ultrasonic testing reproduce short pulses. The band-pass is conditioned by natural frequencies. Calibration allows to find response, pressure, intensity and beam shape. Two methods are used to reach 10 MHz. (Atomindex citation 08:310895)

J. L. Garnier C. Gazanhes

1976-01-01

33

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

34

Absolute Line Intensities for the nu6 Band of H2O2.  

PubMed

The purpose of this work was to obtain reliable absolute intensities for the nu6 band of H2O2. It was undertaken because strong discrepancies exist between the different nu6 band intensities which are presently available in the literature (A. Perrin, A. Valentin, J.-M. Flaud, C. Camy-Peyret, L. Schriver, A. Schriver, and P. Arcas, J. Mol. Spectrosc. 1995. 171, 358), (R. May, J. Quant. Radiat. Transfer 1991. 45, 267), and (R. L. Sams, personal communication). The method which was chosen in the present work was to measure simultaneously the far-infrared absorptions and the nu6 absorptions of H2O2. Consequently, Fourier transform spectra of H2O2 were recorded at Giessen in a spectral range (370-1270 cm-1) which covers both the R branch of the torsion-rotation band and the P branch of the nu6 band which appear at low and high wavenumbers, respectively. From the low wavenumber data, the partial pressure of H2O2 present in the cell during the recording of the spectra was determined by calibrating the observed absorptions in the torsion-rotation band with intensities computed using the permanent H2O2 dipole moment measured by Stark effect (A. Perrin, J.-M. Flaud, C. Camy-Peyret, R. Schermaul, M. Winnewisser, J.-Y. Mandin, V. Dana, M. Badaoui, and J. Koput, J. Mol. Spectrosc. 1996. 176, 287-296) and [E. A. Cohen and H. M. Pickett, J. Mol. Spectrosc. 1981. 87, 582-583). In the high frequency range, this value of the partial pressure of H2O2 was used to measure absolute line intensities in the nu6 band. Finally, the line intensities in the nu6 band were fitted using the theoretical methods described in detail in our previous works. Using these new results on line intensities together with the line position parameters that we obtained previously, a new synthetic spectra of the nu6 band was generated, leading to a total band intensity of 0.185 x 10(-16) cm-1/(molecule.cm-2) at 296 K. It has to be pointed out that the new line intensities agree to within the experimental uncertainties with the individual line intensity measurements performed previously by May and by Sams. Copyright 1999 Academic Press. PMID:10191160

Klee; Winnewisser; Perrin; Flaud

1999-05-01

35

Optical Absorption and Emission Bands of SiC 2 in Carbon Stars  

NASA Astrophysics Data System (ADS)

Observations of the Merrill-Sanford bands of SiC2 in the 4750--5050 A spectral region, seen in absorption in some carbon stars and in emission in IRAS 12311-3509, are reported. Vibrational band assignments based on recent laser-based laboratory electronic spectroscopy of this molecule constitute substantial revisions compared with earlier work. Vibrational hot bands are very strong when present in carbon stars, but were greatly weakened in T Mus for a time in 1994, indicating that the bands were then formed in a cooler region than that typical of carbon star photospheres. Emission bands of SiC2, with intensities that are consistent with optical excitation of cool gas, appear in IRAS 12311-3509 which is probably a J-type carbon star occulted by a dusty disk so that the star is seen by reflection from material out of the plane of the disk.

Sarre, P. J.; Hurst, M. E.; Lloyd Evans, T.

1996-11-01

36

Influence of blue valence absorption band on nonlinear absorption in dysprosium bisphthalocyanine studied by open aperture z-scan  

NASA Astrophysics Data System (ADS)

Study of the optical limiting (OL) effect in a THF solution of bis(2,3,9,10,16,17,23,24-octabutylphthalocyaninato) dysprosium(III) (BuPc2Dy) by the open aperture z-scan technique with 350 ps laser pulses at 532 nm is presented. The presence of the blue valence (BV) band in UV-Vis absorption spectra of bisphthalocyanines (bisPcs) adds complexity to the nonlinear absorption behavior. Luminescence measurements showed that two channels of excitation exist for BuPc2Dy when illuminating at 532 nm. We suggest a new theoretical model which describes the interaction of a bisPc with an intense laser pulse at 532 nm. Excited state lifetimes and the Q band quantum yield were also determined.

Karpo, Alexey B.; Zasedatelev, Anton V.; Pushkarev, Victor E.; Krasovskii, Vitaly I.; Tomilova, Larisa G.

2013-10-01

37

Valence-band photoemission and optical absorption in nickel compounds  

Microsoft Academic Search

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

Atsushi Fujimori; Fujio Minami

1984-01-01

38

Absolute Intensities of the OH Meinel bands in the Nightglow  

NASA Astrophysics Data System (ADS)

Flux-calibrated high resolution spectra of the night sky have been accumulated for the spectral region of 314 - 1054 nm. The spectra are obtained from two sources: (a) the ESI spectrograph on the Keck II telescope at Mauna Kea with a spectral resolution of 6000 and a temporal resolution of 3000 seconds and (b) coadded spectra (1) from the UVES spectrograph on the VLT (Kueyen) telescope at Cerro Paranal with a spectral resolution of 50000. Emission from the OH X2? (v'=3-9) Meinel bands are prominent in the spectra allowing absolute intensities to be measured for discrete rotational lines in the main rotational branches for 16 vibrational bands in the ESI spectra (? v = -6 to -3) and 20 vibrational bands in the UVES spectrum (? v = -7 to -3). Comparison of the band intensities to the earlier photographic measurements of Krassovsky et al.(2) show a systematic deviation with wavelength similar to that deduced by Adler-Golden(3). Several emission bands are observed from most upper state vibrational levels. Comparisons of the band intensity ratios and the rotational branch intensity ratios for these bands show systematic deviations from those calculated using the existing sets of emission coefficients. Progress will be reported on the re-evaluation of the dipole moment function (4) using the present absolute intensities to obtain an improved set of OH emission coefficients. This work was partially supported by NSF grant ATM-0139344. (1) R. W. Hanuschik, Astron. Astrophys. 112, 1157 (2003). (2) V. I. Krassovsky et al., Planet. Space Sci. 9, 883 (1962). (3) S. Adler-Golden, J. Geophys. Res. 102, 19969 (1997). (4) D. D. Nelson et al., J. Chem. Phys. 93, 7003 (1990).

Cosby, P. C.; Slanger, T. G.

2004-12-01

39

Intensity-induced absorption in ZnSe  

SciTech Connect

In a particular sample of ZnSe, working at 10 ..mu..m, a nonlinear absorption was observed that was generated by light intensities greater than 100 MW/cm/sup 2/. This absorption was subsequently bleached by light intensities over 600 MW/cm/sup 2/. This result was obtained using 10-ps pulses from the Los Alamos National Laboratory Free-Electron Laser. 5 refs., 4 figs.

Sollid, J.E.; Feldman, D.W.; Phipps, C.R. Jr.; Warren, R.W.

1988-01-01

40

Coriolis intensity perturbations of the nu/sub 4/ band of SF/sub 6/  

SciTech Connect

In the nu/sub 4/ band of /sup 32/SF/sub 6/ the intensity of absorption by the R branch has been found to exceed that of the P branch by 38%. This is substantially larger than the 15% excess that one calculates from ordinary rotational statistics and the nonnegligible width of the band. The authors attribute this imbalance to Coriolis interactions between the rovibrational sublevels (a) of the nu/sub 3/ and nu/sub 4/ excited vibrational states, and (b) of the ground vibrational state and the l = 1 (F/sub 1g/) level of the nu/sub 3/ + nu/sub 4/ combination state. The intensities of the observed P- and R-branch lines have a superposed Herman-Wallis type F factor of the form F(m) = (1 + xi/sub 4/m)/sup 2/, where m = -J for the P branch, 0 for the Q branch, and +(J + 1) for the R branch, and J is the rotational sublevel in the ground state. Xi/sub 4/ was determined by a new method from the relative intensities of the P, Q, and R branches. New evidence is reported that supports an earlier conclusion that the first derivatives of the dipole moment function, ..mu../sub 3/ = delta ..mu../delta q/sub 3/ and ..mu../sub 4/= delta ..mu../deltaq/sub 4/, have the same sign. The corresponding Coriolis effect is calculated for UF/sub 6/. It is predicted that Coriolis interactions induce weak absorption in the nu/sub 6/ bands of SF/sub 6/ and UF/sub 6/, which would otherwise be inactive according to selection rules for strong infrared absorption or Raman scattering. An order of magnitude estimate of the absorption intensity of the induced nu/sub 6/ band of SF/sub 6/ agrees with a recent observation of that infrared spectral region. 50 references, 4 figures, 10 tables.

Person, W.B.; Krohn, B.J.

1983-01-01

41

Correlation Between Intensities of Auroral Absorption and Precipitated Electrons.  

National Technical Information Service (NTIS)

Particle detectors on the Alouette I satellite and on rockets have been used to study the correlation between the intensity of electrons with energies greater than 40 keV and the intensity of auroral radio-wave absorption. The average relationship between...

D. H. Jelly I. B. McDiarmid J. R. Burrows

1964-01-01

42

Absolute line intensities and self-broadening coefficients in the ?3 - ?1 band of carbon dioxide  

NASA Astrophysics Data System (ADS)

Using a tunable diode-laser spectrometer, we have measured the self-broadening coefficients and strengths of 26 absorption lines in the ?3 - ?1 band of 12CO2 and 13CO2 at room temperature. These lines, ranging from P(34) to R(40), are located around 960.9 and 913.4 cm-1, respectively for the 12CO2 and 13CO2 molecules. The collisional widths and the intensities were obtained by fitting Voigt and Rautian and Sobel'man profiles to the measured shapes of the lines. From the individual line intensities and using a least-squares method, we have determined the vibrational band strength as well as the Herman-Wallis factors for the ?3 - ?1 band of 12CO2 and 13CO2.

Delière, Quentin; Fissiaux, Laurent; Lepère, Muriel

2012-02-01

43

The diffuse interstellar band carriers in interstellar space: all intense bands calculated from He doubly excited states embedded in Rydberg Matter  

NASA Astrophysics Data System (ADS)

The interpretation of the almost 300 diffuse interstellar bands (DIBs) is one of the most long-standing problems in interstellar spectra. The only model showing agreement with a large number of DIBs (>60 bands) is based on transitions in doubly excited atoms embedded in the condensed phase named Rydberg Matter (RM). A similar model is now used to precisely calculate all intense bands from the high-resolution survey by Galazutdinov et al., 63 bands in total. Thus, the RM model interprets at present 120 DIBs accurately in a consistent manner, almost half of the number of DIBs. The origin of almost all intense DIBs is shown to be absorption during electron transitions between co-planar doubly excited He atoms inside RM, and from singly excited He atoms to doubly excited He atoms inside RM. The average error in the assignments is 4 cm-1 (1.4 Å), comparable to the band width. The intense but broad DIB 578.0 nm is part of a series of 10 bands interpreted as RM transitions from n'' = 5 to the conduction band limit. The shape of DIB 579.7 nm is consistent with a rotational band from symmetric top RM clusters at approximately 100 K. Good agreement with observational results like band shapes and correlations among various bands is found.

Holmlid, Leif

2008-02-01

44

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

NASA Astrophysics Data System (ADS)

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.; Yu, W.; Zhuo, H. B.; Zhou, C. T.; Ma, Y. Y.; Yang, X. H.; Yu, T. P.; Zou, D. B.; Luan, S. X.; Yin, Y.; Shao, F. Q.; Peng, X. J.

2013-07-01

45

New Optical Absorption Bands in Atomic Layer Superlattices  

NASA Astrophysics Data System (ADS)

Using atomic layer-by-layer molecular beam epitaxy, atomic layer superlattices can be constructed that exhibit new electronic, optical and lattice effects not present in the individual components. In particular, new optical transitions giving rise to sharp absorption peaks can be created by placing a layer of a material with occupied source states next to a layer of another material with unoccupied destination states. We combine atomic layers of SrTiO3 and LaMnO3 into superlattice structures with component layers as thin as single monolayer and find a new absorption band due to a transition from manganese- to titanium-derived states. The energy of the new transition depends on how the bands line up at the interface. Furthermore, a substantial shift of spectral weight occurs as well, while retaining a constant sum rule. This work was supported by the Department of Energy Basic Energy Sciences at the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana. This work was done in collaboration with Xiaofang Zhai, Mao Zheng, Amish Shah, Chandra Mohapatra, and Jian-Min Zuo.

Eckstein, James

2011-03-01

46

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

47

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

NASA Astrophysics Data System (ADS)

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

Pommerol, Antoine; Schmitt, Bernard

2008-12-01

48

Intensities in Singlet-Triplet Bands of Diatomic Molecules  

Microsoft Academic Search

Intensity formulae are found for the rotational structure of bands arising from transitions between a singlet and a triplet state of a diatomic molecule. These intercombinations occur because the wave functions which diagonalize the orbit-spin interaction contain both singlet and triplet terms. In the transition 1Sigma-3Sigma two cases arise, according as the two states have the same or opposite symmetry

Robert Schlapp

1932-01-01

49

Diode Laser Measurements of CO2 Hot Band Line Intensities at High Temperature Near 4.3 ?m  

NASA Astrophysics Data System (ADS)

Diode laser measurements of CO2 absorption spectra have been made in the 2270-2295 cm-1 spectral region at low pressure (<25 mbar) and at temperatures up to 800 K. Line intensities of several parallel hot bands (20013 <-- 20003, 12212 <-- 12202, 20012 <-- 20002, 12211 <-- 12201, 20011 <-- 20001,and 01121 <-- 01111 bands of 12C16O2, and 01111 <-- 01101 band of 13C16O2) have been obtained. The data are analyzed to derive squared dipole-moment matrix elements and band intensities. Our results for the 01111 <-- 01101 band of 13C16O2 are consistent with previous measurements performed at room temperature. The values obtained for the 12C16O2 bands investigated in this work, which to our knowledge have not been analyzed previously, are in good agreement with available theoretical predictions.

Rosenmann, L.; Langlois, S.; Taine, J.

1993-04-01

50

Absorption of radiation by electrons in intense magnetic fields  

Microsoft Academic Search

This paper presents a quantum-mechanical treatment of photon absorption by a homogeneous electron plasma in a uniform magnetic field, in the anisotropic limit for which the electron energies are concentrated in their motion parallel to the field. The results are intended to be appropriate especially for intense fields (in which quantization effects and highly anisotropic plasmas are to be expected).

J. K. Daugherty; J. Ventura

1978-01-01

51

Nonlinear absorption in biological tissue for high intensity focused ultrasound  

Microsoft Academic Search

In recent years the propagation of the high intensity focused ultrasound (HIFU) in biological tissue is an interesting area due to its potential applications in non-invasive treatment of disease. The base principle of these applications is the heat effect generated by ultrasound absorption. In order to control therapeutic efficiency, it is important to evaluate the heat generation in biological tissue

Xiaozhou Liu; Junlun Li; Xiufen Gong; Dong Zhang

2006-01-01

52

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

PubMed

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

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

2013-05-16

53

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

54

H2O\\/OH-Associated Absorption Band Depth Relationships in Mineral Reflectance Spectra  

Microsoft Academic Search

Reflectance spectra of various minerals exhibit complex relationships between water\\/OH-associated absorption bands. Strong bands in the 3µm region do not necessarily imply significant hydration or large water contents.

E. A. Cloutis

2001-01-01

55

Clustering of germanium atoms in silica glass responsible for the 3.1 eV emission band studied by optical absorption and X-ray absorption fine structure analysis  

Microsoft Academic Search

Correlation between the 3.1eV emission band and local atomic configuration was systematically examined for Ge+ implanted silica glass by UV–vis optical absorption spectroscopy and X-ray absorption fine structure (XAFS) analysis. The 2.7eV emission band, commonly observed in defective silica, was replaced by the sharp and intense 3.1eV emission band for the Ge+ fluence>2×1016cm?2, in which UV–vis absorption spectra suggested clustering

Tomoko Yoshida; Shunsuke Muto; Leny Yuliati; Hisao Yoshida; Yasuhiro Inada

2009-01-01

56

Dependence of Raman spectra G' band intensity on metallicity of single-wall carbon nanotubes  

Microsoft Academic Search

We report the peculiar behavior of the G' band Raman intensity, which is dependent on the metallicity of single-wall carbon nanotubes (SWCNTs). In the metallic SWCNTs, the G' band intensity was enhanced relative to the G band intensity, while the G' band intensity was suppressed in the semiconducting SWCNTs. Resonance Raman spectroscopy (using laser energies of Elaser=2.41 , 1.96, 1.58,

Ki Kang Kim; Jin Sung Park; Sung Jin Kim; Hong Zhang Geng; Kay Hyeok An; Cheol-Min Yang; Kentaro Sato; Riichiro Saito; Young Hee Lee

2007-01-01

57

Dependence of the Raman G' band intensity on metallicity of single-wall carbon nanotubes  

Microsoft Academic Search

We report the peculiar behavior of the G'-band Raman intensity, which is dependent on the metallicity of single-wall carbon nanotubes (SWCNTs). In the metallic SWCNTs, the G'-band intensity was enhanced relative to the G-band intensity, while the G'-band intensity was suppressed in the semiconducting SWCNTs. Resonance Raman spectroscopy (using laser energies of Elaser = 2.41 eV, 1.96 eV, 1.58 eV,

Ki Kang Kim; Jin Sung Park; Sung Jin Kim; Hong Zhang Geng; Kay Hyeok An; Cheol-Min Yang; Kentaro Sato; Riichiro Saito; Young Hee Lee

2008-01-01

58

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

59

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

2013-10-21

60

Optical Absorption and Photoconductivity in the Band Edge of beta-Ga2O3  

Microsoft Academic Search

Optical absorption and photoconductivity have been observed in the ultraviolet in single crystals of nominally pure beta-Ga2O3. At room temperature a steep absorption edge, characteristic of a band-to-band transition, is observed at 2700 Å. The edge is shifted approximately 100 Å toward shorter wavelengths when the temperature is reduced to 77°K. Photoconductivity begins coincident with the absorption edge at 77°K,

H. H. Tippins

1965-01-01

61

Narrow saturated absorption resonances in the transmission band of an active interferometer  

Microsoft Academic Search

The shape of the transmission band of an active interferometer, a resonator with amplification and absorption cells excited\\u000a by an external signal, is studied. Upon tuning the external signal frequency, the narrow saturated absorption resonances can\\u000a be observed in the transmission band of the interferometer. It is shown that, by varying the gain, the resonance absorption\\u000a amplitude can be compensated

S. N. Bagaev; A. A. Kurbatov; E. A. Titov

2000-01-01

62

Ultrafast absorption of intense x rays by nitrogen molecules  

SciTech Connect

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

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

2012-06-07

63

Absorption coefficient of luminescent bodies in the emission band  

Microsoft Academic Search

Einstein's theory associating the coefficients of absorption, induced emission and spontaneous emission cannot be applied to luminescent systems, because the radiative transitions occur with the absorption or emission of phonons. It may be generalised to include luminescent systems by the use of a hollow sphere whose internal walls are covered with a substance irradiated by a Wood lamp, placed at

A. Alexic; K. Nikolic; J. Buric; D. Magnant; H. Payen de La Garanderie

1982-01-01

64

On the origin of the 265 nm absorption band in AlN bulk crystals  

NASA Astrophysics Data System (ADS)

Single crystal AlN provides a native substrate for Al-rich AlGaN that is needed for the development of efficient deep ultraviolet light emitting and laser diodes. An absorption band centered around 4.7 eV (~265 nm) with an absorption coefficient above 1000 cm-1 is observed in these substrates. Based on density functional theory calculations, substitutional carbon on the nitrogen site introduces absorption at this energy. A series of single crystalline wafers were used to demonstrate that this absorption band linearly increased with carbon, strongly supporting the model that CN- is the predominant state for carbon in AlN.

Collazo, Ramón; Xie, Jinqiao; Gaddy, Benjamin E.; Bryan, Zachary; Kirste, Ronny; Hoffmann, Marc; Dalmau, Rafael; Moody, Baxter; Kumagai, Yoshinao; Nagashima, Toru; Kubota, Yuki; Kinoshita, Toru; Koukitu, Akinori; Irving, Douglas L.; Sitar, Zlatko

2012-05-01

65

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

Microsoft Academic Search

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

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

1970-01-01

66

Effective parametrization of overlapping water vapor and carbon dioxide absorption bands  

Microsoft Academic Search

This report presents a new effective method which can be used to compute both the transmittance and the atmospheric radiation fluxes in the overlapping water vapor and carbon dioxide absorption bands.

K. M. Firsov; A. A. Mitsel

1997-01-01

67

Position and Confidence Limits of an Extremum: The Determination of the Absorption Maximum in Wide Bands.  

ERIC Educational Resources Information Center

|Discusses the determination of the position of the absorption maximum in wide bands as well as the confidence limits for such calculations. A simple method, suited for pocket calculators, for the numerical evaluation of these calculations is presented. (BB)|

Heilbronner, Edgar

1979-01-01

68

Enhancement of broadband optical absorption in photovoltaic devices by band-edge effect of photonic crystals.  

PubMed

We numerically investigate broadband optical absorption enhancement in thin, 400-nm thick microcrystalline silicon (µc-Si) photovoltaic devices by photonic crystals (PCs). We realize absorption enhancement by coupling the light from the free space to the large area resonant modes at the photonic band-edge induced by the photonic crystals. We show that multiple photonic band-edge modes can be produced by higher order modes in the vertical direction of the Si photovoltaic layer, which can enhance the absorption on multiple wavelengths. Moreover, we reveal that the photonic superlattice structure can produce more photonic band-edge modes that lead to further optical absorption. The absorption average in wavelengths of 500-1000 nm weighted to the solar spectrum (AM 1.5) increases almost twice: from 33% without photonic crystal to 58% with a 4 × 4 period superlattice photonic crystal; our result outperforms the Lambertian textured structure. PMID:24105557

Tanaka, Yoshinori; Kawamoto, Yosuke; Fujita, Masayuki; Noda, Susumu

2013-08-26

69

Absorption and photodissociation in the Schumann-Runge bands of molecular oxygen in the terrestrial atmosphere  

Microsoft Academic Search

The penetration in the terrestrial atmosphere of solar radiation corresponding to the spectral range of the Schumann-Runge bands of molecular oxygen was analyzed between 1750 and 2050. The variation of the absorption cross section with temperature was taken into account and it is shown that average O2 absorption cross sections cannot lead to the computation of the molecular oxygen photodissociation

G. Kockarts

1976-01-01

70

On the New Absorption Bands of the Oxygen Molecule in the Far Ultraviolet Region  

Microsoft Academic Search

The absorption bands of the oxygen molecule in the extreme ultraviolet region were studied using a 3-meter grazing incidence vacuum spectrograph. Two new progressions of bands were found in the region between 1200A and 1290A (one of which is considered to be a member of the Rydberg series converging to the first ionization potential of the oxygen molecule). There were

Yoshio Tanaka

1952-01-01

71

Nature of the bands of the electronic absorption spectra of acid solutions of aromatic. cap alpha. ,. beta. -unsaturated ketones  

SciTech Connect

The electronic absorption spectra of 34 unsaturated ketones were measured in solutions of 93% sulfuric acid. The curves of the absorption of the hydroxycarbonium ions formed as a result of protonation of the investigated compounds in sulfuric acid solutions, are characterized by the presence of two intense bands of the ..pi..-..pi..* type in the region of 330-630 nm. The nature of the bands of the investigated compounds is discussed on the basis of the calculated data, obtained according to the PPP method, with an estimation of the localization and charge transfer numbers of the electronic transitions on individual fragments. According to the data of calculation and graphical analysis it was shown that the long-wave band in a series of derivatives of diphenylmethane and diphenyl oxide (I, II) should be assigned to the protonated cinnamoyl (C) fragment, while the second (short-wave) band should be assigned to the protonated acetophenone (A) fragment. The long-wave band in the series of derivatives of diphenyl sulfide, diphenylamine, and N-methyldiphenylamine (III-V) was assigned to the protonated acetophenone fragment. The resonance, dipole-dipole and exchange interactions of the fragments A and C is analyzed, and an attempt was undertaken to distinguish various types of interactions.

Chuev, V.P.; Nikitchenko, V.M.; Lavrushin, V.F.

1985-11-01

72

Remote measurement of surface pressure using absorption in the oxygen A-band  

NASA Astrophysics Data System (ADS)

A simple technique is described that measures the atmospheric absorption in the oxygen A-band near 0.76 microns. A narrow interference filter is tilted so that its passband scans through the two branches of the absorption band. By viewing the direct solar beam a differential absorption measurement of the mass of oxygen in the optical path is obtained which is then compared to surface pressure. A transmittance model is described which gives results that agree well with the measurements. The model is also used to investigate the possible extension of the technique to a satellite-borne instrument for estimating surface pressure.

Barton, I. J.; Scott, J. C.

1986-10-01

73

ASSIGNMENT OF 5069 A DIFFUSE INTERSTELLAR BAND TO HC{sub 4}H{sup +}: DISAGREEMENT WITH LABORATORY ABSORPTION BAND  

SciTech Connect

Krelowski et al. have reported a weak, diffuse interstellar band (DIB) at 5069 A which appears to match in both mid-wavelength and width the A {sup 2}{Pi}{sub u}-X {sup 2}{Pi}{sub g} gas-phase origin absorption band of HC{sub 4}H{sup +}. Here, we present laboratory rotational profiles at low temperatures which are then compared with the 5069 A DIB using {approx}0.1 and 0.3 A line widths based on a realistic line-of-sight interstellar velocity dispersion. Neither the band shape nor the wavelength of the maximum absorption match, which makes the association of the 5069 A DIB with HC{sub 4}H{sup +} unlikely. The magnetic dipole transition X {sup 2}{Pi}{sub g} {Omega} = 1/2{yields}X {sup 2}{Pi}{sub g} {Omega} = 3/2 within the ground electronic state which competes with collisional excitation is also considered. In addition, we present the laboratory gas-phase spectrum of the A {sup 2}{Pi}{sub u}-X {sup 2}{Pi}{sub g} transition of HC{sub 4}H{sup +} measured at 25 K in an ion trap and identify further absorption bands at shorter wavelengths for comparison with future DIB data.

Maier, J. P.; Chakrabarty, S.; Mazzotti, F. J.; Rice, C. A.; Dietsche, R. [Department of Chemistry, University of Basel, Klingelbergstr. 80, CH-4056 Basel (Switzerland); Walker, G. A. H. [1234 Hewlett Place, Victoria, BC V8S 4P7 (Canada); Bohlender, D. A., E-mail: j.p.maier@unibas.ch [National Research Council of Canada, Herzberg Institute of Astrophysics, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)

2011-03-10

74

Deposition of energy of high-intensity laser radiation in photo-excited wide band-gap dielectrics  

NASA Astrophysics Data System (ADS)

In this paper we analyze space distribution of energy deposited from high-intensity laser radiation in wide band-gap materials ionized by the radiation. Considering the case of ultra-short laser pulses, we assume photo-ionization to be a dominating mechanism of non-linear absorption. The photo-ionization is described by recently derived formula for the photo-ionization rate rather than by the Keldysh formula. The energy deposition is studied by means of numerical modeling for a system of two coupled nonlinear equations - equation of intensity transfer for laser radiation and rate equation for time evolution of free-electron density. Two characteristic regimes of the ultra-fast laser-solid interactions are analyzed: 1) the regime of photo-ionization suppression at intensity above few TW/cm2; 2) the regime of photo-ionization singularity occurring at intensity close to 10 TW/cm2. In the first regime specific propagation conditions are provided with successful transfer of radiation energy over a large distance at low loss through free-electron absorption and weak avalanche ionization. The singularity effect results in extremely intensive generation of free electrons in sub-surface layer of irradiated dielectric and locking of the ionizing radiation in a very thin surface layer. The singularity threshold corresponds to the threshold of the radiation locking. Presented results are compared with those obtained with the formula for the photo-ionization rate in the approximation of parabolic energy bands.

Gruzdev, V. E.; Chen, J. K.

2007-03-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

76

Lineshape Analysis of the 0-0 Exciton Absorption Band in Pyrene Crystals  

Microsoft Academic Search

The lineshape and the line-width of the 0-0 exciton absorption band associated with the transition 1B3u{<=ftarrow}1A1g are investigated over the temperature range from 300 K to 126 K. The line-width changes linearly with temperature in the b-polarized 0-0 band (b-band), indicating that the exciton state in pyrene is described by a weak scattering scheme. The high-energy side of the b-band

Atsuo Matsui; Kenichi Mizuno

1982-01-01

77

Emergence of very broad infrared absorption band by hyperdoping of silicon with chalcogens  

NASA Astrophysics Data System (ADS)

We report the near through mid-infrared (MIR) optical absorption spectra, over the range 0.05-1.3 eV, of monocrystalline silicon layers hyperdoped with chalcogen atoms synthesized by ion implantation followed by pulsed laser melting. A broad mid-infrared optical absorption band emerges, peaking near 0.5 eV for sulfur and selenium and 0.3 eV for tellurium hyperdoped samples. Its strength and width increase with impurity concentration. Its strength decreases markedly with subsequent thermal annealing. The emergence of a broad MIR absorption band is consistent with the formation of an impurity band from isolated deep donor levels as the concentration of chalcogen atoms in metastable local configurations increases.

Umezu, Ikurou; Warrender, Jeffrey M.; Charnvanichborikarn, Supakit; Kohno, Atsushi; Williams, James S.; Tabbal, Malek; Papazoglou, Dimitris G.; Zhang, Xi-Cheng; Aziz, Michael J.

2013-06-01

78

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

PubMed

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

Ndengué, Steve Alexandre; Schinke, Reinhard; Gatti, Fabien; Meyer, Hans-Dieter; Jost, Rémy

2012-12-11

79

A new parameterization of the absorptance due to the 15-?m band system of carbon dioxide  

NASA Astrophysics Data System (ADS)

A new parameterization for the absorptance due to the 15-?m band system of CO2 is presented. This parameterization is based on that described by Kiehl and Ramanathan (1983), but is more computationally efficient than the original parameterization. A Voigt line correction factor has been added to the parameterization to improve the accuracy of the model for stratospheric applications. Comparison of this band model with absorptances calculated from line-by-line results and a narrow band Malkmus model show good agreement for both homogeneous and inhomogeneous atmospheric cases. Radiative flux changes due to increases in CO2 are also compared between the new broadband model, line-by-line model, and the narrow-band model and are found to be in good agreement. The new broadband model is employed in the latest version of the NCAR Community Climate Model (CCM1).

Kiehl, J. T.; Briegleb, B. P.

1991-05-01

80

Cold Jet Infrared Absorption Spectroscopy: The nu3 Band of UF6  

Microsoft Academic Search

The nu3 band of UF6 is studied at a low rotational and vibrational temperature using a tunable diode laser. Infrared absorption in a pulsed supersonic free jet of UF6 is observed by phase sensitive detection synchronized with the pulse frequency. Absorption lines from P(21) to R(27) are measured for 238UF6 with a Doppler limit resolution. Only Q-branch peaks are observed

Michio Takami; Toshiyuki Oyama; Tsunao Watanabe; Susumu Namba; Ryohei Nakane

1984-01-01

81

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

Microsoft Academic Search

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

B. H. Foing; P. Ehrenfreund

1994-01-01

82

Picosecond laser induced electric field modulation of carotenoid absorption bands  

SciTech Connect

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

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

1994-04-01

83

Survey of Gaseous and Hydrometeor Absorption in the Atmosphere in The 10-100 Ghz Frequency Band.  

National Technical Information Service (NTIS)

Spectrum congestion in the lower frequencies will probably force future space communications to the 10-100 GHz band. In this region atmospheric attenuation is severe due to gaseous absorption and hydrometeorological absorption and scattering. Selection of...

M. S. Fowler A. H. LaGrone

1969-01-01

84

X-ray absorption spectra reveal the inapplicability of the single-band Hubbard model to overdoped cuprate superconductors.  

PubMed

X-ray absorption spectra on the overdoped high-temperature superconductors Tl2Ba2CuO(6+delta) and La(2-x)SrxCuO(4+/-delta) reveal a striking departure in the electronic structure from that of the underdoped regime. The upper Hubbard band, identified with strong correlation effects, is not observed on the oxygen K edge, while the lowest-energy prepeak gains less intensity than expected above p approximately 0.21. This suggests a breakdown of the Zhang-Rice singlet approximation and a loss of correlation effects or a significant shift in the most fundamental parameters of the system, rendering single-band Hubbard models inapplicable. Such fundamental changes suggest that the overdoped regime may offer a distinct route to understanding in the cuprates. PMID:19792760

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

2009-08-19

85

Group Increment Scheme for Infrared Absorption Intensities of Greenhouse Gases.  

National Technical Information Service (NTIS)

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 ...

J. S. Francisco P. P. Bera S. I. Kokkila T. J. Lee

2012-01-01

86

Influence of intramolecular hydrogen bonding on OH-stretching overtone intensities and band positions in peroxyacetic acid.  

PubMed

Vapor phase absorption spectra and integrated band intensities of the OH stretching fundamental as well as first and second overtones (2?(OH) and 3?(OH)) in peroxyacetic acid (PAA) have been measured using a combination of FT-IR and photoacoustic spectroscopy. In addition, ab initio calculations have been carried out to examine the low energy stable conformers of the molecule. Spectral assignment of the primary features appearing in the region of the 2?(OH) and 3?(OH) overtone bands are made with the aid of isotopic substitution and anharmonic vibrational frequency calculations carried out at the MP2/aug-cc-pVDZ level. Apart from features associated with the zeroth-order OH stretch, the overtone spectra are dominated by features assigned to combination bands composed of the respective OH stretching overtone and vibrations involving the collective motion of several atoms in the molecule resulting from excitation of the internal hydrogen bonding coordinate. Integrated absorption cross section measurements reveal that internal hydrogen bonding, the strength of which is estimated to be ?20 kJ/mol in PAA, does not result in a enhanced oscillator strength for the OH stretching fundamental of the molecule, as is often expected for hydrogen bonded systems, but does cause a precipitous drop in the oscillator strength of its 2?(OH) and 3?(OH) overtone bands, reducing them, respectively, by a factor of 165 and 7020 relative to the OH stretching fundamental. PMID:21988092

Hazra, Montu K; Kuang, Xiaobi; Sinha, Amitabha

2011-10-11

87

ANALYSIS OF THE ABSORPTION SPECTRUM OF IBr. I. ROTATIONAL ANALYSIS OF THE NEAR INFRARED BANDS  

Microsoft Academic Search

In a study of the absorption spectrum of iodine bromide, photographs of ; the infrared regions are made in high resolution. The fine structures of the ; bands are resolved, so that rotational analyses can be carried out. The infrared ; system is associated with a ³II⁠Y ¹ SIGMA \\/sub +\\/ ; transition. Vibrational and rotational constants are given.

