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Sample records for absorption bands located

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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).

  6. 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.

  7. Shuttle orbiter C-band beacon antenna location study

    NASA Technical Reports Server (NTRS)

    Lindsey, J. F.

    1975-01-01

    A recommendation for the location of the Space Shuttle C-Band Beacon Antenna(s) to be used during Approach and Landing Tests was made. The study has included an Orbiter-to-ground radar look angle evaluation, a vehicle shadowing evaluation and extensive 1/10-scale antenna pattern measurements. Locations were limited to the cutouts for the S-Band Quads and Hemis to minimize skin perturbation. The results show that a single C-Band Antenna located in the lower Hemi cutout will provide optimum coverage and eliminate the need for switching and the undesirable interferometer effects of two antennas.

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

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

    SciTech Connect

    Aver`yanov, E.M.

    1994-11-01

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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Ozone absorption cross section measurements in the Wulf bands

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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].

  5. 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.

  6. 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.

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  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. 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}.

  18. 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)

  19. Karyotypes, C-banding, and chromosomal location of active nucleolar organizing regions in Tapinoma (Hymenoptera, Formicidae).

    PubMed

    Palomeque, T; Chica, E; Cano, M A; Díaz de la Guardia, R

    1988-04-01

    The haploid and diploid karyotypes of Tapinoma erraticum (n = 8) and Tapinoma nigerrimum (n = 9) were analyzed using C-banding and observation of NOR sites. C-banding showed the existence of heterochromatin in the paracentromeric regions of all chromosomes. The analysis of NOR sites in these species proved the existence of primary activity NOR in one or two chromosomes, respectively, whereas the other chromosomes showed secondary activity NOR, expressed only in a minority of cells. In both species the NOR were located in paracentromeric regions. These results are discussed in relation to a hypothesis of chromosome differentiation of these species.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Alpha band oscillations correlate with illusory self-location induced by virtual reality.

    PubMed

    Lenggenhager, Bigna; Halje, Pär; Blanke, Olaf

    2011-05-01

    Neuroscience of the self has focused on high-level mechanisms related to language, memory or imagery of the self. However, recent evidence suggests that low-level mechanisms such as multisensory and sensorimotor integration may play a fundamental role in self-related processing. Here we used virtual reality technology and visuo-tactile conflict to study such low-level mechanisms and manipulate where participants experienced their self to be localized (self-location). Frequency analysis and electrical neuroimaging of co-recorded high-resolution electroencephalography revealed body-specific alpha band power modulations in bilateral sensorimotor cortices. Furthermore, alpha power in the medial prefrontal cortex (mPFC) was correlated with the degree of experimentally manipulated self-location. We argue that these alpha oscillations in sensorimotor cortex and mPFC reflect self-location as manipulated through multisensory conflict.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Aerosol Scattering and Absorption Properties Over the Central Himalayan Location Nainital: Results from Gvax

    NASA Astrophysics Data System (ADS)

    Gogoi, M. M.; Babu, S.; Nair, V. S.; Satheesh, S.; Naja, M.; Kotamarthi, V. R.

    2012-12-01

    Extensive characterization of aerosols over a central Himalayan location, Nainital (29.4° N, 79.5° E, 1958 m amsl) were carried out during June 2011 to March 2012 under the Ganges Valley Aerosol Experiment (GVAX). Owing to the highly turbid, persistent and increasing aerosol concentration over the Ganges Valley in northern India, their influence on surface dimming, mid-tropospheric warming and monsoon circulations, the experimental site Nainital is best suited for studying the regional distribution of complex aerosol sources, their transport and direct and indirect radiative forcing mechanisms. During the study period, aerosol scattering (absorption) coefficients showed values as high as > 500 Mm-1 (> 50 Mm-1) in local noon time during the onset of winter and early spring and as low as < 300 Mm-1 (< 40 Mm-1) during the summer months. Consequently, aerosol single scattering albedo (SSA) decreased in winter (< 0.9, for 45% of occurrences) with large day-to-day modulations and higher values (> 0.9, for 81% of occurrences) during summer. Based on the spectral distribution of scattering coefficients, fine mode aerosols dominate the summer compared to winter season. The strong absorption during the winter and early spring is associated with the prevalence of biomass burning aerosols and/or dust as reveal by the steep spectral dependence of absorption coefficients (αabs >2.0). These observed seasonal variations are attributed to the dynamics of the atmospheric boundary layer as well as the influence of long range transport over the Himalayan location.

  2. 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.

  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. Dual-band infrared imaging applications: Locating buried minefields, mapping sea ice, and inspecting aging aircraft

    SciTech Connect

    Del Grande, N.K.; Durbin, P.F.; Perkins, D.E.

    1992-09-01

    We discuss the use of dual-band infrared (DBIR) imaging for three quantitative NDE applications: location buried surrogate mines, mapping sea ice thicknesses and inspecting subsurface flaws in aging aircraft parts. Our system of DBIR imaging offers a unique combination of thermal resolution, detectability, and interpretability. Pioneered at Lawrence Livermore Laboratory, it resolves 0.2 {degrees}C differences in surface temperatures needed to identify buried mine sites and distinguish them from surface features. It produces both surface temperature and emissivity-ratio images of sea ice, needed to accurately map ice thicknesses (e.g., by first removing clutter due to snow and surface roughness effects). The DBIR imaging technique depicts subsurface flaws in composite patches and lap joints of aircraft, thus providing a needed tool for aging aircraft inspections.

  11. Dual-band infrared imaging applications: Locating buried minefields, mapping sea ice, and inspecting aging aircraft

    NASA Astrophysics Data System (ADS)

    Delgrande, N. K.; Durbin, P. F.; Perkins, D. E.

    1992-09-01

    We discuss the use of dual-band infrared (DBIR) imaging for three quantitative NDE applications: location buried surrogate mines, mapping sea ice thicknesses, and inspecting subsurface flaws in aging aircraft parts. Our system of DBIR imaging offers a unique combination of thermal resolution, detectability, and interpretability. Pioneered at Lawrence Livermore Laboratory, it resolves 0.2 C differences in surface temperatures needed to identify buried mine sites and distinguish them from surface features. It produces both surface temperature and emissivity-ratio images of sea ice, needed to accurately map ice thicknesses (e.g., by first removing clutter due to snow and surface roughness effects). The DBIR imaging technique depicts subsurface flaws in composite patches and lap joints of aircraft, thus providing a needed tool for aging aircraft inspections.

  12. [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

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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 ).

  20. 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.

  1. 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.

  2. Engineering nanostructured polymer blends with controlled nanoparticle location for excellent microwave absorption: a compartmentalized approach.

    PubMed

    Biswas, Sourav; Kar, Goutam Prasanna; Bose, Suryasarathi

    2015-07-14

    In order to obtain better materials, control over the precise location of nanoparticles is indispensable. It is shown here that ordered arrangements of nanoparticles, possessing different characteristics (electrical/magnetic dipoles), in the blend structure can result in excellent microwave absorption. This is manifested from a high reflection loss of ca. -67 dB for the best blend structure designed here. To attenuate electromagnetic radiation, the key parameters of high electrical conductivity and large dielectric/magnetic loss are targeted here by including a conductive material [multiwall carbon nanotubes, MWNTs], ferroelectric nanostructured material with associated relaxations in the GHz frequency [barium titanate, BT] and lossy ferromagnetic nanoparticles [nickel ferrite, NF]. In this study, bi-continuous structures were designed using 50/50 (by wt) blends of polycarbonate (PC) and polyvinylidene fluoride (PVDF). The MWNTs were modified using an electron acceptor molecule, a derivative of perylenediimide, which facilitates π-π stacking with the nanotubes and stimulates efficient charge transport in the blends. The nanoscopic materials have specific affinity towards the PVDF phase. Hence, by introducing surface-active groups, an ordered arrangement can be tailored. To accomplish this, both BT and NF were first hydroxylated followed by the introduction of amine-terminal groups on the surface. The latter facilitated nucleophilic substitution reactions with PC and resulted in their precise location. In this study, we have shown for the first time that by a compartmentalized approach, superior EM attenuation can be achieved. For instance, when the nanoparticles were localized exclusively in the PVDF phase or in both the phases, the minimum reflection losses were ca. -18 dB (for the MWNT/BT mixture) and -29 dB (for the MWNT/NF mixture), and the shielding occurred primarily through reflection. Interestingly, by adopting the compartmentalized approach wherein the

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Radiofrequency exposure in the French general population: band, time, location and activity variability.

    PubMed

    Viel, Jean-François; Cardis, Elisabeth; Moissonnier, Monika; de Seze, René; Hours, Martine

    2009-11-01

    Information on the exposure of individual persons to radiofrequency (RF) fields is scarce, although such data are crucial in order to develop a suitable exposure assessment method, and frame the hypothesis and design of future epidemiological studies. The main goal of this survey is to assess individual RF exposure on a population basis, while clarifying the relative contribution of different sources to the total exposure. A total of 377 randomly selected people were analyzed. Each participant was supplied with a personal exposure meter for 24-hour measurements (weekday), and kept a time-location-activity diary. Electric field strengths were recorded in 12 different RF bands every 13s. Summary statistics were calculated with the robust regression on order statistics method. Most of the time, recorded field strengths were not detectable with the exposure meter. Total field, cordless phones, WiFi-microwave, and FM transmitters stood apart with a proportion above the detection threshold of 46.6%, 17.2%, 14.1%, and 11.0%, respectively. The total field mean value was 0.201V/m, higher in urban areas, during daytime, among adults, and when moving. When focusing on specific channels, the highest mean exposure resulted from FM sources (0.044V/m), followed by WiFi-microwaves (0.038V/m), cordless phones (0.037V/m), and mobile phones (UMTS: 0.036V/m, UMTS: 0.037V/m). Various factors, however, contributed to a high variability in RF exposure assessment. These population-based estimates should therefore be confirmed by further surveys to better characterize the exposure situation in different microenvironments.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. [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.

  16. 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).

  17. 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

  18. 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.

  19. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  1. Free-end adaptive nudged elastic band method for locating transition states in minimum energy path calculation.

    PubMed

    Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-09-07

    A free-end adaptive nudged elastic band (FEA-NEB) method is presented for finding transition states on minimum energy paths, where the energy barrier is very narrow compared to the whole paths. The previously proposed free-end nudged elastic band method may suffer from convergence problems because of the kinks arising on the elastic band if the initial elastic band is far from the minimum energy path and weak springs are adopted. We analyze the origin of the formation of kinks and present an improved free-end algorithm to avoid the convergence problem. Moreover, by coupling the improved free-end algorithm and an adaptive strategy, we develop a FEA-NEB method to accurately locate the transition state with the elastic band cut off repeatedly and the density of images near the transition state increased. Several representative numerical examples, including the dislocation nucleation in a penta-twinned nanowire, the twin boundary migration under a shear stress, and the cross-slip of screw dislocation in face-centered cubic metals, are investigated by using the FEA-NEB method. Numerical results demonstrate both the stability and efficiency of the proposed method.

  2. Free-end adaptive nudged elastic band method for locating transition states in minimum energy path calculation

    NASA Astrophysics Data System (ADS)

    Zhang, Jiayong; Zhang, Hongwu; Ye, Hongfei; Zheng, Yonggang

    2016-09-01

    A free-end adaptive nudged elastic band (FEA-NEB) method is presented for finding transition states on minimum energy paths, where the energy barrier is very narrow compared to the whole paths. The previously proposed free-end nudged elastic band method may suffer from convergence problems because of the kinks arising on the elastic band if the initial elastic band is far from the minimum energy path and weak springs are adopted. We analyze the origin of the formation of kinks and present an improved free-end algorithm to avoid the convergence problem. Moreover, by coupling the improved free-end algorithm and an adaptive strategy, we develop a FEA-NEB method to accurately locate the transition state with the elastic band cut off repeatedly and the density of images near the transition state increased. Several representative numerical examples, including the dislocation nucleation in a penta-twinned nanowire, the twin boundary migration under a shear stress, and the cross-slip of screw dislocation in face-centered cubic metals, are investigated by using the FEA-NEB method. Numerical results demonstrate both the stability and efficiency of the proposed method.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Variation of slant path Ka/V-band rain attenuation over seven tropical locations in Nigeria using synthetic storm techniques

    NASA Astrophysics Data System (ADS)

    Ojo, J. S.; Adediji, A. T.; Mandeep, J. S.; Ismail, M.

    2016-04-01

    In this paper, rain characteristics and slant path rain attenuation at 30 and 40 GHz using synthetic storm techniques over seven tropical locations in Nigeria have been presented. The technique can be used to predict the local first-order statistical rain attenuation to mitigate the severe fade experienced at higher frequency bands by employing local rainfall rate statistics. Three years rain rate data at seven tropical and equatorial locations in Nigeria were utilized for the purpose of this work. The predicted statistics are in good agreement with those obtained from the propagation beacon measurement (EUTELSAT W4/W7 satellite-12.245 GHz) It could be observed that at 99.99 % link availability over these locations, the fade margin of higher dB (74 and 81 dB) are required at 30 and 40 GHz frequency bands, respectively. When diurnal variation was observed for four time intervals: 00:00-06:00, 06:00-12:00, 12:00-18:00, and 18:00-24:00, there is a variation of the fade margin over the hours of the day. The overall results will be needed for an acceptable planning that can effectively reduce the fade margin to a very low value for an optimum data communication over the studied locations.

  9. A novel RF-based propagation model with tissue absorption for location of the GI tract.

    PubMed

    Wang, Lujia; Liu, Li; Hu, Chao; Meng, Max Q

    2010-01-01

    In order to accurately estimate (build) the radio signal propagation attenuation model, especially inside the gastro-intestine (GI) tract of the human body, the Radio Frequency (RF) absorption characterization in human body is investigated. This characterization provides a criterion to design the Received Signal Strength (RSS) based localization system for the objective inside the human body. In this paper, the Specific Absorption Rate (SAR), E-field, H-field of the near and far field are investigated at frequencies of 434MHz, 868MHz, 1.2GHz and 2.4GHz respectively. Then, the numerical electromagnetic analysis with the finite-differencetime-domain (FDTD) is applied to model the in vivo radio propagation channels by using a dipole antenna. Finally, simulation experiments are carried out in homogenous and heterogeneous mediums. The results show that the electromagnetic (EM) propagation is not only distance and orientation dependent, but also tissue absorption dependent in human body. The proposed model is in agreement with measurements in the simulation experiments.

  10. 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.

  11. Controlling the Curie temperature in (Ga,Mn)As through location of the Fermi level within the impurity band.

    PubMed

    Dobrowolska, M; Tivakornsasithorn, K; Liu, X; Furdyna, J K; Berciu, M; Yu, K M; Walukiewicz, W

    2012-02-19

    The ferromagnetic semiconductor (Ga,Mn)As has emerged as the most studied material for prototype applications in semiconductor spintronics. Because ferromagnetism in (Ga,Mn)As is hole-mediated, the nature of the hole states has direct and crucial bearing on its Curie temperature T(C). It is vigorously debated, however, whether holes in (Ga,Mn)As reside in the valence band or in an impurity band. Here we combine results of channelling experiments, which measure the concentrations both of Mn ions and of holes relevant to the ferromagnetic order, with magnetization, transport, and magneto-optical data to address this issue. Taken together, these measurements provide strong evidence that it is the location of the Fermi level within the impurity band that determines T(C) through determining the degree of hole localization. This finding differs drastically from the often accepted view that T(C) is controlled by valence band holes, thus opening new avenues for achieving higher values of T(C).

  12. 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.

  13. 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.

  14. 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.

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

    PubMed

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

    2012-01-15

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

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Intermediate Band Performance of GaSb Type-II Quantum Dots Located in n-Doped Region of GaAs Solar Cells

    NASA Astrophysics Data System (ADS)

    Kechiantz, Ara; Afanasev, Andrei

    2013-03-01

    The intermediate band (IB) electronic states assist sub-bandgap photons in generation of additional photocurrent in single-junction solar cells. Such non-linear effect of resonant two-photon absorption of concentrated sunlight attracts much attention because it promises up to 63% conversion efficiency in IB solar cells. The main obstacle to achieving high performance is involvement of IB-states in electron-hole recombination that is drastically increasing the dark current and reducing the open circuit voltage of IB solar cells. The IB-states can be composed of quantum dots (QDs). Concentration of sunlight limits recombination through type-II QD IB-states located outside of the depletion region. In this work we model GaAs solar cell with strained GaSb type-II QDs separated from the depletion region. The focus is on type-II QDs located in n-doped region of p-n-junction. Our calculation shows that photovoltaic performance can be essentially improved by concentration of sunlight, and that this improvement is highly sensitive to the doping of materials and the shape of potential barriers surrounding type-II QDs. For instance, strained GaSb type-II QDs may increase the performance of GaAs solar cell by 20% compared to the reference GaAs solar cell without QDs.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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

  13. 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)

  14. 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)

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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)

  20. 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.

  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. 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.

  6. 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.

  7. 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

  8. REAL TIME CONTINUOUS MEASUREMENTS OF [CO2] AND δ13C AT MULTIPLE LOCATIONS USING CAVITY ENHANCED LASER ABSORPTION

    NASA Astrophysics Data System (ADS)

    McAlexander, W. I.; Rau, G. H.; Dobeck, L.; Spangler, L.

    2009-12-01

    A commercial instrument (Los Gatos Research, model 908-0003) utilizing Cavity Enhanced Laser Absorption Spectroscopy was deployed in 2009 at the ZERT carbon release site (Bozeman, MT) for real time measurement of above-ground CO2 concentration and isotope ratio (δ13C). An automated switching system sampled 13 different locations in the field, as well as two known references, over an 8 day period. Real-time Keeling plots were constructed showing distinct signatures of soil (-27.0 ‰) and fossil (-56.0 ‰) sources compared to background air (-8.2 ‰). Instrument performance gave 0.2 ‰ precision with only 100 seconds of averaging per inlet. Sequential sampling of the various inlets gave a temporal and physical mapping of the CO2 release plume that is difficult to obtain using more conventional techniques. The figures show the nature and quality of the data from one of the locations. Details concerning instrument performance, systematics, calibration, and data processing will be discussed. Fig1: Time chart of CO2 concentration and isotope ratio δ13C from one of 13 sample inlet locations at ZERT release field, July, 2009. Fig2: Keeling plot of data from Fig1 illustrating the two source mixing of soil (-27 ‰) and fossil (-56 ‰) CO2 with background air.

  9. 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.

  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. In Situ Measurements of Aerosol Mass Concentration and Spectral Absorption at Three Location in and Around Mexico City

    NASA Astrophysics Data System (ADS)

    Chaudhry, Z.; Martins, V.; Li, Z.

    2006-12-01

    As a result of population growth and increasing industrialization, air pollution in heavily populated urban areas is one of the central environmental problems of the century. As a part of the MILAGRO (Megacity Initiative: Local and Global Research Observations) study, Nuclepore filters were collected in two size ranges (PM10 and PM2.5) at 12 hour intervals at three location in Mexico during March, 2006. Sampling stations were located at the Instituto Mexicano del Petroleo (T0), at the Rancho La Bisnago in the State of Hidalgo (T2) and along the Gulf Coast in Tampico (Tam). Each filter was analyzed for mass concentration, aerosol scattering and absorption efficiencies. Mass concentrations at T0 ranged from 47 to 179 μg/m3 for PM10 with an average concentration of 96 μg/m3, and from 20 to 93 μg/m3 for PM2.5 with an average concentration of 41 μg/m3. Mass concentrations at T2 ranged from 12 to 154 μg/m3 for PM10 with an average concentration of 51 μg/m3, and from 7 to 50 μg/m3 for PM2.5 with an average concentration of 25 μg/m3. Mass concentrations at Tam ranged from 34 to 80 μg/m3 for PM10 with an average concentration of 52 μg/m3, and from 8 to 23 μg/m3 for PM2.5 with an average concentration of 13 μg/m3. While some of the extreme values are likely linked to local emissions, regional air pollution episodes also played important roles. Each of the sampling stations experienced a unique atmospheric condition. The site at T0 was influenced by urban air pollution and dust storms, the site at T2 was significantly less affected by air pollution but more affected by regional dust storms and local dust devils while Tam was influenced by air pollution, dust storms and the natural marine environment. The spectral mass absorption efficiency was measured from 350 to 2500 nm and shows large differences between the absorption properties of soil dust, black carbon, and organic aerosols. The strong spectral differences observed can be related to differences in

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Relative Slowness Estimates for Locations of Repeating Low-Frequency Earthquakes and Narrow-Band Tremor at Fuego Volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Waite, G. P.; Lyons, J. J.

    2009-12-01

    Fuego volcano, Guatemala, is an open-vent basaltic stratovolcano characterized by nearly constant, but low-level eruptive activity since 1999. In January 2008, we deployed small antennas of six broadband seismic and five acoustic sensors 0.9 km north of the active vent to investigate the source of explosions and low-frequency seismicity. The seismic array had stations spaced 30 m apart and a total aperture of ~140 m. The infrasound sensors were deployed in a similar array, but with average station spacing of 50 m. There was no lava effusion during the deployment, but explosions were recorded approximately once per hour, with varied amounts of ash, and with durations from 20-150 s. In addition to the explosions, our seismic array recorded narrow band tremor with dominant frequencies of 1.6 and 1.9 Hz and discrete events that were not generally detected by the acoustic array. The dominant class of these events, which repeated approximately 10-15 times per hour, had an impulsive onset with first motion toward the vent, a short duration of <5 s, and dominant frequencies from 1-3 Hz. Their similarity suggests a nondestructive source process. While waveforms are similar from event to event when viewed on the same channel, the large variation in waveforms across the array yields a large uncertainty in slowness parameter estimates. We take advantage of the high degree of similarity between events to determine relative slowness estimates. After determining the best-fit slowness parameters for a master event, we measured the relative slowness parameters for 203 similar events. The results indicate a stationary source, although subtle variations in waveforms suggest that the source mechanism or source location varied slightly with time. The low-frequency events were located by computing slowness parameters from synthetic waveforms for a volume of sources beneath the summit region. The source is ~150 m directly beneath the active vent, but not associated with explosions. Full

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Oscillatory alpha-band mechanisms and the deployment of spatial attention to anticipated auditory and visual target locations: Supramodal or sensory-specific control mechanisms?

    PubMed Central

    Banerjee, Snigdha; Snyder, Adam C.; Molholm, Sophie; Foxe, John J.

    2011-01-01

    Oscillatory alpha-band activity (8–15 Hz) over parieto-occipital cortex in humans plays an important role in suppression of processing for inputs at to-be-ignored regions of space, with increased alpha-band power observed over cortex contralateral to locations expected to contain distractors. It is unclear if similar processes operate during deployment of spatial attention in other sensory modalities. Evidence from lesion patients suggests that parietal regions house supramodal representations of space. The parietal lobes are prominent generators of alpha-oscillations; raising the possibility that alpha is a neural signature of supramodal spatial attention. Further, when spatial attention is deployed within vision, processing of task-irrelevant auditory inputs at attended locations is also enhanced, pointing to automatic links between spatial deployments across senses. Here, we asked whether lateralized alpha-band activity is also evident in a purely auditory spatial-cueing task, and whether it had the same underlying generator configuration as in a purely visuo-spatial task. If common to both sensory-systems, this would provide strong support for “supramodal” attention theory. Alternately, alpha-band differences between auditory and visual tasks would support a sensory-specific account. Lateralized shifts in alpha-band activity were indeed observed during a purely auditory-spatial task. Crucially, there were clear differences in scalp topographies of this alpha-activity depending on the sensory system within which spatial attention was deployed. Findings suggest that parietally-generated alpha-band mechanisms are central to attentional deployments across modalities but that they are invoked in a sensory-specific manner. The data support an interactivity account, whereby a supramodal system interacts with sensory-specific control systems during deployment of spatial attention. PMID:21734284

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

    SciTech Connect

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

    2011-09-15

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

  16. Ribosomal DNA location in the scarab beetle Thorectes intermedius (Costa) (Coleoptera: Geotrupidae) using banding and fluorescent in-situ hybridization.

