WorldWideScience

Sample records for oxygen absorption band

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

    International Nuclear Information System (INIS)

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

    2013-01-01

    We study the variability of major atmospheric absorption features in the disk-integrated spectra of Earth with future application to Earth-analogs in mind, concentrating on the diurnal timescale. We first analyze observations of Earth provided by the EPOXI mission, and find 5%-20% fractional variation of the absorption depths of H 2 O and O 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 2 O and O 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 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.

  2. An Unusual Strong Visible-Light Absorption Band in Red Anatase TiO2 Photocatalyst Induced by Atomic Hydrogen-Occupied Oxygen Vacancies.

    Science.gov (United States)

    Yang, Yongqiang; Yin, Li-Chang; Gong, Yue; Niu, Ping; Wang, Jian-Qiang; Gu, Lin; Chen, Xingqiu; Liu, Gang; Wang, Lianzhou; Cheng, Hui-Ming

    2018-02-01

    Increasing visible light absorption of classic wide-bandgap photocatalysts like TiO 2 has long been pursued in order to promote solar energy conversion. Modulating the composition and/or stoichiometry of these photocatalysts is essential to narrow their bandgap for a strong visible-light absorption band. However, the bands obtained so far normally suffer from a low absorbance and/or narrow range. Herein, in contrast to the common tail-like absorption band in hydrogen-free oxygen-deficient TiO 2 , an unusual strong absorption band spanning the full spectrum of visible light is achieved in anatase TiO 2 by intentionally introducing atomic hydrogen-mediated oxygen vacancies. Combining experimental characterizations with theoretical calculations reveals the excitation of a new subvalence band associated with atomic hydrogen filled oxygen vacancies as the origin of such band, which subsequently leads to active photo-electrochemical water oxidation under visible light. These findings could provide a powerful way of tailoring wide-bandgap semiconductors to fully capture solar light. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Absorption band Q model for the earth

    International Nuclear Information System (INIS)

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

    1982-01-01

    Body wave, surface wave, and normal mode data are used to place constraints on the frequency dependence of Q in the mantle. With a simple absorption band model it is possible to satisfy the shear sensitive data over a broad frequency range. The quality factor Q/sub s/(ω) is proportional to ω/sup α/ in the band and to ω and ω -1 at higher and lower frequencies, respectively, as appropriate for a relaxation mechanism with a spectrum of relaxation time. The parameters of the band are Q(min) = 80, α = 0.15, and width, 5 decades. The center of the band varies from 10 1 seconds in the upper mantle, to 1.6 x 10 3 seconds in the lower mantle. The shift of the band with depth is consistent with the expected effects of temperature, pressure and stress. High Q, regions of the mantle are attributed to a shift of the absorption band to longer periods. To satisfy the gravest fundamental spheroidal modes and the ScS data, the absorption band must shift back into the short-period seismic band at the base of the mantle. This may be due to a high temperature gradient or high shear stresses. A preliminary attempt is also made to specify bulk dissipation in the mantle and core. Specific features of the absorption band model are low Q in the body wave 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 2 that increases with period, and low Q/sub p//Q/sub s/ at short periods in the middle mantel. The short-period Q/sub s/ increases rapidly at 400 km and is relatively constant from this depth to 2400 km. The deformational Q of the earth at a period of 14 months is predicted to be 463

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

    Energy Technology Data Exchange (ETDEWEB)

    Sevak Singh, Ram; Leong Chow, Wai [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Yingjie Tay, Roland [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Hon Tsang, Siu [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Mallick, Govind [Temasek Laboratories-NTU, 50 Nanyang Avenue, Singapore 639798 (Singapore); Weapons and Materials Research Directorate, U.S. Army Research Laboratory, Aberdeen Proving Ground, Maryland 21005 (United States); Tong Teo, Edwin Hang, E-mail: htteo@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)

    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.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

  6. Diode laser spectroscopy of oxygen electronic band at 760 nm

    International Nuclear Information System (INIS)

    Lucchesini, A.; De Rosa, M.; Gozzini, S.

    1998-01-01

    Collisional broadening and shift coefficients have been obtained by analyzing the line shapes of oxygen absorptions in the 760 nm electronic band. By using a diode laser spectrometer with commercially available etherostructure Al x Ga 1-x As diode lasers operating in 'free-running mode', line shape parameters have been collected at room temperature by varying the gas pressure. A systematic study has been carried on seven absorption lines by scanning the diode laser emission wavelength around the gas resonances. The weak absorption lines have been detected by using the wavelength modulation (WM) spectroscopy technique with second-harmonic detection

  7. Passive ranging using a filter-based non-imaging method based on oxygen absorption.

    Science.gov (United States)

    Yu, Hao; Liu, Bingqi; Yan, Zongqun; Zhang, Yu

    2017-10-01

    To solve the problem of poor real-time measurement caused by a hyperspectral imaging system and to simplify the design in passive ranging technology based on oxygen absorption spectrum, a filter-based non-imaging ranging method is proposed. In this method, three bandpass filters are used to obtain the source radiation intensities that are located in the oxygen absorption band near 762 nm and the band's left and right non-absorption shoulders, and a photomultiplier tube is used as the non-imaging sensor of the passive ranging system. Range is estimated by comparing the calculated values of band-average transmission due to oxygen absorption, τ O 2 , against the predicted curve of τ O 2 versus range. The method is tested under short-range conditions. Accuracy of 6.5% is achieved with the designed experimental ranging system at the range of 400 m.

  8. Glucose Absorption by the Bacillary Band of Trichuris muris.

    Directory of Open Access Journals (Sweden)

    Tina V A Hansen

    2016-09-01

    Full Text Available 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.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.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.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.

  9. Sub-band-gap absorption in Ga2O3

    Science.gov (United States)

    Peelaers, Hartwin; Van de Walle, Chris G.

    2017-10-01

    β-Ga2O3 is a transparent conducting oxide that, due to its large bandgap of 4.8 eV, exhibits transparency into the UV. However, the free carriers that enable the conductivity can absorb light. We study the effect of free carriers on the properties of Ga2O3 using hybrid density functional theory. The presence of free carriers leads to sub-band-gap absorption and a Burstein-Moss shift in the onset of absorption. We find that for a concentration of 1020 carriers, the Fermi level is located 0.23 eV above the conduction-band minimum. This leads to an increase in the electron effective mass from 0.27-0.28 me to 0.35-0.37 me and a sub-band-gap absorption band with a peak value of 0.6 × 103 cm-1 at 3.37 eV for light polarized along the x or z direction. Both across-the-gap and free-carrier absorption depend strongly on the polarization of the incoming light. We also provide parametrizations of the conduction-band shape and the effective mass as a function of the Fermi level.

  10. Airborne Lidar Measurements of Atmospheric Pressure Made Using the Oxygen A-Band

    Science.gov (United States)

    Riris, Haris; Rodriquez, Michael D.; Allan, Graham R.; Hasselbrack, William E.; Mao, Jianping; Stephen, Mark A.; Abshire, James B.

    2012-01-01

    Accurate measurements of greenhouse gas mixing ratios on a global scale are currently needed to gain a better understanding of climate change and its possible impact on our planet. In order to remotely measure greenhouse gas concentrations in the atmosphere with regard to dry air, the air number density in the atmosphere is also needed in deriving the greenhouse gas concentrations. Since oxygen is stable and uniformly mixed in the atmosphere at 20.95%, the measurement of an oxygen absorption in the atmosphere can be used to infer the dry air density and used to calculate the dry air mixing ratio of a greenhouse gas, such as carbon dioxide or methane. OUT technique of measuring Oxygen uses integrated path differential absorption (IPDA) with an Erbium Doped Fiber Amplifier (EDF A) laser system and single photon counting module (SPCM). It measures the absorbance of several on- and off-line wavelengths tuned to an O2 absorption line in the A-band at 764.7 nm. The choice of wavelengths allows us to maximize the pressure sensitivity using the trough between two absorptions in the Oxygen A-band. Our retrieval algorithm uses ancillary meteorological and aircraft altitude information to fit the experimentally obtained lidar O2 line shapes to a model atmosphere and derives the pressure from the profiles of the two lines. We have demonstrated O2 measurements from the ground and from an airborne platform. In this paper we will report on our airborne measurements during our 2011 campaign for the ASCENDS program.

  11. Detection of atomic oxygen in flames by absorption spectroscopy

    International Nuclear Information System (INIS)

    Cheskis, S.; Kovalenko, S.A.

    1994-01-01

    The absolute concentration of atomic oxygen in an atmospheric pressure hydrogen/air flame has been measured using Intracavity Laser Spectroscopy (ICLS) based on a dye laser pumped by an argon-ion laser. Absorptions at the highly forbidden transitions at 630.030 nm and 636.380 nm were observed at an equivalent optical length of up to 10 km. The relatively low intensity of the dye laser avoids photochemical interferences that are inherent to some other methods for detecting atomic oxygen. The detection sensitivity is about 6x10 14 atom/cm 3 and can be improved with better flame and laser stabilization. (orig.)

  12. Plasmonic Band-Pass Microfilters for LWIR Absorption Spectroscopy

    Directory of Open Access Journals (Sweden)

    J. M. Banks

    2012-01-01

    Full Text Available Absorption spectroscopy in the long wave infrared provides an effective method for identification of various hazardous chemicals. We present a theoretical design for plasmonic band-pass filters that can be used to provide wavelength selectivity for uncooled microbolometer sensors. The microfilters consist of a pair of input reflection gratings that couple light into a plasmonic waveguide with a central resonant waveguide cavity. An output transmission grating on the other side of the structure pulls light out of the waveguide where it is detected by a closely spaced sensor. Fabrication of the filters can be performed using standard photolithography procedures. A spectral bandpass with a full-width at half-maximum (FWHM of 100 nm can be obtained with a center wavelength spanning the entire 8–12 μm atmospheric transmission window by simple geometric scaling of only the lateral dimensions. This allows the simultaneous fabrication of all the wavelength filters needed for a full spectrometer on a chip.

  13. Atmospheric Airborne Pressure Measurements Using the Oxygen A Band for the ASCENDS Mission

    Science.gov (United States)

    Riris, Haris; Rodriguez, Mike; Stephen, Mark; Hasselbrack, William; Allan, Graham; Mao, Jiamping,; Kawa, Stephan R.; Weaver, Clark J.

    2011-01-01

    We report on airborne atmospheric pressure measurements using new fiber-based laser technology and the oxygen A-band at 765 nm. Remote measurements of atmospheric temperature and pressure are required for a number of NASA Earth science missions and specifically for the Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission. Accurate measurements of tropospheric CO2 on a global scale are very important in order to better understand its sources and sinks and to improve predictions on any future climate change. The ultimate goal of a CO2 remote sensing mission, such as ASCENDS, is to derive the CO2 concentration in the atmosphere in terms of mole fraction in unit of parts-per-million (ppmv) with regard to dry air. Therefore, both CO2 and the dry air number of molecules in the atmosphere are needed in deriving this quantity. O2 is a stable molecule and uniformly mixed in the atmosphere. Measuring the O2 absorption in the atmosphere can thus be used to infer the dry air number of molecules and then used to calculate CO2 concentration. With the knowledge of atmospheric water vapor, we can then estimate the total surface pressure needed for CO2 retrievals. Our work, funded by the ESTO IIP program, uses fiber optic technology and non-linear optics to generate 765 nm laser radiation coincident with the Oxygen A-band. Our pulsed, time gated technique uses several on- and off-line wavelengths tuned to the O2 absorption line. The choice of wavelengths allows us to measure the pressure by using two adjacent O2 absorptions in the Oxygen A-band. Our retrieval algorithm fits the O2 lineshapes and derives the pressure. Our measurements compare favorably with a local weather monitor mounted outside our laboratory and a local weather station.

  14. Studies on the red absorption band of chlorophyll a in vivo

    NARCIS (Netherlands)

    Thomas, J.B.; Kleinen Hammans, J.W.; Arnolds, W.J.

    1965-01-01

    It was studied whether certain earlier observed weak shoulders on the red absorption band of chlorophyll a in vivo might represent anomalies due to overlap of absorption bands. The results are suggested of the fact that no such anomalies occur. It is therefore concluded that the present study

  15. A Comprehensive X-Ray Absorption Model for Atomic Oxygen

    Science.gov (United States)

    Gorczyca, T. W.; Bautista, M. A.; Hasoglu, M. F.; Garcia, J.; Gatuzz, E.; Kaastra, J. S.; Kallman, T. R.; Manson, S. T.; Mendoza, C.; Raassen, A. J. J.; hide

    2013-01-01

    An analytical formula is developed to accurately represent the photoabsorption cross section of atomic Oxygen for all energies of interest in X-ray spectral modeling. In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects, that accurately predict the absorption oscillator strengths below threshold and merge consistently and continuously to the above-threshold cross section. Further, minor adjustments are made to the threshold energies in order to reliably align the atomic Rydberg resonances after consideration of both experimental and observed line positions. At energies far below or above the K-edge region, the formulation is based on both outer- and inner-shell direct photoionization, including significant shake-up and shake-off processes that result in photoionization-excitation and double-photoionization contributions to the total cross section. The ultimate purpose for developing a definitive model for oxygen absorption is to resolve standing discrepancies between the astronomically observed and laboratory-measured line positions, and between the inferred atomic and molecular oxygen abundances in the interstellar medium from XSTAR and SPEX spectral models.

  16. Glucose Absorption by the Bacillary Band of Trichuris muris

    DEFF Research Database (Denmark)

    Hansen, Tina Vicky Alstrup; Hansen, Michael; Nejsum, Peter

    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 Trich......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...

  17. Cloud Height Retrieval with Oxygen A and B Bands for the Deep Space Climate Observatory (DSCOVR) Mission

    Science.gov (United States)

    Yang, Yuekui; Marshak, Alexander; Mao, Jianping; Lyapustin, Alexei; Herman, Jay

    2012-01-01

    Planned to fly in 2014, the Deep Space Climate Observatory (DSCOVR) would see the whole sunlit half of the Earth from the L 1 Lagrangian point and would provide simultaneous data on cloud and aerosol properties with its Earth Polychromatic Imaging Camera (EPIC). EPIC images the Earth on a 2Kx2K CCD array, which gives a horizontal resolution of about 10 km at nadir. A filter-wheel provides consecutive images in 10 spectral channels ranging from the UV to the near-IR, including the oxygen A and B bands. This paper presents a study of retrieving cloud height with EPIC's oxygen A and B bands. As the first step, we analyzed the effect of cloud optical and geometrical properties, sun-view geometry, and surface type on the cloud height determination. Second, we developed two cloud height retrieval algorithms that are based on the Mixed Lambertian-Equivalent Reflectivity (MLER) concept: one utilizes the absolute radiances at the Oxygen A and B bands and the other uses the radiance ratios between the absorption and reference channels of the two bands. Third, we applied the algorithms to the simulated EPIC data and to the data from SCanning Imaging Absorption SpectroMeter for Atmospheric CartograpHY (SCIAMACHY) observations. Results show that oxygen A and B bands complement each other: A band is better suited for retrievals over ocean, while B band is better over vegetated land due to a much darker surface. Improvements to the MLER model, including corrections to surface contribution and photon path inside clouds, will also be discussed.

  18. Molecular design for improved photovoltaic efficiency: band gap and absorption coefficient engineering

    KAUST Repository

    Mondal, Rajib; Ko, Sangwon; Norton, Joseph E.; Miyaki, Nobuyuki; Becerril, Hector A.; Verploegen, Eric; Toney, Michael F.; Bré das, Jean-Luc; McGehee, Michael D.; Bao, Zhenan

    2009-01-01

    Removing the adjacent thiophene groups around the acceptor core in low band gap polymers significantly enhances solar cell efficiency through increasing the optical absorption and raising the ionization potential of the polymer. © 2009 The Royal Society of Chemistry.

  19. Band gap of corundumlike α -Ga2O3 determined by absorption and ellipsometry

    Science.gov (United States)

    Segura, A.; Artús, L.; Cuscó, R.; Goldhahn, R.; Feneberg, M.

    2017-07-01

    The electronic structure near the band gap of the corundumlike α phase of Ga2O3 has been investigated by means of optical absorption and spectroscopic ellipsometry measurements in the ultraviolet (UV) range (400-190 nm). The absorption coefficient in the UV region and the imaginary part of the dielectric function exhibit two prominent absorption thresholds with wide but well-defined structures at 5.6 and 6.3 eV which have been ascribed to allowed direct transitions from crystal-field split valence bands to the conduction band. Excitonic effects with large Gaussian broadening are taken into account through the Elliott-Toyozawa model, which yields an exciton binding energy of 110 meV and direct band gaps of 5.61 and 6.44 eV. The large broadening of the absorption onset is related to the slightly indirect character of the material.

  20. Oxygen production by molten alkali metal salts using multiple absorption-desorption cycles

    Science.gov (United States)

    Cassano, Anthony A.

    1985-01-01

    A continuous chemical air separation is performed wherein oxygen is recovered with a molten alkali metal salt oxygen acceptor in a series of absorption zones which are connected to a plurality of desorption zones operated in separate parallel cycles with the absorption zones. A greater recovery of high pressure oxygen is achieved at reduced power requirements and capital costs.

  1. Oxygen production by molten alkali metal salts using multiple absorption-desorption cycles

    Science.gov (United States)

    Cassano, A.A.

    1985-07-02

    A continuous chemical air separation is performed wherein oxygen is recovered with a molten alkali metal salt oxygen acceptor in a series of absorption zones which are connected to a plurality of desorption zones operated in separate parallel cycles with the absorption zones. A greater recovery of high pressure oxygen is achieved at reduced power requirements and capital costs. 3 figs.

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

    Science.gov (United States)

    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.

  3. Linewidth of Cyclotron Absorption in Band-Gap Graphene: Relaxation Time Approximation vs. Monte Carlo Method

    OpenAIRE

    S.V. Kryuchkov; E.I. Kukhar’; D.V. Zav’yalov

    2015-01-01

    The power of the elliptically polarized electromagnetic radiation absorbed by band-gap graphene in presence of constant magnetic field is calculated. The linewidth of cyclotron absorption is shown to be non-zero even if the scattering is absent. The calculations are performed analytically with the Boltzmann kinetic equation and confirmed numerically with the Monte Carlo method. The dependence of the linewidth of the cyclotron absorption on temperature applicable for a band-gap graphene in the...

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

    International Nuclear Information System (INIS)

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

    2009-01-01

    Correlation between the 3.1 eV emission band and local atomic configuration was systematically examined for Ge + implanted silica glass by UV-vis optical absorption spectroscopy and X-ray absorption fine structure (XAFS) analysis. The 2.7 eV emission band, commonly observed in defective silica, was replaced by the sharp and intense 3.1 eV emission band for the Ge + fluence > 2 x 10 16 cm -2 , in which UV-vis absorption spectra suggested clustering of Ge atoms with the size ∼1 nm. XAFS spectroscopy indicated that the Ge atoms were under coordinated with oxygen atoms nearly at a neutral valence state on average. The present results are consistent with the previous ESR study but imply that the small Ge clusters rather than the O=Ge: complexes (point defects) are responsible for the 3.1 eV emission band.

  5. Lifetime enhancement for multiphoton absorption in intermediate band solar cells

    International Nuclear Information System (INIS)

    Bezerra, Anibal T; Studart, Nelson

    2017-01-01

    A semiconductor structure consisting of two coupled quantum wells embedded into the intrinsic region of a p – i–n junction is proposed as an intermediate band solar cell with a photon ratchet state, which would lead to increasing the cell efficiency. The conduction subband of the right-hand side quantum well works as the intermediated band, whereas the excited conduction subband of the left-hand side quantum well operates as the ratchet state. The photoelectrons in the intermediate band are scattered through the thin wells barrier and accumulated into the ratchet subband. A rate equation model for describing the charge transport properties is presented. The efficiency of the current generation is analyzed by studying the occupation of the wells subbands, taking into account the charge dynamic behavior provided by the electrical contacts connected to the cell. The current generation efficiency depends essentially from the relations between the generation, recombination rates and the scattering rate to the ratchet state. The inclusion of the ratchet states led to both an increase and a decrease in the cell current depending on the transition rates. This suggests that the coupling between the intermediate band and the ratchet state is a key point in developing an efficient solar cell. (paper)

  6. Lifetime enhancement for multiphoton absorption in intermediate band solar cells

    Science.gov (United States)

    Bezerra, Anibal T.; Studart, Nelson

    2017-08-01

    A semiconductor structure consisting of two coupled quantum wells embedded into the intrinsic region of a p-i-n junction is proposed as an intermediate band solar cell with a photon ratchet state, which would lead to increasing the cell efficiency. The conduction subband of the right-hand side quantum well works as the intermediated band, whereas the excited conduction subband of the left-hand side quantum well operates as the ratchet state. The photoelectrons in the intermediate band are scattered through the thin wells barrier and accumulated into the ratchet subband. A rate equation model for describing the charge transport properties is presented. The efficiency of the current generation is analyzed by studying the occupation of the wells subbands, taking into account the charge dynamic behavior provided by the electrical contacts connected to the cell. The current generation efficiency depends essentially from the relations between the generation, recombination rates and the scattering rate to the ratchet state. The inclusion of the ratchet states led to both an increase and a decrease in the cell current depending on the transition rates. This suggests that the coupling between the intermediate band and the ratchet state is a key point in developing an efficient solar cell.

  7. Theory of two-photon absorption by exciton states in cubic semiconductors with degenerate valence bands

    International Nuclear Information System (INIS)

    Nguyen Ai Viet; Nguyen Toan Thang.

    1987-06-01

    The coefficient of the absorption of two polarized photons is calculated for direct band gap semiconductors with degenerate valence bands. Wannier-Mott exciton states are included in both the intermediate and final states. Numerical calculations are performed for ZnSe and are compared with Sondergeld's experimental and theoretical results. (author). 11 refs, 2 tabs

  8. Optical Absorptions of Oxygenated Carbon Chain Cations in the Gas Phase

    Science.gov (United States)

    Hardy, F.-X.; Rice, C. A.; Chakraborty, A.; Fulara, J.; Maier, J. P.

    2016-06-01

    The gas-phase electronic spectra of linear OC4O+ and a planar C6H2O+ isomer were obtained at a rotational temperature of ≈10 K. Absorption measurements in a 6 K neon matrix were followed by gas-phase observations in a cryogenic radiofrequency ion trap. The origin bands of the 1{}2{{{\\Pi }}}u ≤ftarrow X{}2{{{\\Pi }}}g transition of OC4O+ and the 1{}2A{}2 ≤ftarrow X{}2B1 of HCCC(CO)CCH+ lie at 417.31 ± 0.01 nm and 523.49 ± 0.01 nm, respectively. These constitute the first electronic spectra of oxygenated carbon chain cations studied under conditions that are relevant to the diffuse interstellar bands (DIBs), as both have a visible transition. The recent analysis of the 579.5 nm DIB indicates that small carriers, five to seven heavy atoms, continue to be possible candidates (Huang & Oka 2015). Astronomical implications are discussed regarding this kind of oxygenated molecules.

  9. Fine-Structure Measurements of Oxygen A Band Absorbance for Estimating the Thermodynamic Average Temperature of the Earth's Atmosphere: An Experiment in Physical and Environmental Chemistry

    Science.gov (United States)

    Myrick, M. L.; Greer, A. E.; Nieuwland, A.; Priore, R. J.; Scaffidi, J.; Andreatta, Daniele; Colavita, Paula

    2006-01-01

    The experiment describe the measures of the A band transitions of atmospheric oxygen, a rich series of rotation-electronic absorption lines falling in the deep red portion of the optical spectrum and clearly visible owing to attenuation of solar radiation. It combines pure physical chemistry with analytical and environmental science and provides a…

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

    Science.gov (United States)

    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.

  11. Photolysis mechanism of aqueous tyrosine upon excitation of the second absorption band

    International Nuclear Information System (INIS)

    Shimizu, O.

    1984-01-01

    The formation mechanism of tyrosinyl radical was studied for aqueous solutions of tyrosine under irradiation at 235 nm which falls into the second absorption band. The work is based upon the analysis of the rate of bityrosine production for steady-state excitation at low intensity. The results indicate that monophotonic O-H bond cleavage of tyrosine, presumably involving the upper excited triplet state, is the initial photoprocess leading to the tyrosinyl radical when tyrosine is excited into the second absorption band. (author)

  12. Robust indirect band gap and anisotropy of optical absorption in B-doped phosphorene.

    Science.gov (United States)

    Wu, Zhi-Feng; Gao, Peng-Fei; Guo, Lei; Kang, Jun; Fang, Dang-Qi; Zhang, Yang; Xia, Ming-Gang; Zhang, Sheng-Li; Wen, Yu-Hua

    2017-12-06

    A traditional doping technique plays an important role in the band structure engineering of two-dimensional nanostructures. Since electron interaction is changed by doping, the optical and electrochemical properties could also be significantly tuned. In this study, density functional theory calculations have been employed to explore the structural stability, and electronic and optical properties of B-doped phosphorene. The results show that all B-doped phosphorenes are stable with a relatively low binding energy. Of particular interest is that these B-doped systems exhibit an indirect band gap, which is distinct from the direct one of pure phosphorene. Despite the different concentrations and configurations of B dopants, such indirect band gaps are robust. The screened hybrid density functional HSE06 predicts that the band gap of B-doped phosphorene is slightly smaller than that of pure phosphorene. Spatial charge distributions at the valence band maximum (VBM) and the conduction band minimum (CBM) are analyzed to understand the features of an indirect band gap. By comparison with pure phosphorene, B-doped phosphorenes exhibit strong anisotropy and intensity of optical absorption. Moreover, B dopants could enhance the stability of Li adsorption on phosphorene with less sacrifice of the Li diffusion rate. Our results suggest that B-doping is an effective way of tuning the band gap, enhancing the intensity of optical absorption and improving the performances of Li adsorption, which could promote potential applications in novel optical devices and lithium-ion batteries.

  13. Band gap engineering of tandem structured CIGS compound absorption layer fabricated by sputtering and selenization

    Energy Technology Data Exchange (ETDEWEB)

    Kang, San; Sharma, Rahul; Sim, Jae-Kwan [Semiconductor Materials Processing Laboratory, School of Advanced Materials Engineering, College of Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Deokjin-dong 664-14, Jeonju 561-756 (Korea, Republic of); Lee, Cheul-Ro, E-mail: crlee7@jbnu.ac.kr [Semiconductor Materials Processing Laboratory, School of Advanced Materials Engineering, College of Engineering, Research Center for Advanced Materials Development (RCAMD), Chonbuk National University, Deokjin-dong 664-14, Jeonju 561-756 (Korea, Republic of)

    2013-06-25

    Highlights: ► Systematic band gap engineering to fabricate tandem Cu(In,Ga)Se{sub 2} absorption layers. ► XRD shows prominent (1 1 2) reflection shift for attributed CIS, CIGS, and CGS phases. ► Optical transmittance and reflectance spectrum are improved towards infrared region. ► The Cu/In + Ga and Ga/In + Ga effect is matched with highest efficient solar cell. ► Tandem CIS/CIGS/CGS layer, the band gap is increased from 1.15 to 2.06 eV. -- Abstract: Band gap engineering was executed to fabricate a multi-junction stacked i.e. tandem Cu(In,Ga)Se{sub 2} (CIGS) absorption layer. The CIGS absorption layers consist of multi-junction stacked CIS/CIGS/CGS thin films from bottom to top with increasing band gap. Tandem CIGS layers were fabricated by using three precursor of CuIn, In/CuGa/In, and CuGa onto the Mo coated soda-lime glass (SLG) by the sequential sputtering of CuIn, CuGa, and In targets. The CIG precursors were converted into CIGS absorption thin film by selenization process. From the X-ray diffraction (XRD) pattern of CIS/CIGS/CGS tandem layer, with the prominent peak shift for (1 1 2) reflections was attributed to the individual CIS, CIGS, and CGS phases at 26.76°, 27.15°, and 27.65° diffraction angles, respectively. The morphologies and atomic (at%) composition uniformity onto the surface and along the depth were extensively analyzed with field effect scanning electron microscope (FESEM) attached energy dispersive spectroscopy (EDS) and secondary ion mass spectroscopy (SIMS). The optical properties such as transmittance, reflectance and absorbance were found to improve in the infrared region for all the tandem CIGS layers. Near the fundamental absorption edge, the absorption coefficient was approached to 10{sup 5} cm{sup −1} for CIS/CIGS/CGS tandem layer. The straight-line behavior indicates that the films have a direct band gap. The band gap was found to increase from 1.15 to 1.74 eV with the Ga-grading along the depth of individual CIS, CIGS

  14. Band gap engineering of tandem structured CIGS compound absorption layer fabricated by sputtering and selenization

    International Nuclear Information System (INIS)

    Kang, San; Sharma, Rahul; Sim, Jae-Kwan; Lee, Cheul-Ro

    2013-01-01

    Highlights: ► Systematic band gap engineering to fabricate tandem Cu(In,Ga)Se 2 absorption layers. ► XRD shows prominent (1 1 2) reflection shift for attributed CIS, CIGS, and CGS phases. ► Optical transmittance and reflectance spectrum are improved towards infrared region. ► The Cu/In + Ga and Ga/In + Ga effect is matched with highest efficient solar cell. ► Tandem CIS/CIGS/CGS layer, the band gap is increased from 1.15 to 2.06 eV. -- Abstract: Band gap engineering was executed to fabricate a multi-junction stacked i.e. tandem Cu(In,Ga)Se 2 (CIGS) absorption layer. The CIGS absorption layers consist of multi-junction stacked CIS/CIGS/CGS thin films from bottom to top with increasing band gap. Tandem CIGS layers were fabricated by using three precursor of CuIn, In/CuGa/In, and CuGa onto the Mo coated soda-lime glass (SLG) by the sequential sputtering of CuIn, CuGa, and In targets. The CIG precursors were converted into CIGS absorption thin film by selenization process. From the X-ray diffraction (XRD) pattern of CIS/CIGS/CGS tandem layer, with the prominent peak shift for (1 1 2) reflections was attributed to the individual CIS, CIGS, and CGS phases at 26.76°, 27.15°, and 27.65° diffraction angles, respectively. The morphologies and atomic (at%) composition uniformity onto the surface and along the depth were extensively analyzed with field effect scanning electron microscope (FESEM) attached energy dispersive spectroscopy (EDS) and secondary ion mass spectroscopy (SIMS). The optical properties such as transmittance, reflectance and absorbance were found to improve in the infrared region for all the tandem CIGS layers. Near the fundamental absorption edge, the absorption coefficient was approached to 10 5 cm −1 for CIS/CIGS/CGS tandem layer. The straight-line behavior indicates that the films have a direct band gap. The band gap was found to increase from 1.15 to 1.74 eV with the Ga-grading along the depth of individual CIS, CIGS, and CGS thin films

  15. Band shape of IR-absorption of complex molecules and restricted rotational diffusion

    International Nuclear Information System (INIS)

    Ivanov, E.N.; Umidulaev, Sh.U.

    1989-01-01

    The development of the theory of band shape (and Breadth) IR-absorption of complex molecules (regarding the molecules inside motions) is considered. It is supposed that a molecule fragment being responsible for IR-absorption takes part in the restricted rotational diffusion (RRD) with respect to the frame, and the molecule itself in general makes rotational motion (RM). Both kinds of motions are discussed in accordance with the theory of group motions representations. On the basis of correlative functions calculations of dipole moment a simple expression for the IR-absorption band shape have been obtained, which in itself uses to be the super position of two Lorencians with the semibreadths 2D 1 and 2D 1 +ν 2 0 (ν 2 0 +1D R accordingly (here D 1 is the coefficient of RM, D 2 is the coefficient of RRD, ν 2 0 is the well known function of RRD-cone divergence angle) in case of symmetric rotary abrasive disc. Analysis of experimental band shape of IR-absorption on the basis of the expression obtained allows to get information of MR-molecule parameters in general and RRD. It is really possible to determine the RRD-cone divergency angle from experimental weights of Lorencians. In accordance with experimental semibreadths the coefficient of RM D 1 and the coefficient of RRD D 2 are obtained. In conclusion it is noted that D 1 →0 (in the expression for the band shape of IR-absorption obtained), one of the Lorencians turns to the δ-function and finally there is an expression which describes IR-absorption band shape of molecules in polymer-mats. (author)

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

    Science.gov (United States)

    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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Heera, Pawan, E-mail: sramanb70@mailcity.com [Department of Physics, Himachal Pradesh University, Shimla, INDIA, 171005 (India); Govt. College Amb, Himachal Pradesh, INDIA,177203 (India); Kumar, Anup, E-mail: kumar.anup.sml@gmail.com [Department of Physics, Himachal Pradesh University, Shimla, INDIA, 171005 (India); Physics Department, Govt. College, Kullu, H. P., INDIA, 175101 (India); Sharma, Raman, E-mail: pawanheera@yahoo.com [Department of Physics, Himachal Pradesh University, Shimla, INDIA, 171005 (India)

    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.

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

    International Nuclear Information System (INIS)

    Ding Chunling; Li Jiahua; Yang Xiaoxue

    2011-01-01

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

  19. Sub-band-gap absorption of Cu(In,Ga)Se{sub 2} thin film semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Meessen, Max; Brueggemann, Rudolf; Bauer, Gottfried H. [Carl von Ossietzky University Oldenburg (Germany)

    2012-07-01

    The sub-band-gap absorption of Cu(In,Ga)Se{sub 2} thin films has been studied by photothermal deflection spectroscopy (PDS) in conjunction with optical transmittance spectroscopy. The resulting absorption coefficients are compared to those calculated from photoluminescence spectra using Planck's generalized law. Quantities related to the absorption like Urbach energy and defect densities are derived from the absorption curves. This concept has been applied to a series of bromine-methanol etched Cu(In{sub x-1},Ga{sub x})Se{sub 2} (x=0.3) absorbers with varying thicknesses. A shift in the band gap is observed with both methods and can be related to the gallium gradient in the samples. In contrast, the Urbach energy and defect absorption values are not substantially affected by the etching process. The influence of CdS buffer layers or highly thermally conductive metallic back contacts on PDS results is studied by measuring nominally identical samples with and without those layers.

  20. Pressure broadening of atomic oxygen two-photon absorption laser induced fluorescence

    NARCIS (Netherlands)

    Marinov, D.; Drag, C.; Blondel, C.; Guaitella, O.; Golda, J.; Klarenaar, B.L.M.; Engeln, R.A.H.; Schulz-von der Gathen, V.; Booth, J.-P.

    2016-01-01

    Atomic oxygen, considered to be a determining reactant in plasma applications at ambient pressure, is routinely detected by two-photon absorption laser induced fluorescence (TALIF). Here, pressure broadening of the (2p 4 3 P 2  →  3p 3 P J=0,1,2) two-photon transition in oxygen atoms was

  1. Determination of the Rb atomic number density in dense rubidium vapors by absorption measurements of Rb2 triplet bands

    International Nuclear Information System (INIS)

    Horvatic, Vlasta; Veza, Damir; Niemax, Kay; Vadla, Cedomil

    2008-01-01

    A simple and accurate way of determining atom number densities in dense rubidium vapors is presented. The method relies on the experimental finding that the reduced absorption coefficients of the Rb triplet satellite bands between 740 nm and 750 nm and the triplet diffuse band between 600 nm and 610 nm are not temperature dependent in the range between 600 K and 800 K. Therefore, the absolute values of the reduced absorption coefficients of these molecular bands can provide accurate information about atomic number density of the vapor. The rubidium absorption spectrum was measured by spatially resolved white-light absorption in overheated rubidium vapor generated in a heat pipe oven. The absolute values for the reduced absorption coefficients of the triplet bands were determined at lower vapor densities, by using an accurate expression for the reduced absorption coefficient in the quasistatic wing of the Rb D1 line, and measured triplet satellite bands to the resonance wing optical depth ratio. These triplet satellite band data were used to calibrate in absolute scale the reduced absorption coefficients of the triplet diffuse band at higher temperatures. The obtained values for the reduced absorption coefficient of these Rb molecular features can be used for accurate determination of rubidium atomic number densities in the range from about 5 x 10 16 cm -3 to 1 x 10 18 cm -3

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

    Energy Technology Data Exchange (ETDEWEB)

    Takir, D.; Reddy, V.; Sanchez, J. A.; Corre, L. Le [Planetary Science Institute, 1700 E Fort Lowell Road, Suite 106, Tucson, AZ 85719 (United States); Hardersen, P. S. [Department of Space Studies, University of North Dakota, Grand Forks, ND 58202 (United States); Nathues, A., E-mail: dtakir@psi.edu [Max-Planck-Institute for Solar System Research, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    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

  4. Attempt at interpreting some optical absorption bands in X-ray irradiated fluorine

    International Nuclear Information System (INIS)

    Allain, Yves

    1959-01-01

    According to the results of one of our experiments, the 575 mμ absorption band of fluorine irradiated with X-Rays seams due to F - ion vacancies. Our goal has been to find a color centers model in fluorine colored in various conditions. Reprint of a paper published in Comptes rendus des seances de l'Academie des Sciences, t. 248, p. 2318-2320, sitting of Aril 20, 1959 [fr

  5. Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

    Directory of Open Access Journals (Sweden)

    O. Funk

    2003-03-01

    Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements. Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

  6. Photon path length distributions for cloudy skies – oxygen A-Band measurements and model calculations

    Directory of Open Access Journals (Sweden)

    O. Funk

    Full Text Available This paper addresses the statistics underlying cloudy sky radiative transfer (RT by inspection of the distribution of the path lengths of solar photons. Recent studies indicate that this approach is promising, since it might reveal characteristics about the diffusion process underlying atmospheric radiative transfer (Pfeilsticker, 1999. Moreover, it uses an observable that is directly related to the atmospheric absorption and, therefore, of climatic relevance. However, these studies are based largely on the accuracy of the measurement of the photon path length distribution (PPD. This paper presents a refined analysis method based on high resolution spectroscopy of the oxygen A-band. The method is validated by Monte Carlo simulation atmospheric spectra. Additionally, a new method to measure the effective optical thickness of cloud layers, based on fitting the measured differential transmissions with a 1-dimensional (discrete ordinate RT model, is presented. These methods are applied to measurements conducted during the cloud radar inter-comparison campaign CLARE’98, which supplied detailed cloud structure information, required for the further analysis. For some exemplary cases, measured path length distributions and optical thicknesses are presented and backed by detailed RT model calculations. For all cases, reasonable PPDs can be retrieved and the effects of the vertical cloud structure are found. The inferred cloud optical thicknesses are in agreement with liquid water path measurements.

    Key words. Meteorology and atmospheric dynamics (radiative processes; instruments and techniques

  7. Point-Defect Nature of the Ultraviolet Absorption Band in AlN

    Science.gov (United States)

    Alden, D.; Harris, J. S.; Bryan, Z.; Baker, J. N.; Reddy, P.; Mita, S.; Callsen, G.; Hoffmann, A.; Irving, D. L.; Collazo, R.; Sitar, Z.

    2018-05-01

    We present an approach where point defects and defect complexes are identified using power-dependent photoluminescence excitation spectroscopy, impurity data from SIMS, and density-functional-theory (DFT)-based calculations accounting for the total charge balance in the crystal. Employing the capabilities of such an experimental computational approach, in this work, the ultraviolet-C absorption band at 4.7 eV, as well as the 2.7- and 3.9-eV luminescence bands in AlN single crystals grown via physical vapor transport (PVT) are studied in detail. Photoluminescence excitation spectroscopy measurements demonstrate the relationship between the defect luminescent bands centered at 3.9 and 2.7 eV to the commonly observed absorption band centered at 4.7 eV. Accordingly, the thermodynamic transition energy for the absorption band at 4.7 eV and the luminescence band at 3.9 eV is estimated at 4.2 eV, in agreement with the thermodynamic transition energy for the CN- point defect. Finally, the 2.7-eV PL band is the result of a donor-acceptor pair transition between the VN and CN point defects since nitrogen vacancies are predicted to be present in the crystal in concentrations similar to carbon-employing charge-balance-constrained DFT calculations. Power-dependent photoluminescence measurements reveal the presence of the deep donor state with a thermodynamic transition energy of 5.0 eV, which we hypothesize to be nitrogen vacancies in agreement with predictions based on theory. The charge state, concentration, and type of impurities in the crystal are calculated considering a fixed amount of impurities and using a DFT-based defect solver, which considers their respective formation energies and the total charge balance in the crystal. The presented results show that nitrogen vacancies are the most likely candidate for the deep donor state involved in the donor-acceptor pair transition with peak emission at 2.7 eV for the conditions relevant to PVT growth.

  8. Damping effect of the inner band electrons on the optical absorption and bandwidth of metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ochoo, Lawrence, E-mail: lawijapuonj@yahoo.com; Migwi, Charles; Okumu, John [Kenyatta University, Physics Department (Kenya)

    2012-12-15

    Conflicts and discrepancies around nanoparticle (NP) size effect on the optical properties of metal NPs of sizes below the mean free path of electron can be traced to the internal damping effect of the hybrid resonance of the inner band (IB) and the conduction band (CB) electrons of the noble metals. We present a scheme to show how alternative mathematical formulation of the physics of interaction between the CB and the IB electrons of NP sizes <50 nm justifies this and resolves the conflicts. While a number of controversies exist between classical and quantum theories over the phenomenological factors to attribute to the NP size effect on the absorption bandwidth, this article shows that the bandwidth behavior can be well predicted from a different treatment of the IB damping effect, without invoking any of the controversial phenomenological factors. It finds that the IB damping effect is mainly frequency dependent and only partly size dependent and shows how its influence on the surface plasmon resonance can be modeled to show the influence of NP size on the absorption properties. Through the model, it is revealed that strong coupling of IB and CB electrons drastically alters the absorption spectra, splitting it into distinctive dipole and quadrupole modes and even introduce a behavioral switch. It finds a strong overlap between the IB and the CB absorptions for Au and Cu but not Ag, which is sensitive to the NP environment. The CB modes shift with the changing refractive index of the medium in a way that can allow their independent excitation, free of influence of the IB electrons. Through a hybrid of parameters, the model further finds that metal NP sizes can be established not only by their spectral absorption peak locations but also from a proper correlation of the peak location and the bandwidth (FWHM).

  9. Optical band-edge absorption of oxide compound SnO2

    International Nuclear Information System (INIS)

    Roman, L.S.; Valaski, R.; Canestraro, C.D.; Magalhaes, E.C.S.; Persson, C.; Ahuja, R.; Silva, E.F. da; Pepe, I.; Silva, A. Ferreira da

    2006-01-01

    Tin oxide (SnO 2 ) is an important oxide for efficient dielectrics, catalysis, sensor devices, electrodes and transparent conducting coating oxide technologies. SnO 2 thin film is widely used in glass applications due to its low infra-red heat emissivity. In this work, the SnO 2 electronic band-edge structure and optical properties are studied employing a first-principle and fully relativistic full-potential linearized augmented plane wave (FPLAPW) method within the local density approximation (LDA). The optical band-edge absorption α(ω) of intrinsic SnO 2 is investigated experimentally by transmission spectroscopy measurements and their roughness in the light of the atomic force microscopy (AFM) measurements. The sample films were prepared by spray pyrolysis deposition method onto glass substrate considering different thickness layers. We found for SnO 2 qualitatively good agreement of the calculated optical band-gap energy as well as the optical absorption with the experimental results

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

    International Nuclear Information System (INIS)

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

    2014-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Jagdish; Rani, Mamta [Department of Physics, Panjab University, Chandigarh- 160014 (India); Tripathi, S. K., E-mail: surya@pu.ac.in [Centre of Advanced Study in Physics, Panjab University, Chandigarh- 160014 (India)

    2014-04-24

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

  12. A Unifying Perspective on Oxygen Vacancies in Wide Band Gap Oxides.

    Science.gov (United States)

    Linderälv, Christopher; Lindman, Anders; Erhart, Paul

    2018-01-04

    Wide band gap oxides are versatile materials with numerous applications in research and technology. Many properties of these materials are intimately related to defects, with the most important defect being the oxygen vacancy. Here, using electronic structure calculations, we show that the charge transition level (CTL) and eigenstates associated with oxygen vacancies, which to a large extent determine their electronic properties, are confined to a rather narrow energy range, even while band gap and the electronic structure of the conduction band vary substantially. Vacancies are classified according to their character (deep versus shallow), which shows that the alignment of electronic eigenenergies and CTL can be understood in terms of the transition between cavity-like localized levels in the large band gap limit and strong coupling between conduction band and vacancy states for small to medium band gaps. We consider both conventional and hybrid functionals and demonstrate that the former yields results in very good agreement with the latter provided that band edge alignment is taken into account.

  13. Band gap opening and optical absorption enhancement in graphene using ZnO nanocluster

    Science.gov (United States)

    Monshi, M. M.; Aghaei, S. M.; Calizo, I.

    2018-05-01

    Electronic, optical and transport properties of the graphene/ZnO heterostructure have been explored using first-principles density functional theory. The results show that Zn12O12 can open a band gap of 14.5 meV in graphene, increase its optical absorption by 1.67 times covering the visible spectrum which extends to the infra-red (IR) range, and exhibits a slight non-linear I-V characteristic depending on the applied bias. These findings envisage that a graphene/Zn12O12 heterostructure can be appropriate for energy harvesting, photodetection, and photochemical devices.

  14. Water vapor measurements in the 0.94 micron absorption band - Calibration, measurements and data applications

    Science.gov (United States)

    Reagan, J. A.; Thome, K.; Herman, B.; Gall, R.

    1987-01-01

    This paper describes methods and presents results for sensing the columnar content of atmospheric water vapor via differential solar transmission measurements in and adjacent to the 0.94-micron water-vapor absorption band. Calibration and measurement techniques are presented for obtaining the water vapor transmission from the radiometer measurements. Models are also presented for retrieving the columnar water vapor amount from the estimated transmission. Example retrievals are presented for radiometer measurements made during the 1986 Arizona Monsoon Season to track temporal variations in columnar water vapor amount.

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

    Science.gov (United States)

    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 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 function f(r infinity) and logarithmic Kubelka-Munk function log[f(r infinity)] of the carotene absorption bands at 480 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 59.5% (p < 0.05), 73% (p < 0

  16. Electronic absorption bands of HoCl3 and SmCl3 complexes in alcohols

    International Nuclear Information System (INIS)

    Ramesh Babu, V.; Buddhudu, S.; Rangarajan, V.N.

    1987-01-01

    The normal absorption and second derivative spectra of ten alcoholic complexes of HoCl 3 and SmCl 3 were recorded. From the observed bands, energies and intensity values were measured. To fit in these measured values with the theoretical values, a set of spectroscopic parameters namely, Judd-Ofelt (T 2 , T 4 , T 6 ), intensity (Ω 2 , Ω 4 , Ω 6 ) had been computed. A good fit of intensities was obtained between the experimental and theoretical data. The environmental influences on the intensities of the hypersensitive transitions of Sm(III) and Ho(III) ions were found to be noteworthy. (author). 7 tables, 20 refs

  17. Physical properties and band structure of reactive molecular beam epitaxy grown oxygen engineered HfO{sub 2{+-}x}

    Energy Technology Data Exchange (ETDEWEB)

    Hildebrandt, Erwin; Kurian, Jose; Alff, Lambert [Institute of Materials Science, Technische Universitaet Darmstadt, 64287 Darmstadt (Germany)

    2012-12-01

    We have conducted a detailed thin film growth structure of oxygen engineered monoclinic HfO{sub 2{+-}x} grown by reactive molecular beam epitaxy. The oxidation conditions induce a switching between (111) and (002) texture of hafnium oxide. The band gap of oxygen deficient hafnia decreases with increasing amount of oxygen vacancies by more than 1 eV. For high oxygen vacancy concentrations, defect bands form inside the band gap that induce optical transitions and p-type conductivity. The resistivity changes by several orders of magnitude as a function of oxidation conditions. Oxygen vacancies do not give rise to ferromagnetic behavior.

  18. Influence of flavour absorption on oxygen permentation through LDPE, PP, PC and PET plastics food packaging

    NARCIS (Netherlands)

    Willige, van R.W.G.; Linssen, J.P.H.; Meinders, M.B.J.; Stege, van der H.J.; Voragen, A.G.J.

    2002-01-01

    The effect of flavour absorption on the oxygen permeability of low-density polyethylene (LDPE), polypropylene (PP), polycarbonate (PC) and polyethylene terephthalate (PET) was studied using an isostatic continuous flow system. Polymer samples were exposed to a model solution containing limonene,

  19. Reverse-Engineering Laboratory Astrophysics: Oxygen Inner-shell Absorption in the ISM

    Science.gov (United States)

    Garcia, J.; Gatuzz, E.; Kallman, T. R.; Mendoza, C.; Gorczyca, T. W.

    2017-01-01

    The modeling of X-ray spectra from photoionized astrophysical plasmas has been significantly improved due to recent advancements in the theoretical and numerical frameworks, as well as a consolidated and reliable atomic database of inner-shell transitions for all the relevant ions. We discuss these developments and the current state of X-ray spectral modeling in the context of oxygen cold absorption in the interstellar medium (ISM). Unconventionally, we use high-resolution astrophysical observations to accurately determine line positions, and adjust the theoretical models for a comprehensive interpretation of the observed X-ray spectra. This approach has brought to light standing discrepancies in the neutral oxygen absorption-line positions determined from observations and laboratory measurements. We give an overview of our current efforts to devise a definitive model of oxygen photoabsorption that can help to resolve the existing controversy regarding ISM atomic and molecular fractions.

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

    Science.gov (United States)

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

    2007-04-01

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

  1. Constructing Repairable Meta-Structures of Ultra-Broad-Band Electromagnetic Absorption from Three-Dimensional Printed Patterned Shells.

    Science.gov (United States)

    Song, Wei-Li; Zhou, Zhili; Wang, Li-Chen; Cheng, Xiao-Dong; Chen, Mingji; He, Rujie; Chen, Haosen; Yang, Yazheng; Fang, Daining

    2017-12-13

    Ultra-broad-band electromagnetic absorption materials and structures are increasingly attractive for their critical role in competing with the advanced broad-band electromagnetic detection systems. Mechanically soft and weak wax-based materials composites are known to be insufficient to serve in practical electromagnetic absorption applications. To break through such barriers, here we developed an innovative strategy to enable the wax-based composites to be robust and repairable meta-structures by employing a three-dimensional (3D) printed polymeric patterned shell. Because of the integrated merits from both the dielectric loss wax-based composites and mechanically robust 3D printed shells, the as-fabricated meta-structures enable bear mechanical collision and compression, coupled with ultra-broad-band absorption (7-40 and 75-110 GHz, reflection loss  smaller than -10 dB) approaching state-of-the-art electromagnetic absorption materials. With the assistance of experiment and simulation methods, the design advantages and mechanism of employing such 3D printed shells for substantially promoting the electromagnetic absorption performance have been demonstrated. Therefore, such universal strategy that could be widely extended to other categories of wax-based composites highlights a smart stage on which high-performance practical multifunction meta-structures with ultra-broad-band electromagnetic absorption could be envisaged.

  2. Contributions of oxygen vacancies and titanium interstitials to band-gap states of reduced titania

    Science.gov (United States)

    Li, Jingfeng; Lazzari, Rémi; Chenot, Stéphane; Jupille, Jacques

    2018-01-01

    The spectroscopic fingerprints of the point defects of titanium dioxide remain highly controversial. Seemingly indisputable experiments lead to conflicting conclusions in which oxygen vacancies and titanium interstitials are alternately referred to as the primary origin of the Ti 3 d band-gap states. We report on experiments performed by electron energy loss spectroscopy whose key is the direct annealing of only the very surface of rutile TiO2(110 ) crystals and the simultaneous measurement of its temperature via the Bose-Einstein loss/gain ratio. By surface preparations involving reactions with oxygen and water vapor, in particular, under electron irradiation, vacancy- and interstitial-related band-gap states are singled out. Off-specular measurements reveal that both types of defects contribute to a unique charge distribution that peaks in subsurface layers with a common dispersive behavior.

  3. Electrical transport properties of individual WS2 nanotubes and their dependence on water and oxygen absorption

    Science.gov (United States)

    Zhang, Chaoying; Ning, Zhiyuan; Liu, Yang; Xu, Tingting; Guo, Yao; Zak, Alla; Zhang, Zhiyong; Wang, Sheng; Tenne, Reshef; Chen, Qing

    2012-09-01

    The electrical properties of WS2 nanotubes (NTs) were studied through measuring 59 devices. Important electrical parameters, such as the carrier concentration, mobility, and effective barrier height at the contacts, were obtained through fitting experimental non-linear I-V curves using a metal-semiconductor-metal model. The carrier mobility was found to be several orders of magnitude higher than that have been reported previously for WS2 NTs. Water absorption was found to decrease the conductivity and carrier mobility of the NTs, and could be removed when the sample was dried. Oxygen absorption also slightly decreased the conductivity of WS2 NTs.

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

    International Nuclear Information System (INIS)

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

    2006-01-01

    Collision induced absorption (CIA) spectra of pure D 2 in the first overtone region from 5250 to 7250 cm -1 , recorded at 77, 201 and 298 K, have been analyzed. The observed spectra at 77, 201 and 298 K were modelled by a total of 92, 214 and 267 components respectively of double vibrational transitions at room temperature of the type X 2 (J) +X 0 (J) and X 1 (J) + X 1 (J), where X is O, Q or S transitions. Profile analyses of the spectra were carried out using the Birnbaum-Cohen line-shape function for the individual components of the band, and characteristic line shape parameters were determined from the analysis. The observed and calculated profiles agree well over the whole overtone band, and the agreement is better than 97% in the three cases studied. Binary and ternary absorption coefficients were determined from the integrated absorption of the band. (authors)

  5. Properties of the 4.45 eV optical absorption band in LiF:Mg, Ti

    International Nuclear Information System (INIS)

    Nail, I.; Oster, L.; Horowitz, Y. S.; Biderman, S.; Belaish, Y.

    2006-01-01

    The optical absorption (OA) and thermoluminescence (TL) of dosimetric LiF:Mg,Ti (TLD-100) as well as nominally pure LiF single crystal have been studied as a function of irradiation dose, thermal and optical bleaching in order to investigate the role of the 4.45 eV OA band in low temperature TL. Computerised deconvolution was used to resolve the absorption spectrum into individual gaussian bands and the TL glow curve into glow peaks. Although the 4.45 eV OA band shows thermal decay characteristics similar to the 4.0 eV band its dose filling constant and optical bleaching properties suggest that it cannot be associated with the TL of composite peaks 4 or 5. Its presence in optical grade single crystal LiF further suggests that it is an intrinsic defect or possibly associated with chance impurities other than Mg, Ti. (authors)

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

    Science.gov (United States)

    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.

  7. Modification of pure oxygen absorption equipment for concurrent stripping of carbon dioxide

    Science.gov (United States)

    Watten, B.J.; Sibrell, P.L.; Montgomery, G.A.; Tsukuda, S.M.

    2004-01-01

    The high solubility of carbon dioxide precludes significant desorption within commercial oxygen absorption equipment. This operating characteristic of the equipment limits its application in recirculating water culture systems despite its ability to significantly increase allowable fish loading rates (kg/(L min)). Carbon dioxide (DC) is typically removed by air stripping. This process requires a significant energy input for forced air movement, air heating in cold climates and water pumping. We developed a modification for a spray tower that provides for carbon dioxide desorption as well as oxygen absorption. Elimination of the air-stripping step reduces pumping costs while allowing dissolved nitrogen to drop below saturation concentrations. This latter response provides for an improvement in oxygen absorption efficiency within the spray tower. DC desorption is achieved by directing head-space gases from the spray tower (O2, N2, CO2) through a sealed packed tower scrubber receiving a 2 N NaOH solution. Carbon dioxide is selectively removed from the gas stream, by chemical reaction, forming the product Na 2CO3. Scrubber off-gas, lean with regard to carbon dioxide but still rich with oxygen, is redirected through the spray tower for further stripping of DC and absorption of oxygen. Make-up NaOH is metered into the scrubbing solution sump on an as needed basis as directed by a feedback control loop programmed to maintain a scrubbing solution pH of 11.4-11.8. The spent NaOH solution is collected, then regenerated for reuse, in a batch process that requires relatively inexpensive hydrated lime (Ca(OH)2). A by-product of the regeneration step is an alkaline filter cake, which may have use in bio-solids stabilization. Given the enhanced gas transfer rates possible with chemical reaction, the required NaOH solution flow rate through the scrubber represents a fraction of the spray tower water flow rate. Further, isolation of the water being treated from the atmosphere (1

  8. Enhanced Photocatalytic Activity of La3+-Doped TiO2 Nanotubes with Full Wave-Band Absorption

    Science.gov (United States)

    Xia, Minghao; Huang, Lingling; Zhang, Yubo; Wang, Yongqian

    2018-06-01

    TiO2 nanotubes doped with La3+ were synthesized by anodic oxidation method and the photocatalytic activity was detected by photodegrading methylene blue. As-prepared samples improved the absorption of both ultraviolet light and visible light and have a great enhancement on the photocatalytic activity while contrasting with the pristine TiO2 nanotubes. A tentative mechanism for the enhancement of photocatalytic activity with full wave-band absorption is proposed.

