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Sample records for ev emission band

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  2. Electron impact study of the 100 eV emission cross section and lifetime of the Lyman-Birge-Hopfield band system of N2: Direct excitation and cascade

    NASA Astrophysics Data System (ADS)

    Ajello, J. M.; Malone, C. P.; Holsclaw, G. M.; Hoskins, A. C.; Eastes, R. W.; McClintock, W. E.; Johnson, P. V.

    2017-06-01

    We have measured the 100 eV emission cross section of the optically forbidden Lyman-Birge-Hopfield (LBH) band system (a1Πg → X1Σ+g) of N2 by electron-impact-induced fluorescence. Using a large (1.5 m diameter) vacuum chamber housing an electron gun system and the Mars Atmosphere and Volatile EvolutioN mission Imaging Ultraviolet Spectrograph optical engineering model, we have obtained calibrated spectral measurements of the LBH band system from 115 to 175 nm over a range of lines of sight to capture all of the optical emissions. These measurements represent the first experiment to directly isolate in the laboratory single-scattering electron-impact-induced fluorescence from both direct excitation of the a1Πg state and cascading contributions to the a1Πg state (a'1Σ-u and w1Δu → a1Πg → X1Σ+g). The determination of the total LBH emission cross section is accomplished by measuring the entire cylindrical glow pattern of the metastable emission from electron impact by imaging lines of sight that measure the glow intensity from zero to 400 mm radial distance and calculating the ratio of the integrated intensity from the LBH glow pattern to that of a simultaneously observed optically allowed transition with a well-established cross section: NI 120.0 nm. The "direct" emission cross section of the a1Πg state at 100 eV was determined to be σemdir = (6.41 ± 1.3) × 10-18 cm2. An important observation from the glow pattern behavior is that the total (direct + cascading) emission cross section is pressure dependent due to collision-induced cascade transitions between close-lying electronic states.

  3. Electronic crosstalk in Terra MODIS thermal emissive bands

    NASA Astrophysics Data System (ADS)

    Sun, Junqiang; Madhavan, Sriharsha; Xiong, Xiaoxiong; Wang, Menghua

    2015-09-01

    The MODerate-resolution Imaging Spectroradiometer (MODIS) is a legacy Earth remote sensing instrument in the National Aeronautics and Space Administration (NASA) Earth Observing System (EOS). The first MODIS instrument was launched in December 1999 on board the Terra spacecraft. MODIS has 36 bands, among which bands 20-25 and bands 27-36 are thermal emissive bands covering a wavelength range from 3.7μm to 14.2μm. It has been found that there are severe contaminations in Terra bands 27-30 (6.7 μm - 9.73 μm) due to crosstalk of signals among themselves. The crosstalk effect induces strong striping artifacts in the Earth View (EV) images and causes large long-term drifts in the EV brightness temperature (BT) in these bands. An algorithm using a linear approximation derived from on-orbit lunar observations has been developed to correct the crosstalk effect for them. It was demonstrated that the crosstalk correction can substantially reduce the striping noise in the EV images and significantly remove the long-term drifts in the EV BT in the Long Wave InfraRed (LWIR) water vapor channels (bands 27-28). In this paper, the crosstalk correction algorithm previously developed is applied to correct the crosstalk effect in the remaining LWIR bands 29 and 30. The crosstalk correction successfully reduces the striping artifact in the EV images and removes long-term drifts in the EV BT in bands 29-30 as was done similarly for bands 27-28. The crosstalk correction algorithm can thus substantially improve both the image quality and the radiometric accuracy of the Level 1B (L1B) products of the LWIR PV bands, bands 27-30. From this study it is also understood that other Terra MODIS thermal emissive bands are contaminated by the crosstalk effect and that the algorithm can be applied to these bands for crosstalk correction.

  4. Origin of the -4.4 eV band in CdTe(100)

    NASA Astrophysics Data System (ADS)

    Olguín, D.; Baquero, R.

    1994-07-01

    We calculate the bulk (infinite system), (100)-bulk-projected and (100)-surface-projected Green's functions using the surface-Green's-function matching method and an empirical tight-binding Hamiltonian with tight-binding parameters that describe well the bulk band structure of CdTe. In particular, we analyze the band (B-4) arising at -4.4 eV from the top of the valence band at Γ according to the results of Niles and Höchst and at -4.6 eV according to Gawlik et al., both obtained by angle-resolved photoelectron spectroscopy. We give a theoretical description of this band.

  5. Diffuse Interstellar Bands in Emission

    NASA Astrophysics Data System (ADS)

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

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

  6. Electron-impact excitation of the 31. 4-eV band in N sub 2

    SciTech Connect

    de Souza, G.G.B.; Bielschowsky, C.E.; Lucas, C.A.; Souza, A.C.A. )

    1990-08-01

    Generalized oscillator strengths (GOS) for the dipole-forbidden 31.4-eV band in N{sub 2} have been determined both experimentally and theoretically. The experimental values for the GOS were obtained using a crossed-beam electron spectrometer at 1-keV impact energy. The theoretical results were determined using the first Born approximation with {ital ab} {ital initio} configuration-interaction target wave functions.

  7. The origin of 2.7 eV luminescence and 5.2 eV excitation band in hafnium oxide

    SciTech Connect

    Perevalov, T. V.; Aliev, V. Sh.; Gritsenko, V. A.; Saraev, A. A.; Kaichev, V. V.; Ivanova, E. V.; Zamoryanskaya, M. V.

    2014-02-17

    The origin of a blue luminescence band at 2.7 eV and a luminescence excitation band at 5.2 eV of hafnia has been studied in stoichiometric and non-stoichiometric hafnium oxide films. Experimental and calculated results from the first principles valence band spectra showed that the stoichiometry violation leads to the formation of the peak density of states in the band gap caused by oxygen vacancies. Cathodoluminescence in the non-stoichiometric film exhibits a band at 2.65 eV that is excited at the energy of 5.2 eV. The optical absorption spectrum calculated for the cubic phase of HfO{sub 2} with oxygen vacancies shows a peak at 5.3 eV. Thus, it could be concluded that the blue luminescence band at 2.7 eV and HfO{sub x} excitation peak at 5.2 eV are due to oxygen vacancies. The thermal trap energy in hafnia was estimated.

  8. Periodic gamma-ray emissions from Geminga at or = 10(12) eV

    NASA Technical Reports Server (NTRS)

    Kaul, R. K.; Rawat, H. S.; Sanecha, V. K.; Rannot, R. C.; Sapru, M.; Tickoo, A. K.; Qazi, R. A.; Bhat, C. L.; Razdan, H.; Tonwar, S. C.

    1985-01-01

    Analysis of data from an atmospheric Cerenkov telescope indicated the periodic emission of gamma rays of energy 10 to the 12th power eV, at 60.25 second period, from 2CG 195+4. The gamma ray flux at 99% confidence level is estimated to be 9.5 x 10 to 12 photons/sq cm/s.

  9. An Interpretation of Banded Magnetospheric Radio Emissions

    NASA Technical Reports Server (NTRS)

    Benson, Robert F.; Osherovich, V. A.; Fainberg, J.; Vinas, A. F.; Ruppert, D. R.; Vondrak, Richard R. (Technical Monitor)

    2000-01-01

    Recently-published Active Magnetospheric Particle Tracer Explorer/Isothermal Remanent Magnetization (AMPTE/IRM) banded magnetospheric emissions, commonly referred to as '(n + 1/2)f(sub ce)' emissions where f(sub ce) is the electron gyrofrequency, are analyzed by treating them as analogous to sounder-stimulated ionospheric emissions. We show that both individual AMPTE/IRM spectra of magnetospheric banded emissions, and a statistically-derived spectra observed over the two-year lifetime of the mission, can be interpreted in a self-consistent manner. The analysis, which predicts all spectral peaks within 4% of the observed peaks, interprets the higher-frequency emissions as due to low group-velocity Bernstein-mode waves and the lower-frequency emissions as eigen modes of cylindrical-electromagnetic-plasma-oscillations. The demarcation between these two classes of emissions is the electron plasma frequency f(sub pe), where an emission is often observed. This f(sub pe), emission is not necessarily the strongest. None of the observed banded emissions were attributed to the upper-hybrid frequency. We present Alouette-2 and ISIS-1 plasma-resonance data, and model electron temperature (T(sub e)) values, to support the argument that the frequency-spectrum of ionospheric sounder-stimulated emissions is not strongly temperature dependent and thus that the interpretation of these emissions in the ionosphere is relevant to other plasmas (such as the magnetosphere) where N(sub e) and T(sub e) can be quite different but where the ratio f(sub pe)/f(sub ce) is identical.

  10. Experimental characterization of NIF hohlraum emission in the Rayleigh-Jeans limit (1 eV to 5 eV)

    NASA Astrophysics Data System (ADS)

    Moody, J. D.; Goyon, C. E.; Ross, J. S.; Swadling, G. F.; Moore, A. S.; Baker, K. L.; Thomas, C. A.; Schneider, M. B.; Landen, O. L.; Michel, P. A.; Strozzi, D. J.; Divol, L.; Widmann, K.

    2016-10-01

    We use several measurements to estimate NIF hohlraum emission in the Rayleigh-Jeans limit where hν <eV. The measurements are primarily optical, consisting of hohlraum emission which transmits through the capsule and is collected by an optical photodiode, optical emission emitted from the laser-entrance hole in the 4 eV range, and various other optical measurements. These measurements can help quantify the laser-plasma interaction processes occurring in the hohlraum and may provide insight into the atomic physics of the Au wall at long wavelength. We describe our findings and discuss interpretations. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  11. UNIDENTIFIED INFRARED EMISSION BANDS: PAHs or MAONs?

    SciTech Connect

    Sun Kwok; Yong Zhang

    2013-07-01

    We suggest that the carrier of the unidentified infrared emission (UIE) bands is an amorphous carbonaceous solid with mixed aromatic/aliphatic structures, rather than free-flying polycyclic aromatic hydrocarbon molecules. Through spectral fittings of the astronomical spectra of the UIE bands, we show that a significant amount of the energy is emitted by the aliphatic component, implying that aliphatic groups are an essential part of the chemical structure. Arguments in favor of an amorphous, solid-state structure rather than a gas-phase molecule as a carrier of the UIE are also presented.

  12. Coordinated EV adoption: double-digit reductions in emissions and fuel use for $40/vehicle-year.

    PubMed

    Choi, Dong Gu; Kreikebaum, Frank; Thomas, Valerie M; Divan, Deepak

    2013-09-17

    Adoption of electric vehicles (EVs) would affect the costs and sources of electricity and the United States efficiency requirements for conventional vehicles (CVs). We model EV adoption scenarios in each of six regions of the Eastern Interconnection, containing 70% of the United States population. We develop electricity system optimization models at the multidecade, day-ahead, and hour-ahead time scales, incorporating spatial wind energy modeling, endogenous modeling of CV efficiencies, projections for EV efficiencies, and projected CV and EV costs. We find two means to reduce total consumer expenditure (TCE): (i) controlling charge timing and (ii) unlinking the fuel economy regulations for CVs from EVs. Although EVs provide minimal direct GHG reductions, controlled charging provides load flexibility, lowering the cost of renewable electricity. Without EVs, a 33% renewable electricity standard (RES) would cost $193/vehicle-year more than the reference case (10% RES). Combining a 33% RES, EVs with controlled charging and unlinking would reduce combined electric- and vehicle-sector CO2 emissions by 27% and reduce gasoline consumption by 59% for $40/vehicle-year more than the reference case. Coordinating EV adoption with adoption of controlled charging, unlinked fuel economy regulations, and renewable electricity standards would provide low-cost reductions in emissions and fuel usage.

  13. The Unidentified Infrared Emission Bands: Identified

    NASA Technical Reports Server (NTRS)

    Hudgins, Douglas M.; Allamandola, Louis J.; Sandford, Scott A.; Goorvitch, David (Technical Monitor)

    1998-01-01

    The so-called Unidentified Infrared or simply UIR bands, the infrared emission band spectrum associated with a wide variety of interstellar objects, can be modeled in detail by laboratory spectra of neutral and positively charged polycyclic aromatic hydrocarbon (PAH) mixtures. Fits are presented for the UIR emission from the protoplanetary nebula IRAS 22272+5435, the diffuse galactic medium, and the Orion HII/photodissociation front - a selection of objects which span the evolutionary range of interstellar material. These data directly address the spectroscopic criticisms previously leveled at the PAH hypothesis and demonstrate that PAH-related molecular species are indeed responsible for this widespread emission. Furthermore, these fits reflect the structure, abundance, and ionization state of the interstellar PAHs and, in turn, provide direct insight into the processes of carbon nucleation, growth and evolution in circumstellar shells and the interstellar medium. To date, no other candidate material which has been proposed to account for the UIR emission can as readily and specifically reproduce these spectral variations. Given the ubiquity of these species, this work demonstrates the tremendous potential of these species as probes of a new and heretofore largely unexplored facet of astrochemistry - potential which should make PAHs the probe of the next millennium much as CO has been for the last quarter century.

  14. Fine Structure of Silicon Carbide Transition Bands in the Energy Range 4-35 eV

    NASA Astrophysics Data System (ADS)

    Sobolev, V. V.; Sobolev, V. Val.; Anisimov, D. V.

    2017-07-01

    The full spectral complex of optical functions of the 6H-SiC polytype was determined in the energy range 0-35 eV. Spectra of ɛ2( E), -Im ɛ-1, and -Im (1 + ɛ)-1 were deconvoluted into 15 simple bands, the main parameters of which, e.g., the energy maxima and oscillator strengths, were established. The calculations were based on the experimental reflectance spectrum and used the Kramers-Kronig relation and an improved nonparametric method of Argand diagrams.

  15. Fluorescence light emission at 1 eV from a conjugated polymer

    NASA Astrophysics Data System (ADS)

    Tzamalis, Georgios; Lemaur, Vincent; Karlsson, Fredrik; Holtz, Per Olof; Andersson, Mats; Crispin, Xavier; Cornil, Jérôme; Berggren, Magnus

    2010-04-01

    While polymer light-emitting diodes are currently finding commercial applications in displays and lighting, the development of low bandgap polymers emitting in the infrared has received much less attention in spite of potential applications for instance in the field of communication technologies. We report here a light emission at 1 eV from a low bandgap polymer made of an alternation of dialkoxy-phenylene units and a low bandgap monomer composed of an electron accepting 2-thia-1,3,5,8-tetraaza-cyclopenta[ b]naphthalene group fenced with electron donating thiophene units. The electronic structure of the polymer chains has been characterized at a quantum-chemical level to shed light into the experimental results.

  16. Polarization sensitivity of x-ray photocathodes in the 60-200eV band

    NASA Astrophysics Data System (ADS)

    Fraser, George W.; Pain, M. D.; Pearson, James F.; Lees, John E.; Binns, C. R.; Shaw, Ping S.; Fleischman, Judith R.

    1991-11-01

    In this paper, we briefly describe measurements of the 60 - 200 eV photoemission from Caesium Iodide, Gold, and Aluminum photocathodes made on beamline 6.1 of the SERC Daresbury synchrotron radiation source (SRS). Measurements were made near grazing incidence using both s- (electric vector perpendicular to the plane of incidence) and p- polarized (electric vector parallel to the plane of incidence) radiation. Our data supports the existence of an 'x-ray vectorial effect'--a pronounced linear polarization dependence of the photoyield--observed in earlier experiments at Leicester and Columbia Universities and elsewhere. For CsI, novel measurements are also reported of: radiation damage and annealing, and the temperature dependence of the photoyield.

  17. Magnetic Resonance Studies of the 3.0 eV PL Band in High-Resistivity GaN

    NASA Astrophysics Data System (ADS)

    Glaser, E. R.; Kennedy, T. A.; Freitas, J. A., Jr.; Wickenden, A. E.; Koleske, D. D.

    1997-03-01

    Optically-detected magnetic resonance (ODMR) experiments have been performed on the broad 3.0 eV PL band from high-resistivity (HR) GaN layers. This band has recently been assigned to strongly phonon-coupled distant DAP recombination involving three residual donors (Ed ~34, 54, and 57 meV) and residual acceptors (E_a ~116 meV).(U. Kaufmann et al., Mat. Res. Soc. Proc. Vol. 395, 619 (1996).) Two ODMR signals are found on this band. The first resonance is sharp (ΔB ~3.5 mT) with g ~1.950 and is assigned to EM donors with E_d ~34 meV based on previous observations.(E.R. Glaser et al., Phys. Rev. B 51, 13326 (1995).) The second feature is much broader (ΔB ~18 mT) with a donor-like g-value of ~ 1.977. Due to the larger degree of wavefunction localization inferred from this g-value, the resonance is tentatively assigned to the deeper donor states (partially EM-like) ~ 55 meV below the CB edge. Thus, these donors may be the source of the strong electron-phonon coupling. The acceptors (not observed in ODMR) with E_a ~116 meV may play a role as compensation centers and, hence, with the HR character of these films. Work supported by the Office of Naval Research.

  18. Evidence of donor-acceptor pair recombination from a new emission band in semiconducting diamond

    NASA Astrophysics Data System (ADS)

    Freitas, J. A., Jr.; Klein, P. B.; Collins, A. T.

    1994-04-01

    Presented in this paper are the results of steady state and time-resolved photoluminescence studies of a new red emission band, peaked near 1.84 eV, that was observed recently from boron-doped synthetic diamond grown at high temperature and high pressure. This new band is characterized by the known donor-acceptor pair recombination from distant pairs. Two synthetic type IIb samples were studied namely, SYNTH No. 1 and SYNTH No. 2 which were grown using Ni and Fe-Al as solvent catalyst, respectively.

  19. Evidence of Silicon Band-Edge Emission Enhancement When Interfaced with SiO2:Er Films

    NASA Astrophysics Data System (ADS)

    Abedrabbo, S.; Fiory, A. T.; Ravindra, N. M.

    2017-02-01

    Nearly two-orders of magnitude increase in room-temperature band-to-band (1.067 eV) infrared emission from crystalline silicon, coated with erbium-doped sol-gel films, have been achieved. Phonon-assisted band-to-band emission from coated and annealed p-Si is strongest for the sample annealed at 700°C. In this paper, evidence of the origin of the emission band from the band edge recombination activities is established. Enhancement of radiative recombination of free carriers is reasoned by stresses at the interface due to the annealed sol-gel-deposited silica. Comparative studies with other strained silicon samples are presented.

  20. NIF-scale re-emission sphere measurements of early-time Tr = 100 eV hohlraum symmetry (invited).

    PubMed

    Dewald, E L; Thomas, C; Milovich, J; Edwards, J; Sorce, C; Kirkwood, R; Meeker, D; Jones, O; Izumi, N; Landen, O L

    2008-10-01

    The indirect-drive National Ignition Campaign (NIC) proposes to set the first 2 ns of hohlraum radiation symmetry by observing the instantaneous soft x-ray re-emission pattern from a high-Z sphere in place of the ignition capsule. To assess this technique under NIC conditions, we used the Omega Laser Facility to image the re-emission of Bi coated spheres with 200 ps temporal, 50-100 microm spatial, and 30% spectral resolution. The sphere is driven by 70% NIC-scale vacuum Au hohlraums heated to Tr=100 eV using two cones per side laser beam illumination. The experiments have demonstrated the required accuracies of <3%P(2)/P(0) and <3%P(4)/P(0) Legendre mode flux asymmetry at both 900 and 1200 eV re-emission photon energies. The re-emission patterns at 900 and 1200 eV are also consistent with each other and their relative dependence on radiation temperature. We measured the P(2)/P(0) and P(4)/P(0) dependence to laser cone power ratio. View factor calculations are in agreement with the experimentally measured radiation flux and re-emit images when assuming 55% inner beam and 100 % outer beam coupling into x rays at the hohlraum wall.

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

    NASA Astrophysics Data System (ADS)

    Ummer, Karikkuzhi Variyath; Vijaya, Ramarao

    2015-01-01

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

  2. Frequency band broadening of magnetospheric VLF emissions near the equator

    NASA Technical Reports Server (NTRS)

    Maeda, K.; Lin, C. S.

    1981-01-01

    The broadening of the whistler mode VLF emission band has frequently been observed by the equatorially orbiting S3-A (Explorer 45) satellite outside the midnight sector of the plasmasphere, during periods of geomagnetic disturbance. Prior to the broadening, the band of this emission is narrow with a sharp gap at the half electron gyrofrequency. The gradual broadening of the emission band on the low-frequency side is associated with the simultaneously observed spreading of the anisotropy of the ring current electrons to higher and wider energy ranges. Using the modeled distribution function, the linear growth rates of the cyclotron instability are calculated numerically. The results suggest that broadening of the VLF emission band near the plasmasphere can be caused by spreading of the ring current electron anisotropy toward higher energies.

  3. Subsurface banding poultry litter impacts greenhouse gas emissions

    USDA-ARS?s Scientific Manuscript database

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

  4. Interactions of protons with furan molecules studied by collision-induced emission spectroscopy at the incident energy range of 50-1000 eV

    NASA Astrophysics Data System (ADS)

    Wasowicz, Tomasz J.; Pranszke, Boguslaw

    2016-08-01

    Investigations of the ion-molecule reactions provide insight into many fields ranging from the stellar wind interaction with interstellar media, up to medicine and industrial applications. Besides the applications, the understanding of these processes is itself a problem of fundamental importance. Thus, interactions of protons with the gas-phase furan molecules have been investigated for the first time in the energy range of 50-1000 eV exploiting collision-induced emission spectroscopy. Recorded spectra reveal emission of the atomic H β to H θ lines of the hydrogen Balmer series and the molecular bands of vibrationally and rotationally excited diatomic CH fragments created in the A2 Δ and B2Σ- electronic states. The measurements of the emission yields of the excited fragments by recording their intensities at different projectile energies have been performed. The highest yields have been observed for production of hydrogen atoms which intensities rapidly decreased with increasing principal quantum number n . From the H ( n = 4-7) intensity ratios depopulation factors of hydrogen excited states have been determined at each impact energy and possible collisional mechanisms leading to enhanced production of the hydrogen atoms have been suggested. We compare and discuss our results with improved data set of proton collisions with tetrahydrofuran (THF) molecules, the hydrogenated derivatives of furan.

  5. 100 eV electron temperatures in the Maryland centrifugal experiment observed using electron Bernstein emission

    SciTech Connect

    Reid, R. R.; Romero-Talamás, C. A.; Young, W. C.; Ellis, R. F.; Hassam, A. B.

    2014-06-15

    Thermal electron Bernstein emission has been observed at the second harmonic of the electron cyclotron frequency at the mid-plane of the Maryland Centrifugal eXperiment. The emission is received in the X-mode polarization and coupled to the Bernstein wave by the B-X mode conversion process. The average B-X coupling efficiency is approximately 20%. The observed emission indicates thermal electron temperatures an excess of 100 eV in the core of the rotating plasma. The measured electron temperature is consistent with recent ion temperature measurements and indicates that the total energy confinement time exceeds 500 μs.

  6. Optical band gap demarcation around 2.15 eV depending on preferred orientation growth in red HgI2 films

    NASA Astrophysics Data System (ADS)

    Tyagi, Pankaj

    2017-04-01

    Thermally evaporated stoichiometric films of red HgI2 show preferred orientation growth with either (102) or (002) orientation. The as grown films shows a change from one preferred orientation to another depending on their thickness, open-air heat-treatment and in-situ heat treatment of films. The in-situ heat-treatment of thermally evaporated stoichiometric films of red HgI2 with preferred growth of (102) orientation shows a gradual linear decrease in film thickness with in-situ heat-treatment temperature. On in-situ heat-treatment above 80 °C, it is found that HgI2 films become thinner than 900 nm, which are otherwise difficult to grow due to high vapor pressure of HgI2. For these films the preferred orientation also changed from (102) to (002). The optical band gap (Eg) also found to increase linearly with in-situ heat-treatment temperature. It is interesting to note that in-situ heat-treated films having (002) orientation had higher values of optical band gap than (102) orientation films. On combining these results with those of as grown and open-air heat-treated red HgI2 films reported in the literature, it is evident that there exists an optical band gap demarcation around 2.15 eV for red HgI2 thin films depending on their preferred orientation growth. Films with (102) orientation are found to have optical band gap less than 2.15 eV and those with (002) orientation are found to have optical band gap more than 2.15 eV. This is irrespective of the physical mean of obtaining the preferred orientation. The preferred orientation can be achieved by either physical means such as growing films with higher thickness, heat-treating them for short duration in open air or heat-treating them in-situ.

  7. Magnetic resonance imaging and positron emission tomography of band heterotopia.

    PubMed

    Miura, K; Watanabe, K; Maeda, N; Matsumoto, A; Kumagai, T; Ito, K; Kato, T

    1993-01-01

    A case of band heterotopia was reported with findings of positron emission tomography (PET). The patient was an 8-year-old girl who had mild mental retardation and intractable partial epilepsy. Her MRI showed another diffuse layer of gray matter underlying the normal-looking cortex and separated from it by an apparently normal layer of white matter. PET scan with [18F]fluorodeoxyglucose revealed that band heterotopia had the same degree of glucose metabolism as that of the overlying cortex.

  8. Effects of heat treatment on the 0.8 eV photoluminescence emission in GaAs grown by molecular beam epitaxy at low temperatures

    SciTech Connect

    Yu, P.W.; Stutz, C.E.

    1993-12-01

    We report 0.8 eV photoluminescence (PL) emission of GaAs grown at low temperatures between 325 and 400{degrees}C by molecular beam epitaxy. Effects of heat treatments of the 0.8 eV emission are compared with those of the 1.467 eV sharp bound exciton lines. This allows us to attribute the 0.8 eV emission to the As{sub i}-V{sub Ga} center. We discuss the assigning of the As{sub i}-V{sub Ga} center to the well-known EL6. The PL intensity variation of 0.68 eV EL2 and 0.8 eV As{sub i}-V{sub Ga} seen in substrate materials is explained in terms of dislocation-mediated As{sub i}-V{sub Ga} transformation to EL2 whereas the PL intensity variation of 0.8 eV As{sub i}-V{sub Ga} for molecular beam epitaxy layers can be attributed to the growth condition. 21 refs., 4 figs.

  9. The infrared emission bands. III. Southern IRAS sources.

    PubMed

    Cohen, M; Tielens, A G; Bregman, J; Witteborn, F C; Rank, D M; Allamandola, L J; Wooden, D H; de Muizon, M

    1989-06-01

    We present airborne 5-8 micrometers spectra of southern IRAS sources which reveal strong polycyclic aromatic hydrocarbon (PAH) emission features. The good correlation between the bands, in particular the dominant 6.2 and "7.7" micrometers features, strongly imply a common carrier, reinforcing the PAH hypothesis. However, small but detectable spectral variations exist. Planetaries have a distinctly different ratio of I(6.2)/I(7.7) than other nebulae, accompanied by a redward shift in the actual wavelength of the "7.7" micrometers peak. Further, we have detected a new feature, previously predicted from laboratory spectra of PAH molecules, at 5.2 micrometers in many of these sources. Spectra of two rare [WC 10] planetary nebular nuclei indicate a very prominent plateau of emission, linking the 6.2 and 7.7 micrometers bands. Several of our sources show definite evidence for emission structure between 14 and 23 micrometers in their IRAS Low-Resolution Spectral Atlas spectra: we attribute this structure to PAH bands. too. We have defined the "generic" spectrum of emission bands relating the mean intensities of each band to that of the strongest, near 7.7 micrometers. We have added three more planetary or protoplanetary nebulae to our correlation between 7.7 micrometers band intensity and nebular gas phase C/O ratio, namely NGC 6302, HR 4049, and the highly carbon-rich [WC 10] nucleus, CPD--56 degrees 8032. For the latter we have determined a ratio for C/O of approximately 4.8 from IUE observations. The good correlation between the intensity ratio of the "7.7" micrometers feature relative to the far-infrared dust continuum and nebular C/O also supports a carbonaceous carrier for these emission features.

  10. An Exceptionally Narrow Band-Gap (∼4 eV) Silicate Predicted in the Cubic Perovskite Structure: BaSiO3.

    PubMed

    Hiramatsu, Hidenori; Yusa, Hitoshi; Igarashi, Ryo; Ohishi, Yasuo; Kamiya, Toshio; Hosono, Hideo

    2017-09-05

    The electronic structures of 35 A(2+)B(4+)O3 ternary cubic perovskite oxides, including their hypothetical chemical compositions, were calculated by a hybrid functional method with the expectation that peculiar electronic structures and unique carrier transport properties suitable for semiconductor applications would be hidden in high-symmetry cubic perovskite oxides. We found unique electronic structures of Si-based oxides (A = Mg, Ca, Sr, and Ba, and B = Si). In particular, the unreported cubic BaSiO3 has a very narrow band gap (4.1 eV) compared with conventional nontransition-metal silicates (e.g., ∼9 eV for SiO2 and the calculated value of 7.3 eV for orthorhombic BaSiO3) and a small electron effective mass (0.3m0, where m0 is the free electron rest mass). The narrow band gap is ascribed to the nonbonding state of Si 3s and the weakened Madelung potential. The existence of the predicted cubic perovskite structure of BaSiO3 was experimentally verified by applying a high pressure of 141 GPa. The present finding indicates that it could be possible to develop a new transparent oxide semiconductor of earth abundant silicates if the symmetry of its crystal structure is appropriately chosen. Cubic BaSiO3 is a candidate for high-performance oxide semiconductors if this phase can be stabilized at room temperature and ambient pressure.

  11. Inference of a 7.75 eV lower limit in the ultraviolet pumping of interstellar polycyclic aromatic hydrocarbon cations with resulting unidentified infrared emissions.

    PubMed

    Robinson, M S; Beegle, L W; Wdowiak, T J

    1997-01-01

    The discrete infrared features known as the unidentified infrared (UIR) bands originating in starburst regions of other galaxies, and in H II regions and planetary nebulae within the Milky Way, are widely thought to be the result of ultraviolet pumped infrared fluorescence of polycyclic aromatic hydrocarbon (PAH) molecules and ions. These UIR emissions are estimated to account for 10%-30% of the total energy emitted by galaxies. Laboratory absorption spectra including the vacuum ultraviolet region, as described in this paper, show a weakening of the intensity of absorption features as the population of cations increases, suggesting that strong pi* <-- pi transitions are absent in the spectra of PAH cations. This implies a lower energy bound for ultraviolet photons that pump infrared emissions from such ions at 7.75 eV, an amount greater than previously thought. The implications include size and structure limitations on the PAH molecules and ions which are apparent constituents of the interstellar medium. Also, this might affect estimations of the population of early-type stars in regions of rapid star formation.

  12. Inference of a 7.75 eV lower limit in the ultraviolet pumping of interstellar polycyclic aromatic hydrocarbon cations with resulting unidentified infrared emissions

    NASA Technical Reports Server (NTRS)

    Robinson, M. S.; Beegle, L. W.; Wdowiak, T. J.

    1997-01-01

    The discrete infrared features known as the unidentified infrared (UIR) bands originating in starburst regions of other galaxies, and in H II regions and planetary nebulae within the Milky Way, are widely thought to be the result of ultraviolet pumped infrared fluorescence of polycyclic aromatic hydrocarbon (PAH) molecules and ions. These UIR emissions are estimated to account for 10%-30% of the total energy emitted by galaxies. Laboratory absorption spectra including the vacuum ultraviolet region, as described in this paper, show a weakening of the intensity of absorption features as the population of cations increases, suggesting that strong pi* <-- pi transitions are absent in the spectra of PAH cations. This implies a lower energy bound for ultraviolet photons that pump infrared emissions from such ions at 7.75 eV, an amount greater than previously thought. The implications include size and structure limitations on the PAH molecules and ions which are apparent constituents of the interstellar medium. Also, this might affect estimations of the population of early-type stars in regions of rapid star formation.

  13. Optical Emission Studies of New Band System of Silicon Dimer

    NASA Astrophysics Data System (ADS)

    Gopal, Ram; Ojha, K. S.; Singh, S. C.

    2009-06-01

    Silicon containing molecules such as SiC, SiN and Si_2 are of astrophysical interest and their studies provide information about the construction and evolution of different interstellar bodies. The emission spectrum of silicon dimer is recorded in the region of 360-540 nm using laser ablation technique. A rotating silicon rod of high purity, placed in the ablation chamber under argon atmosphere of 0.1 torr pressure, is irradiated with focused output of 355 nm from pulsed Nd:YAG laser. The plasma thus produced by laser ablation is allowed to cool for 300 ns and emission from the cooled plasma is collected on the entrance slit of Spex TRIAX 320M monochomator with ICCD detector system. About 96 bands including 22 bands reported by previous workers are observed. All these bands are assigned into two new band systems H'-D^3Π_u, I-X^3Σ_u^-, and three already reported H^3Σ_u^- - X^3Σ_g^-, K^3Π_u^-X^3Σ_g^- and L^3Π_g-D^3Π_u band systems of silicon dimer. Out of these 96 bands, 43 bands are assigned to two new band system H'-D and I-X while 33 bands including 17 bands reported by earlier workers in this region are assigned to H-X system of Si_2 molecule. In addition to these bands, two bands are assigned to K-X system while the three bands reported by ^aDouglas and ^bDubious and Leclercq are marked to L-D system. The detailed analyses of these systems are investigated in present work. The (0,0) band of H-X system is observed for the first time during this investigation. The molecular constants along with dissociation energies and internuclear distances are calculated from the observed spectra. ^aA. E. Douglas, Can. J. Phys. 33 (1955) 801-810 ^bI.Dubois, H. Leclercq, Can.J.Phys 49 (1971) 3053-3054

  14. Status of the first NASA EV-I Project, Tropospheric Emissions: Monitoring of Pollution (TEMPO)

    NASA Astrophysics Data System (ADS)

    Chance, K.; Liu, X.; Suleiman, R. M.; Flittner, D. E.; Al-Saadi, J. A.; Janz, S. J.

    2013-12-01

    TEMPO is the first NASA Earth Venture Instrument. It will measure atmospheric pollution for greater North America from space using ultraviolet and visible spectroscopy. TEMPO measures from Mexico City to the Canadian tar sands, and from the Atlantic to the Pacific, hourly and at high spatial resolution (2 km N/S × 4.5 km E/W at the center of its field of regard). The status of TEMPO including progress in instrument definition and implementation of the ground system will be presented. TEMPO provides a minimally-redundant measurement suite that includes all key elements of tropospheric air pollution chemistry. Measurements are from geostationary (GEO) orbit, to capture the inherent high variability in the diurnal cycle of emissions and chemistry. The small spatial footprint resolves pollution sources at sub-urban scale. Together, this temporal and spatial resolution improves emission inventories, monitors population exposure, and enables effective emission-control strategies. TEMPO will be delivered in 2017 for integration onto a NASA-selected GEO host spacecraft for launch as early as 2018. It will provide the spectra required to retrieve O3, NO2, SO2, H2CO, C2H2O2, H2O, aerosols, cloud parameters, and UVB radiation. TEMPO thus measures the major elements, directly or by proxy, in the tropospheric O3 chemistry cycle. Multi-spectral observations provide sensitivity to O3 in the lowermost troposphere, substantially reducing uncertainty in air quality predictions. TEMPO quantifies and tracks the evolution of aerosol loading. It provides near-real-time air quality products that will be made widely, publicly available. Additional gases not central to air quality, including BrO, OClO, and IO will also be measured. TEMPO and its Asian (GEMS) and European (Sentinel-4) constellation partners make the first tropospheric trace gas measurements from GEO, building on the heritage of six spectrometers flown in low-earth-orbit (LEO). These LEO instruments measure the needed

  15. Reflectivity and Emissivity of Sea Foam at L-band

    NASA Astrophysics Data System (ADS)

    Anguelova, M. D.; Burrage, D. M.; Bettenhausen, M. H.

    2015-12-01

    The ubiquitous use of the Global Positioning System (GPS) for navigation is well known. GPS operates at L-band frequencies of 1-2 GHz. Because these low microwave frequencies penetrate clouds and rain, GPS signals can detect the specular reflection and diffuse scattering from flat and rough surfaces. This makes the GPS signals useful for geophysical measurements in all weather conditions. Aircraft and satellite-borne GPS reflectometers have been shown to successfully sense ocean surface wind. L-band reflectometry measures changes in ocean surface reflectivity due to changes of ocean surface roughness as wind increases. The use of GPS, together with other Global Navigation Satellite Systems, will soon provide hundreds of L-band transmitters in space and thus high temporal resolution for geophysical measurements. With its all weather capability and high temporal resolution, GPS reflectometry can provide wind speed data in hurricane conditions. Such capabilities enable the new Cyclone Global Navigation Satellite System (CYGNSS) project which aims to improve the skill of hurricane intensity forecasts. However, wave breaking under high winds produces sea foam (whitecaps) and sea spray, which complicate processes acting at the air-sea interface. Whitecaps and sea spray have high emissivity at L-band and will thus reduce the ocean reflectivity needed for wind speed retrieval. A combination of L-band reflectometry and L-band radiometry can thus help to better understand and model the physical mechanisms governing the L-band sensor responses. We use a radiative transfer model formulated in terms of foam layer thickness and void fraction to evaluate both the reflectivity and emissivity of a foam-covered sea surface. We report on the attenuation of L-band radiation in foam layers, and the corresponding foam reflectivity, for layers with varying thicknesses and void fractions. The reflected GPS signal sensitivity to wind speed variations in the presence of foam is assessed.

  16. Photofield emission spectroscopy of the tungsten <112> band structure

    NASA Astrophysics Data System (ADS)

    Radoń, T.; Jaskółka, S.

    1991-05-01

    Optical transitions in photofield emission (PFE) characteristics from the (112) plane of tungsten have been observed at five values of photon energy in the visible range. To measure very small PFE currents modulated laser radiation and phase-sensitive detection have been used. Shoulders in the characteristics obtained with s-polarized light correspond to transitions in the bulk band structure near the Fermi level in accordance with the theoretical results of Christensen and Feuerbacher [1]. Using p-polarized light, peaks of the surface density of states, lying below the Fermi level, were observed in a good agreement with both the field and photofield emission distributions.

  17. Stimulated emission on impurity – band optical transitions in semiconductors

    SciTech Connect

    Bekin, N A; Shastin, V N

    2015-02-28

    This paper examines conditions for population inversion and amplification in the terahertz range using impurity – band electron transitions in semiconductors and semiconductor structures. Our estimates indicate that stimulated emission on such transitions under optical excitation of impurities can be obtained in a semiconductor with a sufficiently high doping level if electron heating is restricted. At a CO{sub 2} laser pump power density near 0.2 MW cm{sup -2} (photon energy of 117 meV), the gain in n-GaAs may exceed the loss by 50 cm{sup -1} provided the electron gas temperature does not exceed 40 K. We analyse the influence of the carrier effective mass and doping compensation on the gain coefficient and briefly discuss the use of resonance tunnelling for obtaining stimulated emission on impurity – band transitions in quantum cascade heterostructures. (terahertz radiation)

  18. An analysis of the information dependence between MODIS emissive bands

    NASA Astrophysics Data System (ADS)

    Gottipati, Srikanth; Gladkova, Irina; Grossberg, Michael

    2008-08-01

    Multispectral, hyperspectral and ultraspectral imagers and sounders are increasingly important for atmospheric science and weather forecasting. The recent advent of multipsectral and hyperspectral sensors measuring radiances in the emissive IR are providing valuable new information. This is due to the presence of spectral channels (in some cases micro-channels) which are carefully positioned in and out of absorption lines of CO2, ozone, and water vapor. These spectral bands are used for measuring surface/cloud temperature, atmospheric temperature, Cirrus clouds water vapor, cloud properties/ozone, and cloud top altidude etc. The complexity of the spectral structure wherein the emissive bands have been selected presents challenges for lossless data compression; these are qualitatively different than the challenges offered by the reflective bands. For a hyperspectral sounder such as AIRS, the large number of channels is the principal contributor to data size. We have shown that methods combining clustering and linear models in the spectral channels can be effective for lossless data compression. However, when the number of emissive channels is relatively small compared to the spatial resolution, such as with the 17 emissive channels of MODIS, such techniques are not effective. In previous work the CCNY-NOAA compression group has reported an algorithm which addresses this case by sequential prediction of the spatial image. While that algorithm demonstrated an improved compression ratio over pure JPEG2000 compression, it underperformed optimal compression ratios estimated from entropy. In order to effectively exploit the redundant information in a progressive prediction scheme we must, determine a sequence of bands in which each band has sufficient mutual information with the next band, so that it predicts it well. We will provide a covariance and mutual information based analysis of the pairwise dependence between the bands and compare this with the qualitative

  19. SAXES, a high resolution spectrometer for resonant x-ray emission in the 400-1600 eV energy range

    SciTech Connect

    Ghiringhelli, G.; Piazzalunga, A.; Dallera, C.; Trezzi, G.; Braicovich, L.; Schmitt, T.; Strocov, V. N.; Betemps, R.; Patthey, L.; Wang, X.; Grioni, M.

    2006-11-15

    We present a 5 m long spectrometer for soft x rays to be used at a synchrotron radiation beamline for resonant x-ray emission spectroscopy and resonant inelastic x-ray scattering in the 400-1600 eV energy range. It is based on a variable line spacing spherical grating (average groove density of 3200 mm{sup -1}, R=58.55 m) and a charge coupled device two dimensional detector. With an x-ray spot on the sample of 10 {mu}m, the targeted resolving power is higher than 10 000 at all energies below 1100 eV and better than 7000 at 1500 eV. The off-line tests made with Al and Mg K{alpha}{sub 1,2} fluorescence emissions indicate that the spectrometer can actually work at 12 000 and 17 000 resolving power at the L{sub 3} edges of Cu (930 eV) and of Ti (470 eV), respectively. SAXES (superadvanced x-ray emission spectrometer) is mounted on a rotating platform allowing to vary the scattering angle from 25 degree sign to 130 degree sign . The spectrometer will be operational at the ADRESS (advanced resonant spectroscopies) beamline of the Swiss Light Source from 2007.

  20. Visible sub-band gap photoelectron emission from nitrogen doped and undoped polycrystalline diamond films

    NASA Astrophysics Data System (ADS)

    Elfimchev, S.; Chandran, M.; Akhvlediani, R.; Hoffman, A.

    2017-07-01

    In this study the origin of visible sub-band gap photoelectron emission (PEE) from polycrystalline diamond films is investigated. The PEE yields as a function of temperature were studied in the wavelengths range of 360-520 nm. Based on the comparison of electron emission yields from diamond films deposited on silicon and molybdenum substrates, with different thicknesses and nitrogen doping levels, we suggested that photoelectrons are generated from nitrogen related centers in diamond. Our results show that diamond film thickness and substrate material have no significant influence on the PEE yield. We found that nanocrystalline diamond films have low electron emission yields, compared to microcrystalline diamond, due to the presence of high amount of defects in the former, which trap excited electrons before escaping into the vacuum. However, the low PEE yield of nanocrystalline diamond films was found to increase with temperature. The phenomenon was explained by the trap assisted photon enhanced thermionic emission (ta-PETE) model. According to the ta-PETE model, photoelectrons are trapped by shallow traps, followed by thermal excitation at elevated temperatures and escape into the vacuum. Activation energies of trap levels were estimated for undoped nanocrystalline, undoped microcrystalline and N-doped diamond films using the Richardson-Dushman equation, which gives 0.13, 0.39 and 0.04 eV, respectively. Such low activation energy of trap levels makes the ta-PETE process very effective at elevated temperatures.

  1. Imaging of the PAH Emission Bands in the Orion Bar

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse; Harker, David; Rank, David; Temi, Pasqiale; Morrison, David (Technical Monitor)

    1994-01-01

    The infrared spectrum of many planetary nebulae, HII regions, galactic nuclei, reflection nebulae, and WC stars are dominated by a set of narrow and broad features which for many years were called the "unidentified infrared bands". These bands have been attributed to several carbon-rich molecular species which all contain only carbon and hydrogen atoms, and fall into the class of PAH molecules or are conglomerates of PAH skeletons. If these bands are from PAHs, then PAHs contain 1-10% of the interstellar carbon, making them the most abundant molecular species in the interstellar medium after CO. From ground based telescopes, we have studied the emission bands assigned to C-H bond vibrations in PAHs (3.3, 11.3 microns) in the Orion Bar region, and showed that their distribution and intensities are consistent with a quantitative PAH model. We have recently obtained spectral images of the Orion Bar from the KAO at 6.2 and 7.7 microns using a 128 x 128 Si:Ga array camera in order to study the C-C modes of the PAH molecules. We will show these new data along with our existing C-H mode data set, and make a quantitative comparison of the data with the existing PAH model.

  2. Detector stability of the Terra MODIS thermal emissive bands

    NASA Astrophysics Data System (ADS)

    Xiong, Xiaoxiong; Chiang, Kwo-Fu; Chen, Na; Xiong, S.; Wu, Aisheng; Adimi, Farida; Barnes, William L.

    2003-11-01

    The MODerate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for the NASA"s Earth Observing System (EOS). The MODIS ProtoFlight Model (PFM) was launched on-board the EOS Terra spacecraft on December 18, 1999. The science data acquisition started on February 24, 2000. Since then it has been providing the science community and public users unprecedented amount of data sets for the global monitoring of the Earth"s land, oceans, and atmosphere. MODIS has 36 spectral bands with wavelengths ranging from 0.41 micrometer to 14.5 micrometers. Its 16 thermal emissive bands (TEB) range from 3.7 to 14.2 micrometers and have a total of 160 individual detectors (10 detectors per band). The thermal emissive bands are calibrated on-orbit by an on-board calibrator blackbody (OBC BB) on a scan by scan basis. The detectors responses to the BB source track their operational stability and therefore their noise characteristics as well. In this paper, we provide a brief review of the MODIS TEB on-orbit calibration algorithm with a focus on detector stability using over three years of on-orbit calibration data sets. The on-orbit changes in detectors responses from one operational configuration to another, the changes within the same operational condition, and the impact of these changes on the calibration and on the Earth scene observations are carefully examined. Except for a few detectors that were identified from pre-launch or became noisy on-orbit, the overall performance of MODIS TEB detectors is very satisfactory according to the design specifications.

  3. Indirect Band Gap Emission by Hot Electron Injection in Metal/MoS2 and Metal/WSe2 Heterojunctions

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Ezhilarasu, Goutham; Chatzakis, Ioannis; Dhall, Rohan; Chen, Chun-Chung; Cronin, Stephen

    Transition metal dichalcogenides (TMDCs), such as MoS2 and WSe2, are free of dangling bonds, therefore make more `ideal' Schottky junctions than bulk semiconductors, which produce recombination centers at the interface with metals, inhibiting charge transfer. Here, we observe a more than 10X enhancement in the indirect band gap PL of TMDCs deposited on various metals, while the direct band gap emission remains unchanged. We believe the main mechanism of light emission arises from photoexcited hot electrons in the metal that are injected into the conduction band of MoS2 and WSe2, and subsequently recombine radiatively with minority holes. Since the conduction band at the K-point is 0.5eV higher than at the Σ-point, a lower Schottky barrier of the Σ-point band makes electron injection more favorable. Also, the Σ band consists of the sulfur pz orbital, which overlaps more significantly with the electron wavefunctions in the metal. This enhancement only occurs for thick flakes, and is absent in monolayer and few-layer flakes. Here, the flake thickness must exceed the depletion width of the Schottky junction, in order for efficient radiative recombination to occur in the TMDC. The intensity of this indirect peak decreases at low temperatures. Reference: DOI: 10.1021/acs.nanolett.5b00885

  4. Optical spectroscopy of IRAS sources with infrared emission bands. 1: IRAS 21282+5050 and the diffuse interstellar bands

    NASA Technical Reports Server (NTRS)

    Cohen, Martin; Jones, B. F.

    1987-01-01

    Spectroscopy of the starlike optical counterpart to IRAS 21282+5050, a source with the hydrocarbon infrared emission band spectrum, shows an 07(f)-(WC11) planetary nebula nucleus suffering an extinction of 5.7 mag. Emission line widths in the WC spectrum are only approx. 100 km/s, indicating a very slow stellar wind. Optical diffuse interstellar bands (DIBs) are prominent. Five DIBs are strongly enhanced, namely lamda lamda 5797, 6196, 6203, 6283, and 6613. The presence of circumstellar hydrocarbon molecules may explain both the infrared emission bands and the enhanced DIBs.

  5. ALMA Band 8 Continuum Emission from Orion Source I

    NASA Astrophysics Data System (ADS)

    Hirota, Tomoya; Machida, Masahiro N.; Matsushita, Yuko; Motogi, Kazuhito; Matsumoto, Naoko; Kim, Mi Kyoung; Burns, Ross A.; Honma, Mareki

    2016-12-01

    We have measured continuum flux densities of a high-mass protostar candidate, a radio source I in the Orion KL region (Orion Source I) using the Atacama Large Millimeter/Submillimeter Array (ALMA) at band 8 with an angular resolution of 0.″1. The continuum emission at 430, 460, and 490 GHz associated with Source I shows an elongated structure along the northwest-southeast direction perpendicular to the so-called low-velocity bipolar outflow. The deconvolved size of the continuum source, 90 au × 20 au, is consistent with those reported previously at other millimeter/submillimeter wavelengths. The flux density can be well fitted to the optically thick blackbody spectral energy distribution, and the brightness temperature is evaluated to be 700-800 K. It is much lower than that in the case of proton-electron or H- free-free radiations. Our data are consistent with the latest ALMA results by Plambeck & Wright, in which the continuum emission was proposed to arise from the edge-on circumstellar disk via thermal dust emission, unless the continuum source consists of an unresolved structure with a smaller beam filling factor.

  6. Source characteristics of Jovian narrow-band kilometric radio emissions

    NASA Astrophysics Data System (ADS)

    Reiner, M. J.; Fainberg, J.; Stone, R. G.; Kaiser, M. L.; Desch, M. D.; Manning, R.; Zarka, P.; Pedersen, B.-M.

    1993-07-01

    New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery that nKOM radio emission originates from a number of distinct sources located at different Jovian longitudes and at the inner and outermost regions of the Io plasma torus. These sources have been tracked for several Jovian rotations, yielding their corotational lags, their spatial and temporal evolution, and their radiation characteristics at both low latitudes far from Jupiter and at high latitudes near the planet. Both right-hand and left-hand circularly polarized nKOM sources were observed. The polarizations observed for sources in the outermost regions of the torus seem to favor extraordinary mode emission.

  7. Inhomogeneous broadening and peak shift of the 7.6 eV optical absorption band of oxygen vacancies in SiO{sub 2}

    SciTech Connect

    Kajihara, Koichi; Skuja, Linards; Hosono, Hideo

    2014-10-21

    The peak parameters of radiation-induced 7.6 eV optical absorption band of oxygen vacancies (Si-Si bonds) were examined for high-purity synthetic α-quartz and amorphous SiO{sub 2} (a‐SiO{sub 2}) exposed to {sup 60}Co γ-rays. The peak shape is asymmetric with the steeper edge at the lower energy side both in α-quartz and a‐SiO{sub 2}, and the peak energy is larger for α-quartz than that for a‐SiO{sub 2}. The full width at half maximum for a‐SiO{sub 2} is larger by ∼40-60% than that for α-quartz, and it increases with an increase in the disorder of the a‐SiO{sub 2} network, which is enhanced by raising the temperature of preannealing before irradiation, i.e., fictive temperature. These data are interpreted from the viewpoint of the site-to-site distribution of the Si-Si bond length in a‐SiO{sub 2}.

  8. Efficient planar perovskite solar cells based on 1.8 eV band gap CH3NH3PbI2Br nanosheets via thermal decomposition.

    PubMed

    Zhao, Yixin; Zhu, Kai

    2014-09-03

    Hybrid organometallic halide perovskite CH3NH3PbI2Br (or MAPbI2Br) nanosheets with a 1.8 eV band gap were prepared via a thermal decomposition process from a precursor containing PbI2, MABr, and MACl. The planar solar cell based on the compact layer of MAPbI2Br nanosheets exhibited 10% efficiency and a single-wavelength conversion efficiency of up to 86%. The crystal phase, optical absorption, film morphology, and thermogravimetric analysis studies indicate that the thermal decomposition process strongly depends on the composition of precursors. We find that MACl functions as a glue or soft template to control the initial formation of a solid solution with the main MAPbI2Br precursor components (i.e., PbI2 and MABr). The subsequent thermal decomposition process controls the morphology/surface coverage of perovskite films on the planar substrate and strongly affects the device characteristics.

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

    NASA Astrophysics Data System (ADS)

    Kajihara, Koichi; Skuja, Linards; Hosono, Hideo

    2014-10-01

    The peak parameters of radiation-induced 7.6 eV optical absorption band of oxygen vacancies (Si-Si bonds) were examined for high-purity synthetic α-quartz and amorphous SiO2 (a-SiO2) exposed to 60Co γ-rays. The peak shape is asymmetric with the steeper edge at the lower energy side both in α-quartz and a-SiO2, and the peak energy is larger for α-quartz than that for a-SiO2. The full width at half maximum for a-SiO2 is larger by ˜40-60% than that for α-quartz, and it increases with an increase in the disorder of the a-SiO2 network, which is enhanced by raising the temperature of preannealing before irradiation, i.e., fictive temperature. These data are interpreted from the viewpoint of the site-to-site distribution of the Si-Si bond length in a-SiO2.

  10. Generation condition of the Upper-band and Lower-band chorus emissions in the Earth's magnetosphere

    NASA Astrophysics Data System (ADS)

    Habagishi, T.; Yagitani, S.; Omura, Y.; Kojima, H.

    2013-12-01

    In the present study, chorus emissions have been analyzed on the basis of the nonlinear growth theory [1] in the Earth's magnetosphere. A rising-tone chorus emission is initially generated continuously in the frequency range from 0.1 to 0.7 fce0, where fce0 is the gyrofrequency in the generation region. Because of the nonlinear damping mechanism [2] the rising-tone chorus is separated into upper and lower bands at half the local gyrofrequency for the quasi-parallel propagation toward higher latitude (i.e. toward larger gyrofrequencies). Thus the lower cutoff of the upper-band chorus indicates half-gyrofrequency at the observational point (1/2 fce), whereas the upper cutoff of the lower-band chorus indicates half the gyrofrequency in the generation region (1/2fce0). We found an observational evidence of such characteristics of upper-band and lower-band chorus observed by the wave form capture (WFC) and the sweep frequency analyzer (SFA) onboard Geotail [3]. Mainly ';'lower-band-only chorus'' (only the lower-band emission exists) is observed and occasionally ';'dual-band chorus'' (both the upper-band and the lower-band emissions) is observed by Geotail. In this study, we statistically analyze the difference between the lower-band-only chorus and the dual-band chorus, using the SFA data obtained during October, 1992 and August, 2011. It has been confirmed that the dual-band chorus is generated because of the nonlinear damping at half the local gyrofrequency during the propagation. When the dual-band chorus propagates toward higher latitudes with its the upper-band part completely damped at half the local gyrofrequencies, the dual-band chorus becomes the lower-band-only chorus. We assume that the upper cutoff frequency of the lower-band chorus equals to the half-gyrofrequency in the generation region. When 0.7 fce0 (i.e. upper limit frequency of the chorus generation) is higher than local 1/2 fce, the dual-band chorus is possibly observed because the higher

  11. Resonant soft-x-ray emission study in relation to the band structure of cBN

    NASA Astrophysics Data System (ADS)

    Agui, A.; Shin, S.; Fujisawa, M.; Tezuka, Y.; Ishii, T.; Muramatsu, Y.; Mishima, O.; Era, K.

    1997-01-01

    The resonant soft-x-ray emission (SXE) and its total photon yield (TPY) spectra were measured at the B 1s and N 1s edges of cubic boron nitride (cBN) using undulator radiation. The band-gap energy was found to be about 6.2 eV, which is in good agreement with other experiments. It was found that the emission from the high symmetry point in the SXE spectrum is enhanced when the same high symmetry point in the TPY spectrum is excited. The line shapes in both the SXE and N 1s TPY spectra were consistent with the calculated partial density of states, though the total bandwidth was not well reproduced. On the other hand, the exciton effect was found to be strong in the B 1s TPY spectra.

  12. Resonant soft-x-ray emission study in relation to the band structure of cBN

    SciTech Connect

    Agui, A.; Shin, S.; Fujisawa, M.; Tezuka, Y.; Ishii, T.; Muramatsu, Y.; Mishima, O.; Era, K.

    1997-01-01

    The resonant soft-x-ray emission (SXE) and its total photon yield (TPY) spectra were measured at the B 1s and N 1s edges of cubic boron nitride (cBN) using undulator radiation. The band-gap energy was found to be about 6.2 eV, which is in good agreement with other experiments. It was found that the emission from the high symmetry point in the SXE spectrum is enhanced when the same high symmetry point in the TPY spectrum is excited. The line shapes in both the SXE and N 1s TPY spectra were consistent with the calculated partial density of states, though the total bandwidth was not well reproduced. On the other hand, the exciton effect was found to be strong in the B 1s TPY spectra. {copyright} {ital 1997} {ital The American Physical Society}

  13. Terahertz emission upon the band-to-band excitation of Group-IV semiconductors at room temperature

    SciTech Connect

    Zakhar’in, A. O.; Bobylev, A. V.; Egorov, S. V.; Andrianov, A. V.

    2015-03-15

    Terahertz emission upon the band-to-band excitation of Group-IV semiconductors (Si:B and Ge:Ga) at room temperature by a semiconductor laser emitting in the visible range (660 nm) is observed and investigated. It is established that, as the crystal temperature is elevated above room temperature, the emission intensity increases considerably, while the emission spectrum shifts to higher frequencies. The terahertz-emission spectra of germanium and silicon are quite similar to each other. The pump-intensity dependence of the terahertz-emission intensity is nearly linear. The above features make it possible to attribute the observed terahertz emission to the effect of crystal heating by absorbed pump radiation.

  14. VLF-emissions from ring current electrons. An interpretation of the band of missing emissions

    NASA Technical Reports Server (NTRS)

    Maeda, K.; Smith, P. H.; Anderson, R. R.

    1976-01-01

    VLF-emissions associated with the enhancement of ring current electrons during magnetic storms and substorms which were detected by the equatorially orbiting S-A satellite (Explorer 45) are described. The emissions observed near the geomagnetic equator consist of essentially two frequency regimes, i.e., one above the electron gyrofrequency, f sub H at the equator and the other below f sub H. This is indicated as a part of the wide-band data obtained during the main phase of the December 17, 1971 magnetic storm. The upper figure is the ac-magnetic field data measured by the search-coil magnetometer with the upper cutoff of 3kHz and the lower figure is the ac-electric field data obtained by the electric field sensor with the upper cutoff of 10kHz. These figures show the time sequence of the observed emissions along the inbound orbit (No. 101) of the satellite as f sub H changes approximately from 3 kHz at 20 UT to 6 kHz at 21 UT. The emissions above f sub H are electrostatic mode, which peak near the frequencies of (n + 1/2) f sub H where n is positive integer, and sometimes emissions up to n = 10 are observed. The emissions below f sub H are whistler mode, which have a conspicuous gap along exactly half electron gyrofrequency, f sub H/2.

  15. MODIS On-Orbit Thermal Emissive Bands Lifetime Performance

    NASA Technical Reports Server (NTRS)

    Madhavan, Sriharsha; Xiong, Xiaoxiong

    2016-01-01

    MODerate resolution Imaging Spectroradiometer (MODIS), a leading heritage sensor in the fleet of Earth Observing System for the National Aeronautics and Space Administration (NASA) is in space orbit on two spacecrafts. They are the Terra (T) and Aqua (A) platforms. Both instruments have successfully continued to operate beyond the 6 year design life time, with the T-MODIS currently functional beyond 15 years and the A-MODIS operating beyond 13 years respectively. The MODIS sensor characteristics include a spectral coverage from 0.41 micron 14.4 micron, of which wavelengths ranging from 3.7 micron 14. 4 micron cover the thermal infrared region also referred to as the Thermal Emissive Bands (TEBs). The TEBs is calibrated using a v-grooved BlackBody (BB) whose temperature measurements are traceable to the National Institute of Standards and Technology temperature scales. The TEBs calibration based on the onboard BB is extremely important for its high radiometric fidelity. In this paper, we provide a complete characterization of the lifetime instrument performance of both MODIS instruments in terms of the sensor gain, the Noise Equivalent difference Temperature, key instrument telemetry such as the BB lifetime trends, the instrument temperature trends, the Cold Focal Plane telemetry and finally, the total assessed calibration uncertainty of the TEBs.

  16. Detection of marine methane emissions with AVIRIS band ratios

    NASA Astrophysics Data System (ADS)

    Bradley, Eliza S.; Leifer, Ira; Roberts, Dar A.; Dennison, Philip E.; Washburn, Libe

    2011-05-01

    The relative source contributions of methane (CH4) have high uncertainty, creating a need for local-scale characterization in concert with global satellite measurements. However, efforts towards methane plume imaging have yet to provide convincing results for concentrated sources. Although atmospheric CH4 mapping did not motivate the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) design, recent studies suggest its potential for studying concentrated CH4 sources such as the Coal Oil Point (COP) seep field (˜0.015 Tg CH4 yr-1) offshore Santa Barbara, California. In this study, we developed a band ratio approach on high glint COP AVIRIS data and demonstrate the first successful local-scale remote sensing mapping of natural atmospheric CH4 plumes. Plume origins closely matched surface and sonar-derived seepage distributions, with plume characteristics consistent with wind advection. Imaging spectrometer data may also be useful for high spatial-resolution characterization of concentrated, globally-significant CH4 emissions from offshore platforms and cattle feedlots.

  17. Extreme ultraviolet narrow band emission from electron cyclotron resonance plasmas.

    PubMed

    Zhao, H Y; Zhao, H W; Sun, L T; Zhang, X Z; Wang, H; Ma, B H; Li, X X; Zhu, Y H; Sheng, L S; Zhang, G B; Tian, Y C

    2008-02-01

    Extreme ultraviolet lithography (EUVL) is considered as the most promising solution at and below dynamic random access memory 32 nm half pitch among the next generation lithography, and EUV light sources with high output power and sufficient lifetime are crucial for the realization of EUVL. However, there is no EUV light source completely meeting the requirements for the commercial application in lithography yet. Therefore, ECR plasma is proposed as a novel concept EUV light source. In order to investigate the feasibility of ECR plasma as a EUV light source, the narrow band EUV power around 13.5 nm emitted by two highly charged ECR ion sources -- LECR2M and SECRAL -- was measured with a calibrated EUV power measurement tool. Since the emission lines around 13.5 nm can be attributed to the 4d-5p transitions of Xe XI or the 4d-4f unresolved transition array of Sn VIII-XIII, xenon plasma was investigated. The dependence of the EUV throughput and the corresponding conversion efficiency on the parameters of the ion source, such as the rf power and the magnetic confinement configurations, were preliminarily studied.

  18. MODIS on-orbit thermal emissive bands lifetime performance

    NASA Astrophysics Data System (ADS)

    Madhavan, Sriharsha; Wu, Aisheng; Chen, Na; Xiong, Xiaoxiong

    2016-05-01

    MODerate resolution Imaging Spectroradiometer (MODIS), a leading heritage sensor in the fleet of Earth Observing System for the National Aeronautics and Space Administration (NASA) is in space orbit on two spacecrafts. They are the Terra (T) and Aqua (A) platforms. Both instruments have successfully continued to operate beyond the 6 year design life time, with the T-MODIS currently functional beyond 15 years and the A-MODIS operating beyond 13 years respectively. The MODIS sensor characteristics include a spectral coverage from 0.41 μm - 14.4 μm, of which wavelengths ranging from 3.7 μm - 14. 4 μm cover the thermal infrared region also referred to as the Thermal Emissive Bands (TEBs). The TEBs is calibrated using a v-grooved BlackBody (BB) whose temperature measurements are traceable to the National Institute of Standards and Technology temperature scales. The TEBs calibration based on the onboard BB is extremely important for its high radiometric fidelity. In this paper, we provide a complete characterization of the lifetime instrument performance of both MODIS instruments in terms of the sensor gain, the Noise Equivalent difference Temperature, key instrument telemetry such as the BB lifetime trends, the instrument temperature trends, the Cold Focal Plane telemetry and finally, the total assessed calibration uncertainty of the TEBs.

  19. Performance of MODIS Thermal Emissive Bands On-orbit Calibration Algorithms

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Chang, T.

    2009-01-01

    Two nearly identical copies of the Moderate Resolution Imaging Spectroradiometer (MODIS) are currently operated on-board the Terra and Aqua spacecrafts, launched in December 1999 and May 2002, respectively. Together, they have produced an unprecedented amount of science data products, which are widely used for the studies of changes in the Earth's system of land, oceans, and atmosphere. MODIS is a cross-track scanning radiometer, which uses a two-sided scan mirror and collects data continuously over a wide scan angle range (+/-55 degree relative to the instrument nadir) each scan of 1.47 seconds. It has 36 spectral bands with wavelengths ranging from visible (VIS) to long-wave infrared (LWIR). MODIS bands 1-19 and 26 are the reflective solar bands (RSB) and bands 20-25 and 27-36 are the thermal emissive bands (TEB). MODIS was developed and designed with improvements made over its heritage sensors (such as AVHRR and Landsat) and, in particular, with more stringent calibration requirements. Because of this, MODIS was built with a set of state-of-art on-board calibrators (OBC), which include a solar diffuser (SD), a solar diffuser stability monitor (SDSM), a blackbody (BB), a spectroradiometric calibration assembly (SRCA), and a space view (SV) port. With the exception of view angle differences, MODIS OBC measurements and the Earth View (EV) observations are made via the same optical path. MODIS TEB have a total of 160 individual TEB detectors (10 per band), which are located on two cold focal plane assemblies (CFPA). For nominal on-orbit operation, the CFPA temperature is controlled at 83K via a passive radiative cooler. For the TEB, the calibration requirements at specified typical scene radiances are less than or equal to 1% with an exception for the fire detection (low gain) band. MODIS TEB on-orbit calibration is performed on a scan-by-scan basis using a quadratic calibration algorithm, and data collected from sensor responses to the onboard BB and SV. The BB

  20. Direct band gap optical emission from compressively strained Ge films grown on relaxed Si{sub 0.5}Ge{sub 0.5} substrate

    SciTech Connect

    Aluguri, R.; Manna, S.; Ray, S. K.

    2013-10-14

    Compressively strained Ge films have been grown on relaxed Si{sub 0.5}Ge{sub 0.5} virtual substrate in ultra high vacuum using molecular beam epitaxy. Structural characterization has shown that the Ge films are compressively strained with partial strain relaxation in a film thicker than 3.0 nm, due to onset of island nucleation. Photoluminescence spectra exhibit the splitting of degenerate Ge valence band into heavy hole and light hole bands with a broad direct band gap emission peak around 0.81 eV. Temperature and excitation power dependent emission characteristics have been studied to investigate the mechanism of luminescence quenching at high temperatures and the role of non-radiative recombination centers.

  1. Sub-band gap photo-enhanced secondary electron emission from high-purity single-crystal chemical-vapor-deposited diamond

    NASA Astrophysics Data System (ADS)

    Yater, J. E.; Shaw, J. L.; Pate, B. B.; Feygelson, T. I.

    2016-02-01

    Secondary-electron-emission (SEE) current measured from high-purity, single-crystal (100) chemical-vapor-deposited diamond is found to increase when sub-band gap (3.06 eV) photons are incident on the hydrogenated surface. Although the light does not produce photoemission directly, the SEE current increases by more than a factor of 2 before saturating with increasing laser power. In energy distribution curves (EDCs), the emission peak shows a corresponding increase in intensity with increasing laser power. However, the emission-onset energy in the EDCs remains constant, indicating that the bands are pinned at the surface. On the other hand, changes are observed on the high-energy side of the distribution as the laser power increases, with a well-defined shoulder becoming more pronounced. From an analysis of this feature in the EDCs, it is deduced that upward band bending is present in the near-surface region during the SEE measurements and this band bending suppresses the SEE yield. However, sub-band gap photon illumination reduces the band bending and thereby increases the SEE current. Because the bands are pinned at the surface, we conclude that the changes in the band levels occur below the surface in the electron transport region. Sample heating produces similar effects as observed with sub-band gap photon illumination, namely, an increase in SEE current and a reduction in band bending. However, the upward band bending is not fully removed by either increasing laser power or temperature, and a minimum band bending of ˜0.8 eV is established in both cases. The sub-band gap photo-excitation mechanism is under further investigation, although it appears likely at present that defect or gap states play a role in the photo-enhanced SEE process. In the meantime, the study demonstrates the ability of visible light to modify the electronic properties of diamond and enhance the emission capabilities, which may have potential impact for diamond-based vacuum electron

  2. The Origin of Narrow Band Cyclotron Wave Emissions Called Chorus

    NASA Astrophysics Data System (ADS)

    Skoug, Ruth Marie

    1995-01-01

    On May 6, 1993, a sounding rocket experiment designed to study microburst electron precipitation was launched from Poker Flat, Alaska, into a morningside auroral event. This was the first sounding rocket to simultaneously detect microburst electrons and associated very low frequency (VLF) waves. Both microbursts and narrow band VLF chorus (risers) were observed throughout the flight. Waves and electron bursts were observed in association with each other, but no one-to-one correlations were seen between the two phenomena. The association between waves and particles suggests that both phenomena may be produced by a wave -particle interaction. This dissertation discusses the design of the VLF wave antenna, a magnetic search coil, and the analysis of data from this instrument. The data are compared to chorus production theories to determine the source location and mechanism of the observed waves. In this work, the observed chorus emissions are interpreted in terms of a cyclotron resonance interaction. This is the first comprehensive test of the cyclotron resonance theory applied to chorus associated with microburst precipitation. The frequency range of the risers and the observed electron energy range agree with those required to satisfy the cyclotron resonance condition. Using a criterion derived from the conservation of energy during an interaction, it is determined that a cold plasma cyclotron resonance interaction could have produced only the lower frequency portions of the observed chorus risers. We present an extension of the cyclotron resonance theory which uses a warm plasma model of the wave-particle interaction. This model assumes a two-component plasma, with an isotropic cold component and a bi-Maxwellian warm component. The addition of the warm component produces sufficient changes in the wave dispersion relation that the interaction can produce the highest frequencies observed in our data set. As predicted by theory, an anisotropic plasma is required to

  3. Detection of KS -band Thermal Emission from WASP-3b

    NASA Astrophysics Data System (ADS)

    Zhao, Ming; Milburn, Jennifer; Barman, Travis; Hinkley, Sasha; Swain, Mark R.; Wright, Jason; Monnier, John D.

    2012-03-01

    We report the detection of thermal emission from the hot Jupiter WASP-3b in the KS band, using a newly developed guiding scheme for the WIRC instrument at the Palomar Hale 200 inch telescope. Our new guiding scheme has improved the telescope guiding precision by a factor of ~5-7, significantly reducing the correlated systematics in the measured light curves. This results in the detection of a secondary eclipse with depth of 0.181% ± 0.020% (9σ)—a significant improvement in WIRC's photometric precision and a demonstration of the capability of Palomar/WIRC to produce high-quality measurements of exoplanetary atmospheres. Our measured eclipse depth cannot be explained by model atmospheres with heat redistribution but favors a pure radiative equilibrium case with no redistribution across the surface of the planet. Our measurement also gives an eclipse phase center of 0.5045 ± 0.0020, corresponding to an ecos ω of 0.0070 ± 0.0032. This result is consistent with a circular orbit, although it also suggests that the planet's orbit might be slightly eccentric. The possible non-zero eccentricity provides insight into the tidal circularization process of the star-planet system, but might also have been caused by a second low-mass planet in the system, as suggested by a previous transit timing variation study. More secondary eclipse observations, especially at multiple wavelengths, are necessary to determine the temperature-pressure profile of the planet's atmosphere and shed light on its orbital eccentricity.