    PubMed

    Vitturi, R; Colomba, M S; Barbieri, R; Zunino, M

    1999-01-01

    Mitotic metaphase chromosomes of the scarab beetle Thorectes intermedius (Costa) (Coleoptera Scarabaeoidea: Geotrupidae) were analyzed using various banding methods and fluorescent in-situ hybridization (FISH) with a ribosomal probe. The results obtained indicate that silver and CMA3 staining are unable to localize the chromosome sites of nucleolar organizer regions (NORs). Such an inadequacy is a consequence of the extensive silver and CMA3 stainability of both constitutive heterochromatin and heterochromatin associated to the NORs.

  17. 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

  18. 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.

  19. Combining CrIS double CO2 bands for detecting clouds located in different layers of the atmosphere

    NASA Astrophysics Data System (ADS)

    Lin, Lin; Zou, Xiaolei; Weng, Fuzhong

    2017-02-01

    Detection of clouds within certain vertical layers of the atmosphere from satellite infrared instruments is challenging, especially of those optically thin clouds due to their small thermal contrasts to the background. This study develops a new method for cloud detection by using the Cross-track Infrared Sounder (CrIS) hyperspectral radiances at shortwave ( 4.3 µm) and longwave ( 15 µm) CO2 bands. Specifically, CrIS longwave channels are first paired with shortwave channels based on weighting function altitudes and sensitivity to clouds. A linear relationship of brightness temperatures between each paired channel is then derived for predicting the shortwave channel from the longwave channel in clear-sky conditions. A cloud emission and scattering index (CESI) can finally be defined as the difference of the paired shortwave channel between the clear-sky, regression model predicted and the observed brightness temperatures. Spatial distributions of such derived CESI for several paired channels in the troposphere are examined for a winter storm that occurred in the eastern part of the United States during 22-24 January 2016. It is shown that the CESI values over the storm regions with optically thin cirrus, fog, and supercooled water clouds are positively larger than those over optically thick opaque ice and overshooting clouds or in clear-sky conditions. Of particular interest is that an area of fog and water clouds over Gulf of Mexico, which are indicated by the Visible Infrared Imaging Radiometer Suite day and night band observations, is identified by the CESI. The global distribution of CESIs derived from CrIS double CO2 bands with weighting functions peak around 321 hPa agrees well with the distribution of ice cloud optical thickness from the Atmospheric Infrared Sounder version 6 cloud product data set in both daytime and nighttime.

  20. Location, Location, Location!

    ERIC Educational Resources Information Center

    Ramsdell, Kristin

    2004-01-01

    Of prime importance in real estate, location is also a key element in the appeal of romances. Popular geographic settings and historical periods sell, unpopular ones do not--not always with a logical explanation, as the author discovered when she conducted a survey on this topic last year. (Why, for example, are the French Revolution and the…

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  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. 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.

  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. 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.

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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.

  14. 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

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  18. 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.

  19. 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.

  20. 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.

  1. 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}.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Computer programs for absorption spectrophotometry.

    PubMed

    Jones, R N

    1969-03-01

    Brief descriptions are given of twenty-two modular computer programs for performing the basic numerical computations of absorption spectrophotometry. The programs, written in Fortran IV for card input and output, are available from the National Research Council of Canada. The input and output formats are standardized to permit easy interfacing to yield more complex data processing systems. Though these programs were developed for ir spectrophotometry, they are readily modified for use with digitized visual and uv spectrophotometers. The operations covered include ordinate and abscissal unit and scale interconversions, ordinate addition and subtraction, location of band maxima and minima, smoothing and differentiation, slit function convolution and deconvolution, band profile analysis and asymmetry quantification, Fourier transformation to time correlation curves, multiple overlapping band separation in terms of Cauchy (Lorentz), Gauss, Cauchy-Gauss product, and Cauchy-Gauss sum functions and cell path length determination from fringe spacing analysis.

  11. Experimental and theoretical study of absorption spectrum of the (CH3)2CO···HF complex. Influence of anharmonic interactions on the frequency and intensity of the 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  19. 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.

  20. 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.

  1. Effect of defect bands in β-In2S3 thin films

    NASA Astrophysics Data System (ADS)

    Jayakrishnan, R.; Sebastian, Tina; Sudha kartha, C.; Vijayakumar, K. P.

    2012-05-01

    Optical absorption studies in β-In2S3 thin films of band gap 2.66 eV, prepared using chemical spray pyrolysis technique, revealed presence of a defect band which could assist absorption of sub band gap photons. Extrinsic photoconductivity under excitation of 2.33 eV was observed in these films. Photoluminescence studies revealed a green emission from the films providing a recombination path to these carriers. Temperature dependence of photoconductivity showed that the states in the defect band were continuously exchanging carriers with the conduction band which caused the photocurrent to show persistent photoconductivity. Temperature dependence of photocurrent revealed existence of shallow traps located ˜24 meV below the conduction band which played vital role in controlling the photosensitivity of the films. Temporal dependence of photoconductivity revealed decay tails which were identified to be the effect of thermal release of carriers form the shallow traps.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Observation of an Intermediate Band in Sn-doped Chalcopyrites with Wide-spectrum Solar Response

    PubMed Central

    Yang, Chongyin; Qin, Mingsheng; Wang, Yaoming; Wan, Dongyun; Huang, Fuqiang; Lin, Jianhua

    2013-01-01

    Nanostrcutured particles and polycrystalline thin films of Sn-doped chalcopyrite are synthesized by newly-developed methods. Surprisingly, Sn doping introduces a narrow partially filled intermediate band (IB) located ~1.7 eV (CuGaS2) and ~0.8 eV (CuInS2) above the valance band maximum in the forbidden band gap. Diffuse reflection spectra and photoluminescence spectra reveal extra absorption and emission spectra induced by the IBs, which are further supported by first-principle calculations. Wide spectrum solar response greatly enhances photocatalysis, photovoltaics, and photo-induced hydrogen production due to the intermediate band. PMID:23412565

  8. Infrared radiation parameterizations for the minor CO2 bands and for several CFC bands in the window region

    NASA Technical Reports Server (NTRS)

    Kratz, David P.; Chou, Ming-Dah; Yan, Michael M.-H.

    1993-01-01

    Fast and accurate parameterizations have been developed for the transmission functions of the CO2 9.4- and 10.4-micron bands, as well as the CFC-11, CFC-12, and CFC-22 bands located in the 8-12-micron region. The parameterizations are based on line-by-line calculations of transmission functions for the CO2 bands and on high spectral resolution laboratory measurements of the absorption coefficients for the CFC bands. Also developed are the parameterizations for the H2O transmission functions for the corresponding spectral bands. Compared to the high-resolution calculations, fluxes at the tropopause computed with the parameterizations are accurate to within 10 percent when overlapping of gas absorptions within a band is taken into account. For individual gas absorption, the accuracy is of order 0-2 percent. The climatic effects of these trace gases have been studied using a zonally averaged multilayer energy balance model, which includes seasonal cycles and a simplified deep ocean. With the trace gas abundances taken to follow the Intergovernmental Panel on Climate Change Low Emissions 'B' scenario, the transient response of the surface temperature is simulated for the period 1900-2060.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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

  17. Estimates Of Magnetic Plage Filling Factors Using The Cn Band

    NASA Astrophysics Data System (ADS)

    Saar, Steven H.; Judge, Philip

    2016-12-01

    The 388nm CN band (like the better known "G band" of CH) is used in the Sun to locate strong magnetic concentrations. Magnetic network and plage are bright in these molecular bands, since the enhanced chromospheric heating there destroys the molecule, erasing its absorption and allowing the continuum to shine through. We take advantage of this to estimate the filling factor of strong fields in active dwarf stars. CN band depths in active stars can be compared with those of inactive stars of very similar temperature and metallicity, and after an adjustment for line-blanketing, used to estimate a magnetic plage filling factor. We estimate filling factors for a two stars, and compare them to direct Stokes I line-broadening measurements. Limitations, caveats, and future directions are briefly considered.

  18. Aerosol Absorption Measurements in MILAGRO.

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

    During the month of March 2006, a number of instruments were used to determine the absorption characteristics of aerosols found in the Mexico City Megacity and nearby Valley of Mexico. These measurements were taken as part of the Department of Energy's Megacity Aerosol Experiment - Mexico City (MAX-Mex) that was carried out in collaboration with the Megacity Interactions: Local and Global Research Observations (MILAGRO) campaign. MILAGRO was a joint effort between the DOE, NSF, NASA, and Mexican agencies aimed at understanding the impacts of a megacity on the urban and regional scale. A super-site was operated at the Instituto Mexicano de Petroleo in Mexico City (designated T-0) and at the Universidad Technologica de Tecamac (designated T-1) that was located about 35 km to the north east of the T-0 site in the State of Mexico. A third site was located at a private rancho in the State of Hidalgo approximately another 35 km to the northeast (designated T-2). Aerosol absorption measurements were taken in real time using a number of instruments at the T-0 and T-1 sites. These included a seven wavelength aethalometer, a multi-angle absorption photometer (MAAP), and a photo-acoustic spectrometer. Aerosol absorption was also derived from spectral radiometers including a multi-filter rotating band spectral radiometer (MFRSR). The results clearly indicate that there is significant aerosol absorption by the aerosols in the Mexico City megacity region. The absorption can lead to single scattering albedo reduction leading to values below 0.5 under some circumstances. The absorption is also found to deviate from that expected for a "well-behaved" soot anticipated from diesel engine emissions, i.e. from a simple 1/lambda wavelength dependence for absorption. Indeed, enhanced absorption is seen in the region of 300-450 nm in many cases, particularly in the afternoon periods indicating that secondary organic aerosols are contributing to the aerosol absorption. This is likely due

  19. 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.

  20. 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.

  1. Location Privacy

    NASA Astrophysics Data System (ADS)

    Meng, Xiaofeng; Chen, Jidong

    With rapid development of sensor and wireless mobile devices, it is easy to access mobile users' location information anytime and anywhere. On one hand, LBS is becoming more and more valuable and important. On the other hand, location privacy issues raised by such applications have also gained more attention. However, due to the specificity of location information, traditional privacy-preserving techniques in data publishing cannot be used. In this chapter, we will introduce location privacy, and analyze the challenges of location privacy-preserving, and give a survey of existing work including the system architecture, location anonymity and query processing.

  2. 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.

  3. Highly Mismatched Alloys for Intermediate Band Solar Cells

    SciTech Connect

    Walukiewicz, W.; Yu, K.M.; Wu, J.; Ager III, J.W.; Shan, W.; Scrapulla, M.A.; Dubon, O.D.; Becla, P.

    2005-03-21

    It has long been recognized that the introduction of a narrow band of states in a semiconductor band gap could be used to achieve improved power conversion efficiency in semiconductor-based solar cells. The intermediate band would serve as a ''stepping stone'' for photons of different energy to excite electrons from the valence to the conduction band. An important advantage of this design is that it requires formation of only a single p-n junction, which is a crucial simplification in comparison to multijunction solar cells. A detailed balance analysis predicts a limiting efficiency of more than 50% for an optimized, single intermediate band solar cell. This is higher than the efficiency of an optimized two junction solar cell. Using ion beam implantation and pulsed laser melting we have synthesized Zn{sub 1-y}Mn{sub y}O{sub x}Te{sub 1-x} alloys with x<0.03. These highly mismatched alloys have a unique electronic structure with a narrow oxygen-derived intermediate band. The width and the location of the band is described by the Band Anticrossing model and can be varied by controlling the oxygen content. This provides a unique opportunity to optimize the absorption of solar photons for best solar cell performance. We have carried out systematic studies of the effects of the intermediate band on the optical and electrical properties of Zn{sub 1-y}Mn{sub y}O{sub x}Te{sub 1-x} alloys. We observe an extension of the photovoltaic response towards lower photon energies, which is a clear indication of optical transitions from the valence to the intermediate band.

  4. Noise exposure in marching bands

    NASA Astrophysics Data System (ADS)

    Keefe, Joseph

    2005-09-01

    Previous studies involving orchestras have shown that music ensembles can produce hazardous noise levels. There are no similar data for marching bands and pep bands. In order to evaluate the noise levels produced by marching and pep bands, 1/3-octave-band sound-pressure levels were measured while these groups rehearsed and performed. Data were collected while marching with the bands to ensure a realistic environment. Comparing these data to OSHA and NIOSH criteria, marching and pep band exposures often exceed safe values. For typical exposures, OSHA doses range from 11% to 295%, while NIOSH doses range from 35% to 3055%. Exposures that would be considered hazardous in the workplace are common in marching and pep bands; students and band directors should take steps to recognize the risk posed by various instruments and various locations, and should implement hearing conservation efforts.

  5. Backscatter absorption gas imaging systems and light sources therefore

    DOEpatents

    Kulp, Thomas Jan; Kliner, Dahv A. V.; Sommers, Ricky; Goers, Uta-Barbara; Armstrong, Karla M.

    2006-12-19

    The location of gases that are not visible to the unaided human eye can be determined using tuned light sources that spectroscopically probe the gases and cameras that can provide images corresponding to the absorption of the gases. The present invention is a light source for a backscatter absorption gas imaging (BAGI) system, and a light source incorporating the light source, that can be used to remotely detect and produce images of "invisible" gases. The inventive light source has a light producing element, an optical amplifier, and an optical parametric oscillator to generate wavelength tunable light in the IR. By using a multi-mode light source and an amplifier that operates using 915 nm pump sources, the power consumption of the light source is reduced to a level that can be operated by batteries for long periods of time. In addition, the light source is tunable over the absorption bands of many hydrocarbons, making it useful for detecting hazardous gases.

  6. On the nature of absorption features toward nearby stars

    NASA Astrophysics Data System (ADS)

    Kohl, S.; Czesla, S.; Schmitt, J. H. M. M.

    2016-06-01

    Context. Diffuse interstellar absorption bands (DIBs) of largely unknown chemical origin are regularly observed primarily in distant early-type stars. More recently, detections in nearby late-type stars have also been claimed. These stars' spectra are dominated by stellar absorption lines. Specifically, strong interstellar atomic and DIB absorption has been reported in τ Boo. Aims: We test these claims by studying the strength of interstellar absorption in high-resolution TIGRE spectra of the nearby stars τ Boo, HD 33608, and α CrB. Methods: We focus our analysis on a strong DIB located at 5780.61 Å and on the absorption of interstellar Na. First, we carry out a differential analysis by comparing the spectra of the highly similar F-stars, τ Boo and HD 33608, whose light, however, samples different lines of sight. To obtain absolute values for the DIB absorption, we compare the observed spectra of τ Boo, HD 33608, and α CrB to PHOENIX models and carry out basic spectral modeling based on Voigt line profiles. Results: The intercomparison between τ Boo and HD 33608 reveals that the difference in the line depth is 6.85 ± 1.48 mÅ at the DIB location which is, however, unlikely to be caused by DIB absorption. The comparison between PHOENIX models and observed spectra yields an upper limit of 34.0 ± 0.3 mÅ for any additional interstellar absorption in τ Boo; similar results are obtained for HD 33608 and α CrB. For all objects we derive unrealistically large values for the radial velocity of any presumed interstellar clouds. In τ Boo we find Na D absorption with an equivalent width of 0.65 ± 0.07 mÅ and 2.3 ± 0.1 mÅ in the D2 and D1 lines. For the other Na, absorption of the same magnitude could only be detected in the D2 line. Our comparisons between model and data show that the interstellar absorption toward τ Boo is not abnormally high. Conclusions: We find no significant DIB absorption in any of our target stars. Any differences between modeled and

  7. Effect of in-material losses on terahertz absorption, transmission, and reflection in photonic crystals made of polar dielectrics

    SciTech Connect

    Serebryannikov, Andriy E.; Nojima, S.; Alici, K. B.; Ozbay, Ekmel

    2015-10-07

    The effect of the material absorption factor on terahertz absorption (A), transmittance (T), and reflectance (R) for slabs of PhC that comprise rods made of GaAs, a polar dielectric, is studied. The main goal was to illustrate how critical a choice of the absorption factor for simulations is and to indicate the importance of the possible modification of the absorption ability by using either active or lossy impurities. The spectra of A, T, and R are strongly sensitive to the location of the polaritonic gap with respect to the photonic pass and stop bands connected with periodicity that enables the efficient combination of the effects of material and structural parameters. It will be shown that the spectra can strongly depend on the utilized value of the material absorption factor. In particular, both narrow and wide absorption bands may appear owing to a variation of the material parameters with a frequency in the vicinity of the polaritonic gap. The latter are often achieved at wideband suppression of transmission, so that an ultra-wide stop band can appear as a result of adjustment of the stop bands having different origin. The results obtained at simultaneous variation of the absorption factor and frequency, and angle of incidence and frequency, indicate the possibility of the existence of wide ranges of tolerance, in which the basic features do remain. This allows for mitigating the accuracy requirements for the absorption factor in simulations and promises the efficient absorption of nonmonochromatic waves and beams with a wide angular spectrum. Suppression of narrowband effects in transmission is demonstrated at rather large values of the absorption factor, when they appear due to either the defect modes related to structural defects or dispersion inspired variations of the material parameters in the vicinity of the polaritonic gap. Comparison with auxiliary structures helps one to detect the common features and differences of homogeneous slabs and slabs of a

  8. Making Linked, Wound-Filament Bands

    NASA Technical Reports Server (NTRS)

    Bamford, Robert M.; Stephens, James B.

    1987-01-01

    Chains produced by use of rotating mandrel. Mandrel and locating and driving disks assembled around first band. Mandrel and band then mounted in respective positions on filament-winding machine. Second band linked to first by winding filament around first band on rotating mandrel. Short chains made this way have variety of uses; example, thermal isolators, each consisting of two linked bands of insulating material, used to support two separated insulating sheilds surrounding container of liquid helium.

  9. Determination of the major groups of phytoplankton pigments from the absorption spectra of total particulate matter

    NASA Technical Reports Server (NTRS)

    Hoepffner, Nicolas; Sathyendranath, Shubha

    1993-01-01

    The contributions of detrital particles and phytoplankton to total light absorption are retrieved by nonlinear regression on the absorption spectra of total particles from various oceanic regions. The model used explains more than 96% of the variance in the observed particle absorption spectra. The resulting absorption spectra of phytoplankton are then decomposed into several Gaussian bands reflecting absorption by phytoplankton pigments. Such a decomposition, combined with high-performance liquid chromatography data on phytoplankton pigment concentrations, allows the computation of specific absorption coefficients for chlorophylls a, b, and c and carotenoids. The spectral values of these in vivo absorption coefficients are then discussed, considering the effects of secondary pigments which were not measured quantitatively. We show that these coefficients can be used to reconstruct the absorption spectra of phytoplankton at various locations and depths. Discrepancies that do occur at some stations are explained in terms of particle size effect. These coefficients can be used to determine the concentrations of phytoplankton pigments in the water, given the absorption spectrum of total particles.

  10. Determination of the major groups of phytoplankton pigments from the absorption spectra of total particulate matter

    NASA Astrophysics Data System (ADS)

    Hoepffner, Nicolas; Sathyendranath, Shubha

    1993-12-01

    The contributions of detrital particles and phytoplankton to total light absorption are retrieved by nonlinear regression on the absorption spectra of total particles from various oceanic regions. The model used explains more than 96% of the variance in the observed particle absorption spectra. The resulting absorption spectra of phytoplankton are then decomposed into several Gaussian bands reflecting absorption by phytoplankton pigments. Such a decomposition, combined with high-performance liquid chromatography data on phytoplankton pigment concentrations, allows the computation of specific absorption coefficients for chlorophylls a, b, and c and carotenoids. The spectral values of these in vivo absorption coefficients are then discussed, considering the effects of secondary pigments which were not measured quantitatively. We show that these coefficients can be used to reconstruct the absorption spectra of phytoplankton at various locations and depths. Discrepancies that do occur at some stations are explained in terms of particle size effect. These coefficients can be used to determine the concentrations of phytoplankton pigments in the water, given the absorption spectrum of total particles.

  11. 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.

  12. Design of a Ka-Band Propagation Terminal for Atmospheric Measurements in Polar Regions

    NASA Technical Reports Server (NTRS)

    Houts, Jacquelynne R.; Nessel, James A.; Zemba, Michael J.

    2016-01-01

    This paper describes the design and performance of a Ka-Band beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed alongside an existing Ka-Band Radiometer [2] located at the east end of the Svalbard Near Earth Network (NEN) complex. The goal of this experiment is to characterize rain fade attenuation to improve the performance of existing statistical rain attenuation models. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation [3] receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation by directly measuring the propagated signal from the satellite Thor 7.

  13. Design of a Ka-band Propagation Terminal for Atmospheric Measurements in Polar Regions

    NASA Technical Reports Server (NTRS)

    Houts, Jacquelynne R.; Nessel, James A.; Zemba, Michael J.

    2016-01-01

    This paper describes the design and performance of a Ka-Band beacon receiver developed at NASA Glenn Research Center (GRC) that will be installed alongside an existing Ka-Band Radiometer located at the east end of the Svalbard Near Earth Network (NEN) complex. The goal of this experiment is to characterize rain fade attenuation to improve the performance of existing statistical rain attenuation models. The ground terminal developed by NASA GRC utilizes an FFT-based frequency estimation receiver capable of characterizing total path attenuation effects due to gaseous absorption, clouds, rain, and scintillation by directly measuring the propagated signal from the satellite Thor 7.

  14. 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.

  15. 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.

  16. Aerosol Properties From Combined Oxygen A Band Radiances and Lidar

    NASA Technical Reports Server (NTRS)

    Winker, Dave; Zhai, Peng-Wang; Hu, Yongxiang

    2015-01-01

    We have developed a new aerosol retrieval technique based on combing high-resolution A band spectra with lidar profiles. Our goal is the development of a technique to retrieve aerosol absorption, one of the critical parameters affecting the global radiation budget and one which is currently poorly constrained by satellite measurements. Our approach relies on two key factors: 1) the use of high spectral resolution (17,000:1) measurements which resolve the A-band line structure, and 2) the use of co-located lidar profile measurements to constrain the vertical distribution of scatterers in the forward model. The algorithm has been developed to be applied to observations from the CALIPSO and OCO-2 satellites, flying in formation as part of the A-train constellation. We describe the approach and present simulated retrievals to illustrate performance potential.

  17. 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.

  18. 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 ...

  19. An international evaluation of holmium oxide solution reference materials for wavelength calibration in molecular absorption spectrophotometry.

    PubMed

    Travis, John C; Zwinkels, Joanne C; Mercader, Flora; Ruíz, Arquímedes; Early, Edward A; Smith, Melody V; Noël, Mario; Maley, Marissa; Kramer, Gary W; Eckerle, Kenneth L; Duewer, David L

    2002-07-15

    Commercial spectrophotometers typically use absorption-based wavelength calibration reference materials to provide wavelength accuracy for their applications. Low-mass fractions of holmium oxide (Ho2O3) in dilute acidic aqueous solution and in glass matrixes have been favored for use as wavelength calibration materials on the basis of spectral coverage and absorption band shape. Both aqueous and glass Ho2O3 reference materials are available commercially and through various National Metrology Institutes (NMIs). Three NMIs of the North American Cooperation in Metrology (NORAMET) have evaluated the performance of Ho3-(aq)-based Certified Reference Materials (CRMs) under "routine" operating conditions using commercial instrumentation. The study was not intended to intercompare national wavelength scales but to demonstrate comparability of wavelength measurements among the participants and between two versions of the CRMs. It was also designed to acquire data from a variety of spectrophotometers for use in a NIST study of wavelength assignment algorithms and to provide a basis for a possible reassessment of NIST-certified Ho3+(aq) band locations. The resulting data show a substantial level of agreement among laboratories, instruments, CRM preparations, and peak-location algorithms. At the same time, it is demonstrated that the wavelength comparability of the five participating instruments can actually be improved by calibrating all of the instruments to the consensus Ho3+(aq) band locations. This finding supports the value of absorption-based wavelength standards for calibrating absorption spectrophotometers. Coupled with the demonstrated robustness of the band position values with respect to preparation and measurement conditions, it also supports the concept of extending the present approach to additional NMIs in order to certify properly prepared dilute acidic Ho2O3 solution as an intrinsic wavelength standard.

