Science.gov

Sample records for absorption band intensities

  1. Absolute infrared vibrational band intensities of molecular ions determined by direct laser absorption spectroscopy in fast ion beams

    SciTech Connect

    Keim, E.R.; Polak, M.L.; Owrutsky, J.C.; Coe, J.V.; Saykally, R.J. )

    1990-09-01

    The technique of direct laser absorption spectroscopy in fast ion beams has been employed for the determination of absolute integrated band intensities ({ital S}{sup 0}{sub {ital v}}) for the {nu}{sub 3} fundamental bands of H{sub 3}O{sup +} and NH{sup +}{sub 4}. In addition, the absolute band intensities for the {nu}{sub 1} fundamental bands of HN{sup +}{sub 2} and HCO{sup +} have been remeasured. The values obtained in units of cm{sup {minus}2} atm{sup {minus}1} at STP are 1880(290) and 580(90) for the {nu}{sub 1} fundamentals of HN{sup +}{sub 2} and HCO{sup +}, respectively; and 4000(800) and 1220(190) for the {nu}{sub 3} fundamentals of H{sub 3}O{sup +} and NH{sup +}{sub 4}, respectively. Comparisons with {ital ab} {ital initio} results are presented.

  2. Radioprotective Action of Low-Intensity Light into the Red Absorption Band of Endogenous Molecular Oxygen

    NASA Astrophysics Data System (ADS)

    Ivanov, A. V.; Mashalov, A. A.; Zakharov, S. D.

    2016-08-01

    Application of ionizing radiation in oncology (radiation therapy) is a widespread way to eliminate malignant tumors. Normal tissues are inevitable included in any radiation field, and their reliable protection is actual till now. All attempts to solve the problem are based on search of effective radioprotectors, i.e. chemical compounds of various classes, which should be entered into the patient. To date about 50,000 compounds with some radioprotection properties had been tested, but the most effective of them have been simultaneously the most toxic. Here the preliminary results of researches devoted to development of an optical technique on basis of the light-oxygen effect for the protection of women with breast cancer from side effects of the radiation therapy are presented. A low intensity emission of the semiconductor laser in a red spectral interval was used to excite a very small quantity of endogenous molecular oxygen in O2(1Δg) state. It is shown, that application of the method at occurrence of earliest signs of radiation injury allows notably reducing dangerous breaks in radiation therapy course.

  3. 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.

  4. Absolute Absorption Intensities in the Fundamental nu2 and nu5 Bands of 12CH3F.

    PubMed

    Lepère; Blanquet; Walrand; Tarrago

    1998-06-01

    The absolute strengths of 93 lines belonging to the nu2 and nu5 bands of methyl fluoride were measured in the range of 1416-1503 cm-1 using a tunable diode-laser (TDL) spectrometer. These experimental line intensities were obtained from the equivalent width method. The intensities were analyzed within a dyad system, required to account properly for the strong Coriolis coupling between nu2 and nu5. The fit to the experimental data led to the determination of the dipole moment derivatives partial differentialµ/ partial differentialq2 and partial differentialµ/ partial differentialq5, as well as the first-order Herman-Wallis correction in K to partial differentialµ/ partial differentialq5. The intensities were reproduced with an overall standard deviation of 1.44%, to be compared with a mean experimental uncertainty equal to 1.58%. The values derived for the vibrational band strengths of nu2 and nu5 are 2.124 (18) cm-2.atm-1 and 36.96 cm-2.atm-1 at 296 K, respectively. Copyright 1998 Academic Press.

  5. 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.

  6. Temperature dependence of the intensity of the vibration-rotational absorption band ν2 of H2O trapped in an argon matrix

    NASA Astrophysics Data System (ADS)

    Pitsevich, G.; Doroshenko, I.; Malevich, A..; Shalamberidze, E.; Sapeshko, V.; Pogorelov, V.; Pettersson, L. G. M.

    2017-02-01

    Using two sets of effective rotational constants for the ground (000) and the excited bending (010) vibrational states the calculation of frequencies and intensities of vibration-rotational transitions for J″ = 0 - 2; and J‧ = 0 - 3; was carried out in frame of the model of a rigid asymmetric top for temperatures from 0 to 40 K. The calculation of the intensities of vibration-rotational absorption bands of H2O in an Ar matrix was carried out both for thermodynamic equilibrium and for the case of non-equilibrium population of para- and ortho-states. For the analysis of possible interaction of vibration-rotational and translational motions of a water molecule in an Ar matrix by 3D Schrödinger equation solving using discrete variable representation (DVR) method, calculations of translational frequencies of H2O in a cage formed after one argon atom deleting were carried out. The results of theoretical calculations were compared to experimental data taken from literature.

  7. Resonance Raman intensity analysis of the excited state proton transfer dynamics of 2-nitrophenol in the charge-transfer band absorption

    SciTech Connect

    Wang Yaqiong; Wang Huigang; Zhang Shuqiang; Pei Kemei; Zheng Xuming; Lee Phillips, David

    2006-12-07

    Resonance Raman spectra were obtained for 2-nitrophenol in cyclohexane solution with excitation wavelengths in resonance with the charge-transfer (CT) proton transfer band absorption. These spectra indicate that the Franck-Condon region photodissociation dynamics have multidimensional character with motion along more than 15 normal modes: the nominal CCH bend+CC stretch {nu}{sub 12} (1326 cm{sup -1}), the nominal CCC bend {nu}{sub 23} (564 cm{sup -1}), the nominal CO stretch+NO stretch+CC stretch {nu}{sub 14} (1250 cm{sup -1}), the nominal CCH bend+CC stretch+COH bend {nu}{sub 15} (1190 cm{sup -1}); the nominal CCH bend+CC stretch {nu}{sub 17} (1134 cm{sup -1}), the nominal CCC bend+CC stretch {nu}{sub 22} (669 cm{sup -1}), the nominal CCN bend {nu}{sub 27} (290 cm{sup -1}), the nominal NO{sub 2} bend+CC stretch {nu}{sub 21} (820 cm{sup -1}), the nominal CCO bend+CNO bend {nu}{sub 25} (428 cm{sup -1}), the nominal CC stretch {nu}{sub 7} (1590 cm{sup -1}), the nominal NO stretch {nu}{sub 8} (1538 cm{sup -1}), the nominal CCC bend+NO{sub 2} bend {nu}{sub 20} (870 cm{sup -1}), the nominal CC stretch {nu}{sub 6} (1617 cm{sup -1}), the nominal COH bend+CC stretch {nu}{sub 11} (1382 cm{sup -1}), nominal CCH bend+CC stretch {nu}{sub 9} (1472 cm{sup -1}). A preliminary resonance Raman intensity analysis was done and the results for 2-nitrophenol were compared to previously reported results for nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone. The authors briefly discuss the differences and similarities in the CT-band absorption excitation of 2-nitrophenol relative to those of nitrobenzene, p-nitroaniline, and 2-hydroxyacetophenone.

  8. 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.

  9. 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.

  10. Experimental and theoretical study of absorption spectrum of the (CH3)2CO···HF 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

    2014-01-03

    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 2ν(C=O) overtone band of free acetone are reliably measured. The ν1(HF) and ν(C=O) absorption bands of the (CH3)2CO···HF complex are obtained by subtracting the absorption bands of free HF and acetone and absorption lines of atmospheric water from the experimental spectrum of mixtures. The experimental data are compared with theoretical results obtained from variational solutions of 1D-4D vibrational Schrödinger equations. The anharmonic potential energy and dipole moment surfaces used in the calculations were computed in the MP2/6-311++G(2d,2p) approximation with corrections for the basis set superposition error. Comparison of the data derived from solutions for different combinations of vibrational degrees of freedom shows that taking the inter-mode anharmonic interactions into account has different effects on the transition frequencies and intensities. Particular attention has been given to elucidation of the influence of anharmonic coupling of the H-F and 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.

  11. 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.

  12. Concerning the Optical Absorption Band of the Hydrated Electron,

    DTIC Science & Technology

    methylene blue ) showed marked nonlinear absorption due to saturation of optical transitions, no such change was observed for hydrated electrons even though the light intensity was varied by > 10 to the 7th power up to 200 photons per hydrated electron per sq cm. Consequently the photoexcited state lifetime is estimated to be than 6 x 10 to the -12th power sec. This finding is discussed briefly in terms of three possible origins for the absorption band, namely that involving excitation to a bound excited state, as a photoionization efficiency profile or as a distribution

  13. 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.

  14. Absolute integrated intensity for the nu-1 sulfur dioxide band

    NASA Technical Reports Server (NTRS)

    Pilon, P. J.; Young, C.

    1976-01-01

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

  15. Temperature behavior of optical absorption bands in colored LiF crystals

    NASA Astrophysics Data System (ADS)

    Fastampa, Renato; Missori, Mauro; Braidotti, Maria Chiara; Conti, Claudio; Vincenti, Maria Aurora; Montereali, Rosa Maria

    We measured the optical absorption spectra of thermally treated, gamma irradiated LiF crystals, as a function of temperature in the range 16-300 K. The temperature dependence of intensity, peak position and bandwidth of F and M absorption bands were obtained.

  16. e-beam irradiation effects on IR absorption bands in single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ichida, Masao; Nagao, Katsunori; Ikemoto, Yuka; Okazaki, Toshiya; Miyata, Yasumitsu; Kawakami, Akira; Kataura, Hiromichi; Umezu, Ikurou; Ando, Hiroaki

    2017-01-01

    We have measured the absorption and Raman spectral change induced by the irradiation of e-beam. By the irradiation of e-beam on SWNTs thin films, the intensity of defect related Raman band increase, and the peak energy of IR absorption bands shift to the higher energy side. These results indicate that the origin of infrared band is due to the plasmon resonance of finite-length SWNT. We have estimated the effective tube length and defect density from IR absorption peak energy.

  17. 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.

  18. Triple-band metamaterial absorption utilizing single rectangular hole

    NASA Astrophysics Data System (ADS)

    Kim, Seung Jik; Yoo, Young Joon; Kim, Young Ju; Lee, YoungPak

    2017-01-01

    In the general metamaterial absorber, the single absorption band is made by the single meta-pattern. Here, we introduce the triple-band metamaterial absorber only utilizing single rectangular hole. We also demonstrate the absorption mechanism of the triple absorption. The first absorption peak was caused by the fundamental magnetic resonance in the metallic part between rectangular holes. The second absorption was generated by induced tornado magnetic field. The process of realizing the second band is also presented. The third absorption was induced by the third-harmonic magnetic resonance in the metallic region between rectangular holes. In addition, the visible-range triple-band absorber was also realized by using similar but smaller single rectangular-hole structure. These results render the simple metamaterials for high frequency in large scale, which can be useful in the fabrication of metamaterials operating in the optical range.

  19. Absorption enhancement of a dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhong, Min; Han, Gui Ming; Liu, Shui Jie; Xu, Bang Li; Wang, Jie; Huang, Hua Qing

    2017-02-01

    In this paper, we propose and fabricate a dual-band metamaterial absorber in 6-24 THz region. Electric field distribution reveal that the first absorption band is obtained from localized surface plasmon (LSP) modes which are excited both on inside and outside edges of each circular-patterned metal-dielectric stack, while the second absorption band is excited by LSP modes on outside edges of each stack. Measured results indicate that the absorption band width can be tuned by increasing the radius of circular-patterned layers or reducing the thickness of dielectric spacing layers. Moreover, the designed dual-band metamaterial absorber is independent on circular-patterned dielectric layer combinations.

  20. Interpretation of absorption bands in airborne hyperspectral radiance data.

    PubMed

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

    2009-01-01

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

  1. Interpretation of Absorption Bands in Airborne Hyperspectral Radiance Data

    PubMed Central

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

    2009-01-01

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

  2. Increasing efficiency in intermediate band solar cells with overlapping absorptions

    NASA Astrophysics Data System (ADS)

    Krishna, Akshay; Krich, Jacob J.

    2016-07-01

    Intermediate band (IB) materials are promising candidates for realizing high efficiency solar cells. In IB photovoltaics, photons are absorbed in one of three possible electronic transitions—valence to conduction band, valence to intermediate band, or intermediate to conduction band. With fully concentrated sunlight, when the band gaps have been chosen appropriately, the highest efficiency IB solar cells require that these three absorptions be non-overlapping, so absorbed photons of fixed energy contribute to only one transition. The realistic case of overlapping absorptions, where the transitions compete for photons, is generally considered to be a source of loss. We show that overlapping absorptions can in fact lead to significant improvements in IB solar cell efficiencies, especially for IB that are near the middle of the band gap. At low to moderate concentration, the highest efficiency requires overlapping absorptions. We use the detailed-balance method and indicate how much overlap of the absorptions is required to achieve efficiency improvements, comparing with some known cases. These results substantially broaden the set of materials that can be suitable for high-efficiency IB solar cells.

  3. Spectrophotometer spectral bandwidth calibration with absorption bands crystal standard.

    PubMed

    Soares, O D; Costa, J L

    1999-04-01

    A procedure for calibration of a spectral bandwidth standard for high-resolution spectrophotometers is described. Symmetrical absorption bands for a crystal standard are adopted. The method relies on spectral band shape fitting followed by a convolution with the slit function of the spectrophotometer. A reference spectrophotometer is used to calibrate the spectral bandwidth standard. Bandwidth calibration curves for a minimum spectral transmission factor relative to the spectral bandwidth of the reference spectrophotometer are derived for the absorption bands at the wavelength of the band absorption maximum. The family of these calibration curves characterizes the spectral bandwidth standard. We calibrate the spectral bandwidth of a spectrophotometer with respect to the reference spectrophotometer by determining the spectral transmission factor minimum at every calibrated absorption band of the bandwidth standard for the nominal instrument values of the spectral bandwidth. With reference to the standard spectral bandwidth calibration curves, the relation of the spectral bandwidth to the reference spectrophotometer is determined. We determine the discrepancy in the spectrophotometers' spectral bandwidths by averaging the spectral bandwidth discrepancies relative to the standard calibrated values found at the absorption bands considered. A weighted average of the uncertainties is taken.

  4. Glucose Absorption by the Bacillary Band of Trichuris muris

    PubMed Central

    Hansen, Michael; Nejsum, Peter; Mejer, Helena; Denwood, Matthew; Thamsborg, Stig M.

    2016-01-01

    Background A common characteristic of Trichuris spp. infections in humans and animals is the variable but low efficacy of single-dose benzimidazoles currently used in mass drug administration programmes against human trichuriasis. The bacillary band, a specialised morphological structure of Trichuris spp., as well as the unique partly intracellular habitat of adult Trichuris spp. may affect drug absorption and perhaps contribute to the low drug accumulation in the worm. However, the exact function of the bacillary band is still unknown. Methodology We studied the dependency of adult Trichuris muris on glucose and/or amino acids for survival in vitro and the absorptive function of the bacillary band. The viability of the worms was evaluated using a motility scale from 0 to 3, and the colorimetric assay Alamar Blue was utilised to measure the metabolic activity. The absorptive function of the bacillary band in living worms was explored using a fluorescent glucose analogue (6-NBDG) and confocal microscopy. To study the absorptive function of the bacillary band in relation to 6-NBDG, the oral uptake was minimised or excluded by sealing the oral cavity with glue and agarose. Principal Findings Glucose had a positive effect on both the motility (p < 0.001) and metabolic activity (p < 0.001) of T. muris in vitro, whereas this was not the case for amino acids. The 6-NBDG was observed in the pores of the bacillary band and within the stichocytes of the living worms, independent of oral sealing. Conclusions/Significance Trichuris muris is dependent on glucose for viability in vitro, and the bacillary band has an absorptive function in relation to 6-NBDG, which accumulates within the stichocytes. The absorptive function of the bacillary band calls for an exploration of its possible role in the uptake of anthelmintics, and as a potential anthelmintic target relevant for future drug development. PMID:27588682

  5. 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.

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

    PubMed

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

    2015-05-27

    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.

  7. 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.

  8. Constraints on the absorption band model of Q

    NASA Astrophysics Data System (ADS)

    Lundquist, Gary M.; Cormier, Vernon C.

    1980-10-01

    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 τ2, 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., τ2) is estimated to be in the range 1 to 2.5 Hz. (3) Under the constraints of Q model ratios, the depth dependence of τ2 is estimated by assuming that a free-oscillation and a body-wave Q model both measure Q from the same absorption band. The resulting τ2 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, τ2 for the mantle absorption band varies from about 0.09 s in the first 200 km to 4.0 s at 2886 km, and τ2 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.

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

    PubMed

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

    2014-12-01

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

  10. 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.

  11. Excitonic absorption intensity of semiconducting and metallic carbon nanotubes.

    PubMed

    Verdenhalven, Eike; Malić, Ermin

    2013-06-19

    The knowledge of the intrinsic absorption intensity of each carbon nanotube is of crucial importance for the optical assignment of nanotube species and the estimation of their abundance in a sample. Based on a microscopic approach, we calculate excitonic absorption spectra for a variety of semiconducting and metallic nanotubes, revealing a clear diameter, chirality, and family dependence of the absorption intensity. In particular, we also study the appearance of excited excitonic transitions, which are shown to be well pronounced for semiconducting nanotubes, reaching intensities of up to 10% of the main transition. We find that nanotubes with large diameters show the most pronounced absorption intensities, confirming well the experimentally observed trend. Depending on the CNT family and transition, the absorption is enhanced or reduced with the chiral angle. This behavior reflects well the qualitative chirality dependence of the analytically derived optical matrix element.

  12. 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.

  13. Absorption band III kinetics probe the picosecond heme iron motion triggered by nitric oxide binding to hemoglobin and myoglobin.

    PubMed

    Yoo, Byung-Kuk; Kruglik, Sergei G; Lamarre, Isabelle; Martin, Jean-Louis; Negrerie, Michel

    2012-04-05

    To study the ultrafast movement of the heme iron induced by nitric oxide (NO) binding to hemoglobin (Hb) and myoglobin (Mb), we probed the picosecond spectral evolution of absorption band III (∼760 nm) and vibrational modes (iron-histidine stretching, ν(4) and ν(7) in-plane modes) in time-resolved resonance Raman spectra. The time constants of band III intensity kinetics induced by NO rebinding (25 ps for hemoglobin and 40 ps for myoglobin) are larger than in Soret bands and Q-bands. Band III intensity kinetics is retarded with respect to NO rebinding to Hb and to Mb. Similarly, the ν((Fe-His)) stretching intensity kinetics are retarded with respect to the ν(4) and ν(7) heme modes and to Soret absorption. In contrast, band III spectral shift kinetics do not coincide with band III intensity kinetics but follows Soret kinetics. We concluded that, namely, the band III intensity depends on the heme iron out-of-plane position, as theoretically predicted ( Stavrov , S. S. Biopolymers 2004 , 74 , 37 - 40 ).

  14. Collisional Induced Absorption (CIA) bands measured in the IR spectral range .

    NASA Astrophysics Data System (ADS)

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

    In this work we present two experimental setup able to characterize the optical properties of gases, in particular CO_2 and H_2, at typically planetary conditions. The apparatus consists of a Fourier Transform InfraRed (FT-IT) interferometer able to work in a wide spectral range, from 350 to 25000 cm-1 (0.4 to 29 mu m ) with a relatively high spectral resolution, from 10 to 0.07 cm-1. Two dedicated gas cells have been integrated with the FT-IR. The first, called High Pressure High Temperature (HP-HT), can support pressures up to 300 bar, temperatures up to 300oC and is characterized by an optical path of 2 cm. The second one, a Multi Pass (MP) absorption gas cell, is designed to have a variable optical path, from 2.5 to 30 m, can be heated up to 200o and operate at pressures up to 10 bar. In this paper, measurements of Collision-Induced Absorption (CIA) bands in carbon dioxide and hydrogen recorded in the InfraRed spectral range will be presented. In principle, linear symmetric molecules such as CO_2 and H_2 possess no dipole moment, but, even when the pressure is only a few bar, we have observed the Collisional Induced Absorption (CIA) bands. This absorption results from a short-time collisional interaction between molecules. The band integrated intensity shows a quadratic dependence versus density opposed to the absorption by isolated molecules, which follows Beer's law \\citep{Beer's}. This behaviour suggests an absorption by pairs rather than by individual molecules. The bands integrated intensities show a linear dependence vs square density according to \\citep {CIA Shape} and \\citep{CIA posi}. For what concerns the H_2 CIA bands, a preliminary comparison between simulated data obtained with the model described in \\citep{CIA H2}and measured, shows a good agreement. These processes are very relevant in the dense atmospheres of planets, such as those of Venus and Jupiter and also in extrasolar planets. A detailed knowledge of these contributions is very

  15. 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.

  16. 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

  17. Interpretation of unusual absorption bandwidths and resonance Raman intensities in excited state mixed valence.

    PubMed

    Lockard, Jenny V; Valverde, Guadalupe; Neuhauser, Daniel; Zink, Jeffrey I; Luo, Yun; Weaver, Michael N; Nelsen, Stephen F

    2006-01-12

    Excited state mixed valence (ESMV) occurs in molecules in which the ground state has a symmetrical charge distribution but the excited state possesses two or more interchangeably equivalent sites that have different formal oxidation states. Although mixed valence excited states are relatively common in both organic and inorganic molecules, their properties have only recently been explored, primarily because their spectroscopic features are usually overlapped or obscured by other transitions in the molecule. The mixed valence excited state absorption bands of 2,3-di-p-anisyl-2,3-diazabicyclo[2.2.2]octane radical cation are well-separated from others in the absorption spectrum and are particularly well-suited for detailed analysis using the ESMV model. Excited state coupling splits the absorption band into two components. The lower energy component is broader and more intense than the higher energy component. The absorption bandwidths are caused by progressions in totally symmetric modes, and the difference in bandwidths is caused by the coordinate dependence of the excited state coupling. The Raman intensities obtained in resonance with the high and low energy components differ significantly from those expected based on the oscillator strengths of the bands. This unexpected observation is a result of the excited state coupling and is explained by both the averaging of the transition dipole moment orientation over all angles for the two types of spectroscopies and the coordinate-dependent coupling. The absorption spectrum is fit using a coupled two-state model in which both symmetric and asymmetric coordinates are included. The physical meaning of the observed resonance Raman intensity trends is discussed along with the origin of the coordinate-dependent coupling. The well-separated mixed valence excited state spectroscopic components enable detailed electronic and resonance Raman data to be obtained from which the model can be more fully developed and tested.

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  1. 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.

  2. Below-band-gap absorption in undoped GaAs at elevated temperatures

    NASA Astrophysics Data System (ADS)

    Wasiak, Michał; Walczak, Jarosław; Motyka, Marcin; Janiak, Filip; Trajnerowicz, Artur; Jasik, Agata

    2017-02-01

    This paper presents results of measurements of optical absorption in undoped epitaxial GaAs for photon energies below the band gap. Absorption spectra were determined from transmission spectra of a thin GaAs layer at several temperatures between 25 °C and 205 °C. We optimized our experiment to investigate the long-wavelength part of the spectrum, where the absorption is relatively low, but significant from the point of view of applications of GaAs in semiconductor lasers. Absorption of 100 cm-1 was observed over 30 nm below the band gap at high temperatures.

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

    PubMed

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

    2013-08-26

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

  4. 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.

  5. 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.

  6. a Theoretical Model for Wide-Band Infrared-Absorption Molecular Spectra at any Pressure: Fiction or Reality?

    NASA Astrophysics Data System (ADS)

    Buldyreva, Jeanna; Vander Auwera, Jean

    2014-06-01

    Various atmospheric applications require modeling of infrared absorption by the main atmospheric species in wide ranges of frequencies, pressures and temperatures. For different pressure regimes, different mechanisms are responsible for the observed intensities of vibration-rotation line manifolds, and the structure of the bands changes drastically when going from low to high densities. Therefore, no universal theoretical model exists presently to interpret simultaneously collapsed band-shapes observed at very high pressures and isolated-line shapes recorded in sub-atmospheric regimes. Using CO_2 absorption spectra as an example, we introduce some improvements in the non-Markovian Energy-Corrected Sudden model, developed for high-density spectra of arbitrary tensorial rank and generalized recently to parallel and perpendicular infrared absorption bands, and test the applicability of this approach for the case of nearly Doppler pressure regime via comparisons with recently recorded experimental intensities. J.V. Buldyreva and L. Bonamy, Phys. Rev. A 60(1), 370-376 (1999). J. Buldyreva and L. Daneshvar, J. Chem. Phys. 139, 164107 (2013). L. Daneshvar, T. Földes, J. Buldyreva, J. Vander Auwera, J. Quant. Spectrosc. Radiat. Transfer 2014 (to be submitted).

  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. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    We experimentally and theoretically investigated the mechanisms of acoustic absorption in phononic glass to optimize its properties. First, we experimentally studied its locally resonant absorption mechanism. From these results, we attributed its strong sound attenuation to its locally resonant units and its broadband absorption to its networked structure. These experiments also indicated that the porosity and thickness of the phononic glass must be tuned to achieve the best sound absorption at given frequencies. Then, using lumped-mass methods, we studied how the absorption bandgaps of the phononic glass were affected by various factors, including the porosity and the properties of the coating materials. These calculations gave optimal ranges for selecting the porosity, modulus of the coating material, and ratio of the compliant coating to the stiff matrix to achieve absorption bandgaps in the range of 6-30 kHz. This paper provides guidelines for designing phononic glasses with proper structures and component materials to work in specific frequency ranges.

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    Cross-sections of (O-18)2 at 79 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 177.8-197.8 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross-sections of the Schumann-Runge bands (14,0) through (2,0) are, with the exception of the (12,0) band, independent of the instrumental width. The measured cross-sections are presented graphically here and are available at wavenumber intervals of about 0.1/cm as numerical compilations stored on magnetic tape. Band oscillator strengths of those bands have been determined by direct numerical integration of the measured absolute cross-sections and are in excellent agreement with these theoretically calculated values.

  11. 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.

  12. a Comprehensive Intensity Study of the ν_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.

  13. 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.

  14. Hot Bands in Overtone Absorption Transitions: High Temperature Spectra

    DTIC Science & Technology

    1993-03-17

    the overtone transition. ൖ WWIŝST3" 3 24 002 15.NUMBER ,OF ,,A Overtone Spectroscopy, Hot Bands 16. PRKI CODE 17. SECURITY CLASSIFICATION 18...Rev 2-89) aWVPOO AfeD $10 139-18’q wAPI .’ N o, lgi OFFICE OF NAVAL RESEARCH GRANT or CONTRACT N00014-88-K-4130 R&T Code 4131063 Technical Report No...Unannounced fJ Justification ................ Prepared for Publication By ................ Di•.t. ibution I in Availability Codes Avail and /or Dist Special

  15. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  17. 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.

  18. 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.

  19. 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 ρv of light scattered by the pigments lycopene and β-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 ρv 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.

  20. AKARI observations of ice absorption bands towards edge-on YSOs

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    Circumstellar disks and envelopes of low-mass YSOs contain significant amounts of ice. Such icy material will evolve to volatile components of planetary systems, such as comets in our solar system. In order to investigate the composition and evolution of circumstellar ice around low-mass YSOs, we have observed ice absorption bands towards eight YSOs ranging from class 0 to class II, among which seven are associated with edge-on disks. Slit-less spectroscopic observations are performed using the grism mode of Infrared Camera (IRC) on board AKARI, which enables us to obtain full NIR spectra from 2.5 μm to 5 μm, including the CO_2 band and the blue wing of the H_2O band, which are not accessible from the ground. We developed procedures to reduce the spectra of targets with nebulosity. The spectra are fitted with polynomial baselines to derive the absorption spectra. Then we fit the molecular absorption bands with the laboratory spectra from the database, considering the instrumental line profile and the spectral resolution of the dispersion element. Towards the Class 0-I sources, absorption bands of H_2O, CO_2, CO and XCN (OCN^-) are clearly detected. Weak features of 13CO_2, HDO, the C-H band, and gaseous CO are detected as well. OCS ice absorption is tentatively detected towards IRC-L1041-2. The detected features would mostly originate in the cold envelope, while CO gas and OCN^- could originate in the region close to the protostar. Towards class II stars, H_2O ice band is detected. We also detected H_2O ice, CO_2 ice and tentative CO gas features of the foreground component of class II stars.

  1. Full band structure calculation of two-photon indirect absorption in bulk silicon

    SciTech Connect

    Cheng, J. L.; Rioux, J.; Sipe, J. E.

    2011-03-28

    Degenerate two-photon indirect absorption in silicon is an important limiting effect on the use of silicon structures for all-optical information processing at telecommunication wavelengths. We perform a full band structure calculation to investigate two-photon indirect absorption in bulk silicon, using a pseudopotential description of the energy bands and an adiabatic bond charge model to describe phonon dispersion and polarization. Our results agree well with some recent experimental results. The transverse acoustic/optical phonon-assisted processes dominate.

  2. 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.

  3. Emergence of Very Broad Infrared Absorption Band By Hyperdoping of Silicon with Chalcogens

    DTIC Science & Technology

    2013-06-03

    measured by Hall effect in Ref. 9 (crosses) as functions of implanted sulfur dose. (c) Calculated reflectivity by Kramers- Kronig transformation of the...MIR band is small enough, this assumption is reasonable according to the Kramers- Kronig relationship between optical absorption and reflectivity...calculated by a Kramers- Kronig transformation of the absorption spectrum shown in Fig. 1(a) and the results are shown in Fig. 1(c). However, the a value

  4. A band model for melanin deducted from optical absorption and photoconductivity experiments.

    PubMed

    Crippa, P R; Cristofoletti, V; Romeo, N

    1978-01-03

    Natural and synthetic melanins have been studied by optical absorption and photoconductivity measurements in the range 200--700 nm. Both optical absorption and photoconductivity increase in the ultraviolet region, and a negative photoconductivity was observed with a maximum near 500 nm. This behaviour has been interpreted by the band model of amorphous materials and an "optical gap" of 3.4 eV has been determined.

  5. Study of band inversion in the PbxSn1-xTe class of topological crystalline insulators using x-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Mitrofanov, K. V.; Kolobov, A. V.; Fons, P.; Krbal, M.; Tominaga, J.; Uruga, T.

    2014-11-01

    PbxSn1-xTe and PbxSn1-xSe crystals belong to the class of topological crystalline insulators where topological protection is achieved due to crystal symmetry rather than time-reversal symmetry. In this work, we make use of selection rules in the x-ray absorption process to experimentally detect band inversion along the PbTe(Se)-SnTe(Se) tie-lines. The observed significant change in the ratio of intensities of L1 and L3 transitions along the tie-line demonstrates that x-ray absorption can be a useful tool to study band inversion in topological insulators.

  6. Measurement of the absorption coefficient using the sound-intensity technique

    NASA Technical Reports Server (NTRS)

    Atwal, M.; Bernhard, R.

    1984-01-01

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

  7. High sensitivity ultra-broad-band absorption spectroscopy of inductively coupled chlorine plasma

    NASA Astrophysics Data System (ADS)

    Marinov, Daniil; Foucher, Mickaël; Campbell, Ewen; Brouard, Mark; Chabert, Pascal; Booth, Jean-Paul

    2016-06-01

    We propose a method to measure the densities of vibrationally excited Cl2(v) molecules in levels up to v  =  3 in pure chlorine inductively coupled plasmas (ICPs). The absorption continuum of Cl2 in the 250-450 nm spectral range is deconvoluted into the individual components originating from the different vibrational levels of the ground state, using a set of ab initio absorption cross sections. It is shown that gas heating at constant pressure is the major depletion mechanism of the Cl2 feedstock in the plasma. In these line-integrated absorption measurements, the absorption by the hot (and therefore rarefied) Cl2 gas in the reactor centre is masked by the cooler (and therefore denser) Cl2 near the walls. These radial gradients in temperature and density make it difficult to assess the degree of vibrational excitation in the centre of the reactor. The observed line-averaged vibrational distributions, when analyzed taking into account the radial temperature gradient, suggest that vibrational and translational degrees of freedom in the plasma are close to local equilibrium. This can be explained by efficient vibrational-translational (VT) relaxation between Cl2 and Cl atoms. Besides the Cl2(v) absorption band, a weak continuum absorption is observed at shorter wavelengths, and is attributed to photodetachment of Cl- negative ions. Thus, line-integrated densities of negative ions in chlorine plasmas can be directly measured using broad-band absorption spectroscopy.

  8. 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.

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

    PubMed Central

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

    2014-01-01

    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 r2 = 0.87 and ranged from r2 = 0.76 to 0.85 for the RPE O. Therefore, the Thera-Band Perceived Exertion Scale for Resistance Exercise can be used for monitoring elastic band exercise intensity. This would allow the training dosage to be better controlled within and between sessions. Moreover, the construct and concurrent validity indicates that the OMNI-RES EB measures similar properties of exertion as the Thera-Band RPE scale during elastic resistance exercise. Key points This new resistance intensity scale is an appropriate and valid tool for assessing perceived exertion during strength training with elastic bands

  11. 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.

  12. 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.

  13. Intensity dependent absorption/transparency of a reducing BaTiO3

    NASA Astrophysics Data System (ADS)

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

    1993-12-01

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

  14. Stimulus intensity affects early sensory processing: sound intensity modulates auditory evoked gamma-band activity in human EEG.

    PubMed

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

    2007-08-01

    We studied the effect of different sound intensities on the auditory evoked gamma-band response (GBR). Previous studies observed oscillatory gamma activity in the auditory cortex of animals and humans. For the visual modality, it has been demonstrated that the GBR can be modulated by top-down (attention, memory) as well as bottom-up factors (stimulus properties). Therefore, we expected to find a sound intensity modulation for the auditory GBR. 21 healthy participants without hearing deficits were investigated in a forced-choice discrimination task. Sinusoidal tones were presented at three systematically varied sound intensities (30, 45, 60 dB hearing level). The results of the auditory evoked potentials were predominantly consistent with previous studies. Furthermore, we observed an augmentation of the evoked GBR with increasing sound intensity. The analysis indicated that this intensity difference in the GBR amplitude most likely arises from increased phase-locking. The results demonstrate a distinct dependency between sound intensity and gamma-band oscillations. Future experiments that investigate the relationship between auditory evoked GBRs and higher cognitive processes should therefore select stimuli with an adequate sound intensity and control this variable to avoid confounding effects. In addition, it seems that gamma-band activity is more sensitive to exogenous stimulus parameters than evoked potentials.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Cross-sections of (0-16)(0-18) at 79 K have been obtained from photoabsorption measurements on mixtures of (0-16)2, (0-18)2, and (0-16)(0-18) at various pressures throughout the wavelength region 180.5-195.3 nm with a 6.65 m photoelectric scanning spectrometer equipped with a 2400 lines/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross-sections of the (0-16)(0-18) Schumann-Runge bands (11.0)-(3.0) are independent of the instrumental width. The measured cross-sections are presented graphically.