Selin

1962-01-01

88

New Absorption Bands of the Carbon Dioxide Isotopologues in Venus Spectra  

NASA Astrophysics Data System (ADS)

We present new absorption bands of carbon dioxide isotopologues detected by the SOIR instrument on board Venus Express. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter for the order selection. It performs solar occultation measurements 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 to 150 km) with an emphasis on vertical distribution of the gases. The sensitivity of the SOIR instrument and the high concentration of CO2 on Venus, coupled with the long absorption paths sounded during solar occultation, enable us to detect weak absorption bands of the rare CO2 isotopologues in the Venus atmosphere. A systematic study of the recorded spectra is under way and preliminary results will be discussed. So far we have identified the 20001 - 00001 band of 16O13C18O isotopologue and the 21101 - 01101 band of 16O12C18O isotopologue in the SOIR spectra. Rotational analyses were performed for these two new bands and also for the 01111 - 00001 band of 16O12C18O, already reported in [1]. Additional bands are under analysis as well. . 1. Wilquet, V., et al., Line parameters for the 01111-00001 band of 16O12C18O from SOIR measurements of the Venus atmosphere. Journal of Quantitative Spectroscopy and Radiative Transfer, 2008. 109: p. 895-905.

Robert, Severine; Mahieux, Arnaud; Wilquet, Valerie; Drummond, Rachel; Vandaele, Ann-Carine; Borkov, Yu.; Perevalov, V. I.; Tashkun, S. A.; Bertaux, Jean-Loup

2010-05-01

89

Optical band gap studies and estimation of two photon absorption coefficient in alkali bismuth borate glasses  

NASA Astrophysics Data System (ADS)

The optical absorption spectra of the glasses with composition xBi(2)O(3) . (30 - x)R2O . 70B(2)O(3) (R=Li, Na, K) and xBi(2)O(3) . (70 - x)B2O3 . 30Li(2)O (0 less than or equal to x less than or equal to 20) have been recorded in the wavelength range 350-650 nm. The glass samples were prepared by the normal melt-quench technique. The fundamental absorption edge for all the series of glasses is analyzed using the theory of Davis and Mott. The position of absorption edges and the values of optical band gap are dependent on the mol% of Bi2O3. The absorption in these glasses is associated with indirect transitions. The values of Urbach's energy and band tailing parameters are reported. The two photon absorption coefficient,, in these glasses has also been estimated from the optical band gap and its value ranges from 1.3 to 11.6 cm/GW. The relationship between beta and glass composition has also been discussed in terms of the electronic structure of the glass system.

Agarwal, A.; Seth, V. P.; Sanghi, S.; Gahlot, P.; Goyal, D. R.

2003-11-01

90

Absolute local mode vibrational band intensities of AsH 3  

Microsoft Academic Search

The local mode vibrational absolute band intensities of AsH3 molecule were studied experimentally and theoretically. The stretching vibrational band intensities of AsH3 were derived from the infrared spectra recorded by a Bruker IFS 120 HR Fourier transform spectrometer. A three-dimensional As–H stretching dipole moment surface (DMS) was calculated by the density functional theory method. The DMS was used to calculate

Jing-Jing Zheng; Sheng-Gui He; Yun Ding; Lu-Yuan Hao; Xiang-Huai Wang; Shui-Ming Hu; Qing-Shi Zhu

2002-01-01

91

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

NASA Astrophysics Data System (ADS)

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

Pershin, Sergei M.; Bunkin, Aleksei F.; Zakharov, S. D.; Luk'yanchenko, V. A.

2011-01-01

92

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

SciTech Connect

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

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

2011-01-24

93

Interferometric Determination of the Dispersion of Vibrational Polarizability and the Integrated Intensities of Fundamental Bands of 32, 34SF6 and NF3 Molecules  

NASA Astrophysics Data System (ADS)

The refractivity of gaseous SF6 and NH3 in the region of the intense absorption bands of these compounds was measured by two-beam, two-color interferometry using a He-Ne laser and a CO2 laser tunable throughout its emission lines. Quantitative data on the profiles of the absorption bands of these gases were also obtained by IR Fourier spectroscopy. By using the joint processing of the results of refractometric and spectral measurements on the basis of the Kramers-Krönig formalism, the dispersion dependences of the vibrational polarizabilities of the given molecules were calculated and the integrated intensities of their fundamental vibrational bands were refined. A table of values of total and vibrational polarizabilities at the emission frequencies of the CO2 laser was compiled.

Bulanin, M. O.; Burtsev, A. P.; Ladvishchenko, Yu. M.; Sveshnikov, Yu. M.

2001-07-01

94

Environmental effects on vibronic band intensities in pyrene monomer fluorescence and their application in studies of micellar systems  

Microsoft Academic Search

The fluorescence intensities for various vibronic fine structures in the pyrene monomer fluorescence show strong solvent dependence. In the presence of polar solvents, there is a significant enhancement in the intensity of the 0--0 vibronic band at the expense of other bands. This strong perturbation in the vibronic band intensities is more dependent on the solvent dipole moment than on

K. Kalyanasundaram; J. K. Thomas

1977-01-01

95

AKARI observations of ice absorption bands towards edge-on young stellar objects  

NASA Astrophysics Data System (ADS)

Context. Circumstellar disks and envelopes of low-mass young stellar objects (YSOs) contain significant amounts of ice. Such icy material will evolve to become volatile components of planetary systems, such as comets in our solar system. Aims: To investigate the composition and evolution of circumstellar ice around low-mass young stellar objects (YSOs), we observed ice absorption bands in the near infrared (NIR) towards eight YSOs ranging from class 0 to class II, among which seven are associated with edge-on disks. Methods: We performed slit-less spectroscopic observations using the grism mode of the InfraRed Camera (IRC) on board AKARI, which enables us to obtain full NIR spectra from 2.5 ?m to 5 ?m, including the CO2 band and the blue wing of the H2O band, which are inaccessible from the ground. We developed procedures to carefully process the spectra of targets with nebulosity. The spectra were fitted with polynomial baselines to derive the absorption spectra. The molecular absorption bands were then fitted with the laboratory database of ice absorption bands, considering the instrumental line profile and the spectral resolution of the grism dispersion element. Results: Towards the class 0-I sources (L1527, IRC-L1041-2, and IRAS 04302), absorption bands of H2O, CO2, CO, and XCN are clearly detected. Column density ratios of CO2 ice and CO ice relative to H2O ice are 21-28% and 13-46%, respectively. If XCN is OCN-, its column density is as high as 2-6% relative to H2O ice. The HDO ice feature at 4.1 ?m is tentatively detected towards the class 0-I sources and HV Tau. Non-detections of the CH-stretching mode features around 3.5 ?m provide upper limits to the CH3OH abundance of 26% (L1527) and 42% (IRAS 04302) relative to H2O. We tentatively detect OCS ice absorption towards IRC-L1041-2. Towards class 0-I sources, the detected features should mostly originate in the cold envelope, while CO gas and OCN- could originate in the region close to the protostar, where there are warm temperatures and UV radiation. We detect H2O ice band towards ASR41 and 2MASSJ 1628137-243139, which are edge-on class II disks. We also detect H2O ice and CO2 ice towards HV Tau, HK Tau, and UY Aur, and tentatively detect CO gas features towards HK Tau and UY Aur.

Aikawa, Y.; Kamuro, D.; Sakon, I.; Itoh, Y.; Terada, H.; Noble, J. A.; Pontoppidan, K. M.; Fraser, H. J.; Tamura, M.; Kandori, R.; Kawamura, A.; Ueno, M.

2012-02-01

96

Optical Tamm states enhanced broad-band absorption of organic solar cells  

NASA Astrophysics Data System (ADS)

We present a design concept of thin-film organic solar cells using a photonic crystal as the electrode. Through the excitation of optical Tamm states (OTSs), the proposed photonic crystal based organic solar cells (PC-OSCs) exhibit a broad-band absorption enhancement owing to the abnormal refractive index variation of the active layer. The overall absorptivity can be increased by ~35% compared with that of the optimized conventional planar OSC. Remarkably, our easily manufactured planar PC-OSC exhibits almost the same overall absorptivity as the optimized conventional corrugated OSC. The excellent performance comes from the achievement of OTS for both transverse-magnetic and transverse-electric polarized enhanced absorption.

Zhang, Xu-Lin; Song, Jun-Feng; Li, Xian-Bin; Feng, Jing; Sun, Hong-Bo

2012-12-01

97

Electronic band structure, optical absorption, and photocatalytic activity of iron-doped anatase  

NASA Astrophysics Data System (ADS)

Quasi-one-dimensional solid solutions of the composition Ti1 - x Fe x O2 - x/2 (0.005 ? x ? 0.050) with the anatase-type structure and extended aggregates have been prepared by the precursor method. The absorption spectra of the solid solutions have been investigated in the ultraviolet and visible regions, and the photocatalytic activity in the oxidation reaction of hydroquinone in water has been estimated. It has been found that the synthesized solid solutions serve as photocatalysts only under ultraviolet irradiation, and their photoactivity increases with an increase in the dopant concentration. The first-principles calculations of the electronic band structure and optical absorption in iron-doped anatase and rutile have been performed using the pseudopotential method LSDA + U (with the VASP software package). The on-site exchange-correlation parameters have been calibrated in the calculations of the electronic band structure of hematite ?-Fe2O3 and ilmenite FeTiO3. It has been shown that, despite the appearance of impurity states within the band gap of anatase and rutile, doping with iron does not cause substantial absorption in the visible region, which correlates with the increase in photocatalytic activity only under ultraviolet irradiation. The most probable cause of the experimentally observed absorption in the visible region is the presence of finely dispersed hematite impurities in the obtained samples.

Krasil'nikov, V. N.; Zhukov, V. P.; Perelyaeva, L. A.; Baklanova, I. V.; Shein, I. R.

2013-09-01

98

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

PubMed

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

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

2013-04-01

99

The Effect of Deep Level Impurities on Intensity Dependent Absorption in Semiconductors  

Microsoft Academic Search

Intensity dependent absorption (IDA) in selected semiconductors has been studied by repetitively pulsed laser calorimetry. Undoped and deep-level doped GaAs and InP were used to study IDA in direct bandgap materials, while Boron doped Si was used to study the effect of free carrier absorption on the IDA process. The total absorption in each sample was measured as a function

Nien-Lou Li

1985-01-01

100

Sub and Superluminal Propagation of Intense Pulses in Media with Saturated and Reverse Absorption  

Microsoft Academic Search

We develop models for the propagation of intense pulses in solid state media which can have either saturated absorption or reverse absorption. We model subluminal propagation in ruby and superluminal propagation in alexandrite as three and four level systems, respectively, coupled to Maxwell's equations. We present results well beyond the traditional pump-probe approach and explain the experiments of Bigelow et

G. S. Agarwal; Tarak Nath Dey

2004-01-01

101

New Absorption Bands of the Carbon Dioxide Isotopologues in Venus Spectra  

Microsoft Academic Search

We present new absorption bands of carbon dioxide isotopologues detected by the SOIR instrument on board Venus Express. The SOIR instrument combines an echelle spectrometer and an Acousto-Optical Tunable Filter for the order selection. It performs solar occultation measurements in the IR region (2.2 - 4.3 mum) at a resolution of 0.12 - 0.18 cm-1. The wavelength range probed by

Severine Robert; Arnaud Mahieux; Valerie Wilquet; Rachel Drummond; Ann-Carine Vandaele; Yu. Borkov; V. I. Perevalov; S. A. Tashkun; Jean-Loup Bertaux

2010-01-01

102

A Behaviour of the Methane-Ammonia Absorption Bands on Jupiter in 2004  

NASA Astrophysics Data System (ADS)

New CCD-spectrophotometric observations of Jupiter carried out during March-May 2004 as continuing many years program of the Jupiter's methane-ammonia bands behaviour watch. We used grid spectrograph SGS with 4.3 A/pxl dispersion and CCD-camera ST-7XE, both manufactured by SBIG Company. There were recorded during nine nights more 300 CCD-spectrograms of the central meridian and equator of Jupiter and reference spectra of Ganymed. The profiles and equivalent widths (EW) of four absorption bands centered at 619(CH4), 668(NH3), 725(CH4) and 798 (CH4 +NH3) nm were measured for 145-175 points of S-N and W-E cross sections of Jovian disk as well as the depths (Rv) of bands at 619, 668, 702, 725, 787 and 798 nm . General view of the latitudinal variations of the absorptions is similar with the same for preceding years. The 725 nm band (Rv =0.58) shows a depression about 7-10 percent of Rv in EZ, small variations on temperate latitudes, increasing at 15-30 deg and decreasing at 35-50 deg in both hemispheres. A noticeable growth of absorption is observed near 60 deg latitude, especially in N-hemisphere. Then on higher latitudes the absorption is sharply decreased towards the poles to Rv=0.4 or less. Latitudinal variations of Rv for other bands ( besides polar latitudes) are about the limits +/- 5-10 percent and some more irregular than at 725 nm. The changes of the equivalent widths along equator are noticeably different for bands 725 nm and 798 nm. EW 798 nm is more then EW 725 nm in the center of disk but decreases steeply towards the limbs. There are no W-E asymmetry in the center-to-limb variations even at 10 deg phase angle. To reveal longitudinal variations we have calculated averaged means of Rv for latitudes -50 to 50 deg. These variations for all bands are no more than 5 percent. All data are presented as an graphic atlas of the Rv and EW latitudinal and longitudinal distribution and will be used later for next analysis and interpretation.

Tejfel, V. G.; Karimov, A. M.

2004-11-01

103

Optical Absorption in Band-Edge Region of ( CH3NH3)3Bi2I9 Single Crystals  

NASA Astrophysics Data System (ADS)

Optical absorption spectra were measured around the band edge in ( CH3NH3)3Bi2I9 single crystals. In the very thin crystals, an intrinsic exciton band appears clearly at 2.51 eV at low temperatures, and the absorption peak remains even at room temperature reflecting a large binding energy of more than 300 meV. The exciton band does not show a discontinuous shift near the temperature where the methylammonium ions induce a structural phase transition. This fact indicates that the exciton states are independent of the methylammonium ions. The origin of the exciton band is examined on the basis of the annealing effect on the absorption bands in vacuum-evaporated films. The lower energy tail of the exciton band obeys the Urbach rule between 78 and 350 K. The detailed analysis by the Urbach rule reveals that the exciton-phonon interaction in the present system is relatively strong.

Kawai, Taketoshi; Ishii, Atsuko; Kitamura, Takako; Shimanuki, Shigetaka; Iwata, Makoto; Ishibashi, Yoshihiro

1996-05-01

104

Band-Edge Shift and X1-X3 Absorption Depending on Donor Concentration in GaP  

Microsoft Academic Search

The fundamental absorption-edge and the X1-X3 absorption band (alpha1-band) were investigated at 300 K for n-GaP with various doping levels. The correction of the alpha1-band with the donor-electron-related absorptions can not be neglected for high donor concentrations ND. For increasing ND, the optical gap shrinks as Eg10{=}2.233-1.39× 10-8N1\\/3D, the X1-X3 threshold energy delta increases and decreases (increases) the effective mass

Tamio Endo; Kazuhiro Sawa; Yuushi Hirosaki; Shizuo Taniguchi; Koichi Sugiyama

1987-01-01

105

Near-Complete Absorption of Intense, Ultrashort Laser Light by Sub-{lambda} Gratings  

SciTech Connect

We demonstrate near-100% light absorption and increased x-ray emission from dense plasmas created on solid surfaces with a periodic sub-{lambda} structure. The efficacy of the structure-induced surface plasmon resonance, responsible for enhanced absorption, is directly tested at the highest intensities to date (3x10{sup 15} W cm{sup -2}) via systematic, correlated measurements of absorption and x-ray emission. An analytical grating model as well as 2D particle-in-cell simulations conclusively explain our observations. Our study offers a definite, quantitative way forward for optimizing and understanding the absorption process.

Kahaly, Subhendu; Kumar, G. Ravindra [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400005 (India); Yadav, S. K.; Sengupta, S.; Das, A.; Kaw, P. K. [Institute for Plasma Research, Bhat, Gandhinagar 382428 (India); Wang, W. M. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Sheng, Z. M. [Beijing National Laboratory of Condensed Matter Physics, Institute of Physics, CAS, Beijing 100190 (China); Department of Physics, Shanghai Jiao Tong University, Shanghai 200240 (China)

2008-10-03

106

Experimental verification of enhanced electromagnetic field intensities at the photonic stop band edge of 3D polystyrene photonic crystals using Z-Scan technique  

NASA Astrophysics Data System (ADS)

Enhancement of nonlinear absorption of polystyrene (PS) was investigated using 3D PS photonic crystals (PCs) with Z-scan technique. The Z-scan experiment was carried out at 532 nm in the picosecond (ps) regime. The transmittance of the PC was found to get modified because of the nonlinear absorption of PS particularly when 532 nm is near the photonic stop band (PSB) edge of PC. Calculations show that the field gets enhanced by 1.4 times the input field intensity within the crystal when the 532 nm wavelength falls at the PSB edge while keeping the crystal at an angle of 35°.

Alee, K. Shadak; Krishna, M. Bala Murali; Ashok, B.; Rao, D. Narayana

2012-04-01

107

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

Microsoft Academic Search

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

L. V. Sennitskaya; Yu. A. Pentin

1973-01-01

108

Line intensities and self-broadening coefficients for the 3?2 band of monodeuterated methane.  

NASA Astrophysics Data System (ADS)

The 3?2 band of CH3D has been used to measure the D/H ratio in the giant planets. However, agreement among measurements derived from this and other bands is not yet completely satisfactory. A more complete and more accurate set of spectroscopic parameters for this band would provide better constraints on planetary formation and evolution. Towards this goal, the authors have measured intensities and self-broadening coefficients for 221 lines of the 3?2 band of 12CH3D at 6425 cm-1, as well as for 34 assigned lines belonging to a second intermixed band, using laboratory spectra recorded at Kitt Peak National Observatory. From the measured lines it has been possible to estimate the square of the vibrational dipole moment matrix element as equal to (8.8±0.8)×10-7 Debye2 and the intensity of the 3?2 band at 293.5 K as equal to (2.34±0.19)×10-21 cm-1/(molecule cm-2).

Boussin, C.; Lutz, B. L.; de Bergh, C.; Hamdouni, A.

1998-10-01

109

Effects of millimeter band electromagnetic radiation of low intensity on sciatic nerve regeneration in rats  

Microsoft Academic Search

The effect of millimeter-band electromagnetic radiation of low intensity on the regeneration of the sciatic nerve was studied in experiments conducted on rats. The restoration of the functional properties of the nerve following its section and microsurgical suturing was investigated. It was established that irradiation of the site of operation stimulates the growth of nerve fibers and increases the conduction

L. I. Kolosova; G. N. Akoev; V. D. Avelev; O. V. Ryabchikova; K. S. Babu

1993-01-01

110

Shoreline Extraction from RADARSAT-2 Intensity Imagery Using a Narrow Band Level Set Segmentation Approach  

Microsoft Academic Search

This paper presents a semi-automated method for shoreline extraction from RADARSAT-2 intensity imagery. First, a preprocessing is applied to enhance the contrast of the SAR image. Second, thresholding combined with morphological filtering is employed to segment the SAR image into the land and the sea. Third, narrow band level set segmentation is implemented to refine the segmentation result. In the

Yuanming Shu; Jonathan Li; Gary Gomes

2010-01-01

111

Assignment of the 283-nm absorption spectrum of 4-azabenzimidazole as ?*-? by rotational band contour analysis  

NASA Astrophysics Data System (ADS)

The 000 band of the 283-nm system of 4-azabenzimidazole has been analyzed by computer simulation of its rotational contour to establish the character of the S1-S0 electronic transition. The 000 band has been shown to be an A/B hybrid with an intensity ratio B/A = 0.15, so the S1-S0 system can be assigned as A~1A'(?*-?)-X~1A'. Since the 000 band of the 289-nm system for 7-azaindole has also been shown to be of the same type (K. H. Hassan and J. M. Hollas, J. Mol. Spectrosc. 138, 398-412 (1989)), we conclude that the addition of an extra nitrogen in 4-azabenzimidazole does not change the nature of the first singlet electronic transition.

Cané, E.; Trombetti, A.

1991-07-01

112

Quantum interference in absorption and dispersion of a four-level atom in a double-band photonic crystal  

Microsoft Academic Search

The probe absorption-dispersion spectrum of a double V-type four-level atom in a double-band photonic crystal is investigated. In the model used, the double V-type transitions are, respectively, coupled by the free vacuum modes and the photonic band gap modes, leading to the two possible types of quantum interference. Three types of zero absorption (transparency) appear in this model. In the

Samad Roshan Entezar; Habib Tajalli

2007-01-01

113

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

114

Origins of IR Intensity in Overtones and Combination Bands in Hydrogen Bonded Systems  

NASA Astrophysics Data System (ADS)

As the infrared spectra of an increasing number of hydrogen bonded and ion/water complexes have been investigated experimentally, we find that they often contain bands with significant intensity that cannot be attributed to fundamental transitions. In this talk, we explore several sources of the intensity of these overtone and combination bands. A common source of intensity is mode-mode coupling, as is often seen between the proton transfer coordinate and the associated heavy atom vibration. A second important mechanism involves large changes in the dipole moment due the loss of a hydrogen bond. This results in intense overtone transitions involving non-totally symmetric vibrations as well as the introduction of intense combination bands involving intramolecular bending coupled to hindered rotations. These effects will be discussed in the context of several systems, including the spectra of complexes of argon atoms with {H}_3{O}^+, F^-\\cdotH_2O, Cl^-\\cdotH_2O, protonated water clusters,^a and HOONO. T. Guasco, S. Olesen and M. A. Johnson, private communication S. Horvath, A. B. McCoy, J. R. Roscioli and M. A. Johnson, J. Phys. Chem. A, 112, 12337-44 (2008) S. Horvath, A. B. McCoy, B. M. Eliot, G. H. Weddle, J. R. Roscioli and M. A. Johnson, J. Phys. Chem. A, 115, 1556-68 (2010). A. B. McCoy, M. K. Sprague and M. Okumura, J. Phys. Chem. A, 115, 1324-33 (2010)

Horvath, Samantha; McCoy, Anne B.

2010-06-01

115

Calculation of dipole moment functions with density functional theory: application to vibrational band intensities  

NASA Astrophysics Data System (ADS)

We have calculated fundamental and overtone XH stretching vibrational band intensities for H2O, benzene, cyclohexane,1,3-butadiene, and HCN. The band intensities were calculated with a simple harmonically coupled anharmonic oscillator local mode model and a series expanded dipole moment function. The dipole moment functions were obtained from local, non-local and hybrid density functional theory calculations with basis sets ranging from 6-31G(d) to 6-311 G(3df,3pd). The calculated band intensities have been compared with intensities calculated with conventional ab initio methods and with experimental results. Compared with conventional correlated ab initio methods, a carefully chosen density functional method and basis set seems to give better fundamental and overtone intensities with far less resources used. We have found that the density functional methods appear to be less sensitive to the choice of basis set, with little difference between the results obtained with a non-local or hybrid density functional method.

Kjaergaard, Henrik G.

116

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

117

The Search for Extragalactic Diffuse Interstellar Bands via QSO Absorption Line Systems  

NASA Astrophysics Data System (ADS)

How common are the building blocks of life in the Universe? We hope to further our knowledge in this field by searching QSO absorption line systems for organic molecules in extragalactic sources. Within the Milky Way, complex organic molecules are thought to be the cause of 300 absorption features known as the diffuse interstellar bands (DIBs) found mostly within the visible part of the electromagnetic spectrum. Although abundant in the Milky Way, DIBs have only been found in a few extragalactic sources and only in one source via QSO absorption lines. Other researchers in this field have shown tight correlations between a specific DIB equivalent width and reddening as well as DIB equivalent width and neutral hydrogen column density. However, DIB strengths do not correlate with molecular hydrogen. From these observations many conclusions have been ascertained as to the environment of DIBs, as will be discussed within the poster. Due to these results we show why QSO absorption line systems containing very high column densities of neutral hydrogen are the appropriate mechanisms for searching extragalactic sources of DIBs. In particular, we have searched for DIBs using high resolution Keck data in QSO 0827+243 which contains an absorber with log column density of neutral hydrogen equal to 2.0. We have detected no DIBs in this system; however, we have developed a method of estimating the normalized absorption strengths of DIB lines we would expect to see given a neutral hydrogen column density of our target absorber. In this particular case, we would not expect to have found DIBs in 0827+243. We also present future work which includes systematically searching for DIBs in low redshift QSO absorption line systems. This work is being funded by NASA GSRP through the Office of Space Science.

Lawton, B.; Churchill, C. W.

2004-12-01

118

X/sup 2/. sigma -->. B/sup 2/. sigma. absorption band of HgBr: Optically pumped 502-nm laser  

SciTech Connect

The X/sup 2/..sigma../sup +//sub 1/2/..-->..B/sup 2/..sigma../sup +//sub 1/2/ absorption band of HgBr has been observed in the afterglow of a pulsed Ne-N/sub 2/-HgBr/sub 2/ discharge. Peaking in the ultraviolet (UV) near 350 nm, this continuum degrades slowly to the red and at 410 nm the absorption coefficient is 30% of its maximum value. Upon exciting the X..-->..B band with an XeF (351 nm) or frequency tripled Nd:YAG (355 nm) laser, intense lasing is observed in the blue-green (lambdaapprox.502 nm). For lambda/sub pump/ = 351 nm, the energy conversion efficiency (UV to green) is 22% which corresponds to a photon conversion efficiency of 32%. The quantum efficiency for this four level system is 71%.

Greene, D.P.; Killeen, K.P.; Eden, J.G.

1986-05-05

119

Designing low transmission loss silicon slot waveguide at wavelength band of high material absorption  

NASA Astrophysics Data System (ADS)

The transmission loss of silicon slot waveguide is investigated by numerical simulation. With the proper designing, the silicon slot waveguide could operate within the wavelength band of high material absorption, i.e., 800–1100 nm. The minimum propagation loss can be as low as 0.05 dB/mm with optimized structural parameters. Furthermore, a linear relation between the slot width and the operating wavelength is found after optimization, which provides a convenient method to design low-loss slot waveguide.

Li, Xiangdong; Feng, Xue; Cui, Kaiyu; Liu, Fang; Huang, Yidong

2013-10-01

120

Line mixing and collision induced absorption in the oxygen A-band using cavity ring-down spectroscopy.  

PubMed

This paper reports on the absorption of molecular oxygen in the region of the A-band near 760 nm under atmospheric conditions relevant for satellite retrieval studies. We use pulsed laser cavity ring-down spectroscopy with a narrow bandwidth laser and use pressure scans to increase the accuracy of the measured oxygen extinction coefficients. Absolute binary absorption coefficients in minima between absorption lines of the A-band spectrum have been measured and tabulated. We use the so-called adjustable branch coupling model including line mixing to calculate the magnetic dipole absorption in order to determine the contribution of collision induced absorption. The line mixing model has been optimized such that the collision induced absorption spectrum is smooth. PMID:20866137

Spiering, Frans R; Kiseleva, Maria B; Filippov, Nikolay N; Naus, Hans; van Lieshout, Bas; Weijenborg, Chris; van der Zande, Wim J

2010-09-21

121

Correlation Between Absorption Cross Section and Body Surface Area of Human for Far-Field Exposure at GHz Bands  

Microsoft Academic Search

Our previous study revealed that a dominant factor influencing the electromagnetic absorption in a human body for far field exposure at GHz bands is the body surface area. Based on this finding, we discussed the correlation between absorption cross section and body surface area of human for far-field exposure at 2 GHz. We employed an FDTD algorithm for a large-scale

Akimasa Hirata; Yoshio Nagaya; Fujiwara Osamu; A. T. Nagaoka; Soichi Watanabe

2007-01-01

122

Moment analysis for absorption and magnetic circular dichroism bands of atomic P <-- S transitions: Application to matrix-isolated chromium  

Microsoft Academic Search

Equations useful for the moment analysis of magnetic circular dichroism (MCD) and absorption bands of P?S electronic transitions of atoms or ions foranyspinmultiplicity have been derived. In particular, it is shown that the first through third MCD moments, together with the zeroth and second absorption moments may be employed to obtain such electronic and vibronic parameters as (1) the excited

M. Vala; R. Pyzalski; J. Shakhsemampour; M. Eyring; J. Pyka; T. Tipton; J. C. Rivoal

1987-01-01

123

Investigation of absorption and reflection spectra of aqueous suspensions of nanoparticles in the X band of microwave bandwidth  

Microsoft Academic Search

Aqueous suspension of iron oxide nanoparticles stabilized by citric acid has been synthesized. Nanoparticles were characterized by transmission electron microscopy. Nanoparticles size distribution was estimated by dynamic laser light scattering method. Absorption spectra of nanoparticles suspensions at different concentrations were recorded in visible part of optical band. Zeta-potential of nanoparticles was measured. Absorption and reflection spectra of aqueous suspension of

S. A. Sergeev; S. A. Portnov; D. A. Gorin; A. I. Mikhailov; S. S. Rumyantseva; I. V. Taranov; V. V. Kislov; G. B. Sukhorukov

2007-01-01

124

Sub and Superluminal Propagation of Intense Pulses in Media with Saturated and Reverse Absorption  

Microsoft Academic Search

We develop models for the propagation of intense pulses in solid state media\\u000awhich can have either saturated absorption or exhibit reverse absorption . We\\u000ashow that the experiments of Bigelow {\\\\it et al.}[Phys. Rev. Lett. {\\\\bf 90},\\u000a113903 (2003); Science {\\\\bf 301}, 200 (2003).] on subluminal propagation in\\u000aRuby and superluminal propagation in Alexandrite are well explained by\\u000amodelling

G. S. Agarwal; Tarak Nath Dey

2004-01-01

125

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

Microsoft Academic Search

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

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

1994-01-01

126

On the temperature variations of the integrated absorption intensity in the oxygen fundamental  

NASA Astrophysics Data System (ADS)

The goal of this note is to comment on the unusual temperature variations of the integrated absorption intensity measured recently in the region of the oxygen fundamental. More accurate than previous ones and covering wider temperature interval, the observations by Baranov and Lafferty showed that the integrated intensity reaches its minimum at roughly 280K and then increases steadily at elevated temperature. We suggest that this behaviour can be understood in terms of the flatness of intermolecular potential accompanied by the dominance of the absorption inducing collisions at extremely short distances corresponding to repulsive interaction.

Vigasin, A. A.

2004-04-01

127

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

NASA Astrophysics Data System (ADS)

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.

1989-07-01

128

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

129

Application of density functional theory to infrared absorption intensity calculations on main group molecules  

NASA Astrophysics Data System (ADS)

The level of approximation within the DFT formalism that is required for a near quantitative prediction of IR absorption intensities and frequencies is established. LDA and LDA/NL schemes are applied to calculations on the IR vibrational frequencies and absorption intensities of H2O, NH3, H2CO, C2H4, CH3OH, and oxirane. It is demonstrated that vibrational frequencies are relatively insensitive to the level of density functional theory as well as to the choice of basis set. The calculated frequencies are, in general, in better agreement with experiment than values obtained by ab initio Hartree-Fock calculations. The LDA/NL method with a triple-zeta plus polarization basis set affords IR intensities and frequencies of the same quality as post-Hartree-Fock methods with an average deviation in the intensities of 20-40 percent.

Fan, Liangyou; Ziegler, Tom

1992-06-01

130

Absorption Bands of Electrochemically-Colored Films of WO3, MoO3 and MocW1cO3  

Microsoft Academic Search

Optical absorption bands of electrochemically-colored films of amorphous WO3, MoO3 and MocW1-cO3 were investigated. The peak photon energy of the bands depends not only on the amount of injected charges but also on the Mo content. In the WO3 films, the absorption band originates from the intervalence trasfer of electrons. In MoO3 and mixed films, however, the absorption bands are

Yoichi Hiruta; Michihiko Kitao; Shoji Yamada

1984-01-01

131

Line Intensities for the v1, v3, and v1 + v3 Bands of 34SO2  

SciTech Connect

Using both high resolution (0.0018 cm-1) and medium resolution ( 0.112 cm-1) Fourier transform spectra of an enriched 34S (95.3%) sample of sulfur dioxide it has been possible to accurately measure a large number of individual line intensities for some of the strongest of the SO2 bands, i.e. ?1, ?3 and ?1+?3. . These intensities were least squares fitted using a theoretical model which takes into account the vibration-rotation interactions linking the upper energy levels where needed, and, in this way, expansions of the various transition moment operators were determined. The Hamiltonian parameters determined in previous analyses [Lafferty WJ, Flaud J.-M., Sams R.L., Ngom El H A. High resolution analysis of the rotational levels of the (000), (010), (100), (001),(020), (110) and (011) vibrational states of 34S16O2, J. Mol. Spectrosc. (2008), doi:10.1016/j.jms.2008.06.013; Lafferty WJ, Flaud J-M, Ngom El H A, Sams, L. 34S16O2: High resolution analysis of the (030), (101),(111), (002) and (201) vibrational states: Determination of equilibrium rotational constants of sulfur dioxide and anharmonic vibrational constants. J Mol Spectrosc, submitted ] together with these moments were then used to generate synthetic spectra for the bands studied and their corresponding hot bands providing one with an extensive picture of the absorption spectrum of 34SO2 in the spectral domains, 8.7, 7.4 and 4 ?m.

Flaud, Jean-marie; Lafferty, Walter J.; Sams, Robert L.

2009-06-01

132

Analysis of the 2?1+2?3 band of ozone: line positions and intensities.  

NASA Astrophysics Data System (ADS)

The 2?1+2?3 band of ozone, appearing in the 4150 cm-1 region has been observed for the first time, using the high resolution Reims FTS and a large p×l product of 3616 cm×48 torr. 275 transitions have been assigned, involving J and Ka up to 55 and 9, respectively. The fit on the 193 corresponding energy levels using single Watson type Hamiltonian leads to a standard deviation of 1.4×10-3cm-1 on the order of experimental accuracy. Line intensities are also measured and calculated with suitable transition moment operators. The authors report here the set of parameters as well as transition moment operators. A complete list, with a cut-off of: 1×10-26cm-1/mol.cm-1 has been generated which leads to a band intensity Sv(2?1+2?3) = 1.175×10-22cm-1/mol.cm-2.

Barbe, A.; Plateaux, J. J.

1996-04-01

133

ABSORPTIVE CAPACITY AND INNOVATION IN THE KNOWLEDGE INTENSIVE BUSINESS SERVICE SECTOR  

Microsoft Academic Search

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

Andreas Koch; Harald Strotmann

2008-01-01

134

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

NASA Astrophysics Data System (ADS)

An optimization method of smoothing noisy spectra was developed to investigate faint absorption bands in the visual spectral region of reflectance spectra of asteroids and the compositional information derived from their analysis. The smoothing algorithm is called "optimal" because the algorithm determines the best running box size to separate weak absorption bands from the noise. The method is tested for its sensitivity to identifying false features in the smoothed spectrum, and its correctness of forecasting real absorption bands was tested with artificial spectra simulating asteroid reflectance spectra. After validating the method we optimally smoothed 22 vestoid spectra from SMASS1 [Xu, Sh., Binzel, R.P., Burbine, T.H., Bus, S.J., 1995. Icarus 115, 1-35]. We show that the resulting bands are not telluric features. Interpretation of the absorption bands in the asteroid spectra was based on the spectral properties of both terrestrial and meteorite pyroxenes. The bands located near 480, 505, 530, and 550 nm we assigned to spin-forbidden crystal field bands of ferrous iron, whereas the bands near 570, 600, and 650 nm are attributed to the crystal field bands of trivalent chromium and/or ferric iron in low-calcium pyroxenes on the asteroids' surface. While not measured by microprobe analysis, Fe 3+ site occupancy can be measured with Mössbauer spectroscopy, and is seen in trace amounts in pyroxenes. We believe that trace amounts of Fe 3+ on vestoid surfaces may be due to oxidation from impacts by icy bodies. If that is the case, they should be ubiquitous in the asteroid belt wherever pyroxene absorptions are found. Pyroxene composition of four asteroids of our set is determined from the band position of absorptions at 505 and 1000 nm, implying that there can be orthopyroxenes in all range of ferruginosity on the vestoid surfaces. For the present we cannot unambiguously interpret of the faint absorption bands that are seen in the spectra of 4005 Dyagilev, 4038 Kristina, 4147 Lennon, and 5143 Heracles. Probably there are other spectrally active materials along with pyroxenes on the surfaces of these asteroids.