  20. Manifestation of the Hofstadter butterfly in far-infrared absorption

    SciTech Connect

    Gudmundsson, V.; Gerhardts, R.R.

    1996-08-01

    The far-infrared absorption of a two-dimensional electron gas with a square-lattice modulation in a perpendicular constant magnetic field is calculated self-consistently within the Hartree approximation. For strong modulation and short period we obtain intrasubband and intersubband magnetoplasmon modes reflecting the subbands of the Hofstadter butterfly in two or more Landau bands. The character of the absorption and the correlation of the peaks to the number of flux quanta through each unit cell of the periodic potential depends strongly on the location of the chemical potential with respect to the subbands, or equivalently, on the density of electrons in the system. {copyright} {ital 1996 The American Physical Society.}

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Dual-band frequency selective surface with large band separation and stable performance

    NASA Astrophysics Data System (ADS)

    Zhou, Hang; Qu, Shao-Bo; Peng, Wei-Dong; Lin, Bao-Qin; Wang, Jia-Fu; Ma, Hua; Zhang, Jie-Qiu; Bai, Peng; Wang, Xu-Hua; Xu, Zhuo

    2012-05-01

    A new technique of designing a dual-band frequency selective surface with large band separation is presented. This technique is based on a delicately designed topology of L- and Ku-band microwave filters. The two band-pass responses are generated by a capacitively-loaded square-loop frequency selective surface and an aperture-coupled frequency selective surface, respectively. A Faraday cage is located between the two frequency selective surface structures to eliminate undesired couplings. Based on this technique, a dual-band frequency selective surface with large band separation is designed, which possesses large band separation, high selectivity, and stable performance under various incident angles and different polarizations.

  6. 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.

  7. 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.

  8. Electronic- and band-structure evolution in low-doped (Ga,Mn)As

    SciTech Connect

    Yastrubchak, O.; Gluba, L.; Żuk, J.; Sadowski, J.; Krzyżanowska, H.; Domagala, J. Z.; Andrearczyk, T.; Wosinski, T.

    2013-08-07

    Modulation photoreflectance spectroscopy and Raman spectroscopy have been applied to study the electronic- and band-structure evolution in (Ga,Mn)As epitaxial layers with increasing Mn doping in the range of low Mn content, up to 1.2%. Structural and magnetic properties of the layers were characterized with high-resolution X-ray diffractometry and SQUID magnetometery, respectively. The revealed results of decrease in the band-gap-transition energy with increasing Mn content in very low-doped (Ga,Mn)As layers with n-type conductivity are interpreted as a result of merging the Mn-related impurity band with the host GaAs valence band. On the other hand, an increase in the band-gap-transition energy with increasing Mn content in (Ga,Mn)As layers with higher Mn content and p-type conductivity indicates the Moss-Burstein shift of the absorption edge due to the Fermi level location within the valence band, determined by the free-hole concentration. The experimental results are consistent with the valence-band origin of mobile holes mediating ferromagnetic ordering in the (Ga,Mn)As diluted ferromagnetic semiconductor.

  9. Synchrotron-based Fourier transform spectra of the ν23 and ν24 IR bands of hexamethylenetetramine C6N4H12

    NASA Astrophysics Data System (ADS)

    Pirali, O.; Boudon, V.

    2015-09-01

    Hexamethylenetetramine (HMT), C6N4H12 is a spherical top with nine IR-active modes. Because of its relevance for astrophysics, we recorded the absorption spectra in the full range of its fundamental bands. In total, we detected eight fundamental bands and recently published the rotational analysis of the four most intense bands (ν19,ν20,ν21,ν22) located in the 1000-1500 cm-1 range as a support for astronomical searches (Pirali et al., 2014). While the CH stretch modes are unresolved broad features, in this article we report the analysis of the two remaining fundamental bands exhibiting rotationally resolved structures: ν23 -GS and ν24 -GS located at about 820 cm-1 and 670 cm-1, respectively.

  10. 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.

  11. 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

  12. Detection and measurement of the Wing-Ford band in the near-infrared spectra of elliptical galaxies

    NASA Astrophysics Data System (ADS)

    Hardy, Edouardo; Couture, Jean

    1988-02-01

    An absorption feature was detected at the location of the Wing-Ford band near 9916 A in high-quality CCD spectra of five elliptical galaxies taken with the Cerro Tololo 4-m RC spectrograph. Measurements reveal that the mean strength is 0.013 mag (1 sigma of the mean) and individual galaxy strengths have 1 sigma errors of the order 0.002 mag. The (3-4) band of the delta system of TiO with band head at 9986 A was also detected, suggesting that the observed Wing-Ford feature is affected by the (2-3) band of the delta system of TiO at 9899 A which is present in late giants. Therefore, this feature is not due exclusively to the FeH molecule strong in late M dwarfs.

  13. The near-infrared bands of NO2 observed by high-resolution Fourier-transform spectroscopy

    NASA Astrophysics Data System (ADS)

    Orphal, J.; Dreher, S.; Voigt, S.; Burrows, J. P.; Jost, R.; Delon, A.

    1998-12-01

    Fourier-transform absorption spectra of NO2 at 298 K were recorded between 9000-15 000 cm-1 at Doppler-limited resolution (0.012 cm-1), in the region near the à 2B2-X˜ 2A1 conical intersection. The strong rovibronic bands are rather isolated and organized into polyads which can be assigned by the number of bending quanta of the à 2B2 state, corresponding to the transitions with the largest Franck-Condon factors. Around 9735 cm-1, where the origin of the à 2B2-X˜ 2A1 vibronic band system is located and up to about 11 200 cm-1, hot bands dominate the spectrum. The complexity of the spectrum increases with energy due to an increasing density of à 2B2 and X˜ 2A1 vibrational levels. The rotational structure is dense and irregular as already observed for higher bands.

  14. 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.

  15. Satellite retrieval of the absorption coefficient of phytoplankton phycoerythrin pigment: theory and feasibility status.

    PubMed

    Hoge, F E; Wright, C W; Lyon, P E; Swift, R N; Yungel, J K

    1999-12-20

    satellite recovery of PE absorption, the maturity of the retrieval is presently insufficient for routine global application. Instead it must currently be used on a regional basis where localized ship and aircraft validation can be made available. The algorithm was developed for the MODIS (Moderate-Resolution Imaging Spectroradiometer) sensor but is applicable to any sensor having comparable band locations.

  16. 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.

  17. 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.

  18. [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.

  19. Quantification of Myofascial Taut Bands

    PubMed Central

    Chen, Qingshan; Wang, Hua-jun; Gay, Ralph E.; Thompson, Jeffrey M.; Manduca, Armando; An, Kai-Nan; Ehman, Richard E.; Basford, Jeffrey R.

    2015-01-01

    Objective To assess the correlation of clinician identified myofascial taut bands with their presence and characteristics on Magnetic Resonance Elastography (MRE) imaging. Design Cross-sectional study. Setting An MRI research laboratory. Participants A convenience sample of 65 adults (45 women, 20 men) identified by skilled musculoskeletal physicians as having upper trapezius myofascial pain associated taut bands. Interventions Subjects had their taut bands outlined and were positioned within a 1.5T MRI machine. Shear waves were induced with a pneumatic transducer located over the belly of the involved muscle. Wave propagation was visualized with MRE images across a vibration-cycle. Imaging data was assessed independently by two skilled MRE interpreters. Main Outcome Measures The primary outcome measure was the determination of the intra- and inter-rater reliabilities of MRE taut band identification and their correlation with clinician identification of band presence. Secondary outcomes consisted of the elucidation of the physical characteristics of taut bands and their surrounding muscle tissue. Results MRE intra- and inter-rater reliability was excellent with Kappa's and 95% Confidence intervals (CI) of 0.86, [0.68, 1.00]; and 0.93, [0.79, 1.00], respectively. Stiffness in MRE identified taut bands was elevated at a mean of 11.5 KPa (±2.4 KPa) and fell to a mean of 5.8 KPa (± 0.9 KPa) in surrounding muscle tissue (p<0.001); muscular tone in trapezius muscles without a taut band was relatively uniform at a mean of 6.6 KPa (±2.1 KPa). Agreement between the physicians and the MRE raters, however, was relatively poor (63.1%, 95% CI [50.2%, 74.7%]). Conclusions Our findings suggest that while clinicians may overestimate, and current MRE techniques may underestimate, the presence of taut bands, that these bands exist, can be assessed quantitatively, and do represent localized areas of increased muscle stiffness. PMID:26461163

  20. Band Anticrossing in Highly Mismatched Compound Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Yu, Kin Man; Wu, J.; Walukiewicz, W.; Ager, J. W.; Haller, E. E.; Miotkowski, I.; Su, Ching-Hua; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    Compound semiconductor alloys in which metallic anions are partially replaced with more electronegative isoelectronic atoms have recently attracted significant attention. Group IIIN(sub x)V(sub 1-x) alloys with a small amount of the electronegative N substituting more metallic column V elements has been the most extensively studied class of such Highly Mismatched Alloys (HMAs). We have shown that many of the unusual properties of the IIIN(sub x)V(sub 1-x) alloys can be well explained by the Band Anticrossing (BAC) model that describes the electronic structure in terms of an interaction between highly localized levels of substitutional N and the extended states of the host semiconductor matrix. Most recently the BAC model has been also used to explain similar modifications of the electronic band structure observed in Te-rich ZnS(sub x)Te(sub 1-x) and ZnSe(sub y)Te(sub 1-y) alloys. To date studies of HMAs have been limited to materials with relatively small concentrations of highly electronegative atoms. Here we report investigations of the electronic structure of ZnSe(sub y)Te(sub 1-y) alloys in the entire composition range, y between 0 and 1. The samples used in this study are bulk ZnSe(sub y)Te(sub 1-y) crystals grown by either a modified Bridgman method or by physical vapor transport. Photomodulated reflection (PR) spectroscopy was used to measure the composition dependence of optical transitions from the valence band edge and from the spin-orbit split off band to the conduction band. The pressure dependence of the band gap was measured using optical absorption in a diamond anvil cell. We find that the energy of the spin-orbit split off valence band edge does not depend on composition and is located at about 3 eV below the conduction band edge of ZnSe. On the Te-rich side the pressure and the composition dependence of the optical transitions are well explained by the BAC model which describes the downward shift of the conduction band edge in terms of the

  1. Band Anticrossing in Highly Mismatched Compound Semiconductor Alloys

    NASA Technical Reports Server (NTRS)

    Yu, Kin Man; Wu, J.; Walukiewicz, W.; Ager, J. W.; Haller, E. E.; Miotkowski, I.; Ramdas, A.; Su, Ching-Hua; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Compound semiconductor alloys in which metallic anions are partially replaced with more electronegative isoelectronic atoms have recently attracted significant attention. Group IIIN(x)V(1-x), alloys with a small amount of the electronegative N substituting more metallic column V elements has been the most extensively studied class of such Highly Mismatched Alloys (HMAs). We have shown that many of the unusual properties of the IIIN(x),V(1-x) alloys can be well explained by the Band Anticrossing (BAC) model that describes the electronic structure in terms of an interaction between highly localized levels of substitutional N and the extended states of the host semiconductor matrix. Most recently the BAC model has been also used to explain similar modifications of the electronic band structure observed in Te-rich ZnS(x)Te(l-x) and ZnSe(Y)Te(1-y) alloys. To date studies of HMAs have been limited to materials with relatively small concentrations of highly electronegative atoms. Here we report investigations of the electronic structure of ZnSe(y)Te(1-y) alloys in the entire composition range, 0 less than or equal to y less than or equal to 1. The samples used in this study are bulk ZnSe(y)Te(1-y) crystals grown by either a modified Bridgman method or by physical vapor transport. Photomodulated reflection (PR) spectroscopy was used to measure the composition dependence of optical transitions from the valence band edge and from the spin-orbit split off band to the conduction band. The pressure dependence of the band gap was measured using optical absorption in a diamond anvil cell. We find that the energy of the spin-orbit split off valence band edge does not depend on composition and is located at about 3 eV below the conduction band edge of ZnSe. On the Te-rich side the pressure and the composition dependence of the optical transitions are well explained by the BAC model which describes the downward shift of the conduction band edge in terms of the interaction between

  2. 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.

  3. 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)

  4. 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.

  5. Atmospheric Pre-Corrected Differential Absorption Techniques to Retrieve Columnar Water Vapor: Application to AVIRIS 91/95 Data

    NASA Technical Reports Server (NTRS)

    Schlaepfer, Daniel; Borel, Christoph C.; Keller, Johannes; Itten, Klaus I.

    1996-01-01

    Water vapor is one of the main forces for weather development as well as for mesoscale air transport processes. The monitoring of water vapor is therefore an important aim in remote sensing of the atmosphere. Current operational systems for water vapor detection use primarily the emission in the thermal infrared (AVHRR, GOES, ATSR, Meteosat) or in the microwave radiation bands (DMSP). The disadvantage of current satellite systems is either a coarse spatial (horizontal) resolution ranging from one to tens of kilometers or a limited insight into the lower atmosphere. Imaging spectrometry on the other hand measures total column water vapor contents at a high spatial horizontal resolution and has therefore the potential of filling these gaps. The sensors of the AVIRIS instrument are capable of acquiring hyperspectral data in 224 bands located in the visible and near infrared at 10 nm resolution. This data includes the information on constituents of the earth's surface as well as of the atmosphere. The optical measurement of water vapor can be performed using sensor channels located in bands or lines of the absorption spectrum. The AVIRIS sensor has been used to retrieve water vapor and with less accuracy carbon dioxide, oxygen and ozone. To retrieve the water vapor amount, the so called differential absorption technique has been applied. The goal of this technique is to eliminate background factors by taking a ratio between channels within the absorption band and others besides the band. Various ratioing methods on the basis of different channels and calculation techniques were developed. The influence of a trace gas of interest on the radiance at the sensor level is usually simulated by using radiative transfer codes. In this study, the spectral transmittance and radiance are calculated by MODTRAN3 simulations with the new DISORT option. The objective of this work is to test the best performing differential absorption techniques for imaging spectrometry of

  6. Origins of electronic band gap reduction in Cr/N codoped TiO2.

    PubMed

    Parks Cheney, C; Vilmercati, P; Martin, E W; Chiodi, M; Gavioli, L; Regmi, M; Eres, G; Callcott, T A; Weitering, H H; Mannella, N

    2014-01-24

    Recent studies indicated that noncompensated cation-anion codoping of wide-band-gap oxide semiconductors such as anatase TiO2 significantly reduces the optical band gap and thus strongly enhances the absorption of visible light [W. Zhu et al., Phys. Rev. Lett. 103, 226401 (2009)]. We used soft x-ray spectroscopy to fully determine the location and nature of the impurity levels responsible for the extraordinarily large (∼1 eV) band gap reduction of noncompensated codoped rutile TiO2. It is shown that Cr/N codoping strongly enhances the substitutional N content, compared to single element doping. The band gap reduction is due to the formation of Cr 3d3 levels in the lower half of the gap while the conduction band minimum is comprised of localized Cr 3d and delocalized N 2p states. Band gap reduction and carrier delocalization are critical elements for efficient light-to-current conversion in oxide semiconductors. These findings thus raise the prospect of using codoped oxide semiconductors with specifically engineered electronic properties in a variety of photovoltaic and photocatalytic applications.

  7. Metamaterial with electromagnetic transparency under multiband absorptions

    NASA Astrophysics Data System (ADS)

    Zhang, Xu; Qi, Limei

    2017-02-01

    We propose a metal-dielectric-metal (MDM) metamaterial that has an electromagnetic (EM) transparency spectrum under multiband absorptions in the C and the X bands. The ground continuous metal film used in the conventional metamaterial absorber (MA) is replaced by a structured ground plane (SGP) in our design. The band-pass properties of the front patterned metal film and the SGP determine the EM transparency spectrum, while the magnetic and the electric resonances in the MDM structure contribute to the multiband absorptions. Due to the symmetric structure of the unit cell, the absorption bands and the EM transparency spectrum of the metamaterial have the property of polarization independency. Despite the normal incidence, the metamaterial can also be used for non-normal incidence.

  8. High-Absorption-Efficiency Superlattice Solar Cells by Excitons

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kawaharazuka, Atsushi; Onomitsu, Koji; Horikoshi, Yoshiji

    2013-11-01

    The effect of excitonic absorption on solar cell efficiency has been investigated using solar cells with AlGaAs/GaAs superlattice structures. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption of bulk GaAs. Excitonic absorption shows strong and sharp peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of the superlattice solar cells are quite similar to the calculated absorption spectra considering the excitonic effect. The superlattice solar cells are confirmed to have high absorption coefficient compared with the GaAs and AlGaAs bulk solar cells. These results suggest that the enhanced absorption by excitons can increase the quantum efficiency of solar cells. This effect is more prominent for the solar cells with small absorption layer thicknesses.

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

    NASA Technical Reports Server (NTRS)

    Angel, J. R. P.

    1972-01-01

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

  10. 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.

  11. Atmospheric Absorption Parameters for Laser Propagation

    DTIC Science & Technology

    2007-11-02

    high-resolution, good photometric accuracy data for numerous bands in the 3-5 Am region, using the facility at Kitt Peak National Solar Observatory. The...L49-L52 (2001). 44. A. Castrillo, G. Gagliardi, G. Casa , and L. Gianfrani, "Combined interferometric and absorption-spectroscopic technique for...from FT visible solar absorption spectra and evaluation of spectroscopic databases," JQRST 82, 133-150 (2003). 53. D. Jacquemart, R.R. Gamache, and L.S

  12. TRES Survey of Variable Diffuse Interstellar Bands

    NASA Astrophysics Data System (ADS)

    Law, Charles; Milisavljevic, Dan; Crabtree, Kyle; Johansen, Sommer; Patnaude, Daniel

    2017-01-01

    Diffuse interstellar bands (DIBs) are absorption features commonly observed in optical/near-infrared spectra of stars and thought to be associated with polyatomic molecules that comprise a significant reservoir of organic material in the universe. However, because the central wavelengths of DIBs do not correspond with electronic transitions of known atomic or molecular species, the specific physical nature of their carriers remains inconclusive despite decades of observational, theoretical, and experimental research. It is well established that DIB carriers must be located in the interstellar medium, but the recent discovery of time-varying DIBs in the spectra of the extragalactic supernova SN 2012ap suggests that some may be created in massive star environments. We report evidence of short time-scale (˜1-60 days) variations in DIB absorption line substructure toward 3 of 17 massive stars observed as part of a pathfinder survey of variable DIBs. The detections are made in high-resolution optical spectra (R ˜ 44000) from the Tillinghast Reflection Echelle Spectrograph on the 1.5m Tillinghast telescope at the Smithsonian Astrophysical Observatory's Fred L. Whipple Observatory on Mt. Hopkins in Arizona. Our detections have signal-to-noise ratios of 5-15 around the features of interest, and are thus considered significant but requiring further investigation. We find that these changes are potentially consistent with interactions between stellar winds and DIB carriers in close proximity. Our findings motivate a larger survey to further characterize these variations and may establish a powerful new method for probing the poorly understood physical characteristics of DIB carriers.

  13. Absorption of Solar Radiation by Clouds: Observations Versus Models

    NASA Technical Reports Server (NTRS)

    Cess, R. D.; Zhang, M. H.; Minnis, P.; Corsetti, L.; Dutton, E. G.; Forgan, B. W.; Garber, D. P.; Gates, W. L.; Hack, J. J.; Harrison, E. F.; Jing, X.; Kiehl, J. T.; Long, C. N.; Morcrette, J.-J.; Potter, G. L.; Ramanathan, V.; Subasilar, B.; Whitlock, C. H.; Young, D. F.; Zhou, Y.

    1995-01-01

    There has been a long history of unexplained anomalous absorption of solar radiation by clouds. Collocated satellite and surface measurements of solar radiation at five geographically diverse locations showed significant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere than predicted by theoretical models. It has often been suggested that tropospheric aerosols could increase cloud absorption. But these aerosols are temporally and spatially heterogeneous, whereas the observed cloud absorption is remarkably invariant with respect to season and location. Although its physical cause is unknown, enhanced cloud absorption substantially alters our understanding of the atmosphere's energy budget.

  14. Ultraviolet-visible absorption spectra of N-doped TiO2 film deposited on sapphire

    NASA Astrophysics Data System (ADS)

    Park, Jaewon; Lee, Jung-Yup; Cho, Jun-Hyung

    2006-12-01

    The optical-response properties of nitrogen(N)-doped titanium dioxide (TiO2) films are investigated by means of a combination of ultraviolet-visible absorption spectroscopy and first-principles density-functional calculations. The TiO2 films were epitaxially grown on the sapphire substrate by the pulsed laser deposition method. The doping of N atoms was achieved by 70keV of N+ ion implantation, followed by postirradiation heat treatment at 550°C for 2h in air. We find that when 5×1016 (1×1017)Nions/cm2 were implanted into the epitaxially grown TiO2 film, the absorption edge is reproducibly shifted to lower energy by about 0.06 (0.12)eV together with a significant optical absorption extending into the visible-light region. These experimental data can be explained by our calculated band structure of N-doped TiO2, where the bands originating from N 2p states locate above the valence band edge, while the band gap narrowing due to the mixing of N with O 2p states is 0.04eV.

  15. An ultrathin dual-band metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Duan, Junping; Zhang, Wendong; Wang, Wanjun; Zhang, Binzhen

    2016-10-01

    The design and preparation of an ultrathin dual-band metamaterial absorber whose resonant frequency located at radar wave (20 GHz-60 GHz) is presented in this paper. The absorber is composed of a 2-D periodic sandwich featured with two concentric annuluses. The influence on the absorber's performance produced by resonant cell's structure size and material parameters was numerically simulated and analyzed based on the standard full wave finite integration technology in CST. Laser ablation process was adopted to prepare the designed absorber on epoxy resin board coated with on double plane of copper with a thickness that is 1/30 and 1/50 of the resonant wavelength at a resonant frequency of 30.51 GHz and 48.15 GHz. The full width at half maximum (FWHM) reached 2.2 GHz and 2.35 GHz and the peak of the absorptance reached 99.977%. The ultrathin absorber is nearly omnidirectional for all polarizations. The test results of prepared sample testify the designed absorber's excellent absorbing performance forcefully. The absorber expands inspirations of radar stealth in military domain due to its flexible design, cost-effective and other outstanding properties.

  16. Diffuse Interstellar Bands in Emission

    NASA Astrophysics Data System (ADS)

    Williams, T. B.; Sarre, P.; Marshall, C. C. M.; Spekkens, K.; de Naray, R. Kuzio

    Recent Fabry-Pérot observations towards the galaxy NGC 1325 with the Southern African Large Telescope (SALT) led to the serendipitous discovery of an emission feature centered at 661.3 nm arising from material in the interstellar medium (ISM) of our Galaxy; this emission feature lies at the wavelength of one of the sharper and stronger diffuse bands normally seen in absorption. The flux of the feature is 4.2 +/- 0.5 × 10-18 es-1 cm-2 arcsec-2. It appears that this is the first observation of emission from a diffuse band carrier in the ISM, excited in this case by the interstellar radiation field. We present the discovery spectra and describe follow-up measurements proposed for SALT.

  17. 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.

  18. Mean absorption coefficients of He/Ar/N2/(C1-x-y , Ni x , Co y ) thermal plasmas for CNT synthesis

    NASA Astrophysics Data System (ADS)

    Salem, D.; Hannachi, R.; Cressault, Y.; Teulet, Ph; Béji, L.