  16. 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.

  17. Dual-Band Perfect Absorption by Breaking the Symmetry of Metamaterial Structure

    NASA Astrophysics Data System (ADS)

    Hai, Le Dinh; Qui, Vu Dinh; Dinh, Tiep Hong; Hai, Pham; Giang, Trinh Thị; Cuong, Tran Manh; Tung, Bui Son; Lam, Vu Dinh

    2017-02-01

    Since the first proposal of Landy et al. (Phys Rev Lett 100:207402, 2008), the metamaterial perfect absorber (MPA) has rapidly become one of the most crucial research trends. Recently, dual-band, multi-band and broadband MPA have been highly desirable in electronic applications. In this paper, we demonstrate and evaluate a MPA structure which can generate dual-band absorption operating at the microwave frequency by breaking the symmetry of structure. There is an agreement between simulation and experimental results. The results can be explained by using the equivalent LC circuit and the electric field distribution of this structure. In addition, various structures with different symmetry configurations were studied to gain greater insight into the absorption.

  18. Jet-cooled infrared absorption spectrum of the v4 fundamental band of HCOOH and HCOOD

    NASA Astrophysics Data System (ADS)

    Luo, Wei; Zhang, Yulan; Li, Wenguang; Duan, Chuanxi

    2017-04-01

    The jet-cooled absorption spectrum of the v4 fundamental band of normal formic acid (HCOOH) and deuterated formic acid (HCOOD) was recorded in the frequency range of 1370-1392 cm-1 with distributed-feedback quantum cascade lasers (DFB-QCLs) as the tunable infrared radiations. A segmented rapid-scan data acquisition scheme was developed for pulsed supersonic jet infrared laser absorption spectroscopy based on DFB-QCLs with a moderate vacuum pumping capacity. The unperturbed band-origin and rotational constants in the excited vibrational state were determined for both HCOOH and HCOOD. The unperturbed band-origin locates at 1379.05447(11) cm-1 for HCOOH, and 1366.48430(39) cm-1 for HCOOD, respectively.

  19. Absolute Line Intensities in the 2nu(0)(2) Band of Cyanogen Chloride at 12.8 µm.

    PubMed

    Lepère; Blanquet; Walrand

    2000-05-01

    Absolute line intensities were measured at high resolution with a tunable diode laser. This work concerns the 2nu(0)(2) band of cyanogen chloride ClCN in the region 780 cm(-1). Thirty-two absorption lines were recorded for the isotopomer (35)ClCN and 26 lines for (37)ClCN. From the analysis of these lines, we determined the bandstrengths: S(0)(v) = 19.14 cm(-2) atm(-1) for (35)ClCN and S(0)(v) = 17.84 cm(-2) atm(-1) for (37)ClCN. Copyright 2000 Academic Press.

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

    NASA Astrophysics Data System (ADS)

    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.

    2015-06-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  2. 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}.

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  5. Cr(CO)6 photochemistry: semi-classical study of UV absorption spectral intensities and dynamics of photodissociation.

    PubMed

    Crespo-Otero, Rachel; Barbatti, Mario

    2011-04-28

    The UV absorption spectrum of Cr(CO)(6) (chromium hexacarbonyl) in gas phase is investigated by theoretical methods with focus on the absorption intensities. It is shown that in spite of good predictions for the excitation energies, the most frequently employed methods for excited-state calculations produce poor predictions for oscillator strengths and absorption cross sections. In particular, time-dependent DFT predicts relative intensities for the two main spectral bands to be up to five times larger than the experimental results depending on the functional. The best results are obtained by a multireference configuration interaction method based on DFT (DFT/MRCI). Spectral shoulders caused by vibronic-coupling absorption are assigned based on symmetry-restricted spectrum simulations. The dynamics of Cr(CO)(6) photodissociation was also considered at TDDFT/B3LYP level. The estimated time constants for the Cr(CO)(6) relaxation and dissociation are in excellent agreement with experimental values. The time constant for internal conversion, however, is longer than the experimentally observed by factor 2, presumably due to an underestimation of the experimental analysis.

  6. PRINCIPAL INFRARED ABSORPTION BANDS OF SOME DERIVATIVES OF 1,3-DINITROBENZENE AND 1,3,5TRINITROBENZENE,

    DTIC Science & Technology

    The frequencies of the strong infrared absorption bands of 46 derivatives of di- and tri-nitrobenzene were measured and tabulated. The vibrational ... modes producing these absorptions were assigned in most cases. The effect of structure on the frequency of the absorption due to each of the modes is discussed, with emphasis on identifying unknowns. (Author)

  7. Solvatochromic Shifts on Absorption and Fluorescence Bands of N,N-Dimethylaniline.

    PubMed

    Fdez Galván, Ignacio; Elena Martín, M; Muñoz-Losa, Aurora; Aguilar, Manuel A

    2009-02-10

    A theoretical study of the absorption and fluorescence UV/vis spectra of N,N-dimethylaniline in different solvents has been performed, using a method combining quantum mechanics, molecular mechanics, and the mean field approximation. The transitions between the three lowest-lying states have been calculated in vacuum as well as in cyclohexane, tetrahydrofuran, and water. The apparent anomalies experimentally found in water (a blue shift in the absorption bands with respect to the trend in other solvents, and an abnormally high red shift for the fluorescence band) are well reproduced and explained in view of the electronic structure of the solute and the solvent distribution around it. Additional calculations were done with a mixture of cyclohexane and tetrahydrofuran as solvent, which displays a nonlinear solvatochromic shift. Results, although not conclusive, are consistent with experiment and provide a possible explanation for the nonlinear behavior in the solvent mixture.

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

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Chen, Jiyao

    2013-12-01

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

  9. PHASE ANGLE EFFECTS ON 3 μm ABSORPTION BAND ON CERES: IMPLICATIONS FOR DAWN MISSION

    SciTech Connect

    Takir, D.; Reddy, V.; Sanchez, J. A.; Corre, L. Le; 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 NASA’s 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 μm. Ceres has an absorption feature at 3.0 μm due to hydroxyl- and/or water-bearing minerals. We analyzed phase angle-induced spectral effects on the 3 μm absorption band on Ceres using spectra measured with the long-wavelength cross-dispersed (LXD: 1.9–4.2 μm) 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 μm at lower phase angles (0.°7 and 6°) to 3.07 μm 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.

  10. 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

  11. 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

    2015-12-09

    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.

  12. 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.

  13. The Infrared Spectra and Absorption Intensities of Amorphous Ices

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Our research group is carrying out new IR measurements of icy solids relevant to the outer solar system and to the interstellar medium, with an emphasis on amorphous and crystalline ices below ~ 120 K. Our goal is to update and 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 three of the simplest and most abundant components of interstellar and solar-system ices: methane (CH4), carbon dioxide (CO2), and methanol (CH3OH). 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 120 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.

  14. Decomposing the First Absorption Band of OCS Using Photofragment Excitation Spectroscopy.

    PubMed

    Toulson, Benjamin W; Murray, Craig

    2016-09-01

    Photofragment excitation spectra of carbonyl sulfide (OCS) have been recorded from 212-260 nm by state-selectively probing either electronically excited S((1)D) or ground state S((3)P) photolysis products via 2 + 1 resonance-enhanced multiphoton ionization. Probing the major S((1)D) product results in a broad, unstructured action spectrum that reproduces the overall shape of the first absorption band. In contrast, spectra obtained probing S((3)P) products display prominent resonances superimposed on a broad continuum; the resonances correspond to the diffuse vibrational structure observed in the conventional absorption spectrum. The vibrational structure is assigned to four progressions, each dominated by the C-S stretch, ν1, following direct excitation to quasi-bound singlet and triplet states. The S((3)PJ) products are formed with a near-statistical population distribution over the J = 2, 1, and 0 spin-orbit levels across the wavelength range investigated. Although a minor contributor to the S atom yield near the peak of the absorption cross section, the relative yield of S((3)P) increases significantly at longer wavelengths. The experimental measurements validate recent theoretical work characterizing the electronic states responsible for the first absorption band by Schmidt and co-workers.

  15. Origin of absorption peaks in reflection loss spectrum in Ku- frequency band of Co-Zr substituted strontium hexaferrites prepared using sucrose precursor

    NASA Astrophysics Data System (ADS)

    Narang, Sukhleen Bindra; Pubby, Kunal; Chawla, S. K.; Kaur, Prabhjyot

    2017-03-01

    This study presents the detailed explanation of the factors, contributing towards the absorption peaks in reflection loss spectrum of hexaferrites. Cobalt-Zirconium substituted strontium hexaferrites, synthesized using sucrose precursor sol-gel technique, were analyzed in 12.4-18 GHz frequency range. The concepts of impedance matching through quarter wavelength condition, complex thickness, dielectric phase angle and attenuation constant have been used to determine the location as well as intensity of absorption peaks. This study also demonstrates the potential application of three compositions of this series with doping content (x)==0.0, 0.6 and 0.8 as an effective microwave absorbers in Ku-frequency band.

  16. 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.

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

    NASA Technical Reports Server (NTRS)

    Salama, F.; Allamandola, L. J.

    1992-01-01

    The diffuse interstellar band (DIB) absorption features of astronomical spectra are suggested by recent results to be separable from the grains that cause visual extinction. Attention is presently given to laboratory measurements of the optical spectrum of the pyrene cation C16H10(+), which is one of the polycyclic aromatic hydrocarbon (PAH) molecular candidates proposed as carriers for DIBs. This ion exhibits an intense but strangely broad continuum similar to that of the naphthalene cation, so that this may be a common feature of all PAH cations and the basis of an explanation for PAHs' converting of an interstellar radiation fraction as large as that from the UV and visible range down to the IR.

  18. Analysis of intensity dependent near-bandedge absorption in semi-insulating 4H–SiC for photoconductive switch applications

    NASA Astrophysics Data System (ADS)

    Meyers, V.; Chowdhury, A. R.; Mauch, D.; Dickens, J. C.; Neuber, A. A.; Joshi, R. P.

    2017-04-01

    We report on the intensity-dependent behavior of the absorption coefficient (α) in semi-insulating 4H–SiC material. Data from as-received samples show a monotonic decrease in α with incident energy density, with a pronounced change in slope at around 10 mJ cm‑2. Annealed samples, on the other hand, exhibit an experimental trend of increasing α with intensity. Qualitative explanation of the observed behavior is presented that probes the possible role of spontaneous and stimulated emission for as-received samples. With annealing, trap related recombination is strongly reduced leading to higher carrier densities and increased free-carrier absorption with incident intensity. The role of band-filling and permittivity changes are shown to be inconsequential, while changes in internal fields could contribute to decreases in absorption.

  19. Double stop-band structure near half-integer tunes in high-intensity rings

    NASA Astrophysics Data System (ADS)

    Moriya, K.; Ota, M.; Fukushima, K.; Yamaguchi, M.; Ito, K.; Okamoto, H.

    2016-11-01

    This paper addresses a detailed experimental study of collective instability bands generated near every half-integer tune per lattice period by coherent dipole and quadrupole resonances. Both instabilities appear side by side or overlap each other but are mostly separable because the dipole resonance often creates a narrower stop band accompanied by more severe particle losses. The separation of these low-order resonance bands becomes greater as the beam intensity increases. In principle, the double stop-band structure can be formed even without machine imperfections when the beam's initial phase-space profile is deviated from the ideal stationary distribution. The tabletop ion-trap system called "S-POD" is employed to experimentally demonstrate the parameter dependence of the double stop-band structure. Numerical simulations are also performed for comparison with experimental observations.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  1. 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

  2. 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

  3. Absolute integrated intensity for the 3.44-microns NO2 band

    NASA Technical Reports Server (NTRS)

    Shafer, J. H.; Young, C.

    1976-01-01

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

  4. Infrared absorption band in deformed qtz crystals analyzed by combining different microstructural methods

    NASA Astrophysics Data System (ADS)

    Stunitz, Holger; Thust, Anja; Behrens, Harald; Heilbronner, Renee; Kilian, Ruediger

    2016-04-01

    Natural single crystals of quartz have been experimentally deformed in two orientations: (1) normal to one prism-plane, (2) In O+ orientation at temperatures of 900 and 1000°C, pressures of 1.0 and 1.5 GPa, and strain rates of ~1 x 10-6s-1. The starting material is milky quartz, consisting of dry quartz (H2O contents of <150 H/106Si) with fluid inclusions (FI). During pressurization many FÍs decrepitate. Cracks heal and small neonate FÍs form, increasing the number of FÍs drastically. During subsequent deformation, the size of FÍs is further reduced (down to ~10 nm). Sample deformation occurs by dominant dislocation glide on selected slip systems, accompanied by some dynamic recovery. Strongly deformed regions show FTIR spectra with a pointed broad absorption band in the ~3400 cm-1 region as a superposition of molecular H2O bands and three discrete absorption bands (at 3367, 3400, and 3434 cm-1). In addition, there is a discrete absorption band at 3585 cm-1, which only occurs in deformed regions. The 3585 cm-1 band is reduced or even disappears after annealing. This band is polarized and represents structurally bound H, its H-content is estimated to be 1-3% of the total H2O-content and appears to be associated with dislocations. The H2O weakening effect in our FI-bearing natural quartz crystals is assigned to the processes of dislocation generation and multiplication at small FÍs. The deformation processes in these crystals represent a recycling of H2O between FÍs, dislocation generation at very small fluid inclusions, incorporation of structurally bound H into dislocation cores, and release of H2O from dislocations back into FÍs during recovery. Cracking and crack healing play an important role in the recycling process and imply a close interrelationship between brittle and crystal plastic deformation. The H2O weakening by this process is of a disequilibrium nature and thus depends on the amount of H2O available.

  5. Reassignment of the Iron (3) Absorption Bands in the Spectra of Mars

    NASA Technical Reports Server (NTRS)

    Sherman, D. M.

    1985-01-01

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

  6. Near-infrared broad-band cavity enhanced absorption spectroscopy using a superluminescent light emitting diode.

    PubMed

    Denzer, W; Hamilton, M L; Hancock, G; Islam, M; Langley, C E; Peverall, R; Ritchie, G A D

    2009-11-01

    A fibre coupled near-infrared superluminescent light emitting diode that emits approximately 10 mW of radiation between 1.62 and 1.7 microm is employed in combination with a broad-band cavity enhanced spectrometer consisting of a linear optical cavity with mirrors of reflectivity approximately 99.98% and either a dispersive near-infrared spectrometer or a Fourier transform interferometer. Results are presented on the absorption of 1,3-butadiene, and sensitivities are achieved of 6.1 x 10(-8) cm(-1) using the dispersive spectrometer in combination with phase-sensitive detection, and 1.5 x 10(-8) cm(-1) using the Fourier transform interferometer (expressed as a minimum detectable absorption coefficient) over several minutes of acquisition time.

  7. Doping-Induced Absorption Bands in P3HT: Polarons and Bipolarons.

    PubMed

    Enengl, Christina; Enengl, Sandra; Pluczyk, Sandra; Havlicek, Marek; Lapkowski, Mieczyslaw; Neugebauer, Helmut; Ehrenfreund, Eitan

    2016-12-05

    In this work, we focus on the formation of different kinds of charge carriers such as polarons and bipolarons upon p-type doping (oxidation) of the organic semiconductor poly(3- hexylthiophene-2,5-diyl) (P3HT). We elucidate the cyclic voltammogram during oxidation of this polymer and present spectroscopic changes upon doping in the UV/Vis/near-IR range as well as in the mid-IR range. In the low-oxidation regime, two absorption bands related to sub-gap transitions appear, one in the UV/Vis range and another one in the mid-IR range. The UV/Vis absorption gradually decreases upon further doping while the mid-IR absorption shifts to lower energy. Additionally, electron paramagnetic resonance (EPR) measurements are performed, showing an increase of the EPR signal up to a certain doping level, which significantly decreases upon further doping. Furthermore, the absorption spectra in the UV/Vis range are analyzed in relation to the morphology (crystalline vs. amorphous) by using theoretical models. Finally, the calculated charge carriers from cyclic voltammogram are linked together with optical transitions as well as with the EPR signals upon p-type doping. We stress that our results indicate the formation of polarons at low doping levels and the existence of bipolarons at high doping levels. The presented spectroscopic data are an experimental evidence of the formation of bipolarons in P3HT.

  8. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  10. Femtosecond supercontinuum generation in water in the vicinity of absorption bands.

    PubMed

    Dharmadhikari, J A; Steinmeyer, G; Gopakumar, G; Mathur, D; Dharmadhikari, A K

    2016-08-01

    We show that it is possible to overcome the perceived limitations caused by absorption bands in water so as to generate supercontinuum (SC) spectra in the anomalous dispersion regime that extend well beyond 2000 nm wavelength. By choosing a pump wavelength within a few hundred nanometers above the zero-dispersion wavelength of 1048 nm, initial spectral broadening extends into the normal dispersion regime and, in turn, the SC process in the visible strongly benefits from phase-matching and matching group velocities between dispersive radiation and light in the anomalous dispersion regime. Some of the SC spectra are shown to encompass two and a half octaves.

  11. 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

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

    PubMed

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

    2014-10-06

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

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

    SciTech Connect

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

    2014-08-11

    Here, we report that 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.

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

    DOE PAGES

    Bhattacharjee, Anirban; Chavarot-Kerlidou, Murielle; Dempsey, Jillian L.; ...

    2014-08-11

    Here, we report that 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.

  15. 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.

  16. Absolute intensities for the Q-branch of the 3 nu(sub 2) (-) nu(sub 1) (465.161/cm) band of nitrous oxide

    NASA Technical Reports Server (NTRS)

    Sirota, J. Marcos; Reuter, Dennis C.

    1993-01-01

    The absolute intensities of four lines, Q 15-Q 18 in the 03(sup 1)0-10(sup 0)0 band, of N2O have been measured using a tunable diode laser spectrometer at temperatures between 380 and 420 K and pressures between 4 and 15 torr. Even though these transitions are weak and produced only about 2% of absorption at the line center for a pathlength of 52 m, they were measured with a signal to noise ratio of about 20 due to the high sensitivity of the instrument. The band strength derived is 1.03 x 10(exp -24) cm/molec at 296 K.

  17. Constant Intensities of Diffuse Interstellar Bands in the Spectrum of AE Aur

    NASA Astrophysics Data System (ADS)

    Krełowski, J.; Galazutdinov, G. A.; Bondar, A.; Byeong-Cheol, L.

    2017-03-01

    Using spectra of the star AE Aur (HD 34078), covering the period 1997-2016, we prove that all strong diffuse interstellar bands are of the same intensity during the whole period of observations (inside 3-5% of the intensity). This is in sharp contrast to the behavior of both CH and CH+ features which, during the last six years, declined sharply by 13% and 28% respectively. Diffuse bands seem to behave more or less as interstellar atomic lines. We checked also the behavior of CaII lines which should be of constant intensities as the carrier fills the space evenly. Our observations confirm this and allow us to re-estimate the distance to HD 34078.

  18. 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.

  19. Highly vibrationally excited O2 molecules in low-pressure inductively-coupled plasmas detected by high sensitivity ultra-broad-band optical absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Foucher, Mickaël; Marinov, Daniil; Carbone, Emile; Chabert, Pascal; Booth, Jean-Paul

    2015-08-01

    Inductively-coupled plasmas in pure O2 (at pressures of 5-80 mTorr and radiofrequency power up to 500 W) were studied by optical absorption spectroscopy over the spectral range 200-450 nm, showing the presence of highly vibrationally excited O2 molecules (up to vʺ = 18) by Schumann-Runge band absorption. Analysis of the relative band intensities indicates a vibrational temperature up to 10,000 K, but these hot molecules only represent a fraction of the total O2 density. By analysing the (11-0) band at higher spectral resolution the O2 rotational temperature was also determined, and was found to increase with both pressure and power, reaching 900 K at 80 mTorr 500 W. These measurements were achieved using a new high-sensitivity ultra-broad-band absorption spectroscopy setup, based on a laser-plasma light source, achromatic optics and an aberration-corrected spectrograph. This setup allows the measurement of weak broadband absorbances due to a baseline variability lower than 2   ×   10-5 across a spectral range of 250 nm.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The purpose of this note is to report accurate measurements of the positions of O- and S-branch lines of the (1-0) vibration-rotation quadrupole band of molecular nitrogen ((14)N2) and improved Dunham coefficients derived from a simultaneous least-squares analysis of these measurements and selected infrared and far infrared data taken from the literature. The new measurements have been derived from stratospheric solar occultation spectra recorded with Fourier transform spectrometer (FTS) instruments operated at unapodized spectral resolutions of 0.002 and 0.01 /cm. The motivation for the present investigation is the need for improved N2 line parameters for use in IR atmospheric remote sensing investigations. The S branch of the N2 (1-0) quadrupole band is ideal for calibrating the line-of-sight airmasses of atmospheric spectra since the strongest lines are well placed in an atmospheric window, their absorption is relatively insensitive to temperature and is moderately strong (typical line center depths of 10 to 50% in high-resolution ground-based solar spectra and in lower stratospheric solar occultation spectra), and the volume mixing ratio of nitrogen is constant in the atmosphere and well known. However, a recent investigation has'shown the need to improve the accuracies of the N2 fine positions, intensities, air-broadened half-widths, and their temperature dependences to fully exploit this calibration capability (1). The present investigation addresses the problem of improving the accuracy of the N2 line positions.

  1. Spectroscopic analysis of Pr^3+ (4f^2) absorption intensities in a plastic host (HEMA).

    NASA Astrophysics Data System (ADS)

    Stonestreet, David; Nash, Kelly; Dee, Doug; Yow, Raylon; Gruber, John; Sardar, Dhiraj

    2006-10-01

    A spectroscopic investigation has been performed on the Pr^3+ ions embedded in 2-hydroxyethyl methacrylate (HEMA) solid plastic host. The standard Judd-Ofelt analysis was applied to the room temperature absorption intensities of Pr^3+ transitions to determine three phenomenological intensity parameters: φ2, φ4 and φ6. 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 Pr^3+ from the ^3P2, ^1D2, and ^3P0 manifold states to the lower-lying manifolds. The spectroscopic properties Pr^3+ in HEMA will be compared with those in glasses.

  2. 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.

  3. 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.

  4. 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.

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

    PubMed

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

    2013-06-19

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

  6. 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

  7. Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

    2015-05-01

    Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

  8. 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.

  9. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2007-06-01

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

  11. Coherent manipulation of absorption by intense fields in four level ladder system

    NASA Astrophysics Data System (ADS)

    Kumar, Pardeep; Dasgupta, Shubhrangshu

    2016-05-01

    Nonlinear optical processes attributed to the dependence of the susceptibility of the medium on the input fluence can be remarkably manipulated by the quantum interference and coherence. One of these processes, the optical bistability (OB), that refers to the possibilities of two stable outputs for the same input fields, can also be modified by quantum coherence. Further, the nonlinear dependence of the absorption on the power of the input light gives rise to interesting processes like saturable absorption (SA) and reverse saturable absorption (RSA). While the SA corresponds to the decrease in the absorption coefficient with the increase of intensity of input light, the RSA corresponds to otherwise, that finds applications in optical limiting. We show, using a four-level Ladder system, how a control field manipulates these processes for an intense probe field applied in the excited state transition. The nonlinear absorption increases whereas the threshold of OB decreases in presence of a control field. We further delineates how the control field and the decay rates modifies SA and RSA. The control of these processes find applications in optical switching, optical limiting and optical communications.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  13. 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.

  14. 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.

  15. High saturation intensity in InAs/GaAs quantum dot solar cells and impact on the realization of the intermediate band concept at room-temperature

    NASA Astrophysics Data System (ADS)

    Li, Tian; Dagenais, Mario

    2017-02-01

    High optical saturation intensity at room temperature is reported for an ensemble of undoped quantum dots. The non-linearity of the light-generated-current under resonant excitation from the valence band to the intermediate band is shown to be made up of two components: a background two-photon absorption term and a resonant optical saturation term. It is argued that the solar intensity is much lower than the saturation intensities involved for the first and second transitions in the intermediate band solar cell under 1-sun illumination and therefore prevents exciting an appreciable amount of population in the terminal level that can be ionized to the continuum and generate an appreciable additional current. This additional current is required for enhancing the energy conversion efficiency of a solar cell based on the intermediate band concept. Operating at cryogenic temperatures leads to a reduction in the saturation intensity but it might not be sufficient for increasing the energy conversion efficiency, unless concentrated sun light, and/or high density of quantum dots, and/or quantum dots with a lifetime more comparable to the radiative lifetime are used. The conclusions of this paper are also expected to apply to other quantum dot systems.

  16. [Gastric cancer detection using kubelka-Munk spectral function of DNA and protein absorption bands].

    PubMed

    Li, Lan-quan; Wei, Hua-jiang; Guo, Zhou-yi; Yang, Hong-qin; Xie, Shu-sen; Chen, Xue-mei; Li, Li-bo; He, Bol-hua; Wu, Guo-yong; Lu, Jian-jun

    2009-09-01

    Differential diagnosis for epithelial tissues of normal human gastric, undifferentiation gastric adenocarcinoma, gastric squamous cell carcinomas, and poorly differentiated gastric adenocarcinoma were studied using the Kubelka-Munk spectral function of the DNA and protein absorption bands at 260 and 280 nm in vitro. Diffuse reflectance spectra of tissue were measured using a spectrophotometer with an integrating sphere attachment. The results of measurement showed that for the spectral range from 250 to 650 nm, pathological changes of gastric epithelial tissues induced that there were significant differences in the averaged value of the Kubelka-Munk function f(r infinity) and logarithmic Kubelka-Munk function log[f(r infinity)] of the DNA absorption bands at 260 nm between epithelial tissues of normal human stomach and human undifferentiation gastric cancer, between epithelial tissues of normal human stomach and human gastric squamous cell carcinomas, and between epithelial tissues of normal human stomach and human poorly differentiated cancer. Their differences were 68.5% (p < 0.05), 146.5% (p < 0.05), 282.4% (p < 0.05), 32.4% (p < 0.05), 56.00 (p < 0.05) and 83.0% (p < 0.05) respectively. And pathological changes of gastric epithelial tissues induced that there were significant differences in the averaged value of the Kubelka-Munk function f(r infinity) and logarithmic Kubelka-Munk function log[f(r infinity)] of the protein absorption bands at 280 nm between epithelial tissues of normal human stomach and human undifferentiation gastric cancer, between epithelial tissues of normal human stomach and human gastric squamous cell carcinomas, and between epithelial tissues of normal human stomach and human poorly differentiated cancer. Their differences were 86.8% (p < 0.05), 262.9% (p < 0.05), 660.1% (p < 0.05) and 34% (p < 0.05), 72. 2% (p < 0.05), 113.5% (p < 0.05) respectively. And pathological changes of gastric epithelial tissues induced that there were

  17. 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.

  18. Geometrical attenuation, frequency dependence of Q, and the absorption band problem

    NASA Astrophysics Data System (ADS)

    Morozov, Igor B.

    2008-10-01

    A geometrical attenuation model is proposed as an alternative to the conventional frequency-dependent attenuation law Q(f) = Q0(f/f0)η. The new model provides a straightforward differentiation between the geometrical and effective attenuation (Qe) which incorporates the intrinsic attenuation and small-scale scattering. Unlike the (Q0, η) description, the inversion procedure uses only the spectral amplitude data and does not rely on elaborate theoretical models or restrictive assumptions. Data from over 40 reported studies were transformed to the new parametrization. The levels of geometrical attenuation strongly correlate with crustal tectonic types and decrease with tectonic age. The corrected values of Qe are frequency-independent and generally significantly higher than Q0 and show no significant correlation with tectonic age. Several case studies were revisited in detail, with significant changes in the interpretations. The absorption-band and the `10-Hz transition' are not found in the corrected Qe data, and therefore, these phenomena are interpreted as related to geometrical attenuation. The absorption band could correspond to changes in the dominant mode content of the wavefield as the frequency changes from about 0.1 to 100 Hz. Alternatively, it could also be a pure artefact related to the power-law Q(f) paradigm above. The explicit separation of the geometrical and intrinsic attenuation achieves three goals: (1) it provides an unambiguous, assumption- and model-free description of attenuation, (2) it allows relating the observations to the basic physics and geology and (3) it simplifies the interpretation because of reduced emphasis on the apparent Q(f) dependence. The model also agrees remarkably well with the initial attempts for finite-difference short-period coda waveform modelling. Because of its consistency and direct link to the observations, the approach should also help in building robust and transportable coda magnitudes and in seismic

  19. Short Pulse Laser Absorption and Energy Partition at Relativistic Laser Intensities

    SciTech Connect

    Shepherd, R; Chen, H; Ping, Y; Dyer, G; Wilks, S; Chung, H; Kemp, A; Hanson, S; Widmann, K; Fournier, K; Faenov, A; Pikuz, T; Niles, A; Beiersdorfer, P

    2007-02-27

    We have performed experiments at the COMET and Calisto short pulse laser facilities to make the first comprehensive measurements of the laser absorption and energy partition in solid targets heated with an ultrashort laser pulse focused to relativistic laser intensities (>10 10{sup 17} W/cm{sup 2}). The measurements show an exceedingly high absorption for P polarized laser-target interactions above 10{sup 19} W/cm{sup 2}. Additionally, the hot electron population is observed to markedly increase at the same intensity range. An investigation of the relaxation process was initiated u using time sing time-resolved K{sub {alpha}} spectroscopy. Measurements of the time time-resolved K{sub {alpha}} radiation suggest a 10-20 ps relativistic electron relaxation time. However modeling difficulties of these data are apparent and a more detailed investigation on this subject matter is warranted.

  20. Intraband optical absorption in a single quantum ring: Hydrostatic pressure and intense laser field effects

    NASA Astrophysics Data System (ADS)

    Barseghyan, M. G.

    2016-11-01

    The intraband optical absorption in GaAs/Ga0.7Al0.3As two-dimensional single quantum ring is investigated. Considering the combined effects of hydrostatic pressure and intense laser field the energy of the ground and few excited states has been found using the effective mass approximation and exact diagonalization technique. The energies of these states and the corresponding threshold energy of the intraband optical transitions are examined as a function of hydrostatic pressure for the different values of the laser field parameter. We also investigated the dependencies of the intraband optical absorption coefficient as a function of incident photon energy for different values of hydrostatic pressure and laser field parameter. It is found that the effects of hydrostatic pressure and intense laser field lead to redshift and blueshift of the intraband optical spectrum respectively.

  1. 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.

  2. 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

    2015-12-14

    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.

  3. 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.

  4. Band gap reduction in InNxSb1-x alloys: Optical absorption, k . P modeling, and density functional theory

    NASA Astrophysics Data System (ADS)

    Linhart, W. M.; Rajpalke, M. K.; Buckeridge, J.; Murgatroyd, P. A. E.; Bomphrey, J. J.; Alaria, J.; Catlow, C. R. A.; Scanlon, D. O.; Ashwin, M. J.; Veal, T. D.

    2016-09-01

    Using infrared absorption, the room temperature band gap of InSb is found to reduce from 174 (7.1 μm) to 85 meV (14.6 μm) upon incorporation of up to 1.13% N, a reduction of ˜79 meV/%N. The experimentally observed band gap reduction in molecular-beam epitaxial InNSb thin films is reproduced by a five band k . P band anticrossing model incorporating a nitrogen level, EN, 0.75 eV above the valence band maximum of the host InSb and an interaction coupling matrix element between the host conduction band and the N level of β = 1.80 eV. This observation is consistent with the presented results from hybrid density functional theory.

  5. 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.

  6. 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.

  7. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

    The standard Judd-Ofelt model has been applied to the room temperature absorption intensities of Er 3+(4f 11) transitions in a plastic host 2-hydroxyethyl methacrylate, referred to as HEMA, to determine the three phenomenological intensity parameters: Ω2, Ω4, and Ω6. Values are used to determine the spectroscopic quality factor for Er 3+ in HEMA and are compared to those for Er 3+ in crystalline hosts. The intensity parameters are subsequently used to determine the radiative decay rates and branching ratios of the Er 3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds 2 S+1 L J of Er 3+(4f 11) in HEMA. Using the radiative decay rates for Er 3+(4f 11) transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined.

  9. 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.

  10. Line Positions and Intensities for the ν12 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 μm 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 ν12 = 1 state with the nearby torsional ν_6 = 3 state. Line intensities corresponding to each spectrum temperature (130 K, 178 K and 208 K) are reported for 1660 ν12 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.

  11. 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

    2015-07-08

    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.

  12. 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.

  13. Symmetry-Breaking in Cationic Polymethine Dyes: Part 2. Shape of Electronic Absorption Bands Explained by the Thermal Fluctuations of the Solvent Reaction Field.

    PubMed

    Masunov, Artëm E; Anderson, Dane; Freidzon, Alexandra Ya; Bagaturyants, Alexander A

    2015-07-02

    The electronic absorption spectra of the symmetric cyanines exhibit dramatic dependence on the conjugated chain length: whereas short-chain homologues are characterized by the narrow and sharp absorption bands of high intensity, the long-chain homologues demonstrate very broad, structureless bands of low intensity. Spectra of the intermediate homologues combine both features. These broad bands are often explained using spontaneous symmetry-breaking and charge localization at one of the termini, and the combination of broad and sharp features was interpreted as coexistence of symmetric and asymmetric species in solution. These explanations were not supported by the first principle simulations until now. Here, we employ a combination of time-dependent density functional theory, a polarizable continuum model, and Franck-Condon (FC) approximation to predict the absorption line shapes for the series of 2-azaazulene and 1-methylpyridine-4-substituted polymethine dyes. To simulate inhomogeneous broadening by the solvent, the molecular structures are optimized in the presence of a finite electric field of various strengths. The calculated FC line shapes, averaged with the Boltzmann weights of different field strengths, reproduce the experimentally observed spectra closely. Although the polarizable continuum model accounts for the equilibrium solvent reaction field at absolute zero, the finite field accounts for the thermal fluctuations in the solvent, which break the symmetry of the solute molecule. This model of inhomogeneous broadening opens the possibility for computational studies of thermochromism. The choice of the global hybrid exchange-correlation functional SOGGA11-X, including 40% of the exact exchange, plays the critical role in the success of our model.