  4. Influence of growth temperature on carrier localization in InGaN/GaN MQWs with strongly redshifted emission band

    NASA Astrophysics Data System (ADS)

    Mickevičius, J.; Dobrovolskas, D.; Aleksiejūnas, R.; Nomeika, K.; Grinys, T.; Kadys, A.; Tamulaitis, G.

    2017-02-01

    To shift the emission band to long wavelength side, InGaN/GaN multiple quantum wells were grown by metalorganic chemical vapor deposition (MOCVD) using pulsed delivery of the metalorganic precursors at fixed parameters of the pulses but variable growth temperatures and by introducing short-period superlattices (SPSL) as buffer layers. By decreasing the growth temperatures for both SPSL and quantum wells down to 800 °C, a considerable shift of the photoluminescence (PL) band peak down to 2 eV is achieved at reasonably acceptable decrease in PL intensity at low carrier density. However, increase in the carrier density resulted in considerable blue shift of the band, and the efficiency droop onset occurred at rather low carrier densities. The comparison of the data on PL and differential optical transmittance, which were supported by structural analysis, revealed that the large red shift in the PL band position is predominantly caused by an increasing tail of localized states. Meanwhile, the efficiency droop effect in the samples under study is caused predominantly by the enhancement of nonradiative carrier recombination.

  5. Crosstalk effect and its mitigation in thermal emissive bands of remote sensors

    NASA Astrophysics Data System (ADS)

    Sun, J.; Madhavan, S.; Wang, M.

    2016-09-01

    It has been found that there is severe electronic noise in the Terra Moderate Resolution Imaging Spectroradiometer (MODIS) bands 27-30 which corresponds to wavelengths ranging between 6.7 μm to 9.73 μm. The cause for the issue has been identified to be crosstalk, which is significantly amplified since 2010 due to severe degradation in the electronic circuitry. The crosstalk effect causes unexpected discontinuity/change in the calibration coefficients and induces strong striping artifacts in the earth view (EV) images. Also it is noticed, that there are large long-term drifts in the EV brightness temperature (BT) in these bands. An algorithm using a linear approximation derived from on-orbit lunar observations has been developed to correct the crosstalk effect for them. It was demonstrated that the crosstalk correction can remarkably minimize the discontinuity/change in the calibration coefficients, substantially reduce the striping in the EV images, and significantly remove the long-term drift in the EV BT in all these bands. In this paper, we present the recent progresses in the crosstalk effect analysis and its mitigation. In addition, we will show that besides these four bands, the TEBs in other satellite remote sensors also have significant crosstalk contaminations. Further, it will be demonstrated that the crosstalk correction algorithm we developed can be successfully applied to all the contaminated TEBs to significantly reduce the crosstalk effects and substantially improve both the image quality and the radiometric accuracy of Level-1B (L1B) products for the bands.

  6. Noise Characterization and Performance of MODIS Thermal Emissive Bands

    NASA Technical Reports Server (NTRS)

    Madhavan, Sriharsha; Xiong, Xiaoxiong; Wu, Aisheng; Wenny, Brian; Chiang, Kwofu; Chen, Na; Wang, Zhipeng; Li, Yonghong

    2016-01-01

    The MODerate-resolution Imaging Spectroradiometer (MODIS) is a premier Earth-observing sensor of the early 21st century, flying onboard the Terra (T) and Aqua (A) spacecraft. Both instruments far exceeded their six-year design life and continue to operate satisfactorily for more than 15 and 13 years, respectively. The MODIS instrument is designed to make observations at nearly a 100% duty cycle covering the entire Earth in less than two days. The MODIS sensor characteristics include a spectral coverage from 0.41micrometers to 14.4 micrometers, of which those wavelengths ranging from 3.7 micrometers to 14.4 micrometers cover the thermal infrared region which is interspaced in 16 thermal emissive bands (TEBs). Each of the TEB contains ten detectors which record samples at a spatial resolution of 1 km. In order to ensure a high level of accuracy for the TEB-measured top-of-atmosphere radiances, an onboard blackbody (BB) is used as the calibration source. This paper reports the noise characterization and performance of the TEB on various counts. First, the stability of the onboard BB is evaluated to understand the effectiveness of the calibration source. Next, key noise metrics such as the noise equivalent temperature difference and the noise equivalent dn difference (NEdN) for the various TEBs are determined from multiple temperature sources. These sources include the nominally controlled BB temperature of 290 K for T-MODIS and 285 K for A-MODIS, as well as a BB warm up-cool down cycle that is performed over a temperature range from roughly 270 to 315 K. The space-view port that measures the background signal serves as a viable cold temperature source for measuring noise. In addition, a well characterized Earth-view target, the Dome Concordia site located in the Antarctic plateau, is used for characterizing the stability of the sensor, indirectly providing a measure of the NEdN. Based on this rigorous characterization, a list of the noisy and inoperable detectors for

  7. Multicolor emission from intermediate band semiconductor ZnO1-xSex

    NASA Astrophysics Data System (ADS)

    Welna, M.; Baranowski, M.; Linhart, W. M.; Kudrawiec, R.; Yu, K. M.; Mayer, M.; Walukiewicz, W.

    2017-03-01

    Photoluminescence and photomodulated reflectivity measurements of ZnOSe alloys are used to demonstrate a splitting of the valence band due to the band anticrossing interaction between localized Se states and the extended valence band states of the host ZnO matrix. A strong multiband emission associated with optical transitions from the conduction band to lower E- and upper E+ valence subbands has been observed at room temperature. The composition dependence of the optical transition energies is well explained by the electronic band structure calculated using the kp method combined with the band anticrossing model. The observation of the multiband emission is possible because of relatively long recombination lifetimes. Longer than 1 ns lifetimes for holes photoexcited to the lower valence subband offer a potential of using the alloy as an intermediate band semiconductor for solar power conversion applications.

  8. Multicolor emission from intermediate band semiconductor ZnO1−xSex

    PubMed Central

    Welna, M.; Baranowski, M.; Linhart, W. M.; Kudrawiec, R.; Yu, K. M.; Mayer, M.; Walukiewicz, W.

    2017-01-01

    Photoluminescence and photomodulated reflectivity measurements of ZnOSe alloys are used to demonstrate a splitting of the valence band due to the band anticrossing interaction between localized Se states and the extended valence band states of the host ZnO matrix. A strong multiband emission associated with optical transitions from the conduction band to lower E− and upper E+ valence subbands has been observed at room temperature. The composition dependence of the optical transition energies is well explained by the electronic band structure calculated using the kp method combined with the band anticrossing model. The observation of the multiband emission is possible because of relatively long recombination lifetimes. Longer than 1 ns lifetimes for holes photoexcited to the lower valence subband offer a potential of using the alloy as an intermediate band semiconductor for solar power conversion applications. PMID:28287140

  9. Using Lunar Observations to Assess Terra MODIS Thermal Emissive Bands Calibration

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Chen, Hongda

    2010-01-01

    MODIS collects data in both the reflected solar and thermal emissive regions using 36 spectral bands. The center wavelengths of these bands cover the3.7 to 14.24 micron region. In addition to using its on-board calibrators (OBC), which include a full aperture solar diffuser (SD) and a blackbody (BB), lunar observations have been scheduled on a regular basis to support both Terra and Aqua MODIS on-orbit calibration and characterization. This paper provides an overview of MODIS lunar observations and their applications for the reflective solar bands (RSB) and thermal emissive bands (TEB) with an emphasis on potential calibration improvements of MODIS band 21 at 3.96 microns. This spectral band has detectors set with low gains to enable fire detection. Methodologies are proposed and examined on the use of lunar observations for the band 21 calibration. Also presented in this paper are preliminary results derived from Terra MODIS lunar observations and remaining challenging issues.

  10. Mid- and far-infrared emission bands in C-rich proto-planetary nebulae

    NASA Technical Reports Server (NTRS)

    Omont, A.; Cox, P.; Moseley, S. Harvey; Glaccum, W.; Casey, Sean; Forveille, T.; Szczerba, R.; Chan, Kin-Wing

    1995-01-01

    The 16-48 micron spectra of five carbon-rich post-asymptotic giant branch (post-AGB) objects known to have an unidentified 21 micron feature in their IRAS low resolution spectrometer (LRS) spectra have been obtained using the Kuiper Airborne Observatory. A broad emission band extending from 24 to approximately 45 microns is present in the spectra of these objects. The strength of this band is variable from source to source and is not correlated with the strength of the 21 micron band. The possible identifications for the emitting material of both the 21 and 30 micron emission bands is discussed.

  11. RFID Transponders' RF Emissions in Aircraft Communication and Navigation Radio Bands

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Ely, Jay J.; Koppen Sandra V.; Fersch, Mariatheresa S.

    2008-01-01

    Radiated emission data in aircraft communication and navigation bands are presented for several active radio frequency identification (RFID) tags. The individual tags are different in design, operation and transmitting frequencies. The process for measuring the tags emissions in a reverberation chamber is discussed. Measurement issues dealing with tag interrogation, low level measurement in the presence of strong transmissions, and tags low duty factors are discussed. The results show strong emissions, far exceeding aircraft emission limits and can be of potential interference risks.

  12. Defect-Band Emission Photoluminescence Imaging on Multi-Crystalline Si Solar Cells: Preprint

    SciTech Connect

    Yan, F.; Johnston, S.; Zaunbrecher, K.; Al-Jassim, M.; Sidelkheir, O.; Blosse, A.

    2011-07-01

    Defect-band photoluminescence (PL) imaging with an InGaAs camera was applied to multicrystalline silicon (mc-Si) wafers, which were taken from different heights of different Si bricks. Neighboring wafers were picked at six different processing steps, from as-cut to post-metallization. By using different cut-off filters, we were able to separate the band-to-band emission images from the defect-band emission images. On the defect-band emission images, the bright regions that originate from the grain boundaries and defect clusters were extracted from the PL images. The area fraction percentage of these regions at various processing stages shows a correlation with the final cell electrical parameters.

  13. Defect-Band Emission Photoluminescence Imaging on Multi-Crystalline Si Solar Cells

    SciTech Connect

    Yan, F.; Johnston, S.; Zaunbrecher, K.; Al-Jassim, M.; Sidelkheir, O.; Blosse, A.

    2011-01-01

    Defect-band photoluminescence (PL) imaging with an InGaAs camera was applied to multicrystalline silicon (mc-Si) wafers, which were taken from different heights of different Si bricks. Neighboring wafers were picked at six different processing steps, from as-cut to post-metallization. By using different cut-off filters, we were able to separate the band-to-band emission images from the defect-band emission images. On the defect-band emission images, the bright regions that originate from the grain boundaries and defect clusters were extracted from the PL images. The area fraction percentage of these regions at various processing stages shows a correlation with the final cell electrical parameters.

  14. C-H Hot Bands in the Near-IR Emission Spectra of Leonids

    NASA Technical Reports Server (NTRS)

    Freund, F. T.; Scoville, J.; Holm, R.; Seelemann, R.; Freund, M. M.

    2002-01-01

    The reported infrared (IR) emission spectra from 1999 Leonid fireballs show a 3.4 micron C-H emission band and unidentified bands at longer wavelengths. Upon atmospheric entry, the Leonid meteorites were flash-heated to temperatures around 2400K, which would destroy any organics on the surface of the meteorite grains. We propose that the nu(sub )CH emission band in the Leonid emission spectra arises from matrix-embedded C(sub n)-H-O entities that are protected from instant pyrolysis. Our model is based on IR absorption nu(sub )CH bands, which we observed in laboratory-grown MgO and natural olivine single crystals, where they arise from C(sub n)-H-O units imbedded in the mineral matrix, indicative of aliphatic -CH2- and -CH3 organics. Instead of being pyrolyzed, the C(sub n)-H-O entities in the Leonid trails become vibrationally excited to higher levels n = 1, 2, 3 etc. During de-excitation they emit at 3.4 microns, due to the (0 => 1) transition, and at longer wavelengths, due to hot bands. As a first step toward verifying this hypothesis we measured the C-H vibrational manifold of hexane (C6H14). The calculated positions of the (2 => l ) , (3 => 2), and possibly (4 => 3) hot bands agree with the Leonid emission bands at 3.5, 3.8 and 4.l microns.

  15. Si3N4 emissivity and the unidentified infrared bands

    NASA Technical Reports Server (NTRS)

    Russell, Ray W.; Chatelain, M. A.; Hecht, James H.; Stephens, John R.

    1989-01-01

    Infrared spectroscopy of warm (about 150 to 750 K), dusty astronomical sources has revealed a structured emission spectrum which can be diagnostic of the composition, temperature, and in some cases, even size and shape of the grains giving rise to the observed emission. The identifications of silicate emission in oxygen rich objects and SiC in carbon rich object are two examples of this type of analysis. Cometary spectra at moderate resolution have similarly revealed silicate emission, tying together interstellar and interplanetary dust. However, Goebel has pointed out that some astronomical sources appear to contain a different type of dust which results in a qualitatively different spectral shape in the 8 to 13 micron region. The spectra shown make it appear unlikely that silicon nitride can be identified as the source of the 8 to 13 micron emission in either NGC 6572 or Nova Aql 1982. The similarity between the general wavelength and shape of the 10 micron emission from some silicates and that from the two forms of silicon nitride reported could allow a mix of cosmic grains which include some silicon nitride if only the 8 to 13 micron data are considered.

  16. Broad-band transmission spectrum and K-band thermal emission of WASP-43b as observed from the ground

    NASA Astrophysics Data System (ADS)

    Chen, G.; van Boekel, R.; Wang, H.; Nikolov, N.; Fortney, J. J.; Seemann, U.; Wang, W.; Mancini, L.; Henning, Th.

    2014-03-01

    Aims: WASP-43b is the closest-orbiting hot Jupiter, and it has high bulk density. It causes deep eclipse depths in the system's light curve in both transit and occultation that is attributed to the cool temperature and small radius of its host star. We aim to secure a broad-band transmission spectrum and to detect its near-infrared thermal emission in order to characterize its atmosphere. Methods: We observed one transit and one occultation event simultaneously in the g', r', i', z', J, H, K bands using the GROND instrument on the MPG/ESO 2.2-m telescope, where the telescope was heavily defocused in staring mode. After modeling the light curves, we derived wavelength-dependent transit depths and flux ratios and compared them to atmospheric models. Results: From the transit event, we have independently derived WASP-43's system parameters with high precision and improved the period to be 0.81347437(13) days based on all the available timings. No significant variation in transit depths is detected, with the largest deviations coming from the i'-, H-, and K-bands. Given the observational uncertainties, the broad-band transmission spectrum can be explained by either (i) a flat featureless straight line that indicates thick clouds; (ii) synthetic spectra with absorption signatures of atomic Na/K, or molecular TiO/VO that in turn indicate cloud-free atmosphere; or (iii) a Rayleigh scattering profile that indicates high-altitude hazes. From the occultation event, we detected planetary dayside thermal emission in the K-band with a flux ratio of 0.197 ± 0.042%, which confirms previous detections obtained in the 2.09 μm narrow band and KS-band. The K-band brightness temperature 1878+108-116 K favors an atmosphere with poor day- to nightside heat redistribution. We also have a marginal detection in the i'-band (0.037+0.023-0.021%), corresponding to TB = 2225+139-225 K, which is either a false positive, a signature of non-blackbody radiation at this wavelength, or an

  17. Techniques to minimize adjacent band emissions from Earth Exploration Satellites to protect the Space Research (Category B) Earth Stations in the 8400-8450 MHz band

    NASA Technical Reports Server (NTRS)

    Wang, Charles C.; Sue, Miles K.; Manshadi, Farzin

    2004-01-01

    The Earth Exploration Satellites operating in the 8025-8400 MHz band can have strong adjacent band emissions on the8400-8450 MHz band which is allocated for Space Research (Category-B). The unwanted emission may exceed the protection criterion establish by the ITU-R for the protection of the Space Research (Category B) earth stations, i.e., deep-space earth stations. An SFCG Action Item (SF 23/14) was created during the 23rd SFCG meeting to explore technical and operational techniques to reduce the adjacent band emissions. In response to this action item, a study was conducted and results are presented in this document.

  18. Techniques to minimize adjacent band emissions from Earth Exploration Satellites to protect the Space Research (Category B) Earth Stations in the 8400-8450 MHz band

    NASA Technical Reports Server (NTRS)

    Wang, Charles C.; Sue, Miles K.; Manshadi, Farzin

    2004-01-01

    The Earth Exploration Satellites operating in the 8025-8400 MHz band can have strong adjacent band emissions on the8400-8450 MHz band which is allocated for Space Research (Category-B). The unwanted emission may exceed the protection criterion establish by the ITU-R for the protection of the Space Research (Category B) earth stations, i.e., deep-space earth stations. An SFCG Action Item (SF 23/14) was created during the 23rd SFCG meeting to explore technical and operational techniques to reduce the adjacent band emissions. In response to this action item, a study was conducted and results are presented in this document.

  19. Origin of multi-band emission from the microquasar Cygnus X-1

    SciTech Connect

    Zhang, Jianfu; Lu, Jufu; Xu, Bing

    2014-06-20

    We study the origin of non-thermal emissions from the Galactic black hole X-ray binary Cygnus X-1, which is a confirmed high-mass microquasar. By analogy with the methods used in studies of active galactic nuclei, we propose a two-dimensional, time-dependent radiation model from the microquasar Cygnus X-1. In this model, the evolution equation for relativistic electrons in a conical jet are numerically solved by including escape, adiabatic, and various radiative losses. The radiative processes involved are synchrotron emission, its self-Compton scattering, and inverse Compton scatterings of an accretion disk and its surrounding stellar companion. This model also includes an electromagnetic cascade process of an anisotropic γ-γ interaction. We study the spectral properties of electron evolution and its emission spectral characteristic at different heights of the emission region located in the jet. We find that radio data from Cygnus X-1 are reproduced by the synchrotron emission, the Fermi Large Area Telescope measurements by the synchrotron emission and Comptonization of photons of the stellar companion, and the TeV band emission fluxes by the Comptonization of the stellar photons. Our results show the following. (1) The radio emission region extends from the binary system scales to the termination of the jet. (2) The GeV band emissions should originate from the distance close to the binary system scales. (3) The TeV band emissions could be inside the binary system, and these emissions could be probed by the upcoming Cherenkov Telescope Array. (4) The MeV tail emissions, which produce a strongly linearly polarized signal, are emitted inside the binary system. The location of the emissions is very close to the inner region of the jet.

  20. DISCOVERY OF SiO BAND EMISSION FROM GALACTIC B[e] SUPERGIANTS

    SciTech Connect

    Kraus, M.; Oksala, M. E.; Cidale, L. S.; Arias, M. L.; Torres, A. F.; Fernandes, M. Borges

    2015-02-20

    B[e] supergiants (B[e]SGs) are evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulate in a circumstellar disk-like structure. The expelled material is typically dense and cool, providing the cradle for molecule and dust condensation and for a rich, ongoing chemistry. Very little is known about the chemical composition of these disks, beyond the emission from dust and CO revolving around the star on Keplerian orbits. As massive stars preserve an oxygen-rich surface composition throughout their life, other oxygen-based molecules can be expected to form. As SiO is the second most stable oxygen compound, we initiated an observing campaign to search for first-overtone SiO emission bands. We obtained high-resolution near-infrared L-band spectra for a sample of Galactic B[e]SGs with reported CO band emission. We clearly detect emission from the SiO first-overtone bands in CPD-52 9243 and indications for faint emission in HD 62623, HD 327083, and CPD-57 2874. From model fits, we find that in all these stars the SiO bands are rotationally broadened with a velocity lower than observed in the CO band forming regions, suggesting that SiO forms at larger distances from the star. Hence, searching for and analyzing these bands is crucial for studying the structure and kinematics of circumstellar disks, because they trace complementary regions to the CO band formation zone. Moreover, since SiO molecules are the building blocks for silicate dust, their study might provide insight in the early stage of dust formation.

  1. Discovery of SiO Band Emission from Galactic B[e] Supergiants

    NASA Astrophysics Data System (ADS)

    Kraus, M.; Oksala, M. E.; Cidale, L. S.; Arias, M. L.; Torres, A. F.; Borges Fernandes, M.

    2015-02-01

    B[e] supergiants (B[e]SGs) are evolved massive stars in a short-lived transition phase. During this phase, these objects eject large amounts of material, which accumulate in a circumstellar disk-like structure. The expelled material is typically dense and cool, providing the cradle for molecule and dust condensation and for a rich, ongoing chemistry. Very little is known about the chemical composition of these disks, beyond the emission from dust and CO revolving around the star on Keplerian orbits. As massive stars preserve an oxygen-rich surface composition throughout their life, other oxygen-based molecules can be expected to form. As SiO is the second most stable oxygen compound, we initiated an observing campaign to search for first-overtone SiO emission bands. We obtained high-resolution near-infrared L-band spectra for a sample of Galactic B[e]SGs with reported CO band emission. We clearly detect emission from the SiO first-overtone bands in CPD-52 9243 and indications for faint emission in HD 62623, HD 327083, and CPD-57 2874. From model fits, we find that in all these stars the SiO bands are rotationally broadened with a velocity lower than observed in the CO band forming regions, suggesting that SiO forms at larger distances from the star. Hence, searching for and analyzing these bands is crucial for studying the structure and kinematics of circumstellar disks, because they trace complementary regions to the CO band formation zone. Moreover, since SiO molecules are the building blocks for silicate dust, their study might provide insight in the early stage of dust formation. Based on observations collected with the ESO VLT Paranal Observatory under program 093.D-0248(A).

  2. Prospects of efficient band-to-band emission in silicon LEDs

    NASA Astrophysics Data System (ADS)

    Schmitz, Jurriaan

    2016-02-01

    In this paper a review is presented of light emission from forward-biased silicon diodes. After a treatment of the carrier recombination physics governing in this indirect-bandgap material, the article describes important works in this field. Then, routes are proposed for further improvement of the internal quantum efficiency for light emission. A good choice of carrier injection level will limit the impact of both Shockley-Read-Hall recombination and Auger recombination. However, the structural design of the diode has a strong influence on the overall quantum efficiency, as both surface recombination must be dealt with, and contact recombination avoided. New attributes of CMOS such as embedded SiGe offer additional opportunities for silicon LED architectures and their application.

  3. Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands

    NASA Astrophysics Data System (ADS)

    Trautner, Stefan; Jasik, Juraj; Parigger, Christian G.; Pedarnig, Johannes D.; Spendelhofer, Wolfgang; Lackner, Johannes; Veis, Pavel; Heitz, Johannes

    2017-03-01

    Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157 nm F2 laser and 532 nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C2 Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures Te derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925 nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1 wt% feasible.

  4. Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands.

    PubMed

    Trautner, Stefan; Jasik, Juraj; Parigger, Christian G; Pedarnig, Johannes D; Spendelhofer, Wolfgang; Lackner, Johannes; Veis, Pavel; Heitz, Johannes

    2017-03-05

    Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157nmF2 laser and 532nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C2 Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures Te derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1wt% feasible. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. The MAON model of Astronomical Unidentified Infrared Emission Bands

    NASA Astrophysics Data System (ADS)

    Kwok, Sun; Zhang, Yong

    2015-08-01

    Infrared spectroscopic observations of the stretching and bending modes of aliphatic and aromatic compounds are now seen throughout the Universe, from the diffuse interstellar medium of the Milky Way Galaxy to distant galaxies. Observations of evolved stars have revealed a rapid (~10$^3$ year time scale) and continuous synthesis of organic materials from the end of the asymptotic giant branch (AGB), to proto-planetary nebulae, to planetary nebulae. These synthesized products are ejected into the interstellar medium through stellar winds and as a result enriching the Galaxy with complex organics. Analysis of the infrared spectra suggests that the chemical structure of the carrier is consistent with that of mixed aromatic and aliphatic nanoparticles (MAON). These structures are very similar to those of the insoluble organic matter found in meteorites, suggesting that the early solar system may have been enriched by stellar ejecta.ReferencesKwok, S. The Synthesis of Organic and Inorganic Compounds in Evolved Stars, Nature, 430, 985 (2004)Kwok, S. and Zhang, Y. Mixed aromatic/aliphatic organic nanoparticles as carriers of unidentified infrared emission features, Nature, 479, 80 (2011)Kwok, S. Organic Matter in the Universe, Wiley (2011)

  6. Acoustic Emission Activity and Spatial Distribution of Damage Associated with Compaction Band Formation

    NASA Astrophysics Data System (ADS)

    Baud, P.; Klein, E.; Wong, T.

    2001-12-01

    Compaction band has been observed as a localized failure mode in porous sandstones, at stress states that are associated with the transitional regime from brittle faulting to distributed cataclastic flow. Detailed microstructural observations were conducted on the Bentheim, Berea, Boise, Darley Dale and Rothbach sandstones with porosities ranging from 13% to 35% to delineate and quantify the spatial distribution of damage associated with the development of compaction bands. Significant grain crushing and porosity reduction are evident in the localized bands, with crack densities up to 5 times greater than those in areas outside the bands. Two different patterns of strain localization can be distinguished: diffuse conjugate shears at relatively high angles, and discrete compaction bands subperpendicular to the maximum compression direction. Whereas the development of diffuse bands is characterized by the continuous accumulation of acoustic emissions (AE), discrete bands are associated with episodic surges in AE that are characterized by an overall strain hardening trend punctuated by episodic stress drops. The number of discrete bands correlates with the number of AE surges and stress drops. Preliminary permeability measurements indicate appreciable reductions of permeability during compaction band development.

  7. N2 triplet band emissions in the dayglow of Venus, Mars, and Titan

    NASA Astrophysics Data System (ADS)

    Jain, Sonal Kumar; Bhardwaj, Anil

    2012-07-01

    Vegard-Kaplan (VK) and Second Positive emissions of N_2 are common features in the terrestrial dayglow and aurora and have been studied extensively. Recent discoveries of N_2 triplet band emissions on Mars by SPICAM/Mars-Express and on Titan by Cassini UVIS have led planetary scientists to look for the processes governing the N_2 triplet band emissions in different planetary atmospheres. Present work deals with the modeling of N_2 triplet band emission on Mars, Venus, and Titan. A model for N_2 triplet band emissions has been developed and used to explain the recent observations of N_2 Vegard-Kaplan (VK) (A^3Σ_u^+ - X^1Σ^+_g ) band on Mars and Titan. Steady state photoelectron fluxes and volume excitation rates have been calculated using the Analytical Yield Spectra technique. Since interstate cascading is important for triplet states of N_2, the population of any given level of N_2 triplet states is calculated under statistical equilibrium considering direct excitation, cascading, and quenching effects. Relative population of all vibrational levels of each triplet state is calculated in the model. Line of sight intensities and height-integrated overhead intensities have been calculated for VK, First Positive ( B^3Π_g - A^3Σ^+_u ), Second Positive ( C^3Π_u - B^3Π_g ), Wu-Benesch (W^3Δ_u - B^3Π_g), Reverse First Positive, Herman--Kaplan (E → A), E → B, and E → C bands of N_2. The N_2 VK band span wavelength range from far ultraviolet to visible, and some transitions even originate at wavelength more than 1000 nm . Our calculations show that the overhead intensity of VK bands in the wavelength range 400--800, 300--190, 200--300, and 150--200 nm are 22%, 39%, 35%, and 4% of the total VK band emission. Emissions between 600 and 800 nm wavelength consist of about 50% of the total First Positive band system. Major portion of Second Positive band emissions lie in wavelengths between 300 and 400 nm, which is more than 90% of the total Second Positive band

  8. Full-Band Monte Carlo Analysis of Hot-Carrier Light Emission in GaAs

    NASA Astrophysics Data System (ADS)

    Ferretti, I.; Abramo, A.; Brunetti, R.; Jacobini, C.

    1997-11-01

    A computational analysis of light emission from hot carriers in GaAs due to direct intraband conduction-conduction (c-c) transitions is presented. The emission rates have been evaluated by means of a Full-Band Monte-Carlo simulator (FBMC). Results have been obtained for the emission rate as a function of the photon energy, for the emitted and absorbed light polarization along and perpendicular to the electric field direction. Comparison has been made with available experimental data in MESFETs.

  9. Novel fluorescent probe for low density lipoprotein, based on the enhancement of Europium emission band

    NASA Astrophysics Data System (ADS)

    Courrol, L. C.; Monteiro, A. M.; Silva, F. R. O.; Gomes, L.; Vieira, N. D., Jr.; Gidlund, M. A.; Figueiredo Neto, A. M.

    2007-05-01

    We report here the observation of the enhancement of Europium-tetracycline complex emission in Low Density Lipoprotein (LDL) solutions. Europium emission band of tetracycline solution containing Europium (III) chloride hexahydrate was tested to obtain effective enhancement in the presence of native LDL and oxidized LDL. Europium emission lifetime in the presence of lipoproteins was measured, resulting in a simple method to measure the lipoproteins quantity in an aqueous solution at physiological pH. This method shows that the complex can be used as a sensor to determine the different states of native and oxidized LDL in biological fluids.

  10. Mechanism of generation of the emission bands in the dynamic spectrum of the Crab pulsar

    NASA Astrophysics Data System (ADS)

    Ardavan, Houshang; Ardavan, Arzhang; Singleton, John; Perez, Mario R.

    2008-08-01

    We show that the proportionately spaced emission bands in the dynamic spectrum of the Crab pulsar fit the oscillations of the square of a Bessel function whose argument exceeds its order. This function has already been encountered in the analysis of the emission from a polarization current with a superluminal distribution pattern: a current whose distribution pattern rotates (with an angular frequency ω) and oscillates (with a frequency Ω > ω differing from an integral multiple of ω) at the same time. Using the results of our earlier analysis, we find that the dependence on frequency of the spacing and width of the observed emission bands can be quantitatively accounted for by an appropriate choice of the value of the single free parameter Ω/ω. In addition, the value of this parameter, thus implied by Hankins & Eilek's data, places the last peak in the amplitude of the oscillating Bessel function in question at a frequency (~Ω3/ω2) that agrees with the position of the observed ultraviolet peak in the spectrum of the Crab pulsar. We also show how the suppression of the emission bands by the interference of the contributions from differing polarizations can account for the differences in the time and frequency signatures of the interpulse and the main pulse in the Crab pulsar. Finally, we put the emission bands in the context of the observed continuum spectrum of the Crab pulsar by fitting this broad-band spectrum (over 16 orders of magnitude of frequency) with that generated by an electric current with a superluminally rotating distribution pattern.

  11. Light on the 3 μm Emission Band from Space with Molecular Beam Spectroscopy

    NASA Astrophysics Data System (ADS)

    Maltseva, Elena; Mackie, Cameron J.; Candian, Alessandra; Petrignani, Annemieke; Tielens, Xander; Oomens, Jos; Huang, Xinchuan; Lee, Timothy; Buma, Wybren Jan

    2016-06-01

    The majority of interstellar objects shows IR emission features also known as unidentified infrared (UIR) emission bands. These UIR bands are attributed to IR emission of highly-excited gaseous polycyclic aromatic hydrocarbons (PAHs). To understand the physical conditions and chemical evolution of the interstellar environment a precise identification of the emission carriers is desired. The 3 μm UIR feature is represented by a strong band at 3040 cm-1, a plateau from 3150 to 2700 cm-1 and a number of weak features within this plateau. The 3040 cm-1 component is assigned to fundamental CH-stretch vibrations of PAHs, but there still remain many questions on the origin of the other features. In this work we have studied experimentally the 3 μm region of regular, hydrogenated and methylated PAHs (up to 5 rings), combining molecular beam techniques with IR-UV ion dip spectroscopy, and theoretically by density functional theory (DFT) calculations within the harmonic and anharmonic approximation. We find that (a) the 3 μm region of PAHs is dominated by Fermi resonances and thereby cannot be treated within the harmonic approximation; (b) the periphery structure of the molecules strongly affects the shape of the 3 μm band. In particular, the two-component emission interpretation can be explained by the presence of molecules with and without bay-hydrogens; (c) due to strong Fermi resonances of fundamental modes with combination bands regular PAHs can significantly contribute to the 3 μm plateau in the 3150-2950 cm-1, while hydrogenated and methylated species are primarily responsible for features in the 2950-2750 cm-1 region.

  12. Near band edge emission characteristics of sputtered nano-crystalline ZnO films

    SciTech Connect

    Kunj, Saurabh; Sreenivas, K.

    2016-05-06

    Sputtered zinc oxide (ZnO) thin films deposited on unheated glass substrate under different sputtering gas mixtures (Ar+O{sub 2}) have been investigated using X-ray diffraction and photo luminescence spectroscopy. Earlier reported studies on ZnO films prepared by different techniques exhibit either a sharp/broad near band edge (NBE) emission peak depending on the crystalline quality of the film. In the present study zinc oxide films, grown on unheated substrates, are seen to possess a preferred (002) orientation with a microstructure consisting of clustered nano-sized crystallites. The splitting in the near band edge emission (NBE) into three characteristic peaks is attributed to quantum confinement effect, and is observed specifically under an excitation of 270 nm. Deep level emission (DLE) in the range 400 to 700 nm is not observed indicating absence of deep level radiative defects.

  13. RFID Transponders' Radio Frequency Emissions in Aircraft Communication and Navigation Radio Bands

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Ely, Jay J.; Williams, Reuben A.; Koppen, Sandra V.; Salud, Maria Theresa P.

    2006-01-01

    Radiated emissions in aircraft communication and navigation bands are measured from several active radio frequency identification (RFID) tags. The individual tags are different in design and operations. They may also operate in different frequency bands. The process for measuring the emissions is discussed, and includes tag interrogation, reverberation chamber testing, and instrument settings selection. The measurement results are described and compared against aircraft emission limits. In addition, interference path loss for the cargo bays of passenger aircraft is measured. Cargo bay path loss is more appropriate for RFID tags than passenger cabin path loss. The path loss data are reported for several aircraft radio systems on a Boeing 747 and an Airbus A320.

  14. Analysis of multi-band pyrometry for emissivity and temperature measurements of gray surfaces at ambient temperature

    NASA Astrophysics Data System (ADS)

    Araújo, António

    2016-05-01

    A multi-band pyrometry model is developed to evaluate the potential of measuring temperature and emissivity of assumably gray target surfaces at 300 K. Twelve wavelength bands between 2 and 60 μm are selected to define the spectral characteristics of the pyrometers. The pyrometers are surrounded by an enclosure with known background temperature. Multi-band pyrometry modeling results in an overdetermined system of equations, in which the solution for temperature and emissivity is obtained through an optimization procedure that minimizes the sum of the squared residuals of each system equation. The Monte Carlo technique is applied to estimate the uncertainties of temperature and emissivity, resulting from the propagation of the uncertainties of the pyrometers. Maximum reduction in temperature uncertainty is obtained from dual-band to tri-band systems, a small reduction is obtained from tri-band to quad-band, with a negligible reduction above quad-band systems (a reduction between 6.5% and 12.9% is obtained from dual-band to quad-band systems). However, increasing the number of bands does not always reduce uncertainty, and uncertainty reduction depends on the specific band arrangement, indicating the importance of choosing the most appropriate multi-band spectral arrangement if uncertainty is to be reduced. A reduction in emissivity uncertainty is achieved when the number of spectral bands is increased (a reduction between 6.3% and 12.1% is obtained from dual-band to penta-band systems). Besides, emissivity uncertainty increases for pyrometers with high wavelength spectral arrangements. Temperature and emissivity uncertainties are strongly dependent on the difference between target and background temperatures: uncertainties are low when the background temperature is far from the target temperature, tending to very high values as the background temperature approaches the target temperature.

  15. Emission coefficients for the OH Meinel band system; calculations and nightglow comparisons

    NASA Astrophysics Data System (ADS)

    Slanger, T. G.

    2016-12-01

    The OH Meinel band system is an extensive series of bands that are transitions between the vibrational levels of the X2Π ground-state of the molecule. The exothermicity of the source reaction is sufficient to populate up to OH(v = 9), and in fact the nascent reaction puts most of the product into that level. Subsequently, relaxation of the population to lower levels takes place via collisions with the ambient atmosphere and radiation within the OH(v) manifold. Considerable effort has been spent in determining the emission coefficients of the OH Meinel band system. This emission is a prominent feature of the terrestrial nightglow, and because it is relatively intense, there have been numerous investigations, generally based on ground-based instrumentation. The very exothermic source reaction, H + O3 → OH(v) + O2, results in the production of vibrationally and rotationally hot OH(v), and leads to a great number of OH emission lines, covering a wide spectral range, 500-2000 nm. The full range of energy-accessible OH vibrational levels, up to v = 9, is produced in the reaction, and in this presentation we make the case that it is essential to simultaneously measure as many OH bands as possible, to retrieve the maximum amount of spectroscopic and dynamic information. In order to do so, we must agree on the emission coefficients (A-factors) associated with the individual OH bands, and this determination has presented problems in the past. A major advance in the study of atmospheric OH Meinel band emission took place when astronomical sky spectra were utilized to record all accessible OH bands simultaneously, from Mauna Kea [Cosby and Slanger, 2007]. Subsequently, similar studies were undertaken at the VLT [Noll et al. 2015 a,b], and at the GIANO-TNG [Oliva et al., 2015]. With these intensity-calibrated spectra, it becomes possible to compare the OH optical data with sets of A-factor calculations that have been presented over the years [Mies, 1974; Turnbull and Lowe

  16. Polycyclic aromatic hydrocarbons and the unidentified infrared emission bands - Auto exhaust along the Milky Way

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Tielens, A. G. G. M.; Barker, J. R.

    1985-01-01

    The unidentified infrared emission features (UIR bands) are attributed to a collection of partially hydrogenated, positively charged polycyclic aromatic hydrocarbons (PAHs). This assignment is based on a spectroscopic analysis of the UIR bands. Comparison of the observed interstellar 6.2 and 7.7-micron bands with the laboratory measured Raman spectrum of a collection of carbon-based particulates (auto exhaust) shows a very good agreement, supporting this identification. The infrared emission is due to relaxation from highly vibrationally and electronically excited states. The excitation is probably caused by UV photon absorption. The infrared fluorescence of one particular, highly vibrationally excited PAH (chrysene) is modeled. In this analysis the species is treated as a molecule rather than bulk material and the non-thermodynamic equilibrium nature of the emission is fully taken into account. From a comparison of the observed ratio of the 3.3 to 11.3-micron UIR bands with the model calculations, the average number of carbon atoms per molecule is estimated to be about 20. The abundance of interstellar PAHs is calculated to be about 2 x 10 to the -7th with respect to hydrogen.

  17. Polycyclic aromatic hydrocarbons and the unidentified infrared emission bands - Auto exhaust along the Milky Way

    NASA Technical Reports Server (NTRS)

    Allamandola, L. J.; Tielens, A. G. G. M.; Barker, J. R.

    1985-01-01

    The unidentified infrared emission features (UIR bands) are attributed to a collection of partially hydrogenated, positively charged polycyclic aromatic hydrocarbons (PAHs). This assignment is based on a spectroscopic analysis of the UIR bands. Comparison of the observed interstellar 6.2 and 7.7-micron bands with the laboratory measured Raman spectrum of a collection of carbon-based particulates (auto exhaust) shows a very good agreement, supporting this identification. The infrared emission is due to relaxation from highly vibrationally and electronically excited states. The excitation is probably caused by UV photon absorption. The infrared fluorescence of one particular, highly vibrationally excited PAH (chrysene) is modeled. In this analysis the species is treated as a molecule rather than bulk material and the non-thermodynamic equilibrium nature of the emission is fully taken into account. From a comparison of the observed ratio of the 3.3 to 11.3-micron UIR bands with the model calculations, the average number of carbon atoms per molecule is estimated to be about 20. The abundance of interstellar PAHs is calculated to be about 2 x 10 to the -7th with respect to hydrogen.

  18. Field emission analysis of band bending in donor/acceptor heterojunction

    NASA Astrophysics Data System (ADS)

    Xing, Yingjie; Li, Shuai; Wang, Guiwei; Zhao, Tianjiao; Zhang, Gengmin

    2016-06-01

    The donor/acceptor heterojunction plays an important role in organic solar cells. An investigation of band bending in the donor/acceptor heterojunction is helpful in analysis of the charge transport behavior and for the improvement of the device performance. In this work, we report an approach for detection of band bending in a donor/acceptor heterojunction that has been prepared on a small and sharp tungsten tip. In situ field emission measurements are performed after the deposition process, and a linear Fowler-Nordheim plot is obtained from the fresh organic film surface. The thickness-dependent work function is then measured in the layer-by-layer deposited heterojunction. Several different types of heterojunction (zinc phthalocyanine (ZnPc)/C60, copper phthalocyanine (CuPc)/3,4,9,10-perylenetetracarboxylic bisbenzimidazole, and CuPc/C60) are fabricated and analyzed. The different charge transfer directions in the heterojunctions are distinguished by field emission measurements. The calculation method used to determine the band bending is then discussed in detail. A triple layer heterojunction (C60/ZnPc/CuPc) is also analyzed using this method. A small amount of band bending is measured in the outer CuPc layer. This method provides an independent reference method for determination of the band bending in an organic heterojunction that will complement photoemission spectroscopy and current-voltage measurement methods.

  19. Dayglow emissions of the O2 Herzberg bands and the Rayleigh backscattered spectrum of the earth

    NASA Technical Reports Server (NTRS)

    Frederick, J. E.; Abrams, R. B.

    1982-01-01

    It is pointed out that numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242-300 nm. This coincides with the wavelength range used by orbiting spectrometers that observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations suggest that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Sigma) is sufficiently small. It is noted that this is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements have shown a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. Very small quenching rates, however, are adequate to reduce the dayglow emission to negligible levels. Noting that available laboratory data have not definitely established the quenching on the rate of O2(A3Sigma) as a function of vibration level, it is emphasized that such information is required before the Herzberg band contributions can be evaluated with confidence.

  20. Dayglow emissions of the O2 Herzberg bands and the Rayleigh backscattered spectrum of the earth

    NASA Astrophysics Data System (ADS)

    Frederick, J. E.; Abrams, R. B.

    1982-06-01

    It is pointed out that numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242-300 nm. This coincides with the wavelength range used by orbiting spectrometers that observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations suggest that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Sigma) is sufficiently small. It is noted that this is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements have shown a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. Very small quenching rates, however, are adequate to reduce the dayglow emission to negligible levels. Noting that available laboratory data have not definitely established the quenching on the rate of O2(A3Sigma) as a function of vibration level, it is emphasized that such information is required before the Herzberg band contributions can be evaluated with confidence.

  1. Investigation of narrow-band thermal emission from intersubband transitions in quantum wells

    SciTech Connect

    De Zoysa, M.; Asano, T.; Inoue, T.; Mochizuki, K.; Noda, S.

    2015-09-14

    We investigate thermal emission from n-doped GaAs/AlGaAs quantum wells (QWs). Emission peaks with Lorentzian shapes (linewidth 11∼19 meV) that reflect transitions between the first and second conduction subbands are observed in the mid-infrared range. It is demonstrated that the emission characteristics can be tuned by modifying the QW parameters. The peak emissivity is increased from 0.3 to 0.9 by modifying the doping density, and the peak wavelength is tuned from 6 to 10 μm by changing the well width. The obtained results are useful for the design of narrow-band thermal emitters.

  2. Band limited emission with central frequency around 2 Hz accompanying powerful cyclones

    NASA Technical Reports Server (NTRS)

    Troitskaia, V. A.; Shepetnov, K. S.; Dvobnia, B. D.

    1992-01-01

    It has been found that powerful cyclones are proceeded, accompanied and followed by narrow band electromagnetic emission with central frequency around 2 Hz. It is shown that the signal from this emission is unique and clearly distinguishable from known types of magnetic pulsations, spectra of local thunderstorms, and signals from industrial sources. This emission was first observed during an unusually powerful cyclone with tornadoes in the western European part of the Soviet Union, which passed by the observatory of Borok from south to north-east. The emission has been confirmed by analysis of similar events in Antarctica. The phenomenon described presents a new aspect of interactions of processes in the lower atmosphere and the ionosphere.

  3. Photo field-emission spectroscopy of optical transitions in the band structure of rhenium

    NASA Astrophysics Data System (ADS)

    Radoń, T.; Kleint, Ch.

    1984-09-01

    Photo field-emission (PFE) current-voltage curves of clean and barium covered rhenium have been determined with an argon ion laser and phase sensitive detection. Field strength and work function were obtained from Fowler-Nordheim plots of the field emission currents. According to a two-step PFE model the knees of the PFE characteristics are ascribed to optical transitions in the Brillouin zone near the Fermi level. Most of the observed excitations could be correlated to direct transitions in the rhenium band structure as calculated by Mattheiss including spin-orbit coupling.

  4. Evaluating the impact of cold focal plane temperature on Aqua MODIS thermal emissive band calibration

    NASA Astrophysics Data System (ADS)

    Li, Yonghong; Wu, Aisheng; Wenny, Brian; Xiong, Xiaoxiong

    2015-09-01

    Aqua MODIS, the second MODIS instrument of the NASA Earth Observation System, has operated for over thirteen years since launch in 2002. MODIS has sixteen thermal emissive bands (TEB) located on two separate cold focal plane assemblies (CFPA). The TEB are calibrated using onboard blackbody and space view observations. MODIS CFPA temperature is controlled by a radiative cooler and heaters in order to maintain detector gain stability. Beginning in 2006, the CFPA temperature gradually varies from its designed operating temperature with increasing orbital and seasonal fluctuations, with the largest observed impacts on the TEB photoconductive (PC) bands. In Aqua Collection 6 (C6), a correction to the detector gain due to the CFPA temperature variation is applied for data after mid-2012. This paper evaluates the impact of the CFPA temperature variation on the TEB PC band calibration through comparisons with simultaneous nadir overpasses (SNO) measurements from the Infrared Atmospheric Sounding Interferometer (IASI) and Atmospheric Infrared Sounder (AIRS). Our analysis shows that the current L1B product from mid-2011 to mid-2012 is affected by the CFPA temperature fluctuation. The MODIS-IASI comparison results show that no drift is observed in PC bands over the CFPA temperature variation range. Similarly, in the MODIS-AIRS comparison, bands 31-34 show nearly no trend over the range of CFPA temperature while a slight drift in bands 35-36 are seen from the comparison results.

  5. Studies of Breakdown in High Gradient X-Band Accelerator Structures Using Acoustic Emission

    SciTech Connect

    Frisch, Josef C

    2002-08-23

    X-band accelerator structures meeting the Next Linear Collider (NLC) design requirements have been found to suffer damage due to RF breakdown when processed to high gradients. Improved understanding of these breakdown events is desirable for the development of structure designs, fabrication procedures, and processing techniques that minimize structure damage [1]. Acoustic emission sensors attached to an accelerator structure can detect both nominal and breakdown RF pulses [2]. Using an array of acoustic sensors, we have been able to pinpoint both the cell and azimuth location of individual breakdown events. This allows studies of breakdown time and position sequences so that underlying causes can be determined. The technique provided a significant advance in studies of breakdown in the structure input coupler. In this paper we present acoustic emission sensor data and analysis from the breakdown studies in several x-band accelerator structures.

  6. L to X-band scatter and emission measurements of vegetation

    NASA Astrophysics Data System (ADS)

    Hueppi, R.; Schanda, E.

    1986-08-01

    A broad-band H and V polarization radiometer was combined with a noise transmitter to an instrument for measuring active and passive microwave signatures at seven frequencies between L and X band. This radiometer-scatterometer is operated from a cherry picker over agricultural fields. During the growing seasons the development of sugar-beet, wheat, and corn was measured. The geometrical structure of the vegetation cover was described by recording the crop type, the distances between the plants, and the canopy height. The soil underneath was characterized by moisture, temperature profile, and dielectric constant. Another variable was the seasonal change in water content of the plants. Relating these parameters to the microwave signatures reveals the interaction of scatter and emission processes between soil and vegetation. Significant differences of the emission and scattering behavior for the measured crops are found.

  7. Effects of atomic oxygen on OH Meinel emission bands in the MLT region

    NASA Astrophysics Data System (ADS)

    Von Savigny, Christian; Lednyts'kyy, Olexandr

    The OH Meinel airglow is one of the most prominent features of the terrestrial nightglow and has been employed for several decades to remotely sense the mesopause region. However, some aspects of the OH kinetics are still not fully understood. In this contribution we present recent results on the importance of quenching by atomic oxygen on the vertical distribution of different OH Meinel bands. OH Meinel emissions from different vibrational levels are known to occur at slightly different altitudes in the terrestrial airglow with emissions originating from higher vibrational levels peaking at higher altitudes. Our earlier model studies suggested quenching by atomic oxygen to be a principal cause of these vertical shifts. Here we employ the tropical mesopause region - characterized by pronounced semiannual variations - as a natural laboratory to test the hypothesis that vertical shifts between different OH Meinel bands are a consequence of quenching by atomic oxygen. Multiyear nighttime satellite measurements of OH(3-1) and OH(6-2) volume emission rate profiles and atomic oxygen with SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric Chartography) on Envisat are used. The MLT atomic oxygen profiles are retrieved from measurements of the O(1S-1D) green line emission based on the accepted 2-step excitation scheme and a semi-empirical photochemical model. The results clearly demonstrate that vertical shifts between the OH bands investigated are indeed correlated with the amount of atomic oxygen in the upper mesosphere, corroborating the hypothesis that quenching by atomic oxygen is a driver for the vertical shifts between different OH Meinel bands.

  8. Strong Band-Edge Emission from ZnS Quantum Dots Stabilized by Gum Arabic

    NASA Astrophysics Data System (ADS)

    Hatim, Dirar Mohamed El-Khair

    2008-12-01

    ZnS quantum dots (QDs), prepared by soft-condensation, exhibit robust structure of a quantum size equal 3.13 nm mediated two-dimensional gum Arabic surfactant as characterized by scan tunnelling microscope (STM). Strong blue-shifted absorption and emission bands are depicted by optical characterization even for the sample stored under ambient condition for two weeks. These enhancements can be attributed to the completely passivated surface trap states by Gum Arabic.

  9. Anomalous Series of Bands in the Edge Emission Spectra of CdS(О)

    NASA Astrophysics Data System (ADS)

    Morozova, N. K.; Kanakhin, A. A.; Galstyan, V. G.; Shnitnikov, A. S.

    2015-02-01

    The region of the edge emission spectrum of CdS(O) single crystals with cadmium excess is examined. An anomalous series of equidistant bands with leading line at 514 nm and phonon replicas has been revealed. These bands grow in intensity with increase of the excitation density up to 1026-1027 cm-3ṡs-1 at 80 K, and the leading line of the series is observed even at 300 K. It is shown that luminescence is conditioned by the exciton spectrum in perfect bulk single-crystals of CdO. Some characteristics of this spectrum are presented, in particular, the dependence on temperature, excitation intensity, composition and size of the crystals, and the LO interaction. The results experimentally confirm the theoretically calculated magnitude of the direct band gap of CdO.

  10. Electronic structure of an [FeFe] hydrogenase model complex in solution revealed by X-ray absorption spectroscopy using narrow-band emission detection.

    PubMed

    Leidel, Nils; Chernev, Petko; Havelius, Kajsa G V; Schwartz, Lennart; Ott, Sascha; Haumann, Michael

    2012-08-29

    High-resolution X-ray absorption spectroscopy with narrow-band X-ray emission detection, supported by density functional theory calculations (XAES-DFT), was used to study a model complex, ([Fe(2)(μ-adt)(CO)(4)(PMe(3))(2)] (1, adt = S-CH(2)-(NCH(2)Ph)-CH(2)-S), of the [FeFe] hydrogenase active site. For 1 in powder material (1(powder)), in MeCN solution (1'), and in its three protonated states (1H, 1Hy, 1HHy; H denotes protonation at the adt-N and Hy protonation of the Fe-Fe bond to form a bridging metal hydride), relations between the molecular structures and the electronic configurations were determined. EXAFS analysis and DFT geometry optimization suggested prevailing rotational isomers in MeCN, which were similar to the crystal structure or exhibited rotation of the (CO) ligands at Fe1 (1(CO), 1Hy(CO)) and in addition of the phenyl ring (1H(CO,Ph), 1HHy(CO,Ph)), leading to an elongated solvent-exposed Fe-Fe bond. Isomer formation, adt-N protonation, and hydride binding caused spectral changes of core-to-valence (pre-edge of the Fe K-shell absorption) and of valence-to-core (Kß(2,5) emission) electronic transitions, and of Kα RIXS data, which were quantitatively reproduced by DFT. The study reveals (1) the composition of molecular orbitals, for example, with dominant Fe-d character, showing variations in symmetry and apparent oxidation state at the two Fe ions and a drop in MO energies by ~1 eV upon each protonation step, (2) the HOMO-LUMO energy gaps, of ~2.3 eV for 1(powder) and ~2.0 eV for 1', and (3) the splitting between iron d(z(2)) and d(x(2)-y(2)) levels of ~0.5 eV for the nonhydride and ~0.9 eV for the hydride states. Good correlations of reduction potentials to LUMO energies and oxidation potentials to HOMO energies were obtained. Two routes of facilitated bridging hydride binding thereby are suggested, involving ligand rotation at Fe1 for 1Hy(CO) or adt-N protonation for 1HHy(CO,Ph). XAES-DFT thus enables verification of the effects of ligand

  11. OH Vibrational Prompt Emission and Water Hot-Band Fluorescent Emission in C/2000 WM1 (LINEAR)

    NASA Astrophysics Data System (ADS)

    Bonev, B. P.; Mumma, M. J.; Dello Russo, N.; DiSanti, M. A.; Gibb, E. L.; Magee-Sauer, K.; Weaver, H. A.; Chin, G.

    2004-11-01

    Two methods for deriving cometary water production rates from ground-based high-resolution near-infrared spectra have now been developed. The water molecule can be directly sampled through "hot-band" fluorescent emission near 2.0, 2.9, 4.6, and 5.0 μ m [1]. Knowledge of the H2O rotational temperature and ortho-to-para ratio is needed to fully constrain its production rate via this method. More recently, vibrational prompt emission from OH has also been used as a proxy for water production. This method depends on the accuracy of the OH emission efficiencies derived from simultaneous observations of H2O and OH in comets C/1999 H1 (Lee) and C/2001 A2 (Linear) [2]. We report water production rates for a third comet (C/2000 WM1) based on independent analyses of H2O hot-band lines near 2.9 μ m and of OH prompt emission lines near 3046 cm-1, observed with NIRSPEC at the W. M. Keck Observatory. This comparison further reveals the capabilities and potential limitations of the two methods, while placing a special emphasis on the newer OH-based method. This work was supported by grants to M. J. Mumma (RTOP 344-32-30-07) and to H. A. Weaver and G. Chin (NAG5-12230) under NASA's Planetary Astronomy Program, and to N. Dello Russo (NAG5-10795) under NASA's Planetary Atmospheres Program. [1] Dello Russo et al. 2002, JGR, 107 (E11) 5095. [2] Bonev et al. 2004, ApJ, in press.

  12. Origin of the low-energy emission band in epitaxially grown para-sexiphenyl nanocrystallites

    NASA Astrophysics Data System (ADS)

    Kadashchuk, A.; Schols, S.; Heremans, P.; Skryshevski, Yu.; Piryatinski, Yu.; Beinik, I.; Teichert, C.; Hernandez-Sosa, G.; Sitter, H.; Andreev, A.; Frank, P.; Winkler, A.

    2009-02-01

    A comparative study of steady-state and time-resolved photoluminescence of para-sexiphenyl (PSP) films grown by organic molecular beam epitaxy (OMBE) and hot wall epitaxy (HWE) under comparable conditions is presented. Using different template substrates [mica(001) and KCl(001) surfaces] as well as different OMBE growth conditions has enabled us to vary greatly the morphology of the PSP crystallites while keeping their chemical structure virtually untouched. We prove that the broad redshifted emission band has a structure-related origin rather than being due to monomolecular oxidative defects. We conclude that the growth conditions and type of template substrate impacts substantially on the film morphology (measured by atomic force microscopy) and emission properties of the PSP films. The relative intensity of the defect emission band observed in the delayed spectra was found to correlate with the structural quality of PSP crystallites. In particular, the defect emission has been found to be drastically suppressed when (i) a KCl template substrate was used instead of mica in HWE-grown films, and (ii) in the OMBE-grown films dominated by growth mounds composed of upright standing molecules as opposed to the films consisting of crystallites formed by molecules lying parallel to the substrate.

  13. Origin of the low-energy emission band in epitaxially grown para-sexiphenyl nanocrystallites

    SciTech Connect

    Kadashchuk, A.; Schols, S.; Heremans, P.; Skryshevski, Yu.; Piryatinski, Yu.; Beinik, I.; Teichert, C.; Hernandez-Sosa, G.; Sitter, H.; Andreev, A.; Frank, P.; Winkler, A.

    2009-02-28

    A comparative study of steady-state and time-resolved photoluminescence of para-sexiphenyl (PSP) films grown by organic molecular beam epitaxy (OMBE) and hot wall epitaxy (HWE) under comparable conditions is presented. Using different template substrates [mica(001) and KCl(001) surfaces] as well as different OMBE growth conditions has enabled us to vary greatly the morphology of the PSP crystallites while keeping their chemical structure virtually untouched. We prove that the broad redshifted emission band has a structure-related origin rather than being due to monomolecular oxidative defects. We conclude that the growth conditions and type of template substrate impacts substantially on the film morphology (measured by atomic force microscopy) and emission properties of the PSP films. The relative intensity of the defect emission band observed in the delayed spectra was found to correlate with the structural quality of PSP crystallites. In particular, the defect emission has been found to be drastically suppressed when (i) a KCl template substrate was used instead of mica in HWE-grown films, and (ii) in the OMBE-grown films dominated by growth mounds composed of upright standing molecules as opposed to the films consisting of crystallites formed by molecules lying parallel to the substrate.

  14. Rain effect on Aquarius L-band Emissivity and Backscatter Model Functions

    NASA Astrophysics Data System (ADS)

    Tang, W.; Yueh, S. H.; Fore, A.; Neumann, G.; Hayashi, A.

    2012-12-01

    Remote sensing of sea surface salinity (SSS) is being performed by Aquarius and SMOS missions, which are using L-band radiometry to sense the microwave emissions from sea surfaces. To enable accurate SSS retrieval, it is essential to correct the impact of sea surface roughness on L-band brightness temperatures. In addition, the impact of rain has to be carefully assessed and accounted for. Although the atmospheric attenuation caused by raindrops are likely negligible at 1.4GHz, other factors must be considered because they may have indirect but important contribution to the surface roughness and consequently L-band brightness temperatures. For example, the wind speed dependent roughness correction will be corrupted when rain striking the water, creating rings, stalks, and crowns from which the signal scatters. It is also unknown how long the freshwater stays at surface while through the oceanic mixing process at various regions over global oceans. We collocated the Aquarius L-band data with various wind products, including SSM/I, NCEP, ASCAT and WindSAT, as well as the SSM/I and WindSAT rain products. During the first four months of Aquarius mission, near 1.9 million pixels are identified under rain conditions by either SSM/I or WindSAT. We derived the L-band emissivity and backscatter geophysical model functions (GMF), parameterized by SSM/I and NCEP winds for rain-free conditions. However, the residual ocean surface emissivity (the Aquarius measured minus the rain-free model predictions) reveals profound resemblance with global precipitation pattern. In region dominated by rain, e.g. ITCZ, northern hemisphere storm track, and Indian Ocean partially under the influence of summer monsoon, the GMF built using rain free data underestimates excess emissivity about 0.5 to 1 K. The dependence of residual of emissivity and backscatter is shown as a function of wind speed and rain rate. A modified GMF is developed including rain rate as one of the parameters. Due to

  15. Low energy emission bands in a small molecular fluorene derivative for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Lou, S. L.; Yu, H. S.; Ma, W. M.; Jiang, Y.; Zhang, Q.

    2008-11-01

    6,6'-(9H-fluoren-9,9-diyl)bis(2,3-bis(9,9-dihexyl-9H-fluoren-2-yl)quinoxaline) (BFLBBFLYQ) was a novel small molecular fluorene material with fluorescence maxima at 450 nm in spin cast films. Compared to spin cast films, BFLBBFLYQ vacuum evaporated deposition films exhibited different photo-physical properties. The low energy emission bands from 530 to 570 nm were observed from the electroluminescence (EL) and photoluminescence (PL) spectra of BFLBBFLYQ films evaporated deposition in ultrahigh vacuum circumstance, and the origin of these emission features were investigated and discussed. Also, the emissive properties of BFLBBFLYQ spin cast films upon thermal annealing and under UV irradiation in air were characterized for the effect of thermal oxidization and photo-oxidization.

  16. Excitation temperatures determined from H{sup +}{sub 3} hot band emission in the Jovian ionosphere

    SciTech Connect

    Jagod, M.F.; Oka, T.; Geballe, T.R.

    1996-12-31

    Since the observation of the 3.544 {mu}m 2v{sup 0}{sub 2} {r_arrow} v{sub 2} (J = 9, K = 9 {r_arrow} J = 8, G = 9, U = 1) hot band transition of H{sup +}{sub 3} in the polar regions of Jupiter, the authors have pursued the simultaneous detection of additional hot band transitions with fundamental band transitions in order to derive well determined H+ excitation temperatures. The authors report 9 additional resolved 2{nu}{sub 2}{sup 2} {r_arrow} {nu}{sub 2} and {nu}{sub 1} + {nu}{sub 2} {r_arrow} {nu}{sub 1} hot band transitions observed in emission at 3.52, 3.63, 3.66, and 3.84 {mu}m. The hot band transitions have thus far only been detected in the polar regions, with the occasional exception being the 3.544 {mu}m 2{nu}{sup 0}{sub 2} {r_arrow} {nu}{sub 2} transition around 45{degrees}S latitude during the 1994 Comet Shoemaker Levy-9 encounter. Temporal and spatial variation of the excitation temperatures as well as their dependence on vibrational mode will be presented. Anomalous line intensities, e.g. {sup r}R(3,3){sup -b} will also be discussed. All observations were made with the CGS4 spectrometer at the United Kingdom Infrared Telescope on Mauna Kea, Hawaii.

  17. New Optical Emissions in the Terrestrial Nightglow: The O2(c-b) Bands

    NASA Astrophysics Data System (ADS)

    Slanger, T. G.; Cosby, P. C.; Huestis, D. L.

    2002-05-01

    Sky spectra from the Keck I and II telescopes in the 380-450 nm region have revealed the presence of a new O2 band system, the transition between the c1Σu- b1Σg+ states. There is only a Q-branch associated with the transition and the unusual symmetry favors emission from high rotational le vels. Radiation from c(v = 9,10) is particularly pronounced, but O2(c) population is seen over the range v = 5-11. The sparse individual lines of the 9-1 c-b band are as bright as any Herzberg I or Chamberlain band line at wavelengths longer than 365 nm. We have not yet seen lines in the c-X Herzberg II system in the present data set at wavelengths greater than 337 nm. The probable explanation for the c-b transition being evident while the c-X transition is not is that the c-b emission is concentrated in 1/4 as many lines, and the strongest c-X bands are at shorter wavelengths, inaccessible from the ground. We presently estimate an emission intensity of 30 R for the c-b system. As the term energies for both states are accurately known, the lines can be used for precise calibration of aeronomical and astronomical spectra, as well as for investigations on the c1Σu- state. Loss rate coefficients for the c(v = 8-11) levels are currently being determined in the laboratory for the temperature range relevant to the terrestrial upper atmosphere[1]. [1] G. Amaral, G. B. Bressler, E. S. Hwang, K. Kalogerakis, A. Totth, and R. A. Copeland (in preparation); R. A. Copeland, K. Knutsen, M. E. Onishi, and T. Yalcin, J. Chem. Phys. 105, 10340 (1994). This work was supported by a grant from the NSF CEDAR program.

  18. Multiyear On-orbit Calibration and Performance of Terra MODIS Thermal Emissive Bands

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Chiang, Kwo-Fu; Wu, Aisheng; Barnes, William; Guenther, Bruce; Salomonson, Vincent

    2007-01-01

    Since launch in December 1999, Terra MODIS has been making continuous Earth observations for more than seven years. It has produced a broad range of land, ocean, and atmospheric science data products for improvements in studies of global climate and environmental change. Among its 36 spectral bands, there are 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). MODIS thermal emissive bands cover the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions with wavelengths from 3.7 to 14.4pm. They are calibrated on-orbit using an on-board blackbody (BB) with its temperature measured by a set of thermistors on a scan-by-scan basis. This paper will provide a brief overview of MODIS TEB calibration and characterization methodologies and illustrate on-board BB functions and TEB performance over more than seven years of on-orbit operation and calibration. Discussions will be focused on TEB detector short-term stability and noise characterization, and changes in long-term response (or system gain). Results show that Terra MODIS BB operation has been extremely stable since launch. When operated at its nominal controlled temperature of 290K, the BB temperature variation is typically less than +0.30mK on a scan-by-scan basis and there has been no time-dependent temperature drift. In addition to excellent short-term stability, most TEB detectors continue to meet or exceed their specified noise characterization requirements, thus enabling calibration accuracy and science data product quality to be maintained. Excluding the noisy detectors identified pre-launch and those that occurred post-launch, the changes in TEB responses have been less than 0.7% on an annual basis. The optical leak corrections applied to bands 32-36 have been effective and stable over the entire mission

  19. Near Band Edge Emission by Free Exciton Decay and Intrinsic Ferromagnetic Ordering of Cu-Doped SnO2 Hollow Nanofibers.

    PubMed

    Mohanapriya, P; Jaya, N Victor

    2015-03-01

    High quality nanocrystalline pristine and Cu-doped SnO2 hollow nanofibers were successfully prepared through simple and effective electrospinning technique. Nanofibers calcined at 600 °C for 3 h were characterized with different analytical techniques such as X-ray diffraction (XRD), Transmission electron Microscope (TEM) and Vibrating sample magnetometer (VSM). Observed TEM images and XRD patterns were corroborate to the formation of tetragonal crystalline SnO2 hollow nanofibers with rutile phase. Excellent optical behaviour was observed for Cu-doped SnO2. Highly intense near band edge emission at 3.58 eV for Cu-doped SnO2 evidences the free exciton decay process in the hollow nanofibers. For the first time we have reported here the near band edge PL emission in Cu-doped SnO2 tubular hollow nanostructure. This study substantiates that material potential for UV-lasing application. In addition to the above, magnetic measurement ascribes that Cu-doped SnO2 exhibit the intrinsic room temperature ferromagnetism within the low field strength. The occurrence of ferromagnetism in Cu-doped SnO2 is directly related to the p-d ferromagnetic exchange coupling between the local magnetic moment of Cu2+ and the polarized valence electrons of surrounding oxygen. Over all this study provides the primary information about tunable multifunctionality of SnO2 hollow nanostructures by adding the non-magnetic Cu ions.

  20. EXAMINING THE BROADBAND EMISSION SPECTRUM OF WASP-19b: A NEW z-BAND ECLIPSE DETECTION

    SciTech Connect

    Zhou, George; Bayliss, Daniel D. R.; Kedziora-Chudczer, Lucyna; Bailey, Jeremy

    2013-09-10

    WASP-19b is one of the most irradiated hot-Jupiters known. Its secondary eclipse is the deepest of all transiting planets and has been measured in multiple optical and infrared bands. We obtained a z-band eclipse observation with a measured depth of 0.080% {+-} 0.029%, using the 2 m Faulkes Telescope South, which is consistent with the results of previous observations. We combined our measurement of the z-band eclipse with previous observations to explore atmosphere models of WASP-19b that are consistent with its broadband spectrum. We use the VSTAR radiative transfer code to examine the effect of varying pressure-temperature profiles and C/O abundance ratios on the emission spectrum of the planet. We find that models with super-solar carbon enrichment best match the observations, which is consistent with previous model retrieval studies. We also include upper atmosphere haze as another dimension in the interpretation of exoplanet emission spectra and find that particles <0.5 {mu}m in size are unlikely to be present in WASP-19b.

  1. L-Band Emission of Soil Freeze-Thaw State in a Tibetan Meadow Ecosystem

    NASA Astrophysics Data System (ADS)

    Zheng, Donghai; Wang, Xin; van der Velde, Rogier; Su, Zhongbo; Zeng, Yijian; Wen, Jun; Wang, Zuoliang; Schwank, Mike; Ferrazzoli, Paolo

    2017-04-01

    Soil freeze-thaw transition monitoring is essential for quantifying climate change and hydrologic dynamics over cold regions, for instance, the Tibetan Plateau. We investigate the L-band (1.4 GHz) microwave emission characteristics of soil freeze-thaw cycle via analysis of tower-based brightness temperature (TB) measurements using the ELBARA III radiometer in combination with simulations performed by a model of soil emission considering vertical variations of permittivity and soil temperature. Vegetation effects are modelled using the Tor Vergata discrete model. As part of Soil Moisture and Ocean Salinity (SMOS) and Soil Moisture Active Passive (SMAP) calibration and validation activities, the ELBARA III radiometer is installed on a 4.8 m high tower located in a seasonally frozen Tibetan meadow ecosystem to measure diurnal cycles of L-band TB. The daily measurements include elevation scanning sequences toward the ground and zenith (sky) measurements. The angular range considered for the elevation scans is performed every 30 min between 40°-70° (relative to nadir) in steps of 5°. The sky measurement is performed at 23:55 every day with an observation angle of 155°. Supporting micro-meteorological (e.g. solar radiation, air temperature and humidity) as well as soil moisture and temperature profile measurements are also conducted near the radiometer. Analyses of the measurements reveal that the impact on TB caused by diurnal changes of ground permittivity is generally stronger than the effect of changing ground temperature. Moreover, the simulations performed with the integrated Tor Vergata model and Noah land surface model indicate that the TB signatures of diurnal soil freeze-thaw cycle is most sensitive to the liquid water content of the soil surface layer, and the measurements taken at 5 cm depth are less representative for the L-band emission.

  2. Development of a L-band ocean emissivity electromagnetic model using observations from the Aquarius Radiometer

    NASA Astrophysics Data System (ADS)

    Hejazin, Y.; Jones, W.; El-Nimri, S.

    2012-12-01

    The Aquarius/SAC-D ocean salinity measurement mission was launched into polar orbit during the summer of 2011. The prime sensor is an L-band radiometer/scatterometer developed jointly by NASA Goddard Space Flight Center and the Jet Propulsion Laboratory. This paper deals with the development of an ocean emissivity model using AQ radiometer brightness temperature (Tb) observations. This model calculates the ocean surface emissivity as a function of ocean salinity, sea surface temperature, surface wind speed and direction. One unique aspect of this model is that it calculates ocean emissivity over wide ranges of Earth incidence angles (EIAs) from nadir to > 60°and ocean wind speeds from 0 m/s to > 70 m/s. This physical electromagnetic model with empirical coefficients follows the form of Stogryn [1967] that treats the ocean as a mixture of foam and clean rough water. The CFRSL ocean surface emissivity (ɛocean) is modeled as a linear sum of foam (ɛfoam) and foam-free seawater (ɛrough) emissivities, according to ɛocean = FF * ɛfoam + (1 - FF) * ɛrough (1) where FF is the fractional area coverage by foam. The foam emissivity is modeled as ɛfoam = Q(freq, U10, EIA) (2) where Q( ) is the empirical dependence of foam emissivity on radiometer frequency, the 10-m neutral stability wind speed and EIA according to El-Nimri [2010]. Following Stogryn, the foam-free seawater emissivity (ɛrough) is modeled ɛrough = ɛsmooth +Δɛexcess (3) where ɛsmooth = (1 - Γ) is the smooth surface emissivity, Γ is the Fresnel power reflection coefficient, and Δɛexcess is the wind-induced excess emissivity, given by Δɛexcess = G(freq, U10, WDir, EIA) (4) Where G( ) is the empirical signature of foam-free rough ocean, which depends upon the surface wind speed and wind direction. This function is determined empirically from measured AQ radiometer Tb's associated with surface wind vector from collocated NOAA GDAS numerical weather model. Ocean emissivity calculations are compared

  3. Detection of Time Lags between Quasar Continuum Emission Bands Based On Pan-STARRS Light Curves

    NASA Astrophysics Data System (ADS)

    Jiang, Yan-Fei; Green, Paul J.; Greene, Jenny E.; Morganson, Eric; Shen, Yue; Pancoast, Anna; MacLeod, Chelsea L.; Anderson, Scott F.; Brandt, W. N.; Grier, C. J.; Rix, H.-W.; Ruan, John J.; Protopapas, Pavlos; Scott, Caroline; Burgett, W. S.; Hodapp, K. W.; Huber, M. E.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A.; Metcalfe, N.; Tonry, J. T.; Wainscoat, R. J.; Waters, C.