  9. Airborne Measurements of Atmospheric Pressure made Using an IPDA Lidar Operating in the Oxygen A-Band

    Science.gov (United States)

    Riris, Haris; Abshire, James B.; Stephen, Mark; Rodriquez, Michael; Allan, Graham; Hasselbrack, William; Mao, Jianping

    2012-01-01

    We report airborne measurements of atmospheric pressure made using an integrated path differential absorption (IPDA) lidar that operates in the oxygen A-band near 765 nm. Remote measurements of atmospheric temperature and pressure are needed for NASA s Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission to measure atmospheric CO2. Accurate measurements of tropospheric CO2 on a global scale are very important in order to better understand its sources and sinks and to improve our predictions of climate change. The goal of ASCENDS is to determine the CO2 dry mixing ratio with lidar measurements from space at a level of 1 ppm. Analysis to date shows that with current weather models, measurements of both the CO2 column density and the column density of dry air are needed. Since O2 is a stable molecule that uniformly mixed in the atmosphere, measuring O2 absorption in the atmosphere can be used to infer the dry air density. We have developed an airborne (IPDA) lidar for Oxygen, with support from the NASA ESTO IIP program. Our lidar uses DFB-based seed laser diodes, a pulsed modulator, a fiber laser amplifier, and a non-linear crystal to generate wavelength tunable 765 nm laser pulses with a few uJ/pulse energy. The laser pulse rate is 10 KHz, and average transmitted laser power is 20 mW. Our lidar steps laser pulses across a selected line O2 doublet near 764.7 nm in the Oxygen A-band. The direct detection lidar receiver uses a 20 cm diameter telescope, a Si APD detector in Geiger mode, and a multi-channel scalar to detect and record the time resolved laser backscatter in 40 separate wavelength channels. Subsequent analysis is used to estimate the transmission line shape of the doublet for the laser pulses reflected from the ground. Ground based data analysis allows averaging from 1 to 60 seconds to increase SNR in the transmission line shape of the doublet. Our retrieval algorithm fits the expected O2 lineshapes against the measurements and

  10. The impact of different multi-walled carbon nanotubes on the X-band microwave absorption of their epoxy nanocomposites.

    Science.gov (United States)

    Che, Bien Dong; Nguyen, Bao Quoc; Nguyen, Le-Thu T; Nguyen, Ha Tran; Nguyen, Viet Quoc; Van Le, Thang; Nguyen, Nieu Huu

    2015-01-01

    Carbon nanotube (CNT) characteristics, besides the processing conditions, can change significantly the microwave absorption behavior of CNT/polymer composites. In this study, we investigated the influence of three commercial multi-walled CNT materials with various diameters and length-to-diameter aspect ratios on the X-band microwave absorption of epoxy nanocomposites with CNT contents from 0.125 to 2 wt%, prepared by two dispersion methods, i.e. in solution with surfactant-aiding and via ball-milling. The laser diffraction particle size and TEM analysis showed that both methods produced good dispersions at the microscopic level of CNTs. Both a high aspect ratio resulting in nanotube alignment trend and good infiltration of the matrix in the individual nanotubes, which was indicated by high Brookfield viscosities at low CNT contents of CNT/epoxy dispersions, are important factors to achieve composites with high microwave absorption characteristics. The multi-walled carbon nanotube (MWCNT) with the largest aspect ratio resulted in composites with the best X-band microwave absorption performance, which is considerably better than that of reported pristine CNT/polymer composites with similar or lower thicknesses and CNT loadings below 4 wt%. A high aspect ratio of CNTs resulting in microscopic alignment trend of nanotubes as well as a good level of micro-scale CNT dispersion resulting from good CNT-matrix interactions are crucial to obtain effective microwave absorption performance. This study demonstrated that effective radar absorbing MWCNT/epoxy nanocomposites having small matching thicknesses of 2-3 mm and very low filler contents of 0.25-0.5 wt%, with microwave energy absorption in the X-band region above 90% and maximum absorption peak values above 97%, could be obtained via simple processing methods, which is promising for mass production in industrial applications. Graphical AbstractComparison of the X-band microwave reflection loss of epoxy composites of

  11. Absorption spectra of H2-H2 pairs in the fundamental band

    International Nuclear Information System (INIS)

    Meyer, W.; Borysow, A.; Frommhold, L.

    1989-01-01

    For the computation of the induced-dipole moment, the collisional complex consisting of two H 2 molecules is treated like one molecule in the self-consistent-field and size-consistent, coupled electron pair approximations that separates correctly at distant range. The basis set accounts for 95% of the correlation energies. The radial transition matrix elements of the induced-dipole components are obtained for the two cases v 1 =v 2 =0 and v 1 =0,v 2 =1, where the v i are the vibrational quantum numbers of the interacting H 2 molecules (i=1 or 2). The dependence of these elements on the most important rotational states (j 1 , j 1 ',j 2 ,j 2 '=0,...,3) involved is obtained and seen to be significant in the fundamental band. The results are recast in a simple, but accurate analytical form that is used in a quantum formalism for computations of the spectral moments (sum rules) and line shapes of the collision-induced absorption spectra of molecular hydrogen pairs in the infrared 2.4-μm band. The calculations are based on a proven isotropic potential model that we have extended to account for effects of vibrational excitations. Numerical consistency of the line-shape calculations with the sum rules is observed at the 1% level. The comparison of the computational results with the available measurements at temperatures from 20 to 300 K shows agreement within the estimated uncertainties of the best measurements (∼10%). This fact suggests that theory is capable of predicting these spectra reliably at temperatures for which no measurements exist, with an accuracy that compares favorably with that of good laboratory measurements

  12. Pressure and solvent shifts of charge transfer absorption band of iodine complexes

    International Nuclear Information System (INIS)

    Sawamura, Seiji; Taniguchi, Yoshihiro; Suzuki, Keizo

    1979-01-01

    Absorption spectra of the CT band of I 2 complexes were observed in several nonpolar solvents at 1 bar, and in heptane up to 4400 bar. All solvent shifts were red with an increase in (n 2 - 1)/(2n 2 + 1), the refractive index (n) function of solvents, consistent with the solvent shift theory. On the other hand pressure caused a variety of shifts, that is, red shifts in benzene-, toluene-, and mesitylene-I 2 complexes, an inversion shift from red to blue in HMB-I 2 complex, and blue shifts in Et 3 N-, n-Pr 3 N-, and n-Bu 3 N-I 2 complexes, though increase in pressure invariably raises the (n 2 - 1)/(2n 2 + 1) value of solvent. The pressure shifts of I 2 complexes seem to be interpreted by a sum of two effects. One is the increased polarity of the solvent, which causes a red shift. The other is the decrease in the bond distance between a donor and an acceptor, which contributes to a blue shift in a strong CT complex and to a red shift in a week one. The pressure and solvent shifts of I 2 complexes were compared with those of π-donor-TCNE complexes. (author)

  13. Laser absorption spectroscopy of oxygen confined in highly porous hollow sphere xerogel.

    Science.gov (United States)

    Yang, Lin; Somesfalean, Gabriel; He, Sailing

    2014-02-10

    An Al2O3 xerogel with a distinctive microstructure is studied for the application of laser absorption spectroscopy of oxygen. The xerogel has an exceptionally high porosity (up to 88%) and a large pore size (up to 3.6 µm). Using the method of gas-in-scattering media absorption spectroscopy (GASMAS), a long optical path length (about 3.5m) and high enhancement factor (over 300 times) are achieved as the result of extremely strong multiple-scattering when the light is transmitted through the air-filled, hollow-sphere alumina xerogel. We investigate how the micro-physical feature influences the optical property. As part of the optical sensing system, the material's gas exchange dynamics are also experimentally studied.

  14. Influence of defects on the absorption edge of InN thin films: The band gap value

    Science.gov (United States)

    Thakur, J. S.; Danylyuk, Y. V.; Haddad, D.; Naik, V. M.; Naik, R.; Auner, G. W.

    2007-07-01

    We investigate the optical-absorption spectra of InN thin films whose electron density varies from ˜1017tõ1021cm-3 . The low-density films are grown by molecular-beam-epitaxy deposition while highly degenerate films are grown by plasma-source molecular-beam epitaxy. The optical-absorption edge is found to increase from 0.61to1.90eV as the carrier density of the films is increased from low to high density. Since films are polycrystalline and contain various types of defects, we discuss the band gap values by studying the influence of electron degeneracy, electron-electron, electron-ionized impurities, and electron-LO-phonon interaction self-energies on the spectral absorption coefficients of these films. The quasiparticle self-energies of the valence and conduction bands are calculated using dielectric screening within the random-phase approximation. Using one-particle Green’s function analysis, we self-consistently determine the chemical potential for films by coupling equations for the chemical potential and the single-particle scattering rate calculated within the effective-mass approximation for the electron scatterings from ionized impurities and LO phonons. By subtracting the influence of self-energies and chemical potential from the optical-absorption edge energy, we estimate the intrinsic band gap values for the films. We also determine the variations in the calculated band gap values due to the variations in the electron effective mass and static dielectric constant. For the lowest-density film, the estimated band gap energy is ˜0.59eV , while for the highest-density film, it varies from ˜0.60tõ0.68eV depending on the values of electron effective mass and dielectric constant.

  15. Room Temperature Optical Constants and Band Gap Evolution of Phase Pure M1-VO2 Thin Films Deposited at Different Oxygen Partial Pressures by Reactive Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Meng Jiang

    2014-01-01

    Full Text Available Spectroscopic ellipsometry study was employed for phase pure VO2(M1 thin films grown at different oxygen partial pressures by reactive magnetron sputtering. The optical constants of the VO2(M1 thin films have been determined in a photon energy range between 0.73 and 5.05 eV. The near-infrared extinction coefficient and optical conductivity of VO2(M1 thin films rapidly increase with decreasing O2-Ar ratios. Moreover, two electronic transitions can be uniquely assigned. The energy gaps correlated with absorption edge (E1 at varied O2-Ar ratios are almost the same (~2.0 eV; consequently, the absorption edge is not significantly changed. However, the optical band gap corresponding to semiconductor-to-metal phase transition (E2 decreases from 0.53 to 0.18 eV with decreasing O2-Ar ratios.

  16. Estimating Snow Water Equivalent with Backscattering at X and Ku Band Based on Absorption Loss

    Directory of Open Access Journals (Sweden)

    Yurong Cui

    2016-06-01

    Full Text Available Snow water equivalent (SWE is a key parameter in the Earth’s energy budget and water cycle. It has been demonstrated that SWE can be retrieved using active microwave remote sensing from space. This necessitates the development of forward models that are capable of simulating the interactions of microwaves and the snow medium. Several proposed models have described snow as a collection of sphere- or ellipsoid-shaped ice particles embedded in air, while the microstructure of snow is, in reality, more complex. Natural snow usually forms a sintered structure following mechanical and thermal metamorphism processes. In this research, the bi-continuous vector radiative transfer (bi-continuous-VRT model, which firstly constructs snow microstructure more similar to real snow and then simulates the snow backscattering signal, is used as the forward model for SWE estimation. Based on this forward model, a parameterization scheme of snow volume backscattering is proposed. A relationship between snow optical thickness and single scattering albedo at X and Ku bands is established by analyzing the database generated from the bi-continuous-VRT model. A cost function with constraints is used to solve effective albedo and optical thickness, while the absorption part of optical thickness is obtained from these two parameters. SWE is estimated after a correction for physical temperature. The estimated SWE is correlated with the measured SWE with an acceptable accuracy. Validation against two-year measurements, using the SnowScat instrument from the Nordic Snow Radar Experiment (NoSREx, shows that the estimated SWE using the presented algorithm has a root mean square error (RMSE of 16.59 mm for the winter of 2009–2010 and 19.70 mm for the winter of 2010–2011.

  17. Long-term changes in the radiation-induced optical absorption bands of LiF:Mg,Ti

    International Nuclear Information System (INIS)

    Kelemen, A.

    1996-01-01

    Optical absorption spectroscopy plays an exceptional role in the identification of charge traps responsible for the different TL peaks of the TL phosphors. Experiments carried out under different conditions, e.g. with different types of ionising radiation and/or different dose rates, applying different annealing procedures and/or different storage times after the irradiation, may lead to contradictory results. Therefore, a systematic investigation was conducted of the build-up and decay characteristics of the optical absorption bands of different LiF:Mg,Ti single crystal samples. Important changes were found in the long (hours and days) time scale. For example, the 350 nm optical absorption increases continuously in the Mg free LiF:Ti sample, while the intensities of the 310 nm and 380 nm absorption bands decrease in the sample containing Mg even several hours after irradiation with ∼ 5 μs, 4 MeV linear accelerator electron pulses. These experimental results may have serious consequences for the interpretation of optical absorption data and for the understanding of defect and energy storage mechanisms of thermoluminescence in LiF:Mg,Ti. (author)

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

    Energy Technology Data Exchange (ETDEWEB)

    Lambrecht, W.R.L.; Rashkeev, S.N.; Segall, B. [Case Western Reserve Univ., Cleveland, OH (United States)] [and others

    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.

  19. Collision-induced absorption in the region of the ν2 + ν3 band of carbon dioxide

    Science.gov (United States)

    Baranov, Yu. I.

    2018-03-01

    The IR absorption spectra of pure carbon dioxide in the region of the forbidden ν2 + ν3 vibrational transition at 3004 cm-1 have been recorded using a Fourier-transform spectrometer. A multipass-optical cell with the path length of 100 m was used in the study. The data were taken at room temperature of 294.8 K with a resolution of 0.02 cm-1 over the spectral region 2500-3500 cm-1. A sample pressures varied from 207 to 463 kPa (2.04-4.57 atm). The measured binary absorption coefficients provide the band integrated intensity value of (2.39 ± 0.04) ∗ 10-4 cm-2 amagat-2. The result is compared with those from previous works. The observed band profile features are discussed.

  20. Microwave absorption properties of flake-shaped Co particles composites at elevated temperature (293-673 K) in X band

    Science.gov (United States)

    Wang, Guowu; Li, Xiling; Wang, Peng; Zhang, Junming; Wang, Dian; Qiao, Liang; Wang, Tao; Li, Fashen

    2018-06-01

    The complex permeability and permittivity of the easy-plane anisotropic Co/polyimide composite at high temperature (293-673 K) in X band were measured. The results show that both the complex permeability and permittivity increase with the increase of temperature in the measured temperature range. The calculated absorption properties display that the intensity of the reflection loss (RL) peak first increases and then decreases with the increase of temperature, and reaches the maximum (-52 dB) at 523 K. At each temperature, the composite can achieve the RL exceeding -10 dB in the whole X band. The composite can even work stably for more than 20 min with the excellent absorption performance under 673 K. In addition, the RL performance of the composite at high temperature is better than that at room temperature.

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

    Science.gov (United States)

    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.

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

    CERN Document Server

    Yazici, A N

    2003-01-01

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

  3. Atomic Oxygen Abundance in Molecular Clouds: Absorption Toward Sagittarius B2

    Science.gov (United States)

    Lis, D. C.; Keene, Jocelyn; Phillips, T. G.; Schilke, P.; Werner, M. W.; Zmuidzinas, J.

    2001-01-01

    We have obtained high-resolution (approximately 35 km/s) spectra toward the molecular cloud Sgr B2 at 63 micrometers, the wavelength of the ground-state fine-structure line of atomic oxygen (O(I)), using the ISO-LWS instrument. Four separate velocity components are seen in the deconvolved spectrum, in absorption against the dust continuum emission of Sgr B2. Three of these components, corresponding to foreground clouds, are used to study the O(I) content of the cool molecular gas along the line of sight. In principle, the atomic oxygen that produces a particular velocity component could exist in any, or all, of three physically distinct regions: inside a dense molecular cloud, in the UV illuminated surface layer (PDR) of a cloud, and in an atomic (H(I)) gas halo. For each of the three foreground clouds, we estimate, and subtract from the observed O(I) column density, the oxygen content of the H(I) halo gas, by scaling from a published high-resolution 21 cm spectrum. We find that the remaining O(I) column density is correlated with the observed (13)CO column density. From the slope of this correlation, an average [O(I)]/[(13)CO] ratio of 270 +/- 120 (3-sigma) is derived, which corresponds to [O(I)]/[(13)CO] = 9 for a CO to (13)CO abundance ratio of 30. Assuming a (13)CO abundance of 1x10(exp -6) with respect to H nuclei, we derive an atomic oxygen abundance of 2.7x10(exp -4) in the dense gas phase, corresponding to a 15% oxygen depletion compared to the diffuse ISM in our Galactic neighborhood. The presence of multiple, spectrally resolved velocity components in the Sgr B2 absorption spectrum allows, for the first time, a direct determination of the PDR contribution to the O(I) column density. The PDR regions should contain O(I) but not (13)CO, and would thus be expected to produce an offset in the O(I)-(13)CO correlation. Our data do not show such an offset, suggesting that within our beam O(I) is spatially coexistent with the molecular gas, as traced by (13)CO

  4. Easily Dispersible NiFe2O4/RGO Composite for Microwave Absorption Properties in the X-Band

    Science.gov (United States)

    Bateer, Buhe; Zhang, Jianjao; Zhang, Hongchen; Zhang, Xiaochen; Wang, Chunyan; Qi, Haiqun

    2018-01-01

    Composites with good dispersion and excellent microwave absorption properties have important applications. Therefore, an easily dispersible NiFe2O4/reduced graphene oxide (RGO) composite has been prepared conveniently through a simple hydrothermal method. Highly crystalline, small size (about 7 nm) monodispersed NiFe2O4 nanoparticles (NPs) are evenly distributed on the surface of RGO. The microwave absorbability revealed that the NiFe2O4/RGO composite exhibits excellent microwave absorption properties in the X-band (8-12 GHz), and the minimum reflection loss of the NiFe2O4/RGO composite is -27.7 dB at 9.2 GHz. The NiFe2O4/RGO composite has good dispersibility in nonpolar solvent, which facilitates the preparation of stable commercial microwave absorbing coatings. It can be a promising candidate for lightweight microwave absorption materials in many application fields.

  5. Optical properties of oxygen-implanted CdS:O layers in terms of band anticrossing theory

    Energy Technology Data Exchange (ETDEWEB)

    Morozova, N. K., E-mail: MorozovaNK@mail.ru; Kanakhin, A. A.; Miroshnikova, I. N. [Moscow Power Engineering Institute, National Research University (Russian Federation); Galstyan, V. G. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2013-08-15

    The microcathodoluminescence (MCL) and photoreflection spectra of CdS:O layers implanted with oxygen ions to 4 Multiplication-Sign 10{sup 20} cm{sup -3} are investigated. Used method of MCL spectroscopy yields information only about the implanted-layer volume. Exciton MCL spectra, which allow one to determine the concentration of dissolved oxygen in the CdS:O layers and the influence of deviation of the substrates from stoichiometry, are recorded. The homogeneity of the ion-implanted layers is studied by cathodoluminescence (CL) scanning electron microscopy. The relationship between light-emitting areas and the luminescence band at {approx}630 nm is established. The reason for enhancement of this band upon radiation annealing is revealed and its nature as the luminescence of F{sup +} centers in CdS is confirmed. New photoreflection spectroscopy data are obtained, which describe the specific behavioral features of oxygen on the layer surface as an isoelectronic impurity in highly mismatched alloys (HMAs). It is shown that sulfur completely bonds and removes oxygen from CdS:O. Oxygen-free CdS remains on the surface in the form of nanoparticles, the size of which depends on the oxygen concentration in the CdS:O layer bulk. The results obtained are in agreement with the predictions of band anticrossing theory.

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

    International Nuclear Information System (INIS)

    Reddy, Samala Nagaprasad; Mahapatra, S.

    2012-01-01

    Highlights: ► Theoretical study of spectroscopy and dynamics of electronically excited l-C 3 H 2 . ► Construction of ab initio electronic potential energy and diabatic coupling surfaces. ► First principles study of nuclear dynamics on excited electronic states. ► Findings reveal l-C 3 H 2 is a potential molecular carrier of diffuse interstellar bands. ► Electronically excited l-C 3 H 2 decays by ultrafast nonradiative internal conversion. -- Abstract: Observation of broad and diffuse interstellar bands (DIBs) at 4881 Å and 5440 Å assigned to the optical absorption spectrum of Y-shaped propadienylidene (H 2 C=C=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.

  7. A method of retrieving cloud top height and cloud geometrical thickness with oxygen A and B bands for the Deep Space Climate Observatory (DSCOVR) mission: Radiative transfer simulations

    International Nuclear Information System (INIS)

    Yang, Yuekui; Marshak, Alexander; Mao, Jianping; Lyapustin, Alexei; Herman, Jay

    2013-01-01

    The Earth Polychromatic Imaging Camera (EPIC) onboard the Deep Space Climate Observatory (DSCOVR) was designed to measure the atmosphere and surface properties over the whole sunlit half of the Earth from the L1 Lagrangian point. It has 10 spectral channels ranging from the UV to the near-IR, including two pairs of oxygen (O 2 ) A-band (779.5 and 764 nm) and B-band (680 and 687.75 nm) reference and absorption channels selected for the cloud height measurements. This paper presents the radiative transfer analysis pertinent to retrieving cloud top height and cloud geometrical thickness with EPIC A- and B-band observations. Due to photon cloud penetration, retrievals from either O 2 A- or B-band channels alone gives the corresponding cloud centroid height, which is lower than the cloud top. However, we show both the sum and the difference between the retrieved cloud centroid heights in the A and B bands are functions of cloud top height and cloud geometrical thickness. Based on this fact, the paper develops a new method to retrieve cloud top height and cloud geometrical thickness simultaneously for fully cloudy scenes over ocean surface. First, cloud centroid heights are calculated for both A and B bands using the ratios between the reflectances of the absorbing and reference channels; then the cloud top height and the cloud geometrical thickness are retrieved from the two dimensional look up tables that relate the sum and the difference between the retrieved centroid heights for A and B bands to the cloud top height and the cloud geometrical thickness. This method is applicable for clouds thicker than an optical depth of 5. -- Highlights: ► EPIC onboard DSCOVR is equipped with O 2 A and B band channels. ► Photon cloud penetration depths of A and B bands contain information of cloud thickness. ► A method is developed to retrieve cloud top height and cloud geometrical thickness with EPIC O 2 A- and B-band

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

    Energy Technology Data Exchange (ETDEWEB)

    Zha, Hao [Department of Engineering Physics, Tsinghua University, Beijing CN-100086 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Ministry of Education, Beijing (China); The European Organization for Nuclear Research, Geneva CH-1211 (Switzerland); Shi, Jiaru, E-mail: shij@mail.tsinghua.edu.cn [Department of Engineering Physics, Tsinghua University, Beijing CN-100086 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Ministry of Education, Beijing (China); The European Organization for Nuclear Research, Geneva CH-1211 (Switzerland); Wu, Xiaowei; Chen, Huaibi [Department of Engineering Physics, Tsinghua University, Beijing CN-100086 (China); Key Laboratory of Particle and Radiation Imaging, Tsinghua University, Ministry of Education, Beijing (China)

    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.

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

    International Nuclear Information System (INIS)

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

    2016-01-01

    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.

  10. Optical absorption and refractive index near the band gap for InGaAsP

    International Nuclear Information System (INIS)

    Kowalsky, W.; Wehmann, H.H.; Fiedler, F.; Schlachetzki, A.

    1983-01-01

    The optical absorption coefficient α and the refractive index n were measured for a quaternary alloy with bandgap-equivalent wavelength of 1.17 μm and for the ternary alloy, both lattice-matched to InP. α in dependence on the wavelength is characteristic of a direct semiconductor, but with a relative maximum on the order of 50 meV away from the bandgap in the small-absorption range. This peak is tentatively assigned to an acceptor impurity

  11. Infrared absorption, multiphonon processes and time reversal effect on Si and Ge band structure

    International Nuclear Information System (INIS)

    Kunert, H.W.; Machatine, A.G.J.; Malherbe, J.B.; Barnas, J.; Hoffmann, A.; Wagner, M.R.

    2008-01-01

    We have examined the effect of Time Reversal Symmetry (TRS) on vibrational modes and on the electronic band structure of Si and Ge. Most of the primary non-interacting modes are not affected by TRS. Only phonons originating from high symmetry lines S and A of the Brillouin Zone (BZ) indicate extra degeneracy. Selection rules for some two and three phonons originating from high symmetry lines are determined. The states of electrons and holes described by electronic band structure due to spin-inclusion are assigned by spinor representations of the double space group. Inclusion of the TRS into the band structure results in extra degeneracy of electrons and holes, and therefore optical selection rules suppose to be modified

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

    Science.gov (United States)

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

    2012-06-01

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

  13. Oxygen segregation and its impact on the absorption of hydrogen in vanadium; Einfluss der Sauerstoffsegregation auf die Absorption von Wasserstoff in Vanadium

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, H.; Lammers, M. [Inst. fuer Technologie- und Wissenstransfer, Soest (Germany); Mueller, K.H. [Inst. fuer Technologie- und Wissenstransfer, Soest (Germany)]|[Paderborn Univ. (Gesamthochschule), Soest (Germany). Fachbereich 16 - Elektrische Energietechnik; Kiss, G.; Kemeny, Z. [Technical Univ. Budapest (Hungary)

    1998-12-31

    The impact of the dissolved oxygen on the hydrogen absorption in vanadium was analysed with an UHV apparatus. The vanadium specimen with an oxygen content of 230 ppm was treated by a variety of heat treatments. The depth distributions of the induced concentrations of segregated oxygen in the specimen were analysed by SIMS. It was found that the amount of segregated oxygen increases with rising final temperature and tempering period. In a further experiment, the specimen was exposed after each segregation process to a H{sub 2}-pressure of 2.2 x 10{sup -4} Pa for a period of 1800 sec. The hydrogen amounts absorbed in the specimen were determined by thermal desorption mass spectrometry (TDMS). It was found that segregation of oxygen close to the surface of the specimen likewise hampers the absorption of hydrogen. (orig./CB) [Deutsch] Der Einfluss des im Volumen geloesten Sauerstoffs auf die Wasserstoff-Absorption in Vanadium wurde in einer UHV-Apparatur untersucht. Zunaechst wurde die V-Probe mit einem Sauerstoffgehalt von 230 ppm unterschiedlichen thermischen Behandlungen ausgesetzt. Die sich einstellenden Konzentrationstiefenverteilungen des an der Oberflaeche segregierten Sauerstoffs wurden anschliessend mit SIMS untersucht. Dabei nimmt die Menge des segregierten Sauerstoffs mit der Hoehe der Endtemperatur sowie der Temperzeit zu. In einem weiteren Experiment wurde die Probe nach jeder Segregationsprozedur fuer eine Zeit von 1800 sec einem H{sub 2}-Druck von 2.2 x 10{sup -4} Pa ausgesetzt. Die Mengen des dabei aufgenommenen Wasserstoffs wurden mit Hilfe der thermischen Desorptions-Massenspektrometrie TDMS bestimmt. Dabei zeigt sich, dass auch die Segregation von Sauerstoff im oberflaechennahen Bereich die Wasserstoffaufnahme in Vanadium behindert. (orig.)

  14. Information content of OCO-2 oxygen A-band channels for retrieving marine liquid cloud properties

    Science.gov (United States)

    Richardson, Mark; Stephens, Graeme L.

    2018-03-01

    Information content analysis is used to select channels for a marine liquid cloud retrieval using the high-spectral-resolution oxygen A-band instrument on NASA's Orbiting Carbon Observatory-2 (OCO-2). Desired retrieval properties are cloud optical depth, cloud-top pressure and cloud pressure thickness, which is the geometric thickness expressed in hectopascals. Based on information content criteria we select a micro-window of 75 of the 853 functioning OCO-2 channels spanning 763.5-764.6 nm and perform a series of synthetic retrievals with perturbed initial conditions. We estimate posterior errors from the sample standard deviations and obtain ±0.75 in optical depth and ±12.9 hPa in both cloud-top pressure and cloud pressure thickness, although removing the 10 % of samples with the highest χ2 reduces posterior error in cloud-top pressure to ±2.9 hPa and cloud pressure thickness to ±2.5 hPa. The application of this retrieval to real OCO-2 measurements is briefly discussed, along with limitations and the greatest caution is urged regarding the assumption of a single homogeneous cloud layer, which is often, but not always, a reasonable approximation for marine boundary layer clouds.

  15. Propagation losses in photonic crystal waveguides: Effects of band tail absorption and waveguide dispersion

    DEFF Research Database (Denmark)

    Rigal, F.; Joanesarson, Kristoffer Bitsch; Lyasota, A.

    2017-01-01

    Propagation losses in GaAs-based photonic crystal (PhC) waveguides are evaluated near the semiconductor band-edge by measuring the finesse of corresponding Ln cavities. This approach yields simultaneously the propagation losses and the mode reflectivity at the terminations of the cavities. We dem...

  16. Infrared Absorption Band Assignment in Benzanilide and Some of its p

    African Journals Online (AJOL)

    MBI

    2014-07-10

    Jul 10, 2014 ... benzanilide and its p-methyl, p-chloro, p-bromo, p-carboxy, and p-nitro derivatives. Out of the six characteristic. Amide Bands ... (where X = H, methyl, chloro, bromo, carboxyl, and nitro groups). The assignment has been made ..... ion, alkali metal benzoate and salicylates. Spectrochimica Acta 17:486- 502.

  17. Light absorption and the photoformation of hydroxyl radical and singlet oxygen in fog waters

    Science.gov (United States)

    Kaur, R.; Anastasio, C.

    2017-09-01

    The atmospheric aqueous-phase is a rich medium for chemical transformations of organic compounds, in part via photooxidants generated within the drops. Here we measure light absorption, photoformation rates and steady-state concentrations of two photooxidants - hydroxyl radical (•OH) and singlet molecular oxygen (1O2*) - in 8 illuminated fog waters from Davis, California and Baton Rouge, Louisiana. Mass absorption coefficients for dissolved organic compounds (MACDOC) in the samples are large, with typical values of 10,000-15,000 cm2 g-C-1 at 300 nm, and absorption extends to wavelengths as long as 450-600 nm. While nitrite and nitrate together account for an average of only 1% of light absorption, they account for an average of 70% of •OH photoproduction. Mean •OH photoproduction rates in fogs at the two locations are very similar, with an overall mean of 1.2 (±0.7) μM h-1 under Davis winter sunlight. The mean (±1σ) lifetime of •OH is 1.6 (±0.6) μs, likely controlled by dissolved organic compounds. Including calculated gas-to-drop partitioning of •OH, the average aqueous concentration of •OH is approximately 2 × 10-15 M (midday during Davis winter), with aqueous reactions providing approximately one-third of the hydroxyl radical source. At this concentration, calculated lifetimes of aqueous organics are on the order of 10 h for compounds with •OH rate constants of 1 × 1010 M-1 s-1 or higher (e.g., substituted phenols such as syringol (6.4 h) and guaiacol (8.4 h)), and on the order of 100 h for compounds with rate constants near 1 × 109 M-1 s-1 (e.g., isoprene oxidation products such as glyoxal (152 h), glyoxylic acid (58 h), and pyruvic acid (239 h)). Steady-state concentrations of 1O2* are approximately 100 times higher than those of •OH, in the range of (0.1-3.0) × 10-13 M. Since 1O2* is a more selective oxidant than •OH, it will only react appreciably with electron-rich species such as dimethyl furan (lifetime of 2.0 h) and

  18. Strongly correlated quasi-one-dimensional bands: Ground states, optical absorption, and phonons

    International Nuclear Information System (INIS)

    Campbell, D.K.; Gammel, J.T.; Loh, E.Y. Jr.

    1989-01-01

    Using the Lanczos method for exact diagonalization on systems up to 14 sites, combined with a novel ''phase randomization'' technique for extracting more information from these small systems, we investigate several aspects of the one-dimensional Peierls-Hubbard Hamiltonian, in the context of trans-polyacetylene: the dependence of the ground state dimerization on the strength of the electron-electron interactions, including the effects of ''off-diagonal'' Coulomb terms generally ignored in the Hubbard model; the phonon vibrational frequencies and dispersion relations, and the optical absorption properties, including the spectrum of absorptions as a function of photon energy. These three different observables provide considerable insight into the effects of electron-electron interactions on the properties of real materials and thus into the nature of strongly correlated electron systems. 29 refs., 11 figs

  19. Above band gap absorption spectra of the arsenic antisite defect in low temperature grown GaAs and AlGaAs

    DEFF Research Database (Denmark)

    Dankowski, S. U.; Streb, D.; Ruff, M.

    1996-01-01

    coefficients at the band gap are twice as high as for high temperature grown materials. By annealing the samples, we obtained a drastic reduced absorption coefficient below as well as above the band gap. We observed absorption changes up to 17 000 cm(-1) for LT-GaAs and 9000 cm(-1) for LT-AlGaAs taking place......Room temperature absorption spectra of low temperature molecular beam epitaxy grown GaAs (LT-GaAs) and AlGaAs (LT-AlGaAs) are reported. We performed measurements in an extended spectral range from 0.8 eV to photon energies of 2.8 eV far above the band gap. For as-grown LT-materials, the absorption...

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

    International Nuclear Information System (INIS)

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

    2013-01-01

    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

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

    Science.gov (United States)

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

    2013-12-01

    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.

  2. Interferometric Control of Dual-Band Terahertz Perfect Absorption Using a Designed Metasurface

    Science.gov (United States)

    Kang, Ming; Zhang, Huifang; Zhang, Xueqian; Yang, Quanlong; Zhang, Weili; Han, Jiaguang

    2018-05-01

    The coherent perfect absorber (CPA), a time-reversed counterpart to the laser emission, could cause all energy fed to the system to be absorbed. It can also be used as an absorptive interferometer, which could provide applications in controllable optical energy transfer. Here, in order to achieve a terahertz CPA, we propose a designed metasurface and experimentally demonstrate that it can serve as a polarization-insensitive CPA at a one-frequency channel under normal symmetric excitation, while a transverse-electric CPA at two-frequency channels around oblique 40° symmetric incidence. Such phenomena in this system can be attributed to Fano resonance consisting of interacting one bright and one dark mode under normal incidence and an additional operative dark mode under oblique symmetric excitation. The experimental results find good agreement with the fitted coupled-mode theory. Moreover, we show that the output amplitude can be effectively tuned from 0 to 1 only by varying the relative phase between the two input waves. The designed CPA could find potential application in effectively controlling absorption for terahertz imaging and terahertz switches.

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

    Science.gov (United States)

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

    2012-06-01

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

  4. Very high S-band microwave absorption of carbon nanotube buckypapers with Mn nanoparticle interlayers

    Science.gov (United States)

    Lu, Shaowei; Bai, Yaoyao; Wang, Jijie; Zhang, Lu; Tian, Caijiao; Ma, Keming; Wang, Xiaoqiang

    2018-03-01

    Flexible and high-performance electromagnetic absorbing materials of multi-walled carbon nanotube (MWCNT) buckypapers with Mn nanoparticles (NPSs) interlayer were fabricated via monodisperse solutions through layer by layer vacuum filtration method. The morphology and element composition of buckypapers were characterized by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction. The formation of flexible MWCNT buckypapers with Mn NPS (0-30 wt. %) interlayer was attributed to nanostructure and morphology of the samples. When the blended Mn NPS content in buckypapers is 20 wt. %, there are evidently two larger absorption peaks (-13.2 dB at 3.41 GHz, -15.6 dB at 3.52 GHz) of the buckypaper with an absorbing thickness of 0.1 mm. The fundamental microwave absorption mechanism of the buckypapers is discussed. This work opens a new pathway towards tuning microwave absorbers performance and this method can be extended to exploit other excellent microwave absorbers with interlayer.

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

    Science.gov (United States)

    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

  6. Redshift of the purple membrane absorption band and the deprotonation of tyrosine residues at high pH: Origin of the parallel photocycles of trans-bacteriorhodopsin

    OpenAIRE

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

    1991-01-01

    At high pH (> 8) the 570 nm absorption band of all-trans bacteriorhodopsin (bR) in purple membrane undergoes a small (1.5 nm) shift to longer wavelengths, which causes a maximal increase in absorption at 615 nm. The pK of the shift is 9.0 in the presence of 167 mM KCl, and its intrinsic pK is ∼8.3. The red shift of the trans-bR absorption spectrum correlates with the appearance of the fast component in the light-induced L to M transition, and absorption increases at 238 and 297 nm which are a...

  7. Two-photon absorption laser-induced fluorescence of atomic oxygen in the afterglow of pulsed positive corona discharge

    Science.gov (United States)

    Ono, Ryo; Takezawa, Kei; Oda, Tetsuji

    2009-08-01

    Atomic oxygen is measured in the afterglow of pulsed positive corona discharge using time-resolved two-photon absorption laser-induced fluorescence. The discharge occurs in a 14 mm point-to-plane gap in dry air. After the discharge pulse, the atomic oxygen density decreases at a rate of 5×104 s-1. Simultaneously, ozone density increases at almost the same rate, where the ozone density is measured using laser absorption method. This agreement between the increasing rate of atomic oxygen and decreasing rate of ozone proves that ozone is mainly produced by the well-known three-body reaction, O+O2+M→O3+M. No other process for ozone production such as O2(v)+O2→O3+O is observed. The spatial distribution of atomic oxygen density is in agreement with that of the secondary streamer luminous intensity. This agreement indicates that atomic oxygen is mainly produced in the secondary streamer channels, not in the primary streamer channels.

  8. Absorption cross section measurements of oxygen in the wavelength region 195-241 nm of the Herzberg continuum

    International Nuclear Information System (INIS)

    Cheung, A.S.C.; Yoshino, K.; Parkinson, W.H.; Freeman, D.E.

    1985-01-01

    The continuum cross section of oxygen at 296-300 K has been measured with a resolution of 0.13 nm throughout the wavelength region 205-241 nm with oxygen pressures from 5 to 760 torr and optical lengths from 13.3 to 133 m. The three processes contributing to the observed cross section are absorption into two continua, viz., the Herzberg continuum of O 2 and a pressure-dependent continuum involving two molecules of O 2 , and Rayleigh scattering. Comparison between different laboratory measurements and in situ stratospheric studies will also be presented. 1 reference

  9. Application of tunable diode laser absorption spectroscopy in the detection of oxygen

    Science.gov (United States)

    Zhou, Xin; Jin, Xing

    2015-10-01

    Most aircrafts is driven by chemic energy which is released in the combustion process. For improving the capability of engine and controlling the running on-time, the processes of fuel physics and chemistry need to be analysis by kinds of high quality sensor. In the research of designing and improving the processes of fuel physics and chemistry, the concentration, temperature and velocity of kinds of gas in the combustor need to be detected and measured. In addition, these engines and research equipments are always in the harsh environment of high temperature, high pressure and high speed. The harsh environment needs the sensor to be high reliability, well repetition, no cross- sensitivity between gases, and the traditional measurement system can't satisfy the metrical requirement well. Tunable diode laser absorption spectroscopy (TDLAS) analytic measurement technology can well satisfy the measurement in the harsh environment, which can support the whole measurement plan and high quality measurement system. Because the TDLAS sensor has the excellence of small bulk, light weight, high reliability and well specifically measurement, the TDLAS measurement technology has wide prospects. Different from most measurements, only a beam of laser can be pass through the measured environment by TDLAS, and the measurement equipment needn't be set in the harsh environment. So, the TDLAS equipment can't be interrupted by the measured equipment. The ability of subsistence in the harsh environment is very valuable, especially in the measurement on the subject of aerospace with environment of high speed, combustion and plasma. This paper focuses on the collecting the articles on the subject of oxygen detection of TDLAS. By analyzing the research and results of the articles, we conclude the central issues, difficulties and results. And we can get some instructive conclusions.

  10. Confinement effect of laser ablation plume in liquids probed by self-absorption of C2 Swan band emission

    International Nuclear Information System (INIS)

    Sakka, Tetsuo; Saito, Kotaro; Ogata, Yukio H.

    2005-01-01

    The (0,0) Swan band of the C 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 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

  11. Operando Soft X-ray Absorption Spectroscopic Study on a Solid Oxide Fuel Cell Cathode during Electrochemical Oxygen Reduction.

    Science.gov (United States)

    Nakamura, Takashi; Oike, Ryo; Kimura, Yuta; Tamenori, Yusuke; Kawada, Tatsuya; Amezawa, Koji

    2017-05-09

    An operando soft X-ray absorption spectroscopic technique, which enabled the analysis of the electronic structures of the electrode materials at elevated temperature in a controlled atmosphere and electrochemical polarization, was established and its availability was demonstrated by investigating the electronic structural changes of an La 2 NiO 4+δ dense-film electrode during an electrochemical oxygen reduction reaction. Clear O K-edge and Ni L-edge X-ray absorption spectra could be obtained below 773 K under an atmospheric pressure of 100 ppm O 2 /He, 0.1 % O 2 /He, and 1 % O 2 /He gas mixtures. Considerable spectral changes were observed in the O K-edge X-ray absorption spectra upon changing the PO2 and application of electrical potential, whereas only small spectral changes were observed in Ni L-edge X-ray absorption spectra. A pre-edge peak of the O K-edge X-ray absorption spectra, which reflects the unoccupied partial density of states of Ni 3d-O 2p hybridization, increased or decreased with cathodic or anodic polarization, respectively. The electronic structural changes of the outermost orbital of the electrode material due to electrochemical polarization were successfully confirmed by the operando X-ray absorption spectroscopic technique developed in this study. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Reduction of cross-polarized reflection to enhance dual-band absorption

    Science.gov (United States)

    Kundu, Debidas; Mohan, Akhilesh; Chakrabarty, Ajay

    2016-11-01

    In this paper, cross-polarized reflection from a periodic array of metal-dielectric-metal resonator units is reduced to improve its absorbing performance. Through this simple and typical example, it is shown that some reported absorbers are actually poor absorbers but efficient polarization converters, when the cross-polarized reflection is considered. Using a frequency selective surface, sandwiched between the top layer and the ground plane, the cross-polarized reflection is reduced by 7.2 dB at 5.672 GHz and 8.5 dB at 9.56 GHz, while negligibly affecting the co-polarized reflection reduction performance. The polarization conversion ratio is reduced from 90. 74% to 34.12% and 98.51% to 27.2% and total absorption is improved up to 80% from 26% and 21% around the two resonant frequencies. The reflection characteristics of the proposed absorber are quantitatively analyzed using interference theory, where the near field coupling of the resonant geometries and ground is taken into account. Measurement results show good agreement with both the numerically simulated and theoretical results.

  13. Transition state region in the A-Band photodissociation of allyl iodide—A femtosecond extreme ultraviolet transient absorption study

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacherjee, Aditi, E-mail: abhattacherjee@berkeley.edu, E-mail: andrewattar@berkeley.edu; Attar, Andrew R., E-mail: abhattacherjee@berkeley.edu, E-mail: andrewattar@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Leone, Stephen R., E-mail: srl@berkeley.edu [Department of Chemistry, University of California, Berkeley, California 94720 (United States); Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States); Department of Physics, University of California, Berkeley, California 94720 (United States)

    2016-03-28

    Femtosecond extreme ultraviolet (XUV) transient absorption spectroscopy based on a high-harmonic generation source is used to study the 266 nm induced A-band photodissociation dynamics of allyl iodide (CH{sub 2} =CHCH{sub 2}I). The photolysis of the C—I bond at this wavelength produces iodine atoms both in the ground ({sup 2}P{sub 3/2}, I) and spin-orbit excited ({sup 2}P{sub 1/2}, I*) states, with the latter as the predominant channel. Using XUV absorption at the iodine N{sub 4/5} edge (45–60 eV), the experiments constitute a direct probe of not only the long-lived atomic iodine reaction products but also the fleeting transition state region of the repulsive n{sub I}σ{sup ∗}{sub C—I} excited states. Specifically, three distinct features are identified in the XUV transient absorption spectrum at 45.3 eV, 47.4 eV, and 48.4 eV (denoted transients A, B, and C, respectively), which arise from the repulsive valence-excited nσ{sup ∗} states and project onto the high-lying core-excited states of the dissociating molecule via excitation of 4d(I) core electrons. Transients A and B originate from 4d(I) → n(I) core-to-valence transitions, whereas transient C is best assigned to a 4d(I) →σ{sup ∗}(C—I) transition. The measured differential absorbance of these new features along with the I/I* branching ratios known from the literature is used to suggest a more definitive assignment, albeit provisional, of the transients to specific dissociative states within the A-band manifold. The transients are found to peak around 55 fs–65 fs and decay completely by 145 fs–185 fs, demonstrating the ability of XUV spectroscopy to map the evolution of reactants into products in real time. The similarity in the energies of transients A and B with analogous features observed in methyl iodide [Attar et al. J. Phys. Chem. Lett. 6, 5072, (2015)] together with the new observation of transient C in the present work provides a more complete picture of the valence electronic

  14. Deep absorption band in Cu(In,Ga)Se{sub 2} thin films and solar cells observed by transparent piezoelectric photothermal spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Shirakata, Sho; Atarashi, Akiko [Faculty of Engineering, Ehime University, Matsuyama 790-8577 (Japan); Yagi, Masakazu [Kagawa National College of Technology, Mitoyo-shi 769-1192 (Japan)

    2015-06-15

    The photo-acoustic spectroscopy (PAS) using a transparent piezoelectric photo-thermal (Tr-PPT) method was carried out on Cu(In,Ga)Se{sub 2} (CIGS) thin films (both CIGS/Mo/SLG and CdS/CIGS/Mo/SLG) and solar cells (ZnO/CdS/CIGS/Mo/SLG). Using the Tr-PPT method, the high background absorption in the below gap region observed in both a microphone and a conventional transducer PAS spectra was strongly reduced. This high background absorption came from the CIGS/Mo interface. This result proves that the Tr-PPT PAS is the surface sensitive method. In the below-band region, a bell-shape deep absorption band has been observed at 0.76 eV, in which a full-width at the half-maximum value was 70-120 meV. This deep absorption band was observed for both CdS/CIGS/Mo/SLG and ZnO/CdS/CIGS/Mo/SLG structures. The peak energy of the absorption band was independent of the alloy composition for 0.25≤Ga/III≤0.58. Intensity of the PA signal was negatively correlated to the Na concentration at the CIGS film surface. The origin of the 0.76 eV peak is discussed with relation to native defects such as a Cu-vacancy-related defect (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Joint absorption of lithium and oxygen on the tungsten (100) face

    International Nuclear Information System (INIS)

    Gupalo, M.S.; Smereka, T.P.; Babkin, G.V.; Palyukh, B.M.

    1981-01-01

    The paper deals with studying the effect of oxygen on emission-adsorption properties of metal-film Li-W system. Data on work of phi yield and adsorption heat q of lithium on tungsten face (100), preliminarily coated with different quantity of oxygen, are obtained. The method of contact potential difference was used. Strong decrease of yield work with the increase of oxygen coatings, as well as essential growth of initial adsorption heat are observed. Temperature dependence of phi is not practically observed. The data obtained point out, that oxygen presence on the surface causes increase of dipole momentum of lithium adatoms, which results in bond energy growth and reduction phi minimal value of lithium in the presence of oxygen phi=2 eV, q=2.2 eV is obtained at optimal compositions of oxygen-lithium layers on W (100) [ru

  16. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium: The Chandra Grating Spectra of XTE J1817-330

    Science.gov (United States)

    Gatuzz, E.; Garcia, J.; Menodza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra towards the X-ray low-mass binary XTE J1817-330. The 11-25 A broadband is described with a simple absorption model that takes into account the pileup effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 A) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain: a column density of N(sub H) = 1.38 +/- 0.01 x 10(exp 21) cm(exp -2); ionization parameter of log xi = .2.70 +/- 0.023; oxygen abundance of A(sub O) = 0.689(exp +0.015./-0.010); and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval (1998), a rescaling with the revision by Asplund et al. (2009) yields A(sub O) = 0.952(exp +0.020/-0.013, a value close to solar that reinforces the new standard. We identify several atomic absorption lines.K-alpha , K-beta, and K-gamma in O I and O II; and K-alpha in O III, O VI, and O VII--last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated to ISM cold absorption.

  17. Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium:. [The Chandra Grating Spectra of XTE J1817-330

    Science.gov (United States)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, T. R.; Witthoeft, M.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Angstrom broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Angstroms) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the xstar code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N(sub H) = 1.38 +/- 0.01 × 10(exp 21) cm(exp -2); an ionization parameter of log xi = -2.70 +/- 0.023; an oxygen abundance of A(sub O) = 0.689 (+0.015/-0.010); and ionization fractions of O(sub I)/O = 0.911, O(sub II)/O = 0.077, and O(sub III)/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse & Sauval, a rescaling with the revision by Asplund et al. yields A(sub O) = 0.952(+0.020/-0.013), a value close to solar that reinforces the new standard.We identify several atomic absorption lines-K(alpha), K(beta), and K(gamma) in O(sub I) and O(sub II) and K(alpha) in O(sub III), O(sub VI), and O(sub VII)-the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n greater than 2 associated with ISM cold absorption.

  18. PHOTOIONIZATION MODELING OF OXYGEN K ABSORPTION IN THE INTERSTELLAR MEDIUM: THE CHANDRA GRATING SPECTRA OF XTE J1817-330

    International Nuclear Information System (INIS)

    Gatuzz, E.; Mendoza, C.; García, J.; Lohfink, A.; Kallman, T. R.; Witthoeft, M.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    We present detailed analyses of oxygen K absorption in the interstellar medium (ISM) using four high-resolution Chandra spectra toward the X-ray low-mass binary XTE J1817-330. The 11-25 Å broadband is described with a simple absorption model that takes into account the pile-up effect and results in an estimate of the hydrogen column density. The oxygen K-edge region (21-25 Å) is fitted with the physical warmabs model, which is based on a photoionization model grid generated with the XSTAR code with the most up-to-date atomic database. This approach allows a benchmark of the atomic data which involves wavelength shifts of both the K lines and photoionization cross sections in order to fit the observed spectra accurately. As a result we obtain a column density of N H = 1.38 ± 0.01 × 10 21 cm –2 ; an ionization parameter of log ξ = –2.70 ± 0.023; an oxygen abundance of A O = 0.689 +0.015 -0.010 ; and ionization fractions of O I/O = 0.911, O II/O = 0.077, and O III/O = 0.012 that are in good agreement with results from previous studies. Since the oxygen abundance in warmabs is given relative to the solar standard of Grevesse and Sauval, a rescaling with the revision by Asplund et al. yields A O =0.952 +0.020 -0.013 , a value close to solar that reinforces the new standard. We identify several atomic absorption lines—Kα, Kβ, and Kγ in O I and O II and Kα in O III, O VI, and O VII—the last two probably residing in the neighborhood of the source rather than in the ISM. This is the first firm detection of oxygen K resonances with principal quantum numbers n > 2 associated with ISM cold absorption.

  19. Light scattering by rough surfaces for increase of absorption of low band gap light in solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kloppstech, Konstantin; Knabe, Sebastian; Bauer, Gottfried H. [Institute of Physics, Carl von Ossietzky University Oldenburg (Germany)

    2011-07-01

    Scattering of low band gap light for the increase of the absorption of low band gap photons is commonly formulated in phenomenological magnitudes such as haze factors resulting from experiments at particular scattering media. We have formulated analytically and described by numerical simulations the scattering of light by the interaction of photons with rough surfaces based on wave numbers of photons k{sub {lambda}} and wave numbers of the topological surface contour k{sub s} that has been derived in 2 dimensions via AFM analyses of the contour function h(x,y) of the scattering medium, e.g. a glassy diffusor. We have distinguished two regimes: i) k{sub {lambda}}

  20. Error sources in the retrieval of aerosol information over bright surfaces from satellite measurements in the oxygen A band

    Science.gov (United States)

    Nanda, Swadhin; de Graaf, Martin; Sneep, Maarten; de Haan, Johan F.; Stammes, Piet; Sanders, Abram F. J.; Tuinder, Olaf; Pepijn Veefkind, J.; Levelt, Pieternel F.

    2018-01-01

    Retrieving aerosol optical thickness and aerosol layer height over a bright surface from measured top-of-atmosphere reflectance spectrum in the oxygen A band is known to be challenging, often resulting in large errors. In certain atmospheric conditions and viewing geometries, a loss of sensitivity to aerosol optical thickness has been reported in the literature. This loss of sensitivity has been attributed to a phenomenon known as critical surface albedo regime, which is a range of surface albedos for which the top-of-atmosphere reflectance has minimal sensitivity to aerosol optical thickness. This paper extends the concept of critical surface albedo for aerosol layer height retrievals in the oxygen A band, and discusses its implications. The underlying physics are introduced by analysing the top-of-atmosphere reflectance spectrum as a sum of atmospheric path contribution and surface contribution, obtained using a radiative transfer model. Furthermore, error analysis of an aerosol layer height retrieval algorithm is conducted over dark and bright surfaces to show the dependence on surface reflectance. The analysis shows that the derivative with respect to aerosol layer height of the atmospheric path contribution to the top-of-atmosphere reflectance is opposite in sign to that of the surface contribution - an increase in surface brightness results in a decrease in information content. In the case of aerosol optical thickness, these derivatives are anti-correlated, leading to large retrieval errors in high surface albedo regimes. The consequence of this anti-correlation is demonstrated with measured spectra in the oxygen A band from the GOME-2 instrument on board the Metop-A satellite over the 2010 Russian wildfires incident.

  1. Energy band structure and electrical properties of Ga-oxide/GaN interface formed by remote oxygen plasma

    Science.gov (United States)

    Yamamoto, Taishi; Taoka, Noriyuki; Ohta, Akio; Truyen, Nguyen Xuan; Yamada, Hisashi; Takahashi, Tokio; Ikeda, Mitsuhisa; Makihara, Katsunori; Nakatsuka, Osamu; Shimizu, Mitsuaki; Miyazaki, Seiichi

    2018-06-01

    The energy band structure of a Ga-oxide/GaN structure formed by remote oxygen plasma exposure and the electrical interface properties of the GaN metal–oxide–semiconductor (MOS) capacitors with the SiO2/Ga-oxide/GaN structures with postdeposition annealing (PDA) at various temperatures have been investigated. Reflection high-energy electron diffraction and X-ray photoelectron spectroscopy clarified that the formed Ga-oxide layer is neither a single nor polycrystalline phase with high crystallinity. We found that the energy band offsets at the conduction band minimum and at the valence band maximum between the Ga-oxide layer and the GaN surface were 0.4 and 1.2 ± 0.2 eV, respectively. Furthermore, capacitance–voltage (C–V) characteristics revealed that the interface trap density (D it) is lower than the evaluation limit of Terman method without depending on the PDA temperatures, and that the SiO2/Ga-oxide stack can work as a protection layer to maintain the low D it, avoiding the significant decomposition of GaN at the high PDA temperature of 800 °C.

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

    Energy Technology Data Exchange (ETDEWEB)

    Arora, Amit [D.A.V. Institute of Engineering and Technology, Jalandhar (India); Narang, Sukhleen Bindra, E-mail: sukhleen2@yahoo.com [Department of Electronics Technology, Guru Nanak Dev University, Amritsar (India); Pubby, Kunal [Department of Electronics Technology, Guru Nanak Dev University, Amritsar (India)

    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. - Highlights: • Electromagnetic Characterization of M-hexaferrites in K-band (18–26.5 GHz) • Variation of absorption properties with thickness of sample. • Satisfaction of quarter-wavelength condition for absorption properties • Results of double-layer absorbers (not reports till day by anyone).

  3. Infrared absorption spectra of gaseous HD. II. Collision-induced fundamental band of HD in HD--Ne and HD--Ar mixtures at room temperature

    International Nuclear Information System (INIS)

    Prasad, R.D.G.; Reddy, S.P.

    1976-01-01

    The collision-induced infrared absorption spectra of the fundamental band of HD in binary mixtures of HD with Ne and Ar at room temperature have been studied with an absorption path length of 105.2 cm for different base densities of HD in the range 8--20 amagat and a number of total gas densities up to 175 amagat. The observed features of the profiles of the enhancement of absorption in these mixtures resemble closely those of the corresponding profiles of the fundamental band of H 2 in binary mixtures with Ne and Ar. The binary absorption coefficients of the band obtained from the measured integrated intensities are (1.84 +- 0.06) x 10 -35 and (4.41 +- 0.06) x 10 -35 cm 6 s -1 for HD--Ne and HD--Ar, respectively. The characteristic half-width parameters, delta/subd/ and delta/subc/ of the overlap transitions and delta/subq/ (and delta/subq//sub prime/) of the quadrupolar transitions, are obtained from an analysis of the profiles of the enhancement of absorption in both these mixtures. The quantity delta/subc/ which is the half-width of the intercollisional interference dip of the Q branch increases with the density of the perturbing gas Ne or Ar, and for HD--Ne it varies in a manner similar to that for HD--He as described in Paper I of this series

  4. Temperature-Induced Large Broadening and Blue Shift in the Electronic Band Structure and Optical Absorption of Methylammonium Lead Iodide Perovskite.

    Science.gov (United States)

    Yang, Jia-Yue; Hu, Ming

    2017-08-17

    The power conversion efficiency of hybrid halide perovskite solar cells is profoundly influenced by the operating temperature. Here we investigate the temperature influence on the electronic band structure and optical absorption of cubic CH 3 NH 3 PbI 3 from first-principles by accounting for both the electron-phonon interaction and thermal expansion. Within the framework of density functional perturbation theory, the electron-phonon coupling induces slightly enlarged band gap and strongly broadened electronic relaxation time as temperature increases. The large broadening effect is mainly due to the presence of cation organic atoms. Consequently, the temperature-dependent absorption peak exhibits blue-shift position, decreased amplitude, and broadened width. This work uncovers the atomistic origin of temperature influence on the optical absorption of cubic CH 3 NH 3 PbI 3 and can provide guidance to design high-performance hybrid halide perovskite solar cells at different operating temperatures.

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

    Energy Technology Data Exchange (ETDEWEB)

    Narang, Sukhleen Bindra, E-mail: sukhleen2@yahoo.com [Department of Electronics Technology, Guru Nanak Dev University, Amritsar (India); Pubby, Kunal, E-mail: kunalpubby02@gmail.com [Department of Electronics Technology, Guru Nanak Dev University, Amritsar (India); Chawla, S.K., E-mail: sschawla118@gmail.com [Department of Chemistry, Centre for Advanced Studies-I, Guru Nanak Dev University, Amritsar (India); Kaur, Prabhjyot, E-mail: prabhjyot.2525@gmail.com [Department of Chemistry, Centre for Advanced Studies-I, Guru Nanak Dev University, Amritsar (India)

    2017-03-15

    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. - Highlights: • EM analysis of Sr Hexaferrites in Ku-band. • Factors towards absorption peak intensity & location.

  6. Band 3 protein function in teleost fish erythrocytes: effect of oxygenation-deoxygenation

    Czech Academy of Sciences Publication Activity Database

    Russo, A.; Tellone, E.; Ficarra, S.; Giardina, B.; Bellocco, E.; Lagana, G.; Leuzzi, U.; Kotyk, Arnošt; Galtieri, A.