  14. 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)

  15. 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.

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

    PubMed

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

    2011-06-01

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

  17. Efficient energy absorption of intense ps-laser pulse into nanowire target

    NASA Astrophysics Data System (ADS)

    Habara, H.; Honda, S.; Katayama, M.; Sakagami, H.; Nagai, K.; Tanaka, K. A.

    2016-06-01

    The interaction between ultra-intense laser light and vertically aligned carbon nanotubes is investigated to demonstrate efficient laser-energy absorption in the ps laser-pulse regime. Results indicate a clear enhancement of the energy conversion from laser to energetic electrons and a simultaneously small plasma expansion on the surface of the target. A two-dimensional plasma particle calculation exhibits a high absorption through laser propagation deep into the nanotube array, even for a dense array whose structure is much smaller than the laser wavelength. The propagation leads to the radial expansion of plasma perpendicular to the nanotubes rather than to the front side. These features may contribute to fast ignition in inertial confinement fusion and laser particle acceleration, both of which require high current and small surface plasma simultaneously.

  18. Stratospheric observations of the attenuated solar irradiance in the Schumann-Runge band absorption region of molecular oxygen

    NASA Technical Reports Server (NTRS)

    Frederick, J. E.; Hudson, R. D.; Mentall, J. E.

    1981-01-01

    A spectrometer flown on the first Solar Absorption Balloon Experiment (SABE-1) observed the attenuated solar irradiance between 184 and 202 nm from an altitude near 40 km. These measurements provide a check on the absorption cross sections of molecular oxygen in the spectral region of the Schumann-Runge bands. Comparison of the measurements with calculations based on cross sections derived from laboratory data shows a general agreement although the irradiance measurements have large error bars near the centers of the absorption bands. The results imply that the 184-200 nm solar irradiance that penetrates to the stratosphere can be computed to an accuracy of + or - 30% or better by using presently available cross sections.

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

    PubMed

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

    2011-01-17

    Photocatalytic activities of perovskite-type niobium oxynitrides (CaNbO₂N, SrNbO₂N, BaNbO₂N, and LaNbON₂) were examined for hydrogen and oxygen evolution from water under visible-light irradiation. These niobium oxynitrides were prepared by heating the corresponding oxide precursors, which were synthesized using the polymerized complex method, for 15 h under a flow of ammonia. They possess visible-light absorption bands between 600-750 nm, depending on the A-site cations in the structures. The oxynitride CaNbO₂N, was found to be active for hydrogen and oxygen evolution from methanol and aqueous AgNO₃, respectively, even under irradiation by light at long wavelengths (λ<560 nm). The nitridation temperature dependence of CaNbO₂N was investigated and 1023 K was found to be the optimal temperature. At lower temperatures, the oxynitride phase is not adequately produced, whereas higher temperatures produce more reduced niobium species (e. g., Nb³(+) and Nb⁴(+)), which can act as electron-hole recombination centers, resulting in a decrease in activity.

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    Cross sections of O2 at 79 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 179.3-198.0 nm with a 6.65-m photoelectric scanning spectrometer equipped with a 2400-lines/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross sections of the Schumann-Runge bands (12,0) through (2,0) are independent of the instrumental width. The measured cross-sections are presented graphically here and are available at wavenumber intervals of about 0.1/cm as numerical compilations stored on magnetic tape from the National Space Science Data Center, NASA/Goddard. Band oscillator strengths of these bands have been determined by direct numerical integration of the measured cross sections.

  2. 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.

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

    PubMed

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

    2010-03-01

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

  4. 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.

  5. 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.

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

    SciTech Connect

    Turley, R.S.; McFarlane, R.A. ); Steel, D.G.; Remillard, J.

    1988-10-01

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

  7. 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.

  8. Line Positions, Intensities, - and N_2-BROADENING Parameters in the ν_9 Band of Ethane (C_2H_6)

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

  9. Line intensities and temperature-dependent line broadening coefficients of Q-branch transitions in the v2 band of ammonia near 10.4 μm

    NASA Astrophysics Data System (ADS)

    Sur, Ritobrata; Spearrin, R. Mitchell; Peng, Wen Y.; Strand, Christopher L.; Jeffries, Jay B.; Enns, Gregory M.; Hanson, Ronald K.

    2016-05-01

    We report measured line intensities and temperature-dependent broadening coefficients of NH3 with Ar, N2, O2, CO2, H2O, and NH3 for nine sQ(J,K) transitions in the ν2 fundamental band in the frequency range 961.5-967.5 cm-1. This spectral region was chosen due to the strong NH3 absorption strength and lack of spectral interference from H2O and CO2 for laser-based sensing applications. Spectroscopic parameters were determined by multi-line fitting using Voigt lineshapes of absorption spectra measured with two quantum cascade lasers in thermodynamically-controlled optical cells. The temperature dependence of broadening was measured over a range of temperatures between 300 and 600 K. These measurements aid the development of mid-infrared NH3 sensors for a broad range of gas mixtures and at elevated temperatures.

  10. 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.

  11. 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.

  12. 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.

  13. X-ray absorption and reflection as probes of the GaN conduction bands: Theory and experiments

    SciTech Connect

    Lambrecht, W.R.L.; Rashkeev, S.N.; Segall, B.

    1997-04-01

    X-ray absorption measurements are a well-known probe of the unoccupied states in a material. The same information can be obtained by using glancing angle X-ray reflectivity. In spite of several existing band structure calculations of the group III nitrides and previous optical studies in UV range, a direct probe of their conduction band densities of states is of interest. The authors performed a joint experimental and theoretical investigation using both of these experimental techniques for wurtzite GaN.

  14. 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 Iλ{sup 2}≅(0.3−1.2)×10{sup 21} Wcm{sup −2}μm{sup 2} in the plasma target with the electron density of n{sub e}λ{sup 2}∼10{sup 23}cm{sup −3}μm{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 Iλ{sup 2}≅(10{sup 18}−10{sup 20}) Wcm{sup −2}μm{sup 2}, a scaling in vague accordance with current published estimates in the range Iλ{sup 2}≅(0.14−3.5)×10{sup 21} Wcm{sup −2}

  15. 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

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Reddy, Samala Nagaprasad; Mahapatra, S.

    2012-07-01

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

  18. 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.

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

    PubMed

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

    2012-01-01

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

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

    PubMed

    Dai, Weitao; Yap, Daniel; Chen, Gang

    2012-07-02

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

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

    SciTech Connect

    De Groot, J.S.; Liu, J.M.; Matte, J.P.

    1994-02-04

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

  2. Wide angle and narrow-band asymmetric absorption in visible and near-infrared regime through lossy Bragg stacks

    PubMed Central

    Shu, Shiwei; Zhan, Yawen; Lee, Chris; Lu, Jian; Li, Yang Yang

    2016-01-01

    Absorber is an important component in various optical devices. Here we report a novel type of asymmetric absorber in the visible and near-infrared spectrum which is based on lossy Bragg stacks. The lossy Bragg stacks can achieve near-perfect absorption at one side and high reflection at the other within the narrow bands (several nm) of resonance wavelengths, whereas display almost identical absorption/reflection responses for the rest of the spectrum. Meanwhile, this interesting wavelength-selective asymmetric absorption behavior persists for wide angles, does not depend on polarization, and can be ascribed to the lossy characteristics of the Bragg stacks. Moreover, interesting Fano resonance with easily tailorable peak profiles can be realized using the lossy Bragg stacks. PMID:27251768

  3. Annealing-induced optical and sub-band-gap absorption parameters of Sn-doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Tripathi, S. K.

    2016-01-01

    Thin films of Sn-doped CdSe were prepared by thermal evaporation onto glass substrates in an argon gas atmosphere and annealed at different temperatures. Structural evaluation of the films was carried out using X-ray diffraction and their stoichiometry studied by energy-dispersive X-ray analysis. The films exhibit a preferred orientation along the hexagonal direction of CdSe. The optical transmittance of the films shows a red shift of the absorption edge with annealing. The fundamental absorption edge corresponds to a direct energy gap with a temperature coefficient of 3.34 × 10-3 eV K-1. The refractive index, optical conductivity and real and imaginary parts of the dielectric constants were found to increase after annealing. The sub-band gap absorption coefficient was evaluated using the constant photocurrent method. It varies exponentially with photon energy. The Urbach energy, the density of defect states, and the steepness of the density of localized states were evaluated from the sub-band-gap absorption.

  4. Electric-field effects on the OH vibrational frequency and infrared absorption intensity for water

    NASA Astrophysics Data System (ADS)

    Hermansson, Kersti

    1993-07-01

    The variations of the anharmonic OH frequency and the infrared absorption intensity with field strength have been calculated for the uncoupled OH stretching vibration of a water molecule in a static, homogeneous electric field using ab initio methods at the MP4 level with a nearly saturated basis set. The OH frequency is found to be virtually independent of the field components perpendicular to the vibrating OH bond. For the parallel component, the frequency vs field curve is close to quadratic, with a maximum for a slightly negative (directed from H to O) field strength. The external field perturbation, defined as Vext(E∥,rOH)=Vtot(E∥, rOH)-Vfree(rOH), is found to be closely linear in rOH, except when the field strength E∥ is both large and negative. The linear external force constant is almost perfectly accounted for by the sum of two terms, -E∥ṡdμ∥free/drOH and -1/2ṡE∥ṡ∂μ∥induced/∂rOH. These derivatives are quite insensitive to the choice of basis-set. The ∂μ∥induced/∂rOH derivative is approximately proportional to E∥, and gives rise to the arclike shape of the frequency vs field curve. The frequency maximum occurs where ∂μ∥tot/∂rOH≊0. It is the sign of dμ∥free/drOH which determines that the frequency maximum occurs at a negative field strength for water (but at a positive field strength for OH-, for example), i.e., that a frequency red-shift (blue-shift for OH-) occurs when the molecule is bound. The linear relationship between the infrared absorption intensity and frequency of the water OH vibration is derived.

  5. 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 ΔH and ΔS 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.

  6. The C2H, C2, and CN electronic absorption bands in the carbon star HD 19557

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Bregman, J. D.; Cooper, D. M.; Goorvitch, D.; Langhoff, S. R.; Witteborn, F. C.

    1983-01-01

    Infrared spectrophotometry of the R-type carbon star HD 19557 is presented. Two unusual spectroscopic features are seen: a 3.1 micron band is lacking and a 2.8 micron band is present. Identifications are proposed for three previously unreported stellar absorption bands with electronic sequences of C2, CN, and C2H. The latter is proposed to be responsible for the 2.8 micron feature. The atmospheric structure of the star is studied with synthetic spectra, and an effective temperature between 2600 K and 3000 K is suggested. No SiC emission is seen at 11.3 microns, indicating that grain formation is not a viable process around the star. The lack of dust in R stars may suggest a salient difference between R and N types.

  7. 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.

  8. High energy electron irradiation of interstellar carbonaceous dust analogs: Cosmic ray effects on the carriers of the 3.4 µm absorption band.

    PubMed

    Maté, Belén; Molpeceres, Germán; Jiménez-Redondo, Miguel; Tanarro, Isabel; Herrero, Víctor J

    2016-11-01

    The effects of cosmic rays on the carriers of the interstellar 3.4 μm absorption band have been investigated in the laboratory. This band is attributed to stretching vibrations of CH3 and CH2 in carbonaceous dust. It is widely observed in the diffuse interstellar medium (ISM), but disappears in dense clouds. Destruction of CH3 and CH2 by cosmic rays could become relevant in dense clouds, shielded from the external ultraviolet field. For the simulations, samples of hydrogenated amorphous carbon (a-C:H) have been irradiated with 5 keV electrons. The decay of the band intensity vs electron fluence reflects a-C:H dehydrogenation, which is well described by a model assuming that H2 molecules, formed by the recombination of H atoms liberated through CH bond breaking, diffuse out of the sample. The CH bond destruction rates derived from the present experiments are in good accordance with those from previous ion irradiation experiments of HAC. The experimental simplicity of electron bombardment has allowed the use of higher energy doses than in the ion experiments. The effects of cosmic rays on the aliphatic components of cosmic dust are found to be small. The estimated cosmic ray destruction times for the 3.4 μm band carriers lie in the 10(8) yr range and cannot account for the disappearance of this band in dense clouds, which have characteristic lifetimes of 3 × 10(7) yr. The results invite a more detailed investigation of the mechanisms of CH bond formation and breaking in the intermediate region between diffuse and dense clouds.

  9. High energy electron irradiation of interstellar carbonaceous dust analogs: Cosmic ray effects on the carriers of the 3.4 µm absorption band

    PubMed Central

    Maté, Belén; Molpeceres, Germán; Jiménez-Redondo, Miguel; Tanarro, Isabel; Herrero, Víctor J.

    2017-01-01

    The effects of cosmic rays on the carriers of the interstellar 3.4 μm absorption band have been investigated in the laboratory. This band is attributed to stretching vibrations of CH3 and CH2 in carbonaceous dust. It is widely observed in the diffuse interstellar medium (ISM), but disappears in dense clouds. Destruction of CH3 and CH2 by cosmic rays could become relevant in dense clouds, shielded from the external ultraviolet field. For the simulations, samples of hydrogenated amorphous carbon (a-C:H) have been irradiated with 5 keV electrons. The decay of the band intensity vs electron fluence reflects a-C:H dehydrogenation, which is well described by a model assuming that H2 molecules, formed by the recombination of H atoms liberated through CH bond breaking, diffuse out of the sample. The CH bond destruction rates derived from the present experiments are in good accordance with those from previous ion irradiation experiments of HAC. The experimental simplicity of electron bombardment has allowed the use of higher energy doses than in the ion experiments. The effects of cosmic rays on the aliphatic components of cosmic dust are found to be small. The estimated cosmic ray destruction times for the 3.4 μm band carriers lie in the 108 yr range and cannot account for the disappearance of this band in dense clouds, which have characteristic lifetimes of 3 × 107 yr. The results invite a more detailed investigation of the mechanisms of CH bond formation and breaking in the intermediate region between diffuse and dense clouds. PMID:28133388

  10. High-energy Electron Irradiation of Interstellar Carbonaceous Dust Analogs: Cosmic-ray Effects on the Carriers of the 3.4 μm Absorption Band

    NASA Astrophysics Data System (ADS)

    Maté, Belén; Molpeceres, Germán; Jiménez-Redondo, Miguel; Tanarro, Isabel; Herrero, Víctor J.

    2016-11-01

    The effects of cosmic rays on the carriers of the interstellar 3.4 μm absorption band have been investigated in the laboratory. This band is attributed to stretching vibrations of CH3 and CH2 in carbonaceous dust. It is widely observed in the diffuse interstellar medium, but disappears in dense clouds. Destruction of CH3 and CH2 by cosmic rays could become relevant in dense clouds, shielded from the external ultraviolet field. For the simulations, samples of hydrogenated amorphous carbon (a-C:H) have been irradiated with 5 keV electrons. The decay of the band intensity versus electron fluence reflects a-C:H dehydrogenation, which is well described by a model assuming that H2 molecules, formed by the recombination of H atoms liberated through CH bond breaking, diffuse out of the sample. The CH bond destruction rates derived from the present experiments are in good accordance with those from previous ion irradiation experiments of HAC. The experimental simplicity of electron bombardment has allowed the use of higher-energy doses than in the ion experiments. The effects of cosmic rays on the aliphatic components of cosmic dust are found to be small. The estimated cosmic-ray destruction times for the 3.4 μm band carriers lie in the 108 yr range and cannot account for the disappearance of this band in dense clouds, which have characteristic lifetimes of 3 × 107 yr. The results invite a more detailed investigation of the mechanisms of CH bond formation and breaking in the intermediate region between diffuse and dense clouds.

  11. 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.

  12. Influence of the cavity parameters on the output intensity in incoherent broadband cavity-enhanced absorption spectroscopy.

    PubMed

    Fiedler, Sven E; Hese, Achim; Heitmann, Uwe

    2007-07-01

    The incoherent broadband cavity-enhanced absorption spectroscopy is a technique in measuring small absorptions over a broad wavelength range. The setup consists of a conventional absorption spectrometer using an incoherent lamp and a charge coupled device detector, as well as a linear optical cavity placed around the absorbing sample, which enhances the effective path length through the sample. In this work the consequences of cavity length, mirror curvature, reflectivity, different light injection geometries, and spot size of the light source on the output intensity are studied and the implications to the signal-to-noise ratio of the absorption measurement are discussed. The symmetric confocal resonator configuration is identified as a special case with optimum imaging characteristics but with higher requirements for mechanical stability. Larger spot sizes of the light source were found to be favorable in order to reduce the negative effects of aberrations on the intensity.

  13. 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.

  14. First laboratory detection of an absorption line of the first overtone electric quadrupolar band of N2 by CRDS near 2.2 μm

    NASA Astrophysics Data System (ADS)

    Čermák, P.; Vasilchenko, S.; Mondelain, D.; Kassi, S.; Campargue, A.

    2017-01-01

    The extremely weak 2-0 O(14) electric quadrupole transition of N2 has been detected by very high sensitivity Cavity Ring Down spectroscopy near 4518 cm-1. It is the first N2 absorption line in the first overtone band reported so far from laboratory experiments. By combining a feedback narrowed Distributed Feedback laser diode with a passive cell tracking technique, a limit of detection of αmin ∼ 1.2 × 10-11 cm-1 was achieved after one day of spectra averaging. The N2 2-0 O(14) line position and line intensity (about 1.5 × 10-30 cm/molecule) agree with calculated values provided in the HITRAN2012 database.

  15. Donor impurity-related intraband optical absorption in a single quantum ring: Hydrostatic pressure and intense laser field effects

    NASA Astrophysics Data System (ADS)

    Barseghyan, M. G.

    2016-10-01

    The simultaneous influence of hydrostatic pressure and intense laser field on hydrogenic donor impurity states and intraband optical absorption has been investigated in GaAs/Ga_{1-tilde{x}}Al_{tilde{x}}As quantum ring. The one-electron energy spectrum and wave functions have been found using the effective mass approximation and exact diagonalization technique. The intraband absorption coefficient is calculated for different values of the hydrostatic pressure, intense laser field parameter and different locations of hydrogenic donor impurity. The simultaneous influence of hydrostatic pressure and intense laser field shows that while the increment of the first one leads only to the blueshift of the absorption spectrum, the augmentation of the second one makes the redshift. In addition, both blueshift and redshift of the spectrum have been obtained with the changes of impurity location. The obtained theoretical results indicate good controlling means of the optical spectrum of ring-like structures by the combined influence of the considered factors.

  16. Sub-nanometer linewidth perfect absorption in visible band induced by Bloch surface wave

    NASA Astrophysics Data System (ADS)

    Cong, Jiawei; Liu, Wenxing; Zhou, Zhiqiang; Ren, Naifei; Ding, Guilin; Chen, Mingyang; Yao, Hongbing

    2016-12-01

    We demonstrate the unity absorption of visible light with an ultra-narrow 0.1 nm linewidth. It arises from the Bloch surface wave resonance in alternating TiO2/SiO2 multilayers. The total absorption and narrow linewidth are explained from the radiative and absorptive damping, which are quantitatively determined by the temporal coupled mode theory. When a silver film with proper thickness is added to the absorber, the perfect absorption is achieved with only 3 structural bilayers, in contrast with 8 bilayers required without Ag. Furthermore, significant field enhancement and an ultrahigh 2600/RIU sensing figure-of-merit are simultaneously obtained at resonance, which might facilitate applications in nonlinear optical devices and high resolution refractive index sensing.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  18. Broad band nonlinear optical absorption measurements of the laser dye IR26 using white light continuum Z-scan

    NASA Astrophysics Data System (ADS)

    Dey, Soumyodeep; Bongu, Sudhakara Reddy; Bisht, Prem Ballabh

    2017-03-01

    We study the nonlinear optical response of a standard dye IR26 using the Z-scan technique, but with the white light continuum. The continuum source of wavelength from 450 nm to 1650 nm has been generated from the photonic crystal fiber on pumping with 772 nm of Ti:Sapphire oscillator. The use of broadband incident pulse enables us to probe saturable absorption (SA) and reverse saturable absorption (RSA) over the large spectral range with a single Z-scan measurement. The system shows SA in the resonant region while it turns to RSA in the non-resonant regions. The low saturation intensity of the dye can be explained based on the simultaneous excitation from ground states to various higher energy levels with the help of composite energy level diagram. The cumulative effects of excited state absorption and thermal induced nonlinear optical effects are responsible for the observed RSA.

  19. Energy levels and far-infrared optical absorption of impurity doped semiconductor nanorings: Intense laser and electric fields effects

    NASA Astrophysics Data System (ADS)

    Barseghyan, M. G.

    2016-11-01

    The effects of electron-impurity interaction on energy levels and far-infrared absorption in semiconductor nanoring under the action of intense laser and lateral electric fields have been investigated. Numerical calculations are performed using exact diagonalization technique. It is found that the electron-impurity interaction and external fields change the energy spectrum dramatically, and also have significant influence on the absorption spectrum. Strong dependence on laser field intensity and electric field of lowest energy levels, also supported by the Coulomb interaction with impurity, is clearly revealed.

  20. Real-time monitoring of reactive species in downstream etch reactor by VUV broad-band absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Soriano, R.; Vallier, L.; Cunge, G.; Sadeghi, N.

    2016-09-01

    Plasma etching of nanometric size, high aspect-ratio structures is more challenging at each new technological node. Remote plasmas are beginning to find use when damages on nanostructures by ion bombardment become critical or when etching with high selectivity on different materials present on the wafer is necessary (i . e . tungsten oxide etching with fluorine and hydrogen containing plasmas in remote reactor from AMAT). Furthermore, it is expected that downstream plasma will replace many wet chemical etching processes to alleviate the issue of pattern collapses caused by capillary forces when nanometer size high aspect ratio structures are immersed in liquids. In these downstream plasmas, radicals are the main active species and a control of their density is of prime importance. Most of gases used and radicals produced in etching plasmas (HBr, BrCl, Br2, NF3, CH2F2,...) have strong absorption bands in the vacuum UV spectral region and we have shown that very low concentration of these species can be detected by VUV absorption. We have recently improved the technique by using a VUV CCD camera, instead of the PMT, which render possible the Broad-Band absorption spectroscopy in the 120-200 nm range, with a deuterium lamp, or a laser produced xenon arc lamp as light source. The multi-spectral detection ability of the CCD reduces the acquisition time to less than 1 second and can permit the real time control of the process control.

  1. 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.

  2. 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.

  3. 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.

  4. Method for improving terahertz band absorption spectrum measurement accuracy using noncontact sample thickness measurement.

    PubMed

    Li, Zhi; Zhang, Zhaohui; Zhao, Xiaoyan; Su, Haixia; Yan, Fang; Zhang, Han

    2012-07-10

    The terahertz absorption spectrum has a complex nonlinear relationship with sample thickness, which is normally measured mechanically with limited accuracy. As a result, the terahertz absorption spectrum is usually determined incorrectly. In this paper, an iterative algorithm is proposed to accurately determine sample thickness. This algorithm is independent of the initial value used and results in convergent calculations. Precision in sample thickness can be improved up to 0.1 μm. A more precise absorption spectrum can then be extracted. By comparing the proposed method with the traditional method based on mechanical thickness measurements, quantitative analysis experiments on a three-component amino acid mixture shows that the global error decreased from 0.0338 to 0.0301.

  5. Absorption and emission line shapes in the O2 atmospheric bands - Theoretical model and limb viewing simulations

    NASA Technical Reports Server (NTRS)

    Abreu, Vincent J.; Bucholtz, A.; Hays, P. B.; Ortland, D.; Skinner, W. R.

    1989-01-01

    A multiple scattering radiative transfer model has been developed to carry out a line-by-line calculation of the absorption and emission limb measurements that will be made by the High Resolution Doppler Imager to be flown on the Upper Atmosphere Research Satellite. The multiple scattering model uses the doubling and adding methods to solve the radiative transfer equation, modified to take into account a spherical inhomogeneous atmosphere. Representative absorption and emission line shapes in the O2 1Sigma(+)g - 3Sigma(-)g atmospheric bands (A,B, and gamma) and their variation with altitude are presented. The effects of solar zenith angle, aerosol loading, surface albedo, and cloud height on the line shapes are also discussed.

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

    NASA Technical Reports Server (NTRS)

    Rowan, L. C. (Principal Investigator)

    1972-01-01

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

  7. Non-uniform temperature and species concentration measurements in a laminar flame using multi-band infrared absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Ma, Liu Hao; Lau, Lok Yin; Ren, Wei

    2017-03-01

    We report in situ measurements of non-uniform temperature, H2O and CO2 concentration distributions in a premixed methane-air laminar flame using tunable diode laser absorption spectroscopy (TDLAS). A mid-infrared, continuous-wave, room-temperature interband cascade laser (ICL) at 4183 nm was used for the sensitive detection of CO2 at high temperature.The H2O absorption lines were exploited by one distributed feedback (DFB) diode laser at 1343 nm and one ICL at 2482 nm to achieve multi-band absorption measurements with high species concentration sensitivity, high temperature sensitivity, and immunity to variations in ambient conditions. A novel profile-fitting function was proposed to characterize the non-uniform temperature and species concentrations along the line-of-sight in the flame by detecting six absorption lines of CO2 and H2O simultaneously. The flame temperature distribution was measured at different heights above the burner (5-20 mm), and compared with the thermocouple measurement with heat-transfer correction. Our TDLAS measured temperature of the central flame was in excellent agreement (<1.5% difference) with the thermocouple data.The TDLAS results were also compared with the CFD simulations using a detailed chemical kinetics mechanism (GRI 3.0) and considering the heat loss to the surroundings.The current CFD simulation overpredicted the flame temperature in the gradient region, but was in excellent agreement with the measured temperature and species concentration in the core of the flame.

  8. 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.

  9. Theoretical study on the photofragment branching ratios and anisotropy parameters of ICl in the second absorption band

    NASA Astrophysics Data System (ADS)

    Matsuoka, Takahide; Yabushita, Satoshi

    2014-01-01

    Potential energy curves, transition dipole moments, and non-adiabatic coupling terms of the excited states of ICl molecule have been obtained by the spin-orbit configuration interaction method to examine the branching ratios and the anisotropy parameters of the photodissociation process in the second absorption band. The calculation of the branching ratios with the time-dependent coupled Schrödinger equations, including the quantum interference effect between the 0+(III) and 0+(IV) states, shows good agreement with recent experiments, thus resolves the long standing disagreement. The contribution of the quantum interference effect to the photodissociation process is discussed based on a time-dependent perturbation treatment.

  10. 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.

  11. Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: sparse methods for statistical selection of relevant absorption bands

    NASA Astrophysics Data System (ADS)

    Takahama, Satoshi; Ruggeri, Giulia; Dillner, Ann M.

    2016-07-01

    Various vibrational modes present in molecular mixtures of laboratory and atmospheric aerosols give rise to complex Fourier transform infrared (FT-IR) absorption spectra. Such spectra can be chemically informative, but they often require sophisticated algorithms for quantitative characterization of aerosol composition. Naïve statistical calibration models developed for quantification employ the full suite of wavenumbers available from a set of spectra, leading to loss of mechanistic interpretation between chemical composition and the resulting changes in absorption patterns that underpin their predictive capability. Using sparse representations of the same set of spectra, alternative calibration models can be built in which only a select group of absorption bands are used to make quantitative prediction of various aerosol properties. Such models are desirable as they allow us to relate predicted properties to their underlying molecular structure. In this work, we present an evaluation of four algorithms for achieving sparsity in FT-IR spectroscopy calibration models. Sparse calibration models exclude unnecessary wavenumbers from infrared spectra during the model building process, permitting identification and evaluation of the most relevant vibrational modes of molecules in complex aerosol mixtures required to make quantitative predictions of various measures of aerosol composition. We study two types of models: one which predicts alcohol COH, carboxylic COH, alkane CH, and carbonyl CO functional group (FG) abundances in ambient samples based on laboratory calibration standards and another which predicts thermal optical reflectance (TOR) organic carbon (OC) and elemental carbon (EC) mass in new ambient samples by direct calibration of infrared spectra to a set of ambient samples reserved for calibration. We describe the development and selection of each calibration model and evaluate the effect of sparsity on prediction performance. Finally, we ascribe

  12. Active-layer thickness estimation from X-band SAR backscatter intensity

    NASA Astrophysics Data System (ADS)

    Widhalm, Barbara; Bartsch, Annett; Leibman, Marina; Khomutov, Artem

    2017-02-01

    The active layer above the permafrost, which seasonally thaws during summer, is an important parameter for monitoring the state of permafrost. Its thickness is typically measured locally, but a range of methods which utilize information from satellite data exist. Mostly, the normalized difference vegetation index (NDVI) obtained from optical satellite data is used as a proxy. The applicability has been demonstrated mostly for shallow depths of active-layer thickness (ALT) below approximately 70 cm. Some permafrost areas including central Yamal are, however, characterized by larger ALT. Surface properties including vegetation structure are also represented by microwave backscatter intensity. So far, the potential of such data for estimating ALT has not been explored. We therefore investigated the relationship between ALT and X-band synthetic aperture radar (SAR) backscatter of TerraSAR-X (averages for 10 × 10 m window) in order to examine the possibility of delineating ALT with continuous and larger spatial coverage in this area and compare it to the already-established method of using NDVI from Landsat (30 m). Our results show that the mutual dependency of ALT and TerraSAR-X backscatter on land cover types suggests a connection of both parameters. A range of 5 dB can be observed for an ALT range of 100 cm (40-140 cm), and an R2 of 0.66 has been determined over the calibration sites. An increase of ALT with increasing backscatter can be determined. The root mean square error (RMSE) over a comparably heterogeneous validation site with maximum ALT of > 150 cm is 20 cm. Deviations are larger for measurement locations with mixed vegetation types (especially partial coverage by cryptogam crust) with respect to the spatial resolution of the satellite data.

  13. 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.

  14. 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.

  15. Ion irradiation of carbonaceous interstellar analogues. Effects of cosmic rays on the 3.4 μm interstellar absorption band

    NASA Astrophysics Data System (ADS)

    Godard, M.; Féraud, G.; Chabot, M.; Carpentier, Y.; Pino, T.; Brunetto, R.; Duprat, J.; Engrand, C.; Bréchignac, P.; D'Hendecourt, L.; Dartois, E.

    2011-05-01

    Context. A 3.4 μm absorption band (around 2900 cm-1), assigned to aliphatic C-H stretching modes of hydrogenated amorphous carbons (a-C:H), is widely observed in the diffuse interstellar medium, but disappears or is modified in dense clouds. This spectral difference between different phases of the interstellar medium reflects the processing of dust in different environments. Cosmic ray bombardment is one of the interstellar processes that make carbonaceous dust evolve. Aims: We investigate the effects of cosmic rays on the interstellar 3.4 μm absorption band carriers. Methods: Samples of carbonaceous interstellar analogues (a-C:H and soot) were irradiated at room temperature by swift ions with energy in the MeV range (from 0.2 to 160 MeV). The dehydrogenation and chemical bonding modifications that occurred during irradiation were studied with IR spectroscopy. Results: For all samples and all ions/energies used, we observed a decrease of the aliphatic C-H absorption bands intensity with the ion fluence. This evolution agrees with a model that describes the hydrogen loss as caused by the molecular recombination of two free H atoms created by the breaking of C-H bonds by the impinging ions. The corresponding destruction cross section and asymptotic hydrogen content are obtained for each experiment and their behaviour over a large range of ion stopping powers are inferred. Using elemental abundances and energy distributions of galactic cosmic rays, we investigated the implications of these results in different astrophysical environments. The results are compared to the processing by UV photons and H atoms in different regions of the interstellar medium. Conclusions: The destruction of aliphatic C-H bonds by cosmic rays occurs in characteristic times of a few 108 years, and it appears that even at longer time scales, cosmic rays alone cannot explain the observed disappearance of this spectral signature in dense regions. In diffuse interstellar medium, the formation

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

    SciTech Connect

    Duley, W. W.; Hu, Anming E-mail: a2hu@uwaterloo.ca

    2012-12-20

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

  17. meso-meso linked porphyrin-[26]hexaphyrin-porphyrin hybrid arrays and their triply linked tapes exhibiting strong absorption bands in the NIR region.

    PubMed

    Mori, Hirotaka; Tanaka, Takayuki; Lee, Sangsu; Lim, Jong Min; Kim, Dongho; Osuka, Atsuhiro

    2015-02-11

    We describe the synthesis and characterization of directly meso-meso linked porphyrin-[26]hexaphyrin-porphyrin hybrid oligomers and their triply linked (completely fused) hybrid tapes. meso-meso Linked Ni(II) porphyrin-[26]hexaphyrin-Ni(II) porphyrin trimers were prepared by methanesulfonic acid-catalyzed cross-condensation of meso-formyl Ni(II) porphyrins with a 5,10-diaryltripyrrane followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The Ni(II) porphyrin moieties were converted to Zn(II) porphyrins via an indirect route involving reduction of the [26]hexaphyrin to its 28π congener, acid-induced denickelation, oxidation of the [28]hexaphyrin, and finally Zn(II) ion insertion. Over the course of these transformations, porphyrin-[28]hexaphyrin-porphyrin trimers have been revealed to take on a Möbius aromatic twisted structure for the [28]hexaphyrin segment. Oxidation of meso-meso linked hybrid trimer bearing 5,15-diaryl Zn(II) porphyrins with DDQ/Sc(OTf)3 under mild conditions resulted in meso-meso coupling oligomerization, affording the corresponding dimeric (hexamer), trimeric (nonamer), and tetrameric (dodecamer) oligomers. On the other hand, oxidation of a meso-meso linked hybrid trimer bearing 5,10,15-triaryl Zn(II) porphyrin terminals with DDQ/Sc(OTf)3 under harsher conditions afforded a meso-meso, β-β, β-β triply linked hybrid porphyrin tape, which displays a sharp and intense absorption band at 1912 nm. Comparison of this extremely red-shifted absorption band with those of Zn(II) porphyrin tapes suggests that the bathochromic-shifting capability of a [26]hexaphyrin unit is large, almost equivalent to that of four individual Zn(II) porphyrin units. As demonstrated, the fusion of porphyrins to [26]hexaphyrin offers an efficient means to expand their conjugation networks, significantly expanding the capabilities attainable for these chromophores.