    2017-02-01

    We study the time lags between the continuum emission of quasars at different wavelengths, based on more than four years of multi-band (g, r, i, z) light curves in the Pan-STARRS Medium Deep Fields. As photons from different bands emerge from different radial ranges in the accretion disk, the lags constrain the sizes of the accretion disks. We select 240 quasars with redshifts of z ≈ 1 or z ≈ 0.3 that are relatively emission-line free. The light curves are sampled from day to month timescales, which makes it possible to detect lags on the scale of the light crossing time of the accretion disks. With the code JAVELIN, we detect typical lags of several days in the rest frame between the g band and the riz bands. The detected lags are ∼2–3 times larger than the light crossing time estimated from the standard thin disk model, consistent with the recently measured lag in NGC 5548 and microlensing measurements of quasars. The lags in our sample are found to increase with increasing luminosity. Furthermore, the increase in lags going from g ‑ r to g ‑ i and then to g ‑ z is slower than predicted in the thin disk model, particularly for high-luminosity quasars. The radial temperature profile in the disk must be different from what is assumed. We also find evidence that the lags decrease with increasing line ratios between ultraviolet Fe ii lines and Mg ii, which may point to changes in the accretion disk structure at higher metallicity.

  4. Narrow-band single-photon emission in the near infrared for quantum key distribution.

    PubMed

    Wu, E; Jacques, Vincent; Zeng, Heping; Grangier, Philippe; Treussart, François; Roch, Jean-François

    2006-02-06

    We present a detailed study of photophysical properties of single color centers in natural diamond samples emitting in the near infrared under optical excitation. Photoluminescence of these single emitters has several striking features, including narrow-band (FWHM 2 nm) fully polarized emission around 780 nm, a short excited-state lifetime of about 2 ns, and perfect photostability at room temperature under our excitation conditions. Development of a triggered single-photon source relying on this single color center is discussed for application to quantum key distribution.

  5. Quantum simulation of the yellow emission band of CsXe

    NASA Technical Reports Server (NTRS)

    Tellinghuisen, J.; Exton, R. J.

    1980-01-01

    Quantum spectral simulations of the yellow excimer emission band of CsXe are presented. Synthetic spectra as a function of wave number are calculated for the 2 Sigma 1/2 + (7s) - 2 Sigma 1/2 + (6s) transition by the use of the equation of Tellinghuisen et al. (1976) with a theoretical potential for the ground state and a Morse potential curve with an electron frequency of 32/cm for the excited state. Results based on emission studies at 450 K and 200 and 800 torr, are found to be consistent with absorption studies. The undulatory structure observed in the spectrum is attributed not to the vibrational spacing in the excited state, but rather to a characteristic reflection structure associated with nearly parallel upper and lower potential curves.

  6. Band-limited Green's Functions for Quantitative Evaluation of Acoustic Emission Using the Finite Element Method

    NASA Technical Reports Server (NTRS)

    Leser, William P.; Yuan, Fuh-Gwo; Leser, William P.

    2013-01-01

    A method of numerically estimating dynamic Green's functions using the finite element method is proposed. These Green's functions are accurate in a limited frequency range dependent on the mesh size used to generate them. This range can often match or exceed the frequency sensitivity of the traditional acoustic emission sensors. An algorithm is also developed to characterize an acoustic emission source by obtaining information about its strength and temporal dependence. This information can then be used to reproduce the source in a finite element model for further analysis. Numerical examples are presented that demonstrate the ability of the band-limited Green's functions approach to determine the moment tensor coefficients of several reference signals to within seven percent, as well as accurately reproduce the source-time function.

  7. Interstellar polycyclic aromatic hydrocarbons: the infrared emission bands, the excitation/emission mechanism, and the astrophysical implications.

    PubMed

    Allamandola, L J; Tielens, A G; Barker, J R

    1989-12-01

    This article presents a comprehensive treatment of the polycyclic aromatic hydrocarbon (PAH) hypothesis. The interstellar, infrared spectral features which have been attributed to emission from highly vibrationally excited PAHs are discussed in detail. These include major (most intense) bands at 3040, 1615, "1310," 1150, and 885 cm-1 (3.29, 6.2 "7.7," 8.7, and 11.3 micrometers), minor bands and broad features in the 3200-2700 cm-1 [correction of 3200-2700-1] (3.1-3.7 micrometers), 1600-1100 cm-1 (6.0-9 micrometers) and 910-770 cm-1 (11-13 micrometers) regions, as well as the vibrational quasi-continuum spanning the entire mid-IR and the electronic transitions which contribute to the high-frequency IR continuum. All the major and minor bands, as well as the quasi-continuum, can be attributed to vibrational transitions in molecular-sized PAHs. The latter two broad features probably arise from very large PAHs, PAH clusters, and amorphous carbon particles. A precise match of the interstellar spectra with laboratory spectra is not yet possible because laboratory spectra are not available of PAHs in the forms probably present in the interstellar medium (completely isolated, ionized, some completely dehydrogenated, and containing between about 20 and 40 carbon atoms). The method with which one can calculate the IR fluorescence spectrum from a vibrationally excited molecule is also described in detail. Fluorescence band intensities, relaxation rates, and dependence on molecule size and energy content are treated explicitly. Analysis of the interstellar spectra indicates that the PAHs which dominate the infrared spectra contain between about 20 and 40 carbon atoms. The results obtained with this method are compared with the results obtained using a thermal approximation. It is shown that for high levels of vibrational excitation and emission from low-frequency modes, the two methods give similar results. However, at low levels of vibrational excitation and for the high

  8. The solar wind control of Jupiter's broad-band kilometric radio emission

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.; Leblanc, Y.; Desch, M. D.

    1988-01-01

    Observations of the solar wind close to Jupiter are compared with the broad-band kilometric radio emission (bKOM), using data recorded by Voyager 1 and Voyager 2 during 1979. The lower bKOM frequencies, less than about 300 kHz, are found to correlate with the solar wind density and pressure and with the interplanetary magnetic field (IMF) magnitude during periods when there is a well-defined magnetic sector structure. The results suggest that lower frequency bKOM events are most likely to occur after a sector boundary has passed Jupiter during the period when the solar wind density and the IMF magnitude are increasing towards the sector center. The average bKOM energy per Jovian rotation tends to have lower values soon after the sector center has passed. Higher-frequency/higher-energy bKOM emission may be contaminated by hectometric emission (HOM) and differently correlated with solar activity. The solar wind control may also be obscured by some stronger control. It is suggested that electron density fluctuations in the Io torus, where the source is believed to be located, may be responsible for variations in the beaming and hence variations in the observed emission.

  9. Emission from the Local Galactic Halo in the 1/4 keV Band

    NASA Astrophysics Data System (ADS)

    Juda, M.

    1994-12-01

    Pointed observations with the ROSAT PSPC toward clouds at high galactic latitude provide a unique opportunity to probe emission from the local galactic halo in the 1/4 keV band. I present data from five fields toward clouds at |b| > 60(deg) identified through their IRAS 100 microns emission, two in the north galactic hemisphere and three in the south. In four of the five fields significant shadows are detected (2 north, 2 south). The derivation of the brightness of the shadowed component depends strongly on the assumed location and amount of absorbing material. Scaling the IRAS 100 microns emission by 10(20) H atom cm(-2) /MJy sr(-1) and correcting for the difference from the observed average 21 cm derived column density, the implied brightness of the distant emitting component is the same for the two northern latitude fields at { ~ 1.2*E(-3) counts s(-1) arcmin(-2}) ; this brightness is lower than that seen in the direction of Draco (Burrows & Mendenhall 1991, Snowden et al. 1991) and higher than in Ursa Major (Snowden et al. 1994). The two southern fields also have the same derived distant brightness at nearly the same level as the northern fields, { ~ 1.0*E(-3) counts s(-1) arcmin(-2}) . Approximately 20% of this emission may be attributed to an extragalactic background (Hasinger et al. 1993). The remaining emission, { ~ 0.8*E(-3) counts s(-1) arcmin(-2}) , would be provided by the local galactic halo. If these x-rays arise from a collisionally excited plasma at a temperature of 10(6) K the required emission measure is { ~ 0.0033 cm(-6) pc}. Burrows & Mendenhall 1991, Nature, 351, 629. Hasinger et al. 1993, A&A, 275, 1. Snowden et al. 1991, Science, 252, 1529. Snowden et al. 1994, ApJ, 430, 601.

  10. EV Charging Infrastructure Roadmap

    SciTech Connect

    Karner, Donald; Garetson, Thomas; Francfort, Jim

    2016-08-01

    As highlighted in the U.S. Department of Energy’s EV Everywhere Grand Challenge, vehicle technology is advancing toward an objective to “… produce plug-in electric vehicles that are as affordable and convenient for the average American family as today’s gasoline-powered vehicles …” [1] by developing more efficient drivetrains, greater battery energy storage per dollar, and lighter-weight vehicle components and construction. With this technology advancement and improved vehicle performance, the objective for charging infrastructure is to promote vehicle adoption and maximize the number of electric miles driven. The EV Everywhere Charging Infrastructure Roadmap (hereafter referred to as Roadmap) looks forward and assumes that the technical challenges and vehicle performance improvements set forth in the EV Everywhere Grand Challenge will be met. The Roadmap identifies and prioritizes deployment of charging infrastructure in support of this charging infrastructure objective for the EV Everywhere Grand Challenge

  11. High Resolution Emission Spectroscopy of the Alpha Pi-1 - Chi Sigma-1(+) Fourth Positive Band System of CO from Electron Impact

    NASA Technical Reports Server (NTRS)

    Beegle, Luther W.; Ajello, Joseph M.; James, Geoffrey K.; Alvarez, Marcos; Dziczek, Dariusz

    2000-01-01

    We report electron-impact induced fluorescence spectra [300 mA full width at half maximum (FWHM)] of CO for 20 and 100 eV impact energies of the spectral region of 1300 to 2050 A and high resolution spectra (FWHM) of the v'=5 to v"=l and the v'=3 to v"=O bands showing that the rotational structure of the band system are modeled accurately. The excitation function of the (0,1) band (1597 A) was measured from electron impact in the energy range from threshold to 750 eV and placed on an absolute scale from modem calibration standards.

  12. Measurement of the 238U neutron-capture cross section and gamma-emission spectra from 10 eV to 100 keV using the DANCE detector at LANSCE

    SciTech Connect

    Ullmann, John L; Couture, A J; Keksis, A L; Vieira, D J; O' Donnell, J M; Jandel, M; Haight, R C; Rundberg, R S; Kawano, T; Chyzh, A; Baramsai, B; Wu, C Y; Mitchell, G E; Becker, J A; Krticka, M

    2010-01-01

    A careful new measurement of the {sup 238}U(n,{gamma}) cross section from 10 eV to 100 keV has been made using the DANCE detector at LANSCE. DANCE is a 4{pi} calorimetric scintillator array consisting of 160 BaF{sub 2} crystals. Measurements were made on a 48 mg/cm{sup 2} depleted uranium target. The cross sections are in general good agreement with previous measurements. The gamma-ray emission spectra, as a function of gamma multiplicity, were also measured and compared to model calculations.

  13. Thermochromic Luminescent Materials and Multi-Emission Bands in d10 Clusters

    PubMed Central

    Gautier, Romain; Latouche, Camille; Paris, Michael; Massuyeau, Florian

    2017-01-01

    Thermochromic luminescent compounds with d10 metal ions are interesting materials for applications such as sensors or display devices. However, these properties are difficult to predict prior to their synthesis. In this communication, we investigated materials with structural assemblies known to be responsible of distinct luminescence mechanisms and show that they can be interesting potential thermometers. Thus, we compared the synthesis of a zinc halide and a copper halide based compounds which only differ in their ability to create clusters with metallophilic interactions. The compounds synthesized by hydrothermal method have been structurally characterized by Single-crystal X-ray diffraction, Solid-State NMR, FTIR, UV-Visible spectroscopy, thermal analysis and EPR. The photoluminescence properties of the two materials have been characterized at different temperatures. The copper bromide compound shows luminescence thermochromism in a wide spectrum of colors owing to the formation of clusters generating multi-emission bands while the zinc bromide exhibits a single emission band and no thermochromism. PMID:28358142

  14. Capturing electromagnetic emissions in the HF band possibly related to earthquake events

    NASA Astrophysics Data System (ADS)

    Koulouras, Gr; Kontakos, K.; Ninos, K.; Cavouras, D.; Nomicos, C.

    2009-04-01

    The purpose of this project was to capture electromagnetic emissions in the HF band. Possible correlations of these emissions prior to strong earthquakes were investigated. In order to record the variations of the electromagnetic field in a wide spectrum of frequencies up to the VHF band, a new device was designed and implemented by our research team. Ten prototype electromagnetic variation (EMV) field stations have already been installed in Greece, at the locations, Corfu, Ioannina, Ithomi (Kalamata), Kephalonia, Kozani, Mytilini, Rodos, Neapoli (Crete), and Bamos (Crete). This telemetric network was launched in 1999 and since it has been in constant operation. During the period 2005-2008, 14 strong earthquakes occurred in Greece with magnitude over Ms>=6. Of them, three events were recorded as precursor signals by only one station. Fractal analysis showed that these were precursors and not manmade signals. In eight EQs events, two or three stations recorded simultaneously precursor signals. In one EQ event, recordings in all stations were disturbed by strong magnetic storms twenty days before the event. In two EQs, events did not trigger any station in a time window of up to 10 days.

  15. Determination of longwave anisotropic emission factors from combined broad- and narrow-band radiance measurements

    NASA Astrophysics Data System (ADS)

    Stubenrauch, C.; Duvel, J.-Ph.; Kandel, R. S.

    1994-01-01

    The conversion of measured broad-band radiances into radiative fluxes requires application of angular corrections: In the Earth Radiation Budget Experiment (ERBE), the longwave anisotropic emission factors (AEF) were tabulated for different viewing zenith angles, seasons, latitude bands and scence types including four different cloud cover classes. Investigating an alternative approach for the ScaRaB (Scanner for Radiation Balance) instrument, we use a radiative transfer model to parametrize the AEF as a function of viewing zenith angle and a single other variable - `atmospheric pseudo-absorptance' - extracted from simultaneously measured broad-band longwave (LW) and infrared (IR) atmospheric window (10.5-12.5μm) radiances. For validation, we use simultaneous co-located NOAA-9 AVHRR-ERBE data. Compared to the ERBE AEF's the ScaRaB parametrization provides more realistic AEF's as a function of scene brightness temperature which is related to cloud top height. Analysis of classified cloud data indicates that there are only a few extreme cases in which additional anisotropy due to broken clouds will affect the usefulness of our parametrization. We also consider enhanced anisotropy of semitransparent cirrus. Model and data show that although not explicitly treated in our procedure, the parametrization gives good results.

  16. Results and Lessons from MODIS Thermal Emissive Bands Calibration: Pre-launch to On-orbit

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Chiang, K.; Barnes, W. L.; Guenther, B.

    2006-01-01

    MODIS is a major instrument for the NASA EOS Terra (launched in December 1999) and Aqua (launched in May 2002) missions. It was designed and built to enhance and extend its heritage sensors' measurements and data records with applications covering a wide range of studies of the Earth's land, oceans, and atmosphere. Its 16 thermal emissive bands (TEB), each with 10 detectors, are located on the two cold focal plane assemblies (FPAs) controlled by a passive radiative cooler. Because of instrument design complexity and stringent calibration requirements, extensive calibration and characterization activities were conducted pre-launch by the sensor vendor for both Terra and Aqua MODIS. For TEB, these activities include characterization of detectors' noise and non-linearity and evaluation of their radiometric performance in thermal vacuum at difference instrument temperatures and FPA temperatures. In addition TEB system level response versus scan-angle (RVS) and relative spectral response (RSR) were characterized. MODIS TEB radiometric calibration transfer from pre-launch to on-orbit was performed using spectral bands' responses to the instrument on-board blackbody and a laboratory blackbody calibration source (BCS) traceable to NIST standards. This paper provides a summary of MODIS TEB pre-launch and on-orbit calibration and characterization activities, challenges, data analysis results, and lessons learned with focus on sensors' radiometric performance. A comparison between Terra and Aqua MODIS TEB performance is also presented. A similar summary for the reflective solar bands (RSB) is reported in a separate paper in these proceedings.

  17. Terra and Aqua MODIS Thermal Emissive Bands On-Orbit Calibration and Performance

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Wu, Aisheng; Wenny, Brian N.; Madhavan, Sriharsha; Wang, Zhipeng; Li, Yonghong; Chen, Na; Barnes, William L.; Salomonson, Vincent V.

    2015-01-01

    Since launch, the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua spacecraft have operated successfully for more than 14 and 12 years, respectively. A key instrument for National Aeronautics and Space Administration Earth Observing System missions, MODIS was designed to make continuous observations for studies of Earth's land, ocean, and atmospheric properties and to extend existing data records from heritage Earth observing sensors. The 16 thermal emissive bands (TEBs) (3.75-14.24 micrometers) are calibrated on orbit using a temperature controlled blackbody (BB). Both Terra and Aqua MODIS BBs have displayed minimal drift over the mission lifetime, and the seasonal variations of the BB temperature are extremely small in Aqua MODIS. The long-term gain and noise equivalent difference in temperature performance of the 160 TEB detectors on both MODIS instruments have been well behaved and generally very stable. Small but noticeable variations of Aqua MODIS bands 33-36 (13.34-14.24 micrometer) response in recent years are primarily due to loss of temperature control margin of its passive cryoradiative cooler. As a result, fixed calibration coefficients, previously used by bands when the BB temperature is above their saturation temperatures, are replaced by the focal-plane-temperature-dependent calibration coefficients. This paper presents an overview of the MODIS TEB calibration, the on-orbit performance, and the challenging issues likely to impact the instruments as they continue operating well past their designed lifetime of six years.

  18. Terra and Aqua MODIS Thermal Emissive Bands On-Orbit Calibration and Performance

    NASA Technical Reports Server (NTRS)

    Xiong, Xiaoxiong; Wu, Aisheng; Wenny, Brian N.; Madhavan, Sriharsha; Wang, Zhipeng; Li, Yonghong; Chen, Na; Barnes, William L.; Salomonson, Vincent V.

    2015-01-01

    Since launch, the Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua spacecraft have operated successfully for more than 14 and 12 years, respectively. A key instrument for National Aeronautics and Space Administration Earth Observing System missions, MODIS was designed to make continuous observations for studies of Earth's land, ocean, and atmospheric properties and to extend existing data records from heritage Earth observing sensors. The 16 thermal emissive bands (TEBs) (3.75-14.24 micrometers) are calibrated on orbit using a temperature controlled blackbody (BB). Both Terra and Aqua MODIS BBs have displayed minimal drift over the mission lifetime, and the seasonal variations of the BB temperature are extremely small in Aqua MODIS. The long-term gain and noise equivalent difference in temperature performance of the 160 TEB detectors on both MODIS instruments have been well behaved and generally very stable. Small but noticeable variations of Aqua MODIS bands 33-36 (13.34-14.24 micrometer) response in recent years are primarily due to loss of temperature control margin of its passive cryoradiative cooler. As a result, fixed calibration coefficients, previously used by bands when the BB temperature is above their saturation temperatures, are replaced by the focal-plane-temperature-dependent calibration coefficients. This paper presents an overview of the MODIS TEB calibration, the on-orbit performance, and the challenging issues likely to impact the instruments as they continue operating well past their designed lifetime of six years.

  19. Results and Lessons from MODIS Thermal Emissive Bands Calibration: Pre-launch to On-orbit

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Chiang, K.; Barnes, W. L.; Guenther, B.

    2006-01-01

    MODIS is a major instrument for the NASA EOS Terra (launched in December 1999) and Aqua (launched in May 2002) missions. It was designed and built to enhance and extend its heritage sensors' measurements and data records with applications covering a wide range of studies of the Earth's land, oceans, and atmosphere. Its 16 thermal emissive bands (TEB), each with 10 detectors, are located on the two cold focal plane assemblies (FPAs) controlled by a passive radiative cooler. Because of instrument design complexity and stringent calibration requirements, extensive calibration and characterization activities were conducted pre-launch by the sensor vendor for both Terra and Aqua MODIS. For TEB, these activities include characterization of detectors' noise and non-linearity and evaluation of their radiometric performance in thermal vacuum at difference instrument temperatures and FPA temperatures. In addition TEB system level response versus scan-angle (RVS) and relative spectral response (RSR) were characterized. MODIS TEB radiometric calibration transfer from pre-launch to on-orbit was performed using spectral bands' responses to the instrument on-board blackbody and a laboratory blackbody calibration source (BCS) traceable to NIST standards. This paper provides a summary of MODIS TEB pre-launch and on-orbit calibration and characterization activities, challenges, data analysis results, and lessons learned with focus on sensors' radiometric performance. A comparison between Terra and Aqua MODIS TEB performance is also presented. A similar summary for the reflective solar bands (RSB) is reported in a separate paper in these proceedings.

  20. Dual-Polarization Observations of Slowly Varying Solar Emissions from a Mobile X-Band Radar

    PubMed Central

    Gabella, Marco; Leuenberger, Andreas

    2017-01-01

    The radio noise that comes from the Sun has been reported in literature as a reference signal to check the quality of dual-polarization weather radar receivers for the S-band and C-band. In most cases, the focus was on relative calibration: horizontal and vertical polarizations were evaluated versus the reference signal mainly in terms of standard deviation of the difference. This means that the investigated radar receivers were able to reproduce the slowly varying component of the microwave signal emitted by the Sun. A novel method, aimed at the absolute calibration of dual-polarization receivers, has recently been presented and applied for the C-band. This method requires the antenna beam axis to be pointed towards the center of the Sun for less than a minute. Standard deviations of the difference as low as 0.1 dB have been found for the Swiss radars. As far as the absolute calibration is concerned, the average differences were of the order of −0.6 dB (after noise subtraction). The method has been implemented on a mobile, X-band radar, and this paper presents the successful results that were obtained during the 2016 field campaign in Payerne (Switzerland). Despite a relatively poor Sun-to-Noise ratio, the “small” (~0.4 dB) amplitude of the slowly varying emission was captured and reproduced; the standard deviation of the difference between the radar and the reference was ~0.2 dB. The absolute calibration of the vertical and horizontal receivers was satisfactory. After the noise subtraction and atmospheric correction a, the mean difference was close to 0 dB. PMID:28531164

  1. The GOES-R Advanced Baseline Imager: detector spectral response effects on thermal emissive band calibration

    NASA Astrophysics Data System (ADS)

    Pearlman, Aaron J.; Padula, Francis; Cao, Changyong; Wu, Xiangqian

    2015-10-01

    The Advanced Baseline Imager (ABI) will be aboard the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellite R-Series (GOES-R) to supply data needed for operational weather forecasts and long-term climate variability studies, which depend on high quality data. Unlike the heritage operational GOES systems that have two or four detectors per band, ABI has hundreds of detectors per channel requiring calibration coefficients for each one. This increase in number of detectors poses new challenges for next generation sensors as each detector has a unique spectral response function (SRF) even though only one averaged SRF per band is used operationally to calibrate each detector. This simplified processing increases computational efficiency. Using measured system-level SRF data from pre-launch testing, we have the opportunity to characterize the calibration impact using measured SRFs, both per detector and as an average of detector-level SRFs similar to the operational version. We calculated the spectral response impacts for the thermal emissive bands (TEB) theoretically, by simulating the ABI response viewing an ideal blackbody and practically, with the measured ABI response to an external reference blackbody from the pre-launch TEB calibration test. The impacts from the practical case match the theoretical results using an ideal blackbody. The observed brightness temperature trends show structure across the array with magnitudes as large as 0.1 K for and 12 (9.61 µm), and 0.25 K for band 14 (11.2 µm) for a 300 K blackbody. The trends in the raw ABI signal viewing the blackbody support the spectral response measurements results, since they show similar trends in bands 12 (9.61µm), and 14 (11.2 µm), meaning that the spectral effects dominate the response differences between detectors for these bands. We further validated these effects using the radiometric bias calculated between calibrations using the external blackbody and

  2. Variability in the high energy gamma ray emission from Cyg X-3 over a two-year period (1983 - 1984) at E 4 x 10(11) eV

    NASA Technical Reports Server (NTRS)

    Cawley, M. F.; Fegan, D. J.; Gibbs, K.; Gorham, P. W.; Lamb, R. C.; Liebing, D. F.; Porter, N. A.; Stenger, V. J.; Weekes, T. C.; Williams, R. J.

    1985-01-01

    Cygnus X-3 is observed to emit gamma rays with energies in excess of 4 x 10 to the 11th power eV during two out of 9 observational categories over an 18 month time span. The emissions are observed at the 0.6 phase of the characteristic 4.8 hr light curve for this binary system. We estimate a peak flux at phase 0.6 of 5 x 10 to the minus 10th power photons cm-2s-1 at a software threshold of 8 x 10 to the 11th power eV for Oct/Nov 1983. A flux for the June 84 effect cannot be reliably calculated at present due to lack of Monte Carlo simulations for the energy range and spectral region. For the other 7 observational categories the observations are consistent with zero source emission. The light curve would appear to be variable on a time scale of a couple of weeks at these categories. Selection of compact images in accordance with Monte Carlo simulations combined with empirical optimization techniques have led to an enriched gamma ray light curve for the Oct/Nov 1983 data. Selection on the basis of shower orientation, however, has not led to any notable enhancement of the gamma ray content. Individual Cherenko images can be reliably sorted on an event by event basis into either proton-induced or photon-induced showers.

  3. Leaf Level Chlorophyll Fluorescence Emission Spectra: Narrow Band versus Full 650-800 nm Retrievals

    NASA Astrophysics Data System (ADS)

    Middleton, E.; Zhang, Q.; Campbell, P. K.; Huemmrich, K. F.; Corp, L.; Cheng, Y.

    2012-12-01

    nm (r2 = 0.88, RMSE = 7.54 x 107). When perfect retrievals were assumed (0% noise), retrievals remained good in the low emission regions on either side of the peaks-- those associated with the H alpha line at 655 nm (r2 = 0.83, RMSE =8.87 x 107) and the far-NIR wavelengths recently utilized for satellite retrievals: a K line at 770 nm (r2 = 0.85, RMSE = 8.36 x 107) and the 750-770 nm interval (r2 = 0.88, RMSE = 6.92 x 107). However, the atmosphere and satellite observations are expected to add noise to retrievals. Adding 5% random error to these relationships did not seriously impair the retrieval successes in the red and far-red peaks (r2 ~ 0.85, RMSEs = 6.31 x 107). A greater impact occurred (reducing retrieval success by ~10%) when adding 5% noise for the far-NIR narrow band at 770 nm (r2 ~ 0.70, RMSE ~ 8.5 x 107). When a 10% random error was added, the retrieval successes fell to ~68 ± 7% for all retrieval wavebands, and RMSEs increased by a factor of 10. This laboratory approach will be critical to calibrate space borne retrievals, but additional information across plant species is needed. Furthermore, this experiment indicates that ChlF retrievals from space should include information from the red and far-red peak emission regions, since the true total fluorescence signal is the desired parameter for Earth carbon and energy budgets.

  4. PROBING THE IONIZATION STATES OF POLYCYCLIC AROMATIC HYDROCARBONS VIA THE 15–20 μm EMISSION BANDS

    SciTech Connect

    Shannon, M. J.; Stock, D. J.; Peeters, E.

    2015-10-01

    We report new correlations between ratios of band intensities of the 15–20 μm emission bands of polycyclic aromatic hydrocarbons (PAHs) in a sample of 57 sources observed with the Spitzer/Infrared Spectrograph. This sample includes Large Magellanic Cloud point sources from the SAGE-Spec survey, nearby galaxies from the Spitzer Infrared Nearby Galaxies Survey survey, two Galactic interstellar medium cirrus sources, and the spectral maps of the Galactic reflection nebulae NGC 2023 and NGC 7023. We find that the 16.4, 17.4, and 17.8 μm band intensities are inter-correlated in all environments. In NGC 2023 and NGC 7023 these bands also correlate with the 11.0 and 12.7 μm band intensities. The 15.8 μm band correlates only with the 15–18 μm plateau and the 11.2 μm emission. We examine the spatial morphology of these bands and introduce radial cuts. We find that these bands can be spatially organized into three sets: the 12.7, 16.4, and 17.8 μm bands; the 11.2, 15.8 μm bands and the 15–18 μm plateau; and the 11.0 and 17.4 μm bands. We also find that the spatial distribution of the 12.7, 16.4, and 17.8 μm bands can be reconstructed by averaging the spatial distributions of the cationic 11.0 μm and neutral 11.2 μm bands. We conclude that the 17.4 μm band is dominated by cations, the 15.8 μm band by neutral species, and the 12.7, 16.4, and 17.8 μm bands by a combination of the two. These results highlight the importance of PAH ionization for spatially differentiating sub-populations by their 15–20 μm emission variability.

  5. Impact of Conifer Forest Litter on Microwave Emission at L-Band

    NASA Technical Reports Server (NTRS)

    Kurum, Mehmet; O'Neill, Peggy E.; Lang, Roger H.; Cosh, Michael H.; Joseph, Alicia T.; Jackson, Thomas J.

    2011-01-01

    This study reports on the utilization of microwave modeling, together with ground truth, and L-band (1.4-GHz) brightness temperatures to investigate the passive microwave characteristics of a conifer forest floor. The microwave data were acquired over a natural Virginia Pine forest in Maryland by a ground-based microwave active/passive instrument system in 2008/2009. Ground measurements of the tree biophysical parameters and forest floor characteristics were obtained during the field campaign. The test site consisted of medium-sized evergreen conifers with an average height of 12 m and average diameters at breast height of 12.6 cm. The site is a typical pine forest site in that there is a surface layer of loose debris/needles and an organic transition layer above the mineral soil. In an effort to characterize and model the impact of the surface litter layer, an experiment was conducted on a day with wet soil conditions, which involved removal of the surface litter layer from one half of the test site while keeping the other half undisturbed. The observations showed detectable decrease in emissivity for both polarizations after the surface litter layer was removed. A first-order radiative transfer model of the forest stands including the multilayer nature of the forest floor in conjunction with the ground truth data are used to compute forest emission. The model calculations reproduced the major features of the experimental data over the entire duration, which included the effects of surface litter and ground moisture content on overall emission. Both theory and experimental results confirm that the litter layer increases the observed canopy brightness temperature and obscure the soil emission.

  6. Observational studies on the near-infrared unidentified emission bands in galactic H II regions

    SciTech Connect

    Mori, Tamami I.; Onaka, Takashi; Sakon, Itsuki; Ohsawa, Ryou; Bell, Aaron C.; Ishihara, Daisuke; Shimonishi, Takashi

    2014-03-20

    Using a large collection of near-infrared spectra (2.5-5.4 μm) of Galactic H II regions and H II region-like objects, we perform a systematic investigation of astronomical polycyclic aromatic hydrocarbon (PAH) features. Thirty-six objects were observed using the infrared camera on board the AKARI satellite as a part of a director's time program. In addition to the well known 3.3-3.6 μm features, most spectra show a relatively weak emission feature at 5.22 μm with sufficient signal-to-noise ratios, which we identify as the PAH 5.25 μm band (previously reported). By careful analysis, we find good correlations between the 5.25 μm band and both the aromatic hydrocarbon feature at 3.3 μm and the aliphatic hydrocarbon features at around 3.4-3.6 μm. The present results give us convincing evidence that the astronomical 5.25 μm band is associated with C-H vibrations, as suggested by previous studies, and show its potential to probe the PAH size distribution. The analysis also shows that the aliphatic-to-aromatic ratio of I {sub 3.4-3.6} {sub μm}/I {sub 3.3} {sub μm} decreases against the ratio of the 3.7 μm continuum intensity to the 3.3 μm band, I {sub cont,} {sub 3.7} {sub μm}/I {sub 3.3} {sub μm}, which is an indicator of the ionization fraction of PAHs. The midinfrared color of I {sub 9} {sub μm}/I {sub 18} {sub μm} also declines steeply against the ratio of the hydrogen recombination line Brα at 4.05 μm to the 3.3 μm band, I {sub Brα}/I {sub 3.3} {sub μm}. These facts indicate possible dust processing inside or at the boundary of ionized gas.

  7. On-orbit Characterization of RVS for MODIS Thermal Emissive Bands

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Salomonson, V.; Chiang, K.; Wu, A.; Guenther, B.; Barnes, W.

    2004-01-01

    Response versus scan angle (RVS) is a key calibration parameter for remote sensing radiometers that make observations using a scanning optical system, such as a scan mirror in MODIS and GLI or a rotating telescope in SeaWiFS and VIIRS, since the calibration is typically performed at a fixed viewing angle while the Earth scene observations are made over a range of viewing angles. Terra MODIS has been in operation for more than four years since its launch in December 1999. It has 36 spectral bands covering spectral range from visible (VIS) to long-wave infrared (LWIR). It is a cross-track scanning radiometer using a two-sided paddle wheel scan mirror, making observations over a wide field of view (FOV) of +/-55 deg from the instrument nadir. This paper describes on-orbit characterization of MODIS RVS for its thermal emissive bands (TEB), using the Earth view data collected during Terra spacecraft deep space maneuvers (DSM). Comparisons with pre-launch analysis and early on-orbit measurements are also provided.

  8. On-orbit Characterization of RVS for MODIS Thermal Emissive Bands

    NASA Technical Reports Server (NTRS)

    Xiong, X.; Salomonson, V.; Chiang, K.; Wu, A.; Guenther, B.; Barnes, W.

    2004-01-01

    Response versus scan angle (RVS) is a key calibration parameter for remote sensing radiometers that make observations using a scanning optical system, such as a scan mirror in MODIS and GLI or a rotating telescope in SeaWiFS and VIIRS, since the calibration is typically performed at a fixed viewing angle while the Earth scene observations are made over a range of viewing angles. Terra MODIS has been in operation for more than four years since its launch in December 1999. It has 36 spectral bands covering spectral range from visible (VIS) to long-wave infrared (LWIR). It is a cross-track scanning radiometer using a two-sided paddle wheel scan mirror, making observations over a wide field of view (FOV) of +/-55 deg from the instrument nadir. This paper describes on-orbit characterization of MODIS RVS for its thermal emissive bands (TEB), using the Earth view data collected during Terra spacecraft deep space maneuvers (DSM). Comparisons with pre-launch analysis and early on-orbit measurements are also provided.

  9. Development of a 10 kHz high harmonic source up to 140 eV photon energy for ultrafast time-, angle-, and phase-resolved photoelectron emission spectroscopy on solid targets

    NASA Astrophysics Data System (ADS)

    Schmidt, J.; Guggenmos, A.; Chew, S. H.; Gliserin, A.; Högner, M.; Kling, M. F.; Zou, J.; Späth, C.; Kleineberg, U.

    2017-08-01

    We present a newly developed high harmonic beamline for time-, angle-, and carrier-envelope phase-resolved extreme ultraviolet photoemission spectroscopy on solid targets for the investigation of ultrafast band structure dynamics in the low-fs to sub-fs time regime. The source operates at a repetition rate of 10 kHz and is driven by 5 fs few-cycle near-infrared laser pulses generating high harmonic radiation with photon energies up to 120 eV at a feasible flux. The experimental end station consists of a complementary combination of photoelectron detectors which are able to spectroscopically address electron dynamics both in real and in k-space. The versatility of the source is completed by a phase-meter which allows for tracking the carrier-envelope phase for each pulse and which is synchronized to the photoelectron detectors, thus enabling phase sensitive measurements on the one hand and the selection of single attosecond pulses for ultimate time resolution in pump-probe experiments on the other hand. We demonstrate the applicability of the source by an angle- and carrier-envelope phase-resolved photoemission measurement on a tungsten (110) surface with 95 eV extreme ultraviolet radiation.

  10. Spontaneous emission inhibition of telecom-band quantum disks inside single nanowire on different substrates.

    PubMed

    Birowosuto, M D; Zhang, G; Yokoo, A; Takiguchi, M; Notomi, M

    2014-05-19

    We investigate the inhibited spontaneous emission of telecom-band InAs quantum disks (Qdisks) in InP nanowires (NWs). We have evaluated how the inhibition is affected by different disk diameter and thickness. We also compared the inhibition in standing InP NWs and those NWs laying on silica (SiO(2)), and silicon (Si) substrates. We found that the inhibition is altered when we put the NW on the high-refractive-index materials of Si. Experimentally, the inhibition factor ζ of the Qdisk emission at 1,500 nm decreases from 4.6 to 2.5 for NW on SiO(2) and Si substrates, respectively. Those inhibitions are even much smaller than that of 6.4 of the standing NW. The inhibition factors well agree with those calculated from the coupling of the Qdisk to the fundamental guided mode and the continuum of radiative modes. Our observation can be useful for the integration of the NW as light sources in the photonic nanodevices.

  11. Intrinsic single-band upconversion emission in colloidal Yb/Er(Tm):Na3Zr(Hf)F7 nanocrystals.

    PubMed

    Chen, Daqin; Lei, Lei; Zhang, Rui; Yang, Anping; Xu, Ju; Wang, Yuansheng

    2012-11-07

    Novel Yb/Er(Tm):Na(3)MF(7) (M = Zr, Hf) nanocrystals with intrinsic single-band upconversion emission, in contrast to the routine lanthanide-doped fluoride nanocrystals which show typical multi-band upconversion emissions, are reported for the first time. Specifically, the red upconversion intensity of the Yb/Er:Na(3)ZrF(7) nanocrystals is about 5 times as high as that of the hexagonal Yb/Er:NaYF(4) ones with a similar crystal size.

  12. CH^+ Spectrum and Diffuse Interstellar Bands Toward Herschel 36 Excited by Dust Emission

    NASA Astrophysics Data System (ADS)

    Dahlstrom, Julie; Oka, Takeshi; Johnson, Sean; Welty, Daniel E.; Hobbs, Lew M.; York, Donald G.

    2012-06-01

    All electronic CH^+ interstellar absorption lines so far observed had been limited to the R(0) transition starting from the J = 0 ground level; this is because of the very rapid J = 1 → 0 spontaneous emission with the life time of ˜ 140 s. We have observed the R(1) and Q(1) lines of the A^1π ← X^1Σ band from the excited J = 1 level 40.08 K (27.86 cm-1) above the J = 0 level toward Herschel 36 indicating high radiative temperature of T_r = 17.5 K. The high temperature is most likely due to far infrared dust emission from the Her 36 SE. We have also observed the R_1(3/2) line of CH starting from the excited fine structure level J = 3/2 which is 25.76 - 25.57 K above the J = 1/2 level. The effect of high radiative temperature is also noticed as unique lineshapes of diffuse interstellar bands (DIBs) observed toward Her 36. We have examined seven DIBs including λ 5780.5, λ 5797.1, λ 6190.0, and λ 6613.0 that are correlated with each other with correlation coefficients > 0.93. While for ordinary sightlines the lineshapes of these DIBs are more or less symmetric, those toward Her 36 show a long tail toward the red. This is due to far infrared pumping of high J rotational levels of polar carriers of the DIBs by the dust emission. We have developed a model calculation of relaxation taking into account of both radiative and collisional processes. A linear molecule with about 6 carbon atoms can explain some of the DIBs. For the DIBs we have examined, probably the carriers are of this size since we cannot explain the large difference between the DIBs toward ordinary sightlines and toward Her 36 with larger molecules. Goto, M., Stecklum, B., Linz, H., Feldt, M., Henning, Th., Pascucci, I., and Usuda, T. 2006, ApJ, {649} 299.

  13. Observations of high-altitude CO2 hot bands in Mars by the orbiting Thermal Emission Spectrometer

    NASA Astrophysics Data System (ADS)

    Maguire, W. C.; Pearl, J. C.; Smith, M. D.; Conrath, B. J.; Kutepov, A. A.; Kaelberer, M. S.; Winter, E.; Christensen, P. R.

    2002-09-01

    We present limb spectral measurements of the Martian atmosphere for four seasonal periods produced from data acquired by the Mars Global Surveyor/Thermal Emission Spectrometer. Between the altitudes of approximately 50 and 90 km, nonlocal thermodynamic equilibrium (non-LTE) emission from CO2 hot bands is observed at 10 μm. The centroids of these emissions vary in latitude and height with season, and their emission regions extend approximately 120° in latitude. The emission is considerably stronger in the southern summer/northern winter season than in the corresponding northern summer/southern winter season due to large solar flux variations resulting from the eccentricity of the Martian orbit. Modeling of this emission explains its observed altitude, solar zenith angle, and seasonal dependence.

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

    NASA Astrophysics Data System (ADS)

    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.

  15. Use of IRI to Model the Effect of Ionosphere Emission on Earth Remote Sensing at L-Band

    NASA Technical Reports Server (NTRS)

    Abraham, Saji; LeVine, David M.

    2004-01-01

    Microwave remote sensing in the window at 1.413 GHz (L-band) set aside for passive use only is important for monitoring sea surface salinity and soil moisture. These parameters are important for understanding ocean dynamics and energy exchange between the surface and atmosphere, and both NASA and ESA plan to launch satellite sensors to monitor these parameters at L-band (Aquarius, Hydros and SMOS). The ionosphere is an important source of error for passive remote sensing at this frequency. In addition to Faraday rotation, emission from the ionosphere is also a potential source of error at L-band. As an aid for correcting for emission, a regression model is presented that relates ionosphere emission to the integrated electron density (TEC). The goal is to use TEC from sources such as TOPEX, JASON or GPS to obtain estimates of emission over the oceans where the electron density profiles needed to compute emission are not available. In addition, data will also be presented to evaluate the use of the IRI for computing emission over the ocean.

  16. Emission of electrons with energies from 10/sup 4/ to 10/sup 5/ eV upon the fracture of. gamma. -irradiated NaCl crystals

    SciTech Connect

    Khrustalev, Yu.A.; Serdyuk, O.M.; Savenko, V.I.; Bardyshev, I.I.; Deryagin, B.V.

    1986-11-01

    The influence of gamma quanta (in doses up to 100 Mrd) on the parameters of the emission of high-energy electrons upon the fracture of preliminarily irradiated samples of sodium chloride has been studied. No correlation between the concentration of the F color centers, which is linearly dependent on the dose, and the flux of electrons emitted by the freshly formed surface has been discovered. The appearance of vacancy lattice defects of a type more complicated than F centers upon irradiation has an effect on the process of fracture of the crystal, which results in considerable changes in the parameters of the electrons emitted.

  17. Impact of surface roughness on L-band emissivity of the sea ice

    NASA Astrophysics Data System (ADS)

    Miernecki, M.; Kaleschke, L.; Hendricks, S.; Søbjærg, S. S.

    2015-12-01

    In March 2014 a joint experiment IRO2/SMOSice was carried out in the Barents Sea. R/V Lance equipped with meteorological instruments, electromagnetic sea ice thickness probe and engine monitoring instruments, was performing a series of tests in different ice conditions in order to validate the ice route optimization (IRO) system, advising on his route through pack ice. In parallel cal/val activities for sea ice thickness product obtained from SMOS (Soil Moisture and Ocean Salinity mission) L-band radiometer were carried out. Apart from helicopter towing the EMbird thickness probe, Polar 5 aircraft was serving the area during the experiment with L-band radiometer EMIRAD2 and Airborne Laser Scanner (ALS) as primary instruments. Sea ice Thickness algorithm using SMOS brightness temperature developed at University of Hamburg, provides daily maps of thin sea ice (up to 0.5-1 m) in polar regions with resolution of 35-50 km. So far the retrieval method was not taking into account surface roughness, assuming that sea ice is a specular surface. Roughness is a stochastic process that can be characterized by standard deviation of surface height σ and by shape of the autocorrelation function R to estimate it's vertical and horizontal scales respectively. Interactions of electromagnetic radiation with the surface of the medium are dependent on R and σ and they scales with respect to the incident wavelength. During SMOSice the radiometer was observing sea ice surface at two incidence angles 0 and 40 degrees and simultaneously the surface elevation was scanned with ALS with ground resolution of ~ 0.25 m. This configuration allowed us to calculate σ and R from power spectral densities of surface elevation profiles and quantify the effect of surface roughness on the emissivity of the sea ice. First results indicate that Gaussian autocorrelation function is suitable for deformed ice, for other ice types exponential function is the best fit.

  18. The ground-based H-, K-, and L-band absolute emission spectra of HD 209458b

    SciTech Connect

    Zellem, Robert T.; Griffith, Caitlin A.; Deroo, Pieter; Swain, Mark R.; Waldmann, Ingo P.

    2014-11-20

    Here we explore the capabilities of NASA's 3.0 m Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 m Hale telescope with the TripleSpec spectrometer with near-infrared H-, K-, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L band indicate bright emission hypothesized to result from non-LTE CH{sub 4} ν{sub 3} fluorescence. We do not detect a similar bright 3.3 μm feature to ∼3σ, suggesting that fluorescence does not need to be invoked to explain HD 209458b's L-band measurements. The validity of our observation and reduction techniques, which decrease the flux variance by up to 2.8 orders of magnitude, is reinforced by 1σ agreement with existent Hubble/NICMOS and Spitzer/IRAC1 observations that overlap the H, K, and L bands, suggesting that both IRTF/SpeX and Palomar/TripleSpec can measure an exoplanet's emission with high precision.

  19. The Ground-based H-, K-, and L-band Absolute Emission Spectra of HD 209458b

    NASA Astrophysics Data System (ADS)

    Zellem, Robert T.; Griffith, Caitlin A.; Deroo, Pieter; Swain, Mark R.; Waldmann, Ingo P.

    2014-11-01

    Here we explore the capabilities of NASA's 3.0 m Infrared Telescope Facility (IRTF) and SpeX spectrometer and the 5.08 m Hale telescope with the TripleSpec spectrometer with near-infrared H-, K-, and L-band measurements of HD 209458b's secondary eclipse. Our IRTF/SpeX data are the first absolute L-band spectroscopic emission measurements of any exoplanet other than the hot Jupiter HD 189733b. Previous measurements of HD 189733b's L band indicate bright emission hypothesized to result from non-LTE CH4 ν3 fluorescence. We do not detect a similar bright 3.3 μm feature to ~3σ, suggesting that fluorescence does not need to be invoked to explain HD 209458b's L-band measurements. The validity of our observation and reduction techniques, which decrease the flux variance by up to 2.8 orders of magnitude, is reinforced by 1σ agreement with existent Hubble/NICMOS and Spitzer/IRAC1 observations that overlap the H, K, and L bands, suggesting that both IRTF/SpeX and Palomar/TripleSpec can measure an exoplanet's emission with high precision.

  20. Fullerene-Free Organic Solar Cells with an Efficiency of 10.2% and an Energy Loss of 0.59 eV Based on a Thieno[3,4-c]Pyrrole-4,6-dione-Containing Wide Band Gap Polymer Donor.

    PubMed

    Hadmojo, Wisnu Tantyo; Wibowo, Febrian Tri Adhi; Ryu, Du Yeol; Jung, In Hwan; Jang, Sung-Yeon

    2017-09-27

    Although the combination of wide band gap polymer donors and narrow band gap small-molecule acceptors achieved state-of-the-art performance as bulk heterojunction (BHJ) active layers for organic solar cells, there have been only several of the wide band gap polymers that actually realized high-efficiency devices over >10%. Herein, we developed high-efficiency, low-energy-loss fullerene-free organic solar cells using a weakly crystalline wide band gap polymer donor, PBDTTPD-HT, and a nonfullerene small-molecule acceptor, ITIC. The excessive intermolecular stacking of ITIC is efficiently suppressed by the miscibility with PBDTTPD-HT, which led to a well-balanced nanomorphology in the PBDTTPD-HT/ITIC BHJ active films. The favorable optical, electronic, and energetic properties of PBDTTPD-HT with respect to ITIC achieved panchromatic photon-to-current conversion with a remarkably low energy loss (0.59 eV).

  1. EV-GHG Mobile Source

    EPA Pesticide Factsheets

    The EV-GHG Mobile Source Data asset contains measured mobile source GHG emissions summary compliance information on light-duty vehicles, by model, for certification as required by the 1990 Amendments to the Clean Air Act, and as driven by the 2010 Presidential Memorandum Regarding Fuel Efficiency and the 2005 Supreme Court ruling in Massachusetts v. EPA that supported the regulation of CO2 as a pollutant. Manufacturers submit data on an annual basis, or as needed to document vehicle model changes. This asset will be expanded to include medium and heavy duty vehicles in the future.The EPA performs targeted GHG emissions tests on approximately 15% of vehicles submitted for certification. Confirmatory data on vehicles is associated with its corresponding submission data to verify the accuracy of manufacturer submissions beyond standard business rules.Submitted data comes in XML format or as documents, with the majority of submissions sent in XML, and includes descriptive information on the vehicle itself, emissions information, and the manufacturer's testing approach. This data may contain proprietary information (CBI) such as information on estimated sales or other data elements indicated by the submitter as confidential. CBI data is not publically available; however, CBI data can accessed within EPA under the restrictions of the Office of Transportation and Air Quality (OTAQ) CBI policy [RCS Link]. Pollutants data includes CO2, CH4, N2O. Datasets are divided by v

  2. The origin of yellow band emission and cathodoluminescence of Au-catalyzed wurtzite GaN nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, R. S.; Jiao, J. F.; Wu, X.

    2016-06-01

    GaN nanowires with large yield are directly synthesized by simply ammoniating the gallium oxide powders in the presence of ammonia gas at 1000 °C, under the assistance of Au nanocatalysts. The microstructure and crystallinity of as-synthesized GaN nanowires are well studied by using high-resolution transmission electron microscope (HRTEM) and some structural defects such as stacking faults are found in the GaN nano-crystal. Cathodoluminescence measurement shows that a strong near-band-edge (NBE) emission band centered at 384 nm and a broad yellow band in the range of 500-800 nm are observed. Finally, the growth mechanism and possible optical emission process of GaN nanowires are discussed.

  3. Initial Results from a Search for Lunar Radio Emission from Interactions of >= 10(exp 19) eV Neutrinos and Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Gorham, P. W.; Liewer, K. M.; Naudet, C. J.

    2000-01-01

    Using the NASA Goldstone 70m antenna DSS 14 both singly and in coincidence with the 34 m antenna DSS 13 (21.7 km to the southeast), we have acquired approximately 12 hrs of livetime in a search for predicted pulsed radio emission from extremely-high energy cascades induced by neutrinos or cosmic rays in the lunar regolith. In about 4 hrs of single antenna observations, we reduced our sensitivity to impulsive terrestrial interference to a negligible level by use of a veto afforded by the unique capability of DSS 14. In the 8 hrs of dual-antenna observations, terrestrial interference is eliminated as a background. In both observing modes the thermal noise floor limits the sensitivity. We detected no events above statistical background. We report here initial limits based on these data which begin to constrain several predictions of the flux of EHE neutrinos.

  4. Initial Results from a Search for Lunar Radio Emission from Interactions of >= 10(exp 19) eV Neutrinos and Cosmic Rays

    NASA Technical Reports Server (NTRS)

    Gorham, P. W.; Liewer, K. M.; Naudet, C. J.

    2000-01-01

    Using the NASA Goldstone 70m antenna DSS 14 both singly and in coincidence with the 34 m antenna DSS 13 (21.7 km to the southeast), we have acquired approximately 12 hrs of livetime in a search for predicted pulsed radio emission from extremely-high energy cascades induced by neutrinos or cosmic rays in the lunar regolith. In about 4 hrs of single antenna observations, we reduced our sensitivity to impulsive terrestrial interference to a negligible level by use of a veto afforded by the unique capability of DSS 14. In the 8 hrs of dual-antenna observations, terrestrial interference is eliminated as a background. In both observing modes the thermal noise floor limits the sensitivity. We detected no events above statistical background. We report here initial limits based on these data which begin to constrain several predictions of the flux of EHE neutrinos.

  5. Measurement of spontaneous-emission enhancement near the one-dimensional photonic band edge of semiconductor heterostructures

    NASA Astrophysics Data System (ADS)

    Tocci, Michael D.; Scalora, Michael; Bloemer, Mark J.; Dowling, Jonathan P.; Bowden, Charles M.

    1996-04-01

    We present results of an experimental investigation into alteration of the spontaneous emission spectrum of GaAs from within one-dimensional photonic band gap (PBG) structures. The PBG samples are multilayer AlAs/Al0.2Ga0.8As/GaAs p-i-n light-emitting diodes, with layers arranged as a distributed Bragg reflector. The emission spectra normal to the layers are measured, and we use a simple method to model the power spectrum of spontaneous emission from within the structures. We find that the emitted power is enhanced by a factor of 3.5 at the frequencies near the photonic band edge.

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

    SciTech Connect

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

    1998-05-01

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

  7. Update of S-NPP VIIRS Thermal Emissive Bands Radiometric Calibration Stability Monitoring Using the Moon

    NASA Technical Reports Server (NTRS)

    Wang, Zhipeng; Xiong, Xiaoxiong; Li, Yonghong

    2016-01-01

    The Suomi-NPP VIIRS thermal emissive bands (TEB) are radiometrically calibrated on-orbit with reference to an onboard blackbody (BB) regularly operated at approximately 292.5 K. The calibration stability at other temperature ranges can be evaluated based on the observations of remote targets with stable thermal properties, such as the Moon. VIIRS has scheduled viewings of the Moon on a nearly monthly basis at a phase angle of nearly -51 degrees. In this study, the brightness temperatures (BT) of the lunar surface retrieved using the detector gain coefficients calibrated with the BB are trended to monitor the calibration stability of VIIRS TEB. Since the Lunar surface temperatures are spatially non-uniform and vary greatly with the photometric geometry, the BT trending must be based on the same regions of the Moon under the same solar illumination condition. Also, the TEB lunar images are always partially saturated because the highest lunar surface temperatures are beyond the dynamic range of all VIIRS TEB detectors. Therefore, a temporally invariant dynamic mask is designed to clip a fraction of the lunar images corresponding to the regions of the Moon that may saturate the detector at any lunar event. The BT of the remaining hottest pixels are then trended. Results show that, since the launch of VIIRS to mid-2016, the radiometric calibration of all TEB detectors has been stable within 0.4 K at the BT range of as high as 350 K.

  8. S-NPP VIIRS thermal emissive bands on-orbit calibration and performance

    NASA Astrophysics Data System (ADS)

    Efremova, Boryana; McIntire, Jeff; Moyer, David; Wu, Aisheng; Xiong, Xiaoxiong

    2014-09-01

    Presented is an assessment of the on-orbit radiometric performance of the thermal emissive bands (TEB) of the Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) instrument based on data from the first 2 years of operations—from 20 January 2012 to 20 January 2014. The VIIRS TEB are calibrated on orbit using a V-grooved blackbody (BB) as a radiance source. Performance characteristics trended over the life of the mission include the F factor—a measure of the gain change of the TEB detectors; the Noise Equivalent differential Temperature (NEdT)—a measure of the detector noise; and the detector offset and nonlinear terms trended at the quarterly performed BB warm-up cool-down cycles. We find that the BB temperature is well controlled and stable within the 30mK requirement. The F factor trends are very stable and showing little degradation (within 0.8%). The offsets and nonlinearity terms are also without noticeable drifts. NEdT is stable and does not show any trend. Other TEB radiometric calibration-related activities discussed include the on-orbit assessment of the response versus scan-angle functions and an approach to improve the M13 low-gain calibration using onboard lunar measurements. We conclude that all the assessed parameters comply with the requirements, and the TEB provide radiometric measurements with the required accuracy.

  9. Update of S-NPP VIIRS thermal emissive bands radiometric calibration stability monitoring using the moon

    NASA Astrophysics Data System (ADS)

    Wang, Zhipeng; Xiong, Xiaoxiong; Li, Yonghong

    2016-10-01

    The Suomi-NPP VIIRS thermal emissive bands (TEB) are radiometrically calibrated on-orbit with reference to a blackbody (BB) regularly operated at approximately 292.5 K. The calibration stability at other temperature ranges can be evaluated based on the observations of remote targets with stable thermal properties, such as the Moon. VIIRS has scheduled viewings of the Moon on a nearly monthly basis at a phase angle of nearly -51 degrees. In this paper, the brightness temperatures (BT) of the lunar surface retrieved using the detector gain coefficients calibrated with the BB are trended to monitor the calibration stability of VIIRS TEB. Since the Lunar surface temperatures are spatially nonuniform and vary greatly with the solar illumination geometry, the BT trending must be based on the same regions of the Moon under the same solar illumination condition. Also, the TEB lunar images are always partially saturated because the highest lunar surface temperatures are beyond the dynamic range of all VIIRS TEB detectors. Therefore, a temporally dynamic mask is designed to clip a fraction of the lunar images corresponding to the regions of the Moon that may saturate the detector at any lunar event. The BT trending is then based on the hottest pixels not clipped by the mask. Results show that, since the launch of VIIRS to mid-2016, the radiometric calibration of all TEB detectors has been stable within +/-0.4 K at the BT range of as high as 350-260 K.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  11. Out-of-band emission suppression techniques based on a generalized OFDM framework

    NASA Astrophysics Data System (ADS)

    You, Zihao; Fang, Juan; Lu, I.-Tai

    2014-12-01

    Orthogonal frequency division multiplexing (OFDM)-based cognitive radio (CR) systems suffer from the large out-of-band emission (OOBE) that may interfere with other users. Since most existing OFDM OOBE suppression schemes are derived on the base of an original OFDM system without any other scheme, we first propose a generalized OFDM framework that is capable of describing these schemes no matter whether any one or more of the schemes is applied. Then, according to the place where these schemes are implemented in our framework, they are classified into three groups, namely symbol mapping techniques, precoding techniques, and time-domain techniques. Finally, based on the proposed framework, we propose three new schemes by combining a precoding scheme named singular value decomposition (SVD) precoding with three other schemes from the three groups, namely spectral precoding, N-continuous symbol mapping, and filtering. Numerical results show the power spectral density (PSD), peak-to-average power ratio (PAPR), and bit error rate (BER) performances of the three proposed schemes. Since the individual schemes have complementary characteristics, the three proposed combined schemes are constructed to maintain the merits and avoid the drawbacks of the individual schemes involved. Thus, it is demonstrated that the proposed framework can be employed to develop other new combined OOBE suppression schemes tailoring to some specific practical needs.

  12. THE DIFFUSE INTERSTELLAR BANDS AND ANOMALOUS MICROWAVE EMISSION MAY ORIGINATE FROM THE SAME CARRIERS

    SciTech Connect

    Bernstein, L. S.; Cline, J. A.; Clark, F. O.; Lynch, D. K. E-mail: jcline@spectral.com E-mail: dave@thulescientific.com

    2015-11-10

    We argue that the observed spectroscopic and statistical properties of the diffuse interstellar band (DIB) carriers are those that are needed to produce the anomalous microwave emission (AME). We explore this idea using a carrier-impartial model for AME based on the observed DIB statistical properties. We show that an observed distribution of profile widths for narrow DIBs can be mapped into an AME spectrum. The mapping model is applied to width distributions observed for HD 204827 and HD 183143, selected because their spectroscopic and statistical properties bracket those for most other sight lines. The predicted AME spectra for these sight lines agree well with the range of spectral shapes, and peak frequencies, ∼23–31 GHz, typically observed for AME. We use the AME spectral profiles to derive a strong constraint between the average carrier size and its rotational temperature. The constraint is applied to a variety of postulated molecular carrier classes, including polycyclic aromatic hydrocarbons, fulleranes, hydrocarbon chains, and amorphous hydrocarbon clusters. The constraint favors small, cold carriers with average sizes of ∼8–15 carbon atoms, and average rotational temperatures of ∼3–10 K, depending on carrier type. We suggest new observations, analyses, and modeling efforts to help resolve the ambiguities with regard to carrier size and class, and to further clarify the DIB–AME relationship.

  13. Reinvestigation of the Emission γ Band System (A2Σ+-X2Π) of the NO Molecule

    NASA Astrophysics Data System (ADS)

    Danielak, J.; Domin, U.; Ke, R.; Rytel, M.; Zachwieja, M.

    1997-02-01

    In the emission spectrum of the nitric oxide molecule 13 bands of the γ system (A2Σ+-X2Π) were recorded and analyzed. The following bands of this system comprising over 3950 lines were photographed under high resolution by using conventional spectroscopy and Th standard lines: 0-0 through 0-6 and 1-4, 1-5, 2-0, 2-6, 2-7, and 3-4. The analysis of the individual bands and the merged analysis of the entire band system made it possible to unify, extend, and improve the information about the γ system and the energy structure of its participating statesA2Σ+andX2Π. RKR turning points of theAandXstates and Franck-Condon factors andrcentroids for theA-Xsystem were also determined using the precise molecular parameters obtained in the present work.

  14. Suramin inhibits EV71 infection.

    PubMed

    Wang, Yaxin; Qing, Jie; Sun, Yuna; Rao, Zihe

    2014-03-01

    Enterovirus-71 (EV71) is one of the major causative reagents for hand-foot-and-mouth disease. In particular, EV71 causes severe central nervous system infections and leads to numerous dead cases. Although several inactivated whole-virus vaccines have entered in clinical trials, no antiviral agent has been provided for clinical therapy. In the present work, we screened our compound library and identified that suramin, which has been clinically used to treat variable diseases, could inhibit EV71 proliferation with an IC50 value of 40 μM. We further revealed that suramin could block the attachment of EV71 to host cells to regulate the early stage of EV71 infection, as well as affected other steps of EV71 life cycle. Our results are helpful to understand the mechanism for EV71 life cycle and provide a potential for the usage of an approved drug, suramin, as the antiviral against EV71 infection.

  15. The GROUSE project. III. Ks-band observations of the thermal emission from WASP-33b

    NASA Astrophysics Data System (ADS)

    de Mooij, E. J. W.; Brogi, M.; de Kok, R. J.; Snellen, I. A. G.; Kenworthy, M. A.; Karjalainen, R.

    2013-02-01

    Context. In recent years, day-side emission from about a dozen hot Jupiters has been detected through ground-based secondary eclipse observations in the near-infrared. These near-infrared observations are vital for determining the energy budgets of hot Jupiters, since they probe the planet's spectral energy distribution near its peak. Aims: The aim of this work is to measure the Ks-band secondary eclipse depth of WASP-33b, the first planet discovered to transit an A-type star. This planet receives the highest level of irradiation of all transiting planets discovered to date. Furthermore, its host-star shows pulsations and is classified as a low-amplitude δ Scuti. Methods: As part of our GROUnd-based Secondary Eclipse (GROUSE) project we have obtained observations of two separate secondary eclipses of WASP-33b in the Ks-band using the LIRIS instrument on the William Herschel Telescope (WHT). The telescope was significantly defocused to avoid saturation of the detector for this bright star (K ~ 7.5). To increase the stability and the cadence of the observations, they were performed in staring mode. We collected a total of 5100 and 6900 frames for the first and the second night respectively, both with an average cadence of 3.3 s. Results: On the second night the eclipse is detected at the 12 -σ level, with a measured eclipse depth of 0.244-0.020+0.027%. This eclipse depth corresponds to a brightness temperature of 3270-160+115 K. The measured brightness temperature on the second night is consistent with the expected equilibrium temperature for a planet with a very low albedo and a rapid re-radiation of the absorbed stellar light. For the other night the short out-of-eclipse baseline prevents good corrections for the stellar pulsations and systematic effects, which makes this dataset unreliable for eclipse depth measurements. This demonstrates the need of getting a sufficient out-of-eclipse baseline. Appendix A is available in electronic form at http

  16. Passive L-Band H Polarized Microwave Emission During the Corn Growth Cycle

    NASA Astrophysics Data System (ADS)

    Joseph, A. T.; van der Velde, R.; O'Neill, P. E.; Kim, E. J.; Lang, R. H.; Gish, T. J.

    2012-12-01

    Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (TB's) measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These TB measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly TB's could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly TB. Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, hr, on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on TB simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent hr parameterization was responsible for the largest error reduction of TB simulations in the early growth cycle. A.T. Joseph, R. Van der Velde, P.E. O'Neill, R.H. Lang, and T. Gish, "Soil moisture retrieval during a corn growth cycle using L-band (1.6 GHz) radar observations", IEEE Transactions on Geoscience and Remote Sensing, vol. 46, DOI:10.1109/TGRS.2008.917214, Aug. 2008. M.C. Dobson, F.T. Ulaby, M

  17. Hydrogenation of polycyclic aromatic hydrocarbons as a factor affecting the cosmic 6.2 micron emission band

    NASA Technical Reports Server (NTRS)

    Beegle, L. W.; Wdowiak, T. J.; Harrison, J. G.

    2001-01-01

    While many of the characteristics of the cosmic unidentified infrared (UIR) emission bands observed for interstellar and circumstellar sources within the Milky Way and other galaxies, can be best attributed to vibrational modes of the variants of the molecular family known as polycyclic aromatic hydrocarbons (PAH), there are open questions that need to be resolved. Among them is the observed strength of the 6.2 micron (1600 cm(-1)) band relative to other strong bands, and the generally low strength for measurements in the laboratory of the 1600 cm(-1) skeletal vibration band of many specific neutral PAH molecules. Also, experiments involving laser excitation of some gas phase neutral PAH species while producing long lifetime state emission in the 3.3 micron (3000 cm(-1)) spectral region, do not result in significant 6.2 micron (1600 cm(-1)) emission. A potentially important variant of the neutral PAH species, namely hydrogenated-PAH (H(N)-PAH) which exhibit intriguing spectral correlation with interstellar and circumstellar infrared emission and the 2175 A extinction feature, may be a factor affecting the strength of 6.2 micron emission. These species are hybrids of aromatic and cycloalkane structures. Laboratory infrared absorption spectroscopy augmented by density function theory (DFT) computations of selected partially hydrogenated-PAH molecules, demonstrates enhanced 6.2 micron (1600 cm(-1)) region skeletal vibration mode strength for these molecules relative to the normal PAH form. This along with other factors such as ionization or the incorporation of nitrogen or oxygen atoms could be a reason for the strength of the cosmic 6.2 micron (1600 cm(-1)) feature.

  18. Narrow-band tunable terahertz emission from ferrimagnetic Mn{sub 3-x}Ga thin films

    SciTech Connect

    Awari, N.; Kovalev, S. E-mail: c.fowley@hzdr.de Fowley, C. E-mail: c.fowley@hzdr.de Green, B.; Yildirim, O.; Lindner, J.; Fassbender, J.; Deac, A. M.; Gensch, M.; Rode, K. E-mail: c.fowley@hzdr.de Lau, Y.-C.; Betto, D.; Thiyagarajah, N.; Coey, J. M. D.; Gallardo, R. A.

    2016-07-18

    Narrow-band terahertz emission from coherently excited spin precession in metallic ferrimagnetic Mn{sub 3-x}Ga Heusler alloy nanofilms has been observed. The efficiency of the emission, per nanometer film thickness, is comparable or higher than that of classical laser-driven terahertz sources based on optical rectification. The center frequency of the emission from the films can be tuned precisely via the film composition in the range of 0.20–0.35 THz, making this type of metallic film a candidate for efficient on-chip terahertz emitters. Terahertz emission spectroscopy is furthermore shown to be a sensitive probe of magnetic properties of ultra-thin films.

  19. High-power, narrow-band, high-repetition-rate, 5.9 eV coherent light source using passive optical cavity for laser-based angle-resolved photoelectron spectroscopy.

    PubMed

    Omachi, J; Yoshioka, K; Kuwata-Gonokami, M

    2012-10-08

    We demonstrate a scheme for efficient generation of a 5.9 eV coherent light source with an average power of 23 mW, 0.34 meV linewidth, and 73 MHz repetition rate from a Ti: sapphire picosecond mode-locked laser with an output power of 1 W. Second-harmonic light is generated in a passive optical cavity by a BiB(3)O(6) crystal with a conversion efficiency as high as 67%. By focusing the second-harmonic light transmitted from the cavity into a β-BaB(2)O(4) crystal, we obtain fourth-harmonic light at 5.9 eV. This light source offers stable operation for at least a week. We discuss the suitability of the laser light source for high-resolution angle-resolved photoelectron spectroscopy by comparing it with other sources (synchrotron radiation facilities and gas discharge lamp).

  20. Evaluation of VIIRS and MODIS Thermal Emissive Band Calibration Stability Using Ground Target

    NASA Technical Reports Server (NTRS)

    Madhavan, Sriharsha; Brinkmann, Jake; Wenny, Brian N.; Wu, Aisheng; Xiong, Xiaoxiong

    2017-01-01

    The S-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) instrument, a polar orbiting Earth remote sensing instrument built using a strong MODIS background, employs a similarly designed on-board calibrating source - a V-grooved blackbody for the thermal emissive bands (TEB). The central wavelengths of most VIIRS TEBs are very close to those of MODIS with the exception of the 10.7 micron channel. To ensure the long term continuity of climate data records derived using VIIRS and MODIS TEB, it is necessary to assess any systematic differences between the two instruments, including scenes with temperatures significantly lower than blackbody operating temperatures at approximately 290 K. Previous work performed by the MODIS Characterization Support Team (MCST) at NASAGSFC used the frequent observations of the Dome Concordia site located in Antarctica to evaluate the calibration stability and consistency of Terra and Aqua MODIS over the mission lifetime. The near-surface temperature measurements from an automatic weather station (AWS) provide a direct reference useful for tracking the stability and determining the relative bias between the two MODIS instruments. In this study, the same technique is applied to the VIIRS TEB and the results are compared with those from the matched MODIS TEB. The results of this study show a small negative bias when comparing the matching VIIRS and Aqua MODIS TEB, implying a higher scene temperature retrieval for S-VIIRS at the cold end. Statistically no significant drift is observed for VIIRS TEB performance over the first 3.5 years of the mission.

  1. DETECTION OF K{sub S} -BAND THERMAL EMISSION FROM WASP-3b

    SciTech Connect

    Zhao Ming; Wright, Jason; Milburn, Jennifer; Hinkley, Sasha; Barman, Travis; Swain, Mark R.; Monnier, John D.

    2012-03-20

    We report the detection of thermal emission from the hot Jupiter WASP-3b in the K{sub S} band, using a newly developed guiding scheme for the WIRC instrument at the Palomar Hale 200 inch telescope. Our new guiding scheme has improved the telescope guiding precision by a factor of {approx}5-7, significantly reducing the correlated systematics in the measured light curves. This results in the detection of a secondary eclipse with depth of 0.181% {+-} 0.020% (9{sigma})-a significant improvement in WIRC's photometric precision and a demonstration of the capability of Palomar/WIRC to produce high-quality measurements of exoplanetary atmospheres. Our measured eclipse depth cannot be explained by model atmospheres with heat redistribution but favors a pure radiative equilibrium case with no redistribution across the surface of the planet. Our measurement also gives an eclipse phase center of 0.5045 {+-} 0.0020, corresponding to an ecos {omega} of 0.0070 {+-} 0.0032. This result is consistent with a circular orbit, although it also suggests that the planet's orbit might be slightly eccentric. The possible non-zero eccentricity provides insight into the tidal circularization process of the star-planet system, but might also have been caused by a second low-mass planet in the system, as suggested by a previous transit timing variation study. More secondary eclipse observations, especially at multiple wavelengths, are necessary to determine the temperature-pressure profile of the planet's atmosphere and shed light on its orbital eccentricity.