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

2007-04-01

135

A group increment scheme for infrared absorption intensities of greenhouse gases  

NASA Astrophysics Data System (ADS)

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.

2012-02-01

136

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

SciTech Connect

Recent interest in Sommerfeld-Brillouin optical precursors has brought attention to the possibility of optical precursor observation in bulk matter. We investigate the possible formation of optical precursors in an organic dye solution with a sharp absorption band and anomalous dispersion at a wavelength of approximately 800 nm. We explore this regime experimentally with sub-10-fs pulses with a central wavelength of approximately 800 nm from a Ti : sapphire oscillator. The pulses are passed through a thin layer of the dye solution and characterized by interferometric autocorrelation. The obtained autocorrelation traces are compared with simulations, and we observe important dispersion effects on the shape of the propagated pulses, including precursorlike behavior in their time evolution.

Springer, Matthew M.; Yang Wenlong; Kolomenski, Alexandre A.; Schuessler, Hans A.; Strohaber, James; Kattawar, George W.; Sokolov, Alexei V. [Institute for Quantum Studies and Department of Physics and Astronomy, Texas A and M University, College Station, Texas 77843-4242 (United States)

2011-04-15

137

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

NASA Astrophysics Data System (ADS)

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

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

2007-06-01

138

Sun-induced leaf fluorescence retrieval in the O2-B atmospheric absorption band.  

PubMed

Sun-induced leaf fluorescence was inferred by using high resolution (0.5 cm(-1)) radiance measurements and simulated spectra of the solar irradiance at the ground level, in the region of the O(2)-B absorption band. The minimization of a cost function was performed in the Fourier transform domain in order to make an accurate fit of the Instrumental Line- Shape that convoluted the simulated spectrum. Second- order polynomials were used to fit the leaf fluorescence and reflectance in the 100-cm(-1)-wide spectral window. The scale and the instrumental conversion factor were also fitted in order to obtain an accuracy that could not be attained by using the radiance measurements alone. PMID:18545405

Mazzoni, Marina; Falorni, Pierluigi; Del Bianco, Samuele

2008-05-12

139

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 0.5 mm in 2 GHz. 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 -11 dB (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

140

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

NASA Astrophysics Data System (ADS)

We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H2O and O2 bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H2O and O2 bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H2O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

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

2013-03-01

141

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

National Technical Information Service (NTIS)

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

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

1990-01-01

142

Line mixing and speed dependence in CO2 at 6227.9 cm-1: Constrained multispectrum analysis of intensities and line shapes in the 30013 ? 00001 band  

NASA Astrophysics Data System (ADS)

Line position, intensity and line shape parameters (Lorentz widths, pressure shifts, line mixing, speed dependence) are reported for transitions of the 30013 ? 00001 band of 16O12C16O (?0 = 6227.9 cm-1). The results are determined from 26 high-resolution, high signal-to-noise ratio spectra recorded at room temperature with the McMath-Pierce Fourier transform spectrometer. To minimize the systematic errors of the retrieved parameters, we constrained the multispectrum nonlinear least squares retrieval technique to use quantum mechanical expressions for the rovibrational energies and intensities rather than retrieving the individual positions and intensities line by line. Self- and air-broadened Lorentz width and pressure-induced shift, speed dependence and line mixing (off-diagonal relaxation matrix elements) coefficients were adjusted individually. Errors were further reduced by simultaneously fitting the interfering absorptions from the weak 30012 ? 00001 band of 16O13C16O as well as the weak hot bands 31113 ? 01101, 32213 ? 02201, 40014 ? 10002 and 40013 ? 10001 of 16O12C16O in this spectral window. This study complements our previous work on line mixing and speed dependence in the 30012 ? 00001 band (?0 = 6347.8 cm-1) [V.M. Devi, D.C. Benner, L.R. Brown, C.E. Miller, R.A. Toth, J. Mol. Spectrosc. 242 (2007) 90-117] and provides key data needed to improve atmospheric remote sensing of CO2.

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

2007-09-01

143

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

144

Resonant absorption in a self-consistent density profile at moderate intensities  

NASA Astrophysics Data System (ADS)

A model for the nonlinear resonant absorption of an electromagnetic wave in an inhomogeneous collision-dominated plasma at moderate intensities is proposed. The wave propagation equations are numerically solved in the time-independent self-consistent density profile. A density step appears at the critical point, and a surface wave develops which tends to enhance the absorption. Extensions of the model to collisionless situations are given when the damping can be conveniently described by some phenomenological self-consistent collision frequency. Finally, the effect of a plasma expansion across the critical density is briefly discussed.

David, F.; Mora, P.; Pellat, R.

1983-03-01

145

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

NASA Astrophysics Data System (ADS)

The interaction of subpicosecond 1.06 micrometers laser light at intensities up to 1018 W/cm2 with dense preformed plasmas is investigated by measurements of the absorption of the laser light in the plasma and by measurements of the production of bremsstrahlung x- rays. Absorption measurements are made by collecting the scattered light in an Ulbricht sphere. Light scattered in the backward and specular directions is collected separately. Measurements are presented for both high and low Z targets. X-ray production is measured using a nine channel filter/scintillator spectrometer.

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

1993-07-01

146

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

SciTech Connect

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

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

1993-03-01

147

Sub- and Superluminal Propagation of Intense Pulses in Media with Saturated and Reverse Absorption  

NASA Astrophysics Data System (ADS)

We develop models for the propagation of intense pulses in solid state media which can have either saturated absorption or reverse absorption. We model subluminal propagation in ruby and superluminal propagation in alexandrite as three and four level systems, respectively, coupled to Maxwell's equations. We present results well beyond the traditional pump-probe approach and explain the experiments of Bigelow et al. [

Phys. Rev. Lett.PRLTAO0031-9007 90, 113903 (2003); 10.1103/PhysRevLett.90.113903
ScienceSCIEAS0036-8075 301, 200 (2003)
] on solid state materials.

Agarwal, G. S.; Dey, Tarak Nath

2004-05-01

148

Preparation and oscillation of absorption bands of ZnS clusters  

NASA Astrophysics Data System (ADS)

Electric-field-induced transient pore formation (electroporation) in DOPC vesicles is used for the preparation of molecular ZnS clusters. The absence of caps permits (a) continued growth of the ZnS clusters formed, (b) the assessment of their true absorption spectra unaltered by stabilizing ligands, and (c) the previously inaccessible live observation of the growth of the clusters in the molecular-size regime. The ensuing self-aggregation of ZnS is slowed down to month timescales by its adsorption at the exterior surface of the vesicles. The growth of the clusters in the molecular size regime is found to exhibit novel, time-dependent, oscillating red- and blue-shifts of the characteristic UV absorption band in a certain special condition. On the basis of similarities between the oscillating trend of the experimentally observed transition energy and that of the calculated HOMO-LUMO gap of (ZnS)n clusters with n = 1-9, the wavelengths of the sequential spectral peaks can be assigned to the ZnS monomer (ZnS, 217 nm), dimer ((ZnS)2, 253 nm), tetramer ((ZnS)4, 225 nm), heptamer ((ZnS)7, ~250 nm) and nonamer ((ZnS)9, 228 nm).

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

2007-04-01

149

A pulsed optical absorption spectroscopy study of wide band-gap optical materials  

NASA Astrophysics Data System (ADS)

The paper presents the results of a study on the formation and evolution of short-lived radiation-induced defects in wide band-gap optical materials with the mobile cations. The spectra and decay kinetics of transient optical absorption (TOA) of radiation defects in crystals of potassium and ammonium dihydro phosphates (KH2PO4 and NH4H2PO4) were studied by means of the method of pulsed optical absorption spectroscopy with the nanosecond time resolution under excitation with an electron-beam (250 keV, 10 ns). A model of electron tunneling between the electron and hole centers under conditions of the thermally stimulated mobility of one of the recombination process partners was developed. The model describes all the features of the induced optical density relaxation kinetics observed in nonlinear optical crystals KH2PO4 and NH4H2PO4 in a broad decay-time range of 10 ns-10 s after the pulse of radiation exposure. The paper discusses the origin of radiation defects that determine the TOA, as well as the dependence of the decay kinetics of the TOA on the temperature, excitation power and other experimental conditions.

Ogorodnikov, I. N.; Kiseleva, M. S.; Yakovlev, V. Yu.

2012-10-01

150

Measurement of the (?2+2?3) band of methane by photoacoustic and long path absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The optical absorption spectrum of the (?2+2?3) combination band of methane in the 1.33 ?m range was investigated by photoacoustic and FTIR long path spectroscopy. The photoacoustic measurements were performed with a commercial external cavity diode laser (ECDL) and a differential photoacoustic (PA) detector. The absorption spectrum was obtained by scanning the wavelength of the ECDL through the 1317-1343 nm range of the methane (?2+2?3) band. A certified mixture of 1000 ppmV methane in synthetic air was used in a continuous flow mode. A linear concentration dependence of the PA signal was observed in the region of 10-1000 ppmV CH4. The absorption coefficients calculated from the measured sound pressure are in good agreement with the values given in the literature for several R-branch lines. Optical absorption measurements were performed with a long path White cell in combination with a FTIR spectrometer.

Miklós, A.; Hess, P.; Romolini, A.; Spada, C.; Lancia, A.; Kamm, S.; Schäfer, S.

1999-03-01

151

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

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

152

Coriolis-dependent Stark effect of the 2 nu 3 band of methane observed by saturated absorption spectroscopy  

Microsoft Academic Search

We studied the vibration-induced dipole moment of methane by observing Stark-modulation spectra of the 2?3 band centered at 1.66 ?m. The spectral purity of an external cavity semiconductor laser and radiation density in a Fabry–Perot cavity absorption cell are sufficiently high to record sub-Doppler saturated absorption lines with a spectral resolution of 0.8 MHz. First-order Stark shifts of the E-type

Hiroyuki Sasada; Kotaro Suzumura; Chikako Ishibashi

1996-01-01

153

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

Microsoft Academic Search

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

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

1992-01-01

154

Biexcitons in pi-conjugated oligomers: Intensity-dependent femtosecond transient-absorption study  

Microsoft Academic Search

We report femtosecond transient-absorption (TA) studies of a five-ring oligomer of poly(para-phenylene vinylene) prepared in two different forms: solid-state films and dilute solutions. At high pump fluences, in both types of samples, we observe generation of two-exciton states, which are detected by the evolution of TA spectra and dynamics with increasing pump intensity. In solutions, double excitation of molecules results

V. I. Klimov; D. W. McBranch; N. Barashkov; J. Ferraris

1998-01-01

155

Electronic Band Structure Information of GdN Extracted from x-ray Absorption and Emission Spectroscopy  

SciTech Connect

The electronic structure of GdN films grown by pulsed laser deposition has been investigated by soft x-ray absorption (XAS) and x-ray emission spectroscopy (XES) at the N K-edge. Density functional calculations within the local spin density approximation with Hubbard-U corrections of the N p weighted bands and density of states are used to extract band information from the spectra. Gd M{sub 4,5} XAS and XES spectra are also presented. The XES-XAS separation is shown to give information on the f-band spin splitting and the XAS line shapes are shown to reflect atomic multiplet effects.

Preston, A.; Ruck, B; Lambrecht, W; Piper, L; Downes, J; Smith, K; Trodahl, J

2010-01-01

156

Spectra and integrated band intensities of the low order OH stretching overtones in peroxyformic acid: an atmospheric molecule with prototypical intramolecular hydrogen bonding.  

PubMed

The gas phase spectra of several vibrational bands of peroxyformic acid (PFA), an atmospheric molecule exhibiting intramolecular hydrogen bonding, are presented. In the fundamental region, Fourier transform infrared (FT-IR) spectroscopy is used to probe the C-O, O-H and C-H stretching vibrations, while in the region of the first and second OH-stretching overtones (2?(OH) and 3?(OH)) photoacoustic spectroscopy is used. Integrated absorption cross sections for the PFA vibrational bands are determined by comparing their respective peak areas with that for the OH-stretching bands of n-propanol for which the absorption cross section is known. The measured integrated intensities of the OH stretching bands are then compared with a local mode model using a one-dimensional dipole moment function in conjunction with the OH stretching potential computed at both the MP2/aug-cc-pVDZ and CCSD(T)/aug-cc-pVDZ levels. The data allow us to investigate changes in the OH stretch band position and intensity as a function of overtone order arising from the influence of hydrogen bonding. Furthermore, calculations at the MP2/aug-cc-pVDZ level show that there are three stable conformers of PFA with relative energies of 0, 13.54, and 13.76 kJ/mol, respectively. In the room temperature spectra, however, we see evidence for transitions from only the lowest energy conformer. The geometrical parameters and vibrational frequencies of the most stable conformer are presented. PMID:21553873

Hazra, Montu K; Sinha, Amitabha

2011-05-09

157

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

158

Direct retrieval of lineshape parameters: Absolute line intensities for the nu2 band of CH3D  

Microsoft Academic Search

A nonlinear least-squares technique is applied to the nu2 band of CH3D to obtain lineshape parameters (intensity, position, and broadening). Some self-shift parameters are also reported. For the nu2 band of 12CH3D, line intensities with J'' <= 15 and K'' <= 7 are well represented with a squared vibrational transition dipole matrix element and ``Herman-Wallis'' factor equal respectively to (8.798

C. Chackerian; G. Guelachvili

1983-01-01

159

Atlas of the Schumann-Runge Absorption Bands of O2 in the Wavelength Region 175-205 nm.  

National Technical Information Service (NTIS)

After a critical summary of previous wavelength measurements and rotational line assignments of the Schumann-Runge absorption bands of O2, the results of the present study performed at high resolution with a 6.65 m vacuum spectrograph are given.

K. Yoshino D. E. Freeman W. H. Parkinson

1984-01-01

160

Probe absorption dispersion spectra of a driven three-level atom in a double-band photonic crystal  

Microsoft Academic Search

The probe absorption dispersion spectra of a driven three-level atom in a double-band photonic crystal have been investigated. We use the model which assumes the upper levels of the atomic transitions coupled via a classical driving field. One of the transitions interacts with the free vacuum modes, and the other transition couples to the modes of the modified reservoir (photonic

S. Roshan Entezar; H. Tajalli

2006-01-01

161

Analysis of Mars surface hydration through the MEx\\/OMEGA observation of the 3 mum absorption band  

Microsoft Academic Search

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

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

2006-01-01

162

Absorption Bands of Electrochemically-Colored Films of WO3, MoO3 and MocW1-cO3  

NASA Astrophysics Data System (ADS)

Optical absorption bands of electrochemically-colored films of amorphous WO3, MoO3 and MocW1-cO3 were investigated. The peak photon energy of the bands depends not only on the amount of injected charges but also on the Mo content. In the WO3 films, the absorption band originates from the intervalence trasfer of electrons. In MoO3 and mixed films, however, the absorption bands are considered to consist of two different components. The first is the intervalence trasfer band and the second is a component of absorption at higher energies. The second component is considered to be related to Mo atoms. The area under the absorption curve increases linearly with increasing density of injected charges in the WO3 film. In the film with large c, the absorption tends to saturate.

Hiruta, Yoichi; Kitao, Michihiko; Yamada, Shoji

1984-12-01

163

Hydrated silicates on main-belt asteroids: Correlation of the 0.7- and 3 micron absorption bands  

NASA Astrophysics Data System (ADS)

The presence of water and/or hydrated minerals on asteroids constrains solar system formation models and helps our understanding of the relationship of asteroids to meteorites. We have collected observations of main-belt asteroids at 0.7 and 3 microns to clarify the relationship between these bands and determine if the 0.7-micron band is a reliable proxy for hydrated minerals on asteroids. We find that if the 0.7-micron band is seen, the 3-micron band is almost always there as well. However, even when the 0.7-micron band is not seen, nearly 50% of the asteroids have the 3-micron band, and thus there are hydrated minerals. The presence of the 0.7- micron band places a lower limit on the number of asteroids with hydrated minerals. The correlation of these two bands differs between the C-complex and X-complex taxonomic groups as defined by DeMeo [1], and interesting trends are found. On more distant asteroids, the 3-micron absorption band may be due to ice rather than hydrated silicates [2, 3, 4].

Howell, E. S.; Rivkin, A. S.; Vilas, F.; Magri, C.; Nolan, M. C.; Vervack, R. J., Jr.; Fernandez, Y. R.

2011-10-01

164

Conduction-band electronic states of YbInCu{sub 4} studied by photoemission and soft x-ray absorption spectroscopies  

SciTech Connect

We have studied conduction-band (CB) electronic states of a typical valence-transition compound YbInCu{sub 4} by means of temperature-dependent hard x-ray photoemission spectroscopy (HX-PES) of the Cu 2p{sub 3/2} and In 3d{sub 5/2} core states taken at h{nu}=5.95 keV, soft x-ray absorption spectroscopy (XAS) of the Cu 2p{sub 3/2} core absorption region around h{nu}{approx}935 eV, and soft x-ray photoemission spectroscopy (SX-PES) of the valence band at the Cu 2p{sub 3/2} absorption edge of h{nu}=933.0 eV. With decreasing temperature below the valence transition at T{sub V}=42 K, we have found that (1) the Cu 2p{sub 3/2} and In 3d{sub 5/2} peaks in the HX-PES spectra exhibit the energy shift toward the lower binding-energy side by {approx}40 and {approx}30 meV, respectively, (2) an energy position of the Cu 2p{sub 3/2} main absorption peak in the XAS spectrum is shifted toward higher photon-energy side by {approx}100 meV, with an appearance of a shoulder structure below the Cu 2p{sub 3/2} main absorption peak, and (3) an intensity of the Cu L{sub 3}VV Auger spectrum is abruptly enhanced. These experimental results suggest that the Fermi level of the CB-derived density of states is shifted toward the lower binding-energy side. We have described the valence transition in YbInCu{sub 4} in terms of the charge transfer from the CB to Yb 4f states.

Utsumi, Yuki; Kurihara, Hidenao; Maso, Hiroyuki; Tobimatsu, Komei [Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Sato, Hitoshi; Shimada, Kenya; Namatame, Hirofumi [Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046 (Japan); Hiraoka, Koichi [Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577 (Japan); Kojima, Kenichi [Graduate School of Integrated Arts and Sciences, Hiroshima University, Higashi-Hiroshima 739-8521 (Japan); Ohkochi, Takuo; Fujimori, Shin-ichi; Takeda, Yukiharu; Saitoh, Yuji [Synchrotron Radiation Research Center, Japan Atomic Energy Agency, Hyogo 679-5148 (Japan); Mimura, Kojiro [Graduate School of Engineering, Osaka Prefecture University, Sakai 599-8531 (Japan); Ueda, Shigenori; Yamashita, Yoshiyuki; Yoshikawa, Hideki; Kobayashi, Keisuke [NIMS Beamline Station at SPring-8, National Institute for Materials Science, Hyogo 679-5148 (Japan); Oguchi, Tamio [ISIR, Osaka University, Ibaraki 567-0047 (Japan); Taniguchi, Masaki [Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan); Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046 (Japan)

2011-09-15

165

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

166

Optomechanical Shutter Modulated Broad-Band Cavity–Enhanced Absorption Spectroscopy of Molecular Transients of Astrophysical Interest  

NASA Astrophysics Data System (ADS)

We describe a sensitive spectroscopic instrument capable of measuring broad-band absorption spectra through supersonically expanding planar plasma pulses. The instrument utilizes incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) and incorporates an optomechanical shutter to modulate light from a continuous incoherent light source, enabling measurements of durations as low as -400 -s. The plasma expansion is used to mimic conditions in translucent interstellar clouds. The new setup is particularly applicable to test proposed carriers of the diffuse interstellar bands, as it permits swift measurements over a broad spectral range with a resolution comparable to astronomical observations. The sensitivity is estimated to be better than 10 ppm/pass, measured with an effective exposure time of only 1 s.

Walsh, Anton; Zhao, Dongfeng; Ubachs, Wim; Linnartz, Harold

2013-10-01

167

Infrared Intensities and Molecular Structures of Inorganic and Coordination Compounds  

Microsoft Academic Search

The observed infrared absorption band of a vibrating molecule may be characterized by several parameters, including the position, i.e., frequency, the intensity of the absorption areas, and the shapes o r band half-width. Whereas the frequency of a band depends upon the geometrical distribution of masses undergoing oscillation and the forces holding the nuclei together, the intensity is governed mainly

Lalji Dixit

1984-01-01

168

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

PubMed Central

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

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

1991-01-01

169

Production of intense, coherent, tunable narrow-band lyman-alpha radiation  

SciTech Connect

Nearly transform limited pulses of 1216 A radiation have been generated by sum frequency generation in 0.1 to 10 torr of mercury vapor. The summed input beams, consisting of photons at 3127 A and 5454 A originate in 1 MHz band-width ring-dye laser oscillators. The beams are amplified in pulsed-dye amplifiers pumped by the frequency doubled output of a Nd:YAG laser. The 3127 A photons are tuned to be resonant with the two-photon 6{sup 1}S to 7{sup 1}S mercury transition. The VUV radiation can be tuned by varying the frequency of the third non-resonant photon. We have also observed difference frequency generation at 2193 A and intense fluorescence from the 6{sup 1}P state at 1849 A. We have studied the intensity and linewidth dependence of the 1849 A fluorescence and 1216 A sum frequency signals on input beam intensity, mercury density, and buffer gas pressure and composition.

Turley, R.S.; McFarlane, R.A. (Hughes Research Laboratories, Malibu, CA 90265 (US)); Steel, D.G.; Remillard, J. (University of Michigan, Ann Arbor, MI 48109)

1988-10-01

170

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

PubMed

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

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

2012-12-01

171

High Intensity Light Absorption and Picosecond X-ray Radiation from Microstructured Surfaces  

NASA Astrophysics Data System (ADS)

We have characterized absorption and x-ray conversion efficiency in a novel type of nanostructured metallic surface used as a target for high-intensity laser interaction. The infrared to x-ray conversion efficiencies from the interaction of an intense 1-ps laser pulse with this nanowire structure are factors of 4 and 5 times greater than for comparable flat targets in the spectral ranges around 125 eV and above 1 keV respectively. A comparison of x-ray yield from this new nanostructure and more conventional smoke and grating surfaces was made: streak camera measurements in the 125 eV range show highest intensity emission from the nanowire target; the duration (approx. 25ps) is one third of that measured from a comparable smoke target. The duration of keV emission was less than our resolution of 8 ps. We will describe the spatial distribution of the x-ray emission, the yield dependence on the laser angle of incidence and polarization, and recent laser-light absorption measurements.

Kulcsar, G.; Budnik, F.; Zhao, L.; Marjoribanks, R.; Herman, P.; Almawlawi, D.; Moskovits, M.

1996-11-01

172

Vacuum heating absorption and expansion of solid surfaces induced by intense femtosecond laser irradiation  

NASA Astrophysics Data System (ADS)

The first section of the dissertation reports original experimental observation of the vacuum heating absorption mechanism in the interaction of high-intensity laser pulses with solid surfaces. Vacuum heating occurs when a component of the electric field in a laser pulse with intensity I > 1014 W/cm2 accelerates electrons away from the metallic or plasma-like surface and then returns them to a depth on the order of the penetration depth of the laser field. This interrupts the nascent oscillation and leads to absorption of the kinetic energy of the electrons by the solid. This important effect is included in all modern numerical and theoretical descriptions of high intensity laser-solid interactions, but no direct experimental observation has until now been reported. Vacuum heating has been observed in an experiment in which the reflectivity of an Fe target is measured with a 120 fs optical laser pulse with intensity varied from 1011 to 1015 W/cm2. For obliquely incident beams polarized in the plane of incidence a dropping reflectivity appears that cannot be explained through changes in the dielectric constant but that is consistent with vacuum heating. The effect requires a density gradient shorter than the electron excursion length, a condition that has also been experimentally confirmed. We find that approximately 10% of the incident pulse energy is absorbed through vacuum heating at 1015 W/cm2. The second section describes development of a new technique that uses frequency domain interferometry to characterize the dielectric constant of a solid target surface excited by high-intensity short-pulse lasers. The technique yields simultaneous measurement of surface motion, whether it be expansion or contraction. Preliminary results with a Si target reproduce the known transition to a metallic phase after laser melting, and provide tentative identification of a surface contraction.

Grimes, Mikal Keola

173

Integrated absorption intensity and Einstein coefficients for the O2 a 1?g-X 3?g- (0,0) transition: A comparison of cavity ringdown and high resolution Fourier transform spectroscopy with a long-path absorption cell  

NASA Astrophysics Data System (ADS)

The two experimental techniques of cavity ringdown spectroscopy and high-resolution, long-path Fourier transform spectroscopy have been used to measure quantitative absorption spectra and determine the integrated absorption intensity (Sint,B) for the O2 a 1?g-X 3?g- (0,0) band. Einstein A-factors and radiative lifetimes for the O2 a 1?g v=0 state have been derived from the Sint,B values. The two methods give values for the integrated absorption intensity that agree to within 2%. The value recommended from the results of this study is Sint,B=3.10+/-0.10×10-24 cm molecule-1, corresponding to an Einstein-A coefficient of A=2.19+/-0.07×10-4 s-1 and a radiative lifetime of ?rad=76 min. The measurements are in excellent agreement with the recent absorption study of Lafferty et al. [Appl. Opt. 37, 2264 (1998)] and greatly reduce the uncertainty in these parameters, for which accurate values are required for determination of upper stratospheric and mesospheric ozone concentrations.

Newman, Stuart M.; Lane, Ian C.; Orr-Ewing, Andrew J.; Newnham, David A.; Ballard, John

1999-06-01

174

Note: Measurement of saturable absorption by intense vacuum ultraviolet free electron laser using fluorescent material.  

PubMed

Advances in free electron lasers (FELs) which generate high energy photons are expected to open novel nonlinear optics in the x-ray and vacuum ultraviolet (VUV) regions. In this paper, we report a new method for performing VUV-FEL focusing experiments. A VUV-FEL was focused with Kirkpatrick-Baez optics on a multilayer target, which contains fused silica as a fluorescent material. By measuring the fluorescence, a 5.6x4.9 microm(2) focal spot was observed in situ. Fluorescence was used to measure the saturable absorption of VUV pulses in the tin layer. The transmission increases nonlinearly higher with increasing laser intensity. PMID:20370224

Inubushi, Y; Yoneda, H; Higashiya, A; Ishikawa, T; Kimura, H; Kumagai, T; Morimoto, S; Nagasono, M; Ohashi, H; Sato, F; Tanaka, T; Togashi, T; Tono, K; Yabashi, M; Yamaguchi, Y; Kodama, R

2010-03-01

175

Note: Measurement of saturable absorption by intense vacuum ultraviolet free electron laser using fluorescent material  

SciTech Connect

Advances in free electron lasers (FELs) which generate high energy photons are expected to open novel nonlinear optics in the x-ray and vacuum ultraviolet (VUV) regions. In this paper, we report a new method for performing VUV-FEL focusing experiments. A VUV-FEL was focused with Kirkpatrick-Baez optics on a multilayer target, which contains fused silica as a fluorescent material. By measuring the fluorescence, a 5.6x4.9 {mu}m{sup 2} focal spot was observed in situ. Fluorescence was used to measure the saturable absorption of VUV pulses in the tin layer. The transmission increases nonlinearly higher with increasing laser intensity.

Inubushi, Y.; Kumagai, T.; Morimoto, S.; Tanaka, T.; Kodama, R. [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); RIKEN XFEL Project Head Office, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); Yoneda, H. [RIKEN XFEL Project Head Office, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); Institute for Laser Science, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan); Higashiya, A.; Ishikawa, T.; Nagasono, M.; Tono, K.; Yabashi, M. [RIKEN XFEL Project Head Office, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); Kimura, H.; Ohashi, H.; Togashi, T. [RIKEN XFEL Project Head Office, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); Japan Synchrotron Radiation Research Institute, 1-1-1 Koto, Sayo, Hyogo 679-5148 (Japan); Sato, F.; Yamaguchi, Y. [Institute for Laser Science, University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo 182-8585 (Japan)

2010-03-15

176

Note: Measurement of saturable absorption by intense vacuum ultraviolet free electron laser using fluorescent material  

NASA Astrophysics Data System (ADS)

Advances in free electron lasers (FELs) which generate high energy photons are expected to open novel nonlinear optics in the x-ray and vacuum ultraviolet (VUV) regions. In this paper, we report a new method for performing VUV-FEL focusing experiments. A VUV-FEL was focused with Kirkpatrick-Baez optics on a multilayer target, which contains fused silica as a fluorescent material. By measuring the fluorescence, a 5.6×4.9 ?m2 focal spot was observed in situ. Fluorescence was used to measure the saturable absorption of VUV pulses in the tin layer. The transmission increases nonlinearly higher with increasing laser intensity.

Inubushi, Y.; Yoneda, H.; Higashiya, A.; Ishikawa, T.; Kimura, H.; Kumagai, T.; Morimoto, S.; Nagasono, M.; Ohashi, H.; Sato, F.; Tanaka, T.; Togashi, T.; Tono, K.; Yabashi, M.; Yamaguchi, Y.; Kodama, R.

2010-03-01

177

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

178

Evidence for strange stars from joint observation of harmonic absorption bands and of redshift  

NASA Astrophysics Data System (ADS)

From recent reports on terrestrial heavy ion collision experiments it appears that one may not obtain information about the existence of asymptotic freedom (AF) and chiral symmetry restoration (CSR) for quarks of QCD at high density. This information may still be obtained from compact stars - if they are made up of strange quark matter (SQM). Very high gravitational redshift lines (GRL), seen from some compact stars, seem to suggest high ratios of mass and radius (M/R) for them. This is suggestive of strange stars (SS) and can in fact be fitted very well with SQM equation of state (EOS) deduced with built in AF and CSR. In some other stars broad absorption bands (BAB) appear at about ~0.3keV and multiples thereof, that may fit in very well with resonance with harmonic compressional breathing mode frequencies of these SS. Emission at these frequencies are also observed in six stars. If these two features of large GRL and BAB were observed together in a single star, it would strengthen the possibility for the existence of SS in nature and would vindicate the current dogma of AF and CSR that we believe in QCD. Recently, in 4U 1700 - 24, both features appear to be detected, which may well be interpreted as observation of SS - although the group that analyzed the data did not observe this possibility. We predict that if the shifted lines, that has been observed, are from neon with GRL shift z= 0.4- then the compact object emitting it is a SS of mass 1.2Msolar and radius 7km. In addition the fit to the spectrum leaves a residual with broad dips at 0.35keV and multiples thereof, as in 1E 1207 - 5209 which is again suggestive of SS.

Bagchi, Manjari; Ray, Subharthi; Dey, Mira; Dey, Jishnu

2006-05-01

179

The K-band intensity profile of R Leonis probed by VLTI/VINCI  

NASA Astrophysics Data System (ADS)

We present near-infrared K-band interferometric measurements of the Mira star R Leonis obtained in April 2001 and January 2002 with the VLTI, the commissioning instrument VINCI, and the two test siderostats. These epochs correspond to near-maximum stellar variability phases ~0.08 and ~1.02 (one cycle later), respectively. The April 2001 data cover a range of spatial frequencies (31 35 cycles/arcsecond) within the first lobe of the visibility function. These measurements indicate a center-to-limb intensity variation (CLV) that is clearly different from a uniform disk (UD) intensity profile. We show that these measured visibility values are consistent with predictions from recent self-excited dynamic Mira model atmospheres that include molecular shells close to continuum-forming layers. We derive high-precision Rosseland diameters of 28.5 ± 0.4 mas and 26.2 ± 0.8 mas for the April 2001 and January 2002 data, respectively. Together with literature estimates of the distance and the bolometric flux, these values correspond to linear radii of 350+50-40 R_? and 320+50-40 R_?, and to effective temperatures of 2930 ± 270 K and 3080 ± 310 K, respectively. Based on public commissioning data released from the ESO VLTI (www.eso.org/projects/vlti/instru/vinci/ vinci_data_sets.html)

Fedele, D.; Wittkowski, M.; Paresce, F.; Scholz, M.; Wood, P. R.; Ciroi, S.

2005-03-01

180

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

181

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

182

[Generation of reactive oxygen species in water under exposure of visible or infrared irradiation at absorption band of molecular oxygen].  

PubMed

It is found that in bidistilled water saturated with oxygen hydrogen peroxide and hydroxyl radicals are formed under the influence of visible and infrared radiation in the absorption bands of molecular oxygen. Formation of reactive oxygen species (ROS) occurs under the influence of both solar and artificial light sourses, including the coherent laser irradiation. The oxygen effect, i.e. the impact of dissolved oxygen concentration on production of hydrogen peroxide induced by light, is detected. It is shown that the visible and infrared radiation in the absorption bands of molecular oxygen leads to the formation of 8-oxoguanine in DNA in vitro. Physicochemical mechanisms of ROS formation in water when exposed to visible and infrared light are studied, and the involvement of singlet oxygen and superoxide anion radicals in this process is shown. PMID:22567905

Gudkov, S V; Karp, O E; Garmash, S A; Ivanov, V E; Chernikov, A V; Manokhin, A A; Astashev, M E; Iaguzhinski?, L S; Bruskov, V I

183

Electronic structure and anomalous band-edge absorption feature in multiferroic MnWO4 : An optical spectroscopic study  

NASA Astrophysics Data System (ADS)

We investigated the electronic structure and lattice dynamics of multiferroic MnWO4 by optical spectroscopy. With variation in polarization, temperature, and magnetic field, we obtained optical responses over a wide range of photon energies. The electronic structure of MnWO4 near to the Fermi level was examined with interband transitions identified in optical conductivity spectra above a band gap of 2.5 eV. As for the lattice dynamics, we identified all the infrared transverse optical-phonon modes available according to the group-theory analysis. Although we did not observe much change in global electronic structure across the phase-transition temperatures, an optical absorption at around 2.2 eV showed an evident change depending upon the spin configuration and magnetic field. The behavior of this band-edge absorption indicates that spin-orbit coupling plays an important role in multiferroic MnWO4 .

Choi, Woo Seok; Taniguchi, K.; Moon, S. J.; Seo, S. S. A.; Arima, T.; Hoang, H.; Yang, I.-S.; Noh, T. W.; Lee, Y. S.