    2008-01-01

    Roč. 57, č. 1 (2008), s. 49-54 ISSN 0862-8408 Institutional research plan: CEZ:AV0Z50110509 Keywords : erythrocytes * hemoglobin * band 3 protein Subject RIV: CE - Biochemistry Impact factor: 1.653, year: 2008

  7. A cell for extended x-ray absorption fine structure studies of oxygen sensitive products of redox reactions

    International Nuclear Information System (INIS)

    Furenlid, L.R.; Renner, M.W.; Fajer, J.

    1990-01-01

    We describe a cell suitable for extended x-ray absorption fine structure (EXAFS) studies of oxygen and/or water sensitive products of redox reactions. The cell utilizes aluminized Mylar windows that are transparent to x rays, provide low gas permeability, and allow vacuum to be maintained in the cell. The windows are attached to the glassware with an epoxy that resists attack by common organic solvents. Additional side arms allow multiple spectroscopic probes of the same sample under anaerobic and anhydrous conditions

  8. Experimental study and calculations of nitric oxide absorption in the γ(0,0) and γ(1,0) bands for strong temperature conditions

    International Nuclear Information System (INIS)

    Trad, H.; Higelin, P.; Djebaieli-Chaumeix, N.; Mounaim-Rousselle, C.

    2005-01-01

    Absorption spectra of nitric oxide in the γ(0,0) and γ(1,0) bands have been measured for hard temperature conditions up to 1700 K in order to validate a model for the simulation of these two bands. The good agreement between experiments and calculations (relative errors of 2-5% for the γ(0,0) band and 10-15% for the γ(1,0) band) consolidates the two important assumptions concerning the intermediate Hund's case between (a) and (b) for the X 2 Π state of the γ(0,0) and γ(1,0) absorption bands and the use of collisional broadening parameters of γ(0,0) to simulate the γ(1,0) band. Using this simulation, a study of the Beer-Lambert law behavior at high temperature has been carried out. With the instrument resolution used for these experiments, it was shown that a correction of the Beer-Lambert law is necessary. To apply this technique for the measurements of NO concentrations inside the combustion chamber of an optical SI engine, a new formulation of the Beer-Lambert law has been introduced, since the modified form proposed in the literature is no longer applicable in the total column range of interest

  9. Oxygen K-edge absorption spectra of small molecules in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Yang, B.X.; Kirz, J.; Sham, T.K.

    1986-01-01

    The absorption spectra of O/sub 2/, CO, CO/sub 2/ and OCS have been recorded in a transmission mode in the energy region from 500 to 950 eV. Recent observation of EXAFS in these molecules is confirmed in this study. 7 refs., 3 figs.

  10. Oxygen K-edge absorption spectra of small molecules in the gas phase

    International Nuclear Information System (INIS)

    Yang, B.X.; Kirz, J.; Sham, T.K.

    1986-01-01

    The absorption spectra of O 2 , CO, CO 2 and OCS have been recorded in a transmission mode in the energy region from 500 to 950 eV. Recent observation of EXAFS in these molecules is confirmed in this study. 7 refs., 3 figs

  11. Compositional dependence of absorption coefficient and band-gap for Nb2O5-SiO2 mixture thin films

    International Nuclear Information System (INIS)

    Sancho-Parramon, Jordi; Janicki, Vesna; Zorc, Hrvoje

    2008-01-01

    The absorption coefficient of composite films consisting of niobia (Nb 2 O 5 ) and silica (SiO 2 ) mixtures is studied for photon energies around the band gap. The films were deposited by co-evaporation and their composition was varied by changing the ratio of deposition rates of the two materials. Both, as-deposited and thermally annealed films were characterized by different techniques: the absorption coefficient was determined by spectrophotometric measurements and the structural properties were investigated using infrared spectroscopy, transmission electron microscopy and X-ray diffraction. The correlation between the variations of absorption properties and film composition and structure is established. The absorption coefficients determined experimentally are compared with the results derived from effective medium theories in order to evaluate the suitability of these theories for the studied composites

  12. Optical absorption and oxygen passivation of surface states in III-nitride photonic devices

    Science.gov (United States)

    Rousseau, Ian; Callsen, Gordon; Jacopin, Gwénolé; Carlin, Jean-François; Butté, Raphaël; Grandjean, Nicolas

    2018-03-01

    III-nitride surface states are expected to impact high surface-to-volume ratio devices, such as nano- and micro-wire light-emitting diodes, transistors, and photonic integrated circuits. In this work, reversible photoinduced oxygen desorption from III-nitride microdisk resonator surfaces is shown to increase optical attenuation of whispering gallery modes by 100 cm-1 at λ = 450 nm. Comparison of photoinduced oxygen desorption in unintentionally and n+-doped microdisks suggests that the spectral changes originate from the unpinning of the surface Fermi level, likely taking place at etched nonpolar III-nitride sidewalls. An oxygen-rich surface prepared by thermal annealing results in a broadband Q improvement to state-of-the-art values exceeding 1 × 104 at 2.6 eV. Such findings emphasize the importance of optically active surface states and their passivation for future nanoscale III-nitride optoelectronic and photonic devices.

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

    Science.gov (United States)

    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.

  14. Oxygen, Neon, and Iron X-Ray Absorption in the Local Interstellar Medium

    Science.gov (United States)

    Gatuzz, Efrain; Garcia, Javier; Kallman, Timothy R.; Mendoza, Claudio

    2016-01-01

    We present a detailed study of X-ray absorption in the local interstellar medium by analyzing the X-ray spectra of 24 galactic sources obtained with the Chandra High Energy Transmission Grating Spectrometer and the XMM-Newton Reflection Grating Spectrometer. Methods. By modeling the continuum with a simple broken power-law and by implementing the new ISMabs X-ray absorption model, we have estimated the total H, O, Ne, and Fe column densities towards the observed sources. Results. We have determined the absorbing material distribution as a function of source distance and galactic latitude longitude. Conclusions. Direct estimates of the fractions of neutrally, singly, and doubly ionized species of O, Ne, and Fe reveal the dominance of the cold component, thus indicating an overall low degree of ionization. Our results are expected to be sensitive to the model used to describe the continuum in all sources.

  15. Two-photon spectroscopy study of edge absorption peculiarities in oxygen-octahedric ferroelectrics

    International Nuclear Information System (INIS)

    Shablaev, S.I.; Danishevskij, A.M.; Subashiev, V.K.

    1984-01-01

    Two-photon absorption (TPA) spectra of ferroelectric crystals with BaTiO 3 , KTaO 3 and SrTiO 3 perovskite strUcture Were obtained. The detailed investigation of temperature dependence of edge spectrum regions was conducted and on the basis of their analysis the indirect character of edge absorption was concluded for all mentioned crystals. TPA spectra of BaTiO 3 and KTaO 3 are characterized by the regions corresponding to one indirect edge TPA spectra of SrTiO 3 - to two indirect edges. The corresponding inter-zone gaps were determined for all investigated crystals, the energy of phonons, participating in indirect two photon transitions, inter-zone gaps, corresponding to direct transitions were determined as well

  16. Analysis of the intermediate-band absorption properties of type-II GaSb/GaAs quantum-dot photovoltaics

    Science.gov (United States)

    Ramiro, I.; Villa, J.; Tablero, C.; Antolín, E.; Luque, A.; Martí, A.; Hwang, J.; Phillips, J.; Martin, A. J.; Millunchick, J.

    2017-09-01

    Quantum-dot (QD) intermediate-band (IB) materials are regarded as promising candidates for high-efficiency photovoltaics. The sequential two-step two-photon absorption processes that take place in these materials have been proposed to develop high-efficiency solar cells and infrared (IR) photodetectors. In this work, we experimentally and theoretically study the interrelation of the absorptivity with transitions of carriers to and from the IB in type-II GaSb/GaAs QD devices. Our devices exhibit three optical band gaps with: EL=0.49 eV ,EH=1.02 eV , and EG=1.52 eV , with the IB located 0.49 eV above the valence band. These values are well supported by semiempirical calculations of the QDs electronic structure. Through intensity-dependent two-photon photocurrent experiments, we are able to vary the filling state of the IB, thus modifying the absorptivity of the transitions to and from this band. By filling the IB with holes via E =1.32 eV or E =1.93 eV monochromatic illumination, we demonstrate an increase in the EL-related absorptivity of more than two orders of magnitude and a decrease in the EH-related absorptivity of one order of magnitude. The antisymmetrical evolution of those absorptivities is quantitatively explained by a photoinduced shift of the quasi-Fermi level of the IB. Furthermore, we report the observation of a two-photon photovoltage, i.e., the contribution of subband gap two-photon absorption to increase the open-circuit voltage of solar cells. We find that the generation of the two-photon photovoltage is related, in general, to the production of a two-photon photocurrent. However, while photons with energy close to EL participate in the production of the two-photon photocurrent, they are not effective in the production of a two-photon photovoltage. We also report the responsivity of GaSb/GaAs QD devices performing as optically triggered photodetectors. These devices exhibit an amplification factor of almost 400 in the IR spectral region. This high

  17. Collision-induced absorption by D{sub 2} pairs in the first overtone band at 77, 201 and 298 K

    Energy Technology Data Exchange (ETDEWEB)

    Abu-Kharma, M.; Gillard, P.G.; Reddy, S.P. [Memorial University of Newfoundland, Dept. of Physics and Physical Oceanography, Newfoundland (Canada)

    2006-01-15

    Collision induced absorption (CIA) spectra of pure D{sub 2} in the first overtone region from 5250 to 7250 cm{sup -1}, recorded at 77, 201 and 298 K, have been analyzed. The observed spectra at 77, 201 and 298 K were modelled by a total of 92, 214 and 267 components respectively of double vibrational transitions at room temperature of the type X{sub 2}(J) +X{sub 0}(J) and X{sub 1}(J) + X{sub 1}(J), where X is O, Q or S transitions. Profile analyses of the spectra were carried out using the Birnbaum-Cohen line-shape function for the individual components of the band, and characteristic line shape parameters were determined from the analysis. The observed and calculated profiles agree well over the whole overtone band, and the agreement is better than 97% in the three cases studied. Binary and ternary absorption coefficients were determined from the integrated absorption of the band. (authors)

  18. Inferences about pressures and vertical extension of cloud layers from POLDER3/PARASOL measurements in the oxygen A-band

    Science.gov (United States)

    Desmons, Marine; Ferlay, Nicolas; Parol, Frédéric; Vanbauce, Claudine; Mcharek, Linda

    2013-05-01

    We present new inferences about cloud vertical structures from multidirectionnal measurements in the oxygen A-band. The analysis of collocated data provided by instruments onboard satellite platforms within the A-Train, as well as simulations have shown that for monolayered clouds, the cloud oxygen pressure PO2 derived from the POLDER3 instrument was sensitive to the cloud vertical structure in two ways: First, PO2 is actually close to the pressure of the geometrical middle of cloud and we propose a method to correct it to get the cloud top pressure (CTP), and then to obtain the cloud geometrical extent. Second, for the liquid water clouds, the angular standard deviation σPO2 of PO2 is correlated with the geometrical extent of cloud layers, which makes possible a second estimation of the cloud geometrical thickness. The determination of the vertical location of cloud layers from passive measurements, eventually completed from other observations, would be useful in many applications for which cloud macrophysical properties are needed.

  19. Extended x-ray absorption fine structure spectroscopy and x-ray absorption near edge spectroscopy study of aliovalent doped ceria to correlate local structural changes with oxygen vacancies clustering

    Energy Technology Data Exchange (ETDEWEB)

    Shirbhate, S. C.; Acharya, S. A., E-mail: saha275@yahoo.com [Department of Physics, Rashtrasant Tukadoji Maharaj Nagpur University, Nagpur 440033 (India); Yadav, A. K. [Atomic and molecular Physics Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2016-04-04

    This study provides atomic scale insight to understand the role of aliovalent dopants on oxygen vacancies clustering and dissociation mechanism in ceria system in order to enhance the performance of oxy-ion conductor. Dopants induced microscale changes in ceria are probed by extended X-ray absorption fine structure spectroscopy, X-ray absorption near edge spectra, and Raman spectroscopy. The results are explored to establish a correlation between atomic level structural changes (coordination number, interatomic spacing) → formation of dimer and trimer type cation-oxygen vacancies defect complex (intrinsic and extrinsic) → dissociation of oxygen vacancies from defect cluster → ionic conductivity temperature. It is a strategic approach to understand key physics of ionic conductivity mechanism in order to reduce operating temperature of electrolytes for intermediate temperature (300–450 °C) electrochemical devices for the first time.

  20. Importance of doping, dopant distribution, and defects on electronic band structure alteration of metal oxide nanoparticles: Implications for reactive oxygen species

    International Nuclear Information System (INIS)

    Saleh, Navid B.; Milliron, Delia J.; Aich, Nirupam; Katz, Lynn E.; Liljestrand, Howard M.; Kirisits, Mary Jo

    2016-01-01

    Metal oxide nanoparticles (MONPs) are considered to have the potency to generate reactive oxygen species (ROS), one of the key mechanisms underlying nanotoxicity. However, the nanotoxicology literature demonstrates a lack of consensus on the dominant toxicity mechanism(s) for a particular MONP. Moreover, recent literature has studied the correlation between band structure of pristine MONPs to their ability to introduce ROS and thus has downplayed the ROS-mediated toxicological relevance of a number of such materials. On the other hand, material science can control the band structure of these materials to engineer their electronic and optical properties and thereby is constantly modulating the pristine electronic structure. Since band structure is the fundamental material property that controls ROS-producing ability, band tuning via introduction of dopants and defects needs careful consideration in toxicity assessments. This commentary critically evaluates the existing material science and nanotoxicity literature and identifies the gap in our understanding of the role of important crystal structure features (i.e., dopants and defects) on MONPs' electronic structure alteration as well as their ROS-generation capability. Furthermore, this commentary provides suggestions on characterization techniques to evaluate dopants and defects on the crystal structure and identifies research needs for advanced theoretical predictions of their electronic band structures and ROS-generation abilities. Correlation of electronic band structure and ROS will not only aid in better mechanistic assessment of nanotoxicity but will be impactful in designing and developing ROS-based applications ranging from water disinfection to next-generation antibiotics and even cancer therapeutics. - Highlights: • Metal oxide nanoparticles (MONPs) produce reactive oxygen species (ROS) • Band structure of pristine MONPs is different than those with dopants/defects • Dopants/defects modulate

  1. Importance of doping, dopant distribution, and defects on electronic band structure alteration of metal oxide nanoparticles: Implications for reactive oxygen species

    Energy Technology Data Exchange (ETDEWEB)

    Saleh, Navid B., E-mail: navid.saleh@utexas.edu [Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX 78712 (United States); Milliron, Delia J. [McKetta Department of Chemical Engineering, University of Texas, Austin, TX 78712 (United States); Aich, Nirupam [Department of Civil, Structural and Environmental Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260 (United States); Katz, Lynn E.; Liljestrand, Howard M.; Kirisits, Mary Jo [Department of Civil, Architectural, and Environmental Engineering, University of Texas, Austin, TX 78712 (United States)

    2016-10-15

    Metal oxide nanoparticles (MONPs) are considered to have the potency to generate reactive oxygen species (ROS), one of the key mechanisms underlying nanotoxicity. However, the nanotoxicology literature demonstrates a lack of consensus on the dominant toxicity mechanism(s) for a particular MONP. Moreover, recent literature has studied the correlation between band structure of pristine MONPs to their ability to introduce ROS and thus has downplayed the ROS-mediated toxicological relevance of a number of such materials. On the other hand, material science can control the band structure of these materials to engineer their electronic and optical properties and thereby is constantly modulating the pristine electronic structure. Since band structure is the fundamental material property that controls ROS-producing ability, band tuning via introduction of dopants and defects needs careful consideration in toxicity assessments. This commentary critically evaluates the existing material science and nanotoxicity literature and identifies the gap in our understanding of the role of important crystal structure features (i.e., dopants and defects) on MONPs' electronic structure alteration as well as their ROS-generation capability. Furthermore, this commentary provides suggestions on characterization techniques to evaluate dopants and defects on the crystal structure and identifies research needs for advanced theoretical predictions of their electronic band structures and ROS-generation abilities. Correlation of electronic band structure and ROS will not only aid in better mechanistic assessment of nanotoxicity but will be impactful in designing and developing ROS-based applications ranging from water disinfection to next-generation antibiotics and even cancer therapeutics. - Highlights: • Metal oxide nanoparticles (MONPs) produce reactive oxygen species (ROS) • Band structure of pristine MONPs is different than those with dopants/defects • Dopants/defects modulate

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

    Science.gov (United States)

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

    1993-01-01

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

  3. Effect of Co substitution on absorption properties of SrCoxFe12-xO19 hexagonal ferrites based nanocomposites in X-band

    Science.gov (United States)

    Chakraborty, Soma; Bhattacharyya, Nidhi Saxena; Bhattacharyya, Satyajib

    2017-12-01

    Cobalt doped M-type strontium hexaferrite nanoparticles (SrCoxFe12-xO19, x = 0.2-1.2) is synthesized and used as inclusions in Linear Low Density Polyethylene (LLDPE) matrix for developing nano-composites with 60 wt% of these nanoparticles. Absorption performance of the developed nano-composites is evaluated in the X-band. The thickness optimization is carried out for obtaining maximum reflection loss by using the transmission line model (TLM), with measured values of permittivity and permeability of the composite. The best reflection loss is observed experimentally for x = 0.8 with an absorber thickness of 3 mm for which a wide -10 dB bandwidth covering almost the entire X-band is obtained. The composites are light weight and not affected by exposure to water.

  4. Re-investigation of the (3, 0) band in the b4Σ- - a4Π system for nitric oxide by laser absorption spectroscopy

    Science.gov (United States)

    Li, Chuanliang; Shao, Ligang; Wang, Hailing; Zhou, Qinghong; Qiu, Xuanbing; Wei, Jilin; Deng, Lunhua; Chen, Yangqin

    2018-04-01

    Nitric oxide (NO) radicals in the a4Π state were produced by discharging the mixture of NO gas and helium at the audio frequency. In the near infrared region, the spectra of the b4Σ- - a4Π system of the NO radical were studied by optical heterodyne - concentration modulation laser absorption spectroscopy. More than one hundred and thirty lines and eleven branches were recorded for the first time and assigned to the (3, 0) band. A global fitting was carried out to extract the molecular constants. In particular, the parameters D, p, γ and AD were precisely determined.

  5. X-ray absorption spectroscopy on the calcium cofactor to the manganese cluster in photosynthetic oxygen evolution

    Energy Technology Data Exchange (ETDEWEB)

    Cinco, Roehl M. [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    Along with Mn, calcium and chloride ions are necessary cofactors for oxygen evolution in Photosystem II (PS II). To further test and verify whether Ca is close to the Mn cluster, the authors substituted strontium for Ca and probed from the Sr point of view for any nearby Mn. The extended X-ray absorption fine structure (EXAFS) of Sr-reactivated PS II indicates major differences between the intact and NH2OH-treated samples. In intact samples, the Fourier transform of the Sr EXAFS shows a Fourier peak that is missing in inactive samples. This peak II is best simulated by two Mn neighbors at a distance of 3.5 Angstrom, confirming the proximity of Ca (Sr) cofactor to the Mn cluster. In addition, polarized Sr EXAFS on oriented Sr-reactivated samples shows this peak II is dichroic: large magnitude at 10 degrees (angle between the PS II membrane normal and the x-ray electric field vector) and small at 80 degrees. Analysis of the dichroism yields the relative angle between the Sr-Mn vector and membrane normal (23 degrees ± 4 degrees), and the isotropic coordination number for these layered samples. X-ray absorption spectroscopy has also been employed to assess the degree of similarity between the manganese cluster in PS II and a family of synthetic manganese complexes containing the distorted cubane [Mn4O3X] core (X = benzoate, acetate, methoxide, hydroxide, azide, fluoride, chloride or bromide). In addition, Mn4O3Cl complexes containing three or six terminal Cl ligands at three of the Mn were included in this study. The EXAFS method detects the small changes in the core structures as X is varied in this series, and serves to exclude these distorted cubanes of C3v symmetry as a topological model for the Mn catalytic cluster. The sulfur K-edge x-ray absorption near-edge structure (XANES) spectra for the amino acids cysteine, methionine, their corresponding oxidized forms cystine and methionine sulfoxide, and

  6. Previously unreported intense absorption band and the pK/sub A/ of protonated triplet methylene blue

    Energy Technology Data Exchange (ETDEWEB)

    Ohno, T.; Osif, T.L.; Lichtin, N.N.

    1979-01-01

    Excitation by a Q-switched giant ruby laser (1.2 joule output at 694 nm, approx. 50 nsec flash) of 2-10 ..mu..M solutions of methylene blue in water, 30% ethanol in water or 50 v/v% water - CH/sub 3/CN at pH values in the range 2.0 - 9.3 converted the dye essentially completely to its T/sub 1/ state. The absorption spectrum of T/sub 1/ dye was measured in different media at pH 2.0 and 8.2 by kinetic spectrophotometry. Previously reported T-T absorption in the violet in acidic and alkaline solutions and in the near infrared in alkaline solution was confirmed. Values found for these absorptions in the present work with 30% ethanol in water as solvent are lambda/sub max/ approx. 370 nm, epsilon/sub max/ approx. 13,200 M/sup -1/ cm/sup -1/ at pH 2 and lambda/sub max/ approx. 420 nm, epsilon/sub max/ approx. 9,000 M/sup -1/ cm/sup -1/, lambda/sub max/ approx. 840 nm, epsilon/sub max/ approx. 20,000 M/sup -1/ cm/sup -1/ at pH 8.2. Long-wavelength T-T absorption in acidic solution is reported here for the first time: lambda/sub max/ approx. 680 nm, epsilon/sub max/ approx. 19,000 M/sup -1/ cm/sup -1/ in 30% ethanol in water at pH 2. Observation of a pH-independent isobestic point approx. 720 nm confirms that the long-wavelength absorptions are due to different protonated states of the same species, MB/sup +/(T/sub 1/) and MBH/sup 2 +/(T/sub 1/). The pK/sub A/ of MBH/sup 2 +/(T/sub 1/) in water was determined from the dependence on pH of absorption at 700 and 825 nm to be 7.1/sub 4/ +- .1 and from the kinetics of decay of triplet absorption to be 7.2. The specific rate of protonation of MB/sup +/(T/sub 1/) by H/sub 2/PO/sub 4//sup -/ in water at pH 4.4 was found to be 4.5 +- .4 x 10/sup 8/ M/sup -1/ sec/sup -1/.

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

    Science.gov (United States)

    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.

  8. Electrochemical kinetics and X-ray absorption spectroscopy investigations of select chalcogenide electrocatalysts for oxygen reduction reaction applications

    International Nuclear Information System (INIS)

    Ziegelbauer, Joseph M.; Murthi, Vivek S.; O'Laoire, Cormac; Gulla, Andrea F.; Mukerjee, Sanjeev

    2008-01-01

    Transition metal-based chalcogenide electrocatalysts exhibit a promising level of performance for oxygen reduction reaction applications while offering significant economic benefits over the state of the art Pt/C systems. The most active materials are based on Ru x Se y clusters, but the toxicity of selenium will most likely limit their embrace by the marketplace. Sulfur-based analogues do not suffer from toxicity issues, but suffer from substantially less activity and stability than their selenium brethren. The structure/property relationships that result in these properties are not understood due to ambiguities regarding the specific morphologies of Ru x S y -based chalcogenides. To clarify these properties, an electrochemical kinetics study was interpreted in light of extensive X-ray diffraction, scanning electron microscopy, and in situ X-ray absorption spectroscopy evaluations. The performance characteristics of ternary M x Ru y S z /C (M = Mo, Rh, or Re) chalcogenide electrocatalysts synthesized by the now-standard low-temperature nonaqueous (NA) route are compared to commercially available (De Nora) Rh- and Ru-based systems. Interpretation of performance differences is made in regards to bulk and surface properties of these systems. In particular, the overall trends of the measured activation energies in respect to increasing overpotential and the gross energy values can be explained in regards to these differences

  9. Mesoarchean Banded Iron Formation sequences in Dixon Island-Cleaverville Formation, Pilbara Australia: Oxygenic signal from DXCL project

    Science.gov (United States)

    Kiyokawa, S.; Ito, T.; Ikehara, M.; Yamaguchi, K. E.; Naraoka, H.; Onoue, T.; Horie, K.; Sakamoto, R.; Aihara, Y.; Miki, T.

    2013-12-01

    The 3.2-3.1 Ga Dixon island-Cleaverville formations are well-preserved Banded Iron Formation (BIF) within hydrothermal oceanic sequence at oceanic island arc setting (Kiyokawa et al., 2002, 2006, 2012). The stratigraphy of the Dixon Island (3195+15Ma) -Cleaverville (3108+13Ma) formations shows the well preserved environmental condition at the Mesoarchean ocean floor. The stratigraphy of these formations are formed about volcano-sedimentary sequences with hydrothermal chert, black shale and banded iron formation to the top. Based on the scientific drilling of DXCL project at 2007 and 2011, detail lithology between BIF sequence was clearly understood. Four drilling holes had been done at coastal sites; the Dixon Island Formation is DX site (100m) and the Cleaverville Formation is CL2 (40m), CL1 (60m) and CL3 (200m) sites and from stratigraphic bottom to top. Coarsening and thickening upward black shale-BIF sequences are well preserved of the stratigraphy form the core samples. The Dixon Island Formation consists komatiite-rhyolite sequences with many hydrothermal veins and very fine laminated cherty rocks above them. The Cleaverville Formation contains black shale, fragments-bearing pyroclastic beds, white chert, greenish shale and BIF. The CL3 core, which drilled through BIF, shows siderite-chert beds above black shale identified before magnetite lamination bed. U-Pb SHRIMP data of the tuff in lower Dixon Island Formation is 3195+15 Ma and the pyroclastic sequence below the Cleaverville BIF is 3108+13 Ma. Sedimentation rate of these sequence is 2-8 cm/ 1000year. The hole section of the organic carbon rich black shales below BIF are similar amount of organic content and 13C isotope (around -30per mill). There are very weak sulfur MIF signal (less 0.2%) in these black shale sequence. Our result show that thick organic rich sediments may be triggered to form iron rich siderite and magnetite iron beds. The stratigraphy in this sequence quite resemble to other Iron

  10. Improved spectral absorption coefficient grouping strategy of wide band k-distribution model used for calculation of infrared remote sensing signal of hot exhaust systems

    Science.gov (United States)

    Hu, Haiyang; Wang, Qiang

    2018-07-01

    A new strategy for grouping spectral absorption coefficients, considering the influences of both temperature and species mole ratio inhomogeneities on correlated-k characteristics of the spectra of gas mixtures, has been deduced to match the calculation method of spectral overlap parameter used in multiscale multigroup wide band k-distribution model. By comparison with current spectral absorption coefficient grouping strategies, for which only the influence of temperature inhomogeneity on the correlated-k characteristics of spectra of single species was considered, the improvements in calculation accuracies resulting from the new grouping strategy were evaluated using a series of 0D cases in which radiance under 3-5-μm wave band emitted by hot combustion gas of hydrocarbon fuel was attenuated by atmosphere with quite different temperature and mole ratios of water vapor and carbon monoxide to carbon dioxide. Finally, evaluations are presented on the calculation of remote sensing thermal images of transonic hot jet exhausted from a chevron ejecting nozzle with solid wall cooling system.

  11. Intrinsic defect oriented visible region absorption in zinc oxide films

    Science.gov (United States)

    Rakhesh, V.; Shankar, Balakrishnan

    2018-05-01

    Zinc Oxide films were deposited on the glass substrate using vacuum arc sputtering technology. Films were prepared in oxygen ambience for 10mA and 15 mA deposition current separately. The UV-Visible spectroscopy of the samples showed that both samples possess sharp absorption near 3.5eV which is the characteristic band gap absorption energy of ZnO films. The absorption coefficient were calculated for the samples and the (αℎϑ)2 vs energy plot is drawn. The plot suggested that in addition to the sharp band edge absorption, the sample prepared at 10mA deposition current showed sharp absorption edge near 1.51eV and that at 15 mA showed absorption edge near 1.47eV. This refers to the presence of an intrinsic defect level which is likely to be deep in the band gap.

  12. Induced absorption spectra of the infrared fundamental band of molecular deuterium at 77 K: S1( J)+S0( J) transitions

    International Nuclear Information System (INIS)

    Gillard, P.G.; Prasad, R.D.G.; Reddy, S.P.

    1984-01-01

    The collision-induced spectra of the fundamental band of normal D 2 in the high frequency region 3200--3700 cm -1 were recorded for gas densities in the range 80--140 amagat at 77 K with a 2 m absorption cell. The contribution to the intensity of the band in this region comes from the high frequency wings of quadrupolar transitions S 1 ( J) and Q 1 ( J)+S 0 ( J) with J = 0 and 1, and from the group of transitions S 1 (2) and Q 1 ( J)+S 0 (2) with J = 0, 1, and 2 as well as from the relatively weaker double rotational transitions of the type S 1 ( J)+S 0 ( J); the latter transitions arise from the intermolecular interaction between the anisotropic component of the polarizability of one of the colliding pairs of molecules and the quadrupole field of the other. The experimental profiles were analyzed by assuming appropriate line shape functions and using the theoretical matrix elements of the quadrupole moment, isotropic polarizability, and anisotropy of polarizability of the D 2 molecule. From this analysis the characteristic half-width parameters delta/sub q/2 and delta/sub q/4 of the quadrupolar transitions and the binary and ternary absorption coefficients of the S 1 ( J)+S 0 ( J) transitions have been obtained. The experimental value of the binary absorption coefficient of S 1 (0)+S 0 (0) is (2.2 +- 0.1) x 10 -9 cm -1 amagat -2 and the corresponding theoretical value is 1.53 x 10 -9 cm -1 amagat -2

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

    Science.gov (United States)

    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.

  14. Theoretical modeling of deuteration-induced shifts of the 0-0 bands in absorption spectra of selected aromatic amines: the role of the double-well potential.

    Science.gov (United States)

    Andrzejak, Marcin; Kolek, Przemysław

    2013-12-05

    The harmonic approximation fails for inversion of the NH2 group in the ground state of aromatic amines as this vibration is characterized by a symmetric double-well potential with relatively small energy barrier. In such cases, the standard harmonic vibrational analysis is inapplicable: the inversion frequency calculated for the bottom of the potential well is strongly overestimated, while it attains imaginary values for the planar conformation of the molecule. The model calculations are discussed taking explicitly into account the presence of the double-well potential. The study is initially focused on reproduction of the deuteration-induced shifts of the 0-0 absorption band for anthranilic acid. The (incorrect) harmonic frequency of the NH2 inversion is replaced by a better one, obtained from numerical calculations employing a simple, quartic-quadratic model for the double-well potential, which is parametrized using just the harmonic frequency of the inversion and the height of the energy barrier. This operation brings theoretical results to qualitative agreement with experiment. A still better match is achieved with a modified version of the model that accounts for mixing of the NH2 inversion mode with other normal modes while retaining the initial simplicity of one-dimensional approach. The corrected results show surprisingly good accuracy, with deviations of the calculated shifts from the experimental values reduced to less than 5 cm(-1). In order to test the performance of the model for systems with higher energy barrier for the NH2 inversion, we have measured the LIF excitation spectra of three different amminobenzonitriles. Partial assignment of the 0-0 bands has been achieved based on their relative intensities for samples with different isotopic exchange ratios. Calculated shifts are in excellent agreement with experimental values for the identified bands. Theoretical predictions are used to complete the assignment of the 0-0 bands in the spectra of the

  15. Microwave absorption in X and Ku band frequency of cotton fabric coated with Ni–Zn ferrite and carbon formulation in polyurethane matrix

    International Nuclear Information System (INIS)

    Gupta, K.K.; Abbas, S.M.; Goswami, T.H.; Abhyankar, A.C.

    2014-01-01

    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 0.5 Zn 0.5 Fe 2 O 4 ) 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. - Highlights: • Ni–Zn ferrite (Ni 0.5 Zn 0.5 Fe 2 O 4 ) with acetylene black found effective coating for microwave absorption. • Coating formulation containing 40 wt% ferrite, 3 wt% carbon and 57 wt% PU offered 40% absorption, 20% transmission and 40% reflection

  16. Microwave absorption in X and Ku band frequency of cotton fabric coated with Ni–Zn ferrite and carbon formulation in polyurethane matrix

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, K.K., E-mail: krishna62@rediffmail.com [Defence Materials and Stores Research and Development Establishment, Kanpur PO, GT Road, Kanpur 208013 (India); Abbas, S.M.; Goswami, T.H. [Defence Materials and Stores Research and Development Establishment, Kanpur PO, GT Road, Kanpur 208013 (India); Abhyankar, A.C. [Defence Institute of Advanced Technology( DIAT), Giri Nagar, Pune 411025 (India)

    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 {sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) 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. - Highlights: • Ni–Zn ferrite (Ni{sub 0.5}Zn{sub 0.5}Fe{sub 2}O{sub 4}) with acetylene black found effective coating for microwave absorption. • Coating formulation containing 40 wt% ferrite, 3 wt% carbon and 57 wt% PU offered 40% absorption, 20

  17. Effective dielectric function of TiO2 nanoparticles under laser pumping in the fundamental absorption band

    Science.gov (United States)

    Zimnyakov, D. A.; Yuvchenko, S. A.

    2017-06-01

    A nonlinear optical response of TiO2 nanoparticles under pumping by 355-nm laser radiation is experimentally investigated. Using the data obtained by z-scanning with simultaneous measurement of the scattering intensity, the effective permittivity of particles is reconstructed as a function of the pump intensity. It is found that graphical mapping of the relationship between the real and imaginary parts of the permittivity can be obtained using an affine transformation of a similar map of the frequency-dependent dielectric function for the Lorentz model. It is shown that an increase in the pump intensity should lead to a red shift of the absorption maximum of nanoparticles and a rise in the plasma frequency, which is estimated (using a single-oscillator Lorenz model) from the obtained values of the real and imaginary parts of the effective permittivity for the probe radiation wavelength in use.

  18. Atmospheric dayglow diagnostics involving the O2(b-X) Atmospheric band emission: Global Oxygen and Temperature (GOAT) mapping

    Science.gov (United States)

    Slanger, T. G.; Pejaković, D. A.; Kostko, O.; Matsiev, D.; Kalogerakis, K. S.

    2017-03-01

    The terrestrial dayglow displays prominent emission features from the 0-0 and 1-1 bands of the O2 Atmospheric band system in the 760-780 nm region. We present an analysis of observations in this wavelength region recorded by the Space Shuttle during the Arizona Airglow Experiment. A major conclusion is that the dominant product of O(1D) + O2 energy transfer is O2(b, v = 1), a result that corroborates our previous laboratory studies. Moreover, critical to the interpretation of dayglow is the possible interference by N2 and N2+ bands in the 760-780 nm region, where the single-most important component is the N2 1PG 3-1 band that overlaps with the O2(b-X) 0-0 band. When present, this background must be accounted for to reveal the O2(b-X) 0-0 and 1-1 bands for altitudes at which the O2 and N2/N2+ emissions coincide. Finally, we exploit the very different collisional behavior of the two lowest O2(b) vibrational levels to outline a remote sensing technique that provides information on Atmospheric composition and temperature from space-based observations of the 0-0 and 1-1 O2 atmospheric bands.

  19. Measurements and modeling of absorption by CO2 + H2O mixtures in the spectral region beyond the CO2 ν3-band head

    Science.gov (United States)

    Tran, H.; Turbet, M.; Chelin, P.; Landsheere, X.

    2018-05-01

    In this work, we measured the absorption by CO2 + H2O mixtures from 2400 to 2600 cm-1 which corresponds to the spectral region beyond the ν3 band head of CO2. Transmission spectra of CO2 mixed with water vapor were recorded with a high-resolution Fourier-transform spectrometer for various pressure, temperature and concentration conditions. The continuum absorption by CO2 due to the presence of water vapor was determined by subtracting from measured spectra the contribution of local lines of both species, that of the continuum of pure CO2 as well as of the self- and CO2-continua of water vapor induced by the H2O-H2O and H2O-CO2 interactions. The obtained results are in very good agreement with the unique previous measurement (in a narrower spectral range). They confirm that the H2O-continuum of CO2 is significantly larger than that observed for pure CO2. This continuum thus must be taken into account in radiative transfer calculations for media involving CO2+ H2O mixture. An empirical model, using sub-Lorentzian line shapes based on some temperature-dependent correction factors χ is proposed which enables an accurate description of the experimental results.

  20. Control of magnetic properties and band gap by Co/Mn ordering and oxygen distributions of La{sub 2}CoMnO{sub 6}

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Gao, Yu; Chang, Hong, E-mail: changhong@imu.edu.cn; Liu, Yifan; Yun, Yuehou

    2017-08-01

    Highlights: • The stretching vibration of the ordered Co-O-Mn bond is observed in IR-FT curve. • The surface absorbed oxygen transforms to the lattice oxygen is observed at 905 °C. - Abstract: La{sub 2}CoMnO{sub 6} are synthesized at different annealing temperature ranging from 600 °C to 1300 °C, marked as S600, S800, S1000 and S1300. S600 has the R-3c and the rest have the Pnma structure. The DTA curve exhibits two exothermic peaks, at 553 °C for the phase formation and 905 °C for the oxygen redistribution into the lattice. Deduced from xps, S1000 has the highest lattice oxygen. S1300 has one extra xps peak due to the oxygen deficient regions. Even though the xrd refinements are not reliable at telling whether Co/Mn ions are ordered or not, IR-FT, magnetic measurements and energy band gaps indicate that S1000 has the best Co/Mn ordering, and S600 has the worst. A stretching vibration at about 580–595 cm{sup −1} in the IR-FT spectra is attributed to the ordered Co–O–Mn bond. A homogenous atomic distribution in S600, S800 and S1000 leads to one magnetic phase configuration, and the agglomeration of the FM ordered Co/Mn and the AFM disordered regions in S1300 induces the multi magnetic phases. From the aspects of band gap and energy level, S600 is a good candidate for light harvesting.

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

    Science.gov (United States)

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

    2000-01-01

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

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

    International Nuclear Information System (INIS)

    Wainwright, P R

    2003-01-01

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

  3. Oxygen effects on the interfacial electronic structure of titanyl phthalocyanine film: p-Type doping, band bending and Fermi level alignment

    International Nuclear Information System (INIS)

    Nishi, Toshio; Kanai, Kaname; Ouchi, Yukio; Willis, Martin R.; Seki, Kazuhiko

    2006-01-01

    The effect of oxygen doping on titanyl phthalocyanine (TiOPc) film was investigated by ultraviolet photoelectron spectroscopy (UPS). The electronic structure of the interface formed between TiOPc films deposited on highly oriented pyrolytic graphite (HOPG) was clearly different between the films prepared in ultrahigh vacuum (UHV) and under O 2 atmosphere (1.3 x 10 -2 Pa). The film deposited in UHV showed downward band bending characteristic of n-type semiconductor, possibly due to residual impurities working as unintentional n-type dopants. On the other hand, the film deposited under O 2 atmosphere showed upward band bending characteristic of p-type semiconductor. Such trends, including the conversion from n- to p-type, are in excellent correspondence with reported field effect transistor characteristics of TiOPc, and clearly demonstrates that bulk TiOPc film was p-doped with oxygen. In order to examine the Fermi level alignment between TiOPc film and the substrate, the energy of the highest occupied molecular orbital (HOMO) of TiOPc relative to the Fermi level of the conductive substrate was determined for various substrates. The alignment between the Fermi level of conductive substrate and Fermi level of TiOPc film at fixed energy in the bandgap was not observed for the TiOPc film prepared in UHV, possibly because of insufficient charge density in the TiOPc film. This situation was drastically changed when the TiOPc film exposed to O 2 , and clear alignment of the Fermi level fixed at 0.6 eV above the HOMO with the Fermi level of the conducting substrate was observed, probably by p-type doping effect of oxygen. These are the first direct and quantitative information about bulk oxygen doping from the viewpoint of the electronic structure. These results suggest that similar band bending with Fermi level alignment may be also achieved for other organic semiconductors under practical device conditions, and also call for caution at the comparison of experimental

  4. Nanophase Iron Oxides as an Ultraviolet Sunscreen for Ancient Photosynthetic Microbes: A Possible Link Between Early Organisms, Banded-Iron Formations, and the Oxygenation of the Atmosphere

    Science.gov (United States)

    Bishop, Janice L.; Rothschild, Lynn J.; Rothschild, Lynn J.; Rogoff, Dana A.

    2006-01-01

    We propose that nanophase iron oxide-bearing materials provided important niches for ancient photosynthetic microbes on the early Earth that ultimately led to the oxygenation of the Earth s atmosphere and the formation of iron oxide deposits. Atmospheric oxygen and ozone attenuate UV radiation on the Earth today providing substantial protection for photosynthetic organisms. With ultraviolet radiation fluxes likely to have been even higher on the early Earth than today, accessing solar radiation was particularly risky for early organisms. Yet, we know that photosynthesis arose then and played a critical role in subsequent evolution. Of primary importance was protection at approx.250-290 nm, where peak nucleic acid (approx.260 nm) and protein (approx.280 nm) absorptions occur. Nanophase ferric oxide/oxyhydroxide minerals absorb, and thus block, the lethal UV radiation, while transmitting light through much of the visible and near-infrared regions of interest to photosynthesis (400 to 1100 nm). Further, they were available in early environments, and are synthesized by many organisms. Based on ferric oxide/oxyhydroxide spectral properties, likely geologic processes, and the results of experiments with the photosynthetic organisms, Euglena sp. and Chlumydomonus reinhardtii, we propose a scenario where photosynthesis, and ultimately the oxygenation of the atmosphere, depended on the protection of early microbes by nanophase ferric oxides/oxyhydroxides. The results of this study are also applicable to other potentially habitable iron-bearing planetary bodies because of the evolutionary pressure to utilize solar radiation when available as an energy source.

  5. Cloud information content analysis of multi-angular measurements in the oxygen A-band: application to 3MI and MSPI

    Science.gov (United States)

    Merlin, G.; Riedi, J.; Labonnote, L. C.; Cornet, C.; Davis, A. B.; Dubuisson, P.; Desmons, M.; Ferlay, N.; Parol, F.

    2015-12-01

    The vertical distribution of cloud cover has a significant impact on a large number of meteorological and climatic processes. Cloud top altitude and cloud geometrical thickness are then essential. Previous studies established the possibility of retrieving those parameters from multi-angular oxygen A-band measurements. Here we perform a study and comparison of the performances of future instruments. The 3MI (Multi-angle, Multi-channel and Multi-polarization Imager) instrument developed by EUMETSAT, which is an extension of the POLDER/PARASOL instrument, and MSPI (Multi-angles Spectro-Polarimetric Imager) develoloped by NASA's Jet Propulsion Laboratory will measure total and polarized light reflected by the Earth's atmosphere-surface system in several spectral bands (from UV to SWIR) and several viewing geometries. Those instruments should provide opportunities to observe the links between the cloud structures and the anisotropy of the reflected solar radiation into space. Specific algorithms will need be developed in order to take advantage of the new capabilities of this instrument. However, prior to this effort, we need to understand, through a theoretical Shannon information content analysis, the limits and advantages of these new instruments for retrieving liquid and ice cloud properties, and especially, in this study, the amount of information coming from the A-Band channel on the cloud top altitude (CTOP) and geometrical thickness (CGT). We compare the information content of 3MI A-Band in two configurations and that of MSPI. Quantitative information content estimates show that the retrieval of CTOP with a high accuracy is possible in almost all cases investigated. The retrieval of CGT seems less easy but possible for optically thick clouds above a black surface, at least when CGT > 1-2 km.

  6. Erratum: "Photoionization Modeling of Oxygen K Absorption in the Interstellar Medium, the Chandra Grating Spectra of XTE J1817-330" (2013, Apj, 768, 60)

    Science.gov (United States)

    Gatuzz, E.; Garcia, J.; Mendoza, C.; Kallman, Timothy R.; Witthoeft, Michael C.; Lohfink, A.; Bautista, M. A.; Palmeri, P.; Quinet, P.

    2013-01-01

    In the published version of this paper, there are some minor inaccuracies in the absorption-line wavelengths listed in Table 4 as a result of a faulty reduction procedure of the Obs6615 spectrum. The shifts have been detected in a comparison with the wavelengths listed for this spectrum in the Chandra Transmission Grating Catalog and Archive (TGCat8). They are due to incorrect centroid positions of the zero-order image in both reductions as determined by the tgdetect utility which, when disentangled, yield the improved line positions of the amended Table 4 given below. It must also be pointed out that other quantitative findings of the original paper: 1. Table 5, p. 9: the column density (NH), ionization parameter, oxygen abundance of the warmabs model and the normalization and photon index of the power-law model; 2. Table 6, p. 9: the hydrogen column density of the warmabs fit; 3. Table 7, p. 9: the present oxygen equivalent widths of XTE J1817-330; and 4. Table 8, p. 10: the present oxygen column densities of XTE J1817-330 derived from both the curve of growth and warmabs model fit have been revised in the new light and are, within the estimated uncertainty ranges, in good accord with the new rendering.

  7. Study of apical oxygen atoms in a spin-ladder cuprate compound by X-ray absorption spectroscopy near the Cu K edge

    Energy Technology Data Exchange (ETDEWEB)

    Hatterer, C.J.; Eustache, B.; Collin, L.; Beuran, C.F.; Partiot, C.; Germain, P.; Xu, X.Z.; Lagues, M. [CNRS, Paris (France). Surfaces et Supraconducteurs; Michalowicz, A. [Laboratoire de Physique des Milieux Desordonnes, Universite Paris XII Val-de-Marne, 61 avenue du general de Gaulle, 94010, Creteil Cedex (France)]|[LURE, Universite Paris Sud, 91405, Orsay Cedex (France); Moscovici, J. [Laboratoire de Physique des Milieux Desordonnes, Universite Paris XII Val-de-Marne, 61 avenue du general de Gaulle, 94010, Creteil Cedex (France); Deville Cavellin, C. [CNRS, Paris (France). Surfaces et Supraconducteurs]|[Laboratoire d`Electronique, Universite Paris XII Val-de-Marne, 61 av. du general de Gaulle, 94010, Creteil Cedex (France); Traverse, A. [LURE, Universite Paris Sud, 91405, Orsay Cedex (France)

    1997-04-01

    The structure of high-T{sub c} superconducting cuprate compounds is based on CuO{sub 2} planes alternating with blocks that behave as charge reservoirs. The apical oxygen atoms which belong to these reservoirs are suspected to play a role in the mechanism of superconductivity. It thus seems necessary to measure the amount of apical oxygen atoms in various compounds, as a function of the superconducting properties. Polarisation dependent X-ray absorption spectroscopy (XAS) measurements were performed near the Cu K-edge on three types of phases. We collected information about the neighbourhood of the copper atom in the cuprate planes and in the direction perpendicular to these planes. Two of these phases have well known structures: Bi2212 in which copper atoms are on a pyramidal site and infinite layer phase, a square planar cuprate without apical oxygen. We used the obtained results as reference data to study a new copper-rich phase related to the spin-ladder series. (orig.)

  8. Screened coulomb hybrid DFT investigation of band gap and optical absorption predictions of CuVO3, CuNbO3 and Cu 5Ta11O30 materials

    KAUST Repository

    Harb, Moussab

    2014-01-01

    We present a joint theoretical and experimental investigation of the optoelectronic properties of CuVO3, CuNbO3 and Cu 5Ta11O30 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 Cu5Ta 11O30. 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 d0 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. © the Partner Organisations 2014.

  9. Investigation of a 0.52 eV absorption band of n-type Ge1-xSix solid solutions irradiated with fast electrons at 77 K

    International Nuclear Information System (INIS)

    Abbasov, Sh.M.; Allakhverdiev, K.R.; Agaverdieva, G.T.; Bakhyshov, N.A.; Nagiev, A.I.

    1987-01-01

    Solid solutions belonging to the Ge 1-x Si x system are among the promising semiconductor materials. There is no published information on the absorption band in the region of 0.52 eV in Ge 1-x Si x solid solutions irradiated with fast electrons. The authors determined the infrared absorption spectra, impurity photoconductivity, and Hall effect of n-type Ge 1-x Si x solid solutions doped with antimony. These solid solutions were irradiated at 77 K with 5 MeV electrons in doses up to 2 x 10 17 cm -2 . This irradiation was carried out by a method described in Ref. 3

  10. Absolute atomic oxygen and nitrogen densities in radio-frequency driven atmospheric pressure cold plasmas: Synchrotron vacuum ultra-violet high-resolution Fourier-transform absorption measurements

    International Nuclear Information System (INIS)

    Niemi, K.; O'Connell, D.; Gans, T.; Oliveira, N. de; Joyeux, D.; Nahon, L.; Booth, J. P.

    2013-01-01

    Reactive atomic species play a key role in emerging cold atmospheric pressure plasma applications, in particular, in plasma medicine. Absolute densities of atomic oxygen and atomic nitrogen were measured in a radio-frequency driven non-equilibrium plasma operated at atmospheric pressure using vacuum ultra-violet (VUV) absorption spectroscopy. The experiment was conducted on the DESIRS synchrotron beamline using a unique VUV Fourier-transform spectrometer. Measurements were carried out in plasmas operated in helium with air-like N 2 /O 2 (4:1) admixtures. A maximum in the O-atom concentration of (9.1 ± 0.7)×10 20 m −3 was found at admixtures of 0.35 vol. %, while the N-atom concentration exhibits a maximum of (5.7 ± 0.4)×10 19 m −3 at 0.1 vol. %

  11. Determination of density of band-gap states of hydrogenated amorphous silicon suboxide thin films

    International Nuclear Information System (INIS)

    Bacioglu, A.

    2005-01-01

    Variation of density of gap states of PECVD silicon suboxide films with different oxygen concentrations was evaluated through electrical and optical measurements. Optical transmission and constant photocurrent method (CPM) were used to determine absorption coefficient as a function of photon energy. From these measurements the localized density of states between the valance band mobility edge and Fermi level has been determined. To determine the variation of conduction band edge, steady state photoconductivity (SSPC), photoconductivity response time (PCRT) and transient photoconductivity (TPC) measurements were utilized. Results indicate that the conduction and valance band edges, both, widen monotonically with oxygen content

  12. Absorption spectrum and absorption cross sections of the 2ν1 band of HO2 between 20 and 760 Torr air in the range 6636 and 6639 cm-1

    Science.gov (United States)

    Assaf, Emmanuel; Liu, Lu; Schoemaecker, Coralie; Fittschen, Christa

    2018-05-01

    The absorption spectrum of HO2 radicals has been measured in the range 6636-6639 cm-1 at several pressures between 20 and 760 Torr of air. Absolute absorption cross sections of the strongest line at around 6638.2 cm-1 have been determined from kinetic measurements, taking advantage of the well known rate constant of the self-reaction. Peak absorption cross sections of 22.6, 19.5, 14.4, 7.88, 5.12 and 3.23 × 10-20 cm2 were obtained at 20, 50, 100, 200, 400 and 760 Torr, respectively. By fitting these data, an empirical expression has been obtained for the absorption cross section of HO2 in the range 20-760 Torr air: σ6638.2cm-1 = 1.18 × 10-20 + (2.64 × 10-19 × (1-exp (-63.1/p (Torr))) cm2.

  13. Band-gap measurements of bulk and nanoscale hematite by soft x-ray spectroscopy

    DEFF Research Database (Denmark)

    Gilbert, B.; Frandsen, Cathrine; Maxey, E.R.

    2009-01-01

    Chemical and photochemical processes at semiconductor surfaces are highly influenced by the size of the band gap, and ability to control the band gap by particle size in nanomaterials is part of their promise. The combination of soft x-ray absorption and emission spectroscopies provides band......-gap determination in bulk and nanoscale itinerant electron semiconductors such as CdS and ZnO, but this approach has not been established for materials such as iron oxides that possess band-edge electronic structure dominated by electron correlations. We performed soft x-ray spectroscopy at the oxygen K...

  14. Effect of temperature on the valency bands of HDO in water in the liquid and solid states. Effects on the analysis of heavy water using infra-red absorption; Effet de temperature sur les bandes de valence de HDO dans l'eau a l'etat liquide et a l'etat solide - consequences pour l'analyse de l'eau lourde par absorption infra-rouge

    Energy Technology Data Exchange (ETDEWEB)

    Ceccaldi, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1964-07-01

    After, a description of the technique used, a qualitative examination is made of the influence of the temperature on the {nu}{sub OH}(3,400 cm{sup -1}) and {nu}{sub OD} (2,500 cm{sup -1}) valence bands of HDO in the liquid state and then during the passage to the solid state. Quantitative examination with two cells of different thickness makes it possible to define the influence of temperature on the residual absorption of the pure liquid (D{sub 2}O or H{sub 2}O and on the valency bands ({nu}{sub OH} and {nu}{sub OD} respectively). It is found that a similar change occurs in the two bands but that the changes in the background are very different. During the passage from the liquid to the solid state the shape of the bands varies considerably but little change occurs in the total intensity. It has been possible to express these results in a simple form which is directly applicable to analytical problems. (authors) [French] Apres un rappel de la technique utilisee, on examine qualitativement l'influence de la temperature sur les bandes de valence {nu}{sub OH} (3400 cm{sup -1}) et {nu}{sub OD} (2500 cm{sup -1}) de HDO a l'etat liquide puis le passage a l'etat solide. L'examen quantitatif, avec deux cuves d'epaisseurs differentes, permet de preciser l'influence de la temperature sur l'absorption residuelle du liquide pur (D{sub 2}O ou H{sub 2}O) et sur les bandes de valence ( {nu}{sub OH} et {nu}{sub OD} respectivement). On constate une evolution parallele de ces bandes mais un comportement tres different du fond continu. Lors du passage de l'etat liquide a l'etat solide, la forme des bandes varie considerablement mais non l'intensite totale. On a pu formuler ces resultats sous une forme simple applicable directement aux problemes analytiques. (auteurs)

  15. Below band-gap optical absorption and photoluminescence excitation spectroscopy at room temperature in low-defect-density bulk GaN:Fe

    Czech Academy of Sciences Publication Activity Database

    Gladkov, Petar; Hulicius, Eduard; Paskova, T.; Preble, E.; Evans, K.R.

    2012-01-01

    Roč. 100, č. 3 (2012), "031908-1"-"031908-3" ISSN 0003-6951 Grant - others:US Missile Defense Agency(US) HQ 0147-09-C-0005 Institutional support: RVO:68378271 ; RVO:67985882 Keywords : GaN * spectroscopy * optical absorption Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.794, year: 2012

  16. Artificial oxygen transport protein

    Science.gov (United States)

    Dutton, P. Leslie

    2014-09-30

    This invention provides heme-containing peptides capable of binding molecular oxygen at room temperature. These compounds may be useful in the absorption of molecular oxygen from molecular oxygen-containing atmospheres. Also included in the invention are methods for treating an oxygen transport deficiency in a mammal.

  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

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Anran; Zhong, Hao [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, Wei, E-mail: wli@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Gu, Deen; Jiang, Xiangdong [School of Optoelectronic Information, University of Electronic Science and Technology of China, Chengdu 610054 (China); Jiang, Yadong [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2016-10-30

    Highlights: • The increase of Ru concentration leads to a narrower bandgap of a-Si{sub 1-x}Ru{sub x} thin film. • The absorption coefficient of a-Si{sub 1-x}Ru{sub x} is higher than that of SiGe. • A double-layer absorber comprising of a-Si{sub 1-x}Ru{sub x} film and Si nano-holes layer is achieved. - Abstract: 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-Si{sub 1-x}Ru{sub x}) 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-Si{sub 1-x}Ru{sub x} thin film in a finite thickness to avoid unnecessary carrier recombination. A double-layer absorber comprising of a-Si{sub 1-x}Ru{sub x} 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. CEFLES2: the remote sensing component to quantify photosynthetic efficiency from the leaf to the region by measuring sun-induced fluorescence in the oxygen absorption bands

    Czech Academy of Sciences Publication Activity Database

    Rascher, U.; Agati, G.; Alonso, L.; Cecchi, G.; Champaigne, S.; Colombo, R.; Damm, A.; Daumard, F.; de Miguel, E.; Fernandez, G.; Franch, B.; Franke, J.; Gerbig, C.; Gioli, B.; Gomez, J.A.; Goulas, Y.; Guanter, L.; Gutierrez-de-la-Camara, O.; Hamdi, K.; Hostert, P.; Jimenez, M.; Košvancová, Martina; Lognoli, D.; Meroni, M.; Miglietta, F.; Moersch, A.; Moreno, J.; Moya, I.; Neininger, B.; Okujeni, A.; Ounis, A.; Palombi, L.; Raimondi, V.; Schickling, A.; Sobrino, J.A.; Stellmes, M.; Toci, G.; Toscano, P.; Udelhoven, T.; van der Linden, S.; Zaldei, A.

    2009-01-01

    Roč. 6, č. 7 (2009), s. 1181-1198 ISSN 1726-4170 Institutional research plan: CEZ:AV0Z60870520 Keywords : remote sensing * photosynthetic efficiency * fluorescence * CO2 flux * gross primary production * water-stress * steady-state Subject RIV: ED - Physiology Impact factor: 3.246, year: 2009 www.biogeosciences-discuss.net/6/2217/2009/

  19. Origin of the Absorption Band of Bromophenol Blue in Acidic and Basic pH: Insight from a Combined Molecular Dynamics and TD-DFT/MM Study.

    Science.gov (United States)

    Chattopadhyaya, M; Murugan, N Arul; Rinkevicius, Zilvinas

    2016-09-15

    We study the linear and nonlinear optical properties of a well-known acid-base indicator, bromophenol blue (BPB), in aqueous solution by employing static and integrated approaches. In the static approach, optical properties have been calculated using time-dependent density functional theory (TD-DFT) on the fully relaxed geometries of the neutral and different unprotonated forms of BPB. Moreover, both closed and open forms of BPB were considered. In the integrated approach, the optical properties have been computed over many snapshots extracted from molecular dynamics simulation using a hybrid time-dependent density functional theory/molecular mechanics approach. The static approach suggests closed neutral ⇒ anionic interconversion as the dominant mechanism for the red shift in the absorption spectra of BPB due to a change from acidic to basic pH. It is found by employing an integrated approach that the two interconversions, namely open neutral ⇒ anionic and open neutral ⇒ dianionic, can contribute to the pH-dependent shift in the absorption spectra of BPB. Even though both static and integrated approaches reproduce the pH-dependent red shift in the absorption spectra of BPB, the latter one is suitable to determine both the spectra and spectral broadening. Finally, the computed static first hyperpolarizability for various protonated and deprotonated forms of BPB reveals that this molecule can be used as a nonlinear optical probe for pH sensing in addition to its highly exploited use as an optical probe.