  2. Methane oxidation behind reflected shock waves: Ignition delay times measured by pressure and flame band emission

    NASA Technical Reports Server (NTRS)

    Brabbs, T. A.; Robertson, T. F.

    1986-01-01

    Ignition delay data were recorded for three methane-oxygen-argon mixtures (phi = 0.5, 1.0, 2.0) for the temperature range 1500 to 1920 K. Quiet pressure trances enabled us to obtain delay times for the start of the experimental pressure rise. These times were in good agreement with those obtained from the flame band emission at 3700 A. The data correlated well with the oxygen and methane dependence of Lifshitz, but showed a much stronger temperature dependence (phi = 0.5 delta E = 51.9, phi = 1.0 delta = 58.8, phi = 2.0 delta E = 58.7 Kcal). The effect of probe location on the delay time measurement was studied. It appears that the probe located 83 mm from the reflecting surface measured delay times which may not be related to the initial temperature and pressure. It was estimated that for a probe located 7 mm from the reflecting surface, the measured delay time would be about 10 microseconds too short, and it was suggested that delay times less than 100 microsecond should not be used. The ignition period was defined as the time interval between start of the experimental pressure rise and 50 percent of the ignition pressure. This time interval was measured for three gas mixtures and found to be similar (40 to 60 micro sec) for phi = 1.0 and 0.5 but much longer (100 to 120) microsecond for phi = 2.0. It was suggested that the ignition period would be very useful to the kinetic modeler in judging the agreement between experimental and calculated delay times.

  3. L-Band H Polarized Microwave Emission During the Corn Growth Cycle

    NASA Technical Reports Server (NTRS)

    Joseph, A. T.; va der Velde, R.; O'Neill, P. E.; Kim, E.; Lang, R. H.; Gish, T.

    2012-01-01

    Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (T(sub B))'s measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These T(sub B)'s measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly T(sub B)'s could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly T(sub B). Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, h(sub r), on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on T(sub B) simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent h(sub r) parameterization was responsible for the largest error reduction of T(sub B) simulations in the early growth cycle.

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  5. Estimating net rainfall, evaporation and water storage of a bare soil from sequential L-band emissivities

    NASA Technical Reports Server (NTRS)

    Stroosnijder, L.; Lascano, R. J.; Newton, R. W.; Vanbavel, C. H. M.

    1984-01-01

    A general method to use a time series of L-band emissivities as an input to a hydrological model for continuously monitoring the net rainfall and evaporation as well as the water content over the entire soil profile is proposed. The model requires a sufficiently accurate and general relation between soil emissivity and surface moisture content. A model which requires the soil hydraulic properties as an additional input, but does not need any weather data was developed. The method is shown to be numerically consistent.

  6. Estimating net rainfall, evaporation and water storage of a bare soil from sequential L-band emissivities

    NASA Technical Reports Server (NTRS)

    Stroosnijder, L.; Lascano, R. J.; Newton, R. W.; Vanbavel, C. H. M.

    1984-01-01

    A general method to use a time series of L-band emissivities as an input to a hydrological model for continuously monitoring the net rainfall and evaporation as well as the water content over the entire soil profile is proposed. The model requires a sufficiently accurate and general relation between soil emissivity and surface moisture content. A model which requires the soil hydraulic properties as an additional input, but does not need any weather data was developed. The method is shown to be numerically consistent.

  7. Effect of N2 and H2 plasma treatments on band edge emission of ZnO microrods

    PubMed Central

    Rodrigues, Joana; Holz, Tiago; Fath Allah, Rabie; Gonzalez, David; Ben, Teresa; Correia, Maria R.; Monteiro, Teresa; Costa, Florinda M.

    2015-01-01

    ZnO microrods were grown by laser assisted flow deposition technique in order to study their luminescence behaviour in the near band edge spectral region. Transmission electron microscopy analysis put in evidence the high crystallinity degree and microrod’s compositional homogeneity. Photoluminescence revealed a dominant 3.31 eV emission. The correlation between this emission and the presence of surface states was investigated by performing plasma treatments with hydrogen and nitrogen. The significant modifications in photoluminescence spectra after the plasma treatments suggest a connexion between the 3.31 eV luminescence and the surface related electronic levels. PMID:26027718

  8. Frequency spacing of multiple spontaneous otoacoustic emissions shows relation to critical bands: a large-scale cumulative study.

    PubMed

    Braun, M

    1997-12-01

    Multiple spontaneous otoacoustic emissions (SOAEs), recorded in one ear, are not randomly spaced on the frequency scale. Extent and origin of spacing order, however, are not clear. Therefore, the raw data of all human SOAE surveys were pooled, and the intervals of all possible emission pairs in each ear were in total outlined according to size on a distribution diagram (n = 5245, for intervals up to 2/3 octave). Prevalence was increased for intervals between the benchmarks of 1 and 2 critical bands (CB). This CB-2CB range was further characterized by preference of intervals with low-order frequency ratios like 5:4 or 6:5, whereas outside CB 2CB there were no such effects. The results are discussed in the context of current knowledge of the origin of critical bands. Experiments are proposed that test the hypothesis of an influence of the olivocochlear efferents on SOAE spacing.

  9. Research on effect of emission uniformity on X-band relativistic backward oscillator using conformal PIC code

    SciTech Connect

    Chen, Zaigao

    2016-07-15

    Explosive emission cathodes (EECs) are adopted in relativistic backward wave oscillators (RBWOs) to generate intense relativistic electron beam. The emission uniformity of the EEC can render saturation of the power generation unstable and the output mode impure. However, the direct measurement of the plasma parameters on the cathode surface is quite difficult and there are very few related numerical study reports about this issue. In this paper, a self-developed three-dimensional conformal fully electromagnetic particle in cell code is used to study the effect of emission uniformity on the X-band RBWO; the electron explosive emission model and the field emission model are both implemented in the same cathode surface, and the local field enhancement factor is also considered in the field emission model. The RBWO with a random nonuniform EEC is thoroughly studied using this code; the simulation results reveal that when the area ratio of cathode surface for electron explosive emission is 80%, the output power is unstable and the output mode is impure. When the annular EEC does not emit electron in the angle range of 30°, the RBWO can also operate normally.

  10. Systematic Search of the Nearest Stars for Exoplanetary Radio Emission: VLA observations in L and S Bands

    NASA Astrophysics Data System (ADS)

    Winterhalter, D.; Knapp, M.; Bastian, T.

    2016-12-01

    Radio observations have been used as a search tool for exoplanets since before the confirmed discovery of the first extrasolar planet. To date, there have been no definitive detections of exoplanets in the radio regime. We are engaged in an ongoing blind radio survey of the nearest star systems for exoplanetary radio emission. The goal of this survey is to obtain meaningful upper limits on radio emission from (or modulated by) sub-stellar companions of the nearest stars. Nearby stars are strongly preferred because they suffer the least from the dilution of potential radio signals by distance. Targets are selected by distance and observability (both LOFAR and VLA) only. Other properties of target stars, such as stellar type, are not considered to avoid biasing the search. Five survey targets, Procyon, GJ 1111, GJ 725, Ross 614, and UGPSJ072227.51, have been observed with the VLA telescope L- and S-band receivers. P-band observations are ongoing. All targets have multiple L-band observations, while Procyon and Ross 614 also have S-band observations. GJ 725 has been observed with LOFAR at lower frequencies (30-75 MHz) as well. Upper limits on planetary radio flux (and implied magnetic field strength) derived from these VLA observations are presented.

  11. Enhanced Spontaneous Emission of Bloch Oscillation Radiation from a Single Energy Band

    DTIC Science & Technology

    2006-06-30

    electron becomes BPe s =4.3 10−6 meV, and since there are a total of n=5 109 electrons in the active region of the SL, the generated energy achievable...is estimated to be P=n BPe s =21.7 eV, which corresponds to an approximate power generation of W= B /NP0.1 W. In this power estimate, it is noted

  12. Wavelength Shifts of the 7.7 Micron Emission Band in Reflection Nebulae

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse; Temi, Pasquale

    2003-01-01

    Using spatial-spectral data cubes of reflection nebulae obtained by ISOCAM, we have observed a shift in the central wavelength of the 7.7 micron band within several reflection nebulae. The band shifts progressively from approx. 7.8 microns near the edge of the nebulae to approx. 7.6 microns towards the center of the nebulae. The ratio of the 11.3/7.7 micron bands also changes with distance from the central star, first rising from the center towards the edge of the nebula, then falling at the largest distances from the star, consistent with the 11.3/7.7 micron band ratio being controlled by the PAH ionization state. The behavior of the 7.7 micron band center can be explained either by assuming that anions are the origin of the 7.85 micron band and cations the 7.65 micron band, or that the band center wavelength depends on the chemical nature of the PAHs.

  13. Wavelength Shifts of the 7.7 Micron Emission Band in Reflection Nebulae

    NASA Technical Reports Server (NTRS)

    Bregman, Jesse; Temi, Pasquale

    2003-01-01

    Using spatial-spectral data cubes of reflection nebulae obtained by ISOCAM, we have observed a shift in the central wavelength of the 7.7 micron band within several reflection nebulae. The band shifts progressively from approx. 7.8 microns near the edge of the nebulae to approx. 7.6 microns towards the center of the nebulae. The ratio of the 11.3/7.7 micron bands also changes with distance from the central star, first rising from the center towards the edge of the nebula, then falling at the largest distances from the star, consistent with the 11.3/7.7 micron band ratio being controlled by the PAH ionization state. The behavior of the 7.7 micron band center can be explained either by assuming that anions are the origin of the 7.85 micron band and cations the 7.65 micron band, or that the band center wavelength depends on the chemical nature of the PAHs.

  14. The circumstellar dust envelopes of red giant stars. I - M giant stars with the 10-micron silicate emission band

    NASA Technical Reports Server (NTRS)

    Hashimoto, O.; Nakada, Y.; Onaka, T.; Kamijo, F.; Tanabe, T.

    1990-01-01

    Spherical dust envelope models of red giant stars are constructed by solving the radiative transfer equations of the generalized two-stream Eddington approximation. The IRAS observations of M giant stars which show the 10-micron silicate emission band in IRAS LRS spectra are explained by the models with the dirty silicate grains with K proportional to lambda exp -1.5 for lambda greather than 28 microns. Under the assumption of steady mass flow in the envelope, this model analysis gives the following conclusions: (1) the strength of the silicate emission peak at 10 microns is a good indicator of the mass loss rate of the star, (2) no stars with the 10-microns silicate emission feature are observed in the range of mass loss rate smaller than 7 x 10 to the -8th solar mass/yr, and (3) the characteristic time of the mass loss process of M stars does not exceed a few 10,000 years.

  15. Spatially Resolved M-band Emission from Io's Loki Patera-Fizeau Imaging at the 22.8 m LBT

    NASA Astrophysics Data System (ADS)

    Conrad, Albert; de Kleer, Katherine; Leisenring, Jarron; La Camera, Andrea; Arcidiacono, Carmelo; Bertero, Mario; Boccacci, Patrizia; Defrère, Denis; de Pater, Imke; Hinz, Philip; Hofmann, Karl-Heinz; Kürster, Martin; Rathbun, Julie; Schertl, Dieter; Skemer, Andy; Skrutskie, Michael; Spencer, John; Veillet, Christian; Weigelt, Gerd; Woodward, Charles E.

    2015-05-01

    The Large Binocular Telescope Interferometer mid-infrared camera, LMIRcam, imaged Io on the night of 2013 December 24 UT and detected strong M-band (4.8 μm) thermal emission arising from Loki Patera. The 22.8 m baseline of the Large Binocular Telescope provides an angular resolution of ˜32 mas (˜100 km at Io) resolving the Loki Patera emission into two distinct maxima originating from different regions within Loki’s horseshoe lava lake. This observation is consistent with the presence of a high-temperature source observed in previous studies combined with an independent peak arising from cooling crust from recent resurfacing. The deconvolved images also reveal 15 other emission sites on the visible hemisphere of Io including two previously unidentified hot spots.

  16. Calculated hydroxyl A2 sigma --> X2 pi (0, 0) band emission rate factors applicable to atmospheric spectroscopy.

    PubMed

    Cageao, R P; Ha, Y L; Jiang, Y; Morgan, M F; Yung, Y L; Sander, S P

    1997-05-01

    A calculation of the A2 sigma --> X2 pi (0, 0) band emission rate factors and line center absorption cross sections of OH applicable to its measurement using solar resonant fluorescence in the terrestrial atmosphere is presented in this paper. The most accurate available line parameters have been used. Special consideration has been given to the solar input flux because of its highly structured Fraunhofer spectrum. The calculation for the OH atmospheric emission rate factor in the solar resonant fluorescent case is described in detail with examples and intermediate results. Results of this calculation of OH emission rate factors for individual rotational lines are on average 30% lower than the values obtained in an earlier work.

  17. ODMR experiments on the 1.65eV luminescence in GaP:Cu

    NASA Astrophysics Data System (ADS)

    Greidanus, F. J. A. M.; van Roosmalen, J. T. C.

    1987-03-01

    Optically detected magnetic resonance experiments on the 1.65eV emission band in a Cu-doped LPE-grown GaP layer are reported. A strong resonance with a g-value of g = 2.006 ± 0.003 is observed. The linewidth depends on both microwave and laser excitation power. Other resonances, appearing at two and three times the field of the strong resonance, have also been measured. An interpretation of the measurements is given, based on the recombination of exchange coupled donor-acceptor pairs.

  18. Recognizing blue emission in artificial aurora

    NASA Astrophysics Data System (ADS)

    Holma, H.; Kaila, K.; Jussila, J.; Kosch, M.; Rietveld, M.

    On 12th November 2001, during the EISCAT UK/GE artificial aurora campaign, the optical group of University of Oulu performed the optical measurements at the EISCAT site in Ramfjordmoen. That campaign was the first successful attempt of inducing blue emission in artificial aurora at high latitudes. Optical instruments were monitoring emis-sions and they included a photometer, a real speed TV camera and a digital camera. The emissions measured by the photometer are 557.7 nm (OI), 630.0 nm (OI) and 427.8 nm (N2+). The threshold energies for these emissions to arise are 2 eV, 4 eV and 19 eV, re-spectively. In the natural aurora the blue emission at around 427 nm is always highly dominated by N2+ 1NG (0,1) rotational band. However, there are two weak emissions lying under this strong emission. These bands are N2 VK(4,15) (threshold energy 6 eV) and N2 2P(1,5) (threshold 11 eV). These energies are remarkably lower and could obviously have stronger intensity in the spectrum of artificial aurora than in natural aurora that is domi-nated by harder electron bombardment. The auroral photometer of the university of Oulu has been designed for investigating natural aurora, which results some limitations regarding the artificial aurora, to the data that has been obtained. The photometer was equipped with two channels measuring two close wavelength bands around 427 nm. These channels were aimed to be used to de-termine rotational temperature from the ratio of the intensities through the channels. Now they will be used to estimate the intensities of the three overlapping emission bands instead.

  19. Observation of interface band structure by ballistic-electron-emission microscopy

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Kaiser, W. J.

    1988-01-01

    The paper reports an advanced ballistic electron spectroscopy technique that was used to directly measure semiconductor band structure properties at a subsurface interface. Two interface systems having contrasting band structures were investigated by this method: Au-Si and Au-GaAs. It is concluded that the proposed method, based on scanning tunneling microscopy, enables the spatially resolved carrier-transport spectroscopy of interfaces.

  20. Observation of interface band structure by ballistic-electron-emission microscopy

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Kaiser, W. J.

    1988-01-01

    The paper reports an advanced ballistic electron spectroscopy technique that was used to directly measure semiconductor band structure properties at a subsurface interface. Two interface systems having contrasting band structures were investigated by this method: Au-Si and Au-GaAs. It is concluded that the proposed method, based on scanning tunneling microscopy, enables the spatially resolved carrier-transport spectroscopy of interfaces.

  1. Scuss u-Band Emission as a Star-Formation-Rate Indicator

    NASA Astrophysics Data System (ADS)

    Zhou, Zhimin; Zhou, Xu; Wu, Hong; Fan, Xiao-Hui; Fan, Zhou; Jiang, Zhao-Ji; Jing, Yi-Peng; Li, Cheng; Lesser, Michael; Jiang, Lin-Hua; Ma, Jun; Nie, Jun-Dan; Shen, Shi-Yin; Wang, Jia-Li; Wu, Zhen-Yu; Zhang, Tian-Meng; Zou, Hu

    2017-01-01

    We present and analyze the possibility of using optical u-band luminosities to estimate star-formation rates (SFRs) of galaxies based on the data from the South Galactic Cap u band Sky Survey (SCUSS), which provides a deep u-band photometric survey covering about 5000 deg2 of the South Galactic Cap. Based on two samples of normal star-forming galaxies selected by the BPT diagram, we explore the correlations between u-band, Hα, and IR luminosities by combing SCUSS data with the Sloan Digital Sky Survey and Wide-field Infrared Survey Explorer (WISE). The attenuation-corrected u-band luminosities are tightly correlated with the Balmer decrement-corrected Hα luminosities with an rms scatter of ∼0.17 dex. The IR-corrected u luminosities are derived based on the correlations between the attenuation of u-band luminosities and WISE 12 (or 22) μm luminosities, and then calibrated with the Balmer-corrected Hα luminosities. The systematic residuals of these calibrations are tested against the physical properties over the ranges covered by our sample objects. We find that the best-fitting nonlinear relations are better than the linear ones and recommended to be applied in the measurement of SFRs. The systematic deviations mainly come from the pollution of old stellar population and the effect of dust extinction; therefore, a more detailed analysis is needed in future work.

  2. The ALI-ARMS Code for Modeling Atmospheric non-LTE Molecular Band Emissions: Current Status and Applications

    NASA Technical Reports Server (NTRS)

    Kutepov, A. A.; Feofilov, A. G.; Manuilova, R. O.; Yankovsky, V. A.; Rezac, L.; Pesnell, W. D.; Goldberg, R. A.

    2008-01-01

    The Accelerated Lambda Iteration (ALI) technique was developed in stellar astrophysics at the beginning of 1990s for solving the non-LTE radiative transfer problem in atomic lines and multiplets in stellar atmospheres. It was later successfully applied to modeling the non-LTE emissions and radiative cooling/heating in the vibrational-rotational bands of molecules in planetary atmospheres. Similar to the standard lambda iterations ALI operates with the matrices of minimal dimension. However, it provides higher convergence rate and stability due to removing from the iterating process the photons trapped in the optically thick line cores. In the current ALI-ARMS (ALI for Atmospheric Radiation and Molecular Spectra) code version additional acceleration of calculations is provided by utilizing the opacity distribution function (ODF) approach and "decoupling". The former allows replacing the band branches by single lines of special shape, whereas the latter treats non-linearity caused by strong near-resonant vibration-vibrational level coupling without additional linearizing the statistical equilibrium equations. Latest code application for the non-LTE diagnostics of the molecular band emissions of Earth's and Martian atmospheres as well as for the non-LTE IR cooling/heating calculations are discussed.

  3. Origin of the visible emission of black silicon microstructures

    NASA Astrophysics Data System (ADS)

    Fabbri, Filippo; Lin, Yu-Ting; Bertoni, Giovanni; Rossi, Francesca; Smith, Matthew J.; Gradečak, Silvija; Mazur, Eric; Salviati, Giancarlo

    2015-07-01

    Silicon, the mainstay semiconductor in microelectronics, is considered unsuitable for optoelectronic applications due to its indirect electronic band gap that limits its efficiency as light emitter. Here, we univocally determine at the nanoscale the origin of visible emission in microstructured black silicon by cathodoluminescence spectroscopy and imaging. We demonstrate the formation of amorphous silicon oxide microstructures with a white emission. The white emission is composed by four features peaking at 1.98 eV, 2.24 eV, 2.77 eV, and 3.05 eV. The origin of such emissions is related to SiOx intrinsic point defects and to the sulfur doping due to the laser processing. Similar results go in the direction of developing optoelectronic devices suitable for silicon-based circuitry.

  4. Probing the strain effect on near band edge emission of a curved ZnO nanowire via spatially resolved cathodoluminescence

    NASA Astrophysics Data System (ADS)

    Xue, Haizhou; Pan, Nan; Li, Ming; Wu, Yukun; Wang, Xiaoping; Hou, J. G.

    2010-05-01

    Curved ZnO nanowires were deliberately prepared on a Si substrate and the strain effect on their near band edge (NBE) emission was investigated by spatially resolved cathodoluminescence (CL). By moving the electron beam step-by-step across individual curved nanowires and acquiring the CL spectra simultaneously, we found that the NBE emissions from the inner region of the curved nanowires with compressive strain show blueshift, while those from the outer region with tensile strain show redshift. Both the strains have been estimated from the local curvature by a geometrical model and have been further examined by high-resolution transmission electron microscopy. A nearly linear relation between the strain and the peak energy shift in NBE emission was obtained. The result indicates that the optical band gap of ZnO nanowire is quite sensitive to and can be readily modulated by the induced strain via simply curving the nanowire, which has potential applications for designing new optical-electromechanical (OEM) and flexible optoelectronic nanodevices.

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

    SciTech Connect

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

    2012-12-20

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

  6. Control of spontaneous emission of a single quantum emitter through a time-modulated photonic-band-gap environment

    NASA Astrophysics Data System (ADS)

    Calajò, Giuseppe; Rizzuto, Lucia; Passante, Roberto

    2017-08-01

    We consider the spontaneous emission of a two-level quantum emitter, such as an atom or a quantum dot, in a modulated time-dependent environment with a photonic band gap. An example of such an environment is a dynamical photonic crystal or any other environment with a band gap whose properties are modulated in time, in the effective mass approximation. After introducing our model of a dynamical photonic crystal, we show that it allows new possibilities to control and tailor the physical features of the emitted radiation, specifically its frequency spectrum. In the weak-coupling limit and in an adiabatic case, we obtain the emitted spectrum and we show the appearance of two lateral peaks due to the presence of the modulated environment, separated from the central peak by the modulation frequency. We show that the two side peaks are not symmetric in height, and that their height ratio can be exploited to investigate the density of states of the environment. Our results show that a dynamical environment can give further possibilities to modify the spontaneous emission features, such as its spectrum and emission rate, with respect to a static one. Observability of the phenomena we obtain is discussed, as well as relevance for tailoring and engineering radiative processes.

  7. Production of N2 Vegard-Kaplan and other triplet band emissions in the dayglow of Titan

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Anil; Jain, Sonal Kumar

    2012-04-01

    Recently the Cassini Ultraviolet Imaging Spectrograph (UVIS) has revealed the presence of N2 Vegard-Kaplan (VK) band A3Σu+-X1Σg+ emissions in Titan's dayglow limb observation. We present model calculations for the production of various N2 triplet states (viz., A3Σu+,B3Πg,C3Πu,E3Σu,W3Δu, and B3Σu ) in the upper atmosphere of Titan. The Analytical Yield Spectra technique is used to calculate steady state photoelectron fluxes in Titan's atmosphere, which are in agreement with those observed by the Cassini's CAPS instrument. Considering direct electron impact excitation, inter-state cascading, and quenching effects, the population of different levels of N2 triplet states are calculated under statistical equilibrium. Densities of all vibrational levels of each triplet state and volume production rates for various triplet states are calculated in the model. Vertically integrated overhead intensities for the same date and lighting conditions as reported by the UVIS observations for N2 Vegard-Kaplan A3Σu+-X1Σg+, First Positive B3Πg-A3Σu+, Second Positive (C3Πu - B3Πg), Wu-Benesch (W3Δu - B3Πg), and Reverse First Positive bands of N2 are found to be 132, 114, 19, 22, and 22 R, respectively. Overhead intensities are calculated for each vibrational transition of all the triplet band emissions of N2, which span a wider spectrum of wavelengths from ultraviolet to infrared. The calculated limb intensities of total and prominent transitions of VK band are presented. The model limb intensity of VK emission within the 150-190 nm wavelength region is in good agreement with the Cassini UVIS observed limb profile. An assessment of the impact of solar EUV flux on the N2 triplet band emission intensity has been made by using three different solar flux models, viz., Solar EUV Experiment (SEE), SOLAR2000 (S2K) model of Tobiska (Tobiska, W.K. [2004]. Adv. Space Res. 34, 1736-1746), and HEUVAC model of Richards et al. (Richards, P.G., Woods, T.N., Peterson, W.K. [2006]. Adv

  8. Emission spectra and radiative lifetimes of the Cameron bands of CO trapped in solid rare gas matrices

    NASA Astrophysics Data System (ADS)

    Fournier, J.; Mohammed, Hassan H.; Deson, J.; Vermeil, C.; Schamps, J.

    1980-12-01

    The emission spectrum of the Cameron bands (a 3Π→X1 Σ+) of CO molecules trapped in solid Ne, Ar, and Kr has been studied using Xe resonance lamp excitation (λ=147 nm). The lifetime of the a 3Π state has been measured in solid Ne and found to be 90 msec. The decay time of this state is exponential within the range of experimental errors. The lifetime has been calculated assuming spin-orbit mixing between 1Σ+ and 3Π0 states, and found to be 94 msec for J=0. The lifetime values in Ar and Kr matrices are found to be 7.2 and <1 msec, respectively; this is consistent with the matrix shifts in solid Ne, Ar, and Kr, which for the 0-0 bands have been found to be -305, -946, and -2812 cm-1, respectively.

  9. Detection of CO Cameron band emission in comet P/Hartley 2 (1991 XV) with the Hubble Space Telescope

    NASA Astrophysics Data System (ADS)

    Weaver, H. A.; Feldman, P. D.; McPhate, J. B.; A'Hearn, M. F.; Arpigny, C.; Smith, T. E.

    1994-02-01

    Ultraviolet (UV) spectra of comet P/Hartley 2 (1991 XV) taken with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in 1991 September reveal several bands of the Cameron system of CO (a 3 Pi-X 1 Sigma). These band are most likely due to 'prompt' emission from CO2 and, thus, provide a direct tracer of the CO2 abundance in the nucleus. Photodissociative excitation of CO2 is probably the largest contributor to the Cameron band emission, but significant contributions from electron impact excitation of CO, electron impact dissociation of CO2, and dissociative recombination of CO2(+), are also possible. Using our estimate that photodissociative excitation is responsible for approximately 60% of the total excitation of the Cameron system, we derive QCO2 approximately 2.6 x 1027 molecules/s, which implies CO2/H20 approximately 4%. If all of the Cameron band emission is due to photodissociative excitation, then CO2/H2O = 7 +/- 2%. For the largest possible contributions from the other excitation mechanisms considered, the CO2 abundance could be as a small as aproximately 2-3%. We did not detect CO Fourth Positive Group emission in our data and derive an upper limit of CO/H2O less than or equal to 1% (3 sigma) for CO coming directly from the nucleus. Comparison of the relative CO2 and CO abundances in P/Hartley 2 to those in P/Halley (CO2/H2O approximately 3%-4%, CO/H20 approximately 4% for the nucleus source) indicates that selective devolatilization of the nucleus may have occurred for P/Hartley 2. A relatively large CO2/CO ratio (i.e., approximately greater than 1) seems to be a common property of cometary nuclei. Since gas phase chemistry, in either the solar nebula or the interstellar medium (ISM), appears incapable of producing large relative CO2 abundances, the CO2 in cometary nuclei is probably produced either by UV and/or cosmic ray irradiation of ISM grains prior to the formation of the Solar System, or by condensation fractionation in the

  10. Detection of CO Cameron band emission in comet P/Hartley 2 (1991 XV) with the Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    Weaver, H. A.; Feldman, P. D.; Mcphate, J. B.; A'Hearn, M. F.; Arpigny, C.; Smith, T. E.

    1994-01-01

    Ultraviolet (UV) spectra of comet P/Hartley 2 (1991 XV) taken with the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST) in 1991 September reveal several bands of the Cameron system of CO (a 3 Pi-X 1 Sigma). These band are most likely due to 'prompt' emission from CO2 and, thus, provide a direct tracer of the CO2 abundance in the nucleus. Photodissociative excitation of CO2 is probably the largest contributor to the Cameron band emission, but significant contributions from electron impact excitation of CO, electron impact dissociation of CO2, and dissociative recombination of CO2(+), are also possible. Using our estimate that photodissociative excitation is responsible for approximately 60% of the total excitation of the Cameron system, we derive Q(sub CO2) approximately 2.6 x 10(exp 27) molecules/s, which implies CO2/H20 approximately 4%. If all of the Cameron band emission is due to photodissociative excitation, then CO2/H2O = 7 +/- 2%. For the largest possible contributions from the other excitation mechanisms considered, the CO2 abundance could be as a small as aproximately 2-3%. We did not detect CO Fourth Positive Group emission in our data and derive an upper limit of CO/H2O less than or equal to 1% (3 sigma) for CO coming directly from the nucleus. Comparison of the relative CO2 and CO abundances in P/Hartley 2 to those in P/Halley (CO2/H2O approximately 3%-4%, CO/H20 approximately 4% for the nucleus source) indicates that selective devolatilization of the nucleus may have occurred for P/Hartley 2. A relatively large CO2/CO ratio (i.e., approximately greater than 1) seems to be a common property of cometary nuclei. Since gas phase chemistry, in either the solar nebula or the interstellar medium (ISM), appears incapable of producing large relative CO2 abundances, the CO2 in cometary nuclei is probably produced either by UV and/or cosmic ray irradiation of ISM grains prior to the formation of the Solar System, or by condensation

  11. Impact of the wetting layer thickness on the emission wavelength of direct band gap GeSn/Ge quantum dots

    NASA Astrophysics Data System (ADS)

    Ilahi, Bouraoui; Al-Saigh, Reem; Salem, Bassem

    2017-07-01

    The effects of the wetting layer thickness (t WL) on the electronic properties of direct band gap type-I strained dome shaped Ge(1-x)Sn x quantum dot (QD) embedded in Ge matrix is numerically studied. The emission wavelength and the energy difference between S and P electron levels have been evaluated as a function of t WL for different QD size and composition with constant height to diameter ratio. The emission wavelength is found to be red shifted by increasing the wetting layer thickness, with smaller size QD being more sensitive to the variation of t WL. Furthermore, the minimum Sn composition required to fit the directness criteria is found to reduce by increasing the wetting layer thickness.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  13. Emission red shift and unusual band narrowing of Mn2+ in NaCaPO4 phosphor.

    PubMed

    Shi, Liang; Huang, Yanlin; Seo, Hyo Jin

    2010-07-08

    Concentration dependence of Mn(2+) luminescence in NaCaPO(4)/Mn(2+) is investigated by structural analyses and optical and laser excitation spectroscopies in the temperature range 19-300 K. NaCaPO(4)/Mn(2+) forms solid solution over the Mn(2+) concentration range 1.0-22 mol %. We observe the red shift and unusual band narrowing of Mn(2+) emission by increasing Mn(2+) concentration in NaCaPO(4). The lifetime of Mn(2+) emission lengthens unexpectedly for higher Mn(2+) concentration. The results are discussed in relation with crystal structure, photon reabsorption, exchange interaction, and energy transfer and energy migration in NaCaPO(4)/Mn(2+).

  14. Parametric exponentially correlated surface emission model for L-band passive microwave soil moisture retrieval

    USDA-ARS?s Scientific Manuscript database

    Surface soil moisture is an important parameter in hydrology and climate investigations. Current and future satellite missions with L-band passive microwave radiometers can provide valuable information for monitoring the global soil moisture. A factor that can play a significant role in the modeling...

  15. Beyond the Band Function Paradigm : a New Model for GRB Prompt Emission and Possible Impact in Cosmology

    NASA Astrophysics Data System (ADS)

    Guiriec, Sylvain

    Gamma Ray Bursts (GRBs) are the most violent phenomenons in the Universe. They are associated with the birth of stellar mass black holes either from the collapse of hypermassive stars or the merger of compact objects. The Fireball model is the most popular scenario to explain GRBs. In this theoretical framework, GRB central engines release collimated, bipolar and highly relativistic jets mainly composed of electrons, positrons, photons, and a small amount of baryons. During the first phase of the Fireball model, charged particles are accelerated and release non-thermal radiations. The Fireball model also predicts a thermal like component coming from the jet photosphere. This first phase would be responsible for the GRB prompt emission observed by gamma ray telescopes such as Fermi/GBM in the keV-MeV energy range and which is the only phase discussed in this talk. Until now, GRB prompt emission spectra were considered as adequately fitted with the empirical Band function, which is a smoothly broken power law. However, its parameters are very often incompatible with the Fireball model predictions for both the thermal and non-thermal components. We will see that observation with the Fermi Gamma Ray Space Telescope break the paradigm of the Band function and that deviations from this function exists in many GRBs. Those deviations are adequately fitted with an additional thermal-like component -that we consider as the jet photosphere- and/or an additional power law. Importantly, with the three components together, theory and observations are much more in agreement. We will also see how this new model for prompt emission spectra may have an impact beyond the physics of GRBs. Indeed, this work may confirm a relation between the hardness of the GRB prompt emission and its luminosity which may be used to scale GRBs as standard-like candles for use in cosmology.

  16. Modeling of Microwave Emissions from the Marie-Byrd Antarctic Region: A Stable Calibration Target in the L-band

    NASA Astrophysics Data System (ADS)

    Misra, S.; Brown, S.

    2010-12-01

    With the recent launch of SMOS (Soil Moisture Ocean Salinity) and upcoming missions Aquarius and SMAP (Soil Moisture Active Passive), calibration in L-band has become an important issue. The Aquarius mission, due to be launched in April 2011, is responsible for globally mapping sea-surface salinity. Due to the high sensitivity of brightness temperature to salinity and high precision of the Aquarius radiometers, it is necessary to have temporally stable calibration sources. Previously, Dome-C in the east Antarctic region was suggested as a promising area to monitor radiometer calibrations in the L-band toward the hot end of the brightness temperature spectrum (Macelloni et al., 2006; Macelloni et al., 2007). We present the Marie-Byrd region in west Antarctica as an excellent calibration reference, due to both its temporal stability over years as well as spatial vastness. In order to identify stable calibration regions for L-band we used 6-37GHz AMSR-E data. The spatial and temporal variability of AMSR-E brightness temperatures over the Antarctic region was analyzed, and only regions that were stable in both domains (like Marie-Byrd) were identified as radiometrically stable. Using data obtained from Automatic Weather Stations (AWS) near Marie-Byrd, the correlation between surface temperature and deep-ice temperature, as measured by microwaves was calculated. Results indicate that as the microwave frequency is lowered, the peak-to-peak annual variation of brightness temperature decreases. The bulk of emission for low frequencies occurs deep in the ice which is very stable over time and decorrelated with short term surface temperature fluctuations. As a result, at L-band the ice-regions like Marie-Byrd in Antarctica serve as an excellent source of calibration. A coupled ice heat-transport and radiative-transfer model was developed to predict brightness temperatures observed at low microwave frequencies. The ice model takes into account the surface fluctuations of

  17. Spectral modification of the laser emission of a terahertz quantum cascade laser induced by broad-band double pulse injection seeding

    SciTech Connect

    Markmann, Sergej Nong, Hanond Hekmat, Negar; Jukam, Nathan; Pal, Shovon; Scholz, Sven; Kukharchyk, Nadezhda; Ludwig, Arne; Wieck, Andreas D.; Dhillon, Sukhdeep; Tignon, Jérôme; Marcadet, Xavier; Bock, Claudia; Kunze, Ulrich

    2015-09-14

    We demonstrate by injection seeding that the spectral emission of a terahertz (THz) quantum cascade laser (QCL) can be modified with broad-band THz pulses whose bandwidths are greater than the QCL bandwidth. Two broad-band THz pulses delayed in time imprint a modulation on the single THz pulse spectrum. The resulting spectrum is used to injection seed the THz QCL. By varying the time delay between the THz pulses, the amplitude distribution of the QCL longitudinal modes is modified. By applying this approach, the QCL emission is reversibly switched from multi-mode to single mode emission.

  18. Molecular emission bands in the ultraviolet spectrum of the red rectangle star HD 44179

    NASA Technical Reports Server (NTRS)

    Sitko, M. L.

    1981-01-01

    New observations of the ultraviolet spectrum of HD 44179 are reported. Absorption due to the CO molecule is present in the spectrum with NCO approximately 10 to the 18th power per sq cm. Emission due to either CO or a molecule containing C=C, C=N, C-C, and C-H bonds (or both) is also present.

  19. HITEMP derived spectral database for the prediction of jet engine exhaust infrared emission using a statistical band model

    NASA Astrophysics Data System (ADS)

    Lindermeir, E.; Beier, K.

    2012-08-01

    The spectroscopic database HITEMP 2010 is used to upgrade the parameters of the statistical molecular band model which is part of the infrared signature prediction code NIRATAM (NATO InfraRed Air TArget Model). This band model was recommended by NASA and is applied in several codes that determine the infrared emission of combustion gases. The upgrade regards spectral absorption coefficients and line densities of the gases H2O, CO2, and CO in the spectral region 400-5000 cm-1 (2-25μm) with a spectral resolution of 5 cm-1. The temperature range 100-3000 K is covered. Two methods to update the database are presented: the usually applied method as provided in the literature and an alternative, more laborious procedure that employs least squares fitting. The achieved improvements resulting from both methods are demonstrated by comparisons of radiance spectra obtained from the band model to line-by-line results. The performance in a realistic scenario is investigated on the basis of measured and predicted spectra of a jet aircraft plume in afterburner mode.

  20. Temporal behavior of the SO 1.707 μm ro-vibronic emission band in Io's atmosphere

    NASA Astrophysics Data System (ADS)

    Laver, Conor; de Pater, Imke; Roe, Henry; Strobel, Darrell F.

    2007-08-01

    We report observations of the ro-vibronic aΔ→XΣ transition of SO at 1.707 μm on Io. These data were taken while Io was eclipsed by Jupiter, on four nights between July 2000 and March 2003. We analyze these results in conjunction with a previously published night to investigate the temporal behavior of these emissions. The observations were all conducted using the near-infrared spectrometer NIRSPEC on the W.M. Keck II telescope. The integrated emitted intensity for this band varies from 0.8×10 to 2.4×10 photons/s, with a possible link to variations in Loki's infrared brightness. The band-shapes imply rotational temperatures of 550-1000 K for the emitting gas, lending further evidence to a volcanic origin for sulfur monoxide. An attempt to detect the BΣ→XΣ transition of SO at 0.97 μm was unsuccessful; simultaneous detection with the 1.707 μm band would permit determination of the SO column abundance.

  1. Near-infrared Spectroscopic Observations of Comet C/2013 R1 (Lovejoy) by WINERED: CN Red-system Band Emission

    NASA Astrophysics Data System (ADS)

    Shinnaka, Yoshiharu; Kawakita, Hideyo; Kondo, Sohei; Ikeda, Yuji; Kobayashi, Naoto; Hamano, Satoshi; Sameshima, Hiroaki; Fukue, Kei; Matsunaga, Noriyuki; Yasui, Chikako; Izumi, Natsuko; Mizumoto, Misaki; Otsubo, Shogo; Takenaka, Keiichi; Watase, Ayaka; Kawanishi, Takafumi; Nakanishi, Kenshi; Nakaoka, Tetsuya

    2017-08-01

    Although high-resolution spectra of the CN red-system band are considered useful in cometary sciences, e.g., in the study of isotopic ratios of carbon and nitrogen in cometary volatiles, there have been few reports to date due to the lack of high-resolution (R ≡ λ/Δλ > 20,000) spectrographs in the near-infrared region around ˜1 μm. Here, we present the high-resolution emission spectrum of the CN red-system band in comet C/2013 R1 (Lovejoy), acquired by the near-infrared high-resolution spectrograph WINERED mounted on the 1.3 m Araki telescope at the Koyama Astronomical Observatory, Kyoto, Japan. We applied our fluorescence excitation models for CN, based on modern spectroscopic studies, to the observed spectrum of comet C/2013 R1 (Lovejoy) to search for CN isotopologues (13C14N and 12C15N). We used a CN fluorescence excitation model involving both a “pure” fluorescence excitation model for the outer coma and a “fully collisional” fluorescence excitation model for the inner coma region. Our emission model could reproduce the observed 12C14N red-system band of comet C/2013 R1 (Lovejoy). The derived mixing ratio between the two excitation models was 0.94(+0.02/-0.03):0.06(+0.03/-0.02), corresponding to the radius of the collision-dominant region of ˜800-1600 km from the nucleus. No isotopologues were detected. The observed spectrum is consistent, within error, with previous estimates in comets of 12C/13C (˜90) and 14N/15N (˜150).

  2. Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness

    NASA Technical Reports Server (NTRS)

    LeVine, D. M.; Lang, R.; Wentz, F.; Messiner, T.

    2012-01-01

    A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.1 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest.

  3. Stimulated emission within the exciplex band by plasmonic-nanostructured polymeric heterojunctions

    NASA Astrophysics Data System (ADS)

    Zhang, Xinping; Li, Hongwei; Wang, Yimeng; Liu, Feifei

    2015-03-01

    Organic heterojunctions have been extensively employed in the design of light-emitting diodes, photovoltaic devices, and thin-film field-effect transistors, which can be achieved by constructing a bilayer or a multi-layered thin-film deposition, or by blending two or more organic semiconductors with different charge-transport performances. Charge transfer excited states or exciplex may form on the heterointerfaces. Efficient light-emitting diodes have been demonstrated using exciplex emission. However, lasing or stimulated emission processes have not been observed with exciplex formation at organic heterojunctions. In this work, we demonstrate strong coherent interaction between photons and exciplex formation in the blends of poly-9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4-phenylenediamine (PFB) and poly-9,9'-dioctylfluorene-co-benzothiadiazole (F8BT), leading to transient stimulated exciplex emission. The responsible mechanisms involve plasmonic local-field enhancement and plasmonic feedback in a three-dimensional gold-nanoparticle matrix.Organic heterojunctions have been extensively employed in the design of light-emitting diodes, photovoltaic devices, and thin-film field-effect transistors, which can be achieved by constructing a bilayer or a multi-layered thin-film deposition, or by blending two or more organic semiconductors with different charge-transport performances. Charge transfer excited states or exciplex may form on the heterointerfaces. Efficient light-emitting diodes have been demonstrated using exciplex emission. However, lasing or stimulated emission processes have not been observed with exciplex formation at organic heterojunctions. In this work, we demonstrate strong coherent interaction between photons and exciplex formation in the blends of poly-9,9'-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-l,4-phenylenediamine (PFB) and poly-9,9'-dioctylfluorene-co-benzothiadiazole (F8BT), leading to transient

  4. Mapping H-band Scattered Light Emission in the Mysterious SR21Transitional Disk

    NASA Technical Reports Server (NTRS)

    Follette, Katherine B.; Motohide, Tamura; Hashimoto, Jun; Whitney, Barbara; Grady, Carol; Close, Laird; Andrews, Sean M.; Kwon, Jungmi; Wisniewski, John; Brandt, Timothy D.; hide

    2013-01-01

    We present the first near infrared (NIR) spatially resolved images of the circumstellar transitional disk around SR21. These images were obtained with the Subaru HiCIAO camera, adaptive optics, and the polarized differential imaging technique. We resolve the disk in scattered light at H-band for stellocentric 0.1 < or approx. r < or approx. 0.6 (12 < or approx. r < or approx. 75AU). We compare our results with previously published spatially resolved 880 micron continuum Submillimeter Array images that show an inner r < or approx. 36AU cavity in SR21. Radiative transfer models reveal that the large disk depletion factor invoked to explain SR21's sub-mm cavity cannot be "universal" for all grain sizes. Even significantly more moderate depletions (delta = 0.1, 0.01 relative to an undepleted disk) than those that reproduce the sub-mm cavity (delta approx. 10(exp -6) are inconsistent with our H-band images when they are assumed to carry over to small grains, suggesting that surface grains scattering in the NIR either survive or are generated by whatever mechanism is clearing the disk midplane. In fact, the radial polarized intensity profile of our H-band observations is smooth and steeply inwardly-increasing (r(sup -3), with no evidence of a break at the 36AU sub-mm cavity wall. We hypothesize that this profile is dominated by an optically thin disk envelope or atmosphere component.We also discuss the compatibility of our data with the previously postulated existence of a sub-stellar companion to SR21 at r approx. 10-20AU, and find that we can neither exclude nor verify this scenario. This study demonstrates the power of multiwavelength imaging of transitional disks to inform modeling efforts, including the debate over precisely what physical mechanism is responsible for clearing these disks of their large midplane grains.

  5. MAPPING H-BAND SCATTERED LIGHT EMISSION IN THE MYSTERIOUS SR21 TRANSITIONAL DISK

    SciTech Connect

    Follette, Katherine B.; Close, Laird; Tamura, Motohide; Hashimoto, Jun; Kwon, Jungmi; Kandori, Ryo; Whitney, Barbara; Grady, Carol; Andrews, Sean M.; Wisniewski, John; Brandt, Timothy D.; Dong, Ruobing; Mayama, Satoshi; Abe, Lyu; Brandner, Wolfgang; Feldt, Markus; Carson, Joseph; Currie, Thayne; Egner, Sebastian E.; Goto, Miwa; and others

    2013-04-10

    We present the first near infrared (NIR) spatially resolved images of the circumstellar transitional disk around SR21. These images were obtained with the Subaru HiCIAO camera, adaptive optics, and the polarized differential imaging technique. We resolve the disk in scattered light at H-band for stellocentric 0.''1 {<=} r {<=} 0.''6 (12 {approx}< r {approx}< 75 AU). We compare our results with previously published spatially resolved 880 {mu}m continuum Submillimeter Array images that show an inner r {approx}< 36 AU cavity in SR21. Radiative transfer models reveal that the large disk depletion factor invoked to explain SR21's sub-mm cavity cannot be 'universal' for all grain sizes. Even significantly more moderate depletions ({delta} = 0.1, 0.01 relative to an undepleted disk) than those that reproduce the sub-mm cavity ({delta} {approx} 10{sup -6}) are inconsistent with our H-band images when they are assumed to carry over to small grains, suggesting that surface grains scattering in the NIR either survive or are generated by whatever mechanism is clearing the disk midplane. In fact, the radial polarized intensity profile of our H-band observations is smooth and steeply inwardly-increasing (r {sup -3}), with no evidence of a break at the 36 AU sub-mm cavity wall. We hypothesize that this profile is dominated by an optically thin disk envelope or atmosphere component. We also discuss the compatibility of our data with the previously postulated existence of a sub-stellar companion to SR21 at r {approx} 10-20 AU, and find that we can neither exclude nor verify this scenario. This study demonstrates the power of multiwavelength imaging of transitional disks to inform modeling efforts, including the debate over precisely what physical mechanism is responsible for clearing these disks of their large midplane grains.

  6. The electrosphere of macroscopc ""nuclei"": diffuse emissions in the MeV band from dark antimatter

    SciTech Connect

    Forbes, Michael Mcneil; Lawson, Kyle; Zhitnitsky, Ariel R

    2009-01-01

    Using a Thomas-Fermi model, we calculate the structure of the electrosphere of the quark antimatter nuggets postulated to comprise much of the dark matter. This provides a single self-consistent density profile from ultra-rel ativistic densities to the non-relativistic Boltzmann regime. We use this to present a microscopically justified calculation of several properties of the nuggets, including their net charge, and the ratio of MeV to 511 keV emissions from electron annihilation. We find that the calculated parameters agree with previous phenomenological estimates based on the observational supposition that the nuggets are a source of several unexplained diffuse emissions from the galaxy. This provides another nontrivial verification of the dark matter proposal. The structure of the electrosphere is quite general and will also be valid at the surface of strange-quark stars, should they exist.

  7. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    NASA Technical Reports Server (NTRS)

    vanderWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; Koo, D. C.; Ferguson, H. C.; Scarlata, C.; Hathi, N. P.; Dunlop, J. S.; Newman, J. A.; Dickinson, M.; Jahnke, K.; Salmon, B. W.; deMello, D. F.; Kkocevski, D. D.; Lai, K.; Grogin, N. A.; Rodney, S. A.; Guo, Yicheng

    2012-01-01

    We identify an abundant population of extreme emission line galaxies (EELGs) at redshift z approx. 1.7 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 EELG candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared broad-band magnitudes. Supported by spectroscopic confirmation of strong [OIII] emission lines . with rest-frame equivalent widths approx. 1000A in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are galaxies with approx.10(exp 8) Solar Mass in stellar mass, undergoing an enormous starburst phase with M*/M* of only approx. 15 Myr. These bursts may cause outflows that are strong enough to produce cored dark matter profiles in low-mass galaxies. The individual star formation rates and the co-moving number density (3.7x10(exp -4) Mpc(sup -3) can produce in approx.4 Gyr much of the stellar mass density that is presently contained in 10(exp 8) - 10(exp 9) Solar Mass dwarf galaxies. Therefore, our observations provide a strong indication that many or even most of the stars in present-day dwarf galaxies formed in strong, short-lived bursts, mostly at z > 1.

  8. Extreme Emission Line Galaxies in CANDELS: Broad-Band Selected, Star-Bursting Dwarf Galaxies at Z greater than 1

    NASA Technical Reports Server (NTRS)

    VanDerWel, A.; Straughn, A. N.; Rix, H.-W.; Finkelstein, S. L.; Koekemoer, A. M.; Weiner, B. J.; Wuyts, S.; Bell, E. F.; Faber, S. M.; Trump, J. R.; hide

    2011-01-01

    We identify an abundant population of extreme emission line galaxies at redshift z=1.6 - 1.8 in the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey (CANDELS) imaging from Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3). 69 candidates are selected by the large contribution of exceptionally bright emission lines to their near-infrared, broad-band fluxes. Supported by spectroscopic confirmation of strong [OIII] emission lines - with equivalent widths approximately 1000A - in the four candidates that have HST/WFC3 grism observations, we conclude that these objects are dwarf galaxies with approximately 10(exp 8) solar mass in stellar mass, undergoing an enormous star-burst phase with M*/M* of only approximately 10 Myr. The star formation activity and the co-moving number density (3.7 x 10(exp -4) Mpc(exp -3)) imply that strong, short-lived bursts play a significant, perhaps even dominant role in the formation and evolution of dwarf galaxies at z greater than 1. The observed star formation activity can produce in less than 5 Gyr the same amount of stellar mass density as is presently contained in dwarf galaxies. Therefore, our observations provide a strong indication that the stellar populations of present-day dwarf galaxies formed mainly in strong, short-lived bursts, mostly at z greater than 1.

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  10. Broad band simulation of Gamma Ray Bursts (GRB) prompt emission in presence of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Ziaeepour, Houri; Gardner, Brian

    2011-12-01

    The origin of prompt emission in GRBs is not yet well understood. The simplest and most popular model is Synchrotron Self-Compton (SSC) emission produced by internal shocks inside an ultra-relativistic jet. However, recent observations of a delayed high energy component by the Fermi-LAT instrument have encouraged alternative models. Here we use a recently developed formulation of relativistic shocks for GRBs to simulate light curves and spectra of synchrotron and self-Compton emissions in the framework of internal shock model. This model takes into account the evolution of quantities such as densities of colliding shells, and fraction of kinetic energy transferred to electrons and to induced magnetic field. We also extend this formulation by considering the presence of a precessing external magnetic field. These simulations are very realistic and present significant improvement with respect to previous phenomenological GRB simulations. They reproduce light curves of separate peaks of real GRBs and variety of spectral slopes at E > Epeak observed by the Fermi-LAT instrument. The high energy emission can be explained by synchrotron emission and a subdominant contribution from inverse Compton. We also suggest an explanation for extended tail emission and relate it to the screening of the magnetic field and/or trapping of accelerated electrons in the electromagnetic energy structure of the plasma in the shock front. Spectral slopes of simulated bursts at E << Epeak are consistent with theoretical prediction and at E < Epeak can be flatter if the spectrum of electrons is roughly flat or has a shallow slope at low energies. The observed flat spectra at soft gamma-ray and hard x-ray bands is the evidence that there is a significant contribution at E < Epeak from lower Lorentz factor wing of electron distribution which have a roughly random acceleration rather than being thermal. This means that the state of matter in the jet at the time of ejection is most probably

  11. Multi-band Emission Light Curves of Jupiter: Insights on Brown Dwarfs and Directly Imaged Exoplanets

    NASA Astrophysics Data System (ADS)

    Zhang, Xi; Ge, Huazhi; Orton, Glenn S.; Fletcher, Leigh N.; Sinclair, James; Fernandes, Joshua; Momary, Thomas W.; Kasaba, Yasumasa; Sato, Takao M.; Fujiyoshi, Takuya

    2016-10-01

    Many brown dwarfs exhibit significant infrared flux variability (e.g., Artigau et al. 2009, ApJ, 701, 1534; Radigan et al. 2012, ApJ, 750, 105), ranging from several to twenty percent of the brightness. Current hypotheses include temperature variations, cloud holes and patchiness, and cloud height and thickness variations (e.g., Apai et al. 2013, ApJ, 768, 121; Robinson and Marley 2014, ApJ, 785, 158; Zhang and Showman 2014, ApJ, 788, L6). Some brown dwarfs show phase shifts in the light curves among different wavelengths (e.g., Buenzli et al. 2012, ApJ, 760, L31; Yang et al. 2016, arXiv:1605.02708), indicating vertical variations of the cloud distribution. The current observational technique can barely detect the brightness changes on the surfaces of nearby brown dwarfs (Crossfield et al. 2014, Nature, 505, 654) let alone resolve detailed weather patterns that cause the flux variability. The infrared emission maps of Jupiter might shed light on this problem. Using COMICS at Subaru Telescope, VISIR at Very Large Telescope (VLT) and NASA's Infrared Telescope Facility (IRTF), we obtained infrared images of Jupiter over several nights at multiple wavelengths that are sensitive to several pressure levels from the stratosphere to the deep troposphere below the ammonia clouds. The rotational maps and emission light curves are constructed. The individual pixel brightness varies up to a hundred percent level and the variation of the full-disk brightness is around several percent. Both the shape and amplitude of the light curves are significantly distinct at different wavelengths. Variation of light curves at different epochs and phase shift among different wavelengths are observed. We will present principle component analysis to identify dominant emission features such as stable vortices, cloud holes and eddies in the belts and zones and strong emissions in the aurora region. A radiative transfer model is used to simulate those features to get a more quantitative

  12. The effects of soil moisture, surface roughness, and vegetation on L-band emission and backscatter

    NASA Technical Reports Server (NTRS)

    Wang, James R.; Shiue, J. C.; Engman, Edwin T.; Schmugge, Thomas J.; Mo, Tsan

    1987-01-01

    Measurements performed with SIR-B at 1.28 GHz and an airborne multiple-beam push-broom radiometer at 1.4 GHz over agricultural fields near Fresno, California are examined. A theoretical model (Kirchhoff approximation) was used to assess the effects of surface roughness and vegetation (alfalfa and lettuce) with respect to the responses of microwave emission and backscatter to soil-moisture variations. It is found that the surface roughness plays a dominant role compared to the vegetation cover in the microwave backscatter.

  13. Narrow-band light emission from a single carbon nanotube p-n diode

    NASA Astrophysics Data System (ADS)

    Kinoshita, Megumi; Mueller, Thomas; Steiner, Mathias; Perebeinos, Vasili; Bol, Ageeth; Farmer, Damon; Avouris, Phaedon

    2010-03-01

    We present the first observation of electroluminescence from electrostatically-generated carbon nanotube (CNT) p-n junctions[1]. While CNT optoelectronics has made much progress in recent years, observations of emission from electrically excited CNT devices have been limited to the high-bias regime and with low efficiency. Furthermore, the resulting broad linewidths are broad, making it difficult to investigate electronic levels and carrier dynamics. We find that p-n junctions allow for better carrier control at lower power inputs, resulting in emission with near-zero threshold, low self-heating and efficiency two to three orders of magnitude greater compared to previous device configurations. This yields higher signal-to-noise ratio and narrower linewidths (down to ˜35 meV) that allows us to identify localized excitonic transitions that have previously been observed only in photoluminescent studies. [1] T. Mueller, M. Kinoshita, M. Steiner, V. Perebeinos, A. Bol, D. Farmer, and Ph. Avouris, Nature Nanotech., web publication, November 15 2009.

  14. Revealing the surface origin of green band emission from ZnO nanostructures by plasma immersion ion implantation induced quenching

    SciTech Connect

    Yang, Y.; Sun, X. W.; Tay, B. K.; Cao, Peter H. T.; Wang, J. X.; Zhang, X. H.

    2008-03-15

    Surface defect passivation for ZnO nanocombs (NCBs), random nanowires (RNWs), and aligned nanowires (ANWs) was performed through a metal plasma immersion ion implantation with low bias voltages ranging from 0 to 10 kV, where Ni was used as the modification ion. The depth of surface-originated green band (GB) emission is thus probed, revealing the surface origin of the GB. It is also found that the GB is closely related to oxygen gas content during growth of the nanostructures. The GB origin of NCBs and RNWs grown with higher oxygen content is shallower ({approx}0.5 nm), which can be completely quenched with no bias applied. However, the GB origin of ANWs grown at lower oxygen content is much deeper ({approx}7 nm) with a complete quenching bias of 10 kV. Quenching of the GB can be attributed to passivation of the surface hole or electron trapping sites (oxygen vacancies) by Ni ions.

  15. Broad-Band-Emissive Organic-Inorganic Hybrid Semiconducting Nanowires Based on an ABX3-Type Chain Compound.

    PubMed

    Wu, Zhenyue; Li, Lina; Ji, Chengmin; Lin, Guoming; Wang, Sasa; Shen, Yaoguo; Sun, Zhihua; Zhao, Sangen; Luo, Junhua

    2017-08-07

    Organic-inorganic hybrid lead halide (e.g., CH3NH3PbX3, where X = CI, Br, and I) nanowires (NWs) with remarkable electric and optical properties have recently garnered increasing attention, owing to their structural flexibility and tunability compared to inorganic semiconducting NWs. While most recently reported NWs are limited to methylammonium/formamidinium three-dimensional lead halide perovskites, it is urgent to develop new organic-inorganic hybrid semiconducting NWs. Here, broad-band-emissive single-crystal semiconductive NWs based on a new ABX3-type organic-inorganic chain hybrid, (2-methylpiperidine)lead tribromide, are reported. It is believed that this work will enrich the organic-inorganic hybrid semiconducting NWs and may provide potential applications for LED displaying.

  16. Spontaneous emission from a two-level atom in anisotropic one-band photonic crystals: A fractional calculus approach

    SciTech Connect

    Wu, J.-N.; Huang, C.-H.; Cheng, S.-C.; Hsieh, W.-F.

    2010-02-15

    Spontaneous emission (SE) from a two-level atom in an anisotropic photonic crystal (PC) is investigated by the fractional calculus. Physical phenomena of the SE are studied analytically by solving the fractional kinetic equations of the SE. There is a dynamical discrepancy between the SE of anisotropic and isotropic PCs. We find that, contrary to the SE phenomenon of the isotropic PC, the SE near the band edge of an anisotropic PC shows no photon-atom bound state. It is consistent with the experimental results of Barth, Schuster, Gruber, and Cichos [Phys. Rev. Lett. 96, 243902 (2006)] that the anisotropic property of the system enhances the SE. We also study effects of dispersion curvatures on the changes of the photonic density of states and the appearance of the diffusion fields in the SE.

  17. Remote Sensing of lower thermospheric temperature and composition based on observations of O2 Atmospheric band emission.

    NASA Astrophysics Data System (ADS)

    Christensen, A. B.; Yee, J.; Budzien, S. A.; Bishop, R. L.; Hecht, J. H.; Stephan, A. W.; Crowley, G.

    2011-12-01

    upper mesosphere and lower thermosphere from OSIRIS observations of O2 A-band emission spectra, Can. J. Phys. 88, 919-925, 2010. J. H. Yee, (private communication, 2011)

  18. Optical study of the band structure of wurtzite GaP nanowires

    NASA Astrophysics Data System (ADS)

    Assali, S.; Greil, J.; Zardo, I.; Belabbes, A.; de Moor, M. W. A.; Koelling, S.; Koenraad, P. M.; Bechstedt, F.; Bakkers, E. P. A. M.; Haverkort, J. E. M.

    2016-07-01

    We investigated the optical properties of wurtzite (WZ) GaP nanowires by performing photoluminescence (PL) and time-resolved PL measurements in the temperature range from 4 K to 300 K, together with atom probe tomography to identify residual impurities in the nanowires. At low temperature, the WZ GaP luminescence shows donor-acceptor pair emission at 2.115 eV and 2.088 eV, and Burstein-Moss band-filling continuum between 2.180 and 2.253 eV, resulting in a direct band gap above 2.170 eV. Sharp exciton α-β-γ lines are observed at 2.140-2.164-2.252 eV, respectively, showing clear differences in lifetime, presence of phonon replicas, and temperature-dependence. The excitonic nature of those peaks is critically discussed, leading to a direct band gap of ˜2.190 eV and to a resonant state associated with the γ-line ˜80 meV above the Γ8C conduction band edge.

  19. The modeling of emissions of Lyman-Birge-Hopfield and Vegard-Kaplan bands in the atmospheres of planets

    NASA Astrophysics Data System (ADS)

    Kirillov, Andrey S.

    Molecular nitrogen is main component in the atmospheres of Earth, Titan, Triton. Energetic particles interacting with the atmospheres cause electronic excitation of nitrogen molecules. Total quenching rate coefficients of three singlet and four triplet states of molecular nitrogen in the collisions with N2 and O2 molecules are calculated on the basis of quantum-chemical approximations. The calculated rate coefficients of electronic quenching of N2* molecules are compared with available experimental data. An influence of radiational and collisional processes on vibrational populations of electronically excited N2(a1) and N2(A3) molecules and emissions of Lyman-Birge-Hopfield and Vegard-Kaplan bands is studied for the mixture of N2 and O2 at different pressures. It is indicated that molecular collisions cause changes in relative populations of vibrational levels of the states and intensity relations of ultraviolet bands of N2 with the rise in the pressure and O2 admixture. The influence of electronically excited molecules on vibrational kinetics of molecular nitrogen is discussed.

  20. Spatially resolved band alignments at Au-hexadecanethiol monolayer-GaAs(001) interfaces by ballistic electron emission microscopy

    SciTech Connect

    Junay, A.; Guézo, S. Turban, P.; Delhaye, G.; Lépine, B.; Tricot, S.; Ababou-Girard, S.; Solal, F.

    2015-08-28

    We study structural and electronic inhomogeneities in Metal—Organic Molecular monoLayer (OML)—semiconductor interfaces at the sub-nanometer scale by means of in situ Ballistic Electron Emission Microscopy (BEEM). BEEM imaging of Au/1-hexadecanethiols/GaAs(001) heterostructures reveals the evolution of pinholes density as a function of the thickness of the metallic top-contact. Using BEEM in spectroscopic mode in non-short-circuited areas, local electronic fingerprints (barrier height values and corresponding spectral weights) reveal a low-energy tunneling regime through the insulating organic monolayer. At higher energies, BEEM evidences new conduction channels, associated with hot-electron injection in the empty molecular orbitals of the OML. Corresponding band diagrams at buried interfaces can be thus locally described. The energy position of GaAs conduction band minimum in the heterostructure is observed to evolve as a function of the thickness of the deposited metal, and coherently with size-dependent electrostatic effects under the molecular patches. Such BEEM analysis provides a quantitative diagnosis on metallic top-contact formation on organic molecular monolayer and appears as a relevant characterization for its optimization.

  1. WIDE-BAND SUZAKU ANALYSIS OF THE PERSISTENT EMISSION FROM SGR 0501+4516 DURING THE 2008 OUTBURST

    SciTech Connect

    Enoto, T.; Makishima, K.; Nakazawa, K.; Yamada, S.; Rea, N.; Nakagawa, Y. E.; Sakamoto, T.; Esposito, P.; Mereghetti, S.; Tiengo, A.; Goetz, D.; Israel, G. L.; Stella, L.; Kokubun, M.; Murakami, H.; Turolla, R.; Yamaoka, K.; Yoshida, A.; Zane, S.

    2010-05-20

    We observed the soft gamma repeater SGR 0501+4516 with Suzaku for {approx}51 ks on 2008 August 26-27, about 4 days after its discovery. Following the first paper, which reported on the persistent soft X-ray emission and the wide-band spectrum of an intense short burst, this paper presents an analysis of the persistent broadband (1-70 keV) spectra of this source in outburst, taken with the X-ray Imaging Spectrometer (XIS) and the Hard X-ray Detector (HXD). Pulse-phase folding in the 12-35 keV HXD-PIN data on an ephemeris based on multi-satellite timing measurements at soft X-rays revealed the pulsed signals at {approx_gt}99% confidence in the hard X-ray band. The wide-band spectrum clearly consists of a soft component and a separate hard component, crossing over at {approx}7 keV. When the soft component is modeled by a blackbody plus a Comptonized blackbody, the hard component exhibits a 20-100 keV flux of 4.8{sup +0.8}{sub -0.6}(stat.){sup +0.8}{sub -0.4}(sys.) x 10{sup -11} erg s{sup -1} cm{sup -2} and a photon index of {Gamma} = 0.79{sup +0.20}{sub -0.18}(stat.){sup +0.01}{sub -0.06}(sys.). The hard X-ray data are compared with those obtained by INTEGRAL about 1 day later. Combining the present results with those on other magnetars, we discuss a possible correlation between the spectral hardness of magnetars and their characteristic age and magnetic field strengths.

  2. Spatial variation of the 3.29 and 3.40 micron emission bands within reflection nebulae and the photochemical evolution of methylated polycyclic aromatic hydrocarbons.

    PubMed

    Joblin, C; Tielens, A G; Allamandola, L J; Geballe, T R

    1996-02-20

    Spectra of 3 micrometers emission features have been obtained at several positions within the reflection nebulae NGC 1333 SVS3 and NGC 2023. Strong variations of the relative intensities of the 3.29 micrometers feature and its most prominent satellite band at 3.40 micrometers are found. It is shown that (i) the 3.40 micrometers band is too intense with respect to the 3.29 micrometers band at certain positions to arise from hot band emission alone, (ii) the 3.40 micrometers band can be reasonably well matched by new laboratory spectra of gas-phase polycyclic aromatic hydrocarbons (PAHs) with alkyl (-CH3) side groups, and (iii) the variations in the 3.40 micrometers to 3.29 micrometers band intensity ratios are consistent with the photochemical erosion of alkylated PAHs. We conclude that the 3.40 micrometers emission feature is attributable to -CH3 side groups on PAH molecules. We predict a value of 0.5 for the peak intensity ratio of the 3.40 and 3.29 micrometers emission bands from free PAHs in the diffuse interstellar medium, which would correspond to a proportion of one methyl group for four peripheral hydrogens. We also compare the 3 micrometers spectrum of the proto-planetary nebula IRAS 05341+0852 with the spectrum of the planetary nebula IRAS 21282+5050. We suggest that a photochemical evolution of the initial aliphatic and aromatic hydrocarbon mixture formed in the outflow is responsible for the changes observed in the 3 micrometers emission spectra of these objects.

  3. Sub-band gap photo-enhanced secondary electron emission from high-purity single-crystal chemical-vapor-deposited diamond

    SciTech Connect

    Yater, J. E. Shaw, J. L.; Pate, B. B.; Feygelson, T. I.

    2016-02-07

    Secondary-electron-emission (SEE) current measured from high-purity, single-crystal (100) chemical-vapor-deposited diamond is found to increase when sub-band gap (3.06 eV) photons are incident on the hydrogenated surface. Although the light does not produce photoemission directly, the SEE current increases by more than a factor of 2 before saturating with increasing laser power. In energy distribution curves (EDCs), the emission peak shows a corresponding increase in intensity with increasing laser power. However, the emission-onset energy in the EDCs remains constant, indicating that the bands are pinned at the surface. On the other hand, changes are observed on the high-energy side of the distribution as the laser power increases, with a well-defined shoulder becoming more pronounced. From an analysis of this feature in the EDCs, it is deduced that upward band bending is present in the near-surface region during the SEE measurements and this band bending suppresses the SEE yield. However, sub-band gap photon illumination reduces the band bending and thereby increases the SEE current. Because the bands are pinned at the surface, we conclude that the changes in the band levels occur below the surface in the electron transport region. Sample heating produces similar effects as observed with sub-band gap photon illumination, namely, an increase in SEE current and a reduction in band bending. However, the upward band bending is not fully removed by either increasing laser power or temperature, and a minimum band bending of ∼0.8 eV is established in both cases. The sub-band gap photo-excitation mechanism is under further investigation, although it appears likely at present that defect or gap states play a role in the photo-enhanced SEE process. In the meantime, the study demonstrates the ability of visible light to modify the electronic properties of diamond and enhance the emission capabilities, which may have potential impact for diamond-based vacuum electron

  4. Narrow band wave emissions and noise around the plasma frequency in the solar wind

    NASA Astrophysics Data System (ADS)

    Chugunov, Yu. V.; Hayosh, M.; Fiala, V.; Soucek, J.; Santolik, O.; Pickett, J.

    2007-08-01

    The wave data obtained with a wide band instrument were recently used for interpretation of both quasi-thermal noise spectra and narrow band signals observed in the near vicinity of the local plasma frequency on CLUSTER II spacecraft in the solar wind, well upstream of the Earth's bow shock [1, 2] This approach is planned to continue with the large Cluster database and will be of use for other space missions such as Stereo and Solar Orbiter. If available, multi-component and/or multi-point measurements are expected to provide even greater insight in the generation of radio waves in the heliosphere in this frequency range. Our approach is based on a novel study of performance of receiving antennas in resonance regions in a streaming plasma. As far as noise spectra is concerned two distinctive features appear: a cutoff shifted down below the plasma frequency by a factor proportional to the ratio of stream velocity to the electron thermal velocity squared. The spectral maximum depends on the orientation of the antenna axis with respect to the stream velocity; it is shifted above the plasma frequency according to the antenna orientation, which is changing with the spacecraft spin. When the time resolution of the instrument is sufficient, it is possible to follow these changes. The overall form of the spectrum depends on the plasma distribution function, but even with a simplified model of two electron populations with largely different temperatures the estimates of the drift velocity and/or the temperature of the hot component can be obtained. In the case of a quasi-harmonic wave (narrow band signal) incident on the antenna, it is the antenna's effective length that allows for conversion of the open circuit voltage induced on its terminals to the electric field of the incoming wave. We show that this effective length grows by more than an order of magnitude under resonance conditions. This was already confirmed for waves propagating close to the lower oblique resonance

  5. Dynamic measurement of reflectance/emissivity in mid-infrared band

    NASA Astrophysics Data System (ADS)

    Zhang, Tian-yu; Chen, Min-sun; Zhang, Xiang-yu; Jiang, Hou-man

    2016-11-01

    In order to measure the change of laser energy coupling coefficient with temperature in mid-infrared wave band, reflectance integrating sphere experiment system was designed and set up. 915nm CW laser was used to heat samples and the wavelength of probe laser is 3.8μm. Chopper and phase-locked amplifier were adopted in the system. Thermal imager was used to measure and record the temperature of samples during laser irradiation. The reflectance of steel and aluminum plates to 3.8μm was measured during 915nm laser irradiation. EDS analysis was done to investigate the change of elemental composition in the samples respectively. The experimental results show that, the results of reflectance and radiation temperature measured by this system are relatively accurate during laser irradiation. In the process of temperature rising from 300K to 785K, the color of 45# steel plates turns blue and black, while the color of aluminum alloy plates is basically unchanged. When temperature reaches about 700K, reflectance of 45# steel decreases obviously with the increase of temperature, while reflectance of aluminum is almost constant. The reflectance is probably determined by the oxide in the surface of samples which is consistent with the results of EDS analysis. Reflectance decreases with the increase of the content of oxygen in the surface. The reason of why the reflectance of aluminum is almost constant is that aluminum oxide is not generate massively under 750K.