2010-05-01

184

A new technique for the determination of surface adsorbate geometries utilizing second harmonic generation and absorption band shifts  

SciTech Connect

A combination of second harmonic generation (SHG) and a simple dipole--dipole interaction model is presented as a new technique for determining adsorbate geometries on surfaces. The polarization dependence of SHG is used to define possible geometries of the adsorbate about the surface normal. General formulas for absorption band shifts using the geometry constraints imposed by the SHG data are derived for a dimer constructed from two arbitrarily placed monomers on the surface using the dipole--dipole interaction potential. These formulas can be used to determine the orientation of the two monomers relative to each other. A simplified version of this formalism is used to interpret absorption band shifts for a system of rhodamine /ital B/ adsorbed on quartz.

Peterson, E. S.; Harris, C. B.

1989-08-15

185

A modified k-distribution approach applied to narrow band water vapour and oxygen absorption estimates in the near infrared  

Microsoft Academic Search

We apply a modified version of the k-distribution method to derive expressions for the total and in-layer transmission of layered atmospheres in the H2O and O2 absorption bands around 900 and 762 nm, respectively. The calculations are exemplary performed for the channels settings of the forthcoming Medium Resolution Imaging Spectrometer (MERIS), to be launched onboard ESA's Environmental Satellite in 2000,

Ralf Bennartz; Jürgen Fischer

2000-01-01

186

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

187

Study of Time-Delay Four-Wave Mixing with Incoherent Light in Absorption Bands II:. Experiment  

Microsoft Academic Search

A series of experiments of time-delay four-wave mixing with incoherent light (TDFWM-IL) in absorption bands of ruby and dye molecules at 300 K-20 K are reported, which demonstrate that two-level theory fails in the interpretation of the results, and that our multilevel theory of TDFWM-IL should be applied. The following experimental results are emphasized: the normalized delay-time dependences of the

Ruihua Zhang; Xin Mi; Haitian Zhou; Qian Jiang; Peixian Ye

1992-01-01

188

Full-band absorption enhancement in ultrathin-film solar cells through the excitation of multiresonant guided modes.  

PubMed

We demonstrate the optimization of plasmonic thin-film solar cells with broadband absorption enhancements. The solar cells model system consists of a three-dimensional, periodic array of Ag/silica cylinders on a Si film supported by a silica substrate. Particle swarm optimization (PSO) and the finite-difference time domain (FDTD) are combined to achieve the maximum absorption enhancement (Ehm). Through optimization, the optimal system parameters, such as the height and diameter of Ag and the silica cylinder, and the period of periodic array, were obtained. Following this approach, we can attain a 321% enhancement in the integrated quantum efficiency as compared to a cell without metallic structures. The full-band absorption enhancement arises from the near-field enhancement and multiresonant guided modes in the Si waveguide. PMID:22614423

Shi, Linxing; Zhou, Zhen; Tang, Bingshu

2012-05-01

189

Characterization of a bulk semiconductor's band gap via a near-absorption edge optical transmission experiment  

Microsoft Academic Search

An experimental setup that employs lock-in detection to measure the optical transmission data on a bulk semiconductor sample is described. A straightforward manipulation of these data yields the semiconductor's absorption coefficient alpha in the energy range near its absorption edge (0absorption spectra is presented. It is

John M. Essick; Richard T. Mather

1993-01-01

190

Error analysis of infrared transmission measurements: determination of baseline, choice of peak maximum and range truncation in band profile and integrated intensity determination  

NASA Astrophysics Data System (ADS)

The problems of baseline determination, of the choice of band height and of the truncation of band wings are analysed for the cases of band profile analysis and of the integrated intensity measurements taking the Lorentzian and Gaussian bands as models.

Dryja?ski, Piotr

1998-02-01

191

Optical-absorption intensities and intermanifold emission cross sections of trivalent erbium ions in calcium fluorophosphate  

NASA Astrophysics Data System (ADS)

A spectroscopic analysis is performed on trivalent erbium ions, Er3+, doped into calcium fluorophosphate (FAP) to assess this material for its potential as a near-infrared laser host. The Judd-Ofelt model is applied to the orientation-averaged, room-temperature absorption intensities of Er3+ in FAP to obtain the phenomenological intensity parameters: ?2=5.86×10-20 cm2, ?4=0.38×10-20 cm2, and ?6=0.88×10-20 cm2. The intensity parameters are used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds 2S+1LJ of Er3+ in FAP. Using the radiative decay rates for Er3+ transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined in this host. The room temperature fluorescence lifetime and the radiative lifetime of the Er3+ 4I13/2-->4I15/2(1.53 ?m) transition are reported and the quantum efficiency is determined to be 69% for 1.0 wt % Er3+:FAP. In addition, the orientationally resolved emission cross sections for the 4S3/2-->4I15/2 and 4I13/2-->4I15/2 transitions are presented.

Sardar, Dhiraj K.; Coeckelenbergh, Cody H.; Yow, Raylon M.; Gruber, John B.; Allik, Toomas H.

2005-08-01

192

Midwinter intensities of the night airglow O2 (0-1) atmospheric band emission at high latitudes  

Microsoft Academic Search

Absolute intensities of the O2 (0-1) atmospheric band night airglow emission have been observed from near Longyearbyen on West Spitsbergen (78.4 deg N latitude, 15 deg E longitude, geographic) during a 2-month period around winter solstice (1982-1983). Intensities ranging from 110 R to 1590 R with a mean of 570 R + or - 60 R are observed. There is

H. K. Myrabo; C. S. Deehr; G. J. Romick; K. Henriksen

1986-01-01

193

Iron Absorption Band Analysis for the Discrimination of Iron Rich Zones.  

National Technical Information Service (NTIS)

The author has identified the following significant results. A lineament study of the Nevada test site is near completion. Two base maps (1:500,000) have been prepared, one of band 7 lineaments and the other of band 5 lineaments. In general, more lineamen...

L. C. Rowan

1973-01-01

194

Thin-walled boron nitride microtubes exhibiting intense band-edge UV emission at room temperature  

NASA Astrophysics Data System (ADS)

Boron nitride (BN) microtubes were synthesized in a vertical induction furnace using Li2CO3 and B reactants. Their structures and morphologies were investigated using x-ray diffraction, scanning and transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The microtubes have diameters of 1-3 µm, lengths of up to hundreds of micrometers, and well-structured ultrathin walls only ~50 nm thick. A mechanism combining the vapor-liquid-solid (VLS) and template self-sacrificing processes is proposed to explain the formation of these novel one-dimensional microstructures, in which the Li2O-B2O3 eutectic reaction plays an important role. Cathodoluminescence studies show that even at room temperature the thin-walled BN microtubes can possess an intense band-edge emission at ~216.5 nm, which is distinct compared with other BN nanostructures. The study suggests that the thin-walled BN microtubes should be promising for constructing compact deep UV devices and find potential applications in microreactors and microfluidic and drug delivery systems.

Huang, Yang; Bando, Yoshio; Tang, Chengchun; Zhi, Chunyi; Terao, Takeshi; Dierre, Benjamin; Sekiguchi, Takashi; Golberg, Dmitri

2009-02-01

195

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.

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

1997-01-01

196

Biexcitons in {pi}-conjugated oligomers: Intensity-dependent femtosecond transient-absorption study  

SciTech Connect

We report femtosecond transient-absorption (TA) studies of a five-ring oligomer of poly({ital para}-phenylene vinylene) prepared in two different forms: solid-state films and dilute solutions. At high pump fluences, in both types of samples, we observe generation of two-exciton states, which are detected by the evolution of TA spectra and dynamics with increasing pump intensity. In solutions, double excitation of molecules results in the formation of stable biexcitons with enhanced oscillator strength, leading to an increased efficiency of the radiative decay and a superlinear pump dependence of the stimulated emission. In solid-state samples, the two-exciton states are unstable and decay on the subpicosecond time scale due to ultrafast charge transfer, accompanied by generation of interchain excitons. {copyright} {ital 1998} {ital The American Physical Society}

Klimov, V.I.; McBranch, D.W. [Chemical Science and Technology Division, CST-6, Mail Stop J585, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Barashkov, N.; Ferraris, J. [Chemistry Department, University of Texas, Dallas, Texas 75083 (United States)

1998-09-01

197

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

PubMed

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

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

2013-05-21

198

Infrared Absorption Intensity Analysis as a New Tool for Investigation of Salt Effect on Proteins  

NASA Astrophysics Data System (ADS)

The native protein structures in buffer solution are maintained by the electrostatic force as well as the hydrophobic force, salt ions play an important role in maintaining the protein native structures, and their effect on the protein stability has attracted tremendous interests. Infrared spectroscopy has been generally used in molecular structure analysis due to its fingerprint resolution for different species including macromolecules as proteins. However spectral intensities have received much less attention than the vibrational frequencies. Here we report that the spectral intensities of protein amide I band, the finger prints for the protein secondary structures, are very sensitive to the local electric field known as Onsager reaction field caused by salt ions. IR absorbance thermal titrations have been conducted for a series of samples including simple water soluble amino acids, water soluble monomeric protein cytochrome c and dimeric protein DsbC and its single-site mutant G49R. We found that at lower temperature range (10-20 °C), there exists a thermal activated salting-in process, where the IR intensity increases with a rise in the temperature, corresponding to the ions binding of the hydrophobic surface of protein. This process is absent for the amino acids. When further raising the temperature, the IR intensity decreases, this is interpreted as the thermal activated breaking of the ion-protein surface binding. Applying Van't Hoff plot to the thermal titration curves, the thermodynamic parameters such as ?H and ?S for salting-in and ion unbinding processes can be derived for various protein secondary structural components, revealing quantitatively the extent of hydrophobic interaction as well as the strength of the ion-protein binding.

Li, Heng; Xu, Yan-yan; Weng, Yu-xiang

2009-12-01

199

Band gap and type of optical transitions at the interband absorption edge in solid solutions based on bismuth telluride  

NASA Astrophysics Data System (ADS)

The spectra of optical absorption in multicomponent n- and p-type solid solutions based on bismuth and antimony chalcogenides with substitutions in both sublattices of Bi2Te3 have been investigated. It has been found that, in all the solid solutions studied, just as in the parent compound Bi2Te3, direct allowed transitions occur at the interband absorption edge at T = 300 K. The band gap E g in the n-Bi2 - x Sb x Te3 - y - z Se y S z solid solutions weakly increases with increasing number of substituted atoms in the Bi and Te sublattices. These atomic substitutions do not leads to an increase in E g as compared to that of the n-Bi2Te2.7Se0.3 composition. An analysis of the optical absorption spectra suggests that the solid solutions under consideration are weakly degenerate, a conclusion supported by the earlier studies of the thermoelectric and galvanomagnetic properties. It has been established that, in the conduction band of the Bi1.8Sb0.2Te2.7Se0.15S0.15 solid solution, there is an additional extremum lying above the main extremum at a distance no more than 0.1 eV.

Veis, A. N.; Luk'yanova, L. N.; Kutasov, V. A.

2012-11-01

200

Absorption  

NSDL National Science Digital Library

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

Katie Hale (CSUF;)

2002-09-26

201

Total absorptivities and emissivities of particulate coal ash from spectral band emissivity measurements  

Microsoft Academic Search

Previous measurements of the spectral emissivity of coal ashes are converted to total absorptivities and emissivities. Below the temperature at which ash sinters, the total absorptivity of an ash layer-which is necessary for the estimation of radiative transfer in furnances-is shown to depend on both the source (flame) temperature and the ash temperature. Synthetic mixtures of the oxides AlâOâ, SiOâ,

T. F. Wall; M. B. Becker

1984-01-01

202

Absolute Ferrous Absorption Band Strength in the Lunar Feldspathic Highlands Terrane from the Moon Mineralogy Mapper  

NASA Astrophysics Data System (ADS)

We evaluate the ferrous band strength in the feldspathic highlands terrane with M^3 data. We find that the ground truth correction delivered with the M^3 PDS archive improves consistency between data collected over different phases of the mission.

Isaacson, P. J.; Petro, N. E.; Pieters, C. M.; Besse, S.; Boardman, J. W.; Clark, R. N.; Green, R. O.; Lundeen, S.; Malaret, E.; McLaughlin, S.; Sunshine, J. M.; Taylor, L. A.; M^3 Team

2012-03-01

203

Resonance Raman intensity analysis of the A band short-time photochemical dynamics of 4,5-ethylenedithio-1,3-dithiole-2-thione.  

PubMed

Resonance Raman spectra (RRs) for 4,5-ethylenedithio-1,3-dithiole-2-thione (EDDT) were obtained with 397.9 and 416 nm excitation wavelengths, and density functional calculations were performed to elucidate the electronic transitions and the RRs of EDDT in chloroform solvent. The RRs indicate that the Franck-Condon region photodynamics have multidimensional character with nuclear motion predominantly along the C(4)?C(5) stretch and the C(4)?C(5) twist out-of-plane. Resonance Raman cross-sections of A-band absorption have been obtained for the vibrational modes of EDDT with its excitation frequencies spanning the 408 nm. Resonance Raman intensity analysis of the resulting RRs excitation profiles and absorption spectrum using a time-dependent wave packet formalism yields mode-specific nuclear displacement and vibrational reorganizational energies. The intensity analysis results for EDDT were compared to previously reported results for dimethyl 1,3-dithiole-2-thione-4,5-dicarboxylate (DDTD), which shows that the additional six-member heterocycle of EDDT strongly affects the reorganizational energy and energy participation. The authors briefly discuss the differences and similarities of the spectra in terms of molecular symmetry and electron density. PMID:22077490

Wang, Huigang; Zhang, Wenfei; Liu, Bo; Shen, Shaosong; Zheng, Xuming; Pei, Kemei; Chen, Lijiang

2011-11-29

204

Electroabsorption modulator performance predicted from band-edge absorption spectra of bulk, quantum-well, and quantum-well-intermixed InGaAsP structures  

Microsoft Academic Search

Band-edge absorption spectra from bulk, quantum-well, and quantum-well-intermixed InGaAsP material are collected and compared using photocurrent spectroscopy. The expected performances of ideal electroabsorption modulators fabricated from these materials are predicted and compared using the band-edge absorption data. A graphical method for simultaneously considering chirp, insertion-loss, extinction-ratio, and tuning range is presented, and is used to compare the suitability of the

Gordon B. Morrison; James W. Raring; Chad S. Wang; Erik J. Skogen; Yu-Chia Chang; Matt Sysak; L. A. Coldren

2007-01-01

205

Fabrication and sub-band-gap absorption of single-crystal Si supersaturated with Se by pulsed laser mixing  

NASA Astrophysics Data System (ADS)

Selenium supersaturated silicon layers were fabricated by pulsed excimer laser induced liquid-phase mixing of thin Se films on Si(001) wafers. Sufficiently low Se coverage avoids destabilization of rapid epitaxial solidification, resulting in supersaturated solid solutions free of extended defects, as shown by transmission electron microscopy. The amount of retained Se depends on the original film thickness, the laser fluence, and the number of laser pulses irradiating the same spot on the surface. Using this method, Se has incorporated into the topmost 300 nm of the silicon with a concentration of 0.1 at.%. Channeling Rutherford backscattering spectrometry measurements show that the substitutional fraction can be as high as 75% of the total retained Se. These alloys exhibit strong sub-band-gap absorption with optical absorption coefficient ranging up to about 104 cm-1, thus making them potential candidates for applications in Si-based optoelectronic devices.

Tabbal, Malek; Kim, Taegon; Woolf, David N.; Shin, Byungha; Aziz, Michael J.

2010-03-01

206

SiC2 in carbon stars: Merrill-Sanford absorption bands between 4100 and 5500Å  

NASA Astrophysics Data System (ADS)

Observations and identifications of the Merrill-Sanford bands of the silicon dicarbide molecule are reported for a range of N and J stars. The data were recorded at 0.8-1.6Å resolution between 4100 and 5500Å. A full description of the assignments and spectral features in the stars is given. The spectra are characterized by absorption from the ground vibrational level (0,0,0) and from higher-lying vibrational levels involving one quantum of excitation in ?1, and up to two quanta in ?2 and ?3, giving rise to numerous hot-bands. The first results of rotational contour calculations are presented, and are consistent with SiC2 lying in the upper atmosphere of the star with a rotational temperature substantially lower than that of the photosphere.

Sarre, P. J.; Hurst, M. E.; Lloyd Evans, T.

2000-11-01

207

Ageing of chloroplasts in vitro — III. Comparison of the effects of ageing in vitro and senescence on the red absorption band and primary photochemical reactions of sunflower chloroplasts  

Microsoft Academic Search

A comparison of changes in absorption properties and electron transport activities of chloroplasts ageing in vivo and in vitro is made. Chloroplasts from sunflower leaves senescing in vivo during 7 days in dark do not show a blue shift of the red absorption band; in contrast, the shift becomes apparent within 24 h of in vitro ageing of isolated organelles.

P. K. Panigrahi; U. C. Biswal

1983-01-01

208

A New Approach to Describing the Statistical Laws Governing the Formation of the Contour of Individual Bands in the Optical Absorption Spectra of Liquid Systems  

Microsoft Academic Search

A new approach to the problem of a quantitative study of the statistical laws governing the formation of the contour of individual bands in the optical absorption spectra of unordered molecular systems (liquids, solutions, liquid crystals, etc.) was developed. The approach is based on a joint consideration of two independent mechanisms of the inhomogeneous broadening of spectral bands; these mechanisms

N. G. Bakhshiev; Yu. P. Sokolov

2002-01-01

209

Strategies to tailor the UV absorption band of Eu3+:La2O3 downshifting nanocrystals  

NASA Astrophysics Data System (ADS)

The charge transfer state (CTS) band of the Eu3+:La2O3 nanocrystals were studied in detail in order to understand the shift of the maximum of this band. Eu3+:La2O3 nanoparticles present a broad CTS band. However, the maximum is peaking below 300 nm, far below the limit of the solar spectrum arriving to the surface of the Earth and it makes difficult the application of this material as down-shifting in solar cells. In order to shift the CTS band towards blue wavelengths, different synthesis methods such as hydrothermal and sol-gel modified Pechini methods were used to prepare these nanoparticles, and adding additional CTS bands with co-doping ions such as Bi3+ was explored as well. The crystalline structure of Eu3+:La(OH)3, Eu3+:La2O3, Bi3+:Eu3+:La(OH)3 and Bi3+:Eu3+:La2O3 and the cell parameters of Eu3+:La2O3 and Bi3+:Eu3+:La2O3 were analyzed by X-ray powder diffraction technique and their morphology was observed by transmission electron microscopy. Once we obtained the cell parameters refining the XRD patterns by Full-prof software, we were able to calculate the Eu3+-O distance by ATOMS software through the structure previously represented following the Pauling model. The results found suggest that we need to take into account another parameter apart from the Eu3+-O distance to explain the CTS band small shift.

Méndez, M.; Cesteros, Y.; Marsal, L. F.; Salagre, P.; Formentín, P.; Pallarès, J.; Aguiló, M.; Díaz, F.; Carvajal, J. J.

2012-05-01

210

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

SciTech Connect

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

Smith, S.J.

1994-01-01

211

Resonance Raman and density functional theory investigation of the photodissociation dynamics of the A-band absorption of (E)-?-nitrostyrene in cyclohexane solution  

NASA Astrophysics Data System (ADS)

Resonance Raman spectra were obtained for (E)-?-nitrostyrene in cyclohexane solution with excitation wavelengths in resonance with the charge transfer (CT)-band absorption spectrum. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion predominantly along the nominal NO2 symmetric stretch mode (?14), the nominal C=C stretch mode (?8), the nominal benzene ring stretch mode (?9), accompanied by a smaller amount of motion along the nominal ONO symmetric bend/benzene ring stretch mode (?34), the nominal CCH in-plane bending mode (?20), the nominal HC=CH in-plane bending mode (?18), the nominal NO2 asymmetric stretch mode (?11), the nominal C-N stretch/benzene ring breathing mode (?27), and the nominal CCC trigonal bending mode (?25). A preliminary resonance Raman intensity analysis was done and these results for (E)-?-nitrostyrene were compared to results previously reported for several nitrobenzene and trans-stilbene compounds. The differences and similarities between the CT-band resonance Raman spectra and vibrational reorganizational energies for (E)-?-nitrostyrene relative to those for nitrobenzene and trans-stilbene were briefly discussed.

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

2007-05-01

212

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

2011-03-01

213

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

Microsoft Academic Search

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

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

2003-01-01

214

Decomposition of mineral absorption bands using nonlinear least squares curve fitting: Application to Martian meteorites and CRISM data  

NASA Astrophysics Data System (ADS)

This study advances curve-fitting modeling of absorption bands of reflectance spectra and applies this new model to spectra of Martian meteorites ALH 84001 and EETA 79001 and data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). This study also details a recently introduced automated parameter initialization technique. We assess the performance of this automated procedure by comparing it to the currently available initialization method and perform a sensitivity analysis of the fit results to variation in initial guesses. We explore the issues related to the removal of the continuum, offer guidelines for continuum removal when modeling the absorptions and explore different continuum-removal techniques. We further evaluate the suitability of curve fitting techniques using Gaussians/Modified Gaussians to decompose spectra into individual end-member bands. We show that nonlinear least squares techniques such as the Levenberg-Marquardt algorithm achieve comparable results to the MGM model ( Sunshine and Pieters, 1993; Sunshine et al., 1990) for meteorite spectra. Finally we use Gaussian modeling to fit CRISM spectra of pyroxene and olivine-rich terrains on Mars. Analysis of CRISM spectra of two regions show that the pyroxene-dominated rock spectra measured at Juventae Chasma were modeled well with low Ca pyroxene, while the pyroxene-rich spectra acquired at Libya Montes required both low-Ca and high-Ca pyroxene for a good fit.

Parente, Mario; Makarewicz, Heather D.; Bishop, Janice L.

2011-04-01

215

The 217.5 nm Band, Infrared Absorption, and Infrared Emission Features in Hydrogenated Amorphous Carbon Nanoparticles  

NASA Astrophysics Data System (ADS)

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

Duley, W. W.; Hu, Anming

2012-12-01

216

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

SciTech Connect

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

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

2012-12-20

217

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

PubMed

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

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

2012-06-12

218

Energy absorption of free rare gas clusters irradiated by intense VUV pulses of a free electron laser  

Microsoft Academic Search

As one of the first experiments at the free electron laser of the TESLA Test Facility (TTF) the Coulomb explosion of Xenon clusters irradiated with high intensity pulses at a wavelength of 98nm has been observed. Classical trajectory calculations have been performed in order to illuminate the energy absorption process. Comparison with typical parameters in the infrared regime shows that

J. Schulz; H. Wabnitz; T. Laarmann; P. Gürtler; W. Laasch; A. Swiderski; Th. Möller; A. R. B. de Castro

2003-01-01

219

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

USGS Publications Warehouse

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

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

1999-01-01

220

High-performance intensity slope correction method for global process variability band improvement and printability enhancement in RET applications  

NASA Astrophysics Data System (ADS)

A qualitatively new method applicable for process variability band (PVband) improvement and printability enhancement in resolution enhancement technique (RET) applications is reported. The method does not use costly simulations through the process window (PW). Instead, it utilizes a unique feedback mechanism derived from the intensity distribution information available during nominal optical proximity correction (OPC) simulation. Consequently, this Intensity Slope Correction (ISC) method provides superior performance as compared to traditional process window aware OPC tools. Preliminary results are presented. They suggest that this method can successfully be applied for improvement of integral PVband throughout the entire layout leading to global printability optimization.

Komirenko, Sergiy M.

2011-03-01

221

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

SciTech Connect

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

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

2010-08-15

222

Genetic Heterogeneity in Mycobacterium tuberculosis Isolates Reflected in IS6110 Restriction Fragment Length Polymorphism Patterns as Low-Intensity Bands  

Microsoft Academic Search

Mycobacterium tuberculosis isolates with identical IS6110 restriction fragment length polymorphism (RFLP) patterns are considered to originate from the same ancestral strain and thus to reflect ongoing transmission. In this study, we investigated 1,277 IS6110 RFLP patterns for the presence of multiple low-intensity bands (LIBs), which may indicate infections with multiple M. tuberculosis strains. We did not find any multiple LIBs,

ANNETTE S. DE BOER; KRISTIN KREMER; MARTIEN W. BORGDORFF; PETRA E. W. DE HAAS; HERRE F. HEERSMA; DICK VAN SOOLINGEN

2000-01-01

223

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

NASA Astrophysics Data System (ADS)

Electroporation of synthetic vesicles is utilized for the preparation of molecular size uncapped Zn1-xMnxS clusters. The absence of caps permits (i) continued growth of the Zn1-xMnxS clusters formed, (ii) the assessment of their true absorption spectra unaltered by stabilizing ligands, and (iii) the previously inaccessible live observation of the growth of the clusters in the molecular size regime. Upon cluster growth, the UV spectra exhibit novel, time-dependent, oscillation of red and blue shifts of the characteristic absorption band. The structure and electronic properties of ZnN-1MnSN clusters with N = 1-9 are calculated using the first-principles DMol3 package. On the basis of similarities between the oscillating trend of the experimentally observed absorption spectra and that of the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital (HOMO-LUMO) gap of ZnN-1MnSN clusters with N = 1-9, the wavelengths of the sequential spectral peaks can be assigned to Zn2MnS3, Zn3MnS4, Zn4MnS5, Zn6MnS7, and Zn8MnS9, respectively. Our results demonstrate that both the cluster size and the composition can be used to tune the optical properties.

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

2008-02-01

224

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

NASA Astrophysics Data System (ADS)

We have investigated valence band and conduction band electronic structures and interfacial chemical bonding states of nitrogen-plasma-treated HfSiON/SiON gate stacks on Si substrates with and without rapid thermal annealing by photoelectron spectroscopy and x-ray absorption spectroscopy to correlate them with electrical properties. We have found that the N3 component in N 1s can be correlated with electron trapping. Photoelectron spectra and O K-edge absorption spectra confirm the existence of the SiO2-rich phase-separated area in HfSiON films. Band offsets for the HfSiON/Si and the SiO2-rich HfSiON/Si are determined to be 2.5 and 4.2 eV for valence band and 1.7 and 3.6 eV for conduction band, respectively.

Oshima, M.; Takahashi, H.; Okabayashi, J.; Toyoda, S.; Kumigashira, H.; Inoue, M.; Mizutani, M.; Yugami, J.

2006-08-01

225

New analysis of the ?5 and 2?9 bands of HNO3 by infrared and millimeter wave techniques: line positions and intensities  

NASA Astrophysics Data System (ADS)

Nitric acid (HNO3) plays an important role in the Earth's atmosphere as a reservoir molecule of NOx species. It has a strong infrared signature at 11?m which is one of the most commonly used for the infrared retrieval of this species in the atmosphere since this spectral region coincides with an atmospheric window. It is therefore essential to have high quality spectral parameters in this spectral region. The main goal of this work is then to generate as reliable as possible line positions and intensities for the ?5 and 2?9 cold bands centered at 879.1075 and 896.4467cm-1, respectively. In particular the existing line parameters need improvement in the wings of the 11?m window in order to retrieve more accurately the CFC-11 (CCl3F) and CFC-12 (CCl2F2) atmospheric species at ~850 and ~920cm-1, respectively. This work is also motivated by theoretical considerations. Very strong resonances couple indeed the 51 and 92 rotational levels. In addition the ?9 mode (OH torsion) is a ``large amplitude'' motion, and torsional splittings affect both the v9=2 and the v5=1 rotational transitions. In the present study, these effects are accounted for simultaneously both for the line position and line intensity calculations. To calculate the line positions the Hamiltonian matrix accounts for the very strong Fermi and the weaker Coriolis interactions linking the 51<==>92 rotational levels, and the torsional effects are accounted for within the frame of the IAM (Internal Axis Method) approach. In addition, the v-diagonal blocks involve non-orthorhombic operators together with Watson's type rotational operators. This means that the z-quantization axis deviates from the a inertial axis for both the 51 and 92 vibrational states. The line intensity calculations were performed accounting also for the axis switching effects. As far as the experimental line positions are concerned we have used the millimeter wave data available in the literature [J. Mol. Spectrosc., 175 (1996) 395; J. Mol. Spectrosc., 208 (2001) 121; and references therein], as well as new centimeter wave measurements performed in Kiel and new Fourier transform infrared spectra recorded in Giessen. For the line intensities we have used an extensive set of individual line intensities measured recently [J. Mol. Spectrosc., 218 (2003) 151]. All these experimental data were very satisfactorily reproduced using the theoretical model described above and an improved set of line positions and intensities was generated for the ?5 and 2?9 bands allowing one to better model the HNO3 absorption in the 11?m spectral domain.

Perrin, A.; Orphal, J.; Flaud, J.-M.; Klee, S.; Mellau, G.; Mäder, H.; Walbrodt, D.; Winnewisser, M.

2004-12-01

226

Giant and broad-band absorption enhancement in colloidal quantum dot monolayers through dipolar coupling.  

PubMed

The absorption cross section of colloidal quantum dots in close-packed monolayers shows a 4 (CdSe) to 5-fold (PbS) enhancement compared to quantum dots in a dilute dispersion. Quantitative agreement is demonstrated between the value and the size dependence of the enhancement and theoretical model predictions based on dipolar coupling between neighboring quantum dots. This collective optical behavior offers a new degree of freedom in the custom design of optical properties for electro-optical devices. PMID:23297750

Geiregat, Pieter; Justo, Yolanda; Abe, Sofie; Flamee, Stijn; Hens, Zeger

2013-01-11

227

Laser absorption spectrometer using frequency chirped intensity modulation at 1.57 ?m wavelength for CO2 measurement.  

PubMed

We have demonstrated the laser-absorption spectrometer system using frequency chirped intensity modulation at 1.57 ?m wavelength for measurement of CO(2) concentration. Using this technique, backscattered laser radiation from different ranges can be discriminated in the frequency domain of the electrical signal. We have reported the discrimination of two signals from the targets with different ranges. It is shown that stable measurements with short time fluctuation corresponding to 4 ppm (rms) were obtained with 32 s measurement intervals. Furthermore, there is qualitative good agreement on, at least, the diurnal changes between the results of the laser absorption spectrometer system and the in-situCO(2) sensor. PMID:22743496

Imaki, Masaharu; Kameyama, Shumpei; Hirano, Yoshihito; Ueno, Shinichi; Sakaizawa, Daisuke; Kawakami, Shuji; Nakajima, Masakatsu

2012-07-01

228

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

229

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

Microsoft Academic Search

Measurements of near-infrared water vapour continuum using continuous wave cavity ring down spectroscopy (cw-CRDS) have been performed at around 10611.6 and 10685.2cm-1. The continuum absorption coefficients for N2-broadening have been determined to be CF296K=(1.0±0.2)×10-24cm2mol-1atm-1 and CF278K=(1.8±0.4)×10-24cm2mol-1atm-1 at 10611.6cm-1, and CF296K=(1.6±0.5)×10-24cm2mol-1atm-1 and CF278K=(2.1±0.4)×10-24cm2mol-1atm-1 at 10685.2cm-1, respectively.These results represent the first near-IR continuum laboratory data determined within the complex spectral environment in

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

2007-01-01

230

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

Microsoft Academic Search

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

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

2007-01-01

231

Absorption  

PubMed Central

Given that mind–body interventions constitute a major portion of complementary and alternative medicine used by the public, it seems important to explore those human characteristics that may contribute to the efficacy of mind–body interventions in those who are most likely to benefit. One such characteristic, absorption, reflects an individual’s cognitive capacity for involvement in sensory and imaginative experiences in ways that alter an individual’s perception, memory, and mood with behavioral and biological consequences. Thus, one’s level of absorption may potentially create differential treatment effects in mind–body intervention outcomes. Conducting practical clinical trials helps address the challenge of determining whether a specific mind–body modality intervention may be effective. Such trials may be strengthened by including measures of personality dimensions such as absorption.

Menzies, Victoria; Taylor, Ann Gill; Bourguignon, Cheryl

2009-01-01

232

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

233

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

PubMed

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. PMID:23571966

El Amili, Abdelkrim; Kervella, Gaël; Alouini, Mehdi

2013-04-01

234

Only Ku-band microwave absorption by Fe3O4/ferrocenyl-CuPc hybrid nanospheres  

NASA Astrophysics Data System (ADS)

A novel kind of hybrid nanospheres made of Fe3O4 and ferrocenyl-CuPc (FCP) was prepared via effective solvothermal method and performed microwave absorptivity only in Ku-band with minimum reflection loss of -25 dB at 16.0 GHz corresponding to absorbing about 99.7% content of microwave. Scanning electron microscopy images indicated that the nanospheres with uniform particle size distribution have the average diameter of 135 nm. Due to the synergistic reaction between magnetic ferrocenyl-CuPc and Fe3O4, the hybrid nanospheres showed novel electromagnetic properties. The real part of complex permittivity of hybrid nanospheres remains stable in the range of 0.5-12.0 GHz and has a large fluctuation at 16.5 GHz. Moreover, the dielectric loss of hybrid nanospheres also appeared a sharp peak at 16.3 GHz with the value of 2.7. The specific gravity of hybrid nanospheres is about 2.08. On the basis of these results, the novel hybrids are believed to have potential applications in the microwave absorbing area in Ku-band.

Wei, Junji; Zhao, Rui; Liu, Xiaobo

2012-10-01

235

Evidence for the presence of the 802.7/cm band Q branch of HO2NO2 in high resolution solar absorption spectra of the stratosphere  

NASA Astrophysics Data System (ADS)

Stratospheric solar absorption spectra recorded at ?0.01 cm-1 resolution by the ATMOS (Atmospheric Trace Molecule Spectroscopy) Fourier transform spectrometer during the Spacelab 3 Shuttle mission show a weak absorption feature covering ?802.5 - 803.3 cm-1. The authors identify this feature as the unresolved Q branch of the 802.7 cm-1 band of HO2NO2 and report profiles for 31°N and 47°S.

Rinsland, C. P.; Russell, J. M., III; Park, J. H.; Zander, R.; Farmer, C. B.; Norton, R. H.; Brown, L. R.

1986-08-01

236

Infrared absorption band and vibronic structure of the nitrogen-vacancy center in diamond  

NASA Astrophysics Data System (ADS)

Negatively charged nitrogen-vacancy (NV?) color centers in diamond have generated much interest for use in quantum technology. Despite the progress made in developing their applications, many questions about the basic properties of NV? centers remain unresolved. Understanding these properties can validate theoretical models of NV?, improve their use in applications, and support their development into competitive quantum devices. In particular, knowledge of the phonon modes of the 1A1 electronic state is key for understanding the optical pumping process. Using pump-probe spectroscopy, we measured the phonon sideband of the 1E?1A1 electronic transition in the NV? center. From this we calculated the 1E?1A1 one-phonon absorption spectrum and found it to differ from that of the 3E?3A2 transition, a result which is not anticipated by previous group-theoretical models of the NV? electronic states. We identified a high-energy 169-meV localized phonon mode of the 1A1 level.

Kehayias, P.; Doherty, M. W.; English, D.; Fischer, R.; Jarmola, A.; Jensen, K.; Leefer, N.; Hemmer, P.; Manson, N. B.; Budker, D.