    2017-01-01

    In this paper, we present the mean absorption coefficients (MACs) calculated for plasma mixtures of argon-helium-nitrogen-carbon-nickel-cobalt at 60 kPa and in a temperature range from 1 kK to 20 kK. These coefficients have been computed under the assumption of a local thermodynamic equilibrium (LTE), isothermal plasma, including atomic and molecular continuum, molecular bands and lines radiation splitted into nine spectral intervals. The results show that the continuum absorption coefficients strongly depend on photodissociation and photoionization processes of the molecular species N2, CN and C2, with a significant effect on photodetachment processes of C- in a frequency interval lower than 1  ×  1015 Hz and for low temperature (<6 kK). While at high temperature, the main contribution in continuum absorption coefficient comes from radiative recombination processes except in the infrared region (<0.5  ×  1015 Hz) where the inverse bremsstrahlung represents the most important component in continuum processes for all temperature values. On the other hand, the calculation of MAC shows that the role of molecular continuum, molecular bands and line absorption of the neutral catalysis species Ni/Co are only important in a small range of temperature and in a few spectral bands located in visible and infrared regions, while at high temperature and in UV and visible regions, the foremost contributions to MAC come from atomic continuum and line absorption.

  19. Come Join the Band

    ERIC Educational Resources Information Center

    Olson, Cathy Applefeld

    2011-01-01

    A growing number of students in Blue Springs, Missouri, are joining the band, drawn by a band director who emphasizes caring and inclusiveness. In the four years since Melissia Goff arrived at Blue Springs High School, the school's extensive band program has swelled. The marching band alone has gone from 100 to 185 participants. Also under Goff's…

  20. Spectral Classification of Heavily Reddened Stars by CO Absorption Strength

    NASA Astrophysics Data System (ADS)

    Garling, Christopher; Bary, Jeffrey S.; Huard, Tracy L.

    2017-01-01

    The nature of dust grains in dense molecular clouds can be explored by obtaining spectra of giant stars located behind the clouds and examining the wavelength-dependent attentuation of their light. This approach requires the intrinsic spectra of the background stars to be known, which can be achieved by determining their spectral types. In the K-band spectra of cool giant stars, several temperature-sensitive CO absorption bands serve as good spectral type indicators. Taking advantage of the SpeX Infrared Telescope Facility Spectral Library, near-infrared spectra collected with TripleSpec and the 3.5-meter ARC Telescope at Apache Point Observatory, and a previously constructed CO spectral index, we make precise spectral determinations of 20 giant stars located behind two dense cloud cores: CB188 and L429C. With spectral types in hand, we then utilize Markov Chain Monte Carlo techniques to constrain extinctions along these lines of sight. The spectral typing method will be described and assessed as well as its success at finding a couple of incorrectly spectral typed stars in the SpeX Library. Funding for this program was provided by a NSF REU grant to the Keck Northeast Astronomy Consortium and a grant from the NASA Astrophysics Data Analysis Program.

  1. Water-related absorption in fibrous diamonds

    NASA Astrophysics Data System (ADS)

    Zedgenizov, D. A.; Shiryaev, A. A.; Kagi, H.; Navon, O.

    2003-04-01

    Cubic and coated diamonds from several localities (Brasil, Canada, Yakutia) were investigated using spectroscopic techniques. Special emphasis was put on investigation of water-related features of transmission Infra-red and Raman spectra. Presence of molecular water is inferred from broad absorption bands in IR at 3420 and 1640 cm-1. These bands were observed in many of the investigated samples. It is likely that molecular water is present in microinclusions in liquid state, since no clear indications of solid H_2O (ice VI-VII, Kagi et al., 2000) were found. Comparison of absorption by HOH and OH vibrations shows that diamonds can be separated into two principal groups: those containing liquid water (direct proportionality of OH and HOH absorption) and those with stronger absorption by OH group. Fraction of diamonds in every group depends on their provenance. There might be positive correlation between internal pressure in microinclusions (determined using quartz barometer, Navon et al., 1988) and affiliation with diamonds containing liquid water. In many cases absorption by HOH vibration is considerably lower than absorption by hydroxyl (OH) group. This may be explained if OH groups are partially present in mineral and/or melt inclusions. This hypothesis is supported by following fact: in diamonds with strong absorption by silicates and other minerals shape and position of the OH band differs from that in diamonds with low absorption by minerals. Moreover, in Raman spectra of individual inclusions sometimes the broad band at 3100 cm-1 is observed. This band is OH-related. In some samples water distribution is not homogeneous. Central part of the diamond usually contains more water than outer parts, but this is not a general rule for all the samples. Water absorption usually correlated with absorption of other components (carbonates, silicates and others). At that fibrous diamonds with relatively high content of silicates are characterized by molecular water. OH

  2. H i Absorption in the Steep-Spectrum Superluminal Quasar 3C 216.

    PubMed

    Pihlström; Vermeulen; Taylor; Conway

    1999-11-01

    The search for H i absorption in strong compact steep-spectrum sources is a natural way to probe the neutral gas contents in young radio sources. In turn, this may provide information about the evolution of powerful radio sources. The recently improved capabilities of the Westerbork Synthesis Radio Telescope have made it possible to detect a 0.31% (19 mJy) deep neutral atomic hydrogen absorption line associated with the steep-spectrum superluminal quasar 3C 216. The redshift (z=0.67) of the source shifts the frequency of the 21 cm line down to the ultra-high-frequency (UHF) band (850 MHz). The exact location of the H i-absorbing gas remains to be determined by spectral line VLBI observations at 850 MHz. We cannot exclude that the gas might be extended on galactic scales, but we think it is more likely to be located in the central kiloparsec. Constraints from the lack of X-ray absorption probably rule out obscuration of the core region, and we argue that the most plausible site for the H i absorption is in the jet-cloud interaction observed in this source.

  3. Indirect band gap in alpha-ZrO2

    SciTech Connect

    Kwok, C.K.; Aita, C.R.

    1990-08-01

    Measurements of the absorption coefficient on the fundamental optical absorption edge of alpha ZrO2 show that an indirect interband transition at 4.70 eV precedes two previously reported direct transitions. This result is in agreement with recent theoretical calculations of the alpha ZrO2 band structure. (JS)

  4. Engineered band structure for an enhanced performance on quantum dot-sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Jin, Bin Bin; Wang, Ye Feng; Wei, Dong; Cui, Bin; Chen, Yu; Zeng, Jing Hui

    2016-06-01

    A photon-to-current efficiency of 2.93% is received for the Mn-doped CdS (MCdS)-quantum dot sensitized solar cells (QDSSCs) using Mn:ZnO (MZnO) nanowire as photoanode. Hydrothermal synthesized MZnO are spin-coated on fluorine doped tin oxide (FTO) glass with P25 paste to serve as photoanode after calcinations. MCdS was deposited on the MZnO film by the successive ionic layer adsorption and reaction method. The long lived excitation energy state of Mn2+ is located inside the conduction band in the wide bandgap ZnO and under the conduction band of CdS, which increases the energetic overlap of donor and acceptor states, reducing the "loss-in-potential," inhibiting charge recombination, and accelerating electron injection. The engineered band structure is well reflected by the electrochemical band detected using cyclic voltammetry. Cell performances are evidenced by current density-voltage (J-V) traces, diffuse reflectance spectra, transient PL spectroscopy, and incident photon to current conversion efficiency characterizations. Further coating of CdSe on MZnO/MCdS electrode expands the light absorption band of the sensitizer, an efficiency of 4.94% is received for QDSSCs.

  5. Systematic variations in microvilli banding patterns along fiddler crab rhabdoms.

    PubMed

    Alkaladi, Ali; How, Martin J; Zeil, Jochen

    2013-02-01

    Polarisation sensitivity is based on the regular alignment of dichroic photopigment molecules within photoreceptor cells. In crustaceans, this is achieved by regularly stacking photopigment-rich microvilli in alternating orthogonal bands within fused rhabdoms. Despite being critical for the efficient detection of polarised light, very little research has focused on the detailed arrangement of these microvilli bands. We report here a number of hitherto undescribed, but functionally relevant changes in the organisation of microvilli banding patterns, both within receptors, and across the compound eye of fiddler crabs. In all ommatidia, microvilli bands increase in length from the distal to the proximal ends of the rhabdom. In equatorial rhabdoms, horizontal bands increase gradually from 3 rows of microvilli distally to 20 rows proximally. In contrast, vertical equatorial microvilli bands contain 15-20 rows of microvilli in the distal 30 µm of the rhabdom, shortening to 10 rows over the next 30 µm and then increase in length to 20 rows in parallel with horizontal bands. In the dorsal eye, horizontal microvilli occupy only half the cross-sectional area as vertical microvilli bands. Modelling absorption along the length of fiddler crab rhabdoms suggests that (1) increasing band length assures that photon absorption probability per band remains constant along the length of photoreceptors, indicating that individual bands may act as units of transduction or adaptation; (2) the different organisation of microvilli bands in equatorial and dorsal rhabdoms tune receptors to the degree and the information content of polarised light in the environment.

  6. 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.

  7. 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.

  8. [High-order derivative spectroscopy of infrared absorption spectra of the reaction centers from Rhodobacter sphaeroides].

    PubMed

    2005-01-01

    The infrared absorption spectra of reduced and chemically oxidized reaction center preparations from the purple bacterium Rhodobacter sphaeroides were investigated by means of high-order derivative spectroscopy. The model Gaussian band with a maximum at 810 nm and a half-band of 15 nm found in the absorption spectrum of the reduced reaction center preparation is eliminated after the oxidation of photoactive bacteriochlorophyll dimer (P). This band was related to the absorption of the P(+)y excitonic band of P. On the basis of experimental results, it was concluded that the bleaching of the P(+)y absorption band at 810 nm in the oxidized reaction center preparations gives the main contribution to the blue shift of the 800 nm absorption band of Rb. sphaeroides reaction centers.

  9. Laboratory evidence for highly unsaturated hydrocarbons as carriers of some of the diffuse interstellar bands

    NASA Astrophysics Data System (ADS)

    Fulara, J.; Lessen, D.; Freivogel, P.; Maier, J. P.

    1993-12-01

    THERE are many absorption lines in the visible and near-infrared spectra of stars located on the far side of diffuse interstellar clouds. The origin of these 'diffuse interstellar bands' (DIBs) has remained an unanswered question since their discovery almost 70 years ago1,2. There are now over 100 known bands1,3-6 and it is clear from the range of line widths, depths and shapes that the lines are unlikely to come from a single 'carrier'. Many of the proposed carriers, such as gas-phase carbon chains7, fullerenes8 and dust grains9, fail in having ultraviolet absorption lines where none has yet been observed in the stellar spectra. Poly cyclic aromatic species such as Ci16H10+ (ref. 10) and C10H8 (ref. 11) were recently claimed to be good candidates for carriers of some of the DIBs. Here we present laboratory evidence that highly unsaturated hydrocarbons with carbon numbers 6-12 may be the carriers of some of the DIBs in the range 480-1,000 nm. We deposit mass-selected molecules in a neon matrix at 5 K and measure their near-infrared, visible and ultraviolet spectra. Not only do these species have visible and near-infrared lines corresponding to fifteen DIBs, but they also show no absorption lines in the ultraviolet, consistent with astronomical observations.

  10. Dual band metamaterial perfect absorber based on Mie resonances

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    We numerically and experimentally demonstrated a polarization insensitive dual-band metamaterial perfect absorber working in wide incident angles based on the two magnetic Mie resonances of a single dielectric "atom" with simple structure. Two absorption bands with simulated absorptivity of 99% and 96%, experimental absorptivity of 97% and 94% at 8.45 and 11.97 GHz were achieved due to the simultaneous magnetic and electric resonances in dielectric "atom" and copper plate. Mie resonances of dielectric "atom" provide a simple way to design metamaterial perfect absorbers with high symmetry.

  11. High Pressure Noble Gas Alkali Vapor Mixtures and Their Visible and Infrared Excimer Bands.

    DTIC Science & Technology

    1980-02-01

    Dense Alkali Vapors; Near Infrared Lasers; Infrared Absorption and Emission 20. ABSTRACT (Conrfinte on reverse -Ide If nece oeery ed Identify hr block...n,mber) " The infrared absorption of saturated alkali vapors has been measured for the first time. New absorption bands are tentatively assigned to...region of infrared absorption between lu and 2 i in the saturated vapors of sodium, potassium, rubidium and cesium. This new region of absorption appears

  12. Vibrational resonance enhanced broadband multiphoton absorption in a triphenylamine derivative

    SciTech Connect

    Lu Changgui; Cui Yiping; Huang Wei; Yun Binfeng; Wang Zhuyuan; Hu Guohua; Cui Jing; Lu Zhifeng; Qian Ying

    2007-09-17

    Multiphoton absorption of 2,5-bis[4-(2-N,N-diphenylaminostyryl)phenyl]-1,3,4-oxadiazole was experimentally studied by using femtosecond laser pulses. This material demonstrates a very broad multiphoton absorption band of around 300 nm width with two peaks of 1250 and 1475 nm. The first peak results from the three-photon absorption process while the second is attributed to the vibrational resonance enhanced four-photon absorption process. Combination of these two processes provides a much broader multiphoton absorption band. In this letter, the analytical solution to nonlinear transmission of a three-photon absorption process is also given when the incident beam has a Gaussian transverse spatial profile.

  13. Natural dyes adsorbed on TiO2 nanowire for photovoltaic applications: enhanced light absorption and ultrafast electron injection.

    PubMed

    Meng, Sheng; Ren, Jun; Kaxiras, Efthimios

    2008-10-01

    We investigate the electronic coupling between a TiO2 nanowire and a natural dye sensitizer, using state-of-the-art time-dependent first-principles calculations. The model dye molecule, cyanidin, is deprotonated into the quinonoidal form upon adsorption on the wire surface. This results in its highest occupied molecular orbital (HOMO) being located in the middle of the TiO2 bandgap and its lowest unoccupied molecular orbital (LUMO) being close to the TiO2 conduction band minimum (CBM), leading to greatly enhanced visible light absorption with two prominent peaks at 480 and 650 nm. We find that excited electrons are injected into the TiO2 conduction band within a time scale of 50 fs with negligible electron-hole recombination and energy dissipation, even though the dye LUMO is located 0.1-0.3 eV lower than the CBM of the TiO2 nanowire.

  14. 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

  15. Adjustable gastric banding (image)

    MedlinePlus

    ... normal digestive process. In this procedure, a hollow band made of special material is placed around the ... pouch and causes a feeling of fullness. The band can be tightened or loosened over time to ...

  16. Separation of cirrus cloud from clear surface from AVIRIS data using the 1.38 micron water vapor band

    NASA Technical Reports Server (NTRS)

    Gao, Bo-Cai; Goetz, Alexander F. H.

    1992-01-01

    Cirrus clouds play an important role in climate systems because of their large area coverage, persistence, and radiative effects. Thin cirrus clouds are difficult to detect in visible images and infrared images in the 10-12 micron atmospheric window region, particularly over land, because these clouds are partially transparent. Ackerman recently developed a method for detecting cirrus clouds using three narrow channels centered near 8, 11, and 12 microns, respectively, based on the analysis of IR emission spectra measured with a high spectral resolution interferometer. Barton also described a method for estimating cirrus cloud height and amount from measurements with two narrow channel radiometers of the Selective Chopper Radiometer on Nimbus 5. Both channels are located within the strong 2.7 micron water vapor band absorption region. One of the channels includes additional carbon dioxide absorption. A differential absorption technique with sets of empirical coefficients was used in the estimation of cirrus cloud heights and amounts. A technique using narrow channels in the strong 1.38 micron water vapor band absorption region for detecting cirrus clouds from spectral imaging data acquired by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) on 5 Dec. 1991 during the FIRE (The First International Satellite Cloud Climatology Project (ISCCP) Regional Experiment) Phase 2 Field Experiment is described.

  17. M-BAND IMAGING OF THE HR 8799 PLANETARY SYSTEM USING AN INNOVATIVE LOCI-BASED BACKGROUND SUBTRACTION TECHNIQUE

    SciTech Connect

    Galicher, Raphael; Marois, Christian; Macintosh, Bruce; Konopacky, Quinn; Barman, Travis

    2011-10-01

    Multi-wavelength observations/spectroscopy of exoplanetary atmospheres are the basis of the emerging exciting field of comparative exoplanetology. The HR 8799 planetary system is an ideal laboratory to study our current knowledge gap between massive field brown dwarfs and the cold 5 Gyr old solar system planets. The HR 8799 planets have so far been imaged at J- to L-band, with only upper limits available at M-band. We present here deep high-contrast Keck II adaptive optics M-band observations that show the imaging detection of three of the four currently known HR 8799 planets. Such detections were made possible due to the development of an innovative LOCI-based background subtraction scheme that is three times more efficient than a classical median background subtraction for Keck II AO data, representing a gain in telescope time of up to a factor of nine. These M-band detections extend the broadband photometric coverage out to {approx}5 {mu}m and provide access to the strong CO fundamental absorption band at 4.5 {mu}m. The new M-band photometry shows that the HR 8799 planets are located near the L/T-type dwarf transition, similar to what was found by other studies. We also confirm that the best atmospheric fits are consistent with low surface gravity, dusty, and non-equilibrium CO/CH{sub 4} chemistry models.

  18. M-band imaging of the HR 8799 planetary system using an innovative LOCI-based background subtraction technique

    DOE PAGES

    Galicher, Raphael; Marois, Christian; Macintosh, Bruce; ...

    2011-09-02

    Multi-wavelength observations/spectroscopy of exoplanetary atmospheres are the basis of the emerging exciting field of comparative exoplanetology. The HR 8799 planetary system is an ideal laboratory to study our current knowledge gap between massive field brown dwarfs and the cold 5 Gyr old solar system planets. The HR 8799 planets have so far been imaged at J- to L-band, with only upper limits available at M-band. We present here deep high-contrast Keck II adaptive optics M-band observations that show the imaging detection of three of the four currently known HR 8799 planets. Such detections were made possible due to the developmentmore » of an innovative LOCI-based background subtraction scheme that is three times more efficient than a classical median background subtraction for Keck II AO data, representing a gain in telescope time of up to a factor of nine. These M-band detections extend the broadband photometric coverage out to ~5 μm and provide access to the strong CO fundamental absorption band at 4.5 μm. The new M-band photometry shows that the HR 8799 planets are located near the L/T-type dwarf transition, similar to what was found by other studies. Finally, we also confirm that the best atmospheric fits are consistent with low surface gravity, dusty, and non-equilibrium CO/CH4 chemistry models.« less

  19. New Laboratory Data on a Molecular Band at 4429 Å

    NASA Astrophysics Data System (ADS)

    Araki, M.; Linnartz, H.; Kolek, P.; Ding, H.; Boguslavskiy, A.; Denisov, A.; Schmidt, T. W.; Motylewski, T.; Cias, P.; Maier, J. P.

    2004-12-01

    New laboratory data are presented for the previously reported molecular absorption band at 4429 Å observed in a benzene plasma matching the strongest diffuse interstellar band (DIB) at 4428.9 Å. Gas-phase absorption spectra are presented for rotational temperatures of ~15 and 200 K. The observations indicate that it is unlikely that the laboratory band and the 4429 Å DIB are related. Eleven isomers of C5H5(+) and C6H5(+), both neutral and cationic, were considered as possible carriers of the laboratory band in view of the observed rotational profiles and deuterium isotope shifts. The experimental data and theoretical calculations (CASPT3, MRCI) indicate that the HCCHCHCHCH radical, a planar but nonlinear chain with one hydrogen on each carbon, is the most probable candidate causing the 4429 Å laboratory absorption.

  20. Band filling effects on temperature performance of intermediate band quantum wire solar cells

    SciTech Connect

    Kunets, Vas. P. Furrow, C. S.; Ware, M. E.; Souza, L. D. de; Benamara, M.; Salamo, G. J.; Mortazavi, M.

    2014-08-28

    Detailed studies of solar cell efficiency as a function of temperature were performed for quantum wire intermediate band solar cells grown on the (311)A plane. A remotely doped one-dimensional intermediate band made of self-assembled In{sub 0.4}Ga{sub 0.6}As quantum wires was compared to an undoped intermediate band and a reference p-i-n GaAs sample. These studies indicate that the efficiencies of these solar cells depend on the population of the one-dimensional band by equilibrium free carriers. A change in this population by free electrons under various temperatures affects absorption and carrier transport of non-equilibrium carriers generated by incident light. This results in different efficiencies for both the doped and undoped intermediate band solar cells in comparison with the reference GaAs p-i-n solar cell device.

  1. Feature Identification and Location Experiment

    NASA Technical Reports Server (NTRS)

    Sivertson, W. E., Jr.; Wilson, R. G.; Bullock, G. F.; Schappell, R. T.

    1982-01-01

    The Feature Identification and Location Experiment (FILE), which was flown on the second Space Shuttle flight to test a technique for real-time, autonomous classification of water, vegetation and bare land as well as clouds, snow and ice, senses earth radiation in spectral bands centered at 0.65 and 0.85 microns. The radiance ratio classification algorithm has successfully made automatic data selection decisions. A classification image obtained on the mission is providing data needed to evaluate the FILE algorithm and overall system performance.

  2. Low Power Band to Band Tunnel Transistors

    DTIC Science & Technology

    2010-12-15

    the E-field and tunneling at the source- pocket junction you form a parasitic NPN + transistor and the injection mechanism of carriers into the...hypothesis that the 1000 ° C, 5s anneal split lead to a very wide pocket and the accidental formation of a NPN + transistor , while the 1000 ° C, 1s anneal...Low Power Band to Band Tunnel Transistors Anupama Bowonder Electrical Engineering and Computer Sciences University of California at Berkeley

  3. Band of Rubble

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This artist's animation illustrates a massive asteroid belt in orbit around a star the same age and size as our Sun. Evidence for this possible belt was discovered by NASA's Spitzer Space Telescope when it spotted warm dust around the star, presumably from asteroids smashing together.

    The view starts from outside the belt, where planets like the one shown here might possibly reside, then moves into to the dusty belt itself. A collision between two asteroids is depicted near the end of the movie. Collisions like this replenish the dust in the asteroid belt, making it detectable to Spitzer.

    The alien belt circles a faint, nearby star called HD 69830 located 41 light-years away in the constellation Puppis. Compared to our own solar system's asteroid belt, this one is larger and closer to its star - it is 25 times as massive, and lies just inside an orbit equivalent to that of Venus. Our asteroid belt circles between the orbits of Mars and Jupiter.

    Because Jupiter acts as an outer wall to our asteroid belt, shepherding its debris into a series of bands, it is possible that an unseen planet is likewise marshalling this belt's rubble. Previous observations using the radial velocity technique did not locate any large gas giant planets, indicating that any planets present in this system would have to be the size of Saturn or smaller.

    Asteroids are chunks of rock from 'failed' planets, which never managed to coalesce into full-sized planets. Asteroid belts can be thought of as construction sites that accompany the building of rocky planets.

  4. Synopsis of Mid-latitude Radio Wave Absorption in Europe

    NASA Technical Reports Server (NTRS)

    Torkar, K. M.; Friedrich, M.

    1984-01-01

    Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts.

  5. The formation of multiple adiabatic shear bands

    NASA Astrophysics Data System (ADS)

    Zhou, F.; Wright, T. W.; Ramesh, K. T.

    2006-07-01

    In a previous paper, Zhou et al. [2006. A numerical methodology for investigating adiabatic shear band formation. J. Mech. Phys. Solids, 54, 904-926] developed a numerical method for analyzing one-dimensional deformation of thermoviscoplastic materials. The method uses a second order algorithm for integration along characteristic lines, and computes the plastic flow after complete localization with high resolution and efficiency. We apply this numerical scheme to analyze localization in a thermoviscoplastic material where multiple shear bands are allowed to form at random locations in a large specimen. As a shear band develops, it unloads neighboring regions and interacts with other bands. Beginning with a random distribution of imperfections, which might be imagined as arising qualitatively from the microstructure, we obtain the average spacing of shear bands through calculations and compare our results with previously existing theoretical estimates. It is found that the spacing between nucleating shear bands follows the perturbation theory due to Wright and Ockendon [1996. A scaling law for the effect of inertia on the formation of adiabatic shear bands. Int. J. Plasticity 12, 927-934], whereas the spacing between mature shear bands is closer to that predicted by the momentum diffusion theory of Grady and Kipp [1987. The growth of unstable thermoplastic shear with application to steady-wave shock compression in solids. J. Mech. Phys. Solids 35, 95-119]. Scaling laws for the dependence of band spacing on material parameters differ in many respects from either theory.