  20. Cirrus Cloud Optical and Microphysical Property Retrievals from eMAS During SEAC4RS Using Bi-Spectral Reflectance Measurements Within the 1.88 micron Water Vapor Absorption Band

    Science.gov (United States)

    Meyer, K.; Platnick, S.; Arnold, G. T.; Holz, R. E.; Veglio, P.; Yorks, J.; Wang, C.

    2016-01-01

    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 midwave 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 NASAs SEAC4RS field campaign, that selecting two absorbing wavelength channels within the broader 1.88 micron water vapor absorption band, namely the 1.83 and 1.93 micron 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 TOA 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, as well as reduces the frequency of retrieval failures for thin cirrus clouds.

  1. Photodissociation dynamics in the first absorption band of pyrrole. I. Molecular Hamiltonian and the Herzberg-Teller absorption spectrum for the A12(π σ* ) ←X˜ 1 A1(π π ) transition

    Science.gov (United States)

    Picconi, David; Grebenshchikov, Sergy Yu.

    2018-03-01

    This paper opens a series in which the photochemistry of the two lowest πσ* states of pyrrole and their interaction with each other and with the ground electronic state X ˜ are studied using ab initio quantum mechanics. New 24-dimensional potential energy surfaces for the photodissociation of the N-H bond and the formation of the pyrrolyl radical are calculated using the multiconfigurational perturbation theory (CASPT2) for the electronic states X ˜ (π π ) , 11A2(πσ*), and 11B1(πσ*) and locally diabatized. In this paper, the ab initio calculations are described and the photodissociation in the state 11A2(πσ*) is analyzed. The excitation 11 A2←X ˜ is mediated by the coordinate dependent transition dipole moment functions constructed using the Herzberg-Teller expansion. Nuclear dynamics, including 6, 11, and 15 active degrees of freedom, are studied using the multi-configurational time-dependent Hartree method. The focus is on the frequency resolved absorption spectrum as well as on the dissociation time scales and the resonance lifetimes. Calculations are compared with available experimental data. An approximate convolution method is developed and validated, with which absorption spectra can be calculated and assigned in terms of vibrational quantum numbers. The method represents the total absorption spectrum as a convolution of the diffuse spectrum of the detaching H-atom and the Franck-Condon spectrum of the heteroaromatic ring. Convolution calculation requires a minimal quantum chemical input and is a promising tool for studying the πσ* photodissociation in model biochromophores.

  2. Oxygen measurement by multimode diode lasers employing gas correlation spectroscopy.

    Science.gov (United States)

    Lou, Xiutao; Somesfalean, Gabriel; Chen, Bin; Zhang, Zhiguo

    2009-02-10

    Multimode diode laser (MDL)-based correlation spectroscopy (COSPEC) was used to measure oxygen in ambient air, thereby employing a diode laser (DL) having an emission spectrum that overlaps the oxygen absorption lines of the A band. A sensitivity of 700 ppm m was achieved with good accuracy (2%) and linearity (R(2)=0.999). For comparison, measurements of ambient oxygen were also performed by tunable DL absorption spectroscopy (TDLAS) technique employing a vertical cavity surface emitting laser. We demonstrate that, despite slightly degraded sensitivity, the MDL-based COSPEC-based oxygen sensor has the advantages of high stability, low cost, ease-of-use, and relaxed requirements in component selection and instrument buildup compared with the TDLAS-based instrument.

  3. Anomaly of the temperature dependence and nature of the optical absorption band in the 8 μm region in β-rhombohedral boron

    International Nuclear Information System (INIS)

    Yarovaya, R.G.; Tsomaya, K.P.; Gabuniya, D.L.; Nguen Van Doaj.

    1978-01-01

    Temperature dependence of reflection spectra of massive specimens of β-rhombohedral boron in the 7-10 μ region is studied. The specimen were heated from 20 to 450 C deg C in the air. Reflection spectra were measured in reference to standards of non-transparent layers of gold on the glass substrate with the reflection coefficient equal to 98%. Temperature increase was found to result in weakening reflection maximum in the spectral region under investigation and its abnormally fast shifting within the temperature range of 170-350 deg C. In measuring reflection and transmission spectra of B 2 O 3 layers deposited on the boron and rock-salt surfaces it is shown that the reflection peak under study does not involve the oxidation of the boron surface. This peak is supposed to be connected with the existance of inpure oxygen in the bulk

  4. The spectral invariant approximation within canopy radiative transfer to support the use of the EPIC/DSCOVR oxygen B-band for monitoring vegetation

    International Nuclear Information System (INIS)

    Marshak, Alexander; Knyazikhin, Yuri

    2017-01-01

    EPIC (Earth Polychromatic Imaging Camera) is a 10-channel spectroradiometer onboard DSCOVR (Deep Space Climate Observatory) spacecraft. In addition to the near-infrared (NIR, 780 nm) and the ‘red’ (680 nm) channels, EPIC also has the O2 A-band (764±0.2 nm) and B-band (687.75±0.2 nm). The EPIC Normalized Difference Vegetation Index (NDVI) is defined as the difference between NIR and ‘red’ channels normalized to their sum. However, the use of the O2 B-band instead of the ‘red’ channel mitigates the effect of atmosphere on remote sensing of surface reflectance because O2 reduces contribution from the radiation scattered by the atmosphere. Applying the radiative transfer theory and the spectral invariant approximation to EPIC observations, the paper provides supportive arguments for using the O2 band instead of the red channel for monitoring vegetation dynamics. Our results suggest that the use of the O2 B-band enhances the sensitivity of the top-of-atmosphere NDVI to the presence of vegetation. - Highlights: • The use of the O2 B-band channel (688 nm) instead of the red channel (680 nm) mitigates the effect of atmosphere on remote sensing of surface reflectance. • The spectral invariant approach confirms that the synergy of the green, O2 B-band and near IR channels mimics spectral properties of vegetation. • The structural parameter of vegetation retrieved remotely is weakly sensitive to the uncertainty in the atmospheric optical depth.

  5. Kaolinite: Defect defined material properties – A soft X-ray and first principles study of the band gap

    Energy Technology Data Exchange (ETDEWEB)

    Pietzsch, A., E-mail: annette.pietzsch@helmholtz-berlin.de [Institute for Methods and Instrumentation in Synchrotron Radiation Research G-ISRR, Helmholtz-Zentrum für Materialien und Energie GmbH, Albert-Einstein-Str. 15, 12489 Berlin (Germany); Nisar, J. [Pakistan Atomic Energy Commission (PAEC), P.O. Box 2151, Islamabad (Pakistan); Jämstorp, E. [Swiss Light Source, Paul Scherrer Institut, CH-5232 Villigen PSI (Switzerland); Gråsjö, J. [Department of Pharmacy, Uppsala University, Box 580, 75123 Uppsala (Sweden); Århammar, C. [Coromant R& D, S-126 80 Stockholm (Sweden); Ahuja, R.; Rubensson, J.-E. [Department of Physics and Astronomy, Uppsala University, Box 516, 751 20 Uppsala (Sweden)

    2015-07-15

    Highlights: • The respective electronic structure of synthetic and natural kaolinite is compared. • The size of the band gap and thus many important material properties are defined by defect states in the band gap. • The oxygen-based defect states are identified and analyzed. • The band gap of kaolinite decreases significantly due to the forming of defects. - Abstract: By combining X-ray absorption spectroscopy and first principles calculations we have determined the electronic structure of synthetic and natural kaolinite as a model system for engineered and natural clay materials. We have analyzed defect states in the band gap and find that both natural and synthetic kaolinite contain defects where oxygen replaces hydrogen in one of the Al (0 0 1)-hydroxyl groups of the kaolinite clay sheets. The band gap of both synthetic and natural kaolinite is found to decrease by about 3.2 eV as this defect is formed.

  6. Kaolinite: Defect defined material properties – A soft X-ray and first principles study of the band gap

    International Nuclear Information System (INIS)

    Pietzsch, A.; Nisar, J.; Jämstorp, E.; Gråsjö, J.; Århammar, C.; Ahuja, R.; Rubensson, J.-E.

    2015-01-01

    Highlights: • The respective electronic structure of synthetic and natural kaolinite is compared. • The size of the band gap and thus many important material properties are defined by defect states in the band gap. • The oxygen-based defect states are identified and analyzed. • The band gap of kaolinite decreases significantly due to the forming of defects. - Abstract: By combining X-ray absorption spectroscopy and first principles calculations we have determined the electronic structure of synthetic and natural kaolinite as a model system for engineered and natural clay materials. We have analyzed defect states in the band gap and find that both natural and synthetic kaolinite contain defects where oxygen replaces hydrogen in one of the Al (0 0 1)-hydroxyl groups of the kaolinite clay sheets. The band gap of both synthetic and natural kaolinite is found to decrease by about 3.2 eV as this defect is formed

  7. An Extended X-ray Absorption Fine Structure Study of Rhodium-Oxygen Bonds in a Highly Dispersed Rhodium/Aluminum Oxide Catalyst

    NARCIS (Netherlands)

    Koningsberger, D.C.; Zon, J.B.A.D. van; Blik, H.F.J. van 't; Visser, G.J.; Prins, R.; Mansour, A.N.; Sayers, D.E.; Short, D.R.

    1985-01-01

    Analysis of in situ EXAFS measurements on a 2.4 wt % Rh/A120, catalyst, reduced at 473 K after calcination at 623 K, shows the presence of two different rhodium-oxygen bonds (viz. 2.05 and 2.68 A). The oxygen neighbors of rhodium at a distance of 2.05 A disappear after reduction at 673 K. The

  8. Gas in scattering media absorption spectroscopy - GASMAS

    Science.gov (United States)

    Svanberg, Sune

    2008-09-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. GASMAS combines narrow-band diode-laser spectroscopy with diffuse media optical propagation. While solids and liquids have broad absorption features, free gas in pores and cavities in the material is characterized by sharp spectral signatures, typically 10,000 times sharper than those of the host material. Many applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, allowing propagation. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities have been studied. Transport of gas in porous media can readily be studied by first immersing the material in, e.g., pure nitrogen, and then observing the rate at which normal air, containing oxygen, reinvades the material. The conductance of the sinus connective passages can be measured in this way by flushing the nasal cavity with nitrogen. Also other dynamic processes such as drying of materials can be studied. The techniques have also been extended to remote-sensing applications (LIDAR-GASMAS).

  9. Synthesis, singlet-oxygen photogeneration, two-photon absorption, photo-induced DNA cleavage and cytotoxic properties of an amphiphilic β-Schiff-base linked Ru(II) polypyridyl–porphyrin conjugate

    International Nuclear Information System (INIS)

    Ke, Hanzhong; Ma, Wanpeng; Wang, Hongda; Cheng, Guoe; Yuan, Han; Wong, Wai-Kwok; Kwong, Daniel W.J.; Tam, Hoi-Lam; Cheah, Kok-Wai; Chan, Chi-Fai; Wong, Ka-Leung

    2014-01-01

    A novel porphyrin–polypyridyl ruthenium(II) conjugate (TPP–Ru), in which the ruthenium(II) polypyridyl moiety is linked to the β-position of the tetraphenylporphyrin via a Schiff base linkage, has been synthesized and characterized by 1 H NMR, HRMS and UV–visible spectroscopy. The relative singlet oxygen quantum yield and two-photon absorption cross-section of this conjugate, together with its photo-induced DNA cleavage and cytotoxic activities were measured. The results show that the amphiphilic ruthenium(II) polypyridyl–porphyrin conjugate is an effective DNA photocleavage agent, with potential application in one- and two-photon absorption anti-cancer photodynamic therapy. - Highlights: • New porphyrin–ruthenium(II) polypyridyl complexes (TTP–Ru) have been synthesized. • The TTP–Ru shows substantial two-photon absorption cross-section (σ 2 =391 GM). • The TTP–Ru exhibits a substantial 1 O 2 quantum yield (0.64±0.13). • The TTP–Ru exhibits a strong DNA cleavage activity upon photo-excitation. • The TTP–Ru is available for in vitro imaging and as a photodynamic therapy agent

  10. Synthesis, singlet-oxygen photogeneration, two-photon absorption, photo-induced DNA cleavage and cytotoxic properties of an amphiphilic β-Schiff-base linked Ru(II) polypyridyl–porphyrin conjugate

    Energy Technology Data Exchange (ETDEWEB)

    Ke, Hanzhong, E-mail: kehanz@163.com [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, Hubei 430074 (China); Ma, Wanpeng; Wang, Hongda; Cheng, Guoe [Faculty of Material Science and Chemistry, China University of Geosciences, Wuhan, Hubei 430074 (China); Yuan, Han [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Wong, Wai-Kwok, E-mail: wkwong@hkbu.edu.hk [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Institute of Advanced Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Kwong, Daniel W.J. [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Tam, Hoi-Lam; Cheah, Kok-Wai [Department of Physics, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Institute of Advanced Materials, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China); Chan, Chi-Fai; Wong, Ka-Leung [Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong SAR (China)

    2014-10-15

    A novel porphyrin–polypyridyl ruthenium(II) conjugate (TPP–Ru), in which the ruthenium(II) polypyridyl moiety is linked to the β-position of the tetraphenylporphyrin via a Schiff base linkage, has been synthesized and characterized by {sup 1}H NMR, HRMS and UV–visible spectroscopy. The relative singlet oxygen quantum yield and two-photon absorption cross-section of this conjugate, together with its photo-induced DNA cleavage and cytotoxic activities were measured. The results show that the amphiphilic ruthenium(II) polypyridyl–porphyrin conjugate is an effective DNA photocleavage agent, with potential application in one- and two-photon absorption anti-cancer photodynamic therapy. - Highlights: • New porphyrin–ruthenium(II) polypyridyl complexes (TTP–Ru) have been synthesized. • The TTP–Ru shows substantial two-photon absorption cross-section (σ{sub 2}=391 GM). • The TTP–Ru exhibits a substantial {sup 1}O{sub 2} quantum yield (0.64±0.13). • The TTP–Ru exhibits a strong DNA cleavage activity upon photo-excitation. • The TTP–Ru is available for in vitro imaging and as a photodynamic therapy agent.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    Semiconducting oxides have attracted much attention due to their great stability in air or water and the abundance of oxygen. Recent success in synthesizing a metastable phase of CuGaO 2 with direct narrow band gap opens up new applications of semiconducting oxides as absorber layer for photovoltaics. Using first-principles density functional theory calculations, we investigate the thermodynamic and mechanical stabilities as well as the structural and electronic properties of the β-CuGaO 2 phase. Our calculations show that the β-CuGaO 2 structure is dynamically and mechanically stable. The energy band gap is confirmed to be direct at the Γ point of Brillouin zone. The optical absorption occurs right at the band gap edge and the density of states near the valance band maximum is large, inducing an intense absorption of light as observed in experiment. (paper)

  12. Optical absorption of irradiated carbohydrates

    International Nuclear Information System (INIS)

    Supe, A.A.; Tiliks, Yu.E.

    1994-01-01

    The optical absorption spectra of γ-irradiated carbohydrates (glucose, lactose, sucrose, maltose, and starch) and their aqueous solutions were studied. The comparison of the data obtained with the determination of the concentrations of molecular and radical products of radiolysis allows the absorption bands with maxima at 250 and 310 nm to be assigned to the radicals trapped in the irradiated carbohydrates

  13. Time-resolved infrared absorption study of nine TiO{sub 2} photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Yamakata, Akira; Ishibashi, Taka-aki [Kanagawa Academy of Science and Technology (KAST), KSP, Takatsu, Kawasaki 213-0012 (Japan); Onishi, Hiroshi [Kanagawa Academy of Science and Technology (KAST), KSP, Takatsu, Kawasaki 213-0012 (Japan)], E-mail: oni@kobe-u.ac.jp

    2007-10-15

    Electron kinetics of nine TiO{sub 2} catalysts were compared in a microsecond time domain. Each catalyst was band-gap excited with an UV light pulse, and electron-induced absorption of mid infrared light was observed as a function of time delay. The probability of electron-hole recombination in the bulk, electron attachment to adsorbed oxygen, and hole attachment to adsorbed methoxy species was estimated.

  14. Time-resolved infrared absorption study of nine TiO2 photocatalysts

    International Nuclear Information System (INIS)

    Yamakata, Akira; Ishibashi, Taka-aki; Onishi, Hiroshi

    2007-01-01

    Electron kinetics of nine TiO 2 catalysts were compared in a microsecond time domain. Each catalyst was band-gap excited with an UV light pulse, and electron-induced absorption of mid infrared light was observed as a function of time delay. The probability of electron-hole recombination in the bulk, electron attachment to adsorbed oxygen, and hole attachment to adsorbed methoxy species was estimated

  15. Oxygen influence on luminescence properties of rare-earth doped NaLaF{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Tuomela, A., E-mail: anu.tuomela@oulu.fi [Research Center of Molecular Materials, University of Oulu, P.O. Box 3000, FIN-90014 (Finland); Pankratov, V., E-mail: vladimirs.pankratovs@oulu.fi [Research Center of Molecular Materials, University of Oulu, P.O. Box 3000, FIN-90014 (Finland); Sarakovskis, A.; Doke, G.; Grinberga, L. [Institute of Solid State Physics, University of Latvia, 8 Kengaraga, LV-1063 Riga (Latvia); Vielhauer, S. [Institute of Physics, University of Tartu, Riia 142, Tartu 51014 (Estonia); Huttula, M. [Research Center of Molecular Materials, University of Oulu, P.O. Box 3000, FIN-90014 (Finland)

    2016-11-15

    Luminescence properties of erbium and europium doped NaLaF{sub 4} with different oxygen content have been studied. Vacuum ultraviolet (VUV) excitation luminescence spectroscopy technique has been applied by using synchrotron radiation excitation. It was found that oxygen impurity leads to significant degradation of Er{sup 3+} or Eu{sup 3+} emission under VUV excitation. The intensive O{sup 2−}–Er{sup 3+} charge transfer excitation band has been detected from oxygen abundant NaLaF{sub 4} in the 150–165 nm spectral range. This band reveals a competing absorption mechanism in oxygen containing NaLaF{sub 4}. It is clearly demonstrated that one reason for the Er{sup 3+} emission degradation in oxygen abundant NaLaF{sub 4} is strong suppression of 4f–5d transitions in Er{sup 3+} ion. The degradation of the Eu{sup 3+} emission under VUV excitation was explained by diminishing of F{sup −}–Eu{sup 3+} charge transfer absorption band as well as by competing relaxation centers in the oxygen abundant NaLaF{sub 4}.

  16. Role of apical oxygen in 2-1-4 electron-doped superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Richard, P.; Riou, G.; Jandl, S.; Poirier, M.; Fournier, P.; Nekvasil, V.; Divis, M

    2004-08-01

    We report a crystal-field infrared transmission and Raman study of oxygenated and reduced Nd{sub 2-x}Ce{sub x}CuO{sub 4} single crystals. Some Nd{sup 3+} crystal-field absorption bands corresponding to rare-earth ions in non-regular sites are attributed to Nd{sup 3+} ions in the vicinity of apical oxygens. This is correlated with a study of the A{sup *} ({approx}580 cm{sup -1}) Raman local mode and with the transport properties of undoped materials. We show that the apical oxygen is not removed by the reduction.

  17. Polarized X-ray absorption spectroscopy of single-crystal Mn(V) complexes relevant to the oxygen-evolving complex of photosystem II

    DEFF Research Database (Denmark)

    Yano, Junko; Robblee, John; Pushkar, Yulia

    2007-01-01

    High-valent Mn-oxo species have been suggested to have a catalytically important role in the water splitting reaction which occurs in the Photosystem II membrane protein. In this study, five- and six-coordinate mononuclear Mn(V) compounds were investigated by polarized X-ray absorption spectroscopy...... structure of the metal site was then studied by measuring the polarization dependence of X-ray absorption near-edge spectroscopy (XANES) pre-edge spectra (1s to 3d transition) and comparing with the results of density functional theory (DFT) calculations. The Mn(V)-nitrido compound, in which the manganese......-edge peak. This component was interpreted as a 1s to 3d(xz,yz) transition with 4px,y mixing, due to the displacement of the Mn atom out of the equatorial plane. The XANES results have been correlated to DFT calculations, and the spectra have been simulated using a TD (time-dependent)-DFT approach...

  18. Tailoring defect structure and optical absorption of porous anodic aluminum oxide membranes

    International Nuclear Information System (INIS)

    Yan Hongdan; Lemmens, Peter; Wulferding, Dirk; Shi, Jianmin; Becker, Klaus Dieter; Lin, Chengtian; Lak, Aidin; Schilling, Meinhard

    2012-01-01

    Defects influence the optical and electronic properties of nanostructured materials that may be relevant for applications. In self-organized anodic aluminum oxide (AAO) templates we have investigated the effect of annealing, doping and nanoscale metal deposition. Optical absorption spectroscopy has been used as a sensitive probe for the defect density in AAO templates. The electronic spectra are found to be dominated by bands which originate from oxygen-deficient color centers (F + , F and F 2 ). In annealing studies, the integrated absorption of the bands changes non-monotonically with annealing temperature and annealing time. This demonstrates that the concentration of defects can be optimized to tailor the optical properties of the AAO. Metallic Au wires are deposited in the template to establish a plasmonic template or array. The investigations provide an interesting insight into the interplay of reactivity and diffusivity on nanoscales. - Highlights: ► Preparation of metal wire arrays in oxide templates with tailored plasmonic properties. ► Oxygen defects are characterized using optical absorption and fluorescence. ► Optical absorption spectra are assigned to energy levels of oxygen vacancies (color centers). ► Annealing and electrodeposition of Au wires minimize defects maintaining the morphology.

  19. On the red giant titanium oxide bands

    Science.gov (United States)

    Hanni, L.; Sitska, J.

    1985-12-01

    The dependence of TiO absorption in cool oxygen-sequence giant stars on the Teff and log g of their atmospheres is investigated theoretically on the basis of spectra simulated using the computer program described by Hanni (1983) and the giant model atmospheres of Johnson et al. (1980). The temperature dependence of the intensity jumps at the head of the alpha(1.0) band is determined from simulated spectra, and the jumps are related to spectral types using the calibration of Ridgway et al. (1980). The results are presented in tables and graphs and shown to be in good agreement with the empirical Teff/intensity-jump correlation of Boyarchuk (1969).

  20. Irradiation of silver and agar/silver nanoparticles with argon, oxygen glow discharge plasma, and mercury lamp.

    Science.gov (United States)

    Ahmad, Mahmoud M; Abdel-Wahab, Essam A; El-Maaref, A A; Rawway, Mohammed; Shaaban, Essam R

    2014-01-01

    The irradiation effect of argon, oxygen glow discharge plasma, and mercury lamp on silver and agar/silver nanoparticle samples is studied. The irradiation time dependence of the synthesized silver and agar/silver nanoparticle absorption spectra and their antibacterial effect are studied and compared. In the agar/silver nanoparticle sample, as the irradiation time of argon glow discharge plasma or mercury lamp increases, the peak intensity and the full width at half maximum, FWHM, of the surface plasmon resonance absorption band is increased, however a decrease of the peak intensity with oxygen glow plasma has been observed. In the silver nanoparticle sample, as the irradiation time of argon, oxygen glow discharge plasma or mercury lamp increases, the peak intensity of the surface plasmon resonance absorption band is increased, however, there is no significant change in the FWHM of the surface plasmon resonance absorption band. The SEM results for both samples showed nanoparticle formation with mean size about 50 nm and 40 nm respectively. Throughout the irradiation time with the argon, oxygen glow discharge plasma or mercury lamp, the antibacterial activity of several kinds of Gram-positive and Gram-negative bacteria has been examined.

  1. On the initial corrosion mechanism of zirconium alloy: Interaction of oxygen and water with Zircaloy at room temperature and 450 C evaluated by x-ray absorption spectroscopy and photoelectron spectroscopy

    International Nuclear Information System (INIS)

    Doebler, U.; Knop, A.

    1994-01-01

    The initial stages of zirconium oxide formation on Zircaloy after water (H 2 O) and oxygen (O 2 ) exposures have been investigated in situ using photoelectron spectroscopy and X-ray-absorption spectroscopy. The reactivity of the zirconium alloy with O 2 at room temperature is about 1,000 times higher than for H 2 O. Up to 100 L (1 L = 1 Langmuir unit = 1 · 10 -6 mbar · s) H 2 O exposure, the reactivity of the zirconium alloy at 450 C is comparable to the room temperature reaction. At higher H 2 O exposure, a sharp increase in the reaction rate for the high-temperature oxidation is observed. From the energy position of the Zr 3d photo emission line and their oxygen-induced chemical shifts, one can really follow the formation of the oxide films. Two different substoichiometric oxides were found during reaction with water. Suboxide (1) is located at the zirconium/zirconium-oxide interface. Subsequently, a Suboxide (2) is concluded from the chemical shift of the zirconium photoelectrons. After an oxide thickness of 2 nm, the stoichiometric ZrO 2 phase is not yet developed

  2. Calcium absorption

    International Nuclear Information System (INIS)

    Carlmark, B.; Reizenstein, P.; Dudley, R.A.

    1976-01-01

    The methods most commonly used to measure the absorption and retention of orally administered calcium are reviewed. Nearly all make use of calcium radioisotopes. The magnitude of calcium absorption and retention depends upon the chemical form and amount of calcium administered, and the clinical and nutritional status of the subject; these influences are briefly surveyed. (author)

  3. Absorption studies

    International Nuclear Information System (INIS)

    Ganatra, R.D.

    1992-01-01

    Absorption studies were once quite popular but hardly anyone does them these days. It is easier to estimate the blood level of the nutrient directly by radioimmunoassay (RIA). However, the information obtained by estimating the blood levels of the nutrients is not the same that can be obtained from the absorption studies. Absorption studies are primarily done to find out whether some of the essential nutrients are absorbed from the gut or not and if they are absorbed, to determine how much is being absorbed. In the advanced countries, these tests were mostly done to detect pernicious anaemia where vitamin B 12 is not absorbed because of the lack of the intrinsic factor in the stomach. In the tropical countries, ''malabsorption syndrome'' is quire common. In this condition, several nutrients like fat, folic acid and vitamin B 12 are not absorbed. It is possible to study absorption of these nutrients by radioisotopic absorption studies

  4. Microwaves absorption in superconducting materials

    International Nuclear Information System (INIS)

    Biasi, R.S. de; Fernandes, A.A.R.; Pereira, R.F.R.

    1989-01-01

    Microwaves absorption measures in two superconductors ceramics systems, Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O are compared with similars datas obtained in the same band of temperature by a conventional method, mutual inductance. The results suggest that the microwaves absorption can be used as single and non-destructive method for investigating the properties of ceramics superconductors. (C.G.C.) [pt

  5. Probing the Influence of the Conjugated Structure and Halogen Atoms of Poly-Iron-Phthalocyanine on the Oxygen Reduction Reaction by X-ray Absorption Spectroscopy and Density Functional Theory

    International Nuclear Information System (INIS)

    Peng, Yingxiang; Cui, Lufang; Yang, Shifeng; Fu, Jingjing; Zheng, Lirong; Liao, Yi; Li, Kai; Zuo, Xia; Xia, Dingguo

    2015-01-01

    Metal-phthalocyanine (MPc) macrocyclic catalysts have been perceived as promising alternatives to Pt and Pt-based catalysts for the oxygen reduction reaction (ORR). However, the effect of different MPc molecular structures on the ORR has rarely been reported in depth. Herein, iron-phthalocyanine polymers (poly-FePcs) and multi-walled carbon nanotubes (MWCNTs) composites with different structures were synthesized using microwave method. The relationship between their molecular structure and electrocatalytic activity was fully revealed by density functional theory (DFT) and X-ray fine absorption spectroscopy (XAFS). DFT calculations revealed that the introduction of halogen atoms can increase the ion potential (IP) and the dioxo-binding energy () of the poly-FePcs. Meanwhile, their conjugated structure not only facilitates electronic transmission, but also significantly increases . XAFS analysis indicated that the poly-FePc/MWCNTs composites had a square planar structure and a smaller of phthalocyanine ring (Fe-N 4 structure) skeleton structure radius when a larger conjugated structure or introduced halogen atoms was present. The experimental results suggest that the these changes in properties arising from the different structures of the MPc macrocyclic compounds led to a huge effect on their ORR electrochemical activities, and provide a guide to obtaining promising electrochemical catalysts

  6. Probing the influence of the center atom coordination structure in iron phthalocyanine multi-walled carbon nanotube-based oxygen reduction reaction catalysts by X-ray absorption fine structure spectroscopy

    Science.gov (United States)

    Peng, Yingxiang; Li, Zhipan; Xia, Dingguo; Zheng, Lirong; Liao, Yi; Li, Kai; Zuo, Xia

    2015-09-01

    Three different pentacoordinate iron phthalocyanine (FePc) electrocatalysts with an axial ligand (pyridyl group, Py) anchored to multi-walled carbon nanotubes (MWCNTs) are prepared by a microwave method as high performance composite electrocatalysts (FePc-Py/MWCNTs) for the oxygen reduction reaction (ORR). For comparison, tetracoordinate FePc electrocatalysts without an axial ligand anchored to MWCNTs (FePc/MWCNTs) are assembled in the same way. Ultraviolet-visible spectrophotometry (UV-Vis), Raman spectroscopy (RS), and high-resolution transmission electron microscopy (HRTEM) are used to characterize the obtained electrocatalysts. The electrocatalytic activity of the samples is measured by linear sweep voltammetry (LSV), and the onset potential of all of the FePc-Py/MWCNTs electrocatalysts is found to be more positive than that of their FePc/MWCNTs counterparts. X-ray photoelectron spectroscopy (XPS) and X-ray absorption fine structure (XAFS) spectroscopy are employed to elucidate the relationship between molecular structure and electrocatalytic activity. XPS indicates that higher concentrations of Fe3+ and pyridine-type nitrogen play critical roles in determining the electrocatalytic ORR activity of the samples. XAFS spectroscopy reveals that the FePc-Py/MWCNTs electrocatalysts have a coordination geometry around Fe that is closer to the square pyramidal structure, a higher concentration of Fe3+, and a smaller phthalocyanine ring radius compared with those of FePc/MWCNTs.

  7. Folate absorption

    International Nuclear Information System (INIS)

    Baker, S.J.

    1976-01-01

    Folate is the generic term given to numerous compounds of pteroic acid with glutamic acid. Knowledge of absorption is limited because of the complexities introduced by the variety of compounds and because of the inadequacy of investigational methods. Two assay methods are in use, namely microbiological and radioactive. Techniques used to study absorption include measurement of urinary excretion, serum concentration, faecal excretion, intestinal perfusion, and haematological response. It is probably necessary to test absorption of both pteroylmonoglutamic acid and one or more polyglutamates, and such tests would be facilitated by availability of synthesized compounds labelled with radioactive tracers at specifically selected sites. (author)

  8. UV-Vis, infrared, and mass spectroscopy of electron irradiated frozen oxygen and carbon dioxide mixtures with water

    International Nuclear Information System (INIS)

    Jones, Brant M.; Kaiser, Ralf I.; Strazzulla, Giovanni

    2014-01-01

    Ozone has been detected on the surface of Ganymede via observation of the Hartley band through the use of ultraviolet spectroscopy and is largely agreed upon to be formed by radiolytic processing via interaction of magnetospheric energetic ions and/or electrons with oxygen-bearing ices on Ganymede's surface. Interestingly, a clearly distinct band near 300 nm within the shoulder of the UV-Vis spectrum of Ganymede was also observed, but currently lacks an acceptable physical or chemical explanation. Consequently, the primary motivation behind this work was the collection of UV-Vis absorption spectroscopy of ozone formation by energetic electron bombardment of a variety of oxygen-bearing ices (oxygen, carbon dioxide, water) relevant to this moon as well as other solar system. Ozone was indeed synthesized in pure ices of molecular oxygen, carbon dioxide and a mixture of water and oxygen, in agreement with previous studies. The Hartley band of the ozone synthesized in these ice mixtures was observed in the UV-Vis spectra and compared with the spectrum of Ganymede. In addition, a solid state ozone absorption cross section of 6.0 ± 0.6 × 10 –17 cm 2 molecule –1 was obtained from the UV-Vis spectral data. Ozone was not produced in the irradiated carbon dioxide-water mixtures; however, a spectrally 'red' UV continuum is observed and appears to reproduce well what is observed in a large number of icy moons such as Europa.

  9. Linear absorptive dielectrics

    Science.gov (United States)

    Tip, A.

    1998-06-01

    Starting from Maxwell's equations for a linear, nonconducting, absorptive, and dispersive medium, characterized by the constitutive equations D(x,t)=ɛ1(x)E(x,t)+∫t-∞dsχ(x,t-s)E(x,s) and H(x,t)=B(x,t), a unitary time evolution and canonical formalism is obtained. Given the complex, coordinate, and frequency-dependent, electric permeability ɛ(x,ω), no further assumptions are made. The procedure leads to a proper definition of band gaps in the periodic case and a new continuity equation for energy flow. An S-matrix formalism for scattering from lossy objects is presented in full detail. A quantized version of the formalism is derived and applied to the generation of Čerenkov and transition radiation as well as atomic decay. The last case suggests a useful generalization of the density of states to the absorptive situation.

  10. Identification and quantification of oxygen vacancies in CeO{sub 2} nanocrystals and their role in formation of F-centers

    Energy Technology Data Exchange (ETDEWEB)

    Jaffari, G.Hassnain, E-mail: hassnain@qau.edu.pk [Department of Physics, Quaid-i-Azam University Islamabad (Pakistan); Imran, Ali [Department of Physics, Quaid-i-Azam University Islamabad (Pakistan); Bah, M. [Department of Materials Science and Engineering, University of Delaware, 19716, Newark, DE (United States); Ali, Awais; Bhatti, Arshad S. [Centre for Micro and Nano Devices, Department of Physics, COMSATS Institute of Information Technology, Park Road, Islamabad, 44000 (Pakistan); Qurashi, Umar Saeed [Department of Physics, Quaid-i-Azam University Islamabad (Pakistan); Ismat Shah, S. [Department of Materials Science and Engineering, University of Delaware, 19716, Newark, DE (United States); Department of Physics, University of Delaware, 19716, Newark, DE (United States)

    2017-02-28

    Highlights: • Detail crystal and electronic structural analysis was employed to quantify oxygen vacancies. • The Raman F{sub 2g} mode shifted towards lower wave number, exhibiting mode softening with broader and asymmetric peak. • Observation of absorption edge revealed presence of 4f band within the band gap. • PL emission studies revealed presence of F-centers with corresponding energy level located below 4f band. • Transitions associated by the F-center are mainly associated with 4f{sup 0} to 4f{sup 1}, F{sup ++} to 4f{sup 1} and 4f{sup 0} to F{sup +}. - Abstract: In this work we present synthesis and extensive characterization of Cerium oxide (CeO{sub 2}) nanocrystals. Comparison between the properties of as-prepared and air annealed nanoparticles has been carried out, with a goal to clearly identify the effect of oxygen vacancies on crystal, electronic and band structure. Detail crystal and electronic structural analysis was employed to quantify oxygen vacancies. Structural analysis confirmed that the formation of single phase cubic Fluorite structure for both as-prepared and annealed samples. Crystal and electronic structural studies confirmed that Ce ions exists in two oxidation states, Ce{sup +3} and Ce{sup +4}. Concentration of oxygen vacancies was larger in as-synthesis nanocrystal. A drastic decrease in oxygen vacancy concentration was observed for the sample annealed in air at 550 °C. For the as-prepared sample, the Raman allowed F{sub 2g} mode shifted towards lower wavenumber, exhibiting mode softening with broader and asymmetric peak. Observation of absorption edge revealed presence of 4f band within the band gap. Absorption with different band edge, confirmed different energy position of 4f level for the sample possessing oxygen vacancies. Blue shift of the band edge for as-prepared sample has been discussed in terms of increase in lattice parameter, formation of Ce{sup +3} ions, quantum confinement effect etc. Photoluminescence emission

  11. Narrative absorption

    DEFF Research Database (Denmark)

    Narrative Absorption brings together research from the social sciences and Humanities to solve a number of mysteries: Most of us will have had those moments, of being totally absorbed in a book, a movie, or computer game. Typically we do not have any idea about how we ended up in such a state. No...

  12. High resolution measurements of solar induced chlorophyll fluorescence in the Fraunhofer oxigen bands

    Science.gov (United States)

    Mazzoni, M.; Agati, G.; Cecchi, G.; Toci, G.; Mazzinghi, P.

    2017-11-01

    Spectra of solar radiance reflected by leaves close to the Fraunhofer bands show the net contribution of chlorophyll fluorescence emission which adds to the reflected solar spectra. In a laboratory experiment, a low stray light, high resolution, 0.85 m double monochromator was used to filter radiation living leaves still attached to the plant in correspondence of the 687 nm and 760 nm O2 absorption bands. Reference spectra from a non fluorescent white reference were also acquired. Acquisition was performed by a Microchannel plate (MCP) intensified diode array with 512 elements. A fit of the spectral data outside the absorption lines allowed to retrieve the spectral base-line as a function of wavelength for the reference panel and the leaf. Reflectance functions were determined extending the Plascyck equation system to all the resolved lines of the oxygen absorption bands and using the base-lines for the continuum values. Fluorescence was deduced from the same equation system, using both the measured leaf and reference radiance spectra and the leaf reflectance fitting function.

  13. a Study of Oxygen Precipitation in Heavily Doped Silicon.

    Science.gov (United States)

    Graupner, Robert Kurt

    processes. This could lead to more effective control and use of oxygen precipitation for gettering. One of the principal purposes of this thesis is the extension of the infrared interstitial oxygen measurement technique to situations outside the measurement capacities of the standard technique. These situations include silicon slices exhibiting interfering precipitate absorption bands and heavily doped n-type silicon wafers. A new method is presented for correcting for the effect of multiple reflections in silicon wafers with optically rough surfaces. The technique for the measurement of interstitial oxygen in heavily doped n-type wafers is then used to perform a comparative study of oxygen precipitation in heavily antimony doped (.035 ohm-cm) silicon and lightly doped p-type silicon. A model is presented to quantitatively explain the observed suppression of defect formation in heavily doped n-type wafers.

  14. Band-gap engineering and comparative investigation of Ti2Nb10O29 photocatalysts obtained by Various synthetic routes

    Science.gov (United States)

    Xie, Meiling; Zhu, Hekai; Fang, Minghao; Huang, Zhaohui; Liu, Yan'gai; Wu, Xiaowen

    2018-03-01

    Ti2Nb10O29 photocatalysts were successfully synthesized by three different methods. Ti2Nb10O29 fabricated by the solvothermal method (ST-TNO) exhibited unique microspheres compared to the larger irregular particles observed for the samples annealed in air (Air-TNO) and Ar (Ar-TNO). X-ray Photoelectron Spectroscopy (XPS) results revealed that a partial reduction process from Ti4+ into Ti3+ occurs in Ar-TNO, because of the introduction of oxygen defects. Ar-TNO exhibited visible-light absorption with a band gap of 2.85 eV, while the absorption edges of Air-TNO and ST-TNO were approximately 400 nm. Under UV light irradiation (λ semiconductors. Moreover, the novel semiconductor photocatalyst can be further applied for constructing the heterojunction and designing the band structure.

  15. Anomalous optical emission in hot dense oxygen

    Science.gov (United States)

    Santoro, Mario; Gregoryanz, Eugene; Mao, Ho-kwang; Hemley, Russell J.

    2007-11-01

    We report the observation of unusually strong, broad-band optical emission peaked between 590 and 650 nm when solid and fluid oxygen are heated by a near infrared laser at pressures from 3 to 46 GPa. In situ Raman spectra of oxygen were collected and corresponding temperatures were measured from the Stokes/anti-Stokes intensity ratios of vibrational transitions. The intense optical emission overwhelmed the Raman spectrum at temperatures exceeding 750 K. The spectrum was found to be much narrower than Planck-type thermal emission, and the intensity increase with input power was much steeper than expected for the thermal emission. The result places an important general caveat on calculating temperatures based on optical emission spectra in high-pressure laser-heating experiments. The intense emission in oxygen is photo-induced rather than being purely thermal, through multiphoton or multi-step single photon absorption processes related to the interaction with infrared radiation. The results suggest that short lived ionic species are induced by this laser-matter interaction.

  16. Effects of oxygen partial pressure, deposition temperature, and annealing on the optical response of CdS:O thin films as studied by spectroscopic ellipsometry

    Energy Technology Data Exchange (ETDEWEB)

    Junda, Maxwell M.; Grice, Corey R.; Subedi, Indra; Yan, Yanfa; Podraza, Nikolas J. [Department of Physics & Astronomy and The Wright Center for Photovoltaics Innovation & Commercialization, University of Toledo, Toledo, Ohio 43606 (United States)

    2016-07-07

    Ex-situ spectroscopic ellipsometry measurements are made on radio frequency magnetron sputtered oxygenated cadmium sulfide (CdS:O) thin films. Films are deposited onto glass substrates at room temperature and at 270 °C with varying oxygen to total gas flow ratios in the sputtering ambient. Ellipsometric spectra from 0.74 to 5.89 eV are collected before and after annealing at 607 °C to simulate the thermal processes during close-space sublimation of overlying cadmium telluride in that solar cell configuration. Complex dielectric function (ε = ε{sub 1} + iε{sub 2}) spectra are extracted for films as a function of oxygen gas flow ratio, deposition temperature, and post-deposition annealing using a parametric model accounting for critical point transitions and an Urbach tail for sub-band gap absorption. The results suggest an inverse relationship between degree of crystallinity and oxygen gas flow ratio, whereas annealing is shown to increase crystallinity in all samples. Direct band gap energies are determined from the parametric modeling of ε and linear extrapolations of the square of the absorption coefficient. As-deposited samples feature a range of band gap energies whereas annealing is shown to result in gap energies ranging only from 2.40 to 2.45 eV, which is close to typical band gaps for pure cadmium sulfide.

  17. Absorptive products

    International Nuclear Information System (INIS)

    Assarsson, P.G.; King, P.A.

    1976-01-01

    Applications for hydrophile gels produced by the radiation induced cross-linking in aqueous solution of polyethylene oxide and starch, as described in Norwegian patent 133501 (INIS RN 281494), such as sanitary napkins (diapers) and sanitary towels, are discussed. The process itself is also discussed and results, expressed as the percentage of insoluble gel and its absorptive capacity for saline solution as functions of the ratio of polyethylene oxide to starch and the radiation dose, are presented. (JIW)

  18. Zooxanthellae Harvested by Ciliates Associated with Brown Band Syndrome of Corals Remain Photosynthetically Competent▿

    Science.gov (United States)

    Ulstrup, Karin E.; Kühl, Michael; Bourne, David G.

    2007-01-01

    Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae. PMID:17259357

  19. Zooxanthellae harvested by ciliates associated with brown band syndrome of corals remain photosynthetically competent.

    Science.gov (United States)

    Ulstrup, Karin E; Kühl, Michael; Bourne, David G

    2007-03-01

    Brown band syndrome is a new coral affliction characterized by a local accumulation of yet-unidentified ciliates migrating as a band along the branches of coral colonies. In the current study, morphologically intact zooxanthellae (= Symbiodinium) were observed in great numbers inside the ciliates (>50 dinoflagellates per ciliate). Microscale oxygen measurements and variable chlorophyll a fluorescence analysis along with microscopic observations demonstrated that zooxanthellae within the ciliates are photosynthetically competent and do not become compromised during the progression of the brown band zone. Zooxanthellae showed similar trends in light acclimation in a comparison of rapid light curve and steady-state light curve measures of variable chlorophyll a fluorescence. Extended light exposure of steady-state light curves resulted in higher quantum yields of photosystem II. The brown band tissue exhibited higher photosynthetically active radiation absorptivity, indicating more efficient light absorption due to a higher density of zooxanthellae in the ciliate-dominated zone. This caused relatively higher gross photosynthesis rates in the zone with zooxanthella-containing ciliates compared to healthy coral tissue. The observation of photosynthetically active intracellular zooxanthellae in the ciliates suggests that the latter can benefit from photosynthates produced by ingested zooxanthellae and from photosynthetic oxygen production that alleviates diffusion limitation of oxic respiration in the densely populated brown band tissue. It remains to be shown whether the zooxanthellae form a stable symbiotic association with the ciliate or are engulfed incidentally during grazing on coral tissue and then maintained as active inside the ciliate for a period before being digested and replaced by new zooxanthellae.

  20. On pair-absorption in intrinsic vapours

    International Nuclear Information System (INIS)

    Hotop, R.; Niemax, K.; Schlueter, D.

    1982-01-01

    The bound-state pair-absorption bands Cs(6 2 S 1 sub(/) 2 ) + Cs(6 2 S 1 sub(/) 2 ) + hν → Cs(5 2 D 5 sub(/) 2 sub(,) 3 sub(/) 2 ) + Cs(6 2 P 1 sub(/) 2 ) and the K-K continuum-state pair-absorptions in the wavelength region 2.350 <= lambda <= 2.850 Angstroem have been investigated experimentally. In the case of the bound-state pair-absorption bands a theoretical approach for the absorption cross section at the band centre is given which is in good agreement with the experimental observation. Differences between our and the theoretical formulas given by the Stanford group are discussed. (orig.)

  1. Donor impurity-related optical absorption spectra in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells: hydrostatic pressure and {gamma}-X conduction band mixing effects

    Energy Technology Data Exchange (ETDEWEB)

    Mora-Ramos, M.E. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, C.P. 62209, Cuernavaca, MOR (Mexico); Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain); Lopez, S.Y. [Fac. de Educacion, Universidad de Antioquia, AA 1226, Medellin (Colombia); Duque, C.A. [Inst. de Fisica, Universidad de Antioquia, AA 1226, Medellin (Colombia); Velasco, V.R. [Inst. de Ciencia de Materiales de Madrid, CSIC, Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain)

    2007-07-01

    Using a variational procedure within the effective mass approximation, the mixing between the {gamma} and X conduction band valleys in GaAs-Ga{sub 1-x}Al{sub x}As quantum wells is investigated by taking into account the effect of applied hydrostatic pressure. Some optical properties such as donor and/or acceptor binding energy and impurity-related transition energies are calculated and comparisons with available experimental data are presented. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  2. Infrared absorption in PbTe single crystals

    International Nuclear Information System (INIS)

    Kudykina, T.A.

    1982-01-01

    A group-theoretical analysis is conducted to select rules for optical transitions between bands in PbTe single crystals. It is shown that transitions between valence bands which are near a forbidden band are also forbidden. The extra absorption observed in p-PbTe and p-Pbsub(1-x)Snsub(x)Te in the region between the self-absorption edge and the free-carrier absorption edge is probably connected with transitions between one of valence bands and the p-state of the impurity

  3. Band gap engineering of indium zinc oxide by nitrogen incorporation

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, J.J., E-mail: jjosila@hotmail.com [Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esq. Paseo la Bufa, Fracc. Progreso, C.P. 98060 Zacatecas (Mexico); Doctorado Institucional de Ingeniería y Ciencia de Materiales, Universidad Autónoma de San Luis Potosí, Av. Salvador Nava, Zona Universitaria, C.P. 78270 San Luis Potosí (Mexico); Aguilar-Frutis, M.A.; Alarcón, G. [Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada del Instituto Politécnico Nacional, Unidad Legaría, Calz. Legaría No. 694, Col. Irrigación, C.P. 11500 México D.F. (Mexico); Falcony, C. [Departamento de Física, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional campus Zacatenco, Av. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco, C.P. 07360 México D.F. (Mexico); and others

    2014-09-15

    Highlights: • IZON thin films were deposited by RF reactive sputtering at room temperature. • The effects of nitrogen on physical properties of IZO were analyzed. • Optical properties of IZON were studied by SE and UV–vis spectroscopy. • Adachi and classical parameters were quantitative and qualitatively congruent. • Nitrogen induces a gradual narrowing band gap from 3.5 to 2.5 eV on IZON films. - Abstract: The effects of nitrogen incorporation in indium zinc oxide films, as grown by RF reactive magnetron sputtering, on the structural, electrical and optical properties were studied. It was determined that the variation of the N{sub 2}/Ar ratio, in the reactive gas flux, was directly proportional to the nitrogen percentage measured in the sample, and the incorporated nitrogen, which substituted oxygen in the films induces changes in the band gap of the films. This phenomenon was observed by measurement of absorption and transmission spectroscopy in conjunction with spectral ellipsometry. To fit the ellipsometry spectra, the classical and Adachi dispersion models were used. The obtained optical parameters presented notable changes related to the increment of the nitrogen in the film. The band gap narrowed from 3.5 to 2.5 eV as the N{sub 2}/Ar ratio was increased. The lowest resistivity obtained for these films was 3.8 × 10{sup −4} Ω cm with a carrier concentration of 5.1 × 10{sup 20} cm{sup −3}.

  4. Band gap engineering of indium zinc oxide by nitrogen incorporation

    International Nuclear Information System (INIS)

    Ortega, J.J.; Aguilar-Frutis, M.A.; Alarcón, G.; Falcony, C.

    2014-01-01

    Highlights: • IZON thin films were deposited by RF reactive sputtering at room temperature. • The effects of nitrogen on physical properties of IZO were analyzed. • Optical properties of IZON were studied by SE and UV–vis spectroscopy. • Adachi and classical parameters were quantitative and qualitatively congruent. • Nitrogen induces a gradual narrowing band gap from 3.5 to 2.5 eV on IZON films. - Abstract: The effects of nitrogen incorporation in indium zinc oxide films, as grown by RF reactive magnetron sputtering, on the structural, electrical and optical properties were studied. It was determined that the variation of the N 2 /Ar ratio, in the reactive gas flux, was directly proportional to the nitrogen percentage measured in the sample, and the incorporated nitrogen, which substituted oxygen in the films induces changes in the band gap of the films. This phenomenon was observed by measurement of absorption and transmission spectroscopy in conjunction with spectral ellipsometry. To fit the ellipsometry spectra, the classical and Adachi dispersion models were used. The obtained optical parameters presented notable changes related to the increment of the nitrogen in the film. The band gap narrowed from 3.5 to 2.5 eV as the N 2 /Ar ratio was increased. The lowest resistivity obtained for these films was 3.8 × 10 −4 Ω cm with a carrier concentration of 5.1 × 10 20 cm −3

  5. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In2O3 nanowires

    Science.gov (United States)

    Mukherjee, Souvik; Sarkar, Ketaki; Wiederrecht, Gary P.; Schaller, Richard D.; Gosztola, David J.; Stroscio, Michael A.; Dutta, Mitra

    2018-04-01

    We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor-liquid-solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy ({V}{{O}}) defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of {V}{{O}} defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.

  6. Defect induced structural inhomogeneity, ultraviolet light emission and near-band-edge photoluminescence broadening in degenerate In 2 O 3 nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, Souvik; Sarkar, Ketaki; Wiederrecht, Gary P.; Schaller, Richard D.; Gosztola, David J.; Stroscio, Michael A.; Dutta, Mitra

    2018-03-01

    We demonstrate here defect induced changes on the morphology and surface properties of indium oxide (In2O3) nanowires and further study their effects on the near-band-edge (NBE) emission, thereby showing the significant influence of surface states on In2O3 nanostructure based device characteristics for potential optoelectronic applications. In2O3 nanowires with cubic crystal structure (c-In2O3) were synthesized via carbothermal reduction technique using a gold-catalyst-assisted vapor–liquid–solid method. Onset of strong optical absorption could be observed at energies greater than 3.5 eV consistent with highly n-type characteristics due to unintentional doping from oxygen vacancy (VO) defects as confirmed using Raman spectroscopy. A combination of high resolution transmission electron microscopy, x-ray photoelectron spectroscopy and valence band analysis on the nanowire morphology and stoichiometry reveals presence of high-density of VO defects on the surface of the nanowires. As a result, chemisorbed oxygen species can be observed leading to upward band bending at the surface which corresponds to a smaller valence band offset of 2.15 eV. Temperature dependent photoluminescence (PL) spectroscopy was used to study the nature of the defect states and the influence of the surface states on the electronic band structure and NBE emission has been discussed. Our data reveals significant broadening of the NBE PL peak consistent with impurity band broadening leading to band-tailing effect from heavy doping.

  7. Study of thermal treatments and irradiation on natural amethyst by optical absorption

    International Nuclear Information System (INIS)

    Dotto, C.T.

    1987-01-01

    Thermal treatment effects on the samples of amethyst from Minas Gerais and Rio Grande do Sul, through optical absorption measurements, are studied. The effects of cobalt 60 gama ray radiation on the amethyst from Minas Gerais through optical absorption measurements, are studied. The optical absorption spectra shows a basic line and bands in 10,500 cm -1 (k), in 18,300 cm -1 (θ) and in 28,000 cm -1 (ζ). The correlation between thermal treatment effects and radiation effects shows that the θ and ζ bands belongs to a same center and the k band to another center. The basic line vanishes by thermal treatments at 270 0 C. The analyses of the isothermal treatment decay and dose-curve reveal a complex kinetics, suggesting that the kinetic mechanisms involve the electron (s) and hole (s) migration in the lattice. The amethyst from Minas Gerais after being discolored at 470 0 C and irradiated again shows that the optical absorption bands don't recover the original absorbance, suggesting the existence of iron diffusion mechanisms in the lattice. After being isothermally annealed the amethyst from Rio Grande do Sul above 400 0 C temperature yield a yellow-brown color, probably due to the formation of Fe 2 O 3 precipitate. We suggest the this formation is due to iron diffusion and pre-existent oxygen vacancies. This model is reinforced through the observation the amethyst from Minas Gerais, isothermally treated at 470 0 C in highly reducing, also gets a yellow-brown color. (author) [pt

  8. Influences of oxygen incorporation on the structural and optoelectronic properties of Cu_2ZnSnS_4 thin films

    International Nuclear Information System (INIS)

    Yu, Ruei-Sung; Hung, Ta-Chun

    2016-01-01

    Highlights: • Oxygen incorporation in Cu_2ZnSnS_4 changes the energy band structure. • The material has a comparatively high-absorptive capacity for short wavelength. • Absorption coefficients of the film increase from 10"4 to 10"5 cm"−"1. • The oxygen-containing CZTS film has a mixture of crystallite and crystalline states. • The material could be a candidate as an absorber layer in multi-junction solar cells. - Abstract: This study used the sol–gel method to prepare Cu_2ZnSnS_4 thin films containing oxygen and explored the composition, structural, and optoelectronic properties of the films. The non-vacuum process enabled the oxygen content of the Cu_2ZnSnS_4 films to be 8.89 at% and 10.30 at% for two different annealing conditions. In the crystal structure, oxygen was substituted at the positions of sulfur and appeared in the interstitial sites of the lattice. The compositions of the thin films deviated from the stoichiometric ratio. Both films had kesterite structures with no secondary phase structure. The kesterite CZTS film possessed a composite microstructure of crystallite and crystalline states. The microstructure of the Cu_2ZnSnS_4 film with higher oxygen content was denser and the average grain size was smaller. Incorporating oxygen atoms into crystalline Cu_2ZnSnS_4 changed the energy band structure: the direct energy band gaps were, respectively, 2.75 eV and 2.84 eV; the thin films mainly adsorbed photons with wavelengths less than 500 nm; and the absorption coefficients increased from 10"4 cm"−"1 to 10"5 cm"−"1. The films had a comparatively high absorptive capacity for photons less than 350 nm. Increasing the oxygen content of the film lowered the resistivity. Thus, the oxygen-containing Cu_2ZnSnS_4 thin film could be a candidate for the p-type absorber layer material required in multi-junction solar cells.

  9. Absorption and oxidation of no in ionic liquids

    DEFF Research Database (Denmark)

    2013-01-01

    The present invention concerns the absorption and in situ oxidation of nitric oxide (NO) in the presence of water and oxygen in ionic liquid compositions at ambient temperature.......The present invention concerns the absorption and in situ oxidation of nitric oxide (NO) in the presence of water and oxygen in ionic liquid compositions at ambient temperature....

  10. Propionaldehyde infrared cross-sections and band strengths

    Science.gov (United States)

    Köroğlu, Batikan; Loparo, Zachary; Nath, Janardan; Peale, Robert E.; Vasu, Subith S.

    2015-02-01

    The use of oxygenated biofuels reduces the greenhouse gas emissions; however, they also result in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propionaldehyde. These aldehydes are carcinogenic and/or toxic and therefore it is important to understand their formation and destruction pathways in combustion and atmospheric systems. Accurate information about their infrared cross-sections and integrated strengths are crucially needed for development of quantitative detection schemes and modeling tools. Critical to the development of such diagnostics are accurate characterization of the absorption features of these species. In this study, the gas phase infrared spectra of propionaldehyde (also called propanal, CH3-CH2-CHO), a saturated three carbon aldehyde found in the exhaust emissions of biodiesel or diesel fuels, was studied using high resolution Fourier Transform Infrared (FTIR) spectroscopy over the wavenumber range of 750-3300 cm-1 and at room temperature 295 K. The absorption cross sections of propionaldehyde were recorded at resolutions of 0.08 and 0.096 cm-1 and at seven different pressures (4-33 Torr). The calculated band-strengths were reported and the integrated band intensity results were compared with values taken from the Pacific Northwest National Laboratory (PNNL) database (showing less than 2% discrepancy). The peak positions of the 19 different vibrational bands of propionaldehyde were also compared with previous studies taken at a lower resolution of 1 cm-1. To the best of our knowledge, the current FTIR measurements provide the first highest resolution infrared cross section data for propionaldehyde.

  11. Propionaldehyde infrared cross-sections and band strengths

    International Nuclear Information System (INIS)

    Köroğlu, Batikan; Loparo, Zachary; Nath, Janardan; Peale, Robert E.; Vasu, Subith S.