2013-10-01

237

A new approach to describing the statistical laws governing the formation of the contour of individual bands in the optical absorption spectra of liquid systems  

Microsoft Academic Search

A new approach to the problem of a quantitative study of the statistical laws governing the formation of the contour of individual\\u000a bands in the optical absorption spectra of unordered molecular systems (liquids, solutions, liquid crystals, etc.) was developed.\\u000a The approach is based on a joint consideration of two independent mechanisms of the inhomogeneous broadening of spectral bands;\\u000a these mechanisms

N. G. Bakhshiev; Yu. P. Sokolov

2002-01-01

238

CH3D Absorption Bands Between 2.86 And 3.10 Microns In The High-resolution Spectra Of Titan  

Microsoft Academic Search

The nu2 + nu3 band of CH3D near 2.86 microns (Kim et al. 2005) has been detected in absorption in the high-resolution spectra of Titan observed with NIRSPEC at Keck II (Geballe et al. 2003). Between 2.92 and 3.10 microns in the same spectra other weak CH3D band lines have been identified based on a recent line list compiled by

Sang J. Kim; H. Seo; J. Kim; T. R. Geballe; R. Courtin; L. Brown

2006-01-01

239

Genetic engineering of band-egde optical absorption in Si/Ge superlattices  

NASA Astrophysics Data System (ADS)

Integrating optoelectronic functionalities directly into the mature Silicon-Germanium technology base would prove invaluable for many applications. Unfortunately, both Si and Ge display indirect band-gaps unsuitable for optical applications. It was previously shown (Zachai et al. PRL 64 (1990)) that epitaxially grown [(Si)n(Ge)m]p (i. e. a single repeat unit) grown on Si can form direc-gap heterostructures with weak optical transitions as a result of zone folding and quantum confinement. The much richer space of multiple-period superlattices [(Si)n1(Ge)n2(Si)n3(Ge)n4GenN]p has not been considered. If M=?ni is the total number of monolayers, then there are, roughly, 2^M different possible superlattices. To explore this large space, we combine a (i) genetic algorithm for effective configurational search with (ii) empirical pseudopotential designed to accurately reproduce the inter-valley and spin-orbit splittings, as well as hydrostatic and biaxial strains. We will present multiple-period SiGe superlattices with large electric dipole moments and direct gaps at ? yielded by this search. We show this pattern is robust against known difficulties during experimental synthesis.

D'Avezac, Mayeul; Luo, Jun-Wei; Chanier, Thomas; Zunger, Alex

2012-02-01

240

Energy absorption of free rare gas clusters irradiated by intense VUV pulses of a free electron laser  

NASA Astrophysics Data System (ADS)

As one of the first experiments at the free electron laser of the TESLA Test Facility (TTF) the Coulomb explosion of Xenon clusters irradiated with high intensity pulses at a wavelength of 98nm has been observed. Classical trajectory calculations have been performed in order to illuminate the energy absorption process. Comparison with typical parameters in the infrared regime shows that above barrier ionization is suppressed due to the fast oscillating field and thermionic ionization prevails.

Schulz, J.; Wabnitz, H.; Laarmann, T.; Gürtler, P.; Laasch, W.; Swiderski, A.; Möller, Th.; de Castro, A. R. B.

2003-07-01

241

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

NASA Astrophysics Data System (ADS)

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

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

2000-01-01

242

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

243

Use of optically detected magnetic resonance to correlate germanium electron centres with UV absorption bands in x-ray irradiated germanosilicate glasses  

NASA Astrophysics Data System (ADS)

The relationship between paramagnetic defect centres and UV absorption bands simultaneously generated by ionizing radiation in Ge-doped SiO2 glass is investigated using magneto-optical techniques. A sample of 7.0 mol% Ge-doped SiO2 was exposed to x-ray radiation, which resulted in the formation of absorption bands centred at 4.4 eV and 5.7 eV as well as electron spin resonance (ESR) signals attributed to the Ge(1) and Ge(2) defects. To isolate paramagnetic contributions to the induced optical absorption, the magnetic circular dichroism absorption (MCDA) spectrum was measured at several different temperatures over the range 2.00-6.21 eV. The optically detected magnetic resonance (ODMR) spectrum was then obtained at 4.42 eV via microwave-induced changes in the MCDA signals in order to unambiguously correlate this optical transition with a particular ESR signal. The ODMR data indicate that the Ge(1) centre is responsible for this absorption band, providing the first unequivocal correlation of ESR and optical properties for this defect. In addition, evidence of a weakly absorbing paramagnetic defect, that appears to be related to the Ge(2) centre, was found at 5.65 eV.

Poulios, D. P.; Bigelow, N. P.; Spoonhower, J. P.

2000-09-01

244

A New Approach to Describing the Statistical Laws Governing the Formation of the Contour of Individual Bands in the Optical Absorption Spectra of Liquid Systems  

NASA Astrophysics Data System (ADS)

A new approach to the problem of a quantitative study of the statistical laws governing the formation of the contour of individual bands in the optical absorption spectra of unordered molecular systems (liquids, solutions, liquid crystals, etc.) was developed. The approach is based on a joint consideration of two independent mechanisms of the inhomogeneous broadening of spectral bands; these mechanisms are related to fluctuations of the isotropic and anisotropic components of the total interaction potential of a molecule with the surrounding medium. A generalized expression for the total statistical contour was derived, which made it possible to describe quantitatively the Q-band contour in the vibrational-rotational IR absorption spectrum of a HCl solution in CCl4 at room temperature.

Bakhshiev, N. G.; Sokolov, Yu. P.

2002-02-01

245

Anharmonic Resonance in Intense Laser-Matter Interaction: Key to Collisionless Absorption  

NASA Astrophysics Data System (ADS)

We show that anharmonic resonance is the leading mechanism of collisionless absorption in overdense matter (solids, droplets, clusters). It induces a finite phase shift between current density and laser field, produces the fast electrons in single events, in contrast to stochastic and diffusive processes, and creates the hot Maxwellian tail observed in simulations and measured in the experiment. Finally, the difference in interaction of p polarized and circularly polarized laser light follows in the most immediate way. Some of the proposed absorption mechanisms are critically analyzed.

Mulser, P.; Bauer, D.

2010-11-01

246

[Lambda]-splittings and line intensities in the 2 [l arrow] 1 hot band of nitric oxide  

SciTech Connect

Since nitric oxide plays a major role in the chemistry of stratospheric ozone, it is crucial to measure its atmospheric abundance precisely; this requires an accurate knowledge of the [sup 14]N[sup 16]O molecule line parameters. Using Fourier transform spectra, [Lambda]-splittings and absolute line intensities have been measured in the [sup 2][Pi][sub 1/2]-[sup 2][Pi][sub 1/2] and [sup 2][Pi][sub 3/2]-[sup 2][Pi][sub 3/2] allowed subbands of the vibrational 2 [l arrow] 1 hot band of nitric oxide. To retrieve accurate results from the spectra, [lambda]-doubling and hyperfine splittings were carefully taken into account. However, for most of the studied lines, it turned out that the components of the hyperfine structure are close enough so that they have no susceptible effects on the measured line parameters. Well-chosen cases illustrate the method of measurement. The observed [Lambda]-splittings have been compared with the values deduced from the transition wavenumbers available in the HITRAN database, and large discrepancies (up to 0.006 cm[sup [minus]1] for P(22.5)) appeared for the [sup 2][Pi][sub 3/2]-[sup 2][Pi][sub 3/2] subband. The measured line intensities led to the determination of the transition dipole moment as well as the Herman-Wallis coefficients for the studied hot band. The measured intensities have been found to be larger than the HITRAN values by about 7%.

Dana, V.; Mandin, J.Y.; Coudert, L.H.; Badaoui, M. (Univ. Pierre et Marie Curie, Paris (France). Lab. de Physique Moleculaire et Applications); Le Roy, F.; Guelachvili, G. (Univ. Paris-Sud, Orsay (France). Lab. de Physique Moleculaire et Applications); Rothman, L.S. (Phillips Lab., Hanscom AFB, MA (United States). Optical Environment Div.)

1994-06-01

247

Saturation and inverse-saturation absorption line shapes in alexandrite  

Microsoft Academic Search

Through the use of modulation spectroscopy we have measured the absorption spectrum experienced by a weak probe beam in the presence of a saturating pump beam at two different wavelengths within the broad homogeneous absorption band of alexandrite. At 584 nm the absorption saturates at high pump intensities, and a hole (of width 612 Hz) appears at frequencies near that

Michelle S. Malcuit; Robert W. Boyd; Lloyd W. Hillman; Jerzy Krasinski

1984-01-01

248

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

SciTech Connect

Sounding rocket observations of the ultraviolet fluorescent emissions of the nitric oxide molecule in the lower thermospheric dayglow are described and analyzed. The rocket experiment was an ultraviolet spectrometer which took limb-viewing spectra of the dayglow between 90- and 185- km altitude in the spectral region from 2120 to 2505 [angstrom] with a resolution of 2.0 [angstrom]. The flight occurred at local noon on March 7, 1989, from Poker Flat, Alaska. Several NO[gamma] bands were visible at all altitudes of the flight, along with emission features of N[sub 2], O[sup +], and N[sup +]. The data for the NO (1,0) and (0,1)[gamma] bands were modeled with optically thin synthetic spectra and used as diagnostics of nitric oxide concentrations. The resonant NO (1,0)[gamma] band emissions were shown to be attenuated at low altitudes relative to the expected emission rates predicted from comparison with the nonresonant (0,1)[gamma] band. Inversion of the optically thin data resulted in a peak nitric oxide concentration of 3.1x10[sup 8] cm[sup [minus]3] at an altitude of 100km. A self-absorption model using Holstein transmission functions was developed and applied to the (1,0) [gamma] band observation. The model results agree 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. The success of the model also confirms the value adopted for the absorption oscillator strength of the (1,0)[gamma] band transition and the instrument calibration.

Eparvier, F.G.; Barth, C.A. (Univ. of Colorado, Boulder (United States))

1992-09-01

249

Improved high-intensity microwave discharge lamp for atomic resonance absorption and fluorescence spectrometry  

Microsoft Academic Search

An unusually good combination of high intensity and narrow line has been achieved in a microwave discharge lamp by placing the optical window in the center of the microwave cavity. Construction details and performance characteristics are described.

Assa Lifshitz; Gordon B. Skinner; David R. Wood

1978-01-01

250

The J- and H-bands of organic dye aggregates  

NASA Astrophysics Data System (ADS)

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

Eisfeld, A.; Briggs, J. S.

2006-05-01

251

Anomalous V1<--N vibrational band intensities in the low energy electron impact spectra of trans-dienes  

NASA Astrophysics Data System (ADS)

A detailed examination of the extremely broad and diffuse vibrational structure of the V1<--N allowed valence transition in trans-1,3-butadiene, three related trans-dienes (cis-1,3-pentadiene, trans, trans-2,4-hexadiene, and 2,3-dimethyl-1,3-butadiene), and the cis-diene 1,3-cyclohexadiene has shown that the effect observed previously by Doering, in which the lower vibrational bands of the transition are enhanced in intensity relative to the higher bands at low incident electron energies, occurs in all the trans-dienes studied. This result shows that the effect cannot be due to an underlying, forbidden electronic transition. It appears that in these trans-dienes, the configurational composition of the V1 ''state'' depends on the geometry of the molecule and that the configurational components of the excited state that are important in the vertical transition have different electron impact excitation cross sections than those that are important in the adiabatic transition. These results suggest that electron energy loss spectroscopy is a unique tool for probing the configurational composition of certain highly distorted excited states.

McDiarmid, Ruth; Doering, J. P.

1980-11-01

252

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

SciTech Connect

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

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

2010-05-15

253

Si quantum dots with a high absorption coefficient: Analysis based on both intensive and extensive variables  

NASA Astrophysics Data System (ADS)

Silicon quantum dots (Si-QDs) were produced by pulsed laser ablation in liquid. By measuring the absorption spectra and the concentration of the Si-QD solution, two extinction coefficients were obtained from UV to near IR region: the atomic molar extinction coefficient and the quantum dot molar extinction coefficient. The magnitude of the atomic molar extinction coefficient of the Si-QDs was found to be up to 30 and 270 times those of crystalline and amorphous Si, respectively, and up to 740 times that of previously fabricated Si-QDs. The Si-QDs remained stably dispersed in hydrocarbon and alcohol solvents for over 10 months.

Kitasako, Takumi; Saitow, Ken-ichi

2013-10-01

254

Effective absorption coefficient for graded band-gap semiconductors and the expected photocurrent density in solar cells  

Microsoft Academic Search

A simple model for the generation of carriers by photons incident on a (linearly) decreasing band-gap material, such as has been described in recent CIGS solar cells, is developed. The model can be generalized for different cases such as increasing band-gap grading or for having a more complex band-gap profile.The model developed for direct band semiconductors such as CIGS or

Arturo Morales-Acevedo

2009-01-01

255

Comparison of nosespace, headspace, and sensory intensity ratings for the evaluation of flavor absorption by fat.  

PubMed

The goal of this study was to better understand the correspondence between sensory perception and in-nose compound concentration. Five aroma compounds at three different concentrations increasing by factors of 4 were added to four matrixes (water, skim milk, 2.7% fat milk, and 3.8% fat milk). These were evaluated by nosespace analysis with detection by proton transfer reaction mass spectrometry (PTR-MS), using five panelists. These same panelists evaluated the perceived intensity of each compound in the matrixes at the three concentrations. PTR-MS quantification found that the percent released from an aqueous solution swallowed immediately was between 0.1 and 0.6%, depending on the compound. The nosespace and sensory results showed the expected effect of fat on release, where lipophilic compounds showed reductions in release as fat content increases. The effect is less than that observed in headspace studies. A general correlation between nosespace concentration and sensory intensity ratings was found. However, examples of perceptual masking were found where higher fat milks showed reductions in aroma compound intensity ratings, even if the nosespace concentrations were the same. PMID:12769538

Roberts, Deborah D; Pollien, Philippe; Antille, Nicolas; Lindinger, Christian; Yeretzian, Chahan

2003-06-01

256

Absorption intensity analysis of the Er3+(4f11) transitions in calcium fluorophosphate  

NASA Astrophysics Data System (ADS)

A spectroscopic analysis is performed on Er3+(4f11) ions doped in calcium fluorophosphate (FAP) in order to assess this material for its potential as a near infrared laser material. The Judd-Ofelt model is applied to the polarization-dependant room temperature absorbtion intensities of Er3+(4f11) in FAP in order to obtain the three phenomenological intensity parameters. The intensity parameters are used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds 2S+lLJ of Er3+(4f11) in FAP. Using the radiative decay rates of the Er3+(4f11) transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined in this host. Using room temperature fluorescence lifetime and the radiative lifetime of the Er3+ 4I13/2 Dot; 4I15/2 (1.52 ?m)transition, the quantum efficiency is also determined.

Coeckelenbergh, Cody H.; Yow, Raylon M.; Russell, Charles C., III; Sardar, Dhiraj K.

2004-10-01

257

Absorption Bands at 4300 and 6000-8000Å as Signs of Silicate and Organic Matter Separation and Formation of Hydrated Silicates in KBOs and Similar Bodies  

Microsoft Academic Search

Recent spectral observations of some Kuiper Belt Objects (KBOs) (Boehnhardt et al.: 2002, Proc. of ACM 2002, 47-50; Fornasier S. et al., 2004, Astron. Astrophys. 421, 353-363) discovered characteristic absorption bands at 4300 and 6000-8000Å in reflectance spectra of the bodies. Spectral positions and other parameters of the features are similar to those found in reflectance spectra of terrestrial phyllosilicates

V. V. Busarev; V. A. Dorofeeva; A. B. Makalkin

2004-01-01

258

High-resolution X-ray emission and absorption study of the B 2p valence band electronic structure of MgB2  

Microsoft Academic Search

The occupied and unoccupied valence band states of MgB2 have been studied using high-resolution soft X-ray emission and soft X-ray absorption spectroscopies. In particular, the B 2p partial density of states was measured near the Fermi level. The states at the Fermi edge are identified by comparison to calculation as being of B 2pxy origin. Resonant inelastic X-ray scattering indicates

C. McGuinness; K. E. Smith; S. M. Butorin; J. H. Guo; J. Nordgren; T. Vogt; G. Schneider; J. Reilly; J. J. Tu; P. D. Johnson; David K. Shuh

2001-01-01

259

LASER METHODS IN MEDICINE: Light absorption in blood during low-intensity laser irradiation of skin  

NASA Astrophysics Data System (ADS)

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

Barun, V. V.; Ivanov, A. P.

2010-06-01

260

Swift heavy ion irradiation induced modifications in the optical band gap and Urbach’s tail in polyaniline nanofibers  

Microsoft Academic Search

Optical band gap and Urbach tail width of HCl and CSA doped polyaniline (PAni) nanofibers and the ion beam induced modifications in the band gap and Urbach’s tail of the samples have been studied employing UV–Vis absorption spectroscopy. All the major bands appearing in the FTIR spectra exhibit a decrease in intensity and broadening in their band widths upon interaction

Somik Banerjee; A. Kumar

2011-01-01

261

Absolute intensities for the Q-branch of the 4?22?3?23 (581.776 cm-1) band in carbon dioxide.  

NASA Astrophysics Data System (ADS)

Absolute intensity measurements in the Q-branch of the 4?22ý3?23 band of CO2 at 581.776 cm-1 have been performed using tunable diode laser spectroscopy. It was found that the values listed in the HITRAN (Rothman et al., 1992) database, which are calculated by direct numerical diagonalization, are 5% higher than those measured here. The vibrational band strength is 4.963(56)×10-3cm-2atm-1 at 296 K. A vanishing Hermann-Wallis coefficient is adequate to characterize this band up to J = 40.

Steyert, D. W.; Weber, M.; Sirota, J. M.; Reuter, D. C.

1995-11-01

262

Suppression of near-edge optical absorption band in sputter deposited HfO2-Al2O3 nanolaminates containing nonmonoclinic HfO2  

NASA Astrophysics Data System (ADS)

Nanolaminates of polycrystalline (tetragonal+orthorhombic) HfO2 and amorphous Al2O3 are sputter deposited on unheated fused SiO2, air annealed at 573-1273 K, and analyzed by x-ray diffraction and spectrophometry. Significant O 2p-->Hf 5d interband absorption occurs in all films at energy E>=6.2 eV. For E<6.2 eV, films annealed below 1273 K retain a featureless optical absorption edge despite further crystallization. A band with a 5.65 eV onset concurrently develops with m-HfO2 crystallization after a 1273 K anneal, indicating this phase and not nanocrystallinity per se is responsible for increased absorption.

Hoppe, E. E.; Aita, C. R.

2008-04-01

263

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

NASA Astrophysics Data System (ADS)

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

Liverini, V.; Rutz, A.; Keller, U.; Schön, S.

2006-06-01

264

Annihilation processes in the isolated D1-D2-cyt-b559 reaction center complex of photosystem II. An intensity-dependence study of femtosecond transient absorption  

SciTech Connect

The excitation intensity dependence of the kinetics of the primary processes and of the yield of radical pair formation in the isolated D1-D2-cyt-b559 reaction center of photosystem II has been studied by femtosecond transient absorption spectroscopy. It is shown that the kinetics is strongly dependent on the excitation intensity. The radical pair yield as a function of excitation intensity is compared with the theoretical annihilation curve and a good agreement between theory and experiment is observed, indicating that the intensity effects on the kinetics and radical pair yield arise primarily from annihilation processes. Sufficiently annihilation-free measurements require excitation intensities that give rise to <=0.06 absorbed photons/RC while maintaining a high signal/noise ratio of >= 100:1 at most detection wavelengths in order to resolve the complex kinetics. It is shown that such low excitation intensities give rise to absorption changes that are at the edge of the capabilities of present femtosecond absorption equipment. We also compare the excitation conditions that have been used so far by other research groups for published transient absorption data on the isolated D1-D2-cyt-b559 complex. This comparison shows that essentially all published data have been obtained under conditions where annihilation or quenching effects are expected to significantly distort the kinetics and time-resolved spectra and to reduce the radical pair yield. 45 refs., 6 figs., 1 tab.

Mueller, M.G.; Hucke, M.; Reus, M.; Holzwarth, A.R. [Max-Planck-Institut fuer Strahlenchemie, Muelheim a.d. Ruhr (Germany)

1996-05-30

265

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

Microsoft Academic Search

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

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

1996-01-01

266

Analysis of the nu8 + nu9 Band of HNO3, Line Positions and Intensities, and Resonances Involving the v6 = v7 = 1 Dark State.  

PubMed

Using a high-resolution (R = 0.0025 cm-1) Fourier transform spectrum of nitric acid recorded at room temperature in the 1100-1240 cm-1 region, it has been possible to perform a more extended analysis of the nu8 + nu9 band of HNO3 centered at 1205.7075 cm-1. As in a recent analysis of this band [W. F. Wang, P. P. Ong, T. L. Tan, E. C. Looi, and H. H. Teo, J. Mol. Spectrosc. 183, 407-413 (1997)], the Hamiltonian used for the line positions calculation takes into account, for the upper state, the DeltaK = +/-2 anharmonic resonance linking the rotational levels of the v8 = v9 = 1 "bright" vibrational state and those of the "dark" v6 = v7 = 1 vibrational state. More than 4800 lines were assigned in the nu8 + nu9 band, which involve significantly higher rotational quantum numbers than in previous works. On the other hand, and surprisingly as compared to previous studies, the nu8 + nu9 band appears to be a hybrid band. In fact, nonnegligible B-type transitions could be clearly identified among the much stronger A-type lines. Accordingly, a set of individual line intensities were measured for lines of both types and were introduced in a least-squares fit to get the A- and B-type components of the transition moment operator. Finally, a synthetic spectrum of the 8.3-µm region of HNO3 has been generated, using for the line positions and line intensities the Hamiltonian constants and the expansion of the transition moment operator which were determined in this work. In this way, the B-type and the A-type components of the nu8 + nu9 band appear to contribute for about (1/4) and (3/4), respectively, to the total band intensity. Copyright 1999 Academic Press. PMID:9986780

Perrin; Flaud; Keller; Goldman; Blatherwick; Murcray; Rinsland

1999-03-01

267

Site-selection spectroscopy of the reaction center complex of photosystem II. I. Triplet-minus-singlet absorption difference. Search for a second exciton band of P-680  

SciTech Connect

The D1-D2-Cytb559 reaction center complex of photosystem II was studied at 4 K with triplet-minus-singlet (T-S) absorption difference spectroscopy using selective laser excitation. The T-S spectrum is mainly due to the bleaching of P-680 and significantly differs from the T-S spectrum of monomeric Chl a in detergent. The absorption spectrum ascribed to the primary electron donor, P-680, was interpreted in terms of two distinguishable distributions, around 681 and 684 nm, respectively. These spectral forms could be preferentially selected by relatively blue ([lambda][sub exc] = 661-677 nm) and extremely red excitation ([lambda][sub exc] = 691 nm), respectively. In addition to the bleaching at 681-684 nm, a small band at 667 nm was also observed, which had opposite polarization. We attributed the latter to an exciton band, not associated with a single pigment. Thus upon triplet formation a system consisting of N excitonically coupled pigments (N > 1) is reduced by one due to localization of the triplet state on one of the pigments. The simplest, although not the only, case is given by N = 2, for which P-680 is a dimer with exciton bands at 681-684 and 667 nm. 44 refs., 11 figs.

Kwa, S.L.S.; Eijckelhoff, C.; Grondelle, R. van; Dekker, J.P. (Vrije Universiteit, Amsterdam (Netherlands))

1994-08-04

268

Beta-decay intensity distributions for the fission products 139Cs and 140Cs measured with a total absorption ?-ray spectrometer  

NASA Astrophysics Data System (ADS)

A total absorption ?-ray spectrometer has been developed on the 252Cf-based INEL ISOL facility and is being used in a program of measurements of ?--decay intensity distributions of short-lived fission-product nuclei. Spectra for 139Cs and 140Cs have been measured and compared with those simulated for the published decay schemes as a test of the completeness and correctness of these schemes. New ?--intensity distributions have been deduced for the decay of these isotopes.

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

1994-12-01

269

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

Microsoft Academic Search

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

F. K. Reinhart

2005-01-01

270

Modification of band alignment at interface of AlyGa1-ySb/AlxGa1-xAs type-II quantum dots by concentrated sunlight in intermediate-band solar cells with separated absorption and depletion regions  

NASA Astrophysics Data System (ADS)

We propose a new intermediate band GaAs solar cell comprising an AlxGa1-xAs absorber with built-in GaSb type-II quantum dots (QDs) [a gradual AlxGa1-xAs absorber with built-in AlyGa1-ySb QDs (0band alignment at type-II interface by two-photon absorption of concentrated sunlight. Our calculation shows that photogenerated carriers produce localized exciton-like electron-hole pairs spatially separated at QDs. Local field of such pairs may essentially modify potential barrier surrounding QDs, increase recombination lifetime of mobile carriers and additional photocurrent generated by two photon absorption. Concentration of about 300-sun pushes by 15% up the conversion efficiency as compared to the efficiency of the reference single junction GaAs solar cell without QDs.

Kechiantz, A.; Afanasev, A.; Lazzari, J.-L.

2013-03-01

271

PSDF of log-amplitude scintillation for 7 mu m band laser beam with absorption by water vapour  

Microsoft Academic Search

The power spectral density function (PSDF) of the log-amplitude scintillation for an infrared laser beam was measured experimentally. To investigate the contribution of the absorption and the dispersion that cause the scintillation, we chose 16 wavelengths of infrared light and one wavelength of visible light. It is found that the spectral density of scintillation for the infrared beam does not

Naoki Kagawa; Osami Wada; Ryuji Koga

1993-01-01

272

EFFECT OF CENTIMETER BAND RADIO WAVES ON THE ABSORPTION OF AMINO ACIDS, CHLORIDES AND WATER IN THE STOMACH AND INTESTINE  

Microsoft Academic Search

The absorption of amino acids, chlorides, and water was studied in the ; normal state and under the effect of high frequency of the centimeter waveband on ; 8 dogs with Pavlov pouches (3) and isolated loop of the small intestine (3 dogs). ; The effect of a 50 watt radio-wave field acting on the organism for 10 minutes on

Feitelberg-Blank

1962-01-01

273

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

274

Emergence of charge-transfer-to-solvent band in the absorption spectra of hydrogen halides on ice nanoparticles: spectroscopic evidence for acidic dissociation.  

PubMed

Extensive ab initio calculations complemented by a photodissociation experiment at 193 nm elucidate the nature of hydrogen halide molecules bound on free ice nanoparticles. Electronic absorption spectra of small water clusters (up to 5 water molecules) and water clusters doped with hydrogen fluoride, hydrogen chloride and hydrogen bromide were calculated. The spectra were modeled at the time-dependent density functional (TDDFT) level of theory with the BHandHLYP functional using the reflection principle. We observe the emergence of a charge-transfer-to-solvent (CTTS) band in the absorption spectra upon the acidic dissociation of the hydrogen halides. The CTTS band provides a spectroscopically observable feature for the acidic dissociation. The calculated spectra were compared with our new experimental photodissociation data for larger water clusters doped with HCl and HBr. We conclude that HCl and HBr dissociate to a large extent on the surface of ice nanoparticles at temperatures near 120 K and photoactive products are formed. The acidic dissociation of HX leads to an enhancement by about 4 orders of magnitude of the HCl photolysis rate in the 200-300 nm region, which is potentially relevant for the halogen budget in the atmosphere. PMID:18507365

Oncák, Milan; Slavícek, Petr; Poterya, Viktoriya; Fárník, Michal; Buck, Udo

2008-05-29

275

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

276

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

PubMed

The interactions of Pr(III) with nucleosides and nucleotides have been studied in different organic solvents employing absorption difference and comparative absorption spectrophotometry. The magnitudes of the variations in both energy and intensity interaction parameters were used to explore the degree of outer and inner sphere co-ordination, incidence of covalency and the extent of metal 4f-orbital involvement in chemical bonding. Various electronic spectral parameters like Slater-Condon (F(k)), Racah (E(k)), Lande parameter (?(4f)), Nephelauxatic ratio (?), bonding (b(1/2)), percentage covalency (?) and intensity parameters like oscillator strength (P) and Judd Ofelt electronic dipole intensity parameter (T(?), ?=2,4,6) have been evaluated. The variation of these evaluated parameters were employed to interpret the nature of binding of Pr(III) with different ligands i.e. Adenosine/ATP in presence and absence of Ca(2+). PMID:23257345

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

2012-11-16

277

Space - Time Distribution of G-band and Ca ii H-line Intensity Oscillations in Hinode/SOT - FG Observations  

NASA Astrophysics Data System (ADS)

We study the space - time distributions of intensity fluctuations in 2 - 3 hour sequences of multi-spectral, high-resolution, high-cadence, broad-band filtergram images of the Sun made by the SOT - FG system aboard the Hinode spacecraft. In the frequency range 5.5< f<8.0 mHz both G-band and Ca ii H-line oscillations are suppressed in the presence of magnetic fields, but the suppression disappears for f>10 mHz. By looking at G-band frequencies above 10 mHz we find that the oscillatory power, both at these frequencies and at lower frequencies, lies in a mesh pattern with cell scale 2 - 3 Mm, clearly larger than normal granulation, and with correlation times on the order of hours. The mesh pattern lies in the dark lanes between stable cells found in time-integrated G-band intensity images. It also underlies part of the bright pattern in time-integrated H-line emission. This discovery may reflect dynamical constraints on the sizes of rising granular convection cells together with the turbulence created in strong intercellular downflows.

Lawrence, J. K.; Cadavid, A. C.

2010-01-01

278

CH3D Absorption Bands Between 2.86 And 3.10 Microns In The High-resolution Spectra Of Titan  

NASA Astrophysics Data System (ADS)

The ?2 + ?3 band of CH3D near 2.86 microns (Kim et al. 2005) has been detected in absorption in the high-resolution spectra of Titan observed with NIRSPEC at Keck II (Geballe et al. 2003). Between 2.92 and 3.10 microns in the same spectra other weak CH3D band lines have been identified based on a recent line list compiled by one of us. These CH3D lines are useful to investigate stratospheric and tropospheric haze opacities in this wavelength range, because: 1) CH4 mixing ratios during the descendent of Huygens at the landing site are now determined from the in situ measurements of the Gas Chromatograph and Mass Spectrometer (GCMS) (e.g., Niemann et al. 2005); 2) the CH3D/CH4 mixing ratio is believed to be uniform from surface to high-altitude atmosphere, and, therefore, altitude-dependent CH3D mixing ratios should also be derived; and 3) the 2.96 - 3.20 micron range is relatively free from strong absorptions of other molecular bands. We will present preliminary results on the derived optical property of haze layers between 2.86 and 3.10 microns; and we will also test a possibility of the global supersaturation of CH4 in the troposphere of Titan utilizing the CH3D lines. References Geballe, T.R., Kim,S.J., Noll, K.S., and Griffith, C.A. 2003. Ap. J. 583, L39-L42. Kim, S.J., Geballe, T.R., Noll, K.S., and Courtin, R. 2005. Icarus, 173, 522-532.Niemann, H.B., and 17 coauthors. 2005. Nature. 438, 779-784.

Kim, Sang J.; Seo, H.; Kim, J.; Geballe, T. R.; Courtin, R.; Brown, L.

2006-09-01

279

Warm, Dense Gas Near the Massive Protostar AFGL 2136 IRS 1 AS Revealed by Absorption from the ?_1, ?_2, and ?_3 Bands of Water  

NASA Astrophysics Data System (ADS)

We have identified absorption features due to 47 different ro-vibrational transitions of the ?_1 and ?_3 fundamental and ?_2 overtone bands of H_2O between 2.468 ?m and 2.561 ?m toward the massive protostar AFGL 2136 IRS 1, and determined column densities in each rotational level. Analysis of the relative level populations indicates the absorption arises in warm (T?500 K), very dense (n_{ H}>10^{10} cm^{-3}) gas in local thermodynamic equilibrium, with a total water column density of N({ H_{2}O})?10^{19} cm^{-2}. This gas must be very close to the central protostar, either in the inner envelope or a circumstellar disk/torus. Our findings are consistent with results inferred from 4.7 ?m CO observations, 6 ?m H_2O observations, and our own 2.5 ?m HF observations. This study represents the first extensive use of water vapor absorption lines in the near infrared, and we examine the possibility of using such observations to derive physical parameters in the gas surrounding other protostars. Mitchell, G. F., et al. 1990, ApJ, 363, 554 Boonman, A. M. S., & van Dishoeck, E. F. 2003, A&A, 403, 1003 Indriolo, N., Neufeld, D. A., Seifahrt, A., & Richter, M. J. 2013, ApJ, 764, 188

Indriolo, Nick; Neufeld, David A.; Seifahrt, Reas; Richter, Matt J.

2013-06-01

280

DNA-modified silicon nanocrystals studied by X-ray luminescence and X-ray absorption spectroscopies: Observation of a strong infra-red luminescence band  

NASA Astrophysics Data System (ADS)

Silicon nanocrystals (SiNCs) modified with 18-mer DNA oligonucleotides have been studied by X-ray excited optical luminescence (XEOL) and X-ray absorption spectroscopy (XAS) in photoluminescence yield (PLY) and total electron yield (TEY) modes. Luminescence spectra from the DNA-modified SiNCs under X-ray excitation display distinct differences from simple alkyl terminated SiNCs. The DNA-modified SiNCs show strong luminescence at 540 +/- 10 nm under vacuum ultraviolet excitation which is assigned to nitrogen 1s - ?* transitions within the DNA bases. Under excitation at 130 eV the PLY spectra from the same samples show the native nanocrystal ultraviolet emission band is suppressed, and the strongest emission peak is red shifted from 430 +/- 10 nm to 489 +/- 10 nm which we attribute to base nitrogen 1s transitions. In addition, a strong emission band in the infrared region at 815 +/- 10 nm is observed. This clearly resolved strong IR band from the DNA-modified SiNCs may provide a useful luminescence signature in cell-labeling techniques and open up a range of applications for invivo assays.

Coxon, P. R.; Newman, M.; Hunt, M. R. C.; O'Farrell, N.; Horrocks, B. R.; Poolton, N. R. J.; Šiller, L.

2012-03-01

281

Intermodulation distortion suppression for intensity-modulated analog fiber-optic link incorporating optical carrier band processing.  

PubMed

An intermodulation distortion suppression method based on the optical carrier band processing is demonstrated. A systematic analysis of the main optical spectrum contributors for the third-order intermodulation distortion in the nonlinear system is presented. Theoretical analysis shows that the third-order intermodulation distortion terms can cancel each other if a proper phase shifting is imposed to the optical carrier band. We experimentally demonstrate the approach with a two-tone test and a suppression of about 33 dB in the third-order intermodulation distortion is obtained. Experimental results show that an overall fundamental to third-order intermodulation distortion ratio of up to 64 dB is achieved and the link dynamic range is improved by 14.7 dB, compared with the conventional link without the proposed optical carrier band processing. PMID:24104257

Cui, Yan; Dai, Yitang; Yin, Feifei; Dai, Jian; Xu, Kun; Li, Jianqiang; Lin, Jintong

2013-10-01

282

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

NASA Astrophysics Data System (ADS)

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

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

2010-10-01

283

Peculiarities of Human Sleep under Conditions of Continuous Prolonged Influence of Broad-Band Noise of Average Intensity.  