  6. Absorption in Extended Inhomogeneous Clouds

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  7. Dual band metamaterial perfect absorber based on artificial dielectric “molecules”

    PubMed Central

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

    2016-01-01

    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. PMID:27406699

  8. Absorption of light dark matter in semiconductors

    NASA Astrophysics Data System (ADS)

    Hochberg, Yonit; Lin, Tongyan; Zurek, Kathryn M.

    2017-01-01

    Semiconductors are by now well-established targets for direct detection of MeV to GeV dark matter via scattering off electrons. We show that semiconductor targets can also detect significantly lighter dark matter via an absorption process. When the dark matter mass is above the band gap of the semiconductor (around an eV), absorption proceeds by excitation of an electron into the conduction band. Below the band gap, multiphonon excitations enable absorption of dark matter in the 0.01 eV to eV mass range. Energetic dark matter particles emitted from the sun can also be probed for masses below an eV. We derive the reach for absorption of a relic kinetically mixed dark photon or pseudoscalar in germanium and silicon, and show that existing direct detection results already probe new parameter space. With only a moderate exposure, low-threshold semiconductor target experiments can exceed current astrophysical and terrestrial constraints on sub-keV bosonic dark matter.

  9. K-band Polarimetry of NGC 891

    NASA Astrophysics Data System (ADS)

    Montgomery, Jordan; Clemens, Dan P.

    2014-06-01

    We present the first K-band (2.2 um) polarimetry observations of the edge-on galaxy NGC 891. Near-infrared (NIR) polarimetry reveals the plane-of-sky projected magnetic (B) field orientations in dusty, star-forming interstellar media. Previous optical wavelength polarimetry of NGC 891 found predominantly disk-perpendicular polarizations (Scarrott & Draper 1996) while H-band polarimetry revealed mostly disk-parallel polarizations with an interesting 15 degree offset from the major axis position angle (Jones 1997; Montgomery & Clemens 2014). In H-band, Montgomery & Clemens also detected the first NIR polarization null-point, located about 5 kpc northeast of NGC891's center. It may be related to the polarization null-points predicted by Wood (1997) and modeled by Wood & Jones (1997). At the longer K-band wavelength, these new observations better reveal B-field orientation changes in the disk. The Wood (1997) radiative transfer polarization model predicted null-point location changes with wavelengeth. We will use the new K-band polarimetry, along with our H-band polarimetry, to test this prediction. If the null-point location does not depend on wavelength, then the null-point may instead be due to spiral arm aligned B-fields (e.g., Fletcher et al. 2011).This research was supported through NSF grant AST 09-07790.

  10. Production of photocurrent due to intermediate-to-conduction-band transitions: a demonstration of a key operating principle of the intermediate-band solar cell.

    PubMed

    Martí, A; Antolín, E; Stanley, C R; Farmer, C D; López, N; Díaz, P; Cánovas, E; Linares, P G; Luque, A

    2006-12-15

    We present intermediate-band solar cells manufactured using quantum dot technology that show for the first time the production of photocurrent when two sub-band-gap energy photons are absorbed simultaneously. One photon produces an optical transition from the intermediate-band to the conduction band while the second pumps an electron from the valence band to the intermediate-band. The detection of this two-photon absorption process is essential to verify the principles of operation of the intermediate-band solar cell. The phenomenon is the cornerstone physical principle that ultimately allows the production of photocurrent in a solar cell by below band gap photon absorption, without degradation of its output voltage.

  11. Locative Inversion in Cantonese.

    ERIC Educational Resources Information Center

    Mok, Sui-Sang

    This study investigates the phenomenon of "Locative Inversion" in Cantonese. The term "Locative Inversion" indicates that the locative phrase (LP) syntactic process in Cantonese and the appears at the sentence-initial position and its logical subject occurs postverbally. It is demonstrated that this Locative Inversion is a…

  12. Location, Location, Location: Development of Spatiotemporal Sequence Learning in Infancy

    ERIC Educational Resources Information Center

    Kirkham, Natasha Z.; Slemmer, Jonathan A.; Richardson, Daniel C.; Johnson, Scott P.

    2007-01-01

    We investigated infants' sensitivity to spatiotemporal structure. In Experiment 1, circles appeared in a statistically defined spatial pattern. At test 11-month-olds, but not 8-month-olds, looked longer at a novel spatial sequence. Experiment 2 presented different color/shape stimuli, but only the location sequence was violated during test;…

  13. Theory of plasmonic quantum-dot-based intermediate band solar cells.

    PubMed

    Foroutan, Sina; Baghban, Hamed

    2016-05-01

    High scattering cross section of plasmonic nanoparticles in intermediate band solar cells (IBSCs) based on quantum dots (QDs) can obviate the low photon absorption in QD layers. In this report, we present a modeling procedure to extract the optical and electrical characteristics of a GaAs-based plasmonic intermediate band solar cell (PIBSC). It is shown that metal nanoparticles (MNPs) that are responsible for scattering of incident photons in the absorber layer can lead to photocurrent enhancement, provided that an optimum size and density is calculated. Proper design of QD layers that control the intermediate energy band location, as well as the loss-scattering trade-off of MNPs, can result in an efficiency increase of ∼4.2% in the PIBSC compared to a similar IBSC, and an increase of ∼5.9% compared to a reference GaAs PIN cell. A comprehensive discussion on the effect of intermediate band region width and current-voltage characteristics of the designed cell is presented.

  14. High resolution investigation of the v3 band of trifluoromethyliodide (CF3I)

    NASA Astrophysics Data System (ADS)

    Willaert, F.; Roy, P.; Manceron, L.; Perrin, A.; Kwabia-Tchana, F.; Appadoo, D.; McNaughton, D.; Medcraft, C.; Demaison, J.

    2015-09-01

    The high-resolution absorption spectrum of trifluoromethyliodide (CF3I), an alternative gas to chlorofluorocarbons but with potential greenhouse effects, has been recorded at 0.001 cm-1 resolution in the 200-350 cm-1 region with the Bruker IFS125HR Fourier transform spectrometer at synchrotron SOLEIL. Due to the spectral congestion and the presence of numerous hot bands, the spectra have been recorded at the AILES Beamline facility at SOLEIL either at room temperature using a 150 m optical path length cell or at 163 K using the new LISA-SOLEIL cryogenic cell and at the Australian synchrotron using a flow cooling cell. This enables a detailed analysis of the v3 band at 286.29712(3) cm-1 of CF3I. The results of previous microwave measurements in the v3 = 1 and v6 = 1 vibrational states (Walters and Whiffen, 1983; Wahi, 1987) were combined with those of the present infrared analysis of the v3 band to obtain an improved set of parameters for the v3 = 1 (C-I stretching) and v6 = 1 (I-C-F bending) interacting vibrational states accounting for the Coriolis resonance coupling the v3 = 1 energy levels with those of the dark v6 = 1 state (located at ∼261.5 or at ∼267.6 cm-1). Finally, a first investigation of the 2v3 - v3 hot band is also performed.

  15. Methane overtone absorption by intracavity laser spectroscopy

    NASA Technical Reports Server (NTRS)

    Obrien, James J.

    1990-01-01

    Interpretation of planetary methane (CH4) visible-near IR spectra, used to develop models of planetary atmospheres, has been hampered by a lack of suitable laboratory spectroscopic data. The particular CH4 spectral bands are due to intrinsically weak, high overtone-combination transitions too complex for classical spectroscopic analysis. The traditional multipass cell approach to measuring spectra of weakly absorbing species is insufficiently sensitive to yield reliable results for some of the weakest CH4 absorption features and is difficult to apply at the temperatures of the planetary environments. A time modulated form of intracavity laser spectroscopy (ILS), has been shown to provide effective absorption pathlengths of 100 to 200 km with sample cells less than 1 m long. The optical physics governing this technique and the experimental parameters important for obtaining reliable, quantitative results are now well understood. Quantitative data for CH4 absorption obtained by ILS have been reported recently. Illustrative ILS data for CH4 absorption in the 619.7 nm and 681.9 nm bands are presented. New ILS facilities at UM-St. Louis will be used to measure CH4 absorption in the 700 to 1000 nm region under conditions appropriate to the planetary atmospheres.

  16. 47 CFR 95.1203 - Authorized locations.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... SERVICES Medical Device Radiocommunication Service (MedRadio) § 95.1203 Authorized locations. Link to an... authorized under § 95.405, except that use of Medical Body Area Network devices in the 2360-2390 MHz band is..., facilities and beds for use beyond a 24 hour period in rendering medical treatment, and institutions...

  17. Subbarrier absorption in a stationary superlattice

    NASA Technical Reports Server (NTRS)

    Arutyunyan, G. M.; Nerkararyan, K. V.

    1984-01-01

    The calculation of the interband absorption coefficient was carried out in the classical case, when the frequency of light was assumed to bind two miniband subbarrier states of different bands. The influence of two dimensional Mott excitons on this absorption was studied and a comparison was made with the experiment. All of these considerations were done taking into account the photon wave vector (the phase spatial heterogeneity). The basic traits of the energy spectra of superlattice semiconductors, their kinetic and optical properties, and possible means of electromagnetic wave intensification were examined. By the density matrix method, a theory of electrical and electromagnetic properties of superlattices was suggested.

  18. The Korean Solar Radio Burst Locator (KSRBL)

    NASA Astrophysics Data System (ADS)

    Dou, Yujiang; Gary, Dale E.; Liu, Zhiwei; Nita, Gelu M.; Bong, Su-Chan; Cho, Kyung-Suk; Park, Young-Deuk; Moon, Yong-Jae

    2009-05-01

    This paper describes the design and operation of the Korean Solar Radio Burst Locator (KSRBL). The KSRBL is a radio spectrometer designed to observe solar decimeter and microwave bursts over a wide band (0.245–18 GHz) as well as to detect the burst locations without interferometry or mechanical sweeping. As a prototype, it is temporarily observing at the Owens Valley Radio Observatory (OVRO), California, USA, and after commissioning will be operated at the Korea Astronomy and Space Science Institute (KASI), Daejeon, Republic of Korea. The control system can agilely choose four 500 MHz intermediate frequency (IF) bands (2 GHz instantaneous bandwidth) from the entire 0.245–18 GHz band, with a standard time resolution of 100 ms, although higher time resolution is possible subject to data-rate constraints. To cover the entire band requires 10 tunings, which are therefore completed in 1 s. Each 500 MHz band is sampled at a 1 GS s-1 (gigasample per second) rate, and 4096 time samples are Fast Fourier transformed (FFT) to 2048 subchannels for a frequency resolution of 0.24 MHz. To cover the entire range also requires two different feeds, a dual-frequency Yagi centered at 245 and 410 MHz, and a broadband spiral feed covering 0.5–18 GHz. The dynamic range is 35 dB over the 0.5–18 GHz band, and 55 dB in the 245 and 410 MHz bands, set by using switchable attenuators in steps of 5 dB. Each 500 MHz IF has a further 63 dB of settable analog attenuation. The characteristics of the spiral feed provide the ability to locate flaring sources on the Sun to typically 2‧. The KSRBL will provide a broadband view of solar bursts for the purposes of studying solar activity for basic research, and for monitoring solar activity as the source of Space Weather and solar-terrestrial effects.

  19. Sleeping at work: not all about location, location, location.

    PubMed

    Jay, Sarah M; Aisbett, Brad; Sprajcer, Madeline; Ferguson, Sally A

    2015-02-01

    Working arrangements in industries that use non-standard hours sometimes necessitate an 'onsite' workforce where workers sleep in accommodation within or adjacent to the workplace. Of particular relevance to these workers is the widely held (and largely anecdotal) assumption that sleep at home is better than sleep away, particularly when away for work. This narrative review explores the idea that sleep outcomes in these unique work situations are the product of an interaction between numerous factors including timing and duration of breaks, commute length, sleeping environment (noise, movement, vibration, light), circadian phase, demographic factors and familiarity with the sleep location. Based on the data presented in this review, it is our contention that the location of sleep, whilst important, is secondary to other factors such as the timing and duration of sleep periods. We suggest that future research should include measures that allow conceptualisation of other critical factors such as familiarity with the sleeping environment.

  20. A parameterization for the absorption of solar radiation by water vapor in the earth's atmosphere

    NASA Technical Reports Server (NTRS)

    Wang, W.-C.

    1976-01-01

    A parameterization for the absorption of solar radiation as a function of the amount of water vapor in the earth's atmosphere is obtained. Absorption computations are based on the Goody band model and the near-infrared absorption band data of Ludwig et al. A two-parameter Curtis-Godson approximation is used to treat the inhomogeneous atmosphere. Heating rates based on a frequently used one-parameter pressure-scaling approximation are also discussed and compared with the present parameterization.

  1. Wide Band to ''Double Band'' upgrade

    SciTech Connect

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

    1988-06-01

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

  2. 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.

  3. Intracavity Dye-Laser Absorption Spectroscopy (IDLAS) for application to planetary molecules

    NASA Technical Reports Server (NTRS)

    Lang, Todd M.; Allen, John E., Jr.

    1990-01-01

    Time-resolved, quasi-continuous wave, intracavity dye-laser absorption spectroscopy is applied to the investigation of absolute absorption coefficients for vibrational-rotational overtone bands of water at visible wavelengths. Emphasis is placed on critical factors affecting detection sensitivity and data analysis. Typical generation-time dependent absorption spectra are given.

  4. An ASAP treatment of vibrationally excited S2O: The ν3 mode and the ν3 + ν2 - ν2 hot band

    NASA Astrophysics Data System (ADS)

    Thorwirth, S.; Martin-Drumel, M. A.; Endres, C. P.; Salomon, T.; Zingsheim, O.; van Wijngaarden, J.; Pirali, O.; Gruet, S.; Lewen, F.; Schlemmer, S.; McCarthy, M. C.

    2016-01-01

    The fundamental S-S stretching mode ν3 of disulfur monoxide, S2O, located at 679 cm-1, has been investigated using Fourier-transform far-infrared spectroscopy at the SOLEIL synchrotron facility. A spectroscopic analysis has been performed using an Automated Spectral Assignment Procedure (ASAP) which permits accurate determination of more than 2000 energy levels from ν3. In addition, the ν3 + ν2 - ν2 hot band was observed for the first time and some 500 corresponding energy levels were assigned. The high-resolution synchrotron study was complemented with pure rotational spectra of S2O in the (v1, v2, v3) = (0, 0, 1) vibrational state observed in the frequency range from 250 to 280 GHz using a long-path absorption cell. From these combined measurements, extensive molecular parameter sets have been determined and precise band centers have been derived for both vibrational bands.

  5. Perfect electromagnetic absorption at one-atom-thick scale

    SciTech Connect

    Li, Sucheng; Duan, Qian; Li, Shuo; Yin, Qiang; Lu, Weixin; Li, Liang; Hou, Bo; Gu, Bangming; Wen, Weijia

    2015-11-02

    We experimentally demonstrate that perfect electromagnetic absorption can be realized in the one-atom thick graphene. Employing coherent illumination in the waveguide system, the absorbance of the unpatterned graphene monolayer is observed to be greater than 94% over the microwave X-band, 7–13 GHz, and to achieve a full absorption, >99% in experiment, at ∼8.3 GHz. In addition, the absorption characteristic manifests equivalently a wide range of incident angle. The experimental results agree very well with the theoretical calculations. Our work accomplishes the broadband, wide-angle, high-performance absorption in the thinnest material with simple configuration.

  6. Sapphire fiber evanescent wave absorption in turbid media.

    PubMed

    Zhang, Jian; Xiong, Feibing; Djeu, Nicholas

    2009-08-01

    The influence of particulates on sapphire fiber evanescent wave absorption by water has been studied. Suspensions containing micro-sized graphite flakes and glassy carbon powder were used. Conventional free-space transmittance measurements of these samples showed strong absorption and scattering, which severely screened the absorption by water. However, the absorption on the water band determined from the evanescent wave interaction was unaffected by the presence of the graphite flakes. These results indicate that fiber-optic evanescent wave chemical sensors may be suitable for process control applications involving turbid reactor streams.

  7. Investigation of TM Band-to-band Registration Using the JSC Registration Processor

    NASA Technical Reports Server (NTRS)

    Yao, S. S.; Amis, M. L.

    1984-01-01

    The JSC registration processor performs scene-to-scene (or band-to-band) correlation based on edge images. The edge images are derived from a percentage of the edge pixels calculated from the raw scene data, excluding clouds and other extraneous data in the scene. Correlations are performed on patches (blocks) of the edge images, and the correlation peak location in each patch is estimated iteratively to fractional pixel location accuracy. Peak offset locations from all patches over the scene are then considered together, and a variety of tests are made to weed out outliers and other inconsistencies before a distortion model is assumed. Thus, the correlation peak offset locations in each patch indicate quantitatively how well the two TM bands register to each other over that patch of scene data. The average of these offsets indicate the overall accuracies of the band-to-band registration. The registration processor was also used to register one acquisition to another acquisition of multitemporal TM data acquired over the same ground track. Band 4 images from both acquisitions were correlated and an rms error of a fraction of a pixel was routinely obtained.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  9. What band rocks the MTB? (Invited)

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    Magnetotactic bacteria (MTB) are a polyphyletic group of bacteria that have been found in marine and lacustrine environments and soils [e.g. 1]. The hallmark of MTB is their intracellular formation of magnetosomes, single-domain ferrimagnetic particles that are aligned in chains. The chain configuration generates a strong magnetic dipole, which is used as magnetic compass to move the MTB into their favorable habit. The term band corresponds to a frequency window of microwaves in the gigahertz (GHz) range. Ferromagnetic resonance (FMR) spectroscopy uses the microwave absorption in a magnetic field to analyze the anisotropy properties and the domain state of magnetic materials. Specific microwave frequency causes absorption in a characteristic magnetic field range. For the investigation of MTB we use S-band (4.02 GHz), X-band (9.47 GHz), and Q-band (34.16 GHz). Experiments on cultured MTB and on sediment samples of Holocene age showed that absorption in X- and Q-band occurs when the sample is in a saturated or nearly saturated state [2, 3]. By contrast, absorption in the S-band appears in lower magnetic fields, where the sample is far from saturation. All FMR spectra show two distinct low-field features that can be assigned to magnetite particles in chains, aligned parallel and perpendicular to the external magnetic field. The detailed separation of the parallel and perpendicular components in the bulk samples is hampered, because of the random orientation of the chains in the sample. The comparison of S-, X-, and Q-band shows that the lower the frequency the better the separation of the components. In the S-band FMR spectroscopy, the separation of chains parallel to the external magnetic field is supported by the internal field of the sample. This field is caused by the remanence that contributes to the external magnetic field to fulfill the resonance condition [3,4]. Considering the different FMR responses, it can be postulated that a lower microwave frequency

  10. iLocater: a diffraction-limited Doppler spectrometer for the Large Binocular Telescope

    NASA Astrophysics Data System (ADS)

    Crepp, Justin R.; Crass, Jonathan; King, David; Bechter, Andrew; Bechter, Eric; Ketterer, Ryan; Reynolds, Robert; Hinz, Philip; Kopon, Derek; Cavalieri, David; Fantano, Louis; Koca, Corina; Onuma, Eleanya; Stapelfeldt, Karl; Thomes, Joseph; Wall, Sheila; Macenka, Steven; McGuire, James; Korniski, Ronald; Zugby, Leonard; Eisner, Joshua; Gaudi, B. S.; Hearty, Fred; Kratter, Kaitlin; Kuchner, Marc; Micela, Giusi; Nelson, Matthew; Pagano, Isabella; Quirrenbach, Andreas; Schwab, Christian; Skrutskie, Michael; Sozzetti, Alessandro; Woodward, Charles; Zhao, Bo

    2016-08-01

    We are developing a stable and precise spectrograph for the Large Binocular Telescope (LBT) named "iLocater." The instrument comprises three principal components: a cross-dispersed echelle spectrograph that operates in the YJ-bands (0.97-1.30 μm), a fiber-injection acquisition camera system, and a wavelength calibration unit. iLocater will deliver high spectral resolution (R 150,000-240,000) measurements that permit novel studies of stellar and substellar objects in the solar neighborhood including extrasolar planets. Unlike previous planet-finding instruments, which are seeing-limited, iLocater operates at the diffraction limit and uses single mode fibers to eliminate the effects of modal noise entirely. By receiving starlight from two 8.4m diameter telescopes that each use "extreme" adaptive optics (AO), iLocater shows promise to overcome the limitations that prevent existing instruments from generating sub-meter-per-second radial velocity (RV) precision. Although optimized for the characterization of low-mass planets using the Doppler technique, iLocater will also advance areas of research that involve crowded fields, line-blanketing, and weak absorption lines.

  11. A new near-infrared absorption and fluorescent probe based on bombesin for molecular imaging

    NASA Astrophysics Data System (ADS)

    Kujala, Naresh; Zhai, Huifang; Smith, Charles; Prasanphanich, Adam; Sieckman, Gary; Hoffman, Timothy; Volkert, Wynn; Ma, Lixin; Yu, Ping

    2009-02-01

    We have developed a series of new dye bombesin conjugates for site-specific absorption and fluorescence imaging of human prostate and breast cancers. Bombesin (BBN), an amphibian analog to the endogenous ligand, binds to the gastrin releasing peptide (GRP) receptors with high specificity and affinity. Previously, we developed an Alexa Fluor 680-GGG-BBN peptide conjugate which demonstrated high binding affinity and specificity for breast cancer cells in the in vitro and in vivo tests (Ref: Ma et al., Molecular Imaging, vol. 6, no. 3, 2007: 171-180). This probe can not be used as an absorption probe in near-infrared imaging because its absorption peak is in the visible wavelength range. In addition, site specific longer wavelength fluorescent probe is desired for in vivo molecular imaging because long wavelength photons penetrate deeper into tissue. The new absorption and fluorescent probe we developed is based on the last eight-residues of BBN, -Q-W-A-V-G-H-L-M-(NH2), and labeled with AlexaFluor750 through a chemical linker, beta-alanine. The new probe, Alexa Fluor 750-BetaAla-BBN(7-14)NH2, exhibits optimal pharmacokinetics for specific targeting and optical imaging of the GRP receptor over-expressing cancer cells. Absorption spectrum has been measured and showed absorption peaks at 690nm, 720nm and 735nm. Fluorescent band is located at 755nm. In vitro and in vivo investigations have demonstrated the effectiveness of the new conjugates to specifically target human cancer cells overexpressing GRP receptors and tumor xenografts in severely compromised immunodeficient mouse model.

  12. Detection of cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars

    NASA Astrophysics Data System (ADS)

    Fuhrmann, Lars; Larsson, S.; Chiang, J.; Angelakis, E.; Zensus, A.; F-GAMMA Team; Fermi Collaboration

    2014-01-01

    The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we performed a detailed statistical cross-correlation analysis between radio (cm/mm/sub-mm wavelengths, F-GAMMA program) and gamma-ray 3.5 year light curves of 54 Fermi bright blazars. In this talk, the main results of this analysis are highlighted including the first significant detection of multi-band radio/gamma-ray correlations using a stacking analysis. The radio bands are usually lagging the gamma rays with average time delays (source frame) ranging between 76+/-23 and 7+/-9 days, systematically decreasing from cm to mm/sub-mm bands following a power-law frequency dependence. The latter is in good agreement with synchrotron self-absorption dominated opacity effects, whereas a (positive) time lag of 12+/-8 days at 3 mm strongly suggests that the bulk gamma-ray production region is usually located within or even upstream of the innermost mm core region of these sources. Based on our findings we finally demonstrate that the gamma-ray emitting region of quasar 3C 454.3 is located at a distance of > 0.8-1.6 pc from the central supermassive black hole, i.e. at the outer edge of the Broad Line Region or beyond.