    2015-01-01

    The use of oxygenated biofuels reduces the greenhouse gas emissions; however, they also result in increased toxic aldehyde by-products, mainly formaldehyde, acetaldehyde, acrolein, and propionaldehyde. These aldehydes are carcinogenic and/or toxic and therefore it is important to understand their formation and destruction pathways in combustion and atmospheric systems. Accurate information about their infrared cross-sections and integrated strengths are crucially needed for development of quantitative detection schemes and modeling tools. Critical to the development of such diagnostics are accurate characterization of the absorption features of these species. In this study, the gas phase infrared spectra of propionaldehyde (also called propanal, CH 3 –CH 2 –CHO), a saturated three carbon aldehyde found in the exhaust emissions of biodiesel or diesel fuels, was studied using high resolution Fourier Transform Infrared (FTIR) spectroscopy over the wavenumber range of 750−3300 cm −1 and at room temperature 295 K. The absorption cross sections of propionaldehyde were recorded at resolutions of 0.08 and 0.096 cm −1 and at seven different pressures (4−33 Torr). The calculated band-strengths were reported and the integrated band intensity results were compared with values taken from the Pacific Northwest National Laboratory (PNNL) database (showing less than 2% discrepancy). The peak positions of the 19 different vibrational bands of propionaldehyde were also compared with previous studies taken at a lower resolution of 1 cm −1 . To the best of our knowledge, the current FTIR measurements provide the first highest resolution infrared cross section data for propionaldehyde. - Highlights: • High resolution IR spectra of propionaldehyde were measured by FTIR spectrometer. • The discrepancy between the present study and PNNL database was less than 2%. • The fundamental vibrational frequencies were reported at high resolution. • The rovibrational Q

  12. Oxygen toxicity

    Directory of Open Access Journals (Sweden)

    C. A. van der Westhuizen

    1990-07-01

    Full Text Available Oxygen has been discovered about 200 years ago. Since then the vital physiological involvement of oxygen in various biologi­cal processes, mainly energy production, has been established. However, in the body molecular oxygen can be converted to toxic oxygen metabolites such as superoxide anion, hydrogen peroxide, the hydroxyl radical and singlet oxygen. These toxic metabolites are produced mainly in the mitochondria, plasma membranes and endoplasmic reticulum.

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

    Science.gov (United States)

    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

  14. Atmospheric pre-corrected differential absorption techniques to retrieve columnar water vapor: Application to AVIRIS 91/95 data

    Energy Technology Data Exchange (ETDEWEB)

    Schlaepfer, D. [Univ. of Zuerich (Switzerland). Dept. of Geography; Borel, C.C. [Los Alamos National Lab., NM (United States); Keller, J. [Paul Scherrer Institut, Villigen (Switzerland)] [and others

    1996-03-01

    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 run resolution. This data includes 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 rationing 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, spectral transmittance and radiance are calculated by MODTRAN3 simulations with the new DISORT option. This work testS the best performing differential absorption techniques for imaging spectrometry of tropospheric water vapor.

  15. Quantum numbers and band topology of nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Damnjanovic, M [Faculty of Physics, University of Belgrade, POB 368, 11001 Belgrade (Yugoslavia); Milosevic, I [Faculty of Physics, University of Belgrade, POB 368, 11001 Belgrade (Yugoslavia); Vukovic, T [Faculty of Physics, University of Belgrade, POB 368, 11001 Belgrade (Yugoslavia); Maultzsch, J [Institut fuer Festkoerper Physik, Technische Universitaet Berlin, Hardenbergstr. 36, 10623 Berlin (Germany)

    2003-05-30

    Nanotubes as well as polymers and quasi-1D subsystems of 3D crystals have line group symmetry. This allows two types of quantum numbers: roto-translational and helical. The roto-translational quantum numbers are linear and total angular (not conserved) momenta, while the helical quantum numbers are helical and complementary angular momenta. Their mutual relations determine some topological properties of energy bands, such as systematic band sticking or van Hove singularities related to parities. The importance of these conclusions is illustrated by the optical absorption in carbon nanotubes: parity may prevent absorption peaks at van Hove singularities.

  16. Quantum numbers and band topology of nanotubes

    International Nuclear Information System (INIS)

    Damnjanovic, M; Milosevic, I; Vukovic, T; Maultzsch, J

    2003-01-01

    Nanotubes as well as polymers and quasi-1D subsystems of 3D crystals have line group symmetry. This allows two types of quantum numbers: roto-translational and helical. The roto-translational quantum numbers are linear and total angular (not conserved) momenta, while the helical quantum numbers are helical and complementary angular momenta. Their mutual relations determine some topological properties of energy bands, such as systematic band sticking or van Hove singularities related to parities. The importance of these conclusions is illustrated by the optical absorption in carbon nanotubes: parity may prevent absorption peaks at van Hove singularities

  17. Quantum numbers and band topology of nanotubes

    CERN Document Server

    Damnjanovic, M; Vukovic, T; Maultzsch, J

    2003-01-01

    Nanotubes as well as polymers and quasi-1D subsystems of 3D crystals have line group symmetry. This allows two types of quantum numbers: roto-translational and helical. The roto-translational quantum numbers are linear and total angular (not conserved) momenta, while the helical quantum numbers are helical and complementary angular momenta. Their mutual relations determine some topological properties of energy bands, such as systematic band sticking or van Hove singularities related to parities. The importance of these conclusions is illustrated by the optical absorption in carbon nanotubes: parity may prevent absorption peaks at van Hove singularities.

  18. Effect of oxygen deficiency on electronic properties and local structure of amorphous tantalum oxide thin films

    Energy Technology Data Exchange (ETDEWEB)

    Denny, Yus Rama [Department of Physics Education, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Firmansyah, Teguh [Department of Electrical Engineering, University of Sultan Ageng Tirtayasa, Banten 42435 (Indonesia); Oh, Suhk Kun [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Kang, Hee Jae, E-mail: hjkang@cbu.ac.kr [Department of Physics, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Yang, Dong-Seok [Department of Physics Education, Chungbuk National University, Cheongju 28644 (Korea, Republic of); Heo, Sung; Chung, JaeGwan; Lee, Jae Cheol [Analytical Engineering Center, Samsung Advanced Institute of Technology, Suwon 16678 (Korea, Republic of)

    2016-10-15

    Highlights: • The effect of oxygen flow rate on electronic properties and local structure of tantalum oxide thin films was studied. • The oxygen deficiency induced the nonstoichiometric state a-TaOx. • A small peak at 1.97 eV above the valence band side appeared on nonstoichiometric Ta{sub 2}O{sub 5} thin films. • The oxygen flow rate can change the local electronic structure of tantalum oxide thin films. - Abstract: The dependence of electronic properties and local structure of tantalum oxide thin film on oxygen deficiency have been investigated by means of X-ray photoelectron spectroscopy (XPS), Reflection Electron Energy Loss Spectroscopy (REELS), and X-ray absorption spectroscopy (XAS). The XPS results showed that the oxygen flow rate change results in the appearance of features in the Ta 4f at the binding energies of 23.2 eV, 24.4 eV, 25.8, and 27.3 eV whose peaks are attributed to Ta{sup 1+}, Ta{sup 2+}, Ta{sup 3+}/Ta{sup 4+}, and Ta{sup 5+}, respectively. The presence of nonstoichiometric state from tantalum oxide (TaOx) thin films could be generated by the oxygen vacancies. In addition, XAS spectra manifested both the increase of coordination number of the first Ta-O shell and a considerable reduction of the Ta-O bond distance with the decrease of oxygen deficiency.

  19. Oxygen vacancies at the spinel/perovskite γ-Al{sub 2}O{sub 3}/SrTiO{sub 3} heterointerface probed by resonant photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, Philipp; Pfaff, Florian; Zapf, Michael; Gabel, Judith; Dudy, Lenart; Berner, Goetz; Sing, Michael; Claessen, Ralph [Physikalisches Institut and Roentgen Center for Complex Material Systems (RCCM), Universitaet Wuerzburg (Germany); Chen, Yunzhong; Pryds, Nini [Department of Energy Conversion and Storage, Technical University of Denmark, Risoe (Denmark); Schlueter, Christoph; Lee, Tien-Lin [Diamond Light Source Ltd., Harwell Science and Innovation Campus, Didcot (United Kingdom)

    2016-07-01

    The spinel/perovskite heterointerface between the band insulators γ-Al{sub 2}O{sub 3} and SrTiO{sub 3} hosts a two-dimensional electron system (2DES) with exceptionally high electron mobility. Soft x-ray resonant photoelectron spectroscopy at the Ti L absorption edge is used to probe the Ti 3d derived interface states. Marked differences in the resonance behavior are found for the SrTiO{sub 3} valence band and the different interface states, which are observed in the band gap of SrTiO{sub 3}. A comparison to X-ray absorption spectra of Ti 3d{sup 0} and Ti 3d{sup 1} systems reveals the presence of different types of electronic states with Ti 3d character, i.e., oxygen vacancy induced, trapped in-gap states and itinerant states contributing to the 2DES. Exposure to low doses of oxygen during irradiation allows for the reversible manipulation of the oxygen stoichiometry, thus revealing the presence of an oxygen vacancy-induced state, which is characteristic for this spinel/perovskite interface.

  20. Evidence of oxygen vacancy and possible intermediate gap state in layered α-MoO{sub 3} single-crystal nanobelts

    Energy Technology Data Exchange (ETDEWEB)

    Chen, C.Z., E-mail: tcccz@shu.edu.cn; Li, Y.; Tang, X.D.

    2016-01-15

    Multilayered meso-structured MoO{sub 3} nanobelts have been synthesized by thermally oxidizing a molybdenum chip in a reduced oxygen atmosphere, with a view to disclosing the existence of oxygen vacancy and understanding the mechanism behind the influence of oxygen vacancy on the electronic structure of molybdenum oxides. Based on the measurements from X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM) and transmission electron microscope (TEM), it is found that the as-grown sample is single-crystal α-MoO{sub 3} with a (001) preferred orientation, which shows an irregular belt-like morphology being composed of some ~20 nm single-crystal thin layers. The present sample includes a lot of oxygen vacancies in the lattice, as evidenced by the considerably reduced coordination number of the central Mo atoms from X-ray absorption spectra (XAS) as well as the red shift of the main Raman peaks. The existence of the oxygen vacancies are further tested by the photoluminescence (PL) results as the main emission peak shows an obvious red shift with the corresponding optical band gap reduced to 2.3 eV. Very importantly, an extra emission positioned at 738 nm (1.68 eV) is believed to originate from the recombination of the electrons from the intermediate band (IB) to the valence band (VB), and the formation of the IB in the gap is also caused by oxygen-ion vacancies.

  1. Oxygen Therapy

    Science.gov (United States)

    ... their breathing to dangerously low levels. Will I need oxygen when I sleep? Usually if you use supplemental oxygen during the ... your health care provider tells you you only need to use oxygen for exercise or sleep. Even if you feel “fine” off of your ...

  2. Spectral interferences in atomic absorption spectrometry, (5)

    International Nuclear Information System (INIS)

    Daidoji, Hidehiro

    1979-01-01

    Spectral interferences were observed in trace element analysis of concentrated solutions by atomic absorption spectrometry. Molecular absorption and emission spectra for strontium chloride and nitrate, barium chloride and nitrate containing 12 mg/ml of metal ion in airacetylene flame were measured in the wavelength range from 200 to 700 nm. The absorption and emission spectra of SrO were centered near 364.6 nm. The absorption spectra of SrOH around 606.0, 671.0 and 682.0 nm were very strong. And, emission spectrum of BaOH in the wavelength range from 480 to 550 nm was stronger. But, the absorption of this band spectrum was very weak. In the wavelength range from 200 to 400 nm, some unknown bands of absorption were observed for strontium and barium. Absorption spectra of SrCl and BaCl were observed in the argon-hydrogen flame. Also, in the carbon tube atomizer, the absorption spectra of SrCl and BaCl were detected clearly in the wavelength range from 185 to 400 nm. (author)

  3. Congenital Constriction Band Syndrome

    OpenAIRE

    Rajesh Gupta, Fareed Malik, Rishabh Gupta, M.A.Basit, Dara Singh

    2008-01-01

    Congenital constriction bands are anomalous bands that encircle a digit or an extremity. Congenitalconstriction band syndrome is rare condition and is mostly associated with other musculoskeletaldisorders.We report such a rare experience.

  4. High resolution spectral analysis of oxygen. IV. Energy levels, partition sums, band constants, RKR potentials, Franck-Condon factors involving the X3Σg−, a1Δg and b1Σg+ states

    International Nuclear Information System (INIS)

    Yu, Shanshan; Drouin, Brian J.; Miller, Charles E.

    2014-01-01

    We have updated the isotopically invariant Dunham fit of O 2 with newly reported literature transitions to derive (1) the energy levels, partition sums, band-by-band molecular constants, and RKR potentials for the X 3 Σ g − , a 1 Δ g , and b 1 Σ g + states of the six O 2 isotopologues: 16 O 16 O, 16 O 17 O, 16 O 18 O, 17 O 17 O, 17 O 18 O, and 18 O 18 O; (2) Franck-Condon factors for their a 1 Δ g −X 3 Σ g − , b 1 Σ g + −X 3 Σ g − , and a 1 Δ g −b 1 Σ g + band systems. This new spectroscopic parameterization characterizes all known transitions within and between the X 3 Σ g − , a 1 Δ g , and b 1 Σ g + states within experimental uncertainty and can be used for accurate predictions of as yet unmeasured transitions. All of these results are necessary to provide a consistent linelist of all transitions which will be reported in a followup paper

  5. Oxygen Therapy

    Directory of Open Access Journals (Sweden)

    Bonnie Solmes

    2000-01-01

    Full Text Available LTOT is prescribed for people with chronic lung disease in whom there is a decrease in the ability of the lungs to supply enough oxygen to the body. The heart is obliged to pump faster to meet the body's oxygen requirements. This may place undue stress on the heart, resulting in palpitations, dizziness and fatigue. A low oxygen level in arterial blood is also harmful to the heart, the brain and the pulmonary blood vessels. Oxygen therapy is used to break this cycle. A person with low blood oxygen will often be able to accomplish more with less fatigue with the help of supplemental oxygen therapy. Shortness of breath is a mechanical problem resulting from the effects of chronic obstructive pulmonary disease. Oxygen therapy may or may not reduce shortness of breath, but it will help the lungs and heart to function with less stress.

  6. The molecular physics of photolytic fractionation of sulfur and oxygen isotopes in planetary atmospheres (Invited)

    Science.gov (United States)

    Johnson, M. S.; Schmidt, J. A.; Hattori, S.; Danielache, S.; Meusinger, C.; Schinke, R.; Ueno, Y.; Nanbu, S.; Kjaergaard, H. G.; Yoshida, N.

    2013-12-01

    Atmospheric photochemistry is able to produce large mass independent anomalies in atmospheric trace gases that can be found in geological and cryospheric records. This talk will present theoretical and experimental investigations of the molecular mechanisms producing photolytic fractionation of isotopes with special attention to sulfur and oxygen. The zero point vibrational energy (ZPE) shift and reflection principle theories are starting points for estimating isotopic fractionation, but these models ignore effects arising from isotope-dependent changes in couplings between surfaces, excited state dynamics, line densities and hot band populations. The isotope-dependent absorption spectra of the isotopologues of HCl, N2O, OCS, CO2 and SO2 have been examined in a series of papers and these results are compared with experiment and ZPE/reflection principle models. Isotopic fractionation in planetary atmospheres has many interesting applications. The UV absorption of CO2 is the basis of photochemistry in the CO2-rich atmospheres of the ancient Earth, and of Mars and Venus. For the first time we present accurate temperature and isotope dependent CO2 absorption cross sections with important implications for photolysis rates of SO2 and H2O, and the production of a mass independent anomaly in the Ox reservoir. Experimental and theoretical results for OCS have implications for the modern stratospheric sulfur budget. The absorption bands of SO2 are complex with rich structure producing isotopic fractionation in photolysis and photoexcitation.

  7. Observation of intermediate bands in Eu3+ doped YPO4 host: Li+ ion effect and blue to pink light emitter

    Directory of Open Access Journals (Sweden)

    Abdul Kareem Parchur

    2012-09-01

    Full Text Available This article explores the tuning of blue to pink colour generation from Li+ ion co-doped YPO4:5Eu nanoparticles prepared by polyol method at ∼100-120 °C with ethylene glycol (EG as a capping agent. Interaction of EG molecules capped on the surface of the nanoparticles and/or created oxygen vacancies induces formation of intermediate/mid gap bands in the host structure, which is supported by UV-Visible absorption data. Strong blue and pink colors can be observed in the cases of as-prepared and 500 °C annealed samples, respectively. Co-doping of Li+ enhances the emission intensities of intermediate band as well as Eu3+. On annealing as-prepared sample to 500 °C, the intermediate band emission intensity decreases, whereas Eu3+ emission intensity increases suggesting increase of extent of energy transfer from the intermediate band to Eu3+ on annealing. Emission intensity ratio of electric to magnetic dipole transitions of Eu3+ can be varied by changing excitation wavelength. The X-ray photoelectron spectroscopy (XPS study of as-prepared samples confirms the presence of oxygen vacancies and Eu3+ but absence of Eu2+. Dispersed particles in ethanol and polymer film show the strong blue color, suggesting that these materials will be useful as probes in life science and also in light emitting device applications.

  8. Influences of oxygen incorporation on the structural and optoelectronic properties of Cu{sub 2}ZnSnS{sub 4} thin films

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Ruei-Sung, E-mail: rsyu@asia.edu.tw [Department of Photonics and Communication Engineering, Asia University, 500, Lioufeng Rd., Wufeng, Taichung 41354, Taiwan (China); Department of Medical Research, China Medical University Hospital, China Medical University, Taichung 40402, Taiwan (China); Hung, Ta-Chun [Department of Photonics and Communication Engineering, Asia University, 500, Lioufeng Rd., Wufeng, Taichung 41354, Taiwan (China)

    2016-02-28

    Highlights: • Oxygen incorporation in Cu{sub 2}ZnSnS{sub 4} changes the energy band structure. • The material has a comparatively high-absorptive capacity for short wavelength. • Absorption coefficients of the film increase from 10{sup 4} to 10{sup 5} cm{sup −1}. • The oxygen-containing CZTS film has a mixture of crystallite and crystalline states. • The material could be a candidate as an absorber layer in multi-junction solar cells. - Abstract: This study used the sol–gel method to prepare Cu{sub 2}ZnSnS{sub 4} thin films containing oxygen and explored the composition, structural, and optoelectronic properties of the films. The non-vacuum process enabled the oxygen content of the Cu{sub 2}ZnSnS{sub 4} films to be 8.89 at% and 10.30 at% for two different annealing conditions. In the crystal structure, oxygen was substituted at the positions of sulfur and appeared in the interstitial sites of the lattice. The compositions of the thin films deviated from the stoichiometric ratio. Both films had kesterite structures with no secondary phase structure. The kesterite CZTS film possessed a composite microstructure of crystallite and crystalline states. The microstructure of the Cu{sub 2}ZnSnS{sub 4} film with higher oxygen content was denser and the average grain size was smaller. Incorporating oxygen atoms into crystalline Cu{sub 2}ZnSnS{sub 4} changed the energy band structure: the direct energy band gaps were, respectively, 2.75 eV and 2.84 eV; the thin films mainly adsorbed photons with wavelengths less than 500 nm; and the absorption coefficients increased from 10{sup 4} cm{sup −1} to 10{sup 5} cm{sup −1}. The films had a comparatively high absorptive capacity for photons less than 350 nm. Increasing the oxygen content of the film lowered the resistivity. Thus, the oxygen-containing Cu{sub 2}ZnSnS{sub 4} thin film could be a candidate for the p-type absorber layer material required in multi-junction solar cells.

  9. Mechanism of selenium hydride atomization, fate of free atoms and temperature distribution in an argon shielded, highly fuel-rich, hydrogen-oxygen diffusion micro-flame studied by atomic absorption spectrometry

    Czech Academy of Sciences Publication Activity Database

    D'Ulivo, A.; Dědina, Jiří; Lampugnani, L.; Matoušek, Tomáš

    2002-01-01

    Roč. 17, č. 3 (2002), s. 253-257 ISSN 0267-9477 R&D Projects: GA ČR GA203/01/0453; GA ČR GA203/98/0754 Institutional research plan: CEZ:AV0Z4031919 Keywords : hydride atomization * hydride generation * atomic absorption spectrometry Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 4.250, year: 2002

  10. Effect of oxygen vacancies on the electronic and optical properties of tungsten oxide from first principles calculations

    Science.gov (United States)

    Mehmood, Faisal; Pachter, Ruth; Murphy, Neil R.; Johnson, Walter E.; Ramana, Chintalapalle V.

    2016-12-01

    In this work, we investigated theoretically the role of oxygen vacancies on the electronic and optical properties of cubic, γ-monoclinic, and tetragonal phases of tungsten oxide (WO3) thin films. Following the examination of structural properties and stability of the bulk tungsten oxide polymorphs, we analyzed band structures and optical properties, applying density functional theory (DFT) and GW (Green's (G) function approximation with screened Coulomb interaction (W)) methods. Careful benchmarking of calculated band gaps demonstrated the importance of using a range-separated functional, where results for the pristine room temperature γ-monoclinic structure indicated agreement with experiment. Further, modulation of the band gap for WO3 structures with oxygen vacancies was quantified. Dielectric functions for cubic WO3, calculated at both the single-particle, essentially time-dependent DFT, as well as many-body GW-Bethe-Salpeter equation levels, indicated agreement with experimental data for pristine WO3. Interestingly, we found that introducing oxygen vacancies caused appearance of lower energy absorptions. A smaller refractive index was indicated in the defective WO3 structures. These predictions could lead to further experiments aimed at tuning the optical properties of WO3 by introducing oxygen vacancies, particularly for the lower energy spectral region.

  11. Interplay of Cu and oxygen vacancy in optical transitions and screening of excitons in ZnO:Cu films

    International Nuclear Information System (INIS)

    Darma, Yudi; Rusydi, Andrivo; Seng Herng, Tun; Marlina, Resti; Fauziah, Resti; Ding, Jun

    2014-01-01

    We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films

  12. Interplay of Cu and oxygen vacancy in optical transitions and screening of excitons in ZnO:Cu films

    Science.gov (United States)

    Darma, Yudi; Seng Herng, Tun; Marlina, Resti; Fauziah, Resti; Ding, Jun; Rusydi, Andrivo

    2014-02-01

    We study room temperature optics and electronic structures of ZnO:Cu films as a function of Cu concentration using a combination of spectroscopic ellipsometry, photoluminescence, and ultraviolet-visible absorption spectroscopy. Mid-gap optical states, interband transitions, and excitons are observed and distinguishable. We argue that the mid-gap states are originated from interactions of Cu and oxygen vacancy (Vo). They are located below conduction band (Zn4s) and above valence band (O2p) promoting strong green emission and narrowing optical band gap. Excitonic states are screened and its intensities decrease upon Cu doping. Our results show the importance of Cu and Vo driving the electronic structures and optical transitions in ZnO:Cu films.

  13. Optical verification of the valence band structure of cadmium arsenide

    NARCIS (Netherlands)

    Gelten, M.J.; Es, van C.M.; Blom, F.A.P.; Jongeneelen, J.W.F.

    1980-01-01

    Optical absorption measurements were performed on thin single crystalline samples of Cd3As2 at temperatures of 300 K and 10 K. At low temperature the interband absorption coefficient shows clearly two steps due to direct transitions from the heavy hole and light hole valence bands to the conduction

  14. Determinação de diagramas de bandas de energia e da borda de absorção em SnO2, depositado via sol-gel, sobre quartzo Determination of the band energy diagram and absorption fundamental edge in SnO2, deposited via sol-gel, on quartz

    Directory of Open Access Journals (Sweden)

    E. A. Floriano

    2009-03-01

    Full Text Available Propriedades ópticas e estruturais de filmes finos de SnO2, depositados sobre substratos de quartzo, são apresentadas. Os filmes são preparados pela técnica de molhamento via sol-gel. Uma avaliação das propriedades eletrônicas do cristal (bulk e das superfícies (110 e (101 do material é também efetuada, através de cálculos baseados em um método mecânico-quântico que utiliza a Teoria do Funcional da Densidade (DFT em conjunto com o funcional hibrido B3LYP. A borda fundamental de absorção, obtida experimentalmente, é então comparada com os diagramas de bandas de energia do bulk e superfícies (110 e (101, calculadas.Optical and structural properties of SnO2 thin films, deposited on quartz substrates, are presented. Films are prepared by the sol-gel-dip-coating technique. An evaluation of the electronic properties of bulk and surfaces (110 and (101 of the material is also carried out, through calculation based on a quantum-mechanical method using the Density Functional Theory (DFT in conjunction with the hybrid functional B3LYP. The absorption fundamental edge, experimentally obtained, is compared to the calculated band energy diagram of bulk and surfaces (110 and (101.

  15. Effect of annealing ambience on the formation of surface/bulk oxygen vacancies in TiO2 for photocatalytic hydrogen evolution

    Science.gov (United States)

    Hou, Lili; Zhang, Min; Guan, Zhongjie; Li, Qiuye; Yang, Jianjun

    2018-01-01

    The surface and bulk oxygen vacancy have a prominent effect on the photocatalytic performance of TiO2. In this study, TiO2 possessing different types and concentration of oxygen vacancies were prepared by annealing nanotube titanic acid (NTA) at various temperatures in air or vacuum atmosphere. TiO2 with the unitary bulk single-electron-trapped oxygen vacancies (SETOVs) formed when NTA were calcined in air. Whereas, TiO2 with both bulk and surface oxygen vacancies were obtained when NTA were annealed in vacuum. The series of TiO2 with different oxygen vacancies were systematically characterized by TEM, XRD, PL, XPS, ESR, and TGA. The PL and ESR analysis verified that surface oxygen vacancies and more bulk oxygen vacancies could form in vacuum atmosphere. Surface oxygen vacancies can trap electron and hinder the recombination of photo-generated charges, while bulk SETOVs act as the recombination center. The surface or bulk oxygen vacancies attributed different roles on the photo-absorbance and activity, leading that the sample of NTA-A400 displayed higher hydrogen evolution rate under UV light, whereas NTA-V400 displayed higher hydrogen evolution rate under visible light because bulk SETOVs can improve visible light absorption because sub-band formed by bulk SETOVs prompted the secondary transition of electron excited.

  16. Two band model for the cuprates

    Science.gov (United States)

    Liu, Shiu; White, Steven

    2009-03-01

    We use a numerical canonical transformation approach to derive an effective two-band model for the hole-doped cuprates, which keeps both oxygen and copper orbitals but removes double occupancy from each. A similar model was considered previously by Frenkel, Gooding, Shraiman, and Siggia (PRB 41, number 1, page 350). We compare the numerically derived model with previously obtained analytical results. In addition to the usual hopping terms between oxygens tpp and Cu-Cu exchange terms Jdd, the model also includes a strong copper-oxygen exchange interaction Jpd and a Kondo-like spin-flip oxygen-oxygen hopping term Kpdp. We use the density matrix renormalization group to study the charge, spin, and pairing properties of the derived model on ladder systems.

  17. Desorption, dissociation and orientation of oxygen admolecules on a reconstructed platinum(110)(1x2) surface studied by thermal desorption and near-edge X-ray-absorption fine-structure

    International Nuclear Information System (INIS)

    Ohno, Yuichi; Matsushima, Tatsuo; Tanaka, Shin-ichiro; Kamada, Masao

    1993-01-01

    The desorption, dissociation and orientation of oxygen admolecules on a reconstructed Pt(110)(1x2) were studied by means of TDS combined with isotope tracer, NEXAFS, and angle-resolved TDS. The admolecules below half a monolayer lie on the bottom of the trough, being oriented along it. The molecules adsorbed additionally are lying on declining terraces. The desorption flux of the former species shows a simple cosine distribution, suggesting that the molecule is not localized on the bottom in the desorption event. (author)

  18. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.; Franklin, J. B.; Ryan, M. P.; Lee, J.-S.; Ohldag, Hendrik; McLachlan, M. A.; Alford, N. M.; Roqan, Iman S.

    2015-01-01

    . %) at low oxygen deposition pressure (<25 mTorr) were ferromagnetic at room temperature. Negative magnetoresistance, electric transport properties showed that the ferromagnetic exchange is mediated by a spin-split defect band formed due to oxygen deficiency

  19. Measurement of Soot Volume Fraction and Temperature for Oxygen-Enriched Ethylene Combustion Based on Flame Image Processing

    Directory of Open Access Journals (Sweden)

    Weijie Yan

    2017-05-01

    Full Text Available A method for simultaneously visualizing the two-dimensional distributions of temperature and soot volume fraction in an ethylene flame was presented. A single-color charge-coupled device (CCD camera was used to capture the flame image in the visible spectrum considering the broad-response spectrum of the R and G bands of the camera. The directional emissive power of the R and G bands were calibrated and used for measurement. Slightly increased temperatures and reduced soot concentration were predicted in the central flame without self-absorption effects considered, an iterative algorithm was used for eliminating the effect of self-absorption. Nine different cases were presented in the experiment to demonstrate the effects of fuel mass flow rate and oxygen concentration on temperature and soot concentration in three different atmospheres. For ethylene combustion in pure-air atmosphere, as the fuel mass flow rate increased, the maximum temperature slightly decreased, and the maximum soot volume fraction slightly increased. For oxygen fractions of 30%, 40%, and 50% combustion in O2/N2 oxygen-enhanced atmospheres, the maximum flame temperatures were 2276, 2451, and 2678 K, whereas combustion in O2/CO2 atmospheres were 1916, 2322, and 2535 K. The maximum soot volume fractions were 4.5, 7.0, and 9.5 ppm in oxygen-enriched O2/N2 atmosphere and 13.6, 15.3, and 14.8 ppm in oxygen-enriched O2/CO2 atmosphere. Compared with the O2/CO2 atmosphere, combustion in the oxygen-enriched O2/N2 atmosphere produced higher flame temperature and larger soot volume fraction. Preliminary results indicated that this technique is reliable and can be used for combustion diagnosis.

  20. Efficient frequency conversion through absorptive bands of the nonlinear crystal

    OpenAIRE

    Porat, Gil; Arie, Ady

    2012-01-01

    Two simultaneous three wave mixing processes are analyzed, where an input frequency is converted to an output frequency via an intermediate stage. By employing simultaneous phase-matching and an adiabatic modulation of the nonlinear coupling strengths, the intermediate frequency is kept dark throughout the interaction, while obtaining high conversion efficiency. This feat is accomplished in a manner analogous to population transfer in atomic stimulated Raman adiabatic passage (STIRAP). Applic...

  1. Salvianolic acid B Relieves Oxidative Stress in Glucose Absorption ...

    African Journals Online (AJOL)

    Absorption and Utilization of Mice Fed High-Sugar Diet ... Salvianolic acid B, Blood glucose, Reactive oxygen species, Oxidative stress, Sugar diet. ... protein expression in human aortic smooth ... induced by glucose uptake and metabolism [8].

  2. Study of absorption and IR-emission of Er3+, Dy3+, Tm3+ doped high-purity tellurite glasses

    Science.gov (United States)

    Motorin, S. E.; Dorofeev, V. V.; Galagan, B. I.; Sverchkov, S. E.; Koltashev, V. V.; Denker, B. I.

    2018-04-01

    A study of high-purity TeO2-ZnO based tellurite glasses doped with Er3+, Dy3+ or Tm3+ that could be used as laser media in the 2-3 μm spectral range is presented. The glasses are prepared by melting the oxides mixture inside a silica glass reactor in an atmosphere of purified oxygen. The low level of hydroxyl groups absorption allowed to measure correctly the luminescence decay characteristics of the dopants. The rare-earth ions absorption bands, the luminescence spectra and kinetic characteristics of emission from the levels 4I11/2, 4I13/2 of Er3+, 6H13/2 of Dy3+ and 3H4, 3H5, 3F4 of Tm3+ ions are investigated. The results confirm the high potential of tellurite glasses as an active media for bulk, planar waveguide and fiber lasers.

  3. Dual band metamaterial perfect absorber based on Mie resonances

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xiaoming; Lan, Chuwen; Li, Bo; Zhou, Ji, E-mail: zhouji@tsinghua.edu.cn [State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Bi, Ke [School of Science, Beijing University of Posts and Telecommunications, Beijing 100876 (China); Zhao, Qian [State Key Lab of Tribology, Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084 (China)

    2016-08-08

    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.

  4. Band structure of semiconductors

    CERN Document Server

    Tsidilkovski, I M

    2013-01-01

    Band Structure of Semiconductors provides a review of the theoretical and experimental methods of investigating band structure and an analysis of the results of the developments in this field. The book presents the problems, methods, and applications in the study of band structure. Topics on the computational methods of band structure; band structures of important semiconducting materials; behavior of an electron in a perturbed periodic field; effective masses and g-factors for the most commonly encountered band structures; and the treatment of cyclotron resonance, Shubnikov-de Haas oscillatio

  5. UV- Radiation Absorption by Ozone in a Model Atmosphere using ...

    African Journals Online (AJOL)

    UV- radiation absorption is studied through variation of ozone transmittance with altitude in the atmosphere for radiation in the 9.6μm absorption band using Goody's model atmosphere with cubic spline interpolation technique to improve the quality of the curve. The data comprising of pressure and temperature at different ...

  6. Microwave absorption studies of MgB 2 superconductor

    Indian Academy of Sciences (India)

    Microwave absorption studies have been carried out on MgB2 superconductor using a standard X-band EPR spectrometer. The modulated low-field microwave absorption signals recorded for polycrystalline (grain size ∼ 10m) samples suggested the absence of weak-link character. The field dependent direct microwave ...

  7. X-ray absorption spectroscopy study on SiC-side interface structure of SiO2–SiC formed by thermal oxidation in dry oxygen

    Science.gov (United States)

    Isomura, Noritake; Kosaka, Satoru; Kataoka, Keita; Watanabe, Yukihiko; Kimoto, Yasuji

    2018-06-01

    Extended X-ray absorption fine structure (EXAFS) spectroscopy is demonstrated to measure the fine atomic structure of SiO2–SiC interfaces. The SiC-side of the interface can be measured by fabricating thin SiO2 films and using SiC-selective EXAFS measurements. Fourier transforms of the oscillations of the EXAFS spectra correspond to radial-structure functions and reveal a new peak of the first nearest neighbor of Si for m-face SiC, which does not appear in measurements of the Si-face. This finding suggests that the m-face interface could include a structure with shorter Si–C distances. Numerical calculations provide additional support for this finding.

  8. Tuning of optical and electrical properties of wide band gap Fe:SnO{sub 2}/Li:NiO p-n junctions using 80 MeV oxygen ion beam

    Energy Technology Data Exchange (ETDEWEB)

    Mistry, Bhaumik V.; Joshi, U.S. [Gujarat University, Department of Physics, School of Sciences, Ahmedabad (India); Avasthi, D.K. [Inter University Accelerator Centre, New Delhi (India)

    2016-12-15

    Electrical and optical properties of pristine and swift heavy ion (SHI) irradiated p-n junction diode have been investigated for advanced electronics application. Fe:SnO{sub 2}/Li:NiO p-n junction was fabricated by using pulsed laser deposition on c-sapphire substrate. The optical band gaps of Fe:SnO{sub 2} and Li:NiO films were obtained to be 3.88 and 3.37 eV, respectively. The current-voltage characteristics of the oxide-based p-n junction showed a rectifying behaviour with turn-on voltage of 0.95 V. The oxide-based p-n junction diode was irradiated to 80 MeV O{sup +6} ions with 1 x 10{sup 12} ions/cm{sup 2} fluence. Decrease in grain size due to SHI irradiation is confirmed by the grazing angle X-ray diffraction and atomic force microscopy. In comparison with the pristine p-n junction diode, O{sup +6} ion irradiated p-n junction diode shows the increase of surface roughness and decrease of percentage transmittance in visible region. For irradiated p-n junction diode, current-voltage curve has still rectifying behaviour but exhibits lower turn-on voltage than that of virgin p-n junction diode. (orig.)

  9. Impact effects of gamma irradiation on the optical and FT infrared absorption spectra of some Nd3+-doped soda lime phosphate glasses

    Science.gov (United States)

    Marzouk, M. A.; Elkashef, I. M.; Elbatal, H. A.

    2018-04-01

    The main aim of the present work is to study by two collective optical and FTIR spectral measurements some prepared Nd2O3-doped soda lime phosphate glasses before and after gamma irradiation with dose (9 Mrad). The spectral data reveal two strong UV absorption peaks which are correlated with unavoidable trace iron impurities beside extended additional characteristic bands due to Nd3+ ions. Gamma irradiation on the undoped glass produces slight decrease of the intensity of the UV absorption and the generation of an induced visible band and these effects are controlled with two photochemical reduction of some Fe3+ ions to Fe2+ ions together with the formation of nonbridging oxygen hole center (NBOHC) or phosphorous oxygen hole center (POHC). The impact effect of gamma irradiation on the spectra of Nd2O3-doped glasses is limited due to suggested shielding behavior of neodymium ions. FT-infrared spectra show vibrational modes due to main Q2-Q3 phosphate groups and the response of gamma irradiation of the IR spectra is low and the limited variations are related to suggested changes in some bond angles and bond lengths which cause the observed decrease to the intensities of some IR bands.

  10. Tungsten oxides. I. Effects of oxygen vacancies and doping on electronic and optical properties of different phases of WO3

    Science.gov (United States)

    Migas, D. B.; Shaposhnikov, V. L.; Rodin, V. N.; Borisenko, V. E.

    2010-11-01

    In this part we present results of our ab initio calculations indicating that dispersion of the bands near the gap region for different phases of WO3 (namely, ɛ-WO3, δ-WO3, γ-WO3, β-WO3, orth-WO3, α-WO3, and hex-WO3) is rather close. The rapid increase in the absorption coefficient starts at the lower energy range for α-WO3 and hex-WO3 than for the other phases in accordance with the calculated band gaps. An oxygen vacancy has turned out to decrease the gap by 0.50 eV and to shift the absorption coefficient to the lower energy range in the room temperature γ-WO3 phase. We have also traced changes caused by molybdenum and sulfur doping of γ-WO3. Only sulfur doped γ-WO3 has been revealed to display the formation of the impurity band along with a sizable reduction in the gap and the shift in the absorption coefficient to the lower energy range.

  11. Gallic acid as an oxygen scavenger in bio-based multilayer packaging films

    OpenAIRE

    Pant, Astrid; Sängerlaub, Sven; Müller, Kajetan

    2017-01-01

    Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and ...

  12. Cermet based metamaterials for multi band absorbers over NIR to LWIR frequencies

    International Nuclear Information System (INIS)

    Pradhan, Jitendra K; Behera, Gangadhar; Anantha Ramakrishna, S; Agarwal, Amit K; Ghosh, Amitava

    2017-01-01

    Cermets or ceramic-metals are known for their use in solar thermal technologies for their absorption across the solar band. Use of cermet layers in a metamaterial perfect absorber allows for flexible control of infra-red absorption over the short wave infra-red, to long wave infra-red bands, while keeping the visible/near infra-red absorption properties constant. We design multilayered metamaterials consisting of a conducting ground plane, a low metal volume fraction cermet/ZnS as dielectric spacer layers, and a top structured layer of an array of circular discs of metal/high volume metal fraction cermet that give rise to specified absorption bands in the near-infra-red (NIR) frequencies, as well as any specified band at SWIR–LWIR frequencies. Thus, a complete decoupling of the absorption at optical/NIR frequencies and the infra-red absorption behaviour of a structured metamaterial is demonstrated. (paper)

  13. Absorption lineshape of FA centers in alkali halides

    International Nuclear Information System (INIS)

    Baldacchini, G.; Giovenale, E.; De Matteis, F.; Scacco, A.; Somma, F.; Grassano, U.M.

    1988-01-01

    The line shape of the absorption bands of F A centers in alkali halides have been studied for the first time. The new method used for this investigation is based on the determination of the overlap between the F A1 and F A2 bands from luminescence measurements. The experimental results have been compared with calculated values deduced from the theoretical F A bands of different shapes. For both F A (I) centers in KCl:Na + and F A (II) centers in KCl:Li + and RbCl:Li + the absorption lineshape at low temperature is much closer to a sum of two Lorentzian curves than that of two Gaussian or Poissonian bands. This results shows an unexpected difference with the F centers, whose absorption lineshape is known to be Poissonian at the same temperatures

  14. Oxygen measurements in thin ribbon silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hyland, S L; Ast, D G; Baghdadi, A

    1987-03-01

    The oxygen content of thin silicon ribbons grown by the dendritic web technique was measured using a modification of the ASTM method based on Fourier transform infrared spectroscopy. Web silicon was found to have a high oxygen content, ranging from 13 to 19 ppma, calculated from the absorption peak associated with interstitial oxygen and using the new ASTM conversion coefficient. The oxygen concentration changed by about 10% along the growth direction of the ribbon. In some samples, a shoulder was detected on the absorption peak. A similar shoulder in Czochralski grown material has been variously interpreted in the literature as due to a complex of silicon, oxygen, and vacancies, or to a phase of SiO/sub 2/ developed along dislocations in the material. In the case of web silicon, it is not clear which is the correct interpretation.

  15. D-xylose absorption

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/003606.htm D-xylose absorption To use the sharing features on this page, please enable JavaScript. D-xylose absorption is a laboratory test to determine ...

  16. Visible-light activity of N-LiInO{sub 2}: Band structure modifications through interstitial nitrogen doping

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Kaiqiang [College of Material Science and Engineering, Hunan University, Changsha, 410082 (China); Xu, Difa, E-mail: xudifa@sina.com [Hunan Key Laboratory of Applied Environmental Photocatalysis, Changsha University, Changsha, 410022 (China); Zhang, Xiangchao; Luo, Zhuo; Wang, Yutang [Hunan Key Laboratory of Applied Environmental Photocatalysis, Changsha University, Changsha, 410022 (China); Zhang, Shiying, E-mail: cdzhangshiying@163.com [College of Material Science and Engineering, Hunan University, Changsha, 410082 (China); Hunan Key Laboratory of Applied Environmental Photocatalysis, Changsha University, Changsha, 410022 (China)

    2017-01-01

    Highlights: • The interstitial nitrogen doping into LiInO{sub 2} is achieved at low temperature. • The band gap narrowing to an extent of 2.8 eV from 3.5 eV is observed. • The doping favours charge carrier separation and photocatalytic activity. • Superoxide radical is the dominant active specie in the pollutant degradation. - Abstract: Element doping is a promising strategy to improve the photo-response and photocatalytic activity of semiconductor photocatalyst with a wide band gap. To reduce the band gap of LiInO{sub 2} that is considered as a novel photocatalyst, nitrogen-doped LiInO{sub 2} (N-LiInO{sub 2}) is successfully fabricated by treating LiInO{sub 2} and urea at 200 °C. It is found that interstitial instead of substitutional configurations are formed in the crystal structure of N-LiInO{sub 2} due to the low-treating temperature and rich-oxygen conditions. The interstitial N-doping forms a doping state with 0.6 eV above the valence band maximum and a defect state with 0.1 eV below the conduction band minimum, reducing the band gap of LiInO{sub 2} from 3.5 to 2.8 eV. N-LiInO{sub 2} exhibits higher photocatalytic activity towards methylene blue (MB) degradation under 380 nm light irradiation, which is 1.4 times that of pure LiInO{sub 2}. The enhanced photocatalytic activity of N-LiInO{sub 2} is attributed to the extended light absorption and the improved charge carrier separation, which result in more reactive species participating in the photcatalytic process. This work provides a further understanding on tuning the band structure of semiconductor photocatalyst by N-doping strategies.

  17. Threshold nonlinear absorption in Zeeman transitions

    International Nuclear Information System (INIS)

    Narayanan, Andal; Hazra, Abheera; Sandhya, S N

    2010-01-01

    We experimentally study the absorption spectroscopy from a collection of gaseous 87 Rb atoms at room temperature irradiated with three fields. Two of these fields are in a pump-probe saturation absorption configuration. The third field co-propagates with the pump field. The three fields address Zeeman degenerate transitions between hyperfine levels 5S 1/2 , F = 1 and 5P 3/2 , F = 0, F = 1 around the D2 line. We find a sub-natural absorption resonance in the counter-propagating probe field for equal detunings of all three fields. This absorption arises in conjunction with the appearance of increased transmission due to electro-magnetically induced transparency in the co-propagating fields. The novel feature of this absorption is its onset only for the blue of 5P 3/2 , F = 0, as the laser frequency is scanned through the excited states 5P 3/2 , F = 0, F = 1 and F = 2. The absorption rapidly rises to near maximum values within a narrow band of frequency near 5P 3/2 , F = 0. Our experimental results are compared with a dressed atom model. We find the threshold absorption to be a result of coherent interaction between the dressed states of our system.

  18. Aerosol Absorption Measurements in MILAGRO.

    Science.gov (United States)

    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. In vivo integrated photoacoustic and confocal microscopy of hemoglobin oxygen saturation and oxygen partial pressure.

    Science.gov (United States)

    Wang, Yu; Hu, Song; Maslov, Konstantin; Zhang, Yu; Xia, Younan; Wang, Lihong V

    2011-04-01

    We developed dual-modality microscope integrating photoacoustic microscopy (PAM) and fluorescence confocal microscopy (FCM) to noninvasively image hemoglobin oxygen saturation (sO₂) and oxygen partial pressure (pO₂) in vivo in single blood vessels with high spatial resolution. While PAM measures sO₂ by imaging hemoglobin optical absorption at two wavelengths, FCM quantifies pO₂ using phosphorescence quenching. The variations of sO₂ and pO₂ values in multiple orders of vessel branches under hyperoxic (100% oxygen) and normoxic (21% oxygen) conditions correlate well with the oxygen-hemoglobin dissociation curve. In addition, the total concentration of hemoglobin is imaged by PAM at an isosbestic wavelength.

  20. Absorption and excretion tests

    International Nuclear Information System (INIS)

    Berberich, R.

    1988-01-01

    The absorption and excretion of radiopharmaceuticals is still of interest in diagnostic investigations of nuclear medicine. In this paper the most common methods of measuring absorption and excretion are described. The performance of the different tests and their standard values are discussed. More over the basic possibilities of measuring absorption and excretion including the needed measurement equipments are presented. (orig.) [de

  1. X-ray absorption and emission studies of diamond nanoparticles

    International Nuclear Information System (INIS)

    Van Buuren, T.; Willey, T.; Raty, J.Y.; Galli, G.; Terminello, L.J.; Bostedt, C.

    2004-01-01

    Full text: A new family of carbon nanopaticles produced in detonations, are found to have a core of diamond with a coating fullerene- like carbon. X-ray diffraction and TEM show that the nanodiamond powder is crystalline and approximately 4 nm in diameter. These nano-sized diamonds do not display the characteristic property of other group IV nanoparticles: a strong widening of the energy gap between the conduction and valence bands owing to quantum-confinement effects. For nano-sized diamond with a size distribution of 4 nm, there is no shift of the band energies relative to bulk diamond. Although the C1s core exciton feature clearly observed in the K-edge absorption edge of bulk diamond is shifted and broadening due to increased overlap of the excited electron with the core holein the small particle. Also the depth of the second gap in the nanodiamond spectra is shallower than that of bulk diamond. A feature at lower energy in the X-ray absorption spectra that is not present in the bulk samples is consistent with a fullerene like surface reconstruction. By exposing the diamond nanoparticles to an Argon /Oxygen plasma then annealing in a UHV environment we have obtained a hydrogen free surface. The nanodiamonds processed in this manner show an increase fullerene type contribution in the carbon x-ray absorption pre-edge. High spatial resolution EELS measurements of the empty states of a single nanodiamond particle acquired with a ld emission TEM also show the core of the particle is bulk diamond like where as the surface has a fullerene like structure. Standard density-functional calculations on clusters in which the diamond surface bonds are terminated with hydrogen atoms, show that the bandgap begins to increase above the bulk value only for clusters smaller than 1 nm. Surface hydrogen atoms are found to be about as close as they do in molecular hydrogen and can escape as H 2 , forcing the respective carbon atoms to rearrange. A series of such rearrangements can

  2. Grain size dependent optical band gap of CdI2 films

    Indian Academy of Sciences (India)

    Unknown

    absorption data near band edge can be fitted to an indirect band gap of 3 eV. The dependence of band gap ... while to carry out the optical studies on CdI2 films in order to .... replotted as (αhν)1/2 vs hν to determine indirect gap as shown in the ...

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

    Science.gov (United States)

    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.

  4. Transient absorption studies in pure rare gases from 2500 A to 4000 A

    Energy Technology Data Exchange (ETDEWEB)

    Champagne, L F; Chang, R S.F. [Naval Research Lab., Washington, DC (USA)

    1980-01-01

    The broad band absorption in electron beam excited rare gas plasmas was measured for neon, argon, krypton and xenon gas. A broad continuum emission from a xenon flashlamp was used as the probe source. Absorption data was obtained over a 1500 A range. Absorption peaks in argon, neon and xenon correlate well with the predicted peak absorption cross sections for the respective dimer ions. No absorption peak in krypton was observed. Secondary absorption peaks of comparable magnitude to the dimer absorption peak were also observed in argon and xenon.

  5. Optical absorption and electron spin resonance in natural, irradiated and heated spodumene

    International Nuclear Information System (INIS)

    Ito, A.S.; Isotani, S.

    1983-09-01

    Heat treatment and X and γ-Rays irradiation of lylac and colorless natural spodumene, LiAlSi 2 O 6 , have been studied. Irradiation produces a color change, from lylac or colorless to green. Irradiated samples heated at 200 0 C turn lylac and bleach at 400 0 C. Optical absorption spectra were decomposed into gaussian line shape bands and it is observed that green and lylac centers are simultaneously created by irradiation. These centers are independent from each other. Optical absorption, EPR and X-Ray fluorescence results show the spectra of impurities, responsible by the presence of the created centers and indicated Mn participation in the process of centers creation and destruction. Decay Kinetics of green and lylac centers have been studied and it is observed that simple Kinetic models do not apply to these cases. An empirical fit allowed the calculation of activation energies of the lylac and green centers decays. Discussions about the present results led us to propose a new model where the green and lylac centers are due to Mn 3+ ions in two different Al 3+ sites, whose absorption are intensified by the interaction with an electron trapped in a neighbour oxygen. (Author) [pt

  6. Absorption from Neutral Acceptors in GaAs and GaP

    DEFF Research Database (Denmark)

    Christensen, Ove

    1973-01-01

    We present a new calculation of the absorption due to transitions of holes between neutral acceptors and the various valence-band sublevels in GaAs and GaP. The acceptor wave function was approximated by a previously suggested expression for ground-state wave functions appropriate to complicated...... band extrema. Numerical calculations of the absorption from intervalence-band transitions of free holes and neutral acceptors have been performed. Good agreement with experimental results is obtained....

  7. Oxygen safety

    Science.gov (United States)

    ... sure you have working smoke detectors and a working fire extinguisher in your home. If you move around the house with your oxygen, you may need more than one fire extinguisher in different locations. Smoking can be very dangerous. No one should smoke ...

  8. Absorption spectra of trapped holes in anatase TiO2

    DEFF Research Database (Denmark)

    Zawadzki, Pawel

    2013-01-01

    absorption spectroscopy (TAS), but the understanding of the optical absorption due to trapped carriers in TiO2 is incomplete. On the basis of the generalized Δ self-consistent field density functional theory (Δ-SCF DFT) calculations, we attribute the experimentally observed absorption band at 430-550 nm...

  9. Calcium absorption and achlorhydria

    International Nuclear Information System (INIS)

    Recker, R.R.

    1985-01-01

    Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium used as the carrier. Mean calcium absorption (+/- S.D.) in the patients with achlorhydria was 0.452 +/- 0.125 for citrate and 0.042 +/- 0.021 for carbonate (P less than 0.0001). Fractional calcium absorption in the normal subjects was 0.243 +/- 0.049 for citrate and 0.225 +/- 0.108 for carbonate (not significant). Absorption of calcium from carbonate in patients with achlorhydria was significantly lower than in the normal subjects and was lower than absorption from citrate in either group; absorption from citrate in those with achlorhydria was significantly higher than in the normal subjects, as well as higher than absorption from carbonate in either group. Administration of calcium carbonate as part of a normal breakfast resulted in completely normal absorption in the achlorhydric subjects. These results indicate that calcium absorption from carbonate is impaired in achlorhydria under fasting conditions. Since achlorhydria is common in older persons, calcium carbonate may not be the ideal dietary supplement

  10. Oxygen therapy - infants

    Science.gov (United States)

    ... breathe increased amounts of oxygen to get normal levels of oxygen in their blood. Oxygen therapy provides babies with the extra oxygen. Information Oxygen is a gas that the cells in your body need to work properly. The ...

  11. Anionic or Cationic S-Doping in Bulk Anatase TiO 2 : Insights on Optical Absorption from First Principles Calculations

    KAUST Repository

    Harb, Moussab

    2013-05-02

    Using first principles calculations, we investigate the structural, electronic, optical, and energetic properties of S-doped anatase TiO2 bulk systems. To ensure accurate band gap predictions, we use the HSE06 exchange correlation functional, and the absorption spectra are obtained with density functional perturbation (DFPT) theory by employing HSE06. Various oxidation states (anionic and cationic) of sulfur are considered depending on the location in bulk TiO2: in interstitial position or in substitution for either oxygen or titanium atoms. Among the explored structures, two anionic and one cationic configurations induce an improved optical absorption response in the visible region as observed experimentally. Moreover, we undertake a thermodynamic analysis as a function of the chemical potential of oxygen and considering three relevant sulfur chemical doping agents (S 2, H2S, and thiourea). It highlights that cationic configurations (S4+ and S6+) are strongly stabilized in a wide range of oxygen chemical potential (including standard conditions), whereas anionic species are stabilized only at very low chemical potential of oxygen. The metastable cationic Ti(1-2x)O2S2x system involving the presence of S4+ species in substitution for Ti 4+, with the formation of SO2 units, should offer the best compromise between the thermodynamic conditions and the expected optical properties. © 2013 American Chemical Society.

  12. Combined effect of solvents and gamma irradiation on the infrared absorption spectra of polyethylene terephthalate

    International Nuclear Information System (INIS)

    Rabie, S.M.; ElBially, A.; Elshourbaguie, S.

    1991-01-01

    The combined effect of solvents and gamma irradiation on the intensities of infrared absorption bands of polyethylene terephthalate, particularly the bands sensitive to conformational changes, were studied. The results revealed that solvent treatment of PET results in significant changes in the intensities of its infrared absorption bands and the exposure of PET to gamma radiation in the presence of solvents helps in the appearance of the two bands at 1550 and 1630 cm . Also, the combined effect of solvents and gamma irradiation on the intensities of the absorption bands is greater than the effect of each agent alone. The extent of the induced changes depends on the nature of solvent and the applied dosage. Further more, for any given solvent or dosage, the rate of change of the intensities of the trans band is not equal to that of the gauche bands.3 fig

  13. Band gap evaluations of metal-inserted titania nanomaterials

    International Nuclear Information System (INIS)

    Bashir, Sajid; Liu, Jingbo; Zhang Hui; Sun Xuhui; Guo Jinghua

    2013-01-01

    The electronic and crystalline properties of iron-inserted titania (Fe x Ti 1−x O 2 ) nanoparticles were measured using synchrotron-based soft X-ray spectroscopy and high-temperature X-ray powder diffraction (HT-XRD). The data from X-ray absorption and emission spectroscopy were used to examine occupied and unoccupied densities of states for O 2p and Ti/Fe 3d hybrid orbital characteristics. It was found that Fe 3+ insertion resulted in an up-shift of the band gap from 3.20 to 3.46 eV. This observation reflected site occupancy in the TiO 2 lattice by Fe dopant ions. From HT-XRD Rietveld analysis, Ti occupancy was found to be 0.92 and oxygen 1.00. In addition, the crystal structure remained anatase within a temperature range of 25–800 °C, while the lattice distortion increased due to thermal expansion.

  14. Structure and dynamics in liquid water from x-ray absorption spectroscopy

    International Nuclear Information System (INIS)

    Wernet, Philippe

    2009-01-01

    Oxygen K-edge x-ray absorption spectra of water are discussed. The spectra of gas-phase water, liquid water and ice illustrate the sensitivity of oxygen K-edge x-ray absorption spectroscopy to hydrogen bonding in water. Transmission mode spectra of amorphous and crystalline ice are compared to x-ray Raman spectra of ice. The good agreement consolidates the experimental spectrum of crystalline ice and represents an incentive for theoretical calculations of the oxygen K-edge absorption spectrum of crystalline ice. Time-resolved infrared-pump and x-ray absorption probe results are finally discussed in the light of this structural interpretation.

  15. Wide Band to ''Double Band'' upgrade

    International Nuclear Information System (INIS)

    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

  16. What band rocks the MTB? (Invited)

    Science.gov (United States)

    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

  17. Modern Progress and Modern Problems in High Resolution X-ray Absorption from the Cold Interstellar Medium

    Science.gov (United States)

    Corrales, Lia; Li, Haochuan; Heinz, Sebastian

    2018-01-01

    With accurate cross-sections and higher signal-to-noise, X-ray spectroscopy can directly measure Milky Way gas and dust-phase metal abundances with few underlying assumptions. The X-ray energy band is sensitive to absorption by all abundant interstellar metals — carbon, oxygen, neon, silicon, magnesium, and iron — whether they are in gas or dust form. High resolution X-ray spectra from Galactic X-ray point sources can be used to directly measure metal abundances from all phases of the interstellar medium (ISM) along singular sight lines. We show our progress for measuring the depth of photoelectric absorption edges from neutral ISM metals, using all the observations of bright Galactic X-ray binaries available in the Chandra HETG archive. The cross-sections we use take into account both the absorption and scattering effects by interstellar dust grains on the iron and silicate spectral features. However, there are many open problems for reconciling X-ray absorption spectroscopy with ISM observations in other wavelengths. We will review the state of the field, lab measurements needed, and ways in which the next generation of X-ray telescopes will contribute.

