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Sample records for absorption band intensities

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  2. Intensity Measurements and Collision-Broadening Coefficients for the Oxygen A Band Measured by Intracavity Laser Absorption Spectroscopy.

    PubMed

    Yang; Canagaratna; Witonsky; Coy; Steinfeld; Field; Kachanov

    2000-06-01

    High-sensitivity, high-resolution intracavity laser absorption spectroscopy (ICLAS) has been used to measure line intensities, nitrogen-broadening coefficients, and self-broadening coefficients in the A band (b(1)Sigma(+)(g) <-- X(3)Sigma(-)(g)) of oxygen. Both linear cavity and ring cavity ICLAS configurations were used for these measurements, and the results were intercompared. The results were compared to values measured using long-path multiple-reflection cells by K. D. Ritter and T. D. Wilkinson [J. Mol. Spectrosc. 121, 1-19 (1987)] and L. Brown and C. Plymate, [J. Mol. Spectrosc. 199, 166-179 (2000)]. New results are included for weakly absorbing transitions, not observed in the earlier measurements, such as high rotational states (up to J = 39), hot-band transitions (v' = 1 <-- v" = 1), and isotopically substituted species ((18)O(2) and (16)O(18)O). Isotopic variants ((16)O(2), (18)O(2), and (16)O(18)O) have similar broadening coefficients for corresponding rotational levels, but the self-broadening coefficients are larger in the hot band (v' = v" = 1) as compared with v' = v" = 0 transitions. An ECS-EP scaling analysis of the v' = v" = 0 self-broadening data accurately represents the available data, with the exception of the N = 0 and N = 1 levels. Copyright 2000 Academic Press. PMID:10814483

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

    SciTech Connect

    Veremeichik, T. F.

    2009-11-15

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

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    El Ghazi, Haddou; Peter, A. John

    2015-05-01

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

  6. Intensity formulas for triplet bands

    NASA Technical Reports Server (NTRS)

    Budo, A.

    1982-01-01

    Previous work in this area is surveyed and the mathematics involved in determining the quantitative intensity measurements in triplet bands is presented. Explicit expressions for the intensity distribution in the branches of the 3 Sigma-3 Pi and 1 Sigma-3Pi bands valid for all values of the coupling constant Y of the 3 Pi terms are given. The intensity distribution calculated according to the formulas given is compared with measurements of PH, 3 Pi-3 Sigma. Good quantitative agreement is obtained.

  7. Absorption intensity changes and frequency shifts of fundamental and first overtone bands for OH stretching vibration of methanol upon methanol-pyridine complex formation in CCl4: analysis by NIR/IR spectroscopy and DFT calculations.

    PubMed

    Futami, Yoshisuke; Ozaki, Yasushi; Ozaki, Yukihiro

    2016-02-21

    Infrared (IR) and near infrared (NIR) spectra were measured for methanol and the methanol-pyridine complex in carbon tetrachloride. Upon the formation of the methanol-pyridine complex, the frequencies of both the fundamental and first overtone bands of the OH stretching vibration shifted to lower frequencies, and the absorption intensity of the fundamental increased significantly, while that of the first overtone decreased markedly. By using quantum chemical calculations, we estimated the absorption intensities and frequencies of the fundamental and first overtone bands for the OH stretching vibration based on the one-dimensional Schrödinger equation. The calculated results well reproduced the experimental results. The molecular vibration potentials and dipole moment functions of the OH stretching vibration modes were compared between methanol and the methanol-pyridine complex in terms of absorption intensity changes and frequency shifts. The large change in the dipole moment function was found to be the main cause for the variations in absorption intensity for the fundamental and first overtone bands. PMID:26862859

  8. Effect of absorption on photonic band gap

    NASA Astrophysics Data System (ADS)

    Luo, San; Yao, Kailun; Xu, J. Y.; Liu, Zuli; Li, Ch. F.; Zhao, L.

    2001-10-01

    In order to investigate numerically the effect of absorption on the photonic band gap, we consider a one-dimensional (1D) composite photonic crystal composed of alternating layers having complex dielectric constants. We perform calculations on the reflective spectra using the transfer matrix technique for the composite photonic crystal and find that the reflectance depends on material loss tangent Im((epsilon) )/Re((epsilon) ) and the scaled frequency (omega) /(omega) 0. It is shown that the absorption in composite photonic crystal breaks the periodic band structure produced by Bragg reflection in perfect photonic crystal. It pushes stop band-edges down, and raises the bottom of the pass band. The absorption makes the discrete stop bands become gradually a continuous stop band in larger-frequency range as material loss tangent Im((epsilon) )/Re((epsilon) ) increases.

  9. Absorption bands in the spectrum of Io

    NASA Technical Reports Server (NTRS)

    Cruikshank, D. P.; Jones, T. J.; Pilcher, C. B.

    1978-01-01

    Near-infrared spectra of Io in the region from 2.8 to 4.2 microns are reported which show distinct absorption features, the most notable at 4.1 microns. Frozen volatiles or atmospheric gases cannot account for these absorptions, nor do they resemble those seen in common silicate rocks. Several candidate substances, most notably nitrate and carbonate salts, show absorption features in this spectral region; the deepest band in the spectrum may be a nitrate absorption. The satellite surface is shown to be anhydrous, as indicated by the absence of the 3-micron bound water band.

  10. Atmospheric Solar Heating in Minor Absorption Bands

    NASA Technical Reports Server (NTRS)

    Chou, Ming-Dah

    1998-01-01

    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.

  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)

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

    1995-01-01

    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.

  12. Vibrational absorption bands for implanted nitrogen in crystalline silicon

    NASA Astrophysics Data System (ADS)

    Stein, H. J.

    1983-08-01

    Infrared absorption bands for 15N in crystalline silicon have been observed for the first time. Isotopic substitution experiments were performed by N+ ion implantation into crystalline silicon to confirm the role of nitrogen in absorption bands at 764 and 962 cm-1 for 14N and at 748 and 937 cm-1 for 15N. Laser annealing increases the intensity of the higher frequency band. The 962-cm-1 band frequency is close to Si-N stretch frequencies for planar bonded N in crystalline Si3N4. It is suggested that the lower frequency band is associated with a mode that is made IR active by local distortion, consistent with a distorted substitutional N center identified by Brower in electron paramagnetic resonance studies on laser-annealed nitrogen-implanted Si.

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

    PubMed

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

    2014-01-01

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

  14. Photonic band-edge-induced enhancement in absorption and emission

    NASA Astrophysics Data System (ADS)

    Ummer, Karikkuzhi Variyath; Vijaya, Ramarao

    2015-01-01

    An enhancement in photonic band-edge-induced absorption and emission from rhodamine-B dye doped polystyrene pseudo gap photonic crystals is studied. The band-edge-induced enhancement in absorption is achieved by selecting the incident angle of the excitation beam so that the absorption spectrum of the emitter overlaps the photonic band edge. The band-edge-induced enhancement in emission, on the other hand, is possible with and without an enhancement in band-edge-induced absorption, depending on the collection angle of emission. Through a simple set of measurements with suitably chosen angles for excitation and emission, we achieve a maximum enhancement of 70% in emission intensity with band-edge-induced effects over and above the intrinsic emission in the case of self-assembled opals. This is a comprehensive effort to interpret tunable lasing in opals as well as to predict the wavelength of lasing arising as a result of band-edge-induced distributed feedback effects.

  15. Hot bands in overtone absorption transitions: High temperature spectra

    NASA Astrophysics Data System (ADS)

    Hassoon, Salah; Snavely, Deanne

    1993-03-01

    The laser photoacoustic spectra of the 4v sub N-H and 4v sub C-H overtones of pyrrole, the 5v sub c-H of methyl isocyanide and acetonitrile, the 5v sub c-H and 6v sub C-H of isobutane, and the 6v sub c-H of cyclohexane were measured at temperatures up to 140 C (T sub 140) and compared to the room temperature (T sub rt) spectra. Hot bands were identified by their temperature dependence in pyrrole, methyl isocyanide and isobutane. From the change in the relative intensities of the hot band to the main band going from T sub rt to T sub 140, the wavenumbers of the thermally populated states were 405 +/- 80, 410 +/- 80 and 208 +/- 40 /cm for pyrrole, isobutane and methyl isocyanide, respectively. These values compare well to the bending motion frequencies in these molecules. Large red shifts of the hot bands from the main peak were observed, as expected for high overtone transitions due to large anharmonicities. The anharmonic constants determined from these shifts are -25 /cm for the N-H in pyrrole and -20 /cm for the C-H in methyl isocyanide and isobutane. In the case of the N-H absorption the hot band was completely separated from the transition. In the C-H overtone spectra these hot band absorptions were not separated and result in an apparent increased width of the overtone transition.

  16. Absorption band Q model for the Earth

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  17. Infrared band intensities of saturated hydrocarbons

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  18. Deconvolution of mineral absorption bands - An improved approach

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    Although visible and near IR reflectance spectra contain absorption bands that are characteristic of the composition and structure of the absorbing species, deconvolving a complex spectrum is nontrivial. An improved approach to spectral deconvolution is presented that accurately represents absorption bands as discrete mathematical distributions and resolves composite absorption features into individual absorption bands. The frequently used Gaussian model of absorption bands is shown to be inappropriate for the Fe(2+) electronic transition absorptions in pyroxene spectra. A modified Gaussian model is derived using a power law relationship of energy to average bond length. The modified Gaussian model is shown to provide an objective and consistent tool for deconvolving individual absorption bands in the more complex orthopyroxene, clinopyroxene, pyroxene mixtures, and olivine spectra.

  19. Raman band intensities of tellurite glasses

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  20. Raman band intensities of tellurite glasses.

    PubMed

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

    2005-05-15

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

  1. Conformational statistics of molecules with inner rotation and shapes of their electronic absorption bands

    SciTech Connect

    Aver`yanov, E.M.

    1994-10-01

    The effect of conformational statistics of molecules with inner rotation of {pi}-conjugated fragments on the position, intensity, and electronic absorption band shapes is studied in isotropic molecular media. It is shown that the conformational disorder of molecules with one inner rotation degree of freedom exerts an appreciable effect on the shift, inhomogeneous broadening, and asymmetry of the electronic absorption bands. An interpretation of the available experimental data is give. 19 refs., 1 fig.

  2. The Earth as a seismic absorption band.

    PubMed

    Anderson, D L; Kanamori, H; Hart, R S; Liu, H P

    1977-06-01

    Attenuation of seismic waves indicates that the earth is not perfectly elastic. Dispersion accompanying absorption gives frequency-dependent "elastic" moduli, a fact that must be taken into account when inverting seismic data. Normal mode data are reinverted after correcting for absorption. The correction removes the discrepancy between body wave and free oscillation interpretations of earth structure. PMID:17778549

  3. Localized surface plasmon resonnance induced terahertz broad absorption band

    NASA Astrophysics Data System (ADS)

    Zhong, Min

    2015-12-01

    A broad band metamaterial absorber is designed and simulated, which constitutes by double circular-patterned metal-dielectric stacks. A absorption band is obtained from 14.1 to 16.4 THz. Electric field distributions reveal that the absorption band is obtained from localized surface plasmon (LSP) modes which are excited both on outside and inside edges of each stack, while the high-frequency absorption peak is excited by LSP modes which are excited only on outside edges. The absorption band width can be tuned by increasing the radius (R) of circular-patterned layers and reducing the thickness of dielectric layers (Hd). Moreover, the designed broad band metamaterial absorber is independent of circular-patterned dielectric layer combination.

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

    SciTech Connect

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

    2010-11-15

    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.

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

    PubMed

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

    2014-01-01

    In 1913, Maurice de Broglie discovered the presence of X-ray absorption bands of silver and bromine in photographic emulsion. Over the following century, X-ray absorption spectroscopy was established as a standard basis for element analysis, and further applied to advanced investigation of the structures and electronic states of complex materials. Here we show the first observation of an X-ray-induced change of absorption spectra of the iron K-edge for 7.1-keV ultra-brilliant X-ray free-electron laser pulses with an extreme intensity of 10(20)?W?cm(-2). The highly excited state yields a shift of the absorption edge and an increase of transparency by a factor of 10 with an improvement of the phase front of the transmitted X-rays. This finding, the saturable absorption of hard X-rays, opens a promising path for future innovations of X-ray science by enabling novel attosecond active optics, such as lasing and dynamical spatiotemporal control of X-rays. PMID:25270525

  6. Absorption coefficients and band strengths for the 703 nm and 727 bands of methane at 77 K

    SciTech Connect

    O`Brien, J.J.; Singh, K.

    1996-12-31

    The technique of intracavity laser spectroscopy has been used to obtain methane absorption spectra for the vibrational overtone bands that occur around 703 nm and 727 nm. Absorption coefficients for the 690-742 nm range have been obtained for a sample temperature of 77 K at a spectral resolution of <0.02 cm{sup -1}. A new method of data analysis is utilized in obtaining the results. It involves deconvolving the many ILS spectral profiles that comprise the absorption bands and summing the results. Values averaged over 1 cm{sup -1} and 1 {Angstrom} intervals are provided. Band strengths also are obtained. The total intensities of the 703 and 727 nm bands are in reasonable agreement with previous laboratory determinations which were obtained for relatively high pressures of methane at room temperature using lower spectral resolution. The methane bands appear in the reflected sunlight spectra from the outer planets. Results averaged over 1 nm intervals are compared with other laboratory studies and with those derived from observations of the outer planets. The band profiles differ considerably from other laboratory results but are in good accord with the planetary observations. Laboratory spectra of methane at appropriate conditions are required for the proper interpretation of the observational data. Absorption spectra can provide some of the most sensitive diagnostic data on the atmospheres of those bodies.

  7. Laboratory Measurements of the 940, 1130, and 1370 nm Water Vapor Absorption Band Profiles

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    We have used the solar spectral flux radiometer (SSFR) flight instrument with the Ames 25 meter base-path White cell to obtain about 20 moderate resolution (8 nm) pure water vapor spectra from 650 to 1650 nm, with absorbing paths from 806 to 1506 meters and pressures up to 14 torr. We also obtained a set at 806 meters with several different air-broadening pressures. Model simulations were made for the 940, 1130, and 1370 nm absorption bands for some of these laboratory conditions using the Rothman, et al HITRAN-2000 linelist. This new compilation of HITRAN includes new intensity measurements for the 940 nm region. We compared simulations for our spectra of this band using HITRAN-2000 with simulations using the prior HITRAN-1996. The simulations of the 1130 nm band show about 10% less absorption than we measured. There is some evidence that the total intensity of this band is about 38% stronger than the sum of the HITRAN line intensities in this region. In our laboratory conditions the absorption depends approximately on the square root of the intensity. Thus, our measurements agree that the band is stronger than tabulated in HITRAN, but by about 20%, substantially less than the published value. Significant differences have been shown between Doppler-limited resolution spectra of the 1370 nm band obtained at the Pacific Northwest National Laboratory and HITRAN simulations. Additional new intensity measurements in this region are continuing to be made. We expect the simulations of our SSFR lab data of this band will show the relative importance of improving the HITRAN line intensities of this band for atmospheric measurements.

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

    PubMed Central

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

    2015-01-01

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

  9. Thioxanthone: on the shape of the first absorption band.

    PubMed

    Rai-Constapel, Vidisha; Kleinschmidt, Martin; Salzmann, Susanne; Serrano-Andrs, Luis; Marian, Christel M

    2010-08-28

    The equilibrium ground state geometry of thioxanthone (TX) has been investigated and its effect on the vertical excitation energies and photophysical behaviour has been explained. In line with this purpose, the first absorption band of TX has been simulated and analysed in detail. The calculations show that TX is planar, C(2v) symmetric in its ground state. The energy of the low-lying excited states seems to be rather insensitive along the butterfly motion coordinate. The shoulder in the first absorption band (at around 3.43 eV) is shown to be caused by vibrational progression of various in-plane modes and does not justify the hypothesis that two photophysically distinct conformers of TX exist. The calculated vertical excitation spectrum (in vacuum) has been compared with the experimental absorption bands in non-polar solvents. PMID:20607180

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

    NASA Astrophysics Data System (ADS)

    Awano, Teruyoshi; Takahashi, Toshiharu

    2013-07-01

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

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

    PubMed

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

    2012-07-10

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

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

    PubMed

    Morsi, Morsi M; El-Sherbiny, Samya I; Mohamed, Karam M

    2015-06-15

    The effects of carbon, Fe2O3 and Na2SO4 contents on the amber color of glass with composition (wt%) 64.3 SiO2, 25.7 CaO, 10 Na2O were studied. The effect of some additives that could be found in glass batch or cullets on the amber related absorption band(s) was also studied. An amber related absorption band due to the chromophore Fe(3+)O3S(2-) was recorded at 420 nm with shoulder at 440 nm. A second amber related band recorded at 474 nm with shoulder at 483 nm was assigned to FeS. Increasing melting time at 1400C up to 6h caused fainting of the amber color, decreases the intensities of the amber related bands and shifted the first band to 406 nm. Addition of ZnO, Cu2O and NaNO3 to the glass produced decolorizing effect and vanishing of the amber related bands. The effects of melting time and these additives were explained on the bases of destruction the amber chromophore and its conversion into Fe(3+) in tetrahedral sites or ZnS. Addition of Se intensifies the amber related bands and may cause dark coloration due to the formation of Se and polyselenide. Amber color can be monitored through measuring the absorption in the range 406-420 nm. PMID:25795612

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

  14. Universal EUV in-band intensity detector

    DOEpatents

    Berger, Kurt W.

    2004-08-24

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

  15. Shape of impurity electronic absorption bands in nematic liquid crystal

    SciTech Connect

    Aver`yanov, E.M.

    1994-11-01

    The impurity-matrix anisotropic static intermolecular interactions, orientation-statistical properties, and electronic structure of uniaxial impurity molecules are shown to have a significant influence on spectral moments of the electronic absorption bands of impurities in the nematic liquid crystal. 14 refs., 3 figs.

  16. Constraints on the absorption band model of Q

    SciTech Connect

    Lundquist, G.M.; Cormier, V.C.

    1980-10-10

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

  17. CO 1-0 band isotopic lines as intensity standards

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.; Guelachvili, G.; Tipping, R. H.

    1983-01-01

    Fundamental band vibration-rotational line intensities are reported for the (C-12)(O-16), (C-13)(O-16), and (C-12)(O-18) molecules. The intensities were computed using numerically obtained matrix elements of a recently, determined electric dipole moment function. New intensity measurements for some of these lines obtained via high-resolution Fourier spectra are also reported. The overall consistency (approximately 2.2 percent) between calculations, which are based on recent experimental determinations of CO 1-0 band intensities, not including our own, those of the authors, and independent experimental results of the authors suggests that the lines of the fundamental band of CO can be used as absolute intensity standards.

  18. Uncertainty analysis for the coefficient of band-to-band absorption of crystalline silicon

    NASA Astrophysics Data System (ADS)

    Schinke, Carsten; Christian Peest, P.; Schmidt, Jan; Brendel, Rolf; Bothe, Karsten; Vogt, Malte R.; Krger, Ingo; Winter, Stefan; Schirmacher, Alfred; Lim, Siew; Nguyen, Hieu T.; MacDonald, Daniel

    2015-06-01

    We analyze the uncertainty of the coefficient of band-to-band absorption of crystalline silicon. For this purpose, we determine the absorption coefficient at room temperature (295 K) in the wavelength range from 250 to 1450 nm using four different measurement methods. The data presented in this work derive from spectroscopic ellipsometry, measurements of reflectance and transmittance, spectrally resolved luminescence measurements and spectral responsivity measurements. A systematic measurement uncertainty analysis based on the Guide to the expression of uncertainty in measurement (GUM) as well as an extensive characterization of the measurement setups are carried out for all methods. We determine relative uncertainties of the absorption coefficient of 0.4% at 250 nm, 11% at 600 nm, 1.4% at 1000 nm, 12% at 1200 nm and 180% at 1450 nm. The data are consolidated by intercomparison of results obtained at different institutions and using different measurement approaches.

  19. The 3nu1 + nu2 Combination Band of HOCl: Assignments, Perturbations, and Line Intensities

    PubMed

    Charvat; Deppe; Hamann; Abel

    1997-10-01

    The high-resolution spectra (0.012 cm-1) of the 3nu1 + nu2 combination band of hypochlorous acid HO35(37)Cl in the near infrared ( approximately 11 478 cm-1) have been measured using a titanium:sapphire intracavity laser absorption (ICLA) spectrometer. Line assignments, absolute intensities, and the total band intensity for both isotopomers are reported. In the course of the band analysis two Ka branches (Ka = 2,3) were found to be perturbed via low-order Fermi-type (anharmonic) resonances by a dark perturber which has been identified to be the 2nu1 + 2nu2 + 3nu3 state. The data are compared with intensity predictions from simple empirical models and discussed with regard to detection limits for this molecule in the near infrared spectral region of the atmosphere. Copyright 1997 Academic Press. Copyright 1997Academic Press PMID:9398571

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

    NASA Astrophysics Data System (ADS)

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

    1997-10-01

    The high-resolution spectra (0.012 cm-1) of the 3?1+ ?2combination band of hypochlorous acid HO35(37)Cl in the near infrared (?11 478 cm-1) have been measured using a titanium:sapphire intracavity laser absorption (ICLA) spectrometer. Line assignments, absolute intensities, and the total band intensity for both isotopomers are reported. In the course of the band analysis twoKabranches (Ka= 2,3) were found to be perturbed via low-order Fermi-type (anharmonic) resonances by a dark perturber which has been identified to be the 2?1+ 2?2+ 3?3state. The data are compared with intensity predictions from simple empirical models and discussed with regard to detection limits for this molecule in the near infrared spectral region of the atmosphere.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Isothermal decay behaviors, observed at 515, 523, 562, and 693 K, for an optical absorption band at 620 nm in gamma-irradiated Brazilian blue topaz were analyzed using a kinetic model consisting of O- bound small polarons adjacent to recombination centers (electron traps). The kinetic equations obtained on the basis of this model were solved using the method of Runge-Kutta and the fit parameters describing these defects were determined with a grid optimization method. Two activation energies of 0.52±0.08 and 0.88±0.13 eV, corresponding to two different structural configurations of the O- polarons, explained well the isothermal decay curves using first-order kinetics expected from the kinetic model. On the other hand, thermoluminescence (TL) emission spectra measured at various temperatures showed a single band at 400 nm in the temperature range of 373-553 K in which the 620 nm optical absorption band decreased in intensity. Monochromatic TL glow curve data at 400 nm extracted from the TL emission spectra observed were found to be explained reasonably by using the knowledge obtained from the isothermal decay analysis. This suggests that two different structural configurations of O- polarons are responsible for the 620 nm optical absorption band and that the thermal annealing of the polarons causes the 400 nm TL emission band.

  2. 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)

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

    1994-01-01

    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.

  3. New Optical Absorption Bands in Atomic Layer Superlattices

    NASA Astrophysics Data System (ADS)

    Eckstein, James

    2011-03-01

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

  4. Analysis of the 4800- absorption band of Cs 2 by the classical method

    NASA Astrophysics Data System (ADS)

    Tellinghuisen, Joel; Moeller, Michael B.

    1980-09-01

    The broad absorption band in Cs 2 having peak intensity near 4800 is analyzed through computational simulation of the experimental spectrum using the classical method. The absorption, which terminates in a weak satellite at 5223 , can be interpreted in terms of a single transition from the ground state ( Re = 4.65 , ? e = 42 cm -1) to an upper state having Te = 20 470 cm -1, ? e = 33 cm -1 and Re = 5.28 . The absolute absorption strength is roughly consistent with published lifetime data, but its reliability is limited by thermodynamic uncertainties stemming from the remaining uncertainty in the Cs 2 ground state dissociation enegy. The paper includes a summary of diatomic radiation relations pertinent to the analysis of low-resolution spectra, and a brief discussion of the reduced potential method applied to the alkali dimer ground states.

  5. Intensity-modulating graphene metamaterial for multiband terahertz absorption.

    PubMed

    Gao, Run-Mei; Xu, Zong-Cheng; Ding, Chun-Feng; Yao, Jian-Quan

    2016-03-10

    In this paper, we design a tunable strength multiband absorber consisting of a graphene metamaterial structure and a thick dielectric interlayer deposited on a metal ground plane. We investigate the tunable conductivity properties of the graphene metamaterial and demonstrate multiband absorbers with three absorption bands using a polyimide interlayer in the 0-2.25 THz range by numerical simulation. The results show that the mix absorptivity reached 99.8% at 1.99 THz, and the absorptive strength can be tuned with the modulation depth up to 84.2%. We present a theoretical interpretation based on a standing wave field, which shows that the field energy is localized inside the thicker spacer and then dissipated, effectively trapping the light in the metamaterial absorbers with negligible near-field interactions. The standing wave field theory developed here explains all the features of the multiband metamaterial absorbers and provides a profound understanding of the underlying physics. PMID:26974784

  6. Infrared band intensities in ammonium hydroxide and ammonium salts

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  7. The Soret absorption band of isolated chlorophyll a and b tagged with quaternary ammonium ions.

    PubMed

    Stockett, Mark H; Musbat, Lihi; Kjær, Christina; Houmøller, Jørgen; Toker, Yoni; Rubio, Angel; Milne, Bruce F; Brøndsted Nielsen, Steen

    2015-10-21

    We have performed gas-phase absorption spectroscopy in the Soret-band region of chlorophyll (Chl) a and b tagged by quaternary ammonium ions together with time-dependent density functional theory (TD-DFT) calculations. This band is the strongest in the visible region of metalloporphyrins and an important reporter on the microenvironment. The cationic charge tags were tetramethylammonium, tetrabutylammonium, and acetylcholine, and the dominant dissociation channel in all cases was breakage of the complex to give neutral Chl and the charge tag as determined by photoinduced dissociation mass spectroscopy. Two photons were required to induce fragmentation on the time scale of the experiment (microseconds). Action spectra were recorded where the yield of the tag as a function of excitation wavelength was sampled. These spectra are taken to represent the corresponding absorption spectra. In the case of Chl a we find that the tag hardly influences the band maximum which for all three tags is at 403 ± 5 nm. A smaller band with maximum at 365 ± 10 nm was also measured for all three complexes. The spectral quality is worse in the case of Chl b due to lower ion beam currents; however, there is clear evidence for the absorption being to the red of that of Chl a (most intense peak at 409 ± 5 nm) and also a more split band. Our results demonstrate that the change in the Soret-band spectrum when one peripheral substituent (CH3) is replaced by another (CHO) is an intrinsic effect. First principles TD-DFT calculations agree with our experiments, supporting the intrinsic nature of the difference between Chl a and b and also displaying minimal spectral changes when different charge tags are employed. The deviations between theory and experiment have allowed us to estimate that the Soret-band absorption maxima in vacuo for the neutral Chl a and Chl b should occur at 405 nm and 413 nm, respectively. Importantly, the Soret bands of the isolated species are significantly blueshifted compared to those of solvated Chl and Chl-proteins. The protein microenvironment is certainly not innocent of perturbing the electronic structure of Chls. PMID:25873157

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

    PubMed

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

    2013-06-12

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

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

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

    PubMed

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

    2011-01-17

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    PubMed

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

    2015-03-21

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

  13. Identification of Li O absorption bands based on lithium isotope substitutions

    NASA Astrophysics Data System (ADS)

    Nocu?, Marek; Handke, Miros?aw

    2001-09-01

    Isotope substitution method was used to identify the Li-O absorption bands in crystalline lithium silicates (2Li 2O 3SiO 2, Li 2OSiO 2, Li 2O2SiO 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.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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).

  15. Ultrafast absorption of intense x rays by nitrogen molecules

    SciTech Connect

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

    2012-06-07

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

  16. The ?6614 diffuse interstellar absorption band: evidence for internal excitation of the carrier

    NASA Astrophysics Data System (ADS)

    Marshall, Charlotte C. M.; Kre?owski, Jacek; Sarre, Peter J.

    2015-11-01

    An analysis of absorption profiles of the ?6614 diffuse interstellar band recorded along the lines of sight towards HD 179406 (20 Aql) and HD 147889 is described. The difference in band shape is attributed to the degree of internal excitation of the carrier, which is principally due to vibrational hot bands although an electronic component may also be present. The results are discussed with respect to other models of diffuse band spectral line shape.

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

    PubMed

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

    2015-07-21

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

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

    NASA Astrophysics Data System (ADS)

    Le Bris, Karine; Graham, Laura

    2015-01-01

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

  19. Optical Salisbury screen with design-tunable resonant absorption bands

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  20. Multi-band near-perfect absorption via the resonance excitation of dark meta-molecules

    NASA Astrophysics Data System (ADS)

    Tung, Bui Son; Khuyen, Bui Xuan; Dung, Nguyen Van; Lam, Vu Dinh; Kim, Yong Hwan; Cheong, Hyeonsik; Lee, YoungPak

    2015-12-01

    We numerically study a multi-band absorption based on electromagnetic-induced-transparency effect of metamaterial. By exploiting the coupling between bright and dark plasmonic modes of cut-wire triplet, which consists of a vertical wire and two horizontal wires, a dual-band absorption is realized at 243 and 266 THz. Then, the absorber structure is improved by adding two new horizontal wires which play role as second dark meta-molecules. Due to the dark-dark coupling, another absorption band arises so that a triple-band absorption is created at 240, 250 and 264 THz. The role of interaction between dark meta-molecules in triple-band absorption is investigated, revealing a specific non-monotonic characteristic of the second absorption peak. Finally, the influence of incident angle of EM wave on multi-band absorbers shows that the absorption of lowest frequency peak is robust while those of higher frequency peaks are strongly weaken with increasing of the incident angle.

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

    NASA Astrophysics Data System (ADS)

    Haider, S. A.

    1988-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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.

  3. Ozone absorption cross section measurements in the Wulf bands

    NASA Technical Reports Server (NTRS)

    Anderson, Stuart M.; Hupalo, Peter; Mauersberger, Konrad

    1993-01-01

    A tandem dual-beam spectrometer has been developed to determine ozone absorption cross sections for 13 selected wavelengths between 750 and 975 nm at room temperature. The increasingly pronounced structure in this region may interfere with atmospheric trace gas transitions that are useful for remote sensing and complicate the measurement of aerosols. Ozone concentrations were determined by absorption at the common HeNe laser transition near 632.8 nm using the absolute cross section reported previously. The overall accuracy of these room temperature measurements is generally better than 2 percent. A synoptic near-IR spectrum scaled to these measurements is employed for comparison with results of previous studies.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  6. Cause of absorption band shift of disperse red-13 attached on silica spheres

    NASA Astrophysics Data System (ADS)

    Kim, Byoung-Ju; Kim, Hyung-Deok; Kim, Na-Rae; Bang, Byeong-Gyu; Park, Eun-Hye; Kang, Kwang-Sun

    2015-08-01

    A reversible color change and large absorption band shift have been observed for the disperse red-13 (DR-13) attached on the surface of the monodisperse silica spheres. Two step synthetic processes including urethane bond formation and hydrolysis-condensation reactions were used to attach the DR-13 on the surface of the silica spheres. After the reaction, the characteristic absorption peak at 2270 cm-1 representing the -N=C=O asymmetric stretching vibration disappeared, and the a new absorption peak at 1700 cm-1 corresponding the C=O stretching vibration appeared. A visual and reversible color change was observed before and after wetting in alcohol. Although the absorption peak of DR-13 in alcohol is at 510 nm, the absorption peak shifts to 788 nm when it is dried. The absorption peak shifts to 718 nm when it is wetted in alcohol. This result can be explained by the formation of intramolecular charge transfer band.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  8. Evidence for sulphur implantation in Europa's UV absorption band

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  9. Nonequilibrium Green's function formulation of intersubband absorption for nonparabolic single-band effective mass Hamiltonian

    NASA Astrophysics Data System (ADS)

    Kolek, Andrzej

    2015-05-01

    The formulas are derived that enable calculations of intersubband absorption coefficient within nonequilibrium Green's function method applied to a single-band effective-mass Hamiltonian with the energy dependent effective mass. The derivation provides also the formulas for the virtual valence band components of the two-band Green's functions which can be used for more exact estimation of the density of states and electrons and more reliable treatment of electronic transport in unipolar n-type heterostructure semiconductor devices.

  10. Nonequilibrium Green's function formulation of intersubband absorption for nonparabolic single-band effective mass Hamiltonian

    SciTech Connect

    Kolek, Andrzej

    2015-05-04

    The formulas are derived that enable calculations of intersubband absorption coefficient within nonequilibrium Green's function method applied to a single-band effective-mass Hamiltonian with the energy dependent effective mass. The derivation provides also the formulas for the virtual valence band components of the two-band Green's functions which can be used for more exact estimation of the density of states and electrons and more reliable treatment of electronic transport in unipolar n-type heterostructure semiconductor devices.

  11. a Comprehensive Intensity Study of the ?_4 Torsional Band of Ethane

    NASA Astrophysics Data System (ADS)

    Norooz Oliaee, Jalal; Moazzen-Ahmadi, Nasser; Ozier, Irving; Sung, Keeyoon; Crawford, Timothy J.; Brown, Linda; Wishnow, Edward H.; Devi, V. Malathy

    2014-06-01

    The torsional spectrum of C_2H_6 has been investigated from 220 to 330 cm-1 to measure the intensity of the fundamental and the first torsional hot band needed for atmospheric studies of Titan. Several spectra were measured at resolutions of 0.01 and 0.02 cm-1 using the JPL Bruker IFS-125 coupled to a coolable multi-pass absorption cell originally developed at University of British Columbia. Spectra were recorded at several temperatures from 293 K to 166 K, with the lower temperatures relevant to the stratosphere of Titan. Because this spectrum is very weak, a long absorption path of 52 m was used along with substantial sample pressures from 35 to 255 Torr. Intensities were analysed using a quantum mechanical model reported previously. The torsional fundamental of C_2H_6 is observed in the CIRS spectra of Titan. Line parameters for the torsional bands are required for accurate characterization of spectral features of Titan's far-infrared region. The current study should lead to a better understanding of the methane cycle in planetary atmospheres and permit the identification of the other molecular features in the CIRS data. E. H. Wishnow, A. Leung, and H. P. Gush, Rev. Sci. Instr., 70, 23 (1999). N. Moazzen-Ahmadi, A.R.W. McKellar, J.W.C. Johns, and I.Ozier, J. Chem. Phys. 97, 3981 (1992). Research described in this paper was performed, in part, at the Jet Propulsion Laboratory, California Institute of Technology under contracts and cooperative agreements with the NASA.The data were obtained using NASA's OPR Grant awarded to the College of William and Mary. The research conducted at the University of Calgary is supported by the Canadian Space Agency.

  12. C{sub 2} swan band emission intensity as a function of C{sub 2} density.

    SciTech Connect

    Goyette, A. N.; Lawler, J. E.; Anderson, L. W.; Gruen, D. M.; McCauley, T. G.; Zhou, D.; Krauss, A. R.; Univ. of Wisconsin

    1998-05-01

    We report the systematic comparison of the optical emission intensity of the d {sup 3}{Pi} {yields} a {sup 3}{Pi} (0, 0) vibrational band of the C{sub 2} Swan system with the absolute C{sub 2} concentration in Ar/H{sub 2}/CH{sub 4} and Ar/H{sub 2}/C{sub 60} microwave plasmas used in the deposition of nanocrystalline diamond. The absolute C{sub 2} concentration is obtained using white-light absorption spectroscopy. Emission intensity correlates linearly with C{sub 2} density for variations of several plasma parameters and across two decades of species concentration. Although optical emission intensity generally is not an accurate quantitative diagnostic for gas phase species concentrations, these results confirm the reliability of the (0,0) Swan band for relative determination of C{sub 2} density with high sensitivity under conditions used for hydrogen-deficient plasma-enhanced chemical vapor deposition of diamond.

  13. Electromagnetic wave absorption properties of carbon powder from catalysed carbon black in X and Ku bands

    NASA Astrophysics Data System (ADS)

    Wen, Bin; Zhao, Jijun; Duan, Yuping; Zhang, Xingguo; Zhao, Yanbo; Dong, Chuang; Liu, Shunhua; Li, Tingju

    2006-05-01

    Carbon powder from catalysed carbon black (CPCCB) was prepared after a pyrogenation of carbon black (CB) with nanosized iron catalyst at atmospheric pressure and a temperature of 1100 C. The complex relative permittivity and permeability of the CPCCB were measured by a reflection/transmission technique in the X and Ku bands. The reflection loss of CPCCB/paraffin wax composite was recorded. A wider absorption frequency range in the X band and Ku band could be obtained by adding 3 vol.% and 6 vol.% CPCCB in paraffin wax, respectively. Our results indicate that CPCCB could be a promising microwave absorption material.

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

    NASA Technical Reports Server (NTRS)

    Atwal, Mahabir S.; Crocker, Malcolm J.

    1987-01-01

    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 by measuring the intensity incident on the sample and the intensity reflected by the sample placed in a reverberation chamber. Absorption coefficient results obtained by the sound intensity technique were compared with standard techniques, namely the reverberation chamber and the standing wave tube. The major advantages of using the sound intensity technique are that it permits 'in situ' measurements and the absorption coefficient for a large range of frequencies can be obtained from a single measurement.