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

    USGS Publications Warehouse

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

    1999-01-01

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

  19. Presence of terrestrial atmospheric gas absorption bands in standard extraterrestrial solar irradiance curves in the near-infrared spectral region.

    PubMed

    Gao, B C; Green, R O

    1995-09-20

    The solar irradiance curves compiled by Wehrli [Physikalisch-Meteorologisches Observatorium Publ. 615 (World Radiation Center, Davosdorf, Switzerland, 1985)] and by Neckel and Labs [Sol. Phys. 90, 205 (1984)] are widely used. These curves were obtained based on measurements of solar radiation from the ground and from aircraft platforms. Contaminations in these curves by atmospheric gaseous absorptions were inevitable. A technique for deriving the transmittance spectrum of the Sun's atmosphere from high-resolution (0.01 cm(-1)) solar occultation spectra measured above the Earth's atmosphere by the use of atmospheric trace molecule spectroscopy (ATMOS) aboard the space shuttle is described. The comparisons of the derived ATMOS solar transmittance spectrum with the two solar irradiance curves show that he curve derived by Wehrli contains many absorption features in the 2.0-2.5-µm region that are not of solar origin, whereas the curve obtained by Neckel and Labs is completely devoid of weak solar absorption features that should be there. An Earth atmospheric oxygen band at 1.268 µm and a water-vapor band near 0.94 µm are likely present in the curve obtained by Wehrli. It is shown that the solar irradiance measurement errors in some narrow spectral intervals can be as large as 20%. An improved solar irradiance spectrum is formed by the incorporation of the solar transmittance spectrum derived from the ATMOS data into the solar irradiance spectrum from Neckel and Labs. The availability of a new solar spectrum from 50 to 50 000 cm(-1) from the U.S. Air Force Phillips Laboratory is also discussed.

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

    SciTech Connect

    Zhang, J.H.; Ding, J.W.; Cao, J.X.; Zhang, Y.L.

    2011-03-15

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

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

    PubMed

    Bruggemann, B; May, V

    2004-02-01

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

  2. 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.

  3. Broad Band Light Absorption and High Photocurrent of (In,Ga)N Nanowire Photoanodes Resulting from a Radial Stark Effect.

    PubMed

    Kamimura, Jumpei; Bogdanoff, Peter; Corfdir, Pierre; Brandt, Oliver; Riechert, Henning; Geelhaar, Lutz

    2016-12-21

    The photoelectrochemical properties of (In,Ga)N nanowire photoanodes are investigated using H2O2 as a hole scavenger to prevent photocorrosion. Under simulated solar illumination, In0.16Ga0.84N nanowires grown by plasma-assisted molecular beam epitaxy show a high photocurrent of 2.7 mA/cm(2) at 1.2 V vs reversible hydrogen electrode. This value is almost the theoretical maximum expected from the corresponding band gap (2.8 eV) for homogeneous bulk material without taking into account surface effects. These nanowires exhibit a higher incident photon-to-current conversion efficiency over a broader wavelength range and a higher photocurrent than a compact layer with higher In content of 28%. These results are explained by the combination of built-in electric fields at the nanowire sidewall surfaces and compositional fluctuations in (In,Ga)N, which gives rise to a radial Stark effect. This effect enables spatially indirect transitions at energies much lower than the band gap. The resulting broad band light absorption leads to high photocurrents. This benefit of the radial Stark effect in (In,Ga)N nanowires for solar harvesting applications opens up the perspective to break the theoretical limit for photocurrents.

  4. 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.

  5. 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

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

    PubMed

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

    2012-06-21

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

  7. 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.

  8. 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

  9. 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) 2·4H 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) 2·4H 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

  10. On the Use of Difference Bands for Modeling SF_6 Absorption in the 10μm Atmospheric Window

    NASA Astrophysics Data System (ADS)

    Faye, Mbaye; Manceron, Laurent; Roy, P.; Boudon, Vincent; Loete, Michel

    2016-06-01

    To model correctly the SF_6 atmospheric absorption requires the knowledge of the spectroscopic parameters of all states involved in the numerous hot bands in the 10,5μm atmospheric transparency window. However, due to their overlapping, a direct analysis of the hot bands near the 10,5μm absorption of SF_6 in the atmospheric window is not possible. It is necessary to use another strategy, gathering information in the far and mid infrared regions on initial and final states to compute the relevant total absorption. In this talk, we present new results from the analysis of spectra recorded at the AILES beamline at the SOLEIL Synchrotron facility. For these measurements, we used a IFS125HR interferometer combined with the synchrotron radiation in the 100-3200 wn range, coupled to a cryogenic multiple pass cell. The optical path length was varied from 45 to 141m with measuring temperatures between 223 and 153+/-5 K. The new information obtained on νb{2}+νb{4}-νb{5}, 2νb{5}-νb{6} and νb{3}+νb{6}-νb{4} allowed to derive improved parameters for νb{5}, 2νb{5} and νb{3}+νb{6}. In turn, they are used to model the more important νb{3}+νb{5}-νb{5} and νb{3}+νb{6}-νb{6} hot band contributions. By including these new parameters in the XTDS model, we substantially improved the SF_6 parameters used to model the atmosphere. F. Kwabia Tchana, F. Willaert, X. Landsheere, J. M. Flaud, L. Lago, M. Chapuis, P. Roy, L. Manceron. A new, low temperature long-pass cell for mid-IR to THz Spectroscopy and Synchrotron Radiation Use. Rev. Sci. Inst. 84, 093101, (2013) C. Wenger, V. Boudon, M. Rotger, M. Sanzharov, and J.-P. Champion,"XTDS and SPVIEW: Graphical tools for Analysis and Simulation of High Resolution Molecular Spectra", J. Mol. Spectrosc. 251, 102 (2008)

  11. A thermal broadening analysis of absorption spectra of the D1/D2/cytochrome b-559 complex in terms of Gaussian decomposition sub-bands.

    PubMed

    Cattaneo, R; Zucchelli, G; Garlaschi, F M; Finzi, L; Jennings, R C

    1995-11-21

    Absorption spectra of the isolated D1/D2/cytochrome b-559 complex have been measured in the temperature range 80-300 K. All spectra were analyzed in terms of a linear combination of Gaussian bands and the thermal broadening data interpreted in terms of a model in which the spectrum of each pigment site is broadened by (a) a homogeneous component due to linear electron-phonon coupling to a low-frequency protein vibration and (b) an inhomogeneous component associated with stochastic fluctuations at each pigment site. In order to obtain a numerically adequate description of the absorption spectra, a minimum number of five sub-bands is required. Further refinement of this sub-band description was achieved by taking into account published data from hole burning and absorption difference spectroscopy. In this way, both a six sub-band description and a seven sub-band description were generated. In arriving at the seven sub-band description, the original five sub-band wavelength positions were essentially unchanged. Thermal broadening analysis of the seven sub-band description yielded data which displayed the closest correspondence with the literature observations. The wavelength positions of the sub-bands were near 661, 667, 670, and 675 nm, with two bands near 680 and 684 nm. The two almost isoenergetic sub-bands near 680 nm, identified as P680 and pheophytin, have optical reorganization energies around 40 and 16 cm-1, respectively. All other sub-bands, identified as accessory pigments, have optical reorganization energies close to 16 cm-1.(ABSTRACT TRUNCATED AT 250 WORDS)

  12. 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.

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

    NASA Technical Reports Server (NTRS)

    Ockert, Maureen E.; Nelson, Robert M.; Lane, Arthur L.; Matson, Dennis L.

    1987-01-01

    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.

  14. 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.; Brédas, 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.

  15. Energy conversion within infrared plasmonic absorption metamaterials for multi-band resonance

    NASA Astrophysics Data System (ADS)

    Li, Yongqian; Su, Lei; Xu, Xiaolun; Zhang, Chenglin; Wang, Binbin

    2015-05-01

    The energy conversion within the cross-shaped plasmonic absorber metamaterials (PAM) was investigated theoretically and numerically in the infrared range based on the Poynting's theorem of electromagnetic energy. From the microscopic details, the heat generation owing to the electric current accounts for the majority of the energy conversion, while the magnetic resonance plays a negligible role. The PAMs possess three distinct resonant peaks standing independently, which are attributed to the polarization sensitive excitation of plasmonic resonance. Field redistribution and enhancement associated with multiplex resonant electromagnetic wave passing through the PAM medium provided insight into the energy conversion processes inside the nanostructure. The research results will assist the design of novel plasmon enhanced infrared detectors with multiple-band detection.

  16. Off-resonant squeezed vacuum effects on a driven two-level atom: absorption and intensity harmonics

    NASA Astrophysics Data System (ADS)

    Hassan, S. S.; Frege, O. M.; Nayak, N.

    1995-07-01

    The resonance fluorescence system of a coherently driven two-level atom in the presence of a broadband squeezed vacuum field whose central frequency is not in resonance with either the driving field frequency or the atomic transition frequency is analyzed. Solutions of the Bloch equations of the system are presented in terms of continued fractions for arbitrary strength of the coherent driving field. Numerical results are presented for the first-harmonic quadrature components of the absorption spectrum and the fluorescent intensity. The effects of the squeezed vacuum field detuning on the absorption spectrum result in hole burning or a dip structure in the weak-field case and two absorption-amplification peaks in the strong-field case. Results are sensitive to the relative phase of the squeezed vacuum.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Currently, NASA Langley Research Center (LaRC) and ITT are jointly developing algorithms for demonstration of range discrimination using ITT's laser absorption spectrometer (LAS), which is being evaluated for the future NASA Active Sensing of CO2 Emissions during Nights, Days, and Seasons (ASCENDS) mission. The objective of this Decadal Survey mission is to measure atmospheric column CO2 mixing ratios (XCO2) for improved determination of atmospheric carbon sources and sinks. Intensity Modulated Continuous Wave (IM-CW) techniques are used in this LAS approach. The LAS is designed to simultaneously measure CO2 and O2 columns, and these measurements are used to determine the required XCO2 column. The LAS measurements are enabled by the multi-channel operation of the instrument at 1.57 and 1.26-um for CO2 and O2, respectively. The algorithm development for the IM-CW techniques of the multi-channel LAS is focused on addressing key retrieval issues such as surface signal detection, thin cloud and/or aerosol layer rejection, vertical atmospheric range resolution, and optimizing the size of the measurement footprint. With these considerations, the modulation algorithm needs to maintain high enough signal-to-noise ratio (SNR) so that the mission scientific goals can be reached. A basic selection of the modulation algorithms that make XCO2 measurement and thin cloud rejection possible is the stepped frequency modulation scheme and a similar scheme of swept sine modulation. The differences between these two schemes for thin cloud rejection are small, assuming the proper selection of parameters is made. The stepped frequency approach is only a quantified version of swept sine method for the frequencies used. Swept sine scheme is a very common modulation technique for range discrimination, while the consideration of the stepped frequency scheme is based on the history of the rolling-tone modulation used in the instrument in previous successful column CO2 measurements. The

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

    PubMed

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

    2013-04-08

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

  19. Thermodynamic consequence of the new attribution of bands in the electronic absorption spectrum of electron donor-iodine-solvent systems

    NASA Astrophysics Data System (ADS)

    Abramov, Sergey P.

    1999-06-01

    The subject review pays attention to the peculiarities in behaviour of bands in the electronic absorption spectra of electron donor-iodine-solvent systems, the appearance of which is associated with the intermolecular interaction of molecular iodine with electron donor organic molecules. The new concept of the bands’ attribution to the isomeric equilibrium molecular charge-transfer complexes (CTCs) of CTC-I and CTC-II types is considered. The features of possible phase transitions in the solid state are discussed on the basis of the thermodynamic properties and electronic structures of the CTC-I and CTC-II in electron donor-iodine-solvent systems. The stabilisation of the CTC-II structure with the temperature lowering coincided in many cases with the electrons’ localisation in the solid state structures having charge-transfer bonds.

  20. 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)

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

    Recent improvements in high spectral resolution measurements of methane absorption at wavenumbers between 4800 cm-1 and 7919 cm-1 have greatly increased the number of lines with known lower state energies, the number of weak lines, and the number of lines observed at low temperatures (Campargue, A., Wang, L., Kassi, S., Mašát, M., Votava, O. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1141-1151; Campargue, A., Wang, L., Liu, A.W., Hu, S.M., Kassi, S. [2010]. Chem. Phys. 373, 203-210; Mondelain, D., Kassi, S., Wang, L.C. [2011]. Phys. Chem. Chem. Phys. 13, 7985-7996; Nikitin, A.V. et al. [2011a]. J. Mol. Spectrosc. 268, 93-106; Nikitin, A.V. et al. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 2211-2224; Wang, L., Kassi, S., Campargue, A. [2010]. J. Quant. Spectrosc. Radiat. Trans. 111, 1130-1140; Wang, L., Kassi, S., Liu, A.W., Hu, S.M., Campargue, A. [2011]. J. Quant. Spectrosc. Radiat. Trans. 112, 937-951), making it possible to fit near-IR spectra of Titan using line-by-line calculations instead of band models (Bailey, J., Ahlsved, L., Meadows, V.S. [2011]. Icarus 213, 218-232; de Bergh, C. et al. [2011]. Planet. Space Sci. doi:10.1016/j.pss.2011.05.003). Using these new results, we compiled an improved line list relative that used by Bailey et al. by updating several spectral regions with either calculated or more recently measured line parameters, revising lower state energy estimates for lines lacking them, and adding room temperature lines to make the list applicable over a wider range of temperatures. We compared current band models with line-by-line calculations using this new line list, both to assess the behavior of band models, and to identify remaining issues with line-by-line calculations when applied to outer planet atmospheres and over a wider range of wavelengths. Comparisons were made for a selection of uniform paths representing outer planet conditions and for representative non-uniform paths within the atmospheres of Uranus, Saturn

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

    PubMed

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

    2008-08-14

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

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

    PubMed

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

    2014-06-04

    Perovskite-based solar cells have recently been catapulted to the cutting edge of thin-film photovoltaic research and development because of their promise for high-power conversion efficiencies and ease of fabrication. Two types of generic perovskites compounds have been used in cell fabrication: either Pb- or Sn-based. Here, we describe the performance of perovskite solar cells based on alloyed perovskite solid solutions of methylammonium tin iodide and its lead analogue (CH3NH3Sn(1-x)Pb(x)I3). We exploit the fact that, the energy band gaps of the mixed Pb/Sn compounds do not follow a linear trend (the Vegard's law) in between these two extremes of 1.55 and 1.35 eV, respectively, but have narrower bandgap (<1.3 eV), thus extending the light absorption into the near-infrared (~1,050 nm). A series of solution-processed solid-state photovoltaic devices using a mixture of organic spiro-OMeTAD/lithium bis(trifluoromethylsulfonyl)imide/pyridinium additives as hole transport layer were fabricated and studied as a function of Sn to Pb ratio. Our results show that CH3NH3Sn(0.5)Pb(0.5)I3 has the broadest light absorption and highest short-circuit photocurrent density ~20 mA cm(-2) (obtained under simulated full sunlight of 100 mW cm(-2)).

  4. The first UV absorption band for indole is not due to two simultaneous orthogonal electronic transitions differing in dipole moment.

    PubMed

    Catalán, Javier

    2015-05-21

    The currently accepted model for the photophysics of indole assumes that the first UV absorption band encompasses two orthogonal electronic transitions ((1)Lb and (1)La), leading to two electronic states with a markedly different dipole moment. However, there is a body of evidence not explained by this model, which led us to develop a new photophysical model for indole. Based on the new model, the polarity of the electronic ground state (S0) in indoles is very similar to that of the first electronic excited state (S1) producing this structured emission; however, this excited state can lead to a highly dipolar excited state (S1') with largely structureless emission under the influence of the polarity of the medium, and also, very likely, of its viscosity. The molecular structure of the new excited state can be reversibly converted into the normal structure of the compound. Previous observations were confirmed by the absorption, emission, and excitation spectra for indole, as well as by its polarized emission and excitation spectra in various media. Thus, the polarized emission spectra for indole in glycerol at 283 K and 223 K showed the transition dipole moments for the emission from the first two excited states in a polar medium, S1 and S1', to differ by less than 20°.

  5. 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.

  6. Ultrafast Time-Resolved Emission and Absorption Spectra of meso-Pyridyl Porphyrins upon Soret Band Excitation Studied by Fluorescence Up-Conversion and Transient Absorption Spectroscopy.

    PubMed

    Venkatesh, Yeduru; Venkatesan, M; Ramakrishna, B; Bangal, Prakriti Ranjan

    2016-09-08

    A comprehensive study of ultrafast molecular relaxation processes of isomeric meso-(pyridyl) porphyrins (TpyPs) has been carried out by using femtosecond time-resolved emission and absorption spectroscopic techniques upon pumping at 400 nm, Soret band (B band or S2), in 4:1 dichloromethane (DCM) and tetrahydrofuran (THF) solvent mixture. By combined studies of fluorescence up-conversion, time-correlated single photon counting, and transient absorption spectroscopic techniques, a complete model with different microscopic rate constants associated with elementary processes involved in electronic manifolds has been reported. Besides, a distinct coherent nuclear wave packet motion in Qy state is observed at low-frequency mode, ca. 26 cm(-1) region. Fluorescence up-conversion studies constitute ultrafast time-resolved emission spectra (TRES) over the whole emission range (430-710 nm) starting from S2 state to Qx state via Qy state. Careful analysis of time profiles of up-converted signals at different emission wavelengths helps to reveal detail molecular dynamics. The observed lifetimes are as indicated: A very fast decay component with 80 ± 20 fs observed at ∼435 nm is assigned to the lifetime of S2 (B) state, whereas being a rise component in the region of between 550 and 710 nm emission wavelength pertaining to Qy and Qx states, it is attributed to very fast internal conversion (IC) occurring from B → Qy and B → Qx as well. Two distinct components of Qy emission decay with ∼200-300 fs and ∼1-1.5 ps time constants are due to intramolecular vibrational redistribution (IVR) induced by solute-solvent inelastic collisions and vibrational redistribution induced by solute-solvent elastic collision, respectively. The weighted average of these two decay components is assigned as the characteristic lifetime of Qy, and it ranges between 0.3 and 0.5 ps. An additional ∼20 ± 2 ps rise component is observed in Qx emission, and it is assigned to the formation time of

  7. Absorption of Light by Free Charge Carriers in the Crystalline CdS Under Intense Electron Irradiation

    NASA Astrophysics Data System (ADS)

    Kulikov, V. D.; Yakovlev, V. Yu.

    2016-09-01

    The process of light absorption by free electrons in the crystalline cadmium sulfide under irradiation by a nanosecond electron beam with the current density of 8-100 A/cm2 is studied. A superlinear increase in optical absorption is observed if the beam current density is increased from ~8 to 12 A/cm2. The nature of light absorption by thermalized electrons corresponds to the scattering on lattice defects. An increase in the exponent of the power dependence of light absorption on the wavelength with increasing beam current density is associated with the single and double ionization of donors and acceptors. It is concluded that accumulation of charge carriers occurs without capture by traps due to their impact ionization by secondary electrons, whose energy in the thermalization stage is comparable with the band gap of the crystal. According to the results of calculations, the capture cross section of electrons by holes at quadratic recombination is ~10-20 cm2, the Auger recombination coefficient is ~10-31 cm6•s-1, and the charge carrier concentration is ~1.3•1018-1.5•1019 cm-3.

  8. 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 (2.5–3.5 kHz 130 dB SPL, 1 h). The guinea pigs in the control group received no treatment. The hearing function was assessed by the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) recording. The changes of free radicals in the cochlea before noise exposure, and immediately and 7 days after noise exposure were also examined. By Scanning electron microscopy and succinate dehydrogenase staining, we found that pre-treatment with hydrogen-saturated saline significantly reduced noise-induced hair cell damage and hearing loss. We also found that the malondialdehyde, lipid peroxidation, and hydroxyl levels were significantly lower in the hydrogen-saturated saline group after noise trauma, indicating that hydrogen-saturated saline can decrease the amount of harmful free radicals caused by noise trauma. Our findings suggest that hydrogen-saturated saline is effective in preventing intensive narrow band noise-induced hearing loss through the antioxidant effect. PMID:24945316

  9. Hydrogen-saturated saline protects intensive narrow band noise-induced hearing loss in guinea pigs through an antioxidant effect.

    PubMed

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

  10. 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.

  11. 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.

  12. 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.

  13. 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

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

    PubMed

    Lifshitz, A; Skinner, G B; Wood, D R

    1978-09-01

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

  15. Combined Nonlinear Effects in Two-Photon Absorption Chromophores at High Intensities (Preprint)

    DTIC Science & Technology

    2006-08-01

    solutions in THF(cic1es). The solid lines are a Voigt function fit to the data. We seek a simple analytical model that can adequately explain and reliably...photophysical measurements on a system of AFX chromophores and calculate the nonlinear transmission based on an effective three-level model. A numerical... calculate the nonlinear transmission based on an effective three-level model. A numerical model that in- cludes far wing linear absorption has been

  16. Improved Experimental Line Positions for the (1,1) Band of the b 1Σ+ - X 3Σ- Transition of O2 by Intracavity Laser Absorption Spectroscopy

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    We report improved experimental line positions for the (1,1) band of the b 1Σ+ - X 3Σ- transition of O2. Results are comparised with previous experimental measurements and predicted values. Additionally, a new method of producing vibrationally hot molecules for use in absorption spectroscopy of stable gas phase molecules is described.

  17. Dipole Strength Calculation Based on Two-Level System Approximation to Study Q/B-Band Intensity Ratio of ZnTBP in Solvent

    NASA Astrophysics Data System (ADS)

    Rusydi, Febdian; Shukri, Ganes; Saputro, Adithya G.; Agusta, Mohammad K.; Dipojono, Hermawan K.; Suprijadi, Suprijadi

    2017-04-01

    We study the Q/B-band dipole strength of zinc tetrabenzoporphyrin (ZnTBP) using density functional theory (DFT) in various solvents. The solvents are modeled using the polarized continuum model (PCM). The dipole strength calculations are approached by a two-level system, where the Q-band is described by the HOMO → LUMO electronic transition and the B-band by the HOMO-1 → LUMO electronic transition. We compare the results with the experimental data of the Q/B-band intensity ratio. We also perform time-dependent DFT coupled with PCM to calculate the Q/B-band oscillator strength ratio of ZnTBP. The results of both methods show a general trend with respect to the experimental Q/B-band intensity ratio in solvents, except for the calculation in the water solvent. Even so, the approximation is a good starting point for studying the UV-vis spectrum based on DFT study alone.

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

    PubMed

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

    2014-11-21

    Three new thiazolo[5,4-d]thiazole-based organic dyes have been designed and synthesized for employment as DSSC sensitizers. Alternation of the electron poor thiazolothiazole unit with two propylenedioxythiophene (ProDOT) groups ensured very intense light absorption in the visible region (ε up to 9.41 × 10(4) M(-1) cm(-1) in THF solution). The dyes were particularly suitable for application in transparent and opaque thin-layer DSSCs (TiO2 thickness: 5.5-6.5 μm, efficiencies up to 7.71%), thus being good candidates for production of solar cells under simple fabrication conditions.

  19. 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, ɛ.

  20. Effect of orthohydrogen impurity on the absorption intensities of single transitions in a solid parahydrogen crystal

    NASA Astrophysics Data System (ADS)

    Mishra, Adya P.; D'Souza, Richard; Balasubramanian, T. K.

    2006-02-01

    This paper provides insights for the accurate calculation of theoretical intensities of single transitions in a parahydrogen crystal containing trace amounts of orthohydrogen impurity. From the ratio of the experimental intensity to that of theoretical one (α/α) we can deduce the value of the phonon renormalization factors, which are not easily amenable for calculations, a priori and are customarily set equal to unity. The ratio α/α for S transitions varies over a wide range from 0.15 to 0.94. Different reasons are advanced for this wide variation and remedy suggested. A more careful experimental measurement of the intensity of single transitions in a parahydrogen crystal at different, carefully controlled, orthohydrogen concentrations is desirable. The accurate knowledge of the ratio α/α will then lead to a detailed understanding of the theory of phonon renormalization factors in quantum solids.

  1. 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).

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Effect of thickness on microwave absorptive behavior of La-Na doped Co-Zr barium hexaferrites in 18.0-26.5 GHz band

    NASA Astrophysics Data System (ADS)

    Arora, Amit; Narang, Sukhleen Bindra; Pubby, Kunal

    2017-02-01

    In this research, the microwave properties of Lanthanum-Sodium doped Cobalt-Zirconium barium hexaferrites, intended as microwave absorbers, are analyzed on Vector Network Analyzer in K-band. The results indicate that the doping has resulted in lowering of real permittivity and enhancement of dielectric losses. Real permeability has shown increase while magnetic losses have shown decrease in value with doping. All these four properties have shown very small variation with frequency in the scanned frequency range which indicates the relaxation type of behavior. Microwave absorption characteristics of these compositions are analyzed with change in sample thickness. The results demonstrate that the matching frequency of the microwave absorber shifts towards lower side of frequency band with increase in thickness. The complete analysis of the prepared microwave absorbers shows a striking achievement with very low reflection loss and wide absorption bandwidth for all the six compositions in 18-26.5 GHz frequency band.

  7. A tunable, linac based, intense, broad-band THz source forpump-probe experiments

    SciTech Connect

    Schmerge, J.; Adolphsen, C.; Corbett, J.; Dolgashev, V.; Durr, H.; Fazio, M.; Fisher, A.; Frisch, J.; Gaffney, K.; Guehr, M.; Hastings, J.; Hettel, B.; Hoffmann, M.; Hogan, M.; Holtkamp, N.; Huang, X.; Huang, Z.; Kirchmann, P.; LaRue, J.; Limborg, C.; Lindenberg, A.; Loos, H.; Maxwell, T.; Nilsson, A.; Raubenheimer, T.; Reis, D.; Ross, M.; Shen, Z. -X.; Stupakov, G.; Tantawi, S.; Tian, K.; Wu, Z.; Xiang, D.; Yakimenko, V.

    2015-02-02

    We propose an intense THz source with tunable frequency and bandwidth that can directly interact with the degrees of freedom that determine the properties of materials and thus provides a new tool for controlling and directing these ultrafast processes as well as aiding synthesis of new materials with new functional properties. This THz source will broadly impact our understanding of dynamical processes in matter at the atomic-scale and in real time. Established optical pumping schemes using femtosecond visible frequency laser pulses for excitation are extended into the THz frequency regime thereby enabling resonant excitation of bonds in correlated solid state materials (phonon pumping), to drive low energy electronic excitations, to trigger surface chemistry reactions, and to all-optically bias a material with ultrashort electric fields or magnetic fields. A linac-based THz source can supply stand-alone experiments with peak intensities two orders of magnitude stronger than existing laser-based sources, but when coupled with atomic-scale sensitive femtosecond x-ray probes it opens a new frontier in ultrafast science with broad applications to correlated materials, interfacial and liquid phase chemistry, and materials in extreme conditions.

  8. Cloud top height retrieval using the imaging polarimeter (3MI) top-of-atmosphere reflectance measurements in the oxygen absorption band

    NASA Astrophysics Data System (ADS)

    Kokhanovsky, Alexander; Munro, Rose

    2016-04-01

    The determination of cloud top height from a satellite has a number of applications both for climate studies and aviation safety. A great variety of methods are applied using both active and passive observation systems in the optical and microwave spectral regions. One of the most popular methods with good spatial coverage is based on the measurement of outgoing radiation in the spectral range where oxygen strongly absorbs incoming solar light. Clouds shield tropospheric oxygen reducing the depth of the corresponding absorption line as detected by a satellite instrument. Radiative transfer models are used to connect the solar light reflectance, e.g., in the oxygen A-band located around 761nm, and the cloud top height. The inverse problem is then solved e.g. using look-up tables, to determine the cloud top height. In this paper we propose a new fast and robust oxygen A-band method for the retrieval of cloud altitude using the Multi-viewing Multi-channel Multi-polarization Imaging instrument (3MI) on board the EUMETSAT Polar System Second Generation (EPS-SG). The 3MI measures the intensity at the wavelengths of 410, 443, 490, 555, 670, 763, 765, 865, 910, 1370, 1650, and 2130nm, and (for selected channels) the second and third Stokes vector components which allows the degree of linear polarization and the polarization orientation angle of reflected solar light to be derived at up to 14 observation angles. The instrument response function (to a first approximation) can be modelled by a Gaussian distribution with the full width at half maximum (FWHM) equal to 20nm for all channels except 765nm, 865nm, 1370nm, 1650nm, and 2130nm, where it is equal to 40nm. The FWHM at 763nm (the oxygen A-band location) is equal to 10nm. The following 3MI channels are used in the retrieval procedure: 670, 763, and 865nm. The channels at 670 and 865 nm are not affected by the oxygen absorption. The channel at 763nm is affected by the oxygen concentration vertical profile. The higher

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

    PubMed

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

    2011-07-04

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

  10. Big brown bats (Eptesicus fuscus) maintain hearing sensitivity after exposure to intense band-limited noise.

    PubMed

    Simmons, Andrea Megela; Hom, Kelsey N; Simmons, James A

    2017-03-01

    Thresholds to short-duration narrowband frequency-modulated (FM) sweeps were measured in six big brown bats (Eptesicus fuscus) in a two-alternative forced choice passive listening task before and after exposure to band-limited noise (lower and upper frequencies between 10 and 50 kHz, 1 h, 116-119 dB sound pressure level root mean square; sound exposure level 152 dB). At recovery time points of 2 and 5 min post-exposure, thresholds varied from -4 to +4 dB from pre-exposure threshold estimates. Thresholds after sham (control) exposures varied from -6 to +2 dB from pre-exposure estimates. The small differences in thresholds after noise and sham exposures support the hypothesis that big brown bats do not experience significant temporary threshold shifts under these experimental conditions. These results confirm earlier findings showing stability of thresholds to broadband FM sweeps at longer recovery times after exposure to broadband noise. Big brown bats may have evolved a lessened susceptibility to noise-induced hearing losses, related to the special demands of echolocation.

  11. 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.

  12. Investigation of the optical-absorption bands of Nb4+ and Ti3+ in lithium niobate using magnetic circular dichroism and optically detected magnetic-resonance techniques

    NASA Astrophysics Data System (ADS)

    Reyher, H.-J.; Schulz, R.; Thiemann, O.

    1994-08-01

    The magnetic circular dichroism (MCD) of the absorption of Nb4+Li and Ti3+Li centers in LiNbO3 has been selectively measured by applying optically detected magnetic resonance. The attribution of a well-known broad and unstructured absorption band peaking at 1.6 eV to the Nb4+Li bound small polaron is now unambiguously confirmed. In the MCD spectrum of the isoelectronic Ti3+Li center, bands show up, which closely resemble the MCD bands at 1.6 eV of this bound small polaron. This striking similarity is explained by a cluster model, representing both defects. Either TiLi or NbLi is at the center of this cluster. In both cases, the small polaron is bound to the cluster, and its MCD bands correspond to intervalence transfer transitions within the constituents of the cluster. A study of the spin-orbit coupling of the molecular orbitals of the cluster allows one to analyze the structure of the MCD bands at 2.9 eV of Ti3+Li have no counterpart in the Nb4+Li spectrum. These bands are assigned to transitions to excited states, which are specific to the impurity and are related to the 10Dq transitions known for the crystal field states of a d1 ion.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

    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.

  15. 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)

  16. Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience

    NASA Astrophysics Data System (ADS)

    Verma, Ajay; Baishya, Bikash

    2016-05-01

    "Pure shift" NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording.

  17. Real-time bilinear rotation decoupling in absorptive mode J-spectroscopy: Detecting low-intensity metabolite peak close to high-intensity metabolite peak with convenience.

    PubMed

    Verma, Ajay; Baishya, Bikash

    2016-05-01

    "Pure shift" NMR spectra display singlet peak per chemical site. Thus, high resolution is offered at the cost of valuable J-coupling information. In the present work, real-time BIRD (BIlinear Rotation Decoupling) is applied to the absorptive-mode 2D J-spectroscopy to provide pure shift spectrum in the direct dimension and J-coupling information in the indirect dimension. Quite often in metabolomics, proton NMR spectra from complex bio-fluids display tremendous signal overlap. Although conventional J-spectroscopy in principle overcomes this problem by separating the multiplet information from chemical shift information, however, only magnitude mode of the experiment is practical, sacrificing much of the potential high resolution that could be achieved. Few J-spectroscopy methods have been reported so far that produce high-resolution pure shift spectrum along with J-coupling information for crowded spectral regions. In the present work, high-quality J-resolved spectrum from important metabolomic mixture such as tissue extract from rat cortex is demonstrated. Many low-intensity metabolite peaks which are obscured by the broad dispersive tails from high-intensity metabolite peaks in regular magnitude mode J-spectrum can be clearly identified in real-time BIRD J-resolved spectrum. The general practice of removing such spectral overlap is tedious and time-consuming as it involves repeated sample preparation to change the pH of the tissue extract sample and subsequent spectra recording.

  18. 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

  19. Optimal frequency selection of multi-channel O2-band different absorption barometric radar for air pressure measurements

    NASA Astrophysics Data System (ADS)

    Lin, Bing; Min, Qilong

    2017-02-01

    Through theoretical analysis, optimal selection of frequencies for O2 differential absorption radar systems on air pressure field measurements is achieved. The required differential absorption optical depth between a radar frequency pair is 0.5. With this required value and other considerations on water vapor absorption and the contamination of radio wave transmission, frequency pairs of present considered radar system are obtained. Significant impacts on general design of differential absorption remote sensing systems are expected from current results.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2003-03-01

    Spectroscopic and laser properties of three different Er3+-doped garnet systems are characterized by employing the Judd-Ofelt (JO) analysis. The three garnet hosts are Y3Al5O12 (YAG), Y3Sc2Ga3O12 (YSGG), and Gd3Ga5O12 (GGG). The JO model has been applied to the room temperature absorption intensities of Er3+ (4f11) transitions to establish the so-called JO intensity parameters: Ω2, Ω4, and Ω6 in the three garnet hosts. The intensity parameters are used to determine the radiative decay rates (emission probabilities of transitions) and branching ratios of the Er3+ transitions from the excited state J manifolds to the lower-lying J' manifolds. The predicted decay rates and branching ratios of these Er3+ transitions in YAG, YSGG, and GGG hosts are compared. From the radiative decay rates, the radiative lifetimes of the Er3+ excited states are determined in the three garnets and are also compared. We also report the spectroscopic quality factors, Ω4/Ω6, obtained for the three garnets. The quantum efficiencies of the 4I13/2→4I15/2 Er3+ transition in YAG, YSGG, and GGG are determined to be ˜79%, 82%, and 85%, respectively.

