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1

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

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

2

Rovibrational Intensities of the (0003) <-- (1000) Dyad Absorption Bands of 12C16O2  

Microsoft Academic Search

Absolute line intensities of 12C16O2 are experimentally measured for the first time for the (0003)I <-- (1000)II band at 5687.17 cm-1 and the (0003)I <-- (1000)I band at 5584.39 cm-1. The spectra were obtained using a Bomem DA8 Fourier transform spectrometer and a 25-m base-path White cell at NASA-Ames Research Center. The rotationless bandstrengths at a temperature of 296 K

Rohidas J. Kshirsagar; Lawrence P. Giver; Charles Chackerian

2000-01-01

3

Effect of pressure on the intensity of absorption bands in the IR spectra of compacted polyethylene powde  

NASA Astrophysics Data System (ADS)

The investigation of the IR spectra of compacted reactor powders of ultra-high-molecular-weight polyethylene showed that the intensities of the absorption bands depend on the compaction pressure; namely, they decrease with increasing pressure. It is found that the ultimate pressure above which the absorption band intensity ceases to decrease depends on the spectral position of the band; the shorter the wavelength, the higher the ultimate pressure. This pressure is 5-10 MPa for bands in the long-wavelength spectral region (the band at 720 cm-1) and 100 MPa for the short-wavelength region (the band at 5875 cm-1). It is assumed that this phenomenon is related to a change in the size of pores d with pressing. Beams with wavelengths ? < d will undergo multiple diffuse reflections and reach a photodetector that is weaker than beams with ? > d. With increasing pressure, the size of pores decreases and the boundary between the two regions of the spectra shifts to short wavelengths.

Aulov, V. A.

2009-02-01

4

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

5

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

NASA Technical Reports Server (NTRS)

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)2)(sub II) from (01(sup 1)0)(sub I) at 5248/cm, (02(sup 2))(sub I) from (01(sup 1)0)(sub I) at 5291/cm, and (10(sup 0)2)(sub I) from (01(sup 1)0)(sub I) at 5349/cm. The nearby parallel hot band (30(sup 0))(sub I) from (10(sup 0)0)(sub II) at 5218/cm was also included in this study.

Giver, Lawrence P.; Brown, Linda R.; Chackerian, Charles, Jr.; Freedman, Richard S.; Gore, Warren J. (Technical Monitor)

2002-01-01

6

Rovibrational Intensities of the (00 03) ? (10 00) Dyad Absorption Bands of 12C 16O 2  

Microsoft Academic Search

Absolute line intensities of 12C16O2 are experimentally measured for the first time for the (0003)I ? (1000)II band at 5687.17 cm?1 and the (0003)I ? (1000)I band at 5584.39 cm?1. The spectra were obtained using a Bomem DA8 Fourier transform spectrometer and a 25-m base-path White cell at NASA–Ames Research Center. The rotationless bandstrengths at a temperature of 296 K

Rohidas J. Kshirsagar; Lawrence P. Giver; Charles Chackerian Jr.

2000-01-01

7

Saturation Intensity in Excited Channel for Nonlinear Medium With Coincident Absorption and Emission Bands-Part I  

Microsoft Academic Search

Optical properties of nonlinear medium can be considered by using a typical three-level configuration (S0-S1-S2). In this configuration the transition of molecules in principal channel (S0-S1) are occurred by the light fields of intensity I12 at frequency omega0 and the light fields with intensity I23 at frequency omega transmit the excited molecules to second excited level (S2). The absorption and

Jihad S. M. Addasi

2007-01-01

8

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

9

First atmospheric profile measurements of UV\\/visible O4 absorption band intensities: Implications for the spectroscopy, and the formation enthalpy of the O2-O2 dimer  

Microsoft Academic Search

The first atmospheric profiles of the ultraviolet\\/visible (UV\\/vis) absorption bands of the collision complex O2-O2, or O4 in brief, are reported. The O4 absorption profiles are inferred from direct Sun spectra observed from the LPMA\\/DOAS (Laboratoire Physique Moléculaire et Application\\/Differential Optical Absorption Spectroscopy) balloon gondola. Seven O4 absorption bands - centered at ?360.7, 380.2, 446.7, 477.1, 532.2, 577.2, and 630.0

K. Pfeilsticker; H. Bösch; C. Camy-Peyret; R. Fitzenberger; H. Harder; H. Osterkamp

2001-01-01

10

Atomic absorption of ultra intense laser radiation  

Microsoft Academic Search

The authors derive an expression for the rate of absorption by an atomic system (bound or free) of radiation from an ultra intense laser beam. The absorption characteristics are radically different from those of conventional weak-field absorption theory.

S. Geltman; M. R. Teague

1974-01-01

11

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

12

Atmospheric Solar Heating in Minor Absorption Bands  

NASA Technical Reports Server (NTRS)

Solar radiation is the primary source of energy driving atmospheric and oceanic circulations. Concerned with the huge computing time required for computing radiative transfer in weather and climate models, solar heating in minor absorption bands has often been neglected. The individual contributions of these minor bands to the atmospheric heating is small, but collectively they are not negligible. The solar heating in minor bands includes the absorption due to water vapor in the photosynthetically active radiation (PAR) spectral region from 14284/cm to 25000/cm, the ozone absorption and Rayleigh scattering in the near infrared, as well as the O2 and CO2 absorption in a number of weak bands. Detailed high spectral- and angular-resolution calculations show that the total effect of these minor absorption is to enhance the atmospheric solar heating by approximately 10%. Depending upon the strength of the absorption and the overlapping among gaseous absorption, different approaches are applied to parameterize these minor absorption. The parameterizations are accurate and require little extra time for computing radiative fluxes. They have been efficiently implemented in the various atmospheric models at NASA/Goddard Space Flight Center, including cloud ensemble, mesoscale, and climate models.

Chou, Ming-Dah

1998-01-01

13

New metastable absorption bands in KBr  

Microsoft Academic Search

New metastable absorption bands, which appear as a broadening of the F and beta bands, have been observed in X-rayed KBr. They are very likely due to a perturbed F-centre or to a centre with an F-centre as a component.

G. Giuliani; S. Malusa; V. Mitra

1981-01-01

14

Lattice Absorption Bands in Indium Antimonide  

Microsoft Academic Search

A series of detailed measurements of the absorption spectrum of high quality single crystals of n-type indium antimonide has been made in the wavelength range 15 to 130 ?, and over the temperature range 4.2 to 90°K.Some new absorption bands have been found, and an explanation is offered for the positions and temperature dependence of all the principle absorption peaks

S J Fray; F A Johnson; R H Jones

1960-01-01

15

Hitherto Unidentified Absorption Bands of Water Vapour  

Microsoft Academic Search

IN 1912-13, F. E. Fowle1 made studies of the absorption of infra-red radiation by water-vapour at 0.93mu, 1.13mu and 1.47mu, in order to determine spectroscopically the total water-vapour content of the atmosphere. The first two wave-lengths are at the centres of the rho and varphi bands; the last is about 450 cm.-1 from the Psi-band centre.

T. G. Cowling

1943-01-01

16

Infrared band intensities of saturated hydrocarbons  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

17

Absorption band Q model for the Earth  

NASA Technical Reports Server (NTRS)

Attenuation in solids and liquids, as measured by the quality factor Q, is typically frequency dependent. In seismology, however, Q is usually assumed to be independent of frequency. Body wave, surface wave, and normal mode data are used to place constraints on the frequency dependence of Q in the mantle. Specific features of the absorption band model are: low-Q in the seismic band at both the top and the base of the mantle, low-Q for long-period body waves in the outer core, an inner core Q sub s that increases with period, and low Q sub p/Q sub s at short periods in the middle mantle.

Anderson, D. L.; Given, J. W.

1981-01-01

18

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

19

Three components of 3–4 ?m absorption bands  

Microsoft Academic Search

We present 2–4 µm spectra of six infrared sources for which the extinction is not purely interstellar, but is dominated by circumstellar or molecular cloud dust. In all cases the absorption bands differ from the interstellar case, though a component of the interstellar absorption is often present. We also present an improved absorption spectrum for the galactic centre source IRS

D. T. Wickramasinghe; D. A. Allen

1983-01-01

20

New infrared absorption bands of cesium vapor  

Microsoft Academic Search

We have found a new region of absorption by saturated cesium vapor in the infrared region of the spectrum (1.25-2.5 mu). Most likely candidates for this infrared absorption are cesium dimers in the repulsive triplet state (x 3Sigma+u) and higher polymers of cesium (Cs3, Cs4,...).

E. Zouboulis; N. D. Bhaskar; A. Vasilakis; W. Happer

1980-01-01

21

Origin of the diffuse interstellar absorption bands  

Microsoft Academic Search

Evidence is presented that zero phonon lines of defect centres in MgO and CaO are responsible for the diffuse interstellar bands at 5362, 5705, 6425.7, and 6699.4 Å. Phonon sidebands of these lines are identified with the diffuse bands at 5535, 6177, 6196, 6284, and 6314 Å. These features arise in interstellar MgO and CaO particles with sizes ?50 Å.

W. W. Duley

1977-01-01

22

Two-photon absorption coefficients of optical fibers with 240-nm absorption band  

Microsoft Academic Search

Summary form only given. Photosensitivity in germanosilicate fibers has been known to relate to 240-nm absorption band of Ge-related oxygen-deficiency defects. In the blue-green region, Hill-grating formation and second-harmonic generation are attained by two-photon (multiphoton) absorption. However, the spectral dependence of two-photon absorption (TPA) coefficients has not been made clear. The 240-nm absorption and the photosensitivity have been attributed mainly

T. Mizunami; M. Hashimoto; S. Gupta; Y. Uchida; T. Shimomura

1996-01-01

23

Band renormalization of semiconductors by high-intensity infrared laser: One-dimensional model  

Microsoft Academic Search

We present a theoretical framework for the calculation of band structure and the optical absorption spectrum of semiconductors under an intense off-resonant laser field for a one-dimensional model. The Bloch theory and the Floquet theory are successfully combined to exploit the periodicity both in the space and the time domain. It is shown that the intense off-resonant laser field gives

Yoshihiko Mizumoto; Yosuke Kayanuma

2005-01-01

24

The 9300-Å Absorption Band in the Spectrum of Jupiter  

NASA Astrophysics Data System (ADS)

Low-resolution spectrophotometry of Jupiter by Karkoschka (1994, Icarus111, 174-192) revealed a weak apparent absorption feature in the spectrum of Jupiter at 920-940 nm. This is the wavelength of the strong 2? 1+? 3 band of H 2O, and Karkoschka tentatively identified the feature as jovian H 2O absorption. If this spectral feature is indeed due to H 2O absorption, it would offer the exciting possibility of monitoring the jovian H 2O with visible band spectroscopy. This feature has been seen in previous low-resolution spectroscopy of Jupiter such as that of Woodman et al. (1979, Icarus37, 73-83), but was not identified as jovian in origin because of uncertainties in extinction corrections for the very strong telluric H 2O absorption. Cochran et al. (1995, Bull. Am. Astron. Soc.27, 66) tentatively identified the feature as due to NH 3, an identification that was supported by further low-resolution spectrophotometry by Karkoschka (1998, Icarus133, 134-146). Here we present high-resolution spectra ( R=155,000) of Jupiter using the 2dcoudé spectrometer on the 2.7-m Harlan Smith Telescope at McDonald Observatory, in order to make a definitive identification of this absorption feature. Observations were obtained when Jupiter was near quadrature in order to Doppler shift potential jovian H 2O features away from the corresponding telluric lines. We demonstrate conclusively that the absorption band identified by Karkoschka is not, in fact, due to H 2O. We present further evidence that it is most likely to be an absorption band of NH 3. We searched our spectra carefully to attempt to identify absorption lines which are actually due to H 2O, without success.

Cochran, William D.; Cochran, Anita L.

1999-07-01

25

Vibronic properties of the F+ absorption band in calcium oxide  

Microsoft Academic Search

The shape and first four moments of the F+ absorption band in CaO have been studied as a function of temperature between 4.2 K and 300 K. Analysis of these results shows that the properties of the band can be accounted for very well in terms of Jahn-Teller coupling of the excited 2T1u state of the F+ centre to both

C. Escribe; A. E. Hughes

1971-01-01

26

AM1/CI, CNDO/S and ZINDO/S computations of absorption bands and their intensities in the UV spectra of some 4(3H)-quinazolinones  

NASA Astrophysics Data System (ADS)

A detailed analysis of both frontier MOs and electronic transitions in UV spectra of 16 4-quinazolinone derivatives has been carried out in MO terms, by semiempirical methods AM1/CI, CNDO/S and ZINDO/S. On the basis of experimental and theoretical investigations by the ZINDO/S and CNDO/S methods the long-wavelength bands of 4(3H)-quinazolinone and its derivatives have been assigned to n ? ?* transition of the lbond2 C dbnd O fragment and to the transition caused by intramolecular charge transfer from Ph and N dbnd C sbnd N fragments to lbond2 C dbnd O group. It was shown that theoretically obtained electronic transitions applying method AM1/CI are not in agreement with experimental data observed for the 4(3H)-quinazolinone and 2,4(1H,3H)-quinazolinedione. Good correlation of theoretical and experimental data has been obtained by the method ZINDO/S for the wavelengths and the molar extinction coefficients of the compounds studied. Satisfactory correlation of theoretical and experimental data has also been obtained by the method CNDO/S with singly and doubly excited configurations, for the wavelengths only. Such correlations on experimental and theoretical wavelength and molar absorption coefficients of 4-quinazolinone derivatives are carried out for the first time.

Eshimbetov, A. G.; Kristallovich, E. L.; Abdullaev, N. D.; Tulyaganov, T. S.; Shakhidoyatov, Kh. M.

2006-10-01

27

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

Microsoft Academic Search

A theory is described that attributes the diffuse interstellar absorption bands (DIBs) to coherently driven two-photon absorption by H2 molecules present in sheetlike clouds located near hot stars. Results from three-level nonlinear spectroscopy are used to argue that vacuum ultraviolet (VUV) photons from the star impinging on the H2-containing cloud will be primarily absorbed in simultaneous two-photon (Raman-type) transitions, resulting

Peter P. Sorokin; James H. Glownia

1996-01-01

28

New absorption bands in fluorites by heavy gamma irradiation  

Microsoft Academic Search

At least three new bands have been observed in the near infrared region of the absorption spectra of fluorites of different origin after heavy gamma irradiation in the range 106 to 109 R. Studies were also made with a sample of synthetically pure CaF2 crystal and the results indicate that the rare earth impurities abundantly present in the fluorites play

K. S. V. Nambi; T. Higashimura

1971-01-01

29

Asteroid 4 Vesta: Photometry in Visual Range and 0.92 M Pyroxene Absorption Band. Abstract Only.  

National Technical Information Service (NTIS)

The spectrum of the asteroid Vesta has a clear pyroxene absorption band at 0.92 micrometer. However, almost no observations have been performed to study the changes in intensity and profile of this band. Such observations were performed in September to Oc...

V. D. Vdovichenko F. P. Velichko S. M. Gaysin S. A. Mosina S. S. Shumilin

1989-01-01

30

Narrowing the locking band in a laser with nonlinear absorption  

NASA Astrophysics Data System (ADS)

The use of the competing resonances of ring lasers to eliminate frequency locking which imposes a fundamental limitation on the measurement of very low rotational velocities is investigated. It is shown that the width of the locking band is not a constant property and is determined primarily by the nonlinear coupling of the waves because of their reflection from structural elements of the resonator and by the nonlinear interaction of the traveling waves in the laser medium. Since the terms describing this interaction have different signs in amplifying and absorbing media, the nonlinear wave coupling and also the value of the locking band width decrease substantially at frequencies where the nonlinear absorption is most apparent (i.e., near the central frequency of the absorption line). In this situation, the primary contribution to the width of the locking band is eliminated.

Danileiko, M. V.; Nedavnii, A. P.

1981-07-01

31

Absorption Intensity Variation with Ion Association in Peo Based Electrolytes  

NASA Astrophysics Data System (ADS)

The validity of the extended version of Beer's Law, that the integrated absorption of the ?s(CF3) mode in PEO:LiCF3SO3 is independent of CF3SO3- ion association, is tested and found to be valid. An infrared absorption marker, AsF6- is found to be effective for the quantitative comparison of absorption intensity in different samples.

Furneaux, J. E.; McCoy, Allison M.; Seneviratne, Varuni; Frech, Roger

2006-06-01

32

Controllable Absorption and Dispersion Properties of an RF-driven Five-Level Atom in a Double-Band Photonic-Band-Gap Material  

NASA Astrophysics Data System (ADS)

The probe absorption-dispersion spectra of a radio-frequency (RF)-driven five-level atom embedded in a photonic crystal are investigated by considering the isotropic double-band photonic-band-gap (PBG) reservoir. In the model used, the two transitions are, respectively, coupled by the upper and lower bands in such a PBG material, thus leading to some curious phenomena. Numerical simulations are performed for the optical spectra. It is found that when one transition frequency is inside the band gap and the other is outside the gap, there emerge three peaks in the absorption spectra. However, for the case that two transition frequencies lie inside or outside the band gap, the spectra display four absorption profiles. Especially, there appear two sharp peaks in the spectra when both transition frequencies exist inside the band gap. The influences of the intensity and frequency of the RF-driven field on the absorptive and dispersive response are analyzed under different band-edge positions. It is found that a transparency window appears in the absorption spectra and is accompanied by a very steep variation of the dispersion profile by adjusting system parameters. These results show that the absorption-dispersion properties of the system depend strongly on the RF-induced quantum interference and the density of states (DOS) of the PBG reservoir.

Ding, Chun-Ling; Li, Jia-Hua; Yang, Xiao-Xue

2011-01-01

33

Uniform Band Intensities in Fluorescent Dye Terminator Sequencing  

Microsoft Academic Search

The use of Cyanine dye (Cy 5 and Cy5.5) labeled dideoxy terminators with Thermo Sequenase DNA polymerase in DNA sequencing provides uniform band intensity, improved sequence read-length, and accuracy. It also greatly improves the ability to detect single base heterozygotes with dye-terminator sequencing method.

Shiv Kumar; C. W. Fuller; S. Nampalli; M. Khot; I. Livshin; L. Sun; S. B. Samols; J. A. Mamone; K. M. Hujer; B. F. McArdle; J. R. Nelson; S. Duthie

1999-01-01

34

Intensity Measurements of the 01(sup 1)21-00(sup 0)01 Perpendicular CO2 band at 5315 cm (sup -1) and 4 related hot bands  

NASA Technical Reports Server (NTRS)

The near-infrared thermal emission windows in the spectrum of the night-side of Venus have stimulated new determinations of the intensities of weak CO2 bands which are prominent absorption features in Venus spectra. We have previously measured the 31(sup 1)04-00(sup 0)01 band at 4416 cm (sup -1), which dominates a portion of the 2.2 micrometer window, using the 25-meter White absorption cell at Ames. Parameters for many of the unmeasured bands have been recomputed for the HITRAN compilation using direct numerical diagonalization. This procedure has some uncertainties, particularly for higher overtone-combination perpendicular bands, and substantial differences were noted for these bands when comparing the 1986 HITRAN tabulation with the 1992 values. To clarify this situation, we decided to measure the intensities of several of these bands; L.R.B. obtained spectra using the McMath FTS and 6 meter White cell, covering the region 3800 to 7700 cm (sup -1). A table is provided in which we compare our measured intensities and Herman-Wallis al parameters for the 01(sup 1)21-00(sup 0)01 band and 4 associated hot bands with both Hitran tabulations. It is anticipated that these measured values will be useful in further DND calculations of many very weak unmeasurable bands.

Giver, Lawrence P.; Chackerian, Charles, Jr.; Spencer, Mark N.; Brown, Linda R.; Wattson, Richard B.; Gore, Warren J. (Technical Monitor)

1994-01-01

35

Optical absorption band III of deoxyheme proteins as a probe of their structure and dynamics  

NASA Astrophysics Data System (ADS)

Theory of the temperature dependence of a non-Frank-Condon optical absorption band in the case of weak anharmonicity is developed and applied to the interpretation of band III properties of deoxyheme proteins. It is obtained that dependence of the transition dipole moment on the displacement of the iron out of the heme plane, the weak anharmonic coupling between the heme doming and the iron-histidine vibration, and the glass-liquid phase transition cause notable and very specific temperature and pressure dependence of band III. It follows from this study that intensity of band III is sensitive to the iron-porphyrin distance, whereas its position can be affected by both the changes in this distance and protein electric field on the heme. Because the iron-porphyrin distance is affected by the protein, the band intensity and position (and not only width) must be sensitive to the protein structure and dynamics. In particular, intensity of band III can be used as a probe of protein dynamics, its dependence on the solvent viscosity, and protein and heme relaxation in the flash-photolysis experiments.

Stavrov, Solomon S.

2001-09-01

36

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

37

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

NASA Astrophysics Data System (ADS)

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

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

2005-01-01

38

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

SciTech Connect

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

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

2013-07-15

39

Optical absorption of nanoporous silicon: quasiparticle band gaps and absorption spectra  

NASA Astrophysics Data System (ADS)

Silicon is an earth-abundant material of great importance in semiconductors electronics, but its photovoltaic applications are limited by the low absorption coefficient in the visible due to its indirect band gap. One strategy to improve the absorbance is to perforate silicon with nanoscale pores, which introduce carrier scattering that enables optical transitions across the indirect gap. We used density functional and many-body perturbation theory in the GW approximation to investigate the electronic and optical properties of porous silicon for various pore sizes, spacings, and orientations. Our calculations include up to 400 atoms in the unit cell. We will discuss the connection of the band-gap value and absorption coefficient to the underlying nanopore geometry. The absorption coefficient in the visible range is found to be optimal for appropriately chosen nanopore size, spacing, and orientation. Our work allows us to predict porous-silicon structures that may have optimal performance in photovoltaic applications.

Shi, Guangsha; Kioupakis, Emmanouil

2013-03-01

40

Valance-Band photoemission intensities in thorium dioxide  

NASA Astrophysics Data System (ADS)

Resonant photoemission spectra of the O 2 p-derived valence band of insulating ThO 2 are compared to linear muffin-tin orbital (LMTO) density-of-state (DOS) and XPS intensity calculations. At Th 5 d corelevel threshold energies (85 ? hv ? 120 eV), resonance is greatest at the bottom of the O 2 p band where calculated p/d hybrid states are greatest; p/f hybrid content is weak by comparison. We conclude that the dominant hybridization is between O 2 p states and Th 6 d.

Ellis, W. P.; Boring, A. M.; Allen, J. W.; Cox, L. E.; Cowan, R. D.; Pate, B. B.; Arko, A. J.; Lindau, I.

1989-11-01

41

Two-Photon Absorption by H2 Molecules: Origin of the 2175A Astronomical Band?  

NASA Astrophysics Data System (ADS)

The near UV spectra of OB stars are often dominated by a broad extinction band peaking at 2175A. Forty years after its discovery, the origin of this band remains unknown, although it is usually attributed to linear scattering or linear absorption by interstellar dust particles. Here we report that two-photon absorption by H2 molecules in gaseous clouds enveloping OB stars should lead to a strong band peaking near 2175A. We first show that if the product of the H2 density in the gaseous cloud times the emitted stellar VUV flux is sufficiently great, the threshold for stimulated Rayleigh scattering will be exceeded, resulting in the generation of intense, monochromatic VUV light at the rest frame frequencies of H2 B- and C-state resonance lines originating from levels J''=0 and J''=1 of X0. This coherently generated light must necessarily propagate radially inwards towards the photosphere of the illuminating OB star, and therefore cannot be detected externally. However, this same light effectively constitutes intense ``first step'' monochromatic radiation that should induce continuum photons emitted by the OB star near 2175A to be strongly absorbed as ``second steps'' in resonantly-enhanced H2 two-photon transitions to two well known doubly-excited dissociative states of H2. Archival UV and VUV spectra of 185 OB stars strongly support our nonlinear model for the 2175A band.

Sorokin, Peter P.; Glownia, James H.

2007-04-01

42

Uncertainties of the Intensity of the 1130 nm Band of Water Vapor  

NASA Technical Reports Server (NTRS)

Belmiloud, et al have recently suggested that the HITRAN line intensities in the 1130 nm water vapor band are much too weak. Giver, et at corrected unit conversion errors to make the HITRAN intensities compatible with the original measurements of Mandin, et al, but Belmiloud, et al believe that many of those line intensity measurements were too weak, and they propose the total intensity of the 1130 nm water vapor band is 38% stronger than the sum of the HITRAN line intensities in this region. We have made independent assessments of this proposal using 2 spectra obtained with the Ames 25 meter base path White cell. The first was made using the moderate resolution (8 nm) solar spectral flux radiometer (SSFR) flight instrument with a White cell absorbing path of 506 meters and 10 torr water vapor pressure. Modeling this spectrum using the HITRAN linelist gives a reasonable match, and the model is not compatible when the HITRAN line intensities are increased by 38%. The second spectrum was obtained with a White cell path of 1106 meters and 12 torr water vapor pressure, using a Bomem FTIR with near Doppler width resolution. This spectrum is useful for measuring intensities of isolated weak lines to compare with the measurements of Mandin, et al. Unfortunately, as Belmiloud et al point out, at these conditions the strong lines are much too saturated for good intensity measurements. Our measurements of the weak lines are in reasonable agreement with those of Mandin, et al. Neither of our spectra supports the proposal of Belmiloud et al for a general 38% increase of the absorption intensity in the 1130 nm water vapor band.

Giver, L. P.; Pilewskie, P.; Gore, W. J.; Chackerian, C., Jr.; Varanasi, P.; Bergstrom, R.; Freedman, R. S.

2001-01-01

43

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

44

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

45

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

46

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

47

Absorption saturation of heavy- to light-hole band transitions in p-type InSb  

SciTech Connect

We present calculations of the intensity dependence of the free-hole absorption coefficient in p-type indium antimonide for high-intensity light with a wavelength near 10 ..mu..m. The dominant absorption mechanism is direct inter-valence-band transitions, where a hole occupying a state in the heavy-hole band makes a direct transition to a state in the light-hole band. The absorption coefficient due to this mechanism is predicted to decrease with increasing intensity in a manner closely approximated by an inhomogeneously broadened two-level model. Values for the saturation intensity I/sub S/ are reported as a function of the photon energy, lattice temperature, and hole density. The dependence of I/sub S/ on the hole concentration allows considerable tunability of the saturation behavior, so that for a fixed laser intensity, the degree of absorption saturation can be adjusted by controlling the doping density of the sample. For lightly doped samples at a temperature of 77 K, the free-hole absorption begins to saturate at intensities of less than 10 kW/cm/sup 2/, which is between one and two orders of magnitude smaller than the intensities required to saturate the comparable transitions in Ge and GaAs. The calculated results are also important to measurements of the two-photon absorption coefficient K/sub 2/ in InSb, and they indicate that much of the transmission data used to obtain a value for K/sub 2/ must be reevaluated.

James, R.B.; Chang, Y.