  18. Two models for absorption by coloured dissolved organic matter (CDOM

    Directory of Open Access Journals (Sweden)

    Jill N. Schwarz

    2002-06-01

    Full Text Available The standard exponential model for CDOM absorption has been applied to data from diverse waters. Absorption at 440 nm (ag440 ranged between close to zero and 10 m-1, and the slope of the semilogarithmic absorption spectrum over a minimum range of 400 to 440 nm (s440 ranged between < 0.01 and 0.04 nm-1. No relationship was found between ag440 or s440 and salinity. Except in the southern Baltic, s440 was found to have a broad distribution (0.0165 ± 0.0035, suggesting that it should be introduced as an additional variable in bio-optical models when ag440 is large. An alternative model for CDOM absorption was applied to available high quality UV-visible absorption spectra from the Wisla river (Poland. This model assumes that the CDOM absorption spectrum comprises distinct Gaussian absorption bands in the UV, similar to those of benzene. Five bands were fit to the data. The mean central energy of all bands was higher in early summer (E~7.2, 6.6, 6.4, 6.2 and 5.5 eV or 172, 188, 194, 200 and 226 nm than in winter. The higher energy bands were found to decay in both height and width with increasing salinity, while lower energy bands broadened with increasing salinity. s440 was found to be correlated with shape parameters of the bands centred at 6.4 and 5.5 eV. While the exponential model is convenient for optical modelling and remote sensing applications, these results suggest that the Gaussian model offers a deeper understanding of chemical interactions affecting CDOM molecular structure.

  19. Bulk damage and absorption in fused silica due to high-power laser applications

    Science.gov (United States)

    Nürnberg, F.; Kühn, B.; Langner, A.; Altwein, M.; Schötz, G.; Takke, R.; Thomas, S.; Vydra, J.

    2015-11-01

    consists of three different absorption bands centered at 165 nm (peroxy radicals), 215 nm (E'-center), and 265 nm (non-bridging oxygen hole center (NBOH)), which change the transmission behavior of material.

  20. [Study on lead absorption in pumpkin by atomic absorption spectrophotometry].

    Science.gov (United States)

    Li, Zhen-Xia; Sun, Yong-Dong; Chen, Bi-Hua; Li, Xin-Zheng

    2008-07-01

    A study was carried out on the characteristic of lead absorption in pumpkin via atomic absorption spectrophotometer. The results showed that lead absorption amount in pumpkin increased with time, but the absorption rate decreased with time; And the lead absorption amount reached the peak in pH 7. Lead and cadmium have similar characteristic of absorption in pumpkin.

  1. Structural and optical characterization of oxygenated CdTe/Sm3+ in sol-gel silica glasses

    International Nuclear Information System (INIS)

    Mathew, Siby; Rejikumar, P.R.; Adiyodi, Amrutha K.; Jyothy, P.V.; Unnikrishnan, N.V.

    2008-01-01

    Oxygenated cadmium telluride co-doped with rare earth element samarium is prepared by sol-gel method. Sample is air annealed at 200, 500 and 800 deg. C. The absorption and fluorescence spectra are analysed using Judd-Ofelt analysis to obtain J-O parameters. X-ray spectroscopy analysis shows the presence of thermally grown CdTeO 3 phase developed at the expense of CdTe phase on heat treatment for samples annealed at 800 deg. C. The FT-IR spectrum of the sample is taken at different annealing temperatures and the assignments of the absorption bands are compiled which shows the gradual evolution of the rigid glassy network formed. Enhanced fluorescence from air annealed Co-doped samples are also investigated

  2. Atmospheric solar heating rate in the water vapor bands

    Science.gov (United States)

    Chou, Ming-Dah

    1986-01-01

    The total absorption of solar radiation by water vapor in clear atmospheres is parameterized as a simple function of the scaled water vapor amount. For applications to cloudy and hazy atmospheres, the flux-weighted k-distribution functions are computed for individual absorption bands and for the total near-infrared region. The parameterization is based upon monochromatic calculations and follows essentially the scaling approximation of Chou and Arking, but the effect of temperature variation with height is taken into account in order to enhance the accuracy. Furthermore, the spectral range is extended to cover the two weak bands centered at 0.72 and 0.82 micron. Comparisons with monochromatic calculations show that the atmospheric heating rate and the surface radiation can be accurately computed from the parameterization. Comparisons are also made with other parameterizations. It is found that the absorption of solar radiation can be computed reasonably well using the Goody band model and the Curtis-Godson approximation.

  3. Amniotic constriction bands

    Science.gov (United States)

    ... Supplements Videos & Tools Español You Are Here: Home → Medical Encyclopedia → Amniotic band sequence URL of this page: //medlineplus.gov/ency/ ... birth. The baby should be delivered in a medical center that has specialists experienced in caring for babies ... or partial loss of function of a body part. Congenital bands affecting large parts of the body cause the ...

  4. High resolution and high precision absorption spectroscopy using high finesse cavities: application to the study of molecules with atmospheric interest; Cavites de haute finesse pour la spectroscopie d'absorption haute sensibilite et haute precision: application a l'etude de molecules d'interet atmospherique

    Energy Technology Data Exchange (ETDEWEB)

    Motto-Ros, V.

    2005-12-15

    High finesse cavities are used to measure very weak absorption features. Two different methodologies are investigated and applied to the study of molecules with atmospheric interest. First, Continuous Wave - Cavity Ring Down Spectroscopy (CW-CRDS) is used to study the atmospheric spectra of water vapour in the near infrared range. These measurements are performed for temperature and pressure of atmospheric relevance for DIAL applications (Differential Absorption Lidar). This study, financed by the European Space Agency (ESA), goes with the WALES mission (Water Vapour Lidar Experiment in Space). The experimental setup was conceived in order to control pressure, temperature and relative humidity conditions. A particular attention is done to characterize and describe the spectrometer. Then, measurements of red Oxygen B band are performed to demonstrate the huge performance of Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS). The desired optical feedback is obtained by light injection into the high finesse cavity through a glass plate placed inside the cavity and closed to the Brewster angle. We show a measurement dynamical range of 5 orders of magnitude (10{sup -5} to 10{sup -10} /cm) and a sensitivity of 10{sup -10} /cm/{radical} Hz. Also, sampling absorption spectra by the super linear cavity frequency comb allows very precise frequency measurements. This is demonstrated by the determination of Oxygen pressure shifts with an absolute accuracy of around 5 x 10{sup -5} cm{sup -1}/atm. To our knowledge, we provide the highest accuracy ever reported for this parameter. (author)

  5. High resolution and high precision absorption spectroscopy using high finesse cavities: application to the study of molecules with atmospheric interest; Cavites de haute finesse pour la spectroscopie d'absorption haute sensibilite et haute precision: application a l'etude de molecules d'interet atmospherique

    Energy Technology Data Exchange (ETDEWEB)

    Motto-Ros, V

    2005-12-15

    High finesse cavities are used to measure very weak absorption features. Two different methodologies are investigated and applied to the study of molecules with atmospheric interest. First, Continuous Wave - Cavity Ring Down Spectroscopy (CW-CRDS) is used to study the atmospheric spectra of water vapour in the near infrared range. These measurements are performed for temperature and pressure of atmospheric relevance for DIAL applications (Differential Absorption Lidar). This study, financed by the European Space Agency (ESA), goes with the WALES mission (Water Vapour Lidar Experiment in Space). The experimental setup was conceived in order to control pressure, temperature and relative humidity conditions. A particular attention is done to characterize and describe the spectrometer. Then, measurements of red Oxygen B band are performed to demonstrate the huge performance of Optical Feedback Cavity Enhanced Absorption Spectroscopy (OF-CEAS). The desired optical feedback is obtained by light injection into the high finesse cavity through a glass plate placed inside the cavity and closed to the Brewster angle. We show a measurement dynamical range of 5 orders of magnitude (10{sup -5} to 10{sup -10} /cm) and a sensitivity of 10{sup -10} /cm/{radical} Hz. Also, sampling absorption spectra by the super linear cavity frequency comb allows very precise frequency measurements. This is demonstrated by the determination of Oxygen pressure shifts with an absolute accuracy of around 5 x 10{sup -5} cm{sup -1}/atm. To our knowledge, we provide the highest accuracy ever reported for this parameter. (author)

  6. Absorption Spectra of Gold Nanoparticle Suspensions

    Science.gov (United States)

    Anan'eva, M. V.; Nurmukhametov, D. R.; Zverev, A. S.; Nelyubina, N. V.; Zvekov, A. A.; Russakov, D. M.; Kalenskii, A. V.; Eremenko, A. N.

    2018-02-01

    Three gold nanoparticle suspensions are obtained, and mean radii in distributions - (6.1 ± 0.2), (11.9 ± 0.3), and (17.3 ± 0.7) nm - are determined by the transmission electron microscopy method. The optical absorption spectra of suspensions are obtained and studied. Calculation of spectral dependences of the absorption index of suspensions at values of the gold complex refractive index taken from the literature showed a significant deviation of experimental and calculated data in the region of 450-800 nm. Spectral dependences of the absorption of suspensions are simulated within the framework of the Mie-Drude theory taking into account the interband absorption in the form of an additional term in the imaginary part of the dielectric permittivity of the Gaussian type. It is shown that to quantify the spectral dependences in the region of the plasmon absorption band of nanoparticles, correction of the parameters of the interband absorption is necessary in addition to the increase of the relaxation parameter of the Drude theory. Spectral dependences of the dielectric permittivity of gold in nanodimensional state are refined from the solution of the inverse problem. The results of the present work are important for predicting the special features of operation of photonic devices and optical detonators based on gold nanoparticles.

  7. Optical absorption in disordered monolayer molybdenum disulfide

    Science.gov (United States)

    Ekuma, C. E.; Gunlycke, D.

    2018-05-01

    We explore the combined impact of sulfur vacancies and electronic interactions on the optical properties of monolayer MoS2. First, we present a generalized Anderson-Hubbard Hamiltonian that accounts for both randomly distributed sulfur vacancies and the presence of dielectric screening within the material. Second, we parametrize this energy-dependent Hamiltonian from first-principles calculations based on density functional theory and the Green's function and screened Coulomb (GW) method. Third, we apply a first-principles-based many-body typical medium method to determine the single-particle electronic structure. Fourth, we solve the Bethe-Salpeter equation to obtain the charge susceptibility χ with its imaginary part being related to the absorbance A . Our results show that an increased vacancy concentration leads to decreased absorption both in the band continuum and from exciton states within the band gap. We also observe increased absorption below the band-gap threshold and present an expression, which describes Lifshitz tails, in excellent qualitative agreement with our numerical calculations. This latter increased absorption in the 1.0 -2.5 eV range makes defect engineering of potential interest for solar cell applications.

  8. Absorption heat pumps

    International Nuclear Information System (INIS)

    Formigoni, C.

    1998-01-01

    A brief description of the difference between a compression and an absorption heat pump is made, and the reasons why absorption systems have spread lately are given. Studies and projects recently started in the field of absorption heat pumps, as well as criteria usually followed in project development are described. An outline (performance targets, basic components) of a project on a water/air absorption heat pump, running on natural gas or LPG, is given. The project was developed by the Robur Group as an evolution of a water absorption refrigerator operating with a water/ammonia solution, which has been on the market for a long time and recently innovated. Finally, a list of the main energy and cost advantages deriving from the use of absorption heat pumps is made [it

  9. Structural, electronic structure, and band alignment properties at epitaxial NiO/Al{sub 2}O{sub 3} heterojunction evaluated from synchrotron based X-ray techniques

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S. D., E-mail: devsh@rrcat.gov.in; Das, Arijeet; Ajimsha, R. S.; Upadhyay, Anuj; Kamparath, Rajiv; Mukherjee, C.; Misra, P.; Rai, S. K.; Sinha, A. K.; Ganguli, Tapas [Raja Ramanna Centre for Advanced Technology, Indore, Madhya Pradesh 452013 (India); Nand, Mangla; Jha, S. N. [Bhabha Atomic Research Centre, Mumbai, Maharashtra 400085 (India); Shukla, D. K.; Phase, D. M. [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore, Madhya Pradesh 452017 (India)

    2016-04-28

    The valence band offset value of 2.3 ± 0.2 eV at epitaxial NiO/Al{sub 2}O{sub 3} heterojunction is determined from photoelectron spectroscopy experiments. Pulsed laser deposited thin film of NiO on Al{sub 2}O{sub 3} substrate is epitaxially grown along [111] direction with two domain structures, which are in-plane rotated by 60° with respect to each other. Observation of Pendellosung oscillations around Bragg peak confirms high interfacial and crystalline quality of NiO layer deposited on Al{sub 2}O{sub 3} substrate. Surface related feature in Ni 2p{sub 3/2} core level spectra along with oxygen K-edge soft X-ray absorption spectroscopy results indicates that the initial growth of NiO on Al{sub 2}O{sub 3} substrate is in the form of islands, which merge to form NiO layer for the larger coverage. The value of conduction band offset is also evaluated from the measured values of band gaps of NiO and Al{sub 2}O{sub 3} layers. A type-I band alignment at NiO and Al{sub 2}O{sub 3} heterojunction is also obtained. The determined values of band offsets can be useful in heterojunction based light emitting devices.

  10. Absorption spectra of AA-stacked graphite

    International Nuclear Information System (INIS)

    Chiu, C W; Lee, S H; Chen, S C; Lin, M F; Shyu, F L

    2010-01-01

    AA-stacked graphite shows strong anisotropy in geometric structures and velocity matrix elements. However, the absorption spectra are isotropic for the polarization vector on the graphene plane. The spectra exhibit one prominent plateau at middle energy and one shoulder structure at lower energy. These structures directly reflect the unique geometric and band structures and provide sufficient information for experimental fitting of the intralayer and interlayer atomic interactions. On the other hand, monolayer graphene shows a sharp absorption peak but no shoulder structure; AA-stacked bilayer graphene has two absorption peaks at middle energy and abruptly vanishes at lower energy. Furthermore, the isotropic features are expected to exist in other graphene-related systems. The calculated results and the predicted atomic interactions could be verified by optical measurements.

  11. Tunable electromagnetically induced absorption based on graphene

    Science.gov (United States)

    Cao, Maoyong; Wang, Tongling; Zhang, Huiyun; Zhang, Yuping

    2018-04-01

    In this paper, an electronically induced absorption (EIA) structure based on graphene at the infrared frequency is proposed. A pair of nanorods is coupled to a ring resonator, resulting in electronically induced transparency (EIT), and then, Babinet's principle is applied to transform the EIT structure into an EIA structure. Based on the bright and dark modes of the coupling schemes, the adjustment of the coupling strength between the dark and bright modes can be achieved by changing the asymmetry degree. In addition, the transparency window and the absorption peak can be tuned by changing the Fermi energy of graphene. This graphene-based EIA structure can develop the path in narrow-band filtering and, absorptive switching in the future.

  12. Picosecond transient absorption spectra of aminosalicylates in confirmation of the triple excitation mechanism

    International Nuclear Information System (INIS)

    Gormin, D.

    1989-01-01

    Using picosecond transient absorption studies, it is shown that the twisted intramolecular charge-transfer state (TICT) and the excited intramolecular proton-transfer state (ESIPT or PT) of specific aminosalicylates both contribute to the long-wavelength fluorescence band, F 2 , observed as an unresolved band to the red of the normal fluorescence band, F 1 . The transient absorption band for 2-hydroxy-4-(dimethylamino)benzoic acid methyl ester (PDASE) is shown to be a composite of the two excited-state absorption modes: S n double-prime(TICT) left-arrow S 1 double-prime (TICT) and S n '(PT)left-arrow S 1 '(PT). This corroborates previous steady-state fluorescence studies of the unresolved F 2 band. The assignments are based on comparison with the excited-state absorption spectra of various substituted aminosalicylates in polar and nonpolar solvents

  13. Optical analysis of trapped Gas—Gas in Scattering Media Absorption Spectroscopy

    Science.gov (United States)

    Svanberg, S.

    2010-01-01

    An overview of the new field of Gas in Scattering Media Absorption Spectroscopy (GASMAS) is presented. The technique investigates sharp gas spectral signatures, typically 10000 times sharper than those of the host material, in which the gas is trapped in pores or cavities. The presence of pores causes strong multiple scattering. GASMAS combines narrow-band diode-laser spectroscopy, developed for atmospheric gas monitoring, with diffuse media optical propagation, well-known from biomedical optics. Several applications in materials science, food packaging, pharmaceutics and medicine have been demonstrated. So far molecular oxygen and water vapour have been studied around 760 and 935 nm, respectively. Liquid water, an important constituent in many natural materials, such as tissue, has a low absorption at such wavelengths, and this is also true for haemoglobin, making propagation possible in many natural materials. Polystyrene foam, wood, fruits, food-stuffs, pharmaceutical tablets, and human sinus cavities (frontal, maxillary and mastoideal) have been studied, demonstrating new possibilities for characterization and diagnostics. Transport of gas in porous media (diffusion) can be studied by first subjecting the material to, e.g., pure nitrogen, and then observing the rate at which normal, oxygen-containing air, reinvades the material. The conductance of the passages connecting a sinus with the nasal cavity can be objectively assessed by observing the oxygen gas dynamics when flushing the nose with nitrogen. Drying of materials, when liquid water is replaced by air and water vapour, is another example of dynamic processes which can be studied. The technique has also been extended to remote-sensing applications (LIDAR-GASMAS or Multiple-Scattering LIDAR).

  14. Band parameters of phosphorene

    International Nuclear Information System (INIS)

    Lew Yan Voon, L C; Wang, J; Zhang, Y; Willatzen, M

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene. (paper)

  15. Infrared diffuse interstellar bands

    Science.gov (United States)

    Galazutdinov, G. A.; Lee, Jae-Joon; Han, Inwoo; Lee, Byeong-Cheol; Valyavin, G.; Krełowski, J.

    2017-05-01

    We present high-resolution (R ˜ 45 000) profiles of 14 diffuse interstellar bands in the ˜1.45 to ˜2.45 μm range based on spectra obtained with the Immersion Grating INfrared Spectrograph at the McDonald Observatory. The revised list of diffuse bands with accurately estimated rest wavelengths includes six new features. The diffuse band at 15 268.2 Å demonstrates a very symmetric profile shape and thus can serve as a reference for finding the 'interstellar correction' to the rest wavelength frame in the H range, which suffers from a lack of known atomic/molecular lines.

  16. Band parameters of phosphorene

    DEFF Research Database (Denmark)

    Lew Yan Voon, L. C.; Wang, J.; Zhang, Y.

    2015-01-01

    Phosphorene is a two-dimensional nanomaterial with a direct band-gap at the Brillouin zone center. In this paper, we present a recently derived effective-mass theory of the band structure in the presence of strain and electric field, based upon group theory. Band parameters for this theory...... are computed using a first-principles theory based upon the generalized-gradient approximation to the density-functional theory. These parameters and Hamiltonian will be useful for modeling physical properties of phosphorene....

  17. Solar absorption surface panel

    Science.gov (United States)

    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. Nutrition and magnesium absorption

    NARCIS (Netherlands)

    Brink, E.J.

    1992-01-01

    The influence of various nutrients present in dairy products and soybean-based products on absorption of magnesium has been investigated. The studies demonstrate that soybean protein versus casein lowers apparent magnesium absorption in rats through its phytate component. However, true

  19. Zeeman atomic absorption spectroscopy

    International Nuclear Information System (INIS)

    Loos-Vollebregt, M.T.C. de.

    1980-01-01

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  20. Nature of oxygen donors and radiation defects in oxygen-doped germanium

    International Nuclear Information System (INIS)

    Fukuoka, Noboru; Atobe, Kozo; Honda, Makoto; Matsuda, Koji.

    1991-01-01

    The nature of oxygen donors and radiation defects in oxygen-doped germanium were studied through measurements of the infrared absorption spectrum, deep level transient spectroscopy spectrum and carrier concentration. It is revealed that a new donor is not formed in oxygen-doped germanium. An A-center (interstitial oxygen-vacancy pair) forms a complex with a thermal donor in its annealing stage at 60degC-140degC. The introduction rate of defects by 1.5 MeV electron irradiation was enhanced in thermal-donor-doped samples. (author)

  1. Studies on the oxygen precipitation in highly boron doped silicon; Untersuchungen zur Sauerstoffausscheidung in hoch bordotiertem Silicium

    Energy Technology Data Exchange (ETDEWEB)

    Zschorsch, Markus

    2007-12-14

    The aim of this thesis was the getting of new knowledge on the elucidation of the oxygen precipitation in highly doped silicon. In the study of the early phases of the oxygen precipitation boron-oxygen complexes and their kinetics could be indirectly detected. These arise already during the cooling of the crystal and can be destroyed by subsequent temperature processes. The formation of the here as BO assumed species during the cooling after the silicon crystal fabrication could be numerically reproduced. Furthermore the study of early precipitation phases by means of neutron small angle scattering a maximum of the oxygen precipitation at {rho}=9 m{omega}cm. It could be shown that the decreasing of this at increasing boron concentration can be most probably reduced to boron precipitations. Furthermore it could be shown that after a tempering time of 24 hours at 700 C in silicon with {rho}=9 m{omega}cm platelet-shaped precipitates form. By the study of the precipitate growth could be shown that also in this phase the oxygen precipitation in silicon is strongest with a specific resistance of {rho}=9 m{omega}cm. By means of FTIR spectroscopy a new absorption band at a wave number of 1038 cm{sup -1} was found, which could be assigned to a boron species. By different experiments it is considered as probable that at this species it deals with BI respectively B{sub 2}I complexes.

  2. CSF oligoclonal banding - slideshow

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/presentations/100145.htm CSF oligoclonal banding - series—Normal anatomy To use the ... 5 out of 5 Overview The cerebrospinal fluid (CSF) serves to supply nutrients to the central nervous ...

  3. Decay of superdeformed bands

    International Nuclear Information System (INIS)

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

    1995-01-01

    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 194 Hg. 42 refs., 5 figs

  4. Laparoscopic gastric banding

    Science.gov (United States)

    ... eat by making you feel full after eating small amounts of food. After surgery, your doctor can adjust the band ... You will feel full after eating just a small amount of food. The food in the small upper pouch will ...

  5. Colloid bands in silver chloride induced by reactor irradiation at low temperature

    International Nuclear Information System (INIS)

    Atobe, K.; Okada, M.; Nakagawa, M.

    1978-01-01

    It is well known that no trapped electron center exists stably in irradiated silver chlorides even at low temperatures. On the other hand, irradiation by ultra-violet light at room temperature produces a broad absorption (colloid bands) on the long wavelength side of the fundamental absorption. In this report, it is shown that one of the colloid bands appears in undoped AgCl crystals by reactor irradiation at low temperature (20 K) and the other colloid band by thermal annealing after the irradiation. The relation between the bands, which correspond to two types of colloidal silver, is represented. (author)

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

    Science.gov (United States)

    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.

  7. High-temperature measurements of methane and acetylene using quantum cascade laser absorption near 8μm

    KAUST Repository

    Sajid, M.B.; Javed, Tamour; Farooq, Aamir

    2015-01-01

    The mid-infrared wavelength region near 8 mu m contains absorption bands of several molecules such as water vapor, hydrogen peroxide, nitrous oxide, methane and acetylene. A new laser absorption sensor based on the v(4) band of methane and the v(4

  8. Ferritin associates with marginal band microtubules

    International Nuclear Information System (INIS)

    Infante, Anthony A.; Infante, Dzintra; Chan, M.-C.; How, P.-C.; Kutschera, Waltraud; Linhartova, Irena; Muellner, Ernst W.; Wiche, Gerhard; Propst, Friedrich

    2007-01-01

    We characterized chicken erythrocyte and human platelet ferritin by biochemical studies and immunofluorescence. Erythrocyte ferritin was found to be a homopolymer of H-ferritin subunits, resistant to proteinase K digestion, heat stable, and contained iron. In mature chicken erythrocytes and human platelets, ferritin was localized at the marginal band, a ring-shaped peripheral microtubule bundle, and displayed properties of bona fide microtubule-associated proteins such as tau. Red blood cell ferritin association with the marginal band was confirmed by temperature-induced disassembly-reassembly of microtubules. During erythrocyte differentiation, ferritin co-localized with coalescing microtubules during marginal band formation. In addition, ferritin was found in the nuclei of mature erythrocytes, but was not detectable in those of bone marrow erythrocyte precursors. These results suggest that ferritin has a function in marginal band formation and possibly in protection of the marginal band from damaging effects of reactive oxygen species by sequestering iron in the mature erythrocyte. Moreover, our data suggest that ferritin and syncolin, a previously identified erythrocyte microtubule-associated protein, are identical. Nuclear ferritin might contribute to transcriptional silencing or, alternatively, constitute a ferritin reservoir

  9. Gallic Acid as an Oxygen Scavenger in Bio-Based Multilayer Packaging Films.

    Science.gov (United States)

    Pant, Astrid F; Sängerlaub, Sven; Müller, Kajetan

    2017-05-03

    Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O₂/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (a w > 0.86).

  10. Absorption coefficients of silicon: A theoretical treatment

    Science.gov (United States)

    Tsai, Chin-Yi

    2018-05-01

    A theoretical model with explicit formulas for calculating the optical absorption and gain coefficients of silicon is presented. It incorporates direct and indirect interband transitions and considers the effects of occupied/unoccupied carrier states. The indirect interband transition is calculated from the second-order time-independent perturbation theory of quantum mechanics by incorporating all eight possible routes of absorption or emission of photons and phonons. Absorption coefficients of silicon are calculated from these formulas. The agreements and discrepancies among the calculated results, the Rajkanan-Singh-Shewchun (RSS) formula, and Green's data are investigated and discussed. For example, the RSS formula tends to overestimate the contributions of indirect transitions for cases with high photon energy. The results show that the state occupied/unoccupied effect is almost negligible for silicon absorption coefficients up to the onset of the optical gain condition where the energy separation of Quasi-Femi levels between electrons and holes is larger than the band-gap energy. The usefulness of using the physics-based formulas, rather than semi-empirical fitting ones, for absorption coefficients in theoretical studies of photovoltaic devices is also discussed.

  11. Optical absorption in recycled waste plastic polyethylene

    Science.gov (United States)

    Aji, M. P.; Rahmawati, I.; Priyanto, A.; Karunawan, J.; Wati, A. L.; Aryani, N. P.; Susanto; Wibowo, E.; Sulhadi

    2018-03-01

    We investigated the optical properties of UV spectrum absorption in recycled waste plastic from polyethylene polymer type. Waste plastic polyethylene showed an optical spectrum absorption after it’s recycling process. Spectrum absorption is determined using spectrophotometer UV-Nir Ocean Optics type USB 4000. Recycling method has been processed using heating treatment around the melting point temperature of the polyethylene polymer that are 200°C, 220°C, 240°C, 260°C, and 280°C. In addition, the recycling process was carried out with time variations as well, which are 1h, 1.5h, 2h, and 2.5h. The result of this experiment shows that recycled waste plastic polyethylene has a spectrum absorption in the ∼ 340-550 nm wavelength range. The absorbance spectrum obtained from UV light which is absorbed in the orbital n → π* and the orbital π → π*. This process indicates the existence of electron transition phenomena. This mechanism is affected by the temperature and the heating time where the intensity of absorption increases and widens with the increase of temperature and heating time. Furthermore this study resulted that the higher temperature affected the enhancement of the band gap energy of waste plastic polyethylene. These results show that recycled waste plastic polyethylene has a huge potential to be absorber materials for solar cell.

  12. Study of defects created in silicon during thermal annealings - Correlation with the presence of oxygen

    International Nuclear Information System (INIS)

    Olivier, Michel

    1975-01-01

    Defects generation and precipitation phenomena in Czochralski silicon crystals annealed ten of hours at 1000 C have been observed. The defects (perfect dislocation loops emitted by semi-coherent precipitates, Frank loops in correlation with coherent precipitates) are studied by Transmission Electron Microscopy, X-Ray Topography and chemical etching. The generation of defects is connected to the precipitation of interstitial oxygen as it is shown by studying the infrared absorption at 9 μm. We present a lot of experimental results which indicates that the precipitates are SiO 2 clusters; in particular, we show that this hypothesis can explain the presence, after annealing, of an infrared absorption band at 8,2 μm. Some results on Czochralski silicon crystals annealed at 1150 deg. C and 1250 deg. C are then presented. In particular, X-Ray Topography studies show the presence of large (∼100 μm) Frank loops which seem connected to oxygen precipitation. (author) [fr

  13. Quasar Absorption Studies

    Science.gov (United States)

    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.

  14. A Comprehensive X-Ray Absorption Model for Atomic Oxygen

    NARCIS (Netherlands)

    Gorzyca, T.W.; Bautista, M.A.; Hasoglu, M.F.; García, J.; Gatuzz, E.; Kaastra, J.S.; Kallman, T.R.; Manson, S.T.; Mendoza, C.; Raassen, A.J.J.; de Vries, C.P.; Zatsarinny, O.

    2013-01-01

    An analytical formula is developed to accurately represent the photoabsorption cross section of O I for all energies of interest in X-ray spectral modeling. In the vicinity of the K edge, a Rydberg series expression is used to fit R-matrix results, including important orbital relaxation effects,

  15. Oxygenated hemoglobin diffuse reflectance ratio for in vitro detection of human gastric pre-cancer

    Science.gov (United States)

    Li, L. Q.; Wei, H. J.; Guo, Z. Y.; Yang, H. Q.; Wu, G. Y.; Xie, S. S.; Zhong, H. Q.; Li, X. Y.; Zhao, Q. L.; Guo, X.

    2010-07-01

    Oxygenated hemoglobin diffuse reflectance (DR) ratio (R540/R575) method based on DR spectral signatures is used for early diagnosis of malignant lesions of human gastric epithelial tissues in vitro. The DR spectra for four different kinds of gastric epithelial tissues were measured using a spectrometer with an integrating sphere detector in the spectral range from 400 to 650 nm. The results of measurement showed that the average DR spectral intensity for the epithelial tissues of normal stomach is higher than that for the epithelial tissues of chronic and malignant stomach and that for the epithelial tissues of chronic gastric ulcer is higher than that for the epithelial tissues of malignant stomach. The average DR spectra for four different kinds of gastric epithelial tissues show dips at 542 and 577 nm owing to absorption from oxygenated Hemoglobin (HbO2). The differences in the mean R540/R575 ratios of HbO2 bands are 6.84% between the epithelial tissues of normal stomach and chronic gastric ulcer, 14.7% between the epithelial tissues of normal stomach and poorly differentiated gastric adenocarcinoma and 22.6% between the epithelial tissues of normal stomach and undifferentiated gastric adenocarcinoma. It is evident from results that there were significant differences in the mean R540/R575 ratios of HbO2 bands for four different kinds of gastric epithelial tissues in vitro ( P < 0.01).

  16. Uranium absorption study pile

    International Nuclear Information System (INIS)

    Raievski, V.; Sautiez, B.

    1959-01-01

    The report describes a pile designed to measure the absorption of fuel slugs. The pile is of graphite and comprises a central section composed of uranium rods in a regular lattice. RaBe sources and BF 3 counters are situated on either side of the center. A given uranium charge is compared with a specimen charge of about 560 kg, and the difference in absorption between the two noted. The sensitivity of the equipment will detect absorption variations of about a few ppm boron (10 -6 boron per gr. of uranium) or better. (author) [fr

  17. Total photon absorption

    International Nuclear Information System (INIS)

    Carlos, P.

    1985-06-01

    The present discussion is limited to a presentation of the most recent total photonuclear absorption experiments performed with real photons at intermediate energy, and more precisely in the region of nucleon resonances. The main sources of real photons are briefly reviewed and the experimental procedures used for total photonuclear absorption cross section measurements. The main results obtained below 140 MeV photon energy as well as above 2 GeV are recalled. The experimental study of total photonuclear absorption in the nuclear resonance region (140 MeV< E<2 GeV) is still at its beginning and some results are presented

  18. Band-engineering of TiO2 as a wide-band gap semiconductor using organic chromophore dyes

    Science.gov (United States)

    Wahyuningsih, S.; Kartini, I.; Ramelan, A. H.; Saputri, L. N. M. Z.; Munawaroh, H.

    2017-07-01

    Bond-engineering as applied to semiconductor materials refers to the manipulation of the energy bands in order to control charge transfer processes in a device. When the device in question is a photoelectrochemical cell, the charges affected by drift become the focus of the study. The ideal band gap of semiconductors for enhancement of photocatalyst activity can be lowered to match with visible light absorption and the location of conduction Band (CB) should be raised to meet the reducing capacity. Otherwise, by the addition of the chromofor organic dyes, the wide-band gab can be influences by interacation resulting between TiO2 surface and the dyes. We have done the impruvisation wide-band gap of TiO2 by the addition of organic chromophore dye, and the addition of transition metal dopand. The TiO2 morphology influence the light absorption as well as the surface modification. The organic chromophore dye was syntesized by formation complexes compound of Co(PAR)(SiPA)(PAR)= 4-(2-piridylazoresorcinol), SiPA = Silyl propil amine). The result showed that the chromophore groups adsorbed onto TiO2 surface can increase the visible light absorption of wide-band gab semiconductor. Initial absorption of a chromophore will affect light penetration into the material surfaces. The use of photonic material as a solar cell shows this phenomenon clearly from the IPCE (incident photon to current conversion efficiency) measurement data. Organic chromophore dyes of Co(PAR)(SiPA) exhibited the long wavelength absorption character compared to the N719 dye (from Dyesol).

  19. Absorption of ultraviolet radiation by antarctic phytoplankton

    Energy Technology Data Exchange (ETDEWEB)

    Vernet, M.; Mitchell, B.G. (Univ. of California-San Diego, La Jolla (United States))

    1990-01-09

    Antarctic phytoplankton contain UV-absorbing compounds that may block damaging radiation. Compounds that absorb from 320-340 nm were observed in spectral absorption of both particulates and in methanol extracts of the particulates. The decrease in the total concentration of these UV compounds with respect to chlorophyll a, as measured by the ratio of in vitro absorption at 335 nm to absorption at 665 nm is variable and decreases with depth. We observed up to 5-fold decrease in this ratio for samples within the physically mixes surface layer. The absorption of UV radiation in methanol extracts, which peaks from 320 to 340 nm, may be composed of several compounds. Shifts in peak absorption with depth (for example, from 331 nm at surface to 321 nm at 75 m), may be interpreted as a change in composition. Ratios of protective yellow xanthophylls (diadinoxanthin + diatoxanthin) to photosynthetic fucoxanthin-like pigments have highest values in surface waters. As these pigments also absorb in the near UV, their function might extend to protection as well as utilization of UV radiation for photosynthesis. We document strong absorption in the UV from 320-330 nm for Antarctic marine particulates. Below this region of the solar energy spectrum, absolute energy levels of incident radiation drop off dramatically. Only wavelengths shorter than about 320 nm will be significantly enhanced due to ozone depletion. If the absorption we observed serves a protective role for phytoplankton photosynthesis, it appears the peak band is in the region where solar energy increases rapidly, and not in the region where depletion would cause significant variations in absolute flux.

  20. The effect of gold nanoparticles on exchange processes in collision complexes of triplet and singlet oxygen molecules with excited eosin molecules

    Science.gov (United States)

    Bryukhanov, V. V.; Minaev, B. M.; Tsibul'nikova, A. V.; Slezhkin, V. A.

    2015-07-01

    We have studied exchange processes in contact complexes of triplet eosin molecules with oxygen molecules in the triplet (3Σ{/g -}) and singlet (1Δ g ) states in thin polyvinylbutyral films in the presence of gold nanoparticles. Upon resonant excitation of surface plasmons in gold nanoparticles into the absorption band of eosin molecules-singlet oxygen sensitizers-we have obtained an increase in the intensity of the delayed fluorescence and an increase in the lifetime of the dye with simultaneous quenching of the luminescence of singlet oxygen. The kinetics of the delayed fluorescence of the dye as a result of singlet-triplet annihilation of triplet eosin molecules with singlet oxygen molecules has been investigated. To compare theoretical and experimental data, we have numerically simulated energy transfer processes. Rate constants of energy transfer and of singlet-triplet annihilation, as well as quenching constants of triplet states of the dye by molecular oxygen, have been calculated. Luminescence quantum yield 1Δ g of polyvinylbutyral has been estimated. We have analyzed quantum-chemically electronic mechanisms of singlet-triplet annihilation of oxygen and eosin.

  1. Anomalous electromagnetically induced transparency in photonic-band-gap materials

    International Nuclear Information System (INIS)

    Singh, Mahi R.

    2004-01-01

    The phenomenon of electromagnetically induced transparency has been studied when a four-level atom is located in a photonic band gap material. Quantum interference is introduced by driving the two upper levels of the atom with a strong pump laser field. The top level and one of the ground levels are coupled by a weak probe laser field and absorption takes place between these two states. The susceptibility due to the absorption for this transition has been calculated by using the master equation method in linear response theory. Numerical simulations are performed for the real and imaginary parts of the susceptibility for a photonic band gap material whose gap-midgap ratio is 21%. It is found that when resonance frequencies lie within the band, the medium becomes transparent under the action of the strong pump laser field. More interesting results are found when one of the resonance frequencies lies at the band edge and within the band gap. When the resonance frequency lies at the band edge, the medium becomes nontransparent even under a strong pump laser field. On the other hand, when the resonance frequency lies within the band gap, the medium becomes transparent even under a weak pump laser field. In summary, we found that the medium can be transformed from the transparent state to the nontransparent state just by changing the location of the resonance frequency. We call these two effects anomalous electromagnetically induced transparency

  2. Dual-band absorber for multispectral plasmon-enhanced infrared photodetection

    International Nuclear Information System (INIS)

    Yu, Peng; Ashalley, Eric; Wang, Zhiming; Wu, Jiang; Govorov, Alexander

    2016-01-01

    For most of the reported metamaterial absorbers, the peak absorption only occurs at one single wavelength. Here, we investigated a dual-band absorber which is based on simple gold nano-rings. Two absorption peaks can be readily achieved in 3–5 µ m and 8–14 µ m via tuning the width and radius of gold nano-rings and dielectric constant. The average maximum absorption of two bands can be as high as 95.1% (−0.22 dB). Based on the simulation results, the perfect absorber with nano-rings demonstrates great flexibility to create dual-band or triple-band absorption, and thus holds potential for further applications in thermophotovoltaics, multicolor infrared focal plane arrays, optical filters, and biological sensing applications. (paper)

  3. Picosecond absorption relaxation measured with nanosecond laser photoacoustics

    OpenAIRE

    Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin; Wang, Lihong V.

    2010-01-01

    Picosecond absorption relaxation—central to many disciplines—is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, b...

  4. Conduction band-edge d-states in high-k dielectrics due to Jahn-Teller term splittings

    International Nuclear Information System (INIS)

    Lucovsky, G.; Fulton, C.C.; Zhang, Y.; Luning, J.; Edge, L.; Whitten, J.L.; Nemanich, R.J.; Schlom, D.G.; Afanase'v, V.V.

    2005-01-01

    X-ray absorption spectroscopy (XAS) is used to study conduction band edge electronic structure of high-k transition metal (TM) and trivalent lanthanide series rare earth (RE) oxide dielectrics. Empty TM/RE d-states are studied by intra-atomic transitions originating in core level spin-orbit split p-states, and conduction band states are studied in inter-atomic transitions which originate in the oxygen atom 1s core level state. In non-crystalline Zr and Hf silicate alloys, the local bonding symmetry, or crystal field splits these d-states into doubly and triply degenerate features. In nano-crystalline oxides, there are additional d-state splittings due to contributions of more distant neighbors that completely remove d-state degeneracies via the Jahn-Teller effect mechanism. This gives rise to highly localized band edge states that are electronically active in photoconductivity, internal photoemission, and act as bulk traps in metal oxide semiconductor (MOS) devices

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

    International Nuclear Information System (INIS)

    White, W.T. III.

    1985-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  7. Absorption heat pump system

    Science.gov (United States)

    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.

  8. Zeeman atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Hadeishi, T.; McLaughlin, R.

    1978-08-01

    The design and development of a Zeeman atomic absorption spectrometer for trace element analysis are described. An instruction manual is included which details the operation, adjustment, and maintenance. Specifications and circuit diagrams are given

  9. The 14 mu m band of carbon stars

    NARCIS (Netherlands)

    Yamamura, [No Value; de Jong, T; Waters, LBFM; Cami, J; Justtanont, K; LeBertre, T; Lebre, A; Waelkens, C

    1999-01-01

    We have studied the absorption bands around 14 mum in the spectra of 11 carbon stars with mass-loss rates ranging from 10(-8) to 10(-4) M-circle dot yr(-1), based on data obtained with the Short Wavelength Spectrometer (SWS) on board the Infrared Space Observatory (ISO). All stars clearly show a

  10. Effect of conduction band nonparabolicity on the optical properties in ...

    Indian Academy of Sciences (India)

    the bulk conduction band edge, the correction due to nonparabolicity can be important. [9,10]. In a narrow QW under a strong magnetic field, the optical absorption coefficients calculated with the nonparabolicity correction shows remarkable deviation from results obtained using parabolic energy approximation [11].

  11. Revisiting Absorptive Capacity

    DEFF Research Database (Denmark)

    de Araújo, Ana Luiza Lara; Ulhøi, John Parm; Lettl, Christopher

    Absorptive capacity has mostly been perceived as a 'passive' outcome of R&D investments. Recently, however, a growing interest into its 'proactive' potentials has emerged. This paper taps into this development and proposes a dynamic model for conceptualizing the determinants of the complementary...... learning processes of absorptive capacity, which comprise combinative and adaptive capabilities. Drawing on survey data (n=169), the study concludes that combinative capabilities primarily enhance transformative and exploratory learning processes, while adaptive capabilities strengthen all three learning...

  12. Comment on resonant absorption

    International Nuclear Information System (INIS)

    Hammerling, P.

    1977-01-01

    An average over angles of incidence of the usual resonant absorption function is presented. This form is appropriate under experimental conditions where the angles of incidence vary greatly and in an unknown manner. For comparison a lens-ellipsoidal mirror illumination system with a known longitudinal aberration is considered. In the latter example the angles of incidence are readily obtained and the resulting resonance absorption function evaluated. The associated fields are calculated in a similar fashion. (author)

  13. Optical absorption measurement system

    International Nuclear Information System (INIS)

    Draggoo, V.G.; Morton, R.G.; Sawicki, R.H.; Bissinger, H.D.

    1989-01-01

    This patent describes 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

  14. Absolute linestrengths in the H2O2 nu6 band

    Science.gov (United States)

    May, Randy D.

    1991-01-01

    Absolute linestrengths at 295 K have been measured for selected lines in the nu6 band of H2O2 using a tunable diode-laser spectrometer. H2O2 concentrations in a flowing gas mixture were determined by ultraviolet (uv) absorption at 254 nm using a collinear infrared (ir) and uv optical arrangement. The measured linestrengths are approx. 60 percent larger than previously reported values when absorption by hot bands in H2O2 is taken into account.

  15. Carbon dots decorated vertical SnS{sub 2} nanosheets for efficient photocatalytic oxygen evolution

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Zhongzhou [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190 (China); Wang, Fengmei; Shifa, Tofik Ahmed; Liu, Kaili; Huang, Yun; Jiang, Chao; He, Jun, E-mail: hej@nanoctr.cn [CAS Key Laboratory of Nanosystem and Hierarchical Fabrication, National Center for Nanoscience and Technology, Beijing 100190 (China); CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing 100190 (China); Liu, Quanlin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)

    2016-08-01

    Metal sulfides are highly desirable materials for photocatalytic water splitting because of their appropriate energy bands. However, the poor stability under light illumination in water hinders their wide applications. Here, two-dimensional SnS{sub 2} nanosheets, along with carbon dots of the size around 10 nm, are uniformly grown on fluorine doped tin oxide glasses with a layer of nickel nanoparticles. Significantly, strong light absorption and enhanced photocurrent density are achieved after integration of SnS{sub 2} nanosheets with carbon dots. Notably, the rate of oxygen evolution reached up to 1.1 mmol g{sup −1} h{sup −1} under simulated sunlight irradiation featuring a good stability.

  16. Carbon dots decorated vertical SnS_2 nanosheets for efficient photocatalytic oxygen evolution

    International Nuclear Information System (INIS)

    Cheng, Zhongzhou; Wang, Fengmei; Shifa, Tofik Ahmed; Liu, Kaili; Huang, Yun; Jiang, Chao; He, Jun; Liu, Quanlin

    2016-01-01

    Metal sulfides are highly desirable materials for photocatalytic water splitting because of their appropriate energy bands. However, the poor stability under light illumination in water hinders their wide applications. Here, two-dimensional SnS_2 nanosheets, along with carbon dots of the size around 10 nm, are uniformly grown on fluorine doped tin oxide glasses with a layer of nickel nanoparticles. Significantly, strong light absorption and enhanced photocurrent density are achieved after integration of SnS_2 nanosheets with carbon dots. Notably, the rate of oxygen evolution reached up to 1.1 mmol g"−"1 h"−"1 under simulated sunlight irradiation featuring a good stability.

  17. Ultra wide band antennas

    CERN Document Server

    Begaud, Xavier

    2013-01-01

    Ultra Wide Band Technology (UWB) has reached a level of maturity that allows us to offer wireless links with either high or low data rates. These wireless links are frequently associated with a location capability for which ultimate accuracy varies with the inverse of the frequency bandwidth. Using time or frequency domain waveforms, they are currently the subject of international standards facilitating their commercial implementation. Drawing up a complete state of the art, Ultra Wide Band Antennas is aimed at students, engineers and researchers and presents a summary of internationally recog

  18. Correlation of Photocatalytic Activity with Band Structure of Low-dimensional Semiconductor Nanostructures

    Science.gov (United States)

    Meng, Fanke

    Photocatalytic hydrogen generation by water splitting is a promising technique to produce clean and renewable solar fuel. The development of effective semiconductor photocatalysts to obtain efficient photocatalytic activity is the key objective. However, two critical reasons prevent wide applications of semiconductor photocatalysts: low light usage efficiency and high rates of charge recombination. In this dissertation, several low-dimensional semiconductors were synthesized with hydrothermal, hydrolysis, and chemical impregnation methods. The band structures of the low-dimensional semiconductor materials were engineered to overcome the above mentioned two shortcomings. In addition, the correlation between the photocatalytic activity of the low-dimensional semiconductor materials and their band structures were studied. First, we studied the effect of oxygen vacancies on the photocatalytic activity of one-dimensional anatase TiO2 nanobelts. Given that the oxygen vacancy plays a significant role in band structure and photocatalytic performance of semiconductors, oxygen vacancies were introduced into the anatase TiO2 nanobelts during reduction in H2 at high temperature. The oxygen vacancies of the TiO2 nanobelts boosted visible-light-responsive photocatalytic activity but weakened ultraviolet-light-responsive photocatalytic activity. As oxygen vacancies are commonly introduced by dopants, these results give insight into why doping is not always beneficial to the overall photocatalytic performance despite increases in absorption. Second, we improved the photocatalytic performance of two-dimensional lanthanum titanate (La2Ti2 O7) nanosheets, which are widely studied as an efficient photocatalyst due to the unique layered crystal structure. Nitrogen was doped into the La2Ti2O7 nanosheets and then Pt nanoparticles were loaded onto the La2Ti2O7 nanosheets. Doping nitrogen narrowed the band gap of the La2Ti 2O7 nanosheets by introducing a continuum of states by the valence

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

    International Nuclear Information System (INIS)

    Li, L. L.; Xu, W.

    2014-01-01

    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

  20. Optical and X-ray absorption spectroscopy in lead doped lithium fluoride crystals

    Energy Technology Data Exchange (ETDEWEB)

    Somma, F; Aloe, P; D' Acapito, F; Montereali, R M; Polosan, S; Secu, M; Vincenti, M A, E-mail: somma@fis.uniroma3.it

    2010-11-15

    LiF:Pb doped crystals were successfully grown by Kyropoulos method, starting with drying powders. The presence of Pb{sup 2+} ions in the LiF crystals were evidenced by the absorption band at 278 nm and by 375 nm photoluminescence. The presence of some other Pb structures with oxygen compounds in the as made samples was evidenced, decreasing after some annealing procedures. The local environment and valence state of Pb in LiF were studied by X-ray Absorption Spectroscopy at the Pb L{sub III} and L{sub I} edges. XANES data reveal that Pb is present as Pb{sup 2+} whereas EXAFS data show that it is incorporated in the crystal and not forming PbF{sub 2} precipitates. Identical spectra are obtained for samples as prepared and after thermal annealing up to 650 deg. C demonstrating the stability of the incorporation site. Also the concentration of Pb in the crystal has no effect on the location site of the metal as the same spectrum is obtained for specimens with different dopant concentrations.

  1. The development of efficient two-photon singlet oxygen sensitizers

    DEFF Research Database (Denmark)

    Nielsen, Christian Benedikt

    The development of efficient two-photon singlet oxygen sensitizers is addressed focusing on organic synthesis. Photophysical measurements were carried out on new lipophilic molecules, where two-photon absorption cross sections and singlet oxygen quantumyields were measured. Design principles...... for making efficient two-photon singlet oxygen sensitizers were then constructed from these results. Charge-transfer in the excited state of the prepared molecules was shown to play a pivotal role in the generationof singlet oxygen. This was established through studies of substituent effects on both...... the singlet oxygen yield and the two-photon absorption cross section, where it was revealed that a careful balancing of the amount of charge transfer present in theexcited state of the sensitizer is necessary to obtain both a high singlet oxygen quantum yield and a high two-photon cross section. An increasing...

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

    Science.gov (United States)

    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.

  3. Optical absorption of carbon-gold core-shell nanoparticles

    Science.gov (United States)

    Wang, Zhaolong; Quan, Xiaojun; Zhang, Zhuomin; Cheng, Ping

    2018-01-01

    In order to enhance the solar thermal energy conversion efficiency, we propose to use carbon-gold core-shell nanoparticles dispersed in liquid water. This work demonstrates theoretically that an absorbing carbon (C) core enclosed in a plasmonic gold (Au) nanoshell can enhance the absorption peak while broadening the absorption band; giving rise to a much higher solar absorption than most previously studied core-shell combinations. The exact Mie solution is used to evaluate the absorption efficiency factor of spherical nanoparticles in the wavelength region from 300 nm to 1100 nm as well as the electric field and power dissipation profiles inside the nanoparticles at specified wavelengths (mostly at the localized surface plasmon resonance wavelength). The field enhancement by the localized plasmons at the gold surfaces boosts the absorption of the carbon particle, resulting in a redshift of the absorption peak with increased peak height and bandwidth. In addition to spherical nanoparticles, we use the finite-difference time-domain method to calculate the absorption of cubic core-shell nanoparticles. Even stronger enhancement can be achieved with cubic C-Au core-shell structures due to the localized plasmonic resonances at the sharp edges of the Au shell. The solar absorption efficiency factor can exceed 1.5 in the spherical case and reach 2.3 in the cubic case with a shell thickness of 10 nm. Such broadband absorption enhancement is in great demand for solar thermal applications including steam generation.

  4. Spin transport in oxygen adsorbed graphene nanoribbon

    Science.gov (United States)

    Kumar, Vipin

    2018-04-01

    The spin transport properties of pristine graphene nanoribbons (GNRs) have been most widely studied using theoretical and experimental tools. The possibilities of oxidation of fabricated graphene based nano electronic devices may change the device characteristics, which motivates to further explore the properties of graphene oxide nanoribbons (GONRs). Therefore, we present a systematic computational study on the spin polarized transport in surface oxidized GNR in antiferromagnetic (AFM) spin configuration using density functional theory combined with non-equilibrium Green's function (NEGF) method. It is found that the conductance in oxidized GNRs is significantly suppressed in the valance band and the conduction band. A further reduction in the conductance profile is seen in presence of two oxygen atoms on the ribbon plane. This change in the conductance may be attributed to change in the surface topology of the ribbon basal plane due to presence of the oxygen adatoms, where the charge transfer take place between the ribbon basal plane and the oxygen atoms.

  5. Irradiation induced defects containing oxygen atoms in germanium crystal as studied by deep level transient spectroscopy

    International Nuclear Information System (INIS)

    Fukuoka, Noboru; Kambe, Yoshiyuki; Saito, Haruo; Matsuda, Koji.

    1984-05-01

    Deep level transient spectroscopy was applied to the electron trapping levels which are associated with the irradiation induced lattice defects in germanium crystals. The germanium crystals used in the study were doped with oxygen, antimony or arsenic and the defects were formed by electron irradiation of 1.5MeV or 10MeV. The nature of so called ''thermal defect'' formed by heat treatment at about 670K was also studied. The trapping levels at Esub(c)-0.13eV, Esub(c)-0.25eV and Esub(c)-0.29eV were found to be associated with defects containing oxygen atoms. From the experimental results the Esub(c)-0.25eV level was attributed to the germanium A-center (interstitial oxygen atom-vacancy pair). Another defect associated with the 715cm -1 infrared absorption band was found to have a trapping level at the same position at Esub(c)-0.25eV. The Esub(c)-0.23eV and Esub(c)-0.1eV levels were revealed to be associated with thermal donors formed by heat treatment at about 670K. Additional two peaks (levels) were observed in the DLTS spectrum. The annealing behavior of the levels suggests that the thermal donors originate from not a single type but several types of defects. (author)

  6. Temperature dependence of absorption spectra of P-type GaP

    International Nuclear Information System (INIS)

    Mounir, M.; Balloomal, L.S.

    1985-10-01

    The theoretical analysis of the optical absorption due to band-impurity (impurity-band) electron transitions involving deep impurity levels in semi-conductors is considered. Also the data of the experimental absorption spectra of GaP were performed at room temperature and the results were found to be in agreement with the theoretical results if the electron-phonon interaction is taken into consideration. (author)

  7. Microwave absorption studies of MgB2 superconductor

    Indian Academy of Sciences (India)

    band (9–. 10 GHz) spectrometer. Both polycrystalline pellet and single-grain MgB2, having nearly the same Tc (∼ 39 K) and same size (3×2×1 mm3), were used in the present investigations. Low field modulated microwave absorption signals ...

  8. Optical absorption of copper met-myoglobin complexes

    International Nuclear Information System (INIS)

    Lamy, M.T.; Ribeiro, P.C.; Nascimento, O.R.; Bemski, G.

    1976-01-01

    It is reported on the use of a known denaturing agent, namely Cu 2+ ions, to induce a gradual change in the optical spectrum of Mb solutions, in order to identify the absorption bands that undergo similar changes which may be attributed to the transitions between correlated energy levels [pt

  9. Protonation Reaction of Benzonitrile Radical Anion and Absorption of Product

    DEFF Research Database (Denmark)

    Holcman, Jerzy; Sehested, Knud

    1975-01-01

    The rate constant for the protonation of benzonitrile radical anions formed in pulse radiolysis of aqueous benzonitrile solutions is (3.5 ± 0.5)× 1010 dm3 mol–1 s–1. A new 270 nm absorption band is attributed to the protonated benzonitrile anion. The pK of the protonation reaction is determined t...

  10. Band-notched spiral antenna

    Science.gov (United States)

    Jeon, Jae; Chang, John

    2018-03-13

    A band-notched spiral antenna having one or more spiral arms extending from a radially inner end to a radially outer end for transmitting or receiving electromagnetic radiation over a frequency range, and one or more resonance structures positioned adjacent one or more segments of the spiral arm associated with a notch frequency band or bands of the frequency range so as to resonate and suppress the transmission or reception of electromagnetic radiation over said notch frequency band or bands.

  11. Vitamin A absorption

    International Nuclear Information System (INIS)

    Baker, S.J.

    1976-01-01

    Investigation of the absorption of vitamin A and related substances is complicated by the multiplicity of forms in which they occur in the diet and by the possibility that they may be subject to different mechanisms of absorption. Present knowledge of these mechanisms is inadequate, especially in the case of carotenoids. Numerous tests of absorption have been developed. The most common has been the biochemical measurement of the rise in plasma vitamin A after an oral dose of retinol or retinyl ester, but standardization is inadequate. Radioisotope tests based upon assay of serum or faecal activity following oral administration of tritiated vitamin A derivaties hold considerable promise, but again standardization is inadequate. From investigations hitherto performed it is known that absorption of vitamin A is influenced by several diseases, although as yet the consistency of results and the correlation with other tests of intestinal function have often been poor. However, the test of vitamin A absorption is nevertheless of clinical importance as a specialized measure of intestinal function. (author)

  12. Ultraviolet absorption detection of DNA in gels

    International Nuclear Information System (INIS)

    Mahon, A.R.

    1998-01-01

    A method and apparatus for the detection and quantification of large fragments of unlabelled deoxyribonucleic acid (DNA) in agarose gels is presented. The technique is based on ultra-violet (UV) absorption by nucleotides. A deuterium lamp was used to illuminate regions of an electrophoresis gel. As DNA bands passed through the illuminated region of the gel the amount of UV light transmitted was reduced due to DNA absorption. Two detection systems were investigated. In the first system, synthetic chemical vapour deposition (CVD) diamond strip detectors were used to locate regions of DNA in the gels by detecting the transmitted light. CVD diamond has a high indirect band gap of 5.45 eV and is therefore sensitive to UV photons of wavelengths < 224 nm. A number of CVD diamond samples were characterised to investigate their suitability as detectors for this application. The detectors' quantum efficiency, UV response and time response were measured. DNA bands containing as little as 20 ng were detected by the diamond. In a second system, a deuterium lamp was used to illuminate individual sample lanes of an electrophoresis gel via an array of optical fibres. During electrophoresis the regions of DNA were detected with illumination at 260 nm, using a UV-sensitive charge coupled device (CCD). As the absorption coefficient of a DNA sample is approximately proportional to its mass, the technique is inherently quantitative. This system had a detection limit of 0.25 ng compared with 2-10 ng for the most popular conventional technique, ethidium bromide (EtBr) staining. Using this detection technique, the DNA sample remains in its native state. The removal of carcinogenic dyes from the detection procedure greatly reduces associated biological hazards. (author)

  13. Partially filled intermediate band of Cr-doped GaN films

    International Nuclear Information System (INIS)

    Sonoda, S.

    2012-01-01

    We investigated the band structure of sputtered Cr-doped GaN (GaCrN) films using optical absorption, photoelectron yield spectroscopy, and charge transport measurements. It was found that an additional energy band is formed in the intrinsic band gap of GaN upon Cr doping, and that charge carriers in the material move in the inserted band. Prototype solar cells showed enhanced short circuit current and open circuit voltage in the n-GaN/GaCrN/p-GaN structure compared to the GaCrN/p-GaN structure, which validates the proposed concept of an intermediate-band solar cell.