  13. Location, Location, Location: Where Do Location-Based Services Fit into Your Institution's Social Media Mix?

    ERIC Educational Resources Information Center

    Nekritz, Tim

    2011-01-01

    Foursquare is a location-based social networking service that allows users to share their location with friends. Some college administrators have been thinking about whether and how to take the leap into location-based services, which are also known as geosocial networking services. These platforms, which often incorporate gaming elements like…

  14. Locatives in Kpelle.

    ERIC Educational Resources Information Center

    Kuha, Mai

    This paper examines the differences between locative expressions in Kpelle and English, based on the dialect of one native speaker of Kpelle. It discusses the crucial role of the reference object in defining the meaning of locatives in Kpelle, in contrast to English, where the characteristics of the object to be located are less important. An…

  15. Singing with the Band

    ERIC Educational Resources Information Center

    Altman, Timothy Meyer; Wright, Gary K.

    2012-01-01

    Usually band, orchestra, and choir directors work independently. However, the authors--one a choral director, the other a band director--have learned that making music together makes friends. Not only can ensemble directors get along, but joint concerts may be just the way to help students see how music can reach the heart. Combined instrumental…

  16. Rubber Band Science

    ERIC Educational Resources Information Center

    Cowens, John

    2005-01-01

    Not only are rubber bands great for binding objects together, but they can be used in a simple science experiment that involves predicting, problem solving, measuring, graphing, and experimenting. In this article, the author describes how rubber bands can be used to teach the force of mass.

  17. Stretch Band Exercise Program

    ERIC Educational Resources Information Center

    Skirka, Nicholas; Hume, Donald

    2007-01-01

    This article discusses how to use stretch bands for improving total body fitness and quality of life. A stretch band exercise program offers a versatile and inexpensive option to motivate participants to exercise. The authors suggest practical exercises that can be used in physical education to improve or maintain muscular strength and endurance,…

  18. Progressive Band Selection

    NASA Technical Reports Server (NTRS)

    Fisher, Kevin; Chang, Chein-I

    2009-01-01

    Progressive band selection (PBS) reduces spectral redundancy without significant loss of information, thereby reducing hyperspectral image data volume and processing time. Used onboard a spacecraft, it can also reduce image downlink time. PBS prioritizes an image's spectral bands according to priority scores that measure their significance to a specific application. Then it uses one of three methods to select an appropriate number of the most useful bands. Key challenges for PBS include selecting an appropriate criterion to generate band priority scores, and determining how many bands should be retained in the reduced image. The image's Virtual Dimensionality (VD), once computed, is a reasonable estimate of the latter. We describe the major design details of PBS and test PBS in a land classification experiment.

  19. Impedance Matched Absorptive Thermal Blocking Filters

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  20. Impedance Matched Absorptive Thermal Blocking Filters

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

  1. Cirrus cloud detection from airborne imaging spectrometer data using the 1.38 micron water vapor band

    NASA Technical Reports Server (NTRS)

    Gao, Bo-Cai; Goetz, Alexander F. H.; Wiscombe, Warren J.

    1993-01-01

    Using special images acquired by the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) at 20 km altitude, we show that wavelengths close to the center of the strong 1.38 micron water vapor band are useful for detecting thin cirrus clouds. The detection makes use of the fact that cirrus clouds are located above almost all the atmospheric water vapor. Because of the strong water vapor absorption in the lower atmosphere, AVIRIS channels near 1.38 micron receive little scattered solar radiance from the surface of low level clouds. When cirrus clouds are present, however, these channels receive large amounts of scattered solar radiance from the cirrus clouds. Our ability to determine cirrus cloud cover using space-based remote sensing will be improved if channels near the center of the 1.38 micron water vapor band are added to future satellites.

  2. Electronic absorptions of the benzylium cation

    NASA Astrophysics Data System (ADS)

    Dryza, Viktoras; Chalyavi, Nahid; Sanelli, Julian A.; Bieske, Evan J.

    2012-11-01

    The electronic transitions of the benzylium cation (Bz+) are investigated over the 250-550 nm range by monitoring the photodissociation of mass-selected C7H7+-Arn (n = 1, 2) complexes in a tandem mass spectrometer. The Bz+-Ar spectrum displays two distinct band systems, the S1←S0 band system extending from 370 to 530 nm with an origin at 19 067 ± 15 cm-1, and a much stronger S3←S0 band system extending from 270 to 320 nm with an origin at 32 035 ± 15 cm-1. Whereas the S1←S0 absorption exhibits well resolved vibrational progressions, the S3←S0 absorption is broad and relatively structureless. Vibronic structure of the S1←S0 system, which is interpreted with the aid of time-dependent density functional theory and Franck-Condon simulations, reflects the activity of four totally symmetric ring deformation modes (ν5, ν6, ν9, ν13). We find no evidence for the ultraviolet absorption of the tropylium cation, which according to the neon matrix spectrum should occur over the 260 - 275 nm range [A. Nagy, J. Fulara, I. Garkusha, and J. Maier, Angew. Chem., Int. Ed. 50, 3022 (2011)], 10.1002/anie.201008036.

  3. Collisional Line-Shape and Line-Mixing Parameters for CO(2) Absorption near 3340 cm(-1): Measurements and Modeling

    NASA Astrophysics Data System (ADS)

    Buldyreva, Jeanna; Auwera, Jean Vander

    2014-06-01

    class="MsoNormal">The present work is focused on the determination of line-shape parameters for one of the 12C16O2 bands detectable by the SOIR (Solar Occultation in the InfraRed) instrument onboard the ESA Venus Express spacecraft, namely the 21102 - 00001 band located near 3340 cm-1. High-resolution Fourier transform spectra of this band have been recorded at sub-atmospheric pressures and analyzed to extract isolated-line intensities and collisional parameters as well as first-order line-mixing coefficients. Voigt, hard-collision Rautian and Sobel'man, and quadratic-speed-dependent Voigt profiles have been used. The retrieved parameters are compared with previous data available in the literature and with theoretical estimates obtained by an Energy-Corrected Sudden approach (generally, non-Markovian) employing a symmetric metric in the Liouville space. The same approach, supplied with additional hypotheses for basic transition rates for the hot bands, has also been used to model the complete band shapes. The need for accounting of line-narrowing effects at sub-atmospheric pressures has been evidenced from comparison with the recorded spectra, and some improvements have been introduced in the relaxation matrix model, leading to a good agreement of calculated and measured absorptions from nearly Doppler pressure regime to nearly atmospheric pressure.

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

    DOEpatents

    Wanlass, Mark W.

    1994-01-01

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

  5. Iliotibial band friction syndrome

    PubMed Central

    2010-01-01

    Published articles on iliotibial band friction syndrome have been reviewed. These articles cover the epidemiology, etiology, anatomy, pathology, prevention, and treatment of the condition. This article describes (1) the various etiological models that have been proposed to explain iliotibial band friction syndrome; (2) some of the imaging methods, research studies, and clinical experiences that support or call into question these various models; (3) commonly proposed treatment methods for iliotibial band friction syndrome; and (4) the rationale behind these methods and the clinical outcome studies that support their efficacy. PMID:21063495

  6. Enhanced light absorption of solar cells and photodetectors by diffraction

    DOEpatents

    Zaidi, Saleem H.; Gee, James M.

    2005-02-22

    Enhanced light absorption of solar cells and photodetectors by diffraction is described. Triangular, rectangular, and blazed subwavelength periodic structures are shown to improve performance of solar cells. Surface reflection can be tailored for either broadband, or narrow-band spectral absorption. Enhanced absorption is achieved by efficient optical coupling into obliquely propagating transmitted diffraction orders. Subwavelength one-dimensional structures are designed for polarization-dependent, wavelength-selective absorption in solar cells and photodetectors, while two-dimensional structures are designed for polarization-independent, wavelength-selective absorption therein. Suitable one and two-dimensional subwavelength periodic structures can also be designed for broadband spectral absorption in solar cells and photodetectors. If reactive ion etching (RIE) processes are used to form the grating, RIE-induced surface damage in subwavelength structures can be repaired by forming junctions using ion implantation methods. RIE-induced surface damage can also be removed by post RIE wet-chemical etching treatments.

  7. Terahertz absorption spectra of highly energetic chemicals

    NASA Astrophysics Data System (ADS)

    Slingerland, E. J.; Vallon, M. K.; Jahngen, E. G. E.; Giles, R. H.; Goyette, T. M.

    2010-04-01

    Research into absorption spectra is useful for detecting chemicals in the field. Each molecule absorbs a set of specific frequencies, which are dependent on the molecule's structure. While theoretical models are available for predicting the absorption frequencies of a particular molecule, experimental measurements are a more reliable method of determining a molecule's actual absorption behavior. The goal of this research is to explore chemical markers (absorption frequencies) that can be used to identify highly energetic molecules of interest to the remote sensing community. Particular attention was paid to the frequency ranges located within the terahertz transmission windows of the atmosphere. In addition, theoretical derivations, with the purpose of calculating the detection limits of such chemicals, will also be presented.

  8. Performance Analysis of Solution Transportation Absorption Chiller

    NASA Astrophysics Data System (ADS)

    Kiani, Behdad; Hamamoto, Yoshinori; Akisawa, Atsushi; Kashiwagi, Takao

    Thermally activated advanced absorption cycles are considered promising candidates to replace CFCs, HCFCs and HFCs for residential and commercial applications. In such absorption systems, it is desirable to utilize the waste heat from industries for heating and cooling applications in commercial and residential sectors. For this purpose, it is necessary to transport energy over some distance because the waste heat source and demand are generally located apart from each other. Transportation of steam, hot water or chilled water requires high construction costs for insulation. There is an efficient method of energy transportation using absorption system called “ Solution Transportation Absorption System (STA)”. The solution is transported at an ambient temperature so that tube-insulations not required. This paper shows the simulation of the abovementioned system and the optimal result, using mathematical optimization. The optimum system with industry‧s waste heat utilization is obtained. At the end, the effect on the pollution emission and energy conservation is obtained.

  9. High resolution absorption spectrum of dianilino in the vapor phase.

    PubMed

    Bayrakçeken, Fuat

    2009-01-01

    Photophysical and photochemical properties of diradical in the first excited state is recorded for the very first time with the IR, band structure for dianilino molecule at room temperature, in the vapor phase. In this experiment high resolution absorption spectra of anilino free radical, dianilino, aniline in the vapor phase and silicon dioxide in the solid state were recorded by flash photolysis technique photographically. Silicon dioxide absorption band between 250 and 255 nm were also observed for the reaction cell, because the cell and windows of the cell material were spectrosilica grade fused quartz. And this absorption band also used as wavelength calibration for all the photoproducts formed in the reaction cell during optical pumping.

  10. Reversible micromachining locator

    DOEpatents

    Salzer, Leander J.; Foreman, Larry R.

    1999-01-01

    This invention provides a device which includes a locator, a kinematic mount positioned on a conventional tooling machine, a part carrier disposed on the locator and a retainer ring. The locator has disposed therein a plurality of steel balls, placed in an equidistant position circumferentially around the locator. The kinematic mount includes a plurality of magnets which are in registry with the steel balls on the locator. In operation, a blank part to be machined is placed between a surface of a locator and the retainer ring (fitting within the part carrier). When the locator (with a blank part to be machined) is coupled to the kinematic mount, the part is thus exposed for the desired machining process. Because the locator is removably attachable to the kinematic mount, it can easily be removed from the mount, reversed, and reinserted onto the mount for additional machining. Further, the locator can likewise be removed from the mount and placed onto another tooling machine having a properly aligned kinematic mount. Because of the unique design and use of magnetic forces of the present invention, positioning errors of less than 0.25 micrometer for each machining process can be achieved.

  11. Reversible micromachining locator

    DOEpatents

    Salzer, L.J.; Foreman, L.R.

    1999-08-31

    This invention provides a device which includes a locator, a kinematic mount positioned on a conventional tooling machine, a part carrier disposed on the locator and a retainer ring. The locator has disposed therein a plurality of steel balls, placed in an equidistant position circumferentially around the locator. The kinematic mount includes a plurality of magnets which are in registry with the steel balls on the locator. In operation, a blank part to be machined is placed between a surface of a locator and the retainer ring (fitting within the part carrier). When the locator (with a blank part to be machined) is coupled to the kinematic mount, the part is thus exposed for the desired machining process. Because the locator is removably attachable to the kinematic mount, it can easily be removed from the mount, reversed, and reinserted onto the mount for additional machining. Further, the locator can likewise be removed from the mount and placed onto another tooling machine having a properly aligned kinematic mount. Because of the unique design and use of magnetic forces of the present invention, positioning errors of less than 0.25 micrometer for each machining process can be achieved. 7 figs.

  12. Heterogeneity of nervous system mitochondria: location, location, location!

    PubMed

    Dubinsky, Janet M

    2009-08-01

    Mitochondrial impairments have been associated with many neurological disorders, from inborn errors of metabolism or genetic disorders to age and environmentally linked diseases of aging (DiMauro S., Schon E.A. 2008. Mitochondrial disorders in the nervous system. Annu. Rev., Neurosci. 31, 91-123.). In these disorders, specific nervous system components or brain regions appear to be initially more susceptible to the triggering event or pathological process. Such regional variation in susceptibility to multiple types of stressors raises the possibility that inherent differences in mitochondrial function may mediate some aspect of pathogenesis. Regional differences in the distribution or number of mitochondria, mitochondrial enzyme activities, enzyme expression levels, mitochondrial genes or availability of necessary metabolites become attractive explanations for selective vulnerability of a nervous system structure. While regionally selective mitochondrial vulnerability has been documented, regional variations in other cellular and tissue characteristics may also contribute to metabolic impairment. Such environmental variables include high tonic firing rates, neurotransmitter phenotype, location of mitochondria within a neuron, or the varied tissue perfusion pressure of different cerebral arterial branches. These contextual variables exert regionally distinct regulatory influences on mitochondria to tune their energy production to local demands. Thus to understand variations in mitochondrial functioning and consequent selective vulnerability to injury, the organelle must be placed within the context of its cellular, functional, developmental and neuroanatomical environment.

  13. M-band imaging of the HR 8799 planetary system using an innovative LOCI-based background subtraction technique

    SciTech Connect

    Galicher, Raphael; Marois, Christian; Macintosh, Bruce; Barman, Travis; Konopacky, Quinn

    2011-09-02

    Multi-wavelength observations/spectroscopy of exoplanetary atmospheres are the basis of the emerging exciting field of comparative exoplanetology. The HR 8799 planetary system is an ideal laboratory to study our current knowledge gap between massive field brown dwarfs and the cold 5 Gyr old solar system planets. The HR 8799 planets have so far been imaged at J- to L-band, with only upper limits available at M-band. We present here deep high-contrast Keck II adaptive optics M-band observations that show the imaging detection of three of the four currently known HR 8799 planets. Such detections were made possible due to the development of an innovative LOCI-based background subtraction scheme that is three times more efficient than a classical median background subtraction for Keck II AO data, representing a gain in telescope time of up to a factor of nine. These M-band detections extend the broadband photometric coverage out to ~5 μm and provide access to the strong CO fundamental absorption band at 4.5 μm. The new M-band photometry shows that the HR 8799 planets are located near the L/T-type dwarf transition, similar to what was found by other studies. Finally, we also confirm that the best atmospheric fits are consistent with low surface gravity, dusty, and non-equilibrium CO/CH4 chemistry models.

  14. CSF oligoclonal banding

    MedlinePlus

    ... system. Oligoclonal bands may be a sign of multiple sclerosis. How the Test is Performed A sample of ... Performed This test helps support the diagnosis of multiple sclerosis (MS). However, it does not confirm the diagnosis. ...

  15. Decay of superdeformed bands

    SciTech Connect

    Carpenter, M.P.; Khoo, T.L.; Lauritsen, T.

    1995-12-31

    One of the major challenges in the study of superdeformation is to directly connect the large number of superdeformed bands now known to the yrast states. In this way, excitation energies, spins and parities can be assigned to the levels in the second well which is essential to establish the collective and single-particle components of these bands. This paper will review some of the progress which has been made to understand the decay of superdeformed bands using the new arrays including the measurement of the total decay spectrum and the establishment of direct one-step decays from the superdeformed band to the yrast line in {sup 194}Hg. 42 refs., 5 figs.

  16. Absorption of acoustic waves by sunspots. II - Resonance absorption in axisymmetric fibril models

    NASA Technical Reports Server (NTRS)

    Rosenthal, C. S.

    1992-01-01

    Analytical calculations of acoustic waves scattered by sunspots which concentrate on the absorption at the magnetohydrodynamic Alfven resonance are extended to the case of a flux-tube embedded in a uniform atmosphere. The model is based on a flux-tubes of varying radius that are highly structured, translationally invariant, and axisymmetric. The absorbed fractional energy is determined for different flux-densities and subphotospheric locations with attention given to the effects of twist. When the flux is highly concentrated into annuli efficient absorption is possible even when the mean magnetic flux density is low. The model demonstrates low absorption at low azimuthal orders even in the presence of twist which generally increases the range of wave numbers over which efficient absorption can occur. Resonance absorption is concluded to be an efficient mechanism in monolithic sunspots, fibril sunspots, and plage fields.

  17. Solar absorption surface panel

    DOEpatents

    Santala, Teuvo J.

    1978-01-01

    A composite metal of aluminum and nickel is used to form an economical solar absorption surface for a collector plate wherein an intermetallic compound of the aluminum and nickel provides a surface morphology with high absorptance and relatively low infrared emittance along with good durability.

  18. Rectal absorption of propylthiouracil.

    PubMed

    Bartle, W R; Walker, S E; Silverberg, J D

    1988-06-01

    The rectal absorption of propylthiouracil (PTU) was studied and compared to oral absorption in normal volunteers. Plasma levels of PTU after administration of suppositories of PTU base and PTU diethanolamine were significantly lower compared to the oral route. Elevated plasma reverse T3 levels were demonstrated after each treatment, however, suggesting a desirable therapeutic effect at this dosage level for all preparations.

  19. Polygonal deformation bands

    NASA Astrophysics Data System (ADS)

    Antonellini, Marco; Mollema, Pauline Nella

    2015-12-01

    We report for the first time the occurrence of polygonal faults in sandstone, which is compelling given that layer-bound polygonal fault systems have been observed so far only in fine-grained sediments such as clay and chalk. The polygonal faults are shear deformation bands that developed under shallow burial conditions via strain hardening in dm-wide zones. The edges of the polygons are 1-5 m long. The shear deformation bands are organized as conjugate faults along each edge of the polygon and form characteristic horst-like structures. The individual deformation bands have slip magnitudes ranging from a few mm to 1.5 cm; the cumulative average slip magnitude in a zone is up to 10 cm. The deformation bands heaves, in aggregate form, accommodate a small isotropic horizontal extension (strain <0.005). The individual shear deformation bands show abutting T-junctions, veering, curving, and merging where they mechanically interact. Crosscutting relationships are rare. The interactions of the deformation bands are similar to those of mode I opening fractures. The documented fault networks have important implications for evaluating the geometry of km-scale polygonal fault systems in the subsurface, top seal integrity, as well as constraining paleo-tectonic stress regimes.

  20. Multiscale image enhancement of chromosome banding patterns

    NASA Astrophysics Data System (ADS)

    Wu, Qiang; Castleman, Kenneth R.

    1996-10-01

    Visual examination of chromosome banding patterns is an important means of chromosome analysis. Cytogeneticists compare their patient's chromosome image against the prototype normal/abnormal human chromosome banding patterns. Automated chromosome analysis instruments facilitate this by digitally enhancing the chromosome images. Currently available systems employing traditional highpass/bandpass filtering and/or histogram equalization are approximately equivalent to photomicroscopy in their ability to support the detection of band pattern alterations. Improvements in chromosome image display quality, particularly in the detail of the banding pattern, would significantly increase the cost-effectiveness of these systems. In this paper we present our work on the use of multiscale transform and derivative filtering for image enhancement of chromosome banding patterns. A steerable pyramid representation of the chromosome image is generated by a multiscale transform. The derivative filters are designed to detect the bands of a chromosome, and the steerable pyramid transform is chosen based on its desirable properties of shift and rotation invariance. By processing the transform coefficients that correspond to the bands of the chromosome in the pyramid representation, contrast enhancement of the chromosome bands can be achieved with designed flexibility in scale, orientation and location. Compared with existing chromosome image enhancement techniques, this new approach offers the advantage of selective chromosome banding pattern enhancement that allows designated detail analysis. Experimental results indicate improved enhancement capabilities and promise more effective visual aid to comparison of chromosomes to the prototypes and to each other. This will increase the ability of automated chromosome analysis instruments to assist the evaluation of chromosome abnormalities in clinical samples.

  1. Direct discrimination of Parmotrema tinctorum from various location by Fourier transform infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Fam, W. H.; Latip, Jalifah; bin Din, Laily; Samsuddin, Mohd. Wahid

    2014-09-01

    Parmatrema tinctorum collected from various locations of Gohtong Jaya, Genting Highlands, Pahang underwent IR analysis. The analysis is aimed to discriminate the chemical constituents of P. tinctorum living in pristine and polluted area. Based on the FTIR analysis, there is a close resemblance in the absorption bands of all collected samples but differ in terms of their intensity. This suggested all samples produce similar chemical constituents but varies in numbers of metabolites. Student's t test was then performed on the IR spectra and results showed that there is a significant difference between P. tinctorum collected from pristine area and roundabout with heavy traffic. These preliminary results suggested other additional chemical constituents were produced in addition to depsides, depsidones and other aromatic polyketides by P. tinctorum living in the polluted area. Further isolation work is currently on going to identify the secondary metabolites.

  2. Differential absorption lidar measurements of atmospheric temperature and pressure profiles

    NASA Technical Reports Server (NTRS)

    Korb, C. L.

    1981-01-01

    The theory and methodology of using differential absorption lidar techniques for the remote measurement of atmospheric pressure profiles, surface pressure, and temperature profiles from ground, air, and space-based platforms are presented. Pressure measurements are effected by means of high resolution measurement of absorption at the edges of the oxygen A band lines where absorption is pressure dependent due to collisional line broadening. Temperature is assessed using measurements of the absorption at the center of the oxygen A band line originating from a quantum state with high ground state energy. The population of the state is temperature dependent, allowing determination of the temperature through the Boltzmann term. The results of simulations of the techniques using Voigt profile and variational analysis are reported for ground-based, airborne, and Shuttle-based systems. Accuracies in the 0.5-1.0 K and 0.1-0.3% range are projected.

  3. Petawatt laser absorption bounded

    PubMed Central

    Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

    2014-01-01

    The interaction of petawatt (1015 W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials. PMID:24938656

  4. Evidence for active galactic nucleus feedback in the broad absorption lines and reddening of MRK 231 {sup ,}

    SciTech Connect

    Leighly, Karen M.; Baron, Eddie; Lucy, Adrian B.; Terndrup, Donald M.; Dietrich, Matthias; Gallagher, Sarah C.

    2014-06-20

    We present the first J-band spectrum of Mrk 231, which reveals a large He I* λ10830 broad absorption line with a profile similar to that of the well-known Na I broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by Veilleux et al. is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in Type Ia supernovae. The nuclear starburst may be the origin and location of the dust. Spatially resolved emission in the broad absorption line trough suggests nearly full coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the He I* lines (produced in the quasar-photoionized H II region) compared with the Na I and Ca II lines (produced in the corresponding partially ionized zone). Cloudy simulations show that a density increase is required between the H II and partially ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies ∼100 pc from the central engine. These results suggest that the He I* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the Ca II and Na I lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of Na I absorption lines; without the compression along our line of sight, Mrk 231 would appear as an ordinary iron low-ionization, broad absorption line quasar.