  2. 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.

  3. Indirect optical absorption and origin of the emission from β-FeSi2 nanoparticles: Bound exciton (0.809 eV) and band to acceptor impurity (0.795 eV) transitions

    NASA Astrophysics Data System (ADS)

    Lang, R.; Amaral, L.; Meneses, E. A.

    2010-05-01

    We investigated the optical absorption of the fundamental band edge and the origin of the emission from β-FeSi2 nanoparticles synthesized by ion-beam-induced epitaxial crystallization of Fe+ implanted SiO2/Si(100) followed by thermal annealing. From micro-Raman scattering and transmission electron microscopy measurements it was possible to attest the formation of strained β-FeSi2 nanoparticles and its structural quality. The optical absorption near the fundamental gap edge of β-FeSi2 nanoparticles evaluated by spectroscopic ellipsometry showed a step structure characteristic of an indirect fundamental gap material. Photoluminescence spectroscopy measurements at each synthesis stage revealed complex emissions in the 0.7-0.9 eV spectral region, with different intensities and morphologies strongly dependent on thermal treatment temperature. Spectral deconvolution into four transition lines at 0.795, 0.809, 0.851, and 0.873 eV was performed. We concluded that the emission at 0.795 eV may be related to a radiative direct transition from the direct conduction band to an acceptor level and that the emission at 0.809 eV derives from a recombination of an indirect bound exciton to this acceptor level of β-FeSi2. Emissions 0.851 and 0.873 eV were confirmed to be typical dislocation-related photoluminescence centers in Si. From the energy balance we determined the fundamental indirect and direct band gap energies to be 0.856 and 0.867 eV, respectively. An illustrative energy band diagram derived from a proposed model to explain the possible transition processes involved is presented.

  4. Polarization and field dependent two-photon absorption in GaAs/AlGaAs multiquantum well waveguides in the half-band gap spectral region

    NASA Astrophysics Data System (ADS)

    Tsang, H. K.; Penty, R. V.; White, I. H.; Grant, R. S.; Sibbett, W.; Soole, J. B. D.; LeBlanc, H. P.; Andreadakis, N. C.; Colas, E.; Kim, M. S.

    1991-12-01

    We report the observation of two photon absorption which is strongly dependent on the applied electric field and the optical polarization. At 1.55 μm wavelength, the two-photon absorption coefficient of the GaAs/AlGaAs multiquantum well (MQW) waveguides for transverse-magnetic light is about seven times lower than for transverse-electric polarized light and changes by a factor of approximately 4 for a change in applied direct-current electric field of ˜140 kV/cm. Ultrafast nonlinear refraction causing phase changes of over π radians without appreciable excess loss is observed. These measurements demonstrate that GaAs/AlGaAs MQW waveguides could be successfully used for subpicosecond all-optical switching near half-band gap, at wavelengths corresponding to the 1.55 μm optical communications band.

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

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Schmitt, B.

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

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

    NASA Astrophysics Data System (ADS)

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

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

  7. Enhanced Microwave Absorption Properties by Tuning Cation Deficiency of Perovskite Oxides of Two-Dimensional LaFeO3/C Composite in X-Band.

    PubMed

    Liu, Xiang; Wang, Lai-Sen; Ma, Yating; Zheng, Hongfei; Lin, Liang; Zhang, Qinfu; Chen, Yuanzhi; Qiu, Yulong; Peng, Dong-Liang

    2017-03-01

    Development of microwave absorption materials with tunable thickness and bandwidth is particularly urgent for practical applications but remains a great challenge. Here, two-dimensional nanocomposites consisting of perovskite oxides (LaFeO3) and amorphous carbon were successfully obtained through a one pot with heating treatment using sodium chloride as a hard template. The tunable absorption properties were realized by introducing A-site cation deficiency in LaFeO3 perovskite. Among the A-site cation-deficient perovskites, La0.62FeO3/C (L0.62FOC) has the best microwave absorption properties in which the maximum absorption is -26.6 dB at 9.8 GHz with a thickness of 2.94 mm and the bandwidth range almost covers all X-band. The main reason affecting the microwave absorption performance was derived from the A-site cation deficiency which induced more dipoles polarization loss. This work proposes a promising method to tune the microwave absorption performance via introducing deficiency in a crystal lattice.

  8. Quantitative photoluminescence of broad band absorbing melanins: a procedure to correct for inner filter and re-absorption effects

    NASA Astrophysics Data System (ADS)

    Riesz, Jennifer; Gilmore, Joel; Meredith, Paul

    2005-07-01

    We report methods for correcting the photoluminescence emission and excitation spectra of highly absorbing samples for re-absorption and inner filter effects. We derive the general form of the correction, and investigate various methods for determining the parameters. Additionally, the correction methods are tested with highly absorbing fluorescein and melanin (broadband absorption) solutions; the expected linear relationships between absorption and emission are recovered upon application of the correction, indicating that the methods are valid. These procedures allow accurate quantitative analysis of the emission of low quantum yield samples (such as melanin) at concentrations where absorption is significant.

  9. Strong interlayer coupling mediated giant two-photon absorption in MoS e2 /graphene oxide heterostructure: Quenching of exciton bands

    NASA Astrophysics Data System (ADS)

    Sharma, Rituraj; Aneesh, J.; Yadav, Rajesh Kumar; Sanda, Suresh; Barik, A. R.; Mishra, Ashish Kumar; Maji, Tuhin Kumar; Karmakar, Debjani; Adarsh, K. V.

    2016-04-01

    A complex few-layer MoS e2 /graphene oxide (GO) heterostructure with strong interlayer coupling was prepared by a facile hydrothermal method. In this strongly coupled heterostructure, we demonstrate a giant enhancement of two-photon absorption that is in stark contrast to the reverse saturable absorption of a weakly coupled MoS e2 /GO heterostructure and saturable absorption of isolated MoS e2 . Spectroscopic evidence of our study indicates that the optical signatures of isolated MoS e2 and GO domains are significantly modified in the heterostructure, displaying a direct coupling of both domains. Furthermore, our first-principles calculations indicate that strong interlayer coupling between the layers dramatically suppresses the MoS e2 excitonic bands. We envision that our findings provide a powerful tool to explore different optical functionalities as a function of interlayer coupling, which may be essential for the development of device technologies.

  10. Thickness and Composition Tailoring of K- and Ka-Band Microwave Absorption of BaCo x Ti x Fe(12-2 x)O19 Ferrites

    NASA Astrophysics Data System (ADS)

    Narang, Sukhleen Bindra; Pubby, Kunal; Singh, Charanjeet

    2017-02-01

    The goal of this research is to investigate the electromagnetic and microwave absorption properties of M-type barium hexaferrites with chemical formula BaCo x Ti x Fe(12-2 x)O19 ( x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) in K and Ka band. Characterization techniques such as x-ray diffraction analysis and scanning electron microscopy were applied to confirm ferrite formation. The frequency dependence of the complex permittivity and complex permeability was studied for prepared ferrite samples in the frequency range from 18 GHz to 40 GHz. Factors such as the quarter-wavelength condition, impedance matching, high dielectric-magnetic losses, as well as ferromagnetic resonance were investigated to determine their contribution to the absorption characteristics. It was found that the quarter-wavelength ( λ/4) model could be successfully applied to predict and understand the position as well as number of reflection peaks in the microwave absorption spectrum. The origin of the reflection loss peaks is explained and verified based on calculations of input impedance, loss tangent, and ferromagnetic resonance. Reflection loss analysis revealed that all six compositions exhibited reflection loss peaks (absorption >90%) at their matching thicknesses and frequencies. Therefore, these ferrites are potential candidates for use in electromagnetic shielding applications requiring low reflectivity in K and Ka band.

  11. 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.

  12. Evolution of an Intense Warm Frontal Precipitation Band During the GPM Cold-Season Precipitation Experiment (GCPEx)

    NASA Technical Reports Server (NTRS)

    Colle, Brian A.; Naeger, Aaron R.; Molthan, Andrew

    2017-01-01

    The band developed with low-level deformation and frontogenesis along the sloping warm frontal zone, and the vertical motions became large enough to produce graupel on the south side of the band. Embedded convective cells developed earlier in our GCPEx event, but the frontogenesis was weak then and banding was limited. As the deformation increased the stability also increased near the banding location (MPV* 0), which favored the development of single band. Through sensitivity studies (not shown) we found that latent heating helps increase the frontal circulations and resulting band development. Latent cooling also helps increase the frontogenesis given the evaporative and sublimation cooling within the frontal precipitation.

  13. 13C(16)O(2): Global Treatment of Vibrational-Rotational Spectra and First Observation of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) Absorption Bands.

    PubMed

    Tashkun; Perevalov; Teffo; Lecoutre; Huet; Campargue; Bailly; Esplin

    2000-04-01

    The effective operator approach is applied to the calculation of both line positions and line intensities of the (13)C(16)O(2) molecule. About 11 000 observed line positions of (13)C(16)O(2) selected from the literature have been used to derive 84 parameters of a reduced effective Hamiltonian globally describing all known vibrational-rotational energy levels in the ground electronic state. The standard deviation of the fit is 0.0015 cm(-1). The eigenfunctions of this effective Hamiltonian have then been used in fittings of parameters of an effective dipole-moment operator to more than 600 observed line intensities of the cold and hot bands covering the nu(2) and 3nu(2) regions. The standard deviations of the fits are 3.2 and 12.0% for these regions, respectively. The quality of the fittings and the extrapolation properties of the fitted parameters are discussed. A comparison of calculated line parameters with those provided by the HITRAN database is given. Finally, the first observations of the 2nu(1) + 5nu(3) and nu(1) + 2nu(2) + 5nu(3) absorption bands by means of photoacoustic spectroscopy (PAS) is presented. The deviations of predicted line positions from observed ones is found to be less than 0.1 cm(-1), and most of them lie within the experimental accuracy (0.007 cm(-1)) once the observed line positions are included in the global fit. Copyright 2000 Academic Press.

  14. 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

  15. Infrared energy levels and intensities of carbon dioxide.

    PubMed

    Rothman, L S; Benedict, W S

    1978-08-15

    Updated tables of vibrational energy levels, molecular constants, band origins, and intensities for carbon dioxide in the infrared region of the spectrum are presented. These tables are references for the AFGL Atmospheric Absorption Line Parameters Compilation.

  16. Contribution of the transition moments, form of the absorption band, exciton, and the correlation effects in the linear and nonlinear optical properties of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Díaz-Ponce, Javier Alejandro

    2017-04-01

    This work compares the linear and nonlinear optical properties of polyenes and polyenynes. The simulation was made for finite and infinite conjugation of conjugated polymers, such as polyacetylene, β-carotene, bis (p-toluene sulfonate) (PTS) polyenyne, and a short conjugated polyenyne poly-2,6-decadyin-1,6-ylene azelate (PHDAz). The resonance energy and degree of conjugation are determined by fitting the linear absorption spectra. These parameters are then used for calculating the two photon and third-order nonlinear optical properties. The contribution of the transition moment, the form of the absorption band, the exciton, and phonons in the optical properties are determined. The difference of the experimental values is assigned to correlation effects. We found that the exciton, the correlation effects, and the conduction band are more important in the optical properties of polyenynes than of polyenes. In this way, the dependence of the optical properties of polyenynes on the conduction band makes it possible to increase their nonlinear optical properties by interaction with photons (θ ≈ 0). The dependence of the optical properties on the conduction band also produces that the finiteness of the conjugation strongly decreases the optical properties of polyenynes in relation to polyenes with similar conjugation. On the other hand, the phonons are more important in the optical properties of polyenes than of polyenynes. Consequently, the band is indirect for the studied polyenes and direct for the polyenynes. Therefore, the nonlinear optical properties in the resonance frequency of polyenyne PTS are higher than those for polyacetylene. We also found that asymmetric oscillations of χ(3) in the Brillouin zone increases the χ(3) final value in polyenynes. In addition, we found a change of sign of the wave function coefficients by the Peierls distortion of polyenes to become polyenynes, but this change of sign does not affect the optical properties. As a corollary

  17. 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

  18. 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.

  19. 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.

  20. Analysis of the ν 8+ ν 9Band of HNO 3, Line Positions and Intensities, and Resonances Involving the v6= v7= 1 Dark State

    NASA Astrophysics Data System (ADS)

    Perrin, A.; Flaud, J.-M.; Keller, F.; Goldman, A.; Blatherwick, R. D.; Murcray, F. J.; Rinsland, C. P.

    1999-03-01

    Using a high-resolution (R= 0.0025 cm-1) Fourier transform spectrum of nitric acid recorded at room temperature in the 1100-1240 cm-1region, it has been possible to perform a more extended analysis of the ν8+ ν9band of HNO3centered at 1205.7075 cm-1. As in a recent analysis of this band [W. F. Wang, P. P. Ong, T. L. Tan, E. C. Looi, and H. H. Teo,J. Mol. Spectrosc.183, 407-413 (1997)], the Hamiltonian used for the line positions calculation takes into account, for the upper state, the ΔK= ±2 anharmonic resonance linking the rotational levels of thev8=v9= 1 "bright" vibrational state and those of the "dark"v6=v7= 1 vibrational state. More than 4800 lines were assigned in the ν8+ ν9band, which involve significantly higher rotational quantum numbers than in previous works. On the other hand, and surprisingly as compared to previous studies, the ν8+ ν9band appears to be a hybrid band. In fact, nonnegligibleB-type transitions could be clearly identified among the much strongerA-type lines. Accordingly, a set of individual line intensities were measured for lines of both types and were introduced in a least-squares fit to get theA- andB-type components of the transition moment operator. Finally, a synthetic spectrum of the 8.3-μm region of HNO3has been generated, using for the line positions and line intensities the Hamiltonian constants and the expansion of the transition moment operator which were determined in this work. In this way, theB-type and theA-type components of the ν8+ ν9band appear to contribute for about {1}/{4} and {3}/{4}, respectively, to the total band intensity.

  1. Resonance-Enhanced Raman Scattering of Ring-Involved Vibrational Modes in the (1)B(2u) Absorption Band of Benzene, Including the Kekule Vibrational Modes ν(9) and ν(10).

    PubMed

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

    2016-02-04

    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 ν9 (CC stretch Herzberg notation, ν14 Wilson notation) and ν10 (CH-parallel bend Herzberg notation, ν15 Wilson notation) vibrational modes along with the ν2 (CC-stretch or ring-breathing Herzberg notation, ν1 Wilson notation) mode and multiples of the ν18 (CCC-parallel bend Herzberg notation, ν6 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 × ν18 (e2g) mode, with nearly twice the intensity of the ring-breathing mode, ν2. Several overtones and combination modes, especially with ν2 (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.

  2. 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.

  3. Signs of the Biological Effect of ~2 μm Low-Intensity Laser Radiation in Raman and Absorption Spectra of Blood

    NASA Astrophysics Data System (ADS)

    Batay, L. E.; Khodasevich, I. A.; Khodasevich, M. A.; Gorbunova, N. B.; Manina, E. Yu.

    2016-09-01

    Local exposure of experimental animals to low-intensity emission from a thulium laser (λ = 1.96 μm) leads to changes in the Raman and IR absorption spectra of blood. This indicates development of systemic effects caused by direct excitation of water molecules by radiation with wavelength ~2 μm, in particular modifi cation of the hemoglobin molecule.

  4. 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.

  5. 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.

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

    DOE PAGES

    Sheetz, R. Michael; Richter, Ernst; Andriotis, Antonis N.; ...

    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.

  7. Calculating Effect of Point Defects on Optical Absorption Spectra of III-V Semiconductor Superlattices Based on (8x8) k-dot-p Band Structures

    NASA Astrophysics Data System (ADS)

    Huang, Danhong; Iurov, Andrii; Gumbs, Godfrey; Cardimona, David; Krishna, Sanjay

    For a superlattice which is composed of layered zinc-blende structure III-V semiconductor materials, its realistic anisotropic band structures around the Gamma-point are calculated by using the (8x8)k-dot-p method with the inclusion of the self-consistent Hartree potential and the spin-orbit coupling. By including the many-body screening effect, the obtained band structures are further employed to calculate the optical absorption coefficient which is associated with the interband electron transitions. As a result of a reduced quasiparticle lifetime due to scattering with point defects in the system, the self-consistent vertex correction to the optical response function is also calculated with the help of the second-order Born approximation.

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

    PubMed

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

    2014-09-22

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

  9. Predissociation linewidths of the (1,0)-(12,0) Schumann-Runge absorption bands of O2 in the wavelength region 179-202 nm

    NASA Technical Reports Server (NTRS)

    Cheung, A. S.-C.; Yoshino, K.; Esmond, J. R.; Chiu, S. S.-L.; Freeman, D. E.

    1990-01-01

    A nonlinear least-squares method of retrieving predissociation linewidths from the experimental absolute absorption cross sections of Yoshino et al. (1983) has been applied to the (1,0)-(12,0) Schumann-Runge bands of oxygen. The predissociation linewidths deduced are larger than the theoretical predictions of Julienne (1976) and the latest measurements of Lewis et al. (1986). The larger linewidths found will have an impact on calculations of solar flux penetration into the earth atmosphere and of the photodissociation rates of trace species in the upper atmosphere.

  10. Slow-Reduction Synthesis of a Thiolate-Protected One-Dimensional Gold Cluster Showing an Intense Near-Infrared Absorption.

    PubMed

    Takano, Shinjiro; Yamazoe, Seiji; Koyasu, Kiichirou; Tsukuda, Tatsuya

    2015-06-10

    Slow reduction of Au ions in the presence of 4-(2-mercaptoethyl)benzoic acid (4-MEBA) gave Au76(4-MEBA)44 clusters that exhibited a strong (3 × 10(5) M(-1) cm(-1)) near-infrared absorption band at 1340 nm. Powder X-ray diffraction studies indicated that the Au core has a one-dimensional fcc structure that is elongated along the {100} direction.

  11. Intensity-Stabilized Fast-Scanned Direct Absorption Spectroscopy Instrumentation Based on a Distributed Feedback Laser with Detection Sensitivity down to 4 × 10−6

    PubMed Central

    Zhao, Gang; Tan, Wei; Jia, Mengyuan; Hou, Jiajuan; Ma, Weiguang; Dong, Lei; Zhang, Lei; Feng, Xiaoxia; Wu, Xuechun; Yin, Wangbao; Xiao, Liantuan; Axner, Ove; Jia, Suotang

    2016-01-01

    A novel, intensity-stabilized, fast-scanned, direct absorption spectroscopy (IS-FS-DAS) instrumentation, based on a distributed feedback (DFB) diode laser, is developed. A fiber-coupled polarization rotator and a fiber-coupled polarizer are used to stabilize the intensity of the laser, which significantly reduces its relative intensity noise (RIN). The influence of white noise is reduced by fast scanning over the spectral feature (at 1 kHz), followed by averaging. By combining these two noise-reducing techniques, it is demonstrated that direct absorption spectroscopy (DAS) can be swiftly performed down to a limit of detection (LOD) (1σ) of 4 × 10−6, which opens up a number of new applications. PMID:27657082

  12. Accurate ab initio dipole moment surfaces of ozone: First principle intensity predictions for rotationally resolved spectra in a large range of overtone and combination bands.

    PubMed

    Tyuterev, Vladimir G; Kochanov, Roman V; Tashkun, Sergey A

    2017-02-14

    Ab initio dipole moment surfaces (DMSs) of the ozone molecule are computed using the MRCI-SD method with AVQZ, AV5Z, and VQZ-F12 basis sets on a dense grid of about 1950 geometrical configurations. The analytical DMS representation used for the fit of ab initio points provides better behavior for large nuclear displacements than that of previous studies. Various DMS models were derived and tested. Vibration-rotation line intensities of (16)O3 were calculated from these ab initio surfaces by the variational method using two different potential functions determined in our previous works. For the first time, a very good agreement of first principle calculations with the experiment was obtained for the line-by-line intensities in rotationally resolved ozone spectra in a large far- and mid-infrared range. This includes high overtone and combination bands up to ΔV = 6. A particular challenge was a correct description of the B-type bands (even ΔV3 values) that represented major difficulties for the previous ab initio investigations and for the empirical spectroscopic models. The major patterns of various B-type bands were correctly described without empirically adjusted dipole moment parameters. For the 10 μm range, which is of key importance for the atmospheric ozone retrievals, our ab initio intensity results are within the experimental error margins. The theoretical values for the strongest lines of the ν3 band lie in general between two successive versions of HITRAN (HIgh-resolution molecular TRANsmission) empirical database that corresponded to most extended available sets of observations. The overall qualitative agreement in a large wavenumber range for rotationally resolved cold and hot ozone bands up to about 6000 cm(-1) is achieved here for the first time. These calculations reveal that several weak bands are yet missing from available spectroscopic databases.

  13. Accurate ab initio dipole moment surfaces of ozone: First principle intensity predictions for rotationally resolved spectra in a large range of overtone and combination bands

    NASA Astrophysics Data System (ADS)

    Tyuterev, Vladimir G.; Kochanov, Roman V.; Tashkun, Sergey A.

    2017-02-01

    Ab initio dipole moment surfaces (DMSs) of the ozone molecule are computed using the MRCI-SD method with AVQZ, AV5Z, and VQZ-F12 basis sets on a dense grid of about 1950 geometrical configurations. The analytical DMS representation used for the fit of ab initio points provides better behavior for large nuclear displacements than that of previous studies. Various DMS models were derived and tested. Vibration-rotation line intensities of 16O3 were calculated from these ab initio surfaces by the variational method using two different potential functions determined in our previous works. For the first time, a very good agreement of first principle calculations with the experiment was obtained for the line-by-line intensities in rotationally resolved ozone spectra in a large far- and mid-infrared range. This includes high overtone and combination bands up to Δ V = 6. A particular challenge was a correct description of the B-type bands (even Δ V3 values) that represented major difficulties for the previous ab initio investigations and for the empirical spectroscopic models. The major patterns of various B-type bands were correctly described without empirically adjusted dipole moment parameters. For the 10 μ m range, which is of key importance for the atmospheric ozone retrievals, our ab initio intensity results are within the experimental error margins. The theoretical values for the strongest lines of the ν3 band lie in general between two successive versions of HITRAN (HIgh-resolution molecular TRANsmission) empirical database that corresponded to most extended available sets of observations. The overall qualitative agreement in a large wavenumber range for rotationally resolved cold and hot ozone bands up to about 6000 cm-1 is achieved here for the first time. These calculations reveal that several weak bands are yet missing from available spectroscopic databases.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. 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 (ɛ') and dielectric loss (ɛ″) 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Effects of pressure and solvents on the infrared absorption intensity of the O-H stretching mode of phenol in solutions.

    PubMed

    Isogai, Hideto; Kato, Minoru; Taniguchi, Yoshihiro

    2004-11-01

    Effects of pressure and solvents on the infrared spectrum of phenol in solutions have been investigated using a hydrostatic high-pressure cell with synthetic diamond windows. For the first time, we performed a quantitative investigation of the effect of pressure on the absolute intensity of O-H stretching mode up to 150 MPa (in CCl4) and 200 MPa (in CS2). For comparison, we measured the effect of solvents on the absorption intensity. The Polo-Wilson theory, which is the most traditional theory for medium effects on the intensity, was tested for present results. The pressure dependence was in sufficient agreement with their formula, while the solvent dependence is unsatisfactory. This suggests that the traditional intensity correction by Polo-Wilson's formula is practically valid for pressure-tuning infrared experiments.

  1. 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.

  2. 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.

  3. Ultraviolet absorption spectrum of HOCl

    NASA Technical Reports Server (NTRS)

    Burkholder, James B.

    1993-01-01

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

  4. 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.

  5. Band engineering of amorphous silicon ruthenium thin film and its near-infrared absorption enhancement combined with nano-holes pattern on back surface of silicon substrate

    NASA Astrophysics Data System (ADS)

    Guo, Anran; Zhong, Hao; Li, Wei; Gu, Deen; Jiang, Xiangdong; Jiang, Yadong

    2016-10-01

    Silicon is widely used in semiconductor industry but has poor performance in near-infrared photoelectronic devices because of its bandgap limit. In this study, a narrow bandgap silicon rich semiconductor is achieved by introducing ruthenium (Ru) into amorphous silicon (a-Si) to form amorphous silicon ruthenium (a-Si1-xRux) thin films through co-sputtering. The increase of Ru concentration leads to an enhancement of light absorption and a narrower bandgap. Meanwhile, a specific light trapping technique is employed to realize high absorption of a-Si1-xRux thin film in a finite thickness to avoid unnecessary carrier recombination. A double-layer absorber comprising of a-Si1-xRux thin film and silicon random nano-holes layer is formed on the back surface of silicon substrates, and significantly improves near-infrared absorption while the leaky light intensity is less than 5%. This novel absorber, combining narrow bandgap thin film with light trapping structure, may have a potential application in near-infrared photoelectronic devices.

  6. Effects of pressure and solvents on the infrared absorption intensities of C-I stretching modes of methyl and ethyl iodides in solutions.

    PubMed

    Isogai, Hideto; Kato, Minoru; Taniguchi, Yoshihiro

    2008-02-01

    We have investigated effects of pressure and solvents on infrared intensities of methyl and ethyl iodides in solutions using a hydrostatic high-pressure cell with synthetic diamond windows. We focused on the absolute intensity of the C-I stretching mode, which was measured in carbon disulfide solvent up to 300MPa and at 293K, and in n-hexane solvent at 298K. For comparison, we investigated the effect of solvents on the absorption intensity. Effects of pressure and solvents on the infrared intensity were analyzed using two electrostatic models, which assume the shape of solute cavity as sphere or spheroid. The latter model is approximately in agreement with both effects on the intensity, particularly, for the pressure effect. This paper demonstrated that the electrostatic model taking the shape of the cavity into account is useful to explain the medium effect on the infrared intensity and also suggests that more improved models could provide information of the solvation structure from the medium effect on the infrared intensity.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  9. 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.

  10. 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).

  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. 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.

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

    PubMed

    Sobuś, Jan; Ziółek, Marcin

    2014-07-21

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

  14. Optimal design and loss mechanism analysis of microwave absorbing unidirectional SiC fiber composites with broad absorption band and good polarization stability

    NASA Astrophysics Data System (ADS)

    Wan, Guangchao; Jiang, Jianjun; He, Yun; Bie, Shaowei

    2016-04-01

    A microwave-absorbing unidirectional SiC fiber composite with wide absorption and good polarization stability was designed by genetic algorithm. The anisotropic nature of unidirectional fiber composites was considered in the design by characterizing tensor permittivity. This special composite is composed of two kinds of SiC fibers that separately exhibit relatively high conductivity and low conductivity. The electromagnetic loss mechanism of this composite was examined for polarizations that differ in the electric field of the incident wave, applied either in the direction of the fiber or in the transverse direction, perpendicular to the fibers. For both polarizations, the absorption band of our composite can reach 6 GHz and the lowest microwave reflectivity was about -20 dB over a range of 8-18 GHz. When the electric field is polarized parallel to fibers, strong coupling among the high-conductivity fibers can induce a strong current and thus efficiently dissipate the electromagnetic energy. When the electric field is polarized perpendicular to fibers, the electromagnetic loss mechanism in the composite resembles the electric energy loss in capacitors and currents in the transverse direction are obstructed by the fibers resulting in attenuation of the electromagnetic energy in the matrix.

  15. Highly ordered monolayer/bilayer TiO2 hollow sphere films with widely tunable visible-light reflection and absorption bands.

    PubMed

    Li, Jie; Qin, Yao; Jin, Chao; Li, Ying; Shi, Donglu; Schmidt-Mende, Lukas; Gan, Lihua; Yang, Jinhu

    2013-06-07

    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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Rui-gang, Yang

    2011-07-01

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

  18. The origin of the unusual broad and intense visible absorption of tetrathiafulvalene-annulated zinc porphyrazine: a density functional theory study.

    PubMed

    Tao, Wei; Kan, Yu-He; Wu, Shui-Xing; Li, Hai-Bin; Yan, Li-Kai; Sun, Shi-Ling; Su, Zhong-Min

    2012-03-01

    The vertical excitation energies of tetrathiafulvalene (TTF)-annulated zinc porphyrazine (ZnPzTTF) were investigated using time-dependent density functional theory (TDDFT) calculations and compared to the experimental UV-vis spectra. To examine the effects of the aza substitutions and TTF groups on the molecular properties, zinc complexes of porphyrin (ZnP), porphyrazine (ZnPz) and tetraTTF-annulated porphyrin (ZnPTTF) were also selected for comparison. It was shown that numerous electronic transitions with TTF-to-porphyrin or porphyrazine charge transfer character exist and the Q band of ZnPzTTF is dominated by TTF-to-porphyrazine charge transfer transition mixed with porphyrazine core unit itself except for classic porphyrazine π→π* transitions. The Q band of ZnPzTTF mixes with other configurations, which breaks down the Gouterman's classic four-orbital model for the spectral interpretation. The data suggest that TDDFT/SAOP performs best for Q and B bands of ZnPzTTF with the maximum error in excitation energy being 0.17 eV. The CAM-B3LYP, ωB97XD and M06-2X calculations qualitatively predict that the low-lying electronic transitions of ZnPzTTF with TTF-to-porphyrazine charge transfer character located below the Q band. The broad and intense red-shifted Q band suggests that ZnPzTTF can be a candidate for dye-sensitized solar cells.

  19. Cavity Ringdown Absorption Spectrum of the T_1(n,π*) ← 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(π,π*) state, which has a CH_2--twisted equilibrium structure. In solution, the T_1(π,π*) state is typically accessed via intersystem crossing from an intially prepared planar S_1(n,π*) state. An intermediate in this photophysical transformation is the lowest ^3 (n,π*) state, a planar species with adiabatic excitation energy below S_1 and above T_1(π,π*). The present work focuses on this ^3 (n,π*) intermediate state; it is designated T_1(n,π*) as the lowest-energy triplet state of acrolein having a planar equilibrium structure. The T_1(n,π*) ← 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,π*) 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

  20. 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 Fröhlich 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.

  1. 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.

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

    PubMed

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

    2014-12-07

    Vibrational modes ascribed to the stretching of X-H bonds from donor monomers (HXdonor) in complexes presenting hydrogen bonds (HF···HF, HCl···HCl, HCN···HCN, HNC···HNC, HCN···HF, HF···HCl and H2O···HF) exhibit large (4 to 7 times) infrared intensity increments during complexation according to CCSD/cc-pVQZ-mod calculations. These intensity increases are explained by the charge-charge flux-dipole flux (CCFDF) model based on multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) as resulting from a reinforcing interaction between two contributions to the dipole moment derivatives with respect to the vibrational displacements: charge and charge flux. As such, variations that occur in their intensity cross terms in hydrogen bond formation correlate nicely with the intensity enhancements. These stretching modes of HXdonor bonds can be approximately modeled by sole displacement of the positively charged hydrogens towards the acceptor terminal atom with concomitant electronic charge transfers in the opposite direction that are larger than those occurring for the H atom displacements of their isolated donor molecules. This analysis indicates that the charge-charge flux interaction reinforcement on H-bond complexation is associated with variations of atomic charge fluxes in both parent molecules and small electronic charge transfers between them. The QTAIM/CCFDF model also indicates that atomic dipole flux contributions do not play a significant role in these intensity enhancements.

  3. A Southern-Sky Total Intensity Source Catalogue at 2.3 GHz from S-Band Polarisation All-Sky Survey Data

    NASA Astrophysics Data System (ADS)

    Meyers, B. W.; Hurley-Walker, N.; Hancock, P. J.; Franzen, T. M. O.; Carretti, E.; Staveley-Smith, L.; Gaensler, B. M.; Haverkorn, M.; Poppi, S.

    2017-03-01

    The S-band Polarisation All-Sky Survey has observed the entire southern sky using the 64-m Parkes radio telescope at 2.3 GHz with an effective bandwidth of 184 MHz. The surveyed sky area covers all declinations δ ⩽ 0°. To analyse compact sources, the survey data have been re-processed to produce a set of 107 Stokes I maps with 10.75 arcmin resolution and the large scale emission contribution filtered out. In this paper, we use these Stokes I images to create a total intensity southern-sky extragalactic source catalogue at 2.3 GHz. The source catalogue contains 23 389 sources and covers a sky area of 16 600 deg2, excluding the Galactic plane for latitudes |b| < 10°. Approximately, 8% of catalogued sources are resolved. S-band Polarisation All-Sky Survey source positions are typically accurate to within 35 arcsec. At a flux density of 225 mJy, the S-band Polarisation All-Sky Survey source catalogue is more than 95% complete, and 94% of S-band Polarisation All-Sky Survey sources brighter than 500 mJy beam-1 have a counterpart at lower frequencies.

  4. THE STRUCTURE OF THE ULTRAVIOLET ABSORPTION SPECTRA OF CERTAIN PROTEINS AND AMINO ACIDS

    PubMed Central

    Coulter, Calvin B.; Stone, Florence M.; Kabat, Elvin A.

    1936-01-01

    1. The absorption spectra of a number of proteins in the region 2500 to 3000 A. have been found to comprise from six to nine narrow bands. In consequence of variation in the relative intensity of these bands from protein to protein, the absorption curve has a characteristic configuration for each protein. 2. These bands correspond closely in position with the narrow bands which appear in the absorption spectra of tryptophan, tyrosin, and phenylalanine. Tryptophan and tyrosin each present three bands, phenylalanine shows nine. 3. The bands in the proteins are accordingly attributed to these amino acids. In the proteins the bands are displaced from the positions which they occupy in the uncombined amino acids, in most instances, by 10 to 35 A. toward longer wavelengths. 4. The absorption spectrum of Pneumococcus Type I antibody resembles that of normal pseudoglobulin but shows characteristic differences. PMID:19872958

  5. 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.

  6. 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.

  7. Intense laser field effects on the intersubband optical absorption and refractive index change in the δ -doped GaAs quantum wells

    NASA Astrophysics Data System (ADS)

    Sari, H.; Yesilgul, U.; Ungan, F.; Sakiroglu, S.; Kasapoglu, E.; Sökmen, I.