1988-11-15

48

Magneto-optical properties of the UV absorption bands of VK centres in alkali halides  

Microsoft Academic Search

A new UV absorption band below the original UV band has been discovered through the magnetic circular dichroism of the VK centre absorption (MCDA) in seven alkali halide crystals. This new band is attributed to the transition Sigma u to Pi u, which becomes dipole allowed as a result of a loss of inversion symmetry. We attribute this lowered symmetry

U. Rogulis; K. S. Song; J.-M. Spaeth

1995-01-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

50

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

PubMed

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

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

2013-11-20

51

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

PubMed

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

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

2011-01-17

52

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

53

Profile of the Unidentified Interstellar Absorption Band at 4430 Å at Different Galactic Longitudes  

Microsoft Academic Search

THE cause of the diffuse interstellar absorption band centred on 4430 Å is still unknown, thirty years after the recognition of the band's interstellar nature. Because this band, together with other similar bands, can absorb as much visible energy from the radiation of distant stars as is absorbed by the visible Balmer lines, an identification is of obvious interest, and

Harry Seddon

1967-01-01

54

Profile of the Unidentified Interstellar Absorption Band at 6180 Å at Different Galactic Longitudes  

Microsoft Academic Search

THERE is evidence1 that the profile of the unidentified interstellar absorption band at 4430 Å is constant over a range of galactic longitudes. This band is the strongest of a number of apparently similar bands centred on wavelengths of 6180 Å, 4890 Å and 4760 Å. The band at 6180 Å was first noticed by Wilson2, who speculated as to

Harry Seddon

1967-01-01

55

Luminescence of KCl:Bi3+ excited at the X absorption band  

Microsoft Academic Search

The emission from KCl:Bi3+ excited in the X absorption band (i.e. between the A and B absorption bands) was measured as a function of temperature. The polarized emission spectrum and the angular dependence of polarization ratio were also investigated. The X-band excitation produces two emission bands peaking at 345 and 395 nm, the centres of which are not the same.

Youn-Doo Kim; Jun-Gill Kang

1994-01-01

56

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

PubMed

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

Sakamoto, Yosuke; Tonokura, Kenichi

2012-01-12

57

Measurement of the absorption coefficient of acoustical materials using the sound intensity method  

Microsoft Academic Search

In this study the possibility of using the two-microphone sound intensity technique to measure the normal incidence and the random incidence sound absorption coefficient was investigated. The normal incidence absorption coefficient was determined by measuring the intensity incidence on the sample and the intensity reflected by the sample placed in an anechoic chamber. The random incidence absorption coefficient was determined

Mahabir S. Atwal; Malcolm J. Crocker

1987-01-01

58

Ultrafast absorption of intense x rays by nitrogen molecules  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

59

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

60

Identification of Li O absorption bands based on lithium isotope substitutions  

NASA Astrophysics Data System (ADS)

Isotope substitution method was used to identify the Li-O absorption bands in crystalline lithium silicates (2Li 2O 3·SiO 2, Li 2O·SiO 2, Li 2O·2SiO 2) and selected aluminosilicates (?-eucriptite and ?-spodumene). Isotopic shift was established after mathematical decomposition of the IR spectra. Absorption bands connected directly with internal, LiO 4 tetrahedron vibrations are observed in the range 460-250 cm -1. Bending vibrations of Si-O-Li bridges give absorption bands in the range 500-600 cm -1. The exact position of the bands and their isotopic shifts are given.

Nocu?, Marek; Handke, Miros?aw

2001-09-01

61

Vibration + libration absorption bands of OH centres in LiNbO3  

Microsoft Academic Search

Hydrogen centres in the bulk of stoichiometric (VTE) LiNbO3 exhibit a sharp absorption band of the OH(OD) stretching vibration near 3466 (2562) cm?1. In congruent LiNbO3 the OH band ( max = 3484cm?1) is rather broad (FWHM ?30 cm?1) and for the high proton concentration layers in proton exchanged LiNbO3:PE the broad absorption band (FWHM ?30 cm?1) is shifted to

A. Gröne; S. Kapphan

1995-01-01

62

Thermally induced absorption bands with vibronic structure in LiF crystals  

Microsoft Academic Search

Lithium fluoride single crystals obtained from different sources show a series of narrow absorption bands in the ultraviolet when annealed above 250°C in certain vacuum conditions. The ambient pressure and temperature at which annealing rwes place affects the defect production rate, increasing temperature and decreasing total pressure giving larger absorption strengths.The structure of the absorption was similar for all the

G. C. Crittenden; P. D. Townsend

1973-01-01

63

Emission intensities of fourth positive bands of CO in the atmosphere of Mars due to solar EUV interaction  

NASA Astrophysics Data System (ADS)

Theoretical calculations of photoelectron fluxes in the upper atmosphere of Mars are performed and the results are compared with theoretical model calculations for photoelectron impact. Photoelectron impact excitation rate of CO2(+), N2, and CO are calculated and compared with earlier results. Zenith airglow intensities of the fourth positive bands of CO in the atmosphere of Mars due to the interaction of solar EUV radiation are also calculated. Self-absorption in CO is included in the calculations and its effect is shown by comparison with results obtained without absorption. A band transmission function which can be used in the calculation is presented at rotational and kinetic temperatures of 175 and 1000 K for the fourth positive band system of CO.

Haider, S. A.

1988-02-01

64

Absorption of High Intensity Lasers at Solid Density  

NASA Astrophysics Data System (ADS)

Understanding the interaction of very intense lasers (I >=5 x10^19 W/cm^2) with dense plasmas is critical to the fast ignition (FI) approach to confined fusion, as well as other processes such as radiation pressure acceleration (RPA). To investigate this regime we use the particle-in-cell (PIC) code OSIRIS, looking at such lasers interacting directly with solid density targets (n nc). We find that electrons are accelerated in a way distinct from the commonly proposed absorption mechanisms, i.e. Brunel or JxB. Specifically, we see a standing wave structure being setup at the target surface, and electrons accelerated directly by the transverse electric field of this wave in the vacuum region. Furthermore the magnetic field of this structure reflects all electrons except those with sufficient transverse momentum in phase with this wave, meaning that absorption is very low until the target surface heats to keV temperatures, and also for circular laser polarization. Particle tracking in OSIRIS and a test particle simulation confirm that this model explains well the acceleration we see in simulations.

May, J.; Tonge, J.; Fiuza, F.; Fonseca, R. A.; Silva, L. O.; Ren, C.; Mori, W. B.

2011-11-01

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

Vacuum ultraviolet optical absorption band of non-bridging oxygen hole centers in SiO 2 glass  

Microsoft Academic Search

An intense broad vacuum ultraviolet (VUV) optical absorption band with peak at 6.8eV and halfwidth ?1.7eV is identified in irradiated glassy SiO2 and assigned to dangling oxygen bonds (non-bridging oxygen hole centers, NBOHC). It was selectively created by photolysis of silanol (SiO–H) groups by 7.9eV photons of F2 excimer laser at low temperature. Subsequent analysis by VUV absorption, time-resolved luminescence,

Hideo Hosono; Koichi Kajihara; Takenobu Suzuki; Yoshiaki Ikuta; Linards Skuja; Masahiro Hirano

2002-01-01

67

Line mixing effects on the shapes of fluoroform IR absorption bands perturbed by foreign gases  

NASA Astrophysics Data System (ADS)

The IR absorption spectra of CHF 3 in mixtures with He, Ar and N II were recorded in the region of 400-800 cm -1 using the Bruker IFS-28 Fourier transform spectrometer at resolution of 0.6 cm -1. The shapes of the parallel v 3(A I) and perpendicular v 6(E) bands were studied at perturbing gas pressure range of 25-100 atm. The observed behavior of the shapes for these two bands at the pressure increase is similar. The Q-branch widths increase at the pressure rise for all pertubers, but the slopes are quite different from those for individual lines. The Q-branch broadening for He mixture is much smaller than that for Ar mixture (for individual lines these values are close). To the contrary, the Q-branch broadening for Ar and N II mixtures is similar whereas for the lines these values are different. The Hermann-Wallis factor was introduced to describe the line intensity distribution in P and R branches. The shape calculations were performed in the approximation of Lorentzian lines sum. At higher pressures the calculated shapes are totally different from the experimental ones. We attributed this difference to line mixing effect. We used the adjusted branch coupling model in shape calculations to estimate this effect on the observed shapes. The results of the calculations explain qualitatively the observed band shape transformations.

Domanskaya, A. V.; Filippov, N. N.; Kudriavtsev, A. D.; Stupishin, M. A.; Tonkov, M. V.

2006-12-01

68

Spectral variations in narrow band imaging depth-selectivity: mucosal scattering vs. hemoglobin absorption  

NASA Astrophysics Data System (ADS)

Spectral variations in contrast enhancement of mucosal vasculature are a key feature of narrow band imaging (NBI) devices. In prior NBI studies, the enhanced visualization of larger, deeper vessels with green light (e.g., 540 nm) relative to violet light (e.g., 415 nm) has often been attributed to the well-known monotonic decrease in scattering coefficient with wavelength in biological tissues. We have developed and implemented numerical and experimental approaches to elucidate and quantify this and other light-tissue interaction effects relevant to NBI. A Monte Carlo model incorporating vessel-like inclusions with a range of diameters (20 to 400 microns) and depths (20 to 400 microns) was used to predict reflectance and fluence distributions in the tissue and calculate vessel contrast values. These results were compared to experimental measurements based on a liquid phantom with a hemoglobin-filled capillary. By comparing results for cases representing mucosa regions with and without blood, we were able to evaluate the relative significance of absorption and scattering on spectral variations in depth-selectivity. Results indicate that at 415 nm, detection of superficial vasculature with NBI was almost entirely dependent on the absorption coefficient of the blood in the vessel of interest. The enhanced visualization of deep vessels at 540 nm bands relative to 415 nm was due primarily to absorption by the superficial vasculature rather than a decrease in scattering coefficient. While computationally intensive, our numerical modeling approach provides unique insights into the light propagation mechanisms underlying this emerging clinical imaging technology.

Wang, Quanzeng; Le, Du; Ramella-Roman, Jessica C.; Pfefer, Joshua

2013-03-01

69

Structural information from detailed analysis of infrared absorption bands  

Microsoft Academic Search

The OH-stretching band of more than 500 alcohols and phenols have been measured in the apolar solvents CC14 and CS2 under standard conditions and the band parameters have been determined. Based on these data a system is being developed which provides the molecular structure in the surroundings of the hydroxyl group. The scheme of the system is outlined and discussed.

Bert Lutz; John van der Maas

1988-01-01

70

Near resonant absorption by atoms in intense fluctuating laser fields  

NASA Astrophysics Data System (ADS)

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 (approximately less than 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) - (sup 3)P(sub 1), transition at lambda = 555.6 nm in Yb-174; (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

71

Investigation of the short-time photodissociation dynamics of trans-1-bromo-2-iodoethane in the A-band absorption  

NASA Astrophysics Data System (ADS)

We have obtained resonance Raman spectra and absolute Raman cross section measurements at five excitation wavelengths within the A-band absorption for 1-bromo-2-iodoethane in cyclohexane solution. The resonance Raman spectra have most of their intensity in the fundamentals, overtones, and combination bands of six Franck-Condon active vibrational modes; the nominal CCI bend, C-I stretch, C-Br stretch, C-C stretch, CH2 wag with the Br atom attached to the CH2 group, and CH2 wag with the I atom attached to the CH2 group. The resonance Raman intensities and A-band absorption spectrum were simulated using a simple model and time-dependent wave packet calculations. The simulation results and normal mode descriptions were used to find the short-time photodissociation dynamics in terms of internal coordinate displacements. The A-band short-time photodissociation dynamics for trans-1-bromo-2-iodoethane show that the C-I, C-Br, and C-C bonds as well as the CCI, CCBr, HCC, ICH, and BrCH angles have significant changes during the initial stages of the photodissociation reaction. This indicates the photodissociation reaction has a large degree of multidimensional character and suggests that the bromoethyl photofragment receives substantial internal excitation in so far as the short-time photodissociation dynamics determines the energy partitioning. Comparison of our results for 1-bromo-2-iodoethane with the A-band short-time dynamics of iodoethane, 1-chloro-2-iodoethane, and 1,2-diiodoethane and the trends observed for their A-band absorption spectra suggest that both the C-I and C-Br bonds experience a noticeable amount of photoexcitation.

Zheng, Xuming; Phillips, David Lee

1999-01-01

72

Precise Determination of the Absorption Maximum in Wide Bands  

ERIC Educational Resources Information Center

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

Eriksson, Karl-Hugo; And Others

1977-01-01

73

Optical Salisbury screen with design-tunable resonant absorption bands  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

74

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

75

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

NASA Astrophysics Data System (ADS)

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

Krishna Swamy, K. S.

1981-04-01

76

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

SciTech Connect

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

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

2008-10-01

77

Wide-band underwater acoustic absorption based on locally resonant unit and interpenetrating network structure  

Microsoft Academic Search

The interpenetrating network structure provides an interesting avenue to novel materials. Locally resonant phononic crystal (LRPC) exhibits excellent sound attenuation performance based on the periodical arrangement of sound wave scatters. Combining the LRPC concept and interpenetrating network glassy structure, this paper has developed a new material which can achieve a wide band underwater strong acoustic absorption. Underwater absorption coefficients of

Heng Jiang; Yu-Ren Wang; Mi-Lin Zhang; Yan-Ping Hu; Ding Lan; Qun-Li Wu; Huan-Tong Lu

2010-01-01

78

A GAMMA-RAY INDUCED ABSORPTION BAND IN SOME LEAD BORATE GLASSES  

Microsoft Academic Search

Observations made on some lead borate, lead aluminoberate, and lead ; beroaluminosilicate glasses showed that an absorption band is induced at 1.5 ev ; (825 m mu ) by gamma irradiation. Experimental evidence indicates that this band ; is associated with Pb\\/sup 2+\\/ ions and beron in the structure of these glasses. ; On replacing PbO by TlâO in a

ADLI M. BISHAY

1960-01-01

79

Absorption Bands Associated with Anionic Impurities in Potassium Bromide containing Stoichiometric Excess of Metal  

Microsoft Academic Search

Potassium bromide crystals containing small quantities of oxide, nitrate, nitrite, bromate, sulphate and carbonate have been coloured by heating in potasium vapour and in some cases by electrolysis. In a number of instances, absorption bands with maxima in the range 4000-4500 Å are produced. The possible photoconductivity due to these bands is discussed.

W. Dunstan

1963-01-01

80

OPO-pulsed CRDS of the visible collision induced absorption bands of oxygen at low temperature  

Microsoft Academic Search

Collision induced absorption (CIA) bands in molecular oxygen, at 630 and 577 nm, were measured at low temperatures, down to 132 K. Besides providing confirmation of previous room temperature data, and new information about the temperature dependence of CIA bands, these measurements demonstrate the performance of cavity ring down spectroscopy in a rather unusual configuration. The cavity ring down spectroscopy

J. Morville; D Romanini; A Campargue; R Bacis

2002-01-01

81

A new absorption band of BaH at 2991 Å  

Microsoft Academic Search

Summary  A new band of BaH at 2991 Å has been observed in absorption in the third order of a 21 ft concave grating spectrograph. The\\u000a band is shown to be the (0, 0) band of BaH belonging to a new electronic transition which may be calledI\\u000a 2?-X\\u000a 2?. The rotational constants of the upper state have been evaluated and are

M. Aslam Baig; M. Rafi; M. Aslam Khan

1977-01-01

82

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

83

Wide-band suppression of laser intensity noise.  

PubMed

A simple and efficient laser intensity stabilization system was constructed based on an electro-optical modulator (EOM) and a photodetector. It is capable of reducing the laser intensity fluctuations to the shot noise limit within the range of Fourier frequencies from a few tens of hertz to a few megahertz. The achieved bandwidth of the laser control system is limited by the light handling capacity of the photodetector and spurious resonances of the EOM. We discuss the general approach to the design of the laser intensity stabilization system and its noise properties. PMID:19213628

Ivanov, Eugene N

2009-01-01

84

Evidence for sulphur implantation in Europa's UV absorption band  

NASA Astrophysics Data System (ADS)

The UV spectral characteristics of the Galilean satellites are investigated (using data from the International Ultraviolet Explorer (IUE) spacecraft) as a function of the orbital position, large-scale areal variability, and temporal dynamics. The discovery of an absorption feature at 280 nm in Europa's reflection spectrum is reported and observations show that the absorption is strongest on the trailing hemisphere (central longitude 270 degrees). The feature resembles SO2 and seems to result from S-O bond formation between deeply implanted sulphur atoms and the adjacent damaged water-ice-lattice. The sulphur supposedly comes from energetic (hundreds of keV) sulphur ions that are present in the Jovian magnetosphere. An appropriate equilibrium condition can be found to match the observed spectral data if sputtering erosion occurs at no greater than approximately 20 meters per one billion years.

Lane, A. L.; Nelson, R. M.; Matson, D. L.

1981-07-01

85

Evidence for sulphur implantation in Europa's UV absorption band  

NASA Technical Reports Server (NTRS)

The UV spectral characteristics of the Galilean satellites are investigated (using data from the International Ultraviolet Explorer (IUE) spacecraft) as a function of the orbital position, large-scale areal variability, and temporal dynamics. The discovery of an absorption feature at 280 nm in Europa's reflection spectrum is reported and observations show that the absorption is strongest on the trailing hemisphere (central longitude 270 degrees). The feature resembles SO2 and seems to result from S-O bond formation between deeply implanted sulphur atoms and the adjacent damaged water-ice-lattice. The sulphur supposedly comes from energetic (hundreds of keV) sulphur ions that are present in the Jovian magnetosphere. An appropriate equilibrium condition can be found to match the observed spectral data if sputtering erosion occurs at no greater than approximately 20 meters per one billion years.

Lane, A. L.; Nelson, R. M.; Matson, D. L.

1981-01-01

86

Possible spinel absorption bands in S-asteroid visible reflectance spectra  

NASA Technical Reports Server (NTRS)

Minor absorption bands in the 0.55 to 0.7 micron wavelength range of reflectance spectra of 10 S asteroids have been found and compared with those of spinel-group minerals using the modified Gaussian model. Most of these S asteroids are consistently shown to have two absorption bands around 0.6 and 0.67 micron. Of the spinel-group minerals examined in this study, the 0.6 and 0.67 micron bands are most consistent with those seen in chromite. Recently, the existence of spinels has also been detected from the absorption-band features around 1 and 2 micron of two S-asteroid reflectance spectra, and chromite has been found in a primitive achondrite as its major phase. These new findings suggest a possible common existence of spinel-group minerals in the solar system.

Hiroi, T.; Vilas, F.; Sunshine, J. M.

1994-01-01

87

An advanced digital filter for one-dimensional spectroscopic data: minimizing distortion in band shapes and band intensities.  

PubMed

A wide variety of digital filters exist for processing one-dimensional (1D) signals; however, the application of some filters results in pronounced systematic distortions in band shapes and band intensities. In the present contribution, filtering is achieved by optimization in which a general objective function is constructed that possesses a number of desirable qualities, such as (1) smoothness of the resulting spectrum as well as (2) statistical constraints on the residual. Since the residual is explicitly used in the optimization, one can control systematic distortions and therefore avoid over-filtering. In tests using a variety of synthetic as well as real 1D spectroscopic data, the filter adequately preserves both band shapes and band intensities. In addition, the filter appears to accommodate homoscedastic, heteroscedastic, and frequency-dependent noise. Examples of its application and usefulness to powder X-ray diffraction (PXRD), Raman, and Fourier transform infrared (FT-IR) emission data are provided. Tests with synthetic data indicate that considerable noise reduction can be achieved in many applications. Finally, an iterative form of the filter is presented. This iterative form further minimizes distortions in band shapes and band intensities when very high levels of denoising are desired. The present filtering approach is an alternative to existing filters, particular when the quality of the residual is important to the user. PMID:21639988

Guo, Liangfeng; Garland, Marc

2011-06-01

88

Ozone decline and its effect on night airglow intensity of OH (8,3) band  

NASA Astrophysics Data System (ADS)

The paper presents the effect of O3 depletion on OH (8,3) band. It is shown that Bates-Nicolet theory for the excitation of OH band is predominant excitation process. Calculations based on chemical kinetics show that the intensity of OH (8,3) band will also be effected due to the depletion of O3 concentration. O3 is depleted everywhere especially at Antarctica. Intensity of OH (8,3) band is calculated theoretically for Halley Bay (76 deg S, 27 deg W), British Antarctic survey station during the period 1973 to 1984.

Midya, S. K.

89

The absorption property of single crystal LuBiIG garnet film in terahertz band  

NASA Astrophysics Data System (ADS)

In this paper, a hypothesis has been brought forward that the materials with low propagation loss in both optical and microwave band may exhibit good performance in terahertz (THz) band because THz wave band interspaces those two wave bands. Several kinds of single crystal garnet films were investigated and we found that the Lu2.1Bi0.9Fe5O12 film which grows by liquid phase epitaxy (LPE) from PbO-free flux has the best absorption properties in both microwave and optical band. In THz range, our hypothesis is well confirmed by a THz-TDS measurement which shows that the absorption coefficient of LuBiIG film is 0.05-0.3 cm-1, and the minimum value appears at 2.24 THz.

Yang, Qing-Hui; Zhang, Huai-Wu; Wen, Qi-Ye; Liu, Ying-Li

2012-04-01

90

Spectral absorption coefficients for the fundamental and first overtone vibration-rotation bands of CN  

NASA Technical Reports Server (NTRS)

A previous measurement of the transition moment of the fundamental vibration-rotation band of CN is combined with theoretical calculations of relative vibrational transition probabilities in order to compute absorption coefficients for the CN fundamental and first-overtone bands. Line strengths for 121 lines in each branch of all fundamental and first-overtone bands with upper-transition states not greater than 6 are calculated for temperatures of 2000, 3000, and 4000 K; these line strengths are presented as averaged over 8-kayser intervals. The relative vibrational transition moments are placed on an absolute scale, and the wavenumbers of the band origins and heads are given

Bailey, W. L.

1977-01-01

91

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

NASA Astrophysics Data System (ADS)

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

Bondarenko, N. N.

2013-08-01

92

Measurement of the absorption coefficient using the sound-intensity technique  

NASA Technical Reports Server (NTRS)

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

Atwal, M.; Bernhard, R.

1984-01-01

93

Multiexciton Absorption Cross Sections of CdSe Nanocrystals at Band-Edge Energy  

NASA Astrophysics Data System (ADS)

Picosecond transient absorption signals of two kinds of cadmium selenide quantum dots were measured at various excitation intensities. The average number of excitons per quantum dot was calculated from a Poisson model, which together with kinetic parameters was used to determine exciton population kinetics. Exciton and multiexciton absorption cross sections were determined and analyzed in terms of the electronic states of the quantum dots.

Lenngren, N.; Garting, T.; Zheng, K.; Abdellah, M.; Lascoux, N.; Ma, F.; Yartsev, A.; Žídek, K.; Pullerits, T.

2013-03-01

94

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

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

95

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

PubMed

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

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

2012-06-01

96

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

97

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

98

Molar extinction coefficients of IR absorption bands of Cu(II) dipivaloylmethanate  

Microsoft Academic Search

IR absorption spectra of an intracomplex chelate compound of Cu(II) bis-dipivaloylmethanate in the spectral range 4000–300\\u000a cm?1 are investigated. A comparison is made between the spectra of the complex in different aggregative states: as a solution\\u000a in heptane and as condensed films. The molar extinction coefficients of absorption bands are calculated. The extinction coefficients\\u000a found are used to evaluate the

L. F. Bakhturova; V. V. Bakovets; T. M. Levashova; I. P. Dolgovesova; V. O. Borisov

2000-01-01

99

Decay kinetics of CsI: Tl luminescence excited in the A absorption band  

Microsoft Academic Search

Luminescence emission, including decay kinetics, has been investigated for CsI: Tl excited in the A absorption band of Tl, in the temperature range 4–300 K. Three emission bands have been identified and ascribed to transitions from non-equivalent minima on the adiabatic potential surface of the excited state of isolated Tl ion centres. Non-radiative energy transfer processes among these minima are

M. Nikl; J. Hlinka; E. Mihokova; K. Polak; P. Fabeni; G. P. Pazzi

1993-01-01

100

An atlas of synthetic absorption and emission bands of interstellar PAHs  

Microsoft Academic Search

In the framework of the interstellar PAHs hypothesis, absorption bands in the vis\\/UV and far-IR skeletal emission bands are expected to be a fingerprint of specific species in this class. We developed a detailed Monte-Carlo model of the photophysics of isolated interstellar PAHs which provides a powerful tool for single-molecule identification. We present synthetic spectra predicted by the above general

G. Malloci; G. Mulas; C. Joblin; I. Porceddu

2005-01-01

101

Ultraviolet Absorption Bands of Thallous Ions in Potassium Dihydrogen Phosphate Crystals  

Microsoft Academic Search

Optical absorption bands induced by doping thallous ions in KDP single crystals are found at 5.56, 5.76, 6.91, 7.30, and 7.67 eV. They exhibit clear dependence on the polarization of light, reflecting the local symmetry of the impurity centers. Comparison is made between the observed bands in KDP and those in alkali halide crystals. The spectra are interpreted in terms

Ikuo Fujita

1978-01-01

102

Electronic structure of poly(tetrafluoroethylene) studied by UPS, VUV absorption, and band calculations  

Microsoft Academic Search

The electronic structure of poly(tetrafluoroethylene) (PTFE) was studied by UPS, VUV absorption, and ab-initio MO calculations. The UPS spectra give a photoemission threshold energy of 10.6eV, with deeper valence band features consistent with the reported XPS and the oligomer vapour UPS spectra. The UPS spectra are also consistent with the density of states derived from the calculated band structure, which

Kazuhiko Seki; Hiroshi Tanaka; Toshiaki Ohta; Yuriko Aoki; Akira Imamura; Hitoshi Fujimoto; Hiromichi Yamamoto; Hiroo Inokuchi

1990-01-01

103

Visible absorption bands of coal pitch extract - Implications for the diffuse interstellar bands  

Microsoft Academic Search

Visible spectroscopic studies of a coal pitch extract, achieved by matrix isolation spectroscopy are presented, and their implications for the identification of diffuse interstellar bands (DIBs) are discussed. The coal pitch extract under consideration consists mainly of aromatic molecules and, as such, is assumed to be representative to some extent of an interstellar mixture. It is shown that the extract

P. Ehrenfreund; L. D'Hendecourt; C. Joblin; A. Leger

1992-01-01

104

Integrated band intensities in N2O4 in the infrared range  

Microsoft Academic Search

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

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

1993-01-01

105

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

106

An infrared absorption band caused by OH ions in a LiNbO3:Mg, Cr crystal  

Microsoft Academic Search

A new absorption band at 3506 cm-1 has been observed in LiNbO3 doped simultaneously with Mg and Cr. The band is distinctly separated from the well known band at 3485 cm-1 in undoped crystals and from that near 3540 cm-1 due to Mg-OH complexes. The new absorption band is interpreted as an OH- vibration in a Cr3+-OH--Mg2+ association. Variations in

L. Kovács; I. Földvári; I. Cravero; K. Polgár; R. Capelleti

1988-01-01

107

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

108

Intensity dependent absorption\\/transparency of a reducing BaTiO3  

Microsoft Academic Search

We report intensity dependent absorption and transparency as a function of wavelength for barium titanate. The BaTiO3 crystal examined has an as-grown, light-blue color due to an absorption centered at 690 nm, and when reduced in a partial pressure of 10?15 atm of oxygen it has a yellow-orange color due to an absorption centered at 470 nm. Both energy levels

J. Y. Chang; M. H. Garrett; H. P. Jenssen; C. Warde

1993-01-01

109

Intensity Dependent Absorption and Transit Relaxation on the Cesium D1 Line  

Microsoft Academic Search

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

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

1997-01-01

110

Coherent Emission from Ho(3+) Ions by Pumping into the YIG Absorption Band.  