  6. DAY-SIDE z'-BAND EMISSION AND ECCENTRICITY OF WASP-12b

    SciTech Connect

    Lopez-Morales, Mercedes; Rogers, Justin C.; Coughlin, Jeffrey L.; Sing, David K.; Burrows, Adam; Spiegel, David S.; Apai, Daniel; Adams, Elisabeth R.

    2010-06-10

    We report the detection of the eclipse of the very hot Jupiter WASP-12b via z'-band time-series photometry obtained with the 3.5 m Astrophysical Research Consortium telescope at Apache Point Observatory. We measure a decrease in flux of 0.082% {+-} 0.015% during the passage of the planet behind the star. That planetary flux is equally well reproduced by atmospheric models with and without extra absorbers, and blackbody models with f {>=} 0.585 {+-} 0.080. It is therefore necessary to measure the planet at other wavelengths to further constrain its atmospheric properties. The eclipse appears centered at phase {phi} = 0.5100{sup +0.0072}{sub -0.0061}, consistent with an orbital eccentricity of |ecos {omega}| = 0.016{sup +0.011}{sub -0.009} (see note at the end of Section 4). If the orbit of the planet is indeed eccentric, the large radius of WASP-12b can be explained by tidal heating.

  7. A Balloon-borne Limb-Emission Sounder at 650-GHz band for Stratospheric observations

    NASA Astrophysics Data System (ADS)

    Irimajiri, Yoshihisa; Ochiai, Satoshi

    We have developed a Balloon-borne Superconducting Submillimeter-Wave Limb-Emission Sounder (BSMILES) to observe stratospheric minor constituents like ozone, HCl etc. BSMILES carries a 300mm-diameter offset parabolic antenna, a 650-GHz heterodyne superconducting (SIS) low-noise receiver, and an acousto-optical spectrometer (AOS) with the bandwidth of 1GHz and the resolution of 1MHz. Gondola size is 1.35 m x 1.35 m x 1.26 m. Total weight is about 500 kg. Limb observations are made by scanning the antenna beam of about 0.12 degrees (FWHM) in vertical direction. A calibrated hot load (CHL) and elevation angle of 50 degrees are ob-served after each scan for calibration. The DSB system noise temperature of the SIS receiver is less than 460 K at 624-639 GHz with a best value of 330 K that is 11 times as large as the quantum limit. Data acquisition and antenna control are made by on-board PCs. Observed data are recorded to PC card with 2 GB capacity to collect after the observations from the sea, and HK data are transmitted to the ground. Gondola attitude is measured by three-axis fiber-optical gyroscope with accuracy less than 0.01 degrees, three-axis accelerometer, and a two-axis geoaspect sensor. Electric power is supplied by lithium batteries. Total power con-sumption is about 150W. Almost all systems are put in pressurized vessels for waterproofing, heat dissipation, and noise shield, etc. BSMILES was launched from Sanriku Balloon Center of Institute of Space and Astronautical Science (ISAS), Japan Aerospace Exploration Agency (JAXA), at the east coast of Japan, in the summer of 2003, 2004, and 2006. The gondola was carried to an altitude of 35 km by a balloon of 100,000 m3 in volume and the observations were made for 1.5 hours in 2004. All systems operated normally by keeping their temperature within the limit of operation by keeping gondola warm with styrene foam. After the observations, the gondola was dropped and splashed on the Pacific Ocean by a parachute and

  8. Controllable time dependent and dual band emission infrared source to test missile warning systems in flight

    NASA Astrophysics Data System (ADS)

    Cabib, Dario; Davidzon, Larry; Gil, Amir

    2008-10-01

    Proliferation and technological progress of Mid Wave Infrared (MWIR) sensors for Missile Warning Systems (MWS)1,2 and increased sophistication of countermeasures require demanding in-flight testing. The IR sensors are becoming more sensitive for longer range of detection, the spatial resolution is improving for better target detection and identification, spectral discrimination is being introduced for lower False Alarm Rate (FAR), and the imaging frame rate is increasing for faster defensive reaction. As a result, testing a complex MWS/countermeasure system performance before deployment requires ever more realistic simulation of the threats in their natural backgrounds, and faster measurement of the radiometric output, directionality and time response of the countermeasures. In a previous paper3 we have described a system (IRTS or Infrared Threat Stimulator) we developed to test missile warning systems (MWS) mounted on an aircraft. The IRTS is placed in the field and projects a time dependent infrared beam toward the flying aircraft. The time dependent intensity of the beam simulates the infrared emittance of an approaching missile in the 3 to 5 micron spectral range as sensed by an MWS system. Now we have developed a new system based on the IRTS concept allowing the user to separately control the time profiles of two different infrared ranges independently within the 3 to 5 micron range. This is important because MWS instrumentation now has higher spectral discrimination capability in order to be more missile-specific and less prone to be confused by clutter and background signals. In this paper we describe the new dual band IRTS system and its capability (or Dual Color IRTS, DCIRTS).

  9. Band-tunable color cone lasing emission based on dye-doped cholesteric liquid crystals with various pitches and a pitch gradient.

    PubMed

    Lee, C-R; Lin, S-H; Yeh, H-C; Ji, T-D

    2009-12-07

    This study elucidates, for the first time, a novel band-tunable color cone lasing emission (CCLE) based on dye-doped cholesteric liquid crystal (DDCLC) films with various pitches. For several CLC cells with different pitches it was shown experimentally that the lasing band on the CCLE can be tuned among various color regions measured within different angular ranges. Some important features of the tunable CCLE are also identified and discussed. A spatially band-tunable color cone laser, based on a single DDCLC with a gradient pitch, is developed as a real application.

  10. How Do The EV Project Participants Feel About Their EVS?

    SciTech Connect

    Francfort, James E.

    2015-02-01

    The EV Project is an infrastructure study that enrolled over 8,000 residential participants. These participants purchased or leased a Nissan Leaf battery electric vehicle (BEV) or Chevrolet Volt extended range electric vehicle (EREV) and were among the first to explore this new electric drive technology. Collectively, BEV, EREV, and plug-in hybrid electric vehicles (PHEVs) are called plug-in electric vehicles (PEVs). The EV Project participants were very cooperative and enthusiastic about their participation in the project and very supportive in providing feedback and information. The information and attitudes of these participants concerning their experience with their PEVs were solicited using a survey in June 2013. At that time, some had up to 3 years of experience with their PEVs.

  11. A Fluorescent Indicator for Imaging Lysosomal Zinc(II) with Förster Resonance Energy Transfer (FRET)-Enhanced Photostability and a Narrow Band of Emission

    PubMed Central

    Sreenath, Kesavapillai; Yuan, Zhao; Allen, John R.

    2015-01-01

    We demonstrate a strategy to transfer the zinc(II) sensitivity of a fluoroionophore with low photostability and a broad emission band to a bright and photostable fluorophore with a narrow emission band. The two fluorophores are covalently connected to afford an intramolecular Förster resonance energy transfer (FRET) conjugate. The FRET donor in the conjugate is a zinc(II)-sensitive arylvinylbipyridyl fluoroionophore, the absorption and emission of which undergo bathochromic shifts upon zinc(II) coordination. When the FRET donor is excited, efficient intramolecular energy transfer occurs to result in the emission of the acceptor boron dipyrromethene (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene or BODIPY) as a function of zinc(II) concentration. The broad emission band of the donor/zinc(II) complex is transformed into the strong, narrow emission band of the BODIPY acceptor in the FRET conjugates, which can be captured within the narrow emission window that is preferred for multicolor imaging experiments. In addition to competing with other nonradiative decay processes of the FRET donor, the rapid intramolecular FRET of the excited FRET-conjugate molecule protects the donor fluorophore from photobleaching, thus enhancing the photostability of the indicator. FRET conjugates 3 and 4 contain aliphatic amino groups, which selectively target lysosomes in mammalian cells. This subcellular localization preference was verified by using confocal fluorescence microscopy, which also shows the zinc(II)-enhanced emission of 3 and 4 in lysosomes. It was further shown using two-color structured illumination microscopy (SIM), which is capable of extending the lateral resolution over the Abbe diffraction limit by a factor of two, that the morpholino-functionalized compound 4 localizes in the interior of lysosomes, rather than anchoring on the lysosomal membranes, of live HeLa cells. PMID:25382395

  12. Ocean Surface Emissivity at L-band (1.4 GHz): The Dependence on Salinity and Roughness

    NASA Astrophysics Data System (ADS)

    Le Vine, D. M.; Lang, R. H.; Wentz, F. J.; Meissner, T.

    2012-12-01

    A characterization of the emissivity of sea water at L-band is important for the remote sensing of sea surface salinity. Measurements of salinity are currently being made in the radio astronomy band at 1.413 GHz by ESA's Soil Moisture and Ocean Salinity (SMOS) mission and NASA's Aquarius instrument aboard the Aquarius/SAC-D observatory. The goal of both missions is accuracy on the order of 0.2 psu. This requires accurate knowledge of the dielectric constant of sea water as a function of salinity and temperature and also the effect of waves (roughness). The former determines the emissivity of an ideal (i.e. flat) surface and the later is the major source of error from predictions based on a flat surface. These two aspects of the problem of characterizing the emissivity are being addressed in the context of the Aquarius mission. First, laboratory measurements are being made of the dielectric constant of sea water. This is being done at the George Washington University using a resonant cavity. In this technique, sea water of known salinity and temperature is fed into the cavity along its axis through a narrow tube. The sea water changes the resonant frequency and Q of the cavity which, if the sample is small enough, can be related to the dielectric constant of the sample. An extensive set of measurements have been conducted at 1.413 GHz to develop a model for the real and imaginary part of the dielectric constant as a function of salinity and temperature. The results are compared to the predictions of models based on parameterization of the Debye resonance of the water molecule. The models and measurements are close; however, the differences are significant for remote sensing of salinity. This is especially true at low temperatures where the sensitivity to salinity is lowest. Second, observations from Aquarius are being used to develop a model for the effect of wind-driven roughness (waves) on the emissivity in the open ocean. This is done by comparing the measured

  13. OBSERVATIONS OF THE NEAR- TO MID-INFRARED UNIDENTIFIED EMISSION BANDS IN THE INTERSTELLAR MEDIUM OF THE LARGE MAGELLANIC CLOUD

    SciTech Connect

    Mori, Tamami I.; Sakon, Itsuki; Onaka, Takashi; Ohsawa, Ryou; Kaneda, Hidehiro; Umehata, Hideki E-mail: isakon@astron.s.u-tokyo.ac.jp

    2012-01-01

    We present the results of near- to mid-infrared slit spectroscopic observations (2.55-13.4 {mu}m) of the diffuse emission toward nine positions in the Large Magellanic Cloud with the infrared camera on board AKARI. The target positions are selected to cover a wide range of the intensity of the incident radiation field. The unidentified infrared bands at 3.3, 6.2, 7.7, 8.6, and 11.3 {mu}m are detected toward all the targets and ionized gas signatures; hydrogen recombination lines and ionic forbidden lines are detected toward three of them. We classify the targets into two groups: those without the ionized gas signatures (Group A) and those with the ionized signatures (Group B). Group A includes molecular clouds and photodissociation regions, whereas Group B consists of H II regions. In Group A, the band ratios of I{sub 3.3{mu}m}/I{sub 11.3{mu}m}, I{sub 6.2{mu}m}/I{sub 11.3{mu}m}, I{sub 7.7{mu}m}/I{sub 11.3{mu}m}, and I{sub 8.6{mu}m}/I{sub 11.3{mu}m} show positive correlation with the IRAS and AKARI colors, but those of Group B do not follow the correlation. We discuss the results in terms of the polycyclic aromatic hydrocarbon (PAH) model and attribute the difference to the destruction of small PAHs and an increase in the recombination due to the high electron density in Group B. In the present study, the 3.3 {mu}m band provides crucial information on the size distribution and/or the excitation conditions of PAHs and plays a key role in the distinction of Group A from B. The results suggest the possibility of the diagram of I{sub 3.3{mu}m}/I{sub 11.3{mu}m} versus I{sub 7.7{mu}m}/I{sub 11.3{mu}m} as an efficient diagnostic tool to infer the physical conditions of the interstellar medium.

  14. Making Waves—The VIIRS Day/Night Band Reveals Upper Atmospheric Gravity Wave via Sensitivity to Nightglow Emissions

    NASA Astrophysics Data System (ADS)

    Miller, S. D.; Straka, W. C.; Yue, J.; Smith, S. M.; Alexander, M. J.; Hoffmann, L.; Setvak, M.; Partain, P.

    2015-12-01

    Atmospheric gravity waves, which are disturbances to the atmospheric density structure with restoring forces of gravity and buoyancy, represent the principal form of energy exchange between the lower and upper atmosphere. Wave breaking drives the mean upper-atmospheric circulation, driving coupled processes that in turn influence weather and climate patterns throughout the atmosphere on various spatial and temporal scales. Very little is known about upper-level gravity wave characteristics, mainly for lack of global, high-resolution observations from satellite observing systems. Consequently, representations of wave-related processes in global models at present are crude, highly parameterized, and poorly constrained. Shortly after launch of the NOAA/NASA Suomi National Polar-orbiting Partnership environmental satellite instrument, it was discovered that its Visible/Infrared Imaging Radiomter Suite (VIIRS) Day/Night Band (DNB) was able to observe clouds on moonless nights using the reflection of downwelling nightglow—light emitted from a geometrically thin and tenuous emission layer residing near the mesopause (~85-95 km AMSL). Following this revelation, it was discovered that the DNB also held the further ability to resolve gravity structures within the nightglow direct emissions. On moonless nights, the DNB provides all-weather viewing of these waves at unprecedented 0.74 km horizontal resolution as they modulate the temperature and density structure (and hence brightness) of the nightglow layer. The waves are launched by a variety of physical mechanisms, ranging from terrain, to convective storms, to jet streams and strong wind shear, and even seismic and volcanic events. We cross-reference DNB imagery with thermal infrared imagery to discern nightglow wave structures and attribute their sources. The capability stands to advance our basic understanding of a critical yet poorly constrained driver of the general atmospheric circulation.

  15. Recognizing the blue emission in artificial aurora

    NASA Astrophysics Data System (ADS)

    Holma, H.; Kaila, K. U.; Kosch, M. J.; Rietveld, M. T.

    2006-01-01

    On 12th November 2001, during an EISCAT UK/GE artificial aurora campaign, the optical group from the University of Oulu performed optical measurements at the EISCAT site in Ramfjordmoen, including the first measurement of blue emissions in artificial aurora at high latitudes. Optical instruments, including a photometer, a real speed TV camera and a digital camera, were monitoring the emissions. The emissions that the photometer was designed to measure were 557.7 nm (OI), 630.0 nm (OI) and 427.8 nm (N2+). The energy thresholds of these emissions are approximately 2, 4 and 19 eV, respectively. In the natural aurora the blue emission at around 427.8 nm is always dominated by the N2+ 1NG(0, 1) band. However, there are two weak emission bands lying under this strong emission, namely, the N2 VK(4, 15) (threshold energy 6 eV) and N2 2P(1, 5) (threshold 11 eV). These excitation energies are lower than the energy needed to excite N2+ 1NG(0, 1) level and therefore could have a stronger intensity compared with N2+ 1NG(0, 1) in the spectrum of artificial aurora than in natural aurora. The auroral photometer of the University of Oulu has been designed for investigating natural aurora. The photometer was equipped with two channels measuring different wavelength bands around 427.8 nm. These channels were intended to be used to determine rotational temperature from the ratio of the intensities through the channels. However, here we estimate the intensities of the three overlapping emission bands instead.

  16. Optically band-tunable color cone lasing emission in a dye-doped cholesteric liquid crystal with a photoisomerizable chiral dopant

    NASA Astrophysics Data System (ADS)

    Lee, C.-R.; Lin, S.-H.; Ku, H.-S.; Liu, J.-H.; Yang, P.-C.; Huang, C.-Y.; Yeh, H.-C.; Ji, T.-D.

    2010-03-01

    This work demonstrates the feasibility of an optically band-tunable color cone lasing emission (CCLE) based on a dye-doped cholesteric liquid crystal with a photoisomerizable chiral dopant. Experimental results indicate that the lasing band of the formed CCLE can be tuned optically among various color regions by adjusting the UV irradiated fluence. The optical band tunability of the laser is attributed to the presence of two chiral agents with twisting powers of opposite signs in the cell and the UV-irradiation-induced decrease of the right-handed twisting power of the photoisomerizable chiral dopant via trans →cis isomerization, subsequently inducing the other chiral agent to reduce the structural pitch of the cell. Total tunable wavelength range of the laser exceeds 100 nm. Moreover, the band-tunable laser exhibits a high spectral stability under illumination of a visible light or thermal treatment.

  17. First detection of Mars atmospheric hydroxyl: CRISM Near-IR measurement versus LMD GCM simulation of OH Meinel band emission in the Mars polar winter atmosphere

    NASA Astrophysics Data System (ADS)

    Clancy, R. Todd; Sandor, Brad J.; García-Muñoz, Antonio; Lefèvre, Franck; Smith, Michael D.; Wolff, Michael J.; Montmessin, Franck; Murchie, Scott L.; Nair, Hari

    2013-09-01

    Visible and near-IR Meinel band emissions originate from excited OH in the terrestrial upper atmosphere (Meinel, I.A.B. [1950]. Astrophys. J. 111, 555. http://dx.doi.org/10.1086/145296), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29-L33. http://dx.doi.org/10.1051/0004-6361:200809761). Meinel band observations support key studies of transport and photochemistry in both of these atmospheres. In the case of Mars, OH regulates the basic stability of the CO2 atmosphere to photolytic decomposition (to CO and O2, e.g. Parkinson, T.D., Hunten, D.M. [1972]. J. Atmos. Sci. 29, 1380-1390. http://dx.doi.org/10.1175/1520-0469(1972)029<1380:SAAOOO>2.0.CO;2), and yet has never been measured. We present the first detection of Mars atmospheric OH, associated with CRISM near-IR spectral limb observations of polar night Meinel band emissions centered at 1.45 and 2.9 μm. Meinel band (1-0), (2-1), and (2-0) average limb intensities of 990 ± 280, 1060 ± 480, and 200 ± 100 kiloRayleighs (kR), respectively, are determined for 70-90 NS polar winter latitudes over altitudes of 40-56 km. Additional OH bands, such as (3-2), (3-1), and (4-2), present ⩽1σ measurements. Uncertainty in the (4-2) band emission rate contributes to increased uncertainty in the determination of the O2(1Δg) (0-0)/(0-1) band emission ratio A00/A01=47-12+26. An average profile retrieval for Mars OH polar nightglow indicates 45-55 km altitude levels for volume emission rates (VER) of 0.4 (2-0) to 2 (1-0, 2-1) × 104 photons/(cm3 s). Similar to polar night O2(1Δg) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. http://dx.doi.org/10.1029/2011JE004018), Meinel OH band emission is supported by upper level, winter poleward transport of O and H in the deep Hadley solsticial circulations of Mars. The retrieved OH emission rates are compared to polar winter OH nightglow simulated by the LMD (Laboratoire

  18. First detection of Mars atmospheric hydroxyl: CRISM Near-IR measurement versus LMD GCM simulation of OH Meinel band emission in the Mars polar winter atmosphere

    NASA Astrophysics Data System (ADS)

    Todd Clancy, R.; Sandor, Brad J.; García-Muñoz, Antonio; Lefèvre, Franck; Smith, Michael D.; Wolff, Michael J.; Montmessin, Franck; Murchie, Scott L.; Nair, Hari

    2013-09-01

    Visible and near-IR Meinel band emissions originate from excited OH in the terrestrial upper atmosphere (Meinel, I.A.B. [1950]. Astrophys. J. 111, 555. http://dx.doi.org/10.1086/145296), and have recently been detected in the Venus nightside upper mesosphere (Piccioni, G. et al. [2008]. Astron. Astrophys. 483, L29-L33. http://dx.doi.org/10.1051/0004-6361:200809761). Meinel band observations support key studies of transport and photochemistry in both of these atmospheres. In the case of Mars, OH regulates the basic stability of the CO2 atmosphere to photolytic decomposition (to CO and O2, e.g. Parkinson, T.D., Hunten, D.M. [1972]. J. Atmos. Sci. 29, 1380-1390. http://dx.doi.org/10.1175/1520-0469(1972)029<1380:SAAOOO>2.0.CO;2), and yet has never been measured. We present the first detection of Mars atmospheric OH, associated with CRISM near-IR spectral limb observations of polar night Meinel band emissions centered at 1.45 and 2.9 μm. Meinel band (1-0), (2-1), and (2-0) average limb intensities of 990 ± 280, 1060 ± 480, and 200 ± 100 kiloRayleighs (kR), respectively, are determined for 70-90 NS polar winter latitudes over altitudes of 40-56 km. Additional OH bands, such as (3-2), (3-1), and (4-2), present ⩽1σ measurements. Uncertainty in the (4-2) band emission rate contributes to increased uncertainty in the determination of the O2(1Δg) (0-0)/(0-1) band emission ratio A00/A01=47-12+26. An average profile retrieval for Mars OH polar nightglow indicates 45-55 km altitude levels for volume emission rates (VER) of 0.4 (2-0) to 2 (1-0, 2-1) × 104 photons/(cm3 s). Similar to polar night O2(1Δg) emission (e.g. Clancy, R.T. et al. [2012]. J. Geophys. Res. (Planets) 117, E00J10. http://dx.doi.org/10.1029/2011JE004018), Meinel OH band emission is supported by upper level, winter poleward transport of O and H in the deep Hadley solsticial circulations of Mars. The retrieved OH emission rates are compared to polar winter OH nightglow simulated by the LMD (Laboratoire

  19. Band gap and defect states of MgO thin films investigated using reflection electron energy loss spectroscopy

    SciTech Connect

    Heo, Sung; Cho, Eunseog; Lee, Hyung-Ik; Park, Gyeong Su; Kang, Hee Jae; Nagatomi, T.; Choi, Pyungho; Choi, Byoung-Deog

    2015-07-15

    The band gap and defect states of MgO thin films were investigated by using reflection electron energy loss spectroscopy (REELS) and high-energy resolution REELS (HR-REELS). HR-REELS with a primary electron energy of 0.3 keV revealed that the surface F center (FS) energy was located at approximately 4.2 eV above the valence band maximum (VBM) and the surface band gap width (E{sub g}{sup S}) was approximately 6.3 eV. The bulk F center (F{sub B}) energy was located approximately 4.9 eV above the VBM and the bulk band gap width was about 7.8 eV, when measured by REELS with 3 keV primary electrons. From a first-principles calculation, we confirmed that the 4.2 eV and 4.9 eV peaks were F{sub S} and F{sub B}, induced by oxygen vacancies. We also experimentally demonstrated that the HR-REELS peak height increases with increasing number of oxygen vacancies. Finally, we calculated the secondary electron emission yields (γ) for various noble gases. He and Ne were not influenced by the defect states owing to their higher ionization energies, but Ar, Kr, and Xe exhibited a stronger dependence on the defect states owing to their small ionization energies.

  20. The emission and scattering of L-band microwave radiation from rough ocean surfaces and wind speed measurements from the Aquarius sensor

    NASA Astrophysics Data System (ADS)

    Meissner, Thomas; Wentz, Frank J.; Ricciardulli, Lucrezia

    2014-09-01

    In order to achieve the required accuracy in sea surface salinity (SSS) measurements from L-band radiometers such as the Aquarius/SAC-D or SMOS (Soil Moisture and Ocean Salinity) mission, it is crucial to accurately correct the radiation that is emitted from the ocean surface for roughness effects. We derive a geophysical model function (GMF) for the emission and backscatter of L-band microwave radiation from rough ocean surfaces. The analysis is based on radiometer brightness temperature and scatterometer backscatter observations both taken on board Aquarius. The data are temporally and spatially collocated with wind speeds from WindSat and F17 SSMIS (Special Sensor Microwave Imager Sounder) and wind directions from NCEP (National Center for Environmental Prediction) GDAS (Global Data Assimilation System). This GMF is the basis for retrieval of ocean surface wind speed combining L-band H-pol radiometer and HH-pol scatterometer observations. The accuracy of theses combined passive/active L-band wind speeds matches those of many other satellite microwave sensors. The L-band GMF together with the combined passive/active L-band wind speeds is utilized in the Aquarius SSS retrieval algorithm for the surface roughness correction. We demonstrate that using these L-band wind speeds instead of NCEP wind speeds leads to a significant improvement in the SSS accuracy. Further improvements in the roughness correction algorithm can be obtained by adding VV-pol scatterometer measurements and wave height (WH) data into the GMF.

  1. Near band-gap electronics properties and luminescence mechanisms of boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Museur, L.; Kanaev, A.

    2015-08-01

    The deep ultraviolet luminescence (hν ≥ 5 eV) of multiwall boron nitride nanotubes (BNNTs) is studied with time- and energy-resolved photoluminescence spectroscopy. Two luminescence bands are observed at 5.35 and 5.54 eV. Both emissions undergo a large blue shift of several tens of meV with a linear slope Δ E l u m / Δ E e x c < 1 as the excitation energy Eexc increases. When E e x c ≥ 5.8 eV, the spectral band positions become fixed, which marks the transition between the excitation of donor-acceptor pairs and creation of free charge carriers. We assign the 5.35 eV band to quasi donor-acceptor pair transitions and the band at 5.54 eV to free-bound transitions. Boron and nitrogen atoms distributed along characteristic defect lines in BNNTs should be involved in the luminescence process. The presented results permit a revision of previous assignments of electronic transitions in BNNTs.

  2. A 1.1-1.9 GHz SETI SURVEY OF THE KEPLER FIELD. I. A SEARCH FOR NARROW-BAND EMISSION FROM SELECT TARGETS

    SciTech Connect

    Siemion, Andrew P. V.; Korpela, Eric; Werthimer, Dan; Cobb, Jeff; Lebofsky, Matt; Marcy, Geoffrey W.; Demorest, Paul; Maddalena, Ron J.; Langston, Glen; Howard, Andrew W.; Tarter, Jill

    2013-04-10

    We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T{sub eq} > 230 K, stars with five or more detected candidates or stars with a super-Earth (R{sub p} < 3 R{sub Circled-Plus }) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than {approx}1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of {approx}1.5 Multiplication-Sign 10{sup 21} erg s{sup -1}, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be <10{sup -6} M{sub Sun }{sup -1}. Here we describe our observations, data reduction procedures and results.

  3. A 1.1-1.9 GHz SETI Survey of the Kepler Field. I. A Search for Narrow-band Emission from Select Targets

    NASA Astrophysics Data System (ADS)

    Siemion, Andrew P. V.; Demorest, Paul; Korpela, Eric; Maddalena, Ron J.; Werthimer, Dan; Cobb, Jeff; Howard, Andrew W.; Langston, Glen; Lebofsky, Matt; Marcy, Geoffrey W.; Tarter, Jill

    2013-04-01

    We present a targeted search for narrow-band (<5 Hz) drifting sinusoidal radio emission from 86 stars in the Kepler field hosting confirmed or candidate exoplanets. Radio emission less than 5 Hz in spectral extent is currently known to only arise from artificial sources. The stars searched were chosen based on the properties of their putative exoplanets, including stars hosting candidates with 380 K > T eq > 230 K, stars with five or more detected candidates or stars with a super-Earth (R p < 3 R ⊕) in a >50 day orbit. Baseband voltage data across the entire band between 1.1 and 1.9 GHz were recorded at the Robert C. Byrd Green Bank Telescope between 2011 February and April and subsequently searched offline. No signals of extraterrestrial origin were found. We estimate that fewer than ~1% of transiting exoplanet systems host technological civilizations that are radio loud in narrow-band emission between 1 and 2 GHz at an equivalent isotropically radiated power (EIRP) of ~1.5 × 1021 erg s-1, approximately eight times the peak EIRP of the Arecibo Planetary Radar, and we limit the number of 1-2 GHz narrow-band-radio-loud Kardashev type II civilizations in the Milky Way to be {<}10^{-6}\\ M^{-1}_\\odot. Here we describe our observations, data reduction procedures and results.

  4. Overcoming the high cost of EV batteries

    SciTech Connect

    Wright, S.R.

    1995-07-01

    Electric Vehicles (EV`s) are a solution to three major problems facing the US today. The commercialization of EV`s will reduce the growing trade deficit, provide economic gains from a new electric automobile industry, and help alleviate the air pollution problems encountered in many of America`s largest cities. The existence of EV`s is not the answer; their increasing use is. This increase in deployment will largely depend on vehicle price and not range limitations as many would have you believe. The price of an EV will be determined by the auto makers with their economics determining the ultimate price to the consumer. The cost of EV batteries is considered to be a major hurdle in achieving an affordable EV. Prices of EV batteries at this time cannot be controlled by the auto manufacturers. How high is this cost hurdle and what measures can be taken to reduce this obstacle and facilitate the successful commercialization of EV`s? This paper discusses a variety of alternatives. Each sector of industry may favor a particular solution, but, in order for the EV industry to thrive, all sectors must agree to work together to provide for customer needs.

  5. Valence Band Density of States of Cu3Si Studied by Soft X-Ray Emission Spectroscopy and a First-Principle Molecular Orbital Calculation

    NASA Astrophysics Data System (ADS)

    An, Zhenlian; Kamezawa, Chihiro; Hirai, Masaaki; Kusaka, Masahiko; Iwami, Motohiro

    2002-12-01

    A systematic study of the valence band structure of Cu3Si has been performed by soft X-ray emission spectroscopy and a first-principle molecular orbital calculation using the discrete-variational (DV)-Xα cluster model. The existence of Cu 4s, 4p states in the valence band and their important contributions to the valence band as that of Cu 3d are indicated together with previously reported ones. The high-binding energy peak in the Si L2,3 emission spectrum is considered to originate mainly from the Si-Si 3s bonding state but also have a certain contribution of Si 3s bonding state with Cu 4s, 4p. On the other hand, the low-binding energy peaks in the Si L2,3 emission band are attributed to both the antibonding states of Si 3s and the bonding states of Si 3d with Cu 4s, 4p and Cu 3d. The bonding states of Si 3s with Cu 4s, 4p and Cu 3d are expected to exist in the lower part of the valence band for η\\prime-Cu3Si on the basis of the theoretical calculations. As for Si p states, the high-binding energy peak and the low-binding energy peak in the Si Kβ emission spectrum should be attributed to the Si 3p bonding state and antibonding state with Cu 3d and Cu 4s, 4p, respectively, according to the theoretical calculations. A comparison is made between experimental spectra and theoretical density of states.

  6. Spectroscopic study of emission coal mineral plasma produced by laser ablation

    NASA Astrophysics Data System (ADS)

    Vera, L. P.; Pérez, J. A.; Riascos, H.

    2014-05-01

    Spectroscopic analysis of plasma produced by laser ablation of coal samples using 1064 nm radiation pulses from a Q-switched Nd:YAG on different target under air ambient, was performed. The emission of molecular band systems such as C2 Swan System (d3Πg→a3Πu), the First Negative System N2 (Band head at 501,53 nm) and emission lines of the C I, C II, were investigated using the optical emission spectroscopy technique. The C2 molecular spectra (Swan band) were analyzed to determine vibrational temperature (0,62 eV); the density and electron temperature of the plasma have been evaluated using Stark broadening and the intensity of the nitrogen emission lines N II, the found values of 1,2 eV and 2,2 x1018 cm-3 respectively.

  7. Prediction of CO Cameron band and atomic oxygen visible emissions in comets C/2013 A1 (Siding Spring) and 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Raghuram, S.; Bhardwaj, A.

    2014-04-01

    The forbidden emissions of cometary species have special importance in the cometary spectra. The excited species which produce these forbidden emissions can not be populated by direct solar radiation excitation. These metastable species are produced mainly from dissociative excitation and ion-electron recombination reactions. Thus the observed emissions have been used as tracers of parent cometary species. The CO (a3 -X1) is a forbidden transition which produces Cameron band emission in the ultraviolet region during dissociative excitation of CObearing neutrals and the dissociative recombination of CO-ionic species in the cometary coma. Similarly, the forbidden transitions of metastable atomic oxygen 1S-3P (green, 5577 Å), and 1D-3P (red-doublet, 6300 and 6364 Å) produce line emissions in the visible region. These emissions have been used to probe H2O and CO2 abundances in the comets. We have developed a coupled chemistry-emission model to study various production and loss mechanisms of these excited metastable states. The model is applied to comet C/2013 A1 (Siding Spring) which will have a close fly-by of Mars during mid October, 2014, when Indian Mars orbiter Mission and NASA's Maven, would be orbiting the planet. The model is also applied on ESA's Rosetta mission target comet 67P/Churyumov-Gerasimenko which will be useful for different observations over various heliocentric distances. The predicted intensities and quantitative analysis of these emissions can be a theoretical support for various space and ground-based observations.

  8. Telecommunication Wavelength-Band Single-Photon Emission from Single Large InAs Quantum Dots Nucleated on Low-Density Seed Quantum Dots.

    PubMed

    Chen, Ze-Sheng; Ma, Ben; Shang, Xiang-Jun; He, Yu; Zhang, Li-Chun; Ni, Hai-Qiao; Wang, Jin-Liang; Niu, Zhi-Chuan

    2016-12-01

    Single-photon emission in the telecommunication wavelength band is realized with self-assembled strain-coupled bilayer InAs quantum dots (QDs) embedded in a planar microcavity on GaAs substrate. Low-density large QDs in the upper layer active for ~1.3 μm emission are fabricated by precisely controlling the indium deposition amount and applying a gradient indium flux in both QD layers. Time-resolved photoluminescence (PL) intensity suggested that the radiative lifetime of their exciton emission is 1.5~1.6 ns. The second-order correlation function of g (2)(0) < 0.5 which demonstrates a pure single-photon emission.

  9. Ballistic-electron-emission spectroscopy of Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures: Conduction-band offsets, transport mechanisms, and band-structure effects

    SciTech Connect

    OShea, J.J.; Brazel, E.G.; Rubin, M.E.; Bhargava, S.; Chin, M.A.; Narayanamurti, V.

    1997-07-01

    We report an extensive investigation of semiconductor band-structure effects in single-barrier Al{sub x}Ga{sub 1{minus}x}As/GaAs heterostructures using ballistic-electron-emission spectroscopy (BEES). The transport mechanisms in these single-barrier structures were studied systematically as a function of temperature and Al composition over the full compositional range (0{le}x{le}1). The initial ({Gamma}) BEES thresholds for Al{sub x}Ga{sub 1{minus}x}As single barriers with 0{le}x{le}0.42 were extracted using a model which includes the complete transmission probability of the metal-semiconductor interface and the semiconductor heterostructure. Band offsets measured by BEES are in good agreement with previous measurements by other techniques which demonstrates the accuracy of this technique. BEES measurements at 77 K give the same band-offset values as at room temperature. When a reverse bias is applied to the heterostructures, the BEES thresholds shift to lower voltages in good agreement with the expected bias-induced band-bending. In the indirect band-gap regime ({ital x}{gt}0.45), spectra show a weak ballistic-electron-emission microscopy current contribution due to intervalley scattering through Al{sub x}Ga{sub 1{minus}x}As {ital X} valley states. Low-temperature spectra show a marked reduction in this intervalley current component, indicating that intervalley phonon scattering at the GaAs/Al{sub x}Ga{sub 1{minus}x}As interface produces a significant fraction of this{ital X} valley current. A comparison of the BEES thresholds with the expected composition dependence of the Al{sub x}Ga{sub 1{minus}x}As {Gamma}, {ital L}, and {ital X} points yields good agreement over the entire composition range. {copyright} {ital 1997} {ital The American Physical Society}

  10. Two dimensional expansion effects on angular distribution of 13.5 nm in-band extreme ultraviolet emission from laser-produced Sn plasma

    SciTech Connect

    Sequoia, K. L.; Tao, Y.; Yuspeh, S.; Burdt, R.; Tillack, M. S.

    2008-06-02

    The angular distribution of extreme ultraviolet emission at 13.5 nm within 2% bandwidth was characterized for laser irradiated, planar, Sn targets at prototypic conditions for a lithography system. We have found that two dimensional plasma expansion plays a key role in the distribution of in-band 13.5 nm emission under these conditions. The angular distribution was found to have two peaks at 45 deg. and 15 deg. This complex angular distribution arises from the shape of both the emitting plasma and the surrounding absorbing plasma. This research reveals that the detailed angular distribution can be important to the deduction of conversion efficiency.

  11. EV space suit gloves (passive)

    NASA Technical Reports Server (NTRS)

    Fletcher, E. G.; Dodson, J. D.; Elkins, W.; Tickner, E. G.

    1975-01-01

    A pair of pressure and thermal insulating overgloves to be used with an Extravehicular (EV) suit assembly was designed, developed, fabricated, and tested. The design features extensive use of Nomex felt materials in lieu of the multiple layer insulation formerly used with the Apollo thermal glove. The glove theoretically satisfies all of the thermal requirements. The presence of the thermal glove does not degrade pressure glove tactility by more than the acceptable 10% value. On the other hand, the thermal glove generally degrades pressure glove mobility by more than the acceptable 10% value, primarily in the area of the fingers. Life cycling tests were completed with minimal problems. The thermal glove/pressure glove ensemble was also tested for comfort; the test subjects found no problems with the thermal glove although they did report difficulties with pressure points on the pressure glove which were independent of the thermal glove.

  12. Interaction of wide band gap single crystals with 248 nm excimer laser radiation. XII. The emission of negative atomic ions from alkali halides

    SciTech Connect

    Kimura, Kenichi; Langford, S. C.; Dickinson, J. T.

    2007-12-01

    Many wide band gap materials yield charged and neutral emissions when exposed to sub-band-gap laser radiation at power densities below the threshold for optical breakdown and plume formation. In this work, we report the observation of negative alkali ions from several alkali halides under comparable conditions. We observe no evidence for negative halogen ions, in spite of the high electron affinities of the halogens. Significantly, the positive and negative alkali ions show a high degree of spatial and temporal overlap. A detailed study of all the relevant particle emissions from potassium chloride (KCl) suggests that K{sup -} is formed by the sequential attachment of two electrons to K{sup +}.

  13. Single Material Band Gap Engineering in GaAs Nanowires

    SciTech Connect

    Spirkoska, D.; Abstreiter, G.; Efros, A.; Conesa-Boj, S.; Morante, J. R.; Arbiol, J.; Fontcuberta i Morral, A.

    2011-12-23

    The structural and optical properties of GaAs nanowire with mixed zinc-blende/wurtzite structure are presented. High resolution transmission electron microscopy indicates the presence of a variety of shorter and longer segments of zinc-blende or wurtzite crystal phases. Sharp photoluminescence lines are observed with emission energies tuned from 1.515 eV down to 1.43 eV. The downward shift of the emission peaks can be understood by carrier confinement at the wurtzite/zinc-blende heterojunction, in quantum wells and in random short period superlattices existent in these nanowires, assuming the theoretical staggered band-offset between wurtzite and zinc-blende GaAs.

  14. [Effect of oxygen partial pressure on the band-gap of the TiO2 films prepared by DC reactive sputtering].

    PubMed

    Zhao, Qing-nan; Li, Chun-ling; Liu, Bao-shun; Zhao, Xiu-jian

    2004-05-01

    TiO2 films have been deposited on glass substrates using DC reactive magnetron sputtering at different oxygen partial pressures from 0.10 to 0.65 Pa. The photoluminescence (PL) spectra of the films were recorded. The results of the PL spectra showed that there were three emission peaks at 370, 472 and 514 nm for the films sputtered at 0.35 and 0.65 Pa, and there were two peaks at 370 and 490 nm for the films sputtered at 0.10 and 0.15 Pa. The band-gap for the films was 3.35 eV. For the films sputtered at 0.35 and 0.65 Pa there were two defect energy levels at 2.63 and 2.41 eV, corresponding to 0.72 and 0.94 eV below conduction band for the band-gap, respectively. For the films sputtered at 0.10 and 0.15 Pa, there was an energy band formed between 3.12 and 2.06 eV, corresponding to 0.23 and 1.29 eV below the conduction band. With increasing the oxygen partial pressure, the defect energy band changed to two energy levels, and the energy levels nearly disappeared for the film sputtered at 0.65 Pa of oxygen partial pressure.

  15. Electrostatic emissions between electron gyroharmonics in the outer magnetosphere

    NASA Technical Reports Server (NTRS)

    Hubbard, R. F.; Birmingham, T. J.

    1977-01-01

    A scheme was constructed and a theoretical model was developed to classify electrostatic emissions. All of the emissions appear to be generated by the same basic mechanism: an unstable electron plasma distribution consisting of cold electrons (less than 100 eV) and hot loss cone electrons (about 1 keV). Each emission class is associated with a particular range of model parameters; the wide band electric field data can thus be used to infer the density and temperature of the cold plasma component. The model predicts that gyroharmonic emissions near the plasma frequency require large cold plasma densities.

  16. Quantification of fluorine traces in solid samples using CaF molecular emission bands in atmospheric air Laser-Induced Breakdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Alvarez-Llamas, C.; Pisonero, J.; Bordel, N.

    2016-09-01

    Direct solid determination of trace amounts of fluorine using Laser-Induced Breakdown Spectroscopy (LIBS) is a challenging task due to the low excitation efficiency of this element. Several strategies have been developed to improve the detection capabilities, including the use of LIBS in a He atmosphere to enhance the signal to background ratios of F atomic emission lines. An alternative method is based on the detection of the molecular compounds that are formed with fluorine in the LIBS plasma. In this work, the detection of CaF molecular emission bands is investigated to improve the analytical capabilities of atmospheric air LIBS for the determination of fluorine traces in solid samples. In particular, Cu matrix samples containing different fluorine concentration (between 50 and 600 μg/g), and variable amounts of Ca, are used to demonstrate the linear relationships between CaF emission signal and F concentration. Limits of detection for fluorine are improved by more than 1 order of magnitude using CaF emission bands versus F atomic lines, in atmospheric-air LIBS. Furthermore, a toothpaste powder sample is used to validate this analytical method. Good agreement is observed between the nominal and the predicted fluorine mass-content.

  17. Optical spectroscopy of IRAS sources with infrared emission bands. II - IRAS 04324+5106, 06114+1745, 20319+3958, and 22539+5758

    NASA Technical Reports Server (NTRS)

    Cohen, Martin; Jones, B. F.; Walker, H. J.

    1989-01-01

    The paper presents long-slit optical spectra and microwave CO spectra of four nebulous counterparts to IRAS sources showing PAH emission features: 04324+5106, 06114+1745, 20319+3958, and 22539+5758. IRAS 22539+5758 is associated with a bipolar nebula. All are allied with B-type stars that suffer appreciable circumstellar extinction, and whose environs show atomic emission lines; three represent mixed reflection/emission nebulosities. Three show spectroscopic evidence for outflows at about 100 km/s. One, 06114+1745, exhibits indications of enhanced diffuse interstellar bands. It is concluded that extinction alone is insufficient to yield enhanced DIBs and that peculiar circumstellar abundances and/or physical conditions must play a role.

  18. Optical spectroscopy of IRAS sources with infrared emission bands. II. IRAS 04324+5106, 06114+1745, 20319+3958, and 22539+5758

    SciTech Connect

    Cohen, M.; Jones, B.F.; Walker, H.J.; Lick Observatory, Santa Cruz, CA; Search for Extraterrestrial Intelligence Institute, Los Altos, CA )

    1989-06-01

    The paper presents long-slit optical spectra and microwave CO spectra of four nebulous counterparts to IRAS sources showing PAH emission features: 04324+5106, 06114+1745, 20319+3958, and 22539+5758. IRAS 22539+5758 is associated with a bipolar nebula. All are allied with B-type stars that suffer appreciable circumstellar extinction, and whose environs show atomic emission lines; three represent mixed reflection/emission nebulosities. Three show spectroscopic evidence for outflows at about 100 km/s. One, 06114+1745, exhibits indications of enhanced diffuse interstellar bands. It is concluded that extinction alone is insufficient to yield enhanced DIBs and that peculiar circumstellar abundances and/or physical conditions must play a role. 20 refs.

  19. SPATIALLY RESOLVED M-BAND EMISSION FROM IO’S LOKI PATERA–FIZEAU IMAGING AT THE 22.8 m LBT

    SciTech Connect

    Conrad, Albert; Veillet, Christian; Kleer, Katherine de; Pater, Imke de; Leisenring, Jarron; Defrère, Denis; Hinz, Philip; Skemer, Andy; Camera, Andrea La; Bertero, Mario; Boccacci, Patrizia; Arcidiacono, Carmelo; Hofmann, Karl-Heinz; Schertl, Dieter; Weigelt, Gerd; Kürster, Martin; Rathbun, Julie; Skrutskie, Michael; Spencer, John; Woodward, Charles E.

    2015-05-15

    The Large Binocular Telescope Interferometer mid-infrared camera, LMIRcam, imaged Io on the night of 2013 December 24 UT and detected strong M-band (4.8 μm) thermal emission arising from Loki Patera. The 22.8 m baseline of the Large Binocular Telescope provides an angular resolution of ∼32 mas (∼100 km at Io) resolving the Loki Patera emission into two distinct maxima originating from different regions within Loki’s horseshoe lava lake. This observation is consistent with the presence of a high-temperature source observed in previous studies combined with an independent peak arising from cooling crust from recent resurfacing. The deconvolved images also reveal 15 other emission sites on the visible hemisphere of Io including two previously unidentified hot spots.

  20. Serological detection and analysis of anti-VP1 responses against various enteroviruses (EV) (EV-A, EV-B and EV-C) in Chinese individuals

    PubMed Central

    Gao, Caixia; Ding, Yingying; Zhou, Peng; Feng, Jiaojiao; Qian, Baohua; Lin, Ziyu; Wang, Lili; Wang, Jinhong; Zhao, Chunyan; Li, Xiangyu; Cao, Mingmei; Peng, Heng; Rui, Bing; Pan, Wei

    2016-01-01

    The overall serological prevalence of EV infections based on ELISA remains unknown. In the present study, the antibody responses against VP1 of the EV-A species (enterovirus 71 (EV71), Coxsackievirus A16 (CA16), Coxsackievirus A5 (CA5) and Coxsackievirus A6 (CA6)), of the EV-B species (Coxsackievirus B3 (CB3)), and of the EV-C species (Poliovirus 1 (PV1)) were detected and analyzed by a NEIBM (novel evolved immunoglobulin-binding molecule)-based ELISA in Shanghai blood donors. The serological prevalence of anti-CB3 VP1 antibodies was demonstrated to show the highest level, with anti-PV1 VP1 antibodies at the second highest level, and anti-CA5, CA6, CA16 and EV71 VP1 antibodies at a comparatively low level. All reactions were significantly correlated at different levels, which were approximately proportional to their sequence similarities. Antibody responses against EV71 VP1 showed obvious differences with responses against other EV-A viruses. Obvious differences in antibody responses between August 2013 and May 2014 were revealed. These findings are the first to describe the detailed information of the serological prevalence of human antibody responses against the VP1 of EV-A, B and C viruses, and could be helpful for understanding of the ubiquity of EV infections and for identifying an effective approach for seroepidemiological surveillance based on ELISA. PMID:26917423

  1. Serological detection and analysis of anti-VP1 responses against various enteroviruses (EV) (EV-A, EV-B and EV-C) in Chinese individuals.

    PubMed

    Gao, Caixia; Ding, Yingying; Zhou, Peng; Feng, Jiaojiao; Qian, Baohua; Lin, Ziyu; Wang, Lili; Wang, Jinhong; Zhao, Chunyan; Li, Xiangyu; Cao, Mingmei; Peng, Heng; Rui, Bing; Pan, Wei

    2016-02-26

    The overall serological prevalence of EV infections based on ELISA remains unknown. In the present study, the antibody responses against VP1 of the EV-A species (enterovirus 71 (EV71), Coxsackievirus A16 (CA16), Coxsackievirus A5 (CA5) and Coxsackievirus A6 (CA6)), of the EV-B species (Coxsackievirus B3 (CB3)), and of the EV-C species (Poliovirus 1 (PV1)) were detected and analyzed by a NEIBM (novel evolved immunoglobulin-binding molecule)-based ELISA in Shanghai blood donors. The serological prevalence of anti-CB3 VP1 antibodies was demonstrated to show the highest level, with anti-PV1 VP1 antibodies at the second highest level, and anti-CA5, CA6, CA16 and EV71 VP1 antibodies at a comparatively low level. All reactions were significantly correlated at different levels, which were approximately proportional to their sequence similarities. Antibody responses against EV71 VP1 showed obvious differences with responses against other EV-A viruses. Obvious differences in antibody responses between August 2013 and May 2014 were revealed. These findings are the first to describe the detailed information of the serological prevalence of human antibody responses against the VP1 of EV-A, B and C viruses, and could be helpful for understanding of the ubiquity of EV infections and for identifying an effective approach for seroepidemiological surveillance based on ELISA.

  2. GROUND-BASED DETECTIONS OF THERMAL EMISSION FROM THE DENSE HOT JUPITER WASP-43b IN THE H AND K{sub s} BANDS

    SciTech Connect

    Wang, W.; Zhao, G.; Van Boekel, R.; Henning, Th.; Madhusudhan, N.; Chen, G.

    2013-06-10

    We report new detections of thermal emission from the transiting hot Jupiter WASP-43b in the H and K{sub s} bands as observed at secondary eclipses. The observations were made with the WIRCam instrument on the Canada-France-Hawaii Telescope. We obtained a secondary eclipse depth of 0.103{sub -0.017}{sup +0.017}%$ and 0.194{sub -0.029}{sup +0.029} in the H and K{sub s} bands, respectively. The K{sub s}-band depth is consistent with the previous measurement in the narrow band centered at 2.09 {mu}m by Gillon et al. Our eclipse depths in both bands are consistent with a blackbody spectrum with a temperature of {approx}1850 K, slightly higher than the dayside equilibrium temperature without day-night energy redistribution. Based on theoretical models of the dayside atmosphere of WASP-43b, our data constrain the day-night energy redistribution in the planet to be {approx}< 15%-25%, depending on the metal content in the atmosphere. Combined with energy balance arguments, our data suggest that a strong temperature inversion is unlikely in the dayside atmosphere of WASP-43b. However, a weak inversion cannot be strictly ruled out at the current time. Future observations are required to place detailed constraints on the chemical composition of the atmosphere.

  3. Enhancement of band gap and photoconductivity in gamma indium selenide due to swift heavy ion irradiation

    SciTech Connect

    Sreekumar, R.; Jayakrishnan, R.; Sudha Kartha, C.; Vijayakumar, K. P.; Khan, S. A.; Avasthi, D. K.

    2008-01-15

    {gamma}-In{sub 2}Se{sub 3} thin films prepared at different annealing temperatures ranging from 100 to 400 deg. C were irradiated using 90 MeV Si ions with a fluence of 2x10{sup 13} ions/cm{sup 2}. X-ray diffraction analysis proved that there is no considerable variation in structural properties of the films due to the swift heavy ion irradiation. However, photosensitivity and sheet resistance of the samples increased due to irradiation. It was observed that the sample, which had negative photoconductivity, exhibited positive photoconductivity, after irradiation. The negative photoconductivity was due to the combined effect of trapping of photoexcited electrons, at traps 1.42 and 1.26 eV, above the valence band along with destruction of the minority carriers, created during illumination, through recombination. Photoluminescence study revealed that the emission was due to the transition to a recombination center, which was 180 meV above the valence band. Optical absorption study proved that the defects present at 1.42 and 1.26 eV were annealed out by the ion beam irradiation. This allowed photoexcited carriers to reach conduction band, which resulted in positive photoconductivity. Optical absorption study also revealed that the band gap of the material could be increased by ion beam irradiation. The sample prepared at 400 deg. C had a band gap of 2 eV and this increased to 2.8 eV, after irradiation. The increase in optical band gap was attributed to the annihilation of localized defect bands, near the conduction and valence band edges, on irradiation. Thus, by ion beam irradiation, one could enhance photosensitivity as well as the optical band gap of {gamma}-In{sub 2}Se{sub 3}, making the material suitable for applications such as window layer in solar cells.

  4. Auger electron emission initiated by the creation of valence-band holes in graphene by positron annihilation

    PubMed Central

    Chirayath, V. A.; Callewaert, V.; Fairchild, A. J.; Chrysler, M. D.; Gladen, R. W.; Mcdonald, A. D.; Imam, S. K.; Shastry, K.; Koymen, A. R.; Saniz, R.; Barbiellini, B.; Rajeshwar, K.; Partoens, B.; Weiss, A. H.

    2017-01-01

    Auger processes involving the filling of holes in the valence band are thought to make important contributions to the low-energy photoelectron and secondary electron spectrum from many solids. However, measurements of the energy spectrum and the efficiency with which electrons are emitted in this process remain elusive due to a large unrelated background resulting from primary beam-induced secondary electrons. Here, we report the direct measurement of the energy spectra of electrons emitted from single layer graphene as a result of the decay of deep holes in the valence band. These measurements were made possible by eliminating competing backgrounds by employing low-energy positrons (<1.25 eV) to create valence-band holes by annihilation. Our experimental results, supported by theoretical calculations, indicate that between 80 and 100% of the deep valence-band holes in graphene are filled via an Auger transition. PMID:28703225

  5. Fast intrinsic emissions of wide-gap oxides under electron irradiation

    NASA Astrophysics Data System (ADS)

    Lushchik, A.; Savikhin, F.; Tokbergenov, I.

    2003-01-01

    The emission spectra have been measured in the range of 1.6-9.0 eV under irradiation of wide-gap oxides by single electron pulses (3 ns, 300 kV), A fast (tau < 3 ns) continuous and temperature-independent emission, connected mainly with the transitions of hot holes between the levels of the valence band of oxides, can be separated in these spectra at 300-600 K, when the inertial emissions (5-7 eV) of localized excitations undergo a strong thermal quenching. It is suggested that a drastic decrease of the intensity of this so-called hole intraband luminescence (IBL) in a short-wavelength spectral region is caused by the lowering of the density of states at the edges of the valence band and, therefore, supplies information on the width of an anion valence band E-v. The drastic decrease of the IBL, intensity takes place at 6.4-8.6 eV in BaMgAl10O17, SrAl2O4, MgAl4O7, MgO and BeO, that agrees satisfactorily with the values of E-v in these systems obtained by other methods.

  6. Near-infrared Thermal Emission from TrES-3b: A Ks-band Detection and an H-band Upper Limit on the Depth of the Secondary Eclipse

    NASA Astrophysics Data System (ADS)

    Croll, Bryce; Jayawardhana, Ray; Fortney, Jonathan J.; Lafrenière, David; Albert, Loic

    2010-08-01

    We present H- and Ks-band photometry bracketing the secondary eclipse of the hot Jupiter TrES-3b using the Wide-field Infrared Camera on the Canada-France-Hawaii Telescope. We detect the secondary eclipse of TrES-3b with a depth of 0.133+0.018 -0.016% in the Ks band (8σ)—a result that is in sharp contrast to the eclipse depth reported by de Mooij & Snellen. We do not detect its thermal emission in the H band, but place a 3σ limit of 0.051% on the depth of the secondary eclipse in this band. A secondary eclipse of this depth in Ks requires very efficient day-to-nightside redistribution of heat and nearly isotropic reradiation, a conclusion that is in agreement with longer wavelength, mid-infrared Spitzer observations. Our 3σ upper limit on the depth of our H-band secondary eclipse also argues for very efficient redistribution of heat and suggests that the atmospheric layer probed by these observations may be well homogenized. However, our H-band upper limit is so constraining that it suggests the possibility of a temperature inversion at depth, or an absorbing molecule, such as methane, that further depresses the emitted flux at this wavelength. The combination of our near-infrared measurements and those obtained with Spitzer suggests that TrES-3b displays a near-isothermal dayside atmospheric temperature structure, whose spectrum is well approximated by a blackbody. We emphasize that our strict H-band limit is in stark disagreement with the best-fit atmospheric model that results from longer wavelength observations only, thus highlighting the importance of near-infrared observations at multiple wavelengths, in addition to those returned by Spitzer in the mid-infrared, to facilitate a comprehensive understanding of the energy budgets of transiting exoplanets. Based on observations obtained with WIRCam, a joint project of CFHT, Taiwan, Korea, Canada, France, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of

  7. Seasonal and diurnal variation of ELF emission occurrences at 750-Hz band observed at geomagnetically conjugate stations

    SciTech Connect

    Suzuki, Hiroyuki ); Sato, Natsuo )

    1987-06-01

    Statistical characteristics of emission occurrence are examined, using digital data of 750-Hz intensity records obtained at the conuugate pai of statins, Syowa Station in Antarrctica and Husafell in Iceland. The geographic local time at Syowa and Husafell is magnetic local time plus 3 hours and minur 1 hour, respectively. The following notable diurnal variations and seasonal variations were found: (1) The emissions were mostly observed during the daytime in the conjugate region. However, the magnetic local time when the emission occurrence rate reached maximum at Husafell was 2-3 hours later than that at Syowa. (2) The seasonal variations of emission occurrence showed the same tendency at the conjugate stations. The emission intensities showed a maximum during local summer and a minimum during local winter in both hemispheres. The ratio fo average emission intensity in each season to the intensity in winter is approximately 2.1-2.2 for summer, 1.7-1.9 for autumn, and 1.7 for spring. From these statistical characteristics, ELF emission intensity strongly depends on not only magnetic local time but also geographic local time and seasons, suggesting that ELF emissions observed on the ground are strongly controlled by the sunlight effects. The sunlight may affect the asymmetry of wave duct enhancement and wave propagation from the magnetosphere to the ionosphere in both hemisphers. Other effects are also discussed in this paper.

  8. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A2, S/N 108, 08

    NASA Technical Reports Server (NTRS)

    Valdez, A.

    2000-01-01

    This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A2, S/N 108, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  9. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 108 2

    NASA Technical Reports Server (NTRS)

    Valdez, A.

    2000-01-01

    This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1 SIN 108, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  10. Integrated Advanced Microwave Sounding Unit-A (AMSU-A). Engineering Test Report: Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 109

    NASA Technical Reports Server (NTRS)

    Valdez, A.

    2000-01-01

    This is the Engineering Test Report, Radiated Emissions and SARR, SARP, DCS Receivers, Link Frequencies EMI Sensitive Band Test Results, AMSU-A1, S/N 109, for the Integrated Advanced Microwave Sounding Unit-A (AMSU-A).

  11. Temperature profile retrieval in axisymmetric combustion plumes using multilayer perceptron modeling and spectral feature selection in the infrared CO2 emission band.

    PubMed

    García-Cuesta, Esteban; de Castro, Antonio J; Galván, Inés M; López, Fernando

    2014-01-01

    In this work, a methodology based on the combined use of a multilayer perceptron model fed using selected spectral information is presented to invert the radiative transfer equation (RTE) and to recover the spatial temperature profile inside an axisymmetric flame. The spectral information is provided by the measurement of the infrared CO2 emission band in the 3-5 μm spectral region. A guided spectral feature selection was carried out using a joint criterion of principal component analysis and a priori physical knowledge of the radiative problem. After applying this guided feature selection, a subset of 17 wavenumbers was selected. The proposed methodology was applied over synthetic scenarios. Also, an experimental validation was carried out by measuring the spectral emission of the exhaust hot gas plume in a microjet engine with a Fourier transform-based spectroradiometer. Temperatures retrieved using the proposed methodology were compared with classical thermocouple measurements, showing a good agreement between them. Results obtained using the proposed methodology are very promising and can encourage the use of sensor systems based on the spectral measurement of the CO2 emission band in the 3-5 μm spectral window to monitor combustion processes in a nonintrusive way.

  12. Complex organic matter in space: about the chemical composition of carriers of the Unidentified Infrared Bands (UIBs) and protoplanetary emission spectra recorded from certain astrophysical objects.

    PubMed

    Cataldo, Franco; Keheyan, Yeghis; Heymann, Dieter

    2004-02-01

    In this communication we present the basic concept that the pure PAHs (Polycyclic Aromatic Hydrocarbons) can be considered only the ideal carriers of the UIBs (Unidentified Infrared Bands), the emission spectra coming from a large variety of astronomical objects. Instead we have proposed that the carriers of UIBs and of protoplanetary nebulae (PPNe) emission spectra are much more complex molecular mixtures possessing also complex chemical structures comparable to certain petroleum fractions obtained from the petroleum refining processes. The demonstration of our proposal is based on the comparison between the emission spectra recorded from the protoplanetary nebulae (PPNe) IRAS 22272+ 5435 and the infrared absorption spectra of certain 'heavy' petroleum fractions. It is shown that the best match with the reference spectrum is achieved by highly aromatic petroleum fractions. It is shown that the selected petroleum fractions used in the present study are able to match the band pattern of anthracite coal. Coal has been proposed previously as a model for the PPNe and UIBs but presents some drawbacks which could be overcome by adopting the petroleum fractions as model for PPNe and UIBs in place of coal. A brief discussion on the formation of the petroleum-like fractions in PPNe objects is included.

  13. Search for the OH (X(2)Pi) Meinel band emission in meteors as a tracer of mineral water in comets: detection of N(2)(+) (A-X)

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Laux, Christophe O.

    2004-01-01

    We report the discovery of the N(2)(+) A-X Meinel band in the 780-840 nm meteor emission from two Leonid meteoroids that were ejected less than 1000 years ago by comet 55P/Tempel-Tuttle. Our analysis indicates that the N(2)(+) molecule is at least an order of magnitude less abundant than expected, possibly as a result of charge transfer reactions with meteoric metal atoms. This new band was found while searching for rovibrational transitions in the X(2)Pi electronic ground state of OH (the OH Meinel band), a potential tracer of water bound to minerals in cometary matter. The electronic A-X transition of OH has been identified in other Leonid meteors. We did not detect this OH Meinel band, which implies that the excited A state is not populated by thermal excitation but by a mechanism that directly produces OH in low vibrational levels of the excited A(2)Sigma state. Ultraviolet dissociation of atmospheric or meteoric water vapor is such a mechanism, as is the possible combustion of meteoric organics.

  14. Search for the OH (X(2)Pi) Meinel band emission in meteors as a tracer of mineral water in comets: detection of N(2)(+) (A-X).

    PubMed

    Jenniskens, Peter; Laux, Christophe O

    2004-01-01

    We report the discovery of the N(2)(+) A-X Meinel band in the 780-840 nm meteor emission from two Leonid meteoroids that were ejected less than 1000 years ago by comet 55P/Tempel-Tuttle. Our analysis indicates that the N(2)(+) molecule is at least an order of magnitude less abundant than expected, possibly as a result of charge transfer reactions with meteoric metal atoms. This new band was found while searching for rovibrational transitions in the X(2)Pi electronic ground state of OH (the OH Meinel band), a potential tracer of water bound to minerals in cometary matter. The electronic A-X transition of OH has been identified in other Leonid meteors. We did not detect this OH Meinel band, which implies that the excited A state is not populated by thermal excitation but by a mechanism that directly produces OH in low vibrational levels of the excited A(2)Sigma state. Ultraviolet dissociation of atmospheric or meteoric water vapor is such a mechanism, as is the possible combustion of meteoric organics.

  15. High-resolution Fourier transform emission spectroscopy of the A˜ 2Πi -X˜ 2Πi band of the OCS+ ion

    NASA Astrophysics Data System (ADS)

    Nakashima, Yoshihiro; Harada, Kensuke; Tanaka, Keiichi; Tanaka, Takehiko

    2017-04-01

    High resolution Fourier transform emission spectroscopy of the A˜ 2Πi -X˜ 2Πi band of the OCS+ ion was performed in the UV region to observe the ν1 (CO stretch) progression bands (υ1 = 0 → 2-5) for both the Ω =3 /2 and 1/2 spin components. Accurate molecular constants including the rotational constants, B0 = 0.194 765(13) and 0.187 106(13) cm-1, and the spin-orbit interaction constants, A0 = -381.0(56) and -126.5(56) cm-1, were determined for the X˜ 2Π and A˜ 2Π states, respectively, by the simultaneous analysis of the observed progression bands. The CO bond length (rCO = 1.2810 Å) for the A˜ 2Π state, derived from the rotational constant B0 and Franck-Condon factors, is longer by 0.1756 Å than that (1.1054 Å) for the X˜ 2Π state, while the CS bond length for the A˜ 2Π state is shorter by 0.0905 Å than that for the X˜ 2Π state. Pure rotational transition frequencies in the ground X˜ 2Π state are predicted, as well as transition frequencies of the ν1 fundamental band, with the present molecular constants.

  16. Search for the OH (X(2)Pi) Meinel band emission in meteors as a tracer of mineral water in comets: detection of N(2)(+) (A-X)

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter; Laux, Christophe O.

    2004-01-01

    We report the discovery of the N(2)(+) A-X Meinel band in the 780-840 nm meteor emission from two Leonid meteoroids that were ejected less than 1000 years ago by comet 55P/Tempel-Tuttle. Our analysis indicates that the N(2)(+) molecule is at least an order of magnitude less abundant than expected, possibly as a result of charge transfer reactions with meteoric metal atoms. This new band was found while searching for rovibrational transitions in the X(2)Pi electronic ground state of OH (the OH Meinel band), a potential tracer of water bound to minerals in cometary matter. The electronic A-X transition of OH has been identified in other Leonid meteors. We did not detect this OH Meinel band, which implies that the excited A state is not populated by thermal excitation but by a mechanism that directly produces OH in low vibrational levels of the excited A(2)Sigma state. Ultraviolet dissociation of atmospheric or meteoric water vapor is such a mechanism, as is the possible combustion of meteoric organics.

  17. K band SINFONI spectra of two z ~ 5 submillimeter galaxy systems: upper limits to the unobscured star formation from [O II] optical emission line searches

    NASA Astrophysics Data System (ADS)

    Couto, Guilherme S.; Colina, Luis; López, Javier Piqueras; Storchi-Bergmann, Thaisa; Arribas, Santiago

    2016-10-01

    We present deep SINFONI K-band integral field spectra of two submillimeter galaxy systems (SMG): BR 1202-0725 and J1000+0234, at z = 4.69 and 4.55, respectively. Spectra extracted for each object in the two systems do not show any signature of the [O ii]λλ3726, 29 Å emission-lines, placing upper flux limits of 3.9 and 2.5 × 10-18erg s-1 cm-2for BR 1202-0725 and J1000+0234, respectively. Using the relation between the star formation rate (SFR) and the luminosity of the [O ii] doublet, we estimate unobscured SFR upper limits of ~ 10-15 M⊙ yr-1and ~30-40 M⊙ yr-1for the objects of the two systems, respectively. For the SMGs, these values are at least two orders of magnitude lower than those derived from SED and IR luminosities. The differences on the SFR values would correspond to internal extinction of, at least, 3.4-4.9 and 2.1-3.6 mag in the visual for BR 1202-0725 and J1000+0234 SMGs, respectively. The upper limit for the [O ii]-derived SFR in one of the LAEs (Lyα2) in the BR1202-0725 system is at least one order of magnitude lower than the previous SFR derived from infrared tracers, while both estimates are in good agreement for Lyα1. The lower limits to the internal extinction in these two Lyman-alpha emitters are 0.6 mag and 1.3 mag, respectively. No evidence for [O ii] emission associated with Lyα1 is identified in our data, implying that residuals of the K-band sky emission lines after subtraction in medium-band imaging data could provide the adequate flux.

  18. Tuneable luminescence properties of EDTA-assisted ZnS:Mn nanocrystals from a yellow-orange to a red emission band.

    PubMed

    Viswanath, R; Bhojya Naik, H S; Arun Kumar, G; Suresh Gowda, I K; Yallappa, S

    2017-05-16

    Luminescence technology has been improved with the help of semiconductor nanoparticles that possess novel optical and electrical properties compared with their bulk counterpart. The aim of this study was to design semiconductor nanocrystals in their pure (ZnS) or doped form (ZnS:Mn) with different concentrations of Mn(2+) ions by a wet chemical route stabilized by ethylenediamine tetra-acetic acid (EDTA) and to evaluate their luminescence properties. The nanocrystals were characterized by physicochemical techniques such as X-ray diffraction (XRD), High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SEAD), EDS, and ultraviolet (UV)-visible light and photoluminescence (PL) studies. These results showed the presence of cubic phase and spherically shaped nanocrystals. A blue shift with respect to their bulk counterpart was observed. PL emission spectra were observed with a fixed blue peak and the yellow-orange bands were red shifted towards the red region under the same excitation wavelength. The orange-red bands were attributed to the radiation transition of electrons in 3d5 unfilled shells of Mn(2+) ions [(4) T1 ((4) G)-(6) A1 ((6) S)]; the ZnS matrix varied with Mn(2+) concentration. Shift and increase in the intensity of the PL and absorption bands were observed with increase in Mn content. The study showed that Mn(2+) -doped ZnS nanocrystal emission bands can be tuned from the yellow-orange to the red regions under a controlled synthesis process and could be used as promising luminescent emitters in the biology field upon functionalization with suitable materials. Further studies on construction with various other materials will be useful for practical applications. Copyright © 2017 John Wiley & Sons, Ltd.

  19. Dynamically tuning emission band of CdSe/ZnS quantum dots assembled on Ag nanorod array: plasmon-enhanced Stark shift.

    PubMed

    Peng, Xiao-Niu; Zhou, Zhang-Kai; Zhang, Wei; Hao, Zhong-Hua

    2011-11-21

    We demonstrate tuning emission band of CdSe/ZnS semiconductor quantum dots (SQDs) closely-packed in the proximity of Ag nanorod array by dynamically adjusting exciton-plasmon interaction. Large red-shift is observed in two-photon luminescence (TPL) spectra of the SQDs when the longitudinal surface plasmon resonance (LSPR) of Ag nanorod array is adjusted to close to excitation laser wavelength, and the spectral red-shift of TPL reaches as large as 101 meV by increasing excitation power, which is slightly larger than full width at half-maximum of emission spectrum of the SQDs. The observed LSPR-dependent spectral shifting behaviors are explained by a theoretical model of plasmon-enhanced quantum-confined Stark effect. These observations could find the applications in dynamical information processing in active plasmonic and photonic nanodevices.

  20. SIMULTANEOUS K- AND L-BAND SPECTROSCOPY OF Be STARS: CIRCUMSTELLAR ENVELOPE PROPERTIES FROM HYDROGEN EMISSION LINES

    SciTech Connect

    Granada, A.; Arias, M. L.; Cidale, L. S.

    2010-05-15

    We present medium-resolution K- and L-band spectra of a sample of eight Be stars, obtained with Gemini/NIRI. The IR K and L bands contain many lines of different hydrogen series that are used as a diagnosis to the physical conditions in the circumstellar environments. We make an analysis on the optical depths of the line-forming regions based on the intensity ratios of Pf{gamma} and Br{alpha} lines, the behavior of Humphreys' series, and the fluxes of Br{alpha} and Br{gamma} lines. All our targets show spectroscopic and photometric long-term variability; thus, time-resolved K- and L-band spectroscopy is an ideal tool for studying the structure and evolution of the innermost regions of the envelope and to test models on the disk-forming mechanism. We note that the instrumental configuration used allowed us to obtain good quality IR observations and to take profit of Gemini band 3 observing time (allocation time for ranked programs in which the observing conditions are relaxed).

  1. Polycyclic Aromatic Hydrocarbon Emission in Spitzer/IRS Maps. II. A Direct Link between Band Profiles and the Radiation Field Strength

    NASA Astrophysics Data System (ADS)

    Stock, D. J.; Peeters, E.

    2017-03-01

    We decompose the observed 7.7 μm polycyclic aromatic hydrocarbon (PAH) emission complexes in a large sample of over 7000 mid-infrared spectra of the interstellar medium using spectral cubes observed with the Spitzer/IRS-SL instrument. In order to fit the 7.7 μm PAH emission complex we invoke four Gaussian components, which are found to be very stable in terms of their peak positions and widths across all of our spectra, and subsequently define a decomposition with fixed parameters, which gives an acceptable fit for all the spectra. We see a strong environmental dependence on the interrelationships between our band fluxes—in the H ii regions all four components are intercorrelated, while in the reflection nebulae (RNs) the inner and outer pairs of bands correlate in the same manner as previously seen for NGC 2023. We show that this effect arises because the maps of RNs are dominated by emission from strongly irradiated photodissociation regions, while the much larger maps of H ii regions are dominated by emission from regions much more distant from the exciting stars, leading to subtly different spectral behavior. Further investigation of this dichotomy reveals that the ratio of two of these components (centered at 7.6 and 7.8 μm) is linearly related to the UV-field intensity (log G 0). We find that this relationship does not hold for sources consisting of circumstellar material, which are known to have variable 7.7 μm spectral profiles.

  2. On sky characterization of the BAORadio wide band digital backend. Search for HI emission in Abell85, Abell1205 and Abell2440 galaxy clusters

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Campagne, J. E.; Colom, P.; Ferrari, C.; Magneville, Ch.; Martin, J. M.; Moniez, M.; Torrentó, A. S.

    2016-02-01

    We have observed regions of three galaxy clusters at z˜[0.06÷0.09] (Abell85, Abell1205, Abell2440) with the Nançay radiotelescope (NRT) to search for 21 cm emission and to fully characterize the FPGA based BAORadio digital backend. We have tested the new BAORadio data acquisition system by observing sources in parallel with the NRT standard correlator (ACRT) back-end over several months. BAORadio enables wide band instantaneous observation of the [1250,1500] MHz frequency range, as well as the use of powerful RFI mitigation methods thanks to its fine time sampling. A number of questions related to instrument stability, data processing and calibration are discussed. We have obtained the radiometer curves over the integration time range [0.01,10 000] seconds and we show that sensitivities of few mJy over most of the wide frequency band can be reached with the NRT. It is clearly shown that in blind line search, which is the context of H I intensity mapping for Baryon Acoustic Oscillations, the new acquisition system and processing pipeline outperforms the standard one. We report a positive detection of 21 cm emission at 3 σ-level from galaxies in the outer region of Abell85 at ≃1352 MHz (14400 km/s) corresponding to a line strength of ≃0.8 Jy km/s. We also observe an excess power around ≃1318 MHz (21600 km/s), although at lower statistical significance, compatible with emission from Abell1205 galaxies. Detected radio line emissions have been cross matched with optical catalogs and we have derived hydrogen mass estimates.

  3. Production of EV71 vaccine candidates.

    PubMed

    Chong, Pele; Hsieh, Shih-Yang; Liu, Chia-Chyi; Chou, Ai-Hsiang; Chang, Jui-Yuan; Wu, Suh-Chin; Liu, Shih-Jen; Chow, Yen-Hung; Su, Ih-Jen; Klein, Michel

    2012-12-01

    Enterovirus 71 (EV71) is now recognized as an emerging neurotropic virus in Asia and with Coxsackie virus (CV) it is the other major causative agent of hand-foot-mouth diseases (HFMD). Effective medications and/or prophylactic vaccines against HFMD are urgently needed. From a scientific (the feasibility of bioprocess, immunological responses and potency in animal challenge model) and business development (cost of goods) points of view, we in this review address and discuss the pros and cons of different EV71 vaccine candidates that have been produced and evaluated in animal models. Epitope-based synthetic peptide vaccine candidates containing residues 211-225 of VP1 formulated with Freund's adjuvant (CFA/IFA) elicited low EV71 virus neutralizing antibody responses, but were protective in the suckling mouse challenge model. Among recombinant EV71 subunits (rVP1, rVP2 and rVP3) expressed in E. coli, purified and formulated with CFA/IFA, only VP1 elicited mouse antibody responses with measurable EV71-specific virus neutralization titers. Immunization of mice with either a DNA plasmid containing VP1 gene or VP1 expressed in Salmonella typhimurium also generated neutralizing antibody responses and protected animals against a live EV71 challenge. Recombinant EV71 virus-like particles (rVLP) produced from baculovirus formulated either with CFA/IFA or alum elicited good virus neutralization titers in both mice and non-human primates, and were found to be protective in the suckling mouse EV71 challenge model. Synthetic peptides or recombinant EV71 subunit vaccines (rVP1 and rVLP) formulated in alum were found to be poorly immunogenic in rabbits. Only formalin-inactivated (FI) EV71 virions formulated in alum elicited cross-neutralizing antibodies against different EV71 genotypes in mice, rabbits and non-human primates but induced weak neutralizing responses against CAV16. From a regulatory, economic and market acceptability standpoint, FI-EV71 virion vaccines are the most

  4. Production of EV71 vaccine candidates

    PubMed Central

    Chong, Pele; Hsieh, Shih-Yang; Liu, Chia-Chyi; Chou, Ai-Hsiang; Chang, Jui-Yuan; Wu, Suh-Chin; Liu, Shih-Jen; Chow, Yen-Hung; Su, Ih-Jen; Klein, Michel

    2012-01-01

    Enterovirus 71 (EV71) is now recognized as an emerging neurotropic virus in Asia and with Coxsackie virus (CV) it is the other major causative agent of hand-foot-mouth diseases (HFMD). Effective medications and/or prophylactic vaccines against HFMD are urgently needed. From a scientific (the feasibility of bioprocess, immunological responses and potency in animal challenge model) and business development (cost of goods) points of view, we in this review address and discuss the pros and cons of different EV71 vaccine candidates that have been produced and evaluated in animal models. Epitope-based synthetic peptide vaccine candidates containing residues 211–225 of VP1 formulated with Freund’s adjuvant (CFA/IFA) elicited low EV71 virus neutralizing antibody responses, but were protective in the suckling mouse challenge model. Among recombinant EV71 subunits (rVP1, rVP2 and rVP3) expressed in E. coli, purified and formulated with CFA/IFA, only VP1 elicited mouse antibody responses with measurable EV71-specific virus neutralization titers. Immunization of mice with either a DNA plasmid containing VP1 gene or VP1 expressed in Salmonella typhimurium also generated neutralizing antibody responses and protected animals against a live EV71 challenge. Recombinant EV71 virus-like particles (rVLP) produced from baculovirus formulated either with CFA/IFA or alum elicited good virus neutralization titers in both mice and non-human primates, and were found to be protective in the suckling mouse EV71 challenge model. Synthetic peptides or recombinant EV71 subunit vaccines (rVP1 and rVLP) formulated in alum were found to be poorly immunogenic in rabbits. Only formalin-inactivated (FI) EV71 virions formulated in alum elicited cross-neutralizing antibodies against different EV71 genotypes in mice, rabbits and non-human primates but induced weak neutralizing responses against CAV16. From a regulatory, economic and market acceptability standpoint, FI-EV71 virion vaccines are the

  5. Estimation of band gap of muscovite mineral using thermoluminescence (TL) analysis

    NASA Astrophysics Data System (ADS)

    Kalita, J. M.; Wary, G.

    2016-03-01

    In this article thermoluminescence (TL) mechanism in muscovite mineral has been reported in detail. The trap spectroscopy of the mineral has been studied from the TL glow curve of X-ray irradiated sample. A stable TL peak has been observed at around 347 K in the glow curve, however after annealing the sample above 573 K an additional peak is observed at around 408 K. In the TL emission spectra an emission peak has been observed at around 447 nm at TL peak maximum temperatures. The glow curves are analyzed by Tm-Tstop analysis, peak shape method and fractional glow technique. Analyses showed that there is a trap center and a radiative recombination center at depth around 0.71 and 2.78 eV from the conduction band. These two localized centers do not affected by annealing up to 773 K. However, annealing at 573 K (or above) a new electron trap center was found to generate at depth around 1.23 eV. This significant result has been confirmed with the help of phototransfer phenomena observed under UV irradiation. Due to UV irradiation on the excited sample, the transfer of trapped charges from the deeper trap level (1.23 eV) to the shallow level (0.71 eV) has been observed. Based on the analysis a schematic band diagram of muscovite crystal has been proposed. With the help of the band model, radiative as well as non-radiative recombination mechanisms have been discussed. The band gap of the material has been estimated to be around 5.09 eV and verified.

  6. Photosensized controlling benzyl methacrylate-based matrix enhanced Eu(3+) narrow-band emission for fluorescence applications.

    PubMed

    Lee, Jiann-Fong; Chen, Hsuen-Li; Lee, Geneh-Siang; Tseng, Shao-Chin; Lin, Mei-Hsiang; Liau, Wen-Bin

    2012-01-01

    This study synthesized a europium (Eu(3+)) complex Eu(DBM)(3)Cl-MIP (DBM = dibenzoyl methane; Cl-MIP = 2-(2-chlorophenyl)-1-methyl-1H-imidazo[4,5-f][1,10]phenanthroline) dispersed in a benzyl methacrylate (BMA) monomer and treated with ultraviolet (UV) light for polymerization. Spectral results showed that the europium complex containing an antenna, Cl-MIP, which had higher triplet energy into the Eu(3+) energy level, was an energetically enhanced europium emission. Typical stacking behaviors of π-π interactions between the ligands and the Eu(3+)-ion were analyzed using single crystal X-ray diffraction. Regarding the luminescence performance of this europium composite, the ligand/defect emission was suppressed by dispersion in a poly-BMA (PBMA) matrix. The underlying mechanism of the effective enhancement of the pure Eu(3+) emission was attributed to the combined effects of structural modifications, defect emissions, and carrier charge transfer. Fluorescence spectra were compared to the composite of optimized Eu3+ emission where they were subsequently chelated to four metal ions via carboxylate groups on the BMA unit. The optical enhanced europium composite clearly demonstrated highly efficient optical responses and is, therefore a promising application as an optical detection material.

  7. Photosensized Controlling Benzyl Methacrylate-Based Matrix Enhanced Eu3+ Narrow-Band Emission for Fluorescence Applications

    PubMed Central

    Lee, Jiann-Fong; Chen, Hsuen-Li; Lee, Geneh-Siang; Tseng, Shao-Chin; Lin, Mei-Hsiang; Liau, Wen-Bin

    2012-01-01

    This study synthesized a europium (Eu3+) complex Eu(DBM)3Cl-MIP (DBM = dibenzoyl methane; Cl-MIP = 2-(2-chlorophenyl)-1-methyl-1H-imidazo[4,5-f][1,10]phenanthroline) dispersed in a benzyl methacrylate (BMA) monomer and treated with ultraviolet (UV) light for polymerization. Spectral results showed that the europium complex containing an antenna, Cl-MIP, which had higher triplet energy into the Eu3+ energy level, was an energetically enhanced europium emission. Typical stacking behaviors of π–π interactions between the ligands and the Eu3+-ion were analyzed using single crystal X-ray diffraction. Regarding the luminescence performance of this europium composite, the ligand/defect emission was suppressed by dispersion in a poly-BMA (PBMA) matrix. The underlying mechanism of the effective enhancement of the pure Eu3+ emission was attributed to the combined effects of structural modifications, defect emissions, and carrier charge transfer. Fluorescence spectra were compared to the composite of optimized Eu3+ emission where they were subsequently chelated to four metal ions via carboxylate groups on the BMA unit. The optical enhanced europium composite clearly demonstrated highly efficient optical responses and is, therefore a promising application as an optical detection material. PMID:22489178

  8. The first identification of C2 emission bands in comet Scorichenko-George (1989e1) spectrum

    NASA Technical Reports Server (NTRS)

    Churyumov, Klim I.; Chorny, G. F.

    1992-01-01

    Wave lengths from 360 emissions within the spectral range lambda lambda 3380-6290 A in the spectrum of the comet Scorichenko-George, obtained with the help of the TV spectral scanner of a 6-meter reflector BTA (in Special AO) have been determined. The CN, C2, C3, NH, CH, CO, Na, NH2, N2(+), CO(+), CO2(+), H2O(+), and C2(-) emissions have been identified. For the first time, it has been shown that emissions of C2(-) (the transitions 0-0, 0-1, et al.) in the cometary spectrum possibly exist. Molecular ions C2(-) column density with cross-section 1 sq cm is N = 1.44 10(exp -12) cm(exp -2) and their upper limits of gas C2(-) productivity is Q(C2(-)) = 2 10(exp 28) c(exp -1).

  9. Electronic structure descriptor for the discovery of narrow-band red-emitting phosphors

    DOE PAGES

    Wang, Zhenbin; Chu, Iek -Heng; Zhou, Fei; ...

    2016-05-09

    Narrow-band red-emitting phosphors are a critical component of phosphor-converted light-emitting diodes for highly efficient illumination-grade lighting. In this work, we report the discovery of a quantitative descriptor for narrow-band Eu2+-activated emission identified through a comparison of the electronic structures of known narrow-band and broad-band phosphors. We find that a narrow emission bandwidth is characterized by a large splitting of more than 0.1 eV between the two highest Eu2+ 4f7 bands. By incorporating this descriptor in a high-throughput first-principles screening of 2259 nitride compounds, we identify five promising new nitride hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit goodmore » chemical stability, thermal quenching resistance, and quantum efficiency, as well as narrow-band emission. Lastly, our findings provide important insights into the emission characteristics of rare-earth activators in phosphor hosts and a general strategy to the discovery of phosphors with a desired emission peak and bandwidth.« less

  10. Electronic structure descriptor for the discovery of narrow-band red-emitting phosphors

    SciTech Connect

    Wang, Zhenbin; Chu, Iek -Heng; Zhou, Fei; Ong, Shyue Ping

    2016-05-09

    Narrow-band red-emitting phosphors are a critical component of phosphor-converted light-emitting diodes for highly efficient illumination-grade lighting. In this work, we report the discovery of a quantitative descriptor for narrow-band Eu2+-activated emission identified through a comparison of the electronic structures of known narrow-band and broad-band phosphors. We find that a narrow emission bandwidth is characterized by a large splitting of more than 0.1 eV between the two highest Eu2+ 4f7 bands. By incorporating this descriptor in a high-throughput first-principles screening of 2259 nitride compounds, we identify five promising new nitride hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit good chemical stability, thermal quenching resistance, and quantum efficiency, as well as narrow-band emission. Lastly, our findings provide important insights into the emission characteristics of rare-earth activators in phosphor hosts and a general strategy to the discovery of phosphors with a desired emission peak and bandwidth.

  11. Electronic structure descriptor for the discovery of narrow-band red-emitting phosphors

    SciTech Connect

    Wang, Zhenbin; Chu, Iek -Heng; Zhou, Fei; Ong, Shyue Ping

    2016-05-09

    Narrow-band red-emitting phosphors are a critical component of phosphor-converted light-emitting diodes for highly efficient illumination-grade lighting. In this work, we report the discovery of a quantitative descriptor for narrow-band Eu2+-activated emission identified through a comparison of the electronic structures of known narrow-band and broad-band phosphors. We find that a narrow emission bandwidth is characterized by a large splitting of more than 0.1 eV between the two highest Eu2+ 4f7 bands. By incorporating this descriptor in a high-throughput first-principles screening of 2259 nitride compounds, we identify five promising new nitride hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit good chemical stability, thermal quenching resistance, and quantum efficiency, as well as narrow-band emission. Lastly, our findings provide important insights into the emission characteristics of rare-earth activators in phosphor hosts and a general strategy to the discovery of phosphors with a desired emission peak and bandwidth.

  12. Down-shifting emission of Yb3+ ions sensitized by broad charge transfer band of V-O and Yb-O in Ca2V2O7 phosphors

    NASA Astrophysics Data System (ADS)

    Feng, Zhongshan; Jiang, Sha; Luo, Xiaobing; Shen, Jun; Pang, Yu; Li, Li; Zhou, Xianju

    2016-12-01

    Yb3+ singly doped pyrovanadate Ca2V2O7 phosphors were prepared by conventional solid state reaction. The crystal structure of the powders was investigated by X-ray diffraction. The diffuse reflection spectrum, photoluminescence excitation, emission spectra were investigated. The intense near infrared down-shifting emission of Yb3+ ions were demonstrated upon excitation of ultraviolet (UV) photon in a wide range of 250-450 nm. The broad excitation band in UV is attributed to the overlap of Yb3+-O2- and V5+-O2- charge transfer band. With the combination of wide Yb-O charge transfer band, which is seldom reported to sensitize the down-shifting emission of Yb3+ ion, the spectral response of the spectral converting materials is greatly extended. The energy transfer process from V-O and Yb-O charge transfer band to Yb3+ ions and involved mechanism have been discussed.

  13. Simultaneous K- and L-band Spectroscopy of Be Stars: Circumstellar Envelope Properties from Hydrogen Emission Lines

    NASA Astrophysics Data System (ADS)

    Granada, A.; Arias, M. L.; Cidale, L. S.

    2010-05-01

    We present medium-resolution K- and L-band spectra of a sample of eight Be stars, obtained with Gemini/NIRI. The IR K and L bands contain many lines of different hydrogen series that are used as a diagnosis to the physical conditions in the circumstellar environments. We make an analysis on the optical depths of the line-forming regions based on the intensity ratios of Pfγ and Brα lines, the behavior of Humphreys' series, and the fluxes of Brα and Brγ lines. All our targets show spectroscopic and photometric long-term variability; thus, time-resolved K- and L-band spectroscopy is an ideal tool for studying the structure and evolution of the innermost regions of the envelope and to test models on the disk-forming mechanism. We note that the instrumental configuration used allowed us to obtain good quality IR observations and to take profit of Gemini band 3 observing time (allocation time for ranked programs in which the observing conditions are relaxed). Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (USA), the Science and Technology Facilities Council (UK), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência e Tecnologia (Brazil), and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  14. Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source

    SciTech Connect

    Piot, P.; Brau, C. A.; Gabella, W. E.; Ivanov, B.; Mendenhall, M. H.; Choi, B. K.; Blomberg, B.; Mihalcea, D.; Panuganti, H.; Jarvis, J.; Prieto, P.; Reid, J.

    2014-06-30

    We report on the operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of ∼10{sup 6} diamond tips on pyramids. Maximum current on the order of 15 mA was reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed.

  15. The Swift/Fermi GRB 080928 from 1 eV to 150 keV

    NASA Technical Reports Server (NTRS)

    Sonbas, Eda; Rossi, A.; Schulze, S.; Klose, S.; Kann, D. A.; Ferrero, P.; NicuesaGuelbenzu, A.; Rau, A.; Kruehler, T.; Greiner, J.; Schady, P.; Afonso, P. M. J.; Clemens, C.; Filgas, R.; KuepcuYoldas, A.; McBreen, S.; Olivares, F.; Szokoly, G.; Yoldas, A.; Krimm, H. A.; Johannesson, G.; Panaitescu, A.; Yuan, F.; Pandey, S. B.; Akerlof, C. W.

    2010-01-01

    We present the results of a comprehensive study of the Gamma-Ray Burst 080928 and of its afterglow. GRB 08092 was a long burst detected by Swift/BAT and Fermi/GBM, It is one of the exceptional cases where optical emission was already detected when the GRB itself was still radiating in the gamma-ray band. for nearly 100 seconds simultaneous optical X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. Here we analyze the prompt emission, constrain its spectral propertIes. and set lower limits on the initial Lorentz factor of the relativistic outflow, In particular. we show that the SED during the main prompt emission phase is in agreement with synchrotron radiation. We construct the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT. ROTSE-Illa (Australia) and GROND (La Silla) data and compare it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy injections into the forward shock. Furthermore, we provide evidence that the temporal and spectral evolution of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.

  16. The Swift/Fermi GRB 080928 from 1 eV to 150 keV

    NASA Technical Reports Server (NTRS)

    Sonbas, Eda; Rossi, A.; Schulze, S.; Klose, S.; Kann, D. A.; Ferrero, P.; NicuesaGuelbenzu, A.; Rau, A.; Kruehler, T.; Greiner, J.; hide

    2010-01-01

    We present the results of a comprehensive study of the Gamma-Ray Burst 080928 and of its afterglow. GRB 08092 was a long burst detected by Swift/BAT and Fermi/GBM, It is one of the exceptional cases where optical emission was already detected when the GRB itself was still radiating in the gamma-ray band. for nearly 100 seconds simultaneous optical X-ray and gamma-ray data provide a coverage of the spectral energy distribution of the transient source from about 1 eV to 150 keV. Here we analyze the prompt emission, constrain its spectral propertIes. and set lower limits on the initial Lorentz factor of the relativistic outflow, In particular. we show that the SED during the main prompt emission phase is in agreement with synchrotron radiation. We construct the optical/near-infrared light curve and the spectral energy distribution based on Swift/UVOT. ROTSE-Illa (Australia) and GROND (La Silla) data and compare it to the X-ray light curve retrieved from the Swift/XRT repository. We show that its bumpy shape can be modeled by multiple energy injections into the forward shock. Furthermore, we provide evidence that the temporal and spectral evolution of the first strong flare seen in the early X-ray light curve can be explained by large-angle emission. Finally, we report on the results of our search for the GRB host galaxy, for which only a deep upper limit can be provided.

  17. Efficiency of coal use, electricity for EVs versus synfuels for ICEs

    NASA Astrophysics Data System (ADS)

    Mueller, H. G.; Wouk, V.

    1980-02-01

    Data are presented to show how electric vehicles will travel approximately twice as far per ton of coal burned to produce electricity for EV propulsion, than will an ICE vehicle burning the synfuel produced from an equal amount of coal. These figures are based on pessimistic calculations of the efficiencies of electricity generation, transmission, battery charging and EV drivetrains. The synfuel calculations are based on optimistic upper limits of coal conversion efficiency and ICE systems' efficiencies. EVs are less harmful to the environment than conventional vehicles. The emissions from coal-burning power plants are more readily controlled than the pollutants from refineries that convert coal to synfuel. The emissions from EVs are negligible, whereas those from ICEs still have not been reduced to the levels originally mandated for 1976. Synfuels should be reserved mainly for those applications for which electricity is impractical or impossible, such as planes, long-haul trucks and buses, and the petrochemical industry.

  18. A novel method of synthesis of small band gap SnS nanorods and its efficient photocatalytic dye degradation.

    PubMed

    Das, Dipika; Dutta, Raj Kumar

    2015-11-01

    A facile one pot method has been developed for synthesis of stable (ξ=-37.5 mV), orthorhombic structured SnS nanorods capped with mercaptoacetic acid by precipitation method. The SnS nanorods were measured to be about 45 nm long with a diameter of 20 nm, as studied by transmission electron microscopy (TEM). The band gap of the MAA capped SnS nanorods was 1.81 eV, measured by diffused reflectance spectroscopy and was larger than the bulk SnS. The relative positions of highest valence band and lowest conduction band were determined from theoretical band structure calculation as 1.58 eV and -0.23 eV, respectively. The UV-Visible-NIR fluorescence emission spectrum of the SnS nanorods revealed intense emission peak at 1000 nm (1.239 eV) and weaker peaks at 935 nm, 1080 nm, 1160 nm which is likely to be due to Sn(2+) vacancies. The as-synthesized SnS nanorods exhibited more than 95% sunlight induced photocatalytic degradation of trypan blue in 4 h, following first order kinetics with high rate of degradation (k) (0.0124 min(-1)). The observed dye degradation is attributable to generation of reactive oxygen species (ROS), confirmed from terephthalic acid assay. The ROS generation has been explained on the basis of interaction between photoexcited electrons from conduction band with molecular oxygen adhered to the surface of nanorods owing to favourable redox potentials of O2/O2(-) (-0.20 eV) in normal hydrogen electrode (NHE) scale.

  19. Excitation of the Werner bands of H2 by electron impact

    NASA Technical Reports Server (NTRS)

    Stone, E. J.; Zipf, E. C.

    1972-01-01

    Absolute cross sections for the excitation of the H2 Werner band system were measured from energy threshold to 300 eV for electron impact on H2. The bands were observed in emission in the wavelength region 1100A to 1250A. The measured cross sections were compared with published transition probabilities, leading to the conclusion that the Werner bands are suitable as the basis for a relative spectral response calibration only when the bands are observed under sufficiently high resolution. The effect of the perturbation between the C 1Pi u and B 1 Sigma-u states of the hydrogen molecule was clearly observed in anomalies in the rotational intensity distribution in bands of the (3 v '') progression.

  20. Operation of an ungated diamond field-emission array cathode in a L-band radiofrequency electron source

    SciTech Connect

    Piot, P.; Brau, C. A.; Choi, B. K.; Blomberg, B.; Gabella, W. E.; Ivanov, B.; Jarvis, J.; Mendenhall, M. H.; Mihalcea, D.; Panuganti, H.; Prieto, P.; Reid, J.

    2014-06-30

    We report on the first successful operation of a field-emitter-array cathode in a conventional L-band radio-frequency electron source. The cathode consisted of an array of $\\sim 10^6$ diamond diamond tips on pyramids. Maximum current on the order of 15~mA were reached and the cathode did not show appreciable signs of fatigue after weeks of operation. The measured Fowler-Nordheim characteristics, transverse beam density, and current stability are discussed. Numerical simulations of the beam dynamics are also presented.

  1. Enhanced ultraviolet emission and its irreversible temperature antiquenching behavior of twofold coordinated silicon centers in silica glass

    NASA Astrophysics Data System (ADS)

    Nagayoshi, Yu; Uchino, Takashi

    2016-10-01

    It has been well documented that an oxygen divacancy center, or a twofold-coordinated Si center, in silica glass yields a singlet-to-singlet photoluminescence (PL) emission at 4.4 eV with a decay time of ˜4 ns. Although the 4.4-eV PL band is interesting in terms of a deep-ultraviolet light emitter, the emission efficiency has been too low to be considered for a practical application. In this work, we show that a highly luminescent silica glass, with an internal quantum yield of 68% for the 4.4-eV PL band at room temperature, can be prepared when micrometer-sized silica powders are heat treated at ˜1900 °C under inert gas atmosphere by using a high-frequency induction heating unit equipped with a graphite crucible. We also show that the intensity of the 4.4-eV emission in the thus prepared silica glass exhibits an irreversible temperature antiquenching behavior in the temperature region below ˜320 K during heating-cooling cycles. The anomalous temperature dependencies of the 4.4-eV emission can be interpreted in terms of thermally activated trapping-detrapping processes of photoexcited electrons associated with deep trap states.

  2. Secondary Use of PHEV and EV Batteries: Opportunities & Challenges (Presentation)

    SciTech Connect

    Neubauer, J.; Pesaran, A.; Howell, D.

    2010-05-01

    NREL and partners will investigate the reuse of retired lithium ion batteries for plug-in hybrid, hybrid, and electric vehicles in order to reduce vehicle costs and emissions and curb our dependence on foreign oil. A workshop to solicit industry feedback on the process is planned. Analyses will be conducted, and aged batteries will be tested in two or three suitable second-use applications. The project is considering whether retired PHEV/EV batteries have value for other applications; if so, what are the barriers and how can they be overcome?

  3. Highly Efficient Defect Emission from ZnO:Zn and ZnO:S Powders

    NASA Astrophysics Data System (ADS)

    Everitt, Henry

    2013-03-01

    Bulk Zinc Oxide (ZnO) is a wide band gap semiconductor with an ultraviolet direct band gap energy of 3.4 eV and a broad, defect-related visible wavelength emission band centered near 2 eV. We have shown that the external quantum efficiency can exceed 50% for this nearly white emission band that closely matches the human dark-adapted visual response. To explore the potential of ZnO as a rare earth-free white light phosphor, we investigated the mechanism of efficient defect emission in three types of ZnO powders: unannealed, annealed, and sulfur-doped. Annealing and sulfur-doping of ZnO greatly increase the strength of defect emission while suppressing the UV band edge emission. Continuous wave and ultrafast one- and two-photon excitation spectroscopy are used to examine the defect emission mechanism. Low temperature photoluminescence (PL) and PL excitation (PLE) spectra were measured for all three compounds, and it was found that bound excitons mediate the defect emission. Temperature-dependent PLE spectra for the defect and band edge emission were measured to estimate trapping and activation energies of the bound excitons and clarify the role they play in the defect emission. Time-resolved techniques were used to ascertain the role of exciton diffusion, the effects of reabsorption, and the spatial distributions of radiative and non-radiative traps. In unannealed ZnO we find that defect emission is suppressed and UV band edge emission is inefficient (< 2%) because of reabsorption and non-radiative recombination due to a high density of non-radiative bulk traps. By annealing ZnO, bulk trap densities are reduced, and a high density of defects responsible for the broad visible emission are created near the surface. Interestingly, nearly identical PLE spectra are found for both the band edge and the defect emission, one of many indications that the defect emission is deeply connected to bound excitons. Quantum efficiency, also measured as a function of excitation

  4. Visible-ultraviolet vibronic emission of silica nanoparticles.

    PubMed

    Spallino, Luisa; Vaccaro, Lavinia; Sciortino, Luisa; Agnello, Simonpietro; Buscarino, Gianpiero; Cannas, Marco; Gelardi, Franco Mario

    2014-10-28

    We report the study of the visible-ultraviolet emission properties and the structural features of silica nanoparticles prepared through a laboratory sol-gel technique. Atomic force microscopy, Raman and Infrared investigations highlighted the 10 nm size, purity and porosity of the obtained nanoparticles. By using time resolved photoluminescence techniques in air and in a vacuum we were able to single out two contributions in the visible emission: the first, stable in both atmospheres, is a typical fast blue band centered around 2.8 eV; the second, only observed in a vacuum around the 3.0-3.5 eV range, is a vibrational progression with two phonon modes at 1370 cm(-1) and 360 cm(-1). By fully characterizing the spectroscopic features of this structured emission, we determine its vibronic properties and clarify the different origins with respect to the blue luminescent defect.

  5. Size/morphology induced tunable luminescence in upconversion crystals: ultra-strong single-band emission and underlying mechanisms

    NASA Astrophysics Data System (ADS)

    Wang, Zhaofeng; Zeng, Songshan; Yu, Jingfang; Ji, Xiaoming; Zeng, Huidan; Xin, Shuangyu; Wang, Yuhua; Sun, Luyi

    2015-05-01

    In this work, we present a two-step method to controllably synthesize novel and highly efficient upconversion materials, Lu5O4F7:Er3+,Yb3+ nano/micro-crystals, and investigate their size/morphology induced tunable upconversion properties. In addition to the common phenomenon aroused by a surface quenching effect, direct experimental evidence for the regulation of phonon modes is obtained in nanoparticles. The findings in this work advance the existing mechanisms for the general explanation of size/morphology induced upconversion features. Because of the adjustment of phonon energy and density as well as the surface quenching effect, the biocompatible Lu5O4F7:Er3+,Yb3+ nanoparticles exhibit an ultra-strong single-band red upconversion, rendering them promising for biomedical applications.In this work, we present a two-step method to controllably synthesize novel and highly efficient upconversion materials, Lu5O4F7:Er3+,Yb3+ nano/micro-crystals, and investigate their size/morphology induced tunable upconversion properties. In addition to the common phenomenon aroused by a surface quenching effect, direct experimental evidence for the regulation of phonon modes is obtained in nanoparticles. The findings in this work advance the existing mechanisms for the general explanation of size/morphology induced upconversion features. Because of the adjustment of phonon energy and density as well as the surface quenching effect, the biocompatible Lu5O4F7:Er3+,Yb3+ nanoparticles exhibit an ultra-strong single-band red upconversion, rendering them promising for biomedical applications. Electronic supplementary information (ESI) available: Crystal structure analysis, UV-Vis absorption spectra, SEM micrographs, surface micro-structure investigation, biocompatibility of Lu5O4F7: Er3+, Yb3+, as well as morphology and upconversion properties of the control sample NaYF4: Er3+, Yb3+. See DOI: 10.1039/c5nr01008j

  6. Ks-band Detection of Thermal Emission and Color Constraints to the Hot Jupiter CoRoT-1b

    NASA Astrophysics Data System (ADS)

    Rogers, Justin; Apai, D.; Lopez-Morales, M.; Sing, D.; Burrows, A.; Sterzik, M.

    2010-01-01

    We report the detection in Ks-band of the secondary eclipse of the hot Jupiter CoRoT-1b, from time series photometry with the ARC 3.5-m telescope at Apache Point Observatory. The eclipse shows a depth of 0.336 +/- 0.042 percent, and is centered at a phase consistent with a circular orbit. We then perform the first optical to near-infrared multi-band photometric analysis of an exoplanet's atmosphere by combining our result with the recent 0.6, 0.71, and 2.09 micron eclipse detections by Snellen et al. (2009), Gillon et al. (2009), and Alonso et al. (2009). Comparing the multi-wavelength detections to state-of-the-art radiative-convective chemical equilibrium atmosphere models, we find the near-infrared fluxes difficult to reproduce. The best physical model suggests a thermal inversion layer with an extra optical absorber of opacity kappae = 0.05 cm2 g-1 placed near the 0.1-bar atmospheric pressure level, ten times deeper in the atmosphere than the absorbers used in models to fit mid-infrared Spitzer detections of other irradiated hot Jupiters. We also present and discuss preliminary results from secondary eclipse observations of other planets. We are grateful for the critical support provided by the Space Telescope Science Institute Director's Discretionary Research Fund D0101.90131, Hubble Fellowship grant HF-01210.01-A, CNES, NASA grant NNX07AG80G, and National Science Foundation grant AST-0908278.

  7. HIGH-RESOLUTION ELECTRON-IMPACT EMISSION SPECTRA AND VIBRATIONAL EMISSION CROSS SECTIONS FROM 330-1100 nm FOR N{sub 2}

    SciTech Connect

    Mangina, Rao S.; Ajello, Joseph M.; West, Robert A.; Dziczek, Dariusz

    2011-09-01

    Electron-impact emission cross sections for N{sub 2} were measured in the wavelength range of 330-1100 nm at 25 eV and 100 eV impact energies. Cross sections of several molecular emission bands of the first positive band system B {sup 3}{Pi}{sub g} {sup +}({nu}') {yields} A {sup 3}{Sigma}{sub g} {sup +}({nu}'') and the second positive band system C {sup 3}{Pi}{sub u} ({nu}') {yields} B {sup 3}{Pi}{sub g} ({nu}'') of N{sub 2}, the first negative band (1NB) system B {sup 2}{Sigma}{sub u} {sup +}({nu}') {yields} X {sup 2}{Sigma}{sub g} {sup +}({nu}'') and Meinel band system A {sup 2}{Pi}{sub u} ({nu}') {yields} X {sup 2}{Sigma}{sub g} {sup +}({nu}'') of N{sub 2} {sup +} ions as well as line emissions of N (N I) and N{sup +} (N II) in the visible-optical-near-IR wavelength range reported in this work were measured for the first time in a single experimental setup at high spectral resolving power ({lambda}/{Delta}{lambda} {approx} 10000) under single-collision-scattering geometry and optically thin conditions. Rotational emission lines of N{sub 2} and N{sub 2} {sup +} were observed for strong emission bands at a gas temperature of about 300 K. The absolute cross section of the strongest (0,0) vibrational band at 391.43 nm of 1NB was determined using the standard H{sub {alpha}} emission cross sections of H{sub 2} by electron impact at both 25 eV and 100 eV electron-impact energies, and the cross sections for the remainder of the emissions were determined using (0,0) 1NB value. A comparison of the present emission cross sections with the earlier published data from both electron energy loss and electron-impact-induced fluorescence emission is discussed.

  8. Broad-Band Continuum and Line Emission of the gamma-Ray Blazar PKS 0537-441

    NASA Technical Reports Server (NTRS)

    Pian, E.; Falomo, R.; Hartman, R. C.; Maraschi, L.; Tavecchio, F.; Tornikoski, M.; Treves, A.; Urry, C. M.; Ballo, L.; Mukherjee, R.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    PKS 0537-441, a bright gamma ray emitting blazar was observed at radio, optical, UV and X-ray frequencies during various EGRET paintings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all wavelengths. BeppoSAX observations made in 1998, non-simultaneously with exposures at other frequencies, allow us to characterize precisely the spectral shape of the high energy blazer component, which we attribute to inverse Compton scatter in The optical-to-gamma-ray spectral energy distributions at the different epochs show that the gamma-ray luminosity dominates the barometric output. This, together with the presence of optical and UV line emission, suggests that, besides the synchrotron self-Compton mechanism, the Compton upscattering of photons external to the jet (e.g., in the broad line region) may have a significant role for high energy radiation. The multiwavelength variability can be reproduced by changes of the plasma bulk Lorentz factor. The spectrum secured by ICE in 1995 appears to be partially absorbed shortward of approximately 1700 Angstroms. However, this signature is not detected in the HST spectrum taker during a lower state of the source. The presence of intervening absorbers is not supported by optical imaging and spectroscopy of the field.

  9. Confinement effect of laser ablation plume in liquids probed by self-absorption of C{sub 2} Swan band emission

    SciTech Connect

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

    2005-01-01

    The (0,0) Swan band of the C{sub 2} molecules in a laser ablation plume produced on the surface of graphite target submerged in water was used as a probe to estimate the density of C{sub 2} molecules in the plume. Observed emission spectra were reproduced excellently by introducing a self-absorption parameter to the theoretical spectral profile expected by a rotational population distribution at a certain temperature. The optical density of the ablation plume as a function of time was determined as a best-fit parameter by the quantitative fitting of the whole spectral profile. The results show high optical densities for the laser ablation plume in water compared with that in air. It is related to the plume confinement or the expansion, which are the important phenomena influencing the characteristics of laser ablation plumes in liquids.

  10. Capture, storage, and emission of holes in Si/Si 1- xGe x/Si QW's for the determination of the valence band offset by DLTS

    NASA Astrophysics Data System (ADS)

    Chretien, O.; Apetz, R.; Vescan, L.; Souifi, A.; Lüth, H.

    1996-08-01

    We report on the problem of the determination of the valence band offset between strained Si 1- xGe x and unstrained Si layers by deep level transient spectroscopy (DLTS) on Si/Si 1- xGe x/Si quantum well (QW) structures. To observe a DLTS signal, the holes must be stored long enough (>1 ms) in the QW so that the thermal emission is the dominating process. We achieved sufficiently long storage times by using two different structures. The first one was obtained by selective growth which leads to a lateral limitation of the QW-layer, where the holes are localized. For the second ones, the localization of holes is due to the presence of Si 1- xGe x-islands.

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

    PubMed

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

    2016-09-08

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

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

    SciTech Connect

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

    2012-09-01

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

  13. Photoelectron Emission Studies in CsBr at 257 nm

    SciTech Connect

    Maldonado, Juan R.; Liu, Zhi; Sun, Yun; Pianetta, Piero A.; Pease, Fabian W.; /Stanford U., Elect. Eng. Dept. /SLAC, SSRL

    2006-09-28

    CsBr/Cr photocathodes were found [1,2] to meet the requirements of a multi-electron beam lithography system operating with a light energy of 4.8 eV (257nm). The fact that photoemission was observed with a light energy below the reported 7.3 eV band gap for CsBr was not understood. This paper presents experimental results on the presence of intra-band gap absorption sites (IBAS) in CsBr thin film photo electron emitters, and presents a model based on IBAS to explain the observed photoelectron emission behavior at energies below band gap. A fluorescence band centered at 330 nm with a FWHM of about 0.34 eV was observed in CsBr/Cr samples under 257 nm laser illumination which can be attributed to IBAS and agrees well with previously obtained synchrotron photoelectron spectra[1] from the valence band of CsBr films.

  14. Role of oxygen vacancies on light emission mechanisms in SrTiO3 induced by high-energy particles

    DOE PAGES

    Crespillo, M. L.; Graham, J. T.; Agulló-López, F.; ...

    2017-02-23

    Light emission under MeV hydrogen and oxygen ions in stoichiometric SrTiO3 are identified at temperatures of 100 K, 170 K and room-temperature. MeV ions predominately deposit their energies to electrons in SrTiO3 with energy densities orders of magnitude higher than from UV or x-ray sources but comparable to femtosecond lasers. The ionoluminescence (IL) spectra can be resolved into three main Gaussian bands at 2.0 eV, 2.5 eV and 2.8 eV, whose relative contributions strongly depend on irradiation temperature, electronic energy loss and irradiation fluence. Two main bands, observed at 2.5 eV and 2.8 eV, are intrinsic and associated with electron–holemore » recombination in the perfect SrTiO3 lattice. The 2.8 eV band is attributed to recombination of free (conduction) electrons with an in-gap level, possibly related to self-trapped holes. Self-trapped excitons (STEs) are considered suitable candidates for the 2.5 eV emission band, which implies a large energy relaxation in comparison to the intrinsic edge transition. The dynamics of electronic excitation, governs a rapid initial rise of the intensity; whereas, accumulated irradiation damage (competing non-radiative recombination channels) accounts for a subsequent intensity decrease. The previously invoked role of isolated oxygen vacancies for the blue luminescence (2.8 eV) does not appear consistent with the data. An increasing well-resolved band at 2.0 eV dominates at 170 K and below. It has been only previously observed in heavily strained and amorphous SrTiO3, and is, here, attributed to transitions from d(t 2g) conduction band levels to d(e g) levels below the gap. In accordance with ab initio theoretical calculations they are associated to trapped electron states in relaxed Ti3+ centers at an oxygen vacancy within distorted TiO6 octahedra. The mechanism of defect evolution monitored during real-time IL experiments is presented. In conclusion, the light emission data confirm that IL is a useful tool to

  15. How much are Chevrolet Volts in The EV Project driven in EV Mode?

    SciTech Connect

    John Smart

    2013-08-01

    This report summarizes key conclusions from analysis of data collected from Chevrolet Volts participating in The EV Project. Topics include how many miles are driven in EV mode, how far vehicles are driven between charging events, and how much energy is charged from the electric grid per charging event.

  16. Model development for MODIS thermal band electronic cross-talk

    NASA Astrophysics Data System (ADS)

    Chang, Tiejun; Wu, Aisheng; Geng, Xu; Li, Yonghong; Brinkmann, Jake; Keller, Graziela; Xiong, Xiaoxiong (Jack)

    2016-10-01

    MODerate-resolution Imaging Spectroradiometer (MODIS) has 36 bands. Among them, 16 thermal emissive bands covering a wavelength range from 3.8 to 14.4 μm. After 16 years on-orbit operation, the electronic crosstalk of a few Terra MODIS thermal emissive bands develop substantial issues which cause biases in the EV brightness temperature measurements and surface feature contamination. The crosstalk effects on band 27 with center wavelength at 6.7 μm and band 29 at 8.5 μm increased significantly in recent years, affecting downstream products such as water vapor and cloud mask. The crosstalk issue can be observed from nearly monthly scheduled lunar measurements, from which the crosstalk coefficients can be derived. Most of MODIS thermal bands are saturated at moon surface temperatures and the development of an alternative approach is very helpful for verification. In this work, a physical model was developed to assess the crosstalk impact on calibration as well as in Earth view brightness temperature retrieval. This model was applied to Terra MODIS band 29 empirically for correction of Earth brightness temperature measurements. In the model development, the detector nonlinear response is considered. The impacts of the electronic crosstalk are assessed in two steps. The first step consists of determining the impact on calibration using the on-board blackbody (BB). Due to the detector nonlinear response and large background signal, both linear and nonlinear coefficients are affected by the crosstalk from sending bands. The crosstalk impact on calibration coefficients was calculated. The second step is to calculate the effects on the Earth view brightness temperature retrieval. The effects include those from affected calibration coefficients and the contamination of Earth view measurements. This model links the measurement bias with crosstalk coefficients, detector nonlinearity, and the ratio of Earth measurements between the sending and receiving bands. The correction

  17. Carriers of the mid-IR emission bands in PNe reanalysed. Evidence of a link between circumstellar and interstellar aromatic dust

    NASA Astrophysics Data System (ADS)

    Joblin, C.; Szczerba, R.; Berné, O.; Szyszka, C.

    2008-10-01

    Context: It has been shown that the diversity of the aromatic emission features can be rationalized into different classes of objects, in which differences between circumstellar and interstellar matter are emphasised. Aims: We probe the links between the mid-IR emitters observed in planetary nebulae (PNe) and their counterparts in the interstellar medium in order to probe a scenario in which the latter have been formed in the circumstellar environment of evolved stars. Methods: The mid-IR (6-14 μm) emission spectra of PNe and compact H II regions were analysed on the basis of previous work on photodissociation regions (PDRs). Galactic, Large Magellanic Cloud (LMC), and Small Magellanic Cloud (SMC) objects were considered in our sample. Results: We show that the mid-IR emission of PNe can be decomposed as the sum of six components. Some components made of polycyclic aromatic hydrocarbon (PAH) and very small grain (VSG) populations are similar to those observed in PDRs. Others are fitted in an evolutionary scenario involving the destruction of the aliphatic component observed in the post-AGB stage, as well as strong processing of PAHs in the extreme conditions of PNe that leads to a population of very large ionized PAHs. This species called PAHx are proposed as the carriers of a characteristic band at 7.90 μm. This band can be used as part of diagnostics that identify PNe in nearby galaxies and is also observed in galactic compact H II regions. Conclusions: These results support the formation of the aromatic very small dust particles in the envelopes of evolved stars, in the Milky Way, as well as in the LMC and SMC, and their subsequent survival in the interstellar medium. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the

  18. [Spectral properties of broad emission bands of Cr3+ in A3M2Ge3O12 (A = Cd2+, Ca2+; M = AI3+, Ga3+, Sc3+) garnets].

    PubMed

    Liu, X; Zhang, X; Huang, L; Yuan, J

    1999-08-01

    The spectral properties of the Cr3+ broad emission band in A3M2Ge3O2 : Cr(A = Cd2+ ,Ca3+; M = Al3+,Ga3+,Sc3+) germanate garnets at room temperature are reported for the first time. In the order of Al3+ --> Ga3+ --> Sc3+ and Cd2+ --> C2z+ ions which occupy the octahedral and duodeahedral sites, respectively, R-NIR broad emission band of 4T2 --> 4A2 level transition, emission peak, and the spectral long wavelength and short wavelength sides of Cr3+ shift to long wavelengths having lower energy. The reason is that the crystal field strengths in the octahedral decrease, while the cation ionic radii in the A3M2Ge3O12 system garnets increase gradually. The R-NIR emission intensity of Cr3+ is increased with some Sc3+ ions substitution for Al3+ or Ga3+ ions in octahedral sites.

  19. EV71 vaccine, an invaluable gift for children.

    PubMed

    Liang, Zhenglun; Wang, Junzhi

    2014-10-01

    Enterovirus 71 (EV71) is a major pathogen for severe hand, foot and mouth disease (HFMD). Development of vaccines against EV71 would be the most effective approach to prevent the EV71 outbreak. Research and development (R&D) of EV71 vaccine was carried out in several Asian countries. Currently three companies in mainland China have completed Phase III clinical trials of inactivated EV71 whole-virus vaccines, whereas the other two companies have completed Phase I clinical trials separately in Taiwan and in Singapore. Results from those clinical trials have indicated high safety and immunogenicity of EV71 vaccine. Protective efficacies were over 90% on EV71-associated HFMD and over 80% on other EV71-associated diseases. In this paper, we summarize the results from three EV71 vaccine Phase III clinical trials and discuss the challenges of incorporating EV71 vaccine into Expanded Program on Immunization (EPI) in countries with EV71 epidemics.

  20. EV71 vaccine, an invaluable gift for children

    PubMed Central

    Liang, Zhenglun; Wang, Junzhi

    2014-01-01

    Enterovirus 71 (EV71) is a major pathogen for severe hand, foot and mouth disease (HFMD). Development of vaccines against EV71 would be the most effective approach to prevent the EV71 outbreak. Research and development (R&D) of EV71 vaccine was carried out in several Asian countries. Currently three companies in mainland China have completed Phase III clinical trials of inactivated EV71 whole-virus vaccines, whereas the other two companies have completed Phase I clinical trials separately in Taiwan and in Singapore. Results from those clinical trials have indicated high safety and immunogenicity of EV71 vaccine. Protective efficacies were over 90% on EV71-associated HFMD and over 80% on other EV71-associated diseases. In this paper, we summarize the results from three EV71 vaccine Phase III clinical trials and discuss the challenges of incorporating EV71 vaccine into Expanded Program on Immunization (EPI) in countries with EV71 epidemics. PMID:25505956

  1. Smart cards for EV billing. Final report

    SciTech Connect

    1998-05-01

    If electric vehicles are to gain widespread popularity, there will need to be public charging stations for refueling away from home. However, public charging raises some potentially complex issues regarding how individual EV owners will be billed for the electricity they use. It`s easy enough to meter the electricity used at a given battery charger, but the utility bill goes to the EV station merchant rather than the driver who consumed the electricity. So far this has not posed a problem, as many early charging sites have either been providing free electricity or billing only nominal flat fees. As the EV market grows, however, an effective point-of-sale (POS) billing mechanism will need to be established. In 1993, an investigation of POS billing systems for different types of non-home EV charging was conducted. Recently, the Cost Subcommittee of the Infrastructure Working Council`s (IWC) Load Management, Distribution, Power Quality Committee requested that an update be performed on the newest of these POS technologies--smart cards. The same size and shape as regular credit cards, smart cards use a microchip instead of a magnetic stripe to store information. The chip can hold significantly more information than a magnetic stripe, enabling greater security and flexible applications. Since 1993, there have been major advances in smart card technology, and smart card use has grown dramatically in both Europe and Asia. The US has been slower to embrace smart cards due to the entrenched infrastructure of traditional magnetic stripe credit cards. This paper reviews smart card technology and related POS transaction structures, and assesses the technical feasibility and economics of using these versatile cards for EV billing.

  2. Effect of the chemical impurities on the luminescence emission of natural apatites.

    PubMed

    Roman-Lopez, J; Correcher, V; Garcia-Guinea, J; Prado-Herrero, P; Rivera, T; Lozano, I B

    2014-05-21

    This paper reports on both cathodoluminescence (CL) and blue thermoluminescence (TL) emission of well-characterized natural Spanish and Brazilian apatites [Ca5(PO4)3(OH, F, Cl)]. Chemical analyses performed by means of Electron Microprobe Analysis (EMPA) have shown the presence of trace elements that can induce CL bands. In this sense, the apatites shown emission bands peaked at 3.26, 2.86, 2.62, 2.14, 2.02 and 1.94eV are respectively linked to substitutional Ce(3+), Tb(3+), Dy(3+), Pr(3+), Sm(3+) and Mn(2+) in structural Ca(2+) positions. The 3.18eV emission band can be associated with intrinsic electron defects on oxygen of the phosphate group (PO4)(3-). The presence of (UO2)(2+) gives rise to an emission at 2.14eV. All the studied aliquots exhibit one single UV-blue TL peak that modifies the position from one sample to another (370, 256 and 268°C) probably due to (i) the variation in the crystallinity index (from 0.88 to 1.34) and (ii) successive chemical processes such as oxidation, dehydration, dehydroxylation, and fluorine ions losses due to the thermal readout.

  3. Effect of the chemical impurities on the luminescence emission of natural apatites

    NASA Astrophysics Data System (ADS)

    Roman-Lopez, J.; Correcher, V.; Garcia-Guinea, J.; Prado-Herrero, P.; Rivera, T.; Lozano, I. B.

    This paper reports on both cathodoluminescence (CL) and blue thermoluminescence (TL) emission of well-characterized natural Spanish and Brazilian apatites [Ca5(PO4)3(OH, F, Cl)]. Chemical analyses performed by means of Electron Microprobe Analysis (EMPA) have shown the presence of trace elements that can induce CL bands. In this sense, the apatites shown emission bands peaked at 3.26, 2.86, 2.62, 2.14, 2.02 and 1.94 eV are respectively linked to substitutional Ce3+, Tb3+, Dy3+, Pr3+, Sm3+ and Mn2+ in structural Ca2+ positions. The 3.18 eV emission band can be associated with intrinsic electron defects on oxygen of the phosphate group (PO4)3-. The presence of (UO2)2+ gives rise to an emission at 2.14 eV. All the studied aliquots exhibit one single UV-blue TL peak that modifies the position from one sample to another (370, 256 and 268 °C) probably due to (i) the variation in the crystallinity index (from 0.88 to 1.34) and (ii) successive chemical processes such as oxidation, dehydration, dehydroxylation, and fluorine ions losses due to the thermal readout.

  4. Model Development for MODIS Thermal Band Electronic Crosstalk

    NASA Technical Reports Server (NTRS)

    Chang, Tiejun; Wu, Aisheng; Geng, Xu; Li, Yonghonh; Brinkman, Jake; Keller, Graziela; Xiong, Xiaoxiong

    2016-01-01

    MODerate-resolution Imaging Spectroradiometer (MODIS) has 36 bands. Among them, 16 thermal emissive bands covering a wavelength range from 3.8 to 14.4 m. After 16 years on-orbit operation, the electronic crosstalk of a few Terra MODIS thermal emissive bands developed substantial issues that cause biases in the EV brightness temperature measurements and surface feature contamination. The crosstalk effects on band 27 with center wavelength at 6.7 m and band 29 at 8.5 m increased significantly in recent years, affecting downstream products such as water vapor and cloud mask. The crosstalk effect is evident in the near-monthly scheduled lunar measurements, from which the crosstalk coefficients can be derived. The development of an alternative approach is very helpful for independent verification.In this work, a physical model was developed to assess the crosstalk impact on calibration as well as in Earth view brightness temperature retrieval. This model was applied to Terra MODIS band 29 empirically to correct the Earth brightness temperature measurements. In the model development, the detectors nonlinear response is considered. The impact of the electronic crosstalk is assessed in two steps. The first step consists of determining the impact on calibration using the on-board blackbody (BB). Due to the detectors nonlinear response and large background signal, both linear and nonlinear coefficients are affected by the crosstalk from sending bands. The second step is to calculate the effects on the Earth view brightness temperature retrieval. The effects include those from affected calibration coefficients and the contamination of Earth view measurements. This model links the measurement bias with crosstalk coefficients, detector non-linearity, and the ratio of Earth measurements between the sending and receiving bands. The correction of the electronic cross talk can be implemented empirically from the processed bias at different brightness temperature. The implementation

  5. Strong Deep-Level-Emission Photoluminescence in NiO Nanoparticles.

    PubMed

    Gandhi, Ashish Chhaganlal; Wu, Sheng Yun

    2017-08-22

    Nickel oxide is one of the highly promising semiconducting materials, but its large band gap (3.7 to 4 eV) limits its use in practical applications. Here we report the effect of nickel/oxygen vacancies and interstitial defects on the near-band-edge (NBE) and deep-level-emission (DLE) in various sizes of nickel oxide (NiO) nanoparticles. The ultraviolet (UV) emission originated from excitonic recombination corresponding near-band-edge (NBE) transition of NiO, while deep-level-emission (DLE) in the visible region due to various structural defects such as oxygen vacancies and interstitial defects. We found that the NiO nanoparticles exhibit a strong green band emission around ~2.37 eV in all samples, covering 80% integrated intensity of PL spectra. This apparently anomalous phenomenon is attributed to photogenerated holes trapped in the deep level oxygen vacancy recombining with the electrons trapped in a shallow level located just below the conducting band.

  6. Direct band gap carbon superlattices with efficient optical transition

    NASA Astrophysics Data System (ADS)

    Oh, Young Jun; Kim, Sunghyun; Lee, In-Ho; Lee, Jooyoung; Chang, K. J.

    2016-02-01

    We report pure carbon-based superlattices that exhibit direct band gaps and excellent optical absorption and emission properties at the threshold energy. The structures are nearly identical to that of cubic diamond except that defective layers characterized by five- and seven-membered rings are intercalated in the diamond lattice. The direct band gaps lie in the range of 5.6-5.9 eV, corresponding to wavelengths of 210-221 nm. The dipole matrix elements of direct optical transition are comparable to that of GaN, suggesting that the superlattices are promising materials as an efficient deep ultraviolet light emitter. Molecular dynamics simulations show that the superlattices are thermally stable even at a high temperature of 2000 K. We provide a possible route to the synthesis of superlattices through wafer bonding of diamond (100) surfaces.

  7. Dimensional Reduction of a Layered Metal Chalcogenide into a 1D Near-IR Direct Band Gap Semiconductor

    SciTech Connect

    Liu, Yi-Hsin; Porter, Spencer H.; Goldberger, Joshua E.

    2012-07-24

    Reducing the dimensionality of inorganic lattices allows for the creation of new materials that have unique optoelectronic properties. We demonstrate that a layered metal chalcogenide lattice, TiS{sub 2}, can form a dimensionally reduced crystalline one-dimensional hybrid organic/inorganic TiS{sub 2}(ethylenediamine) framework when synthesized from molecular precursors in solution. This solid has strong absorption above 1.70 eV and pronounced emission in the near-IR regime. The energy dependence of the absorption, the near-IR photoluminescence, and electronic band structure calculations confirm that TiS{sub 2}(ethylenediamine) has a direct band gap.

  8. Enhanced 2 μm broad-band emission and NIR to visible frequency up-conversion from Ho3+/Yb3+ co-doped Bi2O3-GeO2-ZnO glasses.

    PubMed

    Biswas, Kaushik; Sontakke, Atul D; Sen, R; Annapurna, K

    2013-08-01

    In this work, a new and non-conventional oxide glass composition based on Bi2O3-GeO2-ZnO system has been formulated with an aim to realize low phonon oxide glass and elucidate its performance when co-doped with Ho(3+)/Yb(3+) for the energy transfer based NIR emission at 2 μm from Ho(3+) ions under Yb(3+) excitation. The glass with 1.0 mol% Ho2O3 and 0.5 mol% Yb2O3 has exhibited maximum energy transfer rate (3602 s(-1)) and energy transfer efficiency (65.92%). Important radiative properties have been predicted for emission transitions of Ho(3+) ions using intensity parameters derived from measured absorption spectra using standard Judd-Ofelt theory. At lower acceptor ion concentration (0.1 mol%), an efficient NIR to visible up-conversion emission has been observed based on two photon absorption process which has found to be reduced significantly at higher Ho(3+) concentrations with simultaneous enhancement in 2 μm emission. Hence, this newly developed glass codoped with Yb(3+)/Ho(3+) is promising glass for sensitized 2 μm emission applications as broad band tunable lasers because of the combination of low phonon energy (707 cm(-1)), high energy transfer efficiency, moderately high emission cross-section (5.33×10(-21) cm(2)) and larger effective half-width of the emission band value of 169 nm.

  9. How Do The EV Project Participants Feel about Charging Their EV at Home?

    SciTech Connect

    Francfort, James E.

    2015-02-01

    Key Observations from the Survey of the EV Project Participants; In June 2013, 72% of EV Project participants were very satisfied with their home charging experience; 21% of participants relied totally on home charging for all of their charging needs; Volt owners relied more on home charging than Leaf owners, who reported more use of away-from-home charging; 74% of participants reported that they plug in their plug-in electric vehicle (PEV) every time they park at home. Others plugged in as they determined necessary to support their driving needs; 40% of participants reported that they would not have or are unsure that in June 2013 whether they would have purchased an alternating current (AC) Level 2 electric vehicle supply equipment (EVSE) for home charging if it had not been provided by The EV Project; and 61% of participants reported that The EV Project incentive was very important or important in their decision to obtain a PEV.

  10. An Optical Megaflare On EV Lac

    NASA Astrophysics Data System (ADS)

    Pettersen, B. R.

    2016-07-01

    We present a U-filter light curve of a very intensive flare on EV Lac, observed at 1 s time resolution with a 2 m telescope at BNAO. The monitoring lasted for 7.4 hours (UT 16:40-UT 24:04) on 01 November 1991, and EV Lac was affected by flaring throughout this time. The data have been corrected for atmospheric extinction and the presence of an optical companion in the photometer diaphragm.A ΔU=7.2 magnitude flare maximum (Lf,U = 4.6 · 1031 ergs s-1) represents an increase of 735 times the flux of the quiescent star. This is twice as large as a flare reported by Roizman and Shevchenko (1982, Sov. Astron. Lett. 8, 85-86) and is 88% of the bolometric luminosity of EV Lac. The eruptive phase of the rise took 72 seconds, and the flare returned to half its maximum value in t0.5 = 39 seconds. The classically peak-shaped flare went into a slow decay phase after about 20 minutes. Several secondary flares were superposed on the > 5 hours decay. The U-filter flare energy released during the major peak was 7.23 · 1033 ergs. It accounts for 93% of the energy released during the entire flare event (EU = 7.8 · 1033 ergs).The flare occurred close to maximum brightness of the 4.4 days rotational modulation of EV Lac, which had a V-amplitude 0.06 mag in 1991.

  11. Role of nonemissive quenchers for the green emission in polyfluorene.

    PubMed

    Liu, Linlin; Lu, Ping; Xie, Zengqi; Wang, Huiping; Tang, Shi; Wang, Zhiming; Zhang, Wu; Ma, Yuguang

    2007-09-13

    The stability of fluorene-based compounds and polymers, especially at the bridged C-9 position under photoirradiation and thermal treatment, has claimed much attention. The emission of fluorenone formed by degradation of the 9-site is regarded as the origin of the low emission band at 2.2-2.3 eV in polyfluorene-based conjugated materials. We have investigated the role of nonemissive quenchers such as alkyl ketones, which were also one of the products of polyfluorene degradation, for the low-energy emission in polyfluorenes. The spectral characteristics of a blend system of polyfluorene/nonemissive quencher/fluorenone are found to accord well with the kinetics of actual polyfluorene degradation. Our results indicate that strong green emission in degraded polyfluorene would be not caused only by fluorenone, but also by nonemissive quenchers for their effectively quenching bulk emission.

  12. Yellow luminescence band in undoped GaN revealed by two-wavelength excited photoluminescence

    NASA Astrophysics Data System (ADS)

    Julkarnain, M.; Kamata, N.; Fukuda, T.; Arakawa, Y.

    2016-10-01

    The below-gap emission components including yellow luminescence (YL) band of an MOCVD grown undoped GaN have been studied by the two-wavelength-excited photoluminescence (TWEPL). The nature of each emission line has been investigated by using an intermittent below-gap excitation (BGE) light of 1.17 eV on an above-gap excitation (AGE) light of 3.49 eV. The intensity of DAP and the YL decreased while it increased for IOX after irradiation of the BGE. The intensity change in PL after addition of the BGE implies the presence of defect levels in the energy position corresponding to the photon energy of the BGE. Possible recombination models are listed and examined. Only the recombination model in which the YL corresponds to the transition from a shallow donor to a deep state at about 1 eV above the valence band maximum satisfies our experimental result. The possible origin of this defect state is discussed.

  13. Development of a Remote Sensing Small Satellite for Temperature Sounding in the Mesosphere/Lower Thermosphere by Measurement of the Oxygen Atmospheric Band Emission

    NASA Astrophysics Data System (ADS)

    Deiml, Michael; Kaufmann, Martin

    2017-04-01

    Coupling processes initiated by gravity waves in the middle atmosphere have increasing importance for the modeling of the climate system and represent one of the larger uncertainties in this field. To support new modeling efforts spatially resolved measurements of wave fields are very beneficial. This contribution proposes a new small satellite mission based on a three unit CubeSat form factor to observe the Oxygen Atmospheric Band emission around 762 nm for temperature derivation in a limb sounding configuration to characterize gravity waves. The satellite instrument resolves individual rotational lines whose intensities follow a Boltzmann law allowing for the derivation of temperature from the relative structure of these lines. The employed Spatial Heterodyne Spectrometer is characterized by its high throughput at a small form factor, allowing to perform scientific remote sensing measurements within a small satellite during day and night. The spectrometer consists of a thermally stabilized solid block and has no moving parts, which increases its reliability in orbit while allowing high precision measurements within a small volume. The instrument is verified in its precursor mission, the Atmospheric Heterodyne Interferometer Test (AtmoHIT), within the REXUS/BEXUS ballistic rocket flight campaign. The description of the flight campaign and the results thereof conclude this contribution.

  14. Inter-Comparison of S-NPP VIIRS and Aqua MODIS Thermal Emissive Bands Using Hyperspectral Infrared Sounder Measurements as a Transfer Reference

    NASA Technical Reports Server (NTRS)

    Li, Yonghong; Wu, Aisheng; Xiong, Xiaoxiong

    2016-01-01

    This paper compares the calibration consistency of the spectrally-matched thermal emissive bands (TEB) between the Suomi National Polar-orbiting Partnership (S-NPP) Visible Infrared Imaging Radiometer Suite (VIIRS) and the Aqua Moderate Resolution Imaging Spectroradiometer (MODIS), using observations from their simultaneous nadir overpasses (SNO). Nearly-simultaneous hyperspectral measurements from the Aqua Atmospheric Infrared Sounder(AIRS) and the S-NPP Cross-track Infrared Sounder (CrIS) are used to account for existing spectral response differences between MODIS and VIIRS TEB. The comparison uses VIIRS Sensor Data Records (SDR) in MODIS five-minute granule format provided by the NASA Land Product and Evaluation and Test Element (PEATE) and Aqua MODIS Collection 6 Level 1 B (L1B) products. Each AIRS footprint of 13.5 km (or CrIS field of view of 14 km) is co-located with multiple MODIS (or VIIRS) pixels. The corresponding AIRS- and CrIS-simulated MODIS and VIIRS radiances are derived by convolutions based on sensor-dependent relative spectral response (RSR) functions. The VIIRS and MODIS TEB calibration consistency is evaluated and the two sensors agreed within 0.2 K in brightness temperature.Additional factors affecting the comparison such as geolocation and atmospheric water vapor content are also discussed in this paper.

  15. Interfacially Al-doped ZnO nanowires: greatly enhanced near band edge emission through suppressed electron-phonon coupling and confined optical field.

    PubMed

    Wu, Yiming; Dai, Yanmeng; Jiang, Shenlong; Ma, Chao; Lin, Yue; Du, Dongxue; Wu, Yukun; Ding, Huaiyi; Zhang, Qun; Pan, Nan; Wang, Xiaoping

    2017-04-05

    Aluminium (Al)-doped zinc oxide (ZnO) nanowires (NWs) with a unique core-shell structure and a Δ-doping profile at the interface were successfully grown using a combination of chemical vapor deposition re-growth and few-layer AlxOy atomic layer deposition. Unlike the conventional heavy doping which degrades the near-band-edge (NBE) luminescence and increases the electron-phonon coupling (EPC), it was found that there was an over 20-fold enhanced NBE emission and a notably-weakened EPC in this type of interfacially Al-doped ZnO NWs. Further experiments revealed a greatly suppressed nonradiative decay process and a much enhanced radiative recombination rate. By comparing the finite-difference time-domain simulation with the experimental results from intentionally designed different NWs, this enhanced radiative decay rate was attributed to the Purcell effect induced by the confined and intensified optical field within the interfacial layer. The ability to manipulate the confinement, transport and relaxation dynamics of ZnO excitons can be naturally guaranteed with this unique interfacial Δ-doping strategy, which is certainly desirable for the applications using ZnO-based nano-photonic and nano-optoelectronic devices.

  16. Simultaneous Hosting of Positive and Negative Trions and the Enhanced Direct Band Emission in MoSe2/MoS2 Heterostacked Multilayers.

    PubMed

    Kim, Min Su; Seo, Changwon; Kim, Hyun; Lee, Jubok; Luong, Dinh Hoa; Park, Ji-Hoon; Han, Gang Hee; Kim, Jeongyong

    2016-06-28

    Heterostacking of layered transition-metal dichalcogenide (LTMD) monolayers (1Ls) offers a convenient way of designing two-dimensional exciton systems. Here we demonstrate the simultaneous hosting of positive trions and negative trions in heterobilayers made by vertically stacking 1L MoSe2 and 1L MoS2. The charge transfer occurring between the 1Ls of MoSe2 and MoS2 converted the polarity of trions in 1L MoSe2 from negative to positive, resulting in the presence of positive trions in the 1L MoSe2 and negative trions in the 1L MoS2 of the same heterostacked bilayer. Significantly enhanced MoSe2 photoluminescence (PL) in the heterostacked bilayers compared to the PL of 1L MoSe2 alone suggests that, unlike other previously reported heterostacked bilayers, direct band transition of 1L MoSe2 in heterobilayer was enhanced after the vertical heterostacking. Moreover, by inserting hexagonal BN monolayers between 1L MoSe2 and 1L MoS2, we were able to adjust the charge transfer to maximize the MoSe2 PL of the heteromultilayers and have achieved a 9-fold increase of the PL emission. The enhanced optical properties of our heterostacked LTMDs suggest the exciting possibility of designing LTMD structures that exploit the superior optical properties of 1L LTMDs.

  17. Sensible Ozone on Mars based on 2-D Maps of O 2(a 1△ g) Emission for L s=102° Comparison of (0,0) and (1,1) Bands

    NASA Astrophysics Data System (ADS)

    Novak, Robert E.; Mumma, Michael J.; Villanueva, Geronimo Luis

    2016-10-01

    We report 2-D maps of the O2(a1△g) emission rate (a tracer for high-altitude ozone) taken during early northern summer (Ls=102° on 30 January 2016) using CSHELL at NASA's IRTF. The entrance slit of the spectrometer was positioned N-S on Mars and stepped E-W at 0.5 arc-sec increments. Spectral extracts were taken at 0.6 arc-sec intervals along the slit. We also took data to compare the emission rates of the O2(a1△g) (1-1) band (1.28 μm) to the (0-0) band (1.27 μm) with the entrance slit centered at the sub-Earth point. A model consisting of the solar continuum with Fraunhofer lines, two-way transmission through Mars' atmosphere, and a one-way transmission through the Earth's atmosphere was used to isolate and analyze individual spectral emission lines from Mars. Boltzmann analysis of these lines yielded a rotational temperature (~165 K) that was used to determine the total emission rates for the a-X system from the measured line intensities. The line-of-sight emission rates were converted to vertical emission rates and O2(a1△g) column densities after geometric correction. The sensible O3 column implied by these data is compared with maps of total O3 in Mars standard atmosphere models.The 2-D map shows increased emission in the southern hemisphere when compared to previously reported results taken at earlier seasonal points (Ls=72° on 3 April 2010 and Ls=88° on 10 February 2014). Emission results of the O2(a1△g) (0-0) band (Local Time ~ 14:30) will be compared with MARCI results (LT ~ 15:00, Clancy et al., Icarus 266 (2016) 112-113). We searched for the (1-1) band in two adjacent wavelength ranges; (0-0) emissions were detected at these settings, but no (1-1) emissions were noticed above the noise level. An upper limit will be presented, and implications discussed.This work was partially funded by grants from NASA's Mars Fundamental Research Program (11-MFRP11-0066) and the NSF-RUI Program (AST-805540). The NASA Astrobiology Institute supported this work

  18. Modeling electron emission and surface effects from diamond cathodes

    SciTech Connect

    Dimitrov, D. A.; Smithe, D.; Cary, J. R.; Ben-Zvi, I.; Rao, T.; Smedley, J.; Wang, E.

    2015-02-05

    We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transverse electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. In this study, using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.

  19. Modeling electron emission and surface effects from diamond cathodes

    DOE PAGES

    Dimitrov, D. A.; Smithe, D.; Cary, J. R.; ...

    2015-02-05

    We developed modeling capabilities, within the Vorpal particle-in-cell code, for three-dimensional (3D) simulations of surface effects and electron emission from semiconductor photocathodes. They include calculation of emission probabilities using general, piece-wise continuous, space-time dependent surface potentials, effective mass and band bending field effects. We applied these models, in combination with previously implemented capabilities for modeling charge generation and transport in diamond, to investigate the emission dependence on applied electric field in the range from approximately 2 MV/m to 17 MV/m along the [100] direction. The simulation results were compared to experimental data. For the considered parameter regime, conservation of transversemore » electron momentum (in the plane of the emission surface) allows direct emission from only two (parallel to [100]) of the six equivalent lowest conduction band valleys. When the electron affinity χ is the only parameter varied in the simulations, the value χ = 0.31 eV leads to overall qualitative agreement with the probability of emission deduced from experiments. Including band bending in the simulations improves the agreement with the experimental data, particularly at low applied fields, but not significantly. In this study, using surface potentials with different profiles further allows us to investigate the emission as a function of potential barrier height, width, and vacuum level position. However, adding surface patches with different levels of hydrogenation, modeled with position-dependent electron affinity, leads to the closest agreement with the experimental data.« less

  20. Red-luminescence band: A tool for the quality assessment of germanium and silicon nanocrystals

    NASA Astrophysics Data System (ADS)

    Fraj, I.; Favre, L.; David, T.; Abbarchi, M.; Liu, K.; Claude, J. B.; Ronda, A.; Naffouti, M.; Saidi, F.; Hassen, F.; Maaref, H.; Aqua, J. N.; Berbezier, I.

    2017-10-01

    We present the photoluminescence (PL) emission of Silicon and Germanium nanocrystals (NCs) of different sizes embedded in two different matrices. Formation of the NCs is achieved via solid-state dewetting during annealing in a molecular beam epitaxy ultra-high vacuum system of ultrathin amorphous Si and Ge layers deposited at room temperature on SiO2. During the dewetting process, the bi-dimensional amorphous layers transform into small pseudo-spherical islands whose mean size can be tuned directly with the deposited thickness. The nanocrystals are capped either ex situ by silicon dioxide or in situ by amorphous Silicon. The surface-state dependent emission (typically in the range 1.74 eV-1.79 eV) exhibited higher relative PL quantum yields compared to the emission originating from the band gap transition. This red-PL emission comes from the radiative transitions between a Si band and an interface level. It is mainly ascribed to the NCs and environment features deduced from morphological and structural analyses. Power dependent analysis of the photoluminescence intensity under continuous excitation reveals a conventional power law with an exponent close to 1, in agreement with the type II nature of the emission. We show that Ge-NCs exhibit much lower quantum efficiency than Si-NCs due to non-radiative interface states. Low quantum efficiency is also obtained when NCs have been exposed to air before capping, even if the exposure time is very short. Our results indicate that a reduction of the non-radiative surface states is a key strategy step in producing small NCs with increased PL emission for a variety of applications. The red-PL band is then an effective tool for the quality assessment of NCs based structures.

  1. Coexistence of strongly and weakly confined energy levels in (Cd,Zn)Se quantum dots: Tailoring the near-band-edge and defect-levels for white light emission

    NASA Astrophysics Data System (ADS)

    Das, Tapan Kumar; Ilaiyaraja, P.; Sudakar, C.

    2017-05-01

    We demonstrate white light emission (WLE) from (Cd,Zn)Se system, which is a composite of Zn alloyed CdSe quantum dot and ZnSe-amorphous (ZnSe-a) phase. Detailed structural and photoluminescence emission studies on pure CdSe and (Cd,Zn)Se show cubic zinc blende structure in the size range of 2.5 to 5 nm. (Cd,Zn)Se quantum dots (QDs) also have a significant fraction of ZnSe-a phase. The near-band-edge green-emission in crystalline CdSe and (Cd,Zn)Se is tunable between 500 to 600 nm. The (Cd,Zn)Se system also exhibits a broad, deep defect level (DL) red-emission in the range 600 to 750 nm and a sharp ZnSe near-band-edge blue-emission (ZS-NBE) between 445 to 465 nm. While DL and CdSe near-band-edge (CS-NBE) emissions significantly shift with the size of QD due to strong confinement effect, the ZS-NBE show minimal change in peak position indicating a weak confinement effect. The intensities of ZS-NBE and DL emissions also exhibit a strong dependence on the QD size. A gamut of emission colors is obtained by combining the CS-NBE with the ZS-NBE emission and broad DL emission in (Cd,Zn)Se system. Interestingly, we find the convergence of Commission Internationale de l'Eclairage (CIE) coordinates towards the white light with increasing Zn concentration in CdSe. We demonstrate by combining these three emissions in a proper weight ratio WLE can be achieved. Cd1-yZnySe (y = 0. 5; QD size ˜4.9 nm) alloy with a maximum quantum yield of 57% exhibits CIE coordinates of (0.39, 0.4), color rendering index (CRI) of 82, correlated color temperature (CCT) of 3922 K, and Duv of 0.0078 which is very promising for white light applications.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  3. Chemical trends of the luminescence in wide band gap II 1-xMn xVI semimagnetic semiconductors

    NASA Astrophysics Data System (ADS)

    Benecke, C.; Busse, W.; Gumlich, H.-E.

    1990-04-01

    Time resolved emission and excitation spectroscopy is used to investigate the Mn correlated luminescence in wide band gap II-VI compounds, i.e. Zn 1-xMn xS, Cd 1-xMn xSe, Zn 1-xMn xTe and Cd 1-xMn xTe. Additional Information has been obtained with CdxZnyMnzTe( x+ y+ z=1) in checking the luminescence by variation of the ratio of the cations Cd and Zn. Generally speaking, at least two distinct emissions bands can be observed for each II 1- xMn xVI compound. One emissions band is attributed to the internal transition 4T 1(G)→ 6A 1(S) of the 3d 5 electron of the Mn 2+ on regular metal sites with energies of about ≈2 eV. The other emission band is found to occur in the near infrared range of about ≈1.3 eV. This emission band is tentatively interpreted as a transition of Mn 2+ ions on interstitial sites or in small Mn chalcogenide clusters, both interpretations assuming cubic symmetry. This model is supported by the existence of low energy excitation bands and by the great similarity of the shape of the two emission bands which lead to comparable Huang-Rhys factors and effective phonon energies. Also the established trend in the experimental data of the II-VI compounds under consideration confirm this interpretation. For both the IR and the yellow Mn 2+ center, the Racah parameters B and C and the crystal field parameter Dq are determined on the basis of experimental data. As a result, the energy of both the emission and the excitation bands is predominantly determined by the sorrounding anions. These bands shift to higher energies when the anions are changed in the fixed order: Te→Se→S. Regularly, there is also a spectral shift when Zn is replaced by Cd, which is smaller than the shift due to the variation of onions.

  4. Effect of cubic phase evolution on field emission properties of boron nitride island films

    SciTech Connect

    Teii, Kungen; Yamao, Ryota; Matsumoto, Seiichiro

    2009-12-01

    Field emission performance of boron nitride (BN) island films is studied in terms of cubic phase evolution in plasma-enhanced chemical vapor deposition. Fine-grained island films with large surface roughness can be grown for initial sp{sup 2}-bonded BN and subsequent cubic BN (cBN) phases by using low-energy (approx20 eV) ion bombardment. Ultraviolet photoelectron spectroscopy reveals that the electron affinity is as low as 0.3 eV for both sp{sup 2}-bonded BN and cBN phases. The evolution of cBN islands reduces the turn-on field down to around 9 V/mum and increases the current density up to 10{sup -4} A/cm{sup 2}. The emission is facilitated by the larger field enhancement due to the larger roughness and the higher conduction of cBN islands. The potential barrier height is estimated to be about 3.4 eV for emission from the Fermi level, while it is only about 0.3 eV for 'conduction band emission'.

  5. Severe paediatric conditions linked with EV-A71 and EV-D68, France, May to October 2016.

    PubMed

    Antona, Denise; Kossorotoff, Manoëlle; Schuffenecker, Isabelle; Mirand, Audrey; Leruez-Ville, Marianne; Bassi, Clément; Aubart, Mélodie; Moulin, Florence; Lévy-Bruhl, Daniel; Henquell, Cécile; Lina, Bruno; Desguerre, Isabelle

    2016-11-17

    We report 59 cases of severe paediatric conditions linked with enterovirus (EV)-A71 and EV-D68 in France between May and October 2016. Fifty-two children had severe neurological symptoms. EV sequence-based typing for 42 cases revealed EV-A71 in 21 (18 subgenotype C1, detected for the first time in France) and EV-D68 in eight. Clinicians should be encouraged to obtain stool and respiratory specimens from patients presenting with severe neurological disorders for EV detection and characterisation. This article is copyright of The Authors, 2016.

  6. Severe paediatric conditions linked with EV-A71 and EV-D68, France, May to October 2016

    PubMed Central

    Antona, Denise; Kossorotoff, Manoëlle; Schuffenecker, Isabelle; Mirand, Audrey; Leruez-Ville, Marianne; Bassi, Clément; Aubart, Mélodie; Moulin, Florence; Lévy-Bruhl, Daniel; Henquell, Cécile; Lina, Bruno; Desguerre, Isabelle

    2016-01-01

    We report 59 cases of severe paediatric conditions linked with enterovirus (EV)-A71 and EV-D68 in France between May and October 2016. Fifty-two children had severe neurological symptoms. EV sequence-based typing for 42 cases revealed EV-A71 in 21 (18 subgenotype C1, detected for the first time in France) and EV-D68 in eight. Clinicians should be encouraged to obtain stool and respiratory specimens from patients presenting with severe neurological disorders for EV detection and characterisation. PMID:27918268

  7. Effects of solar zenith angles on CO Cameron bands emission intensities in the dayside atmosphere of Mars: MEX/SPICAM observations

    NASA Astrophysics Data System (ADS)

    Pothuraju, Thirupathaiah; Haider, Syed A.

    2016-07-01

    We have developed a model to calculate the photoelectron energy fluxes and emission intensities of the CO Cameron bands in the upper atmosphere of Mars between solar zenith angles 0° to 90°. The production and loss mechanisms of CO (a ^{3}Π) are incorporated in the model. The atmospheric neutral parameters are adopted from the Mars Climate Database (v5.2). The required solar EUV fluxes are taken from the Solar2000 model (v2.37) and scaled to Mars. The photoelectron fluxes are calculated at different solar zenith angles using an analytical yield spectrum approach based on the Monte Carlo method. In this model we have assumed that crustal magnetic fields are horizontal in direction. Thus, photoelectrons are losing their energy at the same height where they are produced. This assumption is valid at mid and high latitudes where magnetic fields are mostly horizontal. We have also developed a coupled chemistry model to calculate the ion and electron density at different solar zenith angles, which are used in the airglow model. The model results are compared with the observations provided by the SPICAM onboard MEX. Our model reproduces the observed intensity profiles quite well. The CO (a ^{3}Π) is produced due to photoelectron excitation/dissociation, photodissociation, and dissociative recombination processes. It is destroyed by CO _{2}, CO and radiative decay. It is found that photon and photoelectron dissociation are dominant production processes of CO (a ^{3}Π), while radiative decay is a major loss mechanism of this state. The estimated photoelectron fluxes, production rates and intensities are decreasing with increasing solar zenith angles.

  8. Recombination reactions of 5-eV O(3P) atoms on a MgF2 surface

    NASA Technical Reports Server (NTRS)

    Orient, O. J.; Chutjian, A.; Murad, E.

    1990-01-01

    A source of hyperthermal, ground-state, impurity-free, atomic oxygen of an energy variable in the range 2-100 eV has been developed. Experimental results are presented of emission spectra in the wavelength range 250-850 nm produced by collisions of 5-eV O(3P) atoms with adsorbed NO and CO molecules on a MgF2 surface.

  9. Evidence of satellite valley position in GaN by photoexcited field emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Yilmazoglu, O.; Pavlidis, D.; Hartnagel, H. L.; Evtukh, A.; Litovchenko, V.; Semenenko, N.

    2008-06-01

    GaN field emitter rods with nanometer diameter were fabricated by photoelectrochemical etching on a n+-GaN substrate. Their electron field emission properties were investigated under ultraviolet (UV) illumination. The Fowler-Nordheim plots of the emission current show different slopes for nonilluminated and UV illuminated devices. A model based on the electron emission from valleys having different specific electron affinities is proposed to explain the experimental results. In the absence of illumination, the GaN rods are almost fully depleted and emission takes place only from the lower valley. Upon UV illumination and presence of a high electric field at the emitter tip, the upper valley of the conduction band appears to be occupied by electrons generated at the valence band. The energy difference between the lower and upper valleys was determined to be 1.15eV and is in good agreement with formerly published theoretical and measured values.

  10. Characterization and calibration of 8-channel E-band heterodyne radiometer system for SST-1 tokamak.

    PubMed

    Siju, Varsha; Kumar, Dharmendra; Shukla, Praveena; Pathak, S K

    2014-05-01

    An 8-channel E-band heterodyne radiometer system (74-86 GHz) is designed, characterized, and calibrated to measure the radial electron temperature profile by measuring Electron Cyclotron Emission spectrum at SST-1 Tokamak. The developed radiometer has a noise equivalent temperature of 1 eV and sensitivity of 5 × 10(9) V/W. In order to precisely measure the absolute value of electron temperature, a calibration measurement of the radiometer system is performed using hot-cold Dicke switch method, which confirms the system linearity.

  11. Characterization and calibration of 8-channel E-band heterodyne radiometer system for SST-1 tokamak

    SciTech Connect

    Siju, Varsha; Kumar, Dharmendra; Shukla, Praveena; Pathak, S. K.

    2014-05-15

    An 8-channel E-band heterodyne radiometer system (74–86 GHz) is designed, characterized, and calibrated to measure the radial electron temperature profile by measuring Electron Cyclotron Emission spectrum at SST-1 Tokamak. The developed radiometer has a noise equivalent temperature of 1 eV and sensitivity of 5 × 10{sup 9} V/W. In order to precisely measure the absolute value of electron temperature, a calibration measurement of the radiometer system is performed using hot-cold Dicke switch method, which confirms the system linearity.

  12. Photo Field Emission and Field Emission Energy Distributions from Silicon.

    NASA Astrophysics Data System (ADS)

    Herman, Michael H.

    Electron field emission from semiconductors is investigated both theoretically and experimentally. The theoretical predictions of the general Stratton theory are calculated specifically for silicon, in the {100 }, {110}, and {111} directions. A method of simplifying the calculation of the energy distribution for arbitrary semiconductor bands is obtained, utilizing the effective mass approximation. Experimental field emission energy distributions (FEEDs) are reported for both n- and p-type samples of low resistivity. The experimental distributions are characterized by a high intensity single peak, of energy 0.4 eV or more below the Fermi level, with subsidiary peak of lower intensity, rising from just below the Fermi level. The larger peak drops in energy with increasing field. Presented data demonstrates that this peak lowering is not attributable to sample resistance. Observation of the subsidiary peak is linked to either low sample temperature or low doping, implying that the carrier concentration affects its presence. Experimental FEEDs are compared to those expected theoretically. It is concluded that they are not similar. Comparison with photoemission work indicates that the large peak is due to a band of surface acceptor states. The subsidiary peak is tentatively ascribed to conduction band electrons. Finally, a phenomenological model of photo-field emission (PFE) is proposed. Based upon both FEED and PFE experiments, this model assumes that emission occurs primarily from surface states. A second component of the current is due to tunnelling of photogenerated electrons. In addition to photoconductivity, a self-regulating breakdown mechanism is necessary for qualitative agreement with experimental data. One such mechanism, avalanche, is investigated for the dielectric emitter model. Qualitative agreement is obtained with the characteristic non-linear Fowler-Nordheim behavior observed experimentally.

  13. Photoinduced band filling in strongly confined colloidal PbS quantum dots

    NASA Astrophysics Data System (ADS)

    Ullrich, B.; Xi, H.; Wang, J. S.

    2014-06-01

    Increase in continuous wave laser excitation (6 W/cm2 to 120 W/cm2) of colloidal PbS quantum dots in the strongly quantized regime (diameters 2.0 nm and 4.7 nm) deposited on semi-insulating GaAs and glass causes a clear blue shift (0.019 eV and 0.080 eV) of the emission spectra. Proof of the applicability of a dynamic three-dimensional band filling model is the significance of the presented results and demonstrates the effective electronic coupling in quantum dot arrays similar to superlattices. The work also reveals the influence of quantum dot sizes on photo-doping effects.

  14. Electronic structure of multiferroic BiFeO3 by resonant soft-x-ray emission spectroscopy

    SciTech Connect

    Higuchi, Tohru; Higuchi, T.; Liu, Y.-S.; Yao, P.; Glans, P.-A.; Guo, Jinghua; Chang, C.; Wu, Z.; Sakamoto, W.; Itoh, N.; Shimura, T.; Yogo, T.; Hattori, T.

    2008-07-11

    The electronic structure of multiferroic BiFeO{sub 3} has been studied using soft-X-ray emission spectroscopy. The fluorescence spectra exhibit that the valence band is mainly composed of O 2p state hybridized with Fe 3d state. The band gap corresponding to the energy separation between the top of the O 2p valence band and the bottom of the Fe 3d conduction band is 1.3 eV. The soft-X-ray Raman scattering reflects the features due to charge transfer transition from O 2p valence band to Fe 3d conduction band. These findings are similar to the result of electronic structure calculation by density functional theory within the local spin-density approximation that included the effect of Coulomb repulsion between localized d states.

  15. Electronic structure of multiferroic BiFeO3 by resonant soft x-ray emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Higuchi, Tohru; Liu, Yi-Sheng; Yao, Peng; Glans, Per-Anders; Guo, Jinghua; Chang, Chinglin; Wu, Ziyu; Sakamoto, Wataru; Itoh, Naoyuki; Shimura, Tetsuo; Yogo, Toshinobu; Hattori, Takeshi

    2008-08-01

    The electronic structure of multiferroic BiFeO3 has been studied using soft x-ray emission spectroscopy. The fluorescence spectra exhibit that the valence band is mainly composed of O2p state hybridized with Fe3d state. The band gap corresponding to the energy separation between the top of the O2p valence band and the bottom of the Fe3d conduction band is 1.3 eV. The soft x-ray Raman scattering reflects the features due to the charge-transfer transition from O2p valence band to Fe3d conduction band. These findings are similar to the result of electronic structure calculation by density-functional theory within the local spin-density approximation that included the effect of Coulomb repulsion between localized d states.

  16. Chopper Circuits Developed for EV Drive Application

    NASA Astrophysics Data System (ADS)

    Tsuruta, Yukinori; Kawamura, Atsuo

    In this paper, the technical stream on a high efficiency and high frequency chopper for the automotive industry, new energy and energy conservation technology field is surveyed. QRAS (Quasi-resonant Regenerating Active Snubber) and SAZZ (Snubber Assisted Zero Voltage and Zero Current Transition) topologies aimed for the electric vehicle (EV) drive application are proposed. 25kHz-8kW QRAS, 100kHz-8kW SAZZ choppers and 50kHz-25kW bilateral SAZZ-1 chopper are constructed and tested under rating conditions. It is verified that SAZZ topology retains high efficiency even at the increased operating frequency of 100kHz. It is shown that high efficiency can be realized at high operating frequency even in high power converters by QRAS and newly proposed SAZZ soft switching topologies.

  17. Enhanced Video Surveillance (EVS) with speckle imaging

    SciTech Connect

    Carrano, C J

    2004-01-13

    Enhanced Video Surveillance (EVS) with Speckle Imaging is a high-resolution imaging system that substantially improves resolution and contrast in images acquired over long distances. This technology will increase image resolution up to an order of magnitude or greater for video surveillance systems. The system's hardware components are all commercially available and consist of a telescope or large-aperture lens assembly, a high-performance digital camera, and a personal computer. The system's software, developed at LLNL, extends standard speckle-image-processing methods (used in the astronomical community) to solve the atmospheric blurring problem associated with imaging over medium to long distances (hundreds of meters to tens of kilometers) through horizontal or slant-path turbulence. This novel imaging technology will not only enhance national security but also will benefit law enforcement, security contractors, and any private or public entity that uses video surveillance to protect their assets.

  18. Simple cost model for EV traction motors

    SciTech Connect

    Cuenca, R.M.

    1995-02-01

    A simple cost model has been developed that allows the calculation of the OEM cost of electric traction motors of three different types, normalized as a function of power in order to accommodate different power and size. The model includes enough information on the various elements integrated in the motors to allow analysis of individual components and to factor-in the effects of changes in commodities prices. A scalable cost model for each of the main components of an electric vehicle (EV) is a useful tool that can have direct application in computer simulation or in parametric studies. For the cost model to have wide usefulness, it needs to be valid for a range of values of some parameter that determines the magnitude or size of the component. For instance, in the case of batteries, size may be determined by energy capacity, usually expressed in kilowatt-hours (kWh), while in the case of traction motors, size is better determined by rated power, usually expressed in kilowatts (kW). The simplest case is when the cost of the component in question is a direct function of its size; then cost is simply the product of its specific cost ($/unit size) and the number of units (size) in the vehicle in question. Batteries usually fall in this category (cost = energy capacity x $/kWh). But cost is not always linear with size or magnitude; motors (and controllers), for instance, become relatively less expensive as power rating increases. Traction motors, one of the main components for EV powertrains are examined in this paper, and a simplified cost model is developed for the three most popular design variations.

  19. Simple cost model for EV traction motors

    NASA Astrophysics Data System (ADS)

    Cuenca, R. M.

    1995-02-01

    A simple cost model has been developed that allows the calculation of the OEM (original equipment manufacturer) cost of electric traction motors of three different types, normalized as a function of power in order to accommodate different power and size. The model includes enough information on the various elements integrated in the motors to allow analysis of individual components and to factor-in the effects of changes in commodities prices. A scalable cost model for each of the main components of an electric vehicle (EV) is a useful tool that can have direct application in computer simulation or in parametric studies. For the cost model to have wide usefulness, it needs to be valid for a range of values of some parameter that determines the magnitude or size of the component. For instance, in the case of batteries, size may be determined by energy capacity, usually expressed in kilowatt-hours (kWh), while in the case of traction motors, size is better determined by rated power, usually expressed in kilowatts (kW). The simplest case is when the cost of the component in question is a direct function of its size; then cost is simply the product of its specific cost ($/unit size) and the number of units (size) in the vehicle in question. Batteries usually fall in this category (cost = energy capacity x $/kWh). But cost is not always linear with size or magnitude; motors (and controllers), for instance, become relatively less expensive as power rating increases. Traction motors, one of the main components for EV powertrains, are examined in this paper, and a simplified cost model is developed for the three most popular design variations.

  20. Tunable band gap photoluminescence from atomically thin transition-metal dichalcogenide alloys.

    PubMed

    Chen, Yanfeng; Xi, Jinyang; Dumcenco, Dumitru O; Liu, Zheng; Suenaga, Kazu; Wang, Dong; Shuai, Zhigang; Huang, Ying-Sheng; Xie, Liming

    2013-05-28

    Band gap engineering of atomically thin two-dimensional (2D) materials is the key to their applications in nanoelectronics, optoelectronics, and photonics. Here, for the first time, we demonstrate that in the 2D system, by alloying two materials with different band gaps (MoS2 and WS2), tunable band gap can be obtained in the 2D alloys (Mo(1-x)W(x)S(2) monolayers, x = 0-1). Atomic-resolution scanning transmission electron microscopy has revealed random arrangement of Mo and W atoms in the Mo(1-x)W(x)S(2) monolayer alloys. Photoluminescence characterization has shown tunable band gap emission continuously tuned from 1.82 eV (reached at x = 0.20) to 1.99 eV (reached at x = 1). Further, density functional theory calculations have been carried out to understand the composition-dependent electronic structures of Mo(1-x)W(x)S(2) monolayer alloys.

  1. Battery management systems (BMS) optimization for electric vehicles (EVs) in Malaysia

    NASA Astrophysics Data System (ADS)

    Salehen, P. M. W.; Su'ait, M. S.; Razali, H.; Sopian, K.

    2017-04-01

    Following the UN Climate Change Conference 2009 in Copenhagen, Denmark, Malaysia seriously committed on "Go Green" campaign with the aim to reduce 40% GHG emission by the year 2020. Therefore, the National Green Technology Policy has been legalised in 2009 with transportation as one of its focused sectors, which include hybrid (HEVs), electric vehicles (EVs) and fuel cell vehicles with the purpose of to keep up with the worst scenario. While the number of registered cars has been increasing by 1 million yearly, the amount has doubled in the last two decades. Consequently, CO2 emission in Malaysia reaches up to 97.1% and will continue to increase mainly due to the activities in the transportation sector. Nevertheless, Malaysia is now moving towards on green car which battery-based EVs. This type of transportation mainly needs power performance optimization, which is controlled by the Batteries Management System (BMS). BMS is an essential module which leads to reliable power management, optimal power performance and safe vehicle that lead back for power optimization in EVs. Thus, this paper proposes power performance optimization for various setups of lithium-ion cathode with graphene anode using MATLAB/SIMULINK software for better management performance and extended EVs driving range.

  2. Crew coordination issues of EVS approaches

    NASA Astrophysics Data System (ADS)

    Lorenz, Bernd; Korn, Bernd R.

    2004-08-01

    Enhanced Vision Systems (EVS) are currently developed with the goal to alleviate restrictions in airspace and airport capacity in low visibility conditions. Existing EVS-systems are based on IR-sensors although the penetration of bad weather (dense fog and light rain) by MMW-radar is remarkably better than in the infrared spectrum. But the quality of MMW radar is rather poor compared to IR images. However, the analysis of radar images can be simplified dramatically when simple passive radar retro-reflectors are used to mark the runway. This presentation is the third in a series of studies investigating the use of such simple landing aids. In the first study the feasibility of the radar PAPI concept was determined; the second one provided first promising human performance results in a low-fidelity simulation. The present study examined pilot performance, workload, situation awareness, and crew coordination issues in a high-fidelity simulation of 'Radar-PAPI' visual aids supporting a precision straight-in landing in low visibility (CAT-II). Simulation scenarios were completed in a fixed-base cockpit simulator involving six two-pilot flight-deck crews. Pilots could derive visual cues to correct lateral glide-path deviations from 13 pairs of runway-marking corner reflectors. Vertical deviations were indicated by a set of six diplane reflectors using intensity-coding to provide the PAPI categories needed for the correction of vertical deviations. The study compared three display formats and associated crew coordination issues: (1) PF views a head-down B-scope display and switches to visual landing upon PNF's call-out that runway is in sight; (2) PF views a head-down C-scope display and switches to visual landing upon PNF's call-out that runway is in sight; (3) PF views through a head-up display (HUD) that displays primary flight guidance information and receives vertical and lateral guidance from PNF who views a head-down B-scope. PNF guidance is terminated upon PF

  3. Proteomics analysis of EV71-infected cells reveals the involvement of host protein NEDD4L in EV71 replication.

    PubMed

    Kuo, Rei-Lin; Lin, Ya-Han; Wang, Robert Yung-Liang; Hsu, Chia-Wei; Chiu, Yi-Ting; Huang, Hsing-I; Kao, Li-Ting; Yu, Jau-Song; Shih, Shin-Ru; Wu, Chih-Ching

    2015-04-03

    Enterovirus 71 (EV71) is a human enterovirus that has seriously affected the Asia-Pacific area for the past two decades. EV71 infection can result in mild hand-foot-and-mouth disease and herpangina and may occasionally lead to severe neurological complications in children. However, the specific biological processes that become altered during EV71 infection remain unclear. To further explore host responses upon EV71 infection, we identified proteins differentially expressed in EV71-infected human glioblastoma SF268 cells using isobaric mass tag (iTRAQ) labeling coupled with multidimensional liquid chromatography-mass spectrometry (LC-MS/MS). Network analysis of proteins altered in cells infected with EV71 revealed that the changed biological processes are related to protein and ion transport, regulation of protein degradation, and homeostatic processes. We confirmed that the levels of NEDD4L and PSMF1 were increased and reduced, respectively, in EV71-infected cells compared to mock-infected control cells. To determine the physiological relevance of our findings, we investigated the consequences of EV71 infection in cells with NEDD4L or PSMF1 depletion. We found that the depletion of NEDD4L significantly reduced the replication of EV71, whereas PSMF1 knockdown enhanced EV71 replication. Collectively, our findings provide the first evidence of proteome-wide dysregulation by EV71 infection and suggest a novel role for the host protein NEDD4L in the replication of this virus.

  4. Electron field emission from wide bandgap semiconductors under intervalley carrier redistribution

    NASA Astrophysics Data System (ADS)

    Litovchenko, V.; Grygoriev, A.; Evtukh, A.; Yilmazoglu, O.; Hartnagel, H. L.; Pavlidis, D.

    2009-11-01

    Electron field emission phenomena from semiconductors (and, in particular, wide band gap materials) are analyzed theoretically for the general case, i.e., by taking into consideration aspects that have not been considered earlier such as two (or more) valleys of the energy band structure, nondegenerated statistics for the free electrons, heating of conduction band electrons, intervalley carrier redistribution under applied electrical fields, size quantization of electron band spectra, and change in the field emission characteristics. Comparisons with experiments performed on the highly structured (micro- and nano) surfaces of the GaN wide bandgap semiconductor have been made. The influence of the above factors on the current-voltage Fowler-Nordheim characteristics was demonstrated by theory and experiment. From theoretical and experimental results the intervalley energy difference (ΔE) for GaN quantum-sized cathodes was estimated to be 0.8 eV, which is considerably less than that predicted for bulk semiconductor (ΔE =1.2-1.5 eV). Furthermore the field emission currents were several orders higher than for bulk material. This is in good agreement with the prediction of the proposed theoretical model.

  5. Genomic characterization of two new enterovirus types, EV-A114 and EV-A121.

    PubMed

    Deshpande, Jagadish M; Sharma, Deepa K; Saxena, Vinay K; Shetty, Sushmitha A; Qureshi, Tarique Husain I H; Nalavade, Uma P

    2016-12-01

    Enteroviruses cause a variety of illnesses of the gastrointestinal tract, central nervous system and cardiovascular system. Phylogenetic analysis of VP1 sequences has identified 106 different human enteroviruses classified into four enterovirus species within the genus Enterovirus of the family Picornaviridae. It is likely that not all enterovirus types have been discovered. Between September 2013 and October 2014, stool samples of 6274 apparently healthy children of up to 5 years of age residing in Gorakhpur district, Uttar Pradesh, India were screened for enteroviruses. Virus isolates obtained in RD and Hep-2c cells were identified by complete VP1 sequencing. Enteroviruses were isolated from 3042 samples. A total of 87 different enterovirus types were identified. Two isolates with 71 and 74 % nucleotide sequence similarity to all other known enteroviruses were recognized as novel types. In this paper we report identification and complete genome sequence analysis of these two isolates classified as EV-A114 and EV-A121.

  6. How Do The EV Project Participants Feel About Charging Their EV Away From Home?

    SciTech Connect

    Francfort, James E.

    2015-02-01

    The EV Project is an infrastructure study that enrolled over 8,000 residential participants. These participants purchased or leased a Nissan Leaf battery electric vehicle or Chevrolet Volt extended-range electric vehicle and were among the first to explore this new electric drive technology. Collectively, battery electric vehicles, extended-range electric vehicles, and plug-in hybrid electric vehicles are called PEVs. The EV Project participants were very cooperative and enthusiastic about their participation in the project and very supportive in providing feedback and information. The information and attitudes of these participants concerning their experience with their PEVs were solicited using a survey in June 2013. At that time, some had up to 3 years of experience with their PEVs.

  7. X-ray grating spectrometer for opacity measurements in the 50 eV to 250 eV spectral range at the LULI 2000 laser facilitya)

    NASA Astrophysics Data System (ADS)

    Reverdin, Charles; Thais, Frédéric; Loisel, Guillaume; Busquet, M.; Bastiani-Ceccotti, S.; Blenski, T.; Caillaud, T.; Ducret, J. E.; Foelsner, W.; Gilles, D.; Gilleron, F.; Pain, J. C.; Poirier, M.; Serres, F.; Silvert, V.; Soullie, G.; Turck-Chieze, S.; Villette, B.

    2012-10-01

    An x-ray grating spectrometer was built in order to measure opacities in the 50 eV to 250 eV spectral range with an average spectral resolution ⟨E/δE⟩ ˜ 50. It has been used at the LULI-2000 laser facility at École Polytechnique (France) to measure the Δn = 0, n = 3 transitions of several elements with neighboring atomic number: Cr, Fe, Ni, and Cu in the same experimental conditions. Hence a spectrometer with a wide spectral range is required. This spectrometer features one line of sight looking through a heated sample at backlighter emission. It is outfitted with one toroidal condensing mirror and several flat mirrors cutting off higher energy photons. The spectral dispersion is obtained with a flatfield grating. Detection consists of a streak camera sensitive to soft x-ray radiation. Some experimental results showing the performance of this spectrometer are presented.

  8. Photoluminescence emission spectra of Makrofol® DE 1-1 upon irradiation with ultraviolet radiation

    NASA Astrophysics Data System (ADS)

    El Ghazaly, M.; Aydarous, Abdulkadir

    Photoluminescence (PL) emission spectra of Makrofol® DE 1-1 (bisphenol-A based polycarbonate) upon irradiation with ultraviolet radiation of different wavelengths were investigated. The absorption-and attenuation coefficient measurements revealed that the Makrofol® DE 1-1 is characterized by high absorbance in the energy range 6.53-4.43 eV but for a lower energy than 4.43 eV, it is approximately transparent. Makrofol® DE 1-1 samples were irradiated with ultraviolet radiation of wavelength in the range from 250 (4.28 eV) to 400 (3.10 eV) nm in step of 10 nm and the corresponding photoluminescence (PL) emission spectra were measured with a spectrofluorometer. It is found that the integrated counts and the peak height of the photoluminescence emission (PL) bands are strongly correlated with the ultraviolet radiation wavelength. They are increased at the ultraviolet radiation wavelength 280 nm and have maximum at 290 nm, thereafter they decrease and diminish at 360 nm of ultraviolet wavelength. The position of the PL emission band peak was red shifted starting from 300 nm, which increased with the increase the ultraviolet radiation wavelength. The PL bandwidth increases linearly with the increase of the ultraviolet radiation wavelength. When Makrofol® DE 1-1 is irradiated with ultraviolet radiation of short wavelength (UVC), the photoluminescence emission spectra peaks also occur in the UVC but of a relatively longer wavelength. The current new findings should be considered carefully when using Makrofol® DE 1-1 in medical applications related to ultraviolet radiation.

  9. Magnetic resonance experiments on the green emission in undoped ZnO crystals

    NASA Astrophysics Data System (ADS)

    Leiter, F.; Zhou, H.; Henecker, F.; Hofstaetter, A.; Hofmann, D. M.; Meyer, B. K.

    2001-12-01

    Optically detected magnetic resonance shows that a broad, green emission band in ZnO at 2.45 eV originates from a spintriplet-recombination characterised by g|| c=1.984 and g⊥ c=2.025 (parallel and perpendicular to the crystallographic c-axis, respectively) and a zero-field splitting of D=260×10 -4 cm -1. These parameters and the polarisation properties of the emission are very similar to the anion vacancies in CaO but not compatible with the Zeeman results on ZnO : Cu.

  10. A Method for Compensating Customer Voltage Drops due to Nighttime Simultaneous Charging of EVs Utilizing Reactive Power Injection from Battery Chargers

    NASA Astrophysics Data System (ADS)

    Noda, Taku; Kabasawa, Yuichiro; Fukushima, Kentaro; Nemoto, Koshichi; Uemura, Satoshi

    When we consider the global warming, the reduction of CO2 emission is one of the most important problems which require urgent solutions. One option is to integrate low-CO2-emission generators to the grid as much as possible. Another option is to replace inefficient vehicles based on internal-combustion engines with electric ones (EVs). Due to the latter, we can easily estimate that most consumers will charge EVs' batteries at nighttime. Thus, excessive voltage drops due to the nighttime simultaneous charging are supposed to be a possible future problem. This paper proposes a method for compensating the voltage drops by injecting reactive power from EV battery chargers.

  11. Human SCARB2-mediated entry and endocytosis of EV71.

    PubMed

    Lin, Yi-Wen; Lin, Hsiang-Yin; Tsou, Yueh-Liang; Chitra, Ebenezer; Hsiao, Kuang-Nan; Shao, Hsiao-Yun; Liu, Chia-Chyi; Sia, Charles; Chong, Pele; Chow, Yen-Hung

    2012-01-01

    Enterovirus (EV) 71 infection is known to cause hand-foot-and-mouth disease (HFMD) and in severe cases, induces neurological disorders culminating in fatality. An outbreak of EV71 in South East Asia in 1997 affected over 120,000 people and caused neurological disorders in a few individuals. The control of EV71 infection through public health interventions remains minimal and treatments are only symptomatic. Recently, human scavenger receptor class B, member 2 (SCARB2) has been reported to be a cellular receptor of EV71. We expressed human SCARB2 gene in NIH3T3 cells (3T3-SCARB2) to study the mechanisms of EV71 entry and infection. We demonstrated that human SCARB2 serves as a cellular receptor for EV71 entry. Disruption of expression of SCARB2 using siRNAs can interfere EV71 infection and subsequent inhibit the expression of viral capsid proteins in RD and 3T3-SCARB2 but not Vero cells. SiRNAs specific to clathrin or dynamin or chemical inhibitor of clathrin-mediated endocytosis were all capable of interfering with the entry of EV71 into 3T3-SCARB2 cells. On the other hand, caveolin specific siRNA or inhibitors of caveolae-mediated endocytosis had no effect, confirming that only clathrin-mediated pathway was involved in EV71 infection. Endocytosis of EV71 was also found to be pH-dependent requiring endosomal acidification and also required intact membrane cholesterol. In summary, the mechanism of EV71 entry through SCARB2 as the receptor for attachment, and its cellular entry is through a clathrin-mediated and pH-dependent endocytic pathway. This study on the receptor and endocytic mechanisms of EV71 infection is useful for the development of effective medications and prophylactic treatment against the enterovirus.

  12. An amphidynamic inorganic-organic hybrid crystal of bromoplumbate with 1,5-bis(1-methylimidazolium)pentane exhibiting multi-functionality of a dielectric anomaly and temperature-dependent dual band emissions.

    PubMed

    Tong, Yuan-Bo; Ren, Li-Te; Duan, Hai-Bao; Liu, Jian-Lan; Ren, Xiao-Ming

    2015-10-28

    Organic-inorganic hybrid crystals, [1,5-bis(1-methylimidazolium)pentane][PbBr3]2 (1), were achieved through the mutual diffusion of a bi-imidazolium based ionic liquid and PbBr2 solution of DMF in a glass tube. The hybrid solid crystallizes in the orthorhombic space group Fdd2 at room temperature; and is composed of one-dimensional [PbBr3]∞ chains where the neighbouring PbBr6 coordination octahedra are linked together via the face-sharing mode and the inorganic chains are surrounded by organic cations. The hybrid solid exhibits a dielectric anomaly around 443 K and dielectric relaxation above 400 K, the dielectric response mechanism was investigated using variable-temperature X-ray single crystal and powder diffraction as well as DSC techniques. Fascinatingly, this hybrid solid shows dual band emissions, moreover, the fluorescence nature of the two emission bands exhibits a distinct response to temperature, leading to a temperature-dependent fluorescence color, this feature has promising application in the emission temperature-sensing field.

  13. Potentials and capabilities of the Extracellular Vesicle (EV) Array.

    PubMed

    Jørgensen, Malene Møller; Bæk, Rikke; Varming, Kim

    2015-01-01

    Extracellular vesicles (EVs) and exosomes are difficult to enrich or purify from biofluids, hence quantification and phenotyping of these are tedious and inaccurate. The multiplexed, highly sensitive and high-throughput platform of the EV Array presented by Jørgensen et al., (J Extracell Vesicles, 2013; 2: 10) has been refined regarding the capabilities of the method for characterization and molecular profiling of EV surface markers. Here, we present an extended microarray platform to detect and phenotype plasma-derived EVs (optimized for exosomes) for up to 60 antigens without any enrichment or purification prior to analysis.

  14. The Methods of Choice for Extracellular Vesicles (EVs) Characterization

    PubMed Central

    Szatanek, Rafał; Baj-Krzyworzeka, Monika; Zimoch, Jakub; Lekka, Małgorzata; Siedlar, Maciej; Baran, Jarek

    2017-01-01

    In recent years, extracellular vesicles (EVs) have become a subject of intense study. These membrane-enclosed spherical structures are secreted by almost every cell type and are engaged in the transport of cellular content (cargo) from parental to target cells. The impact of EVs transfer has been observed in many vital cellular processes including cell-to-cell communication and immune response modulation; thus, a fast and precise characterization of EVs may be relevant for both scientific and diagnostic purposes. In this review, the most popular analytical techniques used in EVs studies are presented with the emphasis on exosomes and microvesicles characterization. PMID:28555055

  15. Broad-band X-ray emission and the reality of the broad iron line from the neutron star-white dwarf X-ray binary 4U 1820-30

    NASA Astrophysics Data System (ADS)

    Mondal, Aditya S.; Dewangan, G. C.; Pahari, M.; Misra, R.; Kembhavi, A. K.; Raychaudhuri, B.

    2016-09-01

    Broad relativistic iron lines from neutron star X-ray binaries are important probes of the inner accretion disc. The X-ray reflection features can be weakened due to strong magnetic fields or very low iron abundances such as is possible in X-ray binaries with low mass, first generation stars as companions. Here, we investigate the reality of the broad iron line detected earlier from the neutron-star low-mass X-ray binary 4U 1820-30 with a degenerate helium dwarf companion. We perform a comprehensive, systematic broad-band spectral study of the atoll source using Suzaku and simultaneous NuSTAR and Swift observations. We have used different continuum models involving accretion disc emission, thermal blackbody and thermal Comptonization of either disc or blackbody photons. The Suzaku data show positive and negative residuals in the region of Fe K band. These features are well described by two absorption edges at 7.67 ± 0.14 keV and 6.93 ± 0.07 keV or partial covering photoionized absorption or by blurred reflection. Though, the simultaneous Swift and NuSTAR data do not clearly reveal the emission or absorption features, the data are consistent with the presence of either absorption or emission features. Thus, the absorption based models provide an alternative to the broad iron line or reflection model. The absorption features may arise in winds from the inner accretion disc. The broad-band spectra appear to disfavour continuum models in which the blackbody emission from the neutron-star surface provides the seed photons for thermal Comptonization. Our results suggest emission from a thin accretion disc (kTdisc ˜ 1 keV), Comptonization of disc photons in a boundary layer most likely covering a large fraction of the neutron-star surface and innermost parts of the accretion disc, and blackbody emission (kTbb ˜ 2 keV) from the polar regions.

  16. Charge-transfer emission of compact porphyrin-fullerene dyad analyzed by Marcus theory of electron-transfer

    NASA Astrophysics Data System (ADS)

    Vehmanen, Visa; Tkachenko, Nikolai V.; Imahori, Hiroshi; Fukuzumi, Shunichi; Lemmetyinen, Helge

    2001-09-01

    A porphyrin-fullerene dyad, which is characterized by a close proximity of the porphyrin donor and the fullerene acceptor, was found to undergo a photoinduced electron transfer both in solutions and in solid films. Near-infrared charge-transfer (CT) emission was observed and analyzed in frame of the semi-classical Marcus electron-transfer theory yielding values for the reaction free energy, -Δ G°=1.75 eV, the internal reorganization energy, λv=0.05 eV, and the donor-acceptor vibrational energy, hvv=0.14 eV, both in solution and in solid film. The influence of the environment on the CT properties of the dyad is described by a single parameter, the outer-sphere reorganization energy, λs, which varies from 0.05 eV in non-polar solvents and films to 0.13 eV in solvents of moderate polarity. At low temperatures ( T<200 K), the CT emission consists of distinct bands shifted from each other by value hvv. This is the first direct observation of the vibrational frequencies of a porphyrin-fullerene donor-acceptor system.

  17. Band heterotopia.

    PubMed

    Alam, M S; Naila, N

    2010-01-01

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

  18. Band gap and band offsets for ultrathin (HfO2)x(SiO2)1-x dielectric films on Si (100)

    NASA Astrophysics Data System (ADS)

    Jin, H.; Oh, S. K.; Kang, H. J.; Cho, M.-H.

    2006-09-01

    Energy band profile of ultrathin Hf silicate dielectrics, grown by atomic layer deposition, was studied by using x-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap energy only slightly increases from 5.52eV for (HfO2)0.75(SiO2)0.25 to 6.10eV for (HfO2)0.25(SiO2)0.75, which is much smaller than 8.90eV for SiO2. For ultrathin Hf silicate dielectrics, the band gap is mainly determined by the Hf 5d conduction band state and the O 2p valence band state. The corresponding conduction band offsets are in the vicinity of 1eV, which satisfies the minimum requirement for the carrier barrier heights.

  19. Determination of MgO/AlN heterojunction band offsets by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Yang, A. L.; Song, H. P.; Liu, X. L.; Wei, H. Y.; Guo, Y.; Zheng, G. L.; Jiao, C. M.; Yang, S. Y.; Zhu, Q. S.; Wang, Z. G.

    2009-02-01

    MgO is a promising gate dielectric and surface passivation film for GaN/AlGaN transistors, but little is known of the band offsets in the MgO/AlN system. X-ray photoelectron spectroscopy was used to measure the energy discontinuity in the valence bandEv) of MgO/AlN heterostructures. A value of ΔEv=0.22±0.08 eV was obtained. Given the experimental band gap of 7.83 eV for MgO, a type-I heterojunction with a conduction band offset of ˜1.45 eV is found. The accurate determination of the valence and conduction band offsets is important for use of III-N alloys based electronic devices.

  20. Blue light emission from ZnO-graphene hybrid quantum dot (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Choi, Won Kook; Kim, Hong Hee; Park, Cheolmin; Hwang, Do Kyung; Lee, Yeonju

    2017-03-01

    One of a wide-bandgap semiconductor, Zinc oxide (ZnO) has a near ultraviolet bandgap (3.37 eV) and an exciton binding energy of 60 meV at room temperature (RT), and has several favorable properties, such as high electron mobility, high oscillator strength, and good transparency. In the photoluminescence (PL) spectra of ZnO nanoparticles, the near band edge ultraviolet (UV) emission at 378 nm relevant to direct bandgap of ZnO, and blue light emissions centered at 410, 435, and 465 nm corresponding to Zn interstitial (Zni) to valence band maximum (VBM), and to Zn vacancies (VZn) and green light emission at 540 nm corresponding to conduction band maximum (CBM) to oxygen vacancy (Vo). Ultra-small size quasi consolidated ZnO-graphene nanoparticles was synthesized in which graphene outer layer was chemically attached with ZnO inner core. After attaching graphene to ZnO, green emission completely disappeared whereas the intensity of blue emission was greatly increased. Enhanced blue emission could be well described by both fast electron transfer from CBM of ZnO to graphene having similar molecular energy level with Zni and transition to VBM and Vzn. Glass/ITO/PEDOT:PSS/poly-TPD/ZnO-graphene/Cs2CO3/Al were fabricated and showed the blue emission centered at 435 nm with FWHM of about 90 nm.

  1. Electronic structure and optical properties of noncentrosymmetric LiGaSe2: Experimental measurements and DFT band structure calculations

    NASA Astrophysics Data System (ADS)

    Lavrentyev, A. A.; Gabrelian, B. V.; Vu, V. T.; Ananchenko, L. N.; Isaenko, L. I.; Yelisseyev, A. P.; Khyzhun, O. Y.

    2017-04-01

    We report on measurements of X-ray photoelectron (XP) spectra for pristine and Ar+ ion-irradiated surfaces of LiGaSe2 single crystal grown by Bridgman-Stockbarger method. Electronic structure of the LiGaSe2 compound is studied from a theoretical and experimental viewpoint. In particular, total and partial densities of states of LiGaSe2 are investigated by density functional theory (DFT) calculations employing the augmented plane wave + local orbitals (APW + lo) method and they are verified by data of X-ray spectroscopy measurements. The DFT calculations indicate that the main contributors to the valence band of LiGaSe2 are the Se 4p states, which contribute mainly at the top and in the upper portion of the valence band, with also essential contributions of these states in the lower portion of the band. Other substantial contributions to the valence band of LiGaSe2 emerge from the Ga 4s and Ga 4p states contributing mainly at the lower ant upper portions of the valence band, respectively. With respect to the conduction band, the calculations indicate that its bottom is composed mainly from contributions of the unoccupied Ga s and Se p states. The present calculations are confirmed experimentally when comparing the XP valence-band spectrum of the LiGaS2 single crystal on a common energy scale with the X-ray emission bands representing the energy distribution of the Ga 4p and Se 4p states. Measurements of the fundamental absorption edges at room temperature reveal that bandgap value, Eg, of LiGaSe2 is equal to 3.47 eV and the Eg value increases up to 3.66 eV when decreasing temperature to 80 K. The main optical characteristics of the LiGaSe2 compound are clarified by the DFT calculations.

  2. DOE Field Operations Program EV and HEV Testing

    SciTech Connect

    Francfort, James Edward; Slezak, L. A.

    2001-10-01

    The United States Department of Energy’s (DOE) Field Operations Program tests advanced technology vehicles (ATVs) and disseminates the testing results to provide fleet managers and other potential ATV users with accurate and unbiased information on vehicle performance. The ATVs (including electric, hybrid, and other alternative fuel vehicles) are tested using one or more methods - Baseline Performance Testing (EVAmerica and Pomona Loop), Accelerated Reliability Testing, and Fleet Testing. The Program (http://ev.inel.gov/sop) and its nine industry testing partners have tested over 30 full-size electric vehicle (EV) models and they have accumulated over 4 million miles of EV testing experience since 1994. In conjunction with several original equipment manufacturers, the Program has developed testing procedures for the new classes of hybrid, urban, and neighborhood EVs. The testing of these vehicles started during 2001. The EVS 18 presentation will include (1) EV and hybrid electric vehicle (HEV) test results, (2) operating experience with and performance trends of various EV and HEV models, and (3) experience with operating hydrogen-fueled vehicles. Data presented for EVs will include vehicle efficiency (km/kWh), average distance driven per charge, and range testing results. The HEV data will include operating considerations, fuel use rates, and range testing results.

  3. Immunological evaluation and comparison of different EV71 vaccine candidates.

    PubMed

    Chou, Ai-Hsiang; Liu, Chia-Chyi; Chang, Jui-Yuan; Lien, Shu-Pei; Guo, Meng-Shin; Tasi, Hau-Pong; Hsiao, Kuang-Nan; Liu, Shih-Jen; Sia, Charles; Wu, Suh-Chin; Lee, Min-Shi; Hsiao, Chia-Hsin; Wang, Jen-Ren; Chow, Yen-Hung; Chong, Pele

    2012-01-01

    Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) are major causative agents of hand, foot, and mouth diseases (HFMDs), and EV71 is now recognized as an emerging neurotropic virus in Asia. Effective medications and/or prophylactic vaccines against HFMD are not available. The current results from mouse immunogenicity studies using in-house standardized RD cell virus neutralization assays indicate that (1) VP1 peptide (residues 211-225) formulated with Freund's adjuvant (CFA/IFA) elicited low virus neutralizing antibody response (1/32 titer); (2) recombinant virus-like particles produced from baculovirus formulated with CFA/IFA could elicit good virus neutralization titer (1/160); (3) individual recombinant EV71 antigens (VP1, VP2, and VP3) formulated with CFA/IFA, only VP1 elicited antibody response with 1/128 virus neutralization titer; and (4) the formalin-inactivated EV71 formulated in alum elicited antibodies that cross-neutralized different EV71 genotypes (1/640), but failed to neutralize CVA16. In contrast, rabbits antisera could cross-neutralize strongly against different genotypes of EV71 but weakly against CVA16, with average titers 1/6400 and 1/32, respectively. The VP1 amino acid sequence dissimilarity between CVA16 and EV71 could partially explain why mouse antibodies failed to cross-neutralize CVA16. Therefore, the best formulation for producing cost-effective HFMD vaccine is a combination of formalin-inactivated EV71 and CAV16 virions.

  4. Development of EV71 virus-like particle purification processes.

    PubMed

    Lin, Shih-Yeh; Chiu, Hsin-Yi; Chiang, Bor-Luen; Hu, Yu-Chen

    2015-11-04

    Enterovirus 71 (EV71) causes the outbreaks of hand-foot-and-mouth disease and results in deaths of hundreds of young children. EV71 virus-like particles (VLPs) are empty capsids consisting of viral structural proteins and can elicit potent immune responses, thus holding promise as an EV71 vaccine candidate. However, an efficient, scalable production and purification scheme is missing. For mass production of EV71 VLPs, this study aimed to develop a production and chromatography-based purification process. We first demonstrated the successful EV71 VLPs production in the stirred-tank bioreactor in which High Five™ cells were infected with a recombinant baculovirus co-expressing EV71 structural polyprotein P1 and protease 3CD. The culture supernatant containing the VLPs was subjected to tangential flow filtration (TFF) for concentration/diafiltration, which enabled the removal of >80% of proteins while recovering >80% of VLPs. The concentrated VLPs were next subjected to hydroxyapatite chromatography (HAC) in which the VLPs were mainly found in the flow through. After another TFF concentration/diafiltration, the VLPs were purified by size-exclusion chromatography (SEC) and concentrated/diafiltered by a final TFF. The integrated process yielded an overall VLPs recovery of ≈ 36% and a purity of ≈ 83%, which was better or comparable to the recovery and purity for the purification of live EV71 virus particles. This process thus may move the EV71 VLPs vaccine one step closer to the clinical applications.

  5. Significant Increase in Band Gap and Emission Efficiency of In2O3 Quantum Dots by Size-Tuning around 1 nm in Supermicroporous Silicas.

    PubMed

    Suzuki, Takafumi; Watanabe, Hiroto; Ueno, Taiki; Oaki, Yuya; Imai, Hiroaki

    2017-03-28

    The size of In2O3 quantum dots (QDs) is tuned from 0.57 to 1.80 nm by using supermicroporous silicas (SMPSs) as a template. The band gap energy and photoluminescence quantum yields of In2O3-QDs increase remarkably when their size is decreased below 1 nm.

  6. An origin of orange (2 eV) photoluminescence in SiO{sub 2} films implanted with high Si{sup +}-ion doses

    SciTech Connect

    Tyschenko, I. E.

    2015-09-15

    The photoluminescence and photoluminescence excitation spectra of SiO{sub 2} films implanted with high (3 at %) Si{sup +}-ion doses are studied in relation to the temperature of postimplantation annealing. It is shown that two photoluminescence bands with peaks at 2.7 and 2 eV are dominant in the spectra. As the annealing temperature is increased, the relation between the intensities of the 2.7 and 2 eV bands changes in favor of the former one. Both of the photoluminescence bands have their main excitation peak at the energy 5.1 eV. The excitation spectrum of the ∼2-eV band exhibits also peaks at 3.8 and 4.6 eV. It is concluded that, in the implanted SiO{sub 2} films, the orange photoluminescence band originates from radiative transitions between levels of centers associated with a deficiency of oxygen (≡Si–Si≡ or =Si:) and the levels of nonbridging oxygen (≡Si–O•)

  7. Composition of near-Earth Asteroid 2008 EV5: Potential target for robotic and human exploration

    NASA Astrophysics Data System (ADS)

    Reddy, Vishnu; Corre, Lucille Le; Hicks, Michael; Lawrence, Kenneth; Buratti, Bonnie J.; Abell, Paul A.; Gaffey, Michael J.; Hardersen, Paul S.

    2012-11-01

    We observed Potentially Hazardous Asteroid (PHA) 2008 EV5 in the visible (0.30-0.92 μm) and near-IR (0.75-2.5 μm) wavelengths to determine its surface composition. This asteroid is especially interesting because it is a potential target for two sample return mission proposals (Marco Polo-R and Hayabusa-2) and human exploration due to its low delta-v for rendezvous. The spectrum of 2008 EV5 is essentially featureless with exception of a weak 0.48-μm spin-forbidden Fe3+ absorption band. The spectrum also has an overall blue slope. The albedo of 2008 EV5 remains uncertain with a lower limit at 0.05 and a higher end at 0.20 based on thermal modeling. The Busch et al. (Busch et al. [2011]. Icarus 212, 649-660) albedo estimate of 0.12 ± 0.04 is consistent with our thermal modeling results. The albedo and composition of 2008 EV5 are also consistent with a C-type taxonomic classification (Somers, J.M., Hicks, M.D., Lawrence, K.J. [2008]. Bull. Am. Astron. Soc. 40, 440). The best spectral match is with CI carbonaceous chondrites similar to Orgueil, which also have a weak 0.48-μm feature and an overall blue slope. This 0.48-μm feature is also seen in the spectrum of magnetite. The albedo of CI chondrites is at the lower limit of our estimated range for the albedo of 2008 EV5.

  8. The NASA EV-2 CYGNSS Small Satellite Constellation Mission

    NASA Astrophysics Data System (ADS)

    Ruf, C. S.; Gleason, S.; Jelenak, Z.; Katzberg, S. J.; Ridley, A. J.; Rose, R.; Scherrer, J.; Zavorotny, V.

    2012-12-01

    The NASA EV-2 Cyclone Global Navigation Satellite System (CYGNSS) is a spaceborne mission focused on tropical cyclone (TC) inner core process studies. CYGNSS attempts to resolve the principle deficiencies with current TC intensity forecasts, which lies in inadequate observations and modeling of the inner core. The inadequacy in observations results from two causes: 1) Much of the inner core ocean surface is obscured from conventional remote sensing instruments by intense precipitation in the eye wall and inner rain bands. 2) The rapidly evolving (genesis and intensification) stages of the TC life cycle are poorly sampled in time by conventional polar-orbiting, wide-swath surface wind imagers. CYGNSS is specifically designed to address these two limitations by combining the all-weather performance of GNSS bistatic ocean surface scatterometry with the sampling properties of a constellation of satellites. The use of a dense constellation of nanosatellite results in spatial and temporal sampling properties that are markedly different from conventional imagers. Simulation studies will be presented which examine the sampling as functions of various orbit parameters of the constellation. Historical records of actual TC storm tracks are overlaid onto a simulated time series of the surface wind sampling enabled by the constellation. For comparison purposes, a similar analysis is conducted using the sampling properties of several past and present conventional spaceborne ocean wind scatterometers. Differences in the ability of the sensors to resolve the evolution of the TC inner core are examined. The spacecraft and constellation mission are described. The signal-to-noise ratio of the measured scattered signal and the resulting uncertainty in retrieved surface wind speed are also examined.

  9. Resonance Emission Enhancement (REE) for Narrow Band Red-Emitting A2GeF6:Mn(4+) (A = Na, K, Rb, Cs) Phosphors Synthesized via a Precipitation-Cation Exchange Route.

    PubMed

    Lian, Hongzhou; Huang, Qingming; Chen, Yeqing; Li, Kai; Liang, Sisi; Shang, Mengmeng; Liu, Manman; Lin, Jun

    2017-10-02

    Narrow band red-emitting A2GeF6:Mn(4+) (A = Na, K, Rb, Cs) phosphors were prepared through a two-step precipitation-cation exchange route using a K2MnF6 precursor as the Mn(4+) source. The phase purity, morphology, and constituent were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectric spectroscopy (XPS), and electron paramagnetic resonance (EPR) examination. Optical properties were investigated by photoluminescence spectra (PL and PLE) and high-resolution PL. A temperature-dependent PL examination was performed to investigate the electron-phonon coupling emission mechanism of Mn(4+) in these alkali fluorogermanates. The PL data show that both ordered distribution and appropriate distance between Mn(4+) ions are propitious for enhancement of the emission intensity. A resonance emission enhancement (REE) mechanism has been proposed to explain the intensity increment among these products. These phosphors present bright red emission under blue light (467 nm) illumination, among which Cs2GeF6:0.03Mn(4+) exhibits the most excellent optical properties with a quantum yield (QY) of 93%. A WLED (white light-emitting diode) fabricated with blend of commercial YAG:Ce(3+) and this phosphor emits intense warm white light with low color temperature (CCT = 3385 K) and high color rendering index (Ra = 90.5), implying its potential application as red phosphor in WLEDs.

  10. Huge operation by energy gap of novel narrow band gap Tl1-x In1-x B x Se2 (B = Si, Ge): DFT, x-ray emission and photoconductivity studies

    NASA Astrophysics Data System (ADS)

    Piasecki, M.; Myronchuk, G. L.; Zamurueva, O. V.; Khyzhun, O. Y.; Parasyuk, O. V.; Fedorchuk, A. O.; Albassam, A.; El-Naggar, A. M.; Kityk, I. V.

    2016-02-01

    It is shown that narrow band gap semiconductors Tl1-x In1-x GexSe2 are able effectively to vary the values of the energy gap. DFT simulations of the principal bands during the cationic substitutions is done. Changes of carrier transport features is explored. Relation with the changes of the near the surface states is explored . Comparison on a common energy scale of the x-ray emission Se Kβ 2 bands, representing energy distribution of the Se 4p states, indicates that these states contribute preliminary to the top of the valence band. The temperature dependence of electrical conductivity and spectral dependence photoconductivity for the Tl1-x In1-x Ge x Se2 and Tl1-x In1-x Si x Se2 single crystals were explored and compared with previously reported Tl1-x In1-x Sn x Se2. Based on our investigations, a model of centre re-charging is proposed. Contrary to other investigated crystals in Tl1-x In1-x Ge x Se2 single crystals for x = 0.1 we observe extraordinarily enormous photoresponse, which exceed more than nine times the dark current. X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces of Tl1-x In1-x GexSe2 (x = 0.1 and 0.2) single crystals have been studied. These results indicate that the relatively low hygroscopicity of the studied single crystals is typical for the Tl1-x In1-x Ge x Se2 crystals, a property that is very important for handling these quaternary selenides as infrared materials operating at ambient conditions.

  11. Ionospheric dynamo theory for production of far ultraviolet emissions on Uranus

    SciTech Connect

    Hudson, M.K.; Warren, J.A. ); Clarke, J.T. )

    1989-06-01

    A model is presented to explain diffuse FUV emissions from the outer planets, specifically Uranus, in excess of those diffuse emissions that are currently explainable by scattering of sunlight and/or excitation by photoelectrons. These electroglow emissions in H Ly {alpha} and H{sub 2} bands, which occur in the sunlit hemisphere slightly above the homopause, appear to require particle excitation in the 10- to 50-eV range. The authors propose an in situ mechanism for accelerating photoelectrons (and ions) involving neutral wind dynamo generation of field-aligned currents analogous to what occurs in the Earth's equatorial E and F regions. Sufficiently strong field-aligned currents are found in the model calculation for Uranus to produce a potential drop of {approximately} 100 eV or greater between the F peak and homopause, concentrated at lower altitudes, and capable in principle of accelerating photoelectrons (and ions) to the 10- to 50-eV energies required to explain the observed emissions. The fact that the excitation and ionization cross sections are larger than elastic scattering cross sections in an H{sub 2} atmosphere at these energies makes in situ acceleration feasible for the production of UV on the outer planets.

  12. Ionospheric dynamo theory for production of far ultraviolet emissions on Uranus

    NASA Technical Reports Server (NTRS)

    Hudson, M. K.; Warren, J. A.; Clarke, J. T.

    1989-01-01

    A model is presented to explain diffuse FUV emissions from the outer planets, specifically Uranus, in excess of those diffuse emissions that are currently explainable by scattering of sunlight and/or excitation by photoelectrons. These electroglow emissions in H Ly-alpha and H2 bands, which occur in the sunlit hemisphere slightly above the homopause, appear to require particle excitation in the 10- to 50-eV range. An in situ mechanism for accelerating photoelectrons (and ions is proposed, involving neutral wind dynamo generation of field-aligned currents analogous to what occurs in the earth's equatorial E and F regions. Sufficiently strong field-aligned currents are found in the model calculation for Uranus to produce a potential drop of about 100 eV or greater between the F peak and homopause, concentrated at lower altitudes, and capable in principle of accelerating photoelectrons (and ions) to the 10- to 50-eV energies required to explain the observed emissions. The fact that the excitation and ionization cross sections are larger than elastic scattering cross sections in an H2 atmosphere at these energies makes in situ acceleration feasible for the production of UV on the outer planets.

  13. Effects of excess oxygen on the 4.5-6.3 eV absorption spectra of oxygen-rich high purity silica

    NASA Astrophysics Data System (ADS)

    Magruder, R. H.; Robinson, S. J.

    2016-05-01

    Type III silica samples were implanted with O using a multi-energy process that produced a layer of constant concentration to within ±5% beginning ∼80 nm from the surface and extending to ∼640 nm below the surfaces of the samples. The concentrations of excess oxygen in the layer ranged from 0.035 to ∼2.1at.%. In these samples we show that E‧ centers and NBOHCs, as well as the normal cadre of ODC (II) centers, were suppressed, and the optical absorption from 4.7 to 6.4 eV was primarily due to oxygen excess defects. Using Gaussian fitting techniques to examine the optical difference spectra, we have been able to identify four defect centers that are related to excess oxygen defect bands at 4.76 eV, 5.42 eV, 5.75 eV and 6.25 eV.

  14. High efficiency carbon-based multilayers for LAMP at 250 eV

    NASA Astrophysics Data System (ADS)

    Wen, Mingwu; Huang, Qiushi; She, Rui; Jiang, Li; Zhang, Zhong; Wang, Zhanshan; Feng, Hua; Spiga, Daniele; Giglia, Angelo

    2015-09-01

    X-ray reflection near the Brewster's angle by multilayer mirrors can be used to detect the polarization from X-ray sources. The photon emission spectra from some isolated neutron stars and AGN/blazars etc. show that their emission is peaked at low energies near 250eV, which is just below carbon K-absorption edge. The Lightweight Asymmetry and Magnetism Probe (LAMP) is proposed as a micro-satellite mission dedicated for astronomical X-ray polarimetry working at 250 eV and is currently under early phase study. Co/C multilayers are selected and designed at the energy near 250eV with a grazing incident angle of 45°. The carbon layer thickness ratio is optimized to get the highest integral reflectivity which means larger effective signals in the astrophysics observation. The multilayer coatings were manufactured by direct current magnetron sputtering on D263 glasses and electroformed nickels and characterized using Grazing incidence X-ray reflectometry at 8keV. Reactive sputtering with 4%, 6% and 8% nitrogen were used to improve the Co/C multilayer interfaces respectively. Reflectivity for s-polarization and p-polarization light was measured at BEAR beamline in Elettra synchtron facility. Co/C multilayer deposited with 6% nitrogen exhibits the best performance comparing to other multilayers with different nitrogen content.

  15. The formation of Ti-O tetrahedra and band gap reduction in SiO2 via pulsed ion implantation

    NASA Astrophysics Data System (ADS)

    Green, R. J.; Zatsepin, D. A.; Hunt, A.; Kurmaev, E. Z.; Gavrilov, N. V.; Moewes, A.

    2013-03-01

    Titanium ions are implanted into amorphous SiO2 at two different fluences using pulsed ion implantation, and the resulting samples are annealed. Bulk sensitive soft X-ray absorption spectroscopy of the Ti L2,3 edge reveal strikingly different spectra for the two fluences. Spectral simulations using multiplet crystal field theory show clearly that for low fluence the Ti ions have a local octahedral coordination, while at higher fluence the formation of Ti4+-O tetrahedra dominates. Using O K-edge X-ray absorption and emission, the effect of the Ti states on the valence and conduction bands of the host SiO2 is revealed. With the introduction of Ti tetrahedra, the band gap reduces from about 8 eV to just over 4 eV, due entirely to the Ti 3d conduction band states. These results demonstrate the possibility to obtain Ti-O tetrahedra in silica by Ti ion implantation and a suitable thermal treatment, clarify the mechanism of band gap reduction with Ti doping in SiO2, and demonstrate the sensitivity of L-edge X-ray absorption with a multiplet crystal field theory analysis to the Ti coordination of novel materials.

  16. Photofield Emission Study of Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Gao, Yongli

    In this thesis the efforts made to better understand the mech- anisms and to refine the apparatus of photofield emission are described. Photofield electron yield and photofield emission from surface electronic have been measured. Both demonstrate the surface sensitivity of this new technique. Analyses of laser-induced thermal effects are also reported which allows the simultaneous determination of both the temperature and workfunction of a laser illuminated surface as small as 50(ANGSTROM) in spatial extent. Theoretical calculations of photofield emission based on the relativistic elec- tronic band structure of tungsten are also carried out and the results are compared to experiment. Data from W(110) and W(111) for a number of different photon energies between 2.41eV and 3.54eV are reported. The measured yield is compared to the theoretical models of the photoexcitation process. Based on this comparison, it is concluded that the spatial variation of the vector potential (')A near the metal-vacuum interface is the dominant excitation mechanism in producing the photocurrent from a laser illuminated field emission tip. Photofield emission from surface electronic states is a unique probe to examine the radiation field near the vicinity of a metal sur- face since the surface states are localized within the first atomic layer of the surface. Studies of photofield emission from surface states on W(100), Mo(100) and Ir(111) are presented in the text. Data analysis shows that photofield emission from localized sur- face states depends predominantly on the normal component of the vector potential (')A. Laser-induced thermal effects on various surfaces of tungsten and molybdenum have been studied using field emitted electrons. Energy distributions measured by a dispersive electron energy ana- lyzer allow the temperature increase of a laser-illuminated surface to be determined to within (+OR-)10 K. In addition to estimating the tem - perature rise, small temperature

  17. Procedures for Including Secondary Electron Emission in Numerical Simulations of Plasma-Insulator Interactions

    NASA Technical Reports Server (NTRS)

    Beyst, Brian; Rezvani, Ali; Young, Bin; Friauf, Robert J.

    1991-01-01

    Previous Monte Carlo simulations provide a data base for properties of secondary electron emission (SEE) from insulators and metals. Incident primary electrons are considered at energies up to 1200 eV. The behavior of secondary electrons is characterized by (1) yield vs. primary energy E(sub p), (2) distribution vs. secondary energy E(sub s), and (3) distribution vs. angle of emission theta. Special attention is paid to the low energy range E(sub p) up to 50 eV, where the number and energy of secondary electrons is limited by the finite band gap of the insulator. For primary energies above 50 eV the SEE yield curve can be conveniently parameterized by a Haffner formula. The energy distribution of secondary electrons is described by an empirical formula with average energy about 8.0 eV. The angular distribution of secondaries is slightly more peaked in the forward direction than the customary cos theta distribution. Empirical formulas and parameters are given for all yield and distribution curves. Procedures and algorithms are described for using these results to find the SEE yield, and then to choose the energy and angle of emergence of each secondary electron. These procedures can readily be incorporated into numerical simulations of plasma-solid surface interactions in low earth orbit.

  18. Inhibition of Enterovirus 71 (EV-71) Infections by a Novel Antiviral Peptide Derived from EV-71 Capsid Protein VP1

    PubMed Central

    Tan, Chee Wah; Chan, Yoke Fun; Sim, Kooi Mow; Tan, Eng Lee; Poh, Chit Laa

    2012-01-01

    Enterovirus 71 (EV-71) is the main causative agent of hand, foot and mouth disease (HFMD). In recent years, EV-71 infections were reported to cause high fatalities and severe neurological complications in Asia. Currently, no effective antiviral or vaccine is available to treat or prevent EV-71 infection. In this study, we have discovered a synthetic peptide which could be developed as a potential antiviral for inhibition of EV-71. Ninety five synthetic peptides (15-mers) overlapping the entire EV-71 capsid protein, VP1, were chemically synthesized and tested for antiviral properties against EV-71 in human Rhabdomyosarcoma (RD) cells. One peptide, SP40, was found to significantly reduce cytopathic effects of all representative EV-71 strains from genotypes A, B and C tested, with IC50 values ranging from 6–9.3 µM in RD cells. The in vitro inhibitory effect of SP40 exhibited a dose dependent concentration corresponding to a decrease in infectious viral particles, total viral RNA and the levels of VP1 protein. The antiviral activity of SP40 peptide was not restricted to a specific cell line as inhibition of EV-71 was observed in RD, HeLa, HT-29 and Vero cells. Besides inhibition of EV-71, it also had antiviral activities against CV-A16 and poliovirus type 1 in cell culture. Mechanism of action studies suggested that the SP40 peptide was not virucidal but was able to block viral attachment to the RD cells. Substitutions of arginine and lysine residues with alanine in the SP40 peptide at positions R3A, R4A, K5A and R13A were found to significantly decrease antiviral activities, implying the importance of positively charged amino acids for the antiviral activities. The data demonstrated the potential and feasibility of SP40 as a broad spectrum antiviral agent against EV-71. PMID:22563456

  19. Nitrous oxide emissions in Midwest US maize production vary widely with band-injected liquid N fertilizer rates, timing and nitrapyrin presence

    USDA-ARS?s Scientific Manuscript database

    Nitrification inhibitors have potential to reduce N2O emissions from maize fields. A new micro-encapsulated formulation of nitrapyrin, optimized to be used with liquid fertilizers became available to US farmers in 2010. Our objectives were to: i) 15assess the impacts of urea-ammonium nitrate (UAN) m...

  20. An adenosine nucleoside analogue NITD008 inhibits EV71 proliferation.

    PubMed

    Shang, Luqing; Wang, Yaxin; Qing, Jie; Shu, Bo; Cao, Lin; Lou, Zhiyong; Gong, Peng; Sun, Yuna; Yin, Zheng

    2014-12-01

    Enterovirus 71 (EV71), one of the major causative agents of Hand-Foot-Mouth Disease (HFMD), causes severe pandemics and hundreds of deaths in the Asia-Pacific region annually and is an enormous public health threat. However, effective therapeutic antiviral drugs against EV71 are rare. Nucleoside analogues have been successfully used in the clinic for the treatment of various viral infections. We evaluated a total of 27 nucleoside analogues and discovered that an adenosine nucleoside analogue NITD008, which has been reported to be an antiviral reagent that specifically inhibits flaviviruses, effectively suppressed the propagation of different strains of EV71 in RD, 293T and Vero cells with a relatively high selectivity index. Triphosphorylated NITD008 (ppp-NITD008) functions as a chain terminator to directly inhibit the RNA-dependent RNA polymerase activity of EV71, and it does not affect the EV71 VPg uridylylation process. A significant synergistic anti-EV71 effect of NITD008 with rupintrivir (AG7088) (a protease inhibitor) was documented, supporting the potential combination therapy of NITD008 with other inhibitors for the treatment of EV71 infections.

  1. Weak morphology dependent valence band structure of boron nitride

    NASA Astrophysics Data System (ADS)

    Zhi, Chunyi; Ueda, Shigenori; Zeng, Haibo; Wang, Xuebin; Tian, Wei; Wang, Xi; Bando, Yoshio; Golberg, Dmitri

    2013-08-01

    We report a hard X-ray photoelectron spectroscopy (HX-PES) investigation on valence band structure of Boron Nitrides (BN) having different morphologies, including nanosheets, nanotubes, and micro-sized particles. Very weak morphology/valence band structure dependence was observed. For each case, the B-N π-band overlapping with σ-band between 0 to -12.5 eV and the s-band below -15 eV were identified. No obvious morphology-induced band shifts and intensity variations were observed. First-principles calculations based on density functional theory were performed and the results were compared with the experimental data. This theoretical analysis well explains the weak morphology dependent valence band spectra of BN nanomaterials obtained during HX-PES measurements.

  2. Nitrous oxide emissions in Midwest US maize production vary widely with band-injected N fertilizer rates, timing and nitrapyrin presence

    NASA Astrophysics Data System (ADS)

    Burzaco, Juan P.; Smith, Doug R.; Vyn, Tony J.

    2013-09-01

    Nitrification inhibitors have the potential to reduce N2O emissions from maize fields, but optimal results may depend on deployment of integrated N fertilizer management systems that increase yields achieved per unit of N2O lost. A new micro-encapsulated formulation of nitrapyrin for liquid N fertilizers became available to US farmers in 2010. Our research objectives were to (i) assess the impacts of urea-ammonium nitrate (UAN) management practices (timing, rate and nitrification inhibitor) and environmental variables on growing-season N2O fluxes and (ii) identify UAN treatment combinations that both reduce N2O emissions and optimize maize productivity. Field experiments near West Lafayette, Indiana in 2010 and 2011 examined three N rates (0, 90 and 180 kg N ha-1), two timings (pre-emergence and side-dress) and presence or absence of nitrapyrin. Mean cumulative N2O-N emissions (Q10 corrected) were 0.81, 1.83 and 3.52 kg N2O-N ha-1 for the rates of 0, 90 and 180 kg N ha-1, respectively; 1.80 and 2.31 kg N2O-N ha-1 for pre-emergence and side-dress timings, respectively; and 1.77 versus 2.34 kg N2O-N ha-1 for with and without nitrapyrin, respectively. Yield-scaled N2O-N emissions increased with N rates as anticipated (averaging 167, 204 and 328 g N2O-N Mg grain-1 for the 0, 90 and 180 kg N ha-1 rates), but were 22% greater with the side-dress timing than the pre-emergence timing (when averaged across N rates and inhibitor treatments) because of environmental conditions following later applications. Overall yield-scaled N2O-N emissions were 22% lower with nitrapyrin than without the inhibitor, but these did not interact with N rate or timing.

  3. Multiwavelength campaign on Mrk 509. XV. Global modeling of the broad emission lines in the optical, UV, and X-ray bands

    NASA Astrophysics Data System (ADS)

    Costantini, E.; Kriss, G.; Kaastra, J. S.; Bianchi, S.; Branduardi-Raymont, G.; Cappi, M.; De Marco, B.; Ebrero, J.; Mehdipour, M.; Petrucci, P.-O.; Paltani, S.; Ponti, G.; Steenbrugge, K. C.; Arav, N.

    2016-11-01

    Aims: We model the broad emission lines present in the optical, UV, and X-ray spectra of Mrk 509, a bright type 1 Seyfert galaxy. The broad lines were simultaneously observed during a large multiwavelength campaign, using the XMM-Newton-OM for the optical lines, HST-COS for the UV lines, and XMM-Newton-RGS and Epic for the X-ray lines. We also used FUSE archival data for the broad lines observed in the far-ultraviolet. The goal is to find a physical connection among the lines measured at different wavelengths and to determine the size and the distance from the central source of the emitting gas components. Methods: We used the Locally Optimally emission Cloud (LOC) model which interprets the emissivity of the broad line region (BLR) as regulated by power law distributions of both gas density and distances from the central source. Results: We find that one LOC component cannot model all the lines simultaneously. In particular, we find that the X-ray and UV lines may likely originate in the more internal part of the AGN at radii in the range 5 × 1014-3 × 1017 cm, while the optical lines and part of the UV lines may likely originate farther out at radii 3 × 1017-3 × 1018 cm. These two gas components are parametrized by a radial distribution of the luminosities with a slope γ of 1.15 and 1.10, respectively, both of them covering at least 60% of the source. This simple parametrization points to a structured broad line region where the higher ionized emission comes from closer in, while the emission of the low-ionization lines is more concentrated in the outskirts of the broad line region.

  4. Direct band gap silicon allotropes.

    PubMed

    Wang, Qianqian; Xu, Bo; Sun, Jian; Liu, Hanyu; Zhao, Zhisheng; Yu, Dongli; Fan, Changzeng; He, Julong

    2014-07-16

    Elemental silicon has a large impact on the economy of the modern world and is of fundamental importance in the technological field, particularly in solar cell industry. The great demand of society for new clean energy and the shortcomings of the current silicon solar cells are calling for new materials that can make full use of the solar power. In this paper, six metastable allotropes of silicon with direct or quasidirect band gaps of 0.39-1.25 eV are predicted by ab initio calculations at ambient pressure. Five of them possess band gaps within the optimal range for high converting efficiency from solar energy to electric power and also have better optical properties than the Si-I phase. These Si structures with different band gaps could be applied to multiple p-n junction photovoltaic modules.

  5. Energy band structure of the single crystalline MgO/n-Ge(001) heterojunction determined by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Jeon, Kun-Rok; Lee, Sang-Jun; Park, Chang-Yup; Lee, Hun-Sung; Shin, Sung-Chul

    2010-09-01

    We report the energy band structure of the single crystalline MgO/n-Ge(001) heterojunction characterized by x-ray photoelectron spectroscopy. The valence band offset of ΔEV=3.64±0.07 eV with a 1.49±0.02 eV band bending was obtained. Given the experimental band gap of MgO (7.83 eV), a type-I band alignment with a conduction band offset of ΔEC=3.52±0.07 eV is found. The band alignment of the MgO/n-Ge heterojunction including the large band bending was analyzed by a theoretical model taking into account the formation of the interface dipole.

  6. Change in optimum genetic algorithm solution with changing band discontinuities and band widths of electrically conducting copolymers

    NASA Astrophysics Data System (ADS)

    Kaur, Avneet; Bakhshi, A. K.

    2010-04-01

    The interest in copolymers stems from the fact that they present interesting electronic and optical properties leading to a variety of technological applications. In order to get a suitable copolymer for a specific application, genetic algorithm (GA) along with negative factor counting (NFC) method has recently been used. In this paper, we study the effect of change in the ratio of conduction band discontinuity to valence band discontinuity (Δ Ec/Δ Ev) on the optimum solution obtained from GA for model binary copolymers. The effect of varying bandwidths on the optimum GA solution is also investigated. The obtained results show that the optimum solution changes with varying parameters like band discontinuity and band width of constituent homopolymers. As the ratio Δ Ec/Δ Ev increases, band gap of optimum solution decreases. With increasing band widths of constituent homopolymers, the optimum solution tends to be dependent on the component with higher band gap.

  7. EFFECT OF METALLICITY ON X-RAY EMISSION FROM THE WARM-HOT INTERGALACTIC MEDIUM

    SciTech Connect

    Ursino, E.; Galeazzi, M.; Roncarelli, M.

    2010-09-20

    Hydrodynamic simulations predict that a significant fraction of the gas in the current universe is in the form of high temperature, highly ionized plasma emitting and absorbing primarily in the soft X-ray and UV bands, dubbed the warm-hot intergalactic medium (WHIM). Its signature should be observable in redshifted emission and absorption lines from highly ionized elements. To determine the expected WHIM emission in the soft X-ray band we used the output of a large scale smoothed particle hydrodynamic simulation to generate images and spectra with angular resolution of 14'' and energy resolution of 1 eV. The current biggest limit of any hydrodynamic simulation in predicting the X-ray emission comes from metal diffusion. In our investigation, by using four different models for the WHIM metallicity we have found a strong dependence of the emission on the model used, with differences up to almost an order of magnitude. For each model, we have investigated the redshift distribution and angular scale of the emission, confirming that most photons come from redshift z < 1.2 and that the emission has a typical angular scale of less than a few arcminutes. We also compared our simulations with the few currently available observations and found that, within the variation of the metallicity models, our predictions are in good agreement with current constraints on the WHIM emission, and at this time the weak experimental constraints on the WHIM emission are not sufficient to exclude any of the models used.

  8. Triple-doped KMnF3:Yb3+/Er3+/Tm3+ nanocubes: four-color upconversion emissions with strong red and near-infrared bands

    PubMed Central

    Wang, Hao; Hong, Xiaodong; Han, Renlu; Shi, Junhui; Liu, Zongjun; Liu, Shujuan; Wang, You; Gan, Yang

    2015-01-01

    Triple-doped (Yb3+/Er3+/Tm3+) KMnF3 nanocubes with uniform sizes of 250 nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980 nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660 nm) and NIR (800 nm) peaks, known as two “optical windows” for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions. PMID:26608870

  9. Narrow-band single photon emission at room temperature based on a single nitrogen-vacancy center coupled to an all-fiber-cavity

    SciTech Connect

    Albrecht, Roland; Bommer, Alexander; Becher, Christoph; Pauly, Christoph; Mücklich, Frank; Schell, Andreas W.; Engel, Philip; Benson, Oliver; Schröder, Tim; Reichel, Jakob

    2014-08-18

    We report the realization of a device based on a single Nitrogen-Vacancy (NV) center in diamond coupled to a fiber-cavity for use as single photon source (SPS). The device consists of two concave mirrors each directly fabricated on the facets of two optical fibers and a preselected nanodiamond containing a single NV center deposited onto one of these mirrors. Both, cavity in- and out-put are directly fiber-coupled, and the emission wavelength is easily tunable by variation of the separation of the two mirrors with a piezo-electric crystal. By coupling to the cavity, we achieve an increase of the spectral photon rate density by two orders of magnitude compared to free-space emission of the NV center. With this work, we establish a simple all-fiber based SPS with promising prospects for the integration into photonic quantum networks.

  10. Triple-doped KMnF3:Yb3+/Er3+/Tm3+ nanocubes: four-color upconversion emissions with strong red and near-infrared bands

    NASA Astrophysics Data System (ADS)

    Wang, Hao; Hong, Xiaodong; Han, Renlu; Shi, Junhui; Liu, Zongjun; Liu, Shujuan; Wang, You; Gan, Yang

    2015-11-01

    Triple-doped (Yb3+/Er3+/Tm3+) KMnF3 nanocubes with uniform sizes of 250 nm were synthesized by a facile hydrothermal route using the oleic acid as the capping agent. It was found that these nanocubes can simultaneously exhibited four-color (blue, green, red and NIR) upconversion emissions under a single 980 nm near-infrared (NIR) laser excitation, which should have potential multicolor in vivo imaging applications. Specifically, the red (660 nm) and NIR (800 nm) peaks, known as two “optical windows” for imaging biological tissues, were strong. The spectral and pump analyses indicated the two-photon processes were responsible for the both red and NIR emissions.

  11. Band engineering for surface emission enhancement in Al-rich AlGaN-based deep-ultraviolet light emitting diodes

    NASA Astrophysics Data System (ADS)

    Lu, Huimin; Yu, Tongjun; Chen, Xinjuan; Wang, Jianping; Zhang, Guoyi

    2016-05-01

    The optical polarization properties of Al-rich AlGaN/AlN quantum wells (QWs) with different structure parameters were analyzed using the modified theoretical model based on the effective mass equation. It is demonstrated that the optical polarization properties of AlGaN-based QWs are determined by the valence subband structure, including the energy level order and the valence subband coupling. The results show that the TE-polarized emission is enhanced in Al-rich AlGaN/AlN QWs with smaller well width, a buffer layer inducing compressive stress, and a staggered well layer owing to the change in the valence subband structure. Hence, the enhancement of surface emission from deep-ultraviolet (DUV) AlGaN-based light-emitting diodes (LEDs) can be realized by adjusting the QW structure parameters to induce a valence subband change.

  12. Enhanced Narrow-band, Coherent Emission from a Current Source Immersed in Cut-off of a Plasma-like Medium

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

    In plasma-like media sharing a similar dispersion relation, there exists a cut-off frequency to make the wave number zero. This particular situation has been understood classically in a way that the radiation impedance becomes infinite, resulting in a total reflection of an incident wave. However, in this framework of understanding the cut-off, a pure current source immersed in the cut-off region leads to infinite radiation power from Ohm's law. This is obviously unphysical and requires a different approach to address the problem. In this presentation, we show that by solving the driven time-dependent Schrödinger equation, the radiation at the cut-off frequency can be selectively enhanced by several times the pure vacuum-emission. Important question here is whether such current sources are available in practical systems. We find that quasi-current sources are actually ubiquitous as long as the conversion efficiency from the current driver to the radiation emission is low. We demonstrate two such cases by PIC simulations; THz radiation from a plasma driven by colliding laser pulses, and THz from two-color lasers enclosed by a tapered waveguide. We also discuss the previous experimental results in terms of this enhanced emission concept.

  13. Base fluid in improving heat transfer for EV car battery

    NASA Astrophysics Data System (ADS)

    Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.

    2015-05-01

    This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.

  14. Photoluminescence properties of defect emissions in Al-doped ZnO nanorod array thin films.

    PubMed

    Kim, Soaram; Nam, Giwoong; Park, Hyunggil; Yoon, Hyunsik; Kim, Min Su; Kim, Do Yeob; Kim, Sung-O; Leem, Jae-Young

    2013-09-01

    The power- and temperature-dependent photoluminescence properties of Al-doped ZnO nanorod array thin films grown by the hydrothermal method were investigated. The intensities of both the near-band-edge emission (NBE) and deep-level emission (DLE) as well as the overall spectral line shape were strongly affected by the excitation power. At low excitation power, the blue emission was found to show the highest intensity among the different emission lights. A low-temperature photoluminescence analysis revealed the bound-exciton-related luminescence peak at 3.362 eV. The dependence of peak energy with the excitation power indicates that these DLE processes are generated by DAP transitions. The overall intensity of DLE was found to decrease as the temperature increases. With regard to the blue emission (around 2.52 eV), it showed a well-pronounced shoulder at 200 K. The activation energy for this blue emission was 51.93 meV, which corresponds to the thermal dissociation energy required for the donor-acceptor pair transitions.

  15. Immunological Evaluation and Comparison of Different EV71 Vaccine Candidates

    PubMed Central

    Chou, Ai-Hsiang; Liu, Chia-Chyi; Chang, Jui-Yuan; Lien, Shu-Pei; Guo, Meng-Shin; Tasi, Hau-Pong; Hsiao, Kuang-Nan; Liu, Shih-Jen; Sia, Charles; Wu, Suh-Chin; Lee, Min-Shi; Hsiao, Chia-Hsin; Wang, Jen-Ren; Chow, Yen-Hung; Chong, Pele

    2012-01-01

    Enterovirus 71 (EV71) and coxsackievirus A16 (CVA16) are major causative agents of hand, foot, and mouth diseases (HFMDs), and EV71 is now recognized as an emerging neurotropic virus in Asia. Effective medications and/or prophylactic vaccines against HFMD are not available. The current results from mouse immunogenicity studies using in-house standardized RD cell virus neutralization assays indicate that (1) VP1 peptide (residues 211–225) formulated with Freund's adjuvant (CFA/IFA) elicited low virus neutralizing antibody response (1/32 titer); (2) recombinant virus-like particles produced from baculovirus formulated with CFA/IFA could elicit good virus neutralization titer (1/160); (3) individual recombinant EV71 antigens (VP1, VP2, and VP3) formulated with CFA/IFA, only VP1 elicited antibody response with 1/128 virus neutralization titer; and (4) the formalin-inactivated EV71 formulated in alum elicited antibodies that cross-neutralized different EV71 genotypes (1/640), but failed to neutralize CVA16. In contrast, rabbits antisera could cross-neutralize strongly against different genotypes of EV71 but weakly against CVA16, with average titers 1/6400 and 1/32, respectively. The VP1 amino acid sequence dissimilarity between CVA16 and EV71 could partially explain why mouse antibodies failed to cross-neutralize CVA16. Therefore, the best formulation for producing cost-effective HFMD vaccine is a combination of formalin-inactivated EV71 and CAV16 virions. PMID:23008736

  16. Electron impact excitation of the Rydberg states in O2 in the 7-10 eV energy-loss region

    NASA Technical Reports Server (NTRS)

    Trajmar, S.; Cartwright, D. C.; Hall, R. I.

    1976-01-01

    An experimental investigation was undertaken to identify as many transitions as possible in the 7-10 eV region of the electron impact energy-loss spectrum of 02 at low impact energies and high scattering angles. A number of new transitions were found which do not appear in optical spectra: bands at 8.595, 8.826, 9.045, and 9.27 eV have been assigned to the 3 s sigma g 1Pi(nu prime equals 0, 1, 2, and 3) excitations, respectively, and the identification of the corresponding 3Pi-g bands have been reconfirmed.

  17. Near Zero ev Subexcitation Energy Electrons Break DNA

    NASA Astrophysics Data System (ADS)

    Martin, Frederic; Cai, Zhongli; Cloutier, Pierre; Hunting, Darel; Sanche, Leon

    2004-03-01

    The passage of ionizing radiation through a living cell produces about 4 x 10^4 electrons/MeV, with more than 50% having energies well below the excitation threshold for water (7-8 eV) (M. Michaud et al, Physical Review, 44(9), 5623-5627, (1991)). We have previously shown that 5-20eV electrons cause DNA strand breaks via a resonant process with a maximum at 10eV (B. Boudaiffa et al, Science 287, 1658-1660, (2000)). The present results demonstrate that very low energy electrons in the range of 0 to 5eV cause single strand breaks (SSB) in DNA. Plasmid DNA is extracted from the host bacteria purified and resuspended in distilled and deionised water. It is deposited on a chemically clean tantalum, lyophilised and placed in an UHV chamber for 24 hours before irradiation. After irradiation, plasmid DNA is retrieved from the UHV chamber and the samples are dissolved in tris buffer. The different topological forms of DNA resulting from single strand break formation are separated by electrophoresis gel, stained by SYBR Green 1, scanned by laser and quantified with the imageQuant program. The quantification protocol has been optimized to maximize both sensitivity and linearity. Two resonant peaks are observed with maxima at 0,8 eV and 2,2 eV ( 10,5 and 7,5 ssb per 10^3 electrons, respectively).

  18. Band gap control and photoluminescence properties of Ba(Co2x Ti1-x )O3 thin films prepared by Sol-gel method

    NASA Astrophysics Data System (ADS)

    Srivastava, Anchal; Misra, Kamakhya Prakash

    2014-06-01

    This paper reports on the preparation, characterization and optical properties of transparent Ba(Co2x Ti1-x )O3 (0 ≤ x ≤ 0.06) thin films prepared by sol-gel method and deposited on fused quartz substrate by spin-coating technique. Their formation is confirmed by X-ray diffraction patterns, energy dispersive X-ray spectrometry and Fourier transformed infrared measurements. Hitherto unreported near-band-gap photoluminescence in ultraviolet, at 378 nm (3.28 eV), of exciton origin is observed which remains unaffected with change in excitation wavelength from 320 to 350 nm. A weak defect emission appears in green region. For larger excitation wavelength, i.e., 488 nm, emission arising from localized states again occurs in green region but with lower energy. The occurrence of efficient violet-blue PL emission is related to `direct' band gap and shallow levels with high optical band gap values. Analysis of band gap variation with dopant concentration, determined using Tauc's plot assuming them both of `direct' and `indirect' nature, also indicates the `direct' nature. Co+2 ions as dopants promote a decrease of band gap of films linearly. Scanning electron micrographs show the granular and flakes-like surface growth. Atomic force microscopy images show the presence of ribbon-like nanostructured grains throughout the surface of the films which is smooth with small values of surface roughness.

  19. An interpretation of a mysterious 3.0- to 4.6-kHz emission band observed on Voyager 2 near Neptune

    NASA Technical Reports Server (NTRS)

    Sonwalkar, Vikas S.; Inan, Umran S.; Bell, Timothy F.

    1995-01-01

    A whistler mode interpretation is provided for the narrowband signal (f approx. 3 - 4.6 kHz, Delta f approx. 200 - 800 Hz) detected by the plasma wave instrument on Voyager 2 during its encounter with Neptune. Our analysis indicates that this signal may have been generated in a limited spatial region and that it propagated to other regions of the Neptunian magnetosphere in the nonducted whistler mode with wave normal vectors lying close to the whistler mode resonance cone. The observed frequency variation of the emission along the Voyager 2 trajectory is consistent with this interpretation. The source location is estimated to be near the magnetic equator at L approx. 4 and dipole longitude of 111 deg W (260 deg W longitude in Neptune coordinate system). The source frequency and bandwidth are estimated to be 3.6 kHz and 300 Hz, respectively. The waves most likely would have been generated by energetic electrons with 2- to 20-keV parallel energy via a gyroresonance mechanism. Our interpretation of the narrowband emissions places the following limits on the Neptunian thermal plasma density and temperature: (1) N(sub e, min) greater than 0.16 el/cu cm for 1.2 R(sub N) less than R less than 5 R(sub N), (2) N(sub e, max) = 597.5/cu cm at R - 1.3 R(sub N), (3) T(sub e, max) less than 500-1000 K at R approx. 5 R(sub N). It is also possible that the weak UV aurora observed near Neptune could have been caused by the precipitation of energetic particles by the narrowband emission as a result of wave particle interactions.

  20. An interpretation of a mysterious 3.0- to 4.6-kHz emission band observed on Voyager 2 near Neptune

    NASA Technical Reports Server (NTRS)

    Sonwalkar, Vikas S.; Inan, Umran S.; Bell, Timothy F.

    1995-01-01

    A whistler mode interpretation is provided for the narrowband signal (f approx. 3 - 4.6 kHz, Delta f approx. 200 - 800 Hz) detected by the plasma wave instrument on Voyager 2 during its encounter with Neptune. Our analysis indicates that this signal may have been generated in a limited spatial region and that it propagated to other regions of the Neptunian magnetosphere in the nonducted whistler mode with wave normal vectors lying close to the whistler mode resonance cone. The observed frequency variation of the emission along the Voyager 2 trajectory is consistent with this interpretation. The source location is estimated to be near the magnetic equator at L approx. 4 and dipole longitude of 111 deg W (260 deg W longitude in Neptune coordinate system). The source frequency and bandwidth are estimated to be 3.6 kHz and 300 Hz, respectively. The waves most likely would have been generated by energetic electrons with 2- to 20-keV parallel energy via a gyroresonance mechanism. Our interpretation of the narrowband emissions places the following limits on the Neptunian thermal plasma density and temperature: (1) N(sub e, min) greater than 0.16 el/cu cm for 1.2 R(sub N) less than R less than 5 R(sub N), (2) N(sub e, max) = 597.5/cu cm at R - 1.3 R(sub N), (3) T(sub e, max) less than 500-1000 K at R approx. 5 R(sub N). It is also possible that the weak UV aurora observed near Neptune could have been caused by the precipitation of energetic particles by the narrowband emission as a result of wave particle interactions.

  1. Wideband thulium-holmium-doped fiber source with combined forward and backward amplified spontaneous emission at 1600-2300  nm spectral band.

    PubMed

    Honzatko, Pavel; Baravets, Yauhen; Kasik, Ivan; Podrazky, Ondrej

    2014-06-15

    We have experimentally demonstrated two extremely wideband amplified spontaneous emission (ASE) sources. High bandwidth is achieved by combining the backward and forward ASEs generated in thulium-holmium-doped fiber using appropriate wideband couplers. The ASE source optimized for flat spectral power density covers a spectral range from 1527 to 2171 nm at a -10  dB level. The ASE source optimized for spectroscopy features an enhancement with respect to single-mode fiber (SMF) coupled halogen lamps within the spectral range from 1540 nm to more than 2340 nm covering the 800 nm bandwidth.

  2. Smart EV Energy Management System to Support Grid Services

    NASA Astrophysics Data System (ADS)

    Wang, Bin

    Under smart grid scenarios, the advanced sensing and metering technologies have been applied to the legacy power grid to improve the system observability and the real-time situational awareness. Meanwhile, there is increasing amount of distributed energy resources (DERs), such as renewable generations, electric vehicles (EVs) and battery energy storage system (BESS), etc., being integrated into the power system. However, the integration of EVs, which can be modeled as controllable mobile energy devices, brings both challenges and opportunities to the grid planning and energy management, due to the intermittency of renewable generation, uncertainties of EV driver behaviors, etc. This dissertation aims to solve the real-time EV energy management problem in order to improve the overall grid efficiency, reliability and economics, using online and predictive optimization strategies. Most of the previous research on EV energy management strategies and algorithms are based on simplified models with unrealistic assumptions that the EV charging behaviors are perfectly known or following known distributions, such as the arriving time, leaving time and energy consumption values, etc. These approaches fail to obtain the optimal solutions in real-time because of the system uncertainties. Moreover, there is lack of data-driven strategy that performs online and predictive scheduling for EV charging behaviors under microgrid scenarios. Therefore, we develop an online predictive EV scheduling framework, considering uncertainties of renewable generation, building load and EV driver behaviors, etc., based on real-world data. A kernel-based estimator is developed to predict the charging session parameters in real-time with improved estimation accuracy. The efficacy of various optimization strategies that are supported by this framework, including valley-filling, cost reduction, event-based control, etc., has been demonstrated. In addition, the existing simulation-based approaches do

  3. Single and double photoionization of beryllium below 40 eV

    SciTech Connect

    Wehlitz, R.; Bluett, J.B.; Lukic, D.

    2005-01-01

    We have measured the double-to-single photoionization ratio of beryllium (1s{sup 2}2s{sup 2}) between 28 and 40 eV and determined the relative single- and double-photoionization cross sections. In this energy region only simultaneous but not sequential emission of both 2s electrons can take place. We also compare our data with recent theoretical calculations and find good agreement with our data. The previously found scaling law for the double-to-single photoionization ratio is confirmed with high accuracy.

  4. Straight and chopped DC performance data for a reliance EV-250AT motor with a General Electric EV-1 controller

    NASA Technical Reports Server (NTRS)

    Edie, P. C.

    1981-01-01

    Straight and chopped DC motor performances for a Reliance EV-250AT motor with an EV-1 controller were examined. Effects of motor temperature and operating voltage are shown. It is found that the maximum motor efficiency is approximately 85% at low operating temperatures in the straight DC mode. Chopper efficiency is 95% under all operating conditions. For equal speeds, the motor operated in the chopped mode develops slightly more torque and draws more current than it does in the straight DC mode.

  5. Search for discrete gamma-ray sources emitting at energies greater than 10/sup 15/ eV

    SciTech Connect

    Samorski, M.; Stamm, W.

    1984-02-15

    The data of the extensive air shower experiment at Kiel have been scanned systematically for possible discrete ..gamma..-ray sources in the energy range E>10/sup 15/ eV and in the declination band delta = 25/sup 0/-75/sup 0/. Photon fluxes for celestial positions with the statistically most significant excesses of showers and 3 sigma upper limit photon fluxes for COS B ..gamma..-ray sources visible to the extensive air shower experiment at Kiel are presented.

  6. Band Together!

    ERIC Educational Resources Information Center

    Olson, Cathy Applefeld

    2011-01-01

    After nearly a decade as band director at St. James High School in St. James, Missouri, Derek Limback knows that the key to building a successful program is putting the program itself above everything else. Limback strives to augment not only his students' musical prowess, but also their leadership skills. Key to his philosophy is instilling a…

  7. The study of optical band edge property of bismuth oxide nanowires α-Bi2O3.

    PubMed

    Ho, Ching-Hwa; Chan, Ching-Hsiang; Huang, Ying-Sheng; Tien, Li-Chia; Chao, Liang-Chiun

    2013-05-20

    The α-phase Bi(2)O(3) (α-Bi(2)O(3)) is a crucial and potential visiblelight photocatalyst material needless of intentional doping on accommodating band gap. The understanding on fundamental optical property of α-Bi(2)O(3) is important for its extended applications. In this study, bismuth oxide nanowires with diameters from tens to hundreds nm have been grown by vapor transport method driven with vapor-liquid-solid mechanism on Si substrate. High-resolution transmission electron microscopy and Raman measurement confirm α phase of monoclinic structure for the as-grown nanowires. The axial direction for the as-grown nanowires was along < 122 >. The band-edge structure of α-Bi(2)O(3) has been probed experimentally by thermoreflectance (TR) spectroscopy. The direct band gap was determined accurately to be 2.91 eV at 300 K. Temperaturedependent TR measurements of 30-300 K were carried out to evaluate temperature-energy shift and line-width broadening effect for the band edge of α-Bi(2)O(3) thin-film nanowires. Photoluminescence (PL) experiments at 30 and 300 K were carried out to identify band-edge emission as well as defect luminescence for the α-Bi(2)O(3) nanowires. On the basis of experimental analyses of TR and PL, optical characteristics of direct band edge of α-Bi(2)O(3) nanowires have thus been realized.

  8. Calibrating image plate sensitivity in the 700 to 5000 eV spectral energy range

    NASA Astrophysics Data System (ADS)

    Haugh, Michael J.; Lee, Joshua; Romano, Edward; Schneider, Marilyn

    2013-09-01

    This paper describes a method to calibrate image plate sensitivity for use in the low energy spectral range. Image plates, also known as photostimulable luminescence (PSL) detectors, have often proved to be a valuable tool as a detector for plasma physics studies. Their advantages of large dynamic range, high stopping power, and resistance to neutron damage sometimes outweigh the problems of limited resolution and the remote processing required. The neutron damage resistance is required when the X-ray source is producing a high neutron flux. The Static X-ray Imager (SXI) is a key diagnostic on the National Ignition Facility (NIF) target chamber at LLNL for use in determining the symmetry of the laser beams. The SXI is essential to proper interpretation of the data from the Dante diagnostic to determine the X-ray radiation temperature. It is comprised of two diagnostics located at the top and the bottom of the target chamber. The usual detector is a large array CCD camera. For shots giving high yields of neutrons, the camera would not only be blinded by the neutrons, it would be damaged. To get around this problem, an image plate (IP) is used as the detector. The NIF application covers the energy range from 700 to 5000 eV. The type of image plates typically used for plasma physics are the Fuji BAS-MS, BAS-SR, and BAS-TR models. All models consist of an X-ray sensitive material made of BaF(Br,I):Eu2+ embedded in a plastic binder. X-rays incident on the phosphor ionize the Eu 2+ producing Eu3+ and free electrons that are trapped in lattice defects (F-centers) produced by the absence of halogen ions in the BaF2 crystal. An image plate readout scanner irradiates the IP with a red laser causing reduction of the Eu3+ and emission of a blue photon. The photon is collected using a photomultiplier and digitized to make an electronic image. Image plates are cleared of all F-centers by putting them under a bright light for about 10 minutes. They are then ready for producing a

  9. Direct band gap optical emission from Ge islands grown on relaxed Si{sub 0.5}Ge{sub 0.5}/Si (100) substrate

    SciTech Connect

    Aluguri, R.; Manna, S.; Ray, S. K.

    2014-01-07

    Strained Ge islands have been grown on fully relaxed Si{sub 0.5}Ge{sub 0.5} substrate by pulsed laser ablation technique. The formation of strained Ge islands has been found for film with higher thickness following Stranski–Krastanov growth mechanism. The variation of strain with changing Ge layer thickness has been analyzed using Raman spectroscopy and high-resolution X-ray diffraction techniques. X-ray photoelectron spectra have shown the absence of any Si-Ge intermixing and oxidation of Ge films. A strong no-phonon photoluminescence emission from Ge islands has been observed, showing the superior optical characteristics of the islands grown on relaxed substrate.

  10. A heterotrimetallic Ir(III), Au(III) and Pt(II) complex incorporating cyclometallating bi- and tridentate ligands: simultaneous emission from different luminescent metal centres leads to broad-band light emission.

    PubMed

    Muñoz-Rodríguez, Rebeca; Buñuel, Elena; Fuentes, Noelia; Williams, J A Gareth; Cárdenas, Diego J

    2015-05-14

    Di- and tri-nuclear metal complexes incorporating gold(III), iridium(III) and platinum(II) units linked via a 1,3,5-triethynylbenzene core are reported, together with the corresponding mononuclear complexes as models. The gold(III) and platinum(II) units comprise tridentate, cyclometallating, C^N^C and N^N^C-coordinating ligands, respectively, with the Ar-C≡C- directly bound to the metal at the fourth coordination site. The iridium moiety is an Ir(ppy)2(acac) unit bound to the triethynylbenzene through a phenyl substituent at the 3-position of the acac ligand. The multinuclear compounds are prepared, using a modular synthetic strategy, from the monometallic complexes. All of the compounds are luminescent in solution at room temperature, and their photophysical properties were studied. The triplet excited state energies of the mononuclear complexes lie in the order Au > Ir > Pt. Consistent with this order, energy transfer from Au to Ir and from Au to Pt is observed, leading to quenching of the Au emission in the gold-containing multinuclear complexes. Energy transfer from Ir to Pt occurs at a rate that only partially quenches the Ir-based emission. As a result, the dinuclear Ir-Pt and trinuclear Au-Ir-Pt complexes display broad emission across most of the visible region of the spectrum.

  11. Hydrogen-carbon complexes and the blue luminescence band in GaN

    NASA Astrophysics Data System (ADS)

    Demchenko, Denis; Diallo, Ibrahima; Reshchikov, Michael

    The blue luminescence band with a maximum at 3.0 eV and the zero-phonon line at 3.33 eV (labeled BL2) is observed in high-resistivity GaN. Under prolonged ultraviolet (UV) light exposure, the BL2 band transforms into the yellow luminescence (YL) band with a maximum at 2.2 eV. Our calculations using hybrid functionals suggest that the BL2 band is related to a hydrogen-carbon defect complex, most likely CNON-Hi. The complex creates defect transition level close to the valence band, which is responsible for the BL2 band. Under UV illumination the complex dissociates, leaving as byproduct the source of the YL band (CNON or CN) and interstitial hydrogen. The work was supported by the National Science Foundation (DMR-1410125) and the Thomas F. and Kate Miller Jeffress Memorial Trust.

  12. White light tunable emissions from ZnS: Eu3+ nanophosphors over 330-465 nm excitation range for white LED applications

    NASA Astrophysics Data System (ADS)

    Ahemen, I.; De, D. K.; Dejene, F. B.; Viana, B.

    2016-04-01

    (ZnS: Eu3+ - CMC) nanophosphors of cubic (zinc blende) structure were synthesized using a precipitation technique with doping concentrations of Eu3+ ions 1 mol% and 5 mol%. The crystal sizes were 2.56 nm and 2.91 nm respectively. Annealing at 300 °C in a sulfur-rich atmosphere altered the crystal size to 4.35 nm and 3.65 nm respectively and the band gap from 4.2 eV to 3.76 eV and 3.81 eV respectively. The as-synthesized samples gave pure orange-red emission when excited at wavelengths of 394 nm and 465 nm. After thermal annealing of the samples, a broad emission band in the blue-green region assigned to defect related states emerged or were enhanced. Also enhanced were the emission lines of Eu3+ ions in the orange-red region. A combination of these two transitions gave white light of different shades (recorded on the CIE 1931 chromaticity diagram) from cool white through day-light to warm white light, depending on Eu3+ concentration and the excitation wavelengths (UV-330 to blue 465 nm), thus showing great potential of these nano-phosphors in the generation of high quality white light.

  13. Hydrogen transport diagnostics by atomic and molecular emission line profiles simultaneously measured for large helical device

    SciTech Connect

    Fujii, K.; Shikama, T.; Hasuo, M.; Goto, M.; Morita, S.

    2013-01-15

    We observe the Balmer-{alpha}, -{beta}, and -{gamma} lines of hydrogen atoms and Q branches of the Fulcher-{alpha} band of hydrogen molecules simultaneously with their polarization resolved for large helical device. From the fit including the line splits and the polarization dependences by the Zeeman effect, the emission locations, intensities, and the temperatures of the atoms and molecules are determined. The emission locations of the hydrogen atoms are determined outside but close to the last closed flux surface (LCFS). The results are consistent with a previous work (Phys. Plasmas 12, 042501 (2005)). On the other hand, the emission locations of the molecules are determined to be in the divertor legs, which is farer from those of the atoms. The kinetic energy of the atoms is 1 {approx} 20 eV, while the rotational temperature of molecules is {approx}0.04 eV. Additionally, substantial wings, which originate from high velocity atoms and are not reproduced by the conventional spectral analysis, are observed in the Balmer line profiles. We develop a one-dimensional model to simulate the transport of the atoms and molecules. The model reproduces the differences of the emission locations of the atoms and molecules when their initial temperatures are assumed to be 3 eV and 0.04 eV, respectively. From the model, the wings of the Balmer-{alpha} line is attributed to the high velocity atoms exist deep inside the LCFS, which are generated by the charge exchange collisions with hot protons there.

  14. Determination of satellite valley position in GaN emitter from photoexcited field emission investigations

    NASA Astrophysics Data System (ADS)

    Semenenko, M.; Yilmazoglu, O.; Hartnagel, H. L.; Pavlidis, D.

    2011-01-01

    Argon plasma etched GaN field-emitter rods with nanometer-scale diameter were fabricated on GaN grown on an n+-GaN substrate. Their electron field emission properties were investigated both without and under illumination by using light sources with various wavelengths. The Fowler-Nordheim current-voltage characteristics of the cathodes show a change in slope for illuminated cathodes. The electron affinity difference ΔE between the different valleys in the conduction band has been ascertained and is in the range from 1.18 up to 1.21 eV.

  15. Spectroscopic investigation on the electronic structure of a 5 d band insulator SrHfO3

    NASA Astrophysics Data System (ADS)

    Lee, Yunsang; Seo, Y. K.; Lee, D. J.; Noh, H. J.

    2011-03-01

    We investigated the high-energy electronic structure of a 5d perovskite SrHf O3 . By using optical spectroscopy and O 1 s x-ray absorption spectroscopy, the values of electronic structure parameters are estimated properly. In particular, the crystal field splitting energy, which is closely associated with the p - d hybridization strength, is as high as 5 eV, and the Sr 4 d bands appear to be strongly mixed with the Hf 5 d bands. Moreover, the emission spectra with a 325 nm light excitation exhibit a sizable strength near 500 nm at low temperatures due to oxygen defects. These findings in SrHf O3 are compared with electronic properties of similar compounds, 3 d SrTi O3 and 4 d SrZr O3 .

  16. Bulk band gaps in divalent hexaborides

    SciTech Connect

    Denlinger, Jonathan; Clack, Jules A.; Allen, James W.; Gweon, Gey-Hong; Poirier, Derek M.; Olson, Cliff G.; Sarrao, John L.; Bianchi, Andrea D.; Fisk, Zachary

    2002-08-01

    Complementary angle-resolved photoemission and bulk-sensitive k-resolved resonant inelastic x-ray scattering of divalent hexaborides reveal a >1 eV X-point gap between the valence and conduction bands, in contradiction to the band overlap assumed in several models of their novel ferromagnetism. This semiconducting gap implies that carriers detected in transport measurements arise from defects, and the measured location of the bulk Fermi level at the bottom of the conduction band implicates boron vacancies as the origin of the excess electrons. The measured band structure and X-point gap in CaB6 additionally provide a stringent test case for proper inclusion of many-body effects in quasi-particle band calculations.

  17. NASA's Earth Venture-1 (EV-1) Airborne Science Investigations

    NASA Technical Reports Server (NTRS)

    Guillory, A.; Denkins, T.; Allen, B. Danette; Braun, Scott A.; Crawford, James H.; Jensen, Eric J.; Miller, Charles E.; Moghaddam, Mahta; Maring, Hal

    2011-01-01

    In 2010, NASA announced the first Earth Venture (EV-1) selections in response to a recommendation made by the National Research Council for low-cost investigations fostering innovation in Earth science. The five EV-1 investigations span the Earth science focus areas of atmosphere, weather, climate, water and energy and, carbon and represent earth science researchers from NASA as well as other government agencies, academia and industry from around the world. The EV-1 missions are: 1) Airborne Microwave Observatory of Subcanopy and Subsurface (AirMOSS), 2) Airborne Tropical Tropopause Experiment (ATTREX), 3) Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), 4) Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ), and 5) Hurricane And Severe Storm Sentinel (HS3). The Earth Venture missions are managed out of the Earth System Science Pathfinder (ESSP) Program Office (Allen, et. al. 2010b)

  18. 47 CFR 90.1323 - Emission limits.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 47 Telecommunication 5 2012-10-01 2012-10-01 false Emission limits. 90.1323 Section 90.1323... MOBILE RADIO SERVICES Wireless Broadband Services in the 3650-3700 MHz Band § 90.1323 Emission limits. (a) The power of any emission outside a licensee's frequency band(s) of operation shall be...

  19. 47 CFR 90.1323 - Emission limits.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 47 Telecommunication 5 2013-10-01 2013-10-01 false Emission limits. 90.1323 Section 90.1323... MOBILE RADIO SERVICES Wireless Broadband Services in the 3650-3700 MHz Band § 90.1323 Emission limits. (a) The power of any emission outside a licensee's frequency band(s) of operation shall be...

  20. 47 CFR 90.1323 - Emission limits.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 47 Telecommunication 5 2014-10-01 2014-10-01 false Emission limits. 90.1323 Section 90.1323... MOBILE RADIO SERVICES Wireless Broadband Services in the 3650-3700 MHz Band § 90.1323 Emission limits. (a) The power of any emission outside a licensee's frequency band(s) of operation shall be...

  1. A novel approach to obtain highly intense self-activated photoluminescence emissions in hydroxyapatite nanoparticles

    NASA Astrophysics Data System (ADS)

    Machado, Thales R.; Sczancoski, Júlio C.; Beltrán-Mir, Héctor; Nogueira, Içamira C.; Li, Máximo S.; Andrés, Juan; Cordoncillo, Eloisa; Longo, Elson

    2017-05-01

    Defect-related photoluminescence (PL) in materials have attracted interest for applications including near ultraviolet (NUV) excitable light-emitting diodes and in biomedical field. In this paper, hydroxyapatite [Ca10(PO4)6(OH)2] nanorods with intense PL bands (bluish- and yellowish-white emissions) were obtained when excited under NUV radiation at room temperature. These nanoparticles were synthesized via chemical precipitation at 90 °C followed by distinct heat treatments temperatures (200-800 °C). Intense and broad emission profiles were achieved at 350 °C (380-750 nm) and 400 °C (380-800 nm). UV-Vis spectroscopy revealed band gap energies (5.58-5.78 eV) higher than the excitation energies ( 3.54 and 2.98 eV at 350 and 415 nm, respectively), confirming the contribution of defect energy levels within the forbidden zone for PL emissions. The structural features were characterized by X-ray diffraction, Rietveld refinement, thermogravimetric analysis, and Fourier transform infrared spectroscopy. By means of these techniques, the relation between structural order-disorder induced by defects, chemical reactions at both lattice and surface of the materials as well as the PL, without activator centers, was discussed in details.

  2. Single ionization of helium by 730-eV electrons

    SciTech Connect

    Stevenson, M. A.; Lohmann, B.; Bray, I.; Fursa, D. V.; Stelbovics, A. T.

    2007-03-15

    We present fully differential measurements of 730-eV electron-impact single ionization of the ground state of helium with 205- or 100-eV outgoing electrons. Internormalized data are obtained for coplanar geometries with the fast electron detected at {theta}{sub A}=6 degree sign , 9 degree sign , and 12 degree sign . The data are compared, where possible, with the corresponding data of Catoire et al. [J. Phys. B 39, 2827 (2006)] and the convergent close-coupling theory. An improved agreement is found between the present measurements and the theory.

  3. Deep-level defects related to the emissive pits in thick InGaN films on GaN template and bulk substrates

    NASA Astrophysics Data System (ADS)

    Sumiya, Masatomo; Toyomitsu, Naoki; Nakano, Yoshitaka; Wang, Jianyu; Harada, Yoshitomo; Sang, Liwen; Sekiguchi, Takashi; Yamaguchi, Tomohiro; Honda, Tohru

    2017-01-01

    We studied the emissive pits in InGaN films grown on compressive and strain-free GaN underlying layers. Pit density decreased with the full width at half maximum of ω(0002) of InGaN. The films grew on compressive and strain-free GaN underlying layers with spiral and step-flow modes, respectively. Carbon impurities accumulated inside the pits. Comparison of cathodoluminescence inside the pits and steady-state photocapacitance spectra showed that the energy level of the carbon impurities appeared at ˜2.8 eV below the conduction band (Ec) for both types of pits. Deep-level defects at Ec -2.4 eV resulting in green fluorescence emission were considered to originate from pits related to screw dislocations.

  4. Band structure mapping of bilayer graphene via quasiparticle scattering

    NASA Astrophysics Data System (ADS)

    Yankowitz, Matthew; Wang, Joel I.-Jan; Li, Suchun; Birdwell, A. Glen; Chen, Yu-An; Watanabe, Kenji; Taniguchi, Takashi; Quek, Su Ying; Jarillo-Herrero, Pablo; LeRoy, Brian J.

    2014-09-01

    A perpendicular electric field breaks the layer symmetry of Bernal-stacked bilayer graphene, resulting in the opening of a band gap and a modification of the effective mass of the charge carriers. Using scanning tunneling microscopy and spectroscopy, we examine standing waves in the local density of states of bilayer graphene formed by scattering from a bilayer/trilayer boundary. The quasiparticle interference properties are controlled by the bilayer graphene band structure, allowing a direct local probe of the evolution of the band structure of bilayer graphene as a function of electric field. We extract the Slonczewski-Weiss-McClure model tight binding parameters as γ0 = 3.1 eV, γ1 = 0.39 eV, and γ4 = 0.22 eV.

  5. Band gap opening in bilayer silicene by alkali metal intercalation

    NASA Astrophysics Data System (ADS)

    Liu, Hongsheng; Han, Nannan; Zhao, Jijun

    2014-11-01

    Recently, bilayer and multilayer silicene have attracted increased attention following the boom of silicene, which holds great promise for future applications in microelectronic devices. Herein we systematically investigate all stacking configurations of bilayer silicene and the corresponding electronic properties. Strong coupling is found between two silicene layers, which destroys the Dirac cones in the band structures of pristine silicene and makes bilayer silicene sheets metallic. However, intercalation of alkali metal (especially potassium) can effectively decouple the interaction between two silicene layers. In the K-intercalated bilayer silicene (KSi4), the Dirac cones are recovered with a small band gap of 0.27 eV located about 0.55 eV below the Fermi level. Furthermore, intercalation of K+ cations in bilayer silicene (K+Si4) results in a semiconductor with a moderate band gap of 0.43 eV, making it ideal for microelectronic applications.

  6. Laparoscopic gastric banding

    MedlinePlus

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

  7. Anisotropy of cosmic rays of energy 10 (15) eV to 10 (17) eV observed at Akeno

    NASA Technical Reports Server (NTRS)

    Kifune, T.; Nishijima, K.; Hara, T.; Hatano, Y.; Hayashida, N.; Honda, M.; Kamata, K.; Matsubara, Y.; Nagano, M.; Tanahashi, G.

    1985-01-01

    Anisotropy of cosmic rays is studied with extensive air showers (EAS) data by muon trigger. The present results support those obtained by electron trigger which suggest the significant anisotropy of second harmonics with phase around 100 deg in right ascension for showers of 10 to the 16th power - 10 to the 17th power eV, and predominant arrival direction of 230 deg in right ascension for muon-rich showers. It seems that the phase of the first harmonics in the energy range below 10 to the 11th power eV is about 300 deg in right ascension and the second harmonics near 6 x 10 to the 14th power eV is statistically significant with an amplitude of 0.39 + or - 0.13% in direction of 83 + or - 10 deg in right ascension.

  8. Emission of Cu-related complexes in ZnO:Cu nanocrystals

    NASA Astrophysics Data System (ADS)

    Torchynska, T. V.; El Filali, B.; Ballardo Rodríguez, I. Ch.

    2016-01-01

    Photoluminescence (PL), its temperature dependence, scanning electronic microscopy (SEM) and X ray diffraction (XRD) have been applied for the comparative study of varying the emission, morphology and crystal structure of ZnO and ZnO:Cu nanocrystals (NCs) versus technological routines, as well as the dependence of ZnO:Cu NC parameters on the Cu concentration. A set of ZnO and ZnO Cu NCs was prepared by the electrochemical (anodization) method at a permanent voltage and different etching durations with follows thermal annealing at 400 °C for 2 h in ambient air. The size of ZnO NCs decreases from 300 nm×540 nm down to 200 nm×320 nm with etching duration increasing. XRD study has confirmed that thermal annealing stimulates the ZnO oxidation and crystallization with the formation of wurtzite ZnO crystal lattice. XRD method has been used for monitoring the lattice parameters and for confirming the Cu doping of ZnO Cu NCs. In ZnO Cu NCs four defect related PL bands are detected with the PL peaks at 1.95-2.00 eV (A), 2.15-2.23 eV (B), 2.43-2.50 eV (C) and 2.61-2.69 eV (D). Highest PL intensities of orange, yellow and green emissions have been obtained in ZnO Cu NCs with the Cu concentration of 2.28 at%. At Cu concentration increasing (≥2.28 at%) the PL intensities of the bands A, B, C decrease and the new PL band peaked at 2.61-2.69 eV at 10 K appears in the PL spectrum. The variation of PL intensities for all PL bands versus temperature has been studied and the corresponding activation energies of PL thermal decay have been estimated. The type of Cu-related complexes is discussed using the correlation between the PL spectrum transformation and the variation of XRD parameters in ZnO Cu NCs.

  9. PHEV/EV Li-Ion Battery Second-Use Project, NREL (National Renewable Energy Laboratory) (Poster)

    SciTech Connect

    Newbauer, J.; Pesaran, A.

    2010-05-01

    Plug-in hybrid electric vehicles (PHEVs) and full electric vehicles (Evs) have great potential to reduce U.S. dependence on foreign oil and emissions. Battery costs need to be reduced by ~50% to make PHEVs cost competitive with conventional vehicles. One option to reduce initial costs is to reuse the battery in a second application following its retirement from automotive service and offer a cost credit for its residual value.

  10. A Small Fullerene (C24) may be the Carrier of the 11.2 μm Unidentified Infrared Band

    NASA Astrophysics Data System (ADS)

    Bernstein, L. S.; Shroll, R. M.; Lynch, D. K.; Clark, F. O.

    2017-02-01

    We analyze the spectrum of the 11.2 μm unidentified infrared band (UIR) from NGC 7027 and identify a small fullerene (C24) as a plausible carrier. The blurring effects of lifetime and vibrational anharmonicity broadening obscure the narrower, intrinsic spectral profiles of the UIR band carriers. We use a spectral deconvolution algorithm to remove the blurring, in order to retrieve the intrinsic profile of the UIR band. The shape of the intrinsic profile—a sharp blue peak and an extended red tail—suggests that the UIR band originates from a molecular vibration–rotation band with a blue band head. The fractional area of the band-head feature indicates a spheroidal molecule, implying a nonpolar molecule and precluding rotational emission. Its rotational temperature should be well approximated by that measured for nonpolar molecular hydrogen, ∼825 K for NGC 7027. Using this temperature, and the inferred spherical symmetry, we perform a spectral fit to the intrinsic profile, which results in a rotational constant implying C24 as the carrier. We show that the spectroscopic parameters derived for NGC 7027 are consistent with the 11.2 μm UIR bands observed for other objects. We present density functional theory (DFT) calculations for the frequencies and infrared intensities of C24. The DFT results are used to predict a spectral energy distribution (SED) originating from absorption of a 5 eV photon, and characterized by an effective vibrational temperature of 930 K. The C24 SED is consistent with the entire UIR spectrum and is the dominant contributor to the 11.2 and 12.7 μm bands.

  11. Tuning Ferritin's Band Gap through Mixed Metal Oxide Nanoparticle Formation.

    PubMed

    Olsen, Cameron; Embley, Jacob; Hansen, Kameron; Henrichsen, Andrew; Peterson, J; Colton, John S; Watt, Richard

    2017-03-23

    This study uses the formation of a mixed metal oxide inside ferritin to tune the band gap energy of the ferritin mineral. The mixed metal oxide is composed of both Co and Mn, and is formed by reacting aqueous Co2+ with MnO4- in the presence of apoferritin. Altering the ratio between the two reactants allowed for controlled tuning of the band gap energies. All minerals formed were indirect band gap materials, with indirect band gap energies ranging from 0.52 to 1.30 eV. The direct transitions were also measured, with energy values ranging from 2.71 to 3.11 eV. Tuning the band gap energies of these samples changes the wavelengths absorbed by each mineral, increasing ferritin's potential in solar-energy harvesting. Additionally, the success of using MnO4- in ferritin mineral formation opens the possibility for new mixed metal oxide cores inside ferritin.

  12. Excited ionic and neutral fragments produced by dissociation of the N2(+)* H band

    NASA Technical Reports Server (NTRS)

    Samson, James A. R.; Chung, Y.; Lee, E.-M.

    1991-01-01

    N I and N II fluorescent radiation was observed when N2 was irradiated by undispersed synchrotron radiation with an upper energy limit of approximately 200 eV. The excited fragments originate from dissociation of a band of excited ionic states of N2 lying between 34.7 and 44 eV.

  13. The genome of the Lactobacillus sanfranciscensis temperate phage EV3

    PubMed Central

    2013-01-01

    Background Bacteriophages infection modulates microbial consortia and transduction is one of the most important mechanism involved in the bacterial evolution. However, phage contamination brings food fermentations to a halt causing economic setbacks. The number of phage genome sequences of lactic acid bacteria especially of lactobacilli is still limited. We analysed the genome of a temperate phage active on Lactobacillus sanfranciscensis, the predominant strain in type I sourdough fermentations. Results Sequencing of the DNA of EV3 phage revealed a genome of 34,834 bp and a G + C content of 36.45%. Of the 43 open reading frames (ORFs) identified, all but eight shared homology with other phages of lactobacilli. A similar genomic organization and mosaic pattern of identities align EV3 with the closely related Lactobacillus vaginalis ATCC 49540 prophage. Four unknown ORFs that had no homologies in the databases or predicted functions were identified. Notably, EV3 encodes a putative dextranase. Conclusions EV3 is the first L. sanfranciscensis phage that has been completely sequenced so far. PMID:24308641

  14. Observations from The EV Project in Q4 2013

    SciTech Connect

    John Smart

    2014-02-01

    This is a summary report for The EV Project 4th quarter 2013 reports. It describes electric vehicle driver driving and charging behavior observed in Q4. It is the same report as the previously approved/published Q3 2013 report, only the numbers have been updated. It is for public release and does not have limited distribution.

  15. Philosophical Adventures in the Lands of Oz and Ev

    ERIC Educational Resources Information Center

    Matthews, Gareth B.

    2009-01-01

    In this article, the author talks about the philosophical adventures of the characters in L. Frank Baum's Lands of Oz and Ev stories and discusses how such stories can stimulate reflections on philosophically interesting questions. Frank Baum is considered as the first American writer of philosophical fantasy for children for writing "The…

  16. Philosophical Adventures in the Lands of Oz and Ev

    ERIC Educational Resources Information Center

    Matthews, Gareth B.

    2009-01-01

    In this article, the author talks about the philosophical adventures of the characters in L. Frank Baum's Lands of Oz and Ev stories and discusses how such stories can stimulate reflections on philosophically interesting questions. Frank Baum is considered as the first American writer of philosophical fantasy for children for writing "The…

  17. New Kronig-Penney Equation Emphasizing the Band Edge Conditions

    ERIC Educational Resources Information Center

    Szmulowicz, Frank

    2008-01-01

    The Kronig-Penney problem is a textbook example for discussing band dispersions and band gap formation in periodic layered media. For example, in photonic crystals, the behaviour of bands next to the band edges is important for further discussions of such effects as inhibited light emission, slow light and negative index of refraction. However,…

  18. New Kronig-Penney Equation Emphasizing the Band Edge Conditions

    ERIC Educational Resources Information Center

    Szmulowicz, Frank

    2008-01-01

    The Kronig-Penney problem is a textbook example for discussing band dispersions and band gap formation in periodic layered media. For example, in photonic crystals, the behaviour of bands next to the band edges is important for further discussions of such effects as inhibited light emission, slow light and negative index of refraction. However,…

  19. Ks-Band Detection of Thermal Emission and Color Constraints to CoRoT-1b: A Low-Albedo Planet with Inefficient Atmospheric Energy Redistribution and a Temperature Inversion

    NASA Astrophysics Data System (ADS)

    Rogers, Justin C.; Apai, Dániel; López-Morales, Mercedes; Sing, David K.; Burrows, Adam

    2009-12-01

    We report the detection in Ks-band of the secondary eclipse of the hot Jupiter CoRoT-1b from time series photometry with the ARC 3.5 m telescope at Apache Point Observatory. The eclipse shows a depth of 0.336 ± 0.042% and is centered at phase 0.5022+0.0023 -0.0027, consistent with a zero eccentricity orbit (e cos ω = 0.0035+0.0036 -0.0042). We perform the first optical to near-infrared multi-band photometric analysis of an exoplanet's atmosphere and constrain the reflected and thermal emissions by combining our result with the recent 0.6, 0.71, and 2.09 μm secondary eclipse detections by Snellen et al., Gillon et al., and Alonso et al. Comparing the multi-wavelength detections to state-of-the-art radiative-convective chemical-equilibrium atmosphere models, we find the near-infrared fluxes difficult to reproduce. The closest blackbody-based and physical models provide the following atmosphere parameters: a temperature T = 2460+80 -160 K; a very low Bond albedo AB = 0.000+0.081 -0.000 and an energy redistribution parameter Pn = 0.1, indicating a small but nonzero amount of heat transfer from the day to nightside. The best physical model suggests a thermal inversion layer with an extra optical absorber of opacity κ e = 0.05 cm2 g-1, placed near the 0.1 bar atmospheric pressure level. This inversion layer is located 10 times deeper in the atmosphere than the absorbers used in models to fit mid-infrared Spitzer detections of other irradiated hot Jupiters. Based on observations obtained with the Apache Point Observatory 3.5 m telescope, which is owned and operated by the Astrophysical Research Consortium.

  20. Ks-BAND DETECTION OF THERMAL EMISSION AND COLOR CONSTRAINTS TO CoRoT-1b: A LOW-ALBEDO PLANET WITH INEFFICIENT ATMOSPHERIC ENERGY REDISTRIBUTION AND A TEMPERATURE INVERSION

    SciTech Connect

    Rogers, Justin C.; Apai, Daniel; Lopez-Morales, Mercedes; Sing, David K.; Burrows, Adam

    2009-12-20

    We report the detection in Ks-band of the secondary eclipse of the hot Jupiter CoRoT-1b from time series photometry with the ARC 3.5 m telescope at Apache Point Observatory. The eclipse shows a depth of 0.336 +- 0.042% and is centered at phase 0.5022{sup +0.0023}{sub -0.0027}, consistent with a zero eccentricity orbit (e cos omega = 0.0035{sup +0.0036}{sub -0.0042}). We perform the first optical to near-infrared multi-band photometric analysis of an exoplanet's atmosphere and constrain the reflected and thermal emissions by combining our result with the recent 0.6, 0.71, and 2.09 mum secondary eclipse detections by Snellen et al., Gillon et al., and Alonso et al. Comparing the multi-wavelength detections to state-of-the-art radiative-convective chemical-equilibrium atmosphere models, we find the near-infrared fluxes difficult to reproduce. The closest blackbody-based and physical models provide the following atmosphere parameters: a temperature T = 2460{sup +80}{sub -160} K; a very low Bond albedo A{sub B} = 0.000{sup +0.081}{sub -0.000}; and an energy redistribution parameter P{sub n} = 0.1, indicating a small but nonzero amount of heat transfer from the day to nightside. The best physical model suggests a thermal inversion layer with an extra optical absorber of opacity kappa{sub e} = 0.05 cm{sup 2} g{sup -1}, placed near the 0.1 bar atmospheric pressure level. This inversion layer is located 10 times deeper in the atmosphere than the absorbers used in models to fit mid-infrared Spitzer detections of other irradiated hot Jupiters.

  1. Enhanced High Harmonic Generation from Multiply Ionized Argon above 500 eV through Laser Pulse Self-Compression

    SciTech Connect

    Arpin, P.; Popmintchev, T.; Kapteyn, H. C.; Murnane, M. M.; Wagner, N. L.; Cohen, O.

    2009-10-02

    By combining laser pulse self-compression and high harmonic generation within a single waveguide, we demonstrate high harmonic emission from multiply charged ions for the first time. This approach enhances the laser intensity and counteracts ionization-induced defocusing, extending the cutoff photon energy in argon above 500 eV for the first time, with higher spectral intensity and cutoff energy than He for the same input laser parameters. This Letter demonstrates a pathway for extending high harmonic emission to very high photon energies using large, multiply charged, ions with high ionization potentials.

  2. Deep-UV emission at 219 nm from ultrathin MBE GaN/AlN quantum heterostructures

    NASA Astrophysics Data System (ADS)

    Islam, S. M.; Protasenko, Vladimir; Lee, Kevin; Rouvimov, Sergei; Verma, Jai; Xing, Huili Grace; Jena, Debdeep

    2017-08-01

    Deep ultraviolet (UV) optical emission below 250 nm (˜5 eV) in semiconductors is traditionally obtained from high aluminum containing AlGaN alloy quantum wells. It is shown here that high-quality epitaxial ultrathin binary GaN quantum disks embedded in an AlN matrix can produce efficient optical emission in the 219-235 nm (˜5.7-5.3 eV) spectral range, far above the bulk bandgap (3.4 eV) of GaN. The quantum confinement energy in these heterostructures is larger than the bandgaps of traditional semiconductors, made possible by the large band offsets. These molecular beam epitaxy-grown extreme quantum-confinement GaN/AlN heterostructures exhibit an internal quantum efficiency of 40% at wavelengths as short as 219 nm. These observations together with the ability to engineer the interband optical matrix elements to control the direction of photon emission in such binary quantum disk active regions offer unique advantages over alloy AlGaN quantum well counterparts for the realization of deep-UV light-emitting diodes and lasers.

  3. Occupied and unoccupied band structure of Ag(100) determined by photoemission from Ag quantum wells and bulk samples

    NASA Astrophysics Data System (ADS)

    Paggel, J. J.; Miller, T.; Chiang, T.-C.

    2000-01-01

    Angle-resolved photoemission spectra taken from atomically uniform films of Ag on Fe(100) show layer-resolved quantum-well peaks. The measured peak positions as a function of film thickness permit a unique determination of the initial band dispersion via the Bohr-Sommerfeld quantization rule. This information, combined with normal-emission data taken from a single crystal Ag(100), leads to a unique determination of the final band dispersion. In this study, we employ a two-band model with four adjustable parameters for a simultaneous fit to these experimental results. The initial and final band dispersions deduced from the fit are accurate to better than 0.03 eV at any wave vector k within the range of measurement. The analytic formula for the band dispersions and the parameters for the best fit are given for future reference. The Fermi wave vector along [100], normalized to the Brillouin-zone size, is determined to be kF/kΓX=0.828+/-0.001, which is more accurate than the de Haas-van Alphen result. The corresponding Fermi velocity is νF=1.06 in units of the free-electron value. The combined reflection phase for the electron wave at the two boundaries is also deduced and compared with a semiempirical formula. This comparison allows us to deduce the edges of the hybridization gap in the Fe substrate.

  4. Acoustic emission frequency discrimination

    NASA Technical Reports Server (NTRS)

    Sugg, Frank E. (Inventor); Graham, Lloyd J. (Inventor)

    1988-01-01

    In acoustic emission nondestructive testing, broadband frequency noise is distinguished from narrow banded acoustic emission signals, since the latter are valid events indicative of structural flaws in the material being examined. This is accomplished by separating out those signals which contain frequency components both within and beyond (either above or below) the range of valid acoustic emission events. Application to acoustic emission monitoring during nondestructive bond verification and proof loading of undensified tiles on the Space Shuttle Orbiter is considered.

  5. EOS ASTER thermal infrared band vicarious calibration

    NASA Technical Reports Server (NTRS)

    Palluconi, F.; Tonooka, H.; Hook, S.; Abtahi, A.; Alley, R.; Thompson, T.; Hoover, G.; Zadourian, S.

    2001-01-01

    Calibration of the 5 EOS ASTER instrument emission bands (90 m pixels at surface) is being checked during the operational life of the mission using field measurements simultaneous with the image acquisition.

  6. EOS ASTER thermal infrared band vicarious calibration

    NASA Technical Reports Server (NTRS)

    Palluconi, F.; Tonooka, H.; Hook, S.; Abtahi, A.; Alley, R.; Thompson, T.; Hoover, G.; Zadourian, S.

    2001-01-01

    Calibration of the 5 EOS ASTER instrument emission bands (90 m pixels at surface) is being checked during the operational life of the mission using field measurements simultaneous with the image acquisition.

  7. Photoelectron Spectroscopy of Hexachloroplatinate-Nucleobase Complexes: Nucleobase Excited State Decay Observed via Delayed Electron Emission

    SciTech Connect

    Sen, Ananya; Matthews, Edward M.; Hou, Gao-Lei; Wang, Xue B.; Dessent, Caroline

    2015-11-14

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ~1.7 eV, values that are lower than the RCB of the uncomplexed PtCl6 2- dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl6 2-∙thymine and PtCl6 2-∙adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)4 2-∙nucleobase complexes [Sen et al, J. Phys. Chem. B, 119, 11626, 2015]. The observation of delayed electron emission bands in the PtCl6 2-∙nucleobase spectra obtained in this work, as for the previously studied Pt(CN)4 2-∙nucleobase complexes, is attributed to onephoton excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a “dynamic tag” which has the propensity to emit electrons when the attached nucleobase decays over a timescale long enough to allow autodetachment.

  8. Photoelectron spectroscopy of hexachloroplatinate-nucleobase complexes: Nucleobase excited state decay observed via delayed electron emission.

    PubMed

    Sen, Ananya; Matthews, Edward M; Hou, Gao-Lei; Wang, Xue-Bin; Dessent, Caroline E H

    2015-11-14

    We report low-temperature photoelectron spectra of isolated gas-phase complexes of the hexachloroplatinate dianion bound to the nucleobases uracil, thymine, cytosine, and adenine. The spectra display well-resolved, distinct peaks that are consistent with complexes where the hexachloroplatinate dianion is largely intact. Adiabatic electron detachment energies for the hexachloroplatinate-nucleobase complexes are measured as 2.26-2.36 eV. The magnitudes of the repulsive Coulomb barriers (RCBs) of the complexes are all ∼1.7 eV, values that are lower than the RCB of the uncomplexed PtCl6 (2-) dianion as a result of charge solvation by the nucleobases. In addition to the resolved spectral features, broad featureless bands indicative of delayed electron detachment are observed in the 193 nm photoelectron spectra of the four clusters. The 266 nm spectra of the PtCl6 (2-) ⋅ thymine and PtCl6 (2-) ⋅ adenine complexes also display very prominent delayed electron emission bands. These results mirror recent results on the related Pt(CN)4 (2-) ⋅ nucleobase complexes [A. Sen et al., J. Phys. Chem. B 119, 11626 (2015)]. The observation of delayed electron emission bands in the PtCl6 (2-) ⋅ nucleobase spectra obtained in this work, as for the previously studied Pt(CN)4 (2-) ⋅ nucleobase complexes, is attributed to one-photon excitation of nucleobase-centred excited states that can effectively couple to the electron detachment continuum, producing strong electron detachment. Moreover, the selective, strong excitation of the delayed emission bands in the 266 nm spectra is linked to fundamental differences in the individual nucleobase photophysics at this excitation energy. This strongly supports our previous suggestion that the dianion within these clusters can be viewed as a "dynamic tag" which has the propensity to emit electrons when the attached nucleobase decays over a time scale long enough to allow autodetachment.

  9. Photoluminescence Investigation of the Indirect Band Gap and Shallow Impurities in Icosahedral B12As2

    DTIC Science & Technology

    2012-07-05

    could be effectively modulated by Si doping, resulting in p-type con- duction with a 105 reduction in the resistivity. Hall effect measurements on...conductivity has not been reported in IBA. Other studies of IBA have focused on thermal properties ( Seebeck coefficient, thermal conductivity16...2.56 eV), leading to a band gap of 3.2 eV. This band structure calculation also provided the first determination of the electron and hole effective

  10. Observation of electron excitation into silicon conduction band by slow-ion surface neutralization

    NASA Astrophysics Data System (ADS)

    Shchemelinin, S.; Breskin, A.

    2017-03-01

    Bare reverse biased silicon photodiodes were exposed to 3 eV He+, Ne+, Ar+, N2+, N+ and H2O+ ions. In all cases an increase of the reverse current through the diode was observed. This effect and its dependence on the ionization energy of the incident ions and on other factors are qualitatively explained in the framework of Auger-type surface neutralization theory. Amplification of the ion-induced charge was observed with an avalanche photodiode under high applied bias. The observed effect can be considered as ion-induced internal potential electron emission into the conduction band of silicon. To the best of our knowledge, no experimental evidence of such effect was previously reported. Possible applications are discussed.

  11. Broad-Band X-Ray Telescope spectroscopy of Xi Puppis

    NASA Technical Reports Server (NTRS)

    Corcoran, M. F.; Swank, J. H.; Serlemitsos, P. J.; Boldt, E.; Petre, R.; Marshall, F. E.; Jahoda, K.; Mushotzky, R.; Szymkowiak, A.; Arnaud, K.

    1993-01-01

    The Broad-Band X-Ray Telescope obtained moderate-resolution (about 90 eV) X-ray spectra of the O4 f star Xi Pup during the STS 35/Astro 1 mission in 1990 December. Despite the shortness of the observation (600 s), the data show a surprising amount of detail. We report the detection of an O absorption edge produced by ionized overlying wind material and K-shell line emission from Mg produced by a thermal plasma of temperature near 6 x 10 exp 6 K. The data are used to place constraints on the location,