  5. Relative Band Oscillator Strengths for Carbon Monoxide: Alpha (1)Pi-Chi (1)Sigma(+) Transitions

    NASA Technical Reports Server (NTRS)

    Federman, S. R.; Menningen, K. L.; Lee, Wei; Stoll, J. B.

    1997-01-01

    Band oscillator strengths for CO transitions between the electronic states A (l)Pi and X(1)Sigma(+) were measured via absorption with a synchrotron radiation source. When referenced to the well-characterized (5,0) band oscillator strength, our relative values for the (7,0) to (11,0) bands are most consistent with the recent experiments of Chan et al. and the theoretical predictions of Kirby & Cooper. Since the results from various laboratory techniques and theory now agree, analyses of interstellar CO based on absorption from A-X bands are no longer hindered by uncertainties in oscillator strength.

  6. Novel quad-band terahertz metamaterial absorber based on single pattern U-shaped resonator

    NASA Astrophysics Data System (ADS)

    Wang, Ben-Xin; Wang, Gui-Zhen

    2017-03-01

    A novel quad-band terahertz metamaterial absorber using four different modes of single pattern resonator is demonstrated. Four obvious frequencies with near-perfect absorption are realized. Near-field distributions of the four modes are provided to reveal the physical picture of the multiple-band absorption. Unlike most previous quad-band absorbers that typically require four or more patterns, the designed absorber has only one resonant structure, which is simpler than previous works. The presented quad-band absorber has potential applications in biological sensing, medical imaging, and material detection.

  7. Reversible micromachining locator

    SciTech Connect

    Salzer, Leander J.; Foreman, Larry R.

    2002-01-01

    A locator with a part support is used to hold a part onto the kinematic mount of a tooling machine so that the part can be held in or replaced in exactly the same position relative to the cutting tool for machining different surfaces of the part or for performing different machining operations on the same or different surfaces of the part. The locator has disposed therein a plurality of steel balls placed at equidistant positions around the planar surface of the locator and the kinematic mount has a plurality of magnets which alternate with grooves which accommodate the portions of the steel balls projecting from the locator. The part support holds the part to be machined securely in place in the locator. The locator can be easily detached from the kinematic mount, turned over, and replaced onto the same kinematic mount or another kinematic mount on another tooling machine without removing the part to be machined from the locator so that there is no need to touch or reposition the part within the locator, thereby assuring exact replication of the position of the part in relation to the cutting tool on the tooling machine for each machining operation on the part.

  8. Automatic vehicle location system

    NASA Technical Reports Server (NTRS)

    Hansen, G. R., Jr. (Inventor)

    1973-01-01

    An automatic vehicle detection system is disclosed, in which each vehicle whose location is to be detected carries active means which interact with passive elements at each location to be identified. The passive elements comprise a plurality of passive loops arranged in a sequence along the travel direction. Each of the loops is tuned to a chosen frequency so that the sequence of the frequencies defines the location code. As the vehicle traverses the sequence of the loops as it passes over each loop, signals only at the frequency of the loop being passed over are coupled from a vehicle transmitter to a vehicle receiver. The frequencies of the received signals in the receiver produce outputs which together represent a code of the traversed location. The code location is defined by a painted pattern which reflects light to a vehicle carried detector whose output is used to derive the code defined by the pattern.

  9. Subsurface banding poultry litter impacts greenhouse gas emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The impact subsurface banding poultry litter (PL) has on greenhouse gas emissions is limited. Thus, a study was conducted in established bermudagrass pastures located in Coastal Plain and Piedmont regions to determine the effects subsurface applying PL has on soil flux using two different band spaci...

  10. Skin hydration by spectroscopic imaging using multiple near-infrared bands

    NASA Astrophysics Data System (ADS)

    Attas, E. Michael; Sowa, Michael G.; Posthumus, Trevor B.; Schattka, Bernhard J.; Mantsch, Henry H.; Zhang, Shuliang L.

    2002-03-01

    Near-infrared spectroscopic methods have been developed to determine the degree of hydration of human skin in vivo. Reflectance spectroscopic imaging was used to investigate the distribution of skin moisture as a function of location. A human study in a clinical setting has generated quantitative data showing the effects of a drying agent and a moisturizer on delineated regions of the forearms of eight volunteers. Two digital imaging systems equipped with liquid-crystal tunable filters were used to collect stacks of monochromatic images at 10-nm intervals over the wavelength bands 650-1050 nm and 960-1700 nm. Images generated from measurements of water absorption-band areas at three different near-IR wavelengths (970, 1200, and 1450 nm) showed obvious differences in the apparent distribution of water in skin. Changes resulting from the skin treatments were much more evident in the 1200-nm and 1450-nm images than in the 970-nm ones. The variable sensitivity of the method at different wavelengths has been interpreted as being the result of different penetration depths of the infrared light used in the reflectance studies. Ex-vivo experiments with pigskin have provided evidence supporting the relationship between wavelength and penetration depth. Combining the hydration results from several near-IR water bands allows additional information on hydration depth to be obtained.

  11. AFGL atmospheric absorption line parameters compilation - 1982 edition

    NASA Astrophysics Data System (ADS)

    Rothman, L. S.; Gamache, R. R.; Barbe, A.; Goldman, A.; Gillis, J. R.; Brown, L. R.; Toth, R. A.; Flaud, J.-M.; Camy-Peyret, C.

    1983-08-01

    The latest edition of the AFGL atmospheric absorption line parameters compilation for the seven most active infrared terrestrial absorbers is described. Major modifications to the atlas for this edition include updating of water-vapor parameters from 0 to 4300 per cm, improvements to line positions for carbon dioxide, substantial modifications to the ozone bands in the middle to far infrared, and improvements to the 7- and 2.3-micron bands of methane. The atlas now contains about 181,000 rotation and vibration-rotation transitions between 0 and 17,900 per cm. The sources of the absorption parameters are summarized.

  12. Low-Absorption Liquid Crystals for Infrared Beam Steering

    DTIC Science & Technology

    2013-10-22

    clearing point of 51.5 "C and its melting point is lower than -10 °C due to super-cooling effect . We also measured its transmission spectrum in the...thickness (or effective optical path length) increases, then the absorption will increase exponentially, as Eq. (1) indicates. To improve transmittance... effective mass (m) as: (0 = -yjic/m. (3) As the effective mass increases the vibration frequency decreases, i.e., the absorption band shifts toward a

  13. 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.

  14. Calcific band keratopathy in an alpaca.

    PubMed

    Pucket, Jonathan D; Boileau, Melanie J; Sula, Mee Ja M

    2014-07-01

    A 4-year-old female Suri alpaca was presented for evaluation of acute onset weakness, lethargy, and recent development of opacities in both eyes. On ophthalmic examination, bilaterally symmetrical corneal opacities were noted along the interpalpebral fissures with a few corneal blood vessels intermingled. A presumed diagnosis of calcific band keratopathy was made based on location and appearance. The patient was euthanized a short while after diagnosis due to reasons unrelated to the eyes and histologic examination of the corneas revealed subepithelial calcium and vascularization, consistent with calcific band keratopathy. This case report is the first to document this ocular condition in an alpaca.

  15. Quasar Absorption Studies

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2004-01-01

    The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

  16. Does Broad-Band Seismometer Clip?

    NASA Astrophysics Data System (ADS)

    Tunc, S.; Tunc, B.; Caka, D.; Ada, S.; Rademacher, H.

    2012-12-01

    Any measurement system's dynamic range in decibel (dB), can be defined as proportion of maximum and minimum amplitude (Amax and Amin) which can be measured by the system. Dynamic range defines limitation of the system. Maximum dynamic range, caused by an earthquake with magnitude around 9 is known approximately 220dB in the world. Although the analog feed-back broad-band seismic sensors have 160 dB dynamic range seems to be enough to record most of the earthquakes, these sensors may clip (saturation), when the ground shaking caused by seismic waves is strong enough. Many institutions use broad-band seismometer in Turkey. Because of the clipping of the broad-band seismometers, there were some problems on location and magnitude of the Van Earthquake which occurred October, 23, 2011. To avoid the clipping problem proposed that, relevant sensors choose or install accelerometer simultaneously with the broad-band sensor to the recording system at the seismic stations. In this study, giving information on why the broad-band seismometers clipping, clearing up the general and wrong understanding is "broad-band seismometers do not clip".

  17. Stratospheric infrared continuum absorptions observed by the ATMOS instrument

    NASA Technical Reports Server (NTRS)

    Rinsland, C. P.; Zander, R.; Namkung, J. S.; Farmer, C. B.; Norton, R. H.

    1989-01-01

    A quantitative analysis of infrared continuum absorption features observed in ATMOS/Spacelab 3 (1985) spectra of the lower stratosphere is reported. Continuous absorption produced primarily by the collision-induced fundamental vibration-rotation band of O2 and to a lesser extent by the superposition of H2O far line wings has been observed in the 1400 to 1800/cm interval below tangent heights of about 25 km. Continuum optical depths measured in microwindows nearly free of atmospheric line absorption are 0.78 + or - 0.06 times those calculated with the O2 absorption coefficients of Timofeyev and Tonkov (1978). Transmittance measurements in microwindows between 2395 and 2535/cm have been used to study continuous absorption from the collision induced fundamental vibration-rotation band of N2 and the far wings of strong CO2 lines. The measured transmittances have been analyzed to derive best fit absorption coefficients for the N2 pressure-induced band at lower stratospheric temperatures (about 210 K).

  18. Sensors Locate Radio Interference

    NASA Technical Reports Server (NTRS)

    2009-01-01

    After receiving a NASA Small Business Innovation Research (SBIR) contract from Kennedy Space Center, Soneticom Inc., based in West Melbourne, Florida, created algorithms for time difference of arrival and radio interferometry, which it used in its Lynx Location System (LLS) to locate electromagnetic interference that can disrupt radio communications. Soneticom is collaborating with the Federal Aviation Administration (FAA) to install and test the LLS at its field test center in New Jersey in preparation for deploying the LLS at commercial airports. The software collects data from each sensor in order to compute the location of the interfering emitter.

  19. Four-band Hamiltonian for fast calculations in intermediate-band solar cells

    NASA Astrophysics Data System (ADS)

    Luque, Antonio; Panchak, Aleksandr; Vlasov, Alexey; Martí, Antonio; Andreev, Viacheslav

    2016-02-01

    The 8-dimensional Luttinger-Kohn-Pikus-Bir Hamiltonian matrix may be made up of four 4-dimensional blocks. A 4-band Hamiltonian is presented, obtained from making the non-diagonal blocks zero. The parameters of the new Hamiltonian are adjusted to fit the calculated effective masses and strained QD bandgap with the measured ones. The 4-dimensional Hamiltonian thus obtained agrees well with measured quantum efficiency of a quantum dot intermediate band solar cell and the full absorption spectrum can be calculated in about two hours using Mathematica© and a notebook. This is a hundred times faster than with the commonly-used 8-band Hamiltonian and is considered suitable for helping design engineers in the development of nanostructured solar cells.

  20. Atmospheric pressure and temperature profiling using near IR differential absorption lidar

    NASA Technical Reports Server (NTRS)

    Korb, C. L.; Schwemmer, G. K.; Dombrowski, M.; Weng, C. Y.

    1983-01-01

    The present investigation is concerned with differential absorption lidar techniques for remotely measuring the atmospheric temperature and pressure profile, surface pressure, and cloud top pressure-height. The procedure used in determining the pressure is based on the conduction of high-resolution measurements of absorption in the wings of lines in the oxygen A band. Absorption with respect to these areas is highly pressure sensitive in connection with the mechanism of collisional line broadening. The method of temperature measurement utilizes a determination of the absorption at the center of a selected line in the oxygen A band which originates from a quantum state with high ground state energy.

  1. The tunable electronic structure and optic absorption properties of phosphorene by a normally applied electric field

    NASA Astrophysics Data System (ADS)

    Yang, Mou; Duan, Hou-Jian; Wang, Rui-Qiang

    2016-10-01

    We studied the electronic structure and optical absorption properties of phosphorene (a monolayer black phosphorus) under a normally applied electric field. The electric field enlarges the energy gap, weakens the effective mass anisotropy, and increases the effective mass component along the armchair direction (x-direction) for both conduction and valence bands but provides little change to the component along the zigzag direction (y-direction). The band edge optical absorption is completely polarized in the x-direction, and decreases when increasing the electric field. If the exciting frequency is beyond the energy gap, the absorption for the y-polarized light becomes nonzero, but the absorption is still highly polarized.

  2. Band gap effects of hexagonal boron nitride using oxygen plasma

    SciTech Connect

    Sevak Singh, Ram; Leong Chow, Wai; Yingjie Tay, Roland; Hon Tsang, Siu; Mallick, Govind; Tong Teo, Edwin Hang

    2014-04-21

    Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

  3. Temperature sensitivity of differential absorption lidar measurements of water vapor in the 720-nm region

    NASA Technical Reports Server (NTRS)

    Browell, Edward V.; Ismail, Syed; Grossmann, Benoist E.

    1991-01-01

    Recently measured properties of water vapor (H2O) absorption lines have been used in calculations to evalute the temperature sensitivity of differential absorption lidar (Dial) H2O measurements. This paper estimates the temperature sensitivity of H2O lines in the 717-733-nm region for both H2O mixing ratio and number density measurements, and discusses the influence of the H2O line ground state energies E-double-prime, the H2O absorption linewidths, the linewidth temperature dependence parameter, and the atmospheric temperature and pressure variations with altitude and location on the temperature sensitivity calculations. Line parameters and temperature sensitivity calculations for 67 H2O lines in the 720-nm band are given which can be directly used in field experiments. Water vapor lines with E-double-prime values in the 100-300/cm range were found to be optimum for Dial measurements of H2O number densities, while E-double-prime values in the 250-500/cm range were found to be optimum for H2O mixing ratio measurements.

  4. On-chip, photon-number-resolving, telecommunication-band detectors for scalable photonic information processing

    SciTech Connect

    Gerrits, Thomas; Lita, Adriana E.; Calkins, Brice; Tomlin, Nathan A.; Fox, Anna E.; Linares, Antia Lamas; Mirin, Richard P.; Nam, Sae Woo; Thomas-Peter, Nicholas; Metcalf, Benjamin J.; Spring, Justin B.; Langford, Nathan K.; Walmsley, Ian A.; Gates, James C.; Smith, Peter G. R.

    2011-12-15

    Integration is currently the only feasible route toward scalable photonic quantum processing devices that are sufficiently complex to be genuinely useful in computing, metrology, and simulation. Embedded on-chip detection will be critical to such devices. We demonstrate an integrated photon-number-resolving detector, operating in the telecom band at 1550 nm, employing an evanescently coupled design that allows it to be placed at arbitrary locations within a planar circuit. Up to five photons are resolved in the guided optical mode via absorption from the evanescent field into a tungsten transition-edge sensor. The detection efficiency is 7.2{+-}0.5 %. The polarization sensitivity of the detector is also demonstrated. Detailed modeling of device designs shows a clear and feasible route to reaching high detection efficiencies.

  5. Electronic apex locators.

    PubMed

    Gordon, M P J; Chandler, N P

    2004-07-01

    Prior to root canal treatment at least one undistorted radiograph is required to assess canal morphology. The apical extent of instrumentation and the final root filling have a role in treatment success, and are primarily determined radiographically. Electronic apex locators reduce the number of radiographs required and assist where radiographic methods create difficulty. They may also indicate cases where the apical foramen is some distance from the radiographic apex. Other roles include the detection of root canal perforation. A review of the literature focussed first on the subject of electronic apex location. A second review used the names of apex location devices. From the combined searches, 113 pertinent articles in English were found. This paper reviews the development, action, use and types of electronic apex locators.

  6. Smart Location Mapping

    EPA Pesticide Factsheets

    The Smart Location Database, Access to Jobs and Workers via Transit, and National Walkability Index tools can help assess indicators related to the built environment, transit accessibility, and walkability.

  7. Uranium Location Database Compilation

    EPA Pesticide Factsheets

    EPA has compiled mine location information from federal, state, and Tribal agencies into a single database as part of its investigation into the potential environmental hazards of wastes from abandoned uranium mines in the western United States.

  8. Intestinal Water Absorption Varies with Expected Dietary Water Load among Bats but Does Not Drive Paracellular Nutrient Absorption.

    PubMed

    Price, Edwin R; Brun, Antonio; Gontero-Fourcade, Manuel; Fernández-Marinone, Guido; Cruz-Neto, Ariovaldo P; Karasov, William H; Caviedes-Vidal, Enrique

    2015-01-01

    Rapid absorption and elimination of dietary water should be particularly important to flying species and were predicted to vary with the water content of the natural diet. Additionally, high water absorption capacity was predicted to be associated with high paracellular nutrient absorption due to solvent drag. We compared the water absorption rates of sanguivorous, nectarivorous, frugivorous, and insectivorous bats in intestinal luminal perfusions. High water absorption rates were associated with high expected dietary water load but were not highly correlated with previously measured rates of (paracellular) arabinose clearance. In conjunction with these tests, we measured water absorption and the paracellular absorption of nutrients in the intestine and stomach of vampire bats using luminal perfusions to test the hypothesis that the unique elongated vampire stomach is a critical site of water absorption. Vampire bats' gastric water absorption was high compared to mice but not compared to their intestines. We therefore conclude that (1) dietary water content has influenced the evolution of intestinal water absorption capacity in bats, (2) solvent drag is not the only driver of paracellular nutrient absorption, and (3) the vampire stomach is a capable but not critical location for water absorption.

  9. Protonation effects on the UV/Vis absorption spectra of imatinib: a theoretical and experimental study.

    PubMed

    Grante, Ilze; Actins, Andris; Orola, Liana

    2014-08-14

    An experimental and theoretical investigation of protonation effects on the UV/Vis absorption spectra of imatinib showed systematic changes of absorption depending on the pH, and a new absorption band appeared below pH 2. These changes in the UV/Vis absorption spectra were interpreted using quantum chemical calculations. The geometry of various imatinib cations in the gas phase and in ethanol solution was optimized with the DFT/B3LYP method. The resultant geometries were compared to the experimentally determined crystal structures of imatinib salts. The semi-empirical ZINDO-CI method was employed to calculate the absorption lines and electronic transitions. Our study suggests that the formation of the extra near-UV absorption band resulted from an increase of imatinib trication concentration in the solution, while the rapid increase of the first absorption maximum could be attributed to both the formation of imatinib trication and tetracation.

  10. Lunar Impact Flash Locations

    NASA Technical Reports Server (NTRS)

    Moser, D. E.; Suggs, R. M.; Kupferschmidt, L.; Feldman, J.

    2015-01-01

    A bright impact flash detected by the NASA Lunar Impact Monitoring Program in March 2013 brought into focus the importance of determining the impact flash location. A process for locating the impact flash, and presumably its associated crater, was developed using commercially available software tools. The process was successfully applied to the March 2013 impact flash and put into production on an additional 300 impact flashes. The goal today: provide a description of the geolocation technique developed.

  11. Carrier Lifetimes in a I I I -V -N Intermediate-Band Semiconductor

    NASA Astrophysics Data System (ADS)

    Heyman, J. N.; Schwartzberg, A. M.; Yu, K. M.; Luce, A. V.; Dubon, O. D.; Kuang, Y. J.; Tu, C. W.; Walukiewicz, W.

    2017-01-01

    We use transient absorption spectroscopy to measure carrier lifetimes in the multiband semiconductor GaPyAs1 -x -yNx . These measurements probe the electron populations in the conduction band, intermediate band, and valence band as a function of time after an excitation pulse. Following photoexcitation of GaP0.32As0.67N0.01 , we find that the electron population in the conduction band decays exponentially with a time constant τCB=23 ps . The electron population in the intermediate band exhibits bimolecular recombination with recombination constant r =2 ×10-8 cm3/s . In our experiment, an optical pump pulse excites electrons from the valence band to the intermediate and conduction bands, and the change in interband absorption due to absorption saturation and induced absorption is probed with a delayed white-light pulse. We model the optical properties of our samples using the band anticrossing model to extract carrier densities as a function of time. These results not only identify the short minority-carrier lifetime as a key factor affecting the performance of GaPyAs1 -x -yNx -based intermediate-band solar cells but also provide guidance on ways to address this issue.

  12. Banded transformer cores

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W. T. (Inventor)

    1974-01-01

    A banded transformer core formed by positioning a pair of mated, similar core halves on a supporting pedestal. The core halves are encircled with a strap, selectively applying tension whereby a compressive force is applied to the core edge for reducing the innate air gap. A dc magnetic field is employed in supporting the core halves during initial phases of the banding operation, while an ac magnetic field subsequently is employed for detecting dimension changes occurring in the air gaps as tension is applied to the strap.

  13. Absorption heat pump system

    DOEpatents

    Grossman, G.

    1982-06-16

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  14. Compounds affecting cholesterol absorption

    NASA Technical Reports Server (NTRS)

    Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)

    2004-01-01

    A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

  15. Soliton absorption spectroscopy

    PubMed Central

    Kalashnikov, V. L.; Sorokin, E.

    2010-01-01

    We analyze optical soliton propagation in the presence of weak absorption lines with much narrower linewidths as compared to the soliton spectrum width using the novel perturbation analysis technique based on an integral representation in the spectral domain. The stable soliton acquires spectral modulation that follows the associated index of refraction of the absorber. The model can be applied to ordinary soliton propagation and to an absorber inside a passively modelocked laser. In the latter case, a comparison with water vapor absorption in a femtosecond Cr:ZnSe laser yields a very good agreement with experiment. Compared to the conventional absorption measurement in a cell of the same length, the signal is increased by an order of magnitude. The obtained analytical expressions allow further improving of the sensitivity and spectroscopic accuracy making the soliton absorption spectroscopy a promising novel measurement technique. PMID:21151755

  16. Absorption heat pump system

    DOEpatents

    Grossman, Gershon

    1984-01-01

    The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

  17. Pseudopotential calculations and photothermal lensing measurements of two-photon absorption in solids

    SciTech Connect

    White, W.T. III

    1985-11-04

    We have studied two-photon absorption in solids theoretically and experimentally. We have shown that it is possible to use accurate band structure techniques to compute two-photon absorption spectra within 15% of measured values in a wide band-gap material, ZnS. The empirical pseudopotential technique that we used is significantly more accurate than previous models of two-photon absorption in zinc blende materials, including present tunneling theories (which are essentially parabolic-band results in disguise) and the nonparabolic-band formalism of Pidgeon et al. and Weiler. The agreement between our predictions and previous measurements allowed us to use ZnS as a reference material in order to validate a technique for measuring two-photon absorption that was previously untried in solids, pulsed dual-beam thermal lensing. With the validated technique, we examined nonlinear absorption in one other crystal (rutile) and in several glasses, including silicates, borosilicates, and one phosphate glass. Initially, we believed that the absorption edges of all the materials were comparable; however, subsequent evidence suggested that the effective band-gap energies of the glasses were above the energy of two photons in our measurement. Therefore, we attribute the nonlinear absorption that we observed in glasses to impurities or defects. The measured nonlinear absorption coefficients were of the order of a few cm/TW in the glasses and of the order of 10 cm/GW in the crystals, four orders of magnitude higher than in glasses. 292 refs.

  18. Intermittency on simultaneous observations of riometer at several Antarctic locations

    NASA Astrophysics Data System (ADS)

    Ovalle, E. M.; Foppiano, A. J.; Stepanova, M. V.; Weatherwax, A. T.