National Technical Information Service (NTIS)

Coherent emission from Ho(3+) ions (2.1 micrometer) in a YIG host at 77 K has been observed by optical pumping into the electronic absorption bands of the YIG host material, using (i) a pulsed Nd: glass laser to pump into the tail of the 6A(1g) to 4T(1g) ...

R. G. Stafford H. Masui R. L. Farrow R. K. Chang L. G. van Uitert

1976-01-01

111

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

PubMed

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

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

2009-11-01

112

Electronic band structure and optical absorption of nanotubular zinc oxide doped with Iron, Cobalt, or Copper  

NASA Astrophysics Data System (ADS)

The absorption spectra of the precursor-derived solid solutions Zn1 - x M x O ( M = Fe, Co, Cu) with a tubular morphology of aggregates have been investigated in the ultraviolet and visible regions. The maximum metal concentration x in the Zn1 - x M x O solid solutions is 0.075 for iron, 0.2 for cobalt, and 0.1 for copper. It has been found that the optical absorption and the band gap of the Zn1 - x M x O compounds depend on the type of dopant. The obtained experimental data have been interpreted using the results of the performed ab initio calculations of the electronic band structure and optical absorption.

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

2013-12-01

113

Picosecond study of the near infrared absorption band of hemoglobin after photolysis of carbonmonoxyhemoglobin.  

PubMed Central

Picosecond absorption spectroscopy is used to examine the position and band shape of the near infrared absorption band of hemoglobin as a function of time after the photodissociation of CO from carbonmonoxyhemoglobin. For the earliest delay time probed, 35 ps, the peak of the transient spectrum is at 765 nm, red shifted by 6 nm from that characteristic of equilibrium deoxyhemoglobin. No evolution in either the peak position or band shape is observed for time delays up to 60 ns. In addition, the position and shape of the spectrum are independent of photolysis energies ranging from 15 microJ/pulse to 150 microJ/pulse, spanning conditions under which the photon/heme ratio is varied from 0.01 to 2.0. This indicates that the geometry in the heme group is unrelaxed and that equilibration of the surrounding protein structure occurs on a time scale longer than 60 ns.

Dunn, R C; Simon, J D

1991-01-01

114

Line shapes of narrow optical bands: Infrared absorption by U centers and heavier impurities in alkali halides  

Microsoft Academic Search

The shape of the bands for photon absorption and emission by the local constituents of a solid is governed mainly by processes involving many low-energy acoustic phonons. This applies not only to wide bands, such as those exhibited by F centers, but also to narrow ones, as those observed for infrared absorption by local vibration modes of U centers and

Miguel Lagos; Felipe Asenjo; Roberto Hauyón; Denisse Pastén; Hernán González; Ricardo Henríquez; Roberto Troncoso

2008-01-01

115

Incoherent broad-band cavity-enhanced absorption spectroscopy of liquids  

NASA Astrophysics Data System (ADS)

A new application of incoherent broad-band cavity enhanced absorption spectroscopy (IBBCEAS) to weak transitions in solution through a very straightforward modification of commercially available double-beam UV/VIS absorption spectrometers is reported. The improved sensitivity of the new approach is demonstrated on basis of the weak Franck-Condon inhibited absorption of the fifth C-H stretch overtone in liquid benzene. The theoretical limits of the enhancement of the signal-to-noise ratio of IBBCEAS in comparison with single pass absorption experiments are discussed for a set of given experimental cavity parameters. The optical loss properties of a typical transparent cuvette window in the cavity are also discussed.

Fiedler, Sven E.; Hese, Achim; Ruth, Albert A.

2005-02-01

116

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

NASA Technical Reports Server (NTRS)

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

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

1981-01-01

117

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

118

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

NASA Astrophysics Data System (ADS)

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

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

1998-05-01

119

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

NASA Astrophysics Data System (ADS)

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

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

2003-09-01

120

One-dimensional band-edge absorption in a doped quantum wire.  

PubMed

Low-temperature photoluminescence-excitation spectra are studied in an n-type modulation-doped T-shaped single quantum wire with a gate to tune electron densities. With a nondegenerate one-dimensional (1D) electron gas, the band-edge absorption exhibits a sharp peak structure induced by the 1D density of states. When the dense 1D electron gas is degenerate at a low temperature, we observe a Fermi-edge absorption onset without many-body modifications. PMID:17930538

Ihara, Toshiyuki; Hayamizu, Yuhei; Yoshita, Masahiro; Akiyama, Hidefumi; Pfeiffer, Loren N; West, Ken W

2007-09-21

121

Absolute integrated intensity for the 3.44-microns NO2 band  

NASA Technical Reports Server (NTRS)

A grating monochromator infrared spectrometer and a curve of growth technique were used to obtain the absolute integrated intensity for the 3.44 micron NO2 vibration-rotation band at very small NO2 partial pressures. The intensity was found to be 78.9 plus or minus 1.6/cm/(atm cm) at 296 K at the 95% confidence level. The study has relevance to the infrared spectral measurement of atmospheric NO2.

Shafer, J. H.; Young, C.

1976-01-01

122

Vibrational coherence in Azurin with impulsive excitation of the LMCT absorption band  

NASA Astrophysics Data System (ADS)

We report the results of femtosecond pump-probe measurements on Azurin, a blue copper protein. The decay of the pump-induced ground-state bleaching, following the excitation of the ligand-to-metal charge-transfer absorption band, is modulated by well visible oscillations and occurs exponentially with a time constant of about 270 fs. The Fourier transform of the oscillatory component, besides providing all the vibrational modes found by conventional resonance Raman, presents additional bands whose attribution is discussed also in connection with the protein dynamics.

Cimei, Tiziana; Rita Bizzarri, Anna; Cannistraro, Salvatore; Cerullo, Giulio; De Silvestri, Sandro

2002-08-01

123

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

SciTech Connect

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

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

2012-05-15

124

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

PubMed

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

Salama, F; Allamandola, L J

1992-07-01

125

An alternative model for photodynamic therapy of cancers: Hot-band absorption  

NASA Astrophysics Data System (ADS)

The sulfonated aluminum phthalocyanine (AlPcS), a photosensitizer for photodynamic cancer therapy (PDT), has an absorption tail in the near-infrared region (700-900 nm) which is so-called hot band absorption (HBA). With the HBA of 800 nm, the up-conversion excitation of AlPcS was achieved followed by the anti-Stocks emission (688 nm band) and singlet oxygen production. The HBA PDT of AlPcS seriously damaged the KB and HeLa cancer cells, with a typical light dose dependent mode. Particularly, the in vitro experiments with the AlPcS shielding solutions further showed that the HBA PDT can overcome a self-shielding effect benefiting the PDT applications.

Wang, Jing; Chen, Jiyao

2013-12-01

126

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

127

Magnetic-field effects on the absorption bands of KBr:Tl and KBr:In  

Microsoft Academic Search

Summary  We report the measurements of the magnetically induced circular dichroism in the optical absorption bands of Tl+- and In+-doped potassium bromide crystals performed to test the validity of Cho's theory based on the Jahn-Teller effect. A qualitative\\u000a analysis of the dichroic signal is given in terms of the changes of the moments of the shape function simultaneously utilizing\\u000a the theoretical

C. Bagnato; V. Grasso; P. Perillo; G. Vermiglio

1975-01-01

128

Dynamic EEG Analysis via the Variability of Band Relative Intensity Ratio: A Time-Frequency Method  

Microsoft Academic Search

The effectiveness of band relative intensity ratio (BRIR) based on time-frequency representations (TFRS) was explored as a method to depict brain dynamics in this paper. Electroencephalographic (EEG) signals from 20 subjects through 16 channels have been studied under open eyes state and closed eyes state. The results indicate that EEG rhythm features and the dynamic process of brain activity can

Li Zhang; Wei He; Xiaobo Miao; Jianhong Yang

2005-01-01

129

Modeling and analysis for infrared clutter radiance of atmospheric absorption band sensor  

NASA Astrophysics Data System (ADS)

An extended analytic model for atmospheric clutter radiance in absorption bands is developed. In this model, clutter radiance is mainly due to temperature and reflectance fluctuations of atmospheric, cloud and earth. A simplified line-of-sight (LOS) radiance model for short-wave infrared (SWIR) and mid-wave infrared (MWIR) absorption bands is introduced, based on the one-dimensional radiation transfer equation (RTE) and Young's semi-empirical model for diffuse reflectance of clouds. Under the assumption that atmospheric temperature fluctuations are isotropic horizontally, the relations between clutter radiance and temperature fluctuations as well as other factors are obtained. The clutter radiance characteristics are analyzed in 2.7?m and 4.3?m absorption bands, the long wavelength wing of 2.85?m and 4.35?m shows a much larger clutter contribution from earth and cloud. The models present here are efficient and reasonable by comparing the results of MODTRAN and data from SPIRIT-III radiometer.

Cao, Yiming; Zhang, Wei; Cong, Mingyu; Bao, Wenzhuo; Meng, Xianglong; Cheng, Jun

2009-07-01

130

Incoherent broad-band cavity-enhanced absorption spectroscopy of azulene in a supersonic jet  

NASA Astrophysics Data System (ADS)

The application of incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) to isolated jet-cooled gas-phase species is demonstrated on basis of the S 1 ? S 0 transition of azulene in a continuous supersonic expansion. By focusing white light from a high power Xe-lamp into an optically stable resonator, which is intercepted by the supersonic seeded jet, the absorption is measured over a broad spectral range between 17 300 and 20 255 cm -1 with a resolution of ?4 cm -1. The resolution, which is due to the dispersion of transmitted light by a grating monochromator, is sufficient to monitor the highly congested vibronic structure >3000 cm -1 above the S 1,0 origin of azulene. The sensitivity required for this absorption experiment compares well to that of conventional pulsed cavity ring-down measurements.

Fiedler, Sven E.; Hoheisel, Gerald; Ruth, Albert A.; Hese, Achim

2003-12-01

131

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

132

First-principles simulation of the absorption bands of fluorenone in zeolite L.  

PubMed

The absorption spectrum of fluorenone in zeolite L is calculated from first-principles simulations. The broadening of each band is obtained from the explicit treatment of the interactions between the chromophore and its environment in the statistical ensemble. The comparison between the simulated and measured spectra reveals the main factors affecting the spectrum of the chromophore in hydrated zeolite L. Whereas each distinguishable band is found to originate from a single electronic transition, the bandwidth is determined by the statistical nature of the environment of the fluorenone molecule. The K(+)···O=C motif is retained in all conformations. Although the interactions between K(+) and the fluorenone carbonyl group result in an average lengthening of the C[double bond, length as m-dash]O bond and in a redshift of the lowest energy absorption band compared to gas phase or non-polar solvents, the magnitude of this shift is noticeably smaller than the total shift. An important factor affecting the shape of the band is fluorenone's orientation, which is strongly affected by the presence of water. The effect of direct interactions between fluorenone and water is, however, negligible. PMID:23147475

Zhou, Xiuwen; Wesolowski, Tomasz A; Tabacchi, Gloria; Fois, Ettore; Calzaferri, Gion; Devaux, André

2013-01-01

133

Resonant absorption of an intense electromagnetic waves in an inhomogeneous plasma  

SciTech Connect

The self-consistent steady-state distributions of the field and plasma density are calculated numerically for the intense p-polarized electromagnetic wave obliquely incident on an inhomogeneous plasma slab. The resonant absorption is also calculated. If the wave is sufficiently intense, the density profile in the plasma-resonance region acquires a characteristic step-shaped deformation as a result of the ponderomotive force, and the absorption changes substantially. For both of the loss mechanisms considered (electron collisions and energy conversion into a longitudinal wave) the fraction of the power which is absorbed initially increases with increasing amplitude, approaching 100%, and then it drops markedly.

Gil'denburg, V.B.; Litvak, A.G.; Petrova, T.A.; Feigin, A.M.

1981-07-01

134

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

135

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

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

136

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

NASA Astrophysics Data System (ADS)

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

Liu, Hong; Schumacher, Stefan; Meier, Torsten

2014-04-01

137

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

138

A Group Increment Scheme for Infrared Absorption Intensities of Greenhouse Gases  

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

139

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

PubMed

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

Glass-Maujean, M; Jungen, Ch

2009-11-26

140

Reassignment of the iron (3) absorption bands in the spectra of Mars  

NASA Technical Reports Server (NTRS)

Absorption features in the near-infrared and visible region reflectance spectra of Mars have been assigned to specific Fe (3+) crystal-field and o(2-) yields Fe(3+) charge transfer transitions. Recently, near-ultraviolet absorption spectra of iron oxides were obtained and the energies of o(2-) yields Fe(3+) charge-transfer (LMCT) transitions were determined from accurate SCF-X # alpha-SW molecular orbital calculations on (FeO6)(9-) and (FeO4)(5-) clusters. Both the theoretical and experimental results, together with existing data in the literature, show that some of the previous Fe(3+) band assignments in the spectra of Mars need to be revised. The theory of Fe(3+) spectra in minerals is discussed and applied to the spectrum of Mars.

Sherman, D. M.

1985-01-01

141

Reassignment of the iron (3) absorption bands in the spectra of Mars  

NASA Astrophysics Data System (ADS)

Absorption features in the near-infrared and visible region reflectance spectra of Mars have been assigned to specific Fe (3+) crystal-field and o(2-) yields Fe(3+) charge transfer transitions. Recently, near-ultraviolet absorption spectra of iron oxides were obtained and the energies of o(2-) yields Fe(3+) charge-transfer (LMCT) transitions were determined from accurate SCF-X # alpha-SW molecular orbital calculations on (FeO6)(9-) and (FeO4)(5-) clusters. Both the theoretical and experimental results, together with existing data in the literature, show that some of the previous Fe(3+) band assignments in the spectra of Mars need to be revised. The theory of Fe(3+) spectra in minerals is discussed and applied to the spectrum of Mars.

Sherman, D. M.

1985-04-01

142

Echelle spectroscopy of SN 1986G in NGC 5128 - complex Na absorption and interstellar diffuse bands  

SciTech Connect

Spectroscopy at 0.3 A resolution of the Type Ia supernova 1986G in NGC 5128 has resolved the Na absorption due to NGC 5128 into four components with velocities of 374, 412, 453, and 483 km/s. A fit to the line profiles shows each component to have a column density of about 10 to the 13th/sq cm. The absorption is found to agree well with the velocity structure of the ionized gas in the disk of NGC 5128, and is interpreted to arise from a line of sight that passes through the entire disk of NGC 5128. Interstellar diffuse bands at 5780.4, 5797.0, 6283.9, and 6613.6 A are also positively identified as arising in the dust lane. 17 references.

Rich, R.M.

1987-09-01

143

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

144

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

NASA Technical Reports Server (NTRS)

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

Carter, Gregory A.; Spiering, Bruce A.

2000-01-01

145

Signal to Noise Ratio in Digital Lock-in Detection for Multiple Intensity-Modulated Signals in CO2 Laser Absorption Spectrometer  

NASA Astrophysics Data System (ADS)

NASA Langley Research Center is investigating Intensity-Modulated, Continuous-Wave Laser Absorption Spectrometers (LASs) for the measurement of atmospheric carbon dioxide (CO2) column mixing ratio from both air- and space-borne platforms. The LAS system uses high-power fiber lasers/amplifiers in the 1.57-um CO2 absorption band and the 1.26-um O2 absorption band in the transmitters and simultaneous digital lock-in detection for the multiple intensity-modulated signals with different modulation waveforms , such as simple sinusoidal waves at different frequencies, associated with different wavelengths in the receivers. The Signal to Noise Ratio (SNR) of the simultaneous digital lock-in detection in the system is of interest for the system designs and the performance prediction of airborne and space-borne implementations in the future. This paper will discuss the properties of the signals and various noises in the LAS system, especially for the simultaneous digital lock-in detection with a single detector for the multiple intensity-modulated signals at different frequencies. The numerical simulation of the SNR for the simultaneous digital lock-in detection in terms of relative intensity of the multiple modulated signals and the integration time, and an initial experimental verification will be presented.

CHEN, S.; Lin, B.; Harrison, F. W.; Nehrir, A. R.; Campbell, J. F.; Refaat, T.; Abedin, N. M.; Obland, M. D.; Ismail, S.; Meadows, B. L.

2013-12-01

146

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

147

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

NASA Astrophysics Data System (ADS)

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 61S to 71S 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 61P 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.; Steel, D. G.; Remillard, J.

1988-10-01

148

The formation of carbon monoxide UV absorption bands in media with stochastic velocity fields  

NASA Astrophysics Data System (ADS)

We study the formation of interstellar molecular lines in a turbulent velocity field with finite correlation length, extending previous work to the ultraviolet absorption bands of the A1 II X1 + system of CO. Our results show clearly that a finite correlation length strongly affects the shape of the saturated absorption lines. This in turn leads to ambiguous physical parameters if observed line profiles are analysed on the basis of classical theory. Using a homogeneous plane-parallel model, we apply our theory to the highresolution observations by Sheffer et al. of the A -x (5, 0) and (6, 0) bands of CO towards Oph and deduce the following parameters: Nco =9.5 X 1014 cm 2, ncol= 1.36 x1014 , the ratio of turbulent and thermal velocities J/Vtherm =4.0, and the isotopic ratio Nl2co!NI3co 70. An estimated slab thickness of L -2 pc implies a correlation length 1-0.3 pc. Key words: line: formation - line: profiles - ISM: molecules - ultraviolet: ISM.

Levshakov, S. A.; Kegel, W. H.

1994-11-01

149

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

SciTech Connect

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 first type, there exist two zeroes at the band edge frequencies in the case of isotropic photonic band gap. In the second type, a zero emerges at the middle frequency of two upper levels in the case that the quantum interference takes place in both V-type transitions. Finally, in the third type, a zero occurs at or around the middle frequency of two upper levels in the case that the quantum interference takes place only in the V-type transitions coupled to the free vacuum modes. Ultimately, the probe absorption-dispersion spectrum in the case of the single-band photonic band gap reservoirs compared to those of the double-band photonic band gap reservoirs. The results show that the dispersion property of the system depends on the two types of the quantum interference and the density of states of the photonic band gap reservoir.

Entezar, Samad Roshan; Tajalli, Habib [Research Institute for Applied Physics and Astronomy, Tabriz University, Tabriz (Iran, Islamic Republic of)

2007-02-15

150

New Analysis of the ?3 fundamental band of HDCO: Positions and intensities  

NASA Astrophysics Data System (ADS)

Using high-resolution Fourier transform spectra of mono deuterated formaldehyde (HDCO) recorded in the 5.8-?m spectral range at Giessen (Germany), we carried out an extensive analysis of the strong ?3 fundamental band (carbonyl stretching mode) at 1724.2676 cm -1, starting from results of a previous analysis [J.W.C. Johns, A.R.W. McKellar, J. Mol. Spectrosc. 64 (1977) 327-339]. For this hybrid band (with both A- and B-type transitions) the analysis was pursued up to high rotational quantum numbers. In this way, it was possible to evidence a resonance which perturbs the ?3 lines for high Ka values which is due to the existence of the 2 ?5 and ?5 + ?6 dark bands in the same spectral region. In addition a local resonance is perturbing the 3 1 levels in Ka' = 8 which is due to a crossing with the 4 1 energy levels in Ka = 11. The model used to calculate the energy levels accounts for the observed A- type, B- type C-type Coriolis (and/or) Fermi resonances which couple the 3 1 and the 5 16 1, 5 2, and 4 1 energy levels. However the 4 1 state is also involved in strong vibration-rotation interactions coupling the {5 1,6 1,4 1} system of resonation states of HDCO [A. Perrin, J.M. Flaud, L. Margulès, J. Demaison, H. Mäder, S. Wörmke, J. Mol. Spectrosc. 216 (2002) 214-224]. Therefore the final energy levels calculation was performed for the {5 1,6 1,4 1,3 1,5 2,5 16 1} resonating states and in this way it was possible to reproduce the observed line positions, within their experimental uncertainties. The present work also led to the determination of the intensity ratio of the B- to A-type components of the ?3 band IA/ IB ˜24 band from spectral fittings performed in several parts of the observed spectrum. Finally, using the 5.8 ?m band intensity available in the literature we generated, for the first time, a list of line parameters (positions and intensities) for the 5.8 ?m region of HDCO.

Gomez, L.; Perrin, A.; Mellau, G.

2009-07-01

151

Band tail absorption saturation in CdWO4 with 100 fs laser pulses.  

PubMed

The decay kinetics of the excitonic emission of CdWO4 scintillators was studied under excitation by powerful 100 fs laser pulses in the band tail (Urbach) absorption region. A special imaging technique possessing both spatial and temporal resolution provided a unique insight into the Förster dipole-dipole interaction of self-trapped excitons, which is the main cause of the nonlinear quenching of luminescence in this material. In addition, the saturation of phonon-assisted excitonic absorption due to extremely short excitation pulses was discovered. A model describing the evolution of electronic excitations in the conditions of absorption saturation was developed and an earlier model of decay kinetics based on the Förster interaction was extended to include the saturation effect. Compared to the previous studies, a more accurate calculation yields 3.7 nm as the Förster interaction radius. It was shown that exciton-exciton interaction is the main source of scintillation nonproportionality in CdWO4. A quantitative description using a new model of nonproportionality was presented, making use of the corrected value of the Förster radius. PMID:23709501

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

2013-06-19

152

Total ozone and aerosol optical depths inferred from radiometric measurements in the Chappuis absorption band  

SciTech Connect

A second-derivative smoothing technique, commonly used in inversion work, is applied to the problem of inferring total columnar ozone amounts and aerosol optical depths. The application is unique in that the unknowns (i.e., total columnar ozone and aerosol optical depth) may be solved for directly without employing standard inversion methods. It is shown, however, that by employing inversion constraints, better solutions are normally obtained. The current method requires radiometric measurements of total optical depth through the Chappuis ozone band. It assumes no a priori shape for the aerosol optical depth versus wavelength profile and makes no assumptions about the ozone amount. Thus, the method is quite versatile and able to deal with varying total ozone and various aerosol size distributions. The technique is applied first in simulation, then to 119 days of measurements taken in Tucson, Arizona, that are compared to TOMS values for the same dates. The technique is also applied to two measurements taken at Mauna Loa, Hawaii, for which Dobson ozone values are available in addition to the TOMS values, and the results agree to within 15%. It is also shown through simulations that additional information can be obtained from measurements outside the Chappuis band. This approach reduces the bias and spread of the estimates total ozone and is unique in that it uses measurements from both the Chappuis and Huggins absorption bands. 12 refs., 6 figs., 2 tabs.

Flittner, D.E.; Herman, B.M.; Thome, K.J.; Simpson, J.M.; Reagan, J.A. (Univ. of Arizona, Tucson (United States))

1993-04-15

153

Non-linear Absorption and Ionization of Gases by Intense Femtosecond Laser Pulses  

Microsoft Academic Search

Recent experiments on applications of high-intensity femtosecond pulses for studying multi-photon and tunnel ionization of different gases, including air, are discussed. Mechanisms of non-linear absorption and ionization of pure atomic argon and molecular nitrogen gases by UV femtosecond laser pulses were studied using photogalvanic and photoacoustic technique. The effect of the intermediate Rydberg resonance, its dynamic Stark perturbation and ponderomotive

Andrei A. Ionin; Sergei I. Kudryashov; Yurii N. Ponomarev; Leonid V. Seleznev; Dmitry V. Sinitsyn; B. A. Tikhomirov

2010-01-01

154

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

NASA Astrophysics Data System (ADS)

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

Taran, Michail N.; Koch-Müller, Monika

2011-03-01

155

Restructuring of the energy spectrum and light absorption in a semiconductor in an intense electromagnetic field  

Microsoft Academic Search

The two-band equation of Kane's model of a semiconductor is solved by the Bogoliubov-Mitropolskii method (1974) of averaging and the quasi-energy spectrum of electron-hole excitations in an intense electromagnetic field is investigated. The paramagnetic resonance case, when the frequency of the strong electromagnetic wave omega is close to the width of the energy gap of a semiconductor, is considered. According

I. V. Belousov; V. P. Oleinik

1979-01-01

156

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

157

Optical absorption intensities of trivalent erbium in a 2-hydroxyethyl methacrylate (HEMA) polymeric host  

NASA Astrophysics Data System (ADS)

The standard Judd-Ofelt model has been applied to the room temperature absorption intensities of Er 3+(4f 11) transitions in a plastic host 2-hydroxyethyl methacrylate, referred to as HEMA, to determine the three phenomenological intensity parameters: ?2, ?4, and ?6. Values are used to determine the spectroscopic quality factor for Er 3+ in HEMA and are compared to those for Er 3+ in crystalline hosts. The intensity parameters are subsequently used to determine the radiative decay rates and branching ratios of the Er 3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds 2 S+1 L J of Er 3+(4f 11) in HEMA. Using the radiative decay rates for Er 3+(4f 11) transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined.

Sardar, Dhiraj K.; Yow, Raylon M.; Gruber, John B.

2008-02-01

158

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

159

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

160

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

SciTech Connect

We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H{sub 2}O and O{sub 2} bands, two molecules that have major signatures in the observed range. From a correlation analysis with the cloud map data from the Earth Observing Satellite (EOS), we find that their variation pattern is primarily due to the uneven cloud cover distribution. In order to account for the observed variation quantitatively, we consider a simple opaque cloud model, which assumes that the clouds totally block the spectral influence of the atmosphere below the cloud layer, equivalent to assuming that the incident light is completely scattered at the cloud top level. The model is reasonably successful, and reproduces the EPOXI data from the pixel-level EOS cloud/water vapor data. A difference in the diurnal variability patterns of H{sub 2}O and O{sub 2} bands is ascribed to the differing vertical and horizontal distribution of those molecular species in the atmosphere. On Earth, the inhomogeneous distribution of atmospheric water vapor is due to the existence of its exchange with liquid and solid phases of H{sub 2}O on the planet's surface on a timescale short compared with atmospheric mixing times. If such differences in variability patterns were detected in spectra of Earth-analogs, it would provide the information on the inhomogeneous composition of their atmospheres.