    2017-04-01

    In this paper, we have investigated the effects of the non-resonant intense laser field on the electronic and optical properties such as linear, nonlinear and the total optical absorption coefficient and refractive index change for transitions between two lower-lying electronic states in the GaAs-based δ -doped quantum well. Within the effective mass approximation, we calculated the eigenvalues and corresponding eigenfunctions as a function of the intense laser parameter by solving the Schrödinger equation in the laser-dressed confinement potential. The analytical expressions of the linear and third-order non-linear optical absorption coefficients and refractive index changes are obtained by using the compact-density matrix formalism. The obtained results show that the separation between ground and first excited energy levels in the δ -doped quantum well decreases in energy by the increase of the laser field intensity and this effect leads to an optical red-shift in the intersubband transitions. This behavior gives us a new degree of freedom in tunability of different device applications based on the optical transitions.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  9. Intense, Narrow-band THz Emission from a Current Source Immersed in Cut-off of Plasma-like Media

    NASA Astrophysics Data System (ADS)

    Hur, Min Sup; Ersfeld, Bernhard; Noble, Adam; Suk, Hyyong; Jaroszynski, Dino

    2016-10-01

    Recently we found an interesting behavior of the electromagnetic radiation emerging from cut-off condition of a plasma-like medium, when it is driven by a current source. Differently from conventional total reflection of the incident wave at the cut-off, we found a spatially diffusing and temporally growing electromagnetic field from the current source. Direct result of such diffusion-growth is the selectively enhanced emission (SEE) at the cut-off frequency from a generally broadband current oscillation. We demonstrate examples demonstrating the SEE. One is the two-color-driven THz emission from field ionization of the gas slab located in a tapered waveguide. The emission propagating through the waveguide exhibits a significantly enhanced spectral density at the cut-off frequency. The other example is the THz emission from a magnetized plasma driven by two colliding ultra-short laser pulses. Since a very narrow-band emission can be selectively enhanced from a broadband radiation source, the SEE concept can be used for conversion of a general broadband THz source to a narrow-band one by locating it in a meta-structure such as the waveguide or a plasma-like medium. We discuss other possible systems to which SEE can be applied.

  10. 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.

  11. Global Frequency and Intensity Analysis of the νb{10}/νb{7}/νb{4}/νb{12} Bands System of 12C_2H_4 at 10 μm Using the D2h Top Data System

    NASA Astrophysics Data System (ADS)

    Alkadrou, Abdulsamee; Rotger, Maud; Boudon, Vincent; Vander Auwera, Jean

    2016-06-01

    A global frequency and intensity analysis of the infrared tetrad located in the 600-1500 cm-1 region was carried out using the tensorial formalism developed in Dijon for X_2Y_4 asymmetric-top molecules and a program suite called D2hTDS (now part of the XTDS/SPVIEW spectroscopic software). It relied on spectroscopic information available in the literature and retrieved from absorption spectra recorded in Brussels using a Bruker IFS 120 to 125 HR upgraded Fourier transform spectrometer, in the frame of either the present or previous work. In particular, 645 and 131 lines intensities have been respectively measured for the weak ν10 and ν_4 bands. Including the Coriolis interactions affecting the upper vibrational levels 10^1, 7^1, 4^1 and 12^1, a total of 10737 line positions and 1870 line intensities have been assigned and fitted with global root mean square deviations of 2.6 × 10-4 cm-1 and {2.4} %, respectively. Relying on the results of the present work and available in the literature, a list of parameters for 65420 lines in the ν10, ν7, ν4 and ν12 bands of 12C_2H_4 was generated. The present work provides an obvious improvement over HITRAN and GEISA for the ν10 band (see figure), and a marginally better modeling for the ν7 band (and for the ν4 band hidden beneath it). To the best of our knowledge, this is the first time that a global intensity analysis is carried out in this range of the ethylene spectrum. Raballand W, Rotger M, Boudon V, Loëte M. J Mol Spectrosc 2003;217:239-48. Wenger Ch, Boudon V, Rotger M, Champion JP, Sanzharov M. J Mol Spectrosc 2008;251:102-13. Rotger M, Boudon V, Vander Auwera J. J Quant Spectrosc Radiat Transf 2008;109:952-62.

  12. Absorption of surface acoustic waves by graphene

    NASA Astrophysics Data System (ADS)

    Zhang, S. H.; Xu, W.

    2011-06-01

    We present a theoretical study on interactions of electrons in graphene with surface acoustic waves (SAWs). We find that owing to momentum and energy conservation laws, the electronic transition accompanied by the SAW absorption cannot be achieved via inter-band transition channels in graphene. For graphene, strong absorption of SAWs can be observed in a wide frequency range up to terahertz at room temperature. The intensity of SAW absorption by graphene depends strongly on temperature and can be adjusted by changing the carrier density. This study is relevant to the exploration of the acoustic properties of graphene and to the application of graphene as frequency-tunable SAW devices.

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

    NASA Astrophysics Data System (ADS)

    Kajihara, Koichi; Skuja, Linards; Hosono, Hideo

    2014-10-01

    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 SiO2 (a-SiO2) exposed to 60Co γ-rays. The peak shape is asymmetric with the steeper edge at the lower energy side both in α-quartz and a-SiO2, and the peak energy is larger for α-quartz than that for a-SiO2. The full width at half maximum for a-SiO2 is larger by ˜40-60% than that for α-quartz, and it increases with an increase in the disorder of the a-SiO2 network, which is enhanced by raising the temperature of preannealing before irradiation, i.e., fictive temperature. These data are interpreted from the viewpoint of the site-to-site distribution of the Si-Si bond length in a-SiO2.

  14. Ti3C2 MXenes with Modified Surface for High-Performance Electromagnetic Absorption and Shielding in the X-Band.

    PubMed

    Han, Meikang; Yin, Xiaowei; Wu, Heng; Hou, Zexin; Song, Changqing; Li, Xinliang; Zhang, Litong; Cheng, Laifei

    2016-08-17

    Electromagnetic (EM) absorbing and shielding composites with tunable absorbing behaviors based on Ti3C2 MXenes are fabricated via HF etching and annealing treatment. Localized sandwich structure without sacrificing the original layered morphology is realized, which is responsible for the enhancement of EM absorbing capability in the X-band. The composite with 50 wt % annealed MXenes exhibits a minimum reflection loss of -48.4 dB at 11.6 GHz, because of the formation of TiO2 nanocrystals and amorphous carbon. Moreover, superior shielding effectiveness with high absorption effectiveness is achieved. The total and absorbing shielding effectiveness of Ti3C2 MXenes in a wax matrix with a thickness of only 1 mm reach values of 76.1 and 67.3 dB, while those of annealed Ti3C2 MXenes/wax composites are 32 and 24.2 dB, respectively. Considering the promising performance of Ti3C2 MXenes with the modified surface, this work is expected to open the door for the expanded applications of MXenes family in EM absorbing and shielding fields.

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

    PubMed

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

    2007-10-01

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

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    We present a theoretical study of the electronic structures and polarized absorption properties of quantum dot superlattices (QDSLs) using wide-gap matrix material, InAs/In0.48Ga0.52P QDSLs, for realizing intermediate-band solar cells (IBSCs) with two-step photon-absorption. The plane-wave expanded Burt-Foreman operator ordered 8-band k . p theory is used for this calculation, where strain effect and piezoelectric effect are taken into account. We find that the absorption spectra of the second transitions of two-step photon-absorption can be shifted to higher energy region by using In0.48Ga0.52P, which is lattice-matched material to GaAs substrate, as a matrix material instead of GaAs. We also find that the transverse magnetic polarized absorption spectra in InAs/In0.48Ga0.52P QDSL with a separate IB from the rest of the conduction minibands can be shifted to higher energy region by decreasing the QD height. As a result, the second transitions of two-step photon-absorption by the sunlight occur efficiently. These results indicate that InAs/In0.48Ga0.52P QDSLs are suitable material combination of IBSCs toward the realization of ultrahigh efficiency solar cells.

  19. 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

  20. 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.

  1. 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)(μ-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 (Kß(2,5) emission) electronic transitions, and of Kα 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

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

    PubMed

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

    2013-10-01

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

  3. Energy ranges and pitch angles of outer radiation belt electrons depleted by an intense dayside hydrogen band EMIC wave event on February 23, 2014

    NASA Astrophysics Data System (ADS)

    Engebretson, M. J.; Posch, J. L.; Huang, C. L.; Kanekal, S. G.; Fok, M. C. H.; Rodger, C. J.; Smith, C. W.; Spence, H. E.; Baker, D. N.; Kletzing, C.; Wygant, J. R.

    2015-12-01

    Although most studies of the effect of EMIC waves on relativistic electrons have focused on wave events in the afternoon sector in the outer plasmasphere or plume region, strong magnetospheric compressions provide an additional stimulus for EMIC wave generation across a large range of local times and L shells. We present here observations of the effects of an intense, long-duration hydrogen band EMIC wave event on February 23, 2014 that was stimulated by a gradual 4-hour rise and subsequent sharp increases in solar wind pressure. Large-amplitude linearly polarized hydrogen band EMIC waves (up to 25 nT p-p) that included triggered emissions appeared for over 4 hours at both Van Allen Probes while these spacecraft were outside the plasmapause, in a region with densities ~5-20 cm-3, as they passed near apogee from late morning through local noon. Observations of radiation belt electrons by the REPT and MagEIS instruments on these spacecraft showed that these waves caused significant depletions of more field-aligned electrons at ultrarelativistic energies from 5.2 MeV down to ~2 MeV, and some depletions at energies down to below 1 MeV as well.

  4. 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.

  5. Low-temperature high-resolution absorption spectrum of 14NH3 in the ν1+ν3 band region (1.51 μm)

    NASA Astrophysics Data System (ADS)

    Földes, T.; Golebiowski, D.; Herman, M.; Softley, T. P.; Di Lonardo, G.; Fusina, L.

    2014-09-01

    Jet-cooled spectra of 14NH3 and 15NH3 in natural abundance were recorded using cavity ring-down (CRDS, 6584-6670 cm-1) and cavity enhanced absorption (CEAS, 6530-6700 cm-1) spectroscopy. Line broadening effects in the CRDS spectrum allowed lines with J″-values between 0 and 3 to be identified. Intensity ratios in 14NH3 between the jet-cooled CRDS and literature room-temperature data from Sung et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1066) further assisted the line assignments. Ground state combination differences were extensively used to support the assignments, providing reliable values for J, K and inversion symmetry of the ground state vibrational levels. CEAS data helped in this respect for the lowest J lines, some of which are saturated in the CRDS spectrum. Further information on a/s doublets arose from the observed spectral structures. Thirty-two transitions of 14NH3 were assigned in this way and a limited but significant number (19) of changes in the assignments results, compared to Sung et al. or to Cacciani et al. (J. Quant. Spectrosc. Radiat. Transfer, 113 (2012), 1084). Sixteen known and 25 new low-J transitions were identified for 15NH3 in the CRDS spectrum but the much scarcer literature information did not allow for any more refined assignment. The present line position measurements improve on literature values published for 15NH3 and on some line positions for 14NH3.

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

    Recent spectral observations of some Kuiper Belt Objects (KBOs) (Boehnhardt et al.: 2002, Proc. of ACM 2002, 47-50; Fornasier S. et al., 2004, Astron. Astrophys. 421, 353-363) discovered characteristic absorption bands at 4300 and 6000-8000Å in reflectance spectra of the bodies. Spectral positions and other parameters of the features are similar to those found in reflectance spectra of terrestrial phyllosilicates (e. g., Clark et al., 1990, J. Geophys. Res. 95, 12653-12680; Busarev et al., 2004, The new ROSETTA targets (L. Colangeli et al., eds.), 79-83), CI- and CM-carbonaceous chondrites (e. g., Busarev and Taran, 2002, Proc. of ACM 2002, 933-936), primitive C-, P-, D-, F- and G-class asteroids (Vilas and Gaffey, 1989, Science 246, 790-792) and hydrated M-, S- and E-class asteroids (Busarev and Taran, 2002, Proc. of ACM 2002, 933-936). Hence, these absorption bands may be considered as universal indicators of hydrated silicates on celestial solid bodies including KBOs. However, before phyllosilicates were formed, an aqueous media should spring up and exist a considerable time in the bodies. One more important factor for the spectral features of hydrated silicates to be observed, it is probably an aqueous separation of silicate and darkening CHON (PAH plus more light organic compounds) components in the bodies. To check the assumptions we have performed some calculations (Busarev et al., 2003, Earth, Moon, and Planets 92, 345-357) applicable to KBOs and analogous silicate-icy bodies existed for the first time in the formation zones of neighbouring giant planets. According to the calculations, the decay of the short-lived 26Al at the early stage of the bodies' evolution and their mutual collisions (at velocities >1.5 km s-1) at the subsequent stage were probably the main sources of heating sufficient for melting water ice in their interiors. Because of these processes, an internal ocean of liquid water covered with ˜10-km crust of dirty ice could originate in

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

    PubMed

    Harb, Moussab; Masih, Dilshad; Takanabe, Kazuhiro

    2014-09-14

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

  8. Two-tier calibrated electro-optic sensing system for intense field characterization of high-power W-band gyrotron.

    PubMed

    Kim, Seok; Hong, Young-Pyo; Yang, Jong-Won; Lee, Dong-Joon

    2016-05-16

    We present a field-calibrated electro-optic sensing system for measurement of the electric field radiating from a high-power vacuum oscillator at ~95 GHz. The intense electric field is measured in absolute scale via two probe-calibration steps, associated with a photonic heterodyne scheme. First, a micro-electro-optic probe, fabricated to less than one-tenth the oscillation wavelength scale to minimize field-perturbation due to the probe, is placed on the aperture of a field-calculable WR-10 waveguide to calibrate the probe in V/m scale. Then, using this arrangement as a calibrated reference probe at the first-tier position, another probe-bulkier, and thus more robust and sensitive but not accessible to the aperture-is calibrated at the second-tier position away from the waveguide aperture. This two-tier calibrated probe was utilized to diagnose the sub-MV/m scale of intense electric fields and emissions from a high-power W-band gyrotron. The experimental results obtained proved consistent with calculated analytical results-verifying the efficacy of the developed system.

  9. 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.

  10. Theory of graphene saturable absorption

    NASA Astrophysics Data System (ADS)

    Marini, A.; Cox, J. D.; García de Abajo, F. J.

    2017-03-01

    Saturable absorption is a nonperturbative nonlinear optical phenomenon that plays a pivotal role in the generation of ultrafast light pulses. Here we show that this effect emerges in graphene at unprecedentedly low light intensities, thus opening avenues to new nonlinear physics and applications in optical technology. Specifically, we theoretically investigate saturable absorption in extended graphene by developing a semianalytical nonperturbative single-particle approach, describing electron dynamics in the atomically-thin material using the two-dimensional Dirac equation for massless Dirac fermions, which is recast in the form of generalized Bloch equations. By solving the electron dynamics nonperturbatively, we account for both interband and intraband contributions to the intensity-dependent saturated conductivity and conclude that the former dominates regardless of the intrinsic doping state of the material. We obtain results in qualitative agreement with atomistic quantum-mechanical simulations of graphene nanoribbons including electron-electron interactions, finite-size, and higher-band effects. Remarkably, such effects are found to affect mainly the linear absorption, while the predicted saturation intensities are in good quantitative agreement in the limit of extended graphene. Additionally, we find that the modulation depth of saturable absorption in graphene can be electrically manipulated through an externally applied gate voltage. Our results are relevant for the development of graphene-based optoelectronic devices, as well as for applications in mode-locking and random lasers.

  11. 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.

  12. 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

    2016-02-04

    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.

  13. Mesosphere-thermosphere regions coupling with the lower atmosphere through the inter-annual variations of the hydroxyl OH(8-3) bands, the oxygen 557.7 nm and 630.0 nm lines nightglow intensities

    NASA Astrophysics Data System (ADS)

    Didebulidze, Goderdzi; Javakhishvili, Giorgi; Todua, Maya; Toriashvili, Lekso

    2016-04-01

    The characteristics of the inter-annual/seasonal distributions of the mid-latitude nightglow intensities of the mesopause hydroxyl OH(8-3) bands (maximum luminous layer about 87 km), the thermosphere oxygen green 557.7 nm (main maximum of luminous layer in the lower thermosphere at about 95 km) and the red 630.0 nm line (emitted from the ionosphere F2 region with maximum luminous layer about 230-280 km) intensities are considered by observations from Abastumani (41.75 E; 42.82 E). The observed inter-annual variations of the OH bands and green line, along with the maximal values at spring (March-April) and fall (September-October) equinoxial periods which are noticed also from other regions, exhibit maxima in June as well. The red line intensity mainly tends to decrease at equinoxial months, while it is maximal in summer and is accompanied by relatively small increase in June (compared to May and July). Maximal values of OH band and green line intensities in June are observed both in maximum and minimum phases of solar activity. This is considered as a manifestation of the features of upper and lower atmosphere dynamical coupling of this region of the South Caucasus. Such dynamical coupling can involve the ionosphere F2 region and can be accompanied by relative decrease of the red line intensity in June. It is observed that the increase of OH band and green line intensities is accompanied by the red line intensity decrease at the end of March and beginning of April, which also is considered as a manifestation of lower and upper atmosphere dynamical coupling. Acknowledgements: This work has been supported by Shota Rustaveli National Science Foundation Grants no. 31/56 and 31/81.

  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 κ 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

  15. 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 geo

  16. The effects of the electric and intense laser field on the binding energies of donor impurity states (1s and 2p±) and optical absorption between the related states in an asymmetric parabolic quantum well

    NASA Astrophysics Data System (ADS)

    Kasapoglu, E.; Sakiroglu, S.; Sökmen, I.; Restrepo, R. L.; Mora-Ramos, M. E.; Duque, C. A.

    2016-10-01

    We have calculated the effects of electric and intense laser fields on the binding energies of the ground and some excited states of conduction electrons coupled to shallow donor impurities as well as the total optical absorption coefficient for transitions between 1s and 2p± electron-impurity states in a asymmetric parabolic GaAs/Ga1-x AlxAs quantum well. The binding energies were obtained using the effective-mass approximation within a variational scheme. Total absorption coefficient (linear and nonlinear absorption coefficient) for the transitions between any two impurity states were calculated from first- and third-order dielectric susceptibilities derived within a perturbation expansion for the density matrix formalism. Our results show that the effects of the electric field, intense laser field, and the impurity location on the binding energy of 1s-impurity state are more pronounced compared with other impurity states. If the well center is changed to be Lc<0 (Lc>0), the effective well width decreases (increases), and thus we can obtain the red or blue shift in the resonant peak position of the absorption coefficient by changing the intensities of the electric and non-resonant intense laser field as well as dimensions of the well and impurity positions.

  17. Temperature dependence of infrared bands produced by polycyclic aromatic hydrocarbons

    NASA Astrophysics Data System (ADS)

    Colangeli, L.; Mennella, V.; Bussoletti, E.

    1992-02-01

    The behavior of IR absorption bands with temperature has been examined systematically in the laboratory for three representative polycyclic aromatic hydrocarbon molecules: coronene, chrysene, and 1-methylcoronene. A careful description of both intensity and profile measured for most of the bands is reported. A tentative interpretation of the observed variations is given in terms of extra-molecular effects produced by the anharmonicity of the vibrational energy levels as a function of temperature. These new laboratory data provide an accurate description of the optical properties for representative molecules often used to account for the so-called unidentified infrared bands emitted by astronomical sources.

  18. 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.

  19. A novel design of plasmon-induced absorption sensor

    NASA Astrophysics Data System (ADS)

    Lin, Qi; Zhai, Xiang; Wang, Ling-Ling; Luo, Xin; Liu, Gui-Dong; Liu, Jian-Ping; Xia, Sheng-Xuan

    2016-06-01

    We present a plasmon-induced absorption (PIA) sensor formed by using a notched metallic film and a metallic ground plane separated by dielectric gratings, suggesting perfect absorption and high sensitivity up to ˜105. The absorption mechanism for the narrow-band sensor involves the phase-dependent coupling between the localized surface plasmon resonance and the Fabry-Perot resonance. The intensity and lineshape of the PIA resonance can be controlled by optimizing the coupling distance and thickness of the dielectric gratings, respectively. In particular, the underlying physics and critical condition for pronounced PIA resonance are illustrated by the coupled Lorentzian oscillator model.

  20. Intensity measurements of the 0,0 band of the a/3 Pi/-Chi/1 Sigma/ Cameron system of CO.

    NASA Technical Reports Server (NTRS)

    James, T. C.

    1971-01-01

    The band strength of the 0,0 band of a CO Cameron system has been determined from measurements of the equivalent widths of a number of resolved rotational lines. Equivalent widths were converted to line strengths using a Doppler curve of growth. The result obtained agrees almost exactly with that of Fairbairn (1970).

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

    PubMed

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

    2013-10-15

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

  2. 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.

  3. Effect of pyridine on infrared absorption spectra of copper phthalocyanine.

    PubMed

    Singh, Sukhwinder; Tripathi, S K; Saini, G S S

    2008-02-01

    Infrared absorption spectra of copper phthalocyanine in KBr pellet and pyridine solution in 400-1625 and 2900-3200 cm(-1)regions are reported. In the IR spectra of solid sample, presence of weak bands, which are forbidden according to the selection rules of D4h point group, is explained on the basis of distortion in the copper phthalocyanine molecule caused by the crystal packing effects. Observation of a new band at 1511 cm(-1) and change in intensity of some other bands in pyridine are interpreted on the basis of coordination of the solvent molecule with the central copper ion.

  4. 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.

  5. Atmospheric absorption cell characterization

    NASA Astrophysics Data System (ADS)

    1982-06-01

    The measurement capability of the Avionics Laboratory IR Facility was used to evaluate an absorption cell that will be used to simulate atmospheric absorption over horizontal paths of 1 - 10 km in length. Band models were used to characterize the transmittance of carbon dioxide (CO2), nitrogen (N2), and nitrous oxide (N2O) in the cell. The measured transmittance was compared to the calculated values. Nitrous oxide is important in the 4 - 4.5 micron range in shaping the weak line absorption of carbon dioxide. The absorption cell is adequate for simulating atmospheric absorption over these paths.

  6. 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.

  7. 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

    2015-05-05

    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.

  8. A wide-angle and polarization insensitive infrared broad band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Xie, Ting; Chen, Zhong; Ma, Rongyi; Zhong, Min

    2017-01-01

    In this paper, we present the design and experimental demonstration of a broad single-band metamaterial absorber composed of a simple two-dimensional periodic silver-SiO2-silver sandwich array. The experimental results show that a near-perfect absorption band with a bandwidth of approximately 0.4 μm in the THz region is obtained, which is in reasonable agreement with the simulated results. The calculated electric field intensity distributions indicate that the broad absorption band is achieved by plasmonic hybridization of two plasmon resonances: one originates from outward coupling between adjacent unit cells and the other arises from inward coupling between the two sub-structures. The effects of the structural parameters and the SiO2 layer thickness on the broad absorption band are investigated experimentally. The effect of the angle of incidence on the broad absorption band is also investigated experimentally and the absorption band remains high at large angles of incidence (60°), which thus provides more efficient absorption of obliquely incident beams.

  9. Cirrus cloud optical and microphysical property retrievals from eMAS during SEAC4RS using bi-spectral reflectance measurements within the 1.88 µm water vapor absorption band

    NASA Astrophysics Data System (ADS)

    Meyer, Kerry; Platnick, Steven; Arnold, G. Thomas; Holz, Robert E.; Veglio, Paolo; Yorks, John; Wang, Chenxi

    2016-04-01

    Previous bi-spectral imager retrievals of cloud optical thickness (COT) and effective particle radius (CER) based on the Nakajima and King (1990) approach, such as those of the operational MODIS cloud optical property retrieval product (MOD06), have typically paired a non-absorbing visible or near-infrared wavelength, sensitive to COT, with an absorbing shortwave or mid-wave infrared wavelength sensitive to CER. However, in practice it is only necessary to select two spectral channels that exhibit a strong contrast in cloud particle absorption. Here it is shown, using eMAS observations obtained during NASA's SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 µm water vapor absorption band, namely the 1.83 and 1.93 µm channels that have sufficient differences in ice crystal single scattering albedo, can yield COT and CER retrievals for thin to moderately thick single-layer cirrus that are reasonably consistent with other solar and IR imager-based and lidar-based retrievals. A distinct advantage of this channel selection for cirrus cloud retrievals is that the below-cloud water vapor absorption minimizes the surface contribution to measured cloudy top-of-atmosphere reflectance, in particular compared to the solar window channels used in heritage retrievals such as MOD06. This reduces retrieval uncertainty resulting from errors in the surface reflectance assumption and reduces the frequency of retrieval failures for thin cirrus clouds.

  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. 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.

  12. 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.

  13. Absorption of surface acoustic waves by topological insulator thin films

    NASA Astrophysics Data System (ADS)

    Li, L. L.; Xu, W.

    2014-08-01

    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.

  14. Microwave absorption properties of planar-anisotropy Ce2Fe17N3-δ powders/Silicone composite in X-band

    NASA Astrophysics Data System (ADS)

    Gu, Xisheng; Tan, Guoguo; Chen, Shuwen; Man, Qikui; Chang, Chuntao; Wang, Xinmin; Li, Run-Wei; Che, Shenglei; Jiang, Liqiang

    2017-02-01

    The soft-magnetic properties of planar-anisotropy Ce2Fe17N3-δ powders were reported, and reflection loss (RL) of the powders/Silicone composites with various volume concentrations have been studied in 0.1-18 GHz frequency range. It was found that the optimal RL of this composite absorber with a thickness of 1.72 mm is -60.5 dB at 9.97 GHz and the RL is less than -10 dB in the whole X-band (8-12 GHz). The bandwidth with RL exceeding -10 dB and -20 dB are 5.24 GHz and 1.32 GHz, respectively. Furthermore, all the optimal RL value of the composite with the thickness less than 2.13 mm can reach -20 dB in the range of 8-17 GHz, which indicates that the Ce2Fe17N3-δ/Silicone composite absorber will be a promising candidate in higher gigahertz frequency especially in X-band.

  15. Poster 1: Global frequency and intensity analysis of the ν10/ν7/ν4/ν12 band system of 12C2H4 at 10 µm using the D2h Top Data System

    NASA Astrophysics Data System (ADS)

    Alkadrou, Abdulsamee; Bourgeois, Marie-Therese; Rotger, Maud; Boudon, Vincent; Vander Auwera, Jean

    2016-06-01

    A global frequency and intensity analysis of the infrared tetrad of 12C2H4 located in the 600-1500 cm-1 region was carried out using the tensorial formalism developed in Dijon for X2Y4 asymmetric-top molecules. It relies on spectroscopic information available in the literature and retrieved from high-resolution Fourier transform infrared spectra recorded in Brussels in the frame of either the present or previous work. In particular, 645 and 131 lines intensities have been respectively measured for the weak ν10 and ν4 bands. Including the Coriolis interactions affecting the upper vibrational levels 101, 71, 41 and 121 , a total of 10,737 line positions and 1,867 line intensities have been assigned and fitted with global root mean square deviations of 2.6 10-4 cm-1 and 2.4 %, respectively. Relying on the results of the present work and available in the literature, a list of parameters for 65,420 lines in the ν10, ν7, ν4 and ν12 bands of 12C2H4 was generated. To the best of our knowledge, this is the first time that a global intensity analysis is carried out in this range of the ethylene spectrum.

  16. Global frequency and intensity analysis of the ν10/ν7/ν4/ν12 band system of 12C2H4 at 10 μm using the D2h Top Data System

    NASA Astrophysics Data System (ADS)

    Alkadrou, A.; Bourgeois, M.-T.; Rotger, M.; Boudon, V.; Vander Auwera, J.

    2016-10-01

    A global frequency and intensity analysis of the infrared tetrad of 12C2H4 located in the 600 - 1500cm-1 region was carried out using the tensorial formalism developed in Dijon for X2Y4 asymmetric-top molecules. It relied on spectroscopic information available in the literature and retrieved from high-resolution Fourier transform infrared spectra recorded in Brussels in the frame of either the present or previous work. In particular, 645 and 131 line intensities have been respectively measured for the weak ν10 and ν4 bands. Including the Coriolis interactions affecting the upper vibrational levels 101, 71, 41 and 121, a total of 10 757 line positions and 1645 line intensities have been assigned and fitted with global root mean square deviations of 2.6 ×10-4cm-1 and 2.5%, respectively. Relying on the results of the present work and available in the literature, a list of parameters for 65 776 lines in the ν10, ν7, ν4 and ν12 bands of 12C2H4 was generated. To the best of our knowledge, this is the first time that a global intensity analysis is carried out in this range of the ethylene spectrum.

  17. Electronic absorption spectra of rare earth (III) species in NaCl-2CsCl eutectic based melts

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Ivanov, A. B.; Yakimov, S. M.; Tsarevskii, D. V.; Golovanova, O. A.; Sukhikh, V. V.; Griffiths, T. R.

    2016-09-01

    Electronic absorption spectra of ions of trivalent rare earth elements were measured in the melts based on NaCl-2CsCl eutectic in the wavelength ranges of 190-1350 and 1450-1700 nm. The measurements were performed at 550-850 °C. The EAS of Y, La, Ce and Lu containing melts have no absorption bands in the studied regions. For the remaining REEs (Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb) the absorption bands in the EAS were assigned to the corresponding f-f electron transitions. The Stark effect was observed for Yb(III) F5/2 excited state. Increasing temperature leads to decreasing intensity of the absorption bands, except for the bands resulting from hypersensitive transitions. Beer's law was confirmed up to 0.4 M solutions of REE.

  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. Induced changes in refractive index, optical band gap, and absorption edge of polycarbonate-SiO2 thin films by Vis-IR lasers

    NASA Astrophysics Data System (ADS)

    Ehsani, Hassan; Akhoondi, Somaieh

    2016-09-01

    In this experimental work, we have studied induced changes in refractive index, extinction coefficient, and optical band-gap of Bisphenol-A-polycarbonate (BPA-PC) coated with a uniform and thin, anti-scratch SiO2 film irradiated by visible to near-infrared lasers at 532 nm (green),650 nm(red), and 980 nm (IR)wavelength lasers with different energy densities. Our lasers sources are indium-gallium-aluminum-phosphide, second harmonic of neodymium-YAG-solid state lasers and gallium-aluminum-arsenide-semiconductor laser. The energy densities of our sources have been changed by changing the spot size of incident laser. samples transmission spectra were monitored by carry500 spectrophotometer and induced changes in optical properties are evaluated by using, extrapolation of the transmission spectrum through Swanepoel method and computer application

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

    NASA Astrophysics Data System (ADS)

    Ding, Zhiwen; Wang, Qin; Zheng, Hang

    2012-10-01

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

  1. Absorption of light by colloidal semiconductor quantum dots

    NASA Astrophysics Data System (ADS)

    Pokutnyi, Sergey I.; Ovchinnikov, Oleg V.; Kondratenko, Tamara S.

    2016-07-01

    UV-Vis absorption of colloidal cadmium sulfide quantum dots (QDs) synthesized by an aqueous synthesis in a gelatin matrix was investigated. Using the dipole approximation, taking into account the Coulomb interaction between the electron and hole in a QD and the polarization effects on the spherical boundary of QD and matrix, it was found the change of selection rules for optical transitions. It is shown that the optical absorption edge of QDs is formed by two optical transitions of electron between low-excited levels of size quantization of heavy hole (1S and 2S), located in QDs valence band and fundamental size-quantized states 1Se of conduction band. These transitions are identical in intensity. Estimations of average values of CdS QDs radius were realized using the developed formalism for UV-Vis absorption spectra. These data were compared with experimental values of this parameter, obtained using transmission electron microscope.

  2. Effect of Substitution of Mn, Cu, and Zr on the Structural, Magnetic, and Ku-Band Microwave-Absorption Properties of Strontium Hexaferrite Nanoparticles

    NASA Astrophysics Data System (ADS)

    Rostami, Mohammad; Moradi, Mahmood; Alam, Reza Shams; Mardani, Reza

    2016-08-01

    The ferrites with the compositions of SrMn x Cu x Zr2 x Fe(12-4 x)O19 ( x = 0.0, 0.2, 0.3, 0.4, and 0.5) are synthesized by the coprecipitation method. The formation of M-type hexaferrite is confirmed by x-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses. The morphology of the samples is shown by field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) microscopy. Vibrating sample magnetometer (VSM) analysis has been used for the investigation of the magnetic properties, and the reason for the changes in the magnetic properties as a result of doping, are expressed. The values of coercivity decrease by increasing the amount of substitution, which could be related to the modification of anisotropy form the c-axis toward the c-plane. Finally, we have used vector network analysis to investigate the microwave absorption properties. We find that the samples with the composition of SrMn0.4Cu0.4Zr0.8Fe10.4O19 have the largest reflection loss and the widest bandwidth among these samples.

  3. 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.

  4. Absorption modulation of FSS-polymer nanocomposites through incorporation of conductive nanofillers

    NASA Astrophysics Data System (ADS)

    Jaiswar, Rajkumar; Danlée, Yann; Mesfin, Henok; Delcorte, Arnaud; Hermans, Sophie; Bailly, Christian; Raskin, Jean-Pierre; Huynen, Isabelle

    2017-03-01

    The hybrid concept of utilizing frequency selective surface (FSS) and polymer nanocomposite (PNC) for absorption modulation is presented in 8-18 GHz frequency band. The extruded PNCs are fabricated by incorporating different weight% fraction of conductive fillers, namely carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs), in high, low and mixed nano-filler concentration in a polycarbonate matrix. The FSS metallic resonator is patterned over a dielectric substrate which lies on grounded PNCs. It was found that absorption depends on wt% fraction of conductive inclusions in polycarbonate matrix, i.e., variation in conductivity of grounded PNCs due to varying concentration of conductive fillers results in modulation of absorption. Peaks of nearly 100% magnitude of absorption and modulated absorption band are observed at 8.2 GHz, and between 12 and 18 GHz frequency bands, respectively, by varying conductivity of polymer composite. We demonstrate here that the bandwidth and magnitude of absorption can be fixed by the combination of SSRs (for limits of the band) and concentrations in nanofillers (for intensity of absorption).

  5. 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.