National Technical Information Service (NTIS)

Studies were conducted at the Prof. F. D. Garbov laboratory on the effects of continuous protracted broad band noise on sleep and on the transitional state between sleep and wakefulness to determine the physiological basis for the disturbing effects of no...

V. I. Myasnikov O. P. Kozerenko I. Y. Yakovleva E. I. Matsnev I. P. Lebedeva

1969-01-01

284

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

285

60-GHz oxygen band: precise broadening and central frequencies of fine-structure lines, absolute absorption profile at atmospheric pressure, and revision of mixing coefficients  

NASA Astrophysics Data System (ADS)

The 60-GHz band of 16O2 was studied at room temperature and at low (up to 4 Torr) and atmospheric pressures. Precision measurement of central frequencies, self-broadening, and N2-broadening parameters of fine-structure transitions up to N = 27 was performed by use of a spectrometer with radio-acoustic detection (RAD). The measured parameters are compared with GEISA/HITRAN databanks, MPM92, and other known data. An improved set of the oxygen fine-structure spectroscopic constants is obtained. The absorption profile was recorded in the range 45 96 GHz for laboratory air and pure oxygen at atmospheric pressure by use of a resonator spectrometer with noise level of about ± 0.05 dB/km, and used for deducing the first-order line mixing coefficients and for quantitative assessment of second-order mixing effects. A refined set of MPM parameters is derived from the new data and presented here.

Tretyakov, M. Yu.; Koshelev, M. A.; Dorovskikh, V. V.; Makarov, D. S.; Rosenkranz, P. W.

2005-05-01

286

A Methodology for Estimating the Effect of Solar Spectrum on Photovoltaic Module Performance by Using Average Photon Energy and a Water Absorption Band  

NASA Astrophysics Data System (ADS)

Various photovoltaic (PV) technologies are commercially available today. The effect of solar spectrum on the performance of PV modules should be evaluated quantitatively in order to estimate the module performance with high accuracy and precision. Average photon energy (APE) has been frequently applied to evaluate the effect of solar spectrum. The purpose of this study is to enhance the precision and accuracy by introducing other indexes. In this study, we select solar spectra, the integrated spectral irradiance (ISI) and APE of which are equivalent to those of the standard AM1.5G spectrum. There is a slight difference in shape, although the shapes are approximately similar. We introduce one more index, which defines the spectral irradiance at the atmospheric window or the depth of the water absorption band. The introduction would further improve the accuracy and precision of the evaluation of the effect of solar spectrum.

Ishii, Tetsuyuki; Otani, Kenji; Itagaki, Akihiko; Utsunomiya, Kenji

2012-10-01

287

Orbital structure of FeTiO3 ilmenite investigated with polarization-dependent X-ray absorption spectroscopy and band structure calculations  

NASA Astrophysics Data System (ADS)

We explored the orbital structure of FeTiO3 with polarization-dependent x-ray absorption spectra complemented with electronic structure calculations. The electronic structure, near the bottom of conduction band, is composed of O 2p and Ti 3d orbitals. Ti 3d/4p hybridization dominantly lies on the ab plane. The highly delocalized Ti 4p orbital might hybridize with O 2p orbital and even extend to the next-neighbor Fe atom whereby establishing a linear orbital combination of Ti-O-Fe. A clear picture of the orbital construction in FeTiO3 will help to elucidate the paths of pressure-induced charge transfer and other physical or magnetic characteristics.

Chen, S. W.; Huang, M. J.; Lin, P. A.; Jeng, H. T.; Lee, J. M.; Haw, S. C.; Chen, S. A.; Lin, H. J.; Lu, K. T.; Chen, D. P.; Dou, S. X.; Wang, X. L.; Chen, J. M.

2013-01-01

288

OH density measurement by time-resolved broad band absorption spectroscopy in an Ar-H2O dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

We report results of a novel time-resolved broad-band absorption spectroscopy experiment for OH density measurement applied to a pulsed dielectric barrier discharge in Ar/H2O mixtures. The measurement is aimed at the calibration of our previous OH LIF measurements in the same discharge. The apparatus is simple and cheap, being based on a UV LED light source and a non-intensified, non-cooled, gateable linear CCD array as a detector. The set-up is capable of ruling out both medium/long-term drifts of the UV source and of the discharge, and discharge emission from the measurement. Performances of the set-up are discussed, together with possible improvements for its use as a standalone technique.

Dilecce, G.; Ambrico, P. F.; Simek, M.; De Benedictis, S.

2012-03-01

289

On the Negative Delay Time of a Narrow-Band Signal as It Passes Through the Resonant Filter of Absorption  

NASA Astrophysics Data System (ADS)

It is shown that a narrow-band signal with smoothly varying envelope can have a negative delay time upon filtering by certain physically realizable filters, i.e., the smooth-signal envelope shifts forward rather than backward. We show that this does not contradict the casuality principle, since the advanced appearance of the signal has the nature of prediction of the future signal level from the time dependence of its level in the past. It is shown that in the case of a negative delay time, the time dependence of a switched-off signal can be recovered, i.e., reception of the untransmitted part of the signal is possible. We propose to use these phenomena for predicting signals of natural and artificial origin.

Bukhman, N. S.; Bukhman, S. V.

2004-01-01

290

Measurement of beta--decay intensity distributions of several fission-product isotopes using a total absorption gamma-ray spectrometer  

Microsoft Academic Search

A total absorption gamma-ray spectrometer coupled to the 252Cf-based INEL ISOL facility has been used in a program of systematic study of the distributions of beta--decay intensities of fission-product radionuclides. Cascade-summed gamma-ray spectra measured with the system have been compared with the spectrum simulated from the corresponding decay schemes, as a test of the completeness and correctness of these schemes.

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

1997-01-01

291

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

292

Midinfrared intersubband absorption in wide band gap II-VI ZnxCd1-xSe multiple quantum wells with metastable zincblende MgSe barriers  

NASA Astrophysics Data System (ADS)

The authors report the observation of midinfrared intersubband (ISB) absorption in MgSe/ZnxCd1-xSe multiple quantum wells (MQWs) grown on (001) InP substrates by molecular beam epitaxy. The in situ reflection high energy electron diffraction shows that zincblende MgSe/ZnxCd1-xSe MQWs can be grown with the introduction of ZnxCd1-xSe spacer layers. For quantum wells with the nominal well width of 11-15 ML (3.2-4.4 nm) ISB absorption in the wavelength range of 3.3-4.9 ?m is observed. The conduction band offset (CBO) of the MgSe/ZnxCd1-xSe heterostructure is estimated to be 1.2 eV. Using the estimated CBO, the theoretically calculated interband and ISB transition energies agree well with photoluminescence and Fourier-transform infrared spectroscopy measurements. With such a large CBO, ISB transitions in this material system could be extended to the near infrared region.

Li, B. S.; Shen, A.; Charles, W. O.; Zhang, Q.; Tamargo, M. C.

2008-06-01

293

Time-resolved absorption changes of the pheophytin Q{sub x} band in isolated photosystem II reaction centers at 7 K: Energy transfer and charge separation  

SciTech Connect

The pheophytin a Q{sub x} spectral region of the isolated photosystem II reaction center was investigated at 7 K using femtosecond transient absorption spectroscopy. At this temperature, uphill energy transfer, which greatly complicates the interpretation of the kinetics at or near room temperature, should be essentially shut off. Low-energy ({approximately}100 nJ) pulses at 661 and 683 nm were used to excite the short-wavelength and long-wavelength sides of the composite Q{sub y} band, providing preferential excitation of the accessory pigment pool and P680, respectively. The data analysis uses a background subtraction technique developed earlier (Greenfield et al. J. Phys. Chem. B 1997, 101, 2251--2255) to remove the kinetic components of the data that are due to the large time-dependent changes in the background that are present in this spectral region. The instantaneous amplitude of the bleach of the pheophytin a Q{sub x} band with 683 nm excitation is roughly two-thirds of its final amplitude, providing strong evidence of a multimer description of the reaction center core. The subsequent growth of the bleach shows biphasic kinetics, similar to the earlier results at 278 K. The rate constant of the faster component is (5 ps){sup {minus}1} for 683 nm excitation (a factor of almost two faster than at 278 K), and represents the intrinsic rate constant for charge separation. The bleach growth with 661 nm excitation is also biphasic; however, the faster component appears to be a composite of a (5 ps){sup {minus}1} component corresponding to charge separation following subpicosecond energy transfer to the long-wavelength pigments and a roughly (22 ps){sup {minus}1} component corresponding to charge separation limited by slow energy transfer. The combined quantum yield for these two energy transfer processes is near unity. For both excitation wavelengths, there is also a roughly (100 ps){sup {minus}1} component to the bleach growth. Exposure to high excitation energies ({le} 1 {micro}J) at 683 nm results in a substantial permanent loss of ground-state absorption at 680 nm. The transient behavior of these degraded samples is also examined and is consistent with the (5 ps){sup {minus}1} rate constant for charge separation. The authors results are compared to other low-temperature transient absorption and hole burning studies, as well as to the 278 K results.

Greenfield, S.R.; Seibert, M.; Wasielewski, M.R.

1999-09-30

294

Time-resolved absorption changes of the pheophytin Q{sub x} band in isolated photosystem II reaction centers at 7K : energy transfer and charge separation.  

SciTech Connect

The pheophytin {alpha} Q{sub x} spectral region of the isolated photosystem II reaction center was investigated at 7 K using femtosecond transient absorption spectroscopy. At this temperature, uphill energy transfer, which greatly complicates the interpretation of the kinetics at or near room temperature, should be essentially shut off. Low-energy ({approx}100 nJ) pulses at 661 and 683 nm were used to excite the short-wavelength and long-wavelength sides of the composite Q{sub y} band, providing preferential excitation of the accessory pigment pool and P680, respectively. The data analysis uses a background subtraction technique developed earlier (Greenfield et al. J. Phys. Chem. B 1997, 101, 2251-2255) to remove the kinetic components of the data that are due to the large time-dependent changes in the background that are present in this spectral region. The instantaneous amplitude of the bleach of the pheophytin {alpha} Q{sub x} band with 683 nm excitation is roughly two-thirds of its final amplitude, providing strong evidence of a multimer description of the reaction center core. The subsequent growth of the bleach shows biphasic kinetics, similar to our earlier results at 278 K. The rate constant of the faster component is (5 ps){sup -1} for 683 nm excitation (a factor of almost two faster than at 278 K), and represents the intrinsic rate constant for charge separation. The bleach growth with 661 nm excitation is also biphasic; however, the faster component appears to be a composite of a (5 ps){sup -1} component corresponding to charge separation following subpicosecond energy transfer to the long-wavelength pigments and a roughly (22 ps){sup -1} component corresponding to charge separation limited by slow energy transfer. The combined quantum yield for these two energy transfer processes is near unity. For both excitation wavelengths, there is also a roughly (100 ps){sup -1} component to the bleach growth. Exposure to high excitation energies ({>=}1 {mu}J) at 683 nm results in a substantial permanent loss of ground-state absorption at 680 nm. The transient behavior of these degraded samples is also examined and is consistent with the (5 ps){sup -1} rate constant for charge separation. Our results are compared to other low-temperature transient absorption and hole burning studies, as well as to our 278 K results.

Greenfield, S. R.; Seibert, M.; Wasielewski, M. R.; Chemistry; LANL; NREL; Northwestern Univ.

1999-09-30

295

Electromagnetic properties and microwave absorption properties of BaTiO3-carbonyl iron composite in S and C bands  

NASA Astrophysics Data System (ADS)

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

Rui-gang, Yang

2011-07-01

296

Total absorption gamma-ray spectrometer for measurement of beta-decay intensity distributions for fission product radionuclides  

Microsoft Academic Search

A total absorption gamma-ray spectrometer (TAGS), based on a 25.4 cm diameter × 30.5 cm long NaI(Tl) well detector, has been developed at the INEL on-line isotope separator facility. A Si detector in the well of the NaI(Tl) detector allows one to collect beta-particle-gated coincidence spectra as well as singles spectra. With this system, measurements of the total absorption spectra

R. C. Greenwood; R. G. Helmer; M. A. Lee; M. H. Putnam; M. A. Oates; D. A. Struttmann; K. D. Watts

1992-01-01

297

Intensity of the polarized Raman band at 1340-1345 cm-1 as an indicator of protein alpha-helix orientation: application to Pf1 filamentous virus.  

PubMed

Raman spectra of oriented alpha-helical protein molecules exhibit a prominent band near 1340-1345 cm(-)(1), the intensity of which is highly sensitive to molecular orientation. Polarization of the 1340-1345 cm(-)(1) marker is evident in Raman spectra of alpha-helical poly-L-alanine (alphaPLA) and alpha-helical poly-gamma-benzyl-L-glutamate (alphaPBLG). Corresponding polarization is also observed in Raman spectra of the filamentous virus Pf1, which is an assembly of alpha-helical coat protein molecules. In alphaPLA and alphaPBLG, we assign the band to a normal mode of symmetry type E(2) and specifically to a vibration localized in the (O=C)-C(alpha)-H linkages of the main chain peptide group. Although strict helical symmetry does not apply to coat subunits of filamentous viruses, an approximate E(2)-type mode may be presumed to account for a corresponding Raman band of Pf1 and fd filamentous viruses. Spectroscopic studies of N-methylacetamide and isotopically-edited fd viruses support the present assignment of the 1340-1345 cm(-)(1) band. Polarization anisotropy indicates that this band may be exploited as a novel indicator of protein alpha-helix orientation. Application of this approach to the polarized Raman spectrum of Pf1 suggests that, on average, the axis of the alpha-helical coat protein subunit in the native virion structure forms an angle of 20 +/- 10 degrees with respect to the virion axis. PMID:10704218

Tsuboi, M; Suzuki, M; Overman, S A; Thomas, G J

2000-03-14

298

Absolute intensity, high resolution spectrum of the vortek arc lamp and its spectral match to Nd:YAG bands  

Microsoft Academic Search

A high resolution (1 \\/angstrom\\/), absolute intensity spectrum from 300 to 900 nm was obtained for a high average power (100 kWe) argon arc-lamp. The high average power is obtained due to innovative technology that cools the inside surface of the lamp envelope by means of a spiraling water jet. The optical output between 200 and 2000 nm was measured

1989-01-01

299

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

Microsoft Academic Search

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

Frank Silvio Marzano; Laura Roberti

2003-01-01

300

Absolute Intensity, High Resolution Spectrum of the Vortek Arc Lamp and Its Spectral Match to Nd:YAG Bands.  

National Technical Information Service (NTIS)

A high resolution (1 angstrom), absolute intensity spectrum from 300 to 900 nm was obtained for a high average power (100 kWe) argon arc-lamp. The high average power is obtained due to innovative technology that cools the inside surface of the lamp envelo...

L. E. Zapata

1989-01-01

301

Absolute intensity, high resolution spectrum of the Vortek arc lamp and its spectral match to Nd:YAG bands  

Microsoft Academic Search

A high resolution (1â«), absolute intensity spectrum from 300 to 900 nm was obtained for a high average power (100 kWe) argon arc-lamp. The high average power is obtained due to innovative technology that cools the inside surface of the lamp envelope by means of a spiraling water jet. The optical output between 200 and 2000 nm was measured by

L. E. Zapata; A. J. Pertica

1989-01-01

302

Semiclassical model for the absorption or emission of a photon by a charged particle in an intense static electric field  

Microsoft Academic Search

Quantum simulations made using Floquet methods show that a charged particle can exchange energy with an oscillating potential barrier in discrete quanta h?, where ? is the frequency of oscillation. However, this exchange is classically forbidden because no other mass is included in the model, so that energy and momentum could not both be conserved in the absorption or emission

Mark J. Hagmann

1998-01-01

303

Stimulus intensity affects early sensory processing: visual contrast modulates evoked gamma-band activity in human EEG.  

PubMed

We studied the effect of different contrast levels on the visual evoked gamma-band response (GBR) in order to investigate whether the GBR is modulated in a similar manner as previously reported for visual evoked potentials. Previous studies showed that the GBR can be modulated by individual characteristics (age) and experimental conditions (task difficulty, attention). However, stimulus properties, such as size and spatial frequency, also have a large impact on the GBR, which necessitates identification and control of relevant stimulus properties for optimal experimental setups. Twenty-one healthy participants were investigated during a forced-choice discrimination task. Sinusoidal gratings were presented at three contrast levels with a constant spatial frequency of 5 cycles per degree visual arc (cpd). The present data replicate the results reported for visual evoked potentials and exhibit a contrast dependent modulation of the GBR. Gamma activity is increased for higher contrast levels. These results demonstrate the importance of stimulus contrast for evoked gamma activity. Thus, it appears meaningful to control the contrast of stimuli in experiments investigating the role of gamma activity in perception and information processing. PMID:17599598

Schadow, Jeanette; Lenz, Daniel; Thaerig, Stefanie; Busch, Niko A; Fründ, Ingo; Rieger, Jochem W; Herrmann, Christoph S

2007-06-02

304

Determination of the absorption and scattering coefficients of highly scattering media from the experimentally established temporal distributions of laser pulse intensities  

SciTech Connect

The passage of laser radiation through a scattering medium is studied experimentally. A method of determining the optical characteristics of a scattering media is proposed. The method is based on the measurements of time distributions of the intensity of ultrashort laser pulses for two layer thicknesses of the medium to be studied. The measurements are carried out with the use of a single-photon counting system. The proposed method is used to determine the absorption and scattering coefficients of a model medium from the experimental data.

Danilov, A. A.; Tereshchenko, S. A., E-mail: tsa@miee.ru; P'yanov, I. V.; Gavrikov, A. I. [Moscow State Institute of Electronic Technology (Technical University) (Russian Federation)

2011-12-15

305

The relationship of temperature rise to specific absorption rate and current in the human leg for exposure to electromagnetic radiation in the high frequency band  

NASA Astrophysics Data System (ADS)

Of the biological effects of human exposure to radiofrequency and microwave radiation, the best-established are those due to elevation of tissue temperature. To prevent harmful levels of heating, restrictions have been proposed on the specific absorption rate (SAR). However, the relationship between SAR and temperature rise is not an invariant, since not only the heat capacity but also the efficiency of heat dissipation varies between different tissues and exposure scenarios. For small enough SAR, the relationship is linear and may be characterized by a 'heating factor' DgrT/SAR. Under whole-body irradiation the SAR may be particularly high in the ankles due to the concentration of current flowing through a relatively small cross-sectional area. In a previous paper, the author has presented calculations of the SAR distribution in a human leg in the high frequency (HF) band. In this paper, the heating factor for this situation is derived using a finite element approximation of the Pennes bio-heat equation. The sensitivity of the results to different blood perfusion rates is investigated, and a simple local thermoregulatory model is applied. Both time-dependent and steady-state solutions are considered. Results confirm the appropriateness of the ICNIRP reference level of 100 mA on current through the leg, but suggest that at higher currents significant thermoregulatory adjustments to muscle blood flow will occur.

Wainwright, P. R.

2003-10-01

306

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

307

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

PubMed

We develop a dynamic multi-band OFDM subcarrier allocation scheme to fully utilize the available bandwidth under the restriction of dispersion- and chirp-related power fading. The experimental results successfully demonstrate an intensity-modulation-direct-detection 34.78-Gbps OFDM signal transmissions over 100-km long-reach (LR) passive-optical networks (PONs) based on a cost-effective 10-GHz EAM and a 10-GHz PIN. Considering 0-100-km transmission bandwidth of a 10-GHz EAM, the narrowest bandwidth is theoretically evaluated to occur at ~40 km, instead of 100 km. Consequently, the performances of 20-100-km PONs are experimentally investigated, and at least 33-Gbps capacity is achieved to support LR-PONs of all possible 20-100-km radii. PMID:21935121

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

2011-08-29

308

Total absorption gamma-ray spectrometer for measurement of beta-decay intensity distributions for fission product radionuclides  

NASA Astrophysics Data System (ADS)

A total absorption ?-ray spectrometer (TAGS), based on a 25.4 cm diameter × 30.5 cm long NaI(Tl) well detector, has been developed at the INEL on-line isotope separator facility. A Si detector in the well of the NaI(Tl) detector allows one to collect ?-particle-gated coincidence spectra as well as singles spectra. With this system, measurements of the total absorption spectra have been made for a number of fission product nuclei. The analysis of the measured spectra is based on response functions for single ? rays that are computed with a Monte Carlo code. Routines have been written to use these response functions to simulate the response to a cascade of several ? rays and by extension to a whole decay scheme. The bremsstrahlung from a ground-state ? branch can also be simulated. The quality of the simulation is demonstrated for test spectra of 137Cs, 24Na, 60Co, and 110mAg. As examples of the operation of this system, the measurements and analyses of the ?-decay feeding distributions are described for the decay of 141Ba, 139Cs and 140Cs.

Greenwood, R. C.; Helmer, R. G.; Lee, M. A.; Putnam, M. H.; Oates, M. A.; Struttmann, D. A.; Watts, K. D.

1992-05-01

309

Effect of a finite conduction-band width on XMCD spectra at the L{2,3} absorption edges of mixed-valence Ce and Yb compounds in high magnetic fields  

NASA Astrophysics Data System (ADS)

Effect of a finite conduction-band width is studied in detail on the spectra of X-ray absorption spectroscopy (XAS) and its X-ray magnetic circular dichroism (XMCD) at the L2,3 absorption edges of mixed valence Ce and Yb compounds in high magnetic fields. Calculations are made with an extended single impurity Anderson model and within the leading term approximation in the 1/Nf expansion method, where Nf is the degeneracy of the 4f states. It is shown that a model with a vanishing conduction-band width is applicable, as an approximation method, to the calculation of XAS and XMCD spectra for realistic systems with a finite conduction-band width, if the values of the 4f level and the hybridization strength are renormalized appropriately. This justifies the previous calculations on general features of high-magnetic-field XAS and XMCD spectra with zero conduction-band width. At the same time, it is also shown that for more realistic calculations of high-magnetic-field XMCD spectra of some specific mixed-valence Ce and Yb compounds, the present theory with a finite conduction-band width is more appropriate.

Kotani, A.

2009-12-01

310

Absorption Bands at 4300 and 6000-8000Å as Signs of Silicate and Organic Matter Separation and Formation of Hydrated Silicates in KBOs and Similar Bodies  

NASA Astrophysics Data System (ADS)

Recent spectral observations of some Kuiper Belt Objects (KBOs) (Boehnhardt et al.: 2002, Proc. of ACM 2002, 47-50; Fornasier S. et al., 2004, Astron. Astrophys. 421, 353-363) discovered characteristic absorption bands at 4300 and 6000-8000Å in reflectance spectra of the bodies. Spectral positions and other parameters of the features are similar to those found in reflectance spectra of terrestrial phyllosilicates (e. g., Clark et al., 1990, J. Geophys. Res. 95, 12653-12680; Busarev et al., 2004, The new ROSETTA targets (L. Colangeli et al., eds.), 79-83), CI- and CM-carbonaceous chondrites (e. g., Busarev and Taran, 2002, Proc. of ACM 2002, 933-936), primitive C-, P-, D-, F- and G-class asteroids (Vilas and Gaffey, 1989, Science 246, 790-792) and hydrated M-, S- and E-class asteroids (Busarev and Taran, 2002, Proc. of ACM 2002, 933-936). Hence, these absorption bands may be considered as universal indicators of hydrated silicates on celestial solid bodies including KBOs. However, before phyllosilicates were formed, an aqueous media should spring up and exist a considerable time in the bodies. One more important factor for the spectral features of hydrated silicates to be observed, it is probably an aqueous separation of silicate and darkening CHON (PAH plus more light organic compounds) components in the bodies. To check the assumptions we have performed some calculations (Busarev et al., 2003, Earth, Moon, and Planets 92, 345-357) applicable to KBOs and analogous silicate-icy bodies existed for the first time in the formation zones of neighbouring giant planets. According to the calculations, the decay of the short-lived 26Al at the early stage of the bodies' evolution and their mutual collisions (at velocities >1.5 km s-1) at the subsequent stage were probably the main sources of heating sufficient for melting water ice in their interiors. Because of these processes, an internal ocean of liquid water covered with ˜10-km crust of dirty ice could originate in large KBOs (R>100 km) for about 106 yr and exist a few Myr till their freezing. The water ocean would be vigorously convective (Ra ˜1021) and the temperature should stabilize near 277-280K owing to the rapid radial heat transport through the ocean. A thin nonconvective layer could exist only at the top of the ocean because of the negative thermal expansion coefficient of water between 273 and 277K. As a result, dissolution and/or floating of the main part of a CHON component and sedimentation of silicate particles could occur. It probably finished in large KBOs by formation of a silicate core ( ˜0.7 radius of a body) covered with a water-ice shell enriched with organics. Crushing and removing icy covers under collisions and exposing KBOs' interiors with increased silicate content could facilitate detection of phyllosilicate spectral features.

Busarev, V. V.; Dorofeeva, V. A.; Makalkin, A. B.

2004-12-01

311

Multimodal tissue imaging: using coregistered optical tomography data to estimate tissue autofluorescence intensity change due to scattering and absorption by neoplastic epithelial cells.  

PubMed

ABSTRACT. Autofluorescence (AF) imaging provides valuable information about the structural and chemical states of tissue that can be used for early cancer detection. Optical scattering and absorption of excitation and emission light by the epithelium can significantly affect observed tissue AF intensity. Determining the effect of epithelial attenuation on the AF intensity could lead to a more accurate interpretation of AF intensity. We propose to use optical coherence tomography coregistered with AF imaging to characterize the AF attenuation due to the epithelium. We present imaging results from three vital tissue models, each consisting of a three-dimensional tissue culture grown from one of three epithelial cell lines (HCT116, OVCAR8, and MCF7) and immobilized on a fluorescence substrate. The AF loss profiles in the tissue layer show two different regimes, each approximately linearly decreasing with thickness. For thin cell cultures (<300???m), the AF signal changes as AF(t)/AF(0)=1-1.3t (t is the thickness in millimeter). For thick cell cultures (>400???m), the AF loss profiles have different intercepts but similar slopes. The data presented here can be used to estimate AF loss due to a change in the epithelial layer thickness and potentially to reduce AF bronchoscopy false positives due to inflammation and non-neoplastic epithelial thickening. PMID:24108573

Pahlevaninezhad, Hamid; Cecic, Ivana; Lee, Anthony M D; Kyle, Alastair H; Lam, Stephen; Macaulay, Calum; Lane, Pierre M

2013-10-01

312

Optical transitions, absorption intensities, and intermanifold emission cross sections of Pr3+(4f2) in Ca5(PO4)3F crystal host  

NASA Astrophysics Data System (ADS)

A spectroscopic Judd-Ofelt investigation has been performed on Pr3+ ions doped in calcium fluorapatite, Ca5(PO4)3F, belonging to the apatite structure family. The standard Judd-Ofelt analysis was applied to the room temperature absorption intensities of Pr3+ transitions to determine the phenomenological intensity parameters: ?2, ?4, and ?6. Values of the intensity parameters were subsequently used to determine the decay rates (emission probabilities), radiative lifetimes, and branching ratios of the principal intermanifold transitions of Pr3+ from the 3P2, 1D2, and 3P0 manifold states to the lower-lying manifolds. In addition, the room temperature fluorescence lifetimes and emission cross sections of the 3P2-->3H5, 1D2-->3H4, and 3P0-->3F2 transitions were measured; these values were compared with those of Nd3+:yttritium-aluminum-garnet and Pr3+:Sr5(PO4)3 (known as S-FAP).

Sardar, Dhiraj K.; Russell, Charles C.

2004-05-01

313

Fiber amplification in the 940-nm water vapor absorption band using the \\/sup 4\\/F\\/sub 3\\/2\\/ \\/sup 4\\/I\\/sub 9\\/2\\/ transition in Nd  

Microsoft Academic Search

The measurement of atmospheric water vapor in the 940-nm absorption band may be accomplished using fiber amplifiers based on the 4F 32\\/? 4I 92\\/ transition in Nd. We report initial experimental results on the effects codopants have on the characteristics of this transition in Nd-doped fiber, and present modeled and experimental results of a fiber amplifier. To our knowledge, this

Peter D. Dragic; Liesl M. Little; George C. Papen

1997-01-01

314

VISIBLE AND ULTRAVIOLET ABSORPTION PROPERTIES OF URANIUM DIOXIDE FILMS  

Microsoft Academic Search

Films of uranium dioxide ranging in thickness from 132 to 280 m mu were ; evaporated onto fused silica, annealed at a pressure of 10⁻⁶ mm Hg and 960 ; deg C, and measured for optical absorption between the wavelengths of 210 and 800 ; m mu . A moderately intense band observed at 240 io 500 m mu has

R. J. Ackermann; R. J. Thorn; G. H. Winslow

1959-01-01

315

Production control in succinimide additive synthesis by means of infrared absorption spectra  

Microsoft Academic Search

1.IR absorption spectra can serve as an identifying characteristic of nitrogen-containing additives on the basis of the intense and distinctive absorption bands in the 1700–1800, 1500–1680, 3300, and 1145 cm-1 regions.2.IR absorption spectra can be used to control the starting materials used in additive synthesis.3.The additive SVZ, synthesized by the procedure described in [1], is similar in structure to additive

A. G. Siryuk; K. I. Zimina; N. A. Filippova; V. I. Malevich; N. V. Goncharova; E. I. Sil'chenko; A. F. Lyashenko

1972-01-01

316

Optical characterization of Mn2+: Li2O-K2O-CdO-B2O3 glass system: Absorption edge, optical band gap, optical polarizability and optical basicity  

NASA Astrophysics Data System (ADS)

Mixed alkali borate glasses (30-x)Li2O-xK2O-10CdO-59B2O3 (0 <= × <= 30) implanted with 1mol% manganese ions (LKCBM) were prepared from the melts. These glasses were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC) and density measurements. Optical absorption studies were carried out as a function of alkali content to look for `Mixed Alkali Effect' (MAE) on the spectral properties of these glasses. The optical absorption spectra of LKCBM exhibit a broad band around 21000 cm-1 which has been assigned to the transition 6A1g(S) ? 4T1g(G). From the study of ultraviolet absorption edge, the optical band gap energies and Urbach energies were evaluated. The average electronic polarizability of the oxide ion (?o2-), Optical basicity (wedge) and Yamasita-Kurosawas's interaction parameter (A) were also evaluated for all the glasses. In the present investigation many of the physical parameters like glass transition temperature, density, optical band gap and optical basicity vary non-linearly with alkali concentration (x) indicating MAE.

Padmaja, G.; Kistaiah, P.

2009-07-01

317

Suppression of near-edge optical absorption band in sputter deposited HfO{sub 2}-Al{sub 2}O{sub 3} nanolaminates containing nonmonoclinic HfO{sub 2}  

SciTech Connect

Nanolaminates of polycrystalline (tetragonal+orthorhombic) HfO{sub 2} and amorphous Al{sub 2}O{sub 3} are sputter deposited on unheated fused SiO{sub 2}, air annealed at 573-1273 K, and analyzed by x-ray diffraction and spectrophometry. Significant O 2p{yields}Hf 5d interband absorption occurs in all films at energy E{>=}6.2 eV. For E<6.2 eV, films annealed below 1273 K retain a featureless optical absorption edge despite further crystallization. A band with a 5.65 eV onset concurrently develops with m-HfO{sub 2} crystallization after a 1273 K anneal, indicating this phase and not nanocrystallinity per se is responsible for increased absorption.

Hoppe, E. E.; Aita, C. R. [Advanced Coatings Experimental Laboratory, University of Wisconsin-Milwaukee, P.O. Box 784, Milwaukee, Wisconsin 53201 (United States)

2008-04-07

318

High temperature, high pressure absorption spectra of uranyl chloride solutions under shock conditions  

SciTech Connect

A technique for photographing the absorption spectra of solutions under shock wave conditions was developed. A photograph of the spectrum of a uranyl nitrate solution exposed to a shock wave of 75 kbar showed the absorption to extend beyond 500 mn, the long wavelength limit for uranyl solutions under ordinary conditions. It was found that at room temperature pressure up to 6 kbar had no appreciable effect on absorption. An analysis of the spectrum of uranyl perchlorate solutions has been published. The intensity of very weak absorption bands increased when the solution was heated to 95/sup 0/C, and they were interpreted as hot bands due to absorption from an excited ground state. New absorption measurements made on uranyl solutions heated to 250/sup 0/C at low pressure are presented and an interpretation of the effect observed in the shock experiments is offered.

Ewald, A.H.

1984-01-01

319

Does the association of spectral absorption bands in sunlight with the spectral response of photoreceptors in plants imply coincidence, adaptation or design?  

Microsoft Academic Search

The light-sensitive pigments in plants and seeds control and stimulate complex events that are key to the plant's survival. Light-sensitive pigments respond only to specific wavelengths of sunlight, and there is a close association of the spectral response of plant and seed photopigments with various absorption features in sunlight caused by the solar atmosphere and gases in the Earth's atmosphere.

Forrest M. Mims

320

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

PubMed

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

2013-10-15

321

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.

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

2013-01-01

322

The relationship of temperature rise to specific absorption rate and current in the human leg for exposure to electromagnetic radiation in the high frequency band  

Microsoft Academic Search

Of the biological effects of human exposure to radiofrequency and microwave radiation, the best-established are those due to elevation of tissue temperature. To prevent harmful levels of heating, restrictions have been proposed on the specific absorption rate (SAR). However, the relationship between SAR and temperature rise is not an invariant, since not only the heat capacity but also the efficiency

P R Wainwright

2003-01-01

323

Pressure effects on the intervalence-transfer electronic absorption band of the mixed-valence Creutz-Taube ion in various media  

SciTech Connect

In this paper the authors present the results of a pressure tuning spectroscopy (PTS) study of the intervalence-transfer (IT) band of the (Cl/sub 5/ x 5H/sub 2/O) salt of the Creutz-Taube ion. They studied this compound in three media: (1) as a crystalline solid, (2) doped in the polyelectrolyte poly(styrenesulfonic acid) (PSS), and (3) in water (D/sub 2/O). In all cases the principal effect of pressure on the IT band was found to be a shift of the band to higher energy. For the microcrystalline sample this shift was approx. 400 cm/sup -1/ over a pressure range from 0.001 to 200 kbar (1 kbar = 986.9 atm). In this same pressure range the blue shift of the IT band for the PSS-doped sample was approx. 600 cm/sup -1/. In water (D/sub 2/O) the shift was approx. 35 cm/sup -1/ in a pressure range from 0.001 to 7 kbar. In addition to the Gaussian fits described above they have fit the spectra using a vibronic coupling model developed by Piepho, Krausz, and Schatz (PKS). When analyzed in terms of this simple small-polaron model, this peak shift corresponds primarily to an increase in the electronic coupling between the metal centers of the ion. The degree of vibronic coupling changes either only slightly or not at all with pressure.

Hammack, W.S.; Lowery, M.D.; Hendrickson, D.N.; Drickamer, H.G.