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

2013-03-10

161

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

162

Collision-induced absorption by D2 pairs in the first overtone band at 77, 201 and 298 K  

NASA Astrophysics Data System (ADS)

Collision induced absorption (CIA) spectra of pure D2 in the first overtone region from 5250 to 7250 cm^{-1}, recorded at 77, 201 and 298 K, have been analyzed. The observed spectra at 77, 201 and 298 K were modelled by a total of 92, 214 and 267 components respectively of double vibrational transitions at room temperature of the type X2(J)+X0(J) and X1(J)+X1(J), where X is O, Q or S transitions. Profile analyses of the spectra were carried out using the Birnbaum-Cohen line-shape function for the individual components of the band, and characteristic line shape parameters were determined from the analysis. The observed and calculated profiles agree well over the whole overtone band, and the agreement is better than 97% in the three cases studied. Binary and ternary absorption coefficients were determined from the integrated absorption of the band.

Abu-Kharma, M.; Gillard, P. G.; Reddy, S. P.

2006-01-01

163

Enhancement of light absorption of cadmium sulfide nanoparticle at specific wave band by plasmon resonance shifts  

NASA Astrophysics Data System (ADS)

Cadmium sulfide (CdS) is a common photocatalyst used for photocatalytic processes. Only those photons with energy above or equal to 2.4 eV (corresponding to band gap of CdS) are absorbed and contribute to the photocatalytic behavior. In this paper, the concept of multilayer nanoshell plasmonic photocatalyst is introduced into photocatalysis for hydrogen production based on the water-splitting technique. The optical properties of novel multilayer nanoshells consisting of Ag, SiO 2 and CdS are investigated by means of plasmonics theory and plasmon hybridization model. The optical properties with structural parameters of Ag/SiO 2/CdS composite nanoparticles are studied by discrete dipole approximation (DDA) method. The results show that the absorption performance of this novel multilayer nanoshell is remarkably improved when localized surface plasmon resonance (LSPR) is excited on the surface of Ag nanoparticle exposed under UV-vis illumination. By adjusting the intermediate layer thickness, the resonance wavelength can be conveniently tuned to desired wavelength range. For a thinner intermediate layer, the resonance wavelength is red shifted. Parameter optimization gives rise to the optimal structure of outstanding absorption performance.

Duan, Huiling; Xuan, Yimin

2011-06-01

164

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

165

Compensation for Spherical Geometric and Absorption Effects on Lower Thermospheric Emission Intensities Derived from High Earth Orbit Images  

NASA Technical Reports Server (NTRS)

Remote sensing of the atmosphere from high earth orbit is very attractive due to the large field of view obtained and a true global perspective. This viewpoint is complicated by earth curvature effects so that slant path enhancement and absorption effects, small from low earth orbit, become dominant even at small nadir view angles. The effect is further complicated by the large range of local times and solar zenith angles in a single image leading to a modulation of the image intensity by a significant portion of the diurnal height variation of the absorbing layer. The latter effect is significant in particular for mesospheric, stratospheric and auroral emissions due to their depth in the atmosphere. As a particular case, the emissions from atomic oxygen (130.4 and 135.6 nm) and molecular nitrogen (two LBH bands, LBHS from 140 to 160 nm and LBHL from 160 to 180 nm) as viewed from the Ultraviolet Imager (UVI) are examined. The LBH emissions are of particular interest since LBHS has significant 02 absorption while LBHL does not, In the case of auroral emissions this differential absorption, well examined in the nadir, gives information about the height of the emission and therefore the energy of the precipitating particles. Using simulations of the viewing geometry and images from the UVI we examine these effects and obtain correction factors to adjust to the nadir case with a significant improvement of the derived characteristic energy. There is a surprisingly large effect on the images from the 02 diurnal layer height changes. An empirical compensation to the nadir case is explored based on the local nadir and local zenith angles for each portion of the image. These compensations are demonstrated as applied to the above emissions in both auroral and dayglow images and compared to models. The extension of these findings to other instruments, emissions and spectral regions is examined.

Swift, W.; Germany, G. A.; Richards, P. G.; Parks, G. K.; Brittnacher, M.; Spann, J. F., Jr.

1997-01-01

166

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

167

Absorption band oscillator strengths of N2 transitions between 95.8 and 99.4 nm  

NASA Technical Reports Server (NTRS)

Molecular nitrogen plays a central role in the energetics of the earth's upper atmosphere and is the major constituent of the atmospheres of the planetary satellites Titan and Triton. This paper reports a new set of absorption oscillator strengths measured at higher resolution for seven bands in the 95.8-99.4 nm region. The results are compared with earlier, lower resolution absorption measurements, electron scattering measurements, and calculations based on a deperturbation analysis of the excited states.

Stark, G.; Smith, Peter L.; Huber, K. P.; Yoshino, K.; Stevens, M. H.; Ito, K.

1992-01-01

168

Non-uniform sound intensity distributions when measuring absorption coefficients in reverberation chambers using a phased beam tracing.  

PubMed

Measured absorption coefficients in reverberation chambers often differ from theoretical random incidence absorption coefficients, because ideal assumptions for the theoretical random incidence absorption coefficient are not fulfilled during measurements in actual reverberation chambers. Therefore sound intensity distributions on absorber under measurement conditions have been simulated using a phased beam tracing, and used as correction functions for reducing discrepancies between the measured and theoretical absorption coefficients. Two reverberation rooms were investigated by assuming that a test specimen was attached to a vertical surface and the floor. The frequency-dependent sound intensity distributions on absorbers were found to be affected by the reverberation chamber geometry and dimensions, the absorption capability of the specimen, and the placement of the specimen. High frequency intensity distributions above 1 kHz were similar for all studied cases, but some variations in low frequency intensity distributions were observed. If the non-uniform intensity distribution and a finite size effect are taken into account for correcting the theoretical absorption coefficients, a good agreement is found between corrected and measured statistical absorption coefficients. The non-uniform sound intensity can account for the discrepancy at high frequencies. PMID:20550256

Jeong, Cheol-Ho

2010-06-01

169

Theoretical calculation of absorption intensities of C2H and C2D  

NASA Astrophysics Data System (ADS)

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

Tarroni, Riccardo; Carter, Stuart

2004-01-01

170

High-resolution VUV absorption spectrum of N2, c'4 1Sigmau+ <-- X 1Sigmag+ bands  

Microsoft Academic Search

Absorption spectra of the c'4 1Sigmau+ <-- X 1Sigmag+ Rydberg bands of N2 in the 885 to 995 Å region are photographed at high resolution by a 6.65-m vacuum spectrograph. Rotational analyses of the c'4(v) <-- X(0) and c'4(v) <-- X(1) bands with v = 1-4 are given, together with a preliminary discussion of the homogeneous perturbations c'4 1Sigmau+ ×

K. Yoshino; D. E. Freeman; Y. Tanaka

1979-01-01

171

Absolute integrated intensity and individual line parameters for the 6.2-micron band of NO2. [in solar spectrum  

NASA Technical Reports Server (NTRS)

The absolute integrated intensity of the 6.2-micron band of NO2 at 40 C was determined from quantitative spectra at about 10 per cm resolution by the spectral band model technique. A value of 1430 plus or minus 300 per sq cm per atm was obtained. Individual line parameters, positions, intensities, and ground-state energies were derived, and line-by-line calculations were compared with the band model results and with the quantitative spectra obtained at about 0.5 per cm resolution.

Goldman, A.; Bonomo, F. S.; Williams, W. J.; Murcray, D. G.; Snider, D. E.

1975-01-01

172

Identification of three absorption bands in the 2-um spectrum of Io  

NASA Astrophysics Data System (ADS)

Spectroscopic observations of the trailing face of Io at a resolution of 1.02/cm performed with the FTS (Fourier Transform Spectrometer) on the 3.6-m Canada-France-Hawaii telescope (CFHT) on Mauna Kea confirm the presence of two weak absorption features in the 2-micron region. The first feature occurs at 4704.9 +/- 0.2/cm (2.12545 +/- 0.00010 micron); it is about 6.8% deep and 3/cm wide (FWHM). The second feature is at 5047.1 +/- 1/cm (1.98135 +/- 0.0004 microns) with a broad central core; its depth is about 8% and its width approximately 7/cm. A laboratory investigation of spectra of solid SO2 with relatively thick samples, as well as of mixtures of SO2 with CO2 and H2S, indicates that the two features at 4705/cm and 5047/cm are best explained by the 3nu1 + nu3 and nu1 + 3nu3 modes of solid SO2 around 130 K, respectively. In addition, a careful a posteriori look at our Io spectrum shows the presence of a band at 3933 +/- 1/cm (2.5426 +/- 0.0007 microns) (depth approximately equal to 30% (full width at half maximum (FWHM) approximately equal to 8/cm) due to the 3V3 band of solid SO2, as predicted by our laboratory experiments. The positions and widths of these bands indicate that a temperature gradient may exist between the surface of the frost and several centimeters below and suggest that some SO2 may be mixed at the molecular level with some neutral component. Three different models are proposed to explain the apparent discrepancy between the large variability with longitude on the strong 2457/cm (4.07 micron band and the nearly constant depth of the weak 4705/cm (2.1254 micron) band. The first model involes a large variation in grain sizes (factor 2-3) over Io's hemispheres. The second model assumes a considerable variation in thermal flux with Io's longitude (at 2457/cm, up to 20% of the reflected continuum flux). The third model assumes an uniform layer of coarse grained SO2 frost (a few hundred micrometers in size) with a variable longitudinal coverage of a thin layer of very fine frost grains (less than a few millimeters of micrometer-sized grains). Using the optical constants of solid SO2 measured in the laboratory, we predict the position and depth (greater than or equal to 1%) of about 25 additional absorption features of SO2 frost, in the 2800-5000/cm (2.0-3.6 micron) range, that should be observed in future high quality spectra of Io.

Schmitt, Bernard; de Bergh, Catherine; Lellouch, Emmanuel; Maillard, Jean-Pierre; Barbe, Alain; Doute, Sylvain

1994-09-01

173

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

174

A simple two-band semi-analytical model for retrieval of specific absorption coefficients in coastal waters  

NASA Astrophysics Data System (ADS)

A non-linear iterative method is used to replace the traditional spectral slope technique in initializing the total absorption decomposition model. Based on comparison of absorption coefficient by QAA and two-band semi-analytical model (TSAA) models with field measurements collected from the West Florida Shelf waters and Bohai Sea, it is shown that both models are effective in estimating absorption coefficients from the West Florida Shelf waters, but the TSAA model is superior to the QAA model. Use of the TSAA model in estimating absorption coefficient in the West Florida Shelf and Bohai Sea decreases the uncertainty of estimation by 1.3–74.7% from the QAA model. The TSAA model's sensitivity to the input parameters was evaluated by varying one parameter and keeping the others fixed at their default values. Our results indicate that the TSAA model has quite a strong noise tolerance to addressing the field data of the total absorption coefficient.

Chen, Jun; Cui, Tingwei; Qiu, Zhongfeng; Lin, Changsong

2014-05-01

175

On the Molar Extinction Coefficient and Integrated Molar Absorptivity of the Infrared Absorption Spectra of C60 and C70 Fullerenes  

Microsoft Academic Search

The molar extinction coefficients, known also as molar absorptivity ?, of C60 and C70 fullerenes infrared absorption spectra were determined at room temperature on samples embedded in KBr pellets. Furthermore, the integrated molar absorptivity ? of each absorption infrared band either of C60 and of C70 was measured and reported together with the relative intensity of the infrared absorption bands.

Franco Cataldo; Susana Iglesias-Groth; Arturo Manchado

2012-01-01

176

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

NASA Astrophysics Data System (ADS)

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

Kassi, Samir; Campargue, Alain

2014-06-01

177

Detection of a near infra-red absorption band of ferrohaem a3 in cytochrome c oxidase.  

PubMed

We have detected weak absorption bands in the near infra-red region of reduced mammalian cytochrome c oxidase, analogous to those that we have recently reported to be present in the bacterial cytochrome o (Ingledew, W.J., Bacon, M. and Rich, P.R. (1992) FEBS Lett. 305, 167-170). The major band is centred at 784 nm and has an sigma mM-1.cm-1 of around 0.1. It is shifted to 760 nm in the carbon monoxide compound and is absent in the reduced cyanide complex. We attribute it to a charge transfer band of ferrohaem a3, equivalent to the 'band III' or 'conformational band' of haemoglobin. PMID:1338593

Rich, P R; Moody, A J; Ingledew, W J

1992-07-01

178

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

SciTech Connect

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

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

2009-04-15

179

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

180

Comparison of specific absorption rate (SAR) induced in child-sized and adult heads using a dual band mobile phone  

Microsoft Academic Search

This paper gives a study and comparison of specific absorption rate (SAR) induced in a child-sized head and an adult head using a dual band mobile phone. Both the average SAR over a mass of 10g in the head and the power budget are determined in the two cases using the finite difference in time domain (FDTD) method. The differences

Abdelhamid Hadjem; David Lautru; Christian Dale; Man Fai Wong; V. F. Hanna; J. Wiart

2004-01-01

181

Effects of overlapping optical absorption bands of pyroxene and glass on the reflectance spectra of lunar soils  

Microsoft Academic Search

Reflectance spectra of lunar rocks and soils are dominated by absorptions at about 1000 and 2000 nm caused by Fe(++) in pyroxene. It has been attempted to use the depth of the 1000 nm band in mature lunar soils as an indication of the FeO content of the agglutinitic glass and the soil from which it came. The considered investigation

T. G. Farr; B. A. Bates; R. L. Ralph; J. B. Adams

1980-01-01

182

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

PubMed

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

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

2013-01-01

183

Band gap shift and the optical nonlinear absorption of sputtered ZnO-TiO2 films.  

PubMed

ZnO-TiO2 composite films with different Zn/Ti atomic ratios were prepared with radio frequency reactive sputtering method. The Zn percentage composition (f(Zn)) dependent optical band gap and optical nonlinear absorption were investigated using the transmittance spectrum and the Z-scan technique, respectively. The results showed that composite films with f(Zn) in the range of 23.5%-88.3% are poor crystallized and their optical properties are anomalous which exhibit adjustable optical band gap and large optical nonlinear absorption. The optical absorption edge shifted to the blue wavelength direction with the increasing of f(Zn) and reached the minimum value of 285 nm for the sample with f(Zn) = 70.5%, which has the largest direct band gap of 4.30 eV. Further increasing of f(Zn) resulted in the red-shift of the optical absorption edge. The maximum optical nonlinear absorption coefficient of 1.5 x 10(3) cm/GW was also obtained for the same sample with f(Zn) = 70.5%, which is more than 40 times larger than those of pure TiO2 and ZnO films. PMID:21770138

Han, Yi-Bo; Han, Jun-Bo; Hao, Zhong-Hua

2011-06-01

184

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

185

Homogeneous line width of the different vibronic bands of retinal absorption in bacteriorhodopsin by the hole-burning technique  

SciTech Connect

Using the hole-burning technique, resolved vibrational structure was observed in the retinal absorption sepctrum of bacteriorhodopsin (bR) in poly(vinyl alcohol) (PVA) film at 10 K with 556 and 632 nm irradiation. The homogeneous line widths of {upsilon}=1 and {upsilon}=2 vibronic bands are estimated from the deconvolution of the observed spectrum. The absorption maximum is found to shift by 100-200 cm{sup -1} by using the two excitation wavelengths; resulting from partial site selection due to the contribution of inhomogeneous broadening. The hole width produced by excitation near the zero-phonon band is found to be nearly 1250 cm{sup -1}, which corresponds to a homogeneous width of nearly 600 cm{sup -1}, and the low limit of dephasing time can be estimated as 20 fs. This width is found to be independent of the vibronic band observed. 26 refs., 4 figs., 1 tab.

Kamalov, V.F.; Masciangioli, T.M.; El-Sayed, M.A. [Georgia Inst. of Technology, Atlanta, GA (United States)] [Georgia Inst. of Technology, Atlanta, GA (United States)

1996-02-22

186

Optomechanical shutter modulated broad-band cavity-enhanced absorption spectroscopy of molecular transients of astrophysical interest.  

PubMed

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. PMID:23240889

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

2013-10-01

187

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

188

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

NASA Astrophysics Data System (ADS)

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.

2012-09-01

189

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

190

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

192

Microwave absorption behavior of a polyaniline magnetic composite in the X-band  

NASA Astrophysics Data System (ADS)

The development of nanosized materials is a subject of considerable interest both for understanding of the fundamental properties of magnetic materials for new technological applications. Polyaniline, composites Fe3O4/(PANI) with conducting, magnetic and electromagnetic properties with different amounts of Fe3O4 were successfully prepared. The samples were structurally characterized by scanning electron microscopy (SEM), X-ray diffraction and transmission electron microscopy (TEM) and magnetically, with a superconducting quantum interference device (SQUID) magnetometer. In order to explore microwave-absorbing properties in X-band, the composite nanoparticles were mixed with an epoxy resin to be converted into a microwave-absorbing composite. Microwave behavior with different Fe3O4/(PANI)-epoxy resin ratio was studied using a microwave vector network analyzer (VNA) in the range 7.5 to 13 GHz. For a constant thickness of 1.5 mm, absorption increases with the magnetite contents in the composites and in the oriented samples by the application of a magnetic field.

Aphesteguy, J. C.; Damiani, A.; DiGiovanni, D.; Jacobo, S. E.

2012-08-01

193

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

194

An investigation of the near-infrared collision induced absorption bands of oxygen with SCIAMACHY solar occultation data  

NASA Astrophysics Data System (ADS)

The present work investigates the Collision Induced Absorption (CIA) bands of oxygen that occur at 1065 and 1270 nm from solar occultation data obtained with the space-borne spectrometer SCIAMACHY. The effort is motivated by the interest in these two strong CIA bands in atmospheric research and the paucity of data on them under realistic atmospheric conditions. The observing geometry provides long integration paths and in turn easily measurable absorption signals. Our analysis method relies on the accurate separation of the CIA band signature from the rest of the continuum and structured components over selected spectral intervals. We show that the shapes of the two CIA bands seem well described by specific laboratory determinations over a broad range of tropospheric and low-stratospheric conditions. By analyzing a full month of solar occultation data we find that the ratio of peak binary cross sections in air, ?1270nmpeak/?1065nmpeak, is ?4 and seemingly independent of tangent height from 6 to 18 km. We tentatively estimate the absolute binary cross sections and compare them to existent measurements. A better characterization of the near-infrared CIA bands of oxygen should facilitate their implementation in remote sensing applications in the way it is often done with the CIA bands that occur in the visible.

García Muñoz, A.; Bramstedt, K.

2012-08-01

195

Judd-Ofelt analysis of the absorption intensities in Er3+ -doped garnets  

NASA Astrophysics Data System (ADS)

Spectroscopic and laser properties of Er3+ doped in three different garnet hosts, Y3Al5O12 (YAG), Y3Sc2Ga3O12 (YSGG), and Gd3Ga5O12 (GGG), are characterized by employing the Judd-Ofelt (J-O) analysis. The J-O model has been applied to the room temperature absorption intensities of Er3+ (4f11) transitions to establish the so-called J-O intensity parameters: W2, W4, and W6 in the three garnet hosts. The intensity parameters are used to determine the radiative decay rates (emission probabilities of transitions) and branching ratios of the Er3+ transitions from the excited state J manifolds to the lower-lying J' manifolds. The predicted decay rates and branching ratios of these Er3+ transitions in YAG, YSGG, and GGG hosts are compared. From the radiative decay rates, the radiative lifetimes of the Er3+ excited states are determined in the three garnets and are also compared. We also report the spectroscopic quality factors, W4/W6, obtained for the three garnets. The quantum efficiencies of the 4I13/2 ® 4I15/2 Er3+ transition in YAG, YSGG, and GGG are determined to be approximately 79, 82, and 85

Sardar, Dhiraj

2003-03-01

196

A temperature-induced absorption band centered in the region of 666 nm related to the configuration of the active site in frozen cytochrome oxidase.  

PubMed

The existence of a temperature-induced absorption band centred in the region of 666 nm is demonstrated for both membrane-bound and soluble cytochrome oxidase in the frozen state. The 666 nm band is generated solely by an increase in temperature of both fully reduced and mixed valence state cytochrome oxidase in the presence of CO or O2 within the 'pocket' containing the active site; it is not formed in the absence of both CO and O2 from the sample. The formation of the 666 nm band is entirely reversible when the temperature is decreased again and its formation is not dependent on the presence of liganded CO at the sixth coordination site of haem a3 in the low temperature range (below --120 degrees C) prior to photolysis. The shape and intensity of the 666 nm band are not affected by the extent of CO recombination following flash and photolysis and temperature increase and are not affected by changes in the valence states of the four metal centres when the O2 reaction is in progress. PMID:218627

Denis, M; Clore, G M

1979-03-15

197

Airborne imaging spectrometer data of the Ruby Mountains, Montana: Mineral discrimination using relative absorption band-depth images  

USGS Publications Warehouse

Airborne imaging spectrometer data collected in the near-infrared (1.2-2.4 ??m) wavelength range were used to study the spectral expression of metamorphic minerals and rocks in the Ruby Mountains of southwestern Montana. The data were analyzed by using a new data enhancement procedure-the construction of relative absorption band-depth (RBD) images. RBD images, like bandratio images, are designed to detect diagnostic mineral absorption features, while minimizing reflectance variations related to topographic slope and albedo differences. To produce an RBD image, several data channels near an absorption band shoulder are summed and then divided by the sum of several channels located near the band minimum. RBD images are both highly specific and sensitive to the presence of particular mineral absorption features. Further, the technique does not distort or subdue spectral features as sometimes occurs when using other data normalization methods. By using RBD images, a number of rock and soil units were distinguished in the Ruby Mountains including weathered quartz - feldspar pegmatites, marbles of several compositions, and soils developed over poorly exposed mica schists. The RBD technique is especially well suited for detecting weak near-infrared spectral features produced by soils, which may permit improved mapping of subtle lithologic and structural details in semiarid terrains. The observation of soils rich in talc, an important industrial commodity in the study area, also indicates that RBD images may be useful for mineral exploration. ?? 1989.

Crowley, J. K.; Brickey, D. W.; Rowan, L. C.

1989-01-01

198

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

199

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

NASA Astrophysics Data System (ADS)

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

Heng, Hang; Yang, Li

2014-05-01

200

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

NASA Technical Reports Server (NTRS)

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

May, Randy D.

1992-01-01

201

X-ray Absorption Imaging of High-Intensity Discharge Lamps Using Monochromatic Synchrotron Radiation  

NASA Astrophysics Data System (ADS)

We will report results from the imaging of Hg vapor in high-intensity discharge lamps using synchrotron radiation and digital detectors. These measurements extend previous work on x-ray absorption imaging in arc lamps using an x-ray tube and a passive phosphor image plate detector^i. The large x-ray flux obtained from the Advanced Photon Source (Argonne National Laboratory) combined with the electronic gating capabilities of an intensified charge-coupled device detector have allowed us to obtain time-resolved Hg distributions with high spatial resolution. Monochromatic synchrotron radiation improves the accuracy over what can be obtained with quasi-continuum radiation from an x-ray tube source. ^iJ. J. Curry, M. Sakai, and J. E. Lawler, Journal of Applied Physics 84, 3066 (1998).

Curry, John J.; Sansonetti, Craig J.; Hechtfischer, Ulrich; Adler, Helmar G.

2002-10-01

202

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

2013-05-24

203

Influence of Ion Mass on Laser-Energy Absorption and Synchrotron Radiation at Ultrahigh Laser Intensities  

NASA Astrophysics Data System (ADS)

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 1022W/cm2 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.

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

2013-05-01

204

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

205

The Conduction Bands in 6H and 15R Silicon Carbide. II. Absorption Measurements  

Microsoft Academic Search

It is shown, on the basis of classical theory, that the free carrier absorption in a uniaxial semiconductor having an anisotropic effective mass and relaxation time is characterized by two independent absorption coefficients. For a general multivalley model these absorption coefficients are shown to be quite complicated functions of the effective mass and relaxation time tensors; these functions are considerably

B. Ellis; T. S. Moss

1967-01-01

206

Diode-laser measurements of intensities and halfwidths in the nu6 band of 12CH3D  

Microsoft Academic Search

Absolute line intensities have been determined at room temperature for a total of 22 transitions belonging to rP and pP subbands in the nu6(E) perpendicular band of 12CH3D between 1062 and 1114 cm-1 under Doppler-limited resolution using a tunable diode-laser spectrometer system. Although the line intensities were determined with good precision (~3%), the squared vibrational transition dipole matrix element derived

V. Malathy Devi; D. Chris Benner; Curtis P. Rinsland; Mary Ann H. Smith; K. B. Thakur

1987-01-01

207

Determination of nonlinear absorption and refraction in direct and indirect band gap crystals by Z-scan method.  

PubMed

A systematic investigation on nonlinear optical properties such as three photon absorption (3PA) wavelength dependent of Kerr type nonlinear refraction in direct and indirect band gap crystals has been reported in the present work. The Z-scan measurements are recorded for both ZnO and CdI(2) with femtosecond laser pulses while the wavelength dependent of the Kerr nonlinearity are in agreement with a two band model. The wavelength dependence of the 3PA is determined by [(3E(photon)/E(g))-1](5/2)[(3E(photon)/E(g))](-9) in the case of direct band gap crystal and [(3E(photon)±??/E(g))-1](5/2)[(3E(photon)±??/E(g))](-9) in the case of indirect band gap crystal. In the present investigation the value of 3PA in the case of indirect band gap crystal is lower than the direct band gap crystal which is due to the phonon assisted transition. The materials of large band gap with optical nonlinearity and fast response speed should be dominating factor for further photonic devices such as optical limiters, optical switches and optical modulators. The higher order nonlinear optical effects have also been determined in the present study. PMID:22750336

Gaur, Poonam; Sharma, Dimple; Singh, Nageshwar; Malik, B P; Gaur, Arun

2012-11-01

208

An Absorption Mechanism for High Intensity Lasers at a Steep Overdense Plasma  

NASA Astrophysics Data System (ADS)

In both fast ignition (FI) and the radiation pressure acceleration (RPA) of ions it is essential to understand how electrons are accelerated and reabsorbed at a sharp overdense plasma interface by very intense lasers. To investigate this question, we use the PIC code OSIRIS to model the interaction of high intensity lasers (I >=5 x10^19 W/cm^2) with a sharp boundary of an overdense plasma (n nc). These results indicate that the commonly proposed absorption mechanisms (Brunel, JxB) cannot explain the acceleration of the electrons. Through the use of particle tracking and a test particle model, we propose a new mechanism in which only electrons which can resonantly interact with the standing wave in vacuum can gain energy. Heating can only occur if the plasma temperature is sufficiently high such that electrons leaving the plasma at large angles are able to interact with the peak electric field. For circularly polarized lasers, the surface B field of the standing wave prevents electrons from leaving the plasma leading to significantly less heating. The process is conformed in test particle simulations. Applications to FI and RPA will be discussed.