  6. 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…

  7. Full Spectral Resolution Data Generation from the Cross-track Infrared Sounder on S-NPP at NOAA and its Use to Investigate Uncertainty in Methane Absorption Band Near 7.66 µm

    NASA Astrophysics Data System (ADS)

    Xiong, X.; Peischl, J.; Ryerson, T. B.; Sasakawa, M.; Han, Y.; Chen, Y.; Wang, L.; Tremblay, D.; Jin, X.; Zhou, L.; Liu, Q.; Weng, F.; Machida, T.

    2015-12-01

    The Cross-track Infrared Sounder (CrIS) on Suomi National Polar-orbiting Partnership Satellite (S-NPP) is a Fourier transform spectrometer for atmospheric sounding. CrIS on S-NPP started to provide measurements in 1305 channels in its normal mode since its launch on November 2011 to December 4, 2014, and after that it was switched to the full spectral resolution (FSR) mode, in which the spectral resolutions are 0.625 cm-1 in all the MWIR (1210-1750 cm-1), SWIR (2155-2550 cm-1) and the LWIR bands (650-1095 cm-1) with a total of 2211 channels. While the NOAA operational Sensor Data Record (SDR) processing (IDPS) continues to produce the normal resolution SDRs by truncating full spectrum RDR data, NOAA STAR started to process the FSR SDRs data since December 4, 2014 to present, and the data is being delivered through NOAA STAR website (ftp://ftp2.star.nesdis.noaa.gov/smcd/xxiong/). The current FSR processing algorithm was developed on basis of the CrIS Algorithm Development Library (ADL), and is the baseline of J-1 CrIS SDR algorithm. One major benefit to use the FSR data is to improve the retrieval of atmospheric trace gases, such as CH4, CO and CO2 . From our previous studies to retrieve CH4 using Atmospheric Infrared Sounder (AIRS) and Infrared Atmospheric Sounding Interferometer (IASI), it was found the uncertainty in the CH4 absorption band is up to 1-2%. So, in this study we computed the radiance using the community radiative transfer model (CRTM) and line-by-line model, with the inputs of "truth" of atmospheric temperature and moisture profiles from ECMWF model (and/or RAOB sounding) and CH4 profiles from in-situ aircraft measurements, then convoluted with the response function of CrIS. The difference between the simultaed radiance and the collocated CrIS FSR data is used to exam the uncertainty in these strong absorption channels.Through the improved fitting to the transmittance in these channels, it is expected to improve the retrieval of CH4 using CrIS on S

  8. Influence of transannular interaction over absorption and fluorescent properties of [2.2] paracyclophane and its phenyl derivatives

    NASA Astrophysics Data System (ADS)

    Nurmukhametov, R. N.; Shapovalov, A. V.; Antonov, D. Yu.

    2016-12-01

    A significant bathochromic shift of the fluorescent and long-wavelength absorption bands of [2.2] paracyclophane comparing to corresponding bands of alkyl-benzenes is due to a strong transannular interaction, resulting in formation of a principally new excited state of lower energy. It is concluded that the fluorescent levels for alkylbenzene excimers and for the macrocycle are of the same nature. Analysis of [2.2] paracyclophane mono- and diphenylderivatives spectra shows that their intensive absorption bands (230-310 nm) are originated from electron transitions of biphenyl groups and weak long wavelength absorption (310-340 nm) and fluorescent bands are governed by the same electron transitions between ground and excimer-like excited states as in the case of non-substituted macrocycle.

  9. Line intensity measurements for acetylene between 8980 and 9420 cm-1

    NASA Astrophysics Data System (ADS)

    Béguier, S.; Lyulin, O. M.; Hu, S.-M.; Campargue, A.

    2017-03-01

    The absorption spectrum of acetylene is studied by high-resolution Fourier-transform spectroscopy (FTS) between 8980 and 9420 cm-1. Positions and intensities of 432 12C2H2 absorption lines are retrieved from a spectrum recorded at room temperature (298.5 K) with a pressure of 87.6 hPa and a 105 m path length. The measured lines belong to 11 bands including three bands observed for the first time. The obtained intensity dataset constitutes the first intensity information in the region. The Herman-Wallis coefficients are derived from a fit of the measured intensity values. The reported results will be valuable to complete the spectroscopic databases of acetylene.

  10. 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

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1990-11-01

    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.

  14. Dual band metamaterial perfect absorber based on artificial dielectric "molecules".

    PubMed

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhao, Qian; Zhou, Ji

    2016-07-13

    Dual band metamaterial perfect absorbers with two absorption bands are highly desirable because of their potential application areas such as detectors, transceiver system, and spectroscopic imagers. However, most of these dual band metamaterial absorbers proposed were based on resonances of metal patterns. Here, we numerically and experimentally demonstrate a dual band metamaterial perfect absorber composed of artificial dielectric "molecules" with high symmetry. The artificial dielectric "molecule" consists of four "atoms" of two different sizes corresponding to two absorption bands with near unity absorptivity. Numerical and experimental absorptivity verify that the dual-band metamaterial absorber is polarization insensitive and can operate in wide-angle incidence.

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

    NASA Astrophysics Data System (ADS)

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

    1995-04-01

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

  16. Electronic energy level and intensity correlations in the spectra of the trivalent actinide aquo ions. III. Bk/sup 3 +/

    SciTech Connect

    Carnall, W.T.; Beitz, J.V.; Crosswhite, H.

    1984-03-15

    The solution absorption spectrum of Bk/sup 3 +/(aquo) was measured and the observed band structure interpreted in terms of a free-ion energy level model. The band intensities were successfully analyzed using the Judd--Ofelt theory for transitions within the f/sup tsN/ configuration. Parameters of the theory were then used to compute fluorescence branching ratios from most probable fluorescing states, and an experimental search was successful in yielding evidence for a transition from one excited state to the ground state in D/sub 2/O solvent. Absorption bands attributed to f ..-->.. d transitions were observed and an interpretation of the electronic structure is presented. Band intensities were compared to those observed for Tb/sup 3 +/(aquo).

  17. 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

  18. 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.

  19. 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.

  20. 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

  1. Exposure to omethoate during stapling of ornamental plants in intensive cultivation tunnels: influence of environmental conditions on absorption of the pesticide.

    PubMed

    Aprea, C; Centi, L; Santini, S; Lunghini, L; Banchi, B; Sciarra, G

    2005-11-01

    This report describes a study of exposure to omethoate during manual operations with ornamental plants in two intensive cultivation tunnels (tunnel 8 and tunnel 5). Airborne concentrations of omethoate were in the range 1.48-5.36 nmol/m(3). Total skin contamination in the range 329.94-12,934.46 nmol/day averaged 98.1 +/- 1.1% and 99.3 +/- 0.6% of the total potential dose in tunnel 8 and tunnel 5, respectively. Estimated absorbed doses during work in tunnel 5 were much higher than the acceptable daily intake of omethoate, which is 1.41 nmol/kg b.w. This finding shows that organization of the work or the protective clothing worn in tunnel 5 did not protect the workers from exposure. Urinary excretion of alkylphosphates was significantly higher than in the general population, increasing with exposure and usually showing a peak in the urine sample collected after the work shift. Urinary alkylphosphates showed a good correlation with estimated potential doses during work in tunnel 8 and are confirmed as sensitive biological indicators of exposure to phosphoric esters. The linear regression analysis between the urinary excretion of alkylphosphate, expressed as total nmol excreted in 24 h, and total cutaneous dose allows for estimating that the fraction of omethoate absorbed through the skin during work in tunnel 8 is about 16.5%.

  2. Intensity and linewidth measurements in the 13.7-micron fundamental bands of (C-12)2H2 and (C-12)(C-13)H2 at planetary atmospheric temperatures

    NASA Technical Reports Server (NTRS)

    Varanasi, Prasad

    1992-01-01

    The absolute intensities and collision-broadened half-widths of several lines in the P-,Q-, and R-branches of the nu5-fundamental band of (C-12)2H2 have been measured at various temperatures between 147 and 295 K employing the Doppler-limited spectral resolution (about 10 exp -4/cm) of a tunable diode laser spectrometer. The absolute intensities of R(5), R(7), R(9), and R(20) in the same fundamental belonging to (C-12)(C-13)H2 have also been measured at 294 K. The temperature dependence of the collision-broadened half-width has been determined for some of the lines broadened by planetary atmospheric gases, namely, He, Ar, H2, and N2. Four self-broadened linewidths of (C-12)2H2, as well as three H2-broadened linewidths and a self-broadened half-width of (C-12)(C-13)H2, have also been retrieved from the measurements.

  3. Experimental study of NIR absorption due to Nb4+ polarons in pure and Cr- or Ce-doped SBN crystals

    NASA Astrophysics Data System (ADS)

    Gao, Ming; Kapphan, S.; Porcher, S.; Pankrath, R.

    1999-06-01

    A broad absorption band around 0.72 eV, assigned to the absorption of Nb4+ polarons, is observed in strontium barium niobate (SBN) crystals (nominally pure or Cr- or Ce-doped) either under illumination at low temperature or after a previous reduction treatment. The absorption spectra of Nb4+ polarons at low temperature show considerable dichroism, which in reduced SBN crystals exists even far above room temperature. The peak position of the Nb4+ polaron absorption in reduced SBN crystals shifts to higher energies with decreasing temperature. The dependence on light intensity and temperature of the Nb4+ polaron absorption during the build-up process under illumination and the decay process after the illumination is switched off are investigated in detail. Compared with pure SBN, doping with Ce or Cr creates additional absorption bands in the visible (2.6 eV) and red (1.9 eV for Cr doping) spectral regions. Illumination in these absorption bands at low temperature gives rise to strong Nb4+ polaron absorption in the NIR (0.72 eV), giving evidence of the enhanced sensitivity even in the red spectral region for SBN:Cr. The light-induced charge transfer process and formation of Nb4+ polarons in SBN are briefly discussed.

  4. Band heterotopia.

    PubMed

    Alam, M S; Naila, N

    2010-01-01

    Band heterotopias are one of the rarest groups of congenital disorder that result in variable degree of structural abnormality of brain parenchyma. Band of heterotopic neurons result from a congenital or acquired deficiency of the neuronal migration. MRI is the examination of choice for demonstrating these abnormalities because of the superb gray vs. white matter differentiation, detail of cortical anatomy and ease of multiplanar imaging. We report a case of band heterotopia that showed a bilateral band of gray matter in deep white matter best demonstrated on T2 Wt. and FLAIR images.

  5. First-principles study of direct and narrow band gap semiconducting β -CuGaO2

    DOE PAGES

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; ...

    2015-04-16

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO2 phase. Our calculations show that the β-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. Inmore » conclusion, the optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.« less

  6. On the NH3 absorption depression observable at Northern low latitudes of Jupiter

    NASA Astrophysics Data System (ADS)

    Tejfel, Victor G.; Vdovichenko, Vladimir D.; Lysenko, Peter G.; Karimov, Alibek M.; Kirienko, Galina A.; Bondarenko, Natalya N.; Kharitonova, Galina

    2016-10-01

    From February to April of 2016, we carried out a special series of spectrophotometric observations of Jupiter to study the current behavior of the ammonia absorption at the low latitudes of the Northern hemisphere, where in 2004 we have found a well-defined depression of the 787 nm NH3 absorption band intensity (V.Tejfel et al., Bull.AAS, 2005, Vol. 37, p.682). In subsequent years, an existence of this depression was annually confirmed by spectral observations, although we were noticing its variable character. During observations of 2016 we obtained more than 2,500 CCD-spectrograms, including the spectra of the central meridian, the GRS, and 12 scans of Jovian disk on different dates (70 zonal spectra in each scan). The 787 nm NH3 absorption band was extracted with using of ratios of the Jovian spectra to the Saturn's disk spectrum that was taken as a reference. The depression of absorption in this band begins almost from the equator, and its maximum occurs at the planetographic latitude of 100N then the absorption increases again approaching to the latitude of 200N. The equivalent bandwidths corresponding to these latitudes are equal to 18.7 ± 1.4 A, 14.4 ± 1.0 A and 17.8 ± 0.8A. The 645 nm NH3 absorption band also shows depletion at the low latitudes of the Northern hemisphere, but it is less pronounced. At the temperate latitudes of the Northern hemisphere this band's absorption is systematically lower than the Southern Hemisphere's ones. We will continue research in this direction, especially because recently a significant depletion of gaseous NH3 has also been found with using of the VLA with high resolution (I. de Pater et al., Science, 2016, Vol. 352, Issue 6290, p.1290-1294) at the low latitudes of the Northern hemisphere in the region of the NEB.

  7. Resolving the forbidden band of SF6.

    PubMed

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

    2014-01-28

    Sulfur hexafluoride is an important molecule for modeling thermophysical and polarizability properties. It is also a potent greenhouse gas of anthropogenic origin, whose concentration in the atmosphere, although very low is increasing rapidly; its global warming power is mostly conferred by its strong infrared absorption in the ν3 S-F stretching region near 948 cm(-1). This heavy species, however, features many hot bands at room temperature (at which only 31% of the molecules lie in the ground vibrational state), especially those originating from the lowest, v6 = 1 vibrational state. Unfortunately, the ν6 band itself (near 347 cm(-1)), in the first approximation, is both infrared- and Raman-inactive, and no reliable spectroscopic information could be obtained up to now and this has precluded a correct modeling of the hot bands. It has been suggested theoretically and experimentally that this band might be slightly activated through Coriolis interaction with infrared-active fundamentals and appears in high pressure measurements as a very faint, unresolved band. Using a new cryogenic multipass cell with 93 m optical path length and regulated at 163 ± 2 K temperature, coupled to synchrotron radiation and a high resolution interferometer, the spectrum of the ν6 far-infrared region has been recorded. Low temperature was used to avoid the presence of hot bands. We are thus able to confirm that the small feature in this region, previously viewed at low-resolution, is indeed ν6. The fully resolved spectrum has been analyzed, thanks to the XTDS software package. The band appears to be activated by faint Coriolis interactions with the strong ν3 and ν4 fundamental bands, resulting in the appearance of a small first-order dipole moment term, inducing unusual selection rules. The band center (ν6 = 347.736707(35) cm(-1)) and rovibrational parameters are now accurately determined for the v6 = 1 level. The ν6 perturbation-induced dipole moment is estimated to be 33 ± 3

  8. 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.

  9. Infrared band strengths: Laboratory techniques and applications to astronomical observations

    NASA Astrophysics Data System (ADS)

    Gerakines, P. A.

    2002-09-01

    Whenever an abundance measurement is derived by way of infrared spectroscopy, it will typically make use of a laboratory-obtained conversion factor between the size of an IR absorption feature and the (column) density of the molecule under study. This factor is usually called the "absolute absorption intensity" by a chemist or the "band strength" by a typical IR astronomer. Band strengths have been studied in chemistry since the 1950s, and the commonly quoted "accuracy to with a factor of ten" historically required of astronomical calculations has not required much new input into this area. Today, however, astronomical measurements require much higher precision, and it is time for IR astronomers to ask more of laboratory measurements and to understand when and why to use IR band strengths in a more appropriate manner. The history, interpretation, measurement, and common astrophysical applications of infrared band strengths will be discussed. The "secrets" of the laboratory techniques involved in their measurement are described, and a compilation of results from the literature is given along with some new results. Typical astrophysical applications and appropriate uses will also be discussed. Common misconceptions are confronted and two challenges are presented: (i) to the laboratory astrophysics community to produce and advertise accurate values with caveats when necessary, and (ii) to the observational community to use the most appropriate results for the environment under study.

  10. The first TDDFT and MCD studies of free base triarylcorroles: a closer look into solvent-dependent UV-visible absorption.

    PubMed

    Ziegler, Christopher J; Sabin, Jared R; Geier, G Richard; Nemykin, Victor N

    2012-05-16

    Absorption spectra of several free base triarylcorroles were investigated by MCD spectroscopy. The MCD spectra exhibit unusual sign-reverse (positive-to-negative intensities in ascending energy) features in the Soret- and Q-type band regions, suggesting a rare ΔHOMO < ΔLUMO relationship between π and π* MOs in the corrole core.

  11. Optical absorption and transmission in a molybdenum disulfide monolayer

    NASA Astrophysics Data System (ADS)

    Rukelj, Zoran; Štrkalj, Antonio; Despoja, Vito

    2016-09-01

    Our recently proposed theoretical formulation [presented in D. Novko et al., Phys. Rev. B 93, 125413 (2016), 10.1103/PhysRevB.93.125413] is used to study optical absorption and transmission in molybdenum disulfide (MoS2) monolayer as a function of incident photon energy and angle. The investigation is not focused on exploration of well-documented spin-orbit split excitons around optical absorption onset, but rather on the most intensive features in absorption spectrum in the visible and near-ultraviolet photon energy range (1.7 -4 eV ). It is shown that three most intensive peaks, at 2.7, 3.1, and 3.7 eV, result from transitions between Mo(d ) and S(p ) valence and conduction bands and that the character of their charge/current density fluctuations is intrinsically in plane, located in the molybdenum plane. This also implies that MoS2 monolayer is completely transparent when illuminated by grazing incidence p -polarized light. The validity of the presented results is supported by our effective two-band tight-binding model and finally by good agreement with some recent experimental results.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  13. Giant many-body effects in liquid ammonia absorption spectrum

    NASA Astrophysics Data System (ADS)

    Ziaei, Vafa; Bredow, Thomas

    2016-11-01

    In the present work, we accurately calculate the absorption spectrum of liquid ammonia up to 13 eV using many-body perturbation approach. The electronic bandgap of liquid NH3 is perfectly described as the combination of density functional theory, Coulomb-hole screened exchange, and G0W0 approximation to the electronic self-energy, yielding a direct gap (Γ → Γ) of 7.71 eV, fully consistent with the experimentally measured gap from photo-emission spectroscopy. With respect to the NH3 optical properties, the entire spectrum in particular the low lying first absorption band is extremely affected by electron-hole interactions, leading to a fundamental redistribution of spectral weights of the independent-particle spectrum. Three well separated but broad main peaks are identified at 7.0, 9.8, and 11.8 eV with steadily increasing intensities in excellent agreement with the experimental data. Furthermore, we observe a giant net blue-shift of the first absorption peak of about 1.4 eV from gaseous to liquid phase as the direct consequence of many-body effects, allowing the associated liquid ammonia absorption band exciton to delocalize and feel more effectively the repulsion effects imposed by the surrounding solvent shells. Further, the spectrum is insensitive to the coupling of resonant and anti-resonant contributions. Concerning electronic response structure of liquid NH3, it is most sensitive to excitations at energies lower than its electronic gap.

  14. 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.

  15. 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.

  16. 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.

  17. Measurements of the infrared absorption cross-sections of HCFC-141b (CH3CFCl2)

    NASA Astrophysics Data System (ADS)

    Le Bris, Karine; McDowell, James; Strong, Kimberly

    2012-10-01

    Detection of atmospheric trace gases by optical remote sensing techniques relies on the availability of molecular absorption spectra over a range of relevant temperatures. Absorption cross-sections of a pure vapour of the hydrochlorofluorocarbon HCFC-141b are reported at a resolution of 0.02 cm-1 for a range of temperatures between 223 and 283 K and a spectral range of 570-3100 cm-1. The integrated intensities of the nine main harmonic bands compare well with the data available from previous experimental studies and with theoretical calculations by ab initio and density functional theories.

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

    NASA Astrophysics Data System (ADS)

    Stock, D.; Peeters, E.; Tielens, X.; Otaguro, J.; Bik, A.

    The spatial variations in polycyclic aromatic hydrocarbon (PAH) band intensities are generally attributed to variations of the physical conditions in the environment hosting the emitting PAH molecules. However, in recent years, it has been suggested that such variations are caused mainly by extinction. To resolve this question, we have obtained near-infrared (NIR), mid-infrared (MIR) and radio observations of the compact HII region IRAS 12063-6259. We use these data to construct multiple independent extinction maps and to measure the main PAH feature intensities (6.2, 7.7, 8.6 and 11.2 µ m). Three extinction maps are derived: the first using the NIR hydrogen lines and case B recombination theory; the second combining the NIR data, radio data and case B recombination; and the third making use of the Spitzer/IRS MIR observations to measure the 9.8 µ m silicate absorption feature intensity using the Spoon method and PAHFIT. We conclude that different areas of IRAS 12063-6259 possess markedly different extinction properties, with some regions displaying both silicate absorption and corresponding NIR extinction, and other regions displaying NIR extinction and no corresponding silicate absorption. While such breakdowns of the relationship between the NIR extinction and the silicate absorption strength have been observed in molecular clouds, they have never been observed for HII regions. We then compare the PAH intensity variations in the Spitzer/IRS data after dereddening to those found in the original data. Generally it was found that the PAH band intensity variations persist even after dereddening, implying that extinction is not the main cause of the PAH band intensity variations.

  19. Method and apparatus for aerosol-particle absorption spectroscopy. [DOE patent application

    SciTech Connect

    Campillo, A.J.; Lin, H.B.

    1981-06-25

    A method and apparatus are described 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.

  20. 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 Å break, the efficiencies of BChls are smaller than Chls in the higher temperature stars.

  1. Optical and fundamental band gaps disparity in transparent conducting oxides: new findings for the [Formula: see text] and [Formula: see text] systems.

    PubMed

    Sabino, Fernando P; Nunes Oliveira, Luiz; Wei, Su-Huai; Da Silva, Juarez L F

    2017-03-01

    The optical band gap, extracted from absorption measurements, defines the figure of merit for transparent conducting oxides (TCOs). In many oxides, such as [Formula: see text] or [Formula: see text], inversion symmetry introduces a selection rule that blocks transitions from the valence-band maximum to the conduction-band minimum. This raises the absorption threshold and enlarges the optical gap relative to the fundamental band gap. Here, we present density-functional computations identifying two optical gaps, either of which can be detected, depending on the optical light intensity. Under strong illumination, weak transitions from [Formula: see text]-points near the valence-band maximum contribute significantly to the absorption spectrum and define an optical gap matching the fundamental gap. Low optical intensities by contrast give prominence to the large optical gap determined by the selection rule. While experimental conditions have favored observation of the former optical gap in [Formula: see text], in contrast, absorption measurements in [Formula: see text] have focused on the latter. Our findings explain the disparity between the optical and fundamental gaps in bixbyite [Formula: see text] and predict that, measured under low illumination, the optical gap for rutile [Formula: see text] will increase, from 3.60 eV to 4.34 eV.

  2. 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.

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

    NASA Technical Reports Server (NTRS)

    Reuter, Dennis C.; Sirota, J. Marcos

    1993-01-01

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

  4. 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 ν_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 ν_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 ν_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 ν_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 2ν_6-ν_6 hot band and to reduce the neighboring, stronger ν_4-ν_2 difference band. We are thus able to confirm that the small feature in this region, previously viewed at low-resolution is indeed ν_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).

  5. Electronic absorption spectra and energy gap studies of Er3+ ions in different chlorophosphate glasses.

    PubMed

    Ratnakaram, Y C; Reddy, A Viswanadha; Chakradhar, R P Sreekanth

    2002-06-01

    Spectroscopic properties of Er3+ ions in different chlorophosphate glasses 50P2O5-30Na2HPO4-19.8RCl (R = Li, Na, K, Ca and Pb) are studied. The direct and indirect optical band gaps (Eopt) and the various spectroscopic parameters (E1, E2, E3, and zeta4f and alpha) are reported. The oscillator strengths of the transitions in the absorption spectrum are parameterized in terms of three Judd-Ofelt intensity parameters (omega2, omega4 and omega6). These intensity parameters are used to predict the transition probabilities (A), radiative lifetimes (tauR), branching ratios (beta) and integrated cross sections (sigma) for stimulated emission. Attention has been paid to the trend of the intensity parameters over hypersensitive transitions and optical band gaps. The lifetimes and branching ratios of certain transitions are compared with other glass matrices.

  6. First-principles study of direct and narrow band gap semiconducting β -CuGaO2

    SciTech Connect

    Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

    2015-04-16

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO2 phase. Our calculations show that the β-CuGaO2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. In conclusion, the optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment.

  7. Gas Phase Absorption Spectroscopy of C+60 and C+70 in a Cryogenic Ion Trap: Comparison with Astronomical Measurements

    NASA Astrophysics Data System (ADS)

    Campbell, E. K.; Holz, M.; Maier, J. P.; Gerlich, D.; Walker, G. A. H.; Bohlender, D.

    2016-05-01

    Recent low-temperature laboratory measurements and astronomical observations have proved that the fullerene cation {{{C}}}60+ is responsible for four diffuse interstellar bands (DIBs). These absorptions correspond to the strongest bands of the lowest electronic transition. The gas phase spectrum below 10 {{K}} is reported here for the full wavelength range encompassed by the electronic transition. The absorption spectrum of {{{C}}}70+, with its origin band at 7959.2 {{\\mathringA }}, has been obtained under similar laboratory conditions. Observations made toward the reddened star {HD} 183143 were used in a specific search for the absorption of these fullerene cations in diffuse clouds. In the case of {{{C}}}60+, one further band in the astronomical spectrum at 9348.5 \\mathringA is identified, increasing the total number of assigned DIBs to five. Numerous other {{{C}}}60+ absorptions in the laboratory spectrum are found to lie below the astronomical detection limit. Special emphasis is placed on the laboratory determination of absolute absorption cross-sections. For {{{C}}}60+ this directly yields a column density, N({{{C}}}60+), of 2× {10}13 {{{cm}}}-2 in diffuse clouds, without the need to rely on theoretical oscillator strengths. The intensity of the {{{C}}}70+ electronic transition in the range 7000-8000 Å is spread over many features of similar strength. Absorption cross-section measurements indicate that even for a similar column density, the individual absorption bands of {{{C}}}70+ will be too weak to be detected in the astronomical spectra, which is confirmed giving an upper limit of 2 {{m\\mathringA }} to the equivalent width. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique of France, and the University of Hawaii.

  8. Transition Energies and Absorption Oscillator Strengths for {{c}_{4}}^{\\prime 1}{{{\\rm{\\Sigma }}}_{u}}^{+}-{{\\rm{X}}}^{1}{{{\\rm{\\Sigma }}}_{g}}^{+}, {b}^{\\prime 1}{{{\\rm{\\Sigma }}}_{u}}^{+}-{{\\rm{X}}}^{1}{{{\\rm{\\Sigma }}}_{g}}^{+}, and {{c}_{5}}^{\\prime 1}{{{\\rm{\\Sigma }}}_{u}}^{+}-{{\\rm{X}}}^{1}{{{\\rm{\\Sigma }}}_{g}}^{+} Band Systems in N2

    NASA Astrophysics Data System (ADS)

    Lavín, C.; Velasco, A. M.

    2017-04-01

    Theoretical transition energies and absorption oscillator strengths for the {{c}4}\\prime 1{{{{Σ }}}u}+ (v‧ = 0–2, 5, 7, 8) ‑ {{{X}}}1{{{{Σ }}}g}+(v\\prime\\prime =0{--}14) and {{c}5}\\prime 1{{{{Σ }}}u}+ (v‧ = 0, 2) ‑ {{{X}}}1{{{{Σ }}}g}+ (v″ = 0–14) Rydberg bands, and {b}\\prime 1{{{{Σ }}}u}+ (v‧ = 0–9, 11, 12, 14–19, 21, 22) ‑ {{{X}}}1{{{{Σ }}}g}+ (v″ = 0–14) valence bands of molecular nitrogen are reported. The strong interaction between {}1{{{{Σ }}}u}+ states has been dealt with through a vibronic interaction matrix. As a consequence of the Rydberg-valence interaction, irregularities in the vibrational structure of the above band systems are observed. Good agreement is found with the scarce high-resolution data that are available for oscillator strengths. The new band oscillator strengths reported here may be useful for a reliable interpretation of the spectra from atmospheres of the Earth, Titan, and Triton, where {{{N}}}2 is the mayor constituent.

  9. 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.

  10. 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.

  11. Amorphization-induced strong localization of electronic states in CsPbBr3 and CsPbCl3 studied by optical absorption measurements

    NASA Astrophysics Data System (ADS)

    Kondo, S.; Sakai, T.; Tanaka, H.; Saito, T.

    1998-11-01

    Optical absorption spectra of amorphous CsPbX3 films (X=Br,Cl) are characterized by two Gaussian bands near the fundamental edge, with the optical energy gap largely blueshifted and the absorption intensity strongly reduced as compared with the crystalline films. The peak energies of the bands are close to those of the A and C bands of Pb-doped alkali halides. The spectral features are discussed in terms of a molecular orbital theory based on a quasicomplex Pb2+(X-)6 model similar to the complex model for the doped alkali halides. It is shown that not only Pb2+ 6s and 6p extended states near the band edges but also X- p states contributing to upper valence bands are localized by amorphization. The transitions from the localized Pb2+ 6s to 6p states produce the spin-orbit allowed 3P1 and dipole allowed 1P1 states responsible for the two Gaussians. The localized X- p states lie deeper in energy than the localized Pb2+ 6s state and only contribute to higher-energy absorption above the Gaussian bands, giving the reason for the reduced absorption near the fundamental edge. The blueshift of the optical energy gap is attributed to the disappearance of k dispersions for these one-electron states.

  12. Assignment of the Q-bands of the chlorophylls: coherence loss via Qx - Qy mixing.

    PubMed

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

    2013-09-26

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

  13. 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.

  14. Absorption of CO laser radiation by NO

    NASA Technical Reports Server (NTRS)

    Hanson, R. K.; Monat, J. P.; Kruger, C. H.

    1976-01-01

    The paper describes absorption calculations and measurements at selected infrared CO laser wavelengths which are nearly coincident with absorption lines in the fundamental vibration-rotation band of NO near 5.3 microns. Initial work was directed towards establishing the optimal CO laser-NO absorption line coincidence for high temperature applications. Measurements of the absorption coefficient at this optimal laser wavelength were carried out, first using a room-temperature absorption cell for high-temperature calculations and then using a shock tube, for the temperature range 630-4000 K, to validate the high temperature calculations.

  15. Laparoscopic gastric banding

    MedlinePlus

    ... adjustable gastric banding; Bariatric surgery - laparoscopic gastric banding; Obesity - gastric banding; Weight loss - gastric banding ... gastric banding is not a "quick fix" for obesity. It will greatly change your lifestyle. You must ...

  16. Spectrum of induced absorption of oxygen in mixtures with various gases in the region of the Herzberg photodissociation continuum

    NASA Astrophysics Data System (ADS)

    Zelikina, G. Y.; Kiseleva, M. B.; Burtsev, Andrei P.; Bertsev, V. V.

    1999-01-01

    Values of the binary absorption coefficients are obtained for the region of Herzberg photodissociation continuum in mixtures of oxygen with various foreign gases X, where X - Ar, Kr, Xe, N2, N2O, CH4, C3H8, CO2, NH3, NF3, SF6, CF4, C2F6, C3F8, CF3H, CF3Cl, CF3Br, CF2ClH, CF2Cl2 - group I (the ionization potential of molecules >= 11 eV) and C2H4, CF3I, C2F5I - group II (the ionization potential < 11 eV). The induced absorption of the mixtures of O2 with gases from group I is found to result from the Herzberg III band of oxygen. The obtained regular dependence of the intensity of induced absorption in an O2 - X pair on the ionization potential of a molecule X, confirms the hypothesis that excited electronic states of the ionic type of the molecular pair serve as the main intensity source for the Herzberg III band. The long-wavelength wing of the charge transfer band of the O2 - X pair is shown to contribute to the induced absorption of the mixtures of O2 with gases from group II.

  17. Field test of spectral line intensity parameters for tropospheric water vapor

    NASA Astrophysics Data System (ADS)

    Sierk, B.; Solomon, S.; Daniel, J. S.; Portmann, R. W.; Gutman, S. I.; Langford, A. O.; Eubank, C. S.; Holub, K. H.; Florek, S. V.

    2003-06-01

    We report the results of a field experiment designed to study atmospheric water vapor absorption in the visible and near-infrared spectral regions between 550 and 1000 nm. We carried out spectroscopic ground measurements of direct solar radiation under clear-sky conditions in Boulder, Colorado. The data with a spectral resolution of approximately 1 nm were analyzed using the differential optical absorption spectroscopy (DOAS) technique in five different absorption bands of water vapor. We show that this technique can reveal the broadband effects of errors and inconsistencies in absorption spectra information for the water molecule. Retrievals of column tropospheric water vapor from the field spectra were compared to simultaneous independent estimates from Global Positioning System (GPS) data and radiosonde soundings. The data set is used to critically assess the widely used High-Resolution Transmission Molecular Absorption Database (HITRAN) [, 1998]. The results indicate that line intensities in the 3ν + δ polyad centered at 820 nm are underestimated by 21% with respect to the strong 3ν polyad centered at 940 nm, while the 4ν polyad at 720 nm shows agreement within the measurement accuracy of 3%. Two weaker bands centered at 650 and 590 nm were found to be overestimated by about 8-10%. The effect of the proposed corrections on the absorption of incoming solar flux for a clear-sky atmosphere is estimated to be 0.6 W/m2 for an overhead Sun.

  18. Dynamic perturbation effects upon the circular dichroism intensity induced in an aggregate of dye chromophores bound to biopolymers

    NASA Astrophysics Data System (ADS)

    Kamiya, Mamoru

    1980-11-01

    The dynamic perturbation effects of polarizable monomer perturbers upon the circular dichroism intensity arising from absorption transitions of an arbitrary aggregate of dye chromophores bound to a large host polymer are formulated using the linear response theory in the decorrelation approximation, where the interchromophoric retardation phase factors are eliminated by a first-order Taylor expansion which is compatible with the use of the retarded helix selection rules in the long-wavelength approximation. A space-averaged and closed-form formulation of the non-conservative circular dichroism intensity which is perturbed by intensity with the outside perturber transitions is derived in the limit of the weak dynamic perturbation where perturber—perturber interactions are negligible. The relevant formulation is applied in order to investigate the intercalation model dependence of the non-conservative circular dichroism intensity induced at the visible absorption band of proflavine molecules intercalated in either poly(A—T) or poly(G—C).

  19. PERITONEAL ABSORPTION

    PubMed Central

    Hahn, P. F.; Miller, L. L.; Robscheit-Robbins, F. S.; Bale, W. F.; Whipple, G. H.