  14. Structural disorder and electronic hybridization in NicMg1-cO solid solutions probed by XANES at the oxygen K edge

    International Nuclear Information System (INIS)

    Chen Dongliang; Zhong Jun; Chu Wangsheng; Wu Ziyu; Kuzmin, Alexei; Mironova-Ulmane, Nina; Marcelli, Augusto

    2007-01-01

    A series of Ni c Mg 1-c O solid solutions has been studied for the first time looking at the structural disorder by means of x-ray absorption near-edge-structure (XANES) spectroscopy at the oxygen K edge. The experimental XANES signals were analysed within the full multiple scattering formalism and were interpreted taking into account clusters of up to 15 coordination shells around an absorbing oxygen atom. The substitution of nickel atoms by magnesium atoms results in a dramatic decrease of the empty density of states in the conduction band close to the Fermi level due to an exchange of the 3d(Ni)-2p(O) interaction with 3p(Mg)-2p(O). Besides, a simultaneous small decrease of the 3d(Ni)-2p(O) hybridization is also induced by the lattice expansion, determined by the difference in ionic radii between nickel and magnesium ions

  15. Structural disorder and electronic hybridization in Ni{sub c}Mg{sub 1-c}O solid solutions probed by XANES at the oxygen K edge

    Energy Technology Data Exchange (ETDEWEB)

    Chen Dongliang [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Zhong Jun [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Chu Wangsheng [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Wu Ziyu [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China); Kuzmin, Alexei [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Mironova-Ulmane, Nina [Institute of Solid State Physics, University of Latvia, Kengaraga 8, LV-1063 Riga (Latvia); Marcelli, Augusto [Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare, PO Box 13, 00044 Frascati (Italy)

    2007-09-05

    A series of Ni{sub c}Mg{sub 1-c}O solid solutions has been studied for the first time looking at the structural disorder by means of x-ray absorption near-edge-structure (XANES) spectroscopy at the oxygen K edge. The experimental XANES signals were analysed within the full multiple scattering formalism and were interpreted taking into account clusters of up to 15 coordination shells around an absorbing oxygen atom. The substitution of nickel atoms by magnesium atoms results in a dramatic decrease of the empty density of states in the conduction band close to the Fermi level due to an exchange of the 3d(Ni)-2p(O) interaction with 3p(Mg)-2p(O). Besides, a simultaneous small decrease of the 3d(Ni)-2p(O) hybridization is also induced by the lattice expansion, determined by the difference in ionic radii between nickel and magnesium ions.

  16. Realistic absorption coefficient of ultrathin films

    International Nuclear Information System (INIS)

    Cesaria, M; Caricato, A P; Martino, M

    2012-01-01

    Both a theoretical algorithm and an experimental procedure are discussed of a new route to determine the absorption/scattering properties of thin films deposited on transparent substrates. Notably, the non-measurable contribution of the film–substrate interface is inherently accounted for. While the experimental procedure exploits only measurable spectra combined according to a very simple algorithm, the theoretical derivation does not require numerical handling of the acquired spectra or any assumption on the film homogeneity and substrate thickness. The film absorption response is estimated by subtracting the measured absorption spectrum of the bare substrate from that of the film on the substrate structure but in a non-straightforward way. In fact, an assumption about the absorption profile of the overall structure is introduced and a corrective factor accounting for the relative film-to-substrate thickness. The method is tested on films of a well known material (ITO) as a function of the film structural quality and influence of the film–substrate interface, both deliberately changed by thickness tuning and doping. Results are found fully consistent with information obtained by standard optical analysis and band gap values reported in the literature. Additionally, comparison with a conventional method demonstrates that our route is generally more accurate even if particularly suited for very thin films. (paper)

  17. Realistic absorption coefficient of ultrathin films

    Science.gov (United States)

    Cesaria, M.; Caricato, A. P.; Martino, M.

    2012-10-01

    Both a theoretical algorithm and an experimental procedure are discussed of a new route to determine the absorption/scattering properties of thin films deposited on transparent substrates. Notably, the non-measurable contribution of the film-substrate interface is inherently accounted for. While the experimental procedure exploits only measurable spectra combined according to a very simple algorithm, the theoretical derivation does not require numerical handling of the acquired spectra or any assumption on the film homogeneity and substrate thickness. The film absorption response is estimated by subtracting the measured absorption spectrum of the bare substrate from that of the film on the substrate structure but in a non-straightforward way. In fact, an assumption about the absorption profile of the overall structure is introduced and a corrective factor accounting for the relative film-to-substrate thickness. The method is tested on films of a well known material (ITO) as a function of the film structural quality and influence of the film-substrate interface, both deliberately changed by thickness tuning and doping. Results are found fully consistent with information obtained by standard optical analysis and band gap values reported in the literature. Additionally, comparison with a conventional method demonstrates that our route is generally more accurate even if particularly suited for very thin films.

  18. Band resolution of optical spectra of solvated electrons in water, alcohols, and tetrahydrofuran

    International Nuclear Information System (INIS)

    Jou, F.-Y.; Freeman, G.R.

    1979-01-01

    The optical absorption spectra of solvated electrons in water, alcohols, and tetrahydrofuran are empirically resolved into two Gaussian bands and a continuum tail. The first Gaussian band covers most of the low energy side of the spectrum. The second Gaussian band lies at an energy slightly above that of the absorption maximum of the total spectrum. With the exception of tert-butyl alcohol, in water and alcohols the following were observed: (a) the first Gaussian bands have the same half-width, but the oscillator strength in water is about double that in an alcohol; (b) the second Gaussian bands have similar half-widths and oscillator strengths; (c) the continuum tails have similar half-widths, yet that in water possesses only about one third as much oscillator strength as the one in alcohol. In tert-butyl alcohol and tetrahydrofuran the first Gaussian band and the continuum tail each carry nearly half of the total oscillator strength. (author)

  19. Adiabatic pressure dependence of the 2.7 and 1.9 micron water vapor bands

    Science.gov (United States)

    Mathai, C. V.; Walls, W. L.; Broersma, S.

    1977-01-01

    An acoustic excitation technique is used to determine the adiabatic pressure derivative of the spectral absorptance of the 2.7 and 1.9 micron water vapor bands, and the 3.5 micron HCl band. The dependence of this derivative on thermodynamic parameters such as temperature, concentration, and pressure is evaluated. A cross-flow water vapor system is used to measure spectral absorptance. Taking F as the ratio of nonrigid to rotor line strengths, it is found that an F factor correction is needed for the 2.7 micron band. The F factor for the 1.9 micron band is also determined. In the wings of each band a wavelength can be found where the concentration dependence is predominant. Farther out in the wings a local maximum occurs for the temperature derivative. It is suggested that the pressure derivative is significant in the core of the band.

  20. Modification of ink-jet paper by oxygen-plasma treatment

    Energy Technology Data Exchange (ETDEWEB)

    Vesel, A [Jozef Stefan Institute, Jamova 39, Ljubljana 1000 (Slovenia); Mozetic, M [Jozef Stefan Institute, Jamova 39, Ljubljana 1000 (Slovenia); Hladnik, A [Pulp and Paper Institute, Bogisiceva 8, Ljubljana 1001 (Slovenia); Dolenc, J [Pulp and Paper Institute, Bogisiceva 8, Ljubljana 1001 (Slovenia); Zule, J [Pulp and Paper Institute, Bogisiceva 8, Ljubljana 1001 (Slovenia); Milosevic, S [Institute of Physics, Bijenicka 46, Zagreb 10000 (Croatia); Krstulovic, N [Institute of Physics, Bijenicka 46, Zagreb 10000 (Croatia); Klanjsek-Gunde, M [National Institute of Chemistry, Hajdrihova 19, Ljubljana 1000 (Slovenia); Hauptmann, N [National Institute of Chemistry, Hajdrihova 19, Ljubljana 1000 (Slovenia)

    2007-06-21

    A study on oxygen-plasma treatment of ink-jet paper is presented. Paper was exposed to a weakly ionized, highly dissociated oxygen plasma with an electron temperature of 5 eV, a positive-ion density of 8 x 10{sup 15} m{sup -3} and a density of neutral oxygen atoms of 5 x 10{sup 21} m{sup -3}. Optical emission spectroscopy (OES) was applied as a method for detection of the reaction products during the plasma treatment of the paper. OES spectra between 250 and 1000 nm were measured continuously during the plasma treatment. The wettability of the samples before and after the plasma treatment was determined by measuring the contact angle of a water drop. The appearance of the surface-functional groups was determined by using high-resolution x-ray photoelectron spectroscopy (XPS), while changes in the surface morphology were monitored with scanning electron microscopy (SEM). Already after 1 s of the plasma treatment the surface, which was originally hydrophobic, changed to hydrophilic, as indicated by a high absorption rate of a water drop into the paper. The OES showed a rapid increase of the CO and OH bands for the first few seconds of the plasma treatment, followed by a slow decrease during the next 40 s. The intensity of the O atom line showed reversed behaviour. The XPS analyses showed a gradual increase of oxygen-rich functional groups on the surface, while SEM analyses did not show significant modification of the morphology during the first 10 s of the plasma treatment. The results were explained by degradation of the alkyl ketene dimer sizing agent during the first few seconds of the oxygen-plasma treatment.

  1. Modification of ink-jet paper by oxygen-plasma treatment

    International Nuclear Information System (INIS)

    Vesel, A; Mozetic, M; Hladnik, A; Dolenc, J; Zule, J; Milosevic, S; Krstulovic, N; Klanjsek-Gunde, M; Hauptmann, N

    2007-01-01

    A study on oxygen-plasma treatment of ink-jet paper is presented. Paper was exposed to a weakly ionized, highly dissociated oxygen plasma with an electron temperature of 5 eV, a positive-ion density of 8 x 10 15 m -3 and a density of neutral oxygen atoms of 5 x 10 21 m -3 . Optical emission spectroscopy (OES) was applied as a method for detection of the reaction products during the plasma treatment of the paper. OES spectra between 250 and 1000 nm were measured continuously during the plasma treatment. The wettability of the samples before and after the plasma treatment was determined by measuring the contact angle of a water drop. The appearance of the surface-functional groups was determined by using high-resolution x-ray photoelectron spectroscopy (XPS), while changes in the surface morphology were monitored with scanning electron microscopy (SEM). Already after 1 s of the plasma treatment the surface, which was originally hydrophobic, changed to hydrophilic, as indicated by a high absorption rate of a water drop into the paper. The OES showed a rapid increase of the CO and OH bands for the first few seconds of the plasma treatment, followed by a slow decrease during the next 40 s. The intensity of the O atom line showed reversed behaviour. The XPS analyses showed a gradual increase of oxygen-rich functional groups on the surface, while SEM analyses did not show significant modification of the morphology during the first 10 s of the plasma treatment. The results were explained by degradation of the alkyl ketene dimer sizing agent during the first few seconds of the oxygen-plasma treatment

  2. Optical Characterization of Rare Earth-doped Wide Band Gap Semiconductors

    National Research Council Canada - National Science Library

    Hommerich, Uwe

    1999-01-01

    ...+) PL intensity under below gap excitation. Photoluminescence excitation (PLE) studies revealed that oxygen/carbon introduces a broad below gap PLE band, which provides an efficient pathway for E(3+) excitation...

  3. Present status of intermediate band solar cell research

    International Nuclear Information System (INIS)

    Cuadra, L.; Marti, A.; Luque, A.

    2004-01-01

    The intermediate band solar cell is a theoretical concept with the potential for exceeding the performance of conventional single-gap solar cells. This novel photovoltaic converter bases its superior theoretical efficiency over single-gap solar cells by enhancing its photogenerated current, via the two-step absorption of sub-band gap photons, without reducing its output voltage. This is achieved through a material with an electrically isolated and partially filled intermediate band located within a higher forbidden gap. This material is commonly named intermediate band material. This paper centres on summarising the present status of intermediate band solar cell research. A number of attempts, which aim to implement the intermediate band concept, are being followed: the direct engineering of the intermediate band material, its implementation by means of quantum dots and the highly porous material approach. Among other sub-band gap absorbing proposals, there is a renewed interest on the impurity photovoltaic effect, the quantum well solar cells and the particularly promising proposal for the use of up- and down-converters

  4. Electronic band structure in porous silicon studied by photoluminescence and photoluminescence excitation spectroscopy

    International Nuclear Information System (INIS)

    Lee, Ki-Won; Kim, Young-You

    2004-01-01

    In this research, we used photoluminescence (PL) and photoluminescence excitation (PLE) to visualize the electronic band structure in porous silicon (PS). From the combined results of the PLE measurements at various PL emission energies and the PL measurements under excitation at various PLE absorption energies, we infer that three different electronic band structures, originating from different luminescent origins, give rise to the PL spectrum. Through either thermal activation or diffusive transfer, excited carriers are moved to each of the electronic band structures.

  5. The hierarchically organized splitting of chromosome bands into sub-bands analyzed by multicolor banding (MCB).

    Science.gov (United States)

    Lehrer, H; Weise, A; Michel, S; Starke, H; Mrasek, K; Heller, A; Kuechler, A; Claussen, U; Liehr, T

    2004-01-01

    To clarify the nature of chromosome sub-bands in more detail, the multicolor banding (MCB) probe-set for chromosome 5 was hybridized to normal metaphase spreads of GTG band levels at approximately 850, approximately 550, approximately 400 and approximately 300. It could be observed that as the chromosomes became shorter, more of the initial 39 MCB pseudo-colors disappeared, ending with 18 MCB pseudo-colored bands at the approximately 300-band level. The hierarchically organized splitting of bands into sub-bands was analyzed by comparing the disappearance or appearance of pseudo-color bands of the four different band levels. The regions to split first are telomere-near, centromere-near and in 5q23-->q31, followed by 5p15, 5p14, and all GTG dark bands in 5q apart from 5q12 and 5q32 and finalized by sub-band building in 5p15.2, 5q21.2-->q21.3, 5q23.1 and 5q34. The direction of band splitting towards the centromere or the telomere could be assigned to each band separately. Pseudo-colors assigned to GTG-light bands were resistant to band splitting. These observations are in concordance with the recently proposed concept of chromosome region-specific protein swelling. Copyright 2003 S. Karger AG, Basel

  6. Strongly correlated impurity band superconductivity in diamond: X-ray spectroscopic evidence

    Directory of Open Access Journals (Sweden)

    G. Baskaran

    2006-01-01

    Full Text Available In a recent X-ray absorption study in boron doped diamond, Nakamura et al. have seen a well isolated narrow boron impurity band in non-superconducting samples and an additional narrow band at the chemical potential in a superconducting sample. We interpret the beautiful spectra as evidence for upper Hubbard band of a Mott insulating impurity band and an additional metallic 'mid-gap band' of a conducting 'self-doped' Mott insulator. This supports the basic framework of a recent theory of the present author of strongly correlated impurity band superconductivity (impurity band resonating valence bond, IBRVB theory in a template of a wide-gap insulator, with no direct involvement of valence band states.

  7. Nonequilibrium absorption in semiconductors and the dynamical Franz-Keldysh effect

    DEFF Research Database (Denmark)

    Johnsen, Kristinn; Jauho, Antti-Pekka

    1997-01-01

    We theoretically study free electron light absorption for a sample which is placed in a strong, time-dependent uniform electric field. In the case of static fields one observes the Franz-Keldysh effect: finite absorption for photon energies below the band gap. We refer to this phenomenon as the F...

  8. X-ray absorption spectroscopy of PbMoO 4 single crystals

    Indian Academy of Sciences (India)

    X-ray absorption spectra of PbMoO4 (LMO) crystals have been investigated for the first time in literature. The measurements have been carried out at Mo absorption edge at the dispersive EXAFS beamline (BL-8) of INDUS-2 Synchrotron facility at Indore, India. The optics of the beamline was set to obtain a band of 2000 eV ...

  9. and three-dimensional models for analysis of optical absorption in ...

    Indian Academy of Sciences (India)

    Unknown

    The optical energy gaps of WS2 single crystal were determined from the analysis of the absorption spectrum near ... Optical band gap; two- and three-dimensional; optical absorption. 1. ..... ssion, New Delhi, in the form of a research project is.

  10. Tuning the band gap of PbCrO{sub 4} through high-pressure: Evidence of wide-to-narrow semiconductor transitions

    Energy Technology Data Exchange (ETDEWEB)

    Errandonea, D., E-mail: daniel.errandonea@uv.es [Departamento de Física Aplicada-ICMUV, Universitat de València, MALTA ConsoliderTeam, C/Dr. Moliner 50, 46100 Burjassot (Spain); Bandiello, E.; Segura, A. [Departamento de Física Aplicada-ICMUV, Universitat de València, MALTA ConsoliderTeam, C/Dr. Moliner 50, 46100 Burjassot (Spain); Hamlin, J.J.; Maple, M.B. [Department of Physics, University of California, San Diego, La Jolla, CA 92093 (United States); Rodriguez-Hernandez, P.; Muñoz, A. [Departamento de Física Fundamental II, Instituto de Materiales y Nanotecnología, Universidad de La Laguna, MALTA ConsoliderTeam, La Laguna, 38205 Tenerife (Spain)

    2014-02-25

    Highlights: • Electronic and optical properties of PbCrO{sub 4} are studied under compression. • Band-gap collapses are observed and correlated with structural phase transitions. • PbCrO{sub 4} band-gap is reduced from 2.3 to 0.8 eV in a 20 GPa range. • PbCrO{sub 4} is an n-type semiconductor with donor levels associated to Frenkel defects. • A deep-to-shallow donor transformation at HP induces a large resistivity decrease. -- Abstract: The electronic transport properties and optical properties of lead(II) chromate (PbCrO{sub 4}) have been studied at high pressure by means of resistivity, Hall-effect, and optical-absorption measurements. Band-structure first-principle calculations have been also performed. We found that the low-pressure phase is a direct band-gap semiconductor (Eg = 2.3 eV) that shows a high resistivity. At 3.5 GPa, associated to a structural phase transition, a band-gap collapse takes place, becoming Eg = 1.8 eV. At the same pressure the resistivity suddenly decreases due to an increase of the carrier concentration. In the HP phase, PbCrO{sub 4} behaves as an n-type semiconductor, with a donor level probably associated to the formation of oxygen vacancies. At 15 GPa a second phase transition occurs to a phase with Eg = 1.2 eV. In this phase, the resistivity increases as pressure does probably due to the self-compensation of donor levels and the augmentation of the scattering of electrons with ionized impurities. In the three phases the band gap red shifts under compression. At 20 GPa, Eg reaches a value of 0.8 eV, behaving PbCrO{sub 4} as a narrow-gap semiconductor.

  11. Effects of flavour absorption on foods and their packaging materials

    NARCIS (Netherlands)

    Willige, van R.W.G.

    2002-01-01

    Keywords: flavour absorption, scalping, packaging, food matrix, lldpe, ldpe, pp, pc, pet, pen,b-lactoglobulin, casein, pectin, cmc, lactose, saccharose, oil, modelling, storage, oxygen permeability, taste perception,

  12. Near-infrared free carrier absorption in heavily doped silicon

    International Nuclear Information System (INIS)

    Baker-Finch, Simeon C.; McIntosh, Keith R.; Yan, Di; Fong, Kean Chern; Kho, Teng C.

    2014-01-01

    Free carrier absorption in heavily doped silicon can have a significant impact on devices operating in the infrared. In the near infrared, the free carrier absorption process can compete with band to band absorption processes, thereby reducing the number of available photons to optoelectronic devices such as solar cells. In this work, we fabricate 18 heavily doped regions by phosphorus and boron diffusion into planar polished silicon wafers; the simple sample structure facilitates accurate and precise measurement of the free carrier absorptance. We measure and model reflectance and transmittance dispersion to arrive at a parameterisation for the free carrier absorption coefficient that applies in the wavelength range between 1000 and 1500 nm, and the range of dopant densities between ∼10 18 and 3 × 10 20  cm −3 . Our measurements indicate that previously published parameterisations underestimate the free carrier absorptance in phosphorus diffusions. On the other hand, published parameterisations are generally consistent with our measurements and model for boron diffusions. Our new model is the first to be assigned uncertainty and is well-suited to routine device analysis

  13. Molecular absorption spectra of beryllium, cerium, lanthanum, iron, and platinum salts

    International Nuclear Information System (INIS)

    Daidoji, Hidehiro

    1980-01-01

    The absorption spectra of some salts of beryllium, cerium, lanthanum, iron and platinum in air-acetylene flame were measured in the wavelength range from 200 to 400 nm. A Hitachi 207 type atomic absorption spectrophotometer was used. A deuterium lamp, a home-made continuous radiation lamp and some hollow cathode lamps were used as light sources. The new molecular absorption spectra of cerium, lanthanum and platinum and the absorption spectra due to Be(OH) 2 , LaO, PtH, FeO and FeCl in 200-400 nm region were obtained. Emission spectra of CeO, LaO and FeOH were also obtained. These molecular absorption bands were estimated as absorption errors of maximum 15 times to the sensitivity of each elements in atomic absorption spectrometry. In addition, spectral line interferences of iron were observed in atomic absorption spectrometry of Zn, Cd, Ni, Cu and Cr. (author)

  14. Neutron resonance absorption theory

    International Nuclear Information System (INIS)

    Reuss, P.

    1991-11-01

    After some recalls on the physics of neutron resonance absorption during their slowing down, this paper presents the main features of the theoretical developments performed by the french school of reactor physics: the effective reaction rate method so called Livolant-Jeanpierre theory, the generalizations carried out by the author, and the probability table method [fr

  15. Noble gas absorption process

    International Nuclear Information System (INIS)

    Thomas, J.W.

    1975-01-01

    A method of removing a noble gas from air comprising the use of activated carbon filters in stages in which absorption and desorption steps in succession are conducted in order to increase the capacity of the filters is described. (U.S.)

  16. Total photon absorption

    International Nuclear Information System (INIS)

    Carlos, P.

    1985-01-01

    Experimental methods using real photon beams for measurements of total photonuclear absorption cross section σ(Tot : E/sub γ/) are recalled. Most recent σ(Tot : E/sub γ/)results for complex nuclei and in the nucleon resonance region are presented

  17. Chemical Absorption Materials

    DEFF Research Database (Denmark)

    Thomsen, Kaj

    2011-01-01

    Chemical absorption materials that potentially can be used for post combustion carbon dioxide capture are discussed. They fall into five groups, alkanolamines, alkali carbonates, ammonia, amino acid salts, and ionic liquids. The chemistry of the materials is discussed and advantages and drawbacks...

  18. Ligand-based photooxidations of dithiomaltolato complexes of Ru(II) and Zn(II): photolytic CH activation and evidence of singlet oxygen generation and quenching.

    Science.gov (United States)

    Bruner, Britain; Walker, Malin Backlund; Ghimire, Mukunda M; Zhang, Dong; Selke, Matthias; Klausmeyer, Kevin K; Omary, Mohammad A; Farmer, Patrick J

    2014-08-14

    The complex [Ru(bpy)2(ttma)](+) (bpy = 2,2'-bipyridine; ttma = 3-hydroxy-2-methyl-thiopyran-4-thionate, 1, has previously been shown to undergo an unusual C-H activation of the dithiomaltolato ligand upon outer-sphere oxidation. The reaction generated alcohol and aldehyde products 2 and 3 from C-H oxidation of the pendant methyl group. In this report, we demonstrate that the same products are formed upon photolysis of 1 in presence of mild oxidants such as methyl viologen, [Ru(NH3)6](3+) and [Co(NH3)5Cl](2+), which do not oxidize 1 in the dark. This reactivity is engendered only upon excitation into an absorption band attributed to the ttma ligand. Analogous experiments with the homoleptic Zn(ttma)2, 4, also result in reduction of electron acceptors upon excitation of the ttma absorption band. Complexes 1 and 4 exhibit short-lived visible fluorescence and long-lived near-infrared phosphorescence bands. Singlet oxygen is both generated and quenched during aerobic excitation of 1 or 4, but is not involved in the C-H activation process.

  19. Red photoluminescence and band edge shift from ZnO thin films

    International Nuclear Information System (INIS)

    Marotti, Ricardo E.; Badan, Juan A.; Quagliata, Eduardo; Dalchiele, Enrique A.

    2007-01-01

    The red photoluminescence (PL) band (peaked between 610 and 640 nm) from electrochemically deposited ZnO thin films is studied. The absorption coefficient is obtained from diffuse reflectance measurements. The absorption band edge depends on deposition conditions. The PL peak follows the shift of the band edge. A similar correlation appears when cooling down to 20 K. This suggests that PL is due to a transition from an intrinsic shallow state to an intrinsic deep state. Comparing against ZnO samples showing green PL, the shallow nature of the state is confirmed

  20. Thermionic detection of the ionic fragments of continiuum-state pair absorption systems

    International Nuclear Information System (INIS)

    Hotop, R.; Niemax, K.; Richter, J.; Weber, K.H.

    1981-01-01

    Using a thermionic diode we have detected the ionic fragments formed by associative ionization and dissociation after continuum-state pair absorption processes in Cs-Cs and Cs-K systems. Assuming an ionization probability of unity of the excited species and calibrating the pair absorption bands by taking into account the known photoionization cross section of the atoms we found excellent agreement with data from classical absorption measurements. (orig.)

  1. Absorption of hydrogen in vanadium, enhanced by ion bombardment; Ionenbeschussunterstuetzte Absorption des Wasserstoffs in Vanadium

    Energy Technology Data Exchange (ETDEWEB)

    Paulus, H.; Lammers, M. [Inst. fuer Technologie- und Wissenstransfer, Soest (Germany); Mueller, K.H. [Inst. fuer Technologie- und Wissenstransfer, Soest (Germany)]|[Paderborn Univ. (Gesamthochschule), Soest (Germany). Fachbereich 16 - Elektrische Energietechnik; Kiss, G.; Kemeny, Z. [Technical Univ. Budapest (Hungary)

    1998-12-31

    Prior to hydrogen implantation into vanadium, the vanadium specimen usually is exposed to an activation process and is then heated at 1 atm hydrogen to temperatures between 500 and 600 C, subsequently cooled down in several steps. Within this temperature range, hydrogen solubility increases with declining temperature. A decisive factor determining hydrogen absorption is the fact that at temperatures above 250 C, oxygen desorbs from the material surface and thus no longer inhibits hydrogen absorption. Therefore a different approach was chosen for the experiments reported: Hydrogen absorption under UHV conditions at room temperature. After the usual activation process, the vanadium surface was cleaned by 5 keV Ar{sup +} ion bombardment. Thus oxygen absorption at the specimen surface (and new reactions with oxygen from the remaining gas) could be avoided, or removed. By means of thermal desorption mass spectrometry (TDMS), hydrogen absorption as a function of argon ion dose was analysed. TDMS measurements performed for specimens treated by ion bombardment prior to H{sup 2} exposure showed two H{sup 2} desorption peaks, in contrast to the profiles measured with specimens not exposed to ion bombardment. It is assumed that the ion bombardment disturbs the crystal structure so that further sites for hydrogen absorption are produced. (orig./CB) [Deutsch] Bei der Beladung von Vandium mit Wasserstoff wird ueblicherweise die Probe nach einer Aktivierungsprozedur bei 1 atm Wasserstoff auf Temperaturen im Bereich von 500 bis 600 C hochgeheizt und danach schrittweise abgekuehlt. In diesem Temperaturbereich nimmt die Wasserstoffloeslichkeit mit abnehmender Temperatur zu. Entscheidend fuer die Beladung ist aber auch die Tatsache, dass bei Temperaturen groesser 250 C Sauerstoff von der Oberflaeche desorbiert und dadurch die Absorption von Wasserstoff nicht mehr blockieren kann. Im Rahmen der hier beschriebenen Untersuchungen sollte die Wasserstoffbeladung unter UHV-Bedingungen bei

  2. Noise exposure in marching bands

    Science.gov (United States)

    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.

  3. Effect of hydration on the amide I band in the binary solvents dioxane-D2O and dioxane-H2O

    International Nuclear Information System (INIS)

    Kobayashi, M.; Kobayashi, M.

    1980-01-01

    Hydration of amides in aqueous solutions has been studied by measuring the infrared spectra of amides (benzamide, p-methoxybenzamide, and ropionamide) in dioxane-D 2 O and dioxane-H 2 O mixtures. The absorption due to the C=O stretching (or amide I band) exhibited a very remarkable red shift accompanied by a characteristic change of the band shape as the water content in the medium increased. The spectral change is attributed to the change of the hydration state at the carbonyl oxygen. In the aqueous mixtures, amide molecules participate in an equilibrium among various states of hydration. The weighted mean frequency of the ν/sub C = O/ absorption, anti ν/sub C = O/, varied in proportion to the water contained in the medium. The difference between the anti ν/sub C = O/ value in pure water and that in pure dioxane,Δ anti ν, was used as a measure of the maximum degree of hydration. It was larger for propionamide than for the aromatic amides, suggesting that the steric effect of the substituents is of major importance in hydration. The isotope effect, Δ anti ν/sub D 2 O//Δ anti ν/sub H 2 O/, in the range from 1.4 to 1.6 for all cases examined, indicated that stronger hydration of amides occurred with D 2 O than with H 2 O

  4. MERIS albedo climatology for FRESCO+ O2 A-band cloud retrieval

    Directory of Open Access Journals (Sweden)

    Y. Zhou

    2011-03-01

    Full Text Available A new global albedo climatology for Oxygen A-band cloud retrievals is presented. The climatology is based on MEdium Resolution Imaging Spectrometer (MERIS Albedomap data and its favourable impact on the derivation of cloud fraction is demonstrated for the FRESCO+ (Fast Retrieval Scheme for Clouds from the Oxygen A-band algorithm. To date, a relatively coarse resolution (1° × 1° surface reflectance dataset from GOME (Global Ozone Monitoring Experiment Lambert-equivalent reflectivity (LER is used in FRESCO+. The GOME LER climatology does not account for the usually higher spatial resolution of UV/VIS instruments designed for trace gas remote sensing which introduces several artefacts, e.g. in regions with sharp spectral contrasts like coastlines or over bright surface targets. Therefore, MERIS black-sky albedo (BSA data from the period October 2002 to October 2006 were aggregated to a grid of 0.25° × 0.25° for each month of the year and for different spectral channels. In contrary to other available surface reflectivity datasets, MERIS includes channels at 754 nm and 775 nm which are located close to the spectral windows required for O2 A-band cloud retrievals. The MERIS BSA in the near-infrared compares well to Moderate Resolution Imaging Spectroradiometer (MODIS derived BSA with an average difference lower than 1% and a correlation coefficient of 0.98. However, when relating MERIS BSA to GOME LER a distinctly lower correlation (0.80 and enhanced scatter is found. Effective cloud fractions from two exemplary months (January and July 2006 of Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY data were subsequently derived with FRESCO+ and compared to those from the Heidelberg Iterative Cloud Retrieval Utilities (HICRU algorithm. The MERIS climatology generally improves FRESCO+ effective cloud fractions. In particular small cloud fractions are in better agreement with HICRU. This is of importance for atmospheric

  5. Two-photon absorption of a supramolecular pseudoisocyanine J-aggregate assembly

    International Nuclear Information System (INIS)

    Belfield, Kevin D.; Bondar, Mykhailo V.; Hernandez, Florencio E.; Przhonska, Olga V.; Yao, Sheng

    2006-01-01

    Linear spectral properties, including excitation anisotropy, of pseudoisocyanine or 1,1'-diethyl-2,2'-cyanine iodide (PIC) J-aggregates in aqueous solutions with J-band position at 573 nm were investigated. Two-photon absorption of PIC J-aggregates and monomer molecules was studied using an open aperture Z-scan technique. A strong enhancement of the two-photon absorption cross-section of PIC in the supramolecular J-aggregate assembly was observed in aqueous solution. This enhancement is attributed to a strong coupling of the molecular transition dipoles. No two-photon absorption at the peak of the J-band was detected

  6. Silicon oxide particle formation in RF plasmas investigated by infrared absorption spectroscopy and mass spectrometry

    NARCIS (Netherlands)

    Hollenstein, Ch.; Howling, A.A.; Courteille, C.; Magni, D.; Scholz, S.M.; Kroesen, G.M.W.; Simons, N.; de Zeeuw, W.; Schwarzenbach, W.

    1998-01-01

    In situ Fourier transform infrared absorption spectroscopy has been used to study the composition of particles formed and suspended in radio-frequency discharges of silane - oxygen-argon gas mixtures. The silane gas consumption was observed by infrared absorption. The stoichiometry of the produced

  7. Semiconductors bonds and bands

    CERN Document Server

    Ferry, David K

    2013-01-01

    As we settle into this second decade of the twenty-first century, it is evident that the advances in micro-electronics have truly revolutionized our day-to-day lifestyle. The technology is built upon semiconductors, materials in which the band gap has been engineered for special values suitable to the particular application. This book, written specifically for a one semester course for graduate students, provides a thorough understanding of the key solid state physics of semiconductors. It describes how quantum mechanics gives semiconductors unique properties that enabled the micro-electronics revolution, and sustain the ever-growing importance of this revolution.

  8. X-ray absorption intensity at high-energy region

    International Nuclear Information System (INIS)

    Fujikawa, Takashi; Kaneko, Katsumi

    2012-01-01

    We theoretically discuss X-ray absorption intensity in high-energy region far from the deepest core threshold to explain the morphology-dependent mass attenuation coefficient of some carbon systems, carbon nanotubes (CNTs), highly oriented pyrolytic graphite (HOPG) and fullerenes (C 60 ). The present theoretical approach is based on the many-body X-ray absorption theory including the intrinsic losses (shake-up losses). In the high-energy region the absorption coefficient has correction term dependent on the solid state effects given in terms of the polarization part of the screened Coulomb interaction W p . We also discuss the tail of the valence band X-ray absorption intensity. In the carbon systems C 2s contribution has some influence on the attenuation coefficient even in the high energy region at 20 keV.

  9. Luminescence and optical absorption determination in porous silicon

    International Nuclear Information System (INIS)

    Nogal, U.; Calderon, A.; Marin, E.; Rojas T, J. B.; Juarez, A. G.

    2012-10-01

    We applied the photoacoustic spectroscopy technique in order to obtain the optical absorption spectrum in porous silicon samples prepared by electrochemical anodic etching on n-type, phosphorous doped, (100)-oriented crystal-line silicon wafer with thickness of 300 μm and 1-5 ωcm resistivity. The porous layers were prepared with etching times of 13, 20, 30, 40 and 60 minutes. Also, we realized a comparison among the optical absorption spectrum with the photoluminescence and photo reflectance ones, both obtained at room temperature. Our results show that the absorption spectrum of the samples of porous silicon depends notably of the etching time an it consist of two distinguishable absorption bands, one in the Vis region and the other one in the UV region. (Author)

  10. Pulse radiolysis of LiBr-KBr melts. Optical transient absorption spectra

    International Nuclear Information System (INIS)

    Sawamura, S.; Gebicki, J.L.; Mayer, J.; Kroh, J.

    1990-01-01

    Absorption spectra of the irradiated melts of LiBr and LiBr-KBr mixtures were investigated in the temperature range 673-873 K by nanosecond pulse radiolysis. The visible band ascribed to e s - shows the apparent shift towards longer wavelengths with increasing temperature and increasing content of KBr in the mixture. The UV transient absorption was attributed to superimposed Br 2 - and Br 3 - bands. The relation between the transition energy of visible band and the inverse mean ion distance is given for alkali bromide and chloride systems. (author)

  11. Assessing hafnium on hafnia as an oxygen getter

    International Nuclear Information System (INIS)

    O'Hara, Andrew; Demkov, Alexander A.; Bersuker, Gennadi

    2014-01-01

    Hafnium dioxide or hafnia is a wide band gap dielectric used in a range of electronic applications from field effect transistors to resistive memory. In many of these applications, it is important to maintain control over oxygen stoichiometry, which can be realized in practice by using a metal layer, specifically hafnium, to getter oxygen from the adjacent dielectric. In this paper, we employ density functional theory to study the thermodynamic stability of an interface between (100)-oriented monoclinic hafnia and hafnium metal. The nudged elastic band method is used to calculate the energy barrier for migration of oxygen from the oxide to the metal. Our investigation shows that the presence of hafnium lowers the formation energy of oxygen vacancies in hafnia, but more importantly the oxidation of hafnium through the migration of oxygen from hafnia is favored energetically

  12. Development of a new free radical absorption capacity assay method for antioxidants: aroxyl radical absorption capacity (ARAC).

    Science.gov (United States)

    Nagaoka, Shin-ichi; Nagai, Kanae; Fujii, Yuko; Ouchi, Aya; Mukai, Kazuo

    2013-10-23

    A new free radical absorption capacity assay method is proposed with use of an aroxyl radical (2,6-di-tert-butyl-4-(4'-methoxyphenyl)phenoxyl radical) and stopped-flow spectroscopy and is named the aroxyl radical absorption capacity (ARAC) assay method. The free radical absorption capacity (ARAC value) of each tocopherol was determined through measurement of the radical-scavenging rate constant in ethanol. The ARAC value could also be evaluated through measurement of the half-life of the aroxyl radical during the scavenging reaction. For the estimation of the free radical absorption capacity, the aroxyl radical was more suitable than the DPPH radical, galvinoxyl, and p-nitrophenyl nitronyl nitroxide. The ARAC value in tocopherols showed the same tendency as the free radical absorption capacities reported previously, and the tendency was independent of an oxygen radical participating in the scavenging reaction and of a medium surrounding the tocopherol and oxygen radical. The ARAC value can be directly connected to the free radical-scavenging rate constant, and the ARAC method has the advantage of treating a stable and isolable radical (aroxyl radical) in a user-friendly organic solvent (ethanol). The ARAC method was also successfully applied to a palm oil extract. Accordingly, the ARAC method would be useful in free radical absorption capacity assay of antioxidative reagents and foods.

  13. Multiple infrared bands absorber based on multilayer gratings

    Science.gov (United States)

    Liu, Xiaoyi; Gao, Jinsong; Yang, Haigui; Wang, Xiaoyi; Guo, Chengli

    2018-03-01

    The present study offers an Ag/Si multilayer-grating microstructure based on an Si substrate. The microstructure exhibits designable narrowband absorption in multiple infrared wavebands, especially in mid- and long-wave infrared atmospheric windows. We investigate its resonance mode mechanism, and calculate the resonance wavelengths by the Fabry-Perot and metal-insulator-metal theories for comparison with the simulation results. Furthermore, we summarize the controlling rules of the absorption peak wavelength of the microstructure to provide a new method for generating a Si-based device with multiple working bands in infrared.

  14. Iron absorption studies

    International Nuclear Information System (INIS)

    Ekenved, G.

    1976-01-01

    The main objective of the present work was to study iron absorption from different iron preparations in different types of subjects and under varying therapeutic conditions. The studies were performed with different radioiron isotope techniques and with a serum iron technique. The preparations used were solutions of ferrous sulphate and rapidly-disintegrating tablets containing ferrous sulphate, ferrous fumarate and ferrous carbonate and a slow-release ferrous sulphate tablet of an insoluble matrix type (Duroferon Durules). The serum iron method was evaluated and good correlation was found between the serum iron response and the total amount of iron absorbed after an oral dose of iron given in solution or in tablet form. New technique for studying the in-vivo release properties of tablets was presented. Iron tablets labelled with a radio-isotope were given to healthy subjects. The decline of the radioactivity in the tablets was followed by a profile scanning technique applied to different types of iron tablets. The release of iron from the two types of tablets was shown to be slower in vivo than in vitro. It was found that co-administration of antacids and iron tablets led to a marked reduction in the iron absorption and that these drugs should not be administered sumultaneously. A standardized meal markedly decreased the absorbability of iron from iron tablets. The influence of the meal was more marked with rapidly-disintegrating than with slow-release ferrous sulphate tablets. The absorption from rapidly-disintegrating and slow-release ferrous sulphate tablets was compared under practical clinical conditions during an extended treatment period. The studies were performed in healthy subjects, blood donors and patients with iron deficiency anaemia and it was found that the absorption of iron from the slow-release tablets was significantly better than from the rapidly-disintegrating tablets in all three groups of subjects. (author)

  15. Gamma absorption meter

    International Nuclear Information System (INIS)

    Dincklage, R.D. von.

    1984-01-01

    The absorption meter consists of a radiation source, a trough for the absorbing liquid and a detector. It is characterized by the fact that there is a foil between the detector and the trough, made of a material whose binding energy of the K electrons is a little greater than the energy of the photons emitted by the radiation source. The source of radiation and foil are replaceable. (orig./HP) [de

  16. Total Absorption Spectroscopy

    International Nuclear Information System (INIS)

    Rubio, B.; Gelletly, W.

    2007-01-01

    The problem of determining the distribution of beta decay strength (B(GT)) as a function of excitation energy in the daughter nucleus is discussed. Total Absorption Spectroscopy is shown to provide a way of determining the B(GT) precisely. A brief history of such measurements and a discussion of the advantages and disadvantages of this technique, is followed by examples of two recent studies using the technique. (authors)

  17. Degenerate band edge laser

    Science.gov (United States)

    Veysi, Mehdi; Othman, Mohamed A. K.; Figotin, Alexander; Capolino, Filippo

    2018-05-01

    We propose a class of lasers based on a fourth-order exceptional point of degeneracy (EPD) referred to as the degenerate band edge (DBE). EPDs have been found in parity-time-symmetric photonic structures that require loss and/or gain; here we show that the DBE is a different kind of EPD since it occurs in periodic structures that are lossless and gainless. Because of this property, a small level of gain is sufficient to induce single-frequency lasing based on a synchronous operation of four degenerate Floquet-Bloch eigenwaves. This lasing scheme constitutes a light-matter interaction mechanism that leads also to a unique scaling law of the laser threshold with the inverse of the fifth power of the laser-cavity length. The DBE laser has the lowest lasing threshold in comparison to a regular band edge laser and to a conventional laser in cavities with the same loaded quality (Q ) factor and length. In particular, even without mirror reflectors the DBE laser exhibits a lasing threshold which is an order of magnitude lower than that of a uniform cavity laser of the same length and with very high mirror reflectivity. Importantly, this novel DBE lasing regime enforces mode selectivity and coherent single-frequency operation even for pumping rates well beyond the lasing threshold, in contrast to the multifrequency nature of conventional uniform cavity lasers.

  18. X-ray absorption near-edge structure of GaN with high Mn concentration grown on SiC

    International Nuclear Information System (INIS)

    Sancho-Juan, O; Cantarero, A; Garro, N; Cros, A; Martinez-Criado, G; Salome, M; Susini, J; Olguin, D; Dhar, S

    2009-01-01

    By means of x-ray absorption near-edge structure (XANES) several Ga 1-x Mn x N (0.03 2 ↑ band localized in the gap region, and the corresponding anti-bonding state t 2 ↓, which seem to be responsible for the double structure which appears at the pre-edge absorption region. The shoulders and main absorption peak of the XANES spectra are attributed to transitions from the Mn(1s) band to the conduction bands, which are partially dipole allowed because of the Mn(4p) contribution to these bands.

  19. Recharging processes, radiation induced strain and changes of OH - bands under H + ion implantation in Ti doped lithium niobate

    Science.gov (United States)

    Kumar, P.; Moorthy Babu, S.; Bhaumik, I.; Ganesamoorthy, S.; Karnal, A. K.; Kumar, Praveen; Rodrigues, G. O.; Sulania, I.; Kanjilal, D.; Pandey, A. K.; Raman, R.

    2010-01-01

    A systematic analysis of variations in structural and optical characteristics of Z-cut plates of titanium doped congruent lithium niobate single crystals implanted with 120 keV proton beam at various fluences of 10 15, 10 16 and 10 17 protons/cm 2 is presented. Through, high resolution X-ray diffraction, atomic force microscopy, Fourier transform infrared and UV-visible-NIR analysis of congruent lithium niobate, the correlation of properties before and after implantation are discussed. HRXRD (0 0 6) reflection by Triple Crystal Mode shows that both tensile and compressive strain peak are produced by the high fluence implantation. A distinct tensile peak was observed from implanted region for a fluence of 10 16 protons/cm 2. AFM micrographs indicate mountain ridges, bumps and protrusions on target surface on implantation. UV-visible-NIR spectra reveal an increase in charge transfer between Ti 3+/Ti 4+ and ligand oxygen for implantation with 10 15 protons/cm 2, while spectra for higher fluence implanted samples show complex absorption band in the region from 380-1100 nm. Variations of OH - stretching vibration mode were observed for cLN Pure, cLNT2% virgin, and implanted samples with FTIR spectra. The concentration of OH - ion before and after implantation was calculated from integral absorption intensity. The effect of 120 keV proton implantation induced structural, surface and optical studies were correlated.

  20. Chemical state analysis of heat-treated 6, 13-bis(triisopropylsilylethynyl) pentacene investigated by XPS valence band spectra, XANES spectra and first-principles calculation

    International Nuclear Information System (INIS)

    Muro, Maiko; Natsume, Yutaka; Kikuma, Jun; Setoyama, Hiroyuki

    2014-01-01

    X-ray photoelectron spectroscopy (XPS) valence band spectra reflect the chemical bonding states. To take this advantage, we tried to interpret experimental spectra by the occupied density of states (DOS) based on first principles calculation. In this work, we discussed XPS and X-ray Absorption Near Edge Structure (XANES) spectra of 6, 13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pen), which is well known as an organic semiconductor. We studied chemical structure change of TIPS-Pen caused by heat-treatment at 300degC under nitrogen and under the air. It has been suggested that the structural change of pentacene skeleton by Diels-Alder type reaction occurs in both cases. In addition, the sample heat-treated under the air showed desorption of the isopropyl group and increase of oxygen concentration. (author)

  1. Fine structure of the amide i band in acetanilide

    Science.gov (United States)

    Careri, G.; Gratton, E.; Shyamsunder, E.

    1988-05-01

    Their absorption spectrum of both single crystals and powdered samples of acetanilide (a model system for proteins) has been studied in the amide i region, where a narrow band has been identified as a highly trapped soliton state. The powder-sample spectra have been decomposed using four Lorentzian bands. A strong temperature dependence has been found for the intensity of two of the subbands, which also show a complementary behavior. Polarization studies performed on thin crystals have shown that the subbands have the same polarization. Low-temperature spectra of partially deuterated samples show the presence of the subbands at the same absorption frequencies found using the fitting procedure in the spectra of nondeuterated samples. The soliton model currently proposed to explain the origin of the anomalous amide i component at 1650 cm-1 still holds, but some modification of the model is required to account for the new features revealed by this study.

  2. Wide band ENDOR spectrometer

    International Nuclear Information System (INIS)

    Mendonca Filho, C.

    1973-01-01

    The construction of an ENDOR spectrometer operating from 0,5 to 75 MHz within a single band, with ore Klystron and homodine detection, and no fundamental changes on the electron spin resonance spectrometer was described. The ENDOR signal can be detected both by amplitude modulation of the frequency field, or direct detection of the ESR output, which is taken to a signal analyser. The signal-to-noise ratio is raised by averaging rather than filtering avoiding the use of long time constants, providing natural line widths. The experimental apparatus and the spectra obtained are described. A discussion, relating the ENDOR line amplitudes with the experimental conditions is done and ENDOR mechanism, in which there is a relevant presence of cross relaxation is proposed

  3. Electronic band structure

    International Nuclear Information System (INIS)

    Grosso, G.

    1986-01-01

    The aim of this chapter is to present, in detail, some theoretical methods used to calculate electronic band structures in crystals. The basic strategies employed to attack the problem of electronic-structure calculations are presented. Successive sections present the basic formulations of the tight-binding, orthogonalized-plane-wave, Green'sfunction, and pseudopotential methods with a discussion of their application to perfect solids. Exemplifications in the case of a few selected problems provide further insight by the author into the physical aspects of the different methods and are a guide to the use of their mathematical techniques. A discussion is offered of completely a priori Hartree-Fock calculations and attempts to extend them. Special aspects of the different methods are also discussed in light of recently published related work

  4. Defect-band mediated ferromagnetism in Gd-doped ZnO thin films

    KAUST Repository

    Venkatesh, S.

    2015-01-07

    Gd-doped ZnO thin films prepared by pulsed laser deposition with Gd concentrations varying from 0.02–0.45 atomic percent (at. %) showed deposition oxygen pressure controlled ferromagnetism. Thin films prepared with Gd dopant levels (oxygen deposition pressure (<25 mTorr) were ferromagnetic at room temperature. Negative magnetoresistance, electric transport properties showed that the ferromagnetic exchange is mediated by a spin-split defect band formed due to oxygen deficiency related defect complexes. Mott\\'s theory of variable range of hopping conduction confirms the formation of the impurity/defect band near the Fermi level.

  5. Time evolution of absorption process in nonlinear metallic photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Mahi R.; Hatef, Ali [Department of Physics and Astronomy, University of Western Ontario, London (Canada)

    2009-05-15

    The time evolution of the absorption coefficient in metallic photonic crystals has been studied numerically. These crystals are made from metallic spheres which are arranged periodically in air. The refractive index of the metallic spheres depends on the plasma frequency. Probe and pump fields are applied to monitor the absorption process. Ensembles of three-level particles are embedded in the crystal. Nanoparticles are interacting with the metallic crystals via the electron-photon interaction. It is found that when the resonance states lie away from the band edges system goes to transparent state. (copyright 2009 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Hydrogen bonding interaction of small acetaldehyde clusters studied with core-electron excitation spectroscopy in the oxygen K-edge region

    Science.gov (United States)

    Tabayashi, K.; Chohda, M.; Yamanaka, T.; Tsutsumi, Y.; Takahashi, O.; Yoshida, H.; Taniguchi, M.

    2010-06-01

    In order to examine inner-shell electron excitation spectra of molecular clusters with strong multipole interactions, excitation spectra and time-of-flight (TOF) fragment-mass spectra of small acetaldehyde (AA) clusters have been studied under the beam conditions. The TOF spectra at the oxygen K-edge region showed an intense growth of the protonated clusters, MnH+ (M=CH3CHO) in the cluster beams. "cluster-specific" excitation spectra could be generated by monitoring partial-ion-yields of the protonated clusters. The most intense band of O1s→π*CO was found to shift to a higher energy by 0.15 eV relative to the monomer band upon clusterization. X-ray absorption spectra (XAS) were also calculated for the representative dimer configurations using a computer modelling program based on the density functional theory. The XAS prediction for the most stable (non-planar) configuration was found to give a close comparison with the cluster-band shift observed. The band shift was interpreted as being due to the HOMO-LUMO interaction within the complex where a contribution of vibrationally blue-shifting hydrogen bonding could be identified.

  7. Twisted bilayer blue phosphorene: A direct band gap semiconductor

    Science.gov (United States)

    Ospina, D. A.; Duque, C. A.; Correa, J. D.; Suárez Morell, Eric

    2016-09-01

    We report that two rotated layers of blue phosphorene behave as a direct band gap semiconductor. The optical spectrum shows absorption peaks in the visible region of the spectrum and in addition the energy of these peaks can be tuned with the rotational angle. These findings makes twisted bilayer blue phosphorene a strong candidate as a solar cell or photodetection device. Our results are based on ab initio calculations of several rotated blue phosphorene layers.

  8. Nonlinear refraction at the absorption edge in InAs.

    Science.gov (United States)

    Poole, C D; Garmire, E

    1984-08-01

    The results of measurements of nonlinear refraction at the absorption edge in InAs between 68 and 90 K taken with an HF laser are compared with those of a band-gap resonant model in which the contribution of the light-hole band is included and found to account for more than 40% of the observed nonlinear refraction. A generalized expression for the nonlinear index is derived by using the complete Fermi-Dirac distribution function. Good agreement between theory and experiment is obtained, with no free parameters.

  9. Optical absorption in dendrimers

    International Nuclear Information System (INIS)

    Supritz, C.; Engelmann, A.; Reineker, P.

    2004-01-01

    Dendrimers are highly branched molecules, which are expected to be useful, for example, as efficient artificial light harvesting systems in nano-technological applications. There are two different classes of dendrimers: compact dendrimers with constant distance between neighboring branching points throughout the macromolecule and extended dendrimers, where this distance increases from the system periphery to the center. We investigate the linear absorption spectra of these dendrimer types using the Frenkel exciton concept. The electron-phonon interaction is taken into account by introducing a heat bath that interacts with the exciton in a stochastic manner

  10. Rapidly variable relatvistic absorption

    Science.gov (United States)

    Parker, M.; Pinto, C.; Fabian, A.; Lohfink, A.; Buisson, D.; Alston, W.; Jiang, J.

    2017-10-01

    I will present results from the 1.5Ms XMM-Newton observing campaign on the most X-ray variable AGN, IRAS 13224-3809. We find a series of nine absorption lines with a velocity of 0.24c from an ultra-fast outflow. For the first time, we are able to see extremely rapid variability of the UFO features, and can link this to the X-ray variability from the inner accretion disk. We find a clear flux dependence of the outflow features, suggesting that the wind is ionized by increasing X-ray emission.

  11. Geospatial Absorption and Regional Effects

    Directory of Open Access Journals (Sweden)

    IOAN MAC

    2009-01-01

    Full Text Available The geospatial absorptions are characterized by a specific complexity both in content and in their phenomenological and spatial manifestation fields. Such processes are differentiated according to their specificity to pre-absorption, absorption or post-absorption. The mechanisms that contribute to absorption are extremely numerous: aggregation, extension, diffusion, substitution, resistivity (resilience, stratification, borrowings, etc. Between these mechanisms frequent relations are established determining an amplification of the process and of its regional effects. The installation of the geographic osmosis phenomenon in a given territory (a place for example leads to a homogenization of the geospatial state and to the installation of the regional homogeneity.

  12. Circumstellar ammonia in oxygen-rich evolved stars

    Science.gov (United States)

    Wong, K. T.; Menten, K. M.; Kamiński, T.; Wyrowski, F.; Lacy, J. H.; Greathouse, T. K.

    2018-04-01

    Context. The circumstellar ammonia (NH3) chemistry in evolved stars is poorly understood. Previous observations and modelling showed that NH3 abundance in oxygen-rich stars is several orders of magnitude above that predicted by equilibrium chemistry. Aims: We would like to characterise the spatial distribution and excitation of NH3 in the oxygen-rich circumstellar envelopes (CSEs) of four diverse targets: IK Tau, VY CMa, OH 231.8+4.2, and IRC +10420. Methods: We observed NH3 emission from the ground state in the inversion transitions near 1.3 cm with the Very Large Array (VLA) and submillimetre rotational transitions with the Heterodyne Instrument for the Far-Infrared (HIFI) aboard Herschel Space Observatory from all four targets. For IK Tau and VY CMa, we observed NH3 rovibrational absorption lines in the ν2 band near 10.5 μm with the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infrared Telescope Facility (IRTF). We also attempted to search for the rotational transition within the excited vibrational state (v2 = 1) near 2 mm with the IRAM 30m Telescope. Non-LTE radiative transfer modelling, including radiative pumping to the vibrational state, was carried out to derive the radial distribution of NH3 in the CSEs of these targets. Results: We detected NH3 inversion and rotational emission in all four targets. IK Tau and VY CMa show blueshifted absorption in the rovibrational spectra. We did not detect vibrationally excited rotational transition from IK Tau. Spatially resolved VLA images of IK Tau and IRC +10420 show clumpy emission structures; unresolved images of VY CMa and OH 231.8+4.2 indicate that the spatial-kinematic distribution of NH3 is similar to that of assorted molecules, such as SO and SO2, that exhibit localised and clumpy emission. Our modelling shows that the NH3 abundance relative to molecular hydrogen is generally of the order of 10-7, which is a few times lower than previous estimates that were made without considering radiative

  13. Direct optical band gap measurement in polycrystalline semiconductors: A critical look at the Tauc method

    International Nuclear Information System (INIS)

    Dolgonos, Alex; Mason, Thomas O.; Poeppelmeier, Kenneth R.

    2016-01-01

    The direct optical band gap of semiconductors is traditionally measured by extrapolating the linear region of the square of the absorption curve to the x-axis, and a variation of this method, developed by Tauc, has also been widely used. The application of the Tauc method to crystalline materials is rooted in misconception–and traditional linear extrapolation methods are inappropriate for use on degenerate semiconductors, where the occupation of conduction band energy states cannot be ignored. A new method is proposed for extracting a direct optical band gap from absorption spectra of degenerately-doped bulk semiconductors. This method was applied to pseudo-absorption spectra of Sn-doped In 2 O 3 (ITO)—converted from diffuse-reflectance measurements on bulk specimens. The results of this analysis were corroborated by room-temperature photoluminescence excitation measurements, which yielded values of optical band gap and Burstein–Moss shift that are consistent with previous studies on In 2 O 3 single crystals and thin films. - Highlights: • The Tauc method of band gap measurement is re-evaluated for crystalline materials. • Graphical method proposed for extracting optical band gaps from absorption spectra. • The proposed method incorporates an energy broadening term for energy transitions. • Values for ITO were self-consistent between two different measurement methods.

  14. Biogeochemistry: Oxygen burrowed away

    NARCIS (Netherlands)

    Meysman, F.J.R.

    2014-01-01

    Multicellular animals probably evolved at the seafloor after a rise in oceanic oxygen levels. Biogeochemical model simulations suggest that as these animals started to rework the seafloor, they triggered a negative feedback that reduced global oxygen.

  15. Oxygen transport membrane

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof.......The present invention relates to a novel composite oxygen transport membrane as well as its preparation and uses thereof....

  16. Combining the absorptive and radiative loss in metasurfaces for multi-spectral shaping of the electromagnetic scattering.

    Science.gov (United States)

    Pan, Wenbo; Huang, Cheng; Pu, Mingbo; Ma, Xiaoliang; Cui, Jianhua; Zhao, Bo; Luo, Xiangang

    2016-02-19

    The absorptive and radiative losses are two fundamental aspects of the electromagnetic responses, which are widely occurring in many different systems such as waveguides, solar cells, and antennas. Here we proposed a metasurface to realize the control of the absorptive and radiative loss and to reduce the radar cross section (RCS) in multi-frequency bands. The anti-phase gradient and absorptive metasurfaces were designed that consists of metallic square patch and square loop structure inserted with resistors, acting as an phase gradient material in the X and Ku band, while behaving as an absorber in the S band. The simulation and experiment results verified the double-band, wideband and polarization-independent RCS reduction by the absorptive and anti-phase gradient metasurfaces.