May, J.; Tonge, J.; Mori, W. B.; Fiuza, F.; Fonseca, R.; Silva, L. O.

2010-11-01

209

Radiative Transfer Models of Emission and Absorption in the H2O 6 Micron Vibration-Rotation Band toward Orion-BN-KL  

NASA Astrophysics Data System (ADS)

We report the spectrum of Orion-BN/KL between 5.3 and 7.2 ?m observed with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory. H2O lines of the ?2=1-0 bending mode with ? < 6.3 ?m (the R-branch) are observed in absorption, while lines with ? > 6.3 ?m (the P-branch) are observed in emission. Radiative transfer models including the (0, 0, 0), (0, 1, 0), and (0, 0, 1) vibrational levels show that this effect is produced in a natural way by H2O absorption of 6 ?m continuum photons followed by spontaneous de-excitation to the ground state (resonant scattering). The intensities of the absorption lines can be explained with an H2O column density of a few 1017 cm-2 in gas with a temperature of ~150 K and n(H2)~106 cm-3, although these parameters depend on the assumed location of the absorbing shell. Since the observed intensity of the H2O emission lines are larger than those seen in absorption, we suggest that rovibrational excitation of H2O by collisions in denser and hotter gas, such as found in shocks, also contribute to the P-branch emission of the 6 ?m H2O band. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, The Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

González-Alfonso, Eduardo; Cernicharo, José; van Dishoeck, Ewine F.; Wright, Christopher M.; Heras, Ana

1998-08-01

210

Energetics, structures, vibrational frequencies, vibrational absorption, vibrational circular dichroism and Raman intensities of Leu-enkephalin  

NASA Astrophysics Data System (ADS)

Here we present several low energy conformers of Leu-enkephalin (LeuE) calculated with the density functional theory using the Becke 3LYP hybrid functional and the 6-31G* basis set. The structures, conformational energies, vibrational frequencies, vibrational absorption (VA) intensities, vibrational circular dichroism (VCD) intensities and Raman scattering intensities are reported for the conformers of LeuE which are expected to be populated at room temperature. The species of LeuE present in non-polar solvents is the neutral non-ionic species with the NH2 and CO2H groups, in contrast to the zwitterionic neutral species with the NH3+ and CO2- groups which predominates in aqueous solution and in the crystal. All of our attempts to find the zwitterionic species in the isolated state failed, with the result that a hydrogen atom from the positively charged N-terminus ammonium group transferred either to one of the oxygens of the carboxylate group of the C-terminus or to the oxygen of the amide group of one of the other residues. Hence we conclude that the zwitterionic species of LeuE is not stable in the isolated state. Spectral simulations of the species expected to be found in the isolated state can be compared to the measured VA, VCD and Raman spectra of LeuE in non-polar solvents to identify which conformer or conformers of LeuE are present in these media. Characteristic features in the VCD spectra are more sensitive to conformational changes than those in either the VA or Raman spectra, similar to the characteristic features in electronic circular dichroism spectra with respect to those in the UV-vis electronic absorption spectra. Finally, we have also attempted to stabilize the zwitterionic species by treating the aqueous environment by using a continuum solvent approach, the Onsager model. Here we found that the zwitterionic species is now stable. The neutral species in an aqueous environment was also modelled by the continuum solvent approaches to determine the relative stability of these two species in this new aqueous environment. Here the relative energy of the zwitterionic species is higher than neutral species, in contradiction to experiment. Hence the use of explicit water molecules plus either this or another continuum model to treat the bulk water environment is necessary to make the zwitterionic species more stable than the neutral species. We are pursuing explicit water molecules to treat LeuE in this environment.

Jalkanen, K. J.

2003-05-01

211

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

212

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

213

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

NASA Technical Reports Server (NTRS)

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

Singhroy, Vernon H.; Kruse, Fred A.

1991-01-01

214

Theoretical study of electronic absorption spectroscopy of propadienylidene molecule vis-â-vis the observed diffuse interstellar bands  

NASA Astrophysics Data System (ADS)

Observation of broad and diffuse interstellar bands (DIBs) at 4881 Å and 5440 Å assigned to the optical absorption spectrum of Y-shaped propadienylidene (H2Cdbnd Cdbnd C:) molecule is theoretically examined in this paper. This molecule apparently absorbs in the same wavelength region as the observed DIBs and was suggested to be a potential carrier of these DIBs. This assignment mostly relied on the experimental data from radioastronomy and laboratory measurements. Motivated by these available experimental data we attempt here a theoretical study and investigate the detailed electronic structure and nuclear dynamics underlying the electronic absorption bands of propadienylidene molecule. Our results show that this molecule indeed absorbs in the wavelength region of the recorded DIBs. Strong nonadiabatic coupling between its energetically low-lying electronic states plays major role, initiates ultrafast internal conversion and contributes to the spectral broadening. Theoretical findings are finally compared with the available experimental and theoretical data and discussed in connection with the recorded DIBs.

Reddy, Samala Nagaprasad; Mahapatra, S.

2012-07-01

215

Intensities of the difference bands ?1+ ?3- ?2 and 2 ?3- ?2 of ozone. Comparison with theoretical predictions  

NASA Astrophysics Data System (ADS)

The infrared spectra of 16O 3 in the range 1300-1500 cm -1 have been recorded at high resolution (0.007 cm -1), with a large product p×?=32.4 Torr×3212 cm, and a good S/N ratio?500. This enabled us to observed the 3 ?2- ?2 band and to extend the measurements of the 2 ?2 band (A. Barbe, A. Chichery, Vl.G. Tyuterev, S. Taskhun, S. Mikhailenko, Spectrochimica Acta 54A (1998) 1935-1945). Two difference bands 2 ?3- ?2 and ?1+ ?3- ?2 were observed as well. The positions of the lines are well known due to the studies of cold bands 2 ?1, ?1+ ?3, 2 ?3 as well as ?2. In this region only intensity measurements of the ?1+ ?3- ?2 combination band have been done so far. Here, due to the large pressure×pathlength product, we are able to observe a large range of transitions for ?1+ ?3- ?2 band (up to J=51 and Ka=14), and also for the first time 2 ?3- ?2 band. We have derived the transition moment parameters for 2 ?3- ?2 and estimated an upper limit for 2 ?1- ?2. A complete final calculation is performed for these difference bands. The principal transition moment parameters are compared with theoretical predictions.

Chichery, A.; Barbe, A.; Tyuterev, Vl. G.; Sulakshina, O.; Borkov, Y.

2000-02-01

216

Mollwo–Ivey relations for optical absorption bands of the atomic and F? centres in alkali halides  

Microsoft Academic Search

Evidence indicates that two classes of the transient IR-absorption bands: (a) with maxima at 0.27–0.36eV in NaCl, KCl, KBr, KI and RbCl and due to shallow electron traps or bound polarons according to Jacobs (Phys. Stat. Sol. B 129 (1985) 755) and Korovkin and Lebedkina (Fiz. Tverd. Tela (Russian) 35 (1993) 642), and (b) with maxima at 0.15–0.36eV in NaI,

V. Ziraps

2001-01-01

217

New absorption band in the near IR assigned to a bound triplet state of the f? in NaI  

Microsoft Academic Search

Summary  TheF ? F? optical conversion in NaI is reduced by an external magnetic field, but not completely suppressed. In order to explain such\\u000a unexpected result both a spin mixing in the optical cycle of theF-centre and the existence of a bound triplet state of the F?-centre have been considered. Absorption measurements have disclosed\\u000a a new band at 1.4 eV whose

G. Baldacchini; G. P. Gallerano; U. M. Grassano; F. Lüty

1983-01-01

218

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

219

Experimental and theoretical studies of absorption in microwindows of the ? 4-band of methane and methane–hydrogen  

Microsoft Academic Search

The absorption coefficients of room temperature CH4 and CH4–H2 mixtures were measured in the 1300–1360cm?1 region of the ?4 band at about 295K as a function of pressure. These results were analyzed at frequencies in the most transparent regions of various microwindows in order to study the far wings of self- and H2-broadened lines in the R-branch of the ?4

George Birnbaum; Andrew Buechele; Michael E. Thomas; Matthew Banta; Nathalie Picqué; Guy Guelachvili; Jean-Michel Hartmann

2002-01-01

220

The determination of kinetic parameters of LiF : Mg,Ti from thermal decaying curves of optical absorption bands  

NASA Astrophysics Data System (ADS)

In this paper, the thermal bleaching curves (TBCs) of specific optical absorption bands of LiF : Mg,Ti were measured as a function of temperature. The TBCs obtained were analysed to extract the kinetic parameters (the thermal activation energy (E) and the frequency factor (s)) of some TL glow peaks of LiF : Mg,Ti on the basis of the developed first-order kinetic model over a specified temperature region.

Necmeddin Yazici, A.

2003-06-01

221

Off-axis continuous-wave cavity-enhanced absorption spectroscopy of narrow-band and broadband absorbers using red diode lasers  

NASA Astrophysics Data System (ADS)

We present an application of continuous-wave (cw) cavity-enhanced absorption spectroscopy (CEAS) with off-axis alignment geometry of the cavity and with time integration of the cavity output intensity for detection of narrow-band and broadband absorbers using single-mode red diode lasers at ?=687.1 nm and ?=662 nm, respectively. Off-axis cw CEAS was applied to kinetic studies of the nitrate radical using a broadband absorption line at ?=662 nm. A rate constant for the reaction between the nitrate radical and E-but-2-eneof (3.78+/-0.17)×10-13 cm3molecule-1s-1 was measured using a discharge-flow system. A nitrate-radical noise-equivalent (1?? root-mean-square variation of the signal) detection sensitivity of 5.5×109 moleculecm-3 was achieved in a flow tube with a diameter of 4 cm and for a mirror reflectivity of 99.9% and a lock-in amplifier time constant of 3 s. In this case, a noise-equivalent fractional absorption per one optical pass of 1.6×10-6 was demonstrated at a detection bandwidth of 1 Hz. A wavelength-modulation technique (modulation frequency of 10 kHz) in conjunction with off-axis cw CEAS has also been used for recording 1f- and 2f-harmonic spectra of the RR(15) absorption of the b1?g+-X3?g- (1,0) band of molecular oxygen at /line{? }=14553.947 cm-1. Noise-equivalent fractional absorptions per one optical pass of 1.35×10-5, 6.9×10-7 and 1.9×10-6 were obtained for direct detection of the time-integrated cavity output intensity, 1f- and 2f-harmonic detection, respectively, with a mirror reflectivity of 99.8%, a cavity length of 0.22 m and a detection bandwidth of 1 Hz.

Kasyutich, V. L.; Canosa-Mas, C. E.; Pfrang, C.; Vaughan, S.; Wayne, R. P.

222

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

223

A surrogate climate change experiment with the RegT-Band to investigate the increase of Hydroclimatic Intensity  

NASA Astrophysics Data System (ADS)

The RegT-band version of RegCM4.1 release is used in a surrogate climate change experiment. Ten years of RegT-band simulation have been completed from 1998 to 2007, using the ERA-interim as boundary condition. The same ten years have been completed with a modified version of the model with doubled greenhouse gas concentration and with an increase of 3 temperature degrees in the lateral and boundary conditions for both the atmosphere and the ocean. Change in the hydrological cycle are investigated and in particular the changes in the hydroclimatic intensity are presented by mean of the analysis of the HY-INT index (Giorgi et al., 2011). By using this index both precipitation intensity and dry spell length are taken into account in the same time and the increase of hydroclimatic intensity is confirmed according to the Giorgi et al., 2011 results.

Coppola, E.; Giorgi, F.

2012-04-01

224

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

NASA Technical Reports Server (NTRS)

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

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

1987-01-01

225

Line Absorption Oscillator Strengths for the c'4 1?+ u (3)-X 1?+ g (0-5) Bands in N2  

NASA Astrophysics Data System (ADS)

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

Lavín, C.; Velasco, A. M.

2011-09-01

226

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

227

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

228

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

DOE Data Explorer

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

Greenwood, R.E.

229

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

230

Line intensities from band and diode laser measurements: Neutrino 4 of CH4  

NASA Technical Reports Server (NTRS)

The experimental data and theoretical work on the 7.7 micron band of methane are reviewed. This band is particularly relevant in studies of the atmospheres of Jupiter, Saturn and the other outer planets. Methane spectra taken from the infrared spectrometer (IRIS) aboard Voyager, and a temperature profile derived by inverting those data, both for hydrogen and methane are presented.

Fox, K.

1982-01-01

231

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

232

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

PubMed

Efficient trapping of the light in a photon absorber or a photodetector can improve its performance and reduce its cost. In this paper we investigate two designs for light-trapping in application to infrared absorption. Our numerical simulations demonstrate that nonabsorptive pyramids either located on top of an absorbing film or having embedded absorbing rods can efficiently enhance the absorption in the absorbing material. A spectrally averaged absorptance of 83% is achieved compared to an average absorptance of 28% for the optimized multilayer structure that has the same amount of absorbing material. This enhancement is explained by the coupled-mode theory. Similar designs can also be applied to solar cells. PMID:22828621

Dai, Weitao; Yap, Daniel; Chen, Gang

2012-07-01

233

Some observations on the optical absorption bands in LiF:Mg, Ti  

Microsoft Academic Search

Detailed optical absorption curves of gamma-irradiated LiF:Mg, Ti are presented. Computerised curve-fitting of the spectra allow for the behaviour of the individual peaks to be followed as a function of irradiation dose, optical bleaching and post-irradiation annealing. The absorption spectra, taken at -196 degrees C, consists of at least six major peaks. The authors find no compelling evidence to relate

J. L. Landreth; S. W. S. McKeever

1985-01-01

234

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

NASA Technical Reports Server (NTRS)

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

Pliutau, Denis; Prasad, Narasimha S

2013-01-01

235

The absorption spectrum of H2: CRDS measurements of the (2-0) band, review of the literature data and accurate ab initio line list up to 35000 cm(-1).  

PubMed

Five very weak transitions-O(2), O(3), O(4), O(5) and Q(5)-of the first overtone band of H(2) are measured by very high sensitivity CW-Cavity Ring Down Spectroscopy (CRDS) between 6900 and 7920 cm(-1). The noise equivalent absorption of the recordings is on the order of ?(min)? 5 × 10(-11) cm(-1) allowing for the detection of the O(5) transition with an intensity of 1.1 × 10(-30) cm per molecule, the smallest intensity value measured so far for an H(2) absorption line. A Galatry profile was used to reproduce the measured line shape and derive the line strengths. The pressure shift of the O(2) and O(3) lines was accurately determined from a series of recordings with pressure ranging between 10 and 700 Torr. From an exhaustive review of the literature data, the list of H(2) absorption lines detected so far has been constructed. It includes a total of 39 transitions ranging from the S(0) pure rotational line near 354 cm(-1) up to the S(1) transition of the (5-0) band near 18,908 cm(-1). These experimental values are compared to a highly accurate theoretical line list constructed for pure H(2) at 296 K (0-35,000 cm(-1), intensity cut off of 1 × 10(-34) cm per molecule). The energy levels and transition moments were computed from high level quantum mechanics calculations. The overall agreement between the theoretical and experimental values is found to be very good for the line positions. Some deviations for the intensities of the high overtone bands (V > 2) are discussed in relation with possible pressure effects affecting the retrieved intensity values. We conclude that the hydrogen molecule is probably a unique case in rovibrational spectroscopy for which first principles theory can provide accurate spectroscopic parameters at the level of the performances of the state of the art experimental techniques. PMID:22124257

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

2012-01-14

236

Synthetic rotational profiles of emission and absorption bands of interstellar polycyclic aromatic hydrocarbons  

Microsoft Academic Search

The spectrometers on board Herschel are likely to be able to detect far-IR emission bands from interstellar PAHs, possibly resolving their rotational envelopes. For some specific PAHs we calculated synthetic rotational profiles of their low-energy vibrational modes and of their low-lying permitted electronic transitions, for comparison respectively with the forthcoming Herschel observations and high resolution spectra of Diffuse Interstellar Bands.

G. Malloci; G. Mulas; C. Joblin; D. Toublanc; I. Porceddu

2005-01-01

237

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

NASA Astrophysics Data System (ADS)

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

Guo, Hao; Kimura, Tetsunari; Furutani, Yuji

2013-06-01

238

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

NASA Astrophysics Data System (ADS)

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

Brüggemann, B.; May, V.

2004-02-01

239

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

NASA Technical Reports Server (NTRS)

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

Khanna, R. K.; Zhao, Guizhi

1986-01-01

240

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

241

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

PubMed

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

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

2013-01-01

242

Interpretation of the IR absorption band of CO adsorbed on Ru(001)  

NASA Astrophysics Data System (ADS)

The qualitative variation of the IR absorption spectrum of CO adsorbed at 200 K on Ru(001) in the range of coverage 0 < ? ? {1}/{3} is reproduced by a calculation based on a random configuration of adsorbed molecules and nearest neighbour interactions.

Weaire, D.

243

Interpretation of the IR absorption band of CO adsorbed on Ru(001)  

NASA Astrophysics Data System (ADS)

The qualitative variation of the IR absorption spectrum of CO adsorbed at 200 K on Ru(001) in the range of coverage 0 < ? ? {1}/{3} is reproduced by a calculation based on a random configuration of adsorbed molecules and nearest neighbour interactions.

Weaire, D.

1981-02-01

244

VF and VK+ Aggregate Colour Centres: Origin of the Room-Temperature 350 nm Absorption Band in PbWO4  

Microsoft Academic Search

A PbWO4 (PWO) single crystal has been grown by the advanced Bridgman method. The as-grown PWO crystal exhibits a weak band at 350 nm. This band was fitted into two overlapping bands peaking at 330 nm and 360 nm respectively. The absorption spectra of the as-grown crystal sample on un-polarized light and polarized light are measured respectively. The formation mechanism

Qi-Ren Zhang; Ting-Yu Liu; Fei-Nan Yan

2004-01-01

245

Iron absorption band analysis for the discrimination of iron rich zones  

NASA Technical Reports Server (NTRS)

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 lineaments and more faults are seen on band 5. About 45% of the lineaments appear to be faults and contacts, the others being predominantly streams, roads, railway tracks, and mountain crests. About 25% of the lineaments are unidentified so far. Special attention is being given to unmapped extensions of faults, groups of unmapped lineaments, and known mineralized areas and alteration zones. Earthquake epicenters recorded from 1869 to 1963 have been plotted on the two base maps. Preliminary examination as yet indicates no basic correlation with the lineaments. Attempts are being made to subtract bands optically, using an I2S viewer, an enlarger, and a data color viewer. Success has been limited so far due to technical difficulties, mainly vignetting and poor light sources, within the machines. Some vegetation and rock type differences, however, have been discerned.

Rowan, L. C. (principal investigator)

1973-01-01

246

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

PubMed

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

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

2013-04-28

247

Research Directed Towards the Study of Molecular Band Intensities and Derived Quantities.  

National Technical Information Service (NTIS)

The results of work in the following areas are summarized: Intensity measurement of molecular spectra; identification atlas of molecular spectra; analysis of molecular spectra; shock tube and laser excitation of powdered solids; molecular potentials and v...

R. W. Nicholls

1967-01-01

248

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

249

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

250

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

251

Annealing of divacancy-related infrared absorption bands in boron-doped silicon  

Microsoft Academic Search

This work is devoted to an “old” defect and its annealing characteristics, namely the divacancy centre in silicon. Infrared spectroscopy is applied to study the annealing kinetics of divacancy-related absorption peaks in electron-irradiated Czochralski-grown samples doped with boron. In all specimens the kinetics show an exponential decay (first-order process) and a model taking into account both diffusion and dissociation as

B. G. Svensson; K. Johnsson; D. X. Xu; J. H. Svensson; J. L. Lindström

1989-01-01

252

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

Microsoft Academic Search

Classical molecular dynamics simulations have been carried out for gaseous CO2 starting from various anisotropic intermolecular potential energy surfaces. Through calculations for a large number of molecules treated as rigid rotors, the time evolution of the interaction-induced electric dipole vector is obtained and the Laplace transform of its autocorrelation function gives the collision-induced absorption rototranslational spectrum. The results are successfully

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

2011-01-01

253

Linear state of H2O found from a VUV absorption band  

Microsoft Academic Search

A high-resolution absorption spectrum of H2O was taken photographically using synchrotron radiation as a background. A weak rotational structure was observed for the first time at about 1144 AA and identified as the transition from the ground state (1A1) to a linear state 1 Sigma g. The rotational constant B' and the O1H distance in the upper state 1 Sigma

Y. Morioka; K. Maeda; K. Ito; T. Namioka

1988-01-01

254

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

PubMed Central

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

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

2014-01-01

255

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

256

Algorithm development for intensity modulated continuous wave laser absorption spectrometry in atmospheric CO2 measurements  

NASA Astrophysics Data System (ADS)

Currently, NASA Langley Research Center (LaRC) and ITT are jointly developing algorithms for demonstration of range discrimination using ITT's laser absorption spectrometer (LAS), which is being evaluated for the future NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. The objective of this Decadal Survey mission is to measure atmospheric column CO2 mixing ratios (XCO2) for improved determination of atmospheric carbon sources and sinks. Intensity Modulated Continuous Wave (IM-CW) techniques are used in this LAS approach. The LAS is designed to simultaneously measure CO2 and O2 columns, and these measurements are used to determine the required XCO2 column. The LAS measurements are enabled by the multi-channel operation of the instrument at 1.57 and 1.26-um for CO2 and O2, respectively. The algorithm development for the IM-CW techniques of the multi-channel LAS is focused on addressing key retrieval issues such as surface signal detection, thin cloud and/or aerosol layer rejection, vertical atmospheric range resolution, and optimizing the size of the measurement footprint. With these considerations, the modulation algorithm needs to maintain high enough signal-to-noise ratio (SNR) so that the mission scientific goals can be reached. A basic selection of the modulation algorithms that make XCO2 measurement and thin cloud rejection possible is the stepped frequency modulation scheme and a similar scheme of swept sine modulation. The differences between these two schemes for thin cloud rejection are small, assuming the proper selection of parameters is made. The stepped frequency approach is only a quantified version of swept sine method for the frequencies used. Swept sine scheme is a very common modulation technique for range discrimination, while the consideration of the stepped frequency scheme is based on the history of the rolling-tone modulation used in the instrument in previous successful column CO2 measurements. The stepped frequency approach provides minimal risk in the technology development for thin cloud rejection. To obtain a specified vertical resolution, a requisite bandwidth is needed for the stepped frequency/swept sine schemes. The requirements of horizontal resolution and SNR are obtained through the integration time of either stepped frequency or swept sine approaches. Based on these considerations and instrument hardware limitations, the frequencies for the intensity modulation approaches were selected and implemented in the current LAS. The LAS has six wavelength channels: 3 for CO2, 2 for O2 and 1 for background measurements. The frequencies of the stepped frequency algorithm vary from 200 to about 500 KHz with 100-KHz bandwidth in each individual channel. Reduction of potential spectral interference is also considered in the selection of the frequencies. Details of the development of the IM-CW algorithms and results from flight testing of these techniques during the spring and summer of 2011 are discussed in this paper.

Lin, B.; Harrison, F. W.; Browell, E. V.; Dobler, J. T.; Bryant, R. B.

2011-12-01

257

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

SciTech Connect

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

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

2011-03-15

258

Uniform Supersonic Expansion for FTIR Absorption Spectroscopy: The ? 5 Band of (NO) 2 at 26 K  

NASA Astrophysics Data System (ADS)

A high-resolution Fourier transform interferometer (Bruker IFS 120 HR) was combined with a uniform supersonic expansion produced by means of axisymmetric Laval nozzles. The geometry profile of the nozzle enabled us to work under precise thermodynamic and kinetic conditions. The effect of the cooling rate of different nozzles on cluster nucleation is illustrated. The experimental sensitivity was tested by recording the ? 5 band of (NO) 2 at 26 K.

Benidar, A.; Georges, R.; Le Doucen, R.; Boissoles, J.; Hamon, S.; Canosa, A.; Rowe, B. R.

2000-01-01

259

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

PubMed

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

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

2013-04-01

260

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

261

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

PubMed

Classical molecular dynamics simulations have been carried out for gaseous CO(2) starting from various anisotropic intermolecular potential energy surfaces. Through calculations for a large number of molecules treated as rigid rotors, the time evolution of the interaction-induced electric dipole vector is obtained and the Laplace transform of its autocorrelation function gives the collision-induced absorption rototranslational spectrum. The results are successfully compared with those of previous similar calculations before studies of the influences of the intermolecular potential and induced-dipole components are made. The calculated spectra show a significant sensitivity to anisotropic forces consistently with previous analyses limited to the spectral moments. The present results also demonstrate the importance of vibrational and back-induction contributions to the induced dipole. Comparisons between measured far infrared (0-250 cm(-1)) spectra at different temperatures and results calculated without the use of any adjustable parameter are made. When the best and more complete input data are used, the quality of our predictions is similar to that obtained by Gruszka et al. [Mol. Phys. 93, 1007 (1998)] after the introduction of ad hoc short-range overlap contributions. Our results thus largely obviate the need for such contributions the magnitudes of which remain questioned. Nevertheless, problems remain since, whereas good agreements with measurements are obtained above 50 cm(-1), the calculations significantly underestimate the absorption below, a problem which is discussed in terms of various possible error sources. PMID:21384978

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

2011-03-01

262

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2.  

PubMed

An extensive survey of the D(2) absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90,000-119,000 cm(-1) covers the full depth of the potential wells of the B (1)?(u)(+), B' (1)?(u)(+), and C (1)?(u) electronic states up to the D(1s) + D(2l) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ?0.35 cm(-1). Extended calibration methods are employed to extract line positions of D(2) lines at absolute accuracies of 0.03 cm(-1). The D (1)?(u) and B'' (1)?(u)(+) electronic states correlate with the D(1s) + D(3l]) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D(2). The observations are compared with previous studies, both experimental and theoretical. PMID:22779596

de Lange, Arno; Dickenson, Gareth D; Salumbides, Edcel J; Ubachs, Wim; de Oliveira, Nelson; Joyeux, Denis; Nahon, Laurent

2012-06-21

263

VUV Fourier-transform absorption study of the Lyman and Werner bands in D2  

NASA Astrophysics Data System (ADS)

An extensive survey of the D2 absorption spectrum has been performed with the high-resolution VUV Fourier-transform spectrometer employing synchrotron radiation. The frequency range of 90 000-119 000 cm-1 covers the full depth of the potential wells of the B 1?u+, B' 1?u+, and C 1?u electronic states up to the D(1s) + D(2l) dissociation limit. Improved level energies of rovibrational levels have been determined up to respectively v = 51, v = 13, and v = 20. Highest resolution is achieved by probing absorption in a molecular gas jet with slit geometry, as well as in a liquid helium cooled static gas cell, resulting in line widths of ~0.35 cm-1. Extended calibration methods are employed to extract line positions of D2 lines at absolute accuracies of 0.03 cm-1. The D 1?u and B'' 1?u+ electronic states correlate with the D(1s) + D(3l) dissociation limit, but support a few vibrational levels below the second dissociation limit, respectively, v = 0-3 and v = 0-1, and are also included in the presented study. The complete set of resulting level energies is the most comprehensive and accurate data set for D2. The observations are compared with previous studies, both experimental and theoretical.

de Lange, Arno; Dickenson, Gareth D.; Salumbides, Edcel J.; Ubachs, Wim; Oliveira, Nelson de; Joyeux, Denis; Nahon, Laurent

2012-06-01

264

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

265

Determination of vibration-rotation lines intensities from absorption Fourier spectra  

NASA Technical Reports Server (NTRS)

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

Mandin, J. Y.