    1944-01-01

    The absorption of red cells from the normal peritoneum of the dog can be demonstrated by means of red cells labeled with radio-iron incorporated in the hemoglobin of these red cells. Absorption in normal dogs runs from 20 to 100 per cent of the amount given within 24 hours. Dogs rendered anemic by bleeding absorb red cells a little less rapidly—ranging from 5 to 80 per cent of the injected red cells. Doubly depleted dogs (anemic and hypoproteinemic) absorb even less in the three experiments recorded. This peritoneal absorption varies widely in different dogs and even in the same dog at different times. We do not know the factors responsible for these variations but there is no question about active peritoneal absorption. The intact red cells pass readily from the peritoneal cavity into lymph spaces in diaphragm and other areas of the peritoneum. The red cells move along the lymphatics and through the lymph glands with little or no phagocytosis and eventually into the large veins through the thoracic ducts. PMID:19871404

  20. Nutrient absorption.

    PubMed

    Rubin, Deborah C

    2004-03-01

    Our understanding of nutrient absorption continues to grow, from the development of unique animal models and from studies in which cutting-edge molecular and cellular biologic approaches have been used to analyze the structure and function of relevant molecules. Studies of the molecular genetics of inherited disorders have also provided many new insights into these processes. A major advance in lipid absorption has been the cloning and characterization of several intestinal acyl CoA:monoacylglycerol acyltransferases; these may provide new targets for antiobesity drug therapy. Studies of intestinal cholesterol absorption and reverse cholesterol transport have encouraged the development of novel potential treatments for hyperlipidemia. Observations in genetically modified mice and in humans with mutations in glucose transporter 2 suggest the importance of a separate microsomal membrane transport pathway for glucose transport. The study of iron metabolism has advanced greatly with the identification of the hemochromatosis gene and the continued examination of the genetic regulation of iron absorptive pathways. Several human thiamine transporters have been identified, and their specific roles in different tissues are being explored.

  1. 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.

  2. 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.

  3. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, 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.

  4. 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.

  5. Complementary cavity-enhanced spectrometers to investigate the OH + CH combination band in trans-formic acid.

    PubMed

    Golebiowski, D; Földes, T; Vanfleteren, T; Herman, M; Perrin, A

    2015-07-07

    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 (ν1 + ν2) 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 ν1 + ν2 transition moment is estimated from relative intensities to be 24° away from the principal b-axis of inertia.

  6. 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.

  7. The profile of the 2140 cm-1 solid CO band on different substrates

    NASA Astrophysics Data System (ADS)

    Palumbo, M. E.; Baratta, G. A.; Collings, M. P.; McCoustra, M. R. S.

    We have studied the profile of the 2140 cm-1 fundamental band of solid carbon monoxide (CO) at low temperature (10-15 K) by infrared transmission spectroscopy and by reflection absorption infrared (RAIR) spectroscopy. In particular, transmission spectra have been taken after CO had been adsorbed on a bare crystalline silicon substrate and on pre-adsorbed solid N2 layers of different thickness. RAIR spectra have been taken after CO had been adsorbed on a bare gold substrate and on pre-adsorbed solid N2 layers of different thickness. Laboratory spectra show that the profile of the fundamental CO band at about 2140 cm-1 is different in the different instances considered. In particular, we have found that the relative intensity of the LO and TO modes of the CO band depends on the thickness of the N2 layer. Here we present the experimental results and show that these can be predicted by the elementary electromagnetic theory.

  8. Selective coherent perfect absorption in metamaterials

    SciTech Connect

    Nie, Guangyu; Shi, Quanchao; Zhu, Zheng; Shi, Jinhui

    2014-11-17

    We show multi-band coherent perfect absorption (CPA) in simple bilayered asymmetrically split ring metamaterials. The selectivity of absorption can be accomplished by separately excited electric and magnetic modes in a standing wave formed by two coherent counterpropagating beams. In particular, each CPA can be completely switched on/off by the phase of a second coherent wave. We propose a practical scheme for realizing multi-band coherent perfect absorption of 100% that is allowed to work from microwave to optical frequency.

  9. Two-step photon absorption in InAs/GaAs quantum-dot superlattice solar cells

    NASA Astrophysics Data System (ADS)

    Kada, T.; Asahi, S.; Kaizu, T.; Harada, Y.; Kita, T.; Tamaki, R.; Okada, Y.; Miyano, K.

    2015-05-01

    We studied the two-step photon absorption (TSPA) process in InAs/GaAs quantum-dot superlattice (QDSL) solar cells. TSPA of subband-gap photons efficiently occurs when electrons are pumped from the valence band to the states above the inhomogeneously distributed fundamental states of QDSLs. The photoluminescence (PL)-excitation spectrum demonstrates an absorption edge attributed to the higher excited states of the QDSLs in between the InAs wetting layer states and the fundamental states of QDSLs. When the absorption edge of the excited state was resonantly excited, the superlinear excitation power dependence of the PL intensity demonstrated that the electron and hole created by the interband transition separately relax into QDSLs. Furthermore, time-resolved PL measurements demonstrated that the electron lifetime is extended by thereby inhibiting recombination with holes, enhancing the second subband-gap absorption.

  10. Effects of color centers absorption on the spectrum of the temperature-dependent radiation-induced attenuation in fiber.

    PubMed

    Jin, Jing; Hou, Yunxia; Liu, Chunjing

    2015-02-01

    Spectra ranging from 800 to 1650 nm of the temperature-dependent radiation-induced attenuation (RIA) in the irradiated and sufficiently annealed fiber with germanium and phosphorous dopant has been measured. These RIA spectra were investigated based on the mechanism of color centers absorption. With the configurational coordinate model, these RIA spectra were decomposed by the absorption bands of three kinds of color centers. The effects of color centers absorption on the spectrum of temperature-dependent RIA is discussed by comparing the absorption intensity of different color centers at a same wavelength. Moreover, the temperature-dependent RIA of the fiber has been measured separately at 850, 1310, and 1550 nm. The measured results agreed well with the analysis of RIA spectra.

  11. First-principles calculation of ground and excited-state absorption spectra of ruby and alexandrite considering lattice relaxation

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinta; Sasaki, Tomomi; Taniguchi, Rie; Ishii, Takugo; Ogasawara, Kazuyoshi

    2009-02-01

    We performed first-principles calculations of multiplet structures and the corresponding ground-state absorption and excited-state absorption spectra for ruby (Cr3+:α-Al2O3) and alexandrite (Cr3+:BeAl2O4) which included lattice relaxation. The lattice relaxation was estimated using the first-principles total energy and molecular-dynamics method of the CASTEP code. The multiplet structure and absorption spectra were calculated using the configuration-interaction method based on density-functional calculations. For both ruby and alexandrite, the theoretical absorption spectra, which were already in reasonable agreement with experimental spectra, were further improved by consideration of lattice relaxation. In the case of ruby, the peak positions and peak intensities were improved through the use of models with relaxations of 11 or more atoms. For alexandrite, the polarization dependence of the U band was significantly improved, even by a model with a relaxation of only seven atoms.

  12. Optical and fundamental band gaps disparity in transparent conducting oxides: new findings for the \\mathbf{I}{{\\mathbf{n}}_{\\mathbf{2}}}{{\\mathbf{O}}_{\\mathbf{3}}} and \\mathbf{S}{{\\mathbf{n}}_{{}}}{{\\mathbf{O}}_{\\mathbf{2}}} systems

    NASA Astrophysics Data System (ADS)

    Sabino, Fernando P.; Nunes Oliveira, Luiz; Wei, Su-Huai; Da Silva, Juarez L. F.

    2017-03-01

    The optical band gap, extracted from absorption measurements, defines the figure of merit for transparent conducting oxides (TCOs). In many oxides, such as \\text{I}{{\\text{n}}2}{{\\text{O}}3} or \\text{Sn}{{\\text{O}}2} , inversion symmetry introduces a selection rule that blocks transitions from the valence-band maximum to the conduction-band minimum. This raises the absorption threshold and enlarges the optical gap relative to the fundamental band gap. Here, we present density-functional computations identifying two optical gaps, either of which can be detected, depending on the optical light intensity. Under strong illumination, weak transitions from \\mathbf{k} -points near the valence-band maximum contribute significantly to the absorption spectrum and define an optical gap matching the fundamental gap. Low optical intensities by contrast give prominence to the large optical gap determined by the selection rule. While experimental conditions have favored observation of the former optical gap in \\text{Sn}{{\\text{O}}2} , in contrast, absorption measurements in \\text{I}{{\\text{n}}2}{{\\text{O}}3} have focused on the latter. Our findings explain the disparity between the optical and fundamental gaps in bixbyite \\text{I}{{\\text{n}}2}{{\\text{O}}3} and predict that, measured under low illumination, the optical gap for rutile \\text{Sn}{{\\text{O}}2} will increase, from 3.60 eV to 4.34 eV.

  13. Two-photon absorption spectra of a near-infrared 2-azaazulene polymethine dye: solvation and ground-state symmetry breaking.

    PubMed

    Hu, Honghua; Przhonska, Olga V; Terenziani, Francesca; Painelli, Anna; Fishman, Dmitry; Ensley, Trenton R; Reichert, Matthew; Webster, Scott; Bricks, Julia L; Kachkovski, Alexey D; Hagan, David J; Van Stryland, Eric W

    2013-05-28

    Polymethine dyes (PDs) with absorption bands in the near-infrared region undergo symmetry breaking in polar solvents. To investigate how symmetry breaking affects nonlinear optical responses of PDs, an extensive and challenging experimental characterization of a cationic 2-azaazulene polymethine dye, including linear absorption, fluorescence, two-photon absorption and excited-state absorption, has been performed in two solvents with different polarity. Based on this extensive set of experimental data, a three-electronic-state model, accounting for the coupling of electronic degrees of freedom to molecular vibrations and polar solvation, has been reliably parameterized and validated for this dye, fully rationalizing optical spectra in terms of spectral position, intensities and bandshapes. In low-polarity solvents where the dye is mainly in its symmetric form, a nominally forbidden two-photon absorption band is observed, due to a vibronic activation mechanism. Inhomogeneous broadening plays a major role in polar solvents: absorption spectra represent the weighted sum of contributions from states with a variable amount of symmetry breaking, leading to a complex evolution of linear and nonlinear optical spectra with solvent polarity. In more polar solvents, the dominant role of the asymmetric form leads to the activation of two-photon absorption as a result of the symmetry lowering. The subtle interplay between the two mechanisms for two-photon absorption activation, vibronic coupling and polar solvation, can be fully accounted for within the proposed microscopic model allowing a detailed interpretation of the optical spectra of PDs.

  14. Predissociation linewidths of the (3,0)-(11,0) Schumann-Runge absorption bands of (O-18)2 and O-16O-18 in the wavelength region 180-196 nm

    NASA Technical Reports Server (NTRS)

    Chiu, S. S.-L.; Cheung, A. S.-C.; Yoshino, K.; Esmond, J. R.; Freeman, D. E.

    1990-01-01

    The Yoshino et al. (1988) measurements of absolute cross sections and those of Cheung et al. (1988) for spectroscopic constants are presently used to derive the predissociation linewidths of the (3,0)-(11,0) Schumman-Runge bands of (O-18)2 and O-16O-18, in the 180-196 nm wavelength region. Linewidths are determined as parameters in the nonlinear, least-squares fitting of calculated cross-sections to measured ones. The predissociation linewidths obtained are noted to often be greater than previously obtained experimental values for both isotopic molecules.

  15. UV absorption spectrum of the C2 Criegee intermediate CH3CHOO.

    PubMed

    Smith, Mica C; Ting, Wei-Lun; Chang, Chun-Hung; Takahashi, Kaito; Boering, Kristie A; Lin, Jim Jr-Min

    2014-08-21

    The UV spectrum of CH3CHOO was measured by transient absorption in a flow cell at 295 K. The absolute absorption cross sections of CH3CHOO were measured by laser depletion in a molecular beam to be (1.06 ± 0.09) × 10(-17) cm(2) molecule(-1) at 308 nm and (9.7 ± 0.6) × 10(-18) cm(2) molecule(-1) at 352 nm. After scaling the UV spectrum of CH3CHOO to the absolute cross section at 308 nm, the peak UV cross section is (1.27 ± 0.11) × 10(-17) cm(2) molecule(-1) at 328 nm. Compared to the simplest Criegee intermediate CH2OO, the UV absorption band of CH3CHOO is similar in intensity but blue shifted by 14 nm, resulting in a 20% slower photolysis rate estimated for CH3CHOO in the atmosphere.

  16. UV absorption spectrum of the C2 Criegee intermediate CH3CHOO

    NASA Astrophysics Data System (ADS)

    Smith, Mica C.; Ting, Wei-Lun; Chang, Chun-Hung; Takahashi, Kaito; Boering, Kristie A.; Lin, Jim-Min, Jr.

    2014-08-01

    The UV spectrum of CH3CHOO was measured by transient absorption in a flow cell at 295 K. The absolute absorption cross sections of CH3CHOO were measured by laser depletion in a molecular beam to be (1.06 ± 0.09) × 10-17 cm2 molecule-1 at 308 nm and (9.7 ± 0.6) × 10-18 cm2 molecule-1 at 352 nm. After scaling the UV spectrum of CH3CHOO to the absolute cross section at 308 nm, the peak UV cross section is (1.27 ± 0.11) × 10-17 cm2 molecule-1 at 328 nm. Compared to the simplest Criegee intermediate CH2OO, the UV absorption band of CH3CHOO is similar in intensity but blue shifted by 14 nm, resulting in a 20% slower photolysis rate estimated for CH3CHOO in the atmosphere.

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

    SciTech Connect

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

    2010-10-26

    Previously we have shown that the size of laser induced damage sites in both KDP and SiO{sub 2} is largely governed by the duration of the laser pulse which creates them. Here we present a model based on experiment and simulation that accounts for this behavior. Specifically, we show that solid-state laser-supported absorption fronts are generated during a damage event and that these fronts propagate at constant velocities for laser intensities up to 4 GW/cm{sup 2}. It is the constant absorption front velocity that leads to the dependence of laser damage site size on pulse duration. We show that these absorption fronts are driven principally by the temperature-activated deep sub band-gap optical absorptivity, free electron transport, and thermal diffusion in defect-free silica for temperatures up to 15,000K and pressures < 15GPa. In addition to the practical application of selecting an optimal laser for pre-initiation of large aperture optics, this work serves as a platform for understanding general laser-matter interactions in dielectrics under a variety of conditions.

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

    NASA Astrophysics Data System (ADS)

    Devi, Ch. Victory; Singh, N. Rajmuhon

    2011-03-01

    The interaction between Nd(III) and Calf Thymus DNA (CT-DNA) in physiological buffer (pH 7.4) has been studied using absorption spectroscopy involving 4f-4f transition spectra in different aquated organic solvents. Complexation with CT-DNA is indicated by the changes in absorption intensity following the subsequent changes in the oscillator strengths of different 4f-4f bands and Judd-Ofelt intensity ( Tλ) parameters. The other spectral parameters namely Slator-Condon ( Fk's), nephelauxetic effect ( β), bonding ( b1/2) and percent covalency ( δ) parameters are computed to correlate with the binding of Nd(III) with DNA. The absorption spectra of Nd(III) exhibited hyperchromism and red shift in the presence of DNA. The binding constant, Kb has been determined by absorption measurement. The relative viscosity of DNA decreased with the addition of Nd(III). Thermodynamic parameters have been calculated according to relevant absorption data and Van't Hoff equation. The characterisation of bonding mode has been studied in detail. The results suggested that the major interaction mode between Nd(III) and DNA was external electrostatic binding.

  19. Ab initio calculations for the first-positive bands of N2

    NASA Astrophysics Data System (ADS)

    Ni, Chao; Cheng, Junxia; Cheng, Xinlu

    2017-01-01

    The absolute absorption spectral line intensities of the 0-0, 1-1, 2-2, 3-3, and 4-4 bands of N2(A3Σu+ - B3Пg) are computed for the first time with the accurate potential energy curves (PECs) and transition dipole moment curves (TDMCs) using the ab initio calculation. During the calculation process, the precise multireference configuration interaction (MRCI) approach with the augmented correlation consistent polarized valence quadruple-zeta set (aug-cc-pVQZ) and active space 3110311 are used. The calculated PECs of the two states (A3Σu+, B3Пg) agree well with Rydberg-Klein-Rees (RKR) potential, and the calculated TDMCs are more reasonable than the results of other studies. Our calculated Einstein A coefficients are also well consistent with the recent experiment results. The intensities of five bands are obtained from the summation of their respective absolute line intensities, for instance, the 0-0 band intensities are 3.25 × 10-16 cm-1/(molecule cm-2) at 300 K and 1.65 × 10-16 cm-1/(molecule cm-2) at 3000 K. The theoretical results are credible. They are also beneficial for astrophysics where high temperature dominates.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

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

  1. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, Michael E.; Bien, Fritz; Bernstein, Lawrence S.

    1986-01-01

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined.

  2. Ultraviolet absorption hygrometer

    DOEpatents

    Gersh, M.E.; Bien, F.; Bernstein, L.S.

    1986-12-09

    An ultraviolet absorption hygrometer is provided including a source of pulsed ultraviolet radiation for providing radiation in a first wavelength region where water absorbs significantly and in a second proximate wavelength region where water absorbs weakly. Ultraviolet radiation in the first and second regions which has been transmitted through a sample path of atmosphere is detected. The intensity of the radiation transmitted in each of the first and second regions is compared and from this comparison the amount of water in the sample path is determined. 5 figs.

  3. Near-infrared absorptions of monomethylhydrazine

    NASA Technical Reports Server (NTRS)

    Murray, Mark; Kurtz, Joe

    1993-01-01

    The peak absorption coefficients for two near-infrared absorptions of monomethylhydrazine, CH3-N2H3, (MMH) were measured. Absorption bands located at 1.524 micrometers (6560/cm), 1.557 micrometers (6423/cm), and 1.583 micrometers (6316/cm) are assigned to the Delta upsilon = 2 overtones of the infared N-H stretching fundamentals at 3317, 3245 and 3177/cm. An absorption band located at 1.04 micrometers (9620 +/- 100/cm) is assigned to the Delta upsilon = 3 overtone of one of these fundamentals. The peak absorption coefficients (alpha(sub 10)) at 1.524 micrometers (6560 +/- 20/cm) and 1.04 micrometers (9620 +/- 100/cm) are 31 x 10(exp -3) and 0.97 x 10(exp -3)/(cm atm), respectively. Uncertainties in these coefficients were estimated to be less than +/- 20% due primarily to uncertainties in the partial vapor pressure of MMH.

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

    SciTech Connect

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

    2012-09-01

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

  5. Near-Infrared Band Strengths of Molecules Diluted in N2 and H2O Ice Mixtures Relevant to Interstellar and Planetary Ices

    NASA Technical Reports Server (NTRS)

    Richey, Christina Rae; Gerakines, P.A.

    2012-01-01

    The relative abundances of ices in astrophysical environments rely on accurate laboratory measurements of physical parameters, such as band strengths (or absorption intensities), determined for the molecules of interest in relevant mixtures. In an extension of our previous study on pure-ice samples, here we focus on the near-infrared absorption features of molecules in mixtures with the dominant components of interstellar and planetary ices, H2O and N2. We present experimentally measured near-infrared spectral information (peak positions, widths, and band strengths) for both H2O- and N2-dominated mixtures of CO (carbon monoxide), CO2 (carbon dioxide), CH4 (methane), and NH3 (ammonia). Band strengths were determined during sample deposition by correlating the growth of near-infrared features (10,000-4000 per centimeter, 1-2.5 micrometers) with better-known mid-infrared features (4000-400 per centimeter, 2.5-25 micrometers) at longer wavelengths.

  6. Band Structures of Plasmonic Polarons

    NASA Astrophysics Data System (ADS)

    Caruso, Fabio; Lambert, Henry; Giustino, Feliciano

    2015-03-01

    In angle-resolved photoemission spectroscopy (ARPES), the acceleration of a photo-electron upon photon absorption may trigger shake-up excitations in the sample, leading to the emission of phonons, electron-hole pairs, and plasmons, the latter being collective charge-density fluctuations. Using state-of-the-art many-body calculations based on the `GW plus cumulant' approach, we show that electron-plasmon interactions induce plasmonic polaron bands in group IV transition metal dichalcogenide monolayers (MoS2, MoSe2, WS2, WSe2). We find that the energy vs. momentum dispersion relations of these plasmonic structures closely follow the standard valence bands, although they appear broadened and blueshifted by the plasmon energy. Based on our results we identify general criteria for observing plasmonic polaron bands in the angle-resolved photoelectron spectra of solids.

  7. Giant many-body effects in liquid ammonia absorption spectrum.

    PubMed

    Ziaei, Vafa; Bredow, Thomas

    2016-11-07

    In the present work, we accurately calculate the absorption spectrum of liquid ammonia up to 13 eV using many-body perturbation approach. The electronic bandgap of liquid NH3 is perfectly described as the combination of density functional theory, Coulomb-hole screened exchange, and G0W0 approximation to the electronic self-energy, yielding a direct gap (Γ → Γ) of 7.71 eV, fully consistent with the experimentally measured gap from photo-emission spectroscopy. With respect to the NH3 optical properties, the entire spectrum in particular the low lying first absorption band is extremely affected by electron-hole interactions, leading to a fundamental redistribution of spectral weights of the independent-particle spectrum. Three well separated but broad main peaks are identified at 7.0, 9.8, and 11.8 eV with steadily increasing intensities in excellent agreement with the experimental data. Furthermore, we observe a giant net blue-shift of the first absorption peak of about 1.4 eV from gaseous to liquid phase as the direct consequence of many-body effects, allowing the associated liquid ammonia absorption band exciton to delocalize and feel more effectively the repulsion effects imposed by the surrounding solvent shells. Further, the spectrum is insensitive to the coupling of resonant and anti-resonant contributions. Concerning electronic response structure of liquid NH3, it is most sensitive to excitations at energies lower than its electronic gap.

  8. NEUTRON FLUX INTENSITY DETECTION

    DOEpatents

    Russell, J.T.

    1964-04-21

    A method of measuring the instantaneous intensity of neutron flux in the core of a nuclear reactor is described. A target gas capable of being transmuted by neutron bombardment to a product having a resonance absorption line nt a particular microwave frequency is passed through the core of the reactor. Frequency-modulated microwave energy is passed through the target gas and the attenuation of the energy due to the formation of the transmuted product is measured. (AEC)

  9. Photodissociation of carbon dioxide in singlet valence electronic states. II. Five state absorption spectrum and vibronic assignment.

    PubMed

    Grebenshchikov, Sergy Yu

    2013-06-14

    The absorption spectrum of CO2 in the wavelength range 120-160 nm is analyzed by means of quantum mechanical calculations performed using vibronically coupled potential energy surfaces of five singlet valence electronic states and the coordinate dependent transition dipole moment vectors. The thermally averaged spectrum, calculated for T = 190 K via Boltzmann averaging of optical transitions from many initial rotational states, accurately reproduces the experimental spectral envelope, consisting of a low and a high energy band, the positions of the absorption maxima, their FWHMs, peak intensities, and frequencies of diffuse structures in each band. Contributions of the vibronic interactions due to Renner-Teller coupling, conical intersections, and the Herzberg-Teller effect are isolated and the calculated bands are assigned in terms of adiabatic electronic states. Finally, diffuse structures in the calculated bands are vibronically assigned using wave functions of the underlying resonance states. It is demonstrated that the main progressions in the high energy band correspond to consecutive excitations of the pseudorotational motion along the closed loop of the CI seam, and progressions differ in the number of nodes along the radial mode perpendicular to the closed seam. Irregularity of the diffuse peaks in the low energy band is interpreted as a manifestation of the carbene-type "cyclic" OCO minimum.

  10. Study of Evanescence Wave Absorption in Lindane

    NASA Astrophysics Data System (ADS)

    Marzuki, A.; Prasetyo, E.; Gitrin, M. P.; Suryanti, V.

    2017-02-01

    Evanescent wave field has been studied for the purpose of tailoring fiber sensor capable of detecting lindane concentration in a solution. The mounted fiber was optically polished such that part of the fiber clad is stripped off. To study the evanescent wave field absorption in lindane solution, the unclad fiber was immersed in the solution. Light coming out of the fiber was studied at different wavelength each for different lindane concentration. It was shown that evanescent wave field absorption is stronger at wavelength corresponding to lindane absorption band as has been shown from absorption studies lindane in UV-VIS-NIR spectrophotometer.

  11. [Decomposition of hemoglobin UV absorption spectrum into absorption spectra of prosthetic group and apoprotein by means of an additive model].

    PubMed

    Lavrinenko, I A; Vashanov, G A; Artyukhov, V G

    2015-01-01

    The decomposition pathways of hemoglobin UV absorption spectrum into the absorption spectra of the protein and non-protein components are proposed and substantiated by means of an additive model. We have established that the heme component has an absorption band with a maximum at λ(max) = 269.2 nm (ε = 97163) and the apoprotein component has an absorption band with a maximum at λ(max) = 278.4 nm (ε = 48669) for the wavelength range from 240.0 to 320.0 nm. An integral relative proportion of absorption for the heme fraction (78.8%) and apoprotein (21.2%) in the investigating wavelength range is defined.

  12. Neutral and ionized polycyclic aromatic hydrocarbons, diffuse interstellar bands and the ultraviolet extinction curve

    NASA Technical Reports Server (NTRS)

    Salama, Farid; Allamandola, Louis John

    1993-01-01

    Neutral naphthalene C10H8, phenanthrene C14H10 and pyrene C16H10 absorb strongly in the ultraviolet region 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 13 discrete absorption bands which fall between 6800 and 4500 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 and 6151 A, other 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 Ne, wavelengths which fall very close to the strongest DIB 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. An intense, very broad UV-to-visible continuum is reported which is associated with both ions and could explain how PAHs convert interstellar UV and visible radiation into IR radiation.

  13. Determination of molar absorption coefficients of organic compounds adsorbed in porous media.

    PubMed

    Ciani, Andrea; Goss, Kai-Uwe; Schwarzenbach, René P

    2005-12-01

    The kinetics of direct photochemical transformations of organic compounds in light absorbing and scattering media has been sparsely investigated. This is mostly due to the experimental difficulties to assess the major parameters: light intensity in porous media, the reaction quantum yield and the molar absorption coefficient of the adsorbed compound, epsilon(i) (lambda). Here, we propose a method for the determination of the molar absorption coefficient of compounds adsorbed to air-dry surfaces using the Kubelka-Munk model for the description of radiative transfer. To illustrate the method, the molar absorption coefficients of three compounds, i.e. 4-nitroanisole (PNA), the herbicide trifluralin and the flame retardant decabromodiphenyl ether (DecaBDE), were determined on air-dry kaolinite. The measured diffuse reflectance spectra were evaluated with the Kubelka-Munk model and with previously determined Kubelka-Munk absorption and scattering coefficients (k and s), for kaolinite. For all compounds the maximum absorption band was found to be red shifted and the corresponding epsilon(i) (lambda) values were significantly greater than those determined in solvents. Together with the absorption and scattering coefficient of the medium, the measured epsilon(i) (lambda) can be used to determine the quantum yield of the photochemical reaction in this medium from experimentally determined reaction kinetics.

  14. Microwave radiation absorption: behavioral effects.

    PubMed

    D'Andrea, J A

    1991-07-01

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

  15. Electron Spin Resonance and optical absorption spectroscopic studies of manganese centers in aluminium lead borate glasses.

    PubMed

    SivaRamaiah, G; LakshmanaRao, J

    2012-12-01

    Electron Spin Resonance (ESR) and optical absorption studies of 5Al(2)O(3)+75H(3)BO(3)+(20-x)PbO+xMnSO(4) (where x=0.5, 1,1.5 and 2 mol% of MnSO(4)) glasses at room temperature have been studied. The ESR spectrum of all the glasses exhibits resonance signals with effective isotropic g values at ≈2.0, 3.3 and 4.3. The ESR resonance signal at isotropic g≈2.0 has been attributed to Mn(2+) centers in an octahedral symmetry. The ESR resonance signals at isotropic g≈3.3 and 4.3 have been attributed to the rhombic symmetry of the Mn(2+) ions. The zero-field splitting parameter (zfs) has been calculated from the intensities of the allowed hyperfine lines. The optical absorption spectrum exhibits an intense band in the visible region and it has been attributed to (5)E(g)→(5)T(2g) transition of Mn(3+)centers in an octahedral environment. The optical band gap and the Urbach energies have been calculated from the ultraviolet absorption edges.

  16. Multi-band slow light metamaterial.

    PubMed

    Zhu, Lei; Meng, Fan-Yi; Fu, Jia-Hui; Wu, Qun; Hua, Jun

    2012-02-13

    In this paper, a multi-band slow light metamaterial is presented and investigated. The metamaterial unit cell is composed of three cut wires of different sizes and parallel to each other. Two transparency windows induced by two-two overlaps of absorption bands of three cut wires are observed. The multi-band transmission characteristics and the slow light properties of metamaterial are verified by numerical simulation, which is in a good agreement with theoretical predictions. The impacts of structure parameters on transparency windows are also investigated. Simulation results show the spectral properties can be tuned by adjusting structure parameters of metamaterial. The equivalent circuit model and the synthesis method of the multi-band slow light metamaterial are presented. It is seen from simulation results that the synthesis method accurately predicts the center frequency of the multi-band metamaterial, which opens a door to a quick and accurate construction for multi-band slow light metamaterial.

  17. ABSORPTIONS IN THE VISIBLE OF PROTONATED PYRENE COLLISIONALLY COOLED TO 15 K

    SciTech Connect

    Hardy, F.-X.; Gause, O.; Rice, C. A.; Maier, J. P.

    2013-12-01

    Protonated polycyclic hydrocarbons have been added to the list of suggested carriers of diffuse interstellar absorptions. To test this proposition requires laboratory spectra measured under interstellar conditions, in particular with the rotational and vibrational degrees of freedom equilibrated to low temperatures. This has been achieved for protonated pyrene with absorption bands in the visible, using an ion trap and collisional cooling to ≈15 K. A two-photon excitation-dissociation scheme was employed to record the (1) {sup 1} A' ← X {sup 1} A' electronic spectrum on around 10{sup 5} ions per duty cycle. The origin band of the absorption spectrum of this relatively large polycyclic aromatic species with 27 atoms is located at 4858.86 Å. Two further comparably intense spectral features are present at 4834.48 and 4809.32 Å. This is one of the largest protonated aromatics studied in the gas phase and compared to astronomical observations; however, it is not a carrier of known diffuse interstellar bands.

  18. ABSORPTION ANALYZER

    DOEpatents

    Brooksbank, W.A. Jr.; Leddicotte, G.W.; Strain, J.E.; Hendon, H.H. Jr.

    1961-11-14

    A means was developed for continuously computing and indicating the isotopic assay of a process solution and for automatically controlling the process output of isotope separation equipment to provide a continuous output of the desired isotopic ratio. A counter tube is surrounded with a sample to be analyzed so that the tube is exactly in the center of the sample. A source of fast neutrons is provided and is spaced from the sample. The neutrons from the source are thermalized by causing them to pass through a neutron moderator, and the neutrons are allowed to diffuse radially through the sample to actuate the counter. A reference counter in a known sample of pure solvent is also actuated by the thermal neutrons from the neutron source. The number of neutrons which actuate the detectors is a function of a concentration of the elements in solution and their neutron absorption cross sections. The pulses produced by the detectors responsive to each neu tron passing therethrough are amplified and counted. The respective times required to accumulate a selected number of counts are measured by associated timing devices. The concentration of a particular element in solution may be determined by utilizing the following relation: T2/Ti = BCR, where B is a constant proportional to the absorption cross sections, T2 is the time of count collection for the unknown solution, Ti is the time of count collection for the pure solvent, R is the isotopic ratlo, and C is the molar concentration of the element to be determined. Knowing the slope constant B for any element and when the chemical concentration is known, the isotopic concentration may be readily determined, and conversely when the isotopic ratio is known, the chemical concentrations may be determined. (AEC)

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

    PubMed

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

    2014-05-01

    Amide I' IR spectra are widely used for studies of structural changes in peptides and proteins as a function of temperature. Temperature dependent absorptions of amino acid side-chains that overlap the amide I' may significantly complicate the structural analyses. While the side-chain IR spectra have been investigated previously, thus far their dependence on temperature has not been reported. Here we present the study of the changes in the IR spectra with temperature for side-chain groups of aspartate, glutamate, asparagine, glutamine, arginine, and tyrosine in the amide I' region (in D2O). Band fitting analysis was employed to extract the temperature dependence of the individual spectral parameters, such as peak frequency, integrated intensity, band width, and shape. As expected, the side-chain IR bands exhibit significant changes with temperature. The majority of the spectral parameters, particularly the frequency and intensity, show linear dependence on temperature, but the direction and magnitude vary depending on the particular side-chain group. The exception is arginine, which exhibits a distinctly nonlinear frequency shift with temperature for its asymmetric CN3H5(+) bending signal, although a linear fit can account for this change to within ~1/3 cm(-1). The applicability of the determined spectral parameters for estimations of temperature-dependent side-chain absorptions in peptides and proteins are discussed.

  20. Reflective-tube absorption meter

    NASA Astrophysics Data System (ADS)

    Zaneveld, J. Ronald V.; Bartz, Robert; Kitchen, James C.

    1990-09-01

    The design and calibration of a proposed in situ spectral absorption meter is evaluated using a laboratory prototype. The design includes a silver coated (second-surface) glass tube, a tungsten light source (stabilized by means of optical feedback), a monochromator, and a solid state detector. The device measures the absorption coefficient plus a portion of the volume scattering function. Theoretical analyses and laboratory experiments which explore the magnitude and variation of the errors due to scattering and internal reflections are described. Similar analyses are performed on the Cary 1 18 Spectrophotometer to allow cross calibration. Algorithms to yield the abscrption coefficient and the zenith-sun diffuse attenuation coefficient are presented and evaluated. Simultaneous measurement of the beam attenuation or backscattering coefficient allows use of algoriThms with much narrower error bands. The various methods of obtaining absorption and diffuse attenuation values are compared. Procedures for using reverse osmosis filtration to produce a clean water calibration standard are described. An absorption spectrum for pure water is obtained. Development of the absorption meter is proceeding along two lines: 1) a two-wavelength side-by-side LED is being fabricated to allow an in situ chlorophyll a absorption meter to be constructed, and 2) scientific projects using a shipboard or laboratory flow.-through pumping system are being planned.