1988-04-07

324

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

325

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

Microsoft Academic Search

High-resolution (0.34nm) 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 Fe2+ 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

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

2010-01-01

326

Band structures of TiO2 doped with N, C and B*  

PubMed Central

This study on the band structures and charge densities of nitrogen (N)-, carbon (C)- and boron (B)-doped titanium dioxide (TiO2) by first-principles simulation with the CASTEP code (Segall et al., 2002) showed that the three 2p bands of impurity atom are located above the valence-band maximum and below the Ti 3d bands, and that along with the decreasing of impurity atomic number, the fluctuations become more intensive. We cannot observe obvious band-gap narrowing in our result. Therefore, the cause of absorption in visible light might be the isolated impurity atom 2p states in band-gap rather than the band-gap narrowing.

Xu, Tian-Hua; Song, Chen-Lu; Liu, Yong; Han, Gao-Rong

2006-01-01

327

A Comparative Infrared Spectroscopic Study of Hydroxide and Carbonate Absorption Bands in Spectra of Shark Enameloid, Shark Dentin, and a Geological Apatite  

Microsoft Academic Search

.   The purpose of the present work was to investigate the infrared (IR) spectrum of shark enameloid, especially with regard\\u000a to hydroxide and carbonate bands. With thin sections placed directly in the IR beam it was possible to get high concentrations\\u000a of ions without interfering effects from a dispersion medium (e.g., alkali halides). For comparison, spectra of shark dentin\\u000a and

S. Dahm; S. Risnes

1999-01-01

328

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

NASA Astrophysics Data System (ADS)

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

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

1996-11-01

329

Implementation of the weighted sum of gray gases model to a narrow band: Application and validity  

SciTech Connect

Modeling the nongray behavior of combustion gases, such as water vapor and carbon dioxide, is very important for calculating the radiative heat transfer in furnaces and boilers. Here, the weighted sum of gray gases model (WSGGM) is applied to narrow bands of water vapor for analyzing radiative heat transfer in nongray media. For a given narrow band, the band mean spectral emissivity is represented by a weighted sum of gray gas emissivities expressed in terms of absorption coefficients, weighting factors, absorbing gas density, and path length. Five types of temperature-versus-narrow band absorption coefficient relation are suggested, and comparisons between the modeled emissivity and that of the original narrow band model are made and shown at a few typical bands. Total and low-resolution spectral intensities at the boundary are obtained for uniform, parabolic, boundary-layer-type temperature and parabolic concentration profiles using the WSGGM with five gray gases. Results using the Curtis-Godson approximation are compared with the WSGGM computations for each narrow band. The results using the WSGGM show good agreement with the Curtis-Godson approximation results, and especially, two of the WSGGMs with wave number-dependent absorption coefficient show highly accurate results with a few percent error in the total wall heat flux. The WSGGMs with wave number-independent absorption coefficients are, however, more useful for total spectrum computation, with a slight sacrifice in the accuracy.

Kim, O.J.; Song, T.H. [Korea Advanced Inst. of Science and Technology, Kusong, Taejon (Korea, Republic of). Dept. of Mechanical Engineering

1996-12-01

330

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

NASA Astrophysics Data System (ADS)

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

Ogibalov, Vladimir

331

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

SciTech Connect

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

Borysow, A. (Michigan Technological University, Houghton (United States))

1991-08-01

332

Dielectric constant, magnetic permeability and microwave absorption studies of hot-pressed Ba-CoTi hexaferrite composites in X-band  

Microsoft Academic Search

The microwave absorption, complex permittivity and complex permeability studies of hot-pressed hexaferrite composites prepared with Ba(CoTi)xFe12-2xO19 (x = 0.0, 0.2, 0.4, 0.8, and 1.0) were made in the frequency range from 8.0 to 12.4 GHz. The hexaferrite composites with x > 0.0 exhibit significant dispersion in the complex permittivity (?r?-j?r?). However the dispersion in complex permeability (?r?-j?r?) is not significant and is attributed to the

Praveen Singh; V. K. Babbar; Archana Razdan; S. L. Srivastava; V. K. Agrawal; T. C. Goel

2006-01-01

333

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

Microsoft Academic Search

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

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

2011-01-01

334

Polarization dependence of Raman 2D band in bilayer graphene  

NASA Astrophysics Data System (ADS)

The Raman intensity of the double-resonance 2D band in sigle-layer graphene has a strong polarization dependence(Yoon et al. Nano Lett.). The intensity is maximum when the excitation and detection polarization are parallel and minimum when they are orthogonal, whereas that of G band is isotropic. This strong polariztion dependence is the consequence of inhomogeneous optical absorption and emission mediated by electron-phonon interactions. Here, the polarization dependence of the Raman 2D band in bilayer graphene. The 2D band of bilayer graphene can be decomposed to 4 Lorentzian peaks corresponding to different scattering process involving 2 conduction and 2 valence bands. The 2D band in bialyer graphene shows a similar polarization dependence as that of single layer. Futhermore, the excitation energy dependence was investigated by using 4 different excitation laser wavelenghths. The polarization ratio of each of the 4 Lorentizan peaks seems to reflect the features of the electronic band structure of bilayer graphene in the energy range of the excitation laser.

Lee, Jae-Ung; Mbaye Seck, Ngor; Yoon, Duhee; Cheong, Hyeonsik

2013-03-01

335

Liver imaging at 3.0 T: Diffusion-induced black-blood echo-planar imaging with large anatomic volumetric coverage as an alternative for specific absorption rate-intensive echo-train spin-echo sequences: Feasibility study  

Microsoft Academic Search

Institutional Review Board approval and signed informed consent were obtained by all participants for an ongoing sequence optimization project at 3.0 T. The purpose of this study was to evaluate breath-hold diffusion-induced blackblood echo-planar imaging (BBEPI) as a potential alternative for specific absorption rate (SAR)-intensive spin-echo sequences, in particular, the fast spin-echo (FSE) sequences, at 3.0 T. Fourteen healthy volunteers

Bos van den I. C; S. M. Hussain; G. P. Krestin; P. A. Wielopolski

2008-01-01

336

Optical absorption in semiconductor quantum dots coupling to dispersive phonons of infinite modes  

NASA Astrophysics Data System (ADS)

Optical absorption spectrum of semiconductor quantum dot is investigated by means of an analytical approach based on the Green's function for different forms of coupling strength in an unified method by using the standard model with valence and conduction band levels coupled to dispersive quantum phonons of infinite modes. The analytical expression of the optical absorption coefficient in semiconductor quantum dots is obtained and by this expression the line shape and the peak position of the absorption spectrum are procured. The relation between the properties of absorption spectrum and the forms of coupling strength is clarified, which can be referenced for choosing the proper form of the coupling strength or spectral density to control the features of absorption spectrum of quantum dot. The coupling and confinement induced energy shift and intensity decrease in the absorption spectrum are determined precisely for a wide range of parameters. The results show that the activation energy of the optical absorption is reduced by the effect of exciton-phonon coupling and photons with lower frequencies could also be absorbed in absorption process. With increase of the coupling constant, the line shape of optical absorption spectrum broadens and the peak position moves to lower photon energy with a rapid decrease in intensity at the same time. Both the coupling induced red shift and the confinement induced blue shift conduce to decrease in the intensity of absorption spectrum. Furthermore, this method may have application potential to other confined quantum systems.

Ding, Zhiwen; Wang, Qin; Zheng, Hang

2012-10-01

337

Effect of pressure-induced freezing on the energy of the intervalence electronic absorption band of a binuclear mixed-valence complex  

SciTech Connect

The results of a study of the effect of pressure-induced freezing on the energy of the intravalence-transfer (IT) band of the I/sub 3//sup /minus// salt of the mixed-valence diferrocenylacetylene cation are reported. Spectra taken at pressures below and above the freezing point exhibit peak shifts significantly to lower energy but by less than 40% of the predicted value. It is proposed that for intramolecular electron transfer within a large metal complex with pi electrons, the field supplied by the ligands in addition to that of the electrons in the metal-ligand bond plus that of a relatively rigid solvation shell dilutes the effect of the dielectric continuum. 15 references, 1 figure.

Hammack, W.S.; Drickamer, H.G.; Lowery, M.D.; Hendrickson, D.N.

1988-04-06

338

CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands  

NASA Astrophysics Data System (ADS)

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence.

Rascher, U.; Agati, G.; Alonso, L.; Cecchi, G.; Champagne, S.; Colombo, R.; Damm, A.; Daumard, F.; de Miguel, E.; Fernandez, G.; Franch, B.; Franke, J.; Gerbig, C.; Gioli, B.; Gómez, J. A.; Goulas, Y.; Guanter, L.; Gutiérrez-de-La-Cámara, Ó.; Hamdi, K.; Hostert, P.; Jiménez, M.; Kosvancova, M.; Lognoli, D.; Meroni, M.; Miglietta, F.; Moersch, A.; Moreno, J.; Moya, I.; Neininger, B.; Okujeni, A.; Ounis, A.; Palombi, L.; Raimondi, V.; Schickling, A.; Sobrino, J. A.; Stellmes, M.; Toci, G.; Toscano, P.; Udelhoven, T.; van der Linden, S.; Zaldei, A.

2009-02-01

339

CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands  

NASA Astrophysics Data System (ADS)

The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence.

Rascher, U.; Agati, G.; Alonso, L.; Cecchi, G.; Champagne, S.; Colombo, R.; Damm, A.; Daumard, F.; de Miguel, E.; Fernandez, G.; Franch, B.; Franke, J.; Gerbig, C.; Gioli, B.; Gómez, J. A.; Goulas, Y.; Guanter, L.; Gutiérrez-de-La-Cámara, Ã.`.; Hamdi, K.; Hostert, P.; Jiménez, M.; Kosvancova, M.; Lognoli, D.; Meroni, M.; Miglietta, F.; Moersch, A.; Moreno, J.; Moya, I.; Neininger, B.; Okujeni, A.; Ounis, A.; Palombi, L.; Raimondi, V.; Schickling, A.; Sobrino, J. A.; Stellmes, M.; Toci, G.; Toscano, P.; Udelhoven, T.; van der Linden, S.; Zaldei, A.

2009-07-01

340

Bis-naphthobipyrrolylmethene derived BODIPY complex: an intense near-infrared fluorescent dye.  

PubMed

Synthesis of a novel ?-extended BODIPY derived from naphthobipyrrole is presented. This dye molecule displays very intense near-infrared (NIR) absorption (? > 400?000 M(-1) cm(-1)) and emission bands (>700 nm), accompanied by high quantum yield (?f = 0.65) owing to its extended ?-conjugation along with imposed structural rigidification. PMID:24030220

Sarma, Tridib; Panda, Pradeepta K; Setsune, Jun-Ichiro

2013-09-26

341

Quantitative measurements of O 2 b ? X(2,1,0?0) bands by using cavity ring-down spectroscopy  

Microsoft Academic Search

Quantitative measurements of individual rotational line intensities of molecular oxygen are made for the (0?0), (1?0), (2?0) bands of the b1?g+?X3?g? transition using highly sensitive cavity ring-down spectroscopy (CRDS). The absorption profiles of six rotational lines of the three bands of O2 are measured under pressures up to 1 atm. Corrections have been made to eliminate the effect of laser

Shucheng Xu; Dongxu Dai; Jinchun Xie; Guohe Sha; Cunhao Zhang

1999-01-01

342

Intermediate band photovoltaics overview  

Microsoft Academic Search

Intermediate band photovoltaics bases its theoretical superior performance over single gap solar cells on enhancing the photogenerated solar cell current thanks to the two-step absorption of photons with energy lower than the semiconductor gap without degrading the output voltage. Its presumably better utilisation of the solar spectrum has lately become a topic of research, not only because of that of

L. Cuadra; A. Marti; N. Lopez; A. Luque

2003-01-01

343

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

PubMed

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

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

2006-01-01

344

The stretching vibrational overtone spectra of PH3: Local mode vibrational analysis, dipole moment surfaces from density functional theory and band intensities  

Microsoft Academic Search

The infrared spectra of PH3 molecule were recorded on a Bruker IFS 120HR Fourier transform spectrometer from 4000 to 9500 cm-1. The P-H stretching vibrational frequencies and intensities were derived from the experimental data. The Morse oscillator parameters De and alpha in the anharmonically coupled anharmonic oscillator local mode model were determined by the least-squares fitting with the observed vibrational

Sheng-Gui He; Jing-Jing Zheng; Shui-Ming Hu; Hai Lin; Yun Ding; Xiang-Huai Wang; Qing-Shi Zhu

2001-01-01

345

Linear and nonlinear optical absorption coefficients and refractive index changes in spherical quantum dots: Effects of impurities, electric field, size, and optical intensity  

Microsoft Academic Search

In the present work, the case of a spherical quantum dot with parabolic confinement subjected to an external electric field with the presence of an impurity, the linear and third-order nonlinear optical absorption coefficients as well as refractive index changes have been calculated. The numerical method we are using for the calculation of the energy levels and the corresponding wave

Sotirios Baskoutas

2008-01-01

346

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

SciTech Connect

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

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

1988-01-01

347

Influence of nitrate ions upon the absorption by thallium halide crystals in the medium infrared part of the spectrum  

Microsoft Academic Search

This paper studies the influence of admixed nitrate ions upon the spectral transmission of thallium halide crystals in the medium infrared range of the sectrum and determines the coefficient of proportionality between the concentratin and the intensity of the absorption bands of the nitrate ions. It is shown that in order to obtain thallium-halide crystals, and, from them, lightguides with

V. V. Voitsekhovskii; I. S. Lisitskii; T. L. Likholetova; V. G. Plotnichenko; B. A. Chapyzhnikov

1986-01-01

348

Measurement of water absorption in human cornea with differential absorption optical coherence tomography  

NASA Astrophysics Data System (ADS)

OCT has emerged in recent years to a powerful technique to measure tissue properties. Recently, OCT has been enhanced by methods providing spectroscopic information. Since water is a major constituent of most tissues, the measurement of its concentration in tissue is important for tissue diagnostics. We present measurements of water absorption in human cornea in vitro with a differential absorption optical coherence tomography technique. This technique uses two OCT images recorded simultaneously with two different light sources, one centered within (1488nm) and one centered outside (1312nm) of a water absorption band. To study influences of scattering on the absorption images and on the calculated differential absorption coefficient, the cornea was measured and imaged under three different conditions: At first, the cornea was imaged in a hydrated condition, immediately after removal from the aqueous nutrient solution. Then it was dehydrated and imaged a second time, finally it was rehydrated, however, the water was replaced by Deuterium oxide, which shows negligible absorption in the used wavelength region, but otherwise has similar optical properties as water. The cornea containing H2O is well distinguishable from the cornea containing D2O with our method. For quantitative determination of absorption, we performed a linear regression analysis of logarithmic backscattered intensity versus imaging depth in the cornea for each wavelength. The difference of the slopes corresponds to the difference in the absorption coefficient. If the difference in the water absorption cross section is known, the water concentration in tissue can be calculated. The results are in good agreement with those expected theoretically.

Pircher, Michael; Götzinger, Erich; Leitgeb, Rainer; Fercher, Adolf F.; Hitzenberger, Christoph K.

2003-07-01

349

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

350

EFFECTS OF LASER RADIATION ON MATTER: Photoinduced absorption in chalcogenide glasses  

NASA Astrophysics Data System (ADS)

A dependence of the absorption coefficient on the optical radiation intensity in the range 10 - 5 - 1 W/cm2 was observed for chalcogenide glasses at a photon energy less than the band gap of the material. The absorption coefficient depended on the irradiation time. In the case of arsenic sulfide in the range 1.6-1.7 eV an absorption peak was observed at intensities of the order of 10 - 3 W/cm2. In this part of the spectrum the absorption probably involved metastable As-As, S-Se, and Se-Se "defect" bonds and was similar to the photoinduced degradation of hydrogenated amorphous silicon.

Ponomar', V. V.

1990-08-01

351

Diffuse interstellar bands (DIB): co-planar doubly excited He and metal atoms embedded in Rydberg Matter  

NASA Astrophysics Data System (ADS)

The interpretation of the more than 300 diffuse interstellar bands (DIBs) is one of the most long-standing problems in interstellar spectra since the two first bands were reported in 1921. We now predict the frequencies of 260 diffuse interstellar bands (DIBs) using the Rydberg Matter model we have developed previously. These transitions involve mainly He atoms, but other two-electron atoms like Ca and other metals can take part in the absorption processes. Approximately 70% of the total intensity of the DIBs is due to absorption in doubly excited states and 30% in singly excited He atoms. The doubly excited states are in inverted states while the He atoms are thermal. The possibilities to observe DIBs in the UV and NIR ranges are discussed and band positions are predicted.

Holmlid, Leif

2011-12-01

352

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

SciTech Connect

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

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

2006-08-03

353

Infrared band strengths: Laboratory techniques and applications to astronomical observations  

NASA Astrophysics Data System (ADS)

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

Gerakines, P. A.

2002-09-01

354

Rotational bands of 156Gd  

NASA Astrophysics Data System (ADS)

High-spin states of 156Gd have been studied by using the reaction 150Nd(13C/,?3n). The ground-state band, /? band, and octupole band have been extended up to 26+, 16+, and 21- states respectively. Gamma-ray branchings between E2 decays down the K=1- band and E1 decays across to the ground band are discussed on the basis of the Generalized Intensity Relations. It is found that the /B(E1)/B(E2) ratios have the maximum value at the intermediate spin. This feature is quite similar to the the case of the lowest octupole K=0- band in 238U and is not yet resolved. Moreover a new band in the spin range of /(10,11)<=I<=(20,21) was observed, whose /?-rays turned out to be almost identical in energy to the ones found in the isotone 158Dy.

Sugawara, M.; Mitarai, S.; Kusakari, H.; Oshima, M.; Hayakawa, T.; Toh, Y.; Hatsukawa, Y.; Katakura, J.; Iimura, H.; Zhang, Y. H.; Sugie, M.; Sato, Y.

2001-04-01

355

Band gap tunability of molecular beam epitaxy grown lateral composition modulated GaInP structures by controlling V/III flux ratio  

NASA Astrophysics Data System (ADS)

Lateral composition modulated (LCM) GaInP structures were grown on (001) GaAs substrate by molecular beam epitaxy with different V/III flux ratios. Band gap of LCM structures could be tuned from 1.93 eV to 1.83 eV by decreasing flux ratio while maintaining the same photoluminescence intensity, enhanced light absorption, and widened absorption spectrum. It is shown that for band gap tuning of LCM structures, flux ratio adjustment is a more viable method compared to growth temperature adjustment.

Park, K. W.; Park, C. Y.; Lee, Y. T.

2012-07-01

356

Band gap tunability of molecular beam epitaxy grown lateral composition modulated GaInP structures by controlling V/III flux ratio  

SciTech Connect

Lateral composition modulated (LCM) GaInP structures were grown on (001) GaAs substrate by molecular beam epitaxy with different V/III flux ratios. Band gap of LCM structures could be tuned from 1.93 eV to 1.83 eV by decreasing flux ratio while maintaining the same photoluminescence intensity, enhanced light absorption, and widened absorption spectrum. It is shown that for band gap tuning of LCM structures, flux ratio adjustment is a more viable method compared to growth temperature adjustment.

Park, K. W. [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Park, C. Y. [Micro Systems Laboratory, Samsung Advanced Institute of Technology, Yongin 446-712 (Korea, Republic of); Lee, Y. T. [School of Information and Communications, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of); Department of Photonics and Applied Physics, Gwangju Institute of Science and Technology, Gwangju 500-712 (Korea, Republic of)

2012-07-30

357

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

358

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

359

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

360

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

Microsoft Academic Search

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

Jeremy Vanderover; Matthew A. Oehlschlaeger

2010-01-01

361

Band Structure  

NASA Astrophysics Data System (ADS)

This chapter deals with the ordering of the valence bands - a topic that has controversially been discussed for more than 40 years. The ? 7, ? 9, ? 7 ordering is discussed in the light of very recent ab initio band structure calculations, and the important role is emphasized, which the Zn 3d-band position plays to the sign of the spin-orbit splitting. This topic is touched again from a different point of view in Chap. 6 on free excitons. Then we summarize the experimental findings on the cationic and anionic substitutions in ZnO and random alloy formation essential for quantum hetero-structures. The chapter closes with the data on the valence and conduction band discontinuities in iso- and hetero-valent hetero-structures.

Meyer, B. K.

362

Gastric Banding  

MedlinePLUS

... and certain drugs should not have gastric banding. Surgical Procedure Before Surgery If you are considering whether ... incisions) in the abdomen. A small camera and surgical instruments are placed through the cuts into the ...

363

Transient absorption spectra and dynamics of InSe nanoparticles.  

PubMed

Time-resolved fluorescence and transient absorption results have been obtained for small (approximately 3 nm) and large (approximately 5-8 nm) InSe nanoparticles in room-temperature solutions. The large particles are nonfluorescent, indicating that the conduction band is at M and the optical transition is forbidden. For some fraction of the small particles, the bottom of the conduction band is at Gamma and the optical transition is allowed. The small particle fluorescence measurements indicate that hole trapping occurs on the 200-300 ps time scale. The transient absorption spectra are featureless throughout the visible with a broad maximum at 600-650 nm. The transient absorption kinetics of both small and large particles show a 200-300 ps decay component that is assigned to hole trapping. These kinetics also show a 15 ps decay that has a larger amplitude in the case of the large particles and is assigned to an electron Gamma to M relaxation. The amplitude of this decay indicates that the initial electron and hole intraband transitions result in roughly comparable intensities of the initial transient absorption. PMID:16821867

Yang, Shuming; Kelley, David F

2006-07-13

364

Collision-induced vibrational absorption in molecular hydrogens  

SciTech Connect

Collision induced absorption (CIA) spectra of the first overtone bands of H{sub 2}, D{sub 2}, and HD have been recorded for gas densities up to 500 amagat at 77-300 K. Analyses of these spectra reveal that (1) contrary to the observations in the fundamental bands, the contribution of the isotropic overlap interaction to the first overtone bands is negligible, (2) the squares of the matrix elements B{sub 32}(R)/ea{sub o} [= {lambda}{sub 32} exp(-(R-{sigma})/{rho}{sub 32}) + 3 (R/a{sub o}){sup -4}] where the subscripts 3 and 2 represent L and {lambda}, respectively, account for the absorption intensity of the bands and (3) the mixed term, 2,3 {lambda}{sub 32} exp (-(R-{sigma})/{rho}{sub 32}) <{vert_bar}Q{vert_bar}> <{alpha}> (R/a){sup -4}, gives a negative contribution. In the CIA spectra of H{sub 2} in its second overtone region recorded at 77, 201 and 298 K for gas densities up to 1000 amagat, a dip in the Q branch with characteristic Q{sub p} and Q{sub R} components has been observed. The analysis of the absorption profiles reveals, in addition to the previously known effects, the occurrence of the triple-collision transitions of H{sub 2} of the type Q{sub 1}(J) + Q{sub 1}(J) + Q{sub 1}(J) for the first time. From the profile analysis the absorption coefficient of these transitions is obtained.

Reddy, S.P.

1993-05-01

365

A zero-dispersion monochromator and two-beam output for UV Fourier transform absorption spectrometry  

NASA Astrophysics Data System (ADS)

The motivation for using a zero-dispersion monochromator as a band-pass filter with a Fourier transform spectrometer is discussed, and the design of such an instrument is presented. Benefits in performance over commercial band-pass filters are demonstrated. In addition the advantages of using the second optical output of the spectrometer are discussed, particularly with respect to absorption spectroscopy when the signal from the second output can compensate for fluctuations and drift in the intensity of the background continuum source.

Blackie, D.; Murray, J. E.; Blackwell-Whitehead, R.; Thorne, A. P.; Pickering, J. C.; Willey, B. R.

2011-06-01

366

Generating function approach to the calculation of spectral band shapes of free-base chlorin including Duschinsky and Herzberg-Teller effects.  

PubMed

A generating function approach to the calculation of spectral band shapes including Duschinsky and Herzberg-Teller effects is proposed and applied to the computation of the free-base chlorin Q absorption bands, using molecular geometries and normal vibrations obtained by density functional theory computations. The results clearly show that non-Condon effects can significantly affect the relative intensities of the weakest Q(y) and, to a lesser extent, Q(x) bands. The proposed approach is extremely powerful and can be used in the cases where the molecular size makes the direct calculation of Franck-Condon integrals by recurrence formulas prohibitive. PMID:22978703

Borrelli, Raffaele; Capobianco, Amedeo; Peluso, Andrea

2012-10-03

367

New transient absorption observed in the spectrum of colloidal CdSe nanoparticles pumped with high-power femtosecond pulses  

SciTech Connect

The power dependence of the transient absorption spectrum of CdSe nanoparticle colloids with size distribution of 4.0 {+-} 0.4 nm diameter is studied with femtosecond pump-probe techniques. At the lowest pump laser power, the absorption bleaching (negative spectrum) characteristic of the exciton spectrum is observed with maxima at 560 and 480 nm. As the pump laser power increases, two new transient absorptions at 510 and 590 nm with unresolved fast rise (<100 fs) and long decay times ({much{underscore}gt}150 ps) are observed. The energy of each of the positive absorption is red shifted from that of the bleach bands by {approximately}120 MeV. The origin of this shift is discussed in terms of the effect of the internal electric field of the many electron-hole pairs formed within the quantum dot at the high pump intensity, absorption from a metastable excited state or the formation of biexcitons.

Burda, C.; Link, S.; Green, T.C.; El-Sayed, M.A.

1999-12-09

368

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

369

Identification of the nu3 NO2 Band in the Solar Spectrum observed from a Balloon Borne Spectrometer  

Microsoft Academic Search

SINCE the detection of HNO3 in the atmosphere1, it has been expected that oxides of nitrogen, such as NO2, should also be present. In fact, in a previous paper by some of us1 a tentative identification of NO2 absorption was made. The most intense vibration-rotation band of NO2 is the nu3 fundamental, centred at 1,618 cm-1, near the centre of

A. Goldman; D. G. Murcray; F. H. Murcray; W. J. Williams

1970-01-01

370

Shadow bands  

Microsoft Academic Search

An attempt is given to explain the shadow bands that appear on the ground just before and after totality during a total solar eclipse. Conditions for interference of light, as it passes through a turbulent patch, are derived for an extremely simplified atmospheric model.

V. Miovic

1999-01-01

371

Band Together!  

ERIC Educational Resources Information Center

|After nearly a decade as band director at St. James High School in St. James, Missouri, Derek Limback knows that the key to building a successful program is putting the program itself above everything else. Limback strives to augment not only his students' musical prowess, but also their leadership skills. Key to his philosophy is instilling a…

Olson, Cathy Applefeld

2011-01-01

372

Optical absorption spectra of chemically generated C60 and C70 anions  

NASA Astrophysics Data System (ADS)

For the first time the spectra of the fullerene anions C{60}n- and C{70}n-, for n = 1, 2, and 3, in benzonitrile, in the presence of three reducing agents: Na, K and TDAE, were studied. The fullerene anions reveal characteristic, near IR absorption bands, similar to those observed in electrogenerated anions. In the normalised C{60}?TDAE monoanion spectrum an increase of the intensities of 1042 nm, 1001 nm and 940 nm bands is observed when compared with C{60}Na or C{60}K. This increase can be due to differences in the C{60}- anion symmetry in these salts. Reduction of C{60} in oxygen-containing solvent showed an oxidation of C{60} anion-radical with an appearance of a new absorption band in 900 1000 nm region. Les spectres des anions des fullerènes C{60}n- et C{70}n-, où n=1, 2 et 3 ont été étudiés pour la première fois en solution dans le benzonitrile et en présence de trois réducteurs : Na, K et TDAE. Les anions du fullerène montrent des bandes d'absorption caractéristiques en infrarouge proche, ressemblant aux bandes observées pour les anions générés électrochimiquement. Une augmentation des intensités des bandes à 1042 nm, 1001 nm et 940 nm en comparaison des bandes de C60Na ou C60K est observée pour le sel CTDAE. Cette augmentation peut être causée par des différences de symétrie de l'anion C{60}- de ces sels. Une oxydation de l'anion-radical du C{60} et une apparition d'une bande neuve dans la région spectrale entre 900 et 1000 nm suivent une réduction du C{60} dans une solution qui contient de l'oxygène.

Konarev, D. V.; Drichko, N. V.; Graja, A.

1998-11-01

373

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

374

Sm3+ effects in the Tm3+ doped tellurite glass for S-band amplification  

NASA Astrophysics Data System (ADS)

Thulium doped Samarium codoped tellurite-tungstate glasses were produced. Luminescence properties in the infrared region were investigated looking to observe improved properties for S-band amplification in the co doped samples. Thulium is well-known by the 3H4-3F4 radiative transition emitting around ~1.47?m, which is a self-terminating transition in tellurite hosts due the longer lifetime of the lower level in relation to the upper level of this transition. Analysis of absorption and emission spectra showed that we could quench the 3F4 level significantly, what improved the intensity of the emission at 1.49?m. However, the state 3H4 were also quenched due the cross relaxation process due the absorption bands of Sm3+ around 1.5?m.

Belançon, Marcos P.; Ferenz, Julio; Chillcce, Enver; Barbosa, Luis Carlos

2013-02-01

375

Angular emission and self-absorption studies of a tin laser produced plasma extreme ultraviolet source between 10 and 18 nm  

SciTech Connect

Extreme ultraviolet spectra from a tin laser produced plasma have been recorded over a range of angles between 20 deg. and 90 deg. from the target normal. Absolute intensity measurements are presented of both the 2% band centered on 13.5 nm and the total radiation emitted by the plasma between 10 and 18 nm. The in-band intensity is seen to be relatively constant out to an angle of 60 deg. from the target normal, beyond which it drops off quite steeply. The spectra at wavelengths greater than 13.5 nm are strongly influenced by self-absorption by ions ranging from 6{sup +} to 10{sup +}.

Morris, O.; O'Reilly, F.; Dunne, P. [School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland); Hayden, P. [School of Physical Sciences, Dublin City University, Glasnevin, Dublin 9 (Ireland)

2008-06-09

376

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

PubMed

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

2013-09-26

377

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.

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

2013-01-01

378

Optical Absorption Spectroscopy of Natural and Irradiated Pink Tourmaline.  

National Technical Information Service (NTIS)

The Brazilian natural pink tourmaline is studied through the polarized optical absorption measurements. The effect of increasing doses of gamma -rays from sup 60 Co in the spectra were determined (maximum of 20MGy). The following optical absorption bands ...

M. B. Camargo S. Isotani

1985-01-01

379

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

380

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

PubMed

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

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

2012-08-27

381

Alkali metal diffuse band lasers  

NASA Astrophysics Data System (ADS)

Progress is described on study of a new class of potential excimer lasers based on diffuse bands of the alkali metal vapors. In particular, the violet diffuse bands of sodium vapor and the yellow diffuse bands of potassium vapor have been shown by detailed modeling of single vibrational-rotational level emission to be each composed of overlapping singlet and triplet excimer emission continua of the diatomic molecule. The gain and low absorption loss previously found in the violet and yellow with laser optical pumping of sodium vapor and potassium vapor, respectively, have been quantitatively examined. Prospects for laser oscillation appear to be good at low pressures where quenching is not dominant. Free-bound-free spectra (which include only the triplet portion of the diffuse bands) have been produced and analyzed in sodium, potassium, rubidium and cesium.

Stwalley, William C.

1987-08-01

382

Observation of superdeformed bands in194Hg  

NASA Astrophysics Data System (ADS)

Two rotational bands, with energy spacings characteristic of superdeformed shapes, have been observed following bombardment of150Nd with48Ca. The more intensively populated band consists of 18 transitions and is assigned to194Hg. The depopulation of this band occurs around spin 10. The second band, consisting of at least 16 transitions, was populated less strongly and is tentatively assigned to194Hg also. The lowest level in this band is assigned spin 8. The energy differences between transitions for both bands decrease from ˜40 keV at low rotational frequencies to ˜30 keV at the highest observed frequencies. The moments of inertia of the bands are similar to those of the two previously observed superdeformed bands in191,192Hg. The similarities and differences of the four known bands in the mercury region are discussed.

Beausang, C. W.; Henry, E. A.; Becker, J. A.; Roy, N.; Yates, S. W.; Deleplanque, M. A.; Diamond, R. M.; Stephens, F. S.; Draper, J. E.; Kelly, W. H.; Burde, J.; McDonald, R. J.; Rubel, E.; Brinkman, M. J.; Cizewski, J. A.; Akovali, Y. A.

1990-09-01

383

Optical characterization of wide band gap semiconductors and nanostructures  

NASA Astrophysics Data System (ADS)

The optical properties of ZnO-based wide band semiconductors and their nanostructures deposited by pulsed laser deposition are investigated. The ordinary and extraordinary refractive indices of wurtzite MgxZn 1-xO (x = 0--0.36) single crystalline films in the wavelength range of 457--968 nm are measured for the first time by prism coupling techniques. The excitonic absorption features are clearly visible at room temperature despite the alloy broadening effect. The band gaps and exciton binding energies are obtained by modeling the absorption spectra near the band gap. Intense band-edge photoluminescence (PL) from MgxZn 1-xO films is demonstrated. The luminescence properties of MgZnO/ZnO multiple quantum wells (well width ˜35--80A in a series of samples) grown on c-plane sapphire substrates via a ZnO buffer layer are demonstrated. Despite poorly-defined well/barrier interfaces and high defect densities in the material, the PL peaks shift toward shorter wavelengths relative to the band edge of bulk ZnO when the well width decreases. The mechanism is qualitatively identified as confined-carrier transitions in partially intermixed quantum wells as a result of Mg atom interdiffusion during the deposition. A broad absorption peak around 314 nm and a bright ultraviolet PL peak at 328.6 nm are measured on ZnO quantum dots (average dot size ˜2.5 nm, smaller than the exciton Bohr diameter 3.6 nm) embedded in a polycrystalline AlN matrix. The three-dimensional carrier confinement and recombination centers in Al2O3 are likely to be responsible for the distinct optical characteristics. In contrast with most existing reports on ZnO nanoparticles, the defect luminescence in the visible range is largely absent in our studies. The same technique is also used to deposit crystalline Ge quantum dots (size 73, 130, 160 and 260 A +/- 5%) embedded in Al2O3 or AlN matrices. The spectral positions of E 1/E1 + Deltal and E2 transitions shift to higher energies (DeltaE1 = 1.19 eV, DeltaE2 = 0.57 eV) in the absorption spectra as dot size decreases (73 A) due to the quantum size effect, regardless of the surrounding matrix. The results of this study provide useful information and guidelines on the design of ZnO-based quantum heterostructure optical devices.

Teng, Chia-Wei

384

A Diffraction System with an X-ray Beam of a Band of Wavelengths  

SciTech Connect

New diffraction system has been constructed at the Synchrotron Radiation Center at Ritsumeikan University, in which a parallel X-ray beam of a band of wavelengths is produced by reflection from a multilayer monochromator of depth-graded thicknesses. The band width is 0.013 nm and the useful wavelength range is from 0.16 nm to 0.20 nm. Diffraction patterns were taken from a single crystal of an enantiomorphous ferrocene-derivative compound employing an Imaging Plate as a detector. Bragg reflections are seen elongated with a characteristic intensity profile due to anomalous dispersion. Bijvoet pair of reflections show a clear difference in the profile on the short wavelength side of the absorption edge and distinction between the enantiomers can be made more easily than the classical method based on the comparison of integrated intensities.