1979-01-01

266

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

267

Europa's ultraviolet absorption band (260 to 320 nm). Temporal and spatial evidence from IUE  

SciTech Connect

An analysis of 33 IUE UV spectra of Europa, obtained from 1978 to 1982 for orbital phase angles of 21 to 343 deg, confirms that the Lane et al. (1981) absorption feature, centered at 280 nm, is most clearly revealed when 223-333 deg orbital phase angle spectra are ratioed to those nearest 90 deg. The feature's strength is noted to have persisted over the 5-year period studied, suggesting that no large endogenically or exogenically generated changes in surface sulfur dioxide concentration have occurred. These results further substantiate the Lane et al. hypothesis that the feature is due to the implantation of Io plasma torus-derived sulfur ions on the Europa trailing side's water-ice surface. 31 references.

Ockert, M.E.; Nelson, R.M.; Lane, A.L.; Matson, D.L.

1987-06-01

268

Optimizing organic photovoltaics using tailored heterojunctions: A photoinduced absorption study of oligothiophenes with low band gaps  

NASA Astrophysics Data System (ADS)

A power conversion efficiency of 3.4% with an open-circuit voltage of 1V was recently demonstrated in a thin film solar cell utilizing fullerene C60 as acceptor and a new acceptor-substituted oligothiophene with an optical gap of 1.77eV as donor [K. Schulze , Adv. Mater. (Weinheim, Ger.) 18, 2872 (2006)]. This prompted us to systematically study the energy- and electron transfer processes at the oligothiophene:fullerene heterojunction for a homologous series of these oligothiophenes. Cyclic voltammetry and ultraviolet photoelectron spectroscopy data show that the heterojunction is modified due to tuning of the highest occupied molecular orbital energy for different oligothiophene chain lengths, while the lowest unoccupied molecular orbital energy remains essentially fixed due to the presence of electron-withdrawing end groups (dicyanovinyl) attached to the oligothiophene. Use of photoinduced absorption (PA) allows the study of the electron transfer process at the heterojunction to C60 . Quantum-chemical calculations performed at the density functional theory and/or time-dependent density functional theory level and cation absorption spectra of diluted DCVnT provide an unambiguous identification of the transitions observed in the PA spectra. Upon increasing the effective energy gap of the donor-acceptor pair by increasing the ionization energy of the donor, photoinduced electron transfer is eventually replaced with energy transfer, which alters the photovoltaic operation conditions. The optimum open-circuit voltage of a solar cell is thus a trade-off between efficient charge separation at the interface and maximized effective gap. It appears that the open-circuit voltages of 1.0-1.1V in our solar cell devices have reached an optimum since higher voltages result in a loss in charge separation efficiency.

Schueppel, R.; Schmidt, K.; Uhrich, C.; Schulze, K.; Wynands, D.; Brédas, J. L.; Brier, E.; Reinold, E.; Bu, H.-B.; Baeuerle, P.; Maennig, B.; Pfeiffer, M.; Leo, K.

2008-02-01

269

Determination of glucose concentration in a scattering medium based on selected wavelengths by use of an overtone absorption band  

NASA Astrophysics Data System (ADS)

A method and device for measuring glucose concentration in a scattering medium have been developed. A spectral range of 800-1800 nm is considered for wavelength selection because of its deeper penetration into biological tissue and the presence of a glucose absorption band. An algorithm based on selected wavelengths is proposed to minimize interference from other components. The optimal distance between the light source and the detector for diffuse reflectance measurement minimizes the influence of medium scattering. The proposed algorithm and measuring device are tested with a solution containing milk with added glucose. Glucose concentrations between 0 and 2000 mg/dl are determined with a correlation coefficient of 0.977. We also investigate the influence of concentration variations of other substances such as water, hemoglobin, albumin, and cholesterol when they are mixed in a scattering medium.

Yoon, Gilwon; Amerov, Airat K.; Jeon, Kye Jin; Kim, Yoen-Joo

2002-03-01

270

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

271

Large-amplitude nightglow OH (8-3) band intensity and rotational temperature variations during a 24-hour period at 78 deg N  

Microsoft Academic Search

Results from a continuous 24-hour measurement of the OH (8-3) band emission in the nightglow at 78.4 deg N are reported. A mean temperature of 273 K and a mean band intensity of 596 R were observed. Extreme temperature variations were seen with amplitudes up to + or - 70 K from the mean. It is suggested that these variations

C. S. Deehr; G. G. Sivjee; H. K. Myrabo

1983-01-01

272

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

PubMed

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

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

2008-02-14

273

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

NASA Astrophysics Data System (ADS)

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

Heng, Hang; Yang, Li

2014-06-01

274

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

PubMed

Perovskite-based solar cells have recently been catapulted to the cutting edge of thin-film photovoltaic research and development because of their promise for high-power conversion efficiencies and ease of fabrication. Two types of generic perovskites compounds have been used in cell fabrication: either Pb- or Sn-based. Here, we describe the performance of perovskite solar cells based on alloyed perovskite solid solutions of methylammonium tin iodide and its lead analogue (CH3NH3Sn1-xPbxI3). We exploit the fact that, the energy band gaps of the mixed Pb/Sn compounds do not follow a linear trend (the Vegard's law) in between these two extremes of 1.55 and 1.35 eV, respectively, but have narrower bandgap (<1.3 eV), thus extending the light absorption into the near-infrared (?1,050 nm). A series of solution-processed solid-state photovoltaic devices using a mixture of organic spiro-OMeTAD/lithium bis(trifluoromethylsulfonyl)imide/pyridinium additives as hole transport layer were fabricated and studied as a function of Sn to Pb ratio. Our results show that CH3NH3Sn0.5Pb0.5I3 has the broadest light absorption and highest short-circuit photocurrent density ?20 mA cm(-2) (obtained under simulated full sunlight of 100 mW cm(-2)). PMID:24823301

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

2014-06-01

275

Incoherent broad-band cavity-enhanced absorption spectroscopy of the marine boundary layer species I2, IO and OIO.  

PubMed

The novel combination of incoherent broad-band cavity-enhanced absorption spectroscopy (IBBCEAS) and a discharge-flow tube for the study of three key atmospheric trace species, I(2), IO and OIO, is reported. Absorption measurements of I(2) and OIO at lambda=525-555 nm and IO at lambda=420-460 nm were made using a compact cavity-enhanced spectrometer employing a 150 W short-arc Xenon lamp. The use of a flow system allowed the monitoring of the chemically short-lived radical species IO and OIO to be conducted over timescales of several seconds. We report detection limits of approximately 26 pmol mol(-1) for I(2) (L=81 cm, acquisition time 60 s), approximately 45 pmol mol(-1) for OIO (L=42.5 cm, acquisition time 5 s) and approximately 210 pmol mol(-1) for IO (L=70 cm, acquisition time 60 s), demonstrating the usefulness of this approach for monitoring these important species in both laboratory studies and field campaigns. PMID:18654688

Vaughan, Stewart; Gherman, Titus; Ruth, Albert A; Orphal, Johannes

2008-08-14

276

Optimization of band structure and quantum-size-effect tuning for two-photon absorption enhancement in quantum dots.  

PubMed

The two-photon absorption, 2PA, cross sections of PbS quantum dots, QDs, are theoretically and experimentally investigated and are shown to be enhanced with increasing quantum confinement. This is in contrast to our previous results for CdSe and CdTe QDs where the reduced density of states dominated and resulted in a decrease in 2PA with a decrease in QD size. Qualitatively this trend can be understood by the highly symmetric distribution of conduction and valence band states in PbS that results in an accumulation of allowed 2PA transitions in certain spectral regions. We also measure the frequency nondegenerate 2PA cross sections that are up to five times larger than for the degenerate case. We use a k·p four-band envelope function formalism to model the increasing trend of the two-photon cross sections due to quantum confinement and also due to resonance enhancement in the nondegenerate case. PMID:21314162

Padilha, Lazaro A; Nootz, Gero; Olszak, Peter D; Webster, Scott; Hagan, David J; Van Stryland, Eric W; Levina, Larissa; Sukhovatkin, Vlad; Brzozowski, Lukasz; Sargent, Edward H

2011-03-01

277

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

278

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

PubMed Central

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

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

1995-01-01

279

Charge-Transfer Character of the Low-Energy Chl a Qy Absorption Band in Aggregated Light Harvesting Complexes II.  

PubMed

One of the key functions of the major light harvesting complex II (LHCII) of higher plants is to protect Photosystem II from photodamage at excessive light conditions in a process called "non-photochemical quenching" (NPQ). Using hole-burning (HB) spectroscopy, we investigated the nature of the low-energy absorption band in aggregated LHCII complexes - which are highly quenched and have been established as a good in vitro model for NPQ. Nonresonant holes reveal that the lowest energy state (located near 683.3 nm) is red-shifted by ?4 nm and significantly broader (by a factor of 4) as compared to nonaggregated trimeric LHCII. Resonant holes burned in the low-energy wing of the absorption spectrum (685-710 nm) showed a high electron-phonon (el-ph) coupling strength with a Huang-Rhys factor S of 3-4. This finding combined with the very low HB efficiency in the long-wavelength absorption tail is consistent with a dominant charge-transfer (CT) character of the lowest energy transition(s) in aggregated LHCII. The value of S decreases at shorter wavelengths (<685 nm), in agreement with previous studies (J. Pieper et al., J. Phys. Chem. B 1999, 103, 2422-2428), proving that the low-energy excitonic state is strongly mixed with the CT states. Our findings support the mechanistic model in which Chl-Chl CT states formed in aggregated LHCII are intermediates in the efficient excited state quenching process (M. G. Müller et al., Chem. Phys. Chem. 2010, 11, 1289-1296; Y. Miloslavina et al., FEBS Lett. 2008, 582, 3625-3631). PMID:24838007

Kell, Adam; Feng, Ximao; Lin, Chen; Yang, Yiqun; Li, Jun; Reus, Michael; Holzwarth, Alfred R; Jankowiak, Ryszard

2014-06-12

280

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

281

Calculation of the FH(CN-)-center absorption bands in CsCl  

NASA Astrophysics Data System (ADS)

The FH-center electron energy levels in CsCl(CN-) are calculated with use of a pseudopotential formalism where the model potential incorporates the point-ion potential, ion-size effects, and the interaction with the CN- finite-size permanent electric dipole. Electronic polarization and a radial A1 distortion of the nearest-neighbor cations are treated as perturbations. The presence of the CN- ion in the next-nearest-neighbor position to the vacancy reduces the point symmetry to C4v. When the dipole moment is neglected, the splitting of the FH(1) and FH(2) bands is due to the ion-size effects which are found to be negligible. The calculated splitting is 0.28 eV compared to the experimental value of 0.27 eV when the dipole moment is pointing toward the vacancy. Two-thirds of the splitting is attributed to the dipole's electric field gradient in the vacancy, and the remaining splitting is due to the difference in the localization of the two excited states. The electric field mixing of the S- and P-symmetry basis states is found to be negligible.

Gash, Philip W.

1986-10-01

282

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

283

Photodissociation dynamics of water in the second absorption band. II. Ab initio calculation of the absorption spectra for H2O and D2O and dynamical interpretation of ``diffuse vibrational'' structures  

Microsoft Academic Search

We calculated the absorption spectra of H2O and D2O in the second absorption band around 128 nm using a two-dimensional abinitio potential energy surface for the B˜(1A1) electronic state. Nonadiabatic coupling to the lower states A˜ and X˜ and the vibrational degree of freedom of the OH fragment are completely neglected. Despite these limitations the agreement with the measured spectra

Klaus Weide; Reinhard Schinke

1989-01-01

284

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

Microsoft Academic Search

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

D P Poulios; N P Bigelow; J P Spoonhower

285

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

Microsoft Academic Search

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

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

2000-01-01

286

Influence of the dopant concentration on the OH - absorption band in Fe-doped LiNbO 3 single-crystal fibers  

NASA Astrophysics Data System (ADS)

The growth of iron-doped single-crystal fibers of lithium niobate was performed by the laser heated pedestal growth technique for different Fe 2O 3 contents in the feed rods. The infra-red optical absorption spectra (OH - band) were investigated by IR transmission microscopy. To explain the evolution of the OH - ions concentration in the crystals, a model is proposed involving the partial dissociation of LiNbO 3 in the melt into Li 2O and Nb 2O 5. The constitution of the OH - absorption band is also discussed on the basis of the Nb-vacancy structural model of lithium niobate.

Cochez, M.; Ferriol, M.; Bourson, P.; Aillerie, M.

2003-02-01

287

Infrared absorption from OH ions adjacent to lithium acceptors in hydrothermally grown ZnO  

Microsoft Academic Search

An intense infrared absorption band has been observed in a hydrothermally grown ZnO crystal. At 12 K, the band peaks near 3577.3 cm-1 and has a half width of 0.40 cm-1, and at 300 K, the band peaks at 3547 cm-1 and has a half width of 41.3 cm-1. This absorption band is highly polarized, with its maximum intensity occurring

L. E. Halliburton; Lijun Wang; Lihua Bai; N. Y. Garces; N. C. Giles; M. J. Callahan; Buguo Wang

2004-01-01

288

Moments analysis of the optical absorption and magnetic circular dichroism in the A band of Pb2+ centres in KBr and RbCl  

Microsoft Academic Search

The optical absorption and the magnetic circular dichroism (MCD) in the A band of Pb2+ centres in KBr and RbCl have been measured over the temperature range 5-300K. The moments of the experimental lineshapes have been calculated up to the fourth moment for the absorption and up to the third moment for the dichroic spectra. From these data, the coupling

K. Schmitt; P. W. M. Jacobs; M. J. Stillman

1983-01-01

289

Collision-Induced Absorption of H 2–H 2and H 2–He in the Rotational and Fundamental Bands for Planetary Applications  

Microsoft Academic Search

In recent years there has been significant progress in theab initiocomputation and modeling of the collision-induced absorption in H2–H2and H2–He pairs in the rotovibrational and purely rototranslational bands covering 0–6000 cm?1at temperatures from 40 to 300K. Extensive experimental and theoretical results have been obtained in a number of laboratories regarding this absorption as a function of frequency and temperature. This

George Birnbaum; Aleksandra Borysow; Glenn S. Orton

1996-01-01

290

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

NASA Astrophysics Data System (ADS)

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

Nikolova, B. M.

1993-10-01

291

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

NASA Technical Reports Server (NTRS)

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

Zheng, Chunguang; Borysow, Aleksandra

1995-01-01

292

The correction of reflection intensities for incomplete absorption of high-energy X-rays in the CCD phosphor  

SciTech Connect

It is shown that incomplete absorption of the X-ray beam in the phosphor of an area detector causes an incident-angle dependence of the recorded X-ray intensities. An energy scan of a SMART-6000 CCD (charge-coupled device) phosphor using synchrotron radiation shows the correction to be of importance above about 17 keV. Intensities of single reflections, each collected several times at different angles of incidence on the phosphor surface, show a pronounced angle-dependence at shorter wavelengths. Both conventional structural refinement and multipole charge density studies confirm that an oblique-incidence correction leads to improved quality of the results. Atomic displacement parameters will be systematically biased when the correction is not applied. For a {lambda} = 0.394 {angstrom} data set, neglecting the correction gives rise to artifacts in the deformation density maps that are likely to lead to misinterpretation of the experimental results.

Wu, G.; Rodrigues, B.L.; Coppens, P. (SUNYB)

2009-03-24

293

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

294

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

Microsoft Academic Search

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

Amy Lawrence; Ben Young; Matthew Yarborough

2009-01-01

295

Annealing effects on InGaAsN\\/GaAs quantum wells analyzed using thermally detected optical absorption and ten band k-p calculations  

Microsoft Academic Search

The effects of thermal annealing for In0.25Ga0.75As1-yNy\\/GaAs multiquantum wells (MQWs) have been investigated through thermally detected optical absorption. The QW transition energies have been calculated by using a ten-band k-p model including the band anticrossing model for the description of the InGaAsN band gap variation. The modification of the In concentration profile due to In-Ga interdiffusion during thermal annealing is

T. Bouragba; M. Mihailovic; F. Reveret; P. Disseix; J. Leymarie; A. Vasson; B. Damilano; M. Hugues; J. Massies; J. Y. Duboz

2007-01-01

296

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

297

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

NASA Technical Reports Server (NTRS)

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

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

2000-01-01

298

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

299

RAMAN SCATTERING IN RESONANCE WITH THE ABSORPTION BAND OF THE F CENTRE IN ALKALI HALIDES : BREAKDOWN OF THE SCATTERING SELECTION RULES DUE OF THE SPIN ORBIT INTERACTION  

Microsoft Academic Search

We present the theory and the theoretical evaluations for the cross sections of the polarized Raman scattering in resonance with the F absorption bands of the F centres in alkali halides, characterized by a spin orbit interaction coupling coefficient A different from zero in the excited electronic states. We show that for all the polarizations of the incident and scattered

E. MULAZZI; M. F. BISHOP

1976-01-01

300

Absolute wavenumber measurements of 1-0, 2-0, HF and 2-0, H35Cl, H37Cl absorption bands  

Microsoft Academic Search

Fourier absorption spectra of HCl and HF at room temperature permitted to measure 87 absolute wavenumbers. The absolute observed position of the P(6) line of the 1-0 band of HF is not in agreement with a recent heterodyne determination [3]. It is found equal to 110 725 739 +\\/- 7.5 MHz.

G. Guelachvili

1976-01-01

301

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

302

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

SciTech Connect

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

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

2010-06-23

303

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

304

Influence of the nature of the absorption band on the potential performance of high molar extinction coefficient ruthenium(II) polypyridinic complexes as dyes for sensitized solar cells.  

PubMed

When tested in solar cells, ruthenium polypyridinic dyes with extended ? systems show an enhanced light-harvesting capacity that is not necessarily reflected by a high (collected electrons)/(absorbed photons) ratio. Provided that metal-to-ligand charge transfer bands, MLCT, are more effective, due to their directionality, than intraligand (IL) ?-?* bands for the electron injection process in the solar cell, it seems important to explore and clarify the nature of the absorption bands present in these types of dyes. This article aims to elucidate if all the absorbed photons of these dyes are potentially useful in the generation of electric current. In other words, their potentiality as dyes must also be analyzed from the point of view of their contribution to the generation of excited states potentially useful for direct injection. Focusing on the assignment of the absorption bands and the nature of the emitting state, a systematic study for a series of ruthenium complexes with 4,4'-distyryl-2,2'-dipyridine (LH) and 4,4'-bis[p-(dimethylamino)-?-styryl]-2,2'-bipyridine (LNMe(2)) "chromophoric" ligands was undertaken. The observed experimental results were complemented with TDDFT calculations to elucidate the nature of the absorption bands, and a theoretical model was proposed to predict the available energy that could be injected from a singlet or a triplet excited state. For the series studied, the results indicate that the percentage of MLCT character to the anchored ligand for the lower energy absorption band follows the order [Ru(deebpy)(2)(LNMe(2))](PF(6))(2) > [Ru(deebpy)(2)(LH)](PF(6))(2) > [Ru(deebpy)(LH)(2)](PF(6))(2), where deebpy is 4,4'-bis(ethoxycarbonyl)-2,2'-bipyridine, predicting that, at least from this point of view, their efficiency as dyes should follow the same trend. PMID:21627125

Gajardo, Francisco; Barrera, Mauricio; Vargas, Ricardo; Crivelli, Irma; Loeb, Barbara

2011-07-01

305

Judd-Ofelt analysis of the Er3+ (4f11) absorption intensities in Er3+-doped garnets  

NASA Astrophysics Data System (ADS)

Spectroscopic and laser properties of three different Er3+-doped garnet systems are characterized by employing the Judd-Ofelt (JO) analysis. The three garnet hosts are Y3Al5O12 (YAG), Y3Sc2Ga3O12 (YSGG), and Gd3Ga5O12 (GGG). The JO model has been applied to the room temperature absorption intensities of Er3+ (4f11) transitions to establish the so-called JO intensity parameters: ?2, ?4, and ?6 in the three garnet hosts. The intensity parameters are used to determine the radiative decay rates (emission probabilities of transitions) and branching ratios of the Er3+ transitions from the excited state J manifolds to the lower-lying J' manifolds. The predicted decay rates and branching ratios of these Er3+ transitions in YAG, YSGG, and GGG hosts are compared. From the radiative decay rates, the radiative lifetimes of the Er3+ excited states are determined in the three garnets and are also compared. We also report the spectroscopic quality factors, ?4/?6, obtained for the three garnets. The quantum efficiencies of the 4I13/2-->4I15/2 Er3+ transition in YAG, YSGG, and GGG are determined to be ~79%, 82%, and 85%, respectively.

Sardar, Dhiraj K.; Bradley, William M.; Perez, John J.; Gruber, John B.; Zandi, Bahram; Hutchinson, J. Andrew; Trussell, C. Ward; Kokta, Milan R.

2003-03-01

306

Interband, intraband, and excited-state direct photon absorption of silicon and germanium nanocrystals embedded in a wide band-gap lattice  

NASA Astrophysics Data System (ADS)

Embedded Si and Ge nanocrystals (NCs) in wide band-gap matrices are studied theoretically using an atomistic pseudopotential approach. Small clusters to large NCs containing the order of several thousand atoms are considered. Effective band-gap values as a function of NC diameter reproduce very well the available experimental and theoretical data. It is observed that the highest occupied molecular orbital for both Si and Ge NCs and the lowest unoccupied molecular orbital for Si NCs display oscillations with respect to size among the different irreducible representations of the C3v point group to which these spherical NCs belong. Based on this electronic structure, first, the interband absorption is thoroughly studied, which shows the importance of surface polarization effects that significantly reduce the absorption when included. This reduction is found to increase with decreasing NC size or with increasing permittivity mismatch between the NC core and the host matrix. Reasonable agreement is observed with the experimental absorption spectra where available. The deformation of spherical NCs into prolate or oblate ellipsoids is seen to introduce no pronounced effects for the absorption spectra. Next, intraconduction and intravalence band absorption coefficients are obtained in the wavelength range from far-infrared to visible region. These results can be valuable for the infrared photodetection prospects of these NC arrays. Finally, excited-state absorption at three different optical pump wavelengths, 532, 355, and 266nm are studied for 3 and 4nm diameter NCs. This reveals strong absorption windows in the case of holes and a broad spectrum in the case of electrons, which can especially be relevant for the discussions on achieving gain in these structures.

Bulutay, C.

2007-11-01

307

Absolute intensity measurements of the (11/1/0)II-00/0/0 band of (C-12)(O-16)2 at 5.2 microns  

NASA Technical Reports Server (NTRS)

A nonlinear least-squares fitting procedure has been used to derive absolute intensities for lines in the P, R, and Q branches of the (11/1/0)II-00/0/0 band of (C-12)(O-16)2 (band center = 1932/cm) from long-path 0.01/cm resolution laboratory spectra. The spectral data were recorded at room temperature and low pressure (less than 10 torr) with the Fourier transform spectrometer in the McMath solar telescope complex at Kitt Peak National Observatory. The observed line intensities were analyzed to derive the vibrational band intensity and F-factor coefficients. To obtain a good fit to the data, it was necessary to include terms in the expression for the F factor, which account for Coriolis-type and Fermi-type interactions and centrifugal distortion effects.

Rinsland, C. P.; Benner, D. C.; Richardson, D. J.; Toth, R. A.

1983-01-01

308

Diode laser measurements of intensities, N2-broadening, and self-broadening coefficients of lines of the nu2 band of 14N16O2  

Microsoft Academic Search

A diode laser spectrometer (resolution 0.0013 cm-1) was used to record, in the 12-mum region, high-quality spectra of the nu2 band of NO2. Using these spectra, it was possible to obtain the N2-broadening coefficients and an average self-broadening coefficient from measurements made for seven lines of this band. In addition, 30 single spin-component line intensities were measured. From them, through

V. Malathy Devi; Palash P. Das; A. Bano; K. Narahari Rao; J.-M. Flaud; C. Camy-Peyret; J.-P. Chevillard

1981-01-01

309

Large-Amplitude Nightglow OH (8-3) band intensity and rotational temperature Variations during a 24-hour period at 78°N  

Microsoft Academic Search

The authors report results from a continuous 24-hour measurement of the OH (8-3) band emission in the nightglow at 78.4°N. A mean temperature of 273K and a mean band intensity of 596 R were observed. Extreme temperature variations were seen with amplitudes up to ±70K from the mean. It is suggested that these variations are related to the passage of

H. K. Myrabø; C. S. Deehr; G. G. Sivjee

1983-01-01

310

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

NASA Astrophysics Data System (ADS)

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

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

311

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

NASA Astrophysics Data System (ADS)

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

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

312

Absorption spectrum and gain without inversion of a driven two-level atom with arbitrary probe intensity in a squeezed vacuum  

NASA Astrophysics Data System (ADS)

We examine the response of a coherently driven two-level atom interacting with a broadband squeezed vacuum to a probe beam of arbitrary intensity. The equations of motion for the reduced density matrix elements are numerically solved by nonperturbative matrix inversion methods. For large driving intensities, the absorption spectrum exhibits a number of multiphoton absorption peaks with increasing probe strength in a standard vacuum and in a squeezed vacuum with small photon numbers, while the multiphoton absorption peaks are wiped out for large squeezed photon numbers. Strong gain without inversion at line center can be obtained in the presence of the squeezed vacuum when the probe strength does not exceed the driving one. The absorption spectrum is phase sensitive. We also find the presence of remarkable, very narrow structures at line center. In general, the spectrum is symmetric when ?=0 and ? otherwise, it is asymmetric and displays a dispersivelike profile at line center.

Zhou, Peng; Swain, S.

1997-01-01

313

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

SciTech Connect

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

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

2006-06-01

314

Investigations of the spin-Hamiltonian parameters, optical absorption bands, and local structure for the tetragonal Cu2+ center in Cu2+-doped ZnCdO nanopowder  

NASA Astrophysics Data System (ADS)

The spin-Hamiltonian (or EPR) parameters of tetragonal Cu2+ octahedral centers in ZnCdO nanopowders are calculated from the high-order perturbation formulas based on the cluster approach. In these formulas, the contributions to spin-Hamiltonian parameters due to the admixture between the d orbitals of dn ion and the p orbitals of ligand ions via covalence effect are considered. The crystal field parameters are calculated from the superposition model and so the optical absorption bands (related to the crystal field energy levels) and local structure of Cu2+ octahedral centers in ZnCdO nanopowder are also studied. The calculated spin-Hamiltonian parameters and optical absorption bands are in reasonable agreement with the experimental values. The tetragonal elongation ?R (=R//?R?) of Cu2+ octahedron in ZnCdO nanopowder due to Jahn–Teller effect is acquired from the calculations. The results are discussed.