  17. Wideband absorption in one dimensional photonic crystal with graphene-based hyperbolic metamaterials

    Science.gov (United States)

    Kang, Yongqiang; Liu, Hongmei

    2018-02-01

    A broadband absorber which was proposed by one dimensional photonic crystal (1DPC) containing graphene-based hyperbolic metamaterials (GHMM) is theoretically investigated. For TM mode, it was demonstrated to absorb roughly 90% of all available electromagnetic waves at a 14 THz absorption bandwidth at normal incidence. The absorption bandwidth was affected by Fermi energy and thickness of dielectric layer. When the incident angle was increased, the absorption value decreased, and the absorption band had a gradual blue shift. These findings have potential applications for designing broadband optoelectronic devices at mid-infrared and THz frequency range.

  18. Proterozoic atmospheric oxygen

    DEFF Research Database (Denmark)

    Canfield, Donald Eugene

    2014-01-01

    This article is concerned with the evolution of atmospheric oxygen concentrations through the Proterozoic Eon. In particular, this article will seek to place the history of atmospheric oxygenation through the Proterozoic Eon in the context of the evolving physical environment including the history...... of continental growth and volcanic outgassing, as well as biogeochemical processing of elements within the oceans. The author will seek to explore constraints on the history of oxygenation and understand which processes have regulated oxygen through this eon....

  19. Oxygen evolution reaction catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  20. Measurement of ozone production scaling in a helium plasma jet with oxygen admixture

    Science.gov (United States)

    Sands, Brian; Ganguly, Biswa

    2012-10-01

    Capillary dielectric barrier plasma jet devices that generate confined streamer-like discharges along a rare gas flow can produce significant quantities of reactive oxygen species with average input powers ranging from 100 mW to >1 W. We have measured spatially-resolved ozone production in a He plasma jet with O2 admixture concentrations up to 5% using absorption spectroscopy of the O3 Hartley band system. A 20-ns risetime, 10-13 kV positive unipolar voltage pulse train was used to power the discharge, with pulse repetition rates varied from 1-20 kHz. The discharge was operated in a transient glow mode to scale the input power by adjusting the gap width between the anode and downstream cathodic plane. Peak ozone number densities in the range of 10^16 - 10^17 cm-3 were measured. At a given voltage, the density of ozone increased monotonically up to 3% O2 admixture (6 mm gap) as the peak discharge current decreased by an order of magnitude. Ozone production increased with distance from the capillary, consistent with observations by other groups. Atomic oxygen production inferred from O-atom 777 nm emission intensity did not scale with ozone as the input power was increased. The spatial distribution of ozone and scaling with input power will be presented.

  1. Wavelength dependence of the efficiency of singlet oxygen generation upon photoexcitation of photosensitizers

    Directory of Open Access Journals (Sweden)

    Starukhin A.

    2017-01-01

    Full Text Available The dependence of the efficiency of singlet oxygen (1Δg generation upon excitation of photosensitizer at different wavelength was observed for several derivatives of palladium porphyrin in carbon tetrachloride. The efficiency of singlet oxygen generation upon excitation in a blue region of the spectrum (Soret band exceeds by several times the efficiency at excitation in the red spectral region (Q band. The effect of enhancement of singlet oxygen generation upon CW photoexcitation to Soret band of photosensitizer may be explained by influence of high laying triplet states of a donor molecule on the triplet-triplet energy transfer.

  2. Oxygen negative glow: reactive species and emissivity

    International Nuclear Information System (INIS)

    Sahli, Khaled

    1991-01-01

    This research thesis addresses the study of a specific type of oxygen plasma created by electron beams (1 keV, 20 mA/cm"2), negative glow of a luminescent discharge in abnormal regime. The objective is to test the qualities of this plasma as source of two 'active' species of oxygen (singlet molecular oxygen and atomic oxygen) which are useful in applications. The experiment mainly bears on the use of VUV (120 to 150 nm) absorption spectroscopy measurements of concentrations of these both species, and on the recording of plasma emissivity space profiles in the visible region (450 to 850 nm). It appears that low concentrations of singlet oxygen definitely exclude this type of discharge for iodine laser applications. On the contrary, concentrations measured for atomic oxygen show it is a good candidate for the oxidation of large surfaces by sheets of beams. The satisfying comparison of emissivity results with a published model confirm the prevailing role of fast electrons, and gives evidence of an important effect of temperature: temperature can reach 1000 K, and this is in agreement with the presented measurement [fr

  3. [Domiciliary oxygen therapy].

    Science.gov (United States)

    Abdel Kafi, S

    2010-09-01

    In Belgium, oxygen therapy is becoming more and more accessible. When oxygen is needed for short periods or for special indications as palliative care, an agreement between mutual insurance companies and pharmacists allows the practitioner the home installation of gazeous oxygen cylinder or of oxygen concentrator. When long term oxygen therapy (LTOT) is indicated for patients with respiratory insufficiency, the pneumologist must first ask the INAMI the authorization to install one of the following modalities: oxygen concentrator with or without demand oxygen delivery cylinder and liquid oxygen. The goal of LTOT is to increase survival and quality of life. The principal and well accepted indication for LTOT is severe hypoxemia. The beneficial effects of oxygen therapy limited at night or on exertion are controversial. In order to increase patient's autonomy, oxygen can be prescribed for ambulation, respecting prescription's rules. At each step of oxygen therapy implementing (indication, choice of the device and follow-up) the patient under oxygen may benefit from a joint approach between the general practitioner and the chest specialist.

  4. Aircraft Oxygen Generation

    Science.gov (United States)

    2012-02-01

    An Oxygen Enriched Air System for the AV-8A Harrier (NADC-81198-60).” 70 Horch , T., et. al. “The F-16 Onboard Oxygen Generating System: Performance...Only and Safety Privileged). Horch , T., Miller, R., Bomar, J., Tedor, J., Holden, R., Ikels, K., & Lozano, P. (1983). The F-16 Onboard Oxygen

  5. Picosecond absorption relaxation measured with nanosecond laser photoacoustics.

    Science.gov (United States)

    Danielli, Amos; Favazza, Christopher P; Maslov, Konstantin; Wang, Lihong V

    2010-10-18

    Picosecond absorption relaxation-central to many disciplines-is typically measured by ultrafast (femtosecond or picosecond) pump-probe techniques, which however are restricted to optically thin and weakly scattering materials or require artificial sample preparation. Here, we developed a reflection-mode relaxation photoacoustic microscope based on a nanosecond laser and measured picosecond absorption relaxation times. The relaxation times of oxygenated and deoxygenated hemoglobin molecules, both possessing extremely low fluorescence quantum yields, were measured at 576 nm. The added advantages in dispersion susceptibility, laser-wavelength availability, reflection sensing, and expense foster the study of natural-including strongly scattering and nonfluorescent-materials.

  6. Fundamental absorption edge of NiO nanocrystals

    Energy Technology Data Exchange (ETDEWEB)

    Sokolov, V.I., E-mail: visokolov@imp.uran.ru [Institute of Metal Physics, Ural Branch of RAS, S. Kovalevskaya Street 18, 620990 Yekaterinburg (Russian Federation); Druzhinin, A.V. [Institute of Metal Physics, Ural Branch of RAS, S. Kovalevskaya Street 18, 620990 Yekaterinburg (Russian Federation); Kim, G.A. [Institute of Organic Synthesis Ural Branch of RAS, S. Kovalevskaya Street 20, 620990 Yekaterinburg (Russian Federation); Gruzdev, N.B.; Yermakov, A.Ye.; Uimin, M.A.; Byzov, I.V.; Shchegoleva, N.N.; Vykhodets, V.B.; Kurennykh, T.E. [Institute of Metal Physics, Ural Branch of RAS, S. Kovalevskaya Street 18, 620990 Yekaterinburg (Russian Federation)

    2013-12-01

    NiO nanocrystals with the average size of 5, 10 and 25 nm were synthesized by gas-condensation method. The well-defined increase of the optical density D near the fundamental absorption edge of NiO nanocrystals in the range of 3.5–4.0 eV observed after the annealing in air is caused by the oxygen content growth. It is the direct experimental evidence of the fact that p—d charge transfer transitions form the fundamental absorption edge.

  7. Fundamental absorption edge of NiO nanocrystals

    International Nuclear Information System (INIS)

    Sokolov, V.I.; Druzhinin, A.V.; Kim, G.A.; Gruzdev, N.B.; Yermakov, A.Ye.; Uimin, M.A.; Byzov, I.V.; Shchegoleva, N.N.; Vykhodets, V.B.; Kurennykh, T.E.

    2013-01-01

    NiO nanocrystals with the average size of 5, 10 and 25 nm were synthesized by gas-condensation method. The well-defined increase of the optical density D near the fundamental absorption edge of NiO nanocrystals in the range of 3.5–4.0 eV observed after the annealing in air is caused by the oxygen content growth. It is the direct experimental evidence of the fact that p—d charge transfer transitions form the fundamental absorption edge

  8. Band gap tuning of amorphous Al oxides by Zr alloying

    Energy Technology Data Exchange (ETDEWEB)

    Canulescu, S., E-mail: stec@fotonik.dtu.dk; Schou, J. [Department of Photonics Engineering, Technical University of Denmark, 4000 Roskilde (Denmark); Jones, N. C.; Hoffmann, S. V. [ISA, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus (Denmark); Borca, C. N.; Piamonteze, C. [Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Rechendorff, K.; Nielsen, L. P.; Almtoft, K. P. [Danish Technological Institute, Kongsvang Alle 29, 8000 Aarhus (Denmark); Gudla, V. C.; Bordo, K.; Ambat, R. [Department of Mechanical Engineering, Technical University of Denmark, 2800 Kgs-Lyngby (Denmark)

    2016-08-29

    The optical band gap and electronic structure of amorphous Al-Zr mixed oxides with Zr content ranging from 4.8 to 21.9% were determined using vacuum ultraviolet and X-ray absorption spectroscopy. The light scattering by the nano-porous structure of alumina at low wavelengths was estimated based on the Mie scattering theory. The dependence of the optical band gap of the Al-Zr mixed oxides on the Zr content deviates from linearity and decreases from 7.3 eV for pure anodized Al{sub 2}O{sub 3} to 6.45 eV for Al-Zr mixed oxides with a Zr content of 21.9%. With increasing Zr content, the conduction band minimum changes non-linearly as well. Fitting of the energy band gap values resulted in a bowing parameter of ∼2 eV. The band gap bowing of the mixed oxides is assigned to the presence of the Zr d-electron states localized below the conduction band minimum of anodized Al{sub 2}O{sub 3}.

  9. X-ray photoemission spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) studies of silicate based glasses

    International Nuclear Information System (INIS)

    Karim, D.; Lam, D.J.

    1979-01-01

    The application of the x-ray photoemission spectroscopy (XPS) technique to study the electronic structure and bonding of heavy metal oxides in alkali- and alkali-earth-silicate glasses had been demonstrated. The bonding characteristics of the iron oxide and uranium oxide in sodium silicate glasses were deduced from the changes in the oxygen 1s levels and the heavy metal core levels. It is reasonable to expect that the effect of leaching on the heavy metal ions can be monitored using the appropriate core levels of these ions. To study the effect of leaching on the glass forming network, the valence band structure of the bridging and nonbridging oxygens in sodium silicate glasses were investigated. The measurement of extended x-ray absorption fine-structure (EXAFS) is a relatively new analytical technique for obtaining short range (<5 A) structural information around atoms of a selected species in both solid and fluid systems. Experiments have recently begun to establish the feasibility of using EXAFS to study the bonding of actinides in silicate glasses. Because of the ability of EXAFS to yield specific structural data even in complex multicomponent systems, it could prove to be an invaluable tool in understanding glass structure

  10. Oxidation driven ZnS Core-ZnO shell photocatalysts under controlled oxygen atmosphere for improved photocatalytic solar water splitting

    Science.gov (United States)

    Bak, Daegil; Kim, Jung Hyeun

    2018-06-01

    Zinc type photocatalysts attract great attentions in solar hydrogen production due to their easy availability and benign environmental characteristics. Spherical ZnS particles are synthesized with a facile hydrothermal method, and they are further used as core materials to introduce ZnO shell layer surrounding the core part by partial oxidation under controlled oxygen contents. The resulting ZnS core-ZnO shell photocatalysts represent the heterostructural type II band alignment. The existence of oxide layer also influences on proton adsorption power with an aid of strong base cites derived from highly electronegative oxygen atoms in ZnO shell layer. Photocatalytic water splitting reaction is performed to evaluate catalyst efficiency under standard one sun condition, and the highest hydrogen evolution rate (1665 μmolg-1h-1) is achieved from the sample oxidized at 16.2 kPa oxygen pressure. This highest hydrogen production rate is achieved in cooperation with increased light absorption and promoted charge separations. Photoluminescence analysis reveals that the improved visible light response is obtained after thermal oxidation process due to the oxygen vacancy states in the ZnO shell layer. Therefore, overall photocatalytic efficiency in solar hydrogen production is enhanced by improved charge separations, crystallinity, and visible light responses from the ZnS core-ZnO shell structures induced by thermal oxidation.

  11. Band gap and polarizability of boro-tellurite glass: Influence of erbium ions

    Science.gov (United States)

    Said Mahraz, Zahra Ashur; Sahar, M. R.; Ghoshal, S. K.

    2014-08-01

    Understanding the influence of rare earth ions in improving the structural and optical properties of inorganic glasses are the key issues. Er3+-doped zinc boro-tellurite glasses with composition 30B2O3-10ZnO-(60-x) TeO2-xEr2O3 are prepared (x = 0, 0.5, 1, 1.5 and 2 mol%) using melt quenching technique. The physical and optical characterizations are measured by density and UV-Vis-IR absorption spectroscopy. The color of the glass changed from light yellow to deep pink due to the introduction of Er3+ ions. The maximum density is found to be ∼4.73 g cm-3 for 1 mol% of Er3+ doping. The variations in the polarizability (6.7-6.8 cm3) and the molar volume (27.987-28.827 cm3 mol-1) with dopant concentration are ascribed to the formation of non-bridging oxygen. This observation is consistent with the alteration of number of bonds per unit volume. The direct and indirect optical band gaps are increased while the phonon cut-off wavelength and Urbach energy decreased with the increase of erbium content. A high density and wide transparency range in VIS-IR area are achieved. Our results on high refractive index (∼2.416) and polarizability suggest that these glasses are potential for photonics, solid state lasers and communications devices.

  12. BAND STRUCTURE OF NON-STEIOCHIOMETRIC LARGE-SIZED NANOCRYSTALLITES

    Directory of Open Access Journals (Sweden)

    I.V.Kityk

    2004-01-01

    Full Text Available A band structure of large-sized (from 20 to 35nm non-steichiometric nanocrystallites (NC of the Si2-xCx (1.04 < x < 1.10 has been investigated using different band energy approaches and a modified Car-Parinello molecular dynamics structure optimization of the NC interfaces. The non-steichiometric excess of carbon favors the appearance of a thin prevailingly carbon-contained layer (with thickness of about 1 nm covering the crystallites. As a consequence, one can observe a substantial structure reconstruction of boundary SiC crystalline layers. The numerical modeling has shown that these NC can be considered as SiC reconstructed crystalline films with thickness of about 2 nm covering the SiC crystallites. The observed data are considered within the different one-electron band structure methods. It was shown that the nano-sized carbon sheet plays a key role in a modified band structure. Independent manifestation of the important role played by the reconstructed confined layers is due to the experimentally discovered excitonic-like resonances. Low-temperature absorption measurements confirm the existence of sharp-like absorption resonances originating from the reconstructed layers.

  13. Metallic photonic band-gap materials

    International Nuclear Information System (INIS)

    Sigalas, M.M.; Chan, C.T.; Ho, K.M.; Soukoulis, C.M.

    1995-01-01

    We calculate the transmission and absorption of electromagnetic waves propagating in two-dimensional (2D) and 3D periodic metallic photonic band-gap (PBG) structures. For 2D systems, there is substantial difference between the s- and p-polarized waves. The p-polarized waves exhibit behavior similar to the dielectric PBG's. But, the s-polarized waves have a cutoff frequency below which there are no propagating modes. For 3D systems, the results are qualitatively the same for both polarizations but there are important differences related to the topology of the structure. For 3D structures with isolated metallic scatterers (cermet topology), the behavior is similar to that of the dielectric PBG's, while for 3D structures with the metal forming a continuous network (network topology), there is a cutoff frequency below which there are no propagating modes. The systems with the network topology may have some interesting applications for frequencies less than about 1 THz where the absorption can be neglected. We also study the role of the defects in the metallic structures

  14. Renal vein oxygen saturation in renal artery stenosis

    DEFF Research Database (Denmark)

    Nielsen, K; Rehling, M; Henriksen, Jens Henrik Sahl

    1992-01-01

    Renal vein oxygen-saturation was measured in 56 patients with arterial hypertension and unilateral stenosis or occlusion of the renal artery. Oxygen-saturation in blood from the ischaemic kidney (84.4%, range 73-93%) was significantly higher than that from the 'normal' contralateral kidney (81...... than its blood flow. This is probably due to decreased filtration fraction and filtered sodium with subsequent reduction in absolute tubular re-absorption of sodium ions....

  15. Oxygen configurations in silica

    International Nuclear Information System (INIS)

    Chelikowsky, James R.; Chadi, D. J.; Binggeli, N.

    2000-01-01

    We propose a transition state for oxygen in silica. This state is produced by the insertion of an oxygen molecule into the Si-O-Si bond, i.e., it consists of producing a Si-O-O-O-Si bond. This state allows molecular oxygen diffusion in silica without breaking the molecular O 2 bond and it is energetically more stable than a peroxy configuration. This configuration may allow for exchange of molecular oxygen with the oxygen in the silica framework. (c) 2000 The American Physical Society

  16. Changing optical band structure with single photons

    Science.gov (United States)

    Albrecht, Andreas; Caneva, Tommaso; Chang, Darrick E.

    2017-11-01

    Achieving strong interactions between individual photons enables a wide variety of exciting possibilities in quantum information science and many-body physics. Cold atoms interfaced with nanophotonic structures have emerged as a platform to realize novel forms of nonlinear interactions. In particular, when atoms are coupled to a photonic crystal waveguide, long-range atomic interactions can arise that are mediated by localized atom-photon bound states. We theoretically show that in such a system, the absorption of a single photon can change the band structure for a subsequent photon. This occurs because the first photon affects the atoms in the chain in an alternating fashion, thus leading to an effective period doubling of the system and a new optical band structure for the composite atom-nanophotonic system. We demonstrate how this mechanism can be engineered to realize a single-photon switch, where the first incoming photon switches the system from being highly transmissive to highly reflective, and analyze how signatures can be observed via non-classical correlations of the outgoing photon field.

  17. Trap spectrum of the ``new oxygen donor'' in silicon

    Science.gov (United States)

    Hölzlein, K.; Pensl, G.; Schulz, M.

    1984-07-01

    Electronic properties of the new oxygen donor generated in phosphorus-doped Czochralski-silicon at 650‡C are investigated by deep level transient spectroscopy. A continuous distribution of trap states (1014 1016 cm-3 eV-1) is detected in the upper half of the band gap with increasing values towards the conduction band. The magnitude of the state density observed increases with the oxygen content, the heat duration, and a preanneal at temperatures lower than 650‡C. The continuous trap spectrum of the new donor is explained by interface states occuring at the surface of SiO x precipitates.

  18. On the nature of absorption features toward nearby stars

    Science.gov (United States)

    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

  19. Atomic absorption spectrometry

    International Nuclear Information System (INIS)

    Haswell, S.J.

    1991-01-01

    Atomic absorption spectroscopy is now well established and widely used technique for the determination of trace and major elements in a wide range analyte types. There have been many advances in the atomic spectroscopy over the last decade and for this reason and to meet the demand, it was felt that there was a need for an updated book. Whilst interest in instrumental design has tended to dominate the minds of the spectrocopist, the analyst concerned with obtaining reliable and representative data, in diverse areas of application, has been diligently modifying and developing sample treatment and instrumental introduction techniques. Such methodology is de fundamental part of analysis and form the basis of the fourteen application chapters of this book. The text focuses in the main on AAS; however, the sample handling techniques described are in many cases equally applicable to ICP-OES and ICP-MS analysis. (author). refs.; figs.; tabs

  20. Atomic absorption spectrophotometer

    International Nuclear Information System (INIS)

    Stockdale, T. J.

    1985-01-01

    In atomic absorption spectrophotometer, a reference path may be provided for radiation which excludes the flame. This radiation provides a signal from a detector which varies only with the instrumental drift produced by variations in the radiation source brightness and by variations in detector gain. The signal can be used to compensate for drift in other signals received through a sample path including the flame. In the present invention, radiation passes through the sample path continuously during measurement, and only through the reference path between sample measurements. Movable mirrors shift the radiation between the paths upon externally applied commands. Conveniently, the reference path measurement is made while the flame is stabilized during the change between samples. The reference path measurements are stored and used to correct for drift

  1. Analyzing Water's Optical Absorption

    Science.gov (United States)

    2002-01-01

    A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

  2. Determination of optical band gap of powder-form nanomaterials with improved accuracy

    Science.gov (United States)

    Ahsan, Ragib; Khan, Md. Ziaur Rahman; Basith, Mohammed Abdul

    2017-10-01

    Accurate determination of a material's optical band gap lies in the precise measurement of its absorption coefficients, either from its absorbance via the Beer-Lambert law or diffuse reflectance spectrum via the Kubelka-Munk function. Absorption coefficients of powder-form nanomaterials calculated from absorbance spectrum do not match those calculated from diffuse reflectance spectrum, implying the inaccuracy of the traditional optical band gap measurement method for such samples. We have modified the Beer-Lambert law and the Kubelka-Munk function with proper approximations for powder-form nanomaterials. Applying the modified method for powder-form nanomaterial samples, both absorbance and diffuse reflectance spectra yield exactly the same absorption coefficients and therefore accurately determine the optical band gap.

  3. Design of a five-band terahertz perfect metamaterial absorber using two resonators

    Science.gov (United States)

    Meng, Tianhua; Hu, Dan; Zhu, Qiaofen

    2018-05-01

    We present a polarization-insensitive five-band terahertz perfect metamaterial absorber composed of two metallic circular rings and a metallic ground film separated by a dielectric layer. The calculated results show that the absorber has five distinctive absorption bands whose peaks are greater than 99% on average. The physical origin of the absorber originates from the combination of dipolar, hexapolar, and surface plasmon resonance of the patterned metallic structure, which is different from the work mechanism of previously reported absorbers. In addition, the influence of the structural parameters on the absorption spectra is analyzed to further confirm the origin of the five-band absorption peaks. The proposed absorber has potential applications in terahertz imaging, refractive index sensing, and material detecting.

  4. Nature of the fundamental band gap in GaNxP1-x alloys

    International Nuclear Information System (INIS)

    Shan, W.; Walukiewicz, W.; Yu, K. M.; Wu, J.; Ager, J. W. III; Haller, E. E.; Xin, H. P.; Tu, C. W.

    2000-01-01

    The optical properties of GaN x P 1-x alloys (0.007≤x≤0.031) grown by gas-source molecular-beam epitaxy have been studied. An absorption edge appears in GaN x P 1-x at energy below the indirect Γ V -X C transition in GaP, and the absorption edge shifts to lower energy with increasing N concentration. Strong photomodulation signals associated with the absorption edges in GaN x P 1-x indicate that a direct fundamental optical transition is taking place, revealing that the fundamental band gap has changed from indirect to direct. This N-induced transformation from indirect to direct band gap is explained in terms of an interaction between the highly localized nitrogen states and the extended states at the Γ conduction-band minimum. (c) 2000 American Institute of Physics

  5. Photoionization-driven Absorption-line Variability in Balmer Absorption Line Quasar LBQS 1206+1052

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Luming; Zhou, Hongyan; Ji, Tuo; Jiang, Peng; Liu, Bo; Pan, Xiang; Shi, Xiheng; Zhang, Shaohua [Polar Research Institute of China, 451 Jinqiao Road, Shanghai (China); Liu, Wenjuan; Wang, Jianguo [Yunnan Observatories, Chinese Academy of Sciences, Kunming, Yunnan (China); Wang, Tinggui; Yang, Chenwei [Department of Astronomy, University of Science and Technology of China, 96 Jinzhai Road, Hefei, Anhui (China); Miller, Lauren P., E-mail: lmsun@mail.ustc.edu.cn [Lehigh University, 27 Memorial Drive West, Bethlehem, PA 18015 (United States)

    2017-04-01

    In this paper we present an analysis of absorption-line variability in mini-BAL quasar LBQS 1206+1052. The Sloan Digital Sky Survey spectrum demonstrates that the absorption troughs can be divided into two components of blueshift velocities of ∼700 and ∼1400 km s{sup −1} relative to the quasar rest frame. The former component shows rare Balmer absorption, which is an indicator of high-density absorbing gas; thus, the quasar is worth follow-up spectroscopic observations. Our follow-up optical and near-infrared spectra using MMT, YFOSC, TSpec, and DBSP reveal that the strengths of the absorption lines vary for both components, while the velocities do not change. We reproduce all of the spectral data by assuming that only the ionization state of the absorbing gas is variable and that all other physical properties are invariable. The variation of ionization is consistent with the variation of optical continuum from the V -band light curve. Additionally, we cannot interpret the data by assuming that the variability is due to a movement of the absorbing gas. Therefore, our analysis strongly indicates that the absorption-line variability in LBQS 1206+1052 is photoionization driven. As shown from photoionization simulations, the absorbing gas with blueshift velocity of ∼700 km s{sup −1} has a density in the range of 10{sup 9} to 10{sup 10} cm{sup −3} and a distance of ∼1 pc, and the gas with blueshift velocity of ∼1400 km s{sup −1} has a density of 10{sup 3} cm{sup −3} and a distance of ∼1 kpc.

  6. Absorption and luminescence of crystalline quartz under electron nanosecond irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Gritsenko, B P; Lisitsyn, V M; Stepanchuk, V N [Tomskij Politekhnicheskij Inst. (USSR)

    1981-02-01

    The purpose of the study is continuation of investigations of principal regularities of production and destruction of short-lived defects in quartz and accompanying luminescence under electron pulse irradiation. For investigation purposes samples of crystalline synthetic quartz have been used. The irradiation has been performed at 80-400 K temperatures by means of an electron pulse accelerator with parameters: electron flow pulse duration 10 ns, pulse current density up to 1000 A/cm/sup 2/, electron mean energy 200 keV. Temperature-time characteristics of absorption and luminescence spectrum are studied. It has been found that quartz irradiation by electron pulses of nanosecond duration leads to appearance of short-lived bands of optical absorption at 4.1 and 5.15 eV to which by kinetic parameters correspond luminescence bands at 2.6 and 3.1 eV, respectively. The enumerated absorption bands are induced by quartz irradiation independently of the prehistory and phase state of the sample and are caused obviously by intrinsic radiation defects. Possible models of such defects are suggested.

  7. Metamaterials for perfect absorption

    CERN Document Server

    Lee, Young Pak; Yoo, Young Joon; Kim, Ki Won

    2016-01-01

    This book provides a comprehensive overview of the theory and practical development of metamaterial-based perfect absorbers (MMPAs). It begins with a brief history of MMPAs which reviews the various theoretical and experimental milestones in their development. The theoretical background and fundamental working principles of MMPAs are then discussed, providing the necessary background on how MMPAs work and are constructed. There then follows a section describing how different MMPAs are designed and built according to the operating frequency of the electromagnetic wave, and how their behavior is changed. Methods of fabricating and characterizing MMPAs are then presented. The book elaborates on the performance and characteristics of MMPAs, including electromagnetically-induced transparency (EIT). It also covers recent advances in MMPAs and their applications, including multi-band, broadband, tunability, polarization independence and incidence independence. Suitable for graduate students in optical sciences and e...

  8. Report from the banding lab

    Science.gov (United States)

    Tautin, J.

    1995-01-01

    Mr. Tautin reported on the seemingly everchanging structure of biological science units within the Interior Department. Current Congressional proposals would either change the name of the Bird Banding Lab's parent agency or make it part of the Geological Survey. The current Congress has not looked favorably on science budgets within the Interior Department, and the Banding Lab's budget is being squeezed ever tighter.

  9. Electron paramagnetic resonance and optical absorption study of V{sup 4+} centres in YVO{sub 4} crystals

    Energy Technology Data Exchange (ETDEWEB)

    Garces, N Y [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States); Stevens, K T [Northrop Grumman Space Technology, Synoptics, Charlotte, NC 28273 (United States); Foundos, G K [Northrop Grumman Space Technology, Synoptics, Charlotte, NC 28273 (United States); Halliburton, L E [Department of Physics, West Virginia University, Morgantown, WV 26506 (United States)

    2004-10-06

    Electron paramagnetic resonance (EPR) has been used to characterize three distinct V{sup 4+} centres in undoped Czochralski-grown yttrium orthovanadate (YVO{sub 4}) crystals. These EPR signals are observed at low temperatures, and their average c-axis splittings between adjacent {sup 51}V hyperfine lines are 40 G, 123 G, and 140 G. We refer to these centres as [V{sup 4+}]{sub A}, [V{sup 4+}]{sub B}, and [V{sup 4+}]{sub C}, respectively. The [V{sup 4+}]{sub A} and [V{sup 4+}]{sub B} centres are present in as-grown crystals. Exposure at 77 K to ionizing radiation (x-rays or an ultraviolet laser beam) destroys these centres and creates the [V{sup 4+}]{sub C} centres. The as-grown state of the crystal is restored upon returning to room temperature. Angular dependence data are used to determine the principal values and principal directions of the g tensor and the {sup 51}V hyperfine tensor for each of the centres. We suggest that the [V{sup 4+}]{sub A} centre is a V{sup 4+} ion adjacent to an oxygen vacancy and that the [V{sup 4+}]{sub B} centre is a V{sup 4+} ion substituting for a Y{sup 3+} ion (i.e. a vanadium antisite defect). The [V{sup 4+}]{sub C} centre is assigned to a V{sup 4+} ion at a regular vanadium site with a nearby stabilizing defect, possibly a Zr{sup 4+} on a Y{sup 3+} site. In as-grown crystals, there is a correlation between the number of [V{sup 4+}]{sub A} centres and the intensity (at 380 nm) of a broad near-edge optical absorption band. This band, now associated with oxygen vacancies, gives YVO{sub 4} a 'yellow' appearance.

  10. Blood oxygen saturation determined by transmission spectrophotometry of hemolyzed blood samples

    Science.gov (United States)

    Malik, W. M.

    1967-01-01

    Use of the Lambert-Beer Transmission Law determines blood oxygen saturation of hemolyzed blood samples. This simplified method is based on the difference in optical absorption properties of hemoglobin and oxyhemoglobin.

  11. Origin of the Enhanced Visible-Light Absorption in N-Doped Bulk Anatase TiO 2 from First-Principles Calculations

    KAUST Repository

    Harb, Moussab

    2011-10-06

    Extension of the absorption properties of TiO2 photocatalytic materials to the visible part of the solar spectrum is of major importance for energy and cleaning up applications. We carry out a systematic study of the N-doped anatase TiO2 material using spin-polarized density functional theory (DFT) and the range-separated hybrid HSE06 functional. The thermodynamic stability of competitive N-doped TiO2 structural configurations is studied as a function of the oxygen chemical potential and of various chemical doping agents: N2, (N2 + H2), NH3, N2H4. We show that the diamagnetic TiO (2-3x)N2x system corresponding to a separated substitutional N species (with 2-4% N impurities) and formation of one-half concentration of O vacancies (1-2 atom %) is an optimal configuration thermodynamically favored by NH3, N2H4, and (N2 + H2) chemical doping agents presenting a dual nitrating-reducing character. The simulated UV-vis absorption spectra using the perturbation theory (DFPT) approach demonstrates unambiguously that the diamagnetic TiO(2-3x)N2x system exhibits the enhanced optical absorption in N-doped TiO2 under visible-light irradiation. Electronic analysis further reveals a band gap narrowing of 0.6 eV induced by delocalized impurity states located at the top of the valence band of TiO 2. A fruitful comparison with experimental data is furnished. © 2011 American Chemical Society.

  12. Fluorescence and optical absorption in spodumene

    International Nuclear Information System (INIS)

    Antonini, R.

    1987-01-01

    This work studied the mechanism of the isothermal decay's kinetic of the 15.600 cm-1 optical absorption band (A.O.) of irradiated spodumene, and the phosphorescence of irradiated spodumene in low temperatures. The kinetic mechanisms applying the bimolecular model to liberation, capture and recombination reactions are analysed. The coupled differential equations, resultants of this model, numerically using the Runge-Kutta method is solved, and a computer programs that allowed determine the kinetics parameters by try and error methods is developped. This work showed that the electrons are untrapped according to Arrhernios kinetic and that the parameters of the trap and recombination are proportional to a factor (√T - √T o ), where T o is the cutting temperature, bfore which the reactions do not occur. (author) [pt

  13. Non-linear absorption in solids

    International Nuclear Information System (INIS)

    Brandi, H.S.; Jalbert, G.; Malta, O.L.

    1983-01-01

    Multiphoton transitions in direct-gap crystals are studied considering a 'non-perturbative' approach, similar to Keldysh approximation. A simple two parabolic band model in the effective mass approximation is considered. So that exact solutions associated to the full, crystal plus field, Hamiltonian may be approximated by Volkov wavefunctions. An S-matrix which incorporates the electromagnetic field to all orders in an approximated way is constructed leading to analytical solutions for the multiphoton transition rates. The use of the saddle-point method and its limitations as well as the connection between multiphoton absorption and tunneling is discussed. It is shown that for near threshold excitations the Keldysh approach is fairly accurate as long as terms arising from the saddle-point integration are consistently accounted. (Author) [pt

  14. Non-linear absorption in solids

    International Nuclear Information System (INIS)

    Brandi, H.S.; Jalbert, G.; Malta, O.L.

    1983-06-01

    Multiphoton transitions in direct-gap crystals are studied considering a 'non-perturbative' approach, similar to Keldysh approximation. A simple two parabolic band model in the effective mass approximation is considered, so that exact solutions associate to the full, crystal plus field, Hamiltonian may be approximated by Volkov wavefunctions. In this manner an S matrix is constructed which incorporates the electromagnetic field to all orders in an approximated way, leading to analytical solutions for the multiphoton transition rates. The use of the saddle point method and its limitations as well as the connection between multiphoton absorption and tunneling is discussed. It is shown that the Keldysh approach is fairly accurate as long as terms arising from the saddle point integration are consistently accounted. (Author) [pt

  15. Influence of oxygen partial pressure on defect concentrations and on oxygen diffusion in UO2+x

    International Nuclear Information System (INIS)

    Pizzi, Elisabetta

    2013-01-01

    The hyper-stoichiometric uranium dioxide (UO 2+x ) is stable over a wide range of temperature and compositions. Such variations of composition and the eventual presence of doping elements or impurities lead to a variation of anionic and electronic defect concentrations. Moreover, many properties of this material are affected by its composition modifications, in particular their atomic transport properties. Firstly we developed a point defect model to evaluate the dependence of the electronic and oxygen defect concentrations upon temperature, equilibrium oxygen partial pressure and impurity content. The physical constants of the model, in particular the equilibrium constants of the defect formation reactions were determined from deviation from stoichiometry and electrical conductivity measurements of literature. This work enabled us to interpret our measures of conductivity, oxygen chemical and self- diffusion coefficients. From a quantitative standpoint, the analysis of our experimental results allows to evaluate the oxygen interstitial diffusion coefficient but also its formation energy. Moreover, an estimate of oxygen di-interstitial formation energy is also provided. Presence of oxygen clusters leads oxygen self- and chemical diffusion to decrease. X-ray Absorption Spectroscopy characterization shows the presence of the same defect in the entire deviation from stoichiometry studied, confirming the approach used to develop the model. (author) [fr

  16. Correlating oxygen vacancies and phase ratio/interface with efficient photocatalytic activity in mixed phase TiO2

    International Nuclear Information System (INIS)

    Verma, Ranjana; Samdarshi, S.K.

    2015-01-01

    Graphical abstract: The correlation of interfacial behavior and oxygen vacancies in mixed phase titania nanoparticles on their performance as photocatalyst has been investigated to explain the impact of photoactivity under UV and visible irradiation compared to pristine counterparts. The defects at the junction effectively reduce the band gap as well decrease the carrier recombination to enhance the photocatalytic activity. - Highlights: • Pristine and mixed phases (A/R ratio) TiO 2 synthesized by sol gel route. • Photoactivity variation has been correlated with the changes in the phase ratio. • Enhanced UV and visible activity attributable to oxygen vacancy present at the interface. • Role of A/R ratio and oxygen vacancy in the photoactivity of mixed TiO 2 depicted through a model. - Abstract: The photocatalytic activity is a result of the synergy of a succession of phenomena-photogeneration, separation, and participation of the charge carriers in redox reaction at the catalyst surface. While the extent of photogeneration is assessable in terms of absorption spectrum (band gap), the redox reaction can be correlated to specific surface area. However the respective change in the photocatalytic activity has not been rationally and consistently correlated with the above mentioned parameters. A satisfactory explanation of suppression of recombination based on separation of carriers due to differential mobility/diffusivity in the material phase(s) and/or intrinsic potential barrier exists but its correlation with common identifiable parameter/characteristics is still elusive. This paper attempts to address this issue by correlating the carrier separation with the phase ratio (phase interface) in mixed phase titania and generalizing it with the presence of oxygen vacancy at the phase interface. It essentially appears to complete the quest for identifiable parameters in the sequence of phenomena, which endow a photocatalyst with an efficient activity level. It has

  17. Atomic absorption spectrophotometry in perspective

    International Nuclear Information System (INIS)

    Soffiantini, V.

    1981-01-01

    Atomic absorption spectrophotometry is essentially an analytical technique used for quantitative trace metal analysis in a variety of materials. The speed and specificity of the technique is its greatest advantage over other analytical techniques. What atomic absorption spectrophotometry can and cannot do and its advantages and disadvantages are discussed, a summary of operating instructions are given, as well as a summary of analytical interferences. The applications of atomic absorption spectrophotometry are also shortly discussed

  18. Nonlinear effects in collective absorption

    International Nuclear Information System (INIS)

    Uenoyama, Takeshi; Mima, Kunioki; Watanabe, Tsuguhiro.

    1981-01-01

    The collective absorption of high intensity laser radiation is analyzed numerically. Density profile modification due to the ponderomotive force associating laser radiation and the excited electron plasma waves is self-consistently taken into account, and the intensity dependences of the absorption efficiency are obtained. In the high intensity regime, the absorption efficiency is found to be strongly enhanced in the plasma without flow, but reduced with supersonic flow. (author)

  19. Dual-band infrared camera

    Science.gov (United States)

    Vogel, H.; Schlemmer, H.

    2005-10-01

    Every year, numerous accidents happen on European roads due to bad visibility (fog, night, heavy rain). Similarly, the dramatic aviation accidents of year 2001 in Milan and Zurich have reminded us that aviation safety is equally affected by reduced visibility. A dual-band thermal imager was developed in order to raise human situation awareness under conditions of reduced visibility especially in the automotive and aeronautical context but also for all transportation or surveillance tasks. The chosen wavelength bands are the Short Wave Infrared SWIR and the Long Wave Infrared LWIR band which are less obscured by reduced visibility conditions than the visible band. Furthermore, our field tests clearly show that the two different spectral bands very often contain complementary information. Pyramidal fusion is used to integrate complementary and redundant features of the multi-spectral images into a fused image which can be displayed on a monitor to provide more and better information for the driver or pilot.

  20. Detection Range Estimation of UV Spectral Band Laser Radar

    Directory of Open Access Journals (Sweden)

    V. A. Gorodnichev

    2014-01-01

    Full Text Available Recently, has come into existence an interest in the systems operating in the ultra-violet (UF band of wavelengths, which use other spectral information (coefficients of reflection or radiation in UF range about location objects, than laser systems in the visible, near or average infrared bands. Thus, a point is not only to receive additional (in another spectral range information on location objects. Laser radiation in the UF spectral band of 0.315 – 0.4 microns is safer than laser radiation with the wavelengths of 0.38 – 1.4 microns.The work presents a comparative estimation of the detection systems range of laser radars in the UV and visible spectral bands for the following wavelengths of radiation:- UF band: 0.266 microns (the fourth harmonic of YAG-laser activated by neodymium ions, 0.308 microns (the XeCl-excimer laser, 0.355 microns (the third harmonic of YAG-laser activated by neodymium ions;- visible band: 0.532 microns (the second harmonic of YAG-laser activated by neodymium ions.Results of calculations show that for the horizontal pathway in the terrestrial atmosphere at the selected radiation wavelengths a detection range is in the range of 2510m – 5690 m.The maximum range of detection corresponds to the visible spectral band. A sweep range decreases with transition to the UF band. This is caused by the fact that with transition to the UF band there is a rise of atmosphere attenuation (generally, because of absorption by ozone, this effect being smoothed by reducing background radiation.In the UF band a wavelength of 0.355 microns is the most acceptable. For this wavelength a detection range is about 1,5 times less (in comparison with the visible band of 0.532 microns. However, this is the much more eye-safe wavelength. With transition to the UV band a detection range decreases not that much and can be compensated by changing parameters of transmitting or receiving channels of laser radar.

  1. Femtosecond laser irradiation-induced infrared absorption on silicon surfaces

    Directory of Open Access Journals (Sweden)

    Qinghua Zhu

    2015-04-01

    Full Text Available The near-infrared (NIR absorption below band gap energy of crystalline silicon is significantly increased after the silicon is irradiated with femtosecond laser pulses at a simple experimental condition. The absorption increase in the NIR range primarily depends on the femtosecond laser pulse energy, pulse number, and pulse duration. The Raman spectroscopy analysis shows that after the laser irradiation, the silicon surface consists of silicon nanostructure and amorphous silicon. The femtosecond laser irradiation leads to the formation of a composite of nanocrystalline, amorphous, and the crystal silicon substrate surface with microstructures. The composite has an optical absorption enhancement at visible wavelengths as well as at NIR wavelength. The composite may be useful for an NIR detector, for example, for gas sensing because of its large surface area.

  2. Defects and the optical absorption in nanocrystalline ZnO

    International Nuclear Information System (INIS)

    Dutta, Sreetama; Chattopadhyay, Sanjay; Sutradhar, Manas; Sarkar, Anindya; Chakrabarti, Mahuya; Sanyal, Dirtha; Jana, Debnarayan

    2007-01-01

    The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO

  3. Defects and the optical absorption in nanocrystalline ZnO

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Sreetama [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chattopadhyay, Sanjay [Department of Physics, Taki Government College, Taki 743429 (India); Sutradhar, Manas [Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Sarkar, Anindya [Department of Physics, Bangabasi Morning College, 19 Rajkumar Chakraborty Sarani, Kolkata 700 009 (India); Chakrabarti, Mahuya [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700 064 (India); Sanyal, Dirtha [Variable Energy Cyclotron Centre, 1/AF, Bidhannagar, Kolkata 700 064 (India); Jana, Debnarayan [Department of Physics, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009 (India)

    2007-06-13

    The correlation between the structural and optical properties of mechanically milled high purity ZnO powder is reported in the present work. Reduction of average grain size and enhancement of strain as a result of milling have been estimated from the broadening of x-ray powder diffraction patterns. After milling, the optical bandgap, revealed from absorption spectroscopy, has been red-shifted and the width of the localized states, calculated from the analysis of the Urbach tail below the absorption edge, has been extended more and more into the bandgap. Moreover, the band tailing parameter is seen to vary exponentially with the inverse of the grain size. Finally, the positron annihilation technique has been employed to identify the nature of defects present (or generated due to milling) in the system and thereby to correlate the defect mediated modification of optical absorption in ZnO.

  4. Backscatter absorption gas imaging systems and light sources therefore

    Science.gov (United States)

    Kulp, Thomas Jan [Livermore, CA; Kliner, Dahv A. V. [San Ramon, CA; Sommers, Ricky [Oakley, CA; Goers, Uta-Barbara [Campbell, NY; Armstrong, Karla M [Livermore, CA

    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.

  5. Comparative study of five varieties of spodumene through optical absorption

    International Nuclear Information System (INIS)

    Fujii, A.T.; Isotani, S.

    1983-11-01

    A comparative study of five varieties of spodumene crystals from Brazil through optical absorption spectroscopy, classified according to the colours lylac, colourless I, colourless II, yellow and green is reported. This series shows a consistent increase of the [Fe]/[Mn] ratio. The principal bands in the yellow sample are at 7,000 and 9,000 cm -1 , and in the green sample besides these bands a band at 16,000 cm -1 is observed. In lylac, colourless I and colourless II samples, the principal bands are at 18,000 cm -1 and when irradiated two new bands appears at 15,700 cm -1 (E perpendicular to c) and 11,000 cm -1 (K perpendicular to c). It is suggested that in green and yellow samples the bands are due to Fe 2+ (at 7,000 cm -1 and 9,000 cm -1 ) and due to Fe 2+ - Fe 3+ charge transfer (at 16,000 cm -1 ). In lylac and colourless I samples the model for Mn 3+ at two different sites is applied. The colourless II corresponds to the case in which Mn 3+ is at one site alone, being prohibited from occupying the second site due to higher Fe concentration. (Author) [pt

  6. Broadening microwave absorption via a multi-domain structure

    Directory of Open Access Journals (Sweden)

    Zhengwang Liu

    2017-04-01

    Full Text Available Materials with a high saturation magnetization have gained increasing attention in the field of microwave absorption; therefore, the magnetization value depends on the magnetic configuration inside them. However, the broad-band absorption in the range of microwave frequency (2-18 GHz is a great challenge. Herein, the three-dimensional (3D Fe/C hollow microspheres are constructed by iron nanocrystals permeating inside carbon matrix with a saturation magnetization of 340 emu/g, which is 1.55 times as that of bulk Fe, unexpectedly. Electron tomography, electron holography, and Lorentz transmission electron microscopy imaging provide the powerful testimony about Fe/C interpenetration and multi-domain state constructed by vortex and stripe domains. Benefiting from the unique chemical and magnetic microstructures, the microwave minimum absorption is as strong as −55 dB and the bandwidth (<−10 dB spans 12.5 GHz ranging from 5.5 to 18 GHz. Morphology and distribution of magnetic nano-domains can be facilely regulated by a controllable reduction sintering under H2/Ar gas and an optimized temperature over 450–850 °C. The findings might shed new light on the synthesis strategies of the materials with the broad-band frequency and understanding the association between multi-domain coupling and microwave absorption performance.

  7. X-ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Junko; Yachandra, Vittal K.

    2009-07-09

    This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn4Ca cluster in Photosystem II is presented.

  8. Study of oxygen scavenging PET-based films activated by water

    Energy Technology Data Exchange (ETDEWEB)

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana [Department of Industrial Engineering, University of Salerno Via Giovanni Paolo II, 132 - 84084 Fisciano (Italy)

    2016-05-18

    In this work an active barrier system consisting of a thin and transparent film based on polyethylene terephthalate (PET) was studied. Dynamic oxygen absorption measurements were performed at different values of relative humidity and temperature, pointing out that humidity is a key factor in activating the oxidation of the polymer sample. Moreover, the thermal and optical properties of the films were investigated and a good correlation was found between the crystallinity increase and the consequent transparency reduction occurring after the oxygen absorption.

  9. Study of oxygen scavenging PET-based films activated by water

    Science.gov (United States)

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana

    2016-05-01

    In this work an active barrier system consisting of a thin and transparent film based on polyethylene terephthalate (PET) was studied. Dynamic oxygen absorption measurements were performed at different values of relative humidity and temperature, pointing out that humidity is a key factor in activating the oxidation of the polymer sample. Moreover, the thermal and optical properties of the films were investigated and a good correlation was found between the crystallinity increase and the consequent transparency reduction occurring after the oxygen absorption.

  10. CdSe/CdTe interface band gaps and band offsets calculated using spin-orbit and self-energy corrections

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, M. [Centro de Pesquisas Avancadas Wernher von Braun, Av. Alice de Castro P.N. Mattosinho 301, CEP 13098-392 Campinas, SP (Brazil); Ferreira, L.G. [Departamento de Fisica dos Materiais e Mecanica, Instituto de Fisica, Universidade de Sao Paulo, 05315-970 Sao Paulo, SP (Brazil); Fonseca, L.R.C. [Center for Semiconductor Components, State University of Campinas, R. Pandia Calogeras 90, 13083-870 Campinas, SP (Brazil); Ramprasad, R. [Department of Chemical, Materials and Biomolecular Engineering, Institute of Materials Science, University of Connecticut, 97 North Eagleville Road, Storrs, CT 06269 (United States)

    2012-09-20

    We performed ab initio calculations of the electronic structures of bulk CdSe and CdTe, and their interface band alignments on the CdSe in-plane lattice parameters. For this, we employed the LDA-1/2 self-energy correction scheme to obtain corrected band gaps and band offsets. Our calculations include the spin-orbit effects for the bulk cases, which have shown to be of importance for the equilibrium systems and are possibly degraded in these strained semiconductors. Therefore, the SO showed reduced importance for the band alignment of this particular system. Moreover, the electronic structure calculated along the transition region across the CdSe/CdTe interface shows an interesting non-monotonic variation of the band gap in the range 0.8-1.8 eV, which may enhance the absorption of light for corresponding frequencies at the interface between these two materials in photovoltaic applications.

  11. Satellite bands of the RbCs molecule in the range of highly excited states

    Energy Technology Data Exchange (ETDEWEB)

    Rakić, Mario; Beuc, Robert; Skenderović, Hrvoje, E-mail: hrvoje@ifs.hr [Institute of Physics, Bijenička cesta 46, Zagreb 10000 (Croatia); Bouloufa-Maafa, Nadia; Dulieu, Olivier; Vexiau, Romain [Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Cachan, Université Paris-Saclay, Bât. 505, Campus d’Orsay, Orsay Cedex 91405 (France); Pichler, Goran [Physics Department, Kuwait University, PO Box 5969, Safat—13060 (Kuwait)

    2016-05-28

    We report on the observation of three RbCs satellite bands in the blue and green ranges of the visible spectrum. Absorption measurements are performed using all-sapphire cell filled with a mixture of Rb and Cs. We compare high resolution absorption spectrum of Rb-Cs vapor mixture with pure Rb and Cs vapor spectra from the literature. After detailed analysis, the new satellite bands of RbCs molecule at 418.3 nm, 468.3, and 527.5 nm are identified. The origin of these bands is discussed by direct comparison with difference potentials derived from quantum chemistry calculations of RbCs potential energy curves. These bands originate from the lower Rydberg states of the RbCs molecule. This study thus provides further insight into photoassociation of lower Rydberg molecular states, approximately between Cs(7s) + Rb(5s) and Cs(6s) + Rb(6p) asymptotes, in ultracold gases.

  12. Galactic absorption line coronae

    International Nuclear Information System (INIS)

    Bregman, J.N.

    1981-01-01

    We have investigated whether gaseous coronae around galaxies rise to the absorption systems seen in quasar spectra. In our model, gas originally located in the disk is heated to the million degree range and rises to surround the galaxy; the gas remains bound to the galaxy. Optically thin radiative cooling drives a thermal instability in the hot gas which causes cool clouds (T 4 K) to condense out of the corona. These clouds, which follow ballistic trajectories back to the disk, are the absorption sites. A two-dimensional hydrodynamic code with radiative cooling was used to study the dynamics and thermodynamics of the corona as well as the position rate at which clouds form. Coupled to the code is a galaxy with two mass components, a disk (approx.10 11 M/sub sun/) and a dark halo (approx.10 12 M/sub sun/). In a model where the temperature at the base of the corona (in the disk) is 3 x 10 6 K, absorbing gas of column density NL> or approx. =10 18 cm 2 extends radially to 100 kpc (face-on orientation) and vertically to 60 Kpc (edge-on orientation). The total mass of gas required here (coronal plus cloud gas) is 1.4 x 10 10 M/sub sun/, while the minimum supernova heating rate is one supernova per 27 years. In two other models (base coronal temperatures of 0.50 x 10 6 K and 1 x 10 6 K), coronal gas rises from an extended gaseous disk (in the previous model, the gas comes from a typical gaseous disk approximately 15 kpc in extent). Here, column densities of 10 19 cm -2 out to a radius of 70 kpc (face-on orientation) are achieved with a total gas mass of 1.7 x 10 9 M/sub direct-product/ and 2.0 x 10 9 M/sub sun/ and minimum heating rates of approximately one supernova per 170 years and one supernova per 60 years

  13. Non-invasive multiwavelength photoplethysmography under low partial pressure of oxygen.

    Science.gov (United States)

    Fang, Yung Chieh; Tai, Cheng-Chi

    2016-08-01

    A reduction in partial pressure of oxygen in the environment may be caused by a gain in altitude, which reduces the atmospheric pressure; it may also be caused by the carbon dioxide generated from breathing in an enclosed space. Does inhaling oxygen of lower partial pressure affect the oxygen-carrying function of haemoglobin in vivo? This study uses non-invasive multiwavelength photoplethysmography to measure the effects that inhaling this type of oxygen can have on the plethysmography of the appendages of the body (fingertips). The results indicate that under low partial pressure of oxygen, be it the result of a gain in carbon dioxide concentration or altitude, the change in visible light absorption is the biggest for short wavelengths (approximately 620 or 640 nm) near deoxyhaemoglobin, which has higher absorption coefficient. Moreover, increasing carbon dioxide concentration from 5000 to 10,000 ppm doubly reduces the absorption rate of these short wavelengths.

  14. SINGLE-BAND, TRIPLE-BAND, OR MULTIPLE-BAND HUBBARD MODELS

    NARCIS (Netherlands)

    ESKES, H; SAWATZKY, GA

    1991-01-01

    The relevance of different models, such as the one-band t-J model and the three-band Emery model, as a realistic description of the electronic structure of high-T(c) materials is discussed. Starting from a multiband approach using cluster calculations and an impurity approach, the following

  15. Solar Absorptance of Cermet Coatings Evaluated

    Science.gov (United States)

    Jaworske, Donald A.

    2004-01-01

    Cermet coatings, molecular mixtures of metal and ceramic, are being considered for the heat inlet surface of solar Stirling convertors. In this application, the key role of the cermet coating is to absorb as much of the incident solar energy as possible. To achieve this objective, the cermet coating has a high solar absorptance value. Cermet coatings are manufactured utilizing sputter deposition, and many different metal and ceramic combinations can be created. The ability to mix metal and ceramic at the atomic level offers the opportunity to tailor the composition, and hence, the optical properties of these coatings. The NASA Glenn Research Center has prepared and characterized a wide variety of cermet coatings utilizing different metals deposited in an aluminum oxide ceramic matrix. In addition, the atomic oxygen durability of these coatings has been evaluated.

  16. Integrated turbomachine oxygen plant

    Science.gov (United States)

    Anand, Ashok Kumar; DePuy, Richard Anthony; Muthaiah, Veerappan

    2014-06-17

    An integrated turbomachine oxygen plant includes a turbomachine and an air separation unit. One or more compressor pathways flow compressed air from a compressor through one or more of a combustor and a turbine expander to cool the combustor and/or the turbine expander. An air separation unit is operably connected to the one or more compressor pathways and is configured to separate the compressed air into oxygen and oxygen-depleted air. A method of air separation in an integrated turbomachine oxygen plant includes compressing a flow of air in a compressor of a turbomachine. The compressed flow of air is flowed through one or more of a combustor and a turbine expander of the turbomachine to cool the combustor and/or the turbine expander. The compressed flow of air is directed to an air separation unit and is separated into oxygen and oxygen-depleted air.

  17. Ambient oxygen promotes tumorigenesis.

    Directory of Open Access Journals (Sweden)

    Ho Joong Sung

    2011-05-01

    Full Text Available Oxygen serves as an essential factor for oxidative stress, and it has been shown to be a mutagen in bacteria. While it is well established that ambient oxygen can also cause genomic instability in cultured mammalian cells, its effect on de novo tumorigenesis at the organismal level is unclear. Herein, by decreasing ambient oxygen exposure, we report a ∼50% increase in the median tumor-free survival time of p53-/- mice. In the thymus, reducing oxygen exposure decreased the levels of oxidative DNA damage and RAG recombinase, both of which are known to promote lymphomagenesis in p53-/- mice. Oxygen is further shown to be associated with genomic instability in two additional cancer models involving the APC tumor suppressor gene and chemical carcinogenesis. Together, these observations represent the first report directly testing the effect of ambient oxygen on de novo tumorigenesis and provide important physiologic evidence demonstrating its critical role in increasing genomic instability in vivo.

  18. Bulk band gaps in divalent hexaborides: A soft x-ray emission study

    International Nuclear Information System (INIS)

    Denlinger, Jonathan D.; Gweon, Gey-Hong; Allen, James W.; Bianchi, Andrea D.; Fisk, Zachary

    2001-01-01

    Boron K-edge soft x-ray emission and absorption are used to address the fundamental question of whether divalent hexaborides are intrinsic semimetals or defect-doped bandgap insulators. These bulk sensitive measurements, complementary and consistent with surface-sensitive angle-resolved photoemission experiments, confirm the existence of a bulk band gap and the location of the chemical potential at the bottom of the conduction band

  19. Wave energy absorption by ducks

    OpenAIRE

    Kurniawan, Adi

    2017-01-01

    We study the absorption of wave energy by a single and multiple cam-shaped bodies referred to as ducks. Numerical models are developed under the assumptions of linear theory. We consider wave absorption by a single duck as well as by two lines of ducks meeting at an angle.

  20. Wave energy absorption by ducks

    DEFF Research Database (Denmark)

    Kurniawan, Adi

    2018-01-01

    We study the absorption of wave energy by a single and multiple cam-shaped bodies referred to as ducks. Numerical models are developed under the assumptions of linear theory. We consider wave absorption by a single duck as well as by two lines of ducks meeting at an angle....