Koganezawa, T.; Iwasaki, H.; Yoshimura, Y.; Nakamura, N. [Faculty of Science and Engineering, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan); Shoji, T. [X-ray Research Laboratory, RIGAKU Coorporation, Takatsuki, Osaka 569-1146 (Japan)

2004-05-12

385

Combination Bands in the InfraRed Spectra of CCl4 and SiCl4  

Microsoft Academic Search

It is assumed that the six Raman bands of CCl4 found by Pringsheim and Rosen give the fundamental absorption frequencies. Simple combinations of these frequencies by addition account for all of the absorption bands between 1mu and 16mu, except a few very weak bands. The absorption bands of SiCl4 in the same region are accounted for by similar combinations of

H. H. Marvin

1929-01-01

386

Line shapes and intensities of self-broadened O{sub 2} b {sup 1{Sigma}}{sub g}{sup +}({nu}=1)(leftarrow)X {sup 3{Sigma}}{sub g}{sup -}({nu}=0) band transitions measured by cavity ring-down spectroscopy  

SciTech Connect

We present high-resolution line-shape and line-intensity measurements of self-broadened O{sub 2} b {sup 1{Sigma}}{sub g}{sup +}(v=1)(leftarrow)X {sup 3{Sigma}}{sub g}{sup -}(v=0) band (B-band) transitions measured using the frequency-stabilized cavity ring-down spectroscopy technique under relatively low pressure conditions. We give line-shape parameters describing collisional broadening and shifting, and we treat line narrowing in terms of Dicke narrowing or the speed dependence of collisional broadening. We indicate the importance of the line-narrowing effect which, if neglected, changes the experimentally determined collisional broadening coefficients by up to 48%. We report measured line intensities with relative uncertainties below 0.7% and compare these measurements to published data.

Lisak, D.; Maslowski, P.; Cygan, A.; Bielska, K.; Wojtewicz, S.; Piwinski, M.; Trawinski, R. S.; Ciurylo, R. [Instytut Fizyki, Uniwersytet Mikolaja Kopernika, ul. Grudziadzka 5/7, 87-100 Torun (Poland); Hodges, J. T. [National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899 (United States)

2010-04-15

387

Photoinduced absorption and refractive-index induction in phosphosilicate fibres by radiation at 193 nm  

SciTech Connect

The photoinduced room-temperature-stable increase in the refractive index by {approx}5x10{sup -4} at a wavelength of 1.55 {mu}m was observed in phosphosilicate fibres without their preliminary loading with molecular hydrogen. It is shown that irradiation of preliminary hydrogen-loaded fibres by an ArF laser at 193 nm enhances the efficiency of refractive-index induction by an order of magnitude. The induced-absorption spectra of preforms with a phosphosilicate glass core and optical fibres fabricated from them are studied in a broad spectral range from 150 to 5000 nm. The intense induced-absorption band ({approx}800 cm{sup -1}) at 180 nm is found, which strongly affects the formation of the induced refractive index. The quantum-chemical model of a defect related to this band is proposed. (optical fibres)

Rybaltovsky, A A; Sokolov, V O; Plotnichenko, V G; Lanin, Aleksei V; Semenov, S L; Dianov, Evgenii M [Fiber Optics Research Center, Russian Academy of Sciences, Moscow (Russian Federation); Gur'yanov, A N; Khopin, V F [Institute of Chemistry of High-Purity Substances, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

2007-04-30

388

Quasiparticle band structure and optical spectrum of LiBr  

NASA Astrophysics Data System (ADS)

We report the quasiparticle band structure and optical absorption spectrum of bulk LiBr calculated from first-principles approaches. The quasiparticle band structure is calculated within the GW approximation. Taking the electron-hole interaction into consideration, the optical excitation is investigated by solving the Bethe-Salpeter equation for the electron-hole two-particle Green's function. The obtained results for the band gap and optical absorption spectrum are in good agreement with experimental measurements.

Jiang, Yun-Feng; Wang, Neng-Ping; Rohlfing, Michael

2013-10-01

389

Rotational bands of 159Dy  

NASA Astrophysics Data System (ADS)

High-spin states of 159Dy have been studied by using reaction 150Nd(13C,4n). Two rotational bands based on the configurations /?[521]3/2 and /?[642]5/2 have been extended to 57/2- and 61/2+ states, respectively. A neutron AB crossing has been observed around /??=0.26 MeV in the /?[521]3/2 band. It has been observed that the signature splitting is inverted after the band crossing in the /?[521]3/2 band. The first band crossing has been observed around /??=0.38 MeV in the /?[642]5/2 band. Seven E1 transitions from the /?[521]3/2 band to the /?[642]5/2 band have been observed and discussed on the base of Generalized Intensity Relation. It is found that the /B(E1)/B(E2) ratios for 47/2- and 43/2- states become enhanced relatively to those for the lower-spin states.

Sugawara, M.; Mitarai, S.; Kusakari, H.; Oshima, M.; Hayakawa, T.; Toh, Y.; Hatsukawa, Y.; Katakura, J.; Iimura, H.; Zhang, Y. H.; Sugie, M.; Sato, Y.

2002-03-01

390

Band Spectra which appear near Visible Triplet Lines of Mercury  

Microsoft Academic Search

RECENTLY, H. Kuhn1 has found a band which appears very near the principal series lines of alkali metals in absorption and has explained this band as being due to the diatomic molecules loosely combined by Van der Waals' cohesion forces. In the case of mercury, it seems that bands of the same nature are also emitted very close to the

E. Matuyama

1933-01-01

391

Modeling of phytochrome absorption spectra.  

PubMed

Phytochromes constitute one of the six well-characterized families of photosensory proteins in Nature. From the viewpoint of computational modeling, however, phytochromes have been the subject of much fewer studies than most other families of photosensory proteins, which is likely a consequence of relevant high-resolution structural data becoming available only in recent years. In this work, hybrid quantum mechanics/molecular mechanics (QM/MM) methods are used to calculate UV-vis absorption spectra of Deinococcus radiodurans bacteriophytochrome. We investigate how the choice of QM/MM methodology affects the resulting spectra and demonstrate that QM/MM methods can reproduce the experimental absorption maxima of both the Q and Soret bands with an accuracy of about 0.15 eV. Furthermore, we assess how the protein environment influences the intrinsic absorption of the bilin chromophore, with particular focus on the Q band underlying the primary photochemistry of phytochromes. PMID:23456980

Falklöf, Olle; Durbeej, Bo

2013-03-01

392

Study of instrument measurement of carbon monoxide concentration by absorption spectrum  

NASA Astrophysics Data System (ADS)

This paper presents the measurement of the carbon monoxide concentration in industry field by scanning absorption spectrum. In the measurement, the frequency of DFB laser is stabilized in the central frequency point of absorption peak in 1.57?m absorption band of carbon monoxide by a control system with a standard CO gas chamber, fiber loop, TEC controlled by MCU and its temperature stability is 0.01°C at long time to stabilize the central frequency. In the process of measurement, at first, the CO absorption spectrum will be determined by a standard gas camber to choose a maximum CO absorption peak in its frequency band and its frequency point will be stabilized. The parameters of the operation frequency and environment will be stored in the NV memory in MCU as next operation condition. The concentration can be calculated in a composite algebra operation by first and second harmonic intensity passed through test gas chamber. It has very high measurement precision and real time. The experiment result is consistent with actual gas concentration. It shows that the measurement scheme is valuable for fast, real-time and efficiency measurement.

Guo, Jian-Qiang; Wang, Li; Wang, Zeyong; Li, Jinglong

2010-08-01

393

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

PubMed

Polymethine dyes (PDs) with absorption bands in the near-infrared region undergo symmetry breaking in polar solvents. To investigate how symmetry breaking affects nonlinear optical responses of PDs, an extensive and challenging experimental characterization of a cationic 2-azaazulene polymethine dye, including linear absorption, fluorescence, two-photon absorption and excited-state absorption, has been performed in two solvents with different polarity. Based on this extensive set of experimental data, a three-electronic-state model, accounting for the coupling of electronic degrees of freedom to molecular vibrations and polar solvation, has been reliably parameterized and validated for this dye, fully rationalizing optical spectra in terms of spectral position, intensities and bandshapes. In low-polarity solvents where the dye is mainly in its symmetric form, a nominally forbidden two-photon absorption band is observed, due to a vibronic activation mechanism. Inhomogeneous broadening plays a major role in polar solvents: absorption spectra represent the weighted sum of contributions from states with a variable amount of symmetry breaking, leading to a complex evolution of linear and nonlinear optical spectra with solvent polarity. In more polar solvents, the dominant role of the asymmetric form leads to the activation of two-photon absorption as a result of the symmetry lowering. The subtle interplay between the two mechanisms for two-photon absorption activation, vibronic coupling and polar solvation, can be fully accounted for within the proposed microscopic model allowing a detailed interpretation of the optical spectra of PDs. PMID:23591769

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

2013-04-17

394

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

395

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

NASA Astrophysics Data System (ADS)

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

Thomas, Michael E.

1988-01-01

396

A new model for pressure-induced shifts of electronic absorption bands as applied to neat CS sub 2 and CS sub 2 in n-hexane and dichloromethane solutions  

SciTech Connect

The authors propose a model for the pressure dependence of electronic absorption spectra and apply it to the authors data on CS{sub 2} both in neat phase and in hexane and dichloromethane solid solutions. They believe that their data represent a rather severe test of this model and argue that any model for the pressure dependence of electronic absorption spectra must include certain minimal effects - dispersive or dielectric and repulsive or volume effects - in order to adequately represent the data. They discuss previous models at some length in order to delineate the limits of their applicability. They further acknowledge and define the limits of the applicability of their model to solvent-induced shifts in general.

Agnew, S.F.; Swanson, B.I. (Los Alamos National Lab., NM (USA))

1990-01-25

397

Band gap enhancement of glancing angle deposited TiO2 nanowire array  

NASA Astrophysics Data System (ADS)

Vertically oriented TiO2 nanowire (NW) arrays were fabricated by glancing angle deposition technique. Field emission-scanning electron microscopy shows the formation of two different diameters ~80 nm and ~40 nm TiO2 NW for 120 and 460 rpm azimuthal rotation of the substrate. The x-ray diffraction and Raman scattering depicted the presence of rutile and anatase phase TiO2. The overall Raman scattering intensity decreased with nanowire diameter. The role of phonon confinement in anatase and rutile peaks has been discussed. The red (7.9 cm-1 of anatase Eg) and blue (7.4 cm-1 of rutile Eg, 7.8 cm-1 of rutile A1g) shifts of Raman frequencies were observed. UV-vis absorption measurements show the main band absorption at 3.42 eV, 3.48 eV, and ~3.51 eV for thin film and NW prepared at 120 and 460 rpm, respectively. Three fold enhance photon absorption and intense light emission were observed for NW assembly. The photoluminescence emission from the NW assembly revealed blue shift in main band transition due to quantum confinement in NW structures.

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

2012-09-01

398

Remote sensing of tropospheric aerosol using UV MAX-DOAS during hazy conditions in winter: Utilization of O 4 Absorption bands at wavelength intervals of 338–368 and 367–393 nm  

Microsoft Academic Search

Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) measurements were taken during 12 hazy days in December 2006 in Fresno, USA. We obtained vertical distributions of aerosol extinction coefficients (AECs) and aerosol optical depths (AODs) at UV wavelengths of 353 and 380 nm by applying a recently developed aerosol retrieval algorithm based on O4 slant column densities (SCDs) from MAX-DOAS measurements. A

Hanlim Lee; Hitoshi Irie; Myojeong Gu; Jhoon Kim; Jungbae Hwang

2011-01-01

399

High-density and well-ordered Si-nanodisk array with controllable band gap energy and high photon absorption coefficient for all-silicon tandem solar cell applications  

Microsoft Academic Search

All-Si tandem solar cells comprising quantum dot superlattice (QDSL) have attracted much attention. However, a fabrication to realize uniform and controllable QD size (determines band gap (Eg)) and spacing between QDs (generates miniband) in QDSL is still a big challenge. In this study, we created a two-dimensional sub-10nm-Si-nano-disk array (2D Si-ND array) with a high-density and well-ordered arrangement using bio-template

Chi-Hsien Huang; Makoto Igarashi; M. Fairuz bin Budiman; Xuan-Yu Wang; Ryuji Oshima; Ichiro Yamashita; Yoshitaka Okada; Seiji Samukawa

2010-01-01

400

Two-photon absorption study of 1,3,5-hexatriene by cars and CSRS  

NASA Astrophysics Data System (ADS)

Two-photon absorption spectra of trans- and cis-1,3,5-hexatrienes in the liquid state have been observed in the frequency range of 2? = 30000-50000 cm -1, by analyzing the interference effect of Raman and two-photon resonances in the CARS and CSRS lineshape. In both isomers, a broad two-photon absorption with a maximum absorptivity of about 10 -50 cm 4 s photon -1 molecule -1 was determined to be a few thousand cm -1 higher than an intense dipole-allowed transitions (1 1B u ? 1 1A g or 1 1B 2 ? 1 1A 1) near 40000 cm -1. This band is most probably assigned to the two-photon-allowed state corresponding to the lowest excited singlet already established to be 2 1A g or 2 1A 1 in larger homologues. The relative ordering of the 1 1B and 2 1A levels is discussed.

Fujii, T.; Kamata, A.; Shimizu, M.; Adachi, Y.; Maeda, S.

1985-04-01

401

Intense field electron excitation in transparent materials  

NASA Astrophysics Data System (ADS)

The propagation of an intense laser through transparent materials can only be understood by considering a wide range of nonlinear effects and their simultaneous interaction. Electron plasma formation plays a crucial role and is the focus of this work. The mechanisms of the nonlinear ionization are not well understood. There are two proposed interactions that contribute to electron plasma formation: photoionization and avalanche ionization, but the individual contribution of each of these ionization processes is controversial. Keldysh theory has been proposed as a description of photoionization. Two models for avalanche ionization are used in the literature, but with different intensity dependence. We address and resolve these issues. In this thesis we present a spectrally resolved pump-probe experiment that directly measures the nonlinear ionization rates and plasma evolution in solid state media. Both pump and probe are derived from an 800 nm, 120 fs laser. The maximum ionization rates were obtained in sapphire (˜1.9x10 18 fs-1 ·cm-3), while in water (˜7.2x1017 fs-1 ·cm -3), fused silica (˜8.6x1017 fs -1 ·cm-3) and methanol (˜6.6x10 17 fs-1 ·cm-3) the ionization rates were slightly different. Our measured ionization rates are consistently larger that the theoretical rate given by Keldysh theory, suggesting that this theory does not correctly describe the photoionization process. We also present measurements that separate the two excitation processes and identify the role played by each in the ionization of media. The idea underneath these experiments is a very simple one: since the two ionization processes have different intensity dependence, the absorption of light in the medium should differ similarly. Therefore it should be possible to distinguish the two mechanisms by looking at the energy dependence of the absorption. From our result we find that avalanche and multiphoton ionization have varying relative contributions, depending on the band gap. For example, in sapphire (band gap ˜ 9.0 eV) avalanche accounts for 70% whereas in methanol (band gap ˜ 6.5 eV) contributes only 15%.

Modoran, Georgia C.

402

Geologic Mapping From Airborne Visible And Near-infrared Relative Band Depth Images, Mountain Pass, California  

Microsoft Academic Search

Airborne vi si blelinfrared imaging spectrometer (AVIRIS) data acquired over the Mountain Pass area in southeastern California were examined to evaluate the use of narrow band image data for regional lithologic mapping. Relative absorption band-depth images (RBD) for individual spectral absorption features were generated directly from the data. To determine which RBD images to construct, diagnostic mineral absorption features were

Marguerite J. Kingston

1990-01-01

403

Infrared absorption spectra of serpentine cat’s eye from Sichuan Province of China  

Microsoft Academic Search

Infrared (IR) absorption spectra and X-ray powder diffraction (XRD) patterns of serpentine cat’s eye from Sichuan Province\\u000a have been investigated, and infrared absorption bands of the serpentine have been assigned in this paper. The results indicate\\u000a that the bands near 3 600–3 700 cm?1 belong to the stretching absorption band ?\\u000a OH, the bands in 948–1100 cm?1 are assigned to

Bao-qi Lu; Yi-ben Xia; Li-jian Qi

2005-01-01

404

Nutrient absorption.  

PubMed

Many advances in the study of nutrient absorption have been made with the use of molecular and genetic techniques; however, standard in vivo studies have provided interesting and important new information. Omega-3 long-chain fatty acids have unexpected effects on lipoprotein formation and secretion in neonatal intestinal cells; this needs to be considered in the modification of infant formulas. Rexinoids affect intestinal cholesterol homeostasis via two receptors: retinoic acid receptor/liver X receptor (cholesterol efflux to lumen) and retinoic acid receptor/farnesoid X receptor (cholesterol catabolism). Absorption of the antioxidant plant polyphenol quercetin involves interaction with the glucose transporter and deglycolsylation and conjugation reactions. Cells of the polarized human colon cancer cell line, CaCo-2, take up phenylalanine by two mechanisms: passive uptake across the basolateral membrane, and temperature-dependent transcellular movement from apical to basolateral media. Absorption of vitamins A and E is markedly enhanced in normal and damaged intestine by the administration of restructured triacylglycerols derived from fish oil and medium-chain fatty acids. Surprisingly, dietary protein and phosphorus apparently have no significant effect on the efficiency of calcium absorption in adult women. Finally, many studies examined a variety of genes that regulate iron absorption and homeostasis. PMID:17033282

Nutting, David F; Kumar, N Suresh; Siddiqi, Shadab A; Mansbach, Charles M

2002-03-01

405

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

SciTech Connect

Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

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

2010-10-26

406

Assignment of Red Rectangle Visible Emission Bands  

Microsoft Academic Search

An explanation based upon nonlinear photoexcitation of H2 is offered for the most striking features seen in the visible emission spectrum of the Red Rectangle (RR) nebula - three intense, relatively sharp, red-shaded bands appearing near 5798 Angstroms, 5851 Angstroms, and 6615 Angstroms. In the model, the lambda 5851 band is assigned as an emission step in a Ly-alpha -pumped,

P. P. Sorokin; J. H. Glownia

2000-01-01

407

Bernauer's bands.  

PubMed

Ferdinand Bernauer proposed in his monograph, "Gedrillte" Kristalle (1929), that a great number of simple, crystalline substances grow from solution or from the melt as polycrystalline spherulites with helically twisting radii that give rise to distinct bull's-eye patterns of concentric optical bands between crossed polarizers. The idea that many common molecular crystals can be induced to grow as mesoscale helices is a remarkable proposition poorly grounded in theories of polycrystalline pattern formation. Recent reinvestigation of one of the systems Bernauer described revealed that rhythmic precipitation in the absence of helical twisting accounted for modulated optical properties [Gunn, E. et al. J. Am. Chem. Soc. 2006, 128, 14234-14235]. Herein, the Bernauer hypothesis is re-examined in detail for three substances described in "Gedrillte" Kristalle, potassium dichromate, hippuric acid, and tetraphenyl lead, using contemporary methods of analysis not available to Bernauer, including micro-focus X-ray diffraction, electron microscopy, and Mueller matrix imaging polarimetry. Potassium dichromate is shown to fall in the class of rhythmic precipitates of undistorted crystallites, while hippuric acid spherulites are well described as helical fibrils. Tetraphenyl lead spherulites grow by twisting and rhythmic precipitation. The behavior of tetraphenyl lead is likely typical of many substances in "Gedrillte" Kristalle. Rhythmic precipitation and helical twisting often coexist, complicating optical analyses and presenting Bernauer with difficulties in the characterization and classification of the objects of his interest. PMID:21370378

Shtukenberg, Alexander; Gunn, Erica; Gazzano, Massimo; Freudenthal, John; Camp, Eric; Sours, Ryan; Rosseeva, Elena; Kahr, Bart

2011-03-02

408

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

NASA Astrophysics Data System (ADS)

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 ( Fk's), nephelauxetic effect ( ?), bonding ( b1/2) 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, Kb 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.

Devi, Ch. Victory; Singh, N. Rajmuhon

2011-03-01

409

Low-temperature absorption edge and photoluminescence in layered structured Tl2Ga2S3Se single crystals  

NASA Astrophysics Data System (ADS)

The absorption edge of undoped Tl2Ga2S3Se crystals have been studied through transmission and reflection measurements in the wavelength range 440-1100 nm and in the temperature range 10-300 K. The absorption edge was observed to shift toward lower energy values with increasing temperature. As a result, the rate of the indirect band gap variation with temperature ?=-2.6×10-4 eV/K and the absolute zero value of the band gap energy Egi(0)=2.42 eV were obtained.The emission band spectra of Tl2Ga2S3Se crystals have been studied in the temperature range 10-60 K and in the wavelength region 505-605 nm. A broad photoluminescence (PL) band centered at 550 nm (2.25 eV) was observed at T=10 K. Variation of emission band has been studied as a function of excitation laser intensity in the 0.3-41.5 mW cm-2 range. Radiative transitions from the shallow donor level Ed=0.01 eV to the moderately deep acceptor level Ea=0.16 eV were suggested to be responsible for the observed PL band.

Gasanly, N. M.

2012-11-01

410

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

PubMed

The absorption spectrum of CO2 in the wavelength range 120-160 nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled potential energy surfaces of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T = 190 K via Boltzmann averaging of optical transitions from many initial rotational states, accurately reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that the main progressions in the high energy band correspond to consecutive excitations of the pseudorotational motion along the closed loop of the CI seam, and progressions differ in the number of nodes along the radial mode perpendicular to the closed seam. Irregularity of the diffuse peaks in the low energy band is interpreted as a manifestation of the carbene-type "cyclic" OCO minimum. PMID:23781783

Grebenshchikov, Sergy Yu

2013-06-14

411

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

NASA Astrophysics Data System (ADS)

The absorption spectrum of CO2 in the wavelength range 120-160 nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled potential energy surfaces of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T = 190 K via Boltzmann averaging of optical transitions from many initial rotational states, accurately reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that the main progressions in the high energy band correspond to consecutive excitations of the pseudorotational motion along the closed loop of the CI seam, and progressions differ in the number of nodes along the radial mode perpendicular to the closed seam. Irregularity of the diffuse peaks in the low energy band is interpreted as a manifestation of the carbene-type ``cyclic'' OCO minimum.

Grebenshchikov, Sergy Yu.

2013-06-01

412

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

413

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

414

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

National Technical Information Service (NTIS)

The rotationless transition moment squared for the x(sup 1) sigma (sup +) v=3 (left arrow) v=0 band of CO is measured to be the absolute value of R (sub 3-0) squared = 1.7127(25)x 10(exp -7) Debye squared. This value is about 8.6 percent smaller than the ...

C. Chackerian R. Freedman L. P. Giver L. R. Brown

2001-01-01

415

Far infrared absorption by acoustic phonons in titanium dioxide nanopowders  

Microsoft Academic Search

We report spectral features of far infrared electromagnetic radiation absorption in anatase TiO2 nanopowders which we attribute to absorption by acoustic phonon modes of nanoparticles. The frequency of peak excess absorption above the background level corresponds to the predicted frequency of the dipolar acoustic phonon from continuum elastic theory. The intensity of the absorption cannot be accounted for in a

Daniel B. Murray; Caleb H. Netting; Lucien Saviot; Catherine Pighini; Nadine Millot; Daniel Aymes; Hsiang-Lin Liu

2006-01-01

416

Sequential absorption processes in two-photon-excitation transient absorption spectroscopy in a semiconductor polymer  

NASA Astrophysics Data System (ADS)

We investigate two-photon-excited transient absorption (TA) in poly[ 9,9' -dioctyl-fluorene-co-N-(4-butylphenyl)diphenylamine]. Using excitation pulses at 1.55eV and of around 1-ps duration, we measured the pump intensity dependence of the TA in the visible part of the spectrum and were able to resolve multiple sequential excitation and absorption processes. Polymers in the ground state (S0) were first excited by absorbing two pump photons to the band of two-photon excited states (S2) . There is then fast relaxation from S2 to the lowest singlet excited state (S1) . Based on this transient modulation of the population on the excited states, the S2 and S1 excitons were further excited by absorbing another pump or tunable probe photon to higher-lying excited states of Sn and Sm , respectively. Moreover, the probe photon was also absorbed by the ground-state molecules with the aid of a pump photon (?pump+?probe) for the transition from S0 to S2 . A fraction of higher-energy Sn and Sm excitons dissociated into charges that provided an additional absorption channel for the probe pulses. Comparing the simulation and the experimental results, we evaluated quantitatively the contributions from the above absorption channels to the total TA of the probe. The photocurrent measurement in a photodiode structure confirmed that dissociation of excitons from the higher-lying excited states is the dominant mechanism for charge generation in two-photon excitation.

Zhang, Xinping; Xia, Yajun; Friend, Richard H.; Silva, Carlos

2006-06-01

417

Gaia broad band photometry  

NASA Astrophysics Data System (ADS)

Aims: The scientific community needs to be prepared to analyse the data from Gaia, one of the most ambitious ESA space missions, which is to be launched in 2012. The purpose of this paper is to provide data and tools to predict how Gaia photometry is expected to be. To do so, we provide relationships among colours involving Gaia magnitudes (white light G, blue GBP, red GRP and GRVS bands) and colours from other commonly used photometric systems (Johnson-Cousins, Sloan Digital Sky Survey, Hipparcos and Tycho). Methods: The most up-to-date information from industrial partners has been used to define the nominal passbands, and based on the BaSeL3.1 stellar spectral energy distribution library, relationships were obtained for stars with different reddening values, ranges of temperatures, surface gravities and metallicities. Results: The transformations involving Gaia and Johnson-Cousins V - IC and Sloan DSS g - z colours have the lowest residuals. A polynomial expression for the relation between the effective temperature and the colour GBP - GRP was derived for stars with Teff ? 4500 K. For stars with Teff < 4500 K, dispersions exist in gravity and metallicity for each absorption value in g - r and r - i. Transformations involving two Johnson or two Sloan DSS colours yield lower residuals than using only one colour. We also computed several ratios of total-to-selective absorption including absorption AG in the G band and colour excess E(GBP - GRP) for our sample stars. A relationship involving AG/AV and the intrinsic (V - IC) colour is provided. The derived Gaia passbands have been used to compute tracks and isochrones using the Padova and BASTI models. Finally, the performances of the predicted Gaia magnitudes have been estimated according to the magnitude and the celestial coordinates of the star. Conclusions: The provided dependencies among colours can be used for planning scientific exploitation of Gaia data, performing simulations of the Gaia-like sky, planning ground-based complementary observations and for building catalogues with auxiliary data for the Gaia data processing and validation. Tables 11-13 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/523/A48

Jordi, C.; Gebran, M.; Carrasco, J. M.; de Bruijne, J.; Voss, H.; Fabricius, C.; Knude, J.; Vallenari, A.; Kohley, R.; Mora, A.

2010-11-01

418

Photoluminescence investigation of the indirect band gap and shallow impurities in icosahedral B12As2  

NASA Astrophysics Data System (ADS)

The indirect band gap of icosahedral B12As2 (IBA) has been determined by variable temperature photoluminescence measurements (8 K-294 K) on solution-grown bulk samples. In addition, evidence of three shallow acceptor levels and one shallow donor level is reported. The low-temperature spectra were characterized by broad and intense deep defect emission, donor-acceptor pair (DAP) bands, and exciton recombination. The appearance of DAP emission verifies the incorporation of a donor in IBA, which has not been reported previously. The temperature dependence of the free exciton (FE) intensity reflected a FE binding energy of 45 meV. The variation of the FE peak position with temperature was fitted with both Varshni and Pässler models to determine an expression for the temperature dependence of the indirect band gap. The resulting low and room temperature band gaps are Eg(0) = 3.470 eV and Eg(294 K) = 3.373 eV, respectively. The latter is not consistent with previous reports of the room temperature band gap, 3.20 eV and 3.47 eV, derived from band structure calculations and optical absorption, respectively. The origin of these discrepancies is discussed. The DAP spectra reveal three relatively shallow acceptors with binding energies of ~175, 255, and 291 meV, and a shallow donor with binding energy ~25 meV. Although the identity of the individual acceptors is not known, they appear to be associated with the light-hole band. The small donor binding energy is suggestive of an interstitial donor impurity, which is suspected to be Ni.

Klein, P. B.; Nwagwu, Ugochukwu; Edgar, J. H.; Freitas, J. A.

2012-07-01

419

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

National Technical Information Service (NTIS)

This work was initiated to compare absolute line intensities retrieved with the Kitt Peak FTS (Fourier Transform Spectrometer) and Ames BOMEM FTS. Since thermal contaminations can be a problem using the BOMEM instrument if proper precautions are not taken...

C. Chackerian R. J. Kshirsagar L. P. Giver L. R. Brown

1999-01-01

420

Oxygen partial pressure dependence of optical absorption in lithium niobate  

Microsoft Academic Search

Optical absorption of undoped and Fe-doped LiNbO3 crystals grown under various oxygen partial pressures, PO2, has been investigated. The 2.9 eV band found in undoped crystal forms only during the growth process and is proportional to P14O2. This band consists of the superposition of three broad absorption bands A1, A2, and A3, and is assigned to a hole localized on

Tetsuro Suzuki

1996-01-01

421

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

422

Nonlinear ionization mechanism dependence of energy absorption in diamond under femtosecond laser irradiation  

NASA Astrophysics Data System (ADS)

We present first-principles calculations for nonlinear photoionization of diamond induced by the intense femtosecond laser field. A real-time and real-space time-dependent density functional theory with the adiabatic local-density approximation is applied to describe the laser-material interactions in the Kohn-Sham formalism with the self-interaction correction. For a certain laser wavelength, the intensity dependence of energy absorption on multiphoton and/or tunnel ionization mechanisms is investigated, where laser intensity regions vary from 1012 W/cm2 to 1016 W/cm2. In addition, the effect of laser wavelength on energy absorption at certain ionization mechanism is discussed when the Keldysh parameter is fixed. Theoretical results show that: (1) at the fixed laser wavelength, the relationship between the energy absorption and laser intensity shows a good fit of E = cMIN (N is the number of photons absorbed to free from the valence band) when multiphoton ionization dominates; (2) while when tunnel ionization becomes significant, the relationship coincides with the expression of E = cTIn (n < N).

Wang, Cong; Jiang, Lan; Li, Xin; Wang, Feng; Yuan, Yanping; Qu, Liangti; Lu, Yongfeng

2013-04-01

423

Extinction and Polycyclic Aromatic Hydrocarbon Intensity Variations across the H II Region IRAS 12063-6259  

NASA Astrophysics Data System (ADS)

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 ?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 ?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 ?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.; Tielens, A. G. G. M.; Otaguro, J. N.; Bik, A.

2013-07-01

424

Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses.  

PubMed

Electron Spin Resonance (ESR) and optical absorption studies of 5Al(2)O(3)+75H(3)BO(3)+(20-x)PbO+xMnSO(4) (where x=0.5, 1,1.5 and 2 mol% of MnSO(4)) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ?2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g?2.0 has been attributed to Mn(2+) centers in an octahedral symmetry. The ESR resonance signals at isotropic g?3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn(2+) ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to (5)E(g)?(5)T(2g) transition of Mn(3+)centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges. PMID:23000927

SivaRamaiah, G; LakshmanaRao, J

2012-08-19

425

Taking into account nonselective absorption of light in atomic absorption analysis  

Microsoft Academic Search

We propose a method for quantitatively taking into account nonselective absorption for systems in which the vapor phase contains a single molecular form: sodium and potassium chlorides and iodides. We identified the absorption bands using modern quantum chemistry methods. We have demonstrated good agreement between the experimental data and the calculations. We have tested the correctness of the method we

N. N. Grebenyuk; O. A. Zhikol; A. B. Blank

2006-01-01

426

NEUTRON FLUX INTENSITY DETECTION  

DOEpatents

A method of measuring the instantaneous intensity of neutron flux in the core of a nuclear reactor is described. A target gas capable of being transmuted by neutron bombardment to a product having a resonance absorption line nt a particular microwave frequency is passed through the core of the reactor. Frequency-modulated microwave energy is passed through the target gas and the attenuation of the energy due to the formation of the transmuted product is measured. (AEC)

Russell, J.T.

1964-04-21

427

Free-Carrier Optical Absorption in Niobium-Doped Strontium Titanate.  

National Technical Information Service (NTIS)

The free carrier optical absorption in SrTiO3 doped with Nb and/or reduced in hydrogen has been studied experimentally and a 2.4 eV absorption peak identified as a direct band to band transition from the Ti 3d band to a higher lying mixed conduction p typ...

E. Simanek N. L. H. Liu R. L. Wild

1971-01-01

428

Extending the L-band to 1620 nm using MCS fiber  

Microsoft Academic Search

Compositional modifications to the base MCS (antimony silicate) glass composition permit extension of useable L-band gain from 1615 to 1620 nm. This is achieved by shifting the signal excited state absorption band to longer wavelengths.

A. J. G. Ellison; D. E. Goforth; B. N. Samson; J. D. Minelly; J. P. Trentelman; D. L. McEnroe; B. P. Tyndell

2001-01-01

429

A Simple Band for Gastric Banding.  

PubMed

The author has noted that flexible gastric bands have occasionally stenosed the gastric stoma or allowed it to dilate. A band was developed using a soft outer silicone rubber tube over a holding mechanism made out of a nylon cable tie passed within the silicone tube. This simple, easily applied band is rigid, resisting scar contracture and dilatation. PMID:10757939

Broadbent

1993-08-01

430

Absorption into fluorescence. A method to sense biologically relevant gas molecules  

NASA Astrophysics Data System (ADS)

In this work we present an innovative optical sensing methodology based on the use of biomolecules as molecular gating nano-systems. Here, as an example, we report on the detection of analytes related to climate change. In particular, we focused our attention on the detection of nitric oxide (NO) and oxygen (O2). Our methodology builds on the possibility of modulating the excitation intensity of a fluorescent probe used as a transducer and a sensor molecule whose absorption is strongly affected by the binding of an analyte of interest used as a filter. The two simple conditions that have to be fulfilled for the method to work are: (a) the absorption spectrum of the sensor placed inside the cuvette, and acting as the recognition element for the analyte of interest, should strongly change upon the binding of the analyte and (b) the fluorescence dye transducer should exhibit an excitation band which overlaps with one or more absorption bands of the sensor. The absorption band of the sensor affected by the binding of the specific analyte should overlap with the excitation band of the transducer. The high sensitivity of fluorescence detection combined with the use of proteins as highly selective sensors makes this method a powerful basis for the development of a new generation of analytical assays. Proof-of-principle results showing that cytochrome c peroxidase (CcP) for NO detection and myoglobin (Mb) for O2 detection can be successfully used by exploiting our new methodology are reported. The proposed technology can be easily expanded to the determination of different target analytes.

Strianese, Maria; Varriale, Antonio; Staiano, Maria; Pellecchia, Claudio; D'Auria, Sabato

2011-01-01

431