Feng, Wen-Lin; Wang, Ke; Zhao, Fen; Xue, Ji-Yuan

2014-06-01

315

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

NASA Astrophysics Data System (ADS)

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

Pommerol, A.; Schmitt, B.

316

Extrapolation of earth-based solar irradiance measurements to exoatmospheric levels for broad-band and selected absorption-band observations  

NASA Technical Reports Server (NTRS)

Techniques for extrapolating earth-based spectral band measurements of directly transmitted solar irradiance to equivalent exoatmospheric signal levels were used to aid in determining system gain settings of the Halogen Occultation Experiment (HALOE) sunsensor being developed for the NASA Upper Atmosphere Research Satellite and for the Stratospheric Aerosol and Gas (SAGE) 2 instrument on the Earth Radiation Budget Satellite. A band transmittance approach was employed for the HALOE sunsensor which has a broad-band channel determined by the spectral responsivity of a silicon detector. A modified Langley plot approach, assuming a square-root law behavior for the water vapor transmittance, was used for the SAGE-2 940 nm water vapor channel.

Reagan, John A.; Pilewskie, Peter A.; Scott-Fleming, Ian C.; Herman, Benjamin M.; Ben-David, Avishai

1987-01-01

317

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

PubMed

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

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

2012-05-14

318

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

SciTech Connect

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

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

2013-12-02

319

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

PubMed

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

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

2014-06-01

320

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

NASA Astrophysics Data System (ADS)

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

Dufréchou, Grégory; Granjean, Gilles; Bourguignon, Anne

2014-05-01

321

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

322

Temperature Dependence of Individual Absorptions Bands in Olivine: Implications for Inferring Compositions of Asteroid Surfaces from Spectra  

NASA Technical Reports Server (NTRS)

The temperature variations of individual absorptions in olivine are modeled and found to narrow, move slightly in position, and change in relative strength as predicted by theory. These thermal changes may be confused with compositional differences.

Sunshine, J. M.; Hinrichs, J. L.; Lucey, P. G.

2000-01-01

323

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

324

Fast, Narrow-Band Computer Model for Radiation Calculations  

Microsoft Academic Search

A fast, narrow-band computer model, FASTNB, which predicts the radiation intensity in a general nonisothermal and nonhomogeneous combustion environment, has been developed. The spectral absorption coefficients of the combustion products, including carbon dioxide, water vapor, and soot, are calculated based on the narrow-band model FASTNB provides an accurate calculation at reasonably high speed. Compared with Grosshandler's narrowband model, RADCAL, which

Zhenghua Yan; Göran Holmstedt

1997-01-01

325

Intensities and broadening coefficients for the Q branch of the 4nu-2 - nu-1 + nu-2 (471.511/cm) band of CO2  

NASA Technical Reports Server (NTRS)

Absolute intensities for the Q-branch of the 4nu-2 - nu-1 + nu-1/2 (20,003-11,101) band in CO2 were measured for the first time. Measurements were performed for lines Q10 to Q28, at temperatures ranging from 385 to 426 K, for pressures from 3 to 40 torr, using our long wavelength tunable diode laser spectrometer. The combination of tunable diode lasers, a White cell, and a blocked impurity band detector made it possible to obtain signal to noise ratios greater than 1000 in the 471/cm spectral region, with about 3 x 10 exp -4/cm spectral resolution. The band strength was found to be 8.6(2) x 10 exp -25 cm/molec at 296 K, and the Hermann-Wallis factor was determined. Comparison with the values listed in the HITRAN 92 data base are presented. Self-, N2- and O2-broadening coefficients were also measured.

Sirota, J. M.; Reuter, Dennis C.; Mumma, M. J.

1993-01-01

326

A new method for quantifying the intensity of the C=C band of dimethacrylate dental monomers in their FTIR and Raman spectra  

Microsoft Academic Search

The degree of conversion (DC) of methacrylate dental resins is typically determined by spectroscopically measuring the decrease of the vinyl (C=C) stretching band at 1640cm?1, ratioed before and after polymerization to an internal standard (aromatic ring quadrant stretching vibration (Ph)) at around 1609cm?1. While standard methods exist for measuring the intensity of the C=C and Ph peaks from the FTIR

Marc A. Gauthier; Ivan Stangel; Thomas H. Ellis; X. X. Zhu

2005-01-01

327

Solvatochromism in the visible absorption band of 4-dimethylamino-4?-nitroazobenzene in polystyrene and poly(vinyl acetate), and in model liquid solvents: Effects of temperature, medium polarity, and rigidity  

Microsoft Academic Search

Temperature-induced solvatochromism in the visible absorption band of 4-dimethylamino-4?-nitroazobenzene (diMANA) dissolved in polystyrene (PS) and poly(vinyl acetate) (PVAc), and in toluene and ethyl acetate used as model liquid solvents was investigated. In all solutions under study the absorption band maximum shifts to blue, and the magnitude of the transition moment slightly diminishes as temperature rises. In polymer solid solution the

B. Nadolski; P. Uzna?Ski; M. Kryszewski

1984-01-01

328

Diffuse interstellar bands towards o Per and ? Per  

NASA Astrophysics Data System (ADS)

Spectroscopic characteristics of interstellar matter vary strongly with the direction to the target star. Spectra of o Per and ? Per contain many prominent and weak diffuse interstellar bands as well as absorption lines of some identified interstellar atoms and molecules. Using echelle optical spectra of these bright and moderately reddened stars we selected well detectable diffuse interstellar bands (DIBs). We measured intensities of all well noticeable absorption features to compare them with their counterparts observed in spectra of the other target stars.

Debudej, A.; Kusiak, S.; Ozga, J.; Wszo?ek, B.

2012-03-01

329

New aspects of the photodissociation of water in the first absorption band: How strong is excitation of the first triplet state?  

NASA Astrophysics Data System (ADS)

We consider the possibility of the X~ 1A1-->3B1 excitation of water at wavelengths near 193 nm, i.e., in the red tail of the first absorption band. The corresponding excited-state potential-energy surface is calculated by quantum mechanical methods and the dynamics calculations are performed in the time-dependent representation. It is shown that an absorption cross section for exciting the triplet state 3B1, that at its maximum is about five hundred times (or more) smaller than the corresponding cross section for excitation of the 1B1 state, might explain the surprisingly small H+OD/D+OH branching ratio in the photodissociation of HOD at 193 nm measured by Plusquellic et al. (the foregoing paper). The singlet-triplet transition dipole moment estimated in this way also explains the unexpectedly small cross section ratio for H2O and D2O measured at 193 nm.

Schröder, Thomas; Schinke, Reinhard; Ehara, Masahiro; Yamashita, Koichi

1998-10-01

330

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

NASA Astrophysics Data System (ADS)

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

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

2011-08-01

331

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

332

On nature of the transient IR-absorption STE-like bands at 0.15–0.36 eV in alkali halides  

Microsoft Academic Search

New evidence is given that two classes (A and B) of the transient IR-absorption bands: (A) with max. at 0.15–0.36eV (in NaCl:I, NaBr, NaI, KCl:I, KBr:I, RbCl:I, RbBr:I), due to “on-centre self-trapped exciton” and (B) with max. at 0.27–0.36eV (in NaCl, KCl, KBr, RbCl), due to “shallow trapped electrons” or “bound polarons”, are caused by the same defect—shallow trapped electron

Valters Ziraps

2001-01-01

333

Wavelength-resolved optical extinction measurements of aerosols using broad-band cavity-enhanced absorption spectroscopy over the spectral range of 445-480 nm.  

PubMed

Despite the significant progress in the measurements of aerosol extinction and absorption using spectroscopy approaches such as cavity ring-down spectroscopy (CRDS) and photoacoustic spectroscopy (PAS), the widely used single-wavelength instruments may suffer from the interferences of gases absorption present in the real environment. A second instrument for simultaneous measurement of absorbing gases is required to characterize the effect of light extinction resulted from gases absorption. We present in this paper the development of a blue light-emitting diode (LED)-based incoherent broad-band cavity-enhanced spectroscopy (IBBCEAS) approach for broad-band measurements of wavelength-resolved aerosol extinction over the spectral range of 445-480 nm. This method also allows for simultaneous measurement of trace gases absorption present in the air sample using the same instrument. On the basis of the measured wavelength-dependent aerosol extinction cross section, the real part of the refractive index (RI) can be directly retrieved in a case where the RI does not vary strongly with the wavelength over the relevant spectral region. Laboratory-generated monodispersed aerosols, polystyrene latex spheres (PSL) and ammonium sulfate (AS), were employed for validation of the RI determination by IBBCEAS measurements. On the basis of a Mie scattering model, the real parts of the aerosol RI were retrieved from the measured wavelength-resolved extinction cross sections for both aerosol samples, which are in good agreement with the reported values. The developed IBBCEAS instrument was deployed for simultaneous measurements of aerosol extinction coefficient and NO(2) concentration in ambient air in a suburban site during two representative days. PMID:23320530

Zhao, Weixiong; Dong, Meili; Chen, Weidong; Gu, Xuejun; Hu, Changjin; Gao, Xiaoming; Huang, Wei; Zhang, Weijun

2013-02-19

334

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

PubMed

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

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

2013-07-01

335

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

336

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

SciTech Connect

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

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

2012-06-01

337

A complete study of the line intensities of four bands of CO2 around 1.6 and 2.0 ?m: A comparison between Fourier transform and diode laser measurements  

NASA Astrophysics Data System (ADS)

Atmospheric carbon dioxide is a key specie for the Earth climate. Two spectral windows at 1.6 ?m and 2.0 ?m are of particular interest for the in situ and remote monitoring of carbon dioxide from satellite, balloon or airborne platforms using infrared absorption spectroscopy. A precise knowledge of the line strengths is a prerequisite for an accurate concentration retrieval. In this paper, we have revisited in the laboratory the (3001)III?(0000) and (3001)II ? (0000) bands of CO2 near 1.6 ?m and the (2001)III ? (0000) and (2001)II ? (0000) bands near 2.0 ?m by implementing both a high-resolution Connes-type Fourier-transform spectrometer and a tunable diode laser spectrometer equipped with several telecommunication-type semiconductor laser devices. Approximately 200 (respectively 18) transitions of CO2 have been carefully investigated in spectra recorded with the FT spectrometer (respectively with the tunable diode laser spectrometer). The intensity measurements achieved with both instruments are thoroughly compared to previous instrumental determinations, ab-initio calculations and available atmospheric molecular database.

Régalia-Jarlot, L.; Zéninari, V.; Parvitte, B.; Grossel, A.; Thomas, X.; von der Heyden, P.; Durry, G.

2006-09-01

338

Molecular Line Absorption in a Scattering Atmosphere. Part II: Application to Remote Sensing in the O2 A band  

Microsoft Academic Search

This paper explores the feasibility of using O 2 A-band reflectance spectra in the retrieval of cloud optical and physical properties. Analyses demonstrate that these reflection spectra are sensitive to optical properties of clouds such as optical depth t c and phase function, vertical profile information including cloud-top pressure, pressure thickness, and the surface albedo. An estimation method is developed

Andrew K. Heidinger; Graeme L. Stephens

2000-01-01

339

Saturation Processes in Principal Channel of Dye Solutions with Coincident Absorption and Emission Bands-Part II  

Microsoft Academic Search

A phase response of dye solution and saturation processes can be taken into consideration to describe a nonlinear medium. Nonlinear medium can be modeled by a typical three-level configuration (S0-S1-S2), for which the transition of molecules in principal channel (S0-S1) are occurred by the light fields of intensity I12 at frequency ?0. At the same time, light fields with intensity

Jihad S. M. Addasi; Mohanad Jadan; Saleh A. Abushendi

2007-01-01

340

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

SciTech Connect

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

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

2013-12-16

341

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

342

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

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

343

Sub-Band Gap Absorption in As-Deposited and Annealed nc-CdSe Thin Films Using Constant Photocurrent Method (CPM)  

NASA Astrophysics Data System (ADS)

Nanocrystalline CdSe thin films have been prepared by thermal vaccum evaporation technique using Inert Gas Condensation method using Argon as inert gas. XRD confirms the crystalline cubic nature of nc-CdSe thin films. The optical band gap is calculated for as deposited nc-CdSe and it comes out to be 2.1 eV. CPM has been used to measure sub-band gap absorption in nanocrystalline CdSe thin films. The thin films of nc-CdSe have been annealed at 80 °C for one hour and sub-bandgap absorption in annealed samples has also been calculated. Slope of Urbach tail which is a measure of disorder in both as deposited and annealed samples has been calculated. In the case of as deposited nc-CdSe thin films, Urbach slope is 354 meV. It decreases to the value 198 meV after annealing which shows structural disorder decreases after annealing.

Sharma, Kriti; Al-Kabbi, A. S.; Singh, Baljinder; Saini, G. S. S.; Tripathi, S. K.

2011-12-01

344

High-gradient S-band linac for initial acceleration of the SLC (SLAC linear collider) intense positron bunch.  

National Technical Information Service (NTIS)

Although short lengths of S-band standing-wave, disk-loaded waveguide have been successfully RF-processed to accelerating gradients equivalent to about 175 MeV/m in a traveling-wave structure, the 20 MeV/m gradient of the SLC 50 GeV linac has been the hig...

J. E. Clendenin S. D. Ecklund H. A. Hoag

1989-01-01

345

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

346

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

347

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

348

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

PubMed

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

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

2013-09-13

349

A Multi-Band Analytical Algorithm for Deriving Absorption and Backscattering Coefficients from Remote-Sensing Reflectance of Optically Deep Waters  

NASA Technical Reports Server (NTRS)

A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.

Lee, Zhong-Ping; Carder, Kendall L.

2001-01-01

350

Polarizability tensor theory by Green's function matrix: Circular dichroism and ultraviolet absorption band shape calculations of cyclo(Gly-Pro-Gly-D-Ala-Pro) having ?- and ?-turns  

NASA Astrophysics Data System (ADS)

In a recent paper, we represented the partial polymer polarizability tensor equation in terms of partial monomer polarizability tensors and intermonomer unit dipole-dipole interaction tensors. Here, we represent the same equation in terms of a partial polymer Green's function matrix equation being constructed from partial monomer Green's matrix elements and intermonomer interaction energies. We also show that the circular dichroism (CD) and ultraviolet (UV) absorption band shape functions bear a strong resemblance to DeVoe's scalar representation of the band shape functions, which we have rewritten, using our terminology, in terms of the three terms describing the dipole-dipole coupling, the electromagnetic coupling, and the intrinsic optical activity. The latter is capable of incorporating the one-electron mechanism. The present tensor theory offers five advantages. First, for describing physical phenomena, the tensor form may be more convenient than the scalar forms. Second, in both the partial polarizability tensor theory and DeVoe's partial scalar polarizability theory, it is possible to place different transition dipoles within each monomer in different positions, whereas this is not possible in the usual Fano-DeVoe types of polarizability theories. Third, the intermonomer interaction energy can be represented readily either by the dipole approximation or by the monopole approximation. Fourth, various types of intermonomer interactions can be taken into account flexibly by making use of the Green's matrix equation. Fifth, an efficient algorithm can be derived by reducing the matrix size by the factor 3×3 as compared with the partial polymer polarizability matrix tensor equation. By employing the dipole positions already known or discussed by other authors for the two n?* and ??* transitions within each amide monomer, the theory has been applied to the semiempirical calculations of the CD and UV absorption band shapes of a cyclic pentapeptide, cyclo (Gly-Pro-Gly-D-Ala-Pro), with comments on the adaptability of simplified parameterization.

Ito, Hirotoshi

1998-01-01

351

Study of electronic structures and absorption bands of BaMgF4 crystal with F colour centre  

Microsoft Academic Search

The electronic structures of BaMgF4 crystals containing an F colour centre are studied within the framework of the fully relativistic self-consistent Direc---Slater theory, using a numerically discrete variational (DV-Xalpha) method. It is concluded from the calculated results that the energy levels of the F colour centre are located in the forbidden band. The optical transition energy from the ground state

Ling-Ling Kang; Ting-Yu Liu; Qi-Ren Zhang; Ling-Zhi Xu; Fei-Wu Zhang

2011-01-01

352

Origin of the 420 nm Absorption Band and Effect of Doping Fluorine in PbWO4 Crystals  

Microsoft Academic Search

The electronic structures for three types of PbWO4 (PWO) crystals, the perfect PWO, the PWO containing lead vacancy (PWO-VPb) and fluorine doped PWO crystal (F-:PWO), are systematically studied within the framework of density functional theory. The computational results show that the Pb 6s state situates below the valence band so that Pb2+ ions are unable to trap holes forming Pb3+

Kun Tao; Qi-Ren Zhang; Ting-Yu Liu; Fei-Wu Zhang

2005-01-01

353

Optical properties of diamond film deposited by CVD of Freon: Studies on mechanical properties from the absorption band tail  

Microsoft Academic Search

Polycrystalline diamond films were deposited on quartz (fused silica), glass and Si substrates by chemical vapour deposition of Freon 22 (CHF2Cl ? 10 vol%) and hydrogen with substrate temperature in the range 525–725 K. Films were sp3 rich (85–95%) with high band gap (Eg ? 3.7–3.95 eV on glass and Eg ? 4.5–5.5 eV on quartz). The strain and stress

R. Chakrabarti; K. Chakrabarti; A. B. Maity; S. Chaudhuri; A. K. Pal

1997-01-01

354

Uniform Supersonic Expansion for FTIR Absorption Spectroscopy: The nu(5) Band of (NO)(2) at 26 K.  

PubMed

A high-resolution Fourier transform interferometer (Bruker IFS 120 HR) was combined with a uniform supersonic expansion produced by means of axisymmetric Laval nozzles. The geometry profile of the nozzle enabled us to work under precise thermodynamic and kinetic conditions. The effect of the cooling rate of different nozzles on cluster nucleation is illustrated. The experimental sensitivity was tested by recording the nu(5) band of (NO)(2) at 26 K. Copyright 2000 Academic Press. PMID:10712875

Benidar; Georges; Le Doucen R; Boissoles; Hamon; Canosa; Rowe

2000-01-01

355

Enhanced microwave absorption of ZnO-coated planar anisotropy carbonyl-iron particles in quasimicrowave frequency band  

Microsoft Academic Search

For the aim of thin electromagnetic wave absorbers used in quasimicrowave frequency band, planar anisotropy carbonyl-iron (PACI) particles coated with ZnO nanoshells were prepared by ball milling technique and chemical precipitation method. Compared with the as-milled PACI\\/paraffin composite, lower dielectric constant was obtained for the composite containing PACI at ZnO particles, and hence a dramatic enhancement of reflection loss (RL)

Rui Han; Xiang-hua Han; Liang Qiao; Tao Wang; Fa-shen Li

2011-01-01

356

The Valence Band Structure of Tellurium. III. The Landau Levels  

Microsoft Academic Search

The Landau levels are calculated for two upper valence bands of tellurium. The peak positions and intensities of the cyclotron resonance and of the inter-valence band magneto-absorption are calculated. Effects of the \\\\mbi{k}-linear terms on them are elucidated. For the magnetic field perpendicular to the c-axis, the Landau levels of the uppermost valence band are doubly degenerate at low magnetic

Kenji Nakao; Takao Doi; Hiroshi Kamimura

1971-01-01

357

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

358

Nitrogen dissociation degree in the diffusion region of a helicon plasma source obtained by atomic lines to molecular band intensities ratio  

SciTech Connect

Estimates of the dissociation degree in the diffusion region of a nitrogen helicon plasma source based on optical emission spectroscopy and Langmuir probe measurements are presented. The estimation procedure relies on measurements of the ratios of the intensities of the atomic triplet 3p {sup 4}S{sup 0}{yields}3s {sup 4}P (742.36, 744.23, and 746.83 nm) to the intensity of the 4-2 band of the first positive system (A {sup 3}{sigma}{sub u}{sup +}{yields}B {sup 3}{pi}{sub g}) at 750.39 nm and the measured relative vibrational distribution of the B {sup 3}{pi}{sub g} state. The electron energy distribution function, obtained from the second derivative of the Langmuir probe characteristic, and published excitation cross sections are used to calculate the electron-impact excitation rate coefficients--which are then compared to the atomic line and molecular band intensities to calculate the dissociation degree. For two distinct operating regimes, capacitively and inductively coupled, dissociation fractions of 5% and 13% are obtained in the expansion region of a 10 mTorr, 500 W, 10.74 MHz helicon generated nitrogen plasma. The dissociation degree results suggest that the helicon source can provide excited molecular species for plasma assisted molecular beam epitaxy of III-group nitrides.

Biloiu, Costel; Scime, Earl E.; Biloiu, Ioana A.; Sun, Xuan [Varian Semiconductor Equipment Associates, 35 Dory Road, Gloucester, Massachusetts 01930 (United States); Physics Department, West Virginia University, Morgantown, West Virginia 26506 (United States); Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2007-09-01

359

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

360

Ultraviolet absorption spectrum of HOCl  

NASA Technical Reports Server (NTRS)

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

Burkholder, James B.

1993-01-01

361

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

362

Infrared line intensities of chlorine monoxide  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

363

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

364

Optical absorption of tetraphenylporphyrin thin films in UV-vis-NIR region  

NASA Astrophysics Data System (ADS)

The optical absorption of thermally evaporated tetraphenylporphyrin (TPP) in the UV-vis-NIR region have been studied. The absorption spectra recorded in the UV-vis region for the as deposited and annealed films showed different absorption bands, namely the Soret(B) at region 360-490 nm, Q-band region consist of four bands in the region 500-720 nm and two other bands labeled N and M in UV region. The Soret band always shows its characteristic effect splitting in all the TPP thin films and the effect of annealing on the intensities of these components have been observed. The spectra of the infrared absorption allow characterization of vibrational modes for the powder, as deposited and annealed thin films. Some of the optical absorption parameters, namely molar extinction coefficient, ?, half band width, ? ?, electronic dipole strength, q2 and oscillator strength, f, of the principle optical transitions have also been evaluated.

El-Nahass, M. M.; Zeyada, H. M.; Aziz, M. S.; Makhlouf, M. M.

2005-11-01

365

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

366

Solvation effects in complexation reactions. II. Solvatochromism and the nature of the absorption bands in the electronic spectra of charge transfer complexes between iodine and group VIA heteroorganic compounds  

SciTech Connect

Dipropyl sulfide, diphenyl sulfide, tert-butyl phenyl sulfide, tert-butyl phenyl selenide and diethyl selenide form 1:1 Mulliken complexes with iodine in the aprotic solvents studied with the heteroatom as the active coordination site. The proportionality of the solvatochromic shifts of the long-wavelength band of the complexes to the shifts of the absorption band of free iodine in the noncoordinating solvents and the linear relationship of the long-wavelength band shifts with the change in the complexation enthalpy indicates the iodine origin of the long-wavelength band.

Safin, D.K.; Chmutova, G.A.

1986-05-10

367

Infrared absorption of explosive molecule vapors  

Microsoft Academic Search

Infrared absorption spectra have been obtained for the high explosive molecules TNT, RDX, and PETN in the vapor phase. Integrated band strengths were measured for the symmetric and antisymmetric -NO2 vibrations in each of these molecules. Ab initio calculations of vibrational frequencies and intensities were carried out for comparison with the experimental data. Previous measurements of the heats of vaporization

James Janni; Brian D Gilbert; R. W Field; Jeffrey I Steinfeld

1997-01-01

368

High intensity light propagation in InAs  

NASA Astrophysics Data System (ADS)

The authors present their experimental and theoretical results on nonlinear absorption of light in InAs. The nonlinear variation of output intensity as a function of input intensity and time are calculated by solving four coupled rate equations simultaneously. All required quantities, including two-photon absorption, free-carrier absorption, Auger and radiative recombination lifetimes, and intrinsic carrier densities, have been obtained from the underlying band structures. The calculated thickness and energy-dependent output intensities in InAs agree very well with the values measured in their pump-probe experiments.

Krishnamurthy, Srinivasan; Yu, Zhi Gang; Guha, Shekhar; Gonzalez, Leo

2006-10-01

369

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

Microsoft Academic Search

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

Adrián Montoya; Ricardo Pesse

370

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

371

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

372

Highly ordered monolayer/bilayer TiO2 hollow sphere films with widely tunable visible-light reflection and absorption bands.  

PubMed

Monolayer and bilayer TiO2 hollow hemisphere/sphere (THH/THS) films consisting of highly ordered hexagonal-patterned THHs/THSs with thin shells of ~10 nm and different diameters of ~170 and ~470 nm have been prepared by templating of two-dimensional polystyrene sphere (PS) assembly films coupled with TiO2 sputtering/wet coating approaches. Owing to their precisely adjustable structural parameters, such as THH/THS shape and diameter as well as film layer thickness, the prepared THH/THS films exhibit widely tunable visible-light reflection and absorption bands, i.e. from 380 to 850 nm for reflection and 390 to 520 nm for absorption, respectively. The mechanism of the novel optical behaviors of the THH/THS films has been discussed in depth, combined with some calculations according to Bragg's law. In addition, photocatalytic experiments of RhB degradation employing the THH/THS films as recyclable catalysts have been conducted. The THH/THS films with controlled structures and precisely tunable optical properties are attractive for a wide range of applications, such as recyclable catalysts for photocatalysis, efficient oxide electrodes or scattering layers for solar cells, gas-permeable electrode materials for high-performance sensors and so on. PMID:23636636

Li, Jie; Qin, Yao; Jin, Chao; Li, Ying; Shi, Donglu; Schmidt-Mende, Lukas; Gan, Lihua; Yang, Jinhu

2013-06-01

373

A Study of the ? 1 Fundamental and ? 1 + ? 6 ? ? 6 Hot Band of 12CF 379Br Using the Saturated Absorption Technique  

NASA Astrophysics Data System (ADS)

This paper presents a study of the spectroscopy of 12CF 379Br using the Doppler-free saturated absorption technique. Many lines in the ? 1 fundamental and ? 1 + ? 6 ? ? 6 hot hand of this molecule have been recorded using the 9-?m band of a carbon dioxide laser. The absolute frequencies of the linecenters of these absorptions have been measured to an accuracy of ±25 kHz, using frequencies calibrated against a 4.3-?m fluorescence lock. Hyperfine structure due to the Br nucleus has been resolved, the splittings between individual quadrupole components being measured to a precision of about ±5 kHz. Determination of these splittings provided the means for assignment of many of the lines when reference was made to a concurrent infrared-radiofrequency double resonance experiment. The saturation data were fitted to a vibration-rotation Hamiltonian including centrifugal terms up to sextic. to which was added a hyperfine Hamiltonian based on the one derived by Aliev and Hougen.