    2016-03-01

    It is well known that auroral radio wave absorption, as measured by riometers, consists of periods of relative quiescence which are interrupted by short bursts of activity. Such patterns in activity are observed in systems ranging from the stock market to turbulence, i.e. they exhibit intermittency. In the case of the auroral absorption it has also been found that intermittency strongly depends on the magnetic local time, being largest in the night-time sector. This can be interpreted as indicating that the precipitating particles responsible of the absorption exhibit intermittency, especially near the substorm eye, where the level of turbulence increases. Here, we analyse simultaneous observations of riometer absorption at seven Antarctic locations, to determine whether they exhibit intermittency. We determine the Probability Distribution Functions of the fluctuations of riometer absorption for absorption events larger than 0.1 dB, as well as those for the time-intervals between absorption events. Observations are for locations within the austral auroral absorption zone and on the polar cap. It is found that the parameters of a power law used to describe the calculated PDFs are consistent with the formation of coherent structures being more frequent within the auroral zone, as a manifestation of intermittency.

  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. Phononic glass: a robust acoustic-absorption material.

    PubMed

    Jiang, Heng; Wang, Yuren

    2012-08-01

    In order to achieve strong wide band acoustic absorption under high hydrostatic pressure, an interpenetrating network structure is introduced into the locally resonant phononic crystal to fabricate a type of phononic composite material called "phononic glass." Underwater acoustic absorption coefficient measurements show that the material owns high underwater sound absorption coefficients over 0.9 in 12-30 kHz. Moreover, the quasi-static compressive behavior shows that the phononic glass has a compressive strength over 5 MPa which is crucial for underwater applications.

  1. Optical absorption measurement system

    DOEpatents

    Draggoo, Vaughn G.; Morton, Richard G.; Sawicki, Richard H.; Bissinger, Horst D.

    1989-01-01

    The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

  2. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2003-10-14

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  3. Solar selective absorption coatings

    DOEpatents

    Mahoney, Alan R.; Reed, Scott T.; Ashley, Carol S.; Martinez, F. Edward

    2004-08-31

    A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

  4. Intranasal absorption of oxymorphone.

    PubMed

    Hussain, M A; Aungst, B J

    1997-08-01

    The nasal bioavailability of oxymorphone HCI was determined. Rats were surgically prepared to isolate the nasal cavity, into which a solution of oxymorphone was administered. A reference group of rats was administered oxymorphone HCl intravenously. Plasma oxymorphone concentrations were determined by HPLC. Nasal absorption was rapid, nasal bioavailability was 43%, and the iv and nasal elimination profiles were similar. Oxymorphone HCI appears to have the solubility, potency, and absorption properties required for efficient nasal delivery, which is an alternative to injections.

  5. High absorption efficiency of AlGaAs/GaAs superlattice solar cells

    NASA Astrophysics Data System (ADS)

    Nishinaga, Jiro; Kawaharazuka, Atsushi; Horikoshi, Yoshiji

    2015-05-01

    The effects of excitonic absorption on the solar cell efficiency have been investigated in solar cells with AlGaAs/GaAs superlattice absorption layers. Numerical calculations reveal that excitonic absorption considerably enhances the overall absorption coefficient. The excitonic absorption shows strong peaks at the absorption edge and in the energy region above the band gap. Absorption enhancement is also achieved in the AlGaAs/GaAs superlattice. The measured quantum efficiency spectra of superlattice solar cells at room temperature are reasonably well reproduced by simulations taking excitonic effects into account. The superlattice solar cells are confirmed to have a high absorbance and good temperature stability. The theoretical analysis of the experimental results confirms that the enhanced excitonic absorption in the superlattice absorption layers survives even at 100 °C, which is considered as the actual device temperature under realistic device operations.

  6. 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

  7. Dual-Band Miniaturized Patch Antennas for Microwave Breast Imaging

    PubMed Central

    Al-Joumayly, Mudar A.; Aguilar, Suzette M.; Behdad, Nader; Hagness, Susan C.

    2010-01-01

    We present a miniaturized, dual-band patch antenna array element that is designed for use in a 3-D microwave tomography system for breast imaging. Dual-band operation is achieved by manipulating the fundamental resonant mode of the patch antenna and one of its higher-order modes. Miniaturization and tuning of the resonant frequencies are achieved by loading the antenna with non-radiating slots at strategic locations along the patch. This results in a compact, dual-band antenna with symmetric radiation patterns and similar radiation characteristics at both bands of operation. The performance of the antenna in a biocompatible immersion medium is verified experimentally. PMID:21866218

  8. Dual-band polarization-/angle-insensitive metamaterial absorber

    SciTech Connect

    Xiong, Han; Zhong, Lin-Lin; Luo, Chao-Ming; Hong, Jing-Song

    2015-06-15

    A dual-band metamaterial absorber (MA) based on triangular resonators is designed and investigated in this paper. It is composed of a two-dimensional periodic metal-dielectric-metal sandwiches array on a dielectric substrate. The simulation results clearly show that this absorber has two absorption peaks at 14.9 and 18.9 GHz, respectively, and experiments are conducted to verify the proposed designs effectively. For each polarization, the dual-band absorber is insensitive to the incident angle (up to 60°) and the absorption peaks remain high for both transverse electric (TE) and transverse magnetic (TM) radiation. To study the physical mechanism of power loss, the current distribution at the dual absorption peaks is given. The MA proposed in this paper has potential applications in many scientific and martial fields.

  9. Dual-band polarization-/angle-insensitive metamaterial absorber

    NASA Astrophysics Data System (ADS)

    Xiong, Han; Zhong, Lin-Lin; Luo, Chao-Ming; Hong, Jing-Song

    2015-06-01

    A dual-band metamaterial absorber (MA) based on triangular resonators is designed and investigated in this paper. It is composed of a two-dimensional periodic metal-dielectric-metal sandwiches array on a dielectric substrate. The simulation results clearly show that this absorber has two absorption peaks at 14.9 and 18.9 GHz, respectively, and experiments are conducted to verify the proposed designs effectively. For each polarization, the dual-band absorber is insensitive to the incident angle (up to 60°) and the absorption peaks remain high for both transverse electric (TE) and transverse magnetic (TM) radiation. To study the physical mechanism of power loss, the current distribution at the dual absorption peaks is given. The MA proposed in this paper has potential applications in many scientific and martial fields.

  10. Free-Carrier Absorption in Silicon from First Principles

    NASA Astrophysics Data System (ADS)

    Shi, Guangsha; Kioupakis, Emmanouil

    The absorption of light by free carriers in semiconductors such as silicon results in intraband electron or hole excitations, and competes with optical transitions across the band gap. Free-carrier absorption therefore reduces the efficiency of optoelectronic devices such as solar cells because it competes with the generation of electron-hole pairs. In this work, we use first-principles calculations based on density functional theory to investigate direct and phonon-assisted free-carrier absorption in silicon. We determine the free-carrier absorption coefficient as a function of carrier concentration and temperature and compare to experiment. We also identify the dominant phonon modes that contributing to phonon-assisted free-carrier absorption processes, and analyze the results to evaluate the impact of this loss mechanism on the efficiency of silicon solar cells. This research was supported by the National Science Foundation CAREER award through Grant No. DMR-1254314. Computational resources were provided by the DOE NERSC facility.

  11. Mechanochemical Tuning of Pyrene Absorption Spectrum Using Force Probes.

    PubMed

    Fernández-González, Miguel Ángel; Rivero, Daniel; García-Iriepa, Cristina; Sampedro, Diego; Frutos, Luis Manuel

    2017-02-14

    Control of absorption spectra in chromophores is a fundamental aspect of many photochemical and photophysical processes as it constitutes the first step of the global photoinduced process. Here we explore the use of mechanical forces to modulate the light absorption process. Specifically, we develop a computational formalism for determining the type of mechanical forces permitting a global tuning of the absorption spectrum. This control extends to the excitation wavelength, absorption bands overlap, and oscillator strength. The determination of these optimal forces permits us to rationally guide the design of new mechano-responsive chromophores. Pyrene has been chosen as the case study for applying these computational tools because significant absorption spectra information is available for the chromophore as well as for different strained derivatives. Additionally, pyrene presents a large flexibility, which makes it a good system to test the inclusion of force probes as the strategy to exert forces on the system.

  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. 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.

  15. Multi-Band-SWIFT

    NASA Astrophysics Data System (ADS)

    Idiyatullin, Djaudat; Corum, Curtis A.; Garwood, Michael

    2015-02-01

    A useful extension to SWIFT (SWeep Imaging with Fourier Transformation) utilizing sidebands of the excitation pulse is introduced. This MRI method, called Multi-Band-SWIFT, achieves much higher bandwidth than standard SWIFT by using multiple segmented excitations (bands) of the field of view. A description of the general idea and variants of the pulse sequence are presented. From simulations and semi-phenomenological theory, estimations of power deposition and signal-to-noise ratio are made. MB-SWIFT and ZTE (zero-TE) sequences are compared based on images of a phantom and human mandible. Multi-Band-SWIFT provides a bridge between SWIFT and ZTE sequences and allows greatly increased excitation and acquisition bandwidths relative to standard SWIFT for the same hardware switching parameters and requires less peak amplitude of the radiofrequency field (or greater flip angle at same peak amplitude) as compared to ZTE. Multi-Band-SWIFT appears to be an attractive extension of SWIFT for certain musculoskeletal and other medical imaging applications, as well as for imaging materials.

  16. Multi-Band-SWIFT.

    PubMed

    Idiyatullin, Djaudat; Corum, Curtis A; Garwood, Michael

    2015-02-01

    A useful extension to SWIFT (SWeep Imaging with Fourier Transformation) utilizing sidebands of the excitation pulse is introduced. This MRI method, called Multi-Band-SWIFT, achieves much higher bandwidth than standard SWIFT by using multiple segmented excitations (bands) of the field of view. A description of the general idea and variants of the pulse sequence are presented. From simulations and semi-phenomenological theory, estimations of power deposition and signal-to-noise ratio are made. MB-SWIFT and ZTE (zero-TE) sequences are compared based on images of a phantom and human mandible. Multi-Band-SWIFT provides a bridge between SWIFT and ZTE sequences and allows greatly increased excitation and acquisition bandwidths relative to standard SWIFT for the same hardware switching parameters and requires less peak amplitude of the radiofrequency field (or greater flip angle at same peak amplitude) as compared to ZTE. Multi-Band-SWIFT appears to be an attractive extension of SWIFT for certain musculoskeletal and other medical imaging applications, as well as for imaging materials.

  17. Banded Sunflower Moth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The banded sunflower moth, Cochylis hospes Walsingham, is an important insect pest of cultivated sunflower. Eggs are deposited on the bracts of sunflower heads. Larvae develop through five instars within the heads and are present in fields from mid-July to mid-September. Larvae feed initially on the...

  18. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, R.C.; Biermann, W.J.

    1989-05-09

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.

  19. Seven-effect absorption refrigeration

    DOEpatents

    DeVault, Robert C.; Biermann, Wendell J.

    1989-01-01

    A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

  20. 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.

  1. An EPR and optical absorption study of Cu(2+) doped in disodium malonate trihydrate single crystal.

    PubMed

    Yarbaşi, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

    2009-03-01

    Single crystals and powder electron paramagnetic resonance (EPR) studies of Cu(2+)-doped disodium malonate trihydrate [C(3)H(2)O(4)Na(2).3H(2)O] have been carried out at room temperature. The angular variation of the disodium malonate trihydrate single crystal have shown that two different Cu(2+) complexes are located in different chemical environments, and each environment contains one magnetically inequivalent Cu(2+) sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The principal values of the g and the hyperfine tensors were determined and were found to be in agreement with the literature values. Crystal field around the Cu(2+) ion is nearly rhombic. The optical absorption studies show two bands at 603nm (16584cm(-1)) and 890nm (11236cm(-1)) which confirm the rhombic symmetry. The crystals field parameters and than the wave function are determined.

  2. An EPR and optical absorption study of Cu 2+ doped in disodium malonate trihydrate single crystal

    NASA Astrophysics Data System (ADS)

    Yarbaşı, Zeynep; Karabulut, Bünyamin; Karabulut, Abdulhalik

    2009-03-01

    Single crystals and powder electron paramagnetic resonance (EPR) studies of Cu 2+-doped disodium malonate trihydrate [C 3H 2O 4Na 2·3H 2O] have been carried out at room temperature. The angular variation of the disodium malonate trihydrate single crystal have shown that two different Cu 2+ complexes are located in different chemical environments, and each environment contains one magnetically inequivalent Cu 2+ sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The principal values of the g and the hyperfine tensors were determined and were found to be in agreement with the literature values. Crystal field around the Cu 2+ ion is nearly rhombic. The optical absorption studies show two bands at 603 nm (16584 cm -1) and 890 nm (11236 cm -1) which confirm the rhombic symmetry. The crystals field parameters and than the wave function are determined.

  3. 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.

  4. Determination of band oscillator strengths of atmospheric molecules from high resolution vacuum ultraviolet cross section measurements

    NASA Technical Reports Server (NTRS)

    Parkinson, W. H.

    1986-01-01

    An account is given of progress in work on (1) the determination of band oscillator strengths of the Schumann-Runge absorption bands of (16)O2 and (18)O2 from cross section measurements conducted at 79 K; (2) the determination of the absolute absorption cross section of the Schumann-Runge bands of (16)O(18)O from optical depth measurements performed on mixtures of (16)O2, (18)O2 and (16)O(18)O at 79K; and (3) the influence of Schumann-Runge linewing contributions on the determination of the Herzberg continuum absorption cross section of (16)O2 in the wavelength region 194 to 204 nm. The experimental investigations are effected at high resolution with a 6.65 m scanning spectrometer which is, by virtue of its small instrumental width (EWHM = 0.0013 nm), uniquely suitable for cross section measurements of molecular bands with discrete rotational structure. Absolute cross sections, which are independent of the instrumental function and from which band oscillator strengths are directly determined, are measured for the absorption bands that are most predissociated. Such measurements are needed for (1) accurate calculations of the stratospheric production of atomic oxygen and heavy ozone formed following the photopredissociation of (18)O(16)O by solar radiation penetrating between the absorption lines of (16)O2; (2) elucidation of the mechanism of predissociation of the upper state of the Schumann-Runge bands; and (3) determination of the true shape of the Herzberg continuum cross section.

  5. Evolution of Dust Trails into Bands

    NASA Astrophysics Data System (ADS)

    Vokrouhlický, D.; Nesvorný, D.; Bottke, W. F.

    2008-01-01

    We use numerical simulations to investigate the production of dust trails by asteroid disruption events. Our work shows that asteroid trails evolve into pairs of dust bands over time. Coherent trails typically survive several tens of kyr before evolving into complete bands after ~1 Myr. The transition timescale depends sensitively on the location of the source breakup event in the main asteroid belt. Bands develop more efficiently from sources in the middle/outer belt than in the inner belt, which may not produce observable pairs of bands at all. The infrared structures produced by recent disruption events (<1 Myr) are characterized by a complicated and changing set of incomplete arcs and cusps. Their geometry depends both on the observer's position and on the source's location in terms of heliocentric distance and inclination to the ecliptic. We postulate that the broad orphan trails named C and D by Sykes in 1988 might have been produced by the formation of the Datura asteroid family 450 +/- 50 kyr ago. Additional work will be needed to test this link.

  6. RFI emitter location techniques

    NASA Technical Reports Server (NTRS)

    Rao, B. L. J.

    1973-01-01

    The possibility is discussed of using Doppler techniques for determining the location of ground based emitters causing radio frequency interference with low orbiting satellites. An error analysis indicates that it is possible to find the emitter location within an error range of 2 n.mi. The parameters which determine the required satellite receiver characteristic are discussed briefly along with the non-real time signal processing which may by used in obtaining the Doppler curve. Finally, the required characteristics of the satellite antenna are analyzed.

  7. Marine cable location system

    SciTech Connect

    Zachariadis, R.G.

    1984-05-01

    An acoustic positioning system locates a marine cable at an exploration site, such cable employing a plurality of hydrophones at spaced-apart positions along the cable. A marine vessel measures water depth to the cable as the vessel passes over the cable and interrogates the hydrophones with sonar pulses along a slant range as the vessel travels in a parallel and horizontally offset path to the cable. The location of the hydrophones is determined from the recordings of water depth and slant range.

  8. X-band phase calibration generator coupler

    NASA Technical Reports Server (NTRS)

    Stanton, P. H.

    1987-01-01

    A new type of phase calibration generator (PCG) coupler was developed for the Deep Space Network (DSN) X-band antennas that can be located directly behind the feedhorn. The advantage of this is that the calibration includes more of the system. The disadvantage is that the overmoded waveguide at this location must be coupled in a mode-selective manner. Low-power and high-power PCG couplers have been successfully produced, and the RF test results from a PCG coupler are given.

  9. Infrared absorption spectra of molecular crystals: Possible evidence for small-polaron formation?

    NASA Astrophysics Data System (ADS)

    Pržulj, Željko; Čevizović, Dalibor; Zeković, Slobodan; Ivić, Zoran

    2008-09-01

    The temperature dependence of the position of the so-called anomalous band peaked at 1650cm in the IR-absorption spectrum of crystalline acetanilide (ACN) is theoretically investigated within the small-polaron theory. Its pronounced shift towards the position of the normal band is predicted with the rise of temperature. Interpretation of the IR-absorption spectra in terms of small-polaron model has been critically assessed on the basis of these results.

  10. Uranium Location Database

    EPA Pesticide Factsheets

    A GIS compiled locational database in Microsoft Access of ~15,000 mines with uranium occurrence or production, primarily in the western United States. The metadata was cooperatively compiled from Federal and State agency data sets and enables the user to conduct geographic and analytical studies on mine impacts on the public and environment.

  11. Optimal Facility-Location.

    PubMed

    Goldman, A J

    2006-01-01

    Dr. Christoph Witzgall, the honoree of this Symposium, can count among his many contributions to applied mathematics and mathematical operations research a body of widely-recognized work on the optimal location of facilities. The present paper offers to non-specialists a sketch of that field and its evolution, with emphasis on areas most closely related to Witzgall's research at NBS/NIST.

  12. Particle impact location detector

    NASA Technical Reports Server (NTRS)

    Auer, S. O.

    1974-01-01

    Detector includes delay lines connected to each detector surface strip. When several particles strike different strips simultaneously, pulses generated by each strip are time delayed by certain intervals. Delay time for each strip is known. By observing time delay in pulse, it is possible to locate strip that is struck by particle.

  13. LOCATING AREAS OF CONCERN

    EPA Science Inventory

    A simple method to locate changes in vegetation cover, which can be used to identify areas under stress. The method only requires inexpensive NDVI data. The use of remotely sensed data is far more cost-effective than field studies and can be performed more quickly. Local knowledg...

  14. Locating gravitational potential energy

    NASA Astrophysics Data System (ADS)

    Keeports, David

    2017-01-01

    Where does gravitational potential energy reside when a ball is in the air? The perfectly correct answer is that it is located in the ball-Earth system. Still, mechanical energy conservation problems are routinely solved by assigning a potential energy to the ball alone. Provided here is a proof that such an assignment introduces only an entirely undetectable error.

  15. An automated nudged elastic band method

    NASA Astrophysics Data System (ADS)

    Kolsbjerg, Esben L.; Groves, Michael N.; Hammer, Bjørk

    2016-09-01

    A robust, efficient, dynamic, and automated nudged elastic band (AutoNEB) algorithm to effectively locate transition states is presented. The strength of the algorithm is its ability to use fewer resources than the nudged elastic band (NEB) method by focusing first on converging a rough path before improving upon the resolution around the transition state. To demonstrate its efficiency, it has been benchmarked using a simple diffusion problem and a dehydrogenation reaction. In both cases, the total number of force evaluations used by the AutoNEB method is significantly less than the NEB method. Furthermore, it is shown that for a fast and robust relaxation to the transition state, a climbing image elastic band method where the full spring force, rather than only the component parallel to the local tangent to the path, is preferred especially for pathways through energy landscapes with multiple local minima. The resulting corner cutting does not affect the accuracy of the transition state as long as this is located with the climbing image method. Finally, a number of pitfalls often encountered while locating the true transition state of a reaction are discussed in terms of systematically exploring the multidimensional energy landscape of a given process.

  16. VA Health Care Facilities Locator

    MedlinePlus

    ... VA » Locations » Find Locations Locations Find Locations The javascript used here is for validation purpose only. Your browser doesn't seem to support javascript or has it disabled. This site is a ...

  17. Analysis and machine mapping of the distribution of band recoveries

    USGS Publications Warehouse

    Cowardin, L.M.

    1977-01-01

    A method of calculating distance and bearing from banding site to recovery location based on the solution of a spherical triangle is presented. X and Y distances on an ordinate grid were applied to computer plotting of recoveries on a map. The advantages and disadvantages of tables of recoveries by State or degree block, axial lines, and distance of recovery from banding site for presentation and comparison of the spatial distribution of band recoveries are discussed. A special web-shaped partition formed by concentric circles about the point of banding and great circles at 30-degree intervals through the point of banding has certain advantages over other methods. Comparison of distributions by means of a X? contingency test is illustrated. The statistic V = X?/N can be used as a measure of difference between two distributions of band recoveries and its possible use is illustrated as a measure of the degree of migrational homing.

  18. Microwave absorption properties of pyrolytic carbon nanofilm

    PubMed Central

    2013-01-01

    We analyzed the electromagnetic (EM) shielding effectiveness in the Ka band (26 to 37 GHz) of highly amorphous nanometrically thin pyrolytic carbon (PyC) films with lateral dimensions of 7.2 × 3.4 mm2, which consists of randomly oriented and intertwined graphene flakes with a typical size of a few nanometers. We discovered that the manufactured PyC films, whose thickness is thousand times less than the skin depth of conventional metals, provide a reasonably high EM attenuation. The latter is caused by absorption losses that can be as high as 38% to 20% in the microwave frequency range. Being semi-transparent in visible and infrared spectral ranges and highly conductive at room temperature, PyC films emerge as a promising material for manufacturing ultrathin microwave (e.g., Ka band) filters and shields. PMID:23388194

  19. Spectroscopic Line Parameters in the Infrared Bands of CH3CN and C2H6

    NASA Astrophysics Data System (ADS)

    Devi, V. Malathy

    2010-10-01

    In this paper, measurements of critical spectroscopic line parameters such as positions, absolute intensities and pressure broadened (self- and N2) half-width coefficients for transitions in the ν4 band of CH3CN (acetonitile, ethanenitrile, methyl cyanide) and the ν9 band of C2H6 (ethane) are presented. CH3CN has been measured by remote sensing in the earth's atmosphere, in comets and in interstellar molecular clouds. It is also a constituent in the atmospheres of Titan, Saturn's largest moon. Likewise, C2H6 is also an important constituent in the atmosphere of earth, the giant planets and comets. The 12- μm(˜720-850 cm-1) emission features of this molecule have been observed in spectra from outer solar system bodies of Jupiter, Saturn, Neptune and Titan. Because of their importance in remote sensing measurements, we recently recorded and analyzed a large number of laboratory infrared absorption spectra of pure and N2-broadened spectra of both these molecular bands. Spectra used in these analyses were recorded using either the Bruker IFS 125HR or the Bruker IFS 120HR FTS located at the Pacific Northwest National Laboratory (PNNL), in Richland Washington. To retrieve the various spectral line parameters, a multispectrum nonlinear least squares fitting algorithm was employed and all spectra belonging to each band were fitted simultaneously. Using this fitting technique, the same spectral regions from multiple spectra were fit all at once to maximize the accuracy of the retrieved parameters. The results obtained from present analyses are briefly discussed. In the case of C2H6 both room- and low temperature (˜210-296 K) spectra were recorded, but results from analyzing only room-temperature spectra will be discussed in this work.

  20. Banded electromagnetic stator core

    DOEpatents

    Fanning, Alan W.; Gonzales, Aaron A.; Patel, Mahadeo R.; Olich, Eugene E.

    1996-01-01

    A stator core for an electromagnetic pump includes a plurality of circumferentially adjoining groups of flat laminations disposed about a common centerline axis and collectively defining a central bore and a discontinuous outer perimeter, with adjacent groups diverging radially outwardly to form V-shaped gaps. An annular band surrounds the groups and is predeterminedly tensioned to clamp together the laminations, and has a predetermined flexibility in a radial direction to form substantially straight bridge sections between the adjacent groups.