  15. Absolute absorption coefficients of ClONO2 infrared bands at stratospheric temperatures

    NASA Astrophysics Data System (ADS)

    Ballard, J.; Johnston, W. B.; Gunson, M. R.; Wassell, P. T.

    1988-02-01

    Absolute absorption coefficients in infrared ClONO2 bands were measured at 296 and 213 K using Fourier-transform absorption spectroscopy. The 213-296 K temperature range corresponds to stratospheric temperatures, making these results applicable to retrievals of stratospheric ClONO2 from remote-sensing observations. Room temperature asorption coefficients were found to be about 25 percent higher than previously reported values, and large temperature dependences were observed in all bands studied. The absorption coefficients in the nu(4)Q branch and in the nu(2) band were modeled by equispaced absorption lines, each characterized by a central frequency, strength, lower-state energy, and pressure-broadened width.

  16. Possible spinel absorption bands in S-asteroid visible reflectance spectra

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

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

  18. Varied absorption peaks of dual-band metamaterial absorber analysis by using reflection theory

    NASA Astrophysics Data System (ADS)

    Xiong, Han; Yu, Yan-Tao; Tang, Ming-Chun; Chen, Shi-Yong; Liu, Dan-Ping; Ou, Xiang; Zeng, Hao

    2016-03-01

    Cross-resonator metamaterial absorbers (MMA) have been widely investigated from microwave to optical frequencies. However, only part of the factors influencing the absorption properties were analyzed in previous works at the same time. In order to completely understand how the spacer thickness, dielectric parameter and incidence angle affect the absorption properties of the dual-band MMA, two sets of simulation were performed. It was found that with increasing incident angles, the low-frequency absorption peak showed a blue shift, while the high-frequency absorption peaks showed a red shift. However, with the increase in spacer thickness, both of the absorption peaks showed a red shift. By using the reflection theory expressions, the physical mechanism of the cross-resonator MMA was well explained. This method provides an effective way to analyze multi-band absorber in technology.

  19. Dynamic atomic contributions to infrared intensities of fundamental bands.

    PubMed

    Silva, Arnaldo F; Richter, Wagner E; Bassi, Adalberto B M S; Bruns, Roy E

    2015-11-11

    Dynamic atomic intensity contributions to fundamental infrared intensities are defined as the scalar products of dipole moment derivative vectors for atomic displacements and the total dipole derivative vector of the normal mode. Intensities of functional group vibrations of the fluorochloromethanes can be estimated within 6.5 km mol(-1) by displacing only the functional group atoms rather than all the atoms in the molecules. The asymmetric CF2 stretching intensity, calculated to be 126.5 km mol(-1) higher than the symmetric one, is accounted for by an 81.7 km mol(-1) difference owing to the carbon atom displacement and 40.6 km mol(-1) for both fluorine displacements. Within the Quantum Theory of Atoms in Molecules (QTAIM) model differences in atomic polarizations are found to be the most important for explaining the difference in these carbon dynamic intensity contributions. Carbon atom displacements almost completely account for the differences in the symmetric and asymmetric CCl2 stretching intensities of dichloromethane, 103.9 of the total calculated value of 105.2 km mol(-1). Contrary to that found for the CF2 vibrations intramolecular charge transfer provoked by the carbon atom displacement almost exclusively explains this difference. The very similar intensity values of the symmetric and asymmetric CH2 stretching intensities in CH2F2 arise from nearly equal carbon and hydrogen atom contributions for these vibrations. All atomic contributions to the intensities for these vibrations in CH2Cl2 are very small. Sums of dynamic contributions of the individual intensities for all vibrational modes of the molecule are shown to be equal to mass weighted atomic effective charges that can be determined from atomic polar tensors evaluated from experimental infrared intensities and frequencies. Dynamic contributions for individual intensities can also be determined solely from experimental data. PMID:26508036

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  1. Collagen absorption bands in heated and rehydrated dentine

    NASA Astrophysics Data System (ADS)

    Bachmann, Luciano; Gomes, Anderson S. L.; Zezell, Denise M.

    2005-12-01

    The objective of this work is identifying changes in the collagen bands in heated and rehydrated dentine. We use bovine dentine slices that were heated in oven between 100 and 300 C. The sample hydration was conducted in sodium chloride solution at 0.9 wt.%; the spectra were acquired by a Fourier transform infrared spectrometer in the spectral range of 4000-400 cm -1. Our results show a temperature range ( T ? 175 C) where the dentinal collagen can be partially denatured and reverted to initial conformation; a second region (175 C < T ? 225 C) where this process occurs partially and a third region ( T > 225 C) where the collagen is denatured and no reversion is observed after rehydration. This work identifies an important characteristic that dentinal collagen can assume when the tissue is heated and rehydrated; these results indicate the denaturation temperature of dentinal collagen to be near 175-200 C.

  2. High sensitivity ultra-broad-band absorption spectroscopy applied to inductively-coupled plasmas in Cl/O

    NASA Astrophysics Data System (ADS)

    Foucher, Mickal; Carbone, Emile; Booth, Jean-Paul; Chabert, Pascal; LPP-Plasmas froids Team

    2014-10-01

    Broad-band absorption spectroscopy is a powerful diagnostic for reactive plasmas, allowing measurement of the absolute densities of numerous atoms, molecules and free radicals in ground and various excited states. Previously Xe arc lamps have been used as the continuum light source, but these suffer from spatiotemporal fluctuations which limit the sensitivity to about 10-3 in absorption. More recently UV light-emitting diodes have been used, but these only emit over a very limited spectral range. Our new absorption spectroscopy setup uses a laser-driven plasma light source, achromatic optics and an aberration free spectrograph. This light source has ideal characteristics for absorption spectroscopy (high intensity, stability and a wide spectral range (200--1000 nm)), overcoming previous limitations. Noise levels as low as 10-5 can be achieved in single-pass absorption, covering up to 250 nm in a single spectrum. Measurements were made in a 13.56 MHz inductively-coupled plasma reactor in O, Cl and Cl/O mixtures. We observed absorption by Cl, O and ClxOy molecules, and excited state atoms. Whereas the Clvibrational distribution is close to equilibrium with the gas translational temperature, Omolecules show high vibrational excitation (up to v = 18, Tvib12,000 K). However, high resolution spectra of O indicated rotational temperatures up to only 500 K. Many oxychloride molecules were detected in Cl/O mixtures.

  3. Modelling Alkali Line Absorption and Molecular Bands in Cool DAZs

    NASA Astrophysics Data System (ADS)

    Homeier, D.; Allard, N.; Allard, F.; Hauschildt, P. H.; Schweitzer, A.; Stencil, P. C.; Weck, P. F.

    2005-07-01

    Two peculiar stars showing an apparent extremely broadened and strong Na I D absorption have been discovered in surveys for cool white dwarfs by Oppenheimer et al. (2001) and Harris et al. (2003, SDSS). We discuss the nature of these objects using PHOENIX atmosphere models for metal-poor brown dwarfs/very low mass stars, and new white dwarf LTE and NLTE models for hydrogen- and helium-dominated atmospheres with metals. These include complete molecular formation in chemical equilibrium and a model for the alkali resonance line broadening based on the damping profiles of Allard et al. (2003), as well as new molecular line opacities for metal hydrides. First results of our calculations indicate good agreement with a hydrogen-dominated WD atmosphere with a Na abundance roughly consistent with a state of high accretion. We analyse deviations of the abundances of Na, K, Mg and Ca from the cosmic pattern and comment on implications of these results for standard accretion scenarios.

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

    SciTech Connect

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

    1994-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Anglister, J.; Steinberg, I. Z.

    1981-01-01

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

  6. Line Intensity and Position Measurements and Derived Band Parameters of the 31103-00001 C-12 O-16(2) Band and its Two Nearby Hot Bands

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    A set of CO2 spectra from 4500 to 4780/cm has been obtained an Ames with 1500 m path length using a Bomem DA8 FTS. This spectral region contains a number of weak bands and minor isotopic bands that have been studied at high resolution in the reflection spectrum of Venus by Mandin. Improved laboratory intensity and position measurements should assist modeling the Venus reflection spectra and improve understanding of Venus' upper atmosphere. Also, the laboratory measurements will assist DND intensity computations of weaker bands that cannot be measured, but which are nevertheless significant absorbers in Venus' hot, deep CO2, atmosphere. For example, some of the weaker bands that are members of the same polyads as the bands in this presentation lie in the nearby 2.3 microns emission window in Venus' night-side spectrum.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    PubMed

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

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  10. 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)

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

    1976-01-01

    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.

  11. Tone-burst technique measures high-intensity sound absorption

    NASA Technical Reports Server (NTRS)

    Powell, J. G.; Van Houten, J. J.

    1971-01-01

    Tone-burst technique, in which narrow-bandwidth, short-duration sonic pulse is propagated down a standing-wave tube, measures sound absorbing capacity of materials used in jet engine noise abatement. Technique eliminates effects of tube losses and yields normal-incidence absorption coefficient of specimen.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

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

    SciTech Connect

    Heera, Pawan; Kumar, Anup; Sharma, Raman

    2015-05-15

    We report the preparation and the optical studies on tellurium rich glasses thin films. The thin films of Se{sub 30}Te{sub 70-x} Sn{sub x} system for x= 0, 1.5, 2.5 and 4.5 glassy alloys prepared by melt quenching technique are deposited on the glass substrate using vacuum thermal evaporation technique. The analysis of absorption spectra in the spectral range 400nm–4000 nm at room temperature obtained from UV-VIS-NIR spectrophotometer [Perkin Elmer Lamda-750] helps us in the optical characterization of the thin films under study. The absorption spectrum fitting method is applied by using the Tauc’s model for estimating the optical band gap and the width of the band tail of the thin films. The optical band gap is calculated and is found to decrease with the Sn content.

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

    NASA Astrophysics Data System (ADS)

    Heera, Pawan; Kumar, Anup; Sharma, Raman

    2015-05-01

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

  15. Fully Polarimetric Differential Intensity W-band Imager

    SciTech Connect

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

    2013-05-31

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

  16. Towards absorption enhancement and design optimization of Split-off band infrared photodetectors

    NASA Astrophysics Data System (ADS)

    Shishodia, Manmohan; Unil Perera, A. G.

    2009-11-01

    Room temperature photodetectors operating in infrared (IR) region are important for astronomy, biomedical, defence and security related applications. Recently developed short wavelength infrared (2-5?m) detectors utilizing light absorption through split-off band transitions in mature GaAs/AlGaAs material system may offer an efficient alternative to the intrinsically slow present day microbolometer detectors. The total quantum efficiency of these detectors, defined as the product of absorption efficiency, internal quantum efficiency, and collection efficiency, usually limited by low absorption, can be improved through IR antenna induced surface plasmon enhanced absorption. The antenna induced absorption besides free carrier and split-off absorption should improve the total quantum efficiency (?) and hence the responsivity (R), two being related by R=q??/hc, of these detectors. The optimized detector designs capable of reinforcing absorption due to free carriers and the antenna in the split-off region, and the theoretical results on absorption enhancement and performance improvement will be presented.

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

    PubMed Central

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

    2015-01-01

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

  18. Radiation absorption by the C2 band systems for Jupiter entry conditions

    NASA Technical Reports Server (NTRS)

    Sutton, K.; Moss, J. N.

    1979-01-01

    Revised values of the absorption cross sections for seven electronic band systems of C2 have been calculated using recently published experimental data for the electronic transition moments. Using these revised C2 cross section values, computations were made for the radiating flow field over a Jupiter entry probe with coupled ablation injection from a carbon-phenolic heat shield. Results are presented which show that radiation absorption within the ablation layer for the spectral range of 4 to 6 eV is less than that predicted using previous C2 absorption cross section values. The effect of the reduced radiation absorption by the C2 molecule is an increase in the radiative heating rates and ablation mass loss rates for the Jupiter entry conditions considered in the study.

  19. The aggregation effect on the absorption band shift of disperse red-13 attached on the surface of silica spheres

    NASA Astrophysics Data System (ADS)

    Kang, Kwang-Sun

    2013-12-01

    Optical properties of disperse red-13 (DR-13) attached on the surface of the silica spheres have been investigated. Two step synthetic processes have been used to attach the DR-13 on the surface of the silica spheres. The first step is a urethane bond formation between a DR-13 (OH) and a 3-isocyanatopropyl triethoxysilane (ICPTES, NCO) in pyridine at 50 C. The second step is the hydrolysis and condensation reactions between the resulting compound of the first step reaction (ICPDR) and the silica spheres (ICPDRSS). The absence of a characteristic absorption peak at 2270 cm-1 representing the NCO asymmetric stretching vibration and the existence of a new absorption peat at 1700 cm-1 corresponding the CO stretching vibration indicate the urethane bond formation. The absorption intensity of the DR-13 in methanol, ethanol and 2-propanol linearly increased with the increase of the amount of the DR-13. The ICPDRSS has weak brownish color when it is dried. The field emission scanning electron microscope shows the aggregated ICPDR on the surface of the silica spheres. The average diameter of the spheres is approximately 380 nm. The color of the ICPDRSS changed to intense red when it was wetted in methanol, ethanol and 2-propanol. The absorption peak of the dried ICPDRSS film is at 475 nm. The stopband appears at 788 nm and disappears when the methanol is filled between the spheres due to the low refractive index contrast. New absorption band appears at 718 nm when the methanol is absorbed due to the large aggregation of the ICPDR on the surface of the spheres.

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

    SciTech Connect

    Picconi, David; Grebenshchikov, Sergy Yu.

    2014-08-21

    Photodissociation of ozone in the near UV is studied quantum mechanically in two excited electronic states coupled at a conical intersection located outside the Franck-Condon zone. The calculations, performed using recent ab initio PESs, provide an accurate description of the photodissociation dynamics across the Hartley/Huggins absorption bands. The observed photofragment distributions are reproduced in the two electronic dissociation channels. The room temperature absorption spectrum, constructed as a Boltzmann average of many absorption spectra of rotationally excited parent ozone, agrees with experiment in terms of widths and intensities of diffuse structures. The exit channel conical intersection contributes to the coherent broadening of the absorption spectrum and directly affects the product vibrational and translational distributions. The photon energy dependences of these distributions are strikingly different for fragments created along the adiabatic and the diabatic paths through the intersection. They can be used to reverse engineer the most probable geometry of the non-adiabatic transition. The angular distributions, quantified in terms of the anisotropy parameter β, are substantially different in the two channels due to a strong anticorrelation between β and the rotational angular momentum of the fragment O{sub 2}.

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

    NASA Astrophysics Data System (ADS)

    Kim, Byoung-Ju; Kang, Kwang-Sun

    2014-02-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-09-01

    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.

  4. Absorption spectrum of NO in the {gamma}(O, O) band

    SciTech Connect

    Zobnin, A.V.; Korotkov, A.N.

    1995-05-01

    A promising technique for determining the concentration of nitrogen oxide in the air of an industrial zone and in process gases is the measurement of the absorption of UV radiation by this molecule in the {gamma}(O,O) band with the center of {lambda}{sub 0} = 226.5 nm. This band corresponds to the transition X{sup 2}{Pi}{yields}{Alpha}{sup 2}{Sigma} of the NO molecule and is characterized by a complex rotational structure consisting of about 400 lines. This structure cannot be resolved completely by most spectral instruments. However, if the width of the spread function of the device is perceptibly smaller than the width of the given absorption band ({approx_equal}2 nm), but larger than the characteristic space between rotational lines ({approx_equal}0.02 nm), then the recorded transmission spectra of NO are almost insensitive to a change in the form of this function. In the given case, to describe the transmission spectrum it is possible to use the absorption coefficient averaged over rotational lines. And even though the Bouger-Lambert-Beer law is not strictly applicable for this spectrum, the dependence of the transmission spectrum of NO on the optical thickness, temperature, and pressure of the broadening gas can be represented in the form of an empirical dependence that can be useful in practice, for example, when processing the absorption spectra recorded by dispersion gas analyzers. Thus, the need for complex and laborious calculations is avoided, and this simplifies considerably the instrumental implementation of this method of measuring the concentration of NO. The object of the present work is to determine the empirical dependence of the absorption spectrum of NO in the {gamma}(O, O) band on the optical thickness, temperature, and pressure of the broadening gas in the ranges most frequently encountered in operation of dispersion gas analyzers.

  5. Recent Results from Broad-Band Intensity Mapping Measurements of Cosmic Large Scale Structure

    NASA Astrophysics Data System (ADS)

    Zemcov, Michael B.; CIBER, Herschel-SPIRE

    2016-01-01

    Intensity mapping integrates the total emission in a given spectral band over the universe's history. Tomographic measurements of cosmic structure can be performed using specific line tracers observed in narrow bands, but a wealth of information is also available from broad-band observations performed by instruments capable of capturing high-fidelity, wide-angle images of extragalactic emission. Sensitive to the continuum emission from faint and diffuse sources, these broad-band measurements provide a view on cosmic structure traced by components not readily detected in point source surveys. After accounting for measurement effects and astrophysical foregrounds, the angular power spectra of such data can be compared to predictions from models to yield powerful insights into the history of cosmic structure formation. This talk will highlight some recent measurements of large scale structure performed using broad-band intensity mapping methods that have given new insights on faint, distant, and diffuse components in the extragalactic background light.

  6. The taming of absorption: generating a constant intensity beam in a lossy medium.

    PubMed

    Golub, Ilya; Mirtchev, Theodore; Nuttall, Jonathan; Shaw, Dagan

    2012-07-01

    We report the first observation (to our best knowledge) of a constant intensity, quasi-Bessel/nondiffracting beam in an absorbing medium generated by a novel optical element, "exicon," or exponential intensity axicon. Such absorption-compensated and diffraction-resistant beams can find applications in illumination, remote sensing, free-space communications, imaging in biological tissues, nonlinear optics, and other situations where absorption and diffraction hinder light propagation. PMID:22743453

  7. Semiclassical theory of intensities of vibrational fundamentals, overtones, and combination bands

    SciTech Connect

    Koszykowski, M.L.; Noid, D.W.; Marcus, R.A.

    1982-06-10

    Quantum mechanical and semiclassical results are compared for the spectrum of the Morse oscillator. When an average quantum number ((n + m)/2) trajectory is employed for an n ..-->.. m transition good agreement is obtained between the quantum and semiclassical intensities and between the frequencies, for the fundamental and overtones studied. Spectra of nonrotating OCS in the quasiperiodic and chaotic regions are presented, and the intensities of a number of overtones and combination bands are calculated. Even very low intensity transitions are observed.

  8. Broad band free jet absorption mm-wave spectrum of 3-phenyl-1-propanol

    NASA Astrophysics Data System (ADS)

    Maris, Assimo; Ottaviani, Paolo; Giuliano, Barbara M.; Melandri, Sonia; Caminati, Walther

    2012-10-01

    The rotational broad band spectra of the OH and OD isotopologues of 3-phenyl-1-propanol have been investigated by broad band free-jet absorption millimeter-wave spectroscopy in the 60.0-78.3 GHz frequency range. The spectra of the GGt and of the TGt conformers, where the three labels refer to the torsions of the benzyl, phenylethyl and hydroxyl groups, respectively, have been assigned. Ab initio calculations, performed at the MP2/6-311++G** level, were used to characterize the minima of the conformational potential energy surface.

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

    PubMed

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

    2013-04-01

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

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

    PubMed

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

    2014-12-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    Phase angle-induced spectral effects are important to characterize since they affect spectral band parameters such as band depth and band center, and therefore skew mineralogical interpretations of planetary bodies via reflectance spectroscopy. Dwarf planet (1) Ceres is the next target of NASAs Dawn mission, which is expected to arrive in 2015 March. The visible and near-infrared mapping spectrometer (VIR) on board Dawn has the spatial and spectral range to characterize the surface between 0.25-5.0 ?m. Ceres has an absorption feature at 3.0 ?m due to hydroxyl- and/or water-bearing minerals. We analyzed phase angle-induced spectral effects on the 3 ?m absorption band on Ceres using spectra measured with the long-wavelength cross-dispersed (LXD: 1.9-4.2 ?m) mode of the SpeX spectrograph/imager at the NASA Infrared Telescope Facility. Ceres LXD spectra were measured at different phase angles ranging from 0.7 to 22. We found that the band center slightly increases from 3.06 ?m at lower phase angles (0.7 and 6) to 3.07 ?m at higher phase angles (11 and 22), the band depth decreases by 20% from lower phase angles to higher phase angles, and the band area decreases by 25% from lower phase angles to higher phase angles. Our results will have implications for constraining the abundance of OH on the surface of Ceres from VIR spectral data, which will be acquired by Dawn starting spring 2015.

  12. Simulation of the atmospheric transfer of the solar radiation in water vapor absorption bands

    NASA Astrophysics Data System (ADS)

    Chesnokova, T. Y.; Chentsov, A. V.; Firsov, K. M.

    2015-11-01

    The atmospheric solar spectra are calculated using different spectroscopic databases of H2O absorption line parameters in the temperature and humidity range observed in the mid-latitudes. A comparison of the simulated spectra and measured high-resolution atmospheric spectra in the near-infrared water vapor bands, is carried out. It is shown that the values of H2O atmospheric column, retrieved using different modern spectroscopic databases may vary by more than 3%.

  13. Contrasting levels of absorption of intense femtosecond laser pulses by solids

    PubMed Central

    Singh, Prashant Kumar; Cui, Y. Q.; Adak, Amitava; Lad, Amit D.; Chatterjee, Gourab; Brijesh, P.; Sheng, Z. M.; Kumar, G. Ravindra

    2015-01-01

    The absorption of ultraintense, femtosecond laser pulses by a solid unleashes relativistic electrons, thereby creating a regime of relativistic optics. This has enabled exciting applications of relativistic particle beams and coherent X-ray radiation, and fundamental leaps in high energy density science and laboratory astrophysics. Obviously, central to these possibilities lies the basic problem of understanding and if possible, manipulating laser absorption. Surprisingly, the absorption of intense light largely remains an open question, despite the extensive variations in target and laser pulse structures. Moreover, there are only few experimental measurements of laser absorption carried out under very limited parameter ranges. Here we present an extensive investigation of absorption of intense 30 femtosecond laser pulses by solid metal targets. The study, performed under varying laser intensity and contrast ratio over four orders of magnitude, reveals a significant and non-intuitive dependence on these parameters. For contrast ratio of 10−9 and intensity of 2 × 1019 W cm−2, three observations are revealed: preferential acceleration of electrons along the laser axis, a ponderomotive scaling of electron temperature, and red shifting of emitted second-harmonic. These point towards the role of J × B absorption mechanism at relativistic intensity. The experimental results are supported by particle-in-cell simulations. PMID:26648399

  14. Contrasting levels of absorption of intense femtosecond laser pulses by solids.

    PubMed

    Singh, Prashant Kumar; Cui, Y Q; Adak, Amitava; Lad, Amit D; Chatterjee, Gourab; Brijesh, P; Sheng, Z M; Kumar, G Ravindra

    2015-01-01

    The absorption of ultraintense, femtosecond laser pulses by a solid unleashes relativistic electrons, thereby creating a regime of relativistic optics. This has enabled exciting applications of relativistic particle beams and coherent X-ray radiation, and fundamental leaps in high energy density science and laboratory astrophysics. Obviously, central to these possibilities lies the basic problem of understanding and if possible, manipulating laser absorption. Surprisingly, the absorption of intense light largely remains an open question, despite the extensive variations in target and laser pulse structures. Moreover, there are only few experimental measurements of laser absorption carried out under very limited parameter ranges. Here we present an extensive investigation of absorption of intense 30 femtosecond laser pulses by solid metal targets. The study, performed under varying laser intensity and contrast ratio over four orders of magnitude, reveals a significant and non-intuitive dependence on these parameters. For contrast ratio of 10(-9) and intensity of 2??10(19)?W cm(-2), three observations are revealed: preferential acceleration of electrons along the laser axis, a ponderomotive scaling of electron temperature, and red shifting of emitted second-harmonic. These point towards the role of J??B absorption mechanism at relativistic intensity. The experimental results are supported by particle-in-cell simulations. PMID:26648399

  15. Contrasting levels of absorption of intense femtosecond laser pulses by solids

    NASA Astrophysics Data System (ADS)

    Singh, Prashant Kumar; Cui, Y. Q.; Adak, Amitava; Lad, Amit D.; Chatterjee, Gourab; Brijesh, P.; Sheng, Z. M.; Kumar, G. Ravindra

    2015-12-01

    The absorption of ultraintense, femtosecond laser pulses by a solid unleashes relativistic electrons, thereby creating a regime of relativistic optics. This has enabled exciting applications of relativistic particle beams and coherent X-ray radiation, and fundamental leaps in high energy density science and laboratory astrophysics. Obviously, central to these possibilities lies the basic problem of understanding and if possible, manipulating laser absorption. Surprisingly, the absorption of intense light largely remains an open question, despite the extensive variations in target and laser pulse structures. Moreover, there are only few experimental measurements of laser absorption carried out under very limited parameter ranges. Here we present an extensive investigation of absorption of intense 30 femtosecond laser pulses by solid metal targets. The study, performed under varying laser intensity and contrast ratio over four orders of magnitude, reveals a significant and non-intuitive dependence on these parameters. For contrast ratio of 10?9 and intensity of 2??1019?W cm?2, three observations are revealed: preferential acceleration of electrons along the laser axis, a ponderomotive scaling of electron temperature, and red shifting of emitted second-harmonic. These point towards the role of J??B absorption mechanism at relativistic intensity. The experimental results are supported by particle-in-cell simulations.

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

    NASA Technical Reports Server (NTRS)

    Salama, F.; Allamandola, L. J.

    1992-01-01

    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.

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

    PubMed

    Salama, F; Allamandola, L J

    1992-07-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  20. Study of band-edge optical absorption of silicon nanoparticles using photothermal deflection spectroscopy

    NASA Astrophysics Data System (ADS)

    Theingi, San; Kendrick, Chito; Guan, Tianyuan; Vitti, Lauren; Klafehn, Grant; Bagolini, Luigi; Lusk, Mark; Gorman, Brian; Stradins, Paul; Taylor, Craig; Collins, Reuben

    2014-03-01

    Silicon nanoparticles (SiNPs) are a promising optoelectronic material with unique properties such as a size tunable bandgap, sensitivity to surface termination, and efficient optical emission. Here, we present an optical absorption study of size varied, free standing SiNPs films using photothermal deflection spectroscopy (PDS). In general, it is difficult to directly observe the absorption threshold in SiNPs because of silicon's low absorption coefficient. PDS, which directly measures the optical absorption of materials through the generated heat, is known for its extremely high sensitivity. The SiNPs are grown using a plasma process and deposited as films on quartz substrates. Different amounts of SF6 gas are introduced into the process gas to control the size of these SiNPs. Photoluminescence measurements show a strong blue shift in emission with increased SF6 flow. PDS measurements allow a corresponding blue shift in the band edge absorption which is attributable to quantum confinement to be observed. In addition, PDS measurements also allow us to probe the defect level of our material, and the size distribution of SiNPs in our sample. We acknowledge support from the DOE SunShot program (DE-EE0005326) and NSF REMRSEC (DMR-0820518).

  1. Detection of vibration-rotational band 5-0 of 12C16O X 1sigma+ with cavity ringdown absorption near 0.96 microm.

    PubMed

    Chung, Chao-Yu; Ogilvie, J F; Lee, Yuan-Pern

    2005-09-01

    We have recorded extremely weak absorption in the overtone band 5-0 of 12C16O X 1sigma+ near 0.96 microm with cavity ringdown spectroscopy; the light source was a Raman-shifted dye laser pumped with a frequency-doubled Nd:YAG laser. This band shows lines in branch P to be much more intense than corresponding lines in branch R, in contrast to all lower overtone bands v-0 (v = 1-4). This reversal in relative intensity is explained quantitatively in terms of a radial function for the electric dipolar moment of CO. We have estimated absorption line strengths for P3-P18 in band 5-0 of 12C16O; these strengths are consistent with a pure vibrational matrix element <5/p(x)/0> = (3.6 +/- 0.3) x 10(-36) C m of the electric dipolar moment p(x), a Herman-Wallis coefficient C0(5) of about -0.1, and a band strength of (5.1 +/- 1.3) x 10(-29) m at 293 K. PMID:16834165

  2. Intensity and Self-Broadening Measurements of the 01(exp 1)21-00(exp 0)01 CO2 Perpendicular Band at 5315/cm

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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. Parameters for many unmeasured bands have been recomputed for the HITRAN compilation using direct numerical diagonalization (DND) [Wattson and Rothman, J.Q.S.R.T. 48, 763 (1992)]. To assess these HITRAN values, we have been measuring several of these bands on spectra which were obtained using the Kitt Peak McMath FTS and 6-meter White cell. Last year we presented preliminary intensity measurements of the 01(exp 1)21-00(exp 0)01 perpendicular band and 4 associated hot bands, Five additional McMath FTS spectra have now been obtained covering the region 3800 to 8400/cm. This permits us to finalize our intensity measurements, and to make an assessment of their uncertainties. We anticipate that these measured values will help improve further DND calculations of many weak unmeasureable bands. In addition, self-broadening parameters were determined for some lines of the 01(exp 1)21-00(exp 0)01 perpendicular band on spectra obtained with 65 and 80 torr of CO2. Because of the large spectral range, these measurements could be compared directly to self-broadening parameters of corresponding parallel. band lines measured on the same spectra. This procedure eliminates several possible sources of systematic errors that are important when attempting to determine whether or not corresponding rotational lines in different overtone-combination bands have significant differences. Our measurements thus far have found self-broadening parameters for the 01(exp 1)21-00(exp 0)01 perpendicular band to be slightly larger than similar measurements for the 30(exp 0)14-00(exp 0)01 parallel band at 6076/cm.

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

    SciTech Connect

    Kim, Jinhyun; Yim, Sanggyu

    2012-10-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

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

  5. Intensity measurements for the /2, O/ gamma-band of O2, b 1Sigma-g/+/ - X 3Sigma-g/-/

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

    Line intensities for the P sub P and P sub Q branches of the (2-O) vibrational band of the magnetic dipole electronic transition for the oxygen red system at 6280 A were measured, and the sum of the R sub R and R sub Q branch intensities was taken. A large number of repetitive spectral scans were required for accuracy, because of low absorption values even at optical path lengths from 300 to 600 m. A total of 557 individual measurements of P-branch lines yielded an intensity value for the P-branches, and equivalent widths for 24 spectral scans yielded an intensity value for the R-branch. R-branch to P-branch intensity ratios were taken for the A-band, B-band, and gamma-band (respectively, O-O at 7620 A, 1-O at 6880 A, and 2-O at 6280 A). Intensities for some rotational lines are found, and effects of combined rotation-vibration interaction are probed.

  6. Absolute Intensities and Pressure-Broadening Coefficients of 2-mum CO(2) Absorption Features: Intracavity Laser Spectroscopy.

    PubMed

    Geng, J; Lunine, J I; Atkinson, G H

    2001-05-20

    The high detection sensitivity available from intracavity laser spectroscopy (ILS) is extended into the near infrared by solid-state laser systems operating with relatively narrow (~0.002 mum) bandwidths for three CO(2) absorption features of importance to an understanding of planetary atmospheres. The absolute intensities and pressure-broadening properties of the P(12), P(14), and P(16) lines of the ?-? band (12 degrees 1-00 degrees 0) of CO(2) (at 2.0129, 2.0136, and 2.0143 mum) are measured quantitatively by ILS with a Tm:YAG laser operating near 2.0 mum. The temperature dependencies of these absolute intensities and collisional-broadening parameters for these three CO(2) features are also measured over the 110-300 K range. The 3.0-km equivalent absorption path length available from the ILS Tm:YAG system is used to enhance detection sensitivity by more than a factor of 1.5 x 10(4) while maintaining a physical sample cell path length of ~20 cm. The enhanced detection sensitivity of ILS permits absolute intensities and collisional-broadening parameters to be measured from <1-Torr CO(2) over a series of temperatures, conditions that emulate those found in the atmospheres of Mars, Triton, and Venus. PMID:18357269

  7. Dual band microwave ferromagnetic resonance absorption in annealed cobalt nanowire arrays

    NASA Astrophysics Data System (ADS)

    Yuan, Lixin; Meng, Siqin; Shi, Yunzhou; Zhang, Yao; Yue, Zhenxing; Li, Longtu

    2014-11-01

    In this letter, we present a dual band microwave absorption phenomenon in 60 nm diameter Co ferromagnetic nanowire arrays annealed at 500 C in nitrogen atmosphere. The frequency dependent microwave response of the wires is obtained for applied field parallel to the nanowire axis, below 4 kOe and above saturation magnetization up to 8 kOe, in steps of 1 kOe. For applied magnetic fields above saturation magnetization, two sets of absorption peaks are observed, while below saturation, only one single peak is obtained. Combining structural characterization and ferromagnetic resonance measurements, it is proven that the two ferromagnetic resonance peaks are associated with a coexistence of two kinds of nanopillars with different crystal structure in annealed nanowires, one for nanopillars with hexagonal close packed structure at higher ferromagnetic resonance frequency, and the other with face center cubic structure.

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

    PubMed

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

    2015-03-01

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

  9. Wafer-scale metamaterials for polarization-insensitive and dual-band perfect absorption

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Zhu, Maoxia; Zhang, Nan; Zhang, Haitao; Zhou, Yu; Sun, Shang; Yi, Ningbo; Gao, Shang; Song, Qinghai; Xiao, Shumin

    2015-11-01

    Mid-infrared (IR) perfect absorbers have great potential in practical applications such as biomedical sensing and thermal energy and have been successfully demonstrated in a number of plasmonic metallic nanostructures. However, all the experimental realizations of perfect absorbers are strongly dependent on nanofabrication techniques, which usually require high costs and a long time to fabricate a wafer scale device. Here we propose and experimentally demonstrate a wafer scale, polarization independent, wide angle, and dual-band IR perfect absorber. By fabricating double ``E''-shaped metallic structures on a ZnSe coated gold film, a dual-band metamaterial absorber has been uniformly realized on a 2'' silicon wafer. Two absorption peaks have been realized at 18 and 27 THz, which are well consistent with the designs. We believe that our research will boost the applications of metamaterial perfect absorbers.

  10. Wafer-scale metamaterials for polarization-insensitive and dual-band perfect absorption.

    PubMed

    Liu, Jia; Zhu, Maoxia; Zhang, Nan; Zhang, Haitao; Zhou, Yu; Sun, Shang; Yi, Ningbo; Gao, Shang; Song, Qinghai; Xiao, Shumin

    2015-12-01

    Mid-infrared (IR) perfect absorbers have great potential in practical applications such as biomedical sensing and thermal energy and have been successfully demonstrated in a number of plasmonic metallic nanostructures. However, all the experimental realizations of perfect absorbers are strongly dependent on nanofabrication techniques, which usually require high costs and a long time to fabricate a wafer scale device. Here we propose and experimentally demonstrate a wafer scale, polarization independent, wide angle, and dual-band IR perfect absorber. By fabricating double "E"-shaped metallic structures on a ZnSe coated gold film, a dual-band metamaterial absorber has been uniformly realized on a 2'' silicon wafer. Two absorption peaks have been realized at 18 and 27 THz, which are well consistent with the designs. We believe that our research will boost the applications of metamaterial perfect absorbers. PMID:26525777

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

    SciTech Connect

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

    2014-04-24

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

  12. Collisional Induced Absorption (CIA) bands of CO2 and H2 measured in the IR spectral range

    NASA Astrophysics Data System (ADS)

    Stefani, S.; Piccioni, G.; Snels, M.; Adriani, A.; Grassi, D.

    2015-10-01

    In this paper we present the results on the Collisional Induced Absorption (CIA) bands of CO2 and H2 measured employing two different experimental setup. Each of them allows us to reproduce typical planetary conditions, at a pressure and temperature from 1 up to 50 bar and from 298 up to 500 K respectively. A detailed study on the temperature dependence of the CO2 CIA absorption bands will be presented.

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

    NASA Technical Reports Server (NTRS)

    Carter, Gregory A.; Spiering, Bruce A.

    2000-01-01

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

  14. Laser measurements of ozone absorption cross sections in the Chappuis band

    NASA Technical Reports Server (NTRS)

    Anderson, Stuart M.; Mauersberger, Konrad

    1992-01-01

    A sensitive spectrometer has been developed that exploits several He-Ne laser transitions in the visible for precise, high resolution measurements of Chappuis band ozone absorption cross sections at room temperature. An overall uncertainty of better than one percent has been achieved through a combination of transducer calibrations and an experimental technique that unambiguously determines the impurity content of each ozone sample. Results compare favorably with those from most previous analyses in the visible range, though some are obviously lower than this consensus due probably to errors in ozone density measurements.

  15. Theoretical Modeling of Low Energy Electronic Absorption Bands in Reduced Cobaloximes

    PubMed Central

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

    2015-01-01

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

  16. The nature of splitting of fullerene C{sub 70} polarized absorption bands in liquid-crystal matrices

    SciTech Connect

    Aver`yanov, E.M.

    1994-06-01

    The recently discovered splitting of polarized electronic absorption bands of fullerene C{sub 70} in uniaxial liquid-crystal matrices is shown to result from the spectral dependence of the polarization of these bands relative to the molecular coordinate system. 9 refs.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

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

    PubMed

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

    2015-04-01

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

  19. A Group Increment Scheme for Infrared Absorption Intensities of Greenhouse Gases

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    SciTech Connect

    Smith, WM.H.; Conner, C.P.; Baines, K.H. JPL, Pasadena, CA )

    1990-05-01

    A novel laser intracavity photoacoustic spectroscopy method allowing high sample control accuracy due to the small sample volume required has been used to obtain absorption coefficients for the CH{sub 4} 6190 A band as a function of temperature, from 290 to 100 K. The peak absorption coefficient is found to increase from 0.6 to 1.0/cm, and to be accompanied by significant band shape changes. When used to further constrain the Baines and Bergstrahl (1986) standard model of the Uranus atmosphere, the low-temperature data yield an excellent fit to the bandshape near the 6190 A band's minimum. 18 refs.

  3. Remote sensing of solar-stimulated phytoplankton chlorophyll fluorescence by differential absorption in the oxygen B-band

    NASA Astrophysics Data System (ADS)

    Frouin, Robert; Deschamps, Pierre-Yves; Dubuisson, Philippe

    2009-01-01

    A new methodology is proposed to estimate from space the solar-induced chlorophyll fluorescence of natural waters. The methodology exploits absorption in the oxygen B-band around 687 nm, located near the peak of fluorescence emission at 685 nm. Inside the oxygen absorption lines, the fluorescence signal enhances the reflected solar radiance. By using a pair of spectral bands inside and outside the absorption region, or more generally spectral bands for which oxygen absorption is sufficiently different, the emitted contribution to the measured radiance can be extracted. Feasibility is demonstrated and retrieval accuracy quantified through simulations of the top-of-atmosphere reflectance by a radiation transfer code that fully accounts for multiple scattering and interactions between scattering and absorption. The differential absorption method works well from just above the surface. Pairs of spectral bands centered on the same wavelength provide the best results. Using spectral bands of 686.8-688.3 nm and 683.1-692.0 nm, the expected accuracy on fluorescence retrievals is <10% for chlorophyll concentrations above 1 mgm-3. Performance is degraded from space, due to the influence of aerosol vertical structure on the oxygen transmittance associated with path reflectance. In this case, knowledge of aerosol reflectance and optical thickness is required, but assuming an average aerosol vertical distribution yields reasonable results. In comparison with the standard baseline technique, significant improvements in retrieval accuracy are expected in Case II waters, especially in the presence of sediments.

  4. Remote sensing of solar-stimulated phytoplankton chlorophyll fluorescence by differential absorption in the oxygen B-band

    NASA Astrophysics Data System (ADS)

    Frouin, Robert; Deschamps, Pierre-Yves; Dubuisson, Philippe

    2008-12-01

    A new methodology is proposed to estimate from space the solar-induced chlorophyll fluorescence of natural waters. The methodology exploits absorption in the oxygen B-band around 687 nm, located near the peak of fluorescence emission at 685 nm. Inside the oxygen absorption lines, the fluorescence signal enhances the reflected solar radiance. By using a pair of spectral bands inside and outside the absorption region, or more generally spectral bands for which oxygen absorption is sufficiently different, the emitted contribution to the measured radiance can be extracted. Feasibility is demonstrated and retrieval accuracy quantified through simulations of the top-of-atmosphere reflectance by a radiation transfer code that fully accounts for multiple scattering and interactions between scattering and absorption. The differential absorption method works well from just above the surface. Pairs of spectral bands centered on the same wavelength provide the best results. Using spectral bands of 686.8-688.3 nm and 683.1-692.0 nm, the expected accuracy on fluorescence retrievals is <10% for chlorophyll concentrations above 1 mgm-3. Performance is degraded from space, due to the influence of aerosol vertical structure on the oxygen transmittance associated with path reflectance. In this case, knowledge of aerosol reflectance and optical thickness is required, but assuming an average aerosol vertical distribution yields reasonable results. In comparison with the standard baseline technique, significant improvements in retrieval accuracy are expected in Case II waters, especially in the presence of sediments.

  5. Ultra-wideband microwave absorber by connecting multiple absorption bands of two different-sized hyperbolic metamaterial waveguide arrays

    PubMed Central

    Yin, Xiang; Long, Chang; Li, Junhao; Zhu, Hua; Chen, Lin; Guan, Jianguo; Li, Xun

    2015-01-01

    Microwave absorbers have important applications in various areas including stealth, camouflage, and antenna. Here, we have designed an ultra-broadband light absorber by integrating two different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has wide but different absorption bands due to broadband slow-light response, into a unit cell. Both the numerical and experimental results demonstrate that in such a design strategy, the low absorption bands between high absorption bands with a single-sized tapered HMM waveguide array can be effectively eliminated, resulting in a largely expanded absorption bandwidth ranging from 2.3 to 40 GHz. The presented ultra-broadband light absorber is also insensitive to polarization and robust against incident angle. Our results offer a further step in developing practical artificial electromagnetic absorbers, which will impact a broad range of applications at microwave frequencies. PMID:26477740

  6. Ultra-wideband microwave absorber by connecting multiple absorption bands of two different-sized hyperbolic metamaterial waveguide arrays

    NASA Astrophysics Data System (ADS)

    Yin, Xiang; Long, Chang; Li, Junhao; Zhu, Hua; Chen, Lin; Guan, Jianguo; Li, Xun

    2015-10-01

    Microwave absorbers have important applications in various areas including stealth, camouflage, and antenna. Here, we have designed an ultra-broadband light absorber by integrating two different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has wide but different absorption bands due to broadband slow-light response, into a unit cell. Both the numerical and experimental results demonstrate that in such a design strategy, the low absorption bands between high absorption bands with a single-sized tapered HMM waveguide array can be effectively eliminated, resulting in a largely expanded absorption bandwidth ranging from 2.3 to 40 GHz. The presented ultra-broadband light absorber is also insensitive to polarization and robust against incident angle. Our results offer a further step in developing practical artificial electromagnetic absorbers, which will impact a broad range of applications at microwave frequencies.

  7. Ultra-wideband microwave absorber by connecting multiple absorption bands of two different-sized hyperbolic metamaterial waveguide arrays.

    PubMed

    Yin, Xiang; Long, Chang; Li, Junhao; Zhu, Hua; Chen, Lin; Guan, Jianguo; Li, Xun

    2015-01-01

    Microwave absorbers have important applications in various areas including stealth, camouflage, and antenna. Here, we have designed an ultra-broadband light absorber by integrating two different-sized tapered hyperbolic metamaterial (HMM) waveguides, each of which has wide but different absorption bands due to broadband slow-light response, into a unit cell. Both the numerical and experimental results demonstrate that in such a design strategy, the low absorption bands between high absorption bands with a single-sized tapered HMM waveguide array can be effectively eliminated, resulting in a largely expanded absorption bandwidth ranging from 2.3 to 40 GHz. The presented ultra-broadband light absorber is also insensitive to polarization and robust against incident angle. Our results offer a further step in developing practical artificial electromagnetic absorbers, which will impact a broad range of applications at microwave frequencies. PMID:26477740

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

    SciTech Connect

    Flittner, D.E.; Herman, B.M.; Thome, K.J.; Simpson, J.M.; Reagan, J.A. )

    1993-04-15

    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.

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

    PubMed

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

    2013-08-15

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

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

    SciTech Connect

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

    2009-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

  12. The use of simultaneous confidence bands for comparison of single parameter fluorescent intensity data.

    PubMed

    Kim, Dongha; Donnenberg, Vera S; Wilson, John W; Donnenberg, Albert D

    2016-01-01

    Despite the utility of multiparameter flow cytometry for a wide variety of biological applications, comparing single parameter histograms of fluorescence intensity remains a mainstay of flow cytometric analysis. Even comparisons requiring multiparameter gating strategies often end with single parameter histograms as the final readout. When histograms overlap, analysis relies on comparison of mean or median fluorescence intensities, or determination of percent positive based on an arbitrary cutoff. Earlier attempts to address this problem utilized either simple channel-by-channel subtraction without statistical evaluation, or the Kolmogorov-Smirnov (KS) or Chi-square test statistics, both of which proved to be overly sensitive to small and biologically insignificant differences. Here we present a method for the comparison of two single-parameter histograms based on difference curves and their simultaneous confidence bands generated by bootstrapping raw channel data. Bootstrapping is a nonparametric statistical approach that can be used to generate confidence intervals without distributional assumptions about the data. We have constructed simultaneous confidence bands and show them to be superior to KS and Cox methods. The method constructs 95% confidence bands about the difference curves, provides a P value for the comparison and calculates the area under the difference curve (AUC) as an estimate of percent positive and the area under the confidence band (AUCSCB95 ), providing a lower estimate of the percent positive. To demonstrate the utility of this new approach we have examined single-color fluorescence intensity data taken from a cell surface proteomic survey of a lung cancer cell line (A549) and a published fluorescence intensity data from a rhodamine efflux assay of P-glycoprotein activity, comparing rhodamine 123 loading and efflux in CD4 and CD8 T-cell populations. SAS source code is provided as supplementary material. 2015 International Society for Advancement of Cytometry. PMID:26407241

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

    NASA Astrophysics Data System (ADS)

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

    2002-01-01

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

  14. Polarization-adjustable dual-band absorption in GHz-band metamaterial, based-on no-smoking symbol

    NASA Astrophysics Data System (ADS)

    Yoo, Young Joon; Kim, Young Ju; Lee, YoungPak; Lee, Myung Whan; Lee, Tae Gyun; Kim, Min Woo; Park, Jae Hyun

    2015-11-01

    We propose three kinds of the perfect metamaterial absorbers based on the well-known no-smoking symbol, which can adjust the absorption according to the polarization of incident electromagnetic wave. By modifying no-smoking symbol, a resonance absorption peak at 6.75 GHz can be controlled. In addition, a split-ring structure and the no-smoking symbol also adjust the absorption. We also demonstrate the absorption mechanism for all the structures. These results can be used in controlling absorption by the electromagnetic-wave detector.

  15. Lunar iron abundance determination using the 2-μm absorption band parameters

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Agarwal, G. S.; Dey, Tarak Nath

    2004-05-01

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

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

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

    SciTech Connect

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

    1983-03-01

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

  18. The effect of metal binding on the characteristic infrared band intensities of ligands of biological interest

    NASA Astrophysics Data System (ADS)

    Dudev, Todor; Lim, Carmay

    2012-02-01

    Since 40% of all proteins contain metal ions that perform a wide variety of functions indispensable for life processes, a plethora of experimental and theoretical methods have probed the interactions between metal ions and protein residues. Notably, previous studies have focused on how metal binding affects the protein ligands' vibrational frequencies, but not the corresponding intensities (to the best of our knowledge), even though the latter are generally much more sensitive to structural and environmental alterations than the former. Hence, we have systematically evaluated how metal binding affects not only the protein ligands' vibrational frequencies, but also the corresponding intensities and how these IR parameters depend on properties of the metal and its host ligand using density functional calculations. The results reveal that for a given protein ligand, the IR intensities, particularly those corresponding to bands without vibrational mode mixing, are quite sensitive to metal binding, and their changes are dictated by the metal's charge-accepting ability and the ligand's denticity. The results suggest that IR band intensities, along with vibrational frequencies, may be used to help interpret the IR spectra of protein binding sites in the metal-free and metal-bound states.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

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

    SciTech Connect

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

    2011-04-15

    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.

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

    SciTech Connect

    Zapata, L.E.; Pertica, A.J.

    1989-12-28

    A high resolution (1{angstrom}), absolute intensity spectrum from 300 to 900 nm was obtained for a high average power (100 kWe) argon arc-lamp. The high average power is obtained due to innovative technology that cools the inside surface of the lamp envelope by means of a spiraling water jet. The optical output between 200 and 2000 nm was measured by using a calibrated pyroelectric detector and glass color filters, and accounted for 54% of the electrical input. The argon arc-lamp radiated 35% of the electrical power input in the 400 to 900 nm spectral region when a cerium doped quartz envelope was used; furthermore, 37% of this optical power was emitted as line output between 730 and 830 nm, a region well tuned to Nd{sup 3+}:YAG absorption bands. Lower resolution spectra and fluorescence/transmission measurements of YAG samples were obtained for mixtures of Ar/Kr and Ar/Xe with up to 14% by volume of the heavier species. When the Ar/14%-Kr mixture was used, increased absorption (115%) and net fluorescence (120%) were measured relative to the pure argon arc-lamp. 4 refs., 6 figs., 1 tab.

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

    SciTech Connect

    Zapata, L.E.

    1989-05-10

    A high resolution (1 /angstrom/), absolute intensity spectrum from 300 to 900 nm was obtained for a high average power (100 kWe) argon arc-lamp. The high average power is obtained due to innovative technology that cools the inside surface of the lamp envelope by means of a spiraling water jet. The optical output between 200 and 2000 nm was measured by using a calibrated pyroelectric detector and glass color filters, and accounted for 54% of the electrical input. The agron arc-lamp radiated 35% of the electrical power input in the 400 to 900 nm spectral region when a cerium doped quartz envelope was used; furthermore, 37% of this optical power was emitted as line output between 730 and 830 nm, a region well tuned to Nd/sup 3 +/:YAG absorption bands. Lower resolution spectra and fluorescence/transmission measurements of YAG samples were obtained for mixtures of Ar/Kr and Ar/Xe with up to 14% by volume of the heavier species. When the Ar/14%-Kr mixture was used, increased absorption (115%) and net fluorescence (120%) were measured relative to the pure argon arc-lamp. 5 refs., 8 figs., 1 tab.

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

    SciTech Connect

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

    2013-03-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Flittner, D. E.; Herman, B. M.; Thome, K. J.; Simpson, J. M.; Reagan, J. A.

    1993-01-01

    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 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 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 percent. 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 estimated total ozone and is unique in that it uses measurements from both the Chappuis and Huggins absorption bands.

  6. Absorption intensity tunability in the near infrared region using phase-change nanostructure (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Ozdemir, Abdurrahman; Saraydemir, Safak; Barut, Bilal; Kocer, Hasan

    2015-08-01

    Nanostructured thin film absorbers embedded with phase-change material (PCM) can provide large level of absorption intensity tunability in the near-infrared region. Germanium Antimonide Tellurite (Ge2Sb1Te4-GST) was employed as the phase-change material in the designed structures. The structure is composed of a periodic grating-type array of 200 nm thick Au buried with 100 nm-thick GST layer from the top of the Au layer. The period of the gratings is 2 μm and in each period, GST width is 0.5 μm. GST was selected as the active PCM because its optical properties undergo a substantial change during a structural transition from the amorphous to the crystalline phase. The optical absorption properties of the designed structures with respect to the geometric and material parameters were systematically investigated using finite-difference time-domain computations. It was shown that absorption intensity in the near-infrared region was tuned from the near-perfect to the near-zero level by switching the PCM from its amorphous to crystalline states. The distributions of the electric field and absorbed power at the resonant wavelengths with respect to different phases of the GST were investigated to further explain the physical origin of the absorption tuning. This study provides a path toward the realization of tunable infrared absorbers for the applications, such as selective infrared emitters, infrared camouflage, sensors, and photovoltaic devices.

  7. Investigation of band gap narrowing in nitrogen-doped La2Ti2O7 with transient absorption spectroscopy.

    PubMed

    Yost, Brandon T; Cushing, Scott K; Meng, Fanke; Bright, Joeseph; Bas, Derek A; Wu, Nianqiang; Bristow, Alan D

    2015-11-18

    Doping a semiconductor can extend the light absorption range, however, it usually introduces mid-gap states, reducing the charge carrier lifetime. This report shows that doping lanthanum dititinate (La2Ti2O7) with nitrogen extends the valence band edge by creating a continuum of dopant states, increasing the light absorption edge from 380 nm to 550 nm without adding mid-gap states. The dopant states are experimentally resolved in the excited state by correlating transient absorption spectroscopy with a supercontinuum probe and DFT prediction. The lack of mid-gap states is further confirmed by measuring the excited state lifetimes, which reveal the shifted band edge only increased carrier thermalization rates to the band edge and not interband charge recombination under both ultraviolet and visible excitation. Terahertz (time-domain) spectroscopy also reveals that the conduction mechanism remains unchanged after doping, suggesting the states are delocalized. PMID:26531849

  8. A study of the structure of the ν1(HF) absorption band of the СH3СN…HF complex

    NASA Astrophysics Data System (ADS)

    Gromova, E. I.; Glazachev, E. V.; Bulychev, V. P.; Koshevarnikov, A. M.; Tokhadze, K. G.

    2015-09-01

    The ν1(HF) absorption band shape of the CH3CN…HF complex is studied in the gas phase at a temperature of 293 K. The spectra of gas mixtures CH3CN/HF are recorded in the region of 4000-3400 cm-1 at a resolution from 0.1 to 0.005 cm-1 with a Bruker IFS-120 HR vacuum Fourier spectrometer in a cell 10 cm in length with wedge-shaped sapphire windows. The procedure used to separate the residual water absorption allows more than ten fine-structure bands to be recorded on the low-frequency wing of the ν1(HF) band. It is shown that the fine structure of the band is formed primarily due to hot transitions from excited states of the low-frequency ν7 librational vibration. Geometrical parameters of the equilibrium nuclear configuration, the binding energy, and the dipole moment of the complex are determined from a sufficiently accurate quantum-chemical calculation. The frequencies and intensities for a number of spectral transitions of this complex are obtained in the harmonic approximation and from variational solutions of anharmonic vibrational problems.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  10. Electric field dependence of optical absorption near the band gap of quantum-well structures

    NASA Astrophysics Data System (ADS)

    Miller, D. A. B.; Chemla, D. S.; Damen, T. C.; Gossard, A. C.; Wiegmann, W.; Wood, T. H.; Burrus, C. A.

    1985-07-01

    We report experiments and theory on the effects of electric fields on the optical absorption near the band edge in GaAs/AlGaAs quantum-well structures. We find distinct physical effects for fields parallel and perpendicular to the quantum-well layers. In both cases, we observe large changes in the absorption near the exciton peaks. In the parallel-field case, the excitons broaden with field, disappearing at fields ~104 V/cm; this behavior is in qualitative agreement with previous theory and in order-of-magnitude agreement with direct theoretical calculations of field ionization rates reported in this paper. This behavior is also qualitatively similar to that seen with three-dimensional semiconductors. For the perpendicular-field case, we see shifts of the exciton peaks to lower energies by up to 2.5 times the zero-field binding energy with the excitons remaining resolved at up to ~105 V/cm: This behavior is qualitatively different from that of bulk semiconductors and is explained through a mechanism previously briefly described by us [D. A. B. Miller et al., Phys. Rev. Lett. 53, 2173 (1984)] called the quantum-confined Stark effect. In this mechanism the quantum confinement of carriers inhibits the exciton field ionization. To support this mechanism we present detailed calculations of the shift of exciton peaks including (i) exact solutions for single particles in infinite wells, (ii) tunneling resonance calculations for finite wells, and (iii) variational calculations of exciton binding energy in a field. We also calculate the tunneling lifetimes of particles in the wells to check the inhibition of field ionization. The calculations are performed using both the 85:15 split of band-gap discontinuity between conduction and valence bands and the recently proposed 57:43 split. Although the detailed calculations differ in the two cases, the overall shift of the exciton peaks is not very sensitive to split ratio. We find excellent agreement with experiment with no fitted parameters.

  11. Spectral structure of the water vapour continuum absorption in 2.7 and 6.25 ?m bands

    NASA Astrophysics Data System (ADS)

    Ptashnik, Igor V.; Klimeshina, Tatyana E.; Petrova, Tatyana M.; Solodov, Alexander A.; Solodov, Alexander M.

    2015-11-01

    For the first time, the low-temperature (from -9 to 15 C) Fourier Transform Spectroscopy laboratory measurements of the pure water vapor absorption spectra are performed in the near-infrared spectral region, and self-continuum absorption is retrieved within 1600 cm-1 (6.25 ?m) and 3600 cm-1 (2.7?m) absorption bands. The proportion of true-bound and quasi-bound water dimers in the equilibrium water vapor is derived by fitting their model spectra to the spectral features of the retrieved continuum. The results are in reasonable agreement with statistical calculations and support the idea of complimentary contribution stable and metastable dimers to the spectral structure of water vapor continuum within absorption bands.

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

    PubMed

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

    2011-04-19

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  14. Collision induced absorption in the a1?(v = 2) ? X3?g(-)(v = 0) band of molecular oxygen.

    PubMed

    Spiering, Frans R; van der Zande, Wim J

    2012-07-28

    Using cavity ring-down spectroscopy we measured the collision induced absorption spectrum associated with the a(1)?(v = 2) ?X(3)?(g)(-)(v = 0) band of oxygen near 922 nm both in pure oxygen and in mixtures of oxygen and nitrogen. For pure oxygen, we report for this band an integrated absorption of (1.56 - 0.04/+0.40) 10(-5) cm(-2) amg(-2). We find that collisions between oxygen and nitrogen do not result in any measurable CIA signal. At 1 bar of oxygen, this collision induced transition is much stronger than the allowed magnetic dipole and electric quadrupole transitions. PMID:22699258

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  18. Line Positions and Intensities for the ?12 Band of 13C12CH_6

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    High-resolution, high signal-to-noise spectra of mono-substituted 13C-ethane (13C12CH_6) in the 12.2 ?m region were recorded with a Bruker IFS 125HR Fourier transform spectrometer. The spectra were obtained for four sample pressures at three different temperatures between 130 and 208 K using a 99% 13C-enriched ethane sample contained in a 20.38-cm long coolable absorption cell. A multispectrum nonlinear least squares fitting technique was used to fit the same intervals in the four spectra simultaneously to determine line positions and intensities. Similar to our previous analyses of 12C_2H_6 spectra in this same region, constraints were applied to accurately fit each pair of doublet components arising from torsional Coriolis interaction of the excited ?12 = 1 state with the nearby torsional ?_6 = 3 state. Line intensities corresponding to each spectrum temperature (130 K, 178 K and 208 K) are reported for 1660 ?12 absorption lines for which the assignments are known, and integrated intensities are estimated as the summation of the measured values. The measured line positions and intensities (re-scaled to 296 K) are compared with values in recent editions of spectroscopic databases. K. Sung, A. W. Mantz, L. R. Brown, et al., J. Mol. Spectrosc., 162 (2010) 124-134. D. C. Benner, C. P. Rinsland, V. Malathy Devi, M. A. H. Smith and D. Atkins, JQSRT, 53 (1995) 705-721. V. Malathy Devi, C. P. Rinsland, D. Chris Benner, et al., JQSRT, 111 (2010) 1234-1251 V. Malathy Devi, D. Chris Benner, C. P. Rinsland, et al., JQSRT, 111 (2010) 2481-2504. Research described in this paper was performed at Connecticut College, the College of William and Mary, NASA Langley Research Center and the Jet Propulsion Laboratory, California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration.

  19. 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)

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

    1995-01-01

    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.

  20. Retrieval of phytoplankton and colored detrital matter absorption coefficients with remote sensing reflectance in an ultraviolet band.

    PubMed

    Wei, Jianwei; Lee, Zhongping

    2015-02-01

    The light absorption of phytoplankton and colored detrital matter (CDM), which includes contribution of gelbstoff and detrital matters, has distinctive yet overlapping features in the ultraviolet (UV) and visible domain. The CDM absorption (a(dg)) increases exponentially with decreasing wavelength while the absorption coefficient of phytoplankton (a(ph)) generally decreases toward the shorter bands for the range of 350-450 nm. It has long been envisioned that including ocean color measurements in the UV range may help the separation of these two components from the remotely sensed ocean color spectrum. An attempt is made in this study to provide an analytical assessment of this expectation. We started with the development of an absorption decomposition model [quasi-analytical algorithm (QAA)-UV], analogous to the QAA, that partitions the total absorption coefficient using information at bands 380 and 440 nm. Compared to the retrieval results relying on the absorption information at 410 and 440 nm of the original QAA, our analyses indicate that QAA-UV can improve the retrieval of a(ph) and a(dg), although the improvement in accuracy is not significant for values at 440 nm. The performance of the UV-based algorithm is further evaluated with in situ measurements. The limited improvement observed with the field measurements highlights that the separation of a(dg) and a(ph) is highly dependent on the accuracy of the ocean color measurements and the estimated total absorption coefficient. PMID:25967770

  1. Electronic band structure information of GdN extracted from x-ray absorption and emission spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

    The electronic structure of GdN films grown by pulsed laser deposition has been investigated by soft x-ray absorption (XAS) and x-ray emission spectroscopy (XES) at the N K-edge. Density functional calculations within the local spin density approximation with Hubbard-U corrections of the N p weighted bands and density of states are used to extract band information from the spectra. Gd M4,5 XAS and XES spectra are also presented. The XES-XAS separation is shown to give information on the f-band spin splitting and the XAS line shapes are shown to reflect atomic multiplet effects.

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

    PubMed

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

    2015-07-01

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

  3. Dual-band microwave absorption properties of metamaterial absorber composed of split ring resonator on carbonyl iron powder composites

    NASA Astrophysics Data System (ADS)

    Lim, Jun-Hee; Ryu, Yo-Han; Kim, Sung-Soo

    2015-05-01

    This study investigated the dual-band absorption properties of metamaterial absorbers composed of a split ring resonator (SRR) on a grounded magnetic substrate. Polymer composites of carbonyl iron powders (CIP) of high permeability and magnetic loss were used as the substrate material. Computational tools were used to model the interaction between electromagnetic waves and materials with the SRR structure. For perpendicular polarization with an electric field (E) perpendicular to the SRR gap, dualband absorption peaks are predicted in the simulation result of reflection loss. Magnetic resonance resulting from antiparallel currents between the SRR and the ground plane is observed at the frequencies of two absorption peaks. The first strong absorption peak at the lower frequency (3.3 GHz) is due to magnetic resonance at the wire part of the SRR. The second absorption peak at the higher frequency (7.2 GHz) is due to magnetic resonance at the SRR split gap. The decreased capacitance with increased gap spacing moves the second absorption frequency to higher frequencies, while the first absorption peak is invariant with gap spacing. In the case of dual gaps at the opposite sides of the SRR, a single absorption peak is predicted due to the elimination of low-frequency resonance. For parallel polarization with the E-field parallel to the SRR gap, a single absorption peak is predicted, corresponding to magnetic resonance at the SRR wire.[Figure not available: see fulltext.

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

    SciTech Connect

    Guo Bin

    2009-04-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Ozone plays a crucial role in tropospheric chemistry, is the third largest contributor to greenhouse radiative forcing after carbon dioxide and methane and also a toxic air pollutant affecting human health and agriculture. Long-term measurements of tropospheric ozone have been performed globally for more than 30 years with UV photometers, all relying on the absorption of ozone at the 253.65 nm line of mercury. We have re-determined this cross-section and report a value of 11.27 x 10-18 cm2 molecule-1 with an expanded relative uncertainty of 0.86% (coverage factor k= 2). This is lower than the conventional value currently in use and measured by Hearn (1961) with a relative difference of 1.8%, with the consequence that historically reported ozone concentrations should be increased by 1.8%. In order to perform the new measurements of cross-sections with reduced uncertainties, a system was set up to generate pure ozone in the gas phase together with an optical system based on a UV laser with lines in the Hartley band, including accurate path length measurement of the absorption cell and a careful evaluation of possible impurities in the ozone sample by mass spectrometry and Fourier transform infrared spectroscopy. This resulted in new measurements of absolute values of ozone absorption cross-sections of 9.48 x 10-18, 10.44 x 10-18 and 11.07 x 10-18 cm2 molecule-1, with relative expanded uncertainties better than 0.7%, for the wavelengths (in vacuum) of 244.06, 248.32, and 257.34 nm respectively. The cross-section at the 253.65 nm line of mercury was determined by comparisons using a Standard Reference Photometer equipped with a mercury lamp as the light source. The newly reported value should be used in the future to obtain the most accurate measurements of ozone concentration, which are in closer agreement with non-UV-photometry based methods such as the gas phase titration of ozone with nitrogen monoxide.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

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

    2014-12-31

    Femtosecond interferometry has been used to experimentally study the photoexcitation of the electron subsystem of diamond exposed to femtosecond laser pulses of intensity 10{sup 11} to 10{sup 14} W cm{sup -2}. The carrier concentration has been determined as a function of incident intensity for three harmonics of a Ti : sapphire laser (800, 400 and 266 nm). The results demonstrate that, in a wide range of laser fluences (up to those resulting in surface and bulk graphitisation), a well-defined multiphoton absorption prevails. We have estimated nonlinear absorption coefficients for pulsed radiation at λ = 800 nm (four-photon transition) and at 400 and 266 nm (indirect and direct two-photon transitions, respectively). It has also been shown that, at any considerable path length of a femtosecond pulse in diamond (tens of microns or longer), the laser beam experiences a severe nonlinear transformation, determining the amount of energy absorbed by the lattice, which is important for the development of technology for diamond photostructuring by ultrashort pulses. The competition between wave packet self-focusing and the plasma defocusing effect is examined as a major mechanism governing the propagation of intense laser pulses in diamond. (interaction of laser radiation with matter. laser plasma)

  8. Solar wind speed and He I (1083 nm) absorption line intensity

    SciTech Connect

    Hakamada, Kazuyuki ); Kojima, Masayoshi; Kakinuma, Takakiyo )

    1991-04-01

    Since the pattern of the solar wind was relatively steady during Carrington rotations 1,748 through 1,752 in 1984, an average distribution of the solar windspeed on a so-called source surface can be constructed by superposed epoch analysis of the wind values estimated by the interplanetary scintillation observations. The average distribution of the solar wind speed is then projected onto the photosphere along magnetic field lines computed by a so-called potential model with the line-of-sight components of the photospheric magnetic fields. The solar wind speeds projected onto the photosphere are compared with the intensities of the He I (1,083 nm) absorption line at the corresponding locations in the chromosphere. The authors found that there is a linear relation between the speeds and the intensities. Since the intensity of the He I (1,083 nm) absorption line is coupled with the temperature of the corona, this relation suggests that some physical mechanism in or above the photosphere accelerates coronal plasmas to the solar wind speed in regions where the temperature is low. Further, it is suggested that the efficiency of the solar wind acceleration decreases as the coronal temperature increases.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    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.

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

    PubMed

    Jeong, Cheol-Ho

    2010-06-01

    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

  11. Rainfall Intensity and Drop Size Measurements with Polarimetric X-band Radar

    NASA Astrophysics Data System (ADS)

    Martner, B. E.; Matrosov, S. Y.; Clark, K. A.; Tokay, A.

    2002-12-01

    Most studies for developing quantitative, scanning radar estimates of rainfall have been conducted using 3-GHz (S-band, 10-cm wavelength) weather surveillance radar systems, in order to avoid attenuation effects that significantly impair reflectivity (Z) measurements at shorter wavelengths. However, the recent extension of polarimetric differential phase methods to shorter-wave systems, including X-band (9 GHz, 3-cm), now allows these generally smaller radars to also be used for quantitative rain estimations. Differential phase offers rainfall estimates that are independent of reflectivity data, as well as a way to adjust for partial attenuation effects in X-band reflectivity data. Rainfall intensity and accumulation measurements based on specific differential phase (KDP) alone offer many advantages over traditional reflectivity-based rain estimates. In this study, rain observations obtained with a polarimetric X-band scanning radar are processed with algorithms that estimate rain rate using differential phase, reflectivity, and a combination of the radar's measurements of differential phase with attenuation-corrected reflectivity and differential reflectivity (ZDR). The attenuation-corrected ZDR measurements are also used to estimate mean raindrop diameter. Demonstration measurements were obtained at Wallops Island, Virginia, in 15 storms with rain rates ranging from very light to heavy. The radar estimates are compared with measurements by tipping bucket rain gauges and raindrop disdrometers located a few kilometers away. It was found that the combined Z-ZDR-KDP estimator provided the closest agreement with gauge measurements, having an overall 22 per cent relative standard deviation of differences. The attenuation-adjusted ZDR estimates of mean drop diameter also compared well with the disdrometer measurements.

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

    SciTech Connect

    AbuEl-Rub, Khaled M.

    2012-09-06

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

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

    NASA Astrophysics Data System (ADS)

    AbuEl-Rub, Khaled M.

    2012-09-01

    The MBE growth of short-period InAs/GaSb type-II superlattice structures, varied around 20.5 Å InAs/24 Å 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.

  14. Modeling the absorption of intense, short laser pulses in steep density gradients

    SciTech Connect

    Alley, W.E.

    1991-01-28

    A subroutine which calculates the absorption of short pulse electromagnetic radiation in a material has been installed into the laser fusion modeling program called LASNEX. Calculational results show the necessity for NLTE physics to account for ionization, the development of non-exponential density profiles for the expanding plasma and movement of the critical point toward the surface which results in Doppler shifts of the reflected light. Comparison of calculations of local scale lengths with experiments shows not only good agreement but the correct scaling with intensity. 8 refs., 5 figs.

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

    SciTech Connect

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

    2011-09-15

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

  16. Direct extraction of intense-field-induced polarization in the continuum on the attosecond time scale from transient absorption

    NASA Astrophysics Data System (ADS)

    Li, X.; Haxton, D. J.; Gaarde, M. B.; Schafer, K. J.; McCurdy, C. W.

    2016-02-01

    A procedure is suggested for using transient absorption spectroscopy above the ionization threshold to measure the polarization of the continuum induced by an intense optical pulse. In this way transient absorption measurement can be used to probe subfemtosecond intense field dynamics in atoms and molecules. The method is based on an approximation to the dependence of these spectra on time delay between an attosecond XUV probe pulse and an intense pump pulse that is tested over a wide range of intensities and time delays by all-electrons-active calculations using the multiconfiguration time-dependent Hartree-Fock method in the case of neon.

  17. Structural diversity of the 3-micron absorption band in Enceladus’ plume from Cassini VIMS: Insights into subsurface environmental conditions

    NASA Astrophysics Data System (ADS)

    Dhingra, Deepak; Hedman, Matthew M.; Clark, Roger N.

    2015-11-01

    Water ice particles in Enceladus’ plume display their diagnostic 3-micron absorption band in Cassini VIMS data. These near infrared measurements of the plume also exhibit noticeable variations in the character of this band. Mie theory calculations reveal that the shape and location of the 3-micron band are controlled by a number of environmental and structural parameters. Hence, this band provides important insights into the properties of the water ice grains and about the subsurface environmental conditions under which they formed. For example, the position of the 3-micron absorption band minimum can be used to distinguish between crystalline and amorphous forms of water ice and to constrain the formation temperature of the ice grains. VIMS data indicates that the water ice grains in the plume are dominantly crystalline which could indicate formation temperatures above 113 K [e.g. 1, 2]. However, there are slight (but observable) variations in the band minimum position and band shape that may hint at the possibility of varying abundance of amorphous ice particles within the plume. The modeling results further indicate that there are systematic shifts in band minimum position with temperature for any given form of ice but the crystalline and amorphous forms of water ice are still distinguishable at VIMS spectral resolution. Analysis of the eruptions from individual source fissures (tiger stripes) using selected VIMS observations reveal differences in the 3-micron band shape that may reflect differences in the size distributions of the water ice particles along individual fissures. Mie theory models suggest that big ice particles (>3 micron) may be an important component of the plume.[1] Kouchi, A., T. Yamamoto, T. Kozasa, T. Kuroda, and J. M. Greenberg (1994) A&A, 290, 1009-1018 [2] Mastrapa, R. M. E., W. M. Grundy, and M. S. Gudipati (2013) in M. S. Gudipati and J. Castillo-Rogez (Eds.), The Science of Solar System Ices, pp. 371.

  18. High intensity single bunch operation with heavy periodic transient beam loading in wide band rf cavities

    NASA Astrophysics Data System (ADS)

    Tamura, Fumihiko; Hotchi, Hideaki; Schnase, Alexander; Yoshii, Masahito; Yamamoto, Masanobu; Ohmori, Chihiro; Nomura, Masahiro; Toda, Makoto; Shimada, Taihei; Hasegawa, Katsushi; Hara, Keigo

    2015-09-01

    The rapid cycling synchrotron (RCS) in the Japan Proton Accelerator Research Complex (J-PARC) was originally designed to accelerate two high intensity bunches, while some of neutron experiments in the materials and life science experimental facility and a muon experiment using main ring beams require a single bunch operation mode, in which one of the two rf buckets is filled and the other is empty. The beam intensity in the single bunch operation has been limited by longitudinal beam losses due to the rf bucket distortions by the wake voltage of the odd harmonics (h =1 ,3 ,5 ) in the wide band magnetic alloy cavities. We installed an additional rf feedforward system to compensate the wake voltages of the odd harmonics (h =1 ,3 ,5 ). The additional system has a similar structure as the existing feedforward system for the even harmonics (h =2 ,4 ,6 ). We describe the function of the feedforward system for the odd harmonics, the commissioning methodology, and the commissioning results. The longitudinal beam losses during the single bunch acceleration disappeared with feedforward for the odd harmonics. We also confirmed that the beam quality in the single bunch acceleration are similar to that of the normal operation with two bunches. Thus, high intensity single bunch acceleration at the intensity of 2.3 ×1013 protons per bunch has been achieved in the J-PARC RCS. This article is a follow-up of our previous article, Phys. Rev. ST Accel. Beams 14, 051004 (2011). The feedforward system extension for single bunch operation was successful.

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

    PubMed

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

    2005-03-01

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

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

    USGS Publications Warehouse

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

    1989-01-01

    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.

  1. Generation of Intense Narrow-Band Tunable Terahertz Radiation from Highly Bunched Electron Pulse Train

    NASA Astrophysics Data System (ADS)

    Li, Heting; Lu, Yalin; He, Zhigang; Jia, Qika; Wang, Lin

    2016-02-01

    We present the analysis and start-to-end simulation of an intense narrow-band terahertz (THz) source with a broad tuning range of radiation frequency, using a single-pass free electron laser (FEL) driven by a THz-pulse-train photoinjector. The fundamental radiation frequency, corresponding to the spacing between the electron microbunches, can be easily tuned by varying the spacing time between the laser micropulses. Since the prebunched electron beam is highly bunched at the first several harmonics, with the harmonic generation technique, the radiation frequency range can be further enlarged by several times. The start-to-end simulation results show that this FEL is capable of generating a few tens megawatts power, several tens micro-joules pulse energy, and a few percent bandwidth at the frequencies of 0.5-5 THz. In addition, several practical issues are considered.

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

    PubMed

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

    2013-07-01

    Three-dimensional potential energy surfaces for the two lowest singlet (A?(1)B1 and B?(1)A2) and two lowest triplet (a?(3)B1 and b?(3)A2) 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. PMID:23822301

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

    Three-dimensional potential energy surfaces for the two lowest singlet (tilde A{}^1B_1 and tilde B{}^1A_2 ) and two lowest triplet (tilde a^3 B_1 and tilde b^3 A_2 ) states of SO2 have been determined at the Davidson corrected internally contracted multi-reference configuration interaction level with the augmented correlation-consistent polarized triple-zeta basis set (icMRCI+Q/AVTZ). The non-adiabatically coupled singlet states, which are responsible for the complex Clements bands of the B band, are expressed in a 2 × 2 quasi-diabatic representation. The triplet state potential energy surfaces, which are responsible for the weak A band, were constructed in the adiabatic representation. The absorption spectrum spanning both the A and B bands, which is calculated with a three-state non-adiabatic coupled Hamiltonian, is in good agreement with experiment, thus validating the potential energy surfaces and their couplings.

  4. Mapping atomic and diffuse interstellar band absorption across the Magellanic Clouds and the Milky Way

    NASA Astrophysics Data System (ADS)

    Bailey, Mandy; van Loon, Jacco Th.; Sarre, Peter J.; Beckman, John E.

    2015-12-01

    Diffuse interstellar bands (DIBs) trace warm neutral and weakly ionized diffuse interstellar medium (ISM). Here we present a dedicated, high signal-to-noise spectroscopic survey of two of the strongest DIBs, at 5780 and 5797 Å, in optical spectra of 666 early-type stars in the Small and Large Magellanic Clouds, along with measurements of the atomic Na I D and Ca II K lines. The resulting maps show for the first time the distribution of DIB carriers across large swathes of galaxies, as well as the foreground Milky Way ISM. We confirm the association of the 5797 Å DIB with neutral gas, and the 5780 Å DIB with more translucent gas, generally tracing the star-forming regions within the Magellanic Clouds. Likewise, the Na I D line traces the denser ISM whereas the Ca II K line traces the more diffuse, warmer gas. The Ca II K line has an additional component at ˜200-220 km s-1 seen towards both Magellanic Clouds; this may be associated with a pan-Magellanic halo. Both the atomic lines and DIBs show sub-pc-scale structure in the Galactic foreground absorption; the 5780 and 5797 Å DIBs show very little correlation on these small scales, as do the Ca II K and Na I D lines. This suggests that good correlations between the 5780 and 5797 Å DIBs, or between Ca II K and Na I D, arise from the superposition of multiple interstellar structures. Similarity in behaviour between DIBs and Na I in the Small Magellanic Cloud (SMC), Large Magellanic Cloud (LMC) and Milky Way suggests the abundance of DIB carriers scales in proportion to metallicity.

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

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

  6. An analysis for the broad-band absorption enhancement using plasmonic structures on uncooled infrared detector pixels

    NASA Astrophysics Data System (ADS)

    Lulec, Sevil Z.; Kucuk, Seniz E.; Battal, Enes; Okyay, Ali K.; Tanrikulu, M. Yusuf; Akin, Tayfun

    2012-06-01

    This paper introduces an analysis on the absorption enhancement in uncooled infrared pixels using resonant plasmon modes in metal structures, and it reports, for the first time in literature, broad-band absorption enhancement using integrated plasmonic structures in microbolometers for unpolarized long-wave IR detection. Different plasmonic structures are designed and simulated on a stack of layers, namely gold, polyimide, and silicon nitride in order to enhance absorption at the long-wave infrared. The simulated structures are fabricated, and the reflectance measurements are conducted using an FTIR Ellipsometer in the 8-12 ?m wavelength range. Finite difference time domain (FDTD) simulations are compared to experimental measurement results. Computational and experimental results show similar spectral reflection trends, verifying broad-band absorption enhancement in the spectral range of interest. Moreover, this paper computationally investigates pixel-wise absorption enhancement by plasmonic structures integrated with microbolometer pixels using the FDTD method. Special attention is given during the design to be able to implement the integrated plasmonic structures with the microbolometers without a need to modify the pre-determined microbolometer process flow. The optimized structure with plasmonic layer absorbs 84 % of the unpolarized radiation in the 8-12 ?m spectral range on the average, which is a 22 % increase compared to a reference structure with no plasmonic design. Further improvement may be possible by designing multiply coupled resonant structures.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Grundy, William M.; Fink, Uwe

    1991-01-01

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

  10. High-Resolution Absorption Spectroscopy of the 3nu(1) and 3nu(1) + nu(3) Bands of Propyne.

    PubMed

    Campargue; Bertseva; Graner; Herman

    2000-05-01

    The 3nu(1) and 3nu(1) + nu(3) bands of propyne have been recorded at Doppler-limited resolution by Fourier transform spectroscopy and intracavity laser absorption spectroscopy, respectively. The two bands show a mostly unperturbed J rotational structure for each individual K subband. However, as a rule the K structure ordering is perturbed in overtone transitions of propyne and different effective parameters associated with each K subband have been determined. From the vibrational energy levels, a value of -6.6 cm(-1) has been obtained for the x(13) cross anharmonicity in perfect agreement with the origins of the nu(1) + nu(3) and 2nu(1) + nu(3) combination bands estimated from the FTIR spectrum. Hot bands from the v(9) = 1 and v(10) = 1 levels associated with the 3nu(1) + nu(3) combination band have been partly rotationally analyzed and the retrieved values of x(39) and x(3,10) are in good agreement with literature values. Finally, the 4nu(1) + nu(9) - nu(9) band centered at 12 636.6 cm(-1) has been recorded by ICLAS. The red shift of this hot band relative to 4nu(1) and the DeltaB(v) value are discussed in relation to the anharmonic interaction between the 4nu(1) and 3nu(1) + nu(3) + nu(5) levels. Copyright 2000 Academic Press. PMID:10753622

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

    NASA Astrophysics Data System (ADS)

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

    2005-08-01

    A spectroscopic analysis is performed on trivalent erbium ions, Er3+, doped into calcium fluorophosphate (FAP) to assess this material for its potential as a near-infrared laser host. The Judd-Ofelt model is applied to the orientation-averaged, room-temperature absorption intensities of Er3+ in FAP to obtain the phenomenological intensity parameters: ?2=5.8610-20cm2, ?4=0.3810-20cm2, and ?6=0.8810-20cm2. The intensity parameters are used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds LJ2S+1 of Er3+ in FAP. Using the radiative decay rates for Er3+ transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined in this host. The room temperature fluorescence lifetime and the radiative lifetime of the Er3+I13/24?I15/24(1.53?m) transition are reported and the quantum efficiency is determined to be 69% for 1.0wt%Er3+:FAP. In addition, the orientationally resolved emission cross sections for the S3/24?I15/24 and I13/24?I15/24 transitions are presented.

  12. Collisionless absorption, hot electron generation, and energy scaling in intense laser-target interaction

    NASA Astrophysics Data System (ADS)

    Liseykina, T.; Mulser, P.; Murakami, M.

    2015-03-01

    Among the various attempts to understand collisionless absorption of intense and superintense ultrashort laser pulses, a whole variety of models and hypotheses has been invented to describe the laser beam target interaction. In terms of basic physics, collisionless absorption is understood now as the interplay of the oscillating laser field with the space charge field produced by it in the plasma. A first approach to this idea is realized in Brunel's model the essence of which consists in the formation of an oscillating charge cloud in the vacuum in front of the target, therefore frequently addressed by the vague term "vacuum heating." The investigation of statistical ensembles of orbits shows that the absorption process is localized at the ion-vacuum interface and in the skin layer: Single electrons enter into resonance with the laser field thereby undergoing a phase shift which causes orbit crossing and braking of Brunel's laminar flow. This anharmonic resonance acts like an attractor for the electrons and leads to the formation of a Maxwellian tail in the electron energy spectrum. Most remarkable results of our investigations are the Brunel like spectral hot electron distribution at the relativistic threshold, the minimum of absorption at I λ 2 ≅ ( 0.3 - 1.2 ) × 10 21 Wcm - 2 μ m 2 in the plasma target with the electron density of n e λ 2 ˜ 10 23 cm - 3 μ m 2 , the drastic reduction of the number of hot electrons in this domain and their reappearance in the highly relativistic domain, and strong coupling, beyond expectation, of the fast electron jets with the return current through Cherenkov emission of plasmons. The hot electron energy scaling shows a strong dependence on intensity in the moderately relativistic domain I λ 2 ≅ ( 10 18 - 10 20 ) Wcm - 2 μ m 2 , a scaling in vague accordance with current published estimates in the range I λ 2 ≅ ( 0.14 - 3.5 ) × 10 21 Wcm - 2 μ m 2 , and again a distinct power increase beyond I = 3.5 × 10 21 Wcm - 2 μ m 2 . The low energy electrons penetrate normally to the target surface, the energetic electrons propagate in laser beam direction.

  13. Collisionless absorption, hot electron generation, and energy scaling in intense laser-target interaction

    SciTech Connect

    Liseykina, T.; Mulser, P.; Murakami, M.

    2015-03-15

    Among the various attempts to understand collisionless absorption of intense and superintense ultrashort laser pulses, a whole variety of models and hypotheses has been invented to describe the laser beam target interaction. In terms of basic physics, collisionless absorption is understood now as the interplay of the oscillating laser field with the space charge field produced by it in the plasma. A first approach to this idea is realized in Brunel's model the essence of which consists in the formation of an oscillating charge cloud in the vacuum in front of the target, therefore frequently addressed by the vague term vacuum heating. The investigation of statistical ensembles of orbits shows that the absorption process is localized at the ion-vacuum interface and in the skin layer: Single electrons enter into resonance with the laser field thereby undergoing a phase shift which causes orbit crossing and braking of Brunel's laminar flow. This anharmonic resonance acts like an attractor for the electrons and leads to the formation of a Maxwellian tail in the electron energy spectrum. Most remarkable results of our investigations are the Brunel like spectral hot electron distribution at the relativistic threshold, the minimum of absorption at I?{sup 2}?(0.3?1.2)10{sup 21}?Wcm{sup ?2}?m{sup 2} in the plasma target with the electron density of n{sub e}?{sup 2}?10{sup 23}cm{sup ?3}?m{sup 2}, the drastic reduction of the number of hot electrons in this domain and their reappearance in the highly relativistic domain, and strong coupling, beyond expectation, of the fast electron jets with the return current through Cherenkov emission of plasmons. The hot electron energy scaling shows a strong dependence on intensity in the moderately relativistic domain I?{sup 2}?(10{sup 18}?10{sup 20})?Wcm{sup ?2}?m{sup 2}, a scaling in vague accordance with current published estimates in the range I?{sup 2}?(0.14?3.5)10{sup 21}?Wcm{sup ?2}?m{sup 2}, and again a distinct power increase beyond I=3.510{sup 21}?Wcm{sup ?2}?m{sup 2}. The low energy electrons penetrate normally to the target surface, the energetic electrons propagate in laser beam direction.

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

    NASA Technical Reports Server (NTRS)

    Singhroy, Vernon H.; Kruse, Fred A.

    1991-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  16. The Pt2 (1,0) band of System VI in the near infrared by intracavity laser absorption spectroscopy.

    PubMed

    O'Brien, Leah C; O'Brien, James J

    2011-05-14

    Intracavity laser absorption spectroscopy has been used to record rotationally resolved electronic spectra of Pt(2) in the near infrared. The metal dimers were created using a 50 mm-long, platinum-lined hollow cathode plasma discharge. The observed transition at 12?937 cm(-1) is identified as the (1,0) band of System VI, with state symmetries ? = 0 - X ? = 0. PMID:21568503

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

    SciTech Connect

    Flikweert, A.J.; Nimalasuriya, T.; Groothuis, C.H.J.M.; Kroesen, G.M.W.; Stoffels, W.W.

    2005-10-01

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

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

    PubMed

    Shi, Linxing; Zhou, Zhen; Tang, Bingshu

    2012-05-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

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

    NASA Technical Reports Server (NTRS)

    May, Randy D.

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

    The absorption spectrum of 13CH4 has been recorded at 296 K and 80 K by differential absorption spectroscopy (DAS) in the high energy part of the tetradecad (5853-6201 cm-1) dominated by the 2?3 band near 5988 cm-1. The achieved noise equivalent absorption of the spectra (?min?110-7 cm-1) allowed us to double the number of 13CH4 lines previously measured in the region (our lists include about 7200 and 3700 lines at 296 and 80 K, respectively). Empirical values of the lower state energy level, Eemp, were systematically derived from the intensity ratios of the lines measured at 80 K and 296 K. Overall 2782 Eemp values were determined extending significantly the previous set of about 1200 Eemp values available in the literature. The corresponding empirical values of the rotational quantum number, Jemp, show a clear propensity to be close to an integer, illustrating the validity of the method. The line lists at 296 K and 80 K, provided as Supplementary material, are discussed in relation with line lists and rovibrational assignments available in the literature.

  3. Voigt deconvolution method and its applications to pure oxygen absorption spectrum at 1270nm band.

    PubMed

    Al-Jalali, Muhammad A; Aljghami, Issam F; Mahzia, Yahia M

    2016-03-15

    Experimental spectral lines of pure oxygen at 1270nm band were analyzed by Voigt deconvolution method. The method gave a total Voigt profile, which arises from two overlapping bands. Deconvolution of total Voigt profile leads to two Voigt profiles, the first as a result of O2 dimol at 1264nm band envelope, and the second from O2 monomer at 1268nm band envelope. In addition, Voigt profile itself is the convolution of Lorentzian and Gaussian distributions. Competition between thermal and collisional effects was clearly observed through competition between Gaussian and Lorentzian width for each band envelope. Voigt full width at half-maximum height (Voigt FWHM) for each line, and the width ratio between Lorentzian and Gaussian width (?L?G(-1)) have been investigated. The following applied pressures were at 1, 2, 3, 4, 5, and 8bar, while the temperatures were at 298K, 323K, 348K, and 373K range. PMID:26709019

  4. Voigt deconvolution method and its applications to pure oxygen absorption spectrum at 1270 nm band

    NASA Astrophysics Data System (ADS)

    AL-Jalali, Muhammad A.; Aljghami, Issam F.; Mahzia, Yahia M.

    2016-03-01

    Experimental spectral lines of pure oxygen at 1270 nm band were analyzed by Voigt deconvolution method. The method gave a total Voigt profile, which arises from two overlapping bands. Deconvolution of total Voigt profile leads to two Voigt profiles, the first as a result of O2 dimol at 1264 nm band envelope, and the second from O2 monomer at 1268 nm band envelope. In addition, Voigt profile itself is the convolution of Lorentzian and Gaussian distributions. Competition between thermal and collisional effects was clearly observed through competition between Gaussian and Lorentzian width for each band envelope. Voigt full width at half-maximum height (Voigt FWHM) for each line, and the width ratio between Lorentzian and Gaussian width (?L?G- 1) have been investigated. The following applied pressures were at 1, 2, 3, 4, 5, and 8 bar, while the temperatures were at 298 K, 323 K, 348 K, and 373 K range.

  5. Absorption intensities and emission cross sections of Tb3+ (4f8) in TbAlO3

    NASA Astrophysics Data System (ADS)

    Sardar, Dhiraj K.; Nash, Kelly L.; Yow, Raylon M.; Gruber, John B.; Valiev, Uygun V.; Kokanyan, Edvard P.

    2006-10-01

    Trivalent terbium absorption intensities in single-crystal TbAlO3 are analyzed using the Judd-Ofelt model to assess the crystal's potential as a solid state laser system. The standard Judd-Ofelt model was applied to the room temperature absorption intensities of Tb3+ (4f8) to determine the phenomenological intensity parameters ?2, ?4, and ?6. Seven multiplet manifolds are identified and the absorption intensities of these manifolds are least-squares fitted to the calculated intensities to obtain the intensity parameters: ?2=40.5210-20cm2, ?4=8.7410-20cm2, and ?6=2.2610-20cm2 in TbAlO3. These intensity parameters are then applied to determine the radiative decay rates and branching ratios of Tb3+ transitions from the D45 to the FJ'7 multiplet manifolds. Based on the results, the radiative lifetime of the excited state manifold D45 is determined from the radiative decay rates and found to be 3.5ms. The calculated lifetime is longer than the measured lifetime, reflecting the nonradiative interactions between the Tb3+ ions and the lattice in the pure compound. The intensity parameters, radiative lifetime, and emission cross sections are then compared to those reported in other laser hosts. The quantum efficiency of the laser transition D45?F57 of Tb3+ is approximately 57.0% in TbAlO3.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  7. High-Resolution IR Absorption Spectroscopy of Polycyclic Aromatic Hydrocarbons: Shining Light on the Interstellar 3 Micron Emission Bands

    NASA Astrophysics Data System (ADS)

    Maltseva, Elena; Candian, Alessandra; Tielens, Xander; Petrignani, Annemieke; Oomens, J.; Buma, Wybren Jan

    2015-06-01

    Various astronomical objects show distinctive series of IR emission bands indicated as unidentified infrared emission bands. These features are nowadays mainly attributed to the IR fluorescence of Polycyclic Aromatic Hydrocarbons (PAHs) even though an unambiguous identification of which PAHs are involved has not been possible yet. We present here a high-resolution IR absorption study of a number of jet-cooled polycyclic aromatic hydrocarbons in the 3.3 ?m region obtained by IR-UV ion depletion techniques. The experimental spectra display many more bands than expected, and lead to the conclusion that the appearance of the spectrum is dominated by fourth-order vibrational coupling terms. This has far-reaching consequences since up till now the assignment of infrared emission features observed in different types of space objects in this wavelength region -and the conclusions drawn from these assignments on the evolution of interstellar gas- has relied heavily on harmonic quantum chemical calculations. We also observe that the presence of bay-hydrogen sites in a PAH leads to a shift of the overall spectrum to the high-energy side and to a broadening of the 3 ?m band. This observation provides an appealing explanation for previous speculations that the emission of 3 ?m band consists of two components. Moreover, it paves for using this structure to derive the composition of different objects.

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

    PubMed Central

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

    1997-01-01

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

  9. Ground-based Photon Path Measurements from Solar Absorption Spectra of the O2 A-band

    NASA Technical Reports Server (NTRS)

    Yang, Z.; Wennberg, P. O.; Cageao, R. P.; Pongetti, T. J.; Toon, G. C.; Sander, S. P.

    2005-01-01

    High-resolution solar absorption spectra obtained from Table Mountain Facility (TMF, 34.38degN, 117.68degW, 2286 m elevation) have been analyzed in the region of the O2 A-band. The photon paths of direct sunlight in clear sky cases are retrieved from the O2 absorption lines and compared with ray-tracing calculations based on the solar zenith angle and surface pressure. At a given zenith angle, the ratios of retrieved to geometrically derived photon paths are highly precise (approx.0.2%), but they vary as the zenith angle changes. This is because current models of the spectral lineshape in this band do not properly account for the significant absorption that exists far from the centers of saturated lines. For example, use of a Voigt function with Lorentzian far wings results in an error in the retrieved photon path of as much as 5%, highly correlated with solar zenith angle. Adopting a super-Lorentz function reduces, but does not completely eliminate this problem. New lab measurements of the lineshape are required to make further progress.

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

    SciTech Connect

    Smith, S.J.

    1994-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Pliutau, Denis; Prasad, Narasimha S

    2013-01-01

    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.

  12. Design and Construction of Absorption Cells for Precision Radial Velocities in the K Band Using Methane Isotopologues

    NASA Astrophysics Data System (ADS)

    Anglada-Escudé, Guillem; Plavchan, Peter; Mills, Sean; Gao, Peter; García-Berríos, Edgardo; Lewis, Nathan S.; Sung, Keeyoon; Ciardi, David; Beichman, Chas; Brinkworth, Carolyn; Johnson, John; Davison, Cassy; White, Russel; Prato, Lisa

    2012-06-01

    We present a method to optimize absorption cells for precise wavelength calibration in the near-infrared. We apply it to design and optimize methane isotopologue cells for precision radial velocity measurements in the K band. We also describe the construction and installation of two such cells for the CSHELL spectrograph at NASA's IRTF. We have obtained their high-resolution laboratory spectra, which we can then use in precision radial velocity measurements and which can also have other applications. In terms of obtainable RV precision, methane should outperform other proposed cells, such as the ammonia cell (14NH3) recently demonstrated on CRIRES/VLT. The laboratory spectra of the ammonia and methane cells show strong absorption features in the H band that could also be exploited for precision Doppler measurements. We present spectra and preliminary radial velocity measurements obtained during our first-light run. These initial results show that a precision down to 20-30 m s-1 can be obtained using a wavelength interval of only 5 nm in the K band and S/N ~ 150. This supports the prediction that a precision down to a few meters per second can be achieved on late-M dwarfs using the new generation of NIR spectrographs, thus enabling the detection of terrestrial planets in their habitable zones. Doppler measurements in the NIR can also be used to mitigate the radial velocity jitter due to stellar activity, enabling more efficient surveys on young active stars.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

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

    DOE Data Explorer

    Greenwood, R. E.

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

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

    PubMed

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

    2012-01-15

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

  16. Linear relation between x-ray absorption branching ratio and valence-band spin-orbit expectation value

    NASA Astrophysics Data System (ADS)

    Thole, B. T.; van der Laan, G.

    1988-08-01

    The fraction of the total line strength of one of the core-hole spin-orbit-split manifolds in x-ray absorption is proved to be related to the expectation value of the valence-band spin-orbit operator. The relation obtained, by angular momentum algebra, is valid if the total angular momentum of the core hole is a good quantum number, which is true for deep core levels. Therefore, the branching ratio of deep-core-hole manifolds is probably the most direct probe to measure the valence-band spin-orbit interactions, especially in transition-metal compounds. The branching ratio measures the angular part of the spin-orbit operator and is complementary to magnetic measurements which determine the Land g factor.

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  18. Higher-order mode absorption measurement of X-band choke-mode cavities in a radial line structure

    NASA Astrophysics Data System (ADS)

    Zha, Hao; Shi, Jiaru; Wu, Xiaowei; Chen, Huaibi

    2016-04-01

    An experiment is presented to study the higher-order mode (HOM) suppression of X-band choke-mode structures with a vector network analyzer (VNA). Specific radial line disks were built to test the reflection from the corresponding damping load and different choke geometries. The mismatch between the radial lines and the VNA was calibrated through a special multi-short-load calibration method. The measured reflections of different choke geometries showed good agreement with the theoretical calculations and verified the HOM absorption feature of each geometric design.

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

    NASA Astrophysics Data System (ADS)

    Mndez, M.; Cesteros, Y.; Marsal, L. F.; Salagre, P.; Formentn, P.; Pallars, J.; Aguil, M.; Daz, F.; Carvajal, J. J.

    2012-06-01

    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.

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

    SciTech Connect

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

    2010-06-01

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

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

    NASA Astrophysics Data System (ADS)

    Lacomba-Perales, R.; Ruiz-Fuertes, J.; Errandonea, D.; Martínez-García, D.; Segura, A.

    2008-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Xi, Li; Yang, Yikai

    2011-03-01

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

  3. Absorption in high-Z targets illuminated with 527-nm laser light at high intensity using induced spatial incoherence

    SciTech Connect

    Simpson, J.D.; Bosch, R.A.; Failor, B.H.; Gabl, E. )

    1990-10-20

    We have measured 527-nm absorption for induced spatial incoherence (ISI) and non-ISI illumination of high-Z targets over the 0.5--3.5 {times} 10{sup 14}-W/cm{sup 2} laser intensity range using energy balance with a custom designed 30-cm diam light integrating sphere. Induced spatial incoherence of the laser beam was produced by inserting echelons in the beam path and operating the laser at wide bandwidth (0.2%). To produce ISI and non-ISI data for comparison, we irradiated a large number of 180-{mu}m diam gold disks with 0.5--1.5-ns pulses with echelons in the beam path with and without wide laser bandwidths. Our data show an increase in absorption of 5--11% for the ISI illuminated targets and also suggest a weaker dependence of absorption on laser intensity for ISI illumination than for non-ISI.

  4. Absorption in high-z targets illuminated with 527-nm laser light at high intensity using induced spatial incoherence.

    PubMed

    Simpson, J D; Bosch, R A; Failor, B H; Gabl, E F

    1990-10-20

    We have measured 527-nm absorption for induced spatial incoherence (ISI) and non-ISI illumination of high-Z targets over the 0.5-3.5 x 10(14)-W/cm(2) laser intensity range using energy balance with a custom designed 30-cm diam light integrating sphere. Induced spatial incoherence of the laser beam was produced by inserting echelons in the beam path and operating the laser at wide bandwidth (0.2%). To produce ISI and non-ISI data for comparison, we irradiated a large number of 180-microm diam gold disks with 0.5-1.5-ns pulses with echelons in the beam path with and without wide laser bandwidths. Our data show an increase in absorption of 5-11% for the ISI illuminated targets and also suggest a weaker dependence of absorption on laser intensity for ISI illumination than for non-ISI. PMID:20577408

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

    NASA Technical Reports Server (NTRS)

    Fox, K.

    1982-01-01

    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.

  6. Shape of impurity electronic absorption bands in a nematic liquid crystal

    SciTech Connect

    Aver`yanov, E.M.

    1995-02-01

    It is shown that the anisotropic intermolecular impurity-matrix interactions, statistical orientation properties, and the electronic structure of the uniaxial impurity molecules considerably affect the spectral moments of the impurity electronic adsorption bands in a nematic liquid crystal. 15 refs., 3 figs.

  7. Iron absorption band analysis for the discrimination of iron rich zones

    NASA Technical Reports Server (NTRS)

    Rowan, L. C. (principal investigator)

    1973-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

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

  10. Intense laser field and conduction band-edge nonparabolicity effects on hydrogenic impurity states of InGaN QW

    NASA Astrophysics Data System (ADS)

    El Ghazi, Haddou

    2015-09-01

    In this paper, hydrogenic impurity ground-state binding energy in unstrained wurtzite (In, Ga)N symmetric quantum well is investigated. The heterostructure is considered under the action of an intense laser field (ILF) incorporating an additional internal probe as well as the conduction band-edge nonparabolicity effect (CBENP). The variational approach is used within the framework of single band effective-mass approximation with two-parametric 1S-hydrogenic trial wavefunction. The competition effect between internal and external perturbations is also shown. Our results reveal that the binding energy is the largest for the well width around the effective Bohr radius and is strongly influenced by both parameters. Moreover, the principle effect of ILF (CBENP) is to reduce (enhance) the binding energy. It is found that the lift of the conduction band-edge can be easily eliminated by adjusting the ILF-parameter.

  11. Absorption

    PubMed Central

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

    2009-01-01

    Given that mindbody interventions constitute a major portion of complementary and alternative medicine used by the public, it seems important to explore those human characteristics that may contribute to the efficacy of mindbody interventions in those who are most likely to benefit. One such characteristic, absorption, reflects an individuals cognitive capacity for involvement in sensory and imaginative experiences in ways that alter an individuals perception, memory, and mood with behavioral and biological consequences. Thus, ones level of absorption may potentially create differential treatment effects in mindbody intervention outcomes. Conducting practical clinical trials helps address the challenge of determining whether a specific mindbody modality intervention may be effective. Such trials may be strengthened by including measures of personality dimensions such as absorption. PMID:19126883

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

    SciTech Connect

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

    2013-12-28

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

  13. Fluorinated graphene oxide for enhanced S and X-band microwave absorption

    SciTech Connect

    Sudeep, P. M.; Vinayasree, S.; Mohanan, P.; Ajayan, P. M.; Narayanan, T. N.; Anantharaman, M. R.

    2015-06-01

    Here we report the microwave absorbing properties of three graphene derivatives, namely, graphene oxide (GO), fluorinated GO (FGO, containing 5.6 at. % Fluorine (F)), and highly FGO (HFGO, containing 23 at. % F). FGO is known to be exhibiting improved electrochemical and electronic properties when compared to GO. Fluorination modifies the dielectric properties of GO and hence thought of as a good microwave absorber. The dielectric permittivities of GO, FGO, and HFGO were estimated in the S (2 GHz to 4 GHz) and X (8 GHz to 12 GHz) bands by employing cavity perturbation technique. For this, suspensions containing GO/FGO/HFGO were made in N-Methyl Pyrrolidone (NMP) and were subjected to cavity perturbation. The reflection loss was then estimated and it was found that −37 dB (at 3.2 GHz with 6.5 mm thickness) and −31 dB (at 2.8 GHz with 6 mm thickness) in the S band and a reflection loss of −18 dB (at 8.4 GHz with 2.5 mm thickness) and −10 dB (at 11 GHz with 2 mm thickness) in the X band were achieved for 0.01 wt. % of FGO and HFGO in NMP, respectively, suggesting that these materials can serve as efficient microwave absorbers even at low concentrations.

  14. Double beam near-infrared spectrometer for compensation of background water absorption and instrumental drift in intensity

    NASA Astrophysics Data System (ADS)

    Chang, Min; Peng, Dan; Xu, Ke-Xin

    2007-05-01

    A double beam near-infrared spectrometer is developed to compensate the water absorption and instrumental drift in intensity. The spectrometer may be used for both single and double beam measurements, and the two operation modes are compared. The results show that the double beam technique eliminates instrumental drift in the single beam measurement and therefore the stability of the system increases by more than 20%. The compensation of the double beam system on water absorption is verified by the measurement of fat content in milk. The results show that the spectrum data based on double beam mode get better calibration model and lower prediction error than traditional single beam mode.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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 sideset{^1}{+u}{?}, B^' } sideset{^1}{+u}{?}, and C 1?u electronic states up to the D(1s) + D(2?) 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^' ' } sideset{^1}{+u}{?} electronic states correlate with the D(1s) + D(3?) 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.

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

    PubMed

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

    2013-10-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Khanna, R. K.; Zhao, Guizhi

    1986-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2009-01-01

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

  20. Would the solvent effect be the main cause of band shift in the theoretical absorption spectrum of large lanthanide complexes?

    NASA Astrophysics Data System (ADS)

    Freire, Ricardo O.; Rodrigues, Nailton M.; Rocha, Gerd B.; Gimenez, Iara F.; da Costa Junior, Nivan B.

    2011-06-01

    As most reactions take place in solution, the study of solvent effects on relevant molecular properties - either by experimental or theoretical methods - is crucial for the design of new processes and prediction of technological properties. In spite of this, only few works focusing the influence of the solvent nature specifically on the spectroscopic properties of lanthanide complexes can be found in the literature. The present work describes a theoretical study of the solvent effect on the prediction of the absorption spectra for lanthanide complexes, but other possible relevant factors have been also considered such as the molecular geometry and the excitation window used for interaction configuration (CI) calculations. The [Eu(ETA) 2 nH 2O] +1 complex has been chosen as an ideal candidate for this type of study due to its small number of atoms (only 49) and also because the absorption spectrum exhibits a single band. Two Monte Carlo simulations were performed, the first one considering the [Eu(ETA) 2] +1 complex in 400 water molecules, evidencing that the complex presents four coordinated water molecules. The second simulation considered the [Eu(ETA) 24H 2O] +1 complex in 400 ethanol molecules, in order to evaluate the solvent effect on the shift of the maximum absorption in calculated spectra, compared to the experimental one. Quantum chemical studies were also performed in order to evaluate the effect of the accuracy of calculated ground state geometry on the prediction of absorption spectra. The influence of the excitation window used for CI calculations on the spectral shift was also evaluated. No significant solvent effect was found on the prediction of the absorption spectrum for [Eu(ETA) 24H 2O] +1 complex. A small but significant effect of the ground state geometry on the transition energy and oscillator strength was also observed. Finally it must be emphasized that the absorption spectra of lanthanide complexes can be predicted with great accuracy by the combined use of semiempirical Sparkle/AM1 and INDO/S-CIS as long as the largest possible excitation window is used in the configuration interaction calculation.

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

    SciTech Connect

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

    2006-08-01

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

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

    SciTech Connect

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

    1987-06-01

    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.

  3. Charge recombination in excited donor-acceptor complexes with two absorption bands

    NASA Astrophysics Data System (ADS)

    Ionkin, V. N.; Ivanov, A. I.; Vauthey, E.

    2009-04-01

    The dynamics of charge recombination in a photoexcited donor-acceptor complex comprising 1,2,4-trimethoxybenzene (electron donor) and tetracyanoethylene (electron acceptor) in several polar solvents (acetonitrile, valeronitrile, and octanonitrile) was studied in terms of the stochastic approach. The Gibbs energy of charge recombination and the reorganization energies of the medium and quantum and vibrational degrees of freedom were found by fitting the stationary absorption spectrum. The electronic couplings were determined by analyzing the time dependences of the population of the ionic state in acetonitrile. A comparison of the numerical simulation results with the experimental data showed that the nonstationary model under consideration quantitatively described the dynamics of charge recombination and its dependence on the carrier frequency of excitation pulses and the relaxation properties of solvents.

  4. Jupiter's atmospheric composition and cloud structure deduced from absorption bands in reflected sunlight

    NASA Technical Reports Server (NTRS)

    Sato, M.; Hansen, J. E.

    1979-01-01

    The spectrum of sunlight reflected by Jupiter is analyzed by comparing observations of Woodman (1979) with multiple-scattering computations. The analysis yields information on the vertical cloud structure at several latitudes and on the abundance of CH4 and NH3 in the atmosphere of Jupiter. The abundances of CH4 and NH3 suggest that all ices and rocks are overabundant on Jupiter by a factor of 2 or more, providing an important constraint on models for the formation of Jupiter from the primitive solar nebula. The pressure level of the clouds, the gaseous NH3 abundance, the mean temperature profile, and the Clausius-Clapeyron relation suggest that these clouds are predominantly ammonia crystals with the cloud bottom at 600-700 mb. A diffuse distribution of aerosols exists between 150 and 500 mb, and the spectral variation of albedo reflects a changing bulk absorption coefficient of the material composing the aerosols and is diagnostic of the aerosol composition.

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Huynh, Uyen; Vardeny, Z. Valy

    2015-03-01

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

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

    SciTech Connect

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

    2010-08-11

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

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

    SciTech Connect

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

    2014-07-31

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

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

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

    PubMed Central

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

    2014-01-01

    The purpose of the current study was to evaluate hydrogen-saturated saline protecting intensive narrow band noise-induced hearing loss. Guinea pigs were divided into three groups: hydrogen-saturated saline; normal saline; and control. For saline administration, the guinea pigs were given daily abdominal injections (1 ml/100 g) 3 days before and 1 h before narrow band noise exposure (2.53.5 kHz 130 dB SPL, 1 h). The guinea pigs in the control group received no treatment. The hearing function was assessed by the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recording. The changes of free radicals in the cochlea before noise exposure, and immediately and 7 days after noise exposure were also examined. By Scanning electron microscopy and succinate dehydrogenase staining, we found that pre-treatment with hydrogen-saturated saline significantly reduced noise-induced hair cell damage and hearing loss. We also found that the malondialdehyde, lipid peroxidation, and hydroxyl levels were significantly lower in the hydrogen-saturated saline group after noise trauma, indicating that hydrogen-saturated saline can decrease the amount of harmful free radicals caused by noise trauma. Our findings suggest that hydrogen-saturated saline is effective in preventing intensive narrow band noise-induced hearing loss through the antioxidant effect. PMID:24945316

  11. Irregular Pressure Induced Shift of the First UV-Absorption Band of 4-Nitroanisole in CO2 and CHF3

    NASA Astrophysics Data System (ADS)

    Alvarez, Guillermo A.; Baumann, Wolfram; Neitzel, Frank; Rodrigues, V.

    2009-12-01

    The first UV-absorption band of the polar molecules trans-4-dimethylamino-4'-nitrostilbene (DMANS), 5-dimethylamino-5'-nitro-2,2'-bithiophene (DMANBT), and 4-nitroanisole (NA), and of the slightly polar pesticide diclofop-methyl in the nonpolar supercritical solvent carbon dioxide (CO2) and in the slightly polar supercritical solvent trifluoromethane (CHF3) was measured in the pressure range from 1.5 to 30 MPa and the temperature range from 298 to 353 K with the purpose of studying the solvent-solute interactions in these molecules. The theory of Liptay for the effect of the solvent on the wave number of the electronic absorption of the solute molecule was applied. In this theory the solvent is represented by an isotropic and homogeneous dielectric continuum characterized by a pressure and temperature dependent dielectric constant ɛ (P,T), and an optical refraction index n. For the isotherms which approach the critical point in both solvents there is a change in the slope of the plot of the wave number maximum against the solvent parameter g=(ɛ-1)/(2ɛ+1) which is reminiscent of complex formation. A possible mechanism for this phenomenon is the arrangement of the solvent molecules around the dilute solute in the intermediate region at the (continuous) transition of the solvent from the dense vapour to the supercritical fluid

  12. Visible-band (390-940nm) monitoring of the Pluto absorption spectrum during the New Horizons encounter

    NASA Astrophysics Data System (ADS)

    Smith, Robert J.; Marchant, Jonathan M.

    2015-11-01

    Whilst Earth-based observations obviously cannot compete with New Horizons on-board instrumentation in most regards, the New Horizons data set is essentially a snapshot of Pluto in July 2015. The New Horizons project team therefore coordinated a broad international observing campaign to provide temporal context and to take advantage of the once-in-a-lifetime opportunity to directly link our Earth-based view of Pluto with ground truth provided by in situ measurements. This both adds value to existing archival data sets and forms the basis of long term, monitoring as we watch Pluto recede from the Sun over the coming years. We present visible-band (390-940nm) monitoring of the Pluto absorption spectrum over the period July - October 2015 from the Liverpool Telescope (LT). In particular we wished to understand the well-known 6-day fluctuation in the methane ice absorption spectrum which is observable from Earth in relation to the never-before-available high resolution maps of the Pluto surface. The LT is a fully robotic 2.0m optical telescope that automatically and dynamically schedules observations across 30+ observing programmes with a broad instrument suite. It is ideal for both reactive response to dynamic events (such as the fly-by) and long term, stable monitoring with timing constraints individually optimised to the science requirements of each programme. For example past studies of the observed CH4 absorption variability have yielded ambiguity of whether they were caused by real physical changes or geometric observation constraints, in large part because of the uneven time sampling imposed by traditional telescope scheduling.

  13. Determination of vibration-rotation lines intensities from absorption Fourier spectra

    NASA Technical Reports Server (NTRS)

    Mandin, J. Y.

    1979-01-01

    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.

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

    PubMed

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

    2015-02-24

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

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

    NASA Astrophysics Data System (ADS)

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

    1993-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  17. 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)

    Zheng, Chunguang; Borysow, Aleksandra

    1995-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Borysow, Aleksandra; Borysow, Jacek I.

    1998-01-01

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

  19. Calculations for - and Cis-Polyacetylene of Soft X-Ray Absorption Intensity Including Many-Electron and Dynamic Lattice Effects and of Nonlinear Optical Absorption Including Quantum Lattice Effects

    NASA Astrophysics Data System (ADS)

    Mackie, David Mark

    In part one, we calculate the soft X-ray absorption (SXA) of the conducting/optically-active polymer trans -polyacetylene, (CH)_{rm x} . We show the effect on the SXA spectrum of the final-state rule, of many-electron dipole matrix elements, of multiple final system states, and of electron-electron interactions. Even-chain spectra exhibit a single exciton peak below the conduction band absorption edge, while odd -chain spectra exhibit two exciton peaks plus a soliton peak. The peak size and location are sensitive to electron -electron interactions. Next, we investigate the interaction between SXA and lattice dynamics. The (CH)_ {rm x} lattice responds dramatically to SXA, with chain segmentation and soliton generation occurring on femtosecond timescales, comparable to the carbon 1s Auger lifetime. We derive equations for the transition rate for systems in which the final state is evolving due to the transition, and calculate the effect of the lattice dynamics on SXA in (CH)_ {rm x}. The spectra are asymmetrically broadened to lower energies, but the relative peak and edge intensities are largely unchanged. In part two, we calculate the third order susceptibility of (CH)_{rm x}. Line shapes for even chains are in agreement with recent experiments. Pristine (CH)_{rm x} with neutral solitons and doped (CH)_{rm x} show additional structure below the lowest frequency for which experimental observations have been reported. Our results indicate that nonlinear optical absorption may be useful for studying neutral and charged solitons. Next, we present a semiclassical method for including quantum lattice fluctuation (QLF) effects in calculations of linear polymer properties, and apply the method to soliton-antisoliton (SA) pairs in trans- and cis-(CH)_{rm x}. Our first-order absorption results agree with an earlier calculation. The QLF effects on the third-order absorption are important in the unmeasured region below the interband three-photon peak, and are greatly enhanced for off-center SA's. Lastly, our cis-(CH)_{rm x} results indicate that QLF effects may be important even for materials with a non-degenerate ground state.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Gigolashvili, M.; Kapanadze, N.

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1985-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

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

    PubMed

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

    2015-02-25

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

  8. Acetylene weak bands at 2.5 ?m from intracavity Cr:ZnSe laser absorption observed with time-resolved Fourier transform spectroscopy.

    PubMed

    Girard, Vronique; Farrenq, Robert; Sorokin, Evgeni; Sorokina, Irina T; Guelachvili, Guy; Picqu, Nathalie

    2006-02-26

    The spectral dynamics of a mid-infrared multimode Cr(2+):ZnSe laser located in a vacuum sealed chamber containing acetylene at low pressure is analyzed by a stepping-mode high-resolution time-resolved Fourier transform interferometer. Doppler-limited absorption spectra of C(2)H(2) in natural isotopic abundance are recorded around 4000 cm(-1) with kilometric absorption path lengths and sensitivities better than 3 10(-8) cm(-1). Two cold bands are newly identified and assigned to the ?(1)+?(4) (1) and ?(3)+?(5) (1) transitions of (12)C(13)CH(2). The ?(1)+?(5) (1) band of (12)C(2)HD and fourteen (12)C(2)H(2) bands are observed, among which for the first time ?(2)+2?(4) (2)+?(5) (-1). PMID:21151826

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    PubMed

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

    2003-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2004-10-01

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

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

    SciTech Connect

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

    1992-09-01

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

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

    SciTech Connect

    Barun, V V; Ivanov, A P

    2010-06-23

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

  14. Analysis of Mars surface hydration through the MEx/OMEGA observation of the 3 μm absorption band.

    NASA Astrophysics Data System (ADS)

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

    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

  15. Calculation of vibrational (J=0) excitation energies and band intensities of formaldehyde using the recursive residue generation method

    NASA Astrophysics Data System (ADS)

    Poulin, Nicolas M.; Bramley, Matthew J.; Carrington, Tucker, Jr.; Kjaergaard, Henrik G.; Henry, Bryan R.

    1996-05-01

    We use the recursive residue generation method (RRGM) with an exact kinetic energy operator to calculate vibrational excitation energies and band intensities for formaldehyde. The basis is a product of one-dimensional potential optimized discrete variable representation (PO-DVR) functions for each coordinate. We exploit the symmetry by using symmetry adapted basis functions obtained by taking linear combinations of PO-DVR functions. Our largest basis set consists of 798 600 functions (per symmetry block). The Lanczos tridiagonal representation of the Hamiltonian is generated iteratively (without constructing matrix elements explicitly) by sequential transformations. We determine a six-dimensional dipole moment function from the ab initio dipole moment values computed at the QCISD level with a 6-311++G(d,p) basis set. We converged all A1, B2 and B1 vibrational states up to the combination band with two quanta in the C-O stretch and one quantum in a C-H stretch at about 6 350 cm-1 above zero point energy. We present a simulated (J=0) infrared spectrum of CH2O for transitions from the ground state.

  16. A Analysis of the NU2 Fundamental Infrared Absorption Bands of Sulfur-Hydride and Selenium-Hydride

    NASA Astrophysics Data System (ADS)

    Lane, William Charles

    The (nu)(,2) fundamental infrared absorption bands of H(,2)S and H(,2)Se were run on the 50 cm Fourier transform infrared spectrometer system at the University of Denver with a resolution limit of 0.04 cm('-1) for (nu)(,2) of H(,2)S and 0.025 cm('-1) for (nu)(,2) of H(,2)Se. The two sets of spectra were analyzed at the Molecular Spectroscopy Laboratory at Michigan State University. We initially analyzed the H(,2)('32)S (nu)(,2) spectrum using Typke's Hamiltonian, limited to terms through order P('6). We determined ground state constants for H(,2)('32)S by fitting our infrared ground state combination differences (GSCD's) and the available microwave transitions of Helminger, Cook, and DeLucia. Keeping the ground state constants fixed to the values obtained in our ground state fit, we determined (010) upper state constants for H(,2)('32)S by a fit of the (nu)(,2) spectral lines. We then used an isotopic mass adjustment analysis to simultaneously fit the small number of observed H(,2)('33)S and H(,2)('34)S (nu)(,2) lines together with the many H(,2)('32)S (nu)(,2) lines. Following the report of improved ground state constants for H(,2)S by Flaud, Camy-Peyret, and Johns, we reanalyzed the (nu)(,2) band of H(,2)S with Watson's A-reduced Hamiltonian, including terms through order P('8). Using their H(,2)('32)S, H(,2)('33)S, and H(,2)('34)S ground state constants we determined (010) upper state constants for each of the three isotopic species of H(,2)S by separately fitting the H(,2)('32)S, H(,2)('33)S and H(,2)('34)S (nu)(,2) spectral lines. We similarly analyzed the (nu)(,2) spectra of the five most abundant isotopic species of H(,2)Se as individual spectra, using Watson's A-reduced Hamiltonian. To analyze the small number of assigned H(,2)('74)Se (nu)(,2) lines, we used the method of isotopic mass adjustment to analyze the ground states and the (010) upper states of the six stable isotopic species of H(,2)Se.

  17. Radiative analysis of global mean temperature trends in the middle atmosphere: Effects of non-locality and secondary absorption bands

    NASA Astrophysics Data System (ADS)

    Fomichev, V. I.; Jonsson, A. I.; Ward, W. E.

    2016-02-01

    In this paper, we provide a refined and extended assignment of past and future temperature changes relative to previous analyses and describe and evaluate the relevance of vertical coupling and non-linear and secondary radiative mechanisms for the interpretation of climatic temperature variations in the middle atmosphere. Because of their nature, the latter mechanisms are not adequately accounted for in most regression analyses of temperature trends as a function of local constituent variations. These mechanisms are examined using (1) globally averaged profiles from transient simulations with the Canadian Middle Atmosphere Model (CMAM) forced by changes in greenhouse gases and ozone depleting substances and (2) a one-dimensional radiative-equilibrium model forced using the diagnosed global mean changes in radiatively active constituents as derived from the CMAM model runs. The conditions during the periods 1975 to 1995 and 2010 to 2040 (during which the rates of change in ozone and CO2 differ) provide a suitable contrast for the role of the non-linear and non-local mechanisms being evaluated in this paper to be clearly differentiated and evaluated. Vertical coupling of radiative transfer effects and the influence of secondary absorption bands are important enough to render the results of multiple linear regression analyses between the temperature response and constituent changes misleading. These effects are evaluated in detail using the 1D radiative-equilibrium model using profiles from the CMAM runs as inputs. In order to explain the differences in the CMAM temperature trends prior to and after 2000 these other radiative effects must be considered in addition to local changes in the radiatively active species. The middle atmosphere temperature cools in response to CO2 and water vapor increases, but past and future trends are modulated by ozone changes.

  18. Airborne measurements of NO3 and N2O5 using broad band cavity enhanced absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Ouyang, B.; Kennedy, O. J.; Jones, R.

    2010-12-01

    Active night time chemistry can occur when the concentrations of certain species build up as a result of the weakening of their sinks in the night time. Of this class, NO3 and N2O5 (the latter in equilibrium with NO3 and NO2) are important as they not only control the night-time oxidative capacities of the atmosphere, via reactions between NO3 with VOCs, but can also determine the removal rate of NOx, via heterogeneous deposition of N2O5 to form HNO3 and/or its reaction with some inorganic aerosol components such as Cl-. In this study, a three-channel instrument was constructed and deployed on the British FAAM BAe 146 atmospheric research aircraft to simultaneously measure concentrations of NO3, N2O5 and NO2 in the atmosphere, using the technique of broad band cavity enhanced absorption spectroscopy (BBCEAS) with high power light emitting diodes (LED) as the light source. Spatially highly resolved measurements were achieved by recording the spectra using 0.2 - 0.6 second integration times. Mixing ratios of up to 2 ppbv of N2O5 and 200 pptv of NO3 were observed for the first time in a typical European atmospheric environment. Vertical profiles of these species were captured from altitudes of a few tens of metres, the lowest accessible altitude during missed approaches of the aircraft, to up to 5 km. Analysis of the data suggested highly variable horizontal and vertical profiles of NO3 and N2O5 which were attributable to their very reactive nature in the atmosphere. Finally, comparison is made between these measurements and those previously reported over Eastern USA using cavity ring-down spectroscopy.

  19. The Infrared Spectra and Absorption Intensities of Amorphous Ices: Methane and Carbon Dioxide

    NASA Astrophysics Data System (ADS)

    Gerakines, Perry A.; Hudson, Reggie L.; Loeffler, Mark J.

    2015-11-01

    Our research group is carrying out new IR measurements of icy solids relevant to the outer solar system and the interstellar medium, with an emphasis on amorphous and crystalline ices below ~70 K. Our goal is to add to the relatively meager literature on this subject and to provide electronic versions of state-of-the-art data, since the abundances of such molecules cannot be deduced without accurate reference spectra and IR band strengths. In the past year, we have focused on two of the simplest and most abundant components of icy bodies in the solar system - methane (CH4) and carbon dioxide (CO2). Infrared spectra from ˜ 4500 to 500 cm-1 have been measured for each of these molecules in μm-thick films at temperatures from 10 to 70 K. All known amorphous and crystalline phases have been reproduced and, for some, presented for the first time. We also report measurements of the index of refraction at 670 nm and the mass densities for each ice phase. Comparisons are made to earlier work where possible. Electronic versions of our new results are available at http://science.gsfc.nasa.gov/691/cosmicice/ constants.html.

  20. Complexities in pyroxene compositions derived from absorption band centers: Examples from Apollo samples, HED meteorites, synthetic pure pyroxenes, and remote sensing data

    NASA Astrophysics Data System (ADS)

    Moriarty, D. P.; Pieters, C. M.

    2016-01-01

    We reexamine the relationship between pyroxene composition and near-infrared absorption bands, integrating measurements of diverse natural and synthetic samples. We test an algorithm (PLC) involving a two-part linear continuum removal and parabolic fits to the 1 and 2 ?m bandsa computationally simple approach which can easily be automated and applied to remote sensing data. Employing a suite of synthetic pure pyroxenes, the PLC technique is shown to derive similar band centers to the modified Gaussian model. PLC analyses are extended to natural pyroxene-bearing materials, including (1) bulk lunar basalts and pyroxene separates, (2) diverse lunar soils, and (3) HED meteorites. For natural pyroxenes, the relationship between composition and absorption band center differs from that of synthetic pyroxenes. These differences arise from complexities inherent in natural materials such as exsolution, zoning, mixing, and space weathering. For these reasons, band center measurements of natural pyroxene-bearing materials are compositionally nonunique and could represent three distinct scenarios (1) pyroxene with a narrow compositional range, (2) complexly zoned pyroxene grains, or (3) a mixture of multiple pyroxene (or nonpyroxene) components. Therefore, a universal quantitative relationship between band centers and pyroxene composition cannot be uniquely derived for natural pyroxene-bearing materials without additional geologic context. Nevertheless, useful relative relationships between composition and band center persist in most cases. These relationships are used to interpret M3 data from the Humboldtianum Basin. Four distinct compositional units are identified (1) Mare Humboldtianum basalts, (2) distinct outer basalts, (3) low-Ca pyroxene-bearing materials, and (4) feldspathic materials.

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

    NASA Technical Reports Server (NTRS)

    Reagan, J. A.; Pilewskie, P. A.; Scott-Fleming, I. C.; Hermann, B. M.

    1986-01-01

    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 system 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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  3. Efficient Calculation of Electronic Absorption Spectra by Means of Intensity-Selected Time-Dependent Density Functional Tight Binding.

    PubMed

    Rger, Robert; van Lenthe, Erik; Lu, You; Frenzel, Johannes; Heine, Thomas; Visscher, Lucas

    2015-01-13

    During the last two decades density functional based linear response approaches have become the de facto standard for the calculation of optical properties of small- and medium-sized molecules. At the heart of these methods is the solution of an eigenvalue equation in the space of single-orbital transitions, whose quickly increasing number makes such calculations costly if not infeasible for larger molecules. This is especially true for time-dependent density functional tight binding (TD-DFTB), where the evaluation of the matrix elements is inexpensive. For the relatively large systems that can be studied the solution of the eigenvalue equation therefore determines the cost of the calculation. We propose to do an oscillator strength based truncation of the single-orbital transition space to reduce the computational effort of TD-DFTB based absorption spectra calculations. We show that even a sizable truncation does not destroy the principal features of the absorption spectrum, while naturally avoiding the unnecessary calculation of excitations with small oscillator strengths. We argue that the reduced computational cost of intensity-selected TD-DFTB together with its ease of use compared to other methods lowers the barrier of performing optical property calculations of large molecules and can serve to make such calculations possible in a wider array of applications. PMID:26574214

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  5. 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)

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

    1983-01-01

    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.

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

    SciTech Connect

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

    2013-12-02

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

  7. Absolute Line Intensities and Self-Broadened Half-Width Coefficients in the Ethylene-1-(13)C Bands in the 700-1190 cm(-1) Region

    SciTech Connect

    Flaud, Jean Marie; Lafferty, Walter J.; Malathy Devi, V.; Sams, Robert L.; Benner, D. C.

    2011-06-01

    Accurate individual line intensities have been measured for the five interacting bands V10, V8, V7, V4 and V6 of ethylene-1-13C using a multispectrum nonlinear least squares fitting technique. The measured intensities have been very satisfactorily fit leading to the determination of precise vibrational transition moments. A calculated spectrum accounting for the various rovibrational interactions has been generated. Such a spectrum should be useful for the planetary atmosphere modeling-community. Lorentz self-broadened half-width coefficients have also been measured for nearly 300 transitions in the strongest V7 band.

  8. Complexities in pyroxene compositions derived from absorption band centers: Examples from Apollo samples, HED meteorites, synthetic pure pyroxenes, and remote sensing data

    NASA Astrophysics Data System (ADS)

    Moriarty, D. P.; Pieters, C. M.

    2016-02-01

    We reexamine the relationship between pyroxene composition and near-infrared absorption bands, integrating measurements of diverse natural and synthetic samples. We test an algorithm (PLC) involving a two-part linear continuum removal and parabolic fits to the 1 and 2 μm bands—a computationally simple approach which can easily be automated and applied to remote sensing data. Employing a suite of synthetic pure pyroxenes, the PLC technique is shown to derive similar band centers to the modified Gaussian model. PLC analyses are extended to natural pyroxene-bearing materials, including (1) bulk lunar basalts and pyroxene separates, (2) diverse lunar soils, and (3) HED meteorites. For natural pyroxenes, the relationship between composition and absorption band center differs from that of synthetic pyroxenes. These differences arise from complexities inherent in natural materials such as exsolution, zoning, mixing, and space weathering. For these reasons, band center measurements of natural pyroxene-bearing materials are compositionally nonunique and could represent three distinct scenarios (1) pyroxene with a narrow compositional range, (2) complexly zoned pyroxene grains, or (3) a mixture of multiple pyroxene (or nonpyroxene) components. Therefore, a universal quantitative relationship between band centers and pyroxene composition cannot be uniquely derived for natural pyroxene-bearing materials without additional geologic context. Nevertheless, useful relative relationships between composition and band center persist in most cases. These relationships are used to interpret M3 data from the Humboldtianum Basin. Four distinct compositional units are identified (1) Mare Humboldtianum basalts, (2) distinct outer basalts, (3) low-Ca pyroxene-bearing materials, and (4) feldspathic materials.

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

    SciTech Connect

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

    2006-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  11. Low-intensity aerobic interval training attenuates pathological left ventricular remodeling and mitochondrial dysfunction in aortic-banded miniature swine.

    PubMed

    Emter, Craig A; Baines, Christopher P

    2010-11-01

    Cardiac hypertrophy in response to hypertension or myocardial infarction is a pathological indicator associated with heart failure (HF). A central component of the remodeling process is the loss of cardiomyocytes via cell death pathways regulated by the mitochondrion. Recent evidence has indicated that exercise training can attenuate or reverse pathological remodeling, creating a physiological phenotype. The purpose of this study was to examine left ventricular (LV) function, remodeling, and cardiomyocyte mitochondrial function in aortic-banded (AB) sedentary (HFSED; n = 6), AB exercise-trained (HFTR, n = 5), and control sedentary (n = 5) male Yucatan miniature swine. LV hypertrophy was present in both AB groups before the start of training, as indicated by increases in LV end-diastolic volume, LV end-systolic volume (LVESV), and LV end-systolic dimension (LVESD). Exercise training (15 wk) prevented further increases in LVESV and LVESD (P < 0.05). The heart weight-to-body weight ratio, LV + septum-to-body weight ratio, LV + septum-to-right ventricle ratio, and cardiomyocyte cross-sectional area were increased in both AB groups postmortem regardless of training status. Preservation of LV function after exercise training, as indicated by the maintenance of fractional shortening, ejection fraction, and mean wall shortening and increased stroke volume, was associated with an attenuation of the increased LV fibrosis (23%) and collagen (36%) observed in HFSED animals. LV mitochondrial dysfunction, as measured by Ca(2+)-induced mitochondrial permeability transition, was increased in HFSED (P < 0.05) but not HFTR animals. In conclusion, low-intensity interval exercise training preserved LV function as exemplified by an attenuation of fibrosis, maintenance of a positive inotropic state, and inhibition of mitochondrial dysfunction, providing further evidence of the therapeutic potential of exercise in a clinical setting. PMID:20817828

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

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

    SciTech Connect

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

    2013-08-10

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

  14. Intensity-Modulated Continuous-Wave Laser Absorption Spectrometer at 1.57 Micrometer for Atmospheric CO2 Measurements

    NASA Technical Reports Server (NTRS)

    Lin, Bing

    2014-01-01

    Understanding the earth's carbon cycle is essential for diagnosing current and predicting future climates, which requires precise global measurements of atmospheric CO2 through space missions. The Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission will provide accurate global atmospheric CO2 measurements to meet carbon science requirements. The joint team of NASA Langley Research Center and ITT Exelis, Inc. proposes to use the intensity-modulated, continuous-wave (IM-CW) laser absorption spectrometer (LAS) approach for the ASCENDS mission. Prototype LAS instruments have been developed and used to demonstrate the power, signal-to-noise ratio, precision and accuracy, spectral purity, and stability of the measurement and the instrument needed for atmospheric CO2 observations from space. The ranging capability from laser platform to ground surfaces or intermediate backscatter layers is achieved by transmitted range-encoded IM laser signals. Based on the prototype instruments and current lidar technologies, space LAS systems and their CO2 column measurements are analyzed. These studies exhibit a great potential of using IM-CW LAS system for the active space CO2 mission ASCENDS.

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

    NASA Technical Reports Server (NTRS)

    Chu, Zhiping; Wilkerson, Thomas D.; Singh, Upendra N.

    1993-01-01

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

  16. Resonance-Enhanced Raman Scattering of Ring-Involved Vibrational Modes in the (1)B2u Absorption Band of Benzene, Including the Kekule Vibrational Modes ?9 and ?10.

    PubMed

    Willitsford, Adam H; Chadwick, C Todd; Kurtz, Stewart; Philbrick, C Russell; Hallen, Hans

    2016-02-01

    Resonance Raman spectroscopy provides much stronger Raman signal levels than its off-resonant counterpart and adds selectivity by excitation tuning. Raman preresonance of benzene has been well studied. On-resonance studies, especially at phonon-allowed absorptions, have received less attention. In this case, we observe resonance of many of the vibration modes associated motion of the carbons in the ring while tuning over the (1)B2u absorption, including the related ?9 (CC stretch Herzberg notation, ?14 Wilson notation) and ?10 (CH-parallel bend Herzberg notation, ?15 Wilson notation) vibrational modes along with the ?2 (CC-stretch or ring-breathing Herzberg notation, ?1 Wilson notation) mode and multiples of the ?18 (CCC-parallel bend Herzberg notation, ?6 Wilson notation) vibrational mode. The ring-breathing mode is found to mix with the b2u modes creating higher frequency composites. Through the use of an optical parametric oscillator (OPO) to tune through the (1)B2u absorption band of liquid benzene, a stiffening (increase in energy) of the vibrational modes is observed as the excitation wavelength nears the (1)B2u absorption peak of the isolated molecule (vapor) phase. The strongest resonance amplitude observed is in the 2 ?18 (e2g) mode, with nearly twice the intensity of the ring-breathing mode, ?2. Several overtones and combination modes, especially with ?2 (a1g), are also observed to resonate. Raman resonances on phonon-allowed excitations are narrow and permit the measurement of vibrations not Raman-active in the ground state. PMID:26731431

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  18. Role of charge separation on two-step two photon absorption in InAs/GaAs quantum dot intermediate band solar cells

    NASA Astrophysics Data System (ADS)

    Creti, A.; Tasco, V.; Cola, A.; Montagna, G.; Tarantini, I.; Salhi, A.; Al-Muhanna, A.; Passaseo, A.; Lomascolo, M.

    2016-02-01

    In this work, we report on the competition between two-step two photon absorption, carrier recombination, and escape in the photocurrent generation mechanisms of high quality InAs/GaAs quantum dot intermediate band solar cells. In particular, the different role of holes and electrons is highlighted. Experiments of external quantum efficiency dependent on temperature and electrical or optical bias (two-step two photon absorption) highlight a relative increase as high as 38% at 10 K under infrared excitation. We interpret these results on the base of charge separation by phonon assisted tunneling of holes from quantum dots. We propose the charge separation as an effective mechanism which, reducing the recombination rate and competing with the other escape processes, enhances the infrared absorption contribution. Meanwhile, this model explains why thermal escape is found to predominate over two-step two photon absorption starting from 200 K, whereas it was expected to prevail at lower temperatures (≥70 K), solely on the basis of the relatively low electron barrier height in such a system.

  19. 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)

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

    1993-01-01

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

  20. Cloud and precipitation features of Super Typhoon Neoguri revealed from dual oxygen absorption band sounding instruments on board FengYun-3C satellite

    NASA Astrophysics Data System (ADS)

    Han, Yang; Zou, Xiaolei; Weng, Fuzhong

    2015-02-01

    A new methodology is developed to detect the cloud structures at different vertical levels using the dual oxygen absorption bands located near 60 GHz and 118 GHz, respectively. Observations from Microwave Temperature Sounder (MWTS) and Microwave Humidity Sounder (MWHS) on board the recently launched Chinese FengYun-3C satellite are used to prove the concept. It is shown that a paired oxygen MWTS and MWHS sounding channel with the same peak weighting function altitude allows for detecting the vertically integrated cloud water path above that level. A cloud emission and scattering index (CESI) is defined using dual oxygen band measurements to indicate the amounts of cloud liquid and ice water paths. The CESI distributions from three paired channels reveal unique three-dimensional structures of clouds and precipitation within Super Typhoon Neoguri that occurred in July 2014.

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

    SciTech Connect

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

    2011-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1993-03-01

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

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

    DOE PAGESBeta

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

    2011-08-01

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

  4. CMOS image sensor with organic photoconductive layer having narrow absorption band and proposal of stack type solid-state image sensors

    NASA Astrophysics Data System (ADS)

    Takada, Shunji; Ihama, Mikio; Inuiya, Masafumi

    2006-02-01

    Digital still cameras overtook film cameras in Japanese market in 2000 in terms of sales volume owing to their versatile functions. However, the image-capturing capabilities such as sensitivity and latitude of color films are still superior to those of digital image sensors. In this paper, we attribute the cause for the high performance of color films to their multi-layered structure, and propose the solid-state image sensors with stacked organic photoconductive layers having narrow absorption bands on CMOS read-out circuits.

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

    PubMed

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

    2013-07-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

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

    SciTech Connect

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

    2013-12-04

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

  8. Optical absorption band at 5.8 eV associated with the E{sub {gamma}}{sup '} centers in amorphous silicon dioxide: Optical absorption and EPR measurements

    SciTech Connect

    Agnello, S.; Buscarino, G.; Gelardi, F. M.; Boscaino, R.

    2008-05-15

    Line shape modifications induced by thermal treatment in the optical absorption and electron paramagnetic resonance (EPR) signals associated with the E{sub {gamma}}{sup '} center are experimentally investigated in various types of {gamma}-irradiated amorphous silicon dioxide (a-SiO{sub 2}). The g values of the EPR main resonance line of the E{sub {gamma}}{sup '} center show a shift correlated with the peak energy variation of the absorption band at about 5.8 eV associated with this defect. These spectroscopic changes are proposed to originate from structural modifications of the defect environment. The correlation is theoretically explained considering that the spin-orbit interaction couples the g-tensor's elements and the electronic energy level distribution of the defect. Our results suggest that the optical band at 5.8 eV is due to an intracenter electron promotion from the Si-O bonding states to the dangling bond of the O{identical_to}Si moiety.

  9. Polarization signatures and brightness temperatures caused by horizontally oriented snow particles at microwave bands: Effects of atmospheric absorption

    NASA Astrophysics Data System (ADS)

    Xie, Xinxin; Crewell, Susanne; Lhnert, Ulrich; Simmer, Clemens; Miao, Jungang

    2015-06-01

    This study analyzes the effects of atmospheric absorption and emission on the polarization difference (PD) and brightness temperature (TB) generated by horizontally oriented snow particles. A three-layer plane-parallel atmosphere model is used in conjunction with a simplified radiative transfer (RT) scheme to illustrate the combined effects of dichroic and nondichroic media on microwave signatures observed by ground-based and spaceborne sensors. Based on idealized scenarios which encompass a dichroic snow layer and adjacent nondichroic layers composed of supercooled liquid water (SCLW) droplets and water vapor, we demonstrate that the presence of atmospheric absorption/emission enhances TB and damps PD when observed from the ground. From a spaceborne perspective, however, TB can be reduced or enhanced by an absorbing/emitting layer above the snow layer, while a strong absorbing/emitting layer below the dichroic snow layer may even enhance PD. The induced PD and TB, which rely on snow microphysical assumptions, can vary up to 2 K and 10 K, respectively, due to the temperature-dependent absorption of SCLW. RT calculations based on 223 snowfall profiles selected from European Centre for Medium-Range Weather Forecasts data sets indicate that the existence of SCLW has a noticeable impact on PD and TB at three window frequencies (150 GHz, 243 GHz, and 664 GHz) during snowfall. Our results imply that while polarimetric channels at the three window channels have the potential for snowfall characterization, accurate information on liquid water is required to correctly interpret the polarimetric observations.

  10. Electronic band gap reduction and intense luminescence in Co and Mn ion-implanted SiO{sub 2}

    SciTech Connect

    Green, R. J. St Onge, D. J.; Moewes, A.; Zatsepin, D. A.; Kurmaev, E. Z.; Gavrilov, N. V.; Zatsepin, A. F.

    2014-03-14

    Cobalt and manganese ions are implanted into SiO{sub 2} over a wide range of concentrations. For low concentrations, the Co atoms occupy interstitial locations, coordinated with oxygen, while metallic Co clusters form at higher implantation concentrations. For all concentrations studied here, Mn ions remain in interstitial locations and do not cluster. Using resonant x-ray emission spectroscopy and Anderson impurity model calculations, we determine the strength of the covalent interaction between the interstitial ions and the SiO{sub 2} valence band, finding it comparable to Mn and Co monoxides. Further, we find an increasing reduction in the SiO{sub 2} electronic band gap for increasing implantation concentration, due primarily to the introduction of Mn- and Co-derived conduction band states. We also observe a strong increase in a band of x-ray stimulated luminescence at 2.75?eV after implantation, attributed to oxygen deficient centers formed during implantation.

  11. Microwave absorption properties of LiNb3O8 in X-band prepared by combustion synthesis

    NASA Astrophysics Data System (ADS)

    Goud, J. Pundareekam; Sindam, Bashaiah; Tumuluri, Anil; Raju, K. C. James

    2015-08-01

    Single phase LiNb3O8 powders were prepared using combustion synthesis technique. The powders were prepared by heat treating Li2CO3+Nb2O5/urea mixture in 1:3 ratio. Structural and morphological details have been done to confirm the presence of LiNb3O8. The S-parameters were measured using rectangular waveguide method in the X-band frequency (8.2GHz to 12.4GHz) by Vector Network Analyzer. The dielectric characteristics like dielectric constant (?') and dielectric loss (??) were calculated using Nicolson-Ross-Weir algorithm. Complex permittivity of 28-0.2j and 26-1.0j at 8.2GHz and 12.4GHz respectively are observed. Reflection loss was derived with permittivity and permeability as input parameters. Microwave absorber thickness is optimized and the RL< -20dB is obtained in the X-band frequency.

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

    PubMed

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

    2000-01-01

    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

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

    SciTech Connect

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

    2015-03-15

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

  14. Self-consistent band structures, charge distributions, and optical-absorption spectra in MgO, ?-Al2O3, and MgAl2O4

    NASA Astrophysics Data System (ADS)

    Xu, Yong-Nian; Ching, W. Y.

    1991-02-01

    The electronic structures, the charge-density distributions, and the optical-absorption spectra in MgO, ?-Al2O3, and MgAl2O4 crystals are studied by means of the first-principles self-consistent orthogonalized linear combination of atomic orbitals method. The calculated band structures of MgO and ?-Al2O3 are compared with experimental data and previous calculations. It is concluded that the electronic structure and optical properties of the spinel MgAl2O4 cannot be taken as a simple average of that of MgO and ?-Al2O3. By direct space integration of the calculated charge, it is shown that the ionic nature of these crystals should be best described by the formulas Mg1.83+O1.83-, Al2.63+2O1.75-3, and Mg1.79+Al2.63+2O1.76-4. The charge-density maps also reveal that there are open channels of very low electron density in MgAl2O4, which may be important in ionic conductivity. The calculated optical dielectric functions for the three crystals are compared with recent vacuum ultraviolet data for an energy range up to 40 eV and show good overall agreement. The existence of an excitonic peak near the absorption edge tends to sharpen the edge, thereby increasing the gap as compared with the one-electron local-density calculations. For absorption spectra beyond the excitonic peak, most of the experimentally resolved structures are reproduced by the calculations without the need of an adjustment to widen the gap. It appears that the high conduction-band states in these three crystals, calculated by using the local-density approximation, are reasonably accurate.

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

    NASA Technical Reports Server (NTRS)

    Lee, Zhong-Ping; Carder, Kendall L.

    2001-01-01

    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.

  16. 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)

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

    2013-06-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

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

    SciTech Connect

    Lavin, C.; Velasco, A. M.

    2011-09-20

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

  20. Photoabsorption cross-section measurements of 32S, 33S, 34S, and 36S sulfur dioxide for the B1B1-X1A1 absorption band

    NASA Astrophysics Data System (ADS)

    Danielache, Sebastian O.; Hattori, Shohei; Johnson, Matthew S.; Ueno, Yuichiro; Nanbu, Shinkoh; Yoshida, Naohiro

    2012-12-01

    We report measurements of the ultraviolet absorption cross-sections of32SO2, 33SO2, 34SO2 and 36SO2 recorded from 250 to 320 nm at 293 K with a resolution of 8 cm-1. This is the first reported measurement of the 36SO2cross-section. This work improves earlier measurements of the32SO2, 33SO2 and 34SO2cross-sections and is in good agreement concerning fine structure and peak widths, with localized differences at the peak maxima when isotope effects are taken into account. SO2 samples were produced in an identical process via combustion of isotopically enriched S0, eliminating effects due to variation in oxygen isotopic composition. Peak positions for the rare isotopologues are red shifted relative to the 32SO2 isotopologue. Starting at the origin the shift increases linearly through the band. A linear shift model based on the spectrum of 32SO2was used to estimate the cross-sections of33,34,36SO2; the average of the wavelength resolved absolute difference between the modeled and experimental spectra is 77.4, 107 and 139 respectively. While the peak-to-valley amplitude of36SO2 tends to be smaller than the other isotopologues throughout the spectrum, integrated band intensities for all isotopologues are conserved to within 4% relative to 32SO2. The cross-sections were used in a photochemical model to obtain fractionation constants to compare with photochemical chamber experiments. We conclude that planetary atmospheres will exhibit isotopic fractionation from both photoexcitation and photodissociation, and that experiments in the literature have isotopic imprints arising from both the B1B1-X1A1 and the C1B1-X1A1 bands.

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  2. Impact of dispersion, free carriers, and two-photon absorption on the generation of intense terahertz pulses in ZnTe crystals

    NASA Astrophysics Data System (ADS)

    Vidal, S.; Degert, J.; Tondusson, M.; Oberl, J.; Freysz, E.

    2011-05-01

    We study the evolution of the energy and the spectrum of a terahertz wave generated by optical rectification of an ultrashort laser pulse in ZnTe crystals with different thicknesses. As the pump intensity increases, we observe a shift in the terahertz spectrum toward lower frequencies. Moreover, at high pump intensities, in disagreement with common sense, thin crystals have a better conversion efficiency than thicker ones. These phenomena are accounted for by the pump depletion induced by two-photon absorption, pulse broadening and the impact of the photoinduced free carriers on the complex refractive index of the crystal in the terahertz range.

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

    SciTech Connect

    Li, Zhong-guo; Wei, Tai-Huei; Yang, Jun-yi; Song, Ying-lin; School of Physical Science and Technology, Soochow University, Suzhou 215006

    2013-12-16

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

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

    SciTech Connect

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

    2012-06-01

    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.

  5. Rovibrational intensities for the Delta V = 1 bands of the X 3Sigma(-) NH radical - Experiment and theory

    NASA Technical Reports Server (NTRS)

    Chackerian, C., Jr.; Guelachvili, G.; Lopez-Pineiro, A.; Tipping, R. H.

    1989-01-01

    The vibrational transition dipole moment for the highly reactive radical species NH in its ground electronic state is obtained via the Herman-Wallis effect manifest in emission spectra produced in a plasma reactor. The results of these experiments on the five lowest Delta V = 1 bands are in good agreement with high quality ab initio calculations of the electric dipole moment function.

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

    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.

  7. Confinement effect of laser ablation plume in liquids probed by self-absorption of C{sub 2} Swan band emission

    SciTech Connect

    Sakka, Tetsuo; Saito, Kotaro; Ogata, Yukio H.

    2005-01-01

    The (0,0) Swan band of the C{sub 2} molecules in a laser ablation plume produced on the surface of graphite target submerged in water was used as a probe to estimate the density of C{sub 2} molecules in the plume. Observed emission spectra were reproduced excellently by introducing a self-absorption parameter to the theoretical spectral profile expected by a rotational population distribution at a certain temperature. The optical density of the ablation plume as a function of time was determined as a best-fit parameter by the quantitative fitting of the whole spectral profile. The results show high optical densities for the laser ablation plume in water compared with that in air. It is related to the plume confinement or the expansion, which are the important phenomena influencing the characteristics of laser ablation plumes in liquids.

  8. Charge Transfer or J-Coupling? Assignment of an Unexpected Red-Shifted Absorption Band in a Naphthalenediimide-Based Metal-Organic Framework.

    PubMed

    McCarthy, Brian D; Hontz, Eric R; Yost, Shane R; Van Voorhis, Troy; Dinc?, Mircea

    2013-02-01

    We investigate and assign a previously reported unexpected transition in the metal-organic framework Zn2(NDC)2(DPNI) (1; NDC = 2,6-naphthalenedicarboxylate, DPNI = dipyridyl-naphthalenediimide) that displays linear arrangements of naphthalenediimide ligands. Given the longitudinal transition dipole moment of the DPNI ligands, J-coupling seemed possible. Photophysical measurements revealed a broad, new transition in 1 between 400 and 500 nm. Comparison of the MOF absorption spectra with that of a charge transfer (CT) complex formed by manual grinding of DPNI and H2NDC led to the assignment of the new band in 1 as arising from an interligand CT. Constrained density functional theory utilizing a custom long-range-corrected hybrid functional was employed to determine which ligands were involved in the CT transition. On the basis of relative oscillator strengths, the interligand CT was assigned as principally arising from ?-stacked DPNI/NDC dimers rather than the alternative orthogonal pairs within the MOF. PMID:26281740

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

    NASA Technical Reports Server (NTRS)

    Glownia, James H.; Sorokin, Peter P.

    1994-01-01

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

  10. Imaging the photodissociation of CH3SH in the first and second absorption bands: The CH3(X~ 2A1)+SH(X 2?) channel

    NASA Astrophysics Data System (ADS)

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

    2007-01-01

    The CH3(XA12)+SH(X?2) channel of the photodissociation of CH3SH has been investigated at several wavelengths in the first 1A?1?XA'1 and second 2A?1?XA'1 absorption bands by means of velocity map imaging of the CH3 fragment. A fast highly anisotropic (? =-10.1) CH3(XA12) signal has been observed in the images at all the photolysis wavelengths studied, which is consistent with a direct dissociation process from an electronically excited state by cleavage of the C-S bond in the parent molecule. From the analysis of the CH3 images, vibrational populations of the SH(X?2) counterfragment have been extracted. In the second absorption band, the SH fragment is formed with an inverted vibrational distribution as a consequence of the forces acting in the crossing from the bound 2A?1 second excited state to the unbound 1A?1 first excited state. The internal energy of the SH radical increases as the photolysis wavelength decreases. In the case of photodissociation via the first excited state, the direct production of CH3 leaves the SH counterfragment with little internal excitation. Moreover, at the longer photolysis wavelengths corresponding to excitation to the 1A?1 state, a slower anisotropic CH3 channel has been observed (? =-0.80.1) consistent with a two step photodissociation process, where the first step corresponds to the production of CH3S(XE2) radicals via cleavage of the S-H bond in CH3SH, followed by photodissociation of the nascent CH3S radicals yielding CH3(XA12)+S(XP0,1,23).

  11. 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)

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

    2014-08-01

    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 λ/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.

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

    NASA Technical Reports Server (NTRS)

    Rowan, L. C. (principal investigator)

    1974-01-01

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

  13. Laboratory studies of infrared absorption by NO2 and HNO3

    NASA Technical Reports Server (NTRS)

    Murcray, D. G.; Goldman, A.; Bonomo, F.

    1975-01-01

    Data concerning the quantitative absorption in the 11 and 22 micron region by HNO3 were obtained. Results are presented indicating the temperature dependence of these bands of HNO3 vapor. The 21.8 micron absorption bands of HNO3 vapor at 40 C are discussed along with the integrated intensity and line parameters for the 6.2 micron band of NO2.

  14. Time-Dependent Density Functional Theory Study of Low-Lying Absorption and Fluorescence Band Shapes for Phenylene-Containing Oligoacenes.

    PubMed

    Jun, Ye

    2015-12-24

    Low-lying band shapes of absorption and fluorescence spectra for a member of a newly synthesized family of phenylene-containing oligoacenes (POA 6) reported in J. Am. Chem. Soc. 2012 , 134 , 15351 are studied theoretically with two different approaches with TIPS-anthracene as a comparison. Underlying photophysics and exciton-phonon interactions in both molecules are investigated in details with the aid of the time-dependent density functional theory and multimode Brownian oscillator model. The first two low-lying excited-states of POA 6 were found to exhibit excitation characteristics spanning entire conjugated backbone despite the presence of antiaromatic phenylene section. Absorption and fluorescence spectra calculated from both time-dependent density functional theory and multimode Brownian oscillator model are shown to reach good agreement with experimental ones. The coupling between phonon modes and optical transitions is generally weak as suggested by the multimode Brownian oscillator model. Broader peaks of POA 6 spectra are found to relate to stronger coupling between low frequency phonon modes such as backbone twisting (with frequency <300 cm(-1)) and optical transitions. Furthermore, POA 6 exhibits weaker exciton-phonon coupling for the phonon modes above 1000 cm(-1) compared to TIPS-anthracene owing to extended conjugated backbone. A significant coupling between an in-plane breathing mode localized around the antiaromatic phenylene segment with frequency at 1687 cm(-1) and optical transitions for the first two excited-states of POA 6 is also observed. PMID:26611665

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    SciTech Connect

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

    1985-01-01

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

  18. Strain and temperature dependent absorption spectra studies for identifying the phase structure and band gap of EuTiO3 perovskite films.

    PubMed

    Jiang, Kai; Zhao, Run; Zhang, Peng; Deng, Qinglin; Zhang, Jinzhong; Li, Wenwu; Hu, Zhigao; Yang, Hao; Chu, Junhao

    2015-12-21

    Post-annealing has been approved to effectively relax the out-of-plane strain in thin films. Epitaxial EuTiO3 (ETO) thin films, with and without strain, have been fabricated on (001) LaAlO3 substrates by pulsed laser deposition. The absorption and electronic transitions of the ETO thin films are investigated by means of temperature dependent transmittance spectra. The antiferrodistortive phase transition can be found at about 260-280 K. The first-principles calculations indicate there are two interband electronic transitions in ETO films. Remarkably, the direct optical band gap and higher interband transition for ETO films show variation in trends with different strains and temperatures. The strain leads to a band gap shrinkage of about 240 meV while the higher interband transition an expansion of about 140 meV. The hardening of the interband transition energies in ETO films with increasing temperature can be attributed to the Frhlich electron-phonon interaction. The behavior can be linked to the strain and low temperature modified valence electronic structure, which is associated with rotations of the TiO6 octahedra. PMID:26568432

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  20. First-Principles Simulations of One- and Two-Photon Absorption Band Shapes of the Bis(BF2) Core Complex.

    PubMed

    Zaleśny, Robert; Murugan, N Arul; Tian, Guangjun; Medved', Miroslav; Ågren, Hans

    2016-03-10

    Motivated by the outstanding properties of bis(BF2) core complexes as fluorophore probes, we present a systematic computational study of their vibrationally resolved one- and two-photon absorption spectra in vacuum and in solution. Electronic and vibrational structure calculations were performed using the coupled cluster CC2 method and the Kohn-Sham formulation of density functional theory (DFT). A nonempirical estimation of the inhomogeneous broadening, accomplished using the polarizable embedding (PE) approaches combined with time-dependent DFT and CC2 methods, is used as a key ingredient of the computational protocol employed for simulations of the spectral features in solution. The inhomogeneous broadening is also determined based on the Marcus theory employing linear response and state-specific polarizable continuum model (PCM) methods. It is found that the polarizable embedding CC2 and the state-specific PCM are the most successful approaches for description of environmental broadening. For the 1(1)Ag → 1(1)Bu transition, the non-Condon effects can be safely neglected and a fair agreement between the simulated and experimental band shapes is found. In contrast, the shape of the vibrationally resolved band corresponding to the two-photon allowed 1(1)Ag → 2(1)Ag transition is largely dominated by non-Condon effects. A generalized few-level model was also employed to analyze the mechanism of the electronic two-photon 1(1)Ag → 2(1)Ag excitation. It was found that the most important optical channel involves the 1(1)Bu excited state. Ramifications of the findings for general band shape modeling are briefly discussed. PMID:26840541

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

    NASA Astrophysics Data System (ADS)

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

    2001-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Reinhart, F. K.

    2005-06-01

    The existence of band tails even in nominally undoped and uncompensated GaAs, and the nonparabolic absorption shape above the band gap are the prime examples for the discrepancy between theory and experiments. To overcome this difficulty, we propose a heuristic approach that is guided by the fundamental theoretical aspects and the experimental facts. For this reason, we fit the available absorption data with exponential functions over a photon energy interval from below the band gap to 3eV. This analytical representation remains well within the known experimental uncertainties over a temperature range from cryogenic to room temperature and beyond. The fitting functions are interpreted to represent the absorption contributions by the band tails, the continuum, and the excitons. This descriptive absorption function implicitly results from a perturbation of the imaginary part of the dielectric function that takes a host of unspecified contributions into account. The real part of the dielectric function due to the high-energy critical points is represented by Lorentzian functions with critical energies taken at 3 and 5eV. Its square root defines the refractive index due to these critical points, nh. The refractive index, n, is represented by the sum of nh and the truncated Kramers-Krnig transformation of the absorption function. The determination of nh is made by fitting n to the precise refractive index data of Marple [J. Appl. Phys. 35, 1241 (1964)]. This procedure yields a very precise description (<0.1% below and within experimental uncertainty at and above the band gap) of the published refractive index data from 0to2.2eV (except for the narrow reststrahl band near 0.033eV) over a temperature range similar to that mentioned for the absorption function. We feel confident to predict the refractive index for temperatures as low as 4K. An analytical expression for the refractive index describes the temperature and energy dependences very precisely below the band gap. The analytic expression is also very precise in the band-gap region for a temperature range estimated from 80to400K. We also compare the form of the absorption function derived from photoluminescence spectra. We find that low quasiequilibrium carrier densities lead to important modifications of the absorption function. These experimental findings together with the fitting procedures serve as a basis for a heuristic theory to calculate the electronic and optical properties under injection.

  3. Retrieval of optical depth and vertical distribution of atmospheric aerosols from light intensity and polarization in O2 A and B bands

    NASA Astrophysics Data System (ADS)

    Ding, S.; Wang, J.; Xu, X.; Spurr, R. J. D.

    2014-12-01

    Although UV radiance at the top-of-atmosphere (TOA) is known to be sensitive to the centroid height of absorbing aerosols, several methods were proposed recently to retrieve centroid height of aerosols (in particular, scattering aerosols) from hyperspectral radiation measurements in and around the O2 A and B bands. However, most such retrievals ignore polarization effects in the reflected radiation and are limited to dark surface scenarios. Here, we evaluate the feasibility of combining intensity and polarization measurements in the O2 A and B bands for retrieving aerosol optical depth and aerosol height, especially over bright surfaces. The feasibility study is conducted in two steps. The first step comprises a theoretical analysis of the effects of various aerosols on the behavior of the degree of linear polarization (DOLP) of light in the O2 A and B bands under different surface conditions. We use the Unified Linearized Vector Radiative Transfer Model (UNL-VRTM) to simulate the full Stokes vector and its Jacobians with respect to the aerosol optical depth and parameters characterizing the aerosol vertical profile. In order to identify the most sensitive spectral wavelengths, the concepts of 'Shannon information content (SIC)' and 'degree of freedom for signal (DFS)' are used to examine the information contained in each individual wavelength in both O2 bands. In the second step, case studies are conducted to retrieve the optical depth and vertical distribution of aerosols. Here, we use GOME-2 and/or SCIAMACHY backscatter measurements at selected most sensitive wavelengths in both O2 bands. The retrieval method is based upon non-linear optimal estimation theory. We compare the retrieved aerosol parameters (optical depth and height of aerosols) directly with CALIPSO observations. We also estimate the error of the retrieved parameters due to various sources of uncertainty.

  4. Voltage induced intensity changes in surface raman bands from a 2-chromophore probe, 4-benzyl pyridine adsorbed on roughened silver electrodes and their variation with excitation frequency

    NASA Astrophysics Data System (ADS)

    Busby, C. C.

    1984-05-01

    Voltage induced intensity changes in the surface enhanced Raman bands of 4-benzyl pyridine adsorbed on variously roughened silver electrode surfaces peak at different voltages for different excitation wavelengths. This behaviour, which is known to occur for pyridine and the picolines, is shown to occur for both the pyridyl and benzyl residues, though benzene itself does not exhibit enhancement under the same conditions. Results obtained on conventionally prepared, anodised electrodes are compared with those from novel magic array electrodes and results are consistent with the hypothesis that these latter electrodes are more suited for Raman studies of adsorbates in electrochemical systems. This is because they do not have the excess quantities of surface complexes present on them: these are probably responsible for much of the signal from the anodised electrodes. Explanations for the excitation frequency dependence of the voltage/intensity curves are discussed in relation to electrode specific effects as well as to charge transfer.

  5. A search for formic acid in the upper troposphere - A tentative identification of the 1105-per cm nu-6 band Q branch in high-resolution balloon-borne solar absorption spectra

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Infrared solar absorption spectra recorded at 0.02-per cm resolution during a balloon flight from Alamogordo, NM (33 deg N), on March 23, 1981, have been analyzed for the possible presence of absorption by formic acid (HCOOH). An absorption feature at 1105 per cm has been tentatively identified in upper tropospheric spectra as due to the nu-6 band Q branch. A preliminary analysis indicates a concentration of about 0.6 ppbv and 0.4 ppbv near 8 and 10 km, respectively.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Infrared solar absorption spectra recorded at 0.02/cm resolution during a balloon flight from Alamogordo, N.M. (33 deg N), on March 23, 1981, have been analyzed for the possible presence of absorption by formic acid (HCOOH). An absorption feature at 1105/ cm has been tentatively identified in upper tropospheric spectra as due to the nu(sub 6) band Q branch. A preliminary analysis indicates a concentration of approx. = 0.6 ppbv and approx. = 0.4 ppbv near 8 and 10 km, respectively.

  7. Highly ordered monolayer/bilayer TiO2 hollow sphere films with widely tunable visible-light reflection and absorption bands

    NASA Astrophysics Data System (ADS)

    Li, Jie; Qin, Yao; Jin, Chao; Li, Ying; Shi, Donglu; Schmidt-Mende, Lukas; Gan, Lihua; Yang, Jinhu

    2013-05-01

    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

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  9. Resonant peaks of the linear optical absorption and rectification coefficients in GaAs/GaAlAs quantum well: Combined effects of intense laser, electric and magnetic fields

    NASA Astrophysics Data System (ADS)

    Ozturk, Emine; Sokmen, Ismail

    2015-11-01

    In this study, the resonant peaks of the linear optical absorption (OA) and rectification coefficients in GaAs/GaAlAs quantum well are calculated as dependent on the applied electric field (F), the magnetic field (B) and the laser field intensity parameter (?0). Our results show that the shape of confined potential profile, the energy levels and the dipole moment matrix elements are changed as dependent on the F, B and ?0. Also, the resonant peaks of the OA and rectification coefficients depend on the applied external field effects. Therefore, the variation of the resonant peaks of these coefficients which can be appropriate for various optical modulators and infrared optical device applications can be smoothly obtained by the alteration electric, magnetic and intense laser field.

  10. Optimization of terahertz generation from LiNbO3 under intense laser excitation with the effect of three-photon absorption.

    PubMed

    Zhong, Sen-Cheng; Zhai, Zhao-Hui; Li, Jiang; Zhu, Li-Guo; Li, Jun; Meng, Kun; Liu, Qiao; Du, Liang-Hui; Zhao, Jian-Heng; Li, Ze-Ren

    2015-11-30

    We proposed a three-dimensional model to simulate terahertz generation from LiNbO3 crystal under intense laser excition (up to ~50 mJ/cm2). The impact of three-photon absorption, which leads to free carrier generation and free carrier saturation (when pump fluence above ~10 mJ/cm2) on terahertz generation was investigated. And further with this model, we stated the optimized experimental conditions (incident postion, beam diameter, and pulse duration, etc) for maximum generation efficiency in commonly-used tilted-pulse-front scheme. Red shift of spectrum, spatial distribution "splitting" effects of emitted THz beam, and primilary experimental verification under intense laser excitation are given. PMID:26698758

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

    NASA Astrophysics Data System (ADS)

    Wainwright, P. R.

    2003-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  13. Is actinometry reliable for monitoring Si and silicone halides produced in silicon etching plasmas? A comparison with their absolute densities measured by UV broad band absorption

    NASA Astrophysics Data System (ADS)

    Kogelschatz, M.; Cunge, G.; Sadeghi, N.

    2006-03-01

    SiCl{x} radicals, the silicon etching by-products, are playing a major role in silicon gate etching processes because their redeposition on the wafer leads to the formation of a SiOCl{x} passivation layer on the feature sidewalls, which controls the final shape of the etching profile. These radicals are also the precursors to the formation of a similar layer on the reactor walls, leading to process drifts. As a result, the understanding and modelling of these processes rely on the knowledge of their densities in the plasma. Actinometry technique, based on optical emission, is often used to measure relative variations of the density of the above mentioned radicals, even if it is well known that the results obtained with this technique might not always be reliable. To determine the validity domain of actinometry in industrial silicon-etching high density plasmas, we measure the RF source power and pressure dependences of the absolute densities of SiCl{x} (x=0{-}2), SiF and SiBr radicals, deduced from UV broad band absorption spectroscopy. These results are compared to the evolution of the corresponding actinometry signals from these radicals. It is shown that actinometry predicts the global trends of the species density variations when the RF power is changed at constant pressure (that is to say when only the electron density changes) but it completely fails if the gas pressure, hence the electron temperature, changes.

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

    PubMed

    Wainwright, P R

    2003-10-01

    Of the biological effects of human exposure to radiofrequency and microwave radiation, the best-established are those due to elevation of tissue temperature. To prevent harmful levels of heating, restrictions have been proposed on the specific absorption rate (SAR). However, the relationship between SAR and temperature rise is not an invariant, since not only the heat capacity but also the efficiency of heat dissipation varies between different tissues and exposure scenarios. For small enough SAR, the relationship is linear and may be characterized by a 'heating factor' deltaT/SAR. Under whole-body irradiation the SAR may be particularly high in the ankles due to the concentration of current flowing through a relatively small cross-sectional area. In a previous paper, the author has presented calculations of the SAR distribution in a human leg in the high frequency (HF) band. In this paper, the heating factor for this situation is derived using a finite element approximation of the Pennes bioheat equation. The sensitivity of the results to different blood perfusion rates is investigated, and a simple local thermoregulatory model is applied. Both time-dependent and steady-state solutions are considered. Results confirm the appropriateness of the ICNIRP reference level of 100 mA on current through the leg, but suggest that at higher currents significant thermoregulatory adjustments to muscle blood flow will occur. PMID:14579857

  15. Inhomogeneous broadening and peak shift of the 7.6 eV optical absorption band of oxygen vacancies in SiO{sub 2}

    SciTech Connect

    Kajihara, Koichi; Skuja, Linards; Hosono, Hideo

    2014-10-21

    The peak parameters of radiation-induced 7.6 eV optical absorption band of oxygen vacancies (Si-Si bonds) were examined for high-purity synthetic α-quartz and amorphous SiO{sub 2} (a‐SiO{sub 2}) exposed to {sup 60}Co γ-rays. The peak shape is asymmetric with the steeper edge at the lower energy side both in α-quartz and a‐SiO{sub 2}, and the peak energy is larger for α-quartz than that for a‐SiO{sub 2}. The full width at half maximum for a‐SiO{sub 2} is larger by ∼40-60% than that for α-quartz, and it increases with an increase in the disorder of the a‐SiO{sub 2} network, which is enhanced by raising the temperature of preannealing before irradiation, i.e., fictive temperature. These data are interpreted from the viewpoint of the site-to-site distribution of the Si-Si bond length in a‐SiO{sub 2}.

  16. Rectification of excitation with bathochromic shift induced by intense absorption of organic ligands during emission measurement of Eu(III) complex.

    PubMed

    Zhao, Hui; Su, Wei; Luo, Yanhua; Ji, Yaohui; Li, Zengchang; Jiu, Hongfang; Liang, Hao; Chen, Biao; Zhang, Qijin

    2006-11-01

    Bathochromic shift in excitation spectrum was observed during emission measurement of Eu(DBM)(3)Phen containing dilute solution in methyl methacrylate (MMA). Detailed analysis shows that the reason of bathochromic shift is not the formation of molecule aggregation. It is caused by the intense absorption of ligands in the complex. Based on this model, a new method has been established to rectify excitation spectra before emission measurement of systems with different concentration. There exists a critical value of the absorption strength, which is 0.87 from calculation. Higher absorption than this value will cause the bathochromic shift of excitation peak. The wavelength whose absorbance is 0.87 will be the position of the strongest excitation peak. With 200 ppm and 500 ppm Eu(DBM)(3)Phen as the standard sample, relations between relative concentration and wavelength of excitation peak in Eu(DBM)(3)Phen system were deduced and plotted. Theoretical curves are in good agreement with experiment data except extra-dilute concentration, for partial decomplexation of the beta-diketonate and phenanthroline ligands. PMID:16580249

  17. Charge-transfer optical absorption in linear magnetic insulators in a strong electric field

    NASA Astrophysics Data System (ADS)

    Lyo, S. K.

    1985-12-01

    The effect of a strong electric field on the charge-transfer optical absorption is studied in linear narrow-band Mott-Hubbard insulators (or semiconductors) such as alkali-TCNQ's (tetracyanoquinodimethanes) and antiferromagnetic Heisenberg chains, using the half-filled-band Hubbard model with strong on-site Coulomb repulsion. It is shown that, for an antiferromagnetic ground state, the main effect of the field is to severely (i.e., nonlinearly with the applied field) squeeze the unperturbed continuum absorption band into a narrower band of unevenly spaced discrete rungs of a Stark ladder. The intensity of the absorption into the Stark-ladder states has exponential tails both above and below the main band, showing a discrete version of the Franz-Keldysh effect. For random and ferromagnetic spin configurations, the absorption profile narrows and the discrete absorption resonances smear into sharp continuum structures.

  18. 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)

    Holland, Nicholas Vedder, III

    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.

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

    SciTech Connect

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

    2014-07-07

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

  20. Modification of Nonlinear Optical Properties in CdSe/PBMA Film by High Intensity Light

    NASA Astrophysics Data System (ADS)

    Kovalevskij, V.; Gulbinas, V.

    2005-02-01

    Excitation-relaxation dynamics in CdSe nanocrystals passivated with tri-n-octylphosphine oxide and embedded in the poly(butylmethacrylate) polymer was investigated before and after their irradiation by high intensity laser pulses. The irradiation causes a significant bleaching of the sample absorption as well as the shift of the lowest energy absorption band to the short wavelength side. The film irradiation reduces the nonlinear transient absorption bleaching on the long wavelength side of the low energy absorption band, however, it has only minor influence on the transient absorption relaxation.

  1. Measurements of the ClO radical vibrational band intensity and the ClO + ClO + M reaction product

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

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

    PubMed

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

    2014-11-17

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

  3. Electronic structure of an [FeFe] hydrogenase model complex in solution revealed by X-ray absorption spectroscopy using narrow-band emission detection.

    PubMed

    Leidel, Nils; Chernev, Petko; Havelius, Kajsa G V; Schwartz, Lennart; Ott, Sascha; Haumann, Michael

    2012-08-29

    High-resolution X-ray absorption spectroscopy with narrow-band X-ray emission detection, supported by density functional theory calculations (XAES-DFT), was used to study a model complex, ([Fe(2)(?-adt)(CO)(4)(PMe(3))(2)] (1, adt = S-CH(2)-(NCH(2)Ph)-CH(2)-S), of the [FeFe] hydrogenase active site. For 1 in powder material (1(powder)), in MeCN solution (1'), and in its three protonated states (1H, 1Hy, 1HHy; H denotes protonation at the adt-N and Hy protonation of the Fe-Fe bond to form a bridging metal hydride), relations between the molecular structures and the electronic configurations were determined. EXAFS analysis and DFT geometry optimization suggested prevailing rotational isomers in MeCN, which were similar to the crystal structure or exhibited rotation of the (CO) ligands at Fe1 (1(CO), 1Hy(CO)) and in addition of the phenyl ring (1H(CO,Ph), 1HHy(CO,Ph)), leading to an elongated solvent-exposed Fe-Fe bond. Isomer formation, adt-N protonation, and hydride binding caused spectral changes of core-to-valence (pre-edge of the Fe K-shell absorption) and of valence-to-core (K(2,5) emission) electronic transitions, and of K? RIXS data, which were quantitatively reproduced by DFT. The study reveals (1) the composition of molecular orbitals, for example, with dominant Fe-d character, showing variations in symmetry and apparent oxidation state at the two Fe ions and a drop in MO energies by ~1 eV upon each protonation step, (2) the HOMO-LUMO energy gaps, of ~2.3 eV for 1(powder) and ~2.0 eV for 1', and (3) the splitting between iron d(z(2)) and d(x(2)-y(2)) levels of ~0.5 eV for the nonhydride and ~0.9 eV for the hydride states. Good correlations of reduction potentials to LUMO energies and oxidation potentials to HOMO energies were obtained. Two routes of facilitated bridging hydride binding thereby are suggested, involving ligand rotation at Fe1 for 1Hy(CO) or adt-N protonation for 1HHy(CO,Ph). XAES-DFT thus enables verification of the effects of ligand substitutions in solution for guided improvement of [FeFe] catalysts. PMID:22860512

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

    NASA Astrophysics Data System (ADS)

    Sardar, Dhiraj K.; Russell, Charles C.

    2004-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Cui, Tingwei; Quan, Wenting

    2015-01-01

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

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

    PubMed

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

    2013-09-15

    This study reports the design, preparation, testing and surface characterization of uniform films deposited by sputtering Ag and Ta on non-heat resistant polyester to evaluate the Escherichia coli inactivation by TaON, TaN/Ag, Ag and TaON/Ag polyester. Co-sputtering for 120 s Ta and Ag in the presence of N₂ and O₂ led to the faster E. coli inactivation by a TaON/Ag sample within ∼40 min under visible light irradiation. The deconvolution of TaON/Ag peaks obtained by X-ray photoelectron spectroscopy (XPS) allowed the assignment of the Ta₂O₅ and Ag-species. The shifts observed for the XPS peaks have been assigned to AgO to Ag₂O and Ag(0), and are a function of the applied sputtering times. The mechanism of interfacial charge transfer (IFCT) from the Ag₂O conduction band (cb) to the lower laying Ta₂O₅ (cb) is discussed suggesting a reaction mechanism. The optical absorption of the TaON and TaON/Ag samples found by diffuse reflectance spectroscopy (DRS) correlated well with the kinetics of E. coli inactivation. The TaON/Ag sample microstructure was characterized by contact angle (CA) and by atomic force microscopy (AFM). Self-cleaning of the TaON/Ag polyester after each disinfection cycle enabled repetitive E. coli inactivation. PMID:23867967

  7. Determination of the chemical valence of atoms at a heterophase interface by x-ray diffraction measurements of crystal truncation rod intensity at an atomic absorption edge

    SciTech Connect

    Specht, E.D.; Walker, F.J.

    1992-01-01

    We report the application of a novel technique for determining the oxidation state of atoms at a buried interface. We have measured the energy dependence of the x-ray diffraction from an interface between an Al{sub 2}O{sub 3} substrate and a 100 nm Cr{sub 2}O{sub 3} film. As the energy of the x-rays is tuned through the Cr K absorption edge, diffracted intensity varies with the scattering power of Cr atoms at the interface. By comparing the near edge structure of the interface scattering with that of standard samples, we have determined that Cr{sup +3} is the predominant state at the interface.

  8. Infrared absorption mechanisms of black silicon

    NASA Astrophysics Data System (ADS)

    Cheng, Zhengxi; Chen, Yongping; Ma, Bin

    2014-09-01

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

  9. Quantitative Intracavity Laser Spectroscopy Measurements with a Ti:sapphire Laser: Absorption Intensities for Water Vapor Lines in the 790-800 nm Region.

    PubMed

    Kalmar; O'brien

    1998-12-01

    The intracavity laser spectroscopy (ILS) technique has been shown to be a very sensitive method for observing absorption spectra. By considering quantitative results (line-strengths and pressure broadening coefficients) obtained using the ILS method with a dye laser, the technique has been shown to provide quantitative information that is in excellent agreement with the values afforded by use of more traditional methods for acquiring absorption spectra. A similar investigation has been conducted for an ILS system based on a Ti:sapphire laser. Presented here are quantitative results for water vapor transitions occurring around 795 nm. Line intensities are determined as a function of water vapor pressure and effective path length (i.e., generation time). The line-strengths are compared with values determined by R. A. Toth [J. Mol. Spectrosc. 166, 176-183 (1994)] who used a multipass cell and the Fourier transform spectrometer at the Kitt Peak National Observatory. The good agreement between the results demonstrates that quantitatively accurate data can be obtained using the ILS technique with a Ti:sapphire laser. Copyright 1998 Academic Press. PMID:9831505

  10. EL2 deep level defects and above-band gap two-photon absorption in high gain lateral semi-insulating GaAs photoconductive switch

    NASA Astrophysics Data System (ADS)

    Shi, Wei; Wang, Wei; Niu, Hongjian; Zhang, Xianbin; Ji, Weili

    2005-01-01

    Experiments of a lateral semi-insulating GaAs photoconductive switch, both linear and nonlinear mode of the switch were observed when the switch was triggered by 1064 nm laser pulses, with energy of 1.9 mJ and the pulse width of 60 ns, and operated at biased electric field of 4.37 kV/cm. It"s wavelength is longer than 876nm, but the experiments indicate that the semi-insulating GaAs photoconductive switches can absorb 1064 nm laser obviously, which is out of the absorption range of the GaAs material. It is not possible to explain this behavior by using intrinsic absorption mechanism. We think that there are two mostly kinds of absorption mechanisms play a key part in absorption process, they are the two-steps-single-photon absorption that based on the EL2 energy level and two-photon absorption.

  11. Thionated perylene diimides with intense absorbance in the near-IR.

    PubMed

    Llewellyn, Ben A; Davies, E Stephen; Pfeiffer, Constance R; Cooper, Mick; Lewis, William; Champness, Neil R

    2016-01-26

    A synthetic strategy involving a combination of tetra-thionation and amine substitution in the bay region of a perylene diimide (PDI) leads to remarkable examples of neutral PDIs with intense absorption maxima in the near infrared. Generation of the corresponding monoanions red shifts the absorption profile to give short-wavelength infrared bands. PMID:26689154

  12. 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)

    Padmaja, G.; Kistaiah, P.

    2009-07-01

    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 (αo2-), 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.

  13. Advances In Cryogenic Monolithic Millimeter-wave Integrated Circuit (MMIC) Low Noise Amplifiers For CO Intensity Mapping and ALMA Band 2

    NASA Astrophysics Data System (ADS)

    Samoska, Lorene; Cleary, Kieran; Church, Sarah E.; Cuadrado-Calle, David; Fung, Andy; gaier, todd; gawande, rohit; Kangaslahti, Pekka; Lai, Richard; Lawrence, Charles R.; Readhead, Anthony C. S.; Sarkozy, Stephen; Seiffert, Michael D.; Sieth, Matthew

    2016-01-01

    We will present results of the latest InP HEMT MMIC low noise amplifiers in the 30-300 GHz range, with emphasis on LNAs and mixers developed for CO intensity mapping in the 40-80 GHz range, as well as MMIC LNAs suitable for ALMA Band 2 (67-90 GHz). The LNAs have been developed together with NGC in a 35 nm InP HEMT MMIC process. Recent results and a summary of best InP low noise amplifier data will be presented. This work describes technologies related to the detection and study of highly redshifted spectral lines from the CO molecule, a key tracer for molecular hydrogen. One of the most promising techniques for observing the Cosmic Dawn is intensity mapping of spectral-spatial fluctuations of line emission from neutral hydrogen (H I), CO, and [C II]. The essential idea is that instead of trying to detect line emission from individual galaxies, one measures the total line emission from a number of galaxies within the volume defined by a spectral-spatial pixel. Fluctuations from pixel to pixel trace large scale structure, and the evolution with redshift is revealed as a function of receiver frequency. A special feature of CO is the existence of multiple lines with a well-defined frequency relationship from the rotational ladder, which allows the possibility of cleanly separating the signal from other lines or foreground structure at other redshifts. Making use of this feature (not available to either HI or [C II] measurements) requires observing multiple frequencies, including the range 40-80 GHz, much of which is inaccessible from the ground or balloons.Specifically, the J=1->0 transition frequency is 115 GHz; J=2->1 is 230 GHz; J=3->2 is 345 GHz, etc. At redshift 7, these lines would appear at 14.4, 28.8, and 43.2 GHz, accessible from the ground. Over a wider range of redshifts, from 3 to 7, these lines would appear at frequencies from 14 to 86 GHz. A ground-based CO Intensity mapping experiment, COMAP, will utilize InP-based HEMT MMIC amplifier front ends in the 30 GHz range. Higher frequencies which are difficult to observe from the ground will be necessary to realize the full scientific potential of redshifted CO emission, and results from the latest MMIC LNAs above 40 GHz will be presented here

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

    PubMed

    Sholder, Gabriel; Loechler, Edward L

    2015-01-01

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

  15. Intense Upconversion Luminescence of CaSc2 O4 :Ho(3+) /Yb(3+) from Large Absorption Cross Section and Energy-Transfer Rate of Yb(3.).

    PubMed

    Li, Jing; Zhang, Jiahua; Hao, Zhendong; Chen, Li; Zhang, Xia; Luo, Yongshi

    2015-05-18

    Concentration-optimized CaSc2 O4 :0.2 % Ho(3+) /10 % Yb(3+) shows stronger upconversion luminescence (UCL) than a typical concentration-optimized upconverting phosphor Y2 O3 :0.2 % Ho(3+) /10 %? b(3+) upon excitation with a 980 nm laser diode pump. The (5) F4 +(5) S2 ?(5) I8 green UCL around 545 nm and (5) F5 ?(5) I8 red UCL around 660 nm of Ho(3+) are enhanced by factors of 2.6 and 1.6, respectively. On analyzing the emission spectra and decay curves of Yb(3+) : (2) F5/2 ?(2) F7/2 and Ho(3+) : (5) I6 ?(5) I8 , respectively, in the two hosts, we reveal that Yb(3+) in CaSc2 O4 exhibits a larger absorption cross section at 980 nm and subsequent larger Yb(3+) : (2) F5/2 ?Ho(3+) : (5) I6 energy-transfer coefficient (8.5510(-17) cm(3) s(-1) ) compared to that (4.6310(-17) cm(3) s(-1) ) in Y2 O3 , indicating that CaSc2 O4 :Ho(3+) /Yb(3+) is an excellent oxide upconverting material for achieving intense UCL. PMID:25721224

  16. An Amphiphilic BODIPY-Porphyrin Conjugate: Intense Two-Photon Absorption and Rapid Cellular Uptake for Two-Photon-Induced Imaging and Photodynamic Therapy.

    PubMed

    Zhang, Tao; Lan, Rongfeng; Gong, Longlong; Wu, Baoyan; Wang, Yuzhi; Kwong, Daniel W J; Wong, Wai-Kwok; Wong, Ka-Leung; Xing, Da

    2015-11-01

    The new amphiphilic BODPY-porphyrin conjugate BZnPP and its precursor BZnPH were synthesised, and their linear and two-photon photophysical properties, together with their cellular uptake and photo-cytotoxicity, were studied. This amphiphilic conjugate consists of a hydrophobic BODIPY moiety and a hydrophilic tetra(ethylene glycol) chain bridging a cationic triphenylphosphonium group to an amphiphilic porphyrin ZnP through acetylide linkers at its meso positions. A large two-photon absorption cross-section (?=1725 GM) and a high singlet oxygen quantum yield (0.52) were recorded. Intense linear- and two-photon-induced red emissions were also observed for both BZnPP and BZnPH. Further in vitro studies showed that BZnPP exhibited very efficient cellular uptake and strong photocytotoxic but weak dark cytotoxic properties towards human breast carcinoma MCF-7 cells. In summary, the two-photon-induced emission and the potent photo-cytotoxicity of BZnPP make it an efficacious dual-purpose tumour-imaging and photodynamic therapeutic agent in the tissue-transparent spectral windows. PMID:26345273

  17. Infrared intensities of liquids. XVII. Infrared refractive indices from 8000 to 350 cm - 1, absolute integrated absorption intensities, transition moments, and dipole moment derivatives of methan-d3-ol and methanol-d4 at 25 C

    NASA Astrophysics Data System (ADS)

    Bertie, John E.; Zhang, Shuliang L.

    1994-11-01

    This paper reports absolute infrared absorption intensities of liquids methan-d3-ol (CD3OH) and methanol-d4 (CD3OD) at 25 C between 8000 and 350 cm-1. Measurements were made by multiple attenuated total reflection spectroscopy with the CIRCLE cell, and by transmission spectroscopy with transmission cells fitted with calcium fluoride windows. In both cases, the spectra were converted to infrared real and imaginary refractive index spectra. The refractive indices obtained by these two methods agreed excellently and were combined to yield an imaginary refractive index spectrum k(?) between 7244 and 350 cm-1 for CD3OH and between 5585 and 350 cm-1 for CD3OD. The imaginary refractive index spectrum was arbitrarily set to zero from 8000 to 7244 cm-1 (CD3OH) or 5585 cm-1 (CD3OD), where k is always less than 410-6, in order that the real refractive index can be calculated below 8000 cm-1 by Kramers-Krnig transformation. The results are reported as graphs and tables of the refractive indices between 8000 and 350 cm-1, from which all other infrared properties of the two liquids can be calculated. The estimated accuracy, not precision, of the imaginary refractive index is 3%, except for 10%, where k is less than 410-5. The estimated accuracy of the real refractive index is better than 0.5%. In order to obtain molecular information from the measurements, the spectra of the imaginary polarizability multiplied by wave number ??m` were calculated under the assumption of the Lorentz local field. The area under these ??m` spectra was separated into the integrated intensities of different vibrations. The magnitudes of the transition moments were calculated from the integrated intensities, and the double harmonic approximation was used to calculate the magnitudes of the dipole moment derivatives of the liquid-state molecules with respect to the normal coordinates. Dipole moment derivatives with respect to internal coordinates were calculated under the simplest approximations, the validity of which is demonstrated by the experimental data in many cases. The consistency of the dipole moment derivatives with respect to internal coordinates obtained for different isotopomers is shown through their relative rotational corrections. Results are presented for the O-H, O-D, C-H, and C-D stretches; the C-O-H in-plane bending; and the D-C-O-H and D-C-O-D torsion vibrations.

  18. Demonstration That Calibration of the Instrument Response to Polarizations Parallel and Perpendicular to the Object Space Projected Slit of an Imaging Spectrometer Enable Measurement of the Atmospheric Absorption Spectrum in Region of the Weak CO2 Band for the Case of Arbitrary Polarization: Implication for the Geocarb Mission

    NASA Astrophysics Data System (ADS)

    Kumer, J. B.; Rairden, R. L.; Polonsky, I. N.; O'Brien, D. M.

    2014-12-01

    The Tropospheric Infrared Mapping Spectrometer (TIMS) unit rebuilt to operate in a narrow spectral region, approximately 1603 to 1615 nm, of the weak CO2 band as described by Kumer et al. (2013, Proc. SPIE 8867, doi:10.1117/12.2022668) was used to conduct the demonstration. An integrating sphere (IS), linear polarizers and quarter wave plate were used to confirm that the instrument's spectral response to unpolarized light, to 45° linearly polarized light and to circular polarized light are identical. In all these cases the intensity components Ip = Is where Ip is the component parallel to the object space projected slit and Is is perpendicular to the slit. In the circular polarized case Ip = Is in the time averaged sense. The polarizer and IS were used to characterize the ratio Rθ of the instrument response to linearly polarized light at the angle θ relative to parallel from the slit, for increments of θ from 0 to 90°, to that of the unpolarized case. Spectra of diffusely reflected sunlight passed through the polarizer in increments of θ, and divided by the respective Rθ showed identical results, within the noise limit, for solar spectrum multiplied by the atmospheric transmission and convolved by the Instrument Line Shape (ILS). These measurements demonstrate that unknown polarization in the diffusely reflected sunlight on this small spectral range affect only the slow change across the narrow band in spectral response relative to that of unpolarized light and NOT the finely structured / high contrast spectral structure of the CO2 atmospheric absorption that is used to retrieve the atmospheric content of CO2. The latter is one of the geoCARB mission objectives (Kumer et al, 2013). The situation is similar for the other three narrow geoCARB bands; O2 A band 757.9 to 768.6 nm; strong CO2 band 2045.0 to 2085.0 nm; CH4 and CO region 2300.6 to 2345.6 nm. Polonsky et al have repeated the mission simulation study doi:10.5194/amt-7-959-2014 assuming no use of a geoCARB depolarizer or polarizer. Enabled by measurement of the geoCARB grating efficiencies the simulated intensities Ism include the slow polarization induced spectral change across the band. These Ism are input to the retrieval SW that was used in the original study. There is no significant change to the very positive previous results for the mission objective of gas column retrieval.

  19. Fast, narrow-band computer model for radiation calculations

    SciTech Connect

    Yan, Z.; Holmstedt, G.

    1997-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  1. The Oxygen a Band

    NASA Astrophysics Data System (ADS)

    Benner, D. Chris; Devi, V. Malathy; Hoo, Jiajun; Hodges, Joseph; Long, David A.; Sung, Keeyoon; Drouin, Brian; Okumura, Mitchio; Bui, Thinh Quoc; Rupasinghe, Priyanka

    2014-06-01

    The oxygen A band is used for numerous atmospheric experiments, but spectral line parameters that sufficiently describe the spectrum to the level required by OCO2 and other high precision/accuracy experiments are lacking. Fourier transform spectra from the Jet Propulsion Laboratory and cavity ring down spectra from the National Institute of Standards and Technology were fitted simultaneously using the William and Mary multispectrum nonlinear least squares fitting technique into a single solution including the entire band. In addition, photoacoustic spectra already available from the California Institute of Technology will be added to the solution. The three types of spectrometers are complementary allowing the strengths of each to fill in the weaknesses of the others. With this technique line positions, intensities, widths, shifts, line mixing, Dicke narrowing, temperature dependences and collision induced absorption have been obtained in a single physically consistent fit. D. Chris Benner, C. P. Rinsland, V. M. Devi, M. A. H. Smith, and D. Atkins, JQSRT 1995;53:705-21. Part of the research described in this paper was performed at The College of William and Mary, the, Jet Propulsion Laboratory, California Institute of Technology, under contracts and cooperative agreements with the National Aeronautics and Space Administration and the Jet Propulsion Laboratory. Support for the National Institute of Standards and Technology was provided by the NIST Greenhouse Gas Measurements and Climate Research Program and a NIST Innovations in Measurement Science (IMS) award.

  2. 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)

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

    2001-01-01

    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.

  3. 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)

    Malathy Devi, V.; Benner, D. C.; Rinsland, C. P.; Smith, M. A. H.; Thakur, K. B.

    1986-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    1997-12-01

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

  5. 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)

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

    1991-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    Theoretical descriptions of the abundance and excitation of carbon monoxide in interstellar clouds require accurate data on the vacuum-ultraviolet absorption spectrum of the molecule. The 6.65 m spectrometer at the Photon Factory synchrotron light source was used to measure photoabsorption cross sections of CO features between 91.2 and 100.4 nm. These data were recorded at a resolving power of 170,000, more than 20 times greater than that used in previous work.

  7. Spectroscopic ellipsometry study of the free-carrier and band-edge absorption in ZnO thin films: Effect of non-stoichiometry

    NASA Astrophysics Data System (ADS)

    Singh, Chaman; Nozaki, Shinji; Rath, Shyama

    2015-11-01

    The effect of stoichiometry on the complex dielectric function (?(E) = ?1(E) + i?2(E)), and thereby on the optical and electrical properties, of rf-sputtered polycrystalline ZnO films was investigated using spectroscopic ellipsometry in the UV-VIS-NIR range. The stoichiometry and the density of the films were quantified by Rutherford backscattering spectroscopy. The lineshape of the dielectric function was fitted using the Tauc-Lorentz multi-oscillator and Drude models. The stoichiometric as well as the sub-stoichiometric films showed a high optical transparency in the visible and a bandgap absorption in the UV region. In the NIR region, however, the sub-stoichiometric films showed a significant increase in absorption with decreasing energy while the absorption was negligible for the stoichiometric films. This difference in behavior is attributed to the presence of free-carriers in the sub-stoichiometric films, whose concentration was determined to be around 4 1020 cm-3 from spectroscopic ellipsometry. The high carrier concentration induced by non-stoichiometry is also manifested in a larger value of the optical bandgap. This study shows the power of spectroscopic ellipsometry for the simultaneous determination of the electrical and optical properties of ZnO films and is applicable for a wide range of film thickness.

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

    PubMed

    Lin, Katrina Tao Hua; Silzel, John W

    2015-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Lin, Katrina Tao Hua; Silzel, John W.

    2015-05-01

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

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

    SciTech Connect

    Borysow, A. )

    1991-08-01

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

  11. Vibrational and electronic absorption spectroscopy of dibenzo[b,def]chrysene and its ions.

    PubMed

    Wang, Haiyan; Szczepanski, Jan; Hirata, So; Vala, Martin

    2005-11-01

    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

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

    SciTech Connect

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

    2014-02-07

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

  13. Dust and Diffuse Interstellar Bands in the z{sub a} = 0.524 Absorption System toward AO 0235+164

    SciTech Connect

    Junkkarinen, V.

    2004-08-06

    The authors present new HST STIS NUV-MAMA and STIS CCD observations of the BL Lac object AO 0235+164 and the intervening damped Ly {alpha} (DLA) line at z{sub {alpha}} = 0.524. The line profile gives N(HI) = 5 {+-} 1 x 10{sup 21} cm{sup -2} and, combined with the H I 21 cm absorption data leads to a spin temperature of Ts = 220 K {+-} 60 K. Those spectra also show a strong, broad feature at the expected position of the 2175 {angstrom} graphitic dust feature at z{sup {alpha}} = 0.524. Assuming a Galactic type dust extinction curve at z{sub {alpha}} = 0.524 gives a dust-to-gas ratio of 0.19 Galactic, but the fit, assuming the underlying, un-reddened spectrum is a single power-law, is poor in the far-UV. A dust-to-gas ratio of 0.19 Galactic is similar to the LMC, but the AO 0235+164 spectrum does not fit the LMC extinction curve, or the SMC extinction curve (which has practically no 2175 {angstrom} feature). A possible interpretation includes dust similar to Galactic, but with less of the small particles that produce the far-UV extinction. The metallicity of the z{sub {alpha}} = 0.524 absorber, estimated from the observed N(HI) and excess X-ray absorption (beyond Galactic) derived from contemporaneous and archival ASCA and ROSAT.

  14. Involvement of crystallinity in various luminescent bands in yttrium aluminate

    NASA Astrophysics Data System (ADS)

    Morimoto, Takaaki; Harima, Masayuki; Horii, Yosuke; Ohki, Yoshimichi

    2016-01-01

    When single crystal YAlO3 was implanted with P+ or B+ ions, optical absorption increases significantly at energies slightly lower than the band gap energy, indicating that localized electronic states were induced. Furthermore, the ion implantation decreases the intensity of an X-ray diffraction peak and changes its position randomly, which indicates that the crystalline structure of the sample was deformed. The intensities of photoluminescence (PL) bands due to impurities of Cr3+ and Er3+ and those originating in self-trapped excitons and antisites become smaller or disappear after the ion implantation. On the other hand, the intensity of the PL due to oxygen vacancies does not change. Such contrasting effects of the sample's crystallinity on the luminescence intensity are explained by the different manners of involvement of the crystal structure in the luminescence mechanism among these PLs in YAlO3.

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

    SciTech Connect

    Li, L. L.; Xu, W.

    2014-08-11

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

  16. CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

    NASA Astrophysics Data System (ADS)

    Rascher, U.; Agati, G.; Alonso, L.; Cecchi, G.; Champagne, S.; Colombo, R.; Damm, A.; Daumard, F.; de Miguel, E.; Fernandez, G.; Franch, B.; Franke, J.; Gerbig, C.; Gioli, B.; Gómez, J. A.; Goulas, Y.; Guanter, L.; Gutiérrez-de-La-Cámara, Ó.; Hamdi, K.; Hostert, P.; Jiménez, M.; Kosvancova, M.; Lognoli, D.; Meroni, M.; Miglietta, F.; Moersch, A.; Moreno, J.; Moya, I.; Neininger, B.; Okujeni, A.; Ounis, A.; Palombi, L.; Raimondi, V.; Schickling, A.; Sobrino, J. A.; Stellmes, M.; Toci, G.; Toscano, P.; Udelhoven, T.; van der Linden, S.; Zaldei, A.

    2009-02-01

    The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence.

  17. CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

    NASA Astrophysics Data System (ADS)

    Rascher, U.; Agati, G.; Alonso, L.; Cecchi, G.; Champagne, S.; Colombo, R.; Damm, A.; Daumard, F.; de Miguel, E.; Fernandez, G.; Franch, B.; Franke, J.; Gerbig, C.; Gioli, B.; Gómez, J. A.; Goulas, Y.; Guanter, L.; Gutiérrez-de-La-Cámara, Ã.`.; Hamdi, K.; Hostert, P.; Jiménez, M.; Kosvancova, M.; Lognoli, D.; Meroni, M.; Miglietta, F.; Moersch, A.; Moreno, J.; Moya, I.; Neininger, B.; Okujeni, A.; Ounis, A.; Palombi, L.; Raimondi, V.; Schickling, A.; Sobrino, J. A.; Stellmes, M.; Toci, G.; Toscano, P.; Udelhoven, T.; van der Linden, S.; Zaldei, A.

    2009-07-01

    The CEFLES2 campaign during the Carbo Europe Regional Experiment Strategy was designed to provide simultaneous airborne measurements of solar induced fluorescence and CO2 fluxes. It was combined with extensive ground-based quantification of leaf- and canopy-level processes in support of ESA's Candidate Earth Explorer Mission of the "Fluorescence Explorer" (FLEX). The aim of this campaign was to test if fluorescence signal detected from an airborne platform can be used to improve estimates of plant mediated exchange on the mesoscale. Canopy fluorescence was quantified from four airborne platforms using a combination of novel sensors: (i) the prototype airborne sensor AirFLEX quantified fluorescence in the oxygen A and B bands, (ii) a hyperspectral spectrometer (ASD) measured reflectance along transects during 12 day courses, (iii) spatially high resolution georeferenced hyperspectral data cubes containing the whole optical spectrum and the thermal region were gathered with an AHS sensor, and (iv) the first employment of the high performance imaging spectrometer HYPER delivered spatially explicit and multi-temporal transects across the whole region. During three measurement periods in April, June and September 2007 structural, functional and radiometric characteristics of more than 20 different vegetation types in the Les Landes region, Southwest France, were extensively characterized on the ground. The campaign concept focussed especially on quantifying plant mediated exchange processes (photosynthetic electron transport, CO2 uptake, evapotranspiration) and fluorescence emission. The comparison between passive sun-induced fluorescence and active laser-induced fluorescence was performed on a corn canopy in the daily cycle and under desiccation stress. Both techniques show good agreement in detecting stress induced fluorescence change at the 760 nm band. On the large scale, airborne and ground-level measurements of fluorescence were compared on several vegetation types supporting the scaling of this novel remote sensing signal. The multi-scale design of the four airborne radiometric measurements along with extensive ground activities fosters a nested approach to quantify photosynthetic efficiency and gross primary productivity (GPP) from passive fluorescence.

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

    NASA Technical Reports Server (NTRS)

    Mustel, E. R.

    1979-01-01

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

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

    SciTech Connect

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

    2007-01-10

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

  20. Absorption of monochromatic and narrow band radiation in the visible and near IR by both mitochondrial and non-mitochondrial photoacceptors results in photobiomodulation.

    PubMed

    Passarella, Salvatore; Karu, Tiina

    2014-11-01

    In addition to the major functions performed by in the cell, mitochondria play a major role in cell-light interaction. Accordingly it is generally accepted that mitochondria are crucial in cell photobiomodulation; however a variety of biomolecules themselves proved to be targets of light irradiation. We describe whether and how mitochondria can interact with monochromatic and narrow band radiation in the red and near IR optical regions with dissection of both structural and functional effects likely leading to photobiostimulation. Moreover we also report that a variety of biomolecules localized in mitochondria and/or in other cell compartments including cytochrome c oxidase, some proteins, nucleic acids and adenine nucleotides are light sensitive with major modifications in their biochemistry. All together the reported investigations show that the elucidation of the mechanism of the light interaction with biological targets still remains to be completed, this needing further research, however the light sensitivity of a variety of molecules strongly suggests that photobiomodulation could be used in both in photomedicine and in biotechnology. PMID:25226343

  1. Band models and correlations for infrared radiation

    NASA Technical Reports Server (NTRS)

    Tiwari, S. N.

    1975-01-01

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

  2. On the Ammonia Absorption on Saturn

    NASA Astrophysics Data System (ADS)

    Tejfel, Victor G.; Karimov, A. M.; Lyssenko, P. G.; Kharitonova, G. A.

    2015-11-01

    The ammonia absorption bands centered at wavelengths of 645 and 787 nm in the visible spectrum of Saturn are very weak and overlapped with more strong absorption bands of methane. Therefore, the allocation of these bands is extremely difficult. In fact, the NH3 band 787 nm is completely masked by methane. The NH3 645 nm absorption band is superimposed on a relatively weak shortwave wing of CH4 band, in which the absorption maximum lies at the wavelength of 667 nm. In 2009, during the equinox on Saturn we have obtained the series of zonal spectrograms by scanning of the planet disk from the southern to the northern polar limb. Besides studies of latitudinal variation of the methane absorption bands we have done an attempt to trace the behavior of the absorption of ammonia in the band 645 nm. Simple selection of the pure NH3 profile of the band was not very reliable. Therefore, after normalizing to the ring spectrum and to the level of the continuous spectrum for entire band ranging from 630 to 680 nm in the equivalent widths were calculated for shortwave part of this band (630-652 nm), where the ammonia absorption is present, and a portion of the band CH4 652-680 nm. In any method of eliminating the weak part of the methane uptake in the short wing show an increased ammonia absorption in the northern hemisphere compared to the south. This same feature is observed also in the behavior of weak absorption bands of methane in contrast to the more powerful, such as CH4 725 and 787 nm. This is due to the conditions of absorption bands formation in the clouds at multiple scattering. Weak absorption bands of methane and ammonia are formed on the large effective optical depths and their behavior reflects the differences in the degree of uniformity of the aerosol component of the atmosphere of Saturn.

  3. MRI-detected bone marrow changes within 3weeks after initiation of high-dose corticosteroid therapy: a possible change preceding the subsequent appearance of low-intensity band in femoral head osteonecrosis.

    PubMed

    Kubo, Yusuke; Yamamoto, Takuaki; Motomura, Goro; Tsukamoto, Nobuaki; Karasuyama, Kazuyuki; Sonoda, Kazuhiko; Hatanaka, Hiroyuki; Utsunomiya, Takeshi; Iwamoto, Yukihide

    2015-11-01

    Osteonecrosis of the femoral head is considered to occur early during the course of corticosteroid treatment. However, it remains unclear exactly how early it can develop after initiation of corticosteroid treatment. We report a case of osteonecrosis of the femoral head in which abnormal findings were observed on short-tau inversion recovery (STIR) sequence image performed 2weeks and 4days after initiation of high-dose corticosteroid therapy. A 45-year-old man with hemophagocytic syndrome was started on prednisolone, with a maximum dose of 40mg/day. On day 13 after initiation of this corticosteroid therapy, he transiently experienced left hip pain with no apparent cause. STIR sequence image5days after the onset of pain revealed high-intensity bone marrow lesions at the femoral neck of both hips. At 3months after initiation of corticosteroid therapy, T1-weighted magnetic resonance imaging revealed concave-shaped low-intensity bands, which corresponded to the preceding high-intensity lesions on both hips. Because of the subsequent progression to collapse of the left femoral head, he underwent prosthetic replacement surgery. The high-intensity lesions on STIR sequence image indicate the possibility that osteonecrosis can occur within 3weeks after initiation of high-dose corticosteroid therapy. PMID:26297517

  4. A bi-layered quad-band metamaterial absorber at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Liu, Shuo; Zhuge, Junchuan; Ma, Shaojie; Chen, Haibin; Bao, Di; He, Qiong; Zhou, Lei; Cui, Tie Jun

    2015-12-01

    In this work, a quad-band metamaterial absorber is proposed and experimentally demonstrated at terahertz frequency using a bi-layer isotropic structure. The absorber is designed by distributing four metallic square loops with different lengths on two polyimide layers (PI). The backside of PI is covered by an opaque gold film to eliminate the transmission of terahertz waves. The proposed absorber exhibits almost unity absorptions at 0.51, 0.69, 1.05, and 1.34 THz under the normal illuminance. As the incident angle increases from 0 to 50, the absorption intensities remain above 95%, and the absorption frequencies almost keep stable for both transverse-electric and transverse-magnetic polarizations. The absorption mechanism is interpreted by giving the electromagnetic field distributions at each absorption peak. Experimental results show good agreement with numerical simulations both in the frequency and strength of the four absorption peaks.

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

    PubMed

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

    2014-01-21

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

  6. Polaronic satellites in x-ray-absorption spectra

    NASA Astrophysics Data System (ADS)

    van der Laan, G.

    1990-06-01

    Satellite structure in the 2p absorption spectra of early 3d transition-metal compounds is reported. The spectral shape depends strongly on the local symmetry of the excited atom and gives evidence that in Ti oxides the excitation on the metal is screened by an exciton transition in the oxygen band and not by a charge-transfer or Mott-Hubbard transition as in the case of narrow-band metal compounds. The relative satellite intensities can be used to assess the anisotropy of the local electronic structure and the influence of the excited electron on the screening of the core-hole potential.

  7. Method and apparatus for aerosol particle absorption spectroscopy

    DOEpatents

    Campillo, Anthony J.; Lin, Horn-Bond

    1983-11-15

    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.

  8. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

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

  9. Two-Phonon Absorption

    ERIC Educational Resources Information Center

    Hamilton, M. W.

    2007-01-01

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

  10. Determination of Spectroscopic Band Shapes by Second Derivatives, Part II: Infrared Spectra of Liquid Light and Heavy Water.

    PubMed

    Max, Jean-Joseph; Chapados, Camille

    2015-11-01

    Second derivative and band simulation techniques are used in a synergetic relationship to identify components in the infrared (IR) spectra of liquid light and heavy water. Nine Gaussian components are retrieved in massive OH and OD stretch absorption. In this context, ?1 and ?3 are the principal components along with satellites derived from harmonic and combination bands. The Raman spectrum of light water matches the IR components with intensity variations as expected. PMID:26647051

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

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

    SciTech Connect

    Babaev, A. A.; Kudoyarova, V. Kh.

    2013-07-15

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

  13. Fine structure of the amide i band in acetanilide

    NASA Astrophysics Data System (ADS)

    Careri, G.; Gratton, E.; Shyamsunder, E.

    1988-05-01

    Their absorption spectrum of both single crystals and powdered samples of acetanilide (a model system for proteins) has been studied in the amide i region, where a narrow band has been identified as a highly trapped soliton state. The powder-sample spectra have been decomposed using four Lorentzian bands. A strong temperature dependence has been found for the intensity of two of the subbands, which also show a complementary behavior. Polarization studies performed on thin crystals have shown that the subbands have the same polarization. Low-temperature spectra of partially deuterated samples show the presence of the subbands at the same absorption frequencies found using the fitting procedure in the spectra of nondeuterated samples. The soliton model currently proposed to explain the origin of the anomalous amide i component at 1650 cm-1 still holds, but some modification of the model is required to account for the new features revealed by this study.

  14. SF_6: the Forbidden Band Unveiled

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  15. 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)

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

    1990-01-01

    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.

  16. Gastric Banding

    MedlinePLUS

    ... stomach for weight loss. In this procedure, a silicone band is placed around the upper portion of ... During the surgery, the surgeon places an adjustable silicone band around the upper part of the stomach ...

  17. Bird Banding

    USGS Multimedia Gallery

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

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

    PubMed

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

    2014-11-17

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

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

    PubMed Central

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

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  1. Intensity tunable infrared broadband absorbers based on VO2 phase transition using planar layered thin films

    NASA Astrophysics Data System (ADS)

    Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray

    2015-08-01

    Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20?nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing.

  2. Intensity tunable infrared broadband absorbers based on VO2 phase transition using planar layered thin films.

    PubMed

    Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray

    2015-01-01

    Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20?nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing. PMID:26294085

  3. Intensity tunable infrared broadband absorbers based on VO2 phase transition using planar layered thin films

    PubMed Central

    Kocer, Hasan; Butun, Serkan; Palacios, Edgar; Liu, Zizhuo; Tongay, Sefaattin; Fu, Deyi; Wang, Kevin; Wu, Junqiao; Aydin, Koray

    2015-01-01

    Plasmonic and metamaterial based nano/micro-structured materials enable spectrally selective resonant absorption, where the resonant bandwidth and absorption intensity can be engineered by controlling the size and geometry of nanostructures. Here, we demonstrate a simple, lithography-free approach for obtaining a resonant and dynamically tunable broadband absorber based on vanadium dioxide (VO2) phase transition. Using planar layered thin film structures, where top layer is chosen to be an ultrathin (20 nm) VO2 film, we demonstrate broadband IR light absorption tuning (from ~90% to ~30% in measured absorption) over the entire mid-wavelength infrared spectrum. Our numerical and experimental results indicate that the bandwidth of the absorption bands can be controlled by changing the dielectric spacer layer thickness. Broadband tunable absorbers can find applications in absorption filters, thermal emitters, thermophotovoltaics and sensing. PMID:26294085

  4. A study of the absorption features of Makemake

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  5. EFFECTS OF LASER RADIATION ON MATTER: Photoinduced absorption in chalcogenide glasses

    NASA Astrophysics Data System (ADS)

    Ponomar', V. V.

    1990-08-01

    A dependence of the absorption coefficient on the optical radiation intensity in the range 10 - 5 - 1 W/cm2 was observed for chalcogenide glasses at a photon energy less than the band gap of the material. The absorption coefficient depended on the irradiation time. In the case of arsenic sulfide in the range 1.6-1.7 eV an absorption peak was observed at intensities of the order of 10 - 3 W/cm2. In this part of the spectrum the absorption probably involved metastable As-As, S-Se, and Se-Se "defect" bonds and was similar to the photoinduced degradation of hydrogenated amorphous silicon.

  6. Time-resolved investigations of the excited state absorption in the light-harvesting complex of Rhodospirillum rubrum

    NASA Astrophysics Data System (ADS)

    Vasil'ev, S. S.; Volkov, V. V.; Gorokhov, V. V.; Redlin, H.; Voigt, Joachim; Paschenko, V. Z.

    1995-01-01

    First evidence of the excited state absorption in light-harvesting chlorophyll a/b complexes (LHCII) was obtained using nanosecond pump-probe beam technique in the frequency domain. LHCII preparations and photosystem II (PSII) membrane fragments showed absorption increase and decrease, depending on the pump beam intensity used. Non-linear absorption changes were observed in the narrow wavelength region around the pump wavelength of 620 and 647 nm (absorption bands of Chl b) but not at 670 nm (absorption of CHl a)2. These data were interpreted in terms of excited state absorption of pigment-protein Chl a/b clusters within the subunits of LHCII especially by two-exciton excitations in the Chl-b region. We studied non-linear absorption properties of chromatophores of the purple bacterium Rhodospirillum rubrum at room temperature in the time domain using one-color pump-probe beam laser technique. Pump- and probe-beam wavelength was 590 nm. Two competing effects of non-linear absorption change could be detected -- an additional absorption and a bleaching. The relative strength of both effects was dependent on the pump intensity. Experimental results were interpreted in terms of excited state absorption in clusters of strongly interacting pigment molecules within the antenna system. Good agreement with the experimental results was achieved when they were compared with model calculations for the non-linear absorption in a three-level system of excitonic states from interacting BChl-a pigments.

  7. X-ray relative intensities at incident photon energies across the L{sub i} (i=1–3) absorption edges of elements with 35≤Z≤92

    SciTech Connect

    Puri, Sanjiv

    2014-07-15

    The intensity ratios, I{sub Lk}/I{sub Lα1} (k=l,η,α{sub 2},β{sub 1},β{sub 2,15},β{sub 3},β{sub 4},β{sub 5,7},β{sub 6},β{sub 9,10},γ{sub 1,5},γ{sub 6,8},γ{sub 2,3},γ{sub 4}) and I{sub Lj}/I{sub Lα} (j=β,γ), have been evaluated at incident photon energies across the L{sub i} (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 L{sub i} (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 Lα{sub 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 (L{sub i}−S{sub j}) (S{sub j}=M{sub j}, N{sub j} and i=1–3, j=1–7) resonant Raman scattered (RRS) peak energies for an element at a given incident photon energy (below the L{sub i} 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. -- Highlights: •The L X-ray relative intensities and Lα{sub 1} XRP cross sections are evaluated using physical parameters based on the IPA models. •Comparison of the intensity ratios evaluated using the DHS and DF models based photoionization cross sections is presented. •Importance of many body effects including electron exchange effects is highlighted.

  8. CCSD(T) potential energy and induced dipole surfaces for N2-H2(D2): Retrieval of the collision-induced absorption integrated intensities in the regions of the fundamental and first overtone vibrational transitions

    NASA Astrophysics Data System (ADS)

    Buryak, Ilya; Lokshtanov, Sergei; Vigasin, Andrey

    2012-09-01

    The present work aims at ab initio characterization of the integrated intensity temperature variation of collision-induced absorption (CIA) in N2-H2(D2). Global fits of potential energy surface (PES) and induced dipole moment surface (IDS) were made on the basis of CCSD(T) (coupled cluster with single and double and perturbative triple excitations) calculations with aug-cc-pV(T,Q)Z basis sets. Basis set superposition error correction and extrapolation to complete basis set (CBS) limit techniques were applied to both energy and dipole moment. Classical second cross virial coefficient calculations accounting for the first quantum correction were employed to prove the quality of the obtained PES. The CIA temperature dependence was found in satisfactory agreement with available experimental data.

  9. 5 5 cm silicon photonic crystal slabs on glass and plastic foil exhibiting broadband absorption and high-intensity near-fields.

    PubMed

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

    2014-01-01

    Crystalline silicon photonic crystal slabs are widely used in various photonics applications. So far, the commercial success of such structures is still limited owing to the lack of cost-effective fabrication processes enabling large nanopatterned areas (? 1?cm(2)). We present a simple method for producing crystalline silicon nanohole arrays of up to 5 5?cm(2) size with lattice pitches between 600 and 1000?nm on glass and flexible plastic substrates. Exclusively up-scalable, fast fabrication processes are applied such as nanoimprint-lithography and silicon evaporation. The broadband light trapping efficiency of the arrays is among the best values reported for large-area experimental crystalline silicon nanostructures. Further, measured photonic crystal resonance modes are in good accordance with light scattering simulations predicting strong near-field intensity enhancements greater than 500. Hence, the large-area silicon nanohole arrays might become a promising platform for ultrathin solar cells on lightweight substrates, high-sensitive optical biosensors, and nonlinear optics. PMID:25073935

  10. 5 5 cm2 silicon photonic crystal slabs on glass and plastic foil exhibiting broadband absorption and high-intensity near-fields

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  11. 5 5?cm2 silicon photonic crystal slabs on glass and plastic foil exhibiting broadband absorption and high-intensity near-fields

    PubMed Central

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

    2014-01-01

    Crystalline silicon photonic crystal slabs are widely used in various photonics applications. So far, the commercial success of such structures is still limited owing to the lack of cost-effective fabrication processes enabling large nanopatterned areas (? 1?cm2). We present a simple method for producing crystalline silicon nanohole arrays of up to 5 5?cm2 size with lattice pitches between 600 and 1000?nm on glass and flexible plastic substrates. Exclusively up-scalable, fast fabrication processes are applied such as nanoimprint-lithography and silicon evaporation. The broadband light trapping efficiency of the arrays is among the best values reported for large-area experimental crystalline silicon nanostructures. Further, measured photonic crystal resonance modes are in good accordance with light scattering simulations predicting strong near-field intensity enhancements greater than 500. Hence, the large-area silicon nanohole arrays might become a promising platform for ultrathin solar cells on lightweight substrates, high-sensitive optical biosensors, and nonlinear optics. PMID:25073935

  12. Neuron absorption study and mid-IR optical excitations

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

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

    USGS Publications Warehouse

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

    1976-01-01

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

  14. Polycyclic aromatic hydrocarbon ions and the diffuse interstellar bands

    NASA Technical Reports Server (NTRS)

    Salama, F.; Allamandola, L. J.

    1995-01-01

    Neutral naphthalene (C10H8), phenanthrene (C14H10), and pyrene (C16H10) absorb strongly in the ultraviolet and may contribute to the extinction curve. High abundances are required to produce detectable structures. The cations of these Polycyclic Aromatic Hydrocarbons (PAHs) absorb in the visible. C10H8(+) has 12 discrete absorption bands which fall between 6800 and 5000 A. The strongest band at 6741 A falls close to the weak 6742 A diffuse interstellar band (DIB). Five other weaker bands also match DIBs. The possibility that C10H8(+) is responsible for some of the DIBs can be tested by searching for new DIBS at 6520, 6151, and 5965 A, other moderately strong naphthalene cation band positions. If C10H8(+) is indeed responsible for the 6742 A feature, it accounts for 0.3% of the cosmic carbon. The spectrum of C16H10(+) is dominated by a strong band at 4435 A in an Ar matrix and 4395 A in a Ne matrix, a position which falls very close to the strongest DIB, that at 4430 A. If C16H10(+), or a closely related pyrene-like ion is indeed responsible for the 4430 A feature, it accounts for 0.2% of the cosmic carbon. We also report an intense, very broad UV-to-visible continuum which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR.

  15. Polycyclic aromatic hydrocarbon ions and the diffuse interstellar bands.

    PubMed

    Salama, F; Allamandola, L J

    1995-03-01

    Neutral naphthalene (C10H8), phenanthrene (C14H10), and pyrene (C16H10) absorb strongly in the ultraviolet and may contribute to the extinction curve. High abundances are required to produce detectable structures. The cations of these PAHs absorb in the visible. C10H8+ has 12 discrete absorption bands which fall between 6800 and 5000 angstroms. The strongest band at 6741 angstroms falls close to the weak 6742 angstroms diffuse interstellar band (DIB). Five other weaker bands also match DIBs. The possibility that C10H8+ is responsible for some of the DIBs can be tested by searching for new DIBs at 6520, 6151, and 5965 angstroms, other moderately strong naphthalene cation band positions. If C10H8+ is indeed responsible for the 6742 angstroms feature, it accounts for 0.3% of the cosmic carbon. The spectrum of C16H10+ is dominated by a strong band at 4435 angstroms in an Ar matrix and 4395 angstroms in a Ne matrix, a position which falls very close to the strongest DIB, that at 4430 angstroms. If C16H10+, or a closely related pyrene-like ion is indeed responsible for the 4430 angstroms feature, it accounts for 0.2% of the cosmic carbon. We also report an intense, very broad UV-to-visible continuum which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR. PMID:11539255

  16. Visible absorption spectrum of liquid ethylene

    PubMed Central

    Nelson, Edward T.; Patel, C. Kumar N.

    1981-01-01

    The visible absorption spectrum of liquid ethylene at ? 108 K from 5500 to 7200 was measured by using a pulsed tunable dye laser, immersed-transducer, gated-detection opto-acoustic spectroscopy technique. The absorption features show the strongest band with an absorption coefficient of ?2 10-2 cm-1 and the weakest band with an absorption coefficient of ?1 10-4 cm-1. Proposed assignments of the observed absorption peaks involve combinations of overtones of local and normal modes of vibration of ethylene. PMID:16592978

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

    NASA Technical Reports Server (NTRS)

    Chou, M. D.

    1980-01-01

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

  18. Absorption intensities and emission cross sections of principal intermanifold and inter-Stark transitions of Er{sup 3+}(4f {sup 11}) in polycrystalline ceramic garnet Y{sub 3}Al{sub 5}O{sub 12}

    SciTech Connect

    Sardar, Dhiraj K.; Russell, Charles C. III; Gruber, John B.; Allik, Toomas H.

    2005-06-15

    A comparative spectroscopic study is performed on Er{sup 3+}(4f{sup 11}) ions doped in polycrystalline ceramic garnet Y{sub 3}Al{sub 5}O{sub 12} (YAG) and single-crystal laser rod, both containing nominal 50 at. % of Er{sup 3+}. The standard Judd-Ofelt (JO) model is applied to the room-temperature absorption intensities of Er{sup 3+}(4f{sup 11}) transitions in both hosts to obtain the phenomenological intensity parameters. These parameters are subsequently used to determine the radiative decay rates, radiative lifetimes, and branching ratios of the Er{sup 3+} transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds {sup 2S+1}L{sub J} of Er{sup 3+}(4f{sup 11}) in these garnet hosts. The emission cross sections of the intermanifold Er{sup 3+} {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} (1.5 {mu}m) transition as well as the principal inter-Stark transition Y{sub 1}{yields}Z{sub 4} (1550 nm) within the corresponding multiplet manifolds have been determined. The room-temperature fluorescence lifetimes of the {sup 4}I{sub 13/2}{yields}{sup 4}I{sub 15/2} (1.5 {mu}m) transition in both polycrystalline ceramic and single-crystal YAG samples were measured. From the radiative lifetimes determined from the JO model and the measured fluorescence lifetimes, the quantum efficiencies for both samples were determined. The comparative study of Er{sup 3+}(4f{sup 11}) ions performed suggests that polycrystalline ceramic YAG is an excellent alternative to single-crystal YAG rod for certain applications.

  19. Band gap tunability of molecular beam epitaxy grown lateral composition modulated GaInP structures by controlling V/III flux ratio

    SciTech Connect

    Park, K. W.; Park, C. Y.; Lee, Y. T.

    2012-07-30

    Lateral composition modulated (LCM) GaInP structures were grown on (001) GaAs substrate by molecular beam epitaxy with different V/III flux ratios. Band gap of LCM structures could be tuned from 1.93 eV to 1.83 eV by decreasing flux ratio while maintaining the same photoluminescence intensity, enhanced light absorption, and widened absorption spectrum. It is shown that for band gap tuning of LCM structures, flux ratio adjustment is a more viable method compared to growth temperature adjustment.

  20. Terahertz dual-band metamaterial absorber based on graphene/MgF(2) multilayer structures.

    PubMed

    Su, Zhaoxian; Yin, Jianbo; Zhao, Xiaopeng

    2015-01-26

    We design an ultra-thin terahertz metamaterial absorber based on graphene/MgF(2) multilayer stacking unit cells arrayed on an Au film plane and theoretically demonstrate a dual-band total absorption effect. Due to strong anisotropic permittivity, the graphene/MgF(2) multilayer unit cells possess a hyperbolic dispersion. The strong electric and magnetic dipole resonances between unit cells make the impedance of the absorber match to that of the free space, which induces two total absorption peaks in terahertz range. These absorption peaks are insensitive to the polarization and nearly omnidirectional for the incident angle. But the absorption intensity and frequency depend on material and geometric parameters of the multilayer structure. The absorbed electromagnetic waves are finally converted into heat and, as a result, the absorber shows a good nanosecond photothermal effect. PMID:25835924

  1. Tremor bands sweep Cascadia

    NASA Astrophysics Data System (ADS)

    Ghosh, A.; Vidale, J. E.; Sweet, J. R.; Creager, K. C.; Wech, A.; Houston, H.

    2009-12-01

    In the last few years, the spatiotemporal distribution of non-volcanic tremor (NVT) activity has been watched with intense curiosity in Cascadia, Japan, and San Andreas Fault. During an episodic tremor and slip (ETS) event in the Cascadia Subduction Zone (CSZ), the dominant tremor migration pattern is characterized by along-strike marching of tremor at a rate of 10 km/day. Spatiotemporal evolution gives critical clues on the physical mechanism of NVT, and the evolving state of stress in the fault. However, tremor migration, its variations over different time-scales, and its underlying physics remain poorly understood. We recorded the May 2008 ETS event in Cascadia with a dense small-aperture seismic array, and beamformed to detect and locate tremor with unparalleled resolution [Ghosh et al., GRL, 2009]. The beams reveal that tremor occurs in elongated bands that extend ~50 km in the direction parallel to the convergence of CSZ and only 10-15 km in the along-strike direction. This is in contrast to the wider blobs of tremor locations seen using a conventional envelope cross-correlation method. The peak activities of the tremor bands are well separated in space and time. Each band remains active for a good part of a day, and fades away while the adjacent band is slowly peaking up. During the 2008 ETS event, these convergence-parallel tremor bands swept the Cascadia megathrust from SE to NW in the region most clearly imaged by our array, producing the long-term tremor migration. Embedded within the bands lie long streaks of tremor that show steady and rapid migration on time-scales of several minutes to an hour at velocities of several tens of km/hr. These tremor streaks also propagate mostly convergence-parallel, along a particular band, both up- and down-dip. The elongated shape of the tremor bands may cause by the tendency of the tremor streaks to align parallel to the direction of subduction. We propose that each tremor band is the result of failure of a section of the megathrust with slow slip. The sweeping bands may indicate progressive stress transfer on the subduction fault. One band releases stress from a section of the fault, and loads the adjacent region, which promotes failure and activates the next band. The physical mechanism causing the streaks, however, is not clear. The velocity of migration within the tremor streaks may suggests fluid pressure waves advancing along the linear corrugated weak features on the fault.

  2. OH content dependence of ArF-excimer-laser-induced absorption in type-III fused silica

    SciTech Connect

    Kuzuu, Nobu

    1996-12-31

    OH content dependence of the intensity of ArF-excimer laser induced absorption in fused silica synthesized under reducing condition was investigated. The absorption spectra of each silica has a peak at 220 nm, and the intensity of which increases with decreasing OH content. Above OH content about 1150 ppm, ArF laser induced absorption was not observed. Annealing in He ambient, suppressed the creation of the 220 nm band, and no absorption was observed in the sample containing greater than 800 ppm of OH. The annealing in the H2 ambient was not so effective as in He ambient These results indicate that the fused silica synthesized under reducing conditions and containing OH more than about 1150 ppm was found to be desirable material for excimer laser optics. The fused silica containing more than 800 ppm of OH annealed in the He ambient can also be used as excimer laser optics.

  3. Absorptance of infrared radiation by methane at elevated temperatures

    SciTech Connect

    Fuss, S.P.; Ezekoye, O.A.; Hall, M.J.

    1996-11-01

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

  4. Collision-induced vibrational absorption in molecular hydrogens

    SciTech Connect

    Reddy, S.P.

    1993-05-01

    Collision induced absorption (CIA) spectra of the first overtone bands of H{sub 2}, D{sub 2}, and HD have been recorded for gas densities up to 500 amagat at 77-300 K. Analyses of these spectra reveal that (1) contrary to the observations in the fundamental bands, the contribution of the isotropic overlap interaction to the first overtone bands is negligible, (2) the squares of the matrix elements B{sub 32}(R)/ea{sub o} [= {lambda}{sub 32} exp(-(R-{sigma})/{rho}{sub 32}) + 3 (R/a{sub o}){sup -4}] where the subscripts 3 and 2 represent L and {lambda}, respectively, account for the absorption intensity of the bands and (3) the mixed term, 2,3 {lambda}{sub 32} exp (-(R-{sigma})/{rho}{sub 32}) <{vert_bar}Q{vert_bar}> <{alpha}> (R/a){sup -4}, gives a negative contribution. In the CIA spectra of H{sub 2} in its second overtone region recorded at 77, 201 and 298 K for gas densities up to 1000 amagat, a dip in the Q branch with characteristic Q{sub p} and Q{sub R} components has been observed. The analysis of the absorption profiles reveals, in addition to the previously known effects, the occurrence of the triple-collision transitions of H{sub 2} of the type Q{sub 1}(J) + Q{sub 1}(J) + Q{sub 1}(J) for the first time. From the profile analysis the absorption coefficient of these transitions is obtained.

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

    PubMed

    Mandal, Dhritabrata; Hamann, Thomas W

    2015-05-01

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

  6. Enhanced absorption and fluorescence of gold nanoclusters using initial alkali concentrations

    NASA Astrophysics Data System (ADS)

    Nghia Nguyen, Trong; Hue Do, Thi; Hoang Nguyen, Dinh; Vu, Duong; Hoa Do, Quang; Nhung Tran, Hong; Nghiem, Thi Ha Lien

    2016-02-01

    Understanding carrier dynamics and electromagnetic interactions between emerging quantum-confined nanostructures and plasmonic structures is crucial for future biological applications. In this research, we fabricate gold monolayer-protected clusters (AuMPC). We demonstrate enhanced light absorption and fluorescence of AuMPCs by varying the initial alkali concentration. We measure absorption bands enhanced up to nine times with extended and distinct features centered at 3.33 eV, and fluorescence enhanced up to 3.9 times. An increased alkali concentration changes the charge transfer capability of the surface thiolate ligands through sulfur-gold bonds, which in turn enhance/reduce the fluorescence intensity.

  7. Mid- and far-infrared absorption spectroscopy of Titans aerosols analogues

    NASA Astrophysics Data System (ADS)

    Gautier, Thomas; Carrasco, Nathalie; Mahjoub, Ahmed; Vinatier, Sandrine; Giuliani, Alexandre; Szopa, Cyril; Anderson, Carrie M.; Correia, Jean-Jacques; Dumas, Paul; Cernogora, Guy

    2012-09-01

    In this work we present mid- and far-infrared absorption spectra of Titans aerosol analogues produced in the PAMPRE experimental setup. The evolution of the linear absorption coefficient ? (cm-1) is given as a function of the wavenumber. We provide a complete dataset regarding the influence that the concentration of methane vapor in the gas mixture has on the tholin spectra. Among other effects, the intensity of the 2900 cm-1 (3.4 ?m) pattern (attributed to methyl stretching modes) increases when the methane concentration increases. More generally, tholins produced with low methane concentrations seem to be more amine based polymers, whereas tholins produced with higher methane concentrations contains more aliphatic carbon based structures. Moreover, it is shown that the position of the bands around 2900 cm-1 depends on the chemical environment of the methyl functional group. We conclude that the presence of these absorption bands in Titans atmosphere, as measured with the VIMS instrument onboard Cassini is in agreement with an aerosol contribution. We also compare the far-infrared spectrum of tholin to spectra of Titans aerosols derived from recent Cassini-CIRS observations displaying many similarities, particularly with absorption bands at 325 cm-1, 515 cm-1, and the methyl attributed 1380 cm-1 and 1450 cm-1 bands.

  8. High sensitivity Cavity Ring Down Spectroscopy of N2O near 1.22 ?m: (I) Rovibrational assignments and band-by-band analysis

    NASA Astrophysics Data System (ADS)

    Karlovets, E. V.; Campargue, A.; Kassi, S.; Perevalov, V. I.; Tashkun, S. A.

    2016-01-01

    The absorption spectrum of nitrous oxide (N2O) in natural isotopic abundance has been recorded near 1.22 ?m by Cavity Ring Down Spectroscopy using an External Cavity Diode Laser (ECDL) as light source. The room temperature recordings were performed at a pressure of 10.0 Torr in the 7915-8334 cm-1 spectral range (1.26-1.19 ?m). The typical noise equivalent absorption of the spectra, on the order of ?min~210-11 cm-1, allowed for the detection of lines with intensities on the order of 510-29 cm/molecule. More than 3300 transitions belonging to 64 bands of five nitrous oxide isotopologues (14N216O, 14N15N16O, 15N14N16O, 14N218O and 14N217O) have been rovibrationally assigned on the basis of the predictions of the effective Hamiltonian models developed for each isotopologue. For comparison, only 13 bands were previously measured by Fourier Transform spectroscopy in the studied region. All identified bands belong to the ?P=13 and 14 series of transitions, where P=2V1+V2+4V3 is the polyad number (Vi are vibrational quantum numbers). The line positions and intensities are provided for all assigned lines. The maximum deviations between the measured position values and those predicted by the effective Hamiltonian models are about 0.2 cm-1 for the main isotopologue but reach values larger than 1 cm-1 for the less abundant minor isotopologues. The band-by-band analysis led to the determination of the rovibrational parameters of a total of 62 bands. The typical rms value of the (?obs-?fit) differences is 0.710-3 cm-1. Among the 62 bands, 49 are newly measured, for 13 others the rotational analysis is significantly improved and extended. A few resonance perturbations due to intra- and inter-polyad couplings are identified and discussed.

  9. Modifications in the chemical bonding and optical absorption of PPS by ion bombardment

    NASA Astrophysics Data System (ADS)

    Farenzena, L. S.; Papaléo, R. M.; Hallén, A.; de Araújo, M. A.; Livi, R. P.; Sundqvist, B. U. R.

    1995-11-01

    Commercial-grade thin poly(p-phenylene sulphide) (PPS) foils, 2 μm thick, have been bombarded with 1H + (380 keV), and with 0.61 MeV/amu 4He +, 12C 2+, 16O 3+, 32S 3+, 79Br 9+ and 127I 14+ ions. The completely modified foils have been analyzed by Fourier transform infrared absorption spectroscopy (FTIR) and by ultraviolet-visible absorption spectroscopy (UV-VIS). The bond breaking and rearrangement processes were followed by using the FTIR results. The absorbance of bands related to CS, SS, CH and most of the ring carbon bonds show an exponential decrease as a function of fluence. The absorption bands most sensitive to the ion bombardment are those assigned to CS and SS bonds. The CC and CH bonds are less sensitive and certain absorption band changes indicate carbon-carbon aliphatic and or aromatic conjugation, due to their increasing intensity as a function of the ion fluence. Damage cross sections have been extracted from the plots of IR absorbance versus fluence. The values of the damage cross sections obtained scale roughly with the square of {dE }/{dx } (independent of the nature of the chemical bond). The optical absorption coefficient has also been followed as a function of the ion fluence.

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  11. Reply To: How Does Substitutional Doping Affect Visible Light Absorption in a Series of Homodisperse Ti11 Polyoxotitanate Nanoparticles-A Comment on the Band Gap Determination of the Fe(II) Cages.

    PubMed

    Chen, Yang; Jarzembska, Katarzyna N; Trzop, Elzbieta; Coppens, Philip

    2016-03-18

    A summary of the evidence based on spectroscopy, calculated density of states (DOS) and photo-electrochemistry, for electron transfer from the occupied Fe(2+) (d)-β orbital located within the band gap of the [Ti4 O(OEt)15 (FeBr)] cluster, to its unoccupied Ti(d) orbitals is presented. The importance of the distinction between the concepts of band gap and HOMO-LUMO gap is emphasized. PMID:26928979

  12. Band Together!

    ERIC Educational Resources Information Center

    Olson, Cathy Applefeld

    2011-01-01

    After nearly a decade as band director at St. James High School in St. James, Missouri, Derek Limback knows that the key to building a successful program is putting the program itself above everything else. Limback strives to augment not only his students' musical prowess, but also their leadership skills. Key to his philosophy is instilling a…

  13. New transient absorption observed in the spectrum of colloidal CdSe nanoparticles pumped with high-power femtosecond pulses

    SciTech Connect

    Burda, C.; Link, S.; Green, T.C.; El-Sayed, M.A.

    1999-12-09

    The power dependence of the transient absorption spectrum of CdSe nanoparticle colloids with size distribution of 4.0 {+-} 0.4 nm diameter is studied with femtosecond pump-probe techniques. At the lowest pump laser power, the absorption bleaching (negative spectrum) characteristic of the exciton spectrum is observed with maxima at 560 and 480 nm. As the pump laser power increases, two new transient absorptions at 510 and 590 nm with unresolved fast rise (<100 fs) and long decay times ({much{underscore}gt}150 ps) are observed. The energy of each of the positive absorption is red shifted from that of the bleach bands by {approximately}120 MeV. The origin of this shift is discussed in terms of the effect of the internal electric field of the many electron-hole pairs formed within the quantum dot at the high pump intensity, absorption from a metastable excited state or the formation of biexcitons.

  14. Computational Study of Absorption Spectra of the Photoconvertible Fluorescent Protein EosFP in Different Protonation States.

    PubMed

    Imhof, Petra

    2012-11-13

    Absorption spectra of the green-to-red convertible fluorescent protein EosFP have been computed in a hybrid quantum mechanical/molecular mechanical (QM/MM) framework. The experimentally observed absorption maximum at ?390 nm is well reproduced by the protein with a neutral chromophore, and the anionic form is computed to absorb close to the experimentally determined maximum at ?500 nm. Absorption of a zwitterionic form is calculated to lie in the same spectral region; however, this species cannot be unambiguously assigned to the experimental spectra. Variation of the protonation states of residues surrounding the chromophore do not have significant impact on the positions of the absorption maxima. In particular, protonation of Glu212 leaves the calculated spectra largely unaffected. This is consistent with the spectra of the E212Q mutant, which differ from the wild-type spectra only in the intensities but not in the positions of the absorption bands. PMID:26605635

  15. An analytic formula for heating due to ozone absorption

    NASA Technical Reports Server (NTRS)

    Lindzen, R. S.; Will, D. I.

    1972-01-01

    An attempt was made to devise a simple expression or formula to describe radiative heating in the atmosphere by ozone absorption. Such absorption occurs in the Hartley, Huggins, and Chappuis bands and is only slightly temperature and pressure dependent.

  16. Saturation of intraband absorption and electron relaxation time in n-doped InAs/GaAs self-assembled quantum dots

    NASA Astrophysics Data System (ADS)

    Sauvage, S.; Boucaud, P.; Glotin, F.; Prazeres, R.; Ortega, J.-M.; Lematre, A.; Grard, J.-M.; Thierry-Flieg, V.

    1998-12-01

    We have observed the saturation of intraband absorption in InAs/GaAs self-assembled quantum dots. The investigated n-doped self-assembled quantum dots exhibit an intraband absorption within the conduction band, which is peaked at an 8 ?m wavelength. The saturation of the intraband absorption is achieved with an infrared pump delivered by a pulsed free-electron laser. The saturation of the transition is observed for an intensity around ?0.6 MW cm-2. The electron relaxation time under intraband excitation is measured by time-resolved pump-probe experiments. An electron relaxation time T1?3 ps is reported.

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

    SciTech Connect

    Kerimova, T. G. Guliyev, R. A.

    2011-03-15

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

  18. Sm3+ effects in the Tm3+ doped tellurite glass for S-band amplification

    NASA Astrophysics Data System (ADS)

    Belanon, Marcos P.; Ferenz, Julio; Chillcce, Enver; Barbosa, Luis Carlos

    2013-02-01

    Thulium doped Samarium codoped tellurite-tungstate glasses were produced. Luminescence properties in the infrared region were investigated looking to observe improved properties for S-band amplification in the co doped samples. Thulium is well-known by the 3H4-3F4 radiative transition emitting around ~1.47?m, which is a self-terminating transition in tellurite hosts due the longer lifetime of the lower level in relation to the upper level of this transition. Analysis of absorption and emission spectra showed that we could quench the 3F4 level significantly, what improved the intensity of the emission at 1.49?m. However, the state 3H4 were also quenched due the cross relaxation process due the absorption bands of Sm3+ around 1.5?m.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  20. How does the plasmonic enhancement of molecular absorption depend on the energy gap between molecular excitation and plasmon modes: a mixed TDDFT/FDTD investigation.

    PubMed

    Sun, Jin; Li, Guang; Liang, WanZhen

    2015-07-14

    A real-time time-dependent density functional theory coupled with the classical electrodynamics finite difference time domain technique is employed to systematically investigate the optical properties of hybrid systems composed of silver nanoparticles (NPs) and organic adsorbates. The results demonstrate that the molecular absorption spectra throughout the whole energy range can be enhanced by the surface plasmon resonance of Ag NPs; however, the absorption enhancement ratio (AER) for each absorption band differs significantly from the others, leading to the quite different spectral profiles of the hybrid complexes in contrast to those of isolated molecules or sole NPs. Detailed investigations reveal that the AER is sensitive to the energy gap between the molecular excitation and plasmon modes. As anticipated, two separate absorption bands, corresponding to the isolated molecules and sole NPs, have been observed at a large energy gap. When the energy gap approaches zero, the molecular excitation strongly couples with the plasmon mode to form the hybrid exciton band, which possesses the significantly enhanced absorption intensity, a red-shifted peak position, a surprising strongly asymmetric shape of the absorption band, and the nonlinear Fano effect. Furthermore, the dependence of surface localized fields and the scattering response functions (SRFs) on the geometrical parameters of NPs, the NP-molecule separation distance, and the external-field polarizations has also been depicted. PMID:26058430

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

    PubMed

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

    2012-12-01

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

  2. How Does Substitutional Doping Affect Visible Light Absorption in a Series of Homodisperse Ti11 Polyoxotitanate Nanoparticles-A Comment on the Band Gap Determination of the Fe(II) Cages (Chem. Eur. J. 2015, 21, 11538).

    PubMed

    Matthews, Peter D; Li, Ning; Luo, He-Kuan; Wright, Dominic S

    2016-03-18

    There is no experimental support for the conclusion by Coppens and Chen in a recent paper that the (HOMO-LUMO) band gaps in a series of Fe(II) polyoxotitanate cages are in the range 1.43-1.59 eV. PMID:26929058

  3. Low temperature cavity ring down spectroscopy with off-axis alignment: application to the A- and ?-bands of O2 in the visible at 90 K

    NASA Astrophysics Data System (ADS)

    Perez-Delgado, Y.; Manzanares, C. E.

    2012-03-01

    The cavity ring down (CRD) technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat. The temperature of the cell can be changed between 77 K and 298 K. An off-axis alignment of the laser beam into the cavity is used to increase the number of resonant modes inside the cavity and improve the signal to noise ratio of the absorption bands. To demonstrate the capabilities of the low temperature CRD cell, the absorption spectra of O2 are recorded at 90 K for the A ( ?'=0? ??=0) and ? ( ?'=2? ??=0) bands of the b1sumg^{ +}leftarrow X3sumg^{ -} transition using cavity ring down spectroscopy. The optical cavity performance was tested using two variations of the CRD technique. The A-band is measured using the phase-shift cavity ring down method and the ?-band using the pulsed-laser exponential-decay method. A comparison between experimental and simulated spectra of the O2 bands at 90 K confirms the molecular temperature measured by a sensor localized in the cell. Quantitative measurements of the individual rotational line intensities are made for the oxygen ?-band to confirm the temperature of the cell and calculate the vibrational band intensity. The application of this technique for laboratory studies of planetary atmospheres and the spectroscopy of molecular complexes is emphasized.

  4. EPR, optical absorption and luminescence studies of Cr3+-doped antimony phosphate glasses

    NASA Astrophysics Data System (ADS)

    De Vicente, F. S.; Santos, F. A.; Simes, B. S.; Dias, S. T.; Siu Li, M.

    2014-12-01

    Antimony phosphate glasses (SbPO) doped with 3 and 6 mol% of Cr3+ were studied by Electron Paramagnetic Resonance (EPR), UV-VIS optical absorption and luminescence spectroscopy. The EPR spectra of Cr3+-doped glasses showed two principal resonance signals with effective g values at g = 5.11 and g = 1.97. UV-VIS optical absorption spectra of SbPO:Cr3+ presented four characteristics bands at 457, 641, 675, and 705 nm related to the transitions from 4A2(F) to 4T1(F), 4T2(F), 2T1(G), and 2E(G), respectively, of Cr3+ ions in octahedral symmetry. Optical absorption spectra of SbPO:Cr3+ allowed evaluating the crystalline field Dq, Racah parameters (B and C) and Dq/B. The calculated value of Dq/B = 2.48 indicates that Cr3+ ions in SbPO glasses are in strong ligand field sites. The optical band gap for SbPO and SbPO:Cr3+ were evaluated from the UV optical absorption edges. Luminescence measurements of pure and Cr3+-doped glasses excited with 350 nm revealed weak emission bands from 400 to 600 nm due to the 3P1 ? 1S0 electronic transition from Sb3+ ions. Cr3+-doped glasses excited with 415 nm presented Cr3+ characteristic luminescence spectra composed by two broad bands, one band centered at 645 nm (2E ? 4A2) and another intense band from 700 to 850 nm (4T2 ? 4A2).

  5. Two-Photon Absorption in Organometallic Bromide Perovskites.

    PubMed

    Walters, Grant; Sutherland, Brandon R; Hoogland, Sjoerd; Shi, Dong; Comin, Riccardo; Sellan, Daniel P; Bakr, Osman M; Sargent, Edward H

    2015-09-22

    Organometallic trihalide perovskites are solution-processed semiconductors that have made great strides in third-generation thin film light-harvesting and light-emitting optoelectronic devices. Recently, it has been demonstrated that large, high-purity single crystals of these perovskites can be synthesized from the solution phase. These crystals' large dimensions, clean bandgap, and solid-state order have provided us with a suitable medium to observe and quantify two-photon absorption in perovskites. When CH3NH3PbBr3 single crystals are pumped with intense 800 nm light, we observe band-to-band photoluminescence at 572 nm, indicative of two-photon absorption. We report the nonlinear absorption coefficient of CH3NH3PbBr3 perovskites to be 8.6 cm GW(-1) at 800 nm, comparable to epitaxial single-crystal semiconductors of similar bandgap. We have leveraged this nonlinear process to electrically autocorrelate a 100 fs pulsed laser using a two-photon perovskite photodetector. This work demonstrates the viability of organometallic trihalide perovskites as a convenient and low-cost nonlinear absorber for applications in ultrafast photonics. PMID:26196162

  6. A new model for pressure-induced shifts of electronic absorption bands as applied to neat CS sub 2 and CS sub 2 in n-hexane and dichloromethane solutions

    SciTech Connect

    Agnew, S.F.; Swanson, B.I. )

    1990-01-25

    The authors propose a model for the pressure dependence of electronic absorption spectra and apply it to the authors data on CS{sub 2} both in neat phase and in hexane and dichloromethane solid solutions. They believe that their data represent a rather severe test of this model and argue that any model for the pressure dependence of electronic absorption spectra must include certain minimal effects - dispersive or dielectric and repulsive or volume effects - in order to adequately represent the data. They discuss previous models at some length in order to delineate the limits of their applicability. They further acknowledge and define the limits of the applicability of their model to solvent-induced shifts in general.

  7. UV intensity measurement of 308 nm excimer lamp using chemical actinometer

    NASA Astrophysics Data System (ADS)

    Zhang, Jun-Ying; Esrom, Hilmar; Boyd, Ian W.

    1999-01-01

    Photohydrolysis of 3,4-dimethoxynitrobenzene in alkaline media is used for the determination of the ultraviolet (UV) intensity from a xenon chloride excimer lamp providing intense narrow band radiation at ?=308 nm (XeCl *). The intensity measurement is based on UV spectral absorption measurement of the 2-methoxy-5-nitrophenolate anion formation from photohydrolysis of 3,4-dimethoxynitrobenzene. This actinometer is convenient for photolysis studies and measurements of UV intensities at wavelengths between 200-450 nm. A photokinetic model is presented for the reaction which is generally applicable for any two component photochemical system. The electrical power and distance dependence of the conversion degree and the UV intensity of the lamps was investigated.

  8. Underwater measurements of muon intensity

    NASA Technical Reports Server (NTRS)

    Fedorov, V. M.; Pustovetov, V. P.; Trubkin, Y. A.; Kirilenkov, A. V.

    1985-01-01

    Experimental measurements of cosmic ray muon intensity deep underwater aimed at determining a muon absorption curve are of considerable interest, as they allow to reproduce independently the muon energy spectrum at sea level. The comparison of the muon absorption curve in sea water with that in rock makes it possible to determine muon energy losses caused by nuclear interactions. The data available on muon absorption in water and that in rock are not equivalent. Underground measurements are numerous and have been carried out down to the depth of approx. 15km w.e., whereas underwater muon intensity have been measured twice and only down to approx. 3km deep.

  9. Surface enhanced optical absorption and photoluminescence in nonbonding electrons in small poly(vinylpyrrolidone) molecules

    NASA Astrophysics Data System (ADS)

    Mishra, A.; Ram, S.

    2007-02-01

    Molecularly dispersed poly(vinylpyrrolidone) (PVP) in water (after mechanochemical stirring in hot condition) absorbs strongly in a triplet band (? ??* electronic transitions) in the 200-400nm range. Absorption maximum shifts nonlinearly from 222nm [full width at half maximum (FWHM)22nm] in a dilute solution 0.1g/dl PVP to a value as large as 247nm (FWHM55nm) in 10g/dl PVP. Disobeying the Beer-Lambert relation, the absorbance increased in dilute samples. Irradiating in this region induces two emission groups; (i) 300-580nm and (ii) 600-850nm in six distinct bands in three major PVP conformers. The first band group involves an order of larger intensity in the other group. Strong electron-phonon coupling results in the C ?O group of pyrrolidone ring, which governs the conformation, in a vibronic band 1665cm-1 as intense as the (0,0) band. The group (ii) occurs in part of the energy loss in interactions of excited photons with surrounding in the n ??* transition [band group (i)] in the nonbonding C ?O (2sp4) electrons. Such transitions may be useful for optical switching and other devices.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  11. Limiting efficiency for a multi-band solar cell containing three and four bands

    NASA Astrophysics Data System (ADS)

    Brown, Andrew S.; Green, Martin A.; Corkish, Richard P.

    2002-04-01

    Multi-band solar cells provide a possible approach to obtain photovoltaic efficiencies that are greater than that of a single junction solar cell. In the three-band case, an intermediate band harnesses photons of energy less than that between the two main bands, allowing these photons to contribute to the power output of the device. Previous work has shown that introducing a third band offers an efficiency of 63.2%. This paper extends the theory to four bands and calculates a limiting efficiency of 71.7%. Finite bandwidths of all bands can be used to ensure photon absorption selectivity, assumed in deducing the previous limits, but at the cost of reduced limiting efficiency. The maximum efficiency using this feature for the three and four bands is 58.9% and 59.0%, respectively. Superlattices and quantum dots offer flexibility in artificially designing the energy and widths of the bands.

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

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

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

  13. High Pressure Oxygen A-Band Spectra

    NASA Astrophysics Data System (ADS)

    Drouin, Brian; Sung, Keeyoon; Yu, Shanshan; Lunny, Elizabeth M.; Bui, Thinh Quoc; Okumura, Mitchio; Rupasinghe, Priyanka; Bray, Caitlin; Long, David A.; Hodges, Joseph; Robichaud, David; Benner, D. Chris; Devi, V. Malathy; Hoo, Jiajun

    2015-06-01

    Composition measurements from remote sensing platforms require knowledge of air mass to better than the desired precision of the composition. Oxygen spectra allow determination of air mass since the mixing ratio of oxygen is fixed. The OCO-2 mission is currently retrieving carbon dioxide concentration using the oxygen A-band for air mass normalization. The 0.25% accuracy desired for the carbon dioxide concentration has pushed the state-of-the-art for oxygen spectroscopy. To produce atmospheric pressure A-band cross-sections with this accuracy requires a sophisticated line-shape model (Galatry or Speed-Dependent) with line mixing (LM) and collision induced absorption (CIA). Models of each of these phenomena exist, but an integrated self-consistent model must be developed to ensure accuracy. This presentation will describe the ongoing effort to parameterize these phenomena on a representative data set created from complementary experimental techniques. The techniques include Fourier transform spectroscopy (FTS), photo-acoustic spectroscopy (PAS) and cavity ring-down spectroscopy (CRDS). CRDS data allow long-pathlength measurements with absolute intensities, providing lineshape information as well as LM and CIA, however the subtleties of the lineshape are diminished in the saturated line-centers. Conversely, the short paths and large dynamic range of the PAS data allow the full lineshape to be discerned, but with an arbitrary intensity axis. Finally, the FTS data provides intermediate paths and consistency across a broad pressure range. These spectra are all modeled with the Labfit software using first the spectral line database HITRAN, and then model values are adjusted and fitted for better agreement with the data.

  14. Independence of optical absorption on Auger ionization in single-walled carbon nanotubes revealed by ultrafast e–h photodoping

    NASA Astrophysics Data System (ADS)

    Anderson, Mitchell D.; Beattie, Meghan N.; Alexander-Webber, Jack A.; Nicholas, Robin J.; Fraser, James M.

    2016-02-01

    Auger-ionized free-carriers in a one-dimensional semiconductor are predicted to result in a strong band-gap renormalization. Isolated single-walled carbon nanotubes (SWCNT) under high-intensity laser irradiation exhibit strong nonlinear photoluminescence (PL) due to exciton–exciton annihilation (EEA). The presence of exciton disassociation during the rapid Auger-ionization caused by EEA would lead to a strong nonlinear absorption. By simultaneously measuring SWCNT–PL and optical absorption of isolated SWCNT clusters in the PL saturation regime, we give evidence that Auger-ionized excitons do not disassociate but remain bound.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Golebiowski, D.; Fldes, T.; Vanfleteren, T.; Herman, M.; Perrin, A.

    2015-07-01

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

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

    PubMed

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

    2015-07-01

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

  18. Optical properties of a multibarrier structure under intense laser fields

    NASA Astrophysics Data System (ADS)

    Ospina, D. A.; Akimov, V.; Mora-Ramos, M. E.; Morales, A. L.; Tulupenko, V.; Duque, C. A.

    2015-11-01

    Using the diagonalization method and within the effective mass and parabolic band approximations, the energy spectrum and the wave functions are investigated in biased multibarrier structure taking into account the effects of nonresonant intense laser fields. We calculated the optical properties from the susceptibility using a nonperturbative formalism recently reported. We study the changes in the intersubband optical absorption coefficients and refraction index for several values of the dressing laser parameter and for some specific values of the electric field applied along the growth direction of the heterostructure. It is concluded from our study that the peaks in the optical absorption spectrum have redshifts or blueshifts as a function of the laser parameter and the electric field. These parameters could be suitable tools for tuning the electronic and optical properties of the multibarrier structure.

  19. Atmospheric Pressure Measurements using the Oxygen A Band

    NASA Astrophysics Data System (ADS)

    Stephen, M. A.; Riris, H.; Rodriguez, M.; Mao, J.; Weaver, C. J.; Abshire, J. B.

    2009-12-01

    We report on the atmospheric pressure measurements using a fiber-based laser system using the oxygen A-band. Remote measurements of atmospheric temperature and pressure are required for a number of scientific applications including trace gas detection, weather prediction, and climate modeling. Recently there has been intense interest to provide accurate measurements of tropospheric CO2 abundance with global-coverage, high spatial and temporal resolution in order to quantify processes that regulate CO2 storage by the land and oceans. It is becoming increasingly important to understand the nature and processes of the CO2 sinks and sources, on a global scale, in order to make predictions of future climate change. The ultimate goal of CO2 remote sensing is to derive CO2 concentration in the atmosphere in terms of mole fraction in unit of parts-per-million (ppmv) with regard to dry air. Therefore, both CO2 and dry air number of molecules in the atmosphere are needed in deriving this quantity. O2 is stable and uniformly mixed in the atmosphere. The measurement of O2 absorption in the atmosphere can thus be used to infer dry air number of molecules and then be used to calculate CO2 concentration. With the knowledge of atmospheric water vapor, we can further estimate the total surface pressure that can be used to better define both O2 and CO2 line shape for better retrievals, as both CO2 and O2 absorptions in the near infrared are a function of pressure as well as temperature. Our technique uses several on- and off-line wavelengths tuned to the O2 absorption line. The choice of wavelengths allows us to measure the pressure using two absorptions in the Oxygen A-band. Our retrieval algorithm fits the O2 lineshapes and derives the pressure. Our measurements compare favorably with a local weather monitor mounted outside our laboratory and a local weather station at Andrews Air Force base.

  20. Optical absorption of silicon nanowires

    NASA Astrophysics Data System (ADS)

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stivenard, D.; Lvque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

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