Godwin, D. P.; Gray, A. J.; Butcher, R. J.

1993-03-01

374

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

PubMed

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

Sobu?, Jan; Zió?ek, Marcin

2014-07-21

375

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

NASA Astrophysics Data System (ADS)

BaTiO 3 powders are prepared by sol-gel method. The carbonyl iron powder is prepared via thermal decomposition of iron pentacarbonyl. Then BaTiO 3-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 BaTiO 3/carbonyl iron on the microwave loss properties of the composites is investigated. A possible microwave absorbing mechanism of BaTiO 3-carbonyl iron composite has been proposed. The BaTiO 3-carbonyl iron composite can find applications in suppression of electromagnetic interference, and reduction of radar signature.

Rui-gang, Yang

2011-07-01

376

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

377

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

NASA Astrophysics Data System (ADS)

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

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

1990-01-01

378

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

379

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

380

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

381

Measurements of the ClO radical vibrational band intensity and the ClO + ClO + M reaction product  

NASA Technical Reports Server (NTRS)

There is considerable interest in the kinetics and concentrations of free radicals in the stratosphere. Chlorine monoxide is a critically important radical because of its role in catalytic cycles for ozone depletion. Depletion occurs under a wide variety of conditions including the Antarctic spring when unusual mechanisms such as the BrO sub x/ClO sub x, ClO dimer (Cl sub 2 O sub 2), and ClO sub x/HO sub x cycles are suggested to operate. Infrared spectroscopy is one of the methods used to measure ClO in the stratosphere (Menzies 1979 and 1983; Mumma et al., 1983). To aid the quantification of such infrared measurements, researchers measured the ClO ground state fundamental band intensity.

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

1988-01-01

382

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

383

Highly ordered monolayer/bilayer TiO2 hollow sphere films with widely tunable visible-light reflection and absorption bands  

NASA Astrophysics Data System (ADS)

Monolayer and bilayer TiO2 hollow hemisphere/sphere (THH/THS) films consisting of highly ordered hexagonal-patterned THHs/THSs with thin shells of ~10 nm and different diameters of ~170 and ~470 nm have been prepared by templating of two-dimensional polystyrene sphere (PS) assembly films coupled with TiO2 sputtering/wet coating approaches. Owing to their precisely adjustable structural parameters, such as THH/THS shape and diameter as well as film layer thickness, the prepared THH/THS films exhibit widely tunable visible-light reflection and absorption bands, i.e. from 380 to 850 nm for reflection and 390 to 520 nm for absorption, respectively. The mechanism of the novel optical behaviors of the THH/THS films has been discussed in depth, combined with some calculations according to Bragg's law. In addition, photocatalytic experiments of RhB degradation employing the THH/THS films as recyclable catalysts have been conducted. The THH/THS films with controlled structures and precisely tunable optical properties are attractive for a wide range of applications, such as recyclable catalysts for photocatalysis, efficient oxide electrodes or scattering layers for solar cells, gas-permeable electrode materials for high-performance sensors and so on.Monolayer and bilayer TiO2 hollow hemisphere/sphere (THH/THS) films consisting of highly ordered hexagonal-patterned THHs/THSs with thin shells of ~10 nm and different diameters of ~170 and ~470 nm have been prepared by templating of two-dimensional polystyrene sphere (PS) assembly films coupled with TiO2 sputtering/wet coating approaches. Owing to their precisely adjustable structural parameters, such as THH/THS shape and diameter as well as film layer thickness, the prepared THH/THS films exhibit widely tunable visible-light reflection and absorption bands, i.e. from 380 to 850 nm for reflection and 390 to 520 nm for absorption, respectively. The mechanism of the novel optical behaviors of the THH/THS films has been discussed in depth, combined with some calculations according to Bragg's law. In addition, photocatalytic experiments of RhB degradation employing the THH/THS films as recyclable catalysts have been conducted. The THH/THS films with controlled structures and precisely tunable optical properties are attractive for a wide range of applications, such as recyclable catalysts for photocatalysis, efficient oxide electrodes or scattering layers for solar cells, gas-permeable electrode materials for high-performance sensors and so on. Electronic supplementary information (ESI) available: Raman spectrum and XRD pattern of the THH films (Fig. S1), detailed calculation of reflection and extinction peaks through BL THS film-450 (S1) and multiple views of geometric parameters of BL THS film-450 (Fig. S2). See DOI: 10.1039/c3nr00778b

Li, Jie; Qin, Yao; Jin, Chao; Li, Ying; Shi, Donglu; Schmidt-Mende, Lukas; Gan, Lihua; Yang, Jinhu

2013-05-01

384

Infrared absorption of explosive molecule vapors  

NASA Astrophysics Data System (ADS)

Infrared absorption spectra have been obtained for the high explosive molecules TNT, RDX, and PETN in the vapor phase. Integrated band strengths were measured for the symmetric and antisymmetric -NO 2 vibrations in each of these molecules. Ab initio calculations of vibrational frequencies and intensities were carried out for comparison with the experimental data. Previous measurements of the heats of vaporization of these materials were checked using the temperature dependence of infrared band intensities. Measurements were also carried out on ammonium nitrate; in this case, only the decomposition products NH 3, HNO 3, and N 2O were observed in the vapor phase in equilibrium with the solid.

Janni, James; Gilbert, Brian D.; Field, R. W.; Steinfeld, Jeffrey I.

1997-08-01

385

The relation between the specific absorption rate and electromagnetic field intensity for heterogeneous exposure conditions at mobile communications frequencies.  

PubMed

The relation between the incident electromagnetic field strength and both the whole-body and the local specific absorption rate (SAR) was investigated for typical heterogeneous exposure scenarios for frequencies relevant for mobile communication. The results were compared to results from plane wave exposure. Heterogeneous exposure arises from multiple path propagation of the electromagnetic waves to the location of interest. It is shown that plane wave exposure does not represent worst-case exposure conditions. When the electric field strength arising at plane wave exposure is compared to the electric field strength averaged over the volume of the human body occurring during multipath exposure, 12% of all heterogeneous cases examined represent worse exposure conditions than plane wave exposure for whole-body exposure at 946 MHz, 15% at 1840 MHz, and 22% at 2140 MHz. The deviation between plane wave and heterogeneous whole-body SAR ranges from -54% to 54%. For partial-body SAR averaged over 10 g of tissue, a range from -93% to 209% was found when comparing multiple wave exposure to single incoming plane waves. The investigations performed using the Visible Human as phantom showed that the basic restrictions are met as long as the reference levels are not exceeded. However, this must not be necessarily the case when different phantoms are used to perform similar investigations because recent studies demonstrated that reference levels might not be conservative when phantoms of children are used. Therefore, the results of this work indicate the need to extend the investigations to numerical simulations with additional human phantoms representing parts of the human population having different anatomy and morphology compared to the phantom used within the frame of this project. This also applies to phantoms of children. PMID:19551765

Neubauer, Georg; Preiner, Patrick; Cecil, Stefan; Mitrevski, Niki; Gonter, Johannes; Garn, Heinrich

2009-12-01

386

Absorption spectra, near-field intensity and microscopic cross section of RbTiOPO4 channel waveguide formed by ion implantation  

NASA Astrophysics Data System (ADS)

We report on optical channel waveguide in RbTiOPO4 crystal produced by photographic masking and following direct C3+ ion implantation at 6.0 MeV with a fluence of 5 × 1013 ions/cm2. The absorption spectra show that there are fewer point defects in the waveguide region, forming "crystal waveguide". The bright near field intensity distribution of the transverse-electric mode indicate that the light can be guided in a well confined way almost without leakage. Considering the Fresnel reflection at the air-crystal interface is about 15%, we obtained a loss of 1.7 dB/cm for the channel waveguide at wavelength of 633 nm.

Wang, Liang-Ling; Cui, Xiao-Jun

2012-06-01

387

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

NASA Astrophysics Data System (ADS)

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

Puri, Sanjiv

2014-07-01

388

Effect of Yb3+ doping on upconversion emission intensity and mechanism in Er3+\\/Yb3+-codoped fluorozirconate glasses under 800 nm excitation  

Microsoft Academic Search

Er3+ singly- and Er3+\\/Yb3+-codoped fluorozirconate glasses were prepared. The upconversion emission intensities of the Er3+ ion around both 550 and 660 nm were measured under 800 nm excitation. The absorption band of the Yb3+ ion is located around 980 nm. Though the absorption band of Yb3+ does not interact directly with the incident light at 800 nm, both upconversion intensities

M. Tsuda; K. Soga; H. Inoue; S. Inoue; A. Makishima

1999-01-01

389

Properties of the 800-nm luminescence band in neutron-irradiated magnesium oxide crystals  

NASA Astrophysics Data System (ADS)

We present results on the luminescence at 800 nm which occurs upon excitation of the 573-nm optical absorption band attributed to an aggregate defect in neutron-irradiated MgO crystals both pure and doped. The study was undertaken to evaluate the suitability of this luminescence for a tunable laser. Absorption, luminescence, and excitation spectra were measured before and after isochronal annealing, with the goal of optimizing the luminescence intensity and stability of the responsible defect, and reducing the background absorption in the crystal. The emission intensity is highest after annealing at ~550 K independent of dose. A thermally induced absorption band at 565 nm, which emerges at ~550 K, does not contribute to the emission at 800 nm. Under low-intensity continuous excitation, the 573-nm absorption band is not susceptible to photoconversion. However, when pumped with high-intensity laser light, the band exhibits a decay which recovers within 0.5 s. The luminescence has a single-exponential decay time of 15.5 ns at room temperature, and the band shape remains essentially constant throughout the decay. Tests for laser action using pulsed and cw pump lasers were unsuccessful at 77 and 300 K.

Gonzalez, R.; Chen, Y.; Sebek, R. M.; Williams, G. P., Jr.; Williams, R. T.; Gellermann, W.

1991-03-01

390

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

391

Role of oxygen in reactions of photoconversion of protein molecules irradiated in the region of 'L a and 'L b bands of tryptophanyl absorption spectrum  

Microsoft Academic Search

nis predominant [i, 2]. The absorption spectrum of tryptophan in the near UV region is due to two electronic transitions, 'L a and 'L b . In the spectral range of ~ > 300-305 nm the protein absorption is determined exclusively by the 'L a oscillator [3-5] which is more subjected to intra- and intermolecular interactions than the 'Lb transition

V. A. Mostovnikov; G. R. Mostovnikova; A. I. Zhdanovich; V. Yu. Plavskii; S. A. Tret'yakov

1988-01-01

392

Fast, narrow-band computer model for radiation calculations  

SciTech Connect

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

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

1997-01-01

393

Mn-related absorptive optical nonlinearity and bistability in Zn 1-xMn xSe  

NASA Astrophysics Data System (ADS)

ZnMnSe exhibits a strong nonlinear absorption related to Manganese ions. This absorption is easily bleached when the another narrow-band laser with high intensity illuminates the crystals. The first observation of the absorptive optical bistability is observed in a wider range of excitation power density and excitation wavelength. It is thought that the bistable effect is attributed to the bleaching of absorption concerning Mn energy bands combined with the positive-feedback provided by the light reflection at the perfect crystal surfaces.

Dou, K.; Huang, S. H.; Yu, J. Q.; Qin, W. P.; Jin, C. M.; Zhou, F. C.; Zhang, X. Y.; Xu, X. R.

1990-12-01

394

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

395

Absolute intensities and self-, N2-, and air-broadened Lorentz halfwidths for selected lines in the nu3 band of (C-12)H3D from measurements with a tunable diode laser spectrometer  

NASA Technical Reports Server (NTRS)

Absolute intensities and self-, air- and N2-broadened half-widths have been determined for the first time for individual lines in the nu3(A1) band of (C-12)H3D near 7.6 microns from measurements of individual vibration-rotation lines using a tunable diode laser spectrometer. The intensity measurements are believed to be accurate to within three percent. Within experimental uncertainties, equal broadening efficiencies are found for both air and nitrogen. Self-broadened half-widths determined for three transitions yield an average half-width value of 0.803 + or -0.0010/cm/atm at 296 K.

Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.; Smith, M. A. H.; Thakur, K. B.

1986-01-01

396

High resolution absorption cross-section measurements of the Schumann–Runge bands of O 2 by VUV Fourier transform spectroscopy  

Microsoft Academic Search

The photoabsorption spectrum of the O2 Schumann–Runge bands was measured with resolution comparable to the Doppler widths by using the VUV Fourier transform spectrometer from Imperial College, London, combined with synchrotron radiation as a continuum light source at the Photon Factory, KEK, Japan. The analysis of the (12,0)–(17,0) bands of the Schumann–Runge system provides accurate rotational line positions as well

T. Matsui; A. S.-C. Cheung; K. W.-S. Leung; K. Yoshino; W. H. Parkinson; A. P. Thorne; J. E. Murray; K. Ito; T. Imajo

2003-01-01

397

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

398

pH-dependent absorption in the B and Q bands of oxyhemoglobin and chemically modified oxyhemoglobin (BME) at low Cl- concentrations.  

PubMed Central

We have measured the optical absorbance in the maxima of the Q and B bands for oxyhemoglobin and oxyhemoglobin (BME) in dependence on the pH value of the solution in the region between pH 4.4 and pH 10. From the absorbance data optical titration curves are derived for both bands. These yield for oxyhemoglobin pK values 4.3, 5.3, 6.8, 7.8, and 9.0, whereas for oxyhemoglobin (BME) only one pK value at 4.3 is observed. These data are in good agreement to those derived recently from resonance Raman spectroscopy. The changes of the oscillator strengths in the Q bands are interpreted in terms of Gouterman's four-orbital model to arise from A1g-distortions of the heme group, resulting from changes of the heme-apoprotein interactions due to protonation processes of amino acid-side groups in the beta-chains. The difference between the sets of pK values in oxyhemoglobin and oxyhemoglobin BME is explained from the fact that the bifunctional reagent BME blocks important pathways of heme-apoprotein interactions. The fact that in any case increase of the Q band absorbance is accompanied by a corresponding increase in the B band absorbance leads us to the conclusion that the electronic structure of the B bands has to be described in terms of a six-orbital model, taking into account configurational interaction with the L and N bands.

Brunzel, U; Dreybrodt, W; Schweitzer-Stenner, R

1986-01-01

399

Rovibronic bands of the A~<--X~ transition of CH3OO and CD3OO detected with cavity ringdown absorption near 1.2-1.4 ?m  

NASA Astrophysics Data System (ADS)

We have recorded several rovibronic bands of CH3OO and CD3OO in their A~<--X~ transitions in the range of 1.18-1.40 ?m with the cavity ringdown technique. While the electronic origins for these species have been reported previously, many newly observed rovibronic bands are described here. The experimental vibrational frequencies (given as ? in the unit cm-1 in this paper) for the COO bending (?8) and COO symmetric stretching (?7) modes in the A~ state are 378 and 887 cm-1 for CH3OO, and 348 and 824 cm-1 for CD3OO, respectively. In addition, two other vibrational frequencies were observed for the A~ state of CD3OO, namely, ?5 (954 cm-1) and ?6 (971 cm-1). These experimental vibrational frequencies for the A~ state of both CH3OO and CD3OO are in good agreement with predictions from quantum-chemical calculations at the UB3LYP/aug-cc-pVTZ level. The enhanced activity of the ?5 vibrational mode in CD3OO is rationalized by mode mixing with the ?7 mode, as supported by calculations of multidimensional Franck-Condon factors. In addition, many hot bands involving the methyl torsional mode (?12) are observed for both normal and deuterated methyl peroxy. These bands include the ``typical'' sequence transitions and some ``atypical'' ones due to the nature of the eigenvalues and eigenfunctions which are a consequence of the low, but very different, torsional barriers in the X~ and A~ states. In addition, the 1222 band in CH3OO and the 1233 band in CD3OO show quite different structures than the origin bands, an effect which results from tunneling splittings comparable to the rotational contour.

Chung, Chao-Yu; Cheng, Chi-Wen; Lee, Yuan-Pern; Liao, Hsin-Yi; Sharp, Erin N.; Rupper, Patrick; Miller, Terry A.

2007-07-01

400

Vibrational and electronic absorption spectroscopy of dibenzo[b,def]chrysene and its ions.  

PubMed

The vibrational and electronic absorption spectra of dibenzo[b,def]chrysene (DBC) and its ions in argon matrixes have been recorded. Assignment of the observed infrared (IR) bands has been made by comparison with the density functional theory (DFT) computations of harmonic vibrational frequencies (with 6-31G(d,p) or 6-311+G(d,p) basis sets). Extensive time-dependent (TD) DFT calculations of vertical excitation energies have aided in the assignment of the experimental electronic absorption transitions. In general, the theoretical predictions are in good agreement with the observed ultraviolet and visible bands. By correlating IR and UV-visible band intensities (after UV photolysis), it has been shown that both DBC cations and anions are formed. The IR band intensity distributions of the DBC ions differ markedly from neutral DBC. A synthetic spectrum composed of neutral, cationic, and anionic DBC contributions compares reasonably well with the interstellar features of the "unidentified infrared" (UIR) bands from the reflection nebula NGC 7023. Finally, it is shown that the electronic absorption bands of the DBC ions lie in close proximity to several of the diffuse interstellar visible absorption bands (DIBs). PMID:16833287

Wang, Haiyan; Szczepanski, Jan; Hirata, So; Vala, Martin

2005-11-01

401

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

402

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

403

J-Band Spectroscopy of the z = 5.74 Broad Absorption Line Quasar SDSSp J104433.04-012502.2  

Microsoft Academic Search

We use NIRSPEC, a near-IR spectrometer on Keck II, to obtain moderate-resolution (R=1540) spectroscopy that shows conclusively that the C IV emission line in the z=5.74 quasar SDSSp J104433.04-012502.2 is accompanied by broad, blueshifted C IV absorption. The line has a ``balnicity index'' of 900 km s-1 and a rest-frame equivalent width of 13.1+\\/-1.3 Å relative to the continuum. This

R. W. Goodrich; R. Campbell; F. H. Chaffee; G. M. Hill; D. Sprayberry; W. N. Brandt; D. P. Schneider; S. Kaspi; X. Fan; J. E. Gunn; M. A. Strauss

2001-01-01

404

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

Microsoft Academic Search

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

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

2010-01-01

405

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

Microsoft Academic Search

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

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

2012-01-01

406

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

407

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

NASA Astrophysics Data System (ADS)

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

Derkacheva, O. Yu.

2013-11-01

408

Stepwise optical absorption in amorphous SeTe/CdSe superlattices  

NASA Astrophysics Data System (ADS)

Optical absorption and photoconductivity of new chalcogenide amorphous SeTe/CdSe superlattices of pnpn type are investigated. The optical absorption coefficient ? changes stepwise with the variation of the intensity and duration of the illumination. The analysis of the experimental results indicates the formation of subbands in the conduction and valence band. The essential role of the indirect transitions at sublayer thickness below 100 Å is discussed.

Ionov, Radoslav; Nesheva, Diana

409

Nonlinear optical properties of semiconductor quantum wells under intense terahertz radiation  

Microsoft Academic Search

The nonlinear optical properties of semiconductor quantum wells driven by intense in-plane terahertz electric fields are investigated theoretically by employing the extended semiconductor Bloch equations. The dynamical Franz-Keldysh effect of the optical absorption near the band edge is analyzed with Coulomb correlation among the carriers included. The in-plane terahertz field induces a variety of behavior in the absorption spectra, including

T. Y. Zhang; W. Zhao; X. M. Liu; C. Zhang

2007-01-01

410

Absorption and Dispersion of Indium Antimonide  

Microsoft Academic Search

Transmission measurements have been used to determine absorption coefficients over the wavelength range 1.5-7.5 ?, and interferometric determinations made of the refractive index from 7-20 ?. It is shown that the following four factors contribute significantly to the dispersion: (i) short-wave absorption band centred in the visible region, (ii) tail absorption band, (iii) free carrier absorption, (iv) Restrahlen band. The

T S Moss; S D Smith; T D F Hawkins

1957-01-01

411

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

PubMed

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

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

2014-01-21

412

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

NASA Astrophysics Data System (ADS)

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, CH 3OH, CH 3CN 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?, ? = 2, 4, 6) was discussed. They correlate the interaction between the metal 4f-orbitals of Pr(III) and Nd(III) with the ?-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?(complex)/ T? (aquo)] was calculated and its plot against oscillator strength ( P) is drawn.

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

2006-01-01

413

Effects of compositional variation on absorption spectra of lunar pyroxenes  

NASA Technical Reports Server (NTRS)

Polarized absorption spectra of lunar pyroxenes with a range of iron, calcium, magnesium, titanium and chromium contents were measured on polished, oriented single crystals; spectral data on pure synthetic FeSiO3 were also recorded. The bands at 1 and 2 microns were found to vary significantly in position with composition within the pyroxene quadrilateral; wavelengths increased with increasing calcium and iron. In the visible region, a weak band at 640 nm correlates in intensity with Cr2O3, but not with titanium as had been previously suggested. The 505-nm ferrous iron peak is a sharp doublet in most low-calcium pyroxenes but a singlet in augites. A peak at 475 nm and an intense absorption edge below 700 nm correlated with titanium content.

Hazen, R. M.; Bell, P. M.; Mao, H. K.

1978-01-01

414

Laboratory identification of the 4.62mu M solid state absorption band in the ISO-SWS spectrum of RAFGL 7009S  

NASA Astrophysics Data System (ADS)

We focus on the problem of the assignment of the ``XCN'' solid state feature observed in the spectra of numerous protostellar objects. This feature, located at 4.62?m has been tentatively identified with the molecular ion OCN(-) . New laboratory experiments have been performed in order to confirm this identification. OCN(-) is produced by UV photolysis of mixtures of CO:NH_3 (1:1) deposited on a cold substrate. Simultaneously, the counterion NH(+_4) is also produced to balance the charge in the matrix. The use of electron donor and acceptor dopants incorporated in the mixtures allows us to reduce or enhance the production of the OCN(-) and NH(+_4) features, thus establishing their ionic character. The production of HNCO when an electron acceptor is used, and the formation of the OCN(-) band during thermal annealing, constitute convincing arguments in favour of the formation of OCN(-) and NH(+_4) by acid-base reactions where the acid HNCO transfers a proton to the base NH_3. We consider the astrophysical implications for the interpretation of the ISO-SWS spectrum of the protostellar source RAFGL 7009S. In this source, the 4.62?m band is deep and large, although the derived abundance of this ion, relative to H_2O ice, is on the order of 4%. Identification of OCN(-) is considered in several other sources. The contribution of NH(+_4) to the unidentified 6.85?m feature is discussed. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA.

Demyk, K.; Dartois, E.; D'Hendecourt, L.; Jourdain de Muizon, M.; Heras, A. M.; Breitfellner, M.

1998-11-01

415

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

416

Method and apparatus for aerosol particle absorption spectroscopy  

DOEpatents

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

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

1983-11-15

417

Stimulated Raman Emission and Absorption Spectroscopy. Intensity and Gain Measurements of the Stimulated Raman Emission in Liquid O2 and N2.  

National Technical Information Service (NTIS)

In liquid O2 and N2 the threshold for stimulated Raman emission is found to be much lower than for other nonlinear processes. Thus it is possible to make reliable measurements of the intensity of Raman emission over a large range of incident laser power b...

B. P. Stoicheff A. K. McQuillan J. B. Grun

1968-01-01

418

Saturation of transmitted intensity of CO/sub 2/ laser pulses in germanium  

SciTech Connect

The transmission behavior of 90-ns CO/sub 2/ laser pulses through germanium has been studied at high intensities up to 20 MW/cm/sup 2/. With increasing incident intensity, the transmitted intensity was observed to saturate quite abruptly at a level which decreased with increase in crystal length. The saturated level of transmitted intensity was found to be higher at lower temperatures. The observed transmission behavior is interpreted in terms of multiphoton absorption across the direct band gap, followed by absorption by the excess carriers thus generated. By fitting experimental data to a phenomenological model, a room-temperature seven-photon absorption coefficient of 1.5 x 10/sup -9/ (cm/sup 2//MW)/sup 6/ cm/sup -1/ is obtained for germanium in the 10-..mu..m region.

Yuen, S.Y.; Aggarwal, R.L.; Lax, B.

1980-02-01

419

Band GAP of Forsterite.  

National Technical Information Service (NTIS)

Optical absorption and reflectivity measurements on synthetic forsterite show that this silicate has a wide band gap of the order of 8.4 electron volts; thus it resembles other pure insulating oxides such as MgO. For natural olivines, in which divalent ca...

T. J. Shankland

1968-01-01

420

Laboratory measurements and theoretical calculations of O2 A band electric quadrupole transitions  

NASA Astrophysics Data System (ADS)

Frequency-stabilized cavity ring-down spectroscopy was utilized to measure electric quadrupole transitions within the O162 A band, b?1g+?X?3g-(0,0) . We report quantitative measurements (relative uncertainties in intensity measurements from 4.4% to 11%) of nine ultraweak transitions in the ON , OP , SR , and ST branches with line intensities ranging from 3×10-30 to 2×10-29cmmolec.-1 . A thorough discussion of relevant noise sources and uncertainties in this experiment and other cw-cavity ring-down spectrometers is given. For short-term averaging (t<100s) , we estimate a noise-equivalent absorption of 2.5×10-10cm-1Hz-1/2 . The detection limit was reduced further by co-adding up to 100 spectra to yield a minimum detectable absorption coefficient equal to 1.8×10-11cm-1 , corresponding to a line intensity of ˜2.5×10-31cmmolec.-1 . We discuss calculations of electric quadrupole line positions based on a simultaneous fit of the ground and upper electronic state energies which have uncertainties <3MHz , and we present calculations of electric quadrupole matrix elements and line intensities. The electric quadrupole line intensity calculations and measurements agreed on average to 5%, which is comparable to our average experimental uncertainty. The calculated electric quadrupole band intensity was 1.8(1)×10-27cmmolec.-1 which is equal to only ˜8×10-6 of the magnetic dipole band intensity.

Long, D. A.; Havey, D. K.; Okumura, M.; Pickett, H. M.; Miller, C. E.; Hodges, J. T.

2009-10-01

421

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

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

422

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

NASA Astrophysics Data System (ADS)

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

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

1990-11-01

423

Vacuum-ultraviolet absorption of interstitial O 2 and H 2O molecules in SiO 2 glass  

Microsoft Academic Search

Vacuum-ultraviolet (VUV) absorption of O2 and H2O molecules incorporated in interstitial voids in SiO2 glass by thermal annealings was examined. Interactions of the interstitial molecules with the surrounding SiO2 glass network lead to a redshift of the VUV absorption band of interstitial O2, while a blueshift of that of interstitial H2O, both accompanied by an increase in the intensity of

Koichi Kajihara; Masahiro Hirano; Linards Skuja; Hideo Hosono

2006-01-01

424

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

SciTech Connect

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

Babaev, A. A., E-